The role of copper in the innate immune response to Salmonella enterica serovar Typhimurium

Sian Stafford (2011). The role of copper in the innate immune response to Salmonella enterica serovar Typhimurium PhD Thesis, School of Chemistry & Molecular Bioscience, The University of Queensland.

       
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Author Sian Stafford
Thesis Title The role of copper in the innate immune response to Salmonella enterica serovar Typhimurium
School, Centre or Institute School of Chemistry & Molecular Bioscience
Institution The University of Queensland
Publication date 2011-10
Thesis type PhD Thesis
Supervisor Alastair McEwan
Matthew Sweet
Total pages 171
Total colour pages 18
Total black and white pages 153
Language eng
Subjects 1107 Immunology
0601 Biochemistry and Cell Biology
0605 Microbiology
Abstract/Summary Salmonella enterica sv. Typhimurium (S. Typhimurium) causes gastroenteritis in humans and is used in the mouse as a model for human typhoid fever. It is an intracellular pathogen, which subverts normal phagolysosome formation to reside in specialized vesicles called Salmonella-containing vacuoles (SCV). Salmonella must acquire nutrients and defend against the antimicrobial action of the macrophage to survive in this intracellular environment. The importance of iron in Salmonella pathogenicity has long been recognized; in this study the role of copper in regulating Salmonella survival within macrophages was investigated. Infection of bone marrow-derived macrophages (BMM) with S. Typhimurium or treatment with LPS robustly increased the mRNA expression of genes encoding the copper transporters Ctr1, Ctr2 and Atp7a, divalent cation transporter Nramp1, copper chaperones Atox1, CCS and Cox17, as well as the multicopper ferroxidase Cp (ceruloplasmin), in both its secreted and anchored forms. mRNA expression of genes encoding metallothioneins Mt1 and Mt2 were also induced, as were the antimicrobial effectors gp91 (subunit of phox) and iNOS. Genes encoding Fpn (ferroportin1), Atp7b, Hamp (hepcidin) and Heph (hephaestin) were not induced by these stimuli. Despite being induced at the mRNA level, protein induction in BMM for Cp, Atp7a, Ctr1 and Ctr2 was not found under the conditions of a 24 hr time course after treatment with LPS. The addition of copper to S. Typhimurium-infected macrophages resulted in decreased intracellular bacterial loads, an effect that was rescued by the copper chelator Bathocuproinedisulfonic acid disodium salt (BCS). Infection of Nramp1+ compared to Nramp1- macrophages demonstrated the overriding importance of Nramp1 in the killing of intracellular pathogens. In an attempt to assess the importance of the copper transporters during infection, the use of siRNA for knockdown of mRNA of Ctr1, Ctr2 and Atp7a was employed. No significant effect on intracellular bacterial loads was observed. Consistent and sufficient reduction of the proteins proved difficult, which could have impacted on the results of the infection assays. The results show that the induction of genes involved in copper metabolism upon Salmonella infection. The antimicrobial effect of copper could indicate that this ion has a role in innate immune response to Salmonella enterica serovar Typhimurium. This may reflect the copper requirement for iron-efflux from the macrophage but it may also indicate that copper ions have a more direct role in the antimicrobial activity of macrophages.
Keyword Salmonella enterica serovar Typhimurium
Macrophages
Copper
Iron (fe)
Nramp1
Ctr1
Ctr2
Atp7a
Ceruloplasmin
Additional Notes 26, 29, 30, 33, 37, 40, 51, 71, 73, 80, 91, 92, 93, 94, 95, 110, 127, 128

 
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Created: Wed, 07 Mar 2012, 16:14:11 EST by Sian Stafford on behalf of Library - Information Access Service