Abstract 1654: The Effects of Aspirin on Blood Clot Structure and Fibrinolysis
Blood clot structure predicts the predisposition to atherothrombotic conditions as clots formed from thin fibres and small pores are associated with premature, more severe cardiovascular disease. Aspirin, commonly used for cardiovascular protection, reduces clot formation by inhibiting platelet aggregation. Another potential mode of action of aspirin is related to the direct effects on clot properties. The aim of the present work was to investigate in detail the effects of aspirin on fibrinogen and clot structure. Chinese Hamster Ovary (CHO) cell lines transfected with fibrinogen were grown in the absence (0) and presence of increasing concentrations (1, 10 and 100 mg/L) of aspirin. Fibrinogen was purified from the media using affinity chromatography and clots were made from recombinant protein. Clot structure was studied using turbidity measurements, permeation analysis and electron microscopy. Fibrinolysis rates were determined by turbidity measurements and confocal microscopy. Fibrinogen acetylation was analysed using an antibody directed against acetylated lysine residues. Mean final turbidity [OD(± SEM)] of the fibrin clot was 0.083 (± 0.03), 0.093 (± 0.002), 0.101 (± 0.005) and 0.125 (± 0.003) in the presence of 0, 1, 10 and 100 mg/L aspirin in culture media respectively (p < 0.05). Permeation analysis showed a permeability coefficient [Ks cm2x10−8] of 1.68 (± 0.29) and 4.13 (± 0.33) comparing fibrinogen produced from cells grown with 0 mg/L and 100 mg/L aspirin respectively. Scanning electron microscopy further showed an increased fibre thickness and looser clot structure of aspirin treated fibrinogen, whereas fibrinolysis experiments demonstrated a quicker lysis time, which was evident even with low concentrations of aspirin. Acetylation of the α-chain of fibrinogen, but not β or γ chains, was observed using fibrinogen purified from aspirin treated media. Using recombinant fibrinogen, we have shown that aspirin directly alters clot structure, through acetylation of γ-chain of fibrinogen, resulting in the formation of clots with thicker fibres, bigger pores, which are easier to lyse. This study confirms an alternative mode of action for aspirin, which should be considered in studies evaluating the biochemical efficacy of this agent.