How to manage iron toxicity in post-allogeneic hematopoietic stem cell transplantation?

The Importance and Essentiality of Natural and Synthetic Chelators in Medicine: Increased Prospects for the Effective Treatment of Iron Overload and Iron Deficiency

The supply and control of iron is essential for all cells and vital for many physiological processes. All functions and activities of iron are expressed in conjunction with iron-binding molecules. For example, natural chelators such as transferrin and chelator-iron complexes such as haem play major roles in iron metabolism and human physiology. Similarly, the mainstay treatments of the most common diseases of iron metabolism, namely iron deficiency anaemia and iron overload, involve many iron-chelator complexes and the iron-chelating drugs deferiprone (L1), deferoxamine (DF) and deferasirox. Endogenous chelators such as citric acid and glutathione and exogenous chelators such as ascorbic acid also play important roles in iron metabolism and iron homeostasis. Recent advances in the treatment of iron deficiency anaemia with effective iron complexes such as the ferric iron tri-maltol complex (feraccru or accrufer) and the effective treatment of transfusional iron overload using L1 and L1/DF combinations have decreased associated mortality and morbidity and also improved the quality of life of millions of patients. Many other chelating drugs such as ciclopirox, dexrazoxane and EDTA are used daily by millions of patients in other diseases. Similarly, many other drugs or their metabolites with iron-chelation capacity such as hydroxyurea, tetracyclines, anthracyclines and aspirin, as well as dietary molecules such as gallic acid, caffeic acid, quercetin, ellagic acid, maltol and many other phytochelators, are known to interact with iron and affect iron metabolism and related diseases. Different interactions are also observed in the presence of essential, xenobiotic, diagnostic and theranostic metal ions competing with iron. Clinical trials using L1 in Parkinson's, Alzheimer's and other neurodegenerative diseases, as well as HIV and other infections, cancer, diabetic nephropathy and anaemia of inflammation, highlight the importance of chelation therapy in many other clinical conditions. The proposed use of iron chelators for modulating ferroptosis signifies a new era in the design of new therapeutic chelation strategies in many other diseases. The introduction of artificial intelligence guidance for optimal chelation therapeutic outcomes in personalised medicine is expected to increase further the impact of chelation in medicine, as well as the survival and quality of life of millions of patients with iron metabolic disorders and also other diseases.

Targeting ferroptosis for leukemia therapy: exploring novel strategies from its mechanisms and role in leukemia based on nanotechnology

The latest findings in iron metabolism and the newly uncovered process of ferroptosis have paved the way for new potential strategies in anti-leukemia treatments. In the current project, we reviewed and summarized the current role of nanomedicine in the treatment and diagnosis of leukemia through a comparison made between traditional approaches applied in the treatment and diagnosis of leukemia via the existing investigations about the ferroptosis molecular mechanisms involved in various anti-tumor treatments. The application of nanotechnology and other novel technologies may provide a new direction in ferroptosis-driven leukemia therapies. The article explores the potential of targeting ferroptosis, a new form of regulated cell death, as a new therapeutic strategy for leukemia. It discusses the mechanisms of ferroptosis and its role in leukemia and how nanotechnology can enhance the delivery and efficacy of ferroptosis-inducing agents. The article not only highlights the promise of ferroptosis-targeted therapies and nanotechnology in revolutionizing leukemia treatment, but also calls for further research to overcome challenges and fully realize the clinical potential of this innovative approach. Finally, it discusses the challenges and opportunities in clinical applications of ferroptosis.

Drug Selection and Posology, Optimal Therapies and Risk/Benefit Assessment in Medicine: The Paradigm of Iron-Chelating Drugs

The design of clinical protocols and the selection of drugs with appropriate posology are critical parameters for therapeutic outcomes. Optimal therapeutic protocols could ideally be designed in all diseases including for millions of patients affected by excess iron deposition (EID) toxicity based on personalised medicine parameters, as well as many variations and limitations. EID is an adverse prognostic factor for all diseases and especially for millions of chronically red-blood-cell-transfused patients. Differences in iron chelation therapy posology cause disappointing results in neurodegenerative diseases at low doses, but lifesaving outcomes in thalassemia major (TM) when using higher doses. In particular, the transformation of TM from a fatal to a chronic disease has been achieved using effective doses of oral deferiprone (L1), which improved compliance and cleared excess toxic iron from the heart associated with increased mortality in TM. Furthermore, effective L1 and L1/deferoxamine combination posology resulted in the complete elimination of EID and the maintenance of normal iron store levels in TM. The selection of effective chelation protocols has been monitored by MRI T2* diagnosis for EID levels in different organs. Millions of other iron-loaded patients with sickle cell anemia, myelodysplasia and haemopoietic stem cell transplantation, or non-iron-loaded categories with EID in different organs could also benefit from such chelation therapy advances. Drawbacks of chelation therapy include drug toxicity in some patients and also the wide use of suboptimal chelation protocols, resulting in ineffective therapies. Drug metabolic effects, and interactions with other metals, drugs and dietary molecules also affected iron chelation therapy. Drug selection and the identification of effective or optimal dose protocols are essential for positive therapeutic outcomes in the use of chelating drugs in TM and other iron-loaded and non-iron-loaded conditions, as well as general iron toxicity.

Iron Load Toxicity in Medicine: From Molecular and Cellular Aspects to Clinical Implications

Iron is essential for all organisms and cells. Diseases of iron imbalance affect billions of patients, including those with iron overload and other forms of iron toxicity. Excess iron load is an adverse prognostic factor for all diseases and can cause serious organ damage and fatalities following chronic red blood cell transfusions in patients of many conditions, including hemoglobinopathies, myelodyspasia, and hematopoietic stem cell transplantation. Similar toxicity of excess body iron load but at a slower rate of disease progression is found in idiopathic haemochromatosis patients. Excess iron deposition in different regions of the brain with suspected toxicity has been identified by MRI T2* and similar methods in many neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Based on its role as the major biological catalyst of free radical reactions and the Fenton reaction, iron has also been implicated in all diseases associated with free radical pathology and tissue damage. Furthermore, the recent discovery of ferroptosis, which is a cell death program based on free radical generation by iron and cell membrane lipid oxidation, sparked thousands of investigations and the association of iron with cardiac, kidney, liver, and many other diseases, including cancer and infections. The toxicity implications of iron in a labile, non-protein bound form and its complexes with dietary molecules such as vitamin C and drugs such as doxorubicin and other xenobiotic molecules in relation to carcinogenesis and other forms of toxicity are also discussed. In each case and form of iron toxicity, the mechanistic insights, diagnostic criteria, and molecular interactions are essential for the design of new and effective therapeutic interventions and of future targeted therapeutic strategies. In particular, this approach has been successful for the treatment of most iron loading conditions and especially for the transition of thalassemia from a fatal to a chronic disease due to new therapeutic protocols resulting in the complete elimination of iron overload and of iron toxicity.

The Vital Role Played by Deferiprone in the Transition of Thalassaemia from a Fatal to a Chronic Disease and Challenges in Its Repurposing for Use in Non-Iron-Loaded Diseases

The iron chelating orphan drug deferiprone (L1), discovered over 40 years ago, has been used daily by patients across the world at high doses (75-100 mg/kg) for more than 30 years with no serious toxicity. The level of safety and the simple, inexpensive synthesis are some of the many unique properties of L1, which played a major role in the contribution of the drug in the transition of thalassaemia from a fatal to a chronic disease. Other unique and valuable clinical properties of L1 in relation to pharmacology and metabolism include: oral effectiveness, which improved compliance compared to the prototype therapy with subcutaneous deferoxamine; highly effective iron removal from all iron-loaded organs, particularly the heart, which is the major target organ of iron toxicity and the cause of mortality in thalassaemic patients; an ability to achieve negative iron balance, completely remove all excess iron, and maintain normal iron stores in thalassaemic patients; rapid absorption from the stomach and rapid clearance from the body, allowing a greater frequency of repeated administration and overall increased efficacy of iron excretion, which is dependent on the dose used and also the concentration achieved at the site of drug action; and its ability to cross the blood-brain barrier and treat malignant, neurological, and microbial diseases affecting the brain. Some differential pharmacological activity by L1 among patients has been generally shown in relation to the absorption, distribution, metabolism, elimination, and toxicity (ADMET) of the drug. Unique properties exhibited by L1 in comparison to other drugs include specific protein interactions and antioxidant effects, such as iron removal from transferrin and lactoferrin; inhibition of iron and copper catalytic production of free radicals, ferroptosis, and cuproptosis; and inhibition of iron-containing proteins associated with different pathological conditions. The unique properties of L1 have attracted the interest of many investigators for drug repurposing and use in many pathological conditions, including cancer, neurodegenerative conditions, microbial conditions, renal conditions, free radical pathology, metal intoxication in relation to Fe, Cu, Al, Zn, Ga, In, U, and Pu, and other diseases. Similarly, the properties of L1 increase the prospects of its wider use in optimizing therapeutic efforts in many other fields of medicine, including synergies with other drugs.

Metal Complexes of Omadine (N-Hydroxypyridine-2-thione): Differences of Antioxidant and Pro-Oxidant Behavior in Light and Dark Conditions with Possible Toxicity Implications

Omadine or N-hydroxypyridine-2-thione and its metal complexes are widely used in medicine and show bactericidal, fungicidal, anticancer, and photochemical activity. The redox activity of omadine complexes with iron, copper, and zinc on lipid peroxidation under light and dark conditions has been investigated. The monitoring of the oxidation of linoleic acid micelles, resembling a model of lipid membrane, was carried out using nuclear magnetic resonance (¹H-NMR). It has been shown that the omadine-zinc complex can induce the oxidation of linoleic acid under light irradiation, whereas the complexes with iron and copper are photochemically stable. All the chelating complexes of omadine appear to be redox-inactive in the presence of hydrogen peroxide under dark conditions. These findings suggest that omadine can demonstrate antioxidant behavior in processes involving reactive oxygen species generation induced by transition metals (Fenton and photo-Fenton reactions). However, the omadine complex with zinc, which is widely used in shampoos and ointments, is photochemically active and may cause oxidative cell membrane damage when exposed to light, with possible implications to health.

Deferiprone and Iron-Maltol: Forty Years since Their Discovery and Insights into Their Drug Design, Development, Clinical Use and Future Prospects

The historical insights and background of the discovery, development and clinical use of deferiprone (L1) and the maltol-iron complex, which were discovered over 40 years ago, highlight the difficulties, complexities and efforts in general orphan drug development programs originating from academic centers. Deferiprone is widely used for the removal of excess iron in the treatment of iron overload diseases, but also in many other diseases associated with iron toxicity, as well as the modulation of iron metabolism pathways. The maltol-iron complex is a recently approved drug used for increasing iron intake in the treatment of iron deficiency anemia, a condition affecting one-third to one-quarter of the world's population. Detailed insights into different aspects of drug development associated with L1 and the maltol-iron complex are revealed, including theoretical concepts of invention; drug discovery; new chemical synthesis; in vitro, in vivo and clinical screening; toxicology; pharmacology; and the optimization of dose protocols. The prospects of the application of these two drugs in many other diseases are discussed under the light of competing drugs from other academic and commercial centers and also different regulatory authorities. The underlying scientific and other strategies, as well as the many limitations in the present global scene of pharmaceuticals, are also highlighted, with an emphasis on the priorities for orphan drug and emergency medicine development, including the roles of the academic scientific community, pharmaceutical companies and patient organizations.

New Iron Metabolic Pathways and Chelation Targeting Strategies Affecting the Treatment of All Types and Stages of Cancer

There is new and increasing evidence from in vitro, in vivo and clinical studies implicating the pivotal role of iron and associated metabolic pathways in the initiation, progression and development of cancer and in cancer metastasis. New metabolic and toxicity mechanisms and pathways, as well as genomic, transcription and other factors, have been linked to cancer and many are related to iron. Accordingly, a number of new targets for iron chelators have been identified and characterized in new anticancer strategies, in addition to the classical restriction of/reduction in iron supply, the inhibition of transferrin iron delivery, the inhibition of ribonucleotide reductase in DNA synthesis and high antioxidant potential. The new targets include the removal of excess iron from iron-laden macrophages, which affects anticancer activity; the modulation of ferroptosis; ferritin iron removal and the control of hyperferritinemia; the inhibition of hypoxia related to the role of hypoxia-inducible factor (HIF); modulation of the function of new molecular species such as STEAP4 metalloreductase and the metastasis suppressor N-MYC downstream-regulated gene-1 (NDRG1); modulation of the metabolic pathways of oxidative stress damage affecting mitochondrial function, etc. Many of these new, but also previously known associated iron metabolic pathways appear to affect all stages of cancer, as well as metastasis and drug resistance. Iron-chelating drugs and especially deferiprone (L1), has been shown in many recent studies to fulfill the role of multi-target anticancer drug linked to the above and also other iron targets, and has been proposed for phase II trials in cancer patients. In contrast, lipophilic chelators and their iron complexes are proposed for the induction of ferroptosis in some refractory or recurring tumors in drug resistance and metastasis where effective treatments are absent. There is a need to readdress cancer therapy and include therapeutic strategies targeting multifactorial processes, including the application of multi-targeting drugs involving iron chelators and iron-chelator complexes. New therapeutic protocols including drug combinations with L1 and other chelating drugs could increase anticancer activity, decrease drug resistance and metastasis, improve treatments, reduce toxicity and increase overall survival in cancer patients.

Deferiprone: A Forty-Year-Old Multi-Targeting Drug with Possible Activity against COVID-19 and Diseases of Similar Symptomatology

The need for preparing new strategies for the design of emergency drug therapies against COVID-19 and similar diseases in the future is rather urgent, considering the high rate of morbidity and especially mortality associated with COVID-19, which so far has exceeded 18 million lives. Such strategies could be conceived by targeting the causes and also the serious toxic side effects of the diseases, as well as associated biochemical and physiological pathways. Deferiprone (L1) is an EMA- and FDA-approved drug used worldwide for the treatment of iron overload and also other conditions where there are no effective treatments. The multi-potent effects and high safety record of L1 in iron loaded and non-iron loaded categories of patients suggests that L1 could be developed as a “magic bullet” drug against COVID-19 and diseases of similar symptomatology. The mode of action of L1 includes antiviral, antimicrobial, antioxidant, anti-hypoxic and anti-ferroptotic effects, iron buffering interactions with transferrin, iron mobilizing effects from ferritin, macrophages and other cells involved in the immune response and hyperinflammation, as well as many other therapeutic interventions. Similarly, several pharmacological and other characteristics of L1, including extensive tissue distribution and low cost of production, increase the prospect of worldwide availability, as well as many other therapeutic approach strategies involving drug combinations, adjuvant therapies and disease prevention.

Deferoxamine Inhibits Acute Lymphoblastic Leukemia Progression through Repression of ROS/HIF-1α, Wnt/β-Catenin, and p38MAPK/ERK Pathways

Acute lymphoblastic leukemia (ALL) is the most common type of childhood cancer, with a feature of easy to induce multidrug resistance and relapse. Abundant studies have proved that iron overload strengthens the growth and metastasis of tumor cells. Herein, we found that deferoxamine (DFO) effectively decreased the concentration of intracellular iron in ALL cells. DFO inhibited proliferation, induced apoptosis, and obstructed cell cycle of ALL cells, whereas DFO and dextriferron (Dex) used in combination significantly decreased the sensitivity of ALL cells to DFO. Reactive oxygen species (ROS) level was reduced in ALL cells treated with DFO, and the combination of DFO and Dex reversed the effects of DFO. In vivo, DFO inhibited mouse tumor growth. Besides, cyclinD1, β-catenin, c-Myc, hypoxia inducible factor 1 (HIF-1), p-p38MAPK, and p-ERK1/2 protein levels were significantly downregulated, and the levels of prolyl hydroxylase-2 (PHD-2) were upregulated after treated with DFO, whereas Dex treatment reversed those in vivo and in vitro. In conclusion, DFO inhibited the proliferation and ALL xenograft tumor growth, obstructed the cell cycle, and induced apoptosis of ALL cells, probably via inactivating the ROS/HIF-1α, Wnt/β-catenin, and p38MAPK/ERK signaling.

Questioning Established Theories and Treatment Methods Related to Iron and Other Metal Metabolic Changes, Affecting All Major Diseases and Billions of Patients

The medical and scientific literature is dominated by highly cited historical theories and findings [...].

Mechanistic Insights of Chelator Complexes with Essential Transition Metals: Antioxidant/Pro-Oxidant Activity and Applications in Medicine

The antioxidant/pro-oxidant activity of drugs and dietary molecules and their role in the maintenance of redox homeostasis, as well as the implications in health and different diseases, have not yet been fully evaluated. In particular, the redox activity and other interactions of drugs with essential redox metal ions, such as iron and copper, need further investigation. These metal ions are ubiquitous in human nutrition but also widely found in dietary supplements and appear to exert major effects on redox homeostasis in health, but also on many diseases of free radical pathology. In this context, the redox mechanistic insights of mainly three prototype groups of drugs, namely alpha-ketohydroxypyridines (alpha-hydroxypyridones), e.g., deferiprone, anthraquinones, e.g., doxorubicin and thiosemicarbazones, e.g., triapine and their metal complexes were examined; details of the mechanisms of their redox activity were reviewed, with emphasis on the biological implications and potential clinical applications, including anticancer activity. Furthermore, the redox properties of these three classes of chelators were compared to those of the iron chelating drugs and also to vitamin C, with an emphasis on their potential clinical interactions and future clinical application prospects in cancer, neurodegenerative and other diseases.

Antioxidant Activity of Deferasirox and Its Metal Complexes in Model Systems of Oxidative Damage: Comparison with Deferiprone

Deferasirox is an orally active, lipophilic iron chelating drug used on thousands of patients worldwide for the treatment of transfusional iron overload. The essential transition metals iron and copper are the primary catalysts of reactive oxygen species and oxidative damage in biological systems. The redox effects of deferasirox and its metal complexes with iron, copper and other metals are of pharmacological, toxicological, biological and physiological importance. Several molecular model systems of oxidative damage caused by iron and copper catalysis including the oxidation of ascorbic acid, the peroxidation of linoleic acid micelles and the oxidation of dihydropyridine have been investigated in the presence of deferasirox using UV-visible and NMR spectroscopy. Deferasirox has shown antioxidant activity in all three model systems, causing substantial reduction in the rate of oxidation and oxidative damage. Deferasirox showed the greatest antioxidant activity in the oxidation of ascorbic acid with the participation of iron ions and reduced the reaction rate by about a 100 times. Overall, deferasirox appears to have lower affinity for copper in comparison to iron. Comparative studies of the antioxidant activity of deferasirox and the hydrophilic oral iron chelating drug deferiprone in the peroxidation of linoleic acid micelles showed lower efficiency of deferasirox in comparison to deferiprone.

The Role of Iron in Benign and Malignant Hematopoiesis

Significance: Iron is an essential element required for sustaining a normal healthy life. However, an excess amount of iron in the bloodstream and tissue generates toxic hydroxyl radicals through Fenton reactions. Henceforth, a balance in iron concentration is extremely important to maintain cellular homeostasis in both normal hematopoiesis and erythropoiesis. Iron deficiency or iron overload can impact hematopoiesis and is associated with many hematological diseases. Recent Advances: The mechanisms of action of key iron regulators such as erythroferrone and the discovery of new drugs, such as ACE-536/luspatercept, are of potential interest to treat hematological disorders, such as β-thalassemia. New therapies targeting inflammation-induced ineffective erythropoiesis are also in progress. Furthermore, emerging evidences support differential interactions between iron and its cellular antioxidant responses of hematopoietic and neighboring stromal cells. Both iron and its systemic regulator, such as hepcidin, play a significant role in regulating erythropoiesis. Critical Issues: Significant pre-clinical studies are on the way and new drugs targeting iron metabolism have been recently approved or are undergoing clinical trials to treat pathological conditions with impaired erythropoiesis such as myelodysplastic syndromes or β-thalassemia. Future Directions: Future studies should explore how iron regulates hematopoiesis in both benign and malignant conditions. Antioxid. Redox Signal. 35, 415-432.

Differences between the European Union and United States of America in Drug Regulatory Affairs Affect Global Patient Safety Standards and Public Health Awareness: The Case of Deferasirox and Other Iron Chelating Drugs

Regulatory policies on drugs have a major impact on patient safety and survival. Some pharmaceutical companies employ all possible methods to achieve maximum sales in relation to the monopoly of their patented drugs, leading sometimes to irregularities and illegal activities. Misinformation on the orphan drug deferasirox has reached the stage of criminal investigations and fines exceeding USD 100 million. Additional lawsuits of USD 3.5 billion for damages and civil fines were also filed by the FBI of the USA involving deferasirox and mycophenolic acid, which were later settled with an additional fine of USD 390 million. Furthermore, a USD 345 million fine was also settled for bribes and other illegal overseas operations including an EU country. However, no similar fines for illegal practises or regulatory control violations have been issued in the EU. Misconceptions and a lack of clear guidelines for the use of deferasirox in comparison to deferiprone and deferoxamine appear to reduce the effective treatment prospects and to increase the toxicity risks for thalassaemia and other iron loaded patients. Similar issues have been raised for the activities of other pharmaceutical companies promoting the use of new patented versus generic drugs. Treatments for different categories of patients using new patented drugs are mostly market driven with no clear safeguards or guidelines for risk/benefit assessment indications or for individualised effective and safe optimum therapies. There is a need for the establishment of an international organisation, which can monitor and assess the risk/benefit assessment and marketing of drugs in the EU and globally for the benefit of patients. The pivotal role of the regulatory drug authorities and the prescribing physicians for identifying individualised optimum therapies is essential for improving the survival and safety of millions of patients worldwide.

How I perform hematopoietic stem cell transplantation on patients with a history of invasive fungal disease

Hematopoietic transplantation is the preferred treatment for many patients with hematologic malignancies. Some patients may develop invasive fungal diseases (IFDs) during initial chemotherapy, which need to be considered when assessing patients for transplantation and treatment posttransplantation. Given the associated high risk of relapse and mortality in the post-hematopoietic stem cell transplantation (HSCT) period, IFDs, especially invasive mold diseases, were historically considered a contraindication for HSCT. Over the last 3 decades, advances in antifungal drugs and early diagnosis have improved IFD outcomes, and HSCT in patients with a recent IFD has become increasingly common. However, an organized approach for performing transplantation in patients with a prior IFD is scarce, and decisions are highly individualized. Patient-, malignancy-, transplantation procedure-, antifungal treatment-, and fungus-specific issues affect the risk of IFD relapse. Effective surveillance to detect IFD relapse post-HSCT and careful drug selection for antifungal prophylaxis are of paramount importance. Antifungal drugs have their own toxicities and interact with immunosuppressive drugs such as calcineurin inhibitors. Immune adjunct cytokine or cellular therapy and surgery can be considered in selected cases. In this review, we critically evaluate these factors and provide guidance for the complex decision making involved in the peri-HSCT management of these patients.

Post-transplant ferritin level predicts outcomes after allogeneic hematopoietic stem cell transplant, independent from pre-transplant ferritin level

Allogeneic hematopoietic stem cell transplantation (HCT) is associated with significant morbidity and mortality. Elevated pre-transplant ferritin level (ferritin^Pre-HCT) is reported to be associated with increased mortality following HCT. The present study attempted to determine whether post-transplant ferritin level (ferritin^Post-HCT) is associated with outcomes post-HCT, especially in the subgroups which developed acute or chronic graft-versus-host disease (GVHD). Out of 229 patients with serum ferritin level measured post-HCT, median ferritin^Post-HCT was 2178 ng/mL. Patients were stratified into low- or high-risk groups using recursive partitioning, based on ferritin^Post-HCT (≤ 3169 vs > 3169 ng/mL) and ferritin^Pre-HCT (≤ 669 vs > 669 ng/mL). Compared to the low ferritin^Post-HCT group, the high ferritin^Post-HCT group had lower 3-year overall survival (OS) (40.0% vs 66.7%, p < 0.001) and higher non-relapse mortality (NRM) (48.6% vs 17.8%, p < 0.001), but no difference in relapse (10.5% vs 19.7%, p = 0.079). Multivariate analysis confirmed ferritin^Post-HCT as an independent prognostic factor for OS (p = 0.001, HR = 2.323) and NRM (p < 0.001, HR = 3.905). However, ferritin^Pre-HCT did not stratify well for OS or NRM. Ferritin^Post-HCT was also found to be an independent prognostic marker for OS and NRM in the subgroups which developed GVHD. In our cohort, high ferritin^Post-HCT levels were significantly associated with decreased OS and increased NRM independent of ferritin^Pre-HCT or GVHD. Additional studies including larger sample sizes and prospective investigation are warranted to clarify the prognostic significance and pathophysiology of pre- and post-transplant hyperferritinemia.

Trying to Solve the Puzzle of the Interaction of Ascorbic Acid and Iron: Redox, Chelation and Therapeutic Implications

Iron and ascorbic acid (vitamin C) are essential nutrients for the normal growth and development of humans, and their deficiency can result in serious diseases. Their interaction is of nutritional, physiological, pharmacological and toxicological interest, with major implications in health and disease. Millions of people are using pharmaceutical and nutraceutical preparations of these two nutrients, including ferrous ascorbate for the treatment of iron deficiency anaemia and ascorbate combination with deferoxamine for increasing iron excretion in iron overload. The main function and use of vitamin C is its antioxidant activity against reactive oxygen species, which are implicated in many diseases of free radical pathology, including biomolecular-, cellular- and tissue damage-related diseases, as well as cancer and ageing. Ascorbic acid and its metabolites, including the ascorbate anion and oxalate, have metal binding capacity and bind iron, copper and other metals. The biological roles of ascorbate as a vitamin are affected by metal complexation, in particular following binding with iron and copper. Ascorbate forms a complex with Fe³⁺ followed by reduction to Fe²⁺, which may potentiate free radical production. The biological and clinical activities of iron, ascorbate and the ascorbate–iron complex can also be affected by many nutrients and pharmaceutical preparations. Optimal therapeutic strategies of improved efficacy and lower toxicity could be designed for the use of ascorbate, iron and the iron–ascorbate complex in different clinical conditions based on their absorption, distribution, metabolism, excretion, toxicity (ADMET), pharmacokinetic, redox and other properties. Similar strategies could also be designed in relation to their interactions with food components and pharmaceuticals, as well as in relation to other aspects concerning personalized medicine.

Iron and Chelation in Biochemistry and Medicine: New Approaches to Controlling Iron Metabolism and Treating Related Diseases

Iron is essential for all living organisms. Many iron-containing proteins and metabolic pathways play a key role in almost all cellular and physiological functions. The diversity of the activity and function of iron and its associated pathologies is based on bond formation with adjacent ligands and the overall structure of the iron complex in proteins or with other biomolecules. The control of the metabolic pathways of iron absorption, utilization, recycling and excretion by iron-containing proteins ensures normal biologic and physiological activity. Abnormalities in iron-containing proteins, iron metabolic pathways and also other associated processes can lead to an array of diseases. These include iron deficiency, which affects more than a quarter of the world's population; hemoglobinopathies, which are the most common of the genetic disorders and idiopathic hemochromatosis. Iron is the most common catalyst of free radical production and oxidative stress which are implicated in tissue damage in most pathologic conditions, cancer initiation and progression, neurodegeneration and many other diseases. The interaction of iron and iron-containing proteins with dietary and xenobiotic molecules, including drugs, may affect iron metabolic and disease processes. Deferiprone, deferoxamine, deferasirox and other chelating drugs can offer therapeutic solutions for most diseases associated with iron metabolism including iron overload and deficiency, neurodegeneration and cancer, the detoxification of xenobiotic metals and most diseases associated with free radical pathology.