Yohannes Tesfaigzi, director of the chronic obstructive pulmonary disease program at Lovelace Respiratory Research Institute in Albuquerque, N.M., said chronic bronchitis is commonly associated with COPD.
"Although it is known that chronic mucus secretion is a hallmark of chronic bronchitis, the mechanisms underlying this condition are largely unknown," Tesfaigzi says in a statement. "This study shows that the airway cells that secrete mucus are sustained by cigarette smoke, which suppresses a cell death-inducing protein called Bik."
The researchers examined both human airway tissue samples and mouse models. Human samples were derived from autopsy tissues and from bronchial brushings taken from individuals with chronic bronchitis as well as healthy controls.
Mice were exposed to cigarette smoke for 6 hours per day, five days per week for three weeks. Following exposure, lung tissue samples were collected and examined for the presence of Bik, Tesfaigzi says.
The study, published in the Journal of Respiratory and Critical Care Medicine, determined Bik was significantly reduced in bronchial brushings of patients with chronic bronchitis compared with non-diseased controls. Mice exposed to cigarette smoking also had significantly reduced Bik levels and increased numbers of mucus-producing cells, the study said.