cytochrome-c-t and Teratocarcinoma

Mitochondria likely play a role in Parkinson's disease (PD) neurodegeneration. We modelled PD by creating cytoplasmic hybrid (cybrid) cell lines in which endogenous mitochondrial DNA (mtDNA) from PD or control subject platelets was expressed within human teratocarcinoma (NT2) cells previously depleted of endogenous mtDNA. Complex I activity was reduced in both PD cybrid lines and in the platelet mitochondria used to generate them. Under basal conditions PD cybrids had less ATP, more LDH release, depolarized mitochondria, less mitochondrial cytochrome c, and higher caspase 3 activity. Equivalent MPP+ exposures are more likely to trigger programmed cell death in PD cybrid cells than in control cybrid cells. Our data support a relatively upstream role for mitochondrial dysfunction in idiopathic PD.

Topics: 1-Methyl-4-phenylpyridinium; Adenosine Triphosphate; Aged; Blood Platelets; Case-Control Studies; Caspase 3; Cell Line, Tumor; Cell Nucleus; Cell Survival; Citrate (si)-Synthase; Cytochromes c; DNA, Mitochondrial; Dose-Response Relationship, Drug; Electron Transport Complex IV; Enzyme Activation; Humans; Hybrid Cells; L-Lactate Dehydrogenase; Membrane Potential, Mitochondrial; Middle Aged; Mitochondria; Neurons; Parkinson Disease; Teratocarcinoma

Oxidative stress has been implicated in several pathologies associated with degenerative processes. Mitochondria are involved in cell death by necrosis or apoptosis due to a large load of Ca2+, the formation of reactive oxygen species (ROS), mitochondrial depolarization and the release of cytochrome c that initiates the caspase cascade. Nevertheless, the role of mitochondria in cell death processes induced by hydrogen peroxide (H2O2) has not been fully established. In this study, we analyzed the cytotoxic effect of H2O2 on rho+ human teratocarcinoma (NT2) cells and on mitochondria-DNA depleted rho0 NT2 cells, lacking functional mitochondria. The cells were exposed to H2O2 for 24 h and cell viability was dose-dependently decreased in both cell lines upon H2O2 exposure, although cell susceptibility was higher in rho0 NT2 cells. Moreover a decrease in mitochondrial membrane potential (Deltapsi(m)), mitochondrial cytochrome c release, caspases activation and DNA fragmentation were largely induced by H2O2 and occurred in both cell lines. Nevertheless, increased cell toxicity in rho0 cells upon H2O2 exposure was accompanied by a higher activation of the effector caspases-3 and -6. The data support that, in general, no differences were observed in cells containing functional (rho+) or non-functional (rho0) mitochondria upon H2O2-induced apoptotic cell death.

Topics: Apoptosis; Brain Neoplasms; Caspases; Cell Line, Tumor; Cytochromes c; DNA, Mitochondrial; DNA, Neoplasm; Dose-Response Relationship, Drug; Electron Transport; Enzyme Activation; Fluorometry; Humans; Hydrogen Peroxide; In Situ Nick-End Labeling; Microscopy, Confocal; Mitochondria; Neoplasm Proteins; Oxidants; Teratocarcinoma