Glycyrrhizin inhibits lipopolysaccharide-induced inflammatory response by reducing TLR4 recruitment into lipid rafts in RAW264.7 cells.
BACKGROUND
The aim of this study was to investigate the effect of glycyrrhizin on LPS-induced endotoxemia in mice and clarify the possible mechanism.


METHODS
An LPS-induced endotoxemia mouse model was used to confirm the anti-inflammatory activity of glycyrrhizin in vivo. In vitro, RAW264.7 cells were stimulated with LPS in the presence or absence of glycyrrhizin. The expression of cytokines was determined by ELISA. Toll-like receptor 4 (TLR4) was determined by Western blot analysis. Nuclear factor-kB (NF-κB) and Interferon regulatory factor 3 (IRF3) activation were detected by Western blotting and luciferase assay. Lipid raft staining was detected by immunocytochemistry.


RESULTS
In vivo, the results showed that glycyrrhizin can improve survival during lethal endotoxemia. In vitro, glycyrrhizin dose-dependently inhibited the expression of TNF-α, IL-6, IL-1β and RANTES in LPS-stimulated RAW264.7 cells. Western blot analysis showed that glycyrrhizin suppressed LPS-induced NF-κB and IRF3 activation. However, glycyrrhizin did not inhibit NF-κB and IRF3 activation induced by MyD88-dependent (MyD88, IKKβ) or TRIF-dependent (TRIF, TBK1) downstream signaling components. Moreover, glycyrrhizin did not affect the expression of TLR4 and CD14 induced by LPS. Significantly, we found that glycyrrhizin decreased the levels of cholesterol of lipid rafts and inhibited translocation of TLR4 to lipid rafts. Moreover, glycyrrhizin activated ABCA1, which could induce cholesterol efflux from lipid rafts.


CONCLUSIONS
Glycyrrhizin exerts an anti-inflammatory property by disrupting lipid rafts and inhibiting translocation of TLR4 to lipid rafts, thereby attenuating LPS-mediated inflammatory response.


CONCLUSIONS
Learning the anti-inflammatory mechanism of glycyrrhizin is crucial for the anti-inflammatory drug development.
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Yunhe
Y
Fu
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Ershun
E
Zhou
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Zhengkai
Z
Wei
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Xiaojing
X
Song
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Zhicheng
Z
Liu
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Tiancheng
T
Wang
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Wei
W
Wang
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China.
Naisheng
N
Zhang
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China. Electronic address: liuguowen2008@163.com.
Guowen
G
Liu
Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Jilin University, Changchun, Jilin Province 130062, PR China. Electronic address: yzt@jlu.edu.cn.
Zhengtao
Z
Yang
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D019695:Glycyrrhizic Acid / Q000494:pharmacology*; D050838:Interferon Regulatory Factor-3 / Q000378:metabolism; D016209:Interleukin-8 / Q000096:biosynthesis; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D021962:Membrane Microdomains / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D016328:NF-kappa B / Q000378:metabolism; D021381:Protein Transport; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000378:metabolism*
D000893:Anti-Inflammatory Agents; D050838:Interferon Regulatory Factor-3; D016209:Interleukin-8; C494233:Irf3 protein, mouse; D008070:Lipopolysaccharides; D016328:NF-kappa B; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D019695:Glycyrrhizic Acid
Cytokine; Glycyrrhizin; Interferon regulatory factor 3; Lipid raft; Nuclear factor κB; Toll-like Receptor 4