Human monoamine oxidase A and B genes exhibit identical exon-intron organization

Monoamine oxidase and neurodegeneration: Mechanisms, inhibitors and natural compounds for therapeutic intervention

Mammalian flavoenzyme Monoamine oxidase (MAO) resides on the outer mitochondrial membrane (OMM) and it is involved in the metabolism of different monoamine neurotransmitters in brain. During MAO mediated oxidative deamination of relevant substrates, H2O2 is released as a catalytic by-product, thus serving as a major source of reactive oxygen species (ROS). Under normal conditions, MAO mediated ROS is reported to propel the functioning of mitochondrial electron transport chain and phasic dopamine release. However, due to its localization onto mitochondria, sudden elevation in its enzymatic activity could directly impact the form and function of the organelle. For instance, in the case of Parkinson's disease (PD) patients who are on l-dopa therapy, the enzyme could be a concurrent source of extensive ROS production in the presence of uncontrolled substrate (dopamine) availability, thus further impacting the health of surviving neurons. It is worth mentioning that the expression of the enzyme in different brain compartments increases with age. Moreover, the involvement of MAO in the progression of neurological disorders such as PD, Alzheimer's disease and depression has been extensively studied in recent times. Although the usage of available synthetic MAO inhibitors has been instrumental in managing these conditions, the associated complications have raised significant concerns lately. Natural products have served as a major source of lead molecules in modern-day drug discovery; however, there is still no FDA-approved MAO inhibitor which is derived from natural sources. In this review, we have provided a comprehensive overview of MAO and how the enzyme system is involved in the pathogenesis of different age-associated neuropathologic conditions. We further discussed the applications and drawbacks of the long-term usage of presently available synthetic MAO inhibitors. Additionally, we have highlighted the prospect and worth of natural product derived molecules in addressing MAO associated complications.

Effective factors in the pathogenesis of Toxoplasmagondii

Toxoplasma gondii (T. gondii) is a cosmopolitan protozoan parasite in humans and animals. It infects about 30 % of the human population worldwide and causes potentially fatal diseases in immunocompromised hosts and neonates. For this study, five English-language databases (ScienceDirect, ProQuest, Web of Science, PubMed, and Scopus) and the internet search engine Google Scholar were searched. This review was accomplished to draw a global perspective of what is known about the pathogenesis of T. gondii and various factors affecting it. Virulence and immune responses can influence the mechanisms of parasite pathogenesis and these factors are in turn influenced by other factors. In addition to the host's genetic background, the type of Toxoplasma strain, the routes of transmission of infection, the number of passages, and different phases of parasite life affect virulence. The identification of virulence factors of the parasite could provide promising insights into the pathogenesis of this parasite. The results of this study can be an incentive to conduct more intensive research to design and develop new anti-Toxoplasma agents (drugs and vaccines) to treat or prevent this infection. In addition, further studies are needed to better understand the key agents in the pathogenesis of T. gondii.

Ultrafast Detection of Monoamine Oxidase A in Live Cells and Clinical Glioma Tissues Using an Affinity Binding-Based Two-Photon Fluorogenic Probe

Abnormal expression of monoamine oxidase A (MAO-A) has been implicated in the development of human glioma, making MAO-A a promising target for therapy. Therefore, a rapid determination of MAO-A is critical for diagnosis. Through in silico screening of two-photon fluorophores, we discovered that a derivative of N,N-dimethyl-naphthalenamine (pre-mito) can effectively fit into the entrance of the MAO-A cavity. Substitutions on the N-pyridine not only further explore the MAO-A cavity, but also enable mitochondrial targeting ability. The aminopropyl substituted molecule, CD1, showed the fastest MAO-A detection (within 20 s), high MAO-A affinity and selectivity. It was also used for in situ imaging of MAO-A in living cells, enabling a comparison of the MAO-A content in human glioma and paracancerous tissues. Our results demonstrate that optimizing the affinity binding-based fluorogenic probes significantly improves their detection rate, providing a general approach for rapid detection probe design and optimization.

Pseudoephedrine hydrochloride causes hyperactivity in zebrafish via modulation of the serotonin pathway

This study aimed to explore behavioral changes of embryonic and larval zebrafish caused by pseudoephedrine hydrochloride (PSE) and its underlying mechanism. Zebrafish embryos were exposed to 0.5 µM, 2 µM, and 8 µM PSE at 4 h post-fertilization (4 hpf) or 22-23 hpf. Mortality, hatching rate, coiling frequency, heart rate, behavior changes, and related gene expression were observed at different developmental stages. PSE below 8 µM did not affect zebrafish mortality, hatching rate, and heart rate compared with the control group. For embryos, PSE caused an increase at 16-32 hpf in zebrafish coiling frequency which could be rescued by serotonin antagonist WAY100635. Similarly, PSE caused an increase in the swimming distance of zebrafish larvae at 120 hpf. PSE also elevated the expression of serotonin (5-HT)-related genes 5-htr1ab and tph2 and dopamine-related gene dbh. Behavioral changes in zebrafish embryos and larvae caused by PSE may be closely associated with increased expression of 5-HT and dopamine-related genes. This may be reflected that the behavioral changes in zebrafish are a possible PSE monitoring indicator.

How "Neuronal" Are Human Skin Mast Cells?

Mast cells are evolutionarily old cells and the principal effectors in allergic responses and inflammation. They are seeded from the yolk sac during embryogenesis or are derived from hematopoietic progenitors and are therefore related to other leukocyte subsets, even though they form a separate clade in the hematopoietic system. Herein, we systematically bundle information from several recent high-throughput endeavors, especially those comparing MCs with other cell types, and combine such information with knowledge on the genes’ functions to reveal groups of neuronal markers specifically expressed by MCs. We focus on recent advances made regarding human tissue MCs, but also refer to studies in mice. In broad terms, genes hyper-expressed in MCs, but largely inactive in other myelocytes, can be classified into subcategories such as traffic/lysosomes (MLPH and RAB27B), the dopamine system (MAOB, DRD2, SLC6A3, and SLC18A2), Ca²⁺-related entities (CALB2), adhesion molecules (L1CAM and NTM) and, as an overall principle, the transcription factors and modulators of transcriptional activity (LMO4, PBX1, MEIS2, and EHMT2). Their function in MCs is generally unknown but may tentatively be deduced by comparison with other systems. MCs share functions with the nervous system, as they express typical neurotransmitters (histamine and serotonin) and a degranulation machinery that shares features with the neuronal apparatus at the synapse. Therefore, selective overlaps are plausible, and they further highlight the uniqueness of MCs within the myeloid system, as well as when compared with basophils. Apart from investigating their functional implications in MCs, a key question is whether their expression in the lineage is due to the specific reactivation of genes normally silenced in leukocytes or whether the genes are not switched off during mastocytic development from early progenitors.

A study on methylation of two CpG islands of MAOA gene promoter among opium-addicted males undergoing methadone treatment

The association between methylation of MAOA gene promoter and alcohol and nicotine dependence has been demonstrated in women but not in men yet. Antisocial personality disorder (ASPD) and substance use disorders (SUD) are two types of disorders that could highly be influenced by methylation-induced changes in MAOA function. The aim of the current study is to investigate the effect of opioid addiction on methylation of MAOA gene promoter in males. DNA was extracted from the whole blood of all samples (29 opium-addicted individuals undergoing methadone treatment and 28 healthy people) according to the extraction protocol, followed by treating these samples with bisulfite kits. The investigated region including two CpG islands in the promoter region of MAOA gene contained 35 CpG dinucleotides investigated through Sanger sequencing method. The frequency of methylation at two CpG islands of MAOA gene promoter regions was equal to zero among addicted individuals undergoing methadone treatment and healthy peoples. Then, comparing methylation levels among the study group is not applicable. In conclusion, there was no association between opium addiction and methylation of the MAOA promoter regions in opium-addicted male undergoing methadone treatment.

Emerging evidence for astrocyte dysfunction in schizophrenia

Schizophrenia is a complex, chronic mental health disorder whose heterogeneous genetic and neurobiological background influences early brain development, and whose precise etiology is still poorly understood. Schizophrenia is not characterized by gross brain pathology, but involves subtle pathological changes in neuronal populations and glial cells. Among the latter, astrocytes critically contribute to the regulation of early neurodevelopmental processes, and any dysfunctions in their morphological and functional maturation may lead to aberrant neurodevelopmental processes involved in the pathogenesis of schizophrenia, such as mitochondrial biogenesis, synaptogenesis, and glutamatergic and dopaminergic transmission. Studies of the mechanisms regulating astrocyte maturation may therefore improve our understanding of the cellular and molecular mechanisms underlying the pathogenesis of schizophrenia.

Inverse Molecular Docking Elucidating the Anticarcinogenic Potential of the Hop Natural Product Xanthohumol and Its Metabolites

Natural products from plants exert a promising potential to act as antioxidants, antimicrobials, anti-inflammatory, and anticarcinogenic agents. Xanthohumol, a natural compound from hops, is indeed known for its anticarcinogenic properties. Xanthohumol is converted into three metabolites: isoxanthohumol (non-enzymatically) as well as 8- and 6-prenylnaringenin (enzymatically). An inverse molecular docking approach was applied to xanthohumol and its three metabolites to discern their potential protein targets. The aim of our study was to disclose the potential protein targets of xanthohumol and its metabolites in order to expound on the potential anticarcinogenic mechanisms of xanthohumol based on the found target proteins. The investigated compounds were docked into the predicted binding sites of all human protein structures from the Protein Data Bank, and the best docking poses were examined. Top scoring human protein targets with successfully docked compounds were identified, and their experimental connection with the anticarcinogenic function or cancer was investigated. The obtained results were carefully checked against the existing experimental findings from the scientific literature as well as further validated using retrospective metrics. More than half of the human protein targets of xanthohumol with the highest docking scores have already been connected with the anticarcinogenic function, and four of them (including two important representatives of the matrix metalloproteinase family, MMP-2 and MMP-9) also have a known experimental correlation with xanthohumol. Another important protein target is acyl-protein thioesterase 2, to which xanthohumol, isoxanthohumol, and 6-prenylnaringenin were successfully docked with the lowest docking scores. Moreover, the results for the metabolites show that their most promising protein targets are connected with the anticarcinogenic function as well. We firmly believe that our study can help to elucidate the anticarcinogenic mechanisms of xanthohumol and its metabolites as after consumption, all four compounds can be simultaneously present in the organism.

Toxoplasmosis: Targeting neurotransmitter systems in psychiatric disorders

The most common form of the disease caused by Toxoplasma gondii (T. gondii) is latent toxoplasmosis due to the formation of tissue cysts in various organs, such as the brain. Latent toxoplasmosis is probably a risk factor in the development of some neuropsychiatric disorders. Behavioral changes after infection are caused by the host immune response, manipulation by the parasite, central nervous system (CNS) inflammation, as well as changes in hormonal and neuromodulator relationships. The present review focused on the exact mechanisms of T. gondii effect on the alteration of behavior and neurotransmitter levels, their catabolites and metabolites, as well as the interaction between immune responses and this parasite in the etiopathogenesis of psychiatric disorders. The dysfunction of neurotransmitters in the neural transmission is associated with several neuropsychiatric disorders. However, further intensive studies are required to determine the effect of this parasite on altering the level of neurotransmitters and the role of neurotransmitters in the etiology of host behavioral changes.

Cold-Blooded and on Purpose: A Review of the Biology of Proactive Aggression

Proactive aggression (PA) is a planned and unprovoked form of aggression that is most often enacted for personal gain or in anticipation of a reward. Frequently described as "cold-blooded" or goal oriented, PA is thought to be associated with low autonomic arousal. With this view in mind, we performed a scoping review of the biological correlates of PA and identified 74 relevant articles. Physiological findings indicated a robust association between PA and reduced resting heart rate, and to a lesser extent a relationship between PA and decreased heart rate and skin conductance reactivity, perhaps indicating dampened sympathetic function. The twin literature identified PA as a heritable trait, but little evidence implicates specific genes in the pathogenesis of PA. Neuroimaging studies of PA pinpoint impaired amygdala function in the assessment and conditioning of aversive stimuli, which may influence the establishment of behavioral patterns. Nodes of the default mode network were identified as possible neural correlates of PA, suggesting that altered function of this network may be involved in the genesis of PA. Given the overlap of PA with reactive aggression and the overall behavioral complexity of PA, it is clear that multiple endophenotypes of PA exist. This comprehensive review surveys the most salient neurobiologically informed research on PA.

The Associations between COMT and MAO-B Genetic Variants with Negative Symptoms in Patients with Schizophrenia

Negative symptoms of schizophrenia, including anhedonia, represent a heavy burden on patients and their relatives. These symptoms are associated with cortical hypodopamynergia and impaired striatal dopamine release in response to reward stimuli. Catechol-O-methyltransferase (COMT) and monoamine oxidase type B (MAO-B) degrade dopamine and affect its neurotransmission. The study determined the association between COMT rs4680 and rs4818, MAO-B rs1799836 and rs6651806 polymorphisms, the severity of negative symptoms, and physical and social anhedonia in schizophrenia. Sex-dependent associations were detected in a research sample of 302 patients with schizophrenia. In female patients with schizophrenia, the presence of the G allele or GG genotype of COMT rs4680 and rs4818, as well as GG haplotype rs4818-rs4680, which were all related to higher COMT activity, was associated with an increase in several dimensions of negative symptoms and anhedonia. In male patients with schizophrenia, carriers of the MAO-B rs1799836 A allele, presumably associated with higher MAO-B activity, had a higher severity of alogia, while carriers of the A allele of the MAO-B rs6651806 had a higher severity of negative symptoms. These findings suggest that higher dopamine degradation, associated with COMT and MAO-B genetic variants, is associated with a sex-specific increase in the severity of negative symptoms in schizophrenia patients.

Monoamine Oxidase Inhibitors: A Review of Their Anti-Inflammatory Therapeutic Potential and Mechanisms of Action

Chronic inflammatory diseases are debilitating, affect patients' quality of life, and are a significant financial burden on health care. Inflammation is regulated by pro-inflammatory cytokines and chemokines that are expressed by immune and non-immune cells, and their expression is highly controlled, both spatially and temporally. Their dysregulation is a hallmark of chronic inflammatory and autoimmune diseases. Significant evidence supports that monoamine oxidase (MAO) inhibitor drugs have anti-inflammatory effects. MAO inhibitors are principally prescribed for the management of a variety of central nervous system (CNS)-associated diseases such as depression, Alzheimer's, and Parkinson's; however, they also have anti-inflammatory effects in the CNS and a variety of non-CNS tissues. To bolster support for their development as anti-inflammatories, it is critical to elucidate their mechanism(s) of action. MAO inhibitors decrease the generation of end products such as hydrogen peroxide, aldehyde, and ammonium. They also inhibit biogenic amine degradation, and this increases cellular and pericellular catecholamines in a variety of immune and some non-immune cells. This decrease in end product metabolites and increase in catecholamines can play a significant role in the anti-inflammatory effects of MAO inhibitors. This review examines MAO inhibitor effects on inflammation in a variety of in vitro and in vivo CNS and non-CNS disease models, as well as their anti-inflammatory mechanism(s) of action.

The role of monoamine oxidase enzymes in the pathophysiology of neurological disorders

Monoamine oxidase enzymes are responsible for the degredation of serotonin, dopamine, and norepinephrine in the central neurvous system. Although it has been nearly 100 years since they were first described, we are still learning about their role in the healthy brain and how they are altered in various disease states. The present review provides a survey of our current understanding of monoamine oxidases, with a focus on their contributions to neuropsychiatric, neurodevelopmental, and neurodegenerative disease. Important species differences in monoamine oxidase function and development in the brain are highlighted. Sex-specific monoamine oxidase regulatory mechanisms and their implications for various neurological disorders are also discussed. While our understanding of these critical enzymes has expanded over the last century, gaps exist in our understanding of sex and species differences and the roles monoamine oxidases may play in conditions often comorbid with neurological disorders.

Monoamine Oxidase A Inhibits Lung Adenocarcinoma Cell Proliferation by Abrogating Aerobic Glycolysis

Lung adenocarcinoma (LUAD) accounts for ~30% of all lung cancers and is one of the causes of cancer-related death worldwide. As the role of monoamine oxidase A (MAOA) in LUAD remains unclear, in this study, we examine how MAOA affects LUAD cell proliferation. Analyses of both public data and our data reveal that the expression of MAOA is downregulated in LUAD compared with non-tumor tissue. In addition, the expression of MAOA in tumors correlates with clinicopathologic features, and the expression of MAOA serves as an independent biomarker in LUAD. In addition, the overexpression of MAOA inhibits LUAD cell proliferation by inducing G1 arrest in vitro. Further mechanistic studies show that MAOA abrogates aerobic glycolysis in LUAD cells by decreasing hexokinase 2 (HK2). Finally, the expression of HK2 shows a negative correlation with MAOA in LUAD, and high HK2 predicts poor clinical outcome. In conclusion, our findings indicate that MAOA functions as a tumor suppressor in LUAD. Our results indicate that the MAOA/HK2 axis could be potential targets in LUAD therapy.

Association of variable number of tandem repeats (VNTR) and T941G polymorphism of monoamine oxidase (MAO-A) gene with aggression in Pakistani subjects

Background

Human behavioral traits are known to be significantly heritable. Certain individuals have a greater tendency of negative behavioral aspects including aggression. The quest to identify tunderlying genetic causes has led to identification of a number of genetic markers, one of them is the monoamine oxidase-A (MAO-A) gene.

Objective

We aimed to genotype a variable number of tandem repeats (VNTRs) in the promoter region and a functional SNP within this gene (T941G, dbSNP ID: rs6323) in the recruited cohort of 482 subjects.

Methods

After DNA isolation, genotyping was done by PCR-RFLP and the results were confirmed by sequencing.

Results

For VNTRs, the results showed, highest frequency of 3.5 repeats in males and 4 repeats in females in the promoter region. The genotype frequencies for the SNP in cases were GG=16.3%, TG=20.6% and TT=63.1%, while in controls, the frequencies were GG=12.7%, TG=6.3%, and TT=81.0%. The allele frequencies were significantly different between cases and controls (p=0.015; OR=1.51; CI=1.085–2.102).

Conclusion

The selected VNTR and SNP appeared to be significantly associated with aggression. These VNTRs and SNP have not been studied previously in the Pakistani population, hence they represent a unique ethnic group. These results, however, would have to be replicated in larger cohorts.

Depressive Symptoms among Middle-Aged Women-Understanding the Cause

Menopause is an important event in a woman’s life associated with hormonal changes that play a substantial role in the functioning of her body. A decline in the level of estrogens contributes to depressive symptoms and mood disorders during this period. The severity of depressive symptoms experienced by middle-aged women depends on many factors, including sociodemographic data (e.g., menopause, employment status, and marital status) and genetic variables (MAO-A and 5-HTT gene polymorphisms). In order to assess their influence on the development of depression in females, we analyzed 1453 healthy Polish women in different stages of menopause. Based on the results, we found that the l/l + l/s inheritance model for the 5-HTT gene polymorphism was more common in women without and with moderate depressive symptoms according to the Beck Depression Inventory (BDI), while the l/s model was more often observed in women with mild depression. Moreover, the overdominant 3/3 + 4/4 genotype of the MAO-A gene polymorphism was more often found in respondents without depressive symptoms, while women with depressive symptoms had more often the overdominant 3/4 genotype.

Accelerating the identification of subtype selective inhibitors via Three-Dimensional Biologically Relevant Spectrum (BRS-3D): The monoamine oxidase subtypes as a case study

Subtype-selective drugs are of great therapeutic importance as they are expected to be more effective and with less side-effects. However, discovery of subtype selective inhibitors was hampered by the high similarity of the binding sites within subfamilies. In this study, we further evaluated the applicability of "Three-Dimensional Biologically Relevant Spectrum (BRS-3D)" for the identification of subtype-selective inhibitors. A case study was performed on monoamine oxidase, which has two subtypes related to distinct diseases. The inhibitory activity against MAO-A/B of 347 compounds experimentally tested in this research was reported. Compound M124 (5H-thiazolo[3,2-a]pyrimidin-5-one) with IC₅₀ less than 100 nM (SI = 23) was selected as a probe to investigate the structure selectivity relationship. Similarity search led to the identification of compound M229 and M249 with IC₅₀ values of 7.4 nM, 4 nM and acceptable selectivity index over MAO-A (M229 SI > 1351, M249 SI > 2500). The molecular basis for subtype selectivity was explored through docking study and attention based DNN model. Additionally, in silico ADME properties were characterized. Accordingly, it is found that BRS-3D is a robust method for subtype selectivity in the early stage of drug discovery and the compounds reported here can be promising leads for further experimental analysis.

The role of monoamine oxidase A in the neurobiology of aggressive, antisocial, and violent behavior: A tale of mice and men

Over the past two decades, research has revealed that genetic factors shape the propensity for aggressive, antisocial, and violent behavior. The best-documented gene implicated in aggression is MAOA (Monoamine oxidase A), which encodes the key enzyme for the degradation of serotonin and catecholamines. Congenital MAOA deficiency, as well as low-activity MAOA variants, has been associated with a higher risk for antisocial behavior (ASB) and violence, particularly in males with a history of child maltreatment. Indeed, the interplay between low MAOA genetic variants and early-life adversity is the best-documented gene × environment (G × E) interaction in the pathophysiology of aggression and ASB. Additional evidence indicates that low MAOA activity in the brain is strongly associated with a higher propensity for aggression; furthermore, MAOA inhibition may be one of the primary mechanisms whereby prenatal smoke exposure increases the risk of ASB. Complementary to these lines of evidence, mouse models of Maoa deficiency and G × E interactions exhibit striking similarities with clinical phenotypes, proving to be valuable tools to investigate the neurobiological mechanisms underlying antisocial and aggressive behavior. Here, we provide a comprehensive overview of the current state of the knowledge on the involvement of MAOA in aggression, as defined by preclinical and clinical evidence. In particular, we show how the convergence of human and animal research is proving helpful to our understanding of how MAOA influences antisocial and violent behavior and how it may assist in the development of preventative and therapeutic strategies for aggressive manifestations.

Molecular cloning, sequence analysis, and tissue distribution of marmoset monoamine oxidases A and B

The common marmoset (Callithrix jacchus), a New World primate, is currently attracting much attention as a nonhuman primate model for pharmacological and pharmacokinetic studies in preclinical research. In this study, we newly isolated the cDNAs of marmoset monoamine oxidase A (MAO-A) and MAO-B from liver and brain, respectively. MAO-A and MAO-B cDNAs, respectively, contained open reading frames of 527 and 520 amino acids and were approximately 92% and 95% identical to their human orthologs. Marmoset MAOs were phylogenetically closer to primate MAOs, including human MAOs, than to pig, dog, or rodent MAOs. The genomic and gene structures of marmoset MAOs were similar to those of humans. Among the five marmoset tissue types analyzed, the expression levels of MAO-A mRNA were relatively abundant in lung, liver, kidney, and small intestine, whereas the expression levels of MAO-B mRNA were relatively abundant in brain, liver, kidney, and small intestine; these tissue distributions are similar to those of human MAOs. These results suggest that MAO-A and MAO-B are similar at a molecular level in marmosets and humans.

Genetic interaction between two VNTRs in the MAOA gene is associated with the nicotine dependence

IMPACT STATEMENT

The present study combined the analysis of two transcriptional regulators, uVNTR and dVNTR, in the MAOA gene that is an enzyme responsible for the monoamine degradation and identified genetic interaction between these VNTRs in association with the nicotine dependence. The main impact is that when analyzing different populations in the genetic studies, the functionally meaningful variants should be combined rather than addressing individual elements separately (a mini polygenic risk score for a particular gene/locus). This combination is very rarely analyzed and therefore the study sets an example. Another impact is that we analyzed the genetic variability in the Asian population and therefore our data present a piece of information from underrepresented populations.

Single Heterocyclic Compounds as Monoamine Oxidase Inhibitors: From Past to Present

Inhibitors of monoamine oxidase (MAO) have shown therapeutic values in a variety of neurodegenerative diseases such as depression, Parkinson's disease and Alzheimer's disease. Heterocyclic compounds exhibit a broad spectrum of biological activities and vital leading compounds for the development of chemical drugs. Herein, we focus on the synthesis and screening of novel single heterocyclic derivatives with MAO inhibitory activities during the past decade. This review covers recent pharmacological advancements of single heterocyclic moiety along with structure- activity relationship to provide better correlation among different structures and their receptor interactions.

Novel C7-Substituted Coumarins as Selective Monoamine Oxidase Inhibitors: Discovery, Synthesis and Theoretical Simulation

There is a continued need to develop new selective human monoamine oxidase (hMAO) inhibitors that could be beneficial for the treatment of neurological diseases. However, hMAOs are closely related with high sequence identity and structural similarity, which hinders the development of selective MAO inhibitors. “Three-Dimensional Biologically Relevant Spectrum (BRS-3D)” method developed by our group has demonstrated its effectiveness in subtype selectivity studies of receptor and enzyme ligands. Here, we report a series of novel C7-substituted coumarins, either synthesized or commercially purchased, which were identified as selective hMAO inhibitors. Most of the compounds demonstrated strong activities with IC₅₀ values (half-inhibitory concentration) ranging from sub-micromolar to nanomolar. Compounds, FR1 and SP1, were identified as the most selective hMAO-A inhibitors, with IC₅₀ values of 1.5 nM (selectivity index (SI) < −2.82) and 19 nM (SI < −2.42), respectively. FR4 and FR5 showed the most potent hMAO-B inhibitory activity, with IC₅₀ of 18 nM and 15 nM (SI > 2.74 and SI > 2.82). Docking calculations and molecular dynamic simulations were performed to elucidate the selectivity preference and SAR profiles.

Benzo[b]tiophen-3-ol derivatives as effective inhibitors of human monoamine oxidase: design, synthesis, and biological activity

A series of benzo[b]thiophen-3-ols were synthesised and investigated as potential human monoamine oxidase (hMAO) inhibitors in vitro as well as ex vivo in rat cortex synaptosomes by means of evaluation of 3,4-dihydroxyphenylacetic acid/dopamine (DOPAC/DA) ratio and lactate dehydrogenase (LDH) activity. Most of these compounds possessed high selectivity for the MAO-B isoform and a discrete antioxidant and chelating potential. Molecular docking studies of all the compounds underscored potential binding site interactions suitable for MAO inhibition activity, and suggested structural requirements to further improve the activity of this scaffold by chemical modification of the aryl substituents. Starting from this heterocyclic nucleus, novel lead compounds for the treatment of neurodegenerative disease could be developed.

Emotional stability is associated with the MAOA promoter uVNTR polymorphism in women

BACKGROUND

Neuroticism is associated with low emotional stability, and it is characterized by a tendency to perceive ordinary situations as threatening and difficult to manage. This personality trait has been associated with psychological distress and predicts some mental disorders. Previous studies have shown that women tend to be more neurotic than men and, in general, females have also a higher incidence of anxious and depressive disorders.

METHODS

We analyzed in a sample of 99 female university students (from 18 to 26 years old) if emotional stability, measured using the Big Five Questionnaire, was linked to polymorphic variants in candidate genes related to dopaminergic and serotonergic systems, and other personality variables.

RESULTS

We found that emotional stability and its subdimensions are genetically associated with MAOA-uVNTR polymorphism. Thus, women carriers of the 3-repeat allele (lower MAO-A expression) showed higher levels of emotional stability. No associations were found with other polymorphisms analyzed, including COMT Val¹⁵⁸ Met, 5-HTTLPR, and DAT 3'UTR VNTR. Furthermore, our results showed a negative correlation between emotional stability and depression, state anxiety, and trait anxiety. In fact, MAOA-uVNTR and trait anxiety also explained emotional stability and its subdimensions. We also found that other genetic characteristic, phenylthiocarbamide tasting, explained impulsivity, specifically tasters controlled impulses better than nontasters.

CONCLUSION

Our results indicate that neuroticism might be regulated by MAOA and could be a common factor between different phenotypes, such as aggressive behaviors or personality disorders, observed in women with higher activity genotype who had been exposed to negative environments during childhood. This study could lead to a better understanding of the basis of emotional stability and could lead to future projects for this purpose.

Identification of a Lactic Acid Bacteria to Degrade Biogenic Amines in Chinese Rice Wine and Its Enzymatic Mechanism

A L. plantarum, CAU 3823, which can degrade 40% of biogenic amines (BAs) content in Chinese rice wine (CRW) at the end of post-fermentation, was selected and characterized in this work. It would be an optimal choice to add 106 cfu/mL of selected strain into the fermentation broth to decrease the BAs while keeping the character and quality of CRW. Nine amine oxidases were identified from the strain and separated using Sephadex column followed by LC-MS/MS analysis. The purified amine oxidase mixture showed a high monoamine oxidase activity of 19.8 U/mg, and more than 40% of BAs could be degraded. The biochemical characters of the amine oxidases were also studied. This work seeks to provide a better solution to degrade BAs in CRW prior to keeping the character and quality of CRW and a better understanding of the degradability of the strain to the BAs.

Structure-Based Specific Detection and Inhibition of Monoamine Oxidases and Their Applications in Central Nervous System Diseases

Monoamine oxidases (MAOs) are the enzymes that catalyze the oxidation of monoamines, such as dopamine, norepinephrine, and serotonin, which serve as key neurotransmitters in the central nervous system (CNS). MAOs play important roles in maintaining the homeostasis of monoamines, and the aberrant expression or activation of MAOs underlies the pathogenesis of monoamine neurotransmitter disorders, including neuropsychiatric and neurodegenerative diseases. Clearly, detecting and inhibiting the activities of MAOs is of great value for the diagnosis and therapeutics of these diseases. Accordingly, many specific detection probes and inhibitors have been developed and substantially contributed to basic and clinical studies of these diseases. In this review, progress in the detecting and inhibiting of MAOs and their applications in mechanism exploration and treatment of neurotransmitter-related disorders is summarized. Notably, how the detection probes and inhibitors of MAOs were developed has been specifically addressed. It is hoped that this review will benefit the design of more effective and sensitive probes and inhibitors for MAOs, and eventually the treatment of monoamine neurotransmitter disorders.

Identification of novel monoamine oxidase selective inhibitors employing a hierarchical ligand-based virtual screening strategy

Aim: Due to the pivotal role in the oxidative deamination of monoamine neurotransmitters, two distinct monoamine oxidase (MAO) subtypes, MAO-A and MAO-B, present a significant pharmacological interest. Here, we reported a hierarchical and time-efficient ligand-based virtual screening strategy to identify potent selective and reversible MAO inhibitors. Result: A total of 130 compounds were assessed in dose–response biochemical assay against MAOs. Among them, 70 compounds were active with inhibition higher than 70%, involving 25 compounds with IC50 values less than 1 μM. Conclusion: Our research demonstrated the validity of Biologically Relevant Spectrum (BRS-3D) in predicting subtype-selective ligands and afforded a novel highly efficient way to develop selective inhibitors in the early stage of drug discovery.

Monoamine oxidase-B inhibitors as potential neurotherapeutic agents: An overview and update

Monoamine oxidase (MAO) inhibitors have made significant contributions and remain an indispensable approach of molecular and mechanistic diversity for the discovery of antineurodegenerative drugs. However, their usage has been hampered by nonselective and/or irreversible action which resulted in drawbacks like liver toxicity, cheese effect, and so forth. Hence, the search for selective MAO inhibitors (MAOIs) has become a substantial focus in current drug discovery. This review summarizes our current understanding on MAO-A/MAO-B including their structure, catalytic mechanism, and biological functions with emphases on the role of MAO-B as a potential therapeutic target for the development of medications treating neurodegenerative disorders. It also highlights the recent developments in the discovery of potential MAO-B inhibitors (MAO-BIs) belonging to diverse chemical scaffolds, arising from intensive chemical-mechanistic and computational studies documented during past 3 years (2015-2018), with emphases on their potency and selectivity. Importantly, readers will gain knowledge of various newly established MAO-BI scaffolds and their development potentials. The comprehensive information provided herein will hopefully accelerate ideas for designing novel selective MAO-BIs with superior activity profiles and critical discussions will inflict more caution in the decision-making process in the MAOIs discovery.

Monoamine oxidase isoenzymes: genes, functions and targets for behavior and cancer therapy

Monoamine oxidase (MAO) catalyzes the oxidative deamination of monoamine neurotransmitters and dietary amines. Two pharmacological types with different substrate and inhibitor specificities were reported. Molecular cloning revealed that the two types of MAO were different genes expressed as different proteins with different functions. MAO A and B have identical intron-exon organization derived by duplication of a common ancestral gene thus they are termed isoenzymes. MAO A knockout mice exhibited aggression, the first clear evidence linking genes to behavior. MAO A KO mice exhibited autistic-like behaviors which could be prevented by reducing serotonin levels at an early developmental age (P1-P7) providing potential therapy. MAO B KO mice were non-aggressive and resistant to Parkinsongenic neurotoxin. More recently it was found that MAO A is overexpressed in prostate cancer and correlates with degree of malignancy. The oncogenic mechanism involves a ROS-activated AKT/FOXO1/TWIST1 signaling pathway. Deletion of MAO A reduced prostate cancer stem cells and suppressed invasive adenocarcinoma. MAO A was also overexpressed in classical Hodgkin lymphoma and glioma brain tumors. MAO B was overexpressed in glioma and non-small cell lung cancer. MAO A inhibitors reduce the growth of prostate cancer, drug sensitive and resistant gliomas and classical Hodgkin lymphoma, and enhance standard chemotherapy. Currently, we are developing NIR dye-conjugated clorgyline (MAO A inhibitor) as a novel dual therapeutic/diagnostic agent for cancer. A phase II clinical trial of MAO inhibitor for biochemical recurrent prostate cancer is ongoing. The role of MAO A and B in several cancer types opens new avenues for cancer therapies.

Isoform selectivity of harmine-conjugated 1,2,3-triazoles against human monoamine oxidase

AIM

There is little information available on the monoamine oxidase isoform selectivity of N-alkyl harmine analogs, which exhibit a myriad of activities including MAO-A, DYRK1A and cytotoxicity to several select cancer cell lines.

RESULTS

Compounds 3e and 4c exhibited an IC₅₀ of 0.83 ± 0.03 and 0.43 ± 0.002 μM against MAO-A and an IC₅₀ of 0.26 ± 0.04 and 0.36 ± 0.001 μM against MAO-B, respectively. Molecular docking studies revealed π-π interactions between the synthesized molecules and aromatic amino acid residues. Conclusion & future perspective: The current study delineates the structural requirements for MAO-A selectivity and such information may be helpful in designing selective analogs for kinase, DYRK1A and harmine-based cytotoxics without apparent MAO enzyme inhibition.

From aggression to autism: new perspectives on the behavioral sequelae of monoamine oxidase deficiency

The two monoamine oxidase (MAO) enzymes, A and B, catalyze the metabolism of monoamine neurotransmitters, such as serotonin, norepinephrine, and dopamine. The phenotypic outcomes of MAO congenital deficiency have been studied in humans and animal models, to explore the role of these enzymes in behavioral regulation. The clinical condition caused by MAOA deficiency, Brunner syndrome, was first described as a disorder characterized by overt antisocial and aggressive conduct. Building on this discovery, subsequent studies were focused on the characterization of the role of MAOA in the neurobiology of antisocial conduct. MAO A knockout mice were found to display high levels of intermale aggression; however, further analyses of these mutants unveiled additional behavioral abnormalities mimicking the core symptoms of autism-spectrum disorder. These findings were strikingly confirmed in newly reported cases of Brunner syndrome. The role of MAOB in behavioral regulation remains less well-understood, even though Maob-deficient mice have been found to exhibit greater behavioral disinhibition and risk-taking responses, supporting previous clinical studies showing associations between low MAO B activity and impulsivity. Furthermore, lack of MAOB was found to exacerbate the severity of psychopathological deficits induced by concurrent MAOA deficiency. Here, we summarize how the convergence of clinical reports and behavioral phenotyping in mutant mice has helped frame a complex picture of psychopathological features in MAO-deficient individuals, which encompass a broad spectrum of neurodevelopmental problems. This emerging knowledge poses novel conceptual challenges towards the identification of the endophenotypes shared by autism-spectrum disorder, antisocial behavior and impulse-control problems, as well as their monoaminergic underpinnings.

Privileged scaffolds as MAO inhibitors: Retrospect and prospects

This review aims to be a comprehensive, authoritative, critical, and readable review of general interest to the medicinal chemistry community because it focuses on the pharmacological, chemical, structural and computational aspects of diverse chemical categories as monoamine oxidase inhibitors (MAOIs). Monoamine oxidases (MAOs), namely MAO-A and MAO-B represent an enormously valuable class of neuronal enzymes embodying neurobiological origin and functions, serving as potential therapeutic target in neuronal pharmacotherapy, and hence we have coined the term "Neurozymes" which is being introduced for the first time ever. Nowadays, therapeutic attention on MAOIs engrosses two imperative categories; MAO-A inhibitors, in certain mental disorders such as depression and anxiety, and MAO-B inhibitors, in neurodegenerative disorders like Alzheimer's disease (AD) and Parkinson's disease (PD). The use of MAOIs declined due to some potential side effects, food and drug interactions, and introduction of other classes of drugs. However, curiosity in MAOIs is reviving and the recent developments of new generation of highly selective and reversible MAOIs, have renewed the therapeutic prospective of these compounds. The initial section of the review emphasizes on the detailed classification, structural and binding characteristics, therapeutic potential, current status and future challenges of the privileged pharmacophores. However, the chemical prospective of privileged scaffolds such as; aliphatic and aromatic amines, amides, hydrazines, azoles, diazoles, tetrazoles, indoles, azines, diazines, xanthenes, tricyclics, benzopyrones, and more interestingly natural products, along with their conclusive SARs have been discussed in the later segment of review. The last segment of the article encompasses some patents granted in the field of MAOIs, in a simplistic way.

Emerging PET Radiotracers and Targets for Imaging of Neuroinflammation in Neurodegenerative Diseases: Outlook Beyond TSPO

The dynamic and multicellular processes of neuroinflammation are mediated by the nonneuronal cells of the central nervous system, which include astrocytes and the brain's resident macrophages, microglia. Although initiation of an inflammatory response may be beneficial in response to injury of the nervous system, chronic or maladaptive neuroinflammation can have harmful outcomes in many neurological diseases. An acute neuroinflammatory response is protective when activated neuroglia facilitate tissue repair by releasing anti-inflammatory cytokines and neurotrophic factors. On the other hand, chronic neuroglial activation is a major pathological mechanism in neurodegenerative diseases, likely contributing to neuronal dysfunction, injury, and disease progression. Therefore, the development of specific and sensitive probes for positron emission tomography (PET) studies of neuroinflammation is attracting immense scientific and clinical interest. An early phase of this research emphasized PET studies of the prototypical imaging biomarker of glial activation, translocator protein-18 kDa (TSPO), which presents difficulties for quantitation and lacks absolute cellular specificity. Many alternate molecular targets present themselves for PET imaging of neuroinflammation in vivo, including enzymes, intracellular signaling molecules as well as ionotropic, G-protein coupled, and immunoglobulin receptors. We now review the lead structures in radiotracer development for PET studies of neuroinflammation targets for neurodegenerative diseases extending beyond TSPO, including glycogen synthase kinase 3, monoamine oxidase-B, reactive oxygen species, imidazoline-2 binding sites, cyclooxygenase, the phospholipase A2/arachidonic acid pathway, sphingosine-1-phosphate receptor-1, cannabinoid-2 receptor, the chemokine receptor CX3CR1, purinergic receptors: P2X7 and P2Y12, the receptor for advanced glycation end products, Mer tyrosine kinase, and triggering receptor expressed on myeloid cells-1. We provide a brief overview of the cellular expression and function of these targets, noting their selectivity for astrocytes and/or microglia, and highlight the classes of PET radiotracers that have been investigated in early-stage preclinical or clinical research studies of neuroinflammation.

Design, synthesis, and pharmacological evaluation of 2-amino-5-nitrothiazole derived semicarbazones as dual inhibitors of monoamine oxidase and cholinesterase: effect of the size of aryl binding site

A series of 2-amino-5-nitrothiazole derived semicarbazones were designed, synthesised and investigated for MAO and ChE inhibition properties. Most of the compounds showed preferential inhibition towards MAO-B. Compound 4, (1-(1-(4-Bromophenyl)ethylidene)-4-(5-nitrothiazol-2-yl)semicarbazide) emerged as lead candidate (IC₅₀ = 0.212 µM, SI = 331.04) against MAO-B; whereas compounds 21 1-(5-Bromo-2-oxoindolin-3-ylidene)-4-(5-nitrothiazol-2-yl)semicarbazide (IC₅₀ = 0.264 µM) and 17 1-((4-Chlorophenyl) (phenyl)methylene)-4-(5-nitrothiazol-2-yl)semicarbazide (IC₅₀ = 0.024 µM) emerged as lead AChE and BuChE inhibitors respectively; with activity of compound 21 almost equivalent to tacrine. Kinetic studies indicated that compound 4 exhibited competitive and reversible MAO-B inhibition while compounds 21 and 17 showed mixed-type of AChE and BuChE inhibition respectively. Docking studies revealed that these compounds were well-accommodated within MAO-B and ChE active sites through stable hydrogen bonding and/or hydrophobic interactions. This study revealed the requirement of small heteroaryl ring at amino terminal of semicarbazone template for preferential inhibition and selectivity towards MAO-B. Our results suggest that 5-nitrothiazole derived semicarbazones could be further exploited for its multi-targeted role in development of anti-neurodegenerative agents. [Formula: see text] A library of 2-amino-5-nitrothiazole derived semicarbazones (4-21) was designed, synthesised and evaluated for in vitro MAO and ChE inhibitory activity. Compounds 4, 21 and 17 (shown) have emerged as lead MAO-B (IC₅₀:0.212 µM, competitive and reversible), AChE (IC₅₀:0.264 µM, mixed and reversible) and BuChE (IC₅₀:0.024 µM, mixed and reversible) inhibitor respectively. SAR studies disclosed several structural aspects significant for potency and selectivity and indicated the role of size of aryl binding site in potency and selectivity towards MAO-B. Antioxidant activity and neurotoxicity screening results further suggested their multifunctional potential for the therapy of neurodegenerative diseases.

Monoamine oxidase-B inhibitor protects degenerating spinal neurons, enhances nerve regeneration and functional recovery in sciatic nerve crush injury model

Monoamine oxidase-B (MAOB), a flavin adenine dinucleotide (FAD), is an enzyme which catalyzes the oxidation of amines. MAOB is proposed to play a major role in the pathogenesis of neurodegeneration through the production of reactive oxygen species (ROS) and neurotoxins. The present study was designed to outline the effects of the MAOB inhibitor (MAOB-I) on neuroprotection of spinal neurons, regeneration of sciatic nerve fibers, and recovery of sensory-motor functions in the sciatic nerve crush injury model. Male Wistar rats (4-months-old) were assigned to i) Naïve (N), ii) Sham (S), iii) Sciatic nerve crush and treated with saline (CRUSH + SALINE) and iv) Sciatic nerve crush and treated with MAOB inhibitor (CRUSH + MAOB-I) groups (n = 10/group). In groups iii and iv, the crush injury was produced by crushing the sciatic nerve followed by treatment with saline or MAOB-I (Selegiline^® 2.5 mg/kg) intraperitoneally for 10 days. Behavioral tests were conducted from week 1 to week 6. At the end of the study, sciatic nerve and lumbar spinal cord were examined by immunohistochemistry, light and electron microscopy. MAOB-I treatment showed significant improvement in sensory and motor functions compared to saline treatment (p < 0.05-0.001) in injured nerves. The morphological study showed a significantly increased number of nerve fibers in sciatic nerve distal to the site of injury (p < 0.05), with better myelination pattern in CRUSH + MAOB-I treated group compared to CRUSH + SALINE group. Spinal cord ventral horns showed a significant increase in the number of NeuN-immunoreactive neurons in the MAOB-I treated group compared to Saline treated group (p < 0.01). MAOB-I has a significant potential for protecting the degenerating spinal cord neurons and enhancing the regeneration of injured sciatic nerve fibers following crush injury.

Pilot study indicate role of preferentially transmitted monoamine oxidase gene variants in behavioral problems of male ADHD probands

Background

Attention deficit hyperactivity disorder (ADHD) is an etiologically complex childhood onset neurobehavioral disorder characterized by age-inappropriate inattention, hyperactivity, and impulsivity. Symptom severity varies widely and boys are diagnosed more frequently than girls. ADHD probands were reported to have abnormal transmissions of dopamine, serotonin, and/or noradrenaline. Monoamine oxidase A (MAOA) and B (MAOB), mitochondrial outer membrane bound two isoenzymes, mediate degradation of these neurotransmitters and thus regulating their circulating levels. Case-control analyses in different populations, including Indians, suggested involvement of MAOA and MAOB genes in the etiology of ADHD. Due to high heritability rate of ADHD, we tested familial transmission of MAOA and MAOB variants to ADHD probands in 190 nuclear families having ADHD probands from Indo-Caucasoid ethnicity.

Methods

Subjects were recruited following the Diagnostic and Statistical Manual of Mental Disorders-4th edition (DSM-IV). Appropriate scales were used for measuring the behavioral traits in probands. Genotyping was performed through PCR-based amplification of target sites followed by DNA-sequencing and/or gel-electrophoresis. Data obtained were analyzed by family based statistical methods.

Results

Out of 58 variants present in the analyzed sites only 15 were found to be polymorphic (30 bp-uVNTR, rs5906883, rs1465107, rs1465108, rs5905809, rs5906957, rs6323, rs1137070 from MAOA and rs4824562, rs56220155, rs2283728, rs2283727, rs3027441, rs6324, rs3027440 from MAOB). Statistically significant maternal transmission of alleles to male probands was observed for MAOA rs5905809 ‘G’ (p = 0.04), rs5906957 ‘A’ (p = 0.04), rs6323 ‘G’ (p = 0.0001) and MAOB rs56220155 ‘A’ (p = 0.002), rs2283728 ‘C’ (p = 0.0008), rs2283727 ‘C’ (p = 0.0008), rs3027441 ‘T’ (p = 0.003), rs6324 ‘C’ (p = 0.003), rs3027440 ‘T’ (p = 0.0002). Significantly preferential maternal transmissions of different haplotype combinations to male probands were also noticed (p < 0.05), while female probands did not reveal such transmission bias. Behavioral traits of male probands exhibited significant association with gene variants. Age of the mother at pregnancy also revealed association with risk variants of male probands.

Conclusions

It may be inferred that the MAOA and MAOB variants may contribute to the etiology of ADHD in the Indo-Caucasoid population and could be responsible for higher occurrence of ADHD in the boys.

Electronic supplementary material

The online version of this article (10.1186/s12881-017-0469-5) contains supplementary material, which is available to authorized users.

Type A monoamine oxidase and serotonin are coordinately involved in depressive disorders: from neurotransmitter imbalance to impaired neurogenesis

Type A monoamine oxidase (MAOA) catabolizes monoamine transmitters, serotonin, norepinephrine and dopamine, and plays a major role in the onset, progression and therapy of neuropsychiatric disorders. In depressive disorders, increase in MAOA expression and decrease in brain levels of serotonin and norepinephrine are proposed as the major pathogenic factors. The functional polymorphism of MAOA gene and genes in serotonin signal pathway are associated with depression. This review presents recent advance in studies on the role of MAOA in major depressive disorder and related emotional disorders. MAOA and serotonin regulate the prenatal development and postnatal maintenance of brain architecture and neurocircuit, as shown by MAOA-deficient humans and MAO knockout animal models. Impaired neurogenesis in the mature hippocampus has been proposed as "adult neurogenesis" hypothesis of depression. MAOA modulates the sensitivity to stress in the stages of brain development and maturation, and the interaction of gene-environmental factors in the early stage regulates the onset of depressive behaviors in adulthood. Vice versa environmental factors affect MAOA expression by epigenetic regulation. MAO inhibitors not only restore compromised neurotransmitters, but also protect neurons from cell death in depression through induction of anti-apoptotic Bcl-2 and prosurvival neurotrophic factors, especially brain-derived neurotrophic factor, the deficiency of which is detected in depression. This review discusses novel role of MAOA and serotonin in the pathogenesis and therapy of depressive disorders.

Emerging role of dopamine in neovascularization of pheochromocytoma and paraganglioma

Dopamine is a catecholamine that acts both as a neurotransmitter and as a hormone, exerting its functions via dopamine (DA) receptors that are present in a broad variety of organs and cells throughout the body. In the circulation, DA is primarily stored in and transported by blood platelets. Recently, the important contribution of DA in the regulation of angiogenesis has been recognized. In vitro and in vivo studies have shown that DA inhibits angiogenesis through activation of the DA receptor type 2. Overproduction of catecholamines is the biochemical hallmark of pheochromocytoma (PCC) and paraganglioma (PGL). The increased production of DA has been shown to be an independent predictor of malignancy in these tumors. The precise relationship underlying the association between DA production and PCC and PGL behavior needs further clarification. Herein, we review the biochemical and physiologic aspects of DA with a focus on its relations with VEGF and hypoxia inducible factor related angiogenesis pathways, with special emphasis on DA producing PCC and PGL.-Osinga, T. E., Links, T. P., Dullaart, R. P. F., Pacak, K., van der Horst-Schrivers, A. N. A., Kerstens, M. N., Kema, I. P. Emerging role of dopamine in neovascularization of pheochromocytoma and paraganglioma.

Complete sampling of an enzyme reaction pathway: a lesson from gas phase simulations

With proper sampling strategy, convergence of free energy profiles of biomolecular reactions in the gas phase can be achieved in microseconds of simulation.

Insights into enzyme point mutation effect by molecular simulation: phenylethylamine oxidation catalyzed by monoamine oxidase A

The I335Y point mutation effect on the kinetics of phenylethylamine decomposition catalyzed by monoamine oxidase A was elucidated by means of molecular simulation. The established empirical valence bond methodology was used in conjunction with the free energy perturbation sampling technique and a classical force field representing the state of reactants and products. The methodology allows for the simulation of chemical reactions, in the present case the breaking of the α-C-H bond in a phenylethylamine substrate and the subsequent hydrogen transfer to the flavin cofactor, resulting in the formation of the N-H bond on flavin. The empirical parameters were calibrated against the experimental data for the simulated reaction in a wild type protein and then used for the calculation of the reaction free energy profile in the I335Y mutant. In very good agreement with the measured kinetic data, mutation increases the free energy barrier for the rate limiting step by slightly more than 1 kcal mol(-1) and consequently decreases the rate constant by about an order of magnitude. The magnitude of the computed effect slightly varies with simulation settings, but always remains in reasonable agreement with the experiment. Analysis of trajectories reveals a major change in the interaction between phenyl rings of the substrate and the neighboring Phe352 residue upon the I335Y mutation due to the increased local polarity, leading to an attenuated quadrupole interaction between the rings and destabilization of the transition state. Additionally, the increased local polarity in the mutant allows for a larger number of water molecules to be present near the active site, effectively shielding the catalytic effect of the enzyme and contributing to the increased barrier.

Monoamine oxidase A (MAO A) inhibitors decrease glioma progression

Glioblastoma (GBM) is an aggressive brain tumor which is currently treated with temozolomide (TMZ). Tumors usually become resistant to TMZ and recur; no effective therapy is then available. Monoamine Oxidase A (MAO A) oxidizes monoamine neurotransmitters resulting in reactive oxygen species which cause cancer. This study shows that MAO A expression is increased in human glioma tissues and cell lines. MAO A inhibitors, clorgyline or the near-infrared-dye MHI-148 conjugated to clorgyline (NMI), were cytotoxic for glioma and decreased invasion in vitro. Using the intracranial TMZ-resistant glioma model, clorgyline or NMI alone or in combination with low-dose TMZ reduced tumor growth and increased animal survival. NMI was localized specifically to the tumor. Immunocytochemistry studies showed that the MAO A inhibitor reduced proliferation, microvessel density and invasion, and increased macrophage infiltration. In conclusion, we have identified MAO A inhibitors as potential novel stand-alone drugs or as combination therapy with low dose TMZ for drug-resistant gliomas. NMI can also be used as a non-invasive imaging tool. Thus has a dual function for both therapy and diagnosis.

Modulation of monoamine oxidase (MAO) expression in neuropsychiatric disorders: genetic and environmental factors involved in type A MAO expression

Monoamine oxidase types A and B (MAO-A, MAO-B) regulate the levels of monoamine neurotransmitters in the brain, and their dysfunction may be involved in the pathogenesis and influence the clinical phenotypes of neuropsychiatric disorders. Reversible MAO-A inhibitors, such as moclobemide and befloxatone, are currently employed in the treatment of emotional disorders by inhibiting the enzymatic degradation of dopamine, serotonin and norepinephrine in the central nervous system (CNS). It has been suggested that the irreversible MAO-B inhibitors selegiline and rasagiline exert a neuroprotective effect in Parkinson's and Alzheimer's diseases. This effect, however, is not related to their inhibition of MAO activity; in animal and cellular models, selegiline and rasagiline protect neuronal cells through their anti-apoptotic activity and induction of pro-survival genes. There is increasing evidence that MAO-A activity, but not that of MAO-B, is implicated in the pathophysiology of neurodegenerative disorders, but also in gene induction by MAO-B inhibitors; on the other hand, selegiline and rasagiline increase MAO-A mRNA, protein, and enzyme activity levels. Taken together, these results suggest that each MAO subtype exerts effects that modulate the expression and activity of the other isoenzyme. The roles of MAO-A and -B in the CNS should therefore be re-evaluated with respect to the "type-specificity" of their inhibitors, which may not be unconditional during chronic treatment. Mao-a expression, in particular, may be implicated in pathogenesis and phenotypes in neuropsychiatric disorders. MAO-A expression is modified by mao polymorphisms affecting its transcriptional efficiency, as well as by mutations and polymorphism of parkin, Sirt1, FOXO, microRNA, presenilin-1, and other regulatory proteins. In addition, childhood maltreatment has been shown to have an impact upon adolescent social behavior in children with mao-a polymorphisms of low transcriptional activity. Low MAO-A activity may increase the levels of serotonin and norepinephrine, resulting in disturbed neurotransmitter system development and behavior. This review discusses genetic and environmental factors involved in the regulation of MAO-A expression, in the contexts of neuropsychiatric function and of the regulation of neuronal survival and death.

Polymorphisms in genes implicated in dopamine, serotonin and noradrenalin metabolism suggest association with cerebrospinal fluid monoamine metabolite concentrations in psychosis

BACKGROUND

Homovanillic acid (HVA), 5-hydroxyindoleacetic acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) are the major monoamine metabolites in the central nervous system (CNS). Their cerebrospinal fluid (CSF) concentrations, reflecting the monoamine turnover rates in CNS, are partially under genetic influence and have been associated with schizophrenia. We have hypothesized that CSF monoamine metabolite concentrations represent intermediate steps between single nucleotide polymorphisms (SNPs) in genes implicated in monoaminergic pathways and psychosis.

METHODS

We have searched for association between 119 SNPs in genes implicated in monoaminergic pathways [tryptophan hydroxylase 1 (TPH1), TPH2, tyrosine hydroxylase (TH), DOPA decarboxylase (DDC), dopamine beta-hydroxylase (DBH), catechol-O-methyltransferase (COMT), monoamine oxidase A (MAOA) and MAOB] and monoamine metabolite concentrations in CSF in 74 patients with psychotic disorder.

RESULTS

There were 42 nominally significant associations between SNPs and CSF monoamine metabolite concentrations, which exceeded the expected number (20) of nominal associations given the total number of tests performed. The strongest association (p = 0.0004) was found between MAOB rs5905512, a SNP previously reported to be associated with schizophrenia in men, and MHPG concentrations in men with psychotic disorder. Further analyses in 111 healthy individuals revealed that 41 of the 42 nominal associations were restricted to patients with psychosis and were absent in healthy controls.

CONCLUSIONS

The present study suggests that altered monoamine turnover rates in CNS reflect intermediate steps in the associations between SNPs and psychosis.