Induction and Localization of Cutaneous Interleukin-1β mRNA during Contact Sensitization

Abstract

Chemical allergens that induce contact sensitivity cause changes in levels of epidermal cytokines. In mice one of the earliest epidermal cytokines to be upregulated following sensitization is interleukin-1β (IL-1β). The present study investigated the kinetics and in situ localization of induced IL-1β expression in mouse skin following topical exposure to the contact allergen oxazolone. Mice were exposed topically to 1% oxazolone, with control mice exposed to vehicle (acetone:olive oil 4:1) alone, and at various times thereafter skin was excised for IL-1β mRNA and protein determination by in situ hybridization and enzyme-linked immunosorbant assay (ELISA), respectively. IL-1β mRNA was found to be expressed constitutively at low levels in skin from naı̈ve (untreated) and vehicle-treated mice, with mRNA localized in some hair follicles and sebaceous glands; no IL-1β mRNA was detected in the epidermis of control animals. Following topical exposure of mice to oxazolone for 5–15 min, upregulation of IL-1β mRNA was observed in the epidermis, dermis, hair follicles, and sebaceous glands; at 90 min and beyond the pattern of IL-1β mRNA expression declined toward control. Analysis of whole skin homogenates by ELISA demonstrated cutaneous IL-1β protein to be present constitutively in both vehicle-treated and naı̈ve mice. Following exposure to oxazolone, cutaneous IL-1β protein expression was elevated at 30 min, decreased at 1 h, and fell below the limit of detection of the assay at 2 h before returning to constitutive levels at 4 and 24 h. IL-1β protein levels in vehicle-treated mice, naı̈ve mice, and mice treated with the respiratory allergen trimellitic anhydride were unchanged over this time period. The present study demonstrated that IL-1β mRNA expression was upregulated rapidly and transiently in well-defined regions of mouse epidermis and dermis during contact sensitization, and was succeeded by an elevation in IL-1β protein. This early highly localized upregulation of IL-1β lends further support to the hypothesis that this cytokine plays a key role in the initial stages of skin sensitization. Such information will enhance our understanding of the molecular processes involved in allergic contact dermatitis and may provide a mechanistic basis for designing refined animal and in vitro alternatives to existing models of skin sensitization.