Division of Clinical Medicine, School of Health and Medical Sciences, Örebro University, Örebro, Sweden.
Infect Immun. 2011 Apr;79(4):1489-97. doi: 10.1128/IAI.00777-10. Epub 2011 Jan 24.
Porphyromonas gingivalis is an etiological agent that is strongly associated with periodontal disease, and it correlates with numerous inflammatory disorders, such as cardiovascular disease. Circulating bacteria may contribute to atherogenesis by promoting CD11b/CD18-mediated interactions between neutrophils and platelets, causing reactive oxygen species (ROS) production and aggregation. Lipoxin A₄ (LXA₄) is an endogenous anti-inflammatory and proresolving mediator that is protective of inflammatory disorders. The aim of this study was to investigate the effect of LXA₄ on the P. gingivalis-induced activation of neutrophils and platelets and the possible involvement of Rho GTPases and CD11b/CD18 integrins. Platelet/leukocyte aggregation and ROS production was examined by lumiaggregometry and fluorescence microscopy. Integrin activity was studied by flow cytometry, detecting the surface expression of CD11b/CD18 as well as the exposure of the high-affinity integrin epitope, whereas the activation of Rac2/Cdc42 was examined using a glutathione S-transferase pulldown assay. The study shows that P. gingivalis activates Rac2 and Cdc42 and upregulates CD11b/CD18 and its high-affinity epitope on neutrophils, and that these effects are diminished by LXA₄. Furthermore, we found that LXA₄ significantly inhibits P. gingivalis-induced aggregation and ROS generation in whole blood. However, in platelet-depleted blood and in isolated neutrophils and platelets, LXA₄ was unable to inhibit either aggregation or ROS production, respectively. In conclusion, this study suggests that LXA₄ antagonizes P. gingivalis-induced cell activation in a manner that is dependent on leukocyte-platelet interaction, likely via the inhibition of Rho GTPase signaling and the downregulation of CD11b/CD18. These findings may contribute to new strategies in the prevention and treatment of periodontitis-induced inflammatory disorders, such as atherosclerosis.
牙龈卟啉单胞菌是一种与牙周病密切相关的病因，它与许多炎症性疾病相关，如心血管疾病。循环细菌可能通过促进中性粒细胞和血小板之间的 CD11b/CD18 介导的相互作用，导致活性氧（ROS）的产生和聚集，从而促进动脉粥样硬化的形成。脂氧素 A4（LXA4）是一种内源性抗炎和促解决介质，对炎症性疾病具有保护作用。本研究旨在探讨 LXA4 对牙龈卟啉单胞菌诱导的中性粒细胞和血小板激活的影响，以及 Rho GTPases 和 CD11b/CD18 整合素可能的参与作用。通过发光聚集仪和荧光显微镜检测血小板/白细胞聚集和 ROS 的产生。通过流式细胞术研究整合素活性，检测 CD11b/CD18 的表面表达以及高亲和力整合素表位的暴露，而 Rac2/Cdc42 的激活则使用谷胱甘肽 S-转移酶下拉测定法进行检测。研究表明，牙龈卟啉单胞菌激活 Rac2 和 Cdc42，并上调中性粒细胞上的 CD11b/CD18 及其高亲和力表位，而 LXA4 可减弱这些作用。此外，我们发现 LXA4 可显著抑制全血中牙龈卟啉单胞菌诱导的聚集和 ROS 的产生。然而，在血小板耗竭的血液中和分离的中性粒细胞和血小板中，LXA4 分别不能抑制聚集或 ROS 的产生。总之，本研究表明，LXA4 以依赖于白细胞-血小板相互作用的方式拮抗牙龈卟啉单胞菌诱导的细胞激活，可能通过抑制 Rho GTPase 信号转导和下调 CD11b/CD18。这些发现可能为牙周病引起的炎症性疾病（如动脉粥样硬化）的预防和治疗提供新策略。
