Department of Pharmacology (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China), Harbin Medical University, Harbin, PR China.
Circulation. 2010 Dec 7;122(23):2378-87. doi: 10.1161/CIRCULATIONAHA.110.958967. Epub 2010 Nov 22.
A characteristic of both clinical and experimental atrial fibrillation (AF) is atrial electric remodeling associated with profound reduction of L-type Ca(2+) current and shortening of the action potential duration. The possibility that microRNAs (miRNAs) may be involved in this process has not been tested. Accordingly, we assessed the potential role of miRNAs in regulating experimental AF.
The miRNA transcriptome was analyzed by microarray and verified by real-time reverse-transcription polymerase chain reaction with left atrial samples from dogs with AF established by right atrial tachypacing for 8 weeks and from human atrial samples from AF patients with rheumatic heart disease. miR-223, miR-328, and miR-664 were found to be upregulated by >2 fold, whereas miR-101, miR-320, and miR-499 were downregulated by at least 50%. In particular, miR-328 level was elevated by 3.9-fold in AF dogs and 3.5-fold in AF patients relative to non-AF subjects. Computational prediction identified CACNA1C and CACNB1, which encode cardiac L-type Ca(2+) channel α1c- and β1 subunits, respectively, as potential targets for miR-328. Forced expression of miR-328 through adenovirus infection in canine atrium and transgenic approach in mice recapitulated the phenotypes of AF, exemplified by enhanced AF vulnerability, diminished L-type Ca(2+) current, and shortened atrial action potential duration. Normalization of miR-328 level with antagomiR reversed the conditions, and genetic knockdown of endogenous miR-328 dampened AF vulnerability. CACNA1C and CACNB1 as the cognate target genes for miR-328 were confirmed by Western blot and luciferase activity assay showing the reciprocal relationship between the levels of miR-328 and L-type Ca(2+) channel protein subunits.
miR-328 contributes to the adverse atrial electric remodeling in AF through targeting L-type Ca(2+) channel genes. The study therefore uncovered a novel molecular mechanism for AF and indicated miR-328 as a potential therapeutic target for AF.
临床和实验性心房颤动（房颤）的一个特征是心房电重构，伴有 L 型钙电流的显著减少和动作电位持续时间的缩短。尚未检测到 microRNAs（miRNAs）可能参与此过程的可能性。因此，我们评估了 miRNAs 在调节实验性房颤中的潜在作用。
通过微阵列分析了左心房样本的 miRNA 转录组，并通过实时逆转录聚合酶链反应进行了验证，这些样本来自通过右心房快速起搏建立房颤的犬和风湿性心脏病房颤患者的人类心房样本。发现 miR-223、miR-328 和 miR-664 的上调幅度超过 2 倍，而 miR-101、miR-320 和 miR-499 的下调幅度至少为 50%。特别是，与非房颤患者相比，房颤犬和房颤患者的 miR-328 水平分别升高了 3.9 倍和 3.5 倍。计算预测表明，CACNA1C 和 CACNB1 分别编码心脏 L 型钙通道的α1c-和β1 亚基，是 miR-328 的潜在靶标。通过腺病毒感染在犬心房和转基因方法在小鼠中强制表达 miR-328 重现了房颤的表型，表现为增强的房颤易感性、L 型钙电流减少和心房动作电位持续时间缩短。用反义寡核苷酸使 miR-328 水平正常化逆转了这些情况，而内源性 miR-328 的遗传敲低减弱了房颤易感性。Western blot 和荧光素酶活性测定证实了 CACNA1C 和 CACNB1 作为 miR-328 的同源靶基因，表明 miR-328 水平与 L 型钙通道蛋白亚基之间存在相互关系。
miR-328 通过靶向 L 型钙通道基因导致房颤不良的心房电重构。因此，该研究揭示了房颤的一种新的分子机制，并表明 miR-328 可能是房颤的潜在治疗靶点。
