State Key Laboratory of Trauma, Burns and Combined Injury, Second Department of Research Institute of Surgery, Daping Hospital, Third Military Medical University, Chongqing 400042, P R China.
J Cardiovasc Pharmacol. 2011 Jun;57(6):656-65. doi: 10.1097/FJC.0b013e318215e21d.
We used isolated superior mesenteric arteries (SMAs) from hemorrhagic-shock rats and hypoxia-treated vascular smooth muscle cells (VSMCs; mimicking the shock state) to observe the effects of platelet-derived growth factor (PDGF; Rac1 stimulator) and NSC23766 (Rac1 antagonist) on vascular reactivity and the relationship with the Rho kinase-myosin light-chain phosphatase (MLCP) and p21-activated kinase (PAK)-myosin light-chain kinase (MLCK) signal pathway. The results indicated that the contractile responses of the SMAs and VSMCs were significantly increased at early shock or after transient hypoxia. NSC23766 (Rac1 antagonist) further increased, whereas PDGF (Rac1 stimulator) decreased the contractile responses of SMAs and VSMCs. In the late period of shock or prolonged hypoxia, the contractile responses of SMAs and VSMCs were significantly decreased; NSC23766 increased (whereas PDGF further decreased) the contractile response of the SMAs and VSMCs. Activation of Rac1 with PDGF significantly increased the activity of PAK and MLCP, and decreased Rho kinase and MLCK activity and 20-kDa myosin light-chain phosphorylation in VSMCs. The PAK inhibitor PAK-18 significantly antagonized the PDGF-induced decrease in MLCK activity, whereas the Rho kinase antagonist Y-27632 further enforced the PDGF-induced increase in MLCP activity. Simple fluid resuscitation did not improve but in combination with NSC23766 significantly improved vascular reactivity and animal survival at 24 hours. This suggested that Rac1 has an inhibitory effect on vasoreactivity after shock. Rac1-mediated regulation of vascular reactivity is mainly through activation of PAK, inhibition of MLCK and inhibition of Rho kinase, unpack the inhibition of Rho kinase to MLCP. Rac1 may be a potential target to treat vascular hyporeactivity in many critical conditions.
我们使用失血性休克大鼠的分离肠系膜上动脉（SMAs）和缺氧处理的血管平滑肌细胞（VSMCs；模拟休克状态），观察血小板衍生生长因子（PDGF；Rac1 激动剂）和 NSC23766（Rac1 拮抗剂）对血管反应性的影响，以及与 Rho 激酶-肌球蛋白轻链磷酸酶（MLCP）和 p21 激活激酶（PAK）-肌球蛋白轻链激酶（MLCK）信号通路的关系。结果表明，在早期休克或短暂缺氧后，SMAs 和 VSMCs 的收缩反应明显增加。NSC23766（Rac1 拮抗剂）进一步增加，而 PDGF（Rac1 激动剂）则降低了 SMAs 和 VSMCs 的收缩反应。在休克晚期或缺氧延长时，SMAs 和 VSMCs 的收缩反应明显降低；NSC23766 增加（而 PDGF 进一步降低）SMAs 和 VSMCs 的收缩反应。PDGF 激活 Rac1 显著增加了 PAK 和 MLCP 的活性，降低了 Rho 激酶和 MLCK 的活性以及 20-kDa 肌球蛋白轻链的磷酸化，PAK 抑制剂 PAK-18 显著拮抗了 PDGF 诱导的 MLCK 活性降低，而 Rho 激酶拮抗剂 Y-27632 进一步增强了 PDGF 诱导的 MLCP 活性增加。单纯的液体复苏并不能改善，但与 NSC23766 联合使用可显著改善血管反应性和动物在 24 小时的存活率。这表明 Rac1 对休克后血管反应性具有抑制作用。Rac1 介导的血管反应性调节主要是通过激活 PAK、抑制 MLCK 和抑制 Rho 激酶、解除 Rho 激酶对 MLCP 的抑制来实现的。Rac1 可能是治疗许多危急情况下血管低反应性的一个潜在靶点。
