H2O2 activity on platelet adhesion to fibrinogen and protein tyrosine phosphorylation

Platelets represent a target of reactive oxygen species produced under oxidative stress conditions. Controversial data on the effect of these species on platelet functions have been reported so far. In this study we evaluated the effect of a wide range of H 2 O 2 concentrations on platelet adhesion to immobilized fibrinogen and on pp72 syk and pp125 FAK tyrosine phosphorylation. Our results demonstrate that: (1) H 2 O 2 does not affect the adhesion of unstimulated or apyrase-treated platelets to immobilized fibrinogen; (2) H 2 O 2 does not affect pp72 syk phosphorylation induced by platelet adhesion to fibrinogen-coated dishes; (3) H 2 O 2 reduces, in a dose-dependent fashion, pp125 FAK phosphorylation of fibrinogen-adherent platelets; (4) concentrations of H 2 O 2 near to physiological values (10–12 μM) are able to strengthen the subthreshold activation of pp125 FAK induced by epinephrine in apyrase-treated platelets; (5) H 2 O 2 doses higher than 0.1 mM inhibit ADP-induced platelet aggregation and dense granule secretion. The ability of H 2 O 2 to modulate pp125 FAK phosphorylation suggests a role of this molecule in physiological hemostasis as well as in thrombus generation.