Reproducible loss of CA1 neurons following carotid artery occlusion combined with halothane-induced hypotension

CA1 Hippocampal Pyramidal Cells in Rats, Resuscitated From 8 Minutes of Ventricular Fibrillation Cardiac Arrest, Recover After 20 Weeks of Survival: A Retrospective Pilot Study

PURPOSE

The cornu ammonis 1 (CA1) region of the hippocampus is specifically vulnerable to global ischemia. We hypothesized that histopathological outcome in a ventricular fibrillation cardiac arrest (VFCA) rat model depends on the time point of the examination.

METHODS

Male Sprague-Dawley rats were put into VFCA for 8 min, received chest compressions for 2 min, and were defibrillated to achieve return of spontaneous circulation. Animals surviving for 80 min, 14 days and 140 days were compared with controls. Viable neurons were counted in a 500 μm sector of the CA1 region and layer thickness measured. Microglia cells and astrocytes were counted in a 250×300 μm aspect.

RESULTS

Control and 80 min surviving animals had similar numbers of pyramidal neurons in the CA1 region. In 14 days and 140 days survivors neuron numbers and layer thickness were severely diminished compared with controls (P < 0.001). Two-thirds of the 140 days survivors showed significantly more viable neurons than the last third. Microglia was increased in 14 days survivors compared with controls and 140 days survivors, while astrocytes increased in 14 days and 140 days survivors compared with controls (P < 0.001). 140 days survivors had significantly higher astrocyte counts compared with 14 days survivors.

CONCLUSIONS

The amount and type of brain lesions present after global ischemia depend on the survival time. A consistent reduction in pyramidal cells in the CA1 region was present in all animals 14 days after VFCA, but in two-thirds of animals a repopulation of pyramidal cells seems to have taken place after 140 days.

Proliferative and Nonproliferative Lesions of the Rat and Mouse Central and Peripheral Nervous Systems: New and Revised INHAND Terms

Harmonization of diagnostic terminology used during the histopathologic analysis of rodent tissue sections from nonclinical toxicity studies will improve the consistency of data sets produced by laboratories located around the world. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a cooperative enterprise of 4 major societies of toxicologic pathology to develop a globally accepted standard vocabulary for proliferative and nonproliferative lesions in rodents. A prior manuscript (Toxicol Pathol 2012;40[4 Suppl]:87S-157S) defined multiple diagnostic terms for toxicant-induced lesions, common spontaneous and age-related changes, and principal confounding artifacts in the rat and mouse central nervous system (CNS) and peripheral nervous system (PNS). The current article defines 9 new diagnostic terms and updates 2 previous terms for findings in the rodent CNS and PNS, the need for which has become evident in the years since the publication of the initial INHAND nomenclature for findings in rodent neural tissues. The nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Challenges and Improvements of Developing an Ischemia Mouse Model Through Bilateral Common Carotid Artery Occlusion

Brain ischemia is one of the principal causes of death and disability worldwide in which prevention or an effective treatment does not exist. In order to develop successful treatments, an adequate and useful ischemia model is essential. Transient global cerebral ischemia is one of the most interesting pathological conditions in stroke studies because of the observed degeneration of forebrain and delayed neuronal cell death in selective vulnerable regions such as hippocampus. Transient occlusion of both common carotid arteries is the most convenient model to induce tGCI. Although there are effective rat and gerbil models using this method, the induction of a reproducible and reliable injury after global ischemia in mouse has presented higher variations, mainly because of its size and the necessary monitoring skills in order to accomplish homogeneous and reproducible results. Further, great variability among cerebral vasculature and susceptibility of the different strains and sub-strains is observed. In recent years, some modifications have been made to the model in order to normalize the heterogenic effects. Analysis of posterior communicating artery patency has been proposed as an exclusion parameter due to the direct relationship reported with the reduction of cerebral blood flow. Another method used to significantly reduce blood flow is the induction of hypotension with isoflurane. Each protocol produces distinct injury outcomes. Further improvements are needed to attain a general, simpler, reproducible and globally accepted model that allows comparisons between research groups, progress in understanding ischemia and the consequent development of therapeutic alternatives for ischemic injury.

Myricitrin blocks activation of NF-κB and MAPK signaling pathways to protect nigrostriatum neuron in LPS-stimulated mice

Myricitrin, a bioactive and natural flavonoids, is well known for its anti-inflammatory and antioxidant properties. However, the anti-neuroinflammation and possible mechanism has not been fully elucidated. Therefore, the present study was to investigate the possible mechanism of its neuroprotection and anti-neuroinflammation in the nigrostriatum of LPS-stimulated mice. The results showed that myricitrin improved neuron injury and raised the expressions of PSD-95 protein and TH protein in the nigrostriatum of LPS-stimulated mice. In addition, myricitrin decreased the production of pro-inflammatory factors including IL-1β, IL-6 and TNFα, decreased the level of chemokine MCP-1, and suppressed the expressions of COX-2 and iNOS. Meanwhile, myricitrin suppressed HMGB1, TLR4, and MyD88 expression in the nigrostriatum of LPS-stimulated mice. Furthermore, myricitrin inhibited NF-κB and MAPK signaling pathways activated by LPS. In conclusion, our studies suggest that myricitrin blocks activation of protects NF-κB and MAPK signaling pathways to nigrostiatum neuron from injury in LPS-stimulated mice and is beneficial to treatment nigrostriatum inflammation of PD.

The Phenolic Components of Gastrodia elata improve Prognosis in Rats after Cerebral Ischemia/Reperfusion by Enhancing the Endogenous Antioxidant Mechanisms

Pharmacological or spontaneous thrombolysis in ischemic stroke triggers an outbreak of reactive oxygen species and results in neuron death. Nrf2-mediated antioxidation in cells has been proved as a pivotal target for neuroprotection. This research reports that phenolic components of Gastrodia elata Blume (PCGE), a traditional Chinese medicine, can alleviate the pathological lesions in the penumbra and hippocampus by increasing the survival of neurons and astrocytes and improve neurofunction and cognition after reperfusion in a rat model of middle cerebral artery occlusion. LDH assay indicated that pretreatment of cells with PCGE (25 μg/ml) for 24 h significantly reduced H₂O₂-induced cell death in astrocytes and SH-SY5Y cells. Western blot showed that the nucleus accumulation of Nrf2 and the expression of cellular HO-1 and NQO-1, two of Nrf2 downstream proteins, were increased in both cells. BDNF, an Nrf2-dependent neurotrophic factor, was also upregulated by PCGE in astrocytes. These results illustrated that PCGE can reduce the cerebral ischemia/reperfusion injury and improve prognosis by remedying the cell damage within affected tissues. The protective effects of PCGE seem to be via activation of a Nrf2-mediated cellular defense system. Therefore, PCGE could be a therapeutic candidate for ischemic stroke and other oxidative stress associated neurological disorders.

Preconditioning with morphine protects hippocampal CA1 neurons from ischemia-reperfusion injury via activation of the mTOR pathway

The signaling pathway of chronic morphine treatment to prevent neuronal damage following transient cerebral ischemia is not clear. In this study, we examined the role of mammalian target of rapamycin (mTOR) to identify the neuroprotective effects of chronic morphine preconditioning on the hippocampus following ischemia-reperfusion (I/R) injury. Morphine was administered for 5 days, twice a day, before inducing I/R injury. The possible role of mTOR was evaluated by the injection of rapamycin (5 mg/kg body weight, by intraperitoneal injection) before I/R was induced. The passive avoidance test was used to evaluate memory performance. Neuronal density and apoptosis were measured in the CA1 region, 72 h after I/R injury. The expressions of mTOR and phosphorylated mTOR (p-mTOR), as well as superoxide dismutase (SOD) activity were determined 24 h after I/R injury. Chronic morphine treatment attenuated apoptosis and neuronal loss in the hippocampus after I/R injury, which led to improvement in memory (P < 0.05 vs. untreated I/R) and increase in the expression of p-mTOR (P < 0.05 vs. untreated I/R) and SOD activity (P < 0.05 vs. untreated I/R) in the hippocampus. Pretreatment with rapamycin abolished all the above-mentioned protective effects. These results describe novel findings whereby chronic morphine preconditioning in hippocampal CA1 neurons is mediated by the mTOR pathway, and through increased phosphorylation of mTOR can alleviate oxidative stress and apoptosis, and eventually protect the hippocampus from I/R injury.

New GABAergic Neurogenesis in the Hippocampal CA1 Region of a Gerbil Model of Long-Term Survival after Transient Cerebral Ischemic Injury

We investigated the probability of newly generated neurons that could survive and mature in the ischemic hippocampal CA1 region (CA1) of a gerbil model of transient cerebral ischemia. Neuronal death was shown in the stratum pyramidale (SP) from 4 days post-ischemia, and a significant increase in NeuN-positive ((+) ) neurons was found in the SP at 180 days post-ischemia. 5-Bromo-2-deoxyuridine (BrdU)(+) cells were co-stained with NeuN and glutamic decarboxylase 67 (GAD67). Brain-derived neurotrophic factor (BDNF) immunoreactivity and protein level was shown in nonpyramidal cells from 4 days post-ischemia, and the immunoreactivity was strong at 30 days post-ischemia and not significantly changed until 180 days post-ischemia. Furthermore, TrkB immunoreactivity was co-stained with GAD67 when we examined at 180 days post-ischemia. Myelin basic protein (MBP)(+) nerve fibers were reduced at 4 days post-ischemia and maintained until 60 days post-ischemia, and MBP immunoreactivity and levels were significantly increased at 180 days post-ischemia. In the passive avoidance test, cognitive dysfunction was improved at 180 days post-ischemia. These results suggest that the differentiation of neural progenitor cells into new GABAergic neurons may be promoted via BDNF in the ischemic CA1 and that the neurogenesis may partially mediate the recovery of cognitive impairments via increasing myelinated nerve fibers.

Fluoxetine Maintains a State of Heightened Responsiveness to Motor Training Early After Stroke in a Mouse Model

BACKGROUND AND PURPOSE

Data from both humans and animal models suggest that most recovery from motor impairment after stroke occurs in a sensitive period that lasts only weeks and is mediated, in part, by an increased responsiveness to training. Here, we used a mouse model of focal cortical stroke to test 2 hypotheses. First, we investigated whether responsiveness to training decreases over time after stroke. Second, we tested whether fluoxetine, which can influence synaptic plasticity and stroke recovery, can prolong the period over which large training-related gains can be elicited after stroke.

METHODS

Mice were trained to perform a skilled prehension task to an asymptotic level of performance after which they underwent stroke induction in the caudal forelimb area. The mice were then retrained after a 1- or 7-day delay with and without fluoxetine.

RESULTS

Recovery of prehension after a caudal forelimb area stroke was complete if training was initiated 1 day after stroke but incomplete if it was delayed by 7 days. In contrast, if fluoxetine was administered at 24 hours after stroke, then complete recovery of prehension was observed even with the 7-day training delay. Fluoxetine seemed to mediate its beneficial effect by reducing inhibitory interneuron expression in intact premotor cortex rather than through effects on infarct volume or cell death.

CONCLUSIONS

There is a gradient of diminishing responsiveness to motor training over the first week after stroke. Fluoxetine can overcome this gradient and maintain maximal levels of responsiveness to training even 7 days after stroke.

Effect of modified Bo-yang-Hwan-o-Tang, a polyherbal medicine on the hippocampal neuronal damage in a rat model of global ischemia

Background:

Chronic cerebral hypoperfusion has been well-characterized as a common pathological status contributing to vascular dementia (VD). In this study, the neuroprotective effect of modified Bo-yang-Hwan-O Tang (mBHT), a polyherbal medicine for ischemic stroke, was investigated in a rat model for global ischemia.

Materials and Methods:

Global ischemia model was prepared in Sprague-Dawley rats by the permanent occlusion of bilateral common carotid arteries (two-vessel occlusion [2VO])-induced chronic cerebral hypoperfusion. mBHT at doses of 250 and 500 mg/kg was orally administrated for 4 weeks once a day, 24 h after 2VO. Histopathological change of the hippocampal region was observed by hematoxylin and eosin, Nissl, and Fluoro-Jade B staining and immunohistochemistry with anti-glial fibrillary acidic protein and anti-neuronal nuclei antibodies. The expression of Bax, Bcl-2, and caspase-3 was investigated in the hippocampus by Western blot. The nuclear factor-kappa B (NF-κB) expression was also analyzed in hippocampal CA1 region using immunofluorescence staining.

Results:

The administration of mBHT at doses of 250 and 500 mg/kg significantly inhibited chronic cerebral hypoperfusion-induced neuronal damage and astroglial activation in the hippocampal CA1 region in 2VO rats. mBHT increased the NF-κB expression in the CA1 neuronal cells but decreased in activated astrocytes. In addition, mBHT significantly decreased the hippocampal expression of Bax and caspase-3 and increased the Bcl-2 expression in 2VO rats.

Conclusions:

Our data indicate that mBHT has a neuroprotective property in VD induced by chronic cerebral hypoperfusion through inhibiting the hippocampal neuronal damage and astrogliosis.

Age-dependent modifications in vascular adhesion molecules and apoptosis after 48-h reperfusion in a rat global cerebral ischemia model

Stroke is one of the leading causes of death and permanent disability in the elderly. However, most of the experimental studies on stroke are based on young animals, and we hypothesised that age can substantially affect the stroke response. The two-vessel occlusion model of global ischemia by occluding the common carotid arteries for 15 min at 40 mmHg of blood pressure was carried out in 3- and 18-month-old male Sprague-Dawley rats. The adhesion molecules E- and P-selectin, cell adhesion molecules (CAMs), both intercellular (ICAM-1) and vascular (VCAM-1), as well as glial fibrillary acidic protein (GFAP), and cleaved caspase-3 were measured at 48 h after ischemia in the cerebral cortex and hippocampus using Western blot, qPCR and immunofluorescence techniques. Diametric expression of GFAP and a different morphological pattern of caspase-3 labelling, although no changes in the cell number, were observed in the neurons of young and old animals. Expression of E-selectin and CAMs was also modified in an age- and ischemia/reperfusion-dependent manner. The hippocampus and cerebral cortex had similar response patterns for most of the markers studied. Our data suggest that old and young animals present different time-courses of neuroinflammation and apoptosis after ischemic damage. On the other hand, these results suggest that neuroinflammation is dependent on age rather than on the different vulnerability described for the hippocampus and cerebral cortex. These differences should be taken into account in searching for therapeutic targets.

Recombinant human thioredoxin-1 promotes neurogenesis and facilitates cognitive recovery following cerebral ischemia in mice

Cerebral ischemia (CI) can induce loss of hippocampal neurons, causing cognitive dysfunction such as learning and memory deficits. In adult mammals, the hippocampal dentate gyrus contains neural stem cells (NSCs) that continuously generate newborn neurons and integrate into the pre-existing networks throughout life, which may ameliorate cognitive dysfunction following CI. Recent studies have demonstrated that recombinant human thioredoxin-1 (rhTrx-1) could promote proliferation of human adipose tissue-derived mesenchymal stem cells and angiogenesis. To investigate whether rhTrx-1 also regulates hippocampal neurogenesis following CI and its underlying mechanisms, adult mice were subjected to bilateral common carotid arteries occlusion (BCCAO) to induce CI and treated with rhTrx-1 before reperfusion. Mice treated with rhTrx-1 showed shortened escape latencies in Morris water maze by 30 days and improvements in spatial memory demonstrated by probe trial test. Enhanced NSCs proliferation was observed at day 14, indicated by BrdU and Ki67 immunostaining. Doublecortin (DCX)(+) cells were also significantly increased following rhTrx-1 treatment. Despite increases in BrdU(+)/NeuN(+) cells by day 30, the double-labeling to total BrdU(+) ratio was not affected by rhTrx-1 treatment. The promotive effects of rhTrx-1 on NSCs proliferation and differentiation were further confirmed in in vitro assays. Western blot revealed increased ERK1/2 phosphorylation after rhTrx-1 treatment, and the ERK inhibitor U0126 abrogated the effects of rhTrx-1 on NSCs proliferation. These results provide initial evidence that rhTrx-1 effects neurogenesis through the ERK signaling pathway and are beneficial for improving spatial learning and memory in adult mice following global CI.

Aneurysmal subarachnoid hemorrhage models: do they need a fix?

The discovery of tissue plasminogen activator to treat acute stroke is a success story of research on preventing brain injury following transient cerebral ischemia (TGI). That this discovery depended upon development of embolic animal model reiterates that proper stroke modeling is the key to develop new treatments. In contrast to TGI, despite extensive research, prevention or treatment of brain injury following aneurysmal subarachnoid hemorrhage (aSAH) has not been achieved. A lack of adequate aSAH disease model may have contributed to this failure. TGI is an important component of aSAH and shares mechanism of injury with it. We hypothesized that modifying aSAH model using experience acquired from TGI modeling may facilitate development of treatment for aSAH and its complications. This review focuses on similarities and dissimilarities between TGI and aSAH, discusses the existing TGI and aSAH animal models, and presents a modified aSAH model which effectively mimics the disease and has a potential of becoming a better resource for studying the brain injury mechanisms and developing a treatment.

Proliferative and nonproliferative lesions of the rat and mouse central and peripheral nervous systems

Harmonization of diagnostic nomenclature used in the pathology analysis of tissues from rodent toxicity studies will enhance the comparability and consistency of data sets from different laboratories worldwide. The INHAND Project (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) is a joint initiative of four major societies of toxicologic pathology to develop a globally recognized nomenclature for proliferative and nonproliferative lesions in rodents. This article recommends standardized terms for classifying changes observed in tissues of the mouse and rat central (CNS) and peripheral (PNS) nervous systems. Sources of material include academic, government, and industrial histopathology databases from around the world. Covered lesions include frequent, spontaneous, and aging-related changes as well as principal toxicant-induced findings. Common artifacts that might be confused with genuine lesions are also illustrated. The neural nomenclature presented in this document is also available electronically on the Internet at the goRENI website (http://www.goreni.org/).

Expressional changes in cerebrovascular receptors after experimental transient forebrain ischemia

BACKGROUND

Global ischemic stroke is one of the most prominent consequences of cardiac arrest, since the diminished blood flow to the brain results in cell damage and sometimes permanently impaired neurological function. The post-arrest period is often characterised by cerebral hypoperfusion due to subacute hemodynamic disturbances, the pathophysiology of which are poorly understood. In two other types of stroke, focal ischemic stroke and subarachnoid hemorrhage, it has earlier been demonstrated that the expression of certain vasoconstrictor receptors is increased in cerebral arteries several days after the insult, a phenomenon that leads to increased contraction of cerebral arteries, reduced perfusion of the affected area and worsened ischemic damage. Based on these findings, the aim of the present study was to investigate if transient global cerebral ischemia is associated with upregulation of vasoconstrictive endothelin and 5-hydroxytryptamine receptors in cerebral arteries. Experimental transient forebrain ischemia of varying durations was induced in male wistar rats, followed by reperfusion for 48 hours. Neurological function was assessed daily by three different tests and cerebrovascular expression and contractile function of endothelin and 5-hydroxytryptamine receptors were evaluated by wire myography, immunohistochemistry and western blotting.

RESULTS

Transient forebrain ischemia induced neurological deficits as well as functional upregulation of vasoconstrictive ET(B) and 5-HT(1B) receptors in cerebral arteries supplying mid- and forebrain regions. No receptor upregulation was seen in arteries supplying the hindbrain. Immunohistochemical stainings and western blotting demonstrated expressional upregulation of these receptor subtypes in the mid- and forebrain arteries and confirmed that the receptors were located in the smooth muscle layer of the cerebral arteries.

CONCLUSIONS

This study reveals a new pathophysiological aspect of global ischemic stroke, namely expressional upregulation of vasoconstrictor receptors in cerebral arteries two days after the insult, which might contribute to cerebral hypoperfusion and delayed neuronal damage after cardiac arrest.

Expression of Bcl-2 and Bax after hippocampal ischemia in DHA + EPA treated rats

To determine the impact of ω3 fatty acids on post-ischemic expression of pro- and anti-apoptotic proteins in hippocampus, male rats were received 10 or 100 mg/kg [Docosahexaenoic acid (DHA) + Ecosapentaenoic acid (EPA); gavage; 21 days before ischemia to 2-10 days after ischemia]. Global cerebral ischemia reperfusion (IR) was performed using the four-vessel occlusion model; ischemia 8 min and reperfusion 6, 48 h and 10 days. IR increased Bcl-2 and Bax expression after 48 h (p < 0.05 and p < 0.01 vs. sham) and 10 days (only Bax; p < 0.05), without significant difference with DHA + EPA groups after 6 h. But after 48 h expression of Bcl-2 increased (p < 0.05 vs. IR) and Bax decreased (p < 0.05). At day 10 after ischemia expression of Bax in DHA + EPA acid groups was less than IR (p < 0.05) and in 100 mg/kg DHA + EPA group Bcl-2 expression was more than IR (p < 0.05). These data suggested that long-term gavage with DHA + EPA increase hippocampal neurons survival for days after ischemia, revealed by increased Bcl-2 and decreased Bax expressions.

Predifferentiated brain-derived adult human progenitor cells migrate toward ischemia after transplantation to the adult rat brain

BACKGROUND

The adult human brain contains neural stem/progenitor cells (AHNPCs) that can survive transplantation into the adult rat brain, migrate toward a lesion, and display limited neuronal differentiation in vivo.

OBJECTIVE

To investigate the effect of manipulating AHNPCs before grafting by predifferentiation, ie, initiating neuronal differentiation before transplantation, and to determine whether this cell priming would affect their ability to migrate in vivo.

METHODS

AHNPCs were prepared from temporal lobe resections for epilepsy. Seven days after global brain ischemia, predifferentiated AHNPCs (exposed to basic fibroblast growth factor, heparin, and laminin) were transplanted to the left hippocampus. Four and 10 weeks after transplantation, brain sections were analyzed by immunohistochemistry.

RESULTS

Transplanted primed cells expressed committed neuronal markers at a much earlier stage compared with nonprimed AHNPCs and were found colabeled with human markers within the damaged CA1 region 4 weeks after grafting. Furthermore, predifferentiated AHNPCs migrated preferentially into an ischemic lesion, similar to their undifferentiated counterparts. The chemoattractant effect from the expression of stromal cell-derived factor-1α (SDF-1α) in ischemic CA1 on AHNPCs expressing CXC chemokine receptor 4 (CXCR4) may explain this preference in migration in vivo.

CONCLUSION

The plasticity of neural progenitors derived from the adult human brain may be greater than previously assumed in that manipulation before grafting may influence the phenotypes seen in vivo. The SDF-1α-CXCR4 axis is involved in the targeted migration toward an ischemic lesion in the adult rat brain, similar to previous reports on endogenous progenitors in rats and grafted fetal human neural progenitors.

Prevention of cerebral ischemia-induced memory deficits by inhibition of phosphodiesterase-4 in rats

Inhibition of phosphodiesterase-4 (PDE4) by rolipram, a prototypical PDE4 inhibitor, reverses memory impairment produced pharmacologically or genetically. Comparably, much less is known about the effect of rolipram on cerebral ischemia-induced memory deficits. The objective of this study was to determine the effects of rolipram on ischemia-induced memory deficit, neuronal damage, and alteration of PDE4 activity in the hippocampus. Memory was examined using Morris water-maze and step-through passive avoidance tests in rats subjected to global cerebral ischemia with or without repeated treatment with rolipram (0.3 or 1 mg/kg, i.p.); neuronal damage in the hippocampus and PDE4 activity in hippocampal tissues were determined using Nissl staining and HPLC, respectively. In the water-maze test, cerebral ischemia significantly increased the escape latency to reach the platform during acquisition training and decreased the exploration time in the target quadrant in the probe trial test; these were blocked by rolipram in a dose-dependent manner. Rolipram also reduced the distracted platform searches induced by cerebral ischemia. In the passive avoidance test, ischemia decreased the 24-h latency to the dark compartment, which was also blocked by rolipram treatment. In addition, Nissl staining revealed ischemia-induced neuron loss in hippocampal CA1; this was blocked by rolipram. Further, cerebral ischemia led to increases in activity of PDE, primarily PDE4, in the hippocampus, which also was antagonized by rolipram. These results suggest that rolipram prevents cerebral ischemia-induced memory deficits via inhibition of increased PDE4 activity and attenuation of hippocampal, neuronal damages induced by ischemia. PDE4 may be a target for treatment of cognitive disorders associated with cerebral ischemia.

Long-term survival of human neural stem cells in the ischemic rat brain upon transient immunosuppression

Understanding the physiology of human neural stem cells (hNSCs) in the context of cell therapy for neurodegenerative disorders is of paramount importance, yet large-scale studies are hampered by the slow-expansion rate of these cells. To overcome this issue, we previously established immortal, non-transformed, telencephalic-diencephalic hNSCs (IhNSCs) from the fetal brain. Here, we investigated the fate of these IhNSC's immediate progeny (i.e. neural progenitors; IhNSC-Ps) upon unilateral implantation into the corpus callosum or the hippocampal fissure of adult rat brain, 3 days after global ischemic injury. One month after grafting, approximately one fifth of the IhNSC-Ps had survived and migrated through the corpus callosum, into the cortex or throughout the dentate gyrus of the hippocampus. By the fourth month, they had reached the ipsilateral subventricular zone, CA1-3 hippocampal layers and the controlateral hemisphere. Notably, these results could be accomplished using transient immunosuppression, i.e administering cyclosporine for 15 days following the ischemic event. Furthermore, a concomitant reduction of reactive microglia (Iba1+ cells) and of glial, GFAP+ cells was also observed in the ipsilateral hemisphere as compared to the controlateral one. IhNSC-Ps were not tumorigenic and, upon in vivo engraftment, underwent differentiation into GFAP+ astrocytes, and β-tubulinIII+ or MAP2+ neurons, which displayed GABAergic and GLUTAmatergic markers. Electron microscopy analysis pointed to the formation of mature synaptic contacts between host and donor-derived neurons, showing the full maturation of the IhNSC-P-derived neurons and their likely functional integration into the host tissue. Thus, IhNSC-Ps possess long-term survival and engraftment capacity upon transplantation into the globally injured ischemic brain, into which they can integrate and mature into neurons, even under mild, transient immunosuppressive conditions. Most notably, transplanted IhNSC-P can significantly dampen the inflammatory response in the lesioned host brain. This work further supports hNSCs as a reliable and safe source of cells for transplantation therapy in neurodegenerative disorders.

Triggered by asphyxia neurogenesis seems not to be an endogenous repair mechanism, gliogenesis more like it

We analyzed the long-term consequences of asphyxial cardiac arrest for hippocampal cell proliferation in rats to evaluate if the ischaemia-induced degenerated CA1 region may be repopulated by endogenous (stem) cells. Studies were performed in an asphyxial cardiac arrest model with 5 minutes of asphyxiation and three different survival times: 7, 21, and 90 days. Sham-operated non-asphyxiated rats served as control. Cell proliferation was studied by labeling dividing cells with 5-bromo-2'-deoxy-uridine (BrdU). The neurodegenerative/regenerative pattern at single cell levels was monitored by immunohistochemistry. Alterations of gene expression were analyzed by real-time quantitative RT-PCR. Analysis of BrdU-incorporation demonstrated an increase at 7, 21 as well as 90 days after global ischaemia in the hippocampal CA1 pyramidal cell layer. Similar results were found in the dentate gyrus. Differentiation of BrdU-positive cells, investigated by cell phenotype-specific double fluorescent labeling, showed increased neurogenesis only in the dentate gyrus of animals surviving the cardiac arrest for 7 days. The majority of newcomers, especially in the damaged CA1 region, consisted of glial cells. Moreover, asphyxia seemed to be able to induce the migration of microglia and astroglia from adjacent areas into the damaged area and/or the activation of resident cells. In addition, we show microglia proliferation/activation even 90 days after cardiac arrest. This morphological finding was confirmed by PCR analysis. The results indicate that asphyxia triggers cell proliferation in general and gliogenesis in particular - a possible pro-reparative event. Furthermore, from the finding of microglia proliferation up to 90 days after insult we conclude that delayed cell death processes take place which should be considered for further therapy strategies.

Inhibition of nuclear factor-κB by 6-O-acetyl shanzhiside methyl ester protects brain against injury in a rat model of ischemia and reperfusion

BACKGROUND

Recent studies have demonstrated an inflammatory response associated with the pathophysiology of cerebral ischemia. The beneficial effects of anti-inflammatory drugs in cerebral ischemia have been documented. When screening natural compounds for drug candidates in this category, we isolated 6-O-acetyl shanzhiside methyl ester (ND02), an iridoid glucoside compound, from the leaves of Lamiophlomis rotata (Benth.) Kudo. The objectives of this study were to determine the effects of ND02 on a cultured neuronal cell line, SH-SY5Y, in vitro, and on experimental ischemic stroke in vivo.

METHODS

For TNF-α-stimulated SH-SY5Y cell line experiments in vitro, SH-SY5Y cells were pre-incubated with ND02 (20 μM or 40 μM) for 30 min and then incubated with TNF-α (20 ng/ml) for 15 min. For in vivo experiments, rats were subjected to middle cerebral artery occlusion (MCAO) for 1 h followed by reperfusion for 23 h.

RESULTS

ND02 treatment of SH-SY5Y cell lines blocked TNF-α-induced nuclear factor-κB (NF-κB) and IκB-α phosphorylation and increased Akt phosphorylation. LY294002 blocked TNF-α-induced phosphorylation of Akt and reduced the phosphorylation of both IκB-α and NF-κB. At doses higher than 10 mg/kg, ND02 had a significant neuroprotective effect in rats with cerebral ischemia and reperfusion (I/R). ND02 (25 mg/kg) demonstrated significant neuroprotective activity even after delayed administration 1 h, 3 h and 5 h after I/R. ND02, 25 mg/kg, attenuated histopathological damage, decreased cerebral Evans blue extravasation, inhibited NF-κB activation, and enhanced Akt phosphorylation.

CONCLUSION

These data show that ND02 protects brain against I/R injury with a favorable therapeutic time-window by alleviating cerebral I/R injury and attenuating blood-brain barrier (BBB) breakdown, and that these protective effects may be due to blocking of neuronal inflammatory cascades through an Akt-dependent NF-κB signaling pathway.

Age-dependent modifications in the mRNA levels of the rat excitatory amino acid transporters (EAATs) at 48hour reperfusion following global ischemia

This study reports the mRNA levels of some excitatory amino acid transporters (EAATs) in response to ischemia-reperfusion (I/R) in rat hippocampus and cerebral cortex. The study was performed in 3-month-old and 18-month-old animals to analyze the possible role of age in the I/R response of these transporters. The I/R resulted in a reduced transcription of both the neuronal EAAC1 (excitatory amino acid carrier-1) and the neuronal and glial GLT-1 (glial glutamate transporter 1), while the glial GLAST1a (l-glutamate/l-aspartate transporter 1a) transcription increased following I/R. The changes observed were more striking in 3-month-old animals than in 18-month-old animals. We hypothesize that increases in the GLAST1a mRNA levels following I/R insult can be explained by increases in glial cells, while the GLT-1 response to I/R mirrors neuronal changes. GLAST1a transcription increases in 3-month-old animals support the hypothesis that this transporter would be the main mechanism for extracellular glutamate clearance after I/R. Decreases in EAAC1 and GLT-1 mRNA levels would represent either neuronal changes due to the delayed neuronal death or a putative protective down-regulation of these transporters to decrease the amount of glutamate inside the neurons, which would decrease their glutamate release. This study also reports how the treatment with the anti-inflammatory agent meloxicam attenuates the transcriptional response to I/R in 3-month-old rats and decreases the survival of the I/R-injured animals.

AMPA receptor downregulation induced by ischaemia/reperfusion is attenuated by age and blocked by meloxicam

AIM

Stroke prevalence increases with age, while alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor (AMPAR) and inflammation have been related to ischaemia-induced damage. This study shows how age and treatment with an anti-inflammatory agent (meloxicam) modify the levels of AMPAR subunits GluR1 and GluR2, as well as the mRNA levels of the GluR2-editing enzyme, ADAR2, in a global brain ischaemia/reperfusion (I/R) model.

METHODS

Two days after global ischaemia CA1, CA3, dentate gyrus and cerebral cortex were obtained from sham-operated and I/R-injured 3- and 18-month-old Sprague-Dawley rats. Real time polymerase chain reaction, Western blotting and immunohistochemical assays were performed. Meloxicam treatment was assayed on young animals.

RESULTS

Data showed that age attenuates the downregulation induced by I/R in the AMPAR subunits GluR1 and GluR2 and modifies the GluR1/GluR2 mRNA level ratio in a structure-dependent way. The study of the ADAR2 mRNA levels showed more downregulation in older animals than young ones. Meloxicam treatment prevented the transcriptional arrest induced by I/R.

CONCLUSION

Our data suggest that changes in the AMPAR isoforms could be associated with ageing in the different structures studied. Although GluR2 editing seems to be involved in age-dependent vulnerability to ischaemia supporting the 'GluR2 hypothesis', this alone does not explain the differential vulnerability in the different brain regions. Finally, inflammation could play a role in protection from I/R-induced injury.

Isolation of human multipotent neural progenitors from adult filum terminale

Stem cells have been isolated from several CNS regions, including the spinal cord. However, the terminal end of the spinal cord, filum terminale, has been referred to as a fibrovascular tag without neurogenic potential and of no clinical significance. Recently, we were fortunate to acquire some samples of this tissue. We show for the first time that progenitor cells exhibiting the hallmarks of stem cells can be isolated from adult human filum terminale (FTNPs). More specifically, FTNPs self-renew and proliferate to form neurospheres, and exhibit tripotent differentiation into neurons, astrocytes, and oligodendrocytes. Equally important, FTNPs develop the electrophysiological profile of neurons and glia. Whole-cell patch-clamp recordings show beta-III-tubulin(+) neurons exhibiting overshooting action potentials, displaying both the fast inactivating TTX-sensitive sodium current as well as 4-AP and TEA sensitive potassium currents. To assess potency in vivo, FTNPs were transplanted into the posterior periventricular region of control or ischemic rat brains. Despite a vigorous immune response against the xenograft, FTNPs survived and were found not only in the graft area but had also migrated to the lesioned CA1 region. Notwithstanding the immune response, FTNPs differentiated into astrocytes, but no neuronal differentiation was observed in the transplant milieu tested. However, neuronal differentiation in vivo cannot be ruled out and assessment of the conditions necessary to promote neurogenesis in vivo requires more research. Significantly, no tumor formation or aberrant cell morphology was seen in or adjacent to the graft area. Thus, filum terminale provides a novel source of adult human neural progenitor cells that develop into functional neurons with possible clinical applications.

TTC, fluoro-Jade B and NeuN staining confirm evolving phases of infarction induced by middle cerebral artery occlusion

Considerable debate exists in the literature on how best to measure infarct damage and at what point after middle cerebral artery occlusion (MCAO) infarct is histologically complete. As many researchers are focusing on more chronic endpoints in neuroprotection studies it is important to evaluate histological damage at later time points to ensure that standard methods of tissue injury measurement are accurate. To compare tissue viability at both acute and sub-acute time points, we used 2,3,5-triphenyltetrazolium chloride (TTC), Fluoro-Jade B, and NeuN staining to examine the evolving phases of infarction induced by a 90-min MCAO in mice. Stroke outcomes were examined at 1.5h, 6h, 12h, 24h, 3d, and 7d after MCAO. There was a time-dependent increase in infarct volume from 1.5h to 24h in the cortex, followed by a plateau from 24h to 7d after stroke. Striatal infarcts were complete by 12h. Fluoro-Jade B staining peaked at 24h and was minimal by 7d. Our results indicated that histological damage as measured by TTC and Fluoro-Jade B reaches its peak by 24h after stroke in a reperfusion model of MCAO in mice. TTC staining can be accurately performed as late as 7d after stroke. Neurological deficits do not correlate with the structural lesion but rather transient impairment of function. As the infarct is complete by 24h and even earlier in the striatum, even the most efficacious neuroprotective therapies are unlikely to show any efficacy if given after this point.

Transplantation of stem cells from the adult human brain to the adult rat brain

OBJECTIVE

To investigate the migration, proliferation, and differentiation of stem cells and neural progenitor cells (NPCs) from the adult human brain after transplantation into adult rodent brains.

METHODS

Adult human NPCs were obtained from temporal lobe specimens removed because of medical intractable epilepsy. The cells were transplanted into the posterior periventricular region above the hippocampus in the brains of either healthy adult rats (control) or rats with selective injury of the hippocampal CA1 region (global ischemia).

RESULTS

In the control animals, grafted cells were mainly distributed from the site of transplantation toward the midline along white matter tracts. The density of transplanted cells elsewhere, including the hippocampus, was low and apparently random. In animals with CA1 damage, NPCs showed targeted migration into the injured area. Cell survival at 10 weeks was 4.7 +/- 0.3% (control, n = 3) and 3.7 +/- 1.1% (ischemia, n = 3); at 16 weeks, cell survival was 3.4 +/- 0.6% (control, n = 2) and 7.2 +/- 1.5% (ischemia, n = 2), i.e., comparable to what has been observed earlier when transplanting embryonic tissue into the human brain or progenitor cells between inbred rats. The number of dividing cells decreased with time. Sixteen weeks after transplantation, 4 +/- 1% (n = 4) of the cells showed proliferative activity. We did not observe signs of tumor formation or aberrant cell morphology. Neuronal differentiation was much slower than what has been observed earlier in vitro or after transplantation to the developing nervous system, and 16 weeks after transplantation many surviving cells were still in maturation.

CONCLUSION

The present study shows that adult human NPCs survive, show targeted migration, proliferate, and differentiate after grafting into the adult rat brain.

Quetiapine attenuates spatial memory impairment and hippocampal neurodegeneration induced by bilateral common carotid artery occlusion in mice

Quetiapine, a new atypical antipsychotic drug, has beneficial effects on cognitive impairment and neuropathological changes in treating chronic neurodegenerative diseases. Our previous studies have demonstrated that quetiapine may have neuroprotective properties. In the present study, we investigated the effects of a 2-week pre-administration of quetiapine (10 mg/kg/day, i.p.) on spatial memory impairment and hippocampal neurodegeneration induced by 60-minute bilateral common carotid artery occlusion (CCAO). Following a 7-day recovery phase from CCAO, the spatial memory of the mice was tested using a modified water maze test. After the behavioural test, the mice were sacrificed and brain sections were stained with NeuN (a neuron-specific soluble nuclear antigen), cresyl violet (Nissl), and Fluoro-Jade B. CCAO significantly induced spatial memory impairment and caused neurodegeneration in the hilus of hippocampus, while quetiapine significantly attenuated these changes. This is the first study showing that quetiapine significantly attenuates CCAO-induced spatial memory impairment and this improvement parallels the alleviative effects of quetiapine on CCAO-induced neurodegeneration in the hilus of hippocampus. The results suggest that quetiapine may have defending effects on the impairments induced by cerebral ischemia, which enhances our understanding about the mechanisms of quetiapine.

Fluoro-Jade B staining following zymosan microinjection into the spinal cord white matter

1. The fluorescein derivate Fluoro-Jade B (FJB), which primarily labels dead or dying neurons, was used to study the acute focal inflammation in the spinal cord white matter. Inflammation was induced by microinjection of the yeast particulate zymosan to evaluate the biological effects of intraspinal macrophages activation without the confounding effects of physical trauma. 2. A single bolus of zymosan (Sigma, 75 nL) was stereotaxically injected at the thoracic level into the lateral white matter of rat spinal cord. A standard Fluoro-Jade B staining protocol was applied to spinal cord sections at 6, 12, 24 h and 2, 4 days postinjection. Neutral Red, NADPH-diaphorase, Iba1-IR, and DAPI staining protocols accomplished examination of the cells participating in the acute inflammatory response. 3. Zymosan caused formation of clearly delineated inflammation lesions localized in the lateral white matter of the spinal cord. Fluoro-Jade B stained cells in the area of inflammation were not observed at 12 h postinjection while mild FJB staining appeared at 24 h and intense staining was observed at 2 and 4 days postinjection. 4. This study shows that the acute response to zymosan-induced inflammation in the rat spinal cord white matter causes a gradual appearance of phagocytic microglia/macrophages and delayed FJB staining of the inflammatory cells. 5. FJB, a reliable marker of dying neurons, is a more universal agent than formerly believed. One possible explanation for the gradual appearance of FJB-stained cells in the area of inflammation is that specific time is required for sufficient levels of proteins and/or myelin debris of axonal origin to appear in the cytoplasm of phagocytic microglia/macrophages.

Reappearance of hippocampal CA1 neurons after ischemia is associated with recovery of learning and memory

The pyramidal neurons of the hippocampal CA1 region are essential for cognitive functions such as spatial learning and memory, and are selectively destroyed after cerebral ischemia. To analyze whether degenerated CA1 neurons are replaced by new neurons and whether such regeneration is associated with amelioration in learning and memory deficits, we have used a rat global ischemia model that provides an almost complete disappearance (to approximately 3% of control) of CA1 neurons associated with a robust impairment in spatial learning and memory at two weeks after ischemia. We found that transient cerebral ischemia can evoke a massive formation of new neurons in the CA1 region, reaching approximately 40% of the original number of neurons at 90 days after ischemia (DAI). Co-localization of the mature neuronal marker neuronal nuclei with 5-bromo-2'-deoxyuridine in CA1 confirmed that neurogenesis indeed had occurred after the ischemic insult. Furthermore, we found increased numbers of cells expressing the immature neuron marker polysialic acid neuronal cell adhesion molecule in the adjacent lateral periventricular region, suggesting that the newly formed neurons derive from this region. The reappearance of CA1 neurons was associated with a recovery of ischemia-induced impairments in spatial learning and memory at 90 DAI, suggesting that the newly formed CA1 neurons restore hippocampal CA1 function. In conclusion, these results show that the brain has an endogenous capacity to form new nerve cells after injury, which correlates with a restoration of cognitive functions of the brain.

Experimental subarachnoid hemorrhage induces changes in the levels of hippocampal NMDA receptor subunit mRNA

NMDA receptors may play a crucial role in nerve cell death following subarachnoid hemorrhage (SAH). Changes in NMDA receptor-mediated transmission appear before neuronal death in rodent models of transient ischemia, and NMDA receptor function is known to be dependent on subunit composition. Here, we have investigated whether mRNA expression of the NMDA receptor subunits is altered in the hippocampal formation 3-5 h following experimental SAH, and correlated these early alterations to subsequent delayed cell death. SAH was induced by intraluminal perforation of the internal carotid artery intracranially, and cerebral blood flow (CBF) was bilaterally monitored by laser-Doppler flowmetry. Early changes in NMDA receptor subunit mRNA and early nerve cell death were analyzed at 3-5 h after SAH, and delayed nerve cell death was analyzed at 2-7 days after SAH. Duration of ipsilateral CBF reduction below 30% of baseline (CBF30) was predictive of ipsilateral delayed nerve cell death in the CA1 2-7 days after SAH. At CBF30 > 9 min, we found downregulation of mRNA for NR2A, NR2B, and NR3B at 3-5 h after SAH, whereas the levels of NR1 mRNA were unaffected. The downregulation of NR2A and NR2B mRNA may result in a reduced NMDA receptor function. Such reduction may be sufficient to provide neuroprotection in the dentate gyrus, where no cell death appears, but insufficient to rescue neurons in the hippocampus proper following SAH.