Manipulation of kynurenine pathway for enhanced daptomycin production in Streptomyces roseosporus

Daptomycin is a cyclic lipopeptide natural product produced by Stretptomyces roseosporus, displaying good bactericidal activity against a wide range of gram‐positive pathogens. Daptomycin contains a 13 amino acid and kynurenine (Kyn) is essential for optimal activity of daptomycin. In this study, we characterized the Kyn pathway in S. roseosporus and investigated its role in supplying precursor for daptomycin biosynthesis. Two genes (dptJ and tdo) coding for tryptophan‐2,3‐dioxgenase existed in the chromosome. dptJ is located in the daptomycin biosynthetic gene cluster, while tdo is in other locus. Disruption of dptJ or tdo resulted in reduced yield by ～50%. The introduction of an additional copy of dptJ but not tdo led to enhanced production of daptomycin by 110%. Furthermore, disruption of kyn encoding kynureninase showed improved daptomycin productivity by 30%. Our results demonstrated that the enhancement of Kyn supply through metabolic engineering approach is an efficient way to increase daptomycin production. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:847–852, 2013     

Fouling of nanostructured insect cuticle: adhesion of natural and artificial contaminants

The adhesional properties of contaminating particles of scales of various lengths were investigated for a wide range of micro- and nanostructured insect wing cuticles. The contaminating particles consisted of artificial hydrophilic (silica) and spherical hydrophobic (C₁₈) particles, and natural pollen grains. Insect wing cuticle architectures with an open micro-/nanostructure framework demonstrated topographies for minimising solid–solid and solid–liquid contact areas. Such structuring of the wing membranes allows for a variety of removal mechanisms to contend with particle contact, such as wind and self-cleaning droplet interactions. Cuticles exhibiting high contact angles showed considerably lower particle adhesional forces than more hydrophilic insect surfaces. Values as low as 3 nN were recorded in air for silica of ～28 nm in diameter and <25 nN for silica particles 30 μm in diameter. A similar adhesional trend was also observed for contact with pollen particles.     

Delayed Treatment Effects of Xanthine Oxidase Inhibition on Systolic Overload-Induced Left Ventricular Hypertrophy and Dysfunction

The nonpurine selective xanthine oxidase (XO) inhibitor febuxostat attenuates development of left ventricular (LV) hypertrophy and dysfunction in mice when treatment is initiated within 1 hour of transverse aortic constriction (TAC). This study investigated whether a 7-day delay of treatment with the XO inhibitors febuxostat or allopurinol would reverse TAC-induced changes after onset of heart failure (HF). Neither treatment significantly affected TAC-induced LV hypertrophy; only febuxostat caused a modest improvement in LV function (～10% increase in LV ejection fraction). However, the purine analog allopurinol tended to increase mortality compared with vehicle or febuxostat in HF mice.     

Ang II Enhances Noradrenaline Release from Sympathetic Nerve Endings Thus Contributing to the Up-Regulation of Metalloprotease-2 in Aortic Dissection Patients' Aorta Wall

Object

To test the hypothesis that angiotensin II (Ang II) could enhance noradrenaline (NA) release from sympathetic nerve endings of the aorta thus contributing to the up-regulation of matrix metalloproteinase 2 (MMP-2) during the formation of aortic dissection (AD).

Methods

Ang II, NA, MMP-2, MMP-9 of the aorta sample obtained during operation from aortic dissection patients were detected by High Performance Liquid Chromatography and ELISA and compared with controls. Isotope labelling method was used to test the impact of exogenous Ang II and noradrenaline on the NA release and MMP-2, MMP-9 expression on Sprague Dawley (SD) rat aorta rings in vitro. Two kidneys, one clip, models were replicated for further check of that impact in SD rats in vivo.

Results

The concentration of Ang II, MMP-2, 9 was increased and NA concentration was decreased in aorta samples from AD patients. Exogenous Ang II enhanced while exogenous NA restrained NA release from aortic sympathetic endings. The Ang II stimulated NA release and the following MMP-2 up-regulation could be weakened by Losartan and chemical sympathectomy. Beta blocker did not influence NA release but down-regulated MMP-2. Long term in vivo experiments confirmed that Ang II could enhance NA release and up-regulate MMP-2.

Conclusions

AD is initiated by MMP-2 overexpression as a result of increased NA release from sympathetic nervous endings in response to Ang II. This indicates an interaction of RAS and SAS during the formation of AD.     

A New Coronary Retroinfusion Technique in theRat Infarct Model: Transjugular Cardiac Vein Catheterization

Cell delivery via the retrograde coronary route boasts less vessel embolism, myocardial injury, and arrhythmogenicity when compared with those via antegrade coronary administration or myocardial injection. However, conventional insertion into the coronary sinus and consequent bleeding complication prevent its application in small animals. To overcome the complication of bleeding, we described a modified coronary retroinfusion technique via the jugular vein route in rats with myocardial infarction (MI). A flexible wire with a bent end was inserted into the left internal jugular vein and advanced slowly along the left superior vena cava. Under direct vision, the wire was run into the left cardiac vein by rotating the wire and changing the position of its tip. A fine tube was then advanced along the wire to the left cardiac vein. This modified technique showed less lethal hemorrhage than the conventional technique. Retroinfusion via transjugular catheter enabled efficient fluid or cell dissemination to the majority areas of the free wall of the left ventricle, covering the infarcted anterior wall. In conclusion, transjugular cardiac vein catheterization may make retrocoronary infusion a more safe and practical route for delivering cell, drug, and gene therapy into the infarcted myocardium of rats.     

Inhibition of Fe-induced colon oxidative stress by lactobacilli in mice

Iron (Fe) can promote hydrogen peroxide (H₂O₂) and hydroxyl radical generation in the colonic surface and promote growth of Fe-dependent bacteria. Some Lactobacillus strains are resistant to oxygen free-radicals, allowing them to survive in a Fe-modulated mucosal environment and influence colon microbial ecology and redox state. Here, we investigated the capacity of lactobacilli with different antioxidant abilities to modify the bacterial profile and prevent oxidative stress in the colon of Fe-overloaded mice. Survival time of Lactobacillus rhamnosus LGG (LGG) in the presence of H₂O₂ and hydroxyl radical was significantly longer compared with the mid- and non-antioxidative strains, Lactobacillus paracasei Fn032 and Lactobacillus plantarum Fn001, respectively. Different Lactobacillus strains are specific in free-radical scavenging activities of their cell-free extracts, which increased to varying extent depending on strains when bacteria were exposed to simulated gastric and pancreatic juice. Fe-overloaded mice showed increased colonic luminal ferrous Fe content, Enterococcus and Escherichia coli concentrations, mucosal malondialdehyde and free-radicals, and decreased mucosal total antioxidative capacity and oxidative enzymatic activity. Translocation of endotoxin to the liver was also significantly increased (P < 0.05). Lactobacilli inhibited ferrous Fe accumulation, especially in LGG and Fn032. LGG significantly inhibited the increase of colonic mucosal free-radicals and malondialdehyde content (P < 0.05). Fn032 only inhibited malondialdehyde (P < 0.05). LGG and Fn032 significantly inhibited increases in colonic Enterococcus (P < 0.05). Fn001 showed no significant antioxidative ability in vivo. The difference of these effects in vivo were well agreed with scavenging activities against reactive oxygen species (ROS) of simulated gastrointestinals fluid pretreated cells in vitro. In conclusion, ROS scavenging activities was essential for Lactobacillus to prevent oxidative stress in vivo and inhibition of ROS-producing bacterial growth and mucosal barrier injury.     

凡纳滨对虾MT基因序列及其在卵巢发育和低温胁迫中的表达分析

在低温处理仔虾全长cDNA文库的筛选测序中, 获得凡纳滨对虾(Litopenaeus vannmei)金属硫蛋白基因全长cDNA序列, 该序列含有425个碱基, 包含177 bp开放阅读框, 上游98 bp的非编码区及下游150 bp 的非编码区, 编码58个氨基酸, 其中半胱氨酸含量丰富, 富含金属硫蛋白典型的Cys-X(1-3)-Cys 结构。多序列比对表明, 凡纳滨对虾MT蛋白序列与美洲螯龙虾(Homarus americanus)MT蛋白序列具最高同源性72.4%。Real-time PCR结果表明, 凡纳滨对虾MT基因在卵巢组织中呈优势表达, 在不同发育期的卵巢中的表达量都很高, 在低温处理凡纳滨对虾肝胰腺组织中上调表达。实验所得结果为研究凡纳滨对虾金属硫蛋白基因在生殖发育和低温应激中的功能提供了参考。       

LncRNA OIP5-AS1 regulates radioresistance by targeting DYRK1A through miR-369-3p in colorectal cancer cells

Object

This study aimed to investigate the role of lncRNA OIP5-AS1 in regulating radioresistance of colorectal cancer (CRC) cells.

Discovery of EBI-1051: A novel and orally efficacious MEK inhibitor with benzofuran scaffold

A novel series of benzodihydrofuran derivatives was developed as potent MEK inhibitors through scaffold hopping based on known clinical compounds. Further SAR exploration and optimization led to another benzofuran series with good oral bioavailability in rats. One of the compounds EBI-1051 (28d) demonstrated excellent in vivo efficacy in colo-205 tumor xenograft models in mouse and is suitable for pre-clinical development studies for the treatment of melanoma and MEK associated cancers. Compared to AZD6244, EBI-1051 showed superior potency in some cancer cell lines such as colon-205, A549 and MDA-MB-231.