Abstract
Charcot Marie Tooth (CMT) or hereditary motor and sensory neuropathy is a heterogeneous neurological disorder leading to nerve damage and muscle weakness. Although multiple mutations associated with CMT were identified, the cellular and molecular mechanisms of this pathology are still unclear, although most of the subtype of this disease involve mitochondrial dysfunction and oxidative stress in the mechanism of pathology. Using patients' fibroblasts of autosomal recessive, predominantly demyelinating form of CMT-CMT4B3 subtype, we studied the effect of these mutations on mitochondrial metabolism and redox balance. We have found that CMT4B3-associated mutations decrease mitochondrial membrane potential and mitochondrial NADH redox index suggesting an increase rate of mitochondrial respiration in these cells. However, mitochondrial dysfunction had no profound effect on the overall levels of ATP and on the energy capacity of these cells. Although the rate of reactive oxygen species production in mitochondria and cytosol in fibroblasts with CMT4B3 pathology was not significantly higher than in control, the level of GSH was significantly lower. Lower level of glutathione was most likely induced by the lower level of NADPH production, which was used for a GSH cycling, however, expression levels and activity of the major NADPH producing enzyme Glucose-6-Phosphate Dehydrogenase (G6PDH) was not altered. Low level of GSH renders the fibroblast with CMT4B3 pathology more sensitive to oxidative stress and further treatment of cells with hydroperoxide increases CMT patients' fibroblast death rates compared to control. Thus, CMT4B3 pathology makes cells vulnerable to oxidative stress due to the lack of major endogenous antioxidant GSH.