Anti-thrombotic effects of a nitric oxide-releasing, gastric-sparing aspirin derivative.

Abstract

Effects of a nitroxybutylester derivative of aspirin (NCX 4215) on platelet aggregation and prostanoid synthesis were compared to the effects of aspirin. NCX 4215 was approximately seven times more potent than aspirin as an inhibitor of thrombin-induced human platelet aggregation in vitro, but did not inhibit platelet thromboxane synthesis or gastric prostaglandin synthesis. NCX 4215 released nitric oxide when incubated in the presence of platelets and increased platelet levels of cGMP within 10 min of exposure, while aspirin did not. The anti-aggregatory effects of NCX 4215 in vitro were significantly attenuated by 10 juM hemoglobin.In ex vivo studies of ADP-or collagen-or thrombin-induced rat platelet aggregation, aspirin and NCX 4215 had comparable inhibitory effects 3 h after administration. Aspirin (10-120 mg/kg) caused extensive hemorrhagic erosion formation in the stomach of the rat within 3 h of oral administration, while NCX 4215 did not produce significant damage at doses of up to 300 mg/kg, nor when given daily for two weeks at 166 mg/kg. NCX 4215 did not alter systemic arterial blood pressure when administered intravenously to the rat. These studies demonstrate that NCX 4215 has comparable or enhanced anti-thrombotic activity to that of aspirin, but does not cause gastric damage or alter systemic blood pressure. The anti-thrombotic actions of NCX 4215 are, at least in part, due to generation of nitric oxide. (J. Clin. Invest. 1995. 96:2711-2718

Aspirin causes rapid up‐regulation of cyclo‐oxygenase‐2 expression in the stomach of rats

“…Like COX-2, iNOS is a rapidly inducible enzyme that is expressed at sites of in¯ammation and injury in the gastrointestinal tract. 8 The dose of aspirin used in this study is suf®cient to cause profound suppression of systemic COX activity 27 and prostaglandin synthesis by the stomach. 32 It is therefore possible that the increase in COX-2 expression following aspirin administration occurred as a response to diminished tissue prostaglandin synthesis.…”

“…Oral administration of aspirin at 250 mg/kg, a dose which inhibits systemic COX activity by >99%, 27 signi®cantly increased the expression of COX-2 mRNA in gastric tissues (Figure 2). However, neither of the ethanol concentrations tested, nor indomethacin or salicylate, signi®cantly affected gastric COX-2 mRNA expression.…”

Effects of nitric oxide-releasing aspirin versus aspirin on restenosis in hypercholesterolemic mice

“…In particular, aspirin and other antiplatelet drugs are widely used in patients undergoing PTCA (3,4). However, major limitations to the clinical use of aspirin are the modest therapeutic effects on restenosis and the associated gastrotoxicity, the single most common adverse effect of the medication (5)(6)(7)(8).…”

Thrombin‐induced platelet endostatin release is blocked by a proteinase activated receptor‐4 (PAR4) antagonist

“…Platelet aggregation and endostatin release was studied in response to thrombin and PAR4 activating peptide ex vivo (Wallace et al, 1995;Ma et al, 2001). Aliquots (0.4 ml) of the PRP were placed in the cuvette of a Payton platelet aggregometer.…”

“…Washed platelets were obtained as previously described (Wallace et al, 1995) and lysed with lysis bu er (10 mM TrisHCl pH 7.4, 150 mM NaCl, 1% Triton X-100, 1 mM EDTA, protease inhibitor cocktail, 100 mg ml 71 phenyl-methylsulfonyl¯uoride). Lysates were collected by centrifugation (16,0006g, 48C) for 15 min, and then precleared by incubation with 30 ml protein A agarose with lysis bu er on a rotating incubator for 3 h at 48C, followed by centrifugation.…”