Interleukin-35 regulates the differentiation of regulatory T cells through the JAK-STAT pathway and influences glutamine metabolism in ARDS.

The aim of this study was to elucidate the effect of interleukin (IL)-35 on T-cell differentiation and its mechanism. We evaluated the therapeutic effect of IL-35 on acute respiratory distress syndrome using clinical samples and the mouse cecum ligation and puncture model. The effects of IL-35 on regulatory T cells (Tregs) were verified by flow cytometry, immunohistochemistry, and quantitative real-time reverse transcription polymerase chain reaction. Liquid chromatography-mass spectrometry was used to detect the effects of IL-35 on changes in glutamine metabolites and tricarboxylic acid (TCA) circulation. Western blot was used to detect changes in forkhead box protein 3 (Foxp3), key enzymes, and signal transducer and activator of transcription (STAT) phosphorylation subgroup proteins in the presence of cerdulatinib. Finally, A549 cells were treated with EL-4 cell supernatant to explore the effect of cerdulatinib on the therapeutic effect of IL-35 injury. Inflammatory factors decreased, and Foxp3 increased in response to IL-35. In addition, Foxp3 was upregulated in a glutamine-deficient environment, and notably, glutamine-related metabolism and TCA cycle-related substances were altered with the involvement of IL-35. IL-35 upregulated phosphorylation of STAT isoforms, and cerdulatinib reversed it. Finally, the effects of IL-35 on Foxp3, key enzymes, and glutamine metabolite changes were all reversed by cerdulatinib. Our study shows that IL-35 reduces lung inflammation and promotes Treg differentiation. IL-35 affects the glutamine metabolism and the TCA cycle. In addition, we demonstrated that the relevant functions of IL-35 may be mediated by STAT isoform phosphorylation.