Antioxidant properties of aspirin: Characterization of the ability of aspirin to inhibit silica-induced lipid peroxidation, DNA damage, NF-κB activation, and TNF-α production

Electron spin resonance (ESR) was used to investigate the reaction of aspirin toward reactive oxygen species, such as hydroxyl radicals (^.OH), superoxide radicals (O₂^-) and H₂O₂. The Fenton reaction (Fe(II) + H₂O₂→FE(III) + ^.OH + OR) was used as a source of ^.OH radicals. The results show that aspirin is an efficient ^.OH radical scavenger with a reaction rate constant of k = 3.6 x 10¹⁰ M^-1 sec^-1, which is faster than several well established antioxidants, such as ascorbate, glutathione and cysteine. However, aspirin is not a good scavenger for O₂^- or H₂O₂. Through its antioxidant property, aspirin exhibited a protective effect against silica-induced lipid peroxidation and DNA strand breakage. Aspirin also inhibited the activation of nuclear transcription factor-κβ induced by silica, lipopolysaccharide or the transition metal, Fe(II), as demonstrated by electrophoretic mobility shift assay. The results show that aspirin functions as an antioxidant via its ability to scavenge ^.OH radicals. This antioxidant property may explain some of its various physiological and pharmacological actions.