Mitochondrial Monoamine Oxidase Research Articles

A Novel MAO-B/SSAO Inhibitor Improves Multiple Aspects of Dystrophic Phenotype in mdx Mice.

Duchenne muscular dystrophy (DMD) is one of the most frequent and severe childhood muscle diseases. Its pathophysiology is multifaceted and still incompletely understood, but we and others have previously shown that oxidative stress plays an important role. In particular, we have demonstrated that inhibition of mitochondrial monoamine oxidases could improve some functional and biohumoral markers of the pathology. In the present study we report the use of dystrophic mdx mice to evaluate the efficacy of a dual monoamine oxidase B (MAO-B)/semicarbazide-sensitive amine oxidase (SSAO) inhibitor, PXS-5131, in reducing inflammation and fibrosis and improving muscle function. We found that a one-month treatment starting at three months of age was able to decrease reactive oxygen species (ROS) production, fibrosis, and inflammatory infiltrate in the tibialis anterior (TA) and diaphragm muscles. Importantly, we also observed a marked improvement in the capacity of the gastrocnemius muscle to maintain its force when challenged with eccentric contractions. Upon performing a bulk RNA-seq analysis, PXS-5131 treatment affected the expression of genes involved in inflammatory processes and tissue remodeling. We also studied the effect of prolonged treatment in older dystrophic mice, and found that a three-month administration of PXS-5131 was able to greatly reduce the progression of fibrosis not only in the diaphragm but also in the heart. Taken together, these results suggest that PXS-5131 is an effective inhibitor of fibrosis and inflammation in dystrophic muscles, a finding that could open a new therapeutic avenue for DMD patients.

Oxidative Stress by the Mitochondrial Monoamine Oxidase B Mediates Calcium Pyrophosphate Crystal-Induced Arthritis.

Calcium pyrophosphate (CPP) crystal deposition in the joints is associated with a heterogeneous set of debilitating syndromes characterized by inflammation and pain, for which no effective therapies are currently available. Because we found that the mitochondrial enzyme monoamine oxidase B (MAO-B) plays a fundamental role in promoting inflammatory pathways, this study aims at assessing the efficacy of two clinical-grade inhibitors (iMAO-Bs) in preclinical models of this disease to pave the way for a novel treatment. We tested our hypothesis in two murine models of CPP-induced arthritis, by measuring cytokine and chemokine levels, along with immune cell recruitment. iMAO-Bs (rasagiline and safinamide) were administered either before or after crystal injection. To elucidate the molecular mechanism, we challenged in vitro primed macrophages with CPP crystals and assessed the impact of iMAO-Bs in dampening proinflammatory cytokines and in preserving mitochondrial function. Both in preventive and therapeutic in vivo protocols, iMAO-Bs blunted the release of proinflammatory cytokines (interleukin [IL]-6 and IL1-β) and chemokines (CXCL10, CXCL1, CCL2 and CCL5) (n > 6 mice/group). Importantly, they also significantly reduced ankle swelling (50.3% vs 17.1%; P < 0.001 and 23.1%; P = 0.005 for rasagiline and safinamide, respectively). Mechanistically, iMAO-Bs dampened the burst of reactive oxygen species and the mitochondrial dysfunction triggered by CPP crystals in isolated macrophages. Moreover, iMAO-Bs blunted cytokine secretion and NLRP3 inflammasome activation through inhibition of the NF-κB and STAT3 pathways. iMAO-Bs dampen inflammation in murine models of crystal-induced arthropathy, thereby uncovering MAO-B as a promising target to treat these diseases.

Targeting mitochondria-inflammation circle by renal denervation reduces atheroprone endothelial phenotypes and atherosclerosis

ObjectiveThe disruption of mitochondrial redox homeostasis in endothelial cells (ECs) can cause chronic inflammation, a substantial contributor to the development of atherosclerosis. Chronic sympathetic hyperactivity can enhance oxidative stress to induce endothelial dysfunction. We determined if renal denervation (RDN), the strategy reducing sympathetic tone, can protect ECs by ameliorating mitochondrial reactive oxygen species (ROS)-induced inflammation to reduce atherosclerosis. Methods and resultsApoE deficient (ApoE−/-) mice were conducted RDN or sham operation before 20-week high-fat diet feeding. Atherosclerosis, EC phenotype and mitochondrial morphology were determined. In vitro, human arterial ECs were treated with norepinephrine to determine the mechanisms for RDN-inhibited endothelial inflammation. RDN reduced atherosclerosis, EC mitochondrial oxidative stress and inflammation. Mechanistically, the chronic sympathetic hyperactivity increased circulating norepinephrine and mitochondrial monoamine oxidase A (MAO-A) activity. MAO-A activation-impaired mitochondrial homeostasis resulted in ROS accumulation and NF-κB activation, thereby enhancing expression of atherogenic and proinflammatory molecules in ECs. It also suppressed mitochondrial function regulator PGC-1α, with involvement of NF-κB and oxidative stress. Inactivation of MAO-A by RDN disrupted the positive-feedback regulation between mitochondrial dysfunction and inflammation, thereby inhibiting EC atheroprone phenotypic alterations and atherosclerosis. ConclusionsThe interplay between MAO-A-induced mitochondrial oxidative stress and inflammation in ECs is a key driver in atherogenesis, and it can be reduced by RDN.

Regulatory Effects of Cannabidiol on Mitochondrial Functions: A Review.

Cannabidiol (CBD) is part of a group of phytocannabinoids derived from Cannabis sativa. Initial work on CBD presumed the compound was inactive, but it was later found to exhibit antipsychotic, anti-depressive, anxiolytic, and antiepileptic effects. In recent decades, evidence has indicated a role for CBD in the modulation of mitochondrial processes, including respiration and bioenergetics, mitochondrial DNA epigenetics, intrinsic apoptosis, the regulation of mitochondrial and intracellular calcium concentrations, mitochondrial fission, fusion and biogenesis, and mitochondrial ferritin concentration and mitochondrial monoamine oxidase activity regulation. Despite these advances, current data demonstrate contradictory findings with regard to not only the magnitude of effects mediated by CBD, but also to the direction of effects. For example, there are data indicating that CBD treatment can increase, decrease, or have no significant effect on intrinsic apoptosis. Differences between studies in cell type, cell-specific response to CBD, and, in some cases, dose of CBD may help to explain differences in outcomes. Most studies on CBD and mitochondria have utilized treatment concentrations that exceed the highest recorded plasma concentrations in humans, suggesting that future studies should focus on CBD treatments within a range observed in pharmacokinetic studies. This review focuses on understanding the mechanisms of CBD-mediated regulation of mitochondrial functions, with an emphasis on findings in neural cells and tissues and therapeutic relevance based on human pharmacokinetics.

Abstract 421: Norepinephrine Catabolism Drives Cardiac Fibroblast Activation via Monoamine Oxidase Activity and Rage/β-adrenergic Signaling

The mitochondrial enzyme monoamine oxidase A (MAO-A) plays an increasingly appreciated role in cardiac remodeling induced by diabetes and ischemic injury. Oxidative deamination of norepinephrine (NE) by MAO-A generates 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL) and H 2 O 2 . Isolation and quantification of catechol-modified proteins from cardiac fibroblast lysate using an aminophenylboronic acid resin showed an MAO-dependent accumulation of catechol adducts in NE-treated cells (P&lt;0.05). Our lab has previously observed increased expression and activity of MAO in myocardium of diabetes patients compared with age-matched nondiabetic patients. Moreover, preliminary data suggest that catecholaldehydes and other biogenic aldehydes might contribute to the pathogenesis of cardiac fibrosis in diabetic cardiomyopathy via pro-fibrotic signaling mechanisms. We hypothesize that NE activates fibroblasts by both canonical pathways (i.e, adrenergic receptors) and by monoamine oxidase-mediated catabolism and activation of the receptor for advanced glycation endproducts (RAGE). Treatment of cardiac fibroblasts with NE (1 μM) resulted in accelerated proliferation, enhanced collagen I &amp; III secretion, robust increases in mitochondrial and total cellular ROS, and upregulated pro-fibrotic gene expression. These effects were abrogated by co-administration of RAGE antagonist FPS-ZM1, MAO inhibitors, β-blocker propranolol, and the aldehyde scavenger carnosine (P&lt;0.05). These findings suggest that NE (and other catecholamines) may influence extracellular matrix remodeling via multiple pathways, including adrenergic and also RAGE, via MAO-mediated catabolism.

N-(3-Ethoxy-phenyl)-4-pyrrolidin-1-yl-3-trifluoromethyl-benzamide (EPPTB) prevents 3-iodothyronamine (T1AM)-induced neuroprotection against kainic acid toxicity

Thyroid hormone and thyroid hormone metabolites, including 3-iodothyronamine (T1AM) and 3-iodothyroacetic acid (TA1), activate AKT signaling in hippocampal neurons affording protection from excitotoxic damage. We aim to explore whether the mechanism of T1AM neuroprotection against kainic acid (KA)-induced excitotoxicity included the activation of the trace amine associated receptor isoform 1 (TAAR1), one of T1AM targets.Rat organotypic hippocampal slices were exposed to vehicle (Veh) or to 5 μM kA for 24 h in the absence or presence of 0.1, 1 and 10 μM T1AM or to 0.1, 1 and 10 μM T1AM and 1 μM N-(3-Ethoxy-phenyl)-4-pyrrolidin-1-yl-3-trifluoromethyl-benzamide (EPPTB), the only available TAAR1 antagonist, or to 1 μM T1AM in the absence or in the presence of 10 μM LY294002, an inhibitor of phosphoinositide 3-kinases (PI3Ks). Cell death was evaluated by measuring propidium iodide (PI) levels of fluorescence 24 h after treatment. In parallel, the expression levels of p-AKT and p-PKA were evaluated by Western blot analysis of slice lysates. The activity of mitochondrial monoamine oxidases (MAO) was assayed fluorimetrically.24 h exposure of slices to T1AM resulted in the activation of AKT and PKA. KA exposure induced cell death in the CA3 region and significantly reduced p-AKT and p-PKA levels. The presence of 1 and 10 μM T1AM significantly protected neurons from death and conserved both kinase levels with the essential role of AKT in neuroprotection. Furthermore, EPPTB prevented T1AM-induced neuroprotection, activation of PKA and AKT. Of note, in the presence of EPPTB T1AM degradation by MAO was reduced.Our results indicate that the neuroprotection offered by T1AM depends, as for TA1, on AKT activation but do not allow to conclusively indicate TAAR1 as the target implicated.

Challenges in the Separation of Purified Cardiac Mitochondrial Membranes

BackgroundMitochondria are the bioenergetic engines of the cell, thus maintaining mitochondrial health is essential for meeting energy demands. Mitochondrial function is achieved upon the balance of structural processes that involve mitochondrial biogenesis, fusion and fission. Structural and functional integrity of the mitochondrial membranes, the outer mitochondrial membrane (OMM) and the inner mitochondrial membrane (IMM) is important for the maintenance of the mitochondrial quality control and mitochondrial metabolism. Therefore, elucidation of the individual contribution of each membrane to mitochondrial metabolism and function, as well as mitochondria‐mediated cell survival pathways and cell death is important. In this study, we attempted to set up the methods for isolation of mitoplasts (mitochondria without OMM) and the OMM from the rat heart.MethodsCardiac mitochondria were isolated from Sprague Dawley rats (250–300g) by differential centrifugation and purified via Percoll gradient (continuous layers of 19%, 30% and 60% concentration). Isolation of mitoplasts was performed by incubation in different hypotonic and hypertonic buffers, sonication (20% output/power), and separation of membranes by ultracentrifugation using sucrose continuous gradients (20–80%). Mitochondrial swelling assay was made to confirm the swelling/shrinking method used. Mitoplast formation was validated by monoamine oxidase (MAO) activity, oxygen consumption in the presence and absence of cytochrome‐c and Western Blotting against specific inner and outer mitochondrial membrane proteins.ResultsWestern Blot analysis showed pure isolated mitochondria, validated by the absence of GAPDH (cytosolic marker) upon Percoll gradient. In addition, more than 30% decrease in TOMM20 (OMM specific protein) expression in isolated mitoplasts in comparison to mitochondria. Mitochondrial respiratory rates and MAO activity suggests changes in mitochondrial membrane distribution. Mitochondrial swelling assay showed that cardiac mitochondria were resistant to swelling in hypotonic solution, therefore other methods involving the addition of Ca+2 or EGTA were used to induced separation of mitochondrial membranes.ConclusionDespite application of different preparative approaches, we were not able to isolate purified OMM, and only one method was proved to make a slight reduction of OMM contamination in mitoplasts.Support or Funding InformationSupported by the NIGMS NIH grant SC1GM128210This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effects of combined arsenic and lead exposure on the brain monoaminergic system and behavioral functions in rats: Reversal effect of MiADMSA.

In this study, we evaluated the therapeutic efficacy of monoisoamyldimercaptosuccinic acid (MiADMSA) against individual and combined effects of arsenic (As) and lead (Pb) on the monoaminergic system and behavioral functions in rats. Pregnant rats were exposed to sodium metaarsenite (50 ppm) and lead acetate (0.2%) individually and in combination (As = 25 ppm + Pb = 0.1%) via drinking water from gestation day (GD) 6 to postnatal day (PND) 21. MiADMSA (50 mg/kg body weight) was given orally through gavage for 3 consecutive days to pups from PND 18 to PND 20. The results showed increases in synaptosomal epinephrine, dopamine, and norepinephrine levels with individual metal exposures and decreases with combined exposure to As and Pb in the cortex, cerebellum, and hippocampus in PND 21, PND 28, and 3 months age-group rats. We found decreased activity of mitochondrial monoamine oxidase in the selected brain regions following individual and combined exposures to Pb and As. In addition, rats treated with Pb and As alone or in combination showed significant deficits in open-field behavior, grip strength, locomotor activity, and exploratory behavior at PND 28 and 3 months of age. However, MiADMSA administration showed reversal effects against the As- and/or Pb-induced impairments in the monoaminergic system as well as in behavioral functions of rats. Our data demonstrated that the mixture of Pb and As induced synergistic toxicity to developing brain leading to impairments in neurobehavioral functions and also suggest therapeutic efficacy of MiADMSA against Pb- and/or As-induced developmental neurotoxicity.

Monoamine Oxidase Activity in the Hepatopancreas of the Kamchatka Crab Paralithodes camtschaticus: a Substrate–Inhibitor Specificity

A study of substrate–inhibitor specificity of mitochondrial monoamine oxidase (MAO) in the hepatopancreas of the adult Kamchatka crab Paralithodes camtschaticus revealed specific catalytic properties of the enzyme. On the one hand, crab hepatopancreas MAO, like its classical hepatic counterpart, can deaminate tyramine, tryptamine, dopamine, serotonin, noradrenalin, benzylamine, β-phenylethylamine and N-methylhistamine but shows no sensitivity to 10 mM semicarbazide. On the other hand, MAO deaminates histamine but not putrescine, two classical diamine oxidase (DAO) substrates. It was established that MAO activity was several times higher toward benzylamine, β-phenylethylamine and N-methylhistamine than toward serotonin and noradrenalin. MAO was also found to be almost 500 times more sensitive to its selective inhibitor deprenyl than to chlorogilyn. A substrate–inhibitory analysis with the use of deprenyl and chloroginyl provides an indirect evidence for the existence of a sole MAO molecular form in the Kamchatka crab hepatopancreas.

Neuroprotective potential of phenolic extracts of &lt;i&gt;Capsicum frutescens&lt;/i&gt; as an inhibitor of monoamine oxidase and cholinesterase activities

In this study, we investigated the in vitro antioxidant activity of the extracts from ripe and unripe fruits of Capsicum frutescens . The effects of the extracts on three enzymes which are associated with Parkinson's disease (PD) were also investigated together with quantitation of total phenol, flavonoid and non-flavonoid contents of the extracts. Activities of mitochondrial monoamine oxidase (MAO), acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) from rat brain were determined in the presence of the extracts. 1, 1-diphenyl-2- picrylhydrazyl (DPPH) and OH radicals scavenging abilities, as well as membrane stabilizing effect of the extract via inhibition of Fe 2+ -induced lipid peroxidation in rat brain tissue homogenate were assessed. The results revealed that the extracts exhibited mitochondrial MAO, AChE and BChE inhibitory effects in concentrationdependent manner, with the unripe fruit extract showing significantly higher (P<0.05) inhibitory effects than the ripe fruit extract. However, the ripe fruit extract had significantly higher total phenol and flavonoid contents, as well as exhibited significantly higher (P<0.05) DPPH free radical scavenging and membrane stabilizing effects. The observed antioxidant and enzyme inhibitory properties of ripe and unripe pepper ( C. frutescens ) fruits extracts could be an interplay among their constituent polyphenols. This could be a justification for their use as nutraceutical/dietary intervention in the management of neurodegenerative diseases, especially PD. Collectively, these findings suggest that C. frutescens could serve as a functional food/nutraceutical in the management of PD and our further studies will be directed towards characterization of the biomolecules involved and their mechanism(s) of action in appropriate models. Keywords: Monoamine oxidase, Cholinesterases, Capsicum spp , Neurodegenerative diseases, Functional foods

Central Effects of 3-Iodothyronamine Reveal a Novel Role for Mitochondrial Monoamine Oxidases.

3-Iodothyronamine (T1AM) is the last iodinated thyronamine generated from thyroid hormone alternative metabolism found circulating in rodents and in humans. So far, the physiopathological meaning of T1AM tissue levels is unknown. Much is instead known on T1AM pharmacological effects in rodents. Such evidence indicates that T1AM acutely modifies, with high potency and effectiveness, rodents’ metabolism and behavior, often showing inverted U-shaped dose–response curves. Although several possible targets for T1AM were identified, the mechanism underlying T1AM behavioral effects remains still elusive. T1AM pharmacokinetic features clearly indicate the central nervous system is not a preferential site for T1AM distribution but it is a site where T1AM levels are critically regulated, as it occurs for neuromodulators or neurotransmitters. We here summarize and discuss evidence supporting the hypothesis that central effects of T1AM derive from activation of intracellular and possibly extracellular pathways. In this respect, consisting evidence indicates the intracellular pathway is mediated by the product of T1AM phase-I non-microsomal oxidation, the 3-iodothryoacetic acid, while other data indicate a role for the trace amine-associated receptor, isoform 1, as membrane target of T1AM (extracellular pathway). Overall, these evidence might sustain the non-linear dose–effect curves typically observed when increasing T1AM doses are administered and reveal an interesting and yet unexplored link between thyroid, monoamine oxidases activity and histamine.

Visualization of painful inflammation in patients with pain after traumatic ankle sprain using [11C]-D-deprenyl PET/CT

Background and aimsPositron emission tomography (PET) with the radioligand [11C]-D-deprenyl has shown increased signal at location of pain in patients with rheumatoid arthritis and chronic whiplash injury. The binding site of [11C]-D-deprenyl in peripheral tissues is suggested to be mitochondrial monoamine oxidase in cells engaged in post-traumatic inflammation and tissue repair processes. The association between [11C]-D-deprenyl uptake and the transition from acute to chronic pain remain unknown. Further imaging studies of musculoskeletal pain at the molecular level would benefit from establishing a clinical model in a common and well-defined injury in otherwise healthy and drug-naïve subjects. The aim of this study was to investigate if [11C]-D-deprenyl uptake would be acutely elevated in unilateral ankle sprain and if tracer uptake would be reduced as a function of healing, and correlated with pain localizations and pain experience. MethodsEight otherwise healthy patients with unilateral ankle sprain were recruited at the emergency department. All underwent [11C]-D-deprenyl PET/CT in the acute phase, at one month and 6–14 months after injury. ResultsAcute [11C]-D-deprenyl uptake at the injury site was a factor of 10.7 (range 2.9–37.3) higher than the intact ankle. During healing, [11C]-D-deprenyl uptake decreased, but did not normalize until after 11 months. Patients experiencing persistent pain had prolonged [11C]-D-deprenyl uptake in painful locations. Conclusions and implicationsThe data provide further support that [11C]-D-deprenyl PET can visualize, quantify and follow processes in peripheral tissue that may relate to soft tissue injuries, inflammation and associated nociceptive signaling. Such an objective correlate would represent a progress in pain research, as well as in clinical pain diagnostics and management.

Activity-dependent Regulation of Histone Lysine Demethylase KDM1A by a Putative Thiol/Disulfide Switch

Lysine demethylation of proteins such as histones is catalyzed by several classes of enzymes, including the FAD-dependent amine oxidases KDM1A/B. The KDM1 family is homologous to the mitochondrial monoamine oxidases MAO-A/B and produces hydrogen peroxide in the nucleus as a byproduct of demethylation. Here, we show KDM1A is highly thiol-reactive in vitro and in cellular models. Enzyme activity is potently and reversibly inhibited by the drug disulfiram and by hydrogen peroxide. Hydrogen peroxide produced by KDM1A catalysis reduces thiol labeling and inactivates demethylase activity over time. MALDI-TOF mass spectrometry indicates that hydrogen peroxide blocks labeling of cysteine 600, which we propose forms an intramolecular disulfide with cysteine 618 to negatively regulate the catalytic activity of KDM1A. This activity-dependent regulation is unique among histone-modifying enzymes but consistent with redox sensitivity of epigenetic regulators.

Influence of water-soluble derivatives of [60]fullerene on catalytic activity of monoaminе oxidase B and their membranotropic properties

The effect of two water-soluble derivatives of [60]fullerene (WS[60]FDs) on mitochondrial monoamine oxidase B (MAO-B) involved in oxidative deamination of biogenic amines has been investigated. The studied compounds were shown to be inhibitors of MAO-B. The inhibitory mechanism and the inhibition constants were determined. It was shown that WS[60]FDs I and II penetrate in lipid bilayer of membrane of phosphatidylcholine liposomes and localize in the regions of both polar head and fatty acid groups of phospholipids. The equilibrium constants of fluorescent dye—WS[60]FDs complexes were determined.

Assessment of Mitochondrial Dysfunction and Monoamine Oxidase Contribution to Oxidative Stress in Human Diabetic Hearts.

Mitochondria-related oxidative stress is a pathomechanism causally linked to coronary heart disease (CHD) and diabetes mellitus (DM). Recently, mitochondrial monoamine oxidases (MAOs) have emerged as novel sources of oxidative stress in the cardiovascular system and experimental diabetes. The present study was purported to assess the mitochondrial impairment and the contribution of MAOs-related oxidative stress to the cardiovascular dysfunction in coronary patients with/without DM. Right atrial appendages were obtained from 75 patients randomized into 3 groups: (1) Control (CTRL), valvular patients without CHD; (2) CHD, patients with confirmed CHD; and (3) CHD-DM, patients with CHD and DM. Mitochondrial respiration was measured by high-resolution respirometry and MAOs expression was evaluated by RT-PCR and immunohistochemistry. Hydrogen peroxide (H2O2) emission was assessed by confocal microscopy and spectrophotometrically. The impairment of mitochondrial respiration was substrate-independent in CHD-DM group. MAOs expression was comparable among the groups, with the predominance of MAO-B isoform but no significant differences regarding oxidative stress were detected by either method. Incubation of atrial samples with MAOs inhibitors significantly reduced the H2O2 in all groups. In conclusion, abnormal mitochondrial respiration occurs in CHD and is more severe in DM and MAOs contribute to oxidative stress in human diseased hearts with/without DM.

Kinetics of Inhibition of Monoamine Oxidase Using Curcumin and Ellagic Acid.

Background:Curcumin and ellagic are the natural polyphenols having a wide range of pharmacological actions. They have been reported to have their use in various neurological disorders.Objective:This study was aimed to evaluate the effect of curcumin and ellagic acid on the activity of monoamine oxidase (MAO), the enzyme responsible for metabolism of monoamine neurotransmitters which are pivotal for neuronal development and function.Materials and Methods:The in vitro effects of these selected polyphenols on MAO activities in mitochondria isolated from rat brains were examined. Brain mitochondria were assayed for MAO type-B (MAO-B) using benzylamine as substrates. Rat brain mitochondrial MAO preparation was used to study the kinetics of enzyme inhibition using double reciprocal Lineweaver–Burk plot.Results:MAO activity was inhibited by curcumin and ellagic acid; however, higher half maximal inhibitory concentrations of curcumin (500.46 nM) and ellagic acid (412.24 nM) were required compared to the known MAO-B inhibitor selegiline. It is observed that the curcumin and ellagic acid inhibit the MAO activity with both the competitive and noncompetitive type of inhibitions.Conclusions:Curcumin and ellagic acid can be considered a possible source of MAO inhibitor used in the treatment of Parkinson's and other neurological disorders.SUMMARY Monoamine oxidase (MAO) is involved in a variety of neurological disorders including Parkinson's disease (PD)Curcumin and ellagic acid inhibit the monoamine oxidase activityEllagic acid revealed more potent MAO type-B (MAO-B) inhibitory activity than curcuminKinetic studies of MAO inhibition using different concentrations of curcumin and ellagic acid were plotted as double reciprocal Lineweaver–Burk plotThe mode of inhibition of both compounds toward MAO-B is mixed (competitive and uncompetitive) type of inhibition with both the competitive and noncompetitive type of inhibitions. Abbreviations used: MAO: Monoamine oxidase, IC50: Higher half maximal inhibitory concentrations, PD: Parkinson's disease, LB: Lewy bodies, SNpc: Substantia nigra pars compacta, ROS: Reactive oxygen species, SG: Selegiline, DMC: demethoxycurcumin, BDMC: Bisdemethoxycurcumin.

Catalytic properties of liver monoamine oxidase in the chum salmon Oncorhynchus keta

The substrate and inhibitory specificity of mitochondrial monoamine oxidase (MAO) in the liver of males of the summer form of the chum salmon Oncorhynchus keta was studied. As to the spectrum of deaminated substrates, the hepatic MAO of the chum salmon is similar to MAO of most terrestrial mammals, for eight classical MAO substrates similarity in their substrate characteristics were found. Analysis of the antimonoamine oxidase activity of two derivaties of 2-propinilamine, five derivatives of acridine as well as of pyronine G revealed significant qualitative and quantitative differences as compared to the hepatic enzyme of tuna and whitefish. The compounds tested manifested themselves as irreversible inhibitors of chum salmon's hepatic MAO possessing various efficacy, but lacking the selectivity of action as dependent on the deaminated substrate. The obtained data on the substrate and inhibitory analysis provide an indirect evidence for the presence of a single molecular form of MAO in the chum salmon liver.

Sensitivity of liver monoamine oxidase in the lamprey Lampetra fluviatilis to some tricyclic compounds

A comparative analysis of the effect of the five acridine, three phenothiazine and one xanten (pyronine G) derivatives on the activity of liver mitochondrial monoamine oxidase (MAO) in sexually mature male river lampreys Lampetra fluviatilis has been conducted. Tyramine, dopamine, serotonin, noradrenaline, benzylamine, β-phenylethylamine and N-methylhistamine have been used as substrates for analyzing the monoamine oxidase activity of heterocyclic compounds. The analyzed synthetic hexamerous tricyclic compounds exhibit irreversible inhibition of the enzyme but no specificity depending on the desaminated substrate. The number and identity of heteroatoms in the analyzed heterocyclic compounds have been established to influence their inhibitory efficiency. The data of substrate-inhibitory analysis obtained with the use of the specific substrates provide indirect evidence for the existence of a single MAO form in the lamprey liver.

Hydrogen Peroxide Produced by Mitochondrial Monoamine Oxidase Catalysis: Biological Implications

The biological roles of mitochondrial-produced reactive oxygen species continue to receive intensive investigation since one of the products (H₂O₂) has important cellular signaling roles as well as contributing to apoptotic responses. In general, the source of mitochondrial reactive oxygen species is thought to be the superoxide anion produced from Complex I and Complex III components of the electron transport chain. Superoxide anion readily dismutates to H₂O₂ with subsequent transformation to the hydroxyl radical by Fenton chemistry. An overlooked source of H₂O₂ in the mitochondrion is its production as a catalytic reaction product from the outer membrane enzymes: monoamine oxidases A and B. The literature is reviewed to document identified degenerative reactions attributed to H₂O₂ produced by MAO A and by MAO B catalysis. Available information on the topologies of these enzymes in the mitochondrial outer membrane is also discussed with relevance to H₂O₂ production and involvement in cell signaling functions as well as degenerative effects.

Antidepressant-like Activity of Andrographis paniculata in Type-2 Diabetic Rats

Pharmacological observations suggesting antidepressants-like efficacy of a medicinally used Andrographis paniculata extract (AP) in type-2 diabetic are presented in this communication. Efficacies of 10 daily oral doses of 50, 100 and 200 mg/kg/day AP and 15 mg/kg/day imipramine were compared in behavioral despair and learned helplessness tests using type-2 diabetic rats, and bio- and neuro-chemical alterations in the brain tissue of treated animals subjected to learned helplessness test were quantified. Significant imipramine like antidepressant activity of AP was observed even after its lowest daily tested (50 mg/kg/day) in both behavioral tests used, and such efficacy of the extract dose dependently increased with its increasing dose. Imipramine like effects of AP in elevating lower hippocampal levels of norepinephrine, dopamine, and serotonin observed in diabetic rats towards normal values were also observed after its 50 mg/kg/day doses and such efficacy of the extract increased also with its increasing daily doses. Levels of all the three monoamines quantified in 100 mg/kg/day AP treated diabetic rats were significantly higher than those of the non-diabetic animals. Imipramine had no significant effects on body weight losses, hyperglycemia, insulin deficiency, lower catalase and superoxide dismutase activities and higher lipid peroxides in the frontal cortex, and mitochondrial monoamine oxidase activities observed in diabetic animals. All such quantified biochemical and other pathologies observed in diabetic were significantly antagonized even by 50 mg/kg daily oral doses of AP, and its efficacies always increased with its increasing daily doses. These observations strongly suggest that AP could be an herbal alternative for treatments of diabesity-associated depression resistant to imipramine like antidepressants, and that antidepressants like efficacy of the extract is most probably due to its inhibitory effects on brain mitochondrial monoamine oxidase activities. The observed beneficial of AP on brain oxidative status could be indicative of its neuro-protective potentials as well. In any case its minimal effective doses for all such efficacies should be below or around 50 mg/kg/day.