La maladie de Parkinson (MP) est caractérisée par une dégénérescence des neurones dopaminergiques de la substance noire. Elle est le plus souvent sporadique mais des formes familiales monogéniques existent, notamment dues à des mutations de PARK2 et de PINK1. Ces gènes codent pour l'ubiquitine-protéine ligase cytosolique Parkine et la sérine/thréonine kinase mitochondriale PINK1, deux acteurs majeurs du contrôle de qualité mitochondrial. Ce travail étudie le rôle de leur interaction au niveau de la membrane mitochondriale externe dans la régulation de l'homéostasie mitochondriale.Nous avons montré que l'association de PINK1 et Parkine au complexe d'import mitochondrial TOM lors d'un stress mitochondrial permet l'import de la grande majorité des protéines adressées à la mitochondrie ; que déstabiliser ce complexe suffit à initier la mitophagie ; et que l'activation de Parkine par PINK1 facilite l'import de son substrat HSD17?10. Nous avons développé un biosenseur moléculaire inductible, permettant d'étudier la voie d'import classique des protéines à pré-séquence. Nous avons également montré, dans un modèle neuronal, qu'un stress mitochondrial, en présence de Parkine, induit une forte augmentation de l'expression de gènes clés de la biogenèse mitochondriale ; et que ces gènes sont up-régulés de façon basale dans les neurones PARK2-/-, indiquant une possible altération de la réponse aigüe au stress.Ces résultats approfondissent notre connaissance de la physiopathologie des formes autosomiques récessives de MP en soulignant l'importance de la voie PINK1/Parkine dans l'import et la biogenèse mitochondriaux. / Parkinson’s disease (PD) is linked to a specific loss of dopaminergic neurons of the substancia nigra. The disease is most often sporadic but familial monogenic forms exist, for example due to mutations in PARK2 or PINK1. Those genes encore the cytosolic ubiquitin-protein ligase Parkin and the mitochondrial serine/threonine kinase PINK1, both essential for mitochondrial quality control. This work studies the role of their interaction at the outer mitochondrial membrane in the regulation of mitochondrial homeostasis. We found that the association of PINK1 and Parkin to the mitochondrial import TOM complex during mitochondrial stress induces the import of most proteins targeted to mitochondria; that destabilizing this complex is sufficient to initiate mitophagy; and that Parkin activation by PINK1 facilitates the import of its substrate, HSD17β10. We developed an inducible BRET-based molecular biosensor to study the classical pre-sequence import pathway. We also found, in a neuronal model, that mitochondrial stress induced a strong increase in the expression of mitochondrial biogenesis key genes, in the presence of Parkin; and that these genes are basally up-regulated in PARK2-/- neurons, possibly reflecting an alteration of acute stress response. These results increase our understanding of the pathophysiology of autosomal recessive forms of PD, underlining the importance of the PINK1/Parkin pathway in mitochondrial import and biogenesis.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2017 / This study presents the development of a potentially new biomarker for three different movement disorders: Huntington’s Disease (HD), Parkinson’s Disease (PD) and Essential Tremors (ET). A Leap Motion® gaming device was used to record the trajectories of subjects’ forefinger as they trace simple patterns in the air. The patterns used were stepfunction, triangle and circle. The recorded signals were analysed using transform functions and Fourier analysis. Both analysis types yielded features from which differences between the four categories studied: PD, HD, ET and control subjects, were sought and displayed in both graphical and numerical forms. The X-axis and Y-axis of the signals were separately analysed and yielded different results. For the step-function pattern, no distinct differences between the four categories were found from the transfer function analysis whereas the Y-axis of the signal could distinguish between the categories. For the triangle pattern, the X-axis features provided a discrimination between the categories while the Y-axis feature did not. For the circle pattern, neither X-axis nor Y-axis features were able to distinguish between the categories. A Fourier analysis showed a better discrimination ability for both X- and Y- axis. This study is a preliminary one and all results indicate that more subjects of all categories are needed to develop a bio-marker for the diseases studied and that a higher order transfer function analysis is required. However, the methodology outlined in this work, comprising of both the experimental system and the analysis showed a potential to produce a biomarker for movement disorders. / MT2018

abstract: Parkinson’s disease (PD) is a neurological disorder with complicated and disabling motor and non-motor symptoms. The pathology for PD is difficult and expensive. Furthermore, it depends on patient diaries and the neurologist’s subjective assessment of clinical scales. Objective, accurate, and continuous patient monitoring have become possible with the advancement in mobile and portable equipment. Consequently, a significant amount of work has been done to explore new cost-effective and subjective assessment methods or PD symptoms. For example, smart technologies, such as wearable sensors and optical motion capturing systems, have been used to analyze the symptoms of a PD patient to assess their disease progression and even to detect signs in their nascent stage for early diagnosis of PD. This review focuses on the use of modern equipment for PD applications that were developed in the last decade. Four significant fields of research were identified: Assistance diagnosis, Prognosis or Monitoring of Symptoms and their Severity, Predicting Response to Treatment, and Assistance to Therapy or Rehabilitation. This study reviews the papers published between January 2008 and December 2018 in the following four databases: Pubmed Central, Science Direct, IEEE Xplore and MDPI. After removing unrelated articles, ones published in languages other than English, duplicate entries and other articles that did not fulfill the selection criteria, 778 papers were manually investigated and included in this review. A general overview of PD applications, devices used and aspects monitored for PD management is provided in this systematic review. / Dissertation/Thesis / Masters Thesis Computer Engineering 2019

Parkinson's disease (PD) is a slow-progressive neurodegenerative disorder affecting 5-6 million people around the globe. The disease is manifested by the rapid deterioration of dopaminergic cells in the substantia nigra portion of the brain; however, the pathological mechanism of selective dopaminergic neuronal death is unknown. A reduction in levels of 3,4-dihydroxyphenylacetaldehyde (DOPAL) is biologically critical as this aldehyde has been shown to be toxic to dopaminergic cells and is a highly reactive electrophile. Investigating neuronal protein targets is essential in determining the cause of toxicity. An essential protein-GAPDH (e.g., glyceraldehyde-3-phosphate dehydrogenase) is an abundantly expressed enzyme known for its glycolytic activity, and recent research has implicated its role in oxidative stress-mediated neuronal death. This work positively shows GAPDH as a target for DOPAL modification, and, for the first time, DOPAL is identified as a potent inhibitor for GAPDH enzymatic activity. LC-MS and other chemical probes (ie. thiol and amine modifiers) show that DOPAL modifies specific –Lys, -Arg, and –Cys residues in the cofactor binding-domain of GAPDH. The enzyme inhibition is also time and DOPAL dose-dependent. DOPAL has a unique structure, containing two reactive functional groups: an aldehyde and catechol ring. In-house syntheses of DOPAL analogues, containing the catechol group and lacking the aldehyde, and vice versa have been tested on GAPDH and do not inhibit or modify GAPDH. Therefore, both the catechol and aldehyde groups of DOPAL are specific to binding with GAPDH and are necessary to achieve modification and enzyme inhibition. In addition to finding a novel enzyme inhibited and modified by DOPAL, this work has also confirmed linking DOPAL levels to a fungicide associated with PD risk. This benzimidazole fungicide, benomyl was shown to inhibit ALDH2 in the SH-SY5Y neuroblastoma cell line via an increase in DOPAL and a decrease in DOPAC. The ratios of DOPAL and DOPAC, the product of ALDH, were measured by HPLC-ECD, and found that benomyl does inhibit ALDH2 in this dopaminergic cell model. The cytotoxicity of benomyl, DA, DOPAL and the combination of DA or DOPAL with benomyl was assessed by MTT assay. Surprisingly, the only toxic combination was the combination of DA or DOPAL with benomyl. In fact, this toxicity appears to be synergistic, as none of the single treatments are significantly toxic to the cells. This synergistic effect also affects GAPDH aggregation. The cell morphology is also drastically different in the presence of the combined treatments, compared to individual treatment of DA, DOPAL or benomyl; cells start to ebb and show apoptotic-like features at just 2h. A second class of pesticides, named chlorpyrifos and chlorpyrifos-oxon were tested for toxicity in PC6-3These compounds were toxic to these cells due to DOPAL accumulation reaching high levels in the 100 µM range. Exposure to environmental toxins such as pesticides and fungicides has long been linked to PD risk, but only recently to DOPAL levels. This work provides a novel mechanism by which fungicide exposure may stimulate PD pathogenesis.

Parkinson's disease (PD) is a progressive neurodegenerative and movement disorder that involves specific loss of dopaminergic neurons in the substantia nigra of the brain. Exact causes of PD are unknown. However, cells affected in PD are centers of dopamine (DA) synthesis, storage, and metabolism, which implicate DA as an endogenous neurotoxin that contributes to PD. Furthermore, DA is known to undergo oxidation to radicals and quinones. These reactive species exert deleterious effects on cells through a variety of mechanisms that are relevant to the pathogenesis of PD. Another potential mechanism of toxicity for DA is metabolism to 3,4-dihydroxyphenylacetaldehyde (DOPAL). This reactive metabolite is significantly more toxic than the parent DA. DOPAL has several demonstrated mechanisms of toxicity, including formation of protein-adducts via reaction with amine-type cellular nucleophiles. However, known toxicity mechanisms do not fully account for DOPAL's high toxicity. Oxidation of DOPAL to a reactive quinone or radical could help explain its high toxicity. Therefore, the hypothesis of this work is that DOPAL is capable of undergoing oxidation that leads to increased protein modification and nucleophilic reactivity. Experimentally, oxidation of DOPAL results in formation of a semi-quinone radical and an ortho-quinone, as confirmed by electron paramagnetic resonance spectroscopy and nuclear magnetic resonance spectroscopy, respectively. In agreement with the stated hypothesis, oxidation of DOPAL enhanced its ability to induce protein cross-linking of a model protein (glyceraldehyde 3-phosphate dehydrogenase) as indicated by polyacrylamide gel-electrophoresis. Also, the presence of anti-oxidants (ascorbate, N-acetyl cysteine) attenuated the reactivity of DOPAL with the model aminenucleophile N-acetyl lysine. These results indicate that DOPAL oxidation enhances both protein cross-linking and nucleophilic reactivity. This work resulted in several other important findings. DOPAL is shown to undergo carbonyl-hydration in aqueous media, and spontaneous oxidation of DOPAL results in formation of superoxide. Furthermore, DOPAL is shown to be susceptible to oxidation by cyclooxygenase-2, an enzyme known to be involved in PD. This provides a potential mechanism for formation of the oxidized products identified here. As DA metabolism and oxidation occur in cells affected by PD, the experimental results demonstrated here are likely relevant for understanding the pathogenesis of PD.

Parkinson's disease (PD) is a prevalent neurodegenerative disorder for which the greatest risk factor is age. Four to five percent of 85-year-olds suffer from this debilitating disease, which is characterized by the selective loss of dopaminergic neurons within the substantia nigra and the presence of protein aggregates known as Lewy bodies. While the etiology of this disease is still unknown, recent research implicates oxidative stress, activated microglia, and reactive dopamine (DA) metabolites to play a role in the initiation or progression of the disease. Activated microglia cause injury to dopaminergic neurons via a host of mechanisms, including reactive oxygen species production, release of cytokines, and phagocytic activity. Microglial activation has been detected in the brains of PD patients, but the source of this activation has not been elucidated. Previous research has shown electrophiles and endogenous neurotoxins to play a role in this microglial activation. The interaction between the neurotoxic metabolite of DA, 3,4-dihydroxyphenylacetaldehyde (DOPAL), and microglia has not been explored. DOPAL is a highly reactive, bifunctional electrophile produced by oxidative deamination of DA by monoamine oxidase (MAO). DOPAL is oxidized in the major metabolism pathway to 3,4-dihydroxyphenylacetic acid (DOPAC) by aldehyde dehydrogenase (ALDH). DOPAL has previously been shown to be 100-fold more toxic than DA in vitro and in vivo. Potent inhibition of the rate-limiting enzyme in DA biosynthesis, tyrosine hydroxylase, by DOPAL has been well-established. DOPAL-mediated aggregation of Α-synuclein, the primary component of PD-hallmark Lewy bodies, has been suggested but was further explored in this work. Results presented in this body of work include further determination of the aggregation of Α-synuclein by DOPAL, including evidence of covalent modification. The interaction of DOPAL with BV-2 microglia, an immortalized cell line, was addressed in depth through exploration of DOPAL catabolism, toxicity, and generation of an activational response. Metabolism of DOPAL to DOPAC was altered in activated microglia, with the production of DOPAC reduced by ~40%. Metabolism of DOPAL to DOPAC was also inhibited by both 4-hydroxynonenal and malondialdehyde, gold standards of lipid peroxidation. Both of these compounds were found to be significantly toxic to BV-2 cells at concentrations well below those considered toxic to dopaminergic cells. Alternatively, DOPAL and DA were found to be non-toxic to this cell line, while DOPAL was shown to be significantly toxic to dopaminergic cells at concentrations as low as 10 ΜM. Significant activation of BV-2 microglia by DOPAL was observed at 10 ΜM and above by release of TNF-Α. Morphological changes, release of IL-6, and changes in expression of COX-2 also indicated activation by DOPAL but not DA or DOPAC. BV-2-conditioned media, generated by incubation with DA, DOPAL, or DOPAC, was added to MN9D cells, and toxicity was measured by the MTT assay. BV-2 conditioned media generated by DOPAL incubation produced the greatest toxicity for MN9D cells. These results implicate DOPAL in dopaminergic cell death through microglial activation.

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by a resting tremor combined with varying degrees of rigidity and bradykinesia. Introduced in the 1950s, thalamotomy is used as a surgical procedure to improve brain function in patients and serves as an effective treatment method for the PD tremor where connections within the thalamus are cut. In 1987, deep brain stimulation (DBS), chronic electrical stimulation of deep neural structures using electrodes, was introduced as a clinical treatment for medically refractory tremor in patients with PD. Though thalamotomy has historically been the primary treatment method for PD, an increasing number of patients have chosen to undergo DBS as it has become increasingly touted as an alternative to ablative therapies. The proposed study examines the advantages and disadvantages of both treatment methods to improve cardinal features in highly-skilled, career-oriented PD patients who actively use motor functions in their work. As an alternative to a simple finger-tapping test used for normal PD patients, a more complex strength-dexterity (S-D) test would be performed on 50 skilled patients to evaluate and compare the effectiveness of tremor suppression between both surgeries. The goal of this experiment is to determine which treatment produces the most short-term benefits for the patient to continue with his or her career with minimal future management required. The results of this study will help determine the preferred treatment method when taking into consideration other external factors such as cost, continual management, and preference for short-term vs. long-term results.

Mobility is essential for the independent lifestyle. However, as the US population ages, challenges to mobility start to arise, among them just the aging itself which leads to decreased postural stability, falls and the second most common neurodegenerative disease, that is Parkinson’s disease (PD). We decided to investigate step initiation as it is crucial to mobility: walking is not possible without the first step. Step initiation is impaired in PD. However, the impact of PD on the neural mechanisms of step initiation when some of the step parameters are unpredictable remains unexplored. Cortical preparation for step initiation can be assessed by beta event-related desynchronization (ERD) derived from electroencephalography (EEG) recordings. We hypothesized that subjects with PD would exhibit less cortical modulation between conditions of forward step initiation with and without prior knowledge of limb choice. Further, we hypothesized that decreased cortical modulation in PD would associate with a higher impairment of motor performance. Results identified that the group with PD exhibited decreased beta ERD amplitudes that were similar regardless of condition, whereas control subjects modulated beta ERD amplitudes between conditions, particularly in early stages of pre-movement processing in areas overlying sensory cortex. Subjects with PD presented with delayed and reduced postural preparation with increased step target error across both conditions and exhibited a greater incidence of multiple anticipatory postural adjustments (APAs) in the predictable relative to the unpredictable condition. Delayed postural preparation significantly correlated with lower amplitudes of beta ERD. We concluded that diminished early pre-movement processing over sensory cortex was concomitant with poor pre-selection of the stepping limb in predictable conditions and that a generally diminished amplitude of cortical pre-movement processing relates to delayed step initiation in people with PD. Furthermore, impaired mobility accompanies healthy aging, but there is a need for deeper understanding of how aging changes central control of motor behavior. Using previous study’s method, we compared cortical preparation for step initiation using beta ERD in young and older healthy subjects performing forward steps with and without prior knowledge of limb choice. Our results show that older subjects exhibited increased beta ERD amplitudes before the step regardless of whether they were informed of limb choice or not. Moreover, older subjects exhibited early increases in beta ERD in the “sensory” cluster of electrodes, but only when full limb-choice information was available. Behaviorally, the older subjects also exhibited shortened and increased anticipatory postural adjustments which led to earlier step initiation and similar swing-foot velocities but was also accompanied by greater target step placement errors and decreased postural stability. For the older group, condition-related increases in beta ERD amplitudes and stability correlated with condition-related prolongation of APA durations. We conclude that older subjects exhibited a spectrum across two strategies: (1) a “fast” strategy associated with decreased neural preparation that trades shortened step preparation and higher swing-foot velocity for target step errors and lowered postural stability; and (2) an “accurate” strategy associated with greater neural preparation, longer step-preparation time, and higher stability during step execution. In conclusion, this thesis provides more support for beta ERD as a useful tool for studying cortical preparation non-invasively. We have also established the importance of the signals recorded by “sensory” clusters: in subjects with PD the absence of beta ERD similar to the control group was associated with impaired motor behavior even when conditions were predictable. Similarly, a part of the older group seemed to pre-potentiate its cortex lying beneath the cluster of “sensory” electrodes which was associated with more safe and accurate steps. Further investigations should focus on the importance of sensorimotor integration and its’ changes due to PD or healthy aging and beta ERD may be an excellent tool for this task.

Neurological disorders require varying types and degrees of treatments depending on the symptoms and underlying causes of the disease. Patients suffering from medication-refractory symptoms often undergo further treatment in the form of brain stimulation, e.g. electroconvulsive therapy (ECT), transcranial direct current stimulation (tDCS), deep brain stimulation (DBS), or transcranial magnetic stimulation (TMS). These treatments are popular and have been shown to relieve various symptoms for patients with neurological conditions. However, the underlying effects of the stimulation, and subsequently the causes of symptom-relief, are not very well understood. In particular, TMS is a non-invasive brain stimulation therapy which uses time-varying magnetic fields to induce electric fields on the conductive parts of the brain. TMS has been FDA-approved for treatment of major depressive disorder for patients refractory to medication, as well as symptoms of migraine. Studies have shown that TMS has relieved severe depressive symptoms, although researchers believe that it is the deeper regions of the brain which are responsible for symptom relief. Many experts theorize that cortical stimulation such as TMS causes brain signals to propagate from the cortex to these deep brain regions, after which the synapses of the excited neurons are changed in such a way as to cause plasticity. It has also been widely observed that stimulation of the cortex causes signal firing at the deeper regions of the brain. However, the particular mechanisms behind TMS-caused signal propagation are unknown and understudied. Due to the non-invasive nature of TMS, this is an area in which investigation can be of significant benefit to the clinical community. We posit that a deeper understanding of this phenomenon may allow clinicians to explore the use of TMS for treatment of various other neurological symptoms and conditions. This thesis project seeks to investigate the various effects of TMS in the human brain, with respect to brain tissue stimulation as well as the cellular effects at the level of neurons. We present novel models of motor neuron circuitry and fiber tracts that will aid in the development of deep brain stimulation modalities using non-invasive treatment paradigms.

Parkinson’s Disease (PD) is a common progressive neurodegenerative disorder that leads to both physical and cognitive impairment over time. Eventually, these impairments may include the loss of autonomy, and the individual may require the assistance of an informal caregiver. Informal caregivers are critical in the care of individuals with PD and spend substantial time providing care, which may be associated with negative caregiver outcomes such as burden, mental health issues, as well as poor family dynamics. Although research in the United States and Europe has generally supported these relations, there is very limited research on PD caregiving in Latin America. Given the rapidly aging population of Latin America, research suggests that the prevalence of PD is likely to increase substantially. Although cultural values such as familism may encourage informal caregiving in Latin America, very little is known about either PD patient or caregiver experiences in the region and how they may differ from those in the United States and Europe. As such, the current study built upon Pearlin’s caregiving stress process model to examine how PD-related impairments, caregiver burden and mental health, and family dynamics may differ between the United States and Mexico and to examine connections among the following variables in a sample of PD caregivers from the United States and Mexico: (a) PD-related impairments (motor and non-motor symptoms) and caregiver burden, (b) caregiver burden and caregiver mental health, (c) PD-related impairments and mental health through caregiver burden, and (d) family dynamics which may moderate these relations. The current study consisted of caregivers of individuals with PD (total N = 253) from the United States (N = 105) and Mexico (N = 148). A series of t-tests and mediational models were conducted to determine the connections among PD-related impairments, caregiver burden and mental health, and family dynamics. Results suggested that caregivers from the United States site experienced higher levels of caregiver burden, although there were no significant differences in caregiver mental health. Further, caregiver burden fully mediated the relation between PD-related impairments and caregiver mental health at both study sites, although family dynamics did not moderate these mediational models as hypothesized. Despite the importance of cultural values such as familism in Latin America, family dynamics explained more variance in the model at the United States site than at the Mexico site. Exploratory analyses found that caregivers from the Mexico site more frequently reported suicidal and self-injurious thoughts but did not find a significant disparity in self-reported gender of the caregiver. Overall, the current study identified significant relations among PD-related impairments, caregiver burden and mental health, and family dynamics among caregivers of individuals with PD from the United States and Mexico. Findings from the current study highlight a number of important interventions for caregivers and families, including caregiver burden and mental health, as well as family dynamics.