Aim of the present study was to compare the lipid-lowering, antithrombotic and antiatherogenic properties of NCX-6550, nitropravastatin, a nitric-oxide donating derivative of pravastatin, with those of pravastatin in hypercholesterolemic mice. LDL receptor-deficient mice (LDLR–/–) on a normal diet (ND) showed enhanced cholesterol levels as compared to wild type (WT) mice (6.8±1.2 mmol/L and 2.8±0.82 mmol/L, respectively). High fat diet (HFD) induced a large enhancement of cholesterolemia in

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... –/– mice (23.7±5.7 mmol/L, p<0.0001 vs LDLR–/– ND and WT mice. Treatment with NCX 6550 (48 mg/kg), but not with equimolar pravastatin, reduced cholesterol in LDLR–/–HFD. Platelet adhesion to collagen under high shear rate (3000 sec–1) was significantly higher in LDLR–/– than in normal mice, and further enhanced in LDLR–/–HFD (-27%, p<0.0001 vs untreated). NCX 6550 (48 mg/kg), but not pravastatin, reduced platelet adhesion, especially in LDLR–/–HFD. U46619-induced platelet aggregation ex vivo was also inhibited by NCX 6550 (48 mg/kg) but not by the parent compound. Finally, photochemically-induced acute (1 hr) femoral artery thrombosis and delayed (21 days) intimal thickening was assessed. Thrombus size was larger in LDLR–/– on HFD than in normocholesterolemic mice (0.46±0.04 vs 0.18±0.08 mg) and it was reduced by NCX 6550 (48 mg/kg) (0.08±0.02 mg, p<0.0001), but not by pravastatin (0.4±0.01 mg p=NS). Intimal thickening was greater in hypercholesterolemic than in normal mice (I/M normal=0.53±0.16, LDLR–/–=1.1±0.15, LDLR–/–HFD=1.75 ±0.25). Both NCX 6550 and pravastatin reduced intimal thickening in normal (-95% and -74.5%, respectively) and LDLR–/– mice (-98% and -91%), while in strongly hyperlipidemic animals (LDLR–/–HFD) NCX 6550 was more effective than pravastatin (-98% vs -65%, p<0.0001). NCX 6550 shows greater antithrombotic and antiatherogenic activity than pravastatin in highly hypercholesterolemic mice.