From the Department of Physiology and the Cardiovascular Research Center, Temple University, Philadelphia, PA.
Hypertension. 2018 Apr;71(4):761-770. doi: 10.1161/HYPERTENSIONAHA.117.10305.
MPO (myeloperoxidase) is a peroxidase enzyme secreted by activated leukocytes that plays a pathogenic role in cardiovascular disease, mainly by initiating endothelial dysfunction. The molecular mechanisms of the endothelial damaging action of MPO remain though largely elusive. Calpain is a calcium-dependent protease expressed in the vascular wall. Activation of calpains has been implicated in inflammatory disorders of the vasculature. Using endothelial cells and genetically modified mice, this study identifies the µ-calpain isoform as novel downstream signaling target of MPO in endothelial dysfunction. Mouse lung microvascular endothelial cells were stimulated with 10 nmol/L MPO for 180 minutes. MPO denitrosylated µ-calpain C-terminus domain, and time dependently activated µ-calpain, but not the m-calpain isoform. MPO also reduced Thr AMPK (AMP-activated protein kinase) and Ser eNOS (endothelial nitric oxide synthase) phosphorylation via upregulation of PP2A (protein phosphatase 2) expression. At the functional level, MPO increased endothelial VCAM-1 (vascular cell adhesion molecule 1) abundance and the adhesion of leukocytes to the mouse aorta. In MPO-treated endothelial cells, pharmacological inhibition of calpain activity attenuated expression of VCAM-1 and PP2A, and restored Thr AMPK and Ser eNOS phosphorylation. Compared with wild-type mice, µ-calpain deficient mice experienced reduced leukocyte adhesion to the aortic endothelium in response to MPO. Our data first establish a role for calpain in the endothelial dysfunction and vascular inflammation of MPO. The MPO/calpain/PP2A signaling pathway may provide novel pharmacological targets for the treatment of inflammatory vascular disorders.
髓过氧化物酶（MPO）是一种由激活的白细胞分泌的过氧化物酶，在心血管疾病中发挥致病作用，主要通过引发内皮功能障碍。尽管 MPO 对内皮细胞损伤作用的分子机制在很大程度上仍未被揭示，但钙蛋白酶是一种在血管壁中表达的钙依赖性蛋白酶。钙蛋白酶的激活与血管炎症性疾病有关。本研究使用内皮细胞和基因修饰小鼠，鉴定 µ-钙蛋白酶同工型为 MPO 在内皮功能障碍中的新型下游信号靶标。用 10nmol/LMPO 刺激小鼠肺微血管内皮细胞 180 分钟。MPO 使 µ-钙蛋白酶 C 端结构域去硝基化，并时间依赖性地激活 µ-钙蛋白酶，但不激活 m-钙蛋白酶同工型。MPO 还通过上调 PP2A（蛋白磷酸酶 2）表达来降低 Thr AMPK（AMP 激活的蛋白激酶）和 Ser eNOS（内皮型一氧化氮合酶）磷酸化。在功能水平上，MPO 增加了内皮细胞 VCAM-1（血管细胞黏附分子 1）的含量和白细胞对小鼠主动脉的黏附。在 MPO 处理的内皮细胞中，钙蛋白酶的药理学抑制减弱了 VCAM-1 和 PP2A 的表达，并恢复了 Thr AMPK 和 Ser eNOS 的磷酸化。与野生型小鼠相比，µ-钙蛋白酶缺陷型小鼠在 MPO 刺激下白细胞对主动脉内皮的黏附减少。我们的数据首次确立了钙蛋白酶在 MPO 介导的内皮功能障碍和血管炎症中的作用。MPO/钙蛋白酶/PP2A 信号通路可能为炎症性血管疾病的治疗提供新的药理学靶点。
