Department of Orthopaedic Surgery, UConn Health, Farmington, Connecticut, USA; Department of Medicine, UConn Health, Farmington, Connecticut, USA; UConn Musculoskeletal Institute, UConn Health, Farmington, Connecticut, USA.
Department of Orthopaedic Surgery, UConn Health, Farmington, Connecticut, USA; UConn Musculoskeletal Institute, UConn Health, Farmington, Connecticut, USA.
J Biol Chem. 2023 Dec;299(12):105372. doi: 10.1016/j.jbc.2023.105372. Epub 2023 Oct 20.
Notch regulates the immune and inflammatory response and has been associated with the pathogenesis of osteoarthritis in humans and preclinical models of the disease. Notch2 mice harbor a NOTCH2 gain-of-function and are sensitized to osteoarthritis, but the mechanisms have not been explored. We examined the effects of tumor necrosis factor α (TNFα) in chondrocytes from Notch2 mice and found that NOTCH2 enhanced the effect of TNFα on Il6 and Il1b expression. Similar results were obtained in cells from a conditional model of NOTCH2 gain-of-function, Notch2 mice, and following the expression of the NOTCH2 intracellular domain in vitro. Recombination signal-binding protein for immunoglobulin Kappa J region partners with the NOTCH2 intracellular domain to activate transcription; in the absence of Notch signaling it inhibits transcription, and Rbpj inactivation in chondrocytes resulted in Il6 induction. Although TNFα induced IL6 to a greater extent in the context of NOTCH2 activation, there was a concomitant inhibition of Notch target genes Hes1, Hey1, Hey2, and Heyl. Electrophoretic mobility shift assay demonstrated displacement of recombination signal-binding protein for immunoglobulin Kappa J region from DNA binding sites by TNFα explaining the increased Il6 expression and the concomitant decrease in Notch target genes. NOTCH2 enhanced the effect of TNFα on NF-κB signaling, and RNA-Seq revealed increased expression of pathways associated with inflammation and the phagosome in NOTCH2 overexpressing cells in the absence and presence of TNFα. Collectively, NOTCH2 has important interactions with TNFα resulting in the enhanced expression of Il6 and inflammatory pathways in chondrocytes.
Notch 调节免疫和炎症反应，与人类骨关节炎和疾病的临床前模型的发病机制有关。 Notch2 小鼠携带 Notch2 功能获得性突变，对骨关节炎敏感，但机制尚未探索。我们研究了肿瘤坏死因子 α (TNFα) 在 Notch2 小鼠软骨细胞中的作用，发现 NOTCH2 增强了 TNFα 对 Il6 和 Il1b 表达的影响。在 Notch2 功能获得性条件模型、Notch2 小鼠的细胞中和体外表达 NOTCH2 细胞内结构域时，也得到了类似的结果。免疫球蛋白 Kappa J 区重组信号结合蛋白与 NOTCH2 细胞内结构域结合，激活转录；在没有 Notch 信号的情况下，它抑制转录，软骨细胞中 Rbpj 的失活导致 Il6 的诱导。尽管 TNFα 在 NOTCH2 激活的情况下更能诱导 IL6，但 Notch 靶基因 Hes1、Hey1、Hey2 和 Heyl 的表达也同时受到抑制。电泳迁移率变动分析表明，TNFα 可将免疫球蛋白 Kappa J 区重组信号结合蛋白从 DNA 结合位点上置换下来，从而解释了 Il6 表达增加和 Notch 靶基因同时减少的现象。NOTCH2 增强了 TNFα 对 NF-κB 信号的作用，RNA-Seq 揭示了在缺乏和存在 TNFα的情况下，NOTCH2 过表达细胞中与炎症和吞噬体相关的途径表达增加。总之，NOTCH2 与 TNFα 有重要的相互作用，导致软骨细胞中 Il6 和炎症途径的表达增强。
