Carbon monoxide releasing molecule-2 ameliorates IL-1β-induced IL-8 in human gastric cancer cells

Carbon monoxide (CO), a byproduct of heme oxygenase (HO), presents antioxidant, anti-inflammatory, and anti-tumor properties. Accumulating evidence supports that interleukin (IL)-8 contribute to the vascularity of human gastric cancer. However, the inhibition of IL-8 expression by CO is yet to be elucidated. Here, we utilized CO releasing molecule-2 (CORM-2) to investigate the effect of CO on IL-1β-induced IL-8 expression and the underlying molecular mechanisms in human gastric cancer AGS cells. CORM-2 dose-dependently suppressed IL-1β-induced IL-8 mRNA and protein expression as well as IL-8 promoter activity. IL-1β induced the translocation of p47(phox) to activate reactive oxygen species (ROS)-producing NADPH oxidase (NOX). Moreover, IL-1β activated MAPKs (Erk1/2, JNK1/2, and p38 MAPK) and promoted nuclear factor (NF)-кB and activator protein (AP)-1 binding activities. Pharmacological inhibition and mutagenesis studies indicated that NOX, ROS, Erk1/2, and p38 MAPK are involved in IL-1β-induced IL-8 expression. Transient transfection of deletion mutant constructs of the IL-8 promoter in cells suggested that NF-кB and AP-1 are critical for IL-1β-induced IL-8 transcription. NOX-derived ROS and MAPKs (Erk1/2 and p38 MAPK) functioned as upstream activators of NF-κB and AP-1, respectively. CORM-2 pretreatment significantly mitigated IL-1β-induced activation of ROS/NF-кB and Erk1/2/AP-1 cascades, blocking IL-8 expression and thus significantly reducing endothelial cell proliferation in the tumor microenvironment.