Parkinson’s disease as a multisystem disorder

Seizures due to pyridoxine deficiency in Parkinson's disease

Parkinson's disease (PD) is a complex neurodegenerative disorder characterized not only by its hallmark motor symptoms but also by a myriad of non-motor manifestations, including cognitive decline, autonomic manifestations, and gastrointestinal disturbances. Amidst these, a lesser-known but critical aspect is the increased risk of functional deficiency of pyridoxine (vitamin B6) in patients with PD, which is linked to an increased risk of seizures. This review investigates the intersection of PD, new-onset seizures, and pyridoxine deficiency, aiming to elucidate the significance of these associations and their contributions to the neurologic burden in PD. Case reports documenting the occurrence of seizures in patients with PD, particularly in the context of high-dose dopaminergic therapy and the subsequent revelation of pyridoxine deficiency were included. These cases, which often featured extensive workups revealing unremarkable findings aside from pyridoxine deficiency, underscore the multifaceted nature of PD and its treatment-related complications. The findings in these case reports suggest that dietary insufficiencies, gastrointestinal dysfunctions, and drug-nutrient interactions may eventually precipitate pyridoxine deficiency, which in turn may lead to seizures by disrupting GABAergic neurotransmission. This sheds the light on the need for increased clinical awareness and routine monitoring of pyridoxine levels in patients with PD, especially those undergoing significant therapeutic adjustments or exhibiting comorbidities that might interfere with their dietary intake such as gastrointestinal manifestations or depression. Such proactive measures could potentially mitigate the impact of this complication in patients with PD, ultimately enhancing patient care and quality of life.

Orally administered neohesperidin attenuates MPTP-induced neurodegeneration by inhibiting inflammatory responses and regulating intestinal flora in mice

Parkinson's disease (PD), a neurodegenerative disease, is the leading cause of movement disorders. Neuroinflammation plays a critical role in PD pathogenesis. Neohesperidin (Neo), a natural flavonoid extracted from citric fruits exhibits anti-inflammatory effects. However, the effect of Neo on PD progression is unclear. This study aimed to investigate the effects of Neo on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD in mice and its underlying mechanism. Our results indicated that Neo administration ameliorated motor impairment and neural damage in MPTP-injected mice, by inhibiting neuroinflammation and regulating gut microbial imbalance. Additionally, Neo administration reduced colonic inflammation and tissue damage. Mechanistic studies revealed that Neo suppressed the MPTP-induced inflammatory response by inhibiting excessive activation of NF-κB and MAPK pathways. In summary, the present study demonstrated that Neo administration attenuates neurodegeneration in MPTP-injected mice by inhibiting inflammatory responses and regulating the gut microbial composition. This study may provide the scientific basis for the use of Neo in the treatment of PD and other related diseases.

Linking acetylated α-Tubulin redistribution to α-Synuclein pathology in brain of Parkinson's disease patients

Highly specialized microtubules in neurons are crucial to both health and disease of the nervous system, and their properties are strictly regulated by different post-translational modifications, including α-Tubulin acetylation. An imbalance in the levels of acetylated α-Tubulin has been reported in experimental models of Parkinson's disease (PD) whereas pharmacological or genetic modulation that leads to increased acetylated α-Tubulin successfully rescues axonal transport defects and inhibits α-Synuclein aggregation. However, the role of acetylation of α-Tubulin in the human nervous system is largely unknown as most studies are based on in vitro evidence. To capture the complexity of the pathological processes in vivo, we analysed post-mortem human brain of PD patients and control subjects. In the brain of PD patients at Braak stage 6, we found a redistribution of acetylated α-Tubulin, which accumulates in the neuronal cell bodies in subcortical structures but not in the cerebral cortex, and decreases in the axonal compartment, both in putamen bundles of fibres and in sudomotor fibres. High-resolution and 3D reconstruction analysis linked acetylated α-Tubulin redistribution to α-Synuclein oligomerization and to phosphorylated Ser 129 α-Synuclein, leading us to propose a model for Lewy body (LB) formation. Finally, in post-mortem human brain, we observed threadlike structures, resembling tunnelling nanotubes that contain α-Synuclein oligomers and are associated with acetylated α-Tubulin enriched neurons. In conclusion, we support the role of acetylated α-Tubulin in PD pathogenesis and LB formation.

Cognitive status and sleep quality can explain the fear of falling and fall history in people with Parkinson's disease

Fear of falling (FOF) is highly prevalent in people with Parkinson's disease (PwPD) and contributes to high fall risk. Studies reporting on the relationship between falls, FOF, and non-motor factors such as cognitive function and sleep quality in Parkinson's disease are limited. This study aimed to investigate (1) the relationship of cognitive function and sleep quality with FOF, and history of falls in PwPD; (2) differences in cognitive function and sleep quality between Parkinson's disease fallers and non-fallers; and (3) a cut-off score for cognitive function and sleep quality to discriminate Parkinson's disease fallers from non-fallers. Fifty PwPD were assessed for FOF [Falls Efficacy Scale-International (FES-I)], cognition [Montréal Cognitive Assessment (MOCA)], sleep quality [Pittsburgh Sleep Quality Index (PSQI)], and falls history. The MOCA is significantly associated with FES-I scores ( R2  = 0.429, P  < 0.0001). Both MOCA ( P  = 0.012) and PSQI ( P  = 0.027) were associated with falls history even after adjusting for confounding factors (age, sex, L-dopa use, Parkinson's disease severity). Both MOCA and PSQI scores were able to distinguish fallers from non-fallers with cut-off scores of 15.5 and 7.5, respectively. Although our findings revealed that both cognitive function and sleep quality are important factors influencing falls and FOF in PwPD, it remains to be determined if addressing cognitive impairments and poor sleep quality may favorably impact balance before integrating such screenings into fall prevention programs.

Profiling Analysis of Tryptophan Metabolites in the Urine of Patients with Parkinson's Disease Using LC-MS/MS

Although Parkinson's disease (PD) is a representative neurodegenerative disorder and shows characteristic motor impediments, the pathophysiological mechanisms and treatment targets for PD have not yet been clearly identified. Since several tryptophan metabolites produced by gut microbiota could pass the blood-brain barrier and, furthermore, might influence the central nervous system, tryptophan metabolites within the indole, kynurenine, and serotonin metabolic pathways might be the most potent targets for PD development. Furthermore, most metabolites are circulated via the blood, play roles in and/or are metabolized via the host organs, and finally are excreted into the urine. Therefore, profiling the overall tryptophan metabolic pathways in urine samples of patients with PD is important to understanding the pathological mechanisms, finding biomarkers, and discovering therapeutic targets for PD. However, the development of profiling analysis based on tryptophan metabolism pathways in human urine samples is still challenging due to the wide physiological ranges, the varied signal response, and the structural diversity of tryptophan metabolites in complicated urine matrices. In this study, an LC-MS/MS method was developed to profile 21 tryptophan metabolites within the indole, kynurenine, and serotonin metabolic pathways in human urine samples using ion-pairing chromatography and multiple reaction monitoring determination. The developed method was successfully applied to urine samples of PD patients (n = 41) and controls (n = 20). Further, we investigated aberrant metabolites to find biomarkers for PD development and therapeutic targets based on the quantitative results. Unfortunately, most tryptophan metabolites in the urine samples did not present significant differences between control and PD patients, except for indole-3-acetic acid. Nonetheless, indole-3-acetic acid was reported for the first time for its aberrant urinary levels in PD patients and tentatively selected as a potential biomarker for PD. This study provides accurate quantitative results for 21 tryptophan metabolites in biological samples and will be helpful in revealing the pathological mechanisms of PD development, discovering biomarkers for PD, and further providing therapeutic targets for various PD symptoms. In the near future, to further investigate the relationship between gut microbial metabolites and PD, we will employ studies on microbial metabolites using plasma and stool samples from control and PD patients.

Pink1-/- Rats Demonstrate Swallowing and Gastrointestinal Dysfunction in a Model of Prodromal Parkinson Disease

Early motor and non-motor signs of Parkinson disease (PD) include dysphagia, gastrointestinal dysmotility, and constipation. However, because these often manifest prior to formal diagnosis, the study of PD-related swallow and GI dysfunction in early stages is difficult. To overcome this limitation, we used the Pink1-/- rat, a well-established early-onset genetic rat model of PD to assay swallowing and GI motility deficits. Thirty male rats were tested at 4 months (Pink1-/- = 15, wildtype (WT) control = 15) and 6 months (Pink1-/- = 7, WT = 6) of age; analogous to early-stage PD in humans. Videofluoroscopy of rats ingesting a peanut-butter-barium mixture was used to measure mastication rate and oropharyngeal and pharyngoesophageal bolus speeds. Abnormal swallowing behaviors were also quantified. A second experiment tracked barium contents through the stomach, small intestine, caecum, and colon at hours 0-6 post-barium gavage. Number and weight of fecal emissions over 24 h were also collected. Compared to WTs, Pink1-/- rats showed slower mastication rates, slower pharyngoesophageal bolus speeds, and more abnormal swallowing behaviors. Pink1-/- rats demonstrated significantly delayed motility through the caecum and colon. Pink1-/- rats also had significantly lower fecal pellet count and higher fecal pellet weight after 24 h at 6 months of age. Results demonstrate that swallowing dysfunction occurs early in Pink1-/- rats. Delayed transit to the colon and constipation-like signs are also evident in this model. The presence of these early swallowing and GI deficits in Pink1-/- rats are analogous to those observed in human PD.

FTO-targeted siRNA delivery by MSC-derived exosomes synergistically alleviates dopaminergic neuronal death in Parkinson's disease via m6A-dependent regulation of ATM mRNA

BACKGROUND

Parkinson's disease (PD), characterized by the progressive loss of dopaminergic neurons in the substantia nigra and striatum of brain, seriously threatens human health, and is still lack of effective treatment. Dysregulation of N6-methyladenosine (m6A) modification has been implicated in PD pathogenesis. However, how m6A modification regulates dopaminergic neuronal death in PD remains elusive. Mesenchymal stem cell-derived exosomes (MSC-Exo) have been shown to be effective for treating central nervous disorders. We thus propose that the m6A demethylase FTO-targeted siRNAs (si-FTO) may be encapsulated in MSC-Exo (Exo-siFTO) as a synergistic therapy against dopaminergic neuronal death in PD.

METHODS

In this study, the effect of m6A demethylase FTO on dopaminergic neuronal death was evaluated both in vivo and in vitro using a MPTP-treated mice model and a MPP + -induced MN9D cellular model, respectively. The mechanism through which FTO influences dopaminergic neuronal death in PD was investigated with qRT-PCR, western blot, immumohistochemical staining, immunofluorescent staining and flow cytometry. The therapeutic roles of MSC-Exo containing si-FTO were examined in PD models in vivo and in vitro.

RESULTS

The total m6A level was significantly decreased and FTO expression was increased in PD models in vivo and in vitro. FTO was found to promote the expression of cellular death-related factor ataxia telangiectasia mutated (ATM) via m6A-dependent stabilization of ATM mRNA in dopaminergic neurons. Knockdown of FTO by si-FTO concomitantly suppressed upregulation of α-Synuclein (α-Syn) and downregulation of tyrosine hydroxylase (TH), and alleviated neuronal death in PD models. Moreover, MSC-Exo were utilized to successfully deliver si-FTO to the striatum of animal brain, resulting in the significant suppression of α-Syn expression and dopaminergic neuronal death, and recovery of TH expression in the brain of PD mice.

CONCLUSIONS

MSC-Exo delivery of si-FTO synergistically alleviates dopaminergic neuronal death in PD via m6A-dependent regulation of ATM mRNA.

A mini-review of the role of vesicular glutamate transporters in Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disease implicated in multiple interacting neurotransmitter pathways. Glutamate is the central excitatory neurotransmitter in the brain and plays critical influence in the control of neuronal activity. Impaired Glutamate homeostasis has been shown to be closely associated with PD. Glutamate is synthesized in the cytoplasm and stored in synaptic vesicles by vesicular glutamate transporters (VGLUTs). Following its exocytotic release, Glutamate activates Glutamate receptors (GluRs) and mediates excitatory neurotransmission. While Glutamate is quickly removed by excitatory amino acid transporters (EAATs) to maintain its relatively low extracellular concentration and prevent excitotoxicity. The involvement of GluRs and EAATs in the pathophysiology of PD has been widely studied, but little is known about the role of VGLUTs in the PD. In this review, we highlight the role of VGLUTs in neurotransmitter and synaptic communication, as well as the massive alterations in Glutamate transmission and VGLUTs levels in PD. Among them, adaptive changes in the expression level and function of VGLUTs may exert a crucial role in excitatory damage in PD, and VGLUTs are considered as novel potential therapeutic targets for PD.

Inhibition of carnitine palmitoyl-transferase 1 is a potential target in a mouse model of Parkinson's disease

Glucose metabolism is dysregulated in Parkinson's disease (PD) causing a shift toward the metabolism of lipids. Carnitine palmitoyl-transferase 1A (CPT1A) regulates the key step in the metabolism of long-chain fatty acids. The aim of this study is to evaluate the effect of downregulating CPT1, either genetically with a Cpt1a P479L mutation or medicinally on PD using chronic rotenone mouse models using C57Bl/6J and Park2 knockout mice. We show that Cpt1a P479L mutant mice are resistant to rotenone-induced PD, and that inhibition of CPT1 is capable of restoring neurological function, normal glucose metabolism, and alleviate markers of PD in the midbrain. Furthermore, we show that downregulation of lipid metabolism via CPT1 alleviates pathological motor and non-motor behavior, oxidative stress, and disrupted glucose homeostasis in Park2 knockout mice. Finally, we confirm that rotenone induces gut dysbiosis in C57Bl/6J and, for the first time, in Park2 knockout mice. We show that this dysbiosis is alleviated by the downregulation of the lipid metabolism via CPT1.

Neurochemical, histological, and behavioral profiling of the acute, sub-acute, and chronic MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is a heterogeneous multi-systemic disorder unique to humans characterized by motor and non-motor symptoms. Preclinical experimental models of PD present limitations and inconsistent neurochemical, histological, and behavioral readouts. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD is the most common in vivo screening platform for novel drug therapies; nonetheless, behavioral endpoints yielded amongst laboratories are often discordant and inconclusive. In this study, we characterized neurochemically, histologically, and behaviorally three different MPTP mouse models of PD to identify translational traits reminiscent of PD symptomatology. MPTP was intraperitoneally (i.p.) administered in three different regimens: (i) acute-four injections of 20 mg/kg of MPTP every 2 h; (ii) sub-acute-one daily injection of 30 mg/kg of MPTP for 5 consecutive days; and (iii) chronic-one daily injection of 4 mg/kg of MPTP for 28 consecutive days. A series of behavioral tests were conducted to assess motor and non-motor behavioral changes including anxiety, endurance, gait, motor deficits, cognitive impairment, circadian rhythm and food consumption. Impairments in balance and gait were confirmed in the chronic and acute models, respectively, with the latter showing significant correlation with lesion size. The sub-acute model, by contrast, presented with generalized hyperactivity. Both, motor and non-motor changes were identified in the acute and sub-acute regime where habituation to a novel environment was significantly reduced. Moreover, we report increased water and food intake across all three models. Overall, the acute model displayed the most severe lesion size, while across the three models striatal dopamine content (DA) did not correlate with the behavioral performance. The present study demonstrates that detection of behavioral changes following MPTP exposure is challenging and does not correlate with the dopaminergic lesion extent.

S-Glutathionylation and S-Nitrosylation in Mitochondria: Focus on Homeostasis and Neurodegenerative Diseases

Redox post-translational modifications are derived from fluctuations in the redox potential and modulate protein function, localization, activity and structure. Amongst the oxidative reversible modifications, the S-glutathionylation of proteins was the first to be characterized as a post-translational modification, which primarily protects proteins from irreversible oxidation. However, a growing body of evidence suggests that S-glutathionylation plays a key role in core cell processes, particularly in mitochondria, which are the main source of reactive oxygen species. S-nitrosylation, another post-translational modification, was identified >150 years ago, but it was re-introduced as a prototype cell-signaling mechanism only recently, one that tightly regulates core processes within the cell’s sub-compartments, especially in mitochondria. S-glutathionylation and S-nitrosylation are modulated by fluctuations in reactive oxygen and nitrogen species and, in turn, orchestrate mitochondrial bioenergetics machinery, morphology, nutrients metabolism and apoptosis. In many neurodegenerative disorders, mitochondria dysfunction and oxidative/nitrosative stresses trigger or exacerbate their pathologies. Despite the substantial amount of research for most of these disorders, there are no successful treatments, while antioxidant supplementation failed in the majority of clinical trials. Herein, we discuss how S-glutathionylation and S-nitrosylation interfere in mitochondrial homeostasis and how the deregulation of these modifications is associated with Alzheimer’s, Parkinson’s, amyotrophic lateral sclerosis and Friedreich’s ataxia.

Saposin C, Key Regulator in the Alpha-Synuclein Degradation Mediated by Lysosome

Lysosomal dysfunction has been proposed as one of the most important pathogenic molecular mechanisms in Parkinson disease (PD). The most significant evidence lies in the GBA gene, which encodes for the lysosomal enzyme β-glucocerebrosidase (β-GCase), considered the main genetic risk factor for sporadic PD. The loss of β-GCase activity results in the formation of α-synuclein deposits. The present study was aimed to determine the activity of the main lysosomal enzymes and the cofactors Prosaposin (PSAP) and Saposin C in PD and healthy controls, and their contribution to α-synuclein (α-Syn) aggregation. 42 PD patients and 37 age-matched healthy controls were included in the study. We first analyzed the β-GCase, β-galactosidase (β-gal), β-hexosaminidase (Hex B) and Cathepsin D (CatD) activities in white blood cells. We also measured the GBA, β-GAL, β-HEX, CTSD, PSAP, Saposin C and α-Syn protein levels by Western-blot. We found a 20% reduced β-GCase and β-gal activities in PD patients compared to controls. PSAP and Saposin C protein levels were significantly lower in PD patients and correlated with increased levels of α-synuclein. CatD, in contrast, showed significantly increased activity and protein levels in PD patients compared to controls. Increased CTSD protein levels in PD patients correlated, intriguingly, with a higher concentration of α-Syn. Our findings suggest that lysosomal dysfunction in sporadic PD is due, at least in part, to an alteration in Saposin C derived from reduced PSAP levels. That would lead to a significant decrease in the β-GCase activity, resulting in the accumulation of α-syn. The accumulation of monohexosylceramides might act in favor of CTSD activation and, therefore, increase its enzymatic activity. The evaluation of lysosomal activity in the peripheral blood of patients is expected to be a promising approach to investigate pathological mechanisms and novel therapies aimed to restore the lysosomal function in sporadic PD.

Potential of Whole-Body Vibration in Parkinson’s Disease: A Systematic Review and Meta-Analysis of Human and Animal Studies

Simple Summary

Exercise has shown to have a positive impact on both motor and non-motor functions in Parkinson’s Disease patients. However, particularly in later stages of the disease, reduced cognitive function and motor capacity may lead to an inability to stay physically active. Therefore, alternative strategies for patients with Parkinson’s Disease are necessary to minimize burden for patients, their families and public health care. Whole-Body Vibration could be such an alternative. Whole-Body Vibration is an exercise or treatment method in which subjects are exposed to a mechanical vibration while sitting, standing or exercising on a vibrating platform. Whole-Body Vibration is currently used for physiotherapy, sports and rehabilitation purposes. Whole-Body Vibration treatment is interesting because it affects both the body and brain. The potential of Whole-Body Vibration for, specifically, Parkinson’s Disease patients should be clarified for further application. For this purpose, we conducted an extensive systematic review of the articles investigating the effects of Whole-Body Vibrations (1) on animals and humans with Parkinson’s Disease and (2) on neuropathological Parkinson’s Disease mechanisms. The results show some potential of Whole-Body Vibration for Parkinson’s Disease patients. The recommendations provided by this review can be used by researchers and rehabilitative practitioners implementing Whole-Body Vibration as a treatment for Parkinson’s Disease patients.

Abstract

(1) Background: When the severity of Parkinson’s Disease (PD) increases, patients often have difficulties in performing exercises. Whole-Body Vibration (WBV) may be a suitable alternative. This systematic review aims to clarify if WBV shows potential as rehabilitative therapy for PD patients. (2) Methods: We searched several databases for controlled trials investigating the effects of WBV (1) on PD populations and (2) PD neuropathological mechanisms. We included both human and animal studies and performed meta-analyses. (3) Results: The studies on PD populations (14 studies) show an overall significant, but small, effect in favor of WBV (Hedges’ g = 0.28), for which the effects on stability (Hedges’ g = 0.39) and balance (Hedges’ g = 0.30) are the most prominent. The studies on the neuropathological mechanisms (18 studies) show WBV effects on neuroinflammation (Hedges’ g = –1.12) and several specific WBV effects on neurotransmitter systems, growth factors, neurogenesis, synaptic plasticity and oxidative stress. (4) Conclusions: The effects of WBV on human PD patients remains inconclusive. Nevertheless, WBV protocols with sufficient duration (≥3 weeks), session frequency (≥3 sessions/week) and vibration frequency (≥20 Hz) show potential as a treatment method, especially for motor function. The potential of WBV for PD patients is confirmed by the effects on the neuropathological mechanisms in mostly non-PD populations. We recommend high-quality future studies on both PD patients and PD mouse models to optimize WBV protocols and to examine the neuropathological mechanisms in PD populations.

Neuropathy in parkinson's disease: Risk determinants and impact on quality of life

Neuropathy has been described in significantly higher proportion of PD patients than in control subjects. This study ascertains the prevelance of neuropathy and its determinants in PD patients, in particular relation with nutritional status, along with impact of neuropathy on Quality of life.

Low plasma serotonin linked to higher nigral iron in Parkinson's disease

A growing body of evidence suggests nigral iron accumulation plays an important role in the pathophysiology of Parkinson's disease (PD), contributing to dopaminergic neuron loss in the substantia nigra pars compacta (SNc). Converging evidence suggests this accumulation might be related to, or increased by, serotonergic dysfunction, a common, often early feature of the disease. We investigated whether lower plasma serotonin in PD is associated with higher nigral iron. We obtained plasma samples from 97 PD patients and 89 controls and MRI scans from a sub-cohort (62 PD, 70 controls). We measured serotonin concentrations using ultra-high performance liquid chromatography and regional iron content using MRI-based quantitative susceptibility mapping. PD patients had lower plasma serotonin (p < 0.0001) and higher nigral iron content (SNc: p < 0.001) overall. Exclusively in PD, lower plasma serotonin was correlated with higher nigral iron (SNc: r(58) =  - 0.501, p < 0.001). This correlation was significant even in patients newly diagnosed (< 1 year) and stronger in the SNc than any other region examined. This study reveals an early, linear association between low serotonin and higher nigral iron in PD patients, which is absent in controls. This is consistent with a serotonin-iron relationship in the disease process, warranting further studies to determine its cause and directionality.

Alpha-synuclein oligomers and small nerve fiber pathology in skin are potential biomarkers of Parkinson's disease

The proximity ligation assay (PLA) is a specific and sensitive technique for the detection of αSyn oligomers (αSyn-PLA), early and toxic species implicated in the pathogenesis of PD. We aimed to evaluate by skin biopsy the diagnostic and prognostic capacity of αSyn-PLA and small nerve fiber reduction in PD in a longitudinal study. αSyn-PLA was performed in the ankle and cervical skin biopsies of PD (n = 30), atypical parkinsonisms (AP, n = 23) including multiple system atrophy (MSA, n = 12) and tauopathies (AP-Tau, n = 11), and healthy controls (HC, n = 22). Skin biopsy was also analyzed for phosphorylated αSyn (P-αSyn) and 5G4 (αSyn-5G4), a conformation-specific antibody to aggregated αSyn. Intraepidermal nerve fiber density (IENFD) was assessed as a measure of small fiber neuropathy. αSyn-PLA signal was more expressed in PD and MSA compared to controls and AP-Tau. αSyn-PLA showed the highest diagnostic accuracy (PD vs. HC sensitivity 80%, specificity 77%; PD vs. AP-Tau sensitivity 80%, specificity 82%), however, P-αSyn and 5G4, possible markers of later phases, performed better when considering the ankle site alone. A small fiber neuropathy was detected in PD and MSA. A progression of denervation not of pathological αSyn was detected at follow-up and a lower IENFD at baseline was associated with a greater cognitive and motor decline in PD. A skin biopsy-derived compound marker, resulting from a linear discrimination analysis model of αSyn-PLA, P-αSyn, αSyn-5G4, and IENFD, stratified patients with accuracy (77.8%), including the discrimination between PD and MSA (84.6%). In conclusion, the choice of pathological αSyn marker and anatomical site influences the diagnostic performance of skin biopsy and can help in understanding the temporal dynamics of αSyn spreading in the peripheral nervous system during the disease. Skin denervation, not pathological αSyn is a potential progression marker for PD.

The contribution of cognitive behavioural factors to social anxiety in Parkinson's disease

BACKGROUND

Social anxiety is prevalent in idiopathic Parkinson's disease but why this is, is not yet well understood. Social cognitions, safety-seeking behaviours and internally focused attention are all known to predict social anxiety in the general population. These associated factors have not yet been explored in idiopathic Parkinson's disease, where disease severity and motor symptoms might also influence the experience of social anxiety.

AIMS

This study aimed to explore the relationship between cognitive behavioural factors and social anxiety in Parkinson's disease.

METHOD

Using a cross-sectional design, 124 people with Parkinson's disease completed self-report questionnaires including measures of Parkinson's disease severity, social anxiety, negative social cognitions, safety-seeking behaviours, internally focused attention, anxiety and depression.

RESULTS

The final regression model accounted for 71.6% of variance in social anxiety. Cognitive behavioural variables accounted for the largest magnitude of unique variance (43.5%). Sex, anxiety and depression accounted for 23.4%, and Parkinson non-motor symptom severity for 4.7%. Negative social cognitions and safety-seeking behaviours were statistically significant predictors, while an internal focus of attention was not.

CONCLUSIONS

Social anxiety in Parkinson's disease is associated with negative social cognitions and safety-seeking behaviours. Findings indicate the need for further research into cognitive behavioural approaches to social anxiety in Parkinson's disease.

Oral Health Disorders in Parkinson's Disease: More than Meets the Eye

Despite clinical evidence of poor oral health and hygiene in Parkinson’s disease (PD) patients, the mouth is often overlooked by both patients and the medical community, who generally focus on motor or psychiatric disorders considered more burdensome. Yet, oral health is in a two-way relationship with overall health—a weakened status triggering a decline in the quality of life. Here, we aim at giving a comprehensive overview of oral health disorders in PD, while identifying their etiologies and consequences. The physical (abnormal posture, muscle tone, tremor, and dyskinesia), behavioral (cognitive and neuropsychiatric disorders), and iatrogenic patterns associated with PD have an overall detrimental effect on patients’ oral health, putting them at risk for other disorders (infections, aspiration, pain, malnutrition), reducing their quality of life and increasing their isolation (anxiety, depression, communication issues). Interdisciplinary cooperation for prevention, management and follow-up strategies need to be implemented at an early stage to maintain and improve patients’ overall comfort and condition. Recommendations for practice, including (non-)pharmacological management strategies are discussed, with an emphasis on the neurologists’ role. Of interest, the oral cavity may become a valuable tool for diagnosis and prognosis in the near future (biomarkers). This overlooked but critical issue requires further attention and interdisciplinary research.

A collaborative approach to exercise provision for people with Parkinson's - a feasibility and acceptability study of the PDConnect programme [version 2; peer review: 2 approved]

BACKGROUND

Exercise has been shown to be beneficial for people with Parkinson's (PwP), slowing the rate of decline of motor and nonmotor symptoms, with emerging evidence associating exercise with a neuroprotective effect. Current exercise provision is time-limited, and delivered in the absence of strategies to support long-term adherence to exercise. With a growing Parkinson's population, there is a need to develop long-term sustainable approaches to exercise delivery. The primary aim of this study is to assess the feasibility and acceptability of a multicomponent intervention (PDConnect) aimed at promoting physical activity, and self-management for PwP.

METHODS

A convergent fixed parallel mixed methods design study will be undertaken. The study aims to recruit 30 PwP, who will be randomly allocated into two groups: (i) the usual care group will receive physiotherapy once a week for six weeks delivered via Microsoft Teams. (ii) The PDConnect group will receive physiotherapy once a week for six weeks which combines exercise, education and behaviour change interventions delivered by NHS Parkinson's specialist physiotherapists via Microsoft Teams. This will be followed by 12 weekly sessions of group exercise delivered on Microsoft Teams by fitness instructors specially trained in Parkinson's. Participants will be then contacted by the fitness instructors once per month for three months by video conferencing to support exercise engagement. Primary feasibility data will be collected during the study, with acceptability assessed via semi-structured interviews at the end. Secondary outcomes encompassing motor, non-motor and health and well-being measures will be assessed at baseline, at six, 18, and 30 weeks.

DISCUSSION

This pilot study will establish whether PDConnect is feasible and acceptable to PwP. This will provide a platform for a larger evaluation to assess the effectiveness of PDConnect at increasing exercise participation and self-management within the Parkinson's Community.

TRIAL REGISTRATION

Registered on ISRCTN (ISRCTN11672329, 4th June 2020).

New Avenues for Parkinson's Disease Therapeutics: Disease-Modifying Strategies Based on the Gut Microbiota

Parkinson's disease (PD) is a multifactorial neurodegenerative disorder that currently affects 1% of the population over the age of 60 years, and for which no disease-modifying treatments exist. Neurodegeneration and neuropathology in different brain areas are manifested as both motor and non-motor symptoms in patients. Recent interest in the gut-brain axis has led to increasing research into the gut microbiota changes in PD patients and their impact on disease pathophysiology. As evidence is piling up on the effects of gut microbiota in disease development and progression, another front of action has opened up in relation to the potential usage of microbiota-based therapeutic strategies in treating gastrointestinal alterations and possibly also motor symptoms in PD. This review provides status on the different strategies that are in the front line (i.e., antibiotics; probiotics; prebiotics; synbiotics; dietary interventions; fecal microbiota transplantation, live biotherapeutic products), and discusses the opportunities and challenges the field of microbiome research in PD is facing.

A Pragmatic Approach to the Perioperative Management of Parkinson's Disease

Patients with Parkinson's disease (PD) may undergo several elective and emergency surgeries. Motor fluctuations, the presence of a wide range of non-motor symptoms (NMS), and the use of several medications, often not limited to dopaminergic agents, make the perioperative management of PD challenging. However, the literature on perioperative management of PD is sparse. In this descriptive review article, we comprehensively discuss the issues in the pre-, intra-, and postoperative phases which may negatively affect the PD patients and discuss the approach to their prevention and management. The major preoperative challenges include accurate medication reconciliation and administration of the dopaminergic medications during the nil per os (NPO) state. While the former can be addressed with staff education and PD-specific admission protocols, knowledge of non-oral formulations of dopaminergic agents (apomorphine, inhalational levodopa, and rotigotine transdermal patch) is the key to the management of the Parkinsonian symptoms in NPO state. Deep brain stimulation (DBS) devices should be turned off to avert potential electromagnetic interference with surgical appliances. Choosing the appropriate anesthesia and avoiding and managing respiratory issues and dysautonomia are the major intraoperative challenges. Timely reinitiation of dopaminergic medications, adequate management of pain, nausea, and vomiting, and prevention of postoperative infections and delirium are the postoperative challenges. Overall, a multidisciplinary approach is pivotal to prevent and manage the perioperative complications in PD. Administration of anti-Parkinson medications during NPO state, prevention of anesthesia-related complications, and timely rehabilitation remain the key to healthy surgical outcomes.

Proteotoxicity and Neurodegenerative Diseases

Neurodegenerative diseases are a major burden for our society, affecting millions of people worldwide. A main goal of past and current research is to enhance our understanding of the mechanisms underlying proteotoxicity, a common theme among these incurable and debilitating conditions. Cell proteome alteration is considered to be one of the main driving forces that triggers neurodegeneration, and unraveling the biological complexity behind the affected molecular pathways constitutes a daunting challenge. This review summarizes the current state on key processes that lead to cellular proteotoxicity in Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis, providing a comprehensive landscape of recent literature. A foundational understanding of how proteotoxicity affects disease etiology and progression may provide essential insight towards potential targets amenable of therapeutic intervention.

α-Synuclein oligomers in skin biopsy of idiopathic and monozygotic twin patients with Parkinson's disease

A variety of cellular processes, including vesicle clustering in the presynaptic compartment, are impaired in Parkinson’s disease and have been closely associated with α-synuclein oligomerization. Emerging evidence proves the existence of α-synuclein-related pathology in the peripheral nervous system, even though the presence of α-synuclein oligomers in situ in living patients remains poorly investigated. In this case-control study, we show previously undetected α-synuclein oligomers within synaptic terminals of autonomic fibres in skin biopsies by means of the proximity ligation assay and propose a procedure for their quantification (proximity ligation assay score). Our study revealed a significant increase in α-synuclein oligomers in consecutive patients with Parkinson’s disease compared to consecutive healthy controls (P < 0.001). Proximity ligation assay score (threshold value > 96 using receiver operating characteristic) was found to have good sensitivity, specificity and positive predictive value (82%, 86% and 89%, respectively). Furthermore, to disclose the role of putative genetic predisposition in Parkinson’s disease aetiology, we evaluated the differential accumulation of oligomers in a unique cohort of 19 monozygotic twins discordant for Parkinson’s disease. The significant difference between patients and healthy subjects was confirmed in twins. Intriguingly, although no difference in median values was detected between consecutive healthy controls and healthy twins, the prevalence of healthy subjects positive for proximity ligation assay score was significantly greater in twins than in the consecutive cohort (47% versus 14%, P = 0.019). This suggests that genetic predisposition is important, but not sufficient, in the aetiology of the disease and strengthens the contribution of environmental factors. In conclusion, our data provide evidence that α-synuclein oligomers accumulate within synaptic terminals of autonomic fibres of the skin in Parkinson’s disease for the first time. This finding endorses the hypothesis that α-synuclein oligomers could be used as a reliable diagnostic biomarker for Parkinson’s disease. It also offers novel insights into the physiological and pathological roles of α-synuclein in the peripheral nervous system.

L. L. Pinheiro D, de la Rosa T, G. de Almeida AC, A. Scorza F, A. Scorza C. Propolis as A Potential Disease-Modifying Strategy in Parkinson's Disease: Cardioprotective and Neuroprotective Effects in the 6-OHDA Rat Model

Patients with Parkinson's disease (PD) manifest nonmotor and motor symptoms. Autonomic cardiovascular dysregulation is a common nonmotor manifestation associated with increased morbimortality. Conventional clinical treatment alleviates motor signs but does not change disease progression and fails in handling nonmotor features. Nutrition is a key modifiable determinant of chronic disease. This study aimed to assess the effects of propolis on cardiological features, heart rate (HR) and heart rate variability (HRV) and on nigrostriatal dopaminergic damage, detected by tyrosine hydroxylase (TH) immunoreactivity, in the 6-hydroxydopamine (6-OHDA) rat model of PD. Male Wistar rats were injected bilaterally with 6-OHDA or saline into the striatum and were treated with propolis or water for 40 days. Autonomic function was assessed by time domain parameters (standard deviation of all normal-to-normal intervals (SDNN) and square root of the mean of the squared differences between adjacent normal RR intervals (RMSSD)) of HRV calculated from electrocardiogram recordings. Reductions in HR (p = 1.47×10-19), SDNN (p = 3.42×10-10) and RMSSD (p = 8.2×10-6) detected in parkinsonian rats were reverted by propolis. Propolis attenuated neuronal loss in the substantia nigra (p = 5.66×10-15) and reduced striatal fiber degeneration (p = 7.4×10-5) in 6-OHDA-injured rats, which also showed significant weight gain (p = 1.07×10-5) in comparison to 6-OHDA-lesioned counterparts. Propolis confers cardioprotection and neuroprotection in the 6-OHDA rat model of PD.

Assessment of vitamin D and inflammatory markers profile in cardiac tissue on Parkinson disease animal model

BACKGROUND

Cardiovascular dysfunctions are common non-motor symptoms in patients with Parkinson's disease (PD) that can result in reduced quality of life and even death. Research in animal models designed to characterize the pathological association between PD and cardiovascular abnormalities is still in its infancy. This study assessed the early impact of the nigrostriatal dopaminergic damage on cardiological features in the unilateral 6-OHDA rat model of PD.

METHODS

Male Wistar rats received unilateral intrastriatal injections of 6-OHDA and sham rats were injected with saline. Animals were studied 15 days later. Immunohistochemistry was used for visualization of tyrosine hydroxylase (TH)-positive neurons in the nigrostriatal system. Electrocardiogram recordings of heart rate were performed in conscious rats. Heart levels of vitamin D, inflammatory cytokines and C-reactive protein were assessed through electrochemiluminescence immunoassay, quantitative reverse transcription PCR and turbidimetric method, respectively.

RESULTS

We found a post-injury reduction of TH-immunoreactivity of approximately 45% in the substantia nigra pars compacta and 20% in the striatum. Heart rate reduction was found in 6-OHDA-lesioned rats as compared with sham counterparts. Reduced levels of vitamin D and increased levels of inflammatory factors (C-reactive protein, IL-6, TNF-α and TGF-β) were detected in the heart tissue of PD rats in comparison with sham.

CONCLUSION

Our findings suggest a link between cardiac tissue changes and cardiac functional changes early after the central dopaminergic damage induced by 6-OHDA. Knowledge of the cardiac abnormalities in the 6-OHDA model is critical in identifying future therapeutic targets and disease-modifying approaches for PD non-motor features.

Advanced diffusion magnetic resonance imaging in patients with Alzheimer's and Parkinson's diseases

The prevalence of neurodegenerative diseases is increasing as human longevity increases. The objective biomarkers that enable the staging and early diagnosis of neurodegenerative diseases are eagerly anticipated. It has recently become possible to determine pathological changes in the brain without autopsy with the advancement of diffusion magnetic resonance imaging techniques. Diffusion magnetic resonance imaging is a robust tool used to evaluate brain microstructural complexity and integrity, axonal order, density, and myelination via the micron-scale displacement of water molecules diffusing in tissues. Diffusion tensor imaging, a type of diffusion magnetic resonance imaging technique is widely utilized in clinical and research settings; however, it has several limitations. To overcome these limitations, cutting-edge diffusion magnetic resonance imaging techniques, such as diffusional kurtosis imaging, neurite orientation dispersion and density imaging, and free water imaging, have been recently proposed and applied to evaluate the pathology of neurodegenerative diseases. This review focused on the main applications, findings, and future directions of advanced diffusion magnetic resonance imaging techniques in patients with Alzheimer’s and Parkinson’s diseases, the first and second most common neurodegenerative diseases, respectively.

Research-based Updates in Swallowing and Communication Dysfunction in Parkinson Disease: Implications for Evaluation and Management

PURPOSE

Individuals with Parkinson disease (PD) present with complex and variable symptoms, with recent findings suggesting that the etiology of PD extends beyond the involvement of just the basal ganglia. These symptoms include significant impairments in the speech and swallowing domains, which can greatly affect quality of life and therefore require therapeutic attention. This research-based update reviews the neurophysiological basis for swallowing and speech changes in PD, the effectiveness of various types of treatments, and implications for symptom evaluation and management.

CONCLUSION

The mechanisms responsible for swallowing and speech symptoms in PD remain largely unknown. Dopaminergic medication and deep-brain-stimulation do not provide consistent benefits for these symptoms suggesting a non-dopaminergic network is involved. Importantly, evidence suggests that symptoms of dysphagia and hypokinetic dysarthria may be early indications of PD, so it is critical to investigate the cause of these changes.

The noradrenergic system is necessary for survival of vulnerable midbrain dopaminergic neurons: implications for development and Parkinson's disease

The cause of midbrain dopaminergic (mDA) neuron loss in sporadic Parkinson's disease (PD) is multifactorial, involving cell autonomous factors, cell-cell interactions, and the effects of environmental toxins. Early loss of neurons in the locus coeruleus (LC), the main source of ascending noradrenergic (NA) projections, is an important feature of PD and other neurodegenerative disorders. We hypothesized that NA afferents provide trophic support for vulnerable mDA neurons. We demonstrate that depriving mDA neurons of NA input increases postnatal apoptosis and decreases cell survival in young adult rodents, with relative sparing of calbindin-positive subpopulations known to be resistant to degeneration in PD. As a mechanism, we propose that the neurotrophin brain-derived neurotrophic factor (BDNF) modulates anterograde survival effects of LC inputs to mDA neurons. We demonstrate that the LC is rich in BDNF mRNA in postnatal and young adult brains. Early postnatal NA denervation reduces both BDNF protein and activation of TrkB receptors in the ventral midbrain. Furthermore, overexpression of BDNF in NA afferents in transgenic mice increases mDA neuronal survival. Finally, increasing NA activity in primary cultures of mDA neurons improves survival, an effect that is additive or synergistic in the presence of different concentrations of BDNF. Taken together, our results point to a novel mechanism whereby LC afferents couple BDNF effects and NA activity to provide anterograde trophic support for vulnerable mDA neurons. Early loss of NA activity and anterograde neurotrophin support may contribute to degeneration of vulnerable neurons in PD and other neurodegenerative disorders.

Neuropathology and pathogenesis of extrapyramidal movement disorders: a critical update-I. Hypokinetic-rigid movement disorders

Extrapyramidal movement disorders include hypokinetic rigid and hyperkinetic or mixed forms, most of them originating from dysfunction of the basal ganglia (BG) and their information circuits. The functional anatomy of the BG, the cortico-BG-thalamocortical, and BG-cerebellar circuit connections are briefly reviewed. Pathophysiologic classification of extrapyramidal movement disorder mechanisms distinguish (1) parkinsonian syndromes, (2) chorea and related syndromes, (3) dystonias, (4) myoclonic syndromes, (5) ballism, (6) tics, and (7) tremor syndromes. Recent genetic and molecular-biologic classifications distinguish (1) synucleinopathies (Parkinson's disease, dementia with Lewy bodies, Parkinson's disease-dementia, and multiple system atrophy); (2) tauopathies (progressive supranuclear palsy, corticobasal degeneration, FTLD-17; Guamian Parkinson-dementia; Pick's disease, and others); (3) polyglutamine disorders (Huntington's disease and related disorders); (4) pantothenate kinase-associated neurodegeneration; (5) Wilson's disease; and (6) other hereditary neurodegenerations without hitherto detected genetic or specific markers. The diversity of phenotypes is related to the deposition of pathologic proteins in distinct cell populations, causing neurodegeneration due to genetic and environmental factors, but there is frequent overlap between various disorders. Their etiopathogenesis is still poorly understood, but is suggested to result from an interaction between genetic and environmental factors. Multiple etiologies and noxious factors (protein mishandling, mitochondrial dysfunction, oxidative stress, excitotoxicity, energy failure, and chronic neuroinflammation) are more likely than a single factor. Current clinical consensus criteria have increased the diagnostic accuracy of most neurodegenerative movement disorders, but for their definite diagnosis, histopathological confirmation is required. We present a timely overview of the neuropathology and pathogenesis of the major extrapyramidal movement disorders in two parts, the first one dedicated to hypokinetic-rigid forms and the second to hyperkinetic disorders.

Early signs of colonic inflammation, intestinal dysfunction, and olfactory impairments in the rotenone-induced mouse model of Parkinson's disease

The factors that trigger the pathophysiology of Parkinson's disease (PD) are unknown. However, it is suggested that environmental factors, such as exposure to pesticides, play an important role, in addition to genetic predisposition and aging. Early signs of PD can appear in the gastrointestinal (GI) tract and in the olfactory system, preceding the onset of motor impairments by many years. The present study assessed the effects of oral rotenone administration (30 mg/kg) in inducing GI and olfactory dysfunctions associated with PD in mice. Here we show that rotenone transiently increased myeloperoxidase activity within 24 h of administration. Leucocyte infiltration in the colon, associated with histological damage and disrupted GI motility, were observed following treatment with rotenone for 7 days. Moreover, 7 days of treatment with rotenone disrupted olfactory discrimination in mice without affecting social recognition ability. The presence of specific deficits in olfactory function occurred with a concomitant decrease in tyrosine hydroxylase-positive neurons and an increase in serotonin (5-hydroxytryptamine) turnover in the olfactory bulb. These findings suggest that in Swiss mice, exposure to rotenone induces GI and olfactory dysfunction involving immunological and neurotransmitter alterations, similar to early signs of PD. This provides further evidence for the involvement of the gut-brain axis in PD.

Laryngeal muscle biology in the Pink1-/- rat model of Parkinson disease

Neuromuscular pathology is found in the larynx and pharynx in humans with Parkinson disease (PD); however, it is unknown when this pathology emerges. We hypothesized that pathology occurs in early (premanifest) stages. To address this, we used the Pink1-/- rat model of PD, which shows age-dependent dopaminergic neuron loss, locomotor deficits, and deficits related to laryngeal function. We report findings in the thyroarytenoid muscle (TA) in Pink1-/- rats compared with wild-type (WT) control rats at 4 and 6 mo of age. TAs were analyzed for force production, myosin heavy chain isoform (MyHC), centrally nucleated myofibers, neural cell adhesion molecule, myofiber size, and muscle section size. Compared with WT, Pink1-/- TA had reductions in force levels at 1-Hz stimulation and 20-Hz stimulation, increases in relative levels of MyHC 2L, increases in incidence of centrally nucleated myofibers in the external division of the TA, and reductions in myofiber size of the vocalis division of the TA at 6 mo of age. Alterations of laryngeal muscle biology occur in a rat model of premanifest PD. Although these alterations are statistically significant, their functional significance remains to be determined. NEW & NOTEWORTHY Pathology of peripheral nerves and muscle has been reported in the larynx and pharynx of humans diagnosed with Parkinson disease (PD); however, it is unknown whether differences of laryngeal muscle occur at premanifest stages. This study examined the thyroarytenoid muscles of the Pink1-/- rat model of PD for differences of muscle biology compared with control rats. Thyroarytenoid muscles of Pink1-/- rats at premanifest stages show differences in multiple measures of muscle biology.

Tandem gait abnormality in Parkinson disease: Prevalence and implication as a predictor of fall risk

INTRODUCTION

We report the prevalence of abnormal tandem gait (TG) in patients with idiopathic Parkinson disease (PD) and its association with symptoms of subjective unsteadiness, falls, freezing of gait, and cognitive impairment.

METHODS

We assessed subjective balance impairment, fall history, antero-posterior postural instability, and TG in PD patients (Hoehn and Yahr (HY) stage 0-4). We recorded the age, sex, current medications, HY stage, Schwab and England (S&E) scale score, and MOCA score for each patient. Logistic regression was used to evaluate age-adjusted associations between TG and other demographic and clinical factors.

RESULTS

A total of 102 patients with PD were assessed. Of those, 63.5% of HY 2 patients and 100% of HY 2.5 and 3 patients had a TG abnormality. The presence of TG abnormality was associated with subjective imbalance, falls, freezing of gait, S&E < 80, and MOCA score <24 after adjustment for age.

CONCLUSIONS

TG abnormality is common in PD, precedes the development of antero-posterior postural instability, is associated with cognitive impairment, and may predict fall risk. A longitudinal study will help determine if TG is a predictor of impending progression from HY 2 to HY 3.

Exercise as a therapeutic intervention for motor and non-motor symptoms in Parkinson's disease: Evidence from rodent models

Parkinson's disease (PD) is characterised by degeneration of dopaminergic neurons of the nigrostriatal pathway, which leads to the cardinal motor symptoms of the disease - tremor, rigidity and postural instability. A number of non-motor symptoms are also associated with PD, including cognitive impairment, mood disturbances and dysfunction of gastrointestinal and autonomic systems. Current therapies provide symptomatic relief but do not halt the disease process, so there is an urgent need for preventative strategies. Lifestyle interventions such as aerobic exercise have shown potential to lower the risk of developing PD and to alleviate both motor and non-motor symptoms. However, there is a lack of large-scale randomised clinical trials that have employed exercise in PD patients. This review will focus on the evidence from studies on rodent models of PD, for employing exercise as an intervention for both motor and non-motor symptoms.

Deep Brain Stimulation and L-DOPA Therapy: Concepts of Action and Clinical Applications in Parkinson's Disease

L-DOPA is still the most effective pharmacological therapy for the treatment of motor symptoms in Parkinson's disease (PD) almost four decades after it was first used. Deep brain stimulation (DBS) is a safe and highly effective treatment option in patients with PD. Even though a clear understanding of the mechanisms of both treatment methods is yet to be obtained, the combination of both treatments is the most effective standard evidenced-based therapy to date. Recent studies have demonstrated that DBS is a therapy option even in the early course of the disease, when first complications arise despite a rigorous adjustment of the pharmacological treatment. The unique feature of this therapeutic approach is the ability to preferentially modulate specific brain networks through the choice of stimulation site. The clinical effects have been unequivocally confirmed in recent studies; however, the impact of DBS and the supplementary effect of L-DOPA on the neuronal network are not yet fully understood. In this review, we present emerging data on the presumable mechanisms of DBS in patients with PD and discuss the pathophysiological similarities and differences in the effects of DBS in comparison to dopaminergic medication. Targeted, selective modulation of brain networks by DBS and pharmacodynamic effects of L-DOPA therapy on the central nervous system are presented. Moreover, we outline the perioperative algorithms for PD patients before and directly after the implantation of DBS electrodes and strategies for the reduction of side effects and optimization of motor and non-motor symptoms.

Paradoxical Decision-Making: A Framework for Understanding Cognition in Parkinson's Disease

People with Parkinson's disease (PD) show impaired decision-making when sensory and memory information must be combined. This recently identified impairment results from an inability to accumulate the proper amount of information needed to make a decision and appears to be independent of dopamine tone and reinforcement learning mechanisms. Although considerable work focuses on PD and decisions involving risk and reward, in this Opinion article we propose that the emerging findings in perceptual decision-making highlight the multisystem nature of PD, and that unraveling the neuronal circuits underlying perceptual decision-making impairment may help in understanding other cognitive impairments in people with PD. We also discuss how a decision-making framework may be extended to gain insights into mechanisms of motor impairments in PD.

The effect of light exposure on insomnia and nocturnal movement in Parkinson's disease: an open label, retrospective, longitudinal study

Insomnia, hypersomnia and REM Sleep Behavior Disorder (RSBD) during sleep are major problems for patients suffering from Parkinson's disease (PD) but they are also used to predict its onset. While these secondary symptoms detract from the quality of life in PD patients, few treatment options are available due to limited efficacy or risk of complicating the treatment regimen. Light therapy (LT) has been suggested as a strategy for sleep disorders but it has only been implemented recently for use in PD. An open label, retrospective study was undertaken where PD patients had been undergoing LT, using polychromatic light, for four months to 15 years prior. It was found that 1 h exposure to light, just prior to retiring, significantly improved insomnia and reduced RSBD in as little as one month after commencing LT. In addition, the improvement was maintained as long as LT was continued over a four to six year period. The efficacy of LT in alleviating these sleep related conditions was not compromised by time since diagnosis or age of the patient. These results intimate the value of long term application of non-invasive techniques such as LT for treating sleep disorders in PD and justify further controlled trials on the long term efficacy of LT.

Inhibition of miR-181a promotes midbrain neuronal growth through a Smad1/5-dependent mechanism: implications for Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, and is characterized by the progressive degeneration of nigrostriatal dopaminergic (DA) neurons. Current PD treatments are symptomatic, wear off over time and do not protect against DA neuronal loss. Finding a way to re-grow midbrain DA (mDA) neurons is a promising disease-modifying therapeutic strategy for PD. However, reliable biomarkers are required to allow such growth-promoting approaches to be applied early in the disease progression. miR-181a has been shown to be dysregulated in PD patients, and has been identified as a potential biomarker for PD. Despite studies demonstrating the enrichment of miR-181a in the brain, specifically in neurites of postmitotic neurons, the role of miR-181a in mDA neurons remains unknown. Herein, we used cell culture models of human mDA neurons to investigate a potential role for miR-181a in mDA neurons. We used a bioninformatics analysis to identify that miR-181a targets components of the bone morphogenetic protein (BMP) signalling pathway, including the transcription factors Smad1 and Smad5, which we find are expressed by rat mDA neurons and are required for BMP-induced neurite growth. We also found that inhibition of neuronal miR-181a, resulted in increased Smad signalling, and induced neurite growth in SH-SY5Y cells. Finally, using embryonic rat cultures, we demonstrated that miR-181a inhibition induces ventral midbrain (VM) and cortical neuronal growth. These data describe a new role for miR-181a in mDA neurons, and provide proof of principle that miR-181a dysresgulation in PD may alter the activation state of signalling pathways important for neuronal growth in neurons affected in PD.

Emerging preclinical interest concerning the role of circadian function in Parkinson's disease

The importance of circadian function in the aetiology, progression and treatment of Parkinson's disease is a topic of increasing interest to the scientific and clinical community. While clinical studies on this theme are relatively new and limited in number there are many preclinical studies which explore possible circadian involvement in Parkinson's disease and speculate as to the mechanism by which clinical benefit can be derived by manipulating the circadian system. The present review explores the sequelae of circadian related studies from a historical perspective and reveals mechanisms that may be involved in the aetiology and progression of the disease. A systematic review of these studies also sets the stage for understanding the basic neuroscientific approaches which have been applied and provides new direction from which circadian function can be explored.

Non-human primate models of PD to test novel therapies

Non-human primate (NHP) models of Parkinson disease show many similarities with the human disease. They are very useful to test novel pharmacotherapies as reviewed here. The various NHP models of this disease are described with their characteristics including the macaque, the marmoset, and the squirrel monkey models. Lesion-induced and genetic models are described. There is no drug to slow, delay, stop, or cure Parkinson disease; available treatments are symptomatic. The dopamine precursor, L-3,4-dihydroxyphenylalanine (L-Dopa) still remains the gold standard symptomatic treatment of Parkinson. However, involuntary movements termed L-Dopa-induced dyskinesias appear in most patients after chronic treatment and may become disabling. Dyskinesias are very difficult to manage and there is only amantadine approved providing only a modest benefit. In this respect, NHP models have been useful to seek new drug targets, since they reproduce motor complications observed in parkinsonian patients. Therapies to treat motor symptoms in NHP models are reviewed with a discussion of their translational value to humans. Disease-modifying treatments tested in NHP are reviewed as well as surgical treatments. Many biochemical changes in the brain of post-mortem Parkinson disease patients with dyskinesias are reviewed and compare well with those observed in NHP models. Non-motor symptoms can be categorized into psychiatric, autonomic, and sensory symptoms. These symptoms are present in most parkinsonian patients and are already installed many years before the pre-motor phase of the disease. The translational usefulness of NHP models of Parkinson is discussed for non-motor symptoms.