Research progress of new antibacterial drugs that target bacterial quorum sensing systems / 药学学报

In recent years, antibiotic resistance of bacteria has become a global health crisis. Especially, the new class of "superbug" was found in South Asia, which is resistant to almost known antibiotics and causes worldwide alarm. Through the underlying mechanisms of bacterial pathogenecity, the expression of many pathogen virulence factors is regulated by the process of quorum sensing. Screening efficient quorum sensing inhibitors is an especially compelling approach to the future treatment of bacterial infections and antibiotic resistance. This article focuses on bacterial quorum sensing system, quorum sensing screening model for in vitro and evaluation of animal models in vivo, recent research of quorum sensing inhibitors and so on.

Isolation and Identification of Marine Actinomycetes with Quorum Sensing Inhibitory Activity / 微生物学通报

Quorum sensing systems of pathogens are central regulators for the expression of virulence factors. Increasing evidence implies that targeting the quorum sensing system of many pathogenic bacteria is a promising therapeutic approach to control infections. In this work,we isolated 47 strains of actinomycetes from the mud sample of Jiaozhou Bay. Quorum sensing inhibitory activity was monitored by Chromobacterium violaceum CV026. As a result,the culture broth extract of actinomycetes WA-7 was found to have significant quorum sensing inhibitory activity. This strain was assigned to the genus Streptomyces based on its 16S rDNA sequence. Further investigation revealed that the extract could inhibit the quorum sensing-controlled violacein and proteases production of C. violaceum in a concentration-dependent manner.

Akt1 Silencing Inhibits Lung Metastasis of Murine Breast Cancer Cells / 中国生物工程杂志

Akt1 is a serine-threonine protein kinase that has been implicated in the control of cellular metabolism,survival and growth.Elevated expression of Akt1 has been noted in a significant percentage of human tumors,promoting cellular metastasis.Conversely,some studies have revealed hyperactivated Akt1 inhibited the invasiveness and metastasis of breast cancer cells.To clarify the definite effect of Akt1 on tumorigenesis and development,Akt1 was silenced by RNAi in the highly metastatic murine breast cancer 4T1 cells.Akt1 silencing didn't affect the proliferation of breast cancer cells in MTT assay,while reduced the migration in Transwell assay.Consistent with the above results,Akt1 silencing didn't change the primary tumor weight,but significantly suppressed lung metastasis of 4T1 cells.These observations indicated Akt1 plays an important role in murine breast cancer metastasis,and suggested that Akt1 might be a therapeutic target for breast cancer metastasis.

Regulation of Gene Expression Profile by Twist in Murine Breast Cancer Cell / 中国生物工程杂志

Previous studies have revealed Twist,a basic helix-loop-helix transcription factor,plays an important role in breast cancer metastasis.To clarify the molecular mechanism of its involvement in cancer metastasis,Twist was silenced by RNAi in highly metastatic 4T1 cells.Then microarray chips were used to investigate the gene-expression pattern of the Twist-knockdown 4T1 cells and the normal 4T1 cells.The results indicated that silencing of Twist significantly suppressesed lung metastasis of 4T1 cells in vivo.Direct comparison of gene-expression profiles showed that 167 genes in Twist-knockdown cells differed dramatically in expression levels from those in control cells.Among the 167 genes,26 well-known tumor-associated genes,including 15 up-regulated and 11 down-regulated genes were found.These genes appear to be regulated by Twist during breast tumorigenesis.The findings provide new insights into the mechanism by which Twist is involved in tumorigenesis.

Promoting Effect of N-Acetylglucosaminyltransferase Ⅱ on the Migration of Mouse Breast Cancer Cell / 中国生物工程杂志

It is well documented that altered biosynthesis of cell surface N-linked oligosaccharides is associated with the transformed cells and tumors.N-acetylglucosaminyltransferase Ⅱ(GnT-II;EC 2.4.1.143)is a medial Golgi enzyme that catalyses the incorporation of a GlcNAc residue in ?-1,2 linkage to the Man-?-1,6 arm of the N-glycan core.This is an essential step in the biosynthetic pathway leading from hybrid to complex N-glycans.Because functional GnT-Ⅱ is an prerequisite of N-Acetylglucosaminyltransferase V performance,It was speculated that GnT-Ⅱ was involved in cancer development and progression.The expression of GnT-Ⅱ in mouse breast cancer cells 67NR and 4T1 which have different behavior of metastasis was analysed using RT-PCR.The amounts of GnT-Ⅱ in the highly metastatic cell 4T1 increased to 1.53 times of the lowly metastatic cell 67NR.To determine the association of GnT-Ⅱ with tumor progression,the GnT-Ⅱ encoding gene was amplified with RT-PCR and cloned into retrovirus vector pMSCV,resulting in pMSCV-GnT-Ⅱ.The recombinant plasmid was transfected into 4T1 and the transfected cells were selected in the medium containing puromycin,which were harvested to detect the adhesion ability to fibronection and the migration potential by transwell system.The cell adhesion to fibronectin was weakened by 67% and migration potential was increased by 82%.The data indicates that GnT-Ⅱ mediates cell adhesion and migration,thus may play an important role in cancer metastasis.

Molecular mechanisms of antioxidant effects of propylene glycol mannate sulfate / 药学学报

<p><b>AIM</b>To investigate the antioxidant mechanisms of propylene glycol mannate sulfate (PGMS) in hyperlipidemic rats.</p><p><b>METHODS</b>Male Wistar rats were given high lipid emulsion diet to establish hyperlipidemic model. PGMS was given every day at different doses (37.8 and 75.6 mg.kg-1, ig) to hyperlipidemic rats for three weeks. In addition, diethyldithiocarbamate (DDC) was given 200 mg.kg-1.3 d-1 (i.p.) to inhibit SOD activity. Then, the MDA content was examined using TBA method to show the oxidation level, and the activities of SOD, GSH-Px and CAT were examined following the kit protocols to indicate the capability of eliminating OFR. RT-PCR was applied to study the expression of Cu, Zn-SOD mRNA in rat liver.</p><p><b>RESULTS</b>The MDA content of PGMS treatment groups decreased markedly compared with hyperlipidemic group, and the activities of SOD, GSH-Px and CAT increased distinctly. Cu, Zn-SOD mRNA expression was significantly increased by PGMS treatment. Furthermore, the application of DDC(the SOD inhibitor) reduced total SOD activity and Cu, Zn-SOD mRNA expression induced by PGMS, and the content of MDA increased correspondingly.</p><p><b>CONCLUSION</b>PGMS can induce the activities of antioxidant enzymes and the mRNA expression of Cu, Zn-SOD, which contribute to the elimination of oxygen free radical. This may explain the molecular mechanism of antioxidant effects of PGMS.</p>

Inhibition of MCP-1 mRNA expression by propylene glycol mannate sulfate in hyperlipidemic rat aorta / 药学学报

<p><b>AIM</b>To study the effects of prophylene glycol mannate sulfate (PGMS) on monocyte chemoattractant protein-1 (MCP-1) mRNA expression in hyperlipidemic rat aorta and to clarify the molecular mechanism of PGMS for the prevention of atherosclerosis.</p><p><b>METHODS</b>PGMS (37.8 and 75.6 mg.kg-1.d-1, ig) or PGMS (37.8 and 75.6 mg.kg-1.d-1, ig) combined with diethyldithiocarbamate (DDC, an inhibitor of SOD, 200 mg.kg-1 every three days, i.p.) were given to hyperlipidemic rats for three weeks. The MDA content and SOD activity were determined after 12 h of starvation, and MCP-1 mRNA expression in aorta was detected by reverse transcription-polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>There was significant decrease (29.46% or 58.40)% of MCP-1 mRNA expression in aortic after the therapy. The SOD activity increased markedly and the MDA content decreased at the same time. After treatment with DDC, the SOD activity was inhibited and the MDA content increased, but with no significant effect on MCP-1 mRNA expression.</p><p><b>CONCLUSION</b>PGMS inhibited MCP-1 mRNA expression with no relation to its effect on decreasing MDA content.</p>

Effect of propylene glycol mannate sulfate on blood lipids and lipoprotein lipase in hyperlipidemic rat / 药学学报

<p><b>AIM</b>To study the effect of propylene glycol mannate sulfate (PGMS) on blood lipids and lipoprotein lipase in hyperlipidemic rat, and its anti-hyperlipidemic mechanism.</p><p><b>METHODS</b>PGMS was administered ig at different doses (37.8 mg.kg-1.d-1 and 75.6 mg.kg-1.d-1) to hyperlipidemic rats for three weeks and blood serum was obtained after starved 12 h. Total cholesterol (TC), triglyceride (TG), low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) were examined. The mRNA expression of lipoprotein lipase (LPL) in liver, spleen and artery was detected by reverse transcription polymerase chain reaction (RT-PCR).</p><p><b>RESULTS</b>PGMS significantly decreased the levels of TC, TG and LDL-C and increased that of HDL-C in hyperlipidemic serum dose-dependently. PGMS was shown to increase the level of LPL mRNA expression, which is related directly to the controlling effects of PGMS on blood lipids.</p><p><b>CONCLUSION</b>PGMS modulated blood lipids by promoting mRNA expression of LPL. This may be one important mechanism of PGMS to modulate blood lipids.</p>

Induction of CuZn-SOD mRNA expression and activity by PGMS in rat liver / 药学学报

<p><b>AIM</b>To study the effect of propylene glycol mannate sulfate (PGMS) on induction of CuZn-SOD.</p><p><b>METHODS</b>Wistar rats were given PGMS p.o. at different doses (0, 18.9, 37.8 and 75.6 mg.kg-1.d) for ten days. Then the rats were sacrificed and the total RNA was extracted from the livers. The total RNA samples were loaded on a 1% agarose gel to detect the quality of total RNA. RT-PCR was applied to study the expression of CuZn-SOD mRNA in rat livers. The amplified products were detected by the 1.5% agarose gel electrophoresis. Simultaneously, the CuZn-SOD activities in rat liver were determined by nitrite method.</p><p><b>RESULTS</b>The total RNA extracted from rat livers was integrated without being decomposed by RNase. The level of CuZn-SOD mRNA of the high-dosage group (75.6 mg.kg-1.d) was higher than that of the control group (0 mg.kg-1.d) (P < 0.01); the CuZn-SOD activities of the high-dosage group were significantly higher than those of the control group (P < 0.001) and the CuZn-SOD activities of the middle- (37.8 mg.kg-1.d) and low-dosage groups (18.9 mg.kg-1.d) were higher than those of the control group (P < 0.01).</p><p><b>CONCLUSION</b>PGMS can increase the CuZn-SOD activities as well as CuZn-SOD on mRNA level. Therefore, it is possible for PGMS to counteract Atherosclerosis (AS) by inducing the expression of CuZn-SOD.</p>