The application of brain capillary permeability coefficient measurements to pathological conditions and the selection of agents which cross the blood-brain barrier

Capillary permeability was analyzed in both normal rat brain and intracerebral 9L gliosarcoma tumor and in rhesus monkey brain using a newly derived formula for the capillary permeability coefficient (P).The Pvalue for isotopic urea and sodium was less in monkey brain than in rat brain. The Pvalue for tumor was 1 log unit higher in tumor for all but the most rapidly transported drugs. Amphotericin B increased the normal brain Pvalue for galactitol but not for urea. Glucocorticoids did not alter brain Pvalues for sucrose or urea. Using P,drugs can be categorized in terms of blood-brain barrier (BBB) exclusion, slow BBB passage, moderate BBB passage, and rapid BBB passage. The technique described in this article is applicable to the study of regional differences in brain capillary permeability associated with disease states.This work was supported by NIH Grant CA-15435 and a gift from the Richard Jaenicke family.     

The mechanism of opening of the blood-brain barrier by hypertonic saline

The permeability of the blood-brain barrier was assessed in the cat, using Evan's blue as circulant. Regional blood flow and vascular resistance in various areas of brain were measured using radioactive microspheres. Cardiac output (CO), blood pressure (BP), heart rate (HR), pH, pO2 and pCO2 were also measured. Hypertonic saline (5 M, 0.5 ml/kg), administered intravenously, increased the staining of the brain substance. It also produced a marked increase in cerebral blood flow after 5 min and a marked decrease in blood flow to all the regions of the brain after 20 min. The flow returned to normal after 40 min. The vascular resistance decreased at 5 min, increased at 20 min and returned to normal at 40 min. Cardiac output increased significantly at 5 min and decreased at 20 min, while at 40 min it returned to normal. Blood pressure decreased at 5 min, increased at 20 min, while heart rate steadily decreased. A complete recovery of cardiac output, blood pressure and heart rate occurred in 1 hr. No change was observed in pH, pCO2 and pO2. It is concluded that intravenous administration of hypertonic saline causes marked haemodynamic changes and increases the permeability of the blood-brain barrier due to transient impairment of autoregulation.     

动脉内输注高渗性甘露醇改变大鼠血脑屏障对甲氨喋呤的通透性(英文)

目的:研究高渗性溶液开放血脑屏障能否提高甲氨喋呤在皮层内的含量及这一开放过程的时程变化。方法:1)大鼠颈内动脉注射甘露醇,10分钟后分别从股静脉及颈内动脉给予甲氨喋呤,1小时后测定脑皮层内浓度。2)大鼠颈内动脉注射甘露醇,分别在不同时间间隔给予甲氨喋呤,给药1小时后测定脑皮层内药物浓度及脑皮层密度。结果:给予甘露醇后,静注甲氨喋呤和颈内动脉注射甲氨喋呤可以使相应侧脑皮层内浓度分别提高2.54倍和3.41倍。此作用在给予甘露醇10分钟后达到最大,6小时后完全消失;同时并不伴随明显的皮层密度改变。结论:甘露醇可逆性地开放血脑屏障,提高甲氨喋呤在脑皮层内的浓度,同时不会造成明显的脑损伤。     

肽类物质的跨血脑屏障转运研究进展

血脑屏障（BBB）对大分子肽类药物的通透性直接关系到中枢神经系统疾病的药物治疗效果。肽类物质过去一直被认为是不能透过BBB的,但随着研究方法的不断发展和研究手段的不断改进,已有越来越多的实验表明,肽类物质不仅可以透过BBB,而且很可能主要是靠透过BBB而不是靠神经运输来达到CNS中的作用部位的。文章对血脑屏障的药物转运机制、影响大分子肽类药物血脑屏障通透性的因素以及改变大分子肽类药物血脑屏障通透性的可能途径及其临床意义等作一综述,以期对CNS的药物治疗有新的认识。     

Acute effects of short-chain alkylglycerols on blood-brain barrier properties of cultured brain endothelial cells

Background and Purpose

The blood-brain barrier (BBB) restricts drug penetration to the brain preventing effective treatment of patients suffering from brain tumours. Intra-arterial injection of short-chain alkylglycerols (AGs) opens the BBB and increases delivery of molecules to rodent brain parenchyma in vivo. The mechanism underlying AG-mediated modification of BBB permeability is still unknown. Here, we have tested the effects of AGs on barrier properties of cultured brain microvascular endothelial cells.

Experimental Approach

The effects of two AGs, 1-O-pentylglycerol and 2-O-hexyldiglycerol were examined using an in vitro BBB model consisting of primary cultures of rat brain endothelial cells, co-cultured with rat cerebral glial cells. Integrity of the paracellular, tight junction-based, permeation route was analysed by functional assays, immunostaining for junctional proteins, freeze-fracture electron microscopy, and analysis of claudin-claudin trans-interactions.

Key Results

AG treatment (5 min) reversibly reduced transendothelial electrical resistance and increased BBB permeability for fluorescein accompanied by changes in cell morphology and immunostaining for claudin-5 and β-catenin. These short-term changes were not accompanied by alterations of inter-endothelial tight junction strand complexity or the trans-interaction of claudin-5.

Conclusion and Implications

AG-mediated increase in brain endothelial paracellular permeability was short, reversible and did not affect tight junction strand complexity. Redistribution of junctional proteins and alterations in the cell shape indicate the involvement of the cytoskeleton in the action of AGs. These data confirm the results from in vivo studies in rodents characterizing AGs as adjuvants that transiently open the BBB.     

结构修饰策略改善药物血脑屏障通透性

如何使药物有效地穿越血脑屏障并发挥药效,是治疗中枢神经系统疾病的一大难题。通过结构修饰,可以改善小分子药物的理化性质,使其可由被动扩散的方式到达脑部;另外,可将药物修饰成能借助载体或受体介导的转运系统运输的结构,经由载/受体转运进入脑部。这两种手段是目前常用的改善药物血脑屏障通透性的化学方法。本文简要介绍了药物传送到脑部的主要途径,并重点阐述基于传送途径对小分子药物利用化学手段进行结构修饰以改善药物血脑屏障通透性的方法。     

Development of an in vitro blood-brain barrier model to study the effects of endosulfan on the permeability of tight junctions and a comparative study of the cytotoxic effects of endosulfan on rat and human glial and neuronal cell cultures

Endosulfan, an organochlorine (OC) insecticide that belongs to the cyclodiene group, is one of the most commonly used pesticides to control pests in vegetables, cotton, and fruits. Porcine brain microvascular endothelial cells were used to develop a model to study the effects of endosulfan on the permeability of tight junctions in the blood-brain barrier (BBB). BBB permeability, measured as transendothelial electrical resistance, decreased in a dose- and time-dependent manner when treated with alpha-endosulfan, beta-endosulfan, or endosulfan sulfate. Cytotoxicity testing revealed that the three endosulfans did not cause cell death at concentrations of 10 microM and below. The ratio of the average permeability of the filter-grown endothelial cell monolayer to 14C-endosulfan (Pe) going from the outer to the inner compartments with that going from the inner to the outer compartments was approximately 1:1.2-2.1 after exposure to concentrations of 0.01-10 microM. alpha-Endosulfan, beta-endosulfan, and endosulfan sulfate had cytotoxic effects on rat glial (C6) and neuronal (PC12) cell cultures as well as on human glial (CCF-STTG1) and neuronal (NT2) cell cultures. The effects of alpha-endosulfan were highly selective, with a wide range of LC50 values found in the different cultures, ranging from 11.2 microM for CCF-STTG1 cells to 48.0 microM for PC12 cells. In contrast, selective neurotoxicity was not so manifest in glial and neuronal cell cultures after exposure to endosulfan sulfate, as LC50 values were in the range of 10.4-21.6 microM. CCF-STTG1 cells were more sensitive to alpha-endosulfan and endosulfan sulfate, whereas NT2 cells were more sensitive to beta-endosulfan.