Intestinal epithelial damage-derived mtDNA activates STING-IL12 axis in dendritic cells to promote colitis.

Rationale: The treatment of ulcerative colitis (UC) presents an ongoing clinical challenge. Emerging research has implicated that the cGAS-STING pathway promotes the progression of UC, but conflicting results have hindered the development of STING as a therapeutic target. In the current study, we aim to comprehensively elucidate the origins, downstream signaling and pathogenic roles of myeloid STING in colitis and colitis-associated carcinoma (CAC). Methods: Tmem173 fl/fl Lyz2-Cre ert2 mice were constructed for inducible myeloid-specific deletion of STING. RNA-sequencing, flow cytometry, and multiplex immunohistochemistry were employed to investigate immune responses in DSS-induced colitis or AOM/DSS-induced carcinogenesis. Colonic organoids, primary bone marrow derived macrophages and dendritic cells, and splenic T cells were used for in vitro studies. Results: We observed that myeloid STING knockout in adult mice inhibited macrophage maturation, reduced DC cell activation, and suppressed pro-inflammatory Th1 and Th17 cells, thereby protecting against both acute and chronic colitis and CAC. However, myeloid STING deletion in neonatal or tumor-present mice exhibited impaired immune tolerance and anti-tumor immunity. Furthermore, we found that TFAM-associated mtDNA released from damaged colonic organoids, rather than bacterial products, activates STING in dendritic cells in an extracellular vesicle-independent yet endocytosis-dependent manner. Both IRF3 and NF-κB are required for STING-mediated expression of IL-12 family cytokines, promoting Th1 and Th17 differentiation and contributing to excessive inflammation in colitis. Conclusions: Detection of the TFAM-mtDNA complex from damaged intestinal epithelium by myeloid STING exacerbates colitis through IL-12 cytokines, providing new evidence to support the development of STING as a therapeutic target for UC and CAC.

Si-Ni-San improves experimental colitis by favoring Akkermensia colonization.

ETHNOPHARMACOLOGICAL RELEVANCE: Ulcerative colitis (UC) is widely believed to be a leading risk factor of colorectal cancer. Gut microbiota is a known vital player in the progression of UC. Si-Ni-San (SNS) has been considered to effectively treat colitis in clinical practice during thousands of years, yet whether SNS ameliorated acute colitis mouse model by modulating intestinal flora has not been distinctly elucidated. AIM OF THE STUDY: Our study aimed to elucidate the effect of SNS against acute murine colitis and focused on the underlying mechanisms of SNS targeting gut microbiota. MATERIALS AND METHODS: 16S RNA sequencing, molecular biological analysis, and fecal microbiota transplants (FMT) were conducted to reveal the mechanisms of SNS in regulating gut microbiota. RESULTS: In our study, SNS dramatically inhibited DSS-induced acute inflammatory responses by improving gut microbiota dysbiosis, as evidenced by decreased abundance proinflammatory species, upregulated abundance of anti-inflammatory species and potentially altered microbiota metabolite metabolism. Additionally, intestinal flora knockout and FMT experiments confirmed that the therapeutic effect of SNS on colitis was dependent on gut microbiota, and specifically on favoring the growth of potential probiotics, Akkermansia genus. Furthermore, we found that SNS alone and SNS combined with Akkermansia muciniphila (A. muciniphila) increased Mucin 2 (MUC2) production, thus enhancing the competitive edge of A. muciniphila among pathogenic gut microbiota. CONCLUSION: Our study shed lights on the underlying mechanism of SNS in attenuating acute murine colitis from the perspective of intestinal flora and provides novel insights into the discovery of adjacent therapeutic strategy against colitis based on SNS and probiotics. CLASSIFICATION: Gastro-intestinal system.

Total glucosides of paeony alleviates scleroderma by inhibiting type I interferon responses.

ETHNOPHARMACOLOGICAL RELEVANCE: Type I interferon (IFN) is believed to play a pathogenic role in systemic sclerosis (SSc, also called scleroderma), which is an autoimmune rheumatic disease. Our previous studies have found that Chinese medicine formula Si-Ni-San (SNS, composed of Glycyrrhiza uralensis Fisch., Bupleurum chinense DC., Paeonia lactiflora Pall., and Citrus aurantium L.) had inhibitory effects on type I IFN responses. Among these herbal products, Paeonia lactiflora Pall. has been traditionally used to treat inflammation-related diseases, yet its therapeutic effects against type I IFN-related diseases and potential bioactive ingredients are not characterized. AIM OF THE STUDY: We aim to identify bioactive ingredient with anti-type I IFN activity from herbal products in SNS and further elucidate its therapeutic effect against scleroderma and underlying mechanisms. MATERIALS AND METHODS: We constructed a Gaussia-luciferase (Gluc) reporter assay system to identify ingredients with anti-type I IFN activities from SNS. In RAW264.7 cells, real-time PCR (RT-PCR) and western blotting were used to investigate the induction of type I IFN pathway. Additionally, in a bleomycin (BLM)-induced experimental scleroderma model, the expression of fibrotic genes, type I IFN-related genes, inflammatory cytokines, and cytotoxic granules were measured by RT-PCR, and the histopathological changes were determined by H&E staining, Masson's staining and immunohistochemistry analysis. RESULTS: Our data demonstrated that total glucosides of paeony (TGP) was the bioactive component of SNS that selectively inhibited TLR3-mediated type I IFN responses and blocked type I IFN-induced downstream JAK-STAT signaling pathways. In the BLM-induced scleroderma mouse model, TGP ameliorated skin fibrosis by inhibiting multiple targets in the upstream and downstream of type I IFN signaling. Further research found that TGP hindered polarization of M2 macrophages and their profibrotic effects and reduced cytotoxic T lymphocytes and their cytotoxic granules by suppressing Cxcl9 and Cxcl10 in the skin tissue of scleroderma mice. CONCLUSIONS: Our study not only sheds novel lights into the immunoregulative effects of TGP but also provides convincing evidence to develop TGP-based therapies in the treatment of scleroderma and other autoimmune diseases associated with type I IFN signatures. CLASSIFICATION: Skin.

Decoding the role of immune T cells: A new territory for improvement of metabolic-associated fatty liver disease.

Metabolic-associated fatty liver disease (MAFLD) is a new emerging concept and is associated with metabolic dysfunction, generally replacing the name of nonalcoholic fatty liver disease (NAFLD) due to heterogeneous liver condition and inaccuracies in definition. The prevalence of MAFLD is rising by year due to dietary changes, metabolic disorders, and no approved therapy, affecting a quarter of the global population and representing a major economic problem that burdens healthcare systems. Currently, in addition to the common causative factors like insulin resistance, oxidative stress, and lipotoxicity, the role of immune cells, especially T cells, played in MAFLD is increasingly being emphasized by global scholars. Based on the diverse classification and pathophysiological effects of immune T cells, we comprehensively analyzed their bidirectional regulatory effects on the hepatic inflammatory microenvironment and MAFLD progression. This interaction between MAFLD and T cells was also associated with hepatic-intestinal immune crosstalk and gut microbiota homeostasis. Moreover, we pointed out several T-cell-based therapeutic approaches including but not limited to adoptive transfer of T cells, fecal microbiota transplantation, and drug therapy, especially for natural products and Chinese herbal prescriptions. Overall, this study contributes to a better understanding of the important role of T cells played in MAFLD progression and corresponding therapeutic options and provides a potential reference for further drug development.

Si-Wu-Tang ameliorates bile duct ligation-induced liver fibrosis via modulating immune environment.

Si-Wu-Tang (SWT), a traditional Chinese medicine formula firstly recorded from the Tang dynasty, has been reported to alleviate gynecological and liver diseases. We preliminarily demonstrated that SWT could improve liver fibrosis via modulating intestinal microbiota, but little was known about the mechanisms linking its therapeutic effects to the reshaped immune microenvironment within fibrotic livers. Thus, we established a bile duct ligation (BDL)-induced liver fibrosis murine model to evaluate the hepatoprotective effects and potential mechanisms of SWT. The high-performance liquid chromatography, RNA sequencing and other molecular biological techniques were also performed in our study. Our data demonstrated that SWT significantly improved BDL-induced liver fibrosis and inflammatory responses by inhibiting the expression of genes associated with extracellular matrix synthesis and degradation. Combined with the analysis of immune cell infiltration and gene set enrichment analysis (GSEA), we found that SWT remarkably repaired the unbalanced immune microenvironment by modulating the biological functions of different immune cells, especially for macrophages, neutrophils and CD8+ T cells. In addition, SWT significantly inhibited the activation of M2-like macrophages to reduce the release of profibrotic-cytokines and prevented the activation of neutrophils to suppress neutrophil extracellular trap formation. SWT also efficiently promoted the apoptosis of activated hepatic stellate cells via Fas/FasL signaling pathway, which might be mediated by CD8+ tissue-resident memory T cells. In conclusion, our research not only unraveled the intricate mechanisms underlying the hepatoprotective activities of SWT against liver fibrosis but also provided a novel therapeutic strategy for the treatment of liver fibrosis and its relative complications.

Shouhui Tongbian Capsule ameliorates constipation via gut microbiota-5-HT-intestinal motility axis.

Constipation has become an epidemic enteric medical problem, accompanied with increasing long-term sequelae. Gut microbiota and serotonin (5-HT) have been believed as predominant player in the treatment of constipation. In clinical practices, Shouhui Tongbian Capsule (SHTB) was found to effectively improve constipation symptoms and promote gastrointestinal motility. However, the specific mechanism of SHTB is not clearly elucidated. Our current study aims to explore the therapeutic effects of SHTB against the development of constipation and the underlying mechanisms related to gut bacterial and 5-HT. We established loperamide hydrochloride (LH)-induced experimental constipation mouse model to evaluate the effect of SHTB. 16S RNA sequencing, fecal microbiota transplants (FMT), high performance liquid chromatograph, and molecular biological analysis were performed to investigate the potential mechanisms of SHTB. Our data demonstrated that SHTB significantly ameliorated LH-induced experimental constipation and accelerated enteric motility via promoting 5-HT biosynthesis in enterochromaffin cells and enteric neuron growth of the enteric nervous system (ENS) in both the small intestine and colon. Additionally, SHTB significantly modulated gut microbiota dysbiosis and potentially altered microbiota metabolites to enhance intestinal 5-HT production. Finally, FMT study confirmed that the effects of SHTB on 5-HT production and constipation are dependent on modulating intestinal microbiota dysbiosis. In conclusion, our current study deciphered therapeutic mechanism of SHTB in the treatment of experimental constipation from perspectives of gut microbiota-5-HT-intetinal motility axis and provides novel insights into the appropriate and safe application of SHTB in the clinic.