Carbon Monoxide-Releasing Molecule-3 Regulates the Polarization of Lipopolysaccharide-Induced Macrophages

Macrophages show two main phenotypes, the M1-type (pro-inflammatory) and the M2-type (anti-inflammatory). The purpose of this research was to investigate the regulatory effect of carbon monoxide releasing molecule-3 (CORM-3) on LPS-induced macrophage polarization. LPS-induced RAW264.7 cells were exposed to CORM-3 for 24 h. Polarization of cells was checked by flow cytometry; expression of M1 or M2 macrophage-related factors and NF-κB signaling factors was examined by RT-PCR, ELISA, and Western blot. Male C57 mice were divided into three groups: normal group; periodontitis group, where experimental periodontitis was established in mice; LPS+CORM-3 group, where mice with experimental periodontitis were treated with CORM-3. Polarization of macrophages and the expression of M1 or M2 macrophage-related factors were detected by immunofluorescence, ELISA, and RT-PCR. CORM-3 significantly reduced M1 macrophage proportion, but increased M2 proportion in LPS-stimulated cells. Accordingly, CORM-3 significantly suppressed the expression of M1 macrophage-related TNF-α, iNOS, IL-1β, and IL-6, but promoted M2-related IL-10 and Arg-1. The expression of p-p65, p-p50, and p-IκB induced with LPS was inhibited by CORM-3. In vivo experiments indicated that CORM-3 induced more M2 macrophages in periodontal tissues in mice with experimental periodontitis. The expression of M1 macrophage-related factor in periodontitis was inhibited, but the expression of M2-related factors was increased by CORM-3. CORM-3 inhibits macrophage polarization to pro-inflammatory M1-type and promotes to anti-inflammatory M2-type, which provides scientific basis for the application of CORM-3 in the treatment of periodontitis.