Fibroblast growth factors preserve blood-brain barrier integrity through RhoA inhibition after intracerebral hemorrhage in mice

Fibroblast growth factors (FGFs) maintain and promote vascular integrity; however whether FGFs protect the blood-brain barrier (BBB) after intracerebral hemorrhage (ICH) remains unexplored. In this present study, we hypothesized that exogenous FGF administration attenuates brain injury after ICH, specifically by preserving endothelial adherens junctions, therefore reducing vasogenic brain edema and attenuating neurofunctional deficits in mice subjected to experimental ICH. Acid fibroblast growth factor (FGF1) or basic fibroblast growth factor (FGF2) was administered intracerebroventricularly (ICV) at 0.5 h after intrastriatal injection of bacterial collagenase (cICH) or autologous whole blood (bICH). Fibroblast growth factor receptor (FGFR) inhibitor PD173074 and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 were additionally administered with FGF2. The selective Rho-associated coiled-coil forming protein serine/threonine kinase (ROCK) inhibitor Y27632 was independently administered at 0.5 h after cICH. Brain water content and neurofunctional deficits were evaluated at 24 and 72h after ICH induction. Evans blue extravasation as well as Western blot analysis for the quantification of activated FGFR, Akt, Ras-related C3 botulinum toxin substrate 1 (Rac1), Ras homolog gene family member A (RhoA) and adherens junction proteins (p120-catenin, β-catenin and VE-cadherin) were conducted at 72 h post-cICH. FGF treatment reduced perihematomal brain edema and improved neurofunctional deficits at 72 h after experimental ICH (p<0.05, compared to vehicle); however, FGFR and PI3K inhibition reversed these neuroprotective effects. Exogenous FGF2 increased activated FGFR, Akt, and Rac1 but reduced activated RhoA protein expression at 72 h after cICH (p<0.05, compared to vehicle), which was reversed by FGFR and PI3K inhibition. Y27632 treatment reduced brain injury at 72 h after cICH (p<0.05, compared to vehicle) and increased the expression of catenins (p120-catenin, β-catenin). In conclusion, our findings suggest that exogenous FGF treatment reduced RhoA activity via FGFR-induced activation of the PI3K-Akt-Rac1 signaling pathway, thus preserving BBB integrity, and therefore attenuating secondary brain injury after experimental ICH in mice.     

Imatinib preserves blood–brain barrier integrity following experimental subarachnoid hemorrhage in rats

Blood–brain barrier (BBB) disruption and consequent edema formation contribute to the development of early brain injury following subarachnoid hemorrhage (SAH). Various cerebrovascular insults result in increased platelet‐derived growth factor receptor (PDGFR)‐α stimulation, which has been linked to BBB breakdown and edema formation. This study examines whether imatinib, a PDGFR inhibitor, can preserve BBB integrity in a rat endovascular perforation SAH model. Imatinib (40 or 120 mg/kg) or a vehicle was administered intraperitoneally at 1 hr after SAH induction. BBB leakage, brain edema, and neurological deficits were evaluated. Total and phosphorylated protein expressions of PDGFR‐α, c‐Src, c‐Jun N‐terminal kinase (JNK), and c‐Jun were measured, and enzymatic activities of matrix metalloproteinase (MMP)?2 and MMP‐9 were determined in the injured brain. Imatinib treatment significantly ameliorated BBB leakage and edema formation 24 hr after SAH, which was paralleled by improved neurological functions. Decreased brain expressions of phosphorylated PDGFR‐α, c‐Src, JNK, and c‐Jun as well as reduced MMP‐9 activities were found in treated animals. PDGFR‐α inhibition preserved BBB integrity following experimental SAH; however, the protective mechanisms remain to be elucidated. Targeting PDGFR‐α signaling might be advantageous to ameliorate early brain injury following SAH. © 2014 Wiley Periodicals, Inc.     

Endothelial TREM-1 receptor regulates the blood–brain barrier integrity after intracerebral hemorrhage in mice via SYK/β-catenin signaling

Background

Intracerebral hemorrhage (ICH) is a high mortality and disability stroke subtype. Destruction of the blood–brain barrier (BBB) is a crucial contributor to brain edema and neurological deficit after ICH. Triggering receptor expressed on myeloid cells 1 (TREM-1) has been reported to be expressed in endothelial cells, but its role in ICH remains unclear. This study aims to evaluate the role of TREM-1 on BBB permeability after ICH in mice.

Methods

Two hundred and forty-two CD1 mice were used in this study. The ICH model was established by collagenase injection. LP17 was administered intranasally at 2 or 8 h after ICH to inhibit TREM-1. To explore the underlying mechanism, SYK activation CRISPR was administered intracerebroventricularly with LP17, and Anti-mouse TREM-1 rat IgG2a (a specific TREM-1 agonist) was injected intracerebroventricularly with R406 (a specific SYK inhibitor) intraperitoneally. Neurobehavioral outcome, brain water content, BBB permeability, and protein expression were evaluated.

Results

The expression level of the TREM-1 receptor increased rapidly as early as 6 h after ICH, and it was mainly expressed on the endotheliocytes in the neurovascular unit. Early and delayed administration of LP17 significantly decreased brain edema and improved neurobehavioral outcomes at 24 h after ICH. LP17 reduced the BBB permeability by increasing β-catenin, claudin-5 and ZO-1 expression. Furthermore, SYK activation CRISPR abolished the beneficial effect of LP17 on the expression of the above junction molecules. Meanwhile, R406 reversed the impact of the TREM-1 activator on the downregulation of β-catenin, claudin-5 and ZO-1 expression.

Conclusions

This study demonstrated that TREM-1 deteriorated BBB permeability via modulating the expression of interendothelial junction molecules after ICH, and this regulation is partly mediated by the SYK/β-catenin signaling pathway.     

大鼠脑出血后行为学、组织学及脑水肿相关性研究

目的 探讨胶原酶诱导大鼠脑出血(ICH)后大鼠行为学的改变及其与脑水肿、组织学改变之间的关系.方法 纹状体区立体定向注射胶原酶建立大鼠纹状体ICH模型,动态观察大鼠ICH后28 d内的行为学、组织学及脑含水量改变.行为学评分采用前肢放置实验、Berderson评分法及角落转向实验,组织学观察采用HE染色,脑含水量测定采用干-湿重法.结果 (1)三种行为学试验结果均提示ICH后第2天大鼠出现严重的神经功能障碍,并在4周内神经功能逐渐恢复;(2)组织学观察显示ICH后存在组织损伤和修复过程;(3)脑含水量测定显示ICH后第2天脑水肿最为明显.在14 d内基本消退;(4)ICH后大鼠前肢放置实验评分和脑水肿之间存在负相关(20.774,P<0.05).结论 (1)大鼠ICH后神经功能存在损伤和修复过程;(2)大鼠ICH后神经功能改善仞期与脑水肿消退相关,而后期则可能与组织自身修复过程相关.     

脑出血后脑水肿经时变化机制的探讨

目的 研究脑出血(mtracerebral hemorrhage，ICH)后血肿周围脑水肿与血脑屏障(blood-brain barrier，BBB)随时间变化的机制，从而为预防脑水肿提供依据。方法90只大耳白兔随机分为3组。1组：在立体定向仪下将300μl生理盐水注入兔左侧基底节；2组：注入200μl自身动脉血与100μl生理盐水；3组：注入200μl自身动脉血与100μl水蛭素。每组每时相(6h、12h、24h、48h、72h)各6只兔。脑组织含水量采用干湿重法测量，血脑屏障的通透性测定采用伊文思兰法。结果动脉血组及水蛭素干预组血肿周围脑组织含水量均在48h达到高峰．此后逐步降低。动脉血组伊文思兰(EB)于24h到达高峰，水蛭素干预组伊文思兰(EB)于48h达高峰。结论脑出血后脑水肿是多种因素综合作用的结果。早期可能和血块凝缩、流体静力压有关；至中期时凝血酶是主导因素；后期则主要由于红细胞裂解物的损害。     

Minocycline protects the blood-brain barrier and reduces edema following intracerebral hemorrhage in the rat

Intracerebral hemorrhage (ICH) results from rupture of a blood vessel in the brain. After ICH, the blood–brain barrier (BBB) surrounding the hematoma is disrupted, leading to cerebral edema. In both animals and humans, edema coincides with inflammation, which is characterized by production of pro-inflammatory cytokines, activation of resident brain microglia and migration of peripheral immune cells into the brain. Accordingly, inflammation is an attractive target for reducing edema following ICH. In the present study, BBB damage was assessed by quantifying intact microvessels surrounding the hematoma, monitoring extravasation of IgG and measuring brain water content 3 days after ICH induced by collagenase injection into the rat striatum. In the injured brain, the water content increased in both ipsilateral and contralateral hemispheres compared with the normal brain. Quantitative real-time RT-PCR revealed an up-regulation of inflammatory genes associated with BBB damage; IL1β, TNFα and most notably, MMP-12. Immunostaining showed MMP-12 in damaged microvessels and their subsequent loss from tissue surrounding the hematoma. MMP-12 was also observed for the first time in neurons. Dual-antibody labeling demonstrated that neutrophils were the predominant source of TNFα protein. Intraperitoneal injection of the tetracycline derivative, minocycline, beginning 6 h after ICH ameliorated the damage by reducing microvessel loss, extravasation of plasma proteins and edema; decreasing TNFα and MMP-12 expression; and reducing the numbers of TNFα-positive cells and neutrophils in the brain. Thus, minocycline, administered at a clinically relevant time, appears to target the inflammatory processes involved in edema development after ICH.     

水通道蛋白4与脑出血后脑水肿形成的关系研究

目的：研究水通道蛋白4（AQP4）在脑出血后脑水肿形成中的作用。方法：以AQP4基因敲除（AQP4^-/-）小鼠为研究对象,分别在AQP4^＋/＋和野生型（AQP4^-/-）小鼠右侧基底节区立体定向注入5μL自体全血建立脑出血模型。比较两组小鼠脑出血后神经功能缺损、脑含水量、血肿周围组织脑比重、伊文思蓝漏出量及脑组织毛细血管超微结构间的差异。结果：脑出血后AQP4^＋/＋小鼠脑内AQP4蛋白表达量显著增高。AQP4基因的缺失加剧了脑出血神经功能缺损及患侧大脑半球的含水量,降低了血肿周围组织的脑比重,加剧了伊文思蓝的渗漏及毛细血管超微结构的损坏。结论：AQP4基因缺失加剧了脑出血损伤,包括水肿形成、血脑屏障破坏。对脑出血后AQP4表达增高的保护性机制研究可能会为临床治疗脑出血后脑水肿提供新的靶点及思路。     

Blood-brain barrier disruption following subarchnoid hemorrhage may be faciliated through PUMA induction of endothelial cell apoptosis from the endoplasmic reticulum

The blood–brain barrier (BBB) plays a vital role as both a physiologic and physical barrier in regulating the movement of water from the vasculature to the brain. During a subarachnoid hemorrhage (SAH), the BBB is disrupted by a variety of mediators, one of which can result in endothelial cell death. As a result, in the present study, we investigated the role of PUMA (p53 upregulated modulator of apoptosis) following SAH injury in rats. Specifically evaluating whether through the endoplasmic reticulum (ER), PUMA could orchestrate the induction of endothelial cell apoptosis and cause a disruption in the blood–brain barrier integrity. One hundred twelve male Sprague–Dawley rats were randomly divided into 4 groups: sham, SAH, SAH + control siRNA, SAH + PUMA siRNA. Outcomes measured include mortality rate, brain edema, BBB disruption, and neurobehavioral testing. We also used Western blotting techniques to measure the expression of key pro-apoptotic proteins such as BAX, BAK, and DRP1. PUMA siRNA treatment significantly reduced the mortality rate, cerebral edema, neurobehavioral deficits, and BBB disruption as measured by Evans blue assay following SAH injury. The T2WI images showed there was an increase in vasogenic edema in the brain following SAH, which could be alleviated by PUMA siRNA. Immunohistochemical staining and Western blot analysis demonstrated an increased expression of PUMA, BAX, BAK, GRP78 and DRP1 in the microvascular endothelial cells of the hippocampus, which was accompanied with endothelium apoptosis. This study showed that PUMA induced endothelial cell apoptosis may in fact play a significant role in BBB disruption following SAH and its mediation may be through the endoplasmic reticulum. By blocking the activity of PUMA using siRNA, we were able to prevent the accumulation of cerebral edema that occurs following BBB disruption. This translated into a preservation of functional integrity and an improvement in mortality.     

Sphingosine-1-phosphate receptor 3 is implicated in BBB injury via the CCL2-CCR2 axis following acute intracerebral hemorrhage

BackgroundIntracerebral hemorrhage (ICH) is a catastrophic cerebrovascular disease with high morbidity and mortality. Evidence demonstrated that sphingosine‐1‐phosphate receptor (S1PR) plays a vital role in inflammatory damage via the upregulation of CCL2 expression. However, whether S1PR3 is involved in blood‐brain barrier (BBB) breakdown via CCL2 activation after ICH has not been described.MethodsWe investigated the expression profiles of all S1PRs using high‐throughput RNA‐seq analysis and RT‐PCR. The potential role of S1PR3 and interaction between S1PR3 and CCL2 were evaluated via Western blotting, immunofluorescence, and flow cytometry. BBB disruption was examined via magnetic resonance imaging, transmission electron microscopy, and Evans blue extravasation. Microglial activation, proliferation, and polarization were assessed via histopathological analysis. The expression levels of CCL2, p‐p38 MAPK, ICAM‐1, and ZO‐1 were examined in vitro and in vivo.ResultsThe present results showed that the levels of S1PR3 and its ligand, sphingosine 1‐phosphate (S1P), were dramatically increased following ICH, which regulated the expression of CCL2 and p38MAPK. Moreover, reductions in brain edema volume, amelioration of BBB integrity, and improvements in behavioral deficits were achieved after the administration of CAY10444, an S1PR3 antagonist, to rats. Remarkably increased CCL2, p‐p38MAPK, and ICAM‐1 expression and decreased ZO‐1 expression were observed in cocultured human astrocytes (HAs) and hCMEC/D3 cells after S1P stimulation. However, the expression levels of CCL2, p‐p38 MAPK, and ICAM‐1 were decreased and ZO‐1 expression was increased after S1PR3 inhibition. In addition, microglial proliferation and M1 polarization were attenuated after CAY10444 administration.ConclusionTo the best of our knowledge, this is the first demonstration of the neuroprotective role of S1PR3 modulation in maintaining BBB integrity by inhibiting the S1PR3‐CCL2 axis after ICH, providing a novel treatment for ICH by targeting S1PR3.     

Intracerebral hemorrhage in mice: model characterization and application for genetically modified mice.

Gene knockout or transgenic animals may assist in elucidating the mechanisms of brain injury after intracerebral hemorrhage (ICH). However, almost all commercially available transgenic or knockout animals are mice. The purpose of this study was to develop an ICH model in mice and to investigate the influence of gender and complement C5 genetic differences on outcome after ICH. Male and female C57BL/6 mice and C5-deficient and -sufficient control mice were anesthetized and then received an injection of 30 microL autologous whole blood into the right basal ganglia. Brain water content was studied at 1 and 3 days after ICH. Behavioral tests (fore-limb use asymmetry and corner turn test) were performed at 1, 3, 7, 14, 21, or 28 days after ICH. In male mice, brain water content was significantly increased in the ipsilateral basal ganglia 1 and 3 days after ICH, compared with saline injection controls (P < 0.01). There were marked neurological deficits 1 and 3 days after ICH, with progressive recovery over 28 days. In contrast, although brain edema and behavioral deficits were similar at 1 day after ICH in female and male mice, female mice showed reduced edema at 3 days and a faster recovery of behavioral deficits after ICH. 17 beta-estradiol treatment in male mice markedly reduced ICH-induced edema (P < 0.01). Brain water content was significantly increased in C5-deficient mice compared with C5-sufficient at 3 days after ICH (P < 0.05). These findings suggest that the mouse ICH model is a reproducible and feasible model. These results also suggest that gender and complement C5 are factors affecting brain injury after ICH.     

Effects of Aquaporin-4 on edema formation following intracerebral hemorrhage

ObjectiveIntracerebral hemorrhage (ICH) constitutes 10% to 15% of all strokes and is associated with high morbidity and mortality. To date, little is known about the role of AQP4 (Aquaporin-4), which is abundantly expressed in pericapillary astrocyte foot processes and in edema formation after intracerebral hemorrhage. The purpose of this study was to examine the role of AQP4 in edema formation after ICH by using AQP4^?/? mice.MethodsICH was induced by microinjecting 5 µl autologous whole blood into the striatum of AQP4^+/+ and AQP4^?/? mice. We compared neurological deficits, brain edema contents of whole hemorrhagic ipsilateral hemisphere, specific gravity of brain tissue surrounding hematoma, Evans blue leakage and ultrastructure of brain microvessels between AQP4^+/+ and AQP4^?/? mice following ICH. Histological changes were also detected with Nissl's staining and TUNEL staining.ResultsOur experiments showed a significant increase of AQP4 expression following ICH in AQP4^+/+ mice. AQP4 deletion aggravated neurological deficits and brain edema contents of whole hemorrhagic ipsilateral hemisphere. Besides, it also reduced the specific gravity of brain tissue surrounding hematoma. Moreover, it enhanced Evans blue leakage and ultrastructure of brain microvessel damage. Histology also showed less Nissl's staining and more TUNEL staining in AQP4^?/? mice following ICH.ConclusionsThese results suggest that AQP4 deletion increases ICH damage, including edema formation, blood–brain barrier damage and neuronal death/TUNEL-positive cells. Further studies on the protective role of activated AQP4 expression following ICH may provide useful therapeutic target for ICH-induced brain injury.     

Oxidative brain injury from extravasated erythrocytes after intracerebral hemorrhage

Intracerebral infusion of lysed erythrocytes causes brain edema without inducing ischemic cerebral blood flow. Reports have indicated that oxidative damage contributes to secondary brain injury in stroke. In the present study, we investigated whether erythrocyte lysis after intracerebral hemorrhage (ICH) might result in oxidative brain damage. This study had four parts. Male Sprague-Dawley rats received an infusion of autologous lysed erythrocytes into the right striatum. Control rats only had a needle insertion. Neurological deficits, brain water and ion contents were determined in the first part. In the second part, hemoxygenase-1 (HO-1), manganese superoxide dismutase (Mn-SOD), copper/zinc SOD (CuZn-SOD) and protein carbonyl levels were determined by Western blot analysis. In the third part, immunohistochemistry was performed for HO-1. DNA damage was examined using DNA polymerase I-mediated biotin-dATP nick-translation (PANT) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) in the fourth part. Infusion of lysed RBCs induced marked edema in the ipsilateral striatum and profound neurological deficits. Western blot analysis and immunohistochemistry indicated that HO-1 was upregulated 24 h after infusion of lysed red blood cells. Both Mn-SOD and CuZn-SOD contents decreased, protein carbonyl levels increased in the ipsilateral striatum, and there was the appearance of PANT- and TUNEL-positive cells suggesting oxidative mechanisms in the erythrocyte-induced brain injury. In conclusion, oxidative stress caused by components of the lysed erythrocytes contributes to the brain injury after ICH.     

Lack of Aquaporin 9 Reduces Brain Angiogenesis and Exaggerates Neuronal Loss in the Hippocampus Following Intracranial Hemorrhage in Mice

Intracranial hemorrhage (ICH) is a common subtype of stroke with high morbidity and mortality. However, few clinical therapies that can reduce ICH-induced brain injury and promote the recovery outcome in ICH patients are available to improve the recovery from ICH. Given that aquaporin 9 (AQP9) plays a critical role in brain edema after ischemic stroke and traumatic brain injury and is involved in the regulation of angiogenesis, we examined the role of AQP9 in preventing neuronal loss and in neovascularization in the dorsal hippocampus (DH) after ICH. We found that intra-DH collagenase-induced ICH increased AQP9 protein levels in the hippocampus, which was associated with behavioral deficits in wild-type mice. However, ICH robustly enhanced behavioral deficits in the AQP9-null mice, as compared with the wild-type mice. Furthermore, neovascularization and proliferation of brain microvascular endothelial cells following ICH were severely impaired in the AQP9-null mice, as compared with the wild-type mice. Finally, hippocampal neuronal loss following ICH became severer in the AQP9-null mice, relative to the wild-type mice. Taken together, our findings indicated that AQP9 in the brain may play a compensatory role in response to ICH, promote brain angiogenesis, and prevent subsequent neuronal death, thus preventing the deterioration of neurological outcome of ICH.     

Hemoglobin-Induced Nitric Oxide Synthase Overexpression and Nitric Oxide Production Contribute to Blood–Brain Barrier Disruption in the Rat

Hemoglobin (Hb) released from extravasated erythrocytes may have a critical role in the process of blood–brain barrier (BBB) disruption and subsequent edema formation after intracerebral hemorrhage (ICH). Excessive nitric oxide (NO) production synthesized by nitric oxide synthase (NOS) has been well documented to contribute to BBB disruption. However, considerably less attention has been focused on the role of NO in Hb-induced BBB disruption. This study was designed to examine the hypothesis that Hb-induced NOS overexpression and excessive NO production may contribute to the changes of tight junction (TJ) proteins and subsequent BBB dysfunction. Hemoglobin was infused with stereotactic guidance into the right caudate nucleus of male Sprague Dawley rats. Then, we investigated the effect of Hb on the BBB permeability, changes of TJ proteins (claudin-5, occludin, zonula occludens-1 (ZO-1), and junctional adhesion molecule-1 (JAM-1)), iron deposition, expression of inducible NOS (iNOS) and endothelial NOS (eNOS), as well as NO production. Hb injection caused a significant increase in BBB permeability. Significant reduction of claudin-5, ZO-1, and JAM-1 was observed after Hb injection as evidenced by PCR and immunofluorescence. After a decrease at early stage, occludin showed a fivefold increase in mRNA level at 7 days. Significant iron deposition was detectable from 48 h to 7 days in a time-dependent manner. The iNOS and eNOS levels dramatically increased after Hb injection concomitantly with large quantities of NO released. Furthermore, enhanced iNOS or eNOS immunoreactivity was co-localized with diffused or diminished claudin-5 staining. We concluded that overexpressed NOS and excessive NO production induced by Hb may contribute to BBB disruption, which may provide an important potential therapeutic target in the treatment of ICH.     

实验性脑出血血肿周围脑组织基质金属蛋白酶组织抑制剂-1的表达及其与脑水肿的关系

目的探讨实验性脑出血(ICH)血肿周围脑组织基质金属蛋白酶组织抑制剂-1(TIMP-1)的表达及其与脑水肿的关系。方法采用自体血注入法建立大鼠ICH模型,制模后1h、3h、6h、12h、24h、36h、48h、72h、7d共9个时间点分别用干湿重法测血肿周围脑组织含水量,伊文思蓝(EB)检测血-脑屏障(BBB)通透性,Western Blot方法检测血肿周围组织的TIMP-1的表达;分析三者间的关系,并与假手术组相比较。结果与假手术组比较,ICH后各时间点血肿周围脑组织含水量和EB含量均明显增加(P<0.05～0.01),均于ICH48h达到高峰,且二者呈正相关(r=0.940,P<0.01);TIMP-1在ICH12～36h表达明显减低,ICH1～24h TIMP-1表达量与脑组织含水量以及EB含量呈负相关(r=-0.922,-0.950,均P<0.05)。结论大鼠ICH后血肿周围脑组织TIMP-1表达下调,可能促进了ICH早期的脑水肿形成。     

尼膜同对大鼠脑出血后血脑屏障通透性及水通道蛋白4mRNA表达的影响

目的研究大鼠脑出血后血脑屏障(BBB)通透性与水通道蛋白4(AQP4)的关系及尼膜同的干预作用。方法采用自体动脉血注入尾状核法制成大鼠脑出血模型,RT-PCR法观察AQP4mRNA的表达,伊文思兰法测量BBB通透性,干湿重法计算脑含水量表示脑水肿。结果与对照组相比,脑出血组及尼膜同组BBB通透性均在出血后6h开始升高(0.5955±0.0956、0.5092±0.0309),1d~3d最高(0.8889±0.0968、0.7826±0.0339和0.7914±0.0520、0.7442±0.0753),尼膜同组低于脑出血组(P<0.05);两组AQP4mRNA表达也于6h即开始升高(1.06±0.12、0.90±0.15),3d时达到高峰(1.34±0.14对1.27±0.14),尼膜同组低于脑出血组(P<0.05);BBB通透性与AQP4mRNA表达呈显著正相关(r=0.686,P<0.01),与脑水肿变化趋势一致。结论脑出血后可能通过上调APQ4mRNA表达,增加BBB通透性,参与脑水肿形成,尼膜同可抑制此过程。     

局部亚低温对脑出血后水肿影响的实验研究

目的探讨局部亚低温对大鼠脑出血后水肿形成的影响及其可能机制。方法雄性Wistar大鼠230只随机分为:对照组;脑出血组;脑出血加局部亚低温组;凝血酶加局部亚低温组。应用Evans-Blue测定血脑屏障(BBB)通透性,应用干湿重法测定脑水含量。结果与对照组相比,大鼠注血后6h开始出现脑组织水含量和BBB通透性的增加,在72h达到高峰,然后逐渐消退。不同时程局部亚低温均可以显著降低脑出血后72h时脑组织水含量及BBB通透性(P<0.01),其中给以4h局部亚低温时,降低最明显。注射凝血酶6h后,脑组织水含量及BBB通透性显著增高(P<0.01),于24~48h达高峰,然后逐渐下降。凝血酶 局部亚低温组在各个时间点与凝血酶组相比,脑组织水含量及BBB通透性明显降低(P<0.01)。结论局部亚低温可能是通过抑制凝血酶的毒性作用来减轻脑出血后水肿的形成及血脑屏障的破坏。     

局部亚低温对大鼠脑出血后基质金属蛋白酶-9及血脑屏障通透性的影响

目的探讨局部亚低温对大鼠自体血注入法脑出血模型基质金属蛋白酶-9(matrix metalloproteinase-9,MMP-9)mRNA及蛋白表达的影响以及局部亚低温减轻脑出血后水肿的可能机制。方法雄性Wistar大鼠240只,随机分为脑出血(ICH)组和脑出血加局部亚低温(ICH H)组。每组分为对照、脑出血后6h、24h、72h、5d、7d共6个亚组,ICH H组于注血后立即给以4h的局部亚低温治疗,各亚组分别进行血脑屏障(BBB)通透性、脑水含量的检测以及应用RT-PCR及Western印记对MMP-9进行测定。结果ICH组大鼠脑内注血后6h开始出现脑组织水含量(P<0.01)及BBB通透性(P<0.05)的显著增加,二者在72h达到高峰,然后逐渐消退,ICH组MMP-9蛋白表达量与脑含水量和血脑屏障通透性呈正相关(r=0.88和r=0.96),ICH组MMP-9 mRNA表达量也与脑含水量和血脑屏障通透性呈正相关(r=0.78和r=0.85)。ICH H组大鼠脑组织水含量、BBB通透性以及MMP-9蛋白的表达与ICH组各时间点相比较,明显降低,而MMP-9 mRNA的表达与ICH组相比仅有轻度下降。结论脑出血后MMP-9的变化与BBB通透性和脑水肿密切相关,局部亚低温可以抑制脑出血后MMP-9蛋白表达的增加以及脑水肿的形成。提示局部亚低温可能通过影响MMP-9的变化来抑制脑出血后的水肿形成。     

Role of vasodilator stimulated phosphoprotein in VEGF induced blood–brain barrier permeability in endothelial cell monolayers

The blood–brain barrier (BBB) plays an important role in the pathophysiology of central nervous system (CNS) disorders such as stroke and hypoxic–ischemic brain injury. Vascular endothelial growth factor (VEGF) is involved in angiogenesis and vasogenic edema during stroke and hypoxia. However, the role of VEGF in BBB permeability after hypoxia has not been fully elucidated. We therefore investigated VEGF effects in an in vitro BBB model using rbcec4 endothelial cell line with the stimulation of VEGF or hypoxia. In this study, BBB permeability was studied using ¹⁴C-sucrose detection. The expression of BBB tight junction protein ZO-1, and the expression and phosphorylation of vasodilator stimulated phosphoprotein (VASP), VEGF and VEGF receptor 2 (VEGFR2) were determined using fluorescent immunocytochemistry and western blot analyses. We found that hypoxia upregulated VEGF expression, and VEGF increased BBB permeability. Hypoxia also increased VASP phosphorylation, which was mediated, in part, through VEGFR2. We also found that VASP at tight junctions was co-localized with ZO-1 in cell–cell contacts. Our findings show that VASP phosphorylation is affected by hypoxia and VEGFR2 inhibition suggesting a role for VASP in BBB permeability.     

Dexamethasone potentiates in vitro blood-brain barrier recovery after primary blast injury by glucocorticoid receptor-mediated upregulation of ZO-1 tight junction protein

Owing to the frequent incidence of blast-induced traumatic brain injury (bTBI) in recent military conflicts, there is an urgent need to develop effective therapies for bTBI-related pathologies. Blood-brain barrier (BBB) breakdown has been reported to occur after primary blast exposure, making restoration of BBB function and integrity a promising therapeutic target. We tested the hypothesis that treatment with dexamethasone (DEX) after primary blast injury potentiates recovery of an in vitro BBB model consisting of mouse brain endothelial cells (bEnd.3). DEX treatment resulted in complete recovery of transendothelial electrical resistance and hydraulic conductivity 1 day after injury, compared with 3 days for vehicle-treated injured cultures. Administration of RU486 (mifepristone) inhibited effects of DEX, confirming that barrier restoration was mediated by glucocorticoid receptor signaling. Potentiated recovery with DEX treatment was accompanied by stronger zonula occludens (ZO)-1 tight junction immunostaining and expression, suggesting that increased ZO-1 expression was a structural correlate to BBB recovery after blast. Interestingly, augmented ZO-1 protein expression was associated with specific upregulation of the α⁺ isoform but not the α⁻ isoform. This is the first study to provide a mechanistic basis for potentiated functional recovery of an in vitro BBB model because of glucocorticoid treatment after primary blast injury.