Gambogic Acid Disrupts Toll-like Receptor4 Activation by Blocking Lipopolysaccharides Binding to Myeloid Differentiation Factor 2

  • Lee, Jin Young ;
  • Lee, Byung Ho ;
  • Lee, Joo Young
  • Received : 2014.11.14
  • Accepted : 2014.12.17
  • Published : 2015.03.31


Our body's immune system has defense mechanisms against pathogens such as viruses and bacteria. Immune responses are primarily initiated by the activation of toll-like receptors (TLRs). In particular, TLR4 is well-characterized and is known to be activated by gram-negative bacteria and tissue damage signals. TLR4 requires myeloid differentiation factor 2 (MD2) as a co-receptor to recognize its ligand, lipopolysaccharides (LPS), which is an extracellular membrane component of gram-negative bacteria. Gambogic acid is a xanthonoid isolated from brownish or orange resin extracted from Garcinia hanburyi. Its primary effect is tumor suppression. Since inflammatory responses are related to the development of cancer, we hypothesized that gambogic acid may regulate TLR4 activation. Our results demonstrated that gambogic acid decreased the expression of pro-inflammatory cytokines ($TNF-{\alpha}$, IL-6, IL-12, and $IL-1{\beta}$) in both mRNA and protein levels in bone marrow-derived primary macrophages after stimulation with LPS. Gambogic acid did not inhibit the activation of Interferon regulatory factor 3 (IRF3) induced by TBK1 overexpression in a luciferase reporter gene assay using IFN-${\beta}$-PRD III-I-luc. An in vitro kinase assay using recombinant TBK1 revealed that gambogic acid did not directly inhibit TBK1 kinase activity, and instead suppressed the binding of LPS to MD2, as determined by an in vitro binding assay and confocal microscopy analysis. Together, our results demonstrate that gambogic acid disrupts LPS interaction with the TLR4/MD2 complex, the novel mechanism by which it suppresses TLR4 activation.


Phytochemical;Toll-like receptor;LPS;MD2;Bacterial infection;Immune-suppression


  1. Takeda, K., Kaisho, T. and Akira, S. (2003) Toll-like receptors. Annu. Rev. Immunol., 21, 335-376.
  2. Dixon, D.R. and Darveau, R.P. (2005) Lipopolysaccharides heterogeneity: innate host responses to bacterial modification of lipid a structure. J. Dent. Res., 84, 584-595.
  3. Park, B.S., Song, D.H., Kim, H.M., Choi, B.S., Lee, H. and Lee, J.O. (2009) The structural basis of lipopolysaccharides recognition by the TLR4-MD-2 complex. Nature, 458, 1191-1195.
  4. Geng, J., Xiao, S., Zheng, Z., Song, S. and Zhang, L. (2013) Gambogic acid protects from endotoxin shock by suppressing pro-inflammatory factors in vivo and in vitro. Inflammation Res., 62, 165-172.
  5. Kim, S.Y., Koo, J.E., Seo, Y.J., Tyagi, N., Jeong, E., Choi, J., Lim, K.M., Park, Z.Y. and Lee, J.Y. (2013) Suppression of Toll-like receptor 4 activation by caffeic acid phenethyl ester is mediated by interference of LPS binding to MD2. Br. J. Pharmacol., 168, 1933-1945.
  6. Jeong, E., Koo, J.E., Yeon, S.H., Kwak, M.K., Hwang, D.H. and Lee, J.Y. (2014) PPARdelta deficiency disrupts hypoxiamediated tumorigenic potential of colon cancer cells. Mol. Carcinog., 53, 926-937.
  7. Lee, J.K., Kim, S.Y., Kim, Y.S., Lee, W.H., Hwang, D.H. and Lee, J.Y. (2009) Suppression of the TRIF-dependent signaling pathway of Toll-like receptors by luteolin. Biochem. Pharmacol., 77, 1391-1400.
  8. Koo, J.E., Park, Z.Y., Kim, N.D. and Lee, J.Y. (2013) Sulforaphane inhibits the engagement of LPS with TLR4/MD2 complex by preferential binding to Cys133 in MD2. Biochem. Biophys. Res. Commun., 434, 600-605.
  9. Fitzgerald, K.A., McWhirter, S.M., Faia, K.L., Rowe, D.C., Latz, E., Golenbock, D.T., Coyle, A.J., Liao, S.M. and Maniatis, T. (2003) IKKepsilon and TBK1 are essential components of the IRF3 signaling pathway. Nat. Immunol., 4, 491-496.
  10. Youn, H.S., Lee, J.Y., Fitzgerald, K.A., Young, H.A., Akira, S. and Hwang, D.H. (2005) Specific inhibition of MyD88-independent signaling pathways of TLR3 and TLR4 by resveratrol: molecular targets are TBK1 and RIP1 in TRIF complex. J. Immunol., 175, 3339-3346.
  11. Youn, H.S., Lee, J.Y., Saitoh, S.I., Miyake, K., Kang, K.W., Choi, Y.J. and Hwang, D.H. (2006) Suppression of MyD88-and TRIF-dependent signaling pathways of Toll-like receptor by (-)-epigallocatechin-3-gallate, a polyphenol component of green tea. Biochem. Pharmacol., 72, 850-859.
  12. Tacconelli, E., Cataldo, M.A., Dancer, S.J., De Angelis, G., Falcone, M., Frank, M., Kahlmeter, G., Pan, A., Petrosillo, N., Rodriguez-Bano, J., Singh, N., Venditti, M., Yokoe, D.S., Cookson, B. and European Society of Clinical, M. (2014) ESCMID guidelines for the management of the infection control measures to reduce transmission of multidrug-resistant Gram-negative bacteria in hospitalized patients. Clin. Microbiol. Infect., 20 Suppl 1, 1-55.
  13. Gudiol, C. and Carratala, J. (2014) Antibiotic resistance in cancer patients. Expert Rev. Anti Infect. Ther., 12, 1003-1016.
  14. Klastersky, J., Ameye, L., Maertens, J., Georgala, A., Muanza, F., Aoun, M., Ferrant, A., Rapoport, B., Rolston, K. and Paesmans, M. (2007) Bacteraemia in febrile neutropenic cancer patients. Int. J. Antimicrob. Agents, 30 Suppl 1, S51-59.

Cited by

  1. Molecular targets of gambogic acid in cancer: recent trends and advancements vol.37, pp.10, 2016,
  2. Gambogenic acid inhibits LPS-simulated inflammatory response by suppressing NF-κB and MAPK in macrophages vol.48, pp.5, 2016,
  3. and Its Components vol.33, pp.4, 2017,
  4. Serine-Rich Repeat Adhesins Contribute to Streptococcus gordonii-Induced Maturation of Human Dendritic Cells vol.8, pp.1664-302X, 2017,
  5. Lipoteichoic Acid Inhibits Staphylococcus aureus Biofilm Formation vol.9, pp.1664-302X, 2018,


Supported by : National Research Foundation of Korea (NRF)