| 1. |
- Dentoni, Giacomo, et al.
(författare)
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Mitochondrial Alterations in Neurons Derived from the Murine AppNL-F Knock-In Model of Alzheimer's Disease
- 2022
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 90:2, s. 565-583
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Tidskriftsartikel (refereegranskat)abstract
- Background:Alzheimer’s disease (AD) research has relied on mouse models overexpressing human mutant A βPP; however, newer generation knock-in models allow for physiological expression of amyloid-β protein precursor (AβPP) containing familial AD mutations where murine AβPP is edited with a humanized amyloid-β (Aβ) sequence. The AppNL-F mouse model has shown substantial similarities to AD brains developing late onset cognitive impairment.Objective:In this study, we aimed to characterize mature primary cortical neurons derived from homozygous AppNL-F embryos, especially to identify early mitochondrial alterations in this model.Methods:Primary cultures of AppNL-F neurons kept in culture for 12–15 days were used to measure Aβ levels, secretase activity, mitochondrial functions, mitochondrial-ER contacts, synaptic function, and cell death.Results:We detected higher levels of Aβ42 released from AppNL-F neurons as compared to wild-type neurons. AppNL-F neurons, also displayed an increased Aβ42/Aβ40 ratio, similar to adult AppNL-F mouse brain. Interestingly, we found an upregulation in mitochondrial oxygen consumption with concomitant downregulation in glycolytic reserve. Furthermore, AppNL-F neurons were more susceptible to cell death triggered by mitochondrial electron transport chain inhibition. Juxtaposition between ER and mitochondria was found to be substantially upregulated, which may account for upregulated mitochondrial-derived ATP production. However, anterograde mitochondrial movement was severely impaired in this model along with loss in synaptic vesicle protein and impairment in pre- and post-synaptic function.Conclusion:We show that widespread mitochondrial alterations can be detected in AppNL-F neurons in vitro, where amyloid plaque deposition does not occur, suggesting soluble and oligomeric Aβ-species being responsible for these alterations.
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| 2. |
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| 3. |
- Zyśk, Marlena, et al.
(författare)
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Amyloid-beta accumulation in human astrocytes induces mitochondrial disruption and changed energy metabolism
- 2023
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Ingår i: Journal of Neuroinflammation. - : BioMed Central (BMC). - 1742-2094. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Background: Astrocytes play a central role in maintaining brain energy metabolism, but are also tightly connected to the pathogenesis of Alzheimer's disease (AD). Our previous studies demonstrate that inflammatory astrocytes accumulate large amounts of aggregated amyloid-beta (A beta). However, in which way these A beta deposits influence their energy production remain unclear.Methods: The aim of the present study was to investigate how A beta pathology in astrocytes affects their mitochondria functionality and overall energy metabolism. For this purpose, human induced pluripotent cell (hiPSC)-derived astrocytes were exposed to sonicated A beta(42) fibrils for 7 days and analyzed over time using different experimental approaches.Results: Our results show that to maintain stable energy production, the astrocytes initially increased their mitochondrial fusion, but eventually the A beta-mediated stress led to abnormal mitochondrial swelling and excessive fission. Moreover, we detected increased levels of phosphorylated DRP-1 in the A beta-exposed astrocytes, which co-localized with lipid droplets. Analysis of ATP levels, when blocking certain stages of the energy pathways, indicated a metabolic shift to peroxisomal-based fatty acid beta-oxidation and glycolysis.Conclusions: Taken together, our data conclude that A beta pathology profoundly affects human astrocytes and changes their entire energy metabolism, which could result in disturbed brain homeostasis and aggravated disease progression.
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| 4. |
- Alikhani, Nyosha, et al.
(författare)
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Mitochondria and Alzheimer's disease : amyloid-beta peptide uptake and degradation by the presequence protease, hPreP
- 2009
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Ingår i: Journal of Bioenergetics and Biomembranes. - : Springer Science and Business Media LLC. - 0145-479X .- 1573-6881. ; 41:5, s. 447-451
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Tidskriftsartikel (refereegranskat)abstract
- Several lines of evidence suggest mitochondrial dysfunction as a possible underlying mechanism of Alzheimer's disease (AD). Accumulation of the amyloid-beta peptide (Abeta), a neurotoxic peptide implicated in the pathogenesis of AD, has been detected in brain mitochondria of AD patients and AD transgenic mouse models. In vitro evidence suggests that the Abeta causes mitochondrial dysfunction e.g. oxidative stress, mitochondrial fragmentation and decreased activity of cytochrome c oxidase and TCA cycle enzymes. Here we review the link between mitochondrial dysfunctions and AD. In particular we focus on the mechanism for Abeta uptake by mitochondria and on the recently identified Abeta degrading protease in human brain mitochondria.
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| 5. |
- Ankarcrona, Maria
(författare)
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Mechanisms of apoptosis in secretory and neuronal cells : role of oxidative stress and calcium overload
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Apoptosis is a widespread physiological mechanism to regulate tissue homeostasis both during development and in adult organs. However, the cell deletion program can be inappropriately activated or suppressed under pathological conditions. The present project was designed to study the role of apoptosis in the toxicity caused by oxidative stress and calcium overload. The effects of the free radical nitric oxide (NO ) were studied in a pancreatic beta-cell line (RlNm5F). The NO-releasing compound sodium nitroprusside or interleukin-lbeta (IL-Ibeta) induced endogenous NO-production, stimulated inhibitory auto-ADP-ribosylation of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). At later time-points RlNm5F cells exposed to NO underwent apoptosis. Inhibition of the nitric oxide synthase activity by NG-monomethyl-L-arginine prevented IL-1beta-induced NO generation and apoptotic cell killing. DNA-damage, caused by irradiation or free radicals, can stimulate expression of the tumor suppressor gene p53. The p53 protein is believed to produce growth arrest in G1-S which allows DNA-repair. However, such conditions have also been shown to favor the occurrence of apoptosis. We detected accumulation of the p53 protein prior to onset of apoptosis both in RINm5F cells and RAW 264.7 macrophages. To further characterize the mechanisms involved in the deletion of pancreatic cells during oxidative stress we used 2,3-dimethoxy-1,4-naphthoquinone (DMNQ). We found that DMNQ, depending on the dose, induced cell proliferation, apoptosis or necrosis. Cell proliferation was associated with induction of enzymes involved in intracellular polyaminesynthesis (i.e. ornithine decarboxylase, ODC and S-adenosyl-L-methionine decarboxylase, SAMDC). Conversely, prior to the onset of apoptosis, ODC- and SAMDC activities decreased and cells were rapidly depleted of polyamines. Interestingly, cells were protected from apoptosis when incubated with the phorbol ester TPA to induce ODC and SAMDC or by supplementing spermine. Oxidative stress, calcium overload and NO-production have also been implicated in neuronal damage following ischemia. Thus, primary cultures of cerebellar granule cells (CGC) were used to further study the mechanisms of glutamate-induced cell killing. Part of the CGC population exposed to glutamate rapidly lost their mitochondrial membrane potential and died by necrosis. The surviving population recovered their mitochondrial membrane potential but later underwent apoptosis. Nuclear lamins were degraded prior to DNA-fragmentation, indicating an early activation of proteases in cells triggered to undergo apoptosis. Further studies suggested that protection from loss of mitochondrial membrane potential as well as inhibition of the phosphatase calcineurin play important roles in both necrotic and apoptotic neuronal death. In conclusion, this thesis presents evidence that apoptosis is an important determinant of cell death both in pancreatic and neuronal cells exposed to oxidative stress or calcium overload. Onset of apoptosis was under different conditions associated with depletion of intracellular polyamines, accumulation of p53 or degradation of nuclear larnins. Depending on the dose and duration of exposure as well as cell sensitivity, cells died by apoptosis or necrosis in both systems used. Neuronal apoptosis was shown to be dependent on intact mitochondria supplying energy, while neurons dying by necrosis rapidly lost their mitochondrial membrane potential and were depleted of energy.
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| 6. |
- Ankarcrona, Victoria, et al.
(författare)
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Episiotomy in vacuum extraction, do we cut the levator ani muscle? : A prospective cohort study
- 2022
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Ingår i: International Urogynecology Journal. - : Springer Nature. - 0937-3462 .- 1433-3023. ; 33:12, s. 3391-3399
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Tidskriftsartikel (refereegranskat)abstract
- Introduction and hypothesis Vaginal delivery may lead to levator ani muscle (LAM) injury or avulsion. Episiotomy may reduce obstetric anal sphincter injury in operative vaginal delivery, but may increase the risk of LAM injury. Our aim was to assess whether lateral episiotomy in vacuum extraction (VE) in primiparous women causes LAM injury. Methods A prospective cohort study of 58 primiparous women with episiotomy nested within an ongoing multicenter randomized controlled trial of lateral episiotomy versus no episiotomy in VE (EVA trial) was carried out in Sweden. LAM injury was evaluated using 3D endovaginal ultrasound 6-12 months after delivery and Levator Ani Deficiency (LAD) score. Episiotomy scar properties were measured. Characteristics were described and compared using Chi-squared tests. We stipulated that if a lateral episiotomy cuts the LAM, >= 50% would have a LAM injury. Among those, >= 50% would be side specific. We compared the observed prevalence with a test of one proportion. Results Twelve (20.7%, 95% CI 10.9-32.9) of 58 women had a LAD (p < 0.001, compared with the stipulated 50%). Six (50.0%, 95% CI 21.1% to 78.9%) of 12 women had a LAD on the episiotomy side, including those with bilateral LAD (p = 1.00). Two (16.7%, 95% CI 2.1% to 48.4%) of 12 women had a LAD exclusively on the episiotomy side (p = 0.02). Conclusions There was no excessive risk of cutting the LAM while performing a lateral episiotomy. LAD was not seen in women with episiotomies shorter than 18 mm.
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| 7. |
- Bergendahl, Sandra, et al.
(författare)
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Lateral episiotomy or no episiotomy in vacuum assisted delivery in nulliparous women (EVA) : multicentre, open label, randomised controlled trial
- 2024
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Ingår i: BMJ. British Medical Journal. - : BMJ Publishing Group Ltd. - 0959-8146 .- 0959-535X. ; 385, s. e079014-
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To assess the effect of lateral episiotomy, compared with no episiotomy, on obstetric anal sphincter injury in nulliparous women requiring vacuum extraction. Design: A multicentre, open label, randomised controlled trial.Setting: Eight hospitals in Sweden, 2017-23.Participants: 717 nulliparous women with a single live fetus of 34 gestational weeks or more, requiring vacuum extraction were randomly assigned (1:1) to lateral episiotomy or no episiotomy using sealed opaque envelopes. Randomisation was stratified by study site.Intervention: A standardised lateral episiotomy was performed during the vacuum extraction, at crowning of the fetal head, starting 1-3 cm from the posterior fourchette, at a 60° (45-80°) angle from the midline, and 4 cm (3-5 cm) long. The comparison was no episiotomy unless considered indispensable.Main outcome measures: The primary outcome of the episiotomy in vacuum assisted delivery (EVA) trial was obstetric anal sphincter injury, clinically diagnosed by combined visual inspection and digital rectal and vaginal examination. The primary analysis used a modified intention-to-treat population that included all consenting women with attempted or successful vacuum extraction. As a result of an interim analysis at significance level P<0.01, the primary endpoint was tested at 4% significance level with accompanying 96% confidence interval (CI).Results: From 1 July 2017 to 15 February 2023, 717 women were randomly assigned: 354 (49%) to lateral episiotomy and 363 (51%) to no episiotomy. Before vacuum extraction attempt, one woman withdrew consent and 14 had a spontaneous birth, leaving 702 for the primary analysis. In the intervention group, 21 (6%) of 344 women sustained obstetric anal sphincter injury, compared with 47 (13%) of 358 women in the comparison group (P=0.002). The risk difference was -7.0% (96% CI -11.7% to -2.5%). The risk ratio adjusted for site was 0.47 (96% CI 0.23 to 0.97) and unadjusted risk ratio was 0.46 (0.28 to 0.78). No significant differences were noted between groups in postpartum pain, blood loss, neonatal outcomes, or total adverse events, but the intervention group had more wound infections and dehiscence.Conclusions: Lateral episiotomy can be recommended for nulliparous women requiring vacuum extraction to significantly reduce the risk of obstetric anal sphincter injury. Trial registration: ClinicalTrials.gov NCT02643108.
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| 8. |
- Falkevall, Annelie, et al.
(författare)
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Degradation of the amyloid beta-protein by the novel mitochondrial peptidasome, PreP
- 2006
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 281:39, s. 29096-29104
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Tidskriftsartikel (refereegranskat)abstract
- Recently we have identified the novel mitochondrial peptidase responsible for degrading presequences and other short unstructured peptides in mitochondria, the presequence peptidase, which we named PreP peptidasome. In the present study we have identified and characterized the human PreP homologue, hPreP, in brain mitochondria, and we show its capacity to degrade the amyloid beta-protein (Abeta). PreP belongs to the pitrilysin oligopeptidase family M16C containing an inverted zinc-binding motif. We show that hPreP is localized to the mitochondrial matrix. In situ immuno-inactivation studies in human brain mitochondria using anti-hPreP antibodies showed complete inhibition of proteolytic activity against Abeta. We have cloned, overexpressed, and purified recombinant hPreP and its mutant with catalytic base Glu(78) in the inverted zinc-binding motif replaced by Gln. In vitro studies using recombinant hPreP and liquid chromatography nanospray tandem mass spectrometry revealed novel cleavage specificities against Abeta-(1-42), Abeta-(1-40), and Abeta Arctic, a protein that causes increased protofibril formation an early onset familial variant of Alzheimer disease. In contrast to insulin degrading enzyme, which is a functional analogue of hPreP, hPreP does not degrade insulin but does degrade insulin B-chain. Molecular modeling of hPreP based on the crystal structure at 2.1 A resolution of AtPreP allowed us to identify Cys(90) and Cys(527) that form disulfide bridges under oxidized conditions and might be involved in redox regulation of the enzyme. Degradation of the mitochondrial Abeta by hPreP may potentially be of importance in the pathology of Alzheimer disease.
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| 9. |
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| 10. |
- Hansson Petersen, Camilla A., et al.
(författare)
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The amyloid beta-peptide is imported into mitochondria via the TOM import machinery and localized to mitochondrial cristae
- 2008
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 105:35, s. 13145-13150
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Tidskriftsartikel (refereegranskat)abstract
- The amyloid beta-peptide (Abeta) has been suggested to exert its toxicity intracellularly. Mitochondrial functions can be negatively affected by Abeta and accumulation of Abeta has been detected in mitochondria. Because Abeta is not likely to be produced locally in mitochondria, we decided to investigate the mechanisms for mitochondrial Abeta uptake. Our results from rat mitochondria show that Abeta is transported into mitochondria via the translocase of the outer membrane (TOM) machinery. The import was insensitive to valinomycin, indicating that it is independent of the mitochondrial membrane potential. Subfractionation studies following the import experiments revealed Abeta association with the inner membrane fraction, and immunoelectron microscopy after import showed localization of Abeta to mitochondrial cristae. A similar distribution pattern of Abeta in mitochondria was shown by immunoelectron microscopy in human cortical brain biopsies obtained from living subjects with normal pressure hydrocephalus. Thus, we present a unique import mechanism for Abeta in mitochondria and demonstrate both in vitro and in vivo that Abeta is located to the mitochondrial cristae. Importantly, we also show that extracellulary applied Abeta can be internalized by human neuroblastoma cells and can colocalize with mitochondrial markers. Together, these results provide further insight into the mitochondrial uptake of Abeta, a peptide considered to be of major significance in Alzheimer's disease.
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