Danesch U, Weber P C, Sellmayer A
Institut für Prophylaxe und Epidemiologie der Kreislaufkrankheiten, Klinikum Innenstadt, Universität München, Federal Republic of Germany.
J Biol Chem. 1994 Nov 4;269(44):27258-63.
Studying Swiss 3T3 fibroblasts, we report that arachidonic acid strongly stimulates mRNA levels of the growth-associated immediate early genes c-fos and Egr-1. Structurally related compounds like arachidonic acid methyl ester, arachidonyl alcohol, or eicosatetraynoic acid are ineffective, indicating a specific role of free unesterified arachidonic acid or an arachidonic acid metabolite in c-fos and Egr-1 mRNA accumulation. Blocking the conversion of arachidonic acid to prostaglandins by inhibiting cyclooxygenase abolishes arachidonic acid-induced accumulation of c-fos and Egr-1 mRNA. Inhibition of the lipoxygenase or cytochrome P-450 epoxygenase pathways has no significant effect on arachidonic acid-induced c-fos and Egr-1 mRNA levels, indicating that prostaglandin synthesis is necessary for the increase in c-fos and Egr-1 mRNA. Reversed phase high performance liquid chromatography revealed prostaglandin E2 (PGE2) as the major arachidonic acid metabolite in Swiss 3T3 fibroblasts. When added to the cells, PGE2 stimulates c-fos and Egr-1 mRNA levels to the same degree as arachidonic acid. Also, the inhibition of arachidonic acid-stimulated c-fos and Egr-1 mRNA accumulation by indomethacin is reversed by PGE2. Contrary to reports that PGE2 caused an increase in cAMP levels in Swiss 3T3 fibroblasts, we found that arachidonic acid and PGE2 only minimally increase cAMP levels as compared with untreated cells. In contrast, inhibition of protein kinase C by calphostin C and chelerythrine or down-regulation with phorbol 12-myristate 13-acetate drastically reduces PGE2 and arachidonic acid-induced c-fos and Egr-1 mRNA levels. These data indicate that arachidonic acid exerts its stimulatory effect on c-fos and Egr-1 mRNA via synthesis of PGE2 and subsequent activation of protein kinase C, probably through a PGE2 receptor coupled to phospholipase C.
在对瑞士3T3成纤维细胞的研究中，我们发现花生四烯酸能强烈刺激生长相关即刻早期基因c-fos和Egr-1的mRNA水平。结构相关化合物如花生四烯酸甲酯、花生四烯醇或二十碳四炔酸则无此作用，这表明游离的未酯化花生四烯酸或花生四烯酸代谢产物在c-fos和Egr-1 mRNA积累中具有特定作用。通过抑制环氧化酶来阻断花生四烯酸向前列腺素的转化，可消除花生四烯酸诱导的c-fos和Egr-1 mRNA积累。抑制脂氧合酶或细胞色素P-450环氧合酶途径对花生四烯酸诱导的c-fos和Egr-1 mRNA水平无显著影响，这表明前列腺素合成对于c-fos和Egr-1 mRNA的增加是必需的。反相高效液相色谱显示前列腺素E2（PGE2）是瑞士3T3成纤维细胞中主要的花生四烯酸代谢产物。当添加到细胞中时，PGE2刺激c-fos和Egr-1 mRNA水平的程度与花生四烯酸相同。此外，吲哚美辛对花生四烯酸刺激的c-fos和Egr-1 mRNA积累的抑制作用可被PGE2逆转。与报道称PGE2会导致瑞士3T3成纤维细胞中cAMP水平升高相反，我们发现与未处理细胞相比，花生四烯酸和PGE2仅使cAMP水平略有升高。相比之下，钙磷蛋白C和白屈菜红碱对蛋白激酶C的抑制作用或佛波醇12-肉豆蔻酸酯13-乙酸酯的下调作用会显著降低PGE2和花生四烯酸诱导的c-fos和Egr-1 mRNA水平。这些数据表明，花生四烯酸通过合成PGE2并随后激活蛋白激酶C，可能是通过与磷脂酶C偶联的PGE2受体，对c-fos和Egr-1 mRNA发挥刺激作用。
