Myeloperoxidase Promotes Pneumococcal Clearance And Induces Tissue Damage In Acute Otitis Media

Acute otitis media (AOM) is one of the most common infectious diseases in children, neutrophils are the first effective cells to arrive at a site of infection, and crucial to control the infection of Streptococcus pneumoniae (S.pn). Clinical studies have shown that a high expression level of Myeloperoxidase (MPO) in middle ear fluid and epithelia mucosa layer in patients with otitis media, but its role in otitis media has not been reported. In this research, we want to study the function of MPO in otitis media by constructing a model of S.pn AOM in C57BL/6 mice, and using specific inhibitors in vivo. In S.pn serotype 6B infected model of AOM in mice, we detected a high level of MPO, in addition, S.pn also induced intracellular reactive oxidative species (ROS) and neutrophil elastase (NE) production. In this research, we found that MPO played an important role in the sterilization process, but ROS only participated the scavenging effect on bacteria in early period. Once Inhibiting MPO activity in vivo, ROS production decreased, but did not affect the expression of NE. Further study the effect of them on tissue in AOM, we found all of them induced tissue injury. Finally, this study showed that MPO may induced tissue damage by directly function on epithelium and inducing neutrophil apoptosis and necrosis in AOM. In summary, this study suggests that MPO plays critical roles in killing S.pn and induced tissue injury in S.pn AOM, in addition, ROS and NE also play important roles in tissue damage.