microRNA-29b介导血管平滑肌细胞AT1aR基因DNA去甲基化参与高血压发病机制的研究

Angiotensin II type 1 receptor (AT1R) overexpression is important in the genesis and progression of hypertension. But the mechanism of the upregulation of AT1R is not clear. Our preliminary study discovered that the promoter region of angiotensin II receptor subtype 1a (AT1aR) in vascular smooth muscle cells was getting demethylated during development of hypertension. In addition, miR-29b was upregulated in spontaneously hypertensive rat (SHR). DNA methyltransferase (DNMT)3A, DNMT3B and histone deacetylases (HDAC)4 have been verified as direct target genes of miR-29b. Some previous studies of tumor have suggested that the miR-29b can induce DNA demethylation by directly targeting DNMT3A and DNMT3B. Furthermore, HDACs can induce DNA demethylation by effecting DNMTs. In preliminary experiment，we found that transfection of HDAC4 could induce DNA demethylation and decrease mRNA level of AT1aR. Therefore, we supposed that miR-29b can induce DNA demethylation by targeting directly DNMT3A and DNMT3B and indirectly DNMTs via HDAC4, which promotes the expression and function of AT1aR in hypertension. This study will contribute to elucidating the mechanisms of the abnormal expression and function of AT1R in hypertension, which is beneficial to providing theoretical basis for prevention and treatment of hypertension.

血管紧张素II 1型受体（AT1R）过度表达在高血压发生发展过程中具有重要作用，但AT1R表达上调的机制尚不明确。我们的前期工作发现高血压状态下动脉平滑肌细胞中AT1R的重要亚型-AT1aR启动子区去甲基化并伴有miR-29b高表达。有证据显示DNA甲基转移酶3A/B（DNMT3A/B）和组蛋白去乙酰化酶4（HDAC4）是miR-29b的靶基因。在肿瘤的研究中发现miR-29b可以通过直接靶向抑制DNMT3A/B使DNA去甲基化，HDACs也可通过影响DNMTs影响DNA去甲基化。我们的预实验发现siRNA抑制HDAC4后AT1aR的甲基化水平下调、mRNA水平升高。因此，我们推测miR-29b通过直接抑制DNMTs和靶向抑制HDAC4间接影响DNMTs介导DNA去甲基化，上调AT1aR的表达和功能。此研究有助于揭示高血压状态下AT1aR表达和功能异常的原因，为高血压的防治提供理论基础。

血管紧张素II 1型受体（AT1R）在高血压发生发展过程中具有重要作用，但迄今为止，动脉血管组织中AT1R在高血压发生发展不同阶段的表达变化情况及其调控机制尚不清楚。我们在前期实验中发现：随着高血压的发生发展，动脉平滑肌细胞中AT1R的重要亚型—AT1aR表达增加、启动子区出现去甲基化改变；同时，可能对基因DNA甲基化具有调控作用的miR-29b表达上调。因此，在后续的工作中，我们以不同周龄自发性高血压大鼠（SHR）及其公认对照Wistar-Kyoto大鼠（WKY）为研究对象，对高血压发生发展过程中VSMC内AT1aR基因的表达、miR-29b和DNA甲基化三者之间的相互关系及其对VSMC增殖、迁移的影响进行了探讨。我们发现：在高血压发生发展过程中，VSMCs内源性的DNMT3a表达减少促进AT1aR启动子区甲基化水平降低，进而导致AT1aR的表达升高，促进VSMCs的增殖和迁移；VSMCs内源性的miR-29b表达升高对AT1aR的表达及其启动子区的甲基化水平均无影响，但可能通过其它机制促进VSMCs迁移。我们的研究为进一步从表观遗传学的角度阐明AT1aR在高血压的表达调控机制提供了新线索，相关研究的深入将对完善高血压的发病机制和预防治疗策略的选择提供新依据。

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