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Induction of cytochrome c-mediated apoptosis by amyloid beta 25-35 requires functional mitochondria
Sandra Morais Cardoso1, Russell H Swerdlow, Catarina R Oliveira
1Center for Neuroscience of Coimbra, University of Coimbra, 3004-5004, Portugal. scardoso@cnc.cj.uc.pt
Abstract:
Accumulating data suggest a central role for mitochondria and oxidative stress in neurodegenerative apoptosis. We previously demonstrated that amyloid-beta peptide 25-35 (Abeta 25-35) toxicity in cultured cells is mediated by its effects on functioning mitochondria. In this study, we further explored the hypothesis that Abeta 25-35 might induce apoptotic cell death by altering mitochondrial physiology. Mitochondria in Ntera2 (NT2 rho+) human teratocarcinoma cells exposed to either staurosporine (STS) or Abeta 25-35 were found to release cytochrome c, with subsequent activation of caspases 9 and 3. However, NT2 cells depleted of mitochondrial DNA (rho0 cells), which maintain a normal mitochondrial membrane potential (Deltapsi(m)) despite the absence of a functional electron transport chain (ETC), demonstrated cytochrome c release and caspase activation only with STS. We further observed increased reactive oxygen species (ROS) production and decreased reduced glutathione (GSH) levels in rho+ and rho0 cells treated with STS, but only in rho+ cells treated with Abeta 25-35. We conclude that under in vitro conditions, Abeta can induce oxidative stress and apoptosis only when a functional mitochondrial ETC is present.
Insights
Amyloid-beta peptide 25-35 (Abeta 25-35) induces neurodegeneration by impacting mitochondria. This study shows Abeta 25-35 causes apoptosis only when a functional mitochondrial electron transport chain is present.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Mitochondria and oxidative stress are implicated in neurodegenerative diseases.
- Amyloid-beta peptide 25-35 (Abeta 25-35) toxicity is linked to mitochondrial dysfunction.
- This study investigates the role of mitochondrial physiology in Abeta 25-35-induced apoptosis.
Purpose of the Study:
- To explore how Abeta 25-35 induces apoptotic cell death by altering mitochondrial physiology.
- To determine the necessity of a functional mitochondrial electron transport chain (ETC) for Abeta 25-35-induced apoptosis and oxidative stress.
Main Methods:
- Utilized Ntera2 (NT2 rho+) and mitochondrial DNA-depleted (rho0) human teratocarcinoma cells.
- Exposed cells to staurosporine (STS) or Abeta 25-35.
- Assessed cytochrome c release, caspase activation (caspases 9 and 3), reactive oxygen species (ROS) production, and reduced glutathione (GSH) levels.
Main Results:
- Both STS and Abeta 25-35 induced cytochrome c release and caspase activation in rho+ cells.
- Only STS induced cytochrome c release and caspase activation in rho0 cells.
- Increased ROS and decreased GSH were observed in STS-treated rho+ and rho0 cells, but only in Abeta 25-35-treated rho+ cells.
Conclusions:
- A functional mitochondrial electron transport chain (ETC) is required for Abeta 25-35 to induce oxidative stress and apoptosis in vitro.
- Mitochondrial dysfunction plays a critical role in Abeta-mediated neurotoxicity.