Effect of nitroxyl and nitric oxide on human platelet arachidonate metabolism.

BERMEJO, E; SAENZ, D.; CHIANELLI, M.; BARI, S; LAZZARI, M; ROSENSTEIN, R.

Ginebra, Suiza

Congreso; XXIst Congress of the International Society on Thrombosis and Haemostasis.; 2007

International Society on Thrombosis and Haemostasis

Nitric oxide (NO) plays a key role in platelet physiology regulation. Recent interest has developed in the function of an alternative redox form of NO, namely nitroxyl (HNO), because it is formed by diverse biochemical reactions. We have shown that both HNO and NO significantly inhibited human platelet aggregation induced by thrombin (Thr). The aim of the present work was to study the involvement of arachidonate metabolism in the antiaggregatory effect of HNO and NO. Methods: Human washed platelets (WP) from healthy volunteers were used throughout. Angeli´s salt (AS) and sodium nitroprusside (SNP) were used as HNO and NO releasers, respectively. Cyclic GMP content was assessed by radioimmunoassay, while thiobarbituric acid reactive substances (TBARS) were measured as an index of lipid peroxidation. Thromboxane B2 (TXB2) levels were assessed by an immunoassay kit. Results: Both SNP and AS (3mM) significantly increased cGMP content, although SNP was more effective than AS (control: 7.90.7, AS: 14.20.6*, SNP: 32.23** pmol/10*6 WP). AS, SNP, and a cGMP analogue (8Br-cGMP) significantly decreased the effect of Thr on TBARS content. In addition, both releasers and 8-Br-cGMP significantly decreased the effect of Thr on TXB2 levels. Also in those cases, SNP was more effective than HNO. Both releasers and 8Br-cGMP showed no effect on these parameters in the absence of Thr. Table:   TBARS nmol/mg prot TXB2 ng/10*8 WP control 0.60.1 90.5 Thr 12.21a 12910a Thr + AS 8.5 0.6ab 847ab Thr + SNP 5.8 0.2ab 606ab Thr + 8 Br-cGMP 6.20.5ab 716ab a p<0.01 vs cont, b: p<0.01 vs Thr. Conclusions: It was postulated that platelet TBARS levels represent the amount of malonyldialdehyde formed by thromboxane synthase 1. These results support this hypothesis since AS and SNP significantly decreased both TBARS and TXB2 levels in a similar way. In addition, these results suggest that both NO and HNO regulate platelet physiology by impairing arachidonate metabolism through a cGMP-dependent pathway. References: 1-Wachowicz et al., Plat. 2002, 13, 175-83