title: Inhibitions by hydrogen-occluding silica microcluster to melanogenesis in human pigment cells and tyrosinase reaction.
abstract: We investigated the anti-melanogenetic efficacy of hydrogen-occluding silica microcluster (H2-Silica), which is a silsesquioxane-based compound with hydrogen interstitially embedded in a matrix of caged silica, against melanogenesis in HMV-II human melanoma cells and L-DOPA-tyrosinase reaction [EC1.14.18.1]. HMV-II cells were subjected to oxidative stress by ultraviolet ray-A (UVA) exposure of 3-times of 0.65 J/cm2 summed up to 1.95 J/cm2. After UVA irradiation, HMV-II cells were stimulated to produce melanin by 2.72-fold more abundantly than unirradiated control. When HMV-II cells were treated with H2-Silica of 20 ppm or kojic acid of 28.4 ppm before and after UVA-irradiation, the amount of melanin was repressed to 12.2% or 14.5% as compared to that of UVA-irradiated control, respectively. That is, H2-Silica exhibited a comparable efficacy to the whitening agent kojic acid. The H2-Silica could prevent melanogenesis in HMV-II cells by low-level doses at 1-10 ppm, and cell viability and apoptosis event did not change even by high-level doses at 100-1000 ppm. On the contrary, kojic acid was cytotoxic at the concentration of 14-28 ppm or more. By microscopic observation, H2-Silica suppressed such properties indicative of melanin-rich cells as cellular hypertrophy, cell process formation, and melanogenesis around the outside of nuclei. The enzymatic assay using L-DOPA and mushroom tyrosinase demonstrated that H2-Silica restrained UVA-mediated melanin formation owing to down-regulation of tyrosinase activity, which could be attributed to scavenging of free radicals and inhibition of L-DOPA-to-dopachrome oxidation by hydrogen released from H2-Silica. Thus H2-Silica has a potential to prevent melanin production against UVA and serves as a skin-lightening ingredient for supplements or cosmetics.
authors: Faculty of Life and Environmental Sciences, Prefectural University of Hiroshima, Nanatsuka 562, Shobara, Hiroshima 727-0023, Japan.
authors: Shinya
authors: S
authors: Kato
authors: Yasukazu
authors: Y
authors: Saitoh
authors: Nobuhiko
authors: N
authors: Miwa
mesh_terms: D002214:Capsules / Q000008:administration & dosage; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D006859:Hydrogen / Q000008:administration & dosage*; D008545:Melanoma / Q000201:enzymology / Q000209:etiology* / Q000517:prevention & control*; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D009381:Neoplasms, Radiation-Induced / Q000201:enzymology / Q000209:etiology* / Q000517:prevention & control*; D012822:Silicon Dioxide / Q000008:administration & dosage*; D016896:Treatment Outcome; D014466:Ultraviolet Rays / Q000009:adverse effects
chemical_list: D002214:Capsules; D012822:Silicon Dioxide; D006859:Hydrogen; D014442:Monophenol Monooxygenase