Immunomodulation and Antioxidant Effects of Diffractaic Acid in LPS-Stimulated RAW264.7 Cells Mediated by the Nrf2/HO-1 and NF-κB Signaling Pathways

Abstract

Abstract: Objective: Diffractaic acid is a depside derivative secondary metabolite biosynthesized by lichens. It has been shown that diffractaic acid has analgesic and antipyretic, antiviral, anti-tumoral and anti-proliferative activities. However, studies on the effects of diffractaic acid on antioxidant and anti-inflammatory mechanisms are lacking. This study was conducted to investigate the antioxidant and anti-inflammatory activities through the Nrf2/HO-1 and NF-κB signalling pathways in LPS-stimulated RAW264.7 cells. Material and methods: To investigate the anti-inflammatory effect of diffractive acid on RAW264.7 cells induced by LPS, PGE2, TNF-α, IL-6 and IL-1β production, TNF-α, IL-1β and IL-6 mRNA levels and iNOS, COX-2, Nrf2, HO-1 and p-NF-κB p65 protein expression were detected by enzyme-linked immunosorbent assay (ELISA), real-time polymerase chain reaction (RT-PCR) and Western blotting assays, respectively. Results and discussion: Diffractaic acid treatment triggered a significant reduction on nitrite, PGE2, TNF-α, IL-6, and IL-1β production, TNF-α, IL-1β and IL-6 mRNA levels, iNOS and COX-2 protein expression and phosphorylation of NF-κB p65 protein and increase on Nrf2 and HO-1 protein expression. Conclusions: Diffractaic acid exerted the anti-inflammatory activity by blocking the NF-κB signaling pathway and antioxidant activity by activating the Nrf2/HO-1 signaling pathway. Based on the above results, diffractaic acid may be an attractive therapeutic candidate for the inflammation-related diseases. © Pleiades Publishing, Ltd. 2025.