Bile acids (BAs) control metabolism and inflammation by interacting with several receptors. Here, we report that intravenous infusion of taurodeoxycholate (TDCA) decreases serum pro-inflammatory cytokines, normalizes hypotension, protects against renal injury, and prolongs mouse survival during sepsis. TDCA increases the number of granulocytic myeloid-derived suppressor cells (MDSCLT) distinctive from MDSCs obtained without TDCA treatment (MDSCL) in the spleen of septic mice. FACS-sorted MDSCLT cells suppress T-cell proliferation and confer protection against sepsis when adoptively transferred better than MDSCL. Proteogenomic analysis indicated that TDCA controls chromatin silencing, alternative splicing, and translation of the immune proteome of MDSCLT, which increases the expression of anti-inflammatory molecules such as oncostatin, lactoferrin and CD244. TDCA also decreases the expression of pro-inflammatory molecules such as neutrophil elastase. These findings suggest that TDCA globally edits the proteome to increase the number of MDSCLT cells and affect their immune-regulatory functions to resolve systemic inflammation during sepsis.

Mitochondrial defects and antimitochondrial cardiolipin (CL) antibodies are frequently detected in autoimmune disease patients. CL from dysregulated mitochondria activates various pattern recognition receptors, such as NLRP3. However, the mechanism by which mitochondrial CL activates APCs as a damage-associated molecular pattern to prime antigen-specific naïve T cells, which is crucial for T-cell-dependent anticardiolipin IgG antibody production in autoimmune diseases is unelucidated. Here, we show that CL increases the expression of costimulatory molecules in CD11c APCs both in vitro and in vivo. CL activates CD11c APCs via TLR2-PI3K-PKN1-AKT/p38MAPK-NF-κB signaling. CD11c APCs that have been activated by CL are sufficient to prime H-Y peptide-specific naïve CD4 T cells and OVA-specific naïve CD8 T cells. TLR2 is necessary for anti-CL IgG antibody responses in vivo. Intraperitoneal injection of CL does not activate CD11c APCs in CD14 KO mice to the same extent as in wild-type mice. CL binds to CD14 (Kd = 7 × 10 M). CD14, but not MD2, plays a role in NF-kB activation by CL, suggesting that CD14 macrophages contribute to recognizing CL. In summary, CL activates signaling pathways in CD11c APCs through a mechanism similar to gram (+) bacteria and plays a crucial role in priming antigen-specific naïve T cells.

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