Innate lymphoid cells (ILCs) and CD4
T cells produce IL-22, which is critical for intestinal immunity. The microbiota is central to IL-22 production in the intestines; however, the factors that ...regulate IL-22 production by CD4
T cells and ILCs are not clear. Here, we show that microbiota-derived short-chain fatty acids (SCFAs) promote IL-22 production by CD4
T cells and ILCs through G-protein receptor 41 (GPR41) and inhibiting histone deacetylase (HDAC). SCFAs upregulate IL-22 production by promoting aryl hydrocarbon receptor (AhR) and hypoxia-inducible factor 1α (HIF1α) expression, which are differentially regulated by mTOR and Stat3. HIF1α binds directly to the Il22 promoter, and SCFAs increase HIF1α binding to the Il22 promoter through histone modification. SCFA supplementation enhances IL-22 production, which protects intestines from inflammation. SCFAs promote human CD4
T cell IL-22 production. These findings establish the roles of SCFAs in inducing IL-22 production in CD4
T cells and ILCs to maintain intestinal homeostasis.
T-cells are crucial in maintanence of intestinal homeostasis, however, it is still unclear how microbiota metabolites regulate T-effector cells. Here we show gut microbiota-derived short-chain fatty ...acids (SCFAs) promote microbiota antigen-specific Th1 cell IL-10 production, mediated by G-protein coupled receptors 43 (GPR43). Microbiota antigen-specific Gpr43
CBir1 transgenic (Tg) Th1 cells, specific for microbiota antigen CBir1 flagellin, induce more severe colitis compared with wide type (WT) CBir1 Tg Th1 cells in Rag
recipient mice. Treatment with SCFAs limits colitis induction by promoting IL-10 production, and administration of anti-IL-10R antibody promotes colitis development. Mechanistically, SCFAs activate Th1 cell STAT3 and mTOR, and consequently upregulate transcription factor B lymphocyte-induced maturation protein 1 (Blimp-1), which mediates SCFA-induction of IL-10. SCFA-treated Blimp1
Th1 cells produce less IL-10 and induce more severe colitis compared to SCFA-treated WT Th1 cells. Our studies, thus, provide insight into how microbiota metabolites regulate Th1 cell functions to maintain intestinal homeostasis.
Hydrogen (H)-bonds potentiate diverse cellular functions by facilitating molecular interactions. The mechanism and the extent to which H-bonds regulate molecular interactions are a largely unresolved ...problem in biology because the H-bonding process continuously competes with bulk water. This interference may significantly alter our understanding of molecular function, for example, in the elucidation of the origin of enzymatic catalytic power. We advance this concept by showing that H-bonds regulate molecular interactions via a hitherto unappreciated donor-acceptor pairing mechanism that minimizes competition with water. On the basis of theoretical and experimental correlations between H-bond pairings and their effects on ligand binding affinity, we demonstrate that H-bonds enhance receptor-ligand interactions when both the donor and acceptor have either significantly stronger or significantly weaker H-bonding capabilities than the hydrogen and oxygen atoms in water. By contrast, mixed strong-weak H-bond pairings decrease ligand binding affinity due to interference with bulk water, offering mechanistic insight into why indiscriminate strengthening of receptor-ligand H-bonds correlates poorly with experimental binding affinity. Further support for the H-bond pairing principle is provided by the discovery and optimization of lead compounds targeting dietary melamine and Clostridium difficile toxins, which are not realized by traditional drug design methods. Synergistic H-bond pairings have therefore evolved in the natural design of high-affinity binding and provide a new conceptual framework to evaluate the H-bonding process in biological systems. Our findings may also guide wider applications of competing H-bond pairings in lead compound design and in determining the origin of enzymatic catalytic power.
It has been shown recently that neutrophils are able to produce IL-22 and IL-17, which differentially regulate the pathogenesis of inflammatory bowel disease. However, it is still largely unknown how ...the neutrophil production of IL-22 and IL-17 is regulated, and their role in the pathogenesis of inflammatory bowel disease. In this study, we found that IL-23 promoted neutrophil production of IL-17 and IL-22. IL-23 stimulated the neutrophil expression of IL-23R as well as rorc and ahr. Retinoid acid receptor-related orphan receptor γ t and aryl-hydrocarbon receptor differentially regulated IL-23 induction of neutrophil IL-17 and IL-22. In addition, IL-23 induced the activation of mTOR in neutrophils. Blockade of the mTOR pathway inhibited IL-23-induced expression of rorc and ahr, as well as IL-17 and IL-22 production. By using a microbiota Ag-specific T cell-mediated colitis model, we demonstrated that depletion of neutrophils, as well as blockade of IL-22, resulted in a significant increase in the severity of colitis, thereby indicating a protective role of neutrophils and IL-22 in chronic colitis. Collectively, our data revealed that neutrophils negatively regulate microbiota Ag-specific T cell induction of colitis, and IL-23 induces neutrophil production of IL-22 and IL-17 through induction of rorc and ahr, which is mediated by the mTOR pathway.
G protein–coupled receptor (GPR) 120 has been implicated in regulating metabolic syndromes with anti-inflammatory function. However, the role of GPR120 in intestinal inflammation is unknown. Here, we ...investigated whether and how GPR120 regulates CD4+ T cell function to inhibit colitis development.
Dextran sodium sulfate (DSS)–induced colitis model, Citrobacter rodentium infection model, and CD4+ T cell adoptive transfer model were used to analyze the role of GPR120 in regulating colitis development. The effect of GPR120 on CD4+ T cell functions was analyzed by RNA sequencing, flow cytometry, and Seahorse metabolic assays. Mice were administered GPR120 agonist for investigating the potential of GPR120 agonist in preventing and treating colitis.
Deficiency of GPR120 in CD4+ T cells resulted in more severe colitis in mice upon dextran sodium sulfate insult and enteric infection. Transfer of GPR120-deficient CD4+CD45Rbhi T cells induced more severe colitis in Rag–/– mice with lower intestinal interleukin (IL) 10+CD4+ T cells. Treatment with the GPR120 agonist CpdA promoted CD4+ T cell production of IL10 by up-regulating Blimp1 and enhancing glycolysis, which was regulated by mTOR. GPR120 agonist-treated wild-type, but not IL10-deficient and Blimp1-deficient, T helper 1 cells induced less severe colitis. Furthermore, oral administration of GPR120 agonist protected mice from intestinal inflammation in both prevention and treatment schemes. Gpr120 expression was positively correlated with Il10 expression in the human colonic mucosa, including patients with inflammatory bowel diseases.
Our findings show the role of GPR120 in regulating intestinal CD4+ T cell production of IL10 to inhibit colitis development, which identifies GPR120 as a potential therapeutic target for treating inflammatory bowel diseases.
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Long-chain fatty acid receptor G protein–coupled receptor 120 induces interleukin 10 production in CD4+ T cells to inhibit colitis development through up-regulation of B lymphocyte–induced maturation protein 1 and enhancing glycolysis.
Although the development of T‐cell subsets is mainly regulated by a master transcriptional regulator and phosphorylation of the STAT protein in response to distinct cytokine stimulation, accumulating ...data indicate that other signaling pathways are also involved in regulating or fine‐tuning T‐cell lineage commitment. In this report, we investigated the role of ERK, mitogen‐activated protein kinase (MAPK), in Th17 and Treg cell development. We demonstrate that blockade of ERK activation inhibited Th17‐cell development while upregulating Treg cells under Th17 polarization conditions. Inhibition of ERK decreased IL‐6 induction of RAR‐related orphan receptor γt but enhanced TGF‐β induction of Foxp3, and ERK inhibitor‐treated T cells under Th17 conditions possessed suppressive function in vitro because they produced more IL‐10 and TGF‐β and inhibited naïve T‐cell proliferation and IFN‐γ production at levels comparable with that of Treg cells. Furthermore, ERK inhibitor‐treated T cells under Th17 polarization conditions had a decreased potency to induce colitis in vivo. Collectively, our data demonstrated that the ERK pathway differentially regulates Th17‐ and Treg‐cell differentiation, and thus interfering with the ERK pathway could represent a therapeutic treatment for inflammatory bowel diseases and other Th17‐related autoimmune diseases.
Differentiated CD4+ T cells preserve plasticity under various conditions. However, the stability of Th1 cells is unclear, as is whether Th1 cells can convert into Th17 cells and thereby contribute to ...the generation of IFN‐γ+IL‐17+CD4+ T cells, the number of which correlates with severity of colitis. We investigated whether IFN‐γ+Th1 cells can convert into Th17 cells under intestinal inflammation and the mechanisms involved. IFN‐γThy1.1+ Th1 cells were generated by culturing naïve CD4+ T cells from IFN‐γThy1.1 CBir1 TCR‐Tg reporter mice, whose TCR is specific for an immunodominant microbiota antigen, CBir1 flagellin, under Th1 polarizing conditions. IFN‐γThy1.1+ Th1 cells induced colitis in Rag−/− mice after adoptive transfer and converted into IL‐17+Th17, but not Foxp3+Treg cells in the inflamed intestines. TGF‐β and IL‐6, but not IL‐1β and IL‐23, regulated Th1 conversion into Th17 cells. TGF‐β induction of transcriptional factor Runx1 is crucial for the conversion, since silencing Runx1 by siRNA inhibited Th1 conversion into Th17 cells. Furthermore, TGF‐β enhanced histone H3K9 acetylation but inhibited H3K9 trimethylation of Runx1‐ and ROR‐γt‐binding sites on il‐17 or rorc gene in Th1 cells. We conclude that Th1 cells convert into Th17 cells under inflammatory conditions in intestines, which is possibly mediated by TGF‐β induction of Runx1.
Gut bacteria-derived short-chain fatty acids (SCFAs) play crucial roles in the maintenance of intestinal homeostasis. However, how SCFAs regulate epithelial turnover and tissue repair remain ...incompletely understood. In this study, we investigated how the SCFA propionate regulates cell migration to promote epithelial renewal and repair.
Mouse small intestinal epithelial cells (MSIE) and human Caco-2 cells were used to determine the effects of SCFAs on gene expression, proliferation, migration, and cell spreading in vitro. Video microscopy and single cell tracking were used to assess cell migration kinetically. 5-bromo-2’-deoxyuridine (BrdU) and hydroxyurea were used to assess the effects of SCFAs on migration in vivo. Lastly, an acute colitis model using dextran sulfate sodium (DSS) was used to examine the effects of SCFAs in vivo.
Using video microscopy and single cell tracking, we found that propionate promoted intestinal epithelial cell migration by enhancing cell spreading and polarization, which led to increases in both cell speed and persistence. This novel function of propionate was dependent on inhibition of class I histone deacetylases (HDAC) and GPR43 and required signal transducer and activator of transcription 3 (STAT3). Furthermore, using 5-bromo-2’-deoxyuridine (BrdU) and hydroxyurea in vivo, we found that propionate enhanced cell migration up the crypt-villus axis under homeostatic conditions, while also protecting against ulcer formation in experimental colitis.
Our results demonstrate a mechanism by which propionate stimulates cell migration in an HDAC inhibition, GPR43, and STAT3 dependent manner, and suggest that propionate plays an important role in epithelial migration independent of proliferation.
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Stimulator of interferon genes (STING) has been shown to play a critical role in orchestrating immune responses to various pathogens through sensing cyclic dinucleotides. However, how STING regulates ...intestinal homeostasis is still not completely understood. In this study, we found that STING−/− mice were more susceptible to enteric infection with Citrobacter rodentium compared to wild‐type (WT) mice evidenced by more severe intestinal inflammation and impaired bacterial clearance. STING−/− mice demonstrated lower expression of REG3γ but not β‐defensins and Cramp in IECs. Consistently, STING−/− IECs showed reduced capacity to inhibit bacterial growth. STING agonists, both 10‐carboxymethyl‐9‐acridanone (CMA) and 5,6‐dimethylxanthenone‐4‐acetic acid (DMXAA), promoted REG3γ expression IECs. Furthermore, STING agonists promoted WT but not REG3γ‐deficient IEC bacterial killing. Mechanistically, STING agonists activated STAT3 and promoted glycolysis in IECs. Inhibition of STAT3 pathway and glycolysis suppressed STING‐induced REG3γ production in IECs, and abrogated STING‐mediated IEC killing of C. rodentium. Additionally, treatment with the STING ligand, 2,3‐cGAMP, inhibited C. rodentium‐induced colitis in vivo. Overall, STING promotes IEC REG3γ expression to inhibit enteric infection and intestinal inflammation, thus, maintaining the intestinal homeostasis.
The lumen-dwelling protozoan
is an important parasitic cause of diarrheal disease worldwide. Infection can persist over extended periods with minimal intestinal inflammation, suggesting that
may ...attenuate host responses to ensure its survival, although clearance eventually occurs in most cases. IL-10 is an anti-inflammatory regulator critical for intestinal homeostasis and controlling host responses to bacterial exposure, yet its potential role in coordinating antiprotozoal host defense in the intestine is not known. In this study, we found that murine infection with the natural enteric pathogen
induced a transient IL-10 response after 2-4 wk at the primary site of infection in the upper small intestine, but parasite colonization and eradication were not affected by the absence of the cytokine in gene-targeted mice. However, IL-10 was critical for controlling infection-associated immunological sequelae in the colon because severe and persistent diarrhea and colitis were observed in IL-10-deficient mice within 1-2 wk postinfection but not in uninfected littermate controls. Inflammation was characterized by epithelial hyperplasia, neutrophil and macrophage expansion, and Th1 induction and could be prevented by blockade of IL-12/IL-23 p40 but not depletion of CD11c
dendritic cells. Furthermore, the intestinal microbiota underwent characteristic shifts in composition and was required for disease because antibiotics and loss of TLR signaling in MyD88-deficient mice protected against colitis. Together, our data suggest that transient infection by a luminal and seemingly noninflammatory pathogen can trigger sustained colitis in genetically susceptible hosts, which has broader implications for understanding postinfectious syndromes and other chronic intestinal inflammatory conditions.
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