DIETARY N 3 FATTY ACIDS AND EXPRESSION OF CYCLOOXYGENASE

流行病学和临床研究已经证明有益于 N-3多不饱和脂肪酸在降低风险中的作用 心血管疾病和炎症性疾病。分子和细胞 其有益效果的基础还不是很清楚。结果来自 我们的临床和体外研究表明， N-3PUFA摄入抑制诱导型环氧合酶(COX-2)的表达 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多不饱和脂肪酸抑制了这种表达 单核细胞中致炎细胞因子的含量。这些影响不可能是 根据底物利用率的变化解释 二十烷类化合物的生物合成，流行的有益假说 N-3多不饱和脂肪酸摄入的影响。早期反应基因(COX-2)的诱导 细胞因子)的表达不需要干预蛋白质合成， 这意味着饮食中n-3PUFAs抑制COX-2的表达 通过调节信号通路来调节。研究结果由 US和其他人认为Lyn(单核细胞中主要的Src激酶)和 P21Ras(RAS)是信号通路的上游元件 对内毒素刺激的巨噬细胞COX-2和TNF-α表达的影响。 Src激酶和RAS的功能激活需要定位 到质膜，这反过来需要棕榈酰化(更多 通过脂肪酸准确地酰化)信号分子。因此， 我们的假设是饮食中的n-3PUFA通过抑制COX-2的表达 调控细胞膜定位和功能激活 信号分子；具体目标是：1)确定Lyn和 RAS是内毒素诱导的信号通路的上游组分 导致COX-2在单核细胞系中表达 用Lyn或RAS突变的cDNA转染。2)确定是否 N-3多不饱和脂肪酸富集细胞膜磷脂对膜的影响 LYN和/或RAS的本地化，进而调节 下游效应分子与COX-2在细胞中的稳定表达 用Lyn或RAS突变的cDNA转染。3)确定LYN是否 和RAS被棕榈酸以外的脂肪酸酰化，以及 N-3多不饱和脂肪酸改变了LYN和RAS的棕榈酰化。更改后的 这些信号分子通过n-3多不饱和脂肪酸的活性将导致 下游事件的调制以及最终的细胞响应 细胞外刺激。这些研究的结果可以揭开 对理解心力衰竭发病机制的重大新见解 N-3多不饱和脂肪酸抑制COX-2和某些细胞因子的表达。 此外，这些研究的结果可以提供令人兴奋的新的 有助于阐明分子和细胞的信息 不同膳食脂肪酸改变风险的机制(S) 各种慢性病。

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.