Characterisation of the binding of dihydro-alpha-lipoic acid to fibrinogen and the effects on fibrinogen oxidation and fibrin formation

A reduced form of the alpha-lipoic acid, dihydro-alpha-lipoic acid (DHLA) is a potent, naturally occurring antioxidant which can be consumed as food constituent or as supplement at doses up to 600 mg/day. DHLA has inhibitory effect on coagulation as it can reduce concentrations of some coagulation factors. In this study, a direct interaction between DHLA and fibrinogen, the main protein in coagulation, is described. Binding constant for DHLA/fibrinogen complex is of moderate strength (104) and interaction probably occurs in D regions of fibrinogen, as shown by docking simulations. Fibrinogen stability remains the same with only marginal structural changes in its secondary structure favouring more ordered molecular organisation upon DHLA binding. Fibrinogen with bound DHLA forms fibrin with thicker fibers, as measured by coagulation assay and is protected from oxidation to certain extent. Obtained results support beneficial effects of DHLA on fibrinogen and consequently on coagulation process, suggesting that DHLA supplementation may be indicated for persons with an increased risk of developing thrombotic complications, particularly those whose fibrin is characterised by increased oxidative modification and formation of thinner and less porous fibers. Also, DHLA in complex with fibrinogen can be located at site of injury where it may exert antioxidant effects.