Macrophage extracellular traps are induced by Mycoplasma bovis in bovine macrophages through NADPH oxidase/ROS‐dependent manner and their antibacterial efficacy

Mycoplasma bovis has emerged as a significant pathogen in cattle, leading to considerable economic losses in the cattle industry. It is associated with various clinical syndromes, including pneumoniae, mastitis, and arthritis. The innate immune response, particularly macrophages, plays a crucial role in combating infections caused by such pathogens. The release of macrophage extracellular traps (METs) represents a novel defense mechanism employed by macrophages; however, the impact of M. bovis on the formation of METs in bovine macrophages remains unknown. Therefore, the primary objective of this study is to investigate the mechanism by which M. bovis affects the formation of bovine METs and to evaluate their bactericidal efficacy. Our findings revealed that the bovine macrophage cell lines released DNA fibrils that colocalized with histones and cellular proteins in response to M. bovis infection, as visualized by confocal and scanning electron microscopy. Moreover, the formation of METs was found to depend on NADPH oxidase, which is crucial for reactive oxygen species generation. Importantly, the formation of METs led to cell lysis in response to M. bovis infection, as indicated by the release of lactate dehydrogenase, and this process was found to be independent of apoptosis and pyroptosis. Moreover, the release of METs in response to M. bovis infection was effective in both killing and restricting its growth. Overall, our study first described how METs were produced in bovine macrophages that responded to M. bovis and demonstrated their significant function in bacterial killing, which is helpful to improve our understanding of the host's immune defense against this pathogen.