Pulchellamin G, an amino acid-sesquiterpene lactone, from Saussurea pulchella suppresses lipopolysaccharide-induced inflammatory responses via heme oxygenase-1 expression in murine peritoneal macrophages

Saussurea pulchella (Asteraceae) is widely distributed in Korea and has been used in Korean folk medicine for the treatment of inflammation, hypertension, hepatitis, and arthritis. Pulchellamin G is an amino acid-sesquiterpene lactone conjugate isolated from S. pulchella. In the present study, we focused on the anti-inflammatory effect of pulchellamin G, which acts by inducing the expression of heme oxygenase (HO)-1. HO-1 plays important roles in cytoprotection since it has antioxidant, anti-inflammatory, antiproliferative, and antiapoptotic properties. Pulchellamin G inhibited the mRNA and protein expression of inducible nitric oxide synthase (iNOS), iNOS-derived nitric oxide (NO), and cyclooxygenase (COX)-2 and COX-derived prostaglandin E2 (PGE2) production in lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages. The compound also reduced tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) production and suppressed the phosphorylation and degradation of IκB-α and nuclear translocation of p65 in murine peritoneal macrophages in response to LPS stimulus. The inhibitory effects of pulchellamin G on nuclear factor kappa B (NF-κB) translocation was impaired by co-treatment of the cells with HO activity inhibitor tin protoporphyrin (SnPP). By using SnPP, we verified that the inhibitory effects of pulchellamin G on the pro-inflammatory mediators NO, PGE2, TNF-α, and IL-1β are associated with induction of HO-1 expression. Our data suggest that pulchellamin G might have potent therapeutic effects and it should be considered in the development of treatments for various inflammatory diseases.