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Modern technology has been successfully applied in various fields. Starting from the educational environment, the teaching platform and offline traditional classroom are imperative. This method has the functional characteristics of informatization and interactivity and one of the courses to cultivate students’ world outlook, values and other good conduct. In the construction of the course teaching mode, learning attitude towards the integration of teaching methods has changed differently. In the above situation, this paper studies the behavior changes and teaching effects of ideological and political students from the conditions and in-depth learning optimization. Firstly, the integrated teaching environment based on student behavior is designed and the mean student behavior data in different environments. After obtaining the behavior characteristics of the students, this paper analyzes the influence of the integrated teaching mode on the scores and other factors. Finally, the face recognition model is constructed by using the deep learning technology to capture and calculate the students’ class and examination status. The improvement of students’ learning quality has obvious effects in improving performance and classroom optimization.

We present an efficient context-aware lossy image compression system to participate in the Low Rate track of the CLIC 2020 Image Compression challenge. Our method is based on an autoencoder pipeline augmented with a nested hyperprior model, a PixelCNN-based context model and an adversarial loss to remove artefacts.

Glucocorticoids are commonly used in treating diseases with white matter lesions, including demyelinating diseases and spinal cord injury (SCI). However, glucocorticoids are ineffective in gray matter injuries, such as head injury and stroke. The differential glucocorticoid effects in white and gray matter injuries are unclear. We report here a novel mechanism of methylprednisolone (MP), a synthetic glucocorticoid widely used for treating multiple sclerosis and SCI, in protecting oligodendrocytes (OLGs) against AMPA-induced excitotoxicity, which has been implicated in the white matter injuries and diseases. The cytoprotective action of MP in OLGs is causally related to its upregulation of a neuroprotective cytokine erythropoietin (Epo). MP transactivation of Epo expression involves dual transcription factors: glucocorticoid receptor (GR) and hypoxia-inducible factor-1alpha (HIF-1alpha). Coimmunoprecipitation, chromatin immunoprecipitation analysis, yeast two-hybrid analysis, and structure modeling of three-dimensional protein-protein interactions confirm that MP induces interaction between GR DNA binding domain and HIF-1alpha PAS domain, with subsequent recruitment of HIF-1beta to transactivate Epo expression in OLGs. In contrast, MP activates GR but does not induce GR-HIF-1alpha interaction, HIF-1alpha binding to Epo enhancer/promoter, or Epo expression in cultured cortical neurons. The OLG-specific GR-HIF-1alpha transactivation of Epo provides novel insights into the development of more effective therapies for diseases affecting the white matter.

Dexamethasone (DX) induces apoptosis resistance in most solid malignant tumors during co-treatment with chemotherapy agents, such as camptothecin (CAM). In this study, we investigated the mechanism by which DX reduces chemotherapy efficiency in C6-glioma. DX reduced CAM-increased DNA fragmentation and caspase-3 activation. The DX's protection was negated by RU486, an antagonist of glucocorticoid receptor (GR). DX itself increased anti-apoptotic gene, Bcl-xL expression, and its transcription factor, signaling transducer and activator of transcription 5 (Stat5), DNA binding activity and phospho-Stat5 expression. DX blocked the CAM-decreased Bcl-xL and phospho-Stat5 expression, and Stat5 binding activity. RU486 negated DX's actions. To determine whether Stat5 regulates Bcl-xL expression in CAM-induced cell death, C6-glioma was infected with an adenovirus containing a constitutively activated Stat5-GFP (Ad-Stat5ca). Overexpression of Stat5ca increased Bcl-xL and decreased CAM-induced cell death compared to control adenovirus infected cells; whereas Stat5 siRNA decreased DX-induced Bcl-xL and increased cell death. Phospho-Stat5 expression was observed in the nuclear extract by co-immunoprecipitation with an anti-GR antibody, indicating that Stat5 and GR were interactive and formed a complex in the nuclei. These results suggest that DX's prevention from CAM-induced apoptosis and RU486's antagonism of DX's protection may be through Stat5/Bcl-xL signal pathway regulated by a GR.

Methylprednisolone (MP), a synthetic glucocorticoid agonist, is widely used for the clinical therapy of white matter diseases in the nervous system, such as spinal cord injury and multiple sclerosis. In addition to its potent anti-inflammatory and antioxidant properties, we recently discovered a selective antiapoptotic effect of MP on oligodendrocytes via the activation of the glucocorticoid receptor (GR) and the upregulation of bcl-XL, a splicing isoform of thebcl-xgene. Based on published findings of the functional interactions between GR and STAT5, a transcription factor from the family of signal transducers and activators of transcription (STAT), we examined whether the glucocorticoid signaling pathway interacts with STAT5 to upregulate bcl-XLand protect oligodendrocytes. We show herein that (1) the GR and STAT5 complex is present on the STAT5-binding site of the bcl-x promoter region in oligodendrocytes; (2) the overexpression of an activated form of STAT5 prevents α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-induced oligodendrocyte cell death; and (3) this prevention is lost when theSTAT5gene is knocked down. Thus, our results provide one molecular mechanism underlying the postinjury protective effects of oligodendrocytes by stress hormones.

There is growing recognition that white matter pathology is a common feature in Alzheimer's disease. We have previously reported that the amyloid beta peptide (Abeta) induces apoptosis in oligodendrocytes (OLG), via activation of neutral sphingomyelinase (nSMase) and resultant generation of ceramide. In the current study, we report that both Abeta and ceramide increased expression of the proapoptotic protein DP5/Hrk (DP5), and release of cytochrome C from mitochondria to cytoplasm in OLGs. We provide evidence that the Jun N-terminal kinase (JNK) signaling pathway mediates Abeta- and ceramide-induced apoptosis: Both Abeta and ceramide activated JNK phosphorylation, and subsequent AP-1 DNA binding activity; JNK siRNA decreased AP-1 DNA binding, DP5 expression and reduced cell death. Furthermore, inhibition of nSMase attenuated Abeta-induced JNK phosphorylation, AP-1 DNA binding activity, DP5 expression, and cytochrome C release. Collectively, these results suggest that Abeta-induced apoptosis involves the sequential activation of nSMase with ceramide generation, JNK activation, AP-1 DNA binding, and DP5 expression.

Amyloid-β peptide (Aβ)-induced death in cerebral endothelial cells (CECs) is preceded by mitochondrial dysfunction and signaling events characteristic of apoptosis. Mitochondria-dependent apoptosis engages Bcl-2 family proteins, especially the BH3-only homologues, which play a key role in initiating the apoptotic cascade. Here, we report that the expression ofbim, but not other BH3-only members, was selectively increased in cerebral microvessels isolated from 18-month-old APPsw (Tg2576) mice, a model of cerebral amyloid angiopathy (CAA), suggesting a pivotal role for Bim in Aβ-induced cerebrovascular degenerationin vivo. A similar expression profile was observed in Aβ-treated CECs. Furthermore, Aβ induction ofbimexpression involved a pro-apoptotic transcription factor, FKHRL1. FKHRL1 bound to a consensus sequence in thebimpromoter region and was activated by Aβ beforebimexpression. FKHRL1 activity was negatively regulated by phosphorylation catalyzed by Akt, an anti-apoptotic kinase. Akt upregulation by adenoviral gene transfer inhibited Aβ-induced FKHRL1 activation andbiminduction. In addition, Aβ increased the activity of protein phosphatase 2A (PP2A), a ceramide-activated protein phosphatase. Suppression of PP2A activity by RNA interference or a specific inhibitor, okadaic acid, effectively suppressed Aβ-induced Akt inactivation and FKHRL1 activation, leading to an attenuation ofbimexpression and cell death in CECs. Coimmunoprecipitation experiments revealed that Aβ enhanced the binding of the PP2A regulatory subunit PP2ACαβ to Akt. These results implicate PP2A as an early regulator of Aβ-inducedbimexpression and CEC apoptosis via the Akt/FKHRL1 signaling pathway. We raise the possibility that this pathway may play a role in cerebrovascular degeneration in CAA.

The amyloid-beta peptide (Aβ) induces apoptosis in cerebrovascular endothelial cells (CECs), contributing to the pathogenesis of cerebral amyloid angiopathy. We have previously shown that Aβ induces apoptosis in CECs. In the present study, we report that Aβ25–35-induced CEC apoptosis involves the inactivation of Akt, a signaling kinase important in maintaining cell viability. Akt prevents the activation of death-signaling events by facilitating the inactivation of proapoptotic proteins such as Bad. We applied three strategies to show that Aβ25–35 inactivation of Akt is causally related to Aβ25–35-induced CEC death by preventing Bad activation and subsequent mitochondrial dysfunction (reflected by the release of endonuclease G and Smac, two proapoptotic intermembranous proteins of the mitochondria). Wortmannin, a PI3-kinase inhibitor, enhanced Aβ25–35-induced Bad activation, mitochondrial dysfunction and CEC death. Enhancement of Akt activity by a Tat—Akt fusion protein, or by viral gene transfer of a constitutively active mutant of akt, reduced Bad activation, mitochondrial dysfunction, and CEC death. Using a siRNA strategy to knock down the bad gene, we showed that Bad activation is causally related to Aβ25–35-induced mitochondrial dysfunction and CEC death. Together, these results establish that the Akt—Bad cascade is altered by Aβ25–35, resulting in CEC apoptosis.

Although accumulating evidence demonstrates that white matter degeneration contributes to pathology in Alzheimer's disease (AD), the underlying mechanisms are unknown. In order to study the roles of the amyloid-beta peptide in inducing oxidative stress damage in white matter of AD, we investigated the effects of amyloid-beta peptide 25-35 (Abeta) on proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha)-induced inducible nitric oxide synthase (iNOS) in cultured oligodendrocytes (OLGs). Although Abeta 25-35 by itself had little effect on iNOS mRNA, protein, and nitrite production, it enhanced TNF-alpha-induced iNOS expression and nitrite generation in OLGs. Abeta, TNF-alpha, or the combination of both, increased neutral sphingomyelinase (nSMase) activity, but not acidic sphingomyelinase (aSMase) activity, leading to ceramide accumulation. Cell permeable C2-ceramide enhanced TNF-alpha-induced iNOS expression and nitrite generation. Moreover, the specific nSMase inhibitor, 3-O-methyl-sphingomyelin (3-OMS), inhibited iNOS expression and nitrite production induced by TNF-alpha or by the combination of TNF-alpha and Abeta. Overexpression of a truncated mutant of nSMase with a dominant negative function inhibited iNOS mRNA production. 3-OMS also inhibited nuclear factor kappaB (NF-kappaB) binding activity induced by TNF-alpha or by the combination of TNF-alpha and Abeta. These results suggest that neutral sphingomyelinase/ceramide pathway is required but may not be sufficient for iNOS expression induced by TNF-alpha and the combination of TNF-alpha and Abeta.

Ceramide is a pro-apoptotic lipid messenger that induces oxidative stress and may mediate apoptosis in cerebral endothelial cells (CECs) induced by TNF-alpha/cycloheximide, lipopolysaccharide, oxidized LDL, IL-1, and amyloid peptide. Exposure of CECs to C2 ceramide for 12 h caused cell death in a concentration-dependent manner, with a LC50 of 30 microM. Statins are inhibitors of 3-hydroxyl-3-methyl coenzyme A reductase which is the rate-limiting enzyme for cholesterol biosynthesis. Pretreatment with pravastatin at 20 microM for 16 h substantially attenuated ceramide cytotoxicity in mouse CECs. Increases in vascular endothelial growth factor (VEGF) expression were detected within 1-3 h after pravastatin treatment. This pravastatin action was accompanied by the activation of hypoxia-inducible factor-1 (HIF-1), a transcription factor known to activate VEGF expression. These results raise the possibility that pravastatin may protect CECs against ceramide-induced death via the HIF-VEGF cascade.

We have explored the molecular mechanism underlying amyloid beta-peptide (Abeta)-mediated cytotoxicity in vitro. Exposure of murine cerebral endothelial cells (CECs) or C6 glioma cells to Abeta25-35 resulted in dose-dependent cell death. Ceramide is a pro-apoptotic lipid mediator. Forced elevation of cellular ceramide levels, either by application of an exogenous C2 ceramide analogue or bacterial sphingomyelinase that induces endogenous ceramide release from sphingomyelin, mimicked Abeta25-35 cytotoxicity in both CECs and C6 glioma cells. Abeta25-35-induced synthesis of ceramide was selectively mediated by activation of neutral sphingomyelinase (nSMase), but not acidic sphingomyelinase (aSMase) or ceramide synthase. Both 3-O-Me-SM and N-acetyl-L-cysteine, the selective and nonselective pharmacological inhibitors of nSMase, respectively, suppressed nSMase activation, ceramide production, and cytotoxic action induced by Abeta25-35 in CECs. Furthermore, genetic knockdown of nSMase by an antisense strategy rendered C6 glioma cells specifically resistant to Abeta25-35 cytotoxicity without affecting their vulnerability to serum deprivation. Together, nSMase activation with subsequent ceramide production may contribute, at least partially, to Abeta25-35 cytotoxicity in cell types with cerebral endothelial and glial lineage.

Although mRNA expression of group IIA secretory phospholipase A2 (sPLA2-IIA) has been implicated in responses to injury in the CNS, information on protein expression remains unclear. In this study, we investigated temporal and spatial expression of sPLA2-IIA mRNA and immunoreactivity in transient focal cerebral ischemia induced in rats by occlusion of the middle cerebral artery. Northern blot analysis showed a biphasic increase in sPLA2-IIA mRNA expression following 60-min of ischemia-reperfusion: an early phase at 30 min and a second increase at a late phase ranging from 12 h to 14 days. In situ hybridization localized the early-phase increase in sPLA2-IIA mRNA to the affected ischemic cortex and the late-phase increase to the penumbral area. Besides sPLA2-IIA mRNA, glial fibrillary acidic protein (GFAP) and cyclo-oxygenase-2 mRNAs, but not cytosolic PLA2, also showed an increase in the penumbral area at 3 days after ischemia-reperfusion. Immunohistochemistry of sPLA2-IIA indicated positive cells in the penumbral area similar to the GFAP-positive astrocytes but different from the isolectin B4-positive microglial cells. Confocal microscopy further confirmed immunoreactivity of sPLA2-IIA in reactive astrocytes but not in microglial cells. Taken together, these results demonstrate for the first time an up-regulation of the inflammatory sPLA2-IIA in reactive astrocytes in response to cerebral ischemia-reperfusion.

Background and Purpose— Cells lacking the ATM (ataxia telangectasia mutated) gene are hypersensitive to DNA damage caused by a variety of insults. ATM may regulate oxidative stress–induced signaling cascades involving nuclear factor-κB (NF-κB), a transcription factor that is upstream of a wide variety of stress-responsive genes. We investigated the potential interaction of ATM and NF-κB after oxygen-glucose deprivation (OGD) in cerebral endothelial cells (CECs). Methods— Primary cultures of mouse CECs were subjected to OGD in the absence or presence of ATM antisense oligonucleotides or the NF-κB inhibitor SN50. ATM expression was determined with the use of reverse transcription–polymerase chain reaction and Western blot, and NF-κB activity was assessed by electrophoretic mobility shift assay. Cells were assessed for mitochondrial DNA damage with the use of long polymerase chain reaction and were assessed for caspase-3 and caspase-8 activity with the use of fluorogenic substrates. Cell death was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide and LDH release. Results— OGD stimulated ATM gene expression at the mRNA and protein level in CECs as early as 1 hour after OGD initiation. ATM gene knockdown with the use of an antisense oligonucleotide suppressed OGD-induced ATM protein expression, which was accompanied by an attenuation of NF-κB activation and the subsequent expression of downstream genes, including the antiapoptotic gene c-IAP2. ATM knockdown also accentuated OGD-induced mitochondrial DNA damage and the activation of caspase-3 and caspase-8, leading to enhanced CEC death. The specific NF-κB inhibitor SN50 mimicked the effects of ATM knockdown. Conclusions— We conclude that ATM may play a cytoprotective role in OGD-induced CEC death via a NF-κB–dependent signaling pathway.

The antioxidant and metal-chelating effects of pyrrolidine dithiocarbamate (PDTC) have been extensively studied. PDTC prevents cell death induced by various insults. However, PDTC itself may cause cell death in selected experimental paradigms. PDTC induced bovine cerebral endothelial cell death. However, in serum-depleted medium, PDTC did not affect the cell viability, suggesting that certain factors in serum may mediate the cytotoxic effect of PDTC. The metal chelators bathocuproine disulfonic acid, o-phenanthroline, bathophenanthroline disulfonic acid, and N,N,N',N'-tetrakis(2-pyridyl-methyl)ethylenediamine (TPEN) prevented the cell death induced by PDTC. In a serum-deprived condition, addition of exogenous metals, copper or zinc, restored the cytotoxic effect of PDTC. These data indicate that metals such as copper or zinc in serum may mediate the cytotoxic effect of PDTC. The potency of zinc for PDTC-induced endothelial cell death was greater than that of copper. Zn-EDTA did not block PDTC-induced cell death, whereas Ca-EDTA and Cu-EDTA were able to prevent this PDTC effect. PDTC increased the intracellular fluorescence of the zinc probe dye N-(6-methoxy-8-quinolyl)-p-toluenesulfonamide, which was quenched by TPEN or various EDTA preparations but not by Zn-EDTA. Results suggest that an increase in intracellular zinc concentration is required in PDTC-induced cerebral endothelial cell death.

A possible mechanism for the formation of the substrate-induced interface during the gelation, which leads to heterogeneous polymerization, is proposed. According to this mechanism, a surface polym...

Dividing cells and non-dividing cells are distinct in their cell cycle kinetics, and react differently when facing cytotoxic stimuli. A protein synthesis inhibitor, cycloheximide (CHX), has recently been found to protect neuronal cells from oxidative stress. We investigated whether CHX exerts differential effects on dividing and non-dividing cells in the brain under cytotoxic stimuli. Mitotic C6 rat glioma cells and postmitotic neuronal cells were studied with a cytotoxic regimen combining γ-irradiation (RT) and 1,3-bis,2-chloroethyl-1-nitrosurea (BCNU). Cells were exposed to BCNU (1 µg/ml) for 15 h before γ-irradiation and incubated with CHX (1 µg/ml) from 30 min before and until 5 h after irradiation. Clonogenic assay was used to assess cytotoxic effects on C6 glioma cells. LDH assay was used for the viability of H19-7 postmitotic neuronal cells. A 2.27–3.75 fold enhancement of cytotoxicity was noticed with the addition of CHX to BCNU and 2–10 Gy of radiation. Our data demonstrated that CHX enhanced cytotoxocity of RT plus BCNU, while no additional toxicity was incurred to the postmitotic neuronal cells when CHX was added. We further studied whether the inhibition of DNA repair, assayed by single-cell DNA electrophoresis (comet assay), is a contributing factor for the enhanced cytotoxicity on C6 glioma cells. Interestingly, the initial DNA damage after RT plus BCNU was equivalent; whereas DNA repair was significantly less at 5 h after radiation in CHX-treated C6 glioma cells. Protecting non-dividing neuronal cells to avoid excesive functional deficit is an integral part of a successful brain tumor treatment regimen. Taking advantage of the differential effect of CHX on glioma and neuronal cells may improve tumor control without excessive neural toxicity.

Amyloid beta-peptide (Abeta) of 39-42 amino acid residues is a major constituent of Alzheimer's disease neurite plaques. Abeta aggregates (fibrils) are believed to be responsible for neuronal damage and dysfunction, as well as microglia and astrocyte activation in disease lesions by multiple mechanisms. Since Abeta aggregates possess the multiple valencies of an FAED motif (20th to 23rd amino acid residues), which resembles the putative transforming growth factor-beta (TGF-beta) active site motif, we hypothesize that Abeta monomers and Abeta aggregates may function as TGF-beta antagonists and partial agonists, analogous to previously described monovalent and multivalent TGF-beta peptide antagonists and agonists (Huang, S. S., Liu, Q., Johnson, F. E., Konish, Y., and Huang, J. S. (1997) J. Biol. Chem. 272, 27155-27159). Here, we report that the Abeta monomer, Abeta-(1-40) and its fragment, containing the motif inhibit radiolabeled TGF-beta binding to cell-surface TGF-beta receptors in mink lung epithelial cells (Mv1Lu cells). Abeta-(1-40)-bovine serum albumin conjugate (Abeta-(1-40)-BSA), a multivalent synthetic analogue of Abeta aggregates, exhibited cytotoxicity toward bovine cerebral endothelial cells and rat post-mitotic differentiated hippocampal neuronal cells (H19-7 cells) and inhibitory activities of radiolabeled TGF-beta binding to TGF-beta receptors and TGF-beta-induced plasminogen activator inhibitor-1 expression, that were approximately 100-670 times more potent than those of Abeta-(1-40) monomers. At less than micromolar concentrations, Abeta-(1-40)-BSA but not Abeta-(1-40) monomers inhibited proliferation of Mv1Lu cells. Since TGF-beta is an organizer of responses to neurodegeneration and is also found in neurite plaques, the TGF-beta antagonist and partial agonist activities of Abeta monomers and aggregates may play an important role in the pathogenesis of the disease.

Cytokines, including tumor necrosis factor-alpha (TNF-alpha), may elicit cytotoxic response through the sphingomyelin-ceramide signal transduction pathway by activation of sphingomyelinases and the subsequent release of ceramide: the universal lipid second messenger. Treatment of bovine cerebral endothelial cells (BCECs) with TNF-alpha for 16 h followed by cycloheximide (CHX) for 6 h resulted in an increase in ceramide accumulation, DNA fragmentation, and cell death. Application of a cell permeable ceramide analogue C2 ceramide, but not the biologically inactive C2 dihydroceramide, also induced DNA laddering and BCEC death in a concentration- and time-dependent manner. TNF-alpha/CHX-mediated ceramide production apparently is not a result of sphingomyelin hydrolysis because sphingomyelin content does not decrease in this death paradigm. In addition, an acidic sphingomyelinase inhibitor, desipramine, had no effect on TNF-alpha/CHX-induced cell death. However, addition of fumonisin B1, a selective ceramide synthase inhibitor, attenuated TNF-alpha/CHX-induced intracellular ceramide elevation and BCEC death. Together, these findings suggest that ceramide plays at least a partial role in this paradigm of BCEC death. Our results show, for the first time, that ceramide derived from de novo synthesis is an alternative mechanism to sphingomyelin hydrolysis in the BCEC death process initiated by TNF-alpha/CHX.

Inducible nitric oxide synthase (iNOS) is expressed in response to cytokines by a number of cell types participating in CNS inflammation, including brain cerebral endothelial cells. NF-kappaB, a transcription factor, mediates effector actions of pro-inflammatory cytokines. A combination of tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) enhanced the expression of iNOS in murine cerebral endothelial cells (MCECs). In an attempt to modulate TNF-alpha+IFN-gamma induced expression of iNOS in MCECs, we designed a double-strand hairpin (hp) oligonucleotide carrying the NF-kappaB motif. This hp oligonucleotide inhibited NF-kappaB binding activity and decreased both iNOS mRNA and protein expression induced by TNF-alpha+IFN-gamma. As a control, a mutant hp oligonucleotide was without effect. The present study confirms the role of transcription factor NF-kappaB in iNOS expression induced by TNF-alpha+IFN-gamma in MCECs. More importantly, it demonstrates that an appropriately designed hp oligonucleotide is an effective tool to modulate iNOS expression and may be of potential pharmacological use.

Thebcl-xgene appears to play a critical role in regulating apoptosis in the developing and mature CNS and following CNS injury. Two isoforms of Bcl-x are produced as a result of alternative pre-mRNA splicing: Bcl-xL(the long form) is anti-apoptotic, while Bcl-xS(short form) is pro-apoptotic. Despite the antagonistic activities of these two isoforms, little is known about how regulation of alternative splicing ofbcl-xmay mediate neural cell apoptosis. Here, we report that apoptotic stimuli (staurosporine or C2-ceramide) reciprocally altered Bcl-x splicing in neural cells, decreasing Bcl-xLwhile increasing Bcl-xS. Specific knockdown of Bcl-xSattenuated apoptosis. To further define regulatory elements that influenced Bcl-x splicing, a Bcl-x minigene was constructed. Deletional analysis revealed several consensus sequences within intron 2 that altered splicing. We found that the splicing factor, CUG-binding-protein-1 (CUGBP1), bound to a consensus sequence close to the Bcl-xL5′ splice site, altering the Bcl-xL/Bcl-xSratio and influencing cell death.In vivo, neonatal hypoxia–ischemia reciprocally altered Bcl-x pre-mRNA splicing, similar to thein vitrostudies. Manipulation of the splice isoforms using viral gene transfer of Bcl-xSshRNA into the hippocampus of rats before neonatal hypoxia–ischemia decreased vulnerability to injury. Moreover, alterations in nuclear CUGBP1 preceded Bcl-x splicing changes. These results suggest that alternative pre-mRNA splicing may be an important regulatory mechanism for cell death after acute neurological injury and may potentially provide novel targets for intervention.

The deposition of β-amyloid protein(Aβ) and loss of neurons within the brain are the pathologic hallmarks of Alzheimer's disease (AD). Apoptosis is a crucial pathway in neuronal loss in AD. Tanshinone IIA (tanIIA) is one of ingredients of tanshinone which is the major component of the traditional Chinese herb Danshen. The present study explores the effects of tanIIA on Aβ 1–42 -induced cytotoxicity. Cultured cortical neurons that were treated with 4 μM Aβ 1–42 showed shrunken perikaryon with loss of neurite processes; the survival rate of neurons decreased almost to 57% and the apoptotic rate of neurons increased to 47%. In addition, the level of gene bcl-xl mRNA and Bcl-xL protein decreased significantly. These changes, however, were prevented by pretreatment of neurons with tanIIA for 24 h before Aβ 1–42 , which markedly increased neuron survival rate compared to neurons treated with Aβ 1–42 alone; the apoptotic rate of neurons decreased to 15%, and the decrease in level of gene bcl-xl mRNA and Bcl-xL protein in Aβ-treated neurons, were prevented. Thus, we conclude that tanIIA might serve as an obvious neuroprotection. TanIIA protected neurons against the Aβ-induced cytotoxicity most likely via activation of the Bcl-xL pathway.

Although amino acid deficiencies are known to occur in diabetes patients and are considered to contribute to the occurrence of cardiomyopathy, the mechanisms of the impact of the restoration of amino acids on improved cardiac function are not completely understood. Accordingly, the present study was conducted to examine the beneficial effects of dietary supplementation of taurine, arginine and carnitine, individually or in combination, in an experimental model of chronic diabetes. For inducing diabetes, rats received a single injection of streptozotocin (65 mg/kg body weight). Experimental animals were treated (by oral gavage) daily for three weeks with amino acids before the induction of diabetes; this treatment was continued for an additional eight-week period. Diabetes was observed to induce cardiac dysfunction, myocardial cell damage, and changes in plasma glucose and lipid levels. Treatment of diabetic animals with taurine, unlike carnitine or arginine, attenuated alterations in cardiac function, as evidenced by echocardiography and in vivo catheterization techniques. Taurine, carnitine and arginine, individually or in combination, attenuated diabetes-induced cell damage as revealed by electron microscopy. While carnitine alone reduced plasma levels of triglycerides with an increase in high-density lipoprotein cholesterol, none of the amino acids, alone or in combination, had an effect on myocardial glycogen content, lipid accumulation or hyperglycemia. These results suggest that dietary supplementation of taurine attenuates diabetes-induced changes in cardiac contractile function and ultrastructure without any alterations in plasma lipid and glucose levels.

Although sarpogrelate, a 5-HT2A receptor antagonist, has been reported to exert beneficial effects in diabetes, the mechanisms of its action are not understood. In this study, diabetes was induced in rats by an injection of streptozotocin (65 mg/kg) and the animals were assessed 7 weeks later. Decreased serum insulin as well as increased serum glucose, cholesterol, and triglyceride levels in diabetic animals were associated with increased blood pressure and heart/body weight ratio. Impaired cardiac performance in diabetic animals was evident by decreased heart rate, left ventricular developed pressure, rate of pressure development, and rate of pressure decay. Treatment of diabetic animals with sarpogrelate (5 mg/kg) or insulin (10 units/kg) daily for 6 weeks attenuated the observed changes in serum insulin, glucose, and lipid levels as well as blood pressure and cardiac function by varying degrees. Protein content for membrane glucose transporters (GLUT-1 and GLUT-4) was depressed in diabetic heart; the observed alteration in GLUT-4 was partially prevented by both sarpogrelate and insulin, whereas that in GLUT-1 was attenuated by sarpogrelate only. Incubation of myoblast cells with sarpogrelate and insulin stimulated glucose uptake; these effects were additive. 5-hydroxytryptamine was found to inhibit glucose-induced insulin release from the pancreas; this effect was prevented by sarpogrelate. These results suggest that sarpogrelate may improve cardiac function in chronic diabetes by promoting the expression of membrane glucose transporters as well as by releasing insulin from the pancreas.

Methylprednisolone (MP) is used to treat a variety of neurological disorders involving white matter injury, including multiple sclerosis, acute disseminated encephalomyelitis, and spinal cord injury (SCI). Although its mechanism of action has been attributed to anti-inflammatory or antioxidant properties, we examined the possibility that MP may have direct neuroprotective activities. Neurons and oligodendrocytes treated with AMPA or staurosporine died within 24 h after treatment. MP attenuated oligodendrocyte death in a dose-dependent manner; however, neurons were not rescued by the same doses of MP. This protective effect was reversed by the glucocorticoid receptor (GR) antagonist (11, 17)-11-[4-(dimethylamino)phenyl]-17-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one (RU486) and small interfering RNA directed against GR, suggesting a receptor-dependent mechanism. MP reversed AMPA-induced decreases in the expression of anti-apoptotic Bcl-xL, caspase-3 activation, and DNA laddering, suggesting anti-apoptotic activity in oligodendrocytes. To examine whether MP demonstrated this selective protectionin vivo, neuronal and oligodendrocyte survival was assessed in rats subjected to spinal cord injury (SCI); groups of rats were treated with or without MP in the presence or absence of RU486. Eight days after SCI, MP significantly increased oligodendrocytes (CC-1-immunoreactive cells) after SCI, but neuronal (neuronal-specific nuclear protein-immunoreactive cells) number remained unchanged; RU486 reversed this protective effect. MP also inhibited SCI-induced decreases in Bcl-xLand caspase-3 activation. Consistent with these findings, the volume of demyelination, assessed by Luxol fast blue staining, was attenuated by MP and reversed by RU486. These results suggest that MP selectively inhibits oligodendrocyte but not neuronal cell death via a receptor-mediated action and may be a mechanism for its limited protective effect after SCI.

It has been postulated that the development of amyloid plaques in Alzheimer's disease (AD) may result from an imbalance between the generation and clearance of the amyloid-β peptide (Aβ). Although familial AD appears to be caused by Aβ overproduction, sporadic AD (the most prevalent form) may result from impairment in clearance. Recent evidence suggests that several proteases may contribute to the degradation of Aβ. Furthermore, astrocytes have recently been implicated as a potential cellular mediator of Aβ degradation. In this study, we examined the possibility that matrix metalloproteinases (MMPs), proteases known to be expressed and secreted by astrocytes, could play a role in extracellular Aβ degradation. We found that astrocytes surrounding amyloid plaques showed enhanced expression of MMP-2 and MMP-9 in aged amyloid precursor protein (APP)/presenilin 1 mice. Moreover, astrocyte-conditioned medium (ACM) degraded Aβ, lowering levels and producing several fragments after incubation with synthetic human Aβ1–40and Aβ1–42. This activity was attenuated with specific inhibitors of MMP-2 and -9, as well as in ACM derived frommmp-2or-9knock-out (KO) mice.In vivo, significant increases in the steady-state levels of Aβ were found in the brains ofmmp-2and-9KO mice compared with wild-type controls. Furthermore, pharmacological inhibition of the MMPs withN-[(2R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl]-l-tryptophan methylamide (GM 6001) increased brain interstitial fluid Aβ levels and elimination of half-life in APPsw mice. These results suggest that MMP-2 and -9 may contribute to extracellular brain Aβ clearance by promoting Aβ catabolism.

null background. We are performing A ELISAs, immunoblotting, and immunohisto-chemistry on brains from these mice and their APP transgenic controls collected at 3, 6, and 13 months of age. Results: The absence of NEP results in: a) elevations in the TBS-, NP40-, and guanidine HCl-soluble pools of brain A ; b) marked elevations in hippocampal amyloid plaque burden; and c) a dramatic increase in amyloid angiopathy. We will report further on plasma A levels, A monomer, dimer, and oligomer levels, and the possibility of a NEP gene-dose response. Conclusions: The absence of endogenous NEP in human APP transgenic mice results in elevated levels of brain A , an increased amyloid plaque burden, and the development of amyloid angiopathy.

The pathological hallmark of Alzheimer disease is the senile plaque principally composed of tightly aggregated amyloid-beta fibrils (fAbeta), which are thought to be resistant to degradation and clearance. In this study, we explored whether proteases capable of degrading soluble Abeta (sAbeta) could degrade fAbeta as well. We demonstrate that matrix metalloproteinase-9 (MMP-9) can degrade fAbeta and that this ability is not shared by other sAbeta-degrading enzymes examined, including endothelin-converting enzyme, insulin-degrading enzyme, and neprilysin. fAbeta was decreased in samples incubated with MMP-9 compared with other proteases, assessed using thioflavin-T. Furthermore, fAbeta breakdown with MMP-9 but not with other proteases was demonstrated by transmission electron microscopy. Proteolytic digests of purified fAbeta were analyzed with matrix-assisted laser desorption ionization time-of-flight mass spectrometry to identify sites of Abeta that are cleaved during its degradation. Only MMP-9 digests contained fragments (Abeta(1-20) and Abeta(1-30)) from fAbeta(1-42) substrate; the corresponding cleavage sites are thought to be important for beta-pleated sheet formation. To determine whether MMP-9 can degrade plaques formed in vivo, fresh brain slices from aged APP/PS1 mice were incubated with proteases. MMP-9 digestion resulted in a decrease in thioflavin-S (ThS) staining. Consistent with a role for endogenous MMP-9 in this process in vivo, MMP-9 immunoreactivity was detected in astrocytes surrounding amyloid plaques in the brains of aged APP/PS1 and APPsw mice, and increased MMP activity was selectively observed in compact ThS-positive plaques. These findings suggest that MMP-9 can degrade fAbeta and may contribute to ongoing clearance of plaques from amyloid-laden brains.

There is growing recognition that white matter pathology is a common feature in Alzheimer's disease. We have previously reported that the amyloid beta peptide (Abeta) induces apoptosis in oligodendrocytes (OLG), via activation of neutral sphingomyelinase (nSMase) and resultant generation of ceramide. In the current study, we report that both Abeta and ceramide increased expression of the proapoptotic protein DP5/Hrk (DP5), and release of cytochrome C from mitochondria to cytoplasm in OLGs. We provide evidence that the Jun N-terminal kinase (JNK) signaling pathway mediates Abeta- and ceramide-induced apoptosis: Both Abeta and ceramide activated JNK phosphorylation, and subsequent AP-1 DNA binding activity; JNK siRNA decreased AP-1 DNA binding, DP5 expression and reduced cell death. Furthermore, inhibition of nSMase attenuated Abeta-induced JNK phosphorylation, AP-1 DNA binding activity, DP5 expression, and cytochrome C release. Collectively, these results suggest that Abeta-induced apoptosis involves the sequential activation of nSMase with ceramide generation, JNK activation, AP-1 DNA binding, and DP5 expression.

We test whether inhibition of inducible nitric oxide synthase (iNOS) can exert a cytoprotective effect on cerebral endothelial cells upon stimulation by pro-inflammatory cytokines. Mouse brain endothelial cells were stably transfected to express an antisense RNA against iNOS driven by an endothelium-specific von Willebrand factor (vWF) promoter. Upon stimulation with tumor necrosis factor-alpha (TNF-alpha) plus interferon-gamma (IFN-gamma), antisense transfectants showed less iNOS enzymatic activity with less nitric oxide (NO) when compared to the sense control cells. Correspondingly, the antisense cells showed a reduced LDH release and less cytosolic content of oligonucleosomes. These findings establish a cell-specific antisense strategy and confirm the cytotoxic role of iNOS expression in cultured cerebral endothelial cells.

Amyloid-beta peptide (Abeta) accumulation in senile plaques, a pathological hallmark of Alzheimer's disease (AD), has been implicated in neuronal degeneration. We have recently demonstrated that Abeta induced oligodendrocyte (OLG) apoptosis, suggesting a role in white matter pathology in AD. Here, we explore the molecular mechanisms involved in Abeta-induced OLG death, examining the potential role of ceramide, a known apoptogenic mediator. Both Abeta and ceramide induced OLG death. In addition, Abeta activated neutral sphingomyelinase (nSMase), but not acidic sphingomyelinase, resulting in increased ceramide generation. Blocking ceramide degradation with N-oleoyl-ethanolamine exacerbated Abeta cytotoxicity; and addition of bacterial sphingomyelinase (mimicking cellular nSMase activity) induced OLG death. Furthermore, nSMase inhibition by 3-O-methyl-sphingomyelin or by gene knockdown using antisense oligonucleotides attenuated Abeta-induced OLG death. Glutathione (GSH) precursors inhibited Abeta activation of nSMase and prevented OLG death, whereas GSH depletors increased nSMase activity and Abeta-induced death. These results suggest that Abeta induces OLG death by activating the nSMase-ceramide cascade via an oxidative mechanism.

Insoluble fibrils of amyloid-beta peptide (Abeta) are the major component of senile and vascular plaques found in the brains of Alzheimer's disease (AD) patients. Abeta has been implicated in neuronal and vascular degeneration because of its toxicity to neurons and endothelial cells in vitro; some of these cells die with characteristic features of apoptosis. We used primary cultures of murine cerebral endothelial cells (CECs) to explore the mechanisms involved in Abeta-induced cell death. We report here that Abeta(25-35), a cytotoxic fragment of Abeta, induced translocation of the apoptosis regulator termed second-mitochondria-derived activator of caspase (Smac) from the intramembranous compartment of the mitochondria to the cytosol 24 hr after exposure. In addition, we demonstrated that X chromosome-linked inhibitor-of-apoptosis protein (XIAP) coimmunoprecipitated with Smac, suggesting that the two proteins bound to one another subsequent to the release of Smac from the mitochondria. Abeta(25-35) treatment also led to rapid AP-1 activation and subsequent expression of Bim, a member of the BH3-only family of proapoptotic proteins. Bim knockdown using an antisense oligonucleotide strategy suppressed Abeta(25-35)-induced Smac release and resulted in attenuation of CEC death. Furthermore, AP-1 inhibition, with curcumin or c-fos antisense oligonucleotide, reduced bim expression. These results suggest that Abeta activates an apoptotic cascade involving AP-1 DNA binding, subsequent bim induction, followed by Smac release and binding to XIAP, resulting in CEC death.

Background and Purpose — Oxidative damage of mitochondrial DNA (mtDNA) in the ischemic brain is expected after ischemia/reperfusion injury. A recent study demonstrated limited patterns of mtDNA deletion in the brain after ischemia/reperfusion. We studied the ischemia/reperfusion-induced global changes of mtDNA integrity and its restoration in a rat model of transient focal ischemia in vivo. Methods — Changes in mtDNA content in the ischemic brain were assessed with the use of a rat stroke model featuring transient severe ischemia confined to the cerebral cortex of the right middle cerebral artery territory for 30 or 90 minutes. A new long polymerase chain reaction method, using mouse DNA as an internal standard, was applied to measure the relative content of intact rat mtDNA. Southern hybridization following alkaline gel electrophoresis was conducted in a parallel study to confirm long polymerase chain reaction results. Results — A reduction in mtDNA content was found after ischemia for 30 and 90 minutes. The mtDNA was restored to near nonischemic levels 24 hours after 30- but not 90-minute ischemia. Conclusions — These results confirm that ischemia/reperfusion causes mtDNA damages. Restoration of the mtDNA content to nonischemic levels after 30-minute ischemia raises the possibility that mtDNA repair or repletion occurs after brief ischemia.

Amyloid beta peptide (A beta), a 39 to 43 amino acid fragment of the beta-amyloid precursor protein (betaAPP), forms insoluble fibrillar accumulation in neurofibrillary tangles and vascular plaques. A beta has been implicated in neuronal and vascular degeneration in brain regions susceptible to plaque formation because of its cytotoxic effect on neurons and endothelial cells (ECs). The authors used a murine cerebral endothelial cell (CEC) line and primary cultures of bovine CECs to explore the cytotoxic mechanism of A beta. A beta 1-40 and A beta 25-35 peptides caused cell death in a dose-dependent and time-dependent manner. Exposure to either A beta 25-35 or A beta 1-40 at 10 micromol/L for 48 hours caused at least 40% cell death. Cerebral endothelial cell death was characterized by nuclear condensation, mitochondrial dysfunction, and nuclear and mitochondrial DNA damage. A beta 25-35 activated both caspase-8 and caspase-3 in murine CECs. zVAD-fmk, a broad-spectrum caspase inhibitor, prevented A beta 25-35-induced increase in caspase-3 activity and CEC death. N-acetyl-cysteine, an antioxidant, also prevented A beta-induced cell death. Together, these findings indicate that A beta-mediated CEC death is an apoptotic process that is characterized by increased oxidative stress, caspase activation, mitochondrial dysfunction, and nuclear and mitochondrial DNA damage.

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive dementia. Amyloid-beta peptide (Abeta), a 39-43 amino acid peptide derived from beta-amyloid precursor protein, forms insoluble fibrillar aggregates that have been linked to neuronal and vascular degeneration in AD and cerebral amyloid angiopathy. Here we demonstrate that Abeta 1-40 and a truncated fragment, Abeta 25-35, induced death of oligodendrocytes (OLGs) in vitro in a dose-dependent manner with similar potencies. Abeta-induced OLG death was accompanied by nuclear DNA fragmentation, mitochondrial dysfunction, and cytoskeletal disintegration. Abeta activation of redox-sensitive transcription factors NF-kappaB and AP-1 and antioxidant prevention of Abeta-mediated OLG death suggest that oxidative injury contributes to Abeta cytotoxicity in OLGs. Recent demonstration of Abeta deposition and white matter abnormalities in AD implies a potential pathophysiological role for Abeta-mediated cytotoxicity of OLGs in this neurodegenerative disease.

Background and Purpose —The cerebral endothelial cells (ECs) are a primary target of hypoxic or ischemic brain insults. EC damage may contribute to postischemic secondary injury. Massive production of NO after inducible NO synthase (iNOS) expression has been implicated in cell death. This study aimed to characterize bovine cerebral EC death in relation to iNOS expression after oxygen-glucose deprivation (OGD) in vitro. Methods —OGD in bovine cerebral ECs in culture was induced by deleting glucose in the medium and by incubating the cells in a temperature-controlled anaerobic chamber. The extent of cell death was assessed by trypan blue exclusion, MTT assay, and LDH release. ELISA, gel electrophoresis, and staining by terminal deoxynucleotidyl transferase–mediated dUTP nick end-labeling were used to examine DNA fragmentation. The expression of iNOS mRNA and protein was detected by reverse transcription–polymerase chain reaction and Western blotting, respectively. Nitrotyrosine expression was confirmed with Western blot analysis and immunostaining. Results —Bovine cerebral EC death was dependent on the duration of OGD and showed selected biochemical, morphological, and pharmacological features suggestive of apoptosis. OGD also induced the expression of iNOS mRNA and protein in bovine cerebral ECs. Increased expression of nitrotyrosine, the product formed by peroxynitrite reaction with proteins, was also detected after OGD. The involvement of iNOS in EC death was suggested by partial reduction of cell death by NO synthase inhibitors, including l - N G -(1-iminoethyl)ornithine and nitro- l -arginine, and an NO scavenger, the Fe 2+ - N -methyl- d -glucamine dithiocarbamate complex. Conclusions —OGD-induced bovine cerebral EC death involves an apoptotic process. Induction of iNOS with subsequent peroxynitrite formation may contribute to bovine cerebral EC death caused by OGD.

Post-traumatic inflammatory reaction has been implicated in the secondary injury after SCI. TNF-alpha is a key inflammatory mediator, which plays a pathogenetic role in cell death in inflammatory disorders and traumatic brain injury. TNF-alpha exerts its effector actions, at least partially, through the activation of a pro-inflammatory transcription factor, NF-kB, which in turn upregulates such genes as iNOS, cytokines, adhesive molecules, and others. Consistent with a post-traumatic inflammatory reaction after SCI, we noted an increase in TNF-alpha expression by Western blotting (4.5-fold increase at 1 day after SCI, P

Tumor necrosis factor-alpha (TNF-alpha) expression has been documented extensively in animal models of traumatic spinal cord injury (SCI). However, the pathophysiological significance of TNF-alpha expression in the injured cord remains to be delineated. The TNF receptor (TNFR)-nuclear factor-kappaB (NF-kappaB) signal transduction pathway is important for maintaining cell viability. NF-kappaB exerts anti-apoptotic effects via an endogenous caspase inhibitory system mediated by cellular inhibitor of apoptosis protein 2 (c-IAP2). NF-kappaB transactivates c-IAP2 to inhibit caspase-3 activation. Progressive cell death, including morphological and biochemical features suggestive of apoptosis, has been noted after SCI. We explored the effects of TNFR1 or TNFR2 deletion on the apoptotic events downstream of NF-kappaB in relation to SCI pathology and functional recovery. Nuclear proteins from the injured cords of the TNFR1(-/-) mice had a reduced NF-kappaB binding activity compared with the wild-type controls. This decrease in NF-kappaB activation was accompanied by a reduction in c-IAP2 expression and an increase in the active form of caspase-3 protein. After SCI the TNFR1(-/-) mice had greater numbers of apoptotic cells, a larger lesion size, and worse functional recovery than wild-type mice. TNFR2-deficient mice had a similar, although not as pronounced, consequence as the TNFR1(-/-) mice. These findings support the argument that the TNFR-NF-kappaB pathway is beneficial for limiting apoptotic cell death after SCI and that a defective TNFR-NF-kappaB pathway results in a poorer neurological outcome. A worse functional outcome in TNFR(-/-) mice suggests that an endogenous apoptosis inhibitory mechanism mediated by TNFR activation, NF-kappaB, and c-IAP2 may be of pathophysiological importance.