Influence of ethanol administration on the activity and compartmentation of rat liver monoamine oxidases.

Single-dose ethanol administration to rats caused inhibition of liver mitochondrial monoamine oxidases (MAO) A and B, and an increase in susceptibility of MAO A (but not MAO B) to limited proteolysis. Chronic ethanol feeding resulted in a less distinct alteration in catalytic activity and susceptibility to proteolysis of mitochondrial MAO, but increased the amount of soluble MAO. The sensitivity of membrane-bound MAO to inhibitors (imipramine and chlorpromazine), action of which depends on their lipophilicity and/or hydrophobicity, remained unchanged, compared with controls. Increased amounts of soluble MAO seen after chronic ethanol feeding probably reflect an impairment of insertion of newly synthesized enzyme molecules into the outer mitochondrial membrane, rather than solubilization of MAO from it.

Interaction of indole derivatives with monoamine oxidase A and B. Studies on the structure-inhibitory activity relationship.

Indole and isatin (2,3-dioxindole) analogues were studied as inhibitors of MAO-A and B. They exhibited reversible and competitive MAO inhibition. Three dimensional structures of the compounds tested were constructed and minimized using PC-based molecular graphic software. The QSAR analysis revealed the requirement of co-planar structure of substituents at C2 and C3 of indole ring for selective MAO-A inhibition, whilst type of bond was less essential. The presence of hydroxy group at C5 of isatin increased selectivity of MAO-A inhibition, however simultaneous insertion of substituents into both positions of indole ring (5-hydroxy-2-phenylindole) led to a decrease of MAO-A inhibition. The planar molecules demonstrating potent MAO-A inhibition have the average sizes 7 A in length and 6 A in width. The MAO B inhibition also depended on the sizes of planar molecules however distribution of electron density in the molecules was another precondition for the selective inhibition of the enzyme.

[Medico-biological aspects of biochemistry of amines and other nitrogen bases]. / Mediko-biologicheskie aspekty biokhimii aminov i drugikh azotistykh osnovanii.

The art-of-the-state and possible perspectives for studies of the properties of amine oxidases which are medically significant are briefly outlined. Due to the studies conducted at the Research Institute of Biomedical Chemistry of the Russian Academy of Medical Sciences, the authors discuss the results of studies of the following three problems: 1) modified catalytic properties of amine oxidases in experimental intoxications and abnormalities; 2) natural modulators of amine oxidases; 3) synthetic modulators of amine oxidases.

[Features of the biochemical action of paraquat on oxidative deamination of biogenic amines and other nitrogen compounds]. / Osobennosti biokhimicheskogo deistviia parakvata na protsessy okislitel'nogo dezaminirovaniia biogennykh aminov i drugikh azotistykh soedinenii.

Intoxication of rats with the herbicide paraquat (1,1-dimethyl-4,4-bipyridilium dichloride) was accompanied by accumulation in lungs, brain, heart, liver or kidney of malonic dialdehyde (MDA) (the compounds reacting with 2-thiobarbituric acid), indicating that the intoxication stimulated lipid peroxidation (LPO) in biomembranes. Treatment of the intoxicated rats with the antioxidant diludin (2,6-dimethyl-3,5-diethoxycarbonyl-1,4-dihydropyridine) or with the nucleophilic reagents sodium ascorbate or thiosulphate normalized the content of MDA in lungs, brain, heart, liver or kidney demonstrating the reversibility of the LPO stimulation caused by paraquat. On incubation of mitochondrial fractions of homogenates of lungs, brain, heart, liver or kidney of the intoxicated rats (as compared with the corresponding fractions from the intact animals) a decrease was noted in deamination of the substrates of monoamine oxidases serotonin, tryptamine, benzylamine, tyramine; at the same time, deamination of glucosamine and gamma-aminobutyric acid was increased and deamination of putrescine and L-lysine appeared. These impairments in deamination of nitrogenous compounds caused by paraquat were reversible. All the impairments were normalized by the treatment of the experimental animals with the antioxidative and nucleophilic reagents; a decrease was noted in the rate of development of the lethal paraquat intoxication and appearance of morphological manifestations of normalization. The data obtained suggest that the reversible, qualitative modification ("transformation") of the monoamine oxidases of the type A might explain the peculiarities of the alterations in deamination of nitrogenous compounds in paraquat intoxication.

Endogenous stimulation of lipid peroxidation in brain increases proteolytic inactivation of mitochondrial monoamine oxidases.

Stimulation of lipid peroxidation in vivo (in experimental epilepsy and closed cranio-cerebral injury, as models for endogenous stimulation of lipid peroxidation) affects catalytic activity, substrate specificity of mitochondrial monoamine oxidases and increases their susceptibility to trypsinolysis. It is suggested that increased susceptibility to trypsinolysis reflects an appearance of new hydrophilic site(s) in monoamine oxidase molecules which may be responsible for an involvement of the modified enzymes in the deamination of other important nitrogenous compounds (such as gamma-aminobutyric acid) with subsequent impairment of a ratio between inhibition and excitation processes in the brain.

Monoamine oxidase inhibition by novel antidepressant tetrindole.

The novel antidepressant tetrindole (2,3,3a,4,5,6-hexahydro-8-cyclohexyl-1H[3,2,1-j,k] carbazole) was found to be a selective inhibitor of monoamine oxidase A (MAO A). In vitro it inhibited rat brain mitochondrial MAO A in a competitive manner with Ki value of 0.4 microM. A 60 min preincubation did not change the competitive mode of interaction between enzyme and tetrindole (Ki value was 0.27 microM). The inhibition of rat brain mitochondrial MAO B was of mixed type with Ki value of 110 microM. Dilution or dialysis of mitochondrial suspension did not restore MAO A activity after inhibition by tetrindole both in vitro and in vivo, whereas inhibition of MAO B in vitro was completely reversible. Oral administration of tetrindole inhibited rat brain and liver mitochondrial MAO A by 80% within 0.5-1 hr and the onset of recovery of enzyme activity became evident after 24 hr. A small inhibition of MAO B (-20-30%) was observed in isolated brain and liver mitochondria within 1-6 hr and enzyme activity had completely recovered after 16 hr. The data obtained indicate that antidepressant activity of tetrindole may be explained by selective inhibition of MAO A, however an apparent discrepancy between competitive manner of MAO A inhibition in vitro and poor recovery of enzyme activity in vivo does not allow us to decide whether tetrindole is a "tight-binding" reversible inhibitor or a selective irreversible inhibitor of MAO A.

[Lipid peroxidation processes and activity of brain succinate dehydrogenase in experimental craniocerebral trauma]. / Protsessy perekisnogo okisleniia lipidov i aktivnost' suktsinatdegidrogenazy mozga pri cherepno-mozgovoi travme v éksperimente.

A statistically significant decrease in the activity of succinate dehydrogenase (SDH) was found in the rabbit brain after craniocerebral injury. The decrease in the activity of brain SDH was not shown to result from "competitive inhibition" by malonate accumulated after activation of lipid peroxidation. The activity of brain SDH was normalized by directed modification of the function of the central nervous system via administration of phenamine (amphetamine) into the injured animals.

[An increase in the radioprotective effect of O-methyltyramine and mezaton by monoamine oxidase inhibitors]. / Uvelichenie ingibitorami monoaminoksidazy radiozashchitnogo éffekta O-metiltiramina i mezatona.

Specific 2-propynylamine inhibitors of monoamine oxidase (MAO) pargyline and especially chlorgyline, a selective inhibitor of MAO A (but not deprenyl, a selective inhibitor of MAO B) increase the radioprotective effect of small doses of O-methyltyramine and phenylephrine and do not change the efficacy of large doses. This is consistent with the receptor theory of the mechanism of protective action of amines.

Increase of brain endogenous monoamine oxidase inhibitory activity (tribulin) in experimental audiogenic seizures in rats: evidence for a monoamine oxidase A inhibiting component of tribulin.

Brain tribulin activity in rats with an inherited predisposition to audiogenic epilepsy was studied after seizures of different intensity were induced by an electric bell. Weak seizures (from 0 to 2 arbitrary units) did not produce any changes in endogenous inhibitory activity towards either monoamine oxidase (MAO) A or B. Moderate seizures were characterized by increases in both MAO A and MAO B inhibitory activity (up to 1.9-fold). Complete tonic epileptiform seizures with total areflexia (4 arbitrary units) induced further augmentation (up to 2.5-fold) of MAO A but not of MAO B inhibitory activity. This dissociation between the two inhibitory activities points to the existence of a separate MAO A-inhibiting component of brain tribulin which is different from isatin.

[Multiple forms of monoamine oxidase in the growing human placenta]. / Mnozhestvennye formy monoaminoksidazy v rastushchei platsente cheloveka.

A ratio between two types of monoamine oxidase (MAO) was studied in the mitochondrial fraction of growing human placenta: MAO-A which is predominant in the tissue and the minor MAO-B. Activity of MAO-A with serotonin as a substrate was statistically distinctly lower (by 22%) in placenta within early periods of pregnancy as compared which the mature placenta during the delivery time. In the growing placenta activity of MAO-B with benzylamine as a substrate reached 365% of the MAO-B activity in the mature placenta. The ratio between MAO of the A and B types was altered during pregnancy as shown by inhibitory analysis, carried out using selective inhibitors of the MAO-A and -B types--Lilly 51641 substance and deprenyl as well as with semicarbazide as an inhibitor of benzylamine oxidase. At the early periods of pregnancy the rate of placental MAO-B oxidative deamination of benzylamine was distinctly higher as compared with that during the delivery act. At the same time, content of semicarbazide-sensitive benzylamine oxidase was increased during the delivery period. Possible biological significance of alterations in the amine oxidases ratio in the growing placenta is discussed considering the known property of the MAO-B inhibitor pargyline to cause abortion within early periods of pregnancy.

[Natural modulators of the function of the amine oxidase system in the body]. / O prirodnykh moduliatorakh funktsii sistemy aminoksidaz v organizme.

In cerebrospinal fluid (CSF) obtained from patients with chronic alcoholism natural modulators of monoamine oxidase (MAO) activity, containing in human mitochondrial and microsomal fractions or in rat brain mitochondria, have been found. These modulators, which were previously unknown, did not affect the activity of partially purified diamine oxidase from human placenta with 14C-putrescine as a substrate. The MAO modulators from CSF were thermostable (during 3 min at 100 degrees), penetrated through dialysing membrane thus differing from high molecular modulators of MAO previously described. In the system containing membrane bound MAO from human placenta, where the MAO-A is predominating, the modulators studied mostly inhibited deamination of 14C-serotonin. However, in the system containing membrane bound MAO from rat brain with prevalence of the MAO-B, the modulators from human CSF caused either inhibition or stimulation of oxidative deamination of 14C-serotonin or 14C-beta-phenylethylamine used as substrates. The modulators studied were not similar to tribulin (isatin) or quinolinic acid in their effects on catalytic properties of the amine oxidases investigated.

The role of lipid peroxidation in the possible involvement of membrane-bound monoamine oxidases in gamma-aminobutyric acid and glucosamine deamination in rat brain. Focus on chemical pathogenesis of experimental audiogenic epilepsy.

Incubation of rat brain synaptosomes and mitochondria with LPO inducers (Fe2+ and ascorbate) was accompanied by a decrease of deamination of serotonin (substrate of MAO-A) in mitochondria, but not in synaptosomes, with simultaneous stimulation of GABA and GLCA deamination, apparently owing to modification of catalytic properties of brain membrane-bound MAO. Oxidation of PEA (substrate of MAO-B) was insignificantly altered in both fractions. Reactions of deamination of serotonin, GABA, and GLCA (but not PEA), were highly sensitive to a selective inhibitor of MAO-A pyrazidol (pyrlindole). Isoniazid and hydrazides of quinoline carbonic acids (inhibitors of both modified MAO and copper-containing amine oxidases) strongly inhibited deamination of GABA and GLCA. During epileptiformic seizures in rats, genetically selected for high incidence of audiogenic epilepsia, stimulation in brain synaptosomes and mitochondria of LPO was observed. This was accompanied by a marked decrease in serotonin and PEA deamination, with a simultaneous increase in GABA and GLCA deamination in both fractions. The data obtained suggest that appearance of GABA-deaminating activity owing to modification of catalytic properties of MAO, might be an essential pathogenetic component in the development of epileptic seizures.

[The role of monoamine oxidase in the regulation of mitochondrial energy functions]. / Rol' monoaminoksidaz v reguliatsii énergeticheskikh funktsii mitokhondrii.

Incubation of aldehyde dehydrogenase-free mitochondrial preparations with biogenic amines serotonin, tyramine, 2-phenylethylamine and 5-methoxytryptamine resulted in inhibition of enzymes activity of both outer (rotenone-insensitive NADH-cytochrome c reductase) and inner (succinate dehydrogenase, succinate cytochrome c reductase) mitochondrial membranes. Solubilization of mitochondria after the incubation did not influence the amine-induced alteration of succinate dehydrogenase activity. Pretreatment of the organelles with a mixture containing chlorgyline and deprenyl completely inhibited monoamine oxidase (MAO) activity and prevented the effects of all the amines studied on mitochondrial enzymes. MAO-dependent effects of 5-methoxytryptamine were fully reproduced by 5-methoxyindolyl-3-acetaldehyde (one of probable products of 5-methoxytryptamine deamination). The effect of the aldehyde was not prevented by chlorgyline and deprenyl. After selective inhibition of MAO-A by chlorgyline the order of MAO-B-dependent effects of biogenic amines on mitochondrial enzymes studied was as follows: tyramine greater than or equal to 2-phenylethylamine much greater than serotonin. In deprenyl pretreated mitochondria the potency of MAO-A-dependent effects of these amines was: serotonin greater than tyramine much greater than much greater than 2-phenylethylamine. The data obtained suggest that the product(s) of oxidative deamination of biogenic amines (probably the aldehydes) catalyzed by both types of MAO (MAO-A and MAO-B) are able to regulate the energy functions of mitochondria.

[Comparative characteristics of membrane bound and cytoplasmic monoamine oxidases in human placenta]. / Sravnitel'naia kharakteristika membranno-sviazannykh i tsitoplazmaticheskoi monoaminoksidaz platsenty cheloveka.

Catalytic and physico-chemical properties of human placental monoamine oxidases (MAO) were studied. Both forms of the enzyme, membrane-bound and soluble, exhibited similar properties: optimal activity at pH8.3, equal rate of inhibition with selective MAO inhibitors, identical substrate specificity (the best substrate--serotonin). Some specific differences were found only for cytoplasmic (soluble) MAO: lower affinity for substrates as compared with membrane-bound enzymes, reversible interaction with an inhibitor Lilly 51641 even after long-term preincubation, whereas the mitochondrial MAO bound Lilly 51641 irreversibly. The property of cytoplasmic MAO to form aggregates during storage and/or in gel filtration and concentration did not affect the main catalytic properties of soluble enzyme. Analysis of isoenzyme spectra of membrane-bound and cytoplasmic MAO by means of selective inhibitors and electrophoresis showed that MAO of the two types--A and B were detected in all the subcellular fractions studied. Subunits of MAO of the A type had molecular masses 62, 61 and 61 kDa and of MAO of the B type--51, 55 and 55 kDa in mitochondria, microsomes and cytosol, respectively.

[Change in the catalytic properties of mitochondrial monoamine oxidase in experimental audiogenic epilepsy]. / Izmenenie kataliticheskikh svoistv mitokhondrial'nykh monooksidaz pri audiogennoi épilepsii v éksperimente.

Catalytic properties of mitochondrial monoamine oxidases (MAO) were studied in brain, heart, liver and kidney of rats of Krushinskii-Molodkina strain with inherited audiogenic epilepsia. In brain of these rats a. 2.5-fold decrease of Vmax of serotonin (MAO-A substrate) deamination has been found. During audiogenic epileptiformic attack 2.5-5-fold decrease of Vmax of serotonin deamination in brain and liver and also decrease of benzylamine (MAO-B substrate) oxidation in brain were found. Simultaneously oxidation of glucosamine and gamma-aminobutyric acid was markedly increased (up to 5-fold and more) in brain. The data obtained showed that qualitative transformation occurred in catalytic properties of MAO which may be an important pathogenic factor in the development of epileptiformic attack.

[The action of befol and its derivatives on monoamine oxidase of different origins]. / Deistvie befola i ego proizvodnykh na monoaminoksidazu razlichnogo proiskhozhdeniia.

The effect on deamination of serotonine, dopamine, tiramine and 2-phenylamine of benzamide derivatives befol, moclobemide and LIS-641 was studied. Befol and moclobemide are inhibitors of serotonine deaminating activity of MAO. The different sensitivity of this activity to the effect of the benzamide derivatives in beef or rat brain and human placenta was noted. The inhibition was more distinct in tissue homogenate than in corresponding mitochondrial fractions.

[Changes in kinetics of deaminated biogenic amines in spontaneous hypertension]. / Izmemeniia kinetiki dezaminirovaniia biogennykh aminov pri spontannoi gipertenzii.

Rate of serotonin and benzylamine deamination was increased in liver tissue of rats with spontaneous hypertension. The increase was due to elevation in Vmax value for monoamine oxidases of the A and B types as compared with the corresponding values of control animals. The Vmax value was increased in kidney of hypertensive animals for MAO of the B type (benzylamine as a substrate). At the same time, Km for MAO of the B type was increased in liver tissue, while Km for MAO of the A type was decreased in brain of hypertensive animals. Titration of the MAO active sites exhibited their increased concentration in the B type MAO in liver mitochondria of experimental animals. The data obtained suggest an important role of alterations in the MAO catalytic activity in pathogenesis of spontaneous hypertension.

Studies on mitochondrial metabolic processes in offspring of alcoholized rats--I. Evidence for altered activity and sensitivity to monoamine oxidase-dependent control by biogenic amines of some membrane-bound enzymes.

In the liver mitochondrial fraction of the first generation offspring of alcoholized male rats, decreased activities of monoamine oxidase (MAO) types A and B, rotenone-insensitive NADH-cytochrome c-reductase and succinate dehydrogenase were observed. The MAO-dependent inhibition of rotenone-insensitive NADH-cytochrome c-reductase and succinate dehydrogenase by biogenic amines, incubated with the mitochondrial fraction, was altered in the offspring of alcoholized animals as compared with control rats. The sensitivity of these enzymatic activities towards the inhibitory effect of 5-methoxyindol-3-ylacetaldehyde was markedly increased in the offspring of alcoholized male rats. The data obtained suggest the existence of a genetically determined predisposition of the mitochondrial metabolic processes in the offspring of the alcoholized rats to the effects of ethanol and to the toxic effects of acetaldehyde, formed during ethanol metabolism.

[Multiple forms of monoaminoxidase in the rat brain during experimental catatonia]. / Mnozhestvennye formy monoaminoksidazy golovnogo mozga krysy pri éksperimental'noi katatonii.

Catalytic properties of multiple forms (separated by affinity chromatography) of rats brain mitochondrial monoamine oxidase (MAO, MAO-I, MAO-11 alpha, MAO-11 beta, MAO-111) have been studied in the animals selected for propensity to development of catatonic syndrome considered as an experimental model of the catatonic syndrome occurring in schizophrenia. It was shown that in experimental catatonia (as compared with rats of the corresponding control group) there was a dramatic increase in the brain stem of the rate of oxidative deamination of beta-phenylethylamine catalyzed by MAO-III; there was also a statistically significant (albeit less expressed than in the experiments with beta-phenylethylamine) increase in the rate of deamination of tyramine and a decrease in the rate of deamination of serotonin. In the systems with MAO-II beta we detected statistically significant increase in the rates of deamination of tyramine and beta-phenylethylamine in experimental catatonia as compared with corresponding control. Studies of multiple forms of brain MAO provide more informative data than estimation of "total" MAO activity (without separation of the multiple forms of this enzyme).