Therapies for dopaminergic-induced dyskinesias in parkinson disease

Acupuncture for the Treatment of Neuropsychiatric Symptoms in Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

Neuropsychiatric symptoms (NPSs) of Parkinson's disease (PD) have received increasing attention, but effective treatment options remain limited. Acupuncture may have clinical benefits for NPSs in PD patients, but high-quality evidence supporting this possibility still needs to be discovered. Therefore, we conducted a meta-analysis to evaluate the effect of acupuncture treatment on NPSs in PD patients.

METHODS

Randomized controlled trials (RCTs) of acupuncture treatment for PD retrieved from the following electronic databases: PubMed, Embase, Cochrane Library, Web of Science, and Scopus, were used to evaluate NPSs of PD patients. The Cochrane Intervention System Evaluation Manual assessed the methodological quality.

RESULTS

A total of 13 RCTs involving 719 patients were included. The results showed that compared with medication alone or sham acupuncture, acupuncture improved sleep quality in PD patients, with Parkinson's Disease Sleep Scale (PDSS) [standardized mean difference (SMD)= 0.48, 95% confidence interval (CI)= 0.242 to 0.793, P = 0.001]. The I scores and total scores on Unified Parkinson's Disease Rating Scale (UPDRS) indicated acupuncture treatment was effective (SMD=-0.66, 95%CI=-0.66 to -0.18, P = 0.042; SMD=-0.77, 95%CI=-1.31 to -0.23, P = 0.005). Results of the Epworth Sleepiness Scale (ESS) and Parkinson's Disease Questionnaire-39 (PDQ-39) showed no statistically significant differences (SMD=-0.27, 95%CI=-0.08 to 0.62, P = 0.128; SMD=-0.20, 95%CI=-0.42 to 0.01, P = 0.554). Anxiety and depression research had no significant differences due to the excessive inter-study bias.

CONCLUSION

Acupuncture treatment can improve sleep quality, psychological and behavioral alterations, and the overall condition of PD patients. However, the study revealed no significant positive intervention effects on anxiety, depression, and quality of life, underscoring the necessity for continued research to elucidate these domains' intricacies and develop productive therapeutic approaches.

7-Nitroindazole reduces L-DOPA-induced dyskinesias in non-human Parkinsonian primate

Nitric oxide (NO) plays a pivotal role in integrating dopamine transmission in the basal ganglia and has been implicated in the pathogenesis of Parkinson disease (PD). The objective of this study was to ascertain whether the NO synthase inhibitor, 7-nitroindazole (7-NI), is able to reduce L-DOPA-induced dyskinesias (LIDs) in a non-human primate model of PD chronically intoxicated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Six Parkinsonian macaques were treated daily with L-DOPA for 3-4 months until they developed LIDs. Three animals were then co-treated with a single dose of 7-NI administered 45 min before each L-DOPA treatment. Dyskinetic MPTP-treated monkeys showed a significant decrease in LIDs compared with their scores without 7-NI treatment (p < 0.05). The anti-Parkinsonian effect of L-DOPA was similar in all three monkeys with and without 7-NI co-treatment. This improvement was significant with respect to the intensity and duration of LIDs while the beneficial effect of L-DOPA treatment was maintained and could represent a promising therapy to improve the quality of life of PD patients.

Continuous dopaminergic stimulation counteracts L-DOPA-induced overactivity of Ca2+ in 6-OHDA-lesioned rats

In the clinical treatment of Parkinson's disease (PD), the emergence of L-DOPA-induced dyskinesia (LID) and other motor symptoms remains a restrictive factor for the use of levodopa (L-DOPA). Our objective was to test the effect of continuous dopaminergic stimulation (CDS) on LID and the mechanism of its effect on the calcium (Ca²⁺) signaling pathway. 6-OHDA (6-hydroxydopamine)-treated rats were administered 1% CMC-Na, L-DOPA, rotigotine behenate (RGTB), and L-DOPA + RGTB, respectively, for 28 days. During the treatment, the abnormal involuntary movement (AIM) scores were conducted on days 1, 5, 10, 14, 19, 23 and 28 after the first dose. Subsequently, the number of tyrosine hydroxylase (TH)-positive neurons was detected by immunohistochemistry. Additionally, the changes in Ca²⁺ were detected using a laser confocal technique, and the related proteins, such as neuronal NOS (nNOS), BAX, BCL2, CaMKII, P-CaMKII, and PSD-95, were measured by Western blot. Transmission electron microscopy (TEM) was used to investigate the changes in synaptic structure. The data showed that CDS reduced the AIM scores, increased the expression of TH in the substantia nigra (SN), decreased the expression of nNOS and BAX/BCL2ratio in the striatum, reduced the Ca²⁺ influx induced by L-DOPA and inhibited the Ca²⁺ signaling pathways of dopamine neurons in the striatum. Moreover, the overactivity of synapses induced by L-DOPA was inhibited by CDS. These data further support the hypothesis that continuous delivery of a dopamine agonist reduces the risk of LID induction. Moreover, RGTB could be a promising treatment for PD by simulating CDS.

Breathing new life into neurotoxic-based monkey models of Parkinson's disease to study the complex biological interplay between serotonin and dopamine

Numerous clinical studies have shown that the serotonergic system also degenerates in patients with Parkinson's disease. The causal role of this impairment in Parkinson's symptomatology and the response to treatment remains to be refined, in particular thanks to approaches allowing the two components DA and 5-HT to be isolated if possible. We have developed a macaque monkey model of Parkinson's disease exhibiting a double lesion (dopaminergic and serotonergic) thanks to the sequential use of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and MDMA (3,4-methylenedioxy-N-methamphetamine) (or MDMA prior MPTP). We characterized this monkey model by multimodal imaging (PET, positron emission tomography with several radiotracers; DTI, diffusion tensor imaging), behavioral assessments (parkinsonism, dyskinesia, neuropsychiatric-like behavior) and post-mortem analysis (with DA and 5-HT markers). When administrated after MPTP, MDMA damaged the 5-HT presynaptic system without affecting the remaining DA neurons. The lesion of 5-HT fibers induced by MDMA altered rigidity and prevented dyskinesia and neuropsychiatric-like symptoms induced by levodopa therapy in MPTP-treated animals. Interestingly also, prior MDMA administration aggravates the parkinsonian deficits and associated DA injury. Dystonic postures, action tremor and global spontaneous activities were significantly affected. All together, these data clearly indicate that late or early lesions of the 5-HT system have a differential impact on parkinsonian symptoms in the macaque model of Parkinson's disease. Whether MDMA has an impact on neuropsychiatric-like symptoms such as apathy, anxiety, depression remains to be addressed. Despite its limitations, this toxin-based double-lesioned monkey model takes on its full meaning and provides material for the experimental study of the heterogeneity of patients.

Screening of Parkinsonian subtle fine-motor impairment from touchscreen typing via deep learning

Fine-motor impairment (FMI) is progressively expressed in early Parkinson’s Disease (PD) patients and is now known to be evident in the immediate prodromal stage of the condition. The clinical techniques for detecting FMI may not be robust enough and here, we show that the subtle FMI of early PD patients can be effectively estimated from the analysis of natural smartphone touchscreen typing via deep learning networks, trained in stages of initialization and fine-tuning. In a validation dataset of 36,000 typing sessions from 39 subjects (17 healthy/22 PD patients with medically validated UPDRS Part III single-item scores), the proposed approach achieved values of area under the receiver operating characteristic curve (AUC) of 0.89 (95% confidence interval: 0.80–0.96) with sensitivity/specificity: 0.90/0.83. The derived estimations result in statistically significant (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p<0.05$$\end{document}p<0.05) correlation of 0.66/0.73/0.58 with the clinical standard UPDRS Part III items 22/23/31, respectively. Further validation analysis on 9 de novo PD patients vs. 17 healthy controls classification resulted in AUC of 0.97 (0.93–1.00) with 0.93/0.90. For 253 remote study participants, with self-reported health status providing 252.000 typing sessions via a touchscreen typing data acquisition mobile app (iPrognosis), the proposed approach predicted 0.79 AUC (0.66–0.91) with 0.76/0.71. Remote and unobtrusive screening of subtle FMI via natural smartphone usage, may assist in consolidating early and accurate diagnosis of PD.

l-DOPA and Its Receptor GPR143: Implications for Pathogenesis and Therapy in Parkinson's Disease

l-3,4-Dihydroxyphenylalanine (l-DOPA) is the most effective therapeutic agent for Parkinson's disease (PD). l-DOPA is traditionally believed to be an inert amino acid that exerts actions and effectiveness in PD through its conversion to dopamine. In contrast to this generally accepted idea, l-DOPA is proposed to be a neurotransmitter. Recently, GPR143 (OA1), the gene product of ocular albinism 1 was identified as a receptor candidate for l-DOPA. GPR143 is widely expressed in the central and peripheral nervous system. GPR143 immunoreactivity was colocalized with phosphorylated α-synuclein in Lewy bodies in PD brains. GPR143 may contribute to the therapeutic effectiveness of l-DOPA and might be related to pathogenesis of PD.

Amantadine Extended-Release (GOCOVRI™): A Review in Levodopa-Induced Dyskinesia in Parkinson's Disease

Amantadine extended-release (ER) capsules (GOCOVRI^™) are approved in the USA for the treatment of dyskinesia in patients with Parkinson's disease (PD) receiving levodopa-based therapy, with or without concomitant dopaminergic medications. With a recommended dosage of 274 mg once daily at bedtime, this new formulation of amantadine allows a more gradual time to peak plasma amantadine concentration and higher drug concentrations in the morning and throughout the day, the time period when levodopa-induced dyskinesia (LID) is the most problematic. In 13-week (EASE LID 3) and 25-week (EASE LID), randomized, double-blind phase III trials, once-daily amantadine ER 274 mg capsules significantly improved levodopa-induced dyskinesia (LID), while also increasing ON time without troublesome dyskinesia and reducing OFF time and ON time with troublesome dyskinesia from the morning and throughout the day, compared with placebo. In the ongoing, longer-term EASE LID 2 study (with interim results reported for up to 64 weeks), patients previously treated with amantadine ER maintained improvements in LID, as per patient-reported Unified Dyskinesia Rating Scale (UDysRS) scoring and ON/OFF times. Amantadine ER was generally well tolerated, with most adverse events (AEs) being transient and mild or moderate in severity. The most common (incidence > 15%) treatment-related AEs in the placebo-controlled trials were hallucinations, dizziness, dry mouth and peripheral oedema. While long-term data are needed to establish durability of response and safety, including the completion of the ≈ 2-year EASE LID 2 study, current evidence indicates that amantadine ER is an effective treatment option to consider in the management of LID in PD patients.

Pathophysiology of dyskinesia and behavioral disorders in non-human primates: the role of serotonergic fibers

The MPTP monkey model of Parkinson's disease (PD) has allowed huge advances regarding the understanding of the pathological mechanisms of PD and L-DOPA-induced adverse effects. Among the main findings were the imbalance between the efferent striatal pathways in opposite directions between the hypokinetic and hyperkinetic states of PD. In both normal and parkinsonian monkeys, the combination of behavioral and anatomical studies has allowed the deciphering of the cortico-basal ganglia circuits involved in both movement and behavioral disorders. A major breakthrough has then been made regarding the hypothesis of the involvement of serotonergic fibers in the conversion of L-DOPA to dopamine when dopaminergic neurons are dying and to release it, in an uncontrolled manner, as serotonergic neurons are deprived from the machinery required for buffering dopamine from the synaptic cleft. The crucial involvement of serotonergic fibers underlying L-DOPA-induced dyskinesia (LID) has been demonstrated in both rodent and monkey models of PD, in which dyskinesia induced by L-DOPA is abolished following lesion of the serotonergic system. Moreover, the role of serotonergic fibers goes well beyond dyskinesia, as lesioning of such serotonergic fibers by MDMA in the monkey also decreased other L-DOPA-induced adverse effects such as impulsive compulsive behaviors and visual hallucinations. The same pathological mechanism, i.e., an imbalance between serotonin and dopamine terminals may, therefore, favor L-DOPA-induced adverse effects according to the basal ganglia territory it inhabits. Further non-human primate studies will be needed to demonstrate the role of such a pathological mechanism in both movement and behavioral disorders driven by L-DOPA therapy but also to determine the causal link between serotonin lesions and the expression of non-motor symptoms like apathy, depression and anxiety, frequently observed in PD patients.

The plasmalogen precursor analog PPI-1011 reduces the development of L-DOPA-induced dyskinesias in de novo MPTP monkeys

The gold standard therapy for Parkinson's disease (PD), L-3,4-dihydroxyphenylalanine (L-DOPA), induces dyskinesias in the majority of patients after years of treatment. Ethanolamine plasmalogens (PlsEtn) play critical roles in membrane structure mediated functions and as a storage depot of polyunsaturated fatty acids such as docosahexaenoic acid. We previously showed that a PlsEtn precursor PPI-1011 reduced already established L-DOPA-induced dyskinesias (LID) in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) lesioned monkeys as a PD model. We hypothesize that development of LID can be prevented with a PPI-1011 treatment in de novo MPTP-lesioned monkeys. MPTP-lesioned monkeys were treated once daily for 28days with either L-DOPA or L-DOPA+PPI-1011 (25mg/kg). The antiparkinsonian effect of L-DOPA was maintained throughout the treatment period in MPTP-lesioned monkeys treated with L-DOPA alone and L-DOPA+PPI-1011. Over the 28days of treatment, the mean dyskinesia score increased in L-DOPA-treated monkeys whereas this increase was significantly less in the L-DOPA+PPI-1011 group. This was followed by a washout period of 2 weeks of both experimental groups without treatment. Then both groups were administered once during week 7 and twice during week 8 with L-DOPA with behavioral measures recorded on treatment days. MPTP monkeys of both experimental groups administered L-DOPA in experimental week 7 showed reduced LID. During week 8, the L-DOPA group showed increased LID whereas LID remained low in the group previously treated with L-DOPA+PPI-1011. The present results suggest that PPI-1011 can prevent/delay the development of LID while maintaining the antiparkinsonian activity of L-DOPA.

Controlling Sulfuryl-Transfer Biology

In humans, the cytosolic sulfotransferases (SULTs) catalyze regiospecific transfer of the sulfuryl moiety (-SO3) from 3'-phosphoadenosine 5'-phosphosulfate to thousands of metabolites, including numerous signaling small molecules, and thus regulates their activities and half-lives. Imbalances in the in vivo set points of these reactions leads to disease. Here, with the goal of controlling sulfonation in vivo, molecular ligand-recognition principles in the SULT and nuclear receptor families are integrated in creating a strategy that can prevent sulfonation of a compound without significantly altering its receptor affinity, or inhibiting SULTS. The strategy is validated by using it to control the sulfonation and estrogen receptor (ER) activating activity of raloxifene (a US Food and Drug Administration-approved selective estrogen receptor modulator) and its derivatives. Preventing sulfonation is shown to enhance ER-activation efficacy 10(4)-fold in studies using Ishikawa cells. The strategy offers the opportunity to control sulfuryl transfer on a compound-by-compound basis, to enhance the efficacy of sulfonated drugs, and to explore the biology of sulfuryl transfer with unprecedented precision.

Motor Complications of Dopaminergic Medications in Parkinson's Disease

Motor complications are a consequence of the chronic treatment of Parkinson's disease (PD) and include motor fluctuations (wearing-off phenomenon) and levodopa-induced dyskinesia. Both can have a significant impact on functionality and quality of life; thus, proper recognition and management is essential. The phenomenology and temporal relationship of motor complications to the schedule of levodopa dosing can be helpful in characterizing them. There are several therapeutic approaches to motor complications, including pharmacological and surgical options. The authors summarize the different types of motor complications according to phenomenology and the currently available medical treatments, including ongoing trials for the management of this condition.

Drug-Induced Dyskinesia, Part 1: Treatment of Levodopa-Induced Dyskinesia

Dyskinesias encompass a variety of different hyperkinetic phenomenologies, particularly chorea, dystonia, stereotypies, and akathisia. Levodopa-induced dyskinesia (LID) is one of the main types of drug-induced dyskinesia, occurring in patients with Parkinson's disease (PD) who have been treated with levodopa for long time, but this side effect may be encountered even within a few weeks or months after initiation of levodopa therapy. Based on the temporal pattern in relationship to levodopa dosing, LIDs are divided into "peak-dose dyskinesia," "diphasic dyskinesia," and "wearing off" or "off-period" dyskinesia, of which peak-dose dyskinesia is the most common, followed by off-period, and then diphasic dyskinesia. Treatment strategy includes identifying the kind of dyskinesia and tailoring treatment accordingly. Peak-dose dyskinesia is treated mainly by reducing individual doses of levodopa and adding amantadine and dopamine agonists, whereas off-period dystonia often responds to baclofen and botulinum toxin injections. Diphasic dyskinesias, occurring particularly in patients with young-onset PD, are the most difficult to treat. While fractionation of levodopa dosage is the most frequently utilized strategy, many patients require deep brain stimulation to control their troublesome motor fluctuations and LIDs. A variety of emerging (experimental) drugs currently in development promise to provide better control of LIDs and other levodopa-related complications in the near future.

The structure of the catechin-binding site of human sulfotransferase 1A1

We are just beginning to understand the allosteric regulation of the human cytosolic sulfotransferase (SULTs) family-13 disease-relevant enzymes that regulate the activities of hundreds, if not thousands, of signaling small molecules. SULT1A1, the predominant isoform in adult liver, harbors two noninteracting allosteric sites, each of which binds a different molecular family: the catechins (naturally occurring flavonols) and nonsteroidal antiinflammatory drugs (NSAIDs). Here, we present the structure of an SULT allosteric binding site-the catechin-binding site of SULT1A1 bound to epigallocatechin gallate (EGCG). The allosteric pocket resides in a dynamic region of the protein that enables EGCG to control opening and closure of the enzyme's active-site cap. Furthermore, the structure offers a molecular explanation for the isozyme specificity of EGCG, which is corroborated experimentally. The binding-site structure was obtained without X-ray crystallography or multidimensional NMR. Instead, a SULT1A1 apoprotein structure was used to guide positioning of a small number of spin-labeled single-Cys mutants that coat the entire enzyme surface with a paramagnetic field of sufficient strength to determine its contribution to the bound ligand's transverse (T₂) relaxation from its 1D solution spectrum. EGCG protons were mapped to the protein surface by triangulation using the T₂ values to calculate their distances to a trio of spin-labeled Cys mutants. The final structure was obtained using distance-constrained molecular dynamics docking. This approach, which is readily extensible to other systems, is applicable over a wide range of ligand affinities, requires little protein, avoids the need for isotopically labeled protein, and has no protein molecular weight limitations.

How close are we to individualized medicine for Parkinson's disease?

INTRODUCTION

There is a considerable inter-individual heterogeneity in clinical features, disease course, and treatment response in Parkinson's disease (PD), which can be explained not only by disease process and clinical variables, but also by an impact from genetic factors. Evidence-based medicine relies on large randomized control trials and meta-analysis-average medicine, which ignores individual differences. However, we are now in the early phases of a paradigm shift in medicine relating to individuality and variability. The purpose of individualized medicine is to predict patients' responses to targeted therapy using diagnostic tests based on genetics or other molecular mechanisms, thus providing the right drug at the right dose at the right time.

AREAS COVERED

In this article, we outline current state of individualized medicine for PD. Expert Commentary: Pharmacogenomics, an important element of individualized medicine, is just beginning to be considered in PD. To advance the clinical use of pharmacogenomics, big data cohort for genomic research and multidisciplinary team approaches are necessary.

Target-based metabolomics for the quantitative measurement of 37 pathway metabolites in rat brain and serum using hydrophilic interaction ultra-high-performance liquid chromatography-tandem mass spectrometry

Amino acids, neurotransmitters, purines, and pyrimidines are bioactive molecules that play fundamental roles in maintaining various physiological functions. Their metabolism is closely related to the health, growth, development, reproduction, and homeostasis of organisms. Most recently, comprehensive measurements of these metabolites have shown their potential as innovative approaches in disease surveillance or drug intervention. However, simultaneous measurement of these metabolites presents great difficulties. Here, we report a novel quantitative method that uses hydrophilic interaction ultra-high-performance liquid chromatography-tandem mass spectrometry (HILIC-UPLC-MS/MS), which is highly selective, high throughput, and exhibits better chromatographic behavior than existing methods. The developed method enabled the rapid quantification of 37 metabolites, spanning amino acids, neurotransmitters, purines, and pyrimidines pathways, within 6.5 min. The compounds were separated on an ACQUITY UPLC® BEH Amide column. Serum and brain homogenate were extracted by protein precipitation. The intra- and interday precision of all of the analytes was less than 11.34 %, and the accuracy was between -11.74 and 11.51 % for all quality control (QC) levels. The extraction recoveries of serum ranged from 84.58 % to 116.43 % and those of brain samples from 80.80 % to 119.39 %, while the RSD was 14.61 % or less for all recoveries. This method was used to successfully characterize alterations in the rat brain and, in particular, their dynamics in serum. The following study was performed to simultaneously test global changes of these metabolites in a serotonin antagonist p-chlorophenylalanine (PCPA)-induced anxiety and insomnia rat model to understand the effect and mechanism of PCPA. Taken together, these results show that the method is able to simultaneously monitor a large panel of metabolites and that this protocol may represent a metabolomic method to diagnose toxicological and pathophysiological states.

Neural Differentiation of Human Pluripotent Stem Cells for Nontherapeutic Applications: Toxicology, Pharmacology, and In Vitro Disease Modeling

Human pluripotent stem cells (hPSCs) derived from either blastocyst stage embryos (hESCs) or reprogrammed somatic cells (iPSCs) can provide an abundant source of human neuronal lineages that were previously sourced from human cadavers, abortuses, and discarded surgical waste. In addition to the well-known potential therapeutic application of these cells in regenerative medicine, these are also various promising nontherapeutic applications in toxicological and pharmacological screening of neuroactive compounds, as well as for in vitro modeling of neurodegenerative and neurodevelopmental disorders. Compared to alternative research models based on laboratory animals and immortalized cancer-derived human neural cell lines, neuronal cells differentiated from hPSCs possess the advantages of species specificity together with genetic and physiological normality, which could more closely recapitulate in vivo conditions within the human central nervous system. This review critically examines the various potential nontherapeutic applications of hPSC-derived neuronal lineages and gives a brief overview of differentiation protocols utilized to generate these cells from hESCs and iPSCs.

Roles of Ca(2+)/calmodulin-dependent protein kinase II in subcellular expression of striatal N-methyl-D-aspartate receptors in l-3, 4-dihydroxyphenylalanine-induced dyskinetic rats

BACKGROUND

The role of N-Methyl-D-aspartate (NMDA) receptors is critical to the development of L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesia (LID) in Parkinson's disease (PD). Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is thought to regulate the expression and activation of NMDA receptors in LID, but the interaction between LID and CaMKII-modulated NMDA receptor activity is not clear so far.

METHODS

We used 6-hydroxydopamine-lesioned rats to create PD rat model, and at least 21 days of L-DOPA was administrated followed with or without microinjection of CaMKII inhibitor KN-93 into the lesioned striatum of all the PD rats and sham rats. A surface receptor cross-linking assay was used to distinguish expression of striatal NMDA receptors in surface and intracellular compartments.

RESULTS

L-DOPA treatment enhanced surface levels of GluN1 expression and reduced its intracellular expression, but did not change total levels of GluN1 protein in the lesioned striatum. In contrast, l-DOPA decreased GluN2A surface expression but increased its intracellular expression. L-DOPA increased GluN2B expression preferentially in the surface compartment. We also found that L-DOPA increased CaMKII autophosphorylation at T286 in striatal neurons. The inhibition of CaMKII by microinjecting CaMKII inhibitor KN-93 into the lesioned striatum largely reversed the L-DOPA-induced changes in three subunits. In addition, dyskinetic behaviors of animals were observed alleviated after treatment of KN-93.

CONCLUSION

Our research indicates that long-term L-DOPA administration activates CaMKII in striatal neurons. Activated CaMKII is involved at least in part in mediating L-DOPA-induced changes of NMDA receptors surface/intracellular expression.

Activation of PPAR gamma receptors reduces levodopa-induced dyskinesias in 6-OHDA-lesioned rats

Long-term administration of l-3,4-dihydroxyphenylalanine (levodopa), the mainstay treatment for Parkinson's disease (PD), is accompanied by fluctuations in its duration of action and motor complications (dyskinesia) that dramatically affect the quality of life of patients. Levodopa-induced dyskinesias (LID) can be modeled in rats with unilateral 6-OHDA lesions via chronic administration of levodopa, which causes increasingly severe axial, limb, and orofacial abnormal involuntary movements (AIMs) over time. In previous studies, we showed that the direct activation of CB1 cannabinoid receptors alleviated rat AIMs. Interestingly, elevation of the endocannabinoid anandamide by URB597 (URB), an inhibitor of endocannabinoid catabolism, produced an anti-dyskinetic response that was only partially mediated via CB1 receptors and required the concomitant blockade of transient receptor potential vanilloid type-1 (TRPV1) channels by capsazepine (CPZ) (Morgese et al., 2007). In this study, we showed that the stimulation of peroxisome proliferator-activated receptors (PPAR), a family of transcription factors activated by anandamide, contributes to the anti-dyskinetic effects of URB+CPZ, and that the direct activation of the PPARγ subtype by rosiglitazone (RGZ) alleviates levodopa-induced AIMs in 6-OHDA rats. AIM reduction was associated with an attenuation of levodopa-induced increase of dynorphin, zif-268, and of ERK phosphorylation in the denervated striatum. RGZ treatment did not decrease striatal levodopa and dopamine bioavailability, nor did it affect levodopa anti-parkinsonian activity. Collectively, these data indicate that PPARγ may represent a new pharmacological target for the treatment of LID.

Region- and domain-dependent action of nomifensine

The dopamine (DA) terminal fields in the rat dorsal striatum (DS) and nucleus accumbens core (NAcc) are organized as patchworks of domains that exhibit distinct kinetics of DA release and clearance. The present study used fast-scan cyclic voltammetry recordings of electrically evoked DA overflow to test the hypothesis that nomifensine might exhibit domain-dependent actions within the NAcc, as we previously found to be the case within the DS. Within the NAcc, nomifensine preferentially enhanced evoked DA overflow in the slow domains compared with the fast domains. To seek a kinetic explanation for nomifensine's selective actions, we quantified the apparent KM of DA clearance by numerically evaluating the derivative of the descending phase of the DA signal after the end of the stimulus. For comparison, we likewise quantified the apparent KM in the domains of the DS. As expected, because it is a competitive inhibitor, nomifensine significantly increased the apparent KM in both the fast and slow domains of both the NAcc and DS. However, our analysis also led to the novel finding that nomifensine preferentially increases the apparent KM in the NAcc compared with the DS; the apparent KM increased by ~500% in the NAcc and by ~200% in the DS.

Safety of perioperative treatment with intravenous amantadine in patients with Parkinson disease

OBJECTIVES

Surgery in patients with Parkinson disease is associated with a high rate of complications largely because of difficulties in maintaining the antiparkinsonian treatment regimen perioperatively. The aim of the study was to investigate the safety and efficacy of intravenous administration of amantadine on parkinsonian features during and after surgery.

METHODS

The study group included 6 patients being treated for Parkinson disease who were referred for surgery at a tertiary medical center. After providing written informed consent, participants received intravenous amantadine sulfate 200 mg after induction of anesthesia and 24 hours later. The regular antiparkinsonian regimen was stopped immediately before surgery and restarted after surgery. Patients underwent a neurological evaluation with the Unified Parkinson Disease Rating Scale at 3 time points: preoperatively, 24 to 72 hours postoperatively, and 1 month postoperatively, and the scores were compared.

RESULTS

The mean Unified Parkinson Disease Rating Scale score improved from 24.8 (SD, 10.8) at baseline to 21.3 (SD, 11.1) at 24 to 72 hours postoperatively (P = 0.04); the value at 1 month (in the 5 patients assessed) was 22.5 (SD, 15.5) (P = 0.27). No adverse effects of amantadine or postoperative complications were recorded. All patients were discharged home as planned.

CONCLUSIONS

Amantadine improves the parkinsonian symptoms after surgery, which may be beneficial in preventing complications. It appears to have a high safety profile in this setting. Larger, randomized, and blinded studies are warranted to corroborate these preliminary results and evaluate long-term outcome.

Maladaptive plasticity in levodopa-induced dyskinesias and tardive dyskinesias: old and new insights on the effects of dopamine receptor pharmacology

Maladaptive plasticity can be defined as behavioral loss or even development of disease symptoms resulting from aberrant plasticity changes in the human brain. Hyperkinetic movement disorders, in the neurological or psychiatric realms, have been associated with maladaptive neural plasticity that can be expressed by functional changes such as an increase in transmitter release, receptor regulation, and synaptic plasticity or anatomical modifications such as axonal regeneration, sprouting, synaptogenesis, and neurogenesis. Recent evidence from human and animal models provided support to the hypothesis that these phenomena likely depend on altered dopamine turnover induced by long-term drug treatment. However, it is still unclear how and where these altered mechanisms of cortical plasticity may be localized. This study provides an up-to-date overview of these issues together with some reflections on future studies in the field, particularly focusing on two specific disorders (levodopa-induced dyskinesias in Parkinson’s disease patients and tardive dyskinesias in schizophrenic patients) where the modern neuroimaging approaches have recently provided new fundamental insights.

In vivo effect of apomorphine and haloperidol on MPP neurotoxicity

The involvement of dopaminergic (DAergic) receptor drugs in the neuroprotection against the neurotoxic action of 1-methyl-4-phenylpyridinium (MPP(+)) in the DAergic terminals in striatum was studied using an intracerebral microdialysis technique. Twenty-four hours after surgery (day 1), apomorphine and haloperidol, alone or with 1 mmol/l of MPP(+) perfusion through the microdialysis probe, were systemically administered. Forty-eight hours after surgery (day 2), 1 mmol/l of MPP(+) was perfused for 15 min in all groups of animals and the output of dopamine was measured. The amount of dopamine was directly proportional to the remaining striatal DAergic terminals. The results show that: (1) subcutaneous administration of apomorphine before MPP(+) perfusion prevented MPP(+)-induced neurotoxicity, and (2) intraperitoneal administration of haloperidol before MPP(+) perfusion did not prevent MPP(+)-induced neurotoxicity.

L-DOPA-treatment in primates disrupts the expression of A(2A) adenosine-CB(1) cannabinoid-D(2) dopamine receptor heteromers in the caudate nucleus

The molecular basis of priming for L-DOPA-induced dyskinesias in Parkinson's disease (PD), which depends on the indirect pathway of motor control, is not known. In rodents, the indirect pathway contains striatopallidal GABAergic neurons that express heterotrimers composed of A(2A) adenosine, CB(1) cannabinoid and D(2) dopamine receptors that regulate dopaminergic neurotransmission. The present study was designed to investigate the expression of these heteromers in the striatum of a primate model of Parkinson's disease and to determine whether their expression and pharmacological properties are altered upon L-DOPA treatment. By using the recently developed in situ proximity ligation assay and by identification of a biochemical fingerprint, we discovered a regional distribution of A(2A)/CB(1) /D(2) receptor heteromers that predicts differential D(2)-mediated neurotransmission in the caudate-putamen of Macaca fascicularis. Whereas heteromers were abundant in the caudate nucleus of both naïve and MPTP-treated monkeys, L-DOPA treatment blunted the biochemical fingerprint and led to weak heteromer expression. These findings constitute the first evidence of altered receptor heteromer expression in pathological conditions and suggest that drugs targeting A(2A)-CB(1) -D(2) receptor heteromers may be successful to either normalize basal ganglia output or prevent L-DOPA-induced side effects.

Amantadine induced corneal edema in a patient with primary progressive freezing of gait

Amantadine is commonly used for Parkinsonism. However amantadine can induce adverse corneal reaction. Here we report a patient with primary progressive freezing of gait who had severe corneal edema associated with amantadine, which was reversible after discontinuation of the amantadine. This report alerts neurologists for this reversible but potentially critical corneal edema in patients with Parkinsonism who are receiving amantadine.

Quantitative wearable sensors for objective assessment of Parkinson's disease

There is a rapidly growing interest in the quantitative assessment of Parkinson's disease (PD)-associated signs and disability using wearable technology. Both persons with PD and their clinicians see advantages in such developments. Specifically, quantitative assessments using wearable technology may allow for continuous, unobtrusive, objective, and ecologically valid data collection. Also, this approach may improve patient-doctor interaction, influence therapeutic decisions, and ultimately ameliorate patients' global health status. In addition, such measures have the potential to be used as outcome parameters in clinical trials, allowing for frequent assessments; eg, in the home setting. This review discusses promising wearable technology, addresses which parameters should be prioritized in such assessment strategies, and reports about studies that have already investigated daily life issues in PD using this new technology.

Multiple CNS nicotinic receptors mediate L-dopa-induced dyskinesias: studies with parkinsonian nicotinic receptor knockout mice

Accumulating evidence supports the idea that drugs acting at nicotinic acetylcholine receptors (nAChRs) may be beneficial for Parkinson's disease, a neurodegenerative movement disorder characterized by a loss of nigrostriatal dopaminergic neurons. Nicotine administration to parkinsonian animals protects against nigrostriatal damage. In addition, nicotine and nAChR drugs improve L-dopa-induced dyskinesias, a debilitating side effect of L-dopa therapy which remains the gold-standard treatment for Parkinson's disease. Nicotine exerts its antidyskinetic effect by interacting with multiple nAChRs. One approach to identify the subtypes specifically involved in L-dopa-induced dyskinesias is through the use of nAChR subunit null mutant mice. Previous work with β2 and α6 nAChR knockout mice has shown that α6β2* nAChRs were necessary for the development/maintenance of L-dopa-induced abnormal involuntary movements (AIMs). The present results in parkinsonian α4 nAChR knockout mice indicate that α4β2* nAChRs also play an essential role since nicotine did not reduce L-dopa-induced AIMs in such mice. Combined analyses of the data from α4 and α6 knockout mice suggest that the α6α4β2β3 subtype may be critical. In contrast to the studies with α4 and α6 knockout mice, nicotine treatment did reduce L-dopa-induced AIMs in parkinsonian α7 nAChR knockout mice. However, α7 nAChR subunit deletion alone increased baseline AIMs, suggesting that α7 receptors exert an inhibitory influence on L-dopa-induced AIMs. In conclusion, α6β2*, α4β2* and α7 nAChRs all modulate L-dopa-induced AIMs, although their mode of regulation varies. Thus drugs targeting one or multiple nAChRs may be optimal for reducing L-dopa-induced dyskinesias in Parkinson's disease.

Chronic treatment with MPEP, an mGlu5 receptor antagonist, normalizes basal ganglia glutamate neurotransmission in L-DOPA-treated parkinsonian monkeys

Metabotropic glutamate 5 (mGlu5) receptor antagonists reduce L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesias (LID) in Parkinson's disease (PD). The aim of this study was to investigate the long-term effect of the prototypal mGlu5 receptor antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) on glutamate receptors known to be involved in the development of LID in the de novo chronic treatment of monkeys lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). MPTP monkeys were treated for one month with L-DOPA and developed dyskinesias while those treated with L-DOPA and MPEP (10 mg/kg) developed significantly less. Normal control and saline-treated MPTP monkeys were also included. All MPTP monkeys were extensively and similarly denervated. The basal ganglia [(3)H]ABP688 specific binding (mGlu5 receptors) was elevated in L-DOPA-treated MPTP monkeys compared to controls but not in those treated with L-DOPA and MPEP; dyskinesia scores of these monkeys correlated positively with their [(3)H]ABP688 specific binding. Striatal density (B(max)) of [(3)H]ABP688 specific binding increased in L-DOPA-treated MPTP monkeys compared to other groups and affinity (Kd) remained unchanged. Striatal mGlu5 receptor mRNA remained unchanged following treatments. Elevated basal ganglia specific binding of [(3)H]Ro 25-6981 (NMDA NR1/NR2B receptors), [(3)H]Ro 48-8587 (AMPA receptors) but not [(3)H]CGP-39653 (NMDA NR1/NR2A receptors) was observed only in L-DOPA-treated MPTP monkeys; dyskinesias scores correlated with binding. By contrast, basal ganglia [(3)H]LY341495 specific binding (mGlu2/3 receptors) decreased in L-DOPA-treated MPTP monkeys compared to controls, saline and L-DOPA + MPEP treated MPTP monkeys; dyskinesias scores correlated negatively with this binding. Hence, chronic MPEP treatment reduces the development of LID and is associated with a normalization of glutamate neurotransmission.

The effects of fast-off-D2 receptor antagonism on L-DOPA-induced dyskinesia and psychosis in parkinsonian macaques

3,4-Dihydroxyphenylalanine (L-DOPA) treatment of Parkinson's disease (PD) is compromised by motor side effects, such as dyskinesia and non-motor problems, including psychosis. Because of the marked reduction in brain dopamine in PD and the resultant dopamine D2 receptor supersensitivity, it is impossible to use standard potent dopamine D2 receptor antagonists such as haloperidol to alleviate side effects without compromising the anti-parkinsonian benefits of L-DOPA. Haloperidol antagonizes D2 receptors with high affinity and slowly dissociates from D2 receptors (50% dissociation at 38min). We hypothesized that a rapidly dissociating D2 antagonist might allow some functional dopaminergic transmission and thus have a profile, with respect to reduction of dyskinesia and anti-parkinsonian effects, that was more useful therapeutically. The present study tested the principle of using a fast-off-D2 drug, CLR151 (50% dissociation at 23s) to modify L-DOPA actions in cynomolgus macaques with MPTP-parkinsonism. CLR151 (100mg/kg p.o.) reduced L-DOPA-induced dyskinesia and activity in the parkinsonian macaque by 86% and 52% respectively during peak action. CLR151 (100mg/kg) also reduced psychosis-like behaviour (i.e. reduced apparent visual hallucinations by 78%). Nevertheless, this dose of CLR151 significantly reduced the duration of anti-parkinsonian action of L-DOPA, ON-time (by 90%), and increased parkinsonian disability (by 57%). These data suggest that fast-off-D2 dopamine receptor antagonists, with D2-off-rate values close to those for CLR151, are unlikely to be useful in the treatment of dyskinesia and psychosis in PD. However, fast-off-D2 drugs could provide benefit if new congeners would have an even faster dissociation rate. Such drugs are now becoming available.

Short- and long-term efficacy of intensive rehabilitation treatment on balance and gait in parkinsonian patients: a preliminary study with a 1-year followup

Parkinson's disease (PD) is a neurodegenerative disease in which gait and balance disturbances are relevant symptoms that respond poorly to pharmacological treatment. The aim of this study was to investigate whether a 4-week inpatient multidisciplinary intensive rehabilitation treatment (MIRT) is effective in improving balance and gait and whether improvements persist at a one-year followup. We studied 20 PD inpatients (stage 3 Hoehn-Yahr) who underwent a MIRT. Outcome measures were UPDRS items for balance (30), falls (13), and walk (29), Berg Balance Scale, six-minute walking test, Timed Up and Go Test, and Comfortable-Fast gait speeds. Patients were evaluated at admission, at the end of the 4-week treatment, and at a 1-year followup. Pharmacological therapy was unchanged during MIRT and follow-up. All outcome measures improved significantly at the end of treatment. At 1-year follow-up control, UPDRS walk and Comfortable-Fast gait speeds still maintained better values with respect to admission (P = 0.009, P = 0.03, and P = 0.02, resp.), while the remaining scales did not differ significantly. Our results demonstrate that the MIRT was effective in improving balance and gait and that the improvement in gait performances was partially maintained also after 1 year.

Restricted diffusion of dopamine in the rat dorsal striatum

Recent evidence has shown that the dorsal striatum of the rat is arranged as a patchwork of domains that exhibit distinct dopamine kinetics and concentrations. This raises the pressing question of how these distinct domains are maintained, especially if dopamine is able to diffuse through the extracellular space. Diffusion between the domains would eliminate the concentration differences and, thereby, the domains themselves. The present study is a closer examination of dopamine's ability to diffuse in the extracellular space. We used voltammetry to record dopamine overflow in dorsal striatum while stimulating the medial forebrain bundle over a range of stimulus currents and frequencies. We also examined the effects of drugs that modulated the dopamine release (raclopride and quinpirole) and uptake (nomifensine). Examining the details of the temporal features of the evoked profiles reveals no clear evidence for long-distance diffusion of dopamine between fast and slow domains, even though uptake inhibition by nomifensine clearly prolongs the time that dopamine resides in the extracellular space. Our observations support the conclusion that striatal tissue has the capacity to retain dopamine molecules, thereby limiting its tendency to diffuse through the extracellular space.

Rebalance of striatal NMDA/AMPA receptor ratio underlies the reduced emergence of dyskinesia during D2-like dopamine agonist treatment in experimental Parkinson's disease

Dopamine replacement with levodopa (L-DOPA) represents the mainstay of Parkinson’s disease (PD) therapy. Nevertheless, this well established therapeutic intervention loses efficacy with the progression of the disease and patients develop invalidating side effects, known in their complex as L-DOPA-induced dyskinesia (LID). Unfortunately, existing therapies fail to prevent LID and very few drugs are available to lessen its severity, thus representing a major clinical problem inPDtreatment. D2-like receptor (D2R) agonists are a powerful clinical option as an alternative to L-DOPA, especially in the early stages of the disease, being associated to a reduced risk of dyskinesia development. D2R agonists also find considerable application in the advanced stages of PD, in conjunction with L-DOPA, which is used in this context at lower dosages, to delay the appearance and the extent of the motor complications. In advanced stages of PD, D2R agonists are often effective in delaying the appearance and the extent of motor complications. Despite the great attention paid to the family of D2R agonists, the main reasons underlying the reduced risk of dyskinesia have not yet been fully characterized. Here we show that the striatal NMDA/AMPAreceptor ratio and theAMPAreceptor subunit composition are altered in experimental parkinsonism in rats. Surprisingly, while L-DOPA fails to restore these critical synaptic alterations, chronic treatment with pramipexole is associated not only with a reduced risk of dyskinesia development but is also able to rebalance, in a dose-dependent fashion, the physiological synaptic parameters, thus providing new insights into the mechanisms of dyskinesia.

Striatal molecular signature of subchronic subthalamic nucleus high frequency stimulation in parkinsonian rat

This study addresses the molecular mechanisms underlying the action of subthalamic nucleus high frequency stimulation (STN-HFS) in the treatment of Parkinson's disease and its interaction with levodopa (L-DOPA), focusing on the striatum. Striatal gene expression profile was assessed in rats with nigral dopamine neuron lesion, either treated or not, using agilent microarrays and qPCR verification. The treatments consisted in anti-akinetic STN-HFS (5 days), chronic L-DOPA treatment inducing dyskinesia (LIDs) or the combination of the two treatments that exacerbated LIDs. STN-HFS modulated 71 striatal genes. The main biological processes associated with the differentially expressed gene products include regulation of growth, of apoptosis and of synaptic transmission, and extracellular region is a major cellular component implicated. In particular, several of these genes have been shown to support survival or differentiation of striatal or of dopaminergic neurons. These results indicate that STN HFS may induce widespread anatomo-functional rearrangements in the striatum and create a molecular environment favorable for neuroprotection and neuroplasticity. STN-HFS and L-DOPA treatment share very few common gene regulation features indicating that the molecular substrates underlying their striatal action are mostly different; among the common effects is the down-regulation of Adrb1, which encodes the adrenergic beta-1-receptor, supporting a major role of this receptor in Parkinson's disease. In addition to genes already reported to be associated with LIDs (preprodynorphin, thyrotropin-releasing hormone, metabotropic glutamate receptor 4, cannabinoid receptor 1), the comparison between DOPA and DOPA/HFS identifies immunity-related genes as potential players in L-DOPA side effects.

Management of motor and non-motor symptoms in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder that affects approximately 1 % of people over the age of 60 years. Accurate diagnosis and individualized assessment of the risks and benefits of available antiparkinsonian medications as well as specific clinical features and the phase of disease should guide treatment for patients with PD. Levodopa still remains the gold standard for the treatment of motor symptoms of PD but dopamine agonists (DAs), catechol-O-methyltransferase (COMT) inhibitors and monoamine oxidase B (MAO-B) inhibitors have also been developed to provide more continuous oral delivery of dopaminergic stimulation in order to improve motor outcomes and decrease the risk of levodopa-induced motor complications. Deep-brain stimulation as well as other invasive therapies can be used for the treatment of drug-refractory levodopa-induced motor complications. Despite all of the therapeutic advances achieved within the last 20 years, PD continues to be a progressive disorder leading to severe disability caused by motor and non-motor symptoms. To date, neuroprotective interventions able to modify PD progression are not available. This review focuses on medical and invasive treatment strategies for early and advanced stages of PD as well as on the treatment of PD non-motor symptoms such as mood and behavioural disorders, cognitive and autonomic dysfunction, and sleep disorders, which can antedate PD motor symptoms for years.

Drug-induced dyskinesia in Parkinson's disease. Should success in clinical management be a function of improvement of motor repertoire rather than amplitude of dyskinesia?

BACKGROUND

Dyskinesia, a major complication in the treatment of Parkinson's disease (PD), can require prolonged monitoring and complex medical management.

DISCUSSION

The current paper proposes a new way to view the management of dyskinesia in an integrated fashion. We suggest that dyskinesia be considered as a factor in a signal-to-noise ratio (SNR) equation where the signal is the voluntary movement and the noise is PD symptomatology, including dyskinesia. The goal of clinicians should be to ensure a high SNR in order to maintain or enhance the motor repertoire of patients. To understand why such an approach would be beneficial, we first review mechanisms of dyskinesia, as well as their impact on the quality of life of patients and on the health-care system. Theoretical and practical bases for the SNR approach are then discussed.

SUMMARY

Clinicians should not only consider the level of motor symptomatology when assessing the efficacy of their treatment strategy, but also breadth of the motor repertoire available to patients.

Three-month subchronic intramuscular toxicity study of rotigotine-loaded microspheres in SD rats

Continuous dopaminergic stimulation (CDS) has been an important strategy of drug development for the treatment of Parkinson's disease (PD). Rotigotine is a non-ergoline D3/D2/D1 dopamine agonist for treating PD. As a new treatment option for CDS, rotigotine-loaded microspheres (RoMS), a long-acting sustained-release microspheres for injection with poly(lactide-co-glycolide) as drug carrier, are now being evaluated in clinical trial. In this study, subchronic toxicity of RoMS in SD rats has been characterized via intramuscular administration with RoMS (0-240 mg/kg/week) on a consecutive weekly dosing schedule for 3 months followed by 1-month recovery period. The No Observed Adverse Effect Level (NOAEL) was 45 mg/kg/week. One male at 240 mg/kg died from an extensive pulmonary embolism. The major toxicological effects were associated with the dopamine agonist-related pharmacodynamic properties of rotigotine (e.g. hyperactivity and stereotype, enlarged ovary, sporadic gastric mucous membrane lesions, decreased body weight, food consumption and prolactin, and increased mononuclear cell, neutrophil granulocyte, aspartate aminotransferase and alanine aminotransferase) and foreign body removal reaction induced by poly(lactide-co-glycolide) and carboxymethycellulose sodium. At the end of recovery period, all findings had recovered to a normal level or to a certain degree except foreign body reaction at injection sites. RoMS has exhibited high safety on SD rats.

Parallel dopamine D1 receptor activity dependence of l-Dopa-induced normal movement and dyskinesia in mice

l-3,4-Dihydroxyphenylalanine (l-Dopa)-induced dyskinesia (LID) in Parkinson's disease (PD) is a major clinical problem. The prevailing view is that in PD patients and animal PD models dyskinesia develops after repeated l-dopa use or priming, independent of l-dopa's anti-PD therapeutic effect that occurs immediately. Here we show that in mice with severe and consistent dopamine (DA) loss in the dorsal striatum, rendered by transcription factor Pitx3 null mutation, the very first injection of l-dopa or D1-like agonist SKF81297 induced both normal ambulatory and dyskinetic movements. Furthermore, the robust stimulating effects on normal and dyskinetic movements had an identical time course and parallel dose-response curves. In contrast, D2-like agonist ropinirole stimulated normal and dyskinetic movements relatively modestly. These results demonstrate that severe DA loss in the dorsal striatum sets the stage for dyskinesia to occur on the first exposure to l-dopa or a D1 agonist without any priming. These results also indicate that l-dopa stimulated both normal and dyskinetic movements primarily via D1 receptor activation and that proper D1 agonism is potentially an efficacious therapy for PD motor deficits.

Caffeine consumption and risk of dyskinesia in CALM-PD

BACKGROUND

Adenosine A2A receptor antagonists reduce or prevent the development of dyskinesia in animal models of levodopa-induced dyskinesia.

METHODS

We examined the association between self-reported intake of the A2A receptor antagonist caffeine and time to dyskinesia in the Comparison of the Agonist Pramipexole with Levodopa on Motor Complications of Parkinson's Disease (CALM-PD) and CALM Cohort extension studies, using a Cox proportional hazards model adjusting for age, baseline Parkinson's severity, site, and initial treatment with pramipexole or levodopa.

RESULTS

For subjects who consumed >12 ounces of coffee/day, the adjusted hazard ratio for the development of dyskinesia was 0.61 (95% CI, 0.37-1.01) compared with subjects who consumed <4 ounces/day. For subjects who consumed between 4 and 12 ounces/day, the adjusted hazard ratio was 0.73 (95% CI, 0.46-1.15; test for trend, P = .05).

CONCLUSIONS

These results support the possibility that caffeine may reduce the likelihood of developing dyskinesia.

Levodopa/benserazide microspheres reduced levodopa-induced dyskinesia by downregulating phosphorylated GluR1 expression in 6-OHDA-lesioned rats

Background

Levodopa is the gold standard in the treatment of Parkinson’s disease (PD). However, long-term levodopa replacement therapy is accompanied by abnormal involuntary movements (AIMs), known as levodopa-induced dyskinesia (LID). Until now, the precise mechanisms of LID were only partially understood. Previous studies have shown that continuous dopamine stimulation was helpful in reducing the expression of LID. In addition to dopamine D1 receptor, glutamatergic receptors such as α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor also contribute to the expression of LID. The current authors have previously reported that levodopa/benserazide-loaded microspheres could ameliorate the expression of LID by reducing the protein kinase A signaling pathway in dyskinetic rats. However, whether AMPA receptor is involved in the mechanism by which levodopa/benserazide-loaded microspheres ameliorate the expression of LID in dyskinetic rats was unknown.

Methods

In the present study, as reported previously, levodopa and benserazide were loaded by poly(lactic-co-glycolic acid) microspheres, which can release levodopa and benserazide in a sustained manner. 6-Hydroxydopamine was injected into the right medial forebrain bundle to produce a rat model of PD. Then valid PD rats were treated with levodopa plus benserazide for 3 weeks to induce a rat model of LID. Dyskinetic rats were treated with levodopa/beserazide-loaded microspheres containing levodopa (6 mg/kg) plus benserazide (15 mg/kg) or same dose of levodopa plus benserazide. Abnormal involuntary movements were measured in rats on days 1, 5, 10, 15, and 20 during the treatment. The levels of GluR1 at serine-831 (pGluR1S831) and serine-845 (pGluR1S845) were determined by Western blot. Arc and proenkephalin (Penk) levels were measured by real-time polymerase chain reaction.

Results

Three-week levodopa plus benserazide treatment induced dyskinesia in PD rats. Levodopa/benserazide-loaded microsphere-treated dyskinetic rats showed lower AIM scores than levodopa plus benserazide-treated dyskinetic rats. Microsphere treatment downregulated the phosphrylated levels of pGluR1S831 and pGluR1S845 in the striatum of dyskinetic rats. In addition, microsphere treatment reduced the levels of Arc and Penk.

Conclusion

These data indicated that levodopa/benserazide-loaded microspheres could be used to ameliorate the expression of LID by reducing the expression of pGluR1S831 and pGluR1S845 as well as Arc and Penk.

Three-month subchronic intramuscular toxicity study of rotigotine-loaded microspheres in Cynomolgus monkeys

Continuous dopaminergic stimulation (CDS) is an important drug development strategy in the treatment of Parkinson's disease (PD). Rotigotine is a non-ergoline D(3)/D(2)/D(1) dopamine receptor agonist for treating PD. As a new treatment option for CDS, rotigotine-loaded microspheres (RoMS), long-acting sustained-release microspheres with poly(lactide-co-glycolide) as drug carrier, are now being evaluated in clinical trial. In the present study, the subchronic toxicity in Cynomolgus monkeys has been characterized via intramuscular administration with RoMS at 0, 10, 40 and 160 mg/kg, weekly for 3 months with a 1-month recovery period. The NOAEL was 10 mg/kg/week. One male at 160 mg/kg died from an extensive pulmonary embolism. The major toxicological effects were associated with dopamine agonist-related pharmacodynamic properties of rotigotine (e.g., hyperactivity and stereotype, decreased serum prolactin level) and foreign body removal reaction induced by poly(lactide-co-glycolide) and carboxymethycellulose sodium (e.g., increased mononuclear cells and neutrophils, thymus atrophy and vacuolar degeneration of adrenal cortex, foreign body granuloma with foam cells accumulation at injection sites and foam cells accumulation in spleen and multiple lymph sinuses). At the end of recovery period, above findings recovered to a normal level or to a certain degree except vacuolar degeneration of adrenal gland. RoMS has exhibited high safety on monkeys.

Clinical features, pathophysiology, and treatment of levodopa-induced dyskinesias in Parkinson's disease

Dyskinetic disorders are characterized by excess of motor activity that may interfere with normal movement control. In patients with Parkinson's disease, the chronic levodopa treatment induces dyskinetic movements known as levodopa-induced dyskinesias (LID). This paper analyzed the pathophysiology, clinical manifestations, pharmacological treatments, and surgical procedures to treat hyperkinetic disorders. Surgery is currently the only treatment available for Parkinson's disease that may improve both parkinsonian motor syndrome and LID. However, this paper shows the different mechanisms involved are not well understood.

The effects of rehabilitative training on the behaviors of Parkinson's disease mouse and underlying mechanism

OBJECTIVE

To examine the effects of rehabilitative training on mice behavior improvement in a 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine (MPTP) mice model of Parkinson's disease (PD).

METHODS

MPTP mice model of Parkinson disease was generated. The rehabilitative training included daily running wheel and balance walking; the control group was allowed for free activity. The behaviors of the two groups were investigated at 1 week, 2 weeks, and 4 weeks and the content of dopamine (DA) in striatum of different groups of mice was measured with high-performance liquid chromatography (HPLC).

RESULTS

The results showed that as compared to the control group, the score of climbing pole, traction, swimming tests, and dopamine content was improved in the rehabilitative training group.

CONCLUSION

This suggested that rehabilitative training could improve the locomotor ability and dopamine content in PD mouse model.

MPEP, an mGlu5 receptor antagonist, reduces the development of L-DOPA-induced motor complications in de novo parkinsonian monkeys: biochemical correlates

L-3,4-Dihydroxyphenylalanine (l-DOPA), the gold standard therapy for Parkinson disease (PD), is associated with motor fluctuations and dyskinesias. This study sought to prevent the development of l-DOPA-induced dyskinesias (LID) with the metabotropic glutamate receptor type 5 (mGlu5 receptor) antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) in the de novo treatment of monkeys lesioned with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) as a PD model. MPTP-lesioned monkeys were treated once daily for one month with either l-DOPA or l-DOPA + MPEP (10 mg/kg). MPEP (administered 15 min before l-DOPA) plasma concentrations were elevated during all the l-DOPA motor activation and did not accumulate during a month. The antiparkinsonian effect was maintained throughout the treatment period in MPTP-lesioned monkeys treated with l-DOPA + MPEP, while the duration of this effect decreased over time in MPTP-lesioned monkeys treated with l-DOPA alone, suggesting wearing-off. Over the month-long treatment, the mean dyskinesia score increased in l-DOPA-treated monkeys; interestingly, this increase was reduced by overall 72% in the l-DOPA + MPEP group. Mean dyskinesia scores of monkeys correlated inversely with plasma MPEP concentrations. Normal control and saline-treated MPTP-lesioned monkeys were also included for biochemical analyses. All MPTP-lesioned monkeys were extensively and similarly denervated. [(3)H]ABP688 specific binding to mGlu5 receptors increased in the putamen of l-DOPA-treated monkeys compared to control, saline or l-DOPA + MPEP-treated monkeys. Mean dyskinesia scores of MPTP-lesioned monkeys correlated positively with [(3)H]ABP688 specific binding in the putamen. This study showed a beneficial chronic antidyskinetic effect of MPEP in de novol-DOPA-treated MPTP-lesioned monkeys, supporting the therapeutic use of mGlu5 receptor antagonists in PD to prevent LID. This article is part of a Special Issue entitled 'Metabotropic Glutamate Receptors'.