Riboflavin supplementation does not attenuate hyperoxic lung injury in transgenic (spc-mt)hGR mice

The aims of this study were to test the hypothesis that mice expressing mitochondrially targeted human glutathione reductase (GR) driven by a surfactant protein C promoter ((spc-mt)hGR) are functionally riboflavin deficient and that this deficiency exacerbates hyperoxic lung injury. The authors further hypothesized that dietary supplementation with riboflavin (FADH) will improve the bioactivity of GR, thus enhancing resistance to hyperoxic lung injury. Transgenic (mt-spc)hGR mice and their nontransgenic littermates were fed control or riboflavin-supplemented diets upon weaning. At 6 weeks of age the mice were exposed to either room air (RA) or >95% O(2) for up to 84 hours. GR activities (with and without exogenous FADH) and GR protein levels were measured in lung tissue homogenates. Glutathione (GSH) and glutathione disulfide (GSSG) concentrations were assayed to identify changes in GR activity in vivo. Lung injury was assessed by right lung to body weight ratios and bronchoalveolar lavage protein concentrations. The data showed that enhanced GR activity in the mitochondria of lung type II cells does not protect adult mice from hyperoxic lung injury. Furthermore, the addition of riboflavin to the diets of (spc-mt)hGR mice neither enhances GR activities nor offers protection from hyperoxic lung injury. The results indicated that modulation of mitochondrial GR activity in lung type II cells is not an effective therapy to minimize hyperoxic lung injury.