Sun, inflammation speed aging of skin.

Sun exposure leads to wrinkles in double time, new research shows.

Inflammation makes the difference between young, supple skin and aged skin, say researchers at P&G Beauty, a cosmetics company in Cincinnati. Company scientists, led by immunologist Michael Robinson, compared skin from a group of 18- to 20-year-old Florida women with skin from 60- to 67-year-old women who had spent a lifetime in the Florida sun.

Researchers collected skin from the women's buttocks and outer forearms.

Comparing buttock samples allowed the researchers to determine how skin ages where the sun doesn't shine. The researchers examined which genes are turned on and off in young skin and aged skin.

Older skin cells turned up production of enzymes called proteases that break down collagen and elastin, proteins that give skin its spring and structure, Robinson says. As collagen breaks down, skin collapses into wrinkles.

"It's the equivalent of taking the air out of a balloon. The tension goes out of it, and it begins to sag and fold in on itself," Robinson says.

Inflammation also sets off other skin-damaging processes, such as inhibiting skin's regenerative abilities and changing fatty acid and cholesterol metabolism, which lead to erosion of the protective barrier that holds in moisture.

Arm samples showed that sun exposure hastens "this chronic march down the calendar," Robinson says. Exposure to ultraviolet radiation from the sun increases inflammation, speeding the aging process, he says.