Sundqvist Martina, Christenson Karin, Björnsdottir Halla, Osla Veronica, Karlsson Anna, Dahlgren Claes, Speert David P, Fasth Anders, Brown Kelly L, Bylund Johan
The Phagocyte Research Group, Department of Rheumatology and Inflammation Research, University of Gothenburg, Gothenburg, Sweden.
Department of Pediatrics, Centre for Understanding and Preventing Infection in Children, University of British Columbia, Vancouver, BC, Canada.
Front Immunol. 2017 Dec 21;8:1828. doi: 10.3389/fimmu.2017.01828. eCollection 2017.
Chronic granulomatous disease (CGD) is caused by mutations in genes that encode the NADPH-oxidase and result in a failure of phagocytic cells to produce reactive oxygen species (ROS) this enzyme system. Patients with CGD are highly susceptible to infections and often suffer from inflammatory disorders; the latter occurs in the absence of infection and correlates with the spontaneous production of inflammatory cytokines. This clinical feature suggests that NADPH-oxidase-derived ROS are not required for, or may even suppress, inflammatory processes. Experimental evidence, however, implies that ROS are in fact required for inflammatory cytokine production. By using a myeloid cell line devoid of a functional NADPH-oxidase and primary CGD cells, we analyzed intracellular oxidants, signs of oxidative stress, and inflammatory cytokine production. Herein, we demonstrate that phagocytes lacking a functional NADPH-oxidase, namely primary CGD phagocytes and a gp91-deficient cell line, display elevated levels of ROS derived from mitochondria. Accordingly, these cells, despite lacking the major source of cellular ROS, display clear signs of oxidative stress, including an induced expression of antioxidants and altered oxidation of cell surface thiols. These observed changes in redox state were not due to abnormalities in mitochondrial mass or membrane integrity. Finally, we demonstrate that increased mitochondrial ROS enhanced phosphorylation of ERK1/2, and induced production of IL8, findings that correlate with previous observations of increased MAPK activation and inflammatory cytokine production in CGD cells. Our data show that elevated baseline levels of mitochondria-derived oxidants lead to the counter-intuitive observation that CGD phagocytes are under oxidative stress and have enhanced MAPK signaling, which may contribute to the elevated basal production of inflammatory cytokines and the sterile inflammatory manifestations in CGD.
慢性肉芽肿病（CGD）是由编码NADPH氧化酶的基因突变引起的，导致吞噬细胞无法通过该酶系统产生活性氧（ROS）。CGD患者极易感染，且常患有炎症性疾病；后者在无感染的情况下发生，与炎症细胞因子的自发产生相关。这一临床特征表明，NADPH氧化酶衍生的ROS并非炎症过程所必需，甚至可能抑制炎症过程。然而，实验证据表明，ROS实际上是炎症细胞因子产生所必需的。通过使用缺乏功能性NADPH氧化酶的髓系细胞系和原发性CGD细胞，我们分析了细胞内氧化剂、氧化应激迹象和炎症细胞因子的产生。在此，我们证明，缺乏功能性NADPH氧化酶的吞噬细胞，即原发性CGD吞噬细胞和gp91缺陷细胞系，显示出来自线粒体的ROS水平升高。因此，这些细胞尽管缺乏细胞ROS的主要来源，但仍显示出明显的氧化应激迹象，包括抗氧化剂的诱导表达和细胞表面硫醇氧化的改变。这些观察到的氧化还原状态变化并非由于线粒体质量或膜完整性异常。最后，我们证明线粒体ROS增加会增强ERK1/2的磷酸化，并诱导IL8的产生，这些发现与之前在CGD细胞中观察到的MAPK激活增加和炎症细胞因子产生相关。我们的数据表明，线粒体衍生氧化剂的基线水平升高导致了一个与直觉相反的观察结果，即CGD吞噬细胞处于氧化应激状态，并且MAPK信号增强，这可能导致炎症细胞因子的基础产生增加以及CGD中的无菌性炎症表现。
