Molecular mechanism of naproxen photosensitization in red blood cells.

Red blood cell lysis photosensitized by naproxen was investigated. The photohemolysis rate was enhanced by deuterium oxide and inhibited by butylated hydroxyanisole, reduced glutathione, sodium azide and superoxide dismutase. Photohemolysis was also observed under anaerobic conditions. In the absence of red cells the irradiation of deaerated solutions underwent a decarboxylation process via intermediate radicals, while under aerobic conditions photo-oxidation leading to the photoproduct 6-methoxy-2-acetonaphthone occurred. A molecular mechanism involving free radicals and singlet oxygen as important intermediates and consistent with the overall results is proposed.