Correlation between age and the secretions of melanocyte-stimulating cytokines in cultured keratinocytes and fibroblasts

These findings suggest that IL-1alpha secretion increases as cells grow older, and the increased secretion of IL-1alpha by aged keratinocytes may stimulate HGF production in dermal fibroblasts paracrinely and ET-1 production in keratinocytes autocrinely, which stimulates melanocyte proliferation and induces an increase of tyrosinase activity in melanocytes. Because IL-1alpha is a primary mediator that responds to inflammation and injury, the transcription of genes involved in skin inflammation may be persistently induced in the aged skin. Thus the increased secretion of IL-1alpha by aged keratinocytes in the aged skin may play a role in the accentuated cutaneous pigmentation and other skin ageing.