Swertiamarin ameliorates 2,4,6-trinitrobenzenesulfonic acid-induced colitis in mice by inhibiting intestinal epithelial cell apoptosis
Objective To investigate the mechanism by which swertiamarin(STM)ameliorates CD-like colitis in mice.Methods A Caco-2 cell model of TNF-α-stimulated apoptosis was established and divided into three groups:Con,TNF-α and STM,and the effects of STM on apoptosis and barrier function were assessed by Tunel staining,western blotting,immunofluorescence,and transepithelial electric resistance(TEER).A mouse model of 2,4,6-trinitrobenzenesulfonic acid(TNBS)-induced CD-like colitis was established to assess the effects of STM on colitis,intestinal barrier function and epithelial cell apoptosis.The regulatory role of the PI3K/AKT pathway in STM-induced resistance to intestinal epithelial cell apoptosis was investigated in both the cell model and mouse models.Results TUNEL staining showed that in Caco-2 cells with TNF-α stimulation,STM treatment significantly reduced the percentage of TUNEL-stained cells(P<0.05).STM obviously reduced TNF-α-induced enhancement of cleaved-caspase 3 and Bax expressions(P<0.05),increased Bcl-2 expression(P<0.05),protected intestinal barrier integrity and function by restoring transepithelial electrical resistance(TEER)of the cells,promoted normal localization and expressions of the tight junction proteins(ZO1 and claudin 1)(P<0.05),and inhibited the expression of pro-inflammatory factors(IL-6 and CCL3)(P<0.05)in TNF-α-stimulated Caco-2 cells.In the mouse models,STM significantly alleviated TNBS-induced CD-like colitis and intestinal barrier dysfunction(P<0.05)as shown by improved weight loss,lowered Disease Activity Index(DAI)score and inflammation score,reduction of IL-6 and CCL3 release,and restoration of intestinal barrier permeability,colonic TEER,bacterial translocation,and localization and expressions of the tight junction proteins.Mechanistically,STM inhibited the expressions of p-PI3K and p-AKT in both the cell model and mouse model(P<0.05),and treatment with 740Y-P(a PI3K/AKT pathway activator)significantly attenuated the inhibitory effect of STM on TNF-α-induced apoptosis in Caco-2 cells(P<0.05).Conclusion STM inhibits intestinal epithelial cell apoptosis at least in part by suppressing activation of the PI3K/AKT pathway to ameliorate intestinal barrier dysfunction and colitis in mice.
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