-Tetrahydrocannabinol disrupts mitochondrial function and cell energetics

Sarafian, Theodore A., Shaghig Kouyoumjian, Farnaz Khoshaghideh, Donald P. Tashkin, and Michael D. Roth. 9-Tetrahydrocannabinol disrupts mitochondrial function and cell energetics. Am J Physiol Lung Cell Mol Physiol 284: L298–L306, 2003. First published October 25, 2002; 10.1152/ajplung.00157.2002.—We have observed rapid and extensive depletion of cellular energy stores by 9-tetrahydrocannabinol (THC) in the pulmonary transformed cell line A549. ATP levels declined dose dependently with an IC50 of 7.5 g/ml of THC after 24-h exposure. Cell death was observed only at concentrations 10 g/ml. Studies using JC-1, a fluorescent probe for mitochondrial membrane potential, revealed diminished mitochondrial function at THC concentrations as low as 0.5 g/ml. At concentrations of 2.5 or 10 g/ml of THC, a decrease in mitochondrial membrane potential was observed as early as 1 h after THC exposure. Mitochondrial function remained diminished for at least 30 h after THC exposure. Flow cytometry studies on cells exposed to particulate smoke extracts indicate that JC-1 red fluorescence was fivefold lower in cells exposed to marijuana smoke extract relative to cells exposed to tobacco smoke extract. Comparison with a variety of mitochondrial inhibitors demonstrates that THC produced effects similar to that of carbonyl cyanide p-trifluoromethoxyphenylhydrazone, suggesting uncoupling of electron transport. Loss of red JC-1 fluorescence by THC was suppressed by cyclosporin A, suggesting mediation by the mitochondrial permeability transition pore. This disruption of mitochondrial function was sustained for at least 24 h after removal of THC by extensive washing. These results suggest that exposure of the bronchopulmonary epithelium to THC may have important health and physiological consequences.