Environmental cadmium positively correlates with autophagy and apoptosis in chronic obstructive pulmonary disease patients

Environmental cadmium is closely correlated with several respiratory diseases. Pulmonary autophagy and apoptosis play significant roles in the pathophysiological process of chronic obstructive pulmonary disease (COPD). Nevertheless, the correlations of cadmium exposure with autophagy and apoptosis are obscure in patients with COPD. The main purpose of this research was to explore the correlations among serum cadmium, pulmonary function, pulmonary autophagy and apoptosis in patients with COPD through a case-control study. Lung tissues and serum samples were collected from COPD patients and control cases. Serum cadmium was detected with graphite furnace atomic absorption spectrometry. The protein expression of autophagy and apoptosis were measured in lungs using western blotting. These results indicated that serum cadmium was higher in COPD patients than control cases. Serum cadmium was gradually risen parallelly with the grades of COPD patients. P62, Beclin 1, LC3 Ⅱ and Ⅰ, the markers of autophagy, was elevated in lungs of COPD patients. Additionally, cleaved Caspase 1 and 3, as well as TUNEL positive cells, the molecules of apoptosis, were increased in lungs of COPD patients. In addition, correlational analysis indicated that serum cadmium was positively associated with autophagy and apoptosis in lungs among COPD patients. Besides, pulmonary autophagy and apoptosis were inversely correlated with pulmonary function in COPD patients. In vitro experiments revealed that cadmium exposure induced autophagy and apoptosis in human pulmonary epithelial cells. Consequently, this study firstly shown evidence that cadmium-evoked autophagy activation and apoptosis elevation may, at least partially, contribute to pulmonary function decline in COPD patients.