Cadmium is a toxic
heavy metal ranked seventh on the Priority List of
Hazardous Substances. As a byproduct of smelters,
cadmium is a prevalent environmental contaminant. It is also a major component of cigarette
smoke, and its inhalation is associated with decreased pulmonary function,
lung cancer, and
chronic obstructive pulmonary disease.
Ion channels, including the
cystic fibrosis transmembrane conductance regulator (CFTR), play a central role in maintaining fluid homeostasis and lung functions. CFTR is mostly expressed in epithelial cells, and little is known about the effect of
cadmium exposure on lung epithelial cell function. We show that exposure to
cadmium decreases the expression of the
CFTR protein and subsequent
chloride transport in human airway epithelial cells in vitro. Impairment of
CFTR protein expression was also observed in vivo in the lung of mice after intranasal instillation of
cadmium. We established that the inhibitory effect of
cadmium was not a nonspecific effect of
heavy metals, as
nickel had no effect on
CFTR protein levels. Finally, we show that selected
antioxidants, including
alpha-tocopherol (
vitamin E), but not
N-acetylcysteine, can prevent the
cadmium-induced suppression of CFTR. In summary, we have identified
cadmium as a regulator of the CFTR
chloride channel present in lung epithelial cells. Future strategies to prevent the deleterious effect of
cadmium on epithelial cells and lung functions may benefit from the finding that
alpha-tocopherol protects CFTR expression and function.