Abstract: Objective To investigate the expression of long non-coding RNA (lncRNA) Linc00638 in rheumatoid arthritis (RA) and its regulatory role in inflammation and oxidative stress of synovial fibroblasts in RA patients (RA-FLS). Methods Peripheral blood mononuclear cells (PBMCs) were collected from 20 healthy individuals and 35 RA patients for detecting the expression of Linc00638 using RT-qPCR to analyze the correlation of Linc00638 expression with the clinical indicators of RA patients. A Linc00638 overexpression plasmid and siRNA targeting Linc00638 were transfected into RA-FLS, and the changes in cell viability was observed using CCK8 assay; the changes in the expression levels of interleukin-4 (IL-4), IL-6, reactive oxygen species (ROS) and superoxide dismutase (SOD) in the supernatant were detected using ELISA. Results Compared with the healthy control subjects, RA patients had significantly increased ESR, CRP, RF, anti-CCP, IgA, and C4 levels (P<0.05) and significantly decreased Linc00638 expression in the PBMCs (P<0.01). The area under the receiver-operating characteristic (ROC) curve of Linc00638 was 91.86% with the best cut- off value of 0.74 for diagnosis of RA. Spearman correlation analysis showed that Linc00638 expression level was negatively correlated with age, course of disease, DAS28, ESR, CRP, RF and anti-CCP, and positively correlated with IL-4 and SOD levels (P<0.05). Association rule analysis showed that a decreased Linc00638 expression was strongly correlated with an increase of age (>60 years), a longer disease course (>10 years), elevated levels of ESR, RF and anti-CCP, and decreased levels of IL-4 and SOD. In RA-FLS, over-expression of Linc00638 significantly inhibited while Linc00638 interference obviously enhanced the cell viability. Over-expression of Linc00638 also significantly increased the levels of IL-4 and SOD (P<0.05) and decreased the expressions of IL-6 and ROS (P<0.05), while interference of Linc00638 produced the opposite effects in the cells (P<0.05). Conclusion RA patients have low expression levels of Linc00638, which may participate in disease progression by regulating inflammation and oxidative stress.

Key words: rheumatoid arthritis; long non-coding RNA; inflammation; oxidative stress