Imaging Cognitive Impairment and Impulse Control Disorders in Parkinson's Disease

Dementia and mild forms of cognitive impairment as well as neuropsychiatric symptoms (i. e., impulse control disorders) are frequent and disabling non-motor symptoms of Parkinson's disease (PD). The identification of changes in neuroimaging studies for the early diagnosis and monitoring of the cognitive and neuropsychiatric symptoms associated with Parkinson's disease, as well as their pathophysiological understanding, are critical for the development of an optimal therapeutic approach. In the current literature review, we present an update on the latest structural and functional neuroimaging findings, including high magnetic field resonance and radionuclide imaging, assessing cognitive dysfunction and impulse control disorders in PD

Increased Impulsivity following progressive nigral degenereation and chronic pramipexole treatment in an animal model of Parkinson's disease

Dopamine agonists (DA) that are widely used to treat motor deficits in patients with Parkinson’s disease (PD) are frequently associated with the development of abnormal-impulsive behaviors (AIB). The pathophysiology of AIB is poorly understood and there is a need for reliable animal models. We have analyzed the behavior of parkinsonian (injection of adeno-associated viral vectors (AAV) encoding for A53T mutated hα-syn in the substantia nigra compacta) and control (AAV- GFP expression) rats under chronic treatment with the D2/D3 receptor DA pramipexole (PPX) during 4 weeks, in OFF and ON medication states, using the 5-Choice Serial Reaction Time-Task (5-CSRTT). Before PPX treatment, the dopaminergic lesion increased the premature responses rate (waiting impulsivity) that was further increased with PPX during the 4 weeks of treatment in ON medication state and that was significantly higher than in control rats. A similar pattern of changes was observed in the variables related to attention (reduced accuracy in the responses and increased omissions). Premature response rate before and after treatment (both in ON and OFF medication) were correlated. In turn, premature responses before treatment and in OFF correlated with the striatal dopaminergic depletion (Dopamine transporter (DAT) immunochemistry). No significant changes were observed in OFF medication state in premature responses rate respect to the pretreatment state. The striatal expression of FosB/ΔFosB inversely correlated with the DAT expression and was higher in the lateral region of both striata and in the shell and core of the nucleus accumbens in parkinsonian than in control rats. In conclusion, these results indicate that the dopaminergic lesion is a risk factor to develop abnormal impulsive behaviors in PD under DA treatment and that this model could be a valid tool to investigate the pathophysiology of AIB in PD (DFG11/019, PI11/02109).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Different susceptibility to pramipexole-induced impulsivity in a rat model of parkinson’s disease

Impulse Control Disorders (ICD) in patients with Parkinson’s disease are abnormal behaviors caused by long-term use of dopamine agonists, which pathophysiology is poorly understood. Using parkinsonian rats (adeno-associated viral vectors-mediated overexpression of A53T human α-synuclein in the substantia nigra compacta), we evaluated the impulsive behaviour under acute (0.25 and 3 mg/kg) and chronic (0.25 mg/kg for 4 weeks) administration of pramipexole (PPX) with the Variable Delay-to-Signal (VDS) task (motor and choice impulsivities). Changes in striatal D1 and D2 receptors expression were also analysed. Before treatment, the striatal dopaminergic depletion caused a significant increase of both impulsivity domains with respect to basal condition. In lesioned rats, acutely given PPX 0.25 mg/kg dose increased choice impulsivity only with regard to basal values. Meanwhile, 3 mg/kg PPX increased choice impulsivity compared to their own values at different conditions: basal, before treatment and after acute 0.25 mg/kg PPX administration. After chronic administration, two populations of lesioned animals were distinguished, one showing the same behaviour as control animals and other displaying an increased motor/response (first week of treatment) and cognitive/choice impulsivities (third week of treatment) compared to control animals. This impulsive behaviour disappeared when animals were tested in OFF state. Lower D2 expression in both Caudate-Putamen and Nucleus Accubens and lower D1 levels in Nucleus Accumbens in lesioned rats than in control animals were observed. Therefore, our results indicate that the pro-impulsive effect of PPX in this animal model of PD depends on the dose and administration paradigm employed and the individual predisposition, and it is associated to striatal dopamine receptors expression changes, especially in Nucleus Accumbens. Thus, this model could constitute a valid tool to investigate the pathophysiology of ICD.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. DFG11/019, PI11/0210

Striatal synaptic bioenergetic and autophagic decline in premotor experimental parkinsonism

Synaptic impairment might precede neuronal degeneration in Parkinson’s disease. However, the intimate mechanisms altering synaptic function by the accumulation of presynaptic α-synuclein in striatal dopaminergic terminals before dopaminergic death occurs, have not been elucidated. Our aim is to unravel the sequence of synaptic functional and structural changes preceding symptomatic dopaminergic cell death. As such, we evaluated the temporal sequence of functional and structural changes at striatal synapses before parkinsonian motor features appear in a rat model of progressive dopaminergic death induced by overexpression of the human mutated A53T α-synuclein in the substantia nigra pars compacta, a protein transported to these synapses. Sequential window acquisition of all theoretical mass spectra proteomics identified deregulated proteins involved first in energy metabolism and later, in vesicle cycling and autophagy. After protein deregulation and when α-synuclein accumulated at striatal synapses, alterations to mitochondrial bioenergetics were observed using a Seahorse XF96 analyser. Sustained dysfunctional mitochondrial bioenergetics was followed by a decrease in the number of dopaminergic terminals, morphological and ultrastructural alterations, and an abnormal accumulation of autophagic/endocytic vesicles inside the remaining dopaminergic fibres was evident by electron microscopy. The total mitochondrial population remained unchanged whereas the number of ultrastructurally damaged mitochondria increases as the pathological process evolved. We also observed ultrastructural signs of plasticity within glutamatergic synapses before the expression of motor abnormalities, such as a reduction in axospinous synapses and an increase in perforated postsynaptic densities. Overall, we found that a synaptic energetic failure and accumulation of dysfunctional organelles occur sequentially at the dopaminergic terminals as the earliest events preceding structural changes and cell death. We also identify key proteins involved in these earliest functional abnormalities that may be modulated and serve as therapeutic targets to counterbalance the degeneration of dopaminergic cells to delay or prevent the development of Parkinson’s disease.This study was funded by the Instituto de Salud Carlos III through the projects PI14/00763 and PI19/01915 (co-funded by ERDF/ESF, ‘Investing in your future’). L.M.-G. held a Predoctoral Research Fellowship from the University of the Basque Country (UPV/EHU). T.R.-C. and A.Q.-V. were funded by CIBERNED. T.R.-C. held a Fundación Jesús de Gangoiti Barrera Foundation grant (Bilbao, Spain). H.J.-U. and A.B.-I. held a Predoctoral Research Fellowship from the Government of the Basque Country. Israel Science Foundation (536/19) and the Spanish Ministry of Science (SAF2016-78071-R) funded the contribution of S.K. and A.O

Lewy Body Dementias: A Coin with Two Sides?

Lewy body dementias (LBDs) consist of dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD), which are clinically similar syndromes that share neuropathological findings with widespread cortical Lewy body deposition, often with a variable degree of concomitant Alzheimer pathology. The objective of this article is to provide an overview of the neuropathological and clinical features, current diagnostic criteria, biomarkers, and management of LBD. Literature research was performed using the PubMed database, and the most pertinent articles were read and are discussed in this paper. The diagnostic criteria for DLB have recently been updated, with the addition of indicative and supportive biomarker information. The time interval of dementia onset relative to parkinsonism remains the major distinction between DLB and PDD, underpinning controversy about whether they are the same illness in a different spectrum of the disease or two separate neurodegenerative disorders. The treatment for LBD is only symptomatic, but the expected progression and prognosis differ between the two entities. Diagnosis in prodromal stages should be of the utmost importance, because implementing early treatment might change the course of the illness if disease-modifying therapies are developed in the future. Thus, the identification of novel biomarkers constitutes an area of active research, with a special focus on α-synuclein markers

Using Kinect to classify Parkinson’s disease stages related to severity of gait impairment

Abstract Background Parkinson’s Disease (PD) is a chronic neurodegenerative disease associated with motor problems such as gait impairment. Different systems based on 3D cameras, accelerometers or gyroscopes have been used in related works in order to study gait disturbances in PD. Kinect Ⓡ has also been used to build these kinds of systems, but contradictory results have been reported: some works conclude that Kinect does not provide an accurate method of measuring gait kinematics variables, but others, on the contrary, report good accuracy results. Methods In this work, we have built a Kinect-based system that can distinguish between different PD stages, and have performed a clinical study with 30 patients suffering from PD belonging to three groups: early PD patients without axial impairment, more evolved PD patients with higher gait impairment but without Freezing of Gait (FoG), and patients with advanced PD and FoG. Those patients were recorded by two Kinect devices when they were walking in a hospital corridor. The datasets obtained from the Kinect were preprocessed, 115 features identified, some methods were applied to select the relevant features (correlation based feature selection, information gain, and consistency subset evaluation), and different classification methods (decision trees, Bayesian networks, neural networks and K-nearest neighbours classifiers) were evaluated with the goal of finding the most accurate method for PD stage classification. Results The classifier that provided the best results is a particular case of a Bayesian Network classifier (similar to a Naïve Bayesian classifier) built from a set of 7 relevant features selected by the correlation-based on feature selection method. The accuracy obtained for that classifier using 10-fold cross validation is 93.40%. The relevant features are related to left shin angles, left humerus angles, frontal and lateral bents, left forearm angles and the number of steps during spin. Conclusions In this paper, it is shown that using Kinect is adequate to build a inexpensive and comfortable system that classifies PD into three different stages related to FoG. Compared to the results of previous works, the obtained accuracy (93.40%) can be considered high. The relevant features for the classifier are: a) movement and position of the left arm, b) trunk position for slightly displaced walking sequences, and c) left shin angle, for straight walking sequences. However, we have obtained a better accuracy (96.23%) for a classifier that only uses features extracted from slightly displaced walking steps and spin walking steps. Finally, the obtained set of relevant features may lead to new rehabilitation therapies for PD patients with gait problems

Hippocampal synaptic failure is an early event in experimental parkinsonism with subtle cognitive deficit

Learning and memory mainly rely on correct synaptic function in the hippocampus and other brain regions. In Parkinson's disease, subtle cognitive deficits may even precede motor signs early in the disease. Hence, we set out to unravel the earliest hippocampal synaptic alterations associated with human α-synuclein overexpression prior to and soon after the appearance of cognitive deficits in a parkinsonism model. We bilaterally injected adeno-associated viral vectors encoding A53T-mutated human α-synuclein into the substantia nigra of rats, and evaluated them 1, 2, 4 and 16 weeks post-inoculation by immunohistochemistry and immunofluorescence to study degeneration and distribution of α-synuclein in the midbrain and hippocampus. The object location test was used to evaluate hippocampal-dependent memory. Sequential window acquisition of all theoretical mass spectrometry-based proteomics and fluorescence analysis of single-synapse long-term potentiation were used to study alterations to protein composition and plasticity in isolated hippocampal synapses. The effect of L-DOPA and pramipexole on long-term potentiation was also tested. Human α-synuclein was found within dopaminergic and glutamatergic neurons of the ventral tegmental area, and in dopaminergic, glutamatergic and GABAergic axon terminals in the hippocampus from 1 week post-inoculation, concomitant with mild dopaminergic degeneration in the ventral tegmental area. In the hippocampus, differential expression of proteins involved in synaptic vesicle cycling, neurotransmitter release and receptor trafficking, together with impaired long-term potentiation were the first events observed (1 week post-inoculation), preceding cognitive deficits (4 weeks post-inoculation). Later on, at 16 weeks post-inoculation, there was a deregulation of proteins involved in synaptic function, particularly those involved in the regulation of membrane potential, ion balance and receptor signalling. Hippocampal long-term potentiation was impaired before and soon after the onset of cognitive deficits, at 1 and 4 weeks post-inoculation, respectively. L-DOPA recovered hippocampal long-term potentiation more efficiently at 4 weeks post-inoculation than pramipexole, which partially rescued it at both time points. Overall, we found impaired synaptic plasticity and proteome dysregulation at hippocampal terminals to be the first events that contribute to the development of cognitive deficits in experimental parkinsonism. Our results not only point to dopaminergic but also to glutamatergic and GABAergic dysfunction, highlighting the relevance of the three neurotransmitter systems in the ventral tegmental area-hippocampus interaction from the earliest stages of parkinsonism. The proteins identified in the current work may constitute potential biomarkers of early synaptic damage in the hippocampus and hence, therapies targeting these could potentially restore early synaptic malfunction and consequently, cognitive deficits in Parkinson's disease