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 immunosuppressive cells, inhibit vascular inflammation. Tregs, but not other T cells, are decreased in homocysteine (Hcy) elevatedapolipoprotein E deficient (ApoE/ ) mice. Consequently, HHcypromoted 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 proapoptotic 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 (coinvestigator)? s laboratory that HHcy promotes vascular inflammation and atherosclerosis in cystathionine βsynthase (Cbs)/ / ApoE/ double knockout (KO) mice. Wang?s team was also the first to show that HHcy leads to accumulation of SAH (Sadenosylhomocysteine, a potent inhibitor of methyltransferases) and DNA hypomethylation. In addition, our laboratory has a longstanding 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 HHcyinduced 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 HHcyinduced Treg apoptosis and enhance Treg suppression of HHcy-induced vascular inflammation.

Public Health Relevance

Elevated level of plasma homocysteine (Hcy), termed hyperhomocysteinemia (HHcy), is an independent risk factor for human coronary heart disease (CHD) and stroke. Thus, HHcyinduced chronic vascular inflammation is a major public health problem. This proposal is to study a new molecular roadmap of how HHcy induces vascular inflammations. Success of this project will provide new molecular targets for future development of new therapeutics to treat CHD and stroke.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Atherosclerosis and Inflammation of the Cardiovascular System Study Section (AICS)
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Olive, Michelle
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Temple University
Schools of Medicine
United States
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Lopez-Pastrana, Jahaira; Shao, Ying; Chernaya, Valeria et al. (2015) Epigenetic enzymes are the therapeutic targets for CD4(+)CD25(+/high)Foxp3(+) regulatory T cells. Transl Res 165:221-40
Tan, Hongmei; Shi, Chengwei; Jiang, Xiaohua et al. (2014) Hyperhomocysteinemia promotes vascular remodeling in vein graph in mice. Front Biosci (Landmark Ed) 19:958-66
Mai, Jietang; Virtue, Anthony; Shen, Jerry et al. (2013) An evolving new paradigm: endothelial cells--conditional innate immune cells. J Hematol Oncol 6:61