Hayama M, Akiba S, Fukuzumi M, Sato T
Department of Pathological Biochemistry, Kyoto Pharmaceutical University.
J Biochem. 1997 Dec;122(6):1196-201. doi: 10.1093/oxfordjournals.jbchem.a021881.
The stimulation of prostaglandin E2 (PGE2) production in mesangial cells exposed to a high glucose level was studied from the viewpoint of its implication in the glomerular hyperfiltration in diabetic nephropathy. The basal PGE2 synthesis apparently increased in the cells on incubation with a high glucose level (20 mM) for 3-6 h. Under these conditions, secretory phospholipase A2 activity was not detected in the incubation medium, but cytosolic phospholipase A2 (cPLA2) activity in the cells increased time-dependently up to 6 h, compared with that with a normal glucose level (5 mM). However, no difference in the cPLA2 protein content between the two glucose levels was observed on immunoblot analysis, suggesting that the increased cPLA2 activity under high glucose conditions is not due to stimulation of de novo synthesis. Stimulation with a calcium ionophore markedly enhanced arachidonic acid liberation and PGE2 production by cells exposed to the high glucose level. Furthermore, mitogen-activated protein kinase (MAPK) activity increased time-dependently under high glucose conditions, the rate of increase being consistent with those in cPLA2 activity and PGE2 production under the same conditions. These data suggest that glucose-induced cPLA2 activation through MAPK activation is responsible for the enhancement of PGE2 production in mesangial cells.
从前列腺素E2（PGE2）在糖尿病肾病肾小球高滤过中的作用角度，研究了高糖环境下系膜细胞中PGE2生成的刺激情况。在高糖水平（20 mM）下孵育3 - 6小时后，细胞中基础PGE2合成明显增加。在此条件下，孵育培养基中未检测到分泌型磷脂酶A2活性，但与正常糖水平（5 mM）相比，细胞中胞质磷脂酶A2（cPLA2）活性随时间增加，直至6小时。然而，免疫印迹分析未观察到两种糖水平下cPLA2蛋白含量的差异，这表明高糖条件下cPLA2活性增加并非由于从头合成的刺激。用钙离子载体刺激显著增强了高糖环境下细胞的花生四烯酸释放和PGE2生成。此外，在高糖条件下，丝裂原活化蛋白激酶（MAPK）活性随时间增加，增加速率与相同条件下cPLA2活性和PGE2生成的速率一致。这些数据表明，通过MAPK激活导致的葡萄糖诱导的cPLA2活化是系膜细胞中PGE2生成增强的原因。
