超声波介导的药物转运系统

目的 了解超声波介导的药物靶向转运的研究情况。方法 通过查阅和分析近年来国外超声波介导的药物转运文献。结果 在超声波的作用下,药物能在体内特定部位释放药物,提高药物的局部浓度,以及治疗基因在细胞内的表达,亦增加药物的经皮渗透量。结论 超声波具有良好的促进药物经皮吸收和靶向转运作用,具有一定的研究和应用前景。     

短肽在靶向药物递送系统中的研究进展

近年来研究发现许多肿瘤细胞表面高表达一些肽类受体，这些肽类受体与相应的配体亲和性高，能以配体-受体方式特异性结合。以小片段活性肽作为导向物形成复合物而发展的靶向药物递送系统，能够将药物定向转运到靶细胞内，显示了良好的研究价值和应用前景。如蛙皮素/胃泌素释放肽受体介导的靶向药物递送系统、生长抑素受体介导的靶向药物递送系统、十肽SynB₃受体介导的靶向药物递送系统、黄体酮释放激素受体介导的靶向药物递送系统及其他肽类受体介导的靶向药物递送系统，其中短肽作为靶向基团与阿霉素、吡咯阿霉素、甲氨蝶呤、顺铂和喜树碱等结合形成高效的复合物，用于表达有相应受体的肿瘤，获得靶向治疗的研究非常有意义。     

转运蛋白在药物血脑屏障转运中的重要作用

血脑屏障上存在多种转运蛋白,能够影响药物透过血脑屏障的行为及在脑内的分布程度。对转运蛋白在药物血脑屏障转运中的重要作用进行研究,可深入地解析药物在血脑屏障上的动态并更有效地调控药物转运行为,有助于了解血脑屏障上转运蛋白与底物药物的相互作用,指导脑靶向与非脑靶向药物的研发设计。本文对转运蛋白在药物血脑屏障转运中的重要作用进行了综述。     

线粒体靶向抗氧化剂研究进展

线粒体是细胞呼吸的主要场所,在细胞的生命周期中扮演重要角色,三羧酸循环和氧化磷酸化都是在线粒体中进行。线粒体功能障碍可导致一系列疾病,如缺血-再灌注损伤、败血症和糖尿病等。线粒体是神经退行性病变的治疗靶点,也是药物转运策略研究的引人注目的靶位。虽然线粒体所介导的疾病进程的分子机制尚未完全阐明,但氧化应激是关键的环节。开发线粒体靶向的抗氧化应激保护药物具有诱人的前景。线粒体靶向抗氧化剂是指以线粒体为作用靶位的具有抗氧化作用的药物。该文介绍了现有的线粒体靶向抗氧化剂的概念、分类及其疾病治疗研究进展。     

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。     

穿透血脑屏障的药物传递系统研究近况

综述了药物克服血脑屏障,传递至中枢神经系统,达到脑靶向目的的研究进展。从药物透穿血脑屏障的途径、药物传输系统及给药方法三个方面进行阐述。穿透机制包括被动转运、载体介导的转运、受体介导的转运、吸收介导的转运和外排泵活性的抑制。药物传输系统分为前药系统、大分子载体给药系统、微粒给药系统和植入输注系统。给药方法有脑室内注射、植入疗法和静脉给药等。     

泊洛沙姆在药物穿越血脑屏障中的重要作用

泊洛沙姆是一种具有药理活性的多功能药用辅料，在药剂学中应用广泛。近年来，研究发现泊洛沙姆可以通过多种作用机制帮助药物穿越血脑屏障，抑制血脑屏障上的P-糖蛋白、多药耐药相关蛋白等外排泵系统；吸附血浆中的不同载脂蛋白后，通过与血脑屏障上相应受体的结合，使泊洛沙姆包被的纳米粒主动转运入脑；连接各种配体及单克隆抗体等导向性分子，使其通过受体介导的转运进入脑部。本文综述了泊洛沙姆在促进药物穿越血脑屏障的重要作用，对设计脑靶向药物传递系统具有重要意义。     

口服结肠靶向给药系统的研究进展

口服结肠靶向给药系统在药物转运和治疗结肠局部疾病方面具有重要作用。本文总结了口服结肠靶向给药系统近年来的研究概况,并对结肠靶向药物制剂的体内、外评价方法作一介绍。     

基于膜转运体在药物吸收、分布、代谢和排泄过程中功能的药物设计(英文)

膜转运体介导了多种药物的摄取和外排过程, 在药物吸收、分布、代谢和排泄 (ADME) 过程中起了重要作用。膜转运体的独特性质使其成为药物研发中的潜在靶标, 合理利用这一靶标可使药物具有理想的药动学特征包括靶向分布,临床疗效改进和不良反应的降低。本文综述了目前主要的摄取和外排转运体包括溶质转运蛋白 (SLC) 超家族和三磷酸腺苷结合盒超家族 (ABC) 的特异性组织分布, 转运功能和底物谱。例举了几个基于转运体的改良药物ADME特性的成功例子。在本文最后探讨了药物设计研发中常用于研究药物和转运体之间相互作用的体内体外的研究方法。     

去唾液酸糖蛋白受体介导的肝靶向研究进展

目的 介绍去唾液酸糖蛋白受体(asialoglycoprotein receptor,ASGPR)介导的药物和基因肝靶向作用和机制,及其在治疗肝癌和乙型肝炎实验研究方面的最新进展。方法 查阅和选取针对性强、相关度高的文献,总结和归纳ASGPR介导的药物和基因肝靶向用于治疗肝癌和乙型肝炎的最新研究进展。结果 ASGPR是肝细胞的一种重要且高效的内吞受体,可用于介导药物和基因的肝靶向递送。结论 ASGPR介导的药物和基因肝靶向有望成为肝癌和乙型肝炎治疗的有效手段。     

Development of lipophilic prodrugs of mitomycin C. II. Stability and bioactivation of 1a-N-substituted derivatives with aromatic pro-moiety

The decomposition and bioactivation characteristics of five la-N-substituted derivatives of mitomycin C possessing an aromatic pro-moiety with different linkage structures were studied to assess their suitability for prodrugs. Derivatives were stable in neutral aqueous media except for benzoyloxymethyl mitomycin C which decomposed with a half-life of 3.5 min at pH 7.4. Acyl derivatives such as benzoyl and benzylcarbonyl mitomycin C were stabler than mitomycin C under acidic conditions, but converted relatively rapidly to the parent drug in basic media. Derivatives having an ester bond in their linkages showed enzyme-mediated conversion to the parent drug in rat plasma and liver homogenate. Acyl derivatives were converted only by hepatic enzymes. No practical bioactivation was observed for benzyl mitomycin C. Species differences were observed in these bioactivation phenomena. These results suggested that 5 derivatives have intrinsic regeneration characteristics which might offer successful applications under various conditions of administration.     

不同术式对翼状胬肉的治疗观察

目的 比较翼状胬肉的常规切除+羊膜移植术(amniotic membrane transplantation,AMT)+联合丝裂霉素(MMC)(A组)及翼状胬肉的常规切除+自体角膜缘干细胞移植联合MMC(B组)进行治疗的疗效.方法 234例(239只眼),翼状胬患者随机分为两组,分别采用胬肉切除术+AMT联合MMC及翼状胬肉的常规切除+自体角膜缘干细胞移植联合MMC进行治疗,术后随访7～19个月比较复发率.结果 A组复发率3.25%,B组复发率4.31%,两组比较差异无统计学意义.结论 A组与B组效果均良好.     

Effect of beta-adrenergic stimulants on cytotoxicity of mitomycin C in HeLa cells

Effects of several autonomic agents on the cytotoxicity of mitomycin C in HeLa cells were studied. When beta-adrenergic stimulants such as isoproterenol, epinephrine, terbutaline and turobuterol were added at concentrations over 10(-14) M 15 to 60 min before mitomycin C, the colony-forming ability of HeLa cells was significantly inhibited more than by mitomycin C alone. The action of isoproterenol and epinephrine on the colony-forming ability of the cells was abolished by propranolol. The intracellular cyclic AMP level of HeLa cells reached the peak of about two-fold the basal level at 30 min after the addition of 10(-8) M isoproterenol. In combination with mitomycin C, the high level of intracellular cyclic AMP induced by isoproterenol was maintained for a significantly longer period in comparison with that by isoproterenol alone, while mitomycin C alone caused essentially no change in the cyclic AMP level. The pretreatment with dibutyryl cyclic AMP also enhanced the effect of mitomycin C. From these findings, it is strongly suggested that the synergistic effect of beta-adrenergic stimulants on the cytotoxicity of mitomycin C is mediated via stimulation of the beta-adrenoceptors of HeLa cells which elevates the intracellular cyclic AMP for a long time in combination with mitomycin C.     

DNA alkylation by enzyme-activated mitomycin C

After anaerobic reductive activation by either NADPH cytochrome P-450 reductase (EC 1.6.2.4) or xanthine oxidase (EC 1.2.3.2), mitomycin C readily alkylated DNA. When the mitomycin C-alkylated DNA is digested by DNase, snake venom phosphodiasterase, and alkaline phosphatase, only partial release of the monofunctionally linked mitomycin C nucleotide adduct occurs. Cross-linked adducts are not released into dinucleotides but resist nuclease digestion and remain in oligonucleotides and insoluble precipitates. Kinetic analyses show that the nuclease-resistant fraction which is indicative of DNA cross-linking by mitomycin C takes place quite readily. This nuclease-resistant fraction is particularly significant when the amount of total bound mitomycin C is less than 15 mumol/mmol of DNA. The cross-linked mitomycin C product accounts for more than half of the total alkylation under all pH conditions tested. Our data suggest that particular DNA sites are available for DNA cross-linking by mitomycin C, and these sites are probably the preferred and immediate alkylating targets. Furthermore, DNA cross-links by mitomycin C are not the secondary product of monofunctional adducts. Activity of both flavoenzymes is pH dependent, hence, mitomycin C activation and the rate of DNA alkylation are pH dependent. At elevated mitomycin C alkylation of DNA, the highest amount of cross-linking occurs at neutral pH. High pressure liquid chromatographic separation of the nuclease-digested DNA detected one major and two less prominent mitomycin C adducts. These were verified to be mononucleotide mitosene types by UV spectra showing maximum absorbance at 312 and 250 nm. The major adduct was purified and identified as O6-(2'-deoxyguanosyl)-2,7-diaminomitosene by NMR, indicating that the O6 position of guanine is a preferred site in DNA for at least monofunctional linkage formation.     

Degradation kinetics and mechanism of N6-[(dimethylamino)methylene]mitomycin C in aqueous solutions

The degradation of N6-[(dimethylamino)methylene]mitomycin C, a semisynthetic analogue of mitomycin C, was studied in aqueous solution. The compound degraded rapidly and followed pseudo-first-order kinetics in both acidic (pH less than 5) and basic pH greater than or equal to 9) media. In the near-neutral pH region, however, biphasic kinetics were observed. At the pH of maximum stability (6.5), 10% activity was lost after approximately 6 h at 22 degrees C. Citrate and phosphate species were catalytic at pH 6.5. Spectrophotometric and HPLC methods were used to elucidate the degradation mechanism at pH 7-9. Under these conditions, equilibrium addition of one water molecule into the amidine side chain occurred, followed by parallel formation of mitomycin C and N6-(formyl)mitomycin C. The latter compound subsequently hydrolyzed to mitomycin C.     

Variability of Mitomycin C Adsorption by Activated Charcoal

A saline suspension of mitomycin C adsorbed on activated charcoal and administered intraperitoneally has been reported to be safe and effective in the treatment of gastric carcinoma. Activated charcoal specifically targets tumour and lymph-node tissues and the sustained higher local drug concentration is thought to be beneficial. The charcoal particles used in these suspensions have varied in size from > 147 μm to < 20 nm in diameter, but no data have been published to show how this might affect drug adsorption and delivery. Any variability in drug adsorption could pose a serious clinical risk for drugs with a narrow therapeutic index. We have, therefore, investigated the adsorption of mitomycin C on activated charcoal in-vitro. Activated charcoal was ground and sieved to yield four size-fractions between 180 and 53 μm. Adsorption isotherms (n ≥ 3) were constructed and applied to the Freundlich model with 0–100 μg mL^?1 mitomycin C measured by HPLC with detection at 365 nm. Adsorption of mitomycin C by activated charcoal varied by a factor of three under identical conditions at room temperature (21°C) and at 37°C. The specific adsorption (μg mitomycin C (mg activated charcoal)^?1) was generally higher at 37°C than at room temperature. The variability of mitomycin C adsorption was greatly reduced by addition of the surface-active agent polyvinylpyrollidone, used to determine that adsorption of mitomycin C was independent of activated charcoal particle size. The characteristics of adsorption of mitomycin C by activated charcoal are complex and should be thoroughly investigated to discover the critical controlling factors before submitting the suspensions for further clinical evaluation.     

Uses and complications of mitomycin C in ophthalmology

Mitomycin C is a chemotherapeutic agent that acts by inhibiting DNA synthesis. Its use and application in ophthalmology has been increasing in recent years because of its modulatory effects on wound healing. Current applications include pterygium surgery, glaucoma surgery, corneal refractive surgery, cicatricial eye disease, conjunctival neoplasia and allergic eye disease. Although it has been used successfully in these conditions, it has also been associated with significant complications. This article reviews the current trends and uses of mitomycin C in the eye and its reported complications.     

Uses and complications of mitomycin C in ophthalmology

Mitomycin C is a chemotherapeutic agent that acts by inhibiting DNA synthesis. Its use and application in ophthalmology has been increasing in recent years because of its modulatory effects on wound healing. Current applications include pterygium surgery, glaucoma surgery, corneal refractive surgery, cicatricial eye disease, conjunctival neoplasia and allergic eye disease. Although it has been used successfully in these conditions, it has also been associated with significant complications. This article reviews the current trends and uses of mitomycin C in the eye and its reported complications.     

Additional nucleotide derivatives of mitosenes. Synthesis and activity against parental and multidrug resistant L1210 leukemia

Cytidine 5'-monophosphate and 5'-ara-CMP conjugates of 2,7-diaminomitosene, with the phosphate groups linked to C-1, were prepared by treating mitomycin C with the appropriate nucleotides. 5'-UMP conjugates were prepared from mitomycin A, 7 (M-83), and 8 (BMY-25282) by similar procedures. A conjugate could not be prepared from mitomycin C and 6-MPRP, but a sulfur-linked derivative was made with 6-MP ribonucleoside. The corresponding 1-hydroxy-2-aminomitosenes were prepared from the parent mitomycin analogues for structure-activity comparisons. All compounds were tested against L1210 murine leukemia in the MTT tetrazolium dye assay. In general, the conjugates were less potent than the parent mitomycins; however 5'-ara-CMP conjugate 14 derived from mitomycin C was more potent than the parent compound or any mitomycin tested except mitomycin A. It also was more potent than ara-C. This result establishes the value of this approach to prodrugs, at least in cell culture. Against a multi-drug-resistant L1210 cell line, all of the conjugates derived from mitomycin C were more potent than the parent compound. 6-Mercaptopurine ribonucleoside conjugate 15 was more active against the resistant cells than it was against the parental cell line.     

In Vitro Release Profile of Mitomycin C from Albumin Microspheres: Extrapolation from Macrospheres to Microspheres

To analyze the in vitro release profiles of mitomycin C from albumin microspheres prepared by chemical denaturation in a multiparticulate system, a method to calculate the total cumulative amount of mitomycin C released from a batch of microspheres was developed. Mitomycin C-loaded albumin macrospheres (diameter in mm range) were prepared, and the in vitro release kinetics of mitomycin C from individual macrospheres were determined. Then the relationship between the kinetic parameters and the physical parameters (e.g., diameter, weight) was investigated under the assumption that macrospheres and microspheres behave identically. Further, the size distribution of microspheres was measured, and the total cumulative amount of mitomycin C released from albumin microspheres was calculated. The release profiles of mitomycin C from individual macrospheres fitted first-order release kinetics better than spherical matrix kinetics. The calculated initial mitomycin C contents and first-order release rate constants for individual macrospheres were correlated with the weight and reciprocal of surface area of the macrospheres, respectively. The observed in vitro release profile for the microspheres agreed with the calculated values. These results suggest that this method is valid for calculating drug release from albumin microspheres.