1. Department of Pharmacology, Harbin Medical University (the State-Province Key Laboratories of Biomedicine-Pharmaceutics of China), Harbin, People's Republic of China, 150081.
3. Electron Microscopy Center, Harbin Medical University, Harbin, People's Republic of China, 150081.
Int J Biol Sci. 2015 Feb 15;11(4):390-403. doi: 10.7150/ijbs.10930. eCollection 2015.
Increased incidence of arrhythmias in women after menopause has been widely documented, which is considered to be related to estrogen (E2) deficiency induced cardiac electrophysiological abnormalities. However, its molecular mechanism remains incompletely clear. In the present study, we found cardiac conduction blockage in post-menopausal rats. Thereafter, the results showed that cardiac gap junctions were impaired and Connexin43 (Cx43) expression was reduced in the myocardium of post-menopausal rats. The phenomenon was also observed in ovariectomized (OVX) rats, which was attenuated by E2 supplement. Further study displayed that microRNA-23a (miR-23a) level was significantly increased in both post-menopausal and OVX rats, which was reversed by daily E2 treatment after OVX. Importantly, forced overexpression of miR-23a led to gap junction impairment and Cx43 downregulation in cultured cardiomyocytes, which was rescued by suppressing miR-23a by transfection of miR-23a specific inhibitory oligonucleotide (AMO-23a). GJA1 was identified as the target gene of miR-23a by luciferase assay and miRNA-masking antisense ODN (miR-Mask) assay. We also found that E2 supplement could reverse cardiac conduction blockage, Cx43 downregulation, gap junction remodeling and miR-23a upregulation in post-menopausal rats. These findings provide the evidence that miR-23a mediated repression of Cx43 participates in estrogen deficiency induced damages of cardiac gap junction, and highlights a new insight into molecular mechanism of post-menopause related arrhythmia at the microRNA level.
绝经后女性心律失常的发生率增加已得到广泛证实，这被认为与雌激素（E2）缺乏引起的心脏电生理异常有关。然而，其分子机制尚不完全清楚。在本研究中，我们发现绝经后大鼠存在心脏传导阻滞。此后，结果表明，绝经后大鼠心肌中的心脏缝隙连接受损，连接蛋白 43（Cx43）表达减少。在卵巢切除（OVX）大鼠中也观察到这种现象，E2 补充可减轻这种现象。进一步的研究显示，miR-23a（miR-23a）水平在绝经后和 OVX 大鼠中均显著升高，OVX 后每日 E2 处理可逆转这种升高。重要的是，miR-23a 的强制过表达导致培养的心肌细胞中的缝隙连接受损和 Cx43 下调，通过转染 miR-23a 特异性抑制寡核苷酸（AMO-23a）抑制 miR-23a 可挽救这种下调。GJA1 通过荧光素酶测定和 miRNA 遮蔽反义寡核苷酸（miR-Mask）测定被鉴定为 miR-23a 的靶基因。我们还发现，E2 补充可逆转绝经后大鼠的心脏传导阻滞、Cx43 下调、缝隙连接重塑和 miR-23a 上调。这些发现为 miR-23a 介导的 Cx43 抑制参与雌激素缺乏诱导的心脏缝隙连接损伤提供了证据，并从 miRNA 水平强调了绝经后相关心律失常的分子机制的新见解。
