| Summary: | 碩士 === 國立成功大學 === 分子醫學研究所 === 94 === Activated neutrophils respond to stimuli with a characteristic “respiratory burst” which is mediated by NADPH oxidase. NADPH oxidase consists of a membrane bound factors gp91phox, p22phox and the cytosol factors p47phox, p67phox, p40phox. The active NADPH oxidase triggers rapid reduction of oxygen to the superoxide anion (O2-) and other reactive oxygen species (ROS), which is so called respiratory burst. Numerous studies have demonstrated that ROS generated by NADPH oxidase not only kill invading pathogens and modulate immune response, but also damage the adjacent tissues. Therefore, the excess or deficiency of ROS is a danger in our bodies. Priming of ROS is an important phenotype of activated neutrophils. It is defined as enhancement of superoxide generation in response to a second activating stimulus. Many pro-inflammatory cytokines have been referred to as priming agents. If the molecular mechanisms of priming process are clearly defined, we will be able to use priming agents or their inhibitors to control the level of ROS. C-reactive protein (CRP), a membrane of acute-phase proteins, plays some roles on ROS production. Some studies have shown that it can enhance ROS production, but other studies showed it reduces ROS generation. In this study, we recognized CRP as a priming agent and investigated the molecular mechanisms of CRP priming. Furthermore, we tried to demonstrate how CRP enhances and reduces ROS production. At first, we confirmed that CRP, like GM-CSF and LPS, is a priming agent and it can enhance the highest ROS production after secondary stimulus. The p47phox phosphorylation increased in CRP-primed neutrophils, but the expression of cytochrome b558 on cell surface was not affected. We thus demonstrated that CRP primed neutrophils by the increased p47phox phosphorylation. When CRP was in a high concentration (more than 30μg/ml), the increased ROS production was converted to a slightly reduced level. The p47phox phosphorylation and the expression of cytochrome b558 on cell surface also had slightly decreased. Our results indicated that CRP had a concentration dependent dual effect on ROS productionon neutrophils. Through this study, we delineate the role and the molecular mechanism of CRP in the process of neutrophil priming.
|
|---|
