Abstract

Usnic acid (UA) was isolated for the first time from Parmelia saxatilis and was confirmed by physical and spectral evidence. Its anti-inflammatory effect and mechanism were explored on lipopolysaccharide (LPS)-stimulated RAW264.7 cell line. The effects of UA on pro-inflammatory cytokines including tumor necrosis factor-alfa (TNF-α), interleukin-6 (IL-6) and interleukin-1 beta (IL-1β), pro-inflammatory mediators such as nitric oxide (NO), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were studied by sandwich enzyme-linked immunosorbent assay (ELISA), real-time polymerase chain reaction (PCR) and Western blot analyses. Similarly, the effect of UA on anti-inflammatory cytokine interleukin-10 (IL-10) and anti-inflammatory mediator heme oxygenase-1 (HO-1) were also studied following the same methods. Furthermore, nuclear factor-κB (NF-κB) was assayed by immunocytochemistry. The results showed that UA has anti-inflammatory effect by down-regulatinng iNOS, COX-2, IL-1β, IL-6 and TNF-α, COX-2 gene expression through the suppression of NF-κB activation and increasing anti-inflammatory cytokine IL-10 and anti-inflammatory mediator HO-1 production.

Key words: Parmelia saxatilis, usnic acid, anti-inflammation.