Bacterial exopolysaccharides have always been suggested to play crucial roles in the bacterial initial adhesion and the development of complex architecture in the later stages of bacterial biofilm formation. However, Escherichia coli group II capsular polysaccharide was characterized to exert broad-spectrum biofilm inhibition activity. In this study, we firstly reported that a bacterial exopolysaccharide (A101) not only inhibits biofilm formation of many bacteria but also disrupts established biofilm of some strains. A101 with an average molecular weight of up to 546 KDa, was isolated and purified from the culture supernatant of the marine bacterium Vibrio sp. QY101 by ethanol precipitation, iron-exchange chromatography and gel filtration chromatography. High performance liquid chromatography traces of the hydrolyzed polysaccharides showed that A101 is primarily consisted of galacturonic acid, glucuronic acid, rhamnose and glucosamine. A101 was demonstrated to inhibit biofilm formation by a wide range of Gram-negative and Gram-positive bacteria without antibacterial activity. Furthermore, A101 displayed a significant disruption on the established biofilm produced by Pseudomonas aeruginosa, but not by Staphylococcus aureus. Importantly, A101 increased the aminoglycosides antibiotics' capability of killing P. aeruginosa biofilm. Cell primary attachment to surfaces and intercellular aggregates assays suggested that A101 inhibited cell aggregates of both P. aeruginosa and S. aureus, while the cell-surface interactions inhibition only occurred in S. aureus, and the pre-formed cell aggregates dispersion induced by A101 only occurred in P. aeruginosa. Taken together, these data identify the antibiofilm activity of A101, which may make it potential in the design of new therapeutic strategies for bacterial biofilm-associated infections and limiting biofilm formation on medical indwelling devices. The found of A101 antibiofilm activity may also promote a new recognition about the functions of bacterial exopolysaccharides.

SIRT1 is the most evolutionarily conserved mammalian sirtuin, and it plays a vital role in the regulation of metabolism, stress responses, genome stability, and ageing. As a stress sensor, SIRT1 deacetylase activity is significantly increased during stresses, but the molecular mechanisms are not yet fully clear. Here, we show that SIRT1 is dynamically modified with O-GlcNAc at Ser 549 in its carboxy-terminal region, which directly increases its deacetylase activity both in vitro and in vivo. The O-GlcNAcylation of SIRT1 is elevated during genotoxic, oxidative, and metabolic stress stimuli in cellular and mouse models, thereby increasing SIRT1 deacetylase activity and protecting cells from stress-induced apoptosis. Our findings demonstrate a new mechanism for the activation of SIRT1 under stress conditions and suggest a novel potential therapeutic target for preventing age-related diseases and extending healthspan.

Background: Gangliosides are sialic acid containing glycosphingolipids that are ubiquitously distributed on vertebrate plasma membranes. GM3, a precursor for most of the more complex ganglioside species, is synthesized by GM3 synthase. Although total ganglioside levels are significantly higher in breast tumor tissue than in normal mammary tissue, the roles played by gangliosides in breast cancer formation and metastasis are not clear. Methods: To investigate the roles of gangliosides in breast tumor development, GM3 synthase was silenced in the highly metastatic 4T1 cells and over-expressed in the non-metastatic 67NR cells. The behavior of breast cancer cells was examined in vitro using migration assay, invasion assay, and soft agar assay. Tumor formation and metastasis in vivo were examined using a well established mouse mammary tumor model. Results: GM3 synthase silencing in 4T1 cells significantly inhibited cell migration, invasion and anchorage-independent growth in vitro, and lung metastasis in vivo. In addition, over-expression of GM3 synthase in nonmetastatic 67NR cells significantly induced cell migration and anchorage-independent growth. Further studies indicated that activation of the phosphoinositide-3 kinase/Akt pathway, and consequently inhibition of nuclear factor of activated T cell (NFAT)1 expression, could be the mechanism underlying the suppression of breast cancer migration/invasion induced by GM3 synthase silencing. Conclusion: Our findings indicate that GM3 synthase silencing suppressed lung metastasis in murine breast cancer cells. The molecular mechanism that underlies GM3 synthase mediated migration and invasion was inhibition of the phosphoinositide-3 kinase/Akt pathway. The findings suggest that GM3 synthase may be of value as a therapeutic target in breast cancer.

Background: Lipocalin 2, an iron binding protein, is abnormally expressed in some malignant human cancers and may play an important role in tumor metastasis. However, the roles of lipocalin 2 in breast cancer formation and metastasis have not been clearly shown. This study aimed to investigate the roles of lipocalin 2 in breast tumor metastasis.Methods: Lipocalin 2 was overexpressed in the metastatic 4T1 murine mammary cancer cells. The effects of lipocalin 2 overexpression on the malignancy of breast cancer cells were examined using cell proliferation assay, migration assay, invasion assay, and soft agar assayin vitro. Tumor formation and metastasis abilities were examined using a well established mouse mammary tumor modelin vivo.Results: Lipocalin 2 overexpression significantly enhanced the migration and invasion abilities of 4T1 cellsin vitro, and lung metastasisin vivo. But overexpression of lipocalin 2 in 4T1 cells didn't affect cell proliferation and anchorage-independent growthin vitro, and primary tumor weightin vivo. Further studies demonstrated that the inhibition of the PI3K/Akt pathway could be a causative mechanism for the promotion of breast cancer migration/invasion induced by lipocalin 2 overexpression.Conclusion: These results clarified that lipocalin 2 could promote lung metastasis of 4T1 cells through the inhibition of the PI3K/Akt pathway, suggesting that lipocalin 2 was a potential target for therapy of breast cancer.

Recently, many small non-coding RNAs (sRNAs) with important regulatory roles have been identified in bacteria. As their eukaryotic counterparts, a major class of bacterial trans -encoded sRNAs acts by basepairing with target mRNAs, resulting in changes in translation and stability of the mRNA. RNA interference (RNAi) has become a powerful gene silencing tool in eukaryotes. However, such an effective RNA silencing tool remains to be developed for prokaryotes. In this study, we described first the use of artificial trans -encoded sRNAs (atsRNAs) for specific gene silencing in bacteria. Based on the common structural characteristics of natural sRNAs in Gram-negative bacteria, we developed the designing principle of atsRNA. Most of the atsRNAs effectively suppressed the expression of exogenous EGFP gene and endogenous uidA gene in Escherichia coli . Further studies demonstrated that the mRNA base pairing region and AU rich Hfq binding site were crucial for the activity of atsRNA. The atsRNA-mediated gene silencing was Hfq dependent. The atsRNAs led to gene silencing and RNase E dependent degradation of target mRNA. We also designed a series of atsRNAs which targeted the toxic genes in Staphyloccocus aureus , but found no significant interfering effect. We established an effective method for specific gene silencing in Gram-negative bacteria.