Ma Fang, Yang Shifang, Zhou Mingxu, Lu Yu, Deng Bihua, Zhang Jinqiu, Fan Hongjie, Wang Guangyu
Institute of Veterinary Immunology & Engineering, National Research Center of Engineering and Technology for Veterinary Biologicals, Jiangsu Academy of Agricultural Sciences, Nanjing 210014, China; School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, China; Jiangsu Key Laboratory for Food Quality and Safety-State Key Laboratory Cultivation Base, Ministry of Science and Technology, Nanjing 210014, China.
College of Veterinary Medicine, Nanjing Agriculture University, Nanjing, China.
Vet Microbiol. 2022 May;268:109427. doi: 10.1016/j.vetmic.2022.109427. Epub 2022 Apr 4.
Streptococcus agalactiae (S. agalactiae) continues to be challenging for milk quality in some countries and leads to huge economic losses. A large number of neutrophils are recruited into inflammatory foci when S. agalactiae infection occurs, and most studies have focused on the interaction between neutrophil extracellular traps (NETs) and this bacterium in the context of human pathogenicity. However, there is little information on the NET formation mechanism induced by S. agalactiae in the context of bovine mastitis. Here, neutrophils isolated from BALB/c mice were infected with S. agalactiae SAG-FX17, and NET formation was evaluated. SAG-FX17 could induce NADPH oxidase-derived reactive oxygen species (NOX-ROS)-dependent NET formation, and 21.8% of bacteria could be eliminated by NETs via NET DNA and associated proteins. SAG-FX17 could induce the phosphorylation of p38 MAPK, ERK1/2 MAPK, and JNK/SAPK in neutrophils. However, only ERK1/2 MAPK was shown to play an important role in SAG-FX17-induced NET formation. Importantly, NOX-ROS production occurs upstream of ERK1/2 MAPK activation and then induces NET release. ERK1/2 MAPK phosphorylation can, in turn, enhance NOX-ROS generation, which further contributes to NET release and bacterial elimination. This study provides evidence of the molecular mechanism underlying serotype Ia S. agalactiae SAG-FX17-induced NET formation and the interaction between bacteria and NETs, and these findings will increase our knowledge about bacterial mastitis in dairy cattle and contribute to the prevention and clinical treatment of bovine mastitis.
无乳链球菌在一些国家仍然对牛奶质量构成挑战，并导致巨大的经济损失。当发生无乳链球菌感染时，大量中性粒细胞会被招募到炎症病灶中，并且大多数研究都集中在中性粒细胞胞外陷阱（NETs）与这种细菌在人类致病性背景下的相互作用。然而，关于无乳链球菌在牛乳腺炎背景下诱导NET形成机制的信息很少。在此，用无乳链球菌SAG-FX17感染从BALB/c小鼠分离的中性粒细胞，并评估NET的形成。SAG-FX17可诱导NADPH氧化酶衍生的活性氧（NOX-ROS）依赖性NET形成，并且NETs可通过NET DNA和相关蛋白清除21.8%的细菌。SAG-FX17可诱导中性粒细胞中p38 MAPK、ERK1/2 MAPK和JNK/SAPK的磷酸化。然而，只有ERK1/2 MAPK在SAG-FX17诱导的NET形成中起重要作用。重要的是，NOX-ROS的产生发生在ERK1/2 MAPK激活的上游，然后诱导NET释放。ERK1/2 MAPK磷酸化反过来又可增强NOX-ROS的产生，这进一步促进NET释放和细菌清除。本研究提供了血清型Ia无乳链球菌SAG-FX17诱导NET形成以及细菌与NETs之间相互作用的分子机制证据，这些发现将增加我们对奶牛细菌性乳腺炎的认识，并有助于牛乳腺炎的预防和临床治疗。
