运动锻炼对雌激素缺乏模型心脏保护作用的分子机制——microRNAs的作用

Premenopausal women have a much lower incidence and mortality of coronary heart disease (CHD)than postmenopausal women. However, there is still a lack of safe treatment strategy. Exercise training has been implicated to be one of the non-pharmaceutical strategy for prevention of CRH in premenopausal women. In the preliminary study, we have obtained miRNAs (miRs) expression profiling of primary cultured rdiomyocytes treated by estrogen, and found that estrogen significantly downregulated miR-22 expression, whereas upregulated miR-494 and miR-181c expression. In order to clarify whether estrogen and exercise training modulate these miRs in myocardium of adult rats in vivo, we further examined the effects of estrogen treatment and exercise training on miRs expressions in the myocardium of ovariectomized (OVX) rats. It was found that OVX resulted in an increase in miR-22 expression, as well as decreases in miR-494 and miR-181c, and these effects were significantly reversed by both estrogen replacement therapy and exercise training. Using bioinformatics analysis, we found that these miRs targeted a series of genes associated with maintenance of mitochondrial function, such as peroxisome proliferator-activated receptor (PPAR)-alpha, PPAR-gamma coactivator 1 (PGC-1)-alpha, and silent information regulator 1 (SIRT1) as well as the genes related to inflammation responses and apoptosis. In addition, our preliminary study found that the miR-22 mimic led to mitochondrial dysfunction and cardiomyocyte injury, whereas miR-494 protected cardiomyocytes against oxidative stress-induced cell injury. On the basis of these results, the present proposal will firstly elucidate the molecular mechanism of miRs regulating cardiac function. Then, we will investigate the effects of exercise training on the expressions of miRs and their target genes, mitochondrial function, as well as OVX-associated cardiac injury. Using lentivirus-mediated, cardiac-directed overexpression of miR-22, or cardiac-directed knock-down of miR-494 and miR-181c, we will further clarify whether these miRs contribute to the cardiac protective effect of exercise training in ovariectomized mice. Finally, we will elucidate whether DNA methylation-mediated gene regulation was involved in the mechanisms underlying exercise modulating miRs expression and clarify the transcriptional factors responsible for the expression of these miRs in myocardium. This study not only provides a new theoretical explanation for the cardioprotective effects of exercise training , but also shares alternative non-drug interventions for prevention of heart diseases in postmenopausal women.

绝经后女性冠心病的发病率和死亡率显著升高，运动锻炼被认为是一种非药物辅助措施，但其机制尚不明了。我们通过miRs芯片和整体动物模型在心肌组织中筛选得到了受雌激素和运动锻炼调节的数个miRs如miR-22、miR494和miR-181，且这些miRs可通过调节线粒体功能、细胞存活通路、抗炎等而影响心脏功能。在此基础上，我们将通过心肌组织中特异性过表达或敲低相关miRs的方法，首先进一步研究这些miRs对心功能影响的分子机制；然后研究这些miRs在运动锻炼对去卵巢鼠心肌保护中的作用及相关的通路；最后从DNA甲基化调控miRs基因启动子以及转录因子的角度，研究运动锻炼调节心肌miRs表达的分子机制。本项目的研究成果将有助于阐明运动锻炼调控心肌细胞生物学功能的分子机制，并为运动锻炼作为更年期妇女心肌病防治的辅助手段提供理论依据。

本项目首先探究了雌激素对大鼠心肌保护机制，重点探索了microRNA在其中的作用，在此基础上研究运动锻炼对去卵巢大鼠心肌保护的作用以及microRNA在其中的作用。研究结果显示，雌激素可以促进多种miRNA的表达的改变，如miR-494和miR-22的变化。miR-494可靶向NKRF进而抑制了心肌氧化应激损伤，而雌激素上调miR-494而实现的。缺血再灌注可促使心肌miR-22表达上调，miR-22通过靶向线粒体相关基因Sirt1、PGC1α，导致心肌细胞线粒体氧化应激，进一步诱导心肌组织损伤，而雌激素可下调心肌miR-22的表达。以上结果表明，雌激素可通过调控miR-494和miR-22，进而实现了其对心肌的保护作用。我们的研究结果还显示，运动锻炼可以显著地抑制去卵巢大鼠心肌细胞氧化应激的水平，运动锻炼还可增加去卵巢大鼠的血液中雌激素的水平、心肌中雌激素受体ERα水平、同时还可抑制心肌中miR-22的表达。运动锻炼还能通过调节心肌中的H2S生成酶 CSE的表达，从而增强心肌抗氧化应激和炎症作用，以上结果表明，运动锻炼可以作用于多个信号通路，进而抵抗由于雌激素缺乏导致的心肌氧化应激，最终达到心肌保护目的。