GFAP-immunoreactive Astrocytes Research Articles

Astrocytic changes with aging and Alzheimer's disease-type pathology in chimpanzees.

Astrocytes are the main homeostatic cell of the central nervous system. In addition, astrocytes mediate an inflammatory response when reactive to injury or disease known as astrogliosis. Astrogliosis is marked by an increased expression of glial fibrillary acidic protein (GFAP) and cellular hypertrophy. Some degree of astrogliosis is associated with normal aging and degenerative conditions such as Alzheimer's disease (AD) and other dementing illnesses in humans. The recent observation of pathological markers of AD (amyloid plaques and neurofibrillary tangles) in aged chimpanzee brains provided an opportunity to examine the relationships among aging, AD-type pathology, and astrocyte activation in our closest living relatives. Stereologic methods were used to quantify GFAP-immunoreactive astrocyte density and soma volume in layers I, III, and V of the prefrontal and middle temporal cortex, as well as in hippocampal fields CA1 and CA3. We found that the patterns of astrocyte activation in the aged chimpanzee brain are distinct from humans. GFAP expression does not increase with age in chimpanzees, possibly indicative of lower oxidative stress loads. Similar to humans, chimpanzee layer I astrocytes in the prefrontal cortex are susceptible to AD-like changes. Both prefrontal cortex layer I and hippocampal astrocytes exhibit a high degree of astrogliosis that is positively correlated with accumulation of amyloid beta and tau proteins. However, unlike humans, chimpanzees do not display astrogliosis in other cortical layers. These results demonstrate a unique pattern of cortical aging in chimpanzees and suggest that inflammatory processes may differ between humans and chimpanzees in response to pathology.

Differential regional infarction, neuronal loss and gliosis in the gerbil cerebral hemisphere following 30 min of unilateral common carotid artery occlusion.

The degree of transient ischemic damage in the cerebral hemisphere is different according to duration of transient ischemia and cerebral regions. Mongolian gerbils show various lesions in the hemisphere after transient unilateral occlusion of the common carotid artery (UOCCA) because they have different types of patterns of anterior and posterior communicating arteries. We examined differential regional damage in the ipsilateral hemisphere of the gerbil after 30 min of UOCCA by using 2,3,5-triphenyltetrazolium chloride (TTC) staining, cresyl violet (CV) Nissl staining, Fluoro-Jade B (F-J B) fluorescence staining, and NeuN immunohistochemistry 5 days after UOCCA. In addition, regional differences in reactions of astrocytes and microglia were examined using GFAP and Iba-1 immunohistochemistry. After right UOCCA, neurological signs were assessed to define ischemic symptomatic animals. Moderate symptomatic gerbils showed several infarcts, while mild symptomatic gerbils showed selective neuronal death/loss in the primary motor and sensory cortex, striatum, thalamus, and hippocampus 5 days after UOCCA. In the areas, morphologically changed GFAP immunoreactive astrocytes and Iba-1 immunoreactive microglia were found, and their numbers were increased or decreased according to the damaged areas. In brief, our results demonstrate that 30 min of UOCCA in gerbils produced infarcts or selective neuronal death depending on ischemic severity in the ipsilateral cerebral cortex, striatum, thalamus and hippocampus, showing that astrocytes and microglia were differently reacted 5 days after UOCCA. Taken together, a gerbil model of 30 min of UOCCA can be used to study mechanisms of infarction and/or regional selective neuronal death/loss as well as neurological dysfunction following UOCCA.

Astrocyte-Derived Exosomes Treated With a Semaphorin 3A Inhibitor Enhance Stroke Recovery via Prostaglandin D2 Synthase.

Background and Purpose- Exosomes play a pivotal role in neurogenesis. In the peri-infarct area after stroke, axons begin to regenerate but are inhibited by astrocyte scar formation. The direct effect and underlying molecular mechanisms of astrocyte-derived exosomes on axonal outgrowth after ischemia are not known. Methods- Using a semaphorin 3A (Sema3A) inhibitor, we explored neuronal signaling during axonal outgrowth after ischemia in rats subjected to middle cerebral artery occlusion and in cultured cortical neurons challenged with oxygen-glucose deprivation. Furthermore, we assessed whether this inhibitor suppressed astrocyte activation and regulated astrocyte-derived exosomes to enhance axonal outgrowth after ischemia. Results- In rats subjected to middle cerebral artery occlusion, we administered a Sema3A inhibitor into the peri-infarct area from 7 to 21 days after occlusion. We found that phosphorylated high-molecular weight neurofilament-immunoreactive axons were increased, glial fibrillary acidic protein-immunoreactive astrocytes were decreased, and functional recovery was promoted at 28 days after middle cerebral artery occlusion. In cultured neurons, the Sema3A inhibitor decreased Rho family GTPase 1, increased R-Ras, which phosphorylates Akt and glycogen synthase kinase 3β (GSK-3β), selectively increased phosphorylated GSK-3β in axons, and thereby enhanced phosphorylated high-molecular weight neurofilament-immunoreactive axons after oxygen-glucose deprivation. In cultured astrocytes, the Sema3A inhibitor suppressed activation of astrocytes induced by oxygen-glucose deprivation. Exosomes secreted from ischemic astrocytes treated with the Sema3A inhibitor further promoted axonal elongation and increased prostaglandin D2 synthase expression on microarray analysis. GSK-3β+ and prostaglandin D2 synthase+ neurons were robustly increased after treatment with the Sema3A inhibitor in the peri-infarct area. Conclusions- Neuronal Rho family GTPase 1/R-Ras/Akt/GSK-3β signaling, axonal GSK-3β expression, and astrocyte-derived exosomes with prostaglandin D2 synthase expression contribute to axonal outgrowth and functional recovery after stroke.

Treatment of male rats with finasteride, an inhibitor of 5alpha-reductase enzyme, induces long-lasting effects on depressive-like behavior, hippocampal neurogenesis, neuroinflammation and gut microbiota composition

Persistent alteration of plasma neuroactive steroid levels associated with major depression has been recently reported in men after the suspension of the treatment for androgenetic alopecia with finasteride, an inhibitor of the enzyme 5alpha-reductase. Observations in male rats confirmed persistent alterations in neuroactive steroid levels also in the brain. In the present study, we have ascertained possible effects on depressive-like behavior, neurogenesis, gliosis, neuroinflammation and gut microbiota in male rats after subchronic treatment for 20 days with finasteride and after one month of its withdrawal. At the end of treatment there was an increase in the number of pH3 immunoreactive cells in the subgranular zone of the dentate gyrus together with an increase in the mRNA levels of TNF-α in the hippocampus. By one month after the end of finasteride treatment, rats showed depressive-like behavior coupled with a decrease in the number of pH3 immunoreactive cells in the subgranular zone of the dentate gyrus, a decrease in granule cell density in the granule cell layer and an increase in the number of GFAP immunoreactive astrocytes in the dentate gyrus. Finally, alteration of gut microbiota (i.e., an increase in Bacteroidetes phylum and in Prevotellaceae family at the end of the treatment and a decrease in Ruminococcaceae family, Oscillospira and Lachnospira genus at the end of the withdrawal period) was detected.In conclusion, finasteride treatment in male rats has long term effects on depressive-like behavior, hippocampal neurogenesis and neuroinflammation and gut microbiota composition.

Astrocyte pathology in the ventral prefrontal white matter in depression

Astrocyte functions in white matter are less well understood than in gray matter. Our recent study of white matter in ventral prefrontal cortex (vPFC) revealed alterations in expression of myelin-related genes in major depressive disorder (MDD). Since white matter astrocytes maintain myelin, we hypothesized that morphometry of these cells will be altered in MDD in the same prefrontal white matter region in which myelin-related genes are altered. White matter adjacent to vPFC was examined in 25 MDD and 21 control subjects. Density and size of GFAP-immunoreactive (-ir) astrocyte cell bodies was measured. The area fraction of GFAP-ir astrocytes (cell bodies + processes) was also estimated. GFAP mRNA expression was determined using qRT-PCR. The density of GFAP-ir astrocytes was also measured in vPFC white matter of rats subjected to chronic unpredictable stress (CUS) and control animals. Fibrous and smooth GFAP-ir astrocytes were distinguished in human white matter. The density of both types of astrocytes was significantly decreased in MDD. Area fraction of GFAP immunoreactivity was significantly decreased in MDD, but mean soma size remained unchanged. Expression of GFAP mRNA was significantly decreased in MDD. In CUS rats there was a significant decrease in astrocyte density in prefrontal white matter. The decrease in density and area fraction of white matter astrocytes and GFAP mRNA in MDD may be linked to myelin pathology previously noted in these subjects. Astrocyte pathology may contribute to axon disturbances in axon integrity reported by neuroimaging studies in MDD and interfere with signal conduction in the white matter.

Memantine treatment of juvenile rats with kaolin-induced hydrocephalus

Memantine is a selective, non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist that has previously been shown to have neuroprotective qualities in some animal models of neurologic disease. We hypothesized that memantine therapy would improve behavioral, neuropathological, and/or biochemical outcomes in juvenile rats with kaolin-induced hydrocephalus. Three-week old rats received an injection of kaolin (aluminum silicate) into the cisterna magna. Magnetic resonance imaging was performed one week later to assess ventricle size and stratify rats to three treatment groups. Rats were blindly treated daily for three weeks with saline or 10 or 30 mg/kg/day memantine. Behavior measures were performed weekly. Histologic and biochemical evaluations were performed at termination. Hydrocephalic rats showed no differences in weight among treatment groups. Memantine treatment stabilized ventricular enlargement in both low and high dose groups. The high dose group exhibited increased motor activity in open field chambers compared to the vehicle-treated group. However, there were no significant differences between the three hydrocephalic treatment groups for other behavioral tasks. Ventriculomegaly was associated with periventricular white matter damage. Glial fibrillary acidic protein (GFAP) content was higher in the low dose memantine group compared to vehicle-treated group, but there were no differences in GFAP-immunoreactive astrocytes or Iba-1- immunoreactive microglia between groups. Memantine therapy stabilized ventricular expansion and improved some behavioral measures but did not reduce brain tissue changes in juvenile rats with kaolin-induced hydrocephalus.

Ginsenoside Re protects methamphetamine-induced dopaminergic neurotoxicity in mice via upregulation of dynorphin-mediated \u03ba-opioid receptor and downregulation of substance P-mediated neurokinin 1 receptor

BackgroundWe previously reported that ginsenoside Re (GRe) attenuated against methamphetamine (MA)-induced neurotoxicity via anti-inflammatory and antioxidant potentials. We also demonstrated that dynorphin possesses anti-inflammatory and antioxidant potentials against dopaminergic loss, and that balance between dynorphin and substance P is important for dopaminergic neuroprotection. Thus, we examined whether GRe positively affects interactive modulation between dynorphin and substance P against MA neurotoxicity in mice.MethodsWe examined changes in dynorphin peptide level, prodynorphin mRNA, and substance P mRNA, substance P-immunoreactivity, homeostasis in enzymatic antioxidant system, oxidative parameter, microglial activation, and pro-apoptotic parameter after a neurotoxic dose of MA to clarify the effects of GRe, prodynorphin knockout, pharmacological inhibition of κ-opioid receptor (i.e., nor-binaltorphimine), or neurokinin 1 (NK1) receptor (i.e., L-733,060) against MA insult in mice.ResultsGRe attenuated MA-induced decreases in dynorphin level, prodynorphin mRNA expression in the striatum of wild-type (WT) mice. Prodynorphin knockout potentiated MA-induced dopaminergic toxicity in mice. The imbalance of enzymatic antioxidant system, oxidative burdens, microgliosis, and pro-apoptotic changes led to the dopaminergic neurotoxicity. Neuroprotective effects of GRe were more pronounced in prodynorphin knockout than in WT mice. Nor-binaltorphimine, a κ-opioid receptor antagonist, counteracted against protective effects of GRe. In addition, we found that GRe significantly attenuated MA-induced increases in substance P-immunoreactivity and substance P mRNA expression in the substantia nigra. These increases were more evident in prodynorphin knockout than in WT mice. Although, we observed that substance P-immunoreactivity was co-localized in NeuN-immunreactive neurons, GFAP-immunoreactive astrocytes, and Iba-1-immunoreactive microglia. NK1 receptor antagonist L-733,060 or GRe selectively inhibited microgliosis induced by MA. Furthermore, L-733,060 did not show any additive effects against GRe-mediated protective activity (i.e., antioxidant, antimicroglial, and antiapoptotic effects), indicating that NK1 receptor is one of the molecular targets of GRe.ConclusionsOur results suggest that GRe protects MA-induced dopaminergic neurotoxicity via upregulatgion of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated NK1 R.

Decrease in glucose transporter 1 levels and translocation of glucose transporter 3 in the dentate gyrus of C57BL/6 mice and gerbils with aging

In the present study, we compared the cell-specific expression and changes protein levels in the glucose transporters (GLUTs) 1 and 3, the major GLUTs in the mouse and gerbil brains using immuno-histochemistry and Western blot analysis. In both mouse and gerbils, GLUT1 immunoreactivity was mainly found in the blood vessels in the dentate gyrus, while GLUT3 immunoreactivity was detected in the subgranular zone and the molecular layer of the dentate gyrus. GLUT1-immunoreactivity in blood vessels and GLUT1 protein levels were significantly decreased with age in the mice and gerbils, respectively. In addition, few GLUT3-immunoreactive cells were found in the subgranular zone in aged mice and gerbils, but GLUT3-immunoreactivity was abundantly found in the polymorphic layer of dentate gyrus in mice and gerbils with a dot-like pattern. Based on the double immunofluorescence study, GLUT3-immunoreactive structures in gerbils were localized in the glial fibrillary acidic protein-immunoreactive astrocytes in the dentate gyrus. Western blot analysis showed that GLUT3 expression in the hippocampal homogenates was slightly, although not significantly, decreased with age in mice and gerbils, respectively. These results indicate that the reduction in GLUT1 in the blood vessels of dentate gyrus and GLUT3 in the subgranular zone of dentate gyrus may be associated with the decrease in uptake of glucose into brain and neuroblasts in the dentate gyrus. In addition, the expression of GLUT3 in the astrocytes in polymorphic layer of dentate gyrus may be associated with metabolic changes in glucose in aged hippocampus.

Astrocytic expression of the CXCL12 receptor, CXCR7/ACKR3 is a hallmark of the diseased, but not developing CNS.

Based on our previous demonstration of CXCR7 as the major mediator of CXCL12 signaling in cultured astrocytes, we have now compared astrocytic expression of the CXCL12 receptors, CXCR7 and CXCR4, during CNS development and disease. In addition, we asked whether disease-associated conditions/factors affect expression of CXCL12 receptors in astrocytes. In the late embryonic rat brain, CXCR7+/GFAP+ cells were restricted to the ventricular/subventricular zone while CXCR4 was widely absent from GFAP-positive cells. In the early postnatal and adult brain, CXCR7 and CXCR4 were almost exclusively expressed by GFAP-immunoreactive astrocytes forming the superficial glia limitans. Contrasting the situation in the intact CNS, a striking increase in astrocytic CXCR7 expression was detectable in the cortex of rats with experimental brain infarcts, in the spinal cord of rats with experimental autoimmune encephalomyelitis (EAE) and after mechanical compression, as well as in the in infarcted human cerebral cortex and in the hippocampus of Alzheimer's disease patients. None of these pathologies was associated with substantial increases in astrocytic CXCR4 expression. Screening of various disease-associated factors/conditions further revealed that CXCR7 expression of cultured cortical astrocytes increases with IFNγ as well as under hypoxic conditions whereas CXCR7 expression is attenuated following treatment with IFNβ. Again, none of the treatments affected CXCR4 expression in cultured astrocytes. Together, these findings support the hypothesis of a crucial role of astrocytic CXCR7 in the progression of various CNS pathologies.

Assessing the brain through the eye: New ways to explore hepatic encephalopathy

Background & aimsMinimal hepatic encephalopathy (mHE) has been shown to affect daily functioning, quality of life, driving and overall mortality. However, little is known about treating or diagnosing early impairments in mHE. We studied one of its precipitating factors, portal hypertension which is driving the inflammatory process behind mHE. The purpose was to describe an indirect diagnostic method able to detect the pathology at early stages based on the study of the vascularization and mast cells conjunctival hyperplasia as secondary inflammatory response associated to portal hypertension. Finally, we correlated the presence of histological changes in the eye in mHE with deficits in behavioral task acquisition. MethodsRats were trained on a stimulus-response task and a spatial working memory task using the Morris water maze. Two groups of animals were used: a SHAM (sham-operated) group (n=10) and a portal hypertension (HT) group (n=10). The triple portal vein ligation method was used to create an animal model of mHE. Latencies to reach the platform, number of glial fibrillary acidic protein-immunoreactive astrocytes (GFAP-IR), mast cell expression and presence/absence of blood and lymphatic vessels were examined. ResultsThere were differences in stimulus-response behavioral performance, with a deficit in the acquisition in the HT group. However, no differences between groups were found on the spatial working memory task. At the same time, differences between groups were found in the GFAP-IR density, which was lower in the HT group, and in the number of mast cells and the presence of vessels, which were higher in the HT group. ConclusionsIn this study, we provide the first preliminary insight into the validity of exploring the eye as a possible tool to assess the diagnosis of mHE conditions.

Neuronal injury and tumor necrosis factor-alpha immunoreactivity in the rat hippocampus in the early period of asphyxia-induced cardiac arrest under normothermia.

Low survival rate occurs in patients who initially experience a spontaneous return of circulation after cardiac arrest (CA). In this study, we induced asphyxial CA in adult male Sprague-Daley rats, maintained their body temperature at 37 ± 0.5°C, and then observed the survival rate during the post-resuscitation phase. We examined neuronal damage in the hippocampus using cresyl violet (CV) and Fluore-Jade B (F-J B) staining, and pro-inflammatory response using ionized calcium-binding adapter molecule 1 (Iba-1), glial fibrillary acidic protein (GFAP), and tumor necrosis factor-alpha (TNF-α) immunohistochemistry in the hippocampus after asphyxial CA in rats under normothermia. Our results show that the survival rate decreased gradually post-CA (about 63% at 6 hours, 37% at 1 day, and 8% at 2 days post-CA). Rats were sacrificed at these points in time post-CA, and no neuronal damage was found in the hippocampus until 1 day post-CA. However, some neurons in the stratum pyramidale of the CA region in the hippocampus were dead 2 days post-CA. Iba-1 immunoreactive microglia in the CA1 region did not change until 1 day post-CA, and they were activated (enlarged cell bodies with short and thicken processes) in all layers 2 days post-CA. Meanwhile, GFAP-immunoreactive astrocytes did not change significantly until 2 days post-CA. TNF-α immunoreactivity decreased significantly in neurons of the stratum pyramidale in the CA1 region 6 hours post-CA, decreased gradually until 1 day post-CA, and increased significantly again 2 days post-CA. These findings suggest that low survival rate of normothermic rats in the early period of asphyxia-induced CA is related to increased TNF-α immunoreactivity, but not to neuronal damage in the hippocampal CA1 region.

Disinhibition of the intergeniculate leaflet network in the WAG/Rij rat model of absence epilepsy

The intergeniculate leaflet (IGL) of the thalamus is a retinorecipient structure implicated in orchestrating circadian rhythmicity. The IGL network is highly GABAergic and consists mainly of neuropeptide Y-synthesising and enkephalinergic neurons. A high density of GFAP-immunoreactive astrocytes has been observed in the IGL, with a probable function in guarding neuronal inhibition. Interestingly, putatively enkephalinergic IGL neurons generate action potentials with an infra-slow oscillatory (ISO) pattern in vivo in urethane anesthetised Wistar rats, under light-on conditions only. Absence epilepsy (AE) is a disease characterised by spike-wave discharges present in the encephalogram, directly caused by hypersynchronous thalamo-cortical oscillations. Many pathologies connected with the arousal system, such as abnormalities in sleep architecture and an insufficient brain sleep-promoting system accompany the epileptic phenotype. We hypothesise that disturbances in the function of biological clock structures, controlling this rhythmic physiological process, may be responsible for the observed pathomechanism. To test this hypothesis, we performed an in vitro patch-clamp study on WAG/Rij rats, a well-validated genetic model of AE, in order to assess dampened GABAergic synaptic transmission in the IGL expressed as a lower IPSC amplitude and reduced sIPSC frequency. Moreover, our in vivo extracellular recordings showed higher firing rate of ISO IGL neurons with an abnormal reaction to a change in constant illumination (maintenance of rhythmic neuronal activity in darkness) in the AE model. Additional immunohistochemical experiments indicated astrogliosis in the area of the IGL, which may partially underlie the observed changes in inhibition. Altogether, the data presented here show for the first time the disinhibition of IGL neurons in a model of AE, thereby proposing the possible involvement of circadian-related brain structures in the epileptic phenotype.

Neuroinflammatory Markers in Spontaneously Hypertensive Rat Brain: An Immunohistochemical Study.

Spontaneously hypertensive rats (SHR) represent a model of hypertension and vascular injury. In the past decade, SHR were also considered as a model of vascular dementia. Several studies have shown that cerebrovascular changes in SHR may mimic brain vascular diseases of hypertensive individuals. Vascular and cerebrovascular changes during hypertension are often linked to inflammatory processes. Inflammation frequently affects vascular endothelium, perivascular astrocytes that form blood brain barrier. This inflammatory reaction may lead to neuro-inflammation with consequent damage of brain tissue. A significant brain atrophy, a reduction of white matter volumes, and BBB dysfunction were found in SHR. Micro- and macrogliosis in deep cortical regions were also observed. Based on these findings, this study was designed to define neuroinflammation entity in SHR, using immunohistochemistry technique for different inflammatory markers. Thirty-two-week-old SHR and age-matched Wistar Kyoto rats were used. Brain was processed for immunohistochemistry. Astrogliosis markers for astrocytes (glial fibrillary acidic protein) and microglia (isolectin IB4) were used. The pro-inflammatory interleukins (IL-1b, IL-6) and tumor necrosis factor alpha (TNFa) expression were also evaluated. In SHR brain, an obvious glial reaction was found both for GFAP-immunoreactive astrocytes and for microglia. The pro-inflammatory IL-1b was significantly increased in CA1 sub-field of SHR hippocampus. The TNFa expression was higher in frontal cortex of SHR compared to WKY. The above neuromorphological evidences indicate that SHR are predictive animal models for vascular brain disorders and neuroinflammation. Furthermore, this model may be useful to evaluate anti-inflammatory and neuroprotective effects of different molecules.

Salicylate-Induced Hearing Loss Trigger Structural Synaptic Modifications in the Ventral Cochlear Nucleus of Rats via Medial Olivocochlear (MOC) Feedback Circuit.

Lesion-induced cochlear damage can result in synaptic outgrowth in the ventral cochlear nucleus (VCN). Tinnitus may be associated with the synaptic outgrowth and hyperactivity in the VCN. However, it remains unclear how hearing loss triggers structural synaptic modifications in the VCN of rats subjected to salicylate-induced tinnitus. To address this issue, we evaluated tinnitus-like behavior in rats after salicylate treatment and compared the amplitude of the distortion product evoked otoacoustic emission (DPOAE) and auditory brainstem response (ABR) between control and treated rats. Moreover, we observed the changes in the synaptic ultrastructure and in the expression levels of growth-associated protein (GAP-43), brain-derived neurotrophic factor (BDNF), the microglial marker Iba-1 and glial fibrillary acidic protein (GFAP) in the VCN. After salicylate treatment (300mg/kg/day for 4 and 8days), analysis of the gap prepulse inhibition of the acoustic startle showed that the rats were experiencing tinnitus. The changes in the DPOAE and ABR amplitude indicated an improvement in cochlear sensitivity and a reduction in auditory input following salicylate treatment. The treated rats displayed more synaptic vesicles and longer postsynaptic density in the VCN than the control rats. We observed that the GAP-43 expression, predominantly from medial olivocochlear (MOC) neurons, was significantly up-regulated, and that BDNF- and Iba-1-immunoreactive cells were persistently decreased after salicylate administration. Furthermore, GFAP-immunoreactive astrocytes, which is associated with synaptic regrowth, was significantly increased in the treated groups. Our study revealed that reduced auditory nerve activity triggers synaptic outgrowth and hyperactivity in the VCN via a MOC neural feedback circuit. Structural synaptic modifications may be a reflexive process that compensates for the reduced auditory input after salicylate administration. However, massive increases in excitatory synapses in the VCN may represent a detrimental process that causes central hyperactivity, leading to tinnitus.

Housing Complexity Alters GFAP-Immunoreactive Astrocyte Morphology in the Rat Dentate Gyrus

Rats used in research are typically housed singly in cages with limited sensory stimulation. There is substantial evidence that housing rats in these conditions lead to numerous neuroanatomical and behavioral abnormalities. Alternatively, rats can be housed in an enriched environment in which rats are housed in groups and given room for exercise and exploration. Enriched environments result in considerable neuroplasticity in the rodent brain. In the dentate gyrus of the hippocampus, enriched environments evoke especially profound neural changes, including increases in the number of neurons and the number of dendritic spines. However, whether changes in astrocytes, a type of glia increasingly implicated in mediating neuroplasticity, are concurrent with these neural changes remains to be investigated. In order to assess morphological changes among astrocytes of the rat dentate gyrus, piSeeDB was used to optically clear 250 μm sections of tissue labeled using GFAP immunohistochemistry. Confocal imaging and image analysis were then used to measure astrocyte morphology. Astrocytes from animals housed in EE demonstrated a reduced distance between filament branch points. Furthermore, the most complex astrocytes were significantly more complex among animals housed in EE compared to standard environments.

Density of GFAP-immunoreactive astrocytes is decreased in left hippocampi in major depressive disorder

Neuroimaging and postmortem studies of subjects with major depressive disorder (MDD) reveal smaller hippocampal volume with lengthening duration of illness. Pathology in astrocytes may contribute significantly to this reduced volume and to the involvement of the hippocampus in MDD. Postmortem hippocampal tissues were collected from 17 subjects with MDD and 17 psychiatrically-normal control subjects. Sections from the body of the hippocampus were immunostained for glial fibrillary acidic protein (GFAP), a marker of intermediate filament protein expressed in astrocytes. The density of GFAP-immunoreactive astrocytes was measured in the hippocampus using 3-dimensional cell counting. Hippocampal subfields were also assessed for GFAP-immunoreactive area fraction. In CA1, there was a significant positive correlation between age and either density or area fraction in MDD. The density of astrocytes in the hilus, but not CA1 or CA2/3, was significantly decreased only in depressed subjects not taking an antidepressant drug, but not for depressed subjects taking an antidepressant drug. The area fraction of GFAP-immunoreactivity was significantly decreased in the dentate gyrus in women but not men with depression. In CA2/3, the area fraction of GFAP-immunoreactivity was inversely correlated with the duration of depression in suicide victims. Astrocyte contributions to neuronal function in the hilus may be compromised in depressed subjects not taking antidepressant medication. Due to the cross-sectional nature of the present study of postmortem brain tissue, it remains to be determined whether antidepressant drug treatment prevented a decrease in GFAP-immunoreactive astrocyte density or restored cell density to normal levels.

Main target of minimal hepatic encephalopathy: Morphophysiological, inflammatory and metabolic view

Although often not considered clinically relevant and, therefore, not diagnosed or treated, minimal hepatic encephalopathy (MHE) has been shown to affect daily functioning, quality of life, driving and overall mortality. To discover early impairments involved in MHE, we studied one of its precipitating factors, portal hypertension. Rats were trained on a stimulus–response task using the Morris water maze. Two groups of animals were used: a SHAM (sham-operated) group (n=13) and a portal hypertension (PH) group (n=13). The triple portal vein ligation method was used to create an animal model of an early developmental phase of HE. Brain metabolic activity was studied with cytochrome c-oxidase histochemistry (C.O.). Neuronal nuclear volume was assessed by nucleator probe; the number of glial fibrillary acidic protein-immunoreactive astrocytes (GFAP-IR) and proinflammatory mediators was measured. The results revealed that the PH group was not able to reach the behavioural criterion, in contrast to the SHAM group. The metabolic brain consumption revealed decreased C.O. activity in the ventral striatum. The PH group showed lower density of GFAP-IR and an increase in the tumour necrotic factor-α (TNF-α). The PH group showed decreased neuronal nuclear volume in the dorsal striatum. On the contrary, increased neuronal nuclear volume was found in the ventral striatum. For the first time, a relationship has been established between inflammation, astrocytic and neural damage, and brain metabolic impairment in a model of MHE. Disruption of the striatum and related structures was highlighted as the main target in early stages of HE. Finally, a simple task was presented to assess the subtle impairments found in the clinic, which could provide fresh insights into the development of new tools for the assessment of MHE.

σ1 receptors activate astrocytes via p38 MAPK phosphorylation leading to the development of mechanical allodynia in a mouse model of neuropathic pain.

Spinal astrocytes have emerged as important mechanistic contributors to the genesis of mechanical allodynia (MA) in neuropathic pain. We recently demonstrated that the spinal sigma non-opioid intracellular receptor 1 (σ1 receptor) modulates p38 MAPK phosphorylation (p-p38), which plays a critical role in the induction of MA in neuropathic rats. However, the histological and physiological relationships among σ1, p-p38 and astrocyte activation is unclear. We investigated: (i) the precise location of σ1 receptors and p-p38 in spinal dorsal horn; (ii) whether the inhibition of σ1 receptors or p38 modulates chronic constriction injury (CCI)-induced astrocyte activation; and (iii) whether this modulation of astrocyte activity is associated with MA development in CCI mice. The expression of σ1 receptors was significantly increased in astrocytes on day 3 following CCI surgery. Sustained intrathecal treatment with the σ1 antagonist, BD-1047, attenuated CCI-induced increase in GFAP-immunoreactive astrocytes, and the treatment combined with fluorocitrate, an astrocyte metabolic inhibitor, synergistically reduced the development of MA, but not thermal hyperalgesia. The number of p-p38-ir astrocytes and neurons, but not microglia was significantly increased. Interestingly, intrathecal BD-1047 attenuated the expression of p-p38 selectively in astrocytes but not in neurons. Moreover, intrathecal treatment with a p38 inhibitor attenuated the GFAP expression, and this treatment combined with fluorocitrate synergistically blocked the induction of MA. Spinal σ1 receptors are localized in astrocytes and blockade of σ1 receptors inhibits the pathological activation of astrocytes via modulation of p-p38, which ultimately prevents the development of MA in neuropathic mice.

Histological studies of neuroprotective effects of Curcuma longa Linn. on neuronal loss induced by dexamethasone treatment in the rat hippocampus

Long term exposure to dexamethasone (Dx) is associated with brain damage especially in the hippocampus via the oxidative stress pathway. Previously, an ethanolic extract from Curcuma longa Linn. (CL) containing the curcumin constituent has been reported to produce antioxidant effects. However, its neuroprotective property on brain histology has remained unexplored. This study has examined the effects of a CL extract on the densities of cresyl violet positive neurons and glial fibrillary acidic protein immunoreactive (GFAP-ir) astrocytes in the hippocampus of Dx treated male rats. It showed that 21days of Dx treatment (0.5mg/kg, i.p. once daily) significantly reduced the densities of cresyl violet positive neurons in the sub-areas CA1, CA3 and the dentate gyrus, but not in the CA2 area. However, CL pretreatment (100mg/kg, p.o.) was found to significantly restore neuronal densities in the CA1 and dentate gyrus. In addition, Dx treatment also significantly decreased the densities of the GFAP-ir astrocytes in the sub-areas CA1, CA3 and the dentate gyrus. However, CL pretreatment (100mg/kg, p.o.) failed to protect the loss of astrocytes in these sub-areas. These findings confirm the neuroprotective effects of the CL extract and indicate that the cause of astrocyte loss might be partially reduced by a non-oxidative mechanism. Moreover, the detection of neuronal and glial densities was suitable method to study brain damage and the effects of treatment.

Aromatase Inhibition Exacerbates Pain and Reactive Gliosis in the Dorsal Horn of the Spinal Cord of Female Rats Caused by Spinothalamic Tract Injury

Central pain syndrome is characterized by severe and excruciating pain resulting from a lesion in the central nervous system. Previous studies have shown that estradiol decreases pain and that inhibitors of the enzyme aromatase, which synthesizes estradiol from aromatizable androgens, increases pain sensitivity. In this study we have assessed whether aromatase expression in the dorsal horns of the spinal cord is altered in a rat model of central pain syndrome, induced by the unilateral electrolytic lesion of the spinothalamic tract. Protein and mRNA levels of aromatase, as well as the protein and mRNA levels of estrogen receptors α and β, were increased in the dorsal horn of female rats after spinothalamic tract injury, suggesting that the injury increased estradiol synthesis and signaling in the dorsal horn. To determine whether the increased aromatase expression in this pain model may participate in the control of pain, mechanical allodynia thresholds were determined in both hind paws after the intrathecal administration of letrozole, an aromatase inhibitor. Aromatase inhibition enhanced mechanical allodynia in both hind paws. Because estradiol is known to regulate gliosis we assessed whether the spinothalamic tract injury and aromatase inhibition regulated gliosis in the dorsal horn. The proportion of microglia with a reactive phenotype and the number of glial fibrillary acidic protein-immunoreactive astrocytes were increased by the injury in the dorsal horn. Aromatase inhibition enhanced the effect of the injury on gliosis. Furthermore, a significant a positive correlation of mechanical allodynia and gliosis in the dorsal horn was detected. These findings suggest that aromatase is up-regulated in the dorsal horn in a model of central pain syndrome and that aromatase activity in the spinal cord reduces mechanical allodynia by controlling reactive gliosis in the dorsal horn.