Department of Physiology, University of Kentucky School of Medicine, Lexington, Kentucky 40536, USA.
J Biol Chem. 2010 Mar 19;285(12):8628-38. doi: 10.1074/jbc.M109.057711. Epub 2010 Jan 19.
Previous studies suggest that high glucose-induced RhoA/Rho kinase/CPI-17 activation is involved in diabetes-associated vascular smooth muscle hypercontractility. However, the upstream signaling that links high glucose and RhoA/Rho kinase/CPI-17 activation is unknown. Here we report that calcium-independent phospholipase A(2)beta (iPLA(2)beta) is required for high glucose-induced RhoA/Rho kinase/CPI-17 activation and thereby contributes to diabetes-associated vascular smooth muscle hypercontractility. We demonstrate that high glucose increases iPLA(2)beta mRNA, protein, and iPLA(2) activity in a time-dependent manner. Protein kinase C is involved in high glucose-induced iPLA(2)beta protein up-regulation. Inhibiting iPLA(2)beta activity with bromoenol lactone or preventing its expression by genetic deletion abolishes high glucose-induced RhoA/Rho kinase/CPI-17 activation, and restoring expression of iPLA(2)beta in iPLA(2)beta-deficient cells also restores high glucose-induced CPI-17 phosphorylation. Pharmacological and genetic inhibition of 12/15-lipoxygenases has effects on high glucose-induced CPI-17 phosphorylation similar to iPLA(2)beta inhibition. Moreover, increases in iPLA(2) activity and iPLA(2)beta protein expression are also observed in both type 1 and type 2 diabetic vasculature. Pharmacological and genetic inhibition of iPLA(2)beta, but not iPLA(2)gamma, diminishes diabetes-associated vascular smooth muscle hypercontractility. In summary, our results reveal a novel mechanism by which high glucose-induced, protein kinase C-mediated iPLA(2)beta up-regulation activates the RhoA/Rho kinase/CPI-17 via 12/15-lipoxygenases and thereby contributes to diabetes-associated vascular smooth muscle hypercontractility.
先前的研究表明，高葡萄糖诱导的 RhoA/Rho 激酶/CPI-17 激活参与了糖尿病相关的血管平滑肌收缩过度。然而，将高葡萄糖与 RhoA/Rho 激酶/CPI-17 激活相联系的上游信号尚不清楚。在这里，我们报告钙非依赖性磷脂酶 A2β（iPLA2β）是高葡萄糖诱导的 RhoA/Rho 激酶/CPI-17 激活所必需的，从而有助于糖尿病相关的血管平滑肌收缩过度。我们证明高葡萄糖以时间依赖性方式增加 iPLA2β mRNA、蛋白和 iPLA2 活性。蛋白激酶 C 参与高葡萄糖诱导的 iPLA2β 蛋白上调。用溴烯内酯抑制 iPLA2β 活性或通过基因缺失防止其表达可消除高葡萄糖诱导的 RhoA/Rho 激酶/CPI-17 激活，并且在 iPLA2β 缺陷细胞中恢复 iPLA2β 的表达也可恢复高葡萄糖诱导的 CPI-17 磷酸化。12/15-脂氧合酶的药理学和遗传学抑制对高葡萄糖诱导的 CPI-17 磷酸化的作用与 iPLA2β 抑制相似。此外，在 1 型和 2 型糖尿病血管中也观察到 iPLA2β 活性和 iPLA2β 蛋白表达的增加。药理学和遗传学抑制 iPLA2β，但不是 iPLA2γ，可减轻糖尿病相关的血管平滑肌收缩过度。总之，我们的结果揭示了一种新的机制，即高葡萄糖诱导的、蛋白激酶 C 介导的 iPLA2β 上调通过 12/15-脂氧合酶激活 RhoA/Rho 激酶/CPI-17，从而有助于糖尿病相关的血管平滑肌收缩过度。
