Levodopa-induced dyskinesias

Differential coulometry based on dual screen-printed strips for high accuracy levodopa determination towards Parkinson's disease management

As a vital therapeutic agent for Parkinson's disease, dosage control of levodopa has always been a major obstacle in ensuring efficacy and curbing side effects. Simple and fast electrochemical detection methods are the main force in this field. Here, we presented a differential dual-strip method based on the coulometry for high accuracy determination of levodopa. The difference between the two strip signals with or without the tyrosinase extracted the levodopa signal from the samples. The Prussian Blue modified carbon screen-printed electrode was used to convert and amplify the electrochemical signal upon the presence of levodopa. The system exhibited a linear behavior in the 0-10 μM concentration range and a detection limit of 0.25 μM. Furthermore, it was proved to be stable in effectively distinguishing levodopa from complex samples through anti-interference experiments and serum tests. We demonstrated the superiority of dual-strip differential coulometry for the determination of levodopa towards Parkinson's disease clinical management.

New Sensor and Wearable Technologies to Aid in the Diagnosis and Treatment Monitoring of Parkinson's Disease

Parkinson's disease (PD) is a degenerative disorder of the brain characterized by the impairment of the nigrostriatal system. This impairment leads to specific motor manifestations (i.e., bradykinesia, tremor, and rigidity) that are assessed through clinical examination, scales, and patient-reported outcomes. New sensor-based and wearable technologies are progressively revolutionizing PD care by objectively measuring these manifestations and improving PD diagnosis and treatment monitoring. However, their use is still limited in clinical practice, perhaps because of the absence of external validation and standards for their continuous use at home. In the near future, these systems will progressively complement traditional tools and revolutionize the way we diagnose and monitor patients with PD.

Sex-specific association of urate and levodopa-induced dyskinesia in Parkinson's disease

BACKGROUND AND PURPOSE

As a major antioxidant, uric acid (UA) is known to be associated with the clinical progression of Parkinson's disease (PD). This study investigated whether baseline UA levels are associated with the risk for levodopa-induced dyskinesia (LID) in PD in a sex-dependent manner.

METHODS

In all, 152 patients with de novo PD (78 males and 74 females) who were followed up for >2 years were enrolled. The effect of baseline serum UA levels on LID-free survival was assessed by Cox regression, separately for sex, whilst being adjusted for potential confounding factors. The optimal UA level cut-off value to determine the high-risk group for LID was set using Contal and O'Quigley's method.

RESULTS

Levodopa-induced dyskinesia developed in 23 (29.5%) male patients and 30 (40.5%) female patients. Cox regression showed a significant interaction between UA level and sex. Higher UA levels were associated with a higher risk for LID in male PD patients (hazard ratio 1.380; 95% confidence interval 1.038-1.835; P = 0.027), although this relationship was not observed in female PD patients. The optimal UA level cut-off for LID in male PD was 7.2 mg/dl, and the high UA group had a 5.7-fold higher risk of developing LID than the low UA group.

CONCLUSIONS

Contrary to a presumptive beneficial role of UA, the present study demonstrated that higher UA levels are associated with increased risk of LID occurrence in male patients with PD, suggesting a sex-dependent role of UA in LID.

Parkinson's Disease in Women and Men: What's the Difference?

Increasing evidence points to biological sex as an important factor in the development and phenotypical expression of Parkinson’s disease (PD). Risk of developing PD is twice as high in men than women, but women have a higher mortality rate and faster progression of the disease. Moreover, motor and nonmotor symptoms, response to treatments and disease risk factors differ between women and men. Altogether, sex-related differences in PD support the idea that disease development might involve distinct pathogenic mechanisms (or the same mechanism but in a different way) in male and female patients. This review summarizes the most recent knowledge concerning differences between women and men in PD clinical features, risk factors, response to treatments and mechanisms underlying the disease pathophysiology. Unraveling how the pathology differently affect the two sexes might allow the development of tailored interventions and the design of innovative programs that meet the distinct needs of men and women, improving patient care.

Long-term effectiveness of levodopa-carbidopa intestinal gel on motor and non-motor symptoms in advanced Parkinson's disease: results of the Italian GLORIA patient population

Introduction

The GLORIA registry included 375 advanced Parkinson’s disease (PD) patients and evaluated the efficacy and safety of a 24-month levodopa-carbidopa intestinal gel (LCIG) treatment in routine medical care. This analysis focuses on the Italian population, 60 patients treated with LCIG in 7 specialised PD care centres.

Methods

Hours of “Off” and “On” time were assessed with a modified version of the Unified Parkinson’s Disease Rating Scale (UPDRS) part IV items 39 and 32. Motor fluctuations, dyskinesia, non-motor symptoms, quality of life and safety were evaluated.

Results

Overall, 42 (70%) out of 60 patients completed the registry. LCIG treatment reduced “Off” time (− 3.3 ± 2.7 h at month 24 (M24), P < 0.0001), increased “On” time with dyskinesia (− 2.6 ± 5.2 h at M12, P = 0.0160), and improved UPDRS II and UPDRS III total scores at M24 (− 4.5 ± 10.6, P = 0.0333 and − 4.9 ± 11.7, P = 0.0229, respectively), Non-Motor Symptom Scale (NMSS) total score (− 21.8 ± 28.5, P < 0.0001) and Parkinson’s Disease Questionnaire-8 item (PDQ-8) total score (− 12.5 ± 23.9, P = 0.0173) versus previous oral therapy. Adverse drug reactions (ADR) possibly or probably related to treatment were reported in 16 (28.6%) patients. Decreased weight (7.1%), polyneuropathy (7.1%) and abdominal pain (5.4%) were the most frequent ADRs while device malfunction (5.4%) and medical device change (5.4%) were the most reported device complaints.

Conclusions

LCIG improved motor fluctuations, non-motor symptoms and quality of life over 24 months while tolerability was consistent with the established safety profile.

The TANDEM investigation: efficacy and tolerability of levodopa-carbidopa intestinal gel in (LCIG) advanced Parkinson's disease patients

The TANDEM investigation was carried out in 17 Italian Movement Disorder centers on behalf of a joint initiative of neurologist members of the Italian Academy for Parkinson's disease and Movement Disorders (LIMPE-DISMOV Academy) and gastroenterologist members of the Italian Society of Digestive Endoscopy (SIED) to evaluate the efficacy and tolerability of levodopa-carbidopa intestinal gel (LCIG) in patients with advanced Parkinson's disease (PD) in routine medical care. Motor scores in "ON" and OFF" state (UPDRS-III), complications of therapy (UPDRS-IV), activities of daily living, sleep disorders and quality of life were evaluated at baseline and at two follow-up assessments (FUV1 and FUV2) within the initial 12-month LCIG treatment. In 159 patients (55% males) with a mean age of 69.1 ± 6.6 years and a diagnosis of PD since 13.6 ± 5.5 years, the UPDRS-III total score (in "OFF") decreased from baseline (45.8 ± 13.2) to FUV1 (41.0 ± 17.4; p < 0.001) and FUV2 (40.5 ± 15.5; p < 0.001), the UPDRS-IV total score decreased from baseline (8.8 ± 2.9) to FUV1 (5.1 ± 3.4; p < 0.001) and FUV2 (5.5 ± 3.2; p < 0.001). The percentage of patients exhibiting freezing, dystonia, gait/walking disturbances, falls, pain and sleep disorders was significantly reduced. Twenty-eight device complications were reported and 11 (6.9%) patients prematurely terminated the study. LCIG after 12-month treatment led to sustained improvement of time spent in "OFF", complications of therapy, PD-associated symptoms and sleep disorders. LCIG tolerability was consistent with the established safety profile of LCIG.

MRI of Motor and Nonmotor Therapy-Induced Complications in Parkinson's Disease

Levodopa therapy remains the most effective drug for the treatment of Parkinson's disease, and it is associated with the greatest improvement in motor function as assessed by the Unified Parkinson's Disease Rating Scale. Dopamine agonists have also proven their efficacy as monotherapy in early Parkinson's disease but also as adjunct therapy. However, the chronic use of dopaminergic therapy is associated with disabling motor and nonmotor side effects and complications, among which levodopa-induced dyskinesias and impulse control behaviors are the most common. The underlying mechanisms of these disorders are not fully understood. In the last decade, classic neuroimaging methods and more sophisticated techniques, such as analysis of gray-matter structural imaging and functional magnetic resonance imaging, have given access to anatomical and functional abnormalities, respectively, in the brain. This review presents an overview of structural and functional brain changes associated with motor and nonmotor therapy-induced complications in Parkinson's disease. Magnetic resonance imaging may offer structural and/or functional neuroimaging biomarkers that could be used as predictive signs of development, maintenance, and progression of these complications. Neurophysiological tools, such as theta burst stimulation and transcranial magnetic stimulation, might help us to integrate neuroimaging findings and clinical features and could be used as therapeutic options, translating neuroimaging data into clinical practice. © 2020 International Parkinson and Movement Disorder Society.

Recent Clinical Advances in Pharmacotherapy for Levodopa-Induced Dyskinesia

Onset of involuntary movement patterns of the face, body and limbs are known as dyskinesia. They mostly appear in association with long-term levodopa (L-dopa) therapy in patients with Parkinson's disease. Consequences include patient distress, caregiver embarrassment and reduced quality of life. A severe intensity of this motor complication may result in troublesome disability; however, patients typically prefer motor behaviour with slight, non-troublesome dyskinesia to 'OFF' states. Pharmacotherapy of dyskinesia is complex. Continuous nigrostriatal postsynaptic dopaminergic receptor stimulation may delay onset of L-dopa-associated dyskinesia, while non-physiological, 'pulsatile' receptor stimulation facilitates appearance of dyskinesia. In the past, there have been many clinical trial failures with compounds that were effective in animal models of dyskinesia. Only the N-methyl-D-aspartate antagonist amantadine has shown moderate antidyskinetic effects in small well-designed clinical studies. Amantadine is an old antiviral compound, which moderately improves impaired motor behaviour. Recently, there has been a resurgence of its use due to the US Food and Drug Administration approval of an extended-release (ER) amantadine formulation for treatment of L-dopa-induced dyskinesia. This pharmacokinetic innovation improved dyskinesia and 'OFF' states in pivotal trials, with a once-daily oral application in the evening. Amantadine ER provides higher and more continuous amantadine plasma bioavailability than conventional immediate-release formulations, which require administration up to three times daily.

Long-Term Efficacy of Safinamide on Symptoms Severity and Quality of Life in Fluctuating Parkinson's Disease Patients

BACKGROUND

Parkinson's disease (PD) is characterized by a wide range of motor and non-motor symptoms. Levodopa is still the most effective drug; however, its long-term use is associated with motor complications which may deteriorate patient's quality of life. Safinamide is a unique treatment modulating both dopaminergic and glutamatergic systems. Previous results from two six months, double-blind, placebo-controlled studies demonstrated that safinamide has positive effects on both motor functions and quality of life in PD patients.

OBJECTIVE

To investigate the effects of safinamide 100 mg/day over two-year treatment on PD symptoms severity and quality of life, using data from the study 018.

METHODS

Data from 352 patients were analyzed to evaluate the effects of safinamide on OFF time and ON time (with no or non-troublesome dyskinesia) in the overall population and in subgroups of patients (receiving levodopa monotherapy or with other anti-Parkinson therapies), and the effects of safinamide on motor symptoms/clinical fluctuations (by means of UPDRS III and IV) and on health-related quality of life (using UPDRS II and PDQ-39 summary index score).

RESULTS

Safinamide, administered as add-on to standard therapy in fluctuating PD patients, significantly improved motor symptoms and clinical fluctuations in the overall population and in some subgroups of patients. Additionally, safinamide improved quality of life and activities of daily living, maintaining the efficacy in the long-term.

CONCLUSIONS

The findings of these analyses suggest that safinamide may be considered an appropriate adjunct therapy in patient not sufficiently controlled. Further investigations are desirable to confirm these results in usual care setting.

Effect of Repeated Intravenous Amantadine Infusions in Patients with Parkinson's Disease: An Open‐Label Pilot Study

Amantadine is an antiviral drug available in oral and intravenous forms. Oral amantadine is used to treat the motor symptoms of early Parkinson's disease (PD) and to ameliorate dyskinesia in late‐stage disease. However, the long‐term influence of intravenous amantadine on motor symptoms and dyskinesias in PD has not been investigated. The aim of the present study was to examine the long‐term effect of repeated boosts of intravenous amantadine in patients with PD with and without response fluctuations and dyskinesias. Twelve patients diagnosed with PD, six with levodopa intolerance or insufficient response to antiparkinson medications, and six with response fluctuations and dyskinesias, were treated with intravenous amantadine for 6 months: three sequential infusions over 3 days in the first month followed by five once‐monthly infusions. Changes in motor function and involuntary movements were evaluated with the Unified Parkinson Disease Rating Scale (UPDRS) and Abnormal Involuntary Movement Scale (AIMS; dyskinesia group). A significant immediate improvement in motor scores was documented in both groups after amantadine infusion. However, the difference in mean UPDRS motor score from before the first infusion to after 6 months of treatment was not statistically significant. In patients with dyskinesias, there was a significant improvement in AIMS scores between the first and the last visits (6.3 ± 2.7 vs. 1.6 ± 1.3; P = 0.014). In conclusion, continuous treatment with intravenous amantadine can be useful in patients with PD for immediate relief of motor symptoms and in patients with dyskinesias for progressive reduction of involuntary movements.

Cerebellar connectivity in Parkinson's disease with levodopa-induced dyskinesia

OBJECTIVE

The precise pathogenesis or neural correlates underlying levodopa-induced dyskinesia (LID) remains poorly understood. There is growing evidence of the involvement of the cerebellum in Parkinson's disease (PD). The present study evaluated the role of motor cerebellar connectivity in determining vulnerability to LID.

METHODS

We enrolled 25 de novo patients with PD who developed LID within 5 years of levodopa treatment, 26 propensity score-matched PD patients who had not developed LID, and 24 age- and sex-matched healthy controls. We performed a comparative analysis of resting-state functional connectivity (FC) between the motor cerebellum and whole brain between the groups.

RESULTS

The patients with PD had increased FC bewteen the motor cerebellum and posterior cortical and cerebellar regions, while no gray matter regions had decreased FC with the motor cerebellum compared to the control participant. The patients with PD who were vulnerable to the development of LID had a significantly higher FC between the motor cerebellum lobule VIIIb and the left inferior frontal gyrus than those who were resistant to LID development. The connectivity of the motor cerebellum and left inferior frontal gyrus was negatively correlated with the latency from PD onset to the occurrence of LID.

INTERPRETATION

Increased FC between the motor cerebellum and left inferior frontal gyrus in de novo patients with PD could be an important determinant of vulnerability to LID.

Estimating dyskinesia severity in Parkinson's disease by using a waist-worn sensor: concurrent validity study

Our research team previously developed an accelerometry-based device, which can be worn on the waist during daily life activities and detects the occurrence of dyskinesia in patients with Parkinson’s disease. The goal of this study was to analyze the magnitude of correlation between the numeric output of the device algorithm and the results of the Unified Dyskinesia Rating Scale (UDysRS), administered by a physician. In this study, 13 Parkinson’s patients, who were symptomatic with dyskinesias, were monitored with the device at home, for an average period of 30 minutes, while performing normal daily life activities. Each patient’s activity was simultaneously video-recorded. A physician was in charge of reviewing the recorded videos and determining the severity of dyskinesia through the UDysRS for every patient. The sensor device yielded only one value for dyskinesia severity, which was calculated by averaging the recorded device readings. Correlation between the results of physician’s assessment and the sensor output was analyzed with the Spearman’s correlation coefficient. The correlation coefficient between the sensor output and UDysRS result was 0.70 (CI 95%: 0.33–0.88; p = 0.01). Since the sensor was located on the waist, the correlation between the sensor output and the results of the trunk and legs scale sub-items was calculated: 0.91 (CI 95% 0.76–0.97: p < 0.001). The conclusion is that the magnitude of dyskinesia, as measured by the tested device, presented good correlation with that observed by a physician.

Efficacy and safety of extended-release amantadine in levodopa-induced dyskinesias: a meta-analysis

Aim: To determine the effectiveness and safety of extended-release amantadine (ADS-5102) for levodopa-induced dyskinesias (LID) in patients with Parkinson disease (PD) by conducting a meta-analysis of relevant trials. Methods: The electronic databases were searched on or before March 1, 2019 for relevant trials. Only randomized, double-blind, parallel-group, placebo-controlled trials using ADS-5102 for LID in PD were included. Results: The ADS-5102 showed a reduction in the dyskinesia scores (mean difference: -9.56: CI: -10.05 to -9.07; p < 0.00001) and in the on time without troublesome dyskinesia (mean difference 2.50: CI 2.38 to 2.63; p < 0.00001). The adverse events identified in ADS-5102 were visual hallucinations, constipation, dry mouth and fall. Conclusion: ADS-5102 can be used as an adjunct therapy for LID.

Phosphoramidate derivates as controlled-release prodrugs of l-Dopa

l-Dopa has continued to be a mainstay in the symptomatic treatment of Parkinson's disease (PD). However, extensive peripheral metabolism, a short systemic circulation half-life and development of motor complications called dyskinesia prevents its long-term utilization as a PD therapeutic. Herein, we report a series of phosphoramidate derivatives of l-Dopa and controlled release of l-Dopa at pH 7.4 and 3. The kinetic data for the release of l-Dopa support our hypothesis that a proximal carboxylic acid can promote the pH-triggered hydrolysis of the phosphoramidate PN bond. As expected, esterification of the proximal carboxylic acid protects the scaffold from rapid release at low pH. This latter observation is particularly noteworthy as it suggests that the phosphoramidate-based l-Dopa-conjugate scaffold can be adapted for oral administration as an ester prodrug.

Deep Learning for Medication Assessment of Individuals with Parkinson's Disease Using Wearable Sensors

Motor fluctuations between "OFF" state (with no benefit from medication) and " ON" state (with optimum benefit from medication) are a major focus of clinical managements in individuals with mid-stage and advance Parkinson's disease (PD). In this work, an automated algorithm based on Long Short-Term Memory (LSTM) as a deep learning method is developed to identify motor fluctuations in individuals with PD using wearable sensors during a variety of daily living activities. This network was evaluated on two datasets i.e., Dataset 1 and Dataset 2) that included recordings of 19 individuals with PD using subject-based leave-one-out cross-validation. The designed LSTM network yielded promising results using only one ankle sensor with an average classification rate of 73% and 77% for Dataset 1 and Dataset 2, respectively.

L-DOPA-Induced Motor Impairment and Overexpression of Corticostriatal Synaptic Components Are Improved by the mGluR5 Antagonist MPEP in 6-OHDA-Lesioned Rats

Levodopa (L-DOPA) is still the most effective drug for the treatment of Parkinson's disease (PD). However, the long-term therapy often triggers L-DOPA-induced dyskinesia (LID). Metabotropic glutamate receptor type 5 (mGluR5) is abundant in the basal ganglia, and its inhibition is thought to modulate postsynaptic excitatory synaptic transmission and glutamate hyperactivity in PD and LID. In this report, we examined the effects of mGluR5-specific antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP) on LID and synaptic components in the PD model rat. We found the selective mGluR5 antagonist MPEP attenuated abnormal involuntary movements, prolonged the duration of rotational response, reversed the decrease of left forepaw adjusting steps, and reduced overexpression of striatal mGluR5 in the LID rats. Moreover, our results showed much thicker postsynaptic densities, narrower synapse cleft, as well as the increased ratio of perforated synapses induced by L-DOPA treatment, while coadministration of L-DOPA and MPEP reversed these postsynaptic effects. Finally, MPEP reduced overexpression of the two postsynaptic proteins (PSD-95 and SAP102) induced by L-DOPA treatment. Hence, these results provide evidence that aberrant neural plasticity at corticostriatal synapses in the striatum is closely correlated with the occurrence of LID, and targeted inhibition of mGluR5 by MPEP alleviates LID in the PD rat model.

Roles of the M4 acetylcholine receptor in the basal ganglia and the treatment of movement disorders

Acetylcholine (ACh) released from cholinergic interneurons acting through nicotinic and muscarinic acetylcholine receptors (mAChRs) in the striatum have been thought to be central for the potent cholinergic regulation of basal ganglia activity and motor behaviors. ACh activation of mAChRs has multiple actions to oppose dopamine (DA) release, signaling, and related motor behaviors and has led to the idea that a delicate balance of DA and mAChR signaling in the striatum is critical for maintaining normal motor function. Consistent with this, mAChR antagonists have efficacy in reducing motor symptoms in diseases where DA release or signaling is diminished, such as in Parkinson's disease and dystonia, but are limited in their utility because of severe adverse effects. Recent breakthroughs in understanding both the anatomical sites of action of ACh and the mAChR subtypes involved in regulating basal ganglia function reveal that the M₄ subtype plays a central role in regulating DA signaling and release in the basal ganglia. These findings have raised the possibility that sources of ACh outside of the striatum can regulate motor activity and that M₄ activity is a potent regulator of motor dysfunction. We discuss how M₄ activity regulates DA release and signaling, the potential sources of ACh that can regulate M₄ activity, and the implications of targeting M₄ activity for the treatment of the motor symptoms in movement disorders. © 2019 International Parkinson and Movement Disorder Society.

Non-Linear Dynamical Analysis of Resting Tremor for Demand-Driven Deep Brain Stimulation

Parkinson's Disease (PD) is currently the second most common neurodegenerative disease. One of the most characteristic symptoms of PD is resting tremor. Local Field Potentials (LFPs) have been widely studied to investigate deviations from the typical patterns of healthy brain activity. However, the inherent dynamics of the Sub-Thalamic Nucleus (STN) LFPs and their spatiotemporal dynamics have not been well characterized. In this work, we study the non-linear dynamical behaviour of STN-LFPs of Parkinsonian patients using ε -recurrence networks. RNs are a non-linear analysis tool that encodes the geometric information of the underlying system, which can be characterised (for example, using graph theoretical measures) to extract information on the geometric properties of the attractor. Results show that the activity of the STN becomes more non-linear during the tremor episodes and that ε -recurrence network analysis is a suitable method to distinguish the transitions between movement conditions, anticipating the onset of the tremor, with the potential for application in a demand-driven deep brain stimulation system.

Influence of DRD1 and DRD3 Polymorphisms in the Occurrence of Motor Effects in Patients with Sporadic Parkinson's Disease

Parkinson's disease (PD) is a multisystem disorder that affects 2-3% of the population ≥ 65 years of age. The main pharmacologic agent use in the treatment of clinical symptoms of PD is levodopa (L-DOPA). However, the chronic use of L-DOPA might result in the emergence of motor complications such as motor fluctuation and dyskinesia. Previous studies have shown that the inter-individual variability and pharmacogenetic profile of PD patients seem to influence the occurrence of motor complications. For these reasons, the purpose of this study was to evaluate a possible relationship between DRD1 A48G and DRD3 Ser9Gly genetic variants with the occurrence of motor complications in PD patients in a Brazilian population. A total of 228 patients with idiopathic PD were enrolled. Patients were genotyped for DRD1 A48G and DRD3 Ser9Gly polymorphisms using PCR-RFLP. The univariate and multivariate analyses were performed to assess the association of these polymorphisms with the occurrence of motor fluctuation and dyskinesia in PD patients. Multiple Poisson regression analyses showed a protector effect to the occurrence of dyskinesia for individuals carrying of the DRD1 G/G genotype (PR 0.294; CI 0.09-0.87; p ≤ 0.020) after the threshold Bonferroni's. Besides, we verified risk increased to the occurrence of motor complications with daily L-DOPA dosage, disease duration, and users of rasagiline, selegiline, or entacapone (p < 0.05 for all). Our results suggest that the DRD1 A48G polymorphism and the presence of extrinsic and intrinsic factors may role an effect in the occurrence of dyskinesia in PD patients.

Pathophysiological clues to therapeutic applications of glutamate mGlu5 receptor antagonists in levodopa-induced dyskinesia

Levodopa remains to be the mainstay for treatment of Parkinson disease (PD). Long-term levodopa treatment bears a risk for developing levodopa-induced dyskinesia (LID). LID significantly overshadows patients' quality of life and therapeutic efficacy of levodopa. Pre- and post-synaptic changes in dopamine secretion and signaling, along with altered glutamate receptor expression and glutamatergic signaling in striatal neurons, and the resulting disinhibition-like changes in the corticostriatal circuitry, lead to aberrant activity of motor cortex and formation of LID. Research has highlighted the role of group I metabotropic glutamate receptors especially the metabotropic glutamate receptor 5 (mGlu5) in formation of LID through potentiating of ionotropic glutamate NMDA receptors and dopamine D₁/D₅ receptors in direct pathway. Accordingly, MTEP and MPEP were the first mGlu5 receptor antagonists which were shown to attenuate LID in animal models through suppression of downstream signaling cascades involving mitogen-activated protein kinase (MAPK) and FosB/delta FosB activation, as well as modulation of prodynorphinegic, preproenkephalinergic, and GABA-ergic neurotransmission systems. Beneficial effects of other mGlu5 receptor antagonists such as AFQ056/mavoglurant and ADX48621/dipraglurant in amelioration of LID has been shown not only in animal models but also in clinical trials. Considering the presence of mGlu receptor dysregulation in rapid eye movement (REM) sleep behavior disorder and depression, which are prodromal signs of PD, along with the neuroprotective effects of mGlu receptor antagonists, and their cognitive benefits, potential effectiveness of mGlu receptor antagonists in early prevention of PD remains to be investigated.

Deep brain stimulation of the ventroanterior and ventrolateral thalamus improves motor function in a rat model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease with affected individuals exhibiting motor symptoms of bradykinesia, muscle rigidity, tremor, postural instability and gait dysfunction. The current gold standard treatment is pharmacotherapy with levodopa, but long-term use is associated with motor response fluctuations and can cause abnormal movements called dyskinesias. An alternative treatment option is deep brain stimulation (DBS) with the two FDA-approved brain targets for PD situated in the basal ganglia; specifically, in the subthalamic nucleus (STN) and globus pallidus pars interna (GPi). Both improve quality of life and motor scores by ~50-70% in well-selected patients but can also elicit adverse effects on cognition and other non-motor symptoms. Therefore, identifying a novel DBS target that is efficacious for patients not optimally responsive to current DBS targets with fewer side-effects has clear clinical merit. Here, we investigate whether the ventroanterior (VA) and ventrolateral (VL) motor nuclei of the thalamus can serve as novel and effective DBS targets for PD. In the limb-use asymmetry test (LAT), hemiparkinsonian rats showcased left forelimb akinesia and touched only 6.5 ± 1.3% with that paw. However, these animals touched equally with both forepaws with DBS at 10 Hz, 100 μsec pulse width and 100 uA cathodic stimulation in the VA (n = 7), VL (n = 8) or at the interface between the two thalamic nuclei which we refer to as the VA|VL (n = 12). With whole-cell patch-clamp recordings, we noted that VA|VL stimulation in vitro increased the number of induced action potentials in proximal neurons in both areas albeit VL neurons transitioned from bursting to non-bursting action potentials (APs) with large excitatory postsynaptic potentials time-locked to stimulation. In contrast, VA neurons were excited with VA|VL electrical stimulation but with little change in spiking phenotype. Overall, our findings show that DBS in the VA, VL or VA|VL improved motor function in a rat model of PD; plausibly via increased excitation of residing neurons.

Assessment of response to medication in individuals with Parkinson's disease

BACKGROUND AND OBJECTIVE

Motor fluctuations between akinetic (medication OFF) and mobile phases (medication ON) states are one of the most prevalent complications of patients with Parkinson's disease (PD). There is a need for a technology-based system to provide reliable information about the duration in different medication phases that can be used by the treating physician to successfully adjust therapy.

METHODS

Two KinetiSense motion sensors were mounted on the most affected wrist and ankle of 19 PD subjects (age: 42-77, 14 males) and collected movement signals as the participants performed seven daily living activities in their medication OFF and ON phases. A feature selection and a classification algorithm based on support vector machine with fuzzy labeling was developed to detect medication ON/OFF states using gyroscope signals. The algorithm was trained using approximately 15% of the data from four activities and tested on the remaining data.

RESULTS

The algorithm was able to detect medication ON and OFF states with 90.5% accuracy, 94.2% sensitivity, and 85.4% specificity. It performed equally well for all the activities with an average accuracy of 91.3% for the activities that were used in the training phase and 88.4% for the new activities.

CONCLUSIONS

The developed sensor-based algorithm could provide objective and accurate assessment of medication states that can lead to successful adjustment of the therapy resulting in considerably improved care delivery and quality of life of PD patients.

Serial I-123-FP-CIT SPECT Image Findings of Parkinson's Disease Patients With Levodopa-Induced Dyskinesia

Background: Levodopa-induced dyskinesia (LID) is a major complication of dopamine replacement drug usage in Parkinson's disease (PD) patients. Since the mechanism of LID is yet unclear, we analyzed serial [I-123] N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane (I-123 FP-CIT) single photon emission computed tomography (SPECT) images. We investigated the changes of dopaminergic innervation during the progression of PD in relation to the development of LID.

Methods: Data were obtained from the Parkinson's Progression Markers Initiative (PPMI) database. Two hundred and ninety PD dopamine replacement drug-naïve patients (age 61.0 ± 9.7, M: F = 195: 95) were enrolled. I-123 FP-CIT SPECT images from baseline, 12, 24, and 48 months were analyzed among with clinical factors. specific binding ratios (SBRs) of the striatal regions from I-123 FP-CIT SPECT images were analyzed. We used independent tests and logistic regression for analysis of LID risk association.

Results: Among 290 patients, 36 patients developed LID after 48 months follow-up. Baseline MDS-UPDRS Part II and III scores were significantly higher in the PD patients with LID, compared with the PD patients without LID. Striatal SBRs were significantly lower in the PD patients with LID at baseline, 24 and 48 months (p < 0.001). Multivariate analysis revealed MDS-UPDRS Part II and putaminal SBRs at baseline and 24 months to be significantly associated with the development of LID (p < 0.001). Also, patients who developed LID at 48 months had a higher decrease rate of putaminal SBR at the 24 months (p < 0.05), and 48 months (p < 0.01) period.

Conclusion: In this study, we demonstrated the serial changes of the nigrostriatal dopaminergic innervation in relationship to LID development for the first time. The deterioration rate of dopaminergic innervation was significantly higher in the PD patients who developed LID, compared with the PD patients who did not develop LID. Serial follow up I-123 FP-CIT SPECT acquisition during the course of PD could be helpful in predicting the development of LID.

Chemical management of levodopa-induced dyskinesia in Parkinson's disease patients

INTRODUCTION

Levodopa-induced dyskinesias (LID) appears in more than 50% of Parkinson's disease patients after 5 years of treatment and clinicians always have to ensure that there is a balance between the beneficial effect of the treatment and the potential complications.

AREAS COVERED

In this review, the authors discuss the treatment of LID. Treatment can be divided into strategies for preventing their occurrence, modification of dopaminergic therapy, and providing more continuous dopaminergic stimulation as well as the use of nondopaminergic drugs.

EXPERT OPINION

Amantadine is currently considered the most effective drug for the treatment of LID. Several compounds developed to target adenosine, adrenergic, glutamatergic, and serotonergic receptors have shown to significantly decrease dyskinesias in animal models. However, despite promising preclinical results, translation to clinical practice remains challenging and majority of these compounds failed to decrease LID in randomized controlled trials with moderate-to-advanced parkinsonian patients. Despite promising results with nondopaminergic drugs, treatment of dyskinesias is still challenging and largely due to their side effects. Future research should focus on developing treatments that can provide continuous dopaminergic delivery throughout the day in a noninvasive manner. Studies on the impact of the early administration of long-acting formulations of levo-3,4-dihydroxy-phenylalanine on dyskinesias are also necessary.

DAT gene polymorphisms (rs28363170, rs393795) and levodopa-induced dyskinesias in Parkinson's disease

L-dopa-induced dyskinesias (LID) is a common motor side effect of levodopa therapy of Parkinson's disease (PD). The identified predictors may only partially account for the risk of developing LID and genetic factors may contribute to this variability. The present study is aimed to investigate whether polymorphisms in the dopamine transporter gene (DAT) are associated with the risk of developing LID. Genotyping of the 40-bp VNTR (rs28363170) and rs393795 (A/C) polymorphisms of the DAT gene was performed in a well-characterized cohort of 181 Italian PD patients in treatment with L-DOPA for 3 years or more. The results of our study show that there is no difference in dyskinesias prevalence among carriers of the two DAT gene polymorphisms. However, the combination of the two genotypes 10R/10R (rs28363170) and A carrier (rs393795) of the DAT gene reduces the risk of LID occurrence during long-term therapy with l-DOPA with respect to the PD subjects who did not carry these alleles (OR = 0.31; 95% CI, 0.09-0.88). Also based on a logistic regression analysis, the 10R/10R and the A carrier allele of the rs393795 polymorphisms of the DAT gene, could reduce the susceptibility to develop LID during levodopa therapy adjusted by demographical and clinical variables (OR = 0.19; 95% CI, 0.05-0.69). Additional studies further investigating the rs28363170 and rs393795 polymorphisms with LID in PD are needed to clarify their role in different ethnicities.

The 10-year Landscape of United States-Registered Parkinson Disease Clinical Trials: 2007-2016

Background

We know little about how well the goals and results of clinical trials in Parkinson disease (PD) reflect the priorities of patients and the broader PD community.

Objectives

We conducted a review of registered trials on http://clincialtrials.gov from 2007 to 2016 to explore whether PD trials have moved closer to the therapeutic priority goals articulated by the PD community.

Methods

Using the search terms: Parkinson, interventional trials, phase "0-4," we categorized therapeutic PD studies from http://clinicaltrials.gov between January 1, 2007 and December 31, 2016. Seven hundred and sixty-six trials met the criteria for analysis. We explored temporal trends in the utilization of balance problems and falls; mood symptoms, including stress and anxiety; cognitive dysfunction, including dementia; and dyskinesias as primary outcomes. We analyzed trials where recruitment was listed as "completed" (n = 391) to explore publication rates.

Results

Balance problems and falls were listed as primary outcome measures in 125 studies (16.3%), cognitive measures in 48 (6.3%), mood features in 37 (4.8%), and dyskinesias in 30 (3.9%). Trials using balance problems and falls as a primary outcome increased in frequency per year between 2007 and 2016 (Z = -2.128, p = 0.033) unlike the proportion of trials evaluating cognitive dysfunction including dementia (Z = -0.380, p = 0.704), mood symptoms including stress and anxiety (Z = 0.345, p = 0.730), or dyskinesias (Z = 0.340, p = 0.734), which did not show temporal changes. 231 (59.1%) completed trials had results published in manuscript form as of 5/1/2017, leaving 40.9% of trials unpublished.

Conclusions

PD trials focusing on balance problems and falls are becoming more common. About 40% of completed PD trials are unpublished, reflecting suboptimal utilization of participant efforts.

Opioidergic Modulation of Striatal Circuits, Implications in Parkinson's Disease and Levodopa Induced Dyskinesia

The functional organization of the dorsal striatum is complex, due to the diversity of neural inputs that converge in this structure and its subdivision into direct and indirect output pathways, striosomes and matrix compartments. Among the neurotransmitters that regulate the activity of striatal projection neurons (SPNs), opioid neuropeptides (enkephalin and dynorphin) play a neuromodulatory role in synaptic transmission and plasticity and affect striatal-based behaviors in both normal brain function and pathological states, including Parkinson's disease (PD). We review recent findings on the cell-type-specific effects of opioidergic neurotransmission in the dorsal striatum, focusing on the maladaptive synaptic neuroadaptations that occur in PD and levodopa-induced dyskinesia. Understanding the plethora of molecular and synaptic mechanisms underpinning the opioid-mediated modulation of striatal circuits is critical for the development of pharmacological treatments that can alleviate motor dysfunctions and hyperkinetic responses to dopaminergic stimulant drugs.

Levodopa-induced dyskinesia: clinical features, incidence, and risk factors

Symptoms of Parkinson's disease have been controlled with levodopa for many years; however, motor complications consisting of wearing off of medication effect and dyskinesias tend to occur within a few years of starting levodopa. Motor complications can begin a few months after taking levodopa, with the average time to onset estimated to be 6.5 years. Dyskinesias can be troublesome and require intervention. Levodopa-induced dyskinesia can be composed of a variety of movement disorders including chorea, dystonia, ballism, myoclonus, and akathisia. Based on the clinical pattern, the most common dyskinesia is chorea and choreoathetosis. The clinical manifestations can be divided into three main categories based on their clinical movement patterns and the temporal correlation between the occurrence of dyskinesia and the levodopa dosing: on or peak-dose dyskinesias, biphasic dyskinesias, and Off dyskinesias. Severe cases of dyskinesia have been reported, with the extreme being dyskinesia-hyperpyrexia syndrome. The prevalence of LID has been reported in many studies, but the reported incidence varies. The rate of LID development is from 3 to 94%. The prevalence of LID mainly depends on age at onset, disease duration, and severity, and duration of levodopa therapy. Some of the risk factors for the development of dyskinesia are modifiable. Modifiable risk factors include levodopa dose and body weight. Non-modifiable risk factors include age, gender, duration of disease, clinical subtype, disease progression, disease severity, and genetic factors.

On the neuronal circuitry mediating L-DOPA-induced dyskinesia

With the advent of rodent models of l-DOPA-induced dyskinesia (LID), a growing literature has linked molecular changes in the striatum to the development and expression of abnormal involuntary movements. Changes in information processing at the striatal level are assumed to impact on the activity of downstream basal ganglia nuclei, which in turn influence brain-wide networks, but very little is actually known about systems-level mechanisms of dyskinesia. As an aid to approach this topic, we here review the anatomical and physiological organisation of cortico-basal ganglia-thalamocortical circuits, and the changes affecting these circuits in animal models of parkinsonism and LID. We then review recent findings indicating that an abnormal cerebellar compensation plays a causal role in LID, and that structures outside of the classical motor circuits are implicated too. In summarizing the available data, we also propose hypotheses and identify important knowledge gaps worthy of further investigation. In addition to informing novel therapeutic approaches, the study of LID can provide new clues about the interplay between different brain circuits in the control of movement.

A Kinematic Sensor and Algorithm to Detect Motor Fluctuations in Parkinson Disease: Validation Study Under Real Conditions of Use

BACKGROUND

A new algorithm has been developed, which combines information on gait bradykinesia and dyskinesia provided by a single kinematic sensor located on the waist of Parkinson disease (PD) patients to detect motor fluctuations (On- and Off-periods).

OBJECTIVE

The goal of this study was to analyze the accuracy of this algorithm under real conditions of use.

METHODS

This validation study of a motor-fluctuation detection algorithm was conducted on a sample of 23 patients with advanced PD. Patients were asked to wear the kinematic sensor for 1 to 3 days at home, while simultaneously keeping a diary of their On- and Off-periods. During this testing, researchers were not present, and patients continued to carry on their usual daily activities in their natural environment. The algorithm's outputs were compared with the patients' records, which were used as the gold standard.

RESULTS

The algorithm produced 37% more results than the patients' records (671 vs 489). The positive predictive value of the algorithm to detect Off-periods, as compared with the patients' records, was 92% (95% CI 87.33%-97.3%) and the negative predictive value was 94% (95% CI 90.71%-97.1%); the overall classification accuracy was 92.20%.

CONCLUSIONS

The kinematic sensor and the algorithm for detection of motor-fluctuations validated in this study are an accurate and useful tool for monitoring PD patients with difficult-to-control motor fluctuations in the outpatient setting.

Repurposing sex steroids and related drugs as potential treatment for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder for which a greater prevalence and incidence is described in men. This suggests a protective effect of sex hormones in the brain. Therefore, steroids and drugs to treat endocrine conditions could have additional application for PD. Here, we review the protective effect of sex hormones, particularly estrogens, progesterone, androgens and dehydroepiandrosterone, in animal models of PD and also in human studies. Data also support that drugs affecting estrogen neurotransmission such as selective estrogen receptor modulators or affecting steroid metabolism with 5α-reductase inhibitors could be repositioned for treatment of PD. Sex steroids are also modulator of neurotransmission, thus they could repurposed to treat PD motor symptoms and to modulate the response to PD medication. No drug is yet available to limit PD progression. PD is a complex disease implicating multiple pathological processes and a therapeutic strategy using drugs with several mechanisms of action, such as sex steroids and endocrine drugs are interesting repositioning options for symptomatic treatment and disease-modifying activity for PD. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Molecular basis of dopamine replacement therapy and its side effects in Parkinson's disease

There is currently no cure for Parkinson's disease. The symptomatic therapeutic strategy essentially relies on dopamine replacement whose efficacy was demonstrated more than 50 years ago following the introduction of the dopamine precursor, levodopa. The spectacular antiparkinsonian effect of levodopa is, however, balanced by major limitations including the occurrence of motor complications related to its particular pharmacokinetic and pharmacodynamic properties. Other therapeutic strategies have thus been developed to overcome these problems such as the use of dopamine receptor agonists, dopamine metabolism inhibitors and non-dopaminergic drugs. Here we review the pharmacology and molecular mechanisms of dopamine replacement therapy in Parkinson's disease, both at the presynaptic and postsynaptic levels. The perspectives in terms of novel drug development and prediction of drug response for a more personalised medicine will be discussed.

Animal models of l-dopa-induced dyskinesia in Parkinson's disease

Understanding the biological mechanisms of l-dopa-induced motor complications is dependent on our ability to investigate these phenomena in animal models of Parkinson's disease. The most common motor complications consist in wearing-off fluctuations and abnormal involuntary movements appearing when plasma levels of l-dopa are high, commonly referred to as peak-dose l-dopa-induced dyskinesia. Parkinsonian models exhibiting these features have been well-characterized in both rodent and nonhuman primate species. The first animal models of peak-dose l-dopa-induced dyskinesia were produced in monkeys lesioned with N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and treated chronically with l-dopa to elicit choreic movements and dystonic postures. Seminal studies were performed in these models using both metabolic mapping and electrophysiological techniques, providing fundamental pathophysiological insights that have stood the test of time. A decade later, it was shown possible to reproduce peak-dose l-dopa-induced dyskinesia in rats and mice rendered parkinsonian with nigrostriatal 6-hydroxydopamine lesions. When treated with l-dopa, these animals exhibit abnormal involuntary movements having both hyperkinetic and dystonic components. These models have enabled molecular- and cellular-level investigations into the mechanisms of l-dopa-induced dyskinesia. A flourishing literature using genetically engineered mice is now unraveling the role of specific genes and neural circuits in the development of l-dopa-induced motor complications. Both non-human primate and rodent models of peak-dose l-dopa-induced dyskinesia have excellent construct validity and provide valuable tools for discovering therapeutic targets and evaluating potential treatments. © 2018 International Parkinson and Movement Disorder Society.

Mitochondrial DNA depletion by ethidium bromide decreases neuronal mitochondrial creatine kinase: Implications for striatal energy metabolism

Mitochondrial DNA (mtDNA), the discrete genome which encodes subunits of the mitochondrial respiratory chain, is present at highly variable copy numbers across cell types. Though severe mtDNA depletion dramatically reduces mitochondrial function, the impact of tissue-specific mtDNA reduction remains debated. Previously, our lab identified reduced mtDNA quantity in the putamen of Parkinson's Disease (PD) patients who had developed L-DOPA Induced Dyskinesia (LID), compared to PD patients who had not developed LID and healthy subjects. Here, we present the consequences of mtDNA depletion by ethidium bromide (EtBr) treatment on the bioenergetic function of primary cultured neurons, astrocytes and neuron-enriched cocultures from rat striatum. We report that EtBr inhibition of mtDNA replication and transcription consistently reduces mitochondrial oxygen consumption, and that neurons are significantly more sensitive to EtBr than astrocytes. EtBr also increases glycolytic activity in astrocytes, whereas in neurons it reduces the expression of mitochondrial creatine kinase mRNA and levels of phosphocreatine. Further, we show that mitochondrial creatine kinase mRNA is similarly downregulated in dyskinetic PD patients, compared to both non-dyskinetic PD patients and healthy subjects. Our data support a hypothesis that reduced striatal mtDNA contributes to energetic dysregulation in the dyskinetic striatum by destabilizing the energy buffering system of the phosphocreatine/creatine shuttle.

Dopamine receptors and BDNF-haplotypes predict dyskinesia in Parkinson's disease

OBJECTIVE

Dyskinesia is a known side-effect of the treatment of Parkinson's Disease (PD). We examined the influence of haplotypes in three dopamine receptors (DRD1, DRD2 and DRD3) and the Brain Derived Neurotrophic Factor (BDNF) on dyskinesia.

METHODS

Patient data were drawn from a population-based case-control study. We included 418 patients with confirmed diagnoses by movement disorder specialists, using levodopa and a minimum three years disease duration at the time of assessment. Applying Haploview and Phase, we created haploblocks for DRD1-3 and BDNF. Risk scores for DRD2 and DRD3 were generated. We calculated risk ratios using Poisson regression with robust error variance.

RESULTS

There was no difference in dyskinesia prevalence among carriers of various haplotypes in DRD1. However, one haplotype in each DRD2 haploblocks was associated with a 29 to 50% increase in dyskinesia risk. For each unit increase in risk score, we observed a 16% increase in dyskinesia risk for DRD2 (95%CI: 1.05-1.29) and a 17% (95%CI: 0.99-1.40) increase for DRD3. The BDNF haploblock was not associated, but the minor allele of the rs6265 SNP was associated with dyskinesia (adjusted RR 1.31 (95%CI: 1.01-1.70)).

CONCLUSION

Carriers of DRD2 risk haplotypes and possibly the BDNF variants rs6265 and DRD3 haplotypes, were at increased risk of dyskinesia, suggesting that these genes may be involved in dyskinesia related pathomechanisms. PD patients with these genetic variants might be prime candidates for treatments aiming to prevent or delay the onset of dyskinesia.

Effect of the 5α-reductase enzyme inhibitor dutasteride in the brain of intact and parkinsonian mice

Dutasteride is a 5alpha-reductase inhibitor in clinical use to treat endocrine conditions. The present study investigated the neuroprotective mechanisms of action of dutasteride in intact and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-lesioned mice using a low dose of MPTP not affecting motor activity modeling early stages of Parkinson's disease (PD). We hypothesized that dutasteride neuroprotection is due to altered steroids levels. Dutasteride pre-treatment prevented loss of striatal dopamine (DA) and its metabolite DOPAC. Dutasteride decreased effects of MPTP on striatal dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2) and D2 DA receptor specific binding while D1 receptor specific binding remained unchanged. Dutasteride enhanced DAT specific binding and the glycosylated form of DAT in intact mice. MPTP-lesioned mice had plasma and brain testosterone and dihydrotestosterone levels lower than control mice whereas progesterone and its metabolites (dihydroprogesterone, isopregnanolone and tetrahydroprogesterone) pathway showed increases. Dutasteride treatment by inhibiting transformation of progesterone and testosterone to its metabolites elevated plasma and brain concentrations of testosterone compared to MPTP mice and decreased DHT levels in intact mice. Plasma and brain estradiol levels were low and remained unchanged by MPTP and/or dutasteride treatment. Dutasteride treatment did not affect striatal phosphorylation of Akt and its downstream substrate GSK3β as well as phosphorylation of ERK1/2 in intact and MPTP lesioned MPTP mice. Striatal glial fibrillary acidic protein (GFAP) levels were markedly elevated in MPTP compared to control mice and dutasteride reduced GFAP levels in MPTP mice. Treatment with dutasteride post-lesion left unchanged striatal DA levels. These results suggest dutasteride as promising drug for PD neuroprotection.