Platelet inhibition and increased phosphorylated vasodilator-stimulated phosphoprotein following sodium nitrite inhalation.

In the presence of red blood cells (RBCs), nitrite inhibits platelets through its conversion to nitric oxide (NO) by the reductase activity of partially deoxygenated hemoglobin. Inhaled sodium nitrite is being investigated as a therapy for pulmonary hypertension. Here, we measured platelet aggregation, P-selectin expression, platelet-leukocyte aggregates and phosphorylated vasodilator-stimulated phosphoprotein (P-VASPSer239) following sodium nitrite inhalation in healthy subjects. In vitro incubation of nitrite with deoxygenated whole blood showed an increase in P-VASPSer239, which was inhibited by ODQ, a soluble guanylyl cyclase (sGC) inhibitor. Immediately and 60 min after nitrite inhalation, P-VASPSer239 increased in platelets. Platelet aggregation, P-selectin expression, platelet-monocyte and platelet-lymphocyte aggregates decreased after inhalation. In conclusion, sodium nitrite administered to healthy subjects by inhalation can inhibit platelet activation and increase P-VASPSer239 in platelets. Platelet inhibition by nitrite administration may be useful in disorders associated with platelet hyperactivity.