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.
Highlights
Lichens have been used for medicinal purpose throughout the ages
From petroleum ether fraction of ethanol extract of P. saxatilis, a crytalline compound was isolated which was confirmed as usnic acid by comparing its physical and spectral data with authentic literature (Kumar et al, 1996)
The cytopathic effect (CPE) test gave the same result (Figure 2)
Summary
Lichens have been used for medicinal purpose throughout the ages. As lichens are symbiotic associations between fungus and alga (photobiotic), a number of lichens were screened for antibacterial activity in the 1940s and 1950s following the discovery of penicillin from a fungus (Vartia, 1973) and several compounds were found to be active against mycobacterium species and Gram-positive bacteria. Macrophages and monocytes usually play crucial roles in eliciting response cascade in the acute phase of inflammation (Baumann and Gauldie, 1994) After being stimulated, they produce a number of chemokines and enzymes, such as TNF-α, IL-1β (Bertolini et al, 2001; Mongan et al, 2000), IL-6 (Stadnyk et al, 1997) and IL10 (Hofman, 2004; Inui et al, 2002), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) (Kröncke et al, 1998; Kim et al, 2003), and antiinflammatory mediator (HO-1) (Ogborne et al, 2004), which is macrophage or monocyte-related cytokine, essential for the inflammatory response to pathogenic germs or toxicants. LPS-stimulated RAW264.7 cell line was used as an inflammation cellular model to explore the anti-inflammatory effect of UA and anti-inflammatory mechanism (Kim et al, 2003)
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