EM982, an erythromycin derivative, modulates TLR2 ligand-induced cytokine production

Macrolide antibiotics possess immunomodulatory properties, and they effectively treat both bacterial infections and non-bacterial inflammatory diseases. However, their frequent use has been associated with increased bacterial resistance. We previously developed EM982, an erythromycin derivative that exerts immunomodulatory effects without eliciting antimicrobial activity. EM982 suppresses cytokine production by inhibiting the phosphorylation of the signalling molecules in the Toll-like receptor (TLR) 4-NF-κB pathway. These molecules are shared among multiple other TLR pathways, but the effects of EM982 on such TLR pathways may differ depending on the receptors and ligands. Therefore, the aim of this study was to analyse the effects of EM982 and erythromycin on TLR2 ligand-induced NF-κB activation and cytokine production. This pathway is involved in a wide range of inflammatory pathologies through the recognition of both bacterial and host cell-derived molecules. Pam3CSK4 (synthetic triacylated lipoprotein, TLR2/1 ligand), FSL-1 (synthetic diacylated lipoprotein, TLR2/6 ligand) and gram-negative and gram-positive bacterial cells were employed as TLR2 ligands. NF-κB reporter assays were performed using TLR2-expressing HEK293 and THP-1-Blue NF-κB cells treated with EM982 and erythromycin. To determine the effect of EM982 and erythromycin on cytokine production, cytokine levels in the culture supernatant of THP-1 cells stimulated with TLR2 ligands were measured by ELISA. Compared to erythromycin, EM982 exerted a greater inhibitory effect on TLR2 ligand-induced responses in both reporter cells. Moreover, EM982 and erythromycin suppressed the production of pro-inflammatory cytokines and promoted the production of anti-inflammatory cytokine IL-10. These findings indicate that EM982 exerts immunomodulatory effects against diverse TLR2 ligand-induced inflammatory responses.