Therapeutic STING activation boosts microglia phagocytosis and ameliorates depression-like behaviors during chronic restraint stress

Background The STING-TBK1-IRF3 signaling pathway involves in modulating host innate immunity, however, the potential role of STING signaling pathway in chronic restraint stress model has not been determined. The aim of this study is to explore the underlying role of STING signaling pathway in regulating neuroinflammation, as well as to evaluate the therapeutic potential of STING agonist during chronic restraint stress. Methods C57BL/6 mice were subjected to 14-day intermittent restraint stress. Sucrose preference, elevated plus maze and tail suspension tests were measured in chronic restraint stress mice. Expression levels of proinflammatory cytokines were tested by QT-PCR and Luminex cytokine assays. The fluorescence-labeled latex beads, flow cytometry and CD68 positive cell counts were utilized to evaluate phagocytic abilities of microglia. Then, the ability of intracerebroventricular injection of STING agonist, 2’3-cGAMP, to reverse the depression-like behaviors and inflammatory cytokines was examined. Results We found that the expression levels of STING, p-TBK1, and p-IRF3 were remarkably decreased in chronic restraint stress mice, which was associated with decreased IFN-β secretion. Moreover, the STING agonist, 2’3-cGAMP, significantly alleviated the neuroinflammation and ameliorated depression-like behavior which depends on the functional STING activation. Furthermore, 2’3-cGAMP promoted microglia phagocytosis through STING-dependent IFN-β release, which was essential for recovery from neuroinflammation during chronic restraint stress. Conclusions These findings demonstrate that STING signaling pathway is a critical mediator in regulating microglia phagocytosis and may serve as a novel therapeutic target for chronic stress-related psychiatric diseases.