Figure 1.

Real-time monitoring of compartmentalized NAD⁺/NADH redox ratios in live cells

(A) Scheme showing the domains of SoNar and the sequence of 2× mitochondrial targeting sequence.

(B and C) Representative images of mt-SoNar expression in fibroblasts (B) and epithelial cells (C).

(D) Representative images of mt-SoNar, mt-cpYFP, ct-SoNar, and ct-cpYFP in adult rat cardiomyocytes 3 days after adenovirus-mediated gene expression. Scale bar: 20 μm.

(E and F) Responses of the fluorescence ratio (R_488/405) of mt-SoNar and mt-cpYFP (E) and ct-SoNar and ct-cpYFP (F) to various NAD⁺/NADH ratios in permeabilized H9C2 cardiomyoblasts. n = 3.

(G) Summarized data showing time-dependent changes in mitochondrial NAD⁺/NADH ratio in response to acute addition of ketone bodies acetoacetic acid (AcAc, 1 mM) or β-hydroxybutyrate (β-OHB, 1 mM). n = 5 rats.

(H) Representative examples showing time-dependent changes of mitochondrial or cytosolic NAD⁺/NADH ratio in individual adult cardiomyocyte during ischemia (indicated by the gray area) and reperfusion.

(I and J) Summarized data showing the changes of mitochondrial (I) or cytosolic (J) NAD⁺/NADH ratio during simulated ischemia reperfusion in adult cardiomyocytes. n = 4–5 rats. ∗p < 0.05 versus control (value is set as 1.0).

Data are presented as mean ± SEM. See also Figure S1.