Huot J, Houle F, Marceau F, Landry J
Centre de recherche en cancérologie de l'Université Laval, L'Hôtel-Dieu de Québec, Canada.
Circ Res. 1997 Mar;80(3):383-92. doi: 10.1161/01.res.80.3.383.
Vascular endothelial cells are constantly in contact with oxyradicals and must be especially well equipped to resist their toxic effects and generate appropriate physiological responses. Despite the importance of oxyradicals in the physiopathology of the vascular endothelium, the mechanisms regulating the oxidative response of endothelial cells are poorly understood. In the present study, we observed that H2O2 in concentrations that induced severe fragmentation of F-actin in fibroblasts rather induced a reorganization of F-actin in primary cultures of human umbilical vein endothelial cells (HUVECs) that was characterized by the accumulation of stress fibers, the recruitment of vinculin to focal adhesions, and the loss of membrane ruffles, H2O2 also induced in these cells a strong (10- to 14-fold) activation of the p38 mitogen-activated protein (MAP) kinase, which resulted in activation of MAP kinase-activated protein kinase-2/3 and phosphorylation of the F-actin polymerization modulator, heat shock protein 27 (HSP27). The MAP kinases extracellular-regulated kinase, and c-Jun N-terminal kinase/stress-activated protein kinase were only slightly increased by these treatments. Inhibiting p38 activity with the highly specific inhibitor SB203580 blocked the H2O2-induced endothelial microfilament responses. Moreover, fibroblasts acquired an endothelium-like SB203580-sensitive actin response when HSP27 concentration was increased by gene transfection to the same high level as found in HUVECs. The results indicate that activation of p38 MAP kinase in cells such as endothelial cells, which naturally express high level of HSP27, plays a central role in modulating microfilament responses to oxidative stress. Consequently, the p38 MAP kinase pathway may participate in the several oxyradical-activated functions of the endothelium that are associated with reorganization of microfilament network.
血管内皮细胞持续接触氧自由基，因此必须具备特别完善的机制来抵抗其毒性作用并产生适当的生理反应。尽管氧自由基在血管内皮的生理病理学中具有重要作用，但调节内皮细胞氧化反应的机制仍知之甚少。在本研究中，我们观察到，在成纤维细胞中能诱导F-肌动蛋白严重断裂的过氧化氢浓度，在人脐静脉内皮细胞（HUVECs）原代培养物中却诱导了F-肌动蛋白的重新组织，其特征为应力纤维的积累、纽蛋白募集到粘着斑以及膜褶皱的消失。过氧化氢还在这些细胞中诱导了p38丝裂原活化蛋白（MAP）激酶的强烈（10至14倍）激活，这导致MAP激酶激活的蛋白激酶-2/3的激活以及F-肌动蛋白聚合调节剂热休克蛋白27（HSP27）的磷酸化。这些处理仅使MAP激酶细胞外调节激酶和c-Jun N端激酶/应激激活蛋白激酶略有增加。用高度特异性抑制剂SB203580抑制p38活性可阻断过氧化氢诱导的内皮微丝反应。此外，当通过基因转染使HSP27浓度升高至与HUVECs中相同的高水平时，成纤维细胞获得了类似内皮细胞的对SB203580敏感的肌动蛋白反应。结果表明，在天然表达高水平HSP27的细胞（如内皮细胞）中，p38 MAP激酶的激活在调节微丝对氧化应激的反应中起核心作用。因此，p38 MAP激酶途径可能参与了与微丝网络重组相关的内皮细胞的几种氧自由基激活功能。
