Epidermal
melanin reduces some effects of UV radiation, the major cause of
skin cancer. To examine whether induced
melanin can provide protection from
sunburn injury, 65 subjects completed a trial with the potent synthetic
melanotropin, [Nle4-D-Phe7]-
alpha-melanocyte-stimulating hormone ([Nle4-D-Phe7]-
alpha-MSH) delivered by
subcutaneous injection into the abdomen at 0.16 mg/kg for three 10-day cycles over 3 months.
Melanin density, measured by reflectance spectroscopy, increased significantly in all [Nle4-D-Phe7]-
alpha-MSH-treated subjects. The highest increases were in volunteers with lowest baseline skin
melanin levels. In subjects with low minimal erythemal dose (MED) skin type,
melanin increased by an average of 41% (from 2.55 to 3.59, P < 0.0001 vs placebo) over eight separate skin sites compared with only 12% (from 4.18 to 4.70, P < 0.0001 vs placebo) in subjects with a high-MED skin type. Epidermal
sunburn cells resulting from exposure to 3 MED of UV radiation were reduced by more than 50% after [Nle4-D-Phe7]-
alpha-MSH treatment in the volunteers with low baseline MED.
Thymine dimer formation was also shown to be reduced by 59% (P = 0.002) in the epidermal basal layer. This study has shown for the first time the potential ability of a synthetic
hormone that augments
melanin production to provide photoprotection to people who normally
burn in direct sunlight.