Nitric oxide as a biomarker of intracellular Salmonella viability and identification of the bacteriostatic activity of protein kinase A inhibitor H-89

PLoS One. 2013;8(3):e58873. doi: 10.1371/journal.pone.0058873. Epub 2013 Mar 15.

Abstract

Salmonella enterica serovar Enteritidis is one of the most prevalent Salmonella serovars in poultry and is often associated with human salmonellosis. S. Enteritidis is known to suppress nitric oxide (NO) production in infected chicken macrophage HD11 cells, while dead S. Enteritidis stimulates a high level of NO production, suggesting a bacterial inhibitory effect on NO production. Based on these observations, the present study was conducted to evaluate whether NO production in S. Enteritidis-infected HD11 cells can be used as a biomarker to identify molecules that kill intracellular Salmonella. Since Salmonella are known to manipulate the host cell kinase network to facilitate intracellular survival, we screened a group of pharmaceutical inhibitors of various kinases to test our hypothesis. A protein kinase A inhibitor, H-89, was found to reverse the suppression of NO production in S. Enteritidis-infected HD11 cells. Production of NO in S. Enteritidis-infected HD11 cells increased significantly following treatment with H-89 at or above 20 µM. Inversely, the number of viable intracellular Salmonella decreased significantly in cells treated with H-89 at or above 30 µM. Furthermore, the growth rate of S. Enteritidis in culture was significantly inhibited by H-89 at concentrations from 20 to 100 µM. Our results demonstrate that NO-based screening using S. Enteritidis-infected HD11 cells is a viable tool to identify chemicals with anti-intracellular Salmonella activity. Using this method, we have shown H-89 has bacteriostatic activity against Salmonella, independent of host cell protein kinase A or Akt1 activity.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biomarkers / metabolism
  • Cell Line
  • Chickens
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors*
  • Isoquinolines / pharmacology*
  • Macrophages / drug effects
  • Macrophages / immunology
  • Macrophages / metabolism
  • Macrophages / microbiology
  • Nitric Oxide / metabolism*
  • Phagocytosis / immunology
  • Salmonella Infections, Animal / immunology
  • Salmonella Infections, Animal / metabolism
  • Salmonella enteritidis / drug effects*
  • Salmonella enteritidis / growth & development
  • Salmonella enteritidis / metabolism*
  • Sulfonamides / pharmacology*

Substances

  • Biomarkers
  • Isoquinolines
  • Sulfonamides
  • Nitric Oxide
  • Cyclic AMP-Dependent Protein Kinases
  • N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide

Grants and funding

This study was supported only by USDA-ARS intramural funding. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.