Sauchinone, a lignan from Saururus chinensis, suppresses iNOS expression through the inhibition of transactivation activity of relA of NF-κB

Abstract

Sauchinone, a known lignan, was isolated from the root of Saururus chinensis as an active principle responsible for inhibiting the production of NO in LPS-stimulated RAW264.7 cells by activity-guided fractionation. Sauchinone dose-dependently inhibited not only the production of NO, but also the expression of iNOS mRNA and protein in LPS-stimulated RAW 264.7 cells. Furthermore, sauchinone prevented LPS-induced NF-κB activation, which is known to play a critical role in iNOS expression, assessed by a reporter assay under the control of NF-κB. However, an electrophoretic mobility shift assay (EMSA) demonstrated that sauchinone did not suppress the DNA-binding activity of NF-κB or the degradation of IκB-α induced by LPS. Further analysis revealed that transactivation activity of ReIA subunit of NF-κB was dose-dependently suppressed in the presence of sauchinone. Taken together, our results suggested that sauchinone could inhibit production of NO in LPS-stimulated RAW264.7 cells through the suppression of NF-κB by inhibiting transactivation activity of ReIA subunit.