TrkB‐mediated activation of the phosphatidylinositol‐3‐kinase/Akt cascade reduces the damage inflicted by oxygen–glucose deprivation in area CA3 of the rat hippocampus

The selective vulnerability of hippocampal area CA1 to ischemia‐induced injury is a well‐known phenomenon. However, the cellular mechanisms that confer resistance to area CA3 against ischemic damage remain elusive. Here, we show that oxygen–glucose deprivation–reperfusion (OGD‐RP), an in vitro model that mimic the pathological conditions of the ischemic stroke, increases the phosphorylation level of tropomyosin receptor kinase B (TrkB) in area CA3. Slices preincubated with brain‐derived neurotrophic factor (BDNF) or 7,8‐dihydroxyflavone (7,8‐DHF) exhibited reduced depression of the electrical activity triggered by OGD‐RP. Consistently, blockade of TrkB suppressed the resistance of area CA3 to OGD‐RP. The protective effect of TrkB activation was limited to area CA3, as OGD‐RP caused permanent suppression of CA1 responses. At the cellular level, TrkB activation leads to phosphorylation of the accessory proteins SHC and Gab as well as the serine/threonine kinase Akt, members of the phosphoinositide 3‐kinase/Akt (PI‐3‐K/Akt) pathway, a cascade involved in cell survival. Hence, acute slices pretreated with the Akt antagonist MK2206 in combination with BDNF lost the capability to resist the damage inflicted with OGD‐RP. Consistently, with these results, CA3 pyramidal cells exhibited reduced propidium iodide uptake and caspase‐3 activity in slices pretreated with BDNF and exposed to OGD‐RP. We propose that PI‐3‐K/Akt downstream activation mediated by TrkB represents an endogenous mechanism responsible for the resistance of area CA3 to ischemic damage.     

Zn2+‐induced ERK activation mediates PARP‐1‐dependent ischemic‐reoxygenation damage to oligodendrocytes

Much of the cell death following episodes of anoxia and ischemia in the mammalian central nervous system has been attributed to extracellular accumulation of glutamate and ATP, which causes a rise in [Ca²⁺]_i, loss of mitochondrial potential, and cell death. However, restoration of blood flow and reoxygenation are frequently associated with exacerbation of tissue injury (the oxygen paradox). Herein we describe a novel signaling pathway that is activated during ischemia‐like conditions (oxygen and glucose deprivation; OGD) and contributes to ischemia‐induced oligodendroglial cell death. OGD induced a retarded and sustained increase in extracellular signal‐regulated kinase 1/2 (ERK1/2) phosphorylation after restoring glucose and O₂ (reperfusion‐like conditions). Blocking the ERK1/2 pathway with the MEK inhibitor UO126 largely protected oligodendrocytes against ischemic insults. ERK1/2 activation was blocked by the high‐affinity Zn²⁺ chelator TPEN, but not by antagonists of AMPA/kainate or P2X7 receptors that were previously shown to be involved in ischemic oligodendroglial cell death. Using a high‐affinity Zn²⁺ probe, we showed that ischemia induced an intracellular Zn²⁺ rise in oligodendrocytes, and that incubation with TPEN prevented mitochondrial depolarization and ROS generation after ischemia. Accordingly, exposure to TPEN and the antioxidant Trolox reduced ischemia‐induced oligodendrocyte death. Moreover, UO126 blocked the ischemia‐induced increase in poly‐[ADP]‐ribosylation of proteins, and the poly[ADP]‐ribose polymerase 1 (PARP‐1) inhibitor DPQ significantly inhibited ischemia‐induced oligodendroglial cell death—demonstrating that PARP‐1 was required downstream in the Zn²⁺‐ERK oligodendrocyte cell death pathway. Chelation of cytosolic Zn²⁺, blocking ERK signaling, and antioxidants may be beneficial for treating CNS white matter ischemia‐reperfusion injury. Importantly, all the inhibitors of this pathway protected oligodendrocytes when applied after the ischemic insult. © 2012 Wiley Periodicals, Inc.     

Inhibition of calcium/calmodulin‐dependent protein kinase kinase (CaMKK) exacerbates impairment of endothelial cell and blood–brain barrier after stroke

Brain microvascular endothelial cells play an essential role in maintaining blood–brain barrier (BBB) integrity, and disruption of the BBB aggravates the ischemic injury. CaMKK (α and β) is a major kinase activated by elevated intracellular calcium. Previously, we demonstrated that inhibition of CaMKK exacerbated outcomes, conversely, overexpression reduced brain injury after stroke in mice. Interestingly, CaMKK has been shown to activate a key endothelial protector, sirtuin 1 (SIRT1). We hypothesized that CaMKK protects brain endothelial cells via SIRT1 activation after stroke. In this study, Oxygen‐Glucose Deprivation (OGD) was performed in human brain microvascular endothelial cells. Stroke was induced by middle cerebral artery occlusion (MCAO) in male mice. Knockdown of CaMKK β using siRNA increased cell death following OGD. Inhibition of CaMKK β by STO‐609 significantly and selectively down‐regulated levels of phosphorylated SIRT1 after OGD. Changes in the downstream targets of SIRT1 were observed following STO‐609 treatment. The effect of STO‐609 on cell viability after OGD was absent, when SIRT1 was concurrently inhibited. We also demonstrated that STO‐609 increased endothelial expression of the pro‐inflammatory proteins ICAM‐1 and VCAM‐1 and inhibition of CaMKK exacerbated OGD‐induced leukocyte‐endothelial adhesion. Finally, intracerebroventricular injection of STO‐609 exacerbated endothelial apoptosis and reduced BBB integrity after 24‐hr reperfusion following MCAO in vivo. Collectively, these results demonstrated that CaMKK inhibition reduced endothelial cell viability, exacerbated inflammatory responses and aggravated BBB impairment after ischemia. CaMKK activation may attenuate ischemic brain injury via protection of the microvascular system and a reduction in the infiltration of pro‐inflammatory factors.     

Downregulation of miR‐181b in mouse brain following ischemic stroke induces neuroprotection against ischemic injury through targeting heat shock protein A5 and ubiquitin carboxyl‐terminal hydrolase isozyme L1

Understanding the molecular mechanism of cerebral hypoxic preconditioning (HPC)‐induced endogenous neuroprotection may provide potential therapeutic targets for ischemic stroke. By using bioinformatics analysis, we found that miR‐181b, one of 19 differentially expressed miRNAs, may target aconitate hydratase (ACO2), heat shock protein A5 (HSPA5), and ubiquitin carboxyl‐terminal hydrolase isozyme L1 (UCHL1) among 26 changed protein kinase C isoform‐specific interacting proteins in HPC mouse brain. In this study, the role of miR‐181b in oxygen–glucose deprivation (OGD)‐induced N2A cell ischemic injury in vitro and mouse middle cerebral artery occlusion (MCAO)‐induced cerebral ischemic injury in vivo, and its regulation of ACO2, HSPA5, and UCHL1 were further determined. We found that miR‐181b expression levels significantly decreased in mouse brain following MCAO and in OGD‐treated N2A cells. Up‐ and downregulation of miR‐181b by transfection of pre‐ or anti‐miR‐181b could negatively regulate HSPA5 and UCHL1 (but not ACO2) protein levels as well as N2A cell death and programmed cell death in OGD‐treated N2A cells. By using a T7 promoter‐driven control dual luciferase assay, we confirmed that miR‐181b could bind to the 3′‐untranslated rergions of HSPA5 and UCHL1 mRNAs and repress their translations. miR‐181b antagomir reduced caspase‐3 cleavage and neural cell loss in cerebral ischemic cortex and improved neurological deficit of mice after MCAO. In addition, HSPA5 and UCHL1 short interfering RNAs (siRNAs) blocked anti‐miR‐181b‐mediated neuroprotection against OGD‐induced N2A cell injury in vitro. These results suggest that the downregulated miR‐181b induces neuroprotection against ischemic injury through negatively regulating HSPA5 and UCHL1 protein levels, providing a potential therapeutic target for ischemic stroke. © 2013 Wiley Periodicals, Inc.     

Postconditioning mitigates cell death following oxygen and glucose deprivation in PC12 cells and forebrain reperfusion injury in rats

Postconditioning mitigates ischemia‐induced cellular damage via a modified reperfusion procedure. Mitochondrial permeability transition (MPT) is an important pathophysiological change in reperfusion injury. This study explores the role of MPT modulation underlying hypoxic postconditioning (HPoC) in PC12 cells and studies the neuroprotective effects of ischemic postconditioning (IPoC) on rats. Oxygen‐glucose deprivation (OGD) was performed for 10 hr on PC12 cells. HPoC was induced by three cycles of 10‐min reoxygenation/10‐min rehypoxia after OGD. The MPT inhibitor N‐methyl‐4‐isoleucine cyclosporine (NIM811) and the MPT inducer carboxyatractyloside (CATR) were administered to selective groups before OGD. Cellular death was evaluated by flow cytometry and Western blot analysis. JC‐1 fluorescence signal was used to estimate the mitochondrial membrane potential (△Ψ_m). Transient global cerebral ischemia (tGCI) was induced via the two‐vessel occlusion and hypotension method in male Sprague Dawley rats. IPoC was induced by three cycles of 10‐sec reperfusion/10‐sec reocclusion after index ischemia. HPoC and NIM811 administration attenuated cell death, cytochrome c release, and caspase‐3 activity and maintained △Ψ_m of PC12 cells after OGD. The addition of CATR negated the protection conferred by HPoC. IPoC reduced neuronal degeneration and cytochrome c release and cleaved caspase‐9 expression of hippocampal CA1 neurons in rats after tGCI. HPoC protected PC12 cells against OGD by modulating the MPT. IPoC attenuated degeneration of hippocampal neurons after cerebral ischemia. © 2014 Wiley Periodicals, Inc.     

Regional and time‐dependent neuroprotective effect of hypothermia following oxygen‐glucose deprivation

The neuroprotective effect of hypothermia has been demonstrated in in vivo and in vitro models of cerebral ischemia. In regard to the hippocampus, previous studies have mainly focused on CA1 pyramidal neurons, which are very vulnerable to ischemia. But the dentate gyrus (DG), in which neuronal proliferation occurs, can also be damaged by ischemia. In this study, we explored the neuroprotective effect of postischemic hypothermia in different areas of the hippocampus after mild or severe ischemia. Organotypic hippocampal slice cultures were prepared from 6‐ to 8‐day‐old rats and maintained for 12 days. Cultures were exposed to 25 or 35 min of oxygen and glucose deprivation (OGD). Neuronal damage was quantified after 6, 24, 48, and 72 h by propidium iodide fluorescence. Mild hypothermia (33°C) was induced 1 h after the end of OGD and was maintained for a period of 24 h. Short OGD produced delayed neuronal damage in the CA1 area and in the DG and to a lesser extend in the CA3 area. Damage in CA1 pyramidal cells was totally prevented by hypothermia whereas neuroprotection was limited in the DG. Thirty‐five‐minute OGD induced more rapid and more severe cell death in the three regions. In this case, hypothermia induced 1 h after OGD was unable to protect CA1 pyramidal cells whereas hypothermia induced during OGD was able to prevent cell loss. This study provides evidence that neuroprotection by hypothermia is limited to specific areas and depends on the severity of the ischemia. © 2014 Wiley Periodicals, Inc.     

Comparison of the effects of human dental pulp stem cells and human bone marrow‐derived mesenchymal stem cells on ischemic human astrocytes in vitro

This study assesses the cytoprotective effects of human dental pulp stem cells (hDPSCs) and conditioned medium from hDPSCs (CM‐hDPSCs) on ischemic human astrocytes (hAs) in vitro compared with human bone marrow‐derived mesenchymal stem cells (hMSCs). Ischemia of hAs was induced by oxygen–glucose deprivation (OGD). CM‐hDPSCs and hMSCs were collected after 48 hr of culture. Cell death was determined by 3‐[4,5‐dimethylthialzol‐2‐yl]‐2,5‐diphenyltetrazolium bromide and cellular ATP assays. The expression of glial fibrillary acidic protein (GFAP) and musashi‐1 as markers of reactive astrogliosis was examined with immunochemical staining. mRNA expression and reactive oxygen species (ROS) were analyzed by RT‐PCR and flow cytometry, respectively. OGD increased cytotoxicity in a time‐dependent manner and decreased cellular ATP content concomitantly in hAs. Pretreatment and posttreatment with hDPSCs were associated with greater recovery from OGD‐induced cytotoxicity in hAs compared with hMSCs. Similarly, CM‐hDPSCs had a greater effect on OGD‐induced cytotoxicity in a dose‐dependent manner. Pre‐ and posttreatment with CM‐hDPSCs or CM‐hMSCs attenuated OGD‐induced GFAP, nestin, and musashi‐1 expression in hAs. Furthermore, treatment of cells with CM‐hDPSCs and hMSCs blocked OGD‐induced ROS production and interleukin‐1ß upregulation. This study demonstrates for the first time that hDPSCs and CM‐hDPSCs confer superior cytoprotection against cell death in an in vitro OGD model compared with hMSCs as shown by cell viability assay. Reactive gliosis, ROS production, and inflammatory mediators might contribute to this protective effect. Therefore, hDPSCs could represent an alternative source of cell therapy for ischemic stroke. © 2015 Wiley Periodicals, Inc.     

LncRNA SNHG12 ameliorates brain microvascular endothelial cell injury by targeting miR-199a

Long non-coding RNAs regulate brain microvascular endothelial cell death, the inflammatory response and angiogenesis during and after ischemia/reperfusion and oxygen-glucose deprivation/reoxygenation(OGD/R) insults. The long non-coding RNA, SNHG12, is upregulated after ischemia/reperfusion and OGD/R in microvascular endothelial cells of the mouse brain. However, its role in ischemic stroke has not been studied. We hypothesized that SNHG12 positively regulates ischemic stroke, and therefore we investigated its mechanism of action. We established an OGD/R mouse cell model to mimic ischemic stroke by exposing brain microvascular endothelial cells to OGD for 0, 2, 4, 8, 16 or 24 hours and reoxygenation for 4 hours. Quantitative real-time polymerase chain reaction showed that SNHG12 levels in brain microvascular endothelial cells increased with respect to OGD exposure time. Brain microvascular endothelial cells were transfected with pc DNA-control, pc DNA-SNHG12, si-control, or si-SNHG12. After exposure to OGD for 16 hours, these cells were then analyzed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide, trypan blue exclusion, western blot, and capillary-like tube formation assays. Overexpression of SNHG12 inhibited brain microvascular endothelial cell death and the inflammatory response but promoted angiogenesis after OGD/R, while SNHG12 knockdown had the opposite effects. miR-199a was identified as a target of SNHG12, and SNHG12 overexpression reversed the effect of miR-199a on brain microvascular endothelial cell death, the inflammatory response, and angiogenesis. These findings suggest that SNHG12 suppresses endothelial cell injury induced by OGD/R by targeting miR-199a.     

Micro‐RNA‐30a regulates ischemia‐induced cell death by targeting heat shock protein HSPA5 in primary cultured cortical neurons and mouse brain after stroke

Micro‐RNAs (miRs) have emerged as key gene regulators in many diseases, including stroke. We recently reported that miR‐30a protects N2A cells against ischemic injury, in part through enhancing beclin 1‐mediated autophagy. The present study explores further the involvement of miR‐30a in ischemia‐induced apoptosis and its possible mechanisms in primary cortical neurons and stroked mouse brain. We demonstrate that miR‐30a level is significantly decreased in cortical neurons after 1‐hr oxygen–glucose deprivation (OGD)/24‐hr reoxygenation. Overexpression of miR‐30a aggravated the OGD‐induced neuronal cell death, whereas inhibition of miR‐30a attenuated necrosis and apoptosis as determined by 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐di‐phenyl‐2H‐tetrazolium bromide, lactate dehydrogenase, TUNEL, and cleaved caspase‐3. The amount of HSPA5 protein, which is predicted to be a putative target of miR‐30a by TargetScan, could be reduced by pre‐miR‐30a, whereas it was increased by anti‐miR‐30a. Furthermore, the luciferase reporter assay confirmed that miR‐30a directly binds to the predicted 3′‐UTR target sites of the hspa5 gene. The cell injury regulated by miR‐30a in OGD‐treated cells could be aggravated by HSPA5 siRNA. We also observed an interaction of HSPA5 and caspase‐12 by coimmunoprecipitation and speculate that HSPA5 might be involved in endoplasmic reticulum stress‐induced apoptosis. In vivo, reduced miR‐30a increased the HSPA5 level and attenuated ischemic brain infarction in focal ischemia‐stroked mice. Downregulation of miR‐30a could prevent neural ischemic injury through upregulating HSPA5 protein expression, and decreased ER stress‐induced apoptosis might be one of the mechanisms underlying HSPA5‐mediated neuroprotection. © 2015 Wiley Periodicals, Inc.     

The TIR‐domain‐containing adapter inducing interferon‐β‐dependent signaling cascade plays a crucial role in ischemia–reperfusion‐induced retinal injury,whereas the contribution of the myeloid differentiation primary response 88‐dependent signaling cascade is not as pivotal

Toll‐like receptor 4 (Tlr4) plays an important role in ischemia–reperfusion (IR)‐induced retinal inflammation and damage. However, the role of two Tlr4‐dependent signaling cascades, myeloid differentiation primary response 88 (Myd88) and TIR‐domain‐containing adapter inducing interferon‐β (Trif), in retinal IR injury is poorly understood. In this study, we investigated the contribution of the Myd88‐dependent and Trif‐dependent signaling cascades in retinal damage and inflammation triggered by IR, by using Myd88 knockout (Myd88KO) and Trif knockout (TrifKO) mice. Retinal IR injury was induced by unilateral elevation of intraocular pressure for 45 min by direct corneal cannulation. To study IR‐induced retinal ganglion cell (RGC) death in vitro, we used an oxygen and glucose deprivation (OGD) model. Our data suggested that Myd88 was present in many retinal layers of sham‐operated and ischemic mice, whereas Trif was mainly present in the ganglion cell layer (GCL). The level of Myd88 was increased in the retina after IR. We found that retinas of TrifKO mice had a significantly reduced neurotoxic pro‐inflammatory response and significantly increased survival of the GCL neurons after IR. Although Myd88KO mice had relatively low levels of inflammation in ischemic retinas, their levels of IR‐induced retinal damage were notably higher than those of TrifKO mice. We also found that Trif‐deficient RGCs were more resistant to death induced by OGD than were RGCs isolated from Myd88KO mice. These data suggested that, as compared with the Myd88‐dependent signaling cascade, Trif signaling contributes significantly to retinal damage after IR.     

AMPK对氧糖剥夺再灌注后小胶质细胞介导炎性反应的影响

目的：探讨氧糖剥夺再灌注（OGD／R）损伤后腺苷酸活化蛋白激酶（AM PK ）对小胶质细胞介导的炎性介质释放及信号传导的影响。方法培养BV2细胞株,应用OGD 6 h再灌注24 h建立缺血再灌注损伤离体模型,AICAR（5μmol／L、50μmol／L、100μmol／L）或 Compound C（0．1μmol／L、1μmol／L、10μmol／L）不同程度激活或抑制AMPK磷酸化,MTT法检测细胞活性,免疫印迹及ELISA方法,检测OGD／R后BV2细胞AMPK活性变化,以及对NF－κB信号通路中IκB磷酸化、TNF－α释放的影响。结果各浓度AICAR均能够促进OGD／R后BV2细胞存活（P ＜0．05）,抑制IκB磷酸化水平（P ＜0．05）,AICAR（100μmol／L）能够增加AMPK磷酸化水平（P ＜0．05）,抑制TNF －α的释放（P＜0．01）。而Compound C（10μmol／L）促进BV2细胞死亡（P＜0．01）,降低OGD／R后AMPK及IκB磷酸化水平（P ＜0．05）,促进 TNF －α释放（P ＜0．05）。结论 AMPK 磷酸化激活能够减轻OGD／R后BV2细胞介导的炎性损伤作用,而抑制AM PK磷酸化能够加重神经炎性反应。     

Microglia and macrophages differentially modulate cell death after brain injury caused by oxygen‐glucose deprivation in organotypic brain slices

Macrophage can adopt several phenotypes, process call polarization, which is crucial for shaping inflammatory responses to injury. It is not known if microglia, a resident brain macrophage population, polarizes in a similar way, and whether specific microglial phenotypes modulate cell death in response to brain injury. In this study, we show that both BV2‐microglia and mouse bone marrow derived macrophages (BMDMs) were able to adopt different phenotypes after LPS (M1) or IL‐4 (M2) treatment in vitro, but regulated cell death differently when added to mouse organotypic hippocampal brain slices. BMDMs induced cell death when added to control slices and exacerbated damage when combined with oxygen–glucose deprivation (OGD), independently of their phenotype. In contrast, vehicle‐ and M2‐BV2‐microglia were protective against OGD‐induced death. Direct treatment of brain slices with IL‐4 (without cell addition) was protective against OGD and induced an M2 phenotype in the slice. In vivo, intracerebral injection of LPS or IL‐4 in mice induced microglial phenotypes similar to the phenotypes observed in brain slices and in cultured cells. After injury induced by middle cerebral artery occlusion, microglial cells did not adopt classical M1/M2 phenotypes, suggesting that another subtype of regulatory phenotype was induced. This study highlights functional differences between macrophages and microglia, in response to brain injury with fundamentally different outcomes, even if both populations were able to adopt M1 or M2 phenotypes. These data suggest that macrophages infiltrating the brain from the periphery after an injury may be cytotoxic, independently of their phenotype, while microglia may be protective.     

Sulforaphane protects immature hippocampal neurons against death caused by exposure to hemin or to oxygen and glucose deprivation

Oxidative stress is a mediator of cell death following cerebral ischemia/reperfusion and heme toxicity, which can be an important pathogenic factor in acute brain injury. Induced expression of phase II detoxification enzymes through activation of the antioxidant response element (ARE)/Nrf2 pathway has emerged as a promising approach for neuroprotection. Little is known, however, about the neuroprotective potential of this strategy against injury in immature brain cells. In this study, we tested the hypothesis that sulforaphane (SFP), a naturally occurring isothiocyanate that is also a known activator of the ARE/Nrf2 antioxidant pathway, can protect immature neurons from oxidative stress‐induced death. The hypothesis was tested with primary mouse hippocampal neurons exposed to either O₂ and glucose deprivation (OGD) or hemin. Treatment of immature neurons with SFP immediately after the OGD during reoxygenation was effective in protecting immature neurons from delayed cell death. Exposure of immature hippocampal neurons to hemin induced significant cell death, and both pre‐ and cotreatment with SFP were remarkably effective in blocking cytotoxicity. RT‐PCR analysis indicated that several Nrf2‐dependent cytoprotective genes, including NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase 1 (HO1), and glutamate‐cysteine ligase modifier subunit (GCLM), which is involved in glutathione biosynthesis, were up‐regulated following SFP treatment both in control neurons and following exposure to OGD and hemin. These results indicate that SFP activates the ARE/Nrf2 pathway of antioxidant defense and protects immature neurons from death caused by stress paradigms relevant to those associated with ischemic and traumatic injury to the immature brain. © 2009 Wiley‐Liss, Inc.     

糖氧剥夺再灌注对SH-SY5Y细胞焦亡的影响

目的 探讨细胞焦亡在糖氧剥夺诱导的人神经母细胞瘤细胞(Human neuroblastoma cells,SH-SY5Y)损伤中的作用。方法 用不同糖氧剥夺时间(0、3、6、12 h)处理SH-SY5Y细胞,然后进行再灌注24 h; Hoechst33342/碘化丙啶(Propidine iodide,PI)染色试剂盒观察细胞膜破裂情况; 原位末端标记法(Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling,TUNEL)/天冬氨酰特异性半胱氨酰蛋白酶-1(Cysteinyl aspartate specific proteinase 1,Caspase-1)共染检测细胞焦亡; 蛋白免疫印迹法检测焦亡相关指标[核苷酸结合寡聚化结构导致域样受体蛋白3(Nucleotide-binding oligomerization domain-like receptor protein 3,NLRP3)、Caspase-1、Pro-caspase-1、白介素-1β(Interleukin-1β,IL-1β),Pro-IL-1β]的表达水平; 使用Caspase-1抑制剂(Belnacasan,VX-765)处理糖氧剥夺/再灌注细胞模型,观察其对细胞焦亡的影响。结果 糖氧剥夺再灌注处理呈时间依赖诱导SH-SY5Y细胞损伤,并诱导细胞焦亡,焦亡相关指标(NLRP 3,Caspase-1,IL-1β)表达水平升高。VX-765可减轻糖氧剥夺再灌注诱导的SH-SY5Y细胞焦亡,降低焦亡相关指标(Caspase-1,Pro-IL-1β,IL-1β)的表达水平。结论 细胞焦亡在糖氧剥夺再灌注诱导的SH-SY5Y细胞损伤中起到重要作用。     

Preservation of neuronal functions by exosomes derived from different human neural cell types under ischemic conditions

Stem cell‐based therapies have been reported in protecting cerebral infarction‐induced neuronal dysfunction and death. However, most studies used rat/mouse neuron as model cell when treated with stem cell or exosomes. Whether these findings can be translated from rodent to humans has been in doubt. Here, we used human embryonic stem cell‐derived neurons to detect the protective potential of exosomes against ischemia. Neurons were treated with in vitro oxygen–glucose deprivation (OGD) for 1 h. For treatment group, different exosomes were derived from neuron, embryonic stem cell, neural progenitor cell and astrocyte differentiated from H9 human embryonic stem cell and added to culture medium 30 min after OGD (100 μg/mL). Western blotting was performed 12 h after OGD, while cell counting and electrophysiological recording were performed 48 h after OGD. We found that these exosomes attenuated OGD‐induced neuronal death, Mammalian target of rapamycin (mTOR), pro‐inflammatory and apoptotic signaling pathway changes, as well as basal spontaneous synaptic transmission inhibition in varying degrees. The results implicate the protective effect of exosomes on OGD‐induced neuronal death and dysfunction in human embryonic stem cell‐derived neurons, potentially through their modulation on mTOR, pro‐inflammatory and apoptotic signaling pathways.     

Increased p38 mitogen-activated protein kinase signaling is involved in the oxidative stress associated with oxygen and glucose deprivation in neonatal hippocampal slice cultures

The pathological basis of neonatal hypoxia–ischemia (HI) brain damage is characterized by neuronal cell loss. Oxidative stress is thought to be one of the main causes of HI‐induced neuronal cell death. The p38 mitogen‐activated protein kinase (MAPK) is activated under conditions of cell stress. However, its pathogenic role in regulating the oxidative stress associated with HI injury in the brain is not well understood. Thus, this study was conducted to examine the role of p38 MAPK signaling in neonatal HI brain injury using neonatal rat hippocampal slice cultures exposed to oxygen/glucose deprivation (OGD). Our results indicate that OGD led to a transient increase in p38 MAPK activation that preceded increases in superoxide generation and neuronal death. This increase in neuronal cell death correlated with an increase in the activation of caspase‐3 and the appearance of apoptotic neuronal cells. Pre‐treatment of slice cultures with the p38 MAPK inhibitor, SB203580, or the expression of an antisense p38 MAPK construct only in neuronal cells, through a Synapsin I‐1‐driven adeno‐associated virus vector, inhibited p38 MAPK activity and exerted a neuroprotective effect as demonstrated by decreases in OGD‐mediated oxidative stress, caspase activation and neuronal cell death. Thus, we conclude that the activation of p38 MAPK in neuronal cells plays a key role in the oxidative stress and neuronal cell death associated with OGD.     

Excessive Autophagy Contributes to Neuron Death in Cerebral Ischemia

Aims: To determine the extent to which autophagy contributes to neuronal death in cerebral hypoxia and ischemia. Methods: We performed immunocytochemistry, western blot, cell viability assay, and electron microscopy to analyze autophagy activities in vitro and in vivo. Results: In both primary cortical neurons and SH‐SY5Y cells exposed to oxygen and glucose deprivation (OGD)for 6 h and reperfusion (RP) for 24, 48, and 72 h, respectively, an increase of autophagy was observed as determined by the increased ratio of LC3‐II to LC3‐I and Beclin‐1 (BECN1) expression. Using Fluoro‐Jade C and monodansylcadaverine double‐staining, and electron microscopy we found the increment in autophagy after OGD/RP was accompanied by increased autophagic cell death, and this increased cell death was inhibited by the specific autophagy inhibitor, 3‐methyladenine. The presence of large autolysosomes and numerous autophagosomes in cortical neurons were confirmed by electron microscopy. Autophagy activities were increased dramatically in the ischemic brains 3–7 days postinjury from a rat model of neonatal cerebral hypoxia/ischemia as shown by increased punctate LC3 staining and BECN1 expression. Conclusion: Excessive activation of autophagy contributes to neuronal death in cerebral ischemia.     

Protective effects of placental growth factor on retinal neuronal cell damage

Placental growth factor (PlGF) is a member of the vascular endothelial growth factor family. Although it has been reported that PlGF protects against neuronal damage in the brain, little is known about the effects of PlGF in the retina. Therefore, we investigated the effects of PlGF on retinal neuronal cells. To evaluate the effects of PlGF against L‐buthionine‐(S,R)‐sulfoximine (BSO)/glutamate cell death, oxygen–glucose deprivation (OGD)‐induced cell death, and light‐induced cell death, RGC‐5 and 661W cells were used. We evaluated the mechanism responsible for the protective effects of PlGF against retinal neuronal cell death by performing the examinations with U1026, which is a mitogen‐activated protein kinase (MEK) inhibitor, and LY294002, which is a phosphoinositide 3‐kinase (PI3K) inhibitor. In addition, we measured caspase‐3/7 activity in RGC‐5 cells and 661W cells. PlGF protected against RGC‐5 cell death induced by BSO/glutamate and OGD and against 661W cell death induced by light irradiation. Moreover, an anti‐PlGF antibody negated these protective effects. The protective effects of PlGF against OGD‐induced RGC‐5 cell death and light‐induced 661W cell death were suppressed by using an anti‐PlGF antibody, U1026, and LY294002. Treatment with PlGF suppressed caspase‐3/7 activity in both cell lines. We demonstrated for the first time that PlGF exerts a protective effect by inhibiting the activation of caspase‐3/7 through the MEK and PI3K pathway in retinal neuronal cells. These data suggest that PlGF may be an important protective factor in the retina. © 2013 Wiley Periodicals, Inc.