Distinct signalling mechanisms mediate neutrophil attraction to bacterial infection and tissue injury

The signals that guide neutrophils to sites of tissue injury or infection remain elusive. H2O2 has been implicated in neutrophil sensing of tissue injury and transformed cell, however its role in neutrophil recruitment to infection has not been explored. Here, using a pharmacological inhibitor of NADPH oxidases, diphenyleneiodonium (DPI), and genetic depletion of an epithelial specific NADPH oxidase, we show that H2O2 is not required for neutrophil detection of localized infection with the Gram-negative bacterium Pseudomonas aeruginosa. In contrast, PI3K signaling is required for neutrophil responses to both wounding and infection. In vivo imaging using a H2O2 probe detects dynamic H2O2 generation at wounds but not at infected tissue. Moreover, DPI no longer inhibits neutrophil wound attraction when Pseudomonas aeruginosa is present in the media. Finally, DPI also fails to inhibit neutrophil recruitment to localized infection with the Gram-positive bacterium, Streptococcus iniae. Our findings demonstrate that differential signals are involved in sensitizing neutrophils to pathogen versus non-pathogen induced tissue damage, providing a potential target to preferentially suppress non-specific immune damage without affecting the response to infection.