ApoA-I Helical Domains and Cardiovascular Aging

描述（由申请方提供）：心血管和脑血管老化。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中的沉积和诱导维持血管炎症的氧化事件引起的。载脂蛋白（apo）A-I是血浆中主要的载脂蛋白，通过介导巨噬细胞泡沫细胞中胆固醇的流出来对抗动脉粥样硬化。细胞胆固醇流出过程构成了抗动脉粥样硬化胆固醇逆向转运（RCT）途径中的限速步骤。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。这一问题对于制定心血管疾病治疗的新策略具有重要意义。开发新的治疗策略需要鉴定apoA-I的螺旋片段，其通过介导细胞胆固醇流出启动RCT。apoA-I介导的细胞胆固醇流出依赖于ATP结合盒转运体A1（ABCA 1），ABCA 1通过降解途径下调。该研究的一个目标是确定apoA-I的螺旋结构元件，该螺旋结构元件阻止ABCA 1降解并以ABCA 1依赖性方式介导胆固醇流出。这将使用基于apoA-I两亲性或α-螺旋的合成肽来实现。最近，发现apoA-I的半胱氨酸携带变体，即apoA-I（Milano）是脂质过氧化的有效抑制剂;因此，半胱氨酸突变赋予介导apoA-I的胆固醇流出具有抗氧化能力。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）由于位于两亲性α-螺旋的脂-水界面处的游离硫醇的存在而在磷脂表面上具有断链抗氧化剂。将开发具有和不具有apoA-I（Milano）样抗氧化活性的介导胆固醇流出和稳定ABCA 1的合成肽。将进行体内研究以测试具有抗氧化活性加上胆固醇流出介导性质的肽是否比单独介导胆固醇流出的肽更有效地防止诱导维持衰老小鼠中血管炎症和动脉粥样硬化的关键介质。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.