Investigation of intrinsic factors for angiogenesis and recovery of endothelial cell injury contributed to the convalescenc of ischemic heart disease

我们先前报道了四氢生物蝶呤（BH 4），一氧化氮合酶（NOS）的必需辅因子，在一氧化氮合酶（NOS）产生一氧化氮（NO）中具有调节作用，并且外源性BH 4保护由活性氧（ROS）诱导的内皮细胞（EC）损伤，活性氧由细胞内BH 4还原产生（石井等人，1998年）。此外，BH 4的保护作用似乎涉及ROS清除活性和/或抗氧化活性。（石井。例如，1997，Shimizu等人，1998年）。BH 4还在血管内皮细胞中诱导体外血管生成（Shimizu等人，1999年）。因此，BH 4可能有效地改善由ROS诱导的病理生理状态，如缺血-再灌注。首先，我们研究了BH 4在由浸润的多形核白细胞（PMNs）诱导的内皮细胞损伤中的保护作用。此外，BH 4的内皮细胞减少中性粒细胞诱导的EC损伤。其次，我们评估了PMN粘附到内皮细胞在血管生成中的参与，因为在缺血组织中新生血管周围经常观察到PMN浸润。亚致死量的中性粒细胞在体内外均可诱导血管生成，其促血管生成的机制可能与中性粒细胞通过E-选择素、细胞间粘附分子-1（ICAM-1）和H_2O_2与内皮细胞粘附有关。因此，BH 4可能抑制缺血-再灌注后的组织损伤。因此，在大鼠胃缺血再灌注模型和大鼠心肌梗死模型中研究BH 4的保护作用。BH 4的治疗减少了组织损伤，如缺血-再灌注中的胃溃疡或心肌梗死。以上结果表明，BH_4对缺血再灌注损伤具有保护作用，其部分机制与促进PMN诱导的血管新生有关。

We previously reported that tetrahydrobiopterin (BH4), an essential cofactor for nitric oxide synthase(NOS), has a regulatory role in nitric oxide (NO) production by nitric oxide synthase (N0S), and exogenous BH4 protects endothelial cell(EC) injury induced by reactive oxygen species (ROS) which were produced by intracellular BH4 reduction (Ishii et al., 1998). Moreover, the protective effect of BH4 seems to involve ROS scavenging activity and/or antioxidative activity. (Ishii. et al., 1997, Shimizu et al., 1998). BH4 also induced in vitro angiogenesis in vascular endothelial cell (Shimizu, et al., 1999). Therefore, it is possible that BH4 effectively ameliorates pathophysiological state induced by ROS, such as ischemia-reperfusion. First, we investigated the protective effects of BH4 in endothelial cell injury induced by infiltrated polymorphonuclear leukocytes (PMNs). Addition of BH4 to endothelial cells reduced PMN-induced EC injury. Second, we evaluated the involvement of PMN adhesion to endothelial cells in angiogenesis, because PMN infiltration was often observed around the neovascular vessels in ischemic tissue. Sublethal numbers of PMNs induced angiogenesis in vivo and in vitro, and that mechanism of stimulation of angiogenesis by PMNs may involve the adherence of PMNs to endothelial cells via E-selectin and intercellular adhesion molecule- 1(ICAM-l), and H_2O_2. Thus it is possible that BH4 inhibits tissue injury after ischemia-reperfusion. Hence, the protective effects of BH4 were investigated in rat gastric ischemia-reperfusion model and rat cardiac infarction model. Treatment of BH4 reduced tissue injury such as gastric ulcer or cardiac infarction in ischemia-reperfusion. These results demonstrated that BH4 is able to protect tissue injury after ischemia-reperfusion and the part of mechanisms for the protective effect was related with encouragement of angiogenesis induced by PMNs.