From the Department of Orthopaedic Surgery and Graduate Program in Cell and Developmental Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
J Biol Chem. 2014 Mar 14;289(11):7374-87. doi: 10.1074/jbc.M113.526111. Epub 2014 Jan 24.
The objective of the study was to examine the regulation of CCN2 by inflammatory cytokines, IL-1β, and TNF-α and to determine whether CCN2 modulates IL-1β-dependent catabolic gene expression in nucleus pulposus (NP) cells. IL-1β and TNF-α suppress CCN2 mRNA and protein expression in an NF-κB-dependent but MAPK-independent manner. The conserved κB sites located at -93/-86 and -546/-537 bp in the CCN2 promoter mediated this suppression. On the other hand, treatment of NP cells with IL-1β in combination with CCN2 suppressed the inductive effect of IL-1β on catabolic genes, including MMP-3, ADAMTS-5, syndecan 4, and prolyl hydroxylase 3. Likewise, silencing of CCN2 in human NP cells resulted in elevated basal expression of several catabolic genes and inflammatory cytokines like IL-6, IL-4, and IL-12 as measured by gene expression and cytokine protein array, respectively. Interestingly, the suppressive effect of CCN2 on IL-1β was independent of modulation of NF-κB signaling. Using disintegrins, echistatin, and VLO4, peptide inhibitors to αvβ3 and α5β1 integrins, we showed that CCN2 binding to both integrins was required for the inhibition of IL-1β-induced catabolic gene expression. It is noteworthy that analysis of human tissues showed a trend of altered expression of these integrins during degeneration. Taken together, these results suggest that CCN2 and inflammatory cytokines form a functional negative feedback loop in NP cells that may be important in the pathogenesis of disc disease.
本研究旨在探讨炎症细胞因子 IL-1β 和 TNF-α 对 CCN2 的调控作用,并确定 CCN2 是否调节 NP 细胞中 IL-1β 依赖性的分解代谢基因表达。IL-1β 和 TNF-α 通过 NF-κB 但不依赖 MAPK 途径抑制 CCN2 mRNA 和蛋白表达。CCN2 启动子中的保守 κB 位点(-93/-86 和 -546/-537bp)介导了这种抑制作用。另一方面,IL-1β 与 CCN2 联合处理 NP 细胞可抑制 IL-1β 对包括 MMP-3、ADAMTS-5、 syndecan 4 和脯氨酰羟化酶 3 在内的分解代谢基因的诱导作用。同样,通过基因表达和细胞因子蛋白芯片分别检测到,沉默人 NP 细胞中的 CCN2 会导致几种分解代谢基因和炎症细胞因子(如 IL-6、IL-4 和 IL-12)的基础表达升高。有趣的是,CCN2 对 IL-1β 的抑制作用不依赖于 NF-κB 信号的调节。使用 disintegrins、echistatin 和 VLO4,即 αvβ3 和 α5β1 整合素的肽抑制剂,我们表明 CCN2 与这两种整合素的结合对于抑制 IL-1β 诱导的分解代谢基因表达是必需的。值得注意的是,对人类组织的分析显示,这些整合素的表达在退变过程中存在改变的趋势。综上所述,这些结果表明,CCN2 和炎症细胞因子在 NP 细胞中形成了一个功能性的负反馈回路,这可能在椎间盘疾病的发病机制中具有重要意义。