Mechanism Of Neutrophil Extracellular Traps Formation In Mouse Pneumococcal Acute Otitis Media

Otitis media(OM) is a prevalent pediatric infection, and Streptococcus pneumoniae(S.pn) is one of the most commonly isolated bacteria in OM. In response to invading microbial pathogens, Neutrophils are recruited to the sites of infection firstly. Neutrophils employ three major strategies to combat microbes: phagocytosis, degranulation, and the release of neutrophil extracellular traps(NETs). NETs can bind bacteria and prevent them from spreading. S.pn appears to have evolved several mechanisms to survive such an inflammatory response. NETs may even lead to bacterial persistence or disease chronicity. Therefore, this study is designed to address the mechanisms of NETs formation in mouse pneumococcal AOM. In this study, we stimulated neutrophils isolated from mouse bone marrow with S.pn to establish a stable operation method in vitro, induced mouse AOM via transbullar injection of S.pn, and later compared the formation of NETs between WT and TLR4-/- mice, testified the results by in vitro tests at last. S.pn was found to be a potent inducer of NETs production and the formation of NETs was significantly decreased after being treated with DNase or DPI. NETs were visible in middle ear cavity of mouse infected with S.pn, and formation of NETs was decreased in TLR4-/- mice, at the same time, expression of NE was downregulated. In general, TLR4 may participate in formation of NETs in mouse AOM induced by S.pn through regulating NE activity.