Neuroprotection by propargylamines in Parkinson's disease: suppression of apoptosis and induction of prosurvival genes

Toxic interactions between dopamine, α-synuclein, monoamine oxidase, and genes in mitochondria of Parkinson's disease

Parkinson's disease is characterized by its distinct pathological features; loss of dopamine neurons in the substantia nigra pars compacta and accumulation of Lewy bodies and Lewy neurites containing modified α-synuclein. Beneficial effects of L-DOPA and dopamine replacement therapy indicate dopamine deficit as one of the main pathogenic factors. Dopamine and its oxidation products are proposed to induce selective vulnerability in dopamine neurons. However, Parkinson's disease is now considered as a generalized disease with dysfunction of several neurotransmitter systems caused by multiple genetic and environmental factors. The pathogenic factors include oxidative stress, mitochondrial dysfunction, α-synuclein accumulation, programmed cell death, impaired proteolytic systems, neuroinflammation, and decline of neurotrophic factors. This paper presents interactions among dopamine, α-synuclein, monoamine oxidase, its inhibitors, and related genes in mitochondria. α-Synuclein inhibits dopamine synthesis and function. Vice versa, dopamine oxidation by monoamine oxidase produces toxic aldehydes, reactive oxygen species, and quinones, which modify α-synuclein, and promote its fibril production and accumulation in mitochondria. Excessive dopamine in experimental models modifies proteins in the mitochondrial electron transport chain and inhibits the function. α-Synuclein and familiar Parkinson's disease-related gene products modify the expression and activity of monoamine oxidase. Type A monoamine oxidase is associated with neuroprotection by an unspecific dose of inhibitors of type B monoamine oxidase, rasagiline and selegiline. Rasagiline and selegiline prevent α-synuclein fibrillization, modulate this toxic collaboration, and exert neuroprotection in experimental studies. Complex interactions between these pathogenic factors play a decisive role in neurodegeneration in PD and should be further defined to develop new therapies for Parkinson's disease.

Neurodegenerative Etiology of Aromatic L-Amino Acid Decarboxylase Deficiency: a Novel Concept for Expanding Treatment Strategies

Aromatic l-amino acid decarboxylase deficiency (AADC-DY) is caused by one or more mutations in the DDC gene, resulting in the deficit in catecholamines and serotonin neurotransmitters. The disease has limited therapeutic options with relatively poor clinical outcomes. Accumulated evidence suggests the involvement of neurodegenerative mechanisms in the etiology of AADC-DY. In the absence of neurotransmitters' neuroprotective effects, the accumulation and the chronic presence of several neurotoxic metabolites including 4-dihydroxy-L-phenylalanine, 3-methyldopa, and homocysteine, in the brain of subjects with AADC-DY, promote oxidative stress and reduce the cellular antioxidant and methylation capacities, leading to glial activation and mitochondrial dysfunction, culminating to neuronal injury and death. These pathophysiological processes have the potential to hinder the clinical efficacy of treatments aimed at increasing neurotransmitters' synthesis and or function. This review describes in detail the mechanisms involved in AADC-DY neurodegenerative etiology, highlighting the close similarities with those involved in other neurodegenerative diseases. We then offer novel strategies for the treatment of the disease with the objective to either reduce the level of the metabolites or counteract their prooxidant and neurotoxic effects. These treatment modalities used singly or in combination, early in the course of the disease, will minimize neuronal injury, preserving the functional integrity of neurons, hence improving the clinical outcomes of both conventional and unconventional interventions in AADC-DY. These modalities may not be limited to AADC-DY but also to other metabolic disorders where a specific mutation leads to the accumulation of prooxidant and neurotoxic metabolites.

Neuroprotective Function of Rasagiline and Selegiline, Inhibitors of Type B Monoamine Oxidase, and Role of Monoamine Oxidases in Synucleinopathies

Synucleinopathies are a group of neurodegenerative disorders caused by the accumulation of toxic species of α-synuclein. The common clinical features are chronic progressive decline of motor, cognitive, behavioral, and autonomic functions. They include Parkinson’s disease, dementia with Lewy body, and multiple system atrophy. Their etiology has not been clarified and multiple pathogenic factors include oxidative stress, mitochondrial dysfunction, impaired protein degradation systems, and neuroinflammation. Current available therapy cannot prevent progressive neurodegeneration and “disease-modifying or neuroprotective” therapy has been proposed. This paper presents the molecular mechanisms of neuroprotection by the inhibitors of type B monoamine oxidase, rasagiline and selegiline. They prevent mitochondrial apoptosis, induce anti-apoptotic Bcl-2 protein family, and pro-survival brain- and glial cell line-derived neurotrophic factors. They also prevent toxic oligomerization and aggregation of α-synuclein. Monoamine oxidase is involved in neurodegeneration and neuroprotection, independently of the catalytic activity. Type A monoamine oxidases mediates rasagiline-activated signaling pathways to induce neuroprotective genes in neuronal cells. Multi-targeting propargylamine derivatives have been developed for therapy in various neurodegenerative diseases. Preclinical studies have presented neuroprotection of rasagiline and selegiline, but beneficial effects have been scarcely presented. Strategy to improve clinical trials is discussed to achieve disease-modification in synucleinopathies.

Apoptosis and its therapeutic implications in neurodegenerative diseases

Neurodegenerative disorders are characterized by progressive loss of particular populations of neurons. Apoptosis has been implicated in the pathogenesis of neurodegenerative diseases, including Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. In this review, we focus on the existing notions relevant to comprehending the apoptotic death process, including the morphological features, mediators and regulators of cellular apoptosis. We also highlight the evidence of neuronal apoptotic death in Parkinson disease, Alzheimer disease, Huntington disease, and amyotrophic lateral sclerosis. Additionally, we present evidence of potential therapeutic agents that could modify the apoptotic pathway in the aforementioned neurodegenerative diseases and delay disease progression. Finally, we review the clinical trials that were conducted to evaluate the use of anti-apoptotic drugs in the treatment of the aforementioned neurodegenerative diseases, in order to highlight the essential need for early detection and intervention of neurodegenerative diseases in humans.

Can the interplay between autophagy and apoptosis be targeted as a novel therapy for Parkinson's disease?

Development of efficacious treatments for Parkinson's disease (PD) demands an improved understanding of mechanisms underlying neurodegeneration. Two cellular death pathways postulated to play key roles in PD are autophagy and apoptosis. Molecular overlap between these pathways was investigated through identifying studies that used therapeutic compounds to alter expression of specific molecular components of the pathways. Bcl-2 was identified as an important protein with the ability to suppress autophagy and apoptosis through inhibiting Beclin-1 and Bax, respectively. Involvement of c-Jun N-terminal kinases (JNK) and p38, was evident in the activation of apoptosis through increasing the Bax/Bcl-2 ratio. JNK-mediated phosphorylation also suppresses the inhibiting functions of Bcl-2, indicating an ability to induce not only apoptosis but also autophagy. Additionally, a p38-mediated increase in heme oxygenase-1 expression inhibits apoptosis. Moreover, besides inhibiting mammalian target of rapamycin, Akt is associated with decreased Bax expression, thereby acting as both an autophagy inducer and apoptosis inhibitor. Ultimately, manipulation of molecular components involved in autophagy and apoptosis regulation could be targeted as possible therapies for PD.

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.

Inhibitors of MAO-B and COMT: their effects on brain dopamine levels and uses in Parkinson's disease

MAO-B and COMT are both enzymes involved in dopamine breakdown and metabolism. Inhibitors of these enzymes are used in the treatment of Parkinson's disease. This review article describes the scientific background to the localization and function of the enzymes, the physiological changes resulting from their inhibition, and the basic and clinical pharmacology of the various inhibitors and their role in treatment of Parkinson's disease.

90 years of monoamine oxidase: some progress and some confusion

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

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.

Neuroprotective effects of selegiline on rat neural stem cells treated with hydrogen peroxide

Oxidative stress and reactive oxygen species generation have been implicated in the pathogenesis of several neurological disorders including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis and multiple sclerosis. In the present study, the neuroprotective effects of selegiline against hydrogen peroxide-induced oxidative stress in hippocampus-derived neural stem cells (NSCs) were evaluated. NSCs isolated from neonatal Wistar rats were pretreated with different doses of selegiline for 48 h and then exposed to 125 µM H2O2 for 30 min. Using MTT and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assays, acridine orange/ethidium bromide staining and reverse transcription-quantitative polymerase chain reaction, the effects of selegiline on cell survival, apoptosis and the expression of B-cell lymphoma 2 (Bcl-2) and heat shock protein 4 (Hspa4) in pretreated stem cells were assessed compared with a control group lacking pretreatment. The results indicated that the viability of cells pretreated with 20 µM selegiline was significantly increased compared with the control group (P<0.05). Additionally, 20 µM selegiline increased the mRNA expression of Bcl-2 and Hspa4 (P<0.05 vs. control) and suppressed oxidative stress-induced cell death (apoptosis and necrosis; P<0.05 vs. control and 10 µM groups). From these findings, it was concluded that selegiline may be a therapeutic candidate for the treatment of neurological diseases mediated by oxidative stress.

Salsolinol: an Unintelligible and Double-Faced Molecule-Lessons Learned from In Vivo and In Vitro Experiments

Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline) is a tetrahydroisoquinoline derivative whose presence in humans was first detected in the urine of Parkinsonian patients on l-DOPA (l-dihydroxyphenylalanine) medication. Thus far, multiple hypotheses regarding its physiological/pathophysiological roles have been proposed, especially related to Parkinson’s disease or alcohol addiction. The aim of this review was to outline studies related to salsolinol, with special focus on in vivo and in vitro experimental models. To begin with, the chemical structure of salsolinol together with its biochemical implications and the role in neurotransmission are discussed. Numerous experimental studies are summarized in tables and the most relevant ones are stressed. Finally, the ability of salsolinol to cross the blood–brain barrier and its possible double-faced neurobiological potential are reviewed.

Macrophages with cellular backpacks for targeted drug delivery to the brain

Most potent therapeutics are unable to cross the blood-brain barrier following systemic administration, which necessitates the development of unconventional, clinically applicable drug delivery systems. With the given challenges, biologically active vehicles are crucial to accomplishing this task. We now report a new method for drug delivery that utilizes living cells as vehicles for drug carriage across the blood brain barrier. Cellular backpacks, 7-10 μm diameter polymer patches of a few hundred nanometers in thickness, are a potentially interesting approach, because they can act as drug depots that travel with the cell-carrier, without being phagocytized. Backpacks loaded with a potent antioxidant, catalase, were attached to autologous macrophages and systemically administered into mice with brain inflammation. Using inflammatory response cells enabled targeted drug transport to the inflamed brain. Furthermore, catalase-loaded backpacks demonstrated potent therapeutic effects deactivating free radicals released by activated microglia in vitro. This approach for drug carriage and release can accelerate the development of new drug formulations for all the neurodegenerative disorders.

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.

The novel multitarget iron chelating and propargylamine drug M30 affects APP regulation and processing activities in Alzheimer's disease models

In many of the neurodegenerative diseases, such as Alzheimer's disease (AD) and AD-related disorders, as well as in the regular ageing process, excessive generation of oxidative stress (OS) and accumulation of iron levels and deposition have been observed in specific affected-brain regions and thus, regarded as contributing factors to the pathogenesis of the diseases. In AD, iron promotes amyloid β (Aβ) neurotoxicity by producing free radical damage and OS in brain areas affected by neurodegeneration, presumably by facilitating the aggregation of Aβ. In addition, it was shown that iron modulates intracellular levels of the holo amyloid precursor protein (APP) by iron-responsive elements (IRE) RNA stem loops in the 5' untranslated region (5'UTR) of the APP transcript. As a consequence of these observations, iron chelation is one of the major new therapeutic strategies for the treatment of AD. This review describes the benefits and importance of the multimodal brain permeable chimeric iron-chelating/propargylamine drug M30, concerning its neuroprotective/neurorestorative inter-related activities relevant of the pathological features ascribed to AD, with a special focus on the effect of the drug on APP regulation and processing.

Neurotrophic Effect of Asiatic acid, a Triterpene of Centella asiatica Against Chronic 1-Methyl 4-Phenyl 1, 2, 3, 6-Tetrahydropyridine Hydrochloride/Probenecid Mouse Model of Parkinson's disease: The Role of MAPK, PI3K-Akt-GSK3β and mTOR Signalling Pathways

Regulation of various signalling (Ras-MAPK, PI3K and AKT) pathways by augmented activity of neurotrophic factors (NTFs) could prevent or halt the progress of dopaminergic loss in Parkinson's disease (PD). Various in vitro and in vivo experimental studies indicated anti-parkinsonic potential of asiatic acid (AA), a pentacyclic triterpene obtained from Centella asiatica. So the present study is designed to determine the neurotrophic effect of AA against 1-methyl 4-phenyl 1, 2, 3, 6-tetrahydropyridine hydrochloride/probenecid (MPTP/p) neurotoxicity in mice model of PD. AA treatment for 5 weeks significantly attenuated MPTP/p induced motor abnormalities, dopamine depletion and diminished expressions NTFs and tyrosine kinase receptors (TrKB). We further, revealed that AA treatment significantly inhibited the MPTP/p-induced phosphorylation of MAPK/P38 related proteins such as JNK and ERK. Moreover, AA treatment increased the phosphorylation of PI3K, Akt, GSK-3β and mTOR, suggesting that AA activated PI3K/Akt/mTOR signalling pathway, which might be the cause of neuroprotection offered by AA. The present findings provided more elaborate in vivo evidences to support the neuroprotective effect of AA on dopaminergic neurons of chronic Parkinson's disease mouse model and the potential of AA to be developed as a possible new therapeutic target to treat PD.

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.

Tetramethylpyrazine Ameliorates Rotenone-Induced Parkinson's Disease in Rats: Involvement of Its Anti-Inflammatory and Anti-Apoptotic Actions

Parkinson's disease (PD) is a slowly progressive neurodegenerative movement disorder. Apoptosis, neuroinflammation, and oxidative stress are the current hypothesized mechanisms for PD pathogenesis. Tetramethylpyrazine (TMP), the major bioactive component of Ligusticum wallichii Franchat (ChuanXiong), Family Apiaceae, reportedly has anti-apoptotic, anti-inflammatory and antioxidant effects. This study investigated the role of 'TMP' in preventing rotenone-induced neurobiological and behavioral sequelae. A preliminary dose-response study was conducted where rats received TMP (10, 20, and 40 mg/kg, i.p.) concomitantly with rotenone (2 mg/kg, s.c.) for 4 weeks. Catalepsy, locomotor activity, striatal dopamine content, and tyrosine hydroxylase "TH" and α-synuclein immunoreactivity were evaluated. The selected TMP dose (20 mg/kg) was used for western blot analysis of Bax, Bcl2, and DJ-1, immunohistochemical detection of nuclear factor kappa B (NF-кB), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and glial fibrillary acidic protein (GFAP) expression, in addition to biochemical analysis of caspase-3 activity, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) levels. Results showed that TMP (20 mg/kg) significantly improved midbrain and striatal TH expression and striatal dopamine content as well as the motor deficits, compared to rotenone-treated group. These results were correlated with reduction in caspase-3 activity and α-synuclein expression, along with improvement of midbrain and striatal Bax/Bcl2 ratio compared to rotenone-treated group. TMP also attenuated rotenone-induced upregulation of Nrf2/HO-1 pathway. Furthermore, TMP downregulated rotenone-induced neuroinflammation markers: NF-кB, iNOS, COX2, and GFAP expression in both the midbrain and striatum. Taken together, the current study suggests that TMP is entitled to, at least partially, preventing PD neurobiological and behavioral deficits by virtue of its anti-apoptotic, anti-inflammatory, and antioxidant actions.

Propargylamine as functional moiety in the design of multifunctional drugs for neurodegenerative disorders: MAO inhibition and beyond

Much progress has been made in designing analogues that can potentially confer neuroprotection against debilitating neurodegenerative disorders, yet the multifactorial pathogenesis of this cluster of diseases remains a stumbling block for the successful design of an 'ultimate' drug. However, with the growing popularity of the "one drug, multiple targets" paradigm, many researchers have successfully synthesized and evaluated drug-like molecules incorporating a propargylamine function that shows potential to serve as multifunctional drugs or multitarget-directed ligands. It is the aim of this review to highlight the reported activities of these propargylamine derivatives and their prospect to serve as drug candidates for the treatment of neurodegenerative disorders.

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.

Synthesis, spectroscopy, X-ray crystallography, DFT calculations, DNA binding and molecular docking of a propargyl arms containing Schiff base

A propargyl arms containing Schiff base (L) was synthesized by the condensation of 1-[2-hydroxy-4-(prop-2-yn-1-yloxy)phenyl]ethanone with trans-1,2-diaminocyclohexane. The structure of L was characterized by IR, (1)H NMR, (13)C NMR and UV-Vis spectroscopy and by single crystal X-ray diffraction analysis. The UV-Visible spectral behavior of L in different solvents exhibits positive solvatochromism. Density functional calculation of the L in gas phase was performed by using DFT (B3LYP) method with 6-31G basis set. The computed vibrational frequencies and NMR signals of L were compared with the experimental data. Tautomeric stability study inferred that the enolimine is more stable than the ketoamine form. The charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Electronic absorption and emission spectral studies were used to study the binding of L with CT-DNA. The molecular docking was done to identify the interaction of L with A-DNA and B-DNA.

Neuroprotective and neurorestorative potential of propargylamine derivatives in ageing: focus on mitochondrial targets

The mitochondrial theory of ageing proposes that accumulation of damage to mitochondrial function and DNA mutation lead to ageing of humans and animals. It has been suggested that mitochondria play dynamic roles in regulating synaptogenesis and morphological/functional responses of synaptic activity, and thus, deteriorating of mitochondrial function (e.g., deficits of the mitochondrial respiratory enzymes, reduced calcium influx, increased accumulation of mitochondrial DNA defects/apoptotic proteins and impairment of mitochondrial membrane potential) can lead to severe neuronal energy deficit, and in the long run, to modifications in neuronal synapses and neurodegeneration in the ageing brain. Hence, considering the mechanisms by which mitochondrial impairment can lead to neuronal death, the development of neuroprotective molecules that target various mitochondrial pathogenic processes can be effective in the treatment of ageing and age-related neurodegenerative diseases. This review addresses several aspects of the neuroprotective effects of propargylamine derivatives (e.g., the monoamine oxidase-B inhibitors, selegiline and rasagiline and the multifunctional drugs, ladostigil, M30 and VAR10303) in ageing with a special focus on mitochondrial molecular protective mechanisms.

Novel monoamine oxidase inhibitors: a patent review (2012 - 2014)

INTRODUCTION

Monoamine oxidase (MAO) inhibitors, despite the initial pharmacological interest, are used in clinic for their antidepressant effect and in the management of Parkinson symptoms, due to the established neuroprotective action. Efficacy and tolerability emerged from large-scale and randomized clinical trials.

AREAS COVERED

Thirty-six patents range from April 2012 to September 2014. The number of chemotypes with inhibitory effects on MAO is truly high (40 synthetic compounds, 22 natural products and 6 plant extracts reported and licensed), and the present review is comprehensive of all compounds, which have been patented for their relevance to clinical medicine in this period range (27 patents). Moreover, some of the collected patents deal with new formulations of compounds endowed with MAO inhibitory properties (two patents) and new therapeutic options/drug associations for already known MAO inhibitors (seven patents).

EXPERT OPINION

The patents reported in this review showed that the interest in this field is constant and mainly devoted to the study of selective MAO-B inhibitors, used as drugs for the treatment of neurological disorders. The development of novel human MAO inhibitors took advantage of the discovery of new therapeutic targets (cancer, hair loss, muscle dystrophies, cocaine addiction and inflammation), the recognized role of MAOs as molecular biomarkers and their activity in other tissues.

Design, synthesis, and evaluation of multitarget-directed selenium-containing clioquinol derivatives for the treatment of Alzheimer's disease

A series of selenium-containing clioquinol derivatives were designed, synthesized, and evaluated as multifunctional anti-Alzheimer's disease (AD) agents. In vitro examination showed that several target compounds exhibited activities such as inhibition of metal-induced Aβ aggregation, antioxidative properties, hydrogen peroxide scavenging, and the prevention of copper redox cycling. A parallel artificial membrane permeation assay indicated that selenium-containing clioquinol derivatives possessed significant blood-brain barrier (BBB) permeability. Compound 8a, with a propynylselanyl group linked to the oxine, demonstrated higher hydrogen peroxide scavenging and intracellular antioxidant activity than clioquinol. Furthermore, 8a exhibited significant inhibition of Cu(II)-induced Aβ1-42 aggregation and was capable of disassembling the preformed Cu(II)-induced Aβ aggregates. Therefore, 8a is an excellent multifunctional promising compound for development of novel drugs for AD.

Update on the pharmacology of selective inhibitors of MAO-A and MAO-B: focus on modulation of CNS monoamine neurotransmitter release

Inhibitors of monoamine oxidase (MAO) were initially used in medicine following the discovery of their antidepressant action. Subsequently their ability to potentiate the effects of an indirectly-acting sympathomimetic amine such as tyramine was discovered, leading to their limitation in clinical use, except for cases of treatment-resistant depression. More recently, the understanding that: a) potentiation of indirectly-acting sympathomimetic amines is caused by inhibitors of MAO-A but not by inhibitors of MAO-B, and b) that reversible inhibitors of MAO-A cause minimal tyramine potentiation, has led to their re-introduction to clinical use for treatment of depression (reversible MAO-A inhibitors and new dose form MAO-B inhibitor) and treatment of Parkinson's disease (MAO-B inhibitors). The profound neuroprotective properties of propargyl-based inhibitors of MAO-B in preclinical experiments have drawn attention to the possibility of employing these drugs for their neuroprotective effect in neurodegenerative diseases, and have raised the question of the involvement of the MAO-mediated reaction as a source of reactive free radicals. Despite the long-standing history of MAO inhibitors in medicine, the way in which they affect neuronal release of monoamine neurotransmitters is still poorly understood. In recent years, the detailed chemical structure of MAO-B and MAO-A has become available, providing new possibilities for synthesis of mechanism-based inhibitors. This review describes the latest advances in understanding the way in which MAO inhibitors affect the release of the monoamine neurotransmitters dopamine, noradrenaline and serotonin (5-HT) in the CNS, with an accent on the importance of these effects for the clinical actions of the drugs.

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.

Role of lipid peroxide in the neurodegenerative disorders

Nervous system controls all the organs in the living like a symphony. In this chapter, the mechanism of neuronal death in aged is discussed in relation to oxidative stress. Polyunsaturated fatty acid (PUFA) is known to be rich in the membranous component of the neurons and plays an important role in maintaining the neuronal functions. Recent reports revealed that oxidation of omega-3 and omega-6 PUFAs, such as docosahexaenoic acid (DHA) and arachidonic acid (ARA), are potent antioxidant but simultaneously, their oxidation products are potentially toxic. In this chapter, the existence of early oxidation products of PUFA is examined in the samples from neurodegenerative disorders and the cellular model. Accumulation of proteins with abnormal conformation is suggested to induce neuronal death by disturbance of proteolysis and mitochondrial function. The role of lipid peroxide and lipid-derived aldehyde adduct proteins is discussed in relation to brain ageing and age-related neurodegeneration.

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.

Macrophages offer a paradigm switch for CNS delivery of therapeutic proteins

AIMS

Active targeted transport of the nanoformulated redox enzyme, catalase, in macrophages attenuates oxidative stress and as such increases survival of dopaminergic neurons in animal models of Parkinson's disease. Optimization of the drug formulation is crucial for the successful delivery in living cells. We demonstrated earlier that packaging of catalase into a polyion complex micelle ('nanozyme') with a synthetic polyelectrolyte block copolymer protected the enzyme against degradation in macrophages and improved therapeutic outcomes. We now report the manufacture of nanozymes with superior structure and therapeutic indices.

METHODS

Synthesis, characterization and therapeutic efficacy of optimal cell-based nanoformulations are evaluated.

RESULTS

A formulation design for drug carriers typically works to avoid entrapment in monocytes and macrophages focusing on small-sized nanoparticles with a polyethylene glycol corona (to provide a stealth effect). By contrast, the best nanozymes for delivery in macrophages reported in this study have a relatively large size (≈ 200 nm), which resulted in improved loading capacity and release from macrophages. Furthermore, the cross-linking of nanozymes with the excess of a nonbiodegradable linker ensured their low cytotoxicity, and efficient catalase protection in cell carriers. Finally, the 'alternatively activated' macrophage phenotype (M2) utilized in these studies did not promote further inflammation in the brain, resulting in a subtle but statistically significant effect on neuronal regeneration and repair in vivo.

CONCLUSION

The optimized cross-linked nanozyme loaded into macrophages reduced neuroinflammatory responses and increased neuronal survival in mice. Importantly, the approach for nanoformulation design for cell-mediated delivery is different from the common requirements for injectable formulations.

Exploring the structural basis of the selective inhibition of monoamine oxidase A by dicarbonitrile aminoheterocycles: role of Asn181 and Ile335 validated by spectroscopic and computational studies

Since cyanide potentiates the inhibitory activity of several monoamine oxidase (MAO) inhibitors, a series of carbonitrile-containing aminoheterocycles was examined to explore the role of nitriles in determining the inhibitory activity against MAO. Dicarbonitrile aminofurans were found to be potent, selective inhibitors against MAO A. The origin of the MAO A selectivity was identified by combining spectroscopic and computational methods. Spectroscopic changes induced in MAO A by mono- and dicarbonitrile inhibitors were different, providing experimental evidence for distinct binding modes to the enzyme. Similar differences were also found between the binding of dicarbonitrile compounds to MAO A and to MAO B. Stabilization of the flavin anionic semiquinone by monocarbonitrile compounds, but destabilization by dicarbonitriles, provided further support to the distinct binding modes of these compounds and their interaction with the flavin ring. Molecular modeling studies supported the role played by the nitrile and amino groups in anchoring the inhibitor to the binding cavity. In particular, the results highlight the role of Asn181 and Ile335 in assisting the interaction of the nitrile-containing aminofuran ring. The network of interactions afforded by the specific attachment of these functional groups provides useful guidelines for the design of selective, reversible MAO A inhibitors.

Autophagy and apoptosis dysfunction in neurodegenerative disorders

Autophagy and apoptosis are basic physiologic processes contributing to the maintenance of cellular homeostasis. Autophagy encompasses pathways that target long-lived cytosolic proteins and damaged organelles. It involves a sequential set of events including double membrane formation, elongation, vesicle maturation and finally delivery of the targeted materials to the lysosome. Apoptotic cell death is best described through its morphology. It is characterized by cell rounding, membrane blebbing, cytoskeletal collapse, cytoplasmic condensation, and fragmentation, nuclear pyknosis, chromatin condensation/fragmentation, and formation of membrane-enveloped apoptotic bodies, that are rapidly phagocytosed by macrophages or neighboring cells. Neurodegenerative disorders are becoming increasingly prevalent, especially in the Western societies, with larger percentage of members living to an older age. They have to be seen not only as a health problem, but since they are care-intensive, they also carry a significant economic burden. Deregulation of autophagy plays a pivotal role in the etiology and/or progress of many of these diseases. Herein, we briefly review the latest findings that indicate the involvement of autophagy in neurodegenerative diseases. We provide a brief introduction to autophagy and apoptosis pathways focusing on the role of mitochondria and lysosomes. We then briefly highlight pathophysiology of common neurodegenerative disorders like Alzheimer's diseases, Parkinson's disease, Huntington's disease and Amyotrophic lateral sclerosis. Then, we describe functions of autophagy and apoptosis in brain homeostasis, especially in the context of the aforementioned disorders. Finally, we discuss different ways that autophagy and apoptosis modulation may be employed for therapeutic intervention during the maintenance of neurodegenerative disorders.

Promise of neurorestoration and mitochondrial biogenesis in Parkinson's disease with multi target drugs: an alternative to stem cell therapy

There is an unmet need in progressive neurodegenerative diseases such as Parkinson's and Alzheimer's diseases. The present therapeutics for these diseases at best is symptomatic and is not able to delay disease or possess disease modifying activity. Thus an approach to drug design should be made to slow or halt progressive course of a neurological disorder by interfering with a disease-specific pathogenetic process. This would entail the ability of the drug to protect neurons by blocking the common pathway for neuronal injury and cell death and the ability to promote regeneration of neurons and restoration of neuronal function. We have now developed a number of multi target drugs which possess neuroprotective, and neurorestorative activity as well as being able to active PGC-1α (peroxisome proliferator-activated receptor γ coactivator-1α), SIRT1 (NAD-dependent deacetylase protein) and NTF (mitochondrial transcription factor) that are intimately associated with mitochondrial biogenesis.

Selegiline rescues gait deficits and the loss of dopaminergic neurons in a subacute MPTP mouse model of Parkinson's disease

The monoamine oxidase type-B (MAO-B) inhibitor, selegiline, is often recommended as a first-line treatment for Parkinson's disease (PD) and has been shwon to possess neuroprotective effects. The aim of the present study was to determine whether selegiline increases the levels of the neurotrophic factors (NTFs), glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), and whether it rescues motor dysfunction and the loss of dopaminergic neurons in mice with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced lesions. We found that the oral administration of selegiline (1.0 mg/kg/day for 14 days) successfully suppressed the MPTP-induced reduction of nigral dopaminergic neurons and striatal fibers (192.68 and 162.76% of MPTP-exposed animals, respectively; both P<0.001). Moreover, improvements in gait dysfunction were observed after 7 and 14 days of a low dose of selegiline that is reported not to inhibit MAO‑B. Furthermore, there was a significant increase in GDNF and BDNF mRNA (2.10 and 2.75-fold) and protein levels (143.53 and 157.05%) in the selegiline-treated mice compared with the saline-treated MPTP-exposed mice. In addition, the Bax/Bcl-2 gene and protein expression ratios were significantly increased in the MPTP-exposed mice, and this effect was reversed by selegiline. Correlation analysis revealed that gait measurement and GDNF/BDNF levels positively correlated with the number of dopaminergic neurons. These findings demonstrate that selegiline has neurorescue effects that are possibly associated with the induction of NTFs and anti-apoptotic genes.

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.

Controlled release of rasagiline mesylate promotes neuroprotection in a rotenone-induced advanced model of Parkinson's disease

Microencapsulation of rasagiline mesylate (RM) into PLGA microspheres was performed by method A (O/W emulsion) and method B (W/O/W double emulsion). The best formulation regarding process yield, encapsulation efficiency and in vitro drug release was that prepared with method A, which exhibited constant drug release for two weeks (K(0)=62.3 μg/day/20mg microspheres). Exposure of SKN-AS cells to peroxide-induced oxidative stress (1 mM) resulted in cell apoptosis which was significantly reduced by RM (40.7-102.5 μM) as determined by cell viability, ROS production and DNA fragmentation. Daily doses of rotenone (2 mg/kg) given i.p. to rats for 45 days induced neuronal and behavioral changes similar to those occurring in PD. Once an advanced stage of PD was achieved, animals received RM in saline (1 mg/kg/day) or encapsulated within PLGA microspheres (amount of microspheres equivalent to 15 mg/kg RM given on days 15 and 30). After 45 days RM showed a robust effect on all analytical outcomes evaluated with non-statistically significant differences found between its administration in solution or within microparticles however; with this controlled release system administration of RM could be performed every two weeks thereby making this new therapeutic system an interesting approach for the treatment of PD.

Adjunctive therapy in Parkinson's disease: the role of rasagiline

Parkinson's disease is the second most common neurodegenerative disorder, currently affecting 1.5 million people in the US. In this review, we describe the diagnostic and pathological features of Parkinson's disease, as well as its clinical course. We then review pharmacologic treatments for the disease, with a particular focus on therapies adjunctive to levodopa and specifically the role of rasagiline. We review the four pivotal rasagiline trials, and discuss rasagiline and its use as adjunctive therapy for Parkinson's disease. Finally, we discuss potential side effects, drug interactions, and other practical aspects concerning the use of rasagiline in Parkinson's disease.