Study of brain arachidonic acid metabolism

脑花生四烯酸代谢研究

• 批准号: 6969270
• 负责人: francesca bosetti
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6969270
• 关键词: aging; arachidonate; brain metabolism; calcium ion; eicosanoid metabolism; enzyme activity; gene expression; genetically modified animals; isozymes; laboratory mouse; neuroprotectants; nuclear factor kappa beta; phospholipase A2; prostaglandin endoperoxide synthase

(1) Altered arachidonic acid release and metabolism by the enzymes cPLA2 and COX-2 is thought to be involved in the pathophysiology of a number of neurological and psychiatric disorders. Thus, a better understanding of the mechanisms that control the expression of cPLA2 and COX-2 may provide therapeutic targets to enhance neuroprotection. We used cPLA2 deficient mice to study compensatory mechanisms and coupling between cPLA2 and downstream enzymes in the eicosanoid biosynthetic pathway. We found a significant 50-60% decrease in mRNA, protein, and enzyme activity levels of COX-2, but no change in COX-1, prostaglandin E synthase (PGES), or other arachidonic acid oxygenating enzymes. Enzyme activities and protein levels of Ca2+-independent iPLA2 and secretory sPLA2 were not significantly changed. These results show that other brain PLA2 enzymes do not compensate for the cPLA2 deficiency and that cPLA2 is critical for COX-2-derived eicosanoid production in mouse brain. (2) To further investigate the interaction between upstream and downstream enzymes involved in brain prostaglandin synthesis, we examined expression and activity of COX-1, of different PLA2 enzymes, and of PGES enzymes in COX-2 deficient mice. The PGE2 level was decreased by 52% in the COX-2 knockout mice brain, indicating a significant role of COX-2 in formation of PGE2. However, when we added exogenous arachidonic acid to brain homogenates, COX activity was increased in the COX-2 deficient mice, suggesting a compensatory increase in COX-1 expression and an intracellular compartmentalization of the COX isozymes. Activity and expression of cPLA2 and sPLA2 enzymes, supplying AA to COX, were significantly increased. Our results indicate that compensatory mechanisms exist in COX-2 deficient mice and that microsomal PGES-2 is functionally coupled with COX-2. Thus, this pathway might represent a novel target for anti-inflammatory and neuroprotective drugs.

（1）酶CPLA2和COX-2改变了花生四烯酸的释放和代谢，被认为参与了许多神经系统和精神疾病的病理生理学。因此，对控制CPLA2和COX-2表达的机制有更好的理解可以提供治疗靶标，以增强神经保护作用。我们使用CPLA2不足的小鼠研究了eicosanoid Biosynthetic途径中CPLA2和下游酶之间的补偿机制和耦合。我们发现COX-2的mRNA，蛋白质和酶活性水平显着降低了50-60％，但COX-1，前列腺素E合酶（PGE）或其他花生四烯酸酸氧化酶没有变化。 Ca2+非依赖性IPLA2和分泌SPLA2的酶活性和蛋白质水平没有显着改变。这些结果表明，其他脑PLA2酶不能补偿CPLA2缺乏症，并且CPLA2对于小鼠脑中的Cox-2衍生的类固醇生产至关重要。 （2）为了进一步研究参与脑前列腺素合成的上游和下游酶之间的相互作用，我们检查了COX-1，不同PLA2酶的表达和活性以及Cox-2缺陷小鼠中的PGES酶的表达和活性。在COX-2基因敲除小鼠大脑中，PGE2水平降低了52％，表明COX-2在PGE2形成中起着重要作用。但是，当我们在脑匀浆中添加外源性蛛网膜酸时，COX-2缺乏小鼠的Cox活性增加，这表明COX-1表达的补偿性增加和Cox同工酶的细胞内分室化。 CPLA2和SPLA2酶的活性和表达显着增加了AA。我们的结果表明，COX-2缺陷小鼠中存在补偿机制，并且微粒体PGES-2在功能上与COX-2耦合。因此，该途径可能代表了抗炎和神经保护药物的新靶标。