| 1. |
- Chavez-Valdez, R., et al.
(författare)
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Evidence for Sexual Dimorphism in the Response to TLR3 Activation in the Developing Neonatal Mouse Brain: A Pilot Study
- 2019
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Toll-like receptor (TLR)3 activation during the neonatal period produces responses linked to the origins of neuropsychiatric disorders. Although there is sexual dimorphism in neuropsychiatric disorders, it is unknown if brain responses to TLR3 activation are sex-specific. We hypothesized that poly I:C in a post-natal day (P)8 model induces a sexually dimorphic inflammatory responses. C57BL6 mice received intraperitoneal injection of poly I:C (10 mg/kg) or vehicle [normal saline (NS)] at P8. Pups were killed at 6 or 14 h for caspase 3 and 8 activity assays, NFkB ELISA, IRF3, AP1, and GFAP western blotting and cytokines/chemokines gene expression real time qRT-PCR (4-6/group). A second group of pups were killed at 24 h (P9) or 7 days (P15) after poly I:C to assess astrocytic (GFAP) and microglia (Iba1) activation in the hippocampus, thalamus and cortex using immunohistochemistry, and gene and protein expression of cytokines/chemokines using real time RT-PCR and MSD, respectively (4-6/group). Nonparametric analysis was applied. Six hours after poly I:C, caspase-3 and -8 activities in cytosolic fractions were 1.6 and 2.8-fold higher in poly I:C-treated than in NS-treated female mice, respectively, while gene expressions of pro-inflammatory cytokines were upregulated in both sexes. After poly I:C, IRF3 nuclear translocation occurred earlier (6 h) in female mice and later (14 h) in male mice. At 14 h after poly I:C, only male mice also had increased nuclear NF kappa B levels (88%, p < 0.001) and GFAP expression coinciding with persistent IL-6 and FAS gene upregulation (110 and 77%, respectively; p < 0.001) and IL-10 gene downregulation (-42%, p < 0.05). At 24 h after poly I:C, IL-1 beta, CXCL-10, TNF-alpha, and MCP-1 were similarly increased in both sexes but at 7 days after exposure, CXCL-10 and INF gamma were increased and IL-10 was decreased only in female mice. Accordingly, microglial activation persisted at 7 days after poly I:C in the hippocampus, thalamus and cortex of female mice. This preliminary study suggests that TLR3 activation may produce in the developing neonatal mouse brain a sexually dimorphic response with early activation of caspase-dependent pathways in female mice, activation of inflammatory cascades in both sexes, which then persists in female mice. Further well-powered studies are essential to confirm these sex-specific findings.
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| 2. |
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| 3. |
- Stridh, Linnea, 1983
(författare)
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Inflammation in the immature brain: The role of Toll like receptors
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Infection/inflammation and/or hypoxia-ischemia (HI) are major causes of perinatal brain injury. Toll-like receptors (TLRs), important components of innate immunity, have been shown to be involved in brain injury, both after infectious and endogenous, non-infectious, stimuli. The overall aim of this thesis was to study the expression of TLRs in the immature brain, choroid plexus and endothelial cells after inflammatory stimuli and/or HI, and to investigate the role of TLRs, their adaptor proteins MyD88 and TRIF in brain damaging processes after HI. TLR stimuli, HI or a combination of them both was performed on mice at postnatal day 9. Brain injury and inflammatory responses were evaluated with immunohistochemistry, RT-qPCR and cytokine analyses. All investigated TLRs were expressed under basal conditions in the neonatal brain and several of the receptors were regulated in the brain, choroid plexus and blood brain barrier after inflammatory stimuli and/or HI. Additionally, systemic stimulation of TLR 1/2 and TLR 4 decreased the expression of occludin, a tight junction protein, in the choroid plexus. TLR 2 was constitutively expressed in astrocytes in white matter and in neurons in the paraventricular nucleus and contributed to brain damage following HI. In contrast, MyD88 and TRIF did not appear to play a role in the injury process after HI alone. Both lipopolysaccharide (LPS), a TLR 4 ligand, and Poly I:C, a TLR 3 ligand, sensitized the brain to HI in wild type mice. This effect was blocked in MyD88 and TRIF deficient mice. Both Poly I:C and LPS increased the pro-inflammatory cytokine levels in the brain and this increase was blocked/reduced in the TRIF and MyD88 deficient animals. To conclude, TLRs are expressed under basal conditions and regulated during inflammation in the brain as well as in choroid plexus and blood brain barrier. In particular, we found that TLR 2 contributes to injury following HI, indicating that it has a function in sterile inflammation in the neonatal brain. Further, both MyD88 and TRIF play essential roles in LPS/Poly I:C-sensitized HI neonatal brain injury. These findings suggest that TLRs are important in both physiological and pathological processes in the immature brain and may provide novel targets for neuroprotective therapies in the future.
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| 4. |
- Stridh, Linnea, 1983, et al.
(författare)
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Regulation of Toll-like receptor 1 and -2 in neonatal mouse brain after hypoxia-ischemia.
- 2011
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Ingår i: Journal of neuroinflammation. - : Springer Science and Business Media LLC. - 1742-2094. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: BACKGROUND: Hypoxic-ischemic (HI) brain injury remains a major problem in newborns, resulting in increased risk of neurological disorders. Neonatal HI triggers a broad inflammatory reaction in the brain, including activation of the innate immune system. Toll-like receptors (TLRs), which are key components of the innate immune system, are believed to play a role in adult cerebral ischemic injury. The expression of TLRs in the neonatal brain and their regulation after HI is unknown. METHODS: Wild type C57BL/6, TLR 1 knockout (KO) and TLR 2 KO mice were subjected to HI at postnatal day 9 and sacrificed 30 min, 6h, 24h or 5 days after HI. TLR mRNA expression was determined by RT-qPCR and protein and cell type localisation by immunohistochemistry (IHC). To evaluate brain injury, infarct volume was measured in the injured hemisphere. RESULTS: mRNA expression was detected for all investigated TLRs (TLR1-9), both in normal and HI exposed brains. After HI, TLR-1 was down-regulated at 30 min and up-regulated at 6h and 24h. TLR-2 was up-regulated at 6h and 24h, and TLR-7 at 24h. Both TLR-5 and TLR-8 were down-regulated at 24h and 30 min respectively. IHC showed an increase of TLR-1 in neurons in the ipsilateral hemisphere after HI. TLR-2 was constitutively expressed in astrocytes and in a population of neurons in the paraventricular nucleus in the hypothalamus. No changes in expression were detected following HI. Following HI, TLR-2 KO mice, but not TLR-1 KO, showed a decreased infarct volume compared to wild type (p= 0.0051). CONCLUSIONS: This study demonstrates that TLRs are regulated after HI in the neonatal brain. TLR-1 protein was up-regulated in injured areas of the brain but TLR-1 KO animals were not protected from HI. In contrast, TLR-2 was constitutively expressed in the brain and TLR-2 deficiency reduced HI injury. These data suggest that TLR-2, but not TLR-1, plays a role in neonatal HI brain injury.
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| 5. |
- Stridh, Linnea, 1983, et al.
(författare)
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Regulation of Toll-Like Receptors in the Choroid Plexus in the Immature Brain After Systemic Inflammatory Stimuli
- 2013
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Ingår i: Translational Stroke Research. - : Springer Science and Business Media LLC. - 1868-4483 .- 1868-601X. ; 4:2, s. 220-227
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Tidskriftsartikel (refereegranskat)abstract
- The choroid plexus is the site of the blood–cerebrospinal fluid (CSF) barrier (BCSFB) and has also been considered as a possible route for peripheral immune signals and cells to transfer to the central nervous system. Infection/inflammation stimulates innate and subsequent adaptive immune responses via Toll-like receptors (TLRs). In this study, we have investigated the mRNA expression of TLRs, cytokines, and tight junction proteins in the choroid plexus in the immature brain after systemic inflammation, as well as accumulation of immune cells into the CSF. Specific ligands for TLR-1/2, TLR-3, and TLR-4 were administered to postnatal day 8 mice and mRNA expression for the targeted genes was examined in the choroid plexus. We found that mRNA for all four TLRs was detected in the choroid plexus under control conditions. Following immune stimulation, expression of all the TLRs was upregulated by their respective ligands, except for TLR-4 mRNA, which was downregulated by Pam3CSK4 (PAM; a TLR-1/2 ligand). In addition, we investigated BCSFB regulation after TLR stimulation and found that TLR-1/2 and TLR-4 activation was associated with changes in mRNA expression of the tight junction protein occludin in the choroid plexus. PAM induced choroid plexus transcription of TNF-α and resulted in the most dramatic increase in numbers of white blood cells in the CSF. The data suggest a possible mechanism whereby systemic inflammation stimulates TLRs in the choroid plexus, which may lead to disturbances in choroid plexus barrier function, as well as infiltration of immune cells through the plexus.
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| 6. |
- Stridh, Linnea, 1983, et al.
(författare)
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Toll-Like Receptor-3 Activation Increases the Vulnerability of the Neonatal Brain to Hypoxia-Ischemia
- 2013
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Ingår i: Journal of Neuroscience. - : Society for Neuroscience. - 0270-6474 .- 1529-2401. ; 33:29, s. 12041-12051
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Tidskriftsartikel (refereegranskat)abstract
- Susceptibility and progression of brain injury in the newborn is closely associated with an exacerbated innate immune response, but the underlying mechanisms are often unclear. Toll-like receptors (TLRs) are important innate immune sensors that may influence the vulnerability of the developing brain. In the current study, we provide novel data to show that activation of the viral innate immune receptor TLR-3 sensitizes the neonatal brain to subsequent hypoxic-ischemic (HI) damage. Poly inosinic: poly cytidylic acid (Poly I: C), a synthetic ligand for TLR-3, was administered to neonatal mice 14 h before cerebral HI. Activation of TLR-3 before HI increased infarct volume from 3.0 +/- 0.5 to 15.4 +/- 2.1 mm(3) and augmented loss of myelin basic protein from 13.4 +/- 6.0 to 70.6 +/- 5.3%. The sensitizing effect of Poly I: C was specific for the TLR-3 pathway because mice deficient in the TLR-3 adaptor protein Toll/IL-1R domain-containing adaptor molecule-1 (TRIF) did not develop larger brain damage. The increased vulnerability was associated with a TRIF-dependent heightened inflammatory response, including proinflammatory cytokines, chemokines, and the apoptosis-associated mediator Fas, whereas there was a decrease in reparative M2-like CD11b(+) microglia and phosphorylation of Akt. Because TLR-3 is activated via double-stranded RNA during most viral infections, the present study provides evidence that viral infections during pregnancy or in the neonate could have great impact on subsequent HI brain injury.
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| 7. |
- Stridh, Linnea, 1983, et al.
(författare)
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Toll-like receptor-3 activation increases the vulnerability of the neonatal brain to hypoxia-ischemia.
- 2013
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Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 33:29, s. 12041-51
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Tidskriftsartikel (refereegranskat)abstract
- Susceptibility and progression of brain injury in the newborn is closely associated with an exacerbated innate immune response, but the underlying mechanisms are often unclear. Toll-like receptors (TLRs) are important innate immune sensors that may influence the vulnerability of the developing brain. In the current study, we provide novel data to show that activation of the viral innate immune receptor TLR-3 sensitizes the neonatal brain to subsequent hypoxic-ischemic (HI) damage. Poly inosinic:poly cytidylic acid (Poly I:C), a synthetic ligand for TLR-3, was administered to neonatal mice 14 h before cerebral HI. Activation of TLR-3 before HI increased infarct volume from 3.0 ± 0.5 to 15.4 ± 2.1 mm³ and augmented loss of myelin basic protein from 13.4 ± 6.0 to 70.6 ± 5.3%. The sensitizing effect of Poly I:C was specific for the TLR-3 pathway because mice deficient in the TLR-3 adaptor protein Toll/IL-1R domain-containing adaptor molecule-1 (TRIF) did not develop larger brain damage. The increased vulnerability was associated with a TRIF-dependent heightened inflammatory response, including proinflammatory cytokines, chemokines, and the apoptosis-associated mediator Fas, whereas there was a decrease in reparative M2-like CD11b⁺ microglia and phosphorylation of Akt. Because TLR-3 is activated via double-stranded RNA during most viral infections, the present study provides evidence that viral infections during pregnancy or in the neonate could have great impact on subsequent HI brain injury.
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| 8. |
- Wang, Xiaoyang, 1965, et al.
(författare)
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Lipopolysaccharide Sensitizes Neonatal Hypoxic-Ischemic Brain Injury in a MyD88-Dependent Manner
- 2009
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 183:11, s. 7471-7477
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Tidskriftsartikel (refereegranskat)abstract
- Neurological deficits in children, including cerebral palsy, are associated with prior infection during the perinatal period. Experimentally, we have shown that pre-exposure to the Gram-negative component LPS potentiates hypoxic-ischemic (HI) brain injury in newborn animals. LPS effects are mediated by binding to TLR4, which requires recruitment of the MyD88 adaptor protein or Toll/IL-1R domain-containing adapter inducing IFN-beta for signal transduction. In this study, we investigated the role of MyD88 in neonatal brain injury. MyD88 knockout (MyD88 KO) and wild-type mice were subjected to left carotid artery ligation and 10% O(2) for 50 min on postnatal day 9. LPS or saline were administered i.p. at 14 h before HI. At 5 days after HI in wild-type mice, LPS in combination with HI caused a significant increase in gray and white matter tissue loss compared with the saline-HI group. By contrast, in the MyD88 KO mice there was no potentiation of brain injury with LPS-HI. MyD88 KO mice exhibited reduced NFkappaB activation and proinflammatory cytokine-chemokine expression in response to LPS. The number of microglia and caspase-3 activation was increased in the brain of MyD88 KO mice after LPS exposure. Collectively, these findings indicate that MyD88 plays an essential role in LPS-sensitized HI neonatal brain injury, which involves both inflammatory and caspase-dependent pathways.
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