Effect and mechanism of interleukin 37 on the immune function of regulatory T cells in septic mice / 中华急诊医学杂志

ABSTRACT

Objective:To investigate the effect of interleukin (IL)-37 on the immune function of regulatory T cells (Treg) in sepsis.Methods:TTregs were isolated and purified from the spleen of C57BL/6J mice and cultured in vitro. The cells were divided into the control group, lipopolysaccharide (LPS) group, IL-37 group, LPS+IL-37 group, LPS+3-Methyladenine (3-MA) group, LPS+3-MA+IL-37 group, LPS+Rapamaycin group, and LPS+Rapamaycin+IL-37 group. Culture supernatants and cells were collected, respectively, after cell culture for 24, 48, and 72 h. The secretion of IL-10 and TGF-β by Tregs was detected by ELISA, expressions of forkhead wing-link transcription factor (Foxp3) and cytotoxic T lymphocytes antigen 4 (CTLA-4) were measured by flow cytometry. Formation and number of autophagosomes were observed by transmission electron microscope. Western blot was used to determine expressions of autophagy associated proteins, including LC3I/II and Beclin1. Cecal ligation and puncture (CLP) was used to construct septic mice model, and the differences in survival rates between the groups were recorded and compared.Results:IL-37 was given to Tregs at 24, 48, and 72 h after LPS stimulation. The function of Treg was significantly enhanced after 72 h of synergistically stimulation by both LPS and IL-37. After stimulation with LPS and IL-37, the formation of autophagosomes in Tregs was obviously increased under observation of transmission electron microscopy. Pretreatment with autophagy agonist Rapamycin and autophagy inhibitor 3-MA was applied for altering the activity of cell autophagy. It was noticed that immune function of Treg was significantly decreased in the 3-MA group compared with the control group, while it was enhanced in the Rapamycin group. Secretion of TGF-β in the 3-MA group presented with significant reduction, which showed a marked increase in the Rapamycin group. However, no significant differences were found in IL-10 levels among various groups. Administration of IL-37 improved the survival rates of septic mice, which was much more efficient by treatment prior to the onset of sepsis.Conclusions:IL-37 appears to be capable of augmenting immune function of Tregs in an autophagy-dependent pathway, which might contribute to maintaining homeostasis of immune response in the setting of sepsis, and further improves the survival and prognosis of septic mice.