纳米氧化铝对血脑屏障通透性影响的体外研究

目的建立体外血脑屏障模型,评价纳米氧化铝对血脑屏障通透性的影响。方法粒度仪测定纳米氧化铝粒径及电位,透射电子显微镜观察纳米氧化铝形态与尺寸。从新生1～3 d Wistar鼠取大脑皮质分别原代培养脑微血管内皮细胞和星形胶质细胞,并进行免疫组化鉴定。应用Transwell进行两种细胞共培养建立体外血脑屏障模型,并对模型的有效性进行鉴定。以125、250和500μmol/L的50 nm氧化铝对血脑屏障模型进行染毒,比较染毒前后血脑屏障模型对芦丁通透性变化。以500μmol/L纳米氧化铝对血脑屏障模型进行染毒,分别比较0、2、4、6和8 h不同染毒时间对血脑屏障通透性的改变。结果芦丁吸光值检测显示:与0μmol/L纳米氧化铝组相比,125μmol/L组差异无统计学意义,250和500μmol/L组血脑屏障通透性均明显增加(P<0.05)。与0 h组相比,2、4、6和8 h组血脑屏障通透性均明显增加(P<0.05)。结论体外血脑屏障模型实验研究结果显示,纳米氧化铝可以损伤血脑屏障,引起血脑屏障通透性增加。     

Effect of anticholinesterase compound phosalone on blood-brain barrier (BBB) permeability

To elucidate the role of acetylcholinesterase (AChE) enzyme in BBB function, phosalone, an organophosphorous compound, was studied using rat brain micro vessels in vitro. Phosalone at 100 mg/kg b. wt. induced convulsions and caused a significant inhibition of AChE resulting in increased permeability as assessed by volume distribution. The anaesthetized phosalone treated group also increased permeability as compared to the control but the values were significantly (P<0.05) lower than phosalone alone treated group. The inhibition of AChE enzyme has altered the barrier function at the dose level at which it caused convulsion and had an added effect on permeability of BBB.     

血管紧张素对血脑屏障影响的研究进展

血管紧张素（angiotensin）是一组特异性作用于血管内皮细胞的因子,主要有血管紧张素-1、血管紧张素-2和血管紧张素-33种形式。其中血管紧张素-1和血管紧张素-2对血脑屏障的通透性,血脑屏障在脑缺血导致的损伤的修复以及新的脑内微血管的生成有着很大的影响。     

Methods to assess drug permeability across the blood-brain barrier

Much research has focussed on the development of novel therapeutic agents to target various central nervous system disorders, however less attention has been given to determining the potential of such agents to permeate the blood-brain barrier (BBB), a factor that will ultimately govern the effectiveness of these agents in man. In order to assess the potential for novel compounds to permeate the BBB, various in-vitro, in-vivo and in-silico methods may be employed. Although in-vitro models (such as primary cell culture and immortalized cell lines) are useful as a screening method and can appropriately rank compounds in order of BBB permeability, they often correlate poorly to in-vivo brain uptake due to down-regulation of some BBB-specific transporters. In-vivo models (such as the internal carotid artery single injection or perfusion, intravenous bolus injection, brain efflux index and intracerebral microdialysis) provide more accurate information regarding brain uptake, and these can be complemented with novel imaging techniques (such as magnetic resonance imaging and positron emission tomography), although such methods are not suited to high-throughput permeability assessment. This paper reviews current methods used for assessing BBB permeability and highlights the particular advantages and disadvantages associated with each method, with a particular focus on methods suitable for moderate- to high-throughput screening.     

Enhancement of blood-brain barrier permeability by sodium caprate.

We examined the effect of sodium caprate on the integrity of the tight junctions of brain capillary endothelial cells, using a modified in-situ brain perfusion technique. Model hydrophilic compounds used were [3H]mannitol, [14C]sucrose, [3H]PEG900, [3H]PEG4000, FITC-dextran 4000, FITC-dextran 20000 and FITC-dextran 70000. The brain distribution volume of [14C]sucrose was significantly increased by sodium caprate in a concentration-dependent manner. The effective minimum concentration was 10mM. Furthermore, the effects of sodium caprate on the distribution volumes of hydrophilic compounds, [3H]mannitol, [14C]sucrose, [3H]PEG900, [3H]PEG4000, FITC-dextran 4000, FITC-dextran 20000 and FITC-dextran 70000, showed a molecular weight dependence. A plot of apparent permeation clearance against diffusion coefficient values suggested that 20 mM sodium caprate induced pores so large that the above compounds could pass through the blood-brain barrier with negligible friction within the pore. Our results showed that intracarotid sodium caprate perfusion could enhance the permeation of hydrophilic compounds through the blood-brain barrier.     

Effect of early inorganic lead exposure on rat blood-brain barrier permeability to tyrosine or choline

The primary objective of this research was to test the hypothesis that low level lead (Pb) exposure during early life leads to disruption in blood-brain barrier (BBB) function in the young rat. Newborn rats received lead via milk from lactating dams that were drinking water containing 0.1% lead acetate Pb(Ac)₂. Pups were weaned to, and maintained on, 0.1% Pb(Ac)₂-containing solution up to 70 days of age. Growth was no different from that of coetaneous controls. Experimental animals displayed elevated blood lead (15 μg/dl) within 2 days from the onset of exposure, and it increased to 35–40 μg/dl between 13 and 22 days of age. Following weaning to the higher lead source, blood lead values continued to increase (55 μg/dl) but, then, appeared to decline after 55 days of age. Control animals consistently possessed blood lead values of less then 5 μg/dl. The brain capillary (BBB) transport of the neurotransmitter precursors, choline and tyrosine, was studied at 55 and 70 days of age using intracarotid injections of a bolus containing ¹⁴C-labeled substrate and ³HOH as a diffusable reference (Brain Uptake Index). There was no difference in the transport of either choline of tyrosine in lead-intoxicated rats compared to controls. Suspected adverse psychoneurological effects of low level inorganic lead probably relate to the parenchymal cells of the CNS and not to the brain capillary endothelial cells.     

Aluminum alters the permeability of the blood-brain barrier to some non-peptides

The effect of aluminum administered intraperitoneally (i.p.) on the levels of peripherally injected 99mTc labelled red blood cells in brain and on the penetration of the blood-brain barrier by radioiodinated serum albumin (RISA), thyroxine, iodide, cortisol, N-Tyr-delta sleep-inducing peptide (N-Tyr-DSIP), growth hormone, thyroid stimulating hormone (TSH), prolactin and human and rat luteinizing hormone was examined. Treatment with aluminum did not alter the brain/blood ratio for either 99mTc red blood cells or RISA, although it did increase the blood levels of RISA. These results show that aluminum caused a contraction in the volume of plasma without altering the vascular space of the brain, disrupting the blood-brain barrier, or increasing the "leakiness" of the blood-brain barrier. Aluminum enhanced the permeability of the blood-brain barrier to labelled prolactin, thyroxine, cortisol, growth hormone, N-Tyr-DSIP and rat luteinizing hormone, but not to labelled TSH, iodide, or human luteinizing hormone, a substance with an octanol coefficient markedly different from that of luteinizing hormone from the rat. Incubation of the peptide with aluminum before injection did not increase penetration, demonstrating that aluminum did not increase the permeability of the blood-brain barrier by acting directly on the peptide. Aluminum, administered intraperitoneally, increased the accuracy of lipophilicity as a predictor of penetration of the blood-brain barrier, but the greatest increase in penetration was seen with thyroxine, a substance which crosses the blood-brain barrier by carrier-mediated transport.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nanoparticle surface charges alter blood-brain barrier integrity and permeability

PURPOSE: The blood-brain barrier (BBB) presents both a physical and electrostatic barrier to limit brain permeation of therapeutics. Previous work has demonstrated that nanoparticles (NPs) overcome the physical barrier, but there is little known regarding the effect of NP surface charge on BBB function. Therefore, this work evaluated: (1) effect of neutral, anionic and cationic charged NPs on BBB integrity and (2) NP brain permeability. Methods: Emulsifying wax NPs were prepared from warm oil-in-water microemulsion precursors using neutral, anionic or cationic surfactants to provide the corresponding NP surface charge. NPs were characterized by particle size and zeta potential. BBB integrity and NP brain permeability were evaluated by in situ rat brain perfusion. RESULTS: Neutral NPs and low concentrations of anionic NPs were found to have no effect on BBB integrity, whereas, high concentrations of anionic NPs and cationic NPs disrupted the BBB. The brain uptake rates of anionic NPs at lower concentrations were superior to neutral or cationic formulations at the same concentrations. CONCLUSIONS: (1) Neutral NPs and low concentration anionic NPs can be utilized as colloidal drug carriers to brain, (2) cationic NPs have an immediate toxic effect at the BBB and (3) NP surface charges must be considered for toxicity and brain distribution profiles.     

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。     

Ethanol enhancement of blood-brain barrier permeability to catecholamines in chicks

The effect of ethanol (EtOH) on permeability of the blood-brain barrier (BBB) to parenteral catecholamines was investigated in neonate chicks. Animals simulataneously administered EtOH, 2 g/kg, and norepinephrine (NE), 5 mg/kg, or epinephrine (E), 5 mg/kg, entered a roosting state which was more pronounced than that observed after either amine alone. Roosting chicks were killed 2 min after NE + EtOH and 10 min after E + EtOH for whole brain amine analysis. NE + EtOH treatment resulted in a 220% increase in whole brain NE over controls receiving this amine alone, whereas E + EtOH produced a 29% increase in brain E. EtOH alone did not alter endogenous levels of either amine in brain. Results indicate that EtOH, a solvent whose solubility characteristics allow it to penetrate easily both aqueous and lipoid membrane components, facilitates entry of E and NE into the brain of the neonate chick across an imperfect BBB present at hatching.     

In-vitro characterization of blood-brain barrier permeability to delta sleep-inducing peptide

The diffusion of delta sleep-inducing peptide (DSIP) across the blood-brain barrier (BBB) has been investigated with an in-vitro model comprised of primary cultures of brain microvessel endothelial cell (BMEC) monolayers. The BMEC monolayers were mounted in a side-by-side diffusion apparatus and the transendothelial flux of DSIP analysed by HPLC with UV detection at 280 nm. The transendothelial flux of the peptide was linear with time and increasing concentrations of DSIP (non-saturable), but was not altered by reduced temperature. The apparent permeability coefficient for DSIP penetration of BMEC monolayers was in a range similar to water-soluble substances (e.g. fluorescein, fluorescein isothiocyanate dextrans) that penetrate the blood-brain barrier to a limited degree based on molecular weight. DSIP flux across the BMEC monolayers was also found to be bidirectional, insensitive to metabolic inhibitors, and not altered by high concentrations of tryptophan. Little degradation (apparent t1/2 about 10 h) of DSIP to major metabolites, tryptophan (trp) and des-trp DSIP, occurred over the time of the diffusion experiments. The results of these studies support and confirm observations in-vivo indicating that intact DSIP crosses the BBB by simple transmembrane diffusion.     

Low permeability of the blood-brain barrier to nanomolar concentrations of immunoreactive alpha-melanotropin

The permeability of the blood-brain barrier (BBB) to immunoreactive alpha-melanotropin (-MSH) was quantified in rats pretreated with monosodium l-glutamic acid to deplete their CNS stores of endogenous -MSH. The methodology, suitable for poorly permeable substances, monitored blood and brain tissue concentrations of -MSH over 15 min following intravenous injection of 30 nmol synthetic -MSH. Rate constants for entry of -MSH into brain tissue were estimated from separate nonlinear least-squares fits of connecting two- and one-compartment open models to plasma and extravascular brain tissue concentration data, respectively. Comparisons were made to rate constants measured similarly for ¹⁴C-inulin. The BBB had a low permeability to immunoreactive -MSH, consistent with peptide penetrating the barrier by passive diffusion dependent upon the lipid solubility of the molecule.     

Effect of serum from renal failure and cirrhotic patients on the blood-brain barrier permeability to DL-propranolol in rats

Our previous studies using an in vivo tissue-sampling single-carotid injection method have shown that the transport of DL-propranolol into rat brain is inhibited by the serum from rats with uranyl nitrate-induced acute renal failure. The present studies were designed to examine the effect of serum from patients with renal or liver disease on the transport of DL-propranolol into the rat brain. While the binding of DL-propranolol to serum from cirrhotic patients was significantly decreased compared to normal serum, there was no change for the serum from patients with renal failure. In the carotid injection studies, the brain transport parameters such as the brain uptake index (BUI), the unidirectional extraction ratio (ET), the blood-brain barrier permeability surface area product (PSapp), and PSapp corrected for the unbound fraction (PSuapp) in rats injected with serum from patients with renal failure were significantly reduced to approximately 40-53% of those in controls. No change in BUI, ET, and PSapp was found in rats injected with serum from cirrhotic patients. However, the cirrhotic patients adopted in the present study had relatively mild liver disease (judging from the biochemical blood test), and we cannot refer to the more severe cirrhotic patients only from this study. Moreover, significant correlations were observed between the biochemical parameters (blood urea nitrogen, serum creatinine concentration) representing the degree of renal failure and the transport parameters (ET, PSapp, or PSuapp) of DL-propranolol.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of nanoparticulate polybutylcyanoacrylate and methylmethacrylate-sulfopropylmethacrylate on the permeability of zidovudine and lamivudine across the in vitro blood-brain barrier

Effect of size of nanoscaled polybutylcyanoacrylate (PBCA) and methylmethacrylate-sulfopropylmethacrylate (MMA-SPM) on the permeability of zidovudine (AZT) and lamivudine (3TC) across the blood-brain barrier (BBB) was investigated. Also, influence of alcohol on the permeability of AZT and 3TC incorporated with the two polymeric nanoparticles (NPs) was examined. The loading efficiency and the permeability of AZT and 3TC decreased with an increase in the particle size of the two carriers. By employing PBCA NPs, the BBB permeability of AZT and that of 3TC became, respectively, 8-20 and 10-18 folds. Application of MMA-SPM NPs leaded to about 100% increase in the BBB permeability of the two drugs. In the presence of 0.5% ethanol, 4-12% enhancement in the BBB permeability of the two drugs was obtained in the current carrier-mediated system.     

Influence of profound hypothermia on the blood-brain barrier permeability during acute arterial hypertension.

In hypothermic rats with acute hypertension induced by intravenous injection of adrenalin, regional changes in blood-brain barrier permeability to macromolecules were investigated using Evans blue as indication. Evans blue albumin extravasation was determined as a macroscopic finding and a quantitative estimation with a spectrophotometer using homogenized brain to release the dye was also performed to evaluate the macroscopic findings. Five groups of rats were studied: Group I: normothermia + acute hypertension; Group II: hypothermia + acute hypertension; Group III: control hypothermia; Group IV: normothermia + hypotension; Group V: control normothermia. The rats were anaesthetized with diethyl-ether. Body temperature was lowered by submerging anaesthetized animals in an ice water bath. The colonic temperature was reduced to 20 +/- 1 degrees C. During adrenaline-induced acute hypertension the mean arterial blood pressure increased in both normothermic and hypothermic animals. Blood-brain barrier lesions were present in 40% of normothermic rats, and 60% of hypothermic rats after adrenaline-induced hypertension. Mean value for Evans blue dye in the whole brain was found to be 0.530 +/- 0.202 mg% in the normothermic rats and 0.752 +/- 0.256 mg% in the hypothermic rats during adrenaline-induced hypertension. This difference between normothermic and hypothermic rats was found to be statistically significant (P less than 0.01). Our results showed that the extravasation of Evans blue albumin was most pronounced in the brains of hypothermic rats compared to normothermic rats after adrenaline-induced acute hypertension.