Skip to main content

Advertisement

Log in

The catecholaldehyde hypothesis: where MAO fits in

  • Neurology and Preclinical Neurological Studies - Review Article
  • Published:
Journal of Neural Transmission Aims and scope Submit manuscript

A Correction to this article was published on 21 December 2019

This article has been updated

Abstract

Monoamine oxidase (MAO) plays a central role in the metabolism of the neurotransmitters dopamine, norepinephrine, and serotonin. This brief review focuses on 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is the immediate product of MAO acting on cytoplasmic dopamine. DOPAL is toxic; however, normally DOPAL is converted via aldehyde dehydrogenase (ALDH) to 3,4-dihydroxyphenylacetic acid (DOPAC), which rapidly exits the neurons. In addition to vesicular uptake of dopamine via the vesicular monoamine transporter (VMAT), the two-enzyme sequence of MAO and ALDH keeps cytoplasmic dopamine levels low. Dopamine oxidizes readily to form toxic products that could threaten neuronal homeostasis. The catecholaldehyde hypothesis posits that diseases featuring catecholaminergic neurodegeneration result from harmful interactions between DOPAL and the protein alpha-synuclein, a major component of Lewy bodies in diseases such as Parkinson disease, dementia with Lewy bodies, and pure autonomic failure. DOPAL potently oligomerizes alpha-synuclein, and alpha-synuclein oligomers impede vesicular functions, shifting the fate of cytoplasmic dopamine toward MAO-catalyzed formation of DOPAL—a vicious cycle. When MAO deaminates dopamine to form DOPAL, hydrogen peroxide is generated; and DOPAL, hydrogen peroxide, and divalent metal cations react to form hydroxyl radicals, which peroxidate lipid membranes. Lipid peroxidation products in turn inhibit ALDH, causing DOPAL to accumulate—another vicious cycle. MAO inhibition decreases DOPAL formation but concurrently increases the spontaneous oxidation of dopamine, potentially trading off one form of toxicity for another. These considerations rationalize a neuroprotection strategy based on concurrent treatment with an MAO inhibitor and an anti-oxidant.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Fig. 1
Fig. 2

Similar content being viewed by others

Change history

  • 21 December 2019

    The original version of this article unfortunately contained a mistake. The presentation of Figure 1 was incorrect. The corrected Figure 1 is given below.

Abbreviations

ALDH:

Aldehyde dehydrogenase

AS:

Alpha-synuclein

Cys-DA:

5-S-Cysteinyldopamine

DLB:

Dementia with Lewy bodies

DOPAC:

3,4-Dihydroxyphenylacetic acid

DOPAL:

3,4-Dihydroxyphenylacetaldehyde

DOPAL-Q:

DOPAL-quinone

LAAAD:

L-Aromatic-amino-acid decarboxylase

MSA:

Multiple system atrophy

NE:

Norepinephrine

NET:

Cell membrane norepinephrine transporter

nOH:

Neurogenic orthostatic hypotension

OH:

Orthostatic hypotension

PAF:

Pure autonomic failure

PD:

Parkinson disease

TH:

Tyrosine hydroxylase

VMAT:

Vesicular monoamine transporter

References

Download references

Acknowledgements

Research reported in this review was supported (in part) by the Intramural Research Program of the NIH, NINDS.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to David S. Goldstein.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

The original version of this article was revised: The presentation of Figure 1 was incorrect.

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Goldstein, D.S. The catecholaldehyde hypothesis: where MAO fits in. J Neural Transm 127, 169–177 (2020). https://doi.org/10.1007/s00702-019-02106-9

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00702-019-02106-9

Keywords

Navigation