Caspase-6 mediates resistance against Burkholderia pseudomallei infection and influences the expression of detrimental cytokines

PLoS One. 2017 Jul 7;12(7):e0180203. doi: 10.1371/journal.pone.0180203. eCollection 2017.

Abstract

Caspase-6 is a member of the executioner caspases and known to play a role in innate and adaptive immune processes. However, its role in infectious diseases has rarely been addressed yet. We here examined the impact of caspase-6 in an in vivo infection model using the Gram-negative rod Burkholderia pseudomallei, causing the infectious disease melioidosis that is endemic in tropical and subtropical areas around the world. Caspase-6-/- and C57BL/6 wild type mice were challenged with B. pseudomallei for comparing mortality, bacterial burden and inflammatory cytokine expression. Bone-marrow derived macrophages were used to analyse the bactericidal activity in absence of caspase-6. Caspase-6 deficiency was associated with higher mortality and bacterial burden in vivo after B. pseudomallei infection. The bactericidal activity of caspase-6-/- macrophages was impaired compared to wild type cells. Caspase-6-/- mice showed higher expression of the IL-1β gene, known to be detrimental in murine melioidosis. Expression of the IL-10 gene was also increased in caspase-6-/- mice as early as 6 hours after infection. Treatment with exogenous IL-10 rendered mice more susceptible against B. pseudomallei challenge. Thus, caspase-6 seems to play a crucial role for determining resistance against the causative agent of melioidosis. To our knowledge this is the first report showing that caspase-6 is crucial for mediating resistance in an in vivo infection model. Caspase-6 influences the expression of detrimental cytokines and therefore seems to be important for achieving a well-balanced immune response that contributes for an efficient elimination of the pathogen.

MeSH terms

  • Animals
  • Burkholderia pseudomallei / genetics*
  • Burkholderia pseudomallei / pathogenicity
  • Caspase 6 / genetics*
  • Drug Resistance, Microbial / genetics
  • Gene Expression Regulation / drug effects
  • Humans
  • Interleukin-10 / administration & dosage*
  • Interleukin-10 / biosynthesis
  • Interleukin-1beta / biosynthesis*
  • Interleukin-1beta / genetics
  • Macrophages / metabolism
  • Macrophages / pathology
  • Melioidosis / genetics*
  • Melioidosis / microbiology
  • Melioidosis / pathology
  • Mice
  • Mice, Knockout

Substances

  • IL1B protein, mouse
  • Interleukin-1beta
  • Interleukin-10
  • Caspase 6

Grants and funding

The financial resources for our study were kindly provided by the University of Greifswald.