Activation of flavin-containing oxidases underlies light-induced production of H2O2 in mammalian cells

Violet-blue light is toxic to mammalian cells, and this toxicity has been l inked with cellular production of H2O2. In this report, we show, that viole t-blue light, as well as UVA, stimulated H2O2 production in cultured mouse, monkey, and human cells. T-Ve found that H2O2 originated in peroxisomes an d mitochondria, and it was enhanced in cells overexpressing flavin containi ng oxidases. These results support the hypothesis that photoreduction of fl avoproteins underlies light-induced production of H2O2 in cells. Because H2 O2 and its metabolite, hydroxyl radicals, can cause cellular damage, these reactive oxygen species may contribute to pathologies associated with expos ure to UVA, violet, and blue light. They may also contribute to phototoxici ty often encountered during light microscopy. Because multiphoton excitatio n imaging with 1,047-nm wavelength prevented light-induced H2O2 production in cells, possibly by minimizing photoreduction of flavoproteins, this tech nique may be useful for decreasing phototoxicity during fluorescence micros copy.