Differential activation of MAPK/ERK and p38/SAPK in neurones and glia following focal cerebral ischaemia in the rat

The interregulatory circuit between non-coding RNA and apoptotic signaling in diabetic cardiomyopathy

Diabetes mellitus has surged in prevalence, emerging as a prominent epidemic and assuming a foremost position among prevalent medical disorders. Diabetes constitutes a pivotal risk element for cardiovascular maladies, with diabetic cardiomyopathy (DCM) standing out as a substantial complication encountered by individuals with diabetes. Apoptosis represents a physiological phenomenon observed throughout the aging and developmental stages, giving rise to the programmed cell death, which is implicated in DCM. Non-coding RNAs assume significant functions in modulation of gene expression. Their deviant expression of ncRNAs is implicated in overseeing diverse cellular attributes such as proliferation, apoptosis, and has been postulated to play a role in the progression of DCM. Notably, ncRNAs and the process of apoptosis can mutually influence and cooperate in shaping the destiny of human cardiac tissues. Therefore, the exploration of the interplay between apoptosis and non-coding RNAs holds paramount importance in the formulation of efficacious therapeutic and preventive approaches for managing DCM. In this review, we provide a comprehensive overview of the apoptotic signaling pathways relevant to DCM and subsequently delve into the reciprocal regulation between apoptosis and ncRNAs in DCM. These insights contribute to an enhanced comprehension of DCM and the development of therapeutic strategies.

ERK1/2 modulation in the central nervous system of male and female thiamine-deficient mice with amprolium

Thiamine deficiency experimental models focus on using the pyrithiamine analog in male rodents, making the thiamine deficiency effects in females and the use of other thiamine antagonists, such as amprolium, unknown. We investigated the impact of thiamine deficiency with amprolium in the cerebral cortex and thalamus of male and female mice by evaluating the modulation of ERK1/2 phosphorylation. The animals were exposed for 20 days to thiamine-deficient chow with different doses of amprolium (20, 40, 60 and 80 mg/kg) and at different treatment periods (five, 10, 15 or 20 days) at a dose of 60 mg/kg. After treatments, ERK1/2 phosphorylation was analyzed by western blot. In male mice, we observed a progressive increase in ERK1/2 phosphorylation in both the cerebral cortex and thalamus in response to the dose of amprolium. In females, ERK1/2 phosphorylation did not progressively increase in response to the amprolium dosage. However, an increase in phosphorylation at the higher doses of 60 and 80 mg/kg was observed. We observed a more intense increase in ERK1/2 phosphorylation in males' cerebral cortex and thalamus from 10 days onwards. In females, the ERK1/2 modulation profiles were similar. The results show that thiamine deficiency induction with amprolium is efficient, compatible with other recognized models that use pyrithiamine, showing changes in cell signaling in the nervous system. The study showed differences in response to thiamine deficiency with amprolium between male and female mice in relation to ERK1/2 phosphorylation and demonstrated that females respond positively to the method and can also be used as model animals.

A comprehensive review of stroke-related signaling pathways and treatment in western medicine and traditional Chinese medicine

This review provides insight into the complex network of signaling pathways and mechanisms involved in stroke pathophysiology. It summarizes the historical progress of stroke-related signaling pathways, identifying potential interactions between them and emphasizing that stroke is a complex network disease. Of particular interest are the Hippo signaling pathway and ferroptosis signaling pathway, which remain understudied areas of research, and are therefore a focus of the review. The involvement of multiple signaling pathways, including Sonic Hedgehog (SHH), nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE), hypoxia-inducible factor-1α (HIF-1α), PI3K/AKT, JAK/STAT, and AMPK in pathophysiological mechanisms such as oxidative stress and apoptosis, highlights the complexity of stroke. The review also delves into the details of traditional Chinese medicine (TCM) therapies such as Rehmanniae and Astragalus, providing an analysis of the recent status of western medicine in the treatment of stroke and the advantages and disadvantages of TCM and western medicine in stroke treatment. The review proposes that since stroke is a network disease, TCM has the potential and advantages of a multi-target and multi-pathway mechanism of action in the treatment of stroke. Therefore, it is suggested that future research should explore more treasures of TCM and develop new therapies from the perspective of stroke as a network disease.

Glial Glutamate Transporter Modulation Prevents Development of Complete Freund's Adjuvant-Induced Hyperalgesia and Allodynia in Mice

Glial glutamate transporter (GLT-1) modulation in the hippocampus and anterior cingulate cortex (ACC) is critically involved in nociceptive pain. The objective of the study was to investigate the effects of 3-[[(2-methylphenyl) methyl] thio]-6-(2-pyridinyl)-pyridazine (LDN-212320), a GLT-1 activator, against microglial activation induced by complete Freund's adjuvant (CFA) in a mouse model of inflammatory pain. Furthermore, the effects of LDN-212320 on the protein expression of glial markers, such as ionized calcium-binding adaptor molecule 1 (Iba1), cluster of differentiation molecule 11b (CD11b), mitogen-activated protein kinases (p38), astroglial GLT-1, and connexin 43 (CX43), were measured in the hippocampus and ACC following CFA injection using the Western blot analysis and immunofluorescence assay. The effects of LDN-212320 on the pro-inflammatory cytokine interleukin-1β (IL-1β) in the hippocampus and ACC were also assessed using an enzyme-linked immunosorbent assay. Pretreatment with LDN-212320 (20 mg/kg) significantly reduced the CFA-induced tactile allodynia and thermal hyperalgesia. The anti-hyperalgesic and anti-allodynic effects of LDN-212320 were reversed by the GLT-1 antagonist DHK (10 mg/kg). Pretreatment with LDN-212320 significantly reduced CFA-induced microglial Iba1, CD11b, and p38 expression in the hippocampus and ACC. LDN-212320 markedly modulated astroglial GLT-1, CX43, and, IL-1β expression in the hippocampus and ACC. Overall, these results suggest that LDN-212320 prevents CFA-induced allodynia and hyperalgesia by upregulating astroglial GLT-1 and CX43 expression and decreasing microglial activation in the hippocampus and ACC. Therefore, LDN-212320 could be developed as a novel therapeutic drug candidate for chronic inflammatory pain.

Modulation of α7nAchR by Melatonin Alleviates Ischemia and Reperfusion-Compromised Integrity of Blood-Brain Barrier Through Inhibiting HMGB1-Mediated Microglia Activation and CRTC1-Mediated Neuronal Loss

The only food and drug administration (FDA)-approved drug currently available for the treatment of acute ischemic stroke is tissue plasminogen activator (tPA), yet the therapeutic benefits of this drug are partially outweighed by the increased risk of hemorrhagic transformation (HT). Analysis of the NIH trial has shown that cigarette smoking protected tPA-treated patients from HT; however, the underlying mechanism is not clear. Nicotinic acetylcholine receptors (nAChR) has shown anti-inflammatory effect and modulation nAChR could be a strategy to reduce ischemia/reperfusion-induced blood-brain barrier (BBB) damage. Since melatonin could regulate the expression of α7nAchR and melatonin's neuroprotective effect against ischemic injury is mediated via α7nAChR modulation, here, we aim to test the hypothesis that melatonin reduces ischemia and reperfusion (I/R)-induced BBB damage through modulation of α7nACh receptor (α7nAChR). Mice were subjected to 1.5 h ischemia and 24 h reperfusion and at the onset of reperfusion, mice received intraperitoneal administration (i.p.) of either drug or saline. Mice were randomly assigned into five groups: Saline; α7nAChR agonist PNU282987; Melatonin; Melatonin+Methyllycaconitine (MLA, α7nAChR antagonist), and MLA group. BBB permeability was assessed by detecting the extravasation of Evan's blue and IgG. Our results showed that I/R significantly increased BBB permeability accompanied by occludin degradation, microglia activation, and high mobility group box 1 (HMGB1) release from the neuron. In addition, I/R significantly induced neuronal loss accompanied by the decrease of CREB-regulated transcriptional coactivator 1 (CRTC1) and p-CREB expression. Melatonin treatment significantly inhibited the above changes through modulating α7nAChR. Taken together, these results demonstrate that melatonin provides a protective effect on ischemia/reperfusion-induced BBB damage, at least in part, depending on the modulation of α7nAChR.

A Network-Based Approach to Investigate the Neuroprotective Effects and Mechanisms of Action of Huangqi-Chuanxiong and Sanleng-Ezhu Herb Pairs in the Treatment of Cerebral Ischemic Stroke

Objective: We aimed to investigate the effect and mechanisms of action of two drug pairs [Huangqi-Chuanxiong and Sanleng-Ezhu Herb (HCSE)] on the treatment of ischemic stroke.

Materials and methods: We mined the current literature related to ischemic stroke and formulated a new formulation of Chinese herbs. Then, we identified the main candidate target genes of the new formulation by network pharmacology. Next, we performed enrichment analysis of the target genes to identify the potential mechanism of action of the new formulation in the treatment of ischemic stroke. Next, we experimentally validated the mechanism of action of the new formulation against ischemic stroke. Infarct volume and neurological deficits were evaluated by 2,3,5-triphenyltetrazolium (TTC) staining and Longa’s score, respectively. The predicted pathways of signal-related proteins were detected by western blotting.

Results: We mined the current literature and identified a new formulation of Chinese herbs for the treatment of ischemic stroke. The formulation included Huangqi, Chuanxiong, Sanleng and Ezhu. Next, we used network pharmacological analysis to identify 23 active compounds and 327 target genes for the new formulation. The key target genes were MAPK3, MAPK1, HSP90AA1, STAT3, PIK3R1, PIK3CA and AKT1. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed significant enrichment of the PI3K/AKT and MAPK/ERK signaling pathways. By performing experiments, we found that the new formulation reduced the infarct volume of middle cerebral artery occlusion (MCAO) induced mice and activated the PI3K/AKT and MAPK/ERK signaling pathways. These findings confirmed that the new formulation has a significant protective effect against ischemic stroke injury by activating the PI3K/AKT and MAPK/ERK signaling pathways.

Conclusion: We identified a new treatment formulation for ischemic stroke by data mining and network pharmacological target prediction. The beneficial effects of the new formulation act by regulating multiple target genes and pathways. The mechanism of action of the new formulation may be related to the AKT and ERK signaling pathways. Our findings provide a theoretical basis for the effects of the new formulation on ischemic stroke injury.

1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) Urea Exerts Neuro-Protective Effects Against Ischemic Injury via Suppressing JNK/p38 MAPK-Mediated Mitochondrial Apoptosis Pathway

BACKGROUND

1-trifluoromethoxyphenyl-3-(1- propionylpiperidin-4-yl) urea (TPPU) is a novel soluble epoxide hydrolase inhibitor which can protect against cerebral ischemic injury in middle cerebral artery occlusion rat model. However, the effects and potential mechanisms of TPPU on mitochondrial dysfunction are poorly understood.

MATERIALS AND METHODS

In oxygen-glucose deprivation/reperfusion (OGD/R)-induced cortical neurons, the effect of TPPU on cell viability was measured by MTT assay and apoptosis was evaluated using TUNEL assay. Mitochondria were observed by transmission electron microscopy and Mitotracker green staining assay, mitochondrial membrane potential was determined by JC-1 staining assay, activities of mitochondrial respiratory chain complexes (MRCC) I-IV and ATPase were measured by MRCC Activity Assay Kits and spectrophotometer. Western blot was used to investigate the effects of TPPU on apoptosis-related proteins.

RESULTS

TPPU treatment demonstrated significant protective effect on the OGD/R-induced cortical neurons by reducing cell death and number of apoptotic cells, stabilizing mitochondrial ultrastructure and morphology, increasing mitochondrial membrane potential and activities of MRCC I-IV and ATPase. Furthermore, TPPU treatment might effectively reverse the upregulation of caspase-3, Bax, p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal protein kinase (JNK), alleviate the inhibition of Bcl-2 in OGD/R-induced cortical neurons.

CONCLUSIONS

TPPU exerts a marked neuroprotective effect against mitochondrial dysfunction after cerebral ischemia potentially via suppressing JNK/p38 MAPK-mediated mitochondrial apoptosis signal pathway, it may be a promising neuroprotective agent for cerebral ischemia.

The effect of female sex hormones on Hsp27 phosphorylation and histological changes in prefrontal cortex after tMCAO

BACKGROUND

Female sex hormones are protective factors against many neurological disorders such as brain ischemia. Heat shock protein like HSP27 is activated after tissue injury. The main purpose of the present study is to determine the effect of a combined estrogen / progesterone cocktail on the morphology of astrocytes, neurons and Hsp27 phosphorylation after cerebral ischemia.

METHODS

One hour after the MCAO induction, a single dose of estrogen and progesterone was injected. The infarct volume was calculated by TTC staining 24 h after ischemia. Immunohistochemistry was used to show the effects of estrogen and progesterone on astrocyte and neuron morphology, as well as the Western blot technique used for the quantitation of phosphorylated Hsp27.

RESULTS

The combined dose of estrogen and progesterone significantly decreased astrocytosis after ischemia and increased neuron survival. There was a large increase in Hsp27 phosphorylation in the penumbra ischemic region after stroke, which was significantly reduced by hormone therapy.

CONCLUSION

Our results indicate that the neuroprotective effect of neurosteroids in the brain may be due to the modulation of heat shock proteins.

Mechanistic insight on the role of leukotriene receptors in ischemic-reperfusion injury

Leukotrienes (LT) are a class of inflammatory mediators produced by the 5-lipoxygenase (5-LO) enzyme from arachidonic acid (AA). We discussed the various LT inhibitors and downstream pathway modulators, such as Mitogen-Activated Protein Kinases (MAPK), Phosphatidylinositol 3-Kinase/Protein Kinase B (PI3K/Akt), 5'-Adenosine Monophosphate-Activated Protein Kinase (AMPK), Protein Kinase C (PKC), Nitric Oxide (NO), Bradykinin, Early Growth Response-1 (Egr-1), Nuclear Factor-κB (NF-κB), and Tumor Necrosis Factor-Alpha (TNF-α), which in turn regulate various metabolic and physiological processes involving I/R injury. A systematic literature review of Bentham, Scopus, PubMed, Medline, and EMBASE (Elsevier) databases was carried out to understand the nature and mechanistic interventions of the leukotriene receptor modulations in ischemic injury. In the pathophysiology of I/R injuries, LT has been found to play an important role. I/R injury affects most of the vital organs and is characterized by inflammation, oxidative stress, cell death, and apoptosis leading to morbidity and mortality. sThis present review focuses on the various LT receptors, i.e., CysLT, LTC4, LTD4, and LTE4, involved in developing I/R injury in organs, such as the brain, spinal cord, heart, kidney, liver, and intestine.

Galectin-3 protects against ischemic stroke by promoting neuro-angiogenesis via apoptosis inhibition and Akt/Caspase regulation

Post-stroke neurological deficits and mortality are often associated with vascular disruption and neuronal apoptosis. Galectin-3 (Gal3) is a potent pro-survival and angiogenic factor. However, little is known about its protective role in the cerebral ischemia/reperfusion (I/R) injury. We have previously shown significant up-regulation of Gal3 in the post-stroke rat brain, and that blocking of Gal3 with neutralizing antibody decreases the cerebral blood vessel density. Our current study demonstrates that intracerebral local delivery of the Gal3 into rat brain at the time of reperfusion exerts neuroprotection. Ischemic lesion volume and neuronal cell death were significantly reduced as compared with the vehicle-treated MCAO rat brains. Gal3 increased vessel density and neuronal survival after I/R in rat brains. Importantly, Gal3-treated groups showed significant improvement in motor and sensory functional recovery. Gal3 increased neuronal cell viability under in vitro oxygen-glucose deprivation conditions in association with increased phosphorylated-Akt, decreased phosphorylated-ERK1/2, and reduced caspase-3 activity. Gene expression analysis showed down regulation of pro-apoptotic and inflammatory genes including Fas-ligand, and upregulation of pro-survival and pro-angiogenic genes including Bcl-2, PECAM, and occludin. These results indicate a key role for Gal3 in neuro-vascular protection and functional recovery following ischemic stroke through modulation of angiogenic and apoptotic pathways.

In vitro P38MAPK inhibition in aged astrocytes decreases reactive astrocytes, inflammation and increases nutritive capacity after oxygen-glucose deprivation

Proper astroglial functioning is essential for the development and survival of neurons and oligodendroglia under physiologic and pathological circumstances. Indeed, malfunctioning of astrocytes represents an important factor contributing to brain injury. However, the molecular pathways of this astroglial dysfunction are poorly defined. In this work we show that aging itself can drastically perturb astrocyte viability with an increase of inflammation, cell death and astrogliosis. Moreover, we demonstrate that oxygen glucose deprivation (OGD) has a higher impact on nutritive loss in aged astrocytes compared to young ones, whereas aged astrocytes have a higher activity of the anti-oxidant systems. P38MAPK signaling has been identified to be upregulated in neurons, astrocytes and microglia after ischemic stroke. By using a pharmacological p38α specific inhibitor (PH-797804), we show that p38MAPK pathway has an important role in aged astrocytes for inflammatory and oxidative stress responses with the subsequent cell death that occurs after OGD.

Network Pharmacology-Based Prediction of Catalpol and Mechanisms against Stroke

Aim

To apply the network pharmacology method to screen the target of catalpol prevention and treatment of stroke, and explore the pharmacological mechanism of Catalpol prevention and treatment of stroke.

Methods

PharmMapper, GeneCards, DAVID, and other databases were used to find key targets. We selected hub protein and catalpol which were screened for molecular docking verification. Based on the results of molecular docking, the ITC was used to determine the binding coefficient between the highest scoring protein and catalpol. The GEO database and ROC curve were used to evaluate the correlation between key targets.

Results

27 key targets were obtained by mapping the predicted catalpol-related targets to the disease. Hub genes (ALB, CASP3, MAPK1 (14), MMP9, ACE, KDR, etc.) were obtained in the key target PPI network. The results of KEGG enrichment analysis showed that its signal pathway was involved in angiogenic remodeling such as VEGF, neurotrophic factors, and inflammation. The results of molecular docking showed that ACE had the highest docking score. Therefore, the ITC was used for the titration of ACE and catalpol. The results showed that catalpol had a strong binding force with ACE.

Conclusion

Network pharmacology combined with molecular docking predicts key genes, proteins, and signaling pathways for catalpol in treating stroke. The strong binding force between catalpol and ACE was obtained by using ITC, and the results of molecular docking were verified to lay the foundation for further research on the effect of catalpol on ACE. ROC results showed that the AUC values of the key targets are all >0.5. This article uses network pharmacology to provide a reference for a more in-depth study of catalpol's mechanism and experimental design.

Protein kinase inhibitors in traumatic brain injury and repair: New roles of nanomedicine

Traumatic brain injury (TBI) causes physical injury to the cell membranes of neurons, glial and axons causing the release of several neurochemicals including glutamate and cytokines altering cell-signaling pathways. Upregulation of mitogen associated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) occurs that is largely responsible for cell death. The pharmacological blockade of these pathways results in cell survival. In this review role of several protein kinase inhibitors on TBI induced oxidative stress, blood-brain barrier breakdown, brain edema formation, and resulting brain pathology is discussed in the light of current literature.

Protective role of anticancer drugs in neurodegenerative disorders: A drug repurposing approach

The disease heterogeneity and little therapeutic progress in neurodegenerative diseases justify the need for novel and effective drug discovery approaches. Drug repurposing is an emerging approach that reinvigorates the classical drug discovery method by divulging new therapeutic uses of existing drugs. The common biological background and inverse tuning between cancer and neurodegeneration give weight to the conceptualization of repurposing of anticancer drugs as novel therapeutics. Many studies are available in the literature, which highlights the success story of anticancer drugs as repurposed therapeutics. Among them, kinase inhibitors, developed for various oncology indications evinced notable neuroprotective effects in neurodegenerative diseases. In this review, we shed light on the salient role of multiple protein kinases in neurodegenerative disorders. We also proposed a feasible explanation of the action of kinase inhibitors in neurodegenerative disorders with more attention towards neurodegenerative disorders. The problem of neurotoxicity associated with some anticancer drugs is also highlighted. Our review encourages further research to better encode the hidden potential of anticancer drugs with the aim of developing prospective repurposed drugs with no toxicity for neurodegenerative disorders.

Neuronal p38α mediates age-associated neural stem cell exhaustion and cognitive decline

Neuronal activity regulates cognition and neural stem cell (NSC) function. The molecular pathways limiting neuronal activity during aging remain largely unknown. In this work, we show that p38MAPK activity increases in neurons with age. By using mice expressing p38α-lox and CamkII-Cre alleles (p38α∆-N), we demonstrate that genetic deletion of p38α in neurons suffices to reduce age-associated elevation of p38MAPK activity, neuronal loss and cognitive decline. Moreover, aged p38α∆-N mice present elevated numbers of NSCs in the hippocampus and the subventricular zone. These results reveal novel roles for neuronal p38MAPK in age-associated NSC exhaustion and cognitive decline.

Pro-Nerve Growth Factor Induces Activation of RhoA Kinase and Neuronal Cell Death

We have previously shown that the expression of pro-nerve growth factor (proNGF) was significantly increased, nerve growth factor (NGF) level was decreased, and the expression of p75^NTR was enhanced in Alzheimer’s disease (AD) hippocampal samples. NGF regulates cell survival and differentiation by binding TrkA and p75^NTR receptors. ProNGF is the precursor form of NGF, binds to p75^NTR, and induces cell apoptosis. The objective of this study is to determine whether the increased p75^NTR expression in AD is due to the accumulation of proNGF and Rho kinase activation. PC12 cells were stimulated with either proNGF or NGF. Pull-down assay was carried out to determine the RhoA kinase activity. We found the expression of p75^NTR was enhanced by proNGF compared to NGF. The proNGF stimulation also increased the RhoA kinase activity leading to apoptosis. The expression of active RhoA kinase was found to be increased in human AD hippocampus compared to control. The addition of RhoA kinase inhibitor Y27632 not only blocked the RhoA kinase activity but also reduced the expression of p75^NTR receptor and inhibited the activation of JNK and MAPK induced by proNGF. This suggests that overexpression of proNGF in AD enhances p75^NTR expression and activation of RhoA, leading to neuronal cell death.

USP10 protects against cerebral ischemia injury by suppressing inflammation and apoptosis through the inhibition of TAK1 signaling

Cerebral ischemia is a leading cause of death and long-term disability in the world. Multiple signaling pathways play essential roles in the process. Therefore, identifying the unknown important modulators of these pathways may supply promising therapeutic targets for the treatment of cerebral ischemia. Ubiquitin-specific protease 10 (USP10) is a member of the ubiquitin-specific protease family of cysteine proteases with enzymatic activity to cleave ubiquitin from ubiquitin-conjugated protein substrates, and is involved in multiple pathologies. However, the effects of USP10 in cerebral ischemia-reperfusion (I/R) injury remain unclear. Here, we reported that USP10 expression was markedly decreased in wild type (WT) mice after cerebral I/R injury. USP10 knockout (KO) mice showed significantly elevated infarct size and the neurological deficit score after cerebral I/R operation. USP10 deletion also promoted inflammatory response in ischemic penumbra of cortical regions by further accelerating nuclear factor κB (NF-κB) signaling pathway. In addition, apoptosis was markedly induced in USP10-knockout mice after cerebral I/R injury compared to the WT mice. The c-Jun N-terminal kinase-mitogen-activated protein kinase (JNK-MAPK) signaling induced by cerebral I/R injury was further aggravated in USP10-KO mice. Finally, USP10 was found to display protective effects against cerebral I/R injury through direct interaction with transforming growth factor β-activated kinase 1 (TAK1). Thus, USP10 might be a protective factor in cerebral I/R injury. Modulation of USP10/TAK1 might be a promising strategy to prevent this pathological process.

Sodium Hydrosulfide Post-conditioning Protects Hippocampal CA1 Neurons from Neuronal Cell Injury in the Rat Model of Transient Global Cerebral Ischemia Through Activation of Extracellular-regulated Kinases Signaling

INTRODUCTION

The effect of hydrogen sulfide (H2S) on global cerebral ischemia remains partially understood. This study aimed to investigate the neuroprotective effect of sodium hydrosulfide (NaHS, a donor of H2S) post-conditioning and its underlying mechanism in a transient global cerebral ischemia (tGCI) model.

MATERIALS & METHODS

The tGCI rat model was established by the four-vessel occlusion method. Wistar rats were randomly assigned into 6 groups: sham, tGCI, tGCI +NaHS, tGCI+vehicle, tGCI+U0126 and tGCI+U0126+NaHS groups. Neurons survival was assessed by Nissl staining and NeuN immunostaining. Levels of extracellular extracellular-regulated kinases (ERK)1/2 and p-ERK1/2 were determined by western blot and immunohistochemistry (IHC). Intraperitoneal injection of NaHS (24 µmol/kg) at 24 h post-tGCI attenuated tGCI-induced decrease of the survival and NeuN-positive neurons in the hippocampal CA1 subregion.

RESULTS

Compared to the sham group, tGCI significantly up-regulated p-ERK1/2 protein at 26 and 48 h post-tGCI. NaHS post-conditioning further enhanced the phosphorylation of ERK1/2 at 26, 48 and 168 h post-tGCI. Nevertheless, U0126 (an inhibitor of MEK1/2) pre-treatment reduced the p-ERK1/2 level in both the tGCI+ U0126 group and the tGCI+ U0126+ NaHS group. IHC staining revealed that p-ERK1/2-positive cell could be observed in several hippocampal subregions of the rats receiving NaHS post-conditioning. Immunofluorescence staining showed that some neurons were double-stained with p-ERK1/2 and NeuN. Furthermore, U0126 pre-treatment significantly attenuated the protective effect of NaHS post-conditioning on the neurons survival and NeuNpositive neurons in CA1 subregion.

CONCLUSION

These results suggested that NaHS post-conditioning can protect hippocampal CA1 neurons from tGCI-induced injury, at least partially, through activation of ERK1/2 signaling.

Hollow Prussian Blue Nanozymes Drive Neuroprotection against Ischemic Stroke via Attenuating Oxidative Stress, Counteracting Inflammation, and Suppressing Cell Apoptosis

Ischemic stroke is a devastating disease and one of the leading causes of mortality worldwide. Overproduction of reactive oxygen and nitrogen species (RONS) following ischemic insult is known as a key factor in exacerbating brain damage. Thus, RONS scavengers that can block excessive production of RONS have great therapeutic potential. Herein, we propose an efficient treatment strategy in which an artificial nanozyme with multienzyme activity drives neuroprotection against ischemic stroke primarily by scavenging RONS. Specifically, through a facile, Bi³⁺-assisted, template-free synthetic strategy, we developed hollow Prussian blue nanozymes (HPBZs) with multienzyme activity to scavenge RONS in a rat model of ischemic stroke. The comprehensive characteristics of HPBZs against RONS were explored. Apart from attenuating oxidative stress, HPBZs also suppressed apoptosis and counteracted inflammation both in vitro and in vivo, thereby contributing to increased brain tolerance of ischemic injury with minimal side effects. This study provides a proof of concept for a novel class of neuroprotective nanoagents that might be beneficial for treatment of ischemic stroke and other RONS-related disorders.

Reperfusion Changes After Stroke and Practical Approaches for Neuroprotection

Reperfusion is the first line of care in a growing number of eligible acute ischemic stroke patients. Early reperfusion with thrombolytic drugs and endovascular mechanical devices is associated with improved outcome and lower mortality rates compared with natural history. Reperfusion is not without risk, however, and may result in reperfusion injury, which manifests in hemorrhagic transformation, brain edema, infarct progression, and neurologic worsening. In this article, the functional and structural changes and underlying molecular mechanisms of ischemia and reperfusion are reviewed. The pathways that lead to reperfusion injury and novel neuroprotective strategies with endogenous properties are discussed.

Protease-activated receptor-2 regulates glial scar formation via JNK signaling

The study aimed to determine the effects of protease-activated receptor-2 (PAR-2) on glial scar formation after spinal cord injury (SCI) in Sprague-Dawley (SD) rats and the underlying mechanisms. Rivlin and Tator's acute extradural clip compression injury (CCI) model of severe SCI was established in this study. Animals were divided into four groups: 1) sham group (laminectomy only); 2) model group, treated with normal saline; 3) PAR-2 inhibitor group; 4) PAR-2 activator group. Enhanced GFAP and vimentin expression were the markers of glial scar formation. To determine whether JNK was involved in the effects of PAR-2 on GFAP and vimentin expression, we administered anisomycin (a JNK activator) in the presence of PAR-2 inhibitor and SP600125 (a JNK inhibitor) in the presence of PAR-2 activator. At 1, 7, 14 and 28 day after SCI, Basso, Beattie, and Bresnahan (BBB) locomotor score test was used to assess the locomotor functional recovery; immunofluorescence and western blot analysis were used to assess the expression level of GFAP, vimentin and p-JNK. Double immunofluorescence staining with GFAP and tubulin beta was used to assess the glial scar formation and the remaining neurons. Results suggested that PAR-2 is involved in glial scar formation and reduces neurons residues which can cause a further worsening in the functional outcomes after SCI via JNK signaling. Therefore, it may be effective to target PAR-2 in the treatment of SCI.

Tangeretin protects human brain microvascular endothelial cells against oxygen-glucose deprivation-induced injury

Tangeretin, a citrus flavonoid extracted from the peel of citrus fruits, was reported to possess antiasthmatic, antioxidant, anti-inflammatory, and neuroprotective properties. However, the effect of tangeretin on human brain microvascular endothelial cells (HBMECs) has not been examined. This study was designed to investigate the protective effects of tangeretin on oxygen-glucose deprivation (OGD)-induced injury of HBMECs, and explore the underlying mechanisms. Our results showed that tangeretin improved HBMECs viability in response to OGD. In addition, tangeretin was able to increase the activity of superoxide dismutase and decrease the levels of reactive oxygen species and malondialdehyde (MDA), as well as ameliorate cell apoptosis in OGD-stimulated HBMECs. Mechanistic studies showed that tangeretin prevented the activation of JNK signaling pathway in OGD-stimulated HBMECs. Taken together, our current study demonstrated that tangeretin could ameliorate OGD-induced HBMECs injury through the JNK signaling pathway. Thus, tangeretin might be used as a therapeutic strategy for ischemia-reperfusion brain injury and related diseases.

Melatonin improves vascular cognitive impairment induced by ischemic stroke by remyelination via activation of ERK1/2 signaling and restoration of glutamatergic synapses in the gerbil hippocampus

Vascular dementia affects cognition by damaging axons and myelin. Melatonin is pharmacologically associated with various neurological disorders. In this study, effects of melatonin on cognitive impairment and related mechanisms were investigated in an animal model of ischemic vascular dementia (IVD). Melatonin was intraperitoneally administered to adult gerbils after transient global cerebral ischemia (tGCI) for 25 days beginning 5 days after tGCI. Cognitive impairment was examined using a passive avoidance test and the Barnes maze test. To investigate mechanisms of restorative effects by melatonin, neuronal damage/death, myelin basic protein (MBP, a marker for myelin), Rip (a marker for oligodendrocyte), extracellular signal-regulated protein kinase1/2 (ERK1/2) and phospho-ERK1/2 (p-ERK1/2), and vesicular glutamate transporter (VGLUT)-1 (a glutamatergic synaptic marker) in the hippocampal Cornu Ammonis 1 area (CA1) were evaluated using immunohistochemistry. Melatonin treatment significantly improved tGCI-induced cognitive impairment. Death of CA1 pyramidal neurons after tGCI was not affected by melatonin treatment. However, melatonin treatment significantly increased MBP immunoreactivity and numbers of Rip-immunoreactive oligodendrocytes in the ischemic CA1. In addition, melatonin treatment significantly increased ERK1/2 and p-ERK1/2 immunoreactivities in oligodendrocytes in the ischemic CA1. Furthermore, melatonin treatment significantly increased VGLUT-1 immunoreactive structures in the ischemic CA1. These results indicate that long-term melatonin treatment after tGCI improves cognitive deficit via restoration of myelin, increase of oligodendrocytes which is closely related to the activation of ERK1/2 signaling, and increase of glutamatergic synapses in the ischemic brain area.

MicroRNA-410 inhibition of the TIMP2-dependent MAPK pathway confers neuroprotection against oxidative stress-induced apoptosis after ischemic stroke in mice

Ischemic stroke (IS) is an acute cerebral event characterized by a high incidence rate, high disability rate as well as a high mortality. More recently, accumulative literature has provided evidence highlighting the role played by microRNAs (miRs) in the development of neurons. Hence, the aim of the present study was to investigate the neuroprotective role of miR-410 in IS. Microarray-based gene expression profiling of AMI was conducted in order to identify differentially expressed genes (DEGs) and the corresponding miRs regulating these genes. IS models were established to assess neurology on a scoring basis. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) activity and malondialdehyde (MDA) were all subsequently assessed. The functional role of miR-410 in IS was determined based on ectopic expression, knockdown and reporter assay experiments in hippocampal neurons. The expressions of microRNA-410, TIMP2, ERK, p38MAPK, JNK were all examined accordingly. The survival rate was assessed by MTT assay, and cell cycle and apoptosis by flow cytometry. After the loss of hippocampal neurons, infarct size as well as oxidative stress injury had been detected, microarray technology revealed that TIMP2 was differentially expressed in IS and that miR-410 regulated TIMP2. Initial observations revealed elevated levels of TIMP2 expression and MDA activity, in addition to evidence obtained indicated that the MAPK pathway had been activated along with decreased SOD, GSH-Px activity and miR-410 expression in IS mice. Ectopic expression of miR-410 was observed to inactivate the MAPK pathway, TIMP2 expression and hippocampal neuron apoptosis, while elevated hippocampal neuron survival rates and cell cycle entry were detected. Furthermore, TIMP2 as a direct target gene of miR-410, was determined to be negatively regulated by miR-410, while the MAPK pathway was found to be inhibited following TIMP2 knockdown. Our results revealed that the overexpression of miR-410 could ameliorate hippocampal neuron loss, reduce infarct size and oxidative stress injury in IS mice. Taken together, the key evidence of the current study elucidated the distinct nature of the inhibitory effect on IS as a result of overexpressed miR-410 whereby the conferral of neuroprotection was observed in oxidative stress-induced apoptosis post IS through the TIMP2-dependent repression of the MAPK pathway in mice.

Electroacupuncture Alleviated Neuronal Apoptosis Following Ischemic Stroke in Rats via Midkine and ERK/JNK/p38 Signaling Pathway

This study aimed to evaluate the effects of electroacupuncture (EA) intervention administered at rats of middle cerebral artery occlusion (MCAO)/reperfusion. Fifty-four male Sprague-Dawley rats were divided into three groups, consisting of sham group, MCAO/R group, and EA group. EA treatment at Quchi and Zusanli acupoints was applied in rats of EA group at 24 h after MCAO once per day for 3 days. Our results indicated that EA treatment reduced infarct volumes and neurological deficits, as well alleviated the apoptotic cells in peri-infarct cortex, indicating that EA exerted neuroprotective effect in cerebral ischemic rats. Moreover, EA treatment may effectively reverse the upregulation of caspase-3 and Bim and alleviate the inhibition of Bcl-2 following 72-h ischemic stroke. EA may significantly reverse the promoted relative density level of p-ERK1/2, p-JNK, and p-p38 in the EA group compared with the MCAO/R group. In addition, the growth factor midkine (MK) was upregulated at 72 h after MCAO/R, and EA treatment may significantly prompt expression of MK. Our study demonstrated that EA exerted neuroprotective effect against neuronal apoptosis and the mechanism might involve in upregulation of MK and mediation of ERK/JNK/p38 signal pathway.

The Janus Face of VEGF in Stroke

The family of vascular endothelial growth factors (VEGFs) are known for their regulation of vascularization. In the brain, VEGFs are important regulators of angiogenesis, neuroprotection and neurogenesis. Dysregulation of VEGFs is involved in a large number of neurodegenerative diseases and acute neurological insults, including stroke. Stroke is the main cause of acquired disabilities, and normally results from an occlusion of a cerebral artery or a hemorrhage, both leading to focal ischemia. Neurons in the ischemic core rapidly undergo necrosis. Cells in the penumbra are exposed to ischemia, but may be rescued if adequate perfusion is restored in time. The neuroprotective and angiogenic effects of VEGFs would theoretically make VEGFs ideal candidates for drug therapy in stroke. However, contradictory to what one might expect, endogenously upregulated levels of VEGF as well as the administration of exogenous VEGF is detrimental in acute stroke. This is probably due to VEGF-mediated blood–brain-barrier breakdown and vascular leakage, leading to edema and increased intracranial pressure as well as neuroinflammation. The key to understanding this Janus face of VEGF function in stroke may lie in the timing; the harmful effect of VEGFs on vessel integrity is transient, as both VEGF preconditioning and increased VEGF after the acute phase has a neuroprotective effect. The present review discusses the multifaceted action of VEGFs in stroke prevention and therapy.

Brain penetrant kinase inhibitors: Learning from kinase neuroscience discovery

A recent review of kinase inhibitors in clinical trials for brain cancer noted differences in the properties of these compounds relative to the mean property parameters associated with drugs marketed for CNS-associated conditions. However, many of these kinase drugs arose from opportunistic observations of brain activity, rather than design or flow schemes focused on optimizing CNS penetration. Thus, this digest examines kinase inhibitors that have been developed specifically for neurodegenerative indications such as Alzheimer's or Parkinson's disease, and considers design, flow scheme, and the physicochemical properties associated with compounds that have demonstrated brain penetrance.

Neuroprotective effects of protein tyrosine phosphatase 1B inhibitor on cerebral ischemia/reperfusion in mice

Akt (Protein kinase B, PKB), a serine/threonine kinase, plays a critical role in cell development, growth, and survival. Akt phosphorylation mediates a neuroprotective effect against ischemic injury. Recently, a protein-tyrosine phosphatase-1B (PTP1B) inhibitor (KY-226) was developed to elicit anti-diabetic and anti-obesity effects via enhancement of insulin signaling. Previously, we reported that the nonselective PTP1B inhibitor, sodium orthovanadate, rescued neurons from delayed neuronal death during brain ischemia. In this study, we confirmed the ameliorative effects of KY-226 on ischemia/reperfusion (I/R) injury using a murine model of middle cerebral artery occlusion (MCAO). ICR mice were subjected to MCAO for 2 h followed by reperfusion. Although KY-226 permeability was poor through the blood-brain barrier (BBB) of normal mice, it could penetrate through the BBB of mice after I/R insult. Intraperitoneal KY-226 administration elicited dose-dependent reductions in infarcted brain areas and improved neurological deficits. The neuroprotective effects of KY-266 were obtained when administered within 0.5 h after reperfusion. KY-226 (10 mg/kg) also restored reduced Akt phosphorylation and eNOS phosphorylation (Ser-1177) levels following I/R insult. Moreover, 10 mg/kg of KY-226 improved I/R-induced decreased extracellular signal-regulated kinase (ERK) phosphorylation. Furthermore, KY-226 attenuated the generation of reactive oxygen species (ROS) in mouse cortex. These results suggest that KY-226 may act as a novel therapeutic candidate for ischemic stroke. Activation of Akt and ERK possibly underlie the neuroprotective mechanism of KY-226.

Expression of Hypoxia Inducible Factor 1alpha Is Protein Kinase A-dependent in Primary Cortical Astrocytes Exposed to Severe Hypoxia

The hypoxia inducible factor 1 (HIF-1) and the cyclic AMP-responsive element binding protein (CREB) are two transcription factors that have been studied in the context of neuronal survival and neurodegeneration. HIF-1 upregulation and CREB activation have been observed not only in neurons but also in astrocytes under conditions of hypoxia. We hypothesized that activation of CREB regulate HIF-1α expression in the nucleus of cortical astrocytes under in vitro ischemic condition. To test the hypothesis, we determined the effects of inhibiting the CREB activation pathway on the expression of HIF-1α protein in astrocytes exposed to CoCl₂ and severe hypoxia (near anoxia, 0.1% O₂). The results demonstrated that inhibition of CaMKII and CaMKIV had no effect on both HIF-1α and pCREB expression in cortical astrocytes exposed to CoCl₂ and anoxia. In contrast, PKA inhibition lowered the expression of HIF-1α and pCREB expression. Furthermore, the inhibition of PKA but not CaMKII or CaMKIV increased cell death of astrocytes exposed to near anoxia. The results suggest that PKA plays an important role in the cell survival signaling pathways in astrocytes.

S1PR3 is essential for phosphorylated fingolimod to protect astrocytes against oxygen-glucose deprivation-induced neuroinflammation via inhibiting TLR2/4-NFκB signalling

Fingolimod (FTY720) is used as an immunosuppressant for multiple sclerosis. Numerous studies indicated its neuroprotective effects in stroke. However, the mechanism remains to be elucidated. This study was intended to investigate the mechanisms of phosphorylated FTY720 (pFTY720), which was the principle active molecule in regulating astrocyte‐mediated inflammatory responses induced by oxygen‐glucose deprivation (OGD). Results demonstrated that pFTY720 could protect astrocytes against OGD‐induced injury and inflammatory responses. It significantly decreased pro‐inflammatory cytokines, including high mobility group box 1 (HMGB1) and tumour necrosis factor‐α (TNF‐α). Further, studies displayed that pFTY720 could prevent up‐regulation of Toll‐like receptor 2 (TLR2), phosphorylation of phosphoinositide 3‐kinase (PI3K) and nuclear translocation of nuclear factor kappa B (NFκB) p65 subunit caused by OGD. Sphingosine‐1‐phosphate receptor 3 (S1PR3) knockdown could reverse the above change. Moreover, administration of TLR2/4 blocker abolished the protective effects of pFTY720. Taken together, this study reveals that pFTY720 depends on S1PR3 to protect astrocytes against OGD‐induced neuroinflammation, due to inhibiting TLR2/4‐PI3K‐NFκB signalling pathway.

Neuroprotective Effects of Bioactive Compounds and MAPK Pathway Modulation in "Ischemia"-Stressed PC12 Pheochromocytoma Cells

This review surveys the efforts taken to investigate in vitro neuroprotective features of synthetic compounds and cell-released growth factors on PC12 clonal cell line temporarily deprived of oxygen and glucose followed by reoxygenation (OGD/R). These cells have been used previously to mimic some of the properties of in vivo brain ischemia-reperfusion-injury (IRI) and have been instrumental in identifying common mechanisms such as calcium overload, redox potential, lipid peroxidation and MAPKs modulation. In addition, they were useful for establishing the role of certain membrane penetrable cocktails of antioxidants as well as potential growth factors which may act in neuroprotection. Pharmacological mechanisms of neuroprotection addressing modulation of the MAPK cascade and increased redox potential by natural products, drugs and growth factors secreted by stem cells, in either undifferentiated or nerve growth factor-differentiated PC12 cells exposed to ischemic conditions are discussed for future prospects in neuroprotection studies.

Potassium 2-(1-hydroxypentyl)-benzoate attenuates neuronal apoptosis in neuron-astrocyte co-culture system through neurotrophy and neuroinflammation pathway

Potassium 2-(1-hydroxypentyl)-benzoate (d,l-PHPB), a new drug candidate for ischemic stroke at the phase II clinic trial, has been shown to protect neurons by inhibiting oxidative injury and reducing neuron apoptosis in previous studies. But the mechanisms of d,l-PHPB remain to be studied. In this study, a neuron–astrocytes co-culture system was used to elucidate the roles of astrocytes in neuroprotection of d,l-PHPB under oxygen-glucose deprivation/reoxygenation (OGD/R) condition. Our data showed that d,l-PHPB reduced neuronal apoptosis in mono-culture system and this effect was enhanced in neuron–astrocyte co-culture system under the OGD/R condition. Meanwhile, d,l-PHPB obviously increased the levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), which were mainly secreted from astrocytes, in the co-culture system after OGD/R. The PI3K/AKT and ERK signaling pathways as well as the p-TRKA/B receptors were involved in the process. In addition, the levels of TNF-α and IL-1β secreted from astrocytes after OGD/R were markedly reduced after d,l-PHPB treatment, which was mainly due to the suppression of phosphorylated p38. In conclusion, the present study demonstrates that the neuroprotective effects of d,l-PHPB were improved by astrocytes, mainly mediated by increasing the release of BDNF/NGF and attenuating inflammatory cytokines.

Neurodegenerative signaling factors and mechanisms in Parkinson's pathology

Parkinson's disease (PD) is a chronic and progressive degenerative disorder of central nervous system which is mainly characterized by selective loss of dopaminergic neurons in the nigrostrial pathway. Clinical symptoms of this devastating disease comprise motor impairments such as resting tremor, bradykinesia, postural instability and rigidity. Current medications only provide symptomatic relief but fail to halt the dopaminergic neuronal death. While the etiology of dopaminergic neuronal death is not fully understood, combination of various molecular mechanisms seems to play a critical role. Studies from experimental animal models have provided crucial insights into the molecular mechanisms in disease pathogenesis and recognized possible targets for therapeutic interventions. Recent findings implicate the involvement of abnormal protein accumulation and phosphorylation, mitochondrial dysfunction, oxidative damage and deregulated kinase signaling as key molecular mechanisms affecting the normal function as well survival of dopaminergic neurons. Here we discuss the relevant findings on the PD pathology related mechanisms and recognition of the cell survival mechanisms which could be used as targets for neuroprotective strategies in preventing this devastating disorder.

Synaptopathic mechanisms of neurodegeneration and dementia: Insights from Huntington's disease

Dementia encapsulates a set of symptoms that include loss of mental abilities such as memory, problem solving or language, and reduces a person's ability to perform daily activities. Alzheimer's disease is the most common form of dementia, however dementia can also occur in other neurological disorders such as Huntington's disease (HD). Many studies have demonstrated that loss of neuronal cell function manifests pre-symptomatically and thus is a relevant therapeutic target to alleviate symptoms. Synaptopathy, the physiological dysfunction of synapses, is now being approached as the target for many neurological and psychiatric disorders, including HD. HD is an autosomal dominant and progressive degenerative disorder, with clinical manifestations that encompass movement, cognition, mood and behaviour. HD is one of the most common tandem repeat disorders and is caused by a trinucleotide (CAG) repeat expansion, encoding an extended polyglutamine tract in the huntingtin protein. Animal models as well as human studies have provided detailed, although not exhaustive, evidence of synaptic dysfunction in HD. In this review, we discuss the neuropathology of HD and how the changes in synaptic signalling in the diseased brain lead to its symptoms, which include dementia. Here, we review and discuss the mechanisms by which the 'molecular orchestras' and their 'synaptic symphonies' are disrupted in neurodegeneration and dementia, focusing on HD as a model disease. We also explore the therapeutic strategies currently in pre-clinical and clinical testing that are targeted towards improving synaptic function in HD.

The neuroprotective effects of Tao-Ren-Cheng-Qi Tang against embolic stroke in rats

Background

Combinations of the traditional Chinese and Western medicines have been used to treat numerous diseases throughout the world, and there is a growing body of evidence showing that some of the herbs used in traditional Chinese medicine elicit significant pharmacological effects. The aim of this study was to demonstrate the neuroprotective effects of Tao-Ren-Cheng-Qi Tang (TRCQT) in combination with aspirin following middle cerebral artery occlusion (MCAO)—induced embolic stroke in rats.

Methods

A blood clot was embolized into the middle cerebral artery of rats to induce focal ischemic brain injury. After 24 h of MCAO occlusion, the rats were arbitrarily separated into five groups and subjected to different oral treatment processes with TRCQT and aspirin for 30 days before being evaluated in terms of their neurological behavior using a four-point system. The rats were sacrificed at 30 days after drug treatment and the infarct volumes were measured using a 2,3,5-triphenyltetrazolium chloride staining method. Tumor necrosis factor-α (TNF-α), c-Jun N-terminal kinases (JNK), activated caspase-3 and Bax were detected by western blot analysis. The apoptotic cells were identified by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. ROS generation was also measured by electron spin resonance spectrometry.

Results

Rats treated with TRCQT alone or in combination with aspirin showed a significantly reduced infarct volume (P < 0.001) and improved neurological outcome compared with those treated with distilled water. Rats treated with TRCQT alone (P = 0.021) or in combination with aspirin (P = 0.02) also showed significantly reduced MCAO-induced expression levels of TNF-α and pJNK (P < 0.001) in their ischemic regions. Rats treated with TRCQT alone or in combination with aspirin showed decreased apoptosis by a reduction in the number of TUNEL positive cells, which inhibited the expression of activated caspase-3 (P = 0.038) and Bax (P = 0.004; P = 0.003). TRCQT also led to a significant concentration-dependent reduction in the formation of hydroxyl radicals (P < 0.001).

Conclusions

TRCQT reduced brain infarct volume and improved neurological outcomes by reducing apoptosis, attenuating the expression of TNF-α and p-JNK, and reducing the formation of hydroxyl radicals in MCAO-induced embolic stroke of rats.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-017-0128-y) contains supplementary material, which is available to authorized users.

Inflammatory responses in brain ischemia

Brain infarction causes tissue death by ischemia due to occlusion of the cerebral vessels and recent work has shown that post stroke inflammation contributes significantly to the development of ischemic pathology. Because secondary damage by brain inflammation may have a longer therapeutic time window compared to the rescue of primary damage following arterial occlusion, controlling inflammation would be an obvious therapeutic target. A substantial amount of experimentall progress in this area has been made in recent years. However, it is difficult to elucidate the precise mechanisms of the inflammatory responses following ischemic stroke because inflammation is a complex series of interactions between inflammatory cells and molecules, all of which could be either detrimental or beneficial. We review recent advances in neuroinflammation and the modulation of inflammatory signaling pathways in brain ischemia. Potential targets for treatment of ischemic stroke will also be covered. The roles of the immune system and brain damage versus repair will help to clarify how immune modulation may treat stroke.

Ferulic Acid Administered at Various Time Points Protects against Cerebral Infarction by Activating p38 MAPK/p90RSK/CREB/Bcl-2 Anti-Apoptotic Signaling in the Subacute Phase of Cerebral Ischemia-Reperfusion Injury in Rats

Objectives

This study aimed to evaluate the effects of ferulic acid (FA) administered at various time points before or after 30 min of middle cerebral artery occlusion (MCAo) followed by 7 d of reperfusion and to examine the involvement of mitogen-activated protein kinase (MAPK) signaling pathways in the cortical penumbra.

Methods

FA was intravenously administered to rats at a dose of 100 mg/kg 24 h before ischemia (B-FA), 2 h before ischemia (P-FA), immediately after ischemic insult (I-FA), 2 h after reperfusion (R-FA), or 24 h after reperfusion (D-FA).

Results

Our study results indicated that P-FA, I-FA, and R-FA effectively reduced cerebral infarct areas and neurological deficits. P-FA, I-FA, and R-FA significantly downregulated glial fibrillary acidic protein (GFAP), mitochondrial Bax, cytochrome c, and cleaved caspase-3 expression, and effectively restored the phospho-p38 MAPK (p-p38 MAPK)/p38 MAPK ratio, phospho-90 kDa ribosomal S6 kinase (p-p90RSK) expression, phospho-Bad (p-Bad) expression, the phospho-cAMP response element-binding protein (p-CREB)/CREB ratio, the cytosolic and mitochondrial Bcl-2/Bax ratios, and the cytosolic Bcl-xL/Bax ratio in the cortical penumbra 7 d after reperfusion. SB203580, a specific inhibitor of p38 MAPK, administered 30 min prior to ischemia abrogated the downregulating effects of I-FA on cerebral infarction, and mitochondrial Bax and cleaved caspase-3 expression, and the upregulating effects of I-FA on the p-p38 MAPK/p38 MAPK ratio, p-p90RSK expression, p-Bad expression, and the p-CREB/CREB, and cytosolic and mitochondrial Bcl-2/Bax ratios.

Conclusions

Our study results thus indicate that P-FA, I-FA, and R-FA effectively suppress reactive astrocytosis and exert neuroprotective effects against cerebral infarction by activating p38 MAPK signaling. The regulating effects of P-FA, I-FA, and R-FA on Bax-induced apoptosis result from activation of the p38 MAPK/p90RSK/CREB/Bcl-2 signaling pathway, and eventually contribute to inhibition of the cytochrome c-mediated caspase-3-dependent apoptotic pathway in the cortical penumbra 7 d after reperfusion.

Cell-permeable p38 MAP kinase promotes migration of adult neural stem/progenitor cells

Endogenous neural stem/progenitor cells (NPCs) can migrate toward sites of injury, but the migration activity of NPCs is insufficient to regenerate damaged brain tissue. In this study, we showed that p38 MAP kinase (p38) is expressed in doublecortin-positive adult NPCs. Experiments using the p38 inhibitor SB203580 revealed that endogenous p38 participates in NPC migration. To enhance NPC migration, we generated a cell-permeable wild-type p38 protein (PTD-p38WT) in which the HIV protein transduction domain (PTD) was fused to the N-terminus of p38. Treatment with PTD-p38WT significantly promoted the random migration of adult NPCs without affecting cell survival or differentiation; this effect depended on the cell permeability and kinase activity of the fusion protein. These findings indicate that PTD-p38WT is a novel and useful tool for unraveling the roles of p38, and that this protein provides a reasonable approach for regenerating the injured brain by enhancing NPC migration.

Platelet-activating factor receptor (PAFR) plays a crucial role in experimental global cerebral ischemia and reperfusion

Stroke is one of the most frequent causes of death and disability worldwide leading to a significant clinical and socioeconomic burden. Although different mechanisms are involved in the pathogenesis of stroke, inflammatory response occurs after ischemia and contributes to the expansion of brain injury. Platelet-activating factor receptor (PAF) plays crucial roles in both physiological and pathological conditions in the brain. PAF receptor (PAFR) may be expressed on cellular and nuclear membranes of various cell types, especially leukocytes, platelets, endothelial cells, neuronal cells and microglia. Herein, using mice lacking the PAFR receptor (PAFR(-/-)), we investigate a potential role for this receptor during experimental transient global cerebral ischemia and reperfusion (BCCAo). In PAFR deficiency, we observed a significant improvement in the neurological deficits, which were associated with a reduction of brain infarcted area as evaluated by triphenyltetrazolium chloride (TTC). Moreover, a decrease in the percentage of necrotic cavities areas and in the frequency of ischemic neurons was also found by employing histometric analysis. In addition, in PAFR(-/-) mice there was prevention of caspase-3 activation and decreased vascular permeability and brain edema. Decreased brain levels of the cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and the chemokine (C-X-C motif) ligand 1 (CXCL1) by ELISA were also detected in PAFR(-/-) BCCAo animals. Taken together, our results suggest that PAFR activation might be crucial for the global brain ischemia and reperfusion injury.

Role of adenosine A2A receptor in cerebral ischemia reperfusion injury: Signaling to phosphorylated extracellular signal-regulated protein kinase (pERK1/2)

Following brain ischemia reperfusion (IR), the dramatic increase in adenosine activates A2AR to induce further neuronal damage. Noteworthy, A2A antagonists have proven efficacious in halting IR injury, however, the detailed downstream signaling remains elusive. To this end, the present study aimed to investigate the possible involvement of phospho-extracellular signal-regulated kinase (pERK1/2) pathway in mediating protection afforded by the central A2A blockade. Male Wistar rats (250-270 g) subjected to bilateral carotid occlusion for 45 min followed by a 24-h reperfusion period showed increased infarct size corroborating histopathological damage, memory impairment and motor incoordination as well as increased locomotor activity. Those events were mitigated by the unilateral intrahippocampal administration of the selective A2A antagonist SCH58261 via a decrease in pERK1/2 downstream from diacyl glycerol (DAG) signaling. Consequent to pERK1/2 inhibition, reduced hippocampal microglial activation, glial tumor necrosis factor-alpha (TNF-α) and brain-derived neurotropic factor (BDNF) expression, glutamate (Glu), inducible nitric oxide synthase (iNOS) and thiobarbituric acid reactive substances (TBARS) were evident in animals receiving SCH58261. Additionally, the anti-inflammatory cytokine interleukin-10 (IL-10) increased following nuclear factor (erythroid-derived 2)-like 2 (Nrf-2). Taken all together, these events suppressed apoptotic pathways via a reduction in cytochrome c (Cyt. c) as well as caspase-3 supporting a crucial role for pERK1/2 inhibition in consequent reduction of inflammatory and excitotoxic cascades as well as correction of the redox imbalance.

Purinergic signalling in brain ischemia

Ischemia is a multifactorial pathology characterized by different events evolving in the time. After ischemia a primary damage due to the early massive increase of extracellular glutamate is followed by activation of resident immune cells, i.e microglia, and production or activation of inflammation mediators. Protracted neuroinflammation is now recognized as the predominant mechanism of secondary brain injury progression. Extracellular concentrations of ATP and adenosine in the brain increase dramatically during ischemia in concentrations able to stimulate their respective specific P2 and P1 receptors. Both ATP P2 and adenosine P1 receptor subtypes exert important roles in ischemia. Although adenosine exerts a clear neuroprotective effect through A1 receptors during ischemia, the use of selective A1 agonists is hampered by undesirable peripheral effects. Evidence up to now in literature indicate that A2A receptor antagonists provide protection centrally by reducing excitotoxicity, while agonists at A2A (and possibly also A2B) and A3 receptors provide protection by controlling massive infiltration and neuroinflammation in the hours and days after brain ischemia. Among P2X receptors most evidence indicate that P2X7 receptor contribute to the damage induced by the ischemic insult due to intracellular Ca(2+) loading in central cells and facilitation of glutamate release. Antagonism of P2X7 receptors might represent a new treatment to attenuate brain damage and to promote proliferation and maturation of brain immature resident cells that can promote tissue repair following cerebral ischemia. Among P2Y receptors, antagonists of P2Y12 receptors are of value because of their antiplatelet activity and possibly because of additional anti-inflammatory effects. Moreover strategies that modify adenosine or ATP concentrations at injury sites might be of value to limit damage after ischemia. This article is part of the Special Issue entitled 'Purines in Neurodegeneration and Neuroregeneration'.

Effect of Electroacupuncture on Cell Apoptosis and ERK Signal Pathway in the Hippocampus of Adult Rats with Cerebral Ischemia-Reperfusion

Background. EA therapy is a traditional therapeutic approach for alleviation of cerebral I/R-induced brain injury. We investigated the effect of EA on MCAO rat model to examine the mechanism of apoptosis in the rat hippocampus. Methods. 200 male Sprague-Dawley rats were randomly divided into sham, I/R, EA, ERK inhibitor (PD), and ERK inhibitor+EA (PD+EA) groups. Each group was subdivided into 5 groups according to different time points. Locomotor behaviors were evaluated using neurological scales and morphological examination was performed using HE staining. Apoptosis index of neural cells in local infarcted area was measured by TUNEL and p-ERK expression was detected using immunohistochemistry technique and western blot analysis. Results. Neurological deficit scores and neural apoptosis in the EA group were lower than I/R group at the same time points, respectively. At different time points, p-ERK level was increased in the ischemic hippocampal CA1 in the EA group as compared to I/R group; the increased level was increased most at 1 day, 3 days, and 1 week (p < 0.01). Conclusion. EA alleviates neurological deficit, reduces apoptosis index, and simultaneously upregulates the expression of p-ERK signal pathway in rats subjected to I/R injury.

Protective Effects of UCF-101 on Cerebral Ischemia-Reperfusion (CIR) is Depended on the MAPK/p38/ERK Signaling Pathway

This study was aimed to investigate the treatment mechanisms of 5-[5-(2-nitrophenyl) furfuryliodine]-1,3-diphenyl-2-thiobarbituric acid (UCF-101) in cerebral ischemia-reperfusion (CIR) model rats. Total of 54 healthy male Wistar rats were randomly assigned into three groups, namely sham group, vehicle group, and UCF-101 group. The CIR-injured model was established by right middle cerebral artery occlusion and reperfusion. Neurological function was assessed by an investigator according to the Longa neurologic deficit scores. Meanwhile, the cerebral tissue morphology and apoptotic neurons were evaluated by H&E and TUNEL staining, respectively. Additionally, the expressions of caspase 3, p-p38, and p-ERK were detected by immunohistochemistry or/and Western blotting assays. As results, neurologic deficit and pathological damage were obviously enhanced and TUNEL positive neurons were significantly increased in CIR-injured rats, as compared with those in sham group. Furthermore, the expressions of caspase 3, p-p38, and p-ERK were also significantly increased in vehicle group than those in sham group (P < 0.05). However, UCF-101 treatment could markedly weaken the neurologic deficit with lower scores and improve pathological condition. After UCF-101 treatment, TUNEL positive neurons as well as the expression of caspase 3 were significantly decreased than those in vehicle group (P < 0.05). Besides, p-p38 was decreased while p-ERK was increased in UCF-101 group than those in vehicle group (P < 0.05). Therefore, we concluded that the protective effects of UCF-101 might be associated with apoptosis process and MAPK signaling pathway in the CIR-injured model.