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Diesel Exhaust Plus Cholesterol Equals Cardiovascular Problems

People living in cities with dirty air experience increased rates of heart attack, stroke and other cardiovascular problems. But it's been difficult to determine exactly what part of the air pollution makes people sick, whether it's the chemical gases in pollution or the presence of very small soot particles.

Now, new research from the University of California at Los Angeles sheds light on the connections between the particulate components of air pollution and the processes that cause atherosclerosis. Professor Andre Nel led the research. Nel explains that atherosclerosis is a process by which blood lipids clog arteries. "[The lipids] form lesions in the linings of blood vessels that come from the aorta and feed the coronary arteries and other important organs such as the brain."

Nel took samples of the cells that line the interior of human blood vessels and exposed them to chemicals found in diesel exhaust particles. He and his colleagues found that certain genes in the cells became more active after being exposed. "The group of genes included genes playing a role in inflammation, which is a key pathological process that can contribute to atherosclerosis," Nel says.

"Another interesting group of genes that came to the foreground were genes that protect us against the oxidant chemicals that are present on the particles," the researcher says. "These antioxidant genes may in fact play a role in protecting a lot of us against the bad effects of air pollution."

The next part of the study was to expose animals to air pollution near a Los Angeles freeway. Researchers took mice and placed them in a portable lab parked next to busy roadways. "We kept these animals there for eight weeks," Nel says.

They then studied tissue samples and saw "the same genetic imprint that we saw from the blood vessel lining cells, where the diesel exhaust chemicals interacted with cholesterol to cause an enhanced expression of genes that can play a role in atherosclerosis."

Nel says,indeed, the mice genes did work overtime, causing lipid buildup in the mice's blood vessels. Nel says this work confirms a link between pollution exposure and the processes that cause lipid and cholesterol build up in blood vessels. His research is published in the online journal Genome Biology.