Inhibition of Monoamine Oxidases by Pyridazinobenzylpiperidine Derivatives.

Monoamine oxidase inhibitors (MAOIs) have been crucial in the search for anti-neurodegenerative medications and continued to be a vital source of molecular and mechanistic diversity. Therefore, the search for selective MAOIs is one of the main areas of current drug development. To increase the effectiveness and safety of treating Parkinson's disease, new scaffolds for reversible MAO-B inhibitors are being developed. A total of 24 pyridazinobenzylpiperidine derivatives were synthesized and evaluated for MAO. Most of the compounds showed a higher inhibition of MAO-B than of MAO-A. Compound S5 most potently inhibited MAO-B with an IC50 value of 0.203 µM, followed by S16 (IC50 = 0.979 µM). In contrast, all compounds showed weak MAO-A inhibition. Among them, S15 most potently inhibited MAO-A with an IC50 value of 3.691 µM, followed by S5 (IC50 = 3.857 µM). Compound S5 had the highest selectivity index (SI) value of 19.04 for MAO-B compared with MAO-A. Compound S5 (3-Cl) showed greater MAO-B inhibition than the other derivatives with substituents of -Cl > -OCH3 > -F > -CN > -CH3 > -Br at the 3-position. However, the 2- and 4-position showed low MAO-B inhibition, except S16 (2-CN). In addition, compounds containing two or more substituents exhibited low MAO-B inhibition. In the kinetic study, the Ki values of S5 and S16 for MAO-B were 0.155 ± 0.050 and 0.721 ± 0.074 µM, respectively, with competitive reversible-type inhibition. Additionally, in the PAMPA, both lead compounds demonstrated blood-brain barrier penetration. Furthermore, stability was demonstrated by the 2V5Z-S5 complex by pi-pi stacking with Tyr398 and Tyr326. These results suggest that S5 and S16 are potent, reversible, selective MAO-B inhibitors that can be used as potential agents for the treatment of neurological disorders.

Key Enzymes of the Serotonergic System - Tryptophan Hydroxylase 2 and Monoamine Oxidase A - In the Brain of Rats Selectively Bred for a Reaction toward Humans: Effects of Benzopentathiepin TC-2153.

At the Institute of Cytology and Genetics (Novosibirsk, Russia) for over 85 generations, gray rats have been selected for high aggression toward humans (aggressive rats) or its complete absence (tame rats). Aggressive rats are an interesting model for studying fear-induced aggression. Benzopentathiepin TC-2153 exerts an antiaggressive effect on aggressive rats and affects the serotonergic system: an important regulator of aggression. The aim of this study was to investigate effects of TC-2153 on key serotonergic-system enzymes - tryptophan hydroxylase 2 (TPH2) and monoamine oxidase A (MAOA) - in the brain of aggressive and tame rats. Either TC-2153 (10 or 20 mg/kg) or vehicle was administered once intraperitoneally to aggressive and tame male rats. TPH2 and MAOA enzymatic activities and mRNA and protein levels were assessed. The selection for high aggression resulted in upregulation of Tph2 mRNA in the midbrain, of the TPH2 protein in the hippocampus, and of proteins TPH2 and MAOA in the hypothalamus, as compared to tame rats. MAO enzymatic activity was higher in the midbrain and hippocampus of aggressive rats while TPH2 activity did not differ between the strains. The single TC-2153 administration decreased TPH2 and MAO activity in the hypothalamus and midbrain, respectively. The drug affected MAOA protein levels in the hypothalamus: upregulated them in aggressive rats and downregulated them in tame ones. Thus, this study shows profound differences in the expression and activity of key serotonergic system enzymes in the brain of rats selectively bred for either highly aggressive behavior toward humans or its absence, and the effects of benzopentathiepin TC-2153 on these enzymes may point to mechanisms of its antiaggressive action.

Anti-Depressant Like Effects of Aethoscytus Foveolus Oil by Improving Stress-mediated Alterations of Monoamine Oxidase, Oxidative Stress, and Neuroinflammation In-vivo.

Depression is a neuropsychological disorder with a complex pathophysiology and its pharmacotherapy is compromised by adverse side effects. Addressing the need for effective treatment for depression, the current study aims to characterize the antidepressant activity of oil extract derived from Aethoscytus foveolus, bugs that are widely available in India, in a mice model of stress-induced depression. Chemical moieties characterized by GC-MS of A. foveolus oil extract have shown good affinity for monoamine oxidase A (MAO-A) in-silico. In-vitro MAO-inhibitory assay using mouse brain homogenates also showed similar results at IC50 1.363 nM (R2 = 0.981, SD ± 0.05, n = 3) of it. These results encouraged us to investigate the antidepressant potential of this oil extract in vivo. Stress-exposed mice (Swiss Albino, either sex, 25-30 gm) were administered 5 and 10 mg/kg doses of oil extract and classified as separate groups (N = 6 per group). Behavioral tests like the forced-swim test, tail-suspension test, and open-field test demonstrated significant attenuation of stress-induced depressive-like behavior of mice by both doses (p < 0.0001 with positive control group i.e., stress group), while biochemical tests on mice brain tissues showed amelioration of stress-induced hyperactivation of MAO (p < 0.0001) and oxidative stress (by increasing Superoxide dismutase and catalase, while reducing lipid peroxidase and nitric oxide) (p < 0.0001). The altered mRNA expression of proinflammatory cytokines (NF-κB, IL-6, IL-12, and TNF-α) (p < 0.015) was also improved by this oil extract. In addition, histopathology of hippocampus tissues of mice supports that this oil recovers stress-mediated structural changes of the brain. In conclusion our findings suggest that oil derived from A. foveolus could be beneficial in the alleviation of stress-mediated depressive-like behavior of mice, and in our knowledge, this is the first report identifying anti-neurodegenerative potential of A. foveolus.

Association between serum catecholamine levels and VNTR polymorphism in the promoter region of the monoamine oxidase A gene in forensic autopsy cases.

Monoamine oxidase A (MAOA) catalyzes oxidative deamination of catecholamines. A functional variable number tandem repeat (VNTR) polymorphism in the promoter region of the MAOA gene has been previously reported. In the present study, we measured serum adrenaline (Adr), noradrenaline (Nad), and dopamine (DA) levels in 90 male and 34 female Japanese autopsy cases in which amphetamines or psychotropic drugs were not detected.We examined the frequencies of MAOA-uVNTR alleles in these cases and investigated the effects of the MAOA-uVNTR polymorphism on serum Adr, Nad, and DA levels. Evaluation indicated no significant association between MAOA-uVNTR polymorphism and serum Adr, Nad, or DA levels in males, although a significant association between MAOA-uVNTR polymorphism and serum Adr and DA levels were observed in females. Females with the 3/3 genotype had higher serum Adr and DA levels than those with a 4-repeat allele (3/4 and 4/4 genotypes) (p = 0.048 and 0.020, respectively). There was no significant association between MAOA-uVNTR polymorphism and serum Nad levels in females. The present study indicates that MAOA-uVNTR polymorphism influences serum Adr and DA levels only in females.

Effects of association between resveratrol and ketamine on behavioral and biochemical analysis in mice.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a phenol commonly found in grapes and wine, has been associated as protective in experimental models involving alterations in different neurotransmitter systems. However, studies are reporting that resveratrol could have adverse effects. This study evaluated if the association of a low dose of ketamine and resveratrol could induce behavioral manifestations associated with biochemical alterations. Moreover, the effects of treatment with resveratrol and/or ketamine on monoamine oxidase (MAO) activity, oxidative stress markers, and IL-6 levels in the brain were also investigated. Male Swiss mice received a low dose of ketamine (20 mg/kg) for 14 consecutive days, and resveratrol (10, 30, or 100 mg/kg) from day 8 up to day 14 of the experimental period, intraperitoneally. Locomotor, stereotyped behavior, Y-maze, novel recognition object test (NORT), and social interaction were quantified as well as ex vivo analysis of MAO activity, IL-6 levels, and oxidative stress markers (TBARS and total thiol levels) in brain tissues. Ketamine per se reduced the number of bouts of stereotyped behavior on day 8 of the experimental period. Resveratrol per se reduced the locomotor and exploratory activity in the open field, the time of exploration of new objects in the NORT, MAO-A activity in the striatum and increased the IL-6 levels in the cortex. These effects were attenuated when the mice were co-treated with ketamine and resveratrol. There was a decrease in MAO-A activity in the cortex of mice treated with ketamine + resveratrol 100 mg/kg. No significant alterations were found in oxidative stress markers. Resveratrol does not appear to cause summative effects with ketamine on behavioral alterations. However, the effect of resveratrol per se, mainly on locomotor and exploratory activity, should be better investigated.

Identification and Evaluation of Olive Phenolics in the Context of Amine Oxidase Enzyme Inhibition and Depression: In Silico Modelling and In Vitro Validation.

The Mediterranean diet well known for its beneficial health effects, including mood enhancement, is characterised by the relatively high consumption of extra virgin olive oil (EVOO), which is rich in bioactive phenolic compounds. Over 200 phenolic compounds have been associated with Olea europaea, and of these, only a relatively small fraction have been characterised. Utilising the OliveNetTM library, phenolic compounds were investigated as potential inhibitors of the epigenetic modifier lysine-specific demethylase 1 (LSD1). Furthermore, the compounds were screened for inhibition of the structurally similar monoamine oxidases (MAOs) which are directly implicated in the pathophysiology of depression. Molecular docking highlighted that olive phenolics interact with the active site of LSD1 and MAOs. Protein-peptide docking was also performed to evaluate the interaction of the histone H3 peptide with LSD1, in the presence of ligands bound to the substrate-binding cavity. To validate the in silico studies, the inhibitory activity of phenolic compounds was compared to the clinically approved inhibitor tranylcypromine. Our findings indicate that olive phenolics inhibit LSD1 and the MAOs in vitro. Using a cell culture model system with corticosteroid-stimulated human BJ fibroblast cells, the results demonstrate the attenuation of dexamethasone- and hydrocortisone-induced MAO activity by phenolic compounds. The findings were further corroborated using human embryonic stem cell (hESC)-derived neurons stimulated with all-trans retinoic acid. Overall, the results indicate the inhibition of flavin adenine dinucleotide (FAD)-dependent amine oxidases by olive phenolics. More generally, our findings further support at least a partial mechanism accounting for the antidepressant effects associated with EVOO and the Mediterranean diet.

REM sleep behavior disorder in Brunner syndrome.

Brunner syndrome is a recessive X-linked disorder characterized by intellectual disability and impulsive aggressiveness associated with Monoamine Oxidase-A (MAOA) deficiency leading to increased monoaminergic activity. We report the presence of REM sleep behavior disorder (RBD) in a 46-year-old patient with Brunner syndrome due to a c.1438A>G/iVS14-2 A>G mutation of the MAOA gene. He suffered from mild intellectual disability and psychotic disturbances. He presented a 15-year history of nightmares (chase, attacks and fights), sleep-related vocalizations and motor behaviors characterized by talking, screaming, crying, gesturing, punching, and kicking. Video-polysomnography showed RBD characterized by excessive tonic and phasic muscle activity in the mentalis and limb muscles with dream enacting behaviors during REM sleep. Clonazepam achieved a significant reduction of RBD symptomatology. We conclude that RBD can be a manifestation of Brunner syndrome probably due to an increased monoaminergic neurotransmission occurring in this rare genetic disorder.

Antidepressant-like effects of Cimicifuga dahurica (Turcz.) Maxim. via modulation of monoamine regulatory pathways.

Sheng-ma is recorded in the Compendium of Materia Medica and mainly originates from the rhizomes of Cimicifuga dahurica (Turcz.) Maxim. (CD), Cimicifuga heracleifolia Kom. and Cimicifuga foetida L. The alcoholic extract of Cimicifuga foetida L. (Brand name: Ximingting®) has been approved for the treatment of perimenopausal symptoms accompanying hot flash, depression and anxiety in China. However, there's no further study about the antidepressant-like effects of C. dahurica (CD). The aim of this study is to investigate the antidepressant-like effect of CD extracted by 75% ethanol and its possible mechanisms.The neuro-protective effects of CD on injured PC12 cells induced by corticosterone was measured firstly. Then, forced swim test (FST), tail suspension test (TST), reserpine-induced hypothermia, 5-hydroxytryptophan (5-HTP) induced head twitch response in mice and chronic unpredictable mild stress (CUMS) on sucrose preference tests were executed. Moreover, the potential mechanisms were explored by measuring levels of monoamine neurotransmitter in mice frontal cortex and hippocampus, testing monoamine oxidase enzyme A (MAO-A) activities in the brains of CUMS-exposed mice. Results showed that CD (60, 120 mg/kg) can significantly decreased the immobility period in FST and TST in mice without affecting locomotor activity. CD (30 mg/kg, 60 mg/kg, 120 mg/kg) could significantly counteracted reserpine-induced hypothermia and increased the number of head-twitches in 5-HTP induced head twitch response. It was also found that the monoamine neurotransmitter levels in the hippocampus and frontal cortex were significantly increased in 60 mg/kg and 120 mg/kg CD treated mice. In addition, CD (60 and 120 mg/kg) significantly inhibited MAO-A after 6-week CUMS exposure. CD can effectively produce an antidepressant-like effect, which involved with modulation of monoamine regulatory pathways.

Concerted monoamine oxidase activity following exposure to di-2-ethylhexyl phthalate is associated with aggressive neurobehavioral response and neurodegeneration in zebrafish brain.

Di-2-ethylhexyl phthalate (DEHP) is the most commonly preferred synthetic organic chemical in plastics and its products for making them ductile, flexible and durable. As DEHP is not chemically bound to the macromolecular polymer of plastics, it can be easily leached out to accumulate in food and environment. Our recent report advocated that exposure to DEHP significantly transformed the innate bottom-dwelling and scototaxis behaviour of zebrafish. Our present study aimed to understand the possible role of DEHP exposure pertaining towards the development of aggressive behaviour and its association with amplified monoamine oxidase activity and neurodegeneration in the zebrafish brain. As heightened monoamine oxidase (MAO) is linked with genesis of aggressive behaviour, our observation also coincides with DEHP-persuaded aggressive neurobehavioral transformation in zebrafish. Our preliminary findings also showed that DEHP epitomized as a prime factor in transforming native explorative behaviour and genesis of aggressive behaviour through oxidative stress induction and changes in the neuromorphology in the periventricular grey zone (PGZ) of the zebrafish brain. With the finding demarcating towards heightened chromatin condensation in the PGZ of zebrafish brain, our further observation by immunohistochemistry showed a profound augmentation in apoptotic cell death marker cleaved caspase 3 (CC3) expression following exposure to DEHP. Our further observation by immunoblotting study also demarcated a temporal augmentation in CC3 and tyrosine hydroxylase expression in the zebrafish brain. Therefore, the gross findings of the present study delineate the idea that chronic exposure to DEHP is associated with MAO-instigated aggressive neurobehavioral transformation and neurodegeneration in the zebrafish brain.

Does Cell-Type-Specific Silencing of Monoamine Oxidase B Interfere with the Development of Right Ventricle (RV) Hypertrophy or Right Ventricle Failure in Pulmonary Hypertension?

Increased mitochondrial reactive oxygen species (ROS) formation is important for the development of right ventricular (RV) hypertrophy (RVH) and failure (RVF) during pulmonary hypertension (PH). ROS molecules are produced in different compartments within the cell, with mitochondria known to produce the strongest ROS signal. Among ROS-forming mitochondrial proteins, outer-mitochondrial-membrane-located monoamine oxidases (MAOs, type A or B) are capable of degrading neurotransmitters, thereby producing large amounts of ROS. In mice, MAO-B is the dominant isoform, which is present in almost all cell types within the heart. We analyzed the effect of an inducible cardiomyocyte-specific knockout of MAO-B (cmMAO-B KO) for the development of RVH and RVF in mice. Right ventricular hypertrophy was induced by pulmonary artery banding (PAB). RV dimensions and function were measured through echocardiography. ROS production (dihydroethidium staining), protein kinase activity (PamStation device), and systemic hemodynamics (in vivo catheterization) were assessed. A significant decrease in ROS formation was measured in cmMAO-B KO mice during PAB compared to Cre-negative littermates, which was associated with reduced activity of protein kinases involved in hypertrophic growth. In contrast to littermates in which the RV was dilated and hypertrophied following PAB, RV dimensions were unaffected in response to PAB in cmMAO-B KO mice, and no decline in RV systolic function otherwise seen in littermates during PAB was measured in cmMAO-B KO mice. In conclusion, cmMAO-B KO mice are protected against RV dilatation, hypertrophy, and dysfunction following RV pressure overload compared to littermates. These results support the hypothesis that cmMAO-B is a key player in causing RV hypertrophy and failure during PH.

A Key Mediator and Imaging Target in Alzheimer's Disease: Unlocking the Role of Reactive Astrogliosis Through MAOB.

Astrocytes primarily maintain physiological brain homeostasis. However, under various pathological conditions, they can undergo morphological, transcriptomic, and functional transformations, collectively referred to as reactive astrogliosis. Recent studies have accumulated lines of evidence that reactive astrogliosis plays a crucial role in the pathology of Alzheimer's disease (AD). In particular, monoamine oxidase B, a mitochondrial enzyme mainly expressed in astrocytes, significantly contributes to neuronal dysfunction and neurodegeneration in AD brains. Moreover, it has been reported that reactive astrogliosis precedes other pathological hallmarks such as amyloid-beta plaque deposition and tau tangle formation in AD. Due to the early onset and profound impact of reactive astrocytes on pathology, there have been extensive efforts in the past decade to visualize these cells in the brains of AD patients using positron emission tomography (PET) imaging. In this review, we summarize the recent studies regarding the essential pathological importance of reactive astrocytes in AD and their application as a target for PET imaging.

Kinetic modeling of the monoamine oxidase-B radioligand [18F]SMBT-1 in human brain with positron emission tomography.

This paper describes pharmacokinetic analyses of the monoamine-oxidase-B (MAO-B) radiotracer [18F](S)-(2-methylpyrid-5-yl)-6-[(3-fluoro-2-hydroxy)propoxy]quinoline ([18F]SMBT-1) for positron emission tomography (PET) brain imaging. Brain MAO-B expression is widespread, predominantly within astrocytes. Reactive astrogliosis in response to neurodegenerative disease pathology is associated with MAO-B overexpression. Fourteen elderly subjects (8 control, 5 mild cognitive impairment, 1 Alzheimer's disease) with amyloid ([11C]PiB) and tau ([18F]flortaucipir) imaging assessments underwent dynamic [18F]SMBT-1 PET imaging with arterial input function determination. [18F]SMBT-1 showed high brain uptake and a retention pattern consistent with the known MAO-B distribution. A two-tissue compartment (2TC) model where the K1/k2 ratio was fixed to a whole brain value best described [18F]SMBT-1 kinetics. The 2TC total volume of distribution (VT) was well identified and highly correlated (r2∼0.8) with post-mortem MAO-B indices. Cerebellar grey matter (CGM) showed the lowest mean VT of any region and is considered the optimal pseudo-reference region. Simplified analysis methods including reference tissue models, non-compartmental models, and standard uptake value ratios (SUVR) agreed with 2TC outcomes (r2 > 0.9) but with varying bias. We found the CGM-normalized 70-90 min SUVR to be highly correlated (r2 = 0.93) with the 2TC distribution volume ratio (DVR) with acceptable bias (∼10%), representing a practical alternative for [18F]SMBT-1 analyses.

Non-cytotoxic 3-Acetylcoumarin as an Attractive Target for Human Monoamine Oxidase (HMAO) Enzymes.

BACKGROUND/AIM: Coumarins are a broad class of naturally occurring oxygen-heterocyclic compounds found in plants with diverse biological properties, making them attractive for evaluation as novel therapeutic agents. We herein report the in vitro cytotoxic and monoamine oxidase (MAO) inhibitory activities of 3-acetylcoumarins (6a-e). MATERIALS AND METHODS: The cytotoxic activity was evaluated using crystal violet dye binding assay, and those compounds unable to induce cytotoxicity were further tested for the monoamine oxidase (MAO) activity using the MAO-GloTM kit. RESULTS: The 3-acetylcoumarins (6a-e) were non-cytotoxic (inactive) against MDA MB-231 (estrogen receptor-negative, ER-, highly invasive) and MCF-7 (estrogen receptor-positive, ER+, weakly invasive) breast cancer cell lines, but showed interesting MAOs inhibition activities. Among the synthesized compounds, 3-acetylcoumarin bearing dichloro (-diCl) (6d; IC50=0.31±0.04 µM) at Carbon-7, 8 positions showed higher inhibition, MAO B/A non-selectivity (selectivity index, SI=3.10), reversible inhibition against the hMAO-B enzyme, and neuroprotection against H2O2-treated human neuroblastoma (N2a) cells. CONCLUSION: Compound (6d) can be considered a promising scaffold for further investigation in developing hMAO-B inhibitors (MAOIs).

5,7-dihydroxy-3',4',5'-trimethoxyflavone mitigates lead induced neurotoxicity in rats via its chelating, antioxidant, anti-inflammatory and monoaminergic properties.

Chronic exposure to lead (Pb) induces neurodegenerative changes in animals and humans. Drugs with strong antioxidant properties are effective against Pb-mediated neurotoxicity. In a prior study, we identified 5,7-dihydroxy-3',4',5'-trimethoxyflavone (TMF) from Ocimum basilicum L. leaves as a potent antioxidant and neuroprotective compound. This research explores TMF's neuroprotective effects against Pb-induced brain toxicity in rats to establish it as a therapeutic agent. Rats received lead acetate (100 mg/kg, orally, once daily) for 30 days to induce brain injury, followed by TMF treatment (5 and 10 mg/kg, oral, once daily) 30 min later. Cognitive and motor functions were assessed using Morris Water Maze and horizontal bar tests. Lead, monoamine oxidase (MAO) A and B enzymes, reduced glutathione (GSH), thiobarbituric acid reactive species (TBARS), Tumor necrosis factor-alpha (TNF-α), and IL-6 levels were measured in the hippocampus and cerebellum. Pb exposure impaired cognitive and motor functions, increased Pb, TBARS, TNF-α, and IL-6 levels, and compromised MAO A & B and GSH levels. TMF reversed Pb-induced memory and motor deficits and normalized biochemical anomalies. TMF's neuroprotective effects against lead involve chelating, antioxidant, anti-inflammatory, and monoaminergic properties, suggesting its potential as a treatment for metal-induced brain injury.

Identification and optimization of nitrophenolic analogues as dopamine metabolic enzyme inhibitors for the treatment of Parkinson's disease.

Progressive loss of dopaminergic neurons leads to the depletion of the striatal neurotransmitter dopamine, which is the main cause of Parkinson's disease (PD) motor symptoms. Simultaneous inhibition of the two key dopamine metabolic enzymes, catechol-O-methyltransferase (COMT) and monoamine oxidase B (MAO-B), could potentially be a breakthrough in achieving clinical efficacy. Representative compound C12 exhibits good COMT inhibitory activity (IC50 = 0.37 µM), metal chelation ability, and BBB permeability. Furthermore, results from in vivo biological activity evaluations indicate that C12 can improve dopamine levels and ameliorate MPTP-induced PD symptoms in mice. Preliminary in vivo and in vitro study results highlight the potential of compound C12 in PD treatment.

Dihydroxanthene-based monoamine oxidase A-activated photosensitizers for photodynamic/photothermal therapy of tumors.

Small molecule photosensitizers for combined in vivo tailored cancer diagnostics and photodynamic/photothermal therapy are desperately needed. Monoamine oxidase A (MAO-A)-activated therapeutic and diagnostic compounds provide great selectivity because MAO-A can be employed as a biomarker for associated Tumors. In order to screen photosensitizers with photodynamic therapeutic potential, we have created a range of near-infrared fluorescent molecules in this work by combining dihydroxanthene parent with various heterocyclic fluorescent dyes. The NIR fluorescent diagnostic probe, DHMQ, was created by combining the screened fluorescent dye matrices with the propylamino group, which is the recognition moiety of MAO-A, based on the oxidative deamination mechanism of the enzyme. This probe has a low toxicity level and can identify MAO-A precisely. It has the ability to use fluorescence imaging on mice and cells to track MAO-A activity in real-time. It has strong phototoxicity and can produce singlet oxygen when exposed to laser light. The temperature used in photothermal imaging can get up to 50 °C, which can harm tumor cells permanently and have a positive phototherapeutic impact on tumors grown from SH-SY5Y xenograft mice. The concept of using MAO-A effectively in diseases is expanded by the MAO-A-activated diagnostic-integrated photosensitizers, which offer a new platform for in vivo cancer diagnostics and targeted anticancer treatment.

Rational design, synthesis, biological evaluation, and molecular modeling of novel naphthamide derivatives possessing potent, reversible, and competitive inhibitory mode of action over human monoamine oxidase.

Herein, a novel series of naphthamide derivatives has been rationally developed, synthesized, and evaluated for their inhibitory activity against monoamine oxidase (MAO) and cholinesterase (ChE) enzymes. Compared to the reported naphthalene-based hit IV, the new naphthamide hybrids 2a, 2c, 2g and 2h exhibited promising MAO inhibitory activities; with an IC50 value of 0.294 µM, compound 2c most potently inhibited MAO-A, while compound 2g exhibited most potent MAO-B inhibitory activity with an IC50 value of 0.519 µM. Compounds 2c and 2g showed selectivity index (SI) values of 6.02 for MAO-A and 2.94 for MAO-B, respectively. On the other hand, most compounds showed weak inhibitory activity against ChEs except 2a and 2h over butyrylcholinesterase (BChE). The most potent compounds 2c and 2g were found to be competitive and reversible MAO inhibitors based on kinetic and reversibility studies. Plausible interpretations of the observed biological effects were provided through molecular docking simulations. The drug-likeness predicted by SwissADME and Osiris property explorer showed that the most potent compounds (2a, 2c, 2g, and 2h) obey Lipinski's rule of five. Accordingly, in the context of neurological disorders, hybrids 2c and 2g may contribute to the identification of safe and potent therapeutic approaches in the near future.

A magnetic beads-based ligand fishing method for rapid discovery of monoterpene indoles as monoamine oxidase A inhibitors from Hunteria zeylanica.

In this study, a novel magnetic bead-based ligand fishing method was developed for rapid discovery of monoterpene indoles as monoamine oxidase A inhibitors from natural products. In order to improve the screening efficiency, two different magnetic beads, i.e. amine and carboxyl terminated magnetic beads, were comprehensively compared in terms of their ability to immobilize monoamine oxidase A (MAOA), biocatalytic activity and specific adsorption rates for affinity ligands. Carboxyl terminated magnetic beads performed better for MAOA immobilization and demonstrated superior performance in ligand fishing. The MAOA immobilized magnetic beads were applied to screen novel monoamine oxidase inhibitors in an alkaloid-rich plant, Hunteria zeylanica. Twelve MAOA affinity ligands were screened out, and ten of them were identified as monoterpene indole alkaloids by HPLC-Obitrap-MS/MS. Among them, six ligands, namely geissoschizol, vobasinol, yohimbol, dihydrocorynanthenol, eburnamine and (+)-isoeburnamine which exhibited inhibitory activity against MAOA with low IC50 values. To further explore their inhibitory mechanism, enzyme kinetic analysis and molecular docking studies were conducted.

Simultaneous mass spectrometric quantification of trace amines, their precursors and metabolites.

OBJECTIVES: Trace amines are powerful neuromodulators influencing the release and reuptake of catecholamines. These low concentrated endogenous amines impact mood, cognition, and hormone regulation. Dysregulation of trace amines have been associated with a variety of diseases, such as schizophrenia, Parkinson's disease, migraine, depression and more. Succesfull simultaneous quantification of trace amines, their precursors and metabolites would benefit both research and patient care. Since these compounds have various functional groups and are present in biological matrices with large concentration difference, their simultaneous quantification is an analytical challenge. Our goal was to develop a highly sensitive LC-MS/MS assay to simultaneously quantify trace amines, their precursors and metabolites in plasma. METHODS: Our method is based on a simple two-step in-matrix derivatization protocol: propionic anhydride (PA) and 3-Ethyl-1-[3-(dimethylamino)propyl]carbodiimide (EDC) in combination with 2,2,2-trifluoroethylamine (TFEA) followed by online solid phase extraction combined with LC-MS/MS. Fifteen metabolites can be measured simultaneously, three precursors, eight trace amines and four metabolites. Validation of this method was performed according to international validation guidelines. The pre-analytical stability of trace amines was assessed. RESULTS: This novel method was successful in quantifying trace amines, their precursors, and metabolites in plasma. Using just 50 µl human plasma, we were able to accomplish limit of quantification for 2-phenylethylamine and N-methyl-phenylethylamine of 0.2 nmol/L and 0.1 nmol/L for tyramine and n-methyltyramine. Inter-and intra-assay imprecision was < 15 % for all analytes. Stability assessment showed susceptibility of certain trace amines e.g. 2-phenylethylamine and N-methyl-phenylethylamine to enzymatic degradation in plasma. The addition of the monoamine oxidase inhibitor pargyline to plasma prevented this enzymatic degradation. CONCLUSIONS: We developed a novel LC-MS/MS method that1) uses a new double derivatization technique, 2) is automated with online SPE, 3) uses far less sample volume then previous methods and 4) detects more components in the same sample (eight trace amines, three precursors, and four metabolites) with high specificity and selectivity. Furthermore, addition of MAO A/B inhibitor prevents degradation and guarantees more accurate quantification of trace amines.

Alterations in the brain serotonin system and serotonin-regulated behavior during aging in zebrafish males and females.

The brain serotonin (5-HT) system performs a neurotrophic function and supports the plasticity of the nervous system, while its age-related changes can increase the risk of senile neurodegeneration. Zebrafish brain is highly resistant to damage and neurodegeneration due to its high regeneration potential and it is a promising model object in searching for molecular factors preventing age-related neurodegeneration. In the present study alterations in 5-HT-related behavior in the home tank and the novel tank diving test, as well as 5-HT, 5-HIAA levels, tryptophan hydroxylase (TPH), monoamine oxidase (MAO) activity and the expression of genes encoding TPH, MAO, 5-HT transporter and 5-HT receptors in the brain of 6, 12, 24 and 36 month old zebrafish males and females are investigated. Marked sexual dimorphism in the locomotor activity in the novel tank test is revealed: females of all ages move slower than males. No sexual dimorphism in 5-HT-related traits is observed. No changes in 5-HT and 5-HIAA levels in zebrafish brain during aging is observed. At the same time, the aging is accompanied by a decrease in the locomotor activity, TPH activity, tph2 and htr1aa genes expression as well as an increase in the MAO activity and slc6a4a gene expression in their brain. These results indicate that the brain 5-HT system in zebrafish is resistant to age-related alterations.