1st Department of Internal Medicine, Gastroenterology, and Hepatology, University Medical Center, Johannes Gutenberg-University, Mainz, Germany.
Institute of Translational Immunology, Fibrosis and Metabolism Center, Johannes Gutenberg-University, Mainz, Germany.
Am J Physiol Gastrointest Liver Physiol. 2019 Aug 1;317(2):G195-G202. doi: 10.1152/ajpgi.00088.2019. Epub 2019 Jun 26.
Organic cation transporters (OCT) are responsible for the intracellular uptake and detoxification of a broad spectrum of endogenous and exogenous substrates. OCTs are downregulated in cholestasis, fibrosis, and hepatocellular carcinoma, but the underlying molecular mechanisms and downstream effects of OCT deletion are unknown. Oct3-knockout (; ) and wild-type (WT; ) mice were subject to escalating doses of carbon tetrachloride (CCl) or thioacetamide (TAA) for 6 wk to induce advanced parenchymal liver fibrosis. Secondary biliary fibrosis was generated by bile duct ligation. Liver fibrosis was assessed by hydroxyproline determination, quantitative Sirius red morphometry, and quantitative real-time PCR for fibrosis and inflammation-related genes. Ductular reaction was assessed by bile duct count per field of view in hematoxylin and eosin staining. General gene expression analyses were performed in liver tissue from untreated and WT mice. Finally, primary murine hepatocytes were treated with the nonselective OCT inhibitor quinine, and transforming growth factor-β1 () protein expression was quantified by quantitative real-time PCR and Western blot. mice developed significantly more fibrosis after bile duct ligation and CCl treatment compared with WT mice. Ductular reaction was enhanced in the long-term model. Concomitantly, Oct1 mRNA expression was downregulated during cholestatic and chemically (TAA and CCl) induced fibrogenesis. The downregulation of Oct1 mRNA in fibrotic liver tissue reversed within 4 wk after TAA cessation. Gene expression analysis by next-generation sequencing revealed an enrichment of target genes in mice. mRNA expression was significantly upregulated after chemically induced fibrosis ( < 0.001) in compared with WT mice. Accordingly, in primary murine hepatocytes functional inhibition of OCT led to an upregulation of mRNA expression. Loss of Oct3 promotes fibrogenesis by affecting -mediated homeostasis in mice with chronic biliary and parenchymal liver damage and fibrosis. We show for the first time that organic cation transporter 3 (Oct3) is not only downregulated in fibrosis but loss of Oct3 also leads to an upregulation of transforming growth factor-β contributing to fibrosis progression.
有机阳离子转运体（OCT）负责摄取和解毒广泛的内源性和外源性底物。OCT 在胆汁淤积、纤维化和肝细胞癌中下调，但 OCT 缺失的潜在分子机制和下游影响尚不清楚。Oct3 敲除（; ）和野生型（WT； ）小鼠接受递增剂量的四氯化碳（CCl）或硫代乙酰胺（TAA）治疗 6 周，以诱导晚期实质肝纤维化。次级胆管纤维化通过胆管结扎产生。羟脯氨酸测定、定量天狼猩红形态计量学和纤维化和炎症相关基因的定量实时 PCR 评估肝纤维化。通过苏木精和伊红染色中每个视野的胆管计数评估胆小管反应。在未处理的和 WT 小鼠的肝组织中进行了一般基因表达分析。最后，用非选择性 OCT 抑制剂奎宁处理原代小鼠肝细胞，并通过定量实时 PCR 和 Western blot 定量转化生长因子-β1（）蛋白表达。与 WT 小鼠相比，在胆管结扎和 CCl 处理后，小鼠发生的纤维化明显更多。长期模型中胆小管反应增强。同时，在胆汁淤积和化学（TAA 和 CCl）诱导的纤维化过程中，Oct1 mRNA 表达下调。TAA 停止后 4 周内，纤维化肝组织中 Oct1 mRNA 的下调逆转。下一代测序的基因表达分析显示，纤维化肝组织中富含靶基因。与 WT 小鼠相比，化学诱导纤维化后（<0.001）小鼠的 mRNA 表达显著上调。相应地，在原代小鼠肝细胞中，OCT 的功能抑制导致 mRNA 表达上调。Oct3 的缺失通过影响慢性胆汁淤积和实质肝损伤和纤维化小鼠中的平衡来促进纤维化。我们首次表明，有机阳离子转运体 3（Oct3）不仅在纤维化中下调，而且 Oct3 的缺失也会导致转化生长因子-β的上调，从而促进纤维化的进展。
