Department of Vascular Surgery, The Second People's Hospital of Yunnan Province, Kunming Medical University, Kunming, Yunnan 650200, P.R. China.
Department of Pharmacy, The Third People's Hospital of Yunnan Province, Kunming, Yunnan 650200, P.R. China.
Int J Mol Med. 2019 Mar;43(3):1289-1298. doi: 10.3892/ijmm.2019.4063. Epub 2019 Jan 14.
In cardiac tissues, myoblast atrial myocytes continue to be exposed to mechanical forces including shear stress. However, little is known about the effects of shear stress on atrial myocytes, particularly on ion channel function, in association with disease. The present study demonstrated that the Ca2+‑activated K+ channel (KCa)2.3 serves a vital role in regulating arterial tone. As increased intracellular Ca2+ levels and activation of histone acetyltransferase p300 (p300) are early responses to laminar shear stress (LSS) that result in the transcriptional activation of genes, the role of p300 and the phosphoinositide3‑kinase (PI3K)/protein kinase B (Akt) pathway, an intracellular pathway that promotes the growth and proliferation rather than the differentiation of adult cells, in the LSS‑dependent regulation of KCa2.3 in cardiac myoblasts was examined. In cultured H9c2 cells, exposure to LSS (15 dyn/cm2) for 12 h markedly increased KCa2.3 mRNA expression. Inhibiting PI3K attenuated the LSS‑induced increases in the expression and channel activity of KCa2.3, and decreased the phosphorylation levels of p300. The upregulation of these channels was abolished by the inhibition of Akt through decreasing p300 phosphorylation. ChIP assays indicated that p300 was recruited to the promoter region of the KCa2.3 gene. Therefore, the PI3K/Akt/p300 axis serves a crucial role in the LSS‑dependent induction of KCa2.3 expression, by regulating cardiac myoblast function and adaptation to hemodynamic changes. The key novel insights gained from the present study are: i) KCa2.3 was upregulated in patients with atrial fibrillation (AF) and in patients with AF combined with mitral value disease; ii) LSS induced a profound upregulation of KCa2.3 mRNA and protein expression in H9c2 cells; iii) PI3K activation was associated with LSS‑induced upregulation of the KCa2.3 channel; iv) PI3K activation was mediated by PI3K/Akt‑dependent Akt activation; and v) LSS induction of KCa2.3 involved the binding of p300 to transcription factors in the promoter region of the KCa2.3 gene.
在心脏组织中，成肌细胞仍然会持续受到包括切应力在内的机械力的作用。然而，关于切应力对心房肌细胞的影响，特别是与疾病相关的离子通道功能，人们知之甚少。本研究表明，钙激活钾通道（KCa）2.3 在调节动脉张力方面起着至关重要的作用。由于细胞内 Ca2+水平的增加和组蛋白乙酰转移酶 p300（p300）的激活是层流切应力（LSS）的早期反应，导致基因的转录激活，p300 的作用以及磷酸肌醇 3-激酶（PI3K）/蛋白激酶 B（Akt）通路（一种促进成年细胞生长和增殖而不是分化的细胞内通路）在心肌成肌细胞中 LSS 依赖性调节 KCa2.3 中的作用被研究。在培养的 H9c2 细胞中，暴露于 LSS（15 dyn/cm2）12 h 可显著增加 KCa2.3 mRNA 的表达。抑制 PI3K 减弱了 LSS 诱导的 KCa2.3 表达和通道活性的增加，并降低了 p300 的磷酸化水平。通过降低 p300 磷酸化来抑制 Akt，这些通道的上调被消除。ChIP 测定表明，p300 被募集到 KCa2.3 基因的启动子区域。因此，PI3K/Akt/p300 轴通过调节心肌成肌细胞的功能和适应血液动力学变化，在 LSS 依赖性诱导 KCa2.3 表达中起着至关重要的作用。本研究获得的关键新见解是：i）在心房颤动（AF）患者和 AF 合并二尖瓣疾病患者中上调 KCa2.3；ii）LSS 在 H9c2 细胞中诱导 KCa2.3 mRNA 和蛋白表达的深刻上调；iii）PI3K 激活与 LSS 诱导的 KCa2.3 通道上调有关；iv）PI3K 激活是通过 PI3K/Akt 依赖的 Akt 激活介导的；v）LSS 诱导 KCa2.3 涉及 p300 与 KCa2.3 基因启动子区域转录因子的结合。
