NO regulates LPS-stimulated cyclooxygenase gene expression and activity inpulmonary artery endothelium

We examined whether nitric oxide (NO) inhibits prostanoid synthesis through actions on cyclooxygenase (COX) gene expression and activity. Bovine pulmo nary artery endothelial cells were pretreated for 30 min with the NO donors 1 mMS-nitroso-N-acetylpenicillamine (SNAP), 0.5 mM sodium nitroprusside (S NP), or 0.2 muM spermine NONOate; controls included cells pretreated with e ither 1 mM N-acetyl-D-penicillamine or the NO synthase (NOS) inhibitor 1 mM N-G-nitro- L-arginine methyl ester with and without addition of lipopolysa ccharide (LPS; 0.1 mug/ml) for 8 h. COX-1 and COX-2 gene and protein expres sion were examined by RT-PCR and Western analysis, respectively; prostanoid measurements were made by gas chromatography-mass spectrometry, and COX ac tivity was studied after a 30-min incubation with 30 mM arachidonic acid. L PS induced COX-2 gene and protein expression and caused an increase in COX activity and an eightfold increase in 6-keto-PGF(1 alpha) release. LPS-stim ulated COX-2 gene expression was decreased by similar to 50% by the NO dono rs. In contrast, LPS caused a significant reduction in COX-1 gene expressio n and treatment with NO donors had little effect. SNAP, SNP, and NONOate si gnificantly suppressed LPS-stimulated COX activity and 6-keto-PGF(1 alpha) release. Our data indicate that increased generation of NO attenuates LPS-s timulated COX-2 gene expression and activity, whereas inhibition of endogen ous NOS has little effect.