There's a reason people say "Calm down or you'll have a heart attack." Chronic stress such as that caused by the job, money or relationship problems-is believed to increase the risk of a heart attack. rodents Now researchers studying harassed residents and harassed doctors offered an explanation of how, at a physiological level, stress long term may endanger the cardiovascular system. It revolves around immune cells that circulate in the blood, they propose.
the new discovery is "surprising," said the doctor and atherosclerosis researcher Alan Tall of Columbia University, who was not involved in the new study. "the idea was there that chronic psychosocial stress is associated with increased cardiovascular disease in humans, but what is missing is a mechanism, "he notes.
epidemiological studies have shown that people who face many stressors-those who survive natural disasters to those who work long hours are more likely to develop atherosclerosis, accumulation of fatty plaques within blood vessels. In addition to fats and cholesterol, the plates contain monocytes and neutrophils, immune cells that cause inflammation in the blood vessel walls. And when the plates are detached from the walls where they are housed, they can cause more extreme blockages elsewhere, leading to a stroke or heart accident.
To study the effect of stressful intensive care unit (ICU) moves on resident physicians, biologist Matthias Nahrendorf from Harvard Medical School in Boston recently found that blood samples taken when doctors was the most stressed had the highest levels of neutrophils and monocytes. To probe whether these white blood cells or leukocytes are the missing link between stress and atherosclerosis, he and his colleagues turned to experiments on mice.
team Nahrendorf exposed mice for up to six weeks to stressful situations, including tilting their cages, rapidly alternating light with darkness, or regularly hover between isolation and neighborhoods overcrowded. Compared to control mice, mice-as stressed out doctors had increased levels of neutrophils and monocytes in the blood.
The researchers then housed in on an explanation of the higher levels of immune cells. They already knew that chronic stress increases the blood levels of the hormone norepinephrine; noradrenaline Nahrendorf discovered, binds to a cell surface receptor protein known as β 3 of stem cells in bone marrow. In turn, the chemical environment changes of the bone marrow and there is an increase in the activity of white blood cells produced by the stem cells.
"It is logical that stress wakes these immune cells as an expanded production of leukocytes prepares you for danger, as in a fight where you might get hurt," says Nahrendorf. "But stress chronic is another story there is no injury to heal and no infection. "
in mice living with chronic stress, the team announced today in Nahrendorf Nature Medicine , atherosclerotic plaques more closely resemble known plates to be at greater risk of rupture and cause a heart attack or stroke. When scientists blocked the β 3 receiver, however, stressed mice not only had fewer of these dangerous plaques, but also had reduced levels of active immune cells in their plates, β tracking 3 as an essential link between stress and atherosclerosis.
The discovery could lead to new drugs to help prevent cardiovascular disease, suggests biologist Lynn Hedrick Jolla Institute for the Allergy and Immunology in San Diego, California. "I think it gives us a very direct idea that β 3 receptor is important in regulating the response induced by stress from the bone marrow," says Hedrick. "If we can develop a drug that targets the receptor, this can be very clinically relevant. "
More immediately, the new findings suggest a way that clinicians could screen patients for their risk of atherosclerosis, heart attack, and stroke says Grand. "Rather than asking four questions about the level of stress, we could use the number of white blood cells to monitor psychosocial stress," he said.
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