Regulatory T Cells Restrict Permeability to Bacterial Antigen Translocation and Preserve Short‐Chain Fatty Acids in Experimental Cirrhosis

Abstract

Intestinal permeability to translocation of bacterial products is increased in cirrhosis. Regulatory T cells (Tregs) remain central to the interplay between the host and microbial milieu. We propose that Tregs are involved in promoting gut barrier integrity and a balanced interaction with gut microbiota–derived short‐chain fatty acids (SCFAs). Carbon tetrachloride cirrhosis was induced in wild‐type and recombination activating gene 1 (Rag1)‐/‐ mice. Naive T cells and Treg cells were transferred into Rag1 ‐/‐ mice. Intestinal permeability was assessed in vivo after lipopolysaccharide (LPS) oral administration, and bacterial DNA presence was evaluated in mesenteric lymph nodes. Transcript and protein levels of tight‐junction (TJ) proteins were measured in colonic tissue. Intestinal T helper profile in response to Escherichia coli (E. coli) was determined by flow cytometry. SCFAs were measured by gas chromatography–mass spectrometry in colonic content before and after E. coli challenge. Rag1 ‐/‐ mice showed significantly increased permeability to LPS and bacterial DNA translocation rate compared with control mice. Naive T and Treg cotransfer significantly reduced gut permeability to bacterial antigen translocation and restored TJ protein expression in Rag1 ‐/‐ mice. Naive T and Treg replenishment in Rag1 ‐/‐ mice restrained proinflammatory differentiation of intestinal lymphocytes in response to E. coli. The main SCFA concentration resulted in significant reduction in Rag1 ‐/‐ mice after E. coli administration but remained unaltered after naive T and Tregs cotransfer. The reduced expression of SCFA receptors induced by E. coli was reestablished following naive T and Treg reconstitution in Rag1 ‐/‐ mice. Conclusion: The restriction of gut permeability, local inflammatory differentiation, and loss of bacteria‐derived SCFAs foster the value of Tregs in preventing bacterial translocation in cirrhosis.

Circulating levels of butyrate are inversely related to portal hypertension, endotoxemia, and systemic inflammation in patients with cirrhosis

“…In fact, we have previously shown in mice with induced cirrhosis an association between reduction of SCFA levels, an alteration of the gut barrier integrity, and the increase of BT rates. The loss in serum levels of SCFAs in these mice can be inhibited by the reposition of the T reg cell tolerogenic activity, supporting an active role for these products in the interface between the immune system and gut microbiota (29).…”

Faecal microbiota from patients with cirrhosis has a low capacity to ferment non‐digestible carbohydrates into short‐chain fatty acids

“…SCFAs are one of the major aspects of the host‐microbiome metabolic axis, regulating several physiological processes such as metabolism, appetite, vascular tone and immune responses . Some specific effects of SCFA might be especially relevant in the context of cirrhosis.…”

“…SCFAs account for many physiological interactions between the gut microbiota and the host, that might be relevant in pathological situations including chronic liver disease . These include, among others, maintenance of gut barrier function, immune regulation, anti‐inflammatory effects and blood pressure regulation …”

Bacteroides uniformis combined with fiber amplifies metabolic and immune benefits in obese mice

“…Isolation of intraepithelial cells was conducted as previously described. 54 , 55 In brief, small intestine was washed with cold PBS and longitudinally opened and cut into small pieces. For the isolation of the epithelium, tissue was incubated twice in Hansk´s balanced salt solution with calcium and magnesium (HBSS; ThermoFisher Scientific, Massachusetts, USA) containing 5 mM EDTA (Scharlab), 1 mM DTT, 100 µg/ml streptomycin and 100 U/ml penicillin (Merck, Darmstadt, Germany) for 30 minutes at 37°C with orbital shaking.…”