Effects Of Relief Of Obstructice Jaundice By Internal And External Biliary Drainage On Expression Of Bile Acid Receptor-TGR5 By Rat Kupffer Cells

[Background] Obstructive jaundice (OJ) is associated with a high postoperative complications and mortality. Internal biliary drainage (ID) could recover enterohepatic circulation of bile acid, and reduce endotoxin-related complications and infection rate more obviously than external biliary drainage (ED). The mechanism that ID is superior to ED in relief of OJ remains u nclear. Our precious study demonstrated that ID could reverse the endotoxemia, cytokines and the expression of iNOS mRNA and CD14 mRNA by Kupffer cells. Furthermore, the hydrophilic bile acid salt could prevent Kupffer cells from the affection of endotoxin and cytokine. TGR5 is a novel, membrane-bound bile acid receptor, and it has been suggested that the immunosuppressive effect of bile acids can be mediated by TGR5. We presume that bile acid as a signaling molecule could play a protective role in improving Kupffer cells'immune function by activating bile acid receptor. TGR5 may play an important role for Kupffer cells function and decrease cytokine release.[Aims] The aim of the present study was to explore the effects of relief of OJ by ID and ED on the expression of bile acid receptor-TGR5 and TGR5 mRNA by rat Kupffer cells in order to clarify the mechanism that ID was superior to ED in relief of OJ.[Methods] Male adult Sprague-Dawley rats were randomly assigned to four groups:obstructive jaundice (OJ; n=17), sham operation (SH; n=20), internal biliary drainage (ID; n=14) and external drainage (ED; n=15). Rat models were successfully established by twice operations. OJ was induced by common bile duct (CBD) ligation and division. SH was produced by separating CBD locally but not dividing. ED was performed by exteriorizing a drainage tube at the nape of the rat, while ID was performed by implanting a drainage tube between the dilated end of CBD and duodenum on the 8th day after the first operation. The rats of OJ and SH groups were succumbed and specimen such as livers were taken on the 8th day, but ID and ED groups were on the 15th day. Kupffer cells were isolated by in situ hepatic perfusion and digestion with collagen IV, density gradient centrifuged by Percoll reagent and purified by cell culture attachment. The TGR5 expression in liver tissue was determined by immunohistochemical method and the expression of TGR5 mRNA by the Kupffer cells was detected by Real-time Quantitative Polymerase Chain Reaction (RTQ-PCR)[Results] TGR5 was detected in the plasma membrane and in some intracellular compartments of Kupffer cells, and in the plasma membrane of some sinusoidal endothelial cells and bile ducts'endothelial cells. The expression of TGR5 by Kupffer cells was significantly stronger in OJ group (0.5134±0.0701) (MOD=IOD/area) than that in SH group (0.3050±0.0998) (P=0.001). The expression of TGR5 was significantly downregulated by ID (0.3556±0.0508) (ID vs OJ, P=0.001) and there was no difference between ID group and SH group (ID vs SH, P=0.22), but it cannot be inhibited by ED (0.4389±0.0782)(ED vs OJ, P=0.062). The expression of TGR5 mRNA by Kupffer cells was significantly stronger in OJ group (1.0244±0.3248) (2-AACt) than that in SH group (0.1327±0.0452) (P=0.001). There was no significant difference between ID group (0.3198±0.1147) and SH group (P=0.354). It was significantly stronger in ED group (0.6322±0.2332) compared with that in SH group (P=0.001), and there was significant difference between ED group and OJ group(P=0.003).[Conclusion] The expression of TGR5 and TGR5 mRNA by Kupffer cells were upregulated in OJ rats. ID is superior to external drainage in reversing the changes. These findings indicate that the mechanism of internal biliary drainage is superior to external drainage in relief of obstructive jaundice seems to be based on the regulation process of TGR5 genes.