Having previously established that the reduced ROS level by 6AN in CF cells was likely due to the reduced level of NADPH [23,24], product of G6PDH and substrate of NOX [25], in order to investigate if mitochondrial enzyme NNT, involved in modulating the levels of the reduced pyridine dinucleotides, is implicated in the excessive synthesis of mitochondrial ROS then modulating their production, GSNO effect on ROS level was investigated. The gene discussed is H6PD; the disease is cystic fibrosis.