Smoking cigarettes is not only the principle cause of chronic obstructive pulmonary disease (COPD), but it may change the body's immune responses to bacteria that commonly cause exacerbations of the disease, according to new research in a mouse model.
"It is well established that smoking is the main risk factor for COPD. But our research also suggests that cigarette smoke substantially changes the immune response to bacteria, which means that patients with COPD who smoke are weakening their body's ability to deal effectively with bacterial invaders. This may cause even further progression of the disease," said Martin Stmpfli, Ph.D., an associate professor at McMaster University, the principle investigator of the study.
"We wanted to see whether and how cigarette smoke would change the inflammatory response to the bacteria that is the culprit behind many COPD exacerbations, nontypeable Haemophilus influenzae or NTHI."
Their results were published in the second issue of April of the American Journal of Respiratory and Critical Care Medicine.
Dr. Stmpfli and colleagues tested the effects of cigarette smoke exposure on inflammation and immune response in mice that were exposed to cigarette smoke twice daily five days a week for either eight weeks or four days then challenged with an intranasal inoculation of NTHI. The cigarette smoke exposure roughly approximated that of an "average" human smoker (within the limitations of a model with differing metabolic processes.) Control mice were not exposed to cigarette smoke, but were inoculated with NTHI as were the cigarette smoke-exposed mice.
The researchers found that mice that were exposed to cigarette smoke, whether for four days or for eight weeks, showed distinct shifts in their immune-response profile, namely an increase in inflammation of the lungs after the NTHI challenge, increased weight-loss in response to the bacterial infection and, notably, a shift in th
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American Thoracic Society