Dipyridamole enhances interleukin-1β-stimulated nitric oxide production by cultured rat vascular smooth muscle cells

Abstract

We examined whether dipyridamole affected interleukin-1β-stimulated nitric oxide (NO) production by cultured rat vascular smooth muscle cells. Interleukin-1β stimulated the production of nitrite and nitrate, stable metabolites of NO, in a dose- and time-dependent manner in vascular smooth muscle cells. Dipyridamole (1–100 μM) enhanced interleukin-1β-induced nitrite production in a dose- and time-dependent manner. The mRNA expression of inducible NO synthase was up-regulated by dipyridamole (0.3–10 μM) treatment in a dose-dependent manner. Both 8-bromo-guanosine 3′,5′-cyclic monophosphate (8-bromo-cGMP) and dibutyryl adenosine 3′,5′-cyclic monophosphate (db-cAMP) enhanced the nitrite production in the presence of interleukin-1β. Dipyridamole up-regulated the effect of both 8-bromo-cGMP and db-cAMP on the interleukin-1β-induced nitrite production. Dipyridamole increased the intracellular cAMP content in the presence of interleukin-1β (10 ng/ml), but did not affect the intracellular cGMP content. 8R∗,9S∗,11S∗-(−)-9-hydroxy-9- n-hexyloxy-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1 H,8 H,11 H-2,7b,11a- triazadibenzo-( a,g)-cycloocta( c,d,e)-trinden-1-one (KT 5720), a selective inhibitor of cAMP-dependent protein kinase, abolished the enhancement of interleukin-1β-induced nitrite production by dipyridamole, whereas 8 R∗,9 S∗,11 S∗-(−)-9-methoxy-carbamyl-8-methyl-2,3,9,10-tetrahydro-8,11-epoxy-1 H,8 H,11 H-2,7b,11a-trizadibenzo-( a,g)-c (KT 5823), an inhibitor of cGMP-dependent protein kinase, did not attenuate the enhancement. Furthermore, Rolipram and 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro-20-1724), cAMP-specific phosphodiesterase type IV inhibitors, augmented the interleukin-1β-induced nitrite production. We concluded that dipyridamole enhanced the interleukin-1β-induced NO production via an increase in intracellular cAMP content in cultured rat vascular smooth muscle cells.