Emphysema drugs may boost lung damage.

Emphysema drugs may boost lung damage

Results from a laboratory experiment hint that two drugs commonly used to treat emphysema may actually enhance the progression of this chronic lung disease, which often afflicts cigarette smokers. Scientists caution, however, that the results are based on in vitro studies and thus cannot be used at this time to make recommendations for treating people with emphysema.

Emphysema involves chronic irritation of the bronchial tubes and irreversible damage to the tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place. No cure exists, but physicians often prescribe bronchodilator drugs to widen bronchial tubes and ease labored breathing.

At last week's World Conference on Lung Health in Boston, British researcher Robert A. Stockley reported that two of these bronchodilator agents -- theophylline and terbutaline -- appeared to boost the activity of many white blood cells called neutrophils in a test-tube experiment. Neutrophils normally help fight bacterial infections, but they may do more harm than good when converging on inflamed lungs.

Stockley and David A. Lomas, who collaborated on the study at the Lung Immunobiochemical Research Laboratory in Birmingham, England, suggest these two drugs may increase the number of neutrophils drawn to the lungs, where they can release elastase, an enzyme that can damage the air sacs. Researchers know that lung tissue inflamed by tobacco smoke or other irritants attracts neutrophils circulating in the bloodstream, a process that can lead to emphysema. If the bronchodilators increase the number of neutrophils traveling to the lung, they might actually increase the severity of established lung disease, Stockley and Lomas say.

The researchers obtained blood samples from healthy, nonsmoking volunteers, isolated the neutrophils and bathed some of these cells in either theophylline or terbutaline. On one side of a synthetic membrane they placed the neutrophils; on the other side they placed a protein known to lure neutrophils. Lomas and Stockley discovered that the number of neutrophils traveling through the membrane was 33 percent greater in theophylline-treated cells than in untreated cells, and terbutaline boosted neutrophil migration by 26 percent over untreated cells.

These emphysema drugs "may possibly make the disease worse," comments A. Sonia Buist, a pulmonary researcher at the Oregon Health Sciences University in Portland. However, she emphasizes, drugs that encourage neutrophils to migrate in a test tube will not necessarily cause more neutrophils to cluster in the lung tissue of emphysema patients. Buist is president of the American Thoracic Society in New York City, which co-sponsored the meeting with the American Lung Association.

Lomas says his team plans clinical studies to determine whether theophylline and terbutaline indeed boost the numbers of neutrophils in the lung tissue of emphysema patients. In addition, he says, the researchers must determine whether patients who have used these drugs show more severe lung damage than patients who have not.