RNA and a cell wall component of Enterococcus faecalis IC-1 are required for phagocytosis and interleukin 12 production by the mouse macrophage cell line J774.1

Abstract

Enterococcus faecalis is a resident lactic acid bacterium in the human intestine. Its immunostimulatory action was reported to be enhanced by heat sterilization. To investigate its beneficial actions, we evaluated the ability of 10 E. faecalis strains to induce interleukin-12 (IL-12) production in a mouse macrophage cell line, J774.1 and found that the strain, E. faecalis IC-1, had a potent IL-12-inducing ability. Furthermore, we investigated the underlying mechanism by treating IC-1 cells with RNase or lysozyme. Its activity almost disappeared and an antagonist of Toll-like receptor (TLR) 7 inhibited this activity. Moreover, lysozyme-treated IC-1 bacteria were not phagocytized by J774.1 cells, and did not induce IL-12 production. Based on our results, we propose that macrophages recognize the cell wall components of IC-1, leading to phagocytosis. The IC-1 RNA is then recognized by TLR7, which induces the production of IL-12.

Total RNA and genomic DNA of Lactobacillus gasseri OLL2809 induce interleukin-12 production in the mouse macrophage cell line J774.1 via toll-like receptors 7 and 9

“…There have been several reports indicating that phagocytosis of lactic acid bacteria is required for initiation of IL-12 production from macrophages [ 9 – 11 ]. We first conducted a confocal microscopic analysis to clarify whether phagocytosis of L. gasseri OLL2809 by J774.1 cells is involved in an IL-12 production assay.…”

“…Cell wall components and nucleic acids of lactic acid bacteria act as immunostimulants [ 9 – 12 , 20 ], and the pattern-recognition receptors (PRRs) of immune cells that induce cytokines could be expressed both on the cell surface or inside the cells. Lipopolysaccharide (LPS), a ligand of gram-negative bacteria for cell-surface-expressed TLR4, stimulates IL-12 production without being phagocytosed [ 11 ]. On the other hand, several gram-positive bacterial cell wall components such as peptidoglycan, a ligand for cell-surface expressed TLR2, are also involved in the induction of IL-12 production from macrophages [ 21 , 22 ].…”

“…There are roughly two routes by which immune cells recognize microorganisms and induce inflammatory cytokines for self-defence against their infection: recognition by PRRs expressed on the cell surface or by intracellular organs. These receptors, expressed on both the cell surface and inside the cells, play an important role in the recognition of lactic acid bacteria, and the cytokine induction in the immune cells [11]. CyD, a phagocytosis inhibitor, was used to verify whether L. gasseri OLL2809, which was confirmed to be phagocytized (Fig.…”

“…Some functional lactic acid bacteria are recognized as immunostimulants to the host immune cells, and confer the latter with high cytokine-inducing ability [6][7][8]. Further detailed studies have reported immune cells to recognize cell wall components [9] and nucleic acids [10][11][12] of some immunostimulant lactic acid bacteria via Toll-like receptors (TLRs), resulting in cytokine production. However, in many other functional lactic acid bacteria, the cytokineinducing mechanism remains unclear.…”

Selenomethionine Suppressed TLR4/NF-κB Pathway by Activating Selenoprotein S to Alleviate ESBL Escherichia coli-Induced Inflammation in Bovine Mammary Epithelial Cells and Macrophages

“…ST410(4) E. coli was re-established from frozen stocks by culturing on tryptose soya agar (Difco TM, Becton Dickinson, Sparks, MD, United States) supplemented with 5% defibrinated sheep blood and incubated at 37°C for 72 h, then sub-cultured on Lysogeny broth medium to mid-log phase. The bMECs line MAC-T (Shanghai Jingma Biological Technology, Shanghai, China) and murine macrophage cell line J774A.1 (Sigma-Aldrich, St. Louis, MO, United States) were cultured as previously described ( Nakase et al, 2017 ; Shahid et al, 2017 ). The SeMet was solubilized in distilled water (concentration, 0.1 mol/L) for storage at −80°C and subsequently thawed and diluted with distilled water into working solutions of 200 and 400 μmol/L (μM).…”