RESUMO
Leber's hereditary optic neuropathy (LHON) is one of the most common mitochondrial diseases caused by point mutations in mitochondrial DNA (mtDNA). The majority of diagnosed LHON cases are caused by a point mutation at position 11,778 in the mitochondrial genome. LHON mainly affects young men in their 20s and 30s with usually poor visual prognosis. It remains unexplained why men are more likely to develop the disease and why only retinal ganglion cells are affected. In this study, a cell model was used for the first time to investigate the influence of testosterone on the cell death mechanism apoptosis and on an autophagy/mitophagy. Cells with m.11778G > A were found to be significantly more susceptible to nucleosome formation and effector caspase activation that serve as hallmarks of apoptotic cell death. Cells having this mutation expressed higher levels of mitophagic receptors BNIP3 and BNIP3L/Nix in a medium with testosterone. Moreover, cells having the mutation exhibited greater mitochondrial mass, which suggests these cells have a decreased cell survival. The observed decrease in cell survival was supported by the observed increase in apoptotic cell death. Autophagy was analyzed after inhibition with Bafilomycin A1 (Baf A1). The results indicate impairment in autophagy in LHON cells due to lower autophagic flux supported by observed lower levels of autophagosome marker LC3-II. The observed impaired lower autophagic flux in mutant cells correlated with increased levels of BNIP3 and BNIP3L/Nix in mutant cells.
Assuntos
Autofagia/efeitos dos fármacos , Mitofagia/genética , Atrofia Óptica Hereditária de Leber/tratamento farmacológico , Testosterona/farmacologia , Adulto , Apoptose/efeitos dos fármacos , Células Sanguíneas/efeitos dos fármacos , DNA Mitocondrial/genética , Feminino , Genoma Mitocondrial/genética , Humanos , Macrolídeos/farmacologia , Masculino , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/genética , Nucleossomos/efeitos dos fármacos , Nucleossomos/genética , Atrofia Óptica Hereditária de Leber/genética , Atrofia Óptica Hereditária de Leber/metabolismo , Atrofia Óptica Hereditária de Leber/patologia , Mutação Puntual/genética , Células Ganglionares da Retina/efeitos dos fármacos , Testosterona/metabolismoRESUMO
Mitochondria are key players in cell death through the activation of the intrinsic apoptosis pathway. BNIP3 and BNIP3L/Nix are outer mitochondrial membrane bifunctional proteins which because of containing both BH3 and LIR domains play a role in cellular response to stress by regulation of apoptosis and selective autophagy. Leber's Hereditary Optic Neuropathy (LHON) is the most common mitochondrial disease in adults, characterized by painless loss of vision caused by atrophy of the optic nerve. The disease in over 90% of cases is caused by one of three mutations in the mitochondrial genome: 11778G>A, 3460G>A or 14484T>C. The pathogenic processes leading to optic nerve degeneration are largely unknown, however, the most common explanation is that mtDNA mutations increase the apoptosis level in this tissue. Here we present the results of analysis of BNIP3 and BNIP3L/Nix proteins in cells harboring a combination of the 11778G>A and the 3460G>A LHON mutations. Experiments performed on cybrids revealed that BNIP3 protein level is decreased in LHON cells compared to controls. CCCP treatment resulted in apoptosis induction only in control cells. Moreover, we also noticed reduced level of autophagy in LHON cybrids. The presented results suggest that in cells carrying LHON mutations expression of proteins involved in regulation of apoptosis and autophagy is decreased what in turn may disturb cell death pathways in those cells and affect cellular response to stress.
Assuntos
Proteínas de Membrana/metabolismo , Mutação , Atrofia Óptica Hereditária de Leber/genética , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Adulto , Apoptose , Autofagia , Linhagem Celular , Genoma Mitocondrial/genética , Humanos , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Atrofia Óptica Hereditária de Leber/patologiaRESUMO
Leber's hereditary optic neuropathy (LHON) was the first human disease found to be associated with a mitochondrial DNA (mtDNA) point mutation. The most common LHON mutations are 11778G>A, 3460G>A or 14484T>C. The most common clinical features of LHON are optic nerve and retina atrophy. The affected tissue is not available for studies, therefore a variety of other cell types are used. However, all models face difficulties and limitations in mitochondrial disease research. The advantages and disadvantages of different cell models used to study LHON, recent advances in animal model generation and novel approaches in this field are discussed.
Assuntos
Técnicas Citológicas/métodos , Modelos Animais de Doenças , Modelos Biológicos , Atrofia Óptica Hereditária de Leber/patologia , Animais , Pesquisa Biomédica/tendências , HumanosRESUMO
Perturbations of mitochondrial function, which may be caused by mutations in both nuclear and mitochondrial DNA, cause many human diseases. We describe the most frequent mitochondrial diseases, especially those caused by mutations in the nuclear genome, attempts to treat these diseases and possible ways of preventing the transmission of diseases caused by mutations in mitochondrial DNA to successive generations.
