If you want to stay young, don't light up. Smokers often look old before their time, because they have significantly more wrinkles than nonsmokers of the same age. Now dermatologists think they may have discovered why. A study published in the 24 March issue of The Lancet suggests that smoking stimulates production of an enzyme that makes skin less elastic.
Scientists have known for some time that both smoking and exposure to ultraviolet (UV) light predispose people to premature skin aging. A team of dermatologists headed up by Anthony Young of the St. John's Institute of Dermatology at Kings College London was initially studying how UV light affected the levels of matrix metalloproteinase 1 (MMP-1), an enzyme that chops up proteins. MMPs degrade collagen, a structural protein that is important for maintaining the elasticity of connective tissue and constitutes up to 70% of the dry weight of skin. When collagen is destroyed, the skin begins to sag and crease.
Young and his colleagues divided volunteers into two groups; one group had sites on their buttocks exposed to UV light, while the other didn't. Skin biopsies revealed a curious fact: The levels of MMP-1 mRNA in the controls were not normally distributed, but fell into two distinct groups. The team was puzzled. But then, Young says, he remembered seeing the results of a Japanese in vitro study showing that a solution of tobacco smoke induced the transcription of the MMP-1 gene in human skin cells. When the team asked the participants whether they smoked, they discovered that the smokers tended to have high levels of MMP-1 mRNA. It was a completely "serendipitous finding," Young says. Apparently, one of the thousands of chemicals in tobacco causes MMP-1 levels to go up.
The results are important for several reasons, says Christopher Griffiths of the Dermatology Centre at the University of Manchester. "This study shows that chemicals in cigarette smoke affect the entire body," he says, not just those parts that smoke has direct contact with. "Inhaled products are transported through the bloodstream and come in to contact with every organ." Griffiths also notes that emphysema, a lung disease common in smokers, is marked by a loss of connective tissue and may be related to increased MMP-1 levels.
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