Department of Cardiovascular Science, University of Sheffield, Sheffield S10 2RX, UK.
Circ Res. 2013 Jun 7;112(12):1583-91. doi: 10.1161/CIRCRESAHA.111.300119. Epub 2013 Apr 5.
Hypoxia followed by reoxygenation promotes inflammation by activating nuclear factor κB transcription factors in endothelial cells (ECs). This process involves modification of the signaling intermediary tumor necrosis factor receptor-associated factor 6 with polyubiquitin chains. Thus, cellular mechanisms that suppress tumor necrosis factor receptor-associated factor 6 ubiquitination are potential therapeutic targets to reduce inflammation in hypoxic tissues.
In this study, we tested the hypothesis that endothelial activation in response to hypoxia-reoxygenation can be influenced by Cezanne, a deubiquitinating enzyme that cleaves ubiquitin from specific modified proteins.
Studies of cultured ECs demonstrated that hypoxia (1% oxygen) induced Cezanne via p38 mitogen-activated protein kinase-dependent transcriptional and post-transcriptional mechanisms. Hypoxia-reoxygenation had minimal effects on proinflammatory signaling in unmanipulated ECs but significantly enhanced Lys63 polyubiquitination of tumor necrosis factor receptor-associated factor 6, activation of nuclear factor κB, and expression of inflammatory genes after silencing of Cezanne. Thus, although hypoxia primed cells for inflammatory activation, it simultaneously induced Cezanne, which impeded signaling to nuclear factor κB by suppressing tumor necrosis factor receptor-associated factor 6 ubiquitination. Similarly, ischemia induced Cezanne in the murine kidney in vascular ECs, glomerular ECs, podocytes, and epithelial cells, and genetic deletion of Cezanne enhanced renal inflammation and injury in murine kidneys exposed to ischemia followed by reperfusion.
We conclude that inflammatory responses to ischemia are controlled by a balance between ubiquitination and deubiquitination, and that Cezanne is a key regulator of this process. Our observations have important implications for therapeutic targeting of inflammation and injury during ischemia-reperfusion.
缺氧再复氧会通过激活内皮细胞（ECs）中的核因子 κB 转录因子促进炎症。这一过程涉及 TNF 受体相关因子 6（TRAF6）信号转导中间物的多泛素化修饰。因此，抑制 TRAF6 泛素化的细胞机制可能成为减少缺氧组织炎症的潜在治疗靶点。
本研究旨在通过去泛素化酶 Cezanne 检测内皮细胞对缺氧-复氧反应的激活，验证内皮细胞激活可受 Cezanne 影响的假说。Cezanne 可特异性地从修饰蛋白上切割泛素。
在培养的 ECs 中进行的研究表明，低氧（1%氧气）通过 p38 有丝分裂原激活的蛋白激酶依赖性转录和转录后机制诱导 Cezanne。低氧-复氧对未处理 ECs 的促炎信号作用不大，但在沉默 Cezanne 后，可显著增强 TRAF6 的 Lys63 多泛素化、核因子 κB 的激活和炎症基因的表达。因此，尽管低氧使细胞为炎症激活做好准备，但同时诱导 Cezanne，通过抑制 TRAF6 泛素化来抑制核因子 κB 的信号转导。同样，在血管内皮细胞、肾小球内皮细胞、足细胞和上皮细胞中，缺血诱导 Cezanne 在小鼠肾脏中表达，并且 Cezanne 基因缺失增强了缺血后再灌注小鼠肾脏的炎症和损伤。
我们的结论是，对缺血的炎症反应受泛素化和去泛素化的平衡控制，Cezanne 是该过程的关键调节因子。我们的观察结果对缺血再灌注期间炎症和损伤的治疗靶向具有重要意义。
