Lysophosphatidic acid & tissue factor in atherosclerosis

描述（由申请人提供）：本提案的长期目标是探索LPA（氧化LDL的一种成分）在动脉粥样硬化中的病理作用。该提案的驱动假设是，LPA （oxLDL的一种成分）通过上调TF表达促进动脉粥样硬化的机制之一。这一假设是基于我们的新发现：1)脂质溶血磷脂酸（LPA），最近被证明在动脉粥样硬化病变中高浓度积累，并被鉴定为oxLDL的一个成分，显著增加SMC中TF mRNA、TF蛋白的产生和TF活性；2) LPA诱导的tf基因表达需要激活特定的g蛋白、MAPK、PKC、新型蛋白激酶D （PKD）和核糖体S6激酶（p90RSK）；3) LPA诱导活体动物心脏、肾脏和主动脉中TF mRNA的表达。这一假设也得到了最近其他研究报告的支持：1)组织因子（TF）在动脉粥样硬化的发生发展中起重要作用；2) LPA在动脉粥样硬化病变中高浓度积累；3) LPA诱导大鼠主动脉新生内膜形成。这一假设是创新的，因为在动脉粥样硬化的发展中，这种磷脂LPA的作用是完全未知的，它是在低密度脂蛋白氧化过程中形成的，由活化的血小板分泌。本提案的目标将通过以下具体目标实现：目标1：利用LPA受体的特异性拮抗剂、亲和标记、反义寡核苷酸以及显性-阴性方法，鉴定和确定LPA受体、特异性g蛋白和蛋白激酶C的特定亚型在LPA刺激的TF表达中的作用。目的2：利用选择性抑制剂和显性阴性策略，探索PKD和p90RSK在TF基因调控中的新的生物学作用。目的3：利用成熟的动脉粥样硬化模型- apoe敲除小鼠，确定i) LPA在动脉粥样硬化发展中的作用；ii) TF在体内介导LPA在动脉粥样硬化病变发展中的病理作用。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to explore the pathological role of LPA, a component of oxidized LDL, in atherosclerosis. The driving hypothesis of the proposal is that one of the mechanisms by which LPA, a component of oxLDL, contributes to atherosclerosis is via up-regulation of TF expression. This hypothesis is based on our novel findings that 1) lipid lysophosphatidic acid (LPA), which has recently been shown to accumulate in high concentrations in atherosclerotic lesions and identified as a component of oxLDL, markedly increases TF mRNA, TF protein production and TF activity in SMC; 2) LPA induced-TF gene expression requires the activation of a particular G-protein, MAPK, PKC, the novel protein kinase D (PKD), and ribosome S6 kinase (p90RSK); and 3) LPA induces TF mRNA expression in heart, kidney and aorta of the living animal. This hypothesis is also supported by the observations recently reported by others: 1) Tissue factor (TF) plays an important role in the development of atherosclerosis; 2) LPA accumulates in high concentrations in atherosclerotic lesions; and 3) LPA induces neointimal formation in rat aorta. This hypothesis is innovative because in the development of atherosclerosis, the role of this phospholipid LPA, which forms during oxidation of LDL and is secreted from activated platelets, is totally unknown. The goals of this proposal will be achieved through the following specific aims: Aim 1:To identify and determine the role of LPA receptor, specific G-protein, and the particular isoform of protein kinase C in LPA-stimulated TF expression, using specific antagonists of LPA receptors, affinity labeling, antisense oligonucleotides, as well as the dominant-negative approach. Aim 2: To explore the novel biological role of PKD and p90RSK in TF gene regulation, using selective inhibitors and the dominant-negative strategy. Aim 3: Using a well-established atherosclerotic model-ApoE knockout mouse, to determine i) the role of LPA in the development of atherosclerosis; ii) the role of TF in mediating the pathological effect of LPA in atherosclerotic lesion development in vivo. The information obtained from the proposed studies may lead to the identification of novel therapeutic targets for the prevention and treatment of atherosclerosis. The proposed studies would also contribute to the understanding of the cellular signaling pathway that mediates the biological effects of LPA, specifically the effects on gene regulation in general. The proposed studies would also provide novel insight into the biological and cellular function of PKD and p90RSK in the vascular wall.