After treatment with a pro-oxidant, the ratio of mitochondria to nuclear DNA (evaluated through qPCR) recorded significant low values as compared to parallel controls. What could be the possible reasons ?
It could be possible that mitochondria are targeted for removal by mitophagy if the cells are subjected to a pro-oxidant. The cell tries to keep oxidative stress levels low (and mitochondria are known to be major sources of reactive oxygen species) by (partial) removal of mitochondria. That could be a possible reason for the lowered mtDNA /nDNA ratio. It would be interesting to run an autophagy (mitophagy) assay.
Here is a paper describing the relationship between oxidative stress and mitophagy: http://www.ncbi.nlm.nih.gov/pubmed/22917578
Best regards!
Many thanks Dr. Scheckhuber,
In our experiments, levels of anti-oxidant enzymes GR & SOD were also significantly lowered. Can this also be attributed to mitophagy ?
Reduced levels of GR and SOD suggest that the redox status of the cells is imbalanced (which is understandable due to administration of a pro-oxidant). I think that this is not necessarily due to elevated mitophagy. However, it was shown that
disturbances of the glutathione pool can result in mitophagy stimulation:
http://www.jbc.org/content/284/22/14828.long
I hope that this information is of interest to you.
Prooxidant treatment induces mtDNA breaks which then can lead either to aggregation of DNA or to degradation of the truncated DNA even in mitochondria which are not degraded by autophagy. A reduction of mtDNA is also found in senescent vertebrate cells in culture.
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