Keratinocyte overgrowth after UVB exposure is believed to contribute to skin photoageing and cancer devel-opment. However, little is known about the transcription factors that epigenetically regulate keratinocyte response to UVB. Recently, HIF-1α was found to play a role in epidermal homeostasis by controlling the keratinocyte cell cycle, and thus, we hypothesized that HIF-1α is involved in UVB-induced keratinocyte growth. In cultured keratinocytes, HIF-1α was found to be down-regulated shortly after UVB exposure and to be involved in UVB-induced proliferation. In mice repeatedly treated with UVB, the epidermis became hyperplasic and keratinocytes lacked HIF-1α in nuclei. Based on these results, we suggest that the deregulation of HIF-1α is associated with UVB-induced hyperplasia of the epidermis. This work provides insight of the molecular mechanism underlying UV-induced photoageing and skin cancer development.

Keywords: , hypoxia-inducible factor-1alpha, keratinocyte, skin, ultraviolet