Molecular and Clinical Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health , Bethesda, Maryland.
Critical Care Medicine Department, Clinical Center, National Institutes of Health , Bethesda, Maryland.
Am J Physiol Cell Physiol. 2018 Oct 1;315(4):C494-C501. doi: 10.1152/ajpcell.00336.2017. Epub 2018 Jun 27.
Neutrophils increase production of reactive oxygen species, including superoxide, hydrogen peroxide (HO), and hydroxyl radical, to destroy invading microorganisms under pathological conditions. Conversely, oxidative stress conditions, such as the presence of HO, induce neutrophil apoptosis, which helps to remove neutrophils after inflammation. However, the detailed molecular mechanisms that are involved in the latter process have not been elucidated. In this study, we investigated the potential role of olfactomedin 4 (Olfm4) in HO-induced superoxide production and apoptosis in mouse neutrophils. We have demonstrated that Olfm4 is not required for maximal-dosage PMA- and Escherichia coli bacteria-induced superoxide production, but Olfm4 contributes to suboptimal-dosage PMA- and HO-induced superoxide production. Using an NADPH oxidase inhibitor and gp91phox-deficient mouse neutrophils, we found that NAPDH oxidase was required for PMA-stimulated superoxide production and that Olfm4 mediated HO-induced superoxide production through NADPH oxidase, in mouse neutrophils. We have shown that neutrophils from Olfm4-deficient mice exhibited reduced HO-induced apoptosis compared with neutrophils from wild-type mice. We also demonstrated that neutrophils from Olfm4-deficient mice exhibited reduced HO-stimulated mitochondrial damage and membrane permeability, and as well as reduced caspase-3 and caspase-9 activity, compared with neutrophils from wild-type mice. Moreover, the cytoplasmic translocation of the proapoptotic mitochondrial proteins Omi/HtrA2 and Smac/DIABLO in response to HO was reduced in neutrophils from Olfm4-deficient mice compared with neutrophils from wild-type mice. Our study demonstrates that Olfm4 contributes to HO-induced NADPH oxidase activation and apoptosis in mouse neutrophils. Olfactomedin 4 might prove to be a potential target for future studies on inflammatory neutrophil biology and for inflammatory disease treatment.
中性粒细胞在病理条件下会增加活性氧物质的产生，包括超氧自由基、过氧化氢 (HO) 和羟自由基，以破坏入侵的微生物。相反，氧化应激条件，如 HO 的存在，诱导中性粒细胞凋亡，这有助于炎症后清除中性粒细胞。然而，后者过程中涉及的详细分子机制尚未阐明。在这项研究中，我们研究了嗅觉素 4 (Olfm4) 在 HO 诱导的小鼠中性粒细胞中超氧化物产生和凋亡中的潜在作用。我们已经证明，Olfm4 对于最大剂量 PMA 和大肠杆菌诱导的超氧自由基产生不是必需的，但 Olfm4 有助于亚最佳剂量 PMA 和 HO 诱导的超氧自由基产生。使用 NADPH 氧化酶抑制剂和 gp91phox 缺陷型小鼠中性粒细胞，我们发现 NADPH 氧化酶是 PMA 刺激超氧自由基产生所必需的，而 Olfm4 通过 NADPH 氧化酶介导 HO 诱导的超氧自由基产生，在小鼠中性粒细胞中。我们已经表明，Olfm4 缺陷型小鼠的中性粒细胞与野生型小鼠的中性粒细胞相比，HO 诱导的凋亡减少。我们还表明，与野生型小鼠的中性粒细胞相比，Olfm4 缺陷型小鼠的中性粒细胞表现出 HO 刺激的线粒体损伤和膜通透性降低，以及 caspase-3 和 caspase-9 活性降低。此外，与野生型小鼠的中性粒细胞相比，Olfm4 缺陷型小鼠的中性粒细胞中响应 HO 的促凋亡线粒体蛋白 Omi/HtrA2 和 Smac/DIABLO 的细胞质易位减少。我们的研究表明，Olfm4 有助于 HO 诱导的小鼠中性粒细胞中 NADPH 氧化酶的激活和凋亡。Olfactomedin 4 可能被证明是未来炎症性中性粒细胞生物学和炎症性疾病治疗研究的潜在靶点。
