<div><p>Parkinson’s disease (PD) is a devastating neurodegenerative disorder that affects 10 million people worldwide and is characterized by pronounced motor symptoms. Dementia with Lewy Bodies (DLB) involves both cognitive and motor deficits and affects ~1 million people in the United States. To date there is no cure for PD or DLB, and current treatments address only a subset of the symptoms that define these diseases. PD and DLB are ‘synucleinopathies’, defined as disorders involving the accumulation in patients’ brains of Lewy bodies. Lewy bodies are cellular inclusions that consist largely of aggregated species of alpha-synuclein (aSyn), a presynaptic protein that exists as both cytosolic and membrane-bound forms. Pathophysiological findings suggest that aggregated aSyn is involved in neurodegeneration in PD and DLB. However, mechanisms by which aSyn forms neurotoxic aggregates, and neurotoxic processes that distinguish different synucleinopathies such as PD and DLB, are poorly understood. To address these gaps, we have (i) designed a protocol to establish a primary cell culture model that can recapitulate key neuropathological features of PD, (ii) examined effects of expressing aSyn variants in a rat model of PD, and (iii) examined the expression profiles of neuroprotective genes in PD and DLB brain specimens.</p><p> </p><p>In the first part of my thesis, I describe the development of an optimized protocol to prepare primary midbrain and cortical cultures from rat embryonic brains for the study of PD and other synucleinopathies. The establishment of cellular models that simulate specific aspects of neuropathology can enable the characterization of molecular perturbations that lead to dopaminergic (DA) neuronal death. Our primary midbrain mixed culture model provides an outstanding opportunity to explore therapeutic strategies to rescue DA neurons from toxicity elicited by a range of PD-related insults. In addition, our primary cortical mixed cultures can be used to model cortical neuropathology in various CNS disorders including synucleinopathies.</p><p> </p><p>A number of mutations in the gene that codes for aSyn are associated with familial, early-onset forms of PD. A major goal of my thesis research is to characterize neurotoxic effects of a recently discovered familial substitution, A53E. This mutant was chosen based on the rationale that the introduction of a negatively charged residue at position 53 could potentially interfere with aSyn-membrane interactions and favor A53E aggregation, as we described for other familial aSyn mutants. For the first time, we have reproduced the neurotoxicity of A53E seen in human patients by expressing the mutant protein in rat midbrain. Rats injected unilaterally in the substantia nigra (SN) with rAAV encoding A53E and another familial mutant, A53T, but not rAAV encoding WT aSyn or a vector-control (‘stuffer’) virus, exhibited a significant motor impairment. Immunohistochemical analysis at 14 weeks after the viral injection revealed that brain sections from aSyn-expressing rats exhibit key features reminiscent of neuropathology in human PD, including nigral dopaminergic neuron loss (confirmed by unbiased stereology), striatal terminal depletion, and aSyn inclusion formation. In addition, it was determined that WT aSyn and the A53E and A53T mutants invaded the non-injected substantia nigra, implying that expressed aSyn protein can spread throughout the brain in the rat rAAV-aSyn model. These results yield insights into the molecular basis for the neurotoxicity of A53E and shed light on a potential role for membrane-induced aSyn aggregation in PD pathogenesis in vivo, thus setting the stage for developing therapies to slow neurodegeneration in the brains of familial and idiopathic PD patients. </p><p> </p><p>aSyn neurotoxicity varies with the expression of neuroprotective proteins, and misfolded aSyn affects cellular functions and gene expression. These observations suggest that differential gene expression patterns can inform us about similarities and differences in pathogenic mechanisms of different synucleinopathy disorders. A third phase of my thesis research was aimed at determining the expression levels of a panel of candidate neuroprotective genes in post-mortem brain samples from DLB and PD patients and age-matched controls (5 individuals in each group). mRNAs encoding the following proteins were quantified via qRT-PCR in homogenates prepared from the frontal cortex and the BA24 region encompassing the cingulate gyrus: DJ-1, a protein with antioxidant and chaperone activities; PGC1α, a master regulator of mitochondrial biogenesis and oxidative metabolism; MsrA, an antioxidant enzyme responsible for repairing oxidatively damaged proteins; and ATP13A2, a lysosomal protein involved in autophagy. In addition to yielding new insights into differential gene expression patterns in cortex versus cingulate gyrus, the data revealed differences in mRNA expression levels in DLB versus non-DLB cortical tissue. Although levels of all four neuroprotective mRNAs were increased (or showed a trend towards being increased) in DLB cortex, Western blot analysis revealed that only the DJ-1 and PGC1α proteins showed a trend towards being up-regulated, whereas levels of ATP13A2 and MsrA were unchanged. These findings suggest that there is a failure to induce cellular antioxidant responses and lysosomal autophagy at the protein level in DLB cortex, and in turn this failure could contribute to neuropathology. Interestingly, analysis of the same panel of neuroprotective genes in PD cortical samples did not show significant differences in mRNA or protein levels compared to control samples, suggesting that different neuroprotective mechanisms are induced in DLB versus PD cortex. These studies shed light on brain-region specific changes in gene expression associated with different synucleinopathy disorders, and they set the stage for developing new diagnostic tests and therapeutic strategies.</p></div><br>

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Alzheimer's disease (AD) and Parkinson's disease (PD), including dementia with Lewy bodies (DLB), account for the majority of dementia cases worldwide. Interestingly, a significant number of patients have clinical and neuropathological features of both AD and PD, i.e., the presence of amyloid deposits and Lewy bodies in the neocortex. The identification of α-synuclein peptides in amyloid plaques in DLB brain led to the hypothesis that both peptides mutually interact with each other to facilitate neurodegeneration. In this article, we report the influence of Aβ(1-42) and pGlu-Aβ(3-42) on the aggregation of α-synuclein in vitro. The aggregation of human recombinant α-synuclein was investigated using thioflavin-T fluorescence assay. Fibrils were investigated by means of antibody conjugated immunogold followed by transmission electron microscopy (TEM). Our data demonstrate a significantly increased aggregation propensity of α-synuclein in the presence of minor concentrations of Aβ(1-42) and pGlu-Aβ(3-42) for the first time, but without effect on toxicity on mouse primary neurons. The analysis of the composition of the fibrils by TEM combined with immunogold labeling of the peptides revealed an interaction of α-synuclein and Aβ in vitro, leading to an accelerated fibril formation. The analysis of kinetic data suggests that significantly enhanced nucleus formation accounts for this effect. Additionally, co-occurrence of α-synuclein and Aβ and pGlu-Aβ, respectively, under pathological conditions was confirmed in vivo by double immunofluorescent labelings in brains of aged transgenic mice with amyloid pathology. These observations imply a cross-talk of the amyloid peptides α-synuclein and Aβ species in neurodegeneration. Such effects might be responsible for the co-occurrence of Lewy bodies and plaques in many dementia cases.

In Parkinson's disease, aggregates of α-synuclein within Lewy bodies and Lewy neurites represent neuropathological hallmarks. However, the cellular and molecular mechanisms triggering oligomeric and fibrillary α-synuclein aggregation are not fully understood. Recent evidence indicates that oxidative stress induced by metal ions and post-translational modifications such as phosphorylation, ubiquitination, nitration, glycation, and SUMOylation affect α-synuclein conformation along with its aggregation propensity and neurotoxic profiles. In addition, proteolytic cleavage of α-synuclein by specific proteases results in the formation of a broad spectrum of fragments with consecutively altered and not fully understood physiological and/or pathological properties. In the present review, we summarize the current knowledge on proteolytical α-synuclein cleavage by neurosin, calpain-1, cathepsin D, and matrix metalloproteinase-3 in health and disease. We also shed light on the contribution of the same enzymes to proteolytical processing of pathogenic proteins in Alzheimer's disease and report potential cross-disease mechanisms of pathogenic protein aggregation.

Parkinson’s disease (PD) is a progressive neurodegenerative disorder that is neuropathologically characterized by degeneration of dopaminergic neurons of the substantia nigra (SN) and formation of Lewy bodies and Lewy neurites composed of aggregated α-synuclein. Proteolysis of α-synuclein by matrix metalloproteinases was shown to facilitate its aggregation and to affect cell viability. One of the proteolysed fragments, Gln79-α-synuclein, possesses a glutamine residue at its N-terminus. We argue that glutaminyl cyclase (QC) may catalyze the pyroglutamate (pGlu)79-α-synuclein formation and, thereby, contribute to enhanced aggregation and compromised degradation of α-synuclein in human synucleinopathies. Here, the kinetic characteristics of Gln79-α-synuclein conversion into the pGlu-form by QC are shown using enzymatic assays and mass spectrometry. Thioflavin T assays and electron microscopy demonstrated a decreased potential of pGlu79-α-synuclein to form fibrils. However, size exclusion chromatography and cell viability assays revealed an increased propensity of pGlu79- α-synuclein to form oligomeric aggregates with high neurotoxicity. In brains of wild-type mice, QC and α-synuclein were co-expressed by dopaminergic SN neurons. Using a specific antibody against the pGlu-modified neo-epitope of α-synuclein, pGlu79-α-synuclein aggregates were detected in association with QC in brains of two transgenic mouse lines with human α-synuclein overexpression. In human brain samples of PD and dementia with Lewy body subjects, pGlu79-α-synuclein was shown to be present in SN neurons, in a number of Lewy bodies and in dystrophic neurites. Importantly, there was a spatial co-occurrence of pGlu79-α-synuclein with the enzyme QC in the human SN complex and a defined association of QC with neuropathological structures. We conclude that QC catalyzes the formation of oligomer-prone pGlu79-α-synuclein in human synucleinopathies, which may—in analogy to pGlu-Aβ peptides in Alzheimer’s disease—act as a seed for pathogenic protein aggregation.

Yes / It is unclear whether people with dementia (PwD) have more negative attitudes toward own aging (ATOA) than people without dementia and what factors influence ATOA among PwD. We investigated whether PwD have more negative ATOA than individuals without dementia and whether cognition and dementia subtype are associated with ATOA in PwD. Data from the IDEAL and PROTECT studies were used to compare ATOA between 1502 PwD (mean (SD) age = 76.3 (8.5)) and 6377 individuals without dementia (mean (SD) age = 66.1 (7.1)). Linear regressions and ANOVA were used. PwD reported slightly more negative ATOA than people without dementia; this relationship disappeared after controlling for depression and self-rated health. In PwD more positive ATOA showed negligible associations with better general cognition, memory performance, verbal fluency, and visuospatial ability. However, after adjusting for covariates only better visuospatial ability predicted more positive ATOA. Additional analyses showed that before and after controlling for covariates, individuals with poorer self-reported visual acuity have more negative ATOA. Amongst dementia subtypes, people with Parkinson's disease dementia and dementia with Lewy bodies reported most negative ATOA. ATOA between PwD and people without dementia do not differ. ATOA in PwD appear to be affected not by cognitive impairment but by other characteristics that vary across dementia subtypes. Among PwD, those with Parkinson's disease dementia and dementia with Lewy bodies may have higher risk of experiencing negative ATOA due to the motor and visual impairments that they experience. / Improving the experience of Dementia and Enhancing Active Life: living well with dementia. The IDEAL study’ was funded jointly by the Economic and Social Research Council (ESRC) and the National Institute for Health and Care Research (NIHR) through grant ES/L001853/2. The IDEAL-2 study’ is funded by Alzheimer’s Society, grant number 348, AS-PR2-16-001

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Le trouble comportemental en sommeil paradoxal (TCSP) idiopathique est caractérisé par une activité motrice indésirable et souvent violente au cours du sommeil paradoxal. Le TCSP idiopathique est considéré comme un facteur de risque de certaines maladies neurodégénératives, particulièrement la maladie de Parkinson (MP) et la démence à corps de Lewy (DCL). La dépression et les troubles anxieux sont fréquents dans la MP et la DCL. L’objectif de cette étude est d’évaluer la sévérité des symptômes dépressifs et anxieux dans le TCSP idiopathique. Cinquante-cinq patients avec un TCSP idiopathique sans démence ni maladie neurologique et 63 sujets contrôles ont complété la seconde édition du Beck Depression Inventory (BDI-II) et le Beck Anxiety Inventory (BAI). Nous avons aussi utilisé le BDI for Primary Care (BDI-PC) afin de minimiser la contribution des facteurs confondant dans les symptômes dépressifs. Les patients avec un TCSP idiopathique ont obtenu des scores plus élevés que les sujets contrôles au BDI-II (9.63 ± 6.61 vs. 4.32 ± 4.58; P < 0.001), au BDI-PC (2.20 ± 2.29 vs. 0.98 ± 1.53; P = 0.001) et au BAI (8.37 ± 7.30 vs. 3.92 ± 5.26; P < 0.001). Nous avons également trouvé une proportion plus élevée des sujets ayant des symptômes dépressifs (4/63 ou 6% vs. 12/55 ou 22%; P = 0.03) ou anxieux (9/50 or 18% vs. 21/43 ou 49%; P = 0.003) cliniquement significatifs. La proportion des sujets ayant des symptômes dépressifs cliniquement significatifs ne change pas en utilisant le BDI-PC (11/55 or 20%) Les symptômes dépressifs et anxieux sont fréquents dans le TCSP idiopathique. L’examen de routine des patients avec un TCSP idiopathique devrait inclure un dépistage systématique des symptômes dépressifs et anxieux afin de les prévenir ou les traiter. / Idiopathic rapid-eye-movement sleep behaviour (iRBD) disorder can be a premotor feature of Parkinson’s disease (PD) or dementia with Lewy bodies (DLB). Depressive and anxiety symptoms are frequent nonmotor features in PD or DLB. We assessed the frequency and severity of depressive and anxiety symptoms in patients with iRBD compared to healthy control subjects. Fifty-five iRBD patients and 63 age and sexmatched healthy subjects were studied. Participants completed the Beck Depression Inventory – Second Edition (BDI-II) and Beck Anxiety Inventory (BAI). We assessed the depressive and anxiety symptoms and compared the proportion of participants with clinically significant depressive or anxiety symptoms. We also used the BDI for Primary Care (BDI-PC) to minimize confounding factors that could overestimate depressive symptoms. iRBD patients scored higher than controls on the BDI-II (9.63 ± 6.61 vs. 4.32 ± 4.58; P < 0.001)), BDI-PC (2.20 ± 2.29 vs. 0.98 ± 1.53; P = 0.001) and BAI (8.37 ± 7.30 vs. 3.92 ± 5.26; P < 0.001). Compared to controls, we found a higher proportion of patients with iRBD with either clinically significant depressive (4/63 or 6% vs. 12/55 or 22% P = 0.03) or anxiety symptoms (9/50 or 18% vs. 21/43 or 49%; P = 0.003). The proportion of iRBD patients with clinically significant depressive symptoms remains unchanged using the BDI-PC (11/55 or 20%). Depressive and anxiety symptoms are frequent features in iRBD. Routine examination of patients with iRBD disorder should include an assessment of depressive and anxiety symptoms in order to prevent or treat them.