Escherichia coli Maltose-Binding Protein Induces M1 Polarity of RAW264.7 Macrophage Cells via a TLR2- and TLR4-Dependent Manner

Abstract

Maltose-binding protein (MBP) is a critical player of the maltose/maltodextrin transport system in Escherichia coli. Our previous studies have revealed that MBP nonspecifically induces T helper type 1 (Th1) cell activation and activates peritoneal macrophages obtained from mouse. In the present study, we reported a direct stimulatory effect of MBP on RAW264.7 cells, a murine macrophage cell line. When stimulated with MBP, the production of nitric oxide (NO), IL-1β, IL-6 and IL-12p70, and the expressions of CD80, MHC class II and inducible nitric oxide synthase (iNOS) were all increased in RAW264.7 cells, indicating the activation and polarization of RAW264.7 cells into M1 macrophages induced by MBP. Further study showed that MBP stimulation upregulated the expression of TLR2 and TLR4 on RAW264.7 cells, which was accompanied by subsequent phosphorylation of IκB-α and p38 MAPK. Pretreatment with anti-TLR2 or anti-TLR4 antibodies largely inhibited the phosphorylation of IκB-α and p38 MAPK, and greatly reduced MBP-induced NO and IL-12p70 production, suggesting that the MBP-induced macrophage activation and polarization were mediated by TLR2 and TLR4 signaling pathways. The observed results were independent of lipopolysaccharide contamination. Our study provides a new insight into a mechanism by which MBP enhances immune responses and warrants the potential application of MBP as an immune adjuvant in immune therapies.

GSTO1‐1 is an upstream suppressor of M2 macrophage skewing and HIF‐1α‐induced eosinophilic airway inflammation

“…The inflammation associated with disease can be driven by allergic or non‐allergic mechanisms, where the activation of Toll‐like receptors (TLRs) on epithelial cells and macrophages regulates the initial nature of the innate inflammatory response . TLR4 activation in response to bacterial components, such as lipopolysaccharide (LPS), will drive nuclear factor (NF)‐κB‐driven inflammatory programming towards IL‐1β, IL‐6, and TNF‐α production in macrophages, promoting the activity of type 1 (M1)‐resident populations and neutrophilic inflammation. Conversely, stimulation of the IL‐4 receptor will result in STAT6 activation, which promotes the development of type 2 (M2)‐resident macrophage populations.…”

Atraric Acid Exhibits Anti-Inflammatory Effect in Lipopolysaccharide-Stimulated RAW264.7 Cells and Mouse Models

“…The cells were treated with various concentrations of sample extracts in the presence of LPS (1 μg/mL) for 24 h at 37 °C with 5% CO 2 . Subsequently, the culture supernatant was assayed according to the manufacturer’s instructions [ 9 , 27 ].…”

The Combination of MBP and BCG-Induced Dendritic Cell Maturation through TLR2/TLR4 Promotes Th1 Activation In Vitro and Vivo

“…Using a polymyxin B-agarose column (Sigma-Aldrich, Saint Louis, MO, USA), the endotoxin in the MBP protein was removed using ultrafiltration techniques with Amicon Ultra-15 Centrifugal Filter Units plus Ultracel-10 (Merck Millipore, Billerica, MA, USA). The residual endotoxin level in the MBP protein was examined with a limulus amebocyte lysate-based kit (BioWhittaker, Atlanta, GA, USA) [ 12 , 13 ]. The level of endotoxin in the MBP protein prepared for the experiments was less than 0.05 EU/mL.…”

“…Additionally, TLRs are the most widely studied family of PRRs (pattern recognition receptors) on professional phagocytes such as macrophages and DCs [ 10 , 11 ]. Other studies found that MBP directly induced macrophage activation and M1 polarization through the TLR2 and TLR4 signaling pathways [ 12 , 13 ]. Our latest studies showed that Th1 polarization and TLR2/TLR4/TLR9 activation were synergistically induced by the combination of MBP and BCG and were the first to reveal that the cross-talk between TLR signaling pathways was associated with the activation of Th1 cells by the combination of MBP and BCG [ 14 ].…”