The association of single nucleotide polymorphism of interleukin-21 gene and serum interleukin-21 levels with systemic lupus erythematosus

Circulatory microRNAs and proinflammatory cytokines as predictors of lupus nephritis

Introduction

Lupus nephritis (LN) is one of the most prevalent severe organ manifestations of systemic lupus erythematosus (SLE), impacting 70% of SLE patients. MicroRNAs (miRNAs), are small non-coding RNA molecules which influence the expression of approximately one-third of human genes after the process of transcription. Dysregulation of miRNAs was documented in numerous disorders, including SLE and LN. Cytokines are the orchestrators of the immune response in autoimmune diseases. Our study aims to explore the variation in the levels of circulating miRNAs and proinflammatory cytokines as potential diagnostic biomarkers among LN and SLE patients without LN in comparison to controls.

Methods

The study involved 20 LN patients, 20 SLE patients without LN, and 10 healthy controls. Serum levels of IL-12 and IL-21 in addition to miR-124, miR-146a, miR-199a, and miR-21 were assessed using the enzyme-linked immunosorbent assay (ELISA) for cytokines and quantitative real-time PCR for miRNAs.

Results

A significant downregulation in miR-124 (p<0.001) and a significant overexpression of miR-146a (p=0.005) were found in SLE patients without LN in comparison to controls. In comparison to SLE patients without LN and the control group, miR-199a, miR-21, and miR-146a were significantly upregulated in LN patients (p=<0.001) with high diagnostic values of these miRNAs in discriminating LN from SLE patients without LN according to Receiver operating curve (ROC) analysis. Logistic regression analysis revealed that only miR-199a is an independent predictor of LN (OR 1.69; 95% CI: 1.1-2.6). The expression of miR-124 was reduced in LN patients in comparison to the control but increased in LN patients in comparison to SLE patients without LN. However, there was no statistically significant difference in either scenario. In comparison to both SLE patients without LN and controls, LN patients exhibited the highest serum levels of IL-12 and IL-21, with no statistically significant difference. Regression analysis revealed that only miR-146a was associated with creatinine levels and SLEDAI score (p= 0.009 and 0.03, respectively), while miR-124 was associated with hemoglobin level (p=0.03).

Conclusion

MiR-199a is an independent predictor for LN and might be used as a diagnostic biomarker for this disease. MiR-146a might play an important role in LN pathophysiology.

High Interleukin 21 Levels in Patients with Systemic Lupus Erythematosus: Association with Clinical Variables and rs2221903 Polymorphism

Background: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by autoantibody production and diverse tissue and organ inflammatory affections. Interleukin 21 (IL-21) is implicated in B cell survival, proliferation, differentiation, class switching, and immunoglobulin production; therefore, it is considered a key cytokine in the pathogenesis of SLE. However, its association with disease activity and clinical phenotypes remains unclear. We aimed to evaluate the association of IL-21 levels with the disease activity and clinical phenotypes in patients with SLE. Also, we analyzed the IL21 polymorphisms associated with increased IL-21 levels. Methods: The IL-21 serum levels were determined using the enzyme-linked immunosorbent assay (ELISA) method. The rs2221903 and rs2055979 polymorphisms were assessed in 300 healthy controls (HCs) and 300 patients with SLE by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. The levels of IL-21 were monitored during follow-up visits in 59 patients with SLE. Results: The patients with SLE showed higher IL-21 levels compared to the HCs. The IL-21 levels did not correlate with Mex-SLEDAI and were not different in patients with inactive, mild-moderate, and severe disease. The IL-21 levels were increased in patients with hematological affection. The ROC curve analysis revealed that the IL-21 levels had good predictive power in discriminating among patients with SLE and HCs. In a follow-up analysis, the levels of IL-21 remained higher in the patients with SLE even when the patients were in remission. Also, the rs2221903 polymorphism was associated with increased IL-21 levels. Conclusions: This study highlights the importance of IL-21 as a key cytokine in SLE. IL-21 levels are higher in patients with SLE and remain increased regardless of disease activity. According to the ROC analysis, IL-21 is a potential biomarker of SLE. Further longitudinal studies are needed to explore the relationship between IL-21 and the clinical phenotypes of SLE.

Interleukins 4 and 21 Protect Anti-IgM Induced Cell Death in Ramos B Cells: Implication for Autoimmune Diseases

Interleukins 4 (IL-4) and 21 (IL-21) belong to the common gamma chain cytokine family which are highly involved in the progression of autoimmune diseases. While IL-4 is well known to be involved in the suppression of apoptosis of autoreactive B cells, the role played by IL-21 remains unclear. In the current study, we activated the human Burkitt’s lymphoma Ramos B cells with anti-IgM to mimic B cell hyperactivation observed in patients of autoimmune diseases. Consistent with other reported findings, anti-IgM led to the downregulation of proteins involved in B cell survival and proliferation, as well as the activation of caspase 3 activity and DNA damage, resulting in apoptotic cell death after 48-hour treatment. Although both IL-4 and IL-21 reversed anti-IgM-induced apoptosis and cell cycle arrest, they did so via different mechanisms: while IL-4 could directly suppress anti-IgM-induced caspase 3 activation and marker indicative of DNA damage, IL-21 could induce B cell proliferation in the presence of anti-IgM. Importantly, IL-21 also suppressed activation induced cell death in human primary B cells. Pre-treatment with clinically validated JAK inhibitors completely reversed the effects of IL-4 and IL-21 to rescue anti-IgM induced cell death and DNA damage. The results indicate the underlying mechanisms of how IL-4 and IL-21 differentially promote survival of hyperactivated B cells and provide hints to treat autoimmune diseases.

The potential use of serum interleukin-21 as biomarker for lupus nephritis activity compared to cytokines of the tumor necrosis factor (TNF) family

OBJECTIVE

Lupus nephritis (LN) is a significant consequence of systemic lupus erythematosus (SLE). To the best of our knowledge, this is the first work that focuses on evaluation of serum interleukin (IL-) 21 as a diagnostic biomarker of LN activity, compared to B lymphocyte stimulator (BlyS), tumor necrosis factor ligand superfamily member 13 (TNF-SF13), and traditional techniques of active LN attempting to compare their diagnostic usefulness.

METHODS

Serum levels of IL-21, BlyS, and TNF-SF13 during LN were investigated. Twenty-five biopsy-proven, active LN female patients and 15 SLE patients without active LN and 20 healthy controls (HCs) joined this work.

RESULTS

Serum IL-21 level was significantly higher in active LN group than in inactive LN group. Correlation analysis showed that serum IL-21 levels were significantly correlated with total SLEDAI (r = 0.41, p = 0.03), renal-SLEDAI (r = 0.48, p = 0.04), renal activity index (AI) (r = 0.93; p < 0.001), and 24-h proteinuria (r = 0.51; p > 0.008). Receiver operating characteristic curve (ROC) revealed the ability of serum IL-21 to discriminate between active and inactive LN with 70% sensitivity at >240 pg/ml cutoff point (AUC 0.809).

CONCLUSION

For Egyptian SLE patients, serum levels of IL-21 were superior to TNF-SF13 and BlyS and correlated significantly with the activity indexes of LN, indicating a promising role as a potential biomarker of active LN.