MicroRNA-145通过调控兴奋-转录耦联抑制心脏重构的机制研究

Cardiac remodeling has been one of the most important and common pathophysiological bases，and induced dysfunction of electrical and mechanical activity in multiple cardiovascular diseases. Studies have demonstrated that the inhibition of calcineurin (Cn) and Ca2+/calmodulin-dependent protein kinase II (CaMKII), the two key proteins in excitation-transcription coupling, attenuates cardiac remodeling efficiently. MicroRNA (miR) is a series of small RNA which can regulate gene expression negatively. Previous studies indicate that microRNA-145 (miR-145) is down-regulated in hypertrophy. We analyzed miR-145 by bioinformatics and found that Cn and CaMKII may be the target genes of miR-145. In this study, cell culture in vitro and two rat cardiac remodeling models, which represent different clinical phenotypes (hypertensive cardiomyocytes and diastolic dysfunction induced by hypertension; enlarged cardiac chambers and constractile dysfunction induced by myocardial infarction), will be used to explore the followings: 1) is it true that Cn and CaMKII are the target genes of miR-145? 2) whether the up-regulation of miR-145 can inhibit cardiac electrical and structural remodeling by negatively modulating the expressions of Cn and CaMKII，and therefore reduce the malignant ventricular arrhythmia and improve the heart function, in which whether up-regulation of miR-145 is superior to the inhibition of Cn or CaMKII alone or traditional anti-remodeling drugs? Our results will illuminate the role of miR-145 in cardiac remodeling and the underlying mechanisms. This study maybe provides a new strategy in the therapy of cardiac remodeling in future.

心脏重构是导致众多心脏疾病电、机械活动失调的共同病理生理基础，而抑制兴奋-转录耦联过程中的关键蛋白-钙调磷酸酶（Cn）及钙/钙调素依赖的蛋白激酶II（CaMKII）-能有效抑制心脏重构。MicroRNA（miR）是一类负向调节基因表达的小分子RNA，研究表明miR-145在心肌肥厚时表达下降，而生物信息学预测Cn和CaMKII可能是其靶基因。本课题采用体外实验及2种不同临床表型的心脏重构模型（心室肥厚和舒张功能不全为主的高血压模型；心腔扩张和收缩功能不全为主的心肌梗死模型），探讨以下问题：1）Cn/CaMKII是否为miR-145靶基因；2）上调miR-145能否通过调节Cn/CaMKII表达抑制心脏电重构和结构重构，减少恶性心律失常及改善心功能，且作用是否优于单纯抑制Cn/CaMKII及传统药物治疗。本项目的实施将阐明miR-145在心脏重构中的作用及机制，并为治疗心脏重构提供新的思路。

心脏重构是导致众多心脏疾病电、机械活动失调的共同病理生理基础，而抑制兴奋-转录耦联过程中的关键蛋白-钙调磷酸酶（Cn）及钙/钙调素依赖的蛋白激酶II（CaMKII）能有效抑制心脏重构。我们前期通过生物信息学预测Cn和CaMKII可能是miR-145的靶基因。本项目通过体外实验及2种心脏重构模型证实上调MicroRNA-145（Mir-145）能够抑制心肌重构。我们体外细胞研究发现Mir-145能抑制Cn及CaMKII基因表达，降低二者活性。我们研究发现过表达Mir-145可减小大鼠心梗后一周的心肌梗死面积及心梗后一周的心肌纤维化程度，但不能改善存活大鼠的心功能。与此同时，我们发现心肌肥厚老鼠Mir-145含量显著下降，我们进一步在细胞研究中发现上调Mir-145可以抑制PE介导的心肌细胞表面积增加，而下调Mir-145则增加心肌细胞表面积，并且上调Mir-145腺病毒后PPP3Ca、BNP及β-MHC的mRNA表达下降，Western blot结果示Cn蛋白表达水平下降。