Involvement of Rho and p38 MAPK in Endothelin-1-Induced Expression of PGHS-2 mRNA in Osteoblast-Like Cells
作者:W. Windischhofer、D. Zach、G. Fauler、G. Raspotnig、H. Köfeler、H. J. Leis
DOI:10.1359/jbmr.2002.17.10.1774
日期:——
Prostaglandins (PGs) play an important role in bone remodeling because eicosanoids are local mediators of bone metabolism, which can induce physiological and pathological responses of bone tissue. Biosynthesis of PGs is catalyzed by constitutively expressed PG endoperoxide G/H synthase (PGHS) 1 and by the inducible isoform PGHS‐2. In MC3T3‐E1 osteoblast‐like cells, expression of PGHS‐2 was shown by mechanical forces, cytokines, growth factors, and hormones. Recently, endothelin (ET) 1‐stimulated PGHS‐2 mRNA expression was described, leading to a burst in prostaglandin E2 (PGE2) production. In this study, we investigated ET‐1‐induced signal transduction pathway(s) involved in the PGHS‐2 mRNA production. Time course of PGHS‐2 mRNA expression reaching the maximum within 45 minutes is in good agreement with the concept of an immediate early gene product. Inhibition of phospholipase C (PLC), phospholipase D (PLD), phosphatidylinositol‐3 kinase (PI‐3‐kinase), and protein kinase C (PKC) had no influence on PGHS‐2 synthesis. Using specific blockers of tyrosine kinases indicated involvement of p38 MAPK but not p42/44 MAPK. By preloading cells with exoenzyme C3, we were able to show requirement of the Rho family of G proteins for p38 MAPK phosphorylation and PGHS‐2 mRNA synthesis, whereas pertussis toxin (PTX) and cholera toxin (CTX) had no remarkable effect.
前列腺素(PGs)在骨重塑中发挥重要作用,因为类二十烷酸是骨代谢的局部介质,可以诱导骨组织的生理和病理反应。 PG 的生物合成由组成型表达的 PG 内过氧化物 G/H 合酶 (PGHS) 1 和诱导型同工型 PGHS-2 催化。在 MC3T3-E1 成骨细胞样细胞中,机械力、细胞因子、生长因子和激素显示 PGHS-2 的表达。最近,内皮素 (ET) 1 刺激 PGHS-2 mRNA 表达,导致前列腺素 E2 (PGE2) 产生激增。在这项研究中,我们研究了 ET-1 诱导的参与 PGHS-2 mRNA 产生的信号转导途径。 PGHS-2 mRNA 表达在 45 分钟内达到最大值的时间过程与立即早期基因产物的概念非常一致。磷脂酶 C (PLC)、磷脂酶 D (PLD)、磷脂酰肌醇-3 激酶 (PI-3-激酶) 和蛋白激酶 C (PKC) 的抑制对 PGHS-2 合成没有影响。使用酪氨酸激酶的特异性阻断剂表明 p38 MAPK 参与,但 p42/44 MAPK 不参与。通过用外切酶 C3 预载细胞,我们能够证明 G 蛋白 Rho 家族对 p38 MAPK 磷酸化和 PGHS-2 mRNA 合成的要求,而百日咳毒素 (PTX) 和霍乱毒素 (CTX) 没有显着影响。