Andrographolide Antagonizes INF-α-Induced IL-8 via Inhibition of NADPH Oxidase/ROS/NF-κB and Src/MAPKs/AP-1 Axis in Human Colorectal Cancer HCT116 Cells

Andrographis paniculata Nees is used as a functional food in Japan, Korea, India, and China. Andrographolide, a naturally occurring phytochemical identified in Andrographis paniculata, has been discovered to present anti-inflammatory and anticancer activities. Highly expressed interleukin (IL-8) has been detected in colorectal cancer and is implicated in angiogenesis. However, the effect and molecular mechanisms of IL-8 expression by andrographolide remain obscure in human colorectal cancer cells. The present study was aimed to investigate the effects of andrographolide on TNF-alpha-induced IL-8 expression and its underlying mechanisms. We found that andrographolide concentration-dependently inhibited TNF-alpha-induced IL-8 mRNA (2.23 +/- 0.15 fold at 20 mu M) and protein expression (4.78 +/- 0.31 fold at 20 mu M) and reduced the IL-8 transcriptional activity (2.59 +/- 0.25 fold at 20 mu M). TNF-alpha stimulated the membrane translocation of p47(phox) to activate reactive oxygen species (ROS)producing NADPH oxidase (NOX). Furthermore, TNF-alpha induced Src and MAPKs (Erkl/2, p38 MAPK) phosphorylation, as well as NF-kappa B and AP-1 binding activities. We found that NF-kappa B and AP-1 were the critical transcription factors for TNF-alpha-induced IL-8 expression. Specific inhibitors and mutagenesis studies indicated that Src, Erkl/2, and p38 MAPK are related to TNF-alpha-induced IL-8. NOX-derived ROS and Src/MAPKs (Erkl/2 and p38 MAPK) functioned as upstream activators of NF-kappa B and AP-1, respectively. Taken together, andrographolide antagonizes TNF-alpha-induced IL-8 via inhibition of NADPH oxidase/ ROS/NF-kappa B and Src/MAPKs/AP-1 signaling pathways in HCT116 colorectal cancer cells and then suppresses angiogenesis in the tumor microenvironment.