Chlorine Gas Exposure on Human Bronchial Cells Decreases Mitochondrial Quality and Activates Autophagy

Abstract

Chlorine (Cl2) can cause significant morbidity and mortality when inhaled due to the formation of reactive intermediates. We hypothesized that mitochondria of lung epithelial cells are injured by Cl2 causing decreased bioenergetic capacity of these organelles and membrane depolarization. Human epithelial cells (H441) were exposed to Cl2 (100 ppm for 15 min) and returned to the incubator with air/5% CO2. Measurements of mitochondrial oxygen consumption rate (OCR) using extracellular flux analysis showed a significant reduction of maximal OCR and bioenergetic reserve capacity at 1h post exposure, the values returning to air controls 6 h later. Mitochondrial ROS production, assessed by MitoSOX fluorescence (both by fluorescent microscopy and FACS analysis) showed increased signals at 1 and 6 h post Cl2 exposure. Furthermore, mitochondrial membrane potential showed a 30% decrease when compared with controls at 1h but not 6 h post exposure, indicative of significant but reversible mitochondrial injury (TMRM assay). The recovery of mitochondrial membrane potential at 6h post exposure was accompanied by increased levels of autophagy protein LC3‐II which increased even more 24h post exposure. Taken together these data support the hypothesis that mitochondrial quality is decreased by Cl2 exposure and suggests that autophagy may play a regulatory role in this process. Supported by 5U01ES015676