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 (M Phi). 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 MF (pM Phi) transformed by repetitive low-dose LPS treatment (REPELL-pM Phi). Materials and Methods: Primary pMF were treated with low-dose LPS (1 ng/ml) three times; subsequently, phagocytic activity and gene expression were evaluated. Results: REPELL-pM Phi exhibited high phagocytic activity and elevated expression of Arg1, Gipr, Gdnf, and Fpr2. The gene expression profiles observed in REPELL-pM Phi were distinct from those of REPELL-microglia. Conclusion: REPELL-pM Phi have the potential to promote clearance of xenobiotics and to suppress inflammation. The present study also demonstrates the diversity of tissue-resident M Phi transformation that reflect their tissue origin.