PP4 - Carbon monoxide releasing molecule-3 (CORM-3) modulates progression of M1/M2 phenotypes in alveolar macrophages

Abstract

Background The outcome of the severe systemic disorders (e.g. sepsis, acute lung injury) largely depends on the efficacy of resolution of inflammation. We have reported that water-soluble carbon monoxide releasing molecule-3 (CORM-3) suppresses inflammatory activation in neutrophils and vascular endothelial cells and offers protection against sepsis-induced lung dysfunction in vivo. Alveolar macrophages are key contributors to both the promotion and resolution/remodeling of inflammation and are classified into pro-inflammatory (M1) and anti-inflammatory (M2) groups. The change in M1/M2 balance has been reported in various pulmonary diseases and is considered as a target for therapeutic intervention. The aim of this study was to assess the effects of CORM-3 in modulation of macrophage M1/M2 phenotype under “inflammatory” or “remodeling” conditions. Methods Rat alveolar macrophages (NR8383) in culture were stimulated with LPS (500ng/ml)/IFN-γ (100ng/ml) or IL-4 (1ng/ml)/IL-13(1ng/ml) to induce M1- and M2-phenotypes, respectively. Specific markers of M1-phenotype (iNOS expression) and M2-phenotype (mannose receptor; Man-R, expression) were assessed (western blotting) after 1, 3, 6, or 24 hours in the absence or presence of CORM-3 (0.1mM) treatment. Inactive CORM-3 was used as a control. Results M1-phenotype (iNOS expression) was markedly upregulated (10 to 24 –fold) in LPS/IFN-γ-stimulated macrophage after 6 and 24 hours, respectively. In parallel, IL-4/IL13 stimulation induced M2-phenotype as evidenced by increase in Man-R levels at 6 and 24 hrs. Administration of CORM-3 during macrophage stimulation effectively suppressed development of both, M1- and M2-phenotypes. Paradoxically, treatment of naive (unstimulated) macrophage with CORM-3 increased expression of Man-R after 1 hour (1.8 fold) and iNOS expression after 6 hours (2.5 fold). Conclusion These findings indicate that CORM-3 can modulate progression of M1- and M2-phenotypes in macrophages under inflammatory conditions in vitro.