Nanocarrier-based interventions for the management of MDR/XDR-TB

Emergence of multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB over the past decade presents an unprecedented public health challenge to which countries of concern are responding far too slowly. Global Tuberculosis Report 2014 marks the 20th anniversary of the Global Project on Anti-Tuberculosis Drug Resistance Surveillance, indicating the highest global level of drug-resistance ever recorded detection of 97?000 patients with MDR-TB resulting in 170?000 deaths in 2013. Treatment of MDR-TB is expensive, complex, prolonged (18–24 months) and associated with a higher incidence of adverse events. In this context, nanocarrier delivery systems (NDSs) efficiently encapsulating considerable amounts of second-line anti tubercular drugs (^sATDs), eliciting controlled, sustained and more profound effect to trounce the need to administer ^sATDs at high and frequent doses, would assist in improving patient compliance and avoid hepatotoxicity and/or nephrotoxicity/ocular toxicity/ototoxicity associated with the prevalent ^sATDs. Besides, NDSs are also known to inhibit the P-glycoprotein efflux, reduce metabolism by gut cytochrome P-450 enzymes and circumnavigate the hepatic first-pass effect, facilitating absorption of drugs via intestinal lymphatic pathways. This review first provides a holistic account on MDR-TB and discusses the molecular basis of Mycobacterium tuberculosis resistance to anti-tubercular drugs. It also provides an updated bird’s eye view on current treatment strategies and laboratory diagnostic test for MDR-TB. Furthermore, a relatively pithy view on patent studies on second-line chemotherapy using NDSs will be discussed.     

A tamoxifen derivative,N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine,selectively targets P-glycoprotein-positive multidrug resistant Chinese hamster cells

DPPE, a tamoxifen derivative with antihistamine activity, was previously shown to potentiate the toxicity of chemotherapeutic drugs. Recently, a Phase III clinical study using doxorubicin with DPPE demonstrated significant increase in the overall survival of breast cancer patients. In this study we examined the effects of DPPE alone on the growth of drug sensitive and P-gp positive CHO cell line. Our results demonstrate DPPE is selectively toxic to P-gp positive cells and the sensitivity to DPPE alone correlated with the levels of P-gp expression. Moreover, in MDR cells, DPPE-induced apoptosis was significantly reduced with Bcl2 overexpression and in the presence of P-gp ATPase inhibitor, PSC833. Furthermore, knockdown of P-gp expression in MDR cells with P-gp-siRNA reversed DPPE sensitivity and increased their sensitivity to doxorubicin and taxol but not to cisplatin. The addition of DPPE to membrane fractions led to dose-dependent increase in P-gp ATPase that was inhibited with PSC833. Moreover, incubation of P-gp positive cells with DPPE led to a significant increase in superoxide levels and a drop in cellular ATP and GSH pools that were reversible with inhibitors of P-gp ATPase. The combined presence of DPPE and the mitochondria electron transport complex III inhibitor, antimycin A, synergized in their effects on the growth of MDR cells but had no effect on the growth of parental drug sensitive cells. Collectively, the results of this study provide a possible mechanism that may be relevant to the clinical results of DPPE in breast cancer trial and demonstrates DPPE as P-gp collateral sensitivity drug.     

美洛昔康不诱导胃癌细胞耐药

目的旨在了解环氧合酶-2(cyc looxygenase-2,COX-2)抑制剂美洛昔康对胃癌细胞的长期作用能否导致胃癌细胞对其产生耐药性。方法采用浓度递增法结合大剂量冲击法,美洛昔康长期作用于胃癌SGC7901细胞,时间达6个月,尝试诱导胃癌美洛昔康耐药株,命名为SGC7901/M,并用MTT法测定药物敏感性,光镜、电镜观察细胞形态学改变,活细胞计数法和克隆形成技术了解其生物学特性。结果药物敏感分析显示,胃癌细胞经过美洛昔康长期作用,对美洛昔康并没有出现抗性,其IC50与亲代细胞比较差异无统计学意义(P>0.05),分别为4.6×10-4±2.23×10-4mol.L-1,3.54×10-4±2.34×10-4mol.L-1。SGC7901/M细胞对美洛昔康的耐药指数约为1.3。SGC7901/M细胞与亲代细胞形态学比较,光镜及电镜均未显示差异,两种细胞在经1×10-3mol.L-1美洛昔康作用24 h后,均表现出细胞受到明显损伤和凋亡的形态。无论从生长曲线上还是克隆形成率上都显示SGC7901/M细胞与亲代细胞的生长特性无差异。结论美洛昔康可抑制胃癌细胞生长,长期用药不诱导胃癌细胞产生耐药性。     

Difference in Expression of Bcl-2 and Bcl-xl Genes in Cisplatin- sensitive and Cisplatin-resistant Human in Ovarian Cancer Cell Lines

Apoptosisisthemainmechanismofcelldeathandisregulatedbyalargenumberofgenes.Amongthem ,theBcl 2familiesareconsideredtoplayakeyroleintheexecutionorpreventionofapoptosisinducedbygenotoxicstressthroughthealterationofapoptoticsignals.Epithe lialovariancancerist…     

Glucuronidation as a mechanism of intrinsic drug resistance in colon cancer cells: contribution of drug transport proteins

We have recently shown that drug conjugation catalysed by UDP-glucuronosyltransferases (UGTs) functions as an intrinsic mechanism of resistance to the topoisomerase I inhibitors 7-ethyl-10-hydroxycamptothecin and NU/ICRF 505 in human colon cancer cells and now report on the role of drug transport in this mechanism. The ability of transport proteins to recognise NU/ICRF 505 as a substrate was evaluated in model systems either transfected with breast cancer-resistance protein 1 (Bcrp1), multidrug-resistance protein 2 (Mrp2) or Mrp3, or overexpressing MRP1 or P-170 glycoprotein. Results from chemosensitivity assays suggested that NU/ICRF 505 was not a substrate for any of the above proteins. In drug accumulation studies in human colon cancer cell lines NU/ICRF 505 was taken up avidly and retained in cells lacking UGTs (HCT116), whereas, following equally rapid uptake, it was cleared rapidly from cells displaying UGT activity (HT29) as glucuronide metabolites. HT29 cells were shown to express MRP1 and 3, but not P-170 glycoprotein, MRP2 or breast cancer-resistance protein. The major glucuronide of NU/ICRF 505 inhibited ATP-dependent transport of estradiol 17-beta-glucuronide in Sf9 insect cell membrane vesicles containing MRP1 or MRP3, while co-incubation of HT29 cells with the MRP antagonist, MK571, significantly restored intracellular concentrations of NU/ICRF 505. These data lead us to conclude that the presence of a glucuronide transporter is essential for glucuronidation to represent a major de novo resistance mechanism and that UGTs will contribute more as a primary resistance mechanism when the parent drug (e.g. NU/ICRF 505) is not itself recognised by transport proteins.     

STI571耐药白血病细胞系的建立及其生物学特性初步研究

为了探讨STI571耐药机制和体外诱导建立甲磺酸伊马替尼(imatinib mesylate，又称STI571)耐药的白血病细胞系，采用STI571递增给药的方法诱导裸鼠高致瘤性人慢粒红白血病变细胞系K562-n和多药耐药细胞系K562-n／VCR对STI571耐药，比较它们与各自亲本细胞系问基本生物学特性的异同。结果显示，建立多药耐药基础上对STI571耐药的白血病细胞亚系K562-n／VCR／STI，对STI571耐药倍数为23．41，对长春新碱(VCR)耐药倍数为662．26，对高三尖杉酯碱(HHT)具有交叉耐药性。K562一n经STI571诱导后对多种药物耐受性有所提高，命名为K562-n／STI。K562-n／STI和K562-n／VCR／STI细胞内DNR积聚量分别为33．24和18．76，低于各自亲本细胞系。K562-n／STI与K562-n／VCR／STI均检测到mdr-1基因的mRNA转录。K562-n／STI和K562．n／VCR／STI与亲本细胞系相比，倍增时间延长，增殖指数增高。结论：体外小剂量STI571递增给药的方法能够提高K562-n细胞系对STI571的耐受性，同时mdr-1基因表达阳性，表现一定程度的多药耐受，提示STI571耐药机制与多药耐药机制之间可能存在相关性。由于K562-n为裸鼠高致瘤的人白血病细胞系，K562-n／STI和K562-n／VCR／STI571的建立有可能为耐药机制及耐药逆转的研究提供体外和体内实验模型。     

不同年龄人群自发性气胸的病因和治疗特点分析

目的探讨青年和中老年人群自发性气胸的病因和治疗特点。方法回顾性分析同济大学附属肺科医院急诊科收治的113例自发性气胸患者的发病基础、治疗时间、预后等情况。结果收治的自发性气胸人数占同期急诊人数（124／4538）2．7％,占同期急诊住院人数（113／805）14％。113例气胸中,手术治愈25例,胸腔闭式引流／胸膜黏连治愈83例,未愈出院5例。复发病例44例。年龄〈40岁的青年组共40例,平均年龄（24．25±6．63）岁,扁平胸27例。有明确发病诱因31例。临床症状以胸闷为主,25例胸CT提示肺大疱。胸腔闭式引流28例,平均引流时间（3．54±2．85）d。手术治疗12例。年龄≥40岁的中老年组患者共73例,平均年龄（65．78±13．79）岁,桶状胸57例。有明确发病诱因11例。临床症状以胸闷和咳嗽为主,胸腔闭式引流55例,平均引流时间（6．65±10．2）d。手术治疗13例,未愈5例。结论青年人群气胸的发生和扁平胸有关联,发病诱因明确;肺气肿是中老年气胸的主要病因。无法手术的中老年难治性气胸,是气胸临床治疗的难点。     

Circumvention of the multidrug-resistance protein (MRP-1) by an antitumor drug through specific inhibition of gene transcription in breast tumor cells

Multidrug-resistance protein 1 (MRP-1) confers resistance to a number of clinically important chemotherapeutic agents. The promoter of the mrp-1 gene contains an Sp1-binding site, which we targeted using the antitumor bis-anthracycline WP631. When MCF-7/VP breast cancer cells, which overexpress MRP-1 protein, were incubated with WP631 the expression of the multidrug-resistance protein gene decreased. Conversely, doxorubicin did not alter mrp-1 gene expression. The inhibition of gene expression was followed by a decrease in the activity of the MRP-1 protein. The IC(75) for WP631 (drug concentration required to inhibit cell growth by 75%) circumvented the drug-efflux pump, without addition of resistant modifiers. After treatment with WP631, MCF-7/VP cells were committed to die after entering mitosis (mitotic catastrophe), while treatment with doxorubicin did not affect cell growth. This is the first report on an antitumor drug molecule inhibiting the mrp-1 gene directly, rather than being simply a poor substrate for the transporter-mediated efflux. However, both situations appeared to coexist, thereby a superior cytotoxic effect was attained. Ours results suggest that WP631 offers great potential for the clinical treatment of tumors displaying a multidrug-resistance phenotype.     

多重耐药鲍曼不动杆菌中β内酰胺酶基因的检测

目的调查多重耐药鲍曼不动杆菌中8内酰胺类耐药基因的流行状况。方法收集2012年8月至2013年2月江苏大学附属医院和镇江市第一人民医院住院患者标本中分离得到的多重耐药鲍曼不动杆菌菌株。应用K—B纸片扩散法检测多重耐药鲍曼不动杆菌对抗菌药物的敏感性。应用PCR法检测口内酰胺类耐药基因。结果47株多重耐药鲍曼不动杆菌除对头孢哌酮-舒巴坦,米诺环素和氨苄西林-舒巴坦的耐药率相对较低外,对其他抗菌药物的耐药率均较高。β内酰胺类耐药基因TEM、ADC、OXA-23和0XA51的阳性率分别为91．5％（43株）、93．6％（44株）、93．6％（44株）和95．7％（45株）。结论多重耐药鲍曼不动杆菌对8内酰胺类抗生素耐药可能与8内酰胺类耐药基因的表达相关。     

Radixin is required to maintain apical canalicular membrane structure and function in rat hepatocytes

BACKGROUND & AIMS: Ezrin-radixin-moesin proteins are cross-linkers between the plasma membrane and actin filaments. Radixin, the dominant ezrin-radixin-moesin protein in hepatocytes, has been reported to selectively tether multidrug-resistance-associated protein 2 to the apical canalicular membrane. However, it remains to be determined if this is its primary function. METHODS: An adenovirus-mediated short interfering RNA (siRNA) was used to down-regulate radixin expression in collagen sandwich-cultured rat hepatocytes and morphologic and functional changes were characterized quantitatively. RESULTS: In control cultures, an extensive bile canalicular network developed with properly localized apical and basolateral transporters that provided for functional excretion of fluorescent cholephiles into the bile canalicular lumina. siRNA-induced suppression of radixin was associated with a marked reduction in the canalicular membrane structure as observed by differential interference contrast microscopy and F-actin staining, in contrast to control cells exposed to adenovirus encoding scrambled siRNA. Indirect immunofluorescence showed that apical transporters (multidrug-resistance-associated protein 2, bile salt export pump, and multidrug-resistance protein 1) dissociated from their normal location at the apical membrane and were found largely associated with Rab11-containing endosomes. Localization of the basolateral membrane transporter, organic anion transporting polypeptide 2 (Oatp2), was not affected. Consistent with this dislocation of apical transporters, the biliary excretion of glutathione-methylfluorescein and cholylglycylamido-fluorescein was decreased significantly in the radixin-deficient cells, but not in the control siRNA cells. CONCLUSIONS: Radixin is essential for maintaining the polarized targeting and/or retaining of canalicular membrane transporters and is a critical determinant of the overall structure and function of the apical membrane of hepatocytes.