Molecular targets in cerebral ischemia for developing novel therapeutics

Prevention of Cyclophilin D-Mediated mPTP Opening Using Cyclosporine-A Alleviates the Elevation of Necroptosis, Autophagy and Apoptosis-Related Markers Following Global Cerebral Ischemia-Reperfusion

The mitochondrial permeability transition pore (mPTP) is a complex channel of the inner membrane, the opening of which leads to mitochondrial swelling and dissipation of mitochondrial membrane potential (MMP). Here, we aimed to evaluate the role of the cyclophilin D (CypD) as a prominent mediator of mPTP, on necroptosis and autophagy as well as apoptosis, beyond the global cerebral ischemia-reperfusion (I/R) injury. We showed that while cerebral I/R injury is accompanied by loss of MMP, mitochondrial swelling and programmed cell death, pretreatment with cyclosporine-A (CsA) as a potent inhibitor of CypD, led to partial but significant reduction in necroptosis markers, RIP1 and RIP3 as well as activity of glutamate-ammonia ligase (GLUL) and glutamate dehydrogenase 1 (GLUD1), downstream enzymes of RIP3. Administration of CsA also partially decreased autophagy associated proteins. Furthermore, we demonstrated that Bax/Bcl-2 ratio as well as caspase-3 activation, as the executioner of apoptosis, noticeably decreased by CsA pretreatment. Taken together, our results suggest that the CypD alongside the apoptosis regulation plays a partial role in inducing necroptosis and autophagy.

An integrated shotgun proteomics and bioinformatics approach for analysis of brain proteins from MCAO model using serial affinity chromatograph with four active ingredients from Shengmai preparations as ligands

Identification and validation of disease-relevant target proteins for natural products is an essential component of modern pharmaceutical research. In the present study, an integrated shotgun proteomics and bioinformatics approach was established to profile the interaction of active small molecules derived from ShengMai preparations (SMXZF) with hundreds of endogenously expressed proteins from middle cerebral artery occlusion (MCAO) model. Affinity-based proteomic strategies for isolation and identification of targets for the bioactive components is a classic, but still powerful approach. The proteins bound by SMXZF of the brain tissue proteins from MCAO model via serial affinity chromatograph were analyzed by nano liquid chromatography tandem mass spectrometry (nanoLC-MS/MS) and all MS/MS spectra were then automatically searched by the SEQUEST program. A total of 154 proteins had been identified, with the molecular weight ranging from 21,369.6 to 332,393.21 and the pI from 4.32 to 10.88. Bioinformatic analysis was also implemented to better understand the identified proteins. In the gene ontology (GO) annotation, all the identified proteins were classified into 39, 18 and 12 groups according to biological process, cellular component and molecular function, respectively. KEGG pathways analysis of the identified proteins was conducted with 46 corresponding pathways found. In addition, the gene network was also constructed to analyze the relationship of these genes each other. Further validation of some targets were performed in MCAO model by Western blotting. The results indeed supported the notion that proteins MAPK/ERK1/2, CaMKII and VIM were involved in the disease development of MCAO and played an essential role in the protective effect of SMXZF. This study highlights the effectiveness and reliability of this integrated shotgun proteomics and bioinformatics approach, which is a promising paradigm for target identification and elucidating the mechanism of natural products in future research.

Mitochondrial fission and fusion in secondary brain damage after CNS insults

Mitochondria are dynamically active organelles, regulated through fission and fusion events to continuously redistribute them across axons, dendrites, and synapses of neurons to meet bioenergetics requirements and to control various functions, including cell proliferation, calcium buffering, neurotransmission, oxidative stress, and apoptosis. However, following acute or chronic injury to CNS, altered expression and function of proteins that mediate fission and fusion lead to mitochondrial dynamic imbalance. Particularly, if the fission is abnormally increased through pro-fission mediators such as Drp1, mitochondrial function will be impaired and mitochondria will become susceptible to insertion of proapototic proteins. This leads to the formation of mitochondrial transition pore, which eventually triggers apoptosis. Thus, mitochondrial dysfunction is a major promoter of neuronal death and secondary brain damage after an insult. This review discusses the implications of mitochondrial dynamic imbalance in neuronal death after acute and chronic CNS insults.

LncRNA-N1LR Enhances Neuroprotection Against Ischemic Stroke Probably by Inhibiting p53 Phosphorylation

In recent years, long noncoding RNAs (lncRNAs) have been shown to have critical roles in a broad range of cell biological processes. However, the activities of lncRNAs during ischemic stroke remain largely unknown. In this study, we carried out a genome-wide lncRNA microarray analysis in rat brains with ischemia/reperfusion (I/R) injury. The results revealed the differential expression of a subset of lncRNAs. Through the construction of lncRNA-mRNA co-expression networks, we identified lncRNA-N1LR as a novel I/R-induced lncRNA. The functions of lncRNA-N1LR were assessed by silencing and overexpressing this lncRNA in vitro and in vivo. We found that lncRNA-N1LR enhanced cell cycle progression and cell proliferation, and inhibited apoptosis in N2a cells subjected to in vitro ischemia (oxygen-glucose deprivation/reoxygenation, OGD/R). Furthermore, we showed that lncRNA-N1LR reduced neuronal apoptosis and neural cell loss in I/R-induced mouse brains. Mechanistically, we discovered that lncRNA-N1LR promoted neuroprotection probably through the inhibition of p53 phosphorylation on serine 15 in a manner that was independent of its location-associated gene Nck1. In summary, our results indicated that lncRNA-N1LR promoted neuroprotection against ischemic stroke probably by inactivating p53. Thus, we propose that lncRNA-N1LR may serve as a potential target for therapeutic intervention following ischemic brain injury.

Gonadal steroids block the calpain-1-dependent intrinsic pathway of apoptosis in an experimental rat stroke model

OBJECTIVES

Apoptosis plays an important role in the progression of the ischemic penumbra after reperfusion. Estrogen and progesterone have neuroprotective effects against ischemic brain damage, however the exact mechanisms of neuroprotection and signaling pathways is not completely understood. In this study, we investigated the possible regulatory effects of a combined steroid treatment on extrinsic and intrinsic apoptotic signaling pathways after cerebral ischemia.

METHODS

Adult male Wistar rats were subjected to transient middle cerebral artery occlusion (tMCAO) using an intraluminal filament technique for 1 h followed by 23 h reperfusion. Estrogen and progesterone were immediately injected after tMCAO subcutaneously. Sensorimotor functional tests and the infarct volume were evaluated 24 h after ischemia. Protein expression of calpain-1 and Fas receptor (FasR), key members of intrinsic and extrinsic apoptosis, were determined in the penumbra region of the ischemic brain using western blot analysis, immunohistochemistry, and TUNEL staining.

RESULTS

Neurological deficits and infarct volume were significantly reduced following hormone therapy. Calpain-1 up-regulation and caspase-3 activation were apparent 24 h after ischemia in the peri-infarct area of the cerebral cortex. Steroid hormone treatment reduced infarct pathology and attenuated the induction of both proteases. FasR protein levels were not affected by ischemia and hormone application.

CONCLUSION

We conclude that a combined steroid treatment inhibits ischemia-induced neuronal apoptosis through the regulation of intrinsic pathways.

Profiling of Signaling Proteins in Penumbra After Focal Photothrombotic Infarct in the Rat Brain Cortex

In ischemic stroke, cell damage propagates from infarct core to surrounding tissue. To reveal proteins involved in neurodegeneration and neuroprotection, we explored the protein profile in penumbra surrounding the photothrombotic infarct core induced in rat cerebral cortex by local laser irradiation after Bengal Rose administration. Using antibody microarrays, we studied changes in expression of 224 signaling proteins 1, 4, or 24 h after photothrombotic infarct compared with untreated contralateral cortex. Changes in protein expression were greatest at 4 h after photothrombotic impact. These included over-expression of proteins initiating, regulating, or executing various apoptosis stages (caspases, SMAC/DIABLO, Bcl-10, phosphatidylserine receptor (PSR), prostate apoptosis response 4 (Par4), E2F1, p75, p38, JNK, p53, growth arrest and DNA damage inducible protein 153 (GADD153), glutamate decarboxylases (GAD65/67), NMDAR2a, c-myc) and antiapoptotic proteins (Bcl-x, p63, MDM2, p21WAF-1, ERK1/2, ERK5, MAP kinase-activated protein kinase-2 (MAKAPK2), PKCα, PKCβ, PKCμ, RAF1, protein phosphatases 1α and MAP kinase phosphatase-1 (MKP-1), neural precursor cell expressed, developmentally down-regulated 8 (NEDD8), estrogen and EGF receptors, calmodulin, CaMKIIα, CaMKIV, amyloid precursor protein (APP), nicastrin). Phospholipase Cγ1, S-100, and S-100β were down-regulated. Bidirectional changes in levels of adhesion and cytoskeleton proteins were related to destruction and/or remodeling of penumbra. Following proteins regulating actin cytoskeleton were over-expressed: cofilin, actopaxin, p120CTN, α-catenin, p35, myosin Va, and pFAK were up-regulated, whereas ezrin, tropomyosin, spectrin (α + β), β_IV-tubulin and polyglutamated β-tubulin, and cytokeratins 7 and 19 were down-regulated. Down-regulation of syntaxin, AP2β/γ, and adaptin β1/2 indicated impairment of vesicular transport and synaptic processes. Down-regulation of cyclin-dependent kinase 6 (Cdk6), cell division cycle 7-related protein kinase (Cdc7 kinase), telomeric repeat-binding factor 1 (Trf1), and topoisomerase-1 showed proliferation suppression. Cytoprotection proteins AOP-1 and chaperons Hsp70 and Hsp90 were down-regulated. These data provide the integral view on penumbra response to photothrombotic infarct. Some of these proteins may be potential targets for antistroke therapy.

The CORM ALF-186 Mediates Anti-Apoptotic Signaling via an Activation of the p38 MAPK after Ischemia and Reperfusion Injury in Retinal Ganglion Cells

PURPOSE

Ischemia and reperfusion injury may induce apoptosis and lead to sustained tissue damage and loss of function, especially in neuronal organs. While carbon monoxide is known to exert protective effects after various harmful events, the mechanism of carbon monoxide releasing molecules in neuronal tissue has not been investigated yet. We hypothesize that the carbon monoxide releasing molecule (CORM) ALF-186, administered after neuronal ischemia-reperfusion injury (IRI), counteracts retinal apoptosis and its involved signaling pathways and consecutively reduces neuronal tissue damage.

METHODS

IRI was performed in rat´s retinae for 1 hour. The water-soluble CORM ALF-186 (10 mg/kg) was administered intravenously via a tail vein after reperfusion. After 24 and 48 hours, retinal tissue was harvested to analyze mRNA and protein expression of Bcl-2, Bax, Caspase-3, ERK1/2, p38 and JNK. Densities of fluorogold pre-labeled retinal ganglion cells (RGC) were analyzed 7 days after IRI. Immunohistochemistry was performed on retinal cross sections.

RESULTS

ALF-186 significantly reduced IRI mediated loss of RGC. ALF-186 treatment differentially affected mitogen-activated protein kinases (MAPK) phosphorylation: ALF-186 activated p38 and suppressed ERK1/2 phosphorylation, while JNK remained unchanged. Furthermore, ALF-186 treatment affected mitochondrial apoptosis, decreasing pro-apoptotic Bax and Caspase-3-cleavage, but increasing anti-apoptotic Bcl-2. Inhibition of p38-MAPK using SB203580 reduced ALF-186 mediated anti-apoptotic effects.

CONCLUSION

In this study, ALF-186 mediated substantial neuroprotection, affecting intracellular apoptotic signaling, mainly via MAPK p38. CORMs may thus represent a promising therapeutic alternative treating neuronal IRI.

Effects of IL-6 and cortisol fluctuations in post-stroke depression

Depression is an important post-stroke sequela with negative impact on mortality, functional outcome and quality of life. Changes in cytokines have been hypothesized to be associated with the etiology of post-stroke depression (PSD). The altere dhypothalamic-pituitary-adrenal (HPA) functioning is associated with the onset of depression. The activity of HPA could induce the fluctuations of cortisol levels. In this study, we prospectively checked interleukin 6 (IL-6) and cortisol levels in patients with early ischemic stroke. It was hypothesized that early serum IL-6 and cortisol fluctuations in stroke patients were the predictions of PSD. Totally, 100 participants were selected from stroke inpatients consecutively admitted to the Department of Neurology, Tongji Hospital from July 2014 to December 2015. Fifty health people served as the controls. The serum of all the patients was collected at 8:00 am and 4:00 pm respectively one week after stroke. The serum of controls was collected only at 8:00 am. The levels of IL-6 were analyzed by enzyme-linked immunosorbent assay kit, and those of cortisol were detected by chemiluminescence immunoassay. On the 3rd week after stroke, the patients were enrolled to the PSD group and non-PSD group based on the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) and The Hamilton Depression Rating Scale (HAMD-21, score>7). The IL-6 level (13.24±2.89 ng/L) was elevated significantly in PSD groups as compared with that in non-PSD group and control group respectively (P<0.05 for both), but there was no significant difference in the IL-6 level between non-PSD group and control group. The patients in both PSD group and non-PSD group had significantly elevated morning cortisol levels in comparison with those in the control group (P<0.05; for PSD, non-PSD and control: 508.86±119.51, 420.83±70.04 and 340.40±76.30 nmol/L respectively). Moreover, afternoon cortisol levels in PSD group were significantly higher than those in non-PSD group, and the morning baseline cortisol levels in these two groups were similar (P>0.05). It was suggested that PSD generally runs a chronic course and is related to a variety of adverse health outcomes including increased disability, morbidity and mortality. This study will help the screening of potential PSD in the early stage.

Blood/Brain Biomarkers of Inflammation After Stroke and Their Association With Outcome: From C-Reactive Protein to Damage-Associated Molecular Patterns

Stroke represents one of the most important causes of disability and death in developed countries. However, there is a lack of prognostic tools in clinical practice to monitor the neurological condition and predict the final outcome. Blood biomarkers have been proposed and studied in this indication; however, no biomarker is currently used in clinical practice. The stroke-related neuroinflammatory processes have been associated with a poor outcome in stroke, as well as with poststroke complications. In this review, we focus on the most studied blood biomarkers of this inflammatory processes, cytokines, and C-reactive protein, evaluating its association with outcome and complications in stroke through the literature, and performing a systematic review on the association of C-reactive protein and functional outcome after stroke. Globally, we identified uncertainty with regard to the association of the evaluated biomarkers with stroke outcome, with little added value on top of clinical predictors such as age or stroke severity, which makes its implementation unlikely in clinical practice for global outcome prediction. Regarding poststroke complications, despite being more practical scenarios in which to make medical decisions following a biomarker prediction, not many studies have been performed, although there are now some candidates for prediction of poststroke infections. Finally, as potential new candidates, we reviewed the pathophysiological actions of damage-associated molecular patterns as triggers of the neuroinflammatory cascade of stroke, and their possible use as biomarkers.

Gastrodin ameliorates subacute phase cerebral ischemia‑reperfusion injury by inhibiting inflammation and apoptosis in rats

Gastrodin (GAS), which is extracted from the Chinese herbal medicine Gastrodia elata Blume, has long been used to improve stroke, epilepsy, dizziness and dementia. However, the effects and underlying mechanisms of GAS on subacute phase cerebral ischemia-reperfusion (I/R) injury remain unknown. The aim of the present study was to investigate the effects and mechanisms of GAS on cerebral I/R injury in rats. The rats were pretreated with GAS by gavage for 7 days followed by I/R surgery, and were then treated with GAS for 7 days after I/R surgery. Neurological deficits were assessed on days 1, 3 and 7 post-cerebral I/R injury. 2,3,5-Triphenyltetrazolium chloride staining was using to measure the infarct volume; morphological alterations were observed by hematoxylin and eosin staining under an optical microscope; apoptosis in the hippocampus and cortex was observed by terminal deoxynucleotidyl transferase dUTP nick end labeling staining; and the level of mRNA and protein expression was tested by reverse transcription-quantitative polymerase chain reation and western blot analysis, respectively. GAS markedly attenuated I/R-induced disability and histological damage, alleviated neuronal apoptosis, and reduced the mRNA and protein expression levels of inflammatory and proapoptotic factors, including interleukin-1β, cyclooxygenase-2, inducible nitric oxide synthase and cleaved caspase-3. These findings suggested that GAS may ameliorate subacute phase cerebral I/R injury by inhibiting inflammation and apoptosis in rats; therefore, GAS may be considered a potential candidate for the treatment of cerebral ischemia.

Quinolinic acid neurotoxicity: Differential roles of astrocytes and microglia via FGF-2-mediated signaling in redox-linked cytoskeletal changes

QUIN is a glutamate agonist playing a role in the misregulation of the cytoskeleton, which is associated with neurodegeneration in rats. In this study, we focused on microglial activation, FGF2/Erk signaling, gap junctions (GJs), inflammatory parameters and redox imbalance acting on cytoskeletal dynamics of the in QUIN-treated neural cells of rat striatum. FGF-2/Erk signaling was not altered in QUIN-treated primary astrocytes or neurons, however cytoskeleton was disrupted. In co-cultured astrocytes and neurons, QUIN-activated FGF2/Erk signaling prevented the cytoskeleton from remodeling. In mixed cultures (astrocyte, neuron, microglia), QUIN-induced FGF-2 increased level failed to activate Erk and promoted cytoskeletal destabilization. The effects of QUIN in mixed cultures involved redox imbalance upstream of Erk activation. Decreased connexin 43 (Cx43) immunocontent and functional GJs, was also coincident with disruption of the cytoskeleton in primary astrocytes and mixed cultures. We postulate that in interacting astrocytes and neurons the cytoskeleton is preserved against the insult of QUIN by activation of FGF-2/Erk signaling and proper cell-cell interaction through GJs. In mixed cultures, the FGF-2/Erk signaling is blocked by the redox imbalance associated with microglial activation and disturbed cell communication, disrupting the cytoskeleton. Thus, QUIN signal activates differential mechanisms that could stabilize or destabilize the cytoskeleton of striatal astrocytes and neurons in culture, and glial cells play a pivotal role in these responses preserving or disrupting a combination of signaling pathways and cell-cell interactions. Taken together, our findings shed light into the complex role of the active interaction of astrocytes, neurons and microglia in the neurotoxicity of QUIN.

Infiltration of invariant natural killer T cells occur and accelerate brain infarction in permanent ischemic stroke in mice

Invariant natural killer T (iNKT) cells are a unique subset of T cells that have been implicated in inflammation, atopy, autoimmunity, infections, and cancer. Although iNKT cells have been extensively studied over the past decade, its role in the pathogenesis of ischemic brain injury is still largely unknown. In our study, we determined whether iNKT cells infiltration occur in a mouse model of permanent cerebral ischemia. C57BL6/J male mice were treated with either alpha-galactosylceramide (α-GalCer) or vehicle control before undergoing permanent middle cerebral artery occlusion (pMCAO). α-GalCer, a glycolipid antigen, specifically activates iNKT cells by a CD1d-restricted mechanism. Using flow cytometry, 10,000 leukocytes (CD45 high cells) from the ischemic hemisphere and peripheral blood respectively were analyzed to determine the number of NK1.1⁺CD3⁺ cells at 3, 12, 24 and 48h post-pMCAO. Cerebral infarct size, brain edema and morphological characteristics were measured at the stipulated time points by 2,3,5-triphenyltetrazolium chloride (TTC) staining, weighing, and H&E staining. The levels of IFN-γ and TNF-α in brain tissue and serum were assessed by immunohistochemistry and ELISA respectively. We found that the number of iNKT cells started increasing from 12h (PB sample) and 24h (ischemic hemisphere sample) respectively in the vehicle treated group. iNKT cells infiltration occurred at an earlier time-point compared in the α-GalCer treated group (T=3H vs T=12H in PB sample; T=12H vs T=24H in ischemic hemisphere sample). Brain water content at 12h and 24h was significantly higher in pMCAO+α-GalCer mice compared to pMCAO+vehicle mice which was in turn higher than mice that underwent sham surgery. Aggravated morphological abnormalities in HE-stained neurons and significantly increased neurons with pyknotic nuclei and cavitation in the ischemic region were observed at 24h in the pMCAO+α-GalCer and pMCAO+vehicle groups. Cerebral infarct volume, neurological deficit Scores and brain edema were significantly increased at 24h in the pMCAO+α-GalCer group compared to pMCAO+vehicle group. In the pMCAO+vehicle group, the serum concentrations of TNF-α and IFN-γ were increased at 12h and 24h post-pMCAO, and remained elevated up to 48h. In mice treated with pMCAO+α-GalCer, TNF-α and IFN-γ were both increased at 12h post-pMCAO, and remained elevated up to 48h. Immunohistochemistry showed that protein expression of TNF-α and IFN-γ in brain tissues was higher in α-GalCer-treated mice. Our results demonstrate that within 48h of focal permanent cerebral ischemia, iNKT cells infiltrate into the brain and contribute to brain infarction.

G-protein coupled receptors as therapeutic targets for neurodegenerative and cerebrovascular diseases

Neurodegenerative and cerebrovascular diseases are frequent in elderly populations and comprise primarily of dementia (mainly Alzheimer's disease) Parkinson's disease and stroke. These neurological disorders (NDs) occur as a result of neurodegenerative processes and represent one of the most frequent causes of death and disability worldwide with a significant clinical and socio-economic impact. Although NDs have been characterized for many years, the exact molecular mechanisms that govern these pathologies or why they target specific individuals and specific neuronal populations remain unclear. As research progresses, many similarities appear which relate these diseases to one another on a subcellular level. Discovering these similarities offers hope for therapeutic advances that could ameliorate the conditions of many diseases simultaneously. G-protein coupled receptors (GPCRs) are the most abundant receptor type in the central nervous system and are linked to complex downstream pathways, manipulation of which may have therapeutic application in many NDs. This review will highlight the potential use of neurotransmitter GPCRs as emerging therapeutic targets for neurodegenerative and cerebrovascular diseases.

Potential neuroprotection of protodioscin against cerebral ischemia-reperfusion injury in rats through intervening inflammation and apoptosis

The aim of the current research is to investigate the cerebral-protection of protodioscin on a transient cerebral ischemia-reperfusion (I/R) model and to explore its possible underlying mechanisms. The rats were preconditioned with protodioscin at the doses of 25 and 50mgkg(-1) prior to surgery. Then the animals were subjected to right middle cerebral artery occlusion (MCAO) using an intraluminal method by inserting a thread (90min surgery). After the blood flow was restored in 24h via withdrawing the thread, some representative indicators for the cerebral injury were evaluated by various methods including TTC-staining, TUNEL, immunohistochemistry, and Western blotting. As compared with the operated rats without drug intervening, treatment with protodioscin apparently lowered the death rate and improved motor coordination abilities through reducing the deficit scores and cerebral infarct volume. What's more, an apparent decrease in neuron apoptosis detected in hippocampus CA1 and cortex of the ipsilateral hemisphere might attribute to alleviate the increase in Caspase-3 and Bax/Bcl-2 ratio. Meanwhile, concentrations of several main pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in the serum were also significantly suppressed. Finally, the NF-κB and IκBa protein expressions in the cytoplasm of right injured brain were remarkably up-regulated, while NF-κB in nucleus was down-regulated. Therefore, these observed findings demonstrated that protodioscin appeared to reveal potential neuroprotection against the I/R injury due to its anti-inflammatory and anti-apoptosis properties. This therapeutic effect was probably mediated by the inactivation of NF-κB signal pathways.

Synthesis and biological evaluation of novel hydrogen sulfide releasing nicotinic acid derivatives

Twelve novel hybrids of slowly releasing hydrogen sulfide donor ADT-OH combined with nicotinic acid were synthesized. All of their structures had been confirmed by ¹H NMR, ¹³C NMR and MS spectra. The target compounds were evaluated for their neuroprotective effects on hippocampal neuron HT22 cells against glutamate-induced injury at the concentrations of 1-100μM with MTT assay, and their toxicity on HT22 cells untreated by glutamine at the concentration of 100μM. The active compound was further investigated for its effect on ischemic infarct volume by intraperitoneal injection at 3h after ischemia in mice models of permanent middle cerebral artery occlusion (pMCAO). The results showed that all the compounds significantly protected HT22 cells from glutamate-induced damage at most of the experimental concentrations, and had no or little neurotoxicity on normal HT22 cells at the high concentration. More importantly, compound A6 significantly reduced infarct volume in the pMCAO model. These results suggested that compound A6 may be promising for further evaluation for the intervention of cerebral ischemic injury.

Anti-inflammation Effects of Oxysophoridine on Cerebral Ischemia-Reperfusion Injury in Mice

Oxysophoridine (OSR) is a bioactive alkaloid extracted from the Sophora alopecuroides Linn. Our aim is to explore the potential anti-inflammation mechanism of OSR in cerebral ischemic injury. Mice were intraperitoneally pretreated with OSR (62.5, 125, and 250 mg/kg) or nimodipine (Nim) (6 mg/kg) for 7 days followed by cerebral ischemia. The inflammatory-related cytokines in cerebral ischemic hemisphere tissue were determined by immunohistochemistry staining, Western blot and enzyme-like immunosorbent assay (ELISA). OSR-treated groups observably suppressed the nuclear factor kappa B (NF-κB), intercellular adhesion molecule-1 (ICAM-1), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2). OSR-treated group (250 mg/kg) markedly reduced the inflammatory-related protein prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-8 (IL-8). Meanwhile, it dramatically increased the interleukin-10 (IL-10). Our study revealed that OSR protected neurons from ischemia-induced injury in mice by downregulating the proinflammatory cytokines and blocking the NF-κB pathway.

The Isotropic Fractionator as a Tool for Quantitative Analysis in Central Nervous System Diseases

One major aim in quantitative and translational neuroscience is to achieve a precise and fast neuronal counting method to work on high throughput scale to obtain reliable results. Here, we tested the isotropic fractionator (IF) method for evaluating neuronal and non-neuronal cell loss in different models of central nervous system (CNS) pathologies. Sprague-Dawley rats underwent: (i) ischemic brain damage; (ii) intraperitoneal injection with kainic acid (KA) to induce epileptic seizures; and (iii) monolateral striatal injection with quinolinic acid (QA) mimicking human Huntington's disease. All specimens were processed for IF method and cell loss assessed. Hippocampus from KA-treated rats and striatum from QA-treated rats were carefully dissected using a dissection microscope and a rat brain matrix. Ischemic rat brains slices were first processed for TTC staining and then for IF. In the ischemic group the cell loss corresponded to the neuronal loss suggesting that hypoxia primarily affects neurons. Combining IF with TTC staining we could correlate the volume of lesion to the neuronal loss; by IF, we could assess that neuronal loss also occurs contralaterally to the ischemic side. In the epileptic group we observed a reduction of neuronal cells in treated rats, but also evaluated the changes in the number of non-neuronal cells in response to the hippocampal damage. In the QA model, there was a robust reduction of neuronal cells on ipsilateral striatum. This neuronal cell loss was not related to a drastic change in the total number of cells, being overcome by the increase in non-neuronal cells, thus suggesting that excitotoxic damage in the striatum strongly activates inflammation and glial proliferation. We concluded that the IF method could represent a simple and reliable quantitative technique to evaluate the effects of experimental lesions mimicking human diseases, and to consider the neuroprotective/anti-inflammatory effects of different treatments in the whole brain and also in discrete regions of interest, with the potential to investigate non-neuronal alterations. Moreover, IF could be used in addition or in substitution to classical stereological techniques or TTC staining used so far, since it is fast, precise and easily combined with complex molecular analysis.

A possible therapeutic potential of quercetin through inhibition of μ-calpain in hypoxia induced neuronal injury: a molecular dynamics simulation study

The neuroprotective property of quercetin is well reported against hypoxia and ischemia in past studies. This property of quercetin lies in its antioxidant property with blood-brain barrier permeability and anti-inflammatory capabilities. µ-Calpain, a calcium ion activated intracellular cysteine protease causes serious cellular insult, leading to cell death in various pathological conditions including hypoxia and ischemic stroke. Hence, it may be considered as a potential drug target for the treatment of hypoxia induced neuronal injury. As the inhibitory property of µ-calpain is yet to be explored in details, hence, in the present study, we investigated the interaction of quercetin with µ-calpain through a molecular dynamics simulation study as a tool through clarifying the molecular mechanism of such inhibition and determining the probable sites and modes of quercetin interaction with the µ-calpain catalytic domain. In addition, we also investigated the structure-activity relationship of quercetin with μ-calpain. Affinity binding of quercetin with µ-calpain had a value of -28.73 kJ/mol and a Ki value of 35.87 µM that may be a probable reason to lead to altered functioning of µ-calpain. Hence, quercetin was found to be an inhibitor of µ-calpain which might have a possible therapeutic role in hypoxic injury.

Neuroprotective effects of Danggui-Jakyak-San on rat stroke model through antioxidant/antiapoptotic pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Dangui-Jakyak-San (DJ) is a traditional Korean medicinal polyherb, prescribed typically in patients with insufficient blood supply in Eastern Asia. The DJ also has been reported to have neuroprotective effects in vitro and in vivo studies.

AIM OF STUDY

The therapeutic potential of DJ was examined in stroke rat model, in comparison with donepezil, a reversible acetylcholinesterase inhibitor.

MATERIALS AND METHODS

Ischemic stroke rat model was induced by surgery of permanent occlusion of middle cerebral artery (pMCAO). The model was orally administered with distilled water (pMCAO control), donepezil at 10mg/kg (Donepezil) and DJ at 200, 100 and 50mg/kg (DJ 200, DJ 100 and DJ 50, respectively). Sham had the same surgery excepting for the pMCAO, and it was administered with distilled water (sham control).

RESULTS

After the administration for 28 days, the groups of DJ exhibited dose-dependent reduction in infarct/defect volumes with improvement in sensorimotor and cognitive motor function, comparing to pMCAO control. The DJ treatments seemed to enhance antiapoptotic and antioxidant effects; increases in antiapoptotic expressions (STAT3 and Pim-1) and decreases in lipid peroxidation (MDA) together with increases in contents of endogenous antioxidant (GSH) and activities of antioxidant enzymes (catalase and SOD). The histopathological analyses revealed significant reduction in neuronal apoptosis (caspase-3 and PARP) and neuronal degradation with atrophy and degeneration, in the DJ treatments. Furthermore, the oxidative stresses (nitrotyrosine as an iNOS factor and 4-HNE as a marker of lipid peroxidation) were observed mild. Although the similar neuroprotective effects were observed, the body weight loss was scarcely alleviated in Donepezil comparing to pMCAO control.

CONCLUSION

These suggest that DJ ameliorate the neurological dysfunction of cerebral ischemia through augmentation of antioxidant defense system and up-regulation of STAT3 and Pim-1.

Expression of the Endocannabinoid Receptor 1 in Human Stroke: An Autoptic Study

OBJECTIVE

Stroke is one of the leading causes of disability and death in the world. The endocannabinoid (eCB) system is upregulated in several neurological diseases including stroke. A previous animal study demonstrated an increased expression of the endocannabinoid receptor 1 (CB1R) in the penumbra area surrounding the ischemic core, suggesting a crucial role in inflammation/reperfusion after stroke. Regarding the localization of CB1/CB2 receptors, animal studies showed that cortical neurons, activated microglia, and astroglia are involved. Our aim was to evaluate the cerebral expression of CB1R in the ischemic brain areas of 9 patients who died due to acute cerebral infarction in the middle cerebral artery territory.

METHODS

The cerebral autoptic tissue was collected within 48 hours since death. Ischemic and contralateral normal-appearing areas were identified. After tissue preprocessing, 4-µm-thick cerebral sections were incubated with the primary CB1R antibodies (Cayman Chemical Company, Ann Arbor, MI). Thereafter, all cerebral sections were hematoxylin treated. In each section, the total cell number and CB1R-positive cells were counted and the CB1R-positive cell count ratio was calculated. For statistical analysis, Student's t-test was used.

RESULTS

In normal tissue, CB1R-positive neurons were the majority; a few non-neuronal cells expressed CB1R. In the ischemic areas, a few neurons were detectable. A significant increase in total CB1R staining was found in the ischemic regions compared to contralateral areas.

CONCLUSIONS

We found an increase in CB1R expression in the ischemic region (neuronal and non-neuronal cell staining), suggesting the inflammatory reaction to the ischemic insult. Whether such response might mediate neuroprotective actions or excitotoxicity-related detrimental effects is still unclear.

Tissue Kallikrein Alleviates Cerebral Ischemia-Reperfusion Injury by Activating the B2R-ERK1/2-CREB-Bcl-2 Signaling Pathway in Diabetic Rats

Diabetes mellitus (DM) substantially increases the risk of ischemic stroke and reduces the tolerance to ischemic insults. Tissue kallikrein (TK) has been demonstrated to protect neurons from ischemia/reperfusion (I/R) injury in orthoglycemic model by activating the bradykinin B2 receptor (B2R). Considering the differential effects of B2R or bradykinin B1 receptor (B1R) on cardioprotection and neuroprotection in I/R with or without diabetes, this study was designed to investigate the role of TK during cerebral I/R injury in streptozotocin-induced diabetic rats. Intravenous injection of TK inhibited apoptosis in neurons, alleviated edema and inflammatory reactions after focal cerebral I/R, significantly reduced the infarct volume, and improved functional recovery. These beneficial effects were accompanied by activation of the extracellular signal-regulated kinase 1/2 (ERK1/2), cAMP response element-binding (CREB), and Bcl-2 signal proteins. Inhibition of the B2R or ERK1/2 pathway abated the effects of TK, whereas an antagonist of B1R enhanced the effects. These findings reveal that the neuroprotective effect of TK against cerebral I/R injury in streptozotocin-induced diabetic rats mainly involves the enhancement of B2R and ERK1/2-CREB-Bcl-2 signaling pathway activity.

The interplay of microRNAs and post-ischemic glutamate excitotoxicity: an emergent research field in stroke medicine

Stroke is the second leading cause of death and the most common cause of adult disabilities among elderlies. It involves a complex series of mechanisms among which, excitotoxicity is of great importance. Also, miRNAs appear to play role in post-stroke excitotoxicity, and changes in their transcriptome occur right after cerebral ischemia. Recent data indicate that specific miRNAs such as miRNA-223, miRNA-181, miRNA-125a, miRNA-125b, miRNA-1000, miRNA-132 and miRNA-124a regulate glutamate neurotransmission and excitotoxicity during stroke. However, limitations such as poor in vivo stability, side effects and inappropriate biodistribution in miRNA-based therapies still exist and should be overcome before clinical application. Thence, investigation of the effect of application of these miRNAs after the onset of ischemia is a pivotal step for manipulating these miRNAs in clinical use. Given this, present review concentrates on miRNAs roles in post-ischemic stroke excitotoxicity.

Protein Profile and Morphological Alterations in Penumbra after Focal Photothrombotic Infarction in the Rat Cerebral Cortex

After ischemic stroke, cell damage propagates from infarct core to surrounding tissues (penumbra). To reveal proteins involved in neurodegeneration and neuroprotection in penumbra, we studied protein expression changes in 2-mm ring around the core of photothrombotic infarct induced in the rat brain cortex by local laser irradiation after administration of Bengal Rose. The ultrastructural study showed edema and degeneration of neurons, glia, and capillaries. Morphological changes gradually decreased across the penumbra. Using the antibody microarrays, we studied changes in expression of >200 neuronal proteins in penumbra 4 or 24 h after focal photothrombotic infarct. Diverse cellular subsystems were involved in the penumbra tissue response: signal transduction pathways such as protein kinase Bα/GSK-3, protein kinase C and its β1 and β2 isoforms, Wnt/β-catenin (axin1, GSK-3, FRAT1), Notch/NUMB, DYRK1A, TDP43; mitochondria quality control (Pink1, parkin, HtrA2); ubiquitin-mediated proteolysis (ubiquilin-1, UCHL1); axon outgrowth and guidance (NAV-3, CRMP2, PKCβ2); vesicular trafficking (syntaxin-8, TMP21, Munc-18-3, synip, ALS2, VILIP1, syntaxin, synaptophysin, synaptotagmin); biosynthesis of neuromediators (tryptophan hydroxylase, monoamine oxidase B, glutamate decarboxylase, tyrosine hydroxylase, DOPA decarboxylase, dopamine transporter); intercellular interactions (N-cadherin, PMP22); cytoskeleton (neurofilament 68, neurofilament-M, doublecortin); and other proteins (LRP1, prion protein, β-amyloid). These proteins are involved in neurodegeneration or neuroprotection. Such changes were most expressed 4 h after photothrombotic impact. Immunohistochemical and Western blot studies of expression of monoamine oxidase B, UCHL1, DYRK1A, and Munc-18-3 confirmed the proteomic data. These data provide the integral view on the penumbra response to photothrombotic infarct. Some of these proteins can be potential targets for ischemic stroke therapy.

Angiogenesis in Ischemic Stroke and Angiogenic Effects of Chinese Herbal Medicine

Stroke is one of the major causes of death and adult disability worldwide. The underlying pathophysiology of stroke is highly complicated, consisting of impairments of multiple signalling pathways, and numerous pathological processes such as acidosis, glutamate excitotoxicity, calcium overload, cerebral inflammation and reactive oxygen species (ROS) generation. The current treatment for ischemic stroke is limited to thromolytics such as recombinant tissue plasminogen activator (tPA). tPA has a very narrow therapeutic window, making it suitable to only a minority of stroke patients. Hence, there is great urgency to develop new therapies that can protect brain tissue from ischemic damage. Recent studies have shown that new vessel formation after stroke not only replenishes blood flow to the ischemic area of the brain, but also promotes neurogenesis and improves neurological functions in both animal models and patients. Therefore, drugs that can promote angiogenesis after ischemic stroke can provide therapeutic benefits in stroke management. In this regard, Chinese herbal medicine (CHM) has a long history in treating stroke and the associated diseases. A number of studies have demonstrated the pro-angiogenic effects of various Chinese herbs and herbal formulations in both in vitro and in vivo settings. In this article, we present a comprehensive review of the current knowledge on angiogenesis in the context of ischemic stroke and discuss the potential use of CHM in stroke management through modulation of angiogenesis.

Inhibition of regulated cell death by cell-penetrating peptides

Development of the means to efficiently and continuously renew missing and non-functional proteins in diseased cells remains a major goal in modern molecular medicine. While gene therapy has the potential to achieve this, substantial obstacles must be overcome before clinical application can be considered. A promising alternative approach is the direct delivery of non-permeant active biomolecules, such as oligonucleotides, peptides and proteins, to the affected cells with the purpose of ameliorating an advanced disease process. In addition to receptor-mediated endocytosis, cell-penetrating peptides are widely used as vectors for rapid translocation of conjugated molecules across cell membranes into intracellular compartments and the delivery of these therapeutic molecules is generally referred to as novel prospective protein therapy. As a broad coverage of the enormous amount of published data in this field is unrewarding, this review will provide a brief, focused overview of the technology and a summary of recent studies of the most commonly used protein transduction domains and their potential as therapeutic agents for the treatment of cellular damage and the prevention of regulated cell death.

The reciprocal interaction of sympathetic nervous system and cAMP-PKA-NF-kB pathway in immune suppression after experimental stroke

BACKGROUND

Sympathetic nervous system(SNS) is involved in the mechanism of immune suppression after stroke. Furthermore, as the pro-inflammatory effect of nuclear factor kappa B(NF-kB) is inhibited after stroke, which is regulated by cyclic adenosine monophosphate(cAMP) and proteinkinase A(PKA). The cAMP-PKA-NF-kB pathway might play an important role in noradrenergic-mediated immune dysfunction.

AIM

The purpose of our research is to analyze how SNS interfere with the immune system after acute stroke and the underlying mechanism of cAMP-PKA-NF-kB pathway in regulating the inflammation.

METHODS

32 healthy male Sprague-Dawley rats were divided into 4 groups equally and randomly (1) Sham operation group; (2) middle cerebral artery occlusion; (MCAO) control group; (3) propranolol MCAO group; (4) isopropylarterenol sham group. 72h later after MCAO or sham operation, tumor necrosis factor-α(TNF-α)and interleukine-10(IL-10) in serum as well as cAMP, PKA and NF-kB in spleen cells were tested.

RESULTS

TNF-α decreased while IL-10 increased in serum after acute ischemia stroke (p<0.05). Meanwhile, the levels of cAMP and PKA in spleen both increased in MCAO model while the expression of NF-kB was inhibited (p<0.05). When propranolol was used to inhibit SNS, all of the results reversed (p<0.05). But the reversed results were still significantly different from the sham operation group (p<0.05). Isopropylarterenol administrated rats appeared the same trend as MCAO group when compared to the sham operation group (p<0.05). However, the differences still existed (p<0.05).

CONCLUSION

On account of the SNS activation after stroke, epinephrine activates the expression of cAMP, which further increases the level of PKA. Therefore, the level of nuclear factor NF-kB is down-regulated. Since the pro-inflammatory effect of NF-kB slacked, the immune system may be inhibited after stroke.

The importance of the excitatory amino acid transporter 3 (EAAT3)

The neuronal excitatory amino acid transporter 3 (EAAT3) is fairly ubiquitously expressed in the brain, though it does not necessarily maintain the same function everywhere. It is important in maintaining low local concentrations of glutamate, where its predominant post-synaptic localization can buffer nearby glutamate receptors and modulate excitatory neurotransmission and synaptic plasticity. It is also the main neuronal cysteine uptake system acting as the rate-limiting factor for the synthesis of glutathione, a potent antioxidant, in EAAT3 expressing neurons, while on GABAergic neurons, it is important in supplying glutamate as a precursor for GABA synthesis. Several diseases implicate EAAT3, and modulation of this transporter could prove a useful therapeutic approach. Regulation of EAAT3 could be targeted at several points for functional modulation, including the level of transcription, trafficking and direct pharmacological modulation, and indeed, compounds and experimental treatments have been identified that regulate EAAT3 function at different stages, which together with observations of EAAT3 regulation in patients is giving us insight into the endogenous function of this transporter, as well as the consequences of altered function. This review summarizes work done on elucidating the role and regulation of EAAT3.

Phytochemicals in Ischemic Stroke

Stroke is the second foremost cause of mortality worldwide and a major cause of long-term disability. Due to changes in lifestyle and an aging population, the incidence of stroke continues to increase and stroke mortality predicted to exceed 12 % by the year 2030. However, the development of pharmacological treatments for stroke has failed to progress much in over 20 years since the introduction of the thrombolytic drug, recombinant tissue plasminogen activator. These alarming circumstances caused many research groups to search for alternative treatments in the form of neuroprotectants. Here, we consider the potential use of phytochemicals in the treatment of stroke. Their historical use in traditional medicine and their excellent safety profile make phytochemicals attractive for the development of therapeutics in human diseases. Emerging findings suggest that some phytochemicals have the ability to target multiple pathophysiological processes involved in stroke including oxidative stress, inflammation and apoptotic cell death. Furthermore, epidemiological studies suggest that the consumption of plant sources rich in phytochemicals may reduce stroke risk, and so reinforce the possibility of developing preventative or neuroprotectant therapies for stroke. In this review, we describe results of preclinical studies that demonstrate beneficial effects of phytochemicals in experimental models relevant to stroke pathogenesis, and we consider their possible mechanisms of action.

Clinacanthus nutans Protects Cortical Neurons Against Hypoxia-Induced Toxicity by Downregulating HDAC1/6

Many population-based epidemiological studies have unveiled an inverse correlation between intake of herbal plants and incidence of stroke. C. nutans is a traditional herbal medicine widely used for snake bite, viral infection and cancer in Asian countries. However, its role in protecting stroke damage remains to be studied. Despite of growing evidence to support epigenetic regulation in the pathogenesis and recovery of stroke, a clear understanding of the underlying molecular mechanisms is still lacking. In the present study, primary cortical neurons were subjected to in vitro oxygen-glucose deprivation (OGD)-reoxygenation and hypoxic neuronal death was used to investigate the interaction between C. nutans and histone deacetylases (HDACs). Using pharmacological agents (HDAC inhibitor/activator), loss-of-function (HDAC siRNA) and gain-of-function (HDAC plasmid) approaches, we demonstrated an early induction of HDAC1/2/3/8 and HDAC6 in neurons after OGD insult. C. nutans extract selectively inhibited HDAC1 and HDAC6 expression and attenuated neuronal death. Results of reporter analysis further revealed that C. nutans suppressed HDAC1 and HDAC6 transcription. Besides ameliorating neuronal death, C. nutans also protected astrocytes and endothelial cells from hypoxic-induced cell death. In summary, results support ability for C. nutans to suppress post-hypoxic HDACs activation and mitigate against OGD-induced neuronal death. This study further opens a new avenue for the use of herbal medicines to regulate epigenetic control of brain injury.

Ubisol-Q10 Prevents Glutamate-Induced Cell Death by Blocking Mitochondrial Fragmentation and Permeability Transition Pore Opening

Mitochondrial dysfunction and oxidative stress are the major events that lead to the formation of mitochondrial permeability transition pore (mPTP) during glutamate-induced cytotoxicity and cell death. Coenzyme Q10 (CoQ10) has widely been used for the treatment of mitochondrial disorders and neurodegenerative diseases. Comparing to traditional lipid-soluble CoQ10, water soluble CoQ10 (Ubisol-Q10) has high intracellular and intra-mitochondrial distribution. The aims of the present study are to determine the neuroprotective effects of Ubisol-Q10 on glutamate-induced cell death and to explore its functional mechanisms. HT22 neuronal cells were exposed to glutamate. Cell viability was measured and mitochondrial fragmentation was assessed by mitochondrial imaging. The mPTP opening was determined by mitochondrial membrane potential and calcium retention capacity. The results revealed that the anti-glutamate toxicity effects of Ubisol-Q10 was associated with its ability to block mitochondrial fragmentation, to maintain calcium retention capacity and mitochondrial membrane potential, and to prevent mPTP formation, AIF release, and DNA fragmentation. We concluded that Ubisol-Q10 protects cells from glutamate toxicity by preserving the integrity of mitochondrial structure and function. Therefore, adequate CoQ10 supplementation may be beneficial in preventing cerebral stroke and other disorders that involve mitochondrial dysfunction.

Hydroxysafflor Yellow A Protects Neurons From Excitotoxic Death through Inhibition of NMDARs

Excessive glutamate release causes overactivation of N-methyl d-aspartate receptors (NMDARs), leading to excitatory neuronal damage in cerebral ischemia. Hydroxysafflor yellow A (HSYA), a compound extracted from Carthamus tinctorius L., has been reported to exert a neuroprotective effect in many pathological conditions, including brain ischemia. However, the underlying mechanism of HSYA's effect on neurons remains elusive. In the present study, we conducted experiments using patch-clamp recording of mouse hippocampal slices. In addition, we performed Ca²⁺ imaging, Western blots, as well as mitochondrial-targeted circularly permuted yellow fluorescent protein transfection into cultured hippocampal neurons in order to decipher the physiological mechanism underlying HSYA's neuroprotective effect.

Through the electrophysiology experiments, we found that HSYA inhibited NMDAR-mediated excitatory postsynaptic currents without affecting α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor and γ-aminobutyric acid A-type receptor-mediated currents. This inhibitory effect of HSYA on NMDARs was concentration dependent. HSYA did not show any preferential inhibition of either N-methyl d-aspartate receptor subtype 2A- or N-methyl d-aspartate receptor subtype 2B- subunit-containing NMDARs. Additionally, HSYA exhibits a facilitatory effect on paired NMDAR-mediated excitatory postsynaptic currents. Furthermore, HSYA reduced the magnitude of NMDAR-mediated membrane depolarization currents evoked by oxygen-glucose deprivation, and suppressed oxygen-glucose deprivation–induced and NMDAR-dependent ischemic long-term potentiation, which is believed to cause severe reperfusion damage after ischemia. Through the molecular biology experiments, we found that HSYA inhibited the NMDA-induced and NMDAR-mediated intracellular Ca²⁺ concentration increase in hippocampal cultures, reduced apoptotic and necrotic cell deaths, and prevented mitochondrial damage. Together, our data demonstrate for the first time that HSYA protects hippocampal neurons from excitotoxic damage through the inhibition of NMDARs. This novel finding indicates that HSYA may be a promising pharmacological candidate for the treatment of brain ischemia.

Bryonolic Acid, a Triterpenoid, Protect Against N-methyl-d-Aspartate-Induced Neurotoxicity in PC12 Cells

Calcium overload is considered to be one of the mechanisms of cerebral ischemia. Ca(2+) influx and Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and cAMP response element-binding protein (CREB) phosphorylation are considered to be involved in N-Methyl-d-aspartate (NMDA)-induced apoptosis process. This study investigated the neuroprotective effects of bryonolic acid (BA) in an NMDA-induced rat adrenal pheochromocytoma cell line (PC12) cells and the potential mechanism. PC12 was treated by NMDA to establish an excitotoxicity model. BA (110,100 and 1000 μM final concentration) was added to the medium 24 h prior to the addition of NMDA. Subsequently, a methyl thiazolyl tetrazolium (MTT) assay and a lactate dehydrogenase (LDH) release were performed. Ca(2+) concentration was demonstrated using a scanning-dual wavelength fluorimetric method. In addition, protein and mRNA levels were determined via Western blot and real-time PCR. In the presence of BA, MTT assay and LDH assay showed that more cells were viable in comparison with the NMDA group. Moreover, the concentration of Ca(2+) decreased with the addition of BA in culture. Furthermore, BA could upregulate protein expressions of Bcl-2, p-CREB, and p-CaMKII and downregulate protein expression of Bax. The mRNA results showed that the pattern of mRNA expression were similar to their respective protein levels. All these results indicate that BA protected PC12 cells against NMDA-induced apoptosis by inhibiting Ca(2+) influx and regulating gene expression in the Ca(2+)-CaMKII-CREB signal pathway. Therefore, the present study supports the notion that BA may be a promising neuroprotective agent for the treatment of cerebral ischemia disease.

A novel dual NO-donating oxime and c-Jun N-terminal kinase inhibitor protects against cerebral ischemia-reperfusion injury in mice

The c-Jun N-terminal kinase (JNK) has been shown to be an important regulator of neuronal cell death. Previously, we synthesized the sodium salt of 11H-indeno[1,2-b]quinoxalin-11-one (IQ-1S) and demonstrated that it was a high-affinity inhibitor of the JNK family. In the present work, we found that IQ-1S could release nitric oxide (NO) during its enzymatic metabolism by liver microsomes. Moreover, serum nitrite/nitrate concentration in mice increased after intraperitoneal injection of IQ-1S. Because of these dual actions as JNK inhibitor and NO-donor, the therapeutic potential of IQ-1S was evaluated in an animal stroke model. We subjected wild-type C57BL6 mice to focal ischemia (30min) with subsequent reperfusion (48h). Mice were treated with IQ-1S (25mg/kg) suspended in 10% solutol or with vehicle alone 30min before and 24h after middle cerebral artery (MCA) occlusion (MCAO). Using laser-Doppler flowmetry, we monitored cerebral blood flow (CBF) above the MCA during 30min of MCAO provoked by a filament and during the first 30min of subsequent reperfusion. In mice treated with IQ-1S, ischemic and reperfusion values of CBF were not different from vehicle-treated mice. However, IQ-1S treated mice demonstrated markedly reduced neurological deficit and infarct volumes as compared with vehicle-treated mice after 48h of reperfusion. Our results indicate that the novel JNK inhibitor releases NO during its oxidoreductive bioconversion and improves stroke outcome in a mouse model of cerebral reperfusion. We conclude that IQ-1S is a promising dual functional agent for the treatment of cerebral ischemia and reperfusion injury.

The Role of Monocytes in Ischemic Stroke Pathobiology: New Avenues to Explore

Ischemic stroke accounts for the majority of stroke cases and constitutes a major cause of death and disability in the industrialized world. Inflammation has been reported to constitute a major component of ischemic stroke pathobiology. In the acute phase of ischemic stroke, microglia, the resident macrophages of the brain, are activated, followed by several infiltration waves of different circulating immune cells into the brain. Among these circulating immune cells, monocytes have been shown to play a particularly important role. Following their infiltration, monocytes differentiate into potent phagocytic cells, the monocyte-derived macrophages (MDMs), in the ischemic brain. Initially, the presence of these cells was considered as marker of an exacerbated inflammatory response that contributes to brain damage. However, the recent reports are suggesting a more complex and multiphasic roles of these cells in ischemic stroke pathobiology. Monocytes constitute a heterogeneous group of cells, which comprises two major subsets in rodent and three major subsets in human. In both species, two equivalent subsets exist, the pro-inflammatory subset and the anti-inflammatory subset. Recent data have demonstrated that ischemic stroke differentially regulate monocyte subsets, which directly affect ischemic stroke pathobiology and may have direct implications in ischemic stroke therapies. Here, we review the recent findings that addressed the role of different monocyte subsets in ischemic stroke pathobiology, and the implications on therapies.

A beacon of hope in stroke therapy-Blockade of pathologically activated cellular events in excitotoxic neuronal death as potential neuroprotective strategies

Excitotoxicity, a pathological process caused by over-stimulation of ionotropic glutamate receptors, is a major cause of neuronal loss in acute and chronic neurological conditions such as ischaemic stroke, Alzheimer's and Huntington's diseases. Effective neuroprotective drugs to reduce excitotoxic neuronal loss in patients suffering from these neurological conditions are urgently needed. One avenue to achieve this goal is to clearly define the intracellular events mediating the neurotoxic signals originating from the over-stimulated glutamate receptors in neurons. In this review, we first focus on the key cellular events directing neuronal death but not involved in normal physiological processes in the neurotoxic signalling pathways. These events, referred to as pathologically activated events, are potential targets for the development of neuroprotectant therapeutics. Inhibitors blocking some of the known pathologically activated cellular events have been proven to be effective in reducing stroke-induced brain damage in animal models. Notable examples are inhibitors suppressing the ion channel activity of neurotoxic glutamate receptors and those disrupting interactions of specific cellular proteins occurring only in neurons undergoing excitotoxic cell death. Among them, Tat-NR2B9c and memantine are clinically effective in reducing brain damage caused by some acute and chronic neurological conditions. Our second focus is evaluation of the suitability of the other inhibitors for use as neuroprotective therapeutics. We also discuss the experimental approaches suitable for bridging our knowledge gap in our current understanding of the excitotoxic signalling mechanism in neurons and discovery of new pathologically activated cellular events as potential targets for neuroprotection.

Novel RIPK3 inhibitors discovered through a structure-based approach exert post-ischemic neuroprotection

Necroptosis or programmed necrosis is evident in various neurological disorders such as ischemic stroke. Receptor interacting serine/threonine protein kinase 3 (RIPK3) is one of the crucial targets of necroptosis and inhibition of this protein exerts neuroprotection. However, knowledge regarding the three-dimensional structure and binding site information of this protein is lacking. In the present study, structure-based in silico methods were implemented to identify the key amino acids in the RIPK3 binding site that might be responsible for ligand interactions. Further, novel RIPK3 inhibitors were identified through a dual ensemble screening strategy. Three inhibitors exhibited binding to RIPK3 in micromolar concentrations and exerted post-ischemic neuroprotection in vitro.

Hippocampus and cerebral cortex present a different autophagic response after oxygen and glucose deprivation in an ex vivo rat brain slice model

AIMS

To evaluate the neuroprotective role of autophagy in the cerebral cortex and hippocampus using an ex vivo animal model of stroke in brain slices.

METHODS

Brain slices were maintained for 30 min in oxygen and glucose deprivation (OGD) followed by 3 h in normoxic conditions to simulate the reperfusion that follows ischaemia in vivo (RL, reperfusion-like). Phagophore formation (Beclin 1 and LC3B) as well as autophagy flux (p62/SQSTM1, Atg5, Atg7 and polyubiquitin) markers were quantified by Western blot and/or qPCR. The release of lactate dehydrogenase (LDH) and glutamate in the medium was used as a measure of the mortality in the absence and in the presence of the autophagy inhibitor 3-methyladenine.

RESULTS

Striking differences in the autophagy markers were observed between the hippocampus and cerebral cortex in normoxic conditions. OGD/RL induced increases both in the phagophore formation and in the autophagy flux in the first three hours in the cerebral cortex that were not observed in the hippocampus. The blocking of autophagy increased the OGD/RL-induced mortality, increased the glutamate release in both the cerebral cortex and hippocampus and abolished the OGD-induced decrease in the polyubiquitinated proteins in the cerebral cortex.

CONCLUSIONS

We conclude that OGD induces a rapid autophagic response in the cerebral cortex that plays a neuroprotective role. Polyubiquitination levels and control of the glutamate release appear to be involved in the neuroprotective role of autophagy.

NADPH Oxidase: A Potential Target for Treatment of Stroke

Stroke is the third leading cause of death in industrialized nations. Oxidative stress is involved in the pathogenesis of stroke, and excessive generation of reactive oxygen species (ROS) by mitochondria is thought to be the main cause of oxidative stress. NADPH oxidase (NOX) enzymes have recently been identified and studied as important producers of ROS in brain tissues after stroke. Several reports have shown that knockout or deletion of NOX exerts a neuroprotective effect in three major experimental stroke models. Recent studies also confirmed that NOX inhibitors ameliorate brain injury and improve neurological outcome after stroke. However, the physiological and pathophysiological roles of NOX enzymes in the central nervous system (CNS) are not known well. In this review, we provide a comprehensive summary of our current understanding about expression and physiological function of NOX enzymes in the CNS and its pathophysiological roles in the three major types of stroke: ischemic stroke, intracerebral hemorrhage, and subarachnoid hemorrhage.

Rosiglitazone ameliorates astrocyte over-activation and inflammatory cytokine release induced by global cerebral ischemia/reperfusion

Global cerebral ischemia (GCI) is a leading cause of mortality worldwide and remains the primary cause of long-term neurological disability. Astrocyte over-activation and extensive neuron loss in the ischemic brain are the characteristic pathological features of cerebral ischemia. Rosiglitazone (RSG) is a peroxisome-proliferating activating receptor-γ agonist known for its anti-inflammatory activity. Previous studies have suggested that RSG is able to exert neuroprotection in numerous acute and chronic brain injury models. However, whether RSG treatment is involved in astrocyte over-activation and inflammatory reaction in the cortex remains unclear. The aim of the present study was to investigate whether RSG treatment improved functional impairment induced following GCI and protected against cortex neuron loss, and to elucidate the potential mechanisms underlying these functions. Rats were randomly divided into three groups: Sham-operated, GCI and RSG treatment groups. The RSG treatment group was treated with 2 mg/kg RSG immediately following GCI. The results demonstrated that RSG treatment significantly reduced infarct volume and neuron survival rates in addition to increasing function recovery. Furthermore, these results correlate with a reduction in astrocyte over-activation and inflammatory cytokines in the rat cortex. However, no significant changes in glutamate transporter-1 expression levels were observed following RSG treatment compared with the GCI rats. The results of this investigation provide in vivo evidence that RSG significantly protected rats against ischemia-reperfusion-induced brain injury. In addition, RSG may exert neuroprotective effects by inhibiting astrocyte over-activation, and thereby reducing the levels of inflammatory cytokines in the GCI-injured brain. All data revealed that RSG may be a potential neuroprotective agent for cerebral ischemia.

High-Glucose-Derived Oxidative Stress-Dependent Heme Oxygenase-1 Expression from Astrocytes Contributes to the Neuronal Apoptosis

An elevated level of glucose has been found in the blood of hyperglycemia and diabetes patients associated with several central nervous system (CNS) complications. These disorders may be due to the up-regulation of many neurotoxic mediators by host cells triggered by high glucose (HG). Moreover, heme oxygenase-1 (HO-1) plays a crucial role in tissue pathological changes such as brain injuries. However, the molecular mechanisms underlying HG-induced HO-1 expression in brain cells remain poorly defined. Thus, we use the rat brain astrocytes (RBA-1) as a model to investigate the signaling mechanisms of HO-1 induction by HG and its effects on neuronal cells. We demonstrated that HG induced HO-1 expression via a reactive oxygen species (ROS)-dependent signaling pathway. NADPH oxidase (Nox)- and mitochondrion-dependent ROS generation led to activation of extracellular signal-regulated kinase 1/2 (ERK1/2) and c-Jun-N-terminal kinase (JNK) and then activated the downstream transcriptional factors nuclear factor-kappaB (NF-κB) and c-Fos/activator protein 1 (AP-1), respectively. Subsequently, the activated NF-κB and AP-1 turned on transcription of HO-1 gene. These results indicated that in brain astrocytes, activation of MAPK-mediated NF-κB and c-Fos/AP-1 cascades by Nox/ROS and mitoROS-dependent events is essential for HO-1 up-regulation induced by HG. Moreover, we found that HG-induced extracellular ROS increase and HO-1 expression from astrocytes resulted in neuronal apoptosis. These results offers new insights into the mechanisms and effects of the action of HG, supporting that HG may cause brain disorders in the development of diabetes- and hyperglycemia-induced CNS complications such as neurodegenerative diseases.

The impact of gender on stroke pathology and treatment

Cerebral ischemic stroke is a leading cause of mortality and functional disability. However, unfortunately few effective treatments exist to counteract the deleterious pathological mechanisms triggered following an ischemic event. Epidemiological and experimental studies have revealed a significant difference in the vulnerability of males versus females to both the incidence of stroke and amount of resulting pathology following an ischemic stroke which is also dependent on the stage of lifespan. Here we review the evidence for gender differences in both the overall pathology and cellular mechanisms of injury following ischemic stroke. In addition, we discuss the evidence for any gender differences that may occur in the effectiveness of treatments and how this supports the need for the investigation and development of gender-specific therapies.

Ensembling and filtering: an effective and rapid in silico multitarget drug-design strategy to identify RIPK1 and RIPK3 inhibitors

Necroptosis, a programmed necrosis pathway, is witnessed in diverse human diseases and is primarily regulated by receptor-interacting serine/threonine protein kinase 1 (RIPK1) and RIPK3. Ablation or inhibition of these individual proteins, or both, has been shown to be protective in various in vitro and in vivo disease models involving necroptosis. In this study, we propose an effective and rapid virtual screening strategy to identify multitarget inhibitors of both RIPK1 and RIPK3. It involves ensemble pharmacophore-based screening (EPS) of a compound database, post-EPS filtration (PEPSF) of the ligand hits, and multiple dockings. Structurally diverse inhibitors were identified through ensemble pharmacophore features, and the speed of this process was enhanced by filtering out the compounds containing cross-features. The stability of these inhibitors with both of the proteins was verified by means of molecular dynamics (MD) simulation. Graphical Abstract A generalized workflow employed in this study. Subsequent utilization of EPS and PEPSF might lead to reduced computational time and load.

Neuroinflammatory biomarkers: From stroke diagnosis and prognosis to therapy

Stroke is the third leading cause of death in industrialized countries and one of the largest causes of permanent disability worldwide. Therapeutic options to fight stroke are still limited and the only approved drug is tissue-plasminogen activator (tPA) and/or mechanical thrombectomy. Post-stroke inflammation is well known to contribute to the expansion of the ischemic lesion, whereas its resolution stimulates tissue repair and neuroregeneration processes. As inflammation highly influences susceptibility of stroke patients to overcome the disease, there is an increasing need to develop new diagnostic, prognostic and therapeutic strategies for post-stroke inflammation. This review provides a brief overview of the contribution of the inflammatory mechanisms to the pathophysiology of stroke. It specially focuses on the role of inflammatory biomarkers to help predicting stroke patients' outcome since some of those biomarkers might turn out to be targets to be therapeutically altered overcoming the urgent need for the identification of potent drugs to modulate stroke-associated inflammation. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

Nerve Protective Effect of Asiaticoside against Ischemia-Hypoxia in Cultured Rat Cortex Neurons

Background

Asiaticoside is one of the main functional components of the natural plant Centella asiatica urban. Studies have reported it has several functions such as anti-depression and nerve cell protection. Asiaticoside can reduce the cerebral infarct size in acute focal cerebral ischemia in a mouse model and asiatic acid glycosides can significantly improve neurobehavioral scores. Currently, there is a lack of understanding of asiaticoside in regard to its neural protective mechanism in cerebral ischemia. This study aimed to solve this problem by using an ischemia-hypoxia cell model in vitro.

Material/Methods

An in vitro ischemia hypoxia cell model was successfully established by primary cultured newborn rat cortical neurons. After being treated by asiaticoside for 24 h, cell survival rate, lactate dehydrogenase release quantity, and B-cell lymphoma gene-2 (BCL-2), Bax, and caspase-3 protein expressions was detected.

Results

After 10 nmol/L or 100 nmol/L of asiaticoside were given to the cells, cell survival rate increased significantly and presented concentration dependence. Asiaticoside can reduce lactate dehydrogenase release. Lactate dehydrogenase release in model cells is gradually reduced with the increase of asiaticoside concentration. The lactate dehydrogenase release in asiaticoside 10 nmol/L group, asiaticoside 100 nmol/L group and ischemia hypoxia group were 26.75±1.05, 22.36±2.87 and 52.35±5.46%, respectively (p<0.05). It was also found that asiaticoside could modulate the expression of apoptotic factors, including bcl-2, Bax, and caspase-3.

Conclusions

Asiaticoside helps to protect in vitro ischemia hypoxia neurons. This nerve cell protection may be mediated by the BCL-2 protein.