Baricitinib inhibits the activation of innate immune cells and exerts therapeutic effects on acute peritonitis and systemic inflammatory response syndrome.

Timely treatment of acute inflammatory diseases induced by bacteria or fungi is essential to prevent infectious damage. Baricitinib is an inhibitor of Janus kinases (JAKs) which was approved to treat rheumatoid arthritis, atoptic dermatitis, and alopecia areata. It is also known that JAKs play important roles in innate immunity and inflammatory response. In this study, we investigated the regulatory effects of baricitinib on the activation of macrophages and neutrophils and its therapeutic effects on acute peritonitis and systemic inflammatory response syndrome (SIRS). In addition, we also studied its anti-inflammatory mechanisms by transcriptome and immunoblotting analyses. The results showed that baricitinib inhibited the expression and secretion of multiple inflammatory factors in macrophages induced by multiple Toll-like receptor (TLR) agonists. Baricitinib also moderately suppressed superoxide release of neutrophils stimulated by TLR agonists. In zymosan-induced acute peritonitis, baricitinib significantly reduced the infiltration of neutrophils into peritoneal cavity and the production of inflammatory factors in peritoneal cavity. In addition, baricitinib also slightly decreased the production of inflammatory factors in SIRS. Transcriptome analysis revealed that baricitinib markedly inhibited the mRNA transcription of many interferon-inducible genes, antiviral immune-related genes, transcription factors in JAKs-STATs signaling pathways, inflammatory factors, chemokines, colony-stimulating factor, and immunoglobulin receptors in macrophages induced by lipopolysaccharide (LPS). Furthermore, immunoblotting analysis showed that baricitinib selectively inhibited the phosphorylation of STAT1 and STAT3 in macrophages stimulated by LPS, and almost completely blocked the phosphorylation of STAT1 and STAT3 induced by IFN-γ and IL-6. Collectively, baricitinib can moderately inhibit the activation of macrophages and superoxide production of neutrophils, and exert anti-inflammatory effects by blocking JAKs-STATs signaling pathways, and has potential to be developed into therapeutic drug for acute inflammatory diseases, especially local ones.