Tan-tastic
mice with chemically induced tans are sandwiched between their more pale brothers
:. Orazio et al. Nature 443 340 (21 September 06)
Redheads rejoice! Scientists have found a way to chemically stimulate the tanning process without exposure to sunlight. The approach not only offers the elusive bronze wan tan, but also could one day reduce the risk of melanoma -. A cancer that kills 6,000 people mostly light-skinned per year in the US
The dominant theory of how bronze skin postulates that damage to ultraviolet (UV) light of the DNA of cells called melanocytes, which causes a pigment darkening overproduction of melanin. But a report in tomorrow's issue of Nature reveals that UV light is the night keratinocytes, the most abundant cell type in the skin. Once damaged, the cells release melanocytes stimulating hormone (MSH), a compound that binds to a receptor on melanocytes known as MC1R, which in turn stimulates the production of melanin and blackens the skin.
The discovery explains why many people with fair skin and red hair can not tan, says lead author of the study David Fisher, a medical oncologist at the Dana-Farber Cancer Institute Boston and the Boston children's Hospital. According to a 1995 study, these people tend to have a mutation in their MC1R gene that prevents MSH from binding to the receptor and signaling release melanin.
To see if there is any hope for tanless, Fisher's team applied a topical cream in mice genetically engineered to have clear skin and a dysfunctional MC1R receptor. The cream contains a chemical plant derivative called forskolin, which bypasses the receiver, either directly activating a series of reactions normally stimulated by MC1R. In a few weeks, mice with fair skin turns dark brown. Tests revealed that the melanin in the darkened mice was chemically identical to the melanin produced in normal mice. In addition, the newly tanned rodents gained benefits typically granted to people with dark skin: When repeatedly exposed to UV light, they were much less likely to develop skin cancer than are mice that received no forskolin
But do. t rush and start to mess with the plant extract. Forskolin probably has too many side effects for human use, Fisher said. However, he notes, many currently available drugs stimulate the same pathways as forskolin, including certain prescribed for asthma. "We still do not know if [these results] hold in humans but there is sufficient circumstantial evidence to suggest that this would be the case," said Meenhard Herlyn, a biologist of the tumor at the Wistar Institute in Philadelphia, Pennsylvania . Working with human skin has already begun, said Fisher, who hopes to report preliminary findings in about a year.
Related site
- Learn more about skin cancer from the American Cancer Society
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