POS0451 DEFICIENCY OF PPM1A IN MACROPHAGE AGGRAVATES PRISTANE-INDUCED LUPUS-LIKE DISEASE

Abstract

BackgroundProtein phosphatase Mg2+/Mn2+-dependent 1A (PPM1A) is a phosphatase which regulates various intracellular cell signaling pathways including inflammation. We previously suggested that the inflammatory signal decreased the PPM1A protein level in macrophage and this reduction had correlation with the chronic inflammatory bone disease, implying the possible role of PPM1A in inflammatory responses of macrophage.ObjectivesIn this study, we aim to elucidate the potential role of PPM1A in macrophage to regulate inflammatory response during the disease progression of systemic lupus erythematosus.MethodsWe generated macrophage-specific conditional gene-knockout (PPM1Afl/fl;LysM-Cre) mice and developed a lupus-like disease with immune complex glomerulonephritis in these PPM1Afl/fl;LysM-Cre mice by intraperitoneal pristane injection. Mouse serum was collected every 4 weeks after pristane injection. Serum anti-dsDNA IgG, anti-ssDNA IgG, interleukin-17 (IL-17) and tumor necrosis factor-α (TNF-α) was quantified by ELISA. After 41 weeks from pristane injection, histological changes in the kidney, spleen, and lung tissues were observed. To analyze M1/M2 polarization in vitro, LysM-Cre and PPM1Afl/fl;LysM-Cre mouse bone marrow-derived macrophages were cultured with lipopolysaccharide (LPS)/interferon-γ (IFN-γ) or interleukin-4 (IL-4) to check M1 or M2 related genes.ResultsWe found that macrophages of PPM1Afl/fl;LysM-Cre mice displayed different gene expression with LPS stimulation especially in M1/M2 related genes through the RNA-seq analysis and showed a decrease in both M1 and M2 polarization induced by LPS/IFN-γ or IL-4 stimulation. Notably, we found that PPM1Afl/fl;LysM-Cre mice with pristane injection showed a significant increase of anti-ssDNA IgG compared to LysM-Cre mice. PPM1Afl/fl;LysM-Cre mice showed severe lupus-like phenotypes such as global glomerular enlargement indicated by endocapillary proliferation and glomerular cellularity in kidney and lung inflammation accompanied by fibrosis, compared to LysM-Cre mouse by pristane injection. Together, serum IL-17 and TNF-α, which are proinflammatory cytokines, were increased in PPM1Afl/fl;LysM-Cre after pristane injection. These results indicate that PPM1A depletion in macrophage deteriorates inflammation and contributes to the tissue damage in a lupus-like disease.ConclusionOur findings suggest that the deficiency of PPM1A in macrophages impairs M1/M2 macrophage polarization leading to an immune imbalance in lupus-like disease model, providing a potential link between the loss of function of PPM1A in macrophages and its molecular target for treatment of systemic lupus erythematosus.