Attenuation of cAMP accumulation in adult rat cardiac fibroblasts by IL-1β and NO: role of cGMP-stimulated PDE2

Abstract

Treatment of cultured adult rat cardiac fibroblasts with interleukin-1β (IL-1β) induces the inducible nitric oxide synthase (iNOS) expression, increases nitric oxide (NO) and cGMP production, and attenuates cAMP accumulation in response to isoproterenol by ∼50%. Reduced cAMP accumulation is due to NO production: the effect is mimicked by NO donors and prevented by N G-monomethyl-l-arginine, an NOS inhibitor. Effects of NO are not restricted to the β-adrenergic response; the response to forskolin is similarly diminished. NO donors only slightly (12%) decrease forskolin-stimulated adenylyl cyclase (AC) activity in cardiac fibroblast plasma membranes, suggesting that the main effect of NO is not a direct one on AC. An inhibitor of soluble guanylyl cyclase inhibits the effects of IL-1β and NO donors; inhibition of cGMP-dependent protein kinase is without effect. 3-Isobutyl-1-methylxanthine, a nonspecific phosphodiesterase (PDE) inhibitor, and erythro-9-(2-hydroxy-3-nonyl)adenine, a specific inhibitor of the cGMP-stimulated PDE (PDE2), completely restore cAMP accumulation in sodium nitroprusside-treated fibroblasts and largely reverse the attenuated response in IL-1β-treated fibroblasts. Although NO reportedly acts by reducing AC activity in some cells, in cardiac fibroblasts NO production decreases cAMP accumulation largely by the cGMP-mediated activation of PDE2.