寡肽转运载体PepT1的转运机制及其介导的药物吸收

寡肽转运载体PepT1广泛分布于人和动物体内的多种器官和组织,其底物主要为蛋白水解后的二肽和三肽.本文综合文献,阐述PepT1的体内分布及其质子依赖型的转运机制,从空间结构的角度分析其对底物分子的选择性,介绍评价底物与PepT1二者间亲和活性的体内外模型及PepT1底物修饰策略在促进药物吸收方面的应用.     

纳米载体提高难溶性药物口服生物利用度的研究进展

纳米载体是药剂学备受关注的研究领域,作为一类新型给药系统,它能显著提高难溶性药物的溶解度、生物利用度和稳定性,且具有明显的缓释作用,因此得到了广泛的应用。目前常用于提高难溶性药物口服生物利用度的纳米载体有纳米脂质体、固体脂质纳米粒、纳米胶束、和纳米结晶等,它们的粒径、表面性质及其释药环境等是影响纳米载体药物口服吸收的主要因素。本文对纳米载体提高难溶性药物口服生物利用度的研究进展作一综述。     

吸收促进剂在口服制剂中增强药物生物利用度的作用

本文主要讨论口服制剂中药物的弱透过性、胃肠道的解剖学和生物化学因素,以及吸收途径,阐述了吸收促进剂的基本概念、定义、分类和毒理学作用。在分子水平上讨论了胃肠道上皮细胞膜的生物化学和生物物理特点〉肽类和蛋白质通过粘膜的生化和物理机制。     

药物传递靶蛋白寡肽转运蛋白1的研究进展

目的:为相关临床安全用药和新药研发提供依据。方法:根据文献,综述了寡肽转运蛋白1(PEPT1)的组织分布、分子结构与功能、转运机制、底物、与药物相互作用等方面的内容。结果:PEPT1主要在小肠表达,肝和肾中表达较少;其基因编码的蛋白上有多个N-糖基化和蛋白激酶的识别位点,它们可能参与肽转运的调控,且其上的His-57是最关键的组氨酸残基,可能是转运蛋白发挥吸收功能时最关键的结合位点;其对大多数的二肽和三肽有高亲和性,能转运某些特定四肽,但不能转运更长的肽段;其转运机制为主动转运;其底物为二肽、三肽化合物等,但不包括氨基酸和四肽以上的大分子;其主要介导口服给药的肽类及肽类似物相关药物的相互作用。结论:虽然现国内有关PEPT1的研究才刚起步,但由于PEPT1具有底物丰富,能够转运亲脂性的、带电荷的以及不同大小的药物分子的特点,使其将会成为设计前药很好的靶蛋白。     

肠道转运蛋白在药物吸收中的重要作用

1引言 分子生物学和遗传基因学的发展使得对载体介导膜转运的认识提高到了分子基因水平.转运蛋白的存在在很大程度上决定了某些药物向靶部位及非靶部位的分布特征.     

肝脏转运蛋白在药物肝胆转运中的作用

目的对肝脏转运蛋白在药物肝胆转运中的作用作一综述,为药物肝靶向提供依据。方法根据文献,从药物不良反应、药物的矢量转运、药物肝靶向性、药物之间相互作用4个方面阐述肝脏转运蛋白对药物肝胆排泄产生的影响。结果肝脏转运蛋白引起的药物矢量转运影响药物的肝脏摄取,药物肝靶向性影响药物的疗效,药物之间相互作用影响临床用药安全和不良反应。结论肝脏转运蛋白在药物肝胆转运中起到了重要的作用,它与药物在体内各组织分布、临床疗效均有密切的联系。     

转铁蛋白在蛋白多肽药物口服给药中的应用

转铁蛋白作为一种药物载体,在蛋白多肽药物的口服给药领域有着美好前景。以转铁蛋白作为药物载体,可以使蛋白肽类药物在肠道吸收;对转铁蛋白进行适当的修饰,可以提高其递送效率。本文概述了近年来转铁蛋白在蛋白多肽药物口服给药中的作用及有关转运机制的研究进展。     

提高难溶性药物口服生物利用度的方法

讨论了影响自胃肠道吸收药物生物利用度的因素，对提高难溶性药物口服生物利用度的方法进行了综述。     

阿糖胞苷5’-缬氨酸酯前体药物的小肠吸收机制

目的 研究阿糖胞苷的5’-缬氨酸酯前药在大鼠小肠内的吸收情况。方法 运用单向灌流模型研究药物在小肠内的吸收机制，利用高效液相色谱法测定药物和酚红在灌流液中的浓度。结果 阿糖胞苷 5’-缬氨酸酯前药的小肠渗透率是母药阿糖胞苷的10.6倍，在小肠内的吸收存在浓度依赖性，能够被小肠寡肽转运蛋白的专属底物头孢氨苄明显抑制。结论 阿糖胞苷 5’-缬氨酸酯前药是小肠寡肽转运蛋白的底物，在大鼠小肠内的吸收是由小肠寡肽转运蛋白介导的主动转运过程。     

壳聚糖及其衍生物在促进药物口服吸收中的应用

目的 介绍壳聚糖及其衍生物在促进药物口服吸收中的应用。方法 以国内外发表的文献为依据．总结归纳了壳聚糖及其衍生物促进药物口服吸收中的机理及影响因素。结果与结论 壳聚糖及其衍生物能较好地促进药物的口服吸收。     

Targeting the sodium-dependent multivitamin transporter (SMVT) for improving the oral absorption properties of a retro-inverso Tat nonapeptide

Purpose. To investigate the potential for delivering large peptides orally by altering their absorptive transport pathways and improving intestinal permeability. The absorptive transport of retro-inverso (R.I.-) K-Tat9 and R.I.-K(biotin)-Tat9, novel peptidic inhibitors of the Tat protein of HIV-1, and their interactions with human SMVT (hSMVT), a high affinity, low capacity transporter, were investigated using Caco-2 and transfected CHO cells. Methods. Following synthesis on a PAL resin using Fmoc chemistry, the transport of R.I.-K-Tat9 (0.01-25 M) and R.I.-K(biotin)-Tat9 (0.1-25 M) was evaluated across Caco-2 cells. The transport and kinetics of biotin, biocytin and desthiobiotin (positive controls for SMVT) were also determined. Uptake of R.I.-K-Tat9 and R.I.-K(biotin)-Tat9 (both 0.1-10 M) was determined in CHO/hSMVT and CHO/pSPORT (control) cells. Results. The absorptive transport of R.I.-K-Tat9 was passive, low (P_m1 × 10^–6 cm/sec) and not concentration dependent. R.I.-K(biotin)-Tat9 permeability was 3.2-fold higher than R.I.-K-Tat9 demonstrating active (E_a = 9.1 kcal/mole), concentration dependent and saturable transport (K_m = 3.3 M). R.I.-K(biotin)-Tat9 uptake in CHO/hSMVT cells (K_m = 1.0 M) was 500-fold greater than R.I.-K-Tat9 (at 10 M). R.I.-K(biotin)-Tat9 transport in Caco-2 and CHO/hSMVT cells was significantly inhibited by known substrates of SMVT including biotin, biocytin, and desthiobiotin. Passive uptake of R.I.-K(biotin)-Tat9 was significantly greater than R.I.-K-Tat9 uptake in CHO/pSPORT cells. Conclusions. These results demonstrate that the structural modification of R.I.-K-Tat9 to R.I.-K(biotin)-Tat9 altered its intestinal transport pathway resulting in a significant improvement in its absorptive permeability by enhancing nonspecific passive and carrier-mediated uptake by means of SMVT. The specific interactions between R.I.-K(biotin)-Tat9 and SMVT suggest that targeting approaches utilizing transporters such as SMVT may substantially improve the oral delivery of large peptides.     

Possible interaction of quinolone antibiotics with peptide transporter 1 in oral absorption of peptide‐mimetic drugs

The study investigated whether quinolone antibiotics inhibit the PEPT1‐mediated uptake of its substrates. Among the quinolones examined, lomefloxacin, moxifloxacin (MFLX) and purlifloxacin significantly inhibited the uptake of PEPT1 substrate phenylalanine‐Ψ(CN‐S)‐alanine (Phe‐Ψ‐Ala) in HeLa/PEPT1 cells to 31.6 ± 1.3%, 27.6 ± 2.9%, 36.8 ± 2.2% and 32.6 ± 1.4%, respectively. Further examination showed that MFLX was an uncompetitive inhibitor, with an IC₅₀ value of 4.29 ± 1.29 mm . In addition, MFLX significantly decreased the cephalexin and valacyclovir uptake in HeLa/PEPT1 cells. In an in vivo study in rats, the maximum plasma concentration (C_max) of orally administered Phe‐Ψ‐Ala was significantly decreased in the presence of MFLX (171 ± 1 ng/ml) compared with that in its absence (244 ± 9 ng/ml). The area under the concentration–time curve (AUC) of orally administered Phe‐Ψ‐Ala in the presence of MFLX (338 ± 50 ng/ml · h) tended to decrease compared with that in its absence (399 ± 75 ng/ml · h). The oral bioavailability of Phe‐Ψ‐Ala in the presence and absence of MFLX was 41.7 ± 6.2% and 49.2 ± 9.2%, respectively. The results indicate that administration of quinolone antibiotics concomitantly with PEPT1 substrate drugs may potentially result in drug–drug interaction. Copyright © 2016 John Wiley & Sons, Ltd.     

药物胃肠道吸收屏障及新型促吸收方法

胃肠道屏障是机体的重要保护系统,可阻止毒物及抗原的吸收,但也是限制药物吸收的主要因素,导致许多药物的口服生物利用度低,同时也是造成许多具有较好生物活性的候选化合物不能进入后续开发研究的根本原因。许多中药有效成分如人参皂苷类,虽然被普遍认为是人参及其方剂发挥药效作用的主要物质基础,但同时存在口服生物利用度极     

肠道转运蛋白与中药有效成分的吸收

本文介绍了肠道主要转运蛋白的种类、结构、分布部位、底物、抑制剂或诱导剂,中药成分可作为肠道转运蛋白的底物、抑制剂或诱导剂影响其他药物在肠道中的吸收。有些中药间的配伍通过影响转运蛋白的作用,从而影响有效成分在肠道的吸收。     

Zero-order absorption and linear disposition of oral colchicine in healthy volunteers

Summary The pharmacokinetics of colchicine has been studied in nine healthy male volunteers after oral doses of 0.5, 1, and 1.5 mg as tablets. Plasma and urine samples were collected over 48 h and analysed for colchicine by radioimmunoassay.Individual colchicine concentration profiles in plasma and urine were well described by a two-compartment open model with zero-order input. Considering the absorption variables as specific to each experiment, the lag time (0–0.35 h) and duration (0.39–2.38 h) of absorption were found to be independent of dose, while the zero-order rate constant of absorption (k₀) increased linearly with dose.Disposition variables were taken as common to the three experiments, except in six subjects in whom renal excretion varied significantly across experiments in a dose-independent manner. For seven subjects the terminal half-life was 19.4 h, the oral apparent volume of distribution at steady-state (V_ss/f) was 691 l, and the oral systemic clearance (CL/f) was 33.1 l·h^–1. In the two other subjects, the values were unreliable, but the estimated terminal half-life was greater than 48 h, V_ss/f ranged from 1690 to 3480 l, and CL/f was in the range of the other subjects in 1 subject, and it was about 15l·h^–1 in the other. In the latter subject, these estimates, together with the observation that plasma concentration reached a plateau at 2 to 5 h after ingestion, suggest enterohepatic cycling of colchicine.Overall, the disposition of colchicine was linear in the dose range 0.5–1.5 mg, with a long terminal half-life, and absorption obeyed zero-order kinetics, with k₀ proportional to dose.     

A novel core-shell lipid nanoparticle for improving oral administration of water soluble chemotherapeutic agents: inhibited intestinal hydrolysis and enhanced lymphatic absorption

The oral administration of water-soluble chemotherapeutical agents is limited by their serious gastrointestinal side effects, instability at intestinal pH, and poor absorption. Aiming to solve these problems, we chose topotecan (TPT) as a model drug and developed a novel lipid formulation containing core-shell lipid nanoparticle (CLN) that makes the water-soluble drug to ‘dissolve’ in oil. TPT molecules can be encapsulated into nanoparticles surrounded by oil barrier while avoiding the direct contact with intestinal environment, thus easing the intestinal hydrolytic degradation and gastrointestinal (GI) irritation. Microstructure and mean particle size of TPT-CLN were characterized by Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS), respectively. The average size of nanoparticles was approximately 60?nm with a homogeneous distribution in shapes of spheres or ellipsoid. According to in vitro stability studies, more initial form of TPT was observed in presence of lipid nanoparticle compared with free topotecan solution in artificial intestinal juice (pH 6.5). After oral administration of TPT-CLN in rats, AUC and C_max of TPT were all increased compared with free TPT, indicating significant enhancement of oral absorption. Intestinal lymphatic transport was confirmed as the major way for CLN to enhance oral absorption of TPT by the treatment of blocking chylomicron flow. Lower GI irritation of TPT-CLN was observed in the gastrointestinal damage studies. The in vivo antitumor activity of TPT-CLN showed an improved antitumor efficacy by oral treatment of TPT-CLN compared to free TPT. From the obtained data, the systems appear an attractive progress in oral administration of topotecan.     

Role of glucose transporters in the intestinal absorption of gastrodin,a highly water-soluble drug with good oral bioavailability

Abstract

Gastrodin, a sedative drug, is a highly water-soluble phenolic glucoside with poor liposolubility but exhibits good oral bioavailability. The current study aims to investigate whether glucose transporters (GLTs) are involved in the intestinal absorption of gastrodin. The intestinal absorption kinetics of gastrodin was determined using the rat everted gut sac model, the Caco-2 cell culture model and the perfused rat intestinal model. In vivo pharmacokinetic studies using diabetic rats with high GLT expression were performed. Saturable intestinal absorption of gastrodin was observed in rat everted gut sacs. The apparent permeability (Papp) of gastrodin from the apical (A) to basolateral (B) side in Caco-2 cells was two-fold higher than that from B to A. Glucose or phlorizin, a sodium-dependent GLT (SGLT) inhibitor, reduced the absorption rates of gastrodin from perfused rat intestines. In vivo pharmacokinetic studies showed that the time of maximum plasma gastrodin concentration (T_max) was prolonged from 28 to 72?min when orally co-administered with four times higher dose of glucose. However, the T_max of gastrodin in diabetic rats was significantly lowered to 20?min because of the high intestinal SGLT1 level. In conclusion, our findings indicate that SGLT1 can facilitate the intestinal absorption of gastrodin.     

杏香兔耳风提取物的小肠吸收机制

目的研究杏香兔耳风提取物的小肠吸收机制,并初步考察小肠上皮细胞一元羧酸转运蛋白对提取物吸收的影响。方法采用外翻肠囊模型,以杏香兔耳风提取物中绿原酸和3,5-二咖啡酰基奎宁酸为主要成分考察总酚酸在不同肠段(空肠、回肠)中的膜通透性,同时通过吸收抑制(阿魏酸、苯甲酸、布洛芬)试验,考察了一元羧酸转运蛋白对绿原酸和3,5-二咖啡酰基奎宁酸吸收的影响。结果在空肠和回肠中,绿原酸比3,5-二咖啡酰基奎宁酸的小肠渗透率都要高。三种抑制剂(阿魏酸、苯甲酸、布洛芬)可使绿原酸和3,5-二咖啡酰基奎宁酸在回肠的渗透率降低;对绿原酸和3,5-二咖啡酰基奎宁酸在空肠的渗透率影响较小。结论绿原酸和3,5-二咖啡酰基奎宁酸在小肠的吸收属于一级动力学过程,吸收机制为被动扩散。但是同时还存在以一元羧酸转运蛋白介导的主动转运。     

聚合物胶束口服吸收机制的研究进展

目的对聚合物胶束作为口服给药载体的研究方法和吸收机制进行综述。方法参考近年来国内外文献共19篇,总结有关聚合物胶束作为口服给药载体的研究,对其中涉及到的口服吸收机制做以分类和总结。结果目前在聚合物的口服吸收常用的研究方法有Caco-2细胞模型、小肠翻转模型和动物模型,共同作为研究聚合物口服吸收机制的手段。聚合物胶束作为药物载体口服的吸收机制分为:a.通过抑制P-糖蛋白增加吸收;b.以胞饮形式吸收;c.经被动扩散;d.与胆汗相关的吸收。结论对聚合物胶束作为口服给药载体的研究方法和吸收机制进行了报道,为聚合物口服研究提供了参考。     

西红花苷-1大鼠吸收及排泄的研究

目的:研究经口服给药西红花苷-1的吸收及排泄情况.方法:采用大鼠在体小肠回流实验、西红花苷-1溶液2和4h恒温孵育实验以及灌胃给药吸收及排泄实验.HPLC法测定西红花苷-1的含量.结果:西红花苷-1经大鼠在体小肠回流4h后药量消失率分别为:十二指肠10.1%,空肠9.55%,回肠9.15%,结肠12.24%.在不同肠段的空白回流液中孵育4h,降解率分别为:十二指肠9.85%,空肠10.85%,回肠11.49%,结肠12.64%.大鼠灌胃给药24h后粪及肠内容物药量占给药量的79.9%.在蒸馏水及空白肠回流液中经24h孵育,降解率为15.64%和17.62%.大鼠血和尿中均未检测出西红花苷-1.结论:西红花苷-1口服给药后不能以原形经肠道吸收,有少部分转化为苷元(西红花酸)吸收,但浓度很低.