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Neuroinflammation in Alzheimer's disease: Focus on NF-κB and C/EBP transcription factors
Stockholm University, Faculty of Science, Department of Neurochemistry. (Kerstin Iverfeldt)
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Alzheimer's disease (AD) is the most common form of dementia among elderly. The disease is characterized by amyloid-β (Aβ) plaques, neurofibrillary tangles, loss of synapses and neurons and chronic neuroinflammation. The significance of neuroinflammatory processes in disease on-set and progression has been debated since activated microglia and reactive astrocytes have been attributed both protective and damaging properties. However, patients systematically treated with anti-inflammatory drugs have been shown to develop AD to a lesser extent than average. This indicates an important role of neuroinflammation in AD.

This thesis focuses on two inflammatory related transcription factors, nuclear factor κB (NF-κB) and CCAAT/enhancer binding protein (C/EBP). Both NF-κB and C/EBP are known regulators of many pro-inflammatory genes and may during certain circumstances dimerize with each other.

In paper I we use a new strategy to inhibit NF-κB DNA binding activity in primary astro-microglial cell cultures treated with Aβ and IL-1β. By coupling the NF-κB decoy to a transport peptide both concentration and incubation time can be shortened in comparison to previous studies. Moreover, using the same in vitro model in paper II and III, we show members of the C/EBP family to be dysregulated during AD mimicking conditions. Additional focus was directed towards C/EBPδ, which was shown to respond differently to oligomeric and fibrillar forms of Aβ. Results were also confirmed in vivo using an AD mouse model characterized by high levels of fibrillar Aβ deposits. Finally, in order to get further insight in neurodegenerative processes, induced by Aβ or microglial activation, we present in paper IV a new set of anchored sensors for detection of locally activated caspases in neuronal cells. By anchoring the sensors to tau they become less dynamic and caspase activation can be detected early on in the apoptotic process, in a spatio-temporal and reproducible manner.

Place, publisher, year, edition, pages
Stockholm: Department of Neurochemistry, Stockholm University , 2011. , 65 p.
Keyword [en]
Alzheimer’s disease, neuroinflammation, NF-κB, C/EBP, apoptosis, caspases, FRET
National Category
Natural Sciences
Research subject
Neurochemistry and Neurotoxicology
Identifiers
URN: urn:nbn:se:su:diva-62492ISBN: 978-91-7447-356-8 (print)OAI: oai:DiVA.org:su-62492DiVA: diva2:442318
Public defence
2011-10-28, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Available from: 2011-10-06 Created: 2011-09-21 Last updated: 2011-09-21Bibliographically approved
List of papers
1. Alzheimer amyloid-beta peptides block the activation of C/EBP beta and C/EBP delta in glial cells
Open this publication in new window or tab >>Alzheimer amyloid-beta peptides block the activation of C/EBP beta and C/EBP delta in glial cells
2008 (English)In: Biochemical and Biophysical Research Communications - BBRC, ISSN 0006-291X, E-ISSN 1090-2104, Vol. 370, no 4, 619-622 p.Article in journal (Refereed) Published
Abstract [en]

Members of the CCAAT/enhancer binding protein (C/EBP) family of transcription factors have been reported to be up-regulated in Alzheimer's disease. In the present study, we have investigated the effects of amyloid-beta (A beta) peptides on C/EBP beta and C/EBP delta, previously shown to be induced by inflammatory stimuli in glial cells. Surprisingly, electrophoretic mobility shift assay showed that both A beta(1-42) and A beta(25-35) blocked C/EBP activation induced by the inflammatory cytokine interleukin-1 (IL-1 beta) or lipopolysac-charicle (LPS) in mixed primary glial cell cultures from rat. A beta also blocked IL-1 or LPS-incluced C/EBP protein levels. The most prominent effects were observed on DNA binding activity and protein levels of C/EBP delta. Our results demonstrate a dysregulation of C/EBP when glial cells are activated in the presence of Alzheimer A beta peptides.

Keyword
Alzheimer's disease, amyloid-beta, C/EBP, Glia, neuroinflammation
National Category
Biochemistry and Molecular Biology Biophysics
Identifiers
urn:nbn:se:su:diva-25295 (URN)10.1016/j.bbrc.2008.03.150 (DOI)000255883900018 ()
Available from: 2008-09-04 Created: 2008-09-02 Last updated: 2017-12-13Bibliographically approved
2. The CCAAT/enhancer binding protein (C/EBP) δ is differently regulated by fibrillar and oligomeric forms of the Alzheimer amyloid-β peptide
Open this publication in new window or tab >>The CCAAT/enhancer binding protein (C/EBP) δ is differently regulated by fibrillar and oligomeric forms of the Alzheimer amyloid-β peptide
Show others...
2011 (English)In: Journal of Neuroinflammation, ISSN 1742-2094, E-ISSN 1742-2094, Vol. 8, 34- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND:

The transcription factors CCAAT/enhancer binding proteins (C/EBP) α, β and δ have been shown to be expressed in brain and to be involved in regulation of inflammatory genes in concert with nuclear factor κB (NF-κB). In general, C/EBPα is down-regulated, whereas both C/EBPβ and δ are up-regulated in response to inflammatory stimuli. In Alzheimer's disease (AD) one of the hallmarks is chronic neuroinflammation mediated by astrocytes and microglial cells, most likely induced by the formation of amyloid-β (Aβ) deposits. The inflammatory response in AD has been ascribed both beneficial and detrimental roles. It is therefore important to delineate the inflammatory mediators and signaling pathways affected by Aβ deposits with the aim of defining new therapeutic targets.

METHODS:

Here we have investigated the effects of Aβ on expression of C/EBP family members with a focus on C/EBPδ in rat primary astro-microglial cultures and in a transgenic mouse model with high levels of fibrillar Aβ deposits (tg-ArcSwe) by western blot analysis. Effects on DNA binding activity were analyzed by electrophoretic mobility shift assay. Cross-talk between C/EBPδ and NF-κB was investigated by analyzing binding to a κB site using a biotin streptavidin-agarose pull-down assay.

RESULTS:

We show that exposure to fibril-enriched, but not oligomer-enriched, preparations of Aβ inhibit up-regulation of C/EBPδ expression in interleukin-1β-activated glial cultures. Furthermore, we observed that, in aged transgenic mice, C/EBPα was significantly down-regulated and C/EBPβ was significantly up-regulated. C/EBPδ, on the other hand, was selectively down-regulated in the forebrain, a part of the brain showing high levels of fibrillar Aβ deposits. In contrast, no difference in expression levels of C/EBPδ between wild type and transgenic mice was detected in the relatively spared hindbrain. Finally, we show that interleukin-1β-induced C/EBPδ DNA binding activity to both C/EBP and κB sites is abolished after exposure to Aβ.

CONCLUSIONS:

These data suggest that both expression and function of C/EBPδ are dysregulated in Alzheimer's disease. C/EBPδ seems to be differently regulated in response to different conformations of Aβ. We propose that Aβ induces an imbalance between NF-κB and C/EBP transcription factors that may result in abnormal responses to inflammatory stimuli.

National Category
Natural Sciences
Research subject
Neurochemistry with Molecular Neurobiology
Identifiers
urn:nbn:se:su:diva-58649 (URN)10.1186/1742-2094-8-34 (DOI)000290687600001 ()21492414 (PubMedID)
Available from: 2011-06-07 Created: 2011-06-07 Last updated: 2017-12-11Bibliographically approved
3. Anchored FRET sensors detect local caspase activation prior to neuronal degeneration
Open this publication in new window or tab >>Anchored FRET sensors detect local caspase activation prior to neuronal degeneration
Show others...
2011 (English)In: Molecular Neurodegeneration, ISSN 1750-1326, E-ISSN 1750-1326, Vol. 6, 35- p.Article in journal (Refereed) Published
Abstract [en]

BACKGROUND: Recent studies indicate local caspase activation in dendrites or axons during development and in neurodegenerative disorders such as Alzheimer's disease (AD). Emerging evidences point to soluble oligomeric amyloid-beta peptide as a causative agent in AD.

RESULTS: Here we describe the design of fluorescence resonance energy transfer (FRET)-based caspase sensors, fused to the microtubule associated protein tau. Specific caspase sensors preferentially cleaved by caspase-3, -6 or -9 were expressed in differentiated human neuroblastoma SH-SY5Y cells. The anchoring of the sensors resulted in high FRET signals both in extended neurites and soma and made analysis of spatiotemporal signal propagation possible. Caspase activation was detected as loss of FRET after exposure to different stimuli. Interestingly, after staurosporine treatment caspase-6 activation was significantly delayed in neurites compared to cell bodies. In addition, we show that exposure to oligomer-enriched amyloid-beta peptide resulted in loss of FRET in cells expressing sensors for caspase-3 and -6, but not -9, in both soma and neurites before neurite degeneration was observed.

CONCLUSIONS: Taken together, the results show that by using anchored FRET sensors it is possible to detect stimuli-dependent differential activation of caspases and to distinguish local from global caspase activation in live neuronal cells. Furthermore, in these cells oligomer-enriched amyloid-beta peptide induces a global, rather than local activation of caspase-3 and -6, which subsequently leads to neuronal cell death.

Keyword
Amyloid-beta, Caspases, FRET, Live Cell Imaging, Neurite degeneration, Neurodegeneration, Spatiotemporal analysis
National Category
Biological Sciences Chemical Sciences
Research subject
Biochemistry; Neurochemistry and Neurotoxicology; Neurochemistry with Molecular Neurobiology
Identifiers
urn:nbn:se:su:diva-58646 (URN)10.1186/1750-1326-6-35 (DOI)000291991900001 ()21605370 (PubMedID)
Funder
Swedish Research Council, 2010-4481Swedish Research Council, 2010-4505
Available from: 2011-06-07 Created: 2011-06-07 Last updated: 2017-12-11Bibliographically approved
4. Targeting cytokine expression in glial cells by cellular delivery of an NFκB decoy
Open this publication in new window or tab >>Targeting cytokine expression in glial cells by cellular delivery of an NFκB decoy
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2007 (English)In: Journal of Molecular Neuroscience, ISSN 0895-8696, E-ISSN 1559-1166, Vol. 31, no 3, 209-219 p.Article in journal (Refereed) Published
Abstract [en]

Inhibition of nuclear factor (NF)-κB has emerged as an important strategy for design of anti-inflammatory therapies. In neurodegenerative disorders like Alzheimer’s disease, inflammatory reactions mediated by glial cells are believed to promote disease progression. Here, we report that uptake of a double-stranded oligonucleotide NF-κB decoy in rat primary glial cells is clearly facilitated by noncovalent binding to a cell-penetrating peptide, transportan 10, via a complementary peptide nucleic acid (PNA) sequence. Fluorescently labeled oligonucleotide decoy was detected in the cells within 1 h only when cells were incubated with the decoy in the presence of cell-penetrating peptide. Cellular delivery of the decoy also inhibited effects induced by a neurotoxic fragment of the Alzheimer β amyloid peptide in the presence of the inflammatory cytokine interleukin (IL) 1β. Pretreatment of the cells with the complex formed by the decoy and the cell-penetrating peptide-PNA resulted in 80% and 50% inhibition of the NF-κB binding activity and IL-6 mRNA expression, respectively.

Keyword
β-amyloid, astrocytes, cell-penetrating peptide, inflammation, nuclear factor-κB, peptide nucleic acid
National Category
Biological Sciences
Research subject
Biochemistry; Neurochemistry and Neurotoxicology
Identifiers
urn:nbn:se:su:diva-25921 (URN)10.1385/JMN:31:03:209 (DOI)000246588800003 ()
Available from: 2006-05-18 Created: 2006-05-18 Last updated: 2017-12-13Bibliographically approved

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