| 1. |
- Correa, Fernando, et al.
(författare)
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Activated microglia decrease histone acetylation and Nrf2-inducible anti-oxidant defence in astrocytes: Restoring effects of inhibitors of HDACs, p38 MAPK and GSK3β.
- 2011
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Ingår i: Neurobiology of disease. - : Elsevier BV. - 1095-953X .- 0969-9961. ; 44:1, s. 142-51
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Tidskriftsartikel (refereegranskat)abstract
- Histone deacetylase (HDAC) inhibitors have promising neuroprotective and anti-inflammatory properties although the exact mechanisms are unclear. We have earlier showed that factors from lipopolysaccharide (LPS)-activated microglia can down-regulate the astroglial nuclear factor-erythroid 2-related factor 2 (Nrf2)-inducible anti-oxidant defence. Here we have evaluated whether histone modification and activation of GSK3β are involved in these negative effects of microglia. Microglia were cultured for 24h in serum-free culture medium to achieve microglia-conditioned medium from non-activated cells (MCM(0)) or activated with 10ng/mL of LPS to produce MCM(10). Astrocyte-rich cultures treated with MCM(10) showed a time-dependent (0-72h) increase in astroglial HDAC activity that correlated with lower levels of acetylation of histones H3 and H4 and decreased levels of the transcription factor Nrf2 and γ-glutamyl cysteine ligase modulatory subunit (γGCL-M) protein levels. The HDAC inhibitors valproic acid (VPA) and trichostatin-A (TSA) elevated the histone acetylation levels, restored the Nrf2-inducible anti-oxidant defence and conferred protection from oxidative stress-induced (H(2)O(2)) death in astrocyte-rich cultures exposed to MCM(10). Inhibitors of GSK3β (lithium) and p38 MAPK (SB203580) signaling pathways restored the depressed histone acetylation and Nrf2-related transcription whereas an inhibitor of Akt (Ly294002) caused a further decrease in Nrf2-related transcription. In conclusion, the study shows that well tolerated drugs such as VPA and lithium can restore an inflammatory induced depression in the Nrf2-inducible antioxidant defence, possibly via normalised histone acetylation levels.
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| 2. |
- Correa, Fernando, et al.
(författare)
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Dual TNF alpha-Induced Effects on NRF2 Mediated Antioxidant Defence in Astrocyte-Rich Cultures: Role of Protein Kinase Activation
- 2012
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Ingår i: Neurochemical Research. - : Springer Science and Business Media LLC. - 0364-3190 .- 1573-6903. ; 37:12, s. 2842-2855
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Tidskriftsartikel (refereegranskat)abstract
- Tumor necrosis factor-alpha (TNF alpha) is a pleiotropic molecule that can have both protective and detrimental effects in neurodegeneration. Here we have investigated the temporal effects of TNF alpha on the inducible Nrf2 system in astrocyte-rich cultures by determination of glutathione (GSH) levels, gamma glutamylcysteine ligase (gamma GCL) activity, the protein levels of Nrf2, Keap1, the catalytic and modulatory subunit of gamma GCL (gamma GCL-C and gamma GCL-M respectively). Astrocyte-rich cultures were exposed for 24 or 72 h to different concentrations of TNF alpha. Acute exposure (24 h) of astrocyte-rich cultures to 10 ng/mL of TNF alpha increased GSH, gamma GCL activity, the protein levels of gamma GCL-M, gamma GCL-C and Nrf2 in parallel with decreased levels of Keap1. Antioxidant responsive element (ARE)-mediated transcription was blocked by inhibitors of ERK1/2, JNK and Akt whereas inactivation of p38 and GSK3 beta further enhanced transcription. In contrast treatment with TNF alpha for 72 h decreased components of the Nrf2 system in parallel with an increase of Keap1. Stimulation of the Nrf2 system by tBHQ was intact after 24 h but blocked after 72 h treatment with TNF alpha. This down-regulation after 72 h correlated with activation of p38 MAPK and GSK3 beta, since inhibition of these signalling pathways reversed this effect. The upregulation of the Nrf2 system by TNF alpha (24 h treatment) protected the cells from oxidative stress through elevated gamma GCL activity whereas the down-regulation (72 h treatment) caused pronounced oxidative toxicity. One of the important implications of the results is that in a situation where Nrf2 is decreased, such as in Alzheimer's disease, the effect of TNF alpha is detrimental.
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| 3. |
- Correa, Fernando, et al.
(författare)
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The Nrf2-inducible antioxidant defense in astrocytes can be both up- and down-regulated by activated microglia:Involvement of p38 MAPK.
- 2011
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Ingår i: Glia. - : Wiley. - 1098-1136 .- 0894-1491. ; 59:5, s. 785-99
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Tidskriftsartikel (refereegranskat)abstract
- The effects of microglia-conditioned medium (MCM) on the inducible Nrf2 system in astrocyte-rich cultures were investigated by determination of glutathione (GSH) levels, γglutamylcysteine ligase (γGCL) activity, the protein levels of Nrf2, Keap1, the modulatory subunit of γGCL (γGCL-M) and activated MAP kinases (ERK1/2, JNK and p38). Microglia were either cultured for 24 h in serum-free culture medium to achieve microglia-conditioned medium from non-activated cells (MCM(0) ), used as control condition, or activated with different concentrations (0.1-1,000 ng mL(-1) ) of lipopolysaccharide (LPS) to produce MCM(0.1-1,000) . Acute exposure (24 h) to MCM(100) increased GSH, γGCL activity, the protein levels of γGCL-M, Nrf2, and activated JNK and ERK1/2 in astrocyte-rich cultures. In contrast, treatment with MCM(10) for 24 h decreased components of the Nrf2 system in parallel with activation of p38 MAPK. Stimulation of the Nrf2 system by tBHQ was partly intact after 24 h but blocked after 72 h treatment with MCM(10) and MCM(100) . This down-regulation after 72 h correlated with activation of p38 MAPK and lack of ERK1/2 and JNK activation. The negative effects were partly reversed by an inhibitor of p38 which restored tBHQ mediated protection against oxidative stress. In conclusion, the study showed a negative effect of MCM(10) on the inducible anti-oxidant defense in astrocyte-rich cultures at both 24 and 72 h that correlated with activation of p38 and was partly reversed by a p38 inhibitor. A transient protective effect of MCM(100) on astrocyte-rich cultures against H(2)O(2) toxicity was observed at 24 h which coincided with activation of JNK and ERK1/2.
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| 4. |
- Correa, Fernando, et al.
(författare)
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Time-Dependent Effects of Systemic Lipopolysaccharide Injection on Regulators of Antioxidant Defence Nrf2 and PGC-1α in the Neonatal Rat Brain.
- 2013
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Ingår i: Neuroimmunomodulation. - : S. Karger AG. - 1423-0216 .- 1021-7401. ; 20:4, s. 185-193
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Tidskriftsartikel (refereegranskat)abstract
- Background/Aims: Both excitotoxicity and neuroinflammation are associated with oxidative stress. One transcription factor, nuclear factor E2-related factor 2 (Nrf2), and one transcription cofactor, peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α), increase the endogenous antioxidant defence and can thus modulate neuronal cell death. Here, we investigated the temporal effects (after 24 and 72 h) of systemic (i.p.) administration of lipopolysaccharide (LPS) on the cerebral Nrf2 and PGC-1α systems. Methods and Results: Seven-day-old rat pups were injected with LPS (0.3 mg/kg). After 24 h, the protein levels of γ-glutamylcysteine ligase modulatory subunit, γ-glutamylcysteine ligase catalytic subunit, Nrf2, PGC-1α and manganese superoxide dismutase (MnSOD) were increased in parallel with decreased levels of Keap1. These effects were correlated with an increased level of phosphorylated Akt and elevated acetylation of histone 4. In contrast, 72 h following LPS, a decrease in the components of the Nrf2 system in parallel with an increase in Keap1 was observed. The down-regulation after 72 h correlated with phosphorylation of p38 mitogen-activated protein kinase, while there were no changes in PGC-1α and MnSOD protein levels or the acetylation/methylation pattern of histones. Conclusion: Systemic LPS in neonatal rats induced time-dependent changes in brain Nrf2 and PGC-1α that correlated well with the protective effect observed after 24 h (pre-conditioning) and the deleterious effects observed after 72 h (sensitizing) of systemic LPS reported earlier. Collectively, the results point towards Nrf2 and PGC-1α as a possible mechanism behind these effects.
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| 5. |
- D'angelo, Barbara, et al.
(författare)
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Expression of the Nrf2-system at the blood-CSF barrier is modulated by neonatal inflammation and hypoxia-ischemia
- 2013
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Ingår i: Journal of Inherited Metabolic Disease. - : Wiley. - 0141-8955 .- 1573-2665. ; 36:3, s. 479-490
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Tidskriftsartikel (refereegranskat)abstract
- ORIGINAL ARTICLE Expression of the Nrf2-system at the blood-CSF barrier is modulated by neonatal inflammation and hypoxia-ischemia Barbara D ’ Angelo & C. Joakim Ek & Mats Sandberg & Carina Mallard Received: 29 May 2012 /Revised: 14 September 2012 /Accepted: 10 October 2012 /Published online: 30 October 2012 # SSIEM and Springer Science+Business Media Dordrecht 2012 Abstract Transcription factor NF-E2-related factor-2 (Nrf2) is a key regulator of endogenous anti-oxidant sys- tems shown to play a neuroprotective role in the adult by preserving blood – brain barrier function. The choroid plex- us, site for the blood-CSF barrier, has been suggested to be particularly important in maintaining brain barrier function in development. We investigated the expression of Nrf2- and detoxification-system genes in choroid plexus following systemic LPS injections, unilateral cerebral hypoxia- ischemia (HI) as well as the combination of LPS and HI (LPS/HI). Plexuses were collected at different time points after LPS, HI and LPS/HI in 9-day old mice. mRNA levels of Nrf2 and many of its target genes were analyzed by quantitative PCR. Cell death was analyzed by caspase-3 immunostaining and TUNEL. LPS caused down-regulation of the Nrf2-system genes while HI increased expression at earlier time points. LPS exposure prior to HI prevented many of the HI-induced gene increases. None of the insults resulted in any apparent cell death to choroidal epithelium. These data imply that the function of the inducible anti- oxidant system in the choroid plexus is down-regulated by inflammation, even if choroid cells are not structurally damaged. Further, LPS prevented the endogenous antioxi- dant response following HI, suggesting the possibility that the choroid plexus may be at risk if LPS is united with an insult that increases oxidative stress such as hypoxia- ischemia.
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| 6. |
- Hamsher, Amy E, et al.
(författare)
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Minimizing tissue damage in electroosmotic sampling.
- 2010
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Ingår i: Analytical chemistry. - : American Chemical Society (ACS). - 1520-6882 .- 0003-2700. ; 82:15, s. 6370-6
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Tidskriftsartikel (refereegranskat)abstract
- Electroosmotic sampling is a potentially powerful method for pulling extracellular fluid into a fused-silica capillary in contact with the surface of tissue. An electric field is created in tissue by passing current through an electrolyte-filled capillary and then through the tissue. The resulting field acts on the counterions to the surface charges in the extracellular space to create electroosmotic fluid flow within the extracellular space of a tissue. Part of the development of this approach is to define conditions under which electroosmotic sampling minimizes damage to the tissue, in this case organotypic hippocampal slice cultures (OHSCs). We have assessed tissue damage by measuring fluorescence resulting from exposing sampled tissue to propidium iodide solution 16-24 h after sampling. Sampling has been carried out with a variety of capillary diameters, capillary tip-tissue distances, and applied voltages. Tissue damage is negligible when the power (current x potential drop) created in the tissue is less than 120 microW. In practical terms, smaller capillary i.d.s, lower voltages, and greater tissue to capillary distances lead to lower power.
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| 7. |
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| 8. |
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| 9. |
- Ou, Y. G., et al.
(författare)
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Electroosmotic perfusion of tissue: sampling the extracellular space and quantitative assessment of membrane-bound enzyme activity in organotypic hippocampal slice cultures
- 2014
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Ingår i: Analytical and Bioanalytical Chemistry. - : Springer Science and Business Media LLC. - 1618-2642 .- 1618-2650. ; 406:26, s. 6455-6468
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Tidskriftsartikel (refereegranskat)abstract
- This review covers recent advances in sampling fluid from the extracellular space of brain tissue by electroosmosis (EO). Two techniques, EO sampling with a single fused-silica capillary and EO push-pull perfusion, have been developed. These tools were used to investigate the function of membrane-bound enzymes with outward-facing active sites, or ectoenzymes, in modulating the activity of the neuropeptides leu-enkephalin and galanin in organotypic-hippocampal-slice cultures (OHSCs). In addition, the approach was used to determine the endogenous concentration of a thiol, cysteamine, in OHSCs. We have also investigated the degradation of coenzyme A in the extracellular space. The approach provides information on ectoenzyme activity, including Michaelis constants, in tissue, which, as far as we are aware, has not been done before. On the basis of computational evidence, EO push-pull perfusion can distinguish ectoenzyme activity with a similar to 100 mu m spatial resolution, which is important for studies of enzyme kinetics in adjacent regions of the rat hippocampus.
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| 10. |
- Rupert, Amy E, et al.
(författare)
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A simple method for measuring organotypic tissue slice culture thickness.
- 2011
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Ingår i: Journal of neuroscience methods. - : Elsevier BV. - 1872-678X .- 0165-0270. ; 199:1, s. 78-81
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a simple method to measure tissue slice thicknesses using an ohmmeter. The circuit described here is composed of a metal probe, an ohmmeter, a counter electrode, culture medium or physiological buffer, and tissue slice. The probe and the electrode are on opposite interfaces of an organotypic hippocampal slice culture. The circuit closes when the metal probe makes contact with the surface of the tissue slice. The probe position is recorded and compared to its position when it makes contact with the insert membrane on which the tissue grows, thus yielding a thickness measurement. The method does not reduce the viability of slice cultures. Thicknesses of the slice cultures were measured under a number of culturing protocols. An initial drop in thickness occurred between 0 and 4 days in culture. Thicknesses are rather constant thereafter. The type of culture medium and the initial thickness of the tissue explant influence the thickness. Slice thicknesses were compared to a known technique by using optical measurements of slice cross-sections to obtain thicknesses. In contrast to this known technique, the proposed method does not sacrifice the slice culture for measurement purposes. The proposed measurement technique described is straightforward and rapid, about 1 min per culture.
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