A mouse model of familial ALS has increased CNS levels of endogenous ubiquinol9/10 and does not benefit from exogenous administration of ubiquinol10

Abstract

Oxidative stress and mitochondrial impairment are the main pathogenic mechanisms of Amyotrophic Lateral Sclerosis (ALS), a severe neurodegenerative disease still lacking of effective therapy. Recently, the coenzyme-Q (CoQ) complex, a key component of mitochondrial function and redox-state modulator, has raised interest for ALS treatment. However, while the oxidized form ubiquinone10 was ineffective in ALS patients and modestly effective in mouse models of ALS, no evidence was reported on the effect of the reduced form ubiquinol10, which has better bioavailability and antioxidant properties. In this study we compared the effects of ubiquinone10 and a new stabilized formulation of ubiquinol10 on the disease course of SOD1(G93A) transgenic mice, an experimental model of fALS. Chronic treatments (800 mg/kg/day orally) started from the onset of disease until death, to mimic the clinical trials that only include patients with definite ALS symptoms. Although the plasma levels of CoQ10 were significantly increased by both treatments (from <0.20 to 3.0-3.4 µg/mL), no effect was found on the disease progression and survival of SOD1(G93A) mice. The levels of CoQ10 in the brain and spinal cord of ubiquinone10- or ubiquinol10-treated mice were only slightly higher (≤10%) than the endogenous levels in vehicle-treated mice, indicating poor CNS availability after oral dosing and possibly explaining the lack of pharmacological effects. To further examine this issue, we measured the oxidized and reduced forms of CoQ9/10 in the plasma, brain and spinal cord of symptomatic SOD1(G93A) mice, in comparison with age-matched SOD1(WT). Levels of ubiquinol9/10, but not ubiquinone9/10, were significantly higher in the CNS, but not in plasma, of SOD1(G93A) mice, suggesting that CoQ redox system might participate in the mechanisms trying to counteract the pathology progression. Therefore, the very low increases of CoQ10 induced by oral treatments in CNS might be not sufficient to provide significant neuroprotection in SOD1(G93A) mice.

Figure 1. Ubiquinol₁₀ chronic treatment has no effect on disease course in SOD1^G93A mice.

Effect of oral treatment with 800 mg/kg/day ubiquinone₁₀, ubiquinol₁₀ or vehicle, on motor dysfunction and disease progression of 129Sv SOD1^G93A mice (n = 15 mice per group). Treatment started at the age of 91 days (arrows) until the sacrifice (at the end-stage of the disease, when mice were unable to right themselves within 10 seconds after being placed on both sides). Treatment with ubiquinone₁₀ or ubiquinol₁₀ had no significant effects on body weight (A), on the latency of rotarod (B) and PaGE test (C) (Two-way ANOVA), or on disease onset (D) and survival length (E). Each point represents the mean; for sake of clarity standard deviations are not indicated but they were always less than 15% of the value. Table reports the mean and standard deviations of symptoms onset and life-span for each group.

Figure 2. CoQ_9/10 levels in brain and spinal cord of SOD1^G93A chronically treated with ubiquinol₁₀ or ubiquinone₁₀.

Total levels of CoQ₁₀ (A) and CoQ₉ (B), and CoQ₁₀/CoQ₉ ratio (C), in brain, and in cervicothoracic (CT-SpC) and lumbar (L-SpC) spinal cord of mice chronically treated with 800 mg/kg ubiquinol₁₀ (black) or ubiquinone₁₀ (grey). Each value is the mean±SEM of 10–12 mice and is indicated as percentage of levels measured in mice treated with vehicle. * P<0.05, ** P<0.01 compared to vehicle (Dunnet’s multiple comparison tests following One-way ANOVA).

Figure 3. Increased levels of ubiquinol_9/10 in the brain of symptomatic SOD1^G93A mice.

Endogenous brain levels of CoQ₉ (A–C) and CoQ₁₀ (D–F) in 16 week-old male 129Sv SOD1^WT and SOD1^G93A mice are shown as percentage of the levels measured in age-matched 129Sv non-transgenic mice (absolute values in table S1). Panels A, D show the total CoQs levels, whereas panels B, E and panels C, F show the reduced and oxidized forms, respectively. Each value is the mean±SEM of 4–7 mice. * P<0.05, ** P<0.01 compared to SOD1^WT mice (Student’s T-test).

Figure 4. Increased levels of ubiquinol_9/10 in the lumbar spinal cord of symptomatic SOD1^G93A mice.

Endogenous levels of CoQ₉ (A–C) and CoQ₁₀ (D–F) in the lumbar spinal cord of male 16 week-old 129Sv SOD1^WT and SOD1^G93A mice are shown as percentage of the levels measured in age-matched 129Sv non-transgenic mice (absolute values in table S1). Panels A, D show the total CoQs levels, whereas panels B, E and panels C, F show the reduced and oxidized forms, respectively. Each value is mean±SEM of 4–7 mice. * P<0.05, ** P<0.01 compared to SOD1^WT mice; ° P<0.05 compared to 129Sv NTg mice (Student’s T-test).

Figure 5. Unchanged plasma levels of ubiquinol₉ in symptomatic SOD1^G93A mice.

Levels of CoQ₉ (A), ubiquinol₉ (B) and ubiquinone₉ (C) in plasma of male 16 week-old 129Sv SOD1^WT and SOD1^G93A mice are shown as percentage of the levels measured in age-matched 129Sv non-transgenic mice (table S1). Each value is mean±SEM of 4–7 mice.