Hepcidin and iron homeostasis

The ectodomain of matriptase-2 plays an important nonproteolytic role in suppressing hepcidin expression in mice

Matriptase-2 (MT2), encoded by TMPRSS6, is a membrane-anchored serine protease that plays a key role in suppressing hepatic hepcidin expression. MT2 is synthesized as a zymogen and undergoes autocleavage for activation. Previous studies suggest that MT2 suppresses hepcidin by cleaving hemojuvelin and other components of the bone morphogenetic protein-signaling pathway. However, the underlying mechanism is still debatable. Here we dissected the contributions of the nonproteolytic and proteolytic activities of Mt2 by taking advantage of Mt2 mutants and Tmprss6-/- mice. Studies of the protease-dead full-length Mt2 (Mt2S762A) and the truncated Mt2 that lacks the catalytic domain (Mt2mask) indicate that the catalytic domain, but not its proteolytic activity, was required for Mt2 to suppress hepcidin expression. This process was likely accomplished by the binding of Mt2 ectodomain to Hjv and Hfe. We found that Mt2 specifically cleaved the key components of the hepcidin-induction pathway, including Hjv, Alk3, ActRIIA, and Hfe, when overexpressed in hepatoma cells. Nevertheless, studies of a murine iron-refractory iron-deficiency anemia-causing mutant (Mt2I286F) in the complement protein subcomponents C1r/C1s, urchin embryonic growth factor, and bone morphogenetic protein 1 domain indicate that Mt2I286F can be activated, but it exhibited a largely compromised ability to suppress hepcidin expression. Coimmunoprecipitation analysis revealed that Mt2I286F, but not Mt2S762A, had reduced interactions with Hjv, ActRIIA, and Hfe. In addition, increased expression of a serine protease inhibitor, the hepatocyte growth factor activator inhibitor-2, in the liver failed to alter hepcidin. Together, these observations support the idea that the substrate interaction with Mt2 plays a determinant role and suggest that the proteolytic activity is not an appropriate target to modulate the function of MT2 for clinical applications.

How I treat anemia in the perisurgical setting

Anemia is a common finding in the perioperative setting with significant untoward consequences including worsening of outcomes and diminished quality of life as well as increased risk of allogeneic blood transfusions. Here, we present 3 cases that illustrate how anemia can be perioperatively managed in patients undergoing cardiac, orthopedic, and oncology surgeries. Timely detection of anemia prior to high-blood loss surgeries can allow clinicians to manage it and optimize hemoglobin level, making patients better prepared for the surgery. Treatment of anemia should be guided by the etiology and may include erythropoietic agents, folic acid, B12, and iron preparations. Other blood management strategies geared toward reducing surgical blood loss such as autologous transfusion techniques and agents to optimize hemostasis are used during surgery and in the immediate postoperative period. Patients should be closely monitored following surgery for signs of ongoing bleeding in need of control. Finally, screening for and management of anemia should continue in the postoperative and postdischarge period, as persistence and recurrence of anemia can further undermine patient's outcomes.

Iron Metabolism Disorders for Cognitive Dysfunction After Mild Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the most harmful forms of acute brain injury and predicted to be one of the three major neurological diseases that cause neurological disabilities by 2030. A series of secondary injury cascades often cause cognitive dysfunction of TBI patients leading to poor prognosis. However, there are still no effective intervention measures, which drive us to explore new therapeutic targets. In this process, the most part of mild traumatic brain injury (mTBI) is ignored because its initial symptoms seemed not serious. Unfortunately, the ignored mTBI accounts for 80% of the total TBI, and a large part of the patients have long-term cognitive dysfunction. Iron deposition has been observed in mTBI patients and accompanies the whole pathological process. Iron accumulation may affect long-term cognitive dysfunction from three pathways: local injury, iron deposition induces tau phosphorylation, the formation of neurofibrillary tangles; neural cells death; and neural network damage, iron deposition leads to axonal injury by utilizing the iron sensibility of oligodendrocytes. Thus, iron overload and metabolism dysfunction was thought to play a pivotal role in mTBI pathophysiology. Cerebrospinal fluid-contacting neurons (CSF-cNs) located in the ependyma have bidirectional communication function between cerebral-spinal fluid and brain parenchyma, and may participate in the pathway of iron-induced cognitive dysfunction through projected nerve fibers and transmitted factor, such as 5-hydroxytryptamine, etc. The present review provides an overview of the metabolism and function of iron in mTBI, and to seek a potential new treatment target for mTBI with a novel perspective through combined iron and CSF-cNs.

Iron Availability in Tissue Microenvironment: The Key Role of Ferroportin

Body iron levels are regulated by hepcidin, a liver-derived peptide that exerts its function by controlling the presence of ferroportin (FPN), the sole cellular iron exporter, on the cell surface. Hepcidin binding leads to FPN internalization and degradation, thereby inhibiting iron release, in particular from iron-absorbing duodenal cells and macrophages involved in iron recycling. Disruption in this regulatory mechanism results in a variety of disorders associated with iron-deficiency or overload. In recent years, increasing evidence has emerged to indicate that, in addition to its role in systemic iron metabolism, FPN may play an important function in local iron control, such that its dysregulation may lead to tissue damage despite unaltered systemic iron homeostasis. In this review, we focus on recent discoveries to discuss the role of FPN-mediated iron export in the microenvironment under both physiological and pathological conditions.

The effect of food and nutrients on iron overload: what do we know so far?

There has been no established food and nutrition guidance for diseases characterized by the presence of iron overload (IOL) yet. Hepcidin is a hormone that diminishes iron bioavailability. Its levels increase in response to increased iron stores. Hence, IOL conditions could hypothetically trigger a self-regulatory mechanism for the reduction of the intestinal absorption of iron. In addition, some food substances may modulate intestinal iron absorption and may be useful in the dietary management of patients with IOL. This scoping review aimed to systematize studies that support dietary prescriptions for IOL patients. It was carried out according to the method proposed by the Joanna Briggs Institute and the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Although the need to restrict iron in the diet of individuals with hemochromatosis is quite clear, there is a consensus that IOL diminishes the rate of iron absorption. Reduced iron absorption is also present and has been reported in some diseases with transfusion IOL, in which serum hepcidin is usually high. The consumption of polyphenols and 6-shogaol seems to reduce iron absorption or serum ferritin concentration, while procyanidins do not cause any changes. Vitamin C deficiency is often found in IOL patients. However, vitamin C supplementation and alcohol consumption should be avoided not only because they increase iron absorption, but also because they provoke toxic oxidative reactions when the iron is excessive. Dietary approaches must consider the differences in the pathophysiology and treatment of IOL diseases.

Downregulation of FPN1 acts as a prognostic biomarker associated with immune infiltration in lung cancer

Lung cancer morbidity and mortality remain the leading causes of tumor-associated death worldwide. The discovery of early diagnostic and prognostic markers of lung cancer could significantly improve the survival rate and decrease the mortality rate. FPN1 is the only known mammalian iron exporter. However, the molecular and biological functions of FPN1 in lung cancer remain unclear. Here, FPN1 mRNA expression in lung cancer was estimated using the TCGA, Oncomine, TIMER, and UALCAN databases. The prognostic role of FPN1 was evaluated using Kaplan-Meier plotter and PrognoScan. Associations between FPN1 and immune infiltration in lung cancer were evaluated by the TIMER and CIBERSORT algorithms. FPN1 mRNA and protein expressions were significantly downregulated in lung cancer. Low FPN1 expression was strongly related to worse prognosis in patients with lung cancer. GO and KEGG analyses and GSEA suggested that FPN1 was remarkably related to iron homeostasis and immunity. Importantly, FPN1 was remarkably associated with the infiltrating abundance of multiple immune cells. Moreover, FPN1 displayed a strong correlation with various immune marker sets. We investigated the clinical application value of FPN1 and provided a basis for the sensitive diagnosis, prognostication and targeted therapy of lung cancer.

Pro-inflammatory cytokine interleukin-6-induced hepcidin, a key mediator of periodontitis-related anemia of inflammation

OBJECTIVES

To investigate whether anemia of inflammation (AI) occurs in periodontitis patients and to further explore underlying pathogenesis of periodontitis-related AI by an experimental periodontitis model.

BACKGROUND

Previous studies have reported periodontitis patients could show a tendency toward AI. However, the relationship between periodontitis and AI remains unclear, and the related pathological mechanisms have not been identified.

MATERIALS AND METHODS

Periodontal clinical parameters, inflammatory markers, and anemia-related indicators were compared between 98 aggressive periodontitis (AgP) patients and 103 healthy subjects. An experimental periodontitis model was induced by ligature placement in mice. The changes in mice inflammatory markers, anemia indicators, hepcidin mRNA expression, and serum hepcidin concentrations were measured. Human and mouse liver cells were treated with interleukin-6 (IL-6) for analyzing the changes in hepcidin expression based on mRNA and protein levels.

RESULTS

AgP patients exhibited higher white blood cell counts, IL-6, and C-reactive protein. Adjusted linear regression analyses showed correlations between AgP and decreased hemoglobin (HGB) and hematocrit (HCT). The ligature-induced periodontitis caused systemic inflammation and elevated IL-6 levels. Lower red blood cell counts, HGB, and HCT were detected, whereas the levels of hepcidin mRNA expression and serum hepcidin concentrations increased. The treatment of hepatocytes with IL-6 induced both hepcidin mRNA expression and hepcidin secretion.

CONCLUSIONS

Systemic inflammation induced by periodontitis leads to an increased risk for AI. IL-6-induced hepcidin could play a central mediator role and act as a key pathologic mechanism. Our results demonstrate periodontitis may be considered as an additional inflammatory disease contributing to the development of AI.

Analytical evaluation of serum non-transferrin-bound iron and its relationships with oxidative stress and cardiac load in the general population

Excessive iron accumulation provokes toxic effects, especially in the cardiovascular system. Under iron overload, labile free non-transferrin-bound iron (NTBI) can induce cardiovascular damage with increased oxidative stress. However, the significance of NTBI in individuals without iron overload and overt cardiovascular disease has not been investigated. We aimed to examine the distribution of serum NTBI and its relationship with oxidative stress and cardiac load under physiological conditions in the general population.We enrolled individuals undergoing an annual health check-up and measured serum NTBI and derivatives of reactive oxygen metabolites (d-ROM), an oxidative stress marker. In addition, we evaluated serum levels of B-type natriuretic peptide (BNP) to examine cardiac load. We excluded patients with anemia, renal dysfunction, cancer, active inflammatory disease, or a history of cardiovascular disease.A total of 1244 individuals (57.8 ± 11.8 years) were enrolled, all of whom had detectable serum NTBI. d-ROM and BNP showed significant trends across NTBI quartiles. Multivariable regression analysis revealed that serum iron and low-density lipoprotein cholesterol were positively associated with NTBI but that age, d-ROM, and BNP showed an inverse association with this measure. In logistic regression analysis, NTBI was independently associated with a combination of higher levels of both d-ROM and BNP than the upper quartiles after adjustment for possible confounding factors.Serum NTBI concentration is detectable in the general population and shows significant inverse associations with oxidative stress and cardiac load. These findings indicate that serum NTBI in physiological conditions does not necessarily reflect increased oxidative stress, in contrast to the implications of higher levels in states of iron overload or pathological conditions.

A role of PIEZO1 in iron metabolism in mice and humans

Iron overload causes progressive organ damage and is associated with arthritis, liver damage, and heart failure. Elevated iron levels are present in 1%-5% of individuals; however, iron overload is undermonitored and underdiagnosed. Genetic factors affecting iron homeostasis are emerging. Individuals with hereditary xerocytosis, a rare disorder with gain-of-function (GOF) mutations in mechanosensitive PIEZO1 ion channel, develop age-onset iron overload. We show that constitutive or macrophage expression of a GOF Piezo1 allele in mice disrupts levels of the iron regulator hepcidin and causes iron overload. We further show that PIEZO1 is a key regulator of macrophage phagocytic activity and subsequent erythrocyte turnover. Strikingly, we find that E756del, a mild GOF PIEZO1 allele present in one-third of individuals of African descent, is strongly associated with increased plasma iron. Our study links macrophage mechanotransduction to iron metabolism and identifies a genetic risk factor for increased iron levels in African Americans.

Iron status in athletic females, a shift in perspective on an old paradigm

Iron deficiency is a common nutrient deficiency within athletes, with sport scientists and medical professionals recognizing that athletes require regular monitoring of their iron status during intense training periods. Revised considerations for athlete iron screening and monitoring have suggested that males get screened biannually during heavy training periods and females require screening biannually or quarterly, depending on their previous history of iron deficiency. The prevalence of iron deficiency in female athletes is higher than their male counterparts and is often cited as being a result of the presence of a menstrual cycle in the premenopausal years. This review has sought to revise our current understanding of female physiology and the interaction between primary reproductive hormones (oestrogen and progesterone) and iron homoeostasis in females. The review highlights an apparent symbiotic relationship between iron metabolism and the menstrual cycle that requires additional research as well as identifying areas of the menstrual cycle that may be primed for nutritional iron supplementation.

Exercise training decreases whole-body and tissue iron storage in adults with obesity

NEW FINDINGS

What is the central question of this study? Does exercise training modify tissue iron storage in adults with obesity? What is the main finding and its importance? Twelve weeks of moderate-intensity exercise or high-intensity interval training lowered whole-body iron stores, decreased the abundance of the key iron storage protein in skeletal muscle (ferritin) and tended to lower hepatic iron content. These findings show that exercise training can reduce tissue iron storage in adults with obesity and might have important implications for obese individuals with dysregulated iron homeostasis.

ABSTRACT

The regulation of iron storage is crucial to human health, because both excess and deficient iron storage have adverse consequences. Recent studies suggest altered iron storage in adults with obesity, with increased iron accumulation in their liver and skeletal muscle. Exercise training increases iron use for processes such as red blood cell production and can lower whole-body iron stores in humans. However, the effects of exercise training on liver and muscle iron stores in adults with obesity have not been assessed. The aim of this study was to determine the effects of 12 weeks of exercise training on whole-body iron stores, liver iron content and the abundance of ferritin (the key iron storage protein) in skeletal muscle in adults with obesity. Twenty-two inactive adults (11 women and 11 men; age, 31 ± 6 years; body mass index, 33 ± 3 kg/m² ) completed 12 weeks (four sessions/week) of either moderate-intensity continuous training (MICT; 45 min at 70% of maximal heart rate; n = 11) or high-intensity interval training (HIIT; 10 × 1 min at 90% of maximal heart rate, interspersed with 1 min active recovery; n = 11). Whole-body iron stores were lower after training, as indicated by decreased plasma concentrations of ferritin (P = 3 × 10^-5 ) and hepcidin (P = 0.02), without any change in C-reactive protein. Hepatic R2*, an index of liver iron content, was 6% lower after training (P = 0.06). Training reduced the skeletal muscle abundance of ferritin by 10% (P = 0.03), suggesting lower muscle iron storage. Interestingly, these adaptations were similar in MICT and HIIT groups. Our findings indicate that exercise training decreased iron storage in adults with obesity, which might have important implications for obese individuals with dysregulated iron homeostasis.

Role of the BMP6 protein in breast cancer and other types of cancer

The BMP6 protein (Bone Morphogenetic Protein 6) is part of the superfamily of transforming growth factor-beta (TGF-β) ligands, participates in iron homeostasis, inhibits invasion by increasing adhesions and cell-cell type interactions and induces angiogenesis directly on vascular endothelial cells. BMP6 is coded by a tumor suppressor gene whose subexpression is related to the development and cancer progression; during neoplastic processes, methylation is the main mechanism by which gene silencing occurs. This work presents a review on the role of BMP6 protein in breast cancer (BC) and other types of cancer. The studies carried out to date suggest the participation of the BMP6 protein in the epithelial-mesenchymal transition (EMT) phenotype, cell growth and proliferation; however, these processes are affected in a variable way in the different types of cancer, the methylated CpG sites in BMP6 gene promoter, as well as the interaction with other proteins could be the cause of such variation.

Cancer Related Anemia: An Integrated Multitarget Approach and Lifestyle Interventions

Cancer is often accompanied by worsening of the patient's iron profile, and the resulting anemia could be a factor that negatively impacts antineoplastic treatment efficacy and patient survival. The first line of therapy is usually based on oral or intravenous iron supplementation; however, many patients remain anemic and do not respond. The key might lie in the pathogenesis of the anemia itself. Cancer-related anemia (CRA) is characterized by a decreased circulating serum iron concentration and transferrin saturation despite ample iron stores, pointing to a more complex problem related to iron homeostatic regulation and additional factors such as chronic inflammatory status. This review explores our current understanding of iron homeostasis in cancer, shedding light on the modulatory role of hepcidin in intestinal iron absorption, iron recycling, mobilization from liver deposits, and inducible regulators by infections and inflammation. The underlying relationship between CRA and systemic low-grade inflammation will be discussed, and an integrated multitarget approach based on nutrition and exercise to improve iron utilization by reducing low-grade inflammation, modulating the immune response, and supporting antioxidant mechanisms will also be proposed. Indeed, a Mediterranean-based diet, nutritional supplements and exercise are suggested as potential individualized strategies and as a complementary approach to conventional CRA therapy.

[Expression of iron-regulating erythroid factors in different types of erythropoiesis disorders]

Objective: To investigate the expression of iron-regulating erythroid factors in different types of erythropoiesis disorders. Methods: From January 2016 to November 2019, the plasma concentrations of iron-regulating erythroid factors were measured by ELISA methods in 47 patients with different types of erythropoiesis disorders. The adaptation orientation of iron-regulating erythroid factor expression with bone marrow erythropoiesis activities (represented by bone marrow-nucleated erythrocytes ratio) was analyzed. Results: The median plasma growth differentiation factor (GDF) 15 levels in patients with polycythemia vera (PV) , pure red cell aplasia (PRCA) , autoimmune hemolytic anemia (AIHA) , and myelodysplastic syndrome (MDS) were 266.01 ng/L (112.40, 452.37) , 110.63 ng/L (81.41, 220.42) , 52.11 ng/L (32.61, 171.66) , and 276.53 (132.16, 525.70) ng/L, respectively, which were significantly higher than those in normal patients with 37.45 (19.65, 57.72) ng/L (all P < 0.01) . The plasma TWSG1 expression levels were not significantly different in patients with PV, PRCA, AIHA, and MDS from those of normal patients (P>0.05) . The median plasma GDF11 level in PV was 74.75 (10.95, 121.32) ng/L, which was significantly higher than 36.90 (3.38, 98.34) ng/L in normal control subjects (P<0.01) . However, no statistical differences were observed in the other three subjects (P>0.05) . The median plasma erythroferrone (ERFE) levels in AIHA and PV were 121.76 ng/L (68.12, 343.11) and 129.63 (47.02, 170.03) ng/L, respectively, with the highest level in AIHA in all the studied types of erythropoiesis disorders. The bone marrow-nucleated erythrocytes ratio was significantly and positively correlated with ERFE (r=0.458, P=0.001) but not with GDF15 (r=-0.163, P=0.274) , GDF11 (r=0.120, P=0.421) , and TWSG1 (r=-0.166, P=0.269) . Conclusion: The expression profile of iron-regulating erythroid factors is not exactly the same in different types of erythropoiesis disorders. ERFE demonstrated the highest correlation with erythropoiesis activities.

Time to Start Delivering Iron Chelation Therapy in Newly Diagnosed Severe β-Thalassemia

Background

Iron overload is still a major complication of severe β-thalassemia. Indication to start iron chelation therapy is based on serum ferritin (SF) or transferrin saturation (TS) level or the amount of transfusion. The goal of this study is to analyse the pattern of iron status, the amount of transfusion regarding the time to start iron chelator, and serum hepcidin levels in newly diagnosed severe β-thalassemia.

Methods

A prospective cohort study was performed at Hasan Sadikin General Hospital on newly diagnosed severe β-thalassemia patients. Subjects had not received any blood transfusion with normal liver function test, CRP, and IL-6 levels who consumed normal diet according to age. The SF and TS levels indicate iron status, while hepcidin level indicates iron regulator status. Main indicator to start iron chelation therapy when SF level ≥1.000 ng/mL, TS level ≥70%, or after receiving transfusion at least 10 times. Statistical analysis used Mann–Whitney and Spearman.

Results

Forty-two newly severe β-thalassemia, 30 (71.4%), were diagnosed before 1 year old, mean 9.9 ± 6.4 months, range 2–24 months. Range amount of transfusion until SF level reached ≥1,000 ng/mL were 4-12 times, mean 7 ± 2 times. Mean SF and TS level at diagnosis were 365.6 ± 194.9 ng/mL and 67.3 ± 22.5%, while hepcidin level was normal, mean 242.6 ± 58 ng/mL. 36/42 patients have reached SF >1000 ng/mL with amount of transfusion less than 10 times. There was no significant difference of SF, TS, and hepcidin levels when SF >1000 ng/mL in the group with amount of transfusion 7–12 and less than 7 (p = 0.454, p = 0.084, p = 0.765), respectively. A significant positive correlation between SF and amount of transfusion was observed (p < 0.001; r = 0.781).

Conclusion

Iron overload in severe β-thalassemia patients might occur earlier even before they received 10 times transfusion. Hepcidin serum level tends to increase when iron overload just started.

Recent advances in iron homeostasis and regulation - a focus on epigenetic regulation and stroke

Iron is an element with redox properties. It is active sites of many enzymes and plays an important role in various cellular and biological functions including ATP production and DNA synthesis. However, as a redox element, iron promotes free radical generation and lipid peroxidation, causing oxidative damage and cell death. Iron-mediated oxidation is a central player in ferroptosis, a type of cell death process that is different from apoptosis and necrosis. Thus, iron metabolism and homeostasis are sophisticatedly regulated. There has been exciting progress in understanding iron metabolism and regulation since hepcidin was recognized as the central regulator of iron homeostasis. Hepcidin mainly regulates the iron export function of the ferrous iron permease, ferroportin, which is the only known iron exporter expressed by mammalian cells. Particularly, epigenetic regulation has been a recent focus on iron homeostasis. Epigenetic phenomena have been demonstrated to modulate key proteins including hepcidin in iron metabolism. Here, we review the rapid progress in recent years in understanding molecular mechanisms of iron homeostasis with a focus on epigenetic regulation of hepcidin, ferritin, and ferroptosis. Interactions between methionine oxidation and iron is also discussed. Furthermore, many studies have suggested that the severity of neuronal damage after stroke is proportional to the magnitude of brain iron accumulation. Recent discoveries regarding iron metabolism in stroke is briefly discussed. Understanding the underlying mechanism in iron regulation could provide insight into the treatment of various intractable diseases including stroke.

Perinatal and early-life cobalt exposure impairs essential metal metabolism in immature ICR mice

The objective of the present study was to assess the impact of cobalt (Co) exposure on tissue distribution of iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn), as well as serum hepcidin levels in immature mice (18, 25, 30 days). Pregnant mice were exposed to 75 mg/kg b.w. cobalt chloride (CoCl₂ × 6H2O) with drinking water starting from 3 days before delivery and during lactation. At weaning (day 25) the offspring were separated and housed in individual cages with subsequent exposure to 75 mg/kg b.w. CoCl₂ until 30 days postnatally. Evaluation of tissue metal levels was performed by an inductively coupled plasma-mass spectrometry (ICP-MS). Serum hepcidin level was assayed by enzyme linked immunosorbent assay (ELISA). Cobalt exposure resulted in a time- and tissue-dependent increase in Co levels in kidney, spleen, liver, muscle, erythrocytes, and serum on days 18, 25, and 30. In parallel with increasing Co levels, CoCl₂ exposure resulted in a significant accumulation of Cu, Fe, Mn, and Zn in the studied tissues, with the effect being most pronounced in 25-day-old mice. Cobalt exposure significantly increased serum hepcidin levels only in day18 mice. The obtained data demonstrate that Co exposure may alter essential metal metabolism in vivo.

Coaction of hepatic thioredoxin and glutathione systems in iron overload-induced oxidative stress

In the present study, we demonstrate the coaction of thioredoxin and glutathione (GSH) systems in mouse liver against iron overload-induced oxidative stress (OS). Mice were injected intraperitoneally with an iron dextran solution twice a week for 3 weeks. Iron accumulation in mouse liver was demonstrated spectroscopically. To confirm the iron overload model in the liver, the increased gene expression levels of hepcidin (Hamp), ferroportin (Fpn1), and ferritin (Fth1), which regulate iron trafficking, were observed by a quantitative polymerase chain reaction. In the case of iron overload, the GSH level and the reduced glutathione/oxidized glutathione ratio, which represents a marker of OS, decreased significantly. An increase in the malondialdehyde level, one of the final products of the lipid peroxidation process, was observed. The gene expression of the thioredoxin system, including thioredoxin (Trx1) and thioredoxin reductase (TrxR1), was examined. Though TrxR1 expression decreased, no changes were observed in Trx1. The enzyme activity and semiquantitative protein expression of TRXR1 increased. The activity of GSH reductase and GSH peroxidase increased in the iron overload group. The gene and protein expressions of thioredoxininteracting protein, which is an indicator of the commitment of the cell to apoptosis, were elevated significantly. The increased protein expression of Bcl-2-related X protein and CASPASE-3, which is an indicator of apoptosis, increased significantly. In conclusion, excess iron accumulation in mouse liver tissue causes OS, which affects the redox state of the thioredoxin and GSH systems, inducing cell apoptosis and also ferroptosis due to increased lipid peroxidation and the depletion of GSH level.

Iron homeostasis in host and gut bacteria - a complex interrelationship

Iron deficiency is the most frequent nutritional deficiency in the world with an estimated 1.4 billion people affected. The usual way to fight iron deficiency is iron fortification, but this approach is not always effective and can have undesirable side effects including an increase in the growth and virulence of gut bacterial pathogens responsible for diarrhea and gut inflammation. Iron is mainly absorbed in the duodenum and is tightly regulated in mammals. Unabsorbed iron enters the colonic lumen where many microorganisms, referred to as gut microbiota, reside. Iron is essential for these bacteria, and its availability consequently affects this microbial ecosystem. The aim of this review is to provide further insights into the complex relationship between iron and gut microbiota. Given that overcoming anemia caused by iron deficiency is still a challenge today, gut microbiota could help identify more efficient ways to tackle this public health problem.

Iron Homeostasis and Metabolism: Two Sides of a Coin

Iron is an ancient, essential and versatile transition metal found in almost all living organisms on Earth. This fundamental trace element is used in the synthesis of heme and iron-sulfur (Fe-S) containing proteins and other vital cofactors that are involved in respiration, redox reactions, catalysis, DNA synthesis and transcription. At the same time, the ability of iron to cycle between its oxidized, ferric (Fe³⁺) and its reduced, ferrous (Fe²⁺) state contributes to the production of free radicals that can damage biomolecules, including proteins, lipids and DNA. In particular, the regulated non-apoptotic cell death ferroptosis is driven by Fe²⁺-dependent lipid peroxidation that can be prevented by iron chelation or genetic inhibition of cellular iron uptake. Therefore, iron homeostasis must be tightly regulated to avoid iron toxicity. This review provides an overview of the origin and chemistry of iron that makes it suitable for a variety of biological functions and addresses how organisms evolved various strategies, including their scavenging and antioxidant machinery, to manage redox-associated drawbacks. Finally, key mechanisms of iron metabolism are highlighted in human diseases and model organisms, underlining the perils of dysfunctional iron handlings.

Searching for Novel Candidate Biomarkers of RLS in Blood by Proteomic Analysis

PURPOSE

We performed comparative proteomic analyses of blood of patients with RLS and healthy individuals aiming to identify potential biomarker and therapeutic target candidate for RLS.

PATIENTS AND METHODS

Blood serum samples from 12 patients with a clinical diagnosis of RLS (8 females and 4 males, with a mean age of 68.52 years) and 10 healthy controls (5 females and 5 males, with a mean age of 67.61 years) underwent proteomic profiling by liquid chromatography coupled with tandem mass spectrometry. Pathway analysis incorporating protein-protein interaction networks was carried out to identify pathological processes linked to the differentially expressed proteins.

RESULTS

We quantified 272 proteins in patients with RLS and healthy controls, of which 243 were shared. Five proteins - apolipoprotein C-II, leucine-rich alpha-2-glycoprotein 1, FLJ92374, extracellular matrix protein 1, and FLJ93143 - were substantially increased in RLS patients, whereas nine proteins - vitamin D-binding protein, FLJ78071, alpha-1-antitrypsin, CD5 antigen-like, haptoglobin, fibrinogen alpha chain, complement factor H-related protein 1, platelet factor 4, and plasma protease C1 inhibitor - were decreased. Bioinformatics analyses revealed that these proteins were linked to 1) inflammatory and immune response, and complement activation, 2) brain-related development, cell aging, and memory disorders, 3) pregnancy and associated complications, 4) myocardial infarction, and 5) reactive oxygen species generation and subsequent diabetes mellitus.

CONCLUSION

Our findings shed light on the multifactorial nature of RLS and identified a set of circulating proteins that may have clinical importance as biomarkers and therapeutic targets.

Isolation and thermal stabilization of mouse ferroportin

Ferroportin (Fpn) is an essential mammalian iron transporter that is negatively regulated by the hormone hepcidin. Our current molecular understanding of Fpn‐mediated iron efflux and regulation is limited due to a lack of biochemical, biophysical and high‐resolution structural studies. A critical step towards understanding the transport mechanism of Fpn is to obtain sufficient quantities of pure and stable protein for downstream studies. As such, we detail here an expression and purification protocol for mouse Fpn yielding milligram quantities of pure protein. We have generated deletion constructs exhibiting enhanced thermal stability and which retained iron‐transport activity and hepcidin responsiveness, providing a platform for further biophysical studies of Fpn.

Cytokine and Gene Expression Profiling in Patients with HFE-Associated Hereditary Hemochromatosis according to Genetic Profile

BACKGROUND

Hemochromatosis gene (HFE)-associated hereditary hemochromatosis (HH) is characterized by downregulation of hepcidin synthesis, leading to increased intestinal iron absorption.

OBJECTIVES

The objectives were to characterize and elucidate a possible association between gene expression profile, hepcidin levels, disease severity, and markers of inflammation in HFE-associated HH patients.

METHODS

Thirty-nine HFE-associated HH patients were recruited and assigned to 2 groups according to genetic profile: C282Y homozygotes in 1 group and patients with H63D, as homozygote or in combination with C282Y, in the other group. Eleven healthy first-time blood donors were recruited as controls. Gene expression was characterized from peripheral blood cells, and inflammatory cytokines and hepcidin-25 isoform were quantified in serum. Biochemical disease characteristics were recorded.

RESULTS

Elevated levels of interleukin 8 were observed in a significant higher proportion of patients than controls. In addition, compared to controls, gene expression of ζ-globin was significantly increased among C282Y homozygote patients, while gene expression of matrix metalloproteinase 8, and other neutrophil-secreted proteins, was significantly upregulated in patients with H63D.

CONCLUSION

Different disease signatures may characterize HH patients according to their HFE genetic profile. Studies on larger populations, including analyses at protein level, are necessary to confirm these findings.

Iron Therapeutics in Women's Health: Past, Present, and Future

Iron plays a unique physiological role in the maintenance of homeostasis and the pathological outcomes of the female reproductive tract. The dual nature of elemental iron has created an evolutionary need to tightly regulate its biological concentration. The female reproductive tract is particularly unique due to the constant cycle of endometrial growth and shedding, in addition to the potential need for iron transfer to a developing fetus. Here, iron regulation is explored in a number of physiologic states including the endometrial lining and placenta. While iron dysregulation is a common characteristic in many women's health pathologies there is currently a lack of targeted therapeutic options. Traditional iron therapies, including iron replacement and chelation, are common treatment options for gynecological diseases but pose long term negative health consequences; therefore, more targeted interventions directed towards iron regulation have been proposed. Recent findings show potential benefits in a therapeutic focus on ferritin-hepcidin regulation, modulation of reactive oxygen species (ROS), and iron mediated cell death (ferroptosis). These novel therapeutics are the direct result of previous research in iron's complex signaling pathway and show promise for improved therapy, diagnosis, and prognosis in women's health.

Roxadustat for CKD-related Anemia in Non-dialysis Patients

Introduction

Roxadustat is an oral hypoxia-inducible factor prolyl hydroxylase inhibitor that stimulates erythropoiesis and improves iron metabolism. We assessed the efficacy and tolerability of roxadustat in patients with chronic kidney disease (CKD)-related anemia not on dialysis.

Methods

ANDES was a global Phase 3 randomized study in which adults with stage 3–5 CKD not on dialysis received roxadustat or placebo. Patients were initially dosed thrice weekly; dose was titrated to achieve a hemoglobin level ≥11.0 g/dl, followed by titration for maintenance. The primary endpoints were change in hemoglobin (weeks 28–52) and proportion of patients achieving a hemoglobin response (hemoglobin ≥11.0 g/dl and increase ≥1.0 g/dl [baseline >8.0 g/dl], or increase ≥2.0 g/dl [baseline ≤8.0 g/dl]) (week 24). Treatment-emergent adverse events (TEAEs) and serious adverse events (TESAEs) were recorded.

Results

In roxadustat (n = 616) and placebo (n = 306) groups, hemoglobin mean (SD) change from baseline over weeks 28–52 was significantly larger for roxadustat (2.00 [0.95]) versus placebo (0.16 [0.90]), corresponding to least-squares mean difference of 1.85 g/dl (95% confidence interval [CI] 1.74–1.97; P < 0.0001). The proportion of patients achieving a response at week 24 was larger for roxadustat (86.0%; 95% CI 83.0%–88.7%) versus placebo (6.6%; 95% CI 4.1%–9.9%; P < 0.0001). The proportion of patients receiving rescue therapy at week 52 was smaller for roxadustat (8.9%) versus placebo (28.9%); hazard ratio, 0.19 (95% CI 0.14–0.28; P < .0001). The incidences of TEAEs and TESAEs were comparable.

Conclusion

This study showed that roxadustat corrected and maintained hemoglobin and was well tolerated in patients with CKD-related anemia not on dialysis (ClinicalTrials.gov NCT01750190).

Complications associated with bone marrow sampling in dogs and cats

OBJECTIVES

To evaluate the prevalence of complications during bone marrow sampling and associated patient and procedural factors in dogs and cats.

MATERIALS AND METHODS

Retrospective cohort study, records were evaluated to identify dogs and cats that had bone marrow sampling between 2012 and 2019. Data including signalment, the presence of specific clinicopathological findings, anatomical site of bone marrow sampling, number of attempts, diagnostic quality of sampling, analgesia protocol and complications postprocedure were recorded.

RESULTS

A total of 131 dogs and 29 cats were included in the study. Complications were recorded in 22 of 160 (14%) of cases. Pain was the most common complication of bone marrow sampling in 20 of 22 (91%) of cases with bruising reported in the remaining patients. A local anaesthetic block was used in 98 of 160 (61%) of patients.

CLINICAL SIGNIFICANCE

Excluding pain, complications associated with bone marrow sampling were rare and no clear association were detected between patient or procedural variables. Haemorrhage and infection are rare complications in dogs and cats when thrombocytopenia and neutropenia are present. Peri-procedure analgesia is strongly recommended to minimise complications.

The biology of ergothioneine, an antioxidant nutraceutical

Ergothioneine (ERG) is an unusual thio-histidine betaine amino acid that has potent antioxidant activities. It is synthesised by a variety of microbes, especially fungi (including in mushroom fruiting bodies) and actinobacteria, but is not synthesised by plants and animals who acquire it via the soil and their diet, respectively. Animals have evolved a highly selective transporter for it, known as solute carrier family 22, member 4 (SLC22A4) in humans, signifying its importance, and ERG may even have the status of a vitamin. ERG accumulates differentially in various tissues, according to their expression of SLC22A4, favouring those such as erythrocytes that may be subject to oxidative stress. Mushroom or ERG consumption seems to provide significant prevention against oxidative stress in a large variety of systems. ERG seems to have strong cytoprotective status, and its concentration is lowered in a number of chronic inflammatory diseases. It has been passed as safe by regulatory agencies, and may have value as a nutraceutical and antioxidant more generally.

New concepts in the diagnosis and management approach to iron deficiency in candidates for metabolic surgery: should we change our practice?

The near universal presence of chronic low-grade systemic inflammation among patients with severe obesity disrupts iron homeostasis and underlies the association between obesity and iron deficiency. Immune activation and inflammation result in a reduction in circulating iron and diminished iron bioavailability for erythropoiesis. Inflammation also alters blood levels of commonly measured markers of iron nutrition status, which makes the diagnosis of iron deficiency difficult and has led to new recommendations regarding laboratory markers for the diagnosis. Recent evidence using these newly recommended laboratory markers, which include levels of ferritin, C-reactive protein, and transferrin saturation, suggests that the actual prevalence of iron deficiency among candidates for metabolic surgery may be double or triple the prevalence identified by low levels of ferritin alone. Thus large numbers of surgical candidates have iron deficiency that has been heretofore largely unrecognized and inadequately treated. The assessment of iron status using the currently recommended markers in the presence of chronic inflammatory diseases and repletion of depleted stores for surgical candidates with deficiency during the preoperative period present an important opportunity for mitigating this condition in postoperative patients.

Structure and function of the vacuolar Ccc1/VIT1 family of iron transporters and its regulation in fungi

Iron is an essential micronutrient for most living beings since it participates as a redox active cofactor in many biological processes including cellular respiration, lipid biosynthesis, DNA replication and repair, and ribosome biogenesis and recycling. However, when present in excess, iron can participate in Fenton reactions and generate reactive oxygen species that damage cells at the level of proteins, lipids and nucleic acids. Organisms have developed different molecular strategies to protect themselves against the harmful effects of high concentrations of iron. In the case of fungi and plants, detoxification mainly occurs by importing cytosolic iron into the vacuole through the Ccc1/VIT1 iron transporter. New sequenced genomes and bioinformatic tools are facilitating the functional characterization, evolution and ecological relevance of metabolic pathways and homeostatic networks across the Tree of Life. Sequence analysis shows that Ccc1/VIT1 homologs are widely distributed among organisms with the exception of animals. The recent elucidation of the crystal structure of a Ccc1/VIT1 plant ortholog has enabled the identification of both conserved and species-specific motifs required for its metal transport mechanism. Moreover, recent studies in the yeast Saccharomyces cerevisiae have also revealed that multiple transcription factors including Yap5 and Msn2/Msn4 contribute to the expression of CCC1 in high-iron conditions. Interestingly, Malaysian S. cerevisiae strains express a partially functional Ccc1 protein that renders them sensitive to iron. Different regulatory mechanisms have been described for non-Saccharomycetaceae Ccc1 homologs. The characterization of Ccc1/VIT1 proteins is of high interest in the development of biofortified crops and the protection against microbial-derived diseases.

Intravenous iron: do we adequately understand the short- and long-term risks in clinical practice?

Intravenous (IV) iron as a therapeutic agent is often administered but not always fully understood. The benefits of IV iron are well proven in many fields, particularly in nephrology. IV iron is beneficial not only for true iron deficiency but also for iron-restricted anaemia (functional iron deficiency). Yet, the literature on intravenous iron has many inconsistencies regarding its adverse effects. Over the last several years, newer forms of iron have been developed, leading to the more regular use of iron and in larger doses. This review will summarize some of the older and newer literature regarding the differences among iron products, including the mechanisms and frequency of their adverse events (AEs). The pathway and frequency of an underrecognized adverse event (hypophosphataemia) will be discussed. Recent insights on infection risk and iron handling by macrophages are examined. Potential but presently unproven risks of iron overload due to IV iron are discussed. The impact of these on the risk:benefit ratio and dosing of intravenous iron are considered in different clinical settings, including pregnancy and cancer. IV iron is an essential component of the therapy of anaemia and understanding these issues will enable more informed treatment decisions and knowledgeable use of these drugs.

Phytic Acid Protects from Oxidative Stress Induced by Iron-Overload and High-Fat Diets in ß2-Microglobulin Knockout Mice

The objective of this study was to examine the protective effect of phytic acid (PA) in reducing oxidative stress in an animal model for human hereditary hemochromatosis (HH) fed high-fat diets. Sixty-four ß2 microglobulin knockout (β2m KO) mice were randomly assigned to three treatments by feeding: control (basal), atherogenic (AT), and polyunsaturated fatty acid (PUFA) diets. One-half of the mice in each treatment group were fed 2% (wt/wt) PA. The ß2m+/+ mice (wild type (WT)) were fed a basal diet. All seven groups were fed for 10 weeks with a 50-ppm iron-containing diet (AIN-93G). Free iron and lipids were measured in serum samples. Nonheme iron, thiobarbituric acid-reactive substances (TBARS), superoxide dismutase (SOD), and catalase concentrations were measured in the liver tissue. Nonheme iron concentration in ß2m KO mice (on the basal diet) was 20× higher (p < 0.0001) than in the WT mice. Compared to the WT mice, ß2m KO mice had a significantly higher concentration of free iron in the serum (p < 0.0001), six-fold higher hepatic TBARs (p < 0.0001), and 18% lower hepatic SOD level. When PA was added to the β2m KO basal diet, a reduction (26 to 50%) of iron concentration was seen in the liver and heart. The addition of PA also significantly reduced TBARs in all three dietary groups of the iron-overloaded group, but most effectively in the control group. An increase in SOD concentration was seen only in the PUFA group, but serum triacylglycerol (TG) concentration was reduced in both dietary fat groups. In conclusion, our results suggest that PA protects against oxidative stress-induced by genetic iron overload alone or when fed high fat.

The Pivotal Role of Adipocyte-Na K peptide in Reversing Systemic Inflammation in Obesity and COVID-19 in the Development of Heart Failure

This review summarizes data from several laboratories that have demonstrated a role of the Na/K-ATPase, specifically its α1 subunit, in the generation of reactive oxygen species (ROS) via the negative regulator of Src. Together with Src and other signaling proteins, the Na/K-ATPase forms an oxidant amplification loop (NKAL), amplifies ROS, and participates in cytokines storm in obesity. The development of a peptide fragment of the α1 subunit, NaKtide, has been shown to negatively regulate Src. Several groups showed that the systemic administration of the cell permeable modification of NaKtide (pNaKtide) or its selective delivery to fat tissue-adipocyte specific expression of NaKtide-ameliorate the systemic elevation of inflammatory cytokines seen in chronic obesity. Severe acute respiratory syndrome - coronavirus 2 (SARS-CoV-2), the RNA Coronavirus responsible for the COVID-19 global pandemic, invades cells via the angiotensin converting enzyme 2 (ACE-2) receptor (ACE2R) that is appended in inflamed fat tissue and exacerbates the formation of the cytokines storm. Both obesity and heart and renal failure are well known risks for adverse outcomes in patients infected with COVID-19. White adipocytes express ACE-2 receptors in high concentration, especially in obese patients. Once the virus invades the white adipocyte cell, it creates a COVID19-porphyrin complex which degrades and produces free porphyrin and iron and increases ROS. The increased formation of ROS and activation of the NKAL results in a further potentiated formation of ROS production, and ultimately, adipocyte generation of more inflammatory mediators, leading to systemic cytokines storm and heart failure. Moreover, chronic obesity also results in the reduction of antioxidant genes such as heme oxygenase-1 (HO-1), increasing adipocyte susceptibility to ROS and cytokines. It is the systemic inflammation and cytokine storm which is responsible for many of the adverse outcomes seen with COVID-19 infections in obese subjects, leading to heart failure and death. This review will also describe the potential antioxidant drugs and role of NaKtide and their demonstrated antioxidant effect used as a major strategy for improving obesity and epicardial fat mediated heart failure in the context of the COVID pandemic.

Iron Therapy in Inflammatory Bowel Disease

The most common complication seen in inflammatory bowel disease (IBD) patients is iron deficiency anaemia (IDA). Symptoms such as chronic fatigue can be as debilitating to IBD patients as pathological symptoms of abdominal pain and diarrhoea. Recognising and correcting anaemia may be as important as managing IBD symptoms and improving overall quality of life. Thus, iron replacement should be commenced the moment IDA is identified. Although intravenous iron is now considered standard treatment for IBD patients in Europe, oral iron still appears to be the preferred option. Advantages of oral iron include greater availability, lower costs and ease of applicability. However, its multitude of side effects, impact on the microbiome and further exacerbating IBD activity can have consequences on patient compliance. The newer oral iron formulations show promising safety and efficacy data with a good side effect profile. Intravenous iron formulations bypass the gastrointestinal tract absorption thereby leading to less side effects. Multiple studies have shown its superiority compared to oral formulations although its risk for hypersensitivity reactions continue to lead to clinician hesitancy in prescribing this formulation. This article provides an updated review on diagnosis and management of IDA in IBD patients, discussing the newer oral and intravenous formulations.

L-type calcium channel blockers decrease the iron overload-mediated oxidative stress in renal epithelial cells by reducing iron accumulation

Iron-mediated oxidative stress has been recognized as one of the leading causes of chronic kidney injury. The effect of L-type calcium channel (LTCC) blocker on iron overload has been shown in cardiomyocytes, liver cells, and nerve cells. So far, few studies have examined whether blockers improve kidney iron-mediated oxidative stress. Yet, the precise mechanism through which blockers regulate kidney iron transport still remains unclear. In the present work, treatment with nifedipine or verapamil decreased oxidative stress and reduced the cell apoptosis-induced by ferric ammonium citrate (P < 0.05), decreased cellular iron contents, and prevented the rising of iron level-induced by ferric ammonium citrate (P > 0.05) in HK-2 and HEK293 cells. Besides, nifedipine and verapamil treatments increased the expression of divalent metal transporter 1, divalent metal transporter ZIP14, and ferroportin1 in HK-2 cells and increased ferroportin1 expression in HEK293 cells. In summary, LTCC blockers alleviate iron overload-induced oxidative stress in renal epithelial cells by blocking the iron uptake and enhancing cellular iron transport and/or iron export, thus synergistically reducing the cellular iron accumulation. Consequently, LTCC blockers may be used as a novel treatment for the prevention of primary or secondary iron overload-kidney injury.

Association between Iron Intake and Diabetic Peripheral Neuropathy in Type 2 Diabetes: Significance of Iron Intake and the Ratio between Iron Intake and Polyunsaturated Fatty Acids Intake

We aimed to investigate the association of iron and polyunsaturated fatty acid (PUFA) intake with diabetic peripheral neuropathy (DPN) in individuals with type 2 diabetes. This cross-sectional study included 147 individuals with type 2 diabetes. Dietary intake was assessed using three-day food records. DPN was diagnosed on the basis of a Michigan Neuropathy Screening Instrument—Physical Examination score ≥2.5. Adjusted for total energy intake, iron intake was significantly higher in individuals with DPN than in those without DPN (10.9 ± 4.0 mg vs. 9.9 ± 3.6 mg, p = 0.041). In addition, the iron/PUFA ratio was significantly higher in individuals with DPN (1.4 ± 0.8 vs. 1.1 ± 0.4, p = 0.005). Logistic regression analyses showed that iron intake (odds ratio (OR): 1.152; 95% confidence interval (CI): 1.012, 1.311) and iron/PUFA ratio (OR: 2.283; 95% CI: 1.066, 4.887) were associated with DPN after adjustment for total energy intake, sex, age, body mass index, systolic blood pressure, diabetes duration, estimated glomerular filtration rate, glycated hemoglobin, low-density lipoprotein cholesterol, and smoking. In conclusion, high dietary iron intake and an elevated iron/PUFA ratio were associated with the presence of DPN. The present study suggests the importance of the dietary pattern of iron and PUFA intake in individuals with type 2 diabetes.

A Potential Role for Excess Tissue Iron in Development of Cardiovascular Delayed Effects of Acute Radiation Exposure

Murine hematopoietic-acute radiation syndrome (H-ARS) survivors of total body radiation (TBI) have a significant loss of heart vessel endothelial cells, along with increased tissue iron, as early as 4 mo post-TBI. The goal of the current study was to determine the possible role for excess tissue iron in the loss of coronary artery endothelial cells. Experiments used the H-ARS mouse model with gamma radiation exposure of 853 cGy (LD50/30) and time points from 1 to 12 wk post-TBI. Serum iron was elevated at 1 wk post-TBI, peaked at 2 wk post-TBI, and returned to non-irradiated control values by 4 wk post-TBI. A similar trend was seen for transferrin saturation, and both results correlated inversely with red blood cell number. Perls' Prussian Blue staining, used to detect iron deposition in heart tissue sections, showed myocardial iron was present as early as 2 wk following irradiation. Pretreatment of mice with the iron chelator deferiprone decreased tissue iron but not serum iron at 2 wk. Coronary artery endothelial cell density was significantly decreased as early as 2 wk vs. non-irradiated controls (P<0.05), and the reduced density persisted to 12 wk after irradiation. Deferiprone treatment of irradiated mice prevented the decrease in endothelial cell density at 2 and 4 wk post-TBI compared to irradiated, non-treated mice (P<0.03). Taken together, the results suggest excess tissue iron contributes to endothelial cell loss early following TBI and may be a significant event impacting the development of delayed effects of acute radiation exposure.

Dalteparin as a Novel Therapeutic Agent to Prevent Diabetic Encephalopathy by Targeting Oxidative Stress and Inflammation

Introduction:

Hepcidin is the main modulator of systemic iron metabolism, and its role in the brain has been clarified recently. Studies have shown that hepcidin plays an important role in neuronal iron load and inflammation. This issue is of significance because neuronal iron load and inflammation are pathophysiological processes that are highly linked to neurodegeneration. Moreover, the activity of hepcidin has recently been manipulated to recover the neuronal impairment caused by brain inflammation in animal models.

Methods:

Streptozotocin (STZ) was used to induce type 1 diabetes. Male Wistar rats (n = 40) with a weight range of 200–250 g were divided into control, diabetic, diabetic + insulin, and diabetic + dalteparin groups. Dalteparin (100 mg/kg IP) and insulin (100 mg/kg SC) were administered for 8 weeks. At the end of the experiment, Y-maze and passive avoidance tasks were carried out. The animals were perfused randomly and their hippocampal tissue was isolated for the analysis of markers such as lipid peroxidation like Malondialdehyde (MDA), hepcidin expression, iron, and ferritin. Blood samples were taken for the measurement of serum inflammatory cytokine Interleukin (IL)-6.

Results:

The findings indicated that treatment with dalteparin reduced IL-6, MDA, ferritin, and hepcidin expression in diabetic rats compared to treatment with insulin (P<0.05). Moreover, treatment with dalteparin did not decrease the iron level or prevented its decline.

Conclusion:

Treatment with dalteparin improved the cognitive dysfunctions and symptoms of Alzheimer disease in STZ-induced diabetic rats by appropriately modulating and reducing oxidative stress and neuroinflammation. This may enhance the existing knowledge of therapeutics to reduce cognitive impairment in diabetes and is suggested to be a potential therapeutic agent in diabetes.

Iron Regulation in Elderly Asian Elephants (Elephas maximus) Chronically Infected With Mycobacterium tuberculosis

Restriction of nutrients to pathogens (nutritional immunity) is a critical innate immune response mechanism that operates when pathogens such as Mycobacterium tuberculosis have the potential to evade humoral immunity. Tuberculosis is of growing concern for zoological collections worldwide and is well-illustrated by infections of Asian and African elephants, where tuberculosis is difficult to diagnose. Here, we investigated hematological parameters and iron deposition in liver, lung, and spleen of three Asian elephants (Elephas maximus) infected with Mycobacterium tuberculosis. For reference purposes, we analyzed tissue samples from control M. tuberculosis-negative elephants with and without evidence of inflammation and/or chronic disease. Molecular analyses of bacterial lesions of post mortally collected tissues confirmed M. tuberculosis infection in three elephants. DNA sequencing of the bacterial cultures demonstrated a single source of infection, most likely of human origin. In these elephants, we observed moderate microcytic anemia as well as liver (mild), lung (moderate) and spleen (severe) iron accumulation, the latter mainly occurring in macrophages. Macrophage iron sequestration in response to infection and inflammation is caused by inhibition of iron export via hepcidin-dependent and independent mechanisms. The hepatic mRNA levels of the iron-regulating hormone hepcidin were increased in only one control elephant suffering from chronic inflammation without mycobacterial infection. By contrast, all three tuberculosis-infected elephants showed low hepcidin mRNA levels in the liver and low serum hepcidin concentrations. In addition, hepatic ferroportin mRNA expression was high. This suggests that the hepcidin/ferroportin regulatory system aims to counteract iron restriction in splenic macrophages in M. tuberculosis infected elephants to provide iron for erythropoiesis and to limit iron availability for a pathogen that predominantly proliferates in macrophages. Tuberculosis infections appear to have lingered for more than 30 years in the three infected elephants, and decreased iron availability for mycobacterial proliferation may have forced the bacteria into a persistent, non-proliferative state. As a result, therapeutic iron substitution may not have been beneficial in these elephants, as this therapy may have enhanced progression of the infection.

Re-examining ferritin-bound iron: current and developing clinical tools

Iron is a highly important metal ion cofactor within the human body, necessary for haemoglobin synthesis, and required by a wide range of enzymes for essential metabolic processes. Iron deficiency and overload both pose significant health concerns and are relatively common world-wide health hazards. Effective measurement of total iron stores is a primary tool for both identifying abnormal iron levels and tracking changes in clinical settings. Population based data is also essential for tracking nutritional trends. This review article provides an overview of the strengths and limitations associated with current techniques for diagnosing iron status, which sets a basis to discuss the potential of a new serum marker - ferritin-bound iron - and the improvement it could offer to iron assessment.

Persisting alterations of iron homeostasis in COVID-19 are associated with non-resolving lung pathologies and poor patients' performance: a prospective observational cohort study

BACKGROUND

Severe coronavirus disease 2019 (COVID-19) is frequently associated with hyperinflammation and hyperferritinemia. The latter is related to increased mortality in COVID-19. Still, it is not clear if iron dysmetabolism is mechanistically linked to COVID-19 pathobiology.

METHODS

We herein present data from the ongoing prospective, multicentre, observational CovILD cohort study (ClinicalTrials.gov number, NCT04416100), which systematically follows up patients after COVID-19. 109 participants were evaluated 60 days after onset of first COVID-19 symptoms including clinical examination, chest computed tomography and laboratory testing.

RESULTS

We investigated subjects with mild to critical COVID-19, of which the majority received hospital treatment. 60 days after disease onset, 30% of subjects still presented with iron deficiency and 9% had anemia, mostly categorized as anemia of inflammation. Anemic patients had increased levels of inflammation markers such as interleukin-6 and C-reactive protein and survived a more severe course of COVID-19. Hyperferritinemia was still present in 38% of all individuals and was more frequent in subjects with preceding severe or critical COVID-19. Analysis of the mRNA expression of peripheral blood mononuclear cells demonstrated a correlation of increased ferritin and cytokine mRNA expression in these patients. Finally, persisting hyperferritinemia was significantly associated with severe lung pathologies in computed tomography scans and a decreased performance status as compared to patients without hyperferritinemia.

DISCUSSION

Alterations of iron homeostasis can persist for at least two months after the onset of COVID-19 and are closely associated with non-resolving lung pathologies and impaired physical performance. Determination of serum iron parameters may thus be a easy to access measure to monitor the resolution of COVID-19.

TRIAL REGISTRATION

ClinicalTrials.gov number: NCT04416100.

Exacerbation of Neonatal Hemolysis and Impaired Renal Iron Handling in Heme Oxygenase 1-Deficient Mice

In most mammals, neonatal intravascular hemolysis is a benign and moderate disorder that usually does not lead to anemia. During the neonatal period, kidneys play a key role in detoxification and recirculation of iron species released from red blood cells (RBC) and filtered out by glomeruli to the primary urine. Activity of heme oxygenase 1 (HO1), a heme-degrading enzyme localized in epithelial cells of proximal tubules, seems to be of critical importance for both processes. We show that, in HO1 knockout mouse newborns, hemolysis was prolonged despite a transient state and exacerbated, which led to temporal deterioration of RBC status. In neonates lacking HO1, functioning of renal molecular machinery responsible for iron reabsorption from the primary urine (megalin/cubilin complex) and its transfer to the blood (ferroportin) was either shifted in time or impaired, respectively. Those abnormalities resulted in iron loss from the body (excreted in urine) and in iron retention in the renal epithelium. We postulate that, as a consequence of these abnormalities, a tight systemic iron balance of HO1 knockout neonates may be temporarily affected.

Ferric Uptake Regulator Fur Coordinates Siderophore Production and Defense against Iron Toxicity and Oxidative Stress and Contributes to Virulence in Chromobacterium violaceum

Iron is a highly reactive metal that participates in several processes in prokaryotic and eukaryotic cells. Hosts and pathogens compete for iron in the context of infection. Chromobacterium violaceum, an environmental Gram-negative bacterial pathogen, relies on siderophores to overcome iron limitation in the host. In this work, we studied the role of the ferric uptake regulator Fur in the physiology and virulence of C. violaceum A Δfur mutant strain showed decreased growth and fitness under regular in vitro growth conditions and presented high sensitivity to iron and oxidative stresses. Furthermore, the absence of fur caused derepression of siderophore production and reduction in swimming motility and biofilm formation. Consistent with these results, the C. violaceum Δfur mutant was highly attenuated for virulence and liver colonization in mice. In contrast, a manganese-selected spontaneous fur mutant showed only siderophore overproduction and sensitivity to oxidative stress, indicating that Fur remained partially functional in this strain. We found that mutations in genes related to siderophore biosynthesis and a putative CRISPR-Cas locus rescued the Δfur mutant growth defects, indicating that multiple Fur-regulated processes contribute to maintaining bacterial cell fitness. Overall, our data indicated that Fur is conditionally essential in C. violaceum mainly by protecting cells from iron overload and oxidative damage. The requirement of Fur for virulence highlights the importance of iron in the pathogenesis of C. violaceum IMPORTANCE Maintenance of iron homeostasis, i.e., avoiding both deficiency and toxicity of this metal, is vital to bacteria and their hosts. Iron sequestration by host proteins is a crucial strategy to combat bacterial infections. In bacteria, the ferric uptake regulator Fur coordinates the expression of several iron-related genes. Sometimes, Fur can also regulate several other processes. In this work, we performed an in-depth phenotypic characterization of fur mutants in the human opportunistic pathogen Chromobacterium violaceum We determined that fur is a conditionally essential gene necessary for proper growth under regular conditions and is fully required for survival under iron and oxidative stresses. Fur also controlled several virulence-associated traits, such as swimming motility, biofilm formation, and siderophore production. Consistent with these results, a C. violaceum fur null mutant showed attenuation of virulence. Therefore, our data established Fur as a major player required for C. violaceum to manage iron, including during infection in the host.

General Aspects of Metal Ions as Signaling Agents in Health and Disease

This review focuses on the current knowledge on the involvement of metal ions in signaling processes within the cell, in both physiological and pathological conditions. The first section is devoted to the recent discoveries on magnesium and calcium-dependent signal transduction-the most recognized signaling agents among metals. The following sections then describe signaling pathways where zinc, copper, and iron play a key role. There are many systems in which changes in intra- and extra-cellular zinc and copper concentrations have been linked to important downstream events, especially in nervous signal transduction. Iron signaling is mostly related with its homeostasis. However, it is also involved in a recently discovered type of programmed cell death, ferroptosis. The important differences in metal ion signaling, and its disease-leading alterations, are also discussed.

Overdosing on iron: Elevated iron and degenerative brain disorders

IMPACT STATEMENT

Brain degenerative disorders, which include some neurodevelopmental disorders and age-associated diseases, cause debilitating neurological deficits and are generally fatal. A large body of emerging evidence indicates that iron accumulation in neurons within specific regions of the brain plays an important role in the pathogenesis of many of these disorders. Iron homeostasis is a highly complex and incompletely understood process involving a large number of regulatory molecules. Our review provides a description of what is known about how iron is obtained by the body and brain and how defects in the homeostatic processes could contribute to the development of brain diseases, focusing on Alzheimer's disease and Parkinson's disease as well as four other disorders belonging to a class of inherited conditions referred to as neurodegeneration based on iron accumulation (NBIA) disorders. A description of potential therapeutic approaches being tested for each of these different disorders is provided.

Omega-3 Fatty Acid and Iron Supplementation Alone, but Not in Combination, Lower Inflammation and Anemia of Infection in Mycobacterium tuberculosis-Infected Mice

Progressive inflammation and anemia are common in tuberculosis (TB) and linked to poor clinical outcomes. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have inflammation-resolving properties, whereas iron supplementation in TB may have limited efficacy and enhance bacterial growth. We investigated effects of iron and EPA/DHA supplementation, alone and in combination, on inflammation, anemia, iron status markers and clinical outcomes in Mycobacterium tuberculosis-infected C3HeB/FeJ mice. One week post-infection, mice received the AIN-93 diet without (control) or with supplemental iron (Fe), EPA/DHA, or Fe+EPA/DHA for 3 weeks. Mice supplemented with Fe or EPA/DHA had lower soluble transferrin receptor, ferritin and hepcidin than controls, but these effects were attenuated in Fe+EPA/DHA mice. EPA/DHA increased inflammation-resolving lipid mediators and lowered lung IL-1α, IFN-γ, plasma IL-1β, and TNF-α. Fe lowered lung IL-1α, IL-1β, plasma IL-1β, TNF-α, and IL-6. However, the cytokine-lowering effects in the lungs were attenuated with Fe+EPA/DHA. Mice supplemented with EPA/DHA had lower lung bacterial loads than controls, but this effect was attenuated in Fe+EPA/DHA mice. Thus, individually, post-infection EPA/DHA and iron supplementation lowered systemic and lung inflammation and mitigated anemia of infection in TB, but not when combined. EPA/DHA also enhanced bactericidal effects and could support inflammation resolution and management of anemia.

How Severe Anaemia Might Influence the Risk of Invasive Bacterial Infections in African Children

Severe anaemia and invasive bacterial infections are common causes of childhood sickness and death in sub-Saharan Africa. Accumulating evidence suggests that severely anaemic African children may have a higher risk of invasive bacterial infections. However, the mechanisms underlying this association remain poorly described. Severe anaemia is characterized by increased haemolysis, erythropoietic drive, gut permeability, and disruption of immune regulatory systems. These pathways are associated with dysregulation of iron homeostasis, including the downregulation of the hepatic hormone hepcidin. Increased haemolysis and low hepcidin levels potentially increase plasma, tissue and intracellular iron levels. Pathogenic bacteria require iron and/or haem to proliferate and have evolved numerous strategies to acquire labile and protein-bound iron/haem. In this review, we discuss how severe anaemia may mediate the risk of invasive bacterial infections through dysregulation of hepcidin and/or iron homeostasis, and potential studies that could be conducted to test this hypothesis.

Plasma Levels of Hepcidin and Reticulocyte Haemoglobin during Septic Shock

Septic shock, a serious consequence of disseminated infection that has a high mortality, is due to a dysregulated, severe immune response triggered by the infection. Acute phase reactants play key roles in sepsis, for example, hepcidin regulating iron metabolism. Reticulocyte haemoglobin (Ret-He) depends on available iron in blood, indirectly regulated by hepcidin. This study aimed at exploring rapid changes in hepcidin and Ret-He in patients with septic shock receiving adequate antibiotic treatment. Fifteen patients, included within an hour of admission to the intensive care unit, were evaluated by microbiological tests and cultures, Sequential Organ Failure Assessment score, and plasma levels of hepcidin, Ret-He, heparin-binding protein (HBP), leucocytes, C-reactive protein, procalcitonin (PCT), and lactate. Samples were taken every morning for 7 consecutive days. Maximal levels of hepcidin (median 61 nmol/L; reference 1-12 nmol/L) were seen at the time of inclusion, then declining steadily similar to PCT and lactate levels. Ret-He values decreased transiently in response to increased hepcidin, normalization occurred at 96 h upon decrease of hepcidin levels. Maximal levels of HBP were noted 24 h after inclusion. In conclusion, hepcidin promptly declined within the first 24 h in patients with septic shock receiving adequate antibiotic treatment in contrast to Ret-He and HBP.