Cilostazol inhibits the redistribution of the actin cytoskeleton and junctional proteins on the blood-brain barrier under hypoxia/reoxygenation.

Cilostazol is a selective inhibitor of cyclic nucleotide phosphodiesterase 3 (PDE3), which induces a vasodilatoric antiplatelet effect. In the present study, we investigated the impact of cilostazol on the blood-brain barrier (BBB), while focusing on the actin cytoskeleton (F-actin), the permeability of endothelial cells, and the junctional proteins under hypoxia/reoxygenation (H/R). Cilostazol was thus found to inhibit the cytoskeletal reorganization under H/R, in which F-actin decrease at the cell periphery. Accordingly, cilostazol was able to attenuate the hyperpermeability of endothelial cells in H/R to the level of the permeability in normoxia. However, the adherens junction (AJ) protein VE-cadherin was not preserved in the presence of cilostazol under H/R. On the other hand, beta-catenin was slightly retained by cilostazol. In contrast to the redistribution of these proteins, immunoblotting demonstrated the total amount of AJ and tight junction (TJ) proteins (occludin, ZO-1 and ZO-2) to not show any significant change under H/R stress in either the presence or absence of cilostazol. Taken together, cilostazol potently displayed a protective effect against acute ischemia by preventing an increase in the endothelial permeability through the preservation of the actin cytoskeleton and the redistribution of junctional proteins.     

Evaluation of bEnd5 cell line as an in vitro model for the blood-brain barrier under normal and hypoxic/aglycemic conditions

The purpose of the study was to assess the suitability of the mouse endothelial cell line bEnd5 as a blood-brain barrier (BBB) model under normal or pathologic (stroke) conditions. In comparison to the well-established bovine brain endothelial cell (BBMEC) model, cultured bEnd5 monolayers reached a maximal transendothelial electrical resistance (TEER) of 121 Omega cm(2) on day 7, and possessed oval and spindle shape morphology. Structurally, confluent monolayers of bEnd5 cells and BBMECs exhibit peripheral band staining of the tight junction protein ZO-1 and occludin. Both bEnd5 and BBMECs express important tight junctional proteins, ZO-1, occludin and claudin-1, as well as the transporters P-glycoprotein (P-gp), NKCC, GLUT1, and most PKC isoforms. Marker permeability experiments suggest that bEnd5 cells form a tight barrier that compares to well-established in vitro BBB models, such as the BBMEC. After short durations of hypoxia/aglycemia (H/A), hyperpermeability was seen in the bEnd5 endothelial monolayer compared to later time periods for BBMECs, suggesting that bEnd5 cells are more sensitive to hypoxia/algycemia treatment than BBMECs. Taken together, bEnd5 cell culture model may provide a useful in vitro model of the BBB for drug delivery studies and modeling pathological states such as oxygen glucose deprivation associated with stroke.     

Nicotine and cotinine modulate cerebral microvascular permeability and protein expression of ZO-1 through nicotinic acetylcholine receptors expressed on brain endothelial cells

The blood-brain barrier (BBB) adapts to a variety of pathological processes. Little is known about the effects of nicotine exposure on BBB function and the ability to adapt to stroke conditions. We have demonstrated, using a well-characterized in vitro BBB model, bovine brain microvessel endothelial cells (BBMEC) model, that nicotine and its major metabolite, cotinine, modulate BBB integrity by opening the paracellular route of solute entry into the brain. Additionally, nicotine and cotinine together increase the permeability change observed after 6 h of hypoxia/aglycemia, an in vitro model of stroke. This has important implications for how the BBB initially adapts to stroke in an environment that is previously exposed to nicotine. Nicotine and cotinine exposure also resulted in reduced ZO-1 immunoreactivity (tight junctional protein) that occurred in a time-dependent manner. Interestingly, attenuation of bovine brain microvessel endothelial cell (BBMEC) ZO-1 protein expression was reversed using 10 nM BGT, an alpha7 nicotinic acetycholine receptor (nAChR) antagonist, suggesting that the effects of nicotine on BBMEC protein expression of ZO-1 protein are mediated by nAChR expressed on brain endothelial cells. In addition to alpha7, we found that BBMEC also contain positive immunoreactivity for the alpha3, alpha5, beta2, beta3 nAChR subunit. Both alpha7 and beta2 nAChR subunit protein levels decreased with prior nicotine and cotinine exposure. These data provide evidence that nicotine and cotinine alter BBB permeability and tight junctional protein expression of ZO-1, thereby altering the BBB response to stroke conditions. These changes in brain endothelial cell paracellular permeability are believed to be associated with nicotine binding to nAChRs present at the BBB.     

Inhibitory effect of YC-1 on the hypoxic induction of erythropoietin and vascular endothelial growth factor in Hep3B cells

YC-1 is a newly developed agent that inhibits platelet aggregation and vascular contraction. Although its effects are independent of nitric oxide (NO), it mimics some of the biological actions of NO. For example, it stimulates soluble guanylate cyclase (sGC) and increases intracellular cGMP concentration. Here, we tested the possibility that YC-1 inhibits hypoxia-inducible factor (HIF)-1-mediated hypoxic responses, as does NO. Hep3B cells were used during the course of this work to observe hypoxic induction of erythropoietin (EPO) and vascular endothelial growth factor (VEGF), and the effects of YC-1 were compared with those of a NO donor, sodium nitropurruside (SNP). In hypoxic cells, YC-1 blocked the induction of EPO and VEGF mRNAs, and inhibited the DNA-binding activity of HIF-1. It suppressed the hypoxic accumulation of HIF-1alpha, but not its mRNA level. It also reduced HIF-1alpha accumulation induced by cobalt and desferrioxamine. Treatment with antioxidants did not recover the HIF-1alpha suppressed by YC-1. We examined whether these effects of YC-1 are related to the sGC/cGMP signal transduction system. Two sGC inhibitors examined failed to block the effects of YC-1, and 8-bromo-cGMP did not mimic actions of YC-1. The effects of YC-1 on the hypoxic responses were comparable with those of SNP. These results suggest that YC-1 and SNP suppressed the hypoxic responses by post-translationally inhibiting HIF-1alpha accumulation. The YC-1 effect may be linked with the metal-related oxygen sensing pathway, and is not due to the stimulation of sGC. This observation implies that the inhibitory effects of YC-1 on hypoxic responses can be developed to suppress EPO-overproduction by tumor cells and tumor angiogenesis.     

Morphofunctional aspects of the blood-brain barrier

The blood-brain barrier (BBB) selectively controls the homeostasis of the Central Nervous System (CNS) environment by the specific structural and biochemical features of the endothelial cells, pericytes and glial endfeet, which represent the cellular components of the mature BBB. Endothelial tight junctions (TJs) are the most important structural component of the BBB, and molecular alteration in the phosphorylation state of some TJs proteins, like ZO-1 or occludin, are crucial in determining alterations in the control of BBB vascular permeability. Astrocytes endfeet enveloping the vessels wall, are considered important in the induction and maintenance of the BBB, through secretion of soluble factors, which modulate the expression of enzymatic complexes and antigens by endothelial cells and TJs - associated proteins. Moreover, astrocytes control water flux at BBB site by expressing a specific water channel, namely aquaporin-4 (AQP4), involved in the molecular composition of the orthogonal particles arrays (OAPs) on the perivascular glial endfeet and tightly coupled with the maintenance of the BBB integrity. Disruption of the BBB is a consistent event occurring in the development of several CNS diseases, including demyelinating lesions in the course of relapsing multiple sclerosis, stroke, Duchenne muscular dystrophy (DMD), but also mechanical injures, neurological insults, septic encephalopathy, brain tumors, permanent ischemia or transient ischemia followed by reperfusion. In most cases, these pathological conditions are associated with an increase in microvascular permeability, vasogenic edema, swollen atrocyte endfeet, and BBB disruption.     

Protective action of indapamide, a thiazide-like diuretic, on ischemia-induced injury and barrier dysfunction in mouse brain microvascular endothelial cells

The aim of the present study was to elucidate the effects of indapamide on ischemic damage to the blood-brain barrier (BBB) in vitro. The ischemia/reperfusion conditions employed here significantly decreased the viability of mouse brain capillary endothelial (MBEC4) cells, an effect ameliorated by indapamide. Ischemia increased the permeability of MBEC4 cells to two cellular transport markers, sodium fluorescein and Evan's blue-albumin. Indapamide reduced the ischemia-induced hyperpermeability of cells. These results suggest that indapamide may have a protective role against ischemia-induced injury and dysfunction of the BBB.     

A quassinoid 6alpha-tigloyloxychaparrinone inhibits hypoxia-inducible factor-1 pathway by inhibition of eukaryotic translation initiation factor 4E phosphorylation

Hypoxia-inducible factor-1 (HIF-1) is the central mediator of cellular responses to low oxygen and vital to many aspects of cancer biology. In a search for HIF-1 inhibitors, we identified a quassinoid 6alpha-tigloyloxychaparrinone (TCN) as an inhibitor of HIF-1 activation from Ailantus altissima. We here demonstrated the effect of TCN on HIF-1 activation induced by hypoxia or CoCl(2). TCN showed the potent inhibitory activity against HIF-1 activation induced by hypoxia in various human cancer cell lines. This compound markedly decreased the hypoxia-induced accumulation of HIF-1alpha protein dose-dependently, whereas it did not affect the expressions of HIF-1beta and topoisomerase-I. Furthermore, TCN prevented hypoxia-induced expression of HIF-1 target genes for vascular endothelial growth factor (VEGF) and erythropoietin. Further analysis revealed that TCN strongly inhibited HIF-1alpha protein synthesis, without affecting the expression level of HIF-1alpha mRNA or degradation of HIF-1alpha protein. Moreover, the levels of phosphorylation of extracellular signal-regulated kinase-1/2 (ERK1/2), mitogen-activated protein (MAP) kinase-interacting protein kinase-1 (MNK1) and eukaryotic initiation factor 4E (eIF4E) were significantly suppressed by the treatment of TCN, without changing the total levels of these proteins. Our data suggested that TCN may exhibit anticancer activity by inhibiting HIF-1alpha translation through the inhibition of eIF4E phosphorylation pathway and thus provide a novel mechanism for the anticancer activity of quassinoids. TCN could be a new HIF-1-targeted anticancer agent and be effective on mammalian target of rapamycin (mTOR)-targeted cancer therapy, in which mTOR inhibition increases eIF4E phosphorylation.     

热休克蛋白60对动脉粥样硬化大鼠心肌血管内皮生长因子和缺氧诱导因子-1α表达的影响

目的研究口服热休克蛋白60（HSP60）对动脉粥样硬化（AS）大鼠心肌血管内皮生长因子（VEGF）和缺氧诱导因子-1α（HIF-1α）表达的影响。方法40只4周龄健康雄性SD大鼠,体质量（100±10）g。随机分为4组：健康对照组（C组）,AS未干预组（AS组）,造AS模型前口服HSP60组（HI组）,造模后口服HSP60组（H2组）,以上4组每组10只。本实验采用高脂饲料造AS模型,于大鼠180日龄时采血后处死,并取大鼠心肌作为标本。反转录一聚合酶链反应（RT—PCR）和免疫组织化学检测心肌VEGF和HIF-1α表达情况。结果C组、AS组、H1组、H2组大鼠心肌VEGFmRNA表达分别为：0．37±0．04,0．87±0．05,0．44±0．03,0．58±0．04;HIF-1αmRNA表达分别为：0．46±0．06,0．94±0．03,0．55±0．05,0．62±0．06;VEGF免疫组织化学阳性表达分别为：4．5±0．5,9．2±0．6,5．3±0．4,8．1±0．5;HIF-la免疫组织化学阳性表达分别为：5．8±0．7,13．9±0．4,7．0±0．6,10．4±0．8。结论As大鼠心肌VEGF和HIF-1Q表达较正常对照组增高,口服HSP60能降低VEGF和HIF-1α表达,即减轻心肌缺血缺氧性损伤和血管内皮炎症反应程度,而且越早口服,效果越好。     

VEGF-mediated tight junctions pathological fenestration enhances doxorubicin-loaded glycolipid-like nanoparticles traversing BBB for glioblastoma-targeting therapy

The existence of blood–brain barrier (BBB) greatly hindered the penetration and accumulation of chemotherapeutics into glioblastoma (GBM), accompany with poor therapeutic effects. The growth of GBM supervene the impairment of tight junctions (TJs); however, the pathogenesis of BBB breakdown in GBM is essentially poorly understood. This study found that vascular endothelial growth factor (VEGF) secreted by GBM cells plays an important role in increasing the permeability of BBB by disrupting endothelial tight junction proteins claudin-5 and thus gave doxorubicin (DOX)-loaded glycolipid-like nanoparticles (Ap-CSSA/DOX), an effective entrance to brain tumor region for GBM-targeting therapy. In addition, VEGF downregulates the expression of claudin-5 with a dose-dependent mode, and interfering with the VEGF/VEGFR pathway using its inhibitor axitinib could reduce the permeability of BBB and enhance the integrity of the barrier. Ap-CSSA/DOX nanoparticles showed high affinity to expressed low-density lipoprotein receptor-related proteins 1 (LRP1) in both BBB and GBM. And BBB pathological fenestration in GBM further exposed more LRP1 binding sites for Ap-CSSA/DOX nanoparticles targeting to brain tumor, resulting in a higher transmembrane transport ratio in vitro and a stronger brain tumor biodistribution in vivo, and finally realizing a considerable antitumor effect. Overall, taking advantage of BBB pathological features to design an appropriate nanodrug delivery system (NDDS) might provide new insights into other central nervous system (CNS) diseases treatment.     

PGN刺激对低氧诱导RASF表达VEGF的影响

目的 观察TLR2配体肽聚糖（PGN）刺激对低氧诱导类风湿关节炎滑膜成纤维细胞（RASF）表达低氧诱导因子1 α（HIF-1 α）和血管内皮生长因子（VEGF）的影响.方法 分离RASF 6例,建立体外培养体系,将RASF分为对照组、CoCl2组、PGN组和CoCl2＋PGN组,qRT-PCR检测HIF-1 α表达,ELISA检测VEGF表达,siHIF-1 α后ELISA检测VEGF表达.结果 CoCl2组RASF表达HIF-1 α和VEGF水平高于对照组（P＜0.05）,PGN刺激能明显增强CoGl2诱导RASF表达HIF-1 α和VEGF的水平（P＜0.05）,干扰HIF-1 α后明显下调PGN协同CoCl2诱导RASF产生VEGF的效应（P＜0.05）.结论 TLR2信号激活能明显增强低氧诱导RASF产生VEGF的能力,干扰HIF-1 α是RA治疗的有效策略.     

脑损伤过程中血脑屏障通透性的变化及其调节机制

血脑屏障是由脑微血管内皮细胞、星形神经胶质细胞、外膜细胞、血管周围巨噬细胞和基底膜组成的一个复杂系统,对维持中枢神经系统的正常功能非常重要。脑损伤如脑缺血、脑缺氧、脑外伤和蛛网膜下腔出血过程中伴随血脑屏障通透性的变化。脑缺血及其再灌注后可通过花生四烯酸代谢途径、嘌呤核苷酸代谢途径及一氧化氮途径产生自由基,可能是血脑屏障通透性增加的重要机制。血脑屏障的破坏可加重脑损伤程度;脑血管疾病时,保护血脑屏障的完整性可能是减轻脑损伤的重要措施。     

缺血预适应对局灶性脑缺血再灌注大鼠海马 CA1 区低氧诱导因子-1α、 血管内皮生长因子表达的影响#br#

目的 观察缺血预适应后局灶性脑缺血再灌注大鼠缺血侧海马 CA1 区低氧诱导因子（HIF） -1α、 血管内皮生长因子（VEGF）表达的变化, 探讨缺血预适应的脑保护机制。方法 雄性 SD 大鼠随机分为 3 组： 假手术（SO）组、 脑缺血（MCAO）组和缺血预适应（BIP）组, 后两组按缺血后再灌注时间不同分为再灌注 2、 6、 12、 24、 48、 72 h 6 个亚组。制备大鼠局灶性脑缺血预适应模型, 采用免疫组织化学法与 Western blot 法观察脑缺血后再灌注各个时间点海马 CA1 区 HIF-1α和 VEGF 的表达变化。结果 SO 组未见神经功能缺损症状, 与 MCAO 组相比, BIP 组再灌注各时间点神经功能缺损评分低 （P＜0.05）。MCAO 组、 BIP 组 HIF-1α、 VEGF 阳性细胞及蛋白表达均于再灌注 2 h 开始增多, 6～12 h 表达递增, 24 h 表达至高峰, 随后表达减少, 72 h 表达仍高于 SO 组。两组各时间点 HIF-1α和 VEGF阳性细胞及蛋白表达均高于 SO 组 （P＜0.05）。除再灌注 2 h、 6 h MCAO 组与 BIP 组 HIF-1α的阳性细胞表达差异无统计学意义外, 2 组各时间点 VEGF 阳性细胞表达、 HIF-1α、 VEGF 蛋白表达均是 BIP 组高于 MCAO 组（P＜0.05）。结论 脑缺血预适应可能通过上调 HIF-1α、 VEGF 的表达, 发挥脑保护作用。     

EMP-induced alterations of tight junction protein expression and disruption of the blood–brain barrier

The blood–brain barrier (BBB) is critical to maintain cerebral homeostasis. In this study, we examined the effects of exposure to electromagnetic pulse (EMP) on the functional integrity of BBB and, on the localization and expression of tight junction (TJ) proteins (occludin and ZO-1) in rats. Animals were sham or whole-body exposed to EMP at 200 kV/m for 400 pulses. The permeability of BBB in rat cerebral cortex was examined by using Evans Blue (EB) and lanthanum nitrate as vascular tracers. The localization and expression of TJ proteins were assessed by western blot and immunofluorescence analysis, respectively. The data indicated that EMP exposure caused: (i) increased permeability of BBB, and (ii) altered localization as well as decreased levels of TJ protein ZO-1. These results suggested that the alteration of ZO-1 may play an important role in the disruption of tight junctions, which may lead to dysfunction of BBB after EMP exposure.     

Genistein inhibited hypoxia-inducible factor-1alpha expression induced by hypoxia and cobalt chloride in human retinal pigment epithelium cells

The time-dependent changes of hypoxia-inducible factor-1alpha (HIF-1alpha) expression induced by hypoxia and CoCl2 treatment and the effects of genistein on the level of HIF-1alpha expression in human retinal pigment epithelium cells were examined. Judging by relative fluorescence using a confocal scanning laser microscope coupled to a computer, HIF-1alpha expression was determined. It was found that hypoxia could markedly increase the expression of HIF-1alpha. The highest expression of HIF-1alpha was detected at 1 h, which was 313.9% +/- 38.2% of the control level. After pretreatment with genistein (50, 100, and 200 micromol/l), the hypoxia-evoked HIF-1alpha expression was concentration-dependently inhibited. CoCl2 treatment could significantly elevate the level of HIF-1alpha expression. At 0.5 h after CoCl2 treatment, the highest level was observed, which was 141.4% +/- 14.1% of the control level. Genistein 50, 100, 200 micromol/L could also suppress HIF-1alpha expression in a concentration-dependent manner. These results suggested that the inhibition of HIF-1alpha protein expression by genistein may partly account for its effect on retinal neovascularization in vivo.     

缺氧对血管内皮生长因子诱导牛冠状动脉内皮细胞脂蛋白通透性升高的调控及丹酚酸B的抑制作用

目的　为了了解缺氧对血管内皮生长因子(VEGF)增强血管内皮细胞通透性作用的影响及其与动脉粥样硬化的关系 ,考察了正常和缺氧状态下VEGF对体外培养牛冠状动脉内皮细胞 (BCEC)脂蛋白通透性的影响及丹酚酸B的抑制作用。方法　正常及缺氧条件下 ,将VEGF及丹酚酸B加入BCEC共孵育 ,用SN 695型液闪计数器测 [12 5I]低密度脂蛋白([12 5I]LDL)通过BCEC的百分率。结果　VEGF可显著增强BCEC对 [12 5I]LDL的通透性 ,这种增加具有浓度依赖性。缺氧 3h可促进VEGF所致的的通透性增加。丹酚酸B在正常和缺氧条件下均显著抑制VEGF诱导的BCEC通透性升高。结论　VEGF可增强血管内皮细胞的通透性 ,可能在动脉粥样硬化的形成和发展过程中起一定作用。丹酚酸B对VEGF诱导的血管内皮通透性升高有显著的抑制作用