Literatura científica selecionada sobre o tema "Auto-inducers"

The execution phase of apoptosis is under the control of members of the inhibitor of apoptosis (IAP) family of zinc finger proteins. Several of these proteins contain a C-terminal RING (really interesting new gene) domain that has been postulated to regulate ubiquitination of themselves or their target proteins, thereby modulating thresholds for apoptosis. We demonstrate that the auto-ubiquitination sites of the X-linked IAP (XIAP) are Lys322 and Lys328, located in the third baculovirus IAP repeat domain of the protein. Modification of these sites to arginine dramatically reduces ubiquitination of XIAP, but has no measurable effect on the ability of ectopically expressed IAP to rescue cells from two independent apoptotic inducers. Our data firmly locate the auto-ubiquitination sites, and raise doubts regarding the importance of this event as a mechanism for regulating the levels of XIAP.

Increasing evidence points towards mitochondria as crucial players in the initiation and progression of auto-immune and degenerative disorders, to which impaired cell metabolism is but a facet of the subjacent etiopathogenesis. This review aims to introduce the reader to essential concepts of mitochondrial abnormalities in idiopathic inflammatory myopathy (IIM), underscoring inclusion-body myositis and dermatomyositis. Far surpassing the initial simplistic view of being responsible for energy generation, mitochondria have gathered attention regarding their role in inflammatory processes, being able to fuel autoimmunity, as shown by the presence of anti-mitochondrial antibodies (AMAs) in up to 10% of IIM patients. As cellular respiration takes place, mitochondrial metabolites might help to shape the pro-inflammatory milieu in affected muscle, beyond generating reactive oxygen species, which are well-recognized inducers of damage-associated molecular patterns. A series of mitochondrial components might facilitate the sterile activation of pro-inflammatory cells and the production of several cytokines responsible for enhancing auto-immune responses. Marked variation in the mitochondrial genome has also been reported in IIM patients. As such, we summarize key historical and recent advances linking aberrations and instabilities of mitochondrial DNA to impaired muscle function. Besides discussing mitochondrial dysfunction as an essential part of IIM development, we also highlight possible associations between presence of AMAs and a particular phenotype of IIM, with its own characteristic clinical and radiological pattern. Finally, we present promising treatment approaches targeting mitochondria, while briefly discussing experimental models for gaining deeper insight into the disease process, and ultimately leading to novel drug development.

Abstract Antibodies are potent inducers of inflammation and Fcγ receptors (FcγRs) are considered as important immune-regulators linked to infection immunity, cancer immunity and auto-immunity. We previously reported that CD1b+ dendritic cells (DC) are differentially distributed in leprosy lesions and contribute to the in pathophysiology of the polarized clinical spectrum of the disease. Here we demonstrate that activation of FcγRs on human blood monocytes triggers monocyte differentiation into CD1b+ cells. The CD1b+ population increased in a dose-dependent manner, and the differentiation was blocked by the addition of an anti-CD64 monoclonal antibody. Furthermore, Fcγ receptor ligation triggered transcription of GM-CSF mRNA as measured by real time PCR and CD1b+ cell differentiation was suppressed by the addition of an anti-GM-CSF antibody. Finally, FcγR-induced CD1b+ cells exhibited an immature dendritic cell (DC)-like phenotype. These findings predict that the stimulation of FcγRs induces GM-CSF production that in turn triggers monocyte differentiation into a CD1b+ immature dendritic cell population. In conclusion, these results provide insight into the cross-talk between the humoral and innate immune response as well as new strategies for therapeutic intervention in infectious diseases and autoimmune diseases.

Up to now, the production and role of N-acyl homoserine lactones (AHLs) in activated sludge have been poorly understood. In this study, cross-feeding assays with the reporter strains Agrobacterium tumefaciens NTL4 and Chromobacterium violaceum CV026 were used to investigate AHL signal production by municipal activated sludge samples. AHL signal production was consistently detected from municipal activated sludge when different samples were incubated on nutrient media. From one municipal activated sludge sample, 10 strains producing AHL-like auto inducers were isolated by an overlay technique. 16S rDNA-based phylogenetic analysis showed that eight of the isolates belonged to Aeromonas spp. and two to Pseudomonas spp. Box-PCR indicated that six of these Aeromonas isolates were different strains and the two Pseudomonas strains were identical. The production of AHL or AHL-like compounds by these strains was confirmed by thin layer chromatography and biosensor overlays. The six different Aeromonas strains were found to produce the same set of AHLs, including N-hexanoyl-L-homoserine lactone. These results may indicate the possible presence of AHLs in municipal activated sludge. The potential roles of AHL in this eco system are briefly discussed.Key words: municipal activated sludge, acylated homoserine lactones, Aeromonas spp., bioaggregates, Pseudomonas spp., AHL biosensors.

Strong promoters are one of the fundamental aspects to increase the level of gene expression, and one of approach to improve the recombinant enzyme productivity so that the efficiency of production cost for enzyme production in industrial scale can be reached. Here we assessed the application of a cell density-dependent promoter and media optimation to promote cell growth and protein expression of Bacillus subtilis without excess usage of inducers. An auto-inducible Pylb promoter that is potential to provide inducer-free enzyme production was cloned and introduced into xylanase recombinant system in B. subtilis DB104 by PCR cloning and protoplast transformation. A 200 bp target gene was successfully inserted in between xynCM1 ORF -coding for B. halodurans CM1 xylanase- and its native promoter sequence at the upstream region. The disruption of the native promoter was intended to replace the native promoter with Pylb. Recombinant xylanase gene under Pylb was successfully expressed in B. subtilis DB104 and the enzyme was produced at stationary phase. Different media with various concentrations of glucose and nitrogen were used to optimize recombinant xylanase expression. It achieved a higher level of xylanase expression compared to wild-type and recombinant xylanase with native promoter B. subtilis in media containing a 2-fold recipe of LB media thus leads to increase cell density and xylanase expression (81.461 U mL-1).

Antibiotic resistance is a major problem and a major global health concern. In total, there are 16 million deaths yearly from infectious diseases, and at least 65% of infectious diseases are caused by microbial communities that proliferate through the formation of biofilms. Antibiotic overuse has resulted in the evolution of multidrug-resistant (MDR) microbial strains. As a result, there is now much more interest in non-antibiotic therapies for bacterial infections. Among these revolutionary, non-traditional medications is quorum sensing inhibitors (QSIs). Bacterial cell-to-cell communication is known as quorum sensing (QS), and it is mediated by tiny diffusible signaling molecules known as autoinducers (AIs). QS is dependent on the density of the bacterial population. QS is used by Gram-negative and Gram-positive bacteria to control a wide range of processes; in both scenarios, QS entails the synthesis, identification, and reaction to signaling chemicals, also known as auto-inducers. Since the usual processes regulated by QS are the expression of virulence factors and the creation of biofilms, QS is being investigated as an alternative solution to antibiotic resistance. Consequently, the use of QS-inhibiting agents, such as QSIs and quorum quenching (QQ) enzymes, to interfere with QS seems like a good strategy to prevent bacterial infections. This review sheds light on QS inhibition strategy and mechanisms and discusses how using this approach can aid in winning the battle against resistant bacteria.

Quorum sensing (QS) is known to regulate different functions viz. pathogenesis, biofilm formation, and host colonization, along with other functions by regulating bacterial virulence determinants. Therefore, QS is deemed to be an interesting target to modulate pathogenesis. Also, there have been global reports of continuous emergence of antibiotic-resistant microbes; hence, an alternative treatment that compliments antibiotic activity is highly desirable. One such approach is to look for QS inhibitors, which can quench the virulence phenotypes exerted by pathogenic bacteria and compliment antibiotic treatment. In the present study, Pseudomonas aeruginosa strain was used as the model organism which produces three pigments viz. pyocyanin, pyoverdin and pyorubin. Pyocyanin synthesis is reported to be QS dependent and is one of the virulence factors of P. aeruginosa. Hence, we envisage inhibition of pyocyanin pigment would indicate QS inhibition (QSI). Auto-inducers like N-(3-oxododecanoyl)-L-homoserine lactone (OdDHL/3-oxo-C12-HSL) and N-butyryl-L- homoserine lactone (BHL/C4-HSL) were used to enhance the pyocyanin pigment production by the model strain at different doses and time points. BHL, at 25 μM was found to be a better inducer of pyocyanin. Tannic acid (TA) was tested to suppress this pigment synthesis and it was found to be effective when assessed at different time points. About 5.12 mg/mL TA was found to be the optimum concentration at which pyocyanin was inhibited by 77.3%. Thus, we confirm that TA can be used as a QSI, either in its purest form or in the crude form found in various plant species, and could be considered for development to compliment antibiotic therapy.

: Quorum Sensing (QS) is a phenomenon in which bacterial cells communicate with each other with the help of several low molecular weight compounds. QS is largely dependent on population density, and it triggers when the concentration of quorum sensing molecules accumulate in the environment and crosses a particular threshold. Once a certain population density is achieved and the concentration of molecules crosses a threshold, the bacterial cells show a collective behavior in response to various chemical stimuli referred to as “auto-inducers”. The QS signaling is crucial for several phenotypic characteristics responsible for bacterial survival such as motility, virulence, and biofilm formation. Biofilm formation is also responsible for making bacterial cells resistant to antibiotics. : The human gut is home to trillions of bacterial cells collectively called “gut microbiota” or “gut microbes”. Gut microbes are a consortium of more than 15,000 bacterial species and play a very crucial role in several body functions such as metabolism, development and maturation of the immune system, and the synthesis of several essential vitamins. Due to its critical role in shaping human survival and its modulating impact on body metabolisms, the gut microbial community has been referred to as “the forgotten organ” by O`Hara et al. (2006) [1]. Several studies have demonstrated that chemical interaction between the members of bacterial cells in the gut is responsible for shaping the overall microbial community. : Recent advances in phytochemical research have generated a lot of interest in finding new, effective, and safer alternatives to modern chemical-based medicines. In the context of antimicrobial research various plant extracts have been identified with Quorum Sensing Inhibitory (QSI) activities among bacterial cells. This review focuses on the mechanism of quorum sensing and quorum sensing inhibitors isolated from natural sources.

Diet plays an essential role in human development and growth, contributing to health and well-being. The socio-economic values, cultural perspectives, and dietary formulation in sub-Saharan Africa can influence gut health and disease prevention. The vast microbial ecosystems in the human gut frequently interrelate to maintain a healthy, well-coordinated cellular and humoral immune signalling to prevent metabolic dysfunction, pathogen dominance, and induction of systemic diseases. The diverse indigenous diets could differentially act as biotherapeutics to modulate microbial abundance and population characteristics. Such modulation could prevent stunted growth, malnutrition, induction of bowel diseases, attenuated immune responses, and mortality, particularly among infants. Understanding the associations between specific indigenous African diets and the predictability of the dynamics of gut bacteria genera promises potential biotherapeutics towards improving the prevention, control, and treatment of microbiome-associated diseases such as cancer, inflammatory bowel disease, obesity, type 2 diabetes, and cardiovascular disease. The dietary influence of many African diets (especially grain-base such as millet, maize, brown rice, sorghum, soya, and tapioca) promotes gut lining integrity, immune tolerance towards the microbiota, and its associated immune and inflammatory responses. A fibre-rich diet is a promising biotherapeutic candidate that could effectively modulate inflammatory mediators’ expression associated with immune cell migration, lymphoid tissue maturation, and signalling pathways. It could also modulate the stimulation of cytokines and chemokines involved in ensuring balance for long-term microbiome programming. The interplay between host and gut microbial digestion is complex; microbes using and competing for dietary and endogenous proteins are often attributable to variances in the comparative abundances of Enterobacteriaceae taxa. Many auto-inducers could initiate the process of quorum sensing and mammalian epinephrine host cell signalling system. It could also downregulate inflammatory signals with microbiota tumour taxa that could trigger colorectal cancer initiation, metabolic type 2 diabetes, and inflammatory bowel diseases. The exploitation of essential biotherapeutic molecules derived from fibre-rich indigenous diet promises food substances for the downregulation of inflammatory signalling that could be harmful to gut microbiota ecological balance and improved immune response modulation.

The decline of mammary epithelial cell (MEC) number during mammary gland involution in the cow is due to inhibition of proliferation and induction of apoptosis. Transforming growth factor-beta 1 (TGF-β1) belongs to a group of intramammary auto/paracrine inhibitors of bovine MEC growth and inducers of apoptosis. However, the mechanism responsible for the regulation of TGF-β1 expression in MEC is not known. The present study examined the effect of the hormones, growth hormone (GH), somatostatin (STS), 17-β oestradiol (E2), progesterone (P4), as well as the growth factors, insulin-like growth factor I (IGF-I) and epidermal growth factor (EGF), on TGF-β1 expression in the bovine MEC lines, BME-UV1 and MAC-T. The model of apoptosis in bovine mammary gland in vitro was applied by reduction of fetal bovine serum (FBS) (from 10% to 2% or 0·5% FBS) in the cell environment to show the relationship between TGF-β1 expression and apoptosis in bovine MEC. RT-PCR, Western blot and laser scanning cytometry (LSC) were used for analysis of TGF-β1 transcript and protein level as well as apoptosis and cell cycle in examined MEC. In this model of apoptosis, FBS deficiency (mimicking the naturally occurring decline in the access of bioactive compounds and nutrients at the end of lactation and dry period) was associated with increased TGF-β1 expression at the level of transcript and protein, induction of apoptosis and inhibition of cell cycle. Exogenous TGF-β1, IGF-I, EGF and GH inhibited FBS-deficiency-stimulated TGF-β1 expression. The suppressive effect of GH was reversed when cells were maintained longer in FBS-deficient medium. In general, STS, E2 and P4 increased TGF-β1 expression. However, this effect was dependent on hormone concentration and cell line. BME-UV1 cells were much more responsive to the peptides, GH, STS, IGF-I and EGF, whereas MAC-T cells were more responsive to the steroid sex hormones: E2 and P4.

Les composés organiques volatils (COV), sous-produits du métabolisme émis par l’ensemble desorganismes vivants, sont volatils en conditions environnementales en raison de leurs propriétés physicochimiques.Chez les bactéries, et notamment celles du genre Pseudomonas, les COV sontprincipalement étudiés pour leur capacité à inhiber des microorganismes phytopathogènes. Leur rôledans la communication, un mécanisme indispensable à la coordination des communautés bactérienneslors de la formation de biofilm, est rarement considéré.L'objectif des travaux menés est l'analyse les COVs produits par la souche Pseudomonas fluorescensMFE01 et leur impact sur sa communication. Les voies de communication de MFE01 sont peu connueset ne correspondent pas aux systèmes déjà décrits chez de nombreuses bactéries du genrePseudomonas. La caractérisation du bouquet de molécules émises par MFE01 met en évidence uneforte émission de 1-undécène. Un mutant du gène undA, codant l’enzyme de synthèse du 1-undécène,n’émet plus ce COV et a une capacité réduite à former des biofilms. L’exposition de ce mutant à du 1-undécène exogène restaure la formation de biofilm. Le 1-undécène serait donc une molécule decommunication intraspécifique chez P. fluorescens MFE01. Le gène undA semble être en opéron avecle gène rbdA, codant un senseur putatif. Nous formulons l’hypothèse que Rbda serait impliqué dans laperception du 1-undécène et que la transduction du signal s’effectuerait via la synthèse de di-guanosinemonophosphate cyclique, un messager secondaire connu pour induire la formation de biofilm.L’étude de la voie de régulation Gac/Rsm, connue pour gouverner le métabolisme et la communicationdes Pseudomonas, montre qu’elle module fortement la quantité et le profil de COV émis par MFE01.Cette voie pilote chez MFE01 l’émission de 1-undécène et l’inhibition aérienne du pathogène humainLegionella pneumophila ainsi que celle du phytopathogène Phytophtora infestans. L’expression du gènegacS, codant le senseur principal de la voie Gac/Rsm, serait activée par au moins un COV,potentiellement le 2-tridecanone et/ou le 2-undecanone
Volatile organic compounds (VOCs), by-products of metabolism emitted by all living organisms, arevolatile under environmental conditions due to their physicochemical properties. In bacteria, especiallythose of the genus Pseudomonas, VOCs are mainly studied for their ability to inhibit phytopathogenicmicroorganisms. Their role in communication, which is a crucial mechanism for coordinating bacterialcommunities during biofilm formation, is understudied.This research focuses on investigating VOCs emitted by the Pseudomonas fluorescens MFE01 strainand their implications in its communication. The uncharacterized communications pathways of MFE01are untypical and does not involve pathways already described in others Pseudomonas.Characterization of molecules the emitted by MFE01 reveals a huge emission of 1-undecene. A mutantlacking the undA gene, responsible for 1-undecene synthesis, no longer emits this VOC and exhibitsreduced biofilm formation capabilities. Exposure of this mutant to exogenous 1-undecene restoresbiofilm formation, Therefore, 1-undecene seems to be an intraspecific communication molecule in P.fluorescens MFE01. The undA gene seems to be in an operon with the rbdA gene, encoding a putativesensor. We hypothesize that Rbda is involved in 1-undecene perception with signal transduction likelyoccurring via the synthesis of cyclic di-guanosine monophosphate, a known secondary messenger thatinduces biofilm formation.Additionally, the study of the Gac/Rsm regulatory pathway, a critical regulator of metabolism andcommunication in Pseudomonas, demonstrates that it strongly modulates the quantity and profile ofVOCs emitted by MFE01. This pathway governs 1-undecene emission and the aerial inhibition of humanpathogen Legionella pneumophila and phytopathogen Phytophtora infestans by MFE01. At least oneVOC, possibly 2-tridecanone and/or 2-undecanone, may activate the expression of the gacS gene,which encodes the principal sensor of the Gac/Rsm pathway

Quorum sensing is the cell to cell communication mechanism in microorganism through signalling molecules. Regulation of virulence factor, sporulation, proteolytic enzymes production, biofilm formation, auto-inducers, cell population density are key physiological process mediated through quorum-sensing (QS) signalling. Elevation of innate immune system and antibiotic tolerance of pathogens is highly increased with perspective of quorum-sensing (QS) activity. Development of novel drugs is highly attractive scenario against cell-cell communication of microbes. Design of synthetic drugs and natural compounds against QS signal molecules is vital combat system to attenuate microbial pathogenicity. Quorum sensing inhibitors (QSIs), quorum quenchers (QQs), efflux pump inhibitors (EPIs) act against multi-drug resistance strains (MDR) and other pathogenic microbes through regulation of auto-inducers and signal molecule with perceptive to growth arrest both in-vitro and in-vivo. QQs, QSIs and EPIs compounds has been validated with various animal models for high selection pressure on therapeutics arsenal against microbe’s growth inhibition. Promising QSI are phytochemicals and secondary metabolites includes polyacetylenes, alkaloids, polyphenols, terpenoids, quinones.

Biofilms are the communities of microorganisms, especially bacteria attached to a biotic or abiotic surface. These biofilms live in a self-sustained matrix and produce different substances called extracellular polymeric substances (EPS) which are responsible for the pathogenicity of a number of bacteria such as Pseudomonas aeruginosa, Staphylococcus aureus, Vibrio cholerae, Klebsiella pneumoniae, Escherichia coli, etc. These EPS substance makes it difficult to eradicate the biofilm present on the surface. Biofilm formation is a five-step process. Biofilms can be monospecies or multispecies. In biofilms, cells communicate via Quorum Sensing (QS). QS is the regulation of gene expression in bacteria with respect to changes in cell population density. In QS, bacteria produce various signaling molecules called Auto-inducers (AI). AI concentration increases as the bacterial population increases. Bacteria respond to these AIs results in an alteration of gene expression, which results in the release of various virulence factors. QS involves a two-component signaling process which is different for both Gram-positive and Gram-negative bacteria. QS and EPS make the bacteria resistant to various antibiotics, which make the eradication difficult and hence requires more effective treatment. This article discusses the biofilm structure, phenomenon of biofilm formation, signaling, and pathogenicity to highlight the understanding of processes involved in biofilm formation.

Urokinase was discovered in the late nineteenth century, as an enzymatic principle in urine, that initiates the dissolution of blood clots. The basis of this phenomenon was recognized more than fifty years ago as the activation of plasminogen, the precursor of a tryptic protease, then known as profibrinolysin. Despite this long history, detailed data on the biochemistry of plasminogen activation have only become available recently. Urokinase (now designated urokinase-type plasminogen activator : u-PA) is synthesized and secreted as a single chain polypeptide (Mr-: 53,000) by many cell types. Single chain u-PA (scu-PA) is with equal justification called prourokinase (pro-u-PA), notwithstanding its low catalytic activity for synthetic peptide substrates and plasminogen, as most proenzymes of proteases display a certain degree of activity. The structure of pro-u-PA has been elucidated by protein and cDNA sequencing. It consists of three domains, exhibiting characteristic homology to other proteins: a serine protease domain, homologous to trypsin, chymotrypsin and elastase; a kringle domain, likewise found in prothrombin, plasminogen, tissue-type plasminogen activator (t-PA) and Factor XII; and an epidermal growth factor (EGF)-like domain, found in many other proteins, including certain clotting factors. Pro-u-PA is activated by the cleavage of its LYS158-Ile159 h1 bY either plasmin or kallikrein. This cleavage leads to a high increase of Kcat values with respect to both plasminogen and synthetic peptide substrates, but apparently to a reduction of its affinity to plasminogen. Thrartoin inactivates pro-u-PA irreversibly by the cleavage of the Arg156-Phe157 bond. U-PA but not pro-u-PA rapidly forms ccnplexes with plasminogen activator inhibitors (PAI)-l and PAI-2: second order rate constants Kass are respectively > 107 and 0.9xl06 (M-11sec-1). Unknown enzymes process pro-u-PA and u-PA to low molecular weight (LMW) pro-u-PA and LMW u-PA (Mr: 33,000) by cutting off a fragment consisting of the kr ingle and the EGF—like region. Pro—u—PA mediated plasminogen activation is fibrin dependent in vivo, and to a certain degree in vitro. Hie biochemical basis of this fibrin specificity is at present uncertain, although there are reports indicating that it may require polyvalent cations. Through its EGF-like region HMW pro-u-PA and HMW u-PA are capable of binding to specific membrane protein receptors which are found on many cells. Thus, u-PA activity may be restricted to the cell surface. According to a recent report, binding of u—PA to the receptor may also mediate signal transduction in auto- or paracrine growth control. In cells permissive for the respective pathways, pro-u-PA gene transcription is stimulated by mechanisms of signal transduction, that include the cAMP, the tyrosine specific kinase and the protein kinase C dependent pathways. Glucocorticoid hormones downregulate pro-u-PA gene transcription in cells where the gene is canstitutively expressed. Although different cells vary greatly in their response to agents that stimulate urokinase biosynthesis, growth factors and other mitogens are in many cases effective inducers. Significantly elevated levels of u-PA are also found in many malignant tissues. These findings and many others suggest that plasminogen activation by u-PA provides localized extracellular matrix degradation which is required for invasive growth, cell migration and other forms of tissue remodelling. Fibrin represents in this view only a variant of an extracellular matrix, which is provided through the clotting system in the case of an emergency.