DIETARY N 3 FATTY ACIDS AND EXPRESSION OF CYCLOOXYGENASE

流行病学和临床研究表明， n-3多不饱和脂肪酸（PUFA）在降低风险方面的作用 心血管疾病和炎症性疾病。 分子和细胞 这些有益效果的基础还不清楚。 结果 我们的临床和体外研究表明， 诱导型环氧合酶（考克斯-2）被n-3 PUFA摄入抑制 在脂多糖（LPS）刺激的单核细胞中。 同样，其他 研究人员已经证明，n-3 PUFA抑制了 单核细胞中的促炎细胞因子。 这些影响不能 根据基质可用性的变化进行解释， 类花生酸的生物合成，对有益的普遍假设， n-3 PUFA摄入量的影响。 诱导早期反应基因（考克斯-2 细胞因子）表达不需要干预蛋白质合成， 这意味着通过饮食n-3 PUFA抑制考克斯-2的表达， 通过调节信号通路来介导。 研究结果 我们和其他人认为林恩（单核细胞中主要的Src激酶）和 p21 Ras（Ras）是信号通路的上游组分， LPS刺激巨噬细胞表达考克斯-2和TNF-α。 Src激酶和Ras的功能激活需要定位 到质膜，这反过来又需要棕榈酰化（更多 通过脂肪酸的精确酰化）。 因此，我们认为， 我们的假设是饮食n-3 PUFA通过以下途径抑制考克斯-2的表达： 调节细胞膜定位和功能激活， 具体目的是：1）确定林恩和 Ras是LPS诱导的信号通路的上游成分 导致单核细胞系中考克斯-2的表达 用林恩或Ras突变cDNA转染。 2)以确定是否 用n-3 PUFA富集细胞膜磷脂影响膜 定位林恩和/或Ras，并反过来调节激活 下游效应物和考克斯-2在细胞中的稳定表达 用林恩或Ras突变cDNA转染。 3)为了确定林恩 和Ras被棕榈酸以外的脂肪酸酰化， 林恩和Ras的棕榈酰化被n-3 PUFA改变。 改变 这些信号分子通过n-3 PUFA的活性将导致 调节下游事件并最终调节细胞对 细胞外刺激 这些研究的结果可以揭示 重要的新见解，了解机制， n-3 PUFA抑制考克斯-2和可能的一些细胞因子的表达。 此外，这些研究的结果可以提供令人兴奋的新 这些信息有助于阐明 不同膳食脂肪酸改变风险的机制 各种慢性疾病。

Epidemiological and clinical studies have demonstrated beneficial effects of n-3 polyunsaturated fatty acids (PUFA) in reducing the risks of cardiovascular and inflammatory diseases. The molecular and cellular bases for the beneficial effects are not well understood. Results from our clinical and in vitro studies demonstrated that the expression of the inducible cyclooxygenase (COX-2) is suppressed by n-3 PUFA intake in lipopolysaccharide (LPS)-stimulated monocytes. Similarly, other investigators have demonstrated that n-3 PUFAs suppress the expression of proinflammatory cytokines in monocytes. These effects cannot be explained based on the alteration of substrate availability in eicosanoid biosynthesis , the prevailing hypothesis for the beneficial effects of n-3 PUFA intake. Induction of early response gene (COX-2 cytokines) expression does not require intervening protein synthesis, implying that suppressed expression of COX-2 by dietary n-3 PUFAs is mediated by modulating the signaling pathways. Results from studies by us and others suggest that Lyn (the major Src kinase in monocytes) and p21Ras (Ras) are the upstream components in signaling pathways leading to the expression of COX-2 and TNF-alpha in LPS-stimulated macrophages. The functional activation of Src kinases and Ras requires localization to the plasma membrane, which in turn requires palmitoylation (more accurately acylation by fatty acids) of the signaling molecules. Hence, our hypothesis is that dietary n-3 PUFAs suppress COX-2 expression by modulating membrane localization and functional activation of the signaling molecules; Specific aims are: 1) to determine whether Lyn and Ras are the upstream components in the LPS-induced signaling pathways leading to the expression of COX-2 in the monocytes cell line transfected with Lyn or Ras mutant cDNAs. 2) To determine whether enriching cell membrane phospholipids with n-3 PUFAs affects membrane localization of Lyn and/or Ras, and in turn modulates the activation of downstream effectors and COX-2 expression in the cells stably transfected with Lyn or Ras mutant cDNAs. 3) To determine whether Lyn and Ras are acylated by fatty acids other than palmitic acid and whether the palmitoylation of Lyn and Ras is altered by n-3 PUFAs. Altered activity of these signaling molecules by n-3 PUFAs will lead to the modulation of downstream events and ultimately cellular responses to extracellular stimuli. Results from these studies can unveil significant new insight toward understanding the mechanism for the suppressed expression of COX-2 and perhaps some cytokines by n-3 PUFAs. Furthermore, results from these studies can provide exciting new information that helps elucidate the molecular and cellular mechanisms(s) by which different dietary fatty acids modify the risks of various chronic diseases.