Interaction between rasagiline and Pueraria radix in in vitro models of parkinson’s disease

Caffeine and more specific antagonists of the adenosine A(2A) receptor recently have been found to be neuroprotective in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) model of Parkinson's disease. Here we show that 8-(3-chlorostyryl)caffeine (CSC), a specific A(2A) antagonist closely related to caffeine, also attenuates MPTP-induced neurotoxicity. Because the neurotoxicity of MPTP relies on its oxidative metabolism to the mitochondrial toxin MPP(+), we investigated the actions of CSC on striatal MPTP metabolism in vivo. CSC elevated striatal levels of MPTP but lowered levels of the oxidative intermediate MPDP(+) and of MPP(+), suggesting that CSC blocks the conversion of MPTP to MPDP(+) in vivo. In assessing the direct effects of CSC and A(2A) receptors on monoamine oxidase (MAO) activity, we found that CSC potently and specifically inhibited mouse brain mitochondrial MAO-B activity in vitro with a K(i) value of 100 nm, whereas caffeine and another relatively specific A(2A) antagonist produced little or no inhibition. The A(2A) receptor independence of MAO-B inhibition by CSC was further supported by the similarity of brain MAO activities derived from A(2A) receptor knockout and wild-type mice and was confirmed by demonstrating potent inhibition of A(2A) receptor knockout-derived MAO-B by CSC. Together, these data indicate that CSC possesses dual actions of MAO-B inhibition and A(2A) receptor antagonism, a unique combination suggesting a new class of compounds with the potential for enhanced neuroprotective properties.

Rasagiline is a monoamine oxidase B inhibitor with established disease-modifying effects in Parkinson disease. Preclinical models of amyotrophic

Monoamine oxidase B (MAO-B) is responsible for dopamine metabolism and plays a key role in oxidative stress by changing the redox state of neuronal and glial cells. To date, no disease-modifying therapy for Parkinson’s disease (PD) has been identified. However, MAO-B inhibitors have emerged as a viable therapeutic strategy for PD patients. Herein, a novel series of indole-based small molecules was synthesized as new MAO-B inhibitors with the potential to counteract the induced oxidative stress in PC12 cells. At a single dose concentration of 10 µM, 10 compounds out of 30 were able to inhibit MAO-B with more than 50%. Among them, compounds 7b, 8a, 8b, and 8e showed 84.1, 99.3, 99.4, and 89.6% inhibition over MAO-B and IC50 values of 0.33, 0.02, 0.03, and 0.45 µM, respectively. When compared to the modest selectivity index of rasagiline (II, a well-known MAO-B inhibitor, SI > 50), compounds 7b, 8a, 8b and 8e showed remarkable selectivity indices (SI > 305, 3649, 3278, and 220, respectively). A further kinetic study displayed a competitive mode of action for 8a and 8b over MAO-B with Ki values of 10.34 and 6.63 nM. Molecular docking studies of the enzyme-inhibitor binding complexes in MAO-B revealed that free NH and substituted indole derivatives share a common favorable binding mode: H-bonding with a crucial water “anchor” and Tyr326. Whereas in MAO-A the compounds failed to form favorable interactions, which explained their high selectivity. In addition, compounds 7b, 8a, 8b, and 8e exhibited safe neurotoxicity profiles in PC12 cells and partially reversed 6-hydroxydopamine- and rotenone-induced cell death. Accordingly, we report compounds 7b, 8a, 8b, and 8e as novel promising leads that could be further exploited for their multi-targeted role in the development of a new oxidative stress-related PD therapy.

Parkinson's disease (PD) is a neurodegenerative disorder with a prevalence increasing with age. Oxidative stress and glutamate toxicity are involved in its pathomechanism. There are still many unmet needs of PD patients, including the alleviation of motor fluctuations and dyskinesias, and the development of therapies with neuroprotective potential. To give an overview of the pharmacological properties, the efficacy and safety of the monoamine oxidase B (MAO-B) inhibitors in the treatment of PD, with special focus on the results of randomized clinical trials. A literature search was conducted in PubMed for 'PD treatment', 'MAO-B inhibitors', 'selegiline', 'rasagiline', 'safinamide' and 'clinical trials' with 'MAO-B inhibitors' in 'Parkinson' disease'. MAO-B inhibitors have a favorable pharmacokinetic profile, improve the dopamine deficient state and may have neuroprotective properties. Safinamide exhibits an anti-glutamatergic effect as well. When applied as monotherapy, MAO-B inhibitors provide a modest, but significant improvement of motor function and delay the need for levodopa. Rasagiline and safinamide were proven safe and effective when added to a dopamine agonist in early PD. As add-on to levodopa, MAO-B inhibitors significantly reduced off-time and were comparable in efficacy to COMT inhibitors. Improvements were achieved as regards certain non-motor symptoms as well. Due to the efficacy shown in clinical trials and their favorable side-effect profile, MAO-B inhibitors are valuable drugs in the treatment of PD. They are recommended as monotherapy in the early stages of the disease and as add-on therapy to levodopa in advanced PD.

Monoamine oxidase (EC, 1.4.3.4) or amine oxidoreductase catalyzes the oxidative deamination of biogenic amines. Abnormal action of the monoamine oxidase B has been associated with neurological dysfunctions including parkinson´s disorder. Monoamine oxidase B inhibitors divulged that these agents were effective in the therapeutic management of Parkinson's disease. Understanding the interaction of monoamine oxidase binding site with inhibitors is crucial for the development of pharmaceutical agents. At the molecular docking, the exact prediction of the binding modes between the inhibitors and protein is of central importance in structure-based drug design. In the current study, we examined two classes of monoamine oxidase B inhibitors. We applied Autodock tools 4.2, in order to set up the docking runs and predict the inhibitors binding free energy. The final product of molecular docking was clustered to specify the binding free energy and optimal docking energy conformation that is investigated as the best docked structure. Docking results indicate that the contribution of van der Waals interactions is greater than electrostatic interactions so that, it can be concluded that all of the inhibitors attached to a hydrophobic binding site in monoamine oxidase B. Among the total of molecules tested, it was proved that 2-(2-cycloheptylidenehydrazinyl)-4-(2,4-dichlorophenyl)-1,3-thiazole has the lowest binding free energy and the lowest Van der Waals energy and also the lowest inhibition constant and subsequently the most experimental affinity. As well as, we find out a possible relationship between the estimated results and experimental data. The selective information from this work is crucial for the rational drug design of more potent and selective monoamine oxidase B inhibitors based on the 8-benzyloxycaffeine scaffold.

Monoamine oxidase B (MAO-B) metabolizes dopamine and plays an important role in oxidative stress by altering the redox state of neuronal and glial cells. MAO-B inhibitors are a promising therapeutical approach for Parkinson’s disease (PD). Herein, 24 melatonin analogues (3a–x) were synthesized as novel MAO-B inhibitors with the potential to counteract oxidative stress in neuronal PC12 cells. Structure elucidation, characterization, and purity of the synthesized compounds were performed using 1H-NMR, 13C-NMR, HRMS, and HPLC. At 10 µM, 12 compounds showed >50% MAO-B inhibition. Among them, compounds 3n, 3r, and 3u–w showed >70% inhibition of MAO-B and IC50 values of 1.41, 0.91, 1.20, 0.66, and 2.41 µM, respectively. When compared with the modest selectivity index of rasagiline (II, a well-known MAO-B inhibitor, SI > 50), compounds 3n, 3r, 3u, and 3v demonstrated better selectivity indices (SI > 71, 109, 83, and 151, respectively). Furthermore, compounds 3n and 3r exhibited safe neurotoxicity profiles in PC12 cells and reversed 6-OHDA- and rotenone-induced neuronal oxidative stress. Both compounds significantly up-regulated the expression of the anti-oxidant enzyme, heme oxygenase (HO)-1. Treatment with Zn(II)-protoporphyrin IX (ZnPP), a selective HO-1 inhibitor, abolished the neuroprotective effects of the tested compounds, suggesting a critical role of HO-1 up-regulation. Both compounds increased the nuclear translocation of Nrf2, which is a key regulator of the antioxidative response. Taken together, these data show that compounds 3n and 3r could be further exploited for their multi-targeted role in oxidative stress-related PD therapy.

Effects of MAO‑B inhibitors in life quality of Parkinson's disease patients: A systematic review and meta‑analysis.

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by both non-motor and motor symptoms, due to the loss of dopamine-producing neurons in the brain. Monoamine oxidase-B (MAO-B) inhibitors are essential in the treatment of PD, as they increase dopamine levels and could potentially slow down the progression of the disease. MAO-B inhibitors block the ability of the enzyme to degrade dopamine in the brain. MAO-B inhibitors work by inhibiting this enzyme, which raises dopamine levels and helps reduce motor symptoms, such as akinesia and stiffness in the muscles. In addition to their impact on dopamine levels, MAO-B inhibitors may possess neuroprotective properties. Research indicates that these inhibitors can shield neurons from the harmful byproducts of dopamine breakdown, such as dihydroxy acetaldehyde and hydrogen peroxide. This neuroprotective effect could potentially slow the progression of PD and protect against neuronal damage. MAO-B inhibitors are effective in treating both advanced and early stages of PD. They are recommended as initial treatments for individuals with early PD and can also be used as supplementary therapy in advanced PD to assist in managing motor complications. Additionally, MAO-B inhibitors have shown promise for the treatment of non-motor symptoms of PD, such as fatigue and sleep disturbances. MAO-B inhibitors are an important class of drugs for the treatment of PD, offering both symptomatic relief and potential disease-modifying effects. The goal of ongoing research and development of MAO-B inhibitors is to enhance their safety and selectivity profiles, which could lead to improved treatment approaches for PD and other neurodegenerative disorders.

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

Parkinson's disease is a disorder characterized pathologically by progressive neurodegeneration of the dopaminergic cells of the nigrostriatal pathway. Although the resulting dopamine deficiency is the cause of the typical motor features of Parkinson's disease (bradykinesia, rigidity, tremor), additional non-motor symptoms appear at various timepoints and are the result of non-dopamine nerve degeneration. Monoamine oxidase B (MAO-B) inhibitors are used in the symptomatic treatment of Parkinson's disease as they increase synaptic dopamine by blocking its degradation. Two MAO-B inhibitors, selegiline and rasagiline, are currently licensed in Europe and North America for the symptomatic improvement of early Parkinson's disease and to reduce off-time in patients with more advanced Parkinson's disease and motor fluctuations related to levodopa. A third MAO-B inhibitor (safinamide), which also combines additional non-dopaminergic properties of potential benefit to Parkinson's disease, is currently under development in phase III clinical trials as adjuvant therapy to either a dopamine agonist or levodopa. MAO-B inhibitors have also been studied extensively for possible neuroprotective or disease-modifying actions. There is considerable laboratory evidence that MAO-B inhibitors do exert some neuroprotective properties, at least in the Parkinson's disease models currently available. However, these models have significant limitations and caution is required in assuming that such results may easily be extrapolated to clinical trials. Rasagiline 1 mg/day has been shown to provide improved motor control in terms of Unified Parkinson's Disease Rating Scale (UPDRS) score at 18 months in those patients with early disease who began the drug 9 months before a second group. There are a number of possible explanations for this effect that may include a disease-modifying action; however, the US FDA recently declined an application for the licence of rasagiline to be extended to cover disease modification.

It has been postulated that monoamine oxidase B (MAO-B) inhibitors alter disease progression in Parkinson's disease (PD). Clinical trials have produced conflicting results. To assess the evidence from randomized controlled trials for the effectiveness and safety of long-term use of MAO-B inhibitors in early PD. We searched the following electronic databases: Cochrane Central Register of Controlled trials (CENTRAL) (The Cochrane Library Issue 2, 2004), MEDLINE (last searched 18th August 2004) and EMBASE (last searched 18th August 2004). We also handsearched neurology and movement disorders conference proceedings, checked reference lists of relevant studies and contacted other researchers. We sought to include all unconfounded randomized controlled trials that compared a MAO-B inhibitor with control, in the presence or absence of levodopa or dopamine agonists, in patients with early PD and where treatment and follow up lasted at least one year. Two reviewers independently selected trials for inclusion, assessed the methodological quality, and extracted the data. A small amount of additional data was provided by the original authors. Random-effects models were used to analyse results, where appropriate. Ten trials were included (a total of 2422 patients), nine using selegiline, one using lazabemide. The methodological quality was reasonable although concealment of allocation was definitely adequate in only four trials. The mean follow up was for 5.8 years. MAO-B inhibitors were not associated with a significant increase in deaths (odds ratio (OR) 1.15; 95% confidence interval (CI) 0.92 to 1.44). They provided small benefits over control in impairment (weighted mean difference (WMD) for change in motor UPDRS score was 3.81 points less with MAO-B inhibitors; 95% CI 2.27 to 5.36) and disability (WMD for change in UPDRS ADL score was 1.50 less; 95% CI 0.48 to 2.53) at one year which, although statistically significant, were not clinically significant. There was a marked levodopa-sparing effect with MAO-B inhibitors which was associated with a significant reduction in motor fluctuations (OR 0.75; 95% CI 0.59 to 0.94) but not dyskinesia (OR 0.97; 95% CI 0.76 to 1.25). The reduction in motor fluctuations was, however, not robust in sensitivity analyses. Although adverse events were generally mild and infrequent, withdrawals due to side-effects were higher (OR 2.36; 95% CI 1.32 to 4.20) with MAO-B inhibitors. MAO-B inhibitors do not appear to delay disease progression but may have a beneficial effect on motor fluctuations. There was no statistically significant effect on deaths although the confidence interval does not exclude a small increase with MAO-B inhibitors. At present we do not feel these drugs can be recommended for routine use in the treatment of early Parkinson's disease but further randomized controlled trials should be carried out to clarify, in particular, their effect on deaths and motor complications.

As a famous traditional Chinese medicine, roots of Platycodon grandiflorus (Jacq.) A.DC. have shown multiple effects against neurodegenerative diseases. To investigate the components against Parkinson's disease (PD), the roots of P. grandiflora were selected as the research subject. Screening and identifying of monoamine oxidase B (MAO-B) inhibitors from the roots of P. grandiflorum via enzyme functionalised magnetic nanoparticles (MNPs)-based ligand fishing combined with high-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis. MAO-B functionalised MNPs have been synthesised for screening MAO-B inhibitors from the roots of P. grandiflorum. The ligands were identified by HPLC-MS and nuclear magnetic resonance (NMR) analysis, and their anti-PD activity was evaluated via MAO-B inhibition assay and cell viability assay in vitro. Two MAO-B inhibitors were fished out and identified by HPLC-MS as protocatechuic aldehyde (1) and coumarin (2), with the half maximal inhibitory concentrations of 28.54 ± 0.39 and 25.39 ± 0.29 μM, respectively. Among them, 1 could also significantly increase the viability of 6-hydroxydopamine-damaged PC12 cells. The results are helpful to elucidate the anti-PD activity of the plant, and the ligand fishing method has shown good potential in discovery of MAO-B inhibitors.

Parkinson's disease is a neurodegenerative condition characterized by slow movement (bradykinesia), tremors, and muscle stiffness. These symptoms occur due to the degeneration of dopamine- producing neurons in the substantia nigra region of the brain, leading to reduced dopamine levels. The development of Parkinson's Disease (PD) involves a combination of genetic and environmental factors. PD is associated with abnormal regulation of the monoamine oxidase (MAO) enzyme. Monoamine oxidase inhibitors (MAOIs) are an important class of drugs used to treat PD and other neurological disorders. In the early stages of PD, monotherapy with MAO-B inhibitors has been shown to be both safe and effective. These inhibitors are also commonly used as adjuncts in long-term disease management, as they can improve both motor and non-motor symptoms, reduce "OFF" periods, and potentially slow disease progression. However, current MAO-B inhibitors come with side effects like dizziness, nausea, vomiting, light-headedness, and fainting. Therefore, accelerating the development of new MAO-B inhibitors with fewer side effects is crucial. This review explores natural compounds that may inhibit monoamine oxidase B (MAO-B), focusing on key findings from the past seven years. It highlights the most effective heterocyclic compounds against MAO-B, including thiazolyl hydrazone, pyridoxine-resveratrol, pyridazine, isoxazole, oxadiazole, benzothiazole, benzoxazole, coumarin, caffeine, pyrazoline, piperazine, piperidine, pyrrolidine, and morpholine derivatives. The review covers in vitro, in silico, and in vivo data, along with the structure- activity relationship of these compounds. These findings offer valuable insights for the development of more effective MAO-B inhibitors and advancements in Parkinson's disease research.

Sleep disturbances are common and debilitating non-motor symptoms (NMS) in Parkinson's disease (PD), profoundly affecting quality of life. Despite emerging evidence suggesting that monoamine oxidase B (MAO-B) and catechol-O-methyltransferase (COMT) inhibitors may alleviate NMS, their specific effects on sleep remain unclear. This network meta-analysis (NMA) aimed to compare the efficacy of these inhibitors on sleep problems in PD. Following a systematic search of PubMed, Cochrane, and EMBASE, studies comparing MAO-B or COMT inhibitors and assessing sleep outcomes in PD were identified. An NMA was conducted using data from the seven studies that met our inclusion criteria. Outcomes included subjective sleep quality, daytime sleepiness, and objective polysomnography (PSG) parameters. No statistically significant differences were found among MAO-B and COMT inhibitors in improving subjective sleep quality or daytime sleepiness. However, in analyses of objective PSG data, safinamide was found to significantly increase REM sleep duration (mean difference, 5.70 [95% CI, 2.26, 9.14]) and decrease wake time after sleep onset (mean difference, -10.20 [-19.38, -1.02]) compared to rasagiline and placebo. These findings suggest that safinamide may offer additional value for managing sleep disruptions beyond its known motor benefits in patients with PD. Given the limited number and small scale of available trials, the overall evidence should be interpreted cautiously. Nonetheless, this analysis highlights the need for further high-quality trials focused on sleep outcomes to guide personalized use of MAO-B and COMT inhibitors for sleep disturbances in PD.

Monoamine oxidase B (MAO-B) inhibitors are used to treat the motor symptoms of Parkinson disease. Depression is commonly associated with Parkinson disease, and selective serotonin reuptake inhibitors (SSRIs) are often used for its management. Tertiary sources warn that the combination of MAO-B inhibitors and SSRIs can result in increased serotonergic effects, leading to serotonin syndrome. To explore the mechanism, clinical significance, and management of this potential drug interaction through a review of the supporting evidence. PubMed, MEDLINE (1946 forward), Embase (1947 forward), PsycINFO (1806 forward), and International Pharmaceutical Abstracts (1970 forward) were searched on February 4, 2017. Studies and case reports describing aspects of the potential interaction between MAO-B inhibitors and SSRIs in patients with Parkinson disease and published in English were identified by both title and abstract. The search identified 8 studies evaluating the potential interaction between SSRIs and the MAO-B inhibitors selegiline and rasagiline. The largest, a retrospective cohort study of 1504 patients with Parkinson disease, found no cases of serotonin syndrome with coadministration of rasagiline and an SSRI. A survey of 63 investigators in the Parkinson Study Group identified 11 potential cases of serotonin syndrome among 4568 patients treated with the combination of selegiline and antidepressants (including SSRIs). In addition, 17 case reports describing the onset of serotonin syndrome with coadministration of an SSRI and either selegiline or rasagiline were identified. Following discontinuation or dose reduction of one or both of the agents, the symptoms of serotonin syndrome gradually resolved in most cases, with none being fatal. According to the literature, serotonin syndrome occurs rarely, and the combination of SSRI and MAO-B inhibitor is well tolerated. Therefore, SSRIs and MAO-B inhibitors can be coadministered, provided that their recommended doses are not exceeded and the SSRI dose is kept at the lower end of the therapeutic range. Among the SSRIs, citalopram and sertraline may be preferred.