Stimulant. Nicotine has led to new blood vessels (arrows, right) in these mouse tumors whereas a placebo did not (left).
Nicotine, the addictive ingredient in tobacco smoke, is used in nicotine replacement therapy to help smokers kick the habit, and is considered a treatment for diseases such as Alzheimer's disease and Parkinson's. But a study published in the July issue of Nature Medicine shows another dangerous side of nicotine: At concentrations found in the blood of smokers, nicotine promotes the growth of new blood vessels, or angiogenesis, which is believed to stimulate tumor growth.
cardiologist John Cooke and colleagues at Stanford University in Palo Alto, California, added nicotine to human endothelial cells in culture, the type of cells that vessels of blood lines. Nicotine stimulates their growth and made them form small tubes, blood vessels as. They then tested the effects of nicotine in the four murine disease models: a model of ischemia, where they intersect the blood flow to one of the hind legs, a model of inflammation, wherein a polyvinyl disc was implanted under the skin of the animal, model of lung cancer, and a model of atherosclerosis, where the cholesterol plaques clog blood vessels.
In all cases, they found that nicotine caused new blood vessels to grow in the affected area. These stimulated tumor growth in the model of cancer and plates in the model of atherosclerosis. "We were surprised that [nicotine] enhanced angiogenesis," says Cooke. "We made the mistake of equating the nicotine in tobacco", which reduces the overall growth of blood vessels, he says. The results suggest caution in the use of the treatment of nicotine, Cooke said, because it could promote cancer or cardiovascular disease. Furthermore, nicotine may well be useful to accelerate wound healing, when growth blood vessels is just right.
"the results are intriguing," says researcher Rakesh Jain cancer Harvard Medical School in Boston, Massachusetts. However, other studies seem to contradict the results, said he, for example, nicotine has no effect on the growth of blood vessels in the developing chick and does not raise the risk of heart attack in patients with heart disease and as for the smoking. the picture is even more complicated, because nicotine is only one of some 4,000 chemicals in cigarette smoke, Jain noted, some injured blood vessels.
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