Specific inhibition of MyD88-independent signaling pathways of TLR3 and TLR4 by resveratrol: molecular targets are TBK1 and RIP1 in TRIF complex.
TLRs can activate two distinct branches of downstream signaling pathways. MyD88 and Toll/IL-1R domain-containing adaptor inducing IFN-beta (TRIF) pathways lead to the expression of proinflammatory cytokines and type I IFN genes, respectively. Numerous reports have demonstrated that resveratrol, a phytoalexin with anti-inflammatory effects, inhibits NF-kappaB activation and other downstream signaling pathways leading to the suppression of target gene expression. However, the direct targets of resveratrol have not been identified. In this study, we attempted to identify the molecular target for resveratrol in TLR-mediated signaling pathways. Resveratrol suppressed NF-kappaB activation and cyclooxygenase-2 expression in RAW264.7 cells following TLR3 and TLR4 stimulation, but not TLR2 or TLR9. Further, resveratrol inhibited NF-kappaB activation induced by TRIF, but not by MyD88. The activation of IFN regulatory factor 3 and the expression of IFN-beta induced by LPS, poly(I:C), or TRIF were also suppressed by resveratrol. The suppressive effect of resveratrol on LPS-induced NF-kappaB activation was abolished in TRIF-deficient mouse embryonic fibroblasts, whereas LPS-induced degradation of IkappaBalpha and expression of cyclooxygenase-2 and inducible NO synthase were still inhibited in MyD88-deficient macrophages. Furthermore, resveratrol inhibited the kinase activity of TANK-binding kinase 1 and the NF-kappaB activation induced by RIP1 in RAW264.7 cells. Together, these results demonstrate that resveratrol specifically inhibits TRIF signaling in the TLR3 and TLR4 pathway by targeting TANK-binding kinase 1 and RIP1 in TRIF complex. The results raise the possibility that certain dietary phytochemicals can modulate TLR-derived signaling and inflammatory target gene expression and can alter susceptibility to microbial infection and chronic inflammatory diseases.
Youn
Hyung S
HS
Western Human Nutrition Research Center, Agricultural Research Service, US Department of Agriculture, University of California, Davis, CA 95616, USA
Lee
Joo Y
JY
Fitzgerald
Katherine A
KA
Young
Howard A
HA
Akira
Shizuo
S
Hwang
Daniel H
DH
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000037:antagonists & inhibitors* / Q000502:physiology; D000818:Animals; D000943:Antigens, Differentiation / Q000502:physiology; D002460:Cell Line; D051546:Cyclooxygenase 2; D020690:GTPase-Activating Proteins / Q000037:antagonists & inhibitors* / Q000502:physiology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000502:physiology*; D051379:Mice; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B / Q000378:metabolism; D011070:Poly I-C / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D011956:Receptors, Cell Surface / Q000502:physiology*; D011971:Receptors, Immunologic / Q000037:antagonists & inhibitors* / Q000502:physiology*; D000077185:Resveratrol; D015398:Signal Transduction / Q000187:drug effects*; D013267:Stilbenes / Q000494:pharmacology*; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000943:Antigens, Differentiation; D051546:Cyclooxygenase 2; D020690:GTPase-Activating Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D011070:Poly I-C; D011451:Prostaglandin-Endoperoxide Synthases; D017346:Protein Serine-Threonine Kinases; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D000077185:Resveratrol; D013267:Stilbenes; D051195:Toll-Like Receptor 2; D051196:Toll-Like Receptor 3; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; C507780:Myd88 protein, mouse; C490620:Ralbp1 protein, mouse; C476286:Ticam1 protein, mouse; C493487:Tlr4 protein, mouse; C498588:Tbk1 protein, mouse