Protective effects of triflusal on secondary thrombus growth and vascular cyclooxygenase-2

Background: Carotid residual mural thrombus predisposes to recurrent thrombosis and/or distal embolization (i.e. cerebrovascular ischemia).

Objectives: Our aims were (i) to analyze and compare the efficacy of aspirin, triflusal, and its main metabolite 2-hydroxy-4-trifluorometylbenzoic acid (HTB) on secondary thrombus growth; and (ii) evaluate to what extent the three COX-1 inhibitors influenced vascular COX-1/COX-2 expression and endothelial prostacyclin synthesis.

Methods: In a rabbit model of ex vivo thrombosis, a fresh mural thrombus was formed on damaged vessels at flow conditions typical of mild and severe carotid stenoses. The effects of COX-1 inhibitors administered both intravenously (i.v.) (aspirin 5 mg kg(-1), triflusal 10 mg kg(-1), and HTB 10 mg kg(-1)) and orally (p.o.) (8 days; aspirin 30 mg kg(-1) day(-1), and triflusal 40 mg kg(-1) day(-1)) on secondary thrombus growth were assessed by In-(111)deposited platelets and compared with a placebo control. Arterial COX-1/COX-2 expression after 8-day treatment was evaluated at mRNA and protein levels. Additionally, a drug-related dose-dependent in vitro assay was performed for endothelial PGI(2) release measurement (COX-2 activity).

Results: All COX inhibitors similarly and significantly (P < 0.05) reduced secondary thrombus formation after i.v. and p.o. administration versus placebo control. Treatments exerted no effect on vascular COX-1 mRNA whereas COX-2 mRNA was moderately reduced by aspirin and triflusal (placebo 100% +/- 9%, aspirin 70% +/- 2% and triflusal 70% +/- 2%; P < 0.05). COX-2 protein levels were slightly higher in the triflusal versus aspirin group (placebo 100% +/- 6%, aspirin 35% +/- 10% and triflusal 61% +/- 9%; P < 0.005 versus placebo). Interestingly, in vitro, HTB solely maintained endothelial PGI(2) synthesis levels similar to the control.

Conclusions: At a similar level of efficacy in inhibiting secondary thrombosis, triflusal seems to better preserve COX-2 expression than aspirin and its metabolite HTB was able to protect endothelial prostacyclin production.