Inhibitors of MAO-A and MAO-B in Psychiatry and Neurology

Enhancing monoamine oxidase B inhibitory activity via chiral fluorination: Structure-activity relationship, biological evaluation, and molecular docking study

Parkinson's disease (PD) is a common neurodegenerative disease among the elderly. Currently, monoamine oxidase B (MAO-B) inhibitors are extensively used for PD in clinics. In this work, a series of novel chiral fluorinated pyrrolidine derivatives were designed and synthesized. In vitro biological evaluations revealed that compound D5 was the most potent, selective MAO-B inhibitor (IC₅₀ = 0.019 μM, MAO-A/MAO-B selectivity index = 2440), which was 10-fold than that of miracle drug safinamide (IC₅₀ = 0.163 μM, MAO-A/MAO-B selectivity index = 172). It was verified that the enhanced hydrophobic interaction of D5 improved the activity against MAO-B in molecular docking study. Besides, D5 exhibited excellent metabolic properties and pharmacokinetic profiles in monkeys and rats. Moreover, D5 displayed more efficacious than safinamide in vivo models. In the MPTP-induced PD mouse model, D5 significantly alleviated DA deficits and increased the effect of levodopa on dopamine concentration in the striatum. Meanwhile, D5 produced a prominent reduction in tremulous jaw movements induced by galantamine. Accordingly, we present D5 as a novel, highly potent, and selective MAO-B inhibitor for PD therapy.

Neuroprotective and anxiolytic potential of green rooibos (Aspalathus linearis) polyphenolic extract

South African rooibos (Aspalathus linearis) tea is globally consumed for its health benefits and caffeine free nature, but no information is available on the neuroprotective capacity of (unfermented) green rooibos. Our aim was to investigate the cytoprotective activity of green rooibos in neuronal cells, including probing antioxidant and enzyme inhibitory properties that could explain observed effects in these cells. We also investigated the anxiolytic potential of green rooibos using zebrafish larval models. Green rooibos extract (Green oxithin™) was assessed for its neuroprotective potential in Neuro-2a cells treated with different concentrations of the extract (12.5-25-50-100 μg mL^-1) and different concentrations of hydrogen peroxide (250 or 125 μM) as oxidizing agent. Cell viability (MTT) and redox status (intracellular ROS) were also quantified in these cells. Antioxidant properties of the extract were quantified using cell-free systems (DPPH, ORAC and xanthine/xanthine oxidase), and potential neuroprotection evaluated in terms of its potential to inhibit key enzymes of the CNS (monoamine oxidase A (MOA-A), acetylcholinesterase (AChE) and tyrosinase (TYR)). Results demonstrated that green rooibos extract exerted significant cytoprotective properties in Neuro-2a cells, particularly when exposed to lethal 250 μM hydrogen peroxide, increasing cell survival by more than 100%. This may be ascribed (at least partially) to its capacity to limit intracellular ROS accumulation in these cells. Data from cell-free systems confirmed that green rooibos was able to scavenge free radicals (synthetic and physiological) in a dose dependent manner with a similar profile activity to vitamins C and E. Green rooibos also acted as a moderate MAO-A inhibitor, but had no significant effect on AChE or TYR. Finally, zebrafish larvae treated with lower doses of green rooibos demonstrated a significant anxiolytic effect in the light-dark anxiety model. Using the PTZ excitotoxicity model, green rooibos was shown to rescue GABA receptor signalling, which together with its demonstrated inhibition of MAO-A, may account for the anxiolytic outcome. Current data confirms that green rooibos could be considered a "functional brain food" and may be a good option as starting ingredient in the development of new nutraceuticals.

Rodrigues K, Pinz MP, Biondi JV, Becker NP, Blodorn E, Domingues WB, Larroza A, Campos VF, Alves D, Wilhelm EA, Luchese C. Prospecting for a quinoline containing selenium for comorbidities depression and memory impairment induced by restriction stress in mice

RATIONALE

Depression is often associated with memory impairment, a clinical feature of Alzheimer's disease (AD), but no effective treatment is available. 7-Chloro-4-(phenylselanyl) quinoline (4-PSQ) has been studied in experimental models of diseases that affect the central nervous system.

OBJECTIVES

The pharmacological activity of 4-PSQ in depressive-like behavior associated with memory impairment induced by acute restraint stress (ARS) in male Swiss mice was evaluated.

METHODS

ARS is an unavoidable stress model that was applied for a period of 240 min. Ten minutes after ARS, animals were intragastrically treated with canola oil (10 ml/kg) or 4-PSQ (10 mg/kg) or positive controls (paroxetine or donepezil) (10 mg/kg). Then, after 30 min, mice were submitted to behavioral tests. Corticosterone levels were evaluated in plasma and oxidative stress parameters; monoamine oxidase (MAO)-A and MAO -B isoform activity; mRNA expression levels of kappa nuclear factor B (NF-κB); interleukin (IL)-1β, IL-18, and IL-33; phosphatidylinositol-se-kinase (PI3K); protein kinase B (AKT2), as well as acetylcholinesterase activity were evaluated in the prefrontal cortex and hippocampus.

RESULTS

4-PSQ attenuated the depressive-like behavior, self-care, and memory impairment caused by ARS. Based on the evidence, we believe that effects of 4-PSQ may be associated, at least in part, with the attenuation of HPA axis activation, attenuation of alterations in the monoaminergic system, modulation of oxidative stress, reestablishment of AChE activity, modulation of the PI3K/AKT2 pathway, and reduction of neuroinflammation.

CONCLUSIONS

These results suggested that 4-PSQ exhibited an antidepressant-like effect and attenuated the memory impairment induced by ARS, and it is a promising molecule to treat these comorbidities.

Synthesis of novel thiazolyl hydrazone derivatives as potent dual monoamine oxidase-aromatase inhibitors

The inhibitory effects of 2-thiazolyl hydrazones on monoamine oxidase enzymes are known for a long time. In this study, a new series of 2-thiazolyl hydrazone derivatives were synthesized starting from 6-methoxy-2-naphthaldehyde. All of the synthesized compounds were investigated in terms of their monoamine oxidase (MAO) inhibitory effects and significant results were found. The results showed that compound 2j potently inhibited MAO-A and MAO-B, while compound 2t strongly and selectively inhibited MAO-B compared to standard drugs. Compounds 2k and 2q exhibited selective and satisfying inhibition on MAO-B. In the aromatase inhibition studies of the compounds, it was determined that compounds 2q and 2u had high inhibitory properties. Molecular docking studies on MAO-A, MAO-B, and aromatase enzymes were carried out for the aforementioned compounds. Additionally, molecular dynamics simulation was studied for compound 2q on MAO-B and aromatase complexes. Finally, the Field-based QSAR study was developed and the structure-activity relationship (SAR) was explained. For the first time, dual inhibitors on MAO and aromatase enzyme were investigated together. The aim of this approach is for finding the potential agents that do not cause the cognitive disorders and may even treat neurodegenerative symptoms, thus, the aim was reached successfully.

Brain injury and inflammation genes common to a number of neurological diseases and the genes involved in the genesis of GABAnergic neurons are altered in monoamine oxidase B knockout mice

Monoamine oxidase B (MAO B) oxidizes trace amine phenylethylamine (PEA), and neurotransmitters serotonin and dopamine in the brain. We reported previously that PEA levels increased significantly in all brain regions, but serotonin and dopamine levels were unchanged in MAO B knockout (KO) mice. PEA and dopamine are both synthesized from phenylalanine by aromatic L-amino acid decarboxylase in dopaminergic neurons in the striatum. A high concentration of PEA in the striatum may cause dopaminergic neuronal death in the absence of MAO B. We isolated the RNA from brain tissue of MAO B KO mice (2-month old) and age-matched wild type (WT) male mice and analyzed the altered genes by Affymetrix microarray. Differentially expressed genes (DEGs) in MAO B KO compared to WT mice were analyzed by Partek Genomics Suite, followed by Ingenuity Pathway Analysis (IPA) to assess their functional relationships. DEGs in MAO B KO mice are involved in brain inflammation and the genesis of GABAnergic neurons. The significant DEGs include four brain injury or inflammation genes (upregulated: Ido1, TSPO, AVP, Tdo2), five gamma-aminobutyric acid (GABA) receptors (down-regulated: GABRA2, GABRA3, GABRB1, GABRB3, GABRG3), five transcription factors related to adult neurogenesis (upregulated: Wnt7b, Hes5; down-regulated: Pax6, Tcf4, Dtna). Altered brain injury and inflammation genes in MAO B knockout mice are involved in various neurological disorders: attention deficit hyperactive disorder, panic disorder, obsessive compulsive disorder, autism, amyotrophic lateral sclerosis, Parkinson's diseases, Alzheimer's disease, bipolar affective disorder. Many were commonly involved in these disorders, indicating that there are overlapping molecular pathways.

Dietary Intake of Flavonoids and Carotenoids Is Associated with Anti-Depressive Symptoms: Epidemiological Study and In Silico-Mechanism Analysis

Flavonoids and carotenoids are bioactive compounds that have protective effects against depressive symptoms. Flavonoids and carotenoids are the two main types of antioxidant phytochemicals. This study investigated the association between flavonoid and carotenoid intake and depressive symptoms in middle-aged Korean females. We analyzed the mechanism of these associations using an in silico method. Depressive symptoms were screened using the Beck Depression Inventory-II (BDI-II), and flavonoid and carotenoid intake were assessed using a semi-quantitative food frequency questionnaire. Using a multivariate logistic regression model, we found that flavones, anthocyanins, individual phenolic compounds, lycopene, and zeaxanthin were negatively associated with depressive symptoms. In silico analysis showed that most flavonoids have high docking scores for monoamine oxidase A (MAOA) and monoamine oxidase B (MAOB), which are two important drug targets in depression. The results of the docking of brain-derived neurotrophic factor (BDNF) and carotenoids suggested the possibility of allosteric activation of BDNF by carotenoids. These results suggest that dietary flavonoids and carotenoids can be utilized in the treatment of depressive symptoms.

Brunner syndrome associated MAOA mutations result in NMDAR hyperfunction and increased network activity in human dopaminergic neurons

Monoamine neurotransmitter abundance affects motor control, emotion, and cognitive function and is regulated by monoamine oxidases. Among these, Monoamine oxidase A (MAOA) catalyzes the degradation of dopamine, norepinephrine, and serotonin into their inactive metabolites. Loss-of-function mutations in the X-linked MAOA gene have been associated with Brunner syndrome, which is characterized by various forms of impulsivity, maladaptive externalizing behavior, and mild intellectual disability. Impaired MAOA activity in individuals with Brunner syndrome results in bioamine aberration, but it is currently unknown how this affects neuronal function, specifically in dopaminergic (DA) neurons. Here we generated human induced pluripotent stem cell (hiPSC)-derived DA neurons from three individuals with Brunner syndrome carrying different mutations and characterized neuronal properties at the single cell and neuronal network level in vitro. DA neurons of Brunner syndrome patients showed reduced synaptic density but exhibited hyperactive network activity. Intrinsic functional properties and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-mediated synaptic transmission were not affected in DA neurons of individuals with Brunner syndrome. Instead, we show that the neuronal network hyperactivity is mediated by upregulation of the GRIN2A and GRIN2B subunits of the N-methyl-d-aspartate receptor (NMDAR), resulting in increased NMDAR-mediated currents. By correcting a MAOA missense mutation with CRISPR/Cas9 genome editing we normalized GRIN2A and GRIN2B expression, NMDAR function and neuronal population activity to control levels. Our data suggest that MAOA mutations in Brunner syndrome increase the activity of dopaminergic neurons through upregulation of NMDAR function, which may contribute to the etiology of Brunner syndrome associated phenotypes.

α-Tertiary Propargylamine Synthesis via KA2-Type Coupling Reactions under Solvent-Free CuI-Zeolite Catalysis

The potential of copper(I)-zeolite catalysis was evaluated in the three-component KA²-coupling mediated synthesis of α-tertiary propargylamines. Our archetypal copper(I)-doped zeolite Cu^I-USY proved to be efficient under ligand- and solvent-free conditions at 80 °C. Usable up to four times, this catalytic material enables the coupling of diverse ketones, alkynes, and amines with a broad functional group tolerance. A decarboxylative and a desilylative version, respectively, involving an alkynoic acid and trimethylsilylacetylene as alkyne surrogates, was also set up to bypass selectivity issues and/or to access α-tertiary propargylamines that are unattainable under standard KA² conditions. Interestingly, the KA²-type coupling reactions were successfully linked to other Cu^I-catalyzed reactions, thus resulting in sequential one-pot processes under full Cu^I-USY catalysis.

Chronic methamphetamine-induced neurodegeneration: Differential vulnerability of ventral tegmental area and substantia nigra pars compacta dopamine neurons

Methamphetamine (meth) increases monoamine oxidase (MAO)-dependent mitochondrial stress in substantia nigra pars compacta (SNc) axons; chronic administration produces SNc degeneration that is prevented by MAO inhibition suggesting that MAO-dependent axonal mitochondrial stress is a causal factor. To test whether meth similarly increases mitochondrial stress in ventral tegmental area (VTA) axons, we used a genetically encoded redox biosensor to assess mitochondrial stress ex vivo. Meth increased MAO-dependent mitochondrial stress in both SNc and VTA axons. However, despite having the same meth-induced stress as SNc neurons, VTA neurons were resistant to chronic meth-induced degeneration indicating that meth-induced MAO-dependent mitochondrial stress in axons was necessary but not sufficient for degeneration. To determine whether L-type Ca2+ channel-dependent stress differentiates SNc and VTA axons, as reported in the soma, the L-type Ca2+ channel activator Bay K8644 was used. Opening L-type Ca2+ channels increased axonal mitochondrial stress in SNc but not VTA axons. To first determine whether mitochondrial stress was necessary for SNc degeneration, mice were treated with the mitochondrial antioxidant mitoTEMPO. Chronic meth-induced SNc degeneration was prevented by mitoTEMPO thereby confirming the necessity of mitochondrial stress. Similar to results with the antioxidant, both MAO inhibition and L-type Ca2+ channel inhibition also prevented SNc degeneration. Taken together the presented data demonstrate that both MAO- and L-type Ca2+ channel-dependent mitochondrial stress is necessary for chronic meth-induced degeneration.

ADHD symptoms in neurometabolic diseases: Underlying mechanisms and clinical implications

Neurometabolic diseases (NMDs) are typically caused by genetic abnormalities affecting enzyme functions, which in turn interfere with normal development and activity of the nervous system. Although the individual disorders are rare, NMDs are collectively relatively common and often lead to lifelong difficulties and high societal costs. Neuropsychiatric manifestations, including ADHD symptoms, are prominent in many NMDs, also when the primary biochemical defect originates in cells and tissues outside the nervous system. ADHD symptoms have been described in phenylketonuria, tyrosinemias, alkaptonuria, succinic semialdehyde dehydrogenase deficiency, X-linked ichthyosis, maple syrup urine disease, and several mitochondrial disorders, but are probably present in many other NMDs and may pose diagnostic and therapeutic challenges. Here we review current literature linking NMDs with ADHD symptoms. We cite emerging evidence that many NMDs converge on common neurochemical mechanisms that interfere with monoamine neurotransmitter synthesis, transport, metabolism, or receptor functions, mechanisms that are also considered central in ADHD pathophysiology and treatment. Finally, we discuss the therapeutic implications of these findings and propose a path forward to increase our understanding of these relationships.

Novel Thiosemicarbazone Derivatives: In Vitro and In Silico Evaluation as Potential MAO-B Inhibitors

MAO-B inhibitors are frequently used in the treatment of neurodegenerative diseases such as Parkinson’s and Alzheimer’s. Due to the limited number of compounds available in this field, there is a need to develop new compounds. In the recent works, it was shown that various thiosemicarbazone derivatives show hMAO inhibitory activity in the range of micromolar concentration. It is thought that benzofuran and benzothiophene structures may mimic structures such as indane and indanone, which are frequently found in the structures of such inhibitors. Based on this view, new benzofuran/benzothiophene and thiosemicarbazone hybrid compounds were synthesized, characterized and screened for their hMAO-A and hMAO-B inhibitory activity by an in vitro fluorometric method. The compounds including methoxyethyl substituent (2b and 2h) were found to be the most effective agents in the series against MAO-B enzyme with the IC₅₀ value of 0.042 ± 0.002 µM and 0.056 ± 0.002 µM, respectively. The mechanism of hMAO-B inhibition of compounds 2b and 2h was investigated by Lineweaver–Burk graphics. Compounds 2b and 2h were reversible and non-competitive inhibitors with similar inhibition features as the substrates. The K_i values of compounds 2b and 2h were calculated as 0.035 µM and 0.046 µM, respectively, with the help of secondary plots. The docking study of compound 2b and 2h revealed that there is a strong interaction between the active sites of hMAO-B and analyzed compound.

Efficacy and safety evaluation of safinamide as an add-on treatment to levodopa for parkinson's disease

INTRODUCTION

While levodopa is still the most effective treatment for Parkinson's disease, concerns about long-term complications such as wearing-off and dyskinesia with levodopa usage remain.

AREAS COVERED

Safinamide is a highly selective and reversible monoamine oxidase B inhibitor introduced in the European Union, Japan, and the United States as an adjunctive agent to levodopa in PD patients with motor fluctuation. This review outlines the pharmacological properties, therapeutic effects, and tolerability of safinamide as an adjunct to levodopa in patients with advanced PD. Efficacy and safety findings from double-blind and placebo-controlled clinical trials for safinamide as an adjunct therapy to levodopa for PD are summarized.

EXPERT OPINION

Safinamide was well tolerated as a treatment for PD, and there was no significant difference in the frequency and severity of adverse events between the safinamide and placebo groups. It was also suggested that safinamide had a beneficial effect on the accompanying non-motor symptoms such as PD-related pain. Safinamide may exhibit neuroprotective effects through antioxidant and anti-glutamate effects, and research on the disease-modifying effect of PD is desired in the future.

Association of the MAOB rs1799836 Single Nucleotide Polymorphism and APOE ɛ4 Allele in Alzheimer's Disease

BACKGROUND

The dopaminergic system is functionally compromised in Alzheimer's dis-ease (AD). The activity of monoamine oxidase B (MAOB), the enzyme involved in the degradation of dopamine, is increased during AD. Also, increased expression of MAOB occurs in the post-mortem hippocampus and neocortex of patients with AD. The MAOB rs1799836 polymorphism modulates MAOB transcription, consequently influencing protein translation and MAOB activity. We recently showed that cerebrospinal fluid levels of amyloid β1-42 are decreased in patients carry- ing the A allele in MAOB rs1799836 polymorphism.

OBJECTIVE

The present study compares MAOB rs1799836 polymorphism and APOE, the only con- firmed genetic risk factor for sporadic AD.

METHOD

We included 253 participants, 127 of whom had AD, 57 had mild cognitive impairment, 11 were healthy controls, and 58 suffered from other primary causes of dementia. MAOB and APOE polymorphisms were determined using TaqMan SNP Genotyping Assays.

RESULTS

We observed that the frequency of APOE ɛ4/ɛ4 homozygotes and APOE ɛ4 carriers is sig- nificantly increased among patients carrying the AA MAOB rs1799836 genotype.

CONCLUSION

These results indicate that the MAOB rs1799836 polymorphism is a potential genetic biomarker of AD and a potential target for the treatment of decreased dopaminergic transmission and cognitive deterioration in AD.

Differential Susceptibilities of Catecholamines to Metabolism by Monoamine Oxidases

The endogenous catecholamines dopamine (DA), norepinephrine (NE), and epinephrine (EPI) play key roles in neurobehavioral, cardiovascular, and metabolic processes; various clinical disorders; and effects of numerous drugs. Steps in intracellular catecholamine synthesis and metabolism were delineated long ago, but there remains a knowledge gap. Catecholamines are metabolized by two isoforms of monoamine oxidase (MAO), MAO-A and MAO-B, and although the anatomic localization of MAO-A and MAO-B and substrate specificities of enzyme inhibitors are well characterized, relative susceptibilities of the endogenous catecholamines to enzymatic oxidation by MAO-A and MAO-B have not been studied systematically. MAOs catalyze the conversion of catecholamines to catecholaldehydes-3,4-dihydroxyphenylacetaldehyde (DOPAL) from DA and 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL) from NE and EPI. In this study we exploited the technical ability to assay DOPAL and DOPEGAL simultaneously with the substrate catecholamines to compare DA, NE, and EPI in their metabolism by MAO-A and MAO-B. For both MAO isoforms, DA was the better substrate compared to NE or EPI, which were metabolized equally. Since catecholaminergic neurons express mainly MAO-A, the finding that MAO-A is more efficient than MAO-B in metabolizing endogenous catecholamines reinforces the view that the predominant route of intraneuronal enzymatic oxidation of catecholamines is via MAO-A. The results have implications for clinical neurochemistry, experimental therapeutics, and computational models of catecholaminergic neurodegeneration. For instance, the greater susceptibility of DA than the other catecholamines to both MAO isoforms can help explain relatively high concentrations of the deaminated DA metabolite 3,4-dihydroxyphenylacetic acid than of the NE metabolite 3,4-dihydroxyphenylglycol in human plasma and urine. SIGNIFICANCE STATEMENT: Endogenous catecholamines are metabolized by monoamine oxidase (MAO)-A and -B, yielding the catecholaldehydes 3,4-dihydroxyphenylacetaldehyde (DOPAL) from dopamine (DA) and 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL) from norepinephrine (NE) and epinephrine (EPI). Based on measurements of DOPAL and DOPEGAL production, DA is a better substrate than NE or EPI for both MAO isoforms, and MAO-A is more efficient than MAO-B in metabolizing DA, NE, and EPI. MAO-A is the main route of intraneuronal metabolism of endogenous catecholamines.

Design, Synthesis, and Monoamine Oxidase Inhibitory Activity of (+)-Cinchonaminone and Its Simplified Derivatives

The absolute structure of an indole alkaloid (+)-cinchonaminone by total synthesis of both (+)-cinchonaminone and its enantiomer was determined. The main focus of the study was the enantioselective synthesis of both enantiomers of a chiral cis-3,4-disubstituted piperidine. We also evaluated monoamine oxidase (MAO) inhibitory activities of these enantiomers. Furthermore, its structurally simplified derivatives were synthesized that did not have any chiral center. Two of these derivatives showed stronger MAO inhibitory activities than that of (+)-cinchonaminone.

Development of 2D, 3D-QSAR and Pharmacophore Modeling of Chalcones for the Inhibition of Monoamine Oxidase B

BACKGROUND

Selective and reversible types of MAO-B inhibitors have emerged as promising candidates for the management of neurodegenerative diseases. Several functionalized chalcone derivatives were shown to have potential reversible MAO-B inhibitory activity, which have recently been reported from our laboratory.

METHODS

With the experimental results of about 70 chalcone derivatives, we further developed a pharmacophore modelling, and 2D and 3D- QSAR analyses of these reported chalcones for MAO-B inhibition.

RESULTS

The 2D-QSAR model presented four variables (MATS7v, GATS 1i and 3i, and C-006) from 143 Dragon 7 molecular descriptors, with a r2 value of 0.76 and a Q2cv for cross-validation equal to 0.72. An external validation also was performed using 11 chalcones, obtaining a Q2ext value of 0.74. The second 3D-QSAR model using MLR (multiple linear regression) was built starting from 128 Volsurf+ molecular descriptors, being identified as 4 variables (Molecular descriptors): D3, CW1 and LgS11, and L2LGS. Adetermination coefficient (r2) value of 0.76 and a Q2cv for cross-validation equal to 0.72 were obtained for this model. An external validation also was performed using 11 chalcones and a Q2ext value of 0.74 was found.

CONCLUSION

This report exhibited a good correlation and satisfactory agreement between experiment and theory.

Pharmacological Modulation of Behaviour, Serotonin and Dopamine Levels in Daphnia magna Exposed to the Monoamine Oxidase Inhibitor Deprenyl

This study assessed the effects of the monoamine oxidase (MAO) inhibitor deprenyl in Daphnia magna locomotor activity. The mechanisms of action of deprenyl were also determined by studying the relationship between behaviour, MAO activity and neurotransmitter levels. Modulation of the D. magna monoamine system was accomplished by 24 h exposure to two model psychotropic pharmaceuticals with antagonistic and agonistic serotonin signalling properties: 10 mg/L of 4-chloro-DL-phenylalanine (PCPA) and 1 mg/L of deprenyl, respectively. Contrasting behavioural outcomes were observed for deprenyl and PCPA reflected in decreased basal locomotor activity and enhanced habituation for the former compound and delayed habituation for the latter one. Deprenyl exposure inhibited monoamine oxidase (MAO) activity and increased the concentrations of serotonin, dopamine and the dopamine metabolite 3-methoxytyramine in whole D. magna extracts. Our findings indicate that D. magna is a sensitive and useful nonvertebrate model for assessing the effects of short-term exposure to chemicals that alter monoamine signalling changes.

Antidepressant-like effect of Campomanesia xanthocarpa seeds in mice: Involvement of the monoaminergic system

Background and aim

Campomanesia xanthocarpa Berg. (Myrtaceae) present several pharmacological actions, but there are no reports on its antidepressant-like potential. This study investigated the antidepressant-like effect and mechanism of action of Campomanesia xanthocarpa seeds extract obtained from supercritical CO₂ (40 °C, 250 bar).

Experimental procedure

Mice were orally treated with the extract 1 h before the TST. To investigate the involvement of the monoaminergic system in the antidepressant-like activity of the extract, pharmacological antagonists were administered prior to the acute oral administration of the extract (60 mg/kg). Also, the interaction of the extract with antidepressants was assessed in the tail suspension test (TST). The in vitro inhibitory potential of C. xanthocarpa seeds extract towards MAO A and MAO B enzymes was tested in vitro.

Results and conclusion

Animals treated with Campomanesia xanthocarpa seeds extract showed a significant reduction in the immobility time in the TST. Mice pretreatment with SCH23390, sulpiride, prazosin, yohimbine, and p-chlorophenylalanine prevented the anti-immobility effect of the extract in the TST. The combined administration of sub-effective doses of the extract with imipramine, bupropion and fluoxetine significantly reduced mice immobility time in the TST. The extract showed MAO A inhibitory activity (IC₅₀ = 151.10 ± 5.75 μg/mL), which was greater than that toward MAO B (IC₅₀ > 400 μg/mL).

The extract of Campomanesia xanthocarpa seeds obtained by supercritical CO₂ shows antidepressant-like activity, which relies on the activation of the monoaminergic neurotransmission (serotoninergic, dopaminergic and noradrenergic), suggesting that this species might represent a resource for developing new antidepressants.

•

C. xanthocarpa show antidepressant-like effect in mice tail suspension test.

•

C. xanthocarpa potentiates the effect of antidepressants in tail suspension test.

•

C. xanthocarpa mode of action involves the monoaminergic system.

Curcumin-Coumarin Hybrid Analogues as Multitarget Agents in Neurodegenerative Disorders

Neurodegenerative diseases have a complex nature which highlights the need for multitarget ligands to address the complementary pathways involved in these diseases. Over the last decade, many innovative curcumin-based compounds have been designed and synthesized, searching for new derivatives having anti-amyloidogenic, inhibitory of tau formation, as well as anti-neuroinflammation, antioxidative, and AChE inhibitory activities. Regarding our experience studying 3-substituted coumarins with interesting properties for neurodegenerative diseases, our aim was to synthesize a new series of curcumin–coumarin hybrid analogues and evaluate their activity. Most of the 3-(7-phenyl-3,5-dioxohepta-1,6-dien-1-yl)coumarin derivatives 11–18 resulted in moderated inhibitors of hMAO isoforms and AChE and BuChE activity. Some of them are also capable of scavenger the free radical DPPH. Furthermore, compounds 14 and 16 showed neuroprotective activity against H₂O₂ in SH-SY5Y cell line. Nanoparticles formulation of these derivatives improved this property increasing the neuroprotective activity to the nanomolar range. Results suggest that by modulating the substitution pattern on both coumarin moiety and phenyl ring, ChE and MAO-targeted derivatives or derivatives with activity in cell-based phenotypic assays can be obtained.

Semicarbazones, thiosemicarbazone, thiazole and oxazole analogues as monoamine oxidase inhibitors: Synthesis, characterization, biological evaluation, molecular docking, and kinetic studies

A series of semicarbazone, thiosemicarbazone, thiazole, and oxazole derivatives were designed, synthesized, and examined for monoamine oxidase inhibition using two isoforms, i.e., MAO-A and MAO-B. Among all the analogues, 3c and 3j possessed substantial activity against MAO-A with IC₅₀ values of 5.619 ± 1.04 µM and 0.5781 ± 0.1674 µM, respectively. Whereas 3d and 3j were active against monoamine oxidase B with the IC₅₀ values of 9.952 ± 1.831 µM and 3.5 ± 0.7 µM, respectively. Other derivatives active against MAO-B were 3c and 3g with the IC₅₀ values of 17.67 ± 5.6 µM and 37.18 ± 2.485 µM. Moreover, molecular docking studies were achieved for the most potent compound (3j) contrary to human MAO-A and MAO-B. Kinetic studies were also performed for the most potent analogue to evaluate its mode of interaction with MAO-A and MAO-B.

Monoamine Oxidase-B Inhibition Facilitates α-Synuclein Secretion In Vitro and Delays Its Aggregation in rAAV-Based Rat Models of Parkinson's Disease

Cell-to-cell transmission of α-synuclein (α-syn) pathology is considered to underlie the spread of neurodegeneration in Parkinson's disease (PD). Previous studies have demonstrated that α-syn is secreted under physiological conditions in neuronal cell lines and primary neurons. However, the molecular mechanisms that regulate extracellular α-syn secretion remain unclear. In this study, we found that inhibition of monoamine oxidase-B (MAO-B) enzymatic activity facilitated α-syn secretion in human neuroblastoma SH-SY5Y cells. Both inhibition of MAO-B by selegiline or rasagiline and siRNA-mediated knock-down of MAO-B facilitated α-syn secretion. However, TVP-1022, the S-isomer of rasagiline that is 1000 times less active, failed to facilitate α-syn secretion. Additionally, the MAO-B inhibition-induced increase in α-syn secretion was unaffected by brefeldin A, which inhibits endoplasmic reticulum (ER)/Golgi transport, but was blocked by probenecid and glyburide, which inhibit ATP-binding cassette (ABC) transporter function. MAO-B inhibition preferentially facilitated the secretion of detergent-insoluble α-syn protein and decreased its intracellular accumulation under chloroquine-induced lysosomal dysfunction. Moreover, in a rat model (male Sprague Dawley rats) generated by injecting recombinant adeno-associated virus (rAAV)-A53T α-syn, subcutaneous administration of selegiline delayed the striatal formation of Ser129-phosphorylated α-syn aggregates, and mitigated loss of nigrostriatal dopaminergic neurons. Selegiline also delayed α-syn aggregation and dopaminergic neuronal loss in a cell-to-cell transmission rat model (male Sprague Dawley rats) generated by injecting rAAV-wild-type α-syn and externally inoculating α-syn fibrils into the striatum. These findings suggest that MAO-B inhibition modulates the intracellular clearance of detergent-insoluble α-syn via the ABC transporter-mediated non-classical secretion pathway, and temporarily suppresses the formation and transmission of α-syn aggregates.SIGNIFICANCE STATEMENT The identification of a neuroprotective agent that slows or stops the progression of motor impairments is required to treat Parkinson's disease (PD). The process of α-synuclein (α-syn) aggregation is thought to underlie neurodegeneration in PD. Here, we demonstrated that pharmacological inhibition or knock-down of monoamine oxidase-B (MAO-B) in SH-SY5Y cells facilitated α-syn secretion via a non-classical pathway involving an ATP-binding cassette (ABC) transporter. MAO-B inhibition preferentially facilitated secretion of detergent-insoluble α-syn protein and reduced its intracellular accumulation under chloroquine-induced lysosomal dysfunction. Additionally, MAO-B inhibition by selegiline protected A53T α-syn-induced nigrostriatal dopaminergic neuronal loss and suppressed the formation and cell-to-cell transmission of α-syn aggregates in rat models. We therefore propose a new function of MAO-B inhibition that modulates α-syn secretion and aggregation.

Mapping Chromone-3-Phenylcarboxamide Pharmacophore: Quid Est Veritas?

Chromone-3-phenylcarboxamides (Crom-1 and Crom-2) were identified as potent, selective, and reversible inhibitors of human monoamine oxidase B (hMAO-B). Since they exhibit some absorption, distribution, metabolism, and excretion (ADME)-toxicity liabilities, new derivatives were synthesized to map the chemical structural features that compose the pharmacophore, a process vital for lead optimization. Structure-activity relationship data, supported by molecular docking studies, provided a rationale for the contribution of the heterocycle's rigidity, the carbonyl group, and the benzopyran heteroatom for hMAO-B inhibitory activity. From the study, N-(3-chlorophenyl)-4H-thiochromone-3-carboxamide (31) (hMAO-B IC₅₀ = 1.52 ± 0.15 nM) emerged as a reversible tight binding inhibitor with an improved pharmacological profile. In in vitro ADME-toxicity studies, compound 31 showed a safe cytotoxicity profile in Caco-2, SH-SY5Y, HUVEC, HEK-293, and MCF-7 cells, did not present cardiotoxic effects, and did not affect P-gp transport activity. Compound 31 also protected SH-SY5Y cells from iron(III)-induced damage. Collectively, these studies highlighted compound 31 as the first-in-class and a suitable candidate for in vivo preclinical investigation.

Deciphering the detailed structure-activity relationship of coumarins as Monoamine oxidase enzyme inhibitors-An updated review

In the last few years, Monoamine oxidase (MAO) have emerged as a target for the treatment of many neurodegenerative diseases including anxiety, depression, Alzheimer's, and Parkinson's diseases. The MAO inhibitors especially selective and reversible inhibitors of either of the isoenzymes (MAO-A & MAO-B) have been given more attention as both the form have different therapeutic properties and hence can be used for different neurological disorders. The lack of selective and reversible inhibitors available for both the enzymes and severity of the neuronal disorder in society have opened a new door to the researchers to carry out large and dedicated researches in this field. Among the several classes of the molecule as the inhibitors, coumarins hold a rank as a potent scaffold with its ease of synthesis, high therapeutic potential, and reversibility in inhibiting MAOs. The current review is an update of the research in the field that covers the works during the last six years (2014-2020) with a major focus on the SAR of the coumarin derivatives including synthetic, natural, and hybrids of coumarins with FDA-approved drugs.

Insights into the Mechanism of the Therapeutic Potential of Herbal Monoamine Oxidase Inhibitors in Neurological Diseases

Monoamine oxidase (MAO) is an enzyme that catalyzes the deamination of monoamines and other proteins. MAO's hyperactivation results in the massive generation of reactive oxygen species, which leads to a variety of neurological diseases such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, Huntington's disease, and depression-like disorders. Although synthetic MAO inhibitors are clinically available, they are associated with side effects such as hepatotoxicity, cheese reaction, hypertensive crisis, and so on, necessitating the investigation of alternative MAO inhibitors from a natural source with a safe profile. Herbal medications have a significant impact on the prevention of many diseases; additionally, they have fewer side effects and serve as a precursor for drug development. This review discusses the potential of herbal MAO inhibitors as well as their associated mechanism of action, with an aim to foster future research on herbal MAO inhibitors as potential treatment for neurological diseases.

A Recent Look into Natural Products that have Potential to Inhibit Cholinesterases and Monoamine Oxidase B: Update for 2010-2019

With respect to the unknowns of pathophysiology of Alzheimer's Disease (AD)-, and Parkinson's Disease (PD)-like neurodegenerative disorders, natural product research is still one of the valid tools in order to provide alternative and/or better treatment options. At one hand, various extracts of herbals provide a combination of actions targeting multiple receptors, on the other hand, the discovery of active natural products (i.e., secondary metabolites) generally offers alternative chemical structures either ready to be employed in clinical studies or available to be utilized as important scaffolds for the design of novel agents. Regarding the importance of certain enzymes (e.g. cholinesterase and monoamine oxidase B), for the treatment of AD and PD, we have surveyed the natural product research within this area in the last decade. Particularly novel natural agents discovered within this period, concomitant to novel biological activities displayed for known natural products, are harmonized within the present study.

A Comprehensive Review of Monoamine Oxidase-A Inhibitors in their Syntheses and Potencies

BACKGROUND

Monoamine oxidases (MAOs) play a crucial role during the development of various neurodegenerative disorders. There are two MAO isozymes, MAO-A and MAO-B. MAO-A is a flavoenzyme, which binds to the outer mitochondrial membrane and catalyzes the oxidative transformations of neurotransmitters like serotonin, norepinephrine, and dopamine.

MATERIALS AND METHODS

Focus on synthetic studies has culminated in the preparation of many MAOA inhibitors, and advancements in combinatorial and parallel synthesis have accelerated the developments of synthetic schemes. Here, we provided an overview of the synthetic protocols employed to prepare different classes of MAO-A inhibitors. We classified these inhibitors according to their molecular scaffolds and the synthetic methods used.

RESULTS

Various synthetic and natural derivatives from a different class of MAO-A inhibitors were reported.

CONCLUSION

The review provides a valuable tool for the development of a new class of various selective MAO-A inhibitors for the treatment of depression and other anxiety disorders.

Monoamine Oxidase Inhibitors (MAOIs) in Psychiatric Practice: How to Use them Safely and Effectively

Monoamine oxidase inhibitors (MAOIs) were among the first licensed pharmacological treatments for patients with depression but over time have fallen out of mainstream clinical use. This has led to a loss of clinician training opportunities and reduced availability of MAOIs for prescribing. This article provides a concise and practical overview of how to use MAOIs safely and effectively in psychiatric practice. We consider the history of MAOIs, why they are not used more frequently, their mechanisms of action, availability, indications and efficacy, general tolerability, withdrawal symptoms, and safety considerations (including hypertensive reactions and serotonin syndrome). Practical advice is given in terms of dietary restrictions, interactions with other medications (both prescribed and non-prescribed), and how prescribers can stop and switch MAOIs, both within the drug class and outside of it. We also provide advice on choice of MAOI and treatment sequencing. Lastly, we consider emerging directions and potential additional indications.

Redefining differential roles of MAO-A in dopamine degradation and MAO-B in tonic GABA synthesis

Monoamine oxidase (MAO) is believed to mediate the degradation of monoamine neurotransmitters, including dopamine, in the brain. Between the two types of MAO, MAO-B has been believed to be involved in dopamine degradation, which supports the idea that the therapeutic efficacy of MAO-B inhibitors in Parkinson's disease can be attributed to an increase in extracellular dopamine concentration. However, this belief has been controversial. Here, by utilizing in vivo phasic and basal electrochemical monitoring of extracellular dopamine with fast-scan cyclic voltammetry and multiple-cyclic square wave voltammetry and ex vivo fluorescence imaging of dopamine with GRABDA2m, we demonstrate that MAO-A, but not MAO-B, mainly contributes to striatal dopamine degradation. In contrast, our whole-cell patch-clamp results demonstrated that MAO-B, but not MAO-A, was responsible for astrocytic GABA-mediated tonic inhibitory currents in the rat striatum. We conclude that, in contrast to the traditional belief, MAO-A and MAO-B have profoundly different roles: MAO-A regulates dopamine levels, whereas MAO-B controls tonic GABA levels.

Ex vivo and in vitro inhibitory potential of Kava extract on monoamine oxidase B activity in mice

Background and aim

Experimental procedure

Results

Conclusion

•

Kava extract confirmed anxiolytic-like effect in mice.

•

Kava extract reduced MAO-B activity in cortex and in the region containing substantia nigra in mice.

•

Kava extract inhibited reversibly the MAO-B activity in vitro.

Antidepressants with anti-tumor potential in treating glioblastoma: A narrative review

Glioblastoma multiforme (GBM) is known as the deadliest form of brain tumor. In addition, its high treatment resistance, heterogeneity, and invasiveness make it one of the most challenging tumors. Depression is a common psychological disorder among patients with cancer, especially GBM. Due to the high occurrence rates of depression in GBM patients and the overlap of molecular and cellular mechanisms involved in the pathogenesis of these diseases, finding antidepressants with antitumor effects could be considered as an affordable strategy for the treatment of GBM. Antidepressants exert their antitumor properties through different mechanisms. According to available evidence in this regard, some of them can eliminate the adverse effects resulting from chemo-radiotherapy in several cancers along with their synergistic effects caused by chemotherapy. Therefore, providing comprehensive insight into this issue would guide scientists and physicians in developing further preclinical studies and clinical trials, in order to evaluate antidepressants' antitumor potential. Considering that no narrative review has been recently published on this issue, specifically on these classes of drugs, we present this article with the purpose of describing the antitumor cellular mechanisms of three classes of antidepressants as follows: tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and monoamine oxidase inhibitors (MAOIs) in GBM.

Subchronic effects of plant alkaloids on anxiety-like behavior in zebrafish

Zebrafish provide a valuable emerging complementary model for neurobehavioral research. They offer a powerful way to screen for the potential therapeutic effects of neuroactive drugs. A variety of behavioral tests for zebrafish have been developed and validated for assessing neurobehavioral function. The novel tank diving test is a straightforward, reproducible way of measuring anxiety-like behavior in zebrafish. When introduced into a novel tank, zebrafish normally dive to the bottom of the tank and then gradually explore the higher levels of the water column as time progresses. Buspirone is an effective anxiolytic drug in humans, which has been found, with acute administration, to reduce this anxiety-like response in zebrafish. The current study used the zebrafish model to evaluate the potential anxiolytic effects of alkaloids, commonly found in Solanaceae plants, with known neuropharmacology relevant to mood regulation. In line with previous findings, acute treatment with anxiolytic positive controls buspirone and the plant alkaloid nicotine reduced the anxiety-like diving response in the zebrafish novel tank diving test. Further, both buspirone and nicotine continued to produce anxiolytic-like effects in zebrafish after 5 days of exposure. In the same treatment paradigm, the effects of five other alkaloids-cotinine, anatabine, anabasine, harmane, and norharmane-were investigated. Cotinine, the major metabolite of nicotine, also caused anxiolytic-like effects, albeit at a dose higher than the effective dose of nicotine. Nicotine's anxiolytic-like effect was not shared by the other nicotinic alkaloids, anabasine and anatabine, or by the naturally present monoamine oxidase inhibitors harmane and norharmane. We conclude that nicotine uniquely induces anxiolytic-like effects after acute and subchronic treatment in zebrafish. The zebrafish model with the novel tank diving test could be a useful complement to rodent models for screening candidate compounds for anxiolytic effects in nonclinical studies.

Targeting monoamine oxidase A-regulated tumor-associated macrophage polarization for cancer immunotherapy

Targeting tumor-associated macrophages (TAMs) is a promising strategy to modify the immunosuppressive tumor microenvironment and improve cancer immunotherapy. Monoamine oxidase A (MAO-A) is an enzyme best known for its function in the brain; small molecule MAO inhibitors (MAOIs) are clinically used for treating neurological disorders. Here we observe MAO-A induction in mouse and human TAMs. MAO-A-deficient mice exhibit decreased TAM immunosuppressive functions corresponding with enhanced antitumor immunity. MAOI treatment induces TAM reprogramming and suppresses tumor growth in preclinical mouse syngeneic and human xenograft tumor models. Combining MAOI and anti-PD-1 treatments results in synergistic tumor suppression. Clinical data correlation studies associate high intratumoral MAOA expression with poor patient survival in a broad range of cancers. We further demonstrate that MAO-A promotes TAM immunosuppressive polarization via upregulating oxidative stress. Together, these data identify MAO-A as a critical regulator of TAMs and support repurposing MAOIs for TAM reprogramming to improve cancer immunotherapy.

Three -(pyridin-2-yl)-2-(pyridin-2-ylimino)thiazolidin-4-one as a novel inhibitor of cerebral MAO-B activity with antioxidant properties and low toxicity potential

Some brain diseases are associated with oxidative stress and altered monoamine oxidase (MAO) activity. The objective of this study was to evaluate the antioxidant and neuroprotective actions through MAO inhibition of 3-(pyridin-2-yl)-2-(pyridine-2-ylimino) thiazolidin-4-one (PPIT, a synthetic molecule containing a thiazolidinone nucleus), as well as its effects on toxicity parameters in Swiss female mice. Five in vitro assays were carried out to verify the PPIT antioxidant capacity: protein carbonylation (PC), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picryl-hydrazil (DPPH), ferric ion (Fe³⁺ ) reducing antioxidant power (FRAP), and superoxide dismutase (SOD)-like activity. The results showed that PPIT reduced the level of PC in the homogenate of the brain. This compound did not demonstrate SOD mimetic activity, but it acted as a free radical scavenger (ABTS and DPPH) and exhibited reducing activity in the FRAP assay. In addition, the effects of PPIT on cerebral MAO activity (MAO-A and B isoforms) were investigated in vitro. Our data revealed inhibition of the MAO-B activity by PPIT with no effects on MAO-A. Lastly, an acute oral toxicity test was conducted in mice. No changes in food intake, body weight, and biochemical markers of kidney and liver damage were detected in mice treated with a high dose of PPIT (300 mg/kg). In conclusion, the present study demonstrated that PPIT exhibits antioxidant activity and selectively inhibits the MAO-B isoform without causing apparent toxicity. These findings suggest PPIT as a potential therapeutic candidate to be tested in preclinical models of brain diseases involving perturbations of MAO-B activity and redox status.

Development of Halogenated Pyrazolines as Selective Monoamine Oxidase-B Inhibitors: Deciphering via Molecular Dynamics Approach

Halogens have been reported to play a major role in the inhibition of monoamine oxidase (MAO), relating to diverse cognitive functions of the central nervous system. Pyrazoline/halogenated pyrazolines were investigated for their inhibitory activities against human monoamine oxidase-A and -B. Halogen substitutions on the phenyl ring located at the fifth position of pyrazoline showed potent MAO-B inhibition. Compound 3-(4-ethoxyphenyl)-5-(4-fluorophenyl)-4,5-dihydro-1H-pyrazole (EH7) showed the highest potency against MAO-B with an IC₅₀ value of 0.063 µM. The potencies against MAO-B were increased in the order of –F (in EH7) > –Cl (EH6) > –Br (EH8) > –H (EH1). The residual activities of most compounds for MAO-A were > 50% at 10 µM, except for EH7 and EH8 (IC₅₀ = 8.38 and 4.31 µM, respectively). EH7 showed the highest selectivity index (SI) value of 133.0 for MAO-B, followed by EH6 at > 55.8. EH7 was a reversible and competitive inhibitor of MAO-B in kinetic and reversibility experiments with a Ki value of 0.034 ± 0.0067 µM. The molecular dynamics study documented that EH7 had a good binding affinity and motional movement within the active site with high stability. It was observed by MM-PBSA that the chirality had little effect on the overall binding of EH7 to MAO-B. Thus, EH7 can be employed for the development of lead molecules for the treatment of various neurodegenerative disorders.

New indane derivatives containing 2-hydrazinothiazole as potential acetylcholinesterase and monoamine oxidase-B inhibitors

Although radical treatment of Alzheimer's and Parkinson's disease is not possible yet, it is aimed to slow the course of the disease and increase the life quality of individuals with the drugs used in the clinic at the present time. Successful results have been achieved in the use of cholinesterase inhibitors and monoamine oxidase inhibitors together in these neurodegenerative diseases. In this study, indane ring which are in the structure of anticholinesterase effective molecules and 2-hydrazinothiazole structure whose inhibitory activities reported on monoamine oxidase-B (MAO-B) were combined; 4-(substituted phenyl)-2-[2-(3-phenyl-2,3-dihydro-1H-inden-1-ylidene) hydrazinyl]thiazole derivatives (3a-3i) were synthesized as dual inhibitors. The structures of the compounds were verified by IR, ¹H-NMR, ¹³C-NMR, and HRMS spectroscopy. When enzyme inhibition activities were evaluated, it was determined that the compounds 3a (42.33%) and 3d (42.39%) on acetylcholinesterase (AChE) enzyme; compounds 3g (75.42%) and 3h (60.33%) showed inhibition on MAO-B enzyme at most, at 10^-3 M concentration.

Targeting COVID-19 in Parkinson's Patients: Drugs Repurposed

The last couple of months have witnessed the world in a state of virtual standstill. The SARS-CoV-2 virus has overtaken the globe to economic and social lockdown. Many patients with COVID-19 have compromised immunity, especially in an aged population suffering from Parkinson 's disease (PD). Alteration in dopaminergic neurons and deficiency of dopamine in PD patients are the most common symptoms affecting 1% population above the age of 60 years. The compromised immune system and inflammatory manifestation in PD patients make them an easy target. The most common drugs under trial for COVID-19 are remdesivir, favipiravir, chloroquine and hydroxychloroquine, azithromycin along with adjunct drugs like amantadine with some monoclonal antibodies. Presently, clinically US FDA approved drugs in PD include Levodopa, catechol-O-methyl transferase (COMT) inhibitors, (Entacapone and Tolcapone), dopamine agonists (Bromocriptine, Ropinirole, Pramipexole, and Rotigotine), monoamine oxidase B (MAO-B) inhibitors (Selegiline and Rasagiline), amantadine and antimuscarinic drugs. The drugs have established mechanisms of action on PD patients with known pharmacodynamics and pharmacokinetic properties along with dose and adverse effects. Conclusion and relevance of this review focus on the drugs that can be tried on PD patients with SAR CoV-2 infection, in particular, amantadine that has been approved by all the developed countries as a common drug possessing both antiviral properties by downregulation of CTSL, lysosomal pathway disturbance and change in pH necessary to uncoat the viral proteins and anti- Parkinson properties. To deal with the significant prognostic adverse effect of SARS-CoV-2 on PD, the present-day treatment options, clinical presentation and various mechanisms are the need of the hour.

Pharmacological Modulation of Serotonin Levels in Zebrafish Larvae: Lessons for Identifying Environmental Neurotoxicants Targeting the Serotonergic System

This study examines the effects of acute pharmacological modulation of the serotonergic system over zebrafish larvae’s cognitive, basic, and defense locomotor behaviors, using a medium to high throughput screening assay. Furthermore, the relationship between behavior, enzyme activity related to neurotransmitter metabolism, neurotransmitter levels, and gene expression was also determined. Modulation of larvae serotonergic system was accomplished by 24 h exposure to single and opposite pharmacodynamics co-exposure to three model psychopharmaceuticals with antagonistic and agonistic serotonin signaling properties: 2.5 mM 4-Chloro-DL-phenylalanine (PCPA) and 5 µM deprenyl and 0.5 µM fluoxetine, respectively. Similar behavioral outcome was observed for deprenyl and fluoxetine, which was reflected as hypolocomotion, decrease in larvae defensive responses, and cognitive impairment. Contrarily, PCPA induced hyperlocomotion and increase in larvae escape response. Deprenyl exposure effects were more pronounced at a lower level of organization than fluoxetine, with complete inhibition of monoamine oxidase (MAO) activity, dramatic increase of 5-HT and dopamine (DA) levels, and downregulation of serotonin synthesis and transporter genes. PCPA showed mainly effects over serotonin and dopamine’s main degradation metabolites. Finally, co-exposure between agonistic and antagonist serotonin signaling drugs reviled full recovery of zebrafish impaired locomotor and defense responses, 5-HT synthesis gene expression, and partial recovery of 5-HT levels. The findings of this study suggest that zebrafish larvae can be highly sensitive and a useful vertebrate model for short-term exposure to serotonin signaling changes.

Exploring the Role and Potential of Probiotics in the Field of Mental Health: Major Depressive Disorder

The field of probiotic has been exponentially expanding over the recent decades with a more therapeutic-centered research. Probiotics mediated microbiota modulation within the microbiota–gut–brain axis (MGBA) have been proven to be beneficial in various health domains through pre-clinical and clinical studies. In the context of mental health, although probiotic research is still in its infancy stage, the promising role and potential of probiotics in various mental disorders demonstrated via in-vivo and in-vitro studies have laid a strong foundation for translating preclinical models to humans. The exploration of the therapeutic role and potential of probiotics in major depressive disorder (MDD) is an extremely noteworthy field of research. The possible etio-pathological mechanisms of depression involving inflammation, neurotransmitters, the hypothalamic–pituitary–adrenal (HPA) axis and epigenetic mechanisms potentially benefit from probiotic intervention. Probiotics, both as an adjunct to antidepressants or a stand-alone intervention, have a beneficial role and potential in mitigating anti-depressive effects, and confers some advantages compared to conventional treatments of depression using anti-depressants.

Investigation into MAO B-Mediated Formation of CC112273, a Major Circulating Metabolite of Ozanimod, in Humans and Preclinical Species: Stereospecific Oxidative Deamination of (S)-Enantiomer of Indaneamine (RP101075) by MAO B

Ozanimod, recently approved for treating relapsing multiple sclerosis, produced a disproportionate, active, MAO B-catalyzed metabolite (CC112273) that showed remarkable interspecies differences and led to challenges in safety testing. This study explored the kinetics of CC112273 formation from its precursor RP101075. Incubations with human liver mitochondrial fractions revealed K _Mapp, V _max, and intrinsic clearance (Cl_int) for CC112273 formation to be 4.8 μM, 50.3 pmol/min/mg protein, and 12 μl/min/mg, respectively, whereas Michaelis-Menten constant (K _M) with human recombinant MAO B was 1.1 μM. Studies with liver mitochondrial fractions from preclinical species led to K _Mapp, V _max, and Cl_int estimates of 3.0, 35, and 33 μM, 80.6, 114, 37.3 pmol/min/mg, and 27.2, 3.25, and 1.14 μl/min/mg in monkey, rat, and mouse, respectively, and revealed marked differences between rodents and primates, primarily attributable to differences in the K _M Comparison of Cl_int estimates revealed monkey to be ∼2-fold more efficient and the mouse and rat to be 11- and 4-fold less efficient than humans in CC112273 formation. The influence of stereochemistry on MAO B-mediated oxidation was also investigated using the R-isomer of RP101075 (RP101074). This showed marked selectivity toward catalysis of the S-isomer (RP101075) only. Docking into MAO B crystal structure suggested that although both the isomers occupied its active site, only the orientation of RP101075 presented the C-H on the α-carbon that was ideal for the C-H bond cleavage, which is a requisite for oxidative deamination. These studies explain the basis for the observed interspecies differences in the metabolism of ozanimod as well as the substrate stereospecificity for formation of CC112273. SIGNIFICANCE STATEMENT: This study evaluates the enzymology and the species differences of the major circulating metabolite of ozanimod, CC112273. Additionally, the study also explores the influence of stereochemistry on MAO B-catalyzed reactions. The study is of significance to the DMD readers given that this oxidation is catalyzed by a non-cytochrome P450 enzyme, and that marked species difference and notable stereospecificity was observed in MAO B-catalyzed biotransformation when the indaneamine enantiomers were used as substrates.

Multi-Step Subcritical Water Extracts of Fucus vesiculosus L. and Codium tomentosum Stackhouse: Composition, Health-Benefits and Safety

Mental health and active aging are two of the main concerns in the 21st century. To search for new neuroprotective compounds, extracts of Codium tomentosum Stackhouse and Fucus vesiculosus L. were obtained through multi-step (four step) subcritical water extraction using a temperature gradient. The safety assessment of the extracts was performed by screening pharmaceutical compounds and pesticides by UHPLC-MS/MS, and iodine and arsenic levels by ICP-MS. Although the extracts were free of pharmaceutical compounds and pesticides, the presence of arsenic and high iodine contents were found in the first two extraction steps. Thus, the health-benefits were only evaluated for the fractions obtained in steps 3 and 4 from the extraction process. These fractions were tested against five brain enzymes implicated in Alzheimer’s, Parkinson’s, and major depression etiology as well as against reactive oxygen and nitrogen species, having been observed a strong enzyme inhibition and radical scavenging activities for the step 4 fractions from both seaweed species. Regarding the variation of the chemical composition during the extraction, step 1 fractions were the richest in phenolic compounds. With the increase in temperature, Maillard reaction, caramelization and thermo-oxidation occurred, and the resulting products positively affected the antioxidant capacity and the neuroprotective effects.

Effects of Natural Monoamine Oxidase Inhibitors on Anxiety-Like Behavior in Zebrafish

Monoamine oxidases (MAO) are a valuable class of mitochondrial enzymes with a critical role in neuromodulation. In this study, we investigated the effect of natural MAO inhibitors on novel environment-induced anxiety by using the zebrafish novel tank test (NTT). Because zebrafish spend more time at the bottom of the tank when they are anxious, anxiolytic compounds increase the time zebrafish spend at the top of the tank and vice versa. Using this paradigm, we found that harmane, norharmane, and 1,2,3,4-tetrahydroisoquinoline (TIQ) induce anxiolytic-like effects in zebrafish, causing them to spend more time at the top of the test tank and less time at the bottom. 2,3,6-trimethyl-1,4-naphtoquinone (TMN) induced an interesting mix of both anxiolytic- and anxiogenic-like effects during the first and second halves of the test, respectively. TIQ was unique in having no observable effect on general movement. Similarly, a reference MAO inhibitor clorgyline—but not pargyline—increased the time spent at the top in a concentration-dependent manner. We also demonstrated that the brain bioavailability of these compounds are high based on the ex vivo bioavailability assay and in silico prediction models, which support the notion that the observed effects on anxiety-like behavior in zebrafish were most likely due to the direct effect of these compounds in the brain. This study is the first investigation to demonstrate the anxiolytic-like effects of MAO inhibitors on novel environment-induced anxiety in zebrafish.

Novel 1-(prop-2-yn-1-ylamino)-2,3-dihydro-1H-indene-4-thiol derivatives as potent selective human monoamine oxidase B inhibitors: Design, SAR development, and biological evaluation

Successes have been achieved in developing human monoamine oxidase B (hMAO-B) inhibitors as anti-Parkinson's disease (PD) drugs. However, low efficiency and unwanted side effects of the marketed hMAO-B inhibitors hamper their medical applications, therefore, novel potent selective hMAO-B inhibitors are still of great interest. Herein we report 1-(prop-2-yn-1-ylamino)-2,3-dihydro-1H-indene-4-thiol derivatives as hMAO-B inhibitors, which were designed by employing a fragment-based drug design strategy to link rasagiline to hydrophobic fragments. Among the synthesized 31 compounds, K8 and K24 demonstrated very encouraging hMAO-B inhibitory activities and selectivity over hMAO-A, better than rasagiline and safinamide. In vitro studies indicated that K8 and K24 are nontoxic to nervous tissue cells and they have considerable effects against ROS formation and potential neuroprotective activity. Further mice behavioral tests demonstrated these two compounds have good therapeutic effects on MPTP-induced PD model mice. All these experiment results suggest that compounds K8 and K24 can be promising candidates for further research for treatment of PD.

Hydroxytyrosol as anti-parkinsonian molecule: Assessment using in-silico and MPTP-induced Parkinson's disease model

3-Hydroxytyrosol (HXT) is a natural polyphenol present in extra virgin olive oil. It is a key component of Mediterranean diet and is known for its strong antioxidant activity. The present study evaluated the potential of HXT as an anti-parkinsonian molecule in terms of its ability to inhibit MAO-B and thereby maintaining dopamine (DA) levels in Parkinson's disease (PD). In-silico molecular docking study followed by MMGBSA binding free energy calculation revealed that HXT has a strong binding affinity for MAO-B in comparison to MAO-A. Moreover, rasagiline and HXT interacted with the similar binding sites and modes of interactions. Additionally, molecular dynamics simulation studies revealed stable nature of HXT-MAO-B interaction and also provided information about the amino acid residues involved in binding. Moreover, in vitro studies revealed that HXT inhibited MAO-B in human platelets with IC₅₀ value of 7.78 μM. In vivo studies using MPTP-induced mouse model of PD revealed increase in DA levels with concomitant decrease in DA metabolites (DOPAC and HVA) on HXT treatment. Furthermore, MAO-B activity was also inhibited on HXT administration to PD mice. In addition, HXT treatment prevented MPTP-induced loss of DA neurons in substantia nigra and their nerve terminals in the striatum. HXT also attenuated motor impairments in PD mice assessed by catalepsy bar, narrow beam walk and open field tests. Thus, the present findings reveal HXT as a potential inhibitor of MAO-B, which may be used as a lead molecule for the development of therapeutics for PD.

Phenelzine and Amoxapine Inhibit Tyramine and d-Glucuronic Acid Catabolism in Clinically Significant Salmonella in A Serotype-Independent Manner

Non-typhoidal Salmonella ingeniously scavenges energy for growth from tyramine (TYR) and d-glucuronic acid (DGA), both of which occur in the host as the metabolic byproducts of the gut microbial metabolism. A critical first step in energy scavenging from TYR and DGA in Salmonella involves TYR-oxidation via TYR-oxidoreductase and production of free-DGA via β-glucuronidase (GUS)-mediated hydrolysis of d-glucuronides (conjugated form of DGA), respectively. Here, we report that Salmonella utilizes TYR and DGA as sole sources of energy in a serotype-independent manner. Using colorimetric and radiometric approaches, we report that genes SEN2971, SEN3065, and SEN2426 encode TYR-oxidoreductases. Some Salmonella serotypes produce GUS, thus can also scavenge energy from d-glucuronides. We repurposed phenelzine (monoaminoxidase-inhibitor) and amoxapine (GUS-inhibitor) to inhibit the TYR-oxidoreductases and GUS encoded by Salmonella, respectively. We show that phenelzine significantly inhibits the growth of Salmonella by inhibiting TYR-oxidoreductases SEN2971, SEN3065, and SEN2426. Similarly, amoxapine significantly inhibits the growth of Salmonella by inhibiting GUS-mediated hydrolysis of d-glucuronides. Because TYR and DGA serve as potential energy sources for Salmonella growth in vivo, the data and the novel approaches used here provides a better understanding of the role of TYR and DGA in Salmonella pathogenesis and nutritional virulence.

Targeting the glucocorticoid receptor signature gene Mono Amine Oxidase-A enhances the efficacy of chemo- and anti-androgen therapy in advanced prostate cancer

Despite increasing options for treatment of castration-resistant prostate cancer, development of drug resistance is inevitable. The glucocorticoid receptor (GR) is a prime suspect for acquired therapy resistance, as prostate cancer (PCa) cells are able to increase GR signaling during anti-androgen therapy and thereby circumvent androgen receptor (AR)-blockade and cell death. As standard AR-directed therapies fail to block the GR and GR inhibitors might result in intolerable side effects, the identification of GR signature genes, which are better suited for a targeted approach, is of clinical importance. Therefore, the specific epithelial and stromal GR signature was determined in cancer-associated fibroblasts as well as in abiraterone and enzalutamide-resistant cells after glucocorticoid (GC) treatment. Microarray and ChIP analysis identified MAO-A as a directly up-regulated mutual epithelial and stromal GR target, which is induced after GC treatment and during PCa progression. Elevated MAO-A levels were confirmed in in vitro cell models, in primary tissue cultures after GC treatment, and in patients after neoadjuvant chemotherapy with GCs. MAO-A expression correlates with GR/AR activity as well as with a reduced progression-free survival. Pharmacological MAO-A inhibition combined with 2nd generation AR signaling inhibitors or chemotherapeutics results in impaired growth of androgen-dependent, androgen-independent, and long-term anti-androgen-treated cells. In summary, these findings demonstrate that targeting MAO-A represents an innovative therapeutic strategy to synergistically block GR and AR dependent PCa cell growth and thereby overcome therapy resistance.

Current Developments in Cell Replacement Therapy for Parkinson's Disease

Parkinson's disease (PD) is characterized by tremor, rigidity, and bradykinesia. PD is caused mainly by depletion of the nigrostriatal pathway. Conventional medications such as levodopa are highly effective in the early stage of PD; however, these medications fail to prevent the underlying neurodegeneration. Cell replacement therapy (CRT) is a strategy to achieve long-term motor improvements by preventing or slowing disease progression. Replacement therapy can also increase the number of surviving dopaminergic neurons, an outcome confirmed by positron emission tomography and immunostaining. Several promising cell sources offer authentic and functional dopaminergic replacement neurons. These cell sources include fetal ventral mesencephalic tissue, embryonic stem cells (ESCs), neural stem cells (NSCs), mesenchymal stem cells (MSCs) from various tissues, induced pluripotent stem cells (iPSCs), and induced neural cells. To fully develop the potential of CRT, we need to recognize the advantages and limitations of these cell sources. For example, although fetal ventral midbrain is efficacious in some patients, its ethical issues and the existence of graft-induced dyskinesias (GID) have prevented its use in large-scale clinical applications. ESCs have reliable isolation protocols and the potential to differentiate into dopaminergic progenitors. iPSCs and induced neural cells are suitable for autologous grafting. Here we review milestone improvements and emerging sources for cell-based PD therapy to serve as a framework for clinicians and a key reference to develop replacement therapy for other neurological disorders.

Chronic Serotonergic Overstimulation Mimicking Panic Attacks in a Patient with Parkinson's Disease Receiving Additional Antidepressant Treatment with Moclobemide

Background

The pharmacological treatment options of Parkinson's disease (PD) have considerably evolved during the last decades. However, therapeutic regimes are complicated due to individual differences in disease progression as well as the occurrence of complex nonmotor impairments such as mood and anxiety disorders. Antidepressants in particular are commonly prescribed for the treatment of depressive symptoms and anxiety in PD. Case Presentation. In this case report, we describe a case of a 62-year-old female patient with PD and history of depressive symptoms for which she had been treated with moclobemide concurrent with anti-Parkinson medications pramipexole, rasagiline, and L-DOPA+benserazide retard. An increase in the dosage of moclobemide 12 months prior to admission progressively led to serotonergic overstimulation and psychovegetative exacerbations mimicking the clinical picture of an anxiety spectrum disorder. After moclobemide and rasagiline were discontinued based on the hypothesis of serotonergic overstimulation, the patient's psychovegetative symptoms subsided.

Conclusions

The specific pharmacological regime in this case probably caused drug-drug interactions resulting in a plethora of psychovegetative symptoms. Likely due to the delayed onset of adverse effects, physicians had difficulties in determining the pharmacologically induced serotonin toxicity. This case report emphasizes the complexity of pharmacological treatments and the importance of drug-drug interaction awareness in the treatment of PD patients with complicating nonmotor dysfunctions such as depression.

In Silico Prediction of the Toxic Potential of Neuroprotective Bifunctional Molecules Based on Chiral N-Propargyl-1,2-amino Alcohol Derivatives

N-Propargylamines are useful synthetic scaffolds for the synthesis of bioactive molecules, and in addition, they possess important pharmacological activities. We obtained several neuroprotective molecules, chiral 1,2-amino alcohols and 1,2-diamines, able to reduce by almost 70% the rotenone and oligomycin A-induced damage in SH-SY5Y cells. Furthermore, some molecules assessed also counteracted the toxicity evoked by the Ser/Thr phosphatase inhibitor okadaic acid. Before extrapolating these data to preclinical studies, we analyze the molecules through an in silico prediction system to detect carcinogenicity risk or other toxic effects. In light of these promising results, these molecules may be considered as a lead family of neuroprotective and relatively safe compounds.

Drug-induced peripheral oedema: An aetiology-based review

Many drugs are responsible, through different mechanisms, for peripheral oedema. Severity is highly variable, ranging from slight oedema of the lower limbs to anasarca pictures as in the capillary leak syndrome. Although most often noninflammatory and bilateral, some drugs are associated with peripheral oedema that is readily erythematous (eg, pemetrexed) or unilateral (eg, sirolimus). Thus, drug-induced peripheral oedema is underrecognized and misdiagnosed, frequently leading to a prescribing cascade. Four main mechanisms are involved, namely precapillary arteriolar vasodilation (vasodilatory oedema), sodium/water retention (renal oedema), lymphatic insufficiency (lymphedema) and increased capillary permeability (permeability oedema). The underlying mechanism has significant impact on treatment efficacy. The purpose of this review is to provide a comprehensive analysis of the main causative drugs by illustrating each pathophysiological mechanism and their management through an example of a drug.