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- Andersson, Heléne, 1973, et al.
(författare)
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Trauma-induced reactive gliosis is reduced after treatment with octanol and carbenoxolone
- 2011
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Ingår i: Neurological research. - 0161-6412. ; 33:6, s. 614-624
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Tidskriftsartikel (refereegranskat)abstract
- Background: Reactive gliosis and scar formation after brain injury can inhibit the recovery process. As many glial cells utilize gap junctions for intercellular signaling, this study investigated whether two commonly used gap junction blockers, octanol and carbenoxolone, could attenuate reactive gliosis following a minor traumatic brain injury. Methods: Octanol (710 mg/kg) or carbenoxolone (90 mg/kg) was administered 30 minutes before or after a needle track injury in adult male Sprague-Dawley rats. To mark dividing cells, animals were injected with bromodeoxyuridine (BrdU; 150 mg/kg) intraperitoneally two times per day, 8 hours apart and killed 2 days later. Immunohistochemistry for BrdU and markers for reactive glial cells [glial fibrillary acidic protein (GFAP), ED1, and NG2] were investigated using immunohistochemistry and western blot techniques. Results: Two days after injury, increased cellular proliferation, activated astrocytes and microglia, and upregulation of NG2 expression were observed surrounding the injury site. Octanol and carbenoxolone administrated prior to injury significantly decreased cell proliferation by 60 and 70% respectively. The distance of GFAP immunoreactive astrocytes from the wound margin was decreased by 32 and 18% when octanol was administrated prior to or post injury respectively. Treatment with octanol also decreased the number of reactive microglia by 55% and, when administrated prior to injury, octanol reduced the distance of NG2 expression from the wound by 48%. Conclusion: The present study demonstrates that two important components of reactive gliosis, cellular activation and proliferation, can be attenuated by octanol and carbenoxolone.
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| 3. |
- Faijerson, Jonas, 1977, et al.
(författare)
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Reactive astrogliosis induces astrocytic differentiation of adult neural stem/progenitor cells in vitro.
- 2006
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Ingår i: Journal of neuroscience research. - : Wiley. - 0360-4012 .- 1097-4547. ; 84:7, s. 1415-24
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Tidskriftsartikel (refereegranskat)abstract
- Neural stem cells reside in defined areas of the adult mammalian brain, including the dentate gyrus of the hippocampus. Rat neural stem/progenitor cells (NSPCs) isolated from this region retain their multipotency in vitro and in vivo after grafting into the adult brain. Recent studies have shown that endogenous or grafted NSPCs are activated after an injury and migrate toward lesioned areas. In these areas, reactive astrocytes are present and secrete numerous molecules and growth factors; however, it is not currently known whether reactive astrocytes can influence the lineage selection of NSPCs. We investigated whether reactive astrocytes could affect the differentiation, proliferation, and survival of adult NSPCs by modelling astrogliosis in vitro, using mechanical lesion of primary astrocytes. Initially, it was found that conditioned medium from lesioned astrocytes induced astrocytic differentiation of NSPCs without affecting neuronal or oligodendrocytic differentiation. In addition, NSPCs in coculture with lesioned astrocytes also displayed increased astrocytic differentiation and some of these NSPC-derived astrocytes participated in glial scar formation in vitro. When proliferation and survival of NSPCs were analyzed, no differential effects were observed between lesioned and nonlesioned astrocytes. To investigate the molecular mechanisms of the astrocyte-inducing activity, the expression of two potent inducers of astroglial differentiation, ciliary neurotrophic factor and leukemia inhibitory factor, was analyzed by Western blot and shown to be up-regulated in conditioned medium from lesioned astrocytes. These results demonstrate that lesioned astrocytes can induce astroglial differentiation of NSPCs and provide a mechanism for astroglial differentiation of these cells following brain injury.
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| 4. |
- Li, Lizhen, 1977, et al.
(författare)
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Protective role of reactive astrocytes in brain ischemia.
- 2008
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Ingår i: Journal of cerebral blood flow and metabolism : official journal of the International Society of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 28:3, s. 468-81
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Tidskriftsartikel (refereegranskat)abstract
- Reactive astrocytes are thought to protect the penumbra during brain ischemia, but direct evidence has been lacking due to the absence of suitable experimental models. Previously, we generated mice deficient in two intermediate filament (IF) proteins, glial fibrillary acidic protein (GFAP) and vimentin, whose upregulation is the hallmark of reactive astrocytes. GFAP(-/-)Vim(-/-) mice exhibit attenuated posttraumatic reactive gliosis, improved integration of neural grafts, and posttraumatic regeneration. Seven days after middle cerebral artery (MCA) transection, infarct volume was 210 to 350% higher in GFAP(-/-)Vim(-/-) than in wild-type (WT) mice; GFAP(-/-), Vim(-/-) and WT mice had the same infarct volume. Endothelin B receptor (ET(B)R) immunoreactivity was strong on cultured astrocytes and reactive astrocytes around infarct in WT mice but undetectable in GFAP(-/-)Vim(-/-) astrocytes. In WT astrocytes, ET(B)R colocalized extensively with bundles of IFs. GFAP(-/-)Vim(-/-) astrocytes showed attenuated endothelin-3-induced blockage of gap junctions. Total and glutamate transporter-1 (GLT-1)-mediated glutamate transport was lower in GFAP(-/-)Vim(-/-) than in WT mice. DNA array analysis and quantitative real-time PCR showed downregulation of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of tissue plasminogen activator. Thus, reactive astrocytes have a protective role in brain ischemia, and the absence of astrocyte IFs is linked to changes in glutamate transport, ET(B)R-mediated control of gap junctions, and PAI-1 expression.
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| 5. |
- Nodin, Christina, 1974
(författare)
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Astrocytic communication and cell death during metabolic depression and oxidative stress
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Stroke is a major cause of death and adult disability in the western world. Most often, stroke is caused by the occlusion of a brain artery. Within the perfusion territory of the occluded vessel, various degrees of necrotic and delayed programmed cell death will occur if the occlusion persists, leading to expanding tissue damage. Astrocytes are the most numerous cells in the brain, but the astrocytic response to ischemic conditions and the extent to which these cells can recover after an ischemic insult is not well understood. An increasing amount of evidence indicates that astrocytes are more sensitive to ischemic injury than previously thought. Astrocytic functions are vitally important for neuronal activity during physiological conditions and probably during various pathological situations, including stroke. Astrocytes are highly coupled by intercellular gap junction channels that enable the formation of large cellular networks. These networks provide the basis for several important astrocytic functions including intracellular signalling and transport of molecules and metabolites. In order to investigate astrocytic reactions during metabolic depression we used the glycolytic blocker iodoacetate (IA) in primary astrocyte cultures. This treatment induced a reproducible and concentration-dependent ATP decrease which was associated with a profound increase in the activity of reactive oxygen species (ROS). This suggests that metabolic depression induced oxidative stress. Moreover, programmed cell death was initiated in individual astrocytes or small cell clusters and spread to include large clusters of astrocytes. However, when gap junction communication was inhibited during metabolic depression, programmed cell death was initiated in individual cells but no expansion into large cell clusters was observed. This suggests that gap junction permeable substances contribute to the spreading of cell death in astrocytes. The observed programmed cell death involved translocation of apoptosis inducing factor from the mitochondria to the nucleus. Similar results were observed in a model of oxidative stress using 3-morpholinosyndomine (SIN-1), a compound known to produce equimolar amounts of superoxide and nitric oxide which react to form peroxynitrite. Caspase-activation was not observed in astrocytes exposed to metabolic depression or oxidative stress. Astrocytes and several other cell types express endogenous antioxidant systems. The expression of many of the enzymes involved in this cellular defense is regulated by the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2). The potential protective effect of the Nrf2 system in astrocytes was investigated by using the Nrf2-activating phytochemicals sulforaphane (naturally occurring in broccoli) or curcumin (from turmeric), or the commonly used food additive tert-butylhydroquinone. Exposing the astrocytes to these substances before adding IA or SIN-1, prevented the oxidative stress, enabled the astrocytes to maintain their ATP levels and efficiently prevented cell death. Similar results were observed when the exogenous ROS scavengers trolox (a vitamin E analogue), tempol (a superoxide dismutase analogue) or the free radical scavenger cocktail B27 were used. Finally, we investigated the possibility for the astrocytes to recover following a simulated reperfusion injury where metabolic depression was reversed by washing out IA. Although metabolic depression was interrupted early during the ATP decrease, the astrocytes were not able to recover their ATP levels and widespread cell death occurred. However, pre-treatment with Nrf2 activators or addition of exogenous ROS scavengers enabled recovery of ATP levels and prevented cell death. In summary, these results show that astrocytic cell death mediated by metabolic depression and oxidative stress involves the translocation of apoptosis inducing factor. In addition, gap junction communication was important for the spreading of cell death during metabolic depression. Finally, astrocytes were efficiently protected by activation of Nrf2-regulated endogenous antioxidant systems, which may represent an interesting target for the limitation of ischemic injury
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| 6. |
- Nodin, Christina, 1974, et al.
(författare)
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Decreased oxidative stress during glycolytic inhibition enables maintenance of ATP production and astrocytic survival.
- 2012
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Ingår i: Neurochemistry international. - : Elsevier BV. - 1872-9754 .- 0197-0186. ; 61:3, s. 291-301
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Tidskriftsartikel (refereegranskat)abstract
- Depressed energy metabolism and oxidative stress are common features in many pathological situations in the brain, including stroke. In order to investigate astrocytic responses to such stress, we induced metabolic depression in cultured rat astrocytes. Iodoacetate (IA), an inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used and resulted in a rapid inhibition of GAPDH activity. After 1h of GAPDH inhibition the ATP levels started to decrease and were completely abolished at 4h. In parallel, the activity of reactive oxygen species (ROS) was significantly increased, followed by extensive cell death involving flipping of phosphatidylserine and translocation of apoptosis-inducing factor, but not caspase-3 activation. When IA was combined with azide, a respiratory chain complex IV inhibitor, the ATP levels decreased immediately. Interestingly, with azide present, the ROS activity remained low and the astrocytes remained viable even at very low ATP levels. Addition of exogenous ROS-scavengers prevented the IA-induced ROS activity, the ATP levels were maintained and cell death was prevented. Similar protection could be obtained when astrocytes, prior to addition of IA, were incubated with substances known to activate the nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated endogenous antioxidant system. When IA was washed out, after a relatively moderate ATP depression, massive cell death occurred. This was efficiently prevented by addition of azide or ROS scavengers during the IA treatment or by pre-activation of the Nrf2 system. Our results demonstrate that astrocytes in culture can endure and recover from glycolytic inhibition if the ROS activity remained at a low level and suggest that oxidative stress can be an important component for astrocytic cell death following metabolic stress.
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