The role of astrocytes and complement system in neural plasticity

Electro-acupuncture at LI11 and ST36 acupoints exerts neuroprotective effects via reactive astrocyte proliferation after ischemia and reperfusion injury in rats

Reactive astrogliosis is a common phenomenon in central nervous system (CNS) injuries such as ischemic stroke. The present study aimed to deeply investigate the relationships between the neuroprotective effect of electro-acupuncture (EA) and reactive astrocytes following cerebral ischemia. EA treatment at the Quchi (LI11) and Zusanli (ST36) acupoints at Day 3 attenuated neurological deficits and cerebral infarct volume in ischemia and reperfusion (I/R) injured rats. Animal behavior assessments found that the speed of Catwalk gait, equilibrium and coordination of Rotarod test were improved. Furthermore, EA treatment exerted neuroprotective effects via activation of glial fibrillary acidic protein (GFAP), vimentin and nestin positive cells. Simultaneously, an obvious increase in GFAP/vimentin, GFAP/nestin and GFAP/BrdU co-labeling appeared in the peri-infract cortex and striatum, suggesting EA can promote the proliferation of GFAP/vimentin/nestin-positive reactive astrocytes. The expression of cell cycle-associated proteins Cyclin Dl, CDK4 and phospho-Rb were increased in the peri-infract cortex and striatum, indicating proliferated reactive astrocytes-mediated CyclinDl/CDK4 regulation of the transition of the G1-to-S cell cycle phases. In addition, EA enhanced the localized expression of brain-derived neurotrophic factor (BDNF) in the peri-infract cortex and striatum. These results demonstrated that EA treatment at the LI11 and ST36 acupoints on Day 3 exerted neuroprotection via proliferation of GFAP/vimentin/nestin-positive reactive astrocytes and, potentially, secretion of reactive astrocytes-derived BDNF in I/R injured rats.

Mechanisms underlying AQP4 accumulation in astrocyte endfeet

The brain-blood interface holds the key to our understanding of how cerebral blood flow is regulated and how water and solutes are exchanged between blood and brain. The highly specialized astrocytic membranes that enwrap brain microvessels are salient constituents of the brain-blood interface. These endfoot membranes contain a distinct set of molecules that is anchored to the subendothelial basal lamina forming an endfoot-basal lamina junctional complex. Here we explore the mechanisms underpinning the formation of this complex. By use of a tailor made model system we show that endothelial cells promote AQP4 accumulation by exerting an inductive effect through extracellular matrix components such as agrin, as well as through a direct mechanical interaction with the endfoot processes. Through the compounds they secrete, the endothelial cells also increase AQP4 expression. The present data suggest that the highly specialized gliovascular interface is established through inductive processes that include both chemical and mechanical factors. GLIA 2015;63:2073-2091.

Changes in cannabinoid receptors, aquaporin 4 and vimentin expression after traumatic brain injury in adolescent male mice. Association with edema and neurological deficit

Traumatic brain injury (TBI) incidence rises during adolescence because during this critical neurodevelopmental period some risky behaviors increase. The purpose of this study was to assess the contribution of cannabinoid receptors (CB1 and CB2), blood brain barrier proteins (AQP4) and astrogliosis markers (vimentin) to neurological deficit and brain edema formation in a TBI weight drop model in adolescent male mice. These molecules were selected since they are known to change shortly after lesion. Here we extended their study in three different timepoints after TBI, including short (24h), early mid-term (72h) and late mid-term (two weeks). Our results showed that TBI induced an increase in brain edema up to 72 h after lesion that was directly associated with neurological deficit. Neurological deficit appeared 24 h after TBI and was completely recovered two weeks after trauma. CB1 receptor expression decreased after TBI and was negatively correlated with edema formation and behavioral impairments. CB2 receptor increased after injury and was associated with high neurological deficit whereas no correlation with edema was found. AQP4 increased after TBI and was positively correlated with edema and neurological impairments as occurred with vimentin expression in the same manner. The results suggest that CB1 and CB2 differ in the mechanisms to resolve TBI and also that some of their neuroprotective effects related to the control of reactive astrogliosis may be due to the regulation of AQP4 expression on the end-feet of astrocytes.

Clinical and genetic factors associated with progression of geographic atrophy lesions in age-related macular degeneration

Worldwide, age-related macular degeneration (AMD) is a serious threat to vision loss in individuals over 50 years of age with a pooled prevalence of approximately 9%. For 2020, the number of people afflicted with this condition is estimated to reach 200 million. While AMD lesions presenting as geographic atrophy (GA) show high inter-individual variability, only little is known about prognostic factors. Here, we aimed to elucidate the contribution of clinical, demographic and genetic factors on GA progression. Analyzing the currently largest dataset on GA lesion growth (N = 388), our findings suggest a significant and independent contribution of three factors on GA lesion growth including at least two genetic factors (ARMS2_rs10490924 [P < 0.00088] and C3_rs2230199 [P < 0.00015]) as well as one clinical component (presence of GA in the fellow eye [P < 0.00023]). These correlations jointly explain up to 7.2% of the observed inter-individual variance in GA lesion progression and should be considered in strategy planning of interventional clinical trials aimed at evaluating novel treatment options in advanced GA due to AMD.

Müller glia activation in response to inherited retinal degeneration is highly varied and disease-specific

Despite different aetiologies, most inherited retinal disorders culminate in photoreceptor loss, which induces concomitant changes in the neural retina, one of the most striking being reactive gliosis by Müller cells. It is typically assumed that photoreceptor loss leads to an upregulation of glial fibrilliary acidic protein (Gfap) and other intermediate filament proteins, together with other gliosis-related changes, including loss of integrity of the outer limiting membrane (OLM) and deposition of proteoglycans. However, this is based on a mix of both injury-induced and genetic causes of photoreceptor loss. There are very few longitudinal studies of gliosis in the retina and none comparing these changes across models over time. Here, we present a comprehensive spatiotemporal assessment of features of gliosis in the degenerating murine retina that involves Müller glia. Specifically, we assessed Gfap, vimentin and chondroitin sulphate proteoglycan (CSPG) levels and outer limiting membrane (OLM) integrity over time in four murine models of inherited photoreceptor degeneration that encompass a range of disease severities (Crb1rd8/rd8, Prph2+/Δ307, Rho-/-, Pde6brd1/rd1). These features underwent very different changes, depending upon the disease-causing mutation, and that these changes are not correlated with disease severity. Intermediate filament expression did indeed increase with disease progression in Crb1rd8/rd8 and Prph2+/Δ307, but decreased in the Prph2+/Δ307 and Pde6brd1/rd1 models. CSPG deposition usually, but not always, followed the trends in intermediate filament expression. The OLM adherens junctions underwent significant remodelling in all models, but with differences in the composition of the resulting junctions; in Rho-/- mice, the adherens junctions maintained the typical rod-Müller glia interactions, while in the Pde6brd1/rd1 model they formed predominantly between Müller cells in late stage of degeneration. Together, these results show that gliosis and its associated processes are variable and disease-dependent.

Alcohol and adult hippocampal neurogenesis: promiscuous drug, wanton effects

Adult neurogenesis is now widely accepted as an important contributor to hippocampal integrity and function but also dysfunction when adult neurogenesis is affected in neuropsychiatric diseases such as alcohol use disorders. Excessive alcohol consumption, the defining characteristic of alcohol use disorders, results in a variety of cognitive and behavioral impairments related wholly or in part to hippocampal structure and function. Recent preclinical work has shown that adult neurogenesis may be one route by which alcohol produces hippocampal neuropathology. Alcohol is a pharmacologically promiscuous drug capable of interfering with adult neurogenesis through multiple mechanisms. This review will discuss the primary mechanisms underlying alcohol-induced changes in adult hippocampal neurogenesis including alcohol's effects on neurotransmitters, CREB and its downstream effectors, and the neurogenic niche.

Three-dimensional imaging of HIV-1 virological synapses reveals membrane architectures involved in virus transmission

HIV transmission efficiency is greatly increased when viruses are transmitted at virological synapses formed between infected and uninfected cells. We have previously shown that virological synapses formed between HIV-pulsed mature dendritic cells (DCs) and uninfected T cells contain interdigitated membrane surfaces, with T cell filopodia extending toward virions sequestered deep inside invaginations formed on the DC membrane. To explore membrane structural changes relevant to HIV transmission across other types of intercellular conjugates, we used a combination of light and focused ion beam scanning electron microscopy (FIB-SEM) to determine the three-dimensional (3D) architectures of contact regions between HIV-1-infected CD4(+) T cells and either uninfected human CD4(+) T cells or human fetal astrocytes. We present evidence that in each case, membrane extensions that originate from the uninfected cells, either as membrane sheets or filopodial bridges, are present and may be involved in HIV transmission from infected to uninfected cells. We show that individual virions are distributed along the length of astrocyte filopodia, suggesting that virus transfer to the astrocytes is mediated, at least in part, by processes originating from the astrocyte itself. Mechanisms that selectively disrupt the polarization and formation of such membrane extensions could thus represent a possible target for reducing viral spread.

IMPORTANCE

Our findings lead to new insights into unique aspects of HIV transmission in the brain and at T cell-T cell synapses, which are thought to be a predominant mode of rapid HIV transmission early in the infection process.

Proteomics analysis of amyloid and nonamyloid prion disease phenotypes reveals both common and divergent mechanisms of neuropathogenesis

Prion diseases are a heterogeneous group of neurodegenerative disorders affecting various mammals including humans. Prion diseases are characterized by a misfolding of the host-encoded prion protein (PrP^C) into a pathological isoform termed PrP^Sc. In wild-type mice, PrP^C is attached to the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor and PrP^Sc typically accumulates in diffuse nonamyloid deposits with gray matter spongiosis. By contrast, when mice lacking the GPI anchor are infected with the same prion inoculum, PrP^Sc accumulates in dense perivascular amyloid plaques with little or no gray matter spongiosis. In order to evaluate whether different host biochemical pathways were implicated in these two phenotypically distinct prion disease models, we utilized a proteomics approach. In both models, infected mice displayed evidence of a neuroinflammatory response and complement activation. Proteins involved in cell death and calcium homeostasis were also identified in both phenotypes. However, mitochondrial pathways of apoptosis were implicated only in the nonamyloid form, whereas metal binding and synaptic vesicle transport were more disrupted in the amyloid phenotype. Thus, following infection with a single prion strain, PrP^C anchoring to the plasma membrane correlated not only with the type of PrP^Sc deposition but also with unique biochemical pathways associated with pathogenesis.

Morphological changes in glial fibrillary acidic protein immunopositive astrocytes in the hippocampus of dietary-induced obese mice

Long-term consumption of a high-fat diet (HFD) has been shown to trigger both metabolic and cardiovascular diseases. In contrast, the effect of this type of dietary regime on the central nervous system, particularly outside the hypothalamus, has been investigated poorly. Astrocytes, the most abundant population of glial cells in the brain, are pivotal in regulating glutamatergic transmission as they are responsible for most of the glutamate uptake and metabolism. Mice on an HFD show deficits in learning and memory, together with neurochemical and electrophysiological changes compatible with the impairment in hippocampal glutamatergic activity. Because astrocyte function and morphology have been shown to be interdependent, we speculated whether HFD would trigger changes in astrocyte morphology. For this purpose, we have used a model of diet-induced obesity in mice. We have analyzed astrocyte morphology and density by glial fibrillary acidic protein immunohistochemistry, as well as the expression of the glutamate transporters, GLT-1 (glutamate transporter type-1), and GLAST (astrocyte glutamate transporter), in the CA3 area of the hippocampus. We found that astrocytes from HFD mice showed longer and less abundant projections. These changes were accompanied by the upregulation of both GLT-1 and GLAST. Our data show that the functional impairment detected previously in HFD mice is concomitant with morphological changes within the hippocampus.

Reactive astrogliosis in response to hemorrhagic fever virus: microarray profile of Junin virus-infected human astrocytes

BACKGROUND

Arenavirus Junin is the causative agent of Argentine hemorrhagic fever. Limited information is available concerning the pathogenesis of this human disease, especially the pathogenesis of acute and late neurological symptoms.

METHODS

In our study we present for the first time cDNA microarray profile of human astrocytes infected with the virulent strain of Junin virus. Transcriptional profiling was confirmed by quantitative real-time RT-PCR and cytokine/chemokine/growth factor assay.

RESULTS

We demonstrated the impact of virus infection on immune/inflammatory response/interferon signaling and apoptosis. Pro-apoptotic response and amplification with time of pro-inflammatory cascade of human astrocytes suggested neurodegenerative dysfunctional reactive astrogliosis in response to Junin virus infection.

CONCLUSION

Our results suggest potential pathogenic role of astroglial cells in the development of neurological symptoms and late neurological syndrome during Argentine hemorrhagic fever.

Temporal dynamics of cerebral blood flow, cortical damage, apoptosis, astrocyte-vasculature interaction and astrogliosis in the pericontusional region after traumatic brain injury

Traumatic brain injury (TBI) results in a loss of brain tissue at the moment of impact in the cerebral cortex. Subsequent secondary injury involves the release of molecular signals with dramatic consequences for the integrity of damaged tissue, leading to the evolution of a pericontusional-damaged area minutes to days after in the initial injury. The mechanisms behind the progression of tissue loss remain under investigation. In this study, we analyzed the spatial–temporal profile of blood flow, apoptotic, and astrocytic–vascular events in the cortical regions around the impact site at time points ranging from 5 h to 2 months after TBI. We performed a mild–moderate controlled cortical impact injury in young adult mice and analyzed the glial and vascular response to injury. We observed a dramatic decrease in perilesional cerebral blood flow (CBF) immediately following the cortical impact that lasted until days later. CBF finally returned to baseline levels by 30 days post-injury (dpi). The initial impact also resulted in an immediate loss of tissue and cavity formation that gradually increased in size until 3 dpi. An increase in dying cells localized in the pericontusional region and a robust astrogliosis were also observed at 3 dpi. A strong vasculature interaction with astrocytes was established at 7 dpi. Glial scar formation began at 7 dpi and seemed to be compact by 60 dpi. Altogether, these results suggest that TBI results in a progression from acute neurodegeneration that precedes astrocytic activation, reformation of the neurovascular unit to glial scar formation. Understanding the multiple processes occurring after TBI is critical to the ability to develop neuroprotective therapeutics to ameliorate the short and long-term consequences of brain injury.

Astrocyte transplantation for spinal cord injury: current status and perspective

Spinal cord injury (SCI) often causes incurable neurological dysfunction because axonal regeneration in adult spinal cord is rare. Astrocytes are gradually recognized as being necessary for the regeneration after SCI as they promote axonal growth under both physiological and pathophysiological conditions. Heterogeneous populations of astrocytes have been explored for structural and functional restoration. The results range from the early variable and modest effects of immature astrocyte transplantation to the later significant, but controversial, outcomes of glial-restricted precursor (GRP)-derived astrocyte (GDA) transplantation. However, the traditional neuron-centric view and the concerns about the inhibitory roles of astrocytes after SCI, along with the sporadic studies and the lack of a comprehensive review, have led to some confusion over the usefulness of astrocytes in SCI. It is the purpose of the review to discuss the current status of astrocyte transplantation for SCI based on a dialectical view of the context-dependent manner of astrocyte behavior and the time-associated characteristics of glial scarring. Critical issues are then analyzed to reveal the potential direction of future research.

Ganglioside deficiency causes inflammation and neurodegeneration via the activation of complement system in the spinal cord

Background

Gangliosides, sialic acid-containing glycosphingolipids, are highly expressed in nervous systems of vertebrates and have been considered to be involved in the development, differentiation, and function of nervous tissues. Recent studies with gene-engineered animals have revealed that they play roles in the maintenance and repair of nervous tissues. In particular, knockout (KO) mice of various ganglioside synthase genes have exhibited progressive neurodegeneration with aging. However, neurological disorders and pathological changes in the spinal cord of these KO mice have not been reported to date. Therefore, we examined neurodegeneration in double knockout (DKO) mice of ganglioside GM2/GD2 synthase (B4GANLT1) and GD3 synthase (ST8SIA1) genes to clarify roles of gangliosides in the spinal cord.

Methods

Motor neuron function was examined by gait analysis, and sensory function was analyzed by von Frey test. Pathological changes were analyzed by staining tissue sections with Klüver-Barrera staining and by immunohistochemistry with F4/80 and glial fibrillary acidic protein (GFAP). Gene expression profiles were examined by using DNA micro-array of RNAs from the spinal cord of mice. Triple knockout mice were generated by mating DKO and complement component 3 (C3)-KO mice. Gene expression of the complement system and cytokines was examined by reverse transcription-polymerase chain reaction (RT-PCR) as a function of age.

Results

DKO mice showed progressive deterioration with aging. Correspondingly, they exhibited shrunk spinal cord, reduced thickness of spinal lamina II and III, and reduced neuronal numbers in spinal lamina IX, spinal lamina II, and spinal lamina I. Complement-related genes were upregulated in DKO spinal cord. Moreover, complement activation and inflammatory reactions were detected by GFAP-active astrocyte, microglial accumulation, and increased inflammatory cytokines such as tumor necrosis factor-alpha (TNFα) and interleukin-1-beta (IL-1β). Triple knockout mice showed restoration of reduced neuron numbers in the spinal cord of DKO mice, getting close to levels of wild-type mice.

Conclusions

Disruption in the architecture of lipid rafts in the spinal cord was not so prominent, suggesting that mechanisms distinct from those reported might be involved in the complement activation in the spinal cord of DKO mice. Gene profiling revealed that inflammation and neurodegeneration in the spinal cord of DKO mice are, at least partly, dependent on complement activation.

CDK5-induced p-PPARγ(Ser 112) downregulates GFAP via PPREs in developing rat brain: effect of metal mixture and troglitazone in astrocytes

The peroxisome proliferator-activated receptor gamma (PPARγ), a group of ligand-activated transcriptional factors, is expressed in glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes. Here, we investigated the role of PPARγ in regulating GFAP using a mixture of As, Cd and Pb (metal mixture, MM) that induces apoptosis and aberrant morphology in rat brain astrocytes. We observed a phospho PPARγ (serine 112 (S112)) (p-PPARγ (S112))-mediated downregulation of GFAP in the MM-exposed astrocytes. We validated this using pure PPARγ agonist, troglitazone (TZ). As reported with MM, TZ induced astrocyte damage owing to reduced GFAP. In silico analysis in the non-coding region of GFAP gene revealed two PPARγ response elements (PPREs); inverted repeat 10 and direct repeat 1 sequences. Gel shift and chromatin immunoprecipitation assays demonstrated enhancement in binding of p-PPARγ (S112) to the sequences, and luciferase reporter assay revealed strong repression of GFAP via PPREs, in response to both MM and TZ. This indicated that suppression in GFAP indeed occurs through direct regulation of these elements by p-PPARγ (S112). Signaling studies proved that MM, as well as TZ, activated the cyclin-dependent kinase 5 (CDK5) and enhanced its interaction with PPARγ resulting into increased p-PPARγ (S112). The p-CDK5 levels were dependent on proximal activation of extracellular signal-regulated protein kinase 1/2 and downstream Jun N-terminal kinase. Taken together, these results are the first to delineate downregulation of GFAP through genomic and non-genomic signaling of PPARγ. It also brings forth a resemblance of TZ with MM in terms of astrocyte disarray in developing brain.

Dendritic cells treated with chloroquine modulate experimental autoimmune encephalomyelitis

Chloroquine (CQ), an antimalarial drug, has been shown to modulate the immune system and reduce the severity of experimental autoimmune encephalomyelitis (EAE). The mechanisms of disease suppression are dependent on regulatory T cell induction, although Tregs-independent mechanisms exist. We aimed to evaluate whether CQ is capable to modulate bone marrow-derived dendritic cells (DCs) both phenotypically and functionally as well as whether transfer of CQ-modulated DCs reduces EAE course. Our results show that CQ-treated DCs presented altered ultrastructure morphology and lower expression of molecules involved in antigen presentation. Consequently, T cell proliferation was diminished in coculture experiments. When transferred into EAE mice, DC-CQ was able to reduce the clinical manifestation of the disease through the modulation of the immune response against neuroantigens. The data presented herein indicate that chloroquine-mediated modulation of the immune system is achieved by a direct effect on DCs and that DC-CQ adoptive transfer may be a promising approach for avoiding drug toxicity.

The role of astrocytes in mediating exogenous cell-based restorative therapy for stroke

Astrocytes have not been a major therapeutic target for the treatment of stroke, with most research emphasis on the neuron. Given the essential role that astrocytes play in maintaining physiological function of the central nervous system and the very rapid and sensitive reaction astrocytes have in response to cerebral injury or ischemic insult, we propose to replace the neurocentric view for treatment with a more nuanced astrocytic centered approach. In addition, after decades of effort in attempting to develop neuroprotective therapies, which target reduction of the ischemic lesion, there are no effective clinical treatments for stroke, aside from thrombolysis with tissue plasminogen activator, which is used in a small minority of patients. A more promising therapeutic approach, which may affect nearly all stroke patients, may be in promoting endogenous restorative mechanisms, which enhance neurological recovery. A focus of efforts in stimulating recovery post stroke is the use of exogenously administered cells. The present review focuses on the role of the astrocyte in mediating the brain network, brain plasticity, and neurological recovery post stroke. As a model to describe the interaction of a restorative cell-based therapy with astrocytes, which drives recovery from stroke, we specifically highlight the subacute treatment of stroke with multipotent mesenchymal stromal cell therapy.

Cocaine potentiates MDMA-induced oxidative stress but not dopaminergic neurotoxicity in mice: implications for the pathogenesis of free radical-induced neurodegenerative disorders

RATIONALE

The drugs of abuse 3,4-methylenedioxymethamphetamine (MDMA; "ecstasy") and cocaine both increase the generation of free radicals, and in the case of MDMA, this increase in oxidative stress is involved in the dopaminergic neurotoxicity produced by the drug in mice. Oxidative stress processes are also involved in the pathogenesis of several neurodegenerative diseases.

OBJECTIVES

We aimed to determine the consequences of the combined administration of MDMA and cocaine on oxidative stress and dopaminergic neurotoxicity.

METHODS

Mice received MDMA (20 mg/kg, i.p.; two doses separated by 3 h) followed by cocaine 1, 3, 6, or 24 h after the second MDMA dose. Mice were killed between 1 h and 7 days after cocaine injection.

RESULTS

MDMA decreased dopamine transporter density and dopamine concentration 7 days later. Cocaine did not alter this neurotoxicity. MDMA produced an increase in the concentration of 2,3-dihydroxybenzoic acid in striatal microdialysis samples and an increase in lipid peroxidation in the striatum which were potentiated by cocaine. MDMA and cocaine given together also increased nitrate and 3-nitrotyrosine levels compared with either drug given alone. On the other hand, MDMA increased superoxide dismutase activity and decreased catalase activity, changes which were prevented by cocaine administration. In addition, cocaine administration produced an increase in glutathione peroxidase (GPx) activity in both saline-treated and MDMA-treated mice.

CONCLUSIONS

Cocaine potentiates MDMA-induced oxidative stress but does not produce an increase in the neurotoxicity produced by MDMA, and this lack of potentiation may involve an increase in GPx activity.

MR elastography in a murine stroke model reveals correlation of macroscopic viscoelastic properties of the brain with neuronal density

The aim of this study was to investigate the influence of neuronal density on viscoelastic parameters of living brain tissue after ischemic infarction in the mouse using MR elastography (MRE). Transient middle cerebral artery occlusion (MCAO) in the left hemisphere was induced in 20 mice. In vivo 7-T MRE at a vibration frequency of 900 Hz was performed on days 3, 7, 14 and 28 (n = 5 per group) after MCAO, followed by the analysis of histological markers, such as neuron counts (NeuN). MCAO led to a significant reduction in the storage modulus in the left hemisphere relative to contralateral values (p = 0.03) without changes over time. A correlation between storage modulus and NeuN in both hemispheres was observed, with correlation coefficients of R = 0.648 (p = 0.002, left) and R = 0.622 (p = 0.003, right). The loss modulus was less sensitive to MCAO, but correlated with NeuN in the left hemisphere (R = 0.764, p = 0.0001). In agreement with the literature, these results suggest that the shear modulus in the brain is reduced after transient ischemic insult. Furthermore, our study provides evidence that the in vivo shear modulus of brain tissue correlates with neuronal density. In diagnostic applications, MRE may thus have diagnostic potential as a tool for image-based quantification of neurodegenerative processes.

Targeted over-expression of endothelin-1 in astrocytes leads to more severe brain damage and vasospasm after subarachnoid hemorrhage

Background

Endothelin-1 (ET-1) is a potent vasoconstrictor, and astrocytic ET-1 is reported to play a role in the pathogenesis of cerebral ischemic injury and cytotoxic edema. However, it is still unknown whether astrocytic ET-1 also contributes to vasogenic edema and vasospasm during subarachnoid hemorrhage (SAH). In the present study, transgenic mice with astrocytic endothelin-1 over-expression (GET-1 mice) were used to investigate the pathophysiological role of ET-1 in SAH pathogenesis.

Results

The GET-1 mice experienced a higher mortality rate and significantly more severe neurological deficits, blood–brain barrier breakdown and vasogenic edema compared to the non-transgenic (Ntg) mice following SAH. Oral administration of vasopressin V_1a receptor antagonist, SR 49059, significantly reduced the cerebral water content in the GET-1 mice. Furthermore, the GET-1 mice showed significantly more pronounced middle cerebral arterial (MCA) constriction after SAH. Immunocytochemical analysis showed that the calcium-activated potassium channels and the phospho-eNOS were significantly downregulated, whereas PKC-α expression was significantly upregulated in the MCA of the GET-1 mice when compared to Ntg mice after SAH. Administration of ABT-627 (ET_A receptor antagonist) significantly down-regulated PKC-α expression in the MCA of the GET-1 mice following SAH.

Conclusions

The present study suggests that astrocytic ET-1 involves in SAH-induced cerebral injury, edema and vasospasm, through ET_A receptor and PKC-mediated potassium channel dysfunction. Administration of ABT-627 (ET_A receptor antagonist) and SR 49059 (vasopressin V_1a receptor antagonist) resulted in amelioration of edema and vasospasm in mice following SAH. These data provide a strong rationale to investigate SR 49059 and ABT-627 as therapeutic drugs for the treatment of SAH patients.

Berberine ameliorate oxidative stress and astrogliosis in the hippocampus of STZ-induced diabetic rats

Diabetes mellitus increases the risk of central nervous system (CNS) disorders such as stroke, seizures, dementia, and cognitive impairment. Berberine, a natural isoquinoline alkaloid, is reported to exhibit beneficial effect in various neurodegenerative and neuropsychiatric disorders. Moreover, astrocytes are proving critical for normal CNS function, and alterations in their activity and impaired oxidative stress could contribute to diabetes-related cognitive dysfunction. Metabolic and oxidative insults often cause rapid changes in glial cells. Key indicators of this response are increased synthesis of glial fibrillary acidic protein (GFAP) as an astrocytic marker. Therefore, we examined the effects of berberine on glial reactivity of hippocampus in streptozotocin (STZ)-induced diabetic rats, using GFAP immunohistochemistry. Lipid peroxidation, superoxide dismutase (SOD) activity, and nitrite levels were assessed as the parameters of oxidative stress. Eight weeks after diabetes induction, we observed increased numbers of GFAP(+) astrocytes immunostaining associated with increased lipid peroxidation, decreased superoxide dismutase activity, and elevated nitrite levels in the hippocampus of STZ-diabetic rats. In contrast, chronic treatment with berberine (50 and 100 mg/kg p.o. once daily) lowered hyperglycemia, reduced oxidative stress, and prevented the upregulation of GFAP in the brain of diabetic rats. In conclusion, the present study demonstrated that the treatment with berberine resulted in an obvious reduction of oxidative stress and GFAP-immunoreactive astrocytes in the hippocampus of STZ-induced diabetic rats.

Dexamethasone rescues neurovascular unit integrity from cell damage caused by systemic administration of shiga toxin 2 and lipopolysaccharide in mice motor cortex

Shiga toxin 2 (Stx2)-producing Escherichia coli (STEC) causes hemorrhagic colitis and hemolytic uremic syndrome (HUS) that can lead to fatal encephalopathies. Neurological abnormalities may occur before or after the onset of systemic pathological symptoms and motor disorders are frequently observed in affected patients and in studies with animal models. As Stx2 succeeds in crossing the blood-brain barrier (BBB) and invading the brain parenchyma, it is highly probable that the observed neurological alterations are based on the possibility that the toxin may trigger the impairment of the neurovascular unit and/or cell damage in the parenchyma. Also, lipopolysaccharide (LPS) produced and secreted by enterohemorrhagic Escherichia coli (EHEC) may aggravate the deleterious effects of Stx2 in the brain. Therefore, this study aimed to determine (i) whether Stx2 affects the neurovascular unit and parenchymal cells, (ii) whether the contribution of LPS aggravates these effects, and (iii) whether an inflammatory event underlies the pathophysiological mechanisms that lead to the observed injury. The administration of a sub-lethal dose of Stx2 was employed to study in detail the motor cortex obtained from a translational murine model of encephalopathy. In the present paper we report that Stx2 damaged microvasculature, caused astrocyte reaction and neuronal degeneration, and that this was aggravated by LPS. Dexamethasone, an anti-inflammatory, reversed the pathologic effects and proved to be an important drug in the treatment of acute encephalopathies.

Noninvasive strategies to promote functional recovery after stroke

Stroke is a common and disabling global health-care problem, which is the third most common cause of death and one of the main causes of acquired adult disability in many countries. Rehabilitation interventions are a major component of patient care. In the last few years, brain stimulation, mirror therapy, action observation, or mental practice with motor imagery has emerged as interesting options as add-on interventions to standard physical therapies. The neural bases for poststroke recovery rely on the concept of plasticity, namely, the ability of central nervous system cells to modify their structure and function in response to external stimuli. In this review, we will discuss recent noninvasive strategies employed to enhance functional recovery in stroke patients and we will provide an overview of neural plastic events associated with rehabilitation in preclinical models of stroke.

Abnormal activation of complement C3 in the spinal dorsal horn is closely associated with progression of neuropathic pain

The aim of the present study was to investigate the role of complement activation in the pathogenesis of neuropathic pain (NPP) induced by peripheral nerve injury. We modified a classical chronic constriction injury (CCI) model (mCCI), and verified its reliability in rats. Furthermore, reverse transcription-PCR and immunohistochemistry were conducted to investigate complement activation in the spinal dorsal horn and the effect of a complement inhibitor, cobra venom factor (CVF), on the behavior of the mCCI model rats. We found that rats in the mCCI group presented a better general condition, without signs of autophagy of the toes. Moreover, mCCI induced a significant increase (+40%) in the expression of component 3 (C3) mRNA in the spinal dorsal horn, which was associated with hyperalgesia. Correlation analysis showed a negative correlation between the mechanical pain threshold and the expression of C3 in the spinal cord. Administration of CVF reduced the occurrence of hyperalgesia in mCCI rats and nearly reversed the hyperalgesia. In addition, the mCCI rats exhibited significantly less spinal superoxide dismutase activity and significantly greater levels of maleic dialdehyde compared to the sham-operated rats. Transmission electron micrographs revealed mitochondrial swelling, cell membrane damage, and cristae fragmentation in the neurons of the spinal dorsal horn 14 days after mCCI. Mitochondrial swelling was attenuated in mCCI rats receiving CVF. The findings demonstrated that abnormal complement activation occurred in the dorsal horn of the spinal cord in rats with NPP, and C3 in the spinal dorsal horn could play an important role in the cascade reaction of complements that are involved in the development of hyperalgesia.

Tracking transplanted bone marrow stem cells and their effects in the rat MCAO stroke model

In this study, rat bone marrow stromal stem cells (BMSCs) were tracked after IV administration to rats with experimental stroke caused by middle cerebral artery occlusion (MCAO). In addition, the effects of BMSC treatment on blood cell composition, brain glia and sensorimotor behavior was studied and compared to that which occurred spontaneously during the normal recovery process after stroke. We found that the vast majority of radiolabeled or fluorescently labeled BMSCs traveled to and remained in peripheral organs (lungs, spleen, liver) 3 days after IV injection in the MCAO rat. Once in the circulation, BMSCs also produced rapid alterations in host blood cell composition, increasing both neutrophil and total white blood cell count by 6 hours post-injection. In contrast, few injected BMSCs traveled to the brain and almost none endured there long term. Nonetheless, BMSC treatment produced dramatic changes in the number and activation of brain astroglia and microglia, particularly in the region of the infarct. These cellular changes were correlated with a marked improvement in performance on tests of sensory and motor function as compared to the partial recovery of function seen in PBS-injected control rats. We conclude that the notable recovery in function observed after systemic administration of BMSCs to MCAO rats is likely due to the cellular changes in blood and/or brain cell number, activation state and their cytokine/growth factor products.

Spatial and temporal MRI profile of ischemic tissue after the acute stages of a permanent mouse model of stroke

OBJECT

To characterize the progression of injured tissue resulting from a permanent focal cerebral ischemia after the acute phase, Magnetic Resonance Imaging (MRI) monitoring was performed on adult male C57BL/6J mice in the subacute stages, and correlated to histological analyses.

MATERIAL AND METHODS

Lesions were induced by electrocoagulation of the middle cerebral artery. Serial MRI measurements and weighted-images (T2, T1, T2* and Diffusion Tensor Imaging) were performed on a 9.4T scanner. Histological data (Cresyl-Violet staining and laminin-, Iba1- and GFAP-immunostainings) were obtained 1 and 2 weeks after the stroke.

RESULTS

Two days after stroke, tissues assumed to correspond to the infarct core, were detected as a hyperintensity signal area in T2-weighted images. One week later, low-intensity signal areas appeared. Longitudinal MRI study showed that these areas remained present over the following week, and was mainly linked to a drop of the T2 relaxation time value in the corresponding tissues. Correlation with histological data and immuno-histochemistry showed that these areas corresponded to microglial cells.

CONCLUSION

The present data provide, for the first time detailed MRI parameters of microglial cells dynamics, allowing its non-invasive monitoring during the chronic stages of a stroke. This could be particularly interesting in regards to emerging anti-inflammatory stroke therapies.

Hyposmolality differentially and spatiotemporally modulates levels of glutamine synthetase and serine racemase in rat supraoptic nucleus

Prolonged hyposmotic challenge (HOC) has a dual effect on vasopressin (VP) secretion [Yagil and Sladek (1990) Am J Physiol 258(2 Pt 2):R492-R500]. We describe an electrophysiological correlate of this phenomenon, whereby in vitro HOC transiently reduced the firing activity of VP neurons within the supraoptic nucleus of brain slices, which was followed by a rebound increase of their activity; this was paralleled by changes in the level of proteins relevant to astroglia-neuronal interactions. Hence, in vitro HOC transiently (at 5 min) increased the level of astrocyte-specific glial fibrillary acidic protein (GFAP), which then declined to control or base level (at 20 min); this was blocked by the gliotoxin L-aminoadipic acid, but not by tetanus toxin, which was used to inhibit neurotransmission. Similarly, in vivo HOC led to changes in GFAP level, which after an early increase (10 min) returned to normal (30 min). Immunoassays revealed that neuronal, but not astrocytic, expression of serine racemase (SR) was increased at the late stage of HOC in vivo, whereas at an early stage there was a transient increase in level of the astrocyte-specific glutamine synthetase (GS). Furthermore, there was an increased molecular association between GFAP and GS at 10 min, whereas SR increased its association with the neuronal nuclear antigen NeuN at 30 min. These results suggest that the dual effect of HOC on VP neuronal secretion/activity could be related to metabolic/signaling changes in astrocytes (glutamate-glutamine conversion) and neurons (D-serine synthesis/ammonia production), which may account for the rebound in VP neuronal activity, presumably by promoting the activation of neuronal glutamate receptors.

Determining the threshold for alcohol-induced brain damage: new evidence with gliosis markers

BACKGROUND

Chronic intake of ethanol (EtOH) has been linked to serious health consequences such as cardiac and liver problems, cognitive impairments, and brain damage. Alcohol's detrimental effects depend upon the dose, duration, and pattern of exposure with binge drinking as one of the most common, but most damaging, patterns of intake. Little is known about the threshold of the damaging effects of alcohol. Therefore, these experiments sought to determine a threshold for brain damage using various markers of neurodegeneration.

METHODS

Adult male Sprague-Dawley rats were administered nutritionally complete liquid diet containing either EtOH (25% w/v) or isocaloric dextrose every 8 hours for either 1 (mean dose, 13.4 ± 0.3 g/kg/d; mean blood EtOH concentration (BEC), 336.2 ± 18.8 mg/dl) or 2 days (mean dose, 10.9 ± 0.3 g/kg/d; mean BEC, 369.8 ± 18.1 mg/dl). On the basis of a known time course of various neurodegeneration-associated events, rats were perfused transcardially immediately following, 2 days after, or 7 days post EtOH exposure. To label actively dividing cells, some animals were injected with BromodeoxyUridine (BrdU) 2 hours prior to perfusion. Tissue was then analyzed for the presence of BrdU (cell proliferation), FluoroJade B (degenerative neurons), and vimentin (reactive astrogliosis) immunoreactivity.

RESULTS

One or 2 days of EtOH exposure failed to alter cell proliferation at any of the time points analyzed. However, significant 2- to 9-fold increases in neuronal degeneration in limbic cortex and clear evidence of reactive gliosis as indicated by a 2- to 8-fold upregulation in vimentin immunoreactivity in the hippocampus were observed following as little as 1 day of binge EtOH exposure.

CONCLUSIONS

These results indicate that as little as 1 day (24 hours) of high BEC, binge-like EtOH exposure is enough to elicit signs of alcohol-induced brain damage in adult rats. Further, reactive gliosis may be a more sensitive marker of alcohol-induced damage in the hippocampus.

Complement anaphylatoxin C3a is a potent inducer of embryonic chick retina regeneration

Identifying the initiation signals for tissue regeneration in vertebrates is one of the major challenges in regenerative biology. Much of the research thus far has indicated that certain growth factors have key roles. Here we show that complement fragment C3a is sufficient to induce complete regeneration of the embryonic chick retina from stem/progenitor cells present in the eye, independent of fibroblast growth factor receptor signaling. Instead, C3a induces retina regeneration via STAT3 activation, which in turn activates the injury- and inflammation-responsive factors, IL-6, IL-8 and TNF-α. This activation sets forth regulation of Wnt2b, Six3 and Sox2, genes associated with retina stem and progenitor cells. Thus, our results establish a mechanism for retina regeneration based on injury and inflammation signals. Furthermore, our results indicate a unique function for complement anaphylatoxins that implicate these molecules in the induction and complete regeneration of the retina, opening new avenues of experimentation in the field.

Reactive astrogliosis after spinal cord injury-beneficial and detrimental effects

Reactive astrogliosis is a pathologic hallmark of spinal cord injury (SCI). It is characterised by profound morphological, molecular, and functional changes in astrocytes that occur within hours of SCI and evolves as time elapses after injury. Astrogliosis is a defense mechanism to minimize and repair the initial damage but eventually leads to some detrimental effects. Reactive astrocytes secrete a plethora of both growth promoting and inhibitory factors after SCI. However, the production of inhibitory components surpasses the growth stimulating factors, thus, causing inhibitory effects. In severe cases of injury, astrogliosis results in the formation of irreversible glial scarring that acts as regeneration barrier due to the expression of inhibitory components such as chondroitin sulfate proteoglycans. Scar formation was therefore recognized from a negative perspective for many years. Accumulating evidence from pharmacological and genetic studies now signifies the importance of astrogliosis and its timing for spinal cord repair. These studies have advanced our knowledge regarding signaling pathways and molecular mediators, which trigger and modulate reactive astrocytes and scar formation. In this review, we discuss the recent advances in this field. We also review therapeutic strategies that have been developed to target astrocytes reactivity and glial scaring in the environment of SCI. Astrocytes play pivotal roles in governing SCI mechanisms, and it is therefore crucial to understand how their activities can be targeted efficiently to harness their potential for repair and regeneration after SCI.

Role of complement and perspectives for intervention in ischemia-reperfusion damage

Reperfusion of an organ following prolonged ischemia instigates the pro-inflammatory and pro-coagulant response of ischemia / reperfusion (IR) injury. IR injury is a wide-spread pathology, observed in many clinically relevant situations, including myocardial infarction, stroke, organ transplantation, sepsis and shock, and cardiovascular surgery on cardiopulmonary bypass. Activation of the classical, alternative, and lectin complement pathways and the generation of the anaphylatoxins C3a and C5a lead to recruitment of polymorphonuclear leukocytes, generation of radical oxygen species, up-regulation of adhesion molecules on the endothelium and platelets, and induction of cytokine release. Generalized or pathway-specific complement inhibition using protein-based drugs or low-molecular-weight inhibitors has been shown to significantly reduce tissue injury and improve outcome in numerous in-vitro, ex-vivo, and in-vivo models. Despite the obvious benefits in experimental research, only few complement inhibitors, including C1-esterase inhibitor, anti-C5 antibody, and soluble complement receptor 1, have made it into clinical trials of IR injury. The results are mixed, and the next objectives should be to combine knowledge and experience obtained in the past from animal models and channel future work to translate this into clinical trials in surgical and interventional reperfusion therapy as well as organ transplantation.

Dysregulation of gene expression in a lysosomal storage disease varies between brain regions implicating unexpected mechanisms of neuropathology

The characteristic neurological feature of many neurogenetic diseases is intellectual disability. Although specific neuropathological features have been described, the mechanisms by which specific gene defects lead to cognitive impairment remain obscure. To gain insight into abnormal functions occurring secondary to a single gene defect, whole transcriptome analysis was used to identify molecular and cellular pathways that are dysregulated in the brain in a mouse model of a lysosomal storage disorder (LSD) (mucopolysaccharidosis [MPS] VII). We assayed multiple anatomical regions separately, in a large cohort of normal and diseased mice, which greatly increased the number of significant changes that could be detected compared to past studies in LSD models. We found that patterns of aberrant gene expression and involvement of multiple molecular and cellular systems varied significantly between brain regions. A number of changes revealed unexpected system and process alterations, such as up-regulation of the immune system with few inflammatory changes (a significant difference from the closely related MPS IIIb model), down-regulation of major oligodendrocyte genes even though white matter changes are not a feature histopathologically, and a plethora of developmental gene changes. The involvement of multiple neural systems indicates that the mechanisms of neuropathology in this type of disease are much broader than previously appreciated. In addition, the variation in gene dysregulation between brain regions indicates that different neuropathologic mechanisms may predominate within different regions of a diseased brain caused by a single gene mutation.

Activating transcription factor 3 and reactive astrocytes following optic nerve injury in zebrafish

Nerve regeneration in the central nervous system is restricted in mammals, but fish and amphibians show amazing resiliency following injury to the central nervous system. We have examined the response of zebrafish (Danio rerio) to optic nerve injury to try to understand the differences between fish and mammals that enable fish to regenerate their optic nerves following crushing and severing. In previous work, we have shown that activating transcription factor 3 (atf3) is expressed at higher levels following optic nerve injury. Here we use a polyclonal anti-ATF3 antibody, anti-cytokeratin (KRT-18) and anti-bystin (BYSL) antibodies to show that Atf3 and Bysl colocalize with cytokeratin-expressing astrocytes in the optic nerve following severing. Furthermore, anti-ATF3 antibodies fail to colocalize with GFP in transgenic zebrafish expressing EGFP in astrocytes Tg(gfap:GFP) or oligodendrocytes Tg(olig2:EGFP). Interestingly, labeling of Atf3 was detected in retinal ganglion cell axons in both the nerve fiber layer and the optic nerve on the injured side. Finally, optic nerve astrocytes labeled with anti-bystin antibodies showed evidence of hypertrophy, suggesting that fish astrocytes in the optic nerve raise a bona fide reactive response to injury even though they do not express glial fibrillary acidic protein.

Inflammation during fetal and neonatal life: implications for neurologic and neuropsychiatric disease in children and adults

Inflammation is increasingly recognized as being of both physiological and pathological importance in the immature brain. The rationale of this review is to present an update on this topic with focus on long-term consequences of inflammation during childhood and in adults. The immature brain can be exposed to inflammation in connection with viral or bacterial infection during pregnancy or as a result of sterile central nervous system (CNS) insults. Through efficient anti-inflammatory and reparative processes, inflammation may resolve without any harmful effects on the brain. Alternatively, inflammation contributes to injury or enhances CNS vulnerability. Acute inflammation can also be shifted to a chronic inflammatory state and/or adversely affect brain development. Hypothetically, microglia are the main immunocompetent cells in the immature CNS, and depending on the stimulus, molecular context, and timing, these cells will acquire various phenotypes, which will be critical regarding the CNS consequences of inflammation. Inflammation has long-term consequences and could speculatively modify the risk of a variety of neurological disorders, including cerebral palsy, autism spectrum disorders, schizophrenia, multiple sclerosis, cognitive impairment, and Parkinson disease. So far, the picture is incomplete, and data mostly experimental. Further studies are required to strengthen the associations in humans and to determine whether novel therapeutic interventions during the perinatal period can influence the occurrence of neurological disease later in life.

The relationship between glial distortion and neuronal changes following intestinal ischemia and reperfusion

BACKGROUND

Damage to mucosal epithelial cells, muscle cells and enteric neurons has been extensively studied following intestinal ischemia and reperfusion (I/R). Interestingly, the effects of intestinal I/R on enteric glia remains unexplored, despite knowledge that glia contribute to neuronal maintenance. Here, we describe structural damage to enteric glia and associated changes in distribution and immunoreactivity of the neuronal protein Hu.

METHODS

The mouse small intestine was made ischemic for 3 h and reperfused from 1 to 12 h. Immunohistochemical localisation of glial fibrillary acidic protein (GFAP), Hu and TUNEL were used to evaluate changes.

KEY RESULTS

At all time points glial cells became distorted, which was evident by their altered GFAP immunoreactivity, including an unusual appearance of bright perinuclear GFAP staining and the presence of GFAP globules. The numbers of neurons per ganglion area were significantly fewer in ganglia that contained distorted glia when compared with ganglia that contained glia of normal appearance. The distribution of Hu immunoreactivity was altered at all reperfusion time points. The presence of vacuoles and Hu granules in neurons was evident and an increase in nuclear Hu, relative to cytoplasmic Hu, was observed in ganglia that contained both normal and distorted glial cells. A number of neurons appeared to lose their Hu immunoreactivity, most noticeably in ganglia that contained distorted glial cells. TUNEL reaction occurred in a minority of glial cells and neurons.

CONCLUSIONS & INFERENCES

Structural damage to gliofilaments occurs following I/R and may be associated with damage to neighboring neurons.

Proliferative reactive gliosis is compatible with glial metabolic support and neuronal function

Background

The response of mammalian glial cells to chronic degeneration and trauma is hypothesized to be incompatible with support of neuronal function in the central nervous system (CNS) and retina. To test this hypothesis, we developed an inducible model of proliferative reactive gliosis in the absence of degenerative stimuli by genetically inactivating the cyclin-dependent kinase inhibitor p27^Kip1 (p27 or Cdkn1b) in the adult mouse and determined the outcome on retinal structure and function.

Results

p27-deficient Müller glia reentered the cell cycle, underwent aberrant migration, and enhanced their expression of intermediate filament proteins, all of which are characteristics of Müller glia in a reactive state. Surprisingly, neuroglial interactions, retinal electrophysiology, and visual acuity were normal.

Conclusion

The benign outcome of proliferative reactive Müller gliosis suggests that reactive glia display context-dependent, graded and dynamic phenotypes and that reactivity in itself is not necessarily detrimental to neuronal function.

Progressive neurovascular disturbances in the cerebral cortex of Alzheimer's disease-model mice: protection by atorvastatin and pitavastatin

Structural and functional abnormalities in the neurovascular unit (NVU) have been recently observed in Alzheimer's disease (AD). Statins, which are used clinically for reducing cholesterol levels, can also exert beneficial vascular actions. Thus, we examined the protective effects of statins on NVU disturbances in a mouse AD model. Amyloid precursor protein (APP) transgenic (Tg) mice were used as a model of AD. Atorvastatin (30 mg/kg/day, p.o.) or pitavastatin (3 mg/kg/day, p.o.) were administered from 5 to 20 months of age. Changes in the NVU, including the endothelium and basement membrane, as well as astrogliosis and matrix metalloproteinase-9 (MMP-9) activation, were assessed. There was a reduction in immunopositive staining for N-acetyl glucosamine oligomer (NAGO) in the endothelium and in collagen IV in the APP vehicle (APP/Ve) group, with collagen IV staining most weakest near senile plaques (SPs). There was also an increase in intensity and number of glial fibrillary acidic protein (GFAP)-positive astrocytes, particularly around the SP, where MMP-9 was more strongly labeled. Double immunofluorescent analysis showed that astrocytic endfeet had detached from the capillary endothelium in the APP/Ve group. Treatment with atorvastatin or pitavastatin ameliorated the activation of MMP-9. Overall, these data suggest that statins may have therapeutic potential for AD by protecting NVU.

Upregulated vimentin suggests new areas of neurodegeneration in a model of an alcohol use disorder

Excessive alcohol intake, characteristic of an alcohol use disorder (AUD), results in neurodegeneration as well as cognitive deficits that may recover in abstinence. Neurodegeneration in psychiatric disorders such as AUDs is due to various effects on tissue integrity. Several groups report that alcohol-induced neurodegeneration and recovery include a role for adult neurogenesis. Therefore, the initial purpose of this study was to investigate the effect of alcohol on the temporal profile of neural progenitor cells using the radial glia marker, vimentin, in a model of an AUD. However, striking vimentin expression throughout corticolimbic regions led, instead, to the discovery of a significant gliosis response in this model. Adult male rats were subjected to a 4-day binge model of an AUD and brains harvested for immunohistochemistry at 0, 2, 4, 7, 14, and 28 days following the last dose of ethanol. A prominent increase in vimentin immunoreactivity was apparent at 4 and 7 days post binge that returned to control levels by 14 days in the corticolimbic regions examined. Vimentin-positive cells co-labeled with glial fibrillary acidic protein (GFAP), which suggested that cells were reactive astrocytes. A second experiment supported that increased vimentin was not primarily due to alcohol withdrawal seizures and is more likely due to alcohol-induced cell death. As this gliosis was remarkably distinct in regions where cell death had not previously been reported in this model, adjacent tissue sections were processed for FluoroJade B staining for cell death. FluoroJade B-positive cells were evident immediately following the last ethanol dose as expected, but were significantly elevated in the hippocampal dentate gyrus and CA3 regions and corticolimbic regions from 2 to 7 days post binge. Intriguingly, vimentin labeling of astrogliosis is more widespread than FluoroJade B labeling of cell death, which suggests that 4-day binge ethanol consumption is more damaging than originally realized.

Astroglial reaction to delta opioid peptide [D-Ala2, D-Leu5] enkephalin confers neuroprotection against global ischemia in the adult rat hippocampus

Delta opioid receptor (DOR) is essential for neuronal survival against hypoxic/ischemic damages. However, current understanding on how DOR activation affects astrocytic functions under ischemia remains incomplete. The present study investigated the astroglial responses to [d-Ala2, d-Leu5] enkephalin (DADLE) (a selective DOR agonist)-induced DOR activation after global cerebral ischemia. Adult male rats were preimplanted with intracerebral cannula and subjected to global ischemia for 10 min. The rats were divided into four groups: normal group (without any procedure), sham group (sham procedure with intracerebroventricular injection of ACSF), I/R group (ischemia procedure with intracerebroventricular injection of ACSF) and DAD-treated group (ischemia procedure with intracerebroventricular injection of DADLE). Hippocampal CA1 neuronal survival and activation of astrocytes were measured in the animals at 72 h post-ischemia. The distribution and phenotypes of p-Akt and active caspase-3 were also determined. The ischemic injury resulted in a significant neuronal loss and an increase in the dying astrocytes in the hippocampal CA1 region as compared with those in the sham animals (200.7±22.7/mm(2) vs. 6.6±3.1/mm(2), P<0.001). Improved neuronal survival in the DAD-treated animals was evident, which was accompanied by less dying astrocytes and enhanced astrocytes reaction with more active astrocytes than that in the I/R group (267.6±13.2/mm(2) vs. 157.0±18.1/mm(2), P<0.01) and a significantly increased immunoreactivity of p-Akt. However, the active caspase-3 positive cells were also evident in DAD-treated group (313.0±23.1/mm(2)) and significantly increased as compared with those of the sham group (159.0±15.8/mm(2), P<0.001) or I/R group (193.6±26.2/mm(2), P<0.01). Most of the active caspase-3-expressing cells were colabeled with glial fibrillary acidic protein (GFAP), an astrocytes marker. We conclude that the post-ischemic treatment with DADLE promotes beneficial astrocytes activation and induces astroglial apoptosis 72 h after reperfusion which may be involved in reducing their harmful effect to neurons survival.