title: Niacin protects against UVB radiation-induced apoptosis in cultured             human skin keratinocytes.
abstract: Niacin and its related derivatives have been shown to have effects on cellular             activities. However, the molecular mechanism of its reduced immunosuppressive             effects and photoprotective effects remains unclear. In this study, we investigated             the molecular mechanism of the photoprotective effect of niacin in ultraviolet             (UV)-irradiated human skin keratinocytes (HaCaT cells). We found that niacin effectively             suppressed the UV-induced cell death and cell apoptosis of HaCaT cells. Existing             data have shown that AKT activation is involved in the cell survival process.             Yet, the potential mechanism of niacin in protection against UV-induced skin damage             has thus far not fully been eluvidated. We observed that niacin pretreatment enhances             UV induced activation of AKT (Ser473 phosphorylation) as well as that of the downstream             signal mTOR (S6 and 4E-BP1 phosphorylation). The PI3K/AKT inhibitor, LY294002,             and the mTOR inhibitor, rapamycin, largely neutralized the protective effects             of niacin, suggesting that AKT and downstream signaling mTOR/S6 activation are             necessary for the niacin-induced protective effects against UV-induced cell death             and cell apoptosis. Collectively, our data suggest that niacin may be utilized             to prevent UV-induced skin damage and provide a novel mechanism of its photoprotective             effects against the UV radiation of sunlight by modulating both AKT and downstream             mTOR signaling pathways.
authors.affiliation: Department of Dermatology, Third People's Hospital of Hangzhou, Hangzhou 310009, PR China.
authors.forename: Fuquan
authors.initials: F
authors.lastname: Lin
authors.forename: Wen
authors.initials: W
authors.lastname: Xu
authors.forename: Cuiping
authors.initials: C
authors.lastname: Guan
authors.forename: Miaoni
authors.initials: M
authors.lastname: Zhou
authors.forename: Weisong
authors.initials: W
authors.lastname: Hong
authors.forename: Lifang
authors.initials: L
authors.lastname: Fu
authors.forename: Dongyin
authors.initials: D
authors.lastname: Liu
authors.forename: Aie
authors.initials: A
authors.lastname: Xu
mesh_terms: D017209:Apoptosis / Q000187:drug effects* / Q000528:radiation effects*; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000187:drug effects* / Q000528:radiation effects*; D018613:Microscopy, Confocal; D009525:Niacin / Q000494:pharmacology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D012867:Skin / Q000166:cytology / Q000187:drug effects / Q000528:radiation effects; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D009525:Niacin; C546842:MTOR protein, human; D051057:Proto-Oncogene Proteins c-akt; D058570:TOR Serine-Threonine Kinases