High glucose promotes macrophage switching to M1 phenotype via down-regulating STAT-3 mediated- autophagy

Abstract

Abstract Aim Imbalance of M1/M2 macrophages phenotype activation is a key point in diabetic kidney disease (DKD). Macrophages mainly exhibit M1 phenotype, which contributes to the inflammation and fibrosis in DKD. Studies indicate that autophagy plays an important role in M1/M2 activation. However, the mechanism of autophagy regulating macrophage M1/M2 phenotype in DKD is unknown. Thus, the aim of this study is to explore whether high glucose induced macrophage switch to M1 phenotype via down-regulating STAT-3-mediated autophagy. Methods DKD model rats were established in vivo by intraperitoneal injection of streptozocin (STZ). Rats were sacrificed at 18 weeks for histological and molecular analysis. RAW264.7 cells were cultured in vitro with 30mM glucose in the presence or absence of a STAT-3 activator (Colivelin) and an autophagy activator (Rapamycin). Meanwhile, M1 and M2 macrophage activation models were established as a control group. Immunofluorescence and Western Blot were used to detect the expression of autophagy-related proteins (LC3, Beclin-1), M1 markers (iNOS, TNF-α), and M2 markers (MR, Arg-1). Results In DKD, macrophages exhibited an M1 phenotype and showed less autophagy. Under high glucose conditions, RAW264.7 macrophages switched to the M1 phenotype. Autophagy was downregulated in high glucose induced M1 macrophages. Both the STAT-3 activator and the autophagy activator promoted the transition of glucose-induced M1 macrophages to M2 macrophages. Meanwhile, STAT-3 activation increased the expression of autophagy makers (LC3 and Beclin-1). However, autophagy activator had no effect on STAT-3 phosphorylation. Conclusion High glucose promotes macrophage switching to M1 phenotype via down-regulating STAT-3-mediated autophagy.