Iron chelators: as therapeutic agents in diseases

The concentration of iron is tightly regulated, making it an essential element. Various cellular processes in the body rely on iron, such as oxygen sensing, oxygen transport, electron transfer, and DNA synthesis. Iron excess can be toxic because it participates in redox reactions that catalyze the production of reactive oxygen species and elevate oxidative stress. Iron chelators are chemically diverse; they can coordinate six ligands in an octagonal sequence. Because of the ability of chelators to trap essential metals, including iron, they may be involved in diseases caused by oxidative stress, such as infectious diseases, cardiovascular diseases, neurodegenerative diseases, and cancer. Iron-chelating agents, by tightly binding to iron, prohibit it from functioning as a catalyst in redox reactions and transfer iron and excrete it from the body. Thus, the use of iron chelators as therapeutic agents has received increasing attention. This review investigates the function of various iron chelators in treating iron overload in different clinical conditions.

Iron overload disorders: Growth and gonadal dysfunction in childhood and adolescence

Hemochromatosis (HC) is characterized by the progressive accumulation of iron in the body, resulting in organ damage. Endocrine complications are particularly common, especially when the condition manifests in childhood or adolescence, when HC can adversely affect linear growth or pubertal development, with significant repercussions on quality of life even into adulthood. Therefore, a timely and accurate diagnosis of these disorders is mandatory, but sometimes complex for hematologists without endocrinological support. This is a narrative review focused on puberty and growth disorders during infancy and adolescence aiming to offer guidance for diagnosis, treatment, and proper follow-up. Additionally, it aims to highlight gaps in the existing literature and emphasizes the importance of collaboration among specialists, which is essential in the era of precision medicine.

Aceruloplasminemia: A Severe Neurodegenerative Disorder Deserving an Early Diagnosis

Aceruloplasminemia (ACP) is a rare, adult-onset, autosomal recessive disorder, characterized by systemic iron overload due to mutations in the Ceruloplasmin gene (CP), which in turn lead to absence or strong reduction of CP activity. CP is a ferroxidase that plays a key role in iron export from various cells, especially in the brain, where it maintains the appropriate iron homeostasis with neuroprotective effects. Brain iron accumulation makes ACP unique among systemic iron overload syndromes, e.g., various types of genetic hemochromatosis. The main clinical features of fully expressed ACP include diabetes, retinopathy, liver disease, and progressive neurological symptoms reflecting iron deposition in target organs. However, biochemical signs of the disease, namely a mild anemia mimicking iron deficiency anemia because of microcytosis and low transferrin saturation, but with "paradoxical" hyperferritinemia, usually precedes the onset of clinical symptoms of many years and sometimes decades. Prompt diagnosis and therapy are crucial to prevent neurological complications of the disease, as they are usually irreversible once established. In this mini-review we discuss some major issues about this rare disorder, pointing out the early clues to the right diagnosis, instrumental to reduce significant disability burden of affected patients.

Structural Basis for Xenosiderophore Utilization by the Human Pathogen Staphylococcus aureus

Staphylococcus aureus produces a cocktail of metallophores (staphylopine, staphyloferrin A, and staphyloferrin B) to scavenge transition metals during infection of a host. In addition, S. aureus displays the extracellular surface lipoproteins FhuD1 and FhuD2 along with the ABC transporter complex FhuCBG to facilitate the use of hydroxamate xenosiderophores such as desferrioxamine B (DFOB) for iron acquisition. DFOB is used as a chelation therapy to treat human iron overload diseases and has been linked to an increased risk of S. aureus infections. We used a panel of synthetic DFOB analogs and a FhuD2-selective trihydroxamate sideromycin to probe xenosiderophore utilization in S. aureus and establish structure-activity relationships for Fe(III) binding, FhuD2 binding, S. aureus growth promotion, and competition for S. aureus cell entry. Fe(III) binding assays and FhuD2 intrinsic fluorescence quenching experiments revealed that diverse chemical modifications of the terminal ends of linear ferrioxamine siderophores influences Fe(III) affinity but not FhuD2 binding. Siderophore-sideromycin competition assays and xenosiderophore growth promotion assays revealed that S. aureus SG511 and ATCC 11632 can distinguish between competing siderophores based exclusively on net charge of the siderophore-Fe(III) complex. Our work provides a roadmap for tuning hydroxamate xenosiderophore scaffolds to suppress (net negative charge) or enhance (net positive or neutral charge) uptake by S. aureus for applications in metal chelation therapy and siderophore-mediated antibiotic delivery, respectively.

Clinical Impact and Cellular Mechanisms of Iron Overload-Associated Bone Loss

Diseases/conditions with diverse etiology, such as hemoglobinopathies, hereditary hemochromatosis and menopause, could lead to chronic iron accumulation. This condition is frequently associated with a bone phenotype; characterized by low bone mass, osteoporosis/osteopenia, altered microarchitecture and biomechanics, and increased incidence of fractures. Osteoporotic bone phenotype constitutes a major complication in patients with iron overload. The purpose of this review is to summarize what we have learnt about iron overload-associated bone loss from clinical studies and animal models. Bone is a metabolically active tissue that undergoes continuous remodeling with the involvement of osteoclasts that resorb mineralized bone, and osteoblasts that form new bone. Growing evidence suggests that both increased bone resorption and decreased bone formation are involved in the pathological bone-loss in iron overload conditions. We will discuss the cellular and molecular mechanisms that are involved in this detrimental process. Fuller understanding of this complex mechanism may lead to the development of improved therapeutics meant to interrupt the pathologic effects of excess iron on bone.