Pos0368 citrullination induces epigenetic memory of the innate immune system

Background: During trained immunity, monocytes and macrophages undergo a functional and transcriptional reprogramming toward activation, which is induced by a priming stimulus and results in enhanced responsiveness to subsequent triggers. Monocytes from patients with rheumatoid arthritis (RA) display features consistent with a trained immunity phenotype. Citrullinated proteins as citrullinated vimentin (c-vimentin), which function as damage-associated patterns in RA, may be implicated in the process of trained immunity. Objectives: We aimed to investigate if c-vimentin induces trained immunity in vitro in healthy individuals. Methods: Monocytes were isolated from the peripheral blood (EDTA blood, n=22; buffy coats, n=6) from healthy donors by Ficoll-paque centrifugation and negative selection using CD3/CD19/CD56 magnetic beads. The cells were stimulated with c-vimentin (0.1 μg/ml) for 24h and re-stimulated 5 days later with the lipopolysaccharide of E.coli (LPS) (10 ng/ml). Protein as well as lactate release were estimated in cell culture supernatants at day 6 by ELISA. RT-PCR and/or Western Blotting were applied to measure mRNA and/or protein expression. The Ligand-receptor glycocapture technology LRC-TRiCEPS was used to identify candidate cell surface targets of c-vimentin. The methylation of histone H3 at lysine 4 (H3K4) was examined by chromatin immunoprecipitation. Results: Priming with citrullinated vimentin induced training in human monocytes, as suggested by the significantly increased levels of secreted interleukin-6 (IL-6), upon restimulation with LPS (1.29-fold increase, n=22, p Conclusion: Citrullinated vimentin induces epigenetic modifications and metabolic changes in monocytes, probably through a STING and TBK1-dependent activation, resulting in enhanced cytokine and chemokine production upon restimulation. Inhibition of the STING signaling pathway may be a novel therapeutic target for myeloid activation in RA. Disclosure of Interests: None declared