Department of Rheumatology, Nagasaki Medical Center, Kubara 2-1001-1, Omura, Nagasaki 856-8562, Japan.
Arthritis Res Ther. 2012 May 18;14(3):R119. doi: 10.1186/ar3849.
Monosodium urate (MSU) has been shown to promote inflammasome activation and interleukin-1β (IL-1β) secretion in monocyte/macrophages, but the cellular pathway and nod-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation in synovial tissues, remain elusive. In this study, we investigated the effects of MSU on synovial fibroblasts to elucidate the process of MSU-mediated synovial inflammation.
Human synovial fibroblasts were stimulated with MSU in the presence or absence of serum amyloid A (SAA). The cellular supernatants were analyzed by immunoblotting using anti-IL-1β or anti-caspase-1 antibodies. IL-1β or NLRP3 mRNA expressions were analyzed by real-time PCR or reverse transcription-PCR (RT-PCR) method.
Neither SAA nor MSU stimulation resulted in IL-1β or interleukin-1α (IL-1α) secretions and pro-IL-1β processing in synovial fibroblasts. However, in SAA-primed synovial fibroblasts, MSU stimulation resulted in the activation of caspase-1 and production of active IL-1β and IL-1α. The effect of SAA on IL-1β induction was impaired in cells by silencing NLRP3 using siRNA or treating with caspase-1 inhibitor. In addition, SAA induced the secretion of cathepsin B and NLRP3 mRNA expression in synovial fibroblasts.
Our data demonstrate that exposure of human synovial fibroblasts to SAA promotes MSU-mediated caspase-1 activation and IL-1β secretion in the absence of microbial stimulation. These findings provide insight into the molecular processes underlying the synovial inflammatory condition of gout.
尿酸单钠（MSU）已被证明可促进单核细胞/巨噬细胞中炎症小体的激活和白细胞介素-1β（IL-1β）的分泌，但滑膜组织中的细胞途径和核苷酸结合寡聚化结构域样受体家族，含pyrin 结构域的 3（NLRP3）炎症小体的激活仍不清楚。在这项研究中，我们研究了 MSU 对滑膜成纤维细胞的影响，以阐明 MSU 介导的滑膜炎症过程。
在存在或不存在血清淀粉样蛋白 A（SAA）的情况下，用 MSU 刺激人滑膜成纤维细胞。用抗 IL-1β或抗半胱天冬酶-1 抗体通过免疫印迹分析细胞上清液。通过实时 PCR 或逆转录-PCR（RT-PCR）方法分析 IL-1β或 NLRP3 mRNA 表达。
SAA 或 MSU 刺激均不会导致滑膜成纤维细胞中 IL-1β或白细胞介素-1α（IL-1α）的分泌和前体 IL-1β的加工。然而，在 SAA 预刺激的滑膜成纤维细胞中，MSU 刺激导致半胱天冬酶-1的激活和活性 IL-1β和 IL-1α的产生。用 siRNA 沉默 NLRP3 或用半胱天冬酶-1 抑制剂处理可削弱 SAA 对 IL-1β诱导的作用。此外，SAA 诱导滑膜成纤维细胞中组织蛋白酶 B 的分泌和 NLRP3 mRNA 的表达。
我们的数据表明，暴露于人滑膜成纤维细胞中的 SAA 在没有微生物刺激的情况下促进 MSU 介导的半胱天冬酶-1 的激活和 IL-1β的分泌。这些发现为痛风性滑膜炎症的分子过程提供了深入的了解。
