FRI0297 Macrophage-derived lcn2 contributes to development of lupus nephritis
Authors: W. Chen, L. Sun
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Renal involvement is a major concern in systemic lupus erythematosus (SLE). Many findings have indicated that plasma and urinary LCN2 is a potential marker of the presence and severity of renal involvement in SLE. However, whether LCN2 has a pathogenic or protective role in lupus nephritis (LN) is still unknown. <h3>Objectives</h3> In this study we analysed the expression of LCN2 in lupus patients and determined whether neutralisation of LCN2 with a monoclonal antibody or injection of recombinant LCN2 affects LN in mice. <h3>Methods</h3> Plasma and urine LCN2 was quantified by ELISA in SLE patients and healthy controls (HCs). The correlations between the levels of LCN2 and clinical features were analysed by Spearman'scorrelation test. CD14<sup>+</sup> monocytes were isolated from peripheral blood of HCs and SLE patients. We cultured human monocytes for 7 days with macrophage colony-stimulating factor (M-CSF) to generate macrophages. To investigate the production of LCN2 in lupus mice during progression of LN, plasma and urine LCN2 levels were measured by ELISA, mRNA and protein levels of LCN2 in different tissues were measured by qPCR and western blot respectively at different stages of disease. To investigate whether increased LCN2 levels contribute to the development of LN, the 16-week-old mice received weekly intraperitoneal of anti-LCN2 antibody or recombinant LCN2 for 4 weeks and analysed 1 week after the last injection. The renal pathology, proteinuria, spleen index were evaluated. The frequency of T lymphocyte subpopulation, B cells and plasma cells in spleen and lymph node was analysed by flow cytometry. Bone marrow derived macrophges (BMDMs) were isolated from tibias and femurs in mice. The expression of LCN2 in human macrophages and BMDMs were detected by qPCR. <h3>Results</h3> Plasma and urine LCN2 levels were markedly increased in SLE patients, and plasma LCN2 was positively correlated with urine LCN2. The levels of LCN2 in both plasma and urine were positively correlated with serum creatinine and 24 hour urine protein. The levles of LCN2 in the patients with LN were significantly higher than those without LN. At 10 weeks, when mice do not show any signs of systemic lupus, plasma LCN2 levels were low but increased significantly in 15- and 20-week-old mice. The increased plasma LCN2 was correlated with proteinuria and deposition of IgG in glomeruli. The mRNA level of LCN2 was increased in different tissues including liver, kidney and spleen. The same results were found in protein levels. Administration of LCN2 aggravated the disease with significantly higher renalactivity scoresand more IgG deposition. Neutralisation of LCN2 significantly improved renal pathology and reduced the glomerular deposition of IgG. Furthermore, anti-dsDNA antibody and proteinuria were significantly lower in the anti-LCN2 group. Flow cytometry revealed a significant decrease of T cells, B cells and Th1 cells in the anti-LCN2 group. While LCN2 significantly increased T cells, plasma cells and Th1 cells. LCN2 mRNA level in macrophages was significantly increased in SLE patients. And its expression was also increased in BMDMs with the progression of disease in lupus mice. <h3>Conclusions</h3> These findings suggested that LCN2 over-production by macrophages plays an important role in the pathogenesis of SLE and the progression of lupus nephritis. Thus, blockade of LCN2 may represent a new strategy for treatment of LN. <h3>Disclosure of Interest</h3> None declared