Impaired blood-brain barrier in the microbiota-gut-brain axis: Potential role of bipolar susceptibility gene TRANK1

Bipolar disorder (BD) is a common psychiatric illness with high prevalence and disease burden. Accumulating susceptibility genes for BD have been identified in recent years. However, the exact functions of these genes remain largely unknown. Despite its high heritability, gene and environment interaction is commonly accepted as the major contributing factor to BD pathogenesis. Intestine microbiota is increasingly recognized as a critical environmental factor for human health and diseases via the microbiota-gut-brain axis. BD individuals showed altered diversity and compositions in the commensal microbiota. In addition to pro-inflammatory factors, such as interleukin-6 and tumour necrosis factor-α, type 1 interferon signalling pathway is also modulated by specific intestinal bacterial strains. Disruption of the microbiota-gut-brain axis contributes to peripheral and central nervous system inflammation, which accounts for the BD aetiology. Administration of type 1 interferon can induce the expression of TRANK1, which is associated with elevated circulating biomarkers of the impaired blood-brain barrier in BD patients. In this review, we focus on the influence of intestine microbiota on the expression of bipolar gene TRANK1 and propose that intestine microbiota-dependent type 1 interferon signalling is sufficient to induce the over-expression of TRANK1, consequently causing the compromise of BBB integrity and facilitating the entrance of inflammatory mediators into the brain. Activated neuroinflammation eventually contributes to the occurrence and development of BD. This review provides a new perspective on how gut microbiota participate in the pathogenesis of BD. Future studies are needed to validate these assumptions and develop new treatment targets for BD.     

The blood-brain barrier in health and chronic neurodegenerative disorders

The blood-brain barrier (BBB) is a highly specialized brain endothelial structure of the fully differentiated neurovascular system. In concert with pericytes, astrocytes, and microglia, the BBB separates components of the circulating blood from neurons. Moreover, the BBB maintains the chemical composition of the neuronal "milieu," which is required for proper functioning of neuronal circuits, synaptic transmission, synaptic remodeling, angiogenesis, and neurogenesis in the adult brain. BBB breakdown, due to disruption of the tight junctions, altered transport of molecules between blood and brain and brain and blood, aberrant angiogenesis, vessel regression, brain hypoperfusion, and inflammatory responses, may initiate and/or contribute to a "vicious circle" of the disease process, resulting in progressive synaptic and neuronal dysfunction and loss in disorders such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and others. These findings support developments of new therapeutic approaches for chronic neurodegenerative disorders directed at the BBB and other nonneuronal cells of the neurovascular unit.     

Intermittent Fasting Attenuates Hallmark Vascular and Neuronal Pathologies in a Mouse Model of Vascular Cognitive Impairment

Background - Chronic cerebral hypoperfusion (CCH) is an important pathophysiological mechanism of vascular cognitive impairment (VCI). The heterogeneous effects of CCH complicate establishing single target therapies against VCI and its more severe form, vascular dementia (VaD). Intermittent fasting (IF) has multiple targets and is neuroprotective across a range of disease conditions including stroke, but its effects against CCH-induced neurovascular pathologies remain to be elucidated. We therefore assessed the effect of IF against CCH-associated neurovascular pathologies and investigated its underlying mechanisms.Methods - Male C57BL/6NTac mice were subjected to either ad libitum feeding (AL) or IF (16 hours of fasting per day) for 4 months. In both groups, CCH was experimentally induced by the bilateral common carotid artery stenosis (BCAS) method. Sham operated groups were used as controls. Measures of leaky microvessels, blood-brain barrier (BBB) permeability, protein expression of tight junctions, extracellular matrix components and white matter changes were determined to investigate the effect of IF against CCH-induced neurovascular pathologies.Results - IF alleviated CCH-induced neurovascular pathologies by reducing the number of leaky microvessels, BBB breakdown and loss of tight junctional proteins. In addition, IF mitigated the severity of white matter lesions, and maintained myelin basic protein levels, while concurrently reducing hippocampal neuronal cell death. Furthermore, IF reduced the CCH-induced increase in levels of matrix metalloproteinase (MMP)-2 and its upstream activator MT1-MMP, which are involved in the breakdown of the extracellular matrix that is a core component of the BBB. Additionally, we observed that IF reduced CCH-induced increase in the oxidative stress marker malondialdehyde, and increased antioxidant markers glutathione and superoxide dismutase. Overall, our data suggest that IF attenuates neurovascular damage, metalloproteinase and oxidative stress-associated pathways, and cell death in the brain following CCH in a mouse model of VCI.Conclusion - Although IF has yet to be assessed in human patients with VaD, our data suggest that IF may be an effective means of preventing the onset or suppressing the development of neurovascular pathologies in VCI and VaD.     

Kynurenine pathway metabolism in human blood-brain-barrier cells: implications for immune tolerance and neurotoxicity

The catabolic pathway of l -tryptophan ( l -trp), known as the kynurenine pathway (KP), has been implicated in the pathogenesis of a wide range of brain diseases through its ability to lead to immune tolerance and neurotoxicity. As endothelial cells (ECs) and pericytes of the blood–brain–barrier (BBB) are among the first brain-associated cells that a blood-borne pathogen would encounter, we sought to determine their expression of the KP. Using RT-PCR and HPLC/GC-MS, we show that BBB ECs and pericytes constitutively express components of the KP. BBB ECs constitutively synthesized kynurenic acid, and after immune activation, kynurenine (KYN), which is secreted basolaterally. BBB pericytes produced small amounts of picolinic acid and after immune activation, KYN. These results have significant implications for the pathogenesis of inflammatory brain diseases in general, particularly human immunodeficiency virus (HIV)-related brain disease. Kynurenine pathway activation at the BBB results in local immune tolerance and neurotoxicity: the basolateral secretion of excess KYN can be further metabolized by perivascular macrophages and microglia with synthesis of quinolinic acid. The results point to a mechanism whereby a systemic inflammatory signal can be transduced across an intact BBB to cause local neurotoxicity.     

Oxidative stress activates protein tyrosine kinase and matrix metalloproteinases leading to blood-brain barrier dysfunction

The blood-brain barrier (BBB) formed by brain microvascular endothelial cells (BMVEC) regulates the passage of molecules and leukocytes in and out of the brain. Oxidative stress is a major underlying cause of neurodegenerative and neuroinflammatory disorders and BBB injury associated with them. Using human BMVEC grown on porous membranes covered with basement membrane (BM) matrix (BBB models), we demonstrated that reactive oxygen species (ROS) augmented permeability and monocyte migration across BBB. ROS activated matrix metalloproteinases (MMP-1, -2, and -9) and decreased tissue inhibitors of MMPs (TIMP-1 and -2) in a protein tyrosine kinase (PTK)-dependent manner. Increase in MMPs and PTK activities paralleled degradation of BM protein and enhanced tyrosine phosphorylation of tight junction (TJ) protein. These effects and enhanced permeability/monocyte migration were prevented by inhibitors of MMPs, PTKs, or antioxidant suggesting that oxidative stress caused BBB injury via degradation of BM protein by activated MMPs and by PTK-mediated TJ protein phosphorylation. These findings point to new therapeutic interventions ameliorating BBB dysfunction in neurological disorders such as stroke or neuroinflammation.     

Caveolin-1 regulates nitric oxide-mediated matrix metalloproteinases activity and blood-brain barrier permeability in focal cerebral ischemia and reperfusion injury

The roles of caveolin-1 (cav-1) in regulating blood-brain barrier (BBB) permeability are unclear yet. We previously reported that cav-1 was down-regulated and the production of nitric oxide (NO) induced the loss of cav-1 in focal cerebral ischemia and reperfusion injury. The present study aims to address whether the loss of cav-1 impacts on BBB permeability and matrix metalloproteinases (MMPs) activity during cerebral ischemia-reperfusion injury. We found that focal cerebral ischemia-reperfusion down-regulated the expression of cav-1 in isolated cortex microvessels, hippocampus, and cortex of ischemic brain. The down-regulation of cav-1 was correlated with the increased MMP-2 and -9 activities, decreased tight junction (TJ) protein zonula occludens (ZO)-1 expression and enhanced BBB permeability. Treatment of N(G) -nitro-L-arginine methyl ester [L-NAME, a non-selective nitric oxide synthase (NOS) inhibitor] reserved the expression of cav-1, inhibited MMPs activity, and reduced BBB permeability. To elucidate the roles of cav-1 in regulating MMPs and BBB permeability, we used two approaches including cav-1 knockdown in cultured brain microvascular endothelial cells (BMECs) in vitro and cav-1 knockout (KO) mice in vivo. Cav-1 knockdown remarkably increased MMPs activity in BMECs. Meanwhile, with focal cerebral ischemia-reperfusion, cav-1 deficiency mice displayed higher MMPs activities and BBB permeability than wild-type mice. Interestingly, the effects of L-NAME on MMPs activity and BBB permeability was partly reversed in cav-1 deficiency mice. These results, when taken together, suggest that cav-1 plays important roles in regulating MMPs activity and BBB permeability in focal cerebral ischemia and reperfusion injury. The effects of L-NAME on MMPs activity and BBB permeability are partly mediated by preservation of cav-1.     

Effect of mild hypothermia on blood brain barrier disruption induced by oleic acid in rats

The blood-brain barrier (BBB) is essential for the normal function of the central nervous system. The pathological conditions induced by brain diseases including cerebral ischemia result in the alteration of BBB integrity. This alteration of BBB is relieved by mild hypothermia that has been regarded as an effective therapy for brain injury. Experimental fat embolism by intra-arterial administration of fatty acid induces reversible dysfunction of BBB and is considered as a beneficial method for the research on BBB disruption. However, the implication of hypothermia on the fatty acid-induced BBB disruption is not clear yet. In this study, we aim to investigate the effect of mild hypothermia on BBB disruption by comparing the changes of brain inflammation, free radical production, and matrix metalloproteinases (MMPs) caused by cerebral fatty acid infusion between normothermic (37°C) and hypothermic (33°C) groups. Oleic acid infusion into the carotid artery induced the increase of BBB permeability, which was inhibited by mild hypothermia. Neutrophils were infiltrated and intercellular adhesion molecule-1 (ICAM-1) expression was increased in the vascular structures in the affected brain tissue of normothermic rats at 24 hrs following oleic acid administration. Inducible nitric oxide synthase (iNOS) and nitro-tyrosine immunoreactivities were also observed in the normothermic group. The expression of matrix metalloproteinase (MMP)-2, 3, and 13 were upregulated predominantly in the oleic acid-treated brain of the normothermic rats. In mild hypothermic condition, neutrophil infiltration and ICAM-1 expression were attenuated, whereas the inductions of iNOS, nitrotyrosine and MMPs except MMP3 were not affected. Therefore, we suggest that mild hypothermia contributes to the protective effect on oleic acid-induced BBB damage via reducing neutrophil infiltration and brain inflammation.     

活性氮自由基:脑缺血再灌注损伤过程中引起血脑屏障破坏及调节神经修复的双刃剑(英文)

在脑缺血再灌注损伤中,自由基发挥着重要作用。脑缺血及再灌注可产生大量的自由基,随着这些自由基的聚集,会引发一系列的分子级联反应,从而增加血脑屏障的通透性,诱发脑水肿、出血、炎症反应及细胞死亡。以一氧化氮(NO)及过氧亚硝基阴离子(ONOO-)为代表的活性氮(reactive nitrogen species,RNS),是自由基的重要组成部分,它们在脑缺血再灌注损伤中作用显著。一方面,活性氮能激活基质金属蛋白酶(MMPs),破坏血脑屏障。MMPs作为一大类含2价锌离子的水解酶,其激活可以降解脑血管及神经元细胞外基质。脑缺血再灌注损伤产生NO和ONOO-,它们均可以通过激活MMPs,降解紧密连接蛋白,从而破坏血脑屏障。另一方面,近期研究发现,活性氮也参与了脑缺血后神经再生及修复的调节过程。因此,了解这些活性小分子在血脑屏障破坏及神经再生中的复杂生物活性将很有意义。小窝蛋白1(Caveolin-1)就是活性氮自由基的重要靶分子,它是一种细胞表面的穴样内陷(caveolae)中的膜蛋白,可以通过抑制MMPs的激活保护血脑屏障的完整性。下调Caveolin-1的表达将引起血脑屏障的破坏。脑缺血所产生的NO能下调Caveolin-1的表达,而Caveolin-1的下调,能引起NO合酶的增加,促进生成更多的NO。活性氮与Caveolin-1互相作用,形成了一个反馈回路,通过激活MMPs而造成血脑屏障的不断破坏。此外,Caveolin-1通过调节不同的信号通路,抑制神经干细胞的增长及向神经元分化。因此,活性氮也很可能通过调节Caveolin-1及其他信号通路调控神经再生。在这篇文章中,我们对活性氮在血脑屏障及神经再生中的近期研究进展进行了综述。我们认为,活性氮可能在脑缺血再灌注中起双重作用,既是细胞毒性分子,亦可能是神经再生中的重要信号分子,其作用与其在神经元、内皮细胞及其微环境中产生的量有重要的关系。     

Matrix metalloproteinase-9 deficiency leads to prolonged foreign body response in the brain associated with increased IL-1β levels and leakage of the blood-brain barrier

Matrix metalloproteinases (MMPs) are enzymes with specificity towards extracellular matrix (ECM) components. MMPs, especially MMP-9, have been shown to degrade components of the basal lamina and disrupt the blood-brain barrier (BBB) and thus, contribute to neuroinflammation. In the present study we examined the role of MMP-9 in the foreign body response in the brain. Millipore filters of mixed cellulose ester were implanted into the brain cortex of wild type and MMP-9-null mice for a period of 2 d to 8 wks and the response was analyzed by histology and immunohistochemistry. We observed enhanced and prolonged neuroinflammation in MMP-9-null mice, evidenced by persistence of neutrophils, macrophages/microglia, and reactive astrocytes up to 8 wks post-implantation. In addition, blood vessel density around implants was increased in MMP-9-null mice and detection of mouse serum albumin (MSA) indicated that vessels were leaky. Immunohistochemical and western blot analyses indicated that this defect was associated with the absence of tight junction proteins zonula occludens-1 (ZO-1) and ZO-2 from vessels in proximity to implants. Analysis of brain sections and brain protein extracts revealed that the levels of the pro-inflammatory cytokine interleukin-1β (IL-1β), which is a substrate for MMP-9, were significantly higher in MMP-9-null mice at 8wks post-implantation. Collectively, our studies suggest that increased levels of IL-1β and the delayed repair of BBB are associated with prolongation of the FBR in MMP-9-null mice.     

Ultrasound, microbubbles and the blood-brain barrier

The blood–brain barrier (BBB) is a specialized system of capillary endothelial cells that protects the brain from harmful substances in the blood stream, while supplying the brain with the required nutrients for proper function. The BBB controls transport through both tight junctions and metabolic barriers and is often a rate-limiting factor in determining permeation of therapeutic drugs into the brain. It is a significant obstacle for delivery of both small molecules and macromolecular agents. Although many drugs could be potentially used to treat brain disease, there has been no method that allows non-invasive-targeted delivery through the BBB. Recently, promising studies indicate that ultrasound can be used to locally deliver a drug or gene to a specific region of interest in the brain. If microbubbles are combined with ultrasound exposure, the effects of ultrasound can be focused upon the vasculature to reduce the acoustic intensity needed to produce BBB opening. Several avenues of transcapillary passage after ultrasound sonication have been identified including transcytosis, passage through endothelial cell cytoplasmic openings, opening of tight junctions and free passage through injured endothelium. This article reviews the topic of transient disruption of the BBB with ultrasound and microbubbles and addresses related safety issues. It also discusses possible roles of the BBB in brain disease and potential interactions with ultrasound and microbubbles in such disease states.     

Peripheral inflammatory hyperalgesia modulates morphine delivery to the brain: a role for P-glycoprotein

P-glycoprotein (Pgp, ABCB1) is a critical efflux transporter at the blood-brain barrier (BBB) where its luminal location and substrate promiscuity limit the brain distribution of numerous therapeutics. Moreover, Pgp is known to confer multi-drug resistance in cancer chemotherapy and brain diseases, such as epilepsy, and is highly regulated by inflammatory mediators. The involvement of inflammatory processes in neuropathological states has led us to investigate the effects of peripheral inflammatory hyperalgesia on transport properties at the BBB. In the present study, we examined the effects of lambda-carrageenan-induced inflammatory pain (CIP) on brain endothelium regulation of Pgp. Western blot analysis of enriched brain microvessel fractions showed increased Pgp expression 3 h post-CIP. In situ brain perfusion studies paralleled these findings with decreased brain uptake of the Pgp substrate and opiate analgesic, [(3)H] morphine. Cyclosporin A-mediated inhibition of Pgp enhanced the uptake of morphine in lambda-carrageenan and control animals. This indicates that the CIP induced decrease in morphine transport was the result of an increase in Pgp activity at the BBB. Furthermore, antinociception studies showed decreased morphine analgesia following CIP. The observation that CIP modulates Pgp at the BBB in vivo is critical to understanding BBB regulation during inflammatory disease states.     

Circulating Brain Microvascular Endothelial Cells (cBMECs) as Potential Biomarkers of the Blood–Brain Barrier Disorders Caused by Microbial and Non-Microbial Factors

Despite aggressive research, central nervous system (CNS) disorders, including blood-brain barrier (BBB) injury caused by microbial infection, stroke, abused drugs [e.g., methamphetamine (METH) and nicotine], and other pathogenic insults, remain the world''s leading cause of disabilities. In our previous work, we found that dysfunction of brain microvascular endothelial cells (BMECs), which are a major component of the BBB, could be caused by nicotine, meningitic pathogens and microbial factors, including HIV-1 virulence factors gp41 and gp120. One of the most challenging issues in this area is that there are no available cell-based biomarkers in peripheral blood for BBB disorders caused by microbial and non-microbial insults. To identify such cellular biomarkers for BBB injuries, our studies have shown that mice treated with nicotine, METH and gp120 resulted in increased blood levels of CD146+(endothelial marker)/S100B+ (brain marker) circulating BMECs (cBMECs) and CD133+[progenitor cell (PC) marker]/CD146+ endothelial PCs (EPCs), along with enhanced Evans blue and albumin extravasation into the brain. Nicotine and gp120 were able to significantly increase the serum levels of ubiquitin C-terminal hydrolase 1 (UCHL1) (a new BBB marker) as well as S100B in mice, which are correlated with the changes in cBMECs and EPCs. Nicotine- and meningitic E. coli K1-induced enhancement of cBMEC levels, leukocyte migration across the BBB and albumin extravasation into the brain were significantly reduced in alpha7 nAChR knockout mice, suggesting that this inflammatory regulator plays an important role in CNS inflammation and BBB disorders caused by microbial and non-microbial factors. These results demonstrated that cBMECs as well as EPCs may be used as potential cell-based biomarkers for indexing of BBB injury.     

Roles of microRNAs in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gastrointestinal tract that mainly affects young people. IBD is associated with various gastrointestinal symptoms, and thus, affects the quality of life of patients. Currently, the pathogenesis of IBD is poorly understood. Although intestinal bacteria and host immune response are thought to be major factors in its pathogenesis, a sufficient explanation of their role in its pathophysiologic mechanism has not been presented. MicroRNAs (miRNAs), which are small RNA molecules that regulate gene expression, have gained attention as they are known to participate in the molecular interactions of IBD. Recent studies have confirmed the important role of miRNAs in targeting certain molecules in signaling pathways that regulate the homeostasis of the intestinal barrier, inflammatory reactions, and autophagy of the intestinal epithelium. Several studies have identified the specific miRNAs associated with IBD from colon tissues or serum samples of IBD patients and have attempted to use them as useful diagnostic biomarkers. Furthermore, some studies have attempted to treat IBD through intracolonic administration of specific miRNAs in the form of nanoparticle. This review summarizes the latest findings on the role of miRNAs in the pathogenesis, diagnosis, and treatment of IBD.     

Accumulation of Eu chelates in cells expressing or not P-glycoprotein: Implications for blood-brain barrier crossing

Alzheimer’s disease (AD) is the most commonly form of dementia in the elderly. The development of molecules able to detect biomarkers characteristic of AD is critical to its understanding and treatment. However, such molecules must be able to pass blood-brain barrier (BBB) which is a major impediment to the entry of many therapeutic drugs into the brain. Such a limitation applies to the development of magnetic resonance imaging molecular neuroimaging agents using biomarkers of AD-like β-amyloid deposits, as the common extracellular contrast agents (CAs) are not able to cross an intact BBB. In this work, we have studied the ability of a series of simple Eu³⁺ complexes to enter cells overexpressing or not the ABCB1 (P-gp or P-glycoprotein) protein, which is expressed at the BBB and in human embryonic astrocytes. The intracellular uptake of the Eu³⁺ complexes of linear and macrocyclic polyaminocarboxylate ligands with different charges and lipophilicities was followed by atomic absorption spectrometry. Based on biochemical argument, we propose that lipophilic contrast agents can be efficiently taken up by cells and accumulate inside mitochondria when they are positively charged. The important point is that they are not P-gp substrates, which is one of the major obstacles for them to cross the BBB.     

Annexin A1 restores Aβ1‐42‐induced blood–brain barrier disruption through the inhibition of RhoA‐ROCK signaling pathway

The blood–brain barrier (BBB) is composed of brain capillary endothelial cells and has an important role in maintaining homeostasis of the brain separating the blood from the parenchyma of the central nervous system (CNS). It is widely known that disruption of the BBB occurs in various neurodegenerative diseases, including Alzheimer's disease (AD). Annexin A1 (ANXA1), an anti‐inflammatory messenger, is expressed in brain endothelial cells and regulates the BBB integrity. However, its role and mechanism for protecting BBB in AD have not been identified. We found that β‐Amyloid 1‐42 (Aβ42)‐induced BBB disruption was rescued by human recombinant ANXA1 (hrANXA1) in the murine brain endothelial cell line bEnd.3. Also, ANXA1 was decreased in the bEnd.3 cells, the capillaries of 5XFAD mice, and the human serum of patients with AD. To find out the mechanism by which ANXA1 recovers the BBB integrity in AD, the RhoA‐ROCK signaling pathway was examined in both Aβ42‐treated bEnd.3 cells and the capillaries of 5XFAD mice as RhoA was activated in both cases. RhoA inhibitors alleviated Aβ42‐induced BBB disruption and constitutively overexpressed RhoA‐GTP (active form of RhoA) attenuated the protective effect of ANXA1. When pericytes were cocultured with bEnd.3 cells, Aβ42‐induced RhoA activation of bEnd.3 cells was inhibited by the secretion of ANXA1 from pericytes. Taken together, our results suggest that ANXA1 restores Aβ42‐induced BBB disruption through inhibition of RhoA‐ROCK signaling pathway and we propose ANXA1 as a therapeutic reagent, protecting against the breakdown of the BBB in AD.     

Matrix metalloproteinases inhibition provides neuroprotection against hypoxia-ischemia in the developing brain

The present study was designed to investigate the role of matrix metalloproteinases (MMPs) in the immature brain and the long term effects of early MMPs inhibition after hypoxic-ischemic (HI) injury. HI was induced by unilateral ligation of the right carotid artery followed by hypoxia (8% O₂ for 2 h) in P7 rat pups. GM6001, a broad spectrum MMPs inhibitor, was injected (50 mg/kg or 100 mg/kg) intraperitoneally at 2 h and 24 h after HI injury. Blood-brain barrier (BBB) integrity, brain edema, MMP-2/-9 activity, TIMP-1/-2 and tight junction protein (TJP) level were evaluated using IgG staining, Evan's blue extravasation, brain water content, zymography and western blot. Doxycycline, another MMPs inhibitor, was injected (10 mg/kg or 30 mg/kg) intraperitoneally at 2 h after HI, then BBB integrity and brain edema were measured at 48 h post-HI using brain water content measurement and IgG staining. The long-term effects of early MMPs inhibition (GM6001, 100 mg/kg) were evaluated by neurobehavioral tests, body weight, and brain atrophy measurement. GM6001 attenuated brain edema and BBB disruption at the dosage of 100 mg/kg. MMP-2 activity increased at 24 h and peaked at 48 h after HI, whereas MMP-9 activity peaked at 24 h and tapered by 48 h after HI. MMP-9/-2 activities were significantly attenuated by GM6001 at 24 h and 48 h after HI. The degradation of TJPs (ZO-1 and occludin) at 48 h after HI was reversed by GM6001 treatment. Early MMPs inhibition had long-term effects that attenuated ipsilateral brain tissue loss, and improved neurobehavioral outcomes after HI. These results suggest that early MMPs inhibition with a broad-spectrum inhibitor provides both acute and long-term neuroprotection in the developing brain by reducing TJPs degradation, preserving BBB integrity, and ameliorating brain edema after neonatal HI injury.