Neurodegeneration, parkinsonian syndromes and autonomic failure

Multiple System Atrophy: Many Lessons from the Transcriptome

Multiple system atrophy (MSA) is a complex, multifactorial, debilitating neurodegenerative disease that is often misdiagnosed and misunderstood. MSA has two subclasses, MSA-P and MSA-C, defined by the dominance of parkinsonism or cerebellar dysfunction in the earlier stages of disease, coupled with dysautonomia. This distinction between subclasses becomes largely redundant as the disease progresses. Aggregation of α-synuclein is a clinical marker used to confirm MSA diagnoses, which can only be performed postmortem. Transcriptome profiling provides in-depth information about the diseased state and can contribute to further understanding of MSA, enabling easier and more rapid diagnosis as well as contributing to improving the quality of life of people with MSA. Currently, there is no method of diagnosing MSA with certainty, and there is no cure for this disease. This review provides an update on current advances in investigations of molecular pathology of MSA with particular focus on perturbation of individual gene expression and MSA transcriptome.

The protein Ocular albinism 1 is the orphan GPCR GPR143 and mediates depressor and bradycardic responses to DOPA in the nucleus tractus solitarii

BACKGROUND AND PURPOSE

L-DOPA is generally considered to alleviate the symptoms of Parkinson's disease by its conversion to dopamine. We have proposed that DOPA is itself a neurotransmitter in the CNS. However, specific receptors for DOPA have not been identified. Recently, the gene product of ocular albinism 1 (OA1) was found to exhibit DOPA-binding activity. Here, we have investigated whether OA1 is a functional receptor of DOPA in the nucleus tractus solitarii (NTS).

EXPERIMENTAL APPROACH

We examined immunohistochemical expression of OA1 in the NTS, and the effects of DOPA microinjected into the depressor sites of NTS on blood pressure and heart rate in anaesthetized rats, with or without prior knock-down of OA1 in the NTS, using shRNA against OA1.

KEY RESULTS

Using a specific OA1 antibody, OA1-positive cells and nerve fibres were found in the depressor sites of the NTS. OA1 expression in the NTS was markedly suppressed by microinjection into the NTS of adenovirus vectors carrying the relevant shRNA sequences against OA1. In animals treated with OA1 shRNA, depressor and bradycardic responses to DOPA, but not those to glutamate, microinjected into the NTS were blocked. Bilateral injections into the NTS of DOPA cyclohexyl ester, a competitive antagonist against OA1, suppressed phenylephrine-induced bradycardic responses without affecting blood pressure responses.

CONCLUSION AND IMPLICATIONS

OA1 acted as a functional receptor for DOPA in the NTS, mediating depressor and bradycardic responses. Our results add to the evidence for a central neurotransmitter role for DOPA, without conversion to dopamine.

Bladder dysfunction in Parkinsonism: Mechanisms, prevalence, symptoms, and management

The advent of functional imaging methods has increased our understanding of the neural control of the bladder. This review examines current concepts of the role of brain function in urinary control with particular emphasis on the putative role of dopamine receptors. Dopaminergic mechanisms play a profound role in normal bladder control and the dysfunction of these may result in symptoms of overactive bladder in Parkinsonism. The importance of this nonmotor disorder has been overlooked. We address the problem of bladder dysfunction as it presents to patients and their neurologist. The prevalence of bladder symptoms in Parkinson's disease is high; the most common complaint is nocturia followed by frequency and urgency. In multiple-system atrophy, the combination of urge and urge incontinence and poor emptying may result in a complex combination of complaints. The management of bladder dysfunction in Parkinsonism addresses treatment of overactive detrusor as well as incontinence.

Determinants of autonomic dysfunction in idiopathic Parkinson’s disease

OBJECTIVES

To determine demographic or disease-related factors that may influence the severity of autonomic dysfunction in idiopathic Parkinson's disease (IPD).

METHODS

532 patients with IPD aged between 55 and 75 years were included. Severity of autonomic dysfunction was assessed using a 9-item autonomic dysfunction score (ADS). In addition, several demographic factors (e. g. age, gender, comorbidities) and disease- related (e. g. motor stage, disease duration, antiparkinsonian therapy) factors were recorded. A group of 67 age-matched healthy volunteers served as a control group. Demographic and clinical data of this cross-sectional survey were analyzed by a logistic stepwise regression model to determine independent predictors of autonomic dysfunction.

RESULTS

IPD patients showed significantly higher ADS values than controls, even in the youngest age groups and in mild disease stages. Hoehn & Yahr (H&Y) stage, disease duration, age at onset and various therapy combinations all showed significant correlations with ADS. However, stepwise logistic regression revealed that age (OR 10.71; CI 7.17-16.0) and arterial hypertension (OR 3.05; CI 1.66-5.58) were the only independent risk factors associated with autonomic dysfunction. Linear regression indicated that ADS increases with age in controls as well as in patients, but with a significantly steeper slope in the latter.

CONCLUSIONS

Autonomic dysfunction as an inherent feature of IPD is present already in early disease stages. According to a logistic regression model, the severity of autonomic dysfunction in IPD is primarily related to demographic but not to disease-related factors. This and the differences in predictors for motor versus autonomic decline may indicate at least partly independent neurodegenerative processes.

Pain processing in dementia and its relation to neuropathology

Most clinical studies of pain in dementia have focused on assessment procedures that are sensitive to pain in "demented" or "cognitively impaired" elderly patients. The neuropathology of dementia has not played a major part in pain assessment. In this review, the neuropathological effects of dementia on the medial and the lateral pain systems are discussed. We focus on Alzheimer's disease (AD), vascular dementia, and frontotemporal dementia. Lewy-body disease and Creutzfeldt-Jakob disease are briefly reviewed. The results of the studies reviewed show that, although the subtypes of dementia show common neuropathological features (such as atrophy and white-matter lesions), the degree by which they occur and affect pain-related areas determine the pattern of changes in pain experience. More specifically, in AD and even more so in frontotemporal dementia, a decrease in the motivational and affective components of pain is generally present whereas vascular dementia might be characterised by an increase in affective pain experience. Future studies should combine data from experimental pain studies and neuropathological information for pain assessment in dementia.