HHcy-induced Bax upregulation, Treg apoptosis and vascular disease

描述(由申请人提供)：血浆同型半胱氨酸水平升高，称为高同型半胱氨酸血症，是人类冠心病(CHD)和中风的独立危险因素。然而，HHcy在血管炎症和动脉粥样硬化中的作用机制尚不清楚。大多数免疫细胞促进炎症，而CD4+CD25HighFoxp3+调节性T细胞(Tregs)是最有效的免疫抑制细胞，它抑制血管炎症。在同型半胱氨酸(Hcy)升高的载脂蛋白E缺陷(ApoE-/-)小鼠中，Tregs而不是其他T细胞减少。因此，HHcy促进的Treg减少可能会减弱免疫抑制并加速血管炎症。这个项目的目的是检验我们的中心假设，即HHcy导致Tregs中DNA甲基化的抑制，导致Tregs中促凋亡蛋白Bax的上调和激活，并增加Treg的凋亡，最终导致血管炎症和功能障碍的增加。该项目是基于王宏博士(合作者)S实验室的先驱发现，即HHcy促进胱硫醚合成酶(CBS)-/-/ApoE-/-双基因敲除(KO)小鼠的血管炎症和动脉粥样硬化。王的团队也是第一个证明同型半胱氨酸导致SAH(S-腺苷同型半胱氨酸，一种有效的甲基转移酶抑制剂)积累和dna低甲基化的人。此外，我们的实验室长期以来一直致力于研究Tregs和血管炎症中的细胞凋亡途径。我们的目标将通过执行以下特定目标来实现：(1)表征HHcy小鼠的脾、骨髓(BM)、外周血(PB)和动脉中的Treg细胞凋亡(表型研究)。(2)确定HHcy诱导Treg细胞凋亡和血管炎症的机制(机制研究)。(3)确定DNA低甲基化在Tregs和Treg细胞凋亡中的调节作用和HHcy对Bax表达的影响(治疗性/抑制性研究)。这个项目的成功是巨大的，这可能会导致 旨在开发新的治疗方法来抑制HHcy诱导的Treg凋亡，并增强对HHcy诱导的血管炎症的Treg抑制。

DESCRIPTION (provided by applicant): Elevated level of plasma homocysteine (Hcy), termed hyperhomocysteinemia (HHcy), is an independent risk factor for human coronary heart disease (CHD) and stroke. However, the biochemical mechanisms underlying the effects of HHcy in vascular inflammation and atherosclerosis are poorly defined. The majority of immune cells promote inflammation whereas CD4+CD25highFoxp3+ regulatory T cells (Tregs), the most potent immuno-suppressive cells, inhibit vascular inflammation. Tregs, but not other T cells, are decreased in homocysteine (Hcy) elevated-apolipoprotein E deficient (ApoE-/-) mice. Consequently, HHcy- promoted Treg reduction may weaken immune suppression and accelerate vascular inflammation. The goal of this project is to examine our central hypothesis that HHcy causes the suppression of DNA methylation in Tregs, which leads to upregulation and activation of pro-apoptotic protein Bax in Tregs and increased Treg apoptosis, and finally contribute to increased vascular inflammation and dysfunction. This project is proposed based on the pioneer findings from Dr. Hong Wang (co-investigator)'s laboratory that HHcy promotes vascular inflammation and atherosclerosis in cystathionine ¿-synthase (Cbs)-/-/ApoE-/- double knock-out (KO) mice. Wang's team was also the first to show that HHcy leads to accumulation of SAH (S-adenosylhomocysteine, a potent inhibitor of methyltransferases) and DNA hypomethylation. In addition, our laboratory has a long- standing interest and publication record in characterizing apoptosis pathways in Tregs and vascular inflammation. Our goal will be pursued through the execution of the following specific aims: (1) Characterize Treg apoptosis in the spleen, bone marrow (BM), peripheral blood (PB), and arteries in HHcy mice (phenotypic studies). (2) Determine the mechanisms underlying HHcy-induced Treg apoptosis and vascular inflammation (mechanistic studies). (3) Determine the mediating role of DNA hypomethylation and the causative role of HHcy on Bax expression in Tregs and Treg apoptosis (therapeutic/inhibitory studies). Success of this project is significant, which may lead to the development of new therapeutic approaches to inhibit HHcy-induced Treg apoptosis and enhance Treg suppression of HHcy-induced vascular inflammation.