| AimsUlcerative colitis(UC)is a common digestive disease,UC-related hepatobiliary abnormality has been one of the serious complications of UC,which has been the key factor influencing the mortality of UC.Previous studies have shown that the occurrence of UC-related hepatobiliary abnormality may have close correlation with intrahepatic cholestasis.The aim of this study was to investigate the pathogenesis mechanism of UC-related cholestasis via studying bile acids synthesis,transportation,and the regulatory effect of gut-liver axis.MethodsUC model was developed in rats by rectal administration of TNBS solution.The composition and concentration of bile acids in the liver and content of small intestine were determined by LC-MS/MS;the hepatic content of total bile acids and the serum level of alkaline phosphatase(ALP),glutamyl transpeptidase(GGT),alanine aminotransferase(ALT),as well as aspartate aminotransferase(AST)were tested using biochemical kits;the protein expression of bile acid-related enzymes cholesterol 7α-hydroxylase(Cyp7a1)and sterol 27α-hydroxylase(Cyp27a1)in the liver and bile acid-related transporters,such as Na+/taurocholate Cotransporting Polypeptide(Ntcp),multidrug resistance-associated protein 2(Mrp2),multidrug resistance-associated protein 4(Mrp4),bile salt export pump(Bsep)and apical sodium-dependent bile acid transporter(Asbt),as well as nuclear receptor pregnane X receptor(PXR),constitutive androstane receptor(CAR)and farnesoid receptor(FXR)of UC rats were evaluated respectively by Western Blot technique;the levels of fibroblast growth factor-15(Fgf15)in serum were measured using Elisa kit,and the expression of Fgf15 mRNA level in ileum were determined by RT-qPCR.In addition,UC rats were orally administered with sulfasalazine(SASP,300 mg/kg),the indicators mentioned above were further investigated to evaluate the effect of SASP on bile acids synthesis,transportation,and gut-liver regulation.Results1.The serum level of ALP and GGT were marked increased in UC rats(P<0.05).The content of total bile acids as well as the level of CA and DCA in the liver of UC rats were significantly increased(P<0.05);indicating that there was an intrahepatic cholestasis in UC rats.2.The expression of bile acid-related enzymes Cyp7a1 and Cyp27a1 were significantly increased in the liver of UC rats(P<0.05);and the expression of bile acid receptor Fxr and bile acid efflux transporters Mrp2 and Bsep in the liver were all markedly decreased in UC rats(P<0.05);suggesting the increase of bile acids synthesis and decrease of bile acids efflux in UC rats.3.The expression of bile acids reabsorption transporter Asbt in the terminal ileum of UC rats was marked decreased(P<0.05),the expression of Fxr in the ileum was markedly increased(P<0.05),the mRNA expression of Fgf15 in ileum as well as serum level of Fgf15 of UC rats were significantly decreased(P<0.05),indicating the down-regulation of " gut-liver " axis Asbt-Fxr-Fgf15 signal pathway in UC rats.4.Treatment of UC rats with sulfasalazine(SASP),the hepatic total bile acids as well as the serum level of ALP and GGT were all markedly reduced when compared to that of the UC group(P<0.05),indicating that SASP can improve the intrahepatic cholestasis in UC rats.And,after administration of SASP,the ileum expression of Asbt as well as serum Fgf15 level in SASP-treated rats were all significantly increased(P<0.05);the hepatic expression of Cyp7a1 was significantly decreased(P<0.05),and the expression of Mrp2 was remarkably increased(P<0.05).These results all indicated that SASP treatment can improve UC-related intrahepatic cholestasis.ConclusionsObvious intrahepatic cholestasis was observed in TNBS-induced UC rats,which may result from the increased synthesis and reduced efflux of bile acids in the liver,the down-regulated Asbt-Fxr-Fgf15 signal pathway in “gut-liver” axis may contribute to this alterations.UC-related colon damage as well as UC-related intrahepatic cholestasis were all significantly improved after administration of SASP,indicating that SASP has therapeutic effect on UC-related intrahepatic cholestasis.This study provides preliminary information about the pathogenesis mechanism of UC-related intrahepatic cholestasis,which may give clues for understanding the pathogenesis mechanism as well as provide novel therapeutic target for UC-related hepatobiliary abnormalities. |
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