Department of Pulmonary and Critical Care Medicine, Shengjing Hospital of China Medical University, Shenyang 110004, China.
Department of Oncology, Shengjing Hospital of China Medical University, Shenyang, Liaoning 110000, China.
J Immunol Res. 2021 Nov 13;2021:9409777. doi: 10.1155/2021/9409777. eCollection 2021.
is an intracellular pathogen that can cause Legionnaire's disease by invading alveolar epithelial cells and macrophages. The major outer membrane protein (MOMP) plays an important role in the interaction between bacteria and host cells. However, the role of MOMP in the process of invasion of macrophages and its working mechanism remain unknown. We aimed to explore the effects of MOMP on phagocytosis and chemotaxis of RAW 264.7 macrophages. The chemotactic activity, toxicity, and phagocytosis of RAW 264.7 cocultured with different concentrations of MOMP were determined by Transwell, CCK-8, and neutral red uptake assays, respectively. Target genes were detected by double-luciferase and pull down assays. qRT-PCR and Western blot were performed to analyze the expression of several important proteins involved in the immune response pathway, including coronin-1, interleukins (IL-10), forkhead transcription factor 1 (FOXO1), nucleotide-binding oligomerization domain protein (NOD) 1, NOD2, and receptor-interacting protein (RIP) 2. After coculturing with MOMP, cytological observation indicated a decrease of phagocytosis and a marked increase of chemotaxis in RAW 264.7 macrophages. The phagocytosis degree of RAW 264.7 macrophage varied with the concentration gradient of MOMP in a time-dependent manner. MOMP could increase the expression levels of MCP-1, IL-10, NOD2, and RIP2 and decrease the expression levels of FOXO1 and coronin-1 in cell culture supernatants. In addition, we found that FOXO1 could promote its transcription by binding to the promoter of coronin-1. The results of the present study suggested that MOMP could inhibit phagocytosis and facilitate chemotaxis of RAW 264.7 macrophage, which might be associated with the FOXO1/coronin-1 axis.
是一种细胞内病原体，可通过侵袭肺泡上皮细胞和巨噬细胞引起军团病。主要外膜蛋白（MOMP）在细菌与宿主细胞相互作用中发挥重要作用。然而，MOMP 在巨噬细胞入侵过程中的作用及其工作机制尚不清楚。我们旨在探讨 MOMP 对 RAW 264.7 巨噬细胞吞噬和趋化作用的影响。通过 Transwell、CCK-8 和中性红摄取试验分别测定 RAW 264.7 与不同浓度 MOMP 共培养后的趋化活性、毒性和吞噬作用。双荧光素酶和下拉试验检测靶基因。qRT-PCR 和 Western blot 分析参与免疫反应途径的几种重要蛋白的表达，包括 coronin-1、白细胞介素（IL-10）、叉头转录因子 1（FOXO1）、核苷酸结合寡聚化结构域蛋白（NOD）1、NOD2 和受体相互作用蛋白（RIP）2。与 MOMP 共培养后，细胞学观察表明 RAW 264.7 巨噬细胞的吞噬作用减少，趋化作用明显增加。RAW 264.7 巨噬细胞的吞噬程度随 MOMP 浓度梯度呈时间依赖性变化。MOMP 可增加细胞培养上清液中 MCP-1、IL-10、NOD2 和 RIP2 的表达水平，降低 FOXO1 和 coronin-1 的表达水平。此外，我们发现 FOXO1 可以通过结合 coronin-1 的启动子来促进其转录。本研究结果表明，MOMP 可抑制 RAW 264.7 巨噬细胞的吞噬作用并促进其趋化作用，这可能与 FOXO1/coronin-1 轴有关。
