Esculetin inhibits the inflammatory response by inducing heme oxygenase-1 in cocultured macrophages and adipocytes
Obesity is associated with chronic low-grade inflammation of adipose tissue. In this study, we investigated the anti-inflammatory effects of esculetin (ECT) through up-regulation of heme oxygenase-1 (HO-1) in cocultured macrophages and adipocytes. RAW264.7 macrophages and differentiated 3T3-L1 adipocytes were cocultured in serum-free Dulbecco's modified Eagle's medium with or without ECT for 24 h. Nitric oxide (NO), tumor necrosis factor-α (TNF-α), and monocyte chemoattractant protein-1 (MCP-1) production was measured in the coculture supernatant. ECT decreased the secretion of NO, TNF-α, and MCP-1. The expression of adipogenic proteins, including peroxisome proliferator-activated receptors γ (PPARγ) and CCAAT/enhancer binding protein α (C/EBPα) in cocultured adipocytes and inducible nitric oxide synthase (iNOS) in cocultured macrophages, was inhibited by ECT. Additionally, HO-1 expression was induced in cocultured macrophages and adipocytes. Silencing of HO-1 expression increased the production of NO, TNF-α, and MCP-1 in cocultured cells, in spite of the presence of ECT. This study demonstrated that ECT exhibited anti-inflammatory properties by inhibiting the production of proinflammatory cytokines in the interaction between adipocytes and macrophages through HO-1 expression. ECT may have the potential to improve chronic inflammation in obesity.