Effects of nitric oxide donors on cybrids harbouring the mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) A3243G mitochondrial DNA mutation

Jagdeep K. Sandhu*, Caroline Sodja, Keven McRae, Yan Li, Peter Rippstein, Yau Huei Wei, Boleslaw Lach, Fay Lee, Septimiu Bucurescu, Mary Ellen Harper, Marianna Sikorska

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

23 Scopus citations

Abstract

Reactive nitrogen and oxygen species (O2.-, H 2O2, NO. and ONOO-) have been strongly implicated in the pathophysiology of neurodegenerative and mitochondrial diseases. In the present study, we examined the effects of nitrosative and/or nitrative stress generated by DETA-NO {(Z)-1-[2-aminoethyl-N- (2-ammonio-ethyl)amino]diazen-1-ium-1,2-diolate}, SIN-1 (3-morpholino- sydnonimine hydrochloride) and SNP (sodium nitroprusside) on U87MG glioblastoma cybrids carrying wt (wild-type) and mutant [A3243G (Ala3243 → Gly)] mtDNA (mitochondrial genome) from a patient suffering from MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes). The mutant cybrids had reduced activity of cytochrome c oxidase, significantly lower ATP level and decreased mitochondrial membrane potential. However, endogenous levels of reactive oxygen species were very similar in all cybrids regardless of whether they carried the mtDNA defects or not. Furthermore, the cybrids were insensitive to the nitrosative and/or nitrative stress produced by either DETA-NO or SIN-1 alone. Cytotoxicity, however, was observed in response to SNP treatment and a combination of SIN-1 and glucose-deprivation. The mutant cybrids were significantly more sensitive to these insults compared with the wt controls. Ultrastructural examination of dying cells revealed several characteristic features of autophagic cell death. We concluded that nitrosative and/or nitrative stress alone were insufficient to trigger cytotoxicity in these cells, but cell death was observed with a combination of metabolic and nitrative stress. The vulnerability of the cybrids to these types of injury correlated with the cellular energy status, which were compromised by the MELAS mutation.

Original languageEnglish
Pages (from-to)191-202
Number of pages12
JournalBiochemical Journal
Volume391
Issue number2
DOIs
StatePublished - 15 10 2005
Externally publishedYes

Keywords

  • Caspase-independent
  • Electron transport chain
  • MELAS
  • Mitochondrial DNA mutation
  • Nitric oxide donor
  • Reactive nitrogen and oxygen species

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