Although we are only just now beginning to elucidate the mechanisms of tanning, the dramatic increase in melanoma frequencies has made this an important issue of dermatological study. According to the Skin Cancer Foundation, the frequency of melanoma in women has increased 800% since 1970. This startling increase may be at least partially explained by use of tanning beds and by childhood sunburns accrued on family vacations. Now, I think, is the time to curse any loving family members who may have taken you to the beach.
|DAMN YOU, CARING PARENTS.|
|Melanin in pigmented melanoma|
Merely knowing that melanin is the pigment of a golden tan is remarkably little knowledge. We can easily imagine a variety of ways that UV light could induce darker skin. Hypotheses have included the the stimulation of melanogenesis and changing the shape of the melanin. In the end, a 2005 study published in Nature by Tadokoro and colleagues showed it was neither!
It appears that the main mechanism of action for tanning is the migration of melanin towards the surface of the skin, a process that occurs within one week of UV exposure. Normally, melanin would take closer to four weeks to migrate from the basal layer of skin to the surface.
Although we normally think of UVA light as the rays associated with tanning and UVB light as the rays associated with sunburns, there is evidence suggesting that a secondary tanning mechanism is caused by UVB light: melanogenesis. Indeed, these two mechanisms have been separated out by Miyamura and colleagues. They found that tanning induced by UVA light had no protective effect on DNA damage, but tanning induced by UVB light did have a slight protective effect. Because UVA light merely results in the rearrangement of pre-existing melanin, whereas UVB light stimulates melanin production, only the latter is capable of reducing DNA damage associated with sun exposure.
|The silliest tan lines I have ever had. Always wear sunscreen, but if you wear a fishnet shirt to a Pride Parade, EXTRA wear sunscreen.|