S-acylation inhibition suppresses pro-inflammatory chemokines and disrupts IDO1 in activated THP-1 macrophages

The macrophage inflammatory response is a critical component of innate immunity, but dysregulated or chronic inflammation contributes to numerous diseases. Current therapeutic strategies often target broad inflammatory pathways, leading to systemic side effects. Long-chain S-acylation, a reversible lipid modification, is known to regulate protein localization, stability, and signaling. However, its specific role in modulating macrophage activation and inflammatory cytokine production has remained largely unexplored, representing a significant gap in understanding potential therapeutic targets for inflammatory conditions.

Researchers investigated the role of long-chain S-acylation in macrophage inflammation using THP-1 macrophages. Cells were polarized to either quiescent M0 or pro-inflammatory M(LPS+ IFNɣ) states. They employed stable isotope labeling by amino acids in cell culture (SILAC) combined with site-specific acyl-biotin exchange (ssABE) to map the S-acylation landscape. Pharmacological inhibition of S-acylation was achieved using the broad-spectrum inhibitor 2-bromopalmitate and the GPCR-specific S-acylation stabilizer Palmostatin B. Primary endpoints included quantitative proteomics for S-acylation patterns and assessment of pro-inflammatory chemokine secretion.

Quantitative proteomics revealed distinct S-acylation patterns specific to macrophage polarization states, identifying numerous inflammation-related modification sites. This included novel S-acyl peptidoforms, such as those on WARS at C305 and C309, suggesting their involvement in macrophage activation. Pharmacological intervention demonstrated significant effects on inflammatory mediators. > Pharmacological inhibition of S-acylation with 2-bromopalmitate effectively suppressed the secretion of key pro-inflammatory chemokines, including CXCL9, CXCL10, and CCL4, and disrupted IDO1-mediated tryptophan catabolism. In contrast, Palmostatin B primarily stabilized S-acylation on GPCR signaling proteins, indicating a more targeted effect. These findings collectively position long-chain S-acylation as a crucial regulatory mechanism in macrophage activation, with potential for therapeutic modulation.