Delayed Neuronal Death Research Articles

Na+/HCO3- Co-transporters Inhibitor S0859 Attenuates Global Cerebral Ischemia-reperfusion Injury of the CA1 Neurons in the Gerbil's Hippocampus.

Metabolic acidosis plays a key role in transient global cerebral ischemiareperfusion (I/R) induced delayed neuronal death (DND) of the hippocampal CA1 region of gerbils. Na+ coupled HCO3 - transporters (NBCs) mediated Na+/HCO3- - co-transportation can be activated by the pH gradient of intracellular and extracellular environments induced by acidosis. However, whether NBCs are activated and involved in I/R-induced neuronal injury is unknown. In this work, we studied neuronal apoptosis, astrocyte activation, and hippocampusdependent memory task using a well-established transient global cerebral I/R model of gerbils and investigated whether the specific NBCs inhibitor S0859 could reverse this injury. To explore the role of S0859 in I/R-induced DND, we established a transient global cerebral I/R model of Mongolian gerbils and studied neuronal apoptosis by using Nissl stain and TUNEL assay. The excitability and NBCs current were analyzed by whole-cell patch-clamp, while the cognitive function was evaluated by Barnes maze. We found that I/R increased the NBCs current, inhibited the excitability of CA1 neurons, and led to apoptosis in CA1 neurons. Selective NBCs inhibitor S0859 protected CA1 neurons from I/R induced neuronal cell death, astrocyte accumulation, and spatial memory impairment. These findings indicate that NBCs mediate transient global cerebral I/R induced DND of CA1 neurons, and NBCs inhibitors could be a promising target to protect neuronal functions after I/R.

Activation of p38 MAPK participates in the sulbactam-induced cerebral ischemic tolerance mediated by glial glutamate transporter-1 upregulation in rats

Our previous studies have shown that sulbactam can play a neuroprotection role in hippocampal neurons by upregulating the expression and function of glial glutamate transporter-1 (GLT-1) during ischemic insult. Here, using rat global cerebral ischemia model, we studied in vivo the role of p38 mitogen-activated protein kinases (MAPK) in the sulbactam-induced GLT-1 upregulation and neuroprotection against ischemia. The hippocampal CA1 field was selected as observing target. The expressions of phosphorylated-p38 MAPK and GLT-1 were assayed with western blot analysis and immunohistochemistry. The condition of delayed neuronal death (DND) was assayed with neuropathological evaluation under thionin staining. It was shown that administration of sulbactam protected CA1 hippocampal neurons against ischemic insult accompanied with significantly upregulation in the expressions of phosphorylated-p38 MAPK and GLT-1. The time course analysis showed that sulbactam activated p38 MAPK before the GLT-1 upregulation in either normal or global cerebral ischemic rats. Furthermore, inhibiting p38 MAPK activation by SB203580 blocked the GLT-1 upregulation and neuroprotection induced by sulbactam. The above results suggested that p38 MAPK, at least partly, participated in the sulbactam-induced brain tolerance to ischemia mediated by GLT-1 upregulation in rats.

Nitric Oxide Participates in the Brain Ischemic Tolerance Induced by Intermittent Hypobaric Hypoxia in the Hippocampal CA1 Subfield in Rats.

Previous studies have shown that intermittent hypobaric hypoxia (IH) preconditioning protected neurons survival from brain ischemia. However, the mechanism remains to be elucidated. The present study explored the role of nitric oxide (NO) in the process by measuring the expression of NO synthase (NOS) and NO levels. Male Wistar rats (100) were randomly assigned into four groups: sham group, IH + sham group, ischemia group and IH + ischemia group. Rats for IH preconditioning were exposed to hypobaric hypoxia mimicking 5000m high-altitude (PB = 404mmHg, PO2 = 84mmHg) 6h/day, once daily for 28 days. Global brain ischemia was established by four-vessel occlusion that has been created by Pulsinelli. Rats were sacrificed at 7th day after the ischemia for neuropathological evaluation by thionin stain. In addition, the expression of neuronal NOS (nNOS), inducible NOS (iNOS), and NO content in the hippocampal CA1 subfield were measured at 2nd day and 7th day after the ischemia. Results revealed that global brain ischemia engendered delayed neuronal death (DND), both nNOS and iNOS expression up-regulated, and NO content increased in the hippocampal CA1 subfield. IH preconditioning reduced neuronal injury induced by the ischemia, and prevented the up-regulation of NOS expression and NO production. In addition, L-NAME + ischemia group was designed to detect whether depressing NO production could alleviate the DND. Pre-administration of L-NAME alleviated DND induced by the ischemia. These results suggest that IH preconditioning plays a protective role by inhibiting the over expression of NOS and NO content after brain ischemia.

Upregulating the Expression of Survivin‐HBXIP Complex Contributes to the Protective Role of IMM‐H004 in Transient Global Cerebral Ischemia/Reperfusion

IMM-H004, a 3-piperazinylcoumarin compound derived from coumarin, has been proved effective against CA1 cell loss and spatial learning impairments resulting from transient global ischemia/reperfusion (TGCI/R), while the mechanism is still largely unknown. Here, we confirmed that treatment of rats with IMM-H004 immediately after TGCI/R ameliorated delayed neuronal death (DND) in the CA1 of hippocampus and cortex. Further study suggested that IMM-H004 contributed to the expression of antiapoptotic protein survivin through the activation of PI3K-dependent protein kinase B (PKB/Akt), which led to the phosphorylation of forkhead box O1 (FoxO1), then relieved the inhibiting effect on survivin promoter. Additionally, IMM-H004 also enhanced the expression of hepatitis B X-interacting protein (HBXIP), which formed a complex with survivin to prevent the activation of caspase death cascade, thereby halting apoptotic cell death. Finally, we injected a HBXIP siRNA into hippocampus and performed microelectroporation before ischemia/reperfusion, which abolished the protective effect of IMM-H004. Further study revealed that HBXIP maintained the high expression of Akt and survivin. Collectively, our findings demonstrated that DND after TGCI/R was alleviated by IMM-H004 through promoting the formation of survivin-HBXIP complex, which further emphasized the importance of endogenous protein involved in self-repair after stroke. Support or Funding Information This work was supported by the National Natural Science Foundation of China (81730096, U1402221), CAMS Innovation Fund for Medical Sciences (CIFMS) ( 2016-I2M-1-004), the Scientific Research Foundation of the Higher Education Institutions of Hunan Province (15K091), Beijing Key Laboratory of New Drug Mechanisms and Pharmacological Evaluation Study (BZ0150), PUMC Graduate Education and Teaching Reform Project (10023201600801). Schematic diagram of the neural protective role of IMMH004 after TGCI/R This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Effect of Adipose-Derived Mesenchymal Stem Cell Administration and Mild Hypothermia Induction on Delayed Neuronal Death After Transient Global Cerebral Ischemia

Global cerebral ischemia is a cause of poor prognosis after resuscitation from cardiac arrest. Various attempts have been made to minimize global cerebral ischemia but none been more effective than mild hypothermia induction. A few studies have shown the effect of mesenchymal stem cells on global cerebral ischemia, but no studies have compared this effect with mild hypothermia or assessed any possible interaction. We aimed to show the effect of mesenchymal stem cells on delayed neuronal death after global cerebral ischemia and to compare this effect with mild hypothermia. Experimental study. Animal research laboratory. Adult male Sprague-Dawley rats weighing 250-300 g. Rats were subjected to 7 minutes of transient global cerebral ischemia and randomized into four groups: control, mild hypothermia, injection of human adipose-derived mesenchymal stem cells, and combined application of mild hypothermia and mesenchymal stem cells, along with four sham groups treated identically. Rats were euthanized 7 days after global cerebral ischemia. Degree of neuronal death in hippocampus was significantly higher in control than in other groups. The number of activated microglia was higher in control group than in other groups and was higher in mild hypothermia than shams, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells. Degree of blood-brain barrier disruption and the count of infiltrated neutrophils were significantly higher in control than in other groups. Degree of oxidative injury was significantly higher in control than other groups. It was higher in mild hypothermia than sham groups, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells and was higher in mesenchymal stem cells group than sham groups. Significantly, worse functional results were found in control than in other groups. Administration of mesenchymal stem cells after transient global cerebral ischemia has a prominent protective effect on delayed neuron death, even compared with mild hypothermia.

Regulation of mRNA following brain ischemia and reperfusion.

There is growing appreciation that mRNA regulation plays important roles in disease and injury. mRNA regulation and ribonomics occur in brain ischemia and reperfusion (I/R) following stroke and cardiac arrest and resuscitation. It was recognized over 40 years ago that translation arrest (TA) accompanies brain I/R and is now recognized as part of the intrinsic stress responses triggered in neurons. However, neuron death correlates to a prolonged TA in cells fated to undergo delayed neuronal death (DND). Dysfunction of mRNA regulatory processes in cells fated to DND prevents them from translating stress-induced mRNAs such as heat shock proteins. The morphological and biochemical studies of mRNA regulation in postischemic neurons are discussed in the context of the large variety of molecular damage induced by ischemic injury. Open issues and areas of future investigation are highlighted. A sober look at the molecular complexity of ischemia-induced neuronal injury suggests that a network framework will assist in making sense of this complexity. The ribonomic network sits between the gene network and the various protein and metabolic networks. Thus, targeting the ribonomic network may prove more effective at neuroprotection than targeting specific molecular pathways, for which all efforts have failed to the present time to stop DND in stroke and after cardiac arrest. WIREs RNA 2017, 8:e1415. doi: 10.1002/wrna.1415 For further resources related to this article, please visit the WIREs website.

Stress Granule Induction after Brain Ischemia Is Independent of Eukaryotic Translation Initiation Factor (eIF) 2α Phosphorylation and Is Correlated with a Decrease in eIF4B and eIF4E Proteins

Stress granules (SGs) are cytoplasmic ribonucleoprotein aggregates that are directly connected with the translation initiation arrest response to cellular stresses. Translation inhibition (TI) is observed in transient brain ischemia, a condition that induces persistent TI even after reperfusion, i.e. when blood flow is restored, and causes delayed neuronal death (DND) in selective vulnerable regions. We previously described a connection between TI and DND in the hippocampal cornu ammonis 1 (CA1) in an animal model of transient brain ischemia. To link the formation of SGs to TI and DND after brain ischemia, we investigated SG induction in brain regions with differential vulnerabilities to ischemia-reperfusion (IR) in this animal model. SG formation is triggered by both eukaryotic translation initiation factor (eIF) 2α phosphorylation and eIF4F complex dysfunction. We analyzed SGs by immunofluorescence colocalization of granule-associated protein T-cell internal antigen-1 with eIF3b, eIF4E, and ribosomal protein S6 and studied eIF2 and eIF4F complex. The results showed that IR stress induced SG formation in the CA1 region after 3-day reperfusion, consistent with TI and DND in CA1. SGs were formed independently of eIF2α phosphorylation, and their appearance was correlated with a decrease in the levels of eIF4F compounds, the cap-binding protein eIF4E, and eIF4B, suggesting that remodeling of the eIF4F complex was required for SG formation. Finally, pharmacological protection of CA1 ischemic neurons with cycloheximide decreased the formation of SGs and restored eIF4E and eIF4B levels in CA1. These findings link changes in eIF4B and eIF4E to SG induction in regions vulnerable to death after IR.

Upregulating the Expression of Survivin-HBXIP Complex Contributes to the Protective Role of IMM-H004 in Transient Global Cerebral Ischemia/Reperfusion.

IMM-H004, a 3-piperazinylcoumarin compound derived from coumarin, has been proved effective against CA1 cell loss and spatial learning impairments resulting from transient global ischemia/reperfusion (TGCI/R), while the mechanism is still largely unknown. Here, we confirmed that treatment of rats with IMM-H004 immediately after TGCI/R ameliorated delayed neuronal death (DND) in the CA1 of hippocampus and cortex. Further study suggested that IMM-H004 contributed to the expression of antiapoptotic protein survivin through the activation of PI3K-dependent protein kinase B (PKB/Akt), which led to the phosphorylation of forkhead box O1 (FoxO1), then relieved the inhibiting effect on survivin promoter. Additionally, IMM-H004 also enhanced the expression of hepatitis B X-interacting protein (HBXIP), which formed a complex with survivin to prevent the activation of caspase death cascade, thereby halting apoptotic cell death. Finally, we injected a HBXIP siRNA into hippocampus and performed microelectroporation before ischemia/reperfusion, which abolished the protective effect of IMM-H004. Further study revealed that HBXIP maintained the high expression of Akt and survivin. Collectively, our findings demonstrated that DND after TGCI/R was alleviated by IMM-H004 through promoting the formation of survivin-HBXIP complex, which further emphasized the importance of endogenous protein involved in self-repair after stroke.

Astrocyte GGTI-mediated Rac1 prenylation upregulates NF-κB expression and promotes neuronal apoptosis following hypoxia/ischemia

Stroke is the fifth leading cause of death for Americans, and about 87% of all strokes are ischemic strokes. Astrogliosis plays a crucial role in the pathophysiology of delayed neuronal death (DND) following ischemic stroke. Here we reported that astrocyte geranylgeranyltransferase I (GGTI)-mediated Rac1 activation up-regulated NF-κB expression and promoted the neuronal apoptosis after oxygen–glucose deprivation followed by oxygen–glucose regeneration (OGD/R). We found that GGTIβ (a specific subunit of GGTI) and NF-κB-p65 levels as determined by Western blot and/or immunofluorescent analysis were significantly up-regulated in the reactive astrocytes both in rat transient middle cerebral artery occlusion (tMCAO) and in cell OGD/R models. The increased expression of GGTIβ and p65 was associated with the DND in the ischemic brain. Inhibiting astrocyte GGTI activity by its specific inhibitor GGTi-2147 treatment reduced the activity of Rac1 (one of substrates for GGTI), down-regulated the expression of p65, and ameliorated the OGD/R-induced neuronal apoptosis. Astrocytes transfected with wild type Rac1, but not the unprenylated Rac1, up-regulated the p65 protein levels and promoted the co-cultured neuronal apoptosis. Furthermore, over-expression of unprenylated Rac1 in astrocytes significantly decreased the neuronal apoptosis. In addition, over-expression of NF-κB-p65 in astrocytes significantly increased the co-cultured neuronal apoptosis under OGD/R condition. Our findings suggest that astrocyte GGTI-mediated Rac1 activation contributed to the DND and that GGTI-Rac1-NF-κB signaling may be a potential target for the therapy of ischemic stroke.

Changes in the Expression of Antiapoptotic Protein Bcl-2 in the Rat Neocortex and Hippocampus in Different Hypobaric Hypoxia Regimes

Studies during the 1980s demonstrated delayed neuron death in hippocampal fi eld CA1 several days after ischemia [7]. Subsequent studies also produced similar fi ndings in other parts of the brain with high sensitivity to hypoxia/ ischemia – the neocortex, striatum, and cerebellum. This type of neuron damage was shown to be linked with the mechanism of induction of apoptosis (programmed cell death), which involve genes and killer proteins [8]. A central position in the regulation of the mechanisms of apoptosis is occupied by proteins of the bcl-2 gene family – the proapoptotic Bax and Bcl-xs and the antiapoptotic Bcl-2 and Bcl-xL [6, 9, 10]. Induction of apoptosis after harmful exposure to ischemia/hypoxia in susceptible areas of the brain is associated with increases in the content of proapoptotic and decreases in the content of antiapoptotic proteins. Studies in the early 1990s identifi ed another phenomenon – “ischemic/hypoxic brain tolerance,” induced before the harmful effects of moderate, so-called preconditioning (PC) ischemia/hypoxia, which to a signifi cant extent prevents neuron death in susceptible areas of the brain [1]. PC with moderate hypobaric hypoxia (MHH) was showed to be able to eliminate the structural-functional damage to hippocampal and neocortical neurons, and also to be able to change the ratio of the contents of proand antiapoptotic proteins within them induced by severe hypoxia (SH) [14, 15]. Different PC regimes (number of episodes, duration of episodes) have been found to have effects with different effi cacies on the intracellular protection mechanisms. Further studies seeking optimum PC regimes, inducing effective mobilization of protective mechanisms, especially those involved in regulating apoptosis, are needed [1]. The aim of the present work was to study the effects of various PC regimes using MHH on the expression of the antiapoptotic protein Bcl-2 in neocortical and hippocampal neurons during and after exposure to harmful SH. Changes in the Expression of Antiapoptotic Protein Bcl-2 in the Rat Neocortex and Hippocampus in Different Hypobaric Hypoxia Regimes

Sulbactam Plays Neuronal Protective Effect Against Brain Ischemia via Upregulating GLT1 in Rats.

The study was undertaken to investigate whether sulbactam protects cerebral neurons against ischemia and whether the protection is mediated by regulating the expression and uptake activity of glial glutamate transporter-1 (GLT1) in a rat global brain ischemia model. The CA1 hippocampus was selected as the observing target. Real time quantitative PCR, Western blot and immunohistochemistry assays were used to detect GLT1 expression. Neuropathological evaluation was performed after thionin staining to determine the extent of the delayed neuronal death (DND) of pyramidal neurons. It was found that cerebral ischemia for 8min induced obvious DND of pyramidal neurons and GLT1 downregulation. Sulbactam pretreatment significantly upregulated GLT1 expression in sham rats and prevented or reversed the GLT1 downregulation normally induced in the ischemic rat brain. Meanwhile, sulbactam pretreatment effectively prevented the DND of pyramidal neurons normally induced by brain ischemia in a dose-dependent manner. Sulbactam posttreatment also protected pyramidal neurons against DND induced by brain ischemia although the magnitude of the protective effect was weaker than that in sulbactam pretreatment. Furthermore, either antisense knockdown of GLT1 expression or inhibition of the GLT1 uptake activity with dihydrokainate, a selective inhibitor of GLT1, significantly blocked the neuronal protective effect of sulbactam. These findings indicate that sulbactam has a neuronal protective effect though upregulating GLT1.

Amyloid-β and Tau

The defining features of Alzheimer disease (AD) include conspicuous changes in both brain histology and behavior. The AD brain is characterized microscopically by the combined presence of 2 classes of abnormal structures, extracellular amyloid plaques and intraneuronal neurofibrillary tangles, both of which comprise highly insoluble, densely packed filaments. The soluble building blocks of these structures are amyloid-β (Aβ) peptides for plaques and tau for tangles. Amyloid-β peptides are proteolytic fragments of the transmembrane amyloid precursor protein, whereas tau is a brain-specific, axon-enriched microtubule-associated protein. The behavioral symptoms of AD correlate with the accumulation of plaques and tangles, and they are a direct consequence of the damage and destruction of synapses that mediate memory and cognition. Synapse loss can be caused by the failure of live neurons to maintain functional axons and dendrites or by neuron death. During the past dozen years, a steadily accumulating body of evidence has indicated that soluble forms of Aβ and tau work together, independently of their accumulation into plaques and tangles, to drive healthy neurons into the diseased state and that hallmark toxic properties of Aβ require tau. For instance, acute neuron death, delayed neuron death following ectopic cell cycle reentry, and synaptic dysfunction are triggered by soluble, extracellular Aβ species and depend on soluble, cytoplasmic tau. Therefore, Aβ is upstream of tau in AD pathogenesis and triggers the conversion of tau from a normal to a toxic state, but there is also evidence that toxic tau enhances Aβ toxicity via a feedback loop. Because soluble toxic aggregates of both Aβ and tau can self-propagate and spread throughout the brain by prionlike mechanisms, successful therapeutic intervention for AD would benefit from detecting these species before plaques, tangles, and cognitive impairment become evident and from interfering with the destructive biochemical pathways that they initiate.

Differences in neuronal damage and gliosis in the hippocampus between young and adult gerbils induced by long duration of transient cerebral ischemia

Response to cerebral ischemia in young animals was very different from that in the adult. The aim of this study was to investigate differences in neuronal death and gliosis in the hippocampal CA1 region (CA1) between adult and young gerbils following 5 and 15min of transient cerebral ischemia. Delayed neuronal death (DND) of pyramidal cells occurred in the CA1 was similar in all the adult gerbils after 5 and 15min of ischemia: the DND occurred 4days after ischemia. In the young groups, DND of pyramidal cells in the CA1 region occurred 7 and 3days after 5 and 15min of ischemia, respectively. On the other hand, the activation of GFAP-immunoreactive (+) astrocytes and Iba-1+ microglia was different in the young groups from the adult groups after ischemia. The change pattern of GFAP immunoreactivity in the adult groups was similar in both the adult groups after ischemia; in the young groups, the activation of GFAP+ astrocytes after 5min of ischemia was much delayed than that after 15min of ischemia. Activated Iba-1+ microglia were aggregated in the stratum pyramidale 4days after ischemia in all the adult ischemia-operated groups; in the young groups, activated Iba-1+ microglia were aggregated in the stratum pyramidale 7days after 5min of ischemia and 3days after 15min of ischemia. These observations indicate that DND in young animals is very different from the adult according to different duration of transient cerebral ischemia and glial activation is very different in young animals after different duration of transient ischemia.

Spatio-temporal spread of neuronal death after focal photolysis of caged glutamate in neuron/astrocyte co-cultures

Glutamate-mediated excitotoxicity is now accepted as a major mechanism of ischemic neuronal damage. In the infarct core region, massive neuronal death is observed, but neurons in the surroundings of the core (ischemic penumbra) seem viable at the time of stroke. Several hours or days after a stroke, however, many neurons in the penumbra will undergo delayed neuronal death (DND). The mechanisms responsible for such DND are not fully understood. In this study, we investigated whether and how glutamate-mediated localized excitotoxic neuronal death affects surrounding neurons and astrocytes. To induce spatially-restricted excitotoxic neuronal death, a caged glutamate was focally photolyzed by a UV flash in neuron/astrocyte co-cultures. Uncaging of the glutamate resulted in acute neuronal death in the flashed area. After that, DND was observed in the surroundings of the flashed area late after the uncaging. In contrast, DND was not observed in neuron-enriched cultures, suggesting that functional changes in astrocytes, not neurons, after focal acute neuronal death were involved in the induction of DND. The present in vitro study showed that the spatially-restricted excitotoxic neuronal death resulted in DND in the surroundings of the flashed area, and suggested that the nitric oxide (NO)-induced reduction in the expression of astrocytic GLT-1 was responsible for the occurrence of the DND.

Novel neuroprotective effect of cisternal and intra-cerebral magnesium sulfate solution infusion on delayed cerebral death in rat hippocampal neurons after transient global ischemia

Several neuroprotective strategies such as barbiturate coma and hypothermic therapies have been promising in experimental studies but had limited efficacies in clinical trials. Magnesium ion has vasodilator and neuroprotective properties as a natural calcium blocker. The neuroprotective effects of cisternal and intra-cerebral infusion of magnesium sulfate (MgSO4) solution were evaluated against delayed neuronal death (DND) of CA1 hippocampal pyramidal neurons, and the involvement of changes in cerebral blood flow (CBF) and metabolism were investigated. Osmotic pumps with various MgSO4 solutions were embedded in the Sprague Dawley rat backs on day 1 and either cisternal or intra-cerebral (left CA1) infusion started. Global ischemic insult for 10min was induced on day 3, and the numbers of surviving neurons and dead neurons in the CA1 region were evaluated by hematoxylin–eosin and Fluoro-Jade B staining, respectively, on day 7. The regional CBF and glucose utilization rate (CMRglc) were determined by autoradiographic methods using [14C]iodoantipyrine and [14C]deoxyglucose, respectively, on day 5 after the start of either cisternal or intra-cerebral infusion. In the cisternal infusion experiment, 100mmol/lMgSO4 solution significantly increased the number of surviving neurons and decreased the number of dead neurons. In the intra-cerebral infusion experiment, 1mmol/lMgSO4 and 10mmol/lMgSO4 solution significantly increased the number of surviving neurons and decreased the number of dead neurons in the infusion side in dose-dependent manner. Neither regional CBF or CMRglc changed significantly in the CA1 of the hippocampus. Pretreatment with either cisternal or intra-cerebral infusion with MgSO4 solution can provide neuroprotection against DND without changing the CBF and metabolism.

Comparison of the Immunoreactivity of Trx2/Prx3 Redox System in the Hippocampal CA1 Region Between the Young and Adult Gerbil Induced by Transient Cerebral Ischemia

In the present study, we compared the immunoreactivities and levels of Trx/prx redox system, thioredoxin 2 (Trx2), thioredoxin reductase 2 (TrxR2) and peroxiredoxin 3 (Prx3), as well as neuronal death in the hippocampal CA1 region between the adult and young gerbil after 5 min of transient cerebral ischemia. At 4 days post-ischemia, pyramidal neurons (about 90%) in the adult stratum pyramidale of the CA1 region showed "delayed neuronal death (DND)"; however, at this time point, few pyramidal neurons showed DND in the young stratum pyramidale. At 7 days post-ischemia, about 56% of pyramidal neurons showed DND in the young stratum pyramidale. The immunoreactivities of all the antioxidants in the young sham-group were similar to those in the adult sham-group. At 4 days post-ischemia, the immunoreactivity of TrxR2, not Trx2 and Prx3 in the adult ischemia-group was dramatically decreased in CA1 pyramidal neurons. At this time point, the immunoreactivities of all the antioxidants in the young ischemia-group were apparently increased compared to the adult ischemia-group. From 7 days pots-ischemia, non-pyramidal cells showed the immunoreactivities of all the antioxidants in the ischemic CA1 region; however, in the young ischemia-groups, the immunoreactivities were much lower than those in the adult ischemia-groups. In brief, our results showed that the immunoreactivities of Trx2, TrxR2 and Prx3 were dramatically increased in CA1 pyramidal neurons of the young ischemia-groups at 4 days post-ischemia compared to those in the adult ischemia-groups induced by transient cerebral ischemia.

Cerebral ischemic pre‐conditioning enhances the binding characteristics and glutamate uptake of glial glutamate transporter‐1 in hippocampal CA1 subfield of rats

Glial glutamate transporter-1 (GLT-1) is the predominant subtype of glutamate transporters which are responsible for the homeostasis of extracellular glutamate. Our previous studies have shown that up-regulation in GLT-1 protein expression matches brain ischemic tolerance induced by cerebral ischemic preconditioning (CIP). To specify the role of functional changes of GLT-1 in the induction of brain ischemic tolerance by CIP, the present study was undertaken to examine changes in the binding properties of GLT-1 (including maximum binding and affinity for glutamate) and in GLT-1 mediated glutamate uptake, using L-³H-glutamate assay in the rat hippocampus. The results indicated that CIP was able to increase the maximum binding and affinity, and uptake of GLT-1 for glutamate in hippocampal CA1 subfield either with or without the presence of the subsequent severe brain ischemic insult. Simultaneously, accompanied with the above changes, CIP significantly reduced the delayed neuronal death (DND) in this region induced by lethal global cerebral ischemia. It could be concluded that up-regulation in the maximum binding and affinity and glutamate uptake of GLT-1 contributed to the neuronal protection of CIP against global cerebral ischemic insult.

Lercanidipine rescues hippocampus pyramidal neurons from mild ischemia-induced delayed neuronal death in SHRSP.

Stroke-prone spontaneously hypertensive rats (SHRSPs) are vulnerable to ischemia and delayed neuronal death (DND) of hippocampus pyramidal cells when bilateral carotid arteries are occluded for only 10 min. Since this occlusion induces just mild ischemia, the resulting DND may be an appropriate animal model for dementia in patient with essential hypertension exposed to small ischemic insults. This study was designed to compare the effects of the antihypertensive drugs lercanidipine, nicardipine, lisinopril, valsartan, and hydralazine on occlusion-induced DND in SHRSPs. Drugs were administered for 2 weeks, from 15 to 17 weeks of age. 0.1% Nicardipine and 0.01 or 0.03% lercanidipine were administered in the SP diet (about 61.3, 5.7, and 18.8 mg/kg/day, respectively), and the remaining drugs were administered at 10 mg/kg/day using the mini-osmotic pump. The animals were operated on at 16 weeks of age, and DND was analyzed by histological examination 1 week later. Systolic blood pressure was measured at 15, 16, and 17 weeks of age. For chronic treatment, Calcium-channel blockers were administered from 8 to 17 weeks of age. All antihypertensive drugs significantly lowered systolic blood pressure at 16 weeks of age. Hydralazine and lisinopril were associated with the greatest reduction; however, lercanidipine, nicardipine, and valsartan effectively reduced systolic blood pressure to within a medium range. DND was significantly inhibited only by 0.03% lercanidipine. Chronic treatment with 0.03% lercanidipine also protected pyramidal neurons. The results of this study demonstrate that the long-acting, lipophilic Calcium-channel blocker lercanidipine inhibits occlusion-induced DND in SHRSPs and that lercanidipine may effectively reduce dementia induced by small ischemic insults in patients with essential hypertension.

Edaravone alleviates delayed neuronal death and long-dated cognitive dysfunction of hippocampus after transient focal ischemia in Wistar rat brains

Edaravone is currently being used in acute ischemic stroke both in clinical and experimental research as a potent antioxidant. Here we explore the effects of edaravone on delayed neuronal death (DND) and long-dated cognitive dysfunction of hippocampus after cerebral ischemia-reperfusion (IR) injury and explain the underlying mechanisms and pathways. Our findings suggested that edaravone not only significantly alleviated delayed neuronal death and cognitive dysfunction of hippocampus after cerebral focal ischemia, but also markedly decreased malondialdehyde (MDA) levels. In addition, edaravone increased superoxide dismutase (SOD) levels and reduced the levels of inflammatory cytokines such as IL-1β and TNF-α expression; edaravone, also suppressed glial fibrillary acidic protein (GFAP) proliferation at days 3, 7 and 30 after reperfusion. Overall, the consensus emerging from this body of data indicated that edaravone exerts a later neuroprotective effect to hippocampus through its ability to inhibit inflammation, suppression of astrocyte activation and scavenging free radicals in stroke events.

Alterations of the proteasome in the CA1 neurons after transient ischemia

Objective To investigate the alteration of chaperonine hsp40 and its influence on delayed death of neurons in the CA1 region of hippocampus after transient cerebral ischemia. Method After transient global ischemia for 20 minutes, rat model was made. Following different lengths of reperfusion, all the 28 wistar rats were divided into sham-operation group,4 hour recovery group, 24 hour recovery group and 72 hour recovery group ( n = 7 rats in each group). Immunochemistry and laser scanning confocal microscopy were used to observe the distributional alteration of hsp40 in the neurons. Differential centrifuge and western blot assay were used to analyze the quantitative alteration of hsp40 and its redistribution in the neurons. Results Immunochemistry and laser scanning confocal microscopy showed the progressive reduction of hsp40 occurred at first in the cytosol, then in the nucleus until the death of all the neurons in the CA1 region died. Differential centrifuge and western blot assay showed the level of hsp40 decreased from 1.00 ± 0.21 to 0.23 ± 0.13 ( P ＜ 0.01 ) 24 hours after reperfusion; the quantity of hsp40 in the protein aggregates increased from 1.00±0.18 to 8.61 ± 1.89 (P ＜0.01 =24 h after reperfusion.Conclusions The reduction of hsp40 in the neurons of hippocampus CA1 region is an important role in protein aggregates formation. Key words: Transient ischemia; Hippocampus CA1 region; Delayed neuron death; Proteasome; Activity assay