A Novel Anti-inflammatory Phenotype Transformed by Repetitive Low-dose Lipopolysaccharide in Primary Peritoneal Tissue-resident Macrophages.

BACKGROUND/AIM Our previous studies suggested that oral administration of lipopolysaccharide (LPS) regulates the progression of various diseases via transformation of tissue-resident macrophages (MΦ). Recently, we characterized microglia transformed by repetitive low-dose LPS treatment (REPELL-microglia) in vitro, and this response was similar to that observed in response to oral administration of LPS in vivo. Here, we examined the characteristics of peritoneal tissue-resident MΦ (pMΦ) transformed by repetitive low-dose LPS treatment (REPELL-pMΦ). MATERIALS AND METHODS Primary pMΦ were treated with low-dose LPS (1 ng/ml) three times; subsequently, phagocytic activity and gene expression were evaluated. RESULTS REPELL-pMΦ exhibited high phagocytic activity and elevated expression of Arg1, Gipr, Gdnf, and Fpr2. The gene expression profiles observed in REPELL-pMΦ were distinct from those of REPELL-microglia. CONCLUSION REPELL-pMΦ have the potential to promote clearance of xenobiotics and to suppress inflammation. The present study also demonstrates the diversity of tissue-resident MΦ transformation that reflect their tissue origin.