title: Narrow-band UVB induces apoptosis in human keratinocytes.
abstract: Narrow-band ultraviolet (NB-UVB) phototherapy emits mostly 311/312 nm light and is commonly used in the treatment of inflammatory skin disorders. As a source of UVB irradiation, NB-UVB causes apoptosis in T lymphocytes but its effects on keratinocytes are unknown. Herein, we have investigated the ability of NB-UVB to induce apoptosis in keratinocytes. Two types of human keratinocytes, primary and immortalized, were exposed to NB-UVB and broad-band UVB (BB-UVB; 315-280 nm) and tested for apoptosis. Both UVB light sources induced apoptosis in keratinocytes as determined by the presence of DNA ladders, although NB-UVB required approximately ten fold higher doses; NB-UVB (1000 mJ/cm2) and BB-UVB (125 mJ/cm2). By comparison, lower doses of NB-UVB (750 mJ/cm2) induced apoptosis in T lymphocytes, suggesting cell type specificity for NB-UVB induced apoptosis. Approximately, 50% or more of the cells underwent apoptosis when exposed to NB-UVB or BB-UVB as revealed by TUNEL assay. Electron micrographs showed that NB-UVB irradiated keratinocytes contained marked chromatin condensation, extensive cytoplasmic vacuolization and fragmentation of the nuclear envelope. Furthermore, Western blot analysis confirmed the presence of activated products of caspase 3 in keratinocytes that received apoptotic doses of NB-UVB. This study defines conditions by which NB-UVB irradiation causes apoptosis in keratinocytes.
authors.affiliation: Department of Dermatology, Wayne State University School of Medicine, Detroit, MI, USA.
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Aufiero
authors.forename: Harvinder
authors.initials: H
authors.lastname: Talwar
authors.forename: Chen
authors.initials: C
authors.lastname: Young
authors.forename: Murali
authors.initials: M
authors.lastname: Krishnan
authors.forename: James S
authors.initials: JS
authors.lastname: Hatfield
authors.forename: Hae Kyung
authors.initials: HK
authors.lastname: Lee
authors.forename: Henry K
authors.initials: HK
authors.lastname: Wong
authors.forename: Iltefat
authors.initials: I
authors.lastname: Hamzavi
authors.forename: George J
authors.initials: GJ
authors.lastname: Murakawa
mesh_terms: D017209:Apoptosis / Q000528:radiation effects*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D004789:Enzyme Activation; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000528:radiation effects*; D013601:T-Lymphocytes / Q000166:cytology / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases