Effect of MN (III) tetrakis (4-benzoic acid) porphyrin by photodynamically-generated free radicals on sods keratinocytes

Superoxide, a reactive form of oxygen, can be produced in vivo either in normal and under pathophysiologic conditions or by photosensitizing chemicals, as during photodynamic treatment. Photodynamic therapies (PDT), widely adopted in Dermatology and Oncology, are known to generate reactive oxygen species (ROS) and may contribute to structural alterations and oxidatively generated modifications of cellular antioxidants. We hypothesized that over-production of free radicals would decrease the enzymatic activities of endogenous cellular antioxidants. To test this hypothesis, keratinocytes were treated with the photosensitizer Photofrin plus visible light to produce free radicals and CuZnSOD and MnSOD activities were measured. Photodynamic treatment of keratinocytes increases malonylaldehyde production, nitrotyrosine staining and superoxide production. The enzymatic activities of CuZnSOD and MnSOD were significantly decreased after Photofrin plus visible light treatment. Our results suggest that the main cellular antioxidant system can be inactivated by photodynamically generated ROS. Pretreatment of keratinocytes with free radicals scavenger such as Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) was able to restore the endogenous antioxidant system activities, inhibiting the MDA formation, nitrotyrosine staining and superoxide formation. Antioxidant therapy could therefore be a useful tool in protecting healthy epidermal cells against common side effects induced by antitumor targeted therapies.