Mechanistic Visualization of Mitochondrial Complex I Defects-Induced Mitochondrial Stresses in Astrocytes

Project: National Science and Technology CouncilNational Science and Technology Council Academic Grants

Project Details

Abstract

Mitochondria, in addition to provide energy for cell, potentially arbitrate apoptosis. Upon mitochondrial stresses of elevated mitochondrial reactive oxygen species (mROS) and mitochondrial Ca2+ (mCa2+) mitochondrial membrane permeability increase to initiate lethal proteins release from the mitochondria for cultivating final apoptosis. It has been shown that an unstable or a damaged mitochondrial respiratory chain (RC) augments significantly mitochondrial stress. Using osteosarcoma-originated cytoplasmic hybridization (cybrids) cells, we have demonstrated a common deletion of 4977bp mitochondrial DNA (mtDNA) associated RC defects on complex I, IV and V dose-dependently augments mitochondrial dysfunction for an enhanced apoptosis. To further narrow down how defects in single RC complex involve in neurodegeneration and aging, current study focuses solely on defected mitochondrial complex I (the NADH-ubiquinone oxidoreductase)-induced alteration of mitochondrial and cellular stresses in astrocytes. The complex I serves as a 'gateway' for electrons transferred from NADH to molecular oxygen through the RC. Defects of this complex inhibits directly electrons transfer on the RC for a reduced energy production and is clinically associated with mitochondrial diseases, neurodegeneration, and aging including Parkinsonism. Astrocyte, the most abundant cell type in the CNS, is closely involved not only in neuronal activities but also critical in pathological neurodegeneration and aging. Whether and how complex I defects influences mitochondrial and cellular stresses for astrocytic apoptosis and hence neuronal death, however, is still not clear. The current grant, thus, is proposed to mechanistically visualize how complex I defects alter mitochondrial apoptotic stresses of ROS formation, Ca2+ dysregulation. In particular, how each factor acts alone and/or synergistically with each other to augment mitochondrial membrane permeability transition for an enhanced apoptosis in astrocyte will be precisely investigated. A rotenone-induced complex I defects of astrocytes have been established as a model and will be compared with its control (without rotenone treatment) and mtDNA less astrocytes (harboring no mtDNA and hence containing complex I, III, IV and V defects). In addition, two established cybrids containing mtDNA 4977bp deletion, mtDNA T8993G (complex V defects), mutant mtDNA encoded ND5 or ND6 subunit of complex I will also be used for comparison. Time-lapsed fluorescence digital imaging of live mitochondria in single intact astrocytes will be performed by the application of mitochondrial specific 2 fluorescent probes or proteins coupled with two-or-multiphoton imaging microscopy. The information released from this study will delineate not only the pathological mechanisms for complex I defects-induced mitochondrial stresses in astrocytes but also will contribute significantly to the future therapeutic prevention and treatment of complex I defects-associated neurodegeneration and aging.

Project IDs

Project ID:PC9808-0568
External Project ID:NSC98-2320-B182-005-MY3
StatusFinished
Effective start/end date01/08/0931/07/10

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