Fig. 5
The antioxidant targeted to mitochondria SS31 reduces mitochondrial oxidative stress in AD transgenic mouse neurons. a. Experimental procedure to determine oxidative stress in neuronal mitochondria in mice. b. In vivo images of neurites and cell bodies expressing AAV.hSyn.mt-roGFP in mitochondria in non-Tg (top) and APP/PS1 Tg mice treated with either SS31 (middle) or SS20 (bottom). Field of view shows two-photon images of the expression of the AAV (green), blood vessels (Dextran, red) and amyloid plaques (HS169, red) in the cortex. Ratiometric roGFP imaging shows pseudocolor images according to the pseudocolor scale at the bottom. Scale bar represents 20 μm. c, d. Mitochondrial oxidative stress (Ratio 800/900) comparison between non-Tg and APP/PS1 Tg mice injected with either SS31 or SS20 in neuronal mitochondria (c. Average per field of view, non-Tg SS31: 0.94 ± 0.023, n = 32 z-stacks from 6 mice (4 males, 2 females); APP/PS1 SS31: 0.95 ± 0.024, n = 40 z-stacks from 6 mice (3 males, 3 females); APP/PS1 SS20: 1.11 ± 0.032, n = 30 z-stacks from 5 mice (1 males, 4 females), ***p = 0.0001, **p < 0.01. d. Average per mouse, non-Tg SS31: 0.90 ± 0.016, n = 6 mice (4 males, 2 females); APP/PS1 SS31: 0.94 ± 0.032, n = 6 mice (3 males, 3 females); APP/PS1 SS20: 1.13 ± 0.058, n = 5 mice (1 males, 4 females), *p < 0.05). Error bars represent mean ± SEM. Blue dots denote male and pink dots denote female. e. Histogram of mitochondrial oxidative stress frequency distribution (Ratio 800/900) of the three conditions. f. Difference between males and females (per field of view): Males non-Tg SS31: 0.89 ± 0.019, n = 17 z-stacks; APP/PS1 SS31: 1.03 ± 0.026, n = 18 z-stacks; APP/PS1 SS20: 1.17 ± 0.043, n = 8 z-stacks from 4, 3 and 1 mice respectively, **p = 0.01, ***p = 0.001; Females non-Tg SS31: 0.91 ± 0.042, n = 9 z-stacks; APP/PS1 SS31: 0.87 ± 0.032, n = 22 z-stacks; APP/PS1 SS20: 1.10 ± 0.038, n = 24 z-stacks from 2, 3 and 4 mice respectively, ***p = 0.001. g. For APP/PS1 Tg mice injected with SS31, the probability of finding mitochondrial oxidative stress in neurons was similar at any distance within 70 µm from the edge of a plaque, unlike SS20 (mean ± SEM; APP/PS1 SS31 r (Pearson’s coefficient) 0.21, R2 0.046, n.s., n = 56 plaques from 6 Tg mice; APP/PS1 SS20 r -0.58, R2 0.338, *p < 0.05, n = 19 plaques analysed from 4 Tg mice)