Decreased Coenzyme Q10 Levels in Multiple System Atrophy Cerebellum

Abstract

In familial and sporadic multiple system atrophy (MSA) patients, deficiency of coenzyme Q10 (CoQ10) has been associated with mutations in COQ2, which encodes the second enzyme in the CoQ10 biosynthetic pathway. Cerebellar ataxia is the most common presentation of CoQ10 deficiency, suggesting that the cerebellum might be selectively vulnerable to low levels of CoQ10 To investigate whether CoQ10 deficiency represents a common feature in the brains of MSA patients independent of the presence of COQ2 mutations, we studied CoQ10 levels in postmortem brains of 12 MSA, 9 Parkinson disease (PD), 9 essential tremor (ET) patients, and 12 controls. We also assessed mitochondrial respiratory chain enzyme activities, oxidative stress, mitochondrial mass, and levels of enzymes involved in CoQ biosynthesis. Our studies revealed CoQ10 deficiency in MSA cerebellum, which was associated with impaired CoQ biosynthesis and increased oxidative stress in the absence of COQ2 mutations. The levels of CoQ10 in the cerebella of ET and PD patients were comparable or higher than in controls. These findings suggest that CoQ10 deficiency may contribute to the pathogenesis of MSA. Because no disease modifying therapies are currently available, increasing CoQ10 levels by supplementation or upregulation of its biosynthesis may represent a novel treatment strategy for MSA patients.

Keywords: Cerebellar ataxia; Coenzyme Q10; Multiple system atrophy; Oxidative stress.

FIGURE 1

CoQ₁₀ levels in different brain regions. (a, b) CoQ₁₀ is significantly reduced in the cerebellum of multiple system atrophy ([MSA] n = 12) versus control ([CTRL] n = 12) patients, but not in Parkinson disease ([PD] n = 9) patients. Essential tremor ([ET] n = 9) patient samples had increased CoQ₁₀ levels versus controls. (c, d) CoQ₁₀ levels in MSA occipital cortex (n = 9) (c) and striatum (n = 7) (d) are comparable to those in control occipital cortex (n =10) and striatum (n = 7). *p < 0.05; **p < 0.01; ns, not significant.

FIGURE 2

Cerebellum. (a) Activities of CoQ-dependent respiratory chain enzymes, NADH cytochrome c reductase and succinate cytochrome c reductase (complexes I + III and II + III), in samples from MSA patients are not different from those in control samples. (b) Mitochondrial mass: measurements of TOM20 levels, citrate synthase (CS) activity, indices of mitochondrial mass, and cytochrome c oxidase (COX, complex IV) activity showed no difference between MSA brain and control brain samples. A representative Western blot with 5 controls and 5 MSA cases is shown. CTRL, controls, n = 12; MSA, multiple system atrophy, n = 12; ns, not significant.

FIGURE 3

Oxidative stress in cerebellum. (a) Representative images of immunohistochemistry with anti-4-HNE and anti-8-OHdG (indices of lipid and DNA oxidation, respectively) in samples from controls (CTRL) (n = 4 per staining) and multiple system atrophy (MSA) patients (n = 6 per staining). Figures are representative of 5 different areas per slide. Scale bar: 50 µm. (b) Image J analysis showed increased signals in brains of MSA cases versus controls for HNE but not for 8-OHdG. 4-HNE, 4-hydroxynonenal; 8-OHdG, 8-hydroxy-2’-deoxyguanosine; P, Purkinje cells. *p < 0.05.

FIGURE 4

Anti-α-synuclein and anti-4-HNE double immunofluorescence. (A) Control Purkinje cell. (B) MSA sample Purkinje cell. (C) α-synuclein accumulation in the white matter of a sample from an MSA patient (arrows). 4-HNE, 4-hydroxynonenal.

FIGURE 5

CoQ₁₀ biosynthetic pathway. (a) Measurements of protein steady-state levels of enzymes involved in CoQ biosynthesis and its regulation in MSA and control brains showed significantly decreased levels of PDSS1 and COQ5. (b) Representative Western blot showing the expected sizes bands in 5 MSA and 5 controls. Ctrl, controls, n = 12; MSA, multiple system atrophy, n = 12; *p < 0.05; **p < 0.01.