A ROLE FOR INTERLEUKIN-1 IN EPIDERMAL DIFFERENTIATION - REGULATION BYEXPRESSION OF FUNCTIONAL VERSUS DECOY RECEPTORS

Although human epidermis contains levels of interleukin-1 (IL-1) up to 100 times higher than other tissues, the role of this cytokine in epi dermal biology is unknown. Here, we show that interleukin-1 regulates the expression of mRNAs for two proteins associated with the different iated phenotype of human keratinocytes, cellular retinoic acid-binding protein type II (CRABP II) and small, proline rich protein 1 (SPRR1). The ability of IL-1 to induce these transcripts correlates directly w ith keratinocyte expression of the IL-1 receptor type I(IL-1 RI) durin g differentiation and inversely with the expression of the type II IL- 1 receptor (IL-1 RII), shown in other cell types to be a nonfunctional , decoy receptor. Furthermore, addition to keratinocyte cultures of an IL-1 RI-blocking, but not an IL-1 RII-blocking, antibody reduces the level of CRABP II and SPRR1 mRNAs in these cells. These data suggest t hat epidermal IL-1 functions to promote keratinocyte differentiation a nd that a change in the IL-1 receptor profile of these cells initiates this IL-1 response through a relative enhanced expression of function al IL-1 receptors.