Hereditary hemochromatosis promotes colitis and colon cancer and causes bacterial dysbiosis in mice.

Hereditary hemochromatosis (HH), an iron-overload disease, is a prevalent genetic disorder. As excess iron causes a multitude of metabolic disturbances, we postulated that iron overload in HH disrupts colonic homeostasis and colon-microbiome interaction and exacerbates the development and progression of colonic inflammation and colon cancer. To test this hypothesis, we examined the progression and severity of colitis and colon cancer in a mouse model of HH (Hfe-/-), and evaluated the potential contributing factors. We found that experimentally induced colitis and colon cancer progressed more robustly in Hfe-/- mice than in wild-type mice. The underlying causes were multifactorial. Hfe-/- colons were leakier with lower proliferation capacity of crypt cells, which impaired wound healing and amplified inflammation-driven tissue injury. The host/microflora axis was also disrupted. Sequencing of fecal 16S RNA revealed profound changes in the colonic microbiome in Hfe-/- mice in favor of the pathogenic bacteria belonging to phyla Proteobacteria and TM7. There was an increased number of bacteria adhered onto the mucosal surface of the colonic epithelium in Hfe-/- mice than in wild-type mice. Furthermore, the expression of innate antimicrobial peptides, the first-line of defense against bacteria, was lower in Hfe-/- mouse colon than in wild-type mouse colon; the release of pro-inflammatory cytokines upon inflammatory stimuli was also greater in Hfe-/- mouse colon than in wild-type mouse colon. These data provide evidence that excess iron accumulation in colonic tissue as happens in HH promotes colitis and colon cancer, accompanied with bacterial dysbiosis and loss of function of the intestinal/colonic barrier.

Gut leakage enhances sepsis susceptibility in iron-overloaded ß-thalassemia mice through macrophage hyperinflammatory responses.

Iron overload induces intestinal-permeability defect (gut leakage), and gut translocation of organismal molecules might enhance systemic inflammation and sepsis severity in patients with thalassemia (Thal). Hence, iron administration in Hbbth3/+ mice, heterozygous ß-globin-deficient Thal mice, was explored. Oral iron administration induced more severe secondary hemochromatosis and gut leakage in Thal mice compared with wild-type (WT) mice. Gut leakage was determined by 1) FITC-dextran assay, 2) spontaneous serum elevation of endotoxin (LPS) and (1→3)-ß-d-glucan (BG), molecular structures of gut-organisms, and 3) reduction of tight-junction molecules with increased enterocyte apoptosis (activated caspase-3) by immunofluorescent staining. Iron overload also enhanced serum cytokines and increased Bacteroides spp. (gram-negative bacteria) in feces as analyzed by microbiome analysis. LPS injection in iron-overloaded Thal mice produced higher mortality and prominent cytokine responses. Additionally, stimulation with LPS plus iron in macrophage from Thal mice induced higher cytokines production with lower ß-globin gene expression compared with WT. Furthermore, possible gut leakage as determined by elevated LPS or BG (>60 pg/mL) in serum without systemic infection was demonstrated in 18 out of 41 patients with ß-thalassemia major. Finally, enhanced LPS-induced cytokine responses of mononuclear cells from these patients compared with cells from healthy volunteers were demonstrated. In conclusion, oral iron administration in Thal mice induced more severe gut leakage and increased fecal gram-negative bacteria, resulting in higher levels of endotoxemia and serum inflammatory cytokines compared with WT. Preexisting hyperinflammatory cytokines in iron-overloaded Thal enhanced susceptibility toward infection.NEW & NOTEWORTHY Although the impact of iron accumulation in several organs of patients with thalassemia is well known, the adverse effect of iron accumulation in gut is not frequently mentioned. Here, we demonstrated iron-induced gut-permeability defect, impact of organismal molecules from gut translocation of, and macrophage functional defect upon the increased sepsis susceptibility in thalassemia mice.

Endogenous hepcidin and its agonist mediate resistance to selected infections by clearing non-transferrin-bound iron.

The iron-regulatory hormone hepcidin is induced early in infection, causing iron sequestration in macrophages and decreased plasma iron; this is proposed to limit the replication of extracellular microbes, but could also promote infection with macrophage-tropic pathogens. The mechanisms by which hepcidin and hypoferremia modulate host defense, and the spectrum of microbes affected, are poorly understood. Using mouse models, we show that hepcidin was selectively protective against siderophilic extracellular pathogens (Yersinia enterocolitica O9) by controlling non-transferrin-bound iron (NTBI) rather than iron-transferrin concentration. NTBI promoted the rapid growth of siderophilic but not nonsiderophilic bacteria in mice with either genetic or iatrogenic iron overload and in human plasma. Hepcidin or iron loading did not affect other key components of innate immunity, did not indiscriminately promote intracellular infections (Mycobacterium tuberculosis), and had no effect on extracellular nonsiderophilic Y enterocolitica O8 or Staphylococcus aureus Hepcidin analogs may be useful for treatment of siderophilic infections.

The infectious disease blood safety risk of Australian hemochromatosis donations.

BACKGROUND: It has been suggested that blood donors with hereditary hemochromatosis may pose an increased infectious disease risk and adversely affect recipient outcomes. This study compares the infectious disease risk of whole blood (WB) donors enrolled as therapeutic (T) donors to voluntary WB donors to evaluate the safety of blood products provided by the T donors. STUDY DESIGN AND METHODS: This was a retrospective cohort study of all WB donations at the Australian Red Cross Blood Service who donated between January 1, 2011, and December 31, 2013, comparing a yearly mean of 11,789 T donors with 107,773 total donations and a yearly mean of 468,889 voluntary WB donors with 2,584,705 total donations. We compared postdonation notification of infectious illnesses, bacterial contamination screening results, and positive tests for blood borne viruses in T and WB donors. RESULTS: Rates of transfusion-transmissible infections in donations destined for component manufacture were significantly lower in therapeutic donations compared to voluntary donations (8.4 vs. 21.6 per 100,000 donations). Bacterial contamination (43.0 vs. 45.9 per 100,000 donations) and postdonation illness reporting (136.2 vs. 110.8 per 100,000 donations) were similar in both cohorts. CONCLUSIONS: The Australian therapeutic venisection program enables T donors to provide a safe and acceptable source of donated WB that has a low infectious disease risk profile.

Genetic modification of iron metabolism in mice affects the gut microbiota.

The composition of the gut microbiota is affected by environmental factors as well as host genetics. Iron is one of the important elements essential for bacterial growth, thus we hypothesized that changes in host iron homeostasis, may affect the luminal iron content of the gut and thereby the composition of intestinal bacteria. The iron regulatory protein 2 (Irp2) and one of the genes mutated in hereditary hemochromatosis Hfe , are both proteins involved in the regulation of systemic iron homeostasis. To test our hypothesis, fecal metal content and a selected spectrum of the fecal microbiota were analyzed from Hfe-/-, Irp2-/- and their wild type control mice. Elevated levels of iron as well as other minerals in feces of Irp2-/- mice compared to wild type and Hfe-/- mice were observed. Interestingly significant variation in the general fecal-bacterial population-patterns was observed between Irp2-/- and Hfe-/- mice. Furthermore the relative abundance of five species, mainly lactic acid bacteria, was significantly different among the mouse lines. Lactobacillus (L.) murinus and L. intestinalis were highly abundant in Irp2-/- mice, Enterococcus faecium species cluster and a species most similar to Olsenella were highly abundant in Hfe-/- mice and L. johnsonii was highly abundant in the wild type mice. These results suggest that deletion of iron metabolism genes in the mouse host affects the composition of its intestinal bacteria. Further studying the relationship between gut microbiota and genetic mutations affecting systemic iron metabolism in human should lead to clinical implications.

Hemochromatosis and Vibrio vulnificus wound infections.

There are several reports of persons with hemochromatosis and Vibrio vulnificus primary septicemia, but few accounts of persons with hemochromatosis and V. vulnificus wound infection. A 58-year-old white man developed infection of a forearm injury exposed to seawater in the Gulf of Mexico near the Alabama coast. At age 66, he was diagnosed to have hemochromatosis. Transferrin saturation was 89% and serum ferritin was 4761 pmol/L. HFE genotype was C282Y/C282Y. Serum levels of hepatic enzymes, glucose, IgG, IgA, and IgM, and blood levels of T, B, and natural killer cells were normal. We identified previous reports of only 2 similar cases: a woman from Alabama and a man from northern Australia. Mean age of the 3 subjects was 51 years at diagnosis of infection. Each had elevated serum iron measures or iron overload complications; both men were diagnosed to have hemochromatosis after they developed infection. Each of the 3 had recent exposure of a wound on an extremity to seawater, rapid development of a necrotizing soft tissue infection that required debridement and skin grafting, and positive wound or blood cultures. Each subject survived the infection. V. vulnificus wound infection occurs in some persons with hemochromatosis, but the risk of infection may be small. All patients with V. vulnificus infections should be evaluated for hemochromatosis, iron overload, and liver disorders.

Hereditary hemochromatosis results in decreased iron acquisition and growth by Mycobacterium tuberculosis within human macrophages.

Iron (Fe) acquisition is essential for the growth of intracellular Mycobacterium tuberculosis (M.tb). How this occurs is poorly understood. Hereditary hemochromatosis is an inherited disease in which most cells become overloaded with Fe. However, hereditary hemochromatosis macrophages have lower than normal levels of intracellular Fe. This suggests M.tb growth should be slower in those cells if macrophage intracellular Fe is used by M.tb. Therefore, we compared trafficking and acquisition of transferrin (Tf)- and lactoferrin (Lf)-chelated Fe by M.tb within the phagosome of monocyte-derived macrophages (MDM) from healthy controls and subjects with hereditary hemochromatosis. M.tb in both sets of macrophages acquired more Fe from Lf than Tf. Fe acquisition by M.tb within hereditary hemochromatosis macrophages was decreased by 84% from Tf and 92% from Lf relative to that in healthy control macrophages. There was no difference in Fe acquired from Tf and Lf by the two macrophage phenotypes. Both acquired 3 times more Fe from Lf than Tf. M.tb infection and incubation with interferon gamma (IFN-gamma) reduced macrophage Fe acquisition by 20% and 50%, respectively. Both Tf and Lf colocalized with M.tb phagosomes to a similar extent, independent of macrophage phenotype. M.tb growth was 50% less in hereditary hemochromatosis macrophages. M.tb growing within macrophages from subjects with hereditary hemochromatosis acquire less Fe compared with healthy controls. This is associated with reduced growth of M.tb. These data support a role for macrophage intracellular Fe as a source for M.tb growth.

Intraphagosomal Mycobacterium tuberculosis acquires iron from both extracellular transferrin and intracellular iron pools. Impact of interferon-gamma and hemochromatosis.

Mycobacterium tuberculosis multiplies within the macrophage phagosome and requires iron for growth. We examined the route(s) by which intracellular M. tuberculosis acquires iron. During intracellular growth of the virulent Erdman M. tuberculosis strain in human monocyte-derived macrophages (MDM), M. tuberculosis acquisition of (59)Fe from transferrin (TF) provided extracellularly (exogenous source) was compared with acquisition when MDM were loaded with (59)Fe from TF prior to M. tuberculosis infection (endogenous sources). M. tuberculosis (59)Fe acquisition required viable bacteria and was similar from exogenous and endogenous sources at 24 h and greater from exogenous iron at 48 h. Interferon-gamma treatment of MDM reduced (59)Fe uptake from TF 51% and TF receptor expression by 34%. Despite this, intraphagosomal M. tuberculosis iron acquisition in IFN-gamma-treated cells was decreased by only 30%. Macrophages from hereditary hemochromatosis patients have altered iron metabolism. Intracellular M. tuberculosis acquired markedly less iron in MDM from these individuals than in MDM from healthy donors, regardless of the iron source (exogenous and endogenous): 36 +/- 3.8% and 17 +/- 9.6% of control, respectively. Thus, intraphagosomal M. tuberculosis can acquire iron from both extracellular TF and endogenous macrophage sources. Acquisition of iron from macrophage cytoplasmic iron pools may be critical for the intracellular growth of M. tuberculosis. This acquisition is altered by IFN-gamma treatment to a small extent, but is markedly reduced in macrophages from hemochromatosis patients.

[Multiple hepatosplenic abscesses caused by Yersinia enterocolitica in a patient with hemochromatosis]. / Abscesos hepatoesplénicos múltiples por Yersinia enterocolítica en un paciente con hemocromatosis.

Yersinia enterocolitica is a gram-negative bacillus that thrives in conditions associated with iron overload. We describe an unusual case of a diabetic patient with a previously unrecognized hemochromatosis presenting with Y. enterocolitica septicemia. He was admitted because of a 10 day history of abdominal pain, fever and jaundice. Blood cultures grew Y. enterocolitica. The abdomen CT scan showed multiple liver and splenic abscesses. Antibiotic treatment with ciprofloxacin (2 months) resulted in a good clinical response. Serum iron studies showed iron overload. Liver biopsy revealed moderate fibrosis and early cirrhosis with large amounts of hemosiderin granules deposited in hepatocytes and bile duct epithelium. This report reviews the literature and highlights that iron overload must be ruled out in Yersinia septicemia patients.

[Yersinia bacteremia and iron overload]. / Bactériémie à Yersinia et surcharge en fer.

A retrospective multicentric study was conducted to determine the real prevalence of underlying iron overloads during Yersinia bacteremias. Ninety-seven cases of bacteremias (84 Yersinia enterocolitica, 13 Yersinia pseudotuberculosis) were registered between 1990 and 1996 in eastern France. Available data were collected in 70 cases (72.2%). Laboratory investigations of iron status were done in 53% (37/70). Three patients had a past record of known hemochromatosis, meanwhile in nine other cases an iron overload was discovered during the Yersinia bacteremia. Two cases of hemochromatosis were confirmed by liver histology. In all of these 12 cases, Yersinia enterocolitica was the causal agent. The effective prevalence of underlying iron overload in Yersinia bacteremias is 40% when researched, greater than data commonly published (1.8-14%), showing both epidemiological and clinical under estimation of iron's importance in Yersinia infection pathogenesis. A Yersinia bacteremia must be considered as an indicator of possible iron overload. Yersinia infection must be suspected in febrile hemochromatosic patients. A multicentric study must be conducted to evaluate incidence and characteristics of bacteremias in hemochromatosic patients.

Multiple liver abscesses due to Yersinia enterocolitica discloses primary hemochromatosis: three cases reports and review.

We report three cases of multiple liver abscesses due to Yersinia enterocolitica that led to previously unknown diagnoses of primary hemochromatosis. Y. enterocolitica is an iron-dependent bacterium that relies entirely on exogenous iron for growth. A review of the literature with use of MEDLINE (National Library of Medicine, Bethesda, MD) disclosed 35 cases of Y. enterocolitica liver abscesses; 21 (60%) of these cases were associated with hemochromatosis. In 11 of the remaining 14 cases, two common manifestations of hemochromatosis, diabetes mellitus and cirrhosis of the liver, also were present; these findings were significant. Finally, we emphasize that when iron overload cannot be documented at the time of diagnosis of the liver abscess, long-term follow-up for determination of increasing iron stores is mandatory. With this approach, most manifestations of hemochromatosis in asymptomatic patients can be prevented.

Liver damage in Italian patients with hereditary hemochromatosis is highly influenced by hepatitis B and C virus infection.

We evaluated the prevalence of hepatitis B virus (HBV) and hepatitis C virus (HCV) infection in 78 Italian patients with hereditary hemochromatosis as well as the relation between HCV antibody (anti-HCV) status, hepatitis B surface antigen (HBsAg) and liver histology. None of the patients had been transfused or ever consumed more than 60 g of alcohol per day. Eighteen showed histological signs of chronic hepatitis, active cirrhosis was present in 12, chronic active hepatitis in 4 and chronic persistent hepatitis in 2. Liver fibrosis or cirrhosis without inflammatory activity was observed in 31 subjects, whereas liver histology was normal except for iron overload in 18. The prevalence of HBsAg in the whole series was 5% and of anti-HCV was 20.5%. The prevalence of HBsAg and anti-HCV was significantly higher in the chronic hepatitis group than in the fibrosis/cirrhosis (p = 0.01) and the normal groups (p < 0.01). Fourteen of 18 hereditary hemochromatosis patients with chronic hepatitis were HBsAg (4) or anti-HCV (10) positive and all the latter subgroup had HCV-RNA in their serum as shown by the polymerase chain reaction. Although most of the patients with associated chronic hepatitis had cirrhosis, their serum ferritin levels and amount of mobilizable iron were significantly lower than those of the fibrosis/cirrhosis group (p < 0.01). This indicates that hepatitis viral infection acts synergistically with iron in accelerating the development of liver damage.

Liver abscesses due to Yersinia enterocolitica in patients with haemochromatosis.

Liver abscesses due to Yersinia enterocolitica usually occur in patients with a pathological iron overload. A case of multiple liver abscesses in a patient with haemochromatosis is reported and the literature is reviewed.

Fulminant septicemia caused by Yersinia enterocolitica.

A lethal case of septicemia caused by Yershia enterocolitica serotype 3 is described. A 59-year-old male, previously healthy, presented with 6 weeks of fever, abdominal pains and gradual prostration ending in overhelming septicemia and death before a conclusive diagnosis was established. Necropsy showed cirrhosis, haemochromatosis and numerous abscesses in the liver.