Yamakawa T, Eguchi S, Yamakawa Y, Motley E D, Numaguchi K, Utsunomiya H, Inagami T
Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
Hypertension. 1998 Jan;31(1 Pt 2):248-53. doi: 10.1161/01.hyp.31.1.248.
Lysophosphatidylcholine (lyso-PC) has been implicated in atherogenesis and the inflammatory process. Although lyso-PC has been reported to contribute to the mitogenic effect of oxidized LDL on rat cultured vascular smooth muscle cells (VSMCs), the signaling mechanisms by which lyso-PC promotes its proliferation are poorly characterized. Mitogen-activated protein (MAP) kinases are important mediators involved in the intracellular network of interacting proteins that transduces extracellular cues to intracellular responses. We therefore examined the effect of lyso-PC on MAP kinase activation, proto-oncogene expression, and AP-1 binding activity using cultured rat VSMC. Marked activation of MAP kinase occurred within 10 minutes of lyso-PC treatment, whereupon rapid inactivation ensued. MAP kinase activation by lyso-PC was concentration-dependent (6.25 to 25 micromol/L). Pertussis toxin treatment did not affect lyso-PC-induced MAP kinase phosphorylation. Lyso-PC (25 micromol/L) also increased the mRNA expression of c-fos and c-jun genes. An electrophoretic mobility shift assay showed that AP-1 binding activity was enhanced by lyso-PC. To examine the upstream signaling of MAP kinase, we used several inhibitors on MAP kinase activation induced by lyso-PC. Although lyso-PC induced sustained increase in intracellular Ca2+ concentration, EGTA had no effect on MAP kinase activation induced by lyso-PC. However, protein kinase C inhibitor GF109203X and downregulation of protein kinase C activity by prolonged treatment with phorbol ester inhibited lyso-PC-induced MAP kinase activation. These data suggest that lyso-PC transmits its mitogenic activity through a MAP kinase-AP-1 pathway, which exists downstream of its protein kinase C activation in VSMCs.
溶血磷脂酰胆碱（lyso-PC）与动脉粥样硬化的发生及炎症过程有关。尽管已有报道称lyso-PC可促进氧化型低密度脂蛋白对大鼠培养血管平滑肌细胞（VSMCs）的促有丝分裂作用，但其促进细胞增殖的信号传导机制仍不清楚。丝裂原活化蛋白（MAP）激酶是参与细胞内相互作用蛋白网络的重要介质，该网络可将细胞外信号转化为细胞内反应。因此，我们使用培养的大鼠VSMC研究了lyso-PC对MAP激酶激活、原癌基因表达和AP-1结合活性的影响。lyso-PC处理后10分钟内MAP激酶出现明显激活，随后迅速失活。lyso-PC对MAP激酶的激活呈浓度依赖性（6.25至25微摩尔/升）。百日咳毒素处理不影响lyso-PC诱导的MAP激酶磷酸化。lyso-PC（25微摩尔/升）还增加了c-fos和c-jun基因的mRNA表达。电泳迁移率变动分析表明，lyso-PC增强了AP-1结合活性。为了研究MAP激酶的上游信号传导，我们使用了几种抑制剂来抑制lyso-PC诱导的MAP激酶激活。尽管lyso-PC诱导细胞内Ca2+浓度持续升高，但EGTA对lyso-PC诱导的MAP激酶激活没有影响。然而，蛋白激酶C抑制剂GF109203X以及用佛波酯长时间处理下调蛋白激酶C活性可抑制lyso-PC诱导的MAP激酶激活。这些数据表明，lyso-PC通过MAP激酶-AP-1途径传递其促有丝分裂活性，该途径存在于VSMCs中蛋白激酶C激活的下游。
