Toll-like receptor 2 (TLR2) signaling has been implicated in numerous inflammatory diseases, yet there is no TLR2 inhibitor licensed for human use. For all TLRs except TLR3, recruitment of the adapter, myeloid differentiation primary response gene 88 (MyD88), to TLR TIR domains results in downstream signaling culminating in proinflammatory cytokine production. Here, we report the discovery of an inhibitor to block TLR2 signaling.
Firstly, we analyzed the human TLR2 TIR domain crystal structure revealed a pocket adjacent to the highly conserved P681 and G682 BB loop residues.
Next, nearly 1 million commercially available small compounds, as well as US Food and Drug Administration (FDA)-approved drugs are screened by computer. Of these compounds, 149 chemically diverse small molecules and 20 FDA-approved drug are tested. 34 compounds (C1–C34) were tested in stably transfected HEK-hTLR2 cells for the ability to inhibit TLR2-mediated IL-8 mRNA. C29 failed to inhibit signaling induced by other TLR agonists and TNF-α.
Finally, C29 treatment diminished the interaction between endogenous TLR2 and MyD88 at 15 and 30 min post stimulation with P3C compared with vehicle control and achieved statistical significance. Mice treated with o-vanillin (the derivative of C29) exhibited reduced TLR2-induced inflammation.
To summary, we have identified a new TLR2 inhibitor. Besides, CADD could potentially lead to targeted therapeutics against other TLR family members.