Extracellular superoxide dismutase inhibits innate immune responses and clearance of an intracellular bacterial infection

Timothy J. Break, Sujung Jun, Mohanalaxmi Indramohan, Karen D. Carr, Amy N. Sieve, Ladislav Dory, Rance E. Berg

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

Reactive oxygen species and reactive nitrogen species play important roles during immune responses to bacterial pathogens. Extracellular superoxide dismutase (ecSOD) regulates extracellular concentrations of reactive oxygen species and reactive nitrogen species and contributes to tissue protection during inflammatory insults. The participation of ecSOD in immune responses seems therefore intuitive, yet is poorly understood. In the current study, we used mice with varying levels of ecSOD activity to investigate the involvement of this enzyme in immune responses against Listeria monocytogenes. Surprisingly, our data demonstrate that despite enhanced neutrophil recruitment to the liver, ecSOD activity negatively affected host survival and bacterial clearance. Increased ecSOD activity was accompanied by decreased colocalization of neutrophils with bacteria, as well as increased neutrophil apoptosis, which reduced overall and neutrophil-specific TNF-α production. Liver leukocytes from mice lacking ecSOD produced equivalent NO• compared with liver leukocytes from mice expressing ecSOD. However, during infection, there were higher levels of peroxynitrite (NO 3-) in livers from mice lacking ecSOD compared with livers from mice expressing ecSOD. Neutrophil depletion studies revealed that high levels of ecSOD activity resulted in neutrophils with limited protective capacity, whereas neutrophils from mice lacking ecSOD provided superior protection compared with neutrophils from wild-type mice. Taken together, our data demonstrate that ecSOD activity reduces innate immune responses during bacterial infection and provides a potential target for therapeutic intervention.

Original languageEnglish
Pages (from-to)3342-3350
Number of pages9
JournalJournal of Immunology
Volume188
Issue number7
DOIs
StatePublished - 1 Apr 2012

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