Mechanism underlying anti-apoptotic activity of a (-)deprenyl-related propargylamine, rasagiline

Nano-NiZr4(PO4)6 as a superior catalyst for the synthesis of propargylamines under ultrasound irradiation

An easy and rapid method for the synthesis of propargylamines has been achieved through a three-component reaction of phenylacetylene, aromatic aldehydes, and morpholine or piperidine using nano-NiZr4(PO4)6 under ultrasound irradiation. Atom economy, a wide range of products, excellent yields in short times, reusability of the catalyst, and low catalyst loading are some of the important features of this protocol.

Pharmacological aspects of the neuroprotective effects of irreversible MAO-B inhibitors, selegiline and rasagiline, in Parkinson's disease

The era of MAO-B inhibitors dates back more than 50 years. It began with Kálmán Magyar's outstanding discovery of the selective inhibitor, selegiline. This compound is still regarded as the gold standard of MAO-B inhibition, although newer drugs have also been introduced to the field. It was revealed early on that selective, even irreversible inhibition of MAO-B is free from the severe side effect of the non-selective MAO inhibitors, the potentiation of tyramine, resulting in the so-called 'cheese effect'. Since MAO-B is involved mainly in the degradation of dopamine, the inhibitors lack any antidepressant effect; however, they became first-line medications for the therapy of Parkinson's disease based on their dopamine-sparing activity. Extensive studies with selegiline indicated its complex pharmacological activity profile with MAO-B-independent mechanisms involved. Some of these beneficial effects, such as neuroprotective and antiapoptotic properties, were connected to its propargylamine structure. The second MAO-B inhibitor approved for the treatment of Parkinson's disease, rasagiline also possesses this structural element and shows similar pharmacological characteristics. The preclinical studies performed with selegiline and rasagiline are summarized in this review.

The neuroprotective agent Rasagiline mesylate attenuates cardiac remodeling after experimental myocardial infarction

AIM

Rasagiline mesylate (N-propargyl-1 (R)-aminoindan) (RG) is a selective, potent irreversible inhibitor of monoamine oxidase-B with cardioprotective and anti-apoptotic properties. We investigated whether it could be cardioprotective in a rat model undergoing experimental myocardial infarction (MI) by permanent ligation of the left anterior descending coronary artery.

METHODS AND RESULTS

RG was administered, intraperitoneally, for 28 days (2 mg/kg) starting 24 h after MI induction. Echocardiography analysis revealed a significant reduction in left ventricular end-systolic and diastolic dimensions and preserved fractional shortening in RG-treated compared with normal saline group at 28 days post-MI (31.6 ± 2.3 vs. 19.6 ± 1.8, P < 0.0001), respectively. Treatment with RG prevented tissue fibrosis as indicated by interstitial collagen estimation by immunofluorescence staining and hydroxyproline content and attenuated the number of apoptotic myocytes in the border zone (65%) as indicated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Caspase 3 relative protein levels were significantly decreased in the non-infarcted myocardium. Markedly decreased malondialdehyde levels in the border zone indicate a reduction in tissue oxidative stress.

CONCLUSIONS

Our study demonstrates a positive effect of RG in the post-MI period with a significant attenuation in cardiac remodelling.

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.

Disease-Modifying Drugs in Parkinson's Disease

Despite an increased understanding of the pathogenesis of Parkinson's disease (PD), and a number of drugs designed to ameliorate symptoms, finding an effective neuroprotective therapy remains elusive. For decades now, several promising agents targeting different pathways have been explored as potential treatments that could help slow disease progression, but these have met with limited success. There are hurdles to overcome, particularly given that there is no exact animal model of PD and also no reliable biomarkers for PD. Without biomarkers, it is not possible to demonstrate, in the context of a clinical trial, that an intervention prevents neuronal degeneration. However, given the compelling scientific rationale of several compounds, an unrelenting pursuit continues. There have been hundreds of human studies looking at neuroprotection in PD. This article will briefly summarize several of the neuroprotective treatments that have been evaluated in large clinical trials, and will also outline some of the newer therapies that are currently being explored.

Evaluation of the Inhibitory Effects of Bavachinin and Bavachin on Human Monoamine Oxidases A and B

Monoamine oxidase B inhibitors (MAO-BIs) are used in the early management of Parkinson's disease (PD). Long-term suspected side effects of MAO-B classical inhibitors established the need for safer alternative therapeutic agents. In our study, the flavanone bavachinin (BNN) and its analog bavachin (BVN) found in the seeds of Psoralea corylifolia L. ethanolic extract (PCSEE) were investigated for their human MAO-A and MAO-B (hMAO-A and hMAO-B) inhibition. Both PCSEE and BNN effectively reduced hMAO-B activity more than hMAO-A while BVN had activating effects. BNN showed selective hMAO-B inhibition (IC₅₀ ~ 8.82 μM) more than hMAO-A (IC₅₀2009;~ 189.28 μM). BNN in the crude extract was determined by HPLC, also validated by TLC showing a yield of 0.21% PCSEE dry weight. BNN competitively inhibited hMAO-A and hMAO-B, with a lower hMAO-B K_i than hMAO-A K_i by 10.33-fold, and reduced hMAO-B K_m/V_max efficiency ratio to be comparable to the standard selegiline. Molecular docking examination of BNN and BVN predicted an indirect role of BNN C7-methoxy group for its higher affinity, selectivity, and reversibility as an MAO-BI. These findings suggest that BNN, which is known to be a potent PPAR-γ agonist, is a selective and competitive hMAO-B inhibitor and could be used in the management of PD.

Recent advances in Parkinson’s disease therapy: use of monoamine oxidase inhibitors

Monoamine oxidase inhibitors inhibit dopamine metabolism and are therefore effective in treating Parkinson's disease, a condition associated with progressive striatal dopamine deficiency secondary to degeneration of dopaminergic neurons in the substantia nigra. Selegiline is currently the most widely used monoamine oxidase-B inhibitor for Parkinson's disease, but has a low and variable bioavailability, and is metabolized to L-methamphetamine and L-amphetamine that carry a risk for potential neurotoxicity. There are two new approaches that circumvent these potential disadvantages. First, selegiline orally disintegrating tablets provide a novel delivery form of selegiline, avoiding first pass metabolism by rapid absorption through the oral mucosa, thus leading to significantly lower plasma concentrations of L-metamphetamine and L-amphetamine. Selegiline orally disintegrating tablets prove to be clinically effective and safe in patients with moderately advanced Parkinson's disease. Second, rasagiline is a new monoamine oxidase inhibitor, without known neurotoxic metabolites. In large clinical trials, rasagiline proves effective as monotherapy in early Parkinson's disease, as well as adjunctive therapy to levodopa in advanced disease. Clinical data suggest, in addition, a disease-modifying effect of rasagiline that may correlate with neuroprotective activity of monoamine oxidase-B inhibitors in animal models of Parkinson's disease.

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.

Efficacy and safety of rasagiline as an adjunct to levodopa treatment in Chinese patients with Parkinson's disease: a randomized, double-blind, parallel-controlled, multi-centre trial

Rasagiline mesylate is a highly potent, selective and irreversible monoamine oxidase type B (MAOB) inhibitor and is effective as monotherapy or adjunct to levodopa for patients with Parkinson's disease (PD). However, few studies have evaluated the efficacy and safety of rasagiline in the Chinese population. This study was designed to investigate the safety and efficacy of rasagiline as adjunctive therapy to levodopa treatment in Chinese PD patients. This was a randomized, double-blind, placebo-controlled, parallel-group, multi-centre trial conducted over a 12-wk period that enrolled 244 PD patients with motor fluctuations. Participants were randomly assigned to oral rasagiline mesylate (1 mg) or placebo, once daily. Altogether, 219 patients completed the trial. Rasagiline showed significantly greater efficacy compared with placebo. During the treatment period, the primary efficacy variable--mean adjusted total daily off time--decreased from baseline by 1.7 h in patients treated with 1.0 mg/d rasagiline compared to placebo (p < 0.05). Scores using the Unified Parkinson's Disease Rating Scale also improved during rasagiline treatment. Rasagiline was well tolerated. This study demonstrated that rasagiline mesylate is effective and well tolerated as an adjunct to levodopa treatment in Chinese PD patients with fluctuations.

Peroxynitrite induces neuronal cell death in aging and age-associated disorders: A review

Peroxynitrite produced from nitric oxide and superoxide has been proposed to cause neuronal dysfunction and cell death in aging and age-related degenerative diseases. 3-Nitrotyosine, an oxidation product of tyrosine by peroxynitrite, was reported to increase in degenerating brains. In this paper, involvement of peroxynitrite in neuronal cell death was studied by analyses of human brains and in vitro experiments on cell death induced by a peroxynitrite-generating agent, SIN-1. 3-Nitrotyrosine-containing proteins were detected in lipofuscin, a typical aging-related pigment in human brains. The cytotoxicity of peroxynitrite was examined in human dopaminergic SH-SY5Y cells by use of SIN-1. SIN-1 induced apoptotic cell death in the cells, and increased the level of 3-nitrotyrosine-containing proteins. The intracellular transduction of death signal was studied in apoptosis induced by peroxynitrite. Apoptosis was induced by sequential death cascade, collapse of mitochondrial membrane potential, activation of caspases and fragmentation of nuclear DNA. In addition, phosphorylation of p38 mitogen activated phosphokinase (MAPK) was found to be associated with apoptosis by SIN-1, as shown by inhibition of apoptotic process by SB202190, a p38 inhibitor. Involvement of peroxynitrite in the cell death is discussed in relation to neuronal degeneration in aging and age-associated diseases.

Rasagiline in Parkinson's disease

It has long been recognized that monoamine oxidase (MAO) inhibitors have a role in the management of Parkinson's disease (PD). The MAO-B inhibitor rasagiline has neuroprotective effects in animal models, mediated partly by its antiapoptotic activity. Rasagiline has been shown to be effective as monotherapy for early PD and as an adjunct to dopaminergic therapy. Clinical trials have also shown putative disease-modifying effects, though rasagiline's potential to alter the long-term course of PD remains controversial. Given the demonstrated benefits of rasagiline, along with its safety and tolerability profile, it has an important role to play in PD therapy.

Transcriptional regulation and multiple functions of MAO genes

Monoamine oxidase (MAO) A and MAO B are a crucial pair of isoenzymes, which oxidatively deaminate monoamine neurotransmitters and dietary amines with a production of hydrogen peroxide. These two isoenzymes have different but overlapping substrate and inhibitor specificities. MAO A and MAO B share 70% amino acid sequence identity and show different temporal and spatial expressions in both humans and mice. Abnormal MAO A or MAO B activity has been implicated in numerous neurological and psychiatric disorders. A better understanding of the transcriptional regulation of MAO A and MAO B genes may help explain the differential tissue-specific expression of these two isoenzymes and provide insights into the molecular basis of the disorders associated with MAO dysfunction. This review discusses the recent progress in the transcriptional regulation and multiple functions of MAO A and MAO B genes.

Iron-chelating backbone coupled with monoamine oxidase inhibitory moiety as novel pluripotential therapeutic agents for Alzheimer's disease: a tribute to Moussa Youdim

It is for these authors a great privilege to dedicate this review article to Moussa Youdim, who is one of the most imperative pharmacologists and pioneer investigators in the search and development of novel therapeutics for neurodegenerative diseases. 40 years ago, Moussa Youdim has started studying brain iron, catecholamine receptor and monoamine oxidase (MAO)-A and -B functions. Although Moussa Youdim succeeded in exploring the novel anti-Parkinsonian, selective MAO-B inhibitor drug, rasagiline (Azilect, Teva Pharmaceutical Co.), he did not stop searching for superior therapeutic approaches for neurodegenerative disorders. To date, Moussa Youdim and his research group are designing and synthesizing pluripotential drug candidates possessing diverse pharmacological properties that can act on multiple targets and pathological features ascribed to Parkinson's disease, Alzheimer's disease (AD) and amyotrophic lateral sclerosis. One such example is the multimodal non-toxic, brain-permeable iron-chelating compound, M30 (5-[N-methyl-N-propargylaminomethyl]-8-hydroxyquinoline), which amalgamates the propargyl moiety of rasagiline with the backbone of the potent iron chelator, VK28. This review discusses the multiple effects of several leading compounds of this series, concerning their neuroprotective/neurorestorative molecular mechanisms in vivo and in vitro, with a special focus on the pathological features ascribed to AD, including antioxidant and iron chelating activities, regulation of amyloid precursor protein and amyloid β peptide expression processing, activation of pro-survival signaling pathways and regulation of cell cycle and neurite outgrowth.

Efficacy, safety, and patient preference of monoamine oxidase B inhibitors in the treatment of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease and the most treatable. Treatment of PD is symptomatic and generally focuses on the replacement or augmentation of levodopa. A number of options are available for treatment, both in monotherapy of early PD and to treat complications of advanced PD. This review focuses on rasagiline and selegiline, two medications that belong to a class of antiparkinsonian drugs called monoamine oxidase B (MAO-B) inhibitors. Topics covered in the review include mechanism of action, efficacy in early and advanced PD, effects on disability, the controversy regarding disease modification, safety, and patient preference for MAO-B inhibitors.

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 randomized, double-blind, placebo-controlled, delayed start study to assess rasagiline as a disease modifying therapy in Parkinson's disease (the ADAGIO study): rationale, design, and baseline characteristics

A neuroprotective therapy is the single most important unmet medical need in Parkinson's disease. Several promising agents in the laboratory have been tested in the clinic, but none has been established in clinical trials to have a disease modifying effect despite positive results because of potential confounding symptomatic or pharmacologic effects. The delayed start design was developed to try to avoid a symptomatic confound when testing a putative neuroprotective therapy. In this study design, patients are randomly assigned to study drug or placebo in the first phase of the study, and both groups receive the active drug in the second phase. If benefits seen at the end of phase I persist through the end of phase II, they cannot be readily explained by a symptomatic effect (as patients in both groups are receiving the same medication) and benefits in the early start group must relate to the early initiation of the treatment. Although the precise mechanism responsible for such an effect can be debated, positive results in a delayed start study indicate that patients who receive early treatment have a better outcome than those where the treatment is delayed. We are using the delayed start design to assess the potential disease modifying effects of rasagiline in a prospective double blind controlled trial (the ADAGIO study). We here describe the rationale for the study and baseline characteristics of the 1,176 patients who have been enrolled into the trial.

Polycyclic compounds: ideal drug scaffolds for the design of multiple mechanism drugs?

Recently there has been a resurging interest in developing multi-functional drugs to treat diseases with complex pathological mechanisms. Such drug molecules simultaneously target multiple etiologies that have been found to be important modulators in specific diseases. This approach has significant promise and may be more effective than using one compound specific for one drug target or, by a polypharmaceutical approach, using a cocktail of two or more drugs. Polycyclic ring structures are useful as starting scaffolds in medicinal chemistry programs to develop multi-functional drugs, and may also be useful moieties added to existing structures to improve the pharmacokinetic properties of drugs currently used in the clinic or under development. This review attempts to provide a synopsis of current published research to exemplify the use of polycyclic compounds as starting molecules to develop multi-functional drugs.

Rasagiline (TVP-1012): a new selective monoamine oxidase inhibitor for Parkinson's disease

OBJECTIVE

This article reviews the chemistry, pharmacodynamics, pharmacokinetics, clinical efficacy, tolerability, drug-interaction potential, indications, dosing, and potential role of rasagiline mesylate, a new selective monoamine oxidase (MAO) type B (MAO-B) inhibitor, in the treatment of Parkinson's disease.

METHODS

A MEDLINE/PUBMED search (1986 through September 2006) was conducted to identify studies involving rasagiline written in English. Additional references were obtained from the bibliographies of these studies. All studies evaluating any aspect of rasagiline, including in vitro, in vivo (animal), and human studies, were reviewed.

RESULTS

Rasagiline mesylate was developed with the goal of producing a selective MAO-B inhibitor that is not metabolized to (presumed) toxic metabolites (eg, amphetamine and methamphetamine, which are byproducts of the metabolism of selegiline, another selective MAO-B inhibitor). In vitro and in vivo data have confirmed the drug's selectivity for MAO-B. Rasagiline is almost completely eliminated by oxidative metabolism (catalyzed by cytochrome P-450 [CYP] isozyme 1A2) followed by renal excretion of conjugated parent compound and metabolites. Drug clearance is sufficiently slow to allow once-daily dosing. Several studies have documented its efficacy as monotherapy for early-stage disease and as adjunctive therapy in L-dopa recipients with motor fluctuations. As monotherapy, rasagiline is well tolerated with an adverse-effect profile similar to that of placebo. As adjunctive therapy, it exhibits the expected adverse effects of dopamine excess, which can be ameliorated by reducing the L-dopa dosage. CYP1A2 inhibitors slow the elimination of rasagiline and mandate dosage reduction. Hepatic impairment has an analogous effect. The recommended dosage regimens for monotherapy and adjunctive therapy are 1 and 0.5 mg PO QD, respectively.

CONCLUSIONS

Despite the well-documented selectivity of rasagiline, the manufacturer recommends virtually all of the dietary (vis-à-vis tyramine) and drug restrictions of the nonselective MAO inhibitors. Although useful, selective MAO-B inhibitors have a limited role in Parkinson's disease. Of greater interest is the potential neuroprotective effect of rasagiline and its major metabolite, 1(R)-aminoindan, which may have great utility in a wide variety of neurodegenerative disorders of aging. In addition, bifunctional molecules combining selective MAO-B inhibition (based on the active moiety of rasagiline) with acetylcholinesterase inhibition or iron chelation may eventually be useful in Alzheimer's disease.

Rasagiline is neuroprotective in an experimental model of brain ischemia in the rat

The neuroprotective effects of intravenous rasagiline were investigated in a rat model of stroke. Middle cerebral artery (MCA) occlusion was performed in male rats and the short- (neurological severity score [NSS], infarct size), intermediate- (cognition) and long-term (necrotic area) effects were assessed. A bolus (3 mg/kg) of rasagiline followed by a 3-h infusion (3 mg/kg/h), initiated immediately after MCA occlusion, reduced infarct size by 48.6% and NSS by 32.7% relative to saline treatment. Cognitive function, tested in a water maze 2-3 weeks after occlusion, also significantly improved compared with saline-treated controls. Necrotic brain area was 35-50% smaller with rasagiline than with saline following a single bolus dose. The single bolus rasagiline dose was as effective as a rasagiline bolus followed by rasagiline infusion in short-term outcomes. The neuroprotective effect of rasagiline was fully reproducible when administered at 2 h following occlusion but not after 4 h.

Neuroprotective therapy in Parkinson disease

During the past decade, there has been a remarkable progress in our understanding of the biology of Parkinson disease (PD), which has been translated into searching for novel therapy for PD. Much focus is shifted from the development of drugs that only relieve PD symptoms to new generation of remedies that can potentially protect dopaminergic neurons and modify the disease course. Several novel therapeutic approaches have been tested in preclinical experiments and in clinical trials, including molecules targeting on genes involved in the pathogenesis of the disease, neurotrophic factors critical for dopaminergic neuron survival and function, new generation of dopamine receptor agonists that may possess neuroprotective effects, and agents of antioxidation, antiinflammation, and antiapoptosis. The results of these studies will shed new light to our hope that PD can be cured in the future.

Rasagiline in the pharmacotherapy of Parkinson's disease--a review

Despite the current efficacious symptomatic approaches, the search is on for new therapies for Parkinson's disease that can control the cardinal symptoms of the disease (tremor, rigidity and bradykinesia), control/prevent motor complications induced by long-term levodopa, act on non-motor disease symptoms (dementia, dysautonomia, pain, insomnia, falls) and halt disease progression. Rasagiline is a monoamine oxidase-B inhibitor that has demonstrated efficacy against the cardinal symptoms of Parkinson's disease when used as monotherapy in early Parkinson's disease, and as an adjunct to levodopa in advanced disease stages. It reduces the duration and severity of poor symptom response episodes in fluctuating patients. Preliminary results allow discussion of putative effects of rasagiline on some non-motor signs and disease progression. This article outlines the evidence surrounding the efficacy and safety of rasagiline, and discusses its potential to address some of the currently unmet needs of Parkinson's disease therapy.

Rasagiline: A second-generation monoamine oxidase type-B inhibitor for the treatment of Parkinson's disease

PURPOSE

The pharmacology, pharmacokinetics, clinical efficacy, and safety of rasagiline are reviewed.

SUMMARY

Rasagiline is a novel, investigational propargylamine that irreversibly and selectively inhibits monoamine oxidase type B (MAO-B). Rasagiline demonstrates complete and selective inhibition of MAO-B and is at least five times more potent than selegiline. Unlike selegiline, which is metabolized to amphetamine derivatives, rasagiline is biotransformed to the nonamphetamine compound aminoindan. Clinical studies have revealed that rasagiline is associated with improved outcomes in patients with early Parkinson's disease (PD) and also reduces "off" time in patients with moderate to advanced PD with motor fluctuations. Rasagiline is rapidly absorbed by the gastrointestinal tract and readily crosses the blood-brain barrier. The optimal therapeutic dosage is 0.5-1 mg administered orally once daily. Rasagiline appears to be well tolerated, although elderly patients may be more prone to treatment-emergent adverse cardiovascular and psychiatric effects. At the recommended therapeutic dosage of up to 1 mg once daily, tyramine restriction is unnecessary. In addition to MAO-B inhibition, rasagiline has demonstrated neuroprotective properties in experimental laboratory models. The mechanisms whereby rasagiline exerts neuroprotective effects are multifactorial and include upregulation of cellular antioxidant activity and antiapoptotic factors.

CONCLUSION

Rasagiline is an investigational selective and irreversible inhibitor of MAO-B that has demonstrated efficacy and safety for the treatment of PD. Whether rasagiline is associated with clinically significant neuroprotection is the subject of ongoing clinical trials.

Novel multifunctional neuroprotective iron chelator-monoamine oxidase inhibitor drugs for neurodegenerative diseases. In vivo selective brain monoamine oxidase inhibition and prevention of MPTP-induced striatal dopamine depletion

Several multifunctional iron chelators have been synthesized from hydroxyquinoline pharmacophore of the iron chelator, VK-28, possessing the monoamine oxidase (MAO) and neuroprotective N-propargylamine moiety. They have iron chelating potency similar to desferal. M30 is a potent irreversible rat brain mitochondrial MAO-A and -B inhibitor in vitro (IC50, MAO-A, 0.037 +/- 0.02; MAO-B, 0.057 +/- 0.01). Acute (1-5 mg/kg) and chronic [5-10 mg/kg intraperitoneally (i.p.) or orally (p.o.) once daily for 14 days]in vivo studies have shown M30 to be a potent brain selective (striatum, hippocampus and cerebellum) MAO-A and -B inhibitor. It has little effects on the enzyme activities of the liver and small intestine. Its N-desmethylated derivative, M30A is significantly less active. Acute and chronic treatment with M30 results in increased levels of dopamine (DA), serotonin(5-HT), noradrenaline (NA) and decreases in DOPAC (dihydroxyphenylacetic acid), HVA (homovanillic acid) and 5-HIAA (5-hydroxyindole acetic acid) as determined in striatum and hypothalamus. In the mouse MPTP (N-methy-4-phenyl-1,2,3,6-tetrahydropyridine) model of Parkinson's disease (PD) it attenuates the DA depleting action of the neurotoxin and increases striatal levels of DA, 5-HT and NA, while decreasing their metabolites. As DA is equally well metabolized by MAO-A and -B, it is expected that M30 would have a greater DA neurotransmission potentiation in PD than selective MAO-B inhibitors, for which it is being developed, as MAO-B inhibitors do not alter brain dopamine.

Mitochondrial inhibition and oxidative stress: reciprocating players in neurodegeneration

Although the etiology for many neurodegenerative diseases is unknown, the common findings of mitochondrial defects and oxidative damage posit these events as contributing factors. The temporal conundrum of whether mitochondrial defects lead to enhanced reactive oxygen species generation, or conversely, if oxidative stress is the underlying cause of the mitochondrial defects remains enigmatic. This review focuses on evidence to show that either event can lead to the evolution of the other with subsequent neuronal cell loss. Glutathione is a major antioxidant system used by cells and mitochondria for protection and is altered in a number of neurodegenerative and neuropathological conditions. This review also addresses the multiple roles for glutathione during mitochondrial inhibition or oxidative stress. Protein aggregation and inclusions are hallmarks of a number of neurodegenerative diseases. Recent evidence that links protein aggregation to oxidative stress and mitochondrial dysfunction will also be examined. Lastly, current therapies that target mitochondrial dysfunction or oxidative stress are discussed.

Clinical pharmacology of rasagiline: a novel, second-generation propargylamine for the treatment of Parkinson disease

Rasagiline is a novel second-generation propargylamine that irreversibly and selectively inhibits monoamine oxidase type B (MAO-B). For the management of Parkinson disease (PD), rasagiline is efficacious across the span of PD stages ranging from monotherapy in early disease to adjunctive treatment in patients with advancing disease and motor fluctuations. Rasagiline completely and selectively inhibits MAO-B with a potency 5 to 10 times greater than selegiline. Unlike the prototype propargylamine selegiline, which is metabolized to amphetamine derivatives, rasagiline is biotransformed to aminoindan, a non-amphetamine compound. Rasagiline is well tolerated with infrequent cardiovascular or psychiatric side effects, and at the recommended therapeutic dose of up to 1 mg once daily, tyramine restriction is unnecessary. In addition to MAO-B inhibition, the propargylamine chain also confers dose-related antioxidant and antiapoptotic effects, which have been associated with neuroprotection in multiple experimental models. Thus, in addition to symptomatic benefits, rasagiline offers the promise of clinically relevant neuroprotection.

Bifunctional drug derivatives of MAO-B inhibitor rasagiline and iron chelator VK-28 as a more effective approach to treatment of brain ageing and ageing neurodegenerative diseases

Degeneration of nigrostriatal dopamine neurons and cholinergic cortical neurones are the main pathological features of Parkinson's disease (PD) and for the cognitive deficit in dementia of the Alzheimer' type (AD) and in dementia with Lewy bodies (DLB), respectively. Many PD and DLB subjects have dementia and depression resulting from possible degeneration of cholinergic and noradrenergic and serotonergic neurons. On the other hand, AD patients may also develop extrapyramidal features as well as depression. In both PD and AD there is, respectively, accumulation of iron within the melanin containing dopamine neurons of pars compacta and with in the plaques and tangle. It has been suggested that iron accumulation may contribute to the oxidative stress induced apoptosis reported in both diseases. This may result from increased glia hydrogen peroxide producing monoamine oxidase (MAO) activity that can generate of reactive hydroxyl radical formed from interaction of iron and hydrogen peroxide. We have therefore prepared a series of novel bifunctional drugs from the neuroprotective-antiapoptotic antiparkinson monoamine oxidase B inhibitor, rasagiline, by introducing a carbamate cholinesterase (ChE) inhibitory moiety into it. Ladostigil (TV-3326, N-propargyl-3R-aminoindan-5yl)-ethyl methylcarbamate), has both ChE and MAO-AB inhibitory activity, as potential treatment of AD and DLB or PD subjects with dementia Being a brain selective MAO-AB inhibitor it has limited potentiation of the pressor response to oral tyramine and exhibits antidepressant activity similar to classical non-selective MAO inhibitor antidepressants by increasing brain serotonin and noradrenaline. Ladostigil inhibits brain acetyl and butyrylcholinesterase in rats and antagonizes scopolamine-induced inhibition of spatial learning. Ladostigil like MAO-B inhibitor it prevents MPTP Parkinsonism in mice model and retains the in vitro and in vivo neuroprotective activity of rasagiline. Ladostigil, rasagiline and other propargylamines have been demonstrated to have neuroprotective activity in several in vitro and in vivo models, which have been shown be associated with propargylamines moiety, since propargylamines itself possess these properties. The mechanism of neuroprotective activity has been attributed to the ability of propargylamines-inducing the antiapoptotic family proteins Bcl-2 and Bcl-xl, while decreasing Bad and Bax and preventing opening of mitochondrial permeability transition pore. Iron accumulates in brain regions associated with neurodegenerative diseases of PD, AD, amyotrophic lateral sclerosis and Huntington disease. It is thought to be involved in Fenton chemistry oxidative stress observed in these diseases. The neuroprotective activity of propargylamines led us to develop several novel bifunctional iron chelator from our prototype brain permeable iron chelators, VK-28, possessing propargylamine moiety (HLA-20, M30 and M30A) to iron out iron from the brain. These compounds have been shown to have iron chelating and monoamine oxidase A and B selective brain inhibitory and neuroprotective-antiapoptotic actions.

Other pharmacological treatments for motor complications and dyskinesias

Controlling motor complications becomes increasingly difficult with disease progression. The "wearing-off" phenomenon is the most-common motor fluctuation. Wearing-off can be treated by dietary manipulation, shortening the dosing interval, substituting sustained-release levodopa, adding amantadine, or monoamine oxidase type B inhibitors, and other options, including catechol-O-methyltransferase inhibitors and the approved dopamine agonists addressed in another chapter. The rotigotine constant-delivery system is being developed to treat wearing-off symptoms. Istradefylline (KW-6002), an adenosine A(2A) receptor antagonist, has been studied for wearing-off and the results will be discussed. The on-off fluctuations can be treated with liquid levodopa and the rescue therapy of injectable apomorphine. Patients may also suffer from dyskinesias. Dyskinesias can be treated with small doses of liquefied levodopa-carbidopa, amantadine, and clozapine, an atypical neuroleptic.

Double-blind, randomized, controlled trial of rasagiline as monotherapy in early Parkinson's disease patients

Rasagiline (N-propargyl-1(R)-aminoindan) mesylate is a potent, selective, and irreversible monoamine oxidase-B inhibitor. This study was designed to evaluate the safety, tolerability, and preliminary efficacy of rasagiline monotherapy in early Parkinson's disease (PD) patients not receiving levodopa. The study was performed as a multicenter, parallel-group, double-blind, randomized, placebo-controlled, 10-week study. Fifty-six PD patients were randomly assigned to rasagiline mesylate 1, 2, or 4 mg once daily, or placebo. A 3-week dose-escalation period was followed by a 7-week maintenance phase. At week 10, the mean (+/-SE) changes from baseline in total Unified Parkinson's Disease Rating Scale (UPDRS) score were -1.8 (+/-1.3), -3.6 (+/-1.7), -3.6 (+/-1.2), and -0.5 (+/-0.8) in the rasagiline 1, 2, and 4 mg/day and placebo groups, respectively. Analysis of responders showed that 28% of patients (12 of 43) receiving rasagiline had an improvement in total UPDRS score of greater than 30%, compared with none of the patients receiving placebo (P < 0.05, Fisher's exact test). The frequency and types of adverse events reported by rasagiline-treated and placebo-treated patients were similar. These results suggest that rasagiline monotherapy is well tolerated and efficacious in early PD.

Evaluation of animal models of Parkinson's disease for neuroprotective strategies

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of dopaminergic nigral neurons and striatal dopamine. Despite the advances of modern therapy to treat the symptoms of PD, most of the patients will eventually experience debilitating disability. The need for neuroprotective strategies that will slow or stop the progression of the disease is clear. The progress in the understanding of the cause and pathogenesis of PD is providing clues for the development of disease-modifying strategies. In that regard, animal models of PD and non-human primate models in particular, are essential for the preclinical evaluation and testing of candidate therapies. However, the diversity of models and different outcome measures used by investigators make it challenging to compare results between neuroprotective agents. In this review we will discuss methods for the selection, development and assessment of animal models of PD, the role of non-human primates and the concept of "multiple models/multiple endpoints" to predict the success in the clinic of neuroprotective strategies.

Tolerability, Safety, Pharmacodynamics, and Pharmacokinetics of Rasagiline: A Potent, Selective, and Irreversible Monoamine Oxidase Type B Inhibitor

STUDY OBJECTIVE

To investigate the tolerability, safety, pharmacodynamics, and pharmacokinetics of rasagiline after once-daily oral administration of single or repeated doses.

DESIGN

A randomized, double-blind, placebo-controlled, three-way, single-dose study and a randomized, double-blind, placebo-controlled, repeated-dose study.

SETTING

Clinical research center in France.

SUBJECTS

Healthy male volunteers aged 18-40 years (12 in the single-dose study, 24 in the repeated-dose study).

INTERVENTION

In the single-dose study, subjects received, in a randomized sequence, single doses of placebo, rasagiline 1 mg, and rasagiline 5 mg; or placebo, rasagiline 2 mg, and rasagiline 10 mg. Six subjects received an additional single dose of rasagiline 20 mg. There was a 2-week washout period between each dose. In the repeated-dose study, subjects were randomized to receive rasagiline 2 mg, 5 mg, or 10 mg, or placebo once/day for 10 days.

MEASUREMENTS AND MAIN RESULTS

To assess tolerability and safety, patients underwent physical examinations, vital sign measurements, 12-lead electrocardiograms, clinical laboratory testing, and bleeding time studies. To determine platelet monoamine oxidase type B (MAO-B) activity and rasagiline pharmacokinetics, blood and urine samples were taken. In the single-dose study, rasagiline 1-20 mg was well tolerated. Each dose significantly inhibited platelet MAO-B activity. In the repeated-dose study, all doses of rasagiline were well tolerated; almost full inhibition of platelet MAO-B activity was achieved with each rasagiline dose.

CONCLUSION

Rasagiline is well tolerated at doses up to 20 mg once/day and is a potent inhibitor of platelet MAO-B in humans.

Insulin-like growth factor-I regulates glucose-induced mitochondrial depolarization and apoptosis in human neuroblastoma

Neuroblastoma, a pediatric peripheral nervous system tumor, frequently contains alterations in apoptotic pathways, producing chemoresistant disease. Insulin-like growth factor (IGF) system components are highly expressed in neuroblastoma, further protecting these cells from apoptosis. This study investigates IGF-I regulation of apoptosis at the mitochondrial level. Elevated extracellular glucose causes rapid mitochondrial enlargement coupled with an increase in the mitochondrial membrane potential (Delta Psi(M)) followed by mitochondrial membrane depolarization (MMD), uncoupling protein 3 (UCP3) downregulation, caspase-3 activation and decreased Bcl-2. MMD inhibition by Bongkrekic acid prevents high-glucose-induced loss of UCP3 and apoptosis. Glucose exposure induces caspase-9 cleavage within 30 min, and caspase-9 inhibition prevents glucose-mediated apoptosis. IGF-I prevents caspase activation and mitochondrial events leading to apoptosis. These results suggest that elevated glucose produces early initiator caspase activation, followed by Delta Psi(M) changes, in neuroblastoma cells; in turn, IGF-I prevents apoptosis by preventing downstream caspase activation, maintaining Delta Psi(M) and regulating Bcl proteins.

Neuroprotective strategies in Parkinson's disease : an update on progress

In spite of the extensive studies performed on postmortem substantia nigra from Parkinson's disease patients, the aetiology of the disease has not yet been established. Nevertheless, these studies have demonstrated that, at the time of death, a cascade of events had been initiated that may contribute to the demise of the melanin-containing nigro-striatal dopamine neurons. These events include increased levels of iron and monoamine oxidase (MAO)-B activity, oxidative stress, inflammatory processes, glutamatergic excitotoxicity, nitric oxide synthesis, abnormal protein folding and aggregation, reduced expression of trophic factors, depletion of endogenous antioxidants such as reduced glutathione, and altered calcium homeostasis. To a large extent, the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA) animal models of Parkinson's disease confirm these findings. Furthermore, neuroprotection can be afforded in these models with iron chelators, radical scavenger antioxidants, MAO-B inhibitors, glutamate antagonists, nitric oxide synthase inhibitors, calcium channel antagonists and trophic factors. Despite the success obtained with animal models, clinical neuroprotection is much more difficult to accomplish. Although the negative studies obtained with the MAO-B inhibitor selegiline (deprenyl) and the antioxidant tocopherol (vitamin E) may have resulted from an inappropriate choice of drug (selegiline) or an inadequate dose (tocopherol), the niggling problem that still remains is why these drugs, and others, do work in animals while they fail in the clinic. One reason for this may be related to the fact that in normal human brains the number of dopaminergic neurons falls by around 3-5% every decade, while in Parkinson's disease this decline is greater. Brain autopsy studies have shown that by the time the disease is identified, some 70-75% of the dopamine-containing neurons have been lost. More sensitive reliable methods and clinical correlative markers are required to discern between confoundable symptomatic effects versus a possible neuroprotective action of drugs, namely, the ability to delay or forestall disease progression by protecting or rescuing the remaining dopamine neurons or even restoring those that have been lost.A number of other possibilities for the clinical failure of potential neuroprotectants also exist. First, the animal models of Parkinson's disease may not be totally reflective of the disease and, therefore, the chemical pathologies established in the animal models may not cause, or contribute to, the progression of the disease clinically. Second, because of the series of events occurring in neurodegeneration and our ignorance about which of these factors constitutes the primary event in the pathogenic process, a single drug may not be adequate to induce neuroprotection and, as a consequence, use of a cocktail of drugs may be more appropriate. The latter concept receives support from recent complementary DNA (cDNA) microarray gene expression studies, which show the existence of a gene cascade of events occurring in the nigrostriatal pathway of MPTP, 6-OHDA and methamphetamine animal models of Parkinson's disease. Even with the advent of powerful new tools such as genomics, proteomics, brain imaging, gene replacement therapy and knockout animal models, the desired end result of neuroprotection is still beyond our current capability.

Cytochrome P450-dependent metabolism of l-deprenyl in monkey (Cercopithecus aethiops) and C57BL/6 mouse brain microsomal preparations

The aim of the present investigation was to characterize the cytochrome P450 (CYP)-dependent metabolism of l-deprenyl by brain microsomal preparations obtained from two different animal models that have been extensively used in Parkinson's disease studies, namely monkey (Cercopithecus aethiops) and C57BL/6 mouse. In monkey brain microsomal fractions, the apparent Km values for methamphetamine formation from l-deprenyl were 67.8 +/- 1.0 and 72.0 +/- 1.6 microm, in the cortex and striatum, respectively. Similarly, for nordeprenyl formation from l-deprenyl, Km values in cortex and striatum were 21.3 +/- 3.2 and 27.3 +/- 4.0 microm, respectively. Both metabolic pathways appear to be more efficient in the cortex than in the striatum as the Vmax for microsomal preparation was lower in the striatum for the formation of both metabolites. The formation rate of l-methamphetamine was up to one order of magnitude greater than that of nordeprenyl. Inhibition analysis of both pathways in monkey brain suggested that l-methamphetamine formation is catalysed by CYP2A and CYP3A, whereas only CYP3A appears to be involved in nordeprenyl formation. With microsomal preparations from whole brain of C57BL/6 mice, the only l-deprenyl metabolite that could be detected was methamphetamine and the Km and Vmax values were similar to those determined in monkey cortex (53.6 +/- 2.9 microm and 33.9 +/- 0.4 pmol/min/mg protein, respectively). 4-Methylpyrazole selectively inhibited methamphetamine formation, suggesting the involvement of CYP2E1. In conclusion, the present study indicates that l-deprenyl is effectively metabolised by CYP-dependent oxidases in the brain, giving rise mainly to the formation of methamphetamine, which has been suggested to play a role in the pharmacological effects of the parent drug. The results also demonstrate that there are differences between species in CYP-dependent metabolism of l-deprenyl.

Recent developments in the pharmacological treatment of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder associated with the loss of dopaminergic neurons in the substantia nigra. The decline of dopamine leads to motor dysfunctions manifested as tremor, rigidity and bradykinesia. The pharmacological treatment of choice for the past 30 years has primarily been the dopamine precursor levodopa. Although it is the most effective treatment available, it is clear that other drugs are needed in order to sustain a therapeutic benefit and to alleviate fluctuations in mobility (i.e., motor fluctuations). Furthermore, there is some evidence that levodopa may hasten the occurrence of motor fluctuations and involuntary movements called dyskinesias. Hence, many clinicians delay the use of levodopa and employ the use of other symptomatic treatments including monoamine oxidase type B (MAO-B) inhibitors and dopamine agonists as first-line therapy in de novo patients. Regardless of treatment, the disease continues to progress as there is still no obvious means of altering disease progression (i.e., no neuroprotective therapy), to restore loss of dopamine (i.e., no restorative therapy) or prevent the disease (i.e. preventative therapy). With disease progression, polypharmacy is common and often employs a combination of antiparkinsonian agents. There have been some key advances in treatment with the advent of MAO-B inhibitors, dopamine agonists and catechol-O-methyltransferase inhibitors; however, the arsenal of drug treatment remains limited. As the mechanism of PD is further elucidated, novel drug treatments will continue to emerge in the areas of preventative, restorative or symptomatic therapy. Despite the purpose of treatment, the ideal pharmacological drug for PD will include the presence of a safe side-effect profile, a simple dosing schedule, the ability to provide symptomatic relief and the potential to alter disease progression. The purpose of this article is to examine upcoming antiparkinsonian drugs in clinical trials based on their pharmacology, safety and efficacy.

Selegiline attenuates cardiac oxidative stress and apoptosis in heart failure: association with improvement of cardiac function

We have shown recently that selegiline exerts a cardiac neuroprotective effect in chronic heart failure. Since selegiline has an antioxidant antiapoptotic effect, we proposed to determine whether selegiline attenuates cardiac oxidative stress and myocyte apoptosis in chronic heart failure by modulating Bcl-2 and Bax protein expression, and whether the effects are associated with the improvement of cardiac function. Rabbits with rapid cardiac pacing (360 beats/min) and sham operation without pacing were randomized to receive oral selegiline (1 mg/day) or placebo for 8 weeks. Echocardiography was used to measure left ventricular fractional shortening. After 8 weeks of treatment, animals were studied for arterial norepinephrine and left ventricular systolic function (fractional shortening and dP/dt), and were then sacrificed for measuring the stable oxidative product of myocardial mitochondrial DNA (mtDNA) 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG), myocyte apoptosis by monoclonal antibody to single stranded DNA, and Bcl-2 and Bax protein expression by Western blot and immunohistochemistry. Rapid cardiac pacing increased plasma norepinephrine, cardiac oxidative stress and myocyte apoptosis, reduced Bcl-2 and the Bcl-2 to Bax ratio. These changes were associated with decreased left ventricular fractional shortening and dP/dt. Selegiline treatment in chronic heart failure animals reduced plasma norepinephrine, cardiac oxidative stress and myocyte apoptosis, prevented the changes of Bcl-2 and Bcl-2 to Bax ratio, and improved left ventricular fractional shortening and dP/dt. The findings suggest that the reduction by selegiline of myocyte apoptosis is related to the decrease of cardiac oxidative stress and the modulation of apoptotic and antiapoptotic proteins. The antioxidant antiapoptotic effects of selegiline are potentially beneficial in the improvement of cardiac function in chronic heart failure.