剪切应力对血管内皮细胞NO合成酶活性的影响及其机理探讨

EFFECT OF SHEAR STRESS ON THE NO SYNTHASE IN ENDOTHELIAL CELL AND ITS MECHANISM

目的：观测流体剪切应力对血管内皮细胞ＮＯ合成酶（ｎｉｔｒｉｃ ｏｘｉｄｅｓｙｎｔｈａｓｅ，ＮＯＳ）活性的影响并探讨其发生机制。方法：采用Ｇｒｉｅｓｓ 方法测定不同流体剪切应力作用下血管内皮细胞中ＮＯＳ活性的变化；并观测多种ＮＯＳ干预物质对这种变化的影响。结果：剪切应力显著提高血管内皮细胞中ＮＯＳ活性；地塞米松（ｄｅｘａｍｅｔｈａｓｏｎｅ）实验表明，剪切应力这种作用主要是通过对结构型ＮＯＳ活性的增强实现的，且具有明显的剂量和时间依赖性；放线菌酮（ｃｙｃｌｏｈｅｘｉｍｉｄｅ）非特异性地抑制细胞中ＮＯＳ酶蛋白合成，但ｃｙｃｌｏｈｅｘｉｍｉｄｅ 处理组中受剪切应力作用细胞ＮＯＳ活性仍显著高于其对照细胞，仅升高幅度明显降低。Ａ２３１８７ 处理后细胞中ＮＯＳ活性升高约达２ 倍，其中剪切应力作用细胞的ＮＯＳ活性显著高于其对照，但这种变化程度亦较Ａ２３１８７ 未处理组明显减小。结论：剪切应力显著提高血管内皮细胞ｅＮＯＳ活性：ｅＮＯＳ酶蛋白合成增加和细胞内Ｃａ２＋

Aim: To analyse the effect of shear stress on the NOS activity and investigate its mechanism. Methods: NOS activity in the endothelial cells exposed to different shear stress was measured using Griess assay and effects of the related interfering agents on the NOS activity were also tested. Results: Shear stress dose and time dependently increased the specific activity of NOS. Dexamethasone test showed, the effect of shear stress was realized by increasing the activity of endothelial NO synthase. Cycloheximide suppressed NOS activity via inhibiting protein synthesis, but in cycloheximide treated cells shear stress still caused a significant increase in NOS activity over the control. Ca 2+ ionophor A23187 elevated NOS activity about two-fold both in control and in shear stress exposed cells, however the ionophor induced increase of NOS activity in shear stress exposed cells exceeded that in the control cells, only the range was lower than that in non A23187 treated group. Conclusion:Shear stress specifically increased eNOS activity in endothelial cells, in which the increase of [Ca 2+ ]i and eNOS protein synthesis may play an important role.