Chrysin Derivative CM1 and Exhibited Anti-Inflammatory Action by Upregulating Toll-Interacting Protein Expression in Lipopolysaccharide-Stimulated RAW264.7 Macrophage Cells

Eui-Baek Byun,Woo Sik Kim,Ha-Yeon Song,Eui-Hong Byun,Kwangwook Kim,Ho Seong Seo,Woo Yong Park,Jeong Moo Han

doi:10.3390/molecules26061532

Abstract

Although our previous study revealed that gamma-irradiated chrysin enhanced anti-inflammatory activity compared to intact chrysin, it remains unclear whether the chrysin derivative, CM1, produced by gamma irradiation, negatively regulates toll-like receptor (TLR) signaling. In this study, we investigated the molecular basis for the downregulation of TLR4 signal transduction by CM1 in macrophages. We initially determined the appropriate concentration of CM1 and found no cellular toxicity below 2 μg/mL. Upon stimulation with lipopolysaccharide (LPS), CM1 modulated LPS-stimulated inflammatory action by suppressing the release of proinflammatory mediators (cytokines TNF-α and IL-6) and nitric oxide (NO) and downregulated the mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) signaling pathways. Furthermore, CM1 markedly elevated the expression of the TLR negative regulator toll-interacting protein (Tollip) in dose- and time-dependent manners. LPS-induced expression of cell surface molecules (CD80, CD86, and MHC class I/II), proinflammatory cytokines (TNF-α and IL-6), COX-2, and iNOS-mediated NO were inhibited by CM1; these effects were prevented by the knockdown of Tollip expression. Additionally, CM1 did not affect the downregulation of LPS-induced expression of MAPKs and NF-κB signaling in Tollip-downregulated cells. These findings provide insight into effective therapeutic intervention of inflammatory disease by increasing the understanding of the negative regulation of TLR signaling induced by CM1.

Highlights

TLR4 signaling activation triggers a cascade of events leading to inflammatory response of innate immune cells via nuclear factor (NF)-B activation as well as activated T cell responses, which is considered as the major immunological cause in the onset of inflammatory bowel disease [6,7]
We examined whether CM1 played a modulatory role in the expression of lipopolysaccharide (LPS)-induced proinflammatory cytokines, such as Tumor necrosis factor (TNF)-α and IL-6
To determine whether the negative regulators of toll-like receptor (TLR) mediate the anti-inflammatory effect of CM1, we examined the expression of toll-interacting protein (Tollip), SOCS1, and IRAK-M in the background of CM1 treatment in RAW264.7 cells

Summary

Introduction

The inflammatory response is regarded as a series of complex and unbalanced processes involving multiple cells, and the innate immune system is a major contributor to early inflammation [1]. TLR4 plays a key role in various diseases, such as inflammatory bowel disease, sepsis, Alzheimer’s disease, and cancers; it can induce prolonged and excessive inflammatory signals, resulting in serious damage to various tissues [4,5]. TLR4 signaling activation triggers a cascade of events leading to inflammatory response of innate immune cells via NF-B activation as well as activated T cell responses, which is considered as the major immunological cause in the onset of inflammatory bowel disease [6,7]. TLR4 activation is associated with development of Alzheimer’s disease. Pharmacological inhibitors of TLR4 are considered attractive drugs for the treatment of the above-mentioned diseases

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