Viji R I, Kumar V B Sameer, Kiran M S, Sudhakaran P R
Department of Biochemistry, University of Kerala, Thiruvananthapuram, Kerala 695 581, India.
J Cell Biochem. 2008 Sep 1;105(1):158-66. doi: 10.1002/jcb.21808.
Cyclooxygenases (COX), which catalyze the formation of prostaglandins (PGs), have been implicated in angiogenesis. Adhesion of endothelial cells (ECs) to extracellular matrix (ECM) induces the expression of COX-2 and PG production. The present study was carried out to analyze the influence of the adhesive ECM protein, fibronectin (FN), in modulating COX expression and its implications to angiogenesis using in vitro cultures of human umbilical vein ECs. RT-PCR analysis showed that the level of COX-2 mRNA was significantly high while that of COX-1 decreased in ECs maintained on FN. On treatment with p38 MAPK inhibitor and anti-alpha(5)beta(1) integrin antibody, FN dependent effect on COX expression was not observed. Analysis by ELISA and immunoblotting confirmed FN-dependent upregulation of COX-2 protein. The ratio of PG E(2):PG D(2) was significantly high in cells maintained on FN and on treatment with p38 MAPK inhibitor, the relative level of PG D(2) increased and that of PG E(2) decreased. Concomitant with the modulation of COX-2 and changes in PGs, ECs maintained on FN showed angiogenic response in an alpha(5)beta(1) integrin/p38 MAPK dependent manner as evidenced by the expression of angiogenic markers, CD 31 and E-selectin. These results suggest a FN-alpha(5)beta(1)/FAK/p38 MAPK dependent upregulation of COX-2 causing a shift in the relative levels of PGs in HUVECs which contributes to the angiogenic effect of FN.
环氧化酶（COX）可催化前列腺素（PGs）的形成，与血管生成有关。内皮细胞（ECs）与细胞外基质（ECM）的黏附可诱导COX-2的表达和PG的产生。本研究采用人脐静脉内皮细胞的体外培养，分析黏附性细胞外基质蛋白纤连蛋白（FN）对COX表达的影响及其对血管生成的意义。逆转录聚合酶链反应（RT-PCR）分析表明，在FN上培养的内皮细胞中，COX-2 mRNA水平显著升高，而COX-1水平降低。用p38丝裂原活化蛋白激酶（MAPK）抑制剂和抗α(5)β(1)整合素抗体处理后，未观察到FN对COX表达的依赖性作用。酶联免疫吸附测定（ELISA）和免疫印迹分析证实了FN依赖性上调COX-2蛋白。在FN上培养的细胞中，前列腺素E2（PGE2）与前列腺素D2（PGD2）的比值显著升高，用p38 MAPK抑制剂处理后，PGD2的相对水平升高，PGE2的相对水平降低。与COX-2的调节和PGs的变化同时发生的是，在FN上培养的内皮细胞以α(5)β(1)整合素/p38 MAPK依赖性方式表现出血管生成反应，血管生成标志物CD 31和E选择素的表达证明了这一点。这些结果表明，FN-α(5)β(1)/黏着斑激酶（FAK）/p38 MAPK依赖性上调COX-2导致人脐静脉内皮细胞（HUVECs）中PGs相对水平发生变化，这有助于FN的血管生成作用。
