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1. Experimental colitis promotes sustained, sex-dependent, T-cell-associated neuroinflammation and parkinsonian neuropathology

   https://doi.org/10.1186/s40478-021-01240-4  

   Houser, Madelyn C. ; Caudle, W. Michael ; Chang, Jianjun ; Kannarkat, George T. ; Yang, Yuan ; Kelly, Sean D. ; Oliver, Danielle ; Joers, Valerie ; Shannon, Kathleen M. ; Keshavarzian, Ali ; et al ( August 2021 , Acta Neuropathologica Communications)

   The etiology of sporadic Parkinson’s disease (PD) remains uncertain, but genetic, epidemiological, and physiological overlap between PD and inflammatory bowel disease suggests that gut inflammation could promote dysfunction of dopamine-producing neurons in the brain. Mechanisms behind this pathological gut-brain effect and their interactions with sex and with environmental factors are not well understood but may represent targets for therapeutic intervention.

   We sought to identify active inflammatory mechanisms which could potentially contribute to neuroinflammation and neurological disease in colon biopsies and peripheral blood immune cells from PD patients. Then, in mouse models, we assessed whether dextran sodium sulfate-mediated colitis could exert lingering effects on dopaminergic pathways in the brain and whether colitis increased vulnerability to a subsequent exposure to the dopaminergic neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We assessed the involvement of inflammatory mechanisms identified in the PD patients in colitis-related neurological dysfunction in male and female mice, utilizing mice lacking the Regulator of G-Protein Signaling 10 (RGS10)—an inhibitor of nuclear factor kappa B (NFκB)—to model enhanced NFκB activity, and mice in which CD8⁺T-cells were depleted.

   High levels of inflammatory markers includingCD8Band NFκB p65 were found in colon biopsies from PD patients, and reduced levels of RGS10 were found in immune cells in the blood. Male mice that experienced colitis exhibited sustained reductions in tyrosine hydroxylase but not in dopamine as well as sustained CD8⁺T-cell infiltration and elevatedIfngexpression in the brain. CD8⁺T-cell depletion prevented colitis-associated reductions in dopaminergic markers in males. In both sexes, colitis potentiated the effects of MPTP. RGS10 deficiency increased baseline intestinal inflammation, colitis severity, and neuropathology.

   This study identifies peripheral inflammatory mechanisms in PD patients and explores their potential to impact central dopaminergic pathways in mice. Our findings implicate a sex-specific interaction between gastrointestinal inflammation and neurologic vulnerability that could contribute to PD pathogenesis, and they establish the importance of CD8⁺T-cells in this process in male mice.

    

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2. Immune-Microbiota Crosstalk Underlying Inflammatory Bowel Disease

   https://doi.org/10.1007/978-3-030-91415-8_2  

   Xu, Congmin ; Mac, Quoc D. ; Jia, Qiong ; Qiu, Peng ( November 2021 , In: Wei, Y., Li, M., Skums, P., Cai, Z. (eds) Bioinformatics Research and Applications. ISBRA 2021. Lecture Notes in Computer Science)

   Wei, Yanjie ; Li, Min ; Skums, Pavel ; Cai, Zhipeng (Ed.)

   Long-time evolution has shaped a harmonious host-microbiota symbiosis consisting of intestinal microbiota in conjunction with the host immune system. Inflammatory bowel disease (IBD) is a result of the dysbiotic microbial composition together with aberrant mucosal immune responses, while the underlying mechanism is far from clear. In this report, we creatively proposed that when correlating with the host metabolism, functional microbial communities matter more than individual bacteria. Based on this assumption, we performed a systematic analysis to characterize the co-metabolism of host and gut microbiota established on a set of newly diagnosed Crohn’s disease (CD) samples and healthy controls. From the host side, we applied gene set enrichment analysis on host mucosal proteome data to identify those host pathways associated with CD. At the same time, we applied community detection analysis on the metagenomic data of mucosal microbiota to identify those microbial communities, which were assembled for a functional purpose. Then, the correlation analysis between host pathways and microbial communities was conducted. We discovered two microbial communities negatively correlated with IBD enriched host pathways. The dominant genera for these two microbial communities are known as health-benefits and could serve as a reference for designing complex beneficial microorganisms for IBD treatment. The correlated host pathways are all relevant to MHC antigen presentation pathways, which hints toward a possible mechanism of immune-microbiota cross talk underlying IBD. 

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3. Antibiotic perturbation of gut bacteria does not significantly alter host responses to ocular disease in a songbird species

   https://doi.org/10.7717/peerj.13559  

   Weitzman, Chava L. ; Belden, Lisa K. ; May, Meghan ; Langager, Marissa M. ; Dalloul, Rami A. ; Hawley, Dana M. ( January 2022 , PeerJ)

   Bacterial communities in and on wild hosts are increasingly appreciated for their importance in host health. Through both direct and indirect interactions, bacteria lining vertebrate gut mucosa provide hosts protection against infectious pathogens, sometimes even in distal body regions through immune regulation. In house finches ( Haemorhous mexicanus ), the bacterial pathogen Mycoplasma gallisepticum (MG) causes conjunctivitis, with ocular inflammation mediated by pro- and anti-inflammatory cytokines and infection triggering MG-specific antibodies. Here, we tested the role of gut bacteria in host responses to MG by using oral antibiotics to perturb bacteria in the gut of captive house finches prior to experimental inoculation with MG. We found no clear support for an impact of gut bacterial disruption on conjunctival pathology, MG load, or plasma antibody levels. However, there was a non-significant trend for birds with intact gut communities to have greater conjunctival pathology, suggesting a possible impact of gut bacteria on pro-inflammatory cytokine stimulation. Using 16S bacterial rRNA amplicon sequencing, we found dramatic differences in cloacal bacterial community composition between captive, wild-caught house finches in our experiment and free-living finches from the same population, with lower bacterial richness and core communities composed of fewer genera in captive finches. We hypothesize that captivity may have affected the strength of results in this experiment, necessitating further study with this consideration. The abundance of anthropogenic impacts on wildlife and their bacterial communities, alongside the emergence and spread of infectious diseases, highlights the importance of studies addressing the role of commensal bacteria in health and disease, and the consequences of gut bacterial shifts on wild hosts. 

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4. Resveratrol modulates the gut microbiota to prevent murine colitis development through induction of Tregs and suppression of Th17 cells

   https://doi.org/10.1002/JLB.3A1218-476RR  

   Alrafas, Haider Rasheed ; Busbee, Philip B. ; Nagarkatti, Mitzi ; Nagarkatti, Prakash S. ( March 2019 , Journal of Leukocyte Biology)

   Inflammatory diseases of the gastrointestinal tract are often associated with microbial dysbiosis. Thus, dietary interactions with intestinal microbiota, to maintain homeostasis, play a crucial role in regulation of clinical disorders such as colitis. In the current study, we investigated if resveratrol, a polyphenol found in a variety of foods and beverages, would reverse microbial dysbiosis induced during colitis. Administration of resveratrol attenuated colonic inflammation and clinical symptoms in the murine model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis. Resveratrol treatment in mice with colitis led to an increase in CD4+FOXP3+ and CD4+IL-10+ T cells, and a decrease in CD4+IFN-γ+ and CD4+IL-17+ T cells. 16S rRNA gene sequencing to investigate alterations in the gut microbiota revealed that TNBS caused significant dysbiosis, which was reversed following resveratrol treatment. Analysis of cecal flush revealed that TNBS administration led to an increase in species such as Bacteroides acidifaciens, but decrease in species such as Ruminococcus gnavus and Akkermansia mucinphilia, as well as a decrease in SCFA i-butyric acid. However, resveratrol treatment restored the gut bacteria back to homeostatic levels, and increased production of i-butyric acid. Fecal transfer experiments confirmed the protective role of resveratrol-induced microbiota against colitis inasmuch as such recipient mice were more resistant to TNBS-colitis and exhibited polarization toward CD4+FOXP3+ T cells and decreases in CD4+IFN-γ+ and CD4+IL-17+ T cells. Collectively, these data demonstrate that resveratrol-mediated attenuation of colitis results from reversal of microbial dysbiosis induced during colitis and such microbiota protect the host from colonic inflammation by inducing Tregs while suppressing inflammatory Th1/Th17 cells.

    

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5. Use of the Informatics for Integrating Biology and the Bedside (i2b2) Population to Test Serum Bilirubin Levels and Risk for Inflammatory Bowl Diseases and the Involvement of Uridine Glucuronosyltransferase Genes

   https://doi.org/10.1145/3233547.3233638  

   Gallagher, Carla J. ( January 2018 , Proceedings of the 2018 ACM International Conference on Bioinformatics, Computational Biology, and Health Informatics)

   Chronic inflammation associated with inflammatory bowel disease (IBD) results in increased oxidative stress that damages the colonic microenvironment. A low level of serum bilirubin, an endogenous antioxidant, has been associated with increased risk for Crohn's disease (CD), but no study has tested another common IBD ulcerative colitis (UC). Bilirubin is metabolized in the liver by uridine glucuronosyltransferase 1A1 (UGT1A1) exclusively. Genetic variants cause functional changes in UGT1A1 which result in hyperbilirubinemia, which can be toxic to tissues if untreated and results in a characteristic jaundiced appearance. Approximately 10% of the Caucasian population is homozygous for the microsatellite polymorphism UGT1A1*28, which results in increased total serum bilirubin levels due to reduced transcriptional efficiency of UGT1A1 and an overall 70% reduction in UGT1A1 enzymatic activity. The aim of this study was to examine whether bilirubin levels are associated with the risk for ulcerative colitis (UC). Using the Informatics for Integrating Biology and the Bedside (i2b2), a large case-control population was identified from a single tertiary care center, Penn State Hershey Medical Center (PSU). Similarly, a validation cohort was identified at Virginia Commonwealth University Medical Center. Logistic regression analysis was performed to determine the risk of developing UC with lower concentrations of serum bilirubin. From the PSU cohort, a subset of terminal ileum tissue was obtained at the time of surgical resection to analyze UGT1A1 gene expression (which encodes the enzyme responsible for bilirubin metabolism). Similar to CD patients, UC patients also demonstrated reduced levels of total serum bilirubin. Upon segregating serum bilirubin levels into quartiles, risk of UC increased with reduced concentrations of serum bilirubin. These results were confirmed in our validation cohort. UGT1A1 gene expression was up-regulated in the terminal ileum of a subset of UC patients. Lower levels of the antioxidant bilirubin may reduce the capability of UC patients to remove reactive oxygen species leading to an increase in intestinal injury. One potential explanation for these lower bilirubin levels may be up-regulation of UGT1A1 gene expression, which encodes the only enzyme involved in conjugating bilirubin. Therapeutics that reduce oxidative stress may be beneficial for these patients. 

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