The link between cigarette smoke and cardiac disease is well-established, but research conducted by Professor of Medical Science Chi-Ming Hai found that nicotine alone has negative effects on vascular health. While nicotine replacement products such as patches or gums have long been considered safe alternatives to cigarettes, the results of Hai's study show that nicotine may be a key culprit in the development of atherosclerosis, the hardening of the arteries. Hai presented his results in San Diego at the Biophysical Society 56th Annual Meeting Feb. 26.
Atherosclerosis is the accumulation of plaque in blood vessels caused by an invasion of vascular smooth muscle cells. Plaque formation in blood vessels can contribute to heart disease by stiffening and narrowing vessels. When these plaques break loose, they can lodge in other vessels and deprive the brain or heart of oxygen, leading to heart attack or stroke.
Hai's findings reveal that nicotine may contribute to cardiovascular disease by inducing cellular migration and changes in cell structure. Normally, the layers of blood vessels are separated by extracellular matrix, which serves to prevent cell migration. But in the presence of nicotine, invading smooth muscle cells can remodel the cytoskeleton into structures called podosomes, Hai's research shows. These structures release enzymes that degrade the extracellular matrix, compromising the vessel's integrity and permitting the muscle cells to migrate into the vessel's interior.
"Substituting smoking with nicotine may have limited beneficial effects on atherosclerosis," Hai said.
The study used rat vascular smooth muscle cells, and Hai is now examining this phenomenon using human smooth muscle cells with the help of Patricia Melvin '12.
Melvin described Hai as "a great teacher" and said the projects are progressing smoothly. Preliminary results from her work demonstrate increased cellular migration in the presence of nicotine, thus providing evidence for nicotine-induced risk of atherosclerosis in humans as well. Melvin plans to present her results at the thesis poster day at the end of the semester.
Hai said many people came to view his poster presentation at the Biophysical Society conference, and the society deemed Hai's abstract a highlight of the meeting. Albert Wang, senior scientist at the Boston Biomedical Research Institute, said the study is a good start but is limited because it has only been carried out at the cellular level. Wang recommended Hai study the effects of nicotine in animal models or arteries in culture.
Nicotine products should bear a warning label, Hai added. "Nicotine is not a benign substance," Hai said. "It has detrimental effects, especially on blood vessels." While the use of nicotine patches or gums can help smokers stop the habit, long-term use of nicotine-containing products may be harmful, he said.