Mh. Zou et al., Interleukin 1 beta decreases prostacyclin synthase activity in rat mesangial cells via endogenous peroxynitrite formation, BIOCHEM J, 336, 1998, pp. 507-512
We have reported that peroxynitrite (PON) selectively inactivated prostacyc
lin 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 n
itration can occur under the influence of cytokines. Pretreatment of RMC wi
th interleukin 1 beta (IL-1 beta), which up-regulated cyclo-oxygenase 2 and
inducible nitric oxide synthase (NOS-2), significantly attenuated the conv
ersion of [C-14]prostaglandin H-2 (PGH(2)) into the stable prostacyclin (PG
I(2)) metabolite 6-oxo-prostaglandin F-1 alpha (6-oxo-PGF(1 alpha)). The pr
esence of superoxide dismutase (SOD, 100 units/ml) or the NOS synthase inhi
bitor N-omega-monomethyl-L-arginine (100 mu M) as well as cycloheximide (10
mu M) plus actinomycin(10 mu M) abolished IL-1 beta-mediated down-regulati
on of 6-oxo-PGF(1 alpha) from PGH(2). At the same time, 6-oxo-PGF(1 alpha)
production from arachidonate (AA) increased at the expense of prostaglandin
E-2 (PGE(2)). Neither NO alone generated from different NO donors nor supe
roxide from xanthine/xanthine oxidase (1-100 m-units/ml) inhibited PGI(2) s
ynthesis, either from PGH(2) or from AA. Bolus additions of chemically synt
hesized PON or the PON generator 3-morpholinosydnonimine N-ethyl-carbamide
(SIN-1) exhibited a potent inhibition of 6-oxo-PGF(1 alpha) release from bo
th PGH(2) and AA. In addition, immunoprecipitation of nitrotyrosine-contain
ing proteins from PON- and SIN-1-treated RMC yielded distinct nitrated PGIS
bands but also from IL-1 beta-pretreated cells alone, compared with a lack
of nitrated PGIS in control cells. Taken together, our results strongly su
ggest that IL-1 beta pretreatment of RMC via NOS-2 leads to the production
of PON with the consequence of a partial nitration and inhibition of PGIS.