Figure 5.

Delivery of recombinant NQO1 and NADPH reverses neuronal respiratory inhibition by idebenone. A, OCR measurements from cortical neurons. Cells were first permeabilized with Complex I substrates present (saponin/pyruvate/malate; S/P/M), as in Figure 4A. Next, vehicle, idebenone (Ideb; 80 μm), NADPH (0.5 mm), and recombinant human NQO1 (15–25 U/ml) were injected either individually or in the combinations indicated. Piericidin A (Pier A; 500 nm) was then added to inhibit Complex I, followed by antimycin A (AA; 1 μm). OCR measurements are normalized to the point just before idebenone/vehicle addition (ADP-stimulated baseline). Data are the mean ± SE from four to six independent experiments. B, C, Bar graph representations of data in A and including additional controls not depicted in A for clarity. B, OCR after the addition of idebenone/vehicle plus and minus the indicated treatments, expressed as a percentage of the ADP-stimulated baseline OCR. C, OCR after injection of piericidin A with and without idebenone and the indicated treatments, relative to the ADP-stimulated control (Ctrl) group (point just before piercidin A addition). **p < 0.01 relative to vehicle control; ***p < 0.001 relative to control; ##p < 0.01 between idebenone-treated and vehicle-treated groups; @@p < 0.01 relative to 80 μm idebenone alone; two-way ANOVA followed by Tukey's post hoc test.