Concomitant up-regulation of astroglial high and low affinity nerve growth factor receptors in the CA1 hippocampal area following global transient cerebral ischemia in rat☆ (original) (raw)
Related papers
Brain Research, 2006
In the present study, we observed the changes of endogenous expression of glial-cell-linederived neurotrophic factor (GDNF) and phosphatidylinositol 3-kinase (PI-3 kinase) in the gerbil hippocampus after transient forebrain ischemia and investigated the correlation between GDNF and PI-3 kinase in the ischemic hippocampus. In the sham-operated group, GDNF and PI-3 kinase immunoreactivity was not found in any cells in the hippocampal CA1 region. GDNF, not PI-3 kinase, immunoreactivity was expressed in non-pyramidal cells in the CA1 region at 6 h after ischemic insult. At 12-24 h after ischemia, GDNF and PI-3 kinase immunoreactivity in the CA1 region was similar to that of the sham-operated group. From 2 days after ischemic insult, GDNF-and PI-3-kinase-immunoreactive astrocytes were detected in the CA1 region, and GDNF and PI-3 kinase immunoreactivity in astrocytes was highest in the CA1 region 4 days after ischemic insult. Moreover, at this time point, GDNF and PI-3 kinase were co-localized in some astrocytes. Western blotting showed that ischemia-related changes of GDNF and PI-3 kinase protein levels were similar to the immunohistochemical changes after ischemia. These results suggest that GDNF and PI-3 kinase may be related to delayed neuronal death and that GDNF and PI-3 kinase may be involved in activation of astrocytes.
Experimental Neurology, 2006
An in vitro ischemia model (oxygen, glucose, and serum deprivation) is used to investigate the possible cellular and molecular mechanisms responsible for cerebral ischemia. We have previously demonstrated that supernatants derived from ischemic microglia can protect ischemic brain cells by releasing GDNF and TGF-β1. In the present study, we investigate whether products of ischemic astrocytes can also protect ischemic microglia, astrocytes, and neurons in a similar manner. Supernatants from ischemic astrocytes were collected after various periods of ischemia and incubated with microglia, astrocytes, or neurons individually, under in vitro ischemic conditions. The components responsible for the protective effects of astrocyte-derived supernatants were then identified by Western blot, ELISA, trypan blue dye exclusion, and immunoblocking assays. Results showed that under conditions of in vitro ischemia the number of surviving microglia, astrocytes, and neurons was significantly increased by the incorporation of the astrocyte-derived supernatants. Astrocyte supernatant-mediated protection of ischemic microglia was dependent on TGF-β1 and NT-3, ischemic astrocytes were protected by GDNF, and ischemic neurons were protected by NT-3. In addition, protein expression of TGF-β1 and NT-3 receptors in microglia, GDNF receptors in astrocytes, and NT-3 receptors in neurons was increased by in vitro ischemia. These results suggest that astrocyte-derived protection of ischemic brain cells is dependent not only on factors released from the ischemic astrocytes, but also on the type of receptor present on the responding cells. Therapeutic potential of TGF-β1, GDNF, and NT-3 in the control of cerebral ischemia is further suggested.
Neuroscience Letters, 2004
The interrelationship between microglia and astrocytes in cerebral ischemia was determined in vitro by adding in vitro ischemia-induced supernatant from microglia into astrocytes under the same conditions (glucose-, oxygen-and serum-free). The involvement of glial cell linederived neurotrophic factor (GDNF) was further investigated by immunoblocking assay and Western blot analysis. Results showed that microglia-derived supernatant protected against in vitro ischemia-induced damage of astrocytes and this protection was pre-blocked by anti-GDNF but not normal rabbit serum. In addition, in vitro ischemia appeared to induce the expression of GDNF in microglia. These results indicate that microglia-derived protection on astrocytes during in vitro ischemia is GDNF-dependent. q
Brain Research, 2008
Conditioned medium (CM) collected from cultures of ischemic microglia, astrocytes, and neurons were protective to astrocytes under the in vitro ischemic condition (deprivation of oxygen, glucose and serum). Molecular and signaling pathway(s) responsible for the CMs protective activity were investigated. Results showed that CMs from the ischemic microglia (MCM), astrocytes (ACM) and neurons (NCM) contained glial cell line-derived neurotrophic factor (GDNF), which protects astrocytes against the in vitro ischemia. Expression of extra cellular signal-regulated kinase (ERK1/2) and nuclear factor-kappa B (NF-kB) by GDNF led to the inhibition of apoptosis of the ischemic astrocytes in a caspase 3-independent manner. However, CMs-and GDNF-mediated protection of the ischemic astrocytes was protein kinase B (Akt) independent. These results provided mechanistic data regarding how GDNFand CMs-mediated protection of the ischemic astrocytes is taking place. These observations provide information for the use of GDNF and GDNF containing CMs in the control of cerebral ischemia.
Brain Research, 2003
Transient global ischemia induces intensive neuronal degeneration in the hippocampal CA1 pyramidal layer, accompanied by reactive transformation of glial cells. Previously, we have shown using the double immunostaining method that the NGF receptors (NGFR) p75 and TrkA are expressed mainly on subpopulations of GFAP1 astrocytes, and this expression increases progressively after ischemia. In the presented study, we analyzed quantitatively the morphological transformations of cells immunopositive for GFAP or NGF receptors in the stratum radiatum of the CA1 hippocampal area in different survival periods after ischemia, evoked by 10-min cardiac arrest in adult rats. In control brains, NGF receptors were expressed only on small cells with poorly ramified processes. After ischemia, the NGFR1 cells increased in size and morphological complexity (measured using fractal analysis). However, even 2 weeks after ischemia these cells did not reach the size and value of the fractal dimension typical of the largest GFAP1 astrocytes. Moreover, the reaction of NGFR1 cells was significantly delayed in comparison with the total astrocyte population. The obtained results suggest that NGF receptors are expressed mainly by immature astrocytes and ischemia induces the maturation of these cells.
Protective Effects of Glial Cell Line-Derived Neurotrophic Factor in Ischemic Brain Injury
Annals of The New York Academy of Sciences, 2002
A BSTRACT : Glial cell line-derived neurotrophic factor (GDNF), a member of the transforming growth factor- (TGF- ) superfamily, has been shown to have trophic activity on dopaminergic neurons. Recent studies indicate that GDNF can protect the cerebral hemispheres from damage induced by middle cerebral arterial ligation. We found that such neuroprotective effects are mediated through specific GDNF receptor alpha-1 (GFR ␣ 1). Animals with a deficiency in GFR ␣ -1 have less GDNF-induced neuroprotection. Ischemia also enhances nitric oxide synthase (NOS) activity, which can be attenuated by GDNF. These.data suggest that GDNF can protect against ischemic injury through a GFR ␣ -1/NOS mechanism. We also found that the receptor for GDNF, GFR ␣ 1, and its signaling moiety c-Ret were upregulated, starting immediately after ischemia. This upregulation suggests that activation of an endogenous neuroprotective mechanism occurs so that responsiveness of GDNF can be enhanced at very early stages during ischemia.
Ischemic Neuronal Injury is Ameliorated by Astrocyte Activation
Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques, 1998
ABSTRACT:Background:The motivation of this study was to more precisely define the in vivo role of astrocytes in forebrain ischemia. Controversy exists in the literature as to whether they protect or injure neurons in this setting.Methods:Astrocytes in the rat hippocampus were disabled with stereotactic administration of a gliotoxin, ethidium bromide, 3 days prior to induction of forebrain ischemia. The extent of neuronal injury in this group was compared to a control category receiving intrahippocampal saline only.Results:Saline-injected animals demonstrated decreased hippocampal CA1 sector injury, and increased gliosis on the side of the injection compared to the contralateral side (P < 0.01) or ethidium bromide-treated animals (P < 0.05).Conclusion:The results suggest that activated astrocytes are protective to neurons subjected to an ischemic insult. This may result from their ability to elaborate neurotrophic factors, buffer potassium and metabolize a variety of neurotrans...
Brain Pathology, 2006
The neurotrophin family of growth factors, which includes Nerve Growth Factor (NGF), Brain-Derived Neurotrophic Factor (BDNF), Neurotrophin-3 (NT3) and Neurotrophin-4/5 (NT4/5) bind and activate specific tyrosine kinase (Trk) receptors to promote cell survival and growth of different cell populations. For these reasons, growing attention has been paid to the use of neurotrophins as therapeutic agents in neurodegeneration, and to the regulation of the expression of their specific receptors by the ligands. BDNF expression, as revealed by immunohistochemistry, is found in the pre-subiculum, CA1, CA3, and dentate gyrus of the hippocampus. Strong TrkB immunoreactivity is present in most CA3 neurons but only in scattered neurons of the CA1 area. Weak TrkB immunoreactivity is found in the granule cell layer of the dentate gyrus. Unilateral grafting of BDNF-transfected fibroblasts into the hippocampus resulted in a marked increase in the intensity of the immunoreaction and in the number of TrkB-immunoreactive neurons in the granule cell layer of the dentate gyrus, pre-subiculum and CA1 area in the vicinity of the graft. No similar effects were produced after the injection of control mock-transfected fibroblasts. Delayed cell death in the CA1 area was produced following 5 min of forebrain ischemia in the gerbil. The majority of living cells in the CA1 area at the fourth day were BDNF/TrkB immunoreactive. Unilateral grafting of control mock-transfected or BDNF fibroblasts two days before ischemia resulted in a moderate non-specific protection of TrkB-negative, but not TrkB-positive cells, in the CA1 area of the grafted side. This finding is in line with a vascular and glial reaction, as revealed, by immunohistochemistry using astroglial and microglial cell markers. This astroglial response was higher in the grafted side than in the contralateral side in ischemic gerbils, but no differences were seen between BDNF-producing and non-BDNF-producing grafts. However, grafting of BDNF-producing fibroblasts two days before ischemia significantly and specifically prevented nerve cells from dying in the CA1 area of the ipsilateral hippocampus. Cell survival was associated with increased TrkB immunoreactivity as the majority of living cells were TrkB immunoreactive. Thus, our results show that BDNF is able to up-regulate the expression of TrkB in control and pathological states, and that BDNF prevention of neuronal death following transient forebrain ischemia is associated with increased expression of its specific receptor.
Molecular Brain Research, 1996
Although transforming growth factor-[~ is known to be multifunctional in many physiological systems, its role in the brain is undergoing elucidation. The situation is made more complex by the presence of multiple isoforms, which may be differentially regulated and have various activities in each particular cell type. Because neurons are dependent on neurotrophic factors for survival, we utilized a rat model of transient forebrain ischemia (TFI) to test the hypothesis that TGF-[3 isoforms are important in the hippocampal response to injury. Northern blot analysis demonstrated a differential and temporal alteration in TGF-[3 isoform expression following TFI. In-situ hybridization experiments revealed that at day 1 following TFI, there was a strong neuronal increase in the TGF[3-1 transcript but a reciprocal decrease in TGF-[32 and -[33 transcript levels. Immunohistochemical analysis of all three TGF-[3s demonstrated at day 1 following TFI a loss of the immunoreactive proteins in the vulnerable CA-1 hippocampal neurons, but protein preservation in the CA-2-4 neurons which are more resistant to the ischemic insult. At 3-5 days following TFI, significant extraneuronal changes in TGF-[3 isoform expression were also detected. Double-staining experiments with antibody to glial fibrillary acidic protein (GFAP) as a marker for astrocytes, and lectin isolectin B4 Griffonia simplicifolia for microglia, demonstrated increased expression of all TGF-[3 isoforms in astrocytes but not microglia. Taken together, these results suggest that the TGF-[3 peptides in neurons and astrocytes are important endogenous mediators in the CNS response to ischemic injury.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2001
The glial cell line-derived neurotrophic factor (GDNF) is first characterized for its trophic activity on dopaminergic neurons. Recent data suggested that GDNF could modulate the neuronal death induced by ischemia. The purpose of this study was to characterize the influence of GDNF on cultured cortical neurons subjected to two paradigms of injury (necrosis and apoptosis) that have been identified during cerebral ischemia and to determine the molecular mechanisms involved. First, we demonstrated that both neurons and astrocytes express the mRNA and the protein for GDNF and its receptor complex (GFRalpha-1 and c-Ret). Next, we showed that the application of recombinant human GDNF to cortical neurons and astrocytes induces the activation of the MAP kinase (MAPK) pathway, as visualized by an increase in the phosphorylated forms of extracellular signal-regulated kinases (ERKs). Thereafter, we demonstrated that GDNF fails to prevent apoptotic neuronal death but selectively attenuates slow...