Hydroxychloroquine enhances efferocytosis and inhibits IL-6 and TNF-α productions through upregulating both Gas6/Axl and MFG-E8/TG2 Signaling pathways in Pristine-induced lupus mice

Abstract Objectives Impaired clearance of apoptotic cells (efferocytosis) plays an important role in the pathogenesis of autoimmune diseases, especially systemic lupus erythematosus (SLE). Hydroxychloroquine (HCQ) has been widely used to treat autoimmune diseases. We aimed to investigate the underlying mechanism of efferocytosis in the action of HCQ. Methods Eighteen 6-week-old female BALB/c mice were treated Intraperitoneally with pristine in Pristine-induced lupus mice (PIL). Efferocytosis was performed using mouse cell lines EL4 as apoptotic cells and co-cultured with RAW 264.7 and peritoneal macrophages of PIL to investigate the effect of HCQ on efferocytosis which was analyzed with fluorescent microscopy and flow cytometry. Real time PCR was performed to investigate molecular mRNA expressions of signalling pathways. Protein level was measured by ELISA. Results HCQ could enhance efferocytosis with dose-dependent manner in both RAW264.7 cell lines and peritoneal macrophages of PIL with increased expression of GAS6 and MFG-E8 signallings. Both Gas6/Axl and MFG-E8/TG2 Signalling pathways play important roles in HCQ-enhanced efferocytosis. In HCQ-treated mice of PIL, HCQ reduced of IL-6 (p<0.0036) and TNF-α (p<0.06) protein levels in their ascites. Conclusions Our study shows that HCQ can enhance efferocytosis through both Gas6/Axl and MFG-E8/TG2 Signalling pathways and suppress the production of IL-6 and TNF-α. Our findings provide novel insights into understanding the mechanisms of HCQ, which could have the long-term beneficial effects on the therapy of SLE.