Adiponectin Inhibits LPS‐Induced HMGB1 Release through Heme Oxygenase‐1 Dependent Pathway in RAW 264 Cells

Abstract

IntroductionHigh mobility group protein B1 (HMGB1) is an important late inflammatory mediator in sepsis. Adiponectin, an adipokine predominantly secreted from adipose tissue, has potent anti‐inflammatory properties. However, the possible anti‐inflammatory effects of adiponectin on lipopolysaccharides (LPS)‐induced HMGB1 release are unknown. The aim of this study was to investigate whether adiponectin could inhibit HMGB1 release in LPS‐stimulated RAW 264 cells.Materials and methodsMurine macrophage RAW 264 cells were treated with or without LPS (200 ng/ml) in the presence or absence of adiponectin, interleukin (IL)‐10, HO‐1 inhibitor (ZnPP) and p38 MAPK inhibitor (SB203580). HMGB1 translocation and release were measured by immunofluorescence staining of the cells and western blotting analysis of the medium, respectively. Expression levels of mRNA for toll like receptor (TLR) 4, TLR2, myeloid differentiation factor‐2 (MD‐2), HMGB1, IL‐10, heme oxygenase‐1(HO‐1) and nuclear factor erythoid‐derived 2 related factor 2 (Nrf2) mRNA were assessed by real‐time PCR.Results and discussionTreatment of the cells with LPS induced significant HMGB1 release and obvious translocation from nucleus to cytosol. However, prior treatment with either adiponectin or IL‐10 suppressed the LPS‐induced HMGB1 release and translocation. Adiponectin treatment decreased TLR4 mRNA and induced expression of HO‐1 mRNA, but not IL‐10 mRNA, while IL‐10 treatment decreased TLR2 and HMGB1 mRNA and enhanced both IL‐10 and HO‐1 gene expressions. Treatment of RAW 264 cells with ZnPP before adiponectin and IL‐10 treatment obviated the suppression of HMGB1 release by adiponectin completely, but partially by IL‐10 while treatment with SB203580 didn't had a significant effect. In conclusion, our results indicate that adiponectin suppresses HMGB1 release by LPS through a HO‐1‐dependent while neither HO‐1 nor p38 MAPK was involved in IL‐10 anti‐inflammatory effect. Therefore, both adiponectin and IL‐10 may play a role as an anti‐inflammatory molecule in the late inflammatory process by preventing release of a septic exaggeration factor, HMGB1.