The molecular events leading to emphysema development include generation of oxidative stress and alveolar cell apoptosis. Oxidative stress upregulates ceramides, pro-apoptotic signaling sphingolipids that trigger further oxidative stress and alveolar space enlargement, as shown in an experimental model of emphysema due to VEGF-blockade. As alveolar cell apoptosis and oxidative stress mutually interact to mediate alveolar destruction, we hypothesized that the oxidative stress generated by ceramide is required for its pathogenetic effect on lung alveoli. To model the direct lung effects of ceramide, mice received ceramide intra-tracheally (C_12:0 or C_8:0; 1 mg/kg) or vehicle. Apoptosis was inhibited with a general caspase inhibitor. Ceramide augmentation shown to mimic levels found in human emphysema lungs increased oxidative stress, and decreased, independently of caspase activation, the total and cytoplasmic superoxide dismutase activity at 48h. In contrast to their wild-type littermates, transgenic mice overexpressing human Cu/Zn SOD were significantly protected from ceramide-induced superoxide production, apoptosis, as well as airspace enlargement. Activation of lung acid sphingomyelinase in response to ceramide treatment was abolished in the Cu/Zn SOD transgenics. Since Cu/Zn SOD overexpression was reported to also inhibit cigarette smoke-induced emphysema in mice, to extrapolate the relevance of our findings to the cigarette smoke-emphysema, we documented increased lung ceramides measured by tandem mass spectrometry in adult mice exposed to cigarette smoke for 4 weeks. In conclusion, superoxide accumulation may be a critical step in ceramide-mediated destruction in the lung. This work implicates excessive lung ceramide's as amplifiers of lung injury through redox-dependent mechanisms.