Quercetin suppresses inflammatory cytokine production in rheumatoid arthritis fibroblast-like synoviocytes

Rheumatoid arthritis (RA) is a chronic, progressive and systemic autoimmune disease mainly characterized by symmetric multijoint synovitis. Quercetin has anti-inflammatory, anti-oxidation and immune regulation activities, and therefore shows high medicinal value. The present study aimed to observe the effect of quercetin on fibroblast-like synoviocytes (FLSs) in RA. Rheumatoid arthritis fibroblast-like synoviocytes (RAFLSs) were pretreated with 50 nmol/l quercetin for 2 h and were then stimulated using TNF-α for 24 h for subsequent experiments. RAFLSs were transfected with short interfering (si)-X-inactive specific transcript (XIST), microRNA (miR)-485 mimic, miR-485 inhibitor or si-PSMB8 or combination. ELISA, PCR and western blotting was used to evaluate the effect of quercetin on RAFLSs treated with TNF-α. It was revealed that quercetin inhibited the production of inflammatory cytokines and the expression of XIST in RAFLSs induced by TNF-α. Bioinformatics analysis indicated that XIST acted as a sponge for miR-485 and that proteasome subunit β type-8 (PSMB8) was a direct target of miR-485. Moreover, PSMB8 functioned as a suppressor in inflammatory cytokine production of RAFLSs induced by TNF-α. Overall, quercetin was observed to inhibit the production of inflammatory cytokines and the expression of XIST in RAFLSs induced by TNF-α. Moreover, XIST-silencing could suppress the inflammatory reaction by sponging miR-485 in cells treated with TNF-α. Altogether, quercetin could suppress the development of RA in vitro.

Knockdown of lncRNA NORAD inhibits the proliferation, inflammation and fibrosis of human mesangial cells under high-glucose conditions by regulating the miR-485/NRF1 axis

Long non-coding RNAs (lncRNAs) serve major roles in diabetic nephropathy (DN). The present study investigated the regulatory mechanism of lncRNA non-coding RNA activated by DNA damage (NORAD) on DN in vitro. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to detect the expression of lncRNA NORAD, microRNA-485 (miR-485) and nuclear respiratory factor 1 (NRF1) in the tissues of patients with DN and high-glucose (HG)-induced human mesangial cells (HMCs). The viability of HMCs was determined using an MTT assay. The levels of inflammatory [tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6] and fibrotic [type IV collagen (Col. IV), fibronectin (FN) and plasminogen activator inhibitor 1 (PAI-1)] factors in HMCs were measured by ELISA. The interactions between miR-485 and NORAD/NRF1 were predicted using StarBase and miRDB softwares and confirmed by a dual-luciferase reporter assay. Western blot analysis was utilized to measure NRF1 protein levels. lncRNA NORAD was highly expressed in tissues and HG-induced HMCs. NORAD knockdown suppressed cell viability in HG-induced HMCs. The levels of the inflammatory and fibrotic factors in HG-induced HMCs were inhibited by NORAD knockdown. miR-485 was the direct target of NORAD. NORAD reversed the inhibitory effects of miR-485 on HG-induced HMCs. Furthermore, NRF1 was the target gene of miR-485. Downregulation of miR-485 and upregulation of NRF1 reversed the inhibitory effects of NORAD knockdown on HG-induced HMCs. NORAD knockdown inhibited HG-induced HMC proliferation, inflammation and fibrosis by regulating miR-485/NRF1, providing a possible therapeutic strategy for DN.