The effect of interaction of heat and UVB on human keratinocyte: Novel insights on UVB-induced carcinogenesis of the skin.

BACKGROUND: Skin cancer is an important environmentally-related health issue. Although sun exposure is closely associated with increasing environmental heat, the effects of environmental heat on the skin, especially in the context of photocarcinogenesis, has not been carefully examined.

OBJECTIVES: This study aimed to explore the effects and interactions of UVB radiation and environmental heat on photocarcinogenesis of the skin using cell and animal models.

METHODS: Cultured keratinocytes and hairless mice were exposed to different treatment conditions including UVB radiation and environmental heat. The effects of treatment on keratinocyte and mice skin were evaluated at indicated time points.

RESULTS: UVB induced DNA damage was significantly lower in keratinocytes that were pretreated in an environment with slightly elevated temperature followed by UVB treatment (Heat-UVB) as compared to UVB and UVB radiation followed by exposure to equivalent increase in environmental heat (UVB-Heat) groups. Similar phenomenon was observed in terms of keratinocyte viability. In the animal model, it was found that Heat-UVB treated mice showed delayed and reduced tumor formation as compared to the UVB and UVB-Heat treated groups. Quantum simulation analyses demonstrated that the energy required for CPD formation at environment with higher temperature required considerable higher energy as compared to CPD formation at lower temperature.

CONCLUSION: Taken together, our results demonstrated that with equivalent UVB exposure, higher temperature environment may protect cells against subsequent UVB-induced DNA damages.