Body distribution of polysorbate-80 and doxorubicin-loaded [14C]poly(butyl cyanoacrylate) nanoparticles after i.v. administration in rats

Previously it was shown that poly(butyl cyanoacrylate) (PBCA) nanoparticles coated with polysorbate 80 are able to cross the blood-brain barrier (BBB) after i.v. administration. The objective of the present study was to investigate the influence of polysorbate 80 and doxorubicin-loading on the body distribution in rats. The biodistribution profile and brain concentration of (14)C-radiolabeled PBCA nanoparticles, polysorbate 80 coated (14)C-PBCA nanoparticles, and doxorubicin-loaded (14)C-PBCA nanoparticles were determined by radioactivity counting after i.v. administration in rats. The (14)C-PBCA nanoparticles showed a significant accumulation in the organs of the reticuloendothelial system (RES). Polysorbate 80 coating of the (14)C-PBCA nanoparticles decreased this accumulation to about 40% after 1 h post injection. The brain concentration was increased about 2-fold after polysorbate 80-coating at this time point. The presence of doxorubicin in this preparation, however, decreased the brain concentration to levels similar to uncoated particles, probably caused by the positive charge of this compound. After longer time periods after injection the differences between the three preparations decreased.     

Toxicological studies of doxorubicin bound to polysorbate 80-coated poly(butyl cyanoacrylate) nanoparticles in healthy rats and rats with intracranial glioblastoma.

Polysorbate 80-coated poly(butyl cyanoacrylate) nanoparticles (NP) were shown to enable the transport of a number of drugs including the anti-tumour antibiotic doxorubicin (DOX) across the blood-brain barrier (BBB) to the brain after intravenous administration and to considerably reduce the growth of brain tumours in rats. The objective of the present study was to evaluate the acute toxicity of DOX associated with polysorbate 80-coated NP in healthy rats and to establish a therapeutic dose range for this formulation in rats with intracranially implanted 101/8 glioblastoma. Single intravenous administration of empty poly(butyl cyanoacrylate) NP in the dose range 100-400 mg/kg did not cause mortality within the period of observation. NP also did not affect body weight or weight of internal organs. Association of DOX with poly(butyl cyanoacrylate) NP did not produce significant changes of quantitative parameters of acute toxicity of the anti-tumour agent. Likewise, the presence of polysorbate 80 in the formulations was not associated with changes in toxicity compared with free or nanoparticulate drug. Dose regimen of 3x1.5 mg/kg on days 2, 5, 8 after tumour implantation did not cause drug-induced mortality. The results in tumour-bearing rats were similar to those in healthy rats. These results demonstrate that the toxicity of DOX bound to NP was similar or even lower than that of free DOX.     

Body distribution of polysorbate‐80 and doxorubicin-loaded [14C]poly(butyl cyanoacrylate) nanoparticles after i.v. administration in rats

Previously it was shown that poly(butyl cyanoacrylate) (PBCA) nanoparticles coated with polysorbate 80 are able to cross the blood-brain barrier (BBB) after i.v. administration. The objective of the present study was to investigate the influence of polysorbate 80 and doxorubicin-loading on the body distribution in rats. The biodistribution profile and brain concentration of ¹⁴C-radiolabeled PBCA nanoparticles, polysorbate 80 coated ¹⁴C-PBCA nanoparticles, and doxorubicin-loaded ¹⁴C-PBCA nanoparticles were determined by radioactivity counting after i.v. administration in rats. The ¹⁴C-PBCA nanoparticles showed a significant accumulation in the organs of the reticuloendothelial system (RES). Polysorbate 80 coating of the ¹⁴C-PBCA nanoparticles decreased this accumulation to about 40% after 1 h post injection. The brain concentration was increased about 2-fold after polysorbate 80-coating at this time point. The presence of doxorubicin in this preparation, however, decreased the brain concentration to levels similar to uncoated particles, probably caused by the positive charge of this compound. After longer time periods after injection the differences between the three preparations decreased.     

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.     

Permeability of a capsaicin derivative, [14C]DA-5018 to blood-brain barrier corrected with HPLC method

In the present work, the transport mechanism of a capsaicin derivative, DA-5018, through blood-brain barrier (BBB) has been investigated to evaluate the feasibility of potential drug development. The result of pharmacokinetic parameters obtained from the intravenous injection of plasma volume marker, [3H]RSA and [14C]DA-5018, indicated that both AUC, area under the plasma concentration curve and VD, volume of distribution in brain of [3H]RSA agreed with those reported (1620 +/- 10 percentage injected dose minute per milliliter (%IDmin/ml) and 12.0 +/- 0.1 microliters/g, respectively). Elimination half-life and AUC of [14C]DA-5018 is corrected by the HPLC analysis, 19.6 +/- 1.2 min and 7.69 +/- 0.85% IDmin/ml, respectively. The metabolic rate of [14C] DA-5018 was very rapid. The blood-brain barrier permeability surface area (PS) product of [14C]DA-5018 was calculated to be 0.24 +/- 0.05 microliter/min/g. The result of internal carotid artery perfusion and capillary depletion suggested that [14C]DA-5018 pass through BBB with the time increasingly. Investigation of transport mechanism of [14C]DA-5018 using agonist and antagonist suggested that vanilloid (capsaicin) receptor did not exist in the BBB, and nutrient carrier system in the BBB has no effect on the transport of DA-5018. In conclusion, despite the fact that penetration of DA-5018 through BBB is significant, the intact drug found in the brain tissue is small because of a rapid metabolism. Therefore, for the central analgesic effect of DA-5018, the method to increase the metabolic stability in plasma and the brain permeability should be considered.     

Blood-Brain Barrier Transport of Reduced Folic Acid

Purpose. The brain is relatively resistant to folic acid deficiency, indicating specialized transport systems may exist for this vitamin localized within the brain capillary endothelial wall, which makes up the blood-brain barrier (BBB) in vivo. The present studies quantify the BBB transport of [³H]-methyltetrahydrofolic acid (MTFA) in vivo and in isolated human brain capillaries in vitro. Methods. BBB transport of [³H]-MTFA was compared to that of [¹⁴C]-sucrose, a plasma volume marker, following either intravenous injection or intracarotid perfusion in anesthetized rats. Competition by 10 M MTFA or 10 M folic acid was examined to determine whether folic acid is also transported by the MTFA uptake system. Results. The BBB permeability-surface area (PS) product of [³H]-MTFA, 1.1± 0.3 L/min/g, was 6-fold greater than that of [¹⁴C]-sucrose following intravenous injection. The BBB PS product determined by intracarotid arterial perfusion was not significantly different from the BBB PS product calculated following intravenous injection. A time- and temperature- dependent uptake of [³H]-MTFA in human brain capillaries was observed. The uptake of [³H]-MTFA by either rat brain in vivo or by human brain capillaries in vitro was equally inhibited by 10 M concentrations of either unlabeled MTFA or unlabeled folic acid. Conclusions. (1) A saturable transport system exists at the BBB for folic acid derivatives and since this transport is equally inhibited by either folic acid or MTFA, it is inferred that this transport system is the folic acid receptor, and not the reduced folic acid carrier. (2) The presence of a folate transport system at the BBB may offer an endogenous transport system for brain drug delivery of conjugates of folates and drugs that do not normally cross the BBB in vivo.     

酸敏感阿霉素前药纳米粒的合成及其在治疗脑胶质瘤中的作用

摘要： 目的 合成一类新的具有酸敏感性能的阿霉素前药纳米粒 （PEG-DOX NPs）, 对其结构进行表征, 并研究其在体外抗脑胶质瘤中的作用和透过血脑屏障的效率。方法 通过席夫碱反应合成具有酸敏感的聚乙二醇-阿霉素 （PEG-DOX） 单体, 通过自组装制备 PEG-DOX NPs。利用动态光散射 （DLS） 和核磁对单体进行结构表征, 通过透射电镜 （TEM） 对纳米粒的微观形貌进行观察, 紫外检测法测定 PEG-DOX NPs 在酸性条件下的释放行为, 荧光显微镜观察脑胶质瘤细胞对 PEG-DOX NPs 的摄取行为。利用MTT 法测定 PEG-DOX NPs 与阿霉素 （DOX） 对脑胶质瘤细胞的杀伤作用。PEG-DOX NPs 修饰吐温 80 （PS-80） 获得 PS80-PEG-DOX NPs。将 9 只 BALB/c 小鼠随机均分为 Free DOX 组、 PEG-DOX NPs 组和 PS80-PEG-DOX NPs 组, 利用小动物活体成像系统比较其修饰前后脑及主要脏器内 DOX 的荧光强度。结果 PEG-DOX 能够自组装成直径 100 nm 左右的纳米粒; 在酸性条件下 PEG-DOX NPs 能够快速释放 DOX, 肿瘤细胞对 PEG-DOX NPs 的摄取虽然比 DOX 慢, 但蓄积时间更长; PEG-DOX NPs 和 Free DOX 对 C6 细胞的增殖抑制均呈现浓度依赖性, PEG-DOX NPs 组细胞增殖抑制率在各个浓度下均低于 Free DOX 组。 PS-80 修饰后, PS80-PEG-DOX NPs 透过血脑屏障的效率显著高于 DOX 和 PEG-DOX NPs 组。结论 PEG-DOX NPs 具有良好的体外抗肿瘤作用, 修饰后可高效透过血脑屏障, 使其体内治疗脑胶质瘤成为可能。     

Blood-brain permeability of [3H]-(3-methyl-His2)thyrotropin-releasing hormone (MeTRH) in mice: effects of TRH and its analogues

The present study was undertaken to characterize the transport of (3-methyl-His(2)) thyrotropin-releasing hormone ([(3)H]MeTRH) across the blood-brain barrier in mice and the effects of thyrotropin-releasing hormone (TRH) and its analogues (taltirelin and montirelin) on the transport and brain distribution. Integration plot analysis was used to calculate the influx clearance (CL(in)) of [(3)H]MeTRH after intravenous (i.v.) injection in mice. Furthermore, the capillary depletion method was performed to determine whether [(3)H]MeTRH crossed the blood-brain barrier. The effects of TRH and its analogues on the brain distribution of [(3)H]MeTRH were also examined by co-injection with the radioligand. The brain distribution of [(3)H]MeTRH and [(14)C]sucrose increased with the time after i.v. injection in mice, and the level of [(3)H]MeTRH was significantly higher than that of [(14)C]sucrose 5 min after the injection. The CL(in) value of [(3)H]MeTRH was significantly higher than that of [(14)C]sucrose, and the value of [(3)H]MeTRH was reduced by co-injection with unlabeled MeTRH. Also, capillary depletion showed that [(3)H]MeTRH was distributed largely in the brain parenchyma and this distribution was significantly inhibited by co-injection of TRH and montirelin but not taltirelin. The present study indicates that the transport of [(3)H]MeTRH into the brain may be via a saturable process.     

New positron emission tomography tracer [(11)C]carvedilol reveals P-glycoprotein modulation kinetics

Imaging of P-glycoprotein (P-gp) function in the blood-brain barrier (BBB) may support development of strategies, which will improve drug delivery to the brain. [(11)C]verapamil has been developed as a positron emission tomography (PET) tracer, to image P-gp function in vivo. Ideally, for the purpose of brain imaging, tracers should have a log P between 0.9 and 2.5. The beta-receptor antagonist carvedilol is a P-gp substrate with a log P=2.0, and can be labeled with [(11)C]. The aim of this study was to determine whether the P-gp substrate [(11)C]carvedilol can be used as a PET tracer for visualisation and quantification of the P-gp function in the BBB. Cellular [(11)C]carvedilol accumulation in GLC(4), GLC(4)/P-gp, and GLC(4)/Adr cells increased three-fold in the GLC(4)/P-gp cells after pretreatment with cyclosporin A (CsA) whereas no effect of MK571 could be determined in the GLC(4)/Adr cells. Ex vivo [(11)C]carvedilol biodistribution studies showed that [(11)C]carvedilol uptake in the brain was increased by CsA. [(11)C]carvedilol uptake in other organs was not affected by CsA. Autoradiography studies of rat brains showed that [(11)C]carvedilol was homogeneously distributed over the brain and that pretreatment with CsA increased [(11)C]carvedilol uptake. In vivo PET experiments were performed with and without P-gp modulation by CsA. P-gp mediated transport was quantified by Logan analysis of the PET data, calculating the distribution volume (DV) of [(11)C]carvedilol in the brain. Logan analysis resulted in excellent fits, revealing that [(11)C]carvedilol is not trapped in the brain. Brain DV of [(11)C]carvedilol showed a dose-dependent increase of maximal three-fold after CsA pretreatment. Above 15 mg kg(-1), no change in DV was found. Compared to [(11)C]verapamil less CsA was needed to reach maximal DV, suggesting that [(11)C]carvedilol kinetics is a more sensitive tool to in vivo measure P-gp function.     

A critical evaluation of the brain efflux index method as applied to the nitric oxide synthase inhibitor, aminoguanidine

The Brain Efflux Index (BEI) method is an in vivo procedure designed to quantitate saturable efflux mechanisms resident at the blood--brain barrier (BBB). The present work utilized the BEI method to assess the BBB efflux mechanisms of [(14)C]aminoguanidine, a nitric oxide synthase inhibitor. The BEI for [(14)C]aminoguanidine was >100% (relative to [(3)H]inulin diffusion) over a range of 41-184 pmol after 40 min. The unusually high retention (>100%) of [(14)C]aminoguanidine suggested brain parenchymal sequestration, either by neuronal uptake or tissue protein binding. The uptake of [(14)C]aminoguanidine in dendritic neuronal endings (synaptosomes) showed a saturable concentration dependency, consistent with a carrier-mediated process. Nonlinear least-squares regression yielded the following Michaelis--Menten and diffusional (k(ns)) parameters for synaptosomal [(14)C]aminoguanidine uptake: V(max)=118.50 +/- 28.77 pmol x mg protein(-1)/3 min; K(m)=58.34 +/- 8.33 muM; k(ns)=0.15 +/- 0.029 pmol x mg protein(-1)/3 min/muM; mean +/- SEM; n=3 concentration profiles). Protein binding studies using brain tissue showed negligible binding. In summary, this work identified three principle findings: (1) An apparent lack of quantifiable aminoguanidine BBB efflux; (2) a previously undescribed synaptosomal accumulation process for aminoguanidine; and (3) an interesting limitation of the BEI technique where unusual brain parenchymal sequestration yields values >100%.     

Effects of Particle Size and Surface Modification on Cellular Uptake and Biodistribution of Polymeric Nanoparticles for Drug Delivery

Purpose

To investigate the effects of the particle size and surface coating on the cellular uptake of the polymeric nanoparticles for drug delivery across the physiological drug barrier with emphasis on the gastrointestinal (GI) barrier for oral chemotherapy and the blood–brain barrier (BBB) for imaging and therapy of brain cancer.

Methods

Various sizes of commercial fluorescent polystyrene nanoparticles (PS NPs) (viz 20 50, 100, 200 and 500 nm) were modified with the d-α-tocopheryl polyethylene glycol 1,000 succinate (vitamin E TPGS or TPGS). The size, surface charge and surface morphology of PS NPs before and after TPGS modification were characterized. The Caco-2 and MDCK cells were employed as an in vitro model of the GI barrier for oral and the BBB for drug delivery into the central nerve system respectively. The distribution of fluorescent NPs after i.v. administration to rats was analyzed by the high performance liquid chromatography (HPLC).

Results

The in vitro investigation showed enhanced cellular uptake efficiency for PS NPs in both of Caco-2 and MDCK cells after TPGS surface coating. In vivo investigation showed that the particle size and surface coating are the two parameters which can dramatically influence the NPs biodistribution after intravenous administration. The TPGS coated NPs of smaller size (< 200 nm) can escape from recognition by the reticuloendothelial system (RES) and thus prolong the half-life of the NPs in the blood system.

Conclusions

TPGS-coated PS NPs of 100 and 200 nm sizes have potential to deliver the drug across the GI barrier and the BBB.     

Influence of surfactants, polymer and doxorubicin loading on the anti-tumour effect of poly(butyl cyanoacrylate) nanoparticles in a rat glioma model

Poly(n-butyl cyanoacrylate) nanoparticles coated with polysorbate-80 can enable the transport of bound drugs across the blood-brain barrier (BBB) after i.v. injection. In the present study the influence of different formulation parameters on the anti-tumoural effects of doxorubicin nanoparticles against glioblastoma 101/8 was investigated. The manufacturing parameters of poly(alkyl cyanoacrylate) doxorubicin-loaded nanoparticles were optimized concerning drug loading. The nanoparticles were coated with different surfactants and injected intravenously on days 2, 5 and 8 after intra-cranial implantation of glioblastoma 101/8 to rats. The survival times of all doxorubicin containing preparations, including a doxorubicin solution, increased the survival times significantly compared to untreated tumour-bearing rats. The most pronounced increase in survival was obtained with the poly(n-butyl cyanoacrylate) doxorubicin-loaded nanoparticles coated with polysorbate 80 and 35% of these animals survived for over 180 days (termination of the experiments). The other nanoparticle preparations yielded lower survival times. Poly(n-butyl cyanoacrylate) doxorubicin-loaded nanoparticles coated with polysorbate 80-coated proved to be very efficient against glioblastoma 101/8. The data suggest that the interaction of nanoparticles with the blood after injection as well as the enhanced permeability and retention effect (EPR effect) contributed differently to the anti-tumoural efficacy depending on nanoparticle formulation and surface properties.     

Indirect Evidence that Drug Brain Targeting Using Polysorbate 80-Coated Polybutylcyanoacrylate Nanoparticles Is Related to Toxicity

Purpose. To investigate the mechanism underlying the entry of the analgesic peptide dalargin into brain using biodegradable polybutylcyanoacrylate (PBCA) nanoparticles (NP) overcoated with polysorbate 80. Methods. The investigations were carried out with PBCA NP and with non biodegradable polystyrene (PS) NP (200 nm diameter). Dalargin adsorption was assessed by HPLC. Its entry into the CNS in mice was evaluated using the tail-flick procedure. Locomotor activity measurements were performed to compare NP toxicities. BBB permeabilization by PBCA NP was studied in vitro using a coculture of bovine brain capillary endothelial cells and rat astrocytes. Results. Dalargin loading was 11.7 µg/mg on PBCA NP and 16.5µg/ mg on PS NP. Adding polysorbate 80 to NP led to a complete desorption. Nevertheless, dalargin associated with PBCA NP and polysorbate 80 induced a potent and prolonged analgesia, which could not be obtained using PS NP in place of PBCA NP. Locomotor activity dramatically decreased in mice dosed with PBCA NP, but not with PS NP. PBCA NP also caused occasional mortality. In vitro, PBCA NP (10 µg/ml) induced a permeabilization of the BBB model. Conclusions. A non specific permeabilization of the BBB, probably related to the toxicity of the carrier, may account for the CNS penetration of dalargin associated with PBCA NP and polysorbate 80.     

Effect of P-glycoprotein on intestinal absorption and brain penetration of antiallergic agent bepotastine besilate.

The antiallergic agent bepotastine besilate is a nonsedating, second-generation H1-antagonist with high oral absorption and negligible distribution into brain. To clarify the role of P-glycoprotein (P-gp) in the pharmacokinetics of bepotastine, intestinal absorption and brain penetration studies were performed. [(14)C]Bepotastine transport in P-gp-overexpressed LLC-PK1 cells indicated that bepotastine was a substrate of P-gp. The affinity of bepotastine to P-gp estimated by ATPase activity assay was low, with a K(m) value of 1.25 mM. After i.v. administration, the brain/plasma free concentration ratio in mdr1-knockout mice was 3 times higher than that in wild-type mice. The in situ intestinal absorption studies of [(14)C]bepotastine in rats showed a clear regional difference, showing highest permeability at the upper part of small intestine with a decreasing permeability in the descending part of small intestine. The apparent absorption rate constant (ka) of [(14)C]bepotastine in the small intestine was greatly increased by cyclosporin A and verapamil, especially in the distal portion, and the site-specific absorption of [(14)C]bepotastine disappeared. The concentration dependence of ka of [(14)C]bepotastine was observed with a higher ka at higher concentration (20 mM) compared with that at lower concentration (1 microM). In conclusion, bepotastine is a substrate for P-gp, and P-gp clearly limited the brain distribution of bepotastine, whereas the effect of P-gp on intestinal absorption of bepotastine was minimal, presumably because of high membrane permeability at the upper region of small intestine where P-gp is less expressed. Such intestinal absorption property of bepotastine is distinctly different from the low membrane-permeable P-gp substrate fexofenadine.     

Influence of surfactants,polymer and doxorubicin loading on the anti-tumour effect of poly(butyl cyanoacrylate) nanoparticles in a rat glioma model

Poly(n-butyl cyanoacrylate) nanoparticles coated with polysorbate-80 can enable the transport of bound drugs across the blood–brain barrier (BBB) after i.v. injection. In the present study the influence of different formulation parameters on the anti-tumoural effects of doxorubicin nanoparticles against glioblastoma 101/8 was investigated. The manufacturing parameters of poly(alkyl cyanoacrylate) doxorubicin-loaded nanoparticles were optimized concerning drug loading. The nanoparticles were coated with different surfactants and injected intravenously on days 2, 5 and 8 after intra-cranial implantation of glioblastoma 101/8 to rats. The survival times of all doxorubicin containing preparations, including a doxorubicin solution, increased the survival times significantly compared to untreated tumour-bearing rats. The most pronounced increase in survival was obtained with the poly(n-butyl cyanoacrylate) doxorubicin-loaded nanoparticles coated with polysorbate 80 and 35% of these animals survived for over 180 days (termination of the experiments). The other nanoparticle preparations yielded lower survival times. Poly(n-butyl cyanoacrylate) doxorubicin-loaded nanoparticles coated with polysorbate 80-coated proved to be very efficient against glioblastoma 101/8. The data suggest that the interaction of nanoparticles with the blood after injection as well as the enhanced permeability and retention effect (EPR effect) contributed differently to the anti-tumoural efficacy depending on nanoparticle formulation and surface properties.     

A novel synergetic targeting strategy for glioma therapy employing borneol combination with angiopep-2-modified,DOX-loaded PAMAM dendrimer

Glioma is the most common primary malignant brain tumour and the effect of chemotherapy is hampered by low permeability across the blood–brain-barrier (BBB). Borneol is a time-honoured ‘Guide’ drug in traditional Chinese medicine and has been proved to be capable of promoting free drugs into the brain efficiently, but there are still risks that free drugs, especially anti-glioma drugs, may be disassembled and metabolised before penetrating the BBB and caused the whole brain distribution. The purpose of this paper was to investigate whether borneol intervention could facilitate the BBB penetration and assist glioma treatment by combining with doxorubicin (DOX) loaded PAMAM dendrimers drug delivery system modified with Angiopep-2 (a ligand of the low-density lipoprotein receptor-related protein, which overexpress both in the BBB and gliomas). The results demonstrated that Angiopep-2 modification could actually enhance the affinity between the dendrimers and the targeting cells and finally increase the cell uptake and boost the anti-tumour ability. Borneol physical combination could further enhance the anti-tumour efficiency of this targeting drug delivery system (TDDS) after penetrating BBB. Compared with free DOX solution, this TDDS illustrated obviously sustained and pH-dependent drug release. This suggested that this synergetic strategy provided a promising way for glioma therapy.     

Preparation,transportation mechanisms and brain-targeting evaluation in vivo of a chemical delivery system exploiting the blood–cerebrospinal fluid barrier

Abstract

In recent years, specific transportation mechanisms on the blood–brain barrier (BBB) are extensively employed for brain-targeted drug delivery via colloidal nanocarriers. However, in this study, we purposed to exploit the sodium-dependent vitamin C transporter 2 (SVCT2)-mediated transportation on the blood–cerebrospinal fluid barrier to enhance central nervous system penetration of the highly hydrophilic ibuprofen (IBU) by synthesizing a SVCT2-targeted chemical delivery system (CDS), ibuprofen-C6-O-ascorbic acid (IAA). The physicochemical parameters of IAA were determined, and the transporter-mediated transportation mechanism of IAA was explored on a BBB monolayer mode. The overall brain targeting effect of IAA was assayed on mice by measuring the biodistribution of IBU after i.v. administration and calculating the pharmacokinetic parameters and targeting indexes. Results showed that lipophilicity and solubility of IAA was conspicuously improved compared with IBU. At the physiological pH, IAA was stable while in brain homogenates it was easily degraded. Transport studies on the BBB monolayer mode revealed that IAA displayed higher transepithelial permeability than IBU via SVCT2. The biodistribution study in vivo demonstrated that the overall targeting efficiency of IAA was 1.77-fold greater than that of the IBU. In conclusion, the synthetic IAA might be a promising brain-targeted CDS for smuggling small-molecule hydrophilic pharmaceuticals into the brain.     

Evaluation of blood-brain barrier transporters by co-culture of brain capillary endothelial cells with astrocytes

To investigate the transport function of the blood-brain barrier (BBB), we employed an in vitro model of the BBB, consisting of a co-culture of porcine brain capillary endothelial cells (BCECs) with rat astrocytes. Porcine BCECs were cultured on a filter insert with rat astrocytes on the underlying plastic well. Rat astrocytes induced characteristic BBB properties of porcine BCECs, such as gamma-glutamyl-transpeptidase activity and intercellular adhesion of porcine BCECs. Next, the transport properties of P-glycoprotein (P-gp) substrate and several anionic compounds across the co-cultured porcine BCECs were characterized. Expression of P-gp was detected by immunocytochemistry, and efflux-directed transport of the P-gp substrate [(3)H]daunomycin was observed. Luminal-to-abluminal transport of the monocarboxylic acid transporter 1 (MCT1) substrate [(14)C]benzoic acid was saturable, and the K(m) value (3.05 mM) was similar to that for brain uptake observed in vivo. Abluminal-to-luminal transport of [(14)C]benzoic acid was also saturable, indicating that the monocarboxylic acid transporter of the BBB contributes to the efflux from the brain as well as to blood-to-brain influx. Abluminal-to-luminal transport of organic anions, [(3)H]dehydroepiandrosterone sulfate, [(3)H]estrone sulfate and [(3)H]estradiol 17beta-D-glucuronide was significantly higher than the corresponding luminal-to-abluminal transport. These results demonstrate the presence of multiple efflux transport pathways in this in vitro model.     

In Vivo and in Vitro Blood–Brain Barrier Transport of 3-Hydroxy-3-Methylglutaryl Coenzyme A (HMG-CoA) Reductase Inhibitors

Among the HMG-CoA reductase inhibitors, lovastatin and simvastatin have central nervous system (CNS) side effects, such as sleep disturbance, whereas pravastatin does not. This difference in CNS side effects may be due to a difference in blood–brain barrier (BBB) permeability among these inhibitors. To test this hypothesis, we compared the BBB transport ability of HMG-CoA reductase inhibitors by using an in vivo brain perfusion technique in rats and an in vitro culture system of bovine brain capillary endothelial cells. The in vivo BBB permeability coefficients of the lipophilic inhibitors, [¹⁴C]lovastatin and [¹⁴C]simvastatin, were high. In contrast, that of the hydrophilic inhibitor, [¹⁴C]pravastatin, was low and not significantly different from that of [¹⁴C]sucrose, an extracellular space marker. Similarly, the in vitro BBB permeability coefficients of [¹⁴C]lovastatin and [¹C]simvastatin were high, while that of [¹⁴C]-pravastatin was low. The in vivo and in vitro transcellular permeabilities obtained for HMG-CoA reductase inhibitors were comparable. This study shows that the BBB permeability correlates with the CNS side effects of the HMG-CoA reductase inhibitors.     

Arecoline, but not haloperidol, induces changes in the permeability of the blood-brain barrier in the rat

The aim of the present study was to investigate the existence of alterations of the blood-brain barrier (BBB) permeability in rats injected with centrally acting drugs, by calculating a unidirectional blood-to-brain transfer constant (Ki) for the circulating tracer [14C]-alpha-aminoisobutyric acid. The intraperitoneal (i.p.) injection of the dopaminergic antagonist haloperidol (1 mg kg-1) did not modify the regional BBB permeability. When the cholinomimetic agent arecoline hydrobromide (6.25 mg kg-1) was injected i.p. into methylatropine-pretreated rats, it induced a significant decrease of Ki values within the frontal cortex, parietal cortex, striatum and brain-stem. Our findings emphasize two concepts: (1) centrally acting drugs, such as arecoline, can induce changes in the BBB permeability, through several mechanisms; (2) there is no predictable correlation of drug stimulation of specific brain neuronal pathways and changes in the permeability of the BBB.