Glucocorticoids augment the chemically induced production and gene expression of interleukin-1α through NF-κB and AP-1 activation in murine epidermal cells

Abstract

To clarify the mechanism of the glucocorticoid-induced augmentation of skin response, we attempted to demonstrate the modulatory effect of glucocorticoids on the regulation of cytokines produced by keratinocytes stimulated with various chemicals in vitro. Haptens, irritants, and a superantigen (staphylococcal enterotoxin B) induced a significant release of interleukin-1α and tumor necrosis factor α, but not interleukin-10, from a murine keratinocyte cell line, Pam 212 cells. Glucocorticoids (10-6-10-12 M) significantly augmented the production of interleukin-1α by Pam 212 cells at both the protein and mRNA levels when stimulated by either haptens or irritants, but not by staphylococcal enterotoxin B, whereas glucocorticoids alone had no effect. In contrast, glucocorticoids had no effect on the production of tumor necrosis factor α and interleukin-10 by chemically stimulated Pam 212 cells. Electrophoretic mobility shift assays revealed that chemical stimulation induced NF-κB activation in Pam 212 cells; however, augmented NF-κB activation by 10-6-10-8 M of glucocorticoids was observed in Pam 212 cells stimulated by both haptens and irritants, but not by staphylococcal enterotoxin B. Furthermore, pyrrolidine dithiocarbamate inhibited the hapten-induced interleukin-1α production and NF-κB expression by Pam 212 cells. Pyrrolidine dithiocarbamate did not completely abrogate the hapten-induced interleukin-1α production augmented by glucocorticoids, however. To determine the effect on transcription factors other than NF-κB, AP-1 activity was examined by electrophoretic mobility shift assays. Hapten was founded to induce AP-1 activation in Pam 212 cells. In addition, AP-1 activation was augmented in the hapten-stimulated Pam 212 cells in the presence of 10-8-10-10 M of glucocorticoids. The augmented inflammatory reaction by glucocorticoids may therefore reflect the augmentation of interleukin-1α production by keratinocytes mediated through the NF-κB and AP-1 pathway.