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- Järlestedt, Katarina, et al.
(author)
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Attenuation of reactive gliosis does not affect infarct volume in neonatal hypoxic-ischemic brain injury in mice
- 2010
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In: PLoS One. - 1932-6203. ; 5:4
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Journal article (peer-reviewed)abstract
- BACKGROUND: Astroglial cells are activated following injury and up-regulate the expression of the intermediate filament proteins glial fibrillary acidic protein (GFAP) and vimentin. Adult mice lacking the intermediate filament proteins GFAP and vimentin (GFAP(-/-)Vim(-/-)) show attenuated reactive gliosis, reduced glial scar formation and improved regeneration of neuronal synapses after neurotrauma. GFAP(-/-)Vim(-/-) mice exhibit larger brain infarcts after middle cerebral artery occlusion suggesting protective role of reactive gliosis after adult focal brain ischemia. However, the role of astrocyte activation and reactive gliosis in the injured developing brain is unknown. METHODOLOGY/PRINCIPAL FINDINGS: We subjected GFAP(-/-)Vim(-/-) and wild-type mice to unilateral hypoxia-ischemia (HI) at postnatal day 9 (P9). Bromodeoxyuridine (BrdU; 25 mg/kg) was injected intraperitoneally twice daily from P9 to P12. On P12 and P31, the animals were perfused intracardially. Immunohistochemistry with MAP-2, BrdU, NeuN, and S100 antibodies was performed on coronal sections. We found no difference in the hemisphere or infarct volume between GFAP(-/-)Vim(-/-) and wild-type mice at P12 and P31, i.e. 3 and 22 days after HI. At P31, the number of NeuN(+) neurons in the ischemic and contralateral hemisphere was comparable between GFAP(-/-)Vim(-/-) and wild-type mice. In wild-type mice, the number of S100(+) astrocytes was lower in the ipsilateral compared to contralateral hemisphere (65.0+/-50.1 vs. 85.6+/-34.0, p<0.05). In the GFAP(-/-)Vim(-/-) mice, the number of S100(+) astrocytes did not differ between the ischemic and contralateral hemisphere at P31. At P31, GFAP(-/-)Vim(-/-) mice showed an increase in NeuN(+)BrdU(+) (surviving newly born) neurons in the ischemic cortex compared to wild-type mice (6.7+/-7.7; n = 29 versus 2.9+/-3.6; n = 28, respectively, p<0.05), but a comparable number of S100(+)BrdU(+) (surviving newly born) astrocytes. CONCLUSIONS/SIGNIFICANCE: Our results suggest that attenuation of reactive gliosis in the developing brain does not affect the hemisphere or infarct volume after HI, but increases the number of surviving newborn neurons.
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| 2. |
- Järlestedt, Katarina, et al.
(author)
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Decreased survival of newborn neurons in the dorsal hippocampus after neonatal LPS exposure in mice.
- 2013
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In: Neuroscience. - : Elsevier BV. - 1873-7544 .- 0306-4522. ; 253, s. 21-28
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Journal article (peer-reviewed)abstract
- Experimental studies show that inflammation reduces the regenerative capacity in the adult brain. Less is known about how early postnatal inflammation affects neurogenesis, stem cell proliferation, cell survival and learning and memory in young adulthood. In this study we examined if an early life inflammatory challenge alters cell proliferation and survival in distinct anatomical regions of the hippocampus and whether learning and memory were affected. Lipopolysaccharide (LPS, 1 mg/kg) was administered to mice on postnatal day (P) 9 and proliferation and survival of hippocampal cells born either prior to (24 h before LPS), or during the inflammatory insult (48h after LPS) was evaluated. Long-term cell survival of neurons and astrocytes was determined on P 41 and P 60 in the dorsal and ventral horns of the hippocampus. On day 50 the mice were tested in the trace fear conditioning paradigm.There was no effect on the survival of neurons and astrocytes that were born before LPS injection. In contrast, the number of neurons and astrocytes that were born after LPS injection were reduced on P 41. The LPS-induced reduction in cell numbers was specific for the dorsal hippocampus. Neither early (48 h after LPS) or late (33 days after LPS) proliferation of cells was affected by neonatal inflammation and neonatal LPS did not alter the behaviour of young adult mice in the trace fear conditioning test.These data highlight that neonatal inflammation specifically affects survival of dividing neurons and astrocytes, but not post-mitotic cells. The reduction in cell survival could be attributed to less cell survival in the dorsal hippocampus, but had no effect on learning and memory in the young adult.
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| 3. |
- Järlestedt, Katarina
(author)
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Inflammation and Cell Profileration Following Perinatal Brain Injury
- 2010
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Doctoral thesis (other academic/artistic)abstract
- Inflammation plays an important role in cerebral ischemic injury in the immature brain. The aim of the thesis was to investigate (1) the role of astrocyte activation and reactive gliosis in neonatal hypoxic-ischemic (HI) brain injury, (2) the role of complement derived peptide C3a in neonatal HI brain injury, (3) the effect of neonatal HI brain injury on fear learning and behaviour, (4) the effects of lipopolysaccharide (LPS) induced systemic inflammation on cell proliferation in the developing brain. Glial fibrillary acidic protein and vimentine deficient (GFAP–/–Vim–/–) mice, transgenic mice over-expressing C3a under the control of a GFAP promoter (C3a/GFAP) and wild type mice were exposed to HI at postnatal day 9 (P9). To induce unilateral HI, the left common carotid artery was permanently ligated followed by exposure to a gas mixture of low oxygen content. Bromodeoxyuridine (BrdU) was injected intraperitoneally (i.p.) to detect cell proliferation. Memory was tested in mice exposed to HI by using a trace fear conditioning test. We found no difference in the hemisphere or infarct volume between GFAP–/–Vim–/– and wild-type mice 3 and 22 days after HI. However at P31, GFAP–/–Vim–/– mice showed an increase in NeuN+BrdU+ (surviving newly born) neurons in the ischemic cortex compared to wild-type. C3a/GFAP mice had reduced loss of hippocampal volume in the ipsilateral compared to the contralateral hemisphere and a higher hippocampus/hemisphere ratio compared to the WT in the ipsilateral hemisphere. C3a/GFAP mice showed a higher number of newly born and surviving neurons, astrocytes and microglia in the dentate gyrus in the ischemic hemisphere compared to the wild type mice. However, a reduced number of astrocytes and microglial cells were found in the C3a/GFAP mice in the ipsilateral hemisphere compared to wild-type mice. C3a mRNA expression increased in the ipsilateral subventricular zone, hippocampus and cortex in C3a/GFAP and wild-type neonatal mice between 0 to 6 hours after HI as shown with real time-PCR. Injection of C3a peptide into the ipsilateral cerebral ventricle, in wild-type mice, 1 hour after HI, improved memory function. The trace fear conditioning test with a shock-paired tone and light showed that the control mice remembered the shock-paired context and the shock-paired light and tone while HI treated mice did not. The volume of the ipsilateral hippocampus and the amygdala was reduced in wild-type mice exposed to HI. Wild type mice injected i.p. with LPS on P9 and evaluated at P40 showed that LPS reduces cell proliferation and survival of neurons and astrocytes in the developing brain. Conclusion: Reactive gliosis and LPS-induced systemic inflammation have negative effects on neurogenesis and cell proliferation; whereas the complement derived peptide C3a improves the outcome after neonatal HI. Early targeting treatments that increase cell survival may be important after neonatal HI and C3a could be such a potential therapeutic target in the future.
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| 4. |
- Järlestedt, Katarina, et al.
(author)
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Receptor for complement peptide C3a: a therapeutic target for neonatal hypoxic-ischemic brain injury.
- 2013
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In: FASEB journal : official publication of the Federation of American Societies for Experimental Biology. - Bethesda : Wiley. - 1530-6860 .- 0892-6638. ; 27:9, s. 3797-3804
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Journal article (peer-reviewed)abstract
- Complement is an essential component of inflammation that plays a role in ischemic brain injury. Recent reports demonstrate novel functions of complement in normal and diseased CNS, such as regulation of neurogenesis and synapse elimination. Here, we examined the role of complement-derived peptide C3a in unilateral hypoxia-ischemia (HI), a model of neonatal HI encephalopathy. HI injury was induced at postnatal day 9 (P9), and loss of hippocampal tissue was determined on P31. We compared WT mice with transgenic mice expressing C3a under the control of glial fibrillary acidic protein promoter, which express biologically active C3a only in CNS and without the requirement of a priori complement activation. Further, we injected C3a peptide into the lateral cerebral ventricle of mice lacking the C3a receptor (C3aR) and WT mice and assessed HI-induced memory impairment 41 d later. We found that HI-induced tissue loss in C3a overexpressing mice was reduced by 50% compared with WT mice. C3a peptide injected 1 h after HI protected WT but not C3aR-deficient mice against HI-induced memory impairment. Thus, C3a acting through its canonical receptor ameliorates behavioral deficits after HI injury, and C3aR is a novel therapeutic target for the treatment of neonatal HI encephalopathy.-Järlestedt, K., Rousset, C. I., Ståhlberg, A., Sourkova, H., Atkins, A. L., Thornton, C., Barnum, S. R., Wetsel, R. A., Dragunow, M., Pekny, M., Mallard, C., Hagberg, H., Pekna, M. Receptor for complement peptide C3a: a therapeutic target for neonatal hypoxic-ischemic brain injury.
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| 5. |
- Järlestedt, Katarina, et al.
(author)
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Trace Fear Conditioning Detects Hypoxic-Ischemic Brain Injury in Neonatal Mice.
- 2011
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In: Developmental neuroscience. - Basel : S. Karger AG. - 1421-9859 .- 0378-5866. ; 33:3-4, s. 222-230
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Journal article (peer-reviewed)abstract
- Trace fear conditioning is a well-established test for the assessment of learning deficits in rodents. The aim of this study was to determine whether hypoxia-ischemia (HI) on postnatal day 9 (P9) in mice prevents the acquisition and expression of cued and contextual fear learning in early adulthood. Brain injury was induced in mice on P9 by 30 min of HI. On P49 and P50, animals were tested for: (1) trace fear conditioning with a short delay (2 s) between a shock-paired tone plus light and shock, (2) trace fear conditioning with a longer delay (20 s) between a shock-paired tone and shock, and (3) trace fear conditioning with a 2-second delay between a shock-paired tone and shock with additional visual, olfactory and tactile contextual cues in the fear conditioning apparatus. Outcome was assessed as percent of time spent freezing during a 2-min test. Histological assessment of the hippocampus and amygdala was performed on P51 to determine the extent of HI injury. Both shock-paired tone plus light with a short delay and shock-paired tone with a short delay plus additional contextual cues enhanced tone-induced freezing behavior in a nonhandled control group, but not in the HI group. For trace fear conditioning with a 20-second delay between the tone and the shock, freezing behavior did not differ significantly between nonhandled control and HI animals. Dorsal hippocampal and amygdala volumes were smaller in the ischemic hemispheres of the HI mice that displayed impaired fear memory with shock-paired tone plus light. In summary, we have shown that trace fear conditioning is a sensitive method for detecting memory impairments in adolescent mice following mild HI injury during the neonatal period. Combining a discrete conditioned stimulus (shock-paired tone plus light) with a short trace delay was the most sensitive method for using the fear conditioning paradigm to detect mild HI damage to the hippocampus and amygdala.
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