Biphasic effect of oxygen radicals on prostaglandin production by rat mesangial cells

Abstract

Cultured rat mesangial cells were exposed to a reactive oxygen species (ROS) generating system (xanthine plus xanthine oxidase) to explore the effect of ROS on their metabolism of arachidonic acid (AA). Cell viability, as assessed by 51Cr release, was not affected by the concentrations of xanthine plus xanthine oxidase used. Prostaglandin E2 (PGE2) production following exposure to increasing quantities of xanthine plus xanthine oxidase was significantly decreased to 38.1 +/- 9.7 or 30.8 +/- 6.9% of control levels (P less than 0.05) when cells were stimulated with the calcium ionophore A23187 (1 microgram/ml) or AA (10(-6) M), respectively. Maximum suppression of production was seen within 10 min of ROS exposure. Thromboxane B2 production was similarly decreased to 83.1 +/- 7.6 (0.05 less than P less than 0.10) or 54.9 +/- 2.5% (P less than 0.05). This effect was reversed by addition of catalase to the ROS generating system but not by superoxide dismutase or mannitol, which suggested that H2O2 was the responsible metabolite. High levels of H2O2 (5 x 10(-4) M) suppressed PGE2 production to 44.0 +/- 4.1 or 17.4 +/- 6.2% of A23187- or AA-stimulated production (P less than 0.05). Lower levels of H2O2 resulted in significant stimulation of base-line PGE2 production. Analysis of release of [3H]AA-labeled metabolites from A23187-stimulated cells showed no effect of H2O2 on phospholipase activity. Thus ROS can stimulate or inhibit AA metabolism in the glomerular mesangium, which may have important effects on glomerular hemodynamics during glomerular injury.