Rottlerin enhances IL-1β-induced COX-2 expression through sustained p38 MAPK activation in MDA-MB-231 human breast cancer cells

Eun Jung Park,Taeg Kyu Kwon

doi:10.3858/emm.2011.43.12.077

Abstract

Cyclooxygenase-2 (COX-2) is an important enzyme in inflammation. In this study, we investigated the underlying molecular mechanism of the synergistic effect of rottlerin on interleukin1β (IL-1β)-induced COX-2 expression in MDA-MB-231 human breast cancer cell line. Treatment with rottlerin enhanced IL-1β-induced COX-2 expression at both the protein and mRNA levels. Combined treatment with rottlerin and IL-1β significantly induced COX-2 expression, at least in part, through the enhancement of COX-2 mRNA stability. In addition, rottlerin and IL-1β treatment drove sustained activation of p38 Mitogen-activated protein kinase (MAPK), which is involved in induced COX-2 expression. Also, a pharmacological inhibitor of p38 MAPK (SB 203580) and transient transfection with inactive p38 MAPK inhibited rottlerin and IL-1β-induced COX-2 upregulation. However, suppression of protein kinase C δ (PKC δ) expression by siRNA or overexpression of dominant-negative PKC δ (DN-PKC-δ) did not abrogate the rottlerin plus IL-1β-induced COX-2 expression. Furthermore, rottlerin also enhanced tumor necrosis factor-α (TNF-α), phorbol myristate acetate (PMA), and lipopolysaccharide (LPS)-induced COX-2 expression. Taken together, our results suggest that rottlerin causes IL-1β-induced COX-2 upregulation through sustained p38 MAPK activation in MDA-MB-231 human breast cancer cells.

Highlights

Cyclooxygenase (COX) is the rate-limiting enzyme that catalyzes arachidonic acid into prostanoids and has two subtypes, COX-1 and COX-2
To investigate whether the ERK, JNK, or p38 Mitogen-activated protein kinase (MAPK) pathways are involved in rottlerin and IL-1β-induced COX-2 expression, we examined whether selective MAPK inhibitors could affect rottlerin plus IL-1β-induced COX-2 expression
Because the p38 MAPK inhibitor markedly inhibited COX-2 expression, we assessed the activation of p38 MAPK by detecting its dually phosphorylated form using Western blotting with specific anti-phospho-p38 MAPK antibodies in MDA-MB-231 cells treated with IL-1β alone, rottlerin alone or rottlerin plus IL-1β (Figure 2C)

Summary

Introduction

Cyclooxygenase (COX) is the rate-limiting enzyme that catalyzes arachidonic acid into prostanoids and has two subtypes, COX-1 and COX-2. According to the several previous reports, COX-2 expression is upregulated by diverse agents and is mediated by Mitogen-activated protein kinases (MAPKs), reactive oxygen species (ROS), AP-1 or NF-κB (Mifflin et al, 2004; Shishodia et al, 2004; Song et al, 2007; Chandramohan et al, 2008; Jaimes et al, 2008; Kim et al, 2009; Chiu et al, 2010). Activated p38 MAPK upregulates the production of key inflammatory mediators, including TNF-α, IL-1β and COX-2, by several independent mechanisms, including direct phosphorylation of transcription factors, direct or indirect mRNA stabilization and enhanced translation of mRNAs in various cell types (Ridley et al, 1998; Molina-Holgado et al, 2000; Mifflin et al, 2002, 2004; Di Mari et al, 2007)

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Conclusion