title: Differential modulation of interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta) in human epidermal keratinocytes by UVB.
abstract: Conflicting reports exist concerning ultraviolet-B (UVB) effects on keratinocyte (KC) interleukin-1 (IL-1) expression. To clarify the modulatory effects of UVB on IL-1, the following study was undertaken. Normal human epidermal KCs cultured in a standard low Ca2+ and serum-free medium were irradiated in quiescent phase with UVB. In this study, we used semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) to determine the mRNA level of interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta). After exposure to 100 or 300 J/m2 UVB, a transient increase in mRNA levels was observed within 1 hour for IL-1 alpha and 3 to 6 h for IL-1 beta. Following this transient induction, mRNA levels for both IL-1 alpha and IL-1 beta returned to steady-state levels after 100 J/m2. After 300 J/m2 irradiation, IL-1 alpha and IL-1 beta levels were downregulated compared to unirradiated cultures at 24-h post-irradiation. The half-life for IL-1 alpha and IL-1 beta was estimated using actinomycin D treatment. Both IL-1 alpha and IL-1 beta mRNAs half-lives (t1/2) decreased faster in irradiated cells (t1/2 = 30 minutes for IL-1 alpha and 2 h for IL-1 beta) compared to unirradiated cells (t1/2 = 1 h and 4 h, respectively). These results suggest that IL-1 alpha and IL-1 beta mRNA expression are differentially regulated by UVB. In contrast to down-regulation of mRNA levels, a significant increase in IL-1 alpha protein levels, measured by ELISA, was observed in culture supernatants from 6 h to 24 h after 300 J/m2 UVB irradiation. Cycloheximide treatment did not abrogate this increase in IL-1 alpha protein level. Since this dose of UVB irradiation decreased the stability of IL-1 alpha and IL-1 beta mRNA, this suggests that the release of IL-1 alpha after UVB irradiation was due to leakage from UVB-damaged cells and not from de novo protein synthesis.
authors.affiliation: Division of Dermatology, Sunnybrook Health Science Centre, University of Toronto, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Kondo
authors.forename: D N
authors.initials: DN
authors.lastname: Sauder
authors.forename: T
authors.initials: T
authors.lastname: Kono
authors.forename: K A
authors.initials: KA
authors.lastname: Galley
authors.forename: R C
authors.initials: RC
authors.lastname: McKenzie
mesh_terms: D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D006801:Humans; D007231:Infant, Newborn; D007375:Interleukin-1 / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D015603:Keratinocytes / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
chemical_list: D007375:Interleukin-1; D012333:RNA, Messenger; D003609:Dactinomycin; D003513:Cycloheximide