Effect And Mechanism Of Glycolysis In Acute Otitis Media

Objective—Acute Otitis Media(AOM)is one of the most common infectious diseases in the otolaryngology,especially children.Streptococcus pneumoniae is a common pathogen of acute otitis media.Recent studies indicate that infection induces glycolytic switch in immune cells and regulates immune cell function and inflammatory responses.However,little is known about the immunometabolism in AOM.This study was undertaken to evaluate whether changes in glycolytic pathway in AOM could play a role in inflammation response and middle ear damage.Methods—In a mouse model of acute otitis media via transbullar injection with Streptococcus pneumoniae(S.pn)serotype 19 F,the changes of glycolytic metabolism was evaluated using a glycolysis inhibitor,2-deoxyD-glucose(2DG)or 1400w(iNOS inhibitor).The levels of glycolytic metabolism were determined by measuring the expression of glycolysisrelated genes and the production of metabolic reactants.After S.pneumonia infection,HE stain,immunofluorescence,immunohistochemistry and enzyme-linked immunosorbent assay(ELISA)were performed to measure the effect of 2DG on inflammatory response,S.pn clearance,HIF-1? expression and cytokine secretion in AOM,respectively.Results—The analysis of q-PCR revealed changes of immunometabolism during S.pn AOM that are characterized by upregulation of key glycolytic enzymes and transporters for glucose uptake and lactate secretion.Hypoxia inducible factor 1 alpha(HIF-1?),a regulator of glycolysis metabolism,were also up-regulate during AOM and induced the production of proinflammatory cytokines IL-1? and TNF-?.We found decreased mRNA and protein levels of HIF-1? in middle ear epithelial and inflammatory cells after 2DG treated during AOM accompanied by reduced production of IL-1? and TNF-?.Our results show that glycolytic inhibitors decreased the clearance of S.pn,influx of the cells into infection site and middle ear tissue injury,as well as the ability of neutrophil phagocytosis and kill S.pn was impaired.Moreover,after treatment with iNOS inhibitors,glycolysis-related genes were down regulated and the level of glucose consumption and lactate production was reduced at same time.In addition bacterial clearance was impaired.Conclusion—In summary,our findings suggest that HIF-1? participates in glycolysis metabolism during AOM and the increased of glycolysis facilitates clearance of S.pn and aggravates middle ear injury in response to S.pn infection.The glycolytic inhibitor 2DG reduces the phagocytosis and killing capacity of neutrophils and thereby suppresses the clearance of S.pn in the middle ear cavity.In addition,NO can regulate glycolytic metabolism to exert bactericidal activity.