Post-ischemic brain damage: pathophysiology and role of inflammatory mediators

Regulation of PGE2 Pathway During Cerebral Ischemia Reperfusion Injury in Rat

Stroke is an acute central nervous system disease with high morbidity and mortality rate. Cerebral ischemia reperfusion (I/R) injury is easily induced during the development or treatment of stroke and subsequently leads to more serious brain damage. Prostaglandin E2 (PGE2) is one of the most important inflammatory mediators in the brain and contributes to both physiological and pathophysiological functions. It may be upregulated and subsequently plays a key role in cerebral ischemia reperfusion injury. The synthesis and degradation of PGE2 is an extremely complex process, with multiple key stages and molecules. However, there are few comprehensive and systematic studies conducted to investigate the synthesis and degradation of PGE2 during cerebral I/R injury, which is what we want to demonstrate. In this study, qRT-PCR and immunoblotting demonstrated that the key enzymes in PGE2 synthesis, including COX-1, COX-2, mPGES-1 and mPGES-2, were upregulated during cerebral I/R injury, but 15-PGDH, the main PGE2 degradation enzyme, was downregulated. In addition, two of PGE2 receptors, EP3 and EP4, were also increased. Meanwhile, immunohistochemistry demonstrated the localization of these molecules in ischemic areas, including cortex, striatum and hippocampus, and reflected their expression patterns in different regions. Combining the results of PCR, Western blotting and immunohistochemistry, we can determine where the increase or decrease of these molecules occurs. Overall, these results further indicate a possible pathway that mediates enhanced production of PGE2, and thus that may impact production of inflammatory cytokines including IL-1β and TNF-α during cerebral I/R injury.

Inflammatory Cytokines are in Action: Brain Plasticity and Recovery after Brain Ischemia Due to Delayed Melatonin Administration

OBJECTIVES

Post-ischemic inflammation leads to apoptosis as an indirect cause of functional disabilities after the stroke. Melatonin may be a good candidate for the stroke recovery because of its anti-inflammatory effects. Therefore, we investigated the effect of melatonin on inflammation in the functional recovery of brain by evaluating ipsilesional and contralesional alterations.

MATERIALS AND METHODS

Melatonin (4 mg/kg/day) was intraperitoneally administered into the mice from the 3^rd to the 55^th day of the post-ischemia after 30 min of middle cerebral artery occlusion.

RESULTS

Melatonin produced a functional recovery by reducing the emigration of the circulatory leukocytes and the local microglial activation within the ischemic brain. Overall, the expression of the inflammation-related genes reduced upon melatonin treatment in the ischemic hemisphere. On the other hand, the expression level of the inflammatory cytokine genes raised in the contralateral hemisphere at the 55^th day of the post-ischemia. Furthermore, melatonin triggers an increase in the iNOS expression and a decrease in the nNOS expression in the ipsilateral hemisphere at the earlier times in the post-ischemic recovery. At the 55^th day of the post-ischemic recovery, melatonin administration enhanced the eNOS and nNOS protein expressions.

CONCLUSIONS

The present molecular, biological, and histological data have revealed broad anti-inflammatory effects of melatonin in both hemispheres with distinct temporal and spatial patterns at different phases of post-stroke recovery. These outcomes also established that melatonin act recruitment of contralesional rather than of ipsilesional.

Targeting neutrophils as a novel therapeutic strategy after stroke

Stroke is followed by an intricate immune interaction involving the engagement of multiple immune cells, including neutrophils. As one of the first responders recruited to the brain, the crucial roles of neutrophils in the ischemic brain damage are receiving increasing attention in recent years. Notably, neutrophils are not homogenous, and yet there is still a lack of full knowledge about the extent and impact of neutrophil heterogeneity. The biological understanding of the neutrophil response to both innate and pathological conditions is rapidly evolving as single-cell-RNA sequencing uncovers overall neutrophil profiling across maturation and differentiation contexts. In this review, we scrutinize the latest research that points to the multifaceted role of neutrophils in different conditions and summarize the regulatory signals that may determine neutrophil diversity. In addition, we list several potential targets or therapeutic strategies targeting neutrophils to limit brain damage following ischemic stroke.

Inhibition of PAR-2 Attenuates Neuroinflammation and Improves Short-Term Neurocognitive Functions Via ERK1/2 Signaling Following Asphyxia-Induced Cardiac Arrest in Rats

OBJECTIVE

Global cerebral ischemia-induced neuroinflammation causes neurofunctional impairment following cardiac arrest. Previous studies have demonstrated that the activation of protease-activated receptor-2 (PAR-2) contributes to neuroinflammation. In the present study, we aimed to determine the potential treatment effect of PAR-2 inhibition against neuroinflammation in the setting of asphyxial CA (ACA) in rats.

METHODS

A total of 116 adult, male Sprague-Dawley rats were randomly divided into Sham (n = 18) and ACA (n = 98) groups. Time course, short-term outcome, and mechanism studies were conducted. All drugs were delivered intranasally. The effect of PAR-2 inhibitor FSLLRY-NH2 on neurocognitive functions was assessed by neurologic deficit score, number of seizures, and T-maze test, while hippocampal neuronal degeneration was evaluated by Fluoro-Jade C staining after ACA. Western blotting was performed for the mechanism study at 24 h following ACA. Selective PAR-2 agonist (AC55541) and ERK1/2 inhibitor (PD98059) were used for intervention.

RESULTS

Inhibition of PAR-2 decreased neuroinflammation, reduced the number of degenerating hippocampal neurons and improved neurocognitive functions following ACA. PAR-2 activator alone exerted opposite effects to PAR-2 inhibitor. PAR-2 mediated the augmented brain levels of proinflammatory cytokines by promoting the phosphorylation of ERK1/2.

CONCLUSIONS

PAR-2 inhibition diminished neuroinflammation and thereby reduced hippocampal neuronal degeneration and neurocognitive impairment following ACA. This effect was at least partly mediated via the PAR-2/ERK1/2 signaling.

Emodin Prevented Depression in Chronic Unpredicted Mild Stress-Exposed Rats by Targeting miR-139-5p/5-Lipoxygenase

Background

The use of medicinal plant ingredients is one of the goals of developing potential drugs for treating depression. Compelling evidence suggests that anti-inflammatory medicines may block the occurrence of depression. We studied the effect of a natural compound, emodin, on the development of psychosocial stress-induced depression and the underlying mechanisms.

Methods

Chronic unpredicted mild stress (CUMS) for 7 weeks was performed to replicate psychosocial stress in rats. The sucrose preference test, force swimming test, and open field test were used to evaluate their behaviors. The differentially expressed proteins in the hippocampus were analyzed using proteomics. Nissl staining and Golgi staining were used to detect the loss of neurons and synapses, immunohistochemical staining was used to detect the activation of microglia, and the enzyme-linked immunosorbent assay was used to detect the levels of pro-inflammatory cytokines. Western blotting, immunofluorescence, and quantitative polymerase chain reaction were also performed.

Results

Hippocampal inflammation with up-regulated 5-lipoxygenase (5-LO) was observed in the depressed rats after CUMS exposure. The upregulation of 5-LO was caused by decreased miR-139-5p. To observe the effect of emodin, we screened out depression-susceptible (DeS) rats during CUMS and treated them with emodin (80 mg/kg/day). Two weeks later, emodin prevented the depression behaviors in DeS rats along with a series of pathological changes in their hippocampi, such as loss of neurons and spines, microglial activation, increased interleukin-1β and tumor necrosis factor-α, and the activation of 5-LO. Furthermore, we demonstrated that emodin inhibited its excess inflammatory response, possibly by targeting miR-139-5p/5-LO and modulating glycogen synthase kinase 3β and nuclear factor erythroid 2-related factor 2.

Conclusion

These results provide important evidence that emodin may be a candidate agent for the treatment of depression and established a key role of miR-139-5p/5-LO in the inflammation of depression.

Role of microglial and endothelial CD36 in post-ischemic inflammasome activation and interleukin-1β-induced endothelial activation

Cerebral ischemia is associated with an acute inflammatory response that contributes to the resulting injury. The innate immunity receptor CD36, expressed in microglia and endothelium, and the pro-inflammatory cytokine interleukin-1β (IL-1β) are involved in the mechanisms of ischemic injury. Since CD36 has been implicated in activation of the inflammasome, the main source of IL-1β, we investigated whether CD36 mediates brain injury through the inflammasome and IL-1β. We found that active caspase-1, a key inflammasome component, is decreased in microglia of CD36-deficient mice subjected to transient middle cerebral artery occlusion, an effect associated with a reduction in brain IL-1β. Conditional deletion of CD36 either in microglia or endothelium reduced ischemic injury in mice, attesting to the pathogenic involvement of CD36 in both cell types. Application of an ischemic brain extract to primary brain endothelial cell cultures from wild type (WT) mice induced IL-1β-dependent endothelial activation, reflected by increases in the cytokine colony stimulating factor-3, a response markedly attenuated in CD36-deficient endothelia. Similarly, the increase in colony stimulating factor-3 induced by recombinant IL-1β was attenuated in CD36-deficient compared to WT endothelia. We conclude that microglial CD36 is a key determinant of post-ischemic IL-1β production by regulating caspase-1 activity, whereas endothelial CD36 is required for the full expression of the endothelial activation induced by IL-1β. The data identify microglial and endothelial CD36 as critical upstream components of the acute inflammatory response to cerebral ischemia and viable putative therapeutic targets.

The Association Between Systemic Inflammatory Markers and Post-Stroke Depression: A Prospective Stroke Cohort

Objective

Inflammation plays an important role in stroke. Many inflammatory markers in peripheral blood are proved to be associated with stroke severity or prognosis. But few comprehensive models or scales to evaluate the post-stroke depression (PSD) have been reported. In this study, we aimed to compare the level of systemic inflammation markers between PSD and non-PSD patients and explore the association of these inflammatory markers with PSD.

Methods

Totally, 432 ischemic stroke patients were consecutively enrolled in the study and received 1 month follow-up. We used the 17-Hamilton Rating Scale to measure depressive symptoms at 1 month after stroke. With the Hamilton Depression Scale score of >7, patients were diagnosed with PSD. Systemic immune-inflammation index (SII), neutrophil-to-lymphocyte (NLR), platelet-to-lymphocyte (PLR) and derived neutrophil-to-lymphocyte ratio (dNLR) were calculated from the admission blood work.

Results

Finally, 129 patients (30.5%) were diagnosed with PSD at 1 month. PSD patients showed significantly higher levels of SII (501.27 (345.43-782.58) vs 429.60 (315.64-570.98), P=0.001), NLR (2.36 (1.77-3.82) vs 2.17 (1.56-2.80), P=0.010), dNLR (1.67 (1.30-2.51) vs 1.54 (1.16-1.99), P=0.009), PLR (124.65 (95.25-155.15) vs 109.22 (92.38-142.03), P=0.015), especially SII at admission as compared to non-PSD patients. In the logistic analysis, SII value (>547.30) was independently associated with the occurrence of PSD (OR=2.181, 95% CI=1.274-3.732, p =0.004), better than dNLR (OR=1.833, 95% CI=1.071-3.137, p =0.027), PLR (OR= 1.822, 95% CI=1.063-3.122, p =0.029) and NLR (OR =1.728, 95% CI=1.009-2.958, p =0.046).

Conclusion

Increased SII, PLR, dNLR, NLR, particularly SII at admission, are significantly correlated with PSD and may add some prognostic clues to find early discovery of PSD.

Progress in Mesenchymal Stem Cell Therapy for Ischemic Stroke

Ischemic stroke (IS) is a serious cerebrovascular disease with high morbidity and disability worldwide. Despite the great efforts that have been made, the prognosis of patients with IS remains unsatisfactory. Notably, recent studies indicated that mesenchymal stem cell (MSCs) therapy is becoming a novel research hotspot with large potential in treating multiple human diseases including IS. The current article is aimed at reviewing the progress of MSC treatment on IS. The mechanism of MSCs in the treatment of IS involved with immune regulation, neuroprotection, angiogenesis, and neural circuit reconstruction. In addition, nutritional cytokines, mitochondria, and extracellular vesicles (EVs) may be the main mediators of the therapeutic effect of MSCs. Transplantation of MSCs-derived EVs (MSCs-EVs) affords a better neuroprotective against IS when compared with transplantation of MSCs alone. MSC therapy can prolong the treatment time window of ischemic stroke, and early administration within 7 days after stroke may be the best treatment opportunity. The deliver routine consists of intraventricular, intravascular, intranasal, and intraperitoneal. Furthermore, several methods such as hypoxic preconditioning and gene technology could increase the homing and survival ability of MSCs after transplantation. In addition, MSCs combined with some drugs or physical therapy measures also show better neurological improvement. These data supported the notion that MSC therapy might be a promising therapeutic strategy for IS. And the application of new technology will promote MSC therapy of IS.

New epigenetic players in stroke pathogenesis: From non-coding RNAs to exosomal non-coding RNAs

Non-coding RNAs (ncRNAs) have critical role in the pathophysiology as well as recovery after ischemic stroke. ncRNAs, particularly microRNAs, and the long non-coding RNAs (lncRNAs) are critical for angiogenesis and neuroprotection, and they have been suggested to be therapeutic, diagnostic and prognostic tools in cerebrovascular diseases, including stroke. Moreover, exosomes have been considered as nanocarriers capable of transferring various cargos, such as lncRNAs and miRNAs to recipient cells, with prominent inter-cellular roles in the mediation of neuro-restorative events following strokes and neural injuries. In this review, we summarize the pathogenic role of ncRNAs and exosomal ncRNAs in the stroke.

Enhanced expression of P2X4 purinoceptors in pyramidal neurons of the rat hippocampal CA1 region may be involved ischemia-reperfusion injury

Ischemic stroke is the most serious disease that harms human beings. In principle, its treatment is to restore blood flow supply as soon as possible. However, after the blood flow is restored, it will lead to secondary brain injury, that is, ischemia-reperfusion injury. The mechanism of ischemia-reperfusion injury is very complicated. This study showed that P2X4 receptors in the pyramidal neurons of rat hippocampus were significantly upregulated in the early stage of ischemia-reperfusion injury. Neurons with high expression of P2X4 receptors are neurons that are undergoing apoptosis. Intraventricular injection of the P2X4 receptor antagonist 5-(3-bromophenyl)-1,3-dihydro-2H-benzofuro[3,2-e]-1,4-diazepin-2-one (5-BDBD) and PSB-12062 can partially block neuronal apoptosis, to promote the survival of neurons, indicating that ATP through P2X4 receptors is involved in the process of cerebral ischemia-reperfusion injury. Therefore, identifying the mechanism of neuronal degeneration induced by extracellular ATP via P2X4 receptors after ischemia-reperfusion will likely find new targets for the treatment of ischemia-reperfusion injury, and will provide a useful theoretical basis for the treatment of ischemia-reperfusion injury.

Stroke and immunotherapy: Potential mechanisms and its implications as immune-therapeutics

Ischemia or brain injuries are mostly associated with emergency admissions and huge mortality rates. Stroke is a fatal cerebrovascular malady and second top root of disability and death in both developing and developed countries with a projected rise of 24.9% (from 2010) by 2030. It's the most frequent cause of morbidities and systemic permanent morbidities due to its multi-organ systemic pathology. Brain edema or active immune response cause disturbed or abnormal systemic affects causing inflammatory damage leading to secondary infection and secondary immune response which leads to activation like pneumonia or urine tract infections. There are a variety of post stroke treatments available which claims their usefulness in reducing or inhibiting post stroke and recurrent stroke damage followed by heavy inflammatory actions. Stroke does change the quality of life and also ensures daily chronic rapid neurodegeneration and cognitive decline. The only approved therapies for stroke are alteplase and thrombectomy which is associated with adverse outcomes and are not a total cure for ischemic stroke. Stroke and immune response are reciprocal to the pathology and time of event and it progresses till untreated. The immune reaction during ischemia opens new doors for advanced targeted therapeutics. Nowadays stem cell therapy has shown better results in stroke-prone individuals. Few monoclonal antibodies like natalizumab have shown great impact on pre-clinical and clinical stroke trial studies. In this current review, we have explored an immunology of stroke, current therapeutic scenario and future potential targets as immunotherapeutic agents in stroke therapeutics.

Neobavaisoflavone protects osteoblasts from dexamethasone-induced oxidative stress by upregulating the CRNDE-mediated Nrf2/HO-1 signaling pathway

Neobavaisoflavone (NBIF) is a flavonoid, which has a variety of pharmacological activities. However, the mechanism of NBIF in the treatment of osteoporosis still needs further exploration. The differentiation of osteoblast MC-3T3-E1 cells after treatment was observed by Alizarin red staining. Cell counting kit-8 and flow cytometry were used to detect viability, apoptosis, and reactive oxygen species (ROS) levels of treated MC-3T3-E1 cells, respectively. Malondialdehyde (MDA), lactate dehydrogenase (LDH), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were tested by ELISA kits. The expressions of lncRNA MALAT1, MEG3, CRNDE, Runx2, osteocalcin (OCN), osteopontin (OPN), collagen I (col-I), nuclear Nrf2, cytoplasm Nrf2, heme oxygenase-1 (HO-1) and quinone oxidoreductase 1 (NQO1) in treated MC-3T3-E1 cells were examined by Quantitative real-time PCR or Western blot. Dexamethasone (Dex) inhibited the viability of MC-3T3-E1 cells, while the appropriate amount of NBIF had no significantly effect on cell viability. Dex downregulated CRNDE expression, whereas NBIF upregulated CRNDE. Overexpressed CRNDE and NBIF reversed the inhibitory effects of Dex on cell viability, differentiation and levels of SOD, GSH-Px, Runx2, OCN, OPN, col-I, nuclear Nrf2, HO-1 and NQO1 while reversing the promoting effect of Dex on apoptosis and the levels of ROS, MDA, LDH and cytoplasm Nrf2 in MC-3T3-E1 cells, respectively, but shCRNDE further reversed the effects of NBIF in MC-3T3-E1 cells. NBIF protected osteoblasts from Dex-induced oxidative stress by upregulating the CRNDE-mediated Nrf2/HO-1 signaling pathway.

Astrocyte-induced synapse formation and ischemic stroke

Astrocytes are closely associated with the regulation of synapse formation and function. In addition, astrocytes have been shown to block certain brain impairments, including synaptic damage from stroke and other diseases of the central nervous system (CNS). Although astrocytes do not completely prevent synaptic damage, they appear to be protective and to restore synaptic function following damage. The purpose of this study is to discuss the role of astrocytes in synaptogenesis and synaptic damage in ischemic stroke. I detail the mechanism of action of the multiple factors secreted by astrocytes that are involved in synapse formation. In particular, I describe the characteristics and role in synapse formation of each secreted molecule related to synaptic structure and function. Furthermore, I discuss the effect of astrocytes on synaptogenesis and repair in ischemic stroke and in other CNS diseases. Astrocytes release molecules such as thrombospondin, hevin, secreted protein acidic rich in cysteine, etc., due to activation by ischemia to induce synaptic structure and function, an effect associated with protection of the brain from synaptic damage in ischemic stroke. In conclusion, I show that astrocytes may regulate synaptic transmission while having the potential to block and repair synaptic dysfunction in stroke-associated brain damage.

Pathological changes in neurovascular units: Lessons from cases of vascular dementia

Vascular dementia (VD) is the second leading cause of dementia after Alzheimer's disease (AD). The decrease of cerebral blood flow (CBF) to different degrees is one of the main causes of VD. Neurovascular unit (NVU) is a vessel‐centered concept, emphasizing all the cellular components play an integrated role in maintaining the normal physiological functions of the brain. More and more evidence shows that reduced CBF causes a series of changes in NVU, such as impaired neuronal function, abnormal activation of glial cells, and changes in vascular permeability, all of which collectively play a role in the pathogenesis of VD. In this paper, we review NVU changes as CBF decreases, focusing on each cellular component of NVU. We also highlight remote ischemic preconditioning as a promising approach for VD prevention and treatment from the NVU perspective of view.

Targeting the Immune System for Ischemic Stroke

Stroke is responsible for almost 6 million deaths and more than 10% of all mortalities each year, and two-thirds of stroke survivors remain disabled. With treatments for ischemic stroke still limited to clot lysis and/or mechanical removal, new therapeutic targets are desperately needed. In this review, we provide an overview of the complex mechanisms of innate and adaptive immune cell-mediated inflammatory injury, that exacerbates infarct development for several days after stroke. We also highlight the features of poststroke systemic immunodepression that commonly leads to infections and some mortalities, and argue that safe and effective therapies will need to balance pro- and anti-inflammatory mechanisms in a time-sensitive manner, to maximize the likelihood of an improved long-term outcome.

The Stroke-Induced Blood-Brain Barrier Disruption: Current Progress of Inspection Technique, Mechanism, and Therapeutic Target

Stroke is one of the leading causes of mortality and morbidity worldwide. The blood-brain barrier (BBB) is a characteristic structure of microvessel within the brain. Under normal physiological conditions, the BBB plays a role in the prevention of harmful substances entering into the brain parenchyma within the central nervous system. However, stroke stimuli induce the breakdown of BBB leading to the influx of cytotoxic substances, vasogenic brain edema, and hemorrhagic transformation. Therefore, BBB disruption is a major complication, which needs to be addressed in order to improve clinical outcomes in stroke. In this review, we first discuss the structure and function of the BBB. Next, we discuss the progress of the techniques utilized to study BBB breakdown in in-vitro and in-vivo studies, along with biomarkers and imaging techniques in clinical settings. Lastly, we highlight the mechanisms of stroke-induced neuroinflammation and apoptotic process of endothelial cells causing BBB breakdown, and the potential therapeutic targets to protect BBB integrity after stroke. Secondary products arising from stroke-induced tissue damage provide transformation of myeloid cells such as microglia and macrophages to pro-inflammatory phenotype followed by further BBB disruption via neuroinflammation and apoptosis of endothelial cells. In contrast, these myeloid cells are also polarized to anti-inflammatory phenotype, repairing compromised BBB. Therefore, therapeutic strategies to induce anti-inflammatory phenotypes of the myeloid cells may protect BBB in order to improve clinical outcomes of stroke patients.

XingNaoJing injection ameliorates cerebral ischaemia/reperfusion injury via SIRT1-mediated inflammatory response inhibition

Context: XingNaoJing injection (XNJ), extracted from a traditional compound Chinese medicine Angong niuhuang pill, is well known for treating stroke in the clinic, but the specific effects and mechanisms remain unclear.Objective: We investigated the mechanistic basis for the protective effect of XNJ on cerebral ischaemia/reperfusion (I/R) injury.Materials and methods: Five groups of 10 SD rats underwent 2 h of middle cerebral artery occlusion (MCAO) followed by 24 h reperfusion. XNJ at 10 and 15 mL/kg was intraperitoneally administered 24 h before ischaemia and at the onset of reperfusion respectively. The silent information regulator 1 (SIRT1) inhibitor EX527 was intracerebroventricularly injected 0.5 h before reperfusion. Cerebral infarction size, neurological scores, morphological changes, and expression levels of inflammatory mediators and SIRT1 were measured. Furthermore, human brain microvascular endothelial cells (HBMECs) were subjected to 3 h oxygen and glucose deprivation (OGD) followed by 24 h reoxygenation to mimic cerebral I/R in vitro. EX527 pre-treatment occurred 1 h before OGD. SIRT1 and inflammatory mediator levels were analyzed.Results: Both XNJ doses significantly decreased cerebral infarct area (40.11% vs. 19.66% and 9.87%) and improved neurological scores and morphological changes. Inflammatory mediator levels were remarkably decreased in both model systems after XNJ treatment. XNJ also enhanced SIRT1 expression. Notably, the SIRT1 inhibitor EX527 attenuated the XNJ-mediated decrease in inflammation in vivo and in vitro.Conclusions: XNJ improved cerebral I/R injury through inhibiting the inflammatory response via the SIRT1 pathway, which may be a useful target in treating cerebral I/R injury.

Donepezil attenuates injury following ischaemic stroke by stimulation of neurogenesis, angiogenesis, and inhibition of inflammation and apoptosis

Donepezil has proven to be an effective drug to reduce neuronal death and subsequently injury in neurodegenerative diseases. The current study evaluated the neuroprotective effects of donepezil in a rat model of ischaemic stroke and explored possible mechanisms which by this drug may reduce cell death. Temporary middle cerebral artery occlusion (tMCAO) was exerted for 45 min to induce ischaemic stroke. The animals were assigned into five groups: sham, control, and three groups treated with different doses of donepezil. Donepezil was intraperitoneally (IP) injected 4 h after reperfusion for 10 consecutive days. Infarct size was determined using TTC staining. The expression of proteins was evaluated using immunohistochemistry assays. Compared with the control group, infarct size was significantly reduced in tMCAO rats treated with different doses of donepezil. Moreover, our results showed significant decreased expression levels of apoptotic markers and pro-inflammatory mediators after treatment with different doses of donepezil for 10 days (P < 0.05). Likewise, significant increase of brain-derived neurotrophic factor (BDNF) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) proteins were found in tMCAO rats treated with donepezil compared with the control group (P < 0.05). Collectively, our findings show the validity of donepezil as a new therapeutic agent for attenuation of injury following ischaemic stroke through attenuation of inflammation and improvement of mitochondrial function, neurogenesis, and angiogenesis.

Transient expression of thyrotropin releasing hormone peptide and mRNA in the rat hippocampus following global cerebral ischemia/reperfusion injury

INTRODUCTION

The role of extra-hypothalamic thyrotropin-releasing hormone (TRH) has been investigated by pharmacological studies using TRH or its analogues and found to produce a wide array of effects in the central nervous system.

METHODS

Immunofluorescence, In situ labeling of DNA (TUNEL), in situ hybridization chain reaction and quantitative real-time polymerase chain reaction were used in this study.

RESULTS

We found that the granular cells of the dentate gyrus expressed transiently a significant amount of TRH-like immunoreactivity and TRH mRNA during the 6-24 h period following global cerebral ischemia/reperfusion injury. TUNEL showed that apoptosis of neurons in the CA1 region occurred from 48 h and almost disappeared at 7 days. TRH administration 30 min before or 24 h after the injury could partially inhibit neuronal loss, and improve the survival of neurons in the CA1 region.

CONCLUSION

These data suggest that endogenous TRH expressed transiently in the dentate gyrus of the hippocampus may play an important role in the survival of neurons during the early stage of ischemia/reperfusion injury and that delayed application of TRH still produced neuroprotection. This delayed application of TRH has a promising therapeutic significance for clinical situations.

Methane-Rich Saline Alleviates CA/CPR Brain Injury by Inhibiting Oxidative Stress, Microglial Activation-Induced Inflammatory Responses, and ER Stress-Mediated Apoptosis

Brain injury induced by cardiac arrest/cardiopulmonary resuscitation (CA/CPR) is the leading cause of death among patients who have recovery of spontaneous circulation (ROSC). Inflammatory response, apoptosis, and oxidative stress are proven pathological mechanisms implicated in neuronal damage. Methane-rich saline (MRS) has been proven that exerts a beneficial protectiveness impact in several models of ischemia-reperfusion injury. The goal of this paper is to ascertain the role of MRS in CA/CPR-induced brain injury and its potential mechanisms. The tracheal intubation of Sprague-Dawley (SD) rats was clamped for 6 min to establish an asphyxiating cardiac arrest model. After that, chest compressions were applied; then, MRS or saline was administered immediately post-ROSC, the rats were sacrificed, and brain tissue was collected at the end of 6 hours. We observed that MRS treatment attenuated neuronal damage in the hippocampal CA1 region by inhibiting microglial activation, leading to a decrease in the overexpression of proinflammatory cytokines such as TNF-α, IL-6, and iNOS. The results also illustrated that MRS treatment diminished apoptosis in the hippocampal CA1 region , reduced the expression of apoptosis-associated proteins Bax and cleaved caspase9, and increased Bcl-2 expression, as well as inhibited the expression of endoplasmic reticulum (ER) stress pathway-related proteins GRP78, ATF4, and CHOP. Further findings showed that MRS treatment significantly attenuated hippocampal ROS and MDA levels and increased GSH and SOD antioxidant factor levels, which indicated that MRS treatment could inhibit oxidative stress. Our results suggest that MRS exerts a protective effect against CA/CPR brain injury, by inhibiting oxidative stress, microglial activation-induced inflammatory responses, and ER stress-mediated apoptosis.

A20-Binding Inhibitor of NF-κB 1 Ameliorates Neuroinflammation and Mediates Antineuroinflammatory Effect of Electroacupuncture in Cerebral Ischemia/Reperfusion Rats

A20-binding inhibitor of NF-κB 1 (ABIN1) is an inhibitor of NF-κB and exerts anti-inflammatory effect. Electroacupuncture (EA) is considered as a neuroprotective strategy by inhibiting neuroinflammatory damage after cerebral ischemia. This study was performed to explore the role of ABIN1 and investigate whether the ABIN1 is involved in the mechanism of EA in cerebral ischemia/reperfusion (I/R) rats. Male Sprague-Dawley (SD) rats were subjected to middle cerebral artery occlusion/reperfusion (MCAO/R) and received EA after reperfusion once a day. Lentivirus-mediated ABIN1 gene knockdown was used to detect the role of ABIN1 in neuroinflammation after I/R. ABIN1 expression, proinflammatory cytokine levels, microglial activation, neurological function, infarct volumes, and NF-κB activation were assessed. ABIN1 expression was elevated in the peri-infarct cortex and was further upregulated by EA. ABIN1 knockdown increased the levels of proinflammatory cytokines and activation of microglia, worsened neurological deficits, and enlarged the infarct volume. Moreover, ABIN1 was blocked to partially reverse the neuroprotective effect of EA, and this treatment weakened the ability of EA to suppress NF-κB activity. Based on these findings, ABIN1 is a potential suppressor of neuroinflammation and ABIN1 mediates the antineuroinflammatory effect of EA in cerebral I/R rats.

Mesenchymal Stem Cell-Mediated Mitochondrial Transfer: a Therapeutic Approach for Ischemic Stroke

Stroke is the leading cause of death and adult disability worldwide. Mitochondrial dysfunction is one of the hallmarks of stroke-induced neuronal death, and maintaining mitochondrial function is essential in cell survival and neurological progress following ischemic stroke. Stem cell-mediated mitochondrial transfer represents an emerging therapeutic approach for ischemic stroke. Accumulating evidence suggests that mesenchymal stem cells (MSCs) can directly transfer healthy mitochondria to damaged cells, and rescue mitochondrial damage-provoked tissue degeneration. This review summarizes the research on MSCs-mediated mitochondrial transfer as a therapeutic strategy against ischemic stroke.

Plasma Interleukin-37 is Elevated in Acute Ischemic Stroke Patients and Probably Associated With 3-month Functional Prognosis

Background

Interleukin-37 is a novel cytokine emerging as a natural suppressor of inflammatory responses. Inflammation and the immune response play important roles in acute ischemic stroke. This study aimed at evaluating the plasma levels and the association with 3-month outcomes of interleukin-37 in acute ischemic stroke patients.

Patients and Methods

In total, 152 consecutive patients with acute ischemic stroke and 45 healthy controls were included. Plasma interleukin-37 levels were determined in the first morning after admission using an enzyme-linked immunesorbent assay. The primary outcome was the 3-month functional outcome (modified Rankin Scale score >2). Logistic regression was used to evaluate the risk and 3-month outcome of stroke according to plasma interleukin-37 level.

Results

Plasma interleukin-37 levels were significantly higher in the patients with acute ischaemic stroke than in the healthy controls (182.26 versus 97.89 pg/mL, p<0.001). Patients with large-artery atherosclerosis had significantly higher IL-37 levels than those with small-artery occlusion (202.12±35.82 versus 175.67±33.71pg/mL, p<0.001). Plasma interleukin-37 levels were positively correlated with National Institutes of Health Stroke Scale scores (r=0.521, p<0.0001) and lesion volume (r=0.442, p<0.0001). Ninety-four and 58 patients had favourable and unfavourable 3-month outcomes, respectively. Elevated plasma interleukin-37 levels were independently associated with unfavourable 3-month outcomes (adjusted odds ratio=1.033, p=0.001, 95% confidence interval: 1.015–1.056).

Conclusion

Admission plasma interleukin-37 levels were significantly increased after acute ischemic stroke. Elevated interleukin-37 levels were independently associated with unfavourable 3-month prognoses in acute ischemic stroke patients. Further studies with other populations are needed.

Positron Emission Tomography After Ischemic Brain Injury: Current Challenges and Future Developments

Positron emission tomography (PET) is widely used in clinical and animal studies, along with the development of diverse tracers. The biochemical characteristics of PET tracers may help uncover the pathophysiological consequences of cardiac arrest (CA) and ischemic stroke, which include cerebral ischemia and reperfusion, depletion of oxygen and glucose, and neuroinflammation. PubMed was searched for studies of the application of PET for "cardiac arrest," "ischemic stroke," and "targeted temperature management." Available studies were included and classified according to the biochemical properties involved and metabolic processes of PET tracers, and were summarized. The mechanisms of ischemic brain injuries were investigated by PET with various tracers to elucidate the pathological process from the initial decrease of cerebral blood flow (CBF) to the subsequent abnormalities in energy and oxygen metabolism, to the monitoring of inflammation. In general, the trends of cerebral blood flow and oxygen metabolism after ischemic attack are not unidirectional but closely related to the time point of injury and recovery. Glucose metabolism after injury showed significant differences in different brain regions whereas global cerebral metabolic rate of glucose (CMRglc) declined. PET monitoring of neuroinflammation shows comparable efficacy to immunostaining. The technology of PET targeting in brain metabolism and the development of tracers provide new tools to track and evaluate the brain's pathological changes after ischemic brain injury. Despite no existing evidence for an available PET-based prediction method, discoveries of new tracers are expected to provide more possibilities for the whole field.

Neurodegenerative diseases and Withania somnifera (L.): An update

ETHNOPHARMACOLOGICAL RELEVANCE

Withania somnifera (L.) Dunal also known as 'Ashwaghanda' in Sanskrit and as 'Indian Winter Cherry' in english. is an important medicinal herb in India. It is widely used in Indian systems of medicine as an adaptogen, nerve tonic, anti-stress, memory enhancer and against cognitive deficits, insomnia, anxiety, infectious diseases, infertility, rheumatoid arthritis and gout over thousands of years. Its formulations are mainly used in Unani and Ayurvedic system of medicine. It is a remarkable centuries old herbal Rasayana used to treat neuronal ailments and is known as ''Sattvic Kapha Rasayana.

AIM OF THE STUDY

To review neuroprotective properties of Withania somnifera (L.)extract as well as its active constituents in neurodegenerative diseases and other neurological ailments.

MATERIALS AND METHODS

The sources of information used in present article include Indian system of Medicine reports on the use of natural products, Medicinal books, research articles and scientific databases like PubMed, Google Scholar, Web of Science, Science-Direct, SciFinder, ACS Publications and Wiley Online Library.

RESULTS

Research reports based largely on preclinical studies as well as few clinical trials have highlighted the neuroprotective role of Ashwagandha against many neurodegenerative diseases including Alzheimer's, Huntington's and Parkinson's disease. The protective effects of Ashwagandha were accomplished by restoring mitochondrial and endothelial function, mitigation of apoptosis, inflammation and oxidative stress mechanisms.

CONCLUSION

In this review, we recapitulated neuroprotective properties of Ashwagandha extracts and/or its major constituents and discussed their mechanisms of action and potential therapeutic applications. The pre-clinical as well as clinical studies suggest the use of Withania somnifera (L.) against neurodegenerative disease. However, extensive studies are warranted to validate the use of extract or its single constituents for its clinical use.

Mitochondrial Transfer as a Therapeutic Strategy Against Ischemic Stroke

Stroke is a debilitating disease that remains the second leading cause of death and disability worldwide. Despite accumulating knowledge of the disease pathology, treatments for stroke are limited, and clinical translation of the neuroprotective agents has not been a complete success. Accumulating evidence links mitochondrial dysfunction to brain impairments after stroke. Recent studies have implicated the important roles of healthy mitochondria in neuroprotection and neural recovery following ischemic stroke. New and convincing studies have shown that mitochondrial transfer to the damaged cells can help revive cells energetic in the recipient cells. Hence, mitochondrial transplantation has shown to replace impaired or dysfunctional mitochondria with exogenous healthy mitochondria after ischemic stroke. We highlight the potential of mitochondrial transfer by stem cells as a therapeutic strategy for the treatment of ischemic stroke. This review captures the recent advances in the mitochondrial transfer as a novel and promising treatment for ischemic stroke.

The role of medical gas in stroke: an updated review

Medical gas is a large class of bioactive gases used in clinical medicine and basic scientific research. At present, the role of medical gas in neuroprotection has received growing attention. Stroke is a leading cause of death and disability in adults worldwide, but current treatment is still very limited. The common pathological changes of these two types of stroke may include excitotoxicity, free radical release, inflammation, cell death, mitochondrial disorder, and blood-brain barrier disruption. In this review, we will discuss the pathological mechanisms of stroke and the role of two medical gases (hydrogen and hydrogen sulfide) in stroke, which may potentially provide a new insight into the treatment of stroke.

The impact of single and combined PPAR-α and PPAR-γ activation on the neurological outcomes following cerebral ischemia reperfusion

AIM

The neuronal damage and accompanied functional deficits induced by cerebral ischemia are among the most common causes of disabilities in adults. Activation of subtypes of peroxisome proliferator-activated receptors (PPARs); PPAR-α and PPAR-γ have shown neuroprotective effects in different neurodegenerative diseases including stroke. Thus, this study aimed to compare the effects of two different agonists: PPAR-α (fenofibrate) and PPAR-γ (pioglitazone) as well as the effect of their combination in ameliorating post-ischemia behavioral deficits.

METHODS

Male Wistar rats were either pretreated with vehicle, fenofibrate (100 mg/kg/day p.o), pioglitazone (10 mg/kg/day p.o) or their combination for 14 days prior to bilateral common carotid artery occlusion followed by reperfusion for 24 hoursh. The sensory motor functions of rats were assessed, then rats were sacrificed to determine infarct volume and histopathological changes as well as oxidative stress, inflammatory and apoptotic markers in the brain tissue.

KEY FINDINGS

Pre-treatment with fenofibrate and pioglitazone in addition to their combination improved neurobehavioral dysfunction, reduced cerebral infarct volume, attenuated inflammatory and apoptotic markers and ameliorated histopathological changes in I/R injured rats. The effect of pioglitazone in cerebral cortex was higher than its corresponding effect in fenofibrate while the combined administration of both drugs had additive neuroprotective effect and normalized inflammatory and apoptotic mediators in ischemic rats.

SIGNIFICANCE

The study compared the neuroprotective effects of PPAR-α and PPAR-γ agonists, and tested the impact of their combination. We concluded that no additional benefits on the functional outcomes might be gained upon their combination.

The Protective Effects and Mechanisms of Apelin/APJ System on Ischemic Stroke: A Promising Therapeutic Target

The orphan receptor APJ and its endogenous ligand apelin, which are expressed in the brain, are the major components of the apelin/APJ system. Growing evidence shows that the apelin/APJ system plays a vital role in the pathophysiology of cerebral ischemic injury. Targeting the apelin/APJ system may have protective effects on cerebral ischemic injury. In this review, we sum up the latest research progress relating to the actions and therapeutic potential of the apelin/APJ system in ischemic stroke. An in-depth knowledge of the pathophysiological effects of the apelin/APJ system and the underlying mechanisms will help to develop novel therapeutic interventions for ischemic stroke.

Lixisenatide Reduced Damage in Hippocampus CA1 Neurons in a Rat Model of Cerebral Ischemia-Reperfusion Possibly Via the ERK/P38 Signaling Pathway

Glucagon-like peptide-1 (GLP-1) is a gut-derived peptide that has various physiological actions. One of its main actions is the regulation of blood glucose level when it is elevated as it potentiates insulin release. It is also known that GLP-1 protects neurons from damage caused by neurodegenerative diseases. Lixisenatide is one of the GLP-1 analogues that has a strong affinity to the GLP-1 receptor. Experimental animal studies have shown that it holds a neuroprotective effect in Parkinson, myocardial, and cerebral ischemic disease animal models. The beneficial effect of lixisenatide on the brain after cerebral ischemia-reperfusion (I/R) is not clarified yet; thus, it needs further explanatory studies. Our research is the first to study the effect of lixisenatide on myeloperoxidase (MPO) and toll-like receptors (TLRs)/mitogen-activated protein kinase (MAPK) pathway in a rat model of cerebral I/R. Lixisenatide with 2 doses 0.7 and 7 nmol/kg was given intraperitoneal in 2 different groups for 14 days; then, the bilateral common carotid artery was occluded for 1 h followed by reperfusion for 1 h. Examination of hippocampus CA1 neurons by Nissl stain showed that the number of intact neurons was elevated in the lixisenatide-treated group related to the control group (I/R group). Lixisenatide exhibited neuroprotection action possibly via downregulation of MPO, TLR2/4, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), and pP38 and upregulation of phosphorylated extracellular signal-regulated kinase (pERK1/2); thus, this study gives possible link between lixisenatide and TLR/MAPK pathway following cerebral I/R and supports the use of lixisenatide for neuroprotection against stroke.

Necroptosis in the Pathophysiology of Disease

Over the past 15 years, elegant studies have demonstrated that in certain conditions, programed cell death resembles necrosis and depends on a unique molecular pathway with no overlap with apoptosis. This form of regulated necrosis is represented by necroptosis, in which the receptor-interacting protein kinase-3 and its substrate mixed-lineage kinase domain-like protein play a crucial role. With the development of knockout mouse models and molecular inhibitors unique to necroptotic proteins, this cell death has been found to occur in virtually all tissues and diseases evaluated. There are different immunologic consequences depending on whether cells die through apoptosis or necroptosis. Therefore, distinguishing between these two forms of cell death may be crucial during pathologic evaluations. In this review, we provide an understanding of necroptotic cell-death and highlight diseases in which necroptosis has been found to play a role. We also discuss the inhibitors of necroptosis and the ways these inhibitors have been used in preclinical models of diseases. These two discussions offer an understanding of the role of necroptosis in diseases and will foster efforts to pharmacologically target this unique yet pervasive form of programed cell death in the clinic.

Expression of Cytokines and Chemokines as Predictors of Stroke Outcomes in Acute Ischemic Stroke

Introduction: Ischemic stroke remains one of the most debilitating diseases and is the fifth leading cause of death in the US. The ability to predict stroke outcomes within the acute period of stroke would be essential for care planning and rehabilitation. The Blood and Clot Thrombectomy Registry and Collaboration (BACTRAC; clinicaltrials.gov NCT03153683) study collects arterial blood immediately distal and proximal to the intracranial thrombus at the time of mechanical thrombectomy. These blood samples are an innovative resource in evaluating acute gene expression changes at the time of ischemic stroke. The purpose of this study was to identify inflammatory genes and important immune factors during mechanical thrombectomy for emergent large vessel occlusion (ELVO) and which patient demographics were predictors for stroke outcomes (infarct and/or edema volume) in acute ischemic stroke patients.

Methods: The BACTRAC study is a non-probability sampling of male and female subjects (≥18 year old) treated with mechanical thrombectomy for ELVO. We evaluated 28 subjects (66 ± 15.48 years) relative concentrations of mRNA for gene expression in 84 inflammatory molecules in arterial blood distal and proximal to the intracranial thrombus who underwent thrombectomy. We used the machine learning method, Random Forest to predict which inflammatory genes and patient demographics were important features for infarct and edema volumes. To validate the overlapping genes with outcomes, we perform ordinary least squares regression analysis.

Results: Machine learning analyses demonstrated that the genes and subject factors CCR4, IFNA2, IL-9, CXCL3, Age, T2DM, IL-7, CCL4, BMI, IL-5, CCR3, TNFα, and IL-27 predicted infarct volume. The genes and subject factor IFNA2, IL-5, CCL11, IL-17C, CCR4, IL-9, IL-7, CCR3, IL-27, T2DM, and CSF2 predicted edema volume. The overlap of genes CCR4, IFNA2, IL-9, IL-7, IL-5, CCR3, and IL-27 with T2DM predicted both infarct and edema volumes. These genes relate to a microenvironment for chemoattraction and proliferation of autoimmune cells, particularly Th2 cells and neutrophils.

Conclusions: Machine learning algorithms can be employed to develop prognostic predictive biomarkers for stroke outcomes in ischemic stroke patients, particularly in regard to identifying acute gene expression changes that occur during stroke.

Reactive oxygen species-responsive drug delivery systems for the treatment of neurodegenerative diseases

Neurodegenerative diseases and disorders seriously impact memory and cognition and can become life-threatening. Current medical techniques attempt to combat these detrimental effects mainly through the administration of neuromedicine. However, drug efficacy is limited by rapid dispersal of the drugs to off-target sites while the site of administration is prone to overdose. Many neuropathological conditions are accompanied by excessive reactive oxygen species (ROS) due to the inflammatory response. Accordingly, ROS-responsive drug delivery systems have emerged as a promising solution. To guide intelligent and comprehensive design of ROS-responsive drug delivery systems, this review article discusses the two following topics: (1) the biology of ROS in both healthy and diseased nervous systems and (2) recent developments in ROS-responsive, drug delivery system design. Overall, this review article would assist efforts to make better decisions about designing ROS-responsive, neural drug delivery systems, including the selection of ROS-responsive functional groups.

Protective Effects of Nucleobinding-2 After Cerebral Ischemia Via Modulating Bcl-2/Bax Ratio and Reducing Glial Fibrillary Acid Protein Expression

Introduction

Nucleobinding-2 (NUCB2) or nesfatin-1, a newly identified anorexigenic peptide, has antioxidant, anti-inflammatory, and anti-apoptotic properties. Brain ischemiareperfusion induces irreversible damages, especially in the hippocampus area. However, the therapeutic effects of NUCB2 have not been well investigated in cerebral ischemia. This study was designed for the first time to investigate the protective effects of NUCB2/Nesfatin-1 on the expression of apoptosis-related proteins and reactive astrogliosis level in the CA1 area of hippocampus in an experimental model of transient global cerebral ischemia.

Methods

The male Wistar rats were randomly allocated into 4 groups (sham, NUCB2, ischemia-reperfusion, and ischemia-reperfusion+NUCB21) (n =7). The model of cerebral ischemia was prepared by common carotid arteries occlusion for 20 minutes. Nesfatin-1 (20 μg/kg) and saline (as a vehicle) were injected (intraperitoneally) at the beginning of the reperfusion period. The assessment of the protein expression levels was performed by immunofluorescence and immunohistochemical staining.

Results

NUCB2 significantly reduced the Bax and GFAP protein levels in the CA1 area after ischemia (P<0.05). Also, NUCB2 increased Bcl-2 protein level (P<0.05). NUCB2 exerted protective effects against ischemic injury by the inhibition of astrocytes activation as an inflammatory response and decreased neuronal cell apoptosis.

Conclusion

The present study provides the possible neuroprotective view of nesfatin-1 in the treatment of ischemia injury model in rat hippocampus.

Activation of Pyruvate Dehydrogenase Activity by Dichloroacetate Improves Survival and Neurologic Outcomes After Cardiac Arrest in Rats

No pharmacological interventions are currently available to provide neuroprotection for patients suffering from cardiac arrest. Dichloroacetate (DCA) is a pyruvate dehydrogenase kinase inhibitor, which activates pyruvate dehydrogenase (PDH), and increases cell adenosine triphosphate (ATP) production by promoting influx of pyruvate into the Krebs cycle. In this study, we investigated the effects of DCA on post-resuscitation neurological injury in an asphyxial cardiac arrest rat model. Asphyxial cardiac arrest was established by endotracheal tube clamping. A total of 111 rats were randomized into three groups: Sham group, Control group, and DCA intervention group. Animals in DCA intervention group were intraperitoneally administered DCA with a loading dose of 80 mg/kg at 15 min after return of spontaneous circulation (ROSC), whereas rats in the Control group received equivalent volume of saline. DCA treatment increased 3-day survival time, and reduced neurologic deficit scores at 24, 48, and 72 h after ROSC. It also attenuated cellular apoptosis and neuronal damage in the hippocampal cornuammonis one region by hematoxylin-eosin staining and TdT-mediated dUTP nick-end labeling assay. In addition, DCA reduced the messenger RNA expression of tumor necrosis factor α and interleukin 1β in brain hippocampus and cortex after ROSC. Furthermore, DCA treatment significantly increased ATP production, PDH activity, and decreased blood glucose, lactate, and brain pyruvate levels after ROSC. Our results suggested that DCA has neuroprotective effects on brain injury after cardiac arrest, and its salutary effects were associated with an increase of mitochondrial energy metabolism in the brain through activation of PDH activity.

Neuroinflammation: friend and foe for ischemic stroke

Stroke, the third leading cause of death and disability worldwide, is undergoing a change in perspective with the emergence of new ideas on neurodegeneration. The concept that stroke is a disorder solely of blood vessels has been expanded to include the effects of a detrimental interaction between glia, neurons, vascular cells, and matrix components, which is collectively referred to as the neurovascular unit. Following the acute stroke, the majority of which are ischemic, there is secondary neuroinflammation that both promotes further injury, resulting in cell death, but conversely plays a beneficial role, by promoting recovery. The proinflammatory signals from immune mediators rapidly activate resident cells and influence infiltration of a wide range of inflammatory cells (neutrophils, monocytes/macrophages, different subtypes of T cells, and other inflammatory cells) into the ischemic region exacerbating brain damage. In this review, we discuss how neuroinflammation has both beneficial as well as detrimental roles and recent therapeutic strategies to combat pathological responses. Here, we also focus on time-dependent entry of immune cells to the ischemic area and the impact of other pathological mediators, including oxidative stress, excitotoxicity, matrix metalloproteinases (MMPs), high-mobility group box 1 (HMGB1), arachidonic acid metabolites, mitogen-activated protein kinase (MAPK), and post-translational modifications that could potentially perpetuate ischemic brain damage after the acute injury. Understanding the time-dependent role of inflammatory factors could help in developing new diagnostic, prognostic, and therapeutic neuroprotective strategies for post-stroke inflammation.

Combined Cyclosporin A and Hypothermia Treatment Inhibits Activation of BV-2 Microglia but Induces an Inflammatory Response in an Ischemia/Reperfusion Hippocampal Slice Culture Model

Introduction

Hypothermia attenuates cerebral ischemia-induced neuronal cell death associated with neuroinflammation. The calcineurin inhibitor cyclosporin A (CsA) has been shown to be neuroprotective by minimizing activation of inflammatory pathways. Therefore, we investigated whether the combination of hypothermia and treatment with CsA has neuroprotective effects in an oxygen-glucose deprivation/reperfusion (OGD/R) injury model in neuronal and BV-2 microglia monocultures, as well as in an organotypic hippocampal slice culture (OHSC).

Methods

Murine primary neurons, BV-2 microglia, and OHSC were pretreated with CsA and exposed to 1 h OGD (0.2% O₂) followed by reperfusion at normothermia (37°C) or hypothermia (33.5°C). Cytotoxicity was measured by lactate dehydrogenase and glutamate releases. Damage-associated molecular patterns (DAMPs) high mobility group box 1 (HMGB1), heat shock protein 70 (Hsp70), and cold-inducible RNA-binding protein (CIRBP) were detected in cultured supernatant by western blot analysis. Interleukin-6 (IL-6), Interleukin-1α and -1β (IL-1α/IL1-β), tumor necrosis factor-α (TNF-α), monocyte chemotactic protein 1 (MCP1), inducible nitric oxide synthase (iNOS), glia activation factors ionized calcium-binding adapter molecule 1 (Iba1), and transforming growth factor β1 (TGF-β1) gene expressions were analyzed by RT-qPCR.

Results

Exposure to OGD plus 10 μM CsA was sufficient to induce necrotic cell death and subsequent release of DAMPs in neurons but not BV-2 microglia. Moreover, OGD/R-induced secondary injury was also observed only in the neurons, which was not attenuated by cooling and no increased toxicity by CsA was observed. BV-2 microglia were not sensitive to OGD/R-induced injury but were susceptible to CsA-induced toxicity in a dose dependent manner, which was minimized by hypothermia. CsA attenuated IL-1β and Iba1 expressions in BV-2 microglia exposed to OGD/R. Hypothermia reduced IL-1β and iNOS expressions but induced TNF-α and Iba1 expressions in the microglia. However, these observations did not translate to the ex vivo OHCS model, as general high expressions of most cytokines investigated were observed.

Conclusion

Treatment with CsA has neurotoxic effects on primary neurons exposed to OGD but could inhibit BV-2 microglia activation. However, CsA and hypothermia treatment after ischemia/reperfusion injury results in cytotoxic neuroinflammation in the complex ex vivo OHSC.

Immunomodulatory Therapeutic Strategies in Stroke

The role of immunity in all stages of stroke is increasingly being recognized, from the pathogenesis of risk factors to tissue repair, leading to the investigation of a range of immunomodulatory therapies. In the acute phase of stroke, proposed therapies include drugs targeting pro-inflammatory cytokines, matrix metalloproteinases, and leukocyte infiltration, with a key objective to reduce initial brain cell toxicity. Systemically, the early stages of stroke are also characterized by stroke-induced immunosuppression, where downregulation of host defences predisposes patients to infection. Therefore, strategies to modulate innate immunity post-stroke have garnered greater attention. A complementary objective is to reduce longer-term sequelae by focusing on adaptive immunity. Following stroke onset, the integrity of the blood–brain barrier is compromised, exposing central nervous system (CNS) antigens to systemic adaptive immune recognition, potentially inducing autoimmunity. Some pre-clinical efforts have been made to tolerize the immune system to CNS antigens pre-stroke. Separately, immune cell populations that exhibit a regulatory phenotype (T- and B- regulatory cells) have been shown to ameliorate post-stroke inflammation and contribute to tissue repair. Cell-based therapies, established in oncology and transplantation, could become a strategy to treat the acute and chronic stages of stroke. Furthermore, a role for the gut microbiota in ischaemic injury has received attention. Finally, the immune system may play a role in remote ischaemic preconditioning-mediated neuroprotection against stroke. The development of stroke therapies involving organs distant to the infarct site, therefore, should not be overlooked. This review will discuss the immune mechanisms of various therapeutic strategies, surveying published data and discussing more theoretical mechanisms of action that have yet to be exploited.

Neural Stem Cells Transfected with Leukemia Inhibitory Factor Promote Neuroprotection in a Rat Model of Cerebral Ischemia

Leukemia inhibitory factor (LIF) contributes to the neuroprotection by neural stem cells (NSCs) after ischemic stroke. Our aim was to explore whether LIF-transfected NSCs (LIF-NSCs) can ameliorate brain injury and promote neuroprotection in a rat model of cerebral ischemia. To accomplish this goal, we transfected NSCs with a lentivirus carrying the LIF gene to stably overexpress LIF. The LIF-NSCs reduced caspase 3 activation under conditions of oxygen-glucose deprivation in vitro. Transient cerebral ischemia was induced in rats by 2 h of middle cerebral artery occlusion (MCAo), and LIF-NSCs were intravenously injected at 6 h post-ischemia. LIF-NSC treatment reduced the infarction volume and improved neurological recovery. Moreover, LIF-NSCs improved glial cell regeneration and ameliorated white matter injury in the MCAo rats. The NSCs acted as carriers and increased the expression of LIF in the lesions to protect against cerebral infarction, suggesting that LIF-NSCs could be a potential treatment for cerebral infarction.

Custodiol-N™ cardioplegia lowers cerebral inflammation and activation of hypoxia-inducible factor-1α

OBJECTIVES

Cardioplegic solutions induce cardiac arrest and protect cardiac tissue from ischaemia-reperfusion injury. However, the effects on the brain, which is vulnerable to cardiopulmonary bypass (CPB) surgery and ischaemia-reperfusion injury, mostly remain unknown. We investigated if cardioplegic solutions differ in their effects in altered oxygen conditions and in their ability to induce cerebral inflammation.

METHODS

Thirty pigs were subjected to a midline sternotomy and CPB at 34°C with 90 min cardiac arrest followed by 120 min reperfusion. Following randomization on a 1:1:1 basis, they received either a single shot of histidine-tryptophan-α-ketoglutarate (HTK)-Bretschneider solution (n = 10), histidine-tryptophan-α-ketoglutarate-N (HTK-N; n = 10) or HTK plus 1.2 mg/l cyclosporine A (HTK/CsA; n = 10). Brain regions of interest (frontal cortex, cerebellum, brain stem, diencephalon, colliculus superior) were analysed by real time quantitative reverse transcriptase polymerase chain reaction for hypoxia-inducible factor-1α (HIF-1α), tumour necrosis factor-α, interleukin (IL)-10, IL-1β and IL-1β receptor as well as by immunohistochemical analysis for HIF-1α. Blood gas and electrolyte analyses were performed.

RESULTS

Comparisons between baseline and reperfusion period levels revealed that HTK-N cardioplegia induced a smaller reduction of the haemoglobin content and blood calcium concentrations (hbbaseline: 5.97 ± 0.63 mmol/l; hbreperfusion: 6.16 ± 0.66 mmol/l; P = 0.428; Cabaseline2+: 1.36 ± 0.05 mmol/l; Careperfusion2+: 1.28 ± 0.05 mmol/l; P < 0.001) compared to HTK (hbbaseline: 5.93 ± 0.45 mmol/l; hbreperfusion: 4.72 ± 0.79 mmol/l; P = 0.001; Cabaseline2+: 1.34 ± 0.07 mmol/l; Careperfusion2+: 1.24 ± 0.06 mmol/l; P = 0.004) and HTK/CsA cardioplegia (hbbaseline: 5.88 ± 0.44 mmol/l; hbreperfusion: 5.14 ± 0.87 mmol/l; P = 0.040; Cabaseline2+: 1.38 ± 0.04 mmol/l; Careperfusion2+: 1.20 ± 0.14 mmol/l; P = 0.001). Brain region-specific regulation of the HIF-1α expression, no general HIF-1α activation and a lower tumour necrosis factor-α expression (pto HTK = 0.050, pto HTK/CsA = 0.013) were documented for HTK-N cardioplegia.

CONCLUSIONS

HTK-N (Custodiol-N) induced fewer cerebral effects and less inflammation during CPB surgery than HTK and HTK/CsA cardioplegia. These data suggest that HTK-N exerts brain protective effects during and after CPB surgery.

Assessing the performance of monocyte to high-density lipoprotein ratio for predicting ischemic stroke: insights from a population-based Chinese cohort

Background

Monocyte to high-density lipoprotein cholesterol ratio (MHR) is a recently emerged measure of inflammation and oxidative stress and has been used to predict multiple cardiovascular abnormalities, but data relative to ischemic stroke are lacking. The goal of this study was to estimate the associations of MHR and prevalent ischemic stroke among a large cohort of general Chinese population.

Method

The study analyzed 8148 individuals (mean age: 54.1 years; 45.7% males) enrolled in a cross-sectional population-based Northeast China Rural Cardiovascular Health Study (NCRCHS). We identified 194 patients admitted from January and August 2013 with ischemic stroke.

Results

After adjustment for age, sex, and potential confounders, each standard deviation (SD) increment of MHR was predictive to a greater odd of ischemic stroke (odds ratio, 1.276; 95% confidence interval [CI], 1.082–1.504), with subjects in the highest quartile of MHR levels having a 1.6-fold higher risk of prevalent ischemic stroke (95% CI, 1.045–2.524) as compared with those in the lowest quartile. Moreover, smoothing curve showed a linear positive pattern of this association. The area under the curve (AUC) significantly increased (P = 0.042) to 0.808 (95% CI, 0.779–0.837) when the combined MHR was added to the baseline logistic regression model with ischemic stroke risk factors. Also, MHR (0.004) significantly improved integrated discrimination improvement when added to the baseline model.

Conclusions

The present study demonstrated for the first time a linear relation between MHR levels and the odds of ischemic stroke in a large community-based population. The MHR, a marker of high atherosclerotic burden, demonstrated incremental predictive value over traditional clinical risk factors, thus providing clinical utility in risk stratification in subjects presenting with ischemic stroke. These findings had implications for strategies aimed at lowering MHR to prevent adverse cardiovascular and cerebrovascular outcomes.

Dual Functions of Microglia in Ischemic Stroke

Ischemic stroke is a leading cause of morbidity and mortality worldwide. Resident microglia are the principal immune cells of the brain, and the first to respond to the pathophysiological changes induced by ischemic stroke. Traditionally, it has been thought that microglial activation is deleterious in ischemic stroke, and therapies to suppress it have been intensively explored. However, increasing evidence suggests that microglial activation is also critical for neurogenesis, angiogenesis, and synaptic remodeling, thereby promoting functional recovery after cerebral ischemia. Here, we comprehensively review the dual role of microglia during the different phases of ischemic stroke, and the possible mechanisms controlling the post-ischemic activity of microglia. In addition, we discuss the dynamic interactions between microglia and other cells, such as neurons, astrocytes, oligodendrocytes, and endothelial cells within the brain parenchyma and the neurovascular unit.

Role of acute-phase protein ORM in a mice model of ischemic stroke

The only Food and Drug Administration-approved treatment for acute ischemic stroke is tissue plasminogen activator, and the discovery of novel therapeutic targets is critical. Here, we found orosomucoid (ORM), an acute-phase protein mainly produced by the liver, might act as a treatment candidate for an ischemic stroke. The results showed that ORM2 is the dominant subtype in mice normal brain tissue. After middle cerebral artery occlusion (MCAO), the level of ORM2 is significantly increased in the ischemic penumbra compared with the contralateral normal brain tissue, whereas ORM1 knockout did not affect the infarct size. Exogenous ORM could significantly decrease infarct size and neurological deficit score. Inspiringly, the best administration time point was at 4.5 and 6 hr after MCAO. ORM could markedly decrease the Evans blue extravasation, and improve blood-brain barrier-associated proteins expression in the ischemic penumbra of MACO mice and oxygen-glucose deprivation (OGD)-treated bEnd3 cells. Meanwhile, ORM could significantly alleviate inflammation by inhibiting the production of interleukin 1β (IL-1β), IL-6, and tumor necrosis factor α (TNF-α), reduce oxidative stress by improving the balance of malondialdehyde (MDA) and superoxide dismutase (SOD), inhibit apoptosis by decreasing caspase-3 activity in ischemic penumbra of MCAO mice and OGD-treated bEnd.3 cells. Because of its protective role at multiple levels, ORM might be a promising therapeutic target for ischemic stroke.

NLRP3 inflammasome in ischemic stroke: As possible therapeutic target

Inflammation is a devastating pathophysiological process during stroke, a devastating disease that is the second most common cause of death worldwide. Activation of the NOD-like receptor protein (NLRP3)-infammasome has been proposed to mediate inflammatory responses during ischemic stroke. Briefly, NLRP3 inflammasome activates caspase-1, which cleaves both pro-IL-1 and pro-IL-18 into their active pro-inflammatory cytokines that are released into the extracellular environment. Several NLRP3 inflammasome inhibitors have been promoted, including small molecules, type I interferon, micro RNAs, nitric oxide, and nuclear factor erythroid-2 related factor 2 (Nrf2), some of which are potentially efficacious clinically. This review will describe the structure and cellular signaling pathways of the NLRP3 inflammasome during ischemic stroke, and current evidence for NLRP3 inflammasome inhibitors.

Rab7b Overexpression-Ameliorated Ischemic Brain Damage Following tMCAO Involves Suppression of TLR4 and NF-κB p65

Cerebral stroke is one of the leading causes of death and permanent disability worldwide. Toll-like receptor 4 (TLR4) and nuclear factor-kappa B (NF-κB) p65 play a critical role in brain damage following ischemia-induced stroke. Rab7b, a lysosome-associated small Rab GTPase, has been implicated in TLR4 regulation; however, its role in cerebral stroke is poorly understood. In this study, by investigating a rat model with cerebral stroke, we found that Rab7b was upregulated in the rat brain following the transient middle cerebral artery occlusion (tMCAO). Functionally, overexpression of Rab7b in the brain by DNA transfection reduced cerebral infarction and improved neurological outcome following tMCAO, suggesting that Rab7b alleviates ischemic brain damage. Mechanistically, Rab7b overexpression suppressed the expression of TLR4 and NF-κB p65 and also inhibited the activation of NF-κB p65. Furthermore, Rab7b overexpression suppressed the production of proinflammatory mediators including TNF-α, IFN-γ, IL-1β, and IL-6 in the brain following tMCAO. In summary, these results suggest that Rab7b protects against ischemic brain damage following tMCAO and that this protection may relate to the suppressed inflammatory response mediated by TLR4 and NF-κB p65. Our study might offer Rab7b as a novel therapeutic target in the treatment of cerebral stroke.

Potential therapeutic roles of stem cells in ischemia-reperfusion injury

Ischemia-reperfusion injury (I/RI), produced by an initial interruption of organ blood flow and its subsequent restoration, contributes significantly to the pathophysiologies of stroke, myocardial infarction, renal I/RI, intestinal I/RI and liver I/RI, which are major causes of disability (including transplant failure) and even mortality. While the restoration of blood flow is required to restore oxygen and nutrient requirements, reperfusion often triggers local and systemic inflammatory responses and subsequently elevate the ischemic insult where the duration of ischemia determines the magnitude of I/RI damage. I/RI increases vascular leakage, changes transcriptional and cell death programs, drives leukocyte entrapment and inflammation and oxidative stress in tissues. Therapeutic approaches which reduce complications associated with I/RI are desperately needed to address the clinical and economic burden created by I/RI. Stem cells (SC) represent ubiquitous and uncommitted cell populations with the ability to self-renew and differentiate into one or more developmental 'fates'. Like immune cells, stem cells can home to and penetrate I/R-injured tissues, where they can differentiate into target tissues and induce trophic paracrine signaling which suppress injury and maintain tissue functions perturbed by ischemia-reperfusion. This review article summarizes the present use and possible protective mechanisms underlying stem cell protection in diverse forms of ischemia-reperfusion.

Gastrodin pretreatment alleviates rat brain injury caused by cerebral ischemic-reperfusion

Brain damage, including blood-brain barrier (BBB) dysfunction, neurological behavior deficit, cerebral infarction and inflammation, is commonly caused by ischemic-reperfusion (I/R) injury. Prevention of the above biological process defects is considered beneficial for patient recovery after I/R injury. This study was aimed to assess the neuroprotective effect of Gastrodin (GAS), an herbal agent, in experimentally induced cerebral ischemia. Sprague-Dawley adult rats were randomly divided into six groups: Sham-operated control group (Sham), middle cerebral artery occlusion (MCAO) group, GAS (50, 100, and 200 mg/kg) pretreatment + MCAO groups (GAS) and Nimodipine (NIM) + MCAO, namely, the NIM group. Additionally, an OGD/R model using BV-2 microglia was established in vitro to simulate I/R injury. We showed here that the neurological scores of rats in the GAS groups were significantly improved compared with the MCAO group. Moreover, the area of cerebral infarction in the GAS pretreatment groups and the NIM group was significantly reduced. Furthermore, Evans blue leakage volume was significantly reduced with GAS pretreatment notably at dose 100 mg/kg. Expression of matrix metalloproteinase 2 (MMP2) and MMP9 in GAS groups was markedly decreased when compared with MCAO group. In BV-2 microglia exposed to OGD/R given GAS pretreatment, MMP2 and MMP9 positive cells were reduced in numbers. The present results have shown that GAS pretreatment significantly compensated for neurological behavior defects in rats with I/R-induced injury, reduced brain infarction size, reversed BBB impairment, and attenuated inflammation. It is suggested that pretreatment with GAS before surgery is beneficial during recovery from I/R injury.

The spleen may be an important target of stem cell therapy for stroke

Stroke is the most common cerebrovascular disease, the second leading cause of death behind heart disease and is a major cause of long-term disability worldwide. Currently, systemic immunomodulatory therapy based on intravenous cells is attracting attention. The immune response to acute stroke is a major factor in cerebral ischaemia (CI) pathobiology and outcomes. Over the past decade, the significant contribution of the spleen to ischaemic stroke has gained considerable attention in stroke research. The changes in the spleen after stroke are mainly reflected in morphology, immune cells and cytokines, and these changes are closely related to the stroke outcomes. Autonomic nervous system (ANS) activation, release of central nervous system (CNS) antigens and chemokine/chemokine receptor interactions have been documented to be essential for efficient brain-spleen cross-talk after stroke. In various experimental models, human umbilical cord blood cells (hUCBs), haematopoietic stem cells (HSCs), bone marrow stem cells (BMSCs), human amnion epithelial cells (hAECs), neural stem cells (NSCs) and multipotent adult progenitor cells (MAPCs) have been shown to reduce the neurological damage caused by stroke. The different effects of these cell types on the interleukin (IL)-10, interferon (IFN), and cholinergic anti-inflammatory pathways in the spleen after stroke may promote the development of new cell therapy targets and strategies. The spleen will become a potential target of various stem cell therapies for stroke represented by MAPC treatment.