| 1. |
- Antti, Henrik, et al.
(författare)
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Metabolic profiling for detection of staphylococcus aureus infection and antibiotic resistance
- 2013
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- Due to slow diagnostics, physicians must optimize antibiotic therapies based on clinical evaluation of patients without specific information on causative bacteria. We have investigated metabolomic analysis of blood for the detection of acute bacterial infection and early differentiation between ineffective and effective antibiotic treatment. A vital and timely therapeutic difficulty was thereby addressed: the ability to rapidly detect treatment failures because of antibiotic-resistant bacteria. Methicillin-resistant (MRSA) and methicillin-sensitive (MSSA) were used and for infecting mice, while natural MSSA infection was studied in humans. Samples of bacterial growth media, the blood of infected mice and of humans were analyzed with combined Gas Chromatography/Mass Spectrometry. Multivariate data analysis was used to reveal the metabolic profiles of infection and the responses to different antibiotic treatments. experiments resulted in the detection of 256 putative metabolites and mice infection experiments resulted in the detection of 474 putative metabolites. Importantly, ineffective and effective antibiotic treatments were differentiated already two hours after treatment start in both experimental systems. That is, the ineffective treatment of MRSA using cloxacillin and untreated controls produced one metabolic profile while all effective treatment combinations using cloxacillin or vancomycin for MSSA or MRSA produced another profile. For further evaluation of the concept, blood samples of humans admitted to intensive care with severe sepsis were analyzed. One hundred thirty-three putative metabolites differentiated severe MSSA sepsis (n = 6) from severe sepsis (n = 10) and identified treatment responses over time. Combined analysis of human, , and mice samples identified 25 metabolites indicative of effective treatment of sepsis. Taken together, this study provides a proof of concept of the utility of analyzing metabolite patterns in blood for early differentiation between ineffective and effective antibiotic treatment in acute infections.
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| 2. |
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| 3. |
- Dagar, Janardan, et al.
(författare)
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Compositional and Interfacial Engineering Yield High-Performance and Stable p-i-n Perovskite Solar Cells and Mini-Modules
- 2021
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Ingår i: ACS applied materials & interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:11, s. 13022-13033
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Tidskriftsartikel (refereegranskat)abstract
- Through the optimization of the perovskite precursor composition and interfaces to selective contacts, we achieved a p-i-n-type perovskite solar cell (PSC) with a 22.3% power conversion efficiency (PCE). This is a new performance record for a PSC with an absorber bandgap of 1.63 eV. We demonstrate that the high device performance originates from a synergy between (1) an improved perovskite absorber quality when introducing formamidinium chloride (FACl) as an additive in the "triple cation" Cs0.05FA0.79MA0.16PbBr0.51I2.49 (Cs-MAFA) perovskite precursor ink, (2) an increased open-circuit voltage, VOC, due to reduced recombination losses when using a lithium fluoride (LiF) interfacial buffer layer, and (3) high-quality hole-selective contacts with a self-assembled monolayer (SAM) of [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) on ITO electrodes. While all devices exhibit a high performance after fabrication, as determined from current-density voltage, J-V, measurements, substantial differences in device performance become apparent when considering longer-term stability data. A reduced long-term stability of devices with the introduction of a LiF interlayer is compensated for by using FACl as an additive in the metal-halide perovskite thin-film deposition. Optimized devices maintained about 80% of the initial average PCE during maximum power point (MPP) tracking for >700 h. We scaled the optimized device architecture to larger areas and achieved fully laser patterned series-interconnected mini-modules with a PCE of 19.4% for a 2.2 cm2 active area. A robust device architecture and reproducible deposition methods are fundamental for high performance and stable large-area single junction and tandem modules based on PSCs.
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| 4. |
- Diogenes, Maria Jose, et al.
(författare)
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Extracellular Alpha-Synuclein Oligomers Modulate Synaptic Transmission and Impair LTP Via NMDA-Receptor Activation
- 2012
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 32:34, s. 11750-11762
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Tidskriftsartikel (refereegranskat)abstract
- Parkinson's disease (PD) is the most common representative of a group of disorders known as synucleinopathies, in which misfolding and aggregation of alpha-synuclein (a-syn) in various brain regions is the major pathological hallmark. Indeed, the motor symptoms in PD are caused by a heterogeneous degeneration of brain neurons not only in substantia nigra pars compacta but also in other extrastriatal areas of the brain. In addition to the well known motor dysfunction in PD patients, cognitive deficits and memory impairment are also an important part of the disorder, probably due to disruption of synaptic transmission and plasticity in extrastriatal areas, including the hippocampus. Here, we investigated the impact of a-syn aggregation on AMPA and NMDA receptor-mediated rat hippocampal (CA3-CA1) synaptic transmission and long-term potentiation (LTP), the neurophysiological basis for learning and memory. Our data show that prolonged exposure to a-syn oligomers, but not monomers or fibrils, increases basal synaptic transmission through NMDA receptor activation, triggering enhanced contribution of calcium-permeable AMPA receptors. Slices treated with a-syn oligomers were unable to respond with further potentiation to theta-burst stimulation, leading to impaired LTP. Prior delivery of a low-frequency train reinstated the ability to express LTP, implying that exposure to a-syn oligomers drives the increase of glutamatergic synaptic transmission, preventing further potentiation by physiological stimuli. Our novel findings provide mechanistic insight on how a-syn oligomers may trigger neuronal dysfunction and toxicity in PD and other synucleinopathies.
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| 5. |
- Fagerqvist, Therese, et al.
(författare)
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Monoclonal antibodies selective for α-synuclein oligomers/protofibrils recognize brain pathology in Lewy body disorders and α-synuclein transgenic mice with the disease-causing A30P mutation
- 2013
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Ingår i: Journal of Neurochemistry. - : Wiley-Blackwell. - 0022-3042 .- 1471-4159. ; 126:1, s. 131-144
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Tidskriftsartikel (refereegranskat)abstract
- Inclusions of intraneuronal alpha-synuclein (-synuclein) can be detected in brains of patients with Parkinson's disease and dementia with Lewy bodies. The aggregation of -synuclein is a central feature of the disease pathogenesis. Among the different -synuclein species, large oligomers/protofibrils have particular neurotoxic properties and should therefore be suitable as both therapeutic and diagnostic targets. Two monoclonal antibodies, mAb38F and mAb38E2, with high affinity and strong selectivity for large -synuclein oligomers were generated. These antibodies, which do not bind amyloid-beta or tau, recognize Lewy body pathology in brains from patients with Parkinson's disease and dementia with Lewy bodies and detect pathology earlier in -synuclein transgenic mice than linear epitope antibodies. An oligomer-selective sandwich ELISA, based on mAb38F, was set up to analyze brain extracts of the transgenic mice. The overall levels of -synuclein oligomers/protofibrils were found to increase with age in these mice, although the levels displayed a large interindividual variation. Upon subcellular fractionation, higher levels of -synuclein oligomers/protofibrils could be detected in the endoplasmic reticulum around the age when behavioral disturbances develop. In summary, our novel oligomer-selective -synuclein antibodies recognize relevant pathology and should be important tools to further explore the pathogenic mechanisms in Lewy body disorders. Moreover, they could be potential candidates both for immunotherapy and as reagents in an assay to assess a potential disease biomarker.
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| 6. |
- Fagerqvist, Therese, et al.
(författare)
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Off-pathway alpha-synuclein oligomers seem to alter alpha-synuclein turnover in a cell model but lack seeding capability in vivo
- 2013
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Ingår i: Amyloid. - : Informa UK Limited. - 1350-6129 .- 1744-2818. ; 20:4, s. 233-244
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Tidskriftsartikel (refereegranskat)abstract
- Aggregated α-synuclein is the major component of Lewy bodies, protein inclusions observed in the brain in neurodegenerative disorders such as Parkinson’s disease and dementia with Lewy bodies. Experimental evidence indicates that α-synuclein potentially can be transferred between cells and act as a seed to accelerate the aggregation process. Here, we investigated in vitro and in vivo seeding effects of α-synuclein oligomers induced by the reactive aldehyde 4-oxo-2-nonenal (ONE). As measured by a Thioflavin-T based fibrillization assay, there was an earlier onset of aggregation when α-synuclein oligomers were added to monomeric α-synuclein. In contrast, exogenously added α-synuclein oligomers did not induce aggregation in a cell model. However, cells overexpressing α-synuclein that were treated with the oligomers displayed reduced α-synuclein levels, indicating that internalized oligomers either decreased the expression or accelerated the degradation of transfected α-synuclein. Also in vivo there were no clear seeding effects, as intracerebral injections of α-synuclein oligomers into the neocortex of α-synuclein transgenic mice did not induce formation of Proteinase K resistant α-synuclein pathology. Taken together, we could observe a seeding effect of the ONE-induced α-synuclein oligomers in a fibrillization assay, but neither in a cell nor in a mouse model.
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| 7. |
- Fagerqvist, Therese, et al.
(författare)
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Off-pathway α-synuclein oligomers seem to alter α-synuclein turnover in a cell model but lack seeding capability in vivo
- 2013
-
Ingår i: Amyloid. - : Informa Healthcare. - 1350-6129 .- 1744-2818. ; 20:4, s. 233-244
-
Tidskriftsartikel (refereegranskat)abstract
- Aggregated alpha-synuclein is the major component of Lewy bodies, protein inclusions observed in the brain in neurodegenerative disorders such as Parkinson's disease and dementia with Lewy bodies. Experimental evidence indicates that alpha-synuclein potentially can be transferred between cells and act as a seed to accelerate the aggregation process. Here, we investigated in vitro and in vivo seeding effects of alpha-synuclein oligomers induced by the reactive aldehyde 4-oxo-2-nonenal (ONE). As measured by a Thioflavin-T based fibrillization assay, there was an earlier onset of aggregation when alpha-synuclein oligomers were added to monomeric alpha-synuclein. In contrast, exogenously added alpha-synuclein oligomers did not induce aggregation in a cell model. However, cells overexpressing alpha-synuclein that were treated with the oligomers displayed reduced alpha-synuclein levels, indicating that internalized oligomers either decreased the expression or accelerated the degradation of transfected alpha-synuclein. Also in vivo there were no clear seeding effects, as intracerebral injections of alpha-synuclein oligomers into the neocortex of alpha-synuclein transgenic mice did not induce formation of proteinase K resistant alpha-synuclein pathology. Taken together, we could observe a seeding effect of the ONE-induced alpha-synuclein oligomers in a fibrillization assay, but neither in a cell nor in a mouse model.
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| 8. |
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| 9. |
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| 10. |
- Näsström, Birgit, et al.
(författare)
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A single bolus of a low molecular weight heparin to patients on haemodialysis depletes lipoprotein lipase stores and retards triglyceride clearing.
- 2005
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Ingår i: Nephrology, Dialysis and Transplantation. - : Oxford University Press (OUP). - 0931-0509 .- 1460-2385. ; 20:6, s. 1172-1179
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Low molecular weight heparins (LMWH) are increasingly used during haemodialysis (HD) to prevent clotting in the extracorporeal devices. It has been suggested that LMWH release endothelial-bound lipoprotein lipase (LPL) less efficiently than unfractionated heparin (UFH) does and thereby cause less disturbance of lipid metabolism. Evidence from in vitro studies and from animal experiments indicate, however, that both types of heparin preparations have the same ability to release endothelial LPL, but LMWH are less effective in preventing uptake and degradation of LPL in the liver. Model studies in humans indicate that LMWH cause as much depletion of LPL stores and impaired lipolysis of triglyceride (TG)-rich lipoproteins as UFH does. METHODS: Two anticoagulant regimes based on present clinical practice were compared in nine HD patients. UFH was administered as a primed infusion, whereas the LMWH (dalteparin) was given only as a single bolus pre-dialysis. Blood was sampled regularly for LPL activity and TG. RESULTS: LPL activity in blood was significantly lower during the dialysis with dalteparin. To explore the remaining activity at the endothelium, a bolus of UFH was given after 3 h of dialysis. The bolus brought out about the same amount of LPL, regardless of whether UFH or dalteparin had been used during dialysis. The increase in TG was significantly higher during dialysis with dalteparin. CONCLUSIONS: This study indicates that a single bolus of dalteparin pre-dialysis interferes with the LPL system as much as, or more than an infusion of UFH does.
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| 11. |
- Näsström, Birgit, et al.
(författare)
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Lipoprotein lipase during continuous heparin infusion : Tissue stores become partially depleted
- 2001
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Ingår i: Journal of Laboratory and Clinical Medicine. - : Elsevier BV. - 0022-2143 .- 1532-6543. ; 138:3, s. 206-213
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Tidskriftsartikel (refereegranskat)abstract
- Lipoprotein lipase (LPL) and hepatic lipase (HL) are located at vascular surfaces in extrahepatic tissues and in the liver, respectively. Heparin displaces the enzymes into the circulating blood. Animal studies have shown that the liver takes up and degrades LPL. To explore whether heparin leads to a depletion of tissue stores, we followed the lipase activities in plasma during an 8-hour primed infusion of heparin in 10 healthy subjects. After an initial peak, the HL activity decreased slowly after a time curve similar to that for activated partial thromboplastin time. The time curve for LPL was different. After the initial peak, the activity dropped by almost 80%, from 30 to 120 minutes, and then leveled off to a plateau that corresponded to about 15% of the peak level. A second bolus of heparin was given to 4 subjects after 4 hours. The plasma LPL activity increased, but only to about 35% of the original peak level. We conclude that when heparin releases LPL into plasma, the lipase becomes liable to be taken up and degraded by the liver. After less than 1 hour, the stores of LPL have been exhausted, and recruitment of lipase into plasma depends on a slow but stable delivery of newly synthesized molecules.
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| 12. |
- Näsström, Birgit, et al.
(författare)
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Lipoprotein lipase during heparin infusion : lower activity in hemodialysis patients
- 2003
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Ingår i: Scandinavian Journal of Clinical and Laboratory Investigation. - 0036-5513 .- 1502-7686. ; 63:1, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: [corrected] Patients on hemodialysis often have a moderate hypertriglyceridemia in combination with low HDL cholesterol. A contributing factor may be a derangement of the lipoprotein lipase (LPL) system. During dialysis, with heparin as anticoagulant, the enzyme is released into the circulating blood. METHODS: We have followed LPL activity and triglycerides during ordinary heparin administration in nine hemodialysis patients and controls matched for age and gender. Blood samples were drawn before heparin administration and at 15, 30, 60, 120, 180 and 240 min. RESULTS: LPL activity peaked at 15 or 30 min and then decreased to a plateau that was only 20%, of the peak. The activity was reduced in the patients by about 50% during the peak, and about 20% during the following plateau. During the peak of lipase activity the triglycerides decreased in both groups, but the change was less pronounced in patients, as was expected from the lower circulating lipase activity. During the plateau phase with low lipase activity, the triglycerides increased towards baseline values. CONCLUSIONS: During hemodialysis with heparin, there is a peak in LPL activity as well as a reduction in triglycerides during the first hour. Thereafter LPL activity decreases towards a plateau, while triglycerides increase towards baseline. The peak activity of LPL in the patients was only half that in controls, while the plateau was comparable. The data indicate that during and following each dialysis there is a period when LPL activity becomes depleted to a level that is limiting for normal lipoprotein metabolism.
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| 13. |
- Näsström, Birgit, et al.
(författare)
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Lipoprotein lipase in hemodialysis patients : indications that low molecular weight heparin depletes functional stores, despite low plasma levels of the enzyme.
- 2004
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Ingår i: BMC Nephrology. - : Springer Science and Business Media LLC. - 1471-2369. ; 5:1, s. 17-
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Lipoprotein lipase (LPL) has a central role in the catabolism of triglyceride-rich lipoproteins. The enzyme is anchored to the vascular endothelium through interaction with heparan sulphate proteoglycans and is displaced from this interaction by heparin. When heparin is infused, there is a peak of LPL activity accompanied by a reduction in triglycerides (TG) during the first hour, followed by a decrease in LPL activity to a stable plateau during the remaining session while TG increase towards and beyond baseline. This suggests that tissue stores of LPL become depleted. It has been argued that low molecular weight (LMW) heparins cause less disturbance of the LPL system than conventional heparin does. METHODS: We have followed LPL activity and TG during a dialysis-session with a LMW heparin (dalteparin) using the same patients and regime as in a previous study with conventional heparin, i.e. a primed infusion. RESULTS: The shape of the curve for LPL activity resembled that during the earlier dialyses with conventional heparin, but the values were lower during dialysis with dalteparin. The area under the curve for LPL activity during the peak period (0-180 minutes) was only 27% and for the plateau period (180-240 minutes) it was only 36% of that observed with conventional heparin (p < 0.01). These remarkably low plasma LPL activities prompted us to re-analyze LPL activity and to measure LPL mass in frozen samples from our earlier studies. There was excellent correlation between the new and old values which rules out the possibility of assay variations as a confounding factor. TG increased from 2.14 mmol/L before, to 2.59 mmol/L after the dialysis (p < 0.01). From 30 minutes on, the TG values were significantly higher after dalteparin compared to conventional heparin (p < 0.05). CONCLUSION: These results indicate that LMW heparins disturb the LPL system as much or more than conventional heparin does.
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| 14. |
- Näsström, Birgit, et al.
(författare)
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Lower plasma levels of lipoprotein lipase after infusion of low molecular weight heparin than after administration of conventional heparin indicate more rapid catabolism of the enzyme
- 2003
-
Ingår i: Journal of Laboratory and Clinical Medicine. - 0022-2143 .- 1532-6543. ; 142:2, s. 90-99
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Tidskriftsartikel (refereegranskat)abstract
- The functional pool of lipoprotein lipase (LPL) is anchored to heparan sulfate at the vascular endothelium. Injection of heparin releases the enzyme into the circulating blood. Animal experiments have shown that the enzyme is then extracted and degraded by the liver. Low molecular weight (LMW) heparin preparations are widely used in the clinic and are supposed to release less LPL. In this study, we infused a LMW heparin into healthy volunteers for 8 hours. The peak of LPL activity was only about 30% and the subsequent plateau of LPL activity only about 40% compared with those seen with conventional heparin. When a bolus of heparin was given after 4 hours' infusion of LMW or conventional heparin, only relatively small, and similar, amounts of LPL entered plasma. This suggests that the difference between LMW and conventional heparin lay in the ability to retain LPL in the circulating blood, not in the ability to release the lipase. Triglycerides (TGs) decreased when the heparin infusion was started, as expected from the high circulating LPL activities. After 1 to 2 hours, TG levels increased again, and after 8 hours they were about twice as high as before the heparin infusion. This indicates that the amount of LPL available for lipoprotein metabolism had become critically low in relation to TG transport rates. This study indicates that LMW heparin compared with conventional heparin causes as much or more depletion of LPL and subsequent impairment of TG clearing.
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| 15. |
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| 16. |
- Näsström, Hampus, et al.
(författare)
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Combinatorial inkjet printing for compositional tuning of metal-halide perovskite thin films
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 10:9, s. 4906-4914
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Tidskriftsartikel (refereegranskat)abstract
- To accelerate the materials discovery and development process for a sustainable technology advancement it is imperative to explore and develop combined high-throughput material synthesis and analysis workflows. In this work, we investigate a method of combinatorial inkjet-printing to tune the composition of the inorganic cesium lead mixed halide perovskite solid solution, CsPb(BrxI1-x)3. The compositional variation is achieved by simultaneous printing of different precursor inks with multiple printheads and controlled by varying the number of droplets printed by each printhead throughout the sample. The droplet placement is optimised through an algorithm that allows maximum mixing of the combined inks. The local compositional homogeneity of thin-film samples was investigated as a function of the printing resolution by micrometer-resolution X-ray fluorescence and synchrotron-based grazing-incidence wide-angle X-ray scattering. We show that a combinatorial library of ten compositions between CsPbI3 and CsPbBr2I, printed using the developed algorithm, is locally homogeneous for the optimised printing parameters. An implementation of the algorithm in the high-level programming language Python is provided for easy use in other systems.
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| 17. |
- Näsström, Thomas, et al.
(författare)
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A Capped Peptide of the Aggregation Prone NAC 71-82 Amino Acid Stretch of α-Synuclein Folds into Soluble β-Sheet Oligomers at Low and Elevated Peptide Concentrations
- 2020
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Ingår i: International Journal of Molecular Sciences. - Basel, Switzerland : MDPI. - 1661-6596 .- 1422-0067. ; 21:5
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Tidskriftsartikel (refereegranskat)abstract
- Although Lewy bodies and Lewy neurites are hallmarks of Parkinson's disease (PD) and dementia with Lewy bodies (DLB), misfolded α-synuclein oligomers are nowadays believed to be key for the development of these diseases. Attempts to target soluble misfolded species of the full-length protein have been limited so far, probably due to the fast aggregation kinetics and burial of aggregation prone segments in final cross-β-sheet fibrils. A previous characterisation study of fibrils prepared from a capped peptide of the non-amyloid β-component (NAC) 71-82 amino acid stretch of α-synuclein demonstrated an increased aggregation propensity resulting in a cross-β-structure that is also found in prion proteins. From this, it was suggested that capped NAC 71-82 peptide oligomers would provide interesting motifs with a capacity to regulate disease development. Here, we demonstrated, from a series of circular dichroism spectroscopic measurements and molecular dynamics simulations, the molecular-environment-sensitive behaviour of the capped NAC 71-82 peptide in a solution phase and the formation of β-sheet oligomeric structures in the supernatant of a fibrillisation mixture. These results highlighted the use of the capped NAC 71-82 peptide as a motif in the preparation of oligomeric β-sheet structures that potentially could be used in therapeutic strategies in the fight against progressive neurodegenerative disorders, such as PD and DLB.
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| 18. |
- Näsström, Thomas, et al.
(författare)
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Amyloid fibrils prepared using an acetylated and methyl amidated peptide model of the alpha-Synuclein NAC 71-82 amino acid stretch contain an additional cross-beta structure also found in prion proteins
- 2019
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 9, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- The 71-82 fragment of the non-amyloid-beta component (NAC) region of the Parkinson's disease (PD) and dementia with Lewy bodies (DLB) related protein alpha-Synuclein, has been reported to be important during protein misfolding. Although reports have demonstrated the importance of this fragment for the aggregation properties of the full-length protein, its exact role in pre-fibrillar oligomerisation, fibrillar growth and morphology has not yet been fully elucidated. Here, we provide evidence that fibrils prepared from an acetylated and methyl amidated peptide of the NAC 71-82 amino acid stretch of alpha-Synuclein are amyloid and contain, in addition to the cross-beta structure detected in the full-length protein fibrils, a cross-beta structure previously observed in prion proteins. These results shed light on the aggregation propensity of the NAC 71-82 amino acid stretch of the full-length protein but also the roles of the N- and C-terminal domains of alpha-Synuclein in balancing this aggregation propensity. The results also suggest that early aggregated forms of the capped NAC 71-82 peptide generated structures were stabilised by an anti-parallel and twisted beta-sheet motif. Due to its expected toxicity, this beta-sheet motif may be a promising molecular target for the development of therapeutic strategies for PD and DLB.
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| 19. |
- Näsström, Thomas, et al.
(författare)
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Antibodies against alpha-synuclein reduce oligomerization in living cells
- 2011
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:10, s. e27230-
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Tidskriftsartikel (refereegranskat)abstract
- Recent research implicates soluble aggregated forms of α-synuclein as neurotoxic species with a central role in the pathogenesis of Parkinson’s disease and related disorders. The pathway by which α-synuclein aggregates is believed to follow a step-wise pattern, in which dimers and smaller oligomers are initially formed. Here, we used H4 neuroglioma cells expressing α-synuclein fused to hemi:GFP to study the effects of α-synuclein monoclonal antibodies on the early stages of aggregation, as quantified by Bimolecular Fluorescence Complementation assay. Widefield and confocal microscopy revealed that cells treated for 48 h with monoclonal antibodies internalized antibodies to various degrees. Oligomer-selective and C-terminal specific α-synuclein antibodies reduced the extent of α-synuclein dimerization/oligomerization, as indicated by decreased GFP fluorescence signal. Furthermore, ELISA measurements on lysates and conditioned media from antibody treated cells displayed lower α-synuclein levels compared to untreated cells, suggesting increased protein turnover. Taken together, our results propose that extracellular administration of monoclonal antibodies can modify or inhibit early steps in the aggregation process of α-synuclein, thus providing further support for passive immunization against diseases with α-synuclein pathology.
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| 20. |
- Näsström, Thomas
(författare)
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Characterization of α-synuclein oligomers : Implications for Lewy Body Disorders
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Parkinson’s disease, dementia with Lewy bodies and multiple system atrophy are disorders featuring accumulation of Lewy bodies in brain. The main component of these large insoluble intracellular inclusions is the presynaptic protein alpha-synuclein (α-synuclein). It is generally believed that α-synuclein monomers adopt an abnormal conformation that favors the formation of soluble oligomers or protofibrils and, eventually, insoluble fibrils depositing as Lewy bodies. Notably, the intermediately sized oligomers/protofibrils seem to have particular neurotoxic effects. Several factors may influence the formation of α-synuclein oligomers/protofibrils, e.g. the reactive aldehydes 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE) formed during oxidative stress. The overall aims of this thesis were to investigate biophysical and biochemical properties of in vitro generated α-synuclein oligomers, characterize their functional effects on cell and animal disease models as well as to explore whether their formation could be prevented in a cell culture model for oligomerization. Here, it was found that α-synuclein rapidly formed oligomers after incubation with both ONE and HNE. The resulting oligomers were stable and did not continue to form insoluble fibrils. By comparing HNE- and ONE induced α-synuclein oligomers biochemically they were both found to exhibit extensive β-beta sheet structure and had a molecular size of ~2000 kDa. However, they differed in morphology; the ONE induced α-synuclein oligomers described round amorphous species whereas the HNE induced α-synuclein oligomers appeared as elongated protofibril-like structures. Both these oligomers were cell internalized to varying degrees and induced toxicity in neuroblastoma cells. In addition, the ONE induced α-synuclein oligomers seemed to initiate aggregation of monomeric α-synuclein in vitro, but failed to do so in vivo. Finally, treatment of α-synuclein overexpressing cells with monoclonal antibodies specific for α-synuclein significantly reduced aggregation and lowered levels of the protein, suggesting increased turnover in these cells. To conclude, this thesis has characterized different oligomeric α-synuclein species, which may have properties similar to soluble species central to the pathogenesis of Parkinson’s disease and other disorders with α-synuclein pathology. For therapeutic strategies it is important to selectively target such harmful protein species and avoid interaction with other forms of α-synuclein, which may have vital physiological cellular functions.
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| 21. |
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| 22. |
- Näsström, Thomas, et al.
(författare)
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Synthetic NAC 71-82 Peptides Designed to Produce Fibrils with Different Protofilament Interface Contacts
- 2021
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 22:17
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Tidskriftsartikel (refereegranskat)abstract
- Alpha-synucleinopathies are featured by fibrillar inclusions in brain cells. Although α-synuclein fibrils display structural diversity, the origin of this diversity is not fully understood. We used molecular dynamics simulations to design synthetic peptides, based on the NAC 71-82 amino acid fragment of α-synuclein, that govern protofilament contacts and generation of twisted fibrillar polymorphs. Four peptides with structures based on either single or double fragments and capped or non-capped ends were selected for further analysis. We determined the fibrillar yield and the structures from these peptides found in the solution after fibrillisation using protein concentration determination assay and circular dichroism spectroscopy. In addition, we characterised secondary structures formed by individual fibrillar complexes using laser-tweezers Raman spectroscopy. Results suggest less mature fibrils, based on the lower relative β-sheet content for double- than single-fragment peptide fibrils. We confirmed this structural difference by TEM analysis which revealed, in addition to short protofibrils, more elongated, twisted and rod-like fibril structures in non-capped and capped double-fragment peptide systems, respectively. Finally, time-correlated single-photon counting demonstrated a difference in the Thioflavin T fluorescence lifetime profiles upon fibril binding. It could be proposed that this difference originated from morphological differences in the fibril samples. Altogether, these results highlight the potential of using peptide models for the generation of fibrils that share morphological features relevant for disease, e.g., twisted and rod-like polymorphs.
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| 23. |
- Näsström, Thomas, et al.
(författare)
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The lipid peroxidation metabolite 4-oxo-2-nonenal cross-links alpha-synuclein causing rapid formation of stable oligomers
- 2009
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Ingår i: Biochemical and Biophysical Research Communications - BBRC. - : Elsevier BV. - 0006-291X .- 1090-2104. ; 378:4, s. 872-876
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Tidskriftsartikel (refereegranskat)abstract
- Recently, the aldehyde 4-oxo-2-nonenal (ONE) was identified as a product of lipid peroxidation and found to be an effective protein modifier. In this in vitro study we investigated structural implications of the interaction between ONE and alpha-synuclein, a protein which forms intraneuronal inclusions in neurodegenerative disorders such as Parkinson's disease and dementia with Lewy bodies. Our results demonstrate that ONE induced an almost complete conversion of monomeric alpha-synuclein into 40-80 nm wide and 6-8 nm high soluble beta-sheet-rich oligomers with a molecular weight of approximately 2000 kDa. Furthermore, the ONE-induced alpha-synuclein oligomers displayed a high stability and were not sensitive to treatment with sodium dodecyl sulfate, indicating that ONE stabilized the oligomers by cross-linking individual alpha-synuclein molecules. Despite prolonged incubation the oligomers did not continue to aggregate into a fibrillar state, thus suggesting that these alpha-synuclein species were not on a fibrillogenic pathway.
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| 24. |
- Näsström, Thomas, et al.
(författare)
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The lipid peroxidation products 4-oxo-2-nonenal and 4-hydroxy-2-nonenal promote the formation of α-synuclein oligomers with distinct biochemical, morphological, and functional properties
- 2011
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Ingår i: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849 .- 1873-4596. ; 50:3, s. 428-437
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Tidskriftsartikel (refereegranskat)abstract
- Oxidative stress has been implicated in the etiology of neurodegenerative disorders with alpha-synuclein pathology. Lipid peroxidation products such as 4-oxo-2-nonenal (ONE) and 4-hydroxy-2-nonenal (HNE) can covalently modify and structurally alter proteins. Herein, we have characterized ONE- or HNE-induced alpha-synuclein oligomers. Our results demonstrate that both oligomers are rich in beta-sheet structure and have a molecular weight of about 2000 kDa. Atomic force microscopy analysis revealed that ONE-induced alpha-synuclein oligomers were relatively amorphous, with a diameter of 40-80 nm and a height of 4-8 nm. In contrast, the HNE-induced alpha-synuclein oligomers had a protofibril-like morphology with a width of 100-200 nm and a height of 2-4 nm. Furthermore, neither oligomer type polymerized into amyloid-like fibrils despite prolonged incubation. Although more SDS and urea stable, because of a higher degree of cross-linking, ONE-induced alpha-synuclein oligomers were less compact and more sensitive to proteinase K treatment. Finally, both ONE- and HNE-induced alpha-synuclein oligomers were cytotoxic when added exogenously to a neuroblastoma cell line, but HNE-induced alpha-synuclein oligomers were taken up by the cells to a significantly higher degree. Despite nearly identical chemical structures, ONE and HNE induce the formation of off-pathway alpha-synuclein oligomers with distinct biochemical, morphological, and functional properties.
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| 25. |
- Seidel, André, et al.
(författare)
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Added value by hybrid additive manufacturing and advanced manufacturing approaches
- 2018
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Ingår i: Journal of laser applications. - : American Institute of Physics (AIP). - 1042-346X .- 1938-1387. ; 26:2, s. 6-8
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Tidskriftsartikel (refereegranskat)abstract
- In order to lead to a competitive advantage, there is the need to carefully consider the pros and cons of state-of-the-art manufacturing techniques. This is frequently carried out in a competitive manner, but can also be done in a complementary way. This complementary approach is often used for the processing of difficult-to-machine materials with particular regard to high-tech parts or components. Hybrid machining processes or, more general, advanced machining processes can be brought to the point that the results would not be possible with the individual constituent processes in isolation [Hybrid Machining Processes Perspectives on Machining and Finishing (Springer International Publishing AG, 2016)]. Hence, the controlled interaction of process mechanisms and/or energy sources is frequently applied for a significant increase of the process performance [Advanced Machining Processes of Metallic Materials: Theory, Modelling, and Applications, 2nd ed. (2016)] and will be addressed within the present paper. A via electron beam melting manufactured gamma titanium aluminide nozzle is extended and adapted. This is done via hybrid laser metal deposition. The presented approach considers critical impacts like processing temperatures, temperature gradients, and solidification conditions with particular regard to crucial material properties like the phenomena of lamellar interface cracking [Laser-Based Manufacturing of Components using Materials with High Cracking Susceptibility (Laser Institute of America–LIA), pp. 586–592; Ti-2015: The 13th World Conference on Titanium, Symposium 5]. Furthermore, selected destructive and non-destructive testing is performed in order to prove the material properties. Finally, the results will be evaluated. This will also be done in the perspective of other applications.
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| 26. |
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