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: 7610983
• 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/7610983
• 关键词: Acetyl-CoA Carboxylase; Acute; Adipocytes; Affect; 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(申请人提供)：平滑肌细胞(SMCs)有助于正常的血管功能，但也有助于动脉粥样硬化。目前对SMC胆固醇分布的调节机制知之甚少。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)是由SMC响应IL-1ct合成的，2)诱导胆固醇向内质网(ER)转运，3)下调胆固醇和脂肪酸的合成，4)减少胆固醇和磷脂的积累。此外，SAA介导的胆固醇转运通过减少被称为固醇反应元件结合蛋白-1(SREBP)的转录因子的核积聚来减少脂质合成。此外，SAA下调已知的SREBP调节基因乙酰辅酶A羧基酶的表达。有趣的是，与其他将胆固醇输送到内质网的试剂不同，SAA在没有外源性胆固醇来源的情况下介导了这一效应，这表明了一种重新定向内源性胆固醇池的新机制。我们的基因芯片分析表明，SAA诱导分泌型磷脂酶A2(SPLA2)和钙依赖性胞浆磷脂酶A2(CPLA2)的表达。此外，我们还发现SAA显著增加了sPLA2蛋白的表达。此外，已知的上调sPLA2基因转录的CCAAT/增强子结合蛋白(C/EBP)家族成员受SAA上调。更多的数据表明，cAMP反应元件结合蛋白(CREB)在C/EBP表达的激活中起作用。最后，已被证明抑制sPLA2活性的鞘磷脂抑制了SAA介导的胆固醇向内质网的移动。因此，我们假设SAA激活CREB，CREB上调C/EBPs的表达，进而上调sPLA2基因的表达。我们进一步假设，sPLA2活性引起膜磷脂的水解，产生激活鞘磷脂酶的脂肪酸，有助于内源性胆固醇的运输，从而下调SREBP激活的基因。我们的目标是：1)通过CREB的激活和C/EBP的表达，确定无脂和脂联的SAA对sPLA2基因表达的影响；2)确定无脂和脂联的SAA对sPLA2和cPLA2的表达和活性的影响；b)确定磷脂酶基因激活对鞘磷脂酶活性的影响；3)确定无脂和脂联的SAA介导的磷脂酶激活对SREBP的胆固醇转运、核可获得性和功能的影响。心血管疾病仍然是一个主要的公共卫生问题。阐明促进疾病与预防疾病的机制将导致未来的药物开发战略。