Dataset Information

Iron Homeostasis in Tissues Is Affected during Persistent Chlamydia pneumoniae Infection in Mice.

ABSTRACT: Chlamydia pneumoniae (C. pneumoniae) may be a mediator in the pathogenesis of atherosclerosis. For its growth C. pneumoniae depends on iron (Fe), but how Fe changes in tissues during persistent infection or affects bacterial replication in tissues is unknown. C. pneumoniae-infected C57BL/6J mice were sacrificed on days 4, 8, 20, and 40. Mice had bacteria in the lungs and liver on all days. Inflammatory markers, chemokine Cxcl2 and interferon-gamma, were not affected in the liver on day 40. The copper (Cu)/zinc (Zn) ratio in serum, another marker of infection/inflammation, increased on day 4 and tended to increase again on day 40. The Fe markers, transferrin receptor (TfR), Hepcidin (Hamp1), and ferroportin 1 (Fpn1), increased in the liver on day 4 and then normalized except for TfR that tended to decrease. TfR responses were similar to Fe in serum that increased on day 4 but tended to decrease thereafter. In the liver, Fe was increased on day 4 and also on day 40. The reappearing increases in Cu/Zn on day 40 concomitant with the increase in liver Fe on day 40, even though TfR tended to decrease, and the fact that viable C. pneumoniae was present in the lungs and liver may indicate the early phase of activation of recurrent infection.

SUBMITTER: Edvinsson M

PROVIDER: S-EPMC5485268 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Iron Homeostasis in Tissues Is Affected during Persistent Chlamydia pneumoniae Infection in Mice.

Edvinsson Marie M Tallkvist Jonas J Nyström-Rosander Christina C Ilbäck Nils-Gunnar NG

BioMed research international 20170613

Chlamydia pneumoniae (C. pneumoniae) may be a mediator in the pathogenesis of atherosclerosis. For its growth C. pneumoniae depends on iron (Fe), but how Fe changes in tissues during persistent infection or affects bacterial replication in tissues is unknown. C. pneumoniae-infected C57BL/6J mice were sacrificed on days 4, 8, 20, and 40. Mice had bacteria in the lungs and liver on all days. Inflammatory markers, chemokine Cxcl2 and interferon-gamma, were not aff ...[more]

PMID: 28691023

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Project description:The obligate intracellular, gram-negative bacterium, Chlamydophila pneumoniae (Cpn), has impact as an acute and chronic disease-causing pathogen. Little is known about changes in the Cpn transcriptome during its biphasic developmental cycle (the acute infection) and persistence stages that are linked to chronic diseases. To analyze Cpn CWL029 gene expression, we designed a pathogen-specific oligo microarray and optimized the extraction method for pathogen RNA. Throughout the acute infection, ratio expression profiles for each gene were generated using 48 hours post infection as a reference. Based on these profiles, significantly expressed genes were separated into 12 expression clusters using SOM clustering and manually into the ‘early’, ‘mid’, ‘late’ and ‘tardy’ cluster classes. The latter two were differentiated because the ‘tardy’ class showed steadily increasing expression at the end of the cycle. The transcriptome of the Cpn elementary body (EB) and published EB proteomics data were compared to the cluster profile of the acute infection. We found an intriguing association between ‘late’ genes and genes coding for EB proteins, whereas ‘tardy’ genes were mainly associated with genes coding for EB mRNA. It has been published that iron depletion leads to Cpn persistence. We compared the gene expression profiles during iron depletion-mediated persistence with the expression clusters of the acute infection. This led to the finding that establishment of iron depletion-mediated persistence is more likely a mid-cycle arrest in development rather than a completely distinct gene expression pattern. Taken together, here we describe the Cpn transcriptome during the acute infection with ‘late’ genes correlating to EB proteins and ‘tardy’ genes to EB mRNA. Expression profiles during iron mediated-persistence led us to propose the hypothesis that the transcriptomic ‘clock’ is arrested during acute mid-cycle. Keywords: time course, iron, persistence, Chlamydia, Chlamydophila, pneumoniae, recovery, pathogen, life cycle, developmental cycle

Project description:Neutrophil gelatinase-associated lipocalin (NGAL/Lipocalin-2/Lcn-2) is a 25kDa protein which is involved in host defence against certain Gram negative bacteria upon binding of iron loaded bacterial siderophores thereby limiting the availability of this essential nutrient to bacteria resulting in inhibition of their growth and pathogenicity. As iron is important for the growth of the intracellular bacterium Chlamydia pneumoniae we questioned whether Lcn-2 affects the course of this infection. We employed primary peritoneal macrophages obtained from wildtype and Lcn-2 -/- mice and RAW 264.7 cells which were infected with C. pneumoniae. In addition, we studied C. pneumoniae multiplication in vivo in mice receiving diets with varying iron contents. We analyzed C. pneumoniae numbers by immunohistochemistry and RT-PCR and studied the expression of iron metabolism and cytokine genes by RT-PCR, Western blot or ELISA. Infection with Chlamydiae ex vivo and in vivo revealed a significantly higher bacterial growth in peritoneal macrophages of Lcn-2 -/- than of wildtype mice. These differences were significantly more pronounced upon iron challenge, which stimulated bacterial growth. Accordingly, treatment with an anti-Lnc-2 antibody increased whereas addition of recombinant Lcn-2 reduced bacterial growth in infected macrophages. When investigating the underlying mechanisms we observed partly different expression of several iron metabolism genes between Lcn-2 +/+ and Lcn-2 -/- macrophages and most strikingly an increased formation of the anti-inflammatory cytokine IL-10 by Lcn-2 -/- macrophages. Upon treatment with an anti-IL10 antibody we experienced a significant increase of Chlamydial growth within Lcn-2 -/- macrophages along with a reduction of the major iron storage protein ferritin. Herein we provide first time evidence that Lcn-2 is involved in host defence against Chlamydia presumably by limiting the availability of iron to the pathogen. In the absence of Lcn-2, increased formation of IL-10 exerts protective effects by increasing the intracellular formation of ferritin, thereby reducing the access of iron for bacteria.

Dataset Information

Iron Homeostasis in Tissues Is Affected during Persistent Chlamydia pneumoniae Infection in Mice.

Publications

Iron Homeostasis in Tissues Is Affected during Persistent <i>Chlamydia pneumoniae</i> Infection in Mice.

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