Aminoindan and hydroxyaminoindan, metabolites of rasagiline and ladostigil, respectively, exert neuroprotective properties in vitro

P2B001 (Extended Release Pramipexole and Rasagiline): A New Treatment Option in Development for Parkinson's Disease

Despite levodopa’s superior efficacy in reducing the motor symptoms of Parkinson’s disease (PD), its risk to induce motor complications requires consideration of the pros and cons of initiating treatment with levodopa-sparing strategies. The current drive toward early levodopa monotherapy is primarily driven by safety and tolerability concerns with dopamine agonists and only mild efficacy of other available approaches. Recently, P2B001, a novel once-daily combination of low-dose, extended-release formulations of pramipexole and rasagiline (0.6 mg and 0.75 mg respectively), has entered clinical development. In this drug evaluation, we review the preclinical and current clinical data for P2B001 and its components. The P2B001 combination has the potential to provide greater efficacy than either pramipexole or rasagiline alone and a better tolerability profile compared to higher dosage dopamine agonist monotherapy, while maintaining the advantage of lower motor complication risk than levodopa.

Parkinson’s disease is the fastest growing neurologic disorder across the globe. Once diagnosed, it is now generally agreed that there is no clinical rationale to postpone symptomatic treatment in people who develop Parkinson’s-related disability. There are three main treatment options available for use in early Parkinson’s disease: levodopa, dopamine agonists and monoamine oxidase type B (MAO-B) inhibitors. Of these, there is a current push toward using levodopa as the main first-line therapy. This is primarily because of the significant safety and tolerability concerns with dopamine agonists and only mild efficacy of MAO-B inhibitors. Recently, P2B001, a novel drug formulation combining once-daily, extended-release, low dosages of the dopamine agonist pramipexole and the MAO-B inhibitor rasagiline (0.6 mg and 0.75 mg respectively), has entered clinical development. In this article, the authors review the preclinical and current clinical data on P2B001 and its components. The P2B001 combination has the potential to provide greater efficacy than either pramipexole or rasagiline alone and a better tolerability profile compared to higher dosage dopamine agonist monotherapy, while maintaining the advantage of lower motor complication risk than levodopa.

Preventative effects of 1-methyl-1,2,3,4-tetrahydroisoquinoline derivatives (N-functional group loading) on MPTP-induced parkinsonism in mice

1,2,3,4-Tetrahydroisoquinoline (TIQ) is endogenously present in human brain, and some of its derivatives are thought to contribute to the induction of Parkinson's disease (PD)-like signs in rodents and primates. In contrast, the endogenous TIQ derivative 1-methyl-TIQ (1-MeTIQ) is reported to be neuroprotective. In the present study, we compared the effects of artificially modified 1-MeTIQ derivatives (loading an N-propyl, N-propenyl, N-propargyl, or N-butynyl group) on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD-like signs in mice. In a behavioral study, MPTP-induced bradykinesia was significantly decreased by all compounds. However, only 1-Me-N-propargyl-TIQ showed an inhibitory effect by blocking the MPTP-induced reduction in striatal dopamine content and the number of nigral tyrosine hydroxylase-positive cells. Western blot analysis showed that 1-Me-N-propargyl-TIQ and 1-Me-N-butynyl-TIQ potently prevented the MPTP-induced decrease in dopamine transporter expression, whereas 1-MeTIQ and 1-Me-N-propyl-TIQ did not. These results suggest that although loading an N-propargyl group on 1-MeTIQ clearly enhanced neuroprotective effects, other N-functional groups showed distinct pharmacological properties characteristic of their functional groups. Thus, the number of bonds and length of the N-functional group may contribute to the observed differences in effect.

N-Propargylamine-hydroxypyridinone hybrids as multitarget agents for the treatment of Alzheimer's disease

AD is a progressive brain disorder. Because of the lack of remarkable single-target drugs against neurodegenerative disorders, the multitarget-directed ligand strategy has received attention as a promising therapeutic approach. Herein, we rationally designed twenty-nine hybrids of N-propargylamine-hydroxypyridinone. The designed hybrids possessed excellent iron-chelating activity (pFe³⁺ = 17.09-22.02) and potent monoamine oxidase B inhibitory effects. Various biological evaluations of the optimal compound 6b were performed step by step, including inhibition screening of monoamine oxidase (hMAO-B IC₅₀ = 0.083 ± 0.001 µM, hMAO-A IC₅₀ = 6.11 ± 0.08 µM; SI = 73.5), prediction of blood-brain barrier permeability and mouse behavioral research. All of these favorable results proved that the N-propargylamine-hydroxypyridinone scaffold is a promising structure for the discovery of multitargeted ligands for AD therapy.

D. dos Santos AC, García-Mera X, Rodríguez-Borges JE, Sampaio-Dias IE. Bioinspired design for the assembly of Glypromate® neuropeptide conjugates with active pharmaceutical ingredients

A robust and bioinspired methodology for the efficient conjugation of Glypromate® with active pharmaceutical ingredients for neurodegenerative diseases.

A phenolic amide (LyA) isolated from the fruits of Lycium barbarum protects against cerebral ischemia-reperfusion injury via PKCε/Nrf2/HO-1 pathway

Lyciumamide A (LyA), a dimer of phenolic amide isolated from the fruits of Lycium barbarum, has been confirmed to possess potent antioxidant activity. This study was aimed to investigate the neuroprotection and molecular mechanisms of LyA against cerebral ischemia/reperfusion (I/R) injury via improving antioxidant activity. The model of middle cerebral artery occlusion (MCAO) and SH-SY5Y cells induced by oxygen and glucose deprivation (OGD) were adopted to verify the neuroprotective effects and the potential pharmacology mechanisms of LyA in vivo and in vitro. In MCAO model, treatment with LyA significantly improved neurologic score, reduced infarct volume, and relieved oxidative stress injury at 48 h after reperfusion. Meanwhile, LyA markedly increased the transcription Nrf2 and HO-1 expressions in the ischemic cerebral cortex. In vitro results showed that LyA protected differentiated SH-SY5Y cells against OGD-induced injury. LyA significantly decreased the expression of caspase-3 and the Bax/Bcl-2 ratio. But knockdown of Nrf2 or HO-1 attenuated the protective effect of LyA. Similarly, knockdown of protein kinase Cε (PKCε) inhibited LyA-induced Nrf2/HO-1 activation, and abated its protective effects. In conclusion, this study firstly demonstrated that LyA protects against cerebral I/R injury, ameliorates oxidative damage and neuronal apoptosis, partly via activation of PKCε/Nrf2/HO-1 pathway.

Propargylamine-derived multi-target directed ligands for Alzheimer's disease therapy

Current options for the treatment of Alzheimeŕs disease have been restricted to prescription of acetylcholinesterase inhibitors or N-methyl-d-aspartate receptor antagonist, memantine. Propargylamine-derived multi-target directed ligands, such as ladostigil, M30, ASS234 and contilisant, involve different pathways. Apart from acting as inhibitors of both cholinesterases and monoamine oxidases, they show improvement of cognitive impairment, antioxidant activities, enhancement of iron-chelating activities, protect against tau hyperphosphorylation, block metal-associated oxidative stress, regulate APP and Aβ expression processing by the non-amyloidogenic α-secretase pathway, suppress mitochondrial permeability transition pore opening, and coordinate protein kinase C signaling and Bcl-2 family proteins. Other hybrid propargylamine derivatives are also reported.

Dipropargyl substituted diphenylpyrimidines as dual inhibitors of monoamine oxidase and acetylcholinesterase

Alzheimer's disease (AD) is a multifactorial neurological disorder involving complex pathogenesis. Single target directed drugs proved ineffective and since last few years' different pharmacological strategies including multi-targeting agents are being explored for the effective drug development for AD. A total of 19 dipropargyl substituted diphenylpyrimidines have been synthesized and evaluated for the monoamine oxidase (MAO) and acetylcholinesterase (AChE) inhibition potential. All the compounds were found to be selective and reversible inhibitors of MAO-B isoform. These compounds also displayed good AChE inhibition potential with IC₅₀ values in low micromolar range. AVB4 was found to be the most potent MAO-B inhibitor with IC₅₀ value of 1.49 ± 0.09 μM and AVB1 was found to be the most potent AChE inhibitor with IC₅₀ value of 1.35 ± 0.03 μM. In the ROS protection inhibition studies, AVB1 and AVB4 displayed weak but interesting activity in SH-SY5Y cells. In the cytotoxicity studies involving SH-SY5Y cells, both AVB1 and AVB4 were found to be non-toxic to the tissue cells. In the molecular dynamic simulation studies of 30 ns, the potent compounds were found to be quite stable in the active site of MAO-B and AChE. The results suggested that AVB1 and AVB4 are promising dual inhibitors and have the potential to be developed as anti-Alzheimer's drug.

Aldehyde adducts inhibit 3,4-dihydroxyphenylacetaldehyde-induced α-synuclein aggregation and toxicity: Implication for Parkinson neuroprotective therapy

3,4-Dihydroxyphenylacetaldehyde (DOPAL), the monoamine oxidase (MAO) metabolite of dopamine, plays a role in pathogenesis of Parkinson disease, inducing α-synuclein aggregation. DOPAL generates discrete α-synuclein aggregates. Inhibiting this aggregation could provide therapy for slowing Parkinson disease progression. Primary and secondary amines form adducts with aldehydes. Rasagiline and aminoindan contain these amine groups. DOPAL-induced α-synuclein aggregates were resolved in the presence and absence of rasagiline or aminoindan using quantitative Western blotting. DOPAL levels in incubation mixtures, containing increased rasagiline or aminoindan concentrations, were determined by high pressure liquid chromatography (HPLC). Schiff base adducts between DOPAL and rasagiline or aminoindan were determined using mass spectrometry. A neuroprotective effect of rasagiline and aminoindan against DOPAL-induced toxicity was demonstrated using PC-12 cells. Rasagiline and aminoindan significantly reduced aggregation of α-synuclein of all sizes in test tube and PC-12 cells experiments. Dimethylaminoindan did not reduce aggregation. DOPAL levels in incubation mixtures were reduced with increasing rasagiline or aminoindan concentrations but not with dimethylaminoindan. Schiff base adducts between DOPAL and either rasagiline or aminoindan were demonstrated by mass spectrometry. A neuroprotective effect against DOPAL-induced toxicity in PC-12 cells was demonstrated for both rasagiline and aminoindan. Inhibiting DOPAL-induced α-synuclein aggregation through amine adducts provides a therapeutic approach for slowing Parkinson disease progression.

Novel Neuroprotective Lead Compound Ligustrazine Derivative Mass Spectrometry Fragmentation Rule and Metabolites in Rats by LC/LTQ-Orbitrap MS

The neuroprotective evaluation of ligustrazine derivatives has become a research focus all over the world. A novel ligustrazine derivative, (3,5,6-Trimethylpyrazin-2-yl)methyl(E)-3-(4-((3,5,6-trimethylpyrazin-2-l)methoxy)phenyl)acrylate (T-CA), has shown protective effects against CoCl₂-induced neurotoxicity in a differentiated PC12 cell model and middle cerebral artery occlusion (MCAO) model in our previous studies. However, nearly none of the parent drugs existed after rapid metabolism due to uncertain reasons. Thus, the fragmentation regularities of mass spectra, and metabolites, of T-CA in rats were examined using liquid chromatography-electrospray ionizationion trap mass spectrometry (LC/LTQ-Orbitrap MS) in this research. The main fragment ion, mass spectrum characteristics, and the structural information were elucidated. When compared with a blank sample, we identified five kinds of T-CA metabolites, including three phase I metabolites and two phase II metabolites. The results showed that the metabolic pathways of T-CA in rats via oral administration were hydrolysis (ether bond rupture, ester bond rupture), oxidation, reduction, glucose aldehyde acidification, etc. In addition, three main metabolites were synthesized and their structures were identified by superconducting high-resolution NMR and high-resolution mass spectroscopy (HR-MS). The neuroprotective activity of these metabolites was validated in a PC12 cell model. One of the metabolites (M2) showed significant activity (EC₅₀ = 9.67 μM), which was comparable to the prototype drug T-CA (EC₅₀ = 7.97 μM). The current study provides important information for ligustrazine derivatives, pertaining to the biological conversion process in vivo.

Neuroprotective Effects of Loganin on MPTP-Induced Parkinson's Disease Mice: Neurochemistry, Glial Reaction and Autophagy Studies

Parkinson's disease (PD) is a progressive neurodegenerative disease, involving resting tremor and bradykinesia, for which no recognized therapies or drugs are available to halt or slow progression. In recent years, natural botanic products have been considered relatively safe, with limited side effects, and are expected to become an important source for clinical mediation of PD in the future. Our study focuses on the ability of loganin, a compound derived from fruits of cornus, to mediate neuroprotection in a mouse model of PD. Mice were administered 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) with a dosage of 30 mg/kg daily for 5 days to establish a subacute PD model and treated with loganin. Locomotor activity was assessed by a pole test, then mice were euthanized at 1 and 3 days after the last treatment, and brain tissue was prepared for subsequent assays. Loganin rescued decrease of dopamine levels and tyrosine hydroxylase (TH) expression in the striatum, and shortened total locomotor activity (TLA) time of mice. Furthermore, loganin alleviated microglia and astrocyte activation, and suppressed TNF-α and caspase-3 expression through a c-Abl-p38-NFκB pathway. Loganin also downregulated LC3-II and Drp1 expression, and decreased the level of acidic vesicular organelles (AVOs). Loganin exerts neuroprotective effects on MPTP-induced PD mice by decreasing inflammation, autophagy, and apoptosis, suggesting that loganin could serve as a therapeutic drug to ameliorate PD. J. Cell. Biochem. 118: 3495-3510, 2017. © 2017 Wiley Periodicals, Inc.

Indole-Substituted Benzothiazoles and Benzoxazoles as Selective and Reversible MAO-B Inhibitors for Treatment of Parkinson's Disease

To develop novel, selective, and reversible MAO-B inhibitors for safer treatment of Parkinson's disease, benzothiazole and benzoxazole derivatives with indole moiety were designed and synthesized. Most of the synthesized compounds showed inhibitory activities against MAO-B and selectivity over MAO-A. The most active compound was compound 5b, 6-fluoro-2-(1-methyl-1H-indol-5-yl)benzo[d]thiazole with an IC₅₀ value of 28 nM with no apparent effect on MAO-A activity at 10 μM. Based on the reversibility assay, compound 5b turned out to be fully reversible with over 95% of recovery of enzyme activity after washout of the compound. Compound 5b showed a reasonable stability in human liver microsomes and did not affect the activities of CYP isozymes, suggesting an absence of high-risk drug-drug interaction. In an in vivo MPTP-induced animal model of Parkinson's disease, oral administration of compound 5b showed neuroprotection of nigrostriatal dopaminergic neurons as revealed by tyrosine hydroxylase staining and prevention of MPTP-induced parkinsonism as revealed by motor behavioral assay of vertical grid test. In summary, the novel, reversible, and selective MAO-B inhibitor compound 5b was synthesized and characterized. We propose compound 5b as an effective therapeutic compound for relieving parkinsonism.

Use of monoamine oxidase inhibitors in chronic neurodegeneration

INTRODUCTION

Neurotransmission by biogenic monoamines is important for brain function. Biogenic amine turnover employs the enzymes catechol-O-methyltransferase and monoamine oxidase in neuronal and glial cells. Inhibition of these enzymes elevates biogenic amine levels in the synaptic cleft. Subtype selectivity of inhibition is lost during long-term use of 'selective' monoamine oxidase inhibitors. Areas covered: This narrative review discusses use of monoamine oxidase inhibitors in the context with chronic neurodegeneration. Expert opinion: Antidepressant drugs increase synaptic concentrations of biogenic amines. In the aging brain, then one of the two enzymes involved in degrading synaptic amines, catechol-O-methyl transferase, increasingly catalyzes methylation processes. Therefore, metabolism by monoamine oxidase plays an incremental, predominant role in biogenic amine turnover, leading to greater oxidative stress. In patients with chronic neurodegenerative disorders, symptoms, such as depression and apathy, are often treated with drugs that elevate biogenic amine levels. This therapeutic strategy increases biogenic amine turnover, thereby generating neurotoxic aldehydes and enhanced oxidative stress, each of which influence and accelerate the course of neurodegeneration. We propose that antidepressant therapy should be initiated first with monoamine oxidase inhibitors only. If adequate clinical response is not achieved, only then they should be supplemented with a further antidepressant.

Protocatechualdehyde Protects Against Cerebral Ischemia-Reperfusion-Induced Oxidative Injury Via Protein Kinase Cε/Nrf2/HO-1 Pathway

Oxidative stress is closely related to the pathogenesis of ischemic stroke. Protocatechualdehyde (PCA) is a phenolic acid compound that has the putative antioxidant activities. The present study was aimed to investigate the molecular mechanisms involved in the antioxidative effect of PCA against cerebral ischemia/reperfusion (I/R) injury. The experiment stroke model was produced in Sprague-Dawley rats via middle cerebral artery occlusion (MCAO). To model ischemia-like conditions in vitro, differentiated SH-SY5Y cells were exposed to transient oxygen and glucose deprivation (OGD). Treatment with PCA significantly improved neurologic score, reduced infarct volume and necrotic neurons, and also decreased reactive oxygen species (ROS) production, 4-hydroxynonenal (4-HNE), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) contents at 24 h after reperfusion. Meanwhile, PCA significantly increased the transcription nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) expressions in the ischemic cerebral cortex as shown by immunofluorescence staining and Western blot analysis. In vitro experiment showed that PCA protected differentiated SH-SY5Y cells against OGD-induced injury. Likewise, PCA also increased markedly the Nrf2 and HO-1 expressions in a dose-dependent manner. The neuroprotection effect of PCA was abolished by knockdown of Nrf2 and HO-1. Moreover, knockdown of protein kinase Cε (PKCε) also blocked PCA-induced Nfr2 nuclear translocation, HO-1 expression, and neuroprotection. Taken together, these results provide evidences that PCA can protect against cerebral ischemia-reperfusion-induced oxidative injury, and the neuroprotective effect involves the PKCε/Nrf2/HO-1 pathway.

BDNF levels are increased by aminoindan and rasagiline in a double lesion model of Parkinson׳s disease

The anti-Parkinsonian drug rasagiline is a selective, irreversible inhibitor of monoamine oxidase and is used in the treatment of Parkinson׳s disease (PD). Its postulated neuroprotective effects may be attributed to MAO inhibition, or to its propargylamine moiety. The major metabolite of rasagiline, aminoindan, has shown promising neuroprotective properties in vitro but there is a paucity of studies investigating in vivo effects of this compound. Therefore, we examined neuroprotective effects of rasagiline and its metabolite aminoindan in a double lesion model of PD. Male Fisher 344 rats received i.p. injections of the noradrenergic neurotoxin DSP-4 and intra-striatal stereotaxic microinjections of the dopamine neurotoxin 6-OHDA. Saline, rasagiline or aminoindan (3mg/kg/day s.c.) were delivered via Alzet minipumps for 4 weeks. Rats were then tested for spontaneous locomotion and a novel object recognition task. Following behavioral testing, brain tissue was processed for ELISA measurements of growth factors and immunohistochemistry. Double-lesioned rats treated with rasagiline or aminoindan had reduced behavioral deficits, both in motor and cognitive tasks compared to saline-treated double-lesioned rats. BDNF levels were significantly increased in the hippocampus and striatum of the rasagiline- and aminoindan-lesioned groups compared to the saline-treated lesioned group. Double-lesioned rats treated with rasagiline or aminoindan exhibited a sparing in the mitochondrial marker Hsp60, suggesting mitochondrial involvement in neuroprotection. Tyrosine hydroxylase (TH) immunohistochemistry revealed a sparing of TH-immunoreactive terminals in double-lesioned rats treated with rasagiline or aminoindan in the striatum, hippocampus, and substantia nigra. These data provide evidence of neuroprotection by aminoindan and rasagiline via their ability to enhance BDNF levels.

Novel (Hetero)arylalkenyl propargylamine compounds are protective in toxin-induced models of Parkinson's disease

BACKGROUND

Mitochondrial dysfunction, oxidative stress and their interplay are core pathological features of Parkinson's disease. In dopaminergic neurons, monoamines and their metabolites provide an additional source of reactive free radicals during their breakdown by monoamine oxidase or auto-oxidation. Moreover, mitochondrial dysfunction and oxidative stress have a supraadditive impact on the pathological, cytoplasmic accumulation of dopamine and its subsequent release. Here we report the effects of a novel series of potent and selective MAO-B inhibitory (hetero)arylalkenylpropargylamine compounds having protective properties against the supraadditive effect of mitochondrial dysfunction and oxidative stress.

RESULTS

The (hetero)arylalkenylpropargylamines were tested in vitro, on acute rat striatal slices, pretreated with the complex I inhibitor rotenone and in vivo, using the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induced acute, subchronic, and chronic experimental models of Parkinson's disease in mice. The compounds exhibited consistent protective effects against i) in vitro oxidative stress induced pathological dopamine release and the formation of toxic dopamine quinone in the rat striatum and rescued tyrosine hydroxylase positive neurons in the substantia nigra after rotenone treatment; ii) in vivo MPTP-induced striatal dopamine depletion and motor dysfunction in mice using acute and subchronic, delayed application protocols. One compound (SZV558) was also examined and proved to be protective in a chronic mouse model of MPTP plus probenecid (MPTPp) administration, which induces a progressive loss of nigrostriatal dopaminergic neurons.

CONCLUSIONS

Simultaneous inhibition of MAO-B and oxidative stress induced pathological dopamine release by the novel propargylamines is protective in animal models and seems a plausible strategy to combat Parkinson's disease.

Recent developments on the structure–activity relationship studies of MAO inhibitors and their role in different neurological disorders

Development of MAO inhibitors as effective drug candidates for the management and/or treatment of different neurological disorders.

Rasagiline prevents neurodegeneration in thiamine deficient rats-a longitudinal MRI study

Neuroprotection is a therapeutic approach for the management of neurodegenerative diseases. Experimental thiamine deficiency (TD) in rats provides a model for selective neurodegeneration accompanied by chronic oxidative deficits. Rats exhibit neurological and cognitive impairments, which can be partially reversed by thiamine administration, enabling the study of mechanisms of neurodegeneration as well as neuroprotection. In this magnetic resonance (MR) study we used various techniques to characterize the neuroprotective effects of rasagiline, a selective MAO-B inhibitor. TD was induced by a thiamine-deficient diet and daily injections of the central thiamine antagonist, pyrithiamine. Daily injections of either saline or rasagiline (3mg/kg) were also administered to untreated-TD rats and rasagiline-treated TD rats respectively. With the appearance of neurological symptoms, all injections were terminated and thiamine was restored. MRI scans were performed before induction of TD (control values), on days 10, 12 (before symptoms appear), 14 (symptomatic stage) and during the recuperation period. Both groups were assessed using in-vivo serial T2-weighted imaging and diffusion tensor imaging (DTI), from which apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps were calculated. A histopathological evaluation was correlated with the MRI analysis. Thalamic hyperintensities were significantly smaller and less severe in the rasagiline-treated TD rats. Enlargement of the lateral ventricles was significantly less pronounced in the rasagiline-treated TD group. FA values of the untreated-TD group decreased significantly in the thalamic on days 12 and 14 and in the corpus callosum on day 14. These results demonstrate significant neuroprotection by rasagiline which could have implications for clinical neurodegenerative disorders.

Revelation in the neuroprotective functions of rasagiline and selegiline: the induction of distinct genes by different mechanisms

In Parkinson's disease, cell death of dopamine neurons in the substantia nigra progresses and neuroprotective therapy is required to halt neuronal loss. In cellular and animal models, selegiline [(-)deprenyl] and rasagiline, inhibitors of type B monoamine oxidase (MAO)-B, protect neuronal cells from programmed cell death. In this paper, the authors review their recent results on the molecular mechanisms by which MAO inhibitors prevent the cell death through the induction of antiapoptotic, prosurvival genes. MAO-A mediates the induction of antiapoptotic bcl-2 and mao-a itself by rasagiline, whereas a different mechanism is associated with selegiline. Rasagiline and selegiline preferentially increase GDNF and BDNF in nonhuman primates and Parkinsonian patients, respectively. Enhanced neurotrophic factors might be applicable to monitor the neurorescuing activity of neuroprotection.

Rasagiline and rapid symptomatic motor effect in Parkinson's disease: review of literature

Rasagiline is a monoamine oxidase type-B inhibitor used as monotherapy or in addition to levodopa in the treatment of Parkinson's disease. Once daily administration of rasagiline makes it easy to use, and allows good compliance by patients and adherence to therapy. Several multicenter studies have noted the effectiveness of rasagiline on both motor and non-motor symptoms, which require a complex pharmacologic approach, such as cognitive disorders. A recent study also reported a rapid action of rasagiline on motor symptoms. Positive findings have been highlighted by an economic model study. This review analyzes the main studies of rasagiline, with particular attention to the effectiveness of the drug on motor symptoms.

An update on amine oxidase inhibitors: multifaceted drugs

Although not used as extensively as other antidepressants for the treatment of depression, the monoamine oxidase (MAO) inhibitors continue to hold a niche in psychiatry and to have a relatively broad spectrum with regard to treatment of psychiatric and neurological disorders. Experimental and clinical research on MAO inhibitors has been expanding in the past few years, primarily because of exciting findings indicating that these drugs have neuroprotective properties (often independently of their ability to inhibit MAO). The non-selective and irreversible MAO inhibitors tranylcypromine (TCP) and phenelzine (PLZ) have demonstrated neuroprotective properties in numerous studies targeting elements of apoptotic cascades and neurogenesis. l-Deprenyl and rasagiline, both selective MAO-B inhibitors, are used in the management of Parkinson's disease, but these drugs may be useful in the treatment of other neurodegenerative disorders given that they demonstrate neuroprotective/neurorescue properties in a wide variety of models in vitro and in vivo. Although the focus of studies on the involvement of MAO inhibitors in neuroprotection has been on MAO-B inhibitors, there is a growing body of evidence demonstrating that MAO-A inhibitors may also have neuroprotective properties. In addition to MAO inhibition, PLZ also inhibits primary amine oxidase (PrAO), an enzyme implicated in the etiology of Alzheimer's disease, diabetes and cardiovascular disease. These multifaceted aspects of amine oxidase inhibitors and some of their metabolites are reviewed herein.

Monoamine oxidase inhibitors and neuroprotection: a review

Monoamine oxidase inhibitors have been available for more than 50 years, initially developed as antidepressants but currently used in a variety of psychiatric and neurological conditions. There has been a recent surge of interest in monoamine oxidase inhibitors because of their reported neuroprotective and/or neurorescue properties. Interestingly, it seems that often these properties are independent of their ability to inhibit monoamine oxidase. This review article presents an overview of the neuroprotective/neurorescue properties of these multifaceted drugs and focuses on phenelzine, (-)-deprenyl, rasagiline, ladostigil, tranylcypromine, moclobemide, and clorgyline and their possible neuroprotective mechanisms.

Multi target neuroprotective and neurorestorative anti-Parkinson and anti-Alzheimer drugs ladostigil and m30 derived from rasagiline

Present anti-PD and -AD drugs have limited symptomatic activity and devoid of neuroprotective and neurorestorative property that is needed for disease modifying action. The complex pathology of PD and AD led us to develop several multi-target neuroprotective and neurorestorative drugs with several CNS targets with the ability for possible disease modifying activity. Employing the pharmacophore of our anti-parkinson drug rasagiline (Azilect, N-propagrgyl-1-R-aminoindan), we have developed a series of novel multi-functional neuroprotective drugs (A) [TV-3326 (N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate)], with both cholinesterase-butyrylesterase and brain selective monoamine-oxidase (MAO) A/B inhibitory activities and (B) the iron chelator-radical scavenging-brain selective monoamine oxidase (MAO) A/B inhibitor and M30 possessing the neuroprotective and neurorescuing propargyl moiety of rasagiline, as potential treatment of AD, DLB and PD with dementia. Another series of multi-target drugs (M30, HLA-20 series) which are brain permeable iron chelators and potent selective brain MAO inhibitors were also developed. These series of drugs have the ability of regulating and processing amyloid precursor protein (APP) since APP and alpha-synuclein are metaloproteins (iron-regulated proteins), with an iron responsive element 5"UTR mRNA similar to transferring and ferritin. Ladostigil inhibits brain acetyl and butyrylcholinesterase in rats after oral doses. After chronic but not acute treatment, it inhibits MAO-A and -B in the brain. Ladostigil acts like an anti-depressant in the forced swim test in rats, indicating a potential for anti-depressant activity. Ladostigil prevents the destruction of nigrostriatal neurons induced by infusion of neurotoxin MPTP in mice. The propargylamine moiety of ladostigil confers neuroprotective activity against cytotoxicity induced by ischemia and peroxynitrite in cultured neuronal cells. The multi-target iron chelator M30 has all the properties of ladostigil and similar neuroprotective activity to ladostigil, but is not a ChE inhibitor. M30 has a neurorestorative activity in post-lesion of nigrostriatal dopamine neurons in MPTP, lacatcystin and 6-hydroxydopamine animal models of PD. The neurorestorative activity is related to the ability of the drug to activate hypoxia inducing factor (HIF) which induces the production of such neurotrophins as brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF) and erythropoietin as well as glia-derived neurotrophic factor (GDNF). The unique multiple actions of ladostigil and M30 make the potentially useful drugs for the treatment of dementia with Parkinsonian-like symptoms and depression.

Disease modification in Parkinson’s disease: are we there yet with currently available therapies?

SUMMARY Management of Parkinson’s disease (PD) is currently based primarily on dopamine-replacement therapy for the alleviation of motor symptoms. Current medical and surgical therapies can provide long-lasting symptomatic benefit, but they do not modify progression of the disease. Research is ongoing to find a therapy that can provide neuroprotection, defined herein as preventing vulnerable neurons from dying. Studies of neuroprotection are limited by a lack of adequate biomarkers of PD progression and by the confounding symptomatic effects of many putative neuroprotective therapies. Studies have shown that levodopa prolongs life, but they have not clearly shown that it modifies disease progression. Trials of dopamine agonists have demonstrated symptomatic effect but no unequivocal neuroprotective benefits. While some studies of monamine oxidase B inhibitors have been promising, they have not conclusively proven disease modification. Exercise provides many benefits to patients with PD, may modify the progression of the disease and should be part of each patient’s treatment plan.

Discovery of Multi-Target Agents for Neurological Diseases via Ligand Design

The incidence of neurological disorders in the developed world is rising in concert with an increase in human life expectancy, due in large part to better nutrition and health care. Even as drug discovery efforts are refocused on these disorders, there has been a dearth in the introduction of new disease-modifying therapies to prevent or delay their onset, or reverse their progression. Mounting evidence points to complex and heterogeneous etiopathologies that underlie these diseases. Therefore, it is unlikely that disorders in this class will be mitigated by any single drug that acts exclusively on a single pathway or target. The rational design of novel drug entities with the ability to simultaneously address multiple drug targets of a complex pathophysiology has recently emerged as a new paradigm in drug discovery. Similarly to the concept of multi-target agents within the psychopharmacology field, ligand design has gained an increasing prominence within the medicinal chemistry community. In this chapter we discuss several examples of select chemical scaffolds (polyamines, alkylxanthines, and propargyl carbamates) wherein these concepts were applied to develop novel drug candidates for Alzheimer's disease and Parkinson's disease.

Explaining ADAGIO: a critical review of the biological basis for the clinical effects of rasagiline

The ADAGIO study demonstrated a symptomatic benefit for rasagiline in early Parkinson's disease (PD) and suggested a disease-modifying effect. Evidence indicates that mitochondrial dysfunction plays a role in the pathogenesis of PD and that this may be the site of effect for rasagiline. In this systematic review, evidence for the role of mitochondria in the pathogenesis of PD are reviewed in light of other proposed mechanisms of neuronal degeneration and the actions of rasagiline and its component parts, namely propargylamine and the metabolite, aminoindan. Evidence for the role of mitochondria in the pathogenesis and treatment of PD are reviewed in light of other proposed mechanisms of neuronal degeneration and clinical actions of rasagiline. Monoamine oxidase B (MAO-B) located in the outer mitochondrial membrane controls dopamine metabolism in early PD, and this is the likely location for the symptomatic action of rasagiline. Accumulating evidence indicates that mitochondrial impairment contributes to dopaminergic neuronal loss in PD, either directly or through other mechanisms such as oxidative stress or protein misfolding. Further rasagiline affects numerous mitochondrial mechanisms that prevent apoptotic cell death including prevention of opening of the mitochondrial transition pore, decreased release of cytochrome C, alterations in pro-antiapoptotic genes and proteins, and the nuclear translocation of glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Thus, the functional neuroprotective actions of rasagiline may not be dependent on MAO-B inhibition, but rather may involve actions of the propargylamine moiety and the aminoindan metabolite. An accumulating body of literature indicates a mitochondrial site of action for rasagiline and highlights the neuroprotective action of the drug, providing strong biological plausibility for disease-modifying effects of the drug such as those observed in ADAGIO.

Effects of rasagiline, its metabolite aminoindan and selegiline on glutamate receptor mediated signalling in the rat hippocampus slice in vitro

BACKGROUND

Rasagiline, a new drug developed to treat Parkinson's disease, is known to inhibit monoamine oxidase B. However, its metabolite R-(-)-aminoindan does not show this kind of activity. The present series of in vitro experiments using the rat hippocampal slice preparation deals with effects of both compounds on the pyramidal cell response after electric stimulation of the Schaffer Collaterals in comparison to selegiline, another MAO B inhibitor.

METHOD

Stimulation of the Schaffer Collaterals by single stimuli (SS) or theta burst stimulation (TBS) resulted in stable responses of pyramidal cells measured as population spike amplitude (about 1 mV under control SS conditions or about 2 mV after TBS).

RESULTS

During the first series, this response was attenuated in the presence of rasagiline and aminoindan-to a lesser degree of selegiline-in a concentration dependent manner (5-50 μM) after single stimuli as well as under TBS. During oxygen/glucose deprivation for 10 min the amplitude of the population spike breaks down by 75%. The presence of rasagiline and aminoindan, but rarely the presence of selegiline, prevented this break down. Following glutamate receptor mediated enhancements of neuronal transmission in a second series of experiments very clear differences could be observed in comparison to the action of selegiline: NMDA receptor, AMPA receptor as well as metabotropic glutamate receptor mediated increases of transmission were concentration dependently (0,3 - 2 μM) antagonized by rasagiline and aminoindan, but not by selegiline. On the opposite, only selegiline attenuated kainate receptor mediated increases of excitability. Thus, both monoamino oxidase (MAO) B inhibitors show attenuation of glutamatergic transmission in the hippocampus but interfere with different receptor mediated excitatory modulations at low concentrations.

CONCLUSIONS

Since aminoindan does not induce MAO B inhibition, these effects must be regarded as being independent from MAO B inhibition. The results provide strong evidence for a neuroprotective activity of rasagiline and aminoindan in concert with an extended clinical indication into the direction of other diseases like Alzheimer's disease or stroke.

Neuroprotective multifunctional iron chelators: from redox-sensitive process to novel therapeutic opportunities

Accumulating evidence suggests that many cytotoxic signals occurring in the neurodegenerative brain can initiate neuronal death processes, including oxidative stress, inflammation, and accumulation of iron at the sites of the neuronal deterioration. Neuroprotection by iron chelators has been widely recognized with respect to their ability to prevent hydroxyl radical formation in the Fenton reaction by sequestering redox-active iron. An additional neuroprotective mechanism of iron chelators is associated with their ability to upregulate or stabilize the transcriptional activator, hypoxia-inducible factor-1alpha (HIF-1alpha). HIF-1alpha stability within the cells is under the control of a class of iron-dependent and oxygen-sensor enzymes, HIF prolyl-4-hydroxylases (PHDs) that target HIF-1alpha for degradation. Thus, an emerging novel target for neuroprotection is associated with the HIF system to promote stabilization of HIF-1alpha and increase transcription of HIF-1-related survival genes, which have been reported to be regulated in patient's brains afflicted with diverse neurodegenerative diseases. In accordance, a new potential therapeutic strategy for neurodegenerative diseases is explored, by which iron chelators would inhibit PHDs, target the HIF-1-signaling pathway and ultimately activate HIF-1-dependent neuroprotective genes. This review discusses two interrelated approaches concerning therapy targets in neurodegeneration, sharing in common the implementation of iron chelation activity: antioxidation and HIF-1-pathway activation.

Rasagiline protects against alpha-synuclein induced sensitivity to oxidative stress in dopaminergic cells

Rasagiline is a propargylamine and irreversible monoamine oxidase (MAO) B inhibitor used for the treatment of Parkinson's disease (PD). It has demonstrated neuroprotective properties in laboratory studies. Current concepts of PD aetiopathogenesis include the role of alpha-synuclein, protein aggregation, free radical metabolism and mitochondrial dysfunction in contributing to cell death. We have used a combination of alpha-synuclein and free radical mediated toxicity in a dopaminergic cell line to provide a model of nigral toxicity in order to investigate the potential molecular mechanisms that mediate rasagiline protection. We demonstrate that rasagiline protects against cell death induced by the combination of free radicals generated by paraquat and either wild-type or A53T mutant alpha-synuclein over-expression. This protection was associated with a reduction in caspase 3 activation, a reduction in superoxide generation and a trend to ameliorate the fall in mitochondrial membrane potential. Rasagiline induced an increase in cellular glutathione levels. The results support a role for rasagiline in protecting dopaminergic cells against free radical mediated damage and apoptosis in the presence of alpha-synuclein over-expression. The data are of relevance to the interpretation of the potential mechanisms of action of rasagiline in explaining the results of disease modification trials in PD.

Identification of novel monoamine oxidase B inhibitors by structure-based virtual screening

Parkinson's disease is a severe debilitating neurodegenerative disorder. Recently, it was shown that the peroxisome proliferating-activator receptor-gamma agonist pioglitazone protected mice from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine neurotoxicity due to its ability to inhibit monoamine oxidase B (MAO-B). Docking studies were initiated to investigate pioglitazone's interactions within the substrate cavity of MAO-B. Modeling studies indicated that the thiazolidinedione (TZD) moiety was a likely candidate for its specificity to MAO-B. To explore this potential novel MAO-B scaffold, we performed a structure-based virtual screen to identify additional MAO-B inhibitors. Our search identified eight novel compounds containing the TZD-moiety that allowed for a limited study to identify structural requirements for binding to MAO-B. Inhibition assays identified two TZDs (A6355 and L136662) which were found to inhibit recombinant human MAO-B with IC(50) values of 82 and 195 nM, respectively.

The role of rasagiline in the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder, affecting 1% to 2% of people older than 60 years. Treatment of PD consists of symptomatic therapies while neuroprotective strategies have remained elusive. Rasagiline is a novel, potent, and irreversible monoamine oxidase type B (MAO-B) inhibitor which has been approved for treatment of PD. Rasagiline inhibits MAO-B more potently than selegiline and has the advantage of once-daily dosing. In several large, randomized, placebo-controlled trials, rasagiline has demonstrated efficacy as monotherapy in early PD and as adjunctive therapy in advanced PD. In addition, rasagiline has been shown to have neuroprotective effects in in vitro and in vivo studies. The recently completed delayed-start ADAGIO (Attenuation of Disease Progression with Azilect Given Once-daily) trial suggests a potential disease-modifying effect for rasagiline 1 mg/day, though the clinical import of this finding has yet to be established.

Pharmacological therapy in Parkinson's disease: focus on neuroprotection

Although the number of available therapeutic approaches in Parkinson's disease (PD) is steadily increasing the search for effective neuroprotective agent is continuing. Such research is directed at influencing the key steps in the pathomechanism: the mitochondrial dysfunction, the oxidative stress, the neuroinflammatory processes and the final common apoptotic pathway. Earlier-developed symptomatic therapies were implicated to be neuroprotective, and promising novel disease modifying approaches were brought into the focus of interest. The current review presents a survey of our current knowledge relating to the pathomechanism of PD and discusses the putative neuroprotective therapy.

Metallocorroles as cytoprotective agents against oxidative and nitrative stress in cellular models of neurodegeneration

Water-soluble iron, and manganese(III) complexes of corroles and porphyrins were examined with regard to their neuroprotective/neurorescue activities by using various neuronal cytotoxic models of oxidative and nitrative stress. The present study demonstrates that the metallocorroles significantly protect human neuroblastoma SH-SY5Y and mouse motor neuron-neuroblastoma fusion NSC-34 cell lines against neurotoxicity induced by either the peroxynitrite donor 3-morpholinosydnonimine or the parkinsonism-related neurotoxin 6-hydroxydopamine. The neuronal survival effect is further reflected by the prevention of 3-morpholinosydnonimine-induced protein nitration, inhibition of caspase 3 activation, as well as attenuation of 6-hydroxydopamine-mediated decrease in growth associated protein-43 levels. The iron(III) corrole, but not manganese (III) corrole, also significantly promotes neuronal survival of hydrogen peroxide (H(2)O(2))-impaired SH-SY5Y and NSC-34 cells. A substantial superiority of the metallocorroles relative to the corresponding porphyrin complexes is revealed in all examined aspects. These results highlight the large potential of corrole complexes as novel agents for therapeutic approaches in degenerative disorders of the central and peripheral nervous systems, where oxidative and nitrative stresses are involved.

The neuroprotective mechanism of 1-(R)-aminoindan, the major metabolite of the anti-parkinsonian drug rasagiline

The anti-parkinsonian drug, rasagiline [N-propargyl-1-(R)-aminoindan; Azilect(R)], is a secondary cyclic benzylamine and indane derivative, which provides irreversible, potent monoamine oxidase-B (MAO-B) inhibition and possesses neuroprotective and neurorestorative activities. A prospective clinical trial has shown that rasagiline confers significant symptomatic improvement and demonstrated alterations in Parkinson's disease progression. Rasagiline is primarily metabolized by hepatic cytochrome P-450 to form its major metabolite, 1-(R)-aminoindan, a non-amphetamine, weak reversible MAO-B inhibitor compound. Recent studies indicated the potential neuroprotective effect of 1-(R)-aminoindan, suggesting that it may contribute to the overall neuroprotective and antiapoptotic effects of its parent compound, rasagiline. This review article briefly highlights the molecular mechanisms underlying the neuroprotective properties of the active metabolite of rasagiline, 1-(R)-aminoindan, supporting the valuable potential of rasagiline for disease modification.

A double-blind, delayed-start trial of rasagiline in Parkinson's disease

BACKGROUND

A therapy that slows disease progression is the major unmet need in Parkinson's disease.

METHODS

In this double-blind trial, we examined the possibility that rasagiline has disease-modifying effects in Parkinson's disease. A total of 1176 subjects with untreated Parkinson's disease were randomly assigned to receive rasagiline (at a dose of either 1 mg or 2 mg per day) for 72 weeks (the early-start group) or placebo for 36 weeks followed by rasagiline (at a dose of either 1 mg or 2 mg per day) for 36 weeks (the delayed-start group). To determine a positive result with either dose, the early-start treatment group had to meet each of three hierarchical end points of the primary analysis based on the Unified Parkinson's Disease Rating Scale (UPDRS, a 176-point scale, with higher numbers indicating more severe disease): superiority to placebo in the rate of change in the UPDRS score between weeks 12 and 36, superiority to delayed-start treatment in the change in the score between baseline and week 72, and noninferiority to delayed-start treatment in the rate of change in the score between weeks 48 and 72.

RESULTS

Early-start treatment with rasagiline at a dose of 1 mg per day met all end points in the primary analysis: a smaller mean (+/-SE) increase (rate of worsening) in the UPDRS score between weeks 12 and 36 (0.09+/-0.02 points per week in the early-start group vs. 0.14+/-0.01 points per week in the placebo group, P=0.01), less worsening in the score between baseline and week 72 (2.82+/-0.53 points in the early-start group vs. 4.52+/-0.56 points in the delayed-start group, P=0.02), and noninferiority between the two groups with respect to the rate of change in the UPDRS score between weeks 48 and 72 (0.085+/-0.02 points per week in the early-start group vs. 0.085+/-0.02 points per week in the delayed-start group, P<0.001). All three end points were not met with rasagiline at a dose of 2 mg per day, since the change in the UPDRS score between baseline and week 72 was not significantly different in the two groups (3.47+/-0.50 points in the early-start group and 3.11+/-0.50 points in the delayed-start group, P=0.60).

CONCLUSIONS

Early treatment with rasagiline at a dose of 1 mg per day provided benefits that were consistent with a possible disease-modifying effect, but early treatment with rasagiline at a dose of 2 mg per day did not. Because the two doses were associated with different outcomes, the study results must be interpreted with caution. (ClinicalTrials.gov number, NCT00256204.)