Now, considering the close association between low NADPH and reduced G6PDH activity occurring in CF cells, where NOX-dependent ROS level increased [23,24,25], in order to verify the interdependence of cytosolic G6PDH—essential enzyme for protection against cellular ROS—and NNT—whose reaction direction is strictly dependent upon cell redox state—the NNT activity was studied in the presence of 6AN, G6PDH inhibitor, and, vice versa, the activity of G6PDH in presence of GSNO. The gene discussed is H6PD; the disease is cystic fibrosis.