Mechanisms of cLDL-Induced Endothelial Injury

描述（由申请人提供）： 慢性肾脏病（CKD）的患病率在全球范围内不断增加。在美国，超过2000万成年人患有CKD，传统的心血管风险因素并不能解释这一点。血尿素分解形成氰酸盐，氰酸盐可能通过称为氨甲酰化的过程改变蛋白质，包括低密度脂蛋白（LDL）。我们最近的研究表明，cLDL具有与动脉粥样硬化相关的所有生物学效应：（a）cLDL诱导人冠状动脉内皮细胞损伤;（B）它诱导粘附分子表达和单核细胞粘附在人冠状动脉内皮细胞上;和（c）它引起人冠状动脉平滑肌细胞增殖。此外，我们已经证明，无论是慢性肾功能衰竭或慢性尿素消耗的血浆cLDL浓度升高的结果在小鼠的主动脉粥样硬化的发展。我们在尿毒症患者中的病例对照研究显示，cLDL升高与颈总动脉内膜中层厚度（IMT）增加（一种公认的早期动脉粥样硬化的可量化标志物）之间存在强正相关性。在cLDL暴露于内皮细胞的反应中发生的主要事件之一是诱导DNA断裂和细胞死亡。cLDL诱导内皮细胞损伤（动脉粥样硬化的早期步骤）的机制尚不清楚。 该建议的中心假设是CKD升高的cLDL通过激活EndoG诱导内皮细胞损伤以促进动脉粥样硬化，并且内皮EndoG的失活将减弱尿毒症小鼠中的内皮细胞死亡和动脉粥样硬化形成。我们的初步研究表明，cLDL诱导的内皮细胞死亡依赖于内切核酸酶G（EndoG）的表达，这种核酸酶与非半胱天冬酶依赖的DNA片段化有关。用从野生型（WT）和EndoG无效敲除（KO）小鼠分离的原代内皮细胞进行的离体实验证明，与WT细胞相比，KO细胞被部分保护免受cLDL毒性。我们的研究结果显示，与WT小鼠中的nLDL相比，cLDL注射后漂浮的内皮细胞数量增加，但KO小鼠中没有。这些数据表明EndoG是cLDL对内皮细胞毒性的重要介质，并表明EndoG是cLDL细胞毒性和潜在动脉粥样硬化的潜在治疗靶点。为了研究cLDL-EndoG通路，我们计划：目的1。在体外和体内确定引起EndoG活化的cLDL的分子和细胞靶标。 目标2.评价EndoG可能的上游调节因子在体外和体内cLDL诱导的内皮细胞死亡中的作用。 目标3：测试EndoG的基因失活或EndoG上调机制的抑制是否减轻尿毒症/cLDL诱导的内皮细胞损伤和动脉粥样硬化。 最近的研究表明，在退伍军人中，传统的心血管危险因素CVD和CKD非常普遍，CKD与基线CVD和随访死亡率的风险增加有关。我们的研究旨在确定cLDL介导的EndoG或其上游机制的调节是否可能有益于防止cLDL诱导的急性内皮损伤和动脉粥样硬化。因此，这项研究的结果可能最终挽救人类生命，改善退伍军人的健康和福祉，并减少退伍军人和普通人群的残疾人数。

DESCRIPTION (provided by applicant): The prevalence of chronic kidney disease (CKD) is increasing worldwide. In the United States, over 20 million adults have CKD, and traditional cardiovascular risk factors do not account for this. Blood urea dissociates to form cyanate that may alter proteins including low-density lipoprotein (LDL) by a process known as carbamylation. Our recent studies demonstrate that cLDL has all of the biological effects relevant to atherosclerosis: (a) cLDL induces injury to human coronary artery endothelial cells; (b) it induces adhesion molecule expression and monocyte adhesion on human coronary artery endothelial cells; and (c) it causes proliferation of human coronary artery smooth muscle cells. In addition, we have demonstrated that elevated plasma cLDL concentration from either chronic kidney failure or chronic urea consumption results in the development of aortic atherosclerosis in mice. Our case-control study in uremic patients revealed a strong positive correlation between elevated cLDL and an increase in common carotid artery intima-media thickness (IMT), an accepted quantifiable marker of early atherosclerosis. One of the major events that occurs in response of cLDL exposure to endothelial cells is the induction of DNA fragmentation and cell death. The mechanisms by which cLDL induces endothelial cell injury, an early step in atherosclerosis, are not known. The central hypothesis of this proposal is that cLDL elevated by CKD induces endothelial cell injury by activating EndoG to promote atherosclerosis, and that inactivation of endothelial EndoG will blunt endothelial cell death and atherogenesis in uremic mice. Our preliminary studies show that endothelial cell death induced by cLDL depends on the expression of endonuclease G (EndoG), the nuclease associated with caspase-independent DNA fragmentation. Ex vivo experiments with primary endothelial cells isolated from wild-type (WT) and EndoG null knockout (KO) mice demonstrated that KO cells are partially protected against cLDL toxicity compared to WT cells. Our results showed increased number of floating endothelial cells after cLDL injection compared to nLDL in WT mice but not in KO mice. These data point to EndoG as an important mediator of cLDL toxicity to endothelial cells, and suggest that EndoG is a potential therapeutic target for cLDL cytotoxicity and, potentially, atherosclerosis. To study the cLDL-EndoG pathway, we plan: Aim 1. Determine molecular and cellular targets of cLDL causing activation of EndoG in vitro and in vivo. Aim 2. Evaluate the role of likely upstream regulators of EndoG in cLDL-induced endothelial cell death in vitro and in vivo. Aim 3. Test whether genetic inactivation of EndoG or inhibition of mechanisms upregulating EndoG attenuate uremia/cLDL-induced endothelial cell injury and atherosclerosis. Recent studies showed that among veterans, traditional cardiovascular risk factors CVD and CKD are highly prevalent, and CKD is associated with an increased risk of baseline CVD and follow-up mortality. Our study is aimed to determine whether regulation of the cLDL mediator EndoG or its upstream mechanisms may be beneficial for protection against acute endothelial injury and atherosclerosis induced by cLDL. Therefore, the results of this study may eventually save human lives, improve the health and well being of veterans, and decrease the number of disabilities among veterans and in the general population.