Core and Penumbral Nitric Oxide Synthase Activity During Cerebral Ischemia and Reperfusion

Zhongfeng decoction attenuates cerebral ischemia-reperfusion injury by inhibiting autophagy via regulating the AGE-RAGE signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Tackling phlegm and improving blood circulation is vital in the treatment of ischemic stroke (IS), culminating in the development of Zhongfeng Decoction (ZFD), a method grounded in this approach and serving as an effective therapy for IS. Nonetheless, the defensive mechanism of the ZFD in preventing cerebral ischemia-reperfusion damage remains ambiguous.

AIM OF THE STUDY

Determine the active ingredients in ZFD that have neuroprotective effects, and identify its mechanism of action against IS.

MATERIALS AND METHODS

A cerebral ischemia model in rats was developed, utilizing TTC, Nissl staining, and an oxidative stress kit to evaluate the neuroprotective impact of ZFD on this rat model. Following this, an amalgamation of LC-MS and network pharmacology techniques was employed to pinpoint potential active components, primary targets, and crucial action mechanisms of ZFD in treating IS. Finally, key targets and signaling pathways were detected using qRT-PCR, ELISA, Western blotting, electron microscopy, and other methods.

RESULTS

Through LC-MS and network analysis, 15 active ingredients and 6 hub targets were identified from ZFD. Analysis of pathway enrichment revealed that ZFD predominantly engages in the AGE-RAGE signaling route. Kaempferol, quercetin, luteolin, baicalein, and nobiletin in ZFD are the main active ingredients for treating IS. In vivo validation showed that ZFD can improve nerve damage in cerebral ischemic rats, reduce the mRNA expression of IL6, SERPINE1, CCL2, and TGFB1 related to inflammation. Furthermore, we also confirmed that ZFD can inhibit the protein expression of AGEs, RAGE, p-IKBα/IKBα, p-NF-κB p65/NF-κB p65, reduce autophagy levels, and thus decrease neuronal apoptosis.

CONCLUSIONS

The mechanism of action of ZFD in treating IS primarily includes inflammation suppression, oxidative stress response alleviation, post-stroke cell autophagy and apoptosis regulation, and potential mediation of the AGE-RAGE signaling pathway. This study elucidates how ZFD functions in treating IS, establishing a theoretical basis for its clinical application.

G6PD protects against cerebral ischemia-reperfusion injury by inhibiting excessive mitophagy

AIMS

Cerebral ischemia-reperfusion injury (CIRI) exacerbates post-stroke brain damage. We aimed to understand the role of glucose-6-phosphate dehydrogenase (G6PD) in CIRI and mitophagy.

MATERIALS AND METHODS

Lentivirus and small interfering RNA were utilized to suppress G6PD in tissues and cells, leading to the establishment of in vivo and in vitro models of ischemia-reperfusion following middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation/ reoxygenation (OGD/R). The expression and function of G6PD were investigated through differential gene analysis and weighted correlation network analysis (WGCNA), immunofluorescence, and western blotting (WB).

KEY FINDINGS

G6PD mRNA levels increased 3 d after MCAO, and G6PD protein expression was elevated in the ischemic penumbra of mice and HT22 cells following OGD/R. G6PD knockdown increased neural deficits, enlarged infarct volume in mice after CIRI, and reduced HT22 cell survival during OGD/R. WGCNA indicated a correlation between G6PD and mitophagy in CIRI. Following G6PD knockdown, the p-DRP1/DRP ratio increased, the PINK1/Parkin pathway was further activated, and TOMM20 expression was downregulated. The mitophagy inhibitor Mdivi-1 reversed these changes, as well as the nerve damage caused by G6PD knockdown, and alleviated mitochondrial damage in the ischemic penumbra.

SIGNIFICANCE

The role of G6PD in CIRI was revealed and its interaction with mitophagy was explored, providing important insights for understanding the molecular mechanism of CIRI and developing new therapeutic strategies.

New alternative approaches to stroke treatment: the blood cell-derived secretome shows promise in individuals with obesity

Ischaemic tolerance induced by remote ischaemic conditioning (RIC) has been extensively demonstrated in several preclinical models of cerebral ischaemia. However, animals with common stroke-related comorbidities do not benefit from the recent advances of RIC. Therefore, we investigated two alternative approaches for obese animals with stroke: (1) the efficacy of an additional round of the standard RIC protocol, and (2) the paracrine potential of the blood cell-derived secretome derived from RIC-induced healthy young rats. We found that a second round of remote ischaemic postconditioning (RIPostC) stimulus reduced neurodegeneration and exerted antioxidant effects but failed to decrease the infarct volume and alter glutamate homeostasis. However, when obese rats were administered the secretome from healthy, young RIC-stimulated rats, they exhibited improved neurological post-stroke outcomes. Intravenous administration of the tolerant secretome activated several endogenous mechanisms, including a reduction in the infarct volume and neurodegeneration in the penumbra. Furthermore, the blood cell-derived secretome accelerated brain-to-blood glutamate efflux in obese rats, and demonstrated antioxidant properties that may have contributed to the induction of tolerance in obese rats with stroke. These findings indicate that the blood cell-derived secretome has unique abilities and represents a new potential treatment for individuals with obesity and ischaemic stroke.

Naringenin Protected Against Blood Brain Barrier Breakdown after Ischemic Stroke through GSK-3β/ β-Catenin Pathway

Protection against blood-brain barrier (BBB) dysfunction is key to reduce the cerebral ischemia injury as its breakdown causes edema formation and extravasation of blood components and immune cells. The maintenance of BBB integrity requires the GSK-3β/β-catenin pathway activity. Naringenin (NAR), an effective monomer from Chinese herbal medicine, had potent protective effect on brain inflammatory and oxidative injury. However, whether NAR could protect the integrity of BBB during cerebral ischemia injury and the involvement of GSK-3β/β-catenin pathway in the beneficial effect of NAR was unknown. Therefore, mouse middle cerebral artery occlusion/reperfusion (IR) model was employed to answer these questions. NAR was intraperitoneally administrated once daily for 6 days immediately after IR with the dose of 10 mg/kg. BBB damage was evaluated with Evans blue. Protein levels of GSK-3β and β-catenin in vascular endothelial cells at penumbra were assessed with western blotting and immunofluorescence. The experimental data suggested that NAR improved neurological deficits, decreased the percentage of infarct volumes and neuronal apoptosis at 7d after IR. NAR improved BBB damage as evidenced by a lower permeability of Evans blue dye and upregulation of tight junction proteins such as zonula occludens-1(ZO-1), Occludin and Claudin-5. Importantly, GSK-3β/β-catenin pathway activity was related to the improvement of BBB integrity rendered by NAR. Our findings demonstrated that NAR might become a potential therapeutic drug for IR.

A systematic review and in silico analysis of studies investigating the ischemic penumbra proteome in animal models of experimental stroke

Ischaemic stroke results in the formation of a cerebral infarction bordered by an ischaemic penumbra. Characterising the proteins within the ischaemic penumbra may identify neuro-protective targets and novel circulating markers to improve patient care. This review assessed data from studies using proteomic platforms to compare ischaemic penumbra tissues to controls following experimental stroke in animal models. Proteins reported to differ significantly between penumbra and control tissues were analysed in silico to identify protein-protein interactions and over-represented pathways. Sixteen studies using rat (n = 12), mouse (n = 2) or primate (n = 2) models were included. Heterogeneity in the design of the studies and definition of the penumbra were observed. Analyses showed high abundance of p53 in the penumbra within 24 hours of permanent ischaemic stroke and was implicated in driving apoptosis, cell cycle progression, and ATM- MAPK- and p53- signalling. Between 1 and 7 days after stroke there were changes in the abundance of proteins involved in the complement and coagulation pathways. Favourable recovery 1 month after stroke was associated with an increase in the abundance of proteins involved in wound healing. Poor recovery was associated with increases in prostaglandin signalling. Findings suggest that p53 may be a target for novel therapeutics for ischaemic stroke.

Involvement of Calpain in Neurovascular Unit Damage through Up-regulating PARP-NF-κB Signaling during Experimental Ischemic Stroke

Calpain and PARP-NF-κB signaling are reported to participate in the ischemic brain injury. In this study, it was investigated whether calpain was contributed to the neurovascular unit (NVU) damage through up-regulating PARP-NF-κB signaling during experimental ischemic stroke. Male Sprague-Dawley rats were suffered from 90 min of middle cerebral artery occlusion, followed by reperfusion. The NVU damage was evaluated by the permeability of blood-brain barrier (BBB), the degradation of proteins in extracellular matrix and tight junctions, and ultrastructural changes. The inflammatory response was determined by the expression of inflammatory genes driven by PARP-NF-κB signaling and the activities of myeloperoxidase (MPO). Treatment with MDL 28,170, a calpain inhibitor, improved neurological functions, reduced TUNEL staining index, lessened brain swelling, and decreased infarct volume in ischemic rats. Moreover, it reduced the BBB permeability, enhanced the levels of laminin, collagen IV and occludin, and attenuated the ultrastructural damage of NVU in penumbra and core after induction of ischemia. Meanwhile, it enhanced the levels of cytosolic IκBα, lessened the levels of nuclear PARP and NF-κB p65, reduced the levels of ICAM-1, TNF-α, IL-1β, MMP-9, and MMP-2,and suppressed the activities of MPO in penumbra and core. These data showed that calpain inhibition suppressed PARP-NF-κB signaling-mediated inflammatory response, reduced NVU damage, and protected brain against ischemic stroke, suggesting the involvement of calpain in the NVU damage through up-regulating PARP-NF-κB signaling during brain ischemia.

The protective effects of Axitinib on blood-brain barrier dysfunction and ischemia-reperfusion injury in acute ischemic stroke

BACKGROUND AND PURPOSE

The pathophysiological features of acute ischemic stroke (AIS) often involve dysfunction of the blood-brain barrier (BBB), characterized by the degradation of tight junction proteins (Tjs) leading to increased permeability. This dysfunction can exacerbate cerebral injury and contribute to severe complications. The permeability of the BBB fluctuates during different stages of AIS and is influenced by various factors. Developing effective therapies to restore BBB function remains a significant challenge in AIS treatment. High levels of vascular endothelial growth factor (VEGF) in the early stages of AIS have been shown to worsen BBB breakdown and stroke progression. Our study aimed to investigate the protective effects of the VEGF receptor inhibitor Axitinib on BBB dysfunction and cerebral ischemia/reperfusion-induced injury.

METHODS

BEnd3 cell exposed to oxygen-glucose deprivation (OGD) model was constructed to estimate pharmacological activity of Axitinib (400 ng/ml) on anti-apoptosis and pathological barrier function recovery. In vivo, rats were subjected to a 1 h transient middle cerebral artery occlusion and 23 h reperfusion (tMCAO/R) to investigate the permeability of BBB and cerebral tissue damage. Axitinib was administered through the tail vein at the beginning of reperfusion. BBB integrity was assessed by Evans blue leakage and the expression levels of Tjs claudin-5 and occludin.

RESULTS

Our research revealed that co-incubation with Axitinib enhanced the cell viability of OGD-insulted bEnd3 cells, decreased LDH leakage rate, and suppressed the expression of apoptosis-related proteins cytochrome C and Bax. Axitinib also mitigated the damage to Tjs and facilitated the restoration of transepithelial electrical resistance in OGD-insulted bEnd.3 cells. In vivo, Axitinib administration reduced intracerebral Evans blue leakage and up-regulated the expression of Tjs in the penumbra brain tissue in tMCAO/R rats. Notably, 10 mg/kg Axitinib exerted a significant anti-ischemic effect by decreasing cerebral infarct volume and brain edema volume, improving neurological function, and reducing pro-inflammatory cytokines IL-6 and TNF-α in the brain.

CONCLUSIONS

Our study highlights Axitinib as a potent protectant of blood-brain barrier function, capable of promoting pathological blood-brain barrier recovery through VEGF inhibition and increased expression of tight junction proteins in AIS. This suggests that VEGF antagonism within the first 24 h post-stroke could be a novel therapeutic approach to enhance blood-brain barrier function and mitigate ischemia-reperfusion injury.

A novel p55PIK signaling peptide inhibitor alleviates neuroinflammation via the STAT3/NF-kB signaling pathway in experimental stroke

BACKGROUND

Ischemic stroke remains the predominant contributor to mortality and disability globally. Microglia undergo rapid activation and initiate inflammatory cascade reactions by phenotypic polarization, participating in the regulation of inflammatory injury and tissue repair post-ischemic stroke. Regulating microglia-mediated neuroinflammation is a promising therapeutic strategy for ischemic stroke. Previously, we designed and synthesized a novel p55PIK inhibitor, TAT-N15 polypeptide, which presents inhibitive activity on NF-κB signaling-mediated inflammation in acute conjunctivitis and allergic rhinitis. The present study aimed to explore the therapeutic effect and mechanism of TAT-N15 on ischemia stroke.

METHODS

The mouse model of transient cerebral ischemia was made using the intraluminal filament method. After being treated with daily intraperitoneal injections of TAT-N15 (10 mg/kg) for 7 d, the neurological outcomes and the cerebral infarction volume were evaluated. Histopathology of the ischemia cerebral hemisphere was observed by H&E and Nissl staining. Neuronal survival, astrogliosis, and co-labeling of CD86/Iba1 and CD206/Iba1 were detected by immunofluorescence. The cell apoptosis was estimated by TUNEL staining. The expression levels of apoptosis-associated proteins, proinflammatory cytokines, protein markers of M1 and M2 microglia, and the phosphorylation of NF-κB and STAT3 proteins in the ischemic penumbra were detected by Western blot.

RESULTS

TAT-N15 treatment significantly decreased the infarct volume and alleviated neurological functional impairment, neuronal injury, and neuron apoptosis. Meanwhile, TAT-N15 treatment restrained the activation of microglia and astrocytes as well as the protein expression of proinflammatory cytokine in ischemic penumbra. Additionally, the administration of TAT-N15 treatment resulted in a significant reduction in the density of M1 phenotype microglia while concurrently increasing the density of M2 phenotype microglia within the ischemic penumbra. Finally, mechanical analysis unveiled that TAT-N15 exerted a substantial inhibitory effect on the protein expression of phosphorylated STAT3 and NF-κB.

CONCLUSION

TAT-N15 may inhibit neuroinflammation via regulating microglia activation and polarization through the STAT3/NF-κB pathway, which exhibits the neuroprotection effect in ischemic stroke.

Obesity as a Limiting Factor for Remote Ischemic Postconditioning-Mediated Neuroprotection after Stroke

Background

Remote ischemic postconditioning (RIPostC) may protect the brain from ischemia/reperfusion (I/R) injury. The association between RIPostC and obesity has not yet been extensively studied.

Methods

Twelve-week-old male Zucker diabetic fatty (ZDF; n=68) and Zucker diabetic lean (ZDL; n=51) rats were subjected to focal cerebral ischemia for 90 minutes, followed by 24 hours of reperfusion. RIPostC was performed with 5-minute I/R cycles using a tourniquet on the right hind limb.

Results

The results showed a negative association between obesity and neurological impairment in ischemic animals. We observed a 70% greater infarct size in ZDF rats compared with their lean counterparts, as evaluated by 2,3,5-triphenyltetrazolium chloride staining. To measure the total fragmented DNA in peripheral lymphocytes, comet assay was performed. Obese rats exhibited higher levels of DNA damage (by approximately 135%) in peripheral blood lymphocytes even before the induction of stroke. RIPostC did not attenuate oxidative stress in the blood in obese rats subjected to ischemia. Focal cerebral ischemia increased core and penumbra tissue glutamate release in the brain and decreased it in the blood of ischemic ZDL rats, and these changes improved following RIPostC treatment. However, changes in blood and tissue glutamate content were not detected in ischemic ZDF rats or after RIPostC intervention.

Conclusion

Our findings suggest that obese animals respond more severely to ischemia-reperfusion brain injury. However, obese animals did not achieve neuroprotective benefits of RIPostC treatment.

Neuroprotective effects of Jie-du-huo-xue decoction on microglia pyroptosis after cerebral ischemia and reperfusion--From the perspective of glial-vascular unit

ETHNOPHARMACOLOGICAL RELEVANCE

Ischemic stroke poses a serious risk to public health and quality of life. Jie-Du-Huo-Xue decoction (JDHXD) is a classical and well-known Chinese formula for stroke treatment, but the pharmacological mechanism is still unclear.

AIM OF THE STUDY

This study aims to investigate the mechanism underlying microglial pyroptosis and polarization, as well as the potential efficacy of JDHXD against cerebral ischemia-reperfusion injury (CIRI).

MATERIALS AND METHODS

Models of CIRI were established by the middle cerebral artery occlusion/reperfusion (MCAO/R) method in rats. In the first stage, 36 SD rats were randomly divided into sham group, I/R group, JDHXD-L group (5.36 g/kg/day), JDHXD-M group (10.71 g/kg/day), JDHXD-H group (21.42 g/kg/day), and positive drug edaravone group. The effectiveness of JDHXD on CIRI was confirmed by neurological function testing and cerebral infarct measuring. The best dose (JDXHD-M) was subsequently chosen to perform the tests that followed. In the second stage, 36 SD rats were randomly divided into the sham group, the I/R group, and the JDHXD-M group. Detection of nerve damage using Nissl staining, proteins of pyroptosis, Iba-1, and NeuN expressions were detected by western blotting, and proteins of microglial pyroptosis and M1/M2 phenotypic polarization were detected by immunofluorescence.

RESULTS

In rats after CIRI, JDHXD significantly reduced neurological impairment and cerebral infarction. In addition, JDHXD facilitated the M1-to-M2 transition of microglia in order to minimize neuroinflammation and improve anti-inflammatory repair. In addition, JDXHD inhibited microglial pyroptosis by blocking the cleavage of caspase-1 P10 and gasdermin D, hence reducing neuronal damage and enhancing neuronal survival following reperfusion. Interestingly, JDHXD also demonstrated a protective effect on the glial-vascular unit (GVU).

CONCLUSIONS

Our investigation demonstrated that JDHXD exerted a GVU-protective effect on CIRI rats by decreasing neuroinflammation-associated microglial pyroptosis, suppressing microglial M1 activation, and promoting microglial M2 activation.

Illustrate the distribution and metabolic regulatory effects of pterostilbene in cerebral ischemia-reperfusion rat brain by mass spectrometry imaging and spatial metabolomics

Pterostilbene is a promising molecule with superior pharmacological activities and pharmacokinetic characteristics compared to its structural analogue resveratrol, which could be used to treat ischemic stroke. However, its mechanism is still unclear. The cutting-edge air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI) and spatial metabolomics analysis were applied to investigate the distribution of pterostilbene in ischemic rat brain and the changes of related small molecule metabolic pathways to further explore the potential mechanisms of pterostilbene against cerebral ischemia-reperfusion injury. This research found that pterostilbene could significantly restore cerebral microcirculation blood flow, reduce infarct volume, improve neurological function and ameliorate neuronal damage in ischemic rats. Moreover, pterostilbene was widely and abundantly distributed in ischemic brain tissue, laying a solid foundation for the rescue of ischemic penumbra. Further study revealed that pterostilbene played a therapeutic role in restoring energy supply, rebalancing neurotransmitters, reducing abnormal polyamine accumulation and phospholipid metabolism. These findings offer an opportunity to illustrate novel mechanisms of pterostilbene in the treatment of cerebral ischemia/reperfusion injury resulting from ischemic stroke.

Rectangular method: a modified technique for sampling the ischemic border zone in a rat model of transient middle cerebral artery occlusion

To date, there have been three common methods for sampling the cerebral ischemic border zone in a rat model of transient middle cerebral artery occlusion (tMCAO): the "two o'clock method", the "diagonal method", and the "parallel line method". However, these methods have their own advantages and limitations. Here, we propose a modified technique (the "rectangular method") for sampling the ischemic border zone. A rat tMCAO model was prepared under the support of a compact small animal anesthesia machine. Cerebral blood flow was monitored by high-resolution laser Doppler to control the quality of modeling, and 2,3,5-triphenyl tetrazolium chloride (TTC) staining was used for cerebral infarction location assessment. Superoxide dismutase 2 (SOD2), cysteinyl aspartate specific proteinase (caspase)-3, caspase-9, and heat shock protein 70 (HSP70) were used to verify the reliability and reproducibility of the rectangular method. The expression of biomarkers (SOD2, caspase-3, caspase-9, and HSP70) in the traditional (two o'clock method after TTC staining) and modified (rectangular method) groups were increased. There were no significant differences between the groups. The rectangular method proposed herein is based on a modification of the diagonal method and parallel line method, which could provide a directly observable infarct borderline and a sufficient sampling area for subsequent experimental operations regardless of the cerebral infarct location. The assessed biomarkers (SOD2, caspase-3, caspase-9, and HSP70) demonstrated the reliability and reproducibility of the rectangular method, which may facilitate inter-laboratory comparisons.

Immune pathway activation in neurons triggers neural damage after stroke

Ischemic brain injury is a severe medical condition with high incidences in elderly people without effective treatment for the resulting neural damages. Using a unilateral mouse stroke model, we analyze single-cell transcriptomes of ipsilateral and contralateral cortical penumbra regions to objectively reveal molecular events with single-cell resolution at 4 h and 1, 3, and 7 days post-injury. Here, we report that neurons are among the first cells that sense the lack of blood supplies by elevated expression of CCAAT/enhancer-binding protein β (C/EBPβ). To our surprise, the canonical inflammatory cytokine gene targets for C/EBPβ, including interleukin-1β (IL-1β) and tumor necrosis factor α (TNF-α), are subsequently induced also in neuronal cells. Neuronal-specific silencing of C/EBPβ or IL-1β and TNF-α substantially alleviates downstream inflammatory injury responses and is profoundly neural protective. Taken together, our findings reveal a neuronal inflammatory mechanism underlying early pathological triggers of ischemic brain injury.

Electroacupuncture Alleviates Neuroinflammation by Regulating Microglia Polarization via STAT6/PPARγ in Ischemic Stroke Rats

Previous study showed that electroacupuncture (EA) produced a protective effect on cerebral ischemia-reperfusion injury (CIRI) in rats and may correlate with the anti-inflammatory effects of microglia. This study aimed to investigate further whether EA could modulate neuroinflammation by targeting the Signal Transducer and Activator of Transcription 6 (STAT6) and Peroxisome Proliferator-Activated Receptor γ (PPARγ) pathway, the key regulator of microglia. Middle cerebral artery occlusion (MCAO) rats were used, and 6 h after reperfusion, EA interventions were performed in Chize (LU 5), Hegu (LI 4), Sanyinjiao (SP 6), and Zusanli (ST 36) on the affected side of the rats, the group that received EA + STAT6 phosphorylation inhibitor AS1517499 was used as a parallel control. The degree of neurological impairment, infarct volume, microglia polarization, inflammation levels and activity of STAT6/PPARγ pathway were then assessed by neurological deficit score, triphenyl tetrazolium chloride (TTC) staining, immunofluorescence, western blotting (WB), quantitative real-time PCR (qPCR) and Enzyme linked immunosorbent assay (ELISA). The data showed that EA significantly alleviated nerve injury, reduced infarct volume, enhanced the expression and activity of STAT6/PPARγ pathway, inhibited NF-κB activity, increased M2 microglia numbers and anti-inflammatory factor release, and inhibited microglia M1-type polarization and pro-inflammatory factor expression. In contrast, inhibition of STAT6 phosphorylation exacerbated neural damage, inhibited STAT6/PPARγ pathway activity, promoted microglia M1-type polarization and exacerbated neuroinflammation, resulting in an attenuated positive effect of EA intervention. Therefore, we concluded that EA intervention could attenuate microglia-associated neuroinflammation by enhancing the expression and activity of STAT6/PPARγ pathway, thereby reducing CIRI in MCAO rats.

Synaptotagmin-3 interactions with GluA2 mediate brain damage and impair functional recovery in stroke

Synaptotagmin III (Syt3) is a Ca2+-dependent membrane-traffic protein that is highly concentrated in synaptic plasma membranes and affects synaptic plasticity by regulating post-synaptic receptor endocytosis. Here, we show that Syt3 is upregulated in the penumbra after ischemia/reperfusion (I/R) injury. Knockdown of Syt3 protects against I/R injury, promotes recovery of motor function, and inhibits cognitive decline. Overexpression of Syt3 exerts the opposite effects. Mechanistically, I/R injury augments Syt3-GluA2 interactions, decreases GluA2 surface expression, and promotes the formation of Ca2+-permeable AMPA receptors (CP-AMPARs). Using a CP-AMPAR antagonist or dissociating the Syt3-GluA2 complex via TAT-GluA2-3Y peptide promotes recovery from neurological impairments and improves cognitive function. Furthermore, Syt3 knockout mice are resistant to cerebral ischemia because they show high-level expression of surface GluA2 and low-level expression of CP-AMPARs after I/R. Our results indicate that Syt3-GluA2 interactions, which regulate the formation of CP-AMPARs, may be a therapeutic target for ischemic insults.

Exercise pretreatment alleviates neuroinflammation and oxidative stress by TFEB-mediated autophagic flux in mice with ischemic stroke

BACKGROUND

Neuroinflammation and oxidative stress are important pathological mechanisms underlying cerebral ischemic stroke. Increasing evidence suggests that regulation autophagy in ischemic stroke may improve neurological functions. In this study, we aimed to explore whether exercise pretreatment attenuates neuroinflammation and oxidative stress in ischemic stroke by improving autophagic flux.

METHODS

2,3,5-Triphenyltetrazolium chloride staining was used to determine the infarction volume, and modified Neurological Severity Scores and rotarod test were used to evaluate neurological functions after ischemic stroke. The levels of oxidative stress, neuroinflammation, neuronal apoptosis and degradation, autophagic flux, and signaling pathway proteins were determined using immunofluorescence, dihydroethidium, TUNEL, and Fluoro-Jade B staining, western blotting, and co-immunoprecipitation.

RESULTS

Our results showed that, in middle cerebral artery occlusion (MCAO) mice, exercise pretreatment improved neurological functions and defective autophagy, and reduced neuroinflammation and oxidative stress. Mechanistically, after using chloroquine, impaired autophagy abolished the neuroprotection of exercise pretreatment. And transcription factor EB (TFEB) activation mediated by exercise pretreatment contributes to improving autophagic flux after MCAO. Furthermore, we showed that TFEB activation mediated by exercise pretreatment in MCAO was regulated by the AMPK-mTOR and AMPK-FOXO3a-SKP2-CARM1 signaling pathways.

CONCLUSIONS

Exercise pretreatment has the potential to improve the prognosis of ischemic stroke patients, and it can exert neuroprotective effects in ischemic stroke by inhibiting neuroinflammation and oxidative stress, which might be due to the TFEB-mediated autophagic flux. And targeting autophagic flux may be promising strategies for the treatment of ischemic stroke.

Comparative study of extracellular vesicles derived from mesenchymal stem cells and brain endothelial cells attenuating blood-brain barrier permeability via regulating Caveolin-1-dependent ZO-1 and Claudin-5 endocytosis in acute ischemic stroke

BACKGROUND

Blood-brain barrier (BBB) disruption is a major adverse event after ischemic stroke (IS). Caveolin-1 (Cav-1), a scaffolding protein, played multiple roles in BBB permeability after IS, while the pros and cons of Cav-1 on BBB permeability remain controversial. Numerous studies revealed that extracellular vesicles (EVs), especially stem cells derived EVs, exerted therapeutic efficacy on IS; however, the mechanisms of BBB permeability needed to be clearly illustrated. Herein, we compared the protective efficacy on BBB integrity between bone marrow mesenchymal stem cells derived extracellular vesicles (BMSC-EVs) and EVs from brain endothelial cells (BEC-EVs) after acute IS and investigated whether the mechanism was associated with EVs antagonizing Cav-1-dependent tight junction proteins endocytosis.

METHODS

BMSC-EVs and BEC-EVs were isolated and characterized by nanoparticle tracking analysis, western blotting, and transmission electron microscope. Oxygen and glucose deprivation (OGD) treated b. End3 cells were utilized to evaluate brain endothelial cell leakage. CCK-8 and TRITC-dextran leakage assays were used to measure cell viability and transwell monolayer permeability. Permanent middle cerebral artery occlusion (pMCAo) model was established, and EVs were intravenously administered in rats. Animal neurological function tests were applied, and microvessels were isolated from the ischemic cortex. BBB leakage and tight junction proteins were analyzed by Evans Blue (EB) staining and western blotting, respectively. Co-IP assay and Cav-1 siRNA/pcDNA 3.1 vector transfection were employed to verify the endocytosis efficacy of Cav-1 on tight junction proteins.

RESULTS

Both kinds of EVs exerted similar efficacies in reducing the cerebral infarction volume and BBB leakage and enhancing the expressions of ZO-1 and Claudin-5 after 24 h pMCAo in rats. At the same time, BMSC-EVs were outstanding in ameliorating neurological function. Simultaneously, both EVs treatments suppressed the highly expressed Cav-1 in OGD-exposed b. End3 cells and ischemic cerebral microvessels, and this efficacy was more prominent after BMSC-EVs administration. Cav-1 knockdown reduced OGD-treated b. End3 cells monolayer permeability and recovered ZO-1 and Claudin-5 expressions, whereas Cav-1 overexpression aggravated permeability and enhanced the colocalization of Cav-1 with ZO-1 and Claudin-5. Furthermore, Cav-1 overexpression partly reversed the lower cell leakage by BMSC-EVs and BEC-EVs administrations in OGD-treated b. End3 cells.

CONCLUSIONS

Our results demonstrated that Cav-1 aggravated BBB permeability in acute ischemic stroke, and BMSC-EVs exerted similar antagonistic efficacy to BEC-EVs on Cav-1-dependent ZO-1 and Claudin-5 endocytosis. BMSC-EVs treatment was superior in Cav-1 suppression and neurological function amelioration.

Ischemic stroke protected by ISO-1 inhibition of apoptosis via mitochondrial pathway

Macrophage migration inhibitory factor (MIF) is an immune mediator associated with inflammation, which is upregulated after ischemia in brain tissue. ISO-1 is a potent inhibitor of MIF tautomerase and can protect neurons by reducing the permeability of blood brain barrier (BBB). In this study, we investigated the role of ISO-1 in cerebral ischemia/reperfusion injury by establishing a model of middle cerebral artery occlusion/reperfusion in rats. Rats were randomly divided into four groups: the sham operation group, the ISO-1group, the cerebral I/R group, and the ISO-1 + I/R group. We assessed the degree of neurological deficit in each group and measured the volume of cerebral infarction. We detected the expression of MIF in the core necrotic area and penumbra. We detected the expression of apoptosis-related proteins, apoptosis-inducing factor (AIF), endonuclease G (EndoG) and cytochrome c oxidase-IV (COX-IV) in the ischemic penumbra region. The results showed that MIF was expressed in the ischemic penumbra, while the injection of ISO-1 was able to alleviate neurological damage and reduce the infarction volume. In the cerebral ischemic penumbra region, ISO-1 could reduce the expression of Bax and Caspase3 and inhibit the displacement of AIF and EndoG to the nucleus simultaneously. Besides, ISO-1 also exhibited the ability to reduce apoptosis. In summary, ISO-1 may inhibit neuronal apoptosis through the endogenous mitochondrial pathway and reduce the injury of brain I/R after ischemic stroke.

Electroacupuncture pretreatment induces ischemic tolerance by neuronal TREM2-mediated enhancement of autophagic flux

The mechanism of electroacupuncture (EA) pretreatment-induced neuroprotection remains unclear. In this study, we found that neuronal Triggering receptor expressed on myeloid cells 2 (TREM2) expression was increased and peaked at 48 h and 72 h after ischemia/reperfusion. After specific knockdown of TREM2 in excitatory neurons, neurological function was damaged, and the infarct volume was enlarged. Furthermore, the expression of LC3II/LC3I and Beclin1 was decreased, while the expression of p62 was increased. EA pretreatment enhanced TREM2, LC3II/LC3I and Beclin1 expression while reducing p62 in the ischemic penumbra area. The EA-induced neuroprotective effects and improvements in autophagic flux were abolished by specific knockdown of TREM2 in excitatory neurons. Taken together, our findings provide novel mechanistic insight into EA-induced ischemic tolerance and suggest a promising therapeutic strategy of targeting neuronal TREM2 to treat brain ischemia.

The Protective Effect of Vitexin Compound B-1 on Rat Cerebral I/R Injury through a Mechanism Involving Modulation of miR-92b/NOX4 Pathway

BACKGROUND

Recent studies have uncovered that vitexin compound B-1 (VB-1) can protect neurons against hypoxia/reoxygenation (H/R)-induced oxidative injury through suppressing NOX4 expression.

OBJECTIVE

The aims of this study are to investigate whether VB-1 can protect the rat brain against ischemia/ reperfusion (I/R) injury and whether its effect on NOX4 expression is related to modulation of certain miRNAs expression.

METHODS

Rats were subjected to 2 h of cerebral ischemia followed by 24 h of reperfusion to establish an I/R injury model, which showed an increase in neurological deficit score and infarct volume concomitant with an upregulation of NOX4 expression, increase in NOX activity, and downregulation of miR-92b.

RESULTS

Administration of VB-1 reduced I/R cerebral injury accompanied by a reverse in NOX4 and miR-92b expression. Similar results were achieved in a neuron H/R injury model. Next, we evaluated the association of miR-92b with NOX4 by its mimics in the H/R model. H/R treatment increased neurons apoptosis concomitant with an upregulation of NOX4 and NOX activity while downregulation of miR-92b. All these effects were reversed in the presence of miR-92b mimics, confirming the function of miR-92b in suppressing NOX4 expression.

CONCLUSION

We conclude the protective effect of VB-1 against rat cerebral I/R injury through a mechanism involving modulation of miR-92b/NOX4 pathway.

The effect of Tianjiang Xueshuantong Wan pills on ischemia-reperfusion injury after thrombolysis in acute cerebral infarction

OBJECTIVE

The aim of this study is to investigate the effect of Tianjiang Xueshuantong Wan pills on reperfusion injury after venous thrombolysis in acute cerebral infarction.

METHODS

The strategy used in this study is a randomised controlled clinical trial. In total, 72 cases were included, with 36 in the trial group and 36 in the control group, with a 1:1 ratio. Both groups were given standardised treatment for acute cerebral infarction. Based on the rt-PA intravenous thrombolysis, the test group took Tianjiang Xueshuantong Wan pills orally, whereas the control group solely utilised rt-PA for intravenous thrombolysis and did not take the test medicine orally. The patients' intracranial hemorrhage was clarified by head CT scan, and the occurrence of reperfusion injury was recorded during the entire trial.

RESULTS

There were no significant differences in serum IL-6, MDA, SOD and TNF concentrations and NIHSS scores between the two groups before therapy (P > 0.05). After treatment, the serum concentrations of IL-6, MDA and TNF in the experimental group were significantly decreased compared with the control group, while the serum concentrations of SOD were significantly increased compared with the control group, with statistical significance (P > 0.05). After seven days of treatment, the total effective rate in the experimental group was 88.89%, while the data in the control group was 75%. There was a statistically significant difference between the experimental and control groups.

CONCLUSION

Tianjiang Xueshuantong Wan pills can effectively prevent reperfusion injury following intravenous thrombolysis in individuals with cerebral infarction while improving patients' neurological deficits.

Endothelial caveolin-1 regulates cerebral thrombo-inflammation in acute ischemia/reperfusion injury

BACKGROUND

Thrombo-inflammation is an important checkpoint that orchestrates infarct development in ischemic stroke. However, the underlying mechanism remains largely unknown. Here, we explored the role of endothelial Caveolin-1 (Cav-1) in cerebral thrombo-inflammation.

METHODS

The correlation between serum Cav-1 level and clinical outcome was analyzed in acute ischemic stroke patients with successful recanalization. Genetic manipulations by endothelial-specific adeno-associated virus (AAV) and siRNA were applied to investigate the effects of Cav-1 in thrombo-inflammation in a transient middle cerebral artery occlusion (tMCAO) model. Thrombo-inflammation was analyzed by microthrombosis formation, myeloid cell infiltration, and endothelial expression of adhesion molecules as well as inflammatory factors.

FINDINGS

Reduced circulating Cav-1, with the potential to predict microembolic signals, was more frequently detected in recanalized stroke patients without early neurological improvement. At 24 h after tMCAO, serum Cav-1 was consistently reduced in mice. Endothelial Cav-1 was decreased in the peri-infarct region. Cav-1^-/- endothelium, with prominent barrier disruption, displayed extensive microthrombosis, accompanied by increased myeloid cell inflammatory infiltration after tMCAO. Specific enhanced expression of endothelial Cav-1 by AAV-Tie1-Cav-1 remarkably reduced infarct volume, attenuated vascular hyper-permeability and alleviated thrombo-inflammation in both wild-type and Cav-1^-/- tMCAO mice. Transcriptome analysis after tMCAO further designated Rxrg as the most significantly changed molecule resulting from the knockdown of Cav-1. Supplementation of RXR-γ siRNA reversed AAV-Tie1-Cav-1-induced amelioration of thrombo-inflammation without affecting endothelial tight junction.

INTERPRETATION

Endothelial Cav-1/RXR-γ may regulate infarct volume and neurological impairment, possibly through selectively controlling thrombo-inflammation coupling, in cerebral ischemia/reperfusion.

FUNDING

This work was supported by National Natural Science Foundation of China.

Detection of acute ischemic stroke and backtracking stroke onset time via machine learning analysis of metabolomics

The time window from stroke onset is critical for the treatment decision. However, in unknown onset stroke, it is often difficult to determine the exact onset time because of the lack of assessment methods, which can result in controversial and random treatment decisions. Previous studies have shown that serum biomarkers, in addition to imaging assessment, are useful for determining the stroke onset time. However, as yet there are no specific biomarkers or corresponding methodologies that are accurate and effective for determining the onset time of unknown onset stroke. Herein, we describe our novel advanced metabolites-based machine learning method (termed extreme gradient boost [XGBoost]) combined with recursive feature elimination, which accurately screened five metabolites from 1124 metabolites detected in serum. These metabolites were capable of both detecting acute ischemic stroke and backtracking the acute ischemic stroke onset time. To further investigate the pathological mechanisms of acute ischemic stroke, we also examined characteristic metabolites in different brain regions, and found two metabolites that could distinguish the core infarct area from the ischemic penumbra. Although this study is based on animal experiments, our machine learning framework and selected metabolites may provide a basis for clinical stroke evaluation and treatment.

NOX2-mediated reactive oxygen species are double-edged swords in focal cerebral ischemia in mice

BACKGROUND

Reactive oxygen species (ROS) often promote acute brain injury after stroke, but their roles in the recovery phase have not been well studied. We tested the hypothesis that ROS activity mediated by NADPH oxidase 2 (NOX2) contributes to acute brain injury but promotes functional recovery during the delayed phase, which is linked with neuroinflammation, autophagy, angiogenesis, and the PI3K/Akt signaling pathway.

METHODS

We used the NOX2 inhibitor apocynin to study the role of NOX2 in brain injury and functional recovery in a middle cerebral artery occlusion (MCAO) stroke mouse model. Infarct size, neurological deficits and behavior were evaluated on days 3, 7, 10 and 14 after reperfusion. In addition, dynamic NOX2-induced ROS levels were measured by dihydroethidium (DHE) staining. Autophagy, inflammasomes, and angiogenesis were measured by immunofluorescence staining and western blotting. RNA sequencing was performed, and bioinformatics technology was used to analyze differentially expressed genes (DEGs), as well as the enrichment of biological functions and signaling pathways in ischemia penumbra at 7 days after reperfusion. Then, Akt pathway-related proteins were further evaluated by western blotting.

RESULTS

Our results showed that apocynin injection attenuated infarct size and mortality 3 days after stroke but promoted mortality and blocked functional recovery from 5 to 14 days after stroke. DHE staining showed that ROS levels were increased at 3 days after reperfusion and then gradually declined in WT mice, and these levels were significantly reduced by the NOX2 inhibitor apocynin. RNA-Seq analysis indicated that apocynin activated the immune response under hypoxic conditions. The immunofluorescence and western blot results demonstrated that apocynin inhibited the NLRP3 inflammasome and promoted angiogenesis at 3 days but promoted the NLRP3 inflammasome and inhibited angiogenesis at 7 and 14 days after stroke, which was mediated by regulating autophagy activation. Furthermore, RNA-Seq and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that apocynin injection resulted in PI3K-Akt signaling pathway enrichment after 7 days of MCAO. We then used an animal model to show that apocynin decreased the protein levels of phosphorylated PI3K and Akt and NF-κB p65, confirming that the PI3K-Akt-NF-κB pathway is involved in apocynin-mediated activation of inflammation and inhibition of angiogenesis.

CONCLUSIONS

NOX2-induced ROS production is a double-edged sword that exacerbates brain injury in the acute phase but promotes functional recovery. This effect appears to be achieved by inhibiting NLRP3 inflammasome activation and promoting angiogenesis via autophagy activation.

Moderate Ethanol-Preconditioning Offers Ischemic Tolerance Against Focal Cerebral Ischemic/Reperfusion: Role of Large Conductance Calcium-Activated Potassium Channel

The mechanism underlying moderate ethanol (EtOH)-preconditioning (PC) against ischemic brain injury remains unclear. We evaluated the role of large conductance calcium-sensitive potassium (BK_Ca) channels in EtOH-PC. Almost one hundred and ninety normal adult SD rats (8 to 10 weeks, 320-350 g) were enrolled in this study. Ischemic/reperfusion (I/R) brain injury was induced in rats by middle cerebral artery occlusion for 2 h followed by reperfusion for 24 h. EtOH or the BK_Ca channel opener, NS11021, was administered 24 h before I/R with or without pre-treatment with the BK_Ca channel blocker, paxilline. Infarct volumes were measured by tissue staining and imaging, and neurological functions were assessed by a scoring system. The expression of BK_Ca channel subunit α was detected by Western blotting, and cell apoptosis was assessed using staining. Prior (24 h) administration of ethanol that produced a peak plasma concentration of ~ 45 mg/dl in rats would offer neuroprotection after cerebral I/R. In addition, the expression of BK_Ca channel α-subunit was significantly increased 24 h after EtOH-PC (n = 10; control: 2.00 ± 0.09, EtOH: 1.00 ± 0.06; P < 0.5). Compared to I/R, EtOH-PC enhanced the expression of BK_Ca channel α-subunit both in the penumbra (n = 10; 24 h: I/R: 1.25 ± 0.10, EtOH-PC + I/R: 1.99 ± 0.12; P < 0.01; 4 h: I/R: 1.03 ± 0.03, EtOH-PC + I/R: 1.49 ± 0.05; P < 0.001) and infarct core (n = 10; 4 h: I/R: 1.04 ± 0.04, EtOH-PC + I/R: 1.42 ± 0.05; P < 0.001), improved the neurological function (n = 10; I/R: 14.00 (12.75-15.00), EtOH-PC + I/R: 7.00 (4.75-8.25); P < 0.001), attenuated the apoptosis (n = 10; I/R: 26.80 ± 0.69, EtOH-PC + I/R: 8.46 ± 0.31; P < 0.001), and decreased the infarct volume (n = 10; I/R: 244.00 ± 26.24, EtOH-PC + I/R: 70.09 ± 14.69; P < 0.001) after experimental cerebral I/R. These changes were reversed by paxilline administration. The moderate EtOH-PC protects against I/R-induced brain damage dependent on the upregulation BK_Ca channels.

Treadmill Training Reduces Cerebral Ischemia-Reperfusion Injury by Inhibiting Ferroptosis through Activation of SLC7A11/GPX4

The mechanism by which exercise training attenuates cerebral ischemia/reperfusion (I/R) injury, especially in the regulation of iron level in neuronal damage, has not been systematically studied. Here, we showed that treadmill training inhibited ferroptosis after I/R injury in rats. Modified neurologic severity score (mNSS) test showed that the motor function, reflex, and balance abilities in the I/R injury rats after treadmill intervention were significantly improved. Treadmill training decreased the level of lipid peroxides in the cerebral cortex of ischemic rats. We found that the protein levels of ferroptosis-related proteins including nuclear transcription factor E2-related factor 2 (Nrf2), cystine/glutamate reverse transporter (SLC7A11), and glutathione peroxidase 4 (GPx4) were decreased in rats after cerebral I/R injury, while treadmill training prevented the reduction of these proteins. Furthermore, we demonstrated that erastin- (a ferroptosis activator-) induced downregulation of SLC7A11 reversed the neuroprotective effect of treadmill training. This study provides the first evidence suggesting that treadmill training suppresses ferroptosis by activating the SLC7A11/GPx4 pathway, thereby protecting against cerebral I/R injury.

Inhibition of intracellular proton-sensitive Ca2+-permeable TRPV3 channels protects against ischemic brain injury

Ischemic brain stroke is pathologically characterized by tissue acidosis, sustained calcium entry and progressive cell death. Previous studies focusing on antagonizing N-methyl-d-aspartate (NMDA) receptors have failed to translate any clinical benefits, suggesting a non-NMDA mechanism involved in the sustained injury after stroke. Here, we report that inhibition of intracellular proton-sensitive Ca²⁺-permeable transient receptor potential vanilloid 3 (TRPV3) channel protects against cerebral ischemia/reperfusion (I/R) injury. TRPV3 expression is upregulated in mice subjected to cerebral I/R injury. Silencing of TRPV3 reduces intrinsic neuronal excitability, excitatory synaptic transmissions, and also attenuates cerebral I/R injury in mouse model of transient middle cerebral artery occlusion (tMCAO). Conversely, overexpressing or re-expressing TRPV3 increases neuronal excitability, excitatory synaptic transmissions and aggravates cerebral I/R injury. Furthermore, specific inhibition of TRPV3 by natural forsythoside B decreases neural excitability and attenuates cerebral I/R injury. Taken together, our findings for the first time reveal a causative role of neuronal TRPV3 channel in progressive cell death after stroke, and blocking overactive TRPV3 channel may provide therapeutic potential for ischemic brain injury.

Notoginsenoside R1 ameliorates mitochondrial dysfunction to circumvent neuronal energy failure in acute phase of focal cerebral ischemia

Due to sudden loss of cerebral blood circulation, acute ischemic stroke (IS) causes neuronal energy attenuation or even exhaustion by mitochondrial dysfunction resulting in aggravation of neurological injury. In this study, we investigated if Notoginsenoside R1 ameliorated cerebral energy metabolism by limiting neuronal mitochondrial dysfunction in acute IS. Male Sprague-Dawley rats (260-280 g) were selected and performed by permanent middle cerebral artery occlusion model. In vitro, the oxygen glucose deprivation (OGD) model of Neuro2a (N2a) cells was established. We found Notoginsenoside R1 treatment reduced rats' cerebral infarct volume and neurological deficits, with increased Adenosine triphosphate (ATP) level together with upregulated expression of glucose transporter 1/3, monocarboxylate transporter 1 and citrate synthase in brain peri-ischemic tissue. In vitro, OGD-induced N2a cell death was inhibited, cell mitochondrial morphology was improved. Mitochondrial amount, mitochondrial membrane potential, and mitochondrial DNA copy number were increased by Notoginsenoside R1 administration. Furthermore, mitochondrial energy metabolism-related mRNA array found Atp12a and Atp6v1g3 gene expression were upregulated more than twofold, which were also verified in rat ischemic tissue by quantitative polymerase chain reaction (qPCR) assay. Therefore, Notoginsenoside R1 administration increases cerebral glucose and lactate transportation and ATP levels, ameliorates neuronal mitochondrial function after IS. Notoginsenoside R1 may be a novel protective agent for neuronal mitochondria poststroke.

The Novel microRNA Rno-miR-686-3p Is Associated with the Ischaemic Penumbra

INTRODUCTION

We explored microRNA (miRNA) profiles correlated with the penumbra in three different phases of ischaemic stroke, using a permanent middle cerebral artery occlusion (p-MCAO) rat model.

MATERIALS AND METHODS

A 2-mm coronal section was cut from the optic chiasma in the caudal direction, and the penumbra was located in the area between a longitudinal line approximately 2 mm from the midline and a transverse diagonal line at the "2-o'clock" position. Total RNA was extracted from tissue specimens and peripheral blood samples, followed by deep sequencing analysis.

RESULTS

We identified nine novel miRNA candidates in tissues and evaluated their expression levels using real-time quantitative polymerase chain reaction. In situ hybridization was conducted to assess miRNA localization in the brain. Of these nine candidates, we identified and characterized a novel miRNA, rno-miR-686-3p, which was localized in cell nuclei of the cortex, and associated with the penumbra. rno-miR-686-3p was downregulated at 1 (p = 0.042), 3 (p = 0.032), and 4 h (p = 0.007) post-p-MCAO in the penumbra. A total of 297 potential target genes were predicted. Moreover, functional annotation clustering and pathway enrichment analysis predicted that rno-miR-686-3p participates in transcriptional regulation and the Wnt and cyclic adenosine monophosphate (cAMP) signalling pathways.

CONCLUSION

rno-miR-686-3p is a novel miRNA associated with the ischaemic penumbra that is implicated in transcriptional regulation and modulation of the Wnt and cAMP signalling pathways. Furthermore, it may serve as a possible new biomarker with potential value for detecting the existence of the penumbra.

Protective Effect of Buyang Huanwu Decoction on Cerebral Ischemia Reperfusion Injury by Alleviating Autophagy in the Ischemic Penumbra

Objectives

To evaluate the protective effect of Buyang Huanwu Decoction (BHD) against cerebral ischemia reperfusion and investigate whether autophagy is involved in its mechanism of action.

Methods

Adult male Sprague Dawley rats were randomly divided into three groups: the sham, cerebral ischemia reperfusion (I/R), and I/R + BHD groups. A rat model of cerebral I/R injury was established via middle cerebral artery occlusion (MCAO) for 2 h, followed by 1, 3, and 7 d of reperfusion. Neurological scores and regional cerebral blood flow were assessed to determine whether the model was successfully established. Brain infarct volume was determined by 2,3,5-triphenyl tetrazolium chloride (TTC) staining. The apoptosis rate was detected using TdT-mediated dUTP Nick-End Labeling (TUNEL) staining, and neuronal damage was evaluated by Nissl staining. The Beclin-1 and LC3 protein levels in the ischemic core, penumbra, and contralateral area were analysed by Western blotting. The occurrence of autophagy in the penumbra was observed by transmission electron microscopy (TEM).

Results

BHD treatment alleviated the cerebral infarct volume, neuronal apoptosis rate, and neuronal damage 3 and 7 d after cerebral I/R injury. Furthermore, 3 d after reperfusion, we observed that the Beclin-1 levels were significantly decreased in the core in the I/R group, whereas transformation of LC3 I to LC3 II exhibited no obvious differences between the sham and I/R groups. In the penumbra, the Beclin-1 levels and transformation of LC3 I to LC3 II in the I/R group were significantly increased compared with that in the sham group. However, no significant difference in the contralateral area was noted between the two groups. BHD significantly inhibited the expression of Beclin-1 and the transformation of LC3 I to LC3 II in the penumbra after cerebral I/R injury but yielded no significant changes in the core and contralateral area.

Conclusions

BHD exerts a neuroprotective effect by inhibiting autophagy in neurons in the penumbra after cerebral I/R injury.

Scalp Acupuncture and Treadmill Training Inhibits Neuronal Apoptosis through Activating cIAP1 in Cerebral Ischemia Rats

Stroke is the leading cause of long-term disability in developed countries. Multitudinous evidence suggests that treadmill training treatment is beneficial for balance and stroke rehabilitation; however, the need for stroke therapy remains unmet. In the present study, a cerebral ischemia rat model was established by permanent middle cerebral artery occlusion (pMCAO) to explore the therapeutic effect and mechanism of scalp acupuncture combined with treadmill training on ischemic stroke. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and neuronal nuclear protein (NeuN) double staining and cellular inhibitor of apoptosis protein-1 (cIAP1) and NeuN immunofluorescence double staining were used to detect the short-term and long-term neuroprotective effects of scalp acupuncture combined with treadmill training on pMCAO rats. In addition, the antiapoptotic effect of the combined treatment was evaluated in pMCAO rats transfected with cIAP1 shRNA. Western blotting was used to detect the relative protein expression in the caspase-8/-9/-3 activation pathway downstream of cIAP1 to further clarify its regulatory mechanism. Our results showed that scalp acupuncture combined with treadmill training successfully achieved short-term and long-term functional improvement within 14 days after stroke, significantly inhibited neuronal apoptosis, and upregulated the expression of cIAP1 protein in the ischemic penumbra area of the ischemic brain. However, no significant functional improvement and antiapoptotic effect were found in pMCAO rats transfected with cIAP1 shRNA. Western blotting results showed that the combined therapy markedly inhibited the activation of the caspase-8/-9/-3 pathway. These findings indicate that scalp acupuncture combined with treadmill training therapy may serve as a more effective alternative modality in the treatment of ischemic stroke, playing an antiapoptotic role by upregulating the expression of cIAP1 and inhibiting the activation of the caspase-8/-9/-3 pathway.

Trillium tschonoskii rhizomes' saponins induces oligodendrogenesis and axonal reorganization for ischemic stroke recovery in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Trillium tschonoskii Maxim. is one of traditional Chinese medical herbs that has been utilized to treat brain damages and cephalalgia. The neuroprotective effect of total saponins from Trillium tschonoskii rhizome (TSTT) has been demonstrated efficacy in rats following ischemia. However, the axonal remodeling effect of TSTT and the detailed mechanisms after ischemic stroke have not been investigated.

AIM OF THE STUDY

We aimed to estimate therapeutic role of TSTT in axonal remodeling using magnetic resonance imaging (MRI) technique, and explored possible mechanisms underlying this process followed by histological assays in ischemic rats.

METHODS

Male Sprague-Dawley (SD) rats underwent permanently focal cerebral ischemia induced by occluding right permanent middle cerebral artery. TSTT was intragastrically administrated 6 h after surgery and once daily for consecutive 15 days. Neurological function was assessed by the motor deficit score and beam walking test. T2 relaxation mapping and diffusion tensor imaging (DTI) were applied for detecting cerebral tissues damages and microstructural integrity of axons. Luxol fast blue (LFB) and transmission electron microscope (TEM) were performed to evaluate histopathology in myelinated axons. Double immunofluorescent staining was conducted to assess oligodendrogenesis. Furthermore, the protein expressions regarding to axonal remodeling related signaling pathways were detected by Western blot assays.

RESULTS

TSTT treatment (65, 33 mg/kg) markedly improved motor function after ischemic stroke. T2 mapping MRI demonstrated that TSTT decreased lesion volumes, and DTI further confirmed that TSTT preserved axonal microstructure of the sensorimotor cortex and internal capsule. Meanwhile, diffusion tensor tractography (DTT) showed that TSTT elevated correspondent density and length of fiber in the internal capsule. These MRI measurements were confirmed by histological examinations. Notably, TSTT significantly increased Ki67/NG2, Ki67/CNPase double-labeled cells along the boundary zone of ischemic cortex and striatum. Meanwhile, TSTT treatment up-regulated the phosphorylation level of Ser 9 in GSK-3β, and down-regulated phosphorylated β-catenin and CRMP-2 expression.

CONCLUSION

Taken together, our findings indicated that TSTT (65, 33 mg/kg) enhanced post-stroke functional recovery, amplified endogenous oligodendrogenesis and promoted axonal regeneration. The beneficial role of TSTT might be correlated with GSK-3/β-catenin/CRMP-2 modulating axonal reorganization after ischemic stroke.

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.

Sevoflurane preconditioning protects experimental ischemic stroke by enhancing anti-inflammatory microglia/macrophages phenotype polarization through GSK-3β/Nrf2 pathway

Aims

Sevoflurane preconditioning (SPC) results in cerebral ischemic tolerance; however, the mechanism remains unclear. Promoting microglia/macrophages polarization from pro‐inflammatory state to anti‐inflammatory phenotype has been indicated as a potential treatment target against ischemic stroke. In this study, we aimed to assess the effect of SPC on microglia polarization after stroke and which signaling pathway was involved in this transition.

Methods

Mouse primary microglia with SPC were challenged by oxygen‐glucose deprivation (OGD) or lipopolysaccharide (LPS), and mice with SPC were subjected to middle cerebral artery occlusion (MCAO). Then, the mRNA and protein levels of pro‐inflammatory/anti‐inflammatory factors were analyzed. GSK‐3β phosphorylation and Nrf2 nuclear translocation were measured. The mRNA and protein expression of pro‐inflammatory/anti‐inflammatory factors, neurological scores, infarct volume, cellular apoptosis, the proportion of pro‐inflammatory/anti‐inflammatory microglia/macrophages, and the generation of super‐oxidants were examined after SPC or GSK‐3β inhibitor TDZD treatment with or without Nrf2 deficiency.

Results

Sevoflurane preconditioning promoted anti‐inflammatory and inhibited pro‐inflammatory microglia/macrophages phenotype both in vitro and in vivo. GSK‐3β phosphorylation at Ser9 was increased after SPC. Both SPC and TDZD administration enhanced Nrf2 nuclear translocation, reduced pro‐inflammatory microglia/macrophages markers expression, promoted anti‐inflammatory markers level, and elicited a neuroprotective effect. Nrf2 deficiency abolished the promoted anti‐inflammatory microglia/macrophages polarization and ischemic tolerance induced by TDZD treatment. The reduced percentage of pro‐inflammatory positive cells and super‐oxidants generation induced by SFC or TDZD was also reversed by Nrf2 knockdown.

Conclusions

Our results indicated that SPC exerts brain ischemic tolerance and promotes anti‐inflammatory microglia/macrophages polarization by GSK‐3β‐dependent Nrf2 activation, which provides a novel mechanism for SPC‐induced neuroprotection.

Acupuncture inhibits mammalian target of rapamycin, promotes autophagy and attenuates neurological deficits in a rat model of hemorrhagic stroke

BACKGROUND

Intracerebral hemorrhage (ICH) accounts for approximately 15% of all stroke cases. Previous studies suggested that acupuncture may improve ICH-induced neurological deficits. Therefore, we investigated the effects of acupuncture on neurological deficits in an animal model of ICH.

METHODS

Adult male Sprague-Dawley rats were injected with autologous blood (50 μL) into the right caudate nucleus. Additional rats underwent sham surgery as controls. ICH rats either received acupuncture (GV20 through GB7 on the side of the lesion) or sham acupuncture (1 cm to the right side of the traditional acupuncture point locations). Some ICH rats received acupuncture plus rapamycin injection into the right lateral ventricle. Neurological deficits in the various groups were assessed based on composite neurological score. The perihemorrhagic penumbra was analyzed by histopathology following hematoxylin-eosin staining. Levels of autophagy-related proteins light chain (LC)3 and p62 as well as of mammalian target of rapamycin (mTOR)-related proteins, and phosphorylated (p)-mTOR and p-S6K1 (ribosomal protein S6 kinase beta-1), were assessed by Western blotting.

RESULTS

Acupuncture significantly improved composite neurological scores 7 days after ICH (17.7 ± 1.49 vs 14.8 ± 1.32, p < 0.01). Acupuncture augmented autophagosome and autolysosome accumulation based on transmission electron microscopy. Acupuncture significantly increased expression of LC3 (p < 0.01) but decreased expression of p62 (p < 0.01). Acupuncture also reduced levels of p-mTOR and p-S6K1 (both p < 0.01).

CONCLUSION

Acupuncture improved neurological deficits in a rat model of ICH, possibly by inhibiting the mTOR pathway and activating autophagy.

Adiponectin Treatment Attenuates Cerebral Ischemia-Reperfusion Injury through HIF-1α-Mediated Antioxidation in Mice

Adiponectin (ADPN) plays an important role in cerebral ischemia-reperfusion injury. Although previous studies have confirmed that ADPN pretreatment has a protective effect on ischemic stroke, the therapeutic effect of ADPN on ischemic stroke and the underlying mechanism are still unclear. In order to clarify these questions, focal transient cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) in mice and ADPN was administered for three times at 6 h, 24 h, and 48 h after reperfusion. Meanwhile, a virus-delivered HIF-1α siRNA was used before ADPN administration. The infarct volume, neurological score, cellular apoptosis, and oxidative stress were assessed at 72 h after reperfusion. The long-term outcome of mice after stroke was recorded as well. The results indicated that ADPN treatment reduced the infarct volume (P = 0.032), neurological deficits (P = 0.047), cellular apoptosis (P = 0.041), and oxidative responses (P = 0.031) at 72 h after MCAO. Moreover, ADPN increased both the protein level and transcriptional activity of HIF-1α as evidenced by the transcription levels of VEGF (P = 0.046) and EPO (P = 0.043) at 72 h after MCAO. However, knockdown of HIF-1α partially reversed the antioxidant and treatment effect of ADPN after cerebral ischemia. In the observation of long-term outcome after ADPN treatment, it demonstrated that ADPN not only prevented the cerebral atrophy (P = 0.031) and the neurological function decline (P = 0.048), but also promoted angiogenesis (P = 0.028) after stroke. In conclusion, our findings suggest that ADPN is effective in treatment of ischemic stroke which could be attributed to the increased antioxidant capacity regulated by HIF-1α.

Altered Jagged1-Notch1 Signaling in Enhanced Dysfunctional Neovascularization and Delayed Angiogenesis After Ischemic Stroke in HFD/STZ Induced Type 2 Diabetes Rats

Diabetes exacerbates brain damage in cerebral ischemic stroke. Our previous study has demonstrated that after cerebral ischemia, type 2 diabetes rats displayed worse neurological outcomes, larger cerebral infarction and severer blood-brain barrier disruption. However, our knowledge of the mechanisms of how diabetes impacts the cerebrovascular repair process is limited. This study was aimed to characterize structural alterations and potential mechanisms in brain microvessels before and after ischemic stroke in type 2 diabetic rats treated with high-fat diet and streptozotocin (HFD/STZ). Furtherly, we tested our hypothesis that dysregulated intercellular Jagged1-Notch1 signaling was involved in the dysfunctional cerebral neovascularization both before and after ischemic stroke in HFD/STZ rats. In our study, we found increased yet dysfunctional neovascularization with activated Jagged1-Notch1 signaling in the cerebrovasculature before cerebral ischemia in HFD/STZ rats compared with non-diabetic rats. Furthermore, we observed delayed angiogenesis as well as suppressed Jagged1-Notch1 signaling after ischemic stroke. Our results elucidate the potential mechanisms underlying diabetes-related cerebral microvasculature dysfunction after ischemic stroke.

Baihui (DU20)-penetrating-Qubin (GB7) acupuncture regulates microglia polarization through miR-34a-5p/Klf4 signaling in intracerebral hemorrhage rats

Intracerebral hemorrhage (ICH) is the most devastating subtype of stroke with high morbidity and mortality. The previous study has confirmed the therapeutic effect of Baihui (DU20)-penetrating-Qubin (GB7) acupuncture on ICH, while the related mechanism is left to be revealed. The aim of this study was to investigate the relevant mechanisms. ICH rat models were established utilizing the autologous blood injection method and the beneficial effect was found after DU20-penetrating-GB7 acupuncture along with decreased miR-34a-5p levels in the perihemorrhagic penumbra. Inversely, upregulating miR-34a-5p expression inhibited microglia M2 polarization while accelerated M1 polarization through targeting Krüppel-like factor 4 (Klf4), and thereby diminished the protective effect of DU20-penetrating-GB7 acupuncture on ICH. The results suggested the therapeutic effect of DU20-penetrating-GB7 acupuncture on ICH might be attributed to its modulation on microglia polarization through miR-34a-5p/Klf4 signaling.

Oxiracetam Mediates Neuroprotection Through the Regulation of Microglia Under Hypoxia-Ischemia Neonatal Brain Injury in Mice

In neonatal hypoxic-ischemic brain damage (HIBD), in addition to damage caused by hypoxia and ischemia, over-activation of inflammation leads to further deterioration of the condition, thus greatly shortening the optimal treatment time window. Ischemic penumbra, the edematous area encompassing the infarct core, is characterized by typical activation of microglia and overt inflammation, and prone to incorporate into the infarct core gradually after ischemia onset. If treated in time, the cells located in the penumbra can survive, thereby impeding the expansion of the infarction. We demonstrated for the first time that in the acute phase of HIBD in neonatal mice, treatment of Oxiracetam (ORC) significantly curtailed the size of ischemic penumbra together with drastic reduction of infarction. By staining various cellular markers, we found that the penumbra was defined and concentrated with activated microglia. We also analyzed transmission electron microscopy and Luminex assay results to elucidate the mechanisms involved. We further confirmed that ORC switched polarization of microglia from the inflammatory towards the alternatively activated phenotype, thus promoting microglia from being neurotoxic into neuroprotective. Meanwhile, ORC decreased proliferation of microglia; however, their functions of phagocytosis and autophagy were otherwise enhanced. Last, we clarified that ORC promoted autophagy through the AMPK/mTOR pathway, which further induced the transition of the inflammatory to the alternatively activated phenotype in microglia. The pro-inflammatory factors secretion was inhibited as well, thereby reducing the progression of the infarction. Taken together, it is concluded that Oxiracetam reduced the expansion of ischemic infarction in part via regulating the interplay between microglia activation and autophagy, which would delay the progression of HIBD and effectively prolong the time window for the clinical treatment of HIBD.

Progranulin promotes functional recovery and neurogenesis in the subventricular zone of adult mice after cerebral ischemia

Progranulin (PGRN), a secreted glycosylated protein, has been reported to attenuate ischemia-induced cerebral injury through anti-inflammation, attenuation of blood-brain barrier disruption and neuroprotection. However, the effect of PGRN on neurogenesis in the subventricular zone (SVZ) after cerebral ischemia remains unclear. In this study, adult C57BL/6 mice were subjected to permanent middle cerebral artery occlusion (pMCAO), and different doses of recombinant mouse PGRN (r-PGRN, 0.3 ng, 1 ng, 5 ng) were intracerebroventricularly administered 30 min after pMCAO. Results showed that 1 ng r-PGRN markedly reduced infarct volume and rescued functional deficits 24 h after pMCAO. Meanwhile, 1 ng r-PGRN increased SVZ cell proliferation, as shown by a high number of bromodeoxyuridine-positive (BrdU+) cells and Ki-67+ cells in the ischemic ipsilateral SVZ 7 d after pMCAO. Additionally, PGRN increased the percentage of BrdU+/Doublecortin (DCX)+ cells in the ipsilateral SVZ 14 d after pMCAO and increased the percentage of new neurons (BrdU+/NeuN+ cells) in the peri-infarct striatum 28 d after pMCAO, suggesting that PGRN promotes neuronal differentiation. PGRN also upregulated phosphorylation of ERK1/2 and Akt in the ipsilateral SVZ 3 d after pMCAO. Our data indicate that PGRN treatment promotes acute functional recovery; most importantly, it also stimulates neurogenesis in the SVZ, which could be beneficial for long-term recovery after cerebral ischemia. The increase in neurogenesis could be associated with activation of the MAPK/ERK and PI3K/Akt pathways. These results suggest a potential new strategy utilizing PGRN in ischemic stroke therapy.

Rosmarinic acid protects rats against post-stroke depression after transient focal cerebral ischemic injury through enhancing antioxidant response

Rosmarinic acid (RA), a natural polyphenol, possesses potent antioxidant and anti-inflammatory activities. To evaluate the ability of RA to cure ischemic stroke and post-stroke depression (PSD), rats were treated with various doses of RA after cerebral ischemia. Neurological deficits and infarct volume of the brain were measured. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) were examined at different time points. In addition, a forced swimming test and sucrose preference test were performed to detect the anti-depressive effects of RA. Our results revealed RA administration significantly alleviated neurological deficits and reduced infarct volumes. RA attenuated the decrease of SOD, CAT activities and GSH levels in the ischemic penumbra of the brain. Most importantly, RA treatment alleviated the depression behaviors. Increased expression of Nrf2 was also induced by RA, while down regulation Nrf2 by Nrf2-short-hairpin RNA sequences reversed the increasing activity of SOD and CAT induced by RA, as well as the protection against PSD. The present study indicates that RA exerts a potent neuroprotective effect against stroke and PSD, which could be a promising therapeutic intervention for stroke.

Methylene blue ameliorates brain edema in rats with experimental ischemic stroke via inhibiting aquaporin 4 expression

Brain edema is a common and serious complication of ischemic stroke with limited effective treatment. We previously reported that methylene blue (MB) attenuated ischemic brain edema in rats, but the underlying mechanisms remained unknown. Aquaporin 4 (AQP4) in astrocytes plays a key role in brain edema. We also found that extracellular signal-regulated kinase 1/2 (ERK1/2) activation was involved in the regulation of AQP4 expression in astrocytes. In the present study, we investigated whether AQP4 and ERK1/2 were involved in the protective effect of MB against cerebral edema. Rats were subjected to transient middle cerebral artery occlusion (tMCAO), MB (3 mg/kg, for 30 min) was infused intravenously through the tail vein started immediately after reperfusion and again at 3 h after ischemia (1.5 mg/kg, for 15 min). Brain edema was determined by MRI at 0.5, 2.5, and 48 h after tMCAO. The decreases of apparent diffusion coefficient (ADC) values on diffusion-weighted MRI indicated cytotoxic brain edema, whereas the increase of T2 MRI values reflected vasogenic brain edema. We found that MB infusion significantly ameliorated cytotoxic brain edema at 2.5 and 48 h after tMCAO and decreased vasogenic brain edema at 48 h after tMCAO. In addition, MB infusion blocked the AQP4 increases and ERK1/2 activation in the cerebral cortex in ischemic penumbra at 48 h after tMCAO. In a cell swelling model established in cultured rat astrocyte exposed to glutamate (1 mM), we consistently found that MB (10 μM) attenuated cell swelling, AQP4 increases and ERK1/2 activation. Moreover, the ERK1/2 inhibitor U0126 (10 μM) had the similar effects as MB. These results demonstrate that MB improves brain edema and astrocyte swelling, which may be mediated by the inhibition of AQP4 expression via ERK1/2 pathway, suggesting that MB may be a potential choice for the treatment of brain edema.

Phosphorylation at S548 as a Functional Switch of Sterile Alpha and TIR Motif-Containing 1 in Cerebral Ischemia/Reperfusion Injury in Rats

Sterile alpha and Toll/interleukin-1 receptor motif-containing 1 (SARM1) is a pro-degenerative molecule in Wallerian degeneration, which is mainly expressed in brain/neurons and colocalized with mitochondria and microtubules. The aim of this study was to determine the role of SARM1 in cerebral ischemia/reperfusion (I/R) injury and the underlying mechanisms. In vivo, a middle cerebral artery occlusion/reperfusion (MCAO/R) model in adult male Sprague Dawley rats (250-300 g) was established, and in vitro, cultured primary neurons were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) to imitate I/R injury. Overexpression lentiviruses encoding wild-type SARM1 and SARM1 with serine 548 alanine mutation (S548A) were constructed and administered to rats by intra-penumbral injection. First, the potential role of SARM1 in cerebral I/R injury was confirmed by the increased protein levels of SARM1 within penumbra tissue, especially in neurons. Second, there was an increase in the phosphorylation ratio of p-SARM1(S548)/SARM1 at 2 h after MCAO/R. Third, on the basis of site-specific mutagenesis, we identified S548 as a key site for SARM1 phosphorylation in I/R conditions. Fourth, SARM1 (S548A) overexpression reduced infarct size, neuronal death, and neurobehavioral dysfunction, while wild-type SARM1 overexpression had the opposite effects. Finally, we found that SARM1 phosphorylation at the S548 site switched SARM1 function from promoting mitochondrial transport to inhibiting mitochondrial transport along axons after I/R injury. Restriction of SARM1 phosphorylation at S548 may be a promising intervention target for I/R injury; thus, exogenous administration of SARM1 (S548A) may be a novel strategy for improving neurological outcomes.

Treadmill exercise enhances synaptic plasticity in the ischemic penumbra of MCAO mice by inducing the expression of Camk2a via CYFIP1 upregulation

AIMS

Physical exercise is beneficial to the recovery of patients with ischemic stroke. However, the underlying mechanism by which exercise promotes dendritic remodeling and synaptic plasticity is still obscure. This study explored the mechanism by which treadmill exercise enhances synaptic plasticity and dendritic remodeling in the ischemic penumbra.

MAIN METHODS

A middle cerebral artery occlusion (MCAO) model was generated in C57BL/6 mice, and lentivirus-mediated cytoplasmic FMRP-associated protein 1 (CYFIP1) shRNA expression was utilized to confirm the role of CYFIP1 in the exercise-induced increase in synaptic plasticity and dendritic remodeling. Neurological deficits were measured using the Zea Longa scale. Hematoxylin-eosin (H&E) staining and Nissl staining were performed to assess cerebral ischemic injury. Golgi-Cox staining was used to observe changes in dendritic remodeling and synaptic plasticity. Transmission electron microscopy (TEM) was performed to observe the synaptic ultrastructure. Molecular mechanisms were explored using immunofluorescence staining and western blotting.

KEY FINDINGS

Treadmill training enhanced synaptic plasticity in the penumbra. Additionally, we observed significant increases in the expression of CYFIP1 and calcium/calmodulin-dependent kinase 2a (Camk2a); enhanced neurological recovery and a decreased infarct volume. However, the injection of a lentivirus containing CYFIP1 shRNA into the lateral ventricle exerted negative effects on synaptic plasticity. Moreover, the exercise-induced neuroprotective effects were abolished by lentivirus-mediated CYFIP1 shRNA expression, consistent with the downregulation of Camk2a expression and the deterioration of neurological function.

SIGNIFICANCE

Treadmill training enhances synaptic plasticity and dendritic remodeling in the ischemic penumbra by inducing the expression of Camk2a via upregulation of CYFIP1.

Neuronal extracellular vesicle derived miR-98 prevents salvageable neurons from microglial phagocytosis in acute ischemic stroke

Extracellular vesicles (EVs), as a novel intercellular communication carrier transferring cargo microRNAs (miRNAs), could play important roles in the brain remodeling process after ischemic stroke. However, the detailed mechanisms involved in EVs derived miRNAs-mediated cellular interactions in the brain remain unclear. Several studies indicated that microRNA-98 (miR-98) might participate in the pathogenesis of ischemic stroke. Here, we showed that expression of miR-98 in penumbra field kept up on the first day but dropped sharply on the 3rd day after ischemic stroke in rats, indicating that miR-98 could function as an endogenous protective factor post-ischemia. Overexpression of miR-98 targeted inhibiting platelet activating factor receptor-mediated microglial phagocytosis to attenuate neuronal death. Furthermore, we showed that neurons transferred miR-98 to microglia via EVs secretion after ischemic stroke, to prevent the stress-but-viable neurons from microglial phagocytosis. Therefore, we reveal that EVs derived miR-98 act as an intercellular signal mediating neurons and microglia communication during the brain remodeling after ischemic stroke. The present work provides a novel insight into the roles of EVs in the stroke pathogenesis and a new EVs-miRNAs-based therapeutic strategy for stroke.

Vinpocetine Attenuates Ischemic Stroke Through Inhibiting NLRP3 Inflammasome Expression in Mice

ABSTRACT

Ischemic stroke is the leading cause of globe death and permanent disability, but its therapeutic strategies are limited. Over the past decades, multiprotein complexes called inflammasomes have been shown as promising targets in ischemic stroke. Here, we examined vinpocetine (Vinp), a synthetic drug, playing a neuroprotective role against ischemic stroke in mice through regulating NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation. Middle cerebral artery occlusion/reperfusion (MCAO/R) was applied to mimic ischemic stroke in vivo. Vinp was administrated by intraperitoneal injection with different dose (5 or 10 mg/kg) 1 hour after reperfusion. Then, neurological assessment and infarct size were performed, and interleukin-1β (IL-1β) and IL-18 levels were evaluated using ELISA. The levels of NLRP3 inflammasome components and its upstream nuclear factor-κB (NF-κB) were determined using real-time PCR or Western blot. The experimental results indicated that posttreatment with Vinp decreased cerebral infarct size, improved behavior recover, reduced NLRP3 inflammasome expression, and suppressed the transfer of NF-κB to nucleus and proinflammatory cytokine release in middle cerebral artery occlusion/reperfusion mice. In conclusion, this study demonstrates that Vinp alleviates ischemic stroke by regulating levels of NLRP3 inflammasome, NF-κB, and proinflammatory cytokines in vivo, offering an alternative medication for ischemic stroke associated with inflammation.

Early Electroacupuncture Extends the rtPA Time Window to 6 h in a Male Rat Model of Embolic Stroke via the ERK1/2-MMP9 Pathway

Background. Recombinant tissue plasminogen activator (rtPA) is the only recommended pharmacological treatment for acute ischemic stroke, but it has a restricted therapeutic time window. When administered at time points greater than 4.5 h after stroke onset, rtPA disrupts the blood-brain barrier (BBB), which leads to serious brain edema and hemorrhagic transformation. Electroacupuncture (EA) exerts a neuroprotective effect on cerebral ischemia; however, researchers have not clearly determined whether EA increases the safety of thrombolysis and extends the therapeutic time window of rtPA administration following ischemic stroke. Objective. The present study was conducted to test the hypothesis that EA extends the therapeutic time window of rtPA for ischemic stroke in a male rat model of embolic stroke. Methods. SD rats were randomly divided into the sham operation group, model group, rtPA group, EA+rtPA group, and rtPA+MEK1/2 inhibitor group. An injection of rtPA was administered 6 h after ischemia. Rats were treated with EA at the Shuigou (GV26) and Neiguan (PC6) acupoints at 2 h after ischemia. Neurological function, infarct volume, BBB permeability, brain edema, and hemorrhagic transformation were assessed at 24 h after ischemia. Western blotting and immunofluorescence staining were performed to detect the levels of proteins involved in the ERK1/2 signaling pathway (MEK1/2 and ERK1/2), tight junction proteins (Claudin5 and ZO-1), and MMP9 in the ischemic penumbra at 24 h after stroke. Results. Delayed rtPA treatment aggravated hemorrhagic transformation and brain edema. However, treatment with EA plus rtPA significantly improved neurological function and reduced the infarct volume, hemorrhagic transformation, brain edema, and EB leakage in rats compared with rtPA alone. EA increased the levels of tight junction proteins, inhibited the activation of the ERK1/2 signaling pathway, and reduced MMP9 overexpression induced by delayed rtPA thrombolysis. Conclusions. EA potentially represents an effective adjunct method to increase the safety of thrombolytic therapy and extend the therapeutic time window of rtPA administration following ischemic stroke. This neuroprotective effect may be mediated by the inhibition of the ERK1/2-MMP9 pathway and alleviation of the destruction of the BBB.

Z-Guggulsterone alleviated oxidative stress and inflammation through inhibiting the TXNIP/NLRP3 axis in ischemic stroke

Ischemic stroke is a serious and life-threatening cerebrovascular thrombotic disease; however, the therapeutic strategy is limited for the complicated mechanism and narrow therapeutic window. Our previous study suggested that Z-Guggulsterone (Z-GS), an active component derived from myrrh, is a good candidate for cerebral injury. The object of this study is to investigate the exact mechanisms of Z-GS in cerebral ischemic stroke. Rats were used to conduct middle cerebral artery occlusion (MCAO) model and were treated with different dosage of Z-GS. Morphological results showed that Z-GS significantly alleviated neurological deficits, infarct volume and histopathological damage in MCAO rats. A total of 8276 differentially expressed genes were identified based on microarray analysis. Oxidation-reduction process and inflammatory response were enriched as the significant gene ontology items. TXNIP and NLRP3 were screened as the potential target genes by Series Test of Cluster (STC) analysis. The results were validated by immunohistochemistry and immunofluorescence staining. Besides, Z-GS successfully inhibited oxidative stress and inflammatory response in oxygen-glucose deprivation (OGD) treated neurons. Knockdown of TXNIP significantly decreased the expression of NLRP3 in OGD-induced neurons. In addition, Z-GS treatment scarcely changed the expressions of NLRP3 in siRNA-TXNIP pretreated cells compared with the siRNA-TXNIP alone treatment group, suggesting that the neuroprotective effect of Z-GS was dependent on TXNIP-NLRP3 axis. Taken together, this study revealed that Z-GS exerted neuroprotective property through alleviated oxidative stress and inflammation via inhibiting the TXNIP/NLRP3 axis. Z-GS could be considered as a promising candidate for the treatment of ischemic stroke.

Activation of CB1R-Dependent PGC-1α Is Involved in the Improved Mitochondrial Biogenesis Induced by Electroacupuncture Pretreatment

Electroacupuncture (EA) pretreatment induces cerebral ischemic tolerance; however, the mechanism remains poorly understood. This study aimed to determine the participation of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α)-mediated mitochondrial biogenesis in the neuroprotection of EA and whether cannabinoid receptor 1 (CB1R) is involved in this mechanism. At 2 hours after EA pretreatment, adult male C57BL/6j mice were subjected to 60-minute right middle cerebral artery occlusion (MCAO). Mitochondrial function, the level of mitochondrial biogenesis-related proteins (nuclear transcription factor 1, NRF1; mitochondrial transcription factor A, TFAM), and mitochondrial DNA (mtDNA) were measured. A small interfering RNA (siRNA) targeting PGC-1α and the CB1R antagonists AM251 and SR141716A were given to the animals before EA pretreatment, and mitochondrial function and biogenesis were examined after MCAO. EA ameliorated the mitochondrial function, upregulated the NRF1 and TFAM expression, and increased the mtDNA levels and the volume and number of mitochondria. EA pretreatment increased the expression of PGC-1α, whereas the PGC-1α siRNA and CB1R antagonists reversed the improved neuroprotection and increased mitochondrial biogenesis induced by EA. Our results indicated that EA pretreatment protects the mitochondria and promotes mitochondrial biogenesis by activating CB1R-dependent PGC-1α, which provides a novel mechanism for EA pretreatment-induced ischemic tolerance.