Effects of glutathione peroxidase and catalase on hemolysis and methemoglobin modifications induced by photooxidized psoralen

Abstract Psoralen photooxidation products (POP products) were obtained by UVA irradiation (365 nm, 180–640 W/m 2 ) of an aqueous psoralen solution with fluences of 0–800 kJ/m 2 . Preincubation of POP products with glutathione peroxidase (GSHPer) or catalase, as well as presence of catalase during UVA irradiation of the aqueous psoralen solution did not influence their hemolytic activity. However, both GSHPer and catalase inhibited POP-induced conversion of methemoglobin. This indicates that hydrogen peroxide and psoralen peroxides destructible by GSHPer, which are being produced during psoralen photooxidation, do not possess hemolytic activity. Furthermore, hydrogen peroxide does not appear to serve as an intermediate in the process of hemolysin formation. Hydrogen peroxide generated during psoralen photooxidation is apparently the main POP product responsible for MetHb conversion.