Novel 6-hydroxybenzothiazol-2-carboxamides as potent and selective monoamine oxidase B inhibitors endowed with neuroprotective activity

In neurodegenerative diseases, using a single molecule that can exert multiple effects to modify the disease may have superior activity over the classical "one molecule-one target" approach. Herein, we describe the discovery of 6-hydroxybenzothiazol-2-carboxamides as highly potent and selective MAO-B inhibitors. Variation of the amide substituent led to several potent compounds having diverse side chains with cyclohexylamide 40 displaying the highest potency towards MAO-B (IC50 = 11 nM). To discover new compounds with extended efficacy against neurotoxic mechanisms in neurodegenerative diseases, MAO-B inhibitors were screened against PHF6, R3 tau, cellular tau and α-synuclein (α-syn) aggregation. We identified the phenethylamide 30 as a multipotent inhibitor of MAO-B (IC50 = 41 nM) and α-syn and tau aggregation. It showed no cytotoxic effects on SH-SY5Y neuroblastoma cells, while also providing neuroprotection against toxicities induced by α-syn and tau. The evaluation of key physicochemical and in vitro-ADME properties revealed a great potential as drug-like small molecules with multitarget neuroprotective activity.

Inhibiting Monoamine Oxidase in CNS and CVS would be a Promising Approach to Mitigating Cardiovascular Complications in Neurodegenerative Disorders

The flavoenzyme monoamine oxidases (MAOs) are present in the mitochondrial outer membrane and are responsible for the metabolism of biogenic amines. MAO deamination of biological amines produces toxic byproducts such as amines, aldehydes, and hydrogen peroxide, which are significant in the pathophysiology of multiple neurodegenerative illnesses. In the cardiovascular system (CVS), these by-products target the mitochondria of cardiac cells leading to their dysfunction and producing redox imbalance in the endothelium of the blood vessels. This brings up the biological relationship between the susceptibility of getting cardiovascular disorders in neural patients. In the current scenario, MAO inhibitors are highly recommended by physicians worldwide for the therapy and management of various neurodegenerative disorders. Many interventional studies reveal the benefit of MAO inhibitors in CVS. Drug candidates who can target both the central and peripheral MAO could be a better to compensate for the cardiovascular comorbidities observed in neurodegenerative patients.

Recent advances on the role of monoamine oxidases in cardiac pathophysiology

Numerous physiological and pathological roles have been attributed to the formation of mitochondrial reactive oxygen species (ROS). However, the individual contribution of different mitochondrial processes independently of bioenergetics remains elusive and clinical treatments unavailable. A notable exception to this complexity is found in the case of monoamine oxidases (MAOs). Unlike other ROS-producing enzymes, especially within mitochondria, MAOs possess a distinct combination of defined molecular structure, substrate specificity, and clinically accessible inhibitors. Another significant aspect of MAO activity is the simultaneous generation of hydrogen peroxide alongside highly reactive aldehydes and ammonia. These three products synergistically impair mitochondrial function at various levels, ultimately jeopardizing cellular metabolic integrity and viability. This pathological condition arises from exacerbated MAO activity, observed in many cardiovascular diseases, thus justifying the exploration of MAO inhibitors as effective cardioprotective strategy. In this context, we not only summarize the deleterious roles of MAOs in cardiac pathologies and the positive effects resulting from genetic or pharmacological MAO inhibition, but also discuss recent findings that expand our understanding on the role of MAO in gene expression and cardiac development.

Cytochrome P450 and Other Drug Metabolizing Enzymes as Therapeutic Targets

Cytochrome P450 and other families of drug metabolizing enzymes are commonly thought of and studied for their ability to metabolize xenobiotics and other foreign entities as they are eliminated from the body. Equally as important, however, is the homeostatic role that many of these enzymes play in maintaining the proper levels of endogenous signaling molecules such as lipids, steroids, and eicosanoids, as well as their ability to modulate protein-protein interactions involved in downstream signaling cascades. Throughout the years, many of these endogenous ligands or protein partners of drug metabolizing enzymes have been associated with a wide range of disease states from cancer to various cardiovascular, neurological or inflammatory diseases, prompting an interest in whether or not modulation of drug metabolizing enzyme activity could have a subsequent pharmacological impact or lessening of disease severity. Beyond direct regulation of endogenous pathways, drug metabolizing enzymes have also been proactively targeted for their ability to activate pro-drugs with subsequent pharmacological activity or enhance the efficacy of a co-administered drug by inhibiting the metabolism of that drug through a rationally designed drug-drug interaction (i.e., ritonavir and HIV antiretroviral therapy). The focus of this minireview will be to highlight research aimed at characterizing cytochrome P450 and other drug metabolizing enzymes as therapeutic targets. Examples of successfully marketed drugs as well as early research efforts will be discussed. Finally, emerging areas of research utilizing typical drug metabolizing enzymes to impact clinical outcomes will be discussed. Significance Statement While generally thought of for their drug metabolizing capabilities, enzymes such as the cytochromes P450, glutathione S-transferases, soluble epoxide hydrolases and others play a significant role in regulating key endogenous pathways, making them potential drug targets. This minireview will cover various efforts over the years to modulate drug metabolizing enzyme activity towards pharmacological outcomes.

Bioisosteric replacement based on 1,2,4-oxadiazoles in the discovery of 1H-indazole-bearing neuroprotective MAO B inhibitors

Following a hybridization strategy, a series of 5-substituted-1H-indazoles were designed and evaluated in vitro as inhibitors of human monoamine oxidase (hMAO) A and B. Among structural modifications, the bioisostere-based introduction of 1,2,4-oxadiazole ring returned the most potent and selective human MAO B inhibitor (compound 20, IC₅₀ = 52 nM, SI > 192). The most promising inhibitors were studied in cell-based neuroprotection models of SH-SY5Y and astrocytes line against H₂O₂. Moreover, preliminary drug-like features (aqueous solubility at pH 7.4; hydrolytic stability at acidic and neutral pH) were assessed for selected 1,2,4-oxadiazoles and compared to amide analogues through RP-HPLC methods. Molecular docking simulations highlighted the crucial role of molecular flexibility in providing a better shape complementarity for compound 20 within MAO B enzymatic cleft than rigid analogue 18. Enzymatic kinetics analysis along with thermal stability curves (T_m shift = +2.9 °C) provided clues of a tight-binding mechanism for hMAO B inhibition by 20.

Design, synthesis, and evaluation of N-methyl-propargylamine derivates as isoform-selective monoamine oxidases inhibitors for the treatment of nervous system diseases

A novel series of N-methyl-propargylamine derivates were designed, synthesized, and evaluated as isoform-selective monoamine oxidases (MAO) inhibitors for the treatment of nervous system diseases. The in vitro studies showed some of the compounds exhibited considerable MAO-A selective inhibitory activity (IC₅₀ of 14.86-17.16 nM), while some of the others exhibited great MAO-B selective inhibitory activity (IC₅₀ of 4.37-17.00 nM). Further studies revealed that compounds A2 （IC₅₀ against MAO-A: 17.16 ± 1.17 nM） and A5 (IC₅₀ against MAO-B: 17.00 ± 1.10 nM) had significant abilities to protect PC12 cells from H₂O₂-induced apoptosis and reactive oxygen species (ROS) production. The parallel artificial membrane permeability assay showed A2 and A5 would be potent to cross the blood-brain barrier. The results indicated that A2 showed potential use in the therapy of MAO-A related diseases, such as depression and anxiety; while A5 exhibited promising ability in the treatment of MAO-B related diseases, such as Alzheimer's disease and Parkinson's disease.

In Vivo Study of Monoamine Oxidases Using Multisite Intracerebral Microdialysis

The activity of monoamine oxidases (MAOs) in the brain is often associated with neurodegenerative diseases. The study of MAOs in vivo or ex vivo is generally performed using MAO inhibitors and rarely using substrates. We present a pharmacological approach using intracerebral microdialysis to study the activity of MAO in the striatum and the prefrontal cortex of rats. It consists of applying ascending concentrations of 3-methoxytyramine (3-MT) as a substrate via the probes and measuring the indirect product homovanillic acid generated by MAO activity. We present herein the methodologies comprising our in-house stereotaxic procedures in rats, the microdialysis perfusion system and the substrate application, and the neurochemical analysis of the samples.

Metformin and empagliflozin modulate monoamine oxidase-related oxidative stress and improve vascular function in human mammary arteries

Monoamine oxidases (MAOs), mitochondrial enzymes with two isoforms, A and B, have been recently recognized as significant contributors to oxidative stress in the cardiovascular system. The present study was purported to assess the effect of metformin and empagliflozin on MAO expression, oxidative stress and vascular reactivity in internal mammary arteries harvested from overweight patients with coronary heart disease subjected to bypass grafting. Vascular rings were prepared and acutely incubated (12 h) with high glucose (GLUC, 400 mg/dL) or angiotensin II (AII, 100 nM) and metformin (10 µM) and/or empagliflozin (10 µM) and used for the assessment of MAO expression (qRT-PCR and immune histochemistry), reactive oxygen species (ROS, confocal microscopy and spectrophotometry), and vasomotor function (myograph). Ex vivo stimulation with GLUC or AII increased both MAOs expression, ROS production and impaired relaxation to acetylcholine (ACh) of the vascular rings. All effects were alleviated by incubation with each antidiabetic drug; no cumulative effect was obtained when the drugs were applied together. In conclusion, MAO-A and B are upregulated in mammary arteries after acute stimulation with GLUC and AII. Endothelial dysfunction and oxidative stress were alleviated by either metformin or empagliflozin in both stimulated and non-stimulated vascular samples harvested from overweight cardiac patients.

In-silico evaluations of the isolated phytosterols from polygonum hydropiper L against BACE1 and MAO drug targets

Our previous anti-Alzheimer's studies on crude extracts, essential oils and isolated compounds including β-sitostrol from Polygonum hydropiper L, motivated us for further studies against beta amyloid cleaving enzyme 1 (BACE1) and monoamine oxidases (MAO-A), (MAO-B) enzymes. Before performing detailed studies on the compounds using animal models and immunohistochemistry, molecular docking study was performed against three vital enzymes implicated in several neurological disorders including Alzheimer's disease (AD), Parkinson's disease (PD), depression and anxiety to predict their inhibitory potential against important enzymes. Beta amyloid cleaving enzyme 1 (BACE1) is important enzyme that catalyze pathological amyloidogenic pathway of processing amyloid precursor proteins to form neurotoxic amyloid plaques. Subsequently, BACE1 inhibitors are considered an important tool in the management of AD. MAOs have been categorized in two well-known groups MAO-A and MAO-B, based on their differential affinity for various monoamines substrates. MAO-A has more affinity for norepinephrine and 5-HT, whereas, MAO-B mainly catalyze the breakdown of dopamine and 2-phenylathylamine (PEA) and other monoamines. Subsequently, they have divergent behavioral outcomes and play a significant role in pathophysiology of several neurodegenerative disorders like AD, depression, drug abuse, migraines, schizophrenia, Attention Deficit Disorder (ADD) and Parkinson's disease (PD). Molecular docking was carried out to predict the binding modes of β-sitosterol and stigmasterol in the binding pockets of BACE1 (beta-sectretase 1) and MAO (monoamine oxidase A, B) enzymes. The 3 D structure of BACE1 (PDB ID: 2QP8), MAO A (PDB ID: 2ZPX) and MAO B (PDB ID: 2XFN) were downloaded from protein databank. The 3 D structures were then subjected to protonation and energy minimization using default parameters of MOE. Three dimensional structures of β-sitosterol and stigmasterol were built by using Molecular Builder Module program implemented in MOE and saved as a (.mdb) file for molecular docking. Subsequently, the energy of both the compounds were minimized up to 0.05 Gradient using MMFF 94 s force field implemented in MOE. Both the compounds were docked into the active site of proteins using the Triangular Matching docking method (default) and 10 different conformations for each compound were generated. To obtain minimum energy structures the ligands were allowed to be flexible during docking. At the end of docking, the predicted ligand-protein complexes were analyzed for molecular interactions. Overall the docking results showed that these compounds showed good interaction with active site residues of BACE1 as compare to MAO-A and MAO-B. Furthermore, β-sitosterol showed good interaction with BACE1 as compare to stigmasterol.Communicated by Ramaswamy H. Sarma.

Monoamine oxidase A and B inhibitory activities of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives

Monoamine oxidase (EC 1.4.3.4, MAO) is a flavin adenine dinucleotide-containing flavoenzyme located on the outer mitochondrial membrane and catalyzes the oxidative deamination of monoaminergic neurotransmitters and dietary amines. MAO exists in humans as two isoenzymes, hMAO-A and hMAO-B, which are distinguished by their tertiary structures, preferred substrates and inhibitors, and selective inhibition of these isoenzymes are used in the treatment of different diseases such as Alzheimer's, Parkinson's and depression. In the present study, we report the design, synthesis and characterization of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives as novel and selective inhibitors of hMAO-B. Twenty one compounds (38, 39a-h, 41a-d, 42a-h) were screened for their inhibitory activity against hMAO-A and hMAO-B by using in vitro Amplex Red® reagent based fluorometric method and all compounds were found to be as selective h-MAO-B inhibitors to a different degree. The compound 42e and 42h displayed the highest inhibitory activity against hMAO-B with IC₅₀ values of 2.51 and 2.81 µM, respectively, and more than 25-fold selectivity towards inhibition of hMAO-B. A further kinetic evaluation of the most potent derivative (42e) was also performed and a mixed mode of inhibition of hMAO-B by the compound 42e was determined (K_i = 0,26 µM). According to our findings the [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole emerged as a promising scaffold for the development of novel and selective hMAO-B inhibitors.

Novel propargylamine-based inhibitors of cholinesterases and monoamine oxidases: Synthesis, biological evaluation and docking study

A combination of several pharmacophores in one molecule has been successfully used for multi-target-directed ligands (MTDL) design. New propargylamine substituted derivatives combined with salicylic and cinnamic scaffolds were designed and synthesized as potential cholinesterases and monoamine oxidases (MAOs) inhibitors. They were evaluated invitro for inhibition of acetyl- (AChE) and butyrylcholinesterase (BuChE) using Ellman's method. All the compounds act as dual inhibitors. Most of the derivatives are stronger inhibitors of AChE, the best activity showed 5-bromo-N-(prop-2-yn-1-yl)salicylamide 1e (IC₅₀ = 8.05 µM). Carbamates (4-bromo-2-[(prop-2-yn-1-yl)carbamoyl]phenyl ethyl(methyl)carbamate 2d and 2,4-dibromo-6-[(prop-2-yn-1-yl)carbamoyl]phenyl ethyl(methyl)carbamate 2e were selective and the most active for BuChE (25.10 and 26.09 µM). 4-Bromo-2-[(prop-2-yn-1-ylimino)methyl]phenol 4a was the most potent inhibitor of MAOs (IC₅₀ of 3.95 and ≈10 µM for MAO-B and MAO-A, respectively) along with a balanced inhibition of both cholinesterases being a real MTDL. The mechanism of action was proposed, and binding modes of the hits were studied by molecular docking on human enzymes. Some of the derivatives also exhibited antioxidant properties. Insilico prediction of physicochemical parameters affirm that the molecules would be active after oral administration and able to reach brain tissue.

Chromenone Derivatives as Monoamine Oxidase Inhibitors from Marine-Derived MAR4 Clade Streptomyces sp. CNQ-031

Three compounds were isolated from marine-derived Streptomyces sp. CNQ-031, and their inhibitory activities against monoamine oxidases (MAOs), acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE-1) were evaluated. Compound 1 (5,7-dihydroxy-2-isopropyl-4H-chromen-4-one) was a potent and selective inhibitor of MAO-A, with a 50% inhibitory concentration (IC₅₀) of 2.70 μM and a selectivity index (SI) of 10.0 versus MAO-B. Compound 2 [5,7-dihydroxy-2-(1-methylpropyl)-4H-chromen-4-one] was a potent and low-selective inhibitor of MAO-B, with an IC₅₀ of 3.42 μM and an SI value of 2.02 versus MAO-A. Compound 3 (1-methoxyphenazine) did not inhibit MAO-A or MAO-B. All three compounds showed little inhibitory activity against AChE, BChE, and BACE-1. The K_i value of compound 1 for MAO-A was 0.94 ± 0.28 μM, and the K_i values of compound 2 for MAO-A and MAO-B were 3.57 ± 0.60 and 1.89 ± 0.014 μM, respectively, with competitive inhibition. The 1-methylpropyl group in compound 2 increased the MAO-B inhibitory activity compared with the isopropyl group in compound 1. Inhibition of MAO-A and MAO-B by compounds 1 and 2 was recovered by dialysis experiments. These results suggest that compounds 1 and 2 are reversible, competitive inhibitors of MAOs and can be considered potential therapies for neurological disorders such as depression and Alzheimer's disease.

Monoamine oxidases in age-associated diseases: New perspectives for old enzymes

Population aging is one of the most significant social changes of the twenty-first century. This increase in longevity is associated with a higher prevalence of chronic diseases, further rising healthcare costs. At the molecular level, cellular senescence has been identified as a major process in age-associated diseases, as accumulation of senescent cells with aging leads to progressive organ dysfunction. Of particular importance, mitochondrial oxidative stress and consequent organelle alterations have been pointed out as key players in the aging process, by both inducing and maintaining cellular senescence. Monoamine oxidases (MAOs), a class of enzymes that catalyze the degradation of catecholamines and biogenic amines, have been increasingly recognized as major producers of mitochondrial ROS. Although well-known in the brain, evidence showing that MAOs are also expressed in a variety of peripheral organs stimulated a growing interest in the extra-cerebral roles of these enzymes. Besides, the fact that MAO-A and/or MAO-B are frequently upregulated in aged or dysfunctional organs has uncovered new perspectives on their roles in pathological aging. In this review, we will give an overview of the major results on the regulation and function of MAOs in aging and age-related diseases, paying a special attention to the mechanisms linked to the increased degradation of MAO substrates or related to MAO-dependent ROS formation.

Monoamine Oxidase Inhibitors: From Classic to New Clinical Approaches

Monoamine oxidases (MAOs) are involved in the oxidative deamination of different amines and neurotransmitters. This pointed them as potential targets for several disorders and along the last 70 years a wide variety of MAO inhibitors have been developed as successful drugs for the treatment of complex diseases, being the first drugs approved for depression in the late 1950s. The discovery of two MAO isozymes (MAO-A and B) with different substrate selectivity and tissue expression patterns led to novel therapeutic approaches and to the development of new classes of inhibitors, such as selective irreversible and reversible MAO-B inhibitors and reversible MAO-A inhibitors. Significantly, MAO-B inhibitors constitute a widely studied group of compounds, some of them approved for the treatment of Parkinson's disease. Further applications are under development for the treatment of Alzheimer's disease, amyotrophic lateral sclerosis, and cardiovascular diseases, among others. This review summarizes the most important aspects regarding the development and clinical use of MAO inhibitors, going through mechanistic and structural details, new indications, and future perspectives. Monoamine oxidases (MAOs) catalyze the oxidative deamination of different amines and neurotransmitters. The two different isozymes, MAO-A and MAO-B, are located at the outer mitochondrial membrane in different tissues. The enzymatic reaction involves formation of the corresponding aldehyde and releasing hydrogen peroxide (H₂O₂) and ammonia or a substituted amine depending on the substrate. MAO's role in neurotransmitter metabolism made them targets for major depression and Parkinson's disease, among other neurodegenerative diseases. Currently, these compounds are being studied for other diseases such as cardiovascular ones.

Recent advances of small molecule fluorescent probes for distinguishing monoamine oxidase-A and monoamine oxidase-B in vitro and in vivo

Monoamine oxidases (MAO-A and MAO-B) are the two flavin adenine dinucleotide (FAD) enzymes that play an important role in neurotransmitter homeostasis and in protection against biogenic amines. The two MAO enzymes are related to various diseases such as neurological disorders, cancer or other systemic diseases. It is crucial to distinguish these two subtypes in order to explore the pathogenesis and pathophysiology of different diseases. In this review, the relationship between MAOs and related diseases is briefly introduced. Additionally, we summarize the recent advances in small molecule fluorescent probes for specific detection of MAO-A and MAO-B.

Quantitative Structure-Activity Relationship (QSAR) Studies for the Inhibition of MAOs

Monoamine oxidases are the crucial drug targets for the treatment of neurodegenerative disorders like depression, Parkinson's disease, and Alzheimer's disease. The enzymes catalyze the oxidative deamination of several monoamine containing neurotransmitters, i.e. serotonin (5-HT), melatonin, epinephrine, norepinephrine, phenylethylamine, benzylamine, dopamine, tyramine, etc. The oxidative reaction of monoamine oxidases results in the production of hydrogen peroxide that leads to the neurodegeneration process. Therefore, the inhibition of monoamine oxidases has shown a profound effect against neurodegenerative diseases. At present, the design and development of newer lead molecules for the inhibition of monoamine oxidases are under intensive research in the field of medicinal chemistry. Recently, the advancement in QSAR methodologies has shown considerable interest in the development of monoamine oxidase inhibitors. The present review describes the development of QSAR methodologies, and their role in the design of newer monoamine oxidase inhibitors. It will assist the medicinal chemist in the identification of selective and potent monoamine oxidase inhibitors from various chemical scaffolds.

Mechanism-based pharmacokinetics-pharmacodynamics studies of harmine and harmaline on neurotransmitters regulatory effects in healthy rats: Challenge on monoamine oxidase and acetylcholinesterase inhibition

BACKGROUND

β-Carboline alkaloid harmine (HAR) and harmaline (HAL) are monoamine oxidase (MAO) and acetylcholinesterase (AChE) inhibitors. However, whether HAR and HAL inhibit MAO or AChE selectively and competitively is unclear.

PURPOSE

The purpose of this study was to investigate the potential competition inhibition of HAR and HAL on MAO and AChE in brain endothelial cells (RBE4) and in healthy rats to provide a basis for the application of the inhibitors in the treatment of patients with depression and with Parkinson's disease or Alzheimer's disease.

STUDY DESIGN/METHODS

The transport properties of HAR and HAL by using blood-brain barrier models constructed with RBE4 were systematically investigated. Then, the modulation effects of HAR and HAL on CNS neurotransmitters (NTs) in healthy rat brains were determined by a microdialysis method coupled with LC-MS/MS. The competition inhibition of HAR and HAL on MAO and AChE was evaluated through real time-PCR, Western blot analysis, and molecular docking experiments.

RESULTS

Results showed that HAL and HAR can be detected in the blood and striatum 300 min after intravenous injection (1 mg/kg). Choline (Ch), gamma-aminobutyric acid (GABA), glutamate (Glu), and phenylalanine (Phe) levels in the striatum decreased in a time-dependent manner after the HAL treatment, with average velocities of 1.41, 0.73, 3.86, and 1.10 (ng/ml)/min, respectively. The Ch and GABA levels in the striatum decreased after the HAR treatment, with average velocities of 1.16 and 0.22 ng/ml/min, respectively. The results of the cocktail experiment using the human liver enzyme indicated that the IC₅₀ value of HAL on MAO-A was 0.10 ± 0.08 µm and that of HAR was 0.38 ± 0.21 µm. Their IC₅₀ values on AChE were not obtained. These findings indicated that HAL and HAR selectively acted on MAO in vitro. However, RT-PCR and Western blot analysis results showed that the AChE mRNA and protein expression decreased in a time-dependent manner in RBE4 cells after the HAR and HAL treatments.

CONCLUSION

NT analysis results showed that HAL and HAR selectively affect AChE in vivo. HAL and HAR may be highly and suitably developed for the treatment of Alzheimer's disease.

Offline encoding impaired by epigenetic regulations of monoamines in the guided propagation model of autism

Background

Environmental factors can modify the expression of genes, including those involved in the metabolism of neurotransmitters. Accounting for a control role of monoamine neurotransmitters, the guided propagation (GP) memory model may contribute to investigate the consequences of neuromodulation impairments on development disorders such as autism. A prenatal transient excess of ‘monoamine oxidase A’ enzyme is assumed here to trigger persistent epigenetic regulations that would induce imbalanced metabolisms of synaptic monoamines. When imported into the ‘offline’ encoding cycles of a GP model, the consequent ‘serotoninergic noise’ leads to aberrant memory structures that can be linked with autism symptoms.

Results

In computer experiments, different levels of uncoupling between representations of monoamines correlate with the amount of impaired GP modules, the severity of irrelevant connections, as well as network overgrowth. Two types of faulty connections are respectively assumed to underlie autism traits, namely repetitive behavior and perceptual oversensitivity. Besides computational modelling, a genetic family-tree shows how the autism sex-ratio can result from combinations of pharmacological and epigenetic features.

Conclusions

These results suggest that the current rise of autism is favored by three possible sources of biological masking: (1) during sleep, when cyclic variations of monoamines may undergo disrupted enzymatic activities; (2) across generations of ‘healthy carriers’ protected by the X-chromosome silencing and a specific genetic variant; (3) early in life, as long as the brain development draws on pools of neurons born when the transient enzymatic excess and its persistent epigenetic regulation overlapped, and as long as the B type of monoamine oxidase does not significantly impact dopamine. A disease-modifying therapy can be derived from this study, which involves relevant biomarkers to be first monitored over several months of clinical trial.

Electronic supplementary material

The online version of this article (10.1186/s12868-018-0477-1) contains supplementary material, which is available to authorized users.

Monoamine Oxidase Deficiency Causes Prostate Atrophy and Reduces Prostate Progenitor Cell Activity

Monoamine oxidases (MAOs) degrade a number of biogenic and dietary amines, including monoamine neurotransmitters, and play an essential role in many biological processes. Neurotransmitters and related neural events have been shown to participate in the development, differentiation, and maintenance of diverse tissues and organs by regulating the specialized cellular function and morphological structures of innervated organs such as the prostate. Here we show that mice lacking both MAO isoforms, MAOA and MAOB, exhibit smaller prostate mass and develop epithelial atrophy in the ventral and dorsolateral prostates. The cellular composition of prostate epithelium showed reduced CK5⁺ or p63⁺ basal cells, accompanied by lower Sca-1 expression in p63⁺ basal cells, but intact differentiated CK8⁺ luminal cells in MAOA/B-deficient mouse prostates. MAOA/B ablation also decreased epithelial cell proliferation without affecting cell apoptosis in mouse prostates. Using a human prostate epithelial cell line, we found that stable knockdown of MAOA and MAOB impaired the capacity of prostate stem cells to form spheres, coinciding with a reduced CD133⁺ /CD44⁺ /CD24^- stem cell population and less expression of CK5 and select stem cell markers, including ALDH1A1, TROP2, and CD166. Alternative pharmacological inhibition of MAOs also repressed prostate cell stemness. In addition, we found elevated expression of MAOA and MAOB in epithelial and/or stromal components of human prostate hyperplasia samples compared with normal prostate tissues. Taken together, our findings reveal critical roles for MAOs in the regulation of prostate basal progenitor cells and prostate maintenance. Stem Cells 2018;36:1249-1258.

Synthesis, characterization, monoamine oxidase inhibition, molecular docking and dynamic simulations of novel 2,1-benzothiazine-2,2-dioxide derivatives

In this research work, we report the synthesis and biological evaluation of two new series of 1-benzyl-4-(benzylidenehydrazono)-3,4-dihydro-1H-benzo[c] [1,2]thiazine 2,2-dioxides and 1-benzyl-4-((1-phenylethylidene)hydrazono)-3,4-dihydro-1H-benzo[c][1,2]thiazine 2,2-dioxides. The synthetic plan involves the mesylation of methyl anthranilate with subsequent N-benzylation of the product. The methyl 2-(N-benzylmethylsulfonamido)benzoate was subjected to cyclization reaction in the presence of sodium hydride to obtain 1-benzyl-1H-benzo[c][1,2]thiazin-4(3H)-one 2,2-dioxide which was treated with hydrazine hydrate to get corresponding hydrazone precursor. Finally, the titled compounds were obtained by reaction of hydrazone with various substituted aldehydes and ketones. The synthesized derivatives were subjected to carry out their inhibition activities against monoamine oxidases along with modelling investigations to evaluate their binding interactions and dynamic stability during the docking studies. The inhibition profile of potent compounds was found as competitive for both the isozymes. The compounds were more selective inhibitors of MAO-A as compared to MAO-B. Moreover, drug likeness profile of the derivatives was evaluated to have an additional insight into the physicochemical properties. The molecular dynamic simulations predicted the behaviour of amino acids with the active site residues.

The role of MAO in personality and drug use

Monoamine oxidases, both MAO-A and MAO-B, have been implicated in personality traits and complex behaviour, including drug use. Findings supporting the involvement of MAO-A and MAO-B in shaping personality and in the development of strategies of making behavioural choices come from a variety of studies that have examined either prevalence of gene variants in clinical groups or population-derived samples, estimates of enzyme activity in blood or, by positron emission tomography, in the brain and, most recently, measurement of methylation of the gene. Most of the studies converge in associating MAO-A and MAO-B with impulsive, aggressive or antisocial personality traits or behaviours, including alcohol-related problems, and for MAO-A available evidence strongly supports interaction with adverse environmental exposures in childhood. What is known about genotype effects, and on expression and activity of the enzyme in the brain and in blood has not yet been possible to unite into a mechanistic model of the role of monoamine systems, but the reason for this low degree of generalization is likely caused by the cross-sectional nature of investigation that has not incorporated the developmental effects of MAO-s in critical time windows, including the foetal period. The "risk variants" of both MAO-s appear to increase behavioural plasticity, as supportive environments may particularly well enhance the hidden potential of their carriers. Importantly, male and female brain and behaviours have been found very different with regard to MAO×life events interaction. Future studies need to take into consideration these developmental aspects and sex/gender, as well as to specify the role of different types of environmental factors.

All trans retinoic acid (ATRA) mediated modulation of N-methyl D-aspartate receptor (NMDAR) and Kruppel like factor 11 (KLF11) expressions in the mitigation of ethanol induced alterations in the brain

BACKGROUND

Damaging effects that chronic ethanol exposure causes to the brain and the neurons are well documented. Ethanol and its toxic metabolites increase the oxidative stress in brain. Chronic exposure to ethanol leads to upregulation of N-methyl D-aspartate receptors (NMDAR) and also activates Kruppel like factor 11 (KLF11) mediated death cascade and thereby neurodegeneration.

OBJECTIVE

Ethanol depletes vitamin A stores. But supplementation of vitamin A exacerbates ethanol induced toxicity since alcohol and its metabolites are competitive inhibitors of the enzymes involved in the metabolism of vitamin A. Hence, in this study we investigated the impact of co-administration of ethanol and all trans retinoic acid (ATRA), active metabolite of vitamin A, on ethanol induced alterations to the brain.

MATERIALS AND METHODS

Male Sprague Dawley rats, adolescent, were grouped as follows and maintained for 90 days. I - Control, II - Ethanol (4 g/kg b.w.), III - ATRA (100 µg/kg b.w.), IV - Ethanol (4 g/kg b.w.), +ATRA (100 µg/kg b.w.). Oxidative stress and the mRNA expression of various receptors for the neurotransmitter involved in glutamergic, serotonergic and gabaergic pathways were studied in the brain homogenate.

RESULTS

Ethanol treatment was shown to decrease brain weight and it was increased on ATRA treatment. Increase in oxidative stress due to ethanol treatment was also brought down on ATRA administration. Ethanol induced upregulation of NMDAR and KLF11 was also downregulated on ATRA supplementation. The alterations in the levels of neurotransmitters and the expression of their receptors due to ethanol treatment also were ameliorated on ATRA supplementation.

CONCLUSION

Our results show that ATRA supplementation mitigates the ethanol induced alterations in the brain by reducing oxidative stress in the brain with concurrent suppression of NMDAR and KLF11 expression leading to enhanced catabolism of neurotransmitters.

Monoamine oxidase inhibition prevents mitochondrial dysfunction and apoptosis in myoblasts from patients with collagen VI myopathies

Although mitochondrial dysfunction and oxidative stress have been proposed to play a crucial role in several types of muscular dystrophy (MD), whether a causal link between these two alterations exists remains an open question. We have documented that mitochondrial dysfunction through opening of the permeability transition pore plays a key role in myoblasts from patients as well as in mouse models of MD, and that oxidative stress caused by monoamine oxidases (MAO) is involved in myofiber damage. In the present study we have tested whether MAO-dependent oxidative stress is a causal determinant of mitochondrial dysfunction and apoptosis in myoblasts from patients affected by collagen VI myopathies. We find that upon incubation with hydrogen peroxide or the MAO substrate tyramine myoblasts from patients upregulate MAO-B expression and display a significant rise in reactive oxygen species (ROS) levels, with concomitant mitochondrial depolarization. MAO inhibition by pargyline significantly reduced both ROS accumulation and mitochondrial dysfunction, and normalized the increased incidence of apoptosis in myoblasts from patients. Thus, MAO-dependent oxidative stress is causally related to mitochondrial dysfunction and cell death in myoblasts from patients affected by collagen VI myopathies, and inhibition of MAO should be explored as a potential treatment for these diseases.