Monoamine oxidase-A knockdown in human neuroblastoma cells reveals protection against mitochondrial toxins.
The study examined how the mitochondrial enzyme monoamine oxidase-A (MAO-A), which produces hydrogen peroxide as a catalytic by-product, influences death and survival mechanisms. Targeted microRNA (miRNA) was used to stably knock down MAO-A mRNA, protein, and catalytic activity by 60-70% in SH-SY5Y human neuroblastoma cells. The effects of MAO-A knockdown (KD) on ATP, oxidative stress, electron transport chain, and survival following exposure to mitochondrial toxins were assessed. In control cells, complex I inhibition resulted in caspase-mediated cell death linked with ROS production and reduced ATP, followed by up-regulation of MAO-A mRNA, protein, and enzyme activity levels. Inhibition of complex III and IV resulted in a similar increase in MAO-A expression, while up-regulation of MAO-A was lower following complex II inhibition. MAO-A KD decreased basal reactive oxygen species levels by 50% and increased levels of ATP and reduced glutathione and Bcl-2. MAO-A KD specifically increased the activity of complex I but had no effect on complex II-IV activities. Furthermore, MAO-A KD protected against inhibitors of complex I, III, and IV. In summary, endogenous MAO-A levels influence mitochondrial function, notably complex I activity, and MAO-A may be a target for protection against neurodegenerative conditions that involve oxidative stress and mitochondrial dysfunction as underlying pathogenic factors.
2School of Science and Technology, Nottingham Trent University, Nottingham, NG11 8NS, UK. ellen.billett@ntu.ac.uk.
Julia C
JC
Fitzgerald
Aslihan
A
Ugun-Klusek
George
G
Allen
Luigi A
LA
De Girolamo
Iain
I
Hargreaves
Christoph
C
Ufer
Andrey Y
AY
Abramov
E Ellen
EE
Billett
D000255:Adenosine Triphosphate / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D035683:MicroRNAs / Q000235:genetics; D008928:Mitochondria / Q000378:metabolism; D008995:Monoamine Oxidase / Q000235:genetics / Q000378:metabolism*; D009447:Neuroblastoma / Q000235:genetics / Q000378:metabolism*; D010300:Parkinson Disease / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
D035683:MicroRNAs; D017382:Reactive Oxygen Species; D000255:Adenosine Triphosphate; D008995:Monoamine Oxidase
Parkinson's disease; electron transport chain; neurodegeneration; reactive oxygen species