Acute ischemic stroke: time, penumbra, and reperfusion

Systolic blood pressure reduction strategies in acute ischemic stroke patients following endovascular thrombectomy: a systematic review and meta-analysis

BACKGROUND AND AIMS

There is no clear consensus on ideal systolic blood pressure (SBP) target post-endovascular thrombectomy (EVT) in patients with acute ischemic stroke. This study intends to investigate the relationship between reducing SBP and clinical outcomes and to determine the therapeutic efficacy of moderate and intensive SBP reduction post EVT.

METHODS

A comprehensive search was conducted across five electronic databases to identify studies relevant to our analysis. Data from these studies were then analyzed using pooled relative risk (RR) along with their corresponding 95 % confidence intervals (CI) for our categorical outcomes. functional independence at 90 days post-EVT was defined as a modified Rankin score (mRS) 0-2.

RESULTS

Our meta-analysis included eight studies with 2922 patients: 1376 patients were treated with intensive SBP reduction, 306 with moderate SBP reduction, and 1243 with standard SBP reduction. There was no difference in the risk of functional independence at 90 days post-EVT with both intensive-SBP reduction (target 120-140 mmHg, relative risk (RR) =1.05, 95 % CI 0.82, 1.34, p = 0.72) and moderate-SBP reduction (>160 mm Hg) (RR= 0.95, 95 % CI 0.69, 1.31, p = 0.76) compared with standard SBP reduction (>180 mm Hg). The risk of symptomatic intracranial hemorrhage (sICH) did not significantly differ between standard-SBP reduction and intensive-SBP reduction (RR = 0.93, 95 % CI 0.66, 1.31, p = 0.36) or moderate-SBP reduction (0.72 (95 % CI [0.28, 1.87], p = 0.50) groups, respectively. Intensive-SBP reduction significantly decreased the risk of hemicraniectomy.

CONCLUSIONS

We did not identify any difference in functional independence at 90 days in acute ischemic stroke patients with either intensive-SBP reduction or moderate-SBP reduction compared with standard SBP reduction post-EVT.

Forsythoside B alleviates cerebral ischemia-reperfusion injury via inhibiting NLRP3 inflammasome mediated by SIRT1 activation

BACKGROUND

The inflammatory response is a key factor in the pathogenesis of cerebral ischemia/reperfusion injury (CIRI), and anti-inflammatory interventions may offer a promising therapeutic strategy. Forsythoside B (FB) is a phenylethanoid glycoside isolated from Forsythiae fructus, which has been reported to have anti-inflammatory effects. However, the mechanism of the neuroprotective effect of FB on CIRI remains unclear.

METHODS

Adult male Sprague-Dawley rats were subjected to transient middle cerebral artery occlusion/reperfusion (MCAO/R). FB was administered intraperitoneally for 3 days prior to MCAO/R. Cerebral infarct volume and neurological deficit score were used as indices to evaluate MCAO/R injury. The serum levels of inflammatory factors and antioxidant enzymes were measured. The activation of silent information regulator 2 homolog 1 (Sirt1) and the inhibition of the nucleotide-binding oligomerization domain-like receptor with a pyrin domain 3 (NLRP3) pathway were assessed through western blot and immunohistochemistry analysis. Furthermore, the rats were treated with Sirt1 shRNA 3 days before MCAO/R by stereotactical injection into the ipsilateral hemispheric region to assess the impact of Sirt1 knockdown on the protection of FB during MCAO/R.

RESULTS

FB reduced cerebral infarct volume and neurological deficit score in MCAO/R rats. FB reduced pathological changes and cell apoptosis in the hippocampal CA1 region and cortex on the ischemic side of rats. FB inhibited the serum levels of inflammatory factors and increased the activities of antioxidant enzymes. Further study showed that FB inhibited the activation of the NLRP3 pathway and induced Sirt1 activation.

CONCLUSION

FB demonstrated neuroprotective and anti-inflammatory effects by inhibiting the NLRP3 pathway through Sirt1 activation in CIRI.

M6A-related bioinformatics analysis indicates that LRPPRC is an immune marker for ischemic stroke

Ischemic stroke (IS) is a common cerebrovascular disease whose pathogenesis involves a variety of immune molecules, immune channels and immune processes. 6-methyladenosine (m6A) modification regulates a variety of immune metabolic and immunopathological processes, but the role of m6A in IS is not yet understood. We downloaded the data set GSE58294 from the GEO database and screened for m6A-regulated differential expression genes. The RF algorithm was selected to screen the m6A key regulatory genes. Clinical prediction models were constructed and validated based on m6A key regulatory genes. IS patients were grouped according to the expression of m6A key regulatory genes, and immune markers of IS were identified based on immune infiltration characteristics and correlation. Finally, we performed functional enrichment, protein interaction network analysis and molecular prediction of the immune biomarkers. We identified a total of 7 differentially expressed genes in the dataset, namely METTL3, WTAP, YWHAG, TRA2A, YTHDF3, LRPPRC and HNRNPA2B1. The random forest algorithm indicated that all 7 genes were m6A key regulatory genes of IS, and the credibility of the above key regulatory genes was verified by constructing a clinical prediction model. Based on the expression of key regulatory genes, we divided IS patients into 2 groups. Based on the expression of the gene LRPPRC and the correlation of immune infiltration under different subgroups, LRPPRC was identified as an immune biomarker for IS. GO enrichment analyses indicate that LRPPRC is associated with a variety of cellular functions. Protein interaction network analysis and molecular prediction indicated that LRPPRC correlates with a variety of immune proteins, and LRPPRC may serve as a target for IS drug therapy. Our findings suggest that LRPPRC is an immune marker for IS. Further analysis based on LRPPRC could elucidate its role in the immune microenvironment of IS.

Neuropharmacological insights into Gardenia jasminoides Ellis: Harnessing therapeutic potential for central nervous system disorders

BACKGROUND

In China, Gardenia jasminoides Ellis (GJE) has a longstanding history of application. The Ministry of Health has listed it as one of the first pharmaceutical or food resources. In ethnic, traditional, and folk medicine, GJE has been used to treat fever and cold and relieve nervous anxiety. Recent studies have confirmed the significant efficacy of GJE for treating central nervous system (CNS) disorders, including Alzheimer's disease, Parkinson's disease, and major depressive disorder; however, GJE has not been systematically evaluated.

PURPOSE

This research systematically summarizes global studies on the use of GJE for treating CNS disorders and explores the potential applications and underlying mechanisms via intestinal flora analysis and network pharmacology, aiming to establish a scientific basis for innovative CNS disorder treatment with GJE.

METHODS

The PRISMA guidelines were used, and electronic databases such as the Web of Science, PubMed, and China National Knowledge Infrastructure were searched using the following search terms: "Gardenia jasminoides Ellis" with "central nervous system disease," "neuroprotection," "Alzheimer's disease," "Parkinson's disease," "ischemic stroke," "Epilepsy," and "major depressive disorder." The published literature up to September 2023 was searched to obtain relevant information on the application of GJE for treating CNS disorders.

RESULTS

There has been an increase in research on the material formulation and mechanisms of action of GJE for treating CNS disorders, with marked effects on CNS disorder treatment in different countries and regions. We summarized the research results related to the role of GJE in vitro and in vivo via multitargeted interventions in response to the complex mechanisms of action of CNS disorders.

CONCLUSION

We systematically reviewed the research progress on traditional treatment for GJE and preclinical mechanisms of CNS disorders and explored the potential of optimizing network pharmacology strategies and intestinal flora analysis to elucidate the mechanisms of action of GJE. The remarkable therapeutic efficacy of GJE, an important resource in traditional medicine, has been well documented in the literature, highlighting its significant medicinal potential.

Selective homing of brain-derived reconstituted lipid nanoparticles to cerebral ischemic area enables improved ischemic stroke treatment

Lipid nanoparticles (LNPs) hold great promise as carriers for developing drug delivery systems (DDSs) aimed at managing ischemic stroke (IS). Previous research has highlighted the vital role played by the lipid composition and biophysical characteristics of LNPs, influencing their interactions with cells and tissues. This understanding presents an opportunity to engineer LNPs tailored specifically for enhanced IS treatment. We previously introduced the innovative concept of reconstituted lipid nanoparticles (rLNPs), which not only retain the advantages of conventional LNPs but also incorporate lipids from the originating cell or tissue. Brain-derived rLNPs (B-rLNPs) exhibit significantly superior accumulation within the cerebral ischemic region when compared to liver-derived rLNPs (L-rLNPs). The homing effect of B-rLNPs was then employed to construct 3-n-butylphthalide (NBP) loaded DDS (B-rLNPs/NBP) for the treatment of IS. Our results demonstrated that compared with free NBP, B-rLNPs/NBP can significantly reduce infarct volume, neurological deficits, blood-brain barrier (BBB) leakage rate, brain water content, neutrophil infiltration, alleviate pathological structures, and improve the motor function in MCAO/R model. We also proved that B-rLNPs/NBP showed further reinforced protective effects on the same model than free NBP through the regulation of TLR4/MyD88/NF-κB (anti-inflammation) and Bax/Bcl-2 (anti-apoptosis) pathways. This study offers a promising tool towards improved IS treatment.

Five Tibetan patent medicines orally for ischemic stroke: A systematic review and meta-analysis of randomized controlled trials

ETHNOPHARMACOLOGICAL RELEVANCE

Tibetan Patent Medicines (TPMs) have unique advantages in the treatment of ischemic stroke (IS) with the features of multi-component, multi-channel, and multi-target. In China, five TPMs mainly consisting of precious medicinal materials such as gold, pearls, and agate are widely utilized to treat IS and have achieved good results according to the current clinical practice.

AIM OF THE STUDY

To systematically evaluate the efficacy and safety of the five TPMs orally in treating IS and provide a reference for future clinical application and research.

MATERIALS AND METHODS

We searched the following 24 databases up to December 11, 2022: China National Knowledge Infrastructure (CNKI), Wanfang database, China Science and Technology Journal Database, Chinese Biomedical Database (CBM), PubMed, Embase, Web of Science, MEDLINE, Scopus, the Cochrane Library, ScienceDirect, etc. Comprehensive searches for randomized controlled trials (RCTs) of the five TPMs for IS were conducted. Outcome measures included clinical effective rate, neurological impairment score, activities of daily living (ADL), hematologic indices, and adverse events (AEs). The meta-regression, subgroup analyses, and sensitivity analyses were conducted to explore the sources of heterogeneity. We assessed the evidence grade of outcomes via the GRADE system. TSA software was used for trial sequential analyses of the clinical effective rate, neurological impairment score, and ADL.

RESULTS

17 RCTs (1603 patients) met our criteria. Compared with the control groups, the five TPMs showed greater improvement in clinical effective rate (RR = 1.23, 95% CI 1.17 to 1.29, P < 0.00001), neurological impairment score (SMD = -1.71, 95% CI -2.31 to -1.10, P < 0.00001), ADL (SMD = 1.97, 95% CI 1.26 to 2.68, P < 0.00001), hematocrit (MD = -1.56, 95% CI -2.83 to -0.29, P = 0.02), and hypersensitive-c-reactive-protein (MD = -2.96, 95% CI -3.30 to -2.61, P < 0.00001). AEs were reported in four RCTs and there was no statistical difference between groups (RD = -0.00, 95% CI -0.04 to 0.03, P = 0.82). The quality of evidence of the outcomes was rated as low to very low according to the GRADE system. The results of TSA provided firm evidence for the significant effect of the five TPMs on clinical effective rate, neurological impairment score, and ADL.

CONCLUSIONS

This review showed that the five TPMs were beneficial in improving clinical effective rate, neurological impairment scores, and ADL. However, no definite conclusions for hematologic indices and AEs were drawn due to insufficient studies. Further high-quality clinical trials are required to confirm these findings.

Focal ischemic stroke modifies microglia-derived exosomal miRNAs: potential role of mir-212-5p in neuronal protection and functional recovery

BACKGROUND

Ischemic stroke is a severe type of stroke with high disability and mortality rates. In recent years, microglial exosome-derived miRNAs have been shown to be promising candidates for the treatment of ischemic brain injury and exert neuroprotective effects. Mechanisms underlying miRNA dysregulation in ischemic stroke are still being explored. Here, we aimed to verify whether miRNAs derived from exosomes exert effects on functional recovery.

METHODS

MiR-212-5p agomir was employed to upregulate miR-212-5p expression in a rat model of middle cerebral artery occlusion/reperfusion (MCAO/R) as well as an oxygen-glucose deprivation/reoxygenation (OGD/R) in vitro. Western blot analysis, qRT-PCR and immunofluorescence staining and other methods were applied to explore the underlying mechanisms of action of miR-212-5p.

RESULTS

The results of our study found that intervention with miR-212-5p agomir effectively decreased infarct volume and restored motor function in MCAO/R rats. Mechanistically, miR-212-5p agomir significantly reduced the expression of PlexinA2 (PLXNA2). Additionally, the results obtained in vitro were similar to those achieved in vivo.

CONCLUSION

In conclusion, the present study indicated that PLXNA2 may be a target gene of miR-212-5p, and miR-212-5p has great potential as a target for the treatment and diagnosis of ischemic stroke.

Optimizing intra-arterial hypothermia scheme for acute ischemic stroke in an MCAO/R rat model

Hypothermia is a promising neuroprotective treatment. This study aims to explore and optimize the intervention scheme of intra-arterial hypothermia (IAH) in a middle cerebral artery occlusion and reperfusion (MCAO/R) rat model. The MCAO/R model was established with a thread that could be retracted 2 h after occlusion. Cold normal saline was injected into the internal carotid artery (ICA) through a microcatheter in different infusion conditions. Grouping followed an orthogonal design (L₉[3⁴]) based on three critical factors closely associated with IAH: perfusate temperature (4, 10, 15 °C), infusion flow rate (1/3, 1/2, 2/3 blood flow rate of ICA), and duration (10, 20, 30 min), resulting in 9 subgroups (H₁, H₂ to H₉). A myriad of indexes were monitored, such as vital signs, blood parameters, changes in local ischemic brain tissue temperature (T_b), ipsilateral jugular venous bulb temperature (T_jvb), and the core temperature of the anus (T_core). After 24 h and 72 h of cerebral ischemia, cerebral infarction volume, cerebral water content, and neurological function were assessed to explore the optimal IAH conditions. The results revealed that the three critical factors were independent predictors for cerebral infarction volume, cerebral water content, and neurological function. The optimal perfusion conditions were 4 °C, 2/3 R_ICA (0.50 ml/min) for 20 min, and there was a significant correlation between T_b and T_jvb (R = 0.994, P < 0.001). The vital signs, blood routine tests and biochemical indexes showed no significant abnormal changes. These findings revealed that IAH was safe and feasible with the optimized scheme in an MCAO/R rat model.

Discrimination between progressive penumbra and benign oligemia of the diffusion-perfusion mismatch region by amide proton transfer-weighted imaging

PURPOSE

Amide proton transfer-weighted (APTw) imaging was an effective tool to reveal the tissue acidosis of acute ischemic stroke. This study aimed to evaluate the ability of APTw MRI to distinguish progressive penumbra and benign oligemia in the diffusion-perfusion mismatch region.

MATERIALS AND METHODS

38 acute cerebral infarction patients who underwent a comprehensive MRI examination, including diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), APT imaging, and a follow-up scan in one week were recruited. There were 12 DWI/PWI match cases. The DWI/PWI mismatch patients were divided into 10 progressive cases and 16 stable cases according to the lesion size on the follow-up DWI image compared to the admission scan. Three ROIs: infarction lesion, peripheral, and contralateral normal regions were measured on each subject's MTRasym map. The Friedman test was used to compare the changes of MTRasym among three different regions within each group. The Kruskal-Wallis ANOVA test was used to compare them among the same region of different groups. The correlation between the MTRasym of the peripheral region and the lesion enlargement was analyzed by the Spearman test.

RESULTS

The MTRasym at the infarction lesion of all three groups showed significant decrease to the contralateral normal tissue. In the progressive mismatch group, the MTRasym at the peripheral region within the DWI/PWI mismatch showed a significant difference with the contralateral normal region and no difference with the infarct core. Whereas both the MTRasym at the peripheral region of the stable mismatch and match groups had no significant difference with the contralateral side, but the differences were significant from those of the central core. When comparing the peripheral region of three groups, the MTRasym of the progressive mismatch group showed a significant decrease to that of the stable mismatch and match groups. The MTRasym of the peripheral region showed a negative correlation with lesion enlargement.

CONCLUSION

APTw imaging is promising to stratify the heterogeneous PWI/DWI mismatch region and benefit the clinical treatment.

Circ_0000566 contributes oxygen-glucose deprivation and reoxygenation (OGD/R)-induced human brain microvascular endothelial cell injury via regulating miR-18a-5p/ACVR2B axis

Circular RNAs (circRNAs) exert regulatory roles in cerebrovascular disease. Human brain microvascular endothelial cells (HBMECs) participated in brain vascular dysfunction in ischemic stroke. Herein, the functions of circ_0000566 in oxygen-glucose deprivation and reoxygenation (OGD/R)-induced HBMECs were investigated. The expression of circ_0000566, miR-18a-5p, and Activin receptor type 2B (ACVR2B) was measured via quantitative real-time PCR (qRT-PCR). Cell Counting Kit-8 (CCK-8) and flow cytometry assays were utilized to detect cell viability and cell apoptosis. Western blot assay was employed to measure the levels of apoptotic-related proteins and ACVR2B. The secretion of IL-1β, IL-6, and TNF-α was detected via corresponding kits. The relationship between miR-18a-5p and circ_0000566 or ACVR2B was examined via dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Circ_0000566 and ACVR2B were highly expressed, while miR-18a-5p was down-regulated in OGD/R-treated HBMECs. OGD/R treatment promoted HBMECs apoptosis and inflammation and suppressed cell viability, which could be attenuated by silencing of circ_0000566. Circ_0000566 acted as a miR-18a-5p sponge to contribute to OGD/R-induced HBMECs injury. ACVR2B served as a direct target of miR-18a-5p, and ACVR2B overexpression might abolish the inhibitory role of miR-18a-5p on OGD/R-treated HBMEC injury. Circ_0000566 sponged miR-18a-5p to regulate OGD/R-induced HBMECs injury via regulating ACVR2B expression.

Transport Mechanisms at the Blood–Brain Barrier and in Cellular Compartments of the Neurovascular Unit: Focus on CNS Delivery of Small Molecule Drugs

Ischemic stroke is a primary origin of morbidity and mortality in the United States and around the world. Indeed, several research projects have attempted to discover new drugs or repurpose existing therapeutics to advance stroke pharmacotherapy. Many of these preclinical stroke studies have reported positive results for neuroprotective agents; however, only one compound (3K3A-activated protein C (3K3A-APC)) has advanced to Phase III clinical trial evaluation. One reason for these many failures is the lack of consideration of transport mechanisms at the blood–brain barrier (BBB) and neurovascular unit (NVU). These endogenous transport processes function as a “gateway” that is a primary determinant of efficacious brain concentrations for centrally acting drugs. Despite the knowledge that some neuroprotective agents (i.e., statins and memantine) are substrates for these endogenous BBB transporters, preclinical stroke studies have largely ignored the role of transporters in CNS drug disposition. Here, we review the current knowledge on specific BBB transporters that either limit drug uptake into the brain (i.e., ATP-binding cassette (ABC) transporters) or can be targeted for optimized drug delivery (i.e., solute carrier (SLC) transporters). Additionally, we highlight the current knowledge on transporter expression in astrocytes, microglia, pericytes, and neurons with an emphasis on transport mechanisms in these cell types that can influence drug distribution within the brain.

Outcomes of Mechanical Thrombectomy for Acute Ischemic Stroke When Multiple Passes Are Required and Associated Risk Factors

INTRODUCTION

This study aimed to evaluate the outcomes of mechanical thrombectomy for acute ischemic stroke when multiple passes are required and to identify the associated risk factors.

METHODS

Consecutive patients with acute ischemic stroke treated with mechanical thrombectomy at the Neurology Department of Ninth People's Hospital and the Neurosurgery Department of Xinhua Hospital of Shanghai Jiao Tong University School of Medicine from 2013 to 2018 were included. Patients were divided into 2 groups: those who received ≤2 passes and those who received >2 passes. Outcomes of the 2 groups were compared. Multivariate linear regression was used to determine factors associated with the need for >2 passes. All patient data were reviewed retrospectively.

RESULTS

A total of 122 patients were included, of whom 83 patients required ≤2 passes and 39 patients required >2 passes. After adjusting for sex, atrial fibrillation history, smoking history, and involvement of middle cerebral artery and internal cerebral artery, the National Institutes of Health Stroke Scale (NIHSS) score was associated with a 1.08-times greater risk of >2 passes (95% confidence interval [CI]: 1.01-1.17), and internal carotid artery with a 5.13-times greater risk of >2 passes (95% CI: 1.02-25.69). Having more than 2 passes was associated with significantly higher 7-day (25.6% vs. 6%), 90-day mortality rates (34.2% vs. 16%) and a significantly lower recanalization rate (66.7% vs. 89.2%).

CONCLUSION

Needing more than 2 passes during mechanical thrombectomy is associated with poorer outcomes. Higher preprocedural NIHSS scores and internal carotid artery thrombi are associated with more than 2 passes.

Membrane-Free Stem Cell Extract Enhances Blood–Brain Barrier Integrity by Suppressing NF-κB-Mediated Activation of NLRP3 Inflammasome in Mice with Ischemic Stroke

Membrane-free stem cell extract (MFSCE) of human adipose tissues possesses various biological activities. However, the effects of MFSCE on blood–brain barrier dysfunction and brain damage are unknown. In this study, we determined the role of MFSCE in an ischemic stroke mouse model. Mice were treated with MFSCE once daily for 4 days and 1 h before ischemic damage. Experimental ischemia was induced by photothrombosis. Pretreatment with MFSCE reduced infarct volume and edema and improved neurological, as well as motor functions. Evans blue leakage and water content in the brain tissue were reduced by MFSCE pretreatment relative to those in the vehicle group. MFSCE increased the expression of the tight junction proteins zonula occludens 1 and claudin-5, as well as vascular endothelial-cadherin, but decreased that of matrix metalloproteinase 9. Notably, MFSCE treatment decreased cell death and the level of NOD-like receptor protein 3 inflammasome, consistent with the downregulated expression of the pro-inflammatory cytokines interleukin (IL)-1β and IL-18 in the ischemic brain. These effects might have occurred via the suppression of the expression of Toll-like receptor 4 and activation of nuclear factor-κB. The results highlighted the potential of MFSCE treatment as a novel and preventive strategy for patients at a high risk of ischemic stroke.

Role of N6-methyladenosine modification in pathogenesis of ischemic stroke

INTRODUCTION

N6-Methyladenosine (m6A), the most common and reversible mRNA modification, has attracted considerable attention recently, and accumulating evidence indicates it has an important role in the progression of ischemic stroke (IS).

AREAS COVERED

We first reviewed m6A methylation modification enzymes, including m6A methyltransferases (METTL3, METTL14, and WTAP), demethylases (FTO and ALKBH5), m6A-binding proteins (YTH domain containing 1/2 [YTHDC1/2], YTHDF1/2/3, and insulin like growth factor 2 mRNA binding protein 1/2/3 [IGF2BP1/2/3]), and their-related functions. An alteration in the m6A methylation profile of IS has been reported and m6A is differentially expressed in IS. Thus, we then focused on the underlying mechanism of m6A methylation in IS and the involvement of atherosclerosis (AS), cerebral ischemia/reperfusion (IR) injury, inflammation, oxidative stress, and apoptosis. Furthermore, we also elucidated the effect of m6A-associated single-nucleotide polymorphisms (SNPs) on stroke and uncovered new causal variants for IS. The clinical application of m6A targeting drugs is still in its infancy and will be available in the future.

EXPERT OPINION

: Collectively, the information in the present review is a summary of the latest developments in m6A modification and highlights the mechanisms underlying IS pathogenesis, which may provide novel insights into the mechanisms and therapeutic targets for IS.

Blood-Brain Barrier Transporters: Opportunities for Therapeutic Development in Ischemic Stroke

Globally, stroke is a leading cause of death and long-term disability. Over the past decades, several efforts have attempted to discover new drugs or repurpose existing therapeutics to promote post-stroke neurological recovery. Preclinical stroke studies have reported successes in identifying novel neuroprotective agents; however, none of these compounds have advanced beyond a phase III clinical trial. One reason for these failures is the lack of consideration of blood-brain barrier (BBB) transport mechanisms that can enable these drugs to achieve efficacious concentrations in ischemic brain tissue. Despite the knowledge that drugs with neuroprotective properties (i.e., statins, memantine, metformin) are substrates for endogenous BBB transporters, preclinical stroke research has not extensively studied the role of transporters in central nervous system (CNS) drug delivery. Here, we review current knowledge on specific BBB uptake transporters (i.e., organic anion transporting polypeptides (OATPs in humans; Oatps in rodents); organic cation transporters (OCTs in humans; Octs in rodents) that can be targeted for improved neuroprotective drug delivery. Additionally, we provide state-of-the-art perspectives on how transporter pharmacology can be integrated into preclinical stroke research. Specifically, we discuss the utility of in vivo stroke models to transporter studies and considerations (i.e., species selection, co-morbid conditions) that will optimize the translational success of stroke pharmacotherapeutic experiments.

In vitro analysis of mechanism of pulsed-laser thrombolysis

Thrombolytic therapy in the treatment of cardiogenic acute cerebral embolism caused by coagulated blood carries the risk of hemorrhagic complications, and there is a need to develop safer and more reliable treatment methods. Laser thrombolysis therapy, which utilizes the difference in energy absorption between the thrombus and the arterial wall, has shown promise as a new treatment method because it can selectively act only on the thrombus. It has not been applied clinically, however, and one of the main reasons for this is that its underlying mechanism has not been elucidated. We developed a pulse laser thrombolysis system for treating cerebral blood vessels that consists of a diode-pumped solid-state neodymium-yttrium aluminum garnet laser, which has excellent stability and maintainability and is suitable for clinical applications coupled to a small-diameter optical fiber. Moreover, we analyzed the mechanisms that occur during pulsed laser irradiation of transparent glass tubes and gelatin phantoms. We found that bubbles form as a thermal effect in addition to ablation of the pulsed laser irradiation. Furthermore, we detected no shock waves or water jets associated with the bubbles. We analyzed the bubbles’ dynamics and growth rate, and their effect on a rabbit blood clot phantom. We concluded that the bubbles generated by the laser irradiation physically cut the thrombus and thereby had a thrombectomy effect. We believe that this study will clarify the mechanism of laser thrombolysis therapy and contribute greatly to the realization of its clinical application.

Astragaloside IV Alleviates Cerebral Ischemia-Reperfusion Injury through NLRP3 Inflammasome-Mediated Pyroptosis Inhibition via Activating Nrf2

As one of the fundamental components of Astragalus membranaceus, astragaloside IV (AST IV) exerts protective effects against cerebral ischemia-reperfusion injury (CIRI). Nevertheless, the underlying mechanisms have not yet been conclusively elucidated. To do so, here, we report on the regulatory effects of Nrf2 on NLRP3 inflammasome-mediated pyroptosis. CIRI was induced by middle cerebral artery occlusion-reperfusion (MCAO/R) in Sprague Dawley rats and modeled by oxygen and glucose deprivation/reoxygenation (OGD/R) in SH-SY5Y cells. Cerebral infarct volume and neurological deficit score served as indices to evaluate MCAO/R injury. In addition, the CCK-8 assay was used to assess cell viability, the LDH leakage rate was used as a quantitative index, and propidium iodide (PI) staining was used to visualize cells after OGD/R injury. The NLRP3/Caspase-1/GSDMD pathway, which produces the pores in the cell membrane that are central to the pyroptosis process, was assessed to investigate pyroptosis. Nrf2 activation was assessed by detecting Nrf2 protein levels and immunofluorescence analysis. We show that after MCAO/R of rats, the infarct volume and neurological deficit score of rats were strongly increased, and after OGD/R of cell cultures, cell viability was strongly decreased, and the LDH leakage rate and the proportion of PI-positive cells were strongly increased. In turn, MCAO/R and OGD/R enhanced the protein levels of NLRP3, Caspase-1, IL-1β, GSDMD, and GSDMD-N. Moreover, Nrf2 protein levels increased, and Nrf2 translocation was promoted after CIRI. Interestingly, AST IV (i) reduced the cerebral infarct volume and the neurological deficit score in vivo and (ii) increased the cell viability and reduced the LDH leakage rate and the proportion of PI-positive cells in vitro. AST IV reduced the protein levels of NLRP3, Caspase-1, IL-1β, GSDMD, and GSDMD-N, inhibiting NLRP3 inflammasome-mediated pyroptosis. AST IV also increased the protein levels of Nrf2 and promoted the transfer of Nrf2 to the nucleus, accelerating Nrf2 activation. Particularly revealing was that the Nrf2 inhibitor ML385 partly blocked the above effects of AST IV. Taken together, these results demonstrate that AST IV alleviates CIRI through inhibiting NLRP3 inflammasome-mediated pyroptosis via activating Nrf2.

Sphingosine-1-Phosphate Signaling in Ischemic Stroke: From Bench to Bedside and Beyond

Sphingosine-1-phosphate (S1P) signaling is being increasingly recognized as a strong modulator of immune cell migration and endothelial function. Fingolimod and other S1P modulators in ischemic stroke treatment have shown promise in emerging experimental models and small-scale clinical trials. In this article, we will review the current knowledge of the role of S1P signaling in brain ischemia from the aspects of inflammation and immune interventions, sustaining endothelial functions, regulation of blood-brain barrier integrity, and functional recovery. We will then discuss the current and future therapeutic perspectives of targeting S1P for the treatment of ischemic stroke. Mechanism studies would help to bridge the gap between preclinical studies and clinical practice. Future success of bench-to-bedside translation shall be based on in depth understanding of S1P signaling during stroke and on the ability to have a fine temporal and spatial regulation of the signal pathway.

Value of pre-intervention CT perfusion imaging in acute ischemic stroke prognosis

Noninvasive imaging plays an important role in acute stroke towards diagnosis and ongoing management of patients. Systemic thrombolysis and endovascular thrombectomy (EVT) are proven treatments currently used in standards of care in acute stroke settings. The role of computed tomography angiography (CTA) in selecting patients with large vessel occlusion for EVT is well established. However, the value of CT perfusion (CTP) imaging in predicting outcomes after stroke remains ambiguous. This article critically evaluates the value of multimodal CT imaging in early diagnosis and prognosis of acute ischemic stroke with a focus on the role of CTP in delineating tissue characteristics, patient selection, and outcomes after reperfusion therapy. Insights on various technical and clinical considerations relevant to CTP applications in acute ischemic stroke, recommendations for existing workflow, and future areas of research are discussed.

Treatment of acute ischemic stroke by minimally manipulated umbilical cord-derived mesenchymal stem cells transplantation: A case report

BACKGROUND

Stroke is one of the major causes of disability and death worldwide. Some treatments for stroke exist, but existing treatment methods have limitations such as difficulty in the regeneration of damaged neuronal cells of the brain. Recently, mesenchymal stem cells (MSCs) have been studied as a therapeutic alternative for stroke, and various preclinical and case studies have been reported.

CASE SUMMARY

A 55-year-old man suffered an acute stroke, causing paralysis in the left upper and lower limbs. He intravenously transplanted the minimally manipulated human umbilical cord-derived MSCs (MM-UC-MSCs) twice with an 8-d interval. At 65 wk after transplantation, the patient returned to his previous occupation as a veterinarian with no adverse reactions.

CONCLUSION

MM-UC-MSCs transplantation potentially treats patients who suffer from acute ischemic stroke.

Neovascularization and tissue regeneration by endothelial progenitor cells in ischemic stroke

Endothelial progenitor cells (EPCs) are immature endothelial cells (ECs) capable of proliferating and differentiating into mature ECs. These progenitor cells migrate from bone marrow (BM) after vascular injury to ischemic areas, where they participate in the repair of injured endothelium and new blood vessel formation. EPCs also secrete a series of protective cytokines and growth factors that support cell survival and tissue regeneration. Thus, EPCs provide novel and promising potential therapies to treat vascular disease, including ischemic stroke. However, EPCs are tightly regulated during the process of vascular repair and regeneration by numerous endogenous cytokines that are associated closely with the therapeutic efficacy of the progenitor cells. The regenerative capacity of EPCs also is affected by a range of exogenous factors and drugs as well as vascular risk factors. Understanding the functional properties of EPCs and the factors related to their regenerative capacity will facilitate better use of these progenitor cells in treating vascular disease. Here, we review the current knowledge of EPCs in cerebral neovascularization and tissue regeneration after cerebral ischemia and the factors associated with their regenerative function to better understand the underlying mechanisms and provide more effective strategies for the use of EPCs in treating ischemic stroke.

AIM2 deletion enhances blood-brain barrier integrity in experimental ischemic stroke

Aims

Ischemic stroke is a life‐threatening disease with limited therapeutic strategies. Blood‐brain barrier (BBB) disruption is a critical pathological process that contributes to poor outcomes in ischemic stroke. We previously showed that the microglial inhibition of the inflammasome sensor absent in melanoma 2 (AIM2) suppressed the inflammatory response and protected against ischemic stroke. However, whether AIM2 is involved in BBB disruption during cerebral ischemia is unknown.

Methods

Middle cerebral artery occlusion (MCAO) and oxygen‐glucose deprivation/reoxygenation (OGD/R) were used to mimic cerebral ischemia in mice and brain microvascular endothelial cells (HBMECs), respectively. The infarct volume, neurological deficits, and BBB permeability were measured in mice after MCAO. Transendothelial electrical resistance (TEER) and neutrophil adhesion to the HBMEC monolayer were assessed after OGD/R treatment. Western blot and immunofluorescence analyses were conducted to evaluate the expression of related proteins.

Results

AIM2 was shown to be expressed in brain endothelial cells and upregulated after ischemic stroke in the mouse brain. AIM2 deletion reduced the infarct volume, improved neurological and motor functions, and decreased BBB disruption. In vitro, OGD/R significantly increased the protein levels of AIM2 and ICAM‐1 and decreased those of the tight junction (TJ) proteins ZO‐1 and occludin. AIM2 knockdown effectively protected BBB integrity by promoting the expression of TJ proteins and decreasing ICAM‐1 expression and neutrophil adhesion. Mechanistically, AIM2 knockdown reversed the OGD/R‐induced increases in ICAM‐1 expression and STAT3 phosphorylation in brain endothelial cells. Furthermore, treatment with the p‐STAT3 inhibitor AG490 mitigated the effect of AIM2 on BBB breakdown.

Conclusion

Our findings indicated that inhibiting AIM2 preserved the BBB integrity after ischemic stroke, at least partially by modulating STAT3 activation and that AIM2 may be a promising therapeutic target for cerebral ischemic stroke.

Relevant mediators involved in and therapies targeting the inflammatory response induced by activation of the NLRP3 inflammasome in ischemic stroke

The nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) inflammasome is a member of the NLR family of inherent immune cell sensors. The NLRP3 inflammasome can detect tissue damage and pathogen invasion through innate immune cell sensor components commonly known as pattern recognition receptors (PRRs). PRRs promote activation of nuclear factor kappa B (NF-κB) pathways and the mitogen-activated protein kinase (MAPK) pathway, thus increasing the transcription of genes encoding proteins related to the NLRP3 inflammasome. The NLRP3 inflammasome is a complex with multiple components, including an NAIP, CIITA, HET-E, and TP1 (NACHT) domain; apoptosis-associated speck-like protein containing a CARD (ASC); and a leucine-rich repeat (LRR) domain. After ischemic stroke, the NLRP3 inflammasome can produce numerous proinflammatory cytokines, mediating nerve cell dysfunction and brain edema and ultimately leading to nerve cell death once activated. Ischemic stroke is a disease with high rates of mortality and disability worldwide and is being observed in increasingly younger populations. To date, there are no clearly effective therapeutic strategies for the clinical treatment of ischemic stroke. Understanding the NLRP3 inflammasome may provide novel ideas and approaches because targeting of upstream and downstream molecules in the NLRP3 pathway shows promise for ischemic stroke therapy. In this manuscript, we summarize the existing evidence regarding the composition and activation of the NLRP3 inflammasome, the molecules involved in inflammatory pathways, and corresponding drugs or molecules that exert effects after cerebral ischemia. This evidence may provide possible targets or new strategies for ischemic stroke therapy.

The diagnostic reliability and validity of noninvasive imaging modalities to assess leptomeningeal collateral flow for ischemic stroke patients: A systematic review and meta-analysis

Leptomeningeal collateral flow (LMF) is associated with infarct area and clinical outcome for ischemic stroke patients. Although LMF can be detected by multiple imaging methods, but their diagnostic performance is uncertain.The aim of this study was to evaluate the diagnostic validity or reliability of noninvasive image methods in assessing LMF.Databases included PubMed, Web of Science, Embase, and Cochrane Library.Original observational cohort studies.Ischemic stroke patients.Different noninvasive image methods to assess LMF.Newcastle-Ottawa Scale to evaluate the quality of the studies; forest plot to show pooled results; I2 and Egger test to evaluate the heterogeneity and publication bias.Thirty of the 126 selected studies were eligible. For CT angiography, the interobserver agreement ranged from 0.494 to 0.93 and weighted kappa was 0.888; for patients receiving thrombolysis or endovascular treatment, 0.68 to 0.91; 0.494 to 0.89 for the 2-point system, 0.60 to 0.93 for the 3-point system, 0.68 to 0.87 for the system of >4 points; area under the curve (AUC) was 0.78. For perfusion computed tomography (CTP), the interobserver agreement ranged from 0.724 to 0.872; for patients receiving thrombolysis or endovascular treatment, 0.74 to 0.872; 0.724 for the 2-point system, 0.783 to 0.953 for the 3-point system; the intraobserver agreement was 0.884; AUC was 0.826. For MRI-fluid attenuated inversion recovery (FLAIR), the interobserver agreement ranged from 0.58 to 0.86; for patients receiving thrombolysis or endovascular treatment, 0.75 to 0.86; 0.86 for the two-point system, 0.77 to 0.87 for the system of more than 5 points; AUC was 0.82.No pooled data of CTP and FLAIR. The difference cohort study had difference bias. The unpublished data were not included.CT angiography is a good tool for assessing LMF. CTP shows a good validity and reliability, but its diagnostic value needs more evidence. FLAIR is a good modality to assess LMF. These image methods had better validity and reliability to evaluate LMF of patients receiving thrombolysis or endovascular treatment than all ischemic stroke patients.

Pyroptosis in stroke-new insights into disease mechanisms and therapeutic strategies

Stroke is a common disease with high mortality and disability worldwide. Different forms of cell deaths, including apoptosis and necrosis, occur in ischemic or hemorrhagic brain tissue, among which pyroptosis, a newly discovered inflammation-related programmed cell death, is generally divided into two main pathways, the canonical inflammasome pathway and the non-canonical inflammasome pathway. Caspase-mediated pyroptosis requires the assembly of inflammasomes such as NLRP3, which leads to the release of inflammatory cytokines IL-1β and IL-18 through the pores formed in the plasma membrane by GSDMD followed by neuroinflammation. Recently, pyroptosis and its relationship with inflammation have attracted more and more attention in the study of cerebral ischemia or hemorrhage. In addition, many inhibitors of pyroptosis targeting caspase, NLRP3, and the upstream pathway have been found to reduce brain tissue damage after stroke. In this review, we mainly introduce the pathology of stroke, the molecular mechanism, and process of pyroptosis, as well as the pivotal roles of pyroptosis in stroke, in order to provide new insights for the treatment of stroke.

Preferential Targeting Cerebral Ischemic Lesions with Cancer Cell-Inspired Nanovehicle for Ischemic Stroke Treatment

The poor drug delivery to cerebral ischemic regions is a key challenge of ischemic stroke treatment. Inspired by the intriguing blood-brain barrier (BBB)-penetrating ability of 4T1 cancer cells upon their brain metastasis, we herein designed a promising biomimetic nanoplatform by camouflaging a succinobucol-loaded pH-sensitive polymeric nanovehicle with a 4T1 cell membrane (MPP/SCB), aiming to promote the preferential targeting of cerebral ischemic lesions to attenuate the ischemia/reperfusion injury. In transient middle cerebral artery occlusion (tMCAO) rat models, MPP/SCB could be preferentially delivered to the ischemic hemisphere with a 4.79-fold higher than that in the normal hemisphere. Moreover, MPP/SCB produced notable enhancement of microvascular reperfusion in the ischemic hemisphere, resulting in a 69.9% reduction of infarct volume and showing remarkable neuroprotective effects of tMCAO rats, which was superior to the counterpart uncamouflaged nanovehicles (PP/SCB). Therefore, this design provides a promising nanoplatform to target the cerebral ischemic lesions for ischemic stroke therapy.

Defining Hypoperfusion in Chronic Aphasia: An Individualized Thresholding Approach

Within the aphasia literature, it is common to link location of lesioned brain tissue to specific patterns of language impairment. This has provided valuable insight into the relationship between brain structure and function, but it does not capture important underlying alterations in function of regions that remain structurally intact. Research has demonstrated that in the chronic stage of aphasia, variable patterns of reduced cerebral blood flow (CBF; hypoperfusion) in structurally intact regions of the brain contribute to persisting language impairments. However, one consistent issue in this literature is a lack of clear consensus on how to define hypoperfusion, which may lead to over- or underestimation of tissue functionality. In the current study, we conducted an exploratory analysis in six individuals with chronic aphasia (>1 year post-onset) using perfusion imaging to (1) suggest a new, individualized metric for defining hypoperfusion; (2) identify the extent of hypoperfused tissue in perilesional bands; and (3) explore the relationship between hypoperfusion and language impairment. Results indicated that our individualized metric for defining hypoperfusion provided greater precision when identifying functionally impaired tissue and its effects on language function in chronic aphasia. These results have important implications for intervention approaches that target intact (or impaired) brain tissue.

Modified middle cerebral artery occlusion model provides detailed intraoperative cerebral blood flow registration and improves neurobehavioral evaluation

BACKGROUND

Middle cerebral artery occlusion (MCAO) with 1 -h ischemia followed by reperfusion is a widely used stroke model in rodents that has significant limitations such as high mortality and severe neurological deficit hampering comprehensive neurobehavioral evaluation. The goal of this study was to establish a mouse model of 30-minute MCAO followed by 48 h of reperfusion and compare it with 1 -h MCAO followed by 24 h of reperfusion.

NEW METHOD

Here we propose a modified MCAO model that is favorable for both neurobehavioral and infarct volume evaluation. The model includes shorter ischemic time (30 min) of MCAO followed by 48 h of reperfusion and use of standardized intraoperative partial and total reperfusion, which allows for the detailed evaluation of initial and total reperfusion by means of the monitoring of CBF by LDF.

RESULTS AND COMPARISON WITH EXISTING METHOD

Intraoperative CBF parameters and infarct volume (1-h MCAO at 24 h: 69 ± 9; 30-minute MCAO at 48 h: 65 ± 14 mm³) did not significantly differ between groups. Neurological deficit was less severe in 30-minute MCAO group where mice also had significantly longer ambulatory distance and time, lower resting time, and higher vertical count on the OPF. The latency to fall in the rotarod test was significantly higher in 30-minute MCAO group. The mortality was higher after 1 -h MCAO.

CONCLUSIONS

30-minute MCAO followed by 48 h of reperfusion causes intraoperative ischemia, reperfusion and infarct volume comparable with 1 -h MCAO followed by 24 h of reperfusion but results in lower mortality with milder neurological deficit allowing for more extensive neurobehavioral evaluation.

Endothelial S1P1 Signaling Counteracts Infarct Expansion in Ischemic Stroke

RATIONALE

Cerebrovascular function is critical for brain health, and endogenous vascular protective pathways may provide therapeutic targets for neurological disorders. S1P (Sphingosine 1-phosphate) signaling coordinates vascular functions in other organs, and S1P1 (S1P receptor-1) modulators including fingolimod show promise for the treatment of ischemic and hemorrhagic stroke. However, S1P1 also coordinates lymphocyte trafficking, and lymphocytes are currently viewed as the principal therapeutic target for S1P1 modulation in stroke.

OBJECTIVE

To address roles and mechanisms of engagement of endothelial cell S1P1 in the naive and ischemic brain and its potential as a target for cerebrovascular therapy.

METHODS AND RESULTS

Using spatial modulation of S1P provision and signaling, we demonstrate a critical vascular protective role for endothelial S1P1 in the mouse brain. With an S1P1 signaling reporter, we reveal that abluminal polarization shields S1P1 from circulating endogenous and synthetic ligands after maturation of the blood-neural barrier, restricting homeostatic signaling to a subset of arteriolar endothelial cells. S1P1 signaling sustains hallmark endothelial functions in the naive brain and expands during ischemia by engagement of cell-autonomous S1P provision. Disrupting this pathway by endothelial cell-selective deficiency in S1P production, export, or the S1P1 receptor substantially exacerbates brain injury in permanent and transient models of ischemic stroke. By contrast, profound lymphopenia induced by loss of lymphocyte S1P1 provides modest protection only in the context of reperfusion. In the ischemic brain, endothelial cell S1P1 supports blood-brain barrier function, microvascular patency, and the rerouting of blood to hypoperfused brain tissue through collateral anastomoses. Boosting these functions by supplemental pharmacological engagement of the endothelial receptor pool with a blood-brain barrier penetrating S1P1-selective agonist can further reduce cortical infarct expansion in a therapeutically relevant time frame and independent of reperfusion.

CONCLUSIONS

This study provides genetic evidence to support a pivotal role for the endothelium in maintaining perfusion and microvascular patency in the ischemic penumbra that is coordinated by S1P signaling and can be harnessed for neuroprotection with blood-brain barrier-penetrating S1P1 agonists.

The Pharmacological Action of Kaempferol in Central Nervous System Diseases: A Review

Kaempferol (KPF) is a flavonoid antioxidant found in fruits and vegetables. Many studies have described the beneficial effects of dietary KPF in reducing the risk of chronic diseases, especially cancer. Nevertheless, little is known about the cellular and molecular mechanisms underlying KPF actions in the central nervous system (CNS). Also, the relationship between KPF structural properties and their glycosylation and the biological benefits of these compounds is unclear. The aim of this study was to review studies published in the PubMed database during the last 10 years (2010–2020), considering only experimental articles that addressed the isolated cell effect of KPF (C₁₅H₁₀O₆) and its derivatives in neurological diseases such as Alzheimer's disease, Parkinson, ischemia stroke, epilepsy, major depressive disorder, anxiety disorders, neuropathic pain, and glioblastoma. 27 publications were included in the present review, which presented recent advances in the effects of KPF on the nervous system. KPF has presented a multipotential neuroprotective action through the modulation of several proinflammatory signaling pathways such as the nuclear factor kappa B (NF-kB), p38 mitogen-activated protein kinases (p38MAPK), serine/threonine kinase (AKT), and β-catenin cascade. In addition, there are different biological benefits and pharmacokinetic behaviors between KPF aglycone and its glycosides. The antioxidant nature of KPF was observed in all neurological diseases through MMP2, MMP3, and MMP9 metalloproteinase inhibition; reactive oxygen species generation inhibition; endogenous antioxidants modulation as superoxide dismutase and glutathione; formation and aggregation of beta-amyloid (β-A) protein inhibition; and brain protective action through the modulation of brain-derived neurotrophic factor (BDNF), important for neural plasticity. In conclusion, we suggest that KPF and some glycosylated derivatives (KPF-3-O-rhamnoside, KPF-3-O-glucoside, KPF-7-O-rutinoside, and KPF-4′-methyl ether) have a multipotential neuroprotective action in CNS diseases, and further studies may make the KPF effect mechanisms in those pathologies clearer. Future in vivo studies are needed to clarify the mechanism of KPF action in CNS diseases as well as the impact of glycosylation on KPF bioactivity.

Protosappanin A Maintains Neuronal Mitochondrial Homeostasis through Promoting Autophagic Degradation of Bax

Cerebral ischemia is accompanied by mitochondrial integrity destruction. Thus, reversion of mitochondrial damage holds great potential for cerebral ischemia therapy. As a crucial Bcl-2 family member, pro-apoptotic Bax protein is a main effector of mitochondrial permeabilization and plays an important role in mitochondrial homeostasis. However, there is still a lack of an effective cerebral protective strategy through selectively targeting Bax. In this study, we reported that natural small-molecule protosappanin A (PTA) showed a significant mitochondrial protective effect on oxygen-glucose deprivation/reperfusion (OGD/R)-induced PC12 cells injury through increasing ATP production and maintaining mitochondrial DNA (mtDNA) content. The mechanism study revealed that PTA selectively induced pro-apoptotic protein Bax degradation, without affecting other Bcl-2 family members such as Bcl-2, Bcl-xl, Bad, Puma, Bid, Bim, and Bik. In addition, we found that PTA promoted the association of autophagosomal marker LC3B to Bax for its degradation via an autophagy-dependent manner but not the ubiquitin-proteasome pathway. Collectively, our findings offered a new pharmacological strategy for maintaining mitochondrial function by inducing autophagic degradation of Bax and also provided a novel drug candidate against ischemic neuronal injury.

Regulation of blood-brain barrier integrity by microglia in health and disease: A therapeutic opportunity

The blood-brain barrier (BBB) is a critical regulator of CNS homeostasis. It possesses physical and biochemical characteristics (i.e. tight junction protein complexes, transporters) that are necessary for the BBB to perform this physiological role. Microvascular endothelial cells require support from astrocytes, pericytes, microglia, neurons, and constituents of the extracellular matrix. This intricate relationship implies the existence of a neurovascular unit (NVU). NVU cellular components can be activated in disease and contribute to dynamic remodeling of the BBB. This is especially true of microglia, the resident immune cells of the brain, which polarize into distinct proinflammatory (M1) or anti-inflammatory (M2) phenotypes. Current data indicate that M1 pro-inflammatory microglia contribute to BBB dysfunction and vascular "leak", while M2 anti-inflammatory microglia play a protective role at the BBB. Understanding biological mechanisms involved in microglia activation provides a unique opportunity to develop novel treatment approaches for neurological diseases. In this review, we highlight characteristics of M1 proinflammatory and M2 anti-inflammatory microglia and describe how these distinct phenotypes modulate BBB physiology. Additionally, we outline the role of other NVU cell types in regulating microglial activation and highlight how microglia can be targeted for treatment of disease with a focus on ischemic stroke and Alzheimer's disease.

Diabetes Mellitus/Poststroke Hyperglycemia: a Detrimental Factor for tPA Thrombolytic Stroke Therapy

Intravenous administration of tissue-type plasminogen activator (IV tPA) therapy has long been considered a mainstay in ischemic stroke management. However, patients respond to IV tPA therapy unequally with some subsets of patients having worsened outcomes after treatment. In particular, diabetes mellitus (DM) is recognized as a clinically important vascular comorbidity that leads to lower recanalization rates and increased risks of hemorrhagic transformation (HT). In this short-review, we summarize the recent advances in understanding of the underlying mechanisms involved in post-IV tPA worsening of outcome in diabetic stroke. Potential pathologic factors that are related to the suboptimal tPA recanalization in diabetic stroke include higher plasma plasminogen activator inhibitor (PAI)-1 level, diabetic atherogenic vascular damage, glycation of the tPA receptor annexin A2, and alterations in fibrin clot density. While factors contributing to the exacerbation of HT in diabetic stroke include hyperglycemia, vascular oxidative stress, and inflammation, tPA neurovascular toxicity and imbalance in extracellular proteolysis are discussed. Besides, impaired collaterals in DM also compromise the efficacy of IV tPA therapy. Additionally, several tPA combination approaches developed from experimental studies that may help to optimize IV tPA therapy are also briefly summarized. In summary, more research efforts are needed to improve the safety and efficacy of IV tPA therapy in ischemic stroke patients with DM/poststroke hyperglycemia.

Citicoline for treating people with acute ischemic stroke

BACKGROUND

Stroke is one of the leading causes of long-lasting disability and mortality and its global burden has increased in the past two decades. Several therapies have been proposed for the recovery from, and treatment of, ischemic stroke. One of them is citicoline. This review assessed the benefits and harms of citicoline for treating patients with acute ischemic stroke.

OBJECTIVES

To assess the clinical benefits and harms of citicoline compared with placebo or any other control for treating people with acute ischemic stroke.

SEARCH METHODS

We searched in the Cochrane Stroke Group Trials Register, CENTRAL, MEDLINE Ovid, Embase Ovid, LILACS until 29 January 2020. We searched the World Health Organization Clinical Trials Search Portal and ClinicalTrials.gov. Additionally, we also reviewed reference lists of the retrieved publications and review articles, and searched the websites of the US Food and Drug Administration (FDA) and European Medicines Agency (EMA).

SELECTION CRITERIA

We included randomized controlled trials (RCTs) in any setting including participants with acute ischemic stroke. Trials were eligible for inclusion if they compared citicoline versus placebo or no intervention.

DATA COLLECTION AND ANALYSIS

We selected RCTs, assessed the risk of bias in seven domains, and extracted data by duplicate. Our primary outcomes of interest were all-cause mortality and the degree of disability or dependence in daily activities at 90 days. We estimated risk ratios (RRs) for dichotomous outcomes. We measured statistical heterogeneity using the I² statistic. We conducted our analyses using the fixed-effect and random-effects model meta-analyses. We assessed the overall quality of evidence for six pre-specified outcomes using the GRADE approach.

MAIN RESULTS

We identified 10 RCTs including 4281 participants. In all these trials, citicoline was given either orally, intravenously, or a combination of both compared with placebo or standard care therapy. Citicoline doses ranged between 500 mg and 2000 mg per day. We assessed all the included trials as having high risk of bias. Drug companies sponsored six trials. A pooled analysis of eight trials indicates there may be little or no difference in all-cause mortality comparing citicoline with placebo (17.3% versus 18.5%; RR 0.94, 95% CI 0.83 to 1.07; I² = 0%; low-quality evidence due to risk of bias). Four trials found no difference in the proportion of patients with disability or dependence in daily activities according to the Rankin scale comparing citicoline with placebo (21.72% versus 19.23%; RR 1.11, 95% CI 0.97 to 1.26; I² = 1%; low-quality evidence due to risk of bias). Meta-analysis of three trials indicates there may be little or no difference in serious cardiovascular adverse events comparing citicoline with placebo (8.83% versus 7.77%; RR 1.04, 95% CI 0.84 to 1.29; I² = 0%; low-quality evidence due to risk of bias). Overall, either serious or non-serious adverse events - central nervous system, gastrointestinal, musculoskeletal, etc. - were poorly reported and harms may have been underestimated. Four trials assessing functional recovery with the Barthel Index at a cut-off point of 95 points or more did not find differences comparing citicoline with placebo (32.78% versus 30.70%; RR 1.03, 95% CI 0.94 to 1.13; I² = 24%; low-quality evidence due to risk of bias). There were no differences in neurological function (National Institutes of Health Stroke Scale at a cut-off point of ≤ 1 points) comparing citicoline with placebo according to five trials (24.31% versus 22.44%; RR 1.08, 95% CI 0.96 to 1.21; I² = 27%, low-quality evidence due to risk of bias). A pre-planned Trial Sequential Analysis suggested that no more trials may be needed for the primary outcomes but no trial provided information on quality of life.

AUTHORS' CONCLUSIONS

This review assessed the clinical benefits and harms of citicoline compared with placebo or any other standard treatment for people with acute ischemic stroke. The findings of the review suggest there may be little to no difference between citicoline and its controls regarding all-cause mortality, disability or dependence in daily activities, severe adverse events, functional recovery and the assessment of the neurological function, based on low-certainty evidence. None of the included trials assessed quality of life and the safety profile of citicoline remains unknown. The available evidence is of low quality due to either limitations in the design or execution of the trials.

The Expression and Localization of Histone Acetyltransferases HAT1 and PCAF in Neurons and Astrocytes of the Photothrombotic Stroke-Induced Penumbra in the Rat Brain Cortex

Stroke is one of the leading reasons of human death. Ischemic penumbra that surrounds the stroke-induced infarction core is potentially salvageable, but molecular mechanisms of its formation are poorly known. Histone acetylation induces chromatin decondensation and stimulates gene expression. We studied the changes in the levels and localization of histone acetyltransferases HAT1 and PCAF in penumbra after photothrombotic stroke (PTS, a stroke model). In PTS, laser irradiation induces local occlusion of cerebral vessels after photosensitization by Rose Bengal. HAT1 and PCAF are poorly expressed in normal cortical neurons and astrocytes, but they are overexpressed 4-24 h after PTS. Their predominant localization in neuronal nuclei did not change after PTS, but their levels in the astrocyte nuclei significantly increased. Western blotting showed the increase of HAT1 and PCAF levels in the cytoplasmic fraction of the PTS-induced penumbra. In the nuclear fraction, PCAF level did not change, and HAT1 was overexpressed only at 24 h post-PTS. PTS-induced upregulation of HAT1 and PCAF in the penumbra was mainly associated with overexpression in the cytoplasm of neurons and especially astrocytes. HAT1 and PCAF did not co-localize with TUNEL-positive cells that indicated their nonparticipation in PTS-induced apoptosis.

Methyltransferase 3 Mediated miRNA m6A Methylation Promotes Stress Granule Formation in the Early Stage of Acute Ischemic Stroke

The modification of methyltransferase-like (METTL) enzymes plays important roles in various cellular responses by regulating microRNA expression. However, how m6A modification is involved in stress granule (SG) formation in the early stage of acute ischemic stroke by affecting the biogenesis processing of microRNAs remains unclear. Here, we established a middle cerebral artery occlusion (MCAO) model in rats and an oxygen-glucose deprivation/reperfusion (OGD/R) model in primary cortical neurons and PC12 cells to explore the potential mechanism between m6A modification and SG formation. The in vivo results showed that the level of infarction and apoptosis increased while SG formation decreased significantly within the ischemic cortex with improved reperfusion time after 2 h of ischemia. Consistent with the in vivo data, an inverse association between the apoptosis level and SG formation was observed in PC12 cells during the reperfusion period after 6 h of OGD stimulation. Both in vivo and in vitro results showed that the expression of METTL3 protein, m6A and miR-335 was significantly decreased with the reperfusion period. Overexpression of the METTL3 and METTL3 gene-knockdown in PC12 cells were achieved via plasmid transfection and CRISPR-Cas9 technology, respectively. Overexpression or knockdown of METTL3 in oxygen-glucose deprivation of PC12 cells resulted in functional maturation of miR-335, SG formation and apoptosis levels. In addition, we found that miR-335 enhanced SG formation through degradation of the mRNA of the eukaryotic translation termination factor (Erf1). In conclusion, we found that METTL3-mediated m6A methylation increases the maturation of miR-335, which promotes SG formation and reduces the apoptosis level of injury neurons and cells, and provides a potential therapeutic strategy for AIS.

Impact of complete recanalization on clinical recovery in cardioembolic stroke patients with M2 occlusion

BACKGROUND AND PURPOSE

We investigated the impact of complete recanalization beyond partial recanalization in distal (M2) middle cerebral artery (MCA) occlusion.

METHODS

Data regarding M2 occlusion patients treated with endovascular thrombectomy (EVT) and/or intravenous thrombolysis (tPA) were reviewed from our prospective EVT registry and multicenter tPA (YAMATO study) data bank. Complete recanalization was modified thrombolysis with cerebral infarction score (TICI) of 3 at the end of EVT or similar appearances of both MCAs on magnetic resonance angiography (MRA) within 1.5 h after tPA. Partial recanalization was defined as TICI ≥2b or > 50% recanalization on MRA. At 3 months, favorable outcome was defined as a modified Rankin Scale score ≤ 2.

RESULT

Data on 121 patients were analyzed. EVT-alone was in 38 patients; combined EVT and tPA in 28; and tPA-alone in 55. Complete recanalization was achieved in 27 (22%), partial recanalization in 48 (40%), and no-to-limited recanalization in 46 (38%). At 3 months, 51% of patients had favorable outcomes, and this rate was significantly higher in the complete recanalization group than in the partial and no-to-limited recanalization groups (75% vs. 41% vs. 49%, p = .043). Multivariate regression analysis showed that complete recanalization was an independent parameter related to favorable outcomes (odds ratio 4.78, 95% CI: 1.16-19.73, p = .030). However, combined complete and partial recanalization was not associated with favorable outcomes (odds ratio 1.49, 95% CI 0.53-4.22, p = .449).

CONCLUSION

Complete recanalization, but not partial recanalization, at the end of EVT and tPA therapy is associated with favorable outcomes in patients with M2 occlusion.

Molecular and Pharmacological Modulation of CALHM1 Promote Neuroprotection against Oxygen and Glucose Deprivation in a Model of Hippocampal Slices

Calcium homeostasis modulator 1 (CALHM1) is a calcium channel involved in the regulation of cytosolic Ca²⁺ levels. From a physiological point of view, the open state of CALHM1 depends not only on voltage but also on the extracellular concentration of calcium ([Ca²⁺]) ions. At low [Ca²⁺]_e or depolarization, the channel is opened, allowing Ca²⁺ influx; however, high extracellular [Ca²⁺]_e or hyperpolarization promote its resting state. The unique Ca²⁺ permeation of CALHM1 relates to the molecular events that take place in brain ischemia, such as depolarization and extracellular changes in [Ca²⁺]_e, particularly during the reperfusion phase after the ischemic insult. In this study, we attempted to understand its role in an in vitro model of ischemia, namely oxygen and glucose deprivation, followed by reoxygenation (OGD/Reox). To this end, hippocampal slices from wild-type Calhm1^+/+, Calhm1^+/−, and Calhm1^−/− mice were subjected to OGD/Reox. Our results point out to a neuroprotective effect when CALHM1 is partially or totally absent. Pharmacological manipulation of CALHM1 with CGP37157 reduced cell death in Calhm1^+/+ slices but not in that of Calhm1^−/− mice after exposure to the OGD/Reox protocol. This ionic protection was also verified by measuring reactive oxygen species production upon OGD/Reox in Calhm1^+/+ and Calhm1^−/− mice, resulting in a downregulation of ROS production in Calhm1^−/− hippocampal slices and increased expression of HIF-1α. Taken together, we can conclude that genetic or pharmacological inhibition of CALHM1 results in a neuroprotective effect against ischemia, due to an attenuation of the neuronal calcium overload and downregulation of oxygen reactive species production.

Transporter-Mediated Delivery of Small Molecule Drugs to the Brain: A Critical Mechanism That Can Advance Therapeutic Development for Ischemic Stroke

Ischemic stroke is the 5th leading cause of death in the United States. Despite significant improvements in reperfusion therapies, stroke patients still suffer from debilitating neurocognitive deficits. This indicates an essential need to develop novel stroke treatment paradigms. Endogenous uptake transporters expressed at the blood-brain barrier (BBB) provide an excellent opportunity to advance stroke therapy via optimization of small molecule neuroprotective drug delivery to the brain. Examples of such uptake transporters include organic anion transporting polypeptides (OATPs in humans; Oatps in rodents) and organic cation transporters (OCTs in humans; Octs in rodents). Of particular note, small molecule drugs that have neuroprotective properties are known substrates for these transporters and include 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (i.e., statins) for OATPs/Oatps and 1-amino-3,5-dimethyladamantane (i.e., memantine) for OCTs/Octs. Here, we review current knowledge on specific BBB transporters that can be targeted for improvement of ischemic stroke treatment and provide state-of-the-art perspectives on the rationale for considering BBB transport properties during discovery/development of stroke therapeutics.

Dl-3-N-butylphthalide attenuates ischemic reperfusion injury by improving the function of cerebral artery and circulation

Dl-3-N-butylphthalide (NBP) is approved in China for the treatment of ischemic stroke. Previous studies have shown that NBP promotes recovery after stroke via multiple mechanisms. However, the effect of NBP on vascular function and thrombosis remains unclear. Here, we aim to study the effect of NBP on vascular function using a rat model of transient middle cerebral artery occlusion (MCAO) and a state-of-the-art high-resolution synchrotron radiation angiography. Eighty SD rats underwent MCAO surgery. NBP (90 mg/kg) was administrated daily by gavage. Synchrotron radiation angiography was used to evaluate the cerebral vascular perfusion, vasoconstriction, and vasodilation in real-time. Neurological scores, brain infarction and atrophy were evaluated. Real-time PCR was used to assess the expression levels of thrombosis and vasoconstriction-related genes. Results revealed that NBP attenuated thrombosis after MCAO and reduced brain infarct and atrophy volume. NBP administrated at 1 and 4 h after MCAO prevented the vasoconstriction of the artery and maintained its diameter at normal level. Administrated at one week after surgery, NBP functioned as a vasodilator in rats after MCAO while displayed no vasodilating effect in sham group. Our results suggested that NBP attenuates brain injury via increasing the regional blood flow by reducing thrombosis and vasoconstriction.

Expression of Histone Deacetylases HDAC1 and HDAC2 and Their Role in Apoptosis in the Penumbra Induced by Photothrombotic Stroke

In ischemic stroke, vascular occlusion rapidly induces tissue infarct. Over the ensuing hours, damage spreads to adjacent tissue and forms transition zone (penumbra), which is potentially salvageable. Epigenetic regulation of chromatin structure controls gene expression and protein synthesis. We studied the expression of histone deacetylases HDAC1 and HDAC2 in the penumbra at 4 or 24 h after photothrombotic stroke (PTS) in the rat brain cortex. PTS increased the expression of HDAC1 and HDAC2 in penumbra and caused the redistribution of HDAC1 but not HDAC2 from the neuronal nuclei to cytoplasm. In astrocytes, HDAC1 expression and localization did not change. In neurons, HDAC2 localized exclusively in nuclei, but in astrocytes, it was also observed in processes. PTS induced neuronal apoptosis in the penumbra. TUNEL-stained apoptotic neurons co-localized with HDAC2 but not HDAC1. These data suggest that HDAC2 may represent the potential target for anti-stroke therapy and its selective inhibition may be a promising strategy for the protection of the penumbra tissue after ischemic stroke.

Kaempferol attenuates neuroinflammation and blood brain barrier dysfunction to improve neurological deficits in cerebral ischemia/reperfusion rats

Kaempferol has been reported to act as an anti-inflammatory agent in LPS-induced neuroinflammation in vitro and in vivo, but its role in the inflammation after cerebral ischemia/reperfusion (I/R) is unclear. The present study was to investigate the effect of kaempferol on inflammation in ischemic brain tissue and explore its mechanisms in cerebral I/R rats. Cerebral I/R rat model was established by middle cerebral artery occlusion for 60 min and following reperfusion. Kaempferol at doses of 25, 50 and 100 mg/kg was administered for 7 days after cerebral I/R. Kaempferol treatment significantly reduced cerebral infarct volume, attenuated inflammation and blood-brain barrier (BBB) disruption after cerebral I/R, thus improved neurological outcomes at the day 7 after cerebral I/R. Furthermore, the results also showed kaempferol treatment decreased the phosphorylation and nuclear transposition of transcription factor NF-κB p65, thus inhibited expression of various pro-inflammatory proteins. In conclusion, kaempferol attenuates neuroinflammation and blood brain barrier dysfunction to improve neurological deficits in cerebral I/R rats, its mechanism is related to NF-κB pathway.

Epigenetic Alterations Induced by Photothrombotic Stroke in the Rat Cerebral Cortex: Deacetylation of Histone h3, Upregulation of Histone Deacetylases and Histone Acetyltransferases

Ischemic penumbra that surrounds a stroke-induced infarction core is potentially salvageable; however, mechanisms of its formation are not well known. Covalent modifications of histones control chromatin conformation, gene expression and protein synthesis. To study epigenetic processes in ischemic penumbra, we used photothrombotic stroke (PTS), a stroke model in which laser irradiation of the rat brain cortex photosensitized by Rose Bengal induces local vessel occlusion. Immunoblotting and immunofluorescence microscopy showed decrease in acetylation of lysine 9 in histone H3 in penumbra at 1, 4 or 24 h after PTS. This was associated with upregulation of histone deacetylases HDAC1 and HDAC2, but not HDAC4, which did not localize in the nuclei. HDAC2 was found in cell nuclei, HDAC4 in the cytoplasm and HDAC1 both in nuclei and cytoplasm. Histone acetyltransferases HAT1 and PCAF (p300/CBP associated factor) that acetylated histone H3 synthesis were also upregulated, but lesser and later. PTS increased localization of HDAC2 and HAT1 in astroglia. Thus, the cell fate in PTS-induced penumbra is determined by the balance between opposite tendencies leading either to histone acetylation and stimulation of gene expression, or to deacetylation and suppression of transcriptional processes and protein biosynthesis. These epigenetic proteins may be the potential targets for anti-stroke therapy.

Integrated metabolomic and transcriptomic analysis of brain energy metabolism in the male Oriental river prawn (Macrobrachium nipponense) in response to hypoxia and reoxygenation

Hypoxia is as an endocrine disruptor, and, in crustaceans, the energy metabolic consequences of hypoxia in the brain tissue are still poorly understood. We combined gas chromatography-mass spectrometry (GC-MS)-based metabolomic analysis and high-throughput RNA sequencing to evaluate the metabolic effects and subjacent regulatory pathways in the brain tissue of the male Oriental river prawn (Macrobrachium nipponense) in response to hypoxia and reoxygenation. We recorded LC₅₀ and heartbeats per minute of male M. nipponense juveniles. Hypoxia resulted in the generation of reactive oxygen species in the brain cells and alterations in gene expression and metabolite concentrations in the prawn brain tissue in a time-dependent manner. The transcriptomic analyses revealed specific changes in the expression of genes associated with metabolism pathways, which was consistent with the changes in energy metabolism indicated by the GC-MS metabolomic analysis. Quantitative real-time polymerase chain reaction and western blot confirmed the transcriptional induction of these genes because of hypoxia. The lactate levels increased significantly during hypoxia and decreased to normal after reoxygenation; this is consistent with a shift towards anaerobic metabolism, which may cause metabolic abnormalities in the brain tissue of M. nipponense. Overall, these results are consistent with metabolic disruption in the brain of M. nipponense exposed to hypoxia and will help in understanding how crustacean brain tissue adapts and responds to hypoxia and reoxygenation.

Clinical outcome prediction after thrombectomy of proximal middle cerebral artery occlusions by the appearance of lenticulostriate arteries on magnetic resonance angiography: A retrospective analysis

Post-ischemic vasodynamic changes in infarcted brain parenchyma are common and range from hypo- to hyperperfusion. In the present study, appearance of the lenticulostriate arteries (LSAs) on postinterventional 3T time-of-flight (TOF)-MRA suggestive for altered post-stroke vasodynamics following thrombectomy was investigated. Patients who underwent thrombectomy for a proximal MCA occlusion and for whom postinterventional 3T TOF-MRA (median at day 3) was available, were included in this retrospective analysis (n=98). LSA appearance was categorized into presence (LSA-sign⁺) or absence (LSA-sign^-) of vasodilatation in the ischemic hemisphere. Functional outcome was determined using the modified Rankin scale (mRS). LSA-sign⁺ was observed in 64/98 patients. Hypertension (adjusted OR: 0.171, 95% CI: 0.046-0.645) and preinterventional IV rtPA (adjusted OR: 0.265, 95% CI: 0.088-0.798) were associated with absence of the LSA-sign⁺. In multivariate logistic regression, LSA-sign⁺ was associated with substantial neurologic improvement (adjusted OR: 10.18, 95% CI: 2.69-38.57) and good functional outcome (discharge-mRS ≤ 2, adjusted OR: 7.127, 95% CI: 1.913-26.551 and day 90 mRS ≤ 2, adjusted OR: 3.786, 95% CI: 1.026-13.973) after correcting for relevant confounders. For all clinical endpoints, model fit improved when including the LSA-sign term (p<0.05). Asymmetrical dilatation of LSAs following successful thrombectomy indicates favorable neurologic and mid-term functional outcomes. This may indicate preserved cerebral blood flow regulatory mechanisms.