Academic literature on the topic 'Tachykinin'

Tachykinin peptides such as substance P (SP) function as neurotransmitters and neuromodulators in the mammalian central and peripheral nervous systems. Here, we provide evidence that they may also play an important role in the morphogenesis of some nonneural organs where epithelial-mesenchymal interactions are involved. We show the following. (1) mRNA encoding tachykinin precursor proteins is expressed transiently in condensing mesenchyme during the development of mouse tooth germ, mammary gland, limb bud, external auditory meatus and genital tubercle. (2) In developing tooth germ and mammary gland; mRNA encoding the neutral endopeptidase (NEP) that degrades secreted tachykinins is spatially and temporally co-expressed with tachykinin precursor mRNA. (3) SP and the mRNA encoding SP receptors are also expressed in the developing tooth germ. (4) Tooth development in explant cultures is blocked both by tachykinin-precursor-specific antisense oligonucleotide and by an SP receptor antagonist: in both cases the block is relieved by exogenous SP. Together, these findings suggest a surprising new role for tachykinins in tooth and mammary gland morphogenesis, and possibly also in limb, ear and external genitalia morphogenesis.

In an attempt to answer the question of whether or not the so-called tachykinin-like region of the Alzheimer β-amyloid protein [Aβ(25–35)] can act as a tachykinin, the sequences Aβ(25–35), Aβ(25–35)amide and their norleucine-35 and phenylalanine-31 analogues were synthesized. These peptides were examined with ligand binding studies, electron microscopy, CD and NMR. In all cases some differences were found between the Aβ(25–35) analogue and the corresponding Phe31 peptide. In addition, in ligand displacement studies on tachykinin NK1 receptors, only the Phe31 analogue showed activity comparable to that of genuine tachykinins. We conclude that peptides based on Aβ(25–35) but with a Phe residue at position 31 do display properties typical of a tachykinin, but that peptides with Ile at this position do not.

The tachykinins substance P, neurokinin A, and neurokinin B are natural agonists for NK1, NK2, and NK3 receptors, respectively. Evidence from biochemical, neurophysiological, pharmacological, and molecular biology studies indicates that the tachykinin-containing pathways within the brain contribute to central cardiovascular and endocrine regulation and to the control of motor activity. The hypothalamus, which represents a site for the integration of central neuroendocrine and autonomic processes, is rich in tachykinin nerve endings and tachykinin receptors. Stimulation of periventricular or hypothalamic NK1 receptors in conscious rats induces an integrated cardiovascular, behavioural, and endocrine response. The cardiovascular response is associated with increased sympathoadrenal activity and comprises an increase in blood pressure and heart rate, mesenteric and renal vasoconstriction, and hind-limb vasodilatation. The behavioural response consists of increased locomotion and grooming behaviour. This response pattern is consistent with an integrated stress response to nociceptive stimuli and pain in rodents. Several studies have demonstrated rapid changes in substance P levels and its receptors in distinct brain areas following acute stress. These data indicate that substance P and other tachykinins, in addition to serving as nociceptive and pain transmitters in the spinal cord, may act in the brain as neurotransmitters–neuromodulators within the neuronal circuits mediating central stress responses.Key words: tachykinins, substance P, central nervous system, defence reaction, stress.

The pineal gland, through its hormone melatonin, influences the function of the hypothalamic–pituitary–gonadal axis. Tachykinins are bioactive peptides whose presence has been demonstrated in the pineal gland, hypothalamus, anterior pituitary gland and the gonads, in addition to other central and peripheral structures. Tachykinins have been demonstrated to influence the function of the hypothalamic–pituitary–gonadal axis, acting as paracrine factors at each of these levels. In the present review, we examine the available evidence supporting a role for melatonin in the regulation of reproductive functions, the possible role of tachykinins in pineal function and the possible interactions between melatonin and tachykinins in the hypothalamic–pituitary–gonadal axis. Evidence is presented showing that melatonin, given to pregnant rats, influences the developmental pattern of tachykinins in the hypothalamus and the anterior pituitary gland of the offspring during postnatal life. In the gonads, the effects of melatonin on the tachykinin developmental pattern were rather modest. In particular, in the present review, we have included a summary of our own work performed in the past few years on the effect of melatonin on tachykinin levels in the hypothalamic–pituitary–gonadal axis.

To investigate whether prostaglandin F2 alpha (PGF2 alpha) stimulates the release of tachykinins and whether the tachykinins play a role in the PGF2 alpha-induced bronchial contraction, we examined the contractile response to PGF2 alpha in the presence or absence of a neutral endopeptidase (NEP) inhibitor phosphoramidon in the guinea pig main bronchus in vitro. Because NEP effectively cleaves tachykinins, we hypothesized that the inhibition of NEP would enhance a PGF2 alpha-induced bronchial contraction if PGF2 alpha stimulates the release of tachykinins. Phosphoramidon significantly enhanced the concentration-response curve to PGF2 alpha. And it also significantly enhanced 10(-5) M PGF2 alpha-induced contraction. The enhancement was significantly attenuated in tissues where the tachykinins had been depleted by treatment with capsaicin. Furthermore, the enhancement of contraction was also significantly attenuated in the presence of tachykinin antagonist FK-224 (10(-5) M). Tetrodotoxin, a sodium-channel blocker that blocks nerve conduction, did not affect the enhancement. From these results we conclude that 1) PGF2 alpha causes the release of tachykinin-like substances, 2) these substances play a role in bronchial contraction in tissues where NEP activity is inhibited, and 3) nerve conduction is not necessary for the release of these substances in the guinea pig bronchus.

Tachykinins are present in lamprey spinal cord. The goal of this study was to investigate whether an endogenous release of tachykinins contributes to the activity of the spinal network generating locomotor activity. The locomotor network of the isolated lamprey spinal cord was activated by bath-applied N-methyl-d-aspartate (NMDA) and the efferent activity recorded from the ventral roots. When spantide II, a tachykinin receptor antagonist, was bath-applied after reaching a steady-state burst frequency (>2 h), it significantly lowered the burst rate compared with control pieces from the same animal. In addition, the time to reach the steady-state burst frequency (>2 h) was lengthened in spantide II. These data indicate that an endogenous tachykinin release contributes to the ongoing activity of the locomotor network by modulating the glutamate–glycine neuronal network responsible for the locomotor pattern. We also explored the effects of a 10-min exogenous application of substance P (1 μM), a tachykinin, and showed that its effect on the burst rate depended on the initial NMDA induced burst frequency. At low initial burst rates (∼0.5 Hz), tachykinins caused a marked further slowing to 0.1 Hz, whereas at higher initial burst rates, it instead caused an enhanced burst rate as previously reported, and in addition, a slower modulation (0.1 Hz) of the amplitude of the motor activity. These effects occurred during an initial period of ∼1 h, whereas a modest long-lasting increase of the burst rate remained after >2 h.

The respiratory tract is innervated by irritant-responsive sensory nerves, which, on stimulation, release tachykinin neuropeptides in the lung. Tachykinins modulate inflammatory responses to injury by binding to tachykinin (neurokinin) receptors present on various pulmonary cell types. In the present study, the activation of the proinflammatory transcription factor NF-κB in lung epithelial cells was investigated as a mechanism by which tachykinins stimulate inflammatory processes. In A549 human lung epithelial cells transfected with the tachykinin-1 receptor (Tacr1), treatment with the Tacr1 ligand substance P (SP) resulted in NF-κB activation, as judged by transcription of an NF-κB-luciferase reporter gene and production of interleukin-8, a chemokine whose expression is upregulated by NF-κB. SP caused a dose-dependent activation of NF-κB that was inhibited by the selective Tacr1 antagonist RP67580. Tacr1 is a G protein-coupled receptor capable of activating both the Gq and Gs families of G proteins. Expression of inhibitory peptides and constitutively active G protein mutants revealed that Gq signaling was both necessary for Tacr1-induced NF-κB activation and sufficient for NF-κB activation in the absence of any other treatment. Treatment with pharmacological inhibitors to investigate events downstream of Gq revealed that Tacr1-induced NF-κB activation proceeded through an intracellular signaling pathway that was dependent on phospholipase C, calcium, Ras, Raf-1, MEK, Erk, and proteasome function. These results identify intracellular signaling mechanisms that underlie the proinflammatory effects of tachykinins, which previously have been implicated in lung injury and disease.

The tachykinins are highly active mediators of neuronal action in the CNS. In order to understand their action and provide templates for drug development, analogues based on the active sequence of Substance P have recently been synthesised. These analogues often have conformational constraints incorporated into their sequence. For instance, the linear agonists [L and D-Pro9]SP6-11 (l) & (2) and [SucAsp6, NMePhe8]SP6-11 (3) have receptor subtype selectivities for NK1, NK2 and NK3 respectively. The novel cyclic peptides [GlnTrpPheGlyLeuMet] (4) and [GlnTrpPheGly[ANC-2]MetLeu] (5), and their linear counterpart AcLeuMetGlnTrpPheGlyNH2 (6) have high antagonist activity for the NK2 receptor. The NK2 receptor is the preferred subtype for endogenous agonist neurokinin A (7). Knowing their conformational properties and rationalising these against their activities, may provide the basis for understanding the process of molecular recognition and lead to directed drug design. The conformational properties of these peptides in DMSO and methanol were investigated using 1 and 2D NMR techniques. Particularly important was the application of the recently developed ROESY and TOCSY experiments, which greatly simplify the assignment and conformational analysis of these compounds. Distinct conformations were found for the linear analogues (1), (2) and (3). This was shown to be due to cis/trans isomerism about the N-alkylated peptide bond. However, despite the known turn preferences for the constraints incorporated into these peptides, no global conformational characteristics were identified. All the linear peptides were found to exist in a chiefly extended state in DMSO. Peptides (1) and (2) occupied 'random coil' conformational space in methanol. The cyclic peptides (4) and (5) exhibited specific conformational preferences. Using restraints provided by their NMR parameters, molecular modelling showed a ss II turn in the LeuMet region for both of these peptides. The similarity in conformation of these cyclics may explain their analogous pharmacology. The synthesis of novel Substance P analogues with a beta-lactam constraint in the (RS)Phe[ANC-2]Gly position is presented, together with the attempted cyclisation of the resulting linear peptides.

L’objectif de cette thèse est d’étudier le rôle de neuropeptides cérébraux, telle que la Neurokinin B codée par le gène tac3, dans le contrôle de la reproduction d’une espèce en danger, l’anguille Européenne, Anguilla anguilla. La maturation sexuelle de l’anguille est bloquée à un stade prépubertaire avant la migration océanique. Etant donnée sa position phylogénétique basale parmi les téléostéens, l’anguille est un modèle pertinent pour étudier l’évolution moléculaire et fonctionnelle de neuropeptides d’intérêt. Deux gènes paralogues tachykinine 3 (tac3) ont été identifiés dans le génome de l’anguille, chacun codant pour deux peptides. Ces gènes paralogues résultent de la duplication complète du génome spécifique aux téléostéens, comme le montrent les analyses phylogénétiques et synténiques. Les analyses de qPCR montrent que les deux gènes sont exprimés dans le cerveau. Les quatre peptides d’anguille ont été synthétisés et testés sur des cultures primaires de cellules hypophysaires d’anguille. Les quatre peptides inhibent l’expression de l’hormone lutéinisante et d’un récepteur à la gonadolibérine, révélant un double rôle inhibiteur dans le contrôle de la reproduction
The aim of this PhD is to investigate the role of brain neuropeptides, such as neurokinin B, encoded by tac3 gene, in the control of reproduction of an endangered species, the European eel, Anguilla anguilla. The sexual maturation of the eel is blocked at a prepubertal stage before the oceanic migration. Due to its basal phylogenetic position among teleosts, the eel is also a relevant model for studying molecular and functional evolution of key neuropeptides. Two tachykinin 3 (tac3) paralogous genes were identified in the eel genome, each encoding two peptides. These paralogs result from the teleost-specific whole genome duplication, as shown by phylogeny and synteny analyses. Both genes are expressed in the brain as shown by qPCR. The four eel peptides were synthesized and tested on primary cultures of eel pituitary cells. The four peptides inhibited the expression of luteinizing hormone and gonadotropin-releasing hormone receptor, revealing a dual inhibitory role in the control of reproduction

The purpose of this series of investigations was to elucidate the endogenous control mechanisms active at primary afferent terminals of nociceptive origin in the dorsal laminae of the spinal cord grey matter. Such studies may enable the researcher to make certain conclusions about endogenous mechanisms of pain control in vivo. Furthermore, these studies may help to identify novel areas for the development of analgesic drugs or protocols of therapeutic value in both human and veterinary pain management. Experiments were centred on one particular family of neuropeptides, the tachykinin peptides, and their release in response to peripheral noxious stimulation as determined by the antibody microprobe technique. A review of the anatomy and physiology of tachykinins in the spinal cord is presented at the start of this thesis. The antibody microprobe technique itself is also fully described. Various means of moduling tachykinin release pharmacologically were tested and are presented in this thesis. The results presented here relate to studies on 1) morphine, 2) noradrenaline and the imidazoline derivative drug, medetomidine, 3) neuropeptide Y. A short review on the pharmacological actions of each of these drugs is included. All the results presented are derived from experiments on barbiturate anaesthetised, spinalised cats.

En aquesta tesi doctoral, s’han aplicat metodologies biofísiques per estudiar i caracteritzar l'estructura dels pèptids substància P (SP), neuroquinina A (NKA) i scyliorinina I (ScyI), que pertanyen a la família de les taquiquinines (TK), així com la seva manera d'interacció amb membranes model. Els pèptids TKS són agonistes dels receptors de neuroquinina acoblats a la proteïna G. Els TKS estan involucrats en diversos processos fisiològics i malalties com el càncer, malalties neurodegeneratives i respostes inflamatòries, i això els converteix en un objecte de gran interès per a l'estudi estructural en la recerca d'agents terapèuticament rellevants. Els tres pèptids SP, NKA i ScyI mostren una seqüència comuna en el domini C-terminal i es diferencien en el seu domini N-terminal. Per tant, sorgeixen preguntes: Què determina el seu diferent potencial d’activació? Quina és la conformació activa dels pèptids quan interactuen amb el receptor de NK per transferir la senyal? Quina és la seva manera d'interacció amb la superfície de la membrana? La superfície de la membrana, afecta la conformació del pèptid? Tenen els pèptids capacitat d’associar-se i si és així, quin tipus d'estructures formen i en quines condicions? A la primera part dels resultats i discussió, s’utilitzen diferents mètodes d'espectroscòpia de fluorescència, per estudiar les interaccions dels sistemes de membranes amb TKS mimètics (micel·les SDS i vesícules DMPG / DMPC). Les cadenes laterals Trp i Phe CN es van utilitzar com fluoròfors intrínsecs, mentre la fluoresceïna fosfatidiletanolamina (FPE) i els lípids bromats es van utilitzar com sondes externes. Ja que SP i NKA no posseeixen el residu Trp, es va substituir el residu Phe en la posició 6 i 8 amb Trp, respectivament per als pèptids SP i NKA. L’espectroscòpia CD va confirmar la similitud de l'estructura general de SP i NKA amb els seus anàlegs. A més, mitjançant l'ús d'espectroscòpia de fluorescència de Trp (principalment λmax), es demostra que, en solució i en estat sub-micel·lar de SDS, la cadena lateral de Trp en SPW i NKAW està en un entorn hidròfob, mentre que apareix desplaçat a ambient hidrofílic després de la formació de micel·les. D'altra banda, l'espectroscòpia de CD mostra la transició de l’estructura PPII dominant en solució, a estructura α helicoïdal (en cas de SP i ScyI) o a la barreja de conformació desordenada i d’hèlix α (en el cas de NKA) una vegada es formen micel · les. Aplicant una metodologia de fluorescència diferent, ha sigut possible separar el procés d'unió del pèptid a la superfície de la membrana, del procés d'inserció del pèptid / plegament al nucli hidrofòbic. SP, NKA i ScyI interaccionen amb DMPC i amb els liposomes amb càrrega negativa DMPG. No obstant això, les afinitats d'unió dels pèptids als liposomes de DMPC estan en el rang de 20-40 vegades menor, en comparació amb les afinitats a DMPG. A més, les afinitats d'unió de SP, NKA i ScyI correlacionen amb les seves càrregues netes, quan interactuen amb DMPG, però no amb DMPC. A la segona part dels resultats i discussions, els factors que regeixen les estructures secundàries de les taquiquinines en estat monomèric (com el medi, la càrrega neta del pèptid i la càrrega superficial de la membrana) s’estudien per espectroscòpia CD. A més, es va aplicar la dispersió de raigs X d'angle petit per determinar l'estructura secundària del NKA en solució. En solució aquosa, l'estructura dominant de totes les taquiquininas és PPII. Per espectroscòpia d'infraroig, l’estructura flexible desordenada es va detectar per les taquiquininas en una concentració de 1,5 mM en solució. A més, en aquestes condicions, les estructures girs β i estructures esteses de làmina β es van detectar, respectivament, per SP i ScyI. En TFE, l'estructura dominant de les taquiqinines és helicoïdal, indicant la propensió helicoïdal intrínsec dels pèptids. Igual que en solució, les taquiquinines mostren estructura PPII en presència de vesícules d’ions híbrids. En els liposomes carregats negativament, SP i ScyI posseeixen estructura α mentre NKA mostra una barreja d’estructura desordenada i conformacions en hèlix α. Els canvis conformacionals de les taquiquinines en augmentar la fracció de DMPG de la vesícula composta de DMPC / DMPG demostren clarament que l’estructura α dels pèptids depèn fortament de la quantitat relativa de DMPG aniònic en les vesícules. Això reflecteix la importància de les interaccions electrostàtiques dels pèptids amb els caps de la membrana. A la part III dels resultats i discussió, s'estudia l'estat d'agregació de les taquiquinines. Es mostra que les taquiquinines són capaces de formar estructures fibril·lars. En solució, les taquiquinines a una concentració de 3 mM formen fibril·les amb diferent morfologia. En SP, es veuen llargues fibril·les retorçades i filaments individuals rectes, mentre que en ScyI i NKA només s’observen fibril·les rectes. Les taquiquinines en una concentració per sobre de 1,5 mm formen fibril·les immediatament en presència de vesícules de càrrega negativa, mentre que no es van detectar en les fibril·les de DMPC. Aquest fet indica la importància de les càrregues negatives en el procés de fibril·lizació. L’espectroscòpia FTIR mostra un augment significatiu de l'estructura de làmina β per les taquiquinines a una concentració de 3 mM i en presència de les vesícules de DMPG, que s'atribueix a la formació de fibril·les. A més, en aquesta condició, FTIR mostra estructura helicoïdal en tots els TKS i algunes conformacions de gir β per SP i NKA. Sobre la base de TEM i espectroscòpia de CD, es mostra que la fibril·lizació de SP (100 mM) es produeix durant la transició d'estructura PPII a fulla β després de la incubació en concentracions de SDS prop de la CMC. En contrast, SPW no mostra fibril·lizació en les mateixes condicions. Sobre la base d'assaig THT, es van detectar fibril·les amiloides per NKA però de moment no tenim cap evidència sobre la formació amiloide en SP i ScyI. Els resultats indiquen que la formació d'amiloide en NKA disminueix a pH alcalí. En contrast, NKAW és capaç de formar fibril·les amiloides a pH àcid i alcalí però no a pH neutre. Analitzant l'activitat metabòlica de la línia cel·lular PC12 mitjançant la prova de TMM, es demostra que NKA a una concentració de més de 25 µM pot induir toxicitat, mentre que no es va observar cap disminució significativa de l'activitat metabòlica en presència de fins a 250 µM de SP o de ScyI
In this doctoral thesis, biophysical methodologies were applied to study and characterize the structures of substance P (SP), neurokinin A (NKA) and scyliorhinin I (ScyI) peptides, which belong to the tachykinin (TK) family, and their mode of interaction with model membranes. The TKs peptides are agonists of Neurokinin G-protein coupling receptors. TKs are involved in several physiological processes and diseases such as neurodegenerative disorders, cancer and inflammatory responses, what make them an object of high interest for structural study in search of relevant therapeutically agents. The three peptides SP, NKA and ScyI are homologous sharing common C domain –terminal and differ in their N terminal domain. Therefore, questions arise: What determine their different activity potential? What is the active conformation of the peptides when they interact with the NK receptor to transfer the signal? What is their mode of interaction with the membrane surface? Does the membrane surface affect the peptide conformation? Do the peptides self associate and if they have these ability, what kind of structure they form and at which conditions? In part I of the Results and Discussion, by using different fluorescence spectroscopy approaches, the mode of the interactions of TKs with membrane mimetic systems (SDS micelles and DMPG/DMPC vesicles) were studied. The Trp and Phe-CN amino acids were used as intrinsic fluorophores, while fluorescein phosphatidylethanolamine (FPE) and brominated lipids were used as external probes. Since SP and NKA lack the intrinsic Trp residue, we substituted Phe residue in position 6 and 8 with Trp, respectively for SP and NKA peptides. CD spectroscopy confirmed the similarity of the overall structure of SP and NKA with their analogues. Furthermore, by using Trp fluorescence spectroscopy (mainly λmax), we understood that in solution and in sub-micellar state of SDS, the Trp side chain of SPW and NKAW are in a hydrophobic environment, while they appear displaced to hydrophilic environment upon formation of micelles. On the other hand, CD spectroscopy show the transition of the dominant PPII helical structure in solution to α helical structure (in case of SP and ScyI) or to the mixture of unordered and α helical conformation (in the case of NKA) upon formation of micelles. Applying different fluorescence methodology it was possible to separate the process of peptide binding to a membrane surface from the process of peptide insertion/folding into the hydrophobic core. SP, NKA and ScyI bind to both zwitterionic DMPC and negatively charged DMPG liposomes. However, binding affinities of the peptides to DMPC liposomes are in the range 20-40 times lower, compared to the affinities to DMPG. Moreover the binding affinities of SP, NKA and ScyI correlate with their net charges, when they interact with DMPG, but not with DMPC. In part II of the Results and Discussions, the factors governing the secondary structures of the tachykinins in monomeric state (such as environment, peptide net charge and membrane surface charge) are studied by CD spectroscopy. Moreover, small angle X-ray scattering was applied to determine the NKA secondary structure in solution. In aqueous solution, the dominant structure of all tachykinins is PPII. By FTIR spectroscopy, flexible unordered structure was detected for tachykinins in a concentration of 1.5 mM in solution. Moreover, in these condition, β turn and extended β sheet structures were detected, respectively for SP and ScyI. In the TFE the dominant structure of tachykinins is alpha helical which indicates the intrinsic helical propensity of peptides. Like in solution, tachykinins have PPII structure in the presence of the zwitterionic vesicles. In negatively charged liposomes, SP and ScyI are in α helical structure while NKA shows a mixture of the unordered and α helical conformations. Conformational changes of tachykinins upon increasing of the DMPG fraction of the vesicle composed of DMPC/DMPG demonstrate clearly that the α helical fold of peptides strongly depends on the relative amount of anionic DMPG in the vesicles and reflecting the importance of the electrostatic interactions of peptides with headgroup of the membrane. In part III of the Results and Discussion, the aggregation state of the tachykinins is studied. We understood that tachykinins are able to form fibrillar structures. In solution, 3 mM of tachykinins formed fibrils with different morphology. In SP long twisted fibrils and straight single filaments were seen while in ScyI and NKA fibrils are only single-straight. Tachykinins in a concentration of above 1.5 mM formed fibrils immediately in the presence of negatively charge vesicles, while no fibrils were detected in DMPC for any tachykinins. This fact indicates the importance of the negatively surface charges on fibrillization. FTIR spectroscopy shows a significant increase of the β sheet structure for tachykinins in a concentration of 3 mM and in the presence of the DMPG vesicles which is attributed to the fibrils formation. Moreover, in this condition, FTIR shows helical structure in all TKs and some β turn conformations for SP and NKA. Based on TEM and CD spectroscopy, we understood that fibrillization of SP (100 µM) occurs upon transition of PPII structure of peptide to β sheet after incubation in SDS concentrations close to CMC. In contrast, SPW was not able to make fibrils in the same condition. Based on ThT assay, amiloid fibrils were detected for NKA but at the moment we do not have any evidence about the amiloid formation of SP and ScyI. Moreover we found that amyloid formation of NKA decreases at alkaline pH. In contrast, NKAW is able to form amyloid fibrils at acidic and alkaline pH but not at the neutral pH. Analyzing of the PC12 cell line metabolic activity by TMM test indicates that NKA in a concentration of more than 25 µM can induce toxicity, while no significant decrease of metabolic activity was seen in the presence of up to 250 µM SP or ScyI.

Apart from its traditional role in disease control, recent body of evidence has implicated a role of the immune system in regulating metabolic homeostasis. Owing to the importance of this “immune-metabolic alignment” in dictating a state of health or disease, a proper mechanistic understanding of this alignment is crucial in opening up for promising therapeutic approaches against a broad range of chronic, metabolic, and inflammatory disorders like obesity, diabetes, and inflammatory bowel syndrome. In this project, we addressed the role of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) innate immune pathway in regulating different metabolic parameters using the Drosophila melanogaster (DM) fruit fly model organism. Mutant JAK/STAT pathway flies with a systemic knockdown of either Domeless (Dome) [domeG0282], the receptor that activates JAK/STAT signaling, or the signal-transducer and activator of transcription protein at 92E (Stat92E) [stat92EEY10528], were used. The results of the study revealed that blocking JAK/STAT signaling alters the metabolic profile of mutant flies. Both domeG0282 and stat92EEY10528 mutants had an increase in body weight, lipid deprivation from their fat body (lipid storage organ in flies), irregular accumulation of lipid droplets in the gut, systemic elevation of glucose and triglyceride levels, and differential down-regulation in the relative gene expression of different peptide hormones (Tachykinin, Allatostatin C, and Diuretic hormone 31) known to regulate metabolic homeostasis in flies. Because the JAK/STAT pathway is evolutionary conserved between invertebrates and vertebrates, our potential findings in the fruit fly serves as a platform for further immune-metabolic translational studies in more complex mammalian systems including humans.

Enterobacteriaceae, a large family of facultative anaerobic bacteria, encloses a broad spectrum of bacterial species including Escherichia coli, Salmonella enterica, and Shigella sonnei, that produce enterotoxins and cause gastrointestinal tract diseases. While much is known about the regulation and function of enterotoxins within the intestine of the host; the lack of cheap, practical, and genetically tractable model organisms has restricted the investigation of others facets of this host-pathogen interaction. Our group, among others, has employed Drosophila melanogaster, as a model organism to shed more light on some aspects of host-pathogen interplays. In this project, we addressed the effect of Escherichia coli, Salmonella enterica, and Shigella sonnei infection on altering the metabolic homeostasis of the host. Drosophila melanogaster flies were orally infected with Escherichia coli, Salmonella enterica, or Shigella sonnei, a method that mimics the natural route used by enteric pathogens to gain access to the gastrointestinal tract in humans. The results of our study revealed that both Escherichia coli and Shigella sonnei pathogens were capable of colonizing the host gut, resulting in a reduction in the life span of the infected host. Escherichia coli and Shigella sonnei infected flies also exhibited altered metabolic profiles including lipid droplets deprivation from their fat body (normal lipid storage organ in flies), irregular accumulation of lipid droplets in their gut, and significant elevation of systemic glucose and triglyceride levels. These metabolic alterations could be mechanistically attributed to the differential down-regulation in the expression of metabolic peptide hormones (Allatostatin A, Diuretic hormone 31, and Tachykinin) detected in the gut of Escherichia coli and Shigella sonnei infected flies. Salmonella enterica; however, was unable to colonize the gut of the host; and therefore, Salmonella enterica infected flies exhibited a relatively normal metabolic status as that of non infected flies. Gaining a proper mechanistic understanding of infection-induced metabolic alterations helps in modulating the pathogenesis of gastrointestinal tract diseases in a host and opens up for promising therapeutic approaches for infection induced metabolic disorders