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Monoamine oxidase and mitochondrial respiration
1Department of Neurology and Center for Neurobiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
Journal of Neurochemistry
|December 3, 1999
Summary
Neurotransmitter metabolism by monoamine oxidase (MAO) can damage mitochondria, impairing cellular respiration. This mechanism may explain mitochondrial defects in neurodegenerative diseases.
Area of Science:
- Biochemistry
- Neuroscience
- Cell Biology
Background:
- Mitochondrial defects, particularly in electron transport chain complexes I-IV, are implicated in numerous neurodegenerative diseases.
- The precise link between these mitochondrial lesions and genetic factors remains incompletely understood.
Purpose of the Study:
- To elucidate a general mechanism by which neurotransmitter metabolism by monoamine oxidase (MAO) contributes to mitochondrial damage.
- To investigate the impact of MAO activity on mitochondrial function and protein thiol status.
Main Methods:
- Incubation of rat brain mitochondria with tyramine, a substrate for both MAO-A and MAO-B.
- Assessment of mitochondrial respiration (state 3 and state 5) and MTT dye reduction.
- Quantification of protein-glutathione mixed disulfides to evaluate protein thiol status.
Main Results:
- Incubation with tyramine significantly suppressed state 3 (32.8%) and state 5 (40.1%) mitochondrial respiration.
- A tenfold increase in protein-glutathione mixed disulfides was observed, indicating altered protein thiol status.
- MTT dye reduction assays corroborated the observed impairments in mitochondrial electron flow.
Conclusions:
- Enzymatic metabolism of neurotransmitters by MAO can directly damage mitochondria.
- This damage involves alterations in protein thiol status and suppression of mitochondrial respiration.
- The findings suggest that natural neurotransmitter turnover could be a source of mitochondrial lesions in susceptible individuals, potentially contributing to neurodegeneration.