RESUMEN
A/J mice are a mouse model of age-related hearing loss. It has been demonstrated that a mutation in gene of citrate synthase (CS) contributes to the early onset of hearing loss occurring at about one month of age. To understand the effects of a decreased CS activity that results from the mutation in Cs gene on hearing loss in A/J mice, human kidney cell line (293T) was transiently transfected with short hairpin RNA for Cs (shRNA-Cs) to reduce expression of CS. In comparison with those of cells transfected with a scrambled sequence (shRNA-NC), the oxygen consumption rate and adenosine trisphosphate (ATP) production level were decreased in 293T cells transfected with shRNA-Cs. Meanwhile, excessive superoxide production was induced as determined by mitochondrial superoxide formation assay (MitoSOX) and superoxide dismutase 2 (SOD2) detection. Moreover, the expression levels of BIP (binding immunoglobulin protein) and CHOP (CCAAT/enhancer-binding protein-homologous protein), markers of endoplasmic reticulum stress, were upregulated. Furthermore, apoptosis related molecule caspase-3 and the mitochondrial membrane potential were reduced. It is therefore concluded that downregulation of Cs expression in 293T cells leads to low level of ATP production, excessive superoxide formation and cell apoptosis, which implies a possible mechanism for hearing loss in A/J mice.
Asunto(s)
Apoptosis/genética , Citrato (si)-Sintasa/genética , Interferencia de ARN , Superóxidos/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Western Blotting , Caspasa 3/metabolismo , Citrato (si)-Sintasa/metabolismo , Modelos Animales de Enfermedad , Chaperón BiP del Retículo Endoplásmico , Células HEK293 , Pérdida Auditiva/genética , Proteínas de Choque Térmico/metabolismo , Humanos , Potencial de la Membrana Mitocondrial , Ratones Endogámicos A , Ratones Noqueados , Microscopía Fluorescente , Mitocondrias/metabolismo , Mitocondrias/fisiología , Superóxido Dismutasa/genética , Superóxido Dismutasa/metabolismo , Factor de Transcripción CHOP/metabolismoRESUMEN
Age-related hearing loss (AHL), or presbycusis, is the most common neurodegenerative disorder and top communication deficit of the aged population. Genetic predisposition is one of the major factors in the development of AHL. Generally, AHL is associated with an age-dependent loss of sensory hair cells, spiral ganglion neurons and stria vascularis cells in the inner ear. Although the mechanisms leading to genetic hearing loss are not completely understood, caspase-family proteases function as important signals in the inner ear pathology. It is now accepted that mouse models are the best tools to study the mechanism of genetic hearing loss or AHL. Here, we provide a brief review of recent studies on hearing improvement in mouse models of AHL by anti-apoptotic treatment.