Background:Lupus nephritis (LN) is one of the most severe complications of systemic lupus erythematosus (SLE). Circular RNAs(circRNAs) can act as competitive endogenous RNAs (ceRNAs) to regulate gene transcription, which is involved in mechanism of many diseases, such as, autoimmunity diseases. However, the role of circRNA in lupus nephritis has been rarely reported.Objectives:In this study, we aim to investigate the clinical value of circRNAs and explore the mechanism of circRNA involvement in the pathogenesis of LN.Methods:Renal tissues from three untreated LN patients and three normal controls (NCs) were used to identify differently expressed circRNAs by RNA sequencing (RNA-seq). Validated assays were used by quantitative reverse transcription polymerase chain reaction (qRT-PCR). Correlation analysis and receiver operating characteristic (ROC) curve were used to reveal the clinical value of selected circRNA, miRNA and mRNA. The interactions between circRNA and miRNA, or miRNA and mRNA were further determined by luciferase reporter assay. The degrees of renal fibrosis between the two groups were compared by Masson-trichome staining and immunohistochemistry staining.Results:159 circRNAs were significantly dysregulated in LN patients compared with NC group. The expression of hsa_circ_0123190 was significantly decreased in renal tissues of patients with LN (p=0.014), as same as the sequencing results. The area under the ROC curve of hsa_circ_0123190 in renal tissues was 0.820. Bio-informatic analysis and luciferase reporter assay illustrated that hsa_circ_0123190 can act as a sponge for hsa-miR-483-3p which was also validated to interact with APLNR mRNA. APLNR mRNA expression was positively related with chronicity index (CI) of LN (R2=0.452,p=0.033). Finally, the factors of renal fibrosis, especially TGF-β (p=0.018), were more pronounced in the LN group.Conclusion:Hsa_circ_0123190 could function as a ceRNA to regulate APLNR expression involved in renal fibrosis by sponging hsa-miR-483-3p in LNReferences:[1]Aljaberi N, Bennett M, Brunner HI, Devarajan P. Proteomic profiling of urine: implications for lupus nephritis. Expert review of proteomics. 2019;16(4):303-13.[2]Zheng ZH, Zhang LJ, Liu WX, Lei YS, Xing GL, Zhang JJ, et al. Predictors of survival in Chinese patients with lupus nephritis. Lupus. 2012;21(10):1049-56.[3]Chen LL. The biogenesis and emerging roles of circular RNAs. Nature reviews Molecular cell biology. 2016;17(4):205-11.[4]Mahmoudi E, Cairns MJ. Circular RNAs are temporospatially regulated throughout development and ageing in the rat. Scientific reports. 2019;9(1):2564.[5]Liang D, Wilusz JE. Short intronic repeat sequences facilitate circular RNA production. Genes & development. 2014;28(20):2233-47.[6]Tan WL, Lim BT, Anene-Nzelu CG, Ackers-Johnson M, Dashi A, See K, et al. A landscape of circular RNA expression in the human heart. Cardiovascular research. 2017;113(3):298-309.[7]Zhao Z, Li X, Jian D, Hao P, Rao L, Li M. Hsa_circ_0054633 in peripheral blood can be used as a diagnostic biomarker of pre-diabetes and type 2 diabetes mellitus. Acta diabetologica. 2017;54(3):237-45.[8]Ouyang Q, Huang Q, Jiang Z, Zhao J, Shi GP, Yang M. Using plasma circRNA_002453 as a novel biomarker in the diagnosis of lupus nephritis. Molecular immunology. 2018;101(undefined):531-8.[9]Luan J, Jiao C, Kong W, Fu J, Qu W, Chen Y, et al. CircHLA-C Plays an Important Role in Lupus Nephritis by Sponging miR-150. Molecular therapy Nucleic acids. 2018;10(undefined):245-53.[10]Kuschnerus K, Straessler ET, Müller MF, Lüscher TF, Landmesser U, Kränkel N. Increased Expression of miR-483-3p Impairs the Vascular Response to Injury in Type 2 Diabetes. Diabetes. 2019;68(2):349-60.[11]Huang Z, Wu L and Chen L. Apelin/APJ system: A novel potential therapy target for kidney disease. Journal of cellular physiology. 2018;233(5): 3892-900.Disclosure of Interests:None declared

Background:SLE is a multisystem autoimmune disease characterized by the production of multiple autoantibodies and loss of immunity against autoantigens in various tissues. SLE patients have significantly elevated RNA editing levels and the potential to produce new autoantigens.1ADAR1 is an RNA A-I editing enzyme that converts adenine to hypoxanthine and contributes to SLE pathogenesis.2Objectives:Dama demonstrated the upregulation of ADAR1p150 expression in SLE T cells, B cells, PBMCs, and NK cells;3however, the following issues were not reported in detail: 1. specific alterations in ADAR1 expression in PBMCs collected from SLE patients with varying degrees of the disease and its correlation with serum IFN-α levels; 2. association between ADAR1 and clinical indicators; and 3. ADAR1 expression in renal tissue of LN patients. Our study therefore aimed to elucidate the abovementioned points.Methods:We used qRT-PCR to determine ADAR1 expression levels in PBMCs and renal tissues of controls and SLE patients. We also conducted immunohistochemical studies to detect positive ADAR1 expression rate in renal cells of controls and LN patients.Results:ADAR1 expression was higher in PBMCs of SLE patients than in those of controls and was positively correlated with SLEDAI. When serum IFN-α levels in SLE patients decreased <260.0 pg/mL, ADAR1 expression in PBMCs increased with the increase in IFN-α concentration, and serum IFN-α may regulate ADAR1 level in PBMC in SLE patients, which may require the participation of serum IgG antibody and related immune complex. However, there was no significant difference between the expression in renal tissues in all patients.Conclusion:There was a certain correlation between ADAR1 expression and serum IFN-α levels in PBMCs of SLE patients.References:[1]Roth SH, Danan-Gotthold M, Ben-Izhak M, et al. Increased RNA Editing May Provide a Source for Autoantigens in Systemic Lupus Erythematosus.Cell Rep2018; 23: 50-57.[2]Hogg M, Paro S, Keegan LP and O’Connell MA. RNA editing by mammalian ADARs.Adv Genet2011; 73: 87-120.[3]Laxminarayana D, Khan IU, O’Rourke KS and Giri B. Induction of 150-kDa adenosine deaminase that acts on RNA (ADAR)-1 gene expression in normal T lymphocytes by anti-CD3-epsilon and anti-CD28.Immunology2007; 122: 623-633.Figure 1.Analysis of ADAR1 expression levels. a. The ADAR1 expression in PBMCs was higher in SLE patients (n=30) than in healthy controls (n = 30) (p<0.05). b. SLE patients were divided into three groups: NSLE (SLEDAI 0–4, n = 6), LSLE (SLEDAI 5–9, n = 12), and SSLE (SLEDAI ≥10, n = 12) according to SLEDAI score. c. Based on the effect of the disease on the kidneys, the patients were divided into the SLE#group (#:SLE patient group without the kidney involved, n = 17) and LN group (lupus nephritis group, n = 13). d. There was no significant difference observed between the renal tissues of controls (n = 5) and LN patients (n = 10) (p>0.05).Figure 2.a. Immunohistochemical image of renal tissues from the two groups (200×). b. There was no significant difference in the ADAR1 cell positive rate between controls (n = 5), LN patients(n = 20), and different pathological subgroups (class III, n = 5; class IV, n = 5; class V, n = 5; class III+IV, n = 5) (p>0.05). c. The positive expression rate of ADAR1 in renal tubular cells was higher than that in glomerular cells both in the two groups (p<0.05).Figure 3.a. Correlation between ADAR1 and serum IFN-α levels in PBMCs of SLE patients. b. Correlation between ADAR1p150 and serum IFN-α levels in PBMCs of SLE patients.Figure 4.In vitroPBMCs assay. a. Western blot (WB) analysis of ADAR1p150 and ADAR1p110 in PBMCs using different concentrations of IFN-α, combined with 1.5 mg/mL IgG purified from the serum of SLE patients or without it, and cultured for 24 hours. b. The line graph depicts the trend of ADAR1, ADAR1p150, and ADAR1p110 expression with increase in IFN-α concentrationin vitroPBMCs co-cultured with serum IgG from SLE patients.Disclosure of Interests:None declared