Smooth muscle cell lipid metabolism and serum amyloid A

平滑肌细胞脂质代谢与血清淀粉样蛋白A

• 批准号: 7391577
• 负责人: BARBARA M SCHREIBER
• 金额: $ 35.5万
• 依托单位: BOSTON UNIVERSITY MEDICAL CAMPUS
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7391577
• 关键词: Acetyl-CoA Carboxylase; Acute; Adipocytes; Affect; Appendix; Arterial Fatty Streak; Atherosclerosis; Binding Proteins; Blood Vessels; CCAAT-Enhancer-Binding Proteins; Calcium; Cardiovascular Diseases; Cell membrane; Cholesterol; Cyclic AMP-Responsive DNA-Binding Protein; Cytosolic Phospholipase A2; Data; Deposition; Disease; Endoplasmic Reticulum; Family; Family member; Fatty Acids; Future; Gene Activation; Gene Expression; Genes; Genetic Transcription; Hydrolysis; Inflammatory; Lead; Lesion; Lipids; Lipoproteins; Liver; Mediating; Membrane; Microarray Analysis; Movement; Nuclear; Pathway interactions; Performance; Peripheral; Phase; Phospholipase; Phospholipase A2; Phospholipids; Plasma; Protein Family; Protein Isoforms; Proteins; Public Health; Response Elements; Role; Serum amyloid A protein; Smooth Muscle Myocytes; Source; Sphingomyelinase; Sphingomyelins; Sterols; Stimulus; Tissues; Work; cholesterol trafficking; drug development; gene repression; lipid metabolism; novel; protein activation; protein expression; response; trafficking; transcription factor

DESCRIPTION (provided by applicant): Smooth muscle cells (SMCs) contribute to proper vascular function but also to atherosclerosis. Little is known of the mechanisms mediating SMC cholesterol distribution. Serum amyloid A (SAA) accumulates in atherosclerotic plaques by deposition from plasma lipoproteins and/or local synthesis. We showed that SAA 1) is synthesized by SMCs in response to IL-1ct, 2) induces trafficking of cholesterol to the endoplasmic reticulum (ER), 3) down-regulates cholesterol and fatty acid synthesis and 4) decreases accumulation of cholesterol and phospholipid. Furthermore, SAA-mediated cholesterol trafficking decreases lipid synthesis by decreasing nuclear accumulation of the transcription factor known as sterol response element binding protein-1 (SREBP). Moreover, SAA down-regulates expression of the known SREBP-regulated gene acetyl CoA carboxylase. Interestingly, unlike other agents that traffic cholesterol to the ER, SAA mediates this effect without an exogenous cholesterol source, suggesting a novel mechanism of redirecting endogenous cholesterol pools. Our gene microarray analysis showed that SAA induces expression of secretory phospholipase A2 (sPLA2) and calcium-dependent cytosolic phospholipase A2 (cPLA2). Moreover, we show that SAA dramatically increases expression of sPLA2 protein. Additionally, CCAAT/enhancer binding protein (C/EBP) family members, known to up-regulate sPLA2 gene transcription, are up-regulated by SAA. Additional data suggest a role for cAMP response element-binding protein (CREB) in activation of C/EBP expression. Lastly, sphingomyelin, which has been shown to inhibit sPLA2 activity, inhibits the SAA- mediated movement of cholesterol to the ER. Thus, we hypothesize that SAA activates CREB, which up- regulates expression of C/EBPs, which in turn up-regulate expression of the sPLA2 gene. We further hypothesize that sPLA2 activity causes hydrolysis of membrane phospholipids, generating fatty acids that activate sphingomyelinase, contributing to endogenous cholesterol trafficking and hence down-regulation of genes activated by SREBP. Our aims are to 1) determine the role of lipid-free and lipid-associated SAA on sPLA2 gene expression via CREB activation and C/EBP expression 2) establish the effect of lipid-free and lipid-associated SAA on a) sPLA2 vs. cPLA2 expression and activity and b) to determine the role of phospholipase gene activation on sphingomyelinase activity and 3) establish the effect of lipid-free and lipid- associated SAA-mediated phospholipase activation on cholesterol trafficking, nuclear availability and function of SREBP. Cardiovascular disease remains a major public health concern. Elucidation of mechanisms that promote disease vs. protect against it will lead to future strategies for drug development.

描述（由申请人提供）：平滑肌细胞（SMC）有助于正常的血管功能，但也有助于动脉粥样硬化。对于介导 SMC 胆固醇分布的机制知之甚少。血清淀粉样蛋白 A (SAA) 通过血浆脂蛋白沉积和/或局部合成在动脉粥样硬化斑块中积聚。我们发现 SAA 1) 由 SMC 响应 IL-1ct 合成，2) 诱导胆固醇转运至内质网 (ER)，3) 下调胆固醇和脂肪酸合成，4) 减少胆固醇和磷脂的积累。此外，SAA 介导的胆固醇运输通过减少称为甾醇反应元件结合蛋白-1 (SREBP) 的转录因子的核积累来减少脂质合成。此外，SAA 下调已知的 SREBP 调节基因乙酰 CoA 羧化酶的表达。有趣的是，与其他将胆固醇输送到内质网的药物不同，SAA 在没有外源胆固醇来源的情况下介导这种作用，这表明了一种重新引导内源胆固醇池的新机制。我们的基因微阵列分析表明，SAA 诱导分泌性磷脂酶 A2 (sPLA2) 和钙依赖性胞质磷脂酶 A2 (cPLA2) 的表达。此外，我们发现 SAA 显着增加了 sPLA2 蛋白的表达。此外，已知可上调 sPLA2 基因转录的 CCAAT/增强子结合蛋白 (C/EBP) 家族成员也会被 SAA 上调。其他数据表明 cAMP 反应元件结合蛋白 (CREB) 在 C/EBP 表达激活中的作用。最后，鞘磷脂已被证明可以抑制 sPLA2 活性，从而抑制 SAA 介导的胆固醇向 ER 的移动。因此，我们假设 SAA 激活 CREB，CREB ​​上调 C/EBP 的表达，进而上调 sPLA2 基因的表达。我们进一步假设 sPLA2 活性导致膜磷脂水解，产生激活鞘磷脂酶的脂肪酸，促进内源性胆固醇运输，从而下调 SREBP 激活的基因。我们的目标是 1) 通过 CREB ​​激活和 C/EBP 表达确定无脂和脂质相关 SAA 对 sPLA2 基因表达的作用 2) 确定无脂和脂质相关 SAA 对 a) sPLA2 与 cPLA2 表达和活性的影响，b) 确定磷脂酶基因激活对鞘磷脂酶活性的作用，以及 3) 确定无脂 SAA 对鞘磷脂酶活性的影响 以及脂质相关的 SAA 介导的磷脂酶激活对胆固醇运输、核可用性和 SREBP 功能的影响。心血管疾病仍然是主要的公共卫生问题。阐明促进疾病与预防疾病的机制将有助于制定未来的药物开发策略。