ADENOSINE STIMULATES NITRIC-OXIDE SYNTHESIS IN VASCULAR SMOOTH-MUSCLECELLS

Objective: The aim was to investigate the effects of adenosine on nitr ic oxide (NO) synthesis in vascular smooth muscle cells. Methods: NO a nd cAMP synthesis was measured in confluent rat vascular smooth muscle cells in culture at passage 5-10, using Griess reagent and an enzyme immunoassay kit, respectively. The expression of inducible NO synthase mRNA was assayed by Northern blotting. Results: Incubation of culture s with interleukin-1 beta (10 ng/ml) for 24 h caused a significant inc rease in nitrite production. The interleukin-1 beta-induced nitrite pr oduction by vascular smooth muscle cells was significantly increased b y adenosine or its stable analogue, 2-chloroadenosine, in a dose-depen dent manner. The adenosine A(2a) receptor antagonist, KF17837, but not the A(1) receptor antagonist; DPCPX, significantly inhibited 2-chloro adenosine-mediated nitrite production. The 2-chloroadenosine-induced n itrite production by interleukin-1 beta-stimulated cells was accompani ed by increased inducible NO synthase mRNA accumulation. In the presen ce of dibutyryl-cAMP(1 mM), interleukin-1 beta-induced nitrite accumul ation was further increased, but the effect of 2-chloroadenosine was n ot additive or synergistic. Addition of 2-chloroadenosine dose-depende ntly increased intracellular cAMP levels of vascular smooth muscle cel ls. Conclusions: These results indicate that adenosine acts on A(2) re ceptors and augments NO synthesis in interleukin-1 beta-stimulated vas cular smooth muscle cells, at least partially through a cAMP-dependent pathway.