Antiinflammatory activity of soluble guanylate cyclase: cGMP-dependent down-regulation of P-selectin expression and leukocyte recruitment

Nitric oxide (NO) production by the vascular endothelium maintains an essential antiinflammatory, cytoprotective influence on the blood vessel wall. A key component of this activity is attributed to prevention of leukocyte-endothelial cell interactions, yet the underlying mechanisms remain unclear. The NO receptor, soluble guanylate cyclase (sGC), is expressed in endothelial cells but fulfils an unknown function. Therefore, we used intravital microscopy in mesenteric postcapillary venules from WT and endothelial nitric oxide synthase (eNOS) knockout (eNOS-/-) mice, and an sGC activator (BAY 41-2272), to investigate a potential role for sGC in the regulation of adhesion molecule expression and leukocyte recruitment. Leukocyte rolling and adhesion was 6-fold greater in eNOS-/- than WT animals. BAY 41-2272 and the NO-donor, diethylamine-NONOate, reduced leukocyte rolling and adhesion in eNOS-/- mice to levels observed in WT animals. These effects were blocked by the sGC inhibitor ODQ [1 H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one], which itself caused a 6-fold increase in leukocyte rolling and adhesion in WT mice. Increased leukocyte rolling and adhesion in IL-1β-treated mice was also inhibited by BAY 41-2272. Fluorescence-activated cell sorting analysis in vitro and a specific P-selectin neutralizing antibody in vivo revealed that selective down-regulation of P-selectin expression accounted for the anti-adhesive effects of sGC activation. These data demonstrate that sGC plays a key antiinflammatory role by inhibiting P-selectin expression and leukocyte recruitment.