The in vitro receptor profile of rotigotine: a new agent for the treatment of Parkinson’s disease

Small Molecules in Parkinson's Disease Therapy: From Dopamine Pathways to New Emerging Targets

Parkinson's disease (PD) is a chronic, progressive neurological disorder affecting approximately 10 million people worldwide, with prevalence expected to rise as the global population ages. It is characterized by the degeneration of dopamine-producing neurons in the substantia nigra pars compacta, leading to motor symptoms such as tremor, rigidity, bradykinesia, postural instability, and gait disturbances, as well as non-motor symptoms including olfactory disturbances, sleep disorders, and depression. Currently, no cure exists for PD, and most available therapies focus on symptom alleviation. This dopamine deficiency impairs motor control, and since dopamine itself cannot cross the blood-brain barrier (BBB), the precursor L-Dopa is commonly used in treatment. L-Dopa is administered with enzyme inhibitors to prevent premature conversion outside the brain, allowing it to cross the BBB and convert to dopamine within the central nervous system. Although these therapies have improved symptom management, recent research has revealed additional molecular factors in PD pathology, such as α-synuclein aggregation, mitochondrial dysfunction, and lysosomal abnormalities, contributing to its complexity. These discoveries open up possibilities for neuroprotective therapies that could slow disease progression. In this review, we categorize PD therapeutic targets into two main groups: currently used therapies and targets under active research. We also introduce promising small-molecule compounds studied between 2019 and 2023, which may represent future treatment options. By examining both established and emerging targets, we aim to highlight effective strategies and potential directions for future drug development in Parkinson's disease therapy.

Chronic endothelial dopamine receptor stimulation improves endothelial function and hemodynamics in autosomal dominant polycystic kidney disease

Altered polycystin-mediated endothelial flow mechanosensitivity contributes to the development of hypertension and cardiovascular complications in patients with autosomal dominant polycystic kidney disease (ADPKD). Stimulation of endothelial type 5 dopamine receptors (DR5) can acutely compensate for the endothelial consequences of polycystin deficiency, but the chronic impact of this approach must be evaluated in ADPKD. Nineteen patients with ADPKD on standard of care therapy were randomized to receive a 2-month treatment with the DR agonist rotigotine using transdermal patches, nine at 2 mg/24hours and ten at 4 mg/24hours or while ten were untreated. Rotigotine at the dose of 4 mg/24hours significantly increased nitric oxide release (nitrite levels from 10±30 to 46±34 nmol/L) and radial artery endothelium-dependent flow-mediated dilatation (from 16.4±6.3 to 22.5±7.3%) in response to hand skin heating. Systemic hemodynamics were not significantly modified but aplanation tonometry showed that rotigotine at 4 mg/24hours reduced aortic augmentation index and pulse pressure without affecting carotid-to femoral pulse wave velocity. Plasma creatinine and urea, urinary cyclic AMP, which contributes to cyst growth in ADPKD and copeptin, a surrogate marker of vasopressin, were not affected by rotigotine. In mice with a specific deletion of polycystin-1 in endothelial cells, chronic infusion of the peripheral DR5 agonist fenoldopam also improved mesenteric artery flow-mediated dilatation and reduced blood pressure. Thus, our study demonstrates that in patients with ADPKD, chronic administration of rotigotine improves conduit artery endothelial function through the restoration of flow-induced nitric oxide release as well as hemodynamics suggesting that endothelial DR5 activation may represent a promising pharmacological approach to prevent cardiovascular complications of ADPKD.

Mdm2-mediated ubiquitination of PKCβII is responsible for insulin-induced heterologous desensitization of dopamine D3 receptor

The insulin and dopaminergic systems in the brain are associated with schizophrenia and Parkinson's disease with respect to etiology and treatment. The present study investigated the crosstalk between the insulin receptor (IR) and dopamine receptor and found that insulin stimulation selectively inhibits signaling of D3 R in a PKCβII-dependent manner. Upon insulin stimulation, E3 ligase enzyme Mdm2 moves out of the nucleus to ubiquitinate PKCβII. Subsequently, ubiquitinated PKCβII translocates to the cell membrane and interacts with D3 R in a phosphorylation-dependent manner at S229/257, resulting in the attenuation of D3 R signaling and initiating clathrin-mediated endocytosis and downregulation. Considering that both IR and D3 R are closely related to some neuropsychosis, this study could provide new molecular insight into the etiology of the disorder.

A preclinical secondary pharmacology resource illuminates target-adverse drug reaction associations of marketed drugs

In vitro secondary pharmacology assays are an important tool for predicting clinical adverse drug reactions (ADRs) of investigational drugs. We created the Secondary Pharmacology Database (SPD) by testing 1958 drugs using 200 assays to validate target-ADR associations. Compared to public and subscription resources, 95% of all and 36% of active (AC50 < 1 µM) results are unique to SPD, with bias towards higher activity in public resources. Annotating drugs with free maximal plasma concentrations, we find 684 physiologically relevant unpublished off-target activities. Furthermore, 64% of putative ADRs linked to target activity in key literature reviews are not statistically significant in SPD. Systematic analysis of all target-ADR pairs identifies several putative associations supported by publications. Finally, candidate mechanisms for known ADRs are proposed based on SPD off-target activities. Here we present a freely-available resource for benchmarking ADR predictions, explaining phenotypic activity and investigating clinical properties of marketed drugs.

Dopamine agonists in Parkinson's disease: Impact of D1-like or D2-like dopamine receptor subtype selectivity and avenues for future treatment

Dopamine agonists (DAs) have demonstrated efficacy for the treatment of Parkinson's disease (PD) but are limited by adverse effects (AEs). DAs can vary considerably in their receptor subtype selectivity and affinity, chemical composition, receptor occupancy, and intrinsic activity on the receptor. Most currently approved DAs for PD treatment primarily target D2/D3 (D2-like) dopamine receptors. However, selective activation of D1/D5 (D1-like) dopamine receptors may enable robust activation of motor function while avoiding AEs related to D2/D3 receptor agonism. Full D1/D5 receptor-selective agonists have been explored in small, early-phase clinical studies, and although their efficacy for motor symptoms was robust, challenges with pharmacokinetics, bioavailability, cardiovascular AEs, and dyskinesia rates similar to levodopa prevented clinical advancement. Generally, repeated dopaminergic stimulation with full DAs is associated with frontostriatal dysfunction and sensitization that may induce plastic changes in the motor system, and neuroadaptations that produce long-term motor and nonmotor complications, respectively. Recent preclinical and clinical studies suggest that a D1/D5 receptor-selective partial agonist may hold promise for providing sustained, predictable, and robust motor control, while reducing risk for motor complications (e.g., levodopa-induced dyskinesia) and nonmotor AEs (e.g., impulse control disorders and excessive daytime sleepiness). Clinical trials are ongoing to evaluate this hypothesis. The potential emerging availability of novel dopamine receptor agonists with selective dopamine receptor pharmacology suggests that the older terminology "dopamine agonist" may need revision to distinguish older-generation D2/D3-selective agonists from D1/D5-selective agonists with distinct efficacy and tolerability characteristics.

Safety review of current pharmacotherapies for levodopa-treated patients with Parkinson's disease

INTRODUCTION

Levodopa remains the gold standard for treatment of Parkinson's disease (PD). Patients develop complications with disease progression, necessitating adjunctive therapy to control fluctuations in motor and non-motor symptoms and dyskinesia. Knowledge of medication safety and tolerability is critical to ascertain the benefit-risk ratio and select an adjunctive therapy that provides the highest chance for medication adherence. Posing a challenge are the sheer abundance of options, stemming from the development of several new drugs in recent years, as well as differences in commercial drug availability worldwide.

AREAS COVERED

This review evaluates the efficacy, safety, and tolerability of current US FDA-approved pharmacotherapies for levodopa-treated PD patients, including dopamine agonists, monoamine oxidase type-B inhibitors, catechol-O-methyltransferase inhibitors, the N-methyl-D-aspartate receptor antagonist amantadine, and the adenosine receptor antagonist istradefylline. Data were taken from pivotal phase III randomized controlled and post-surveillance studies, when available, that directly led to FDA-approval.

EXPERT OPINION

No strong evidence exists to support use of a specific adjunctive treatment for improving Off time. Only one medication has demonstrated improvement in dyskinesia in levodopa-treated PD patients; however, every patient cannot tolerate it and therefore adjunctive therapy should be tailored to an individual's symptoms and risk for specific adverse effects.

Role of dopamine agonists in Parkinson's disease therapy

Dopamine agonists are an important component of Parkinson's therapy. When weighing up the various therapy options, therapy with levodopa has recently been increasingly preferred due to its stronger efficacy and the ostensibly lower rate of side effects. The advantage of the lower incidence of motor complications during therapy with dopamine agonists was neglected. The occurrence of side effects can be explained by the different receptor affinity to the individual dopaminergic and non-dopaminergic receptors of the individual dopamine agonists. However, the different affinity to individual receptors also explains the different effect on individual Parkinson symptoms and can, therefore, contribute to a targeted use of the different dopamine agonists. Since comparative studies on the differential effect of dopamine agonists have only been conducted for individual substances, empirical knowledge of the differential effect is of great importance. Therefore, the guidelines for the treatment of Parkinson's disease do not consider the differential effect of the dopamine agonists. The historical consideration of dopamine agonists within Parkinson's therapy deserves special attention to be able to classify the current discussion about the significance of dopamine agonists.

G protein-coupled receptors in neurodegenerative diseases and psychiatric disorders

Neuropsychiatric disorders are multifactorial disorders with diverse aetiological factors. Identifying treatment targets is challenging because the diseases are resulting from heterogeneous biological, genetic, and environmental factors. Nevertheless, the increasing understanding of G protein-coupled receptor (GPCR) opens a new possibility in drug discovery. Harnessing our knowledge of molecular mechanisms and structural information of GPCRs will be advantageous for developing effective drugs. This review provides an overview of the role of GPCRs in various neurodegenerative and psychiatric diseases. Besides, we highlight the emerging opportunities of novel GPCR targets and address recent progress in GPCR drug development.

The complex molecular pharmacology of the dopamine D2 receptor: Implications for pramipexole, ropinirole, and rotigotine

With L-DOPA, dopamine agonists such as pramipexole, ropinirole and rotigotine constitute key therapeutic options for the management of motor symptoms of Parkinson's disease. These compounds exert their beneficial effect on motor behaviours by activating dopamine D₂-class receptors and thereby compensating for the declining dopaminergic transmission in the dorsal striatum. Despite a strong similarity in their mechanism of action, these three dopamine agonists present distinct clinical profiles, putatively underpinned by differences in their pharmacological properties. In this context, this review aims at contributing to close the gap between clinical observations and data from molecular neuropharmacology by exploring the properties of pramipexole, ropinirole and rotigotine from both the clinical and molecular perspectives. Indeed, this review first summarizes and compares the clinical features of these three dopamine agonists, and then explores their binding profiles at the different dopamine receptor subtypes. Moreover, the signalling profiles of pramipexole, ropinirole and rotigotine at the D₂ receptor are recapitulated, with a focus on biased signalling and the potential therapeutic implications. Overall, this review aims at providing a unifying framework of interpretation for both clinicians and fundamental pharmacologists interested in a deep understanding of the pharmacological properties of pramipexole, ropinirole and rotigotine.

Mechanisms of D1/D2-like dopaminergic agonist, rotigotine, on lower urinary tract function in rat model of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative condition caused by the loss of dopaminergic neurons in the substantia nigra pars compacta. As activation of dopaminergic receptors is fundamentally involved in the micturition reflex in PD, the objective of this study was to determine the effect of a single dose of rotigotine ([-]2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin) on intercontraction interval (ICI) and voiding pressure (VP) in a rat model of PD. We used 27 female rats, PD was induced by injecting 6-hydroxydopamine (6-OHDA; 8 μg in 2 μL of 0.9% saline containing 0.3% ascorbic acid), and rotigotine was administrated at doses of 0.125, 0.25, or 0.5 mg/kg, either intravenous or subcutaneous injection. In rats with 6-OHDA-induced PD, intravenous injection of 0.25 or 0.5 mg/kg rotigotine led to a significantly lower ICI than after vehicle injection (p < 0.05). Additionally, VP was significantly lower in animals administered rotigotine compared to those injected with vehicle (p < 0.05). Compared to vehicle-injected animals, subcutaneous administration of rotigotine (0.125, 0.25, or 0.5 mg/kg) led to a significantly higher ICI at 2 h after injection (p < 0.05); however, there was no change in ICI after injection with (+)-SCH23390 hydrochloride. Dermal administration of rotigotine in a rat model of PD could suppress an overactive bladder.

Cognition and serotonin in Parkinson's disease

Cognitive impairment affects up to 80% of patients with Parkinson's disease (PD) and is associated with poor quality of life. PD cognitive dysfunction includes poor working memory, impairments in executive function and difficulty in set-shifting. The pathophysiology underlying cognitive impairment in PD is still poorly understood, but there is evidence to support involvements of the cholinergic, dopaminergic, and noradrenergic systems. Only rivastigmine, an acetyl- and butyrylcholinesterase inhibitor, is efficacious for the treatment of PD dementia, which limits management of cognitive impairment in PD. Whereas the role of the serotonergic system in PD cognition is less understood, through its interactions with other neurotransmitters systems, namely, the cholinergic system, it may be implicated in cognitive processes. In this chapter, we provide an overview of the pharmacological, clinical and pathological evidence that implicates the serotonergic system in mediating cognition in PD.

Rotigotine: A Review of Analytical Methods for the Raw Material, Pharmaceutical Formulations, and Its Impurities

BACKGROUND

Rotigotine is a dopaminergic agonist developed for the treatment of Parkinson's disease and restless leg syndrome. The pure levorotatory enantiomer is marketed in several countries as a transdermal patch. Reports of oxidation and instability in a previous formulation indicate the need to evaluate impurities in both the raw material and pharmaceutical dosage forms of rotigotine to ensure product quality.

OBJECTIVE

This review examines the main analytical methods for analyzing rotigotine in raw material and its transdermal patches with the aim of assisting the development of new pharmaceutical formulations and stability studies.

METHODS

Analytical methods based on high-performance liquid chromatography for rotigotine from pharmacopoeias and literature were evaluated. A comparison was made between the methods found in the literature and official rotigotine monographs described by the United States, European, and British Pharmacopoeias, including a discussion of their acceptance limits for impurities related to the drug. The different impurities from the synthesis processes and degradation studies of rotigotine were also evaluated, as well as the main articles that describe methods for assessing their chiral purity.

RESULTS

Qualified and unofficial official impurities found in forced degradation studies were verified. The methods presented show adequate specificity and selectivity in determining the drug in the presence of its impurities.

CONCLUSIONS

The approached methods are promising, but more detailed studies on the stability of rotigotine are still lacking, mainly in the pharmacokinetic and toxicological characterization of its impurities.

Polymorphisms of Dopamine Receptor Genes and Parkinson's Disease: Clinical Relevance and Future Perspectives

Parkinson’s disease (PD) is a neurodegenerative disease caused by loss of dopaminergic neurons in the midbrain. PD is clinically characterized by a variety of motor and nonmotor symptoms, and treatment relies on dopaminergic replacement. Beyond a common pathological hallmark, PD patients may present differences in both clinical progression and response to drug therapy that are partly affected by genetic factors. Despite extensive knowledge on genetic variability of dopaminergic receptors (DR), few studies have addressed their relevance as possible influencers of clinical heterogeneity in PD patients. In this review, we summarized available evidence regarding the role of genetic polymorphisms in DR as possible determinants of PD development, progression and treatment response. Moreover, we examined the role of DR in the modulation of peripheral immunity, in light of the emerging role of the peripheral immune system in PD pathophysiology. A better understanding of all these aspects represents an important step towards the development of precise and personalized disease-modifying therapies for PD.

Rotigotine Transdermal Patch for Motor and Non-motor Parkinson's Disease: A Review of 12 Years' Clinical Experience

Motor and non-motor symptoms (NMS) have a substantial effect on the health-related quality of life (QoL) of patients with Parkinson's disease (PD). Transdermal therapy has emerged as a time-tested practical treatment option, and the rotigotine patch has been used worldwide as an alternative to conventional oral treatment for PD. The efficacy of rotigotine on motor aspects of PD, as well as its safety and tolerability profile, are well-established, whereas its effects on a wide range of NMS have been described and studied but are not widely appreciated. In this review, we present our overall experience with rotigotine and its tolerability and make recommendations for its use in PD and restless legs syndrome, with a specific focus on NMS, underpinned by level 1-4 evidence. We believe that the effective use of the rotigotine transdermal patch can address motor symptoms and a wide range of NMS, improving health-related QoL for patients with PD. More specifically, the positive effects of rotigotine on non-motor fluctuations are also relevant. We also discuss the additional advantages of the transdermal application of rotigotine when oral therapy cannot be used, for instance in acute medical emergencies or nil-by-mouth or pre/post-surgical scenarios. We highlight evidence to support the use of rotigotine in selected cases (in addition to general use for motor benefit) in the context of personalised medicine.

Neuronal Dopamine D3 Receptors: Translational Implications for Preclinical Research and CNS Disorders

Dopamine (DA), as one of the major neurotransmitters in the central nervous system (CNS) and periphery, exerts its actions through five types of receptors which belong to two major subfamilies such as D1-like (i.e., D1 and D5 receptors) and D2-like (i.e., D2, D3 and D4) receptors. Dopamine D3 receptor (D3R) was cloned 30 years ago, and its distribution in the CNS and in the periphery, molecular structure, cellular signaling mechanisms have been largely explored. Involvement of D3Rs has been recognized in several CNS functions such as movement control, cognition, learning, reward, emotional regulation and social behavior. D3Rs have become a promising target of drug research and great efforts have been made to obtain high affinity ligands (selective agonists, partial agonists and antagonists) in order to elucidate D3R functions. There has been a strong drive behind the efforts to find drug-like compounds with high affinity and selectivity and various functionality for D3Rs in the hope that they would have potential treatment options in CNS diseases such as schizophrenia, drug abuse, Parkinson’s disease, depression, and restless leg syndrome. In this review, we provide an overview and update of the major aspects of research related to D3Rs: distribution in the CNS and periphery, signaling and molecular properties, the status of ligands available for D3R research (agonists, antagonists and partial agonists), behavioral functions of D3Rs, the role in neural networks, and we provide a summary on how the D3R-related drug research has been translated to human therapy.

The Gαi protein subclass selectivity to the dopamine D2 receptor is also decided by their location at the cell membrane

Background

G protein-coupled receptor (GPCR) signaling via heterotrimeric G proteins plays an important role in the cellular regulation of responses to external stimuli. Despite intensive structural research, the mechanism underlying the receptor–G protein coupling of closely related subtypes of Gαi remains unclear. In addition to the structural changes of interacting proteins, the interactions between lipids and proteins seem to be crucial in GPCR-dependent cell signaling due to their functional organization in specific membrane domains. In previous works, we found that Gαs and Gαi₃ subunits prefer distinct types of membrane-anchor lipid domains that also modulate the G protein trimer localization. In the present study, we investigated the functional selectivity of dopamine D₂ long receptor isoform (D₂R) toward the Gαi₁, Gαi₂, and Gαi₃ subunits, and analyzed whether the organization of Gαi heterotrimers at the plasma membrane affects the signal transduction.

Methods

We characterized the lateral diffusion and the receptor–G protein spatial distribution in living cells using two assays: fluorescence recovery after photobleaching microscopy and fluorescence resonance energy transfer detected by fluorescence-lifetime imaging microscopy. Depending on distribution of data differences between Gα subunits were investigated using parametric approach–unpaired T-test or nonparametric–Mann–Whitney U test.

Results

Despite the similarities between the examined subunits, the experiments conducted in the study revealed a significantly faster lateral diffusion of the Gαi₂ subunit and the singular distribution of the Gαi₁ subunit in the plasma membrane. The cell membrane partitioning of distinct Gαi heterotrimers with dopamine receptor correlated very well with the efficiency of D₂R-mediated inhibition the formation of cAMP.

Conclusions

This study showed that even closely related subunits of Gαi differ in their membrane-trafficking properties that impact on their signaling. The interactions between lipids and proteins seem to be crucial in GPCR-dependent cell signaling due to their functional organization in specific membrane domains, and should therefore be taken into account as one of the selectivity determinants of G protein coupling.

How to introduce a rotigotine patch to Parkinson's disease patients taking oral dopamine agonists

OBJECTIVE

Ways of introducing a rotigotine patch to Parkinson disease (PD) patients include initial induction for dopamine agonist (DA)-free patients and overnight switch (OS), cross-titration (CT), and add-on (AO) for patients already taking oral DAs. We investigated whether or not the introductions method affects the continuation rate of rotigotine patch.

METHODS

The subjects were 188 PD patients who started using a rotigotine patch at the Department of Neurology, Fukuoka University Hospital. The rate of successful continuation of rotigotine patch for one year after initiation and the reasons for discontinuation were investigated; for the patients who discontinued due to poor efficacy, the DA dose before and after the start of rotigotine patch treatment was determined.

RESULTS

The 1-year continuation rates were 38.5 % (20/52) in the OS group, 61.5 % (8/13) in the CT group, 35.3 % (6/17) in the AO group, and 50.9 % (54/106) in the de novo group. The most common reason for discontinuation in all groups was skin reactions. Compared with the de novo group, only the OS group had a significantly higher discontinuation rate due to poor efficacy (3.8 % vs. 21.2 %, P <  0.001). However, in the OS group, the continuation rate in the subjects with an increased total DA dose, after rotigotine was introduced, was significantly higher than that in the subjects with a decreased total DA dose (p = 0.031).

CONCLUSION

The use of a rotigotine patch with an equivalent dose should be considered when switching from oral DAs, and appropriate care should be administered for any skin reactions. The present findings suggested that not the introduction method but the use of an equivalent dose between DA formulations might affect the continuation rate of rotigotine patch.

Dopamine receptors in emesis: Molecular mechanisms and potential therapeutic function

Dopamine is a member of the catecholamine family and is associated with multiple physiological functions. Together with its five receptor subtypes, dopamine is closely linked to neurological disorders such as schizophrenia, Parkinson's disease, depression, attention deficit-hyperactivity, and restless leg syndrome. Unfortunately, several dopamine receptor-based agonists used to treat some of these diseases cause nausea and vomiting as impending side-effects. The high degree of cross interactions of dopamine receptor ligands with many other targets including G-protein coupled receptors, transporters, enzymes, and ion-channels, add to the complexity of discovering new targets for the treatment of nausea and vomiting. Using activation status of signaling cascades as mechanism-based biomarkers to foresee drug sensitivity combined with the development of dopamine receptor-based biased agonists may hold great promise and seems as the next step in drug development for the treatment of such multifactorial diseases. In this review, we update the present knowledge on dopamine and dopamine receptors and their potential roles in nausea and vomiting. The pre- and clinical evidence provided in this review supports the implication of both dopamine and dopamine receptor agonists in the incidence of emesis. Besides the conventional dopaminergic antiemetic drugs, potential novel antiemetic targeting emetic protein signaling cascades may offer superior selectivity profile and potency.

A Study for Expanding Application Sites for Rotigotine Transdermal Patch

The rotigotine transdermal patch (RTP) is a dopamine agonist used to treat Parkinson’s disease (PD). Some PD patients cannot continue RTP treatment due to application site reactions. We explored sites for RTP where application site reactions are less severe than those in the six approved application sites. Thirty PD patients (12 men, mean age = 76 years) who underwent RTP at the approved sites and had some application site reactions were enrolled in this study. When applying the RTP to the approved application sites for more than four weeks (pre-RTP) and then on the shin for the following four weeks (post-RTP), skin reactions, itching evaluated using the skin irritation score, motor symptoms, clinical global impressions scale, and plasma rotigotine concentration were examined. The mean visual analogue scale and skin irritation score in the post-RTP group were significantly lower than those in the pre-RTP group. The mean Movement Disorder Society-Unified Parkinson’s Disease Rating Scale part III score in the post-RTP group was slightly but significantly lower than that in the pre-RTP group. Plasma rotigotine concentration in the post-RTP group was slightly but significantly lower than that in the pre-RTP group. These results indicate that the shin can be a useful application site for RTP.

Tannic acid acts as an agonist of the dopamine D2L receptor, regulates immune responses, and ameliorates experimentally induced colitis in mice

Tannic acid (TA) is an herbal polyphenol containing a galloyl group that has been prescribed to treat gastroenteritis, diarrhea, and irritable bowel syndrome. TA has anti-inflammatory, anti-cancer, and anti-viral properties; however, the molecular mechanisms of these potential therapeutic effects are still largely unknown. Here, we examined the ability of TA to induce anti-inflammatory responses. TA was found to be an agonist of the dopamine D2L receptor. TA reduced interferon (IFN)-γ and interleukin (IL)-1β secretion but upregulated tumor necrosis factor α and IL-10 secretion from lipopolysaccharide (LPS)-stimulated mouse splenocytes. TA also reduced IFN-γ secretion but enhanced IL-10 secretion from anti-cluster of differentiation (CD) 3/CD28 antibody-stimulated splenocytes. An immune subset study confirmed that TA regulated cytokine secretion by various types of immune cells in the context of stimulation with LPS or anti-CD3/CD28 antibodies. Administration of TA to mice with experimentally induced colitis strikingly suppressed weight loss, colon shrinkage, and IL-17 secretion from mesenteric lymph node lymphocytes in response to CD3/CD28 stimulation. These data suggest that TA suppresses inflammatory responses in colitis by regulating cytokine secretion by immune cells in the colon.

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Tannic acid is an agonist of the dopamine D2L receptor.

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Tannic acid suppresses IFN-γ secretion by LPS-stimulated splenocytes.

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Tannic acid modulates anti-CD3/CD28 antibody-stimulated cytokine levels in CD4⁺ T cells.

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Tannic acid ameliorates dextran sodium salt (DSS)-induced colitis in C57BL/6 mice.

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Tannic acid reduces production of IL-17 in DSS-induced colitis.

Current Status and Challenges in Rotigotine Delivery

Rotigotine is a non-ergoline, high lipophilic dopamine agonist. It is indicated as the first-line therapy for Parkinson's disease (PD) and Restless Leg Syndrome (RLS). However, the precise mechanism of rotigotine is yet to be known. Rotigotine has similar safety and tolerability to the other oral non-ergolinic dopamine antagonists in clinical trials, which include nausea, dizziness and somnolence. Neupro® was the first marketed transdermal patch formulation having rotigotine. The transdermal delivery system is advantageous as it enables continuous administration of the drug, thus providing steady-state plasma drug concentration for 24-hours. Intranasal administration of rotigotine allows the drug to bypass the blood-brain barrier enabling it to reach the central nervous system within minutes. Rotigotine can also be formulated as an extended-release microsphere for injection. Some challenges remain in other routes of rotigotine administration such as oral, parenteral and pulmonary, whereby resolving these challenges will be beneficial to patients as they are less invasive and comfortable in terms of administration. This review compiles recent work on rotigotine delivery, challenges and its future perspective.

Regulation of BDNF-TrkB Signaling and Potential Therapeutic Strategies for Parkinson's Disease

Brain-derived neurotrophic factor (BDNF) and its receptor tropomyosin-related kinase receptor type B (TrkB) are widely distributed in multiple regions of the human brain. Specifically, BDNF/TrkB is highly expressed and activated in the dopaminergic neurons of the substantia nigra and plays a critical role in neurophysiological processes, including neuro-protection and maturation and maintenance of neurons. The activation as well as dysfunction of the BDNF-TrkB pathway are associated with neurodegenerative diseases. The expression of BDNF/TrkB in the substantia nigra is significantly reduced in Parkinson's Disease (PD) patients. This review summarizes recent progress in the understanding of the cellular and molecular roles of BNDF/TrkB signaling and its isoform, TrkB.T1, in Parkinson's disease. We have also discussed the effects of current therapies on BDNF/TrkB signaling in Parkinson's disease patients and the mechanisms underlying the mutation-mediated acquisition of resistance to therapies for Parkinson's disease.

Novel Diels-Alder Type Adducts from Morus alba Root Bark Targeting Human Monoamine Oxidase and Dopaminergic Receptors for the Management of Neurodegenerative Diseases

In this study, we delineate the human monoamine oxidase (hMAO) inhibitory potential of natural Diels–Alder type adducts, mulberrofuran G (1), kuwanon G (2), and albanol B (3), from Morus alba root bark to characterize their role in Parkinson’s disease (PD) and depression, focusing on their ability to modulate dopaminergic receptors (D₁R, D_2LR, D₃R, and D₄R). In hMAO-A inhibition, 1–3 showed mild effects (50% inhibitory concentration (IC₅₀): 54‒114 μM). However, 1 displayed moderate inhibition of the hMAO-B isozyme (IC₅₀: 18.14 ± 1.06 μM) followed by mild inhibition by 2 (IC₅₀: 57.71 ± 2.12 μM) and 3 (IC₅₀: 90.59 ± 1.72 μM). Our kinetic study characterized the inhibition mode, and the in silico docking predicted that the moderate inhibitor 1 would have the lowest binding energy. Similarly, cell-based G protein-coupled receptors (GPCR) functional assays in vector-transfected cells expressing dopamine (DA) receptors characterized 1–3 as D₁R/D_2LR antagonists and D₃R/D₄R agonists. The half-maximum effective concentration (EC₅₀) of 1–3 on DA D₃R/D₄R was 15.13/17.19, 20.18/21.05, and 12.63/‒ µM, respectively. Similarly, 1–3 inhibited 50% of the DA response on D₁R/D_2LR by 6.13/2.41, 16.48/31.22, and 7.16/18.42 µM, respectively. A computational study revealed low binding energy for the test ligands. Interactions with residues Asp110, Val111, Tyr365, and Phe345 at the D₃R receptor and Asp115 and His414 at the D₄R receptor explain the high agonist effect. Likewise, Asp187 at D₁R and Asp114 at D_2LR play a crucial role in the antagonist effects of the ligand binding. Our overall results depict 1–3 from M. alba root bark as good inhibitors of hMAO and potent modulators of DA function as D₁R/D_2LR antagonists and D₃R/D₄R agonists. These active constituents in M. alba deserve in-depth study for their potential to manage neurodegenerative disorders (NDs), particularly PD and psychosis.

Dopaminergic neuroprotective effects of rotigotine via 5-HT1A receptors: Possibly involvement of metallothionein expression in astrocytes

Astrocytes exert neuroprotective effects through production of antioxidant molecules and neurotrophic factors. A recent study showed that stimulation of astrocyte serotonin 1A (5-HT1A) receptors promotes astrocyte proliferation and upregulation of the antioxidant molecules metallothionein (MT)-1,2, which protect dopaminergic neurons against oxidative stress. Rotigotine, an anti-parkinsonian drug, can bind to dopamine and 5-HT1A receptors. In this study, we examined neuroprotective effects of rotigotine in models of Parkinson's disease and involvement of astrocyte 5-HT1A receptors in neuroprotective effects of rotigotine against dopaminergic neurodegeneration. Rotigotine increased the number of astrocytes and MT-1,2 expression in cultured astrocytes. Pretreatment with conditioned media from rotigotine-treated astrocytes significantly inhibited 6-hydroxydopamine (6-OHDA)-induced dopaminergic neurotoxicity. These effects were completely blocked by a 5-HT1A antagonist or MT-1,2 specific antibody. Subcutaneous administration of rotigotine increased MT-1,2 expression in striatal astrocytes and prevented reduction of dopaminergic neurons in the substantia nigra of a 6-OHDA-lesioned mouse model of Parkinson's disease. These effects were blocked by co-administration with a 5-HT1A antagonist. These results suggest that rotigotine exerts neuroprotective effects through upregulation of MT expression in astrocytes by targeting 5-HT1A receptors. Our findings provide a possible therapeutic application of rotigotine to prevent dopaminergic neurodegeneration in Parkinson's disease.

The efficacy and safety of rotigotine transdermal patch for the treatment of sleep disorders in Parkinson's disease: a meta-analysis

OBJECTIVES

Sleep disturbances are one of the most common non-motor symptoms in Parkinson's disease (PD), and more frequently in advancing stage, almost 67-78.6% of PD patients experience some form of sleep disturbance [1-3]. Our objective is to conduct a meta-analysis of randomized controlled trials to demonstrate the efficacy and safety of rotigotine (RTG) transdermal patch for the treatment of sleep disorder in PD.

METHODS

RevMan5.3 from the Cochrane Library was used to conduct a meta-analysis, primary outcome measure was score of sleep scale in Parkinson's Disease, the mean change in scores of each subscale was treated as a continuous variable and the weighted mean difference (WMD) was calculated as the difference between the mean scale of sleep score in the treatment and control groups.

RESULTS

A total of five studies were included, and primary outcome measured by "PDSS" or "PDSS-2" score revealed a significant improvement in RTG treated patients compared to control [WMD: -6.66, 95% CI: (-8.54, -4.79), p < 0.0001], after the removal of two articles with high heterogeneity, the meta-analysis conclusion remained robust to methodological changes [WMD -3.90, 95%CI (-6.11, -1.69), p = 0.0005] and distinctly decreased heterogeneity was shown in the final result (I² = 7%).

CONCLUSIONS

As for the safety of RTG, it is well tolerated and safe [WMD: 1.68, 95%CI: (1.33, 2.13), p < 0.0001], application site reaction and nausea are among the most frequent side effects.

Rotigotine Transdermal Patch: A Review in Parkinson's Disease

Rotigotine (Neupro^®), a non-ergolinic dopamine agonist (DA), is administered once daily via a transdermal patch (TP) that delivers the drug over a 24-h period. In the EU, the rotigotine TP is approved as monotherapy for the treatment of early Parkinson's disease (PD) and as combination therapy with levodopa throughout the course of the disease. It is also approved for the treatment of PD in numerous other countries, including Australia, the USA, China and Japan. Rotigotine TP effectively improved motor and overall functioning in clinical trials in Caucasian and Asian patients with early PD (as monotherapy) or advanced PD (in combination with levodopa); treatment benefits appeared to be maintained in open-label extensions that followed patients for up to 6 years. Rotigotine TP was not consistently non-inferior to ropinirole and pramipexole in studies that included these oral non-ergolinic DAs as active comparators. Rotigotine TP variously improved some non-motor symptoms of PD, in particular sleep disturbances and health-related quality of life (HRQOL), based on findings from individual studies and/or a meta-analysis. Rotigotine TP was generally well tolerated, with an adverse event profile characterized by adverse events typical of dopaminergic stimulation and transdermal patch application. Available for more than a decade, rotigotine TP is a well-established, once-daily DA formulation for use in the short- and longer-term treatment of PD. It offers a convenient alternative when non-oral administration of medication is preferred and may be particularly useful in patients with gastrointestinal disturbances that reduce the suitability of oral medication.

The current status of pharmacotherapy for the treatment of Parkinson's disease: transition from single-target to multitarget therapy

Parkinson's disease (PD) is a neurodegenerative disorder characterized by degeneration of dopaminergic neurons. Motor features such as tremor, rigidity, bradykinesia and postural instability are common traits of PD. Current treatment options provide symptomatic relief to the condition but are unable to reverse disease progression. The conventional single-target therapeutic approach might not always induce the desired effect owing to the multifactorial nature of PD. Hence, multitarget strategies have been proposed to simultaneously target multiple proteins involved in the development of PD. Herein, we provide an overview of the pathogenesis of PD and the current pharmacotherapies. Furthermore, rationales and examples of multitarget approaches that have been tested in preclinical trials for the treatment of PD are also discussed.

Available and future treatments for atypical parkinsonism. A systematic review

AIMS

Success in treating patients with atypical parkinsonian syndromes, namely progressive supranuclear palsy (PSP), cortico-basal degeneration (CBD), multiple system atrophy (MSA), Parkinson's disease with dementia (PDD), and Lewy body dementia with (LBD), remains exceedingly low. The present work overviews the most influential research literature collected on MEDLINE, ISI Web of Science, Cochrane Library, and Scopus for available treatment in atypical parkinsonisms without time restriction.

DISCUSSION

Transdermal rotigotine, autologous mesenchymal stem cells, tideglusib, and coenzyme Q10 along with donepezil, rivastigmine, memantine, and the deep brain stimulation have shown some benefits in alleviating symptoms in APS. Moreover, many new clinical trials are ongoing testing microtubule stabilizer, antitau monoclonal antibody, tau acetylation inhibition, cell replacement, selective serotonin reuptake inhibitor, active immunization, inhibition of toxic α-synuclein oligomers formation, and inhibition of microglia.

CONCLUSION

A detailed knowledge of the pathological mechanism underlying the disorders is needed, and disease-modifying therapies are required to offer better therapeutic options to physician and caregivers of APS patients.

Dopamine effects on frontal cortical blood flow and motor inhibition in Parkinson's disease

Parkinson's disease (PD) is characterized by dysfunction in frontal cortical and striatal networks that regulate action control. We investigated the pharmacological effect of dopamine agonist replacement therapy on frontal cortical activity and motor inhibition. Using Arterial Spin Labeling MRI, we examined 26 PD patients in the off- and on-dopamine agonist medication states to assess the effect of dopamine agonists on frontal cortical regional cerebral blood flow. Motor inhibition was measured by the Simon task in both medication states. We applied the dual process activation suppression model to dissociate fast response impulses from motor inhibition of incorrect responses. General linear regression model analyses determined the medication effect on regional cerebral blood flow and motor inhibition, and the relationship between regional cerebral blood flow and motor inhibitory proficiency. We show that dopamine agonist administration increases frontal cerebral blood flow, particularly in the pre-supplementary motor area (pre-SMA) and the dorsolateral prefrontal cortex (DLPFC). Higher regional blood flow in the pre-SMA, DLPFC and motor cortex was associated with better inhibitory control, suggesting that treatments which improve frontal cortical activity could ameliorate motor inhibition deficiency in PD patients.

Switching from an oral dopamine receptor agonist to rotigotine transdermal patch: a review of clinical data with a focus on patient perspective

INTRODUCTION

Dopamine receptor agonists (DAs) are commonly used to treat Parkinson's disease (PD) and restless legs syndrome (RLS). In certain situations, switching from oral DAs to rotigotine transdermal patch may be beneficial for the patient (e.g., optimal symptom control/side effects/perioperative management, preference for once-daily/non-oral administration, RLS augmentation treatment). Areas covered: This narrative review summarizes available data on DA dose equivalency, dose conversions, switching schedules, safety, tolerability, efficacy and patient treatment preferences of switching from oral DAs to rotigotine (and vice versa) in patients with PD/RLS. The studies were identified in a PubMed search (up to 8 November 2016) using terms ('dopamine receptor agonist' OR 'rotigotine') AND 'switch'. Expert commentary: Randomized controlled studies often do not address the challenges clinicians face in practice, e.g., switching medications within the same class when dosing is not a one-to-one ratio. The authors describe three open-label studies in PD where oral DAs were successfully switched to rotigotine, and review three studies in RLS where oral DAs/levodopa were switched to rotigotine. Finally, the authors provide a suggested tool for switching from oral DAs to rotigotine, which includes dose conversion factors and switching schedules. The authors' view is that low-dose oral DAs (equivalent to ≤8 mg/24 h rotigotine) may be switched overnight.

The combination of the opioid glycopeptide MMP-2200 and a NMDA receptor antagonist reduced l-DOPA-induced dyskinesia and MMP-2200 by itself reduced dopamine receptor 2-like agonist-induced dyskinesia

Dopamine (DA)-replacement therapy utilizing l-DOPA is the gold standard symptomatic treatment for Parkinson's disease (PD). A critical complication of this therapy is the development of l-DOPA-induced dyskinesia (LID). The endogenous opioid peptides, including enkephalins and dynorphin, are co-transmitters of dopaminergic, GABAergic, and glutamatergic transmission in the direct and indirect striatal output pathways disrupted in PD, and alterations in expression levels of these peptides and their precursors have been implicated in LID genesis and expression. We have previously shown that the opioid glycopeptide drug MMP-2200 (a.k.a. Lactomorphin), a glycosylated derivative of Leu-enkephalin mediates potent behavioral effects in two rodent models of striatal DA depletion. In this study, the mixed mu-delta agonist MMP-2200 was investigated in standard preclinical rodent models of PD and of LID to evaluate its effects on abnormal involuntary movements (AIMs). MMP-2200 showed antiparkinsonian activity, while increasing l-DOPA-induced limb, axial, and oral (LAO) AIMs by ∼10%, and had no effect on dopamine receptor 1 (D1R)-induced LAO AIMs. In contrast, it markedly reduced dopamine receptor 2 (D2R)-like-induced LAO AIMs. The locomotor AIMs were reduced by MMP-2200 in all three conditions. The N-methyl-d-aspartate receptor (NMDAR) antagonist MK-801 has previously been shown to be anti-dyskinetic, but only at doses that induce parkinsonism. When MMP-2200 was co-administered with MK-801, MK-801-induced pro-parkinsonian activity was suppressed, while a robust anti-dyskinetic effect remained. In summary, the opioid glycopeptide MMP-2200 reduced AIMs induced by a D2R-like agonist, and MMP-2200 modified the effect of MK-801 to result in a potent reduction of l-DOPA-induced AIMs without induction of parkinsonism.

Randomized, double-blind, crossover study of the adhesiveness of two formulations of rotigotine transdermal patch in patients with Parkinson's disease

OBJECTIVE

In patch-based transdermal drug delivery, adhesiveness is critical for safe and effective treatment, especially in Parkinson's disease (PD) where excessive sweating is common. This study compared the adhesiveness of two transdermal patch formulations of rotigotine (improved room temperature-stable [PR2.3.1/Treatment A] and intermediate cold storage product [PR2.1.1/Treatment B]), using the largest patch size (40 cm²).

METHODS

PD0018 (NCT02230904) was a multicenter, randomized, double-blind, crossover study. PD patients received Treatments A and B in randomized order for 2 days each. Patch adhesiveness was measured immediately after patch application and 24 hours thereafter (before removal). Primary variable: change in average investigator-rated adhesiveness score between treatments, per modified European Medicines Agency scale (EMA/CHMP/QWP/911254/2011, 2012).

RESULTS

Fifty-seven patients were randomized; 56 patients completed the study. Five patients were excluded from analysis for accidental unblinding. Treatment A had better average adhesiveness score (mean ± SD Treatment A - Treatment B: 1.115 ± 1.635). A higher percentage of patients on both days had patch adhesiveness ≥95% at 24 hours for Treatment A (first day: 65.4%, second day: 71.2%) vs. Treatment B (46.2%, 36.5%), and were satisfied with patch adhesiveness of Treatment A (first day: 75.0%, second day: 73.1%) vs. Treatment B (65.4%, 59.6%). Average patch-wear duration was similar between formulations (23.761 hours vs. 23.495 hours per patch). Both formulations were well tolerated with no new safety observations.

CONCLUSION

Results indicated greater adhesiveness for the improved room temperature-stable formulation (PR2.3.1) vs. intermediate cold storage product (PR2.1.1) using the largest patch-size, with comparable safety and skin tolerability.

Rotigotine Improves Abnormal Circadian Rhythm of Blood Pressure in Parkinson's Disease

INTRODUCTION

Cardiovascular autonomic failure is commonly associated with Parkinson's disease (PD), affecting the daily lives of patients. Rotigotine was recently reported not to influence cardiovascular autonomic responses in contrast to other dopaminergic drugs. The effect of rotigotine on daily blood pressure (BP) fluctuations might reflect autonomic failure in patients with PD.

METHODS

Twenty-five PD patients who were receiving rotigotine and 12 patients not receiving rotigotine were recruited. Systolic BP during the daytime and nighttime was measured by 24-h BP monitoring at an interval of 2 years. The patients were divided into 3 groups according to the BP fluctuation type: dippers (nocturnal fall in BP ≥10%), non-dippers (0-10%), and risers (< 0%). The time course of BP was compared between the patients given rotigotine and those not given rotigotine.

RESULTS

Among the 25 patients who received rotigotine, the BP type worsened in 2 patients, was unchanged in 16 patients, and improved in 7 patients. Among the 12 patients who were not receiving rotigotine, the BP type worsened in 5 patients, was unchanged in 4 patients, and improved only in 3 patients (p = 0.042).

CONCLUSION

Rotigotine improves the abnormal circadian rhythm of BP in patients with PD. Rotigotine was suggested to have favorable effects on cardiovascular autonomic responses and circadian rhythm in patients with PD.

Efficacy of transdermal rotigotine in chronic cluster headache: A case series

Cluster headache (CH) is one of the most severe forms of headache, but the number of effective treatments is still limited. Recently, we reported the case of a drug-resistant CH patient responsive to the rotigotine transdermal patch, which is used in the treatment of Parkinson’s disease. This report formed the basis for a case series where other drug-resistant CH patients were treated with rotigotine. Here are the results of this study. Twenty-two CH patients underwent the treatment. Eight were episodic cluster headache (ECH) patients and 14 were chronic cluster headache (CCH) patients. Of the eight ECH patients, four reported that their CH had been stopped by the treatment. Of the 14 CCH patients, 11 were considered responders to the treatment (5 experienced a full resolution of headache, and 6 had a headache reduction of at least 50% in terms of mean monthly number of attacks). Our case series confirms the previous observation that rotigotine could be helpful in the treatment of CH. It may even influence the monoaminergic system that has a key role in the pathogenesis of CH.

Efficacy of Rotigotine at Different Stages of Parkinson's Disease Symptom Severity and Disability: A Post Hoc Analysis According to Baseline Hoehn and Yahr Stage

Background: The efficacy of rotigotine has been demonstrated in studies of patients with early (i.e. not receiving levodopa) and advanced (i.e. not adequately controlled on levodopa; average 2.5 h/day in ‘off’ state) Parkinson’s disease (PD).

Objective: To further investigate the efficacy of rotigotine transdermal patch across different stages of PD symptom severity and functional disability, according to baseline Hoehn and Yahr (HY) staging.

Methods:Post hoc analysis of six placebo-controlled studies of rotigotine in patients with early PD (SP506, SP512, SP513; rotigotine ≤8 mg/24 h) or advanced-PD (CLEOPATRA-PD, PREFER, SP921; rotigotine ≤16 mg/24 h). Data were pooled and analyzed according to baseline HY stage (1, 2, 3 or 4) for change from baseline to end of maintenance in Unified Parkinson’s Disease Rating Scale (UPDRS) II (activities of daily living), UPDRS III (motor) and UPDRS II+III; statistical tests are exploratory.

Results: Data were available for 2057 patients (HY 1 : 262; HY 2 : 1230; HY 3 : 524; HY 4 : 41). Patients at higher HY stages were older, had a longer time since PD diagnosis and higher baseline UPDRS II+III scores vs patients at lower HY stages. Rotigotine improved UPDRS II+III versus placebo for each individual HY stage (p < 0.05 for each HY stage), with treatment differences increasing with increasing HY stages. Similar results were observed for UPDRS II and UPDRS III.

Conclusions: This post hoc analysis suggests that rotigotine may be efficacious across a broad range of progressive stages of PD symptom severity and functional disability (HY stages 1–4).

Rotigotine in Combination with the MAO-B Inhibitor Selegiline in Early Parkinson's Disease: A Post Hoc Analysis

Background: Monoamine oxidase B (MAO-B) inhibitors and dopamine receptor agonists are common first-line treatment options in early Parkinson’s disease (PD).

Objective: To evaluate the efficacy and safety of rotigotine transdermal patch as an add-on therapy to an MAO-B inhibitor in patients with early-PD.

Methods: In two Phase III, randomized, double-blind, placebo-controlled studies in early-PD (SP512, SP513), patients were randomized to rotigotine (titrated to optimal dose ≤8 mg/24 h) or placebo, and maintained for 24 (SP512) or 33 (SP513) weeks. Post hoc analyses were performed on pooled data for patients receiving an MAO-B inhibitor (selegiline) at a stable dose at randomization and throughout the studies, with groups defined as “Selegiline+Rotigotine” and “Selegiline+Placebo”. Outcome measures included change from baseline in Unified Parkinson’s Disease Rating Scale (UPDRS) II (activities of daily living), III (motor), UPDRS II+III and responders (patients achieving ≥20%, ≥25% or ≥30% decrease in UPDRS II+III). As post hoc analyses, p-values are exploratory.

Results: 130 patients were evaluable for efficacy analyses (“Selegiline+Rotigotine”: 84, “Selegiline+Placebo”: 46). Combined treatment with rotigotine and selegiline improved UPDRS III and UPDRS II+III scores versus selegiline alone (LS-mean [95% CI] treatment difference for UPDRS III: –4.89 [–7.87 to –1.91], p = 0.0015; for UPDRS II+III: –5.76 [–9.71 to –1.82], p = 0.0045). Higher proportion of patients in the “Selegiline+Rotigotine” group were classified as ≥20%, ≥25% or ≥30% responders (all p < 0.001). Combined treatment appeared more effective in patients aged ≤65 years versus > 65 years (although patient numbers in the subgroups were low). Adverse event profile was consistent with the known safety profile of rotigotine.

Conclusions: In these post hoc analyses, adjunctive treatment with rotigotine in patients already receiving an MAO-B inhibitor improved UPDRS II+III score; this appeared to be largely driven by improvements in the motor aspects of PD.

Rotigotine, a dopamine receptor agonist, increased BDNF protein levels in the rat cortex and hippocampus

Brain-derived neurotrophic factor (BDNF) critically controls the fate and function of the neuronal network and has received much attention as a target of many brain diseases. Dopaminergic system dysfunction has also been implicated in a variety of neuropsychiatric diseases. Rotigotine, a non-ergot dopamine receptor agonist, is used in the treatment of Parkinson's disease and restless legs syndrome. To investigate the effects of rotigotine on neuronal functions both in vivo and in vitro, rats and primary cortical neurons were administered rotigotine, and the mRNA and protein expression levels of BDNF, its receptor TrkB and downstream signaling molecules, and synaptic proteins were determined. We found that BDNF protein was increased in the cortex and hippocampus of rats after 7days of rotigotine treatment. In contrast, BDNF mRNAs were reduced 6h after rotigotine treatment in cultured neurons presumably through the transient suppression of neuronal activity. We identified differential expression of D1, D2, and D3 receptors in the rat brain and cultured neurons. The observed increase in the expression of BDNF protein in the cortex and hippocampus after subchronic administration of rotigotine suggests that it may exert its medical effect in part through improving BDNF function in the brain. In addition, our results highlight the complex relationships between rotigotine and BDNF expression, which depend on the brain region, time course, and dose of the drug.

Rotigotine transdermal patch and sleep in Parkinson's disease: where are we now?

A wide range of sleep dysfunction complicates Parkinson’s disease during its course from prodromal to palliative stage. It is now increasingly acknowledged that sleep disturbances are thus integral to the disease and pose a significant burden impacting on quality of life of patients. Sleep fragmentation, restless legs syndrome, nocturia, and nocturnal pain are regarded as one of the main components of night-time sleep dysfunction with possible secondary impact on cognition and well-being. The role of dopaminergic therapies, particularly using a continuous drug delivery strategy in managing some of these sleep issues, have been reported but the overall concept remains unclear. This review provides an overview of several aspects of night-time sleep dysfunction in Parkinson’s disease and describes all available published open-label and blinded studies that investigated the use of rotigotine transdermal patch targeting sleep. Blinded studies have suggested beneficial effects of rotigotine transdermal patch on maintenance insomnia and restless legs syndrome in Parkinson’s disease patients. Open-label studies support these observations and also suggest beneficial effects on nocturia and nocturnal pain.

Abnormalities of Dopamine D3 Receptor Signaling in the Diseased Brain

Dopamine D₃ receptors (D₃R) modulate neuronal activity in several brain regions including cortex, striatum, cerebellum, and hippocampus. A growing body of evidence suggests that aberrant D₃R signaling contributes to multiple brain diseases, such as Parkinson’s disease, essential tremor, schizophrenia, and addiction. In line with these findings, D₃R has emerged as a potential target in the treatment of neurological disorders. However, the mechanisms underlying neuronal D₃R signaling are poorly understood, either in healthy or diseased brain. Here, I review the molecular mechanisms involved in D₃R signaling via monomeric D₃R and heteromeric receptor complexes (e.g., D₃R-D₁R, D₃R-D₂R, D₃R-A_2aR, and D₃R-D₃nf). I focus on D₃R signaling pathways that, according to recent reports, contribute to pathological brain states. In particular, I describe evidence on both quantitative (e.g., increased number or affinity) and qualitative (e.g., switched signaling) changes in D₃R that has been associated with brain dysfunction. I conclude with a description of basic mechanisms that modulate D₃R signaling such as desensitization, as disruption of these mechanisms may underlie pathological changes in D₃R signaling. Because several lines of evidence support the idea that imbalances in D₃R signaling alter neural function, a better understanding of downstream D₃R pathways is likely to reveal novel therapeutic strategies toward dopamine-related brain disorders.

Rotigotine transdermal patch in Chinese patients with advanced Parkinson's disease: A randomized, double-blind, placebo-controlled pivotal study

INTRODUCTION

Rotigotine was demonstrated to be efficacious and well-tolerated in three placebo-controlled studies (CLEOPATRA-PD/PREFER/SP921) of patients with advanced-stage Parkinson's disease (PD), most of whom were Caucasian. This multicenter phase 3 study (SP1037; NCT01646255) was the first to investigate the efficacy and safety of rotigotine in Chinese patients with advanced-stage PD.

METHODS

Chinese patients with PD, inadequately controlled on levodopa (stable dose ≥200 mg/day), with ≥2.5 h/day "off" time, and Hoehn & Yahr stage 2-4, were randomized 1:1 to receive transdermal rotigotine or placebo, titrated over ≤7 weeks, maintained at optimal/maximum dose (4-16 mg/24 h) for 12 weeks. Primary efficacy variable: mean change in absolute "off" time (according to patient diaries) from baseline to end of maintenance. Safety variables included adverse events (AEs) and discontinuations due to AEs.

RESULTS

346 patients were randomized and 89.9% completed the study (87.8% placebo; 92.0% rotigotine). All were Chinese (58.7% male; mean ± SD age: 62.2 ± 8.9 years; mean ± SD time since PD diagnosis: 6.62 ± 3.70 years). Rotigotine significantly reduced "off" time vs placebo (LS mean [95% CI] treatment difference: -1.20 h/day [-1.83, -0.57]; p = 0.0002), and resulted in more responders (≥30% decrease in "off" time: 36.9% placebo; 48.8% rotigotine; p = 0.0269). AEs were reported for 86 (50.0%) placebo- and 103 (59.2%) rotigotine-treated patients; 15 discontinued due to AEs (placebo 7; rotigotine 8). The most common AEs (≥5%) were dizziness, nausea, pruritus, and dyskinesia.

CONCLUSIONS

Rotigotine was efficacious in Chinese patients with advanced-stage PD as add-on therapy to levodopa, significantly reducing "off" time vs placebo; the treatment difference was similar to that observed in previous studies of mainly Caucasian patients. Rotigotine was generally well-tolerated and had a similar AE profile to those observed in previous studies.

Clinical management of restless legs syndrome in end-stage renal disease patients

Restless legs syndrome (RLS) is a common neurological movement disorder, characterized by restless and unpleasant sensations in the deep inside of legs. The symptoms of RLS are less noticeable during daytime, but more prevalent at night. Therefore, the disorder can induce low quality of life, insomnia, and impairment of daytime activity. RLS in end-stage renal disease (ESRD) patients is especially problematic due to premature discontinuation of dialysis and increased mortality. The prevalence of RLS among dialysis patients is much higher compared to the prevalence of the same disorder in patients with normal renal functions. Even though there are recommended treatment guidelines for the general population established by Medical Advisory Board of the RLS foundation, which include the use of dopamine agonists, levodopa, gabapentin, benzodiazepines, and opioids, limited information is available on the effects of these therapies in ESRD patients. Since the existing clinical data were extrapolated from small sample sizes in short-term clinical trials, further clinical studies are still needed to better assess the efficacy, safety, and tolerability of these medications in patients with ESRD.

New Pharmacological Approaches to Treating Non-Motor Symptoms of Parkinson's Disease

PURPOSE OF REVIEW

Non-motor symptoms in patients with Parkinson's Disease (PD) are better predictors of quality of life changes, caregiver burden, and mortality than motor symptoms. Levodopa has limited, and sometimes detrimental, effects on these symptoms. In this review we discuss recent evidence on pharmacological treatments for non-motor symptoms.

RECENT FINDINGS

Breakthroughs have been made in the treatment of psychosis and sleep dysfunction. Pimavanserin has become the first FDA approved drug for PD psychosis. There is also new research supporting cholinesterase inhibitors for sleep disorders in PD. Other studies, including several novel treatments, have shown mixed results for apathy, depression, and fatigue.

SUMMARY

Further research is needed to develop treatments for non-motor symptoms in PD. Preclinical and postmortem studies indicate that non-motor symptoms in PD may arise from pathology in non-dopamine systems. Although sometimes used off-label, therapies that target such systems have been under-utilized in treating non-motor symptoms and warrant further clinical investigation.