基于Nrf2-UGT2B7/BSEP/MRP2通路研究熊果酸与齐墩果酸抗肝损伤作用机制

The acute hepatic injury often company with the retention and accumulation of bile acids, which in turn aggravate ongoing liver injury processes. Stimulation of bile acids secretion may be an effective strategy for protecting against the additional liver injury. Bile acids are secreted into blie via ATP-dependent bile salt excretory pump (BSEP) and multiple drug resistant proteins (MRPs) after being metabolized by UGT2B7 in liver. The expression of UGT2B7, BSEP and MRP2 was regulated by the transcription factor of nuclear factor erythroid 2-related factor 2 (Nrf2). Many studies demonstrated that ursolic acid(UA) and oleanolic acid(OA) have significant activation on Nrf2. UA and OA are isomers, and well known for their hepatoprotective effects for both acute chemically induced liver injury and chronic liver fibrosis and cirrhosis. Little is known about the mechanism. Therefore, we hypothesize that UA and OA can against hepatotoxins through the Nrf2- UGT2B7/BSEP/MRP2 signal pathway. Both of them can activate the nuclear receptor Nrf2, and upregulate the gene expression of UGT2B7/BSEP/MRP2, promote the efflux of bile acid, and against the liver damages. In the project, we will investigate the changes in the expression and activation of Nrf2, UGT2B7, BSEP, MRP2 in cells or tissues, the change of hepatic function in rats and the concentration of bile acid in plasma by using primary human hepatocytes, HepG2 and HEK293T cells, the animal model of liver injury, transient transfection with plasmid construct, and gene silencing technology.

急性肝损伤时可因胆汁淤积及胆汁酸储留产生毒性加重肝损害，促进胆汁酸外排可有效地改善肝损伤状态。业已证实，胆汁酸经肝脏UGT2B7代谢后由胆道BSEP与MRP2介导排泄，可见UGT2B7/BSEP/MRP2的表达与胆汁酸外排密切关联。诸多研究表明，UGT2B7/BSEP/MRP2的表达受核受体Nrf2调控，熊果酸（UA）与齐墩果酸（OA）均对核受体Nrf2有着明确的激活效应和显著的护肝作用，此药效是否为激活Nrf2，上调UGT2B7/BSEP/MRP2基因表达，进而促进胆汁酸外排所致尚属未知却值得深入探究。本课题拟采用HepG2与HEK293T等细胞模型及质粒构建瞬时共转染与基因沉默技术，研究UA和OA干预对细胞或组织中Nrf2、UGT2B7、BSEP、MRP2表达的影响及血浆胆汁酸浓度的变化，深入阐明UA和OA基于Nrf2-UGT2B7/BSEP/MRP2调控通路的抗肝损伤作用新机制。