Antibacterial and Antibiofilm Activities of Novel Antimicrobial Peptides against Multidrug-Resistant Enterotoxigenic Escherichia Coli

Post-weaning diarrhea due to enterotoxigenic Escherichia coli (ETEC) is a common disease of piglets and causes great economic loss for the swine industry. Over the past few decades, decreasing effectiveness of conventional antibiotics has caused serious problems because of the growing emergence of multidrug-resistant (MDR) pathogens. Various studies have indicated that antimicrobial peptides (AMPs) have potential to serve as an alternative to antibiotics owing to rapid killing action and highly selective toxicity. Our previous studies have shown that AMP GW-Q4 and its derivatives possess effective antibacterial activities against the Gram-negative bacteria. Hence, in the current study, we evaluated the antibacterial efficacy of GW-Q4 and its derivatives against MDR ETEC and their minimal inhibition concentration (MIC) values were determined to be around 2~32 μg/mL. Among them, AMP Q4-15a-1 with the second lowest MIC (4 μg/mL) and the highest minimal hemolysis concentration (MHC, 256 μg/mL), thus showing the greatest selectivity (MHC/MIC = 64) was selected for further investigations. Moreover, Q4-15a-1 showed dose-dependent bactericidal activity against MDR ETEC in time–kill curve assays. According to the cellular localization and membrane integrity analyses using confocal microscopy, Q4-15a-1 can rapidly interact with the bacterial surface, disrupt the membrane and enter cytosol in less than 30 min. Minimum biofilm eradication concentration (MBEC) of Q4-15a-1 is 4× MIC (16 μg/mL), indicating that Q4-15a-1 is effective against MDR ETEC biofilm. Besides, we established an MDR ETEC infection model with intestinal porcine epithelial cell-1 (IPEC-1). In this infection model, 32 μg/mL Q4-15a-1 can completely inhibit ETEC adhesion onto IPEC-1. Overall, these results suggested that Q4-15a-1 may be a promising antibacterial candidate for treatment of weaned piglets infected by MDR ETEC.     

Web信息抽取技术综述*

快速高效地获取网页主题信息的需求使得Web信息抽取技术成为信息技术领域的研究热点。现有的Web信息抽取技术大致可以归纳为基于统计理论的、基于视觉特征的、基于DOM树结构的和基于模板的几类。由于网页文本本身具有树结构并且具有一定的相似性,基于DOM树结构和基于模板的抽取技术发展很快而且已经得到了广泛的应用。分别论述了上述几类技术在近几年来的研究进展,从自动化程度、适用范围和复杂性三个角度分析对比了几类技术的优缺点。     

Structure–Function Relationships in the Human P-Glycoprotein (ABCB1): Insights from Molecular Dynamics Simulations

P-Glycoprotein (P-gp) is a transmembrane protein belonging to the ATP binding cassette superfamily of transporters, and it is a xenobiotic efflux pump that limits intracellular drug accumulation by pumping compounds out of cells. P-gp contributes to a reduction in toxicity, and has broad substrate specificity. It is involved in the failure of many cancer and antiviral chemotherapies due to the phenomenon of multidrug resistance (MDR), in which the membrane transporter removes chemotherapeutic drugs from target cells. Understanding the details of the ligand–P-gp interaction is therefore critical for the development of drugs that can overcome the MDR phenomenon, for the early identification of P-gp substrates that will help us to obtain a more effective prediction of toxicity, and for the subsequent outdesign of substrate properties if needed. In this work, a series of molecular dynamics (MD) simulations of human P-gp (hP-gp) in an explicit membrane-and-water environment were performed to investigate the effects of binding different compounds on the conformational dynamics of P-gp. The results revealed significant differences in the behaviour of P-gp in the presence of active and non-active compounds within the binding pocket, as different patterns of movement were identified that could be correlated with conformational changes leading to the activation of the translocation mechanism. The predicted ligand–P-gp interactions are in good agreement with the available experimental data, as well as the estimation of the binding-free energies of the studied complexes, demonstrating the validity of the results derived from the MD simulations.     

Elevated STAT3 Signaling-Mediated Upregulation of MMP-2/9 Confers Enhanced Invasion Ability in Multidrug-Resistant Breast Cancer Cells

The development of multidrug resistance greatly impedes effective cancer therapy. Recent advances in cancer research have demonstrated that acquisition of multidrug resistance by cancer cells is usually accompanied by enhanced cell invasiveness. Several lines of evidence indicated that cross activation of other signaling pathways during development of drug resistance may increase invasive potential of multidrug-resistant (MDR) cancer cells. However, the accurate mechanism of this process is largely undefined. In this study, to better understand the associated molecular pathways responsible for cancer progression induced by drug resistance, a MDR human breast cancer cell line SK-BR-3/EPR with P-glycoprotein overexpression was established using stepwise long-term exposure to increasing concentration of epirubicin. The SK-BR-3/EPR cell line exhibited decreased cell proliferative activity, but enhanced cell invasive capacity. We showed that the expression of metastasis-related matrix metalloproteinase (MMP)-2/9 was elevated in SK-BR-3/EPR cells. Moreover, SK-BR-3/EPR cells showed elevated activation of STAT3. Activation of STAT3 signaling is responsible for enhanced invasiveness of SK-BR-3/EPR cells through upregulation of MMP-2/9. STAT3 is a well-known oncogene and is frequently implicated in tumorigenesis and chemotherapeutic resistance. Our findings augment insight into the mechanism underlying the functional association between MDR and cancer invasiveness.     

使用Fibreflow碎浆的废纸脱墨生产线

本文介绍广州造纸（厂）有限公司采用Fibreflow碎浆的废纸脱墨生产线的运行情况，并就其配套的设备特性作了说明，该脱墨生产线包括由Fibreflow碎浆机，浮选脱墨槽和先进的筛选净化系统等所组成，现日产脱墨浆250t，应用于纸机作为浆料配比的组份生产胶印新闻纸。     

导入以腺病毒为载体多药耐药基因的脐血有核细胞对化疗药物的耐受性

通过腺病毒载体介导使多药耐药基因转染入脐血有核细胞,提高其对化疗药物的耐受性.结果表明,与未转染的脐血有核细胞相比,转染MDR1基因的脐血有核细胞对化疗药物有明显的抵抗性(P<0.01).通过腺病毒介导的MDR1基因转染脐血有核细胞能有效的抵抗化疗药物对其损伤,从而有望对临床肿瘤的大剂量化疗提供一种有效防护细胞损伤的方法,提高化疗效果.     

Ganciclovir and Its Hemocompatible More Lipophilic Derivative Can Enhance the Apoptotic Effects of Methotrexate by Inhibiting Breast Cancer Resistance Protein (BCRP)

Efflux transporters, namely ATP-binding cassette (ABC), are one of the primary reasons for cancer chemoresistance and the clinical failure of chemotherapy. Ganciclovir (GCV) is an antiviral agent used in herpes simplex virus thymidine kinase (HSV-TK) gene therapy. In this therapy, HSV-TK gene is delivered together with GCV into cancer cells to activate the phosphorylation process of GCV to active GCV-triphosphate, a DNA polymerase inhibitor. However, GCV interacts with efflux transporters that are responsible for the resistance of HSV-TK/GCV therapy. In the present study, it was explored whether GCV and its more lipophilic derivative (1) could inhibit effluxing of another chemotherapeutic, methotrexate (MTX), out of the human breast cancer cells. Firstly, it was found that the combination of GCV and MTX was more hemocompatible than the corresponding combination with compound 1. Secondly, both GCV and compound 1 enhanced the cellular accumulation of MTX in MCF-7 cells, the MTX exposure being 13–21 times greater compared to the MTX uptake alone. Subsequently, this also reduced the number of viable cells (41–56%) and increased the number of late apoptotic cells (46–55%). Moreover, both GCV and compound 1 were found to interact with breast cancer resistant protein (BCRP) more effectively than multidrug-resistant proteins (MRPs) in these cells. Since the expression of BCRP was higher in MCF-7 cells than in MDA-MB-231 cells, and the cellular uptake of GCV and compound 1 was smaller but increased in the presence of BCRP-selective inhibitor (Fumitremorgin C) in MCF-7 cells, we concluded that the improved apoptotic effects of higher MTX exposure were raised mainly from the inhibition of BCRP-mediated efflux of MTX. However, the effects of GCV and its derivatives on MTX metabolism and the quantitative expression of MTX metabolizing enzymes in various cancer cells need to be studied more thoroughly in the future.     

丁香酚对多重耐药大肠杆菌的抑菌活性及其作用机制研究

为研究丁香酚对多重耐药大肠杆菌(Multidrug-resistant Escherichia coli,MDR E.coli)的抑菌活性,利用微量二倍稀释法和琼脂扩散法确定丁香酚对多重耐药大肠杆菌的最低抑菌浓度(Minimum inhibitory concentration,MIC)和最低杀菌浓度(Minimum bactericidal concentration,MBC),并利用紫外分光光度法、考马斯亮蓝法等方法初步分析其作用机制。结果表明,丁香酚对MDR E.coli的MIC和MBC分别为2.50 mg/mL和5.00 mg/mL;丁香酚可延长MDR E.coli迟缓期进入对数生长期的进程,改变菌体结构,增加菌株可溶性蛋白的含量和胞外核酸的量,增大菌体培养液中的电导率,对MDR E.coli具有较强的抑菌作用,这些作用可能归因于丁香酚对其细胞结构的破坏。本研究为临床有效缓解或解决多重耐药大肠杆菌的耐药、感染和致死率等问题提供新的思路、新途径,并为其在医药和食品开发领域的应用奠定理论基础。     

The ability of gallate and pyrogallol moieties of catechins to inhibit P-glycoprotein function

The role of structure–activity relationships in the ability of catechins to inhibit P-glycoprotein (P-gp) function was investigated with respect to gallate and pyrogallol moieties. Experiments using octyl derivatives of gallic acid indicated that the gallate moiety required the catechol group and a neighboring carbonyl group to inhibit P-gp. On the other hand, the pyrogallol moiety appeared to require three hydroxyl groups to inhibit P-gp, according to comparisons between (−)-epicatechin gallate (ECG) and (−)-epigallocatechin gallate (EGCG). The difference in the number of hydroxyl groups that gallate or pyrogallol moieties required for P-gp inhibition, was due to the presence of a carbonyl group. The P-gp inhibition by catechins was restricted by their hydrophobicity. The pyrogallol moiety of EGC did not appear to inhibit P-gp because of its low hydrophobicity. The P-gp inhibitory activity of EGCG was speculated to be increased by the addition of long carbon chains to the C3″of gallate moieties.     

Titanium Incorporation into Zr‐Porphyrinic Metal–Organic Frameworks with Enhanced Antibacterial Activity against Multidrug‐Resistant Pathogens

This study uses metal–organic frameworks (MOFs) alone without any added antibacterial ingredients as the nonantibiotic agent for photodynamic therapy (PDT) of chronic wounds infected by multidrug‐resistant (MDR) bacteria. Nanoparticles (NPs) of MOFs (PCN‐224) are incorporated with titanium through a facile cation exchange strategy. The obtained bimetallic PCN‐224(Zr/Ti) shows greatly enhanced photocatalytic performance for the generation of reactive oxygen species under visible light, which is responsible for the effective antibacterial activities. The PCN‐224(Zr/Ti) NPs are loaded onto lactic‐co‐glycolic acid nanofibers to prepare a wound dressing, which shows high biocompatibility and minimal cytotoxicity. The wound dressing is efficient for PDT‐based in vivo healing of the chronic wound infected by MDR bacteria. Most importantly, this work does not involve any additional antibacterial agents, which is facile, low cost, and in particular, greatly explores the potential of MOFs as a powerful nonantibiotic agent in PDT.