G. R. Scott Budinger1,2,*, Gökhan M. Mutlu1,*, Daniela Urich2, Saul Soberanes1, Leonard J. Buccellato1, Keenan Hawkins1, Sergio E. Chiarella1, Kathryn A. Radigan1, James Eisenbart1, Hemant Agrawal1, Sara Berkelhamer3, Siegfried Hekimi4, Jianke Zhang5, Harris Perlman1, Paul T. Schumacker1,2,3, Manu Jain1 and Navdeep S. Chandel1,2. Published ahead of print on October 19, 2010, doi:10.1164/rccm.201002-0181OC. American Journal of Respiratory and Critical Care Medicine Vol 183. pp. 1043-1054, (2011)
Rationale: Acute lung injury and the acute respiratory distress syndrome are characterized by increased lung oxidant stress and apoptotic cell death. The contribution of epithelial cell apoptosis to the development of lung injury is unknown.
Objectives: To determine whether oxidant-mediated activation of the intrinsic or extrinsic apoptotic pathway contributes to the development of acute lung injury.
Methods: Exposure of tissue-specific or global knockout mice or cells lacking critical components of the apoptotic pathway to hyperoxia, a well-established mouse model of oxidant-induced lung injury, for measurement of cell death, lung injury, and survival.
Measurements and Main Results: We found that the overexpression of SOD2 prevents hyperoxia-induced BAX activation and cell death in primary alveolar epithelial cells and prolongs the survival of mice exposed to hyperoxia. The conditional loss of BAX and BAK in the lung epithelium prevented hyperoxia-induced cell death in alveolar epithelial cells, ameliorated hyperoxia-induced lung injury, and prolonged survival in mice. By contrast, Cyclophilin D–deficient mice were not protected from hyperoxia, indicating that opening of the mitochondrial permeability transition pore is dispensable for hyperoxia-induced lung injury. Mice globally deficient in the BH3-only proteins BIM, BID, PUMA, or NOXA, which are proximal upstream regulators of BAX and BAK, were not protected against hyperoxia-induced lung injury suggesting redundancy of these proteins in the activation of BAX or BAK.
Conclusions: Mitochondrial oxidant generation initiates BAX- or BAK-dependent alveolar epithelial cell death, which contributes to hyperoxia-induced lung injury.
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