Role of oxidative damage in Friedreich's ataxia
J L Bradley1, S Homayoun, P E Hart
1Department of Clinical Neuroscience, Royal Free and University College Medical School, University College London, Rowland Hill Street, London NW3 2PF, United Kingdom.
Abstract:
Plasma malondialdehyde (MDA) levels were raised in Friedreich's ataxia (FRDA) patients. These levels correlated with increasing age and disease duration, suggesting lipid peroxidation increased with disease progression. Using fibroblasts from FRDA patients we observed that GSH levels and aconitase activities were normal, suggesting their antioxidant status was unchanged. When exposed to various agents to increase free radical generation we observed that intracellular superoxide generation induced by paraquat caused enhanced oxidative damage. This correlated with the size of the GAA1 expansion, suggesting decreased frataxin levels may render the cells more vulnerable to mild oxidative stress. More severe oxidative stress induced by hydrogen peroxide caused increased cell death in FRDA fibroblasts but was not significantly different from control cells. We propose that abnormal respiratory chain function and iron accumulation may lead to a progressive increase in oxidative damage, but increased sensitivity to free radicals may not require detectable respiratory chain dysfunction.
Insights
Friedreich
Area of Science:
- Biochemistry
- Neurodegenerative Diseases
- Cell Biology
Background:
- Friedreich's ataxia (FRDA) is a rare inherited disease.
- Oxidative stress is implicated in FRDA pathogenesis.
- Understanding oxidative damage mechanisms is crucial for FRDA research.
Purpose of the Study:
- To investigate plasma malondialdehyde (MDA) levels in FRDA patients.
- To assess the antioxidant status and oxidative stress response in FRDA fibroblasts.
- To correlate oxidative damage with disease progression and genetic factors.
Main Methods:
- Measurement of plasma MDA levels.
- Analysis of glutathione (GSH) levels and aconitase activity in fibroblasts.
- Exposure of fibroblasts to oxidative stressors (paraquat, hydrogen peroxide).
- Correlation analysis with age, disease duration, and GAA1 expansion size.
Main Results:
- Elevated plasma MDA levels in FRDA patients, increasing with age and disease duration.
- Normal GSH levels and aconitase activity in FRDA fibroblasts.
- Enhanced oxidative damage in FRDA fibroblasts upon paraquat exposure, linked to GAA1 expansion size.
- Increased cell death in FRDA fibroblasts under severe oxidative stress (hydrogen peroxide) was not significantly different from controls.
Conclusions:
- Lipid peroxidation increases with FRDA disease progression.
- FRDA cells show heightened vulnerability to mild oxidative stress, potentially due to frataxin deficiency.
- Progressive oxidative damage in FRDA may stem from mitochondrial dysfunction and iron accumulation, independent of detectable respiratory chain defects.
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