title: Augmentation of ultraviolet B radiation-induced tumor necrosis factor production by the epidermal platelet-activating factor receptor.
abstract: Ultraviolet B radiation (UVB) has been shown to damage human keratinocytes in part by inducing oxidative stress and cytokine production. Indeed, UVB-induced production of the pro-inflammatory and cytotoxic cytokine tumor necrosis factor alpha (TNF-alpha) has been implicated in the epidermal damage seen in response to acute solar radiation. Though the lipid mediator platelet-activating factor (PAF) is synthesized in response to oxidative stress, and keratinocytes express PAF receptors linked to cytokine biosynthesis, it is not known whether PAF is involved in UVB-induced epidermal cell cytokine production. These studies examined the role of the PAF system in UVB-induced epidermal cell TNF-alpha biosynthesis using a novel model system created by retroviral-mediated transduction of the PAF receptor-negative human epidermal cell line KB with the human PAF receptor (PAF-R). Treatment of PAF-R-expressing KB cells with the metabolically stable PAF-R agonist carbamoyl-PAF resulted in increased TNF-alpha mRNA and protein, indicating that activation of the epidermal PAF-R was linked to TNF-alpha production. UVB irradiation of PAF-R-expressing KB cells resulted in significant increases in both TNF-alpha mRNA and protein in comparison to UVB-treated control KB cells. However, UVB treatment up-regulated cyclooxygenase-2 mRNA levels to the same extent in both PAF-R-expressing and control KB cells. Pretreatment with the antioxidant vitamin E or the PAF-R antagonists WEB 2086 and A-85783 inhibited UVB-induced TNF-alpha production in the PAF-R-positive but not control KB cells. These studies suggest that the epidermal PAF-R may be a pharmacological target for UVB in skin.
authors.affiliation: Department of Dermatology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
authors.forename: L C
authors.initials: LC
authors.lastname: Dy
authors.forename: Y
authors.initials: Y
authors.lastname: Pei
authors.forename: J B
authors.initials: JB
authors.lastname: Travers
mesh_terms: D001381:Azepines / Q000494:pharmacology; D002478:Cells, Cultured; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D013844:Thiazoles / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*; D014466:Ultraviolet Rays; D014810:Vitamin E / Q000494:pharmacology
chemical_list: D001381:Azepines; D007211:Indoles; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D013844:Thiazoles; D014230:Triazoles; D014409:Tumor Necrosis Factor-alpha; C039351:platelet activating factor receptor; C052518:WEB 2086; D014810:Vitamin E; C093307:A 85783.0