Role of extracellular DNA in Enterococcus faecalis biofilm formation and its susceptibility to sodium hypochlorite.

OBJECTIVE: This study investigated the role of extracellular deoxyribonucleic acid (eDNA) on Enterococcus faecalis ( E. faecalis ) biofilm and the susceptibility of E. faecalis to sodium hypochlorite (NaOCl). METHODOLOGY: E. faecalis biofilm was formed in bovine tooth specimens and the biofilm was cultured with or without deoxyribonuclease (DNase), an inhibitor of eDNA. Then, the role of eDNA in E. faecalis growth and biofilm formation was investigated using colony forming unit (CFUs) counting, eDNA level assay, crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy. The susceptibility of E. faecalis biofilm to low (0.5%) or high (5%) NaOCl concentrations was also analyzed by CFU counting. RESULTS: CFUs and biofilm formation decreased significantly with DNase treatment (p<0.05). The microstructure of DNase-treated biofilms exhibited less structured features when compared to the control. The volume of exopolysaccharides in the DNase-treated biofilm was significantly lower than that of control (p<0.05). Moreover, the CFUs, eDNA level, biofilm formation, and exopolysaccharides volume were lower when the biofilm was treated with DNase de novo when compared to when DNase was applied to matured biofilm (p<0.05). E. faecalis in the biofilm was more susceptible to NaOCl when it was cultured with DNase (p<0.05). Furthermore, 0.5% NaOCl combined with DNase treatment was as efficient as 5% NaOCl alone regarding susceptibility (p>0.05). CONCLUSIONS: Inhibition of eDNA leads to decrease of E. faecalis biofilm formation and increase of susceptibility of E. faecalis to NaOCl even at low concentrations. Therefore, our results suggest that inhibition of eDNA would be beneficial in facilitating the efficacy of NaOCl and reducing its concentration.

Role of extracellular DNA in Enterococcus faecalis biofilm formation and its susceptibility to sodium hypochlorite

Abstract Objective This study investigated the role of extracellular deoxyribonucleic acid (eDNA) on Enterococcus faecalis ( E. faecalis ) biofilm and the susceptibility of E. faecalis to sodium hypochlorite (NaOCl). Methodology E. faecalis biofilm was formed in bovine tooth specimens and the biofilm was cultured with or without deoxyribonuclease (DNase), an inhibitor of eDNA. Then, the role of eDNA in E. faecalis growth and biofilm formation was investigated using colony forming unit (CFUs) counting, eDNA level assay, crystal violet staining, confocal laser scanning microscopy, and scanning electron microscopy. The susceptibility of E. faecalis biofilm to low (0.5%) or high (5%) NaOCl concentrations was also analyzed by CFU counting. Results CFUs and biofilm formation decreased significantly with DNase treatment (p<0.05). The microstructure of DNase-treated biofilms exhibited less structured features when compared to the control. The volume of exopolysaccharides in the DNase-treated biofilm was significantly lower than that of control (p<0.05). Moreover, the CFUs, eDNA level, biofilm formation, and exopolysaccharides volume were lower when the biofilm was treated with DNase de novo when compared to when DNase was applied to matured biofilm (p<0.05). E. faecalis in the biofilm was more susceptible to NaOCl when it was cultured with DNase (p<0.05). Furthermore, 0.5% NaOCl combined with DNase treatment was as efficient as 5% NaOCl alone regarding susceptibility (p>0.05). Conclusions Inhibition of eDNA leads to decrease of E. faecalis biofilm formation and increase of susceptibility of E. faecalis to NaOCl even at low concentrations. Therefore, our results suggest that inhibition of eDNA would be beneficial in facilitating the efficacy of NaOCl and reducing its concentration.

Change in Expression of Survivin Caused by Using Oxaliplatin in HCT116 Colon Cancer Cells.

PURPOSE: Oxaliplatin is a third-generation platinum compound, and it has no nephrotoxicity and has reduced bone marrow toxicity. Cancer cells that are resistant to cisplatin are sensitive to oxaliplatin. Oxaliplatin is used widely for the treatment of colon cancers. Recently, oxaliplatin was reported to inhibit the expression of survivin, which protects cell apoptosis. However, there are no reports on the expressions of survivin variants and the changes in intracellular localization of survivin in cancer cells. We studied the expression of survivin caused by oxaliplatin in HCT116 colon cancer cells, and we observed the localization of survivin in the mitotic phase. METHODS: We treated the HCT116 colon cancer cells with 2.0 µM of oxaliplatin, and we studied the expressions of survivin protein, and survivin mRNA variants, as well as the changes in intracellular localization, by using the Western blot method, RT-PCR, immunocytochemistry, and flowcytometry. RESULTS: Oxaliplatin inhibits the expression of the survivin protein and survivin mRNA in HCT116 colon cancer cells. The expression of the survivin-2B variants, which have no antiapoptotic activity but control cell mitosis by localization on a microtubule, is reduced continuously 2 days after treatment with oxaliplatin. In immunocytochemistry, expression of survivin in the cytoplasm is reduced and especially is not expressed in microtubules and contractile rings. CONCLUSION: One of the mechanisms of oxaliplatin is to inhibit the expression of and to change the localization of survivin. Based on these results, we suggest that changes in the expression of survivin variants and in their localization are two effects of oxaliplatin.