Modulation der intestinalen Homöostase und Entzündung durch Prevotella intestinalis (nov. sp.)

Intestinal homeostasis is maintained by the dynamic interplay between the gut microbiota and the host immune system. Alterations in the composition and function of the gut microbiota have been associated with increased susceptibility to intestinal inflammation, but whether these candidate microbes actively modulate host phenotypes is frequently not known. The role of members of the Prevotella genus within the intestinal microbiota and their effects on the host is not completely understood and somewhat conflicting interpretations have been reported. Whereas association with plant-rich diet and improved glucose metabolism suggested Prevotella spp. are beneficial for the host, their increased relative abundances in microbial ecosystems at multiple body sites have been associated with diverse diseases. Yet, whether Prevotella spp. actively contribute to the development of these diseases is not known. The detailed investigation of the immunomodulatory properties of Prevotella spp. has been prohibited by the poor characterization of Prevotella species and high strain diversity, as well as the lacking availability of diverse intestinal Prevotella isolates. In the present work, we isolated three novel intestinal Prevotella species from mice prone to intestinal inflammation. Characterization of the impact of Prevotella colonization on the interplay between host and the microbiota during intestinal homeostasis and inflammation was performed using P. intestinalis, which among the three novel species shared the highest similarity to the predominant human gut Prevotella species - P. copri. We identified that colonization by this novel member of the Prevotella genus significantly decreased the production of the bacterial fermentation product SCFAs and the immunomodulatory cytokine IL-18, which was associated with an increase in the severity of intestinal inflammation. Our findings suggested that Prevotella-mediated intestinal injury may be influenced via different pathways, yet the ability to ameliorate Prevotella-induced disease severity by supplementation of IL-18 suggested that remodeling of the microbial metabolome and specifically SCFA production may be the dominating pathomechanism. Finally, the consequences of modulation of SCFA production in the intestine by Prevotella spp. may have far-reaching consequences for the host, as SCFA have immunomodulatory effects in distant sites such as the liver, bones or the brain.Die intestinale Homöostase wird durch dynamische Wechselwirkungen der Darmmikrobiota und dem Immunsystem aufrecherhalten. Verämderungen bei der Zusammensetzung und Funktion der Mikrobiota wurden mit diversen Krankheitsbildern im Menschen assoziiert, jedoch bleiben die ursächlichen Mikroben, welche die auftretenden Phenotypen aktiv modulieren, unbekannt. Die Rolle von Bakterien aus dem Prevotella Genus und ihre Effekte auf den Wirt im Kontext von Darmentzündungen führte zu gegensätzliche Interpretationen. Zum einen wurde eine erhöhte Anzahl an Prevotella spp. mit einer pflanzenreichen Ernährung und einem verbesserten Glucose-Metabolismus assoziiert, zum anderen wurde Prevotella spp. in mikrobiellen Gemeinschaften mit diversen Krankheiten in Verbindung gebracht. Ob Prevotella spp. aktiv bei der Entstehung dieser Krankheiten beiträgt ist nicht bekannt. Eine detaillierte Untersuchung der immunmodulatorischen Eigenschaften von Prevotella spp. wurde bisher durch mangelnde Charakterisierungen der Prevotella-Spezies, die große Vielfalt der bekannten Stränge und die fehlende Verfügbarkeit verschiedener Prevotella-Isolate des Darmes erschwert. In dieser Arbeit wurden drei neue intestinale Prevotella Spezies aus Mäusen isoliert, die anfällig für intestinale Entzündungen sind. Die Rolle von Prevotella beim Wechselspiel zwischen Wirt und der Mikrobiota bei intestinaler Homöostase und Entzündung wurde mit dem Isolat P.intestinalis untersucht, welches von den neu isolierten Spezies die höchste Ähnlichkeit zu der im humanen Darm dominanten Prevotella Spezies aufweist. Es konnte gezeigt werden, dass eine Besiedlung mit dieser P. intestinalis sowohl die bakterielle Produktion von kurzkettigen Fettsäuren (SCFAs) als auch die Bildung des immunmodulatorischen Zytokins IL-18 signifikant verringert, was wiederrum mit einem erhöhten Schweregrad einer intestinalen Entzündung assoziiert wird. Da die Prevotella-induzierte Krankheitsschwere durch eine Supplementierung von IL-18 gelindert werden kann, stellt die Veränderung des mikrobiellen Metaboloms und vor allem der Bildung der SCFAs möglicherweise den dominierenden Pathomechanismus dar. Da SCFAs immunmodulatorische Effekte an unterschiedlichsten Stellen des Körpers wie Leber, Knochen oder Gehirn haben, hat die Modulierung der SCFA-Produktion im Darm durch Prevotella spp. damit letztendlich vermutlich weitreichende Folgen für den Wirt

Frequency and type of eyelid neoplasia in Tuzla region, Bosnia and Herzegovina

Introduction: Benign and malignant tumors can arise from each of the eyelid layers. Our aim was to investigate the frequency and distribution of the eyelid tumors in tertiary health institution in Tuzla Region in Bosnia and Herzegovina.             Methods: We analyzed medical records for all the patients treated for eyelid malignancies in University Clinical Center Tuzla, from January 2012 to December 2016. Demographic, clinical and pathological data were collected and analyzed.           Results: A total of 89 patients were treated during the 5 year period. Forty seven of the patients were male (52 %) and 42 (48 %) were female. Patient age ranged from 11 to 92 years, with the mean age of 66.6 years. The most common eyelid malignancy was basal cell carcinoma (80.95%), followed by squamous cell carcinoma (14.29%), merkel cell carcinoma (3.17%) and melanoma (1.59%). Conclusion: The annual incidence of eyelid tumors in Tuzla region is about 3.73/100 000 population. Majority of the malignant tumors were basal cell carcinoma, while melanoma was the least frequent. Most frequent benign lesions were seborrheic keratosis and benign nevi

Shaping of Intestinal Microbiota in Nlrp6- and Rag2-Deficient Mice Depends on Community Structure

Contradicting observations have been made regarding the relative contributions of immune sensors to shaping the microbiome, yet the reasons for these discrepancies are not fully understood. Here, we investigated the contribution of environmental factors in shaping the microbiome in mice deficient in adaptive immunity (Rag2−/−) and Nlrp6, an immune sensor proposed to be involved in regulation of microbiota composition. In conventionally housed Nlrp6−/− mice, familial transmission has a significant effect on microbiota composition, complicating the analysis of genotype-dependent effects. Notably, after rederivation into standardized specific pathogen-free (SPF) conditions devoid of pathobionts, microbiota composition was indistinguishable between WT, Rag2−/−, and Nlrp6−/− mice. However, upon reintroduction of a pathobiont-containing community host, genotype-dependent differences reappear, specifically affecting the relative abundance of pathobionts such as Helicobacter spp. Our results show that the impact of Nlrp6 and also of adaptive immunity on microbiota composition depends on community structure and primarily influences pathobionts but not commensals

Modulation of inflammatory responses by gastrointestinal Prevotella spp. - From associations to functional studies.

Numerous studies have associated alterations in the gut microbiota composition with almost every known inflammatory disease. However, proving the biological relevance of distinct microbial signatures and linking specific microorganisms to host phenotypes, remains a considerable challenge. Correspondingly, increased abundance of members of Prevotella genus within microbial communities colonizing distinct mucosal surfaces has been found in individuals diagnosed with rheumatoid arthritis, periodontitis, metabolic disorders, and intestinal and vaginal dysbiosis. Still, the role of Prevotella spp. in the incidence of these diseases continues to be debated. For many years, poor understanding of Prevotella biology could be in large part attributed to the lack of experimental tools. However, in the recent years significant advances have been made towards overcoming these limitations, including increased number of isolates and improved understanding of genetic diversity. Besides discussing the most relevant associations between Prevotella spp. and inflammatory disorders, in the present review we examine the recent efforts to expand the Prevotella experimental "toolbox" and we highlight remaining experimental challenges that should advance future research and our understanding of Prevotella-host interplay

A versatile genetic toolbox for Prevotella copri enables studying polysaccharide utilization systems.

Prevotella copri is a prevalent inhabitant of the human gut and has been associated with plant-rich diet consumption and diverse health states. The underlying genetic basis of these associations remains enigmatic due to the lack of genetic tools. Here, we developed a novel versatile genetic toolbox for rapid and efficient genetic insertion and allelic exchange applicable to P. copri strains from multiple clades. Enabled by the genetic platform, we systematically investigated the specificity of polysaccharide utilization loci (PULs) and identified four highly conserved PULs for utilizing arabinan, pectic galactan, arabinoxylan, and inulin, respectively. Further genetic and functional analysis of arabinan utilization systems illustrate that P. copri has evolved two distinct types of arabinan-processing PULs (PULAra ) and that the type-II PULAra is significantly enriched in individuals consuming a vegan diet compared to other diets. In summary, this genetic toolbox will enable functional genetic studies for P. copri in future

Dietary Short-Term Fiber Interventions in Arthritis Patients Increase Systemic SCFA Levels and Regulate Inflammation.

Chronic inflammatory diseases are often initiated and guided by the release of proinflammatory mediators. Rheumatoid arthritis (RA) is caused by an imbalance between the pro- and anti-inflammatory mediators in the joints, thereby favoring chronic inflammation and joint damage. Here, we investigate if short-term high-fiber dietary intervention shifts this towards anti-inflammatory mediators. Healthy controls (n = 10) and RA patients (n = 29) under routine care received daily high-fiber bars for 15 or 30 days, respectively. Stool and sera were analyzed for pro- and anti-inflammatory mediators. A high-fiber dietary intervention resulted in increased anti-inflammatory short-chain fatty acids (SCFA), decreased proarthritic cytokine concentrations, along with a durable shift in the Firmicutes-to-Bacteroidetes ratio. Together, these results further strengthen high-fiber dietary interventions as a practical approach complementing existing pharmacological therapies

Distinct Microbial Communities Trigger Colitis Development upon Intestinal Barrier Damage via Innate or Adaptive Immune Cells

Summary: Inflammatory bowel disease comprises a group of heterogeneous diseases characterized by chronic and relapsing mucosal inflammation. Alterations in microbiota composition have been proposed to contribute to disease development, but no uniform signatures have yet been identified. Here, we compare the ability of a diverse set of microbial communities to exacerbate intestinal inflammation after chemical damage to the intestinal barrier. Strikingly, genetically identical wild-type mice differing only in their microbiota composition varied strongly in their colitis susceptibility. Transfer of distinct colitogenic communities in gene-deficient mice revealed that they triggered disease via opposing pathways either independent or dependent on adaptive immunity, specifically requiring antigen-specific CD4+ T cells. Our data provide evidence for the concept that microbial communities may alter disease susceptibility via different immune pathways despite eventually resulting in similar host pathology. This suggests a potential benefit for personalizing IBD therapies according to patient-specific microbiota signatures. : Alterations in the microbiota contribute to the development of intestinal inflammation. Roy et al. demonstrate that distinct intestinal microbial communities cause colitis via opposing effector mechanisms independent or dependent on adaptive immunity. Their findings suggest that personalized immunomodulatory treatment according to distinct microbial signatures may be beneficial for IBD patients. Keywords: gut microbiota, IBD, innate colitis, adaptive colitis, colitis pathogenesis, DSS coliti

Distinct Polysaccharide Utilization Determines Interspecies Competition between Intestinal Prevotella spp.

CD81 plays a role in a variety of physiological and pathological processes. Recent structural analysis of CD81 indicates that it contains an intramembrane cholesterol-binding pocket and that interaction with cholesterol may regulate a conformational switch in the extracellular domain of CD81. Therefore, CD81 possesses a potential cholesterol sensing mechanism; however, its relevance for protein function is thus far unknown. In this study we investigate CD81 cholesterol sensing in the context of its activity as a receptor for hepatitis C virus. Structure-led mutagenesis of the cholesterol-binding pocket reduced CD81-cholesterol association, but had disparate effects on HCV, both reducing and enhancing CD81 receptor activity. We reasoned that this could be explained by alterations in the consequences of cholesterol binding. To investigate this further we performed molecular dynamic simulations of CD81 with and without cholesterol; this identified an allosteric mechanism by which cholesterol binding regulates the conformation of CD81. To test this, we designed further mutations to force CD81 into either the open (cholesterol unbound) or closed (cholesterol bound) conformation. The open mutant of CD81 exhibited reduced receptor activity whereas the closed mutant was enhanced. These data are consistent with cholesterol switching CD81 between a receptor active and inactive state. CD81 interactome analysis also suggests that conformational switching may modulate the assembly of CD81-partner networks. This work furthers our understanding of the molecular mechanism of CD81 cholesterol sensing, how this relates to HCV entry and CD81's function as a molecular scaffold; these insights are relevant to CD81's varied roles in health and disease

Short-chain fatty acids regulate systemic bone mass and protect from pathological bone loss

Short-chain fatty acids (SCFA) are a main class of metabolites derived from fermentation of dietary fibre in the intestine. Here, the authors show that dietary administration of SCFA is associated with inhibition of osteoclast differentiation, increased bone mass, and reduced pathological bone loss in mice

Perturbation of the gut microbiome by Prevotella spp. enhances host susceptibility to mucosal inflammation.

Diverse microbial signatures within the intestinal microbiota have been associated with intestinal and systemic inflammatory diseases, but whether these candidate microbes actively modulate host phenotypes or passively expand within the altered microbial ecosystem is frequently not known. Here we demonstrate that colonization of mice with a member of the genus Prevotella, which has been previously associated to colitis in mice, exacerbates intestinal inflammation. Our analysis revealed that Prevotella intestinalis alters composition and function of the ecosystem resulting in a reduction of short-chain fatty acids, specifically acetate, and consequently a decrease in intestinal IL-18 levels during steady state. Supplementation of IL-18 to Prevotella-colonized mice was sufficient to reduce intestinal inflammation. Hence, we conclude that intestinal Prevotella colonization results in metabolic changes in the microbiota, which reduce IL-18 production and consequently exacerbate intestinal inflammation, and potential systemic autoimmunity