Inhibitors of TLR8 reduce TNF production from human rheumatoid synovial membrane cultures.
The advent of anti-TNF biologicals has been a seminal advance in the treatment of rheumatoid arthritis (RA) and has confirmed the important role of TNF in disease pathogenesis. However, it is unknown what sustains the chronic production of TNF. In this study, we have investigated the anti-inflammatory properties of mianserin, a serotonin receptor antagonist. We discovered mianserin was able to inhibit the endosomal TLRs 3, 7, 8, and 9 in primary human cells and inhibited the spontaneous release of TNF and IL-6 from RA synovial membrane cultures. This suggested a role for these TLRs in production of TNF and IL-6 from RA which was supported by data from chloroquine, an inhibitor of endosomal acidification (a prerequisite for TLRs 3, 7, 8, and 9 activation) which also inhibited production of these cytokines from RA synovial cultures. Only stimulation of TLR 3 or 8 induced TNF from these cultures, indicating that TLR7 and TLR9 were of less consequence in this model. The key observation that indicated the importance of TLR8 was the inhibition of spontaneous TNF production by imiquimod, which we discovered to be an inhibitor of TLR8. Together, these data suggest that TLR8 may play a role in driving TNF production in RA. Because this receptor can be inhibited by small m.w. molecules, it may prove to be an important therapeutic target.
Sacre
Sandra M
SM
Kennedy Institute of Rheumatology Division, Faculty of Medicine, Imperial College of Science, Technology and Medicine, London, United Kingdom.
Lo
Alexandra
A
Gregory
Bernard
B
Simmonds
Rachel E
RE
Williams
Lynn
L
Feldmann
Marc
M
Brennan
Fionula M
FM
Foxwell
Brian M
BM
D000634:Aminoquinolines / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000473:pathology; D002478:Cells, Cultured; D006801:Humans; D000077271:Imiquimod; D007369:Interferon Inducers / Q000494:pharmacology; D015850:Interleukin-6 / Q000276:immunology; D008954:Models, Biological; D013583:Synovial Membrane / Q000276:immunology* / Q000473:pathology; D051196:Toll-Like Receptor 3 / Q000276:immunology; D051199:Toll-Like Receptor 7 / Q000276:immunology; D051200:Toll-Like Receptor 8 / Q000037:antagonists & inhibitors / Q000276:immunology*; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology*
D000634:Aminoquinolines; C508600:IL6 protein, human; D007369:Interferon Inducers; D015850:Interleukin-6; C495344:TLR3 protein, human; C495348:TLR7 protein, human; C495349:TLR8 protein, human; C439524:TNF protein, human; D051196:Toll-Like Receptor 3; D051199:Toll-Like Receptor 7; D051200:Toll-Like Receptor 8; D014409:Tumor Necrosis Factor-alpha; D000077271:Imiquimod