Interleukin 1β decreases prostacyclin synthase activity in rat mesangial cells via endogenous peroxynitrite formation

Abstract

We have reported that peroxynitrite (PON) selectively inactivated prostacyclin synthase (PGIS) by a mechanism of tyrosine nitration at the active site [Zou, Martin and Ullrich (1997) Biol. Chem. Hoppe–Seyler 378, 707–713]. We have now extended our studies on rat mesangial cells (RMC) and show that nitration can occur under the influence of cytokines. Pretreatment of RMC with interleukin 1β (IL-1β), which up-regulated cyclo-oxygenase 2 and inducible nitric oxide synthase (NOS-2), significantly attenuated the conversion of [14C]prostaglandin H2 (PGH2) into the stable prostacyclin (PGI2) metabolite 6-oxo-prostaglandin F1α (6-oxo-PGF1α). The presence of superoxide dismutase (SOD, 100 units/ml) or the NOS synthase inhibitor Nω-monomethyl-l-arginine (100 µM) as well as cycloheximide (10 µM) plus actinomycin (10 µM) abolished IL-1β-mediated down-regulation of 6-oxo-PGF1α from PGH2. At the same time, 6-oxo-PGF1α production from arachidonate (AA) increased at the expense of prostaglandin E2 (PGE2). Neither NO alone generated from different NO donors nor superoxide from xanthine/xanthine oxidase (1–100 m-units/ml) inhibited PGI2 synthesis, either from PGH2 or from AA. Bolus additions of chemically synthesized PON or the PON generator 3-morpholinosydnonimine N-ethylcarbamide (SIN-1) exhibited a potent inhibition of 6-oxo-PGF1α release from both PGH2 and AA. In addition, immunoprecipitation of nitrotyrosine-containing proteins from PON- and SIN-1-treated RMC yielded distinct nitrated PGIS bands but also from IL-1β-pretreated cells alone, compared with a lack of nitrated PGIS in control cells. Taken together, our results strongly suggest that IL-1β pretreatment of RMC via NOS-2 leads to the production of PON with the consequence of a partial nitration and inhibition of PGIS.