Prevalence of Propionibacterium acnes in diseased prostates and its inflammatory and transforming activity on prostate epithelial cells.

Prostate cancer (PCa) is the second leading cause of male cancer deaths in the Western world. Mounting evidence has revealed that chronic inflammation can be an important initiating factor of PCa. Recent work has detected the anaerobic Gram-positive bacterium Propionibacterium acnes in cancerous prostates, but with wide-ranging detection rates. Here, using in situ immunofluorescence (ISIF), P. acnes was found in 58 out of 71 (81.7%) tested cancerous prostate tissue samples, but was absent from healthy prostate tissues (20 samples) and other cancerous tissue biopsies (59 mamma carcinoma samples). Live P. acnes bacteria were isolated from cancerous prostates and cocultured with the prostate epithelial cell line RWPE1. Microarray analysis showed that the host cell responded to P. acnes with a strong multifaceted inflammatory response. Active secretion of cytokines and chemokines, such as IL-6 and IL-8, from infected cells was confirmed. The host cell response was likely mediated by the transcriptional factors NF-κB and STAT3, which were both activated upon P. acnes infection. The P. acnes-induced host cell response also included the activation of the COX2-prostaglandin, and the plasminogen-matrix metalloproteinase pathways. Long-term exposure to P. acnes altered cell proliferation, and enabled anchorage-independent growth of infected epithelial cells, thus initiating cellular transformation. Our results suggest that P. acnes infection could be a contributing factor to the initiation or progression of PCa.

Helicobacter pylori induces miR-155 in T cells in a cAMP-Foxp3-dependent manner.

Amongst the most severe clinical outcomes of life-long infections with Helicobacter pylori is the development of peptic ulcers and gastric adenocarcinoma--diseases often associated with an increase of regulatory T cells. Understanding H. pylori-driven regulation of T cells is therefore of crucial clinical importance. Several studies have defined mammalian microRNAs as key regulators of the immune system and of carcinogenic processes. Hence, we aimed here to identify H. pylori-regulated miRNAs, mainly in human T cells. MicroRNA profiling of non-infected and infected human T cells revealed H. pylori infection triggers miR-155 expression in vitro and in vivo. By using single and double H. pylori mutants and the corresponding purified enzymes, the bacterial vacuolating toxin A (VacA) and gamma-glutamyl transpeptidase (GGT) plus lipopolysaccharide (LPS) tested positive for their ability to regulate miR-155 and Foxp3 expression in human lymphocytes; the latter being considered as the master regulator and marker of regulatory T cells. RNAi-mediated knockdown (KD) of the Foxp3 transcription factor in T cells abolished miR-155 expression. Using adenylate cyclase inhibitors, the miR-155 induction cascade was shown to be dependent on the second messenger cyclic adenosine monophosphate (cAMP). Furthermore, we found that miR-155 directly targets the protein kinase A inhibitor alpha (PKIalpha) mRNA in its 3'UTR, indicative of a positive feedback mechanism on the cAMP pathway. Taken together, our study describes, in the context of an H. pylori infection, a direct link between Foxp3 and miR-155 in human T cells and highlights the significance of cAMP in this miR-155 induction cascade.

Activities of antimicrobial peptides and synergy with enrofloxacin against Mycoplasma pulmonis.

We showed in a previous study that associations of antimicrobial peptides (AMPs), which are key components of the innate immune systems of all living species, with the fluoroquinolone enrofloxacin can successfully cure HeLa cell cultures of Mycoplasma fermentans and M. hyorhinis contamination. In the present work, the in vitro susceptibility of M. pulmonis, a murine pathogen, to enrofloxacin and four AMPs (alamethicin, globomycin, gramicidin S, and surfactin) was investigated, with special reference to synergistic associations and the effect of the mycoplasma cell concentration. Enrofloxacin and globomycin displayed the lowest MICs (0.4 microM), followed by gramicidin S (3.12 microM), alamethicin (6.25 microM), and surfactin (25 microM). When the mycoplasma cell concentration was varied from 10(4) to 10(8) CFU/ml, the MICs of enrofloxacin and globomycin increased while those of the three other molecules remained essentially constant. The minimal bactericidal concentration of enrofloxacin (0.8 microM) was also lower than those of the peptides (6.25 to 100 microM), but the latter killed the mycoplasma cells much faster than enrofloxacin (2 h versus 1 day). The use of the AMPs in association with enrofloxacin revealed synergistic effects with alamethicin and surfactin. Interestingly, the mycoplasma-killing activities of the two combinations enrofloxacin (MIC/2) plus alamethicin (MIC/4) and enrofloxacin (MIC/2) plus surfactin (MIC/16) were about 2 orders of magnitude higher than those of the three molecules used separately. These results support the interest devoted to AMPs as a novel class of antimicrobial agents and pinpoint their ability to potentiate the activities of conventional antibiotics, such as fluoroquinolones.