McNicol A, Philpott C L, Shibou T S, Israels S J
Department of Oral Biology and Pharmacology, University of Manitoba, Winnipeg, Canada.
Biochem Pharmacol. 1998 Jun 1;55(11):1759-67. doi: 10.1016/s0006-2952(97)00632-1.
The role of mitogen-activated protein (MAP) kinase cascades in platelet function remains to be determined. Several studies have suggested a role in the activation of phospholipase A2; however, other functions seem likely. The object of the present study was to determine the role of the MAP kinase cascade in platelet function. An inhibitor of the mitogen-activated protein kinase kinase MEK1, 2-(2'-amino-3'-methoxyphenyl)-oxanaphthalen-4-one (PD98059), was used, at concentrations consistent with those reported to inhibit MEK1, to examine the role that this enzyme plays in platelet function. PD98059 inhibited aggregation in response to low-dose collagen and arachidonic acid, but not that in response to high-dose collagen, thrombin, thrombin receptor-activating peptide (TRAP), 9,11-dideoxy-11alpha, 9alpha-epoxymethano-prostaglandin F2alpha (U46619), or phorbol ester. Thrombin, thrombin receptor-activating peptide, U46619, collagen, and arachidonic acid each caused the release of [3H]serotonin from dense granules, but only that elicited by low-dose collagen and arachidonic acid was inhibited by PD98059. The release of [3H]arachidonic acid in response to thrombin or collagen was unaffected by PD98059 pretreatment. In contrast, collagen- and arachidonic acid-induced thromboxane formation was inhibited by PD98059. These data suggest that MEK1 is not involved in the platelet response to thrombin or U46619. Furthermore, the inhibitory effects of PD98059 on collagen- and arachidonic acid-induced responses suggest that PD98059 may inhibit the conversion of arachidonic acid to thromboxane, in addition to its reported effects on MEK1.
丝裂原活化蛋白（MAP）激酶级联反应在血小板功能中的作用尚待确定。多项研究表明其在磷脂酶A2激活中发挥作用；然而，可能还存在其他功能。本研究的目的是确定MAP激酶级联反应在血小板功能中的作用。使用丝裂原活化蛋白激酶激酶MEK1的抑制剂2-(2'-氨基-3'-甲氧基苯基)-氧杂萘-4-酮（PD98059），其浓度与报道的抑制MEK1的浓度一致，以研究该酶在血小板功能中所起的作用。PD98059抑制低剂量胶原蛋白和花生四烯酸诱导的聚集，但不抑制高剂量胶原蛋白、凝血酶、凝血酶受体激活肽（TRAP）、9,11-二脱氧-11α,9α-环氧甲撑前列腺素F2α（U46619）或佛波酯诱导的聚集。凝血酶、凝血酶受体激活肽、U46619、胶原蛋白和花生四烯酸均可引起致密颗粒中[3H]血清素的释放，但只有低剂量胶原蛋白和花生四烯酸诱导的释放受到PD98059的抑制。PD98059预处理对凝血酶或胶原蛋白诱导的[3H]花生四烯酸释放没有影响。相反，胶原蛋白和花生四烯酸诱导的血栓素形成受到PD98059的抑制。这些数据表明MEK1不参与血小板对凝血酶或U46619的反应。此外，PD98059对胶原蛋白和花生四烯酸诱导反应的抑制作用表明，除了其对MEK1的已知作用外，PD98059可能还抑制花生四烯酸向血栓素的转化。
