The G-protein coupled bile salt receptor TGR5 is expressed in liver sinusoidal endothelial cells
The G-protein coupled bile salt receptor TGR5 is expressed in liver sinusoidal endothelial cells
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DOI：
10.1002/hep.21458
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发表时间：
2007-03-01
期刊：
影响因子：
13.5
通讯作者：
Kubitz, Ralf
中科院分区：
文献类型：
--
作者：
Keitel, Verena;Reinehr, Roland;Kubitz, Ralf
正弦内皮细胞（SEC）构成肝细胞和血液之间的可渗透屏障。 SEC 暴露于来自肠肝循环的高浓度胆汁盐。 SEC 是否对胆汁盐有反应尚不清楚。 TGR5 是一种 G 蛋白偶联胆汁酸受体，可触发 cAMP 形成，最近在巨噬细胞中被发现。在这项研究中，克隆了大鼠 TGR5，并开发了针对大鼠 TGR5 C 末端的抗体，该抗体在转染的 HepG2 细胞中检测到 TGR5 作为糖蛋白。除库普弗细胞外，大鼠肝脏 SEC 中还检测到了 TGR5。 SEC 在整个腺泡上表达 TGR5，而门静脉或中央静脉的内皮细胞对 TGR5 抗体没有免疫反应。在分离的 SEC 中，通过逆转录 (RT) PCR、免疫荧光显微镜和蛋白质印迹分析检测 TGR5 mRNA 和蛋白质。胆盐增加了分离的 SEC 中的 cAMP，并诱导内皮 NO 合酶 (eNOS)（一种已知的 cAMP 依赖性基因）的 mRNA 表达。此外，胆汁酸通过 eNOS 在氨基酸位置 1177 处的磷酸化来激活 eNOS。与 eNOS 激活一致，胆汁酸诱导肝切片中 NO 的产生。这是关于 TGR5 在 SEC 中表达的第一份报告。结论：数据表明 SEC 对特定胆汁盐有直接反应。 TGR5 对 SEC 中 eNOS 的调节将胆盐与肝脏血流动力学联系起来。当胆汁盐浓度增加时，这对于胆汁淤积性肝脏尤为重要。
Sinusoidal endothelial cells (SEC) constitute a permeable barrier between hepatocytes and blood. SEC are exposed to high concentrations of bile salts from the enterohepatic circalation. Whether SEC are responsive to bile salts is unknown. TGR5, a G-protein-coupled bile acid receptor, which triggers cAMP formation, has been discovered recently in macrophages. In this study, rat TGR5 was cloned and antibodies directed against the C-terminus of rat TGR5 were developed, which detected TGR5 as a glycoprotein in transfected HepG2-cells. Apart from Kupffer cells, TGR5 was detected in SEC of rat liver. SEC expressed TGR5 over the entire acinus, whereas endothelial cells of the portal or central veins were not immunoreactive toward TGR5 antibodies. In isolated SEC, TGR5 mRNA and protein were detected by reverse transcription (RT) PCR, immunofluorescence microscopy, and Western blot analysis. Bile salts increased cAMP in isolated SEC and induced mRNA expression of endothelial NO synthase (eNOS), a known cAMP-dependent gene. In addition, bile acids activated eNOS by phosphorylation of eNOS at amino acid position 1177. In line with eNOS activation, bile acids induced NO production in liver slices. This is the first report on the expression of TGR5 in SEC. Conclusion: The data suggest that SEC are directly responsive toward specific bile salts. Regulation of eNOS in SEC by TGR5 connects bile salts with hepatic hemodynamics. This is of particular importance in cholestatic livers when bile salt concentrations are increased.