Yarushkin Andrei A, Kazantseva Yuliya A, Kobelev Vyacheslav S, Pustylnyak Yuliya A, Pustylnyak Vladimir O
The Institute of Molecular Biology and Biophysics, Timakova str., 2/12, Novosibirsk 630117, Russia.
The Institute of Molecular Biology and Biophysics, Timakova str., 2/12, Novosibirsk 630117, Russia; Novosibirsk State University, Pirogova str., 1, Novosibirsk 630090, Russia.
Eur J Pharmacol. 2017 Feb 15;797:39-44. doi: 10.1016/j.ejphar.2017.01.016. Epub 2017 Jan 15.
Although NR1C3 agonists inhibit cell growth, the molecular mechanism of their action has not been thoroughly characterized to date. A recent study demonstrated that NR1C3 can regulate miR-122 by binding to its promoter. Given that miR-122 can indirectly regulate cMyc-mediated promitogenic signaling by targeting E2f1, we hypothesized that NR1C3 activation inhibits hepatocyte proliferation through miR-122-mediated cMyc downregulation. In the present study, we examined if liver hyperplasia induced by a strong chemical mitogen for the liver, 1,4-bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP), which is an agonist of NR1I3, can be repressed by NR1C3 activation through miR-122 upregulation. Acute TCPOBOP treatment caused a significant increase in liver-to-body weight ratio. The liver mass increase was accompanied with miR-122 downregulation. ChIP assays demonstrated that TCPOBOP-activated NR1I3 accumulated on the DR1 site in the pri-miR-122 promoter; and the NR1I3 accumulation is accompanied by a decrease in miR-122 and an increase in E2f1 and its transcription target cMyc. Rosiglitazone (Ros) treatment, which is an agonist of NR1C3, caused an opposite effect on liver-to-body weight ratio. When Ros was given with TCPOBOP, it attenuated the inhibitory effect of TCPOBOP on miR-122. Moreover, Ros treatment inhibited the NR1I3 binding with the DR1 site in the pri-miR-122 promoter. Furthermore, the increase of miR-122 produced by Ros was correlated with the downregulation of its targets, E2f1 and cMyc. Thus, our finding demonstrated that the liver growth inhibitory effect of NR1C3 activation was at least partly related to the decrease of cMyc though the activation of miR-122 and the downregulation of E2f1.
尽管NR1C3激动剂可抑制细胞生长，但迄今为止其作用的分子机制尚未得到充分阐明。最近一项研究表明，NR1C3可通过与miR-122启动子结合来调节miR-122。鉴于miR-122可通过靶向E2f1间接调节cMyc介导的促有丝分裂信号传导，我们推测NR1C3激活通过miR-122介导的cMyc下调来抑制肝细胞增殖。在本研究中，我们检测了由强效肝脏化学促有丝分裂剂1,4-双[2-(3,5-二氯吡啶氧基)]苯（TCPOBOP，一种NR1I3激动剂）诱导的肝脏增生是否可通过上调miR-122激活NR1C3来抑制。急性TCPOBOP处理导致肝体重比显著增加。肝脏重量增加伴随着miR-122下调。染色质免疫沉淀分析表明，TCPOBOP激活的NR1I3聚集在pri-miR-122启动子中的DR1位点；并且NR1I3聚集伴随着miR-122减少以及E2f1及其转录靶点cMyc增加。罗格列酮（Ros）处理作为NR1C3激动剂，对肝体重比产生相反的作用。当Ros与TCPOBOP同时给予时，它减弱了TCPOBOP对miR-122的抑制作用。此外，Ros处理抑制了NR1I3与pri-miR-122启动子中DR1位点的结合。此外，Ros产生的miR-122增加与其靶点E2f1和cMyc的下调相关。因此，我们的研究结果表明，激活NR1C3对肝脏生长的抑制作用至少部分与通过激活miR-122和下调E2f1导致的cMyc减少有关。
