The Impact of Autophagy on the Cigarette Smoke Extract-Induced Apoptosis of Bronchial Epithelial Cells

BACKGROUND Previous studies report that apoptosis and autophagy are involved in the pathogenesis of emphysema, and macroautophagy is one of the processes regulating the apoptosis pathway. However, few studies have evaluated whether chaperone-mediated autophagy (CMA) contributes to the regulation of apoptosis. In this study, we investigated the impact of autophagy, including both macroautophagy and CMA, on the apoptosis in bronchial epithelial cells. METHODS Cigarette smoke extract (CSE) was injected intratracheally into C57BL/6 mice, and emphysema and apoptosis were evaluated in the lungs. After treatment with CSE, apoptosis, macroautophagy, and CMA were measured in BEAS2-B cells, and the impact of autophagy on the apoptosis was evaluated following knockdown of autophagy-related genes by short interfering RNAs (siRNAs). RESULTS Intratracheal CSE injection resulted in the development of emphysema and an increase in apoptosis in mice. CSE increased the apoptosis in BEAS2-B cells, and also elevated the expression of proteins related to both macroautophagy and CMA in BEAS2-B cells. The knockdown experiment with siRNAs showed that macroautophagy increases apoptosis in BEAS2-B cells, while CMA suppresses apoptosis. CONCLUSION The intratracheal injection of CSE induces pulmonary emphysema and an increase in apoptosis in mice. CSE also induces apoptosis, macroautophagy, and CMA of bronchial epithelial cells. Macroautophagy and CMA regulate apoptosis in opposite directions.