1. ^*Departments of Dermatology, Indianapolis, Indiana, U.S.A.
2. ^†Departments of Pharmacology and Toxicology, Indianapolis, Indiana, U.S.A.
3. ^‡Departments of Biochemistry and Molecular Biology, Indianapolis, Indiana, U.S.A.
4. ^§Departments of Pediatrics and the H.B Wells Center for Pediatric Research, Indiana University School of Medicine, Indianapolis, Indiana, U.S.A.

Correspondence: Dr Jeffrey B. Travers, H.B Wells Center for Pediatric Research, James Whitcomb Riley Hospital for Children Rm 2659, Indiana University School of Medicine, 702 Barnhill Drive, Indianapolis, IN 46202. Email: jtravers@iupui.edu

Received 5 October 1999; Revised 8 May 2000; Accepted 25 May 2000.

Abstract

Ultraviolet B radiation has been shown to generate cutaneous inflammation in part through inducing oxidative stress and cytokine production in human keratinocytes. Amongst the proinflammatory cytokines synthesized in response to ultraviolet B radiation is the potent chemoattractant interleukin-8. 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 ultraviolet-B-induced epidermal cell cytokine production. These studies examined the role of the PAF system in ultraviolet-B-induced epidermal cell interleukin-8 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. Treatment of PAF-receptor-expressing KB cells with the metabolically stable PAF receptor agonist carbamoyl-PAF resulted in increased interleukin-8 mRNA and protein, indicating that activation of the epidermal PAF receptor was linked to interleukin-8 production. Ultraviolet B irradiation of PAF-receptor-expressing KB cells resulted in significant increases in both interleukin-8 mRNA and protein in comparison to ultraviolet-B-treated control KB cells. Pretreatment with PAF receptor antagonists inhibited both carbamoyl-PAF-induced and ultraviolet-B-induced interleukin-8 production in the PAF-receptor-positive cells, but not in control KB cells. Similarly, treatment of the PAF-receptor-expressing primary cultures of human keratinocytes or the human epidermal cell line A-431 with carbamoyl-PAF or ultraviolet B radiation resulted in interleukin-8 production that was partially inhibited by PAF receptor antagonists. These studies suggest that the epidermal PAF receptor may be a pharmacologic target for ultraviolet B radiation in skin and thus may act to augment ultraviolet-B-mediated production of cytokines such as interleukin-8.