Seguchi Harumichi, Kobayashi Toshihiro
Department of Anatomy and Cell Biology, Kochi Medical School, Nankoku-shi, Japan.
J Electron Microsc (Tokyo). 2002;51(2):87-91. doi: 10.1093/jmicro/51.2.87.
Neutrophils represent the first line of defence against invading microorganisms. An important part of this defence mechanism is the generation of superoxide (O2*-) and its reactive derivatives after stimulation by a variety of agents. This oxidant production is linked to the activation of NADPH oxidase, which is composed of cytosolic components (p47-phox and p67-phox) and membrane components (p22-phox and gp91-phox). Previous studies have shown that NADPH oxidase resides in the plasma membrane and the traditional view holds that cytoplasmic components of NADPH oxidase are brought into the neighbourhood of the plasma membrane and then conjugated with its membrane components upon stimulation. This review focuses on the evaluation of NADPH oxidase-activated sites in human neutrophils. Based on electron microscopic analysis, O2*- is first generated upon stimulation with certain stimulants, such as phorbol myristate acetate, within a specialized intracellular compartment containing alkaline phosphatase, and not on the plasma membrane, as previously thought. In addition, the cytosolic component of NADPH oxidase, p47-phox, accumulates at the juxtaposition of intracellular compartments but not of the plasma membrane. These results demonstrate that initial O2*- production occurs in an intracellular pool in human neutrophils. The oxidant-producing granules then bind directly to the plasma membrane or fuse to form larger structures that eventually become to be associated with the plasma membrane, and O2*- is released extracellularly from the neutrophils.
中性粒细胞是抵御入侵微生物的第一道防线。这种防御机制的一个重要部分是在多种因子刺激后产生超氧化物（O2*-）及其活性衍生物。这种氧化剂的产生与NADPH氧化酶的激活有关，NADPH氧化酶由胞质成分（p47-phox和p67-phox）和膜成分（p22-phox和gp91-phox）组成。先前的研究表明，NADPH氧化酶存在于质膜中，传统观点认为，NADPH氧化酶的胞质成分在受到刺激后被带到质膜附近，然后与质膜成分结合。这篇综述着重评估人类中性粒细胞中NADPH氧化酶的激活位点。基于电子显微镜分析，在用某些刺激物（如佛波酯）刺激后，O2*-首先在含有碱性磷酸酶的特定细胞内区室中产生，而不是如先前认为的那样在质膜上产生。此外，NADPH氧化酶的胞质成分p47-phox在细胞内区室的并列处积累，而不是在质膜处积累。这些结果表明，人类中性粒细胞中最初的O2*-产生发生在细胞内池。产生氧化剂的颗粒然后直接与质膜结合或融合形成更大的结构，最终与质膜相关联，O2*-从中性粒细胞释放到细胞外。
