The mitochondrial monoamine oxidase-aldehyde dehydrogenase pathway: a potential site of action of daidzin.

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Rooke N, Li DJ, Li J, Keung WM

The mitochondrial monoamine oxidase-aldehyde dehydrogenase pathway: a potential site of action of daidzin.

J Med Chem. 2000 Nov 2;43(22):4169-79.

PubMed ID

11063613 [ View in PubMed

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Abstract

Recent studies showed that daidzin suppresses ethanol intake in ethanol-preferring laboratory animals. In vitro, it potently and selectively inhibits the mitochondrial aldehyde dehydrogenase (ALDH-2). Further, it inhibits the conversion of monoamines such as serotonin (5-HT) and dopamine (DA) into their respective acid metabolites, 5-hydroxyindole-3-acetic acid (5-HIAA) and 3,4-dihydroxyphenylacetic acid (DOPAC) in isolated hamster or rat liver mitochondria. Studies on the suppression of ethanol intake and inhibition of 5-HIAA (or DOPAC) formation by six structural analogues of daidzin suggested a potential link between these two activities. This, together with the finding that daidzin does not affect the rates of mitochondria-catalyzed oxidative deamination of these monoamines, raised the possibility that the ethanol intake-suppressive (antidipsotropic) action of daidzin is not mediated by the monoamines but rather by their reactive biogenic aldehyde intermediates such as 5-hydroxyindole-3-acetaldehyde (5-HIAL) and/or 3,4-dihydroxyphenylacetaldehyde (DOPAL) which accumulate in the presence of daidzin. To further evaluate this possibility, we synthesized more structural analogues of daidzin and tested and compared their antidipsotropic activities in Syrian golden hamsters with their effects on monoamine metabolism in isolated hamster liver mitochondria using 5-HT as the substrate. Effects of daidzin and its structural analogues on the activities of monoamine oxidase (MAO) and ALDH-2, the key enzymes involved in 5-HT metabolism in the mitochondria, were also examined. Results from these studies reveal a positive correlation between the antidipsotropic activities of these analogues and their abilities to increase 5-HIAL accumulation during 5-HT metabolism in isolated hamster liver mitochondria. Daidzin analogues that potently inhibit ALDH-2 but have no or little effect on MAO are most antidipsotropic, whereas those that also potently inhibit MAO exhibit little, if any, antidipsotropic activity. These results, although inconclusive, are consistent with the hypothesis that daidzin may act via the mitochondrial MAO/ALDH pathway and that a biogenic aldehyde such as 5-HIAL may be important in mediating its antidipsotropic action.

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Binding Properties

Drug	Target	Property	Measurement	pH	Temperature (°C)
Daidzin	Aldehyde dehydrogenase, mitochondrial	IC 50 (nM)	40	N/A	N/A	Details