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: 7215578
• 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/7215578
• 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）有助于适当的血管功能，但也有助于动脉粥样硬化。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）由SMC响应IL-1 α合成，2）诱导胆固醇向内质网（ER）的运输，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介导的胆固醇运输通过减少称为固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调节基因乙酰辅酶A羧化酶的表达。有趣的是，与其他将胆固醇运输到ER的药物不同，SAA在没有外源性胆固醇来源的情况下介导这种作用，这表明了一种重新定向内源性胆固醇库的新机制。我们的基因芯片分析表明，SAA诱导分泌型磷脂酶A2（sPLA 2）和钙依赖性胞浆型磷脂酶A2（cPLA 2）的表达。此外，我们发现SAA显著增加sPLA 2蛋白的表达。此外，已知上调sPLA 2基因转录的CCAAT/增强子结合蛋白（C/EBP）家族成员也被SAA上调。额外的数据表明cAMP反应元件结合蛋白（CREB）在C/EBP表达的激活中的作用。最后，已显示抑制sPLA 2活性的鞘磷脂抑制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，C/EBP又上调sPLA 2基因的表达。我们进一步假设sPLA 2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。我们的目的是1）确定无脂质和脂质相关的SAA通过CREB活化和C/EBP表达对sPLA 2基因表达的作用2）确定无脂质和脂质相关的SAA对a）sPLA 2相对于cPLA 2表达和活性的作用和B）确定磷脂酶基因活化对鞘磷脂酶活性的作用和3）确定无脂质和脂质相关的SAA的作用。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策略。