Figure 3

Compartment-specific changes in free NADH fractions with imposed extracellular oxidative (0 mV) and reductive (−150 mV) states across ages of NTg and 3xTg-AD mice for both female (A–C) and male (D–F) neurons. (A,D) Mitochondrial free NADH fractions in response to the imposed external Cys/CySS reductive states at −150 mV and imposed oxidized state at 0 mV in all ages (p < 0.001) of both NTg and 3xTg-AD mice. With external reductive treatment, mitochondrial free NADH fractions can be rescued to the levels of young age at untreated condition (orange circles). Untreated condition of −50 mV was a control for comparison. At the untreated condition, age effect drove declines in mitochondrial free NADH from young to old age of each genotype (p < 0.001). Moreover, free NADH fractions with genetic load appear to be lower than that of age- and redox- matched NTg neurons (p < 0.001). The imposed oxidative stress depleted free NADH fractions in all ages (p < 0.001). Notably, mitochondrial free NADH fractions in young age always presented highest than the levels of middle and old age in response to the external redox shifts. (B,E) Cytoplasmic free NADH fractions and (C,F) Nuclear free NADH fractions of female neurons illustrated depletion with oxidative stress (p < 0.001) and elevation in reductive states (p < 0.001) across ages in NTg and 3xTg-AD mice. Similarly, in male neurons. For gender difference, male neurons exhibited lower free NADH fractions than the age-, genotype- and redox-matched female neurons in each compartment, (Mito. F(1, 59) = 13, p < 0.001; Cytoplasm F(1, 59) = 25, p < 0.001; Nuclei F(1, 59) = 13, p < 0.001); This sex-driven redox orders remain unchanged with external oxidized stress, (Mito. F(1, 59) = 33, p < 0.001; Cytoplasm F(1, 59) = 24, p < 0.001; Nuclei F(1, 59) = 5, p = 0.03) and with the imposed reductive state (Mito. F(1, 59) = 22, p < 0.001; Cytoplasm F(1, 59) = 3.7, p = 0.06; Nuclei F(1, 59) = 22, p < 0.001); Genotype effect drove a lower free NADH fraction in 3xTg-AD neurons than the NTg neurons in each age, redox state and compartment (n = 20 female neurons or n = 10 male neurons/compartment/redox state/age/genotype).