In Vitro Comparison of the Effects of Probiotic, Commensal and Pathogenic Strains on Macrophage Polarization

• Published in: Probiotics and antimicrobial proteins 2014-03, Vol.6 (1), p.1-10
• Main Authors: Christoffersen, Trine Eker, Hult, Lene Therese Olsen, Kuczkowska, Katarzyna, Moe, Kim Marius, Skeie, Siv, Lea, Tor, Kleiveland, Charlotte Ramstad
• Format: Article
• Language: English
• Subjects: adaptive immunity; Animals; Applied Microbiology; Arginase - genetics; Arginase - metabolism; bacteria; Cell Proliferation; Cell Survival; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; cytokines; Enterococcus - physiology; Enterococcus faecalis; Escherichia coli; Escherichia coli - classification; Escherichia coli - physiology; Food Contamination; Food Microbiology; Gastrointestinal Microbiome; gene expression; Gene Expression Regulation; Humans; inducible nitric oxide synthase; Interleukin-10 - secretion; Interleukin-2 - secretion; Intestines - microbiology; Lactobacillus; Lactobacillus - physiology; Lactococcus; Lactococcus - physiology; macrophages; Macrophages - microbiology; Mice; Microbiology; Nitric Oxide Synthase Type II - genetics; Nitric Oxide Synthase Type II - metabolism; Nutrition; pathogens; Probiotics; Protein Science; quantitative polymerase chain reaction; RAW 264.7 Cells; reverse transcriptase polymerase chain reaction; Salmonella; Salmonella enterica - physiology; secretion; Tumor Necrosis Factor-alpha - secretion; virulent strains
• ISSN: 1867-1306; 1867-1314
• DOI: 10.1007/s12602-013-9152-0

Macrophages are important with respect to both innate and adaptive immune responses and are known to differentiate into pro-inflammatory M1- or anti-inflammatory M2-phenotypes following activation. In order to study how different bacteria affect macrophage polarization, we exposed murine RAW 264.7 macrophages to sixteen different strains representing probiotic strains, pathogens, commensals and strains of food origin. Increased inducible nitric oxide synthase (iNOS) or arginase-1 gene expression indicates M1 or M2 polarization, respectively, and was quantified by qRT-PCR. Strains of Escherichia and Salmonella elevated iNOS expression more so than strains of Enterococcus, Lactobacillus and Lactococcus, indicating that Gram-negative strains are more potent M1 inducers. However, strain-specific responses were observed. For instance, Escherichia coli Nissle 1917 was a poor inducer of iNOS gene expression compared to the other E. coli strains, while Enterococcus faecalis Symbioflor-1 was more potent in this respect compared to all the eleven Gram-positive strains tested. Macrophage polarization was further characterized by quantifying secreted pro- and anti-inflammatory cytokines. Exposure to the pathogen E. coli 042 produced a cytokine profile indicating M1 differentiation, which is in accordance with the PCR data. However, exposure to most strains resulted in either high or low secretion levels of all cytokines tested, rather than a clear M1 or M2 profile. In general, the Gram-negative strains induced high levels of cytokine secretion compared to the Gram-positive strains. Interestingly, strains of human origin had a higher impact on macrophages compared to strains of food origin.