title: Chloroquine inhibits Rhodococcus equi replication in murine and foal alveolar macrophages by iron-starvation.
abstract: Rhodococcus equi preferentially infects macrophages causing pyogranulomatous pneumonia in young foals. Both the vapA and rhbC genes are up-regulated in an iron (Fe)-deprived environment, such as that found within macrophages. Chloroquine (CQ) is a drug widely used against malaria that suppresses the intracellular availability of Fe in eukaryotic cells. The main objective of this study was to evaluate the ability of CQ to inhibit replication of virulent R. equi within murine (J774A.1) and foal alveolar macrophages (AMs) and to verify whether the mechanism of inhibition could be Fe-deprivation-dependent. CQ effect on R. equi extracellular survival and toxicity to J774A.1 were evaluated. R. equi survival within J774A.1 and foal AMs was evaluated under CQ (10 and 20μM), bovine saturated transferrin (bHTF), and bovine unsaturated transferrin (bATF) exposure. To explore the action mechanism of CQ, the superoxide anion production, the lysozyme activity, as well as the relative mRNA expression of vapA and rhbC were examined. CQ at≤20μM had no effect on R. equi extracellular multiplication and J774A.1 viability. Exposure to CQ significantly and markedly reduced survival of R. equi within J774A.1 and foal AMs. Treatment with bHTF did not reverse CQ effect on R. equi. Exposure to CQ did not affected superoxide anion production or lysozyme activity, however vapA and rhbC expression was significantly increased. Our results reinforce the hypothesis that intracellular availability of Fe is required for R. equi survival, and our initial hypothesis that CQ can limit replication of R. equi in J774A.1 and foal AMs, most likely by Fe starvation.
authors.affiliation: Laboratory of Bacteriology, Department of Preventive Veterinary Medicine, Federal University of Santa Maria, Av. Roraima 1000, Camobi, Santa Maria, RS 97105-900, Brazil.
authors.forename: Leticia T
authors.initials: LT
authors.lastname: Gressler
authors.affiliation: Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77845, United States.
authors.forename: Angela I
authors.initials: AI
authors.lastname: Bordin
authors.affiliation: Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77845, United States.
authors.forename: Cole M
authors.initials: CM
authors.lastname: McQueen
authors.affiliation: Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Texas A&M University, College Station, TX 77845, United States. Electronic address: NCOHEN@cvm.tamu.edu.
authors.forename: Noah D
authors.initials: ND
authors.lastname: Cohen
authors.affiliation: Laboratory of Bacteriology, Department of Preventive Veterinary Medicine, Federal University of Santa Maria, Av. Roraima 1000, Camobi, Santa Maria, RS 97105-900, Brazil. Electronic address: agueda.vargas@gmail.com.
authors.forename: Agueda Castagna
authors.initials: AC
authors.lastname: de Vargas
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D002460:Cell Line; D002738:Chloroquine / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006736:Horses; D007501:Iron / Q000378:metabolism; D016676:Macrophages, Alveolar / Q000166:cytology / Q000382:microbiology*; D051379:Mice; D050296:Microbial Viability / Q000187:drug effects; D009113:Muramidase / Q000378:metabolism; D016929:Rhodococcus equi / Q000166:cytology / Q000187:drug effects*
chemical_list: D001426:Bacterial Proteins; D002738:Chloroquine; D007501:Iron; D009113:Muramidase
keywords: Chloroquine; Iron; Macrophage; Rhodococcus equi; rhbC; vapA