Metabolism of selegiline [(-)-deprenyl)].

Selegiline (1) [(-)-deprenyl] is used to treat patients with Parkinson's disease. Nevertheless, in much higher doses it has beneficial effects in depression, and dementia of the aged patients. Selegiline (1) undergoes a complex metabolic pathway. Its major metabolites include (-)-desmethyldeprenyl (2), (-)-methamphetamine (3) and (-)-amphetamine (4), deprenyl-N-oxide (5) and formaldehyde (6) as a small metabolic fragment. In addition, more than 40 minor metabolites of selegiline (1) have also been either detected or proposed by investigators and researchers. This review analyses the pharmacological activity, generation pathway and the detection method of the major metabolites of selegiline (1).

Cardioprotection by resveratrol: A human clinical trial in patients with stable coronary artery disease.

Several beneficial effects of resveratrol (RES), a natural antioxidant present in red wine have already been described. The aim of our study was to investigate if RES had a clinically measurable cardioprotective effect in patients after myocardial infarction. In this double-blind, placebo controlled trial 40 post-infarction Caucasian patients were randomized into two groups. One group received 10 mg RES capsule daily for 3 months. Systolic and diastolic left ventricular function, flow-mediated vasodilation (FMD), several laboratory and hemorheological parameters were measured before and after the treatment. Left ventricular ejection fraction showed an increasing tendency (ns) by RES treatment. However, left ventricular diastolic function was improved significantly (p < 0.01) by RES. A significant improvement in endothelial function measured by FMD was also observed (p < 0.05). Low-density lipoprotein (LDL) level significantly decreased (p < 0.05) in the RES treated group. Red blood cell deformability decreased and platelet aggregation increased significantly in the placebo group (p < 0.05), while resveratrol treatment has prevented these unfavourable changes. Concerning other measured parameters no significant changes were observed neither in placebo nor in RES group. Our results show that resveratrol improved left ventricle diastolic function, endothelial function, lowered LDL-cholesterol level and protected against unfavourable hemorheological changes measured in patients with coronary artery disease (CAD).

R-deprenyl: pharmacological spectrum of its activity.

Deprenyl has been discovered by Knoll and co-workers. The R-enantiomer of deprenyl (selegiline) is a selective and irreversible inhibitor of the B-isoform of monoamine oxidase (MAO-B) enzyme. Due to its dopamine potentiating and possible neuroprotective properties it has an established role in the treatment of parkinsonian patients. By inhibiting MAO-B enzyme, R-deprenyl decreases the formation of hydrogen peroxide, alleviating the oxidative stress also reduced by increased expression of antioxidant enzymes (superoxide dismutases and catalase) reported during chronic treatment. It was shown to prevent the detrimental effects of neurotoxins like MPTP and DSP-4. R-Deprenyl elicits neuroprotective and neuronal rescue activities in concentrations too low to inhibit MAO-B. It is extensively metabolized and some of the metabolites possess pharmacological activities, thus their contribution to neuroprotective properties was also suggested. The recently identified deprenyl-N-oxide is extensively studied in our laboratory. Effects other than neuroprotection, like influencing cell adhesion and proliferation cannot be neglected.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein 1: recent developments concerning substrates and inhibitors of a promising therapeutic target.

SSAO/VAP-1 is not only involved in the metabolism of biogenic and xenobiotic primary amines and in the production of metabolites with cytotoxic effects or certain physiological actions, but also plays a role, for example, as an adhesion molecule, in leukocyte trafficking, in regulating glucose uptake and in adipocyte homeostasis. Interest in the enzyme has been stimulated by the findings that the activities of the SSAOs are altered (mostly increased) in various human disorders, including diabetes, congestive heart failure, liver cirrhosis, Alzheimer's disease and several inflammatory diseases, although the underlying causes are often unknown. On the basis of their insulin-mimicking effect, SSAO substrates are possibly capable of ameliorating metabolic changes in diabetes, while SSAO inhibitors (somewhat of a contradiction) are of potential benefit in preventing diabetes complications, atherosclerosis and oxidative stress contributing to several disorders or modulating inflammation, and hence may be of substantial therapeutic value. Great efforts have been made to develop novel compounds which may lead to future drugs useful in therapy, based on their effects on SSAO/VAP-1, and some of the results relating to novel substrates and inhibitors are surveyed in the present review.

Pharmacokinetic studies of (-)-deprenyl and some of its metabolites in mouse.

(-)-Deprenyl is a selective irreversible inhibitor of MAO-B. The parent compound is responsible for the enzyme inhibitory effect, but its metabolites are also playing a role in the complex pharmacological activity of the substance. In the present studies male NMRI mice were treated orally, subcutaneously, intraperitoneally and intravenously with 5 mg/kg of (-)-deprenyl. The time related changes of the plasma concentrations of the parent compound and its main metabolites (methamphetamine, desmethyl-deprenyl and amphetamine) were determined by GC/ MSD technique. The main pharmacokinetic parameters (C(max), t(max), t1/2beta, AUC(0-6), AUC(0-infinity)) have been calculated. (-)-Deprenyl is well absorbed after oral and parental treatment. The peak concentrations (C(max)) were reached at 15 min after treatment and the absorption was followed by a fast elimination (t1/2beta < or = 2h). (-)-Deprenyl has an intensive "first pass" metabolism after oral treatment; only 25% of the parent compound reaches the systemic circulation. Increased bioavailability was detected after subcutaneous (87.1%) and intraperitoneal (78.7%) administration. The main metabolic pathway of (-)-deprenyl is the N-depropargylation, leading to the formation of methamphetamine. N-demethylation of (-)-deprenyl leads to formation of desmethyl-deprenyl. Amphetamine is produced from both former metabolites. After oral treatment the plasma concentrations of methamphetamine are higher during the first 6 h than that of (-)-deprenyl, while the opposite was found after parental treatment. The results indicate, that (-)-deprenyl, a potent MAO-B inhibitor, might induce a different spectrum of activity (e.g. antidepressant), when it is administered parenterally (transdermally). The new spectrum can be due to the special pharmacokinetic behaviour of the inhibitor.

P2 purinoceptor antagonists inhibit the non-adrenergic, non-cholinergic relaxation of the human colon in vitro.

Neurotransmitters released by myenteric neurons regulate movements of intestinal smooth muscles. There has been little pharmacological evidence for a role of purinergic mechanisms in the non-adrenergic, non-cholinergic (NANC) relaxation of the human large intestine. We used P(2) purinoceptor antagonists to assess whether such receptors are involved in the NANC relaxation of the circular muscle of the human sigmoid colon. It was also investigated whether the guanylate cyclase enzyme mediates the NANC response. Human colonic circular strips were tested in organ bath experiments with isotonic recording. NANC, non-nitrergic relaxations induced by electrical field stimulation (1 and 10 Hz, in the presence of atropine, guanethidine, and 100 microM N(G)-nitro-L-arginine [L-NOARG]) were strongly inhibited by a combination of the P(2) purinoceptor antagonists pyridoxal-phosphate-6-azophenyl-2',4'-sulfonic acid (PPADS) (50 microM) and suramin (100 microM). PPADS plus suramin was ineffective in the absence of L-NOARG. L-NOARG alone significantly reduced the NANC relaxation to electrical stimulation. PPADS plus suramin strongly inhibited the relaxation in response to exogenous alpha,beta-methylene ATP. The guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) (3 microM) inhibited the NANC relaxation, but did not add to its reduction by L-NOARG. L-NOARG was still slightly effective in the presence of ODQ. Vasoactive intestinal polypeptide tachyphylaxis failed to influence the non-nitrergic NANC relaxation. It is concluded that nitric oxide (NO) and ATP co-mediate, in a non-additive manner, the NANC relaxation. NO probably acts through the guanylate cyclase, though a small fraction of its effect might be mediated by other mechanisms. Activators of the guanylate cyclase other than NO do not seem to participate in the NANC relaxation.

Alteration of serum semicarbazide-sensitive amine oxidase activity in chronic renal failure.

Despite recent intensive investigations, physiological and pathological role of semicarbazide-sensitive amine oxidase (SSAO) is far from clear. In this study, serum SSAO activity was determined, radiochemically, in various groups of uremic patients: haemodialysed (HD), peritoneally dialysed (PD) and those receiving conservative treatment but still not dialysed (ND), as well as in controls. Reduced enzyme activity was found in HD uremic patients before and after dialysis treatment, compared to controls (5260 +/- 862 and 6011 +/- 958 pmol/h/ml vs. 8601 +/- 283 pmol/h/ml, p < 0.01 and p < 0.05, respectively). The activity was slightly lower in PD, and normal in ND patients. In HD patients SSAO activity was also determined by an assay based on the formation of hydrogen peroxide, and was found to be elevated compared to controls (2384 +/- 323 pmol/h/ml vs. 1437 +/- 72 pmol/h/ml, p < 0.05). The elevated serum SSAO activity measured through the detection of the enzyme-generated hydrogen peroxide in HD patients might indicate its contribution to the accelerated atherosclerotic disease observed in uremia.

Studies on the insulinomimetic effects of benzylamine, exogenous substrate of semicarbazide-sensitive amine oxidase enzyme in streptozotocin induced diabetic rats.

Semicarbazide-sensitive amine oxidase/vascular adhesion protein-1 (SSAO) is believed to be a bifunctional membrane protein. It is localized extracellularly and preferentially oxidizes short chain primary amines to aldehydes, hydrogen peroxide and ammonia, but also functions as an adhesion molecule, which is involved in leukocyte migration. Serum SSAO activity is increased in diabetic patients and animals and the aldehydes formed in the enzyme reaction may contribute to vascular damage. However, administration of exogenous substrates has been shown to improve glucose tolerance and reduce hyperglycaemia in diabetic animals. Hydrogen peroxide and/or its vanadate complexes have been suggested responsible for these effects. Streptozotocin induced diabetic rats were treated with benzylamine (BZA) +/- vanadate (V) or insulin. In contrast to insulin, BZA + V treatment did not reduce HbA(1C) levels. However, it reduced the elevated serum SSAO activity, decreased the accumulation of advanced-glycation end products and increased the bioavailability of nitric oxide in diabetic animals, similarly to insulin. BZA alone did not affect any of these parameters.

Pregnancy stage and number of fetuses may influence maternal plasma leptin in ewes.

Maternal plasma leptin is elevated in ewes during pregnancy. The authors studied whether there was any relation between maternal plasma leptin and insulin concentrations, the number of fetuses and the circulating and faecal levels of gestagens. At the end of the breeding season in January the ovarian activity of Prolific Merino ewes was induced/synchronised with gestagen + eCG treatment. Ewes were inseminated artificially (AI) by laparoscopy. Blood and faecal samples were collected before AI (day 0) and again 41, 81 and 101 days later. The plasma levels of leptin (pL), insulin and progesterone (pP4), and the faecal P4 metabolite (P4-met) content were determined. The day 0 level of pL was significantly higher in pregnant (n = 24) than in non-pregnant ewes (n = 32). By day 41 the pL of pregnant animals had doubled, it showed a further moderate increase on day 81, and decreased slightly thereafter. During pregnancy pP4 and faecal P4-met rose continuously and were positively correlated at all stages. The mean levels of pL and pP4 and the faecal content of P4-met were lower in ewes bearing single (n = 12) than in those with 2 (n = 6) or 3-5 fetuses (n = 6). Analysis of variance demonstrated significant differences according to the number of fetuses in the pL and pP4, but not in P4-met (p = 0.042, 0.044, and 0.051, respectively). Leptin showed positive correlation with insulin before the AI but not during pregnancy. On days 41 and 81 pL showed a slight positive correlation with P4 and P4-met, which decreased slightly by day 101. This study shows that although leptinaemia is affected by the number of fetuses and the level of P4, pregnancy stage is a more important regulator than these additional factors.

Deprenyl: from chemical synthesis to neuroprotection.

During the last decades (-)-deprenyl has become the golden standard of MAO-B inhibitors. It possesses dopamine potentiating and antioxidant properties; however, its effects cannot be explained solely by the enzyme inhibitory action. (-)-Deprenyl prevents the toxicity of certain selective neurotoxins and recently it was demonstrated to increase cell-cell adhesion as well. The complexity of its pharmacological effects reflects the action of both the parent compound and the active metabolites. (-)-Deprenyl and related propargylamines (DRPs) show neuroprotective features in a variety of in vitro and in vivo models that is dependent on the propargyl moiety. The main presumptive targets to date include glyceraldehyde-3-phosphate dehydrogenase, poly(ADP-ribose) polymerase, some kinase cascades, as well as pro- and antiapoptotic proteins, beside the inhibition of MAO-B. The antiapoptotic activity of DRPs converges upon the maintenance of mitochondrial integrity, due to the initiation of a complex transcriptional program, the details of which are yet to be elucidated.

Low dose (-)deprenyl is cytoprotective: it maintains mitochondrial membrane potential and eliminates oxygen radicals.

Hypoxia leads to a collapse in mitochondrial transmembrane potential (Deltapsi(M)), a fall in the ATP/ADP ratio, and finally cell death. Since (-)deprenyl directly modulates Deltapsi(M) and production of reactive oxygen species (ROS) by altering the respiratory function of mitochondria, we were interested in the dose-response relations of these effects. The changes in JC-1 red/green signal ratios {mitochondrial transmembrane potential}, and the changes in the cerium staining (intracellular ROS) in hypoxic and normoxic PC12 cell cultures were measured following 1 h of Argon hypoxia and 24 h of re-oxygenation in the absence and in the presence of various concentrations of (-)deprenyl. Deltapsi(M) shifted to lower values following hypoxia/re-oxygenation and all cells had decreased and uniform Deltapsi(M) levels. The amount of ROS increased. Following 24 h of treatment with various concentrations of (-)deprenyl during the re-oxygenation period, survival increased, the Deltapsi(M) shift caused by oxygen deprivation was reversed and the peroxy radical levels decreased except for at 10(-3) M.

[Electrogenic Na+/Ca2+-exchange regulation by alpha2-receptor in peripheral sympathetic nerve]. / Elektrogén Na+/Ca2+-csere alpha2-receptor regulációja perifériás szimpatikus idegen.

Electrical depolarisation-(2 Hz, 1 ms)-induced [3H]noradrenaline ([3H]NA) release was measured from the isolated main pulmonary artery of the rabbit in the presence of uptake blockers (cocaine, 3 x 10(-5)M; corticosterone, 5 x 10(-5)M) and after blocking the MAO-enzyme by pargyline (1,2 x 10(-4)M). Substitution of most of the external Na+ by Li+ (113 mM; [Na+]0: 25 mM) slightly potentiated the stimulation-induced release of [3H]NA in a tetrodotoxin (TTX, 10(-7)M) sensitive manner. The reverse Na+/Ca2+-exchange inhibitor KB-R7943 (3 x 10(-5)M) failed to inhibit the stimulation-evoked release of [3H]NA, but increased the resting outflow of neurotransmitter. The 'N-type' voltage-sensitive Ca2+-channel (VSCC) blocker omega-conotoxin (omega-CgTx) GVIA (10(-8)M) significantly and irreversibly inhibited the release of [3H]NA on stimulation (approximately 60-70%). The 'residual release' of NA was abolished either by TTX or by reducing external Ca2+ from 2,5 to 0,25 mM. The 'residual release' of NA was also blocked by the non-selective VSCC-blocker neomycin (3 x 10(-3)M). Direct correlation was obtained between the extent of VSCC-inhibition and the transmitter release enhancing-effect of presynaptic alpha2-receptor blocker yohimbine (3 x 10(-7)M). When the release of [3H]NA was blocked by omega-CgTx GVIA plus neomycin, yohimbine was ineffective. Inhibition of the Na+-pump by removal of K+ from the external medium increased both the resting and the stimulation-evoked release of [3H]NA in the absence of functioning VSCCs (i.e. in the presence of neomycin and after omega-CgTx treatment). Under these conditions the stimulation-evoked release of NA was abolished either by TTX or by external Ca2+-removal (+1 mM EGTA). Similarly, external Li+ (113 mM) or the reverse Na+/Ca2+ exchange blocker KB-R7943 (3 x 10(-5)M) significantly inhibited the nerve-evoked release of NA in 'K+-free' solution. KB-R7943 decreased the resting outflow of NA as well. Under conditions, in which the Na+-pump was inhibited in the absence of functioning VSCCs, yohimbine (3 x 10(-7)M) further enhanced the release of neurotransmitter, while l-noradrenaline (l-NA, 10(-6)M), an agonist of presynaptic alpha2-receptors, inhibited it. The yohimbine-induced enhancement of NA-release was abolished by Li+-substitution and significantly inhibited by KB-R7943 application. It is concluded that after blockade of VSCCs, brief depolarising pulses may reverse Na+/Ca2+-exchange and release neurotransmitter in Na+-loaded sympathetic nerves. Further, similar to that of VSCCs, the reverse Na+/Ca2+-exchange may also be inhibited by presynaptic alpha2-receptor activation.

Increased cell-cell adhesion, a novel effect of R-(-)-deprenyl.

The neuroprotective effect of the antiparkinsonian monoamine oxidase (MAO)-B inhibitor, R-(-)-deprenyl has been under investigation for years. Cytoskeleton, a main component of cell adhesion, is involved in the development of R-(-)-deprenyl-responsive diseases, the effect of the drug on cell adhesion, however, is not known. We examined the effect of R-(-)-deprenyl on cell-cell adhesion of neuronal and non-neuronal cells. R-(-)-deprenyl treatment resulted in a cell type- and concentration-dependent increase in cell-cell adhesion of PC12 and NIH3T3 cells at concentrations lower than those required for MAO-B inhibition, while S-(+)-deprenyl was not effective. This acitvity of R-(-)-deprenyl was not prevented by the cytochrome P-450 inhibitor, SKF525A, while deprenyl-N-oxide, a newly described metabolite, also induced an increase in cell-cell adhesion. The effect of R-(-)-deprenyl was not reversible during a 24-hour recovery period. In summary, we described a new, MAO-B independent effect of R-(-)-deprenyl on cell-cell adhesion which can contribute to its neuroprotective function.

Pharmacological aspects of (-)-deprenyl.

Deprenyl, the selective irreversible inhibitor of monoamine oxidase-B (MAO-B), has been synthesised as a potential antidepressant, however, due to its dopamine potentiating capacity, became a registered drug in the treatment of Parkinson's disease. Deprenyl possesses a wide range of pharmacological activities; some of them are not related to its MAO-B inhibitory potency. Beside its dopamine potentiating effect, it renders protection against a number of dopaminergic, cholinergic and noradrenergic neurotoxins with a complex mechanism of action. By inducing antioxidant enzymes and decreasing the formation of reactive oxygen species, deprenyl is able to combat an oxidative challenge implicated as a common causative factor in neurodegenerative diseases. In a dose substantially lower than required for MAO-B inhibition (10(-9)-10(-13) M), deprenyl interferes with early apoptotic signalling events induced by various kinds of insults in cell cultures of neuroectodermal origin, thus protecting cells from apoptotic death. Deprenyl requires metabolic conversion to a hitherto unidentified metabolite to exert its antiapoptotic effect, which serves to protect the integrity of the mitochondrion by inducing transcriptional and translational changes. Pharmacokinetic and metabolism studies have revealed that deprenyl undergoes intensive first pass metabolism, and its major metabolites also possess pharmacological activities. The ratio of the parent compound and its metabolites reaching the systemic circulation and the brain are highly dependent on the routes of administration. Therefore, in the treatment of neurodegenerative diseases, reconsideration of the dosing schedule, by lowering the dose of deprenyl and choosing the most appropriate route of administration, would diminish undesired adverse effects, with unaltered neuroprotective potency.

Semicarbazide-sensitive amine oxidase: current status and perspectives.

Semicarbazide-sensitive amine-oxidase (SSAO) is present in various human tissues and in plasma. Oxidative deamination of short-chain aliphatic amines is catalyzed by this enzyme to afford the corresponding aldehydes, ammonia and hydrogen peroxide. Methylamine and aminoacetone have been recognized to be physiological substrates for SSAO. There are several pathological states where increased serum SSAO activity have been found, such as diabetes mellitus, congestive heart failure, multiple types of cerebral infarction, uraemia, and hepatic cirrhosis. The role of SSAO in pathophysiology of diabetes has been most extensively investigated. The elevated formation of the potentially cytotoxic products of the enzyme may contribute to the endothelial injury of blood vessels, resulting in the early development of severe atherosclerosis; it may also contribute to the pathogenesis of diabetic angiopathy. It is now suggested that SSAO inhibitors may prevent the development of atherosclerosis and diabetic complications as well. Inhibitors can be conveniently subdivided into the main groups of hydrazine derivatives, arylalkylamines, propenyl- and propargylamines, oxazolidinones, and haloalkylamines. Of them, aryl(alkyl)hydrazines, and 3-halo-2-phenylallylamines are generally very strong SSAO inhibitors. Most of these inhibitors of SSAO have been originally developed for other purposes, or they are simple chemical reagents with highly reactive structural element(s); these compounds have not been able to fulfil all criteria of high potency, selectivity, and acceptable toxicity. New potent compounds with selectivity and low toxicity are needed, which may prove useful tools for understanding the roles and function of SSAO, or they may even be valuable substances for treatment of various diseases.

Altered nitric oxide production in mouse brain after administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridin or methamphetamine.

Several studies have demonstrated the involvement of reactive nitrogen and oxygen species (RNOS) in the neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydro-pyridin (MPTP) and methamphetamine (METH), so the contribution of altered nitric oxide synthase (NOS) enzyme function can be suspected. In this study, about 50% increase in nitric oxide (NO) production in the mouse striatum was found between 4 and 12 h after a single MPTP injection, allowing an increased peroxynitrite (ONOO-) formation in the target brain region. However, METH injection induced a rapid decrease of NO formation both in mouse striatum and hippocampus, reaching its minimum level at 2 h, and restored to the control value after 6 h in the striatum and 12 h in the hippocampus. The uncoupled function of NOS with increased superoxide (O2*-) production after METH injection is suggested.

Pro-apoptotic and anti-apoptotic molecules affecting pathways of signal transduction.

Selective inhibition of the "false" proliferative signals via targeting tyrosine kinases resulting in the induction of apoptosis by depletion of the "survival factors" is one of the most studied and widely accepted concepts of modern chemotherapy. We have synthesized a series of potent tyrosine kinase inhibitors and tested these compounds for apoptosis induction. Some of the tyrosine kinase inhibitors caused either apoptotic or cytoplasmic vacuolar cell death in various tumor cell cultures. The somatostatin analogue oligopeptide TT-232, which indirectly inhibits tyrosine kinases, exerted a dose-dependent apoptosis-inducing effect. The tumor growth-inhibitory effect of TT-232 and some tyrosine kinase inhibitors has also been proven by in vivo experiments, using human tumor xenografts. On the other hand, a dose-dependent pro- or anti-apoptotic activity of (-)-deprenyl has been shown in melanoma cell cultures, the lower doses inhibiting and the higher doses inducing apoptosis. Various metabolites of (-)-deprenyl are responsible for these actions. The effect of (-)-deprenyl is connected with depolarization of mitochondrial membranes. The kinase inhibitors act on the growth factor receptor signaling pathways (survival factor pathways) and initiate the caspase cascade. The key enzyme for the action of both pro-apoptotic and anti-apoptotic compounds is caspase 3.

The influence of metabolism on the MAO-B inhibitory potency of selegiline.

(-)-Deprenyl (selegiline), a propargylamine derivative of methylamphetamine, is a potent, irreversible inhibitor of monoamine-oxidase type B (MAO-B). The MAO-B inhibitory effects of various doses (0.1-0.25-0.5 mg/kg) of (-)-deprenyl in rat brain and liver were compared, using either oral or subcutaneous drug administration. The intensity of the first pass metabolism of (-)-deprenyl was also estimated. The effect of pre-treatment with phenobarbitone (80 mg/kg i.p., daily for three days) or proadifen (SKF-525A, 50 mg/kg i.p., single dose) on the MAO-B inhibitory potency of (-)-deprenyl was also studied. The oral and subcutaneous administration of selegiline induced a significantly different degree of MAO-B enzyme inhibition in the rat brain, but not in the liver. The inhibitory potency of (-)-deprenyl on MAO-B activity was markedly influenced by pre-treatment of rats with an inducer (phenobarbitone), or an inhibitor (SKF-525A) of cytochrome P-450 mono-oxygenases in the liver. Our results suggest, that (-)-deprenyl is metabolised mainly in the liver by microsomal cytochrome P-450 dependent mono-oxygenases, and it has an intensive first-pass metabolism. The parent compound is responsible for the inhibition of MAO-B enzyme activity.

Protective effect of 7-nitroindazole against DSP-4 induced noradrenaline depletion in mouse hippocampus.

N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) is a selective noradrenaline (NA) uptake blocker, capable of inducing a long-lasting depletion of NA in some noradrenergic axon terminals originating from the locus coeruleus in rodents. Pretreatment with 7-nitroindazole, a fairly selective inhibitor of neuronal nitric oxide synthase in vivo, partially prevented DSP-4 induced NA depletion in mouse hippocampus measured seven days after the neurotoxic insult. Administration of L-arginine, the substrate of nitric oxide synthase, altered neither the NA depletion induced by DSP-4, nor the protective effect of 7-nitroindazole. Inhibition of nitric oxide synthesis by N(G)-nitro-L-arginine methyl ester did not attenuate the NA depleting effect of DSP-4. Thus, the contribution of neuronal nitric oxide synthase inhibition to the protective effect of 7-nitroindazole needs further studies. As 7-nitroindazole did not block NA uptake, this cannot play a part in the protective effect. The possible contribution of monoamine oxidase B enzyme inhibition by 7-nitroindazole to the protective effect is also discussed.

Anti-apoptotic and apoptotic action of (-)-deprenyl and its metabolites.

The mode of cytoprotective action of the monoamine oxydase B inhibitor (-)-deprenyl was studied using A-2058 human melanoma cells in culture. Serum deprivation caused apoptosis of the cultured cells, which could be decreased by administration of 10(-9) - 10(-13)M (-)-deprenyl. The known metabolites of (-)-deprenyl, (-)-desmethyl-deprenyl, (-)- and (+)-methylamphetamine failed to exert the same effect. The anti-apoptotic activity of (-)-deprenyl was prevented by the simultaneous application of the microsomal drug-metabolizing enzyme inhibitor SKF-525A. These results show that (-)-deprenyl needs metabolic conversion in order to be anti-apoptotic, but the effective metabolite is still unknown. On the other hand, higher dose (10(-13)M) of (-)-deprenyl, (-)-desmethyl-deprenyl, (-)- and (+)-methylamphetamine induced apoptosis in the non-serum-deprived A-2058 cell culture. SKF-525A did not prevent the apoptosis-inducing effect of (-)-deprenyl, which means that no metabolic changes are needed for this activity. High dose (10(-3)M) of (-)-deprenyl induced very high Caspase 3 activity in non-serum-deprived A-2058 cell culture, low doses (10(-9) - 10(-3) M) of (-)-deprenyl maintained Caspase 3 activity on control level in case of serum-deprivation.