Drug transfer across the blood-brain barrier and improvement of brain delivery

The blood-brain barrier is formed by the endothelial cells of the brain capillaries. Its primary characteristic is the impermeability of the capillary wall due to the presence of complex tight junctions and a low endocytic activity. Essential nutrients are delivered to the brain by selective transport mechanisms, such as the glucose transporter and a variety of amino acid transporters. Although most drugs enter the brain by passive diffusion through the endothelial cells depending on their lipophilicity, degree of ionization, molecular weight, relative brain tissue and plasma bindings, some others can use specific endogenous transporters. In such cases, binding competition on the transporter with endogenous products or nutrients can occur and limits drug transfer. The blood-brain barrier can be a major impediment for the treatment of diseases of the central nervous system, since many drugs are unable to reach this organ at therapeutic concentrations. Various attempts have been made to overcome the limiting access of drugs to the brain, e.g. chemical modification, development of more hydrophobic analogs or linking an active compound to a specific carrier. Transient opening of the blood-brain barrier in humans has been achieved by intracarotid infusion of hypertonic mannitol solutions or of bradykinin analogs. Another way to increase or decrease brain delivery of drugs is to modulate the P-glycoprotein (P-gp) whose substrates are actively pumped out the cell into the capillary lumen. Many P-gp inhibitors or inducers are available to enhance the therapeutic effects of centrally acting drugs or to decrease central adverse effects of peripherally active drugs.     

脑出血后血脑屏障损伤机制的研究进展

多种病因能诱发ICH,如高血压、阿兹海默病、血管畸形和凝血病。ICH后继发性血脑屏障损伤机制研究分别在分子及细胞信号领域上已取得了长足进展,而血液成分中的凝血酶、血红蛋白、铁和继发性炎症反应在ICH诱导的继发性血脑屏障功能紊乱中都发挥了极其重要的作用。所以如何深入理解ICH后继发性血脑屏障功能紊乱的内在机理,对于我们进一步研究脑出血性脑卒中发病机制来说尤为关键。     

Protis软件在血脑屏障功能评估中的临床运用

目的探讨Protis软件在血脑屏障功能评估中的实用价值。方法用散射比浊法平行测定66例患者脑脊液与血清中免疫球蛋白（IgG、IgA、IgM）和清蛋白（albumin,ALB）的含量,并利用分析软件Protis进行数据和图形处理。结果正常8例,单纯血脑屏障受损15例,仅有鞘内合成23例,血脑屏障受损伴有鞘内合成23例。结论 Protis软件能辅助临床对中枢神经系统疾病作出初步的诊断和鉴别诊断,该软件的应用为临床提供了一种快速、可靠、直观、系统的辅助诊断方法。     

低频诊断超声联合脂氟显微泡开放小鼠血脑屏障的可逆性研究

目的探讨低频诊断超声联合脂氟显微泡开放小鼠血脑屏障(blood-brain barrier,BBB)的可逆性及伊文思蓝(Evans blue,EB)透过率。方法健康C57BL/6小鼠48只,随机分为对照组6只和观察组42只。观察组再随机分为0、0.5、1、2、3、8、10 h亚组各6只,低频诊断超声辐照同时经尾静脉注射脂氟显微泡1 mL/kg,并分别于超声辐照0、0.5、1、2、3、8、10 h经尾静脉注射质量分数2%EB溶液50 mg/kg;对照组不进行低频诊断超声辐照,经尾静脉注射1 mL/kg生理盐水后注射质量分数2%EB溶液50 mg/kg。注射1 h后处死小鼠取脑组织,观察脑组织蓝染深度及面积,采用紫外分光光度法定量分析脑组织EB含量。结果对照组及观察组8、10 h亚组未见脑实质蓝染,观察组0、0.5、1、2、3 h亚组辐照区脑实质均有不同程度蓝染,且1 h时蓝染深度最深、面积最大;观察组0、0.5、1、2、3 h亚组脑组织EB含量[(45.43±2.89)、(50.94±1.25)、(79.79±1.12)、(51.55±1.20)、(31.60±1.77)μg/g]均高于对照组[(8.32±0.12)μg/g](P<0.05),8、10 h亚组脑组织EB含量[(8.34±0.09)、(8.31±0.07)μg/g]与对照组比较差异无统计学意义(P>0.05);观察组0、0.5、1 h亚组脑组织EB含量依次升高(P<0.05),1、2、3 h亚组脑组织EB含量依次降低(P<0.05)。结论低频诊断超声联合脂氟显微泡开放小鼠BBB呈动态可逆的过程,BBB在超声辐照后1 h开放程度最大,于超声辐射8 h恢复正常。     

Insulin increases glucose transfer across the blood-brain barrier in man.

The influence of insulin on unidirectional flux of glucose across the blood-brain barrier and on net uptake of glucose by the brain was investigated in seven fasting patients. The unidirectional extraction, E, of [14C]D-glucose was determined using 36Cl- as an intravascular reference, by the indicator dilution method. 0.4 U insulin/kg body wt was infused intravenously over 30 min while blood glucose was maintained constant by glucose infusion. Six determinations were made in each patient, two before, two during insulin infusion, and two after. In connection with each blood-brain barrier study, arterial and cerebral venous samples were taken for measurement of glucose, oxygen, insulin, K+, and phosphate. Cerebral blood flow (CBF) was measured in each patient. The main finding was an increased extraction of glucose from 14 to 21% and a highly significant increase in unidirectional flux (CBF X unidirectional extraction X arterial glucose concentration) from 0.46 to 0.66 mumol/g X min during insulin infusion (plasma insulin approximately 1,500 microU/ml). The net brain uptake of glucose (CBF X arterio-venous difference for glucose) as unaltered during the investigation period of 45 min, which is too short a time for insulin to penetrate the barrier. It follows that the backflux of glucose from the brain was increased during insulin application. The effect of insulin might be a speeding up of the glucose carrier in analogy to heart muscle.     

MR灌注加权成像评估创伤性脑损伤血脑屏障改变研究进展

血脑屏障(BBB)破坏是创伤性脑损伤(TBI)所致重要病理变化之一,及时治疗及判断预后具有重要临床意义。目前监测TBI后BBB改变越来越受到重视。本文对TBI后BBB改变、MR灌注加权成像(PWI)及MR PWI研究TBI进展进行综述。     

高压氧对缺血再灌注小鼠脑组织细胞因子IL-10及血脑屏障通透性的影响

目的：探讨高压氧（HBO）对缺血再灌注小鼠脑组织中细胞因子IL-10含量、mRNA的表达、血脑屏障（BBB）通透性的影响。方法：复制清醒小鼠脑缺血再灌注模型，并于再灌注期间行0．25MPa（CBFATA）HBO治疗5次，在处死动物前1h经尾静脉注射2％伊文思兰（Evansblue，EB），采用比色法、ABC—ELISA、RT—PCR分别检测脑组织中细胞因子IL-10含量、mRNA的表达及EB的含量的变化。结果：脑组织EB的渗出于缺血再灌注后第4h为最多，于再灌注后第11h、23h、48h、72h逐渐下降；HBO＋脑缺血再灌注组脑组织EB的渗出与相应时间的脑缺血再灌注组相比明显降低（P〈0．01）。HBO组脑组织EB的渗出与相应时间的假手术组相比变化不明显（P〉0．05）。脑缺血再灌注组细胞因子IL-10含量于再灌注11h开始增加并于再灌注23h达到高峰，再灌注48h、72h逐渐下降。脑缺血再灌注组细胞因子IL-10含量与相应时间的假手术组相比于再灌注后11h、23h、48h、72h都明显增高（P〈0．01）。HBO＋脑缺血再灌注组细胞因子IL-10含量于再灌注后11h、23h、48h、72h与相应时间的脑缺血再灌注组相比变化不明显（P〉0．05）；而IL-10mRNA的表达明显增加（P〈0．01）。HBO组与相应时间的假手术组相比IL一10含量和mRNA的表达变化都不明显（P〉0．05）。结论：HBO从基因水平可明显增加脑缺血再灌注72h细胞因子IL-10mRNA的表达，从而具有保护血脑屏障的作用；HBO对正常脑组织中IL-10含量、mRNA的表达作用不明显。     

脑小血管疾病血脑屏障通透性与MRI总负担的相关性

目的 通过动态增强MRI（DCE-MRI）探讨血脑屏障（BBB）通透性与脑小血管疾病（CSVD）MRI总负担之间的关系。方法 对104例患者以5分制CSVD影像学总负担评分表进行评价，包括腔隙性梗死（lacunes）、脑白质高信号（WMH）、脑微出血（CMB）、血管周围间隙扩大（EPVS）和脑萎缩（BA），并根据得分0~5分为CSV0组（0分）~CSVD5组（5分）共6组。对各组均行DCE-MRI，并以Patlak双室药代动力学模型测量WMH、常规MRI表现正常的脑白质区（NAWM）、皮层灰质区（CGM）以及深部灰质区（DGM）BBB通透性。结果 最终纳入99名，校正年龄、性别和血管危险因素后，NAWM、WMH、CGM及DGM 4个区域的CSVD影像学总负担与渗漏速率（K_trans）和曲线下面积（AUC）均呈显著正相关（P均<0.05）；NAWM、CGM及DGM区域CSVD影像学总负担与局部脑血浆容量（V_p）呈显著负相关（P<0.05）。结论 CSVD患者BBB通透性增高与其MRI所示总CSVD负担相关；BBB受损可能是CSVD病理生理过程的关键因素之一。     

脑出血患者血脑屏障介入治疗临床疗效对比研究

目的 研究介入治疗与介入非治疗对高血压脑出血患者血脑屏障(BBB)的临床疗效对比.方法 观察脑出血患者常规治疗(非介入治疗)组26例和常规治疗 颅内血肿清除术(介入治疗)组26例,对照分析其BBB指数和S100蛋白的变化,并分别与正常对照组做对比.结果 非介入治疗组的BBB指数明显高于介入治疗组(P＜0.05).该两组患者BBB指数均高于正常对照组(P＜0.01);介入治疗组血清S100蛋白浓度明显低于非介入治疗组(P＜0.01),该两组患者S100蛋白浓度均高于正常对照组(P＜0.01).结论 脑出血的介入治疗可以减轻细胞毒性对血脑屏障的损伤,从而减轻脑水肿.     

亚低温对脑缺血再灌注后血脑屏障损伤及明胶酶活性的影响

目的：应用MRI动态监测亚低温对脑缺血再灌注后血脑屏障损伤的影响,并探讨其保护机制。方法：雄性Wistar大鼠42只,随机分为常温缺血组、亚低温缺血组和假手术组。线栓法建立大鼠大脑中动脉缺血再灌注模型,分别于再灌注3.5h、24h和5d行T1WI增强扫描,再灌注24h和5d进行大鼠神经功能缺损评分,脑组织明胶酶活性测定,以及明胶酶活性与磁共振表现的相关分析。结果：亚低温治疗明显减小了各时间点T1WI信号强化的范围和强度,显著降低缺血再灌注早期及晚期神经功能缺损评分和脑组织明胶酶活性。常温缺血组再灌注24h后MMP-9活性与T1WI信号强化范围正相关。结论：亚低温能明显减轻缺血再灌注后血脑屏障损伤的范围和程度,促进神经功能恢复,其保护机制可能与亚低温降低MMP-9、MMP-2的活性有关。     

水蛭素对大鼠脑出血后细胞黏附分子1mRNA表达及血脑屏障通透性的影响

目的 探讨水蛭素对大鼠脑出血后细胞黏附分子1(ICAM-1)mRNA的表达及血脑屏障通透性的影响.方法 采用自体动脉血注入大鼠尾状核建立脑出血模型,将75只大鼠分成对照组、脑出血组、水蛭素组.各实验组分6小时、1天、3天、5天、7天5个时间点,每个时间点各5只大鼠.分别采用逆转录聚合酶链反应(RT-PCR)、伊文思兰染色法测定不同时间点的ICAM-1 mRNA表达量和血脑屏障通透性的变化.结果 ICAM-1 mRNA表达和血脑屏障通透性在脑出血后6小时开始升高(1.220±0.044,0.592±0.106),3天达到高峰(1.638±0.071,0.791±0.520),5～7天开始下降.给予术蛏素治疗后,二者均明显下降,水蛭素组与脑出血组在各个时段差异有统计学意义(P＜0.01).结论 水蛭素可以减轻脑出血后的ICAM-1 mRNA的高表达及血脑屏障通透性的增加,从而减轻脑水肿程度.     

高压氧修复缺血再灌注损伤大鼠血脑屏障的自噬机制

目的 观察高压氧舱治疗对缺血再灌注损伤大鼠脑血管内皮细胞微管相关蛋白1轻链3 (LC3)和Beclin-1表达的影响,探究高压氧修复缺血再灌注损伤大鼠血脑屏障的机制。方法 54只成年雌性Sprague-Dawley大鼠随机分为假手术组(n=12)、缺血再灌注损伤模型组(n=18)、高压氧组(n=12)和抑制剂组(n=12)。模型组、高压氧组和抑制剂组采用线栓法建立大鼠大脑中动脉缺血2 h再灌注损伤模型。高压氧组和抑制剂组建模后予高压氧舱治疗;抑制剂组治疗前侧脑室注射3-甲基腺嘌呤。损伤后72 h,各组进行伊文思蓝染色,观察梗死区伊文思蓝含量;模型组采用免疫荧光双标法观察LC3在CD₃₁⁺血管内皮细胞的表达;采用Western blotting检测各组梗死区皮质微血管段LC3-Ⅱ和Beclin-1的表达水平。结果 与假手术组相比,模型组梗死区伊文思蓝含量明显升高(P < 0.01);与模型组相比,高压氧组梗死区伊文思蓝含量明显降低(P < 0.01);与高压氧组相比,抑制剂组梗死区伊文思蓝含量增高(P<0.05)。模型组损伤区CD₃₁⁺血管内皮细胞可见LC3表达;模型组梗死区微血管段Beclin-1和LC3-Ⅱ的表达水平均明显高于假手术组(P < 0.01);高压氧组的LC3-Ⅱ和Beclin-1蛋白表达水平较模型组均升高(P<0.05);抑制剂组较高压氧组和模型组均明显下降(P<0.01)。结论 缺血再灌注损伤大鼠损伤区的血管内皮细胞存在自噬现象,高压氧舱治疗能够上调梗死区血管内皮细胞自噬蛋白LC3-Ⅱ和Beclin-1的表达,从而促进血脑屏障修复。     

Observation on the integrity of the blood-brain barrier after microbubble destruction by diagnostic transcranial color-coded sonography.

OBJECTIVE: To investigate alteration of the blood-brain barrier from ultrasonic contrast agent destruction by diagnostic transcranial color-coded sonography using gadolinium-enhanced magnetic resonance imaging. METHODS: Healthy male volunteers received 10 mL (400 mg/dL) of Levovist (SH U 508A; Schering AG, Berlin, Germany; n = 6) or 3 mL of Optison (FS069; Mallinckrodt Inc, St Louis, MO; n = 4) followed by 0.3 mmol/kg magnetic resonance imaging contrast agent (Magnevist; Schering) intravenously. Then transcranial color-coded sonography was performed with a conventional color duplex sonographic system, which insonated the brain in a slightly angulated axial plane with temporal average intensity of less than 700 mW/cm2 or acoustic pressure amplitude of less than 2.69 MPa, attenuated by the temporal bone. Before, immediately after, and 2 hours after insonation, T1-weighted axial magnetic resonance imaging was performed. All magnetic resonance images were individually assessed, and T1 signal intensities were measured in 2 regions of interest in both hemispheres at the 3 time points. RESULTS: No focal contrast enhancement or damage to the brain and no significant difference between T1 signal intensities in the right and left brain regions could be detected during early or late phases when either ultrasonic contrast agent was used. CONCLUSIONS: This bioeffects study gives further evidence of the safety of ultrasonic destruction of Levovist and Optison microbubbles by diagnostic transcranial color-coded sonography. However, more subtle local effects may have been missed by gadolinium-enhanced magnetic resonance imaging. Studies on diagnostic contrast-enhanced transcranial color-coded sonography as well as microbubble-based drug delivery strategies should consider ultrasonic contrast agent microbubble characteristics and concentration as well as ultrasound transmission power levels.     

Effective gene transfer into central nervous system following ultrasound-microbubbles-induced opening of the blood-brain barrier

To investigate whether ultrasound-targeted microbubble destruction (UTMD) could transfer gene into central nervous system (CNS) following blood-brain barrier disruption (BBBD), DNA-loaded microbubbles were infused into the mice intravenously following ultrasonic exposure. Opening of the BBB, changes of mRNA and expression of enhanced green fluorescent protein (EGFP), and safety evaluation were measured. By UTMD, EGFP were substantially expressed in the cytoplasm of the neurons at the sonicated area with minor erythrocytes extravasation and the mRNA and expression of EGFP were markedly enhanced by about 15-fold and 10-fold, respectively, than that with US alone (p < 0.01). No EGFP was detected in the mice treated with DNA-loaded microbubbles or plasmid alone. The gene expression reached a climax at 48 h, gradually reduced to a much lower level thereafter. These results demonstrated UTMD could effectively enhance exogenous gene delivery and expression in CNS following BBBD, and this technique may provide a new method for CNS gene therapy.     

促甲状腺素释放激素类似物YM14673对大鼠脑外伤后脑水肿及血脑屏障通透性的影响

目的观察促甲状腺素释放激素 (TRH)类似物YM 14 673对脑外伤后血脑屏障的影响。方法制作大鼠急性脑外伤模型 ,外伤前静脉注入伊文氏蓝。大鼠分为假手术组、生理盐水组、给药组Ⅰ ( 0 1mg/kg)、给药组Ⅱ ( 1mg/kg)。伤后 2 4h处死 ,测定脑水含量及脑组织和血浆中的伊文氏蓝含量。结果大鼠脑外伤后 ,生理盐水组脑组织脑水含量明显高于假手术组 (P <0 0 1) ,遭受直接打击的左侧半球脑水含量明显高于右半球 (P <0 0 1)。经药物YM 14 673处理后 ,左右半球的脑水含量均下降 (P <0 0 5 ) ,而不同剂量治疗组之间脑水含量无显著性差异 (P >0 0 5 )。急性脑外伤后 ,脑组织中伊文氏蓝含量明显升高 ,YM 14 673对其没有影响。结论YM 14 673可减轻急性脑外伤引起的脑水肿 ,但对血脑屏障通透性没有影响。     

Circular RNA circ-FoxO3 attenuates blood-brain barrier damage by inducing autophagy during ischemia/reperfusion

1. Download : Download high-res image (111KB)
2. Download : Download full-size image

     

Urapidil permeates the intact blood-brain barrier

Objective To determine the plasma and cerebrospinal fluid (CSF) levels of urapidil after i.v. administration and the effect on CSF serotonin and 5-hydroxyindoleacetic acid (5-HIAA) concentrations.Design Open, single-dose study.Setting Post-surgery following neurosurgical removal of the hypophysis (n=5) or aneurysm clipping (n=1).Patients 6 patients, aged 32–71 years, with intact bloodbrain barrier (BBB); 1 patient was studied twice.Interventions Single dose of 25 mg urapidil i.v. as prophylaxis of BP increase during extubation or as treatment of hypertensive episodes.Measurements and results Urapidil, serotonin and 5-HIAA were measured by HPLC in CSF during 8 h after urapidil administration. Urapidil was detected in CSF as soon as 5 min after injection in 3 patients. The concentration ratio of plasma/CSF after the distribution phase was about 51. No significant effect on serotonin and 5-HIAA in CSF was seen.Conclusion After administration of a therapeutic dose, urapidil permeates the BBB and may interact with central 5-HT_1A-receptors.The study was performed at the Department of Anaesthesia, University of the Saarland, Homburg, Germany     

Neutrophils and the blood-brain barrier dysfunction after trauma

Despite the fact that neutrophils are essential for the protection from invading pathogens, hyperactive neutrophils may elicit detrimental cerebral damage after severe trauma. The neutrophil interactions with the neurovascular unit entail endothelial dysfunction involving endothelial leakage, formation of edema, coagulation abnormalities, disturbed hemodynamics, tissue infiltration etc. These elements of the "whole body inflammation," designated systemic inflammatory response syndrome (SIRS) in conjunction with intracerebral proinflammatory activities, are important triggers of post-traumatic cerebral damage and mortality according to the "second hit" concept. From the immunologic point of view, the brain is an immune privileged site, known to resist autodestructive inflammatory activity much more efficiently than other organs because of the highly efficient diverse functions of the blood-brain barrier (BBB). However, both the underlying strategy of the BBB to maintain cerebral protecting functions against the post-traumatic neutrophil-mediated "second hit" and how activated neutrophils may overcome the BBB are currently unknown. Therefore, this review summarizes the current understanding of the "second hit," the BBB physiology, and its role in the maintenance of cerebral immune privilege, and discusses recent findings that may explain the pathophysiologic neutrophil-BBB interactions occurring after severe trauma, thus offering novel therapeutic options to protect from post-traumatic brain damage.     

经颅脑超声造影对血脑屏障通透性的影响

目的探讨经颅脑超声造影检查中血脑屏障通透性改变后其自行恢复时间，以探讨脑超声造影检查对血脑屏障通透性改变是否为可逆性。方法70只清洁级SD大鼠，经尾静脉注射剂量为1ml／kg的“脂氟显”超声造影剂，辅以机械指数为1．3的经颅脑超声造影检查，观察超声辐照后不同时间点血脑屏障通透性的变化。结果在造影检查后12h，血脑屏障通透性与对照组相比差异无统计学意义，且随着脑超声造影检查后时间的推移，血脑屏障通透性逐渐恢复。结论高机械指数的体表超声辅以高剂量超声造影剂在经颅脑超声造影中可导致血脑屏障通透性增加，但在造影检查后，这种改变可自行恢复。     

Targeting the central nervous system in lysosomal storage diseases: Strategies to deliver therapeutics across the blood-brain barrier

1. Download : Download high-res image (241KB)
2. Download : Download full-size image