Epidermal Cell Proliferation and Modulation of the Protective Potency of Dexamethasone Against Phorbol Ester-Induced Ornithine Decarboxylase Activity

The study investigated the effects of dexamethasone (DXME) on mouse skin treated with 12-O-tetradecanoyl-phorbol-13-acetate (TPA). DXME, when applied after TPA, inhibited both the dermal inflammatory reaction and the induction of epidermal ornithine decarboxylase (ODC) activity. During the hyperplastic stage, DXME continued to counteract inflammation but only weakly inhibited ODC induction. Interestingly, in DXME-protected skin, the hyperplastic stage was delayed, and TPA strongly induced ODC activity in the epidermal cell layer before this stage. The study suggested that as the proliferation process was induced, epidermal cells became more sensitive to TPA, potentially becoming less reliant on inflammatory factors for ODC induction.