[Show abstract][Hide abstract]ABSTRACT: TREM2 expression was not observed in oligodendrocytes. Double immunofluorescence was performed for colocalization study of TREM2 (green) with (A) olig2 (red), a pan marker of oligodencrocytes and (B) PDGFRalpha (red), a marker for early oligodendrocyte progenitors. No expression of TREM2 was observed in oligodendrocytes at any time or region studied. DAPI was used for nuclear staining (blue) Scale bar = 20 µm.
[Show abstract][Hide abstract]ABSTRACT: Phenotypic characterization of TREM2+ microglia in fimbria. TREM2 co-expression with: CD206 (A–B), CD16/32 (C–D), CD86 (E–F) and MHCII (G–H) was studied at P1 (A, C, E and G) and P7 (B, D, F and H). Insets beside each figure represent separated channels: CD206, CD16/32, CD86 and MHCII in red, TREM2 in green and Iba1 in blue. Triple colocalization can be seen in purple. fim: fimbria. Scale bar for A and B = 50 µm; scale bar for C–H = 20 µm.
[Show abstract][Hide abstract]ABSTRACT: Developmental expression of TREM2. (A–D), developmental expression of TREM2 in rostral corpus callosum (ros cc) at P1 (A), P3 (B), P5 (C) and P7 (D), showing no difference in expression pattern. (E–H) Changes in cortex (cx) at P1 (E), P3 (F), P5 (G) and P7 (H), showing a progressive reduction in TREM2 expression from P3. (I–L) TREM2 expression in caudate-putamen (cp) at P1 (I), P3 (J), P5 (K) and P7 (L), showing no changes. (M–P) TREM2 expression in thalamus (tl) at P1 (M), P3 (N), P5 (O) and P7 (P), showing a progressive reduction on TREM2 expression after P3. Scale bar = 50 µm.
[Show abstract][Hide abstract]ABSTRACT: During postnatal development, microglia, the resident innate immune cells of the central nervous system are constantly monitoring the brain parenchyma, cleaning the cell debris, the synaptic contacts overproduced and also maintaining the brain homeostasis. In this context, the postnatal microglia need some control over the innate immune response. One such molecule recently described to be involved in modulation of immune response is TREM2 (triggering receptor expressed on myeloid cells 2). Although some studies have observed TREM2 mRNA in postnatal brain, the regional pattern of the TREM2 protein has not been described. We therefore characterized the distribution of TREM2 protein in mice brain from Postnatal day (P) 1 to 14 by immunostaining. In our study, TREM2 protein was expressed only in microglia/macrophages and is developmentally downregulated in a region-dependent manner. Its expression persisted in white matter, mainly in caudal corpus callosum, and the neurogenic subventricular zone for a longer time than in grey matter. Additionally, the phenotypes of the TREM2+ microglia also differ; expressing CD16/32, MHCII and CD86 (antigen presentation markers) and CD68 (phagocytic marker) in different regions as well as with different intensity till P7. The mannose receptor (CD206) colocalized with TREM2 only at P1-P3 in the subventricular zone and cingulum, while others persisted at low intensities till P7. Furthermore, the spatiotemporal expression pattern and characterization of TREM2 indicate towards its other plausible roles in phagocytosis, progenitor's fate determination or microglia phenotype modulation during postnatal development. Hence, the increase of TREM2 observed in pathologies may recapitulate their function during postnatal development, as a better understanding of this period may open new pathway for future therapies.
[Show abstract][Hide abstract]ABSTRACT: Phenotypic characterization of cortical TREM2+ microglia. TREM2 co-expression with: CD206 (A–B), CD16/32 (C–D), CD86 (E–F) and MHCII (G–H) was studied in cortex at P1 (A, C, E and G) and P7 (B, D, F and H). Insets beside each figure represent separated channels: CD206, CD16/32, CD86 and MHCII in red, TREM2 in green and Iba1 in blue. Triple colocalization can be seen in purple. Arrows represent cytoplasmatic expression of MHCII. Cx: cortex; Scale bar for A and B = 50 µm; scale bar for C–H = 20 µm.
[Show abstract][Hide abstract]ABSTRACT: Hypoxia/ischemia (HI) is a prevalent reason for neonatal brain injury with inflammation being an inevitable phenomenon following such injury; but there is a scarcity of data regarding the signaling pathway involved and the effector molecules. The signal transducer and activator of transcription factor 3 (STAT3) is known to modulate injury following imbalance between pro- and anti-inflammatory cytokines in peripheral and central nervous system injury making it a potential molecule for study. The current study investigates the temporal expression of interleukin (IL)-6, IL-1β, tumor necrosis factor-α, IL-1ra, IL-4, IL-10, IL-13 and phosphorylated STAT3 (pSTAT3) after carotid occlusion and hypoxia (8% O2, 55 min) in postnatal day 7 C57BL/6 mice from 3 h to 21 days after hypoxia. Protein array illustrated notable changes in cytokines expressed in both hemispheres in a time-dependent manner. The major pro-inflammatory cytokines showing immediate changes between ipsi- and contralateral hemispheres were IL-6 and IL-1β. The anti-inflammatory cytokines IL-4 and IL-13 demonstrated a delayed augmentation with no prominent differences between hemispheres, while IL-1ra showed two distinct peaks of expression spread over time. We also illustrate for the first time the spatiotemporal activation of pSTAT3 (Y705 phosphorylation) after a neonatal HI in mice brain. The main regions expressing pSTAT3 were the hippocampus and the corpus callosum. pSTAT3+ cells were mostly a subpopulation of activated astrocytes (GFAP+) and microglia/macrophages (F4/80+) seen only in the ipsilateral hemisphere at most time points studied (till 7 days after hypoxia). The highest expression of pSTAT3+ cells was observed to be around 24-48 h, where the presence of pSTAT3+ astrocytes and pSTAT3+ microglia/macrophages was seen by confocal micrographs. In conclusion, our study highlights a synchronized expression of some pro- and anti-inflammatory cytokines, especially in the long term not previously defined. It also points towards a significant role of STAT3 signaling following micro- and astrogliosis in the pathophysiology of neonatal HI-related brain injury. In the study, a shift from pro-inflammatory to anti-inflammatory cytokine profile was also noted as the injury progressed. We suggest that while designing efficient neuroprotective therapies using inflammatory molecules, the time of intervention and balance between the pro- and anti-inflammatory cytokines must be considered.
[Show abstract][Hide abstract]ABSTRACT: Background:
The zinc finger protein A20 is an ubiquitinating/deubiquitinating enzyme essential for the termination of inflammatory reactions through the inhibition of nuclear factor kappaB (NF-kappaB) signaling. Moreover, it also shows anti-apoptotic activities in some cell types and proapoptotic/pronecrotic effects in others. Although it is known that the regulation of inflammatory and cell death processes are critical in proper brain functioning and that A20 mRNA is expressed in the CNS, its role in the brain under physiological and pathological conditions is still unknown.
In the present study, we have evaluated the effects of A20 overexpression in mixed cortical cultures in basal conditions: the in vivo pattern of endogenous A20 expression in the control and N-methyl-d-aspartate (NMDA) excitotoxically damaged postnatal day 9 immature rat brain, and the post-injury effects of A20 overexpression in the same lesion model.
Our results show that overexpression of A20 in mixed cortical cultures induced significant neuronal death by decreasing neuronal cell counts by 45 ± 9%. in vivo analysis of endogenous A20 expression showed widespread expression in gray matter, mainly in neuronal cells. However, after NMDA-induced excitotoxicity, neuronal A20 was downregulated in the neurodegenerating cortex and striatum at 10-24 hours post-lesion, and it was re-expressed at longer survival times in reactive astrocytes located mainly in the lesion border. When A20 was overexpressed in vivo 2 hours after the excitotoxic damage, the lesion volume at 3 days post-lesion showed a significant increase (20.8 ± 7.0%). No A20-induced changes were observed in the astroglial response to injury.
A20 is found in neuronal cells in normal conditions and is also expressed in astrocytes after brain damage, and its overexpression is neurotoxic for cortical neurons in basal mixed neuron-glia culture conditions and exacerbates postnatal brain excitotoxic damage.
Full-text Article · Dec 2012 · Neurological Research
[Show abstract][Hide abstract]ABSTRACT: The CD200/CD200R inhibitory immune ligand-receptor system regulates microglial activation/quiescence in adult brain. Here, we investigated CD200/CD200R at different stages of postnatal development, when microglial maturation takes place. We characterized the spatiotemporal, cellular, and quantitative expression pattern of CD200 and CD200R in the developing and adult C57/BL6 mice brain by immunofluorescent labeling and Western blotting. CD200 expression increased from postnatal day 1 (P1) to P5-P7, when maximum levels were found, and decreased to adulthood. CD200 was located surrounding neuronal bodies, and very prominently in cortical layer I, where CD200(+) structures included glial fibrillary acidic protein (GFAP)(+) astrocytes until P7. In the hippocampus, CD200 was mainly observed in the hippocampal fissure, where GFAP(+) /CD200(+) astrocytes were also found until P7. CD200(+) endothelium was seen in the hippocampal fissure and cortical blood vessels, notably from P14, showing maximum vascular CD200 in adults. CD200R(+) cells were a population of ameboid/pseudopodic Iba1(+) microglia/macrophages observed at all ages, but significantly decreasing with increasing age. CD200R(+) /Iba1(+) macrophages were prominent in the pial meninges and ventricle lining, mainly at P1-P5. CD200R(+) /Iba1(+) perivascular macrophages were observed in cortical and hippocampal fissure blood vessels, showing maximum density at P7, but being prominent until adulthood. CD200R(+) /Iba1(+) ameboid microglia in the cingulum at P1-P5 were the only CD200R(+) cells in the nervous tissue. In conclusion, the main sites of CD200/CD200R interaction seem to include the molecular layer and pial surface in neonates and blood vessels from P7 until adulthood, highlighting the possible role of the CD200/CD200R system in microglial development and renewal.
Article · Aug 2012 · The Journal of Comparative Neurology
[Show abstract][Hide abstract]ABSTRACT: Understanding the evolution of neonatal hypoxic/ischemic is essential for novel neuroprotective approaches. We describe the neuropathology and glial/inflammatory response, from 3 hours to 100 days, after carotid occlusion and hypoxia (8% O
, 55 minutes) to the C57/BL6 P7 mouse. Massive tissue injury and atrophy in the ipsilateral (IL) hippocampus, corpus callosum, and caudate-putamen are consistently shown. Astrogliosis peaks at 14 days, but glial scar is still evident at day 100. Microgliosis peaks at 3–7 days and decreases by day 14. Both glial responses start at 3 hours in the corpus callosum and hippocampal fissure, to progressively cover the degenerating CA field. Neutrophils increase in the ventricles and hippocampal vasculature, showing also parenchymal extravasation at 7 days. Remarkably, delayed milder atrophy is also seen in the contralateral (CL) hippocampus and corpus callosum, areas showing astrogliosis and microgliosis during the first 72 hours. This detailed and long-term cellular response characterization of the ipsilateral and contralateral hemisphere after H/I may help in the design of better therapeutic strategies.
Full-text Article · Jun 2012 · Neurology Research International
[Show abstract][Hide abstract]ABSTRACT: Antiinflammatory cytokines such as interleukin-10 (IL-10) have been used to modulate and terminate inflammation and provide neuroprotection. Recently, we reported that the modular recombinant transfection vector NLSCt is an efficient tool for transgene overexpression in vivo, which induces neuroprotection as a result of its RGD-mediated integrin-interacting capacity. We here sought to evaluate the putative synergic neuroprotective action exerted by IL-10 overexpression using NLSCt as a transfection vector after an excitotoxic injury to the postnatal rat brain. For this purpose, lesion volume, neurodegeneration, astroglial and microglial responses, neutrophil infiltration, and proinflammatory cytokine production were analyzed at several survival times after intracortical NMDA injection in postnatal day 9 rats, followed by injection of NLSCt combined with the IL-10 gene, a control transgene, or saline vehicle solution. Our results show no combined neuroprotective effect between RGD-interacting vectors and IL-10 gene therapy; instead, IL-10 overexpression using NLSCt as transfection vector increased lesion volume and neuronal degeneration at 12 hr and 3 days postlesion. In parallel, NLSCt/IL-10 treated animals displayed increased density of neutrophils and microglia/macrophages, and a reduced astroglial content of GFAP and vimentin. Moreover, NLSCt/IL-10 treated animals did not show any variation in interleukin-1β or tumor necrosis factor-α expression but a slight increase in interleukin-6 content at 7 days postlesion. In conclusion, overexpression of IL-10 by using NLSCt transfection vector did not synergistically neuroprotect the excitotoxically damaged postnatal rat brain but induced changes in the astroglial and microglial and inflammatory cell response.
Full-text Article · Jan 2012 · Journal of Neuroscience Research
[Show abstract][Hide abstract]ABSTRACT: Brain aging is associated to several morphological and functional alterations that influence the evolution and outcome of CNS damage. Acute brain injury such as an excitotoxic insult induces initial tissue damage followed by associated inflammation and oxidative stress, partly attributed to neutrophil recruitment and the expression of oxidative enzymes such as myeloperoxidase (MPO), among others. However, to date, very few studies have focused on how age can influence neutrophil infiltration after acute brain damage. Therefore, to evaluate the age-dependent pattern of neutrophil cell infiltration following an excitotoxic injury, intrastriatal injection of N-methyl-d-aspartate was performed in young and aged male Wistar rats. Animals were sacrificed at different times between 12h post-lesion (hpl) to 14 days post-lesion (dpl). Cryostat sections were processed for myeloperoxidase (MPO) immunohistochemistry, and double labeling for either neuronal cells (NeuN), astrocytes (GFAP), perivascular macrophages (ED-2), or microglia/macrophages (tomato lectin histochemistry). Our observations showed that MPO + cells were observed in the injured striatum from 12 hpl (when maximum values were found) until 7 dpl, when cell density was strongly diminished. However, at all survival times analyzed, the overall density of MPO + cells was lower in the aged versus the adult injured striatum. MPO + cells were mainly identified as neutrophils (especially at 12 hpl and 1 dpl), but it should be noted that MPO + neurons and microglia/macrophages were also found. MPO + neurons were most commonly observed at 12 hpl and reduced in the aged. MPO + microglia/macrophages were the main population expressing MPO from 3 dpl, when density was also reduced in aged subjects. These results point to neutrophil infiltration as another important factor contributing to the different responses of the adult and aged brain to damage, highlighting the need of using aged animals for the study of acute age-related brain insults.
Full-text Article · May 2011 · Experimental gerontology
[Show abstract][Hide abstract]ABSTRACT: CD200/CD200R signalling had been highlighted to contribute to
immune privileged status of the CNS. The developing brain exhibits
distinct characteristics, along with an exacerbated inflammatory
response. Hence the aim of our study is to characterize the expression
pattern of CD200-CD200R in developing and adult mice brain.
Wild-type C57/BL6 mice postnatal days-1, 3, 5, 7, 10, 14,and 21 and
adult were perfused with 4% paraformaldehyde intracardially under
anaesthesia and sacrificed. Brains removed, cryoprotected, frozen and cut
into 30 μmsections for immunohistochemistry. Animalswere perfused in
PBS, brain dissected, freezed in liquid N2 and then stored at −80 °C till
used for immunoblotting. CD200 is highly expressed in gray matter
regions as cerebral cortex, hippocampus and striatum where immunoreactivity
appeared surrounding neurons in all the age groups displaying
an age dependent decrease in intensitywith increasing age. Blood vessels
(BVs) labelled by Tomato lectin, expressed CD200 at all ages but were
more pronounced in P21 and adult. A distinct CD200 labelling was
observed in the hippocampal fissure (hf) along with the meninges in all
the ages with decreasing intensity from P1 to adult. Many oval to round
meagrely ramified NeuN− and Iba1− cells, some of them GFAP+ were
present all across the hf at early postnatal ages but were much reduced/
absent in adults. At P21 and adult, hippocampal CD200 wasmainly found
as a stronger labelling in the inner commissural-associational zone of the
molecular layer of DG. The western blot showed a gradual decrease in
CD200 expression with increasing age. CD200R immunolabelling was
mainly observed in Iba-1+ macrophages present in the meninges and in
the lateral and dorsal 3rdventricle lining,mainly fromP1 to P7, fromwhen
there was a drastic reduction in CD200R+ cells in these regions that
paralleled an increased density of Iba-1+ CD200R− primary ramified
microglial cells in the parenchyma. Moreover, Iba-1+ CD200R+ameboid
microglial cells were also seen in the cingulum bundle at P1–P10 brains,
and in close opposition to laminin+ basal lamina in BVs located in the hf
from P7 until adulthood, and in large cortical BV at P21 and adult brain.
The CD200–CD200R double-staining suggested a physical binding
between CD200 and CD200R at the BV wall mainly in the hf and cortex.
These data indicate that CD200/CD200R signalling might play a
role in modulating microglial development and migration, mediating
immune regulation in neonates.
[Show abstract][Hide abstract]ABSTRACT: CD200, a cell surface glycoprotein elicits suppressive effects on
myeloid cells including microglia by interacting with the CD200
receptor contributing to immune privileged status of the central nervous
system. The immature brain exhibits distinct morphological and
physiological characteristics determining a peculiar response to injury
showing an aggravated susceptibility to excitotoxicity and proinflammatory
cytokines along with an exacerbated inflammatory
response. In these contexts the aim of the present study is to characterize
the spatio-temporal and cellular expression of CD200 in the
developing and adult mice brain by immunohistochemistry. Wildtype
C57/BL6 mice postnatal day- 1,3,5,7,10,14,21 and adult were
perfused intracardially under ketamine anaesthesia. Brains were
removed, cryoprotected, frozen and cut into 30 lm sections. CD200
is highly expressed in gray matter regions including cerebral cortex,
hippocampus and striatum where immunoreactivity appeared surrounding
neurons in all age groups displaying an age dependent
decrease in intensity through the early postnatal period to adult. Blood
vessels labelled by Tomato lectin, expressed CD200 at all ages but
were more pronounced in P21 and adult. A distinct CD200 labelling
was observed in the hippocampal fissure (hf) along with the meninges
in all ages with decreasing intensity from P1 to adult. Many oval to
round meagrely ramified cells not stained by either NeuN or Iba1, but
some of them labelled with GFAP were present all across the hf in
postnatal groups but were much reduced or absent in adult mice. At
P21 and adult, hippocampal CD200 was mainly found as a stronger
labelling in the inner commissural-associational zone of the molecular
layer than in the outer molecular layer of DG. Microglial cells were
not found to be labelled with CD200. These data indicate that CD200
expression mediates immune regulation in neonates. Further study
with CD200R will shed light on their role in the exacerbated
inflammatory response in neonates.
[Show abstract][Hide abstract]ABSTRACT: In order to evaluate proinflammatory cytokine levels and their producing cell types in the control aged rat brain and after acute excitotoxic damage, both adult and aged male Wistar rats were injected with N-methyl-D-aspartate in the striatum. At different survival times between 6 hr and 7 days after lesioning, interleukin-1 beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-alpha) were analyzed by enzyme-linked immunosorbent assay and by double immunofluorescence of cryostat sections by using cell-specific markers. Basal cytokine expression was attributed to astrocytes and was increased in the normal aged brain showing region specificity: TNF-alpha and IL-6 displayed age-dependent higher levels in the aged cortex, and IL-1beta and IL-6 in the aged striatum. After excitotoxic striatal damage, notable age-dependent differences in cytokine induction in the aged vs. the adult were seen. The adult injured striatum exhibited a rapid induction of all cytokines analyzed, but the aged injured striatum showed a weak induction of cytokine expression: IL-1beta showed no injury-induced changes at any time, TNF-alpha presented a late induction at 5 days after lesioning, and IL-6 was only induced at 6 hr after lesioning. At both ages, in the lesion core, all cytokines were early expressed by neurons and astrocytes, and by microglia/macrophages later on. However, in the adjacent lesion border, cytokines were found in reactive astrocytes. This study highlights the particular inflammatory response of the aged brain and suggests an important role of increased basal levels of proinflammatory cytokines in the reduced ability to induce their expression after damage.
Full-text Article · Aug 2009 · Journal of Neuroscience Research
[Show abstract][Hide abstract]ABSTRACT: Inflammation is an important determinant of the severity and outcome of central nervous system injury. The endogenous anti-inflammatory cytokine interleukin-10 (IL-10) is upregulated in the injured adult central nervous system where it controls and terminates inflammatory processes. The developing brain, however, displays differences in susceptibility to insults and in associated inflammatory responses from the adult brain; the anatomic and temporal patterns of injury-induced IL-10 expression in the immature brain after excitotoxic injury are unknown. We analyzed the spaciotemporal gene and protein expression of IL-10 and its receptor (IL-10RI) in N-methyl-d-aspartate-induced excitotoxic injury in 9-day-old and control rats using quantitative reverse transcriptase polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. In noninjected control brains, both molecules were expressed mainly in white matter on glial cells and blood vessels; IL-10 was also observed on blood vessels in gray matter and in glial fibrillary acidic protein-positive processes in the hippocampus and near leptomeningeal and ventricle surfaces. In N-methyl-d-aspartate-injected brains, IL-10 gene and protein expression were maximal at 72 hours postinjection; IL-10RI gene and protein expression peaked at 48 hours postinjection. Interleukin-10 and IL-10RI expression in injured areas was mainly found in reactive astrocytes and in microglia/macrophages. The expression patterns of IL-10 and IL-10R suggest possible developmental roles, and their upregulation after injury suggests that this expression may have anti-inflammatory effects in distinct anatomic sites in the immature brain.
Full-text Article · May 2009 · Journal of Neuropathology and Experimental Neurology
[Show abstract][Hide abstract]ABSTRACT: Microglial and inflammatory responses to acute damage in aging are still poorly understood, although the aged brain responds differently to injury, showing poor lesion outcome. In this study, excitotoxicity was induced by intrastriatal injection of N-methyl-D-aspartate in adult (3-4 months) and aged (22-24 months) rats. Cryostat brain sections were processed for the analysis of microglial response by lectin histochemistry and cyclooxygenase 2 (COX2) and inducible nitric oxide synthase (iNOS) expression by immunohistochemistry and confocal analysis. Aged injured animals showed more widespread area of microglial response at 12 hr postlesion (hpl) and greater microglia/macrophage density at 3 days postlesion (dpl). However, aged reactive microglia showed prevalence of ramified morphologies and fewer amoeboid/round forms. Aged injured animals presented a diminished area of COX2 expression, but a significantly larger density of COX2(+) cells, with higher numbers of COX2(+) neurons during the first 24 hpl and COX2(+) microglia/macrophages later. In contrast, the amount of COX2(+) neutrophils was diminished in the aged. iNOS was more rapidly induced in the aged injured striatum, with higher cell density at 12 hpl, when expression was mainly neuronal. From 1 dpl, both the iNOS(+) area and the density of iNOS(+) cells were reduced in the aged, with lower numbers of iNOS(+) neurons, microglia/macrophages, neutrophils, and astrocytes. In conclusion, excitotoxic damage in aging induces a distinct pattern of microglia/macrophage response and expression of inflammatory enzymes, which may account for the changes in lesion outcome in the aged, and highlight the importance of using aged animals for the study of acute age-related insults.
Full-text Article · Nov 2008 · Journal of Neuroscience Research
[Show abstract][Hide abstract]ABSTRACT: The burden of neurological diseases in western societies has accentuated the need to develop effective therapies to stop the progression of chronic neurological diseases. Recent discoveries regarding the role of the immune system in brain damage coupled with the development of new technologies to manipulate the immune response make immunotherapies an attractive possibility to treat neurological diseases. The wide repertoire of immune responses and the possibility to engineer such responses, as well as their capacity to promote tissue repair, indicates that immunotherapy might offer benefits in the treatment of neurological diseases, similar to the benefits that are being associated with the treatment of cancer and autoimmune diseases. However, before applying such strategies to patients it is necessary to better understand the pathologies to be targeted, as well as how individual subjects may respond to immunotherapies, either in isolation or in combination. Due to the powerful effects of the immune system, one priority is to avoid tissue damage due to the activity of the immune system, particularly considering that the nervous system does not tolerate even the smallest amount of tissue damage.
[Show abstract][Hide abstract]ABSTRACT: Mammalian SVZ progenitors continuously generate new neurons in the olfactory bulb. After injury, changes in SVZ cell number suggest injury-induced migration. Studies that trace the migration of SVZ precursors into neurodegenerating areas are lacking. Previously, we showed a decrease in BrdU+SVZ cells following excitotoxic damage to the immature rat cortex. Here, we demonstrate that NMDA-induced injury forces endogenous Cell Tracker Green (CTG) labeled VZ/SVZ precursors out of the SVZ into the neurodegenerating cortex. CTG+/Nestin+/Filamin A+ precursors are closely associated with vimentin+/GFAP+/GLAST+ filaments and express both chemokine receptor CXCR4 and Robo1. In the cortex, SVZ-derived progenitors show a progressive expression of developing, migrating and mature neurons and glial markers. CTG+/GFAP+ astrocytes greatly outnumber CTG+/MAP2+/NeuN+ neurons. SVZ-derived progenitors differentiate into both tbr1+ cortical glutamatergic neurons and calretinin+ interneurons. But, there is little integration of these neurons into the existing circuitry, as seen by Fluorogold retrograde tracing from the internal capsule.
Full-text Article · Jul 2008 · Molecular and Cellular Neuroscience
[Show abstract][Hide abstract]ABSTRACT: Following immature excitotoxic brain damage, distinct patterns of caspase activation have been described in neurons and glial cells. Neuronal cells show activation of the mitochondrial apoptosis pathway, caspase-3 cleavage and apoptotic cell death, while reactive astrocytes show caspase-3 cleavage that is not always correlated with enzymatic protease activity and does not generally terminate in cell death. Accordingly, the aim of the present study was to evaluate the astrocytic colocalization of cleaved caspase-3 and several anti-apoptotic proteins of the inhibitor of apoptosis proteins family (IAPs), such as survivin and cellular inhibitor of apoptosis-2 (cIAP-2), and the heat shock proteins (HSPs) family, Hsp25/27 and Hsc70/Hsp70, which can all prevent caspases from cleaving their substrates. At several survival times ranging from 4 h to 14 days after cortical excitotoxic damage induced by N-methyl-d-aspartate (NMDA) injection at postnatal day 9 in rat pups, single and double immunohistochemical techniques were performed in free floating cryostat sections and sections were analyzed by confocal microscopy. Our results show that survivin and Hsp25/27 are primarily expressed in reactive astrocytes of the damaged cortex and the adjacent white matter. In addition, both molecules strongly colocalize with cleaved caspase-3. Survivin is primarily located in the nucleus, like cleaved caspase-3; while Hsp25/27 is cytoplasmic but very frequently found in cells showing nuclear caspase-3. cIAP-2 was mostly found in damaged neurons but also in some glial scar reactive astrocytes and showed fewer correlation with caspase-3. Hsc70/Hsp70 was only expressed in injured neurons and did not correlate with caspase-3. Thus, we conclude that primarily survivin and Hsp25/27 may participate in the inhibition of cleaved caspase-3 in reactive astrocytes and may be involved in protecting astrocytes after injury.
[Show abstract][Hide abstract]ABSTRACT: Although cleaved caspase-3 is known to be involved in apoptotic cell death mechanisms in neurons, it can also be involved in a nonapoptotic role in astrocytes after postnatal excitotoxic injury. Here we evaluate participation of upstream pathways activating caspase-3 in neurons and glial cells, by studying the intrinsic pathway via caspase-9, the extrinsic pathway via caspase-8, and activation of the p53-dependent pathway. N-methyl-D-aspartate (NMDA) was injected intracortically in 9-day-old postnatal rats, which were sacrificed at several survival times between 4 hr postlesion (pl) and 7 days pl. We analyzed temporal and spatial expression of caspase-8, caspase-9, and p53 and correlation with neuronal and glial markers and caspase-3 activation. Caspase-9 was significantly activated at 10 hpl, strongly correlating with caspase-3. It was present mainly in damaged cortical and hippocampal neurons but was also seen in astrocytes and oligodendrocytes in layer VI and corpus callosum (cc). Caspase-8 showed a diminished correlation with caspase-3. It was present in cortical neurons at 10-72 hpl, showing layer specificity, and also in astroglial and microglial nuclei, mainly in layer VI and cc. p53 Expression increased at 10-72 hpl but did not correlate with caspase-3. p53 Was seen in neurons of the degenerating cortex and in some astrocytes and microglial cells of layer VI and cc. In conclusion, after neonatal excitotoxicity, mainly the mitochondrial intrinsic pathway mediates neuronal caspase-3 and cell death. In astrocytes, caspase-3 is not widely correlated with caspase-8, caspase-9, or p53, except in layer VI-cc astrocytes, where activation of upstream cascades occurs.
Full-text Article · Dec 2007 · Journal of Neuroscience Research