Background: Macrophage M2b polarization conferred by self-DNA immunization initiates and propagates lupus nephritis.
Results: Knockdown of DNA-dependent activator of interferon-regulatory factors (DAI) ameliorates SLE syndrome via blunting macrophage M2b polarization.
Conclusion: DAI functions as a DNA sensor in self-DNA-induced macrophage M2b polarization and lupus nephritis.
Significance: We disclose the mechanism by which self-DNA induces macrophage M2b polarization and lupus nephritis DNA-dependent activator of interferon-regulatory factors (DAI) functions as a cytoplasmic DNA sensor that activates the innate immune system. We previously found that activated lymphocyte-derived self-apoptotic DNA (ALD-DNA) immunization led to pathological macrophage activation and M2b polarization, which could initiate and propagate murine lupus nephritis. However, the specific DNA sensor(s) as well as underlying molecular mechanisms involved in ALD-DNA-induced macrophage M2b polarization in systemic lupus erythematosus (SLE) disease remains unknown. In this study, we reported that DAI expression was significantly increased in SLE patients as well as in lupus mice. Gain- and loss-of-function studies revealed that DAI was involved in ALD-DNA-induced macrophage activation and M2b polarization. Moreover, ALD-DNA notably induced dimerization/oligomerization of DAI and consequently activation of nuclear factor κB (NF-κB) and interferon regulatory factor 3 (IRF3) signaling pathways via calcium signaling, resulting in macrophage activation and M2b polarization. More importantly, blockade of DAI in vivo or selective knockdown of DAI in macrophages could ameliorate SLE syndrome via blunting macrophage M2b polarization and inhibiting inflammatory response in lupus mice. Our results suggest that DAI could function as a DNA sensor and a regulator in ALD-DNA-induced macrophage M2b polarization and lupus nephritis, providing the possible molecular mechanisms involved in ALD-DNA-induced macrophage M2b polarization in SLE disease and making DAI as a potential therapeutic target for the treatment of SLE.
Keywords: Autoimmune Diseases; Calcium; DAI (DLM-1/ZBP1); DNA Sensor; Inflammation; Innate immunity; Lupus Nephritis; Macrophage Polarization; Macrophages; Systemic Lupus Erythematosus (SLE).