HOMOCYSTEINE--VASCULAR BIOCHEMISTRY AND METABOLISM

高同型半胱氨酸血症与心血管疾病的关系是 久负盛名。年发病率和死亡率的主要原因 常染色体隐性遗传性同型半胱氨酸尿症为时过早 动脉粥样硬化合并动脉和静脉血栓形成。最近的几个 涉及3000多名患者的临床研究表明， 轻度至轻度高同型半胱氨酸血症与 冠状动脉疾病、脑血管疾病和外周血管疾病 闭塞性疾病，不受传统风险因素的影响，如 高血压、吸烟、高脂血症和糖尿病。早期工作，由 内皮损伤反应假说表明，高 同型半胱氨酸和同型半胱氨酸硫内酯的超生理学水平 对血管内皮细胞有损伤和细胞毒性作用。然而， 对同型半胱氨酸诱导的细胞毒性的机制知之甚少。 甚至同型半胱氨酸是如何在内皮细胞中代谢的。此外， 实际上，人们对它们之间的化学相互作用一无所知。 同型半胱氨酸和血浆蛋白。我们的工作将集中在生物化学上 和同型半胱氨酸在血管系统中的代谢及其影响 同型半胱氨酸水平升高可能对致动脉粥样硬化和 血管内皮细胞的血栓前功能。我们假设 主动脉和冠状动脉内皮细胞对升高的反应敏感 同型半胱氨酸，因为它们的硫化途径是不活跃的 细胞。此外，升高的同型半胱氨酸诱导血管紧张素转换酶表达 黏附分子，从而促进单核细胞募集。具体的 这项研究的目的是： 1)研究同型半胱氨酸与特异性 使用体外模型的血浆蛋白将使我们能够确定 它们与同型半胱氨酸的结合能力和交换分析 同型半胱氨酸和蛋白结合半胱氨酸之间的动力学。隔离， 同型半胱氨酸内源性携带者的鉴定 正常和高同型半胱氨酸血症血浆； 2)测定培养人同型半胱氨酸代谢途径 检测钴胺(B12)依赖的蛋氨酸对主动脉内皮细胞的影响 依赖吡哆醛的半胱硫氨酸合成酶(3-合成酶和 亚甲基四氢叶酸还原酶，并与 新鲜人冠状动脉制备物中的酶活性 红心 3)确定同型半胱氨酸的生理浓度的影响 对内皮细胞功能的影响，特别是对单核细胞的促进作用 黏附于培养的主动脉内皮细胞，并获得一种 对这种现象的理解。 这些研究将提供关于血管的有价值的新见解。 同型半胱氨酸的生物化学和代谢，并可能提出一个 用于治疗高同型半胱氨酸血症。

The association between hyperhomocysteinemia and cardiovascular disease is well established. The principal cause of morbidity and mortality in autosomal recessive inheritable homocystinuria is premature atherosclerosis with arterial and venous thrombosis. Several recent clinical studies involving over 3,000 patients have shown a relationship between slight to mild hyperhomocysteinemia and the development of coronary artery disease, cerebrovascular disease and peripheral vascular occlusive disease, independent of traditional risk factors such as hypertension, smoking, hyperlipidemia and diabetes. Early work, guided by the endothelial response-to-injury hypothesis, showed that high supraphysiological levels of homocysteine and homocysteine thiolactone were injurious and cytotoxic to vascular endothelial cells. However, little is known about the mechanism of homocysteine-induced cytotoxicity, or even how homocysteine is metabolized in endothelial cells. Furthermore, practically nothing is known about the chemical interactions between homocysteine and plasma proteins. Our work will focus on the biochemistry and metabolism of homocysteine in the vascular system and the effect that elevated levels of homocysteine might have on proatherogenic and prothrombogenic functions of endothelial cells. We hypothesize that aortic and coronary artery endothelial cells are sensitive to elevated homocysteine because the transsulfuration pathway is inactive in these cells. Furthermore elevated homocysteine induces the expression of adhesion molecules, thereby promoting monocyte recruitment. The specific aims of this study are: 1) to investigate the interactions between homocysteine and specific plasma proteins using in vitro models that will allow us to determine their binding capacity for homocysteine and to analyze the exchange kinetics between homocysteine and protein-bound cysteine. Isolate, characterize and identify the endogenous carriers of homocysteine in normal and hyperhomocysteinemic plasma; 2) to determine the pathways of homocysteine metabolism in cultured human aorta endothelial cells by measuring cobalamin (B 12)-dependent methionine synthase, pyridoxal-dependent cystathionine (3-synthase and methylenetetrahydrofolate reductase and to compare these measurements with enzyme activities in fresh preparations of coronary arteries from human hearts 3) to establish the effect of physiological concentrations of homocysteine on endothelial cell function, especially the promotion of monocytic adhesion to cultured aortic endothelial cells, and to gain a mechanistic understanding of this phenomenon. These studies will provide valuable new insights on the vascular biochemistry and metabolism of homocysteine and may suggest a rationale for the treatment of hyperhomocysteinemia.