In this study, tomentosin, a sesquiterpene lactone was isolated from Inulae flos and its biological activities were investigated. The effects of tomentosin on the production of inflammatory mediators as well as on nuclear factor (NF)-κB and mitogen-activated protein (MAP) kinase activation were evaluated in RAW264.7 cells. Tomentosin decreased the production of nitric oxide (NO) and prostaglandin E 2 (PGE 2 ) by suppressing the protein expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2, respectively. Additionally, tomentosin reduced the release of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Tomentosin not only attenuated lipopolysaccharide (LPS)-induced NF-κB activation via the abrogation of inhibitory (I)κBα degradation and caused a subsequent decrease in nuclear p65 level, but it also suppressed the phosphorylation of MAP kinases (p38 and c-Jun N terminal kinase (JNK)). These results indicate that tomentosin exerts anti-inflammatory activities through the inhibition of inflammatory mediators (NO, iNOS, PGE 2 , COX-2, TNF-α, and IL-6) by regulating NF-κB activation and phosphorylation of p38/JNK kinases in macrophages, thus suggesting that tomentosin could be a potential agent for the treatment of inflammatory diseases.
Key words tomentosin; inflammatory mediator; nuclear factor (NF)-κB; mitogen-activated protein (MAP) kinaseInflammation is the host response to infection and injury, but if it is left uncontrolled, the inflammatory mediators become involved in the pathogenesis of many inflammatory disorders.1) Macrophages play a crucial role in both the specific and non-specific immune responses to microbial and viral infections. When activated by stimuli such as lipopolysaccharide (LPS), macrophages produce a variety of inflammatory mediators such as prostaglandin E 2 (PGE 2 ) and nitric oxide (NO) and pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin-1beta (IL-1β) and IL-6.Expression of these inflammatory mediators is regulated by the activation of nuclear factor-kappaB (NF-κB).2) Also, inflammatory mediators including cytokines or mitogenactivated protein (MAP) kinases such as p38 and c-Jun N terminal kinase (JNK) stimulate the pathways by activating the inhibitor κB kinase (IKK).3,4) In unstimulated cells, NF-κB is located in the cytoplasm as an inactive complex bound to its inhibitory protein (IκB). During the process of inflammation, the IKK phosphorylates IκB, inducing its ubiquitination and degradation of IκBα. The free NF-κB then translocates to the nucleus, where it binds to κB-binding sites in the promoter regions of target genes and regulates the expression of various genes, including inducible NO synthase (iNOS) and cyclooxygenase 2 (COX-2), and inflammatory cytokines.
5-7)Our previous studies have shown that the ethanol extract of Inulae flos is a potent inhibitor of inflammatory mediators.
8)Recently, it was shown that britanin isolated from Inulae flos inhibited the production of inflammatory medi...