title: Eradication of intracellular Salmonella enterica serovar Typhimurium with a small-molecule, host cell-directed agent.
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.
authors.affiliation: Division of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, Ohio State University, Columbus, OH 43210, USA.
authors.forename: Hao-Chieh
authors.initials: HC
authors.lastname: Chiu
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Kulp
authors.forename: Shilpa
authors.initials: S
authors.lastname: Soni
authors.forename: Dasheng
authors.initials: D
authors.lastname: Wang
authors.forename: John S
authors.initials: JS
authors.lastname: Gunn
authors.forename: Larry S
authors.initials: LS
authors.lastname: Schlesinger
authors.forename: Ching-Shih
authors.initials: CS
authors.lastname: Chen
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000009:adverse effects / Q000138:chemical synthesis / Q000494:pharmacology* / Q000627:therapeutic use; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000502:physiology; D001343:Autophagy / Q000187:drug effects; D000071193:Autophagy-Related Protein 7; D000071186:Beclin-1; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D015151:Immunoblotting; D008264:Macrophages / Q000378:metabolism / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008856:Microscopy, Fluorescence; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000502:physiology; D012480:Salmonella Infections / Q000188:drug therapy / Q000382:microbiology; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D051017:Apoptosis Regulatory Proteins; C502661:Atg7 protein, mouse; D000071186:Beclin-1; C115010:Becn1 protein, mouse; D008869:Microtubule-Associated Proteins; C514862:Akt1 protein, mouse; D051057:Proto-Oncogene Proteins c-akt; D000071193:Autophagy-Related Protein 7