Aqueous extract of Achillea millefolium L. (Asteraceae) inflorescences suppresses lipopolysaccharide-induced inflammatory responses in RAW 264.7 murine macrophages

Yarrow Achillea millefolium L. (Asteraceae), is a perennial herb highly recognized in traditional medicine for its anti-inflammatory properties. However, studies on molecular mechanisms underlying these properties are scarce. The present work focuses on examining the effect of aqueous extract of A. millefolium L. inflorescences on the inflammatory responses of RAW 264.7 macrophages challenged with LPS. Applied at a concentration range of 25 - 300 mu g/ml, the extract did not affect cell viability. LPS-induced NO production was strongly suppressed and correlated with a dose-dependent downregulation of iNOS protein expression. The extract exerted no significant effect on PGE(2) synthesis and protein COX-2 levels. The secretion of GM-CSF and IL-10 was decreased, while the production of TNF-alpha and IL-1 beta was enhanced. The levels of IL-6 were not significantly altered. The anti-inflammatory effects of the extract were partially mediated by the suppression of the activation of transcription factor NF-kappa B and p38 MAPK signaling cascade. In addition, at the higher concentrations tested, the extract demonstrated good free radical scavenging activity and ability to decrease the levels of intracellular ROS. The present work corroborates the traditional use of A. millefolium L. infusions as antiphlogistic drug.