C29

C29 is a Toll-like receptor 2 (TLR2) inhibitor. C29, inhibited TLR2/1 and TLR2/6 signaling induced by synthetic and bacterial TLR2 agonists in human HEK-TLR2 and THP-1 cells, but only TLR2/1 signaling in murine macrophages. C29 failed to inhibit signaling induced by other TLR agonists and TNF-α. Mutagenesis of BB loop pocket residues revealed an indispensable role for TLR2/1, but not TLR2/6, signaling, suggesting divergent roles ^[1].

C29 inhibited TLR2/1-mediated NF-κB activation (IC₅₀ 0.87µM), and inhibited TLR2/6 heterodimer with IC₅₀ 23µM ^[2]. C29 and o-vanillin may function by specifically targeting the BB loop pocket of the TLR2 TIR domain, altering its function and/or position ^[1].

Mice were pretreated with C29 before the administration of hepatitis B e antigen (HBeAg), to verify the roles of TLR-2 in vivo, the expression of IL-6, TNF-α, and CCL-2 was significantly alleviated, but IL-10 was upregulated in the liver ^[3]. C29 did not affect lipid accumulation, but the adipogenesis inhibitory effects of exopolysaccharide (EPS) significantly decreased in the C29-treated group. The results showed that activation of the AMPK signalling pathway by EPS was inhibited in the early stage (day 4) of adipogenic differentiation, when TLR2 and myeloid differentiation primary response 88 (MyD88) expression is inhibited by C29, indicating that EPS activates the AMPK signalling pathway by interacting with TLR2, consequently inhibiting adipogenesis ^[4].

References:
[1]. Mistry P, Laird MH, Schwarz RS, Greene S, Dyson T, Snyder GA, et al. Inhibition of TLR2 signaling by small molecule inhibitors targeting a pocket within the TLR2 TIR domain. Proc Natl Acad Sci U S A (2015) 112(17):5455-60. doi:10.1073/pnas.1422576112
[2]. Grabowski, M.; Murgueitio, M.S.; Bermudez, M.; Wolber, G.; Weindl, G. The novel small-molecule antagonist MMG-11 preferentially inhibits TLR2/1 signaling. Biochem. Pharmacol. 2020, 171, 113687.
[3]. Xie X, Lv H, Liu C, Su X, Yu Z, Song S, et al. HBeAg Mediates Inflammatory Functions of Macrophages by TLR2 Contributing to Hepatic Fibrosis. BMC Med (2021) 19:247. doi: 10.1186/s12916-021-02085-3
[4]. Lee, J.; Park, S.; Oh, N.; Park, J.; Kwon, M.; Seo, J.; Roh, S. Oral intake of Lactobacillus plantarum L-14 extract alleviates TLR2-and AMPK-mediated obesity- associated disorders in hight-fat-diet-induced obese C57BL/6J mice. Cell Prolif. 2021, 54, e13039