AB0126 EXPRESSION CHARACTERISTICS OF ADENOSINE DEAMINASES ACTING ON RNA-1 IN SYSTEMIC LUPUS ERYTHEMATOSUS AND ITS CORRELATION WITH SERUM IFN-Α
Authors: X. Di, F. Gao, C. Gao, C. Zhang, W. Sun, W. Liang, M. Yao, Q. Wang, Z. Zheng
Journal: Annals of the Rheumatic Diseases (2020)

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. 1 ADAR1 is an RNA A-I editing enzyme that converts adenine to hypoxanthine and contributes to SLE pathogenesis. 2 Objectives: Dama demonstrated the upregulation of ADAR1p150 expression in SLE T cells, B cells, PBMCs, and NK cells; 3 however, 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 &lt;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 Rep 2018; 23: 50-57. [2]Hogg M, Paro S, Keegan LP and O’Connell MA. RNA editing by mammalian ADARs. Adv Genet 2011; 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. Immunology 2007; 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 &lt;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 &gt;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 &gt;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 &lt;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 vitro PBMCs 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 concentration in vitro PBMCs co-cultured with serum IgG from SLE patients. Disclosure of Interests: None declared