Rheumatoid arthritis (RA) is a prototypical autoimmune disorder mainly characterized by joint inflammation and cartilage destruction. Neutrophils actively take part in the initiation and progression of RA. Neutrophils express inflammatory mediators, including cytokines and chemokines. Aberrant formation of neutrophil extracellular traps (NETs) has been demonstrated in the pathogenesis of RA. Thus, neutrophils are regarded as important therapeutic targets in RA treatment. Quercetin is one of the major flavonoids found in fruits and vegetables. Previous studies have demonstrated that quercetin is a potential agent for the treatment of RA. However, the underlying antiarthritic mechanism of quercetin has not been investigated clearly. In this study, we analyzed the therapeutic mechanism of quercetin for RA. Our results showed that quercetin ameliorates inflammation in RA mice by inhibiting neutrophil activities. Quercetin inhibited neutrophil infiltration and reduced the plasma levels of inflammatory cytokines. Quercetin promoted the apoptosis of activated neutrophils. In addition, quercetin inhibited NET formation by suppressing autophagy. These findings suggest that quercetin may be an alternative agent for the treatment of RA by inhibiting neutrophil activities.

类风湿关节炎（RA）是一种典型的自身免疫性疾病，主要特征是关节发炎和软骨破坏。中性粒细胞积极参与RA的发生和发展。中性粒细胞表达炎性介质，包括细胞因子和趋化因子。在RA的发病机理中已证实嗜中性粒细胞胞外陷阱（NETs）的异常形成。因此，中性粒细胞被认为是RA治疗中的重要治疗靶标。槲皮素是水果和蔬菜中发现的主要类黄酮之一。先前的研究表明槲皮素是治疗RA的潜在药物。但是，槲皮素的潜在抗关节炎机制尚未明确研究。在这项研究中，我们分析了槲皮素对RA的治疗机制。我们的研究结果表明，槲皮素通过抑制中性粒细胞活性改善了RA小鼠的炎症。槲皮素抑制中性粒细胞浸润并降低血浆炎性细胞因子水平。槲皮素促进活化的中性粒细胞的凋亡。此外，槲皮素通过抑制自噬抑制了NET的形成。这些发现表明槲皮素可能通过抑制嗜中性粒细胞活性而成为治疗RA的替代药物。