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PubMedDate not supplied

Use of TLC and multivariate mathematical statistical methods to study the interaction of monoamine oxidase inhibitory drugs with amino acids.

The interaction of 17 monoamine oxidase inhibitory drugs (propargylamine derivatives) with amino acids was studied by charge-transfer chromatography. The data set was evaluated by principal component analysis (PCA). To assess the effect of the information loss caused by normalization, PCA was separately carried out on the covariance and on the correlation matrix. The strength and selectivity of interaction was separated by the spectral mapping technique. Calculation proved that the amino group of the drugs interacted with the second carboxyl group of dicarboxylic amino acids, and that the interaction was of electrostatic character. This finding made probable the direct interaction between the drugs and the target enzyme or enzymes. The results of both PCA methods were similar. However, coordinates of the spectral map showed only slight correlation with the corresponding coordinates of the two-dimensional nonlinear maps proving the different information content of the methods.

Amino Acids↗

PubMed2000

The EcoRV genetic polymorphism of human monoamine oxidase type A is not associated with Parkinson's disease and does not modify the effect of smoking on Parkinson's disease.

We previously observed an association with Parkinson's (PD), and modification of the effect of smoking on PD, by a polymorphism of the monoamine oxidase B (MAO-B) gene. The A form of monoamine oxidase (MAO-A) shares with MAO-B many characteristics that could be relevant to PD, especially proneuroxicant bioactivation and dopamine metabolism. MAO-A is also inhibited by tobacco smoke, which bears an apparent protective effect on PD. We investigated the possibility that MAO-A genetic variants may also be involved in predisposition to PD and in modification of the effect of smoking. Three-hundred and seventy-one subjects--145 idiopathic PD cases and 226 age/gender-matched controls--were genotyped for the EcoRV polymorphism of MAO-A gene which has been related to increased enzyme activity. MAO-A EcoRV polymorphism was neither significantly associated with PD nor did it modify the inverse relationship with smoking. These results suggest that the EcoRV polymorphism of MAO-A is not an important biomarker of PD risk.

Adult↗

PubMed1990

Thyroid hormone-inducible monoamine oxidase inhibitor in rat liver cytosol.

An endogenous inhibitor of monoamine oxidase (MAO) was separated by gel-filtration from 105,000 g supernate of T4-treated rat liver cytosol. The inhibition by this inhibitor was concentration-dependent and more potent for A-form MAO than for B-form MAO. The mode of inhibition was competitive either with 5-hydroxytryptamine or beta-phenylethylamine. The molecular weight of this inhibitor was estimated to be 600-700 by gel filtration. The pI value was determined to be 3.0 by isoelectric focusing. This inhibitor was proved to be heat-stable and resistant to protease treatment. MAO inhibition activity was much lower in the cytosol of thyroidectomized, non-T4-treated rats than T4-treated rats, suggesting that this inhibitor is induced by thyroid hormone T4. MAO activity in rat liver might be regulated by the level of this inhibitor.

Animals↗

PubMed1980

Low platelet monoamine oxidase activity: a possible biochemical correlate of borderline schizophrenia.

Platelet monoamine oxidase (MAO) activity, psychiatric disorders, and family history of psychopathology were studied in 115 nonhospitalized, previously undiagnosed college student volunteers. Subjects were classified into two extreme groups: those with platelet MAO activity two standard deviations below the mean ("low-MAO" probands) and those with platelet MAO activity two standard deviations above the mean ("high"-MAO probands). Low-MAO probands were found to have a significant increase in the incidence of borderline schizophrenia and other psychiatric disorders compared to high-MAO probands. First-degree relatives of low-MAO probands were more often affected with psychiatric disorders and borderline schizophrenia than relatives of high-MAO probands. The data suggest that reduced platelet MAO activity is associated with psychiatric vulnerability and that the spectrum of schizophrenia may be more closely related to this vulnerability than other psychiatric disorders.

Adult↗

PubMed1996

Monoamine oxidase released into plasma treated with the hepatotoxin allyl formate.

Monoamine oxidase (MAO) released from the rat liver into plasma and the activity levels of lipid peroxide (LPO) and superoxide dismutase (SOD) in liver tissue were investigated after pretreatment of rats with the perilobular hepatotoxin allyl formate (AF). When 3H-pargyline was given to AF-pretreated rats, the levels of 3H-pargyline labelled MAO in rat plasma were increased to 38% (p < 0.01 vs control), but the radioactivity was decreased to 35% (p < 0.05 vs control). The molecular weight of MAO subunits in plasma was similar to that of MAO subunits in liver (about 60,000) as determined by SDS electrophoresis. Liver tissue LPO levels in these rats were increased, whereas SOD activity was decreased. These results suggest that MAO in liver mitochondria was released into plasma as a consequence of membrane disorder.

Animals↗

PubMed1993

Spontaneous hypertensive reactions with monoamine oxidase inhibitors.

Despite long-standing concerns over hypertensive reactions, monoamine oxidase inhibitors (MAOIs) have grown in popularity and are now used in a variety of psychiatric disorders. The risk of hypertensive episodes is less than 1%. This is most likely the result of careful dietary instructions and prudent prescribing of concomitant medications. The possibility exists of spontaneous or unprovoked hypertensive crises in patients receiving MAOIs. In this report, we review the literature on spontaneous hypertensive episodes and present a case report. There has been a total of 11 cases described in six separate reports. We discuss the possible mechanism, risk factors, treatment, and safety of rechallenging the patients with the MAOI. Further research is needed to clarify this reaction. For now, it remains a rare but worrisome phenomenon. It should stand as an additional source of concern for clinicians who are already well aware of the risk of hypertensive episodes in patients receiving MAOIs.

Adult↗

PubMed1993

A discontinuous luminometric assay for monoamine oxidase.

A simple, sensitive and convenient discontinuous luminometric assay for monoamine oxidase (MAO) is described. It is based on measurement of the light production from the peroxidase-catalysed chemiluminescent oxidation of 5-amino-2,3-dihydro-1,4-phthalazinedione (luminol) by the hydrogen peroxide produced in the MAO reaction. The procedure is suitable for use with a wide range of MAO substrates, although 5-hydroxytryptamine, adrenaline and noradrenaline are too readily oxidized by hydrogen peroxide to be used. A particular advantage of this procedure is that it is applicable to the oxidation of substrates which do not yield products, such as an aldehyde or free ammonia, which form the basis of several alternative substrate-independent assay procedures. The application of the procedure to assay the oxidation of benzylamine, tyramine and 2-n-pentylaminoacetamide (milacemide) by a crude mitochondrial preparation from rat liver and purified ox liver MAO-B is demonstrated.

Animals↗

PubMed1991

Vitamin B12-induced reduction of platelet monoamine oxidase activity in patients with dementia and pernicious anaemia.

Platelet monoamine oxidase (MAO) activity has previously been shown to be increased in patients with senile dementia of Alzheimer type (SDAT) and in patients with megaloblastic anaemia. Moreover, low serum B12 levels were found to be 4-5 times more frequent in SDAT compared with an unselected population of similar age. In the present investigation, platelet MAO activity was estimated in 14 SDAT patients with relatively low serum B12 levels and in 4 patients with pernicious anaemia. Before B12 therapy, platelet MAO activity was significantly increased in both patient groups compared with a control group. After B12 therapy, platelet MAO activity was significantly reduced in both patient groups to apparently normal levels. The present results show that B12 status is a controlling factor of platelet MAO activity and confirm that a significant connection exists between vitamin B12 deficiency and primary degenerative dementia disorders, such as SDAT.

Aged↗

PubMed1978

Decreased platelet monoamine oxidase activity in chronic schizophrenia, shown with novel substrates.

Platelet monoamine oxidase (MAO) was kinetically evaluated in chronic schizophrenics and matched controls, using substrates of major physiologic importance and substrates of particular interest in the study of schizophrenia, such as serotonin (5-ht), N,N-dimethyltryptamine (DMT), 5-methoxytryptamine (5-MT), and dopamine (DA). Substrates were measured at six concentrations; values for maximal velocity (Vmax) and Michaelis constant (Km) were obtained by using Lineweaver-Burk plots. The Vmax was decreased for all substrates in chronic schizophrenia and the Km was decreased for DA, 5-HT, and DMT, but remained unchanged for 5-MT. The value of Km/Vmax was similar for schizophrencis and normal persons when DA, 5-HT, and DMT were used as substrates, which may indicate that "uncompetitive" inhibition is responsible for the observed decrease in activity among chronic schizophrenics. The finding of a decreased Vmax but unchanged Km with 5-MT would be consistent with noncompetitive inhibition.

5-Methoxytryptamine↗

PubMed1978

Differences in platelet monoamine oxidase activity in subgroups of schizophrenic and depressive disorders.

Platelet monoamine oxidase (MAO) activity was measured in patients with nonaffective schizophrenic disorders (i.e., without prominent symptoms of depressions or manias), and in patients with schizophrenia-related depressions. MAO activity was significantly lower than control values in a subgroup of 16 patients with nonaffective schizophrenic disorders (most of whom were paranoid) characterized by the presence of auditory hallucinations and delusions. Platelet MAO activity was not reduced in 16 other nonaffective schizophrenic patients without auditory hallucinations. Platelet MAO activity was significantly higher than control values in a group of 8 depressed patients with schizophrenia-related depressions characterized by the presence of chronic asocial, eccentric, or bizarre behavior. These findings of differences in platelet MAO activity in clinically defined subgroups of nonaffective schizophrenic disorders and the schizophrenia-related depressive disorders may help to account for some of the discrepancies in findings among the various studies of platelet MAO activity in schizophrenic and affective disorders.

Adult↗

PubMed1978

Monoamine oxidase activity in different density gradient fractions of human platelets.

Monoamine oxidase (MAO) activity measured in human platelets is reportedly altered by such drugs as epinephrine, lithium carbonate, and imipramine, and also reduced in a number of clinical disorders. To evaluate whether MAO activity might differ in platelet subpopulations, density gradient centrifugation with arabino-galactan was used to prepare four platelet fractions that differed in weight and volume. MAO activity in the lightest and smallest platelet subpopulation was approximately one-half that in the heaviest and largest subpopulation. Because platelet weight and size are thought to be related to platelet age, it is possible that some drug effects on platelet MAO activity might represent changes in platelet turnover. Factors other than platelet turnover rates may contribute to individual differences in platelet MAO activity, however, since one group of individuals with markedly reduced platelet MAO activity exhibited no shift in the proportion of lighter versus heavier platelets nor in the relative amount of MAO activity in each density gradient subfraction.

Blood Platelets↗

PubMed1982

Monoamine oxidase: to B or not to B?

That the enzyme, monoamine oxidase (E.C. 1.4.3.4. amine: O2 oxidoreductase, MAO) exists in multiple forms was first suggested by Johnston (1) who studied the effects of the irreversible inhibitor clorgyline on MAO. It has been proposed that MAO can be classified into two types, A and B, according to their inhibitor sensitivity and substrate specificity. Type A MAO was found to be solely responsible for the deamination of 5-hydroxytryptamine (5-HT) and shows high sensitivity to clorgyline, while type B MAO metabolizes 2-phenethylamine (PEA) and benzylamine (BA) and is less sensitive to clorgyline. Subsequently, it was shown that type B MAO is highly sensitive to the irreversible inhibitor deprenyl (2). Recently, the "multiple forms" concept has been questioned (3-5) mainly because of increasing evidence which is contradictory to some earlier findings. As an alternative, another hypothesis was put forward insinuating that MAO is an enzyme with multiple binding sites but only one molecular entity (3,4,6,7). This account will focus on some experimental findings accumulated mainly since 1978 and which, although equivocal, strongly support the "one molecular entity" hypothesis of MAO.

Animals↗

PubMed1985

Expression of A and B types of monoamine oxidase in differentiated neuroblastoma hybrid cells.

The total activities of monoamine oxidase (MAO) and the ratio of type B/type A activities were determined in mouse neuroblastoma N1E-115 cells, and in NX31T and NG108-15 hybrid cells derived from mouse neuroblastoma X rat sympathetic ganglion hybrid or mouse neuroblastoma X rat glioma hybrid cells. N1E-115 and NX31T cells possessed type A activities exclusively, although NG108-15 cells showed both type A (65-90%) and type B (10-35%) MAO activities. The activity of type A MAO in NX31T and N1E-115 cells was relatively constant during culturing periods in the presence or absence of dibutyryl cyclic AMP (Bt2cAMP), whereas total MAO activity and the ratio of type B MAO/type A MAO in NG108-15 cells increased as a function of culture periods. Prostaglandin E1 (PGE1) and theophylline, the best known combination to increase intracellular cyclic AMP content of NG108-15 cells, caused similar increases of MAO and of the type B/type A ratio in NG108-15 cells. The results suggest that MAO activity and expression of MAO B activity are regulated in NG108-15 cells in a cyclic AMP-dependent manner.

Alprostadil↗

PubMed1987

Modification of dopamine and norepinephrine metabolism in the rat brain by monoamine oxidase inhibitors.

The treatment of Sprague-Dawley rats with monoamine oxidase (MAO) inhibitors (pargyline, tranylcypromine) profoundly affects dopamine (DA) and norepinephrine (NE) metabolism in the brain. In these rats injection of L-dopa led to large increases in norepinephrine (NE), normetanephrine (NMN) and 3-methoxytyramine (3-MT) in brain tissues. The response of MAO-inhibited rats to L-dopa contrasted sharply with those not treated with the MAO inhibitor; the latter showed no change in NE, NMN and 3-MT after similar administration of L-dopa. The increase of NE in pargyline-treated rats correlated closely with that of DA in the hypothalamus and in the brain stem. This response was greatly diminished in rats previously treated with the neurotoxin 6-hydroxydopamine, but was restored when the treatment with 6-hydroxydopamine was accompanied by desimipramine. This suggests that noradrenergic neurons were the origin of the NE response. The NMN and 3-MT increases occurring only in the rats treated with a MAO inhibitor were highly correlated. The results suggested that MAO inhibitor may affect entry of DA into catecholaminergic storage where NE synthesis takes place and from where DA is released.

Animals↗

PubMed1989

Modification of substrate-inhibitor affinities of human platelet monoamine oxidase B in vitro.

The rate of benzylamine utilization by monoamine oxidase (MAO)-B from human blood platelets was 2-4 times higher than that for octopamine. Both activities were inhibited 100% by 10(-7) M deprenyl (a specific MAO-B inhibitor) and were not affected by clorgyline (a specific MAO-A inhibitor) or by polyclonal antibodies to MAO-A. The preincubation of platelet MAO-B with purified MAO-A from mitochondrial membranes of human placenta resulted in appearance of excess octopamine activity. This additional activity was not precipitated by antibodies to MAO-A or inhibited by deprenyl but was inhibited by clorgyline. Incubation of the MAO-A preparation from placenta at 45 degrees C for 15 min before its preincubation with MAO-B caused 50% loss of both activities. Protease inhibitors had no effect on the modification of MAO. These data indicate that MAO-A or a factor tightly bound to it can modify MAO-B yielding a form of the enzyme with both MAO-A and MAO-B substrate and inhibitor affinities and MAO-B immunospecificity.

Antibodies↗

PubMed2006

The association of monoamine oxidase B functional polymorphism with postoperative pain intensity.

OBJECTIVES: The monoamine oxidase B (MAO-B) is an enzyme involved in metabolism of dopamine, benzylamine, phenylethylamine, tyramine and tryptamine. The A/G polymorphism in intron 13 of the MAO-B gene has been previously found to be associated with variability of the MAO-B enzyme activity. The aim of the present association study has been to examine the relationship between the A/G polymorphism in intron 13 and postoperative pain intensity. METHODS: 284 subjects (105 males and 179 females) undergoing planned tonsillectomy were examined. The intensity of pain was evaluated using 100-mm visual analogue scale (VAS). A PCR method with allele specific primers for detection of A/G polymorphism was used. RESULTS: We found a relationship between the A/G polymorphism in intron 13 of the MAO-B gene and average intensity of postoperative pain in male subjects. Higher average intensity of postoperative pain was detected in males with the G allele (3.96) in comparison with males with the A allele (3.45) and the difference was statistically significant (p<0,03). CONCLUSIONS: Results of this study indicate the relationship between the MAO-B polymorphism and postoperative pain intensity in the Czech male population. A potential role of MAO-B in the perception of pain intensity is discussed.

Female↗

PubMed1979

The vectorial orientation of human monoamine oxidase in the mitochondrial outer membrane.

1. The localization of monoamine oxidase in the mitochondrial outer membrane was studied in preparations of human liver mitochondrial and brain-cortex non-synaptosomal and synaptosomal mitochondria. 2. Immunochemical accessibility in iso-osmotic and hypo-osmotic mitochondrial preparations was used to localize the enzyme. 3. It was shown that the immunochemically accessible tyramine-oxidizing activity was distributed approximately equally on both surfaces of the membrane in human liver and brain-cortex non-synaptosomal mitochondria. However, the immunochemically accessible beta-phenethylamine-oxidizing activity was situated predominantly on the outer surface, and the immunochemically accessible 5-hydroxytryptamine-oxidizing activity was situated predominantly on the inner surface of the mitochondrial outer membrane in liver and brain-cortex non-synaptosomal mitochondrial preparations. 4. Considerable variation in the distribution of the enzyme in preparations of synaptosomal mitochondria was seen. 5. The simplest model consistent with our observations is that, in liver and brain-cortex non-synaptosomal mitochondria, the tyramine-oxidizing activity is distributed on both sides of the mitochondrial outer membrane, the beta-phenethylamine-oxidizing activity is located on the outer surface of the outer membrane and the 5-hydroxytryptamine-oxidizing activity is located on the inner surface of the mitochondria outer membrane.

Aged↗

PubMed1987

Immunocytochemical localization of monoamine oxidases A and B in human peripheral tissues and brain.

Monoamine oxidases (MAO; EC 1.4.3.4.) A and B occur in the outer mitochondrial membrane and oxidize a number of important biogenic and xenobiotic amines. Monoclonal antibodies specific for human MAO A or B and immunocytochemical techniques were used to visualize the respective enzymes in human placenta, platelets, lymphocytes, liver, brain, and a human hepatoma cell line. MAO A was observed in the syncytiotrophoblast layer of term placenta, liver, and a subset of neurons in brain, but was not observed in platelets or lymphocytes, which are known to lack type A enzyme. MAO B was observed in platelets, lymphocytes, and liver, but not in placenta, which contains little or no MAO B. MAO B was also observed in a subset of neurons in the brain that was distinct from that which contained MAO A. MAO A and MAO B were also observed in some glia. Unlike most tissues examined, liver cells appeared to contain both forms of the enzyme. These studies show that MAO A and MAO B can be specifically visualized by immunocytochemical means in a variety of human cells and tissues and can provide a graphic demonstration of the high degree of cell specificity of expression of the two forms of the enzyme.

Antibodies, Monoclonal↗