Parkinson’s disease management strategies

Developing a Multi-target Model to Predict the Activity of Monoamine Oxidase A and B Drugs

INTRODUCTION

Monoamine oxidase inhibitors (MAOIs) are compounds largely used in the treatment of Parkinson's disease (PD), Alzheimer's disease and other neuropsychiatric disorders since they are closely related to the MAO enzymes activity. The two isoforms of the MAO enzymes, MAO-A and MAO-B, are responsible for the degradation of monoamine neurotransmitters and due to this, relevant efforts have been devoted to finding new compounds with more selectivity and less side effects. One of the most used approaches is based on the use of computational approaches since they are time and money-saving and may allow us to find a more relevant structure-activity relationship.

OBJECTIVE

In this manuscript, we will review the most relevant computational approaches aimed at the prediction and development of new MAO inhibitors. Subsequently, we will also introduce a new multitask model aimed at predicting MAO-A and MAO-B inhibitors.

METHODS

The QSAR multi-task model herein developed was based on the use of the linear discriminant analysis. This model was developed gathering 5,759 compounds from the public dataset Chembl. The molecular descriptors used was calculated using the Dragon software. Classical statistical tests were performed to check the validity and robustness of the model.

RESULTS

The herein proposed model is able to correctly classify all the 5,759 compounds. All the statistical performed tests indicated that this model is robust and reproducible.

CONCLUSION

MAOIs are compounds of large interest since they are largely used in the treatment of very serious illness. These inhibitors may lose efficacy and produce severe side effects. Due to this, the development of selective MAO-A or MAO-B inhibitors is crucial for the treatment of these diseases and their effects. The herein proposed multi-target QSAR model may be a relevant tool in the development of new and more selective MAO inhibitors.

Perampanel but Not Amantadine Prevents Behavioral Alterations and Epileptogenesis in Pilocarpine Rat Model of Status Epilepticus

Pilocarpine-induced status epilepticus (SE), which results in the development of spontaneous recurrent seizures (SRSs) activates glutamatergic receptors that contribute to seizure sustenance and neuronal cell death. In the current study, we evaluate whether the exposure to perampanel, an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor blocker, or amantadine, a N-methyl-D-aspartic acid (NMDA) receptor blocker would reduce the SE-induced long-term consequences. SE was induced in adult male Sprague Dawley rats with pilocarpine. Perampanel or amantadine was injected 10 or 60 min after SE onset. The efficacy of either, in overcoming pilocarpine-induced SE was assessed using electroencephalogram (EEG) recordings. In addition, alterations in cognitive function, development of spontaneous recurrent seizures (SRSs), and hippocampal damage that are generally encountered after SE were also assessed at 72 h and 5 weeks after the induction of SE. Our results indicate that both early and late treatment with perampanel but not amantadine significantly reduced seizure activity. Furthermore, perampanel but not amantadine, reversed the memory deficits in Y-maze and novel object recognition (NOR) tests and retarded the appearance of SRSs. Moreover, perampanel treatment led to reduced SE-induced caspase-3 activation in the hippocampal lysates. Taken together, the data obtained from the study reveals that blocking AMPA receptors by perampanel can modify SE-induced long-term consequences. Our results may provide a proof of principle for the potential therapeutic application of perampanel in clinical use for status epilepticus in future.

Safinamide: a new hope for Parkinson's disease?

The loss of dopaminergic neurons (DAn) and reduced dopamine (DA) production underlies the reasoning behind the gold standard treatment for Parkinson's disease (PD) using levodopa (L-DOPA). Recently licensed by the European Medicine Agency (EMA) and US Food and Drug Administration (FDA), safinamide [a monoamine oxidase B (MOA-B) inhibitor] is an alternative to L-DOPA; as we discuss here, it enhances dopaminergic transmission with decreased secondary effects compared with L-DOPA. In addition, nondopaminergic actions (neuroprotective effects) have been reported, with safinamide inhibiting glutamate release and sodium/calcium channels, reducing the excitotoxic input to dopaminergic neuronal death. Effects of safinamide have been correlated with the amelioration of non-motor symptoms (NMS), although these remain under discussion. Overall, safinamide can be considered to have potential antidyskinetic and neuroprotective effects and future trials and/or studies should be performed to provide further evidence for its potential as an anti-PD drug.

Actinobacterial melanins: current status and perspective for the future

Melanins are enigmatic pigments that are produced by a wide variety of microorganisms including several species of bacteria and fungi. Melanins are biological macromolecules with multiple important functions, yet their structures are not well understood. Melanins are frequently used in medicine, pharmacology, and cosmetics preparations. Melanins also have great application potential in agriculture industry. They have several biological functions including photoprotection, thermoregulation, action as free radical sinks, cation chelators, and antibiotics. Plants and insects incorporate melanins as cell wall and cuticle strengtheners, respectively. Actinobacteria are the most economically as well as biotechnologically valuable prokaryotes. However, the melanin properties are, in general, poorly understood. In this review an evaluation is made on the present state of research on actinobacterial melanins and its perspectives. The highlights include the production and biotechnological applications of melanins in agriculture, food, cosmetic and medicinal fields. With increasing advancement in science and technology, there would be greater demands in the future for melanins produced by actinobacteria from various sources.

Rational, combinatorial, and genomic approaches for engineering L-tyrosine production in Escherichia coli

Although microbial metabolic engineering has traditionally relied on rational and knowledge-driven techniques, significant improvements in strain performance can be further obtained through the use of combinatorial approaches exploiting phenotypic diversification and screening. Here, we demonstrate the combined use of global transcriptional machinery engineering and a high-throughput L-tyrosine screen towards improving L-tyrosine production in Escherichia coli. This methodology succeeded in generating three strains from two separate mutagenesis libraries (rpoA and rpoD) exhibiting up to a 114% increase in L-tyrosine titer over a rationally engineered parental strain with an already high capacity for production. Subsequent strain characterization through transcriptional analysis and whole genome sequencing allowed complete phenotype reconstruction from well-defined mutations and point to important roles for both the acid stress resistance pathway and the stringent response of E. coli in imparting this phenotype. As such, this study presents one of the first examples in which cell-wide measurements have helped to elucidate the genetic and biochemical underpinnings of an engineered cellular property, leading to the total restoration of metabolite overproduction from specific chromosomal mutations.

Binding of anti-Parkinson's disease drugs to human serum albumin is allosterically modulated

Binding of drugs to plasma proteins is an important determinant for their efficacy because it modulates drug availability to the intended target. Co-administered drugs may bind to the same protein site or to different functionally linked clefts following competitive and allosteric mechanisms. Here, we report a thermodynamic and computational characterization of the binding mode of apomorphine and benserazide, two therapeutic agents co-administered in the treatment of Parkinson's disease, to human serum albumin (HSA). Apomorphine binds to HSA with a simple equilibrium (K(d) = 3.1 x 10(-6) M). Conversely, benserazide binds to HSA with two independent equilibria (K(d1)< or = 10(-6) M and K(d2) = 5.0 x 10(-5) M). Values of K(d) and K(d2) increase to 1.5 x 10(-5) M and 5.0 x 10(-4) M, respectively, in the presence of heme. Accordingly, the K(d) value for heme binding to HSA increases from 5.0 x 10(-7) M to 4.8 x 10(-6) M and 9.2 x 10(-7) M, in the presence of saturating amounts of apomorphine and benserazide, respectively. The K(d1) value for benserazide binding to HSA is not affected by heme binding, whereas apomorphine and benserazide inhibit warfarin binding to HSA, and vice versa. Therefore, apomorphine and the second benserazide molecule bind to the warfarin site, allosterically linked to the heme site. Simulated docking of apomorphine and benserazide into the warfarin site provides favorable values of intermolecular energy (-23.0 kJ mol(-1) and -15.2 kJ mol(-1), respectively). Considering the apomorphine, benserazide, and HSA-heme plasma levels and the possible co-administration of warfarin, these results appear relevant in the management of patients affected by Parkinson's disease.

Pharmacokinetic-pharmacodynamic interaction between nebicapone, a novel catechol-o-methyltransferase inhibitor, and controlled-release levodopa/carbidopa 200 mg/50 mg : randomized, double-blind, placebo-controlled, crossover study in healthy subjects

BACKGROUND AND OBJECTIVES

Levodopa is the most effective symptomatic treatment for Parkinson's disease (PD), but its use is often associated with development of motor complications. These adverse responses to fluctuations in dopaminergic stimulation can be reduced by concomitant administration of a catechol-O-methyltransferase (COMT) inhibitor. Nebicapone is a new COMT inhibitor currently being developed for use as an adjunct to levodopa/dopa decarboxylase inhibitor in the treatment of PD. This article aimed to investigate the effect of single oral doses (50 mg, 100 mg and 200 mg) of nebicapone on levodopa pharmacokinetics and erythrocyte-soluble COMT (S-COMT) activity when coadministered with a single dose of controlled-release (CR) levodopa/carbidopa 200 mg/50 mg (Sinemet((R)) CR 200/50) in healthy subjects (n = 16).

METHODS

This was a randomized, double-blind, placebo-controlled, four-way crossover study in healthy subjects, with at least 5 days of washout between treatment periods.

RESULTS

There was a dose-dependent and significant increase in levodopa extent of exposure (area under the plasma concentration-time curve from time zero to infinity [AUC(infinity)]) without a significant change in peak exposure (maximum plasma concentration; [C(max)]). Using placebo as a reference, levodopa geometric mean ratios (GMRs) and 90% CIs following nebicapone 50 mg, 100 mg and 200 mg were, respectively, 1.13 (0.98, 1.30), 1.04 (0.90, 1.19) and 1.10 (0.96, 1.27) for C(max) and 1.26 (1.16, 1.34), 1.37 (1.27, 1.75) and 1.47 (1.42, 1.65) for AUC(infinity). For 3-O-methyldopa (3-OMD), the GMRs and 90% CIs were, respectively, 0.61 (0.55, 0.67), 0.45 (0.41, 0.50) and 0.33 (0.30, 0.36) for C(max) and 0.69 (0.61, 0.78), 0.53 (0.41, 0.61) and 0.41 (0.37, 0.47) for AUC(infinity). Nebicapone dose dependently and significantly decreased COMT activity. Maximum COMT inhibition occurred at 1.5-2.4 hours post-dose and ranged from 56% to 73% with nebicapone 50 mg and 200 mg, respectively. There was a good correlation between plasma concentrations of nebicapone and inhibition of S-COMT activity. Treatments were well tolerated.

CONCLUSION

Following concomitant administration with levodopa/carbidopa CR 200 mg/50 mg, single doses of nebicapone 50 mg, 100 mg and 200 mg significantly and dose-dependently inhibited S-COMT activity, increased systemic exposure to levodopa, and reduced 3-OMD formation.

Contributions of non-human primates to neuroscience research

Non-human primates have a small but important role in basic and translational biomedical research, owing to similarities with human beings in physiology, cognitive capabilities, neuroanatomy, social complexity, reproduction, and development. Although non-human primates have contributed to many areas of biomedical research, we review here their unique contributions to work in neuroscience, and focus on four domains: Alzheimer's disease, neuroAIDS, Parkinson's disease, and stress. Our discussion includes, for example, the role of non-human primates in development of new treatments (eg, stem cells, gene transfer) before phase I clinical trials in patients; basic research on disease pathogenesis; and understanding neurobehavioural outcomes resulting from genotype-environment interactions.

Effects of nebicapone on levodopa pharmacokinetics, catechol-O-methyltransferase activity, and motor fluctuations in patients with Parkinson disease

OBJECTIVE

To investigate the effects of nebicapone, a new catechol-O-methyltransferase (COMT) inhibitor, on levodopa pharmacokinetics, COMT activity, and motor fluctuations in Parkinson disease in comparison to placebo and entacapone.

METHODS

Randomized, double-blind, placebo-controlled, 4-way crossover study consisting of 4 treatment periods (6-9 days duration each) in 19 patients (65.3 +/- 8.5 years) treated with carbidopa/levodopa 3 to 7 times per day. Nebicapone/entacapone/placebo and carbidopa/levodopa doses were administered concomitantly. At the end of each period, a levodopa test was performed, and levodopa and 3-O-methyldopa levels and COMT activity were assayed.

RESULTS

After 75 mg nebicapone, 150 mg nebicapone, and 200 mg entacapone, levodopa area under the plasma concentration time curve significantly increased 28.1, 48.4, and 33.3%, and 3-O-methyldopa area under the plasma concentration time curve significantly decreased 59.2, 70.8, and 59.1%, respectively. Peak COMT inhibition was similar between active treatments, but extent of COMT inhibition was more sustained with 75 and 150 mg nebicapone than with 200 mg entacapone. After the levodopa test doses, ON time significantly increased 29 minutes with 75 mg nebicapone, 45 minutes with 150 mg nebicapone, and 16 minutes with 200 mg entacapone. Patients' diaries showed a decrease in daily OFF time of 109 minutes with 75 mg nebicapone, 103 minutes with 150 mg nebicapone, and 71 minutes with 200 mg entacapone, and an increase in daily ON time of 74, 101, and 74 minutes, respectively. Treatments were generally well tolerated and safe; no relevant changes in liver function tests were reported.

CONCLUSIONS

Nebicapone, a new COMT inhibitor, significantly decreased COMT activity, increased systemic exposure to levodopa, and improved motor response. Nebicapone deserves further evaluation in larger samples of patients.

Nonhuman Primate Models of Parkinson's Disease

Nonhuman primate (NHP) models of Parkinson's disease (PD) play an essential role in the understanding of PD pathophysiology and the assessment of PD therapies. NHP research enabled the identification of environmental risk factors for the development of PD. Electrophysiological studies in NHP models of PD identified the neural circuit responsible for PD motor symptoms, and this knowledge led to the development of subthalamic surgical ablation and deep brain stimulation. Similar to human PD patients, parkinsonian monkeys are responsive to dopamine replacement therapies and present complications associated with their long-term use, a similarity that facilitated the assessment of new symptomatic treatments, such as dopaminergic agonists. New generations of compounds and novel therapies that use directed intracerebral delivery of drugs, cells, and viral vectors benefit from preclinical evaluation in NHP models of PD. There are several NHP models of PD, each with characteristics that make it suitable for the study of different aspects of the disease or potential new therapies. Investigators who use the models and peer scientists who evaluate their use need information about the strengths and limitations of the different PD models and their methods of evaluation. This article provides a critical review of available PD monkey models, their utilization, and how they compare to emerging views of PD as a multietiologic, multisystemic disease. The various models are particularly useful for representing different aspects of PD at selected time points. This conceptualization provides clues for the development of new NHP models and facilitates the clinical translation of findings. As ever, successful application of any model depends on matching the model to the scientific question to be answered. Adequate experimental designs, with multiple outcome measures of clinical relevance and an appropriate number of animals, are essential to minimize the limitations of models and increase their predictive clinical validity.

The Lee Silverman Voice Treatment® for voice, speech and other orofacial disorders in patients with Parkinson’s disease

Parkinson’s disease (PD) impairs voice, speech, swallowing and facial expressions, thus affecting communication, food intake, work, socialization and overall health and quality of life. This article reviews current research on the characteristics and features of these disorders in individuals with PD, and the types of treatment techniques available (medical, surgical or behavioral), with emphasis on the Lee Silverman Voice Treatment (LSVT®) as the treatment of choice to improve voice, speech and other orofacial functions. LSVT addresses major deficits underlying voice and speech in PD, namely, impaired scaling of movement amplitude and poor perception and self-regulation of vocal output. Based upon this, LSVT emphasizes increased amplitude of vocal output through intensive training in increased vocal loudness (with good voice quality), recalibration of vocal loudness perception and self-regulation of vocal effort. The potential contribution of LSVT and analogous behavioral treatment approaches to neural plasticity is also addressed, as are directions for future research.