The hypothesis that the NO/cGMP pathway modulates PMN adhesion to human brain microvessel endothelial cells (HBMEC) was examined. Human PMN were incubated with resting or TNF-alpha-treated endothelial monolayers, and adhesion was quantified by light microscopy. TNF-alpha upregulated PMN adhesion in a time-dependent manner. Treatment of HBMEC with the NO donors SNP and DETA NONOate for 4 or 24 h decreased PMN adhesion. This was completely reversed by the guanylyl cyclase inhibitor ODQ, while addition of a cGMP agonist (8-Br-cGMP) decreased PMN adhesion. NO donors did not affect the levels of E-selectin or ICAM-1 in HBMEC. However, pre-treatment of PMN with NO donors or 8-Br-cGMP decreased their adhesion to recombinant E-selectin and ICAM-1, suggesting an effect of NO on PMN. These findings indicate that NO modulates PMN-HBMEC interactions through cGMP and decreases the binding of PMN to the adhesion molecules E-selectin and ICAM-1. (C) 2004 Elsevier Inc. All rights reserved.