Overcoming multidrug resistance with nanomedicines

Introduction: Cancer remains the leading cause of death worldwide. Numerous therapeutic strategies that include smart biological treatments toward specific cellular pathways are being developed. Yet, inherent and acquired multidrug resistance (MDR) to chemotherapeutic drugs remains the major obstacle in effective cancer treatments.

Areas covered: Herein, we focused on an implementation of nanoscale drug delivery strategies (nanomedicines) to treat tumors that resist MDR. Specifically, we briefly discuss the MDR phenomenon and provide structural and functional characterization of key proteins that account for MDR. We next describe the strategies to target tumors using nanoparticles and provide a mechanistic overview of how changes in the influx:efflux ratio result in overcoming MDR.

Expert opinion: Various strategies have been applied in preclinical and clinical settings to overcome cancer MDR. Among them are the use of chemosensitizers that aim to sensitize the cancer cells to chemotherapeutic treatment and the use of nanomedicines as delivery vehicles that can increase the influx of drugs into cancer cells. These strategies can enhance the therapeutic response in resistant tumors by bypassing efflux pumps or by increasing the nominal amounts of therapeutic payloads into the cancer cells at a given time point.     

真菌多药耐药外排机制的研究进展

真菌多药耐药性是指真菌细胞对结构不同、作用靶点不同的药物同时具有耐药性的现象,是导致临床抗真菌治疗失败的重要原因之一。本文综述了酿酒酵母、条件致病真菌白假丝酵母、光滑假丝酵母和烟曲霉中多药耐药相关转运蛋白、药物外排机制以及基因表达调控网络的研究进展,旨在为深入了解真菌多药耐药性的机制、探讨克服多药耐药性的策略和提高抗真菌药物的药效提供参考。     

Efflux as a mechanism of antimicrobial drug resistance in clinical relevant microorganisms: the role of efflux inhibitors

Introduction: Microbial resistance against antibiotics is a serious threat to the effective treatment of infectious diseases. Several mechanisms exist through which microorganisms can develop resistance against antimicrobial drugs, of which the overexpression of genes to produce efflux pumps is a major concern. Several efflux transporters have been identified in microorganisms, which infer resistance against specific antibiotics and even multidrug resistance.

Areas covered: This paper focuses on microbial resistance against antibiotics by means of the mechanism of efflux and gives a critical overview of studies conducted to overcome this problem by combining efflux pump inhibitors with antibiotics. Information was obtained from a literature search done with MEDLINE, Pubmed, Scopus, ScienceDirect, OneSearch and EBSCO host.

Expert opinion: Efflux as a mechanism of multidrug resistance has presented a platform for improved efficacy against resistant microorganisms by co-administration of efflux pump inhibitors with antimicrobial agents. Although proof of concept has been shown for this approach with in vitro experiments, further research is needed to develop more potent inhibitors with low toxicity which is clinically effective.     

多药耐药相关蛋白及其在肿瘤耐药中的作用

多药耐药(multidrug resistance,MDR)是导致肿瘤患者化疗失败的主要原因。介导多药耐药的重要机制之一是多药耐药相关蛋白(multidrug resistance-associated proteins,MRPs)的表达增加。MRPs是一类ATP能量依赖型跨膜转运蛋白,是具有选择性和特异性的药物外排泵。本文主要针对MRPs的生理特征、结构特点、耐药谱特征及其逆转进行综述。     

药物耐药性外排泵抑制剂的研究进展

外排泵抑制剂可以抑制耐药细菌和肿瘤细胞对进入胞体内药物的外排作用,提高对药物的敏感性.它在改善药物的药动学特性等方面也有广泛的作用.研制开发外排泵抑制剂,逆转现有药物的耐药性将是改善药物疗效的一种有效的治疗方法.简要阐述近年来外排泵抑制剂的研究进展.     

GSH-responsive poly-resveratrol based nanoparticles for effective drug delivery and reversing multidrug resistance

Cancer poses a serious threat to human health and is the most common cause of human death. Polymer-based nanomedicines are presently used to enhance the treatment effectiveness and decrease the systemic toxicity of chemotherapeutic agents. However, the disadvantage of currently polymeric carriers is without therapy procedure. Herein, for the first time, glutathione (GSH)-responsive polymer (PRES) with anti-cancer effect was synthesized following the condensation–polymerization method using resveratrol (RES) and 3,3′-dithiodipropionic acid. PRES can not only suppress the tumor cells growth but can also self-assemble into nanoparticles (∼93 nm) for delivering antitumor drugs, such as paclitaxel (PTX@PRES NPs). The system could achieve high drug loading (∼7%) and overcome multidrug resistance (MDR). The results from the in vitro studies revealed that the NPs formed of PRES were stable in the systemic circulation, while could be efficiently degraded in tumor cells high GSH environment. Results from cytotoxicity tests confirmed that PTX@PRES NPs could effectively suppress the growth of cancer cells (A549) and drug-resistant cells (A549/PTX). The NPs could also be used to significantly increase the therapeutic efficacy of the drugs in A549/PTX tumor-bearing mice. In vivo investigations also demonstrated that the PRES-based NPs exhibited tumor inhibition effects. In summary, we report that the GSH-responsive polymer synthesized by us exhibited multiple interesting functions and could be used for effective drug delivery. The polymer exhibited good therapeutic effects and could be used to overcome MDR. Thus, the synthesized system can be used to develop a new strategy for treating cancer.     

Naringenin Enhances the Anti-Tumor Effect of Doxorubicin Through Selectively Inhibiting the Activity of Multidrug Resistance-Associated Proteins but not P-glycoprotein

Purpose  Naringenin has shown paradoxical results to modulate the function of multidrug resistance-associated proteins (MRPs). The aim of this study is to interpret whether naringenin can reverse intrinsic and/or acquired resistance of cancer cells to chemotherapeutic agents. Methods  The effects of naringenin on the uptake, retention and cytotoxicity of doxorubicin were investigated in A549, MCF-7, HepG2 and MCF-7/DOX cells. Cellular efflux pathways modulated by naringenin were assessed with their specific substrates and inhibitors. The improved antitumor activity of doxorubicin in combination with naringenin was also investigated in vivo. Results  The IC₅₀ values of doxorubicin in combination with naringenin in A549 and MCF-7 cells were approximately 2-fold lower than that of doxorubicin alone. The increased sensitivity to doxorubicin by naringenin in HepG2 and MCF-7/DOX cells was not observed. Naringenin increased the cellular doxorubicin accumulation through inhibiting doxorubicin efflux in the cells expressing MRPs but not P-gp. In contrast to doxorubicin alone, doxorubicin in combination with naringenin enhanced antitumor activity in vivo with low systemic toxicity. Conclusion  Naringenin enhances antitumor effect of doxorubicin by selective modulating drug efflux pathways. Naringenin will be a useful adjunct to improve the effectiveness of chemotherapeutic agents in treatment of human cancers.     

多药耐药基因-1、脑源性神经营养因子基因的两个多态性与小儿耐药性癫痫的关联研究

目的探讨多药耐药基因-1、脑源性神经营养因子(BDNF)基因的两个多态性与小儿耐药性癫痫的关联性。方法选取多药耐药基因-1的T-129C多态性、BDNF基因的C270T多态性作为研究的位点,利用聚合酶链反应—限制性片段长度多态性分析技术,在耐药性癫痫组41例患儿、药物有效癫痫组43例患儿、正常对照组30例儿童中进行这两个多态性检测,比较3组之间基因型分布及等位基因频率的差异。结果耐药性癫痫组MDR1基因T-129C多态性的TT基因型分布频率、T等位基因频率高于药物有效癫痫组及正常对照组,差异有显著性(P<0.05)。耐药性癫痫组BDNF基因C270T多态性的CC、CT、TT基因型分布频率和C、T等位基因频率与药物有效癫痫组及正常对照组差异无显著性(P>0.05)。结论MDR1基因T-129C多态性可能与小儿耐药性癫痫存在关联,在小儿耐药性癫痫的发生中可能起作用;而BDNF基因C270T多态性与小儿耐药性癫痫可能无关联。     

多重耐药泵抑制剂提高肠球菌对氟喹诺酮药物敏感性的研究

目的　研究临床分离肠球菌对诺氟沙星、环丙沙星、氧氟沙星等氟喹诺酮药物耐药的主动泵出机制。方法　收集临床分离肠球菌 ;用琼脂二倍稀释法测定多重耐药泵抑制剂利舍平或维拉帕米应用前后 ,菌株对氟喹诺酮药物 MIC的变化。结果　利舍平使所有被检测的 2 9株肠球菌对诺氟沙星的敏感性增加 (MIC下降至原值的 1/ 2或以下 ) ,使 2 3株肠球菌对环丙沙星的敏感性增加 ,但仅能增加 3株肠球菌对氧氟沙星的敏感性。应用利舍平以后 ,12株耐诺氟沙星粪肠球菌对诺氟沙星 MIC值均下降 ,11株耐环丙沙星粪肠球菌有7株对环丙沙星 MIC值下降。维拉帕米的抑制效果和利舍平相比略有差异。结论　诺氟沙星、环丙沙星的主动泵出机制普遍存在于临床分离肠球菌 ,并且是粪肠球菌对诺氟沙星、环丙沙星的耐药机制之一。     

P糖蛋白与配体相互作用的结构基础及其肿瘤耐药逆转的研究

P糖蛋白（P-glycoprotein,P-gp）是一种多药外排转运体,对控制各种抗癌药物的生物学活性具有重要意义。P-gp转运体作为生理屏障阻滞药物渗透,从而使药物发挥效应受限。传统的化疗增敏剂通过对转运体的调节可有效改善抗肿瘤药物的药代动力学并逆转多药耐药。本文将简要概述近年来有关P-gp与配体相互作用的结构信息以及肿瘤耐药逆转策略的研究进展。     

多药耐药基因MDR1多态性的研究进展

MDR1所编码的P-糖蛋白是ABC蛋白家族成员之一,它在体内药物的转运和处置中发挥着重要作用。本文就近几年有关MDR1基因多态性对P-糖蛋白在组织中表达的影响、以及MDR1多态性对药物处置、临床疗效以及疾病风险等影响进行综述。     

2011年我院常见病原菌的分布及耐药性分析

目的了解该院临床常见病原菌的分布及耐药特征,为临床抗感染治疗提供参考依据。方法采用K-B法进行细菌培养和药敏试验,参照CLSI标准判断药敏结果。结果 2011年该院细菌检出数为2 182株,其中细菌检出率前5位的分别是大肠埃希菌(20.5%)、鲍曼不动杆菌(17.2%)、铜绿假单胞菌(11.2%)、肺炎克雷伯菌属(9.4%)和金黄色葡萄球菌(9.0%)。结论该院检出常见病原菌表现为多药耐药,临床应结合细菌培养和药敏试验,及时调整抗菌药物,延缓新的耐药菌株产生与扩散。     

Partial synthesis and biological evaluation of bisbenzylisoquinoline alkaloids derivatives: potential modulators of multidrug resistance in cancer

A series of new bisbenzylisoquinoline alkaloids was partially synthesized from tetrandrine and fangchinoline and evaluated for their ability to reverse P-glycoprotein-mediated multidrug resistance (MDR) in cancer cells. All the test compounds increased the intracellular accumulation rate of rhodamine 123 in MDR cells (Bel7402 and HCT8), and most exhibited more potent MDR-reversing activity relative to the reference compound verapamil. Compounds 8, 10, 13, and 14 enhanced intracellular accumulation of doxorubicin in Bel7402 and HCT8 cells.     

维拉帕米逆转肿瘤多药耐药性的研究进展

肿瘤细胞对化疗药物产生的多药耐药（MDR）已成为当前影响肿瘤化学治疗疗效的主要障碍，寻找低毒有效的MDR逆转剂是提高化疗疗效的关键。MDR产生机制复杂，由mdrl基因编码的P-糖蛋白（P-glycoprotein P-gp）的过表达是产生MDR的主要原因。维拉帕米是应用最早的MDR逆转剂之一，但其毒副作用大大限制了临床应用。从维拉帕米分离出的光学异构体R-型维拉帕米，在逆转肿瘤MDR时，更加高效安全，具有良好的临床应用前景。     

肿瘤多药耐药模型的建立与评价方法

开发多药耐药肿瘤的细胞模型和动物模型对于其相关基础研究和药物评价意义重大。综述了肿瘤多药耐药模型的建模方法,分别对细胞模型和荷瘤动物模型的建立类型、各自特点、评价手段及研究意义等进行了分析和总结。为建立优势肿瘤多药耐药模型、优化现有抗肿瘤药物评价方法提供参考,有助于阐明多药耐药相关机制,并为临床用药提供指导。     

白念珠菌耐药机制的研究进展

近年来白念珠菌感染发病率剧增,随着抗真菌药物的广泛使用,耐药菌株不断出现,耐药现象已经成为药物治疗的严峻挑战。目前已经明确的耐药机制包括：膜转运蛋白的过度表达,药物作用靶酶基因过度表达或突变,甾醇合成通路中其他酶的改变,生物被膜的形成,小囊状空泡的影响等。本文对白念珠菌的耐药机制做一综述。     

Inhibition of bacterial efflux pumps: a new strategy to combat increasing antimicrobial agent resistance

Resistance to multiple drugs in medically important bacteria results in therapeutic challenges for the clinician. The mechanisms by which bacteria evade the effects of antimicrobial agents are many, but in recent years it has become apparent that efflux is a significant means of resistance and probably explains the intrinsic resistance to numerous drugs observed in species such as Pseudomonas aeruginosa. Drug efflux is mediated by membrane-based hydrophobic proteins belonging to several distinct families, the members of which are related by structural characteristics, mechanism of action and energy source for the transport process. The multi-drug efflux transporters are particularly problematic as they are capable of extruding numerous structurally dissimilar drugs. Inhibition of these pumps, and even those with more limited substrate specificity, has been shown to decrease intrinsic resistance, reverse acquired resistance and reduce the emergence of mutants with higher-level target-based mutational resistance. Combining broad spectrum efflux pump inhibitors with current drugs that are pump substrates can recover clinically relevant activity of those compounds and thus may reduce the need for the discovery and development of new antimicrobial agents that are not pump substrates. Additional effort toward the identification, characterisation and determination of the clinical utility of efflux pump inhibitors is warranted.     

胶束传递系统逆转肿瘤多药耐药的研究进展

肿瘤多药耐药是目前肿瘤治疗的一大障碍。研究采用药物传递系统如胶束、脂质体、纳米粒等, 以逆转多药耐药, 显示其安全可靠, 并具有良好的应用前景。本文重点综述了药物传递系统中的聚合物胶束逆转多药耐药的研究结果及其可能的作用机制。随着研究的深入, 药物传递系统在逆转肿瘤多药耐药的研究领域将发挥更加重要的作用。     

细菌耐药的现状与防治策略

随着抗生素应用的日益增多，细菌耐药性日趋严重。本文对近年来几种主要病原菌，包括葡萄球菌、肺炎链球菌、肠球菌、产超广谱β-内酰胺酶（ESBLs）的革兰阴性菌、产头孢菌素酶（AMPC酶）菌株、铜绿假单胞菌等的耐药趋势、耐药性的预防与控制的研究情况进行评述。     

中药逆转肺癌多药耐药的研究新进展

肺癌发病率和死亡率居全球恶性肿瘤首位,作为治疗主导方向的化疗,药物推陈出新,方案不断优化,疗效却已达“平台期”,究其原因,肺癌细胞的多药耐药(MDR)不容忽视。寻找肺癌化疗耐药逆转剂,逆转MDR 是肿瘤领域的研究热点。中药活性广泛而显著,高效小毒,多靶点逆转MDR,临床药效逐步得到肯定,但明确的逆转机制尚待研究。