Increase In Reactive Astrocytes Research Articles

Effect of recurrent severe insulin-induced hypoglycemia on the cognitive function and brain oxidative status in the rats

BackgroundEpisodes of recurrent or severe hypoglycemia can occur in patients with diabetes mellitus, insulinoma, neonatal hypoglycemia, and medication errors. However, little is known about the short-term and long-term effects of repeated episodes of acute severe hypoglycemia on the brain, particularly in relation to hippocampal damage and cognitive dysfunction.MethodsThirty-six wistar rats were randomly assigned to either the experimental or control group. The rats were exposed to severe hypoglycemia, and assessments were conducted to evaluate oxidative stress in brain tissue, cognitive function using the Morris water maze test, as well as histopathology and immunohistochemistry studies. The clinical and histopathological evaluations were conducted in the short-term and long-term.ResultsThe mortality rate attributed to hypoglycemia was 34%, occurring either during hypoglycemia or within 24 h after induction. Out of the 14 rats monitored for 7 to 90 days following severe/recurrent hypoglycemia, all exhibited clinical symptoms, which mostly resolved within three days after the last hypoglycemic episode, except for three rats. Despite the decrease in catalase activity in the brain, the total antioxidant capacity following severe insulin-induced hypoglycemia increased. The histopathology findings revealed that the severity of the hippocampal damage was higher compared to the brain cortex 90 days after hypoglycemia. Memory impairments with neuron loss particularly pronounced in the dentate gyrus region of the hippocampus were observed in the rats with severe hypoglycemia. Additionally, there was an increase in reactive astrocytes indicated by GFAP immunoreactivity in the brain cortex and hippocampus.ConclusionRecurrent episodes of severe hypoglycemia can lead to high mortality rates, memory impairments, and severe histopathological changes in the brain. While many histopathological and clinical changes improved after three months, it seems that the vulnerability of the hippocampus and the development of sustained changes in the hippocampus were greater and more severe compared to the brain cortex following severe and recurrent hypoglycemia. Furthermore, it does not appear that oxidative stress plays a central role in neuronal damage following severe insulin-induced hypoglycemia. Further research is necessary to assess the consequences of repeated hypoglycemic episodes on sustained damage across various brain regions.

Neurogenesis impairment with glial activation in the hippocampus-connected regions of intracerebroventricular streptozotocin-injected mice

Adult neurogenesis in the hippocampus and subventricular zone (SVZ) is impaired by intracerebroventricular administration of streptozotocin (icv-STZ) to rodents. Although neural cells in the several brain regions which connect with the hippocampus or SVZ is thought to be involved in the adult neurogenesis, few studies have investigated morphological alterations of glial cells in these areas. The present study revealed that icv-STZ induces reduction of neural progenitor cells and a dramatic increase in reactive astrocytes and microglia especially in the hippocampus and various hippocampus-connected brain areas. In contrast, there was no significant neuronal damage excluding demyelination of the stria medullaris. The results indicate the hippocampal neurogenesis impairment of this model might be occurred by activated glial cells in the hippocampus, or hippocampus-connected regions.

Identifying cellular markers of focal cortical dysplasia type II with cell-type deconvolution and single-cell signatures

Focal cortical dysplasia (FCD) is a brain malformation that causes medically refractory epilepsy. FCD is classified into three categories based on structural and cellular abnormalities, with FCD type II being the most common and characterized by disrupted organization of the cortex and abnormal neuronal development. In this study, we employed cell-type deconvolution and single-cell signatures to analyze bulk RNA-seq from multiple transcriptomic studies, aiming to characterize the cellular composition of brain lesions in patients with FCD IIa and IIb subtypes. Our deconvolution analyses revealed specific cellular changes in FCD IIb, including neuronal loss and an increase in reactive astrocytes (astrogliosis) when compared to FCD IIa. Astrogliosis in FCD IIb was further supported by a gene signature analysis and histologically confirmed by glial fibrillary acidic protein (GFAP) immunostaining. Overall, our findings demonstrate that FCD II subtypes exhibit differential neuronal and glial compositions, with astrogliosis emerging as a hallmark of FCD IIb. These observations, validated in independent patient cohorts and confirmed using immunohistochemistry, offer novel insights into the involvement of glial cells in FCD type II pathophysiology and may contribute to the development of targeted therapies for this condition.

MP49-19 TIME COURSE CHANGES IN VOIDING INTERVAL IN RATS WITH FOCAL CEREBRAL INFARCTION INDUCED BY PHOTOCHEMICALLY-INDUCED THROMBOSIS

You have accessJournal of UrologyCME1 May 2022MP49-19 TIME COURSE CHANGES IN VOIDING INTERVAL IN RATS WITH FOCAL CEREBRAL INFARCTION INDUCED BY PHOTOCHEMICALLY-INDUCED THROMBOSIS Yuya Ota, Yasue Kubota, Yuji Hotta, Mami Matsumoto, Nayuka Matsuyama, Taiki Kato, Takashi Hamakawa, Tomoya Kataoka, Kazunori Kimura, Kazunobu Sawamoto, and Takahiro Yasui Yuya OtaYuya Ota More articles by this author , Yasue KubotaYasue Kubota More articles by this author , Yuji HottaYuji Hotta More articles by this author , Mami MatsumotoMami Matsumoto More articles by this author , Nayuka MatsuyamaNayuka Matsuyama More articles by this author , Taiki KatoTaiki Kato More articles by this author , Takashi HamakawaTakashi Hamakawa More articles by this author , Tomoya KataokaTomoya Kataoka More articles by this author , Kazunori KimuraKazunori Kimura More articles by this author , Kazunobu SawamotoKazunobu Sawamoto More articles by this author , and Takahiro YasuiTakahiro Yasui More articles by this author View All Author Informationhttps://doi.org/10.1097/JU.0000000000002624.19AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail Abstract INTRODUCTION AND OBJECTIVE: The Photochemically-induced thrombosis (photothrombosis), which is easy to implement and minimally invasive, can create focal cerebral infarcts in the superficial layers of the cerebrum. Using this, we aimed to establish a new rat model of increases in urinary frequency after focal cerebral infarction, characterized by its simplicity, nonlethal nature, and high reproducibility. METHODS: A total of 90 11-week-old female Wistar-ST rats were assigned to the sham or photothrombosis-treated (PT) group. Photothrombosis was used to induce focal infarcts in the prefrontal and anterior cingulate cortices, which are involved in lower urinary tract control. A fiber optic cable delivering a light source was placed stereotactically onto the skull 1 mm anterior to the bregma on the midline. Rose Bengal solution (30 mg/mL/kg) was injected into the tail vein, and the skull was irradiated. Neurological, cystometric, and immunohistochemical evaluation of the brain were performed preoperatively and on postoperative days 1, 7, 14, and 28. RESULTS: Cystometric analysis indicated that micturition intervals significantly shortened in photothrombosis-treated rats compared with that in the sham group on Days 1 and 7 (P < 0.01), and prolonged after 14 days, with no difference between the groups (Figure A). Baseline pressure, micturition threshold pressure, and maximum intravesical pressure did not differ between the groups. Neurological evaluation revealed that only motor disturbances in the hind limbs improved with time in the PT group. Immunopathological evaluation revealed an accumulation of activated microglia, and subsequent increase in reactive astrocytes, at the peri-infarct zone after photothrombotic stroke. Throughout the study, all postphotothrombosis rats showed cerebral infarction in the prefrontal cortex and anterior cingulate cortex; no rats showed fatal cerebral infarction. CONCLUSIONS: This novel photothrombosis model, combining non-lethality and high reproducibility, observed changes in micturition status. This photothrombosis method may be able to contribute to the understanding of neural control of urinary function by regulating the number and volume of the infarcted areas. Source of Funding: GSK Japan Research Grant 2019 © 2022 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 207Issue Supplement 5May 2022Page: e861 Advertisement Copyright & Permissions© 2022 by American Urological Association Education and Research, Inc.MetricsAuthor Information Yuya Ota More articles by this author Yasue Kubota More articles by this author Yuji Hotta More articles by this author Mami Matsumoto More articles by this author Nayuka Matsuyama More articles by this author Taiki Kato More articles by this author Takashi Hamakawa More articles by this author Tomoya Kataoka More articles by this author Kazunori Kimura More articles by this author Kazunobu Sawamoto More articles by this author Takahiro Yasui More articles by this author Expand All Advertisement PDF DownloadLoading ...

Evaluation of suprachiasmatic nucleus in Alzheimer’s disease with non-invasive magnetic resonance methods

Evaluation of suprachiasmatic nucleus in Alzheimer’s disease with non-invasive magnetic resonance methods

Change in the central control of the bladder function of rats with focal cerebral infarction induced by photochemically-induced thrombosis.

The photochemically-induced thrombosis (photothrombosis) method can create focal cerebral infarcts anywhere in the relatively superficial layers of the cerebrum; it is easy to implement and minimally invasive. Taking advantage of this versatility, we aimed to establish a new rat model of urinary frequency with focal cerebral infarction, which was characterized by its simplicity, nonlethal nature, and high reproducibility. The prefrontal cortex and the anterior cingulate cortex, which are involved in lower urinary tract control, were targeted for focal cerebral infarction, and urinary parameters were measured by cystometrogram. Cystometric analysis indicated that micturition intervals significantly shortened in photothrombosis-treated rats compared with those in the sham operative group on Days 1 and 7 (P < 0.01), but prolonged after 14 days, with no difference between the two groups. Immunopathological evaluation showed an accumulation of activated microglia, followed by an increase in reactive astrocytes at the peri-infarct zone after photothrombotic stroke. Throughout this study, all postphotothrombosis rats showed cerebral infarction in the prefrontal cortex and anterior cingulate cortex; there were no cases of rats with fatal cerebral infarction. This model corresponded to the clinical presentation, in that the micturition status changed after stroke. In conclusion, this novel model combining nonlethality and high reproducibility may be a suitable model of urinary frequency after focal cerebral infarction.

Neurodegeneration in juvenile Iberian pigs with diet-induced nonalcoholic fatty liver disease.

The objective of this study was to investigate whether juvenile Iberian pigs with diet-induced nonalcoholic fatty liver disease (NAFLD), cholestasis, and gut dysbiosis would develop histological and metabolic markers of neurodegeneration in the frontal cortex (FC) and whether supplementing probiotics would influence the response to the diet. Twenty-eight juvenile Iberian pigs were fed for 10 wk either a control (CON) or high-fructose high-fat (HFF) diet with or without a commercial probiotic mixture. Compared with CON, HFF-fed pigs had a decreased number of neurons and an increase in reactive astrocytes in FC tissue. There was also a decrease in one-carbon metabolites choline and betaine and a marked accumulation of bile acids, cholesteryl esters, and polyol pathway intermediates in FC of HFF-fed pigs, which were associated with markers of neurodegeneration and accentuated with the severity of NAFLD. Betaine depletion in FC tissue was negatively correlated with choline-derived phospholipids in colon content, whereas primary conjugated bile acids in FC were associated with cholestasis. Plasma kynurenine-to-tryptophan quotient, as a marker of indoleamine 2,3-dioxygenase activity, and intestinal dysbiosis were also correlated with neuronal loss and astrogliosis. Recognition memory test and FC levels of amyloid-β and phosphorylated Tau did not differ between diets, whereas probiotics increased amyloid-β and memory loss in HFF-fed pigs. In conclusion, our results show evidence of neurodegeneration in FC of juvenile Iberian pigs and establish a novel pediatric model to investigate the role of gut-liver-brain axis in diet-induced NAFLD.

Inhibition of STAT3 phosphorylation attenuates impairments in learning and memory in 5XFAD mice, an animal model of Alzheimer's disease

The pathophysiological roles of astrocytes in the reactive state are thought to have important significance in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). However, the detailed mechanisms underlying the transition of astrocytes from the resting state to the reactive state during neurodegenerative disease largely remain to be defined. Here, we investigated the pathways involved in activating astrocytes from the resting state to the reactive state in primary cultured astrocytes treated with oligomeric Aβ and in the hippocampus of 5XFAD mice. Treatment with oligomeric Aβ induced an increase in reactive astrocytes, as assessed by the protein level of glial fibrillary acidic protein (GFAP) and this increase was caused by STAT3 phosphorylation in primary cultured astrocytes. The administration of Stattic, an inhibitor of STAT3, rescued the activation of astrocytes in primary cultured astrocytes and in the hippocampus of 6-month-old 5XFAD mice as well as impairments in learning and memory. Collectively, these results demonstrated that reactive astrocytes in the AD brain are induced via STAT3 and the impairments in learning and memory observed in 5XFAD mice are rescued by STAT3 inhibition, suggesting that the inhibition of STAT3 phosphorylation in astrocytes may be a novel therapeutic target for cognitive impairment in AD.

Early postnatal manganese exposure causes arousal dysregulation and lasting hypofunctioning of the prefrontal cortex catecholaminergic systems.

Studies have reported associations between environmental manganese (Mn) exposure and impaired cognition, attention, impulse control, and fine motor function in children. Our recent rodent studies established that elevated Mn exposure causes these impairments. Here, rats were exposed orally to 0, 25, or 50mg Mnkg-1 day-1 during early postnatal life (PND 1-21) or lifelong to determine whether early life Mn exposure causes heightened behavioral reactivity in the open field, lasting changes in the catecholaminergic systems in the medial prefrontal cortex (mPFC), altered dendritic spine density, and whether lifelong exposure exacerbates these effects. We also assessed astrocyte reactivity (glial fibrillary acidic protein, GFAP), and astrocyte complement C3 and S100A10 protein levels as markers of A1 proinflammatory or A2 anti-inflammatory reactive astrocytes. Postnatal Mn exposure caused heightened behavioral reactivity during the first 5-10min intervals of daily open field test sessions, consistent with impairments in arousal regulation. Mn exposure reduced the evoked release of norepinephrine (NE) and caused decreased protein levels of tyrosine hydroxylase (TH), dopamine (DA) and NE transporters, and DA D1 receptors, along with increased DA D2 receptors. Mn also caused a lasting increase in reactive astrocytes (GFAP) exhibiting increased A1 and A2 phenotypes, with a greater induction of the A1 proinflammatory phenotype. These results demonstrate that early life Mn exposure causes broad lasting hypofunctioning of the mPFC catecholaminergic systems, consistent with the impaired arousal regulation, attention, impulse control, and fine motor function reported in these animals, suggesting that mPFC catecholaminergic dysfunction may underlie similar impairments reported in Mn-exposed children.

Lipopolysaccharide-Induced Microglia Activation Promotes the Survival of Midbrain Dopaminergic Neurons In Vitro

Microglia are the resident immune cells of the central nervous system (CNS) and respond to a variety of endogenous and exogenous stimuli in order to restore cell and tissue homeostasis. Lipopolysaccharide (LPS) is one of these exogenous stimuli, constitutes a major component of the outer membrane of Gram-negative bacteria, and binds to the microglial pattern recognition receptor Toll-like receptor 4 (TLR4). LPS-induced microglia activation is believed to promote neurodegeneration by release of neurotoxic factors such as interleukin-1β, tumor necrosis factor α, or nitric oxide. In the present study, we investigated whether the physical presence of microglia is required to promote neurotoxicity and whether microglia-derived factors are essential. Interestingly, we observed that dopaminergic (mDA) neuron survival was only affected in mixed neuron-glia cultures containing microglia but not in neuron-enriched cultures. Moreover, we clearly demonstrate that microglia-conditioned medium (MCM) after LPS treatment increased mDA neuron survival, process numbers as well as process length. The observed protective effects of MCM was rather caused by microglia-derived factors and only partially dependent on the increase in reactive astrocytes. These results indicate that LPS-induced microglia activation does not necessarily have detrimental effects on mDA neurons and further support the hypothesis that activated microglia support neuron survival by release of neurotrophic and neuroprotective factors.

616. Tailored Expression of a Transgene to Specific Cell Types in the Central Nervous System After Peripheral Injection of AAV9

Because of their efficient tropism for the neural tissue and their well-established safety and tolerability profile, adeno-associated vectors (AAV) hold great potential to express therapeutic genes in the context of various neurodegenerative disorders. Importantly, the characterization of novel AAV serotypes (AAV9; rhAAV10, etc …) that can cross the blood brain barrier after intravenous delivery now offer an opportunity for non-invasive delivery to the brain. However, in absence of a well-tailored system, the use of a peripheral route injection may lead to undesirable transgene expression in various cell types of the nervous system as well as in other organs. In order to refine this approach, the present study characterizes the transduction profiles of newly engineered self-complement AAV9 (scAAV9) expressing the Green Fluorescent Protein (GFP) either under an astrocyte (GFA’) or neuronal (Synapsin, Syn) promoter, after a single injection in the lateral tail vein of adult mice (5×10e11vg/animal). We report that our scAAV9-GFA’-GFP and scAAV9-Syn-GFP respectively led to robust and long-lasting transduction of astrocytes (10%) and neurons (8%) throughout the entire cerebral tissue, in the absence of aberrant expression leakage in other cell types of the brain or in the liver. GFP positive excitatory as well as inhibitory neurons could be observed in the CNS, while motor neurons were also efficiently transduced in the PNS. In addition, both activated (GFAP positive) and resting astrocytes expressed the reporter gene. Quantitative stereological assessment demonstrated an increase in reactive astrocytes after transduction with scAAV9 but did not lead to any obvious detrimental phenotype in any animals. These data suggest the potential interest of tailoring AAV to drive expression of therapeutic genes specifically in astrocytes or neurons of the CNS after intravenous delivery, thus preventing adverse side-effects associated with peripheral expression.

A high calorie diet causes memory loss, metabolic syndrome and oxidative stress into hippocampus and temporal cortex of rats.

A high calorie intake can induce the appearance of the metabolic syndrome (MS), which is a serious public health problem because it affects glucose levels and triglycerides in the blood. Recently, it has been suggested that MS can cause complications in the brain, since chronic hyperglycemia and insulin resistance are risk factors for triggering neuronal death by inducing a state of oxidative stress and inflammatory response that affect cognitive processes. This process, however, is not clear. In this study, we evaluated the effect of the consumption of a high-calorie diet (HCD) on both neurodegeneration and spatial memory impairment in rats. Our results demonstrated that HCD (90 day consumption) induces an alteration of the main energy metabolism markers, indicating the development of MS in rats. Moreover, an impairment of spatial memory was observed. Subsequently, the brains of these animals showed activation of an inflammatory response (increase in reactive astrocytes and interleukin1-β as well as tumor necrosis factor-α) and oxidative stress (reactive oxygen species and lipid peroxidation), causing a reduction in the number of neurons in the temporal cortex and hippocampus. Altogether, these results suggest that a HCD promotes the development of MS and contributes to the development of a neurodegenerative process and cognitive failure. In this regard, it is important to understand the relationship between MS and neuronal damage in order to prevent the onset of neurodegenerative disorders.

VEGF overexpression enhances the accumulation of phospho-S292 MeCP2 in reactive astrocytes in the adult rat striatum following cerebral ischemia

PurposeAstrocytes can be reactivated after cerebral ischemia by expressing nestin and other characteristic markers of neural stem cells (NSCs). However, the epigenetic features of reactive astrocytes are not well known. Methyl-CpG-binding protein 2 (MeCP2) is a vital transcriptional modulator in brain development. Although the expression and function of some phosphorylated MeCP2 isoforms have been clarified, phospho-serine 292 (pS292) MeCP2 has not yet drawn much attention. In this study, we used western blot analysis and immunohistochemical and immunofluorescent staining to reveal the expressive features of pS292 MeCP2 and MeCP2 in the adult rat striatum following transient middle cerebral artery occlusion (MCAO). ResultsWe first discovered that the ischemia-induced expression of cytoplasmic pS292 MeCP2 is primarily accumulated in nestin-positive reactive astrocytes in the stroke-injured striatum. Moreover, the enhancement of astrocytic pS292 MeCP2 was correlated with the augmentation of VEGF in astrocytes, as determined by the substantial co-localization of pS292 MeCP2 and VEGF after stroke. Finally, the exogenous overproduction of VEGF further promoted the expression of pS292 MeCP2 in reactive astrocytes, and this effect was accompanied by a marked increase in reactive astrocytes. On the contrary, MeCP2 was predominantly expressed in the neuronal nucleus, and the level of this protein was not significantly altered after ischemic injury and VEGF overproduction. ConclusionOur data provide the first demonstration that overexpression of VEGF enhances the accumulation of pS292 MeCP2 in reactive astrocytes in the ischemic-injured rat striatum, implicating a pS292 MeCP2-related epigenetic role of exogenous VEGF in reactive astrocytes following cerebral ischemia.

A phenotypic model recapitulating the neuropathology of Parkinson's disease

This study was undertaken to develop a phenotypic model recapitulating the neuropathology of Parkinson's disease (PD). Such a model would show loss of dopamine in the basal ganglia, appearance of Lewy bodies, and the early stages of motor dysfunction. The model was developed by subcutaneously injecting biodegradable microspheres of rotenone, a complex I inhibitor in 8–9 month old, ovariectomized Long–Evans rats. Animals were observed for changes in body weight and motor activity. At the end of 11–12 weeks animals were euthanized and the brains examined for histopathological changes. Rotenone treated animals gain weight and appear normal and healthy as compared to controls but showed modest hypokinesia around 5–6 weeks posttreatment. Animals showed loss of dopaminergic (DA) neurons and the appearance of putative Lewy bodies in the substantia nigra. Neuroinflammation and oxidative stress were evidenced by the appearance of activated microglia, iron precipitates, and 8-oxo-2′-deoxyguanosine a major product of DNA oxidation. The dorsal striatum, the projection site of midbrain DA neurons, showed a significant reduction in tyrosine hydroxylase immunostaining, together with an increase in reactive astrocytes, an early sign of DA nerve terminal damage. Levels of vesicular monoamine transporter 2 (VMAT2) were significantly reduced in the dorsal striatum; however, there was an unexpected increase in dopamine transporter (DAT) levels. Old, ovariectomized females treated with rotenone microspheres present with normal weight gain and good health but a modest hypokinesia. Accompanying this behavioral phenotype are a constellation of neuropathologies characteristic of PD that include loss of DA neurons, microglia activation, oxidative damage to nuclear DNA, iron deposition, and appearance of putative Lewy bodies. This phenotypic model recapitulating the neuropathology of Parkinson's disease could provide insight into early mechanisms of pathogenesis and could aid in the identification of biomarkers to identify patients in early stage, PD.

Reactive astrocytosis, microgliosis and inflammation in rats with neonatal hydrocephalus

The deleterious effects of hydrocephalus, a disorder that primarily affects children, include reactive astrocytosis, microgliosis and inflammatory responses; however, the roles that these mechanisms play in the pathophysiology of hydrocephalus are still not clear in terms of cytopathology and gene expression. Therefore we have examined neuroinflammation at both the cellular and the molecular levels in an experimental model of neonatal obstructive hydrocephalus. On post-natal day 1, rats received an intracisternal injection of kaolin to induce hydrocephalus; control animals received saline injections. Prior to sacrifice on post-natal day 22, animals underwent magnetic resonance imaging to quantify ventricular enlargement, and the parietal cortex was harvested for analysis. Immunohistochemistry and light microscopy were performed on 5 hydrocephalic and 5 control animals; another set of 5 hydrocephalic and 5 control animals underwent molecular testing with Western blots and a gene microarray. Scoring of immunoreactivity on a 4-point ranking scale for GFAP and Iba-1 demonstrated an increase in reactive astrocytes and reactive microglia respectively in the hydrocephalic animals compared to controls (2.90 ± 0.11 vs. 0.28 ± 0.26; 2.91 ± 0.11 vs. 0.58 ± 0.23, respectively). Western blots confirmed these results. Microarray analysis identified significant (1.5-fold) changes in 1729 of 33,951 genes, including 26 genes out of 185 genes (26/185) in the cytokine–cytokine receptor interaction pathway, antigen processing and presentation pathways (15/66), and the apoptosis pathway (10/69). Collectively, these results demonstrate alterations in normal physiology and an up-regulation of the inflammatory response. These findings lead to a better understanding of neonatal hydrocephalus and begin to form a baseline for future treatments that may reverse these effects.

Oral administration of grape polyphenol extract ameliorates cerebral ischemia/reperfusion-induced neuronal damage and behavioral deficits in gerbils: comparison of pre- and post-ischemic administration

Oxidative stress has been regarded as an important underlying cause for the delayed neuronal death (DND) after cerebral ischemia. In this study, the effects of short-term oral administration of grape polyphenol extract (GPE) on ischemia/reperfusion (I/R) injury in a gerbil global ischemia model were determined. Ischemia was induced by occlusion of the common carotid arteries for 5 min. GPE (30 mg/ml)-containing formula or formula without GPE was administered daily via gavage for 4 days prior to and/or for 4 days after I/R. I/R resulted in hyperlocomotion, extensive DND, oxidative and fragmented DNA damage, and an increase in reactive astrocytes and microglial cells in the hippocampal CA1 region. GPE administration for 4 days prior to I/R and for 4 days after I/R attenuated DND, DNA damage and glial cell activation. However, neuroprotection was more pronounced when GPE was administered for 4 days after I/R than when administered for 4 days prior to I/R. GPE administration after I/R attenuated I/R-induced hyperlocomotion. These findings indicate that oral GPE intake may confer protection against I/R injury and emphasize that early intervention may be an effective therapeutic measure for ameliorating brain injury in stroke.

Ischemia induces cell proliferation and neurogenesis in the gerbil hippocampus in response to neuronal death

We studied hippocampal cellular proliferation and neurogenesis processes in a model of transient global cerebral ischemia in gerbils by labelling dividing cells with 5′-Bromo-2′-deoxyuridine (BrdU). Surrounding the region of selective neuronal death (CA1 pyramidal layer of the hippocampus), an important increase in reactive astrocytes and BrdU-labelled cells was detected 5 days after ischemia. A similar result was found in the dentate gyrus (DG) 12 days after ischemia. The differentiation of the BrdU+ cells was investigated 28 days after BrdU administration by analyzing the morphology, anatomic localization and cell phenotype by triple fluorescent labelling (BrdU, adult neural marker NeuN and DNA marker TOPRO-3) using confocal laser-scanning microscopy. This analysis showed increased neurogenesis in the DG in case of ischemia and triple positive labelling in some newborn cells in CA1. Seven brain hemispheres from gerbils subjected to ischemia did not develop CA1 neuronal death; hippocampus from these hemispheres did not show any of the above mentioned findings. Our results indicate that ischemia triggers proliferation in CA1 and neurogenesis in the DG in response to CA1 pyramidal neuronal death, independently of the reduced cerebral blood flow or the cell migration from subventricular zone (SVZ).

Dietary grape supplement ameliorates cerebral ischemia-induced neuronal death in gerbils

Oxidative damage has been implicated as one of the leading causes for neuronal cell death in a number of neurodegenerative diseases including stroke. Many vegetables and fruits are enriched in polyphenolic compounds known to exhibit antioxidant properties. This study is to investigate whether dietary supplement with grape powder (GP) may offer protection against neuronal damage due to global cerebral ischemia induced to Mongolian gerbils by occlusion of the common carotid arteries, a model known to cause delayed neuronal death (DND) in the hippocampal CA1 area. Gerbils were fed either a control diet (AIN76a) or a control diet supplemented with low (5.0 g/kg diet) or high (50 g/kg diet) levels of GP for two months. Four days after ischemia/reperfusion (I/R), the extent of DND, glial cell activation, nuclear DNA oxidation, and apoptotic terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) reaction in hippocampal CA1 region were assessed. Ischemia-induced extensive DND in the CA1 region was accompanied by oxidative and fragmented DNA damage and a marked increase in reactive astrocytes and microglial cells. Dietary GP supplementation significantly protected neurons against I/R-induced DND, DNA damage, and apoptosis as well as attenuated glial cell activation. These results demonstrate that due to the antioxidant properties of polyphenols in GP, nutritional diets supplemented with grape can protect the brain against ischemic damage. The neuroprotective effects of GP supplement may have wide implication in the future for prevention/protection against other neurodegenerative damage.

Resveratrol protects against global cerebral ischemic injury in gerbils

Increased oxidative stress has been implicated in the mechanisms of delayed neuronal cell death (DND) following cerebral ischemic insult. In this study, we investigated whether resveratrol, a polyphenolic antioxidant enriched in grape, may ameliorate ischemia-induced neuron cell death. Mongolian gerbils were divided into three groups, namely, sham control, ischemia and ischemia treated with resveratrol. Transient global cerebral ischemia was induced by occlusion of both common carotid arteries (CCA) for 5 min. Resveratrol was injected i.p. (30 mg/kg body weight), either during or shortly after CCA occlusion, and again at 24 h after ischemia. Cerebral blood flow was monitored before and during CCA occlusion using a laser Doppler flowmeter. Brain sections were immuno-stained for neurons, astrocytes and microglial cells. A time course study was also carried out to assess the bioavailability of resveratrol in serum, liver and brain using high performance liquid chromatography (HPLC). Morphometric measurements indicated extensive DND in the hippocampal CA1 region 4 days after ischemia and that neuron cell death was marked by the increase in reactive astrocytes and microglial cells. Administration of resveratrol, either during or after CCA occlusion, significantly ( P<0.05) decreased DND as well as glial cell activation. Analysis of resveratrol after i.p. injection indicated its presence in serum, liver and brain with peak activity at 1, 4 and 4 h, respectively. This study demonstrated for the first time that resveratrol, a polyphenolic antioxidant, can cross the blood–brain barrier and exert protective effects against cerebral ischemic injury.

Sodium channel beta1-subunit expression is increased in reactive astrocytes in a rat model for mesial temporal lobe epilepsy.

As several epilepsy syndromes are associated with changes in sodium channel subunits we investigated the expression of beta1 sodium channel protein in a rat epilepsy model. In this model a chronic epileptic syndrome develops after electrically induced status epilepticus (SE). Many neuropathological characteristics of mesial temporal lobe epilepsy can be reproduced (cell loss, gliosis and synaptic reorganization). In control hippocampus beta1 subunit protein was moderately expressed in neurons and weakly expressed in resting astrocytes. beta1 sodium channel immunoreactivity increased markedly within 1 week after SE mainly in astrocytes that were colocalized with vimentin (marker for reactive astrocytes). This up-regulation was still present in reactive astrocytes of chronic epileptic rats (> 3 months after SE). Considering the fact that the beta1 subunits may function as cell adhesion molecules interacting with extracellular matrix, the observed increase in reactive astrocytes might subserve a function in cellular and synaptic reorganization during epileptogenesis.