Biochemical and Biophysical Research Communications, Vol.491, No.2, 486-492, 2017
gamma-Oryzanol suppresses COX-2 expression by inhibiting reactive oxygen species-mediated Erk1/2 and Egr-1 signaling in LPS-stimulated RAW264.7 macrophages
Cyclooxygenase (COX)-2 produces prostanoids, which contribute to inflammatory responses. Nuclear factor (NF)-kappa B is a key transcription factor mediating COX-2 expression. gamma-Oryzanol is an active component in rice bran oil, which inhibits lipopolysaccharide (LPS)-mediated COX-2 expression by inhibiting NF-kappa B. However, the inhibition of COX-2 expression by gamma-oryzanol independently of NF-kappa B is poorly understood. We found that LPS upregulated Egr-1 expression at the transcriptional level. Forced expression of Egr-1 trans-activated the Cox-2 promoter independently of NF-kappa B. In contrast, silencing of Egr-1 abrogated LPS-mediated COX-2 expression. LPS produced reactive oxygen species (ROS), which, in turn, induced Egr-1 expression via the Erk1/2 MAPK pathway. ROS scavenging activity of gamma-oryzanol suppressed Egr-1 expression by inhibiting the Erk1/2 MAPK pathway. Our results suggest that gamma-oryzanol inhibits LPS-mediated COX-2 expression by suppressing Erk1/2-mediated Egr-1 expression. This study supports that gamma-oryzanol may be useful for ameliorating LPS-mediated inflammatory responses. (C) 2017 Elsevier Inc. All rights reserved.