Eradication of intracellular Salmonella enterica serovar Typhimurium with a small-molecule, host cell-directed agent

Antimicrob Agents Chemother. 2009 Dec;53(12):5236-44. doi: 10.1128/AAC.00555-09. Epub 2009 Oct 5.

Abstract

Eradication of intracellular pathogenic bacteria with host-directed chemical agents has been an anticipated innovation in the treatment of antibiotic-resistant bacteria. We previously synthesized and characterized a novel small-molecule agent, AR-12, that induces autophagy and inhibits the Akt kinase in cancer cells. As both autophagy and the Akt kinase have been shown recently to play roles in the intracellular survival of several intracellular bacteria, including Salmonella enterica serovar Typhimurium, we investigated the effect of AR-12 on the intracellular survival of Salmonella serovar Typhimurium in macrophages. Our results show that AR-12 induces autophagy in macrophages, as indicated by increased autophagosome formation, and potently inhibits the survival of serovar Typhimurium in macrophages in association with increased colocalization of intracellular bacteria with autophagosomes. Intracellular bacterial growth was partially rescued in the presence of AR-12 by the short hairpin RNA-mediated knockdown of Beclin-1 or Atg7 in macrophages. Moreover, AR-12 inhibits Akt kinase activity in infected macrophages, which we show to be important for its antibacterial effect as the enforced expression of constitutively activated Akt1 in these cells reverses the AR-12-induced inhibition of intracellular serovar Typhimurium survival. Finally, oral administration of AR-12 at 2.5 mg/kg/day to serovar Typhimurium-infected mice reduced hepatic and splenic bacterial burdens and significantly prolonged survival. These findings show that AR-12 represents a proof of principle that the survival of intracellular bacteria can be suppressed by small-molecule agents that target both innate immunity and host cell factors modulated by bacteria.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Anti-Bacterial Agents / adverse effects
  • Anti-Bacterial Agents / chemical synthesis
  • Anti-Bacterial Agents / pharmacology*
  • Anti-Bacterial Agents / therapeutic use
  • Apoptosis Regulatory Proteins / genetics
  • Apoptosis Regulatory Proteins / physiology
  • Autophagy / drug effects
  • Autophagy-Related Protein 7
  • Beclin-1
  • Cell Survival / drug effects
  • Female
  • Immunoblotting
  • Macrophages / metabolism
  • Macrophages / microbiology
  • Mice
  • Mice, Inbred BALB C
  • Microscopy, Fluorescence
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / physiology
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / physiology
  • Salmonella Infections* / drug therapy
  • Salmonella Infections* / microbiology
  • Salmonella typhimurium / drug effects*
  • Salmonella typhimurium / metabolism

Substances

  • Anti-Bacterial Agents
  • Apoptosis Regulatory Proteins
  • Atg7 protein, mouse
  • Beclin-1
  • Becn1 protein, mouse
  • Microtubule-Associated Proteins
  • Akt1 protein, mouse
  • Proto-Oncogene Proteins c-akt
  • Autophagy-Related Protein 7