Augmentation of the inhibitory effect of blue light on the growth of B16 melanoma cells by riboflavin

Abstract

We have demonstrated that blue light has anticancer effects in cultured cancer cells and tumor-bearing animals. Based on our experimental findings, in addition to cytostatic activity that suppresses the proliferation of B16 melanoma cells, blue light may exert cytocidal activity through interaction with vitamin(s) contained in the culture medium. The present study was undertaken to identify the specific vitamins with which blue light interacts and to investigate the factors responsible for its cytocidal activity. B16 melanoma cells were incubated in media supplemented with various vitamins and exposed to blue light for 10 min. Cell necrosis was observed only in media containing riboflavin (0.4 mg/l). The effects of other components of visible light on riboflavin were also studied. Riboflavin-containing media were exposed to light of each of the three primary colors (red, green and blue) and the effects on the colony-forming capacity of B16 melanoma cells were evaluated. Cell necrosis was induced only in media exposed to blue light. The effects of riboflavin increased in a concentration-dependent manner in the range from 0.3 to 1.0 mg/l in blue-light-exposed media and were antagonized by the presence of catalase (200 U/ml). These findings suggest that cell necrosis is probably induced by active oxygen species such as hydrogen peroxide formed by the reaction of riboflavin with blue light.

Violet Light Down-Regulates the Expression of Specific Differentiation Markers through Rhodopsin in Normal Human Epidermal Keratinocytes

“…For examples, 7-dehydrocholesterol (7-DHC) absorbs UVB radiation in the skin and is transformed to previtamin D 3 , which is eventually isomerized to vitamin D 3 in a temperature-dependent manner [15], [16]. Cytochrome c oxidase in visible-to-near IR light and porphyrin-containing enzymes and flavoproteins in blue light are good examples of photoreceptors that contain chromophores [17]–[20]. Thus, there might be photoreceptors that elicit visible light phototransduction in the skin.…”

Intra‐ and extracellular reactive oxygen species generated by blue light

“…15,19,23 This hypothesis predicts that riboflavin (or other extracellular components) produce ROS that migrate intracellularly and affect cell responses. The current results demonstrate that peroxide concentrations generated in…”

Mechanism of endogenetic chromophore mediated photo-damage and its applications

“…There are two kinds of pathways mediating cellular photobiomodulation, one kind is specific, which is mediated by the resonant interaction of light with molecules such as cytochrome nitrosyl complexes of mitochondrial electron transfer chain 24,25 , singlet oxygen 26 , hemoglobin 27 or photosensitizer 8 such as riboflavin 9 , endogenous porphyrines 28 , the other kind is non-specific, which is mediated by the non-resonant interaction of light with membrane proteins 29,30,31 . Obviously, the photo-damage should be mediated by the specific pathways.…”

“…However, many cellular experiments [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] , animal experiments [16][17][18] or clinic studies [19][20][21][22][23] with light or laser irradiation which intensity is not so high that it directly destroys cells have found no photobiomodulation but cell compartment damage, apoptosis or necrosis so that a new concept, a moderate intensity laser or monochromatic light (MIL), should be defined if its intensity is so high that no photobiomodulation can be observed, but is so low that it can not directly destroy cells.…”