The benefits of exercise for the heart have long been touted, but little is known about how, for instance, jogging protects blood vessels against cardiovascular disease. Now scientists suggest that simply getting your blood going is what helps. In experiments with cow arteries, they find that fast-flowing blood has an anti-inflammatory effect as powerful as that of some steroid drugs that protect arteries.
Scientists have known for years that the hardened plaques that are a major factor in heart disease tend to form in areas where blood slows, and that inflammation in these areas contributes to the disease. Curiously, when vessel walls experience increased drag from faster blood flow, the cells lining the blood vessel walls make more of some molecules that protect the arteries. Tying the evidence together, Scott Diamond, a biomedical engineer at the University of Pennsylvania in Philadelphia, hypothesized that the drag itself could activate anti-inflammatory pathways much as do steroid drugs such as dexamethasone.
Diamond and colleagues put endothelial cells from cow arteries into a special chamber that mimics the conditions of arterial blood flow. They tagged a steroid receptor in the cytoplasm of the cells with a green fluorescent protein. When they pumped fluid over the cells to create shear stress, the receptor ducked into the nucleus of the cell--just as if the cell had been exposed to dexamethasone. Once inside the nucleus, the receptor turned on a steroid-sensitive gene, the team reports online 24 January in Circulation. Finally, the team repeated the experiments in segments of human arteries and found a similar effect.
The work is important because it really connects changes in blood flow with protection against heart disease, says Peter Davies, a vascular biologist at the University of Pennsylvania, who is not associated with the project. "This system may be the manifestation of [exercise's] protective effect." The next step, Diamond and Davies agree, is to see if increased blood flow triggers this anti-inflammatory pathway in living animals.