Background/Purpose: To identify new candidate genes regulated by micro RNAs (miRNAs) and involved in the pathogenesis of systemic lupus erythematosus (SLE), we integrated miRNA and messenger RNA (mRNA) expression profiling data in CD4⁺ splenic T cells derived from lupus-prone MRL/MpJ-Fas^lpr /J (MRL/lpr) mice and C57BL6/J (B6) mice. The reduction of sphingosine-1-phosphate receptor 1 (S1pr1) and upregulation of miR-223-3p in the splenic T cells in MRL/lpr was identified and we investigated the role of S1pr1 as a predicted target of miR-223 (Mir223) in SLE.

Methods: L transduction particles containing luciferase reporter and S1pr1-3’UTR region was infected into human umbilical vein endothelial cells (HUVECs) for luciferase miRNA target screening. Luciferase reporter assay following co-transfection of lentiviral particles containing reporter vector with miR-223-3p mimic or nontargeting miRNA into HUVECs was performed. To further confirm that S1pr1 is a target of miR-223-3p, miR-223-3p mimic or nontargeting miRNA was transfected into EL4 mouse T cell lines by lipofection. The transfection efficacy of miR-223-3p was confirmed by quantitative PCR (qPCR). The endogenous S1pr1 mRNA and protein levels were detected by qPCR and Western blot analysis. To explore the involvement of miR-223-3p in SLE pathogenesis, we generated and analyzed Mir223 knockout lupus-prone B6.MRL-Fas^lpr mice (Mir223^-/-Fas^lpr/lpr) until 44 weeks of age. The total IgG and titer of anti-ds-DNA antibodies in serum were measured by ELISA. Histopathological grading of glomerular, renal vascular and tubulointerstitial lesions were performed and the glomerular immune complex deposition was assessed by C3 and IgG staining. To clarify the cell types which infiltrates in glomerular lesion, immunofluorescence staining with CD4, CD8 and S1PR1 antibodies was performed. The cell population including apoptotic cells and S1PR1 positive cells in the lymph nodes and spleen were analyzed by flow cytometry. We also investigated the expression levels of S1pr1 mRNA and miR-223-3p in circulating CD4⁺ T cells isolated from SLE patients and healthy subjects.

Results: Transfection of HUVEC with mimic miR-223-3p significantly suppressed a luciferase-reporter containing the S1pr1-3’UTR. The mRNA levels of S1pr1 was significantly decreased after miR-223-3p overexpression. Mir223 deficiency increased the production of serum IgG2b and the proportion of CD3⁺ T cells, CD3⁺CD4^–CD8^– T cells, CD19⁺ B cells, CD19^–CD138⁺ cells (Plasma cells), CD3⁺S1PR1⁺ T cells and CD3⁺CD4⁺S1PR1⁺ T cells in spleen and the proportion of early apoptotic cells in CD4⁺ and CD8⁺ T cells in lymph nodes. Lupus nephritis in Mir223 knockout mice was exacerbated accompanied with glomerulonephritis with infiltration of CD4⁺S1PR1⁺ T cells in glomerulus. S1pr1 mRNA was significantly decreased in CD4⁺ T cells from the patients with SLE. miR-223-3p tended to upregulate in lupus patients than healthy control. There was significant correlation between miR-223-3p and serum IgM titer.

Conclusion: Deletion of Mir223 exacerbated the lupus phenotypes associated with increasing S1pr1 expression in CD4⁺T cells and their enhanced infiltration in inflamed kidney tissues.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/deletion-of-mir-223-exacerbates-lupus-nephritis-by-targeting-s1pr1-in-faslpr-lpr-mice/