脆弱拟杆菌六型分泌系统对肠道屏障的影响及机制OA北大核心CSTPCD

[Objective]To investigate the effect and mechanism of Bacteroides fragilis type Ⅵ protein secretion system(T6SS)on the intestinal barrier.[Method]Suicide vector was used to construct B.fragilis T6SS mutant strain.The dextran sulfate sodium(DSS)salt-induced colitis mouse model was constructed,and supplemented mice with PBS,B.fragilis WT,and B.fragilis ΔT6SS,respectively.The disease characters and intestinal barrier integrity were compared among the three groups.Quantitative PCR and immunohistochemistry were used to detect the expressions of tight junction proteins.Untargeted metabolomics was used to compare gut differential metabolites in each group of mice.[Result]The deletion of T6SS did not affect bio-viability of B.fragilis.B.fragilis WT showed the improvements in body weight loss and colon length compared to PBS controls,demonstrating the protection to DSS-induced colitis;while this protection was lost with the absence of T6SS.The fluorescein isothiocyanate dextran concentration in the mouse serum and histological examination in intestinal pathological sections indicated that B.fragilis T6SS improved the integrity of the intestinal barrier in mice.T6SS mutation affected intestinal tight junction protein expression,confirmed by quantitative PCR and immunohistochemistry.Untargeted metabolomics analysis revealed 96 up-regulated differentially expressed metabolites in the B.fragilis WT group,compared to the B.fragilis ΔT6SS group,with multiple metabolites enriched in cholinergic synaptic metabolism and glycerophospholipid metabolism-related pathways.[Conclusion]B.fragilis T6SS alters intestinal metabolome and increases the expression of tight junction protein in intestinal cells,thus improving the permeability of intestinal barrier,being involved in the protection of B.fragilis to the intestinal barrier.