Emerging role of monoamine oxidase as a therapeutic target for cardiovascular disease

The evaluation of 1-tetralone and 4-chromanone derivatives as inhibitors of monoamine oxidase

Abstract

Monoamine oxidase (MAO) is of much clinical relevance, and inhibitors of this enzyme are used in the treatment for neuropsychiatric and neurodegenerative disorders such as depression and Parkinson’s disease. The present study synthesises and evaluates the MAO inhibition properties of a series of 33 1-tetralone and 4-chromanone derivatives in an attempt to discover high-potency compounds and to expand on the structure–activity relationships of MAO inhibition by these classes. Among these series, eight submicromolar MAO-A inhibitors and 28 submicromolar MAO-B inhibitors are reported, with all compounds acting as specific inhibitors of the MAO-B isoform. The most potent inhibitor was a 1-tetralone derivative (1h) with IC₅₀ values of 0.036 and 0.0011 µM for MAO-A and MAO-B, respectively. Interestingly, with the reduction of 1-tetralones to the corresponding alcohols, a decrease in MAO inhibition potency is observed. Among these 1-tetralol derivatives, 1p (IC₅₀ = 0.785 μM) and 1o (IC₅₀ = 0.0075 μM) were identified as particularly potent inhibitors of MAO-A and MAO-B, respectively. Potent compounds such as those reported here may act as leads for the future development of MAO-B specific inhibitors.

Graphic abstract

The present study describes the MAO inhibitory activities of a series of 1-tetralone and 4-chromanone derivatives. Numerous high-potency MAO-B specific inhibitors were identified.

Electronic supplementary material

The online version of this article (10.1007/s11030-020-10143-w) contains supplementary material, which is available to authorised users.

A comprehensive review of monoamine oxidase inhibitors as Anti-Alzheimer's disease agents: A review

Monoamine oxidases (MAO-A and MAO-B) are mammalian flavoenzyme, which catalyze the oxidative deamination of several neurotransmitters like norepinephrine, dopamine, tyramine, serotonin, and some other amines. The oxidative deamination produces several harmful side products like ammonia, peroxides, and aldehydes during the biochemical reaction. The concentration of biochemical neurotransmitter alteration in the brain by MAO is directly related with several neurological disorders like Alzheimer's disease and Parkinson's disease (PD). Activated MAO also contributes to the amyloid beta (Aβ) aggregation by two successive cleft β-secretase and γ-secretase of amyloid precursor protein (APP). Additionally, activated MAO is also involved in aggregation of neurofibrillary tangles and cognitive destruction through the cholinergic neuronal damage and disorder of the cholinergic system. MAO inhibition has general anti-Alzheimer's disease effect as a consequence of oxidative stress reduction prompted by MAO enzymes. In this review, we outlined and addressed recent understanding on MAO enzymes such as their structure, physiological function, catalytic mechanism, and possible therapeutic goals in AD. In addition, it also highlights the current development and discovery of potential MAO inhibitors (MAOIs) from various chemical scaffolds.

Hydride Abstraction as the Rate-Limiting Step of the Irreversible Inhibition of Monoamine Oxidase B by Rasagiline and Selegiline: A Computational Empirical Valence Bond Study

Monoamine oxidases (MAOs) catalyze the degradation of a very broad range of biogenic and dietary amines including many neurotransmitters in the brain, whose imbalance is extensively linked with the biochemical pathology of various neurological disorders, and are, accordingly, used as primary pharmacological targets to treat these debilitating cognitive diseases. Still, despite this practical significance, the precise molecular mechanism underlying the irreversible MAO inhibition with clinically used propargylamine inhibitors rasagiline and selegiline is still not unambiguously determined, which hinders the rational design of improved inhibitors devoid of side effects current drugs are experiencing. To address this challenge, we present empirical valence bond QM/MM simulations of the rate-limiting step of the MAO inhibition involving the hydride anion transfer from the inhibitor α-carbon onto the N5 atom of the flavin adenin dinucleotide (FAD) cofactor. The proposed mechanism is strongly supported by the obtained free energy profiles, which confirm a higher reactivity of selegiline over rasagiline, while the calculated difference in the activation Gibbs energies of ΔΔG^‡ = 3.1 kcal mol^-1 is found to be in very good agreement with that from the measured literature k_inact values that predict a 1.7 kcal mol^-1 higher selegiline reactivity. Given the similarity with the hydride transfer mechanism during the MAO catalytic activity, these results verify that both rasagiline and selegiline are mechanism-based irreversible inhibitors and offer guidelines in designing new and improved inhibitors, which are all clinically employed in treating a variety of neuropsychiatric and neurodegenerative conditions.

Regulation of Vascular Function and Inflammation via Cross Talk of Reactive Oxygen and Nitrogen Species from Mitochondria or NADPH Oxidase-Implications for Diabetes Progression

Oxidative stress plays a key role for the development of cardiovascular, metabolic, and neurodegenerative disease. This concept has been proven by using the approach of genetic deletion of reactive oxygen and nitrogen species (RONS) producing, pro-oxidant enzymes as well as by the overexpression of RONS detoxifying, antioxidant enzymes leading to an amelioration of the severity of diseases. Vice versa, the development and progression of cardiovascular diseases is aggravated by overexpression of RONS producing enzymes as well as deletion of RONS detoxifying enzymes. We have previously identified cross talk mechanisms between different sources of RONS, which can amplify the oxidative stress-mediated damage. Here, the pathways and potential mechanisms leading to this cross talk are analyzed in detail and highlighted by selected examples from the current literature and own data including hypoxia, angiotensin II (AT-II)-induced hypertension, nitrate tolerance, aging, and others. The general concept of redox-based activation of RONS sources via “kindling radicals” and enzyme-specific “redox switches” as well as the interaction with redox-sensitive inflammatory pathways are discussed. Here, we present evidence for the existence of such cross talk mechanisms in the setting of diabetes and critically assess their contribution to the severity of diabetic complications.

Mitochondrial ROS Formation in the Pathogenesis of Diabetic Cardiomyopathy

Diabetic cardiomyopathy is a result of diabetes-induced changes in the structure and function of the heart. Hyperglycemia affects multiple pathways in the diabetic heart, but excessive reactive oxygen species (ROS) generation and oxidative stress represent common denominators associated with adverse tissue remodeling. Indeed, key processes underlying cardiac remodeling in diabetes are redox sensitive, including inflammation, organelle dysfunction, alteration in ion homeostasis, cardiomyocyte hypertrophy, apoptosis, fibrosis, and contractile dysfunction. Extensive experimental evidence supports the involvement of mitochondrial ROS formation in the alterations characterizing the diabetic heart. In this review we will outline the central role of mitochondrial ROS and alterations in the redox status contributing to the development of diabetic cardiomyopathy. We will discuss the role of different sources of ROS involved in this process, with a specific emphasis on mitochondrial ROS producing enzymes within cardiomyocytes. Finally, the therapeutic potential of pharmacological inhibitors of ROS sources within the mitochondria will be discussed.

Stereoselective Activity of 1-Propargyl-4-styrylpiperidine-like Analogues That Can Discriminate between Monoamine Oxidase Isoforms A and B

The resurgence of interest in monoamine oxidases (MAOs) has been fueled by recent correlations of this enzymatic activity with cardiovascular, neurological, and oncological disorders. This has promoted increased research into selective MAO-A and MAO-B inhibitors. Here, we shed light on how selective inhibition of MAO-A and MAO-B can be achieved by geometric isomers of cis- and trans-1-propargyl-4-styrylpiperidines. While the cis isomers are potent human MAO-A inhibitors, the trans analogues selectively target only the MAO-B isoform. The inhibition was studied by kinetic analysis, UV-vis spectrum measurements, and X-ray crystallography. The selective inhibition of the MAO-A and MAO-B isoforms was confirmed ex vivo in mouse brain homogenates, and additional in vivo studies in mice show the therapeutic potential of 1-propargyl-4-styrylpiperidines for central nervous system disorders. This study represents a unique case of stereoselective activity of cis/trans isomers that can discriminate between structurally related enzyme isoforms.

A Prospective Repurposing of Dantrolene as a Multitarget Agent for Alzheimer's Disease

The orphan drug dantrolene (DAN) is the only therapeutic treatment for malignant hyperthermia (MH), a pharmacogenetic pathology affecting 0.2 over 10,000 people in the EU. It acts by inhibiting ryanodine receptors, which are responsible for calcium recruitment in striatal muscles and brain. Because of its involvement in calcium homeostasis, DAN has been successfully investigated for its potential as neuroprotecting small molecule in several animal models of Alzheimer’s disease (AD). Nevertheless, its effects at a molecular level, namely on putative targets involved in neurodegeneration, are still scarcely known. Herein, we present a prospective study on repurposing of DAN involving, besides the well-known calcium antagonism, inhibition of monoamine oxidase B and acetylcholinesterase, cytoprotection from oxidative insult, and activation of carnitine/acylcarnitine carrier, as concurring biological activities responsible for neuroprotection.

Insight into structural requirements of ACE inhibitory dipeptides: QSAR and molecular docking studies

The angiotensin I-converting enzyme (ACE) has been found to exhibit inhibitory capability against blood pressure. Recently, several ACE inhibitors with different structures have been reported. In the present work, molecular modeling studies using quantitative structure-activity relationship (QSAR) and molecular docking simulations were carried out. Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) were firstly used to generate 3D-QSAR models. The results indicate that the best CoMFA model has [Formula: see text] = 0.504, [Formula: see text] = 0.5896, and the best CoMSIA model has [Formula: see text] = 0.525, [Formula: see text] = 0.5666. Furthermore, 2D-QSAR models developed by multiple linear regression/MLR, partial least squares regression/PLSR, and support vector machine regression/SVR methods provide highly significant squared correlation coefficient R_tr² values of 0.8380, 0.8650, and 0.8230, external validated correlation coefficient Q_te² of 0.8279, 0.8223, and 0.7255, respectively. The statistical results show satisfactory goodness-of-fit, robustness, and perfect external predictive performance. Moreover, molecular docking studies were employed to predict the binding mode between dipeptides and ACE receptor. The combination of QSAR studies and molecular docking indicates the requirement of certain physicochemical parameters for better ACE inhibitors.

Inhibition of serotonin synthesis: A novel therapeutic paradigm

The rate-limiting enzyme in serotonin synthesis is tryptophan hydroxylase (TPH). There are two independent serotonin systems in the body characterized by two isoforms of TPH, TPH1 and TPH2. While TPH2 synthesizes serotonin in the brain, TPH1 is expressed in the gut and in other peripheral tissues and supplies platelets in the circulation with serotonin. This duality of the serotonin system is enforced by the blood-brain barrier which is impermeable for serotonin. In the brain serotonin acts as neurotransmitter and is a main target for the treatment of psychiatric disorders. In the periphery it is released by platelets at the site of activation and elicits numerous physiological effects. TPH1 deficient mice were shown to be protected from diverse diseases including hemostatic, inflammatory, fibrotic, gastrointestinal, and metabolic disorders and therefore serotonin synthesis inhibition emerged as a reasonable therapeutic paradigm. Recently the first TPH inhibitor, telotristat ethyl, came on the market for the treatment of carcinoid syndrome. This review summarizes the state of development and the therapeutic opportunities of such compounds.

Attenuation of Ischemic Stroke-Caused Brain Injury by a Monoamine Oxidase Inhibitor Involves Improved Proteostasis and Reduced Neuroinflammation

Mitochondrial dysfunction and oxidative stress play a key role in ischemia/reperfusion (I/R) induced brain injury. We previously showed that ubiquilin-1 (Ubqln1), a ubiquitin-like protein, improves proteostasis and protects brains against oxidative stress and I/R induced brain injury. We demonstrate here that nialamide (NM), a non-selective monoamine oxidase (MAO) inhibitor, upregulated Ublqn1 and protected neurons from oxygen-glucose deprivation- and I/R-caused cell death in in vitro and in vivo, respectively. Post-ischemic administration of the NM in a stroke mouse model even at 3 h following I/R still reduced neuronal injury and improved functional recovery and survival. Treating stroke animals with NM also increased the association of Ubqln1 with mitochondria and decreased the total oxidized and polyubiquitinated protein levels. Intriguingly, NM-enhanced proteostasis was also associated with reduced I/R-caused neuroinflammation, as reflected by attenuated activation of microglia and astrocytes as well as reduced TNF-α level. Thus, our results suggest that MAO inhibition-induced neuroprotection following I/R involves improved proteostasis and reduced neuroinflammation.

Computational Insight into the Mechanism of the Irreversible Inhibition of Monoamine Oxidase Enzymes by the Antiparkinsonian Propargylamine Inhibitors Rasagiline and Selegiline

Monoamine oxidases (MAOs) are flavin adenine dinucleotide containing flavoenzymes that catalyze the degradation of a range of brain neurotransmitters, whose imbalance is extensively linked with the pathology of various neurological disorders. This is why MAOs have been the central pharmacological targets in treating neurodegeneration for more than 60 years. Still, despite this practical importance, the precise chemical mechanisms underlying the irreversible inhibition of the MAO B isoform with clinical drugs rasagiline (RAS) and selegiline (SEL) remained unknown. Here we employed a combination of MD simulations, MM-GBSA binding free energy evaluations, and QM cluster calculations to show the MAO inactivation proceeds in three steps, where, in the rate-limiting first step, FAD utilizes its N5 atom to abstracts a hydride anion from the inhibitor α-CH₂ group to ultimately give the final inhibitor-FAD adduct matching crystallographic data. The obtained free energy profiles reveal a lower activation energy for SEL by 1.2 kcal mol^-1 and a higher reaction exergonicity by 0.8 kcal mol^-1, with the former being in excellent agreement with experimental ΔΔG^‡_EXP = 1.7 kcal mol^-1, thus rationalizing its higher in vivo reactivity over RAS. The calculated ΔG_BIND energies confirm SEL binds better due to its bigger size and flexibility allowing it to optimize hydrophobic C-H···π and π···π interactions with residues throughout both of enzyme's cavities, particularly with FAD, Gln206 and four active site tyrosines, thus overcoming a larger ability of RAS to form hydrogen bonds that only position it in less reactive orientations for the hydride abstraction. Offered results elucidate structural determinants affecting the affinity and rates of the inhibition reaction that should be considered to cooperate when designing more effective compounds devoid of untoward effects, which are of utmost significance and urgency with the growing prevalence of brain diseases.

Benextramine and derivatives as novel human monoamine oxidases inhibitors: an integrated approach

The two human monoamine oxidase isoforms (namely MAO A and MAO B) are enzymes involved in the catabolism of monoamines, including neurotransmitters, and for this reason are well-known and attractive pharmacological targets in neuropsychiatric and neurodegenerative diseases, for which novel pharmacological approaches are necessary. Benextramine is a tetraamine disulfide mainly known as irreversible α-adrenergic antagonist, but able to hit additional targets involved in neurodegeneration. As the molecular structures of monoamine oxidases contain nine cysteine residues, the aim of this study was to evaluate benextramine and eleven structurally related polyamine disulfides as potential MAO inhibitors. Most of the compounds were found to induce irreversible inactivation of MAOs with inactivation potency depending on both the polyamine structure and the enzyme isoform. The more effective compounds generally showed preference for MAO B. Structure-activity relationships studies revealed the key role played by the disulfide core of these molecules in the inactivation mechanism. Docking experiments pointed to Cys323, in MAO A, and Cys172, in MAO B, as target of this type of inhibitors thus suggesting that their covalent binding inside the MAO active site sterically impedes the entrance of substrate towards the FAD cofactor. The effectiveness of benextramine in inactivating MAOs was demonstrated in SH-SY5Y neuroblastoma cell line. These results demonstrated for the first time that benextramine and its derivatives can inactivate human MAOs exploiting a mechanism different from that of the classical MAO inhibitors and could be a starting point for the development of pharmacological tools in neurodegenerative diseases.

New opportunities for targeting redox dysregulation in cardiovascular disease

Despite substantial promise, the use of antioxidant therapy to improve cardiovascular outcomes has been disappointing. Whilst the fundamental biology supporting their use continues to build, the challenge now is to differentially target dysregulated redox signalling domains and to identify new ways to deliver antioxidant substances. Looking further afield to other disciplines, there is an emerging ‘tool-kit’ containing sophisticated molecular and drug delivery applications. Applying these to the cardiovascular redox field could prove a successful strategy to combat the increasing disease burden. Excessive reactive oxygen species production and protein modifications in the mitochondria has been the target of successful drug development with several positive outcomes emerging in the cardiovascular space, harnessing both improved delivery mechanisms and enhanced understanding of the biological abnormalities. Using this as a blueprint, similar strategies could be applied and expanded upon in other redox-hot-spots, such as the caveolae sub-cellular region, which houses many of the key cardiovascular redox proteins such as NADPH oxidase, endothelial nitric oxide synthase, angiotensin II receptors, and beta adrenoceptors. The expanded tool kit of drug development, including gene and miRNA therapies, nanoparticle technology and micropeptide targeting, can be applied to target dysregulated redox signalling in subcellular compartments of cardiovascular cells. In this review, we consider the opportunities for improving cardiovascular outcomes by utilizing new technology platforms to target subcellular ‘bonfires’ generated by dysregulated redox pathways, to improve clinical outcomes.

Monoamine Oxidase-Related Vascular Oxidative Stress in Diseases Associated with Inflammatory Burden

Monoamine oxidases (MAO) with 2 isoforms, A and B, located at the outer mitochondrial membrane are flavoenzyme membranes with a major role in the metabolism of monoaminergic neurotransmitters and biogenic amines in the central nervous system and peripheral tissues, respectively. In the process of oxidative deamination, aldehydes, hydrogen peroxide, and ammonia are constantly generated as potential deleterious by-products. While being systematically studied for decades as sources of reactive oxygen species in brain diseases, compelling evidence nowadays supports the role of MAO-related oxidative stress in cardiovascular and metabolic pathologies. Indeed, oxidative stress and chronic inflammation are the most common pathomechanisms of the main noncommunicable diseases of our century. MAO inhibition with the new generation of reversible and selective drugs has recently emerged as a pharmacological strategy aimed at mitigating both processes. The aim of this minireview is to summarize available information regarding the contribution of MAO to the vascular oxidative stress and endothelial dysfunction in hypertension, metabolic disorders, and chronic kidney disease, all conditions associated with increased inflammatory burden.

Recent advances in reaction-based fluorescent probes for detecting monoamine oxidases in living systems

This Minireview summarizes the recent advances in reaction based MAO type fluorescent probes and their imaging applications in living systems.

Novel monoamine oxidase inhibitors based on the privileged 2-imidazoline molecular framework

Series of structurally diverse 2-imidazoline derivatives have been synthesized by condensation of substituted aldehydes with ethylenediamine, Pd-catalyzed N-arylation of 2-imidazolines and by the formation of 1,2,4-oxadiazoles and benzoxazepines from 2-imidazoline-containing precursors. The 2-imidazoline derivatives were evaluated as potential inhibitors of human monoamine oxidase (MAO) A and B. Among the 2-imidazolines, good potency inhibitors were discovered with compound 9p (IC₅₀ = 0.012 µM) being the most potent MAO-B inhibitor, while compound 9d (IC₅₀ = 0.751 µM) was the most potent MAO-A inhibitor of the series. These potencies are in the same range as those of reference MAO inhibitors used in the clinic. Among 33 compounds evaluated, 13 exhibited IC₅₀ values in the submicromolar range for the inhibition of an MAO isoform. It is postulated that the imidazoline moieties of some of these inhibitors may be recognized by the imidazoline I₂-binding site of MAO. Good potency MAO inhibitors may be useful for the treatment of neuropsychiatric and neurodegenerative disorders such as depression and Parkinson's disease, and future application for the treatment of prostate cancer, congestive heart failure and Alzheimer's disease. In addition, high potency 2-imidazoline-derived MAO inhibitors may be used as potential probes for the imidazoline binding sites of the MAOs, as well as to determine alternative binding regions of imidazoline within the MAO active site.

Monoamine oxidase inhibitors, and iron chelators in depressive illness and neurodegenerative diseases

In early 1920s, tyramine oxidase was discovered that metabolized tyramine and in 1933 Blaschko demonstrated that this enzyme also metabolized adrenaline, noradrenaline and dopamine. Zeller gave it the name monoamine oxidase (MAO) to distinguish it from the enzyme that oxidatively deaminated diamines. MAO was recognized as an enzyme of crucial interest to pharmacologists because it catalyzed the major inactivation pathway for the catecholamines (and, later, 5-hydroxytryptamine, as well). Within the few decade, the inhibitors of MAO were discovered and introduced for the treatment of depressive illness which was established clinically. However, the first clinical use exposed serious side effects, pharmacological interest in, and investigation of, MAO continued, resulting in the characterization of two forms, distinct forms, MAO-A and -B, and selective inhibitors for them. Selective inhibitors of MAO-B (selegiline, rasagiline and safinamide) have found a therapeutic role in the treatment of Parkinson's disease and reversible inhibitors of MAO-A offered antidepressant activity without the serious side effects of the earlier nonselective MAO inhibitors. Subsequent molecular pharmacological have also generated the concept of neuroprotection, reflecting the possibility of slowing, halting and maybe reversing, neurodegeneration in Parkinson's or Alzheimer's diseases. Increased levels of oxidative stress through the accumulation of iron in the Parkinsonian and Alzheimer brains has been suggested to be critical for the initiation and progress of neurodegeneration. Selective inhibition of brain MAO could contribute importantly to lowering such stress, preventing the formation of hydrogen peroxide. Interaction of Iron with hydrogen peroxide and lead to Fenton reaction and production of the most reactive radical, namely hydroxyl radical. There are complex interactions between free iron levels in brain and MAO, and cascade of neurotoxic events may have practical outcomes for depressive disorders and neurodegenerative diseases. As consequence recent novel therapeutic drugs for neurodegenerative diseases has led to the development of multi target drugs, that possess selective brain MAO A and B inhibitory moiety, iron chelating and antioxidant activities and the ability to increase brain levels of endogenous neurotrophins, such as BDNF, GDNF VEGF and erythropoietin and induce mitochondrial biogenesis.

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.

Membrane Reconstitution of Monoamine Oxidase Enzymes on Supported Lipid Bilayers

Monoamine oxidase A and B (MAO-A and B) are mitochondrial outer membrane enzymes that are implicated in a number of human diseases, and the pharmacological inhibition of these enzymes is a promising therapeutic strategy to alleviate disease symptoms. It has been suggested that optimal levels of enzymatic activity occur in the membrane-associated state, although details of the membrane association process remain to be understood. Herein, we have developed a supported lipid bilayer platform to study MAO-A and B binding and evaluate the effects of known pharmacological inhibitors on the membrane association process. By utilizing the quartz crystal microbalance-dissipation (QCM-D) technique, it was determined that both MAOs exhibit tight binding to negatively and positively charged bilayers with distinct concentration-dependent binding profiles while only transiently binding to neutral bilayers. Importantly, in the presence of known inhibitors, the MAOs showed increased binding to negatively charged bilayers, although there was no effect of inhibitor treatment on binding to positively charged bilayers. Taken together, our findings establish that the membrane association of MAOs is highly dependent on membrane surface charge, and we outline an experimental platform to support the in vitro reconstitution of monoamine oxidases on synthetic membranes, including the evaluation of pharmacological drug candidates.

Mitochondria "THE" target of myocardial conditioning

Several interventions, such as ischemic preconditioning, remote pre/perconditioning, or postconditioning, are known to decrease lethal myocardial ischemia-reperfusion injury. While several signal transduction pathways become activated by such maneuvers, they all have a common end point, namely, the mitochondria. These organelles represent an essential target of the cardioprotective strategies, and the preservation of mitochondrial function is central for the reduction of ischemia-reperfusion injury. In the present review, we address the role of mitochondria in the different conditioning strategies; in particular, we focus on alterations of mitochondrial function in terms of energy production, formation of reactive oxygen species, opening of the mitochondrial permeability transition pore, and mitochondrial dynamics induced by ischemia-reperfusion.

Analysis and Evaluation of the Inhibitory Mechanism of a Novel Angiotensin-I-Converting Enzyme Inhibitory Peptide Derived from Casein Hydrolysate

Casein hydrolysates exert various biological activities, and the responsible functional peptides are being identified from them continuously. In this study, the tryptic casein hydrolysate was fractionated by an ultrafiltration membrane (3 kDa), and the peptides were identified by capillary electrophoresis-quadrupole-time-of-flight-tandem mass spectrometry. Meanwhile, in silico methods were used to analyze the toxicity, solubility, stability, and affinity between the peptides and angiotensin-I-converting enzyme (ACE). Finally, a new angiotensin-I-converting enzyme inhibitory (ACEI) peptide, EKVNELSK, derived from α_s1-casein (fragment 35-42) was screened. The half maximal inhibitory concentration value of the peptide is 5.998 mM, which was determined by a high-performance liquid chromatography method. The Lineweaver-Burk plot indicated that this peptide is a mixed-type inhibitor against ACE. Moreover, Discovery Studio 2017 R2 software was adopted to perform molecular docking to propose the potential mechanisms underlying the ACEI activity of the peptide. These results indicated that EKVNELSK is a new ACEI peptide identified from casein hydrolysate.

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.

90 years of monoamine oxidase: some progress and some confusion

It would not be practical to attempt to deal with all the advances that have informed our understanding of the behavior and functions of this enzyme over the past 90 years. This account concentrates key advances that explain why the monoamine oxidases remain of pharmacological and biochemical interest and on some areas of continuing uncertainty. Some issues that remain to be understood or are in need of further clarification are highlighted.

Cardioprotective Exercise and Pharmacologic Interventions as Complementary Antidotes to Cardiovascular Disease

Exercise and pharmacologic therapies to prevent and treat cardiovascular disease have advanced largely through independent efforts. Understanding of first-line drug therapies, findings from preclinical animal studies, and the need for research initiatives related to complementary cardioprotective exercise-pharma interventions are reviewed from the premise that contemporary cardioprotective therapies must include adjunctive exercise and lifestyle interventions in addition to pharmacologic agents.

Measurement of Mitochondrial ROS Formation

Reactive oxygen species (ROS) are involved in both physiological and pathological processes. This widely accepted concept is based more on the effects of antioxidant interventions than on reliable assessments of rates and sites of intracellular ROS formation. This argument applies also to mitochondria that are generally considered the major site for ROS formation, especially in skeletal and cardiac myocytes.Detection of oxidative modifications of intracellular or circulating molecules is frequently used as a marker of ROS formation. However, this approach provides limited information on spatiotemporal aspects of ROS formation that have to be defined in order to elucidate the role of ROS in a given pathophysiological condition. This information can be obtained by means of fluorescent probes that allow monitoring ROS formation in cell-free extracts and isolated cells. Thus, this approach can be used to characterize ROS formation in both isolated mitochondria and mitochondria within intact cells. This chapter describes three major examples of the use of fluorescent probes for monitoring mitochondrial ROS formation. Detailed methods description is accompanied by a critical analysis of the limitations of each technique, highlighting the possible sources of errors in performing the assay and results interpretation.