During vascular interventions, oxidized low-density lipoprotein and lysophosphatidylcholine (lysoPC) accumulate at the site of arterial injury, inhibiting endothelial cell (EC) migration and arterial healing. LysoPC activates canonical transient receptor potential 6 (TRPC6) channels, leading to a prolonged increase in intracellular calcium ion concentration that inhibits EC migration. However, an initial increase in intracellular calcium ion concentration is required to activate TRPC6, and this mechanism remains elusive. We hypothesized that lysoPC activates the lipid-cleaving enzyme phospholipase A2 (PLA2), which releases arachidonic acid (AA) from the cellular membrane to open arachidonate-regulated calcium channels, allowing calcium influx that promotes externalization and activation of TRPC6 channels. The focus of this study was to identify the roles of calcium-dependent and/or calcium-independent PLA2 in lysoPC-induced TRPC6 externalization. We show that lysoPC induced PLA2 enzymatic activity and caused AA release in bovine aortic ECs. To identify the specific subgroup and the isoform(s) of PLA2 involved in lysoPC-induced TRPC6 activation, transient knockdown studies were performed in the human endothelial cell line EA.hy926 using siRNA to inhibit the expression of genes encoding cPLA2α, cPLA2γ, iPLA2β, or iPLA2γ. Downregulation of the β isoform of iPLA2 blocked lysoPC-induced release of AA from EC membranes and TRPC6 externalization, as well as preserved EC migration in the presence of lysoPC. We propose that blocking TRPC6 activation and promoting endothelial healing could improve the outcomes for patients undergoing cardiovascular interventions.

中文翻译：

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细胞溶质钙非依赖性磷脂酶 A2 β 异构体的激活通过花生四烯酸的释放促进 TRPC6 外化。

在血管介入期间，氧化低密度脂蛋白和溶血磷脂酰胆碱 (lysoPC) 在动脉损伤部位积聚，抑制内皮细胞 (EC) 迁移和动脉愈合。LysoPC 激活经典瞬时受体电位 6 (TRPC6) 通道，导致细胞内钙离子浓度长期增加，从而抑制 EC 迁移。然而，激活 TRPC6 需要细胞内钙离子浓度的初始增加，而这种机制仍然难以捉摸。我们假设 lysoPC 激活脂质裂解酶磷脂酶 A2 (PLA2)，它从细胞膜释放花生四烯酸 (AA) 以打开花生四烯酸调节的钙通道，允许钙流入促进 TRPC6 通道的外化和激活。本研究的重点是确定钙依赖性和/或钙非依赖性 PLA2 在 lysoPC 诱导的 TRPC6 外化中的作用。我们表明 lysoPC 诱导 PLA2 酶活性并导致牛主动脉 EC 中的 AA 释放。为了鉴定参与 lysoPC 诱导的 TRPC6 激活的 PLA2 的特定亚群和同种型，使用 siRNA 在人内皮细胞系 EA.hy926 中进行了瞬时敲低研究，以抑制编码 cPLA2α、cPLA2γ、iPLA2β、或 iPLA2γ。iPLA2 的 β 同种型的下调阻止了 lysoPC 诱导的 AA 从 EC 膜和 TRPC6 外化的释放，以及在 lysoPC 存在下保留的 EC 迁移。