Leber's Hereditary Optic Neuropathy (LHON) Pathogenic Mutations Induce Mitochondrial-dependent Apoptotic Death in Transmitochondrial Cells Incubated with Galactose Medium

Abstract

Leber's hereditary optic neuropathy (LHON), a maternally inherited form of central vision loss, is associated with mitochondrial DNA pathogenic point mutations affecting different subunits of complex I. We here report that osteosarcoma-derived cytoplasmic hybrids (cybrid) cell lines harboring one of the three most frequent LHON pathogenic mutations, at positions 11778/ND4, 3460/ND1, and 14484/ND6, undergo cell death when galactose replaces glucose in the medium, contrary to control cybrids that maintain some growth capabilities. This is a well known way to produce a metabolic stress, forcing the cells to rely on the mitochondrial respiratory chain to produce ATP. We demonstrate that LHON cybrid cell death is apoptotic, showing chromatin condensation and nuclear DNA laddering. Moreover, we also document the mitochondrial involvement in the activation of the apoptotic cascade, as shown by the increased release of cytochrome c into the cytosol in LHON cybrid cells as compared with controls. Cybrids bearing the 3460/ND1 and 14484/ND6 mutations seemed more readily prone to undergo apoptosis as compared with the 11778/ ND4 mutation. In conclusion, LHON cybrid cells forced by the reduced rate of glycolytic flux to utilize oxidative metabolism are sensitized to an apoptotic death through a mechanism involving mitochondria.

Recent Advances in the Molecular Pathogenesis of Dystonia-Plus Syndromes and Heredodegenerative Dystonias

“…There are three main pathogenic mutations causing LHON (11778/ND4, 3460/ND1,14484/ND6) all disrupting components of complex 1 of the mitochondrial respiratory chain [70]. The malfunction of mitochondrial oxidative phosphorylation may cause neuronal degeneration by energy depletion and generation of reactive oxygen species (ROS).…”

Effects of OPA1 mutations on mitochondrial morphology and apoptosis: Relevance to ADOA pathogenesis

“…Since both the R290Q and ∆58 alleles of OPA1 increased the sensitivity of cells to apoptosis this may represent the pathophysiological process leading to the neurodegeneration of RGC, as suggested for mitochondrial DNA mutations associated with the LHON syndrome (43)(44)(45)(46). In the RGC, the limits within which the mitochondrial morphology remains compatible with their function may be narrower than in other cells, rendering RGC more sensitive to apoptosis when mitochondrial morphology is not accurately controlled (Fig.…”

Defective Oxidative Phosphorylation in Thyroid Oncocytic Carcinoma Is Associated with Pathogenic Mitochondrial DNA Mutations Affecting Complexes I and III

“…Cells (4 Â 10 4 ) were seeded into 24-well plates and, after 24 hours, were incubated in DMEM glucose-free medium supplemented with 5 mmol/L galactose, 5 mmol/L Na-pyruvate, and 10% FBS (DMEM-galactose medium). The MTT assay was done as previously described (14).…”