Modeling Combination Chelation Regimes To Optimize Cellular Iron Removal and Explore Mechanisms Of Enhanced Chelation

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2200-2200
Author(s):  
Evangelia Vlachodimitropoulou ◽  
Garbowski Maciej ◽  
John B Porter
Keyword(s):  
Iron Concentration ◽  
Dual Therapy ◽  
Iron Chelator ◽  
Iron Removal ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Synergy Index ◽  
Cellular Iron ◽  
Low Concentrations ◽  
Oral Chelators

Abstract Introduction Monotherapy with clinically available chelators, namely deferoxaime (DFO), deferasirox (DFX) or deferiprone (DFP) is effective but often slow and suboptimal. Combinations of DFO with DFP have been used clinically to enhance cellular iron mobilization but the conditions under which this occurs have not been studied systematically. With the emergence of DFX, the possibility exists to combine this with either DFO or DFP to enhance chelation. We have developed a system to study the optimal concentrations and times of exposure to these chelators, alone or in combination for maximising cellular iron removal. Isobol modeling has been used to determine whether interaction is additive or synergistic. The demonstration of synergy would imply the primary chelator acting as a ‘sink’ for iron chelated and donated to this sink by low concentrations of a secondary ‘shuttle’ chelator as shown in plasma (Evans et al. TransL. Res, 2010). Methods Human hepatocellular carcinoma (HuH-7) cells were chosen as hepatocytes are the major cell of iron storage in iron overload. Iron concentration was determined using the ferRozine (Riemer et al. Anal Biochem. 2004). A threefold increase of intracellular iron compared to control was obtained by serially treating cells with 10% FBS RPMI media. The cells were then exposed to iron chelator then lysed and intracellular iron concentration determined via the ferrozine assay, normalized against protein content. Cell viability was assessed using 0.4% Trypan blue as well as Acridine Orange /Propidium Iodide and was consistently > 98%. Isobolograms were constructed (Tallarida et al, Pharmacol Ther, 2010) as well as a the synergy index (QUOTE 1-1/R) x 100 (%), where R = difference of areas between the line of additivity and the curve of synergy on the isobologram. This index represents how much of the obtained effect exceeds that expected by additivity of two chelators. Results Monotherapy with DFP, DFX or DFO at clinically relevant concentrations of 1 to 30µM iron binding equivalents (IBE), induced both dose and time dependent cellular iron removal. Dual therapy combinations of all 3 chelators enhanced iron removal at 4, 8 and 12 hours. At 4 hours of incubation, whereas 10µM DFO alone had no demonstrable effect on cellular iron removal, addition of DFP at as little as 1µM IBE increased cellular iron removal. Table 1 shows examples of cellular iron removal at specimen chelator concentrations alone or in combination at 8h. The combination of DFX with DFO, DFX with DFP and DFP with DFO all resulted in enhanced cellular iron removal. The combination of DFP and DFX was the most effective. Isobol plot analysis from multiple chelator concentrations demonstrated synergy for all pairs at 4 and 8 hours of exposure. The derived synergy index at 8h indicates that when DFX and DFO are combined, 49% of the chelation effect is due to synergy in this system and 51% in the case of DFP and DFO combination. Most interestingly, the synergistic effect is even greater, in the case of the two oral chelators DFP and DFX when in combination (59%). Figure 1. Conclusion Remarkably low concentrations of a second chelator are required to enhance cellular iron removal by the primary chelator. Isobol analysis shows synergy rather than additivity as the mechanism for enhanced chelation for all 3 combinations, implying a ‘shuttle’ and ‘sink’ effect. Interestingly, the combination of two oral chelators DFP and DFX showed the most marked enhancement of cellular iron removal, without cellular toxicity, suggesting a potentially powerful therapeutic approach, provided this is also well tolerated clinically. The long plasma half life of once daily oral DFX will allow a continuous ‘sink’ for iron shuttled by the shorter acting DFP. Line of Additivity Curve of Synergy below the line Disclosures: Porter: Novartis: Consultancy, Honoraria, Research Funding; Shire: Consultancy, Honoraria; Celgene: Consultancy.

scholarly journals Eltrombopag Mobilizes Intracellular Iron Stores at Concentrations Lower Than Those Required with Other Clinically Available Iron Chelators

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1353-1353 ◽  
Author(s):  
Evangelia Vlachodimitropoulou Koumoutsea ◽  
Nichola Cooper ◽  
Bethan Psaila ◽  
Martha Sola-Visner ◽  
John B Porter
Keyword(s):  
Cell Viability ◽  
Cell Line ◽  
Conflicts Of Interest ◽  
Iron Concentration ◽  
Iron Removal ◽  
Iron Chelators ◽  
Intracellular Iron ◽  
Time Points ◽  
Iron Mobilization ◽  
Cellular Iron

Abstract INTRODUCTION Eltrombopag (EP) is an orally bioavailable thrombopoietin receptor agonist developed to increase platelet production in a range of conditions associated with thrombocytopaenia. The finding that EP, in addition to increasing platelet counts in myelodysplastic syndromes (MDS), also slowed progression to acute myeloid leukemia has been linked to antiproliferative effects potentially mediated by chelation of labile intracellular iron pools in leukaemia cell lines (Roth et al, 2012, Blood). However, the ability of EP to progressively decrease total cellular iron and its relative efficacy in this regard compared with clinically available iron chelators such as Desferrioxamine (DFO), Deferiprone (DFP) and Deferasirox (DFX) have not been reported. Using a cell based assay system for total cellular iron we therefore compared cellular iron mobilization with EP to that achieved with clinically established iron chelators. METHODS The permanent cardiomyocyte cell line H9C2 derived from embryonic rat ventricle was chosen to model iron mobilization, as heart failure secondary to iron overload is the most common cause of death among patients with transfusion-dependent anaemias. Iron concentration was determined using the ferrozine assay (Riemer et al. Anal Biochem. 2004). A two fold increase of intracellular iron compared to control was obtained by serially treating cells with 10% FBS DMEM media. The cells were then exposed to iron chelators/EP, lysed, and intracellular iron concentration determined via the ferrozine assay, normalized against protein content. The LDH enzymatic viability assay was used to ensure viability was consistently >98% during experiments, and to assess the toxicity of EP on the cardiomyocyte cell line. RESULTS EP induced both dose and time dependent cellular iron removal from cells at 1, 2, 4 and 8 hours. At 1µM, EP was able to remove 42% of total cellular iron following 8 hours of treatment, and 60.1% and 65.62% at 10µM and 30µM respectively (Figure 1). Figure 2 shows that cell viability is compromised at concentrations of 10µM and 30µM to 96% and 92% respectively with eltrombopag, but not with the commercially used iron chelators, DFO, DFP and DFX. However, at 1µM EP the viability of the monolayer is maintained at >98%. The high effects of iron release noted in figure 1 by EP at 10µM and 30µM could be partially attributed to toxicity of the drug on the monolayer. In table 1 the difference in iron removal between EP and commercially used iron chelators after 8 hours of treatment is shown. Interestingly, with EP at only 1µM, 42.9% of cellular iron was removed, compared to 22.7 %, 34.9% and 19.3% in the case of DFO, DFX and DFP respectively, all at higher concentrations of 30µM iron binding equivalents (IBE). DISCUSSION AND CONCLUSION­­ Remarkably low concentrations of EP (1µM) are required to mobilize cellular iron in our cell system while maintaining cell viability at this concentration. This concentration is achievable clinically (Cmax 2-3 µM two to six hours post administration of 75mg orally) (Neito et al, Haematologica, 2011; Deng et al, Drug Metabolism and Disposition, 2011), and when considered alongside with the long plasma half life and elimination in urine and feces, could render it an effective iron chelator for other indications, particularly if combined with existing iron chelation regimes. It would be of interest to explore how EP performed in an animal iron overloaded/MDS model in isolation or as an adjunct to established chelation therapies. Figure 1: Percentage of intracellular iron removed from cardiomyocytes by increasing concentrations of Eltrombopag at different time points up until 8 hours Figure 1:. Percentage of intracellular iron removed from cardiomyocytes by increasing concentrations of Eltrombopag at different time points up until 8 hours Figure 2: Percentage cytotoxicity of cardiomyocyte monolayer following 8 hours of treatment with Eltrombopag and commercially used iron chelators Figure 2:. Percentage cytotoxicity of cardiomyocyte monolayer following 8 hours of treatment with Eltrombopag and commercially used iron chelators Table 1: Comparison of iron mobilization by Eltrombopag and commercially used iron chelators following 8 hours of treatment. Chelator Iron/protein (nmol/mg) SD % iron removal control 26.78 2.5 - DFO 30μM ibe 20.70 2.2 22.70 DFP 30μM ibe 17.43 1.4 34.89 DFX 30μM ibe 21.61 1.0 19.28 Eltrombopag 1μM 15.53 1.9 42.94 Eltrombopag 10μM 10.70 1.2 60.06 Eltrombopag 30μM 9.21 0.3 65.62 Disclosures No relevant conflicts of interest to declare.

scholarly journals Nifedipine Potentiates Susceptibility of Salmonella Typhimurium to Different Classes of Antibiotics

Antibiotics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1200
Author(s):  
David Haschka ◽  
Manuel Grander ◽  
Johannes Eibensteiner ◽  
Stefanie Dichtl ◽  
Sabine Koppelstätter ◽  
...  
Keyword(s):  
Salmonella Typhimurium ◽  
Bacterial Resistance ◽  
Additive Effect ◽  
Lipocalin 2 ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Cellular Iron ◽  
Essential Nutrient ◽  
Conventional Antibiotics ◽  
Significant Additive Effect

The calcium channel blocker nifedipine induces cellular iron export, thereby limiting the availability of the essential nutrient iron for intracellular pathogens, resulting in bacteriostatic activity. To study if nifedipine may exert a synergistic anti-microbial activity when combined with antibiotics, we used the mouse macrophage cell line RAW267.4, infected with the intracellular bacterium Salmonella Typhimurium, and exposed the cells to varying concentrations of nifedipine and/or ampicillin, azithromycin and ceftriaxone. We observed a significant additive effect of nifedipine in combination with various antibiotics, which was not observed when using Salmonella, with defects in iron uptake. Of interest, increasing intracellular iron levels increased the bacterial resistance to treatment with antibiotics or nifedipine or their combination. We further showed that nifedipine increases the expression of the siderophore-binding peptide lipocalin-2 and promotes iron storage within ferritin, where the metal is less accessible for bacteria. Our data provide evidence for an additive effect of nifedipine with conventional antibiotics against Salmonella, which is partly linked to reduced bacterial access to iron.

scholarly journals Iron storage in ferritin following intracellular hemoglobin denaturation in erythroleukemic cells

Blood ◽  
1983 ◽  
Vol 62 (4) ◽  
pp. 928-930 ◽  
Author(s):  
E Fibach ◽  
ER Bauminger ◽  
AM Konijn ◽  
S Ofer ◽  
EA Rachmilewitz
Keyword(s):  
Cell Lines ◽  
Storage Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Cellular Iron ◽  
Ferritin Iron ◽  
Induction Of Differentiation ◽  
K 562 Cells ◽  
Murine Erythroleukemia ◽  
Erythroleukemic Cells

Abstract Murine erythroleukemia (MEL) and human K-562 cell lines were cultured in the presence of 57Fe, and the quantities of cellular iron-containing compounds were determined with the aid of Mossbauer spectroscopy. Upon induction of differentiation, both ferritin-iron and hemoglobin (Hb) iron could be detected. Treatment of the cells with 0.01%-0.02% acetylphenylhydrazine (APH) resulted in gradual denaturation of Hb and incorporation of the released Hb-iron into ferritin. Following treatment with APH, the ratio of Hb-57Fe to ferritin-57Fe decreased from 2.6 to 0.2 in MEL cells and from 0.56 to 0.12 in K-562 cells. No change was observed in the total intracellular iron. Using fluorescence ELISA, an increased level of immunologically detectable ferritin was found in hemoglobinized K-562 cells treated with APH, as compared to the amount of ferritin found in untreated cells. Ferritin may thus function not only as an intermediate during Hb synthesis, but also as storage protein for iron released during Hb denaturation.

HFE Downregulates Iron Uptake From Transferrin and Induces Iron-Regulatory Protein Activity in Stably Transfected Cells

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3915-3921 ◽  
Author(s):  
H.D. Riedel ◽  
M.U. Muckenthaler ◽  
S.G. Gehrke ◽  
I. Mohr ◽  
K. Brennan ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Regulatory Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron

Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder of iron metabolism. More than 80% of HH patients are homozygous for a point mutation in a major histocompatibility complex (MHC) class I type protein (HFE), which results in a lack of HFE expression on the cell surface. A previously identified interaction of HFE and the transferrin receptor suggests a possible regulatory role of HFE in cellular iron absorption. Using an HeLa cell line stably transfected with HFE under the control of a tetracycline-sensitive promoter, we investigated the effect of HFE expression on cellular iron uptake. We demonstrate that the overproduction of HFE results in decreased iron uptake from diferric transferrin. Moreover, HFE expression activates the key regulators of intracellular iron homeostasis, the iron-regulatory proteins (IRPs), implying that HFE can affect the intracellular “labile iron pool.” The increase in IRP activity is accompanied by the downregulation of the iron-storage protein, ferritin, and an upregulation of transferrin receptor levels. These findings are discussed in the context of the pathophysiology of HH and a possible role of iron-responsive element (IRE)-containing mRNAs.

A Potential Novel Application of Eltrombopag: A Combination Agent to Enhance Iron Chelation Therapy

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3357-3357 ◽  
Author(s):  
Evangelia Vlachodimitropoulou Koumoutsea ◽  
John B Porter ◽  
Nichola Cooper ◽  
Bethan Psaila ◽  
Martha Sola-Visner
Keyword(s):  
Cell Line ◽  
Cell Lines ◽  
Iron Chelation ◽  
Iron Chelator ◽  
Iron Chelators ◽  
Target Tissue ◽  
Intracellular Iron ◽  
Platelet Counts ◽  
Iron Mobilization ◽  
Cellular Iron

Abstract INTRODUCTION Eltrombopag (ELT) is an orally available, non-peptide, small-molecule thrombopoietin receptor (TPO-R) agonist approved for the treatment of chronic immune thrombocytopenic purpura (ITP). Additionally ELT appears to bind intracellular iron (Roth et al, 2012, Blood) and our group has previously demonstrated its ability to progressively mobilize iron from cardiomyocytes in vitro. (Vlachodimitropoulou et al, Blood 2014, Volume 124, 21). The ELT concentrations at which iron was mobilized were substantially less (1µM) than with the clinically available iron chelators Desferrioxamine (DFO), Deferiprone (DFP) and Deferasirox (DFX), where 30µM iron binding equivalents (ibe) were required to achieve similar effects (Vlachodimitropoulou et al, 2014. Blood, Volume 124, 21). Importantly , the 1µM effective concentration of ELT for mobilizing cellular iron is nearly twenty-fold less than peak plasma concentrations reported clinically, even with low doses (30mg) of ELT (Gabianski, Journal of Clinical Pharmacology, 2011;51:842-856). At this low dose, increments in platelet counts do not typically exceed 1.2 x the baseline values in healthy volunteers with repeat dosing (Jenkins et al 2007, Blood, 109; 11 ). Hence it is predicted that effective chelating doses of ELT could be given without promoting unacceptable thombocytosis. In principle, still lower concentrations could be used for iron chelation if combined with another iron chelator. Here we explore and compare the concentrations at which effective cellular chelation is achieved with ELT alone or in combination with another chelator. METHODS As cardiomyocytes are a target tissue for transfusional iron overload and provide a particular therapeutic challenge once iron has accumulated in them, the cardiomyocyte cell line H9C2, derived from embryonic rat ventricle, was chosen for investigation. As hepatocytes represent the cell type with the largest quantity of iron deposition, a human hepatocarcinoma HuH7 cell line was also evaluated. Cellular iron loading and iron mobilization were measured as a decrease in cellular iron content using the ferrozine assay (Vlachodimitropoulou et al 2015, British Journal of Haematology). The cells loaded with iron using 10% FBS containing media and then exposed to iron chelators/ELT. Cells were then lysed and intracellular iron concentration determined via the ferrozine assay, normalized against protein content. Acridine Orange/Propidium Iodide staining was used to ensure viability was consistently >98% during experiments, and to assess the toxicity of ELT on the cardiomyocyte and hepatocyte cell lines. RESULTS Monotherapy with 1µM ELT removed 42% of total cardiomyocyte iron following 8 hours of treatment. This was notably more efficient than in hepatocytes, where only 7% of cellular iron was removed with 1µM ELT monotherapy (Table 1). In Table 1 we can see the difference in iron removal between ELT monotherapy and combination with chelators after 8 hours. The effect in combination with all chelators was substantial. Viability was unaffected by combinations of 1µM ELT with other chelators. The hydrophilic hydroxypridinone iron chelator CP40, which has no iron mobilizing effects when used alone, enhanced iron mobilization by ELT, indicating that ELT can shuttle iron from cells onto a second chelator. CONCLUSION Remarkably low concentrations of ELT monotherapy mobilize cellular iron from cardiomyocytes compared with conventional iron chelators. Furthermore, when used at as little as 1μΜ, in combination with standard therapeutic concentrations of DFO, DFP and DFX, the percentage of iron mobilized from cardiomyocytes more than doubled. Experiments with CP40 indicate that ELT acts as a shuttle molecule for chelated iron onto a second 'sink chelator' and that this is the likely mechanism for the enhanced iron mobilization with other iron chelators. While the action of ELT on the TPO-R is highly species-specific and occurs only in humans and primates, we found effective iron mobilization from both rat cardiomyocytes and human hepatocyte cell lines. This is consistent with an iron chelating mechanismdistinct from the TPO-R downstream signaling mechanism of ELT. The concentrations of ELT used to achieve iron mobilization in combination are clinically achievable and are unlikely to increase platelet counts in patients without thrombocytopaenia. Disclosures Porter: Celgene: Consultancy; Shire: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding.

scholarly journals Iron storage in ferritin following intracellular hemoglobin denaturation in erythroleukemic cells

Blood ◽  
1983 ◽  
Vol 62 (4) ◽  
pp. 928-930 ◽  
Author(s):  
E Fibach ◽  
ER Bauminger ◽  
AM Konijn ◽  
S Ofer ◽  
EA Rachmilewitz
Keyword(s):  
Cell Lines ◽  
Storage Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Cellular Iron ◽  
Ferritin Iron ◽  
Induction Of Differentiation ◽  
K 562 Cells ◽  
Murine Erythroleukemia ◽  
Erythroleukemic Cells

Murine erythroleukemia (MEL) and human K-562 cell lines were cultured in the presence of 57Fe, and the quantities of cellular iron-containing compounds were determined with the aid of Mossbauer spectroscopy. Upon induction of differentiation, both ferritin-iron and hemoglobin (Hb) iron could be detected. Treatment of the cells with 0.01%-0.02% acetylphenylhydrazine (APH) resulted in gradual denaturation of Hb and incorporation of the released Hb-iron into ferritin. Following treatment with APH, the ratio of Hb-57Fe to ferritin-57Fe decreased from 2.6 to 0.2 in MEL cells and from 0.56 to 0.12 in K-562 cells. No change was observed in the total intracellular iron. Using fluorescence ELISA, an increased level of immunologically detectable ferritin was found in hemoglobinized K-562 cells treated with APH, as compared to the amount of ferritin found in untreated cells. Ferritin may thus function not only as an intermediate during Hb synthesis, but also as storage protein for iron released during Hb denaturation.

scholarly journals Simultaneous Analysis of Bacterioferritin Gene Expression and Intracellular Iron Status in Pseudomonas putida KT2440 by Using a Rapid Dual Luciferase Reporter Assay

2008 ◽  
Vol 75 (3) ◽  
pp. 866-868 ◽  
Author(s):  
Shicheng Chen ◽  
William F. Bleam ◽  
William J. Hickey
Keyword(s):  
Pseudomonas Putida ◽  
Iron Status ◽  
Iron Concentration ◽  
Luciferase Reporter ◽  
Iron Level ◽  
Reporter Assay ◽  
Intracellular Iron ◽  
Pseudomonas Putida Kt2440 ◽  
Cellular Iron ◽  
Dual Luciferase Reporter Assay

ABSTRACT A dual luciferase reporter (DLR) system utilizing firefly and Renilla luciferases was developed and tested in a model rhizobacterium, Pseudomonas putida KT2440. The DLR was applied to simultaneously analyze expression of three putative bacterioferritin genes (bfrα, bfrβ, and bfr) and assess the cellular iron status of strain KT2440 by monitoring expression of the Fur-regulated fepA-fes promoter. The DLR proved to be reproducible and sensitive. Expression of bfrα (PP0482) and bfrβ (PP1082) was consistent with expectations for bacterioferritin and varied directly with the iron level. However, expression of bfr (PP4856) was inversely related to the iron concentration and it was thus more likely to encode a Dps-like protein rather than a bacterioferritin.

HFE Downregulates Iron Uptake From Transferrin and Induces Iron-Regulatory Protein Activity in Stably Transfected Cells

Blood ◽  
1999 ◽  
Vol 94 (11) ◽  
pp. 3915-3921 ◽  
Author(s):  
H.D. Riedel ◽  
M.U. Muckenthaler ◽  
S.G. Gehrke ◽  
I. Mohr ◽  
K. Brennan ◽  
...  
Keyword(s):  
Transferrin Receptor ◽  
Iron Uptake ◽  
Iron Homeostasis ◽  
Hereditary Hemochromatosis ◽  
Regulatory Protein ◽  
Intracellular Iron ◽  
Iron Storage ◽  
Iron Regulatory Proteins ◽  
Cellular Iron

Abstract Hereditary hemochromatosis (HH) is a common autosomal-recessive disorder of iron metabolism. More than 80% of HH patients are homozygous for a point mutation in a major histocompatibility complex (MHC) class I type protein (HFE), which results in a lack of HFE expression on the cell surface. A previously identified interaction of HFE and the transferrin receptor suggests a possible regulatory role of HFE in cellular iron absorption. Using an HeLa cell line stably transfected with HFE under the control of a tetracycline-sensitive promoter, we investigated the effect of HFE expression on cellular iron uptake. We demonstrate that the overproduction of HFE results in decreased iron uptake from diferric transferrin. Moreover, HFE expression activates the key regulators of intracellular iron homeostasis, the iron-regulatory proteins (IRPs), implying that HFE can affect the intracellular “labile iron pool.” The increase in IRP activity is accompanied by the downregulation of the iron-storage protein, ferritin, and an upregulation of transferrin receptor levels. These findings are discussed in the context of the pathophysiology of HH and a possible role of iron-responsive element (IRE)-containing mRNAs.

scholarly journals Coxiella burnetii Infection Increases Transferrin Receptors on J774A.1 Cells

1999 ◽  
Vol 67 (7) ◽  
pp. 3236-3241 ◽  
Author(s):  
Dale Howe ◽  
Louis P. Mallavia
Keyword(s):  
Coxiella Burnetii ◽  
Iron Concentration ◽  
Fold Increase ◽  
Fluorescent Labeling ◽  
Host Cells ◽  
Transferrin Receptors ◽  
Intracellular Iron ◽  
Cellular Iron ◽  
A Minor

ABSTRACT Inoculation with viable, but not inactivated, Coxiella burnetii resulted in the increased expression of transferrin receptors (TfR) in the murine macrophage-like cell line J774A.1. This upregulation was evident in immunoblots as early as 6 h postinfection, with TfR levels continuing to increase through the first 24 h of infection. Fluorescent labeling revealed that TfR upregulation occurred throughout infected monolayers, eliminating the possibility that it reflected a response by a minor subset of host cells. In addition, TfR trafficking did not appear to be affected byC. burnetii infection. Consistent with the increase in TfRs, inoculation with viable C. burnetii resulted in a 2.5-fold increase in total cellular iron by 12 h postinoculation. Our further findings that the chelation of intracellular iron arrestsC. burnetii replication and that C. burnetiimetabolic activities in vitro are affected by iron concentration suggest that TfR upregulation is a salient factor in C. burnetii infection, and we speculate that it may represent a significant virulence mechanism.

scholarly journals Iron depletion limits intracellular bacterial growth in macrophages

Blood ◽  
2008 ◽  
Vol 112 (3) ◽  
pp. 866-874 ◽  
Author(s):  
Prasad N. Paradkar ◽  
Ivana De Domenico ◽  
Nina Durchfort ◽  
Irene Zohn ◽  
Jerry Kaplan ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Legionella Pneumophila ◽  
Bacterial Infections ◽  
Iron Chelator ◽  
Chlamydia Psittaci ◽  
Loss Of Function ◽  
Intracellular Growth ◽  
Intracellular Iron ◽  
Cellular Iron

AbstractMany intracellular pathogens infect macrophages and these pathogens require iron for growth. Here we demonstrate in vitro that the intracellular growth of Chlamydia psittaci, trachomatis, and Legionella pneumophila is regulated by the levels of intracellular iron. Macrophages that express cell surface ferroportin, the only known cellular iron exporter, limit the intracellular growth of these bacteria. Hepcidin is an antimicrobial peptide secreted by the liver in response to inflammation. Hepcidin binds to ferroportin mediating its internalization and degradation. Addition of hepcidin to infected macrophages enhanced the intracellular growth of these pathogens. Macrophages from flatiron mice, a strain heterozygous for a loss-of-function ferroportin mutation, showed enhanced intracellular bacterial growth independent of the presence of exogenous hepcidin. Macrophages, from wild-type or flatiron mice, incubated with the oral iron chelator deferriprone or desferasirox showed reduced intracellular bacterial growth suggesting that these chelators might be therapeutic in chronic intracellular bacterial infections.

Sign in / Sign up

Export Citation Format

Share Document