The vasodilator-stimulated phosphoprotein (VASP): Target of YC-1 and nitric oxide effects in human and rat platelets

The effects of the different types of soluble guanylate cyclase (sGC) stimu lators on the phosphorylation status of vasodilator-stimulated phosphoprote in (VASP) in both human and rat platelets were studied under in vitro and i n vivo conditions. sGC-dependent VASP phosphorylation (at Ser(239) and Ser( 157)) both by the new direct sGC stimulator YC-1 and by NO donors was exami ned by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS/PAGE) with different antibodies. One antibody: which recognizes VASP independent of its phosphorylation state, was used to detect the mobility shift of VASP caused by Ser(157) phosphorylation. The other antibody was specifically di rected against VASP phosphorylated at Ser(239), the cGMP-dependent protein kinase (PKG) preferred phosphorylation site of VASP. in vitro YC-1 increase d both VASP phosphorylation and cyclic guanosine monophosphate (cGMP) level s as did the NO donors 2-(N,N-diethylamino)-diazenolate-2-oxide (DEA/NO) an d sodium nitroprusside (SNP). The combination of both types induced a syner gistic effect in both VASP phosphorylation and cGMP increase. In rat platel ets, similar effects could be shown in vitro. In vivo we observed a signifi cant increase in cGMP and a distinct effect on VASP phosphorylation in rat platelets 1 h after oral administration of YC-1. These biochemical alterati ons are supported by a significant prolongation in rat-tail bleeding time. Direct stimulators of sGC Like YC-1 are on the one hand direct potent stimu lators of the cGMP/PKG/VASP pathway in platelets and on the other hand syne rgize with NO, the physiologic stimulator of sGC. Therefore YC-1-like subst ances are interesting tools for the development of new cardiovascular drugs with vasodilatory and antithrombotic properties.