Author + information
- Krittapoom Akrawinthawong,
- Jiwon Park,
- Barbora Piknova,
- Nathawut Sibmooh,
- Suthat Fucharoen and
- Alan N. Schechter
In the last decade nitrite ions have been shown to be an important source of the multifunctional gas, nitric oxide (NO), by various enzymatic and non–enzymatic reductive processes. NO has long been known to be a potent inhibitor of platelet function but the physiological implication of this has not been well clarified. We recently showed that nitrite ions in the presence of red blood cells inhibit platelet aggregation and this effect was enhanced by deoxygenation of the erythrocytes. In order to study these effects more thoroughly, we have been developing flow–cytometric methods to study cellular changes known to correlate with platelet activaion and aggregation.
We investigated the role of nitrite in platelet rich plasma (PRP) under the presence of different concentrations of erythrocyte (hematocrit of 15.4 ± 1.8 %, 23.0 ± 2.3 %, 36.7 ± 1.6 % and 40.2 ± 1.2 %) and oxygen levels (97.4 ± 4.2, 58.2 ± 6.2 and 26.7 ± 2.8 mmHg.) by flow cytometry. Monoclonal antibody for P–selectin (CD62P) and activated GpIIb/IIIa (PAC–1) were used as markers for platelet reactivity induced by adenosine 5’ diphosphate (ADP, 20 µM), collagen (20µg/mL) and thrombin (1.0 U/mL).
Nitrite (0.1–1.0 µM, log IC50 of −5.95 to −6.27) significantly inhibited platelet activation (p<0.05) only when there were adequate erythrocytes (hematocrit was at least 23.0 ± 2.3%) and could be augmented by deoxygenation (mean O2 was 49.4 mmHg. or below) and increased concentration of erythrocytes. This effect could be abrogated by 2–(4–carboxyphenyl)–4,4,5,5–tetramethylimidazole–1–oxyl 3–oxide (C–PTIO: a NO scavenger, p = 0.01), but not NG–Nitro–L–Arginine Methyl Ester (L–NAME, an endothelial NOS inhibitor) or oxypurinol (xanthine oxidoreductase inhibitor), p > 0.05.
Physiological levels of nitrite ions in the blood can modulate platelet activation and aggregation in the presence of partially deoxygenated erythrocytes by the reduction to NO. These processes may explain certain differences between arterial and venous thrombosis and also be amenable to therapeutic intervention.
Poster Sessions, Expo North
Sunday, March 10, 2013, 9:45 a.m.–10:30 a.m.
Session Title: Spotlight on the Endothelium
Abstract Category: 33. Vascular Medicine: Basic
Presentation Number: 1211–170
- 2013 American College of Cardiology Foundation