Autonomic dysfunction in Parkinson's disease

The Pathogenesis and Treatment of Cardiovascular Autonomic Dysfunction in Parkinson's Disease: What We Know and Where to Go

Cardiovascular autonomic dysfunctions (CAD) are prevalent in Parkinson’s disease (PD). It contributes to the development of cognitive dysfunction, falls and even mortality. Significant progress has been achieved in the last decade. However, the underlying mechanisms and effective treatments for CAD have not been established yet. This review aims to help clinicians to better understand the pathogenesis and therapeutic strategies. The literatures about CAD in patients with PD were reviewed. References for this review were identified by searches of PubMed between 1972 and March 2021, with the search term “cardiovascular autonomic dysfunctions, postural hypotension, orthostatic hypotension (OH), supine hypertension (SH), postprandial hypotension, and nondipping”. The pathogenesis, including the neurogenic and non-neurogenic mechanisms, and the current pharmaceutical and non-pharmaceutical treatment for CAD, were analyzed. CAD mainly includes four aspects, which are OH, SH, postprandial hypotension and nondipping, among them, OH is the main component. Both non-neurogenic and neurogenic mechanisms are involved in CAD. Failure of the baroreflex circulate, which includes the lesions at the afferent, efferent or central components, is an important pathogenesis of CAD. Both non-pharmacological and pharmacological treatment alleviate CAD-related symptoms by acting on the baroreflex reflex circulate. However, pharmacological strategy has the limitation of failing to enhance baroreflex sensitivity and life quality. Novel OH treatment drugs, such as pyridostigmine and atomoxetine, can effectively improve OH-related symptoms via enhancing residual sympathetic tone, without adverse reactions of supine hypertension. Baroreflex impairment is a crucial pathological mechanism associated with CAD in PD. Currently, non-pharmacological strategy was the preferred option for its advantage of enhancing baroreflex sensitivity. Pharmacological treatment is a second-line option. Therefore, to find drugs that can enhance baroreflex sensitivity, especially via acting on its central components, is urgently needed in the scientific research and clinical practice.

Pathophysiological Changes in the Enteric Nervous System of Rotenone-Exposed Mice as Early Radiological Markers for Parkinson's Disease

Parkinson's disease (PD) is known to involve the peripheral nervous system (PNS) and the enteric nervous system (ENS). Functional changes in PNS and ENS appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients like constipation, that can precede the appearance of motor symptoms by years. Here we analyzed the effect of the pesticide rotenone, a mitochondrial Complex I inhibitor, on the function and neuronal composition of the ENS by measuring intestinal contractility in a tissue bath and by analyzing related protein expression. Our results show that rotenone changes the normal physiological response of the intestine to carbachol, dopamine and electric field stimulation (EFS). Changes in the reaction to EFS seem to be related to the reduction in the cholinergic input but also related to the noradrenergic input, as suggested by the non-adrenergic non-cholinergic (NANC) reaction to the EFS in rotenone-exposed mice. The magnitude and direction of these alterations varies between intestinal regions and exposure times and is associated with an early up-regulation of dopaminergic, cholinergic and adrenergic receptors and an irregular reduction in the amount of enteric neurons in rotenone-exposed mice. The early appearance of these alterations, that start occurring before the substantia nigra is affected in this mouse model, suggests that these alterations could be also observed in patients before the onset of motor symptoms and makes them ideal potential candidates to be used as radiological markers for the detection of Parkinson's disease in its early stages.

Autonomic Dysfunctions in Parkinson's Disease: Prevalence, Clinical Characteristics, Potential Diagnostic Markers, and Treatment

Parkinson's disease (PD) is a common neurodegenerative disease in the middle-aged and the elderly. Symptoms of autonomic dysfunctions are frequently seen in PD patients, severely affecting the quality of life. This review summarizes the epidemiology, clinical manifestations, and treatment options of autonomic dysfunctions. The clinical significance of autonomic dysfunctions in PD early diagnosis and differential diagnosis is also discussed.

Autonomic failure in Parkinson's disease is associated with striatal dopamine deficiencies

Autonomic dysfunction is a common non-motor symptom in Parkinson's disease (PD). Dopamine and serotonin are known to play a role in autonomic regulation, and, therefore, PD-related degeneration of serotonergic and dopaminergic neurons in these regions may be associated with autonomic dysfunction. We sought to clarify the association between extrastriatal serotonergic and striatal dopaminergic degeneration and the severity of autonomic symptoms, including gastrointestinal, pupillomotor, thermoregulatory, cardiovascular, and urinary dysfunction. We performed hierarchical multiple regression analyses to determine the relationships between (extra)striatal serotonergic and dopaminergic degeneration and autonomic dysfunction in 310 patients with PD. We used [¹²³I]FP-CIT SPECT binding to presynaptic serotonin (SERT) and dopamine (DAT) transporters as a measure of the integrity of these neurotransmitter systems, and the SCOPA-AUT (Scales for Outcomes in Parkinson's Disease-Autonomic) questionnaire to evaluate the perceived severity of autonomic dysfunction. Motor symptom severity, medication status, and sex were added to the model as covariates. Additional analyses were also performed using five subdomains of the SCOPA-AUT: cardiovascular, gastrointestinal, urinary, thermoregulatory, and pupillomotor symptoms. We found that autonomic symptoms were most significantly related to lower [¹²³I]FP-CIT binding ratios in the right caudate nucleus and were mainly driven by gastrointestinal and cardiovascular dysfunction. These results provide a first look into the modest role of dopaminergic projections towards the caudate nucleus in the pathophysiology of autonomic dysfunction in PD, but the underlying mechanism warrants further investigation.

Gut-Brain Axis and Neurodegeneration: State-of-the-Art of Meta-Omics Sciences for Microbiota Characterization

Recent advances in the field of meta-omics sciences and related bioinformatics tools have allowed a comprehensive investigation of human-associated microbiota and its contribution to achieving and maintaining the homeostatic balance. Bioactive compounds from the microbial community harboring the human gut are involved in a finely tuned network of interconnections with the host, orchestrating a wide variety of physiological processes. These includes the bi-directional crosstalk between the central nervous system, the enteric nervous system, and the gastrointestinal tract (i.e., gut-brain axis). The increasing accumulation of evidence suggest a pivotal role of the composition and activity of the gut microbiota in neurodegeneration. In the present review we aim to provide an overview of the state-of-the-art of meta-omics sciences including metagenomics for the study of microbial genomes and taxa strains, metatranscriptomics for gene expression, metaproteomics and metabolomics to identify and/or quantify microbial proteins and metabolites, respectively. The potential and limitations of each discipline were highlighted, as well as the advantages of an integrated approach (multi-omics) to predict microbial functions and molecular mechanisms related to human diseases. Particular emphasis is given to the latest results obtained with these approaches in an attempt to elucidate the link between the gut microbiota and the most common neurodegenerative diseases, such as multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS).

Exosome/microvesicle content is altered in leucine-rich repeat kinase 2 mutant induced pluripotent stem cell-derived neural cells

Extracellular vesicles, including exosomes/microvesicles (EMVs), have been described as sensitive biomarkers that represent disease states and response to therapies. In light of recent reports of disease-mirroring EMV molecular signatures, the present study profiled two EMVs from different Parkinson's disease (PD) tissue sources: (a) neural progenitor cells derived from an endogenous adult stem/progenitor cell, called adult human neural progenitor (AHNP) cells, that we found to be pathological when isolated from postmortem PD patients' substantia nigra; and (b) leucine-rich repeat kinase 2 (LRRK2) gene identified patient induced pluripotent stem cells (iPSCs), which were used to isolate EMVs and begin to characterize their cargoes. Initial characterization of EMVs derived from idiopathic patients (AHNPs) and mutant LRRK2 patients showed differences between both phenotypes and when compared with a sibling control in EMV size and release based on Nanosight analysis. Furthermore, molecular profiling disclosed that neurodegenerative-related gene pathways altered in PD can be reversed using gene-editing approaches. In fact, the EMV cargo genes exhibited normal expression patterns after gene editing. This study shows that EMVs have the potential to serve as sensitive biomarkers of disease state in both idiopathic and gene-identified PD patients and that following gene-editing, EMVs reflect a corrected state. This is relevant for both prodromal and symptomatic patient populations where potential responses to therapies can be monitored via non-invasive liquid biopsies and EMV characterizations.

Eplingiella fruticosa leaf essential oil complexed with β-cyclodextrin produces a superior neuroprotective and behavioral profile in a mice model of Parkinson's disease

Evidence indicates that oxidative stress has an important role in the onset and progression of Parkinson's disease (PD). Antioxidant agents from natural products have shown neuroprotective effects in animal models of PD. Eplingiella fruticosa is an aromatic and medicinal plant of the Lamiaceae family that include culinary herbs. The essential oil (EPL) has anti-inflammatory and antioxidant activities. Cyclodextrins are used to enhances pharmacological profile of essential oil. We obtained the EPL from leaves and complexed with β-cyclodextrin (EPL-βCD). Phytochemical analysis showed as main constituents: β-caryophyllene, bicyclogermacrene and 1,8-cineole. We evaluated the effects of EPL and EPL-βCD (5 mg/kg, p.o. for 40 days) on male mice submitted to the progressive reserpine PD model. Behavioral evaluations, lipid peroxidation quantification and immunohistochemistry for tyrosine hydroxylase were conducted. EPL delayed the onset of catalepsy and decreased membrane lipid peroxides levels in the striatum. EPL-βCD also delayed the onset of catalepsy, reduced the frequency of oral diskynesia, restored memory deficit, produced anxiolytic activity and protected against dopaminergic depletion in the striatum and SNpc. These findings showed that EPL has a potential neuroprotective effect in a progressive PD animal model. Further, EPL-βCD enhanced this protective effects, suggesting a novel therapeutic approach to ameliorate the symptoms of PD.

Distribution of non-motor symptoms in idiopathic Parkinson's disease and secondary Parkinsonism

Background

Non-motor symptoms (NMS) are frequent in patients with idiopathic Parkinson’s disease (IPD). Clinical expressions, postulated pathophysiological mechanisms, and responsiveness to antiparkinson medication represent differences between IPD and secondary Parkinsonism (SP).

Objective

To evaluate NMS expressions in IPD, SP, and a matched control group.

Methods

The accepted criteria for IPD and SP were controlled for the participants who were consecutively recruited at two outdoor patient clinics. The Well-Being Map™ was used as the evaluation instrument. These were completed by the participants before their visit. The controls consisted of non-Parkinsonian individuals who were matched by age and gender.

Results

A total of 185 participants participated in the study, IPD/SP/controls; n=73/53 and 59, respectively. The mean age was 74 years, and the median duration of disease was 6/3 years. Differences were shown between the combined IPD/SP groups and the controls. Limited differences between the IPD and SP groups could be demonstrated. Symptoms such as pain, decreased taste, as well as sleep and bladder disturbances were more frequent in the IPD group. When more than minor problems with moving were reported, disturbances in sleep and digestion were also noted to a large extent.

Conclusion

Despite differences in the pathophysiological mechanisms between IPD and SP, the study showed only minor differences in the expression of NMS. IPD and SP reported statistically more significant problems in all items compared to the controls. Sleeping problems were strongly associated with symptoms from the gastrointestinal tract, but sleep was only affected by longer disease duration to a minor extent. Motor symptoms, such as morning stiffness, were common in all three groups. Neurodegenerative diseases might have more complex expressions in common than what we have known before and it is certainly not a part of normal aging.

Does resistance training modulate cardiac autonomic control? A systematic review and meta-analysis

PURPOSE

To systematically evaluate the literature on the effects of resistance training (RT) on cardiac autonomic control in healthy and diseased individuals.

METHODS

Electronic databases Pubmed, PEDro, and Scopus were systematically searched from their inception up to June 2018. Randomized controlled trials, quasi-experimental trials, and cross-over controlled trials investigating the effect of RT (of at least 4 weeks duration) on cardiac autonomic control assessed either by linear or non-linear measures of heart rate variability (HRV), baroreflex sensitivity, or post-exercise heart rate recovery were included. Of the studies retrieved, 28 were included in the systematic review. Meta-analysis was performed on 21 studies of the total 28 studies.

RESULTS

Quality and characteristic assessment revealed fair quality evidence. The majority of literature on healthy humans suggested no change in cardiac autonomic control following RT. Standardized mean differences (SMD) showed a significant effect of RT on root mean square of successive differences between adjacent inter-beat (R-R) intervals (RMSSD) [SMD 0.96, 95% confidence interval (CI) 0.20-1.73; p = 0.01], ratio of low- to high-frequency power of HRV (LF/HF ratio; SMD -0.72, 95% CI -1.03 to -0.42; p < 0.00001), standard deviation of the instantaneous beat-to-beat variability (SD1; SMD 1.78, 95% CI 1.07-2.49, p < 0.00001), and sample entropy (SMD 1.17, 95% CI 0.36-1.97, p = 0.005) in diseased individuals.

CONCLUSION

This rigorous systematic analysis revealed that RT has no or minimal effects on cardiac autonomic control of healthy individuals, but RT leads to improvement in cardiac autonomic control of diseased individuals.

Combined LRRK2 mutation, aging and chronic low dose oral rotenone as a model of Parkinson's disease

Aging, genetics and environmental toxicity are important etiological factors in Parkinson’s disease (PD). However, its pathogenesis remains unclear. A major obstacle is the lack of an appropriate experimental model which incorporates genetic susceptibility, aging and prolonged environmental toxicity. Here, we explored the interplay amongst these factors using mutant LRRK2^R1441G (leucine-rich-repeat-kinase-2) knockin mice. We found that mutant primary cortical and mesencephalic dopaminergic neurons were more susceptible to rotenone-induced ATP deficiency and cell death. Compared with wild-type controls, striatal synaptosomes isolated from young mutant mice exhibited significantly lower dopamine uptake after rotenone toxicity, due to reduced striatal synaptosomal mitochondria and synaptic vesicular proton pump protein (V-ATPase H) levels. Mutant mice developed greater locomotor deficits in open-field tests than wild-type mice following low oral rotenone doses given twice weekly over 50 weeks (half their lifespan). The increased locomotor deficit was associated with specific reduction in striatal mitochondrial Complex-I (NDUFS4) in rotenone-treated mutant but not in similarly treated wild-type mice. Our unique experimental model which incorporates genetic effect, natural aging and prolonged oral environmental toxicity administered to mutant knockin LRRK2 mice over half their life span, with observable and measurable phenotype, is invaluable in further studies of the pathogenic process and therapeutics of PD.

Dysautonomia Differentially Influences the Effect of Affective Pain Perception on Quality of Life in Parkinson's Disease Patients

Background. Our aim was to evaluate the real effect of dysautonomic symptoms on the influence of affective pain perception on quality of life in PD patients. Methods. An observational cross-sectional study was carried out using 105 Parkinson's disease (PD) patients of the Movement Disorders Unit, Hospital de Cruces (Bilbao, Spain) [men 59 (56.2%), women 46 (43.85%)]. Statistical analysis was made in order to evaluate the possible association of pain with life quality. Results. Quality of life measured by PDQ-39 (Parkinson's Disease Questionnaire for quality of life) was statistically associated with affective dimension of pain (PRIA, affective pain rating index). However, the influence of this dimension on PDQ-39 was different in the specific case of PD patients that experimented a high score (>12) in SCOPA-AUT (Scale for Outcomes in PD-Autonomic scale). Conclusions. These results confirm the effect of affective perception of pain in life quality of PD patients, indicating the critical role of autonomic symptoms in the modulation of the influence of pain on quality of life and showing the possible utility of dysautonomia as clinical prognostic indicator of quality of life in PD patients affected by pain.

Changes in the sympathetic innervation of the gut in rotenone treated mice as possible early biomarker for Parkinson's disease

Introduction

Involvement of the peripheral nervous system (PNS) is relatively common in Parkinson’s disease (PD) patients. PNS alterations appear early in the course of the disease and are responsible for some of the non-motor symptoms observed in PD patients. In previous studies, we have shown that environmental toxins can trigger the disease by acting on the enteric nervous system.

Material and methods

Here, we analyzed the effect of mitochondrial Complex I inhibition on sympathetic neuritis in vivo and sympathetic neurons in vitro. Combining in vivo imaging and protein expression profiling.

Results

we found that rotenone, a widely used mitochondrial Complex I inhibitor decreases the density of sympathetic neurites innervating the gut in vivo, while in vitro, it induces the redistribution of intracellular alpha-synuclein and neurite degeneration. Interestingly, sympathetic neurons are much more resistant to rotenone exposure than mesencephalic dopaminergic neurons.

Conclusion

Altogether, these results suggest that enteric sympathetic denervation could be an initial pre-motor alteration in PD progression that could be used as an early biomarker of the disease.

Electronic supplementary material

The online version of this article (doi:10.1007/s10286-016-0358-6) contains supplementary material, which is available to authorized users.

Oral biomarkers in exercise-induced neuroplasticity in Parkinson's disease

In this article, we review candidate biomarkers for Parkinson's disease (PD) in oral cavity, potential of oral biomarkers as markers of neuroplasticity, and literature on the effects of exercise on oral cavity biomarkers in PD. We first describe how pathophysiological pathways of PD may be transduced from brain stem and ganglia to oral cavity through the autonomic nervous system or transduced by a reverse path. Next we describe the effects of exercise in PD and potential impact on oral cavity. We propose that biomarkers in oral cavity may be useful targets for describing exercise-induced brain neuroplasticity in PD. Nevertheless, much research remains to be carried out before applying these biomarkers for the determination of disease state and therapeutic response to develop strategies to mitigate motor or non-motor symptoms in PD.

Aging and computational systems biology

Aging research is undergoing a paradigm shift, which has led to new and innovative methods of exploring this complex phenomenon. The systems biology approach endeavors to understand biological systems in a holistic manner, by taking account of intrinsic interactions, while also attempting to account for the impact of external inputs, such as diet. A key technique employed in systems biology is computational modeling, which involves mathematically describing and simulating the dynamics of biological systems. Although a large number of computational models have been developed in recent years, these models have focused on various discrete components of the aging process, and to date no model has succeeded in completely representing the full scope of aging. Combining existing models or developing new models may help to address this need and in so doing could help achieve an improved understanding of the intrinsic mechanisms which underpin aging.

Constipation is reduced by beta-blockers and increased by dopaminergic medications in Parkinson's disease

BACKGROUND

Constipation is one of most frequent non-motor symptoms of Parkinson's disease (PD) and it may precede the clinical diagnosis of PD by years, with negative effects on quality of life. In contrast to motor features, levodopa is ineffective and possibly detrimental on constipation. Treatment of constipation in PD is non-specific and frequently unsuccessful. Stemming from a clinical observation of unexpected relief of bothersome constipation, abdominal bloating and pain after treatment with the beta-blocker carvedilol in one patient, we have evaluated the association between the use of beta-blockers and the presence of constipation in a large, unselected PD cohort.

METHODS

Retrospective review of the medical records of every patient with a diagnosis of PD seen in the Movement Disorders clinic at Cedars-Sinai Medical Center from October 2010 to April 2014.

RESULTS

341 medical records with a primary diagnosis of PD were reviewed, 336 of which contained information about constipation. Overall, 205/336 patients (61%) reported constipation. Among the 66 subjects treated with beta-blockers at the time of the encounter of record, only 28 (42.4%) reported constipation. By comparison, among the 270 subjects not treated with beta-blockers, 177 (65.5%) had constipation (χ(2) test p value = 0.001). Multivariate logistic analysis showed an odds ratio (OR) of 0.293 for beta-blockers (95% C.I. 0.161-0.535, p = 0.0001), 2.287 for levodopa (95% C.I. 1.271-4.117, p = 0.006) and 1.805 for dopamine agonists (95% C.I. 1.039-3.136, p = 0.036).

CONCLUSIONS

Beta-blockers are associated with a lower risk of constipation, while dopaminergic treatments appear to increase risk of constipation.

An activated sympathetic nervous system affects white adipocyte differentiation and lipolysis in a rat model of Parkinson's disease

Weight loss is an important nonmotor symptom associated with Parkinson's disease (PD). However, the cellular factors responsible for PD-induced weight loss remain unclear. Because the sympathetic nervous system plays an important role in lipid metabolism and fat cell differentiation, this study investigates whether PD-induced changes to this system are associated with weight loss in a rat model of PD. Body weight and food intake were measured in control and PD-model rats. After 10 weeks, retroperitoneal white adipose tissues (RWAT) were removed and weighed. Markers of the sympathetic nervous system were measured in the brainstem dorsal medulla and RWAT. Free fat acids (FFA), triglycerides (TG), adipocyte differentiation-related genes, and lipolysis-related molecules in the RWAT and serum were analyzed. Differences in body weight and food intake were insignificant in PD-model rats and control rats; however, relative RWAT weight and adipocyte surface area were significantly reduced in the PD group. Changes in markers of the sympathetic nervous system were observed in the brainstem dorsal medulla and RWAT of PD rats. Decreased mRNA expression levels of genes involved in adipocyte differentiation, decreased TG levels in RWAT, increased FFA in RWAT, and increased lipolysis-related molecules in RWAT and serum FFA were observed in PD rats. This study demonstrates that degenerated dopaminergic neurons in the nigrostriatal system correlate with increases in sympathetic nervous system function, resulting in lipolysis and inhibition of fat cell differentiation. These factors ultimately result in the decrease of RWAT in PD-model rats.

New perspectives in the diagnosis and management of enteric neuropathies

Chronic disturbances of gastrointestinal function encompass a wide spectrum of clinical disorders that range from common conditions with mild-to-moderate symptoms to rare diseases characterized by a severe impairment of digestive function, including chronic pain, vomiting, bloating and severe constipation. Patients at the clinically severe end of the spectrum can have profound changes in gut transit and motility. In a subset of these patients, histopathological analyses have revealed abnormalities of the gut innervation, including the enteric nervous system, termed enteric neuropathies. This Review discusses advances in the diagnosis and management of the main clinical entities--achalasia, gastroparesis, intestinal pseudo-obstruction and chronic constipation--that result from enteric neuropathies, including both primary and secondary forms. We focus on the various evident neuropathologies (degenerative and inflammatory) of these disorders and, where possible, present the specific implications of histological diagnosis to contemporary treatment. This knowledge could enable the future development of novel targeted therapeutic approaches.

Enteric alpha-synuclein expression is increased in Parkinson's disease but not Alzheimer's disease

BACKGROUND AND OBJECTIVE

Alpha-synuclein (α-Syn) is immunohistochemically detectable in enteric neurons in some subjects. We determined its age distribution in the general autopsy population and in an age-matched subset investigated differences with Parkinson's (PD) and Alzheimer's diseases (AD).

METHODS

Archival autopsy samples of colon from 95 cases (77 general population, 10 PD, and 8 AD) were immunostained with monoclonal antibody KM51. α-Syn detectability was semiquantitatively graded 1 to 3.

RESULTS

α-Syn was detectable in 52% of the general population, and its level of expression did not change between ages 40 and 91. All PD subjects were α-Syn positive, with higher prevalence (P = 0.001) and grade (P = 0.003) than age-matched controls. AD subjects were no more likely to be α-Syn positive or have a higher grade than controls.

CONCLUSIONS

Either PD develops selectively in the enterically α-Syn-positive population subset or PD induces this expression. Absence of increased α-Syn expression in AD points to differences in pathogenesis.