NE对心理应激致同型半胱氨酸蓄积的调节作用及其机制研究

Homocysteine (Hcy), a cytotoxic sulfur-containing amino acid, is an intermediary metabolite in methionine/cysteine metabolism. The elevated plasma level of Hcy is termed hyperhomocysteinemia (HHcy), and regulation of Hcy is critically important for health maintenance since several diseases are related to HHcy. Metabolism of Hcy has two main routes: re-methylation and trans-sulfuration. Stress has been associated with various pathological conditions. It has been reported that plasma total Hcy levels increased after acute psychological stress in human and animal studies. Our results also found that psychological stress could significantly elevate plasma Hcy levels of the rat. However, its pathological mechanisms remain largely unknown. .CBS occupies a crucial regulatory position between the methionine cycle and trans-sulfuration of Hcy metabolism. CBS is the rate-limiting step in the transsulfuration pathway and irreversibly converts Hcy to cysteine. Our previous results showed the development of HHcy induced by psychological stress was mainly derived from a reduction of CBS activity in the liver, which was accompanied by a significant decrease in its mRNA level. It suggested that the hepatic CBS enzyme regulated by stress at the level of transcription would have a profound effect on circulating Hcy levels. Sp1/Sp3 belong to the Specificity Protein transcription factor family, which activate or repress transcription of many genes in response to physiological and pathological stimuli. Sp1/Sp3 have been suggested as potential transactivators for the human CBS-1b promoter. .The aim of the present study was to elucidate the molecular mechanism by which CBS expression was regulated in the rat liver during the psychological stress process. We supposed that over-secreted adrenaline and noradrenaline during stress resulted in the increase of IL-6 level in serum of stressed rat by activating β-adrenaline receptor, subsequently IL-6 activated NF-κB and enhanced Sp3 activity, which inhibited cbs transcription and CBS activity. Thus lead to the disorder of homocysteine metabolism.

以应激实验动物去甲肾上腺素的释放和IL-6的分泌为观测指标，认识应激机体血浆HCY水平的变化规律及其与IL-6分泌的关系，探讨应激致高同型半胱氨酸血症发生的神经内分泌免疫调节机制。进而以HCY转硫代谢途径的限速酶CBS为切入点，从整体与细胞水平研究应激致HCY异常代谢时肝脏CBS转录调控的关键环节。分析转录因子Sp1/Sp3复合体对CBS活性的调节，以及应激水平IL-6对肝细胞Sp1/Sp3活性及CBS转录过程的调控，确认参与CBS活化调控的信号蛋白，进而揭示应激反应的神经内分泌免疫网络对HCY代谢过程的调控乃至高同型半胱氨酸血症形成的分子机制，以期为高同型半胱氨酸血症的临床诊断与有效防治提供新的靶标与科学依据。

人类75％-90％的疾病的发生发展与机体应激损伤机制的激活密切相关，其中交感/肾上腺髓质系统是应激反应的主要传导体系之一，其主要特征是神经内分泌网络多级联信号的传导调控，肾上腺素和去甲肾上腺素等儿茶酚胺类激素的过量分泌是其重要生物学基础。同型半胱氨酸（Hcy）是机体甲硫氨酸循环过程中的中间代谢产物，是一种含硫氨基酸，本身并不参与蛋白质合成，在生理状况下，血浆中Hcy含量甚微，其代谢紊乱可诱导高同型半胱氨酸血症（HHcy）的发生，是多种疾病的危险因子。转硫途径是体内Hcy唯一的代谢清除途径，而胱硫醚β-合成酶（CBS）是转硫途径中的限速酶，负责转化体内约50%的Hcy。.本研究发现应激机体肾上腺素和去甲肾上腺素分泌增强，血清中IL-6水平异常升高，而应激机体IL-6血清水平的变化效应可被β-肾上腺素能受体阻断剂普萘洛尔逆转，糖皮质激素受体阻断剂RU486则对其无作用，表明（去甲）肾上腺素通过β-肾上腺素能受体的介导引起了应激机体IL-6的高分泌。IL-6通过酪氨酸磷酸化作用使肝细胞转录因子NF-κB磷酸化，调节NF-κB的活性，酪氨酸磷酸化同时介入了NF-κB与Hcy代谢酶cbs负性转录调节因子Sp3之间的蛋白相互作用，使Sp3活化。NF-κB抑制剂IκB的转染使Sp3核内水平下调，提示NF-κB是IL-6作用下肝细胞Sp3活化过程的关键调节因素，而cbs正性转录调节因子Sp1核内水平不变，活性相对降低，进而导致肝脏cbs基因转录抑制，CBS活性降低，Hcy转硫代谢障碍，造成Hcy体内蓄积。表明在应激致高同型半胱氨酸血症的发生过程中，神经内分泌免疫网络和细胞信号传导通路发挥了重要作用，并为探寻高同型半胱氨酸血症的临床诊断与有效防治提供了靶点和科学依据。已发表SCI期刊论文3篇，会议论文5篇，培养研究生3人。