Olea europaea Suppresses Inflammation by Targeting TAK1-Mediated MAP Kinase Activation.

Chaoran Song,Mi-Yeon Kim,Jae Youl Cho

doi:10.3390/molecules26061540

Abstract

Possessing a variety of medicinal functions, Olea europaea L. is widely cultivated across the world. However, the anti-inflammatory mechanism of Olea europaea is not yet fully elucidated. In this study, how the methanol extract of the leaves of Olea europaea (Oe-ME) can suppress in vitro inflammatory responses was examined in terms of the identification of the target protein. RAW264.7 and HEK293T cells were used to study macrophage-mediated inflammatory responses and to validate the target protein using PCR, immunoblotting, nuclear fraction, overexpression, and cellular thermal shift assay (CETSA) under fixed conditions. Oe-ME treatment inhibited the mRNA expression levels of cyclooxygenase (COX)-2, matrix metallopeptidase (MMP)-9, and intercellular adhesion molecule-1 (ICAM-1) in activated RAW264.7 cells. Oe-ME diminished the activation of activator protein (AP)-1 and the phosphorylation of its upstream signaling cascades, including extracellular signal regulated kinase (ERK), mitogen-activated protein kinase kinase 1/2 (MEK1/2), c-Jun N-terminal kinase (JNK), mitogen-activated protein kinase kinase 3/6 (MKK3/6), p38, MKK7, and transforming growth factor-β-activated kinase 1 (TAK1), in stimulated-RAW264.7 cells. Overexpression and CETSA were carried out to verify that TAK1 is the target of Oe-ME. Our results suggest that the anti-inflammatory effect of Oe-ME could be attributed to its control of posttranslational modification and transcription of TAK1.

Highlights

Inflammation is a defense response of living cells to inflammatory factors, local damage, bacteria, virus, and fungi
The mRNA expression levels of IL-2, IL-6, COX-2, matrix metallopeptidase (MMP)-9, intercellular adhesion molecule-1 (ICAM-1), TNF-α, and MCP1 were sharply elevated by LPS, while their expression was decreased by Oe-ME treatment in a dose-dependent manner (Figure 1e)
Consistent with the above data, Oe-ME decreased the nuclear protein levels of c-Fos and c-Jun under induction by different Toll-like receptors (TLRs) ligands (Figure 2). These results suggest that upstream signal molecules which increase nuclear translocation of c-Jun/c-Fos, subunits of activator protein (AP)-1, could be the target of Oe-ME

Summary

Introduction

Inflammation is a defense response of living cells to inflammatory factors, local damage, bacteria, virus, and fungi. Toll-like receptors (TLRs) of innate immune cells recognize extracellular stimuli and produce inflammatory responses. MAPKKs or IKK phosphorylate MAPK [c-Jun-N-terminal kinase (JNK), extracellular signal-regulated kinase1/2 (ERK1/2), and p38] or the inhibitor of κBα (IκBα) to activate activator (AP)-1 or NF-κB for transcription of pro-inflammatory genes [7,8]. The members of MAPKKs include MEK1/2, MEK5, MKK4/7, and MKK3/6, which phosphorylate and activate subsequent downstream enzyme MAPKs. JNK, ERK1/2/5, and p38 subsequently phosphorylate AP-1 subunits (e.g., c-Fos and c-Jun) to induce translocation of activator protein (AP-1) by the interaction between subgroups of MAPKs and the amino-terminal activation domain of c-Fos and c-Jun [7,9]

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Results

Conclusion