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Journal articles on the topic 'Pumping epithelia'
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1
Brown, D., and S. Breton. "Mitochondria-rich, proton-secreting epithelial cells." Journal of Experimental Biology 199, no. 11 (November 1, 1996): 2345–58. http://dx.doi.org/10.1242/jeb.199.11.2345.
Full textAbstract:
Several transporting epithelia in vertebrates and invertebrates contain cells that are specialized for proton or bicarbonate secretion. These characteristic 'mitochondria-rich' (MR) cells have several typical features, the most important of which is an extremely high expression of a vacuolar-type proton-pumping ATPase (H+V-ATPase) both on intracellular vesicles and on specific domains of their plasma membrane. Physiological modulation of proton secretion is achieved by recycling the H+V-ATPase between the plasma membrane and the cytoplasm in a novel type of nonclathrin-coated vesicle. In the kidney, these cells are involved in urinary acidification, while in the epididymis and vas deferens they acidify the luminal environment to allow normal sperm development. Osteoclasts are non-epithelial MR cells that use H+V-ATPase activity for bone remodeling. In some insects, similar cells in the midgut energize K+ secretion by means of a plasma membrane H+V-ATPase. This review emphasizes important structural and functional features of proton-secreting cells, describes the tissue distribution of these cells and discusses the known functions of these cells in their respective epithelia.
2
Vagin, Olga, Laura A. Dada, Elmira Tokhtaeva, and George Sachs. "The Na-K-ATPase α1β1 heterodimer as a cell adhesion molecule in epithelia." American Journal of Physiology-Cell Physiology 302, no. 9 (May 1, 2012): C1271—C1281. http://dx.doi.org/10.1152/ajpcell.00456.2011.
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The ion gradients generated by the Na-K-ATPase play a critical role in epithelia by driving transepithelial transport of various solutes. The efficiency of this Na-K-ATPase-driven vectorial transport depends on the integrity of epithelial junctions that maintain polar distribution of membrane transporters, including the basolateral sodium pump, and restrict paracellular diffusion of solutes. The review summarizes the data showing that, in addition to pumping ions, the Na-K-ATPase located at the sites of cell-cell junction acts as a cell adhesion molecule by interacting with the Na-K-ATPase of the adjacent cell in the intercellular space accompanied by anchoring to the cytoskeleton in the cytoplasm. The review also discusses the experimental evidence on the importance of a specific amino acid region in the extracellular domain of the Na-K-ATPase β1 subunit for the Na-K-ATPase trans-dimerization and intercellular adhesion. Furthermore, a possible role of N-glycans linked to the Na-K-ATPase β1 subunit in regulation of epithelial junctions by modulating β1-β1 interactions is discussed.
3
Păunescu, Teodor G., Abigail C. Jones, Robert Tyszkowski, and Dennis Brown. "V-ATPase expression in the mouse olfactory epithelium." American Journal of Physiology-Cell Physiology 295, no. 4 (October 2008): C923—C930. http://dx.doi.org/10.1152/ajpcell.00237.2008.
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The vacuolar proton-pumping ATPase (V-ATPase) is responsible for the acidification of intracellular organelles and for the pH regulation of extracellular compartments. Because of the potential role of the latter process in olfaction, we examined the expression of V-ATPase in mouse olfactory epithelial (OE) cells. We report that V-ATPase is present in this epithelium, where we detected subunits ATP6V1A (the 70-kDa “A” subunit) and ATP6V1E1 (the ubiquitous 31-kDa “E” subunit isoform) in epithelial cells, nerve fiber cells, and Bowman's glands by immunocytochemistry. We also located both isoforms of the 56-kDa B subunit, ATP6V1B1 (“B1,” typically expressed in epithelia specialized in regulated transepithelial proton transport) and ATP6V1B2 (“B2”) in the OE. B1 localizes to the microvilli of the apical plasma membrane of sustentacular cells and to the lateral membrane in a subset of olfactory sensory cells, which also express carbonic anhydrase type IV, whereas B2 expression is stronger in the subapical domain of sustentacular cells. V-ATPase expression in mouse OE was further confirmed by immunoblotting. These findings suggest that V-ATPase may be involved in proton secretion in the OE and, as such, may be important for the pH homeostasis of the neuroepithelial mucous layer and/or for signal transduction in CO2 detection.
4
Numata, M., S. Ohkuma, and S. Iseki. "Expression and localization of mRNA for the 16 KD subunit of V-ATPase in the rat embryo." Journal of Histochemistry & Cytochemistry 43, no. 8 (August 1995): 761–69. http://dx.doi.org/10.1177/43.8.7622839.
Full textAbstract:
Vacuolar H(+)-ATPase (V-ATPase), an enzyme composed of multisubunits, is located in the membrane of intracellular organelles (e.g., lysosomes, and endosomes) and maintains the intraorganellar acidic pH by pumping protons across the membrane. Although there is growing evidence for some important role of V-ATPase in cell proliferation and differentiation, the functional significance of V-ATPase in vivo during mammalian development remains obscure. In the present study we investigated the expression and localization of mRNA for the 16 KD subunit of V-ATPase, an essential sector for enzymatic activity, in prenatal rat by Northern blot analysis and in situ hybridization with a specific oligonucleotide probe. With Northern blot analysis, consistent expression of the mRNA was observed in the embryos throughout the period examined (E14-E20). On in situ hybridization, mRNA signal was distributed with various intensities in both the epithelial and mesenchymal tissues at embryonic day 14 (E14). In E17 and E20 embryos, localization of strong signal became more restricted to distinct mesenchymal cells such as fibroblasts adjacent to the epithelia of skin, lung, and intestine, the cells of perichondrium, and myoblasts in the process of fusion. These results suggest that V-ATPase performs specific functions during the later stages of embryogenesis, especially at sites of mesenchymal differentiation and epithelium-mesenchyme interaction.
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Klein, U. "THE INSECT V-ATPase, A PLASMA MEMBRANE PROTON PUMP ENERGIZING SECONDARY ACTIVE TRANSPORT: IMMUNOLOGICAL EVIDENCE FOR THE OCCURRENCE OF A V-ATPase IN INSECT ION-TRANSPORTING EPITHELIA." Journal of Experimental Biology 172, no. 1 (November 1, 1992): 345–54. http://dx.doi.org/10.1242/jeb.172.1.345.
Full textAbstract:
Active electrogenic K+ transport in insects serves as the energy source for secretion or absorption in gastrointestinal epithelia or for the receptor current in sensory epithelia. In the larval midgut of the tobacco hornworm Manduca sexta, a vacuolar-type proton pump (V-ATPase) and a K+/nH+ antiport represent the functional elements of the potassium pump. Several immunological findings support the hypothesis that active K+ transport in other insect epithelia may also be energized by a V-ATPase. In immunoblots, crude homogenates of sensilla-rich antennae and Malpighian tubules of M. sexta cross reacted with an immune serum directed to the purified plasma membrane V-ATPase from the midgut; the M. sexta midgut V-ATPase cross reacted with polyclonal antibodies to endomembrane V-ATPases from xenic origin. In immunocytochemical investigations of larvae of M. sexta and adults of Antheraea pernyi, monoclonal antibodies to defined subunits of the purified midgut V-ATPase or polyclonal antibodies to xenic endomembrane V-ATPase labelled the sites of active K+ transport: the goblet cell apical membrane in the midgut, the brush border of Malpighian tubules and the apical projections of the auxiliary cells in antennal sensilla. The functional mechanism of a primary H+-pumping V-ATPase and a secondary H+-dependent K+ transport postulated for K+-transporting insect epithelia may be further applicable to active Na+ or Cl- transport and would provide a unifying concept for all ouabain-insensitive electrogenic ion transport in insects. The findings from the midgut investigations, however, are the first instance in which a V-ATPase provides an alternative to the Na+/K+-ATPase in energizing secondary active transport in animal plasma membranes.
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RAGGERS, René J., Ilse VOGELS, and Gerrit van MEER. "Multidrug-resistance P-glycoprotein (MDR1) secretes platelet-activating factor." Biochemical Journal 357, no. 3 (July 25, 2001): 859–65. http://dx.doi.org/10.1042/bj3570859.
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The human multidrug-resistance (MDR1) P-glycoprotein (Pgp) is an ATP-binding-cassette transporter (ABCB1) that is ubiquitously expressed. Often its concentration is high in the plasma membrane of cancer cells, where it causes multidrug resistance by pumping lipophilic drugs out of the cell. In addition, MDR1 Pgp can transport analogues of membrane lipids with shortened acyl chains across the plasma membrane. We studied a role for MDR1 Pgp in transport to the cell surface of the signal-transduction molecule platelet-activating factor (PAF). PAF is the natural short-chain phospholipid 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine. [14C]PAF synthesized intracellularly from exogenous alkylacetylglycerol and [14C]choline became accessible to albumin in the extracellular medium of pig kidney epithelial LLC-PK1 cells in the absence of vesicular transport. Its translocation across the apical membrane was greatly stimulated by the expression of MDR1 Pgp, and inhibited by the MDR1 inhibitors PSC833 and cyclosporin A. Basolateral translocation was not stimulated by expression of the basolateral drug transporter MRP1 (ABCC1). It was insensitive to the MRP1 inhibitor indomethacin and to depletion of GSH which is required for MRP1 activity. While efficient transport of PAF across the apical plasma membrane may be physiologically relevant in MDR1-expressing epithelia, PAF secretion in multidrug-resistant tumours may stimulate angiogenesis and thereby tumour growth.
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Lignot, Jean-Hervé, and Guy Charmantier. "Immunolocalization of NA+,K+-ATPase in the Branchial Cavity During the Early Development of the European Lobster Homarus Gammarus (Crustacea, Decapoda)." Journal of Histochemistry & Cytochemistry 49, no. 8 (August 2001): 1013–23. http://dx.doi.org/10.1177/002215540104900809.
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We examined the ontogeny of the osmoregulatory sites of the branchial cavity in embryonic and early postembryonic stages of the European lobster Homarus gammarus through transmission electron microscopy, immunofluorescence microscopy, and immunogold electron microscopy using a monoclonal antibody IgGα5 raised against the avian α-subunit of the Na+,K+-ATPase. In mid-late embryos, Na+,K+-ATPase was located along the pleurites and within the epipodite buds. In late embryos just before hatching, the enzyme was confined to the epipodite epithelia. After hatching, slight differentiations of ionocytes occured in the epipodites of larval stages. Na+,K+-ATPase was also located in the ionocytes of the epipodites of larvae exposed to seawater (35.0‰) and to dilute seawater (22.1 ‰). After metamorphosis, the inner-side branchiostegite epithelium appeared as an additional site of enzyme location in postlarvae held in dilute seawater. Within the ionocytes, Na+,K+-ATP-ase was mostly located along the basolateral infoldings. These observations are discussed in relation to the physiological shift from osmoconforming larvae to slightly hyper-regulating (in dilute seawater) postmetamorphic stages. The acquisition of the ability to hyper-osmo-regulate probably originates from the differentiation, on the epipodites and mainly along the branchiostegites, of ionocytes that are the site of ion pumping as evidenced by the location of Na+,K+-ATPase. (J Histochem Cytochem 49:1013–1023, 2001)
8
Fedorova, Larisa V., Vanamala Raju, Nasser El-Okdi, Amjad Shidyak, David J. Kennedy, Sandeep Vetteth, David R. Giovannucci, et al. "The cardiotonic steroid hormone marinobufagenin induces renal fibrosis: implication of epithelial-to-mesenchymal transition." American Journal of Physiology-Renal Physiology 296, no. 4 (April 2009): F922—F934. http://dx.doi.org/10.1152/ajprenal.90605.2008.
Full textAbstract:
We recently demonstrated that the cardiotonic steroid marinobufagenin (MBG) induced fibrosis in rat hearts through direct stimulation of collagen I secretion by cardiac fibroblasts. This stimulation was also responsible for the cardiac fibrosis seen in experimental renal failure. In this study, the effect of MBG on the development of renal fibrosis in rats was investigated. Four weeks of MBG infusion triggered mild periglomerular and peritubular fibrosis in the cortex and the appearance of fibrotic scars in the corticomedullary junction of the kidney. MBG also significantly increased the protein levels and nuclear localization of the transcription factor Snail in the tubular epithelia. It is known that activation of Snail is associated with epithelial-to-mesenchymal transition (EMT) during renal fibrosis. To examine whether MBG alone can trigger EMT, we used the porcine proximal tubular cell line LLC-PK1. MBG (100 nM) caused LLC-PK1 cells grown to confluence to acquire a fibroblast-like shape and have an invasive motility. The expressions of the mesenchymal proteins collagen I, fibronectin, and vimentin were increased twofold. However, the total level of E-cadherin remained unchanged. These alterations in LLC-PK1 cells in the presence of MBG were accompanied by elevated expression and nuclear translocation of Snail. During the time course of EMT, MBG did not have measurable inhibitory effects on the ion pumping activity of its natural ligand, Na+-K+-ATPase. Our data suggest that the MBG may be an important factor in inducing EMT and, through this mechanism, elevated levels of MBG in chronic renal failure may play a role in the progressive fibrosis.
9
Brown, D., and S. Breton. "H(+)V-ATPase-dependent luminal acidification in the kidney collecting duct and the epididymis/vas deferens: vesicle recycling and transcytotic pathways." Journal of Experimental Biology 203, no. 1 (January 1, 2000): 137–45. http://dx.doi.org/10.1242/jeb.203.1.137.
Full textAbstract:
Many vertebrate transporting epithelia contain characteristic ‘mitochondria-rich’ cells that express high levels of a vacuolar proton-pumping ATPase (H(+)V-ATPase) on their plasma membrane and on intracellular vesicles. In the kidney cortex, A-cells and B-cells are involved in proton secretion and bicarbonate secretion, respectively, in the distal nephron and collecting duct. A-cells have an H(+)V-ATPase on their apical plasma membrane and on intracellular vesicles, whereas the cellular location of the H(+)V-ATPase can be apical, basolateral, bipolar or diffuse in B-cells. The rat epididymis and vas deferens also contain a distinct population of H(+)V-ATPase-rich epithelial cells. These cells are involved in generating a low luminal pH, which is involved in sperm maturation and in maintaining sperm in an immotile state during their passage through the epididymis and vas deferens. In both kidney and reproductive tract, H(+)V-ATPase-rich cells have a high rate of apical membrane recycling. H(+)V-ATPase molecules are transported between the cell surface and the cytoplasm in vesicles that have a well-defined ‘coat’ structure formed of the peripheral V(1) subunits of the H(+)V-ATPase. In addition, we propose that B-type intercalated cells have a transcytotic pathway that enables them to shuttle H(+)V-ATPase molecules from apical to basolateral plasma membrane domains. This hypothesis is supported by data showing that A-cells and B-cells have different intracellular trafficking pathways for LGP120, a lysosomal glycoprotein. LGP120 was found both on the basolateral plasma membrane and in lysosomes in B-cells, whereas no LGP120 was detectable in the plasma membrane of A-cells. We propose that the ‘polarity reversal’ of the H(+)V-ATPase in B-intercalated cells is mediated by a physiologically regulated transcytotic pathway that may be similar to that existing in some other cell types.
10
Brown, D., S. Gluck, and J. Hartwig. "Structure of the novel membrane-coating material in proton-secreting epithelial cells and identification as an H+ATPase." Journal of Cell Biology 105, no. 4 (October 1, 1987): 1637–48. http://dx.doi.org/10.1083/jcb.105.4.1637.
Full textAbstract:
Specialized proton-secreting cells known collectively as mitochondria-rich cells are found in a variety of transporting epithelia, including the kidney collecting duct (intercalated cells) and toad and turtle urinary bladders. These cells contain a population of characteristic tubulovesicles that are believed to be involved in the shuttling of proton pumps (H+ATPase) to and from the plasma membrane. These transporting vesicles have a dense, studlike material coating the cytoplasmic face of their limiting membranes and similar studs are also found beneath parts of the plasma membrane. We have recently shown that this membrane coat does not contain clathrin. The present study was performed to determine the structure of this coat in rapidly frozen and freeze-dried tissue, and to determine whether the coat contains a major membrane protein transported by these vesicles, a proton pumping H+ATPase. The structure of the coat was examined in proton-secreting, mitochondria-rich cells from toad urinary bladder epithelium by rapidly freezing portions of apical membrane and associated cytoplasm that were sheared away from the remainder of the cell using polylysine-coated coverslips. Regions of the underside of these apical membranes as large as 0.2 micron2 were decorated by studlike projections that were arranged into regular hexagonal arrays. Individual studs had a diameter of 9.5 nm and appeared to be composed of multiple subunits arranged around a central depression, possibly representing a channel. The studs had a density of approximately 16,800 per micron2 of membrane. Similar arrays of studs were also found on vesicles trapped in the residual band of cytoplasm that remained attached to the underside of the plasma membrane, but none were seen in adjacent granular cells. To determine whether these arrays of studs contained H+ATPase molecules, we examined a preparation of affinity-purified bovine medullary H+ATPase, using the same technique, after incorporation of the protein eluted from a monoclonal antibody affinity column into phospholipid liposomes. The affinity-purified protein was shown to be capable of ATP-dependent acidification. In such preparations, large paracrystalline arrays of studs identical in appearance to those seen in situ were found. The dimensions of the studs as well as the number per square micrometer of membrane were identical to those of toad bladder mitochondria-rich cells: 9.5 nm in diameter, 16,770 per micron2 of membrane.(ABSTRACT TRUNCATED AT 400 WORDS)
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Maningat, Patricia D., Partha Sen, Agneta L. Sunehag, Darryl L. Hadsell, and Morey W. Haymond. "Regulation of gene expression in human mammary epithelium: effect of breast pumping." Journal of Endocrinology 195, no. 3 (October 2, 2007): 503–11. http://dx.doi.org/10.1677/joe-07-0394.
Full textAbstract:
Little is known of the molecular regulation of human milk production because of limitations in obtaining mammary tissue from lactating women. Our objectives were to evaluate whether RNA isolated from breast milk fat globules (MFGs) could be an alternative to mammary biopsies and to determine whether intense breast pumping, which increases prolactin (PRL) secretion, will upregulate α-lactalbumin (α-LA, a major determinant of lactose synthesis) transcription. RNA was isolated from MFG and transcripts of interest were identified and quantitated by real-time RT-PCR using an external standard for normalization. In addition, we performed microarray studies to determine MFG RNA gene expression profile. Ten lactating women were studied using two protocols: protocol A with intense pumping from 0800 to 0814 h followed by short pumping and protocol B with intense pumping from 1200 to 1214 h preceded by short pumping. Plasma PRL and MFG α-LA mRNA expression were measured. During protocol A, plasma PRL (61±7–248±43 μg/l by 14 min) and α-LA (3.5±0.9 fold by 6 h; P<0.03) increased. During protocol B, PRL gradually increased over 4 h from 69±14 to 205±28 μg/l, and further to 329±23 μg/l by 12 min of intense pumping; α-LA mRNA expression did not increase significantly. We conclude that MFGs provide a unique source to study the in vivo regulation of gene expression in mammary epithelial cells. α-LA mRNA is abundant in the MFG and its expression may be regulated by hormonal and temporal factors.
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Jeong, Yu-Da, Yun-Jae Park, Yeoung-Gyu Ko, Sung-Soo Lee, Sang-Hoon Lee, Jinwook Lee, Kwan-Woo Kim, Sung Woo Kim, and Bongki Kim. "Development and Differentiation of Epididymal Epithelial Cells in Korean Native Black Goat." Animals 10, no. 8 (July 25, 2020): 1273. http://dx.doi.org/10.3390/ani10081273.
Full textAbstract:
The acidic luminal environment of the epididymis is regulated by the communication networks among epididymal epithelial cells; it is necessary for sperm maturation and storage. To characterize epididymal epithelial cell differentiation, the localization and expression of hydrogen-pumping vacuolar ATPase (V-ATPase) and cytokeratin 5 (KRT5) in the clear and basal cells, respectively, of immature and mature goat epididymis and vas deferens was examined. The epididymides and vas deferens were obtained from goats aged 1, 2, and 12–14 months. To assess the localization and expression patterns of V-ATPase and KRT5 in the caput, corpus, and cauda of the epididymis and proximal vas deferens, the tissue sections were subjected to immunofluorescence labeling and observed by confocal microscopy. Both clear and basal cells progressively started to differentiate in a retrograde manner. Clear cells disappeared from the cauda region after puberty, and they were maintained only in the caput and corpus regions of the adult goat epididymis. V-ATPase and KRT5 were co-expressed in the differentiated cells located at the base of the epithelium (i.e., basal cells). This cell type-specific differentiation and distribution of the epithelial cells plays a critical role in establishing a unique luminal environment for sperm maturation and storage in the goat epididymis.
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Mallatt, Jon, Richard L. Ridgway, and Charles Paulsen. "Ultrastructural effects of 3-trifluormethyl-4-nitrophenol on gills of the larval lamprey Petromyzon marinus." Canadian Journal of Zoology 63, no. 1 (January 1, 1985): 155–64. http://dx.doi.org/10.1139/z85-024.
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Lamprey larvae (ammocoetes) are susceptible to 3-trifluormethyl-4-nitrophenol (TFM), a lampricidal toxicant which is administered through the ambient water. While this organic acid readily diffuses across gill cytomembranes, its actual mode of toxicity is uncertain. In this ultrastructural study, we examined the gills of larval Petromyzon marinus exposed to a nearly lethal dose (2.25 mg/L for 9 h, which is a median lethal concentration). Toxicant-associated damage was limited almost exclusively to a single gill epithelial cell type: presumed ion-uptake cells. These mitochondria-rich cells, which in normal ammocoete gills constitute the major portion of the respiratory surface, showed ultrastructural alterations ranging from abnormalities in microvilli and (or) cytoplasmic vacuolization to hypertrophy or even cytolysis. TFM-poisoned gills also differed from controls in having widened intercellular spaces within both respiratory lamellar epithelium and branchial interlamellar epithelium. Such intercellular spaces were particularly large in the vicinity of ion-uptake cells. These findings are consistent with a proposal that fish branchial ion-pumping cells function in extracting and extruding blood-borne organic acids, yet succumb to the damaging effects of such acids when intracellular concentrations exceed certain levels.
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Park, Yun-Jae, Ji-Hyuk Kim, Hack-Youn Kim, Hee-Bok Park, Juhui Choe, Gye-Woong Kim, Sun-Young Baek, Hak-Jae Chung, Yoo-Jin Park, and Bongki Kim. "The expression and localization of V-ATPase and cytokeratin 5 during postnatal development of the pig epididymis." Asian-Australasian Journal of Animal Sciences 33, no. 7 (July 1, 2020): 1077–86. http://dx.doi.org/10.5713/ajas.19.0587.
Full textAbstract:
Objective: We examined the localization and expression of H<sup>+ pumping vacuolar ATPase (V-ATPase) and cytokeratin 5 (KRT5) in the epididymis of pigs, expressed in clear and basal cells, respectively, during postnatal development.Methods: Epididymides were obtained from pigs at 1, 7, 21, 60, 120, and 180 days of age; we observed the localization and expression patterns of V-ATPase and KRT5 in the different regions of these organs, namely, the caput, corpus, and cauda. The differentiation of epididymal epithelial cells was determined by immunofluorescence labeling using cell-type-specific markers and observed using confocal microscopy.Results: At postnatal day 5 (PND5), the localization of clear cells commenced migration from the cauda toward the caput. Although at PND120, goblet-shaped clear cells were detected along the entire length of the epididymis, those labeled for V-ATPase had disappeared from the corpus to cauda and were maintained only in the caput epididymis in adult pigs. In contrast, whereas basal cells labeled for KRT5 were only present in the vas deferens at birth, they were detected in all regions of the epididymis at PND60. These cells were localized at the base of the epithelium; however, no basal cells characterized by luminally extending cell projections were observed in any of the adult epididymides examined.Conclusion: The differentiation of clear and basal cells progressively initiates in a retrograde manner from the cauda to the caput epididymis. The cell-type-specific distribution and localization of the epithelial cells play important roles in establishing a unique luminal environment for sperm maturation and storage in the pig epididymis.
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Starck, J. M., and K. Beese. "Structural flexibility of the intestine of Burmese python in response to feeding." Journal of Experimental Biology 204, no. 2 (January 15, 2001): 325–35. http://dx.doi.org/10.1242/jeb.204.2.325.
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The small intestine of Burmese pythons, Python molurus bivittatus, undergoes a remarkable size increase shortly after feeding. We studied the dynamics, reversibility and repeatability of organ size changes using noninvasive imaging techniques. We employed light and electron microscopy, flow cytometry and immunohistology to study the cytological mechanisms that drive the size changes of the small intestine. Within 2 days of feeding, the size of the small intestine increased to up to three times the fasting value. The size changes were fully reversible and could be elicited repeatedly by feeding. These enormous size changes were possible because the mucosal epithelium of the small intestine is a transitional epithelium that allows for considerable size changes without cell proliferation. Histological evidence suggested that a fluid pressure-pump system (lymphatic, blood pressure) was the driving force that inflated the intestinal villi. The rates of cell proliferation were not elevated immediately after feeding but peaked 1 week later when small intestine size was already declining. In contrast to the current paradigm, we suggest that the small intestine is not part of the previously proposed ‘pay-before-pumping’ model. Instead, the size of the python's small intestine may be upregulated without major metabolic investment. It can occur even if the individual is energetically exhausted. An evolutionary perspective of the transitional epithelium mechanism suggests superior functionality compared with the pay-before-pumping model because it allows for long periods of fasting and depletion of energy reserves, while still enabling the snake to digest prey and absorb nutrients.
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Cox, Jonathan P. L. "Hydrodynamic aspects of fish olfaction." Journal of The Royal Society Interface 5, no. 23 (January 9, 2008): 575–93. http://dx.doi.org/10.1098/rsif.2007.1281.
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Flow into and around the olfactory chamber of a fish determines how odorant from the fish's immediate environment is transported to the sensory surface (olfactory epithelium) lining the chamber. Diffusion times in water are long, even over comparatively short distances (millimetres). Therefore, transport from the external environment to the olfactory epithelium must be controlled by processes that rely on convection (i.e. the bulk flow of fluid). These include the beating of cilia lining the olfactory chamber and the relatively inexpensive pumping action of accessory sacs. Flow through the chamber may also be induced by an external flow. Flow over the olfactory epithelium appears to be laminar. Odorant transfer to the olfactory epithelium may be facilitated in several ways: if the olfactory organs are mounted on stalks that penetrate the boundary layer; by the steep velocity gradients generated by beating cilia; by devices that deflect flow into the olfactory chamber; by parallel arrays of olfactory lamellae; by mechanical agitation of the chamber (or olfactory stalks); and by vortices. Overall, however, our knowledge of the hydrodynamics of fish olfaction is far from complete. Several areas of future research are outlined.
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Novotny, J. A., and E. Jakobsson. "Computational studies of ion-water flux coupling in the airway epithelium. I. Construction of model." American Journal of Physiology-Cell Physiology 270, no. 6 (June 1, 1996): C1751—C1763. http://dx.doi.org/10.1152/ajpcell.1996.270.6.c1751.
Full textAbstract:
A mathematical model of ion and water transport across the airway epithelium is presented. The model consists of 12 state variables representing ion concentrations, volumes, and membrane potentials. All osmotically significant membrane transport processes for which there is conclusive experimental evidence are included: passive apical sodium and chloride movement, basolateral sodium-potassium pumping, basolateral sodium-potassium-chloride cotransport, passive basolateral potassium movement, nonselective passive paracellular ion motion, and water transport across all membranes. Ion movements are described by Michaelis-Menten kinetics or by the constant field flux equation. Model parameters are established with Ussing chamber data. Model behavior is validated by comparing in vitro simulations with experimental results. The model accurately reproduces short-circuit chloride and sodium fluxes, short-circuit current, and open-circuit membrane potentials from Ussing chamber data in the secreting and nonsecreting states. The model is then used to describe the behavior of the airway epithelium in vivo, in which case the apical electrolyte compartment is small and of variable size and ionic composition.
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Rahman, Nawreen, Lavoisier Ramos-Espiritu, Teresa A. Milner, Jochen Buck, and Lonny R. Levin. "Soluble adenylyl cyclase is essential for proper lysosomal acidification." Journal of General Physiology 148, no. 4 (September 26, 2016): 325–39. http://dx.doi.org/10.1085/jgp.201611606.
Full textAbstract:
Lysosomes, the degradative organelles of the endocytic and autophagic pathways, function at an acidic pH. Lysosomes are acidified by the proton-pumping vacuolar ATPase (V-ATPase), but the molecular processes that set the organelle’s pH are not completely understood. In particular, pH-sensitive signaling enzymes that can regulate lysosomal acidification in steady-state physiological conditions have yet to be identified. Soluble adenylyl cyclase (sAC) is a widely expressed source of cAMP that serves as a physiological pH sensor in cells. For example, in proton-secreting epithelial cells, sAC is responsible for pH-dependent translocation of V-ATPase to the luminal surface. Here we show genetically and pharmacologically that sAC is also essential for lysosomal acidification. In the absence of sAC, V-ATPase does not properly localize to lysosomes, lysosomes fail to fully acidify, lysosomal degradative capacity is diminished, and autophagolysosomes accumulate.
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Brown, D., B. Lui, S. Gluck, and I. Sabolic. "A plasma membrane proton ATPase in specialized cells of rat epididymis." American Journal of Physiology-Cell Physiology 263, no. 4 (October 1, 1992): C913—C916. http://dx.doi.org/10.1152/ajpcell.1992.263.4.c913.
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Acidification of the luminal fluid in the epididymis is believed to play an important role in sperm maturation. Previous studies have shown that specialized cells in the epithelium lining the epididymis contain high levels of carbonic anhydrase and that these cells have rod-shaped intramembraneous particles when examined by freeze fracture. Both of these features are characteristic of proton-transporting intercalated cells in the kidney collecting duct. We now show that apical cells in the head of the epididymis and clear cells in the body and tail of the epididymis express high levels of a vacuolar proton-pumping adenosinetriphosphatase on their apical plasma membranes and on intracellular vesicles. By analogy with kidney intercalated cells, these cell types may be specialized for acid secretion in the epididymis.
20
Bischof, G., B. Illek, W. W. Reenstra, and T. E. Machen. "Role for tyrosine kinases in carbachol-regulated Ca entry into colonic epithelial cells." American Journal of Physiology-Cell Physiology 268, no. 1 (January 1, 1995): C154—C161. http://dx.doi.org/10.1152/ajpcell.1995.268.1.c154.
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We studied a possible role of tyrosine kinases in the regulation of Ca entry into colonic epithelial cells HT-29/B6 using digital image processing of fura 2 fluorescence. Both carbachol and thapsigargin increased Ca entry to a similar extent and Ca influx was reduced by the tyrosine kinase inhibitor genistein (50 microM). Further experiments were performed in solutions containing 95 mM K to depolarize the membrane potential, and the effects of different inhibitors on influx of Ca, Mn, and Ba were compared. Genistein, but not the inactive analogue daidzein nor the protein kinase C inhibitor 1-(5-isoquinolinylsulfonyl)-2- methylpiperazine, decreased entry of all three divalent cations by 47-59%. In high-K solutions, carbachol or thapsigargin both caused intracellular Ca to increase to a plateau of 223 +/- 19 nM. This plateau was reduced by the tyrosine kinase inhibitors genistein (to 95 +/- 8 nM), lavendustin A (to 155 +/- 17 nM), and methyl-2,5-dihydroxycinnamate (to 39 +/- 3 nM). Orthovanadate, a protein tyrosine phosphatase inhibitor, prevented the inhibitory effect of genistein. Ca pumping was unaffected by genistein. Carbachol increased tyrosine phosphorylation (immunoblots with anti-phosphotyrosine antibodies) of 110-, 75-, and 70-kDa proteins, and this phosphorylation was inhibited by genistein. We conclude that carbachol and thapsigargin increase Ca entry, and tyrosine phosphorylation of some key proteins may be important for regulating this pathway.
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Ambasch, Karina, Z. Ioav Cabantchik, and Itzchak N. Slotki. "Effects of hypotonic and hypoionic media on drug pumping by P-glycoprotein expressed in epithelial and nonepithelial cell lines." Journal of Cellular Physiology 164, no. 1 (July 1995): 117–22. http://dx.doi.org/10.1002/jcp.1041640115.
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Moyo, Siphosanele Mafa, June C. Serem, Megan J. Bester, Vuyo Mavumengwana, and Eugenie Kayitesi. "Hydrothermal Processing and In Vitro Simulated Human Digestion Affects the Bioaccessibility and Bioactivity of Phenolic Compounds in African Pumpkin (Momordica balsamina) Leaves." Molecules 26, no. 17 (August 27, 2021): 5201. http://dx.doi.org/10.3390/molecules26175201.
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The African pumpkin (Momordica balsamina) contains bioactive phenolic compounds that may assist in reducing oxidative stress in the human body. The leaves are mainly consumed after boiling in water for a specific time; this hydrothermal process and conditions of the gastrointestinal tract may affect the presence and bioactivity of phenolics either positively or negatively. In this study, the effects of hydrothermal processing (boiling) and in vitro simulated human digestion on the phenolic composition, bioaccessibility and bioactivity in African pumpkin were investigated in comparison with those of spinach (Spinacia oleracea). A high-resolution ultra-performance liquid chromatography, coupled with diode array detection, quadrupole time-of-flight and mass spectrometer (UPLC-DAD-QTOF-MS) was used to profile phenolic metabolites. Metabolites such as 3-caffeoylquinic acid, 5-caffeoylquinic acid, 3,4-dicaffeoylquinic acid, 3,5-dicaffeoylquinic acid and 4,5-dicaffeoylquinic acid were highly concentrated in the boiled vegetable extracts compared to the raw undigested and all digested samples. The majority of African pumpkin and spinach extracts (non-digested and digested) protected Deoxyribonucleic acid (DNA), (mouse fibroblast) L929 and human epithelial colorectal adenocarcinoma (Caco-2) cells from 2,2′-Azobis(2-methylpropionamidine) dihydrochloride (AAPH)-induced oxidative damage. From these results, the consumption of boiled African pumpkin leaves, as well as spinach, could be encouraged, as bioactive metabolites present may reduce oxidative stress in the body.
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Dvoriashyna, Mariia, Alexander J. E. Foss, Eamonn A. Gaffney, and Rodolfo Repetto. "Fluid and solute transport across the retinal pigment epithelium: a theoretical model." Journal of The Royal Society Interface 17, no. 163 (February 2020): 20190735. http://dx.doi.org/10.1098/rsif.2019.0735.
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The retina is composed of two main layers—the neuroretina and the retinal pigment epithelium (RPE)—that are separated by a potential gap termed the sub-retinal space (SRS). Accumulation of fluid in the SRS may result in a retinal detachment. A key function of the RPE is to prevent fluid accumulation in the SRS by actively pumping fluid from this space to the choroid. We have developed a mathematical model of this process that incorporates the transport of seven chemical species: Na + , K + , Cl − , HCO 3 − , H + , CO 2 and H 2 CO 3 . This allows us to estimate solute and water fluxes and to understand the role of the different membrane ion channels. We have performed a global sensitivity analysis using the extended Fourier amplitude sensitivity test to investigate the relative importance of parameters in generating the model outputs. The model predicts that flow across the RPE is driven by an osmotic gradient in the cleft gap between adjacent cells. Moreover, the model estimates how water flux is modified in response to inhibition of membrane ion channels and carbonic anhydrase (CA). It provides a possible explanation for how CA inhibitors, which are used clinically to prevent fluid accumulation in the SRS, may be acting.
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Yajima, Shinya, Makoto Kubota, Takashi Nakakura, Takahiro Hasegawa, Nobuto Katagiri, Hideaki Tomura, Yuichi Sasayama, Masakazu Suzuki, and Shigeyasu Tanaka. "Cloning and Expression of Vacuolar Proton-Pumping ATPase Subunits in the Follicular Epithelium of the Bullfrog Endolymphatic Sac." Zoological Science 24, no. 2 (February 2007): 147–57. http://dx.doi.org/10.2108/zsj.24.147.
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Păunescu, Teodor G., Nicolas Da Silva, Leileata M. Russo, Mary McKee, Hua A. J. Lu, Sylvie Breton, and Dennis Brown. "Association of soluble adenylyl cyclase with the V-ATPase in renal epithelial cells." American Journal of Physiology-Renal Physiology 294, no. 1 (January 2008): F130—F138. http://dx.doi.org/10.1152/ajprenal.00406.2007.
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Activation of soluble adenylyl cyclase (sAC) by bicarbonate causes local cAMP generation, indicating that sAC might act as a pH and/or bicarbonate sensor in kidney cells involved in acid-base homeostasis. Therefore, we examined the expression of sAC in renal acid-base transporting intercalated cells (IC) and compared its distribution to that of the vacuolar proton pumping ATPase (V-ATPase) under different conditions. In all IC, sAC and V-ATPase showed considerable overlap under basal conditions, but sAC staining was also found in other cellular locations in the absence of V-ATPase. In type A-IC, both sAC and V-ATPase were apically and subapically located, whereas in type B-IC, significant basolateral colocalization of sAC and the V-ATPase was seen. When apical membrane insertion of the V-ATPase was stimulated by treatment of rats with acetazolamide, sAC was also concentrated in the apical membrane of A-IC. In mice that lack a functional B1 subunit of the V-ATPase, sAC was colocalized apically in A-IC along with V-ATPase containing the alternative B2 subunit isoform. The close association between these two enzymes was confirmed by coimmunoprecipitation of sAC from kidney homogenates using anti-V-ATPase antibodies. Our data show that sAC and the V-ATPase colocalize in IC, that they are concentrated in the IC plasma membrane under conditions that “activate” these proton secretory cells, and that they are both present in an immunoprecipitated complex. This suggests that these enzymes have a close association and could be part of a protein complex that is involved in regulating renal distal proton secretion.
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Raeburn, David, and Jeffrey S. Fedan. "The effects of alterations in electrogenic Na+/K+-pumping in guinea-pig isolated trachealis: their modulation by the epithelium." British Journal of Pharmacology 98, no. 2 (October 1989): 343–50. http://dx.doi.org/10.1111/j.1476-5381.1989.tb12602.x.
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Brown, Dennis, Richard Bouley, Teodor G. Pǎunescu, Sylvie Breton, and Hua A. J. Lu. "New insights into the dynamic regulation of water and acid-base balance by renal epithelial cells." American Journal of Physiology-Cell Physiology 302, no. 10 (May 15, 2012): C1421—C1433. http://dx.doi.org/10.1152/ajpcell.00085.2012.
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Maintaining tight control over body fluid and acid-base homeostasis is essential for human health and is a major function of the kidney. The collecting duct is a mosaic of two cell populations that are highly specialized to perform these two distinct processes. The antidiuretic hormone vasopressin (VP) and its receptor, the V2R, play a central role in regulating the urinary concentrating mechanism by stimulating accumulation of the aquaporin 2 (AQP2) water channel in the apical membrane of collecting duct principal cells. This increases epithelial water permeability and allows osmotic water reabsorption to occur. An understanding of the basic cell biology/physiology of AQP2 regulation and trafficking has informed the development of new potential treatments for diseases such as nephrogenic diabetes insipidus, in which the VP/V2R/AQP2 signaling axis is defective. Tubule acidification due to the activation of intercalated cells is also critical to organ function, and defects lead to several pathological conditions in humans. Therefore, it is important to understand how these “professional” proton-secreting cells respond to environmental and cellular cues. Using epididymal proton-secreting cells as a model system, we identified the soluble adenylate cyclase (sAC) as a sensor that detects luminal bicarbonate and activates the vacuolar proton-pumping ATPase (V-ATPase) via cAMP to regulate tubular pH. Renal intercalated cells also express sAC and respond to cAMP by increasing proton secretion, supporting the hypothesis that sAC could function as a luminal sensor in renal tubules to regulate acid-base balance. This review summarizes recent advances in our understanding of these fundamental processes.
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Borgatti, Monica, Stefania Mazzitelli, Giulia Breveglieri, Roberto Gambari, and Claudio Nastruzzi. "Induction by TNF-αof IL-6 and IL-8 in Cystic Fibrosis Bronchial IB3-1 Epithelial Cells Encapsulated in Alginate Microbeads." Journal of Biomedicine and Biotechnology 2010 (2010): 1–11. http://dx.doi.org/10.1155/2010/907964.
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We have developed a microencapsulation procedure for the entrapment and manipulation of IB3-1 cystic fibrosis cells. The applied method is based on generation of monodisperse droplets by a vibrational nozzle. Different experimental parameters were analyzed, including frequency and amplitude of vibration, polymer pumping rate and distance between the nozzle and the gelling bath. We have found that the microencapsulation procedure does not alter the viability of the encapsulated IB3-1 cells. The encapsulated IB3-1 cells were characterized in term of secretomic profile, analyzing the culture medium by Bio-Plex strategy. The experiments demonstrated that most of the analyzed proteins, were secreted both by the free and encapsulated cells, even if in a different extent. In order to determine the biotechnological applications of this procedure, we determined whether encapsulated IB3-1 cells could be induced to pro-inflammatory responses, after treatment with TNF-α. In this experimental set-up, encapsulated and free IB3-1 cells were treated with TNF-α, thereafter the culture media from both cell populations were collected. As expected, TNF-αinduced a sharp increase in the secretion of interleukins, chemokines and growth factors. Of great interest was the evidence that induction of interleukin-6 and interleukin-8 occurs also by encapsulated IB3-1 cells.
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Cammarata, P. R., D. Tse, and T. Yorio. "Uncoupling of Attenuated myo-[3H]Inositol Uptake and Dysfunction in Na+-K+-ATPase Pumping Activity in Hypergalactosemic Cultured Bovine Lens Epithelial Cells." Diabetes 40, no. 6 (June 1, 1991): 731–37. http://dx.doi.org/10.2337/diab.40.6.731.
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Xie, Joe, Qiqi Ye, Xiaoyu Cui, Namrata Madan, Qiying Yi, Sandrine V. Pierre, and Zijian Xie. "Expression of rat Na-K-ATPase α2 enables ion pumping but not ouabain-induced signaling in α1-deficient porcine renal epithelial cells." American Journal of Physiology-Cell Physiology 309, no. 6 (September 15, 2015): C373—C382. http://dx.doi.org/10.1152/ajpcell.00103.2015.
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Na-K-ATPase is a fundamental component of ion transport. Four α isoforms of the Na-K-ATPase catalytic α subunit are expressed in human cells. The ubiquitous Na-K-ATPase α1 was recently discovered to also mediate signal transduction through Src kinase. In contrast, α2 expression is limited to a few cell types including myocytes, where it is coupled to the Na+/Ca2+ exchanger. To test whether rat Na-K-ATPase α2 is capable of cellular signaling like its α1 counterpart in a recipient mammalian system, we used an α1 knockdown pig renal epithelial cell (PY-17) to create an α2-expressing cell line with no detectable level of α1 expression. These cells exhibited normal ouabain-sensitive ATPase, but failed to effectively regulate Src. In contrast to α1-expressing cells, ouabain did not stimulate Src kinase or downstream effectors such as ERK and Akt in α2 cells, although their signaling apparatus was intact as evidenced by EGF-mediated signal transduction. Additionally, α2 cells were unable to rescue caveolin-1. Unlike the NaKtide sequence derived from Na-K-ATPase α1, which downregulates basal Src activity, the corresponding α2 NaKtide was unable to inhibit Src in vitro. Finally, coimmunoprecipitation of cellular Src was diminished in α2 cells. These findings indicate that Na-K-ATPase α2 does not regulate Src and, therefore, may not serve the same role in signal transduction as α1. This further implies that the signaling mechanism of Na-K-ATPase is isoform specific, thereby supporting a model where α1 and α2 isoforms play distinct roles in mediating contraction and signaling in myocytes.
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Cammarata, P. R., D. Tse, and T. Yorio. "Uncoupling of attenuated myo-[3H]inositol uptake and dysfunction in Na(+)-K(+)-ATPase pumping activity in hypergalactosemic cultured bovine lens epithelial cells." Diabetes 40, no. 6 (June 1, 1991): 731–37. http://dx.doi.org/10.2337/diabetes.40.6.731.
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Allman, Erik, David Johnson, and Keith Nehrke. "Loss of the apical V-ATPase a-subunit VHA-6 prevents acidification of the intestinal lumen during a rhythmic behavior in C. elegans." American Journal of Physiology-Cell Physiology 297, no. 5 (November 2009): C1071—C1081. http://dx.doi.org/10.1152/ajpcell.00284.2009.
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In Caenorhabditis elegans, oscillations of intestinal pH contribute to the rhythmic defecation behavior, but the acid-base transport mechanisms that facilitate proton movement are not well understood. Here, we demonstrate that VHA-6, an intestine-specific a-subunit of the H+-K+-ATPase complex (V-ATPase), resides in the apical membrane of the intestinal epithelial cells and is required for luminal acidification. Disruption of the vha-6 gene led to early developmental arrest; the arrest phenotype could be complemented by expression of a fluorescently labeled vha-6 transgene. To study the contribution of vha-6 to pH homeostasis in larval worms, we used a partial reduction of function through postembryonic single-generation RNA interference. We demonstrate that the inability to fully acidify the intestinal lumen coincides with a defect in pH recovery of the intestinal epithelial cells, suggesting that VHA-6 is essential for proton pumping following defecation. Moreover, intestinal dipeptide accumulation and fat storage are compromised by the loss of VHA-6, suggesting that luminal acidification promotes nutrient uptake in worms, as well as in mammals. Since acidified intracellular vesicles and autofluorescent storage granules are indistinguishable between the vha-6 mutant and controls, it is likely that the nutrient-restricted phenotype is due to a loss of plasma membrane V-ATPase activity specifically. These data establish a simple genetic model for proton pump-driven acidification. Since defecation occurs at 45-s intervals in worms, this model represents an opportunity to study acute regulation of V-ATPase activity on a short time scale and may be useful in the study of alternative treatments for acid-peptic disorders.
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Wong, CK, and DK Chan. "Effects of cortisol on chloride cells in the gill epithelium of Japanese eel, Anguilla japonica." Journal of Endocrinology 168, no. 1 (January 1, 2001): 185–92. http://dx.doi.org/10.1677/joe.0.1680185.
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The purpose of the present study was to determine the effects of cortisol on the development of the freshwater chloride cell (CC), using flow cytometry. Scanning electron microscopy was used to determine the corresponding modifications in CC apical structure. Simultaneously, biochemical analyses were conducted to determine the activities of transport ATPases, mitochondrial enzymes (succinate dehydrogenase (SDH) and Mg(2+)-ATPase) and lactate dehydrogenase (Ldh). The effects of daily i.m. injection of 2 microg/g cortisol were compared with sham-injected freshwater-, control freshwater- and seawater-adapted fish. The hormone did not affect the activities of Ca(2+)-ATPases in CCs. However, it stimulated the proliferation and differentiation of the two freshwater CC subtypes (F1, 66+/-2.18% (s.e.m. ) and F2, 34+/-2.18%), in which the relative proportion of F1 CCs was transiently reduced in the first 5 days of treatment (F1, 53+/-1.83%; F2, 47+/-1.83%) but was then restored to a higher relative percentage on day 10 (F1, 70+/-1.42%; F2, 30+/-1.42%). Biochemically, it induced the activities of Na(+)/K(+)-ATPase, Mg(2+)-ATPase, SDH and Ldh, suggesting an increase in ion pumping and its associated metabolic activities. CCs from cortisoltreated fish demonstrated recessed apical morphology, accompanied by an increase in cell density (2012 to 2413/mm(2)). Nevertheless, the extent of cell proliferation and differentiation and the biochemical changes were significantly lower than those of seawater fish. Our results indicate that cortisol alone cannot stimulate a complete differentiation of freshwater CCs to seawater CCs. However, the respective roles of the two CC subtypes in freshwater and seawater environments are indicated.
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Azuma, M., and Y. Ohta. "Changes in H+-translocating vacuolar-type ATPase in the anterior silk gland cell of Bombyx mori during metamorphosis." Journal of Experimental Biology 201, no. 4 (February 15, 1998): 479–86. http://dx.doi.org/10.1242/jeb.201.4.479.
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A proton-translocating vacuolar-type ATPase (V-ATPase) was identified and characterized in the anterior silk gland of Bombyx mori. By incubating the intact tissue with the fluorescent dye Acridine Orange, the acidified compartment was detected at the apical pole of the epithelial cells. This was observed throughout the feeding period of the fifth-instar larva until the onset of spinning. Acidification was prevented completely and reversibly by 0.8 micromol l-1 bafilomycin A1, a specific inhibitor of V-ATPase. The presence of V-ATPase in a microsomal fraction was verified by immunoblots using an antiserum to the V-ATPase holoenzyme from Manduca sexta midgut. The antiserum localized the V-ATPase to the apical plasma membrane of the anterior silk gland cells, suggesting that the enzyme is functionally active in pumping protons out of the cell towards the glandular lumen of feeding silkworm larvae. In spinning larvae, the acidification produced by the V-ATPase appears to cease, because acidic compartments were seen rarely and only in the periphery of basal cytoplasm, and because immunocytochemical staining for the V-ATPase was greatly reduced at the apical surface. The metamorphic changes in relation to the occurrence of V-ATPase corresponded well with the ultrastructural changes in the anterior silk gland cell of Bombyx mori larvae.
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Frangiamone, Massimo, Alessandra Cimbalo, Manuel Alonso-Garrido, Guillermina Font, and Lara Manyes. "Transcriptomic changes after exposure to pumpkin extract in human epithelial cells of a blood brain barrier model." Free Radical Biology and Medicine 165 (March 2021): 49–50. http://dx.doi.org/10.1016/j.freeradbiomed.2020.12.402.
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MOFFETT, DAVID F., and ALAN R. KOCH. "Electrophysiology of K+ Transport by Midgut Epithelium of Lepidopteran Insect Larvae: II. The Transapical Electrochemical Gradients." Journal of Experimental Biology 135, no. 1 (March 1, 1988): 39–49. http://dx.doi.org/10.1242/jeb.135.1.39.
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The apical surface of the midgut of Manduca sexta larvae is composed of the apical membranes of columnar cells, in the form of microvilli, and the apical goblet of goblet cells. Considerable evidence has suggested that the apical electrogenic pump that is responsible for transepithelial K+ transport is located on the apical membrane of goblet cells. In the present study the transapical potentials and K+ chemical activity [(K+)] gradients of columnar and goblet cells of posterior midgut were examined in the short-circuited gut. In some experiments the recording site was localized by ionophoresis of NiCl2 followed immediately by fixation in rubeanic acid. The (K+) of goblet cavities was substantially higher than that of the free solution on the gut luminal side (mean value of 94mmoll−1 in standard bathing solution). The goblet cavity was electrically positive to the gut lumen (mean value of 40 mV in standard bathing solution). When the rate of pumping of K+ into the goblet cavity was decreased by hypoxia or decreased bathing solution [K+], the electrical potential gradient between cytoplasm and goblet cavity decreased while intracellular (K+) and goblet cavity (K+) were relatively stable. These studies provide evidence that a negatively charged goblet matrix is present in goblet cavities. Furthermore, they suggest that it is the voltage-sensitivity of the apical pump to the electrical component of the transapical electrochemical gradient, and not a concentrationdependence of the pump, that exercises the major role in determining the relationship between extracellular (K+) and net K+ transport by the isolated gut.
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Yang, H., and E. B. Jeung. "203 PLASMA MEMBRANE Ca2+-PUMPING ATPase 1 IS ABUNDANTLY EXPRESSED AND DISTINCTLY REGULATED BY ESTROGEN IN HUMAN ENDOMETRIUM DURING THE MENSTRUAL CYCLE." Reproduction, Fertility and Development 23, no. 1 (2011): 201. http://dx.doi.org/10.1071/rdv23n1ab203.
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Plasma membrane Ca2+-pumping ATPases (PMCA) play a critical role in maintaining cellular Ca2+ homeostasis. The PMCA mRNA are encoded on 4 genes, designated PMCA1 to PMCA4. In a previous study, we found that both PMCA1 and PMCA4 are expressed at similar levels in astrocytes and in neurons. Although PMCA1b is expressed in the uterus of rats during the oestrous cycle, the expression of PMCA1 and its potential roles has not been elucidated during the menstrual cycle in the human endometrium. Thus, in the current study, the expression pattern of PMCA1 was examined to predict its roles in the human endometrium during the menstrual cycle. Human uterine tissues (total n = 40) were separated into 3 groups according to menstrual cycle phase: menstrual phase, proliferative phase (early, mid, late), and secretory phase (early, mid, late). Using real-time PCR and Western blot analysis, uterine expression of PMCA1 mRNA and protein increased to 1.5-fold in the early-, mid- and late-proliferative phases in the endometrium of the human uterus, compared with other menstrual phases. In addition, uterine PMCA1 was abundantly localised in the cytoplasm of the luminal and glandular epithelial cells in the menstrual phases, indicating that this protein may participate in the uterine Ca balance of the human endometrium during the menstrual cycle. Taken together, these results suggest that a high level of uterine PMCA1 expression may be involved in reproductive functions during the menstrual cycle of humans.
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Kim, Y. K., H. Yang, and E. B. Jeung. "191 TRANSIENT RECEPTOR POTENTIAL SUPERFAMILY OF ION CHANNELS, TRPV6, IS CONSTITUTIVELY EXPRESSED AND REGULATED BY ESTROGEN IN THE HUMAN UTERUS DURING THE MENSTRUAL CYCLE." Reproduction, Fertility and Development 23, no. 1 (2011): 196. http://dx.doi.org/10.1071/rdv23n1ab191.
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Two highly selective calcium channels at the apical sides of cells, members of the transient receptor potential (TRP) superfamily of ion channels (TRPV6 and TRPV5), are the main calcium ion entry channels. Previously, the location of TRPV6 has been described in the intestine in several species, including humans. It is located in the apical brush-border membrane of the intestinal enterocyte, where it regulates calcium entry into the cell. It is most abundant in the proximal small intestine (duodenum and jejunum), where calbindin and the calcium-pumping ATPase are also found. The TRPV6 calcium transporter is also found in the human placenta, pancreas, and prostate gland in some species. However, TRPV6 expression and its potential roles remain to be clarified in the endometrium of humans during the menstrual cycle. In this study, we used a human endometrial model to examine the expression of TRPV6 and its potential roles in the human menstrual cycle. A significant increase (1.5-fold) in the TRPV6 transcript and protein was observed in the human uterus at the proliferation phase compared with other phases. In addition, the spatial localization of TRPV6 in the human uterus was determined by immunohistochemistry. Uterine TRPV6 was abundantly localised in the cytoplasm of the endometrial and glandular epithelial cells in the menstrual phases. Overall, these results demonstrate that TRPV6 is abundantly expressed in human uterine tissue, suggesting that this protein may be involved in reproductive functions during the menstrual cycle in humans.
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Negulescu, P. A., B. Rubinsky, G. L. Fletcher, and T. E. Machen. "Fish antifreeze proteins block Ca entry into rabbit parietal cells." American Journal of Physiology-Cell Physiology 263, no. 6 (December 1, 1992): C1310—C1313. http://dx.doi.org/10.1152/ajpcell.1992.263.6.c1310.
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Many fish and insects have adapted to life at subfreezing temperatures by evolving so-called antifreeze proteins (AFP) that noncolligatively depress the freezing temperatures of aqueous solutions without affecting the melting temperature. AFP have been thought to function solely as antifreezes. Recently, however, we discovered that AFP also protect mammalian cells and organs from damage caused by exposure to hypothermic (above freezing) temperatures. It has been proposed that hypothermic damage is caused by changes in intracellular ionic content due to a reduction of active transport that is required to balance passive ion transport across cell membranes. Given this possibility, we tested whether AFP isolated from the Newfoundland ocean pout might reduce the Ca ion permeability of a mammalian cell, the rabbit gastric parietal cell, which has been particularly well studied in terms of Ca transport and signaling. Digital image processing of the Ca-sensitive fluorescent indicator fura-2 was used to measure intracellular free Ca in these cells. During stimulation with the cholinergic agonist carbachol, AFP inhibited passive Ca entry across the cell membrane without interfering with either the release of Ca from internal stores (indicating that the carbachol receptor and other signaling events were operational) or the normal active rates of Ca efflux from the cell (indicating that Ca pumping was also still intact). These results suggest that, in addition to their actual antifreeze properties, AFP may also help to confer cold tolerance in animals by preventing passive Ca entry into epithelial cells.
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Liu, Wen, Núria M. Pastor-Soler, Carlos Schreck, Beth Zavilowitz, Thomas R. Kleyman, and Lisa M. Satlin. "Luminal flow modulates H+-ATPase activity in the cortical collecting duct (CCD)." American Journal of Physiology-Renal Physiology 302, no. 1 (January 1, 2012): F205—F215. http://dx.doi.org/10.1152/ajprenal.00179.2011.
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Epithelial Na+ channel (ENaC)-mediated Na+ absorption and BK channel-mediated K+ secretion in the cortical collecting duct (CCD) are modulated by flow, the latter requiring an increase in intracellular Ca2+ concentration ([Ca2+]i), microtubule integrity, and exocytic insertion of preformed channels into the apical membrane. As axial flow modulates HCO3− reabsorption in the proximal tubule due to changes in both luminal Na+/H+ exchanger 3 and H+-ATPase activity (Du Z, Yan Q, Duan Y, Weinbaum S, Weinstein AM, Wang T. Am J Physiol Renal Physiol 290: F289–F296, 2006), we sought to test the hypothesis that flow also regulates H+-ATPase activity in the CCD. H+-ATPase activity was assayed in individually identified cells in microperfused CCDs isolated from New Zealand White rabbits, loaded with the pH-sensitive dye BCECF, and then subjected to an acute intracellular acid load (NH4Cl prepulse technique). H+-ATPase activity was defined as the initial rate of bafilomycin-inhibitable cell pH (pHi) recovery in the absence of luminal K+, bilateral Na+, and CO2/HCO3−, from a nadir pH of ∼6.2. We found that 1) an increase in luminal flow rate from ∼1 to 5 nl·min−1·mm−1 stimulated H+-ATPase activity, 2) flow-stimulated H+ pumping was Ca2+ dependent and required microtubule integrity, and 3) basal and flow-stimulated pHi recovery was detected in cells that labeled with the apical principal cell marker rhodamine Dolichos biflorus agglutinin as well as cells that did not. We conclude that luminal flow modulates H+-ATPase activity in the rabbit CCD and that H+-ATPases therein are present in both principal and intercalated cells.
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Appleby, Peter A., Saqib Shabir, Jennifer Southgate, and Dawn Walker. "Cell-type-specific modelling of intracellular calcium signalling: a urothelial cell model." Journal of The Royal Society Interface 10, no. 86 (September 6, 2013): 20130487. http://dx.doi.org/10.1098/rsif.2013.0487.
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Calcium signalling plays a central role in regulating a wide variety of cell processes. A number of calcium signalling models exist in the literature that are capable of reproducing a variety of experimentally observed calcium transients. These models have been used to examine in more detail the mechanisms underlying calcium transients, but very rarely has a model been directly linked to a particular cell type and experimentally verified. It is important to show that this can be achieved within the general theoretical framework adopted by these models. Here, we develop a framework designed specifically for modelling cytosolic calcium transients in urothelial cells. Where possible, we draw upon existing calcium signalling models, integrating descriptions of components known to be important in this cell type from a number of studies in the literature. We then add descriptions of several additional pathways that play a specific role in urothelial cell signalling, including an explicit ionic influx term and an active pumping mechanism that drives the cytosolic calcium concentration to a target equilibrium. The resulting one-pool model of endoplasmic reticulum (ER)-dependent calcium signalling relates the cytosolic, extracellular and ER calcium concentrations and can generate a wide range of calcium transients, including spikes, bursts, oscillations and sustained elevations in the cytosolic calcium concentration. Using single-variate robustness and multivariate sensitivity analyses, we quantify how varying each of the parameters of the model leads to changes in key features of the calcium transient, such as initial peak amplitude and the frequency of bursting or spiking, and in the transitions between bursting- and plateau-dominated modes. We also show that, novel to our urothelial cell model, the ionic and purinergic P2Y pathways make distinct contributions to the calcium transient. We then validate the model using human bladder epithelial cells grown in monolayer cell culture and show that the model robustly captures the key features of the experimental data in a way that is not possible using more generic calcium models from the literature.
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Curry, Gordon B., A. D. Ansell, M. James, and L. Peck. "Physiological constraints on living and fossil brachiopods." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 80, no. 3-4 (1989): 255–62. http://dx.doi.org/10.1017/s0263593300028698.
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ABSTRACTAsh-free-dry-weight determinations for a representative range of living brachiopod genera have revealed that a consistently high proportion of total organic mass is contained within the shell, partly as the organic matrix for biomineralisation and partly as minute extensions of the mantle tissues (caeca) housed within hollow endopunctae permeating the shell. On average 40% to 50% of the total organic mass of both articulate and inarticulate brachiopods is situated within the shell. This is true even for a rhynchonellid brachiopod which does not possess endopunctae, but which has a more dense protein matrix in its shell. The effectively hidden constituent of brachiopod tissue mass which is included in this component has often been overlooked, and as a result total metabolic tissue mass has been underestimated. This throws into question some previous interpretations of brachiopod respiratory and metabolic data.The oxygen consumption rates of several living brachiopods have been measured, and when respiring tissue in caeca in the shell is taken into consideration, it is clear that brachiopod metabolic rates are low when compared with other marine invertebrates (e.g. between 10% and 50% of the oxygen uptake of comparable gastropods and bivalve molluscs held in similar conditions). This low rate cannot be attributed to a slower pumping rate by the brachiopod lophophore, as has been suggested, because the rate of water movement is comparable to that across the bivalve gill.Nitrogen excretion rates have also been measured for a few living brachiopods, allowing a comparison with rates of oxygen consumption and providing an indication of the metabolic substrates used. These data on oxygen: nitrogen ratios suggest that one Antarctic brachiopod utilises exclusively protein as a metabolic substrate, while a temperate latitude species uses mainly protein during winter but lipids and carbohydrates during summer months. Histological observations, particularly of Terebratulina retusa from temperate waters, show that a specialised tissue layer in the brachiopod outer mantle epithelium proximal to the shell may be the site of storage of the protein that is metabolised during winter, and of carbohydrate mobilised during gonadal development in summer. The caeca have also been suggested as sites of storage of metabolites, and the possible relationships between these areas of mantle are discussed. It seems that the ability to store nutrients in the mantle, combined with flexibility of substrate utilisation and an inherently low metabolic rate, have been important factors in brachiopod evolution.
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Dow, JA. "pH GRADIENTS IN LEPIDOPTERAN MIDGUT." Journal of Experimental Biology 172, no. 1 (November 1, 1992): 355–75. http://dx.doi.org/10.1242/jeb.172.1.355.
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Lepidopteran larvae demonstrate several remarkable specialisations of the alimentary canal: the most active epithelial transport known; a unique cell type, called a goblet cell; and the highest pH values known to be generated by a biological system. The electrogenic K+ pump in midgut is now known to be energised by a H+-pumping V-ATPase, and net alkali metal transport is achieved by linking it to a nH+/alkali metal exchanger, which recycles H+ into the cytoplasm. Generation of high luminal pH is modelled as a passive (Nernstian) distribution of protons in the electrical field generated by the V-type ATPase. Electrode impalements show that the potential difference across the goblet cavity membrane is extremely high. Measurements of pH gradients generated in vitro confirm that the midgut itself generates such a gradient, that this process relies on metabolic energy, and that the differential ability of midgut subregions to perform acid-base transport maps to their differing morphologies and to the pH profiles observed along the gut in vivo. During larval/larval moults, K+ transport is suppressed. The transepithelial potential difference (PD) across the gut collapses and recovers in phase with the loss and recovery of the gut pH gradient, and with tissue V-ATPase activity, confirming that these processes are intimately linked. Acridine Orange partitions into acidic compartments and might be expected to be concentrated in goblet cavities, as these are the compartments toward which the V-ATPase pumps protons. However, under normal conditions, Acridine Orange is excluded from the cavities. Red metachromasia of the cavities (implying low pH) is only observed when the ion transport status of the tissue is compromised. It thus seems likely that, under physiological conditions, K+/H+ exchange is tight enough to produce a neutral or alkaline, rather than acidic, cavity. Molecular analysis of the 16 000 Mr subunit from Manduca midgut reveals it to be closely similar to other known 16 000 Mr sequences, particularly that from Drosophila brain. It is thus likely to be a true H+ channel, rather than one modified for K+ transport. The cavity can be modelled in two ways: (i) to isolate the site of proton equilibration electrically from the main gut lumen, and thus allow larger pH gradients to develop, or (ii) to buffer the V-ATPase from the alkaline pH in the gut lumen, which would otherwise destroy the gradient driving the exchange of H+ for alkali metal cations. The first model would predict a high cavity pH, whereas the second would predict a near neutral pH and would imply a non-cavity route for transport of base equivalents. Work with both pH-sensitive dyes and pH-sensitive electrodes so far tends to support the second model.
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"Консервативные методы лечения эндотелиально-эпителиальной дистрофии роговицы." Dalʹnevostočnyj medicinskij žurnal, no. 2 (June 2020): 97–101. http://dx.doi.org/10.35177/1994-5191-2020-2-96-100.
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Endothelial-epithelial dystrophy (EED) is one of the most severe pathological conditions of the cornea. The main pathophysiological mechanism of EED formation is considered to be a violation of the barrier and pumping function of the corneal endothelium. In damaged cells, the production of cytokines responsible for collagenogenesis is impaired, leading to a progressively increasing hydration of the stroma with degeneration of keratocytes, detachment of the epithelium and the appearance of the corneal syndrome. The choice of method treatment depends on the stage of EED pathological process. All kinds of treatment of this disease are divided into conservative and surgical. The literature review demonstrates the basic principles of conservative treatment of endothelial-epithelial corneal dystrophy.
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Xu, Quanfu, Yuli Yang, Jianwen Hou, Taizhong Chen, Yudong Fei, Qian Wang, Qing Zhou, Wei Li, Jing Ren, and Yi-Gang Li. "A carbon nanotubes based in situ multifunctional power assist system for restoring failed heart function." BMC Biomedical Engineering 3, no. 1 (March 26, 2021). http://dx.doi.org/10.1186/s42490-021-00051-x.
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Abstract Background End-stage heart failure is a major risk of mortality. The conductive super-aligned carbon nanotubes sheets (SA-CNTs) has been applied to restore the structure and function of injured myocardium through tissue engineering, and developed as efficient cardiac pacing electrodes. However, the interfacial interaction between SA-CNTs and the surface cells is unclear, and it remains challenge to restore the diminished contraction for a seriously damaged heart. Results A concept of a multifunctional power assist system (MPS) capable of multipoint pacing and contraction assisting is proposed. This device is designed to work with the host heart and does not contact blood, thus avoiding long-term anticoagulation required in current therapies. Pacing electrode constructed by SA-CNTs promotes the epithelial-mesenchymal transition and directs the migration of pro-regenerative epicardial cells. Meanwhile, the power assist unit reveals an excellent frequency response to alternating voltage, with natural heart mimicked systolic/diastolic amplitudes. Moreover, this system exhibits an excellent pacing when attached to the surface of a rabbit heart, and presents nice biocompatibility in both in vitro and in vivo evaluation. Conclusions This MPS provides a promising non-blood contact strategy to restore in situ the normal blood-pumping function of a failed heart.
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Pagano, Ester, Joshua E. Elias, Georg Schneditz, Svetlana Saveljeva, Lorraine M. Holland, Francesca Borrelli, Tom H. Karlsen, Arthur Kaser, and Nicole C. Kaneider. "Activation of the GPR35 pathway drives angiogenesis in the tumour microenvironment." Gut, March 23, 2021, gutjnl—2020–323363. http://dx.doi.org/10.1136/gutjnl-2020-323363.
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ObjectivePrimary sclerosing cholangitis (PSC) is in 70% of cases associated with inflammatory bowel disease. The hypermorphic T108M variant of the orphan G protein-coupled receptor GPR35 increases risk for PSC and ulcerative colitis (UC), conditions strongly predisposing for inflammation-associated liver and colon cancer. Lack of GPR35 reduces tumour numbers in mouse models of spontaneous and colitis associated cancer. The tumour microenvironment substantially determines tumour growth, and tumour-associated macrophages are crucial for neovascularisation. We aim to understand the role of the GPR35 pathway in the tumour microenvironment of spontaneous and colitis-associated colon cancers.DesignMice lacking GPR35 on their macrophages underwent models of spontaneous colon cancer or colitis-associated cancer. The role of tumour-associated macrophages was then assessed in biochemical and functional assays.ResultsHere, we show that GPR35 on macrophages is a potent amplifier of tumour growth by stimulating neoangiogenesis and tumour tissue remodelling. Deletion of Gpr35 in macrophages profoundly reduces tumour growth in inflammation-associated and spontaneous tumour models caused by mutant tumour suppressor adenomatous polyposis coli. Neoangiogenesis and matrix metalloproteinase activity is promoted by GPR35 via Na/K-ATPase-dependent ion pumping and Src activation, and is selectively inhibited by a GPR35-specific pepducin. Supernatants from human inducible-pluripotent-stem-cell derived macrophages carrying the UC and PSC risk variant stimulate tube formation by enhancing the release of angiogenic factors.ConclusionsActivation of the GPR35 pathway promotes tumour growth via two separate routes, by directly augmenting proliferation in epithelial cells that express the receptor, and by coordinating macrophages’ ability to create a tumour-permissive environment.