ApoA-I Helical Domains and Cardiovascular Aging

描述(申请人提供)：心脑血管老化。衰老与动脉粥样硬化的发展有关，动脉壁中胆固醇的沉积和维持血管炎症的氧化事件的诱导导致了动脉粥样硬化。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中胆固醇的外流来对抗动脉粥样硬化。细胞胆固醇外流的过程构成了抗动脉粥样硬化的胆固醇反向转运(RCT)途径的限速步骤。目前尚不清楚RCT的刺激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。这个问题对于设计治疗心血管疾病的新策略很重要。新的治疗策略的开发需要识别apoA-I的螺旋片段，这些螺旋片段通过介导细胞胆固醇外流来启动RCT。载脂蛋白A-I介导的细胞胆固醇外流依赖于ATP结合盒转运体A1(ABCA1)，而ABCA1通过降解途径下调。拟议研究的一个目标是确定apoA-I的螺旋结构元件，它可以阻止ABCA1的降解并以ABCA1依赖的方式调节胆固醇外流。这将使用基于apoA-I两亲性或α-螺旋的合成肽来实现。最近，载脂蛋白A-I的半胱氨酸突变体，即载脂蛋白A-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载脂蛋白A-I的胆固醇外流具有抗氧化能力。ApoA-I(Milano)抗氧化活性的机制基础将在拟议的研究中阐明。假设apoA-I(Milano)在磷脂表面具有断链抗氧化剂，这是因为在两亲性α-螺旋的脂水界面上存在一个游离的硫醇。调节胆固醇外流和稳定ABCA1的合成肽将被开发出具有和不具有apoA-I(Milano)样抗氧化活性的产品。将进行体内研究，以测试具有抗氧化活性和调节胆固醇外流特性的多肽是否比仅介导胆固醇外流的多肽更有效地防止在衰老小鼠中诱导维持血管炎症和动脉粥样硬化的关键介质。这些研究对于设计对抗心血管老化的新策略具有重要意义。

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.