Department of Rheumatology and Immunology, Peking University People's Hospital, , Beijing, China.
Ann Rheum Dis. 2014 May;73(5):928-36. doi: 10.1136/annrheumdis-2012-202444. Epub 2013 May 3.
Hyperplasia of synovial fibroblasts, infiltration with lymphocytes and tissue hypoxia are major characteristics of rheumatoid arthritis (RA). Extensive data support a key role for toll-like receptors (TLRs) in RA. Little is known regarding the impact of hypoxia on TLR-induced inflammation in RA. The aim of this study was to reveal the effects of hypoxia and its regulator, hypoxia-inducible factor-1α (HIF-1α), on the inflammatory response of RA synovial fibroblasts (RASF) to TLR ligands.
Hypoxia was induced in RASF by incubation with Na2S2O4. TLR3 ligand polyIC, TLR2 ligand peptidoglycan, TLR4 ligand LPS and TLR9 ligand CpG were used to stimulate the cells. Effects of hypoxia on TLR-induced inflammatory mediators were determined by RT-PCR, qPCR and ELISA. Overexpression of HIF-1α as well as knocking-down its expression was used to reveal its fundamental role. RASF-induced inflammatory T cell expansion was determined by flow cytometry analysis of T helper (Th)1/Th17 cells, and IFN-γ/IL-17 production by ELISA after RASF/T cell coculture.
Hypoxia potentiated the expression of inflammatory cytokines, metalloproteinases and VEGF in RASF stimulated by different TLR ligands, especially polyIC, a synthetic mimic of dsRNA from viruses or apoptotic cells. HIF-1α played a fundamental role in this synergy. Moreover, HIF-1α overexpression enhanced RASF-mediated expansion of inflammatory Th1 and Th17 cells, leading to proinflammatory IFN-γ and IL-17 production.
Our findings suggest that hypoxia and HIF-1α may function in conjunction with TLR-stimulated innate immune responses to drive inflammation in RA. This pathway may serve as a therapeutic target for the disease.
滑膜成纤维细胞增生、淋巴细胞浸润和组织缺氧是类风湿关节炎（RA）的主要特征。大量数据支持 Toll 样受体（TLR）在 RA 中起关键作用。关于缺氧对 RA 中 TLR 诱导炎症的影响知之甚少。本研究旨在揭示缺氧及其调节因子缺氧诱导因子-1α（HIF-1α）对 RA 滑膜成纤维细胞（RASF）对 TLR 配体炎症反应的影响。
通过用 Na2S2O4 孵育诱导 RASF 缺氧。使用 TLR3 配体 polyIC、TLR2 配体肽聚糖、TLR4 配体 LPS 和 TLR9 配体 CpG 刺激细胞。通过 RT-PCR、qPCR 和 ELISA 测定缺氧对 TLR 诱导的炎症介质的影响。过表达 HIF-1α 及其敲低其表达以揭示其基本作用。通过流式细胞术分析 Th1/Th17 细胞，以及 RASF/T 细胞共培养后 ELISA 测定 IFN-γ/IL-17 产生，测定 RASF 诱导的炎症性 T 细胞扩增。
缺氧增强了不同 TLR 配体刺激的 RASF 中炎症细胞因子、金属蛋白酶和 VEGF 的表达，尤其是 polyIC，一种病毒或凋亡细胞 dsRNA 的合成模拟物。HIF-1α 在这种协同作用中起基本作用。此外，HIF-1α 过表达增强了 RASF 介导的炎症性 Th1 和 Th17 细胞的扩增，导致促炎 IFN-γ 和 IL-17 的产生。
我们的研究结果表明，缺氧和 HIF-1α 可能与 TLR 刺激的先天免疫反应一起作用，驱动 RA 中的炎症。该途径可能成为该疾病的治疗靶点。
