Apomorphine in the treatment of Parkinson's disease: a review

Behaviorally conditioned effects of psychoactive drugs in experimental animals: What we have learned from nearly a century of research and what remains to be learned

Continuous treatment with drugs is a crucial requirement for managing various clinical conditions, including chronic pain and neuropsychiatric disorders such as depression or schizophrenia. Associative learning processes, i.e. Pavlovian conditioning, can play an important role for the effects of drugs and could open new avenues for optimizing patient treatment. In this narrative literature review, we summarize available data in experimental animals regarding the behaviorally conditioned effects of psychostimulants such as d-amphetamine and cocaine, the dopamine receptor agonist apomorphine, the dopamine receptor antagonist haloperidol, morphine and antidepressant drugs. In each section, the drug under discussion is briefly introduced, followed by a detailed examination of conditioning features, including doses and dosing regimens, characteristics of the conditioning process such as test environments or specific conditioned stimuli, testing and conditioned response characteristics, possible extinction or reconditioning or reversal training, neural mechanisms, and finally, the potential clinical relevance of the research area related to the drug. We focus on key outcomes, delve into methodical issues, identify gaps in current knowledge, and suggest future research directions.

Sublingual apomorphine in treatment of Parkinson's disease: a review

PURPOSE

A majority of advanced Parkinson's disease (PD) patients on oral levodopa experience motor fluctuations, including sudden OFF and delayed ON periods. Fast-acting rescue medications are a vital part of the clinician's armamentarium in the treatment of motor fluctuations. Sublingual apomorphine is the first sublingual rescue medication on the market for the treatment of OFF times in PD.Materials and Methods: Here, we review the development and pharmacology of apomorphine in the treatment of PD as well as the safety and efficacy of sublingual apomorphine established in clinical trials. Finally, we compare sublingual apomorphine to the other rescue medications available and provide our opinion on the use of sublingual apomorphine in clinical practice.Results: Clinical trials have demonstrated that sublingual apomorphine is a safe and effective option in the treatment of motor fluctuations in PD. In a Phase II trial, 100% of patients who achieved a full ON response did so within 30 min and 40% did so within 15 min. The mean duration of effect was 50 min. In a Phase III trial, 77.3% of patients achieved a full ON response. Side effects such as nausea, dizziness and somnolence were common but were generally mild. No patients experienced worsening dyskinesia.Conclusions: Sublingual apomorphine will provide patients with motor fluctuations due to advanced PD another safe and effective option for the treatment of OFF times.

Tyrosine Hydroxylase Inhibitors and Dopamine Receptor Agonists Combination Therapy for Parkinson's Disease

There are currently no disease-modifying therapies for Parkinson's disease (PD), a progressive neurodegenerative disorder associated with dopaminergic neuronal loss. There is increasing evidence that endogenous dopamine (DA) can be a pathological factor in neurodegeneration in PD. Tyrosine hydroxylase (TH) is the key rate-limiting enzyme for DA generation. Drugs that inhibit TH, such as alpha-methyltyrosine (α-MT), have recently been shown to protect against neurodegeneration in various PD models. DA receptor agonists can activate post-synaptic DA receptors to alleviate DA-deficiency-induced PD symptoms. However, DA receptor agonists have no therapeutic effects against neurodegeneration. Thus, a combination therapy with DA receptor agonists plus TH inhibitors may be an attractive therapeutic approach. TH inhibitors can protect and promote the survival of remaining dopaminergic neurons in PD patients' brains, whereas DA receptor agonists activate post-synaptic DA receptors to alleviate PD symptoms. Additionally, other PD drugs, such as N-acetylcysteine (NAC) and anticholinergic drugs, may be used as adjunctive medications to improve therapeutic effects. This multi-drug cocktail may represent a novel strategy to protect against progressive dopaminergic neurodegeneration and alleviate PD disease progression.

How to Use the New European Academy of Neurology/Movement Disorder Society European Section Guideline for Invasive Therapies in Parkinson's Disease

BACKGROUND

The decision to choose invasive treatments for Parkinson's disease (PD) is complex and needs careful consideration.

OBJECTIVES

Although the recommendations of the European Academy of Neurology/Movement Disorder Society European Section guideline for invasive therapies of PD are useful, the different clinical profiles of people with PD who seek advice for possible invasive therapy need further attention.

METHODS AND RESULTS

Here we describe 8 clinical standard situations of people with PD unsatisfied with their current oral treatment where invasive therapies may be considered. These are PD patients presenting with the following symptoms: (1) severe motor fluctuations, (2) beginning of levodopa-responsive fluctuations, severe tremor at (3) young or (4) advanced age, (5) impulse control disorders and related behavioral disorders, (6) hallucinations and psychosis, (7) minimal cognitive impairment or mild dementia, and (8) patients in need of palliative care. For some of these conditions, evidence at lower level or simple clinical considerations exist.

CONCLUSIONS

There are no one-fits-all answers, but physician and patient should discuss each option carefully considering symptom profile, psychosocial context, availability of therapy alternatives, and many other factors. The current paper outlines our proposed approach to these circumstances.

Exercise training has a protective effect in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mice model with improved neural and intestinal pathology and modified intestinal flora

Parkinson's disease (PD) is a common neurodegenerative disease with the exact etiology still unclear, but gut microbial disorders are thought to be related to the initiation and progression of it. Exercise training has a significant effect on the intestinal flora, so to investigate the promotion effect of exercise training on Parkinson's disease, we performed a rotarod walking training (5 times a week at 25 rpm for 20 min for 8 weeks) on a chronic mouse model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and observed the locomotor function of mice, function of dopaminergic neurons, intestinal mucosal barrier condition, intestinal inflammation and the structure and composition of intestinal flora. The results showed in these PD mice, exercise training improved their motility, increased the dopamine (DA) content in the striatum, along with promoted the gene expression of tyrosine hydroxylase and brain-derived neurotrophic factor in the striatum, which suggests this exercise training might protect striatal dopaminergic neurons from MPTP damage; the results also showed exercise training promoted recovery from ileal pathology, reduced the gene expression of intestinal inflammatory factors, and significantly altered the composition and structure of the intestinal flora in these mice.

Molecular and Cellular Interactions in Pathogenesis of Sporadic Parkinson Disease

An increasing number of the population all around the world suffer from age-associated neurodegenerative diseases including Parkinson’s disease (PD). This disorder presents different signs of genetic, epigenetic and environmental origin, and molecular, cellular and intracellular dysfunction. At the molecular level, α-synuclein (αSyn) was identified as the principal molecule constituting the Lewy bodies (LB). The gut microbiota participates in the pathogenesis of PD and may contribute to the loss of dopaminergic neurons through mitochondrial dysfunction. The most important pathogenetic link is an imbalance of Ca²⁺ ions, which is associated with redox imbalance in the cells and increased generation of reactive oxygen species (ROS). In this review, genetic, epigenetic and environmental factors that cause these disorders and their cause-and-effect relationships are considered. As a constituent of environmental factors, the example of organophosphates (OPs) is also reviewed. The role of endothelial damage in the pathogenesis of PD is discussed, and a ‘triple hit hypothesis’ is proposed as a modification of Braak’s dual hit one. In the absence of effective therapies for neurodegenerative diseases, more and more evidence is emerging about the positive impact of nutritional structure and healthy lifestyle on the state of blood vessels and the risk of developing these diseases.

Exosomes in Parkinson: Revisiting Their Pathologic Role and Potential Applications

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by bradykinesia, rigidity, and tremor. Considerable progress has been made to understand the exact mechanism leading to this disease. Most of what is known comes from the evidence of PD brains' autopsies showing a deposition of Lewy bodies-containing a protein called α-synuclein (α-syn)-as the pathological determinant of PD. α-syn predisposes neurons to neurotoxicity and cell death, while the other associated mechanisms are mitochondrial dysfunction and oxidative stress, which are underlying precursors to the death of dopaminergic neurons at the substantia nigra pars compacta leading to disease progression. Several mechanisms have been proposed to unravel the pathological cascade of these diseases; most of them share a particular similarity: cell-to-cell communication through exosomes (EXOs). EXOs are intracellular membrane-based vesicles with diverse compositions involved in biological and pathological processes, which their secretion is driven by the NLR family pyrin domain-containing three proteins (NLRP3) inflammasome. Toxic biological fibrils are transferred to recipient cells, and the disposal of damaged organelles through generating mitochondrial-derived vesicles are suggested mechanisms for developing PD. EXOs carry various biomarkers; thus, they are promising to diagnose different neurological disorders, including neurodegenerative diseases (NDDs). As nanovesicles, the applications of EXOs are not only restricted as diagnostics but also expanded to treat NDDs as therapeutic carriers and nano-scavengers. Herein, the aim is to highlight the potential incrimination of EXOs in the pathological cascade and progression of PD and their role as biomarkers and therapeutic carriers for diagnosing and treating this neuro-debilitating disorder.

Apomorphine Reduces A53T α-Synuclein-Induced Microglial Reactivity Through Activation of NRF2 Signalling Pathway

The chiral molecule, apomorphine, is currently used for the treatment of Parkinson’s disease (PD). As a potent dopamine receptor agonist, this lipophilic compound is especially effective for treating motor fluctuations in advanced PD patients. In addition to its receptor-mediated actions, apomorphine has also antioxidant and free radical scavenger activities. Neuroinflammation, oxidative stress, and microglia reactivity have emerged as central players in PD. Thus, modulating microglia activation in PD may be a valid therapeutic strategy. We previously reported that murine microglia are strongly activated upon exposure to A53T mutant α-synuclein. The present study was designed to investigate whether apomorphine enantiomers could modulate this A53T-induced microglial activation. Taken together, the results provided evidence that apomorphine enantiomers decrease A53T-induced microgliosis, through the activation of the NRF2 signalling pathway, leading to a lower pro-inflammatory state and restoring the phagocytic activity. Suppressing NRF2 recruitment (trigonelline exposure) or silencing specifically Nfe2l2 gene (siRNA treatment) abolished or strongly decreased the anti-inflammatory activity of apomorphine. In conclusion, apomorphine, which is already used in PD patients to mimic dopamine activity, may also be suitable to decrease α-synuclein-induced microglial reactivity.

Personalized Medicine Approach in Treating Parkinson's Disease, Using Oral Administration of Levodopa/Carbidopa Microtablets in Clinical Practice

Background: The most effective symptomatic treatment in Parkinson’s disease (PD) is levodopa in standard doses. However, as the disease progresses, there may be a need for a more personalized approach and fine tuning, in accordance with the patients’ needs. This study aims to evaluate the individual experience of levodopa/carbidopa 5/1.25 mg microtablets (LC-5) in clinical practice with respect to efficacy, tolerability, and usability. The method used was as follows: patients answered a questionnaire concerning the effect and usability of LC-5, and their medical records were reviewed. Regarding results, thirty-five survey responses were obtained, and 29 patients’ medical records were reviewed. The LC-5 dose dispenser usability was generally rated positively and facilitated medication adherence. The majority (85%) of patients reported symptom improvement while using LC-5, compared with previous standard treatments. These results suggest that LC-5 therapy is generally well-tolerated, with favorable patient-reported efficacy and user friendliness, as well as the possibility for an individualized, fine-tuned PD treatment. Further studies with a prospective design and larger study population are needed to confirm the results.

Personalized Medicine in Parkinson's Disease: New Options for Advanced Treatments

Parkinson’s disease (PD) presents varying motor and non-motor features in each patient owing to their different backgrounds, such as age, gender, genetics, and environmental factors. Furthermore, in the advanced stages, troublesome symptoms vary between patients due to motor and non-motor complications. The treatment of PD has made great progress over recent decades and has directly contributed to an improvement in patients’ quality of life, especially through the progression of advanced treatment. Deep brain stimulation, radiofrequency, MR–guided focused ultrasound, gamma knife, levodopa-carbidopa intestinal gel, and apomorphine are now used in the clinical setting for this disease. With multiple treatment options currently available for all stages of PD, we here discuss the most recent options for advanced treatment, including cell therapy in advanced PD, from the perspective of personalized medicine.

Cost-Effectiveness of Device-Aided Therapies in Parkinson's Disease: A Structured Review

Background:

Despite optimal dopaminergic treatment most patients in moderate to advanced stages of Parkinson’s disease (PD) experience progressively increasing disabilities, necessitating a shift from oral medication to device-aided therapies, including deep brain stimulation (DBS), intrajejunal levodopa-carbidopa infusion (IJLI), and continuous subcutaneous apomorphine infusion (CSAI). However, these therapies are costly, limiting their implementation.

Objectives:

To perform a systematic review on cost-effectiveness analyses for device-aided therapies in PD.

Methods:

References were identified by performing a systematic search in the PubMed and Web of Science databases in accordance with the PRISMA statement. In the absence of universal cost-effectiveness definitions, the gross domestic product per capita (GDP) in the country where a study was performed was used as a cut-off for cost-effectiveness based on cost per quality adjusted life year (QALY) gained.

Results:

In total 30 studies were retrieved. All device-aided therapies improved quality of life compared to best medical treatment, with improvements in QALYs between 0.88 and 1.26 in the studies with long temporal horizons. For DBS, nearly all studies showed that cost per QALY was below the GDP threshold. For infusion therapies only three studies showed a cost per QALY below this threshold, with several studies with long temporal horizons showing costs below or near the GDP threshold.

Conclusion:

Of the device-aided therapies, DBS can be considered cost-effective, but the majority of infusion therapy studies showed that these were less cost-effective. However, long-term use of the infusion therapies appears to improve their cost-effectiveness and in addition, several strategies are underway to reduce these high costs.

High-content screening identifies inhibitors of oxidative stress-induced parthanatos: cytoprotective and anti-inflammatory effects of ciclopirox

BACKGROUND AND PURPOSE

Excessive oxidative stress can induce PARP1-mediated programmed necrotic cell death, termed parthanatos. Inhibition of parthanatos may be therapeutically beneficial in a wide array of diseases associated with tissue injury and inflammation. Our goal was to identify novel molecules inhibiting parthanatos.

EXPERIMENTAL APPROACH

A small library of 774 pharmacologically active compounds was screened in a Sytox Green uptake assay, which identified 20 hits that reduced hydrogen-peroxide-induced parthanatos with an efficiency comparable to the benchmark PARP inhibitor, PJ34.

KEY RESULTS

Of these hits, two compounds, antifungal ciclopirox and dopamine receptor agonist apomorphine, inhibited PAR polymer synthesis. These two compounds prevented the binding of PARP1 to oxidatively damaged DNA but did not directly interfere with the interaction between DNA and PARP1. Both compounds inhibited mitochondrial superoxide and H₂ O₂ production and suppressed DNA breakage. Since H₂ O₂ -induced damage is dependent on Fe²⁺ -catalysed hydroxyl radical production (Fenton chemistry), we determined the iron chelation activity of the two test compounds and found that ciclopirox and, to a lesser extent, apomorphine act as iron chelators. We also show that the Fe²⁺ chelation and indirect PARP inhibitory effects of ciclopirox translate to anti-inflammatory actions as demonstrated in a mouse dermatitis model, where ciclopirox reduced ear swelling, inflammatory cell recruitment and poly(ADP-ribosyl)ation.

CONCLUSION AND IMPLICATIONS

Our findings indicate that the antimycotic drug, ciclopirox, acts as an iron chelator and thus targets an early event in hydrogen-peroxide-induced parthanatos. Ciclopirox has the potential to be repurposed as a cytoprotective and anti-inflammatory agent.

Treating hallucinations in Parkinson's disease

Introduction: Hallucinations in Parkinson's disease are common, can complicate medication management and significantly impact upon the quality of life of patients and their carers.Areas covered: This review aims to examine current evidence for the management of hallucinations in Parkinson's disease.Expert opinion: Treatment of hallucinations in Parkinson's disease should be both individualized and multifaceted. Screening, education, medication review and the avoidance of common triggers are important. For well-formed visual hallucinations, acetylcholinesterase inhibitors are recommended first-line. Refractory or severe symptoms may require the cautious use of atypical antipsychotics. Antidepressants may be beneficial in the appropriate setting. Unfortunately, current therapies for hallucinations offer only limited benefits and future research efforts are desperately required to improve the management of these challenging symptoms.

Apomorphine facilitates loss of respiratory chain activity in human epithelial ovarian cancer and inhibits angiogenesis in vivo

Apomorphine, a therapeutic agent for neurological diseases, is structurally similar to dopamine, and thereby holds potential in cancer therapy. However, there are no reports regarding its anti-cancer effects on human epithelial ovarian cancers (EOCs); therefore, we aimed to elucidate the mechanism underlying its action after drug repositioning. Apomorphine inhibited the proliferation of ES2 and OV90 EOC cells by inducing caspase activation and mitochondrion-associated apoptosis; it also promoted endoplasmic reticulum stress and mitochondrial dysfunction through mitochondrial membrane potential depolarization and mitochondrial calcium overload. Moreover, following apomorphine treatment, we noted the loss of respiratory chain activity by reduction of oxidative phosphorylation and energy-production shift in EOC cells. Further, we verified the anti-angiogenic capacity of apomorphine using fli:eGFP transgenic zebrafish. As a preclinical assessment, we demonstrated the synergistic anti-cancer effects of apomorphine and paclitaxel combination.

Identification of C10 nitrogen-containing aporphines with dopamine D1 versus D5 receptor selectivity

New aporphines containing C10 nitrogen substituents (viz. nitro, aniline or amide moieties), were synthesized and evaluated for affinity at human serotonin 5-HT_1A and 5-HT_2A receptors and at human dopamine D₁, D₂ and D₅ receptors. Two series of analogs were investigated: series A which contain a sole C10 nitrogen substituent on the tetracyclic aporphine core and series B which are 1,2,10-trisubstituted aporphines. Remarkably, compounds from both series lacked affinity for the D₅ receptor, thus attaining D₁ versus D₅ selectivity. Compound 20c was the most potent D₁ ligand identified. Docking studies at D₁ and D₅ receptors indicate that the binding mode of 20c at the D₁ receptor allows for stronger hydrophobic contacts, (primarily with Phe residues) as compared to the D₅ receptor, accounting for its D₁ versus D₅ selectivity. Considering the lack of affinity for the D₅ receptor (and low affinity at other receptors tested), compound 20c represents an interesting starting point for further structural diversification of aporphines as sub-type selective D₁ receptor tools.

Diagnosis and Treatment of Parkinson Disease: A Review

IMPORTANCE

Parkinson disease is the most common form of parkinsonism, a group of neurological disorders with Parkinson disease-like movement problems such as rigidity, slowness, and tremor. More than 6 million individuals worldwide have Parkinson disease.

OBSERVATIONS

Diagnosis of Parkinson disease is based on history and examination. History can include prodromal features (eg, rapid eye movement sleep behavior disorder, hyposmia, constipation), characteristic movement difficulty (eg, tremor, stiffness, slowness), and psychological or cognitive problems (eg, cognitive decline, depression, anxiety). Examination typically demonstrates bradykinesia with tremor, rigidity, or both. Dopamine transporter single-photon emission computed tomography can improve the accuracy of diagnosis when the presence of parkinsonism is uncertain. Parkinson disease has multiple disease variants with different prognoses. Individuals with a diffuse malignant subtype (9%-16% of individuals with Parkinson disease) have prominent early motor and nonmotor symptoms, poor response to medication, and faster disease progression. Individuals with mild motor-predominant Parkinson disease (49%-53% of individuals with Parkinson disease) have mild symptoms, a good response to dopaminergic medications (eg, carbidopa-levodopa, dopamine agonists), and slower disease progression. Other individuals have an intermediate subtype. For all patients with Parkinson disease, treatment is symptomatic, focused on improvement in motor (eg, tremor, rigidity, bradykinesia) and nonmotor (eg, constipation, cognition, mood, sleep) signs and symptoms. No disease-modifying pharmacologic treatments are available. Dopamine-based therapies typically help initial motor symptoms. Nonmotor symptoms require nondopaminergic approaches (eg, selective serotonin reuptake inhibitors for psychiatric symptoms, cholinesterase inhibitors for cognition). Rehabilitative therapy and exercise complement pharmacologic treatments. Individuals experiencing complications, such as worsening symptoms and functional impairment when a medication dose wears off ("off periods"), medication-resistant tremor, and dyskinesias, benefit from advanced treatments such as therapy with levodopa-carbidopa enteral suspension or deep brain stimulation. Palliative care is part of Parkinson disease management.

CONCLUSIONS AND RELEVANCE

Parkinson disease is a heterogeneous disease with rapidly and slowly progressive forms. Treatment involves pharmacologic approaches (typically with levodopa preparations prescribed with or without other medications) and nonpharmacologic approaches (such as exercise and physical, occupational, and speech therapies). Approaches such as deep brain stimulation and treatment with levodopa-carbidopa enteral suspension can help individuals with medication-resistant tremor, worsening symptoms when the medication wears off, and dyskinesias.