Increased oxidative stress is responsible for severer cerebral infarction in stroke-prone spontaneously hypertensive rats

Aims: To examine the role of increased oxidative stress in the pathogenesis of cerebral infarction in stroke in stroke‐prone spontaneously hypertensive rats (SHR‐SP). Methods: The differentially expressed brain protein profile was examined in spontaneously hypertensive rats (SHR) (control group) and SHR‐SP using two‐dimensional fluorescent difference gel electrophoresis (2D‐DIGE). In addition, oxidative stress indicators including total antioxidation capacity (TAC), glutathione peroxidase (GPx) activity, and maleic dialdehyde (MDA) were also measured. Lastly, SHR‐SP were randomly divided into untreated and treated (vitamins C (200 mg/kg/day) and E (100 mg/kg/day)) groups. After treatment for 4 weeks, half of the animals were sacrificed for detection of TAC, GPx, and MDA. The remaining rats underwent middle cerebral artery occlusion (MCAO) and the infarct areas were measured. Results: Compared with SHR, the infarct area of SHR‐SP was larger (P < 0.01), and the antioxidative proteins including glutathione S‐transferase (GST) Pi2 and GST A5 were lower; TAC and GPx activities were decreased and MDA levels. Treatment with vitamins C and E decreased MDA, and increased TAC and GPx activity significantly in SHR‐SP, while also decreasing the infarct area (P < 0.01). Conclusions: Our findings indicate that oxidative stress plays an important role in the pathogenesis of cerebral ischemia.     

Risperidone Enhances the Vulnerability to Stroke in Hypertensive Rats

Background: Stroke is the second most common cause of death and a major cause of disability worldwide. Risperidone is an atypical antipsychotic drug that may increase the risk of stroke. The present work examined whether risperidone enhances the vulnerability to stroke in hypertensive rats and the potential mechanisms underlying such action. Methods: Experiment 1: Wistar‐Kyoto (WKY) rats, spontaneously hypertensive rats (SHRs) and stroke‐prone SHRs (SHR‐SPs) were treated with risperidone (0.8 and 2.4 mg/kg/d) or vehicle for 30 consecutive days. Tissue damage in response to middle cerebral artery occlusion (MCAO) was measured microscopically. The activity of superoxide dismutase, glutathione peroxidase, the levels of malondialdehyde were also determined. Experiment 2: Survival data were recorded in SHR‐SPs that received daily risperidone perpetually. Experiment 3: Effect of risperidone on interleukin‐6 and tumor necrosis factor‐α was examined in quiescent or LPS‐activated cortical microglias from WKY rats. Experiment 4: Potential damage of risperidone exposure to neurons was examined in primary neuronal culture obtained from WKY rats, SHRs, and SHR‐SPs. Results: Risperidone increased infarct areas upon MCAO in SHR‐SPs and SHRs, but not in WKY rats. Survival time in SHR‐SPs was shortened by risperidone. Apoptosis was augmented by risperidone through enhanced Bax. Risperidone also increased endothelial injury. Conclusions: Risperidone enhances the vulnerability to stroke in hypertensive rats through increasing neuronal apoptosis and endothelial injury.     

Striatal astrocytes transdifferentiate into functional mature neurons following ischemic brain injury

To determine whether reactive astrocytes stimulated by brain injury can transdifferentiate into functional new neurons, we labeled these cells by injecting a glial fibrillary acidic protein (GFAP) targeted enhanced green fluorescence protein plasmid (pGfa2‐eGFP plasmid) into the striatum of adult rats immediately following a transient middle cerebral artery occlusion (MCAO) and performed immunolabeling with specific neuronal markers to trace the neural fates of eGFP‐expressing (GFP⁺) reactive astrocytes. The results showed that a portion of striatal GFP⁺ astrocytes could transdifferentiate into immature neurons at 1 week after MCAO and mature neurons at 2 weeks as determined by double staining GFP‐expressing cells with βIII‐tubulin (GFP⁺‐Tuj‐1⁺) and microtubule associated protein‐2 (GFP⁺‐MAP‐2⁺), respectively. GFP⁺ neurons further expressed choline acetyltransferase, glutamic acid decarboxylase, dopamine receptor D2‐like family proteins, and the N‐methyl‐d ‐aspartate receptor subunit R2, indicating that astrocyte‐derived neurons could develop into cholinergic or GABAergic neurons and express dopamine and glutamate receptors on their membranes. Electron microscopy analysis indicated that GFP⁺ neurons could form synapses with other neurons at 13 weeks after MCAO. Electrophysiological recordings revealed that action potentials and active postsynaptic currents could be recorded in the neuron‐like GFP⁺ cells but not in the astrocyte‐like GFP⁺ cells, demonstrating that new GFP⁺ neurons possessed the capacity to fire action potentials and receive synaptic inputs. These results demonstrated that striatal astrocyte‐derived new neurons participate in the rebuilding of functional neural networks, a fundamental basis for brain repair after injury. These results may lead to new therapeutic strategies for enhancing brain repair after ischemic stroke. GLIA 2015;63:1660–1670     

Expression of MCP‐1 and fractalkine on endothelial cells and astrocytes may contribute to the invasion and migration of brain macrophages in ischemic rat brain lesions

Some macrophages expressing NG2 chondroitin sulfate proteoglycan (NG2) and the macrophage marker Iba1 accumulate in the ischemic core of a rat brain subjected to transient middle cerebral artery occlusion (MCAO) for 90 min. These cells are termed BINCs (for brain Iba1⁺/NG2⁺ cells) and may play a neuroprotective role. Because BINCs are bone marrow‐derived cells, they are able to invade ischemic tissue after the onset of an ischemic insult. In this study, chemokine‐based mechanisms underlying the invasion of BINCs or their progenitor cells were investigated. We found that isolated BINCs expressed mRNA encoding CCR2 and CX3CR1 at high levels. Cultured astrocytes expressed mRNA encoding their ligands, MCP‐1 and fractalkine. Recombinant MCP‐1 and/or fractalkine, as well as astrocytes, induced the migration of BINCs in vitro. mRNA for MCP‐1, fractalkine, CCR2, and CX3CR1 was expressed in the ischemic core during the acute phase of the ischemic event. Immunohistochemical studies revealed that vascular endothelial cells and astrocytic endfeet expressed MCP‐1 and fractalkine, respectively, in the ischemic core during the acute phase. CCR2⁺/Iba1⁺ monocytes attached to the inside of the vascular wall at 1 day postreperfusion (dpr), and there were CCR2⁺/CX3CR1⁺ macrophage‐like cells in the parenchyma in the ischemic lesion core at 2 dpr, which may be the progenitors for BINCs. These results suggest that CCR2⁺ monocytes are first attracted to the ischemic lesion by MCP‐1⁺ endothelial cells and migrate toward fractalkine⁺ astrocytic endfeet through the disrupted blood–brain barrier. Thus, chemokines may play a critical role in the accumulation of neuroprotective BINCs. © 2013 Wiley Periodicals, Inc.     

SOX17 is expressed in regenerating oligodendrocytes in experimental models of demyelination and in multiple sclerosis

We have previously demonstrated that Sox17 expression is prominent at developmental stages corresponding to oligodendrocyte progenitor cell (OPC) cycle exit and onset of differentiation, and that Sox17 promotes initiation of OPC differentiation. In this study, we examined Sox17 expression and regulation under pathological conditions, particularly in two animal models of demyelination/remyelination and in post‐mortem multiple sclerosis (MS) brain lesions. We found that the number of Sox17 expressing cells was significantly increased in lysolecithin (LPC)‐induced lesions of the mouse spinal cord between 7 and 30 days post‐injection, as compared with controls. Sox17 immunoreactivity was predominantly detected in Olig2⁺ and CC1⁺ oligodendrocytes and rarely in NG2⁺ OPCs. The highest density of Sox17⁺ oligodendrocytes was observed at 2 weeks after LPC injection, coinciding with OPC differentiation. Consistent with these findings, in cuprizone‐treated mice, Sox17 expression was highest in newly generated and in maturing CC1⁺ oligodendrocytes, but low in NG2⁺ OPCs during the demyelination and remyelination phases. In MS tissue, Sox17 was primarily detected in actively demyelinating lesions and periplaque white matter. Sox17 immunoreactivity was co‐localized with NOGO‐A+ post‐mitotic oligodendrocytes both in active MS lesions and periplaque white matter. Taken together, our data: (i) demonstrate that Sox17 expression is highest in newly generated oligodendrocytes under pathological conditions and could be used as a marker of oligodendrocyte regeneration, and (ii) are suggestive of Sox17 playing a critical role in oligodendrocyte differentiation and lesion repair. GLIA 2013;61:1659–1672     

Focal cerebral ischemia induces a multilineage cytogenic response from adult subventricular zone that is predominantly gliogenic

The purpose of this study was to ascertain the relative contribution of neural stem/progenitor cells (NSPCs) of the subventricular zone (SVZ) to lineages that repopulate the injured striatum following focal ischemia. We utilized a tamoxifen‐inducible Cre/loxP system under control of the nestin promoter, which provides permanent YFP labeling of multipotent nestin⁺ SVZ‐NSPCs prior to ischemic injury and continued YFP expression in all subsequent progeny following stroke. YFP reporter expression was induced in adult male nestin‐CreER^T2:R26R‐YFP mice by tamoxifen administration (180 mg kg⁻¹, daily for 5 days). Fourteen days later, mice were subjected to 60‐min transient middle cerebral artery occlusion (MCAO) and sacrificed at 2 days, 2 weeks, or 6 weeks post‐MCAO for phenotypic fate mapping of YFP⁺ cells using lineage‐specific markers. Migration of YFP⁺ cells from SVZ into the injured striatal parenchyma was apparent at 2 and 6 weeks, but not 2 days, post‐MCAO. At 2 weeks post‐MCAO, the average percent distribution of YFP⁺ cells within the injured striatal parenchyma was as follows: 10% Dcx⁺ neuroblasts, 15–20% oligodendrocyte progenitors, 59% GFAP⁺ astrocytes, and only rare NeuN⁺ postmitotic neurons. A similar phenotypic distribution was observed at 6 weeks, except for an increased average percentage of YFP⁺ cells that expressed Dcx⁺ (20%) or NeuN (5%). YFP⁺ cells did not express endothelial markers, but displayed unique anatomical relationships with striatal vasculature. These results indicate that nestin⁺ NSPCs within the SVZ mount a multilineage response to stroke that includes a gliogenic component more predominant than previously appreciated. © 2010 Wiley‐Liss, Inc.     

Activated microglia in a rat stroke model express NG2 proteoglycan in peri‐infarct tissue through the involvement of TGF‐β1

We investigated activated microglia in ischemic brain lesions from rats that had been subjected to transient middle cerebral artery occlusion. Activated microglia expressing NG2 chondroitin sulfate proteoglycan (NG2) were found only in the narrow zone (demarcation zone) that demarcated the peri‐infarct tissue and ischemic core. NG2^? activated microglia were abundantly distributed in the peri‐infarct tissue outside the demarcation zone. NG2⁺ microglia but not NG2^? microglia expressed both CD68 and a triggering receptor expressed on myeloid cells 2 (TREM‐2), suggesting that NG2⁺ microglia eliminated apoptotic neurons. In fact, NG2⁺ microglia often attached to degenerating neurons and sometimes internalized NeuN⁺ or neurofilament protein⁺ material. Kinetic studies using quantitative real‐time RT‐PCR revealed that expression of transforming growth factor‐β1 (TGF‐β1) was most evident in the ischemic core; with this marker produced mainly by macrophages located in this region. TGF‐β receptor mRNA expression peaked at 3 days post reperfusion (dpr) in the peri‐infarct tissue, including the demarcation zone. Primary cultured rat microglia also expressed the receptor mRNA. In response to TGF‐β1, primary microglia enhanced the expression of NG2 protein and TREM‐2 mRNA as well as migratory activity. A TGF‐β1 inhibitor, SB525334, abolished these effects. The present results suggest that TGF‐β1 produced in the ischemic core diffused toward the peri‐infarct tissue, driving activated microglial cells to eliminate degenerating neurons. Appropriate control of NG2⁺ microglia in the demarcation zone might be a novel target for the suppression of secondary neurodegeneration in the peri‐infarct tissue. GLIA 2014;62:185–198     

DL-3-n-Butylphthalide, an anti-oxidant agent, prevents neurological deficits and cerebral injury following stroke per functional analysis, magnetic resonance imaging and histological assessment

DL-3-n-Butylphthalide (NBP) is a synthetic compound based on L-3-n-Butylphthalide which was isolated from seeds of Apium graveolens. The present study aims at evaluating the outcome of NBP given prior to and after the onset of ischemic stroke in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Stroke was induced by the middle cerebral artery occlusion (MCAO) in SHR and WKY. For pre-treatment, NBP was administered to SHR and WKY daily for two months prior to MCAO. For post-treatment, NBP was given daily for seven consecutive days after MCAO. Seven days post-surgery, rats were tested for the presence of neurological deficits. Magnetic resonance imaging (MRI) and 2,3,5-triphenyltetrazolium chloride (TTC) staining were employed to calculate the infarct volume. The cerebral cortex and corpus striatum in the ischemic penumbra area were examined microscopically for pathological changes. In SHR, NBP pre- and post-treatment significantly lowered neurological deficit scores, reduced infarct volume, and minimized pathological changes in the penumbra area when compared to oil-vehicle treated controls. In WKY, these beneficial effects were observed only in the post-treatment group. The beneficial effects of NBP post-treatment were greater in WKY than in SHR. Results indicated that NBP could exert both preventive and therapeutic effects on ischemic stroke in SHR, but only exerted therapeutic effect in WKY.     

Novel NG2‐CreERT2 knock‐in mice demonstrate heterogeneous differentiation potential of NG2 glia during development

NG2 (nerve/glia antigen‐2) is a type I transmembrane glycoprotein and also known as chondroitin sulfate proteoglycan 4. In the parenchyma of the central nervous system, NG2‐expressing (NG2⁺) cells have been identified as a novel type of glia with a strong potential to generate oligodendrocytes (OLs) in the developing white matter. However, the differentiation potential of NG2 glia remained controversial, largely attributable to shortcomings of transgenic mouse models used for fate mapping. To minimize these restrictions and to more faithfully mimic the endogenous NG2 expression in vivo, we generated a mouse line in which the open reading frame of the tamoxifen‐inducible form of the Cre DNA recombinase (CreERT2) was inserted into the NG2 locus by homologous recombination. Results from this novel mouse line demonstrate that at different developmental stages of the brain, NG2⁺ cells either stayed as NG2 glia or differentiated into OLs during the whole life span. Interestingly, when Cre activity was induced at embryonic stages, a significant number of reporter⁺ astrocytes could be detected in the gray matter after birth. However, in other brain regions, such as olfactory bulb, brain stem, and cerebellum, all of the NG2 glia was restricted to the OL lineage. In addition, tamoxifen‐sensitive and NG2 gene locus‐dependent gene recombination could be detected in a small, but persistent population of cortical NeuN⁺ neurons starting from the second postnatal week. GLIA 2014;62:896–913     

Sympathetic nerve activity: a link to stroke?

Spontaneously hypertensive rats (SHR) have been shown to have an increased capacity for superior cervical sympathetic nerve activity which may protect against stroke (Mueller et al: Stroke 13: 115, 1982). Sympathetic nerve activity has never been examined in the stroke-prone substrain of SHR (SP). In this study we measured superior cervical sympathetic nerve activity during rest and during a maximal sympathetic response in SHR, SP, and their normotensive controls, Wistar-Kyoto (WKY). The resting superior cervical sympathetic nerve activity of SP was significantly less than SHR (p less than 0.02) but not different from WKY. During central ischemia, used to induce maximal sympathetic response, the increase in SP sympathetic nerve activity was significantly less than SHR (p less than 0.001) but was not different from WKY. This diminished capacity for elevated superior cervical sympathetic nerve activity in stroke-prone SHR may relate to their increased predisposition to stroke because sympathetic hyperactivity cannot protect cerebral vessels during acute hypertension.     

Down‐regulation of microglia and NG2‐positive cells reaction in trimethyltin‐injured hippocampus of rats treated with myelin basic protein‐reactive T cells: Possible contribution to the neuroprotective effect of T cells

In our previous investigations, we demonstrated that CD4⁺ antimyelin basic protein (MBP) T cells protect hippocampal neurons against trimethyltin‐induced damage. We hypothesized involvement of T cells, interacting with the various glial populations activated during the neurodegeneration process. In this study, we employ immunocytochemical methods to investigate the influence of administration of T cells on the response of microglia and of NG2⁺ cells to trimethyltin (TMT)‐induced damage. Female Lewis rats were treated with anti‐MBP CD4⁺ T cells (4 million per animal, i.v) 24 hr after TMT (8 mg/kg, i.p) intoxication. TMT caused degeneration of CA4 hipppocampal neurons and evoked an abundant reaction of microglial and NG2⁺ cells in the injured region. The cells changed morphology into the activated state, and the number of OX42⁺ and NG2⁺ cells increased about 4.5‐fold and 3‐fold, respectively, relative to controls as assessed on day 21 after TMT treatment. Additionally, the cells of ameboid morphology, which expressed NG2 or microglial antigens, appeared in the zone of neurodegeneration. Furthermore, certain cells of ameboid phenotype shared both antigens. In rats treated with T cells, down‐regulation of the activation of both glial classes and reduction of formation of their ameboid forms was observed. The number of the total OX42⁺ and NG2⁺ cells decreased by 21% and 54%, respectively, and the number of their ameboid forms decreased by 46% and 73%, respectively. Our data suggest that the diminished activation of microglia and NG2⁺ cells, particularly the reduced number of their ameboid forms, may contribute to the neuroprotective effect of T cells. © 2009 Wiley‐Liss, Inc.     

Structural alterations of tight junctions are associated with loss of polarity in stroke-prone spontaneously hypertensive rat blood–brain barrier endothelial cells

The mechanisms leading to stroke in stroke-prone spontaneously hypertensive rats (SHRSP) are not well understood. We tested the hypothesis that the endothelial tight junctions of the blood–brain barrier are altered in SHRSP prior to stroke. We investigated tight junctions in 13-week-old SHRSP, spontaneously hypertensive stroke-resistant rats (SHR) and age-matched Wistar–Kyoto rats (WKY) by electron microscopy and immunocytochemistry. Ultrathin sections showed no difference in junction structure of cerebral capillaries from SHRSP, SHR and WKY, respectively. However, using freeze-fracturing, we observed that the blood–brain barrier specific distribution of tight junction particles between P- and E-face in WKY (58.7±3.6%, P-face; 41.2±5.59%, E-face) and SHR (53.2±19.3%, P-face; 55.6±13.25%, E-face) was changed to an 89.4±9.9% predominant E-face association in cerebral capillaries from SHRSP. However, the expression of the tight junction molecules ZO-1, occludin, claudin-1 and claudin-5 was not changed in capillaries of SHRSP. Permeability of brain capillaries from SHRSP was not different compared to SHR and WKY using lanthanum nitrate as a tracer. In contrast, analysis of endothelial cell polarity by distribution of the glucose-1 transporter (Glut-1) revealed that its abluminal:luminal ratio was reduced from 4:1 in SHR and WKY to 1:1 in endothelial cells of cerebral capillaries of SHRSP. In summary, we demonstrate that early changes exist in cerebral capillaries from a genetic model of hypertension-associated stroke. We suggest that a disturbed fence function of the tight junctions in SHRSP blood–brain barrier endothelial cells may lead to subtle changes in polarity. These changes may contribute to the pathogenesis of stroke.     

Opioid peptides in pituitary gland, brain regions and peripheral tissues of spontaneously hypertensive and Wistar-Kyoto normotensive rats

The concentrations of β-endorphin (β-END), dynorphin (DYN) and methionine-enkephalin (MEK) in pituitary, brain regions, heart, kidney and adrenal of 8 week old male spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) normotensive rats were determined by radioimmunoassay and compared. The brain regions examined were hypothalamus, striatum, pons + medulla, midbrain and cortex. The concentration of β-END in pituitary of SHR rats was 49% higher than those of WKY rats. The concentration of β-END in the striatum of SHR rats was 71% lower as compared to WKY rats. The concentration of β-END in the heart, adrenals and kidney of SHR rats was significantly lower (92. 48 and 57%, respectively), than those of WKY rat tissues. The concentration of DYN in pituitary, striatum and heart were lower by 38, 55 and 46%, respectively, in SHR compared to WKY rats, but in hypothalamus it was greater (33%) than in WKY rats. The concentration of DYN in other brain areas and in kidney and adrenal did not differ. The tissues of SHR and WKY rats which showed significant difference in the concentration of MEK were pituitary, pons + medulla, cerebral cortex and adrenals. The concentration of MEK was greater in SHR rats with pons + medulla, cortex and adrenals showing 33, 40, 268% higher levels, respectively, over the WKY rat tissues. However, the concentration of MEK in pituitary of SHR rats was 40% lower than that of WKY rats. These studies suggest that the endogenous opioid peptides of both central and peripheral tissues may be important in the regulation of blood pressure in SHR rats.     

17α‐Oestradiol‐Induced Neuroprotection in the Brain of Spontaneously Hypertensive Rats

17β‐oestradiol is a powerful neuroprotective factor for the brain abnormalities of spontaneously hypertensive rats (SHR). 17α‐Oestradiol, a nonfeminising isomer showing low affinity for oestrogen receptors, is also endowed with neuroprotective effects in vivo and in vitro. We therefore investigated whether treatment with 17α‐oestradiol prevented pathological changes of the hippocampus and hypothalamus of SHR. We used 20‐week‐old male SHR with a blood pressure of approximately 170 mmHg receiving s.c. a single 800 μg pellet of 17α‐oestradiol dissolved in cholesterol or vehicle only for 2 weeks Normotensive Wistar–Kyoto (WKY) rats were used as controls. 17α‐Oestradiol did not modify blood pressure, serum prolactin, 17β‐oestradiol levels or the weight of the testis and pituitary of SHR. In the brain, we analysed steroid effects on hippocampus Ki67+ proliferating cells, doublecortin (DCX) positive neuroblasts, glial fibrillary acidic protein (GFAP)+ astrocyte density, aromatase immunostaining and brain‐derived neurotrophic factor (BDNF) mRNA. In the hypothalamus, we determined arginine vasopressin (AVP) mRNA. Treatment of SHR with 17α‐oestradiol enhanced the number of Ki67+ in the subgranular zone and DCX+ cells in the inner granule cell layer of the dentate gyrus, increased BDNF mRNA in the CA1 region and gyrus dentatus, decreased GFAP+ astrogliosis in the CA1 subfield, and decreased hypothalamic AVP mRNA. Aromatase expression was unmodified. By contrast to SHR, normotensive WKY rats were unresponsive to 17α‐oestradiol. These data indicate a role for 17α‐oestradiol as a protective factor for the treatment of hypertensive encephalopathy. Furthermore, 17α‐oestradiol is weakly oestrogenic in the periphery and can be used in males.     

Rosiglitazone reverses increased duodenal inhibitory response in spontaneously hypertensive rats

Background Thiazolidinediones (TZDs) including rosiglitazone (ROSI) are insulin sensitizing agents with beneficial gastrointestinal effects. However, no studies are available on TZDs effect in gastrointestinal motility. We evaluated the effects of ROSI on gastrointestinal inhibitory neurotransmission focusing on the modulatory roles of nitric oxide synthase/nitric oxide (NOS/NO) and heme oxygenase/carbon monoxide (HO/CO) pathways. Methods Spontaneously hypertensive rats (SHR) were used as model of insulin resistance. Duodenal strips were obtained from vehicle‐treated SHR, ROSI‐treated SHR (5 mg kg^?1 by gavage daily per 6 weeks), and Wistar Kyoto (WKY). Inhibitory responses to electrical field stimulation (EFS) were evaluated in the presence of HO inhibitor zinc protoporphyrin IX (ZnPPIX, 10 μmol L^?1) or NOS inhibitor N^G‐nitro‐l ‐arginine (L‐NNA, 100 μmol L^?1), alone and in combination. Protein levels of HO and NOS isoforms were evaluated by immunohistochemistry and western blot analysis. Key Results Basal responses to EFS were significantly increased in duodenum strips from vehicle‐treated SHR vs WKY. This effect was reversed in ROSI‐treated SHR. The EFS‐mediated relaxation was comparably reduced by ZnPPIX in WKY and SHR, but not in ROSI‐treated SHR animals. The L‐NNA reduced EFS response to a similar extent in WKY and ROSI ‐treated SHR, but its effect was significantly higher in vehicle‐treated SHR. Expression of HO‐1 protein was significantly lower, whereas HO‐2 protein levels were unchanged in ROSI‐treated SHR with respect to vehicle‐treated SHR. Finally, increased levels of nNOS in vehicle‐treated SHR were reduced in ROSI‐treated SHR. Conclusions & Inferences Chronic ROSI treatment reverses increased SHR duodenal inhibitory response acting on CO and NO components.     

GPR17 expressing NG2‐Glia: Oligodendrocyte progenitors serving as a reserve pool after injury

In the adult brain NG2‐glia continuously generate mature, myelinating oligodendrocytes. To which extent the differentiation process is common to all NG2‐glia and whether distinct pools are recruited for repair under physiological and pathological conditions still needs clarification. Here, we aimed at investigating the differentiation potential of adult NG2‐glia that specifically express the G‐protein coupled receptor 17 (GPR17), a membrane receptor that regulates the differentiation of these cells at postnatal stages. To this aim, we generated the first BAC transgenic GPR17‐iCreER^T2 mouse line for fate mapping studies. In these mice, under physiological conditions, GPR17⁺ cells —in contrast to GPR17^‐ NG2‐glia— did not differentiate within 3 months, a peculiarity that was overcome after cerebral damage induced by acute injury or ischemia. After these insults, GPR17⁺ NG2‐glia rapidly reacted to the damage and underwent maturation, suggesting that they represent a ‘reserve pool’ of adult progenitors maintained for repair purposes. GLIA 2016;64:287–299     

Cerebral small vessel endothelial structural changes predate hypertension in stroke-prone spontaneously hypertensive rats: a blinded, controlled immunohistochemical study of 5- to 21-week-old rats

E. L. Bailey, J. M. Wardlaw, D. Graham, A. F. Dominiczak, C. L. M. Sudlow and C. Smith (2011) Neuropathology and Applied Neurobiology 37, 711–726 Cerebral small vessel endothelial structural changes predate hypertension in stroke‐prone spontaneously hypertensive rats: a blinded, controlled immunohistochemical study of 5‐ to 21‐week‐old rats Aims: The spontaneously hypertensive stroke‐prone rat (SHRSP) is a potential animal model of human lacunar stroke, but there is little information on SHRSP small vessel pathology, especially in young rats. We investigated the structural changes that occur in cortical and subcortical vessels and adjacent tissue in SHRSP before, during and after the onset of hypertension. Methods: We examined brains from SHRSP and Wistar Kyoto rats (WKY) at 5, 16 and 21 weeks of age. Structural changes in small arterioles and adjacent tissue were studied using antibodies to investigate different components of the neurovascular unit. We quantified staining in three standard regions, at two coronal levels. Results: Immunostaining for claudin‐5, a marker of endothelial tight junctions, was reduced in SHRSP at all ages compared to age‐matched WKY controls. Smooth muscle actin, glial fibrillary acidic protein and ionized calcium‐binding adaptor molecule 1 were increased in SHRSP vs. WKY by 16 weeks. Additionally, 21‐week‐old WKY and SHRSP rats fed a high‐salt diet showed differences in claudin‐5, glial fibrillary acidic protein and matrix metalloproteinase 9 staining compared to those fed a normal diet. Conclusion: Endothelial tight junction alterations of SHRSP rats from the earliest ages point towards increased susceptibility to blood–brain barrier dysfunction and stroke, which is exacerbated by salt loading. Salt loading may also damage the neurovascular unit in WKY controls.     

Cognitive impairment in spontaneously hypertensive rats: role of central nicotinic receptors. I

Both human essential hypertension and genetically induced hypertension in rats have been associated with a range of impairments of cognitive ability. The spontaneous hypertensive rat (SHR) previously has been shown to exhibit a decrease in the expression of brain nicotinic acetylcholine receptors, a factor that could play a role in the impaired ability of this strain in the performance of learning and memory-related tasks. The purpose of this study was to help determine whether task impairment by SHR was related to the reduced expression of central nicotinic acetylcholine receptors. Twelve-week-old SHR were tested in two phases of a water maze (spatial memory) task, and their performance was compared with that of two age-matched normotensive strains, Wistar Kyoto (WKY) and Wistar rats. During Phase 1, SHR exhibited significantly increased latencies to locate a hidden platform as compared with either WKY or Wistar rats. During Phase 2 (subsequent series of trials after a 4-day inter-phase period), where rats were required to find a new platform location, SHR again exhibited significantly impaired performance compared to the normotensive strains. In a single trial passive avoidance paradigm, SHR again displayed significantly reduced avoidance behavior as compared with both WKY and Wistar rats. In consecutive coronal sections, the density of [³H]cytisine binding sites was decreased in SHR by up to 25% in about half of the brain regions examined, with the deficits particularly apparent in cephalic regions. The binding of [¹²⁵I]α-bungarotoxin to brain sections also was decreased in SHR; however, only certain brain areas exhibited significant interstrain differences. These alterations in the expression of putative nicotinic receptor subtypes in SHR were not due to changes in the density of cholinergic neurons since there were no interstrain differences in the binding densities for [³H]vesamicol, which labels the vesicular acetylcholine transporter. Moreover, the magnitude of nicotine-stimulated rubidium efflux from cortical and striatal synaptosomes in vitro was significantly reduced in samples derived from SHR as compared with those from normotensive rats. These results are consistent with the possibility that a reduction in the expression of cortical nicotinic receptors in SHR plays a role in this strain's impaired performance of both spatial and non-spatial learning and memory-related tasks.     

Transplanted bone marrow stromal cells protect neurovascular units and ameliorate brain damage in stroke‐prone spontaneously hypertensive rats

This study was aimed to assess whether bone marrow stromal cells (BMSC) could ameliorate brain damage when transplanted into the brain of stroke‐prone spontaneously hypertensive rats (SHR‐SP). The BMSC or vehicle was stereotactically engrafted into the striatum of male SHR‐SP at 8 weeks of age. Daily loading with 0.5% NaCl‐containing water was started from 9 weeks. MRIs and histological analysis were performed at 11 and 12 weeks, respectively. Wistar‐Kyoto rats were employed as the control. As a result, T2‐weighted images demonstrated neither cerebral infarct nor intracerebral hemorrhage, but identified abnormal dilatation of the lateral ventricles in SHR‐SP. HE staining demonstrated selective neuronal injury in their neocortices. Double fluorescence immunohistochemistry revealed that they had a decreased density of the collagen IV‐positive microvessels and a decreased number of the microvessels with normal integrity between basement membrane and astrocyte end‐feet. BMSC transplantation significantly ameliorated the ventricular dilatation and the breakdown of neurovascular integrity. These findings strongly suggest that long‐lasting hypertension may primarily damage neurovascular integrity and neurons, leading to tissue atrophy and ventricular dilatation prior to the occurrence of cerebral stroke. The BMSC may ameliorate these damaging processes when directly transplanted into the brain, opening the possibility of prophylactic medicine to prevent microvascular and parenchymal‐damaging processes in hypertensive patients at higher risk for cerebral stroke.