| 1. |
- Buck, Kerstin, et al.
(författare)
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Ser129 phosphorylation of endogenous α-synuclein induced by overexpression of polo-like kinases 2 and 3 in nigral dopamine neurons is not detrimental to their survival and function.
- 2015
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Ingår i: Neurobiology of Disease. - : Elsevier BV. - 0969-9961. ; 78:Mar 25, s. 100-114
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Tidskriftsartikel (refereegranskat)abstract
- Phosphorylation of the α-synuclein (α-syn) protein at Ser129 [P(S129)-α-] was found to be the most abundant form in intracellular inclusions in brains from Parkinson's disease (PD) patients. This finding suggests that P(S129)-α-syn plays a central role in the pathogenesis of PD. However, it is at present unclear whether P(S129)-α-syn is pathogenic driving the neurodegenerative process. Rodent studies using neither the phosphomimics of human α-syn nor co-expression of human wild-type α-syn and kinases phosphorylating α-syn at Ser129 gave consistent results. One major concern in interpreting these findings is that human α-syn was expressed above physiological levels inducing neurodegeneration in rat nigral neurons. In order to exclude this confounding factor, we took a different approach and increased the phosphorylation level of endogenous α-syn. For this purpose, we took advantage of recombinant adeno-associated viral (rAAV) vectors to deliver polo-like kinase 2 (PLK2) or PLK3 in the substantia nigra and investigated whether increased levels of P(S129)-α-syn compromised the function and survival of nigral dopaminergic neurons. Interestingly, we observed that hyperphosphorylated α-syn did not induce nigral dopaminergic cell death, as assessed at 1 and 4months. Furthermore, histological analysis did not show any accumulation of α-syn protein or formation of inclusions. Using in vivo microdialysis, we found that the only measurable functional alteration was the depolarisation-induced release of dopamine, while the in vivo synthesis rate of DOPA and dopamine baseline release remained unaltered. Taken together, our results suggest that phosphorylation of α-syn at Ser129 does not confer a toxic gain of function per se.
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| 2. |
- Cuellar-Baena, Sandra, et al.
(författare)
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Assessment of brain metabolite correlates of AAV-mediated overexpression of human alpha-synuclein in cortical neurons by in vivo(1) H-MR spectroscopy at 9.4 T.
- 2016
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Ingår i: Journal of Neurochemistry. - : Wiley. - 1471-4159 .- 0022-3042. ; 137:5, s. 806-819
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we used proton-localized spectroscopy ((1) H-MRS) for the acquisition of the neurochemical profile longitudinally in a novel rat model of human wild type alpha-synuclein (a-syn) overexpression. Our goal was to find out if the increased a-syn load in this model could be linked to changes in metabolites in the frontal cortex. Animals injected with AAV vectors encoding for human a-syn formed the experimental group, whereas green fluorescent protein (GFP) expressing animals were used as the vector-treated control group and a third group of uninjected animals were used as naïve controls. Data was acquired at 2, 4 and 8 month time-points. Nineteen metabolites were quantified in the MR spectra using LCModel software. Based on 92 spectra, we evaluated any potential gender effect and found that Lactate levels were lower in males compared to females, while the opposite was observed for Ascorbate. Next, we assessed the effect of age and found increased levels of GABA, Tau and GPC+PCho. Finally, we analyzed the effect of treatment and found that Lactate levels (p=0.005) were specifically lower in the a-syn group compared to the GFP and control groups. Additionally, Ascorbate levels (p=0.05) were increased in the vector-injected groups, while glucose levels remained unchanged. This study indicates that the metabolic switch between Glucose-Lactate could be detectable in-vivo and might be modulated by Ascorbate. No concomitant changes were found in markers of neuronal integrity (e.g. NAA) consistent with the fact that a-syn overexpression in cortical neurons did not result in neurodegeneration in this model. This article is protected by copyright. All rights reserved.
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| 3. |
- Hall, Helene, et al.
(författare)
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Characterization of cognitive deficits in rats overexpressing human alpha-synuclein in the ventral tegmental area and medial septum using recombinant adeno-associated viral vectors.
- 2013
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Intraneuronal inclusions containing alpha-synuclein (a-syn) constitute one of the pathological hallmarks of Parkinson's disease (PD) and are accompanied by severe neurodegeneration of A9 dopaminergic neurons located in the substantia nigra. Although to a lesser extent, A10 dopaminergic neurons are also affected. Neurodegeneration of other neuronal populations, such as the cholinergic, serotonergic and noradrenergic cell groups, has also been documented in PD patients. Studies in human post-mortem PD brains and in rodent models suggest that deficits in cholinergic and dopaminergic systems may be associated with the cognitive impairment seen in this disease. Here, we investigated the consequences of targeted overexpression of a-syn in the mesocorticolimbic dopaminergic and septohippocampal cholinergic pathways. Rats were injected with recombinant adeno-associated viral vectors encoding for either human wild-type a-syn or green fluorescent protein (GFP) in the ventral tegmental area and the medial septum/vertical limb of the diagonal band of Broca, two regions rich in dopaminergic and cholinergic neurons, respectively. Histopathological analysis showed widespread insoluble a-syn positive inclusions in all major projections areas of the targeted nuclei, including the hippocampus, neocortex, nucleus accumbens and anteromedial striatum. In addition, the rats overexpressing human a-syn displayed an abnormal locomotor response to apomorphine injection and exhibited spatial learning and memory deficits in the Morris water maze task, in the absence of obvious spontaneous locomotor impairment. As losses in dopaminergic and cholinergic immunoreactivity in both the GFP and a-syn expressing animals were mild-to-moderate and did not differ from each other, the behavioral impairments seen in the a-syn overexpressing animals appear to be determined by the long term persisting neuropathology in the surviving neurons rather than by neurodegeneration.
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| 4. |
- Hall, Helene, et al.
(författare)
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Hippocampal Lewy pathology and cholinergic dysfunction are associated with dementia in Parkinson's disease.
- 2014
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Ingår i: Brain. - : Oxford University Press (OUP). - 1460-2156 .- 0006-8950. ; 137:Jul 24, s. 2493-2508
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Tidskriftsartikel (refereegranskat)abstract
- The neuropathological substrate of dementia in patients with Parkinson's disease is still under debate, particularly in patients with insufficient alternate neuropathology for other degenerative dementias. In patients with pure Lewy body Parkinson's disease, previous post-mortem studies have shown that dopaminergic and cholinergic regulatory projection systems degenerate, but the exact pathways that may explain the development of dementia in patients with Parkinson's disease remain unclear. Studies in rodents suggest that both the mesocorticolimbic dopaminergic and septohippocampal cholinergic pathways may functionally interact to regulate certain aspects of cognition, however, whether such an interaction occurs in humans is still poorly understood. In this study, we performed stereological analyses of the A9 and A10 dopaminergic neurons and Ch1, Ch2 and Ch4 cholinergic neurons located in the basal forebrain, along with an assessment of α-synuclein pathology in these regions and in the hippocampus of six demented and five non-demented patients with Parkinson's disease and five age-matched control individuals with no signs of neurological disease. Moreover, we measured choline acetyltransferase activity in the hippocampus and frontal cortex of eight demented and eight non-demented patients with Parkinson's disease, as well as in the same areas of eight age-matched controls. All patients with Parkinson's disease exhibited a similar 80-85% loss of pigmented A9 dopaminergic neurons, whereas patients with Parkinson's disease dementia presented an additional loss in the lateral part of A10 dopaminergic neurons as well as Ch4 nucleus basalis neurons. In contrast, medial A10 dopaminergic neurons and Ch1 and Ch2 cholinergic septal neurons were largely spared. Despite variable Ch4 cell loss, cortical but not hippocampal cholinergic activity was consistently reduced in all patients with Parkinson's disease, suggesting significant dysfunction in cortical cholinergic pathways before frank neuronal degeneration. Patients with Parkinson's disease dementia were differentiated by a significant reduction in hippocampal cholinergic activity, by a significant loss of non-pigmented lateral A10 dopaminergic neurons and Ch4 cholinergic neurons (30 and 55% cell loss, respectively, compared with neuronal preservation in control subjects), and by an increase in the severity of α-synuclein pathology in the basal forebrain and hippocampus. Overall, these results point to increasing α-synuclein deposition and hippocampal dysfunction in a setting of more widespread degeneration of cortical dopaminergic and cholinergic pathways as contributing to the dementia occurring in patients with pure Parkinson's disease. Furthermore, our findings support the concept that α-synuclein deposition is associated with significant neuronal dysfunction in the absence of frank neuronal loss in Parkinson's disease.
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| 5. |
- Landeck, Natalie, et al.
(författare)
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A novel multiplex assay for simultaneous quantification of total and S129 phosphorylated human alpha-synuclein
- 2016
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Ingår i: Molecular Neurodegeneration. - : Springer Science and Business Media LLC. - 1750-1326. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Alpha-synuclein (asyn) has been shown to play an important role in the neuropathology of Parkinson's disease (PD). In the diseased brain, classic intraneuronal inclusions called Lewy bodies contain abnormal formations of asyn protein which is mostly phosphorylated at serine 129 (pS129 asyn). This suggests that post-translational modifications may play a role in the pathogenic process. To date, several uniplex assays have been developed in order to quantify asyn not only in the brain but also in cerebrospinal fluid and blood samples in order to correlate asyn levels to disease severity and progression. Notably, only four assays have been established to measure pS129 asyn specifically and none provide simultaneous readout of the total and pS129 species. Therefore, we developed a sensitive high-throughput duplex assay quantifying total and pS129 human asyn (h-asyn) in the same well hence improving accuracy as well as saving time, consumables and samples. Results: Using our newly established duplex assay we measured total and pS129 h-asyn in vitro showing that polo-like kinase 2 (PLK2) can phosphorylate asyn up to 41 % in HEK293 cells and in vivo the same kinase phosphorylated h-asyn up to 17 % in rat ventral midbrain neurons. Interestingly, no increase in phosphorylation was observed when PLK2 and h-asyn were co-expressed in rat striatal neurons. Furthermore, using this assay we investigated h-asyn levels in brain tissue samples from patients with PD as well as PD dementia and found significant differences in pS129 h-asyn levels not only between disease tissue and healthy control samples but also between the two distinct disease states especially in hippocampal tissue samples. Conclusions: These results demonstrate that our duplex assay for simultaneous quantification is a useful tool to study h-asyn phosphorylation events in biospecimens and will be helpful in studies investigating the precise causative link between post-translational modification of h-asyn and PD pathology.
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| 6. |
- Landeck, Natalie
(författare)
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Pathogenic effects of alpha-synuclein: modifications and toxicity
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accumulation of intraneuronal inclusions, containing mainly a protein called alpha-synuclein (asyn), is thought to play a critical role in neurodegenerative disorders such as Parkinson's disease (PD). In these so called Lewy bodies, the majority of asyn is phosphorylated at serine 129 (pS129) suggesting that post-translational modifications may play a critical role in the process of aggregate formation. To date, the precise pathological aspects and molecular mechanisms underlying asyn aggregation remain unclear. Previous studies have aimed to elucidate which region of human asyn (h-asyn) is influencing its aggregation properties and therefore possibly its toxicity towards neuronal cells. By investigating truncated h-asyn as well as naturally occurring asyn variants, it has been shown that synuclein lacking the central hydrophobic region is less prone to aggregate in vitro, although not all experimental studies support this view.To address this critical issue, we directly compared several human and rodent synuclein variants in a dose-depended manner to determine their toxic effects in vivo. Interestingly, we found that all human variants followed the same toxicity profile while rat asyn (r-asyn) did not induce neurodegeneration. Whereas phosphorylation levels of h-asyn was greater than that of r-asyn, increasing the amount of endogenous pS129 r-asyn did not result in neurotoxicity. Additionally, using our newly established duplexing assay to measure total and pS129 asyn simultaneously, we showed that endogenous pS129 h-asyn levels are naturally higher than that of r-asyn. This could point to phosphorylation being a side effect of h-asyn accumulation.Interestingly, both rat and mouse asyn are 95% homologous to h-asyn but show no accumulation or neurotoxicity over time in vivo. Furthermore, rodent asyn naturally contains a threonine at position 53 (T53), which in humans causes familial PD. To investigate why rodent asyn is less toxic especially when containing a T53 residue, we altered two C-terminally located amino acids of h-asynA53T to the mouse asyn (m-asyn) sequence and could demonstrate that dopaminergic neurodegeneration was reduced in the rat nigra. Moreover, mutating the C-terminal region of m-asyn to the human amino acids results in an increase of toxicity in vivo. These changes in the neurotoxicity profile could be due to the alterations we observed in the membrane-induced aggregation and vesicle disruption property of asyn.Taken together, these findings not only have an impact on our understanding of the formation and toxicity of asyn aggregates but could also lead to the development of novel therapeutic strategies targeting specifically the C-terminal region of h-asyn in PD.
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| 7. |
- Landeck, Natalie, et al.
(författare)
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Toxic effects of human and rodent variants of alpha-synuclein in vivo
- 2017
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Ingår i: European Journal of Neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 45:4, s. 536-547
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Tidskriftsartikel (refereegranskat)abstract
- In Parkinson's disease, abnormal alpha-synuclein (asyn) accumulation leads to the formation of soluble oligomeric species thought to be toxic to cells as well as intraneuronal inclusions. To date, the precise mechanisms leading to aggregation of asyn in the brain is not well-understood. Previous studies in yeast, drosophila, and transgenic mice suggested that a non-A beta component depleted version of human asyn [h-asyn(D70-83)] or human beta-synuclein (h-bsyn), naturally lacking this centrally located hydrophobic region, are less prone to form aggregates in vitro and are expected to be less toxic compared to h-asyn in vivo, although not all experimental studies unequivocally support the latter view. To address this outstanding issue, we directly compared the neurotoxicity of human asyn against that of h-asyn(D70-83), h-bsyn as well as rat asyn using an adeno-associated viral vector to express these proteins in a dose-response study where the vector load was varied over two orders of magnitude. By quantifying the neurodegeneration of rat substantia nigra dopamine neurons here we show that h-asyn, h-bsyn, and h-asyn(D70-83) display comparable neurotoxicity across the vector doses tested. On the other hand, rat asyn and GFP control vectors displayed a different profile, where no detectable neurodegeneration was seen except at the highest vector titer. Thus, the two main conclusions of our study are that (i) deletion of the central hydrophobic region in h-asyn is not sufficient to alter its neurotoxic properties and (ii) expression of the widely used GFP control protein can cause measurable neurodegeneration at high titers.
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| 8. |
- Landeck, Natalie, et al.
(författare)
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Two C-terminal sequence variations determine differential neurotoxicity between human and mouse α-synuclein
- 2020
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Ingår i: Molecular Neurodegeneration. - : Springer Science and Business Media LLC. - 1750-1326. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: α-Synuclein (aSyn) aggregation is thought to play a central role in neurodegenerative disorders termed synucleinopathies, including Parkinson's disease (PD). Mouse aSyn contains a threonine residue at position 53 that mimics the human familial PD substitution A53T, yet in contrast to A53T patients, mice show no evidence of aSyn neuropathology even after aging. Here, we studied the neurotoxicity of human A53T, mouse aSyn, and various human-mouse chimeras in cellular and in vivo models, as well as their biochemical properties relevant to aSyn pathobiology. Methods: Primary midbrain cultures transduced with aSyn-encoding adenoviruses were analyzed immunocytochemically to determine relative dopaminergic neuron viability. Brain sections prepared from rats injected intranigrally with aSyn-encoding adeno-associated viruses were analyzed immunohistochemically to determine nigral dopaminergic neuron viability and striatal dopaminergic terminal density. Recombinant aSyn variants were characterized in terms of fibrillization rates by measuring thioflavin T fluorescence, fibril morphologies via electron microscopy and atomic force microscopy, and protein-lipid interactions by monitoring membrane-induced aSyn aggregation and aSyn-mediated vesicle disruption. Statistical tests consisted of ANOVA followed by Tukey's multiple comparisons post hoc test and the Kruskal-Wallis test followed by a Dunn's multiple comparisons test or a two-tailed Mann-Whitney test. Results: Mouse aSyn was less neurotoxic than human aSyn A53T in cell culture and in rat midbrain, and data obtained for the chimeric variants indicated that the human-to-mouse substitutions D121G and N122S were at least partially responsible for this decrease in neurotoxicity. Human aSyn A53T and a chimeric variant with the human residues D and N at positions 121 and 122 (respectively) showed a greater propensity to undergo membrane-induced aggregation and to elicit vesicle disruption. Differences in neurotoxicity among the human, mouse, and chimeric aSyn variants correlated weakly with differences in fibrillization rate or fibril morphology. Conclusions: Mouse aSyn is less neurotoxic than the human A53T variant as a result of inhibitory effects of two C-terminal amino acid substitutions on membrane-induced aSyn aggregation and aSyn-mediated vesicle permeabilization. Our findings highlight the importance of membrane-induced self-assembly in aSyn neurotoxicity and suggest that inhibiting this process by targeting the C-terminal domain could slow neurodegeneration in PD and other synucleinopathy disorders.
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| 9. |
- Lillethorup, Thea Pinholt, et al.
(författare)
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In vivo quantification of glial activation in minipigs overexpressing human α-synuclein
- 2018
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Ingår i: Synapse. - : Wiley. - 0887-4476. ; 72:12
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Tidskriftsartikel (refereegranskat)abstract
- Parkinson’s disease is characterized by a progressive loss of substantia nigra (SN) dopaminergic neurons and the formation of Lewy bodies containing accumulated alpha-synuclein (α-syn). The pathology of Parkinson’s disease is associated with neuroinflammatory microglial activation, which may contribute to the ongoing neurodegeneration. This study investigates the in vivo microglial and dopaminergic response to overexpression of α-syn. We used positron emission tomography (PET) and the 18 kDa translocator protein radioligand, [11C](R)PK11195, to image brain microglial activation and (+)-α-[11C]dihydrotetrabenazine ([11C]DTBZ), to measure vesicular monoamine transporter 2 (VMAT2) availability in Göttingen minipigs following injection with recombinant adeno-associated virus (rAAV) vectors expressing either mutant A53T α-syn or green fluorescent protein (GFP) into the SN (4 rAAV-α-syn, 4 rAAV-GFP, 5 non-injected control minipigs). We performed motor symptom assessment and immunohistochemical examination of tyrosine hydroxylase (TH) and transgene expression. Expression of GFP and α-syn was observed at the SN injection site and in the striatum. We observed no motor symptoms or changes in striatal [11C]DTBZ binding potential in vivo or striatal or SN TH staining in vitro between the groups. The mean [11C](R)PK11195 total volume of distribution was significantly higher in the basal ganglia and cortical areas of the α-syn group than the control animals. We conclude that mutant α-syn expression in the SN resulted in microglial activation in multiple sub- and cortical regions, while it did not affect TH stains or VMAT2 availability. Our data suggest that microglial activation constitutes an early response to accumulation of α-syn in the absence of dopamine neuron degeneration.
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| 10. |
- Lillethorup, Thea P., et al.
(författare)
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Longitudinal monoaminergic PET imaging of chronic proteasome inhibition in minipigs
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Impairment of the ubiquitin proteasome system has been implicated in Parkinson’s disease. We used positron emission tomography to investigate longitudinal effects of chronic intracerebroventricular exposure to the proteasome inhibitor lactacystin on monoaminergic projections and neuroinflammation. Göttingen minipigs were implanted in the cisterna magna with a catheter connected to a subcutaneous injection port. Minipigs were imaged at baseline and after cumulative doses of 200 and 400 μg lactacystin, respectively. Main radioligands included [11C]-DTBZ (vesicular monoamine transporter type 2) and [11C]-yohimbine (α2-adrenoceptor). [11C]-DASB (serotonin transporter) and [11C]-PK11195 (activated microglia) became available later in the study and we present their results in a smaller subset of animals for information purposes only. Striatal [11C]-DTBZ binding potentials decreased significantly by 16% after 200 μg compared to baseline, but the decrease was not sustained after 400 μg (n = 6). [11C]-yohimbine volume of distribution increased by 18–25% in the pons, grey matter and the thalamus after 200 μg, which persisted at 400 μg (n = 6). In the later subset of minipigs, we observed decreased [11C]-DASB (n = 5) and increased [11C]-PK11195 (n = 3) uptake after 200 μg. These changes may mimic monoaminergic changes and compensatory responses in early Parkinson’s disease.
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