UVA Radiation Damages DNA in Human Melanocyte Skin Cells and Can Lead to Melanoma

Studies show that UVA radiation damages the DNA in human melanocyte cells, causing mutations that can lead to melanoma. Melanocytes darkens the skin to protect it from ultraviolet rays of the sun. "For the first time, UVA rays have been shown to cause significant damage to the DNA of human melanocyte skin cells," says Moon-shong Tang, PhD, professor of environmental medicine, pathology and medicine at NYU School of Medicine. "And because melanocytes have a reduced capacity to repair DNA damage from UVA radiation, they mutate more frequently, potentially leading to the development of melanoma."

Sunlight in the form of UVA radiation causes oxygen in melanocytes to damage DNA. Oxidative DNA damage adversely affects transcription and DNA replication in melanocytes. Researchers exposed lightly and darkly pigmented human melanocytes to UVA radiation and assessed DNA

damage and the capacity of these cells to repair damaged DNA. DNA damage was detected in all melanocyte cells and these cells were unable to repair the damage. Normal skin cells were also exposed to UVA light but no damage to their DNA was observed.

In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye, and immune system. UVA, UVB and UVC can all damage collagen fibers and thereby accelerate aging of the skin. The Sun emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the atmosphere's ozone layer, 99% of the ultraviolet radiation that reaches the Earth's surface is UVA.

The authors concluded that UVA-induced oxidative DNA damage in melanocytes and the inherently reduced repair capacity in these cells are the two key factors that contribute to melanoma on the skin. The authors also discovered the underlying mechanism to explain why melanoma can also develop in areas never exposed to sunlight: Because melanocytes generally have a limited capacity to repair any DNA damage, they have a higher mutation frequency rate and are more susceptible to the development of melanoma -- even without the effects of the sun.

http://www.sciencedaily.com/releases/2010/07/100701103415.htm

http://www.sciencedaily.com/articles/u/ultraviolet.htm

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