Protection Of Blood-brain Barrier Integrity Research Articles

Disruption of blood-brain barrier and endothelial-to-mesenchymal transition are attenuated by Astragalus polysaccharides mediated through upregulation of ETS1 expression in experimental autoimmune encephalomyelitis

Blood-brain barrier (BBB) breakdown, an early hallmark of multiple sclerosis (MS), remains crucial for MS progression. Our previous works have confirmed that Astragalus polysaccharides (APS) can significantly ameliorate demyelination and disease progression in experimental autoimmune encephalomyelitis (EAE) mice. However, it remains unclear whether APS protects BBB and the potential mechanism. In this study, we found that APS effectively reduced BBB leakage in EAE mice, which was accompanied by a decreased level of endothelial-to-mesenchymal transition (EndoMT) in the central nervous system (CNS). We further induced EndoMT in the mouse brain endothelial cells (bEnd.3) by interleukin-1β (IL-1β) in vitro. The results showed that APS treatment could inhibit IL-1β-induced EndoMT and endothelial cell dysfunction. In addition, the transcription factor ETS1 is a central regulator of EndoMT related to the compromise of BBB. We tested the regulation of APS on ETS1 and identified the expression of ETS1 was upregulated in both EAE mice and bEnd.3 cells by APS. ETS1 knockdown facilitated EndoMT and endothelial cell dysfunction, which completely abolished the regulatory effect of APS. Collectively, APS treatment could protect BBB integrity by inhibiting EndoMT, which might be associated with upregulating ETS1 expression. Our findings indicated that APS has potential value in the prevention of MS.

Neutrophil membrane-derived nanoparticles protect traumatic brain injury via inhibiting calcium overload and scavenging ROS

The secondary injury is more serious after traumatic brain injury (TBI) compared with primary injury. Release of excessive reactive oxygen species (ROS) and Ca2+ influx at the damaged site trigger the secondary injury. Herein, a neutrophil-like cell membrane-functionalized nanoparticle was developed to prevent ROS-associated secondary injury. NCM@MP was composed of three parts: (1) Differentiated neutrophil-like cell membrane (NCM) was synthesized, with inflammation-responsive ability to achieve effective targeting and to increase the retention time of Mn3O4 and nimodipine (MP) in deep injury brain tissue via C-X-C chemokine receptor type 4, integrin beta 1 and macrophage antigen-1. (2) Nimodipine was used to inhibit Ca2+ influx, eliminating the ROS at source. (3) Mn3O4 further eradicated the existing ROS. In addition, NCM@MP also exhibited desirable properties for T1 enhanced imaging and low toxicity which may serve as promising multifunctional nanoplatforms for precise therapies. In our study, NCM@MP obviously alleviated oxidative stress response, reduced neuroinflammation, protected blood–brain barrier integrity, relieved brain edema, promoted the regeneration of neurons, and improved the cognition of TBI mice. This study provides a promising TBI management to relieve the secondary spread of damage.Graphical

A novel PROTAC molecule dBET1 alleviates pathogenesis of experimental autoimmune encephalomyelitis in mice by degrading BRD4

Neuroinflammation and neurodegeneration are hallmarks of multiple sclerosis (MS). Bromodomain-containing protein 4 (BRD4), a bromodomain and extra-terminal domain (BET) protein family member, is indispensable for the transcription of pro-inflammatory genes. Therefore, inhibiting BRD4 may be a prospective therapeutic approach for modulating the inflammatory response and regulating the course of MS. dBET1, a newly synthesized proteolysis-targeting chimera (PROTAC), exhibits effectively degrades of BRD4. However, the precise effects of dBET1 on MS require further investigation. Therefore, we assessed the effect of dBET1 in experimental autoimmune encephalomyelitis (EAE), a typical MS experimental model. Our findings revealed that BRD4 is mainly expressed in astrocytes and neurons of the spinal cords, and is up-regulated in the spinal cords of EAE mice. The dBET1 attenuated lipopolysaccharide-induced expression of astrocytic pro-inflammatory mediators and inhibited deleterious molecular activity in astrocytes. Correspondingly, dBET1, used in preventive and therapeutic settings, alleviated the behavioral symptoms in EAE mice, as demonstrated by decreased demyelination, alleviated leukocyte infiltration, reduced microglial and astrocyte activation, and diminished inflammatory mediator levels. In addition, dBET1 corrected the imbalance in peripheral T cells and protected blood–brain barrier integrity in EAE mice. The underlying mechanism involved suppressing the phosphoinositide-3-kinase/protein kinase B, mitogen-activated protein kinase /extracellular signal-regulated kinase, and nuclear factor kappa B pathways. In summary, our data strongly suggests that dBET1 is a promising treatment option for MS.

Adjudin protects blood–brain barrier integrity and attenuates neuroinflammation following intracerebral hemorrhage in mice

Secondary brain injury exacerbates neurological dysfunction and neural cell death following intracerebral hemorrhage (ICH), targeting the pathophysiological mechanism of the secondary brain injury holds promise for improving ICH outcomes. Adjudin, a potential male contraceptive, exhibits neuroprotective effects in brain injury disease models, yet its impact in the ICH model remains unknown. In this study, we investigated the effects of adjudin on brain injury in a mouse ICH model and explored its underlying mechanisms. ICH was induced in male C57BL/6 mice by injecting collagenase into the right striatum. Mice received adjudin treatment (50 mg/kg/day) for 3 days before euthanization and the perihematomal tissues were collected for further analysis. Adjudin significantly reduced hematoma volume and improved neurological function compared with the vehicle group. Western blot showed that Adjudin markedly decreased the expression of MMP-9 and increased the expression of tight junctions (TJs) proteins, Occludin and ZO-1, and adherens junctions (AJs) protein VE-cadherin. Adjudin also decreased the blood–brain barrier (BBB) permeability, as indicated by the reduced albumin and Evans Blue leakage, along with a decrease in brain water content. Immunofluorescence staining revealed that adjudin noticeably reduced the infiltration of neutrophil, activation of microglia/macrophages, and reactive astrogliosis, accompanied by an increase in CD206 positive microglia/macrophages which exhibit phagocytic characteristics. Adjudin concurrently decreased the generation of proinflammatory cytokines, such as TNF-α and IL-1β. Additionally, adjudin increased the expression of aquaporin 4 (AQP4). Furthermore, adjudin reduced brain cell apoptosis, as evidenced by increased expression of anti-apoptotic protein Bcl-2, and decreased expression of apoptosis related proteins Bax, cleaved caspase-3 and fewer TUNEL positive cells. Our data suggest that adjudin protects against ICH-induced secondary brain injury and may serve as a potential neuroprotective agent for ICH treatment.

Exosome-like nanovesicles derived from Momordica charantia ameliorate delayed t-PA thrombolysis-induced hemorrhagic transformation by inhibiting the ONOO−/HMGB1/MMP-9 pathway

Hemorrhagic transformation (HT) and restrictive therapeutic time window are significant limitations of delayed t-PA (tissue-type plasminogen activator) thrombolytic therapy in ischemic stroke patients. Plant Momordica charantia-derived exosome-like nanovesicles (MC-ELNs) can protect the blood–brain barrier (BBB) and inhibit neuronal apoptosis in stroke rats by inhibiting matrix metalloproteinase 9(MMP-9) expression. This study explored the therapeutic function and underlying mechanisms of MC-ELNs in treating HT. In delayed t-PA-treated ischemia-reperfusion rats, MC-ELNs significantly reduced mortality, HT, and cell apoptosis; MC-ELNs improved neurological function and BBB's integrity. MC-ELNs reduced ONOO− and MMP-9 expression and inhibited the release of HMGB1 from intracellular to extracellular in vivo and in vitro. ONOO− donor SIN-1 directly induced extracellular secretion of HMGB1, MC-ELNs and FeTmPyP (ONOO− decomposition catalyst, PDC) significantly reduced the expression of HMGB1 and inhibited MMP-9 activation in vitro. These findings indicate that MC-ELNs could protect BBB integrity and improve t-PA-induced HT by inhibiting the ONOO−/HMGB1/MMP-9 pathway.

Engineered Wnt7a ligands rescue blood-brain barrier and cognitive deficits in a COVID-19 mouse model.

Respiratory infection with SARS-CoV-2 causes systemic vascular inflammation and cognitive impairment. We sought to identify the underlying mechanisms mediating cerebrovascular dysfunction and inflammation following mild respiratory SARS-CoV-2 infection. To this end, we performed unbiased transcriptional analysis to identify brain endothelial cell signalling pathways dysregulated by mouse adapted SARS-CoV-2 MA10 in aged immunocompetent C57Bl/6 mice in vivo. This analysis revealed significant suppression of Wnt/β-catenin signalling, a critical regulator of blood-brain barrier (BBB) integrity. We therefore hypothesized that enhancing cerebrovascular Wnt/β-catenin activity would offer protection against BBB permeability, neuroinflammation, and neurological signs in acute infection. Indeed, we found that delivery of cerebrovascular-targeted, engineered Wnt7a ligands protected BBB integrity, reduced T-cell infiltration of the brain, and reduced microglial activation in SARS-CoV-2 infection. Importantly, this strategy also mitigated SARS-CoV-2 induced deficits in the novel object recognition assay for learning and memory and the pole descent task for bradykinesia. These observations suggest that enhancement of Wnt/β-catenin signalling or its downstream effectors could be potential interventional strategies for restoring cognitive health following viral infections.

Characterization of withanolides and bacoside A-loaded proniosomes: effect on oxidative stress and survival under hypergravity in rodent model

Objective This work provides characterization of withanolides and bacoside A proniosomes, and evaluating their potency in rat model for combating oxidative stress-induced blood–brain barrier (BBB) damage and their survival under hypergravity. Significance The delivery system was aimed for sustained drug release in plasma and brain, which could improve their efficiency and provide a therapeutic approach to combat oxidative damage and restore BBB integrity. Methods Proniosomes were prepared using withanolides extracted from the roots of W. somnifera and bacoside A derived from the leaf extract of B. monnieri by thin film hydration technique. In vitro release of withanolides and bacoside A from the proniosomes was studied. In vivo experiments were conducted in Wistar Albino rat model to evaluate the efficacy of drug-loaded proniosomes in improving the antioxidant activity in plasma and brain, restoring BBB integrity and combating hypergravity conditions. Results The withanolides and bacoside A-loaded proniosomes showed slow and sustained release of just 62.0 ± 2.87 and 62.9 ± 3.41%, respectively, in 9 h period against the release of 98–99% for the extracts that served as control. Trials conducted in vivo revealed a significant (p < .05) increase in the activity of antioxidant enzymes in both plasma and brain. Also, minimal extravasation of Evans blue dye into the brain (15 ± 0.03 and 16 ± 0.03 ng/g in treated groups against 110 ± 0.01 ng/g in control) of the rats fed with drug-loaded proniosomes was indicative of minimal damage to BBB. Rats fed with drug-loaded proniosomes survived to the extent of 75–83.3% against simulated hypergravity as compared to the control group in which only 50% survived. Conclusion Proniosomes provided sustained release of drugs, which helped to protect BBB integrity, thereby combating hypergravity.

Hyperglycemia disrupted the integrity of the blood-brain barrier following diffuse axonal injury through the sEH/NF-κB pathway.

We aimed to investigate the role of soluble epoxide hydrolase for hyperglycemia induced-disruption of blood-brain barrier (BBB) integrity after diffuse axonal injury (DAI). Rat DAI hyperglycemia model was established by a lateral head rotation device and intraperitoneal injection of 50% glucose. Glial fibrillary acidic protein, ionized calcium-binding adapter molecule-1, β-amyloid precursor protein, neurofilament light chain, and neurofilament heavy chain was detected by immunohistochemistry. Cell apoptosis was examined by terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay. The permeability of blood-brain barrier (BBB) was assessed by expression of tight junction proteins, leakage of Evans blue and brain water content. The soluble epoxide hydrolase (sEH) pathway was inhibited by 1-trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl) urea (TPPU) and the nuclear transcription factor kappa B (NF-κB) pathway was inhibited by pyrrolidine dithiocarbamate and activated by phorbol-12-myristate-13-acetate in vivo and/or vitro, respectively. The inflammatory factors were detected by enzyme-linked immunosorbent assay. Hyperglycemia could exacerbate axonal injury, aggravate cell apoptosis and glial activation, worsen the loss of BBB integrity, increase the release of inflammatory factors, and upregulate the expression of sEH and NF-κB. Inhibition of sEH could reverse all these damages and protect BBB integrity by upregulating the expression of tight junction proteins and downregulating the levels of inflammatory factors in vivo and vitro, while the agonist of NF-κB pathway abrogated the protective effects of TPPU on BBB integrity in vitro. sEH was involved in mediating axonal injury induced by hyperglycemia after DAI by disrupting BBB integrity through inducing inflammation via the NF-κB pathway.

Cottonseed oil alleviates ischemic stroke injury by inhibiting ferroptosis.

Ferroptosis has recently been recognized as a new cause of ischemia reperfusion injury due to blood-brain barrier (BBB) disruption followed by secondary iron-loaded transferrin (TF) influx. As a novel and independent cell death pathway, ferroptosis was characterized by iron-dependent lipid peroxidation, decline of GSH, GPX4, and shrinking mitochondria. Cottonseed oil (CSO), a liposoluble solvent, can alleviate ischemia stroke injuries and oxidative stress. However, the effect of CSO on ischemic stroke-induced ferroptosis has not been explored. In this study, we investigated the effect of CSO on ferroptosis caused by cerebral ischemic injury in rats. We conducted the subcutaneous injection of 1.3mL/kg CSO every other day for 3 weeks on rats with middle cerebral artery occlusion-reperfusion (MCAO-R) injury. We used Garcia Test, TTC staining, HE, Nissl and NeuN staining, Evans blue test, 68 Ga-citrate PET, Western blot, immunofluorescence staining, Elisa kits, and transmission electron microscopy to detect the infarct volume, neural injuries, and ferroptosis-related indexes. CSO treatment could significantly ameliorate MCAO-R-induced neurological dysfunction in a male rat model. Furthermore, it reduced infarct volume and neuronal injuries; protected BBB integrity; reduced the influx of iron ion, TF, and TF receptors; up-regulated anti-ferroptosis proteins (GPX4, xCT, HO1, FTH1), while down-regulating ferroptosis-related protein ACSL4; increased the activity of GSH and SOD; and decreased MDA and LPO levels. Mitochondrial destruction induced by ischemic stroke was also alleviated by CSO treatment. CSO treatment can alleviate ischemic stroke injury via ferroptosis inhibition, which provides a new potential therapeutic mechanism for CSO neuroprotection against ischemic stroke.

Inhibition of lysophosphatidic acid receptor 1 relieves PMN recruitment in CNS via LPA1/TSP1/CXCR2 pathway and alleviates disruption on blood-brain barrier following intracerebral haemorrhage in mice

BackgroudThe frequencies of morbidity and impairment associated with spontaneous intracerebral haemorrhage (ICH) are comparatively high. Blood-brain barrier (BBB) integrity was compromised due to subsequent brain injury induced by ICH, which is crucial for a poor prognosis. Polymorphonuclear leukocyte (PMN) strongly modulate the disruption of BBB in the central nervous system (CNS). The lysophosphatidic acid receptor 1 (LPA1) mediated thrombospondin-1 (TSP1) regulation in astrocytes, which induce macrophage inflammatory protein 2(MIP2) secretion. MIP2 enhance PMN recruitment through CXC chemokine type 2 (CXCR2) activation. The purpose of this study was to investigate whether the LPA1-mediated inhibition of PMN recruitment and BBB protection after ICH is regulated by TSP1 and CXCR2 networks.MethodsICH induction was performed in CD1 mice using collagenase administration. AM966, a targeted LPA1 antagonist, was orally administered 1 and 12 h following ICH. further identify possible LPA1-mediated BBB protection mechanisms, we intracerebroventricularly (ICV) administered a CXCR2 ligand MIP2, as well as TSP1 CRISPR activation (ACT) with AM966. Consequently, we performed neurobehavioral, brain water content (BWC), Evans blue staining (EBS), immunofluorescence (IF), and western blot (WB) analyses.ResultsAfter ICH, astrocytes showed signs of LPA1, which peaked after 24 h, while PMN\\ displayed evidence of CXCR2. The AM966-mediated LPA1 suppression relieved PMN recruitment, diminished brain oedema, demonstrated extravasation (as evidenced by EBS), protected BBB integrity, and enhanced neurologic activity following ICH. AM966 treatment strongly reduced TSP1, CXCR2, Occludin, and Claudin-5 expressions and PMN recruitment following ICH, and their expressions were restored by MIP2 and TSP1 CRISPR (ACT).ConclusionsThis study shows that LAP1 suppression reduced PMN recruitment after ICH in mice via TSP1/CXCR2 signalling, which minimized BBB disruption and improved the CNS’s neurobehavioral functioning. Hence, LPA1 is a strong candidate for therapy to reduce PMN recruitment and offer protection of BBB integrity after ICH.

Clarifying the mechanism of apigenin against blood-brain barrier disruption in ischemic stroke using systems pharmacology.

Currently, recombinant tissue plasminogen activator (rtPA) is an effective therapy for ischemic stroke (IS). However, blood-brain barrier (BBB) disruption is a serious side effect of rtPA therapy and may lead to patients' death. The natural polyphenol apigenin has a good therapeutic effect on IS. Apigenin has potential BBB protection, but the mechanism by which it protects the BBB integrity is not clear. In this study, we used network pharmacology, bioinformatics, molecular docking and molecular dynamics simulation to reveal the mechanisms by which apigenin protects the BBB. Among the 146 targets of apigenin for the treatment of IS, 20 proteins were identified as core targets (e.g., MMP-9, TLR4, STAT3). Apigenin protects BBB integrity by inhibiting the activity of MMPs through anti-inflammation and anti-oxidative stress. These mechanisms included JAK/STAT, the toll-like receptor signaling pathway, and Nitrogen metabolism signaling pathways. The findings of this study contribute to a more comprehensive understanding of the mechanism of apigenin in the treatment of BBB disruption and provide ideas for the development of drugs to treat IS.

Purinergic signaling: A gatekeeper of blood-brain barrier permeation.

This review outlined evidence that purinergic signaling is involved in the modulation of blood-brain barrier (BBB) permeability. The functional and structural integrity of the BBB is critical for maintaining the homeostasis of the brain microenvironment. BBB integrity is maintained primarily by endothelial cells and basement membrane but also be regulated by pericytes, neurons, astrocytes, microglia and oligodendrocytes. In this review, we summarized the purinergic receptors and nucleotidases expressed on BBB cells and focused on the regulation of BBB permeability by purinergic signaling. The permeability of BBB is regulated by a series of purinergic receptors classified as P2Y1, P2Y4, P2Y12, P2X4, P2X7, A1, A2A, A2B, and A3, which serve as targets for endogenous ATP, ADP, or adenosine. P2Y1 and P2Y4 antagonists could attenuate BBB damage. In contrast, P2Y12-mediated chemotaxis of microglial cell processes is necessary for rapid closure of the BBB after BBB breakdown. Antagonists of P2X4 and P2X7 inhibit the activation of these receptors, reduce the release of interleukin-1 beta (IL-1β), and promote the function of BBB closure. In addition, the CD39/CD73 nucleotidase axis participates in extracellular adenosine metabolism and promotes BBB permeability through A1 and A2A on BBB cells. Furthermore, A2B and A3 receptor agonists protect BBB integrity. Thus, the regulation of the BBB by purinergic signaling is complex and affects the opening and closing of the BBB through different pathways. Appropriate selective agonists/antagonists of purinergic receptors and corresponding enzyme inhibitors could modulate the permeability of the BBB, effectively delivering therapeutic drugs/cells to the central nervous system (CNS) or limiting the entry of inflammatory immune cells into the brain and re-establishing CNS homeostasis.

Inducible Pluripotent Stem Cell-Derived Small Extracellular Vesicles Rejuvenate Senescent Blood-Brain Barrier to Protect against Ischemic Stroke in Aged Mice.

Blood-brain barrier (BBB) breakdown after ischemic stroke exacerbates brain injury and BBB senescence can cause severe neurological deficits in aged ischemic stroke population. Recent evidence reveals that inducible pluripotent stem cell-derived small extracellular vesicles (iPSC-sEVs) possess phenomenal antisenescence capability. However, whether iPSC-sEVs can rejuvenate BBB senescence to improve stroke outcomes in aged mice remains unknown. Here, we showed that long-term treatment with iPSC-sEVs alleviated aging-induced BBB senescence in aged mice. In aged stroke mice, iPSC-sEVs significantly mitigated BBB integrity damage, reduced the following infiltration of peripheral leukocytes, and decreased the release of pro-inflammatory factors from the leukocytes, which ultimately inhibited neuronal death and improved neurofunctional recovery. Mechanism studies showed that iPSC-sEVs could activate the endothelial nitric oxide synthase (eNOS) and up-regulate sirtuin 1 (Sirt1) in senescent endothelial cells. Blocking the activation of eNOS abolished iPSC-sEV-mediated rejuvenation of BBB senescence and the protection of BBB integrity. Proteomics results demonstrated that iPSC-sEVs were enriched with bioactive factors including AKT serine/threonine kinase 1 (AKT1) and calmodulin (CALM) to activate the eNOS-Sirt1 axis. Further investigation showed that AKT1 and CALM inhibitors blocked iPSC-sEV-afforded activation of the eNOS-Sirt1 axis in senescent endothelial cells. Taken together, iPSC-sEVs can protect against ischemic stroke in aged mice by rejuvenating BBB senescence, partially, through delivering AKT1 and CALM to activate eNOS-Sirt1 axis, which indicates that iPSC-sEVs treatment is an effective alternative to treat ischemic stroke in the aged population.

VEGF regulates the blood‑brain barrier through MMP‑9 in a rat model of traumatic brain injury.

Blood-brain barrier (BBB) damage is closely related to morbidity and mortality in patients with traumatic brain injury (TBI). Inhibition of VEGF effectively protects BBB integrity in clinical ischemic stroke. Protecting BBB integrity, reducing brain edema and alleviating post-TBI secondary brain injury are key to a favorable patient prognosis. MMP-9 affects BBB integrity by destroying the tight junction of vascular endothelial cells and inhibiting the transport and enzymatic systems. The present study aimed to examine the possible interplay between VEGF and MMP-9 in TBI. A TBI model was established in 87 male Sprague-Dawley rats. Reverse transcription-quantitative PCR, western blotting, wet-dry brain edema assessment, TUNEL and Fluoro-Jade C staining were performed to analyze the brain tissue samples of the rats. The results showed that compared with in the Sham group rats, the mRNA and protein expression levels of VEGF and MMP-9 were increased at 24 h post-TBI. After bevacizumab treatment, BBB permeability and nerve cell apoptosis were markedly reduced. In conclusion, the present study revealed a potential role for TBI-associated VEGF and MMP-9 upregulation in BBB disruption and nerve damage post-TBI.

Walnut-derived peptides ameliorate d-galactose-induced memory impairments in a mouse model via inhibition of MMP-9-mediated blood–brain barrier disruption

Disruption of the blood–brain barrier (BBB) has been observed in several neurological diseases. This study explored the protective effect of the walnut-derived peptide TWLPLPR (TW-7) against d-galactose (d-gal)-induced cognitive disturbance in mice and its potential protection mechanism in β-amyloid 25–35 (Aβ25-35)-injured bEnd.3 cells. TW-7 improved the learning ability and memory of the cognitive impairment mice. Transmission electron microscopy showed that the BBB integrity in the hippocampus was restored; while immunofluorescence analysis and western blotting indicated that the protection of BBB integrity was associated with increased expression levels of tight junction (TJ) proteins. In Aβ25-35-damaged bEnd.3 cells, treatment with a matrix metalloproteinase 9 (MMP-9) activator and inhibitor confirmed that TW-7 partially reduced MMP-9 expression and increased zonula occludin-1 (ZO-1) and Claudin-5 expression. Furthermore, TW-7 reduced MMP-9 levels by forming stable complexes with it and by inhibiting the NF-κB p65/iNos pathway. These data suggested that TW-7 maintains BBB integrity by inhibiting the expression and activity of MMP-9, and TW-7 improves learning and memory ability in mice.

Melatonin Offers Dual-Phase Protection to Brain Vessel Endothelial Cells in Prolonged Cerebral Ischemia-Recanalization Through Ameliorating ER Stress and Resolving Refractory Stress Granule.

Ischemic-reperfusion injury limits the time window of recanalization therapy in cerebral acute ischemic stroke (AIS). Brain vessel endothelial cells (BVECs) form the first layer of the blood-brain barrier (BBB) and are thus the first sufferer of ischemic-reperfusion disorder. The current study demonstrates that melatonin can reduce infarct volume, alleviate brain edema, ameliorate neurological deficits, and protect BBB integrity in prolonged-stroke mice. Here, we demonstrate that endoplasmic reticulum (ER)-associated injury contributes to BVEC death in the dural phase of reperfusion after prolonged ischemia. When encountering ischemia, ER stress arises, specifically activating PERK-EIF2α signaling and the subsequent programmed cell death. Prolonged ischemia leads stress granules (SGs) to be refractory, which remain unresolved and accumulate in ER during recanalization. During reperfusion, refractory SGs activate PKR-EIF2α and further exacerbate BVEC injury. We report that melatonin treatment downregulates ER stress in the ischemic period and enhances dissociation of the refractory SGs during reperfusion, thus offering dual-phase protection to BVECs in prolonged cerebral stroke. Mechanistically, melatonin enhances autophagy in BVECs, which preserves ER function and resolves refractory SGs. We, therefore, propose that melatonin is a potential treatment to extend the time window of delayed recanalization therapy in AIS.

Dexmedetomidine post-conditioning protects blood-brain barrier integrity by modulating microglia/macrophage polarization via inhibiting NF-κB signaling pathway in intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) is one of the most devastating forms of stroke. Dexmedetomidine (DEX) has shown certain neuroprotective roles in ICH. Nevertheless, the details concerning the underlying molecular mechanism of DEX’s protective effects still need further elucidation. Herein, a model of ICH was established. The rats were randomly divided into the sham group, the ICH group, and the ICH + DEX group. Neurological outcomes, neuronal injury, and apoptosis were evaluated. Brain water content, Evans blue extravasation, and the expression of tight junction-associated proteins were also detected to assess the blood-brain barrier (BBB) integrity. Subsequently, the microglia/macrophage polarization state and inflammatory cytokine levels were observed. To further explore the underlying mechanism, NF-κB signaling pathway-associated proteins were detected. The results showed that DEX exerted neuroprotective effects against ICH-induced neurological deficits. DEX significantly increased the numbers of the surviving neurons and ameliorated neuronal cell loss and apoptosis in ICH. The rats that received the DEX displayed a lower level of brain water content and EB extravasation, moreover, ZO-1, occludin, and claudin-5 were markedly increased by DEX. Additionally, DEX facilitated M2 microglia/macrophage polarization, the M1-associated markers were reduced by DEX, while the M2-associated identification significantly increased. We found that DEX dramatically diminished pro-inflammatory cytokines expression, simultaneously promoting anti-inflammatory cytokines expression. DEX inhibited nuclear translocation of NF-κB in ICH rats. Our data suggest that DEX post-conditioning protects BBB integrity by modulating microglia/macrophage polarization via inhibiting the NF-κB signaling pathway in ICH.

Microglia Regulate Blood-Brain Barrier Integrity via MiR-126a-5p/MMP9 Axis during Inflammatory Demyelination.

Blood–brain barrier (BBB) impairment is an early prevalent feature of multiple sclerosis (MS), and remains vital for MS progression. Microglial activation precedes BBB disruption and cellular infiltrates in the brain of MS patients. However, little is known about the function of microglia in BBB impairment. Here, microglia acts as an important modulator of BBB integrity in inflammatory demyelination. Microglial depletion profoundly ameliorates BBB impairment in experimental autoimmune encephalomyelitis (EAE). Specifically, miR‐126a‐5p in microglia is positively correlated with BBB integrity in four types of MS plaques. Mechanistically, microglial deletion of miR‐126a‐5p exacerbates BBB leakage and EAE severity. The protective effect of miR‐126a‐5p is mimicked and restored by specific inhibition of MMP9 in microglia. Importantly, Auranofin, an FDA‐approved drug, is identified to protect BBB integrity and mitigate EAE progression via a microglial miR‐126a‐5p dependent mechanism. Taken together, microglia can be manipulated to protect BBB integrity and ameliorate inflammatory demyelination. Targeting microglia to regulate BBB permeability merits consideration in therapeutic interventions in MS.

Targeting Oxidative Stress and Inflammatory Response for Blood-Brain Barrier Protection in Intracerebral Hemorrhage.

Significance: Blood-brain barrier (BBB) disruption is a major pathological change after intracerebral hemorrhage (ICH) and is both the cause and result of oxidative stress and of the immune response post-ICH. These processes contribute to ICH-induced brain injury. Recent Advances: After the breakdown of cerebral vessels, blood components, including erythrocytes and their metabolites, thrombin, and fibrinogen, can access the cerebral parenchyma through the compromised BBB, triggering oxidative stress and inflammatory cascades. These aggravate BBB disruption and contribute to further infiltration of blood components, resulting in a vicious cycle that exacerbates brain edema and neurological injury after ICH. Experimental and clinical studies have highlighted the role of BBB disruption in ICH-induced brain injury. Critical Issues: In this review, we focus on the strategies to protect the BBB in ICH. Specifically, we summarize the evidence and the underlying mechanisms, including the ICH-induced process of oxidative stress and inflammatory response, and we highlight the potential therapeutic targets to protect BBB integrity after ICH. Future Directions: Future studies should probe the mechanism of ferroptosis as well as oxidative stress-inflammation coupling in BBB disruption after ICH and investigate the effects of antioxidants and immunomodulatory agents in more ICH clinical trials. Antioxid. Redox Signal. 37, 115-134.

Nicotinamide Mononucleotide Adenylyltransferase 1 Regulates Cerebral Ischemia-Induced Blood-Brain Barrier Disruption Through NAD+/SIRT1 Signaling Pathway.

The molecular mechanisms of blood-brain barrier (BBB) disruption in the early stage after ischemic stroke are poorly understood. In the present study, we investigated the potential role of nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) in ischemia-induced BBB damage using an animal middle cerebral artery occlusion (MCAO) model of ischemic stroke. Recombinant human NMNAT1 (rh-NMNAT1) was administered intranasally and Sirtuin 1 (SIRT1) siRNA was administered by intracerebroventricular injection. Our results indicate that rh-NMNAT1 reduced infarct volume, improved functional outcome, and decreased BBB permeability in mice after ischemic stroke. Furthermore, rh-NMNAT1 prevented the loss of tight junction proteins (occludin and claudin-5) and reduced cell apoptosis in ischemic microvessels. NMNAT1-mediated BBB permeability was correlated with the elevation of nicotinamide adenine dinucleotide (NAD+)/NADH ratio and SIRT1 level in brain microvascular endothelial cells. In addition, rh-NMNAT1 treatment significantly decreased the levels of acetylated nuclear factor-κB, acetylated p53, and matrix metalloproteinase-9 in ischemic microvessels. Moreover, the protective effects of rh-NMNAT1 could be reversed by SIRT1 siRNA. In conclusion, these findings indicate that rh-NMNAT1 protects BBB integrity after cerebral ischemia via the NAD+/SIRT1 signaling pathway in brain microvascular endothelial cells. NMNAT1 may be a novel potential therapeutic target for reducing BBB disruption after ischemic stroke.