Effect of Afzelin on 2,4,6-Trinitrobenzene Sulfonic Acid-Induced Colitis in Mice

Objective To investigate the role and mechanism of afzelin(AFZ)in treating Crohn's disease-like colitis.Methods A mouse model of 2,4,6-trinitrobenzene sulfonic acid-induced colitis was established to assess the effect of AFZ on experimental colitis in vivo.A Caco-2 cell model of tumor necrosis factor(TNF)-α-induced inflammation was established to evaluate the effects of AFZ on the intestinal barrier function,intestinal epithelial cell apoptosis,and mitochondrial function in vitro.The animal and cell experiments were performed to validate the regulatory role of the adenosine monophosphate-activated protein kinase(AMPK)/silent information regulater 1(SIRT1)/peroxisome proliferator-activated receptor gamma coactivator(PGC)-1α pathway in the treatment of colitis with AFZ.Results AFZ reduced the disease activity index(P=0.003),weight loss(P<0.001),colon shortening(P<0.001),inflammation score(P=0.002),pro-inflammatory cytokine release(interleukin-6:P<0.001;TNF-α:P=0.010),and intestinal barrier permeability(fluorescein isothiocyanate dextran 4:P<0.001;intestinal-type fatty acid-binding protein:P=0.013).Meanwhile,AFZ increased the colonic transepithelial electric resistance(P=0.001),reduced bacterial translocation(P<0.001),and promoted the localization and up-regulated the expression of tight junction proteins [zonula occluden-1(P=0.005) and Claudin-1(P=0.024)].AFZ exerted a protective effect on the Caco-2 cells exposed to TNF-α in terms of intestinal epithelial cell permeability(P=0.017),transepithelial electric resistance(P=0.014),and tight junction protein[zonula occluden-1(P=0.014) and Claudin-1(P=0.006)] localization and expression.Furthermore,the cell and animal experiments confirmed that AFZ reduced the percentage of apoptosis(P<0.001,P=0.013)and the expression of cleaved-caspase 3(P=0.028,P=0.004)and Bax(P=0.004,P=0.020),and upregulated the Bcl2(P=0.020,P=0.006)level in intestinal epithelial cells.Additionally,AFZ increased the number of mitochondria,mitochondrial membrane potential,and copy number of mitochondrial DNA(P=0.007)in intestinal epithelial cells,while enhancing the activities of mitochondrial respiratory chain complex Ⅰ(P=0.005)and complex Ⅳ(P=0.001).The activation of the AMPK/SIRT1/PGC-1α pathway was involved in the protective effects of AFZ on mitochondrial function and apoptosis in intestinal epithelial cells.Conclusion AFZ alleviates mitochondrial dysfunction and apoptosis in intestinal epithelial cells by activating the AMPK/SIRT1/PGC-1α pathway,thereby ameliorating intestinal barrier dysfunction and experimental colitis.