Anti-Inflammatory Effects of 6,7-Dihydroxy-4-Methylcoumarin on LPS-Stimulated Macrophage Phosphorylation in MAPK Signaling Pathways

Abstract

Coumarin derivatives, such as esculetin, have various physiological functions, including antioxidant, anti-inflammatory, antibacterial, antiviral, and anti-cancer. 6,7-Dihydroxy-4-methylcoumarin (6,7-DH-4MC) is a derivative of esculetin, and its anti-inflammatory effect and mechanism in macrophages have not been studied. In this study, the anti-inflammatory activity of 6,7-DH-4MC was evaluated by measuring the expression of inflammatory factors (NO and PGE2) and pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) in LPS-stimulated RAW 264.7 macrophages. The results revealed that 6,7-DH-4MC significantly reduced NO levels and PGE2 expression without inducing cytotoxicity; it was confirmed that the inhibition of NO and PGE2 expression was related to iNOS and COX-2 downregulation in response to 6,7-DH-4MC treatment. Moreover, 6,7-DH-4MC decreased the levels of pro-inflammatory cytokines, such as IL-1β and IL-6, in a dose-dependent manner. Mechanistic studies revealed reduced phosphorylation of ERK and p38-MAPK upon 6,7-DH-4MC treatment. Furthermore, the degradation of IκB-α and phosphorylation of NF-κB in cells treated with LPS were interrupted by 6,7-DH-4MC treatment. These results suggest that 6,7-DH-4MC is a potential therapeutic agent for inflammatory diseases. To the best of our knowledge, this is the first report demonstrating the anti-inflammatory effects of 6,7-DH-4MC in RAW 264.7 cells via MAPK and NF-κB signaling pathways.