ApoA-I Helical Domains and Cardiovascular Aging

描述（申请人自述）：心脑血管老化。衰老与动脉粥样硬化的发展有关，动脉粥样硬化是由胆固醇在动脉壁的沉积和维持血管炎症的氧化事件的诱导引起的。载脂蛋白（apo） A-I是主要的血浆载脂蛋白，通过调节巨噬细胞泡沫细胞的胆固醇外排来对抗动脉粥样硬化。细胞胆固醇外排过程构成抗动脉粥样硬化逆向胆固醇转运（RCT）途径的限速步骤。目前尚不清楚刺激RCT是否足以减弱在衰老过程中维持血管炎症和动脉粥样硬化的关键介质的慢性诱导。这个问题对于制定治疗心血管疾病的新策略很重要。开发新的治疗策略需要鉴定通过介导细胞胆固醇外排启动RCT的apoA-I的螺旋段。apoA-I介导的细胞胆固醇外流依赖于atp结合盒转运蛋白A1 (ABCA1)， ABCA1通过降解途径下调。拟议研究的一个目标是确定防止ABCA1降解和以ABCA1依赖的方式介导胆固醇外排的apoA-I的螺旋结构元件。这将通过基于apoA-I两亲性或α -螺旋的合成肽来实现。最近，一种携带半胱氨酸的apoA-I变体，即apoA-I(Milano)，被发现是一种有效的脂质过氧化抑制剂；因此，半胱氨酸突变使介导胆固醇外排的apoa - 1具有抗氧化能力。apoA-I（Milano）抗氧化活性的机制基础将在拟议的研究中得到阐明。据推测，apoA-I（Milano）在磷脂表面具有断链抗氧化剂，这是由于位于两亲α -螺旋的脂-水界面上的游离硫醇的存在。介导胆固醇外排和稳定ABCA1的合成肽将被开发，无论是否具有apoA-I（Milano）样抗氧化活性。将进行体内研究，以测试具有抗氧化活性和胆固醇外排介导特性的肽是否比单独介导胆固醇外排的肽在防止诱导维持衰老小鼠血管炎症和动脉粥样硬化的关键介质方面更有效。这些研究与设计对抗心血管衰老的新策略有关。

DESCRIPTION (provided by applicant): Cardiovascular and Cerebrovascular aging. Aging is associated with the development of atherosclerosis resulting from the deposition of cholesterol in the artery wall and the induction of oxidative events that sustain vascular inflammation. Apolipoprotein (apo) A-I, the major plasma apolipoprotein, is equipped to combat atherosclerosis by mediating the efflux of cholesterol from macrophage foam-cells. The process of cellular cholesterol efflux constitutes the rate-limiting step in the anti-atherogenic reverse cholesterol transport (RCT) pathway. It is not known whether stimulation of RCT is sufficient to attenuate the chronic induction of key mediators that sustain vascular inflammation and atherosclerosis during aging. This issue is important for devising new strategies for the treatment of cardiovascular disease. The development of new therapeutic strategies requires the identification of the helical segments of apoA-I that initiate RCT by mediating cellular cholesterol efflux. Cellular cholesterol efflux mediated by apoA-I is dependent on the ATP-binding cassette transporter A1 (ABCA1) which is down regulated via a degradation pathway. One goal of the proposed studies is to identify the helical structural elements of apoA-I that prevent ABCA1 degradation and mediate cholesterol efflux in an ABCA1-dependent manner. This will be achieved using synthetic peptides based on apoA-I amphipathic or alpha-helices. Recently, a cysteine-bearing variant of apoA-I, i.e. apoA-I(Milano), was found to be a potent inhibitor of lipid peroxidation; thus, the cysteine mutation endows the cholesterol efflux mediating apoA-I with antioxidant capability. The mechanistic basis for the antioxidant activity of apoA-I(Milano) will be elucidated in proposed studies. It is hypothesized that apoA-I(Milano) possesses chain-breaking antioxidant on phospholipid surfaces due to the presence of a free thiol located at the lipid-water interface of an amphipathic alpha-helix. Synthetic peptides that mediate cholesterol efflux and stabilize ABCA1 will be developed with and without apoA-I(Milano)-like antioxidant activity. In vivo studies will be conducted to test whether a peptide with antioxidant activity plus cholesterol efflux-mediating properties is more effective than a peptide that mediates cholesterol efflux alone in preventing the induction of key mediators that sustain vascular inflammation and atherosclemsis in aging mice. These studies are relevant for devising novel strategies to combat cardiovascular aging.