Notopterygium forbesii Boiss extract and its active constituent phenethyl ferulate attenuate pro-inflammatory responses to lipopolysaccharide in RAW 264.7 macrophages. A "protective" role for oxidative stress?

Oxidative stress and oxidative modification of biomolecules are involved in several physiological and pathophysiological processes. We have previously reported that Notopterygium forbesii Boiss (NF), a traditional Chinese medicine, and its active constituents, including phenethyl ferulate (PF), bergaptol, and isoimperatorin, induced oxidative stress with increased levels of reactive species and heme oxygenase-1 in human fetal hepatocytes. The current study determined the effects of NF and PF on the inflammatory effects of lipopolysaccharide (LPS). Exposure of RAW 264.7 macrophages to LPS increased the expression of inducible nitric oxide synthase and cyclooxygenase 2 and stimulated the formation of reactive nitrogen species. In a coculture system, the LPS-activated macrophages also induced expression of cell adhesion molecules (including E-selectin, intercellular cell adhesion molecule 1, and vascular cell adhesion molecule 1) in human umbilical vein endothelial cells (HUVEC) and vascular smooth muscle cells (VSMC). Preincubation of macrophages with NF or PF attenuated the effects of LPS on macrophages as well as their effects on HUVEC and VSMC. These inhibitory effects of NF and PF were decreased in the presence of N-acetyl-l-cysteine (NAC). At the same time, NAC also reduced NF- or PF-induced increases in reactive oxygen species (ROS) and Hsp32 protein levels and the formation of protein carbonyls in the macrophages. These results suggest that NF- or PF-induced ROS generation and oxidative modifications of intracellular proteins may be responsible for the inhibitory actions of NF and PF on LPS-induced inflammatory responses. These data add to the growing literature that ROS may sometimes be anti-inflammatory.