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Acute iron overload in mice: pathogenesis of Salmonella typhimurium infection.

The bacterial growth in the tissues of C3D2F1 male mice was measured during an experimental infection with two Salmonella typhimurium strains (high virulence, strain 2386/74; low virulence, strain L15403). This experimental model was used for evaluation of the pathogenesis in normal and iron-overloaded animals. Acute iron overload was accomplished by intramuscular injections of chelated iron (with 2,3-dihydroxybenzoic acid and citrate) with a single dose of 100 micrograms of iron per mouse. Bacteria were given intraperitoneally 1 h after the iron injection. Serum iron levels, transferrin levels, and the bacteria counts in blood and liver were measured simultaneously in all animals. There was a significant increase of bacterial growth in all tissues in the iron-treated animals. Iron abolished the normal clearance of the bacteria with low virulence from the blood. This study demonstrates that a general iron overload, as determined by an increased serum iron level, resulting from preinjection of iron, enhances bacterial growth.

Animals↗

Effect of iron overload on the metabolism and urinary recovery of 3-hydroxypyridin-4-one chelating agents in the rat.

Three orally active iron chelating agents from the 3-hydroxypyridin-4-one series of compounds were administered by gavage to both normal and iron-overloaded (500 mg Fe/kg) rats at a dose of 450 mumol/kg to investigate the effect of iron loading on metabolism and urinary recovery. Compounds selected for investigation were either poorly metabolized [1-(2'-hydroxyethyl) derivative, CP102] or predominantly biotransformed by either phase I [1,2-diethyl derivative, CP94] or phase II (1,2-dimethyl derivative, CP20) metabolic pathways. Unchanged drug and metabolite(s) recovered in urine were determined by HPLC and iron levels by atomic absorption spectrometry. Significant differences in recovery of unchanged drug were seen for both CP20 (L1) and CP94 between normal and iron-overloaded animals. In contrast, no such difference was seen for the poorly metabolized compound, CP102. For CP20 (L1), the proportion of unchanged drug excreted in the urine increased from 36.2 +/- 9.9% in normal animals to 78.7 +/- 8.1% (p < or = 0.02) in iron-loaded animals and 20.1 +/- 4.5% to 39.9 +/- 8.6% for CP94 (p < or = 0.05). A significant decrease in metabolite recovery of CP20 (L1) was seen with the 3-O-glucuronide conjugate decreasing from 38.2 +/- 8.8% in normal animals to 2.5 +/- 2.0% in the iron-overloaded group. The decrease of the 2-(1'-hydroxyethyl) metabolite of CP94 from 41.4 +/- 6.6% to 29.4 +/- 4.6% in the iron-loaded animals was, however, not statistically significant. Total dose recovered in the urine between normal and iron-overloaded animals was only significant for CP94 (p < or = 0.05).

Animals↗

The synergistic effects of vitamin E and selenium in iron-overloaded mouse hearts.

OBJECTIVES: To determine whether supplementation with vitamin E and selenium can improve myocardial antioxidant defenses in iron-overloaded mouse hearts. INTERVENTIONS: Iron-overload state was created in B6D2F1 mice (n = 20) by daily injection of iron dextran (5 mg intraperitoneally/mouse) for four weeks. The mice were also simultaneously randomly assigned to receive vitamin E (alpha-tocopherol acetate, 40 mg intraperitoneally, n = 5), selenium (sodium selenite, 1 part/million orally, n = 5), both (vitamin E + selenium, n = 5) or iron-only treatment (n = 5). The hearts were harvested for determination of selenium concentration and glutathione peroxidase activity. In a subsequent study, 15 B6D2F1 mice were randomly assigned to receive daily injections of iron (n = 5) or iron and combined antioxidant treatment (vitamin E + selenium, n = 5), or to serve as controls (n = 5) for four weeks. The hearts were harvested for determination of total iron concentrations. MAIN RESULTS: Significantly greater concentrations of heart selenium and glutathione peroxidase activity were observed in groups supplemented with both agents, as opposed to iron-only treated or single supplemented mice. Significantly lower concentrations of iron were found in controls and in those receiving combined iron and antioxidant treatment (vitamin E + selenium) than in iron-only treated mice. CONCLUSIONS: Vitamin E and selenium function synergistically in the myocardium to provide important antioxidant defenses in iron-overload states, including increased concentrations of selenium, increased glutathione peroxidase activity and decreased concentrations of iron.

Animals↗

[Iron overload in congenital hemolytic anemia caused by pyruvate kinase deficiency. A major late complication].

Twelve patients (5 women and 7 men, aged from 19 to 54 years) presenting with congenital, non-spherocytic haemolytic anaemia due to erythrocyte pyruvate kinase (PK) deficiency were investigated for systemic iron overload 18 to 27 years after the diagnosis was made. One patient had, beside PK deficiency, idiopathic haemochromatosis demonstrated by the HLA A3 and B14 markers. Another, 21-year old male patient had received more than 100 blood transfusions. In both patients, blood ferritin levels were as high as 5,584 and 9,665 g/litre respectively. Among the remaining 10 patients, 9 had biochemical signs of iron overload, such as high serum iron levels, reduced total siderophilin saturation capacity and blood ferritin levels of about 1,500 g/litre. Hepatic histology could be obtained from 5 patients and showed significant iron overload with cirrhosis in one case and clear-cut portal fibrosis in 3 cases. In all but the patient with multiple transfusions the iron overload was unrelated to transfusions, being present in their absence, usually during the 3rd and 4th decades of their life. The finding of iron overload requires preventive measures such as limitation of transfusions and elimination of iron by deferoxamine therapy.

Adult↗

Iron overload and psychiatric illness.

Seven patients with varying psychiatric disorders were found to have iron overload as manifested by abnormal serum ferritin, transferrin saturation index (TSI), or excessive urinary iron. All possible sources of secondary iron overload were ruled out. The patients were treated with the specific iron chelator, deferoxamine, given IM for seven to 22 weeks which resulted in significant clinical improvements. These cases indicate a need to be aware that disordered iron metabolism is a somatic cause of psychiatric illness and that there is clinical improvement upon lowering elevated iron levels in patients with iron overload.

Adult↗

Iron overload in Africans and African-Americans and a common mutation in the SCL40A1 (ferroportin 1) gene.

The product of the SLC40A1 gene, ferroportin 1, is a main iron export protein. Pathogenic mutations in ferroportin 1 lead to an autosomal dominant hereditary iron overload syndrome characterized by high serum ferritin concentration, normal transferrin saturation, iron accumulation predominantly in macrophages, and marginal anemia. Iron overload occurs in both the African and the African-American populations, but a possible genetic basis has not been established. We analyzed the ferroportin 1 gene in 19 unrelated patients from southern Africa (N = 15) and the United States (N = 4) presenting with primary iron overload. We found a new c. 744 C-->T (Q248H) mutation in the SLC40A1 gene in 4 of these patients (3 Africans and 1 African-American). Among 22 first degree family members, 10 of whom were Q248H heterozygotes, the mutation was associated with a trend to higher serum ferritin to amino aspartate transferase ratios (means of 14.8 versus 4.3 microg/U; P = 0.1) and lower hemoglobin concentrations (means of 11.8 versus 13.2 g/dL; P = 0.1). The ratio corrects serum ferritin concentration for alcohol-induced hepatocellular damage. We also found heterozygosity for the Q248H mutation in 7 of 51 (14%) southern African community control participants selected because they had a serum ferritin concentration below 400 microg/L and in 5 of 100 (5%) anonymous African-Americans, but we did not find the change in 300 Caucasians with normal iron status and 25 Caucasians with non-HFE iron overload. The hemoglobin concentration was significantly lower in the African community controls with the Q248H mutation than in those without it. We conclude that the Q248H mutation is a common polymorphism in the ferroportin 1 gene in African populations that may be associated with mild anemia and a tendency to iron loading.

Black or African American↗

Genetic hyperferritinaemia and reticuloendothelial iron overload associated with a three base pair deletion in the coding region of the ferroportin gene (SLC11A3).

Iron overload may predominantly involve parenchymal or reticuloendothelial cells, the prototype of parenchymal iron overload being HFE-related genetic haemochromatosis. We studied a family with autosomal dominant hyperferritinaemia in whom the proband showed selective iron accumulation in the Kupffer cells on liver biopsy. Analysis of L and H ferritin genes excluded mutations responsible for hereditary hyperferritinaemia/cataract syndrome or similar translational disorders. Sequence analysis of the ferroportin gene (SLC11A3) in four individuals with hyperferritinaemia singled out a three base pair deletion in a region that contains four TTG repeats. This mutation removes a TTG unit from 780 to 791, and predicts the loss of one of three sequential valine residues 160-162. Denaturing high performance liquid chromatography can be used for its detection. SLC11A3 polymorphism analysis indicates that this probably represents a recurrent mutation due to slippage mispairing. Affected individuals may show marginally low serum iron and transferrin saturation, and young women may have marginally low haemoglobin concentration levels. Serum ferritin levels are directly related to age, but are 10-20 times higher than normal. Heterozygosity for the ferroportin Val 162 deletion represents the prototype of selective reticuloendothelial iron overload, and should be taken into account in the differential diagnosis of hereditary or congenital hyperferritinaemias.

Adult↗

Effect of dietary iron overload on lipid peroxidation, prostaglandin synthesis and lymphocyte proliferation in young and old rats.

The effect of dietary iron overload on lipid peroxidation (LP), prostaglandin (PG) synthesis and lymphocyte proliferation was examined in young and old F344 rats. Rats 4 and 19-22 mo old were fed AIN-76 diet for 11-12 wk supplemented with 2.5% carbonyl iron obtained from two sources (Type A and B). Animals supplemented with Type A iron showed reduced food intake and weight gain associated with marked increases in extrahepatic and hepatic iron concentration. Rats receiving Type B iron had food intakes and body weights similar to those of controls but exhibited small increases in tissue iron concentration. Old control rats compared to young had significantly higher conjugated dienes (CD) in hepatic microsomes. Feeding Type A iron diets induced a significantly higher level of CD in hepatic microsomes from old rats compared to young rats. Iron overloaded rats also showed highly correlated (r = 0.94) increases in the urinary excretion of thiobarbituric acid-reactive substances and PG metabolites indicating increased in vivo LP and PG synthesis. Mitogen-stimulated PGE2 synthesis in young rats was increased at 4 wk in association with enhanced T-cell proliferation stimulated by Concanavalin A. Lymphocyte proliferation was significantly lower in old than in young control or iron-treated rats. The lack of efficacy of Type B vs. Type A iron appears due to a larger particle size and lower bioavailability. In conclusion, iron overloading increases in vivo LP and PG metabolism. Furthermore, the mitogenic response to Concanavalin A in young rats is enhanced after 4 wk of iron overloading.

Aging↗

Iron overload due to mutations in ferroportin.

Iron overload disease due to mutations in ferroportin has a dominant inheritance and a variable clinical phenotype, such that some patients show early Küpffer cell iron loading and low transferrin saturation, while others show hepatocyte iron loading and high transferrin saturation. Studies expressing ferroportin mutant proteins in cultured cells have shown that mutant proteins fall into two main classes; proteins that do not localize to the cell surface and are unable to export iron, and those that localize to the cell surface but are unable to respond to the antimicrobial peptide hepcidin. Patients with mutant ferroportin proteins that do not localize to the cell surface show typical ferroportin disease with low transferrin saturation and early Küpffer cell iron loading, while patients with mutant proteins unable to respond to hepcidin show high transferrin saturation and early hepatocyte iron loading similar to classic hereditary hemochromatosis. The dominant genetic transmission of ferroportin-linked disorders is explained by the in vitro data, which suggest that ferroportin is a multimer and that the behavior of the mutant protein can affect the behavior of the wild type protein.

Cation Transport Proteins↗

HLA haplotype A*03-B*07 in hemochromatosis probands with HFE C282Y homozygosity: frequency disparity in men and women and lack of association with severity of iron overload.

Before the discovery of HFE, reports suggested that hemochromatosis patients with the ancestral haplotype (or some element thereof) have more severe iron overload than those without the haplotype. We performed univariate and multivariate analyses of the relationships of human leukocyte antigen (HLA)-A*03 and HLA haplotype A*03-B*07 to iron measures (serum iron concentration, transferrin saturation, and serum ferritin concentration at diagnosis and units of phlebotomy to achieve iron depletion) in hemochromatosis probands homozygous for HFE C282Y diagnosed in medical care. Iron overload was defined by demonstration of hepatic iron index of > or =1.9 or removal of > or =2.0 g Fe by therapeutic phlebotomy. We tabulated the phenotype frequencies of HLA-A*03 and the frequencies of common HLA haplotypes A*01-B*08, A*02-B*44, A*03-B*07, and A*03-B*14 in three groups of white adults: (1) 141 hemochromatosis probands with C282Y homozygosity; (2) 195 index cases with IgG subclass deficiency (IgGSD) or common variable immunodeficiency (CVID), disorders typically linked to Ch6p, and (3) 750 control subjects. Among probands, 86 men and 42 women had iron overload. Frequencies of HLA-A and -B alleles in probands did not depart significantly from Hardy-Weinberg equilibrium. The phenotype frequency of A*03 did not differ significantly between men and women in the each of the respective three groups. The frequency of haplotype A*03-B*07 was greater in men than women with hemochromatosis (0.3081 vs. 0.1455; P = 0.0019). The frequency of A*03-B*014 was significantly greater in women than men with hemochromatosis (0.1182 vs. 0.0407, respectively; P = 0.0134). Mean values of most iron measures were not affected by numbers of copies of A*03 or by presence of A*03-B*07 in either men or women in univariate analysis. ANOVA models of sex, age at diagnosis, and all HLA alleles and haplotypes in probands were used to determine effects of these variables on iron measures. ANOVA models revealed that (1) there were no significant predictors for serum iron concentration; (2) B*14 is associated with higher transferrin saturation in women and lower transferrin saturation in men; (3) A*01-B*08 is associated with a trend of higher serum ferritin levels; and (4) A*03-B*14 is associated with exaggeration of the age-associated upward trend in units of phlebotomy to achieve iron depletion. In hemochromatosis probands with HFE C282Y homozygosity, we conclude that (1) disparate frequencies of HLA haplotypes A*03-B*07 and A*03-B*14 occur in men and women and (2) HLA-A*03 and HLA-A*03-B*07 are not independent variables associated with iron overload severity.

Adolescent↗

Idiopathic haemochromatosis: magnetic resonance signal intensity ratios permit non-invasive diagnosis of low levels of iron overload.

OBJECTIVE: The detection of low levels of iron overload by magnetic resonance imaging. METHODS: Eight consecutive patients suspected of having idiopathic haemochromatosis. Comparison of signal intensity ratios and absolute iron content of liver. RESULTS: There was a good correlation between the signal intensity ratios and iron content in the range 2-30 micrograms Fe/mg dry weight. CONCLUSIONS: The ability of a non-invasive technique to detect low levels of iron overload could be useful in the assessment of therapy and in the screening of relatives of probands with idiopathic haemochromatosis.

Adult↗

A unique rodent model for both the cardiotoxic and hepatotoxic effects of prolonged iron overload.

BACKGROUND: Hemochromatosis is a disease of excessive iron storage leading to tissue damage and fibrosis. Both genetic hemochromatosis, which can affect 1 in 500 of some populations, and the form of this disease which occurs as a secondary consequence of the hemoglobinopathy, homozygous beta-thalassemia, with 40 million carriers worldwide, have a common pathology. The cardiotoxicity and hepatotoxicity, which occurs with this disease, have never been produced experimentally in other species. EXPERIMENTAL DESIGN: Using a regimen of iron dextran administered subcutaneously to gerbils on a weekly basis for 7 weeks, we have produced severe hemosiderosis, especially of the liver and heart. By examining gerbils at 1, 2 and 3 months after the final iron injections we followed the subsequent development of hemochromatosis in the hearts and livers of iron overloaded animals. RESULTS: Hemochromatosis of the liver was evident as a scarring fibrosis in all cases between 1 and 3 months after iron dextran administration to gerbils. The iron burden in the cardiac myocytes of gerbils gradually increased between 1 and 3 months, resulting in hemochromatosis of the heart 2 and 3 months after the final iron dextran injections. CONCLUSIONS: Repeated parenteral injections of iron dextran to gerbils resulted in hemochromatosis affecting the liver and heart with a pathology which is the same as occurs in the end-stage disease in man. This model will allow the detailed study of the mechanism of iron induced, free radical tissue damage, which is though to be the cause of these lesions and will also be useful in the evaluation of iron chelating therapies to determine whether the hepatic and cardiac pathology of iron overload can be modulated over a long period.

Animals↗

Iron overload, but not treatment with desferrioxamine favours the development of septicemia in patients on maintenance hemodialysis.

During a 19-month period we determined the incidence of bacterial infection among 39 patients treated with desferrioxamine who had end-stage renal disease and were undergoing maintenance hemodialysis. Twenty-three received desferrioxamine because of aluminum-related bone disease, and 16 because of iron overload. A control group of 193 patients on maintenance hemodialysis but without desferrioxamine was used. No difference was found in the incidence of septicemia or of all bacterial infections between the patients with aluminum-related bone disease treated with desferrioxamine and the control patients (0.12 vs. 0.12 septicemia per patient-therapy-year, p greater than 0.05; 0.23 vs. 0.26 bacterial infections per patient-therapy-year, p greater than 0.05). The incidence of septicemia in patients treated with desferrioxamine for iron overload, however, was almost three times that in the control patients (0.36 vs. 0.12 septicemia per patient-therapy-year, p less than 0.01). To assess the effect of iron overload itself, we determined the frequency of bacterial infection in patients on regular hemodialysis who have never received desferrioxamine. These were subdivided into three groups according to serum ferritin level which indicated normal or low iron stores (Group I: serum ferritin 10-330 micrograms/l, n = 125), moderate (Group II: serum ferritin 331-1000 micrograms/l, n = 49) or more advanced iron overload (Group III: serum ferritin 1001-2000 micrograms/l, n = 10). Compared to patients with normal or low serum ferritin levels (Group I), we found a significantly higher rate of bacterial infection among patients in Group II compared with Group I (0.18 vs. 0.34 infections per patient-therapy-year, p less than 0.05) and Group III compared with Group I (0.18 vs. 0.58 infections per patient-therapy-year, p less than 0.01). These results suggest that treatment with desferrioxamine does not favour the development of septicemia or bacterial infection independently of iron overload and that iron overload itself may predispose patients on regular hemodialysis to bacterial infection.

Aged↗

Effects of phlebotomy therapy on cytochrome P450 2e1 activity and oxidative stress markers in dysmetabolic iron overload syndrome: a randomized trial.

AIM: To assess the effects of iron removal on cytochrome P450 2E1 activity and oxidative stress in dysmetabolic iron overload syndrome. METHODS: Forty-eight patients were randomized to phlebotomy therapy consisting of removal of 300-500 mL of blood every 14 days until serum ferritin levels dropped under 100 microg/L or to follow-up without phlebotomy therapy. Cytochrome P450 2E1 activity was measured at baseline and at the end of treatment by using the 6-hydroxychlorzoxazone/chlorzoxazone blood metabolic ratio, 2 h after the intake of 500 mg of chlorzoxazone. RESULTS: In the treatment group, a mean of 3.9 +/- 1.3 L of blood was removed and serum ferritin levels dropped from 715 +/- 397 to 74 +/- 34 microg/L. Variation of cytochrome P450 2E1 activity was not significantly different between the 2 groups (0.07 +/- 0.26 vs. 0.03 +/- 0.19, P = 0.36). In the treatment group, low-density lipoprotein cholesterol and vitamin E were lowered after treatment compared with control group (-0.15 +/- 0.51 vs. 0.24 +/- 0.58, P = 0.002 and -1.3 +/- 4.4 vs. 2.3 +/- 5.2, P = 0.03, respectively). Inversely, vitamin C was increased (0.5 +/- 3.5 vs. -1.8 +/- 3.9, P = 0.03). CONCLUSIONS: In dysmetabolic iron overload syndrome, reduction of iron stores does not significantly influence cytochrome P450 2E1 activity but is associated with a significant decrease of low-density lipoprotein cholesterol, suggesting that venesection therapy may be a suitable option in these patients.

Ascorbic Acid↗

Risk of iron overload is decreased in beating heart coronary artery surgery compared to conventional bypass.

Conventional cardiopulmonary bypass surgery (CCPB) increases the iron loading of plasma transferrin often to a state of plasma iron overload, with the presence of low molecular mass iron. Such iron is a potential risk factor for oxidative stress and microbial virulence. Here we assess 'off-pump' coronary artery surgery on the beating heart for changes in plasma iron chemistry. Seventeen patients undergoing cardiac surgery using the 'Octopus' myocardial wall stabilisation device were monitored at five time points for changes in plasma iron chemistry. This group was further divided into those (n=9) who had one- or two- (n=8) vessel grafts, and compared with eight patients undergoing conventional coronary artery surgery. Patients undergoing beating heart surgery had significantly lower levels of total plasma non-haem iron, and a decreased percentage saturation of their transferrin at all time points compared to conventional bypass patients. Plasma iron overload occurred in only one patient undergoing CCPB. Beating heart surgery appears to decrease red blood cell haemolysis, and tissue damage during the operative procedures and thereby significantly decreases the risk of plasma iron overload associated with conventional bypass.

Adult↗

Effects of vitamin E deficiency on hepatic mitochondrial lipid peroxidation and oxidative metabolism in rats with chronic dietary iron overload.

Peroxidative decomposition of organelle membrane phospholipids with subsequent organelle dysfunction is a postulated mechanism of liver cell injury in parenchymal iron overload. We studied the effects of different alpha-tocopherol concentrations on hepatic mitochondrial lipid peroxidation and oxidative metabolism in rats with chronic dietary iron overload. There was no evidence of mitochondrial lipid peroxidation (conjugated dienes) or alteration in mitochondrial oxidative metabolism in alpha-tocopherol-deficient rats with normal hepatic iron levels. Significant reductions in mitochondrial respiratory control ratios and oxidative phosphorylation ratios were seen in association with increased conjugated dienes in all three groups of iron-loaded rats regardless of the alpha-tocopherol status (deficient, normal or excess); thus, the alpha-tocopherol deficiency associated with dietary iron overload in this experimental model is not responsible for the mitochondrial abnormalities observed. In addition, chronic parenteral administration of alpha-tocopherol to iron-loaded animals, which increased hepatic levels of this substance 3-fold, did not ameliorate the hepatic mitochondrial lipid peroxidation or the defects in mitochondrial oxidative metabolism resulting from iron overload.

Animals↗

Iron overload in congenital erythrocyte pyruvate kinase deficiency.

Severe iron overload developed in two patients with congenital erythrocyte pyruvate kinase deficiency. In one of them this was complicated by hepatic cirrhosis and endocrine dysfunction. In both patients, the institution of intermittent subcutaneous administration of desferrioxamine resulted in significant urinary iron excretion and a reduction in the degree of iron overload.

Adult↗

Effect of mild iron overload on liver and kidney lipid peroxidation.

1. Hepatotoxicity is the most common finding in patients with iron overload since the liver is the major recipient of iron excess, even though the kidney could be a target of iron toxicity. The effect of iron overload was studied in the early stages after iron-dextran injection in rats, as a model for secondary hemocromatosis. 2. Total hepatic and kidney iron content was markedly elevated over control values 20 h after the iron administration. Plasma GOT, GPT and LDH activities were not affected, suggesting that liver cell permeability was not affected by necrosis. 3. Spontaneous liver chemiluminescence was measured as an indicator of oxidative stress and lipid peroxidation. Light emission was increased four-fold 6 h after iron supplementation. 4. Increases in the generation of thiobarbituric acid reactive substances (TBARS in liver and kidney homogenates were detected after iron administration. 5. The activities of catalase, SOD and glutathione peroxidase were determined. Enzymatic activities declined in liver homogenates by 25, 36 and 32%, respectively, 20 h after iron injection. These activities were not affected in kidney as compared to control values, except for SOD activity that was decreased by 26%. 6. The content of alpha-tocopherol was decreased by 31% in whole kidney homogenates and by 40% in plasma. 7. Our data indicate that lipid peroxidation occurs after mild iron overload both in liver and kidney. Enzymatic antioxidants are consumed significantly in liver and alpha-tocopherol content decreases in kidney, suggesting an organ-specific antioxidant effect.

Animals↗