Oleuropein as An Effective Suppressor of Inflammation and MicroRNA-146a Expression in Patients with Rheumatoid Arthritis

OBJECTIVE: Rheumatoid arthritis (RA) is a common progressive autoimmune disorder that causes chronic inflammation of the joints and damage to other organs. Previous studies have reported the important role of miRNA-146a in the pathogenesis of RA. In addition, the anti-inflammatory and modulatory effects of oleuropein (OLEU) on the expression pattern of microRNAs (miRNAs) have been shown in different diseases. Therefore, this study aimed to evaluate both the sensitivity and specificity of miRNA-146a and determine the potential effects of OLEU on the expression levels of miRNA-146a and tumour necrosis factor-alpha (TNF-α) in RA patients. MATERIALS AND METHODS: The participants in this experimental study were divided into 2 groups: RA (n=45) and healthy controls (n=30). The isolated peripheral blood mononuclear cells (PBMCs) were treated with different concentrations of OLEU; and the level of TNF-α expression, anti-citrullinated protein, and miRNA-146a were determined using enzyme-linked immunoassay and real-time polymerase chain reaction, respectively. In addition, the receiver operating characteristic (ROC) curve analysis evaluated the sensitivity and specificity of miRNA-146a in RA patients. RESULTS: Results revealed a positive correlation between the levels of miRNA-146a expression with the serum levels of C-reactive protein (CRP) and rheumatoid factor (RF) in RA patients. In addition, OLEU treatment decreased the levels of TNF-α and miRNA-146a expression in treated PBMCs samples compared with untreated cells. The ROC curve analysis showed an 85% sensitivity and 100% specificity of miRNA-146a in RA patients. CONCLUSION: Therefore, miRNA-146a can be used as a useful biomarker for RA diagnosis, particularly for early detection. In addition, OLEU could suppress inflammation in RA patients through the regulation of miRNA-146a.