Paneth cells and their antimicrobial products are critical in mediating small intestinal host defense under homeostatic conditions and after injury or infection. In addition, Paneth cells have also been shown to gain stem-like properties and repropagate intestinal crypts after intestinal injury. The specific role of intestinal IL-17A or its receptor (IL-17RA) signaling in Paneth cells to gain stem-like features has yet to be investigated. Using Paneth cell-specific IL-17RA (Il17rafl/fl;Defa6-cre) knockout mice, anti-IL-17A neutralizing studies and lineage tracer (Defa6-cre;mT/mG) mice, we show that after injury IL-17RA signaling is required for Paneth cell to gain stem-like properties to regenerate the intestinal epithelium. Increased susceptibility of Il17rafl/fl;Defa6-cre mice is associated with reduced expression Adam17 in the terminal ileum. Adam17 overexpression in Il17rafl/fl;Defa6-cre mice rescues the epithelial regeneration defect in these mice. IL-17A induces Nox1 in Paneth cells and H2O2 induces ADAM17 enzymatic activity. Finally, using Paneth cell-specific Adam17 (Adam17fl/fl;Defa6-cre) knockout mice, we show that ADAM17 in Paneth cells is required for tissue regeneration. Collectively, our data reveal an essential role of the IL-17RA-ADAM17 pathways in Paneth cells for tissue regeneration.

Abstract The aryl hydrocarbon receptor (AHR) plays a central role in orchestrating gut barrier and mucosal immune functions in the pathogenesis of inflammatory bowel disease (IBD). Nevertheless, activation of the AHR by diverse ligands yields varied outcomes, and the downstream pathways responsible for these effects remain unknown. Here, we report that selective activation of AHR in mouse intestinal epithelial cells (IEC) by the microbial metabolite, urolithin A (UroA), triggers the Nod-like receptor pyrin domain-containing protein 6 (NLRP6) inflammasome, resulting in the release of interleukin (IL)−18 but not IL-1β. Further, we show that UroA-induced IL-18 in IECs is critical for IL-22, mucin 2 and REG3γ production, as well as protection against colitis. Moreover, UroA significantly upregulates IL-18 and IL-22 levels in IECs and type-3 innate lymphoid cells, respectively, in intestinal biopsies from patients with IBD patients. These results demonstrate that activation of AHR by UroA modulates intestinal barrier function through an NLRP6-IL-18-IL-22 pathway in both healthy and IBD conditions.

Multiple sclerosis (MS) is an autoimmune disorder of the central nervous system associated with alterations in gut commensals, including Akkermansia muciniphila (A. muciniphila). However, its role in MS remains unclear. Here, we report elevated serum lipopolysaccharide (LPS) and anti-LPS IgG levels in patients with relapsing-remitting MS (RRMS), indicating compromised gut barrier integrity. Notably, RRMS patients also exhibited increased serum anti-A. muciniphila IgA and enhanced A. muciniphila-induced Th17 responses in peripheral blood mononuclear cells (PBMCs). Using experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, we found that A. muciniphila colonization worsened EAE severity, with increased infiltration of GM-CSF+CD4+ and IL-17A+CD4+ T cells in spinal cord. Mechanistically, A. muciniphila colonization enhanced tryptophan metabolism and elevated levels of aryl hydrocarbon receptor (AhR) agonists, including indole derivatives, during EAE. Although A. muciniphila does not directly metabolize tryptophan, it promotes expansion of tryptophan-utilizing bacterium Alistipes onderdonkii (A. onderdonkii) through mucin degradation. We further demonstrate that A. onderdonkii utilizes mucin-derived metabolites, including galactose and N-acetylneuraminic acid (NANA). Importantly, dietary tryptophan restriction significantly attenuated EAE severity. Collectively, these findings reveal a cross-feeding mechanism in which A. muciniphila supports growth of A. onderdonkii, thereby enhancing microbial tryptophan metabolism and production of AhR agonists that drive Th17-mediated neuroinflammation.

Interleukin (IL)-22 has been shown to play an important role in intestinal host defense and ameliorating high-fat diet (HFD)-induced metabolic disorders primarily through signaling in intestinal epithelial cells. Adipocytes have emerged as key immune–metabolic regulators that influence intestinal inflammation in inflammatory bowel disease (IBD). However, the role of IL-22RA1 signaling in adipocytes has not been explored. In the present study, we examined the role of IL-22RA1 signaling in adipocytes in response to dextran sulfate sodium (DSS)-mediated gut inflammation. To do this, we subjected adipocyte specific Il22ra1 knockout mice ( Il22ra1Adipo ) to intestinal inflammation under normal chow and HFD conditions. Compared to littermate controls, Il22ra1Adipo mice displayed significant weight loss on day 9 of DSS treatment and showed altered expression of immune response– and lipid metabolism–related genes in white adipose tissue (WAT) under a normal chow diet. Notably, when mice were primed with HFD prior to DSS-induced intestinal injury, WAT from Il22ra1Adipo mice showed a significant reduction in Fabp4 expression and a marked increase in the proliferation marker Ki67. These findings indicate that loss of IL-22RA1 signaling in adipocytes disrupts adipocyte differentiation and lipid metabolism, leading to increased proliferation of preadipocytes or stromal cells without proper maturation. Importantly, this altered adipose tissue response occurred despite similar levels of colonic inflammation between knockout and control mice, suggesting a critical role for adipocyte IL-22RA1 signaling in maintaining metabolic and inflammatory homeostasis in WAT during combined metabolic and intestinal inflammatory stress. ### Competing Interest Statement The authors have declared no competing interest. * HFD : High Fat Diet DSS : Dextran Sulfate Sodium WAT : White Adipose Tissue IBD : Inflammatory Bowel Disease CrohnM-BM-^Rs and Colitis Foundation, CCF 476637, CCF 1168040

The interleukin (IL)-22 cytokine can be protective or inflammatory in the intestine. It is unclear if IL-22 receptor (IL-22Ra1)-mediated protection involves a specific type of intestinal epithelial cell (IEC). By using a range of IEC type-specific Il22Ra1 conditional knockout mice and a dextran sulfate sodium (DSS) colitis model, we demonstrate that IL-22Ra1 signaling in MATH1+ cells (goblet and progenitor cells) is essential for maintaining the mucosal barrier and intestinal tissue regeneration. The IL-22Ra1 signaling in IECs promotes mucin core-2 O-glycan extension and induces beta-1,3-galactosyltransferase 5 (B3GALT5) expression in the colon. Adenovirus-mediated expression of B3galt5 is sufficient to rescue Il22Ra1IEC mice from DSS colitis. Additionally, we observe a reduction in the expression of B3GALT5 and the Tn antigen, which indicates defective mucin O-glycan, in the colon tissue of patients with ulcerative colitis. Lastly, IL-22Ra1 signaling in MATH1+ progenitor cells promotes organoid regeneration after DSS injury. Our findings suggest that IL-22-dependent protective responses involve O-glycan modification, proliferation, and differentiation in MATH1+ progenitor cells.

The role of FasL in initiating death signals through Fas is well characterized. However, the reverse signaling pathway downstream of FasL in effector lymphocytes is poorly understood. Here, we identify that FasL functions as an independent activation receptor in NK cells. Activation via FasL results in the production of LFN-γ, GM-CSF, RANTES, MIP-1α, and MIP1-β. Proximal signaling of FasL requires Lck and Fyn. Upon activation, FasL facilitates the phosphorylation of PI(3)K-p85α/p55α subunits. A catalytically inactive PI(3)K-p110δD910A mutation significantly impairs the cytokine and chemokine production by FasL. Activation of ITK and LAT downstream of FasL plays a central role in recruiting and phosphorylating PLC-γ2. Importantly, Fyn-mediated recruitment of ADAP links FasL to the Carmal/ Bcl10/Tak1 signalosome. Lack of Carma1, CARD domain of Carma1, or Tak1 significantly reduces FasL-mediated cytokine and chemokine production. These findings, for the first time, provide a detailed molecular blueprint that defines FasL-mediated reverse signaling.

IL-22 is critical for ameliorating obesity-induced metabolic disorders. However, it is unknown where IL-22 acts to mediate these outcomes. Here we examine the importance of tissue-specific IL-22RA1 signaling in mediating long-term high fat diet (HFD) driven metabolic disorders. To do so, we generated intestinal epithelium-, liver-, and white adipose tissue (WAT)-specific Il22ra1 knockout and littermate control mice. Intestinal epithelium- and liver-specific IL-22RA1 signaling upregulated systemic glucose metabolism. Intestinal IL-22RA1 signaling also mediated liver and WAT metabolism in a microbiota-dependent manner. We identified an association between Oscillibacter and elevated WAT inflammation, likely induced by Mmp12 expressing macrophages. Mechanistically, transcription of intestinal lipid metabolism genes is regulated by IL-22 and potentially IL-22-induced IL-18. Lastly, we show that Paneth cell-specific IL-22RA1 signaling, in part, mediates systemic glucose metabolism after HFD. Overall, these results elucidate a key role of intestinal epithelium-specific IL-22RA1 signaling in regulating intestinal metabolism and alleviating systemic obesity-associated disorders.

The role of FasL in initiating death signals through Fas is well characterized. However, the reverse signaling pathway downstream of FasL in effector lymphocytes is poorly understood. Here, we identify that FasL functions as an independent activation receptor in NK cells. Activation via FasL results in the production of LFN-γ, GM-CSF, RANTES, MIP-1α, and MIP1-β. Proximal signaling of FasL requires Lck and Fyn. Upon activation, FasL facilitates the phosphorylation of PI(3)K-p85α/p55α subunits. A catalytically inactive PI(3)K-p110δD910A mutation significantly impairs the cytokine and chemokine production by FasL. Activation of ITK and LAT downstream of FasL plays a central role in recruiting and phosphorylating PLC-γ2. Importantly, Fyn-mediated recruitment of ADAP links FasL to the Carmal/ Bcl10/Tak1 signalosome. Lack of Carma1, CARD domain of Carma1, or Tak1 significantly reduces FasL-mediated cytokine and chemokine production. These findings, for the first time, provide a detailed molecular blueprint that defines FasL-mediated reverse signaling.

Multiple sclerosis (MS) is an autoimmune neurological disorder of central nervous system. Multiple groups have independently reported the alteration of commensals especially Akkermansia muciniphila (A. muciniphila), a type of gram-negative bacteria, in the feces of MS patients. The protective or damaging role of gut microbiota including A. muciniphila in MS remains poorly understood. Here, we observed elevated lipopolysaccharides (LPS) and anti-LPS IgG in relapsing-remitting multiple sclerosis (RRMS) patient serum, indicating a compromised gut barrier. Furthermore, A. muciniphila-induced Th17 responses were enhanced in RRMS patients. Therefore, we used experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, to assess the involvement of A. muciniphila in autoimmunity. Using multiple A. muciniphila colonization approaches, we generated A. muciniphila+ and A. muciniphila- specific pathogen free (SPF) mice and found that A. muciniphila colonization worsened the EAE score and severity. Elevated infiltration of GM-CSF+CD4+ and IL-17A+CD4+ T cells into the spinal cord was observed in A. muciniphila+ mice. Furthermore, the neutralization of IL-17A in A. muciniphila+ mice protected the mice from EAE, suggesting that A. muciniphila exacerbates EAE by inducing IL-17A production. Mechanistically, A. muciniphila colonization elicits IL-17A production in spinal cord infiltrating leukocytes in an antigen-dependent manner. Moreover, enhanced tryptophan metabolism and elevated aryl hydrocarbon receptor (AhR) agonists including indole derivatives were uncovered in A. muciniphila+ mice during EAE. However, A. muciniphila does not hydrolyze tryptophan to indole. Instead, A. muciniphila expands tryptophan utilizer Alistipes by foraging on mucin. We showed that Alistipes ondersonkii (A. onderdonkii) was capable of utilizing mucin-derived metabolites with preference to galactose and N-acetylneuraminic acid (NANA). Moreover, mucin supplementation leads to a shift of A. muciniphila to utilize exogenous mucin and alleviates EAE. Taken together, our findings report that A. muciniphilaexpands tryptophan utilizer Alistipes and exacerbates EAE by promoting Th17 responses, suggesting a significant role of A. muciniphila in neurological disorders and autoimmune diseases.

The Th17 cell-lineage-defining cytokine IL-17A contributes to host defense and inflammatory disease by coordinating multicellular immune responses. The IL-17 receptor (IL-17RA) is expressed by diverse intestinal cell types, and therapies targeting IL-17A induce adverse intestinal events, suggesting additional tissue-specific functions. Here, we used multiple conditional deletion models to identify a role for IL-17A in secretory epithelial cell differentiation in the gut. Paneth, tuft, goblet, and enteroendocrine cell numbers were dependent on IL-17A-mediated induction of the transcription factor ATOH1 in Lgr5+ intestinal epithelial stem cells. Although dispensable at steady state, IL-17RA signaling in ATOH1+ cells was required to regenerate secretory cells following injury. Finally, IL-17A stimulation of human-derived intestinal organoids that were locked into a cystic immature state induced ATOH1 expression and rescued secretory cell differentiation. Our data suggest that the cross talk between immune cells and stem cells regulates secretory cell lineage commitment and the integrity of the mucosa.

Abstract BACKGROUND IL-17A/F signaling through the IL-17RA/RC receptor complex plays a vital role in immunity and inflammation. The expression of IL-17RA/RC by diverse intestinal epithelial cell types including Paneth cells and the observation that therapies neutralizing IL-17A or IL-17RA in Crohn’s disease (CD) patients induce adverse events suggest essential homeostatic functions of this cytokine. Paneth cells and their antimicrobial products (a-defensins, lysozyme etc.) play a critical role in mediating small intestinal host defense under homeostatic conditions as well as after injury or infection, and their dysregulation constitutes a pathogenic factor for CD. The specific role of intestinal IL-17A signaling in Paneth cells to regulate host defense at steady state or after intestinal inflammation remains poorly understood. Thus, we hypothesize that intestinal IL-17A signaling, specifically in Paneth cells, plays an important role in regulating microbiota colonization as well as maintaining intestinal integrity after gamma radiation induced injury. METHODS To examine the importance of IL-17RA signaling to Paneth cells, we utilized total, entire gut epithelium (Il17rafl/fl;villin-cre) and Paneth cell-specific IL-17RA knockout mice (Il17rafl/fl;Defa6-cre+). We subjected these mice with gamma irradiation (1200 cGy) to study intestinal injury and regenerative responses. Mice were sacrificed 3/5 days post irradiation. Terminal ilium was collected from naïve or irradiated mice for immunofluorescence imaging, RT-PCR, RNA sequencing, and enteroid cultures. RESULTS Our preliminary data from irradiated Il17ra-/- and Il17rafl/fl;villin-cre mice suggest that IL-17A signaling is important in maintaining intestinal barrier integrity. Specifically, these mice revealed increased microbial dissemination to liver and spleen compared to their respective control mice. Reduced expression of Lyz1 3 days post radiation in the terminal ileum of Il17ra-/- mice suggest impaired Paneth cell function. Cessation of Paneth cell specific IL-17RA signaling, also resulted in systemic bacterial dissemination 5 days post radiation. We also observed increased level of fecal Lcn2 in irradiated Il17rafl/fl;Defa6-cre+ mice. To understand Paneth cell-specific IL-17RA functions, we performed 16S microbial and RNA sequencing from ileum luminal contents and terminal ilea of naïve Il17rafl/fl;Defa6-cre+/- mice, respectively. While microbial 16s sequencing revealed no change to the overall microbial community, specific changes were observed at a select family level. Specifically, the level of Streptococcaceae was increased. RNA sequencing data showed no difference in Paneth cell antimicrobial peptides but did show reduced Caspase 4 expression in Il17rafl/fl;Defa6-cre+ mice. Collectively, our data revealed an important role of IL-17RA signaling in Paneth cell function at steady state and after injury.

Interleukin-22 plays both beneficial and deleterious role in intestinal inflammation. Further investigation is required to understand cell target and mechanism of action of IL-22 in large intestine. By using various intestinal cell specific IL-22Ra1 knockout mice models, such as entire intestinal epithelial cell (IL-22Ra1ΔIEC), Paneth (IL-22Ra1ΔDefa6), tamoxifen inducible Lgr5+ intestinal stem cell (IL-22Ra1ΔLgr5) and RU486 inducible secretory cell (IL-22Ra1ΔMath1-PGR). We tried to identify specific cell target of IL-22 in intestine. To induce experimental colitis, 8 days dextran sulphate sodium (DSS, 2%) was provided in drinking water followed by two days of normal water. On assessing colitis severity, more weight loss, histopathological changes and reduced colon length was observed in IL-22ra1ΔIEC mice. Increased expression of inflammatory cytokine genes and Lgr5+ stem cell related Olfm4 transcript were observed in distal colon of IL-22ra1ΔIEC as compared to IL-22ra1fl/fl mice. IL-22Ra1 signaling in IL-22Ra1ΔLgr5 and IL-22Ra1ΔDefa6 mice were dispensable in DSS induced colitis. Although goblet cell number was unaltered, expression of selective glycosyltransferases (causing O-glycosylation of mucin) were significantly reduced in colon of DSS treated IL-22Ra1ΔIEC as compared to IL-22Ra1fl/fl mice. Type-O glycan profile analysis of colon mucin using MALDI-TOF reveal premature termination of core 1 and 2 structure in IL-22Ra1ΔIEC mice as compared to IL-22Ra1fl/fl mice at steady state. Our preliminary data show that IL-22Ra1ΔMath1-PGR mice are more susceptible to DSS induced colitis. IL-22 may act by inducing expression of glycosyltransferases in Math1+ cell to abrogate development of experimental colitis.

Multiple sclerosis patients have been shown to have increased Akkermansia muciniphila (Akk) colonization. However, the role of Akk to regulate MS remains poorly understood. Here, we utilized fecal microbiota transplantation (FMT) model and generated Akk+ and Akk− SPF C57BL/6 mice. When subjected to EAE, Akk+ mice displayed worse clinical scores. An increase of spinal cord infiltrating IL-17A-producing and GM-CSF-producing CD4+ T cells was observed in Akk+ mice at 15 days post EAE induction. Moreover, ileum explant culture showed an elevated IL-17A production in Akk+ mice. Furthermore, we found dysregulated tryptophan in the cecal contents of naïve Akk+ mice. Additionally, using Kovac’s reagent, Akk was confirmed to utilize tryptophan and produce indole, an aryl hydrocarbon receptor (AhR) ligand. AhR activation has previously been shown to promote Th17 differentiation. Therefore, we performed Th17 differentiation in vitro. The treatment of Akk-derived tryptophan metabolites significantly induced IL-17A response. CH-223191, an AhR antagonist, abrogated the induction of Akk-mediated Th17 differentiation, suggesting that Akk-mediated Th17 differentiation was dependent on AhR. In addition, increased AhR agonists were observed in the feces of MOG immunized Akk+ mice as compared to Akk− mice. In conclusion, our data showed that Akk exacerbated EAE possibly by tryptophan-dependent induction of IL-17A-producing CD4+ T cells.

Key Points Nrf2 regulates IL-22 responses in CD4+ T cells. Nrf2 activation inhibits IL-17A response in multiple sclerosis patient–derived PBMCs. IL-17A and IL-22 derived from Th17 cells play a significant role in mucosal immunity and inflammation. TGF-β and IL-6 promote Th17 differentiation; however, these cytokines have multiple targets. The identification and screening of additional molecules that regulate IL-17A and IL-22 responses in certain inflammatory conditions is of great clinical significance. In this study, we show that CDDO-Im, a specific Nrf2 activator, promotes IL-17A and IL-22 responses in murine Th17 cells. In contrast, CDDO-Im inhibits IL-17A response in multiple sclerosis patient-derived PBMCs. However, Nrf2 specifically regulates IL-22 response in vivo. Nrf2 acts through the regulation of antioxidant response element (ARE) binding motifs in target genes to induce or repress transcription. Promoter analysis revealed that Il17a, Rorc, and Ahr genes have several ARE motifs. We showed that Nrf2 bound to ARE repressor (ARE-R2) of Rorc and inhibited Rorc-dependent IL-17A transactivation. The luciferase reporter assay data showed that CDDO-Im regulated Ahr promoter activity. Chromatin immunoprecipitation quantitative PCR data showed that Nrf2 bound to ARE of AhR. Finally, we confirmed that the CDDO-Im–mediated induction of IL-22 production in CD4+ T cells was abrogated in CD4-specific Ahr knockout mice (AhrCD4). CH-223191, a specific AhR antagonist, inhibits CDDO-Im–induced IL-22 production in CD4+ T cells, which further confirmed the AhR-dependent regulation. Collectively, our data showed that Nrf2 via AhR pathways regulated IL-22 response in CD4+ T cells.

Necrotizing enterocolitis (NEC) is a deadly intestinal inflammatory disorder that primarily affects premature infants and lacks adequate therapeutics. Interleukin (IL)-22 plays a critical role in gut barrier maintenance, promoting epithelial regeneration, and controlling intestinal inflammation in adult animal models. However, the importance of IL-22 signaling in neonates during NEC remains unknown. We investigated the role of IL-22 in the neonatal intestine under homeostatic and inflammatory conditions by using a mouse model of NEC. Our data reveal that Il22 expression in neonatal murine intestine is negligible until weaning, and both human and murine neonates lack IL-22 production during NEC. Mice deficient in IL-22 or lacking the IL-22 receptor in the intestine display a similar susceptibility to NEC, consistent with the lack of endogenous IL-22 during development. Strikingly, treatment with recombinant IL-22 during NEC substantially reduces inflammation and enhances epithelial regeneration. These findings may provide a new therapeutic strategy to attenuate NEC.

Interleukin (IL)-22 has been shown to protect against detrimental high fat diet (HFD)-induced phenotypes. However, it is unknown where IL-22Ra1 signaling specifically occurs to regulate HFD-induced metabolic disorders. To examine this, we utilized intestinal epithelium-specific Il22Ra1fl/fl;Villin-cre+ (IL22Ra1ΔIEC), white adipose tissue (WAT)-specific Il22Ra1fl/fl;Adipoq-cre+ (IL22Ra1ΔWAT), and liver-specific Il22Ra1fl/fl;Albumin-cre+ (IL22Ra1ΔLiver) knockout mice as well as their respective littermate cre-(IL22Ra1fl/fl), mice. When placed on long term HFD, IL22Ra1ΔIECand IL22Ra1ΔLiver mice but not IL22Ra1ΔWAT mice displayed impaired systemic glucose metabolism. We specifically observed that impaired glucose metabolism of IL22Ra1ΔIEC mice was microbiota dependent. IL22Ra1ΔIEC mice also possessed altered lipid metabolism since their intestinal tissues expressed increased levels of peroxisomal β-oxidation genes. Furthermore, extra-intestinal tissues from IL22Ra1ΔIEC mice displayed altered metabolism. Liver tissue of IL22Ra1ΔIEC mice displayed decreased expression of G6PC, a key glycolytic enzyme, and WAT displayed increased expression of peroxisomal Acox1 and decreased levels of certain fatty acids. These liver- and WAT-specific changes were dependent on IL-22 since Il22−/− mice displayed opposite trends in gene expression. We decided to examine where intestinal IL-22Ra1 signaling may specifically occur to mediate these effects. Interestingly, we observed a unique role of Paneth cell-specific IL-22Ra1 signaling in mediating systemic glucose metabolism. Overall, our data highlight a specific importance of intestinal IL-22Ra1 signaling in regulating HFD-induced metabolic disorders.

Little is known about how interactions of diet, intestinal stem cells (ISCs), and immune cells affect early-stage intestinal tumorigenesis. We show that a high-fat diet (HFD) reduces the expression of the major histocompatibility complex class II (MHC class II) genes in intestinal epithelial cells, including ISCs. This decline in epithelial MHC class II expression in a HFD correlates with reduced intestinal microbiome diversity. Microbial community transfer experiments suggest that epithelial MHC class II expression is regulated by intestinal flora. Mechanistically, pattern recognition receptor (PRR) and interferon-gamma (IFNγ) signaling regulates epithelial MHC class II expression. MHC class II-negative (MHC-II-) ISCs exhibit greater tumor-initiating capacity than their MHC class II-positive (MHC-II+) counterparts upon loss of the tumor suppressor Apc coupled with a HFD, suggesting a role for epithelial MHC class II-mediated immune surveillance in suppressing tumorigenesis. ISC-specific genetic ablation of MHC class II increases tumor burden cell autonomously. Thus, HFD perturbs a microbiome-stem cell-immune cell interaction that contributes to tumor initiation in the intestine.

IL-22 is known to play both protective and inflammatory role in the intestine. Thus, the effect of IL-22 in intestine is complex, and cell type-specific function of this cytokine requires further investigation. To identify target cell type of IL-22, we have used entire intestinal epithelial cell (IL-22Ra1ΔIEC), Paneth (IL-22Ra1ΔDefa6) and Lgr5+ intestinal stem cell (IL-22Ra1ΔLgr5)-specific IL-22Ra1 knockout mice models. Experimental colitis was developed by providing dextran sulphate sodium (DSS) in drinking water for first 8 days, and change to normal water for next two days. On examining DSS induced colitis development, significant increase in disease severity as revealed by reduced colon length, greater weight loss and histopathological changes in tissues were observed in IL-22ra1ΔIEC as compared to IL-22ra1fl/fl mice. No difference in disease severity was observed in IL-22ra1ΔDefa6 and IL-22ra1ΔLgr5 mice compared to their respective littermate control IL-22Ra1fl/fl mice. Quantitative PCR data show increased expression of inflammatory cytokines in distal colon of IL-22ra1ΔIEC compared to IL-22ra1fl/fl mice. Alcian blue staining revealed no difference in goblet cell number, however, expression of selective glycosyltransferase, required for mucin type-O glycosylation core extension, was significantly reduced in distal colon of IL-22Ra1ΔIEC compared to IL-22Ra1fl/fl mice on day 10 DSS/water treatment. Mucin type-O glycan analysis by MALDI-TOF revealed an increase in core 1 and decrease in core 4 structure in IL-22Ra1ΔIEC mice compared to IL-22Ra1fl/fl mice at steady state. Thus, IL-22 through glycosyltransferase activity may maintain intestinal barrier integrity and alleviate severity of experimental colitis.

Previous studies indicate that IL-17A plays an important role in mediating the intestinal micro biota and systemic metabolic functions. However, it is not known where IL-17RA signaling occurs to mediate these effects. To investigate this question, we used intestinal epithelial -specific (Il17raIEC) and liver-specific (Il17raLiv e r) IL-17RA knockout mice as well as littermate control mice. Our results indicate that intestinal IL-17RA signaling helps mediate systemic metabolic functions upon exposure to prolonged high-fat diet. Il17raIEC mice display impaired glucose metabolism, altered hormone and adipokine levels, increased visceral adiposity, and greater hepatic lipid deposition when compared with their littermate controls. We show that IL-17RA-driven changes in microbiota composition are responsible for regulating systemic glucose metabolism. Altogether, our data elucidate the importance of intestinal IL-17RA signaling in regulating high-fat diet -mediated systemic glucose and lipid metabolism