Iron regulatory protein 2 in ovarian endometrial cysts

Redox-Regulated Iron Metabolism and Ferroptosis in Ovarian Cancer: Molecular Insights and Therapeutic Opportunities

Ovarian cancer (OC), known for its lethality and resistance to chemotherapy, is closely associated with iron metabolism and ferroptosis-an iron-dependent cell death process, distinct from both autophagy and apoptosis. Emerging evidence suggests that dysregulation of iron metabolism could play a crucial role in OC by inducing an imbalance in the redox system, which leads to ferroptosis, offering a novel therapeutic approach. This review examines how disruptions in iron metabolism, which affect redox balance, impact OC progression, focusing on its essential cellular functions and potential as a therapeutic target. It highlights the molecular interplay, including the role of non-coding RNAs (ncRNAs), between iron metabolism and ferroptosis, and explores their interactions with key immune cells such as macrophages and T cells, as well as inflammation within the tumor microenvironment. The review also discusses how glycolysis-related iron metabolism influences ferroptosis via reactive oxygen species. Targeting these pathways, especially through agents that modulate iron metabolism and ferroptosis, presents promising therapeutic prospects. The review emphasizes the need for deeper insights into iron metabolism and ferroptosis within the redox-regulated system to enhance OC therapy and advocates for continued research into these mechanisms as potential strategies to combat OC.

Ovaries of estrogen receptor 1-deficient mice show iron overload and signs of aging

Introduction

Estrogens are crucial regulators of ovarian function, mediating their signaling through binding to estrogen receptors. The disruption of the estrogen receptor 1 (Esr1) provokes infertility associated with a hemorrhagic, cystic phenotype similar to that seen in diseased or aged ovaries. Our previous study indicated the possibility of altered iron metabolism in Esr1-deficient ovaries showing massive expression of lipocalin 2, a regulator of iron homeostasis.

Methods

Therefore, we examined the consequences of depleting Esr1 in mouse ovaries, focusing on iron metabolism. For that reason, we compared ovaries of adult Esr1-deficient animals and age-matched wild type littermates.

Results and discussion

We found increased iron accumulation in Esr1-deficient animals by using laser ablation inductively coupled plasma mass spectrometry. Western blot analysis and RT-qPCR confirmed that iron overload alters iron transport, storage and regulation. In addition, trivalent iron deposits in form of hemosiderin were detected in Esr1-deficient ovarian stroma. The depletion of Esr1 was further associated with an aberrant immune cell landscape characterized by the appearance of macrophage-derived multinucleated giant cells (MNGCs) and increased quantities of macrophages, particularly M2-like macrophages. Similar to reproductively aged animals, MNGCs in Esr1-deficient ovaries were characterized by iron accumulation and strong autofluorescence. Finally, deletion of Esr1 led to a significant increase in ovarian mast cells, involved in iron-mediated foam cell formation. Given that these findings are characteristics of ovarian aging, our data suggest that Esr1 deficiency triggers mechanisms similar to those associated with aging.

Rhodamine-based Fluorescent Probe With Quick Response and High Selectivity for Imaging Labile Ferrous Iron in Living Cells and Zebrafish

The transition between its various oxidation states of Iron plays a crucial part in various chemical transformation of cells. Misregulation of iron can give rise to the iron-catalyzed reactive oxygen species disorder which have been linked to a variety of diseases, so it is crucial to monitor the labile iron pool in vivo for clinical diagnosis. According to iron autoxidation and hydrogen abstraction reaction, we reported a novel "off-on" fluorescent probe to response to ferrous (Fe2+) both in solutions and biological systems. The probe responds to Fe2+ with good selectivity toward competing metal ions. What's more, the probe presents significant fluorescent enhancement to Fe2+ in less than 1 min, making real-time sensing in biological system possible. The applications of the probe in bioimaging revealed the changes in labile iron pool by iron autoxidation or diverse stimuli.

The role of iron in the pathogenesis of endometriosis: a systematic review

STUDY QUESTION

What is the role of iron in the pathophysiology of endometriosis?

SUMMARY ANSWER

Iron excess is demonstrated wherever endometriotic tissues are found and is associated with oxidative stress, an inflammatory micro-environment, and cell damage; the iron-mediated oxidative stress is independently linked to subfertility, symptom severity, and malignant transformation.

WHAT IS KNOWN ALREADY

Iron is found in excess in endometriotic tissues, and multiple mechanisms have been studied and posited to explain this. It is clear that iron excess plays a vital role in promoting oxidative stress and cell damage. The evidence base is large, but no comprehensive reviews exist to summarize our understanding and highlight the overarching themes to further our understanding and suggest future directions of study for the field.

STUDY DESIGN SIZE DURATION

This systematic review with a thematic analysis retrieved studies from the PubMed, Embase, Web of Science, and Cochrane Library databases and searches were conducted from inception through to August 2022. Human and animal studies published in the English language were included and identified using a combination of exploded MeSH terms ('Iron' and 'Endometriosis') and free-text search terms ('Iron', 'Ferric', 'Ferrous', 'Endometriosis', 'Endometrioma').

PARTICIPANTS/MATERIALS SETTING METHODS

This review was reported in accordance with the PRISMA guidelines. All studies reporting original data concerning the role of iron or iron complexes in the pathophysiology of endometriosis were included. Studies that did not report original data or provided a review of the field were excluded. Bias analysis was completed for each included study by using the Newcastle-Ottawa scoring system.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 776 records identified and these were screened down to 53 studies which met the eligibility criteria, including 6 animal and 47 human studies, with 3556 individual participants. Iron excess is demonstrated in various tissues and fluids, including ovarian endometriomas, ovarian follicles, ectopic endometriotic lesions, and peritoneal fluid. Markers of oxidative stress are strongly associated with high iron levels, and aberrant expression of iron-transport proteins has been demonstrated. Abnormal resistance to ferroptosis is likely. Iron-mediated oxidative stress is responsible for a pro-inflammatory micro-environment and is linked to subfertility, symptom severity, and, possibly, malignant transformation.

LIMITATIONS REASONS FOR CAUTION

A minority of the included studies were of objectively low quality with a high risk of bias and may lead to misleading conclusions. Additionally, multiple studies failed to appropriately characterize the included patients by known confounding variables, such as menstrual cycle phase, which may introduce bias to the findings.

WIDER IMPLICATIONS OF THE FINDINGS

Current literature depicts a central role of aberrant iron mechanics and subsequent oxidative stress in endometriosis. It is likely that iron excess is at least partly responsible for the persistence and proliferation of ectopic endometriotic lesions. As such, iron mechanics represent an attractive target for novel therapeutics, including iron chelators or effectors of the iron-oxidative stress pathway. There are significant gaps in our current understanding, and this review highlights and recommends several topics for further research. These include the role of iron chelation, resistance to ferroptosis, the relationship between iron excess and localized hypoxia, systemic iron pathophysiology in endometriosis, and the role of oxidative stress in malignant transformation.

STUDY FUNDING/COMPETING INTERESTS

J.W. and S.G.P. are supported by clinical fellowships at Liverpool University Hospital NHS Foundation trust. No additional funding was requested or required for the completion of this work. C.J.H. is supported by a Wellbeing of Women project grant (RG2137). D.K.H. is supported by a Wellbeing of Women project grant (RG2137) and an MRC clinical research training fellowship (MR/V007238/1). The authors have no conflicts of interest to declare.

REGISTRATION NUMBER

A protocol was prospectively registered with the PROSPERO database in August 2021 (CRD42021272818).

The Role of Iron and Cobalt in Gynecological Diseases

Iron and cobalt are micronutrients that play an important role in the regulation of cellular processes, being part of the centre of catalases, peroxidases, cytochromes and metalloproteins such as hemoglobin and myoglobin (Fe). Cobalt primarily functions as a component of hydroxycobalamin, which is essential for regulating red blood cell production. Maintaining normal levels of cobalt and iron in the human body is important, as a deficiency can lead to anaemia. These elements are also involved in reactions during which oxidative stress occurs and are therefore considered to be a cause of tumor formation. This paper will discuss aspects of the influence of cobalt and iron on mechanisms that may contribute to the growth of gynecological tumors, as well as other obstetric-gynecological disease entities, by altering the conditions of the microenvironment. In addition, the following review also highlights the role of cobalt and iron in the treatment of gynecological tumors.

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.

Fluorescent probes for the detection of catalytic Fe(II) ion

Iron (Fe) is the most abundant redox-active metal ion in the human body, and its redox-active inter-convertible multiple oxidation states contributes to numerous essential biological processes. Moreover, iron overload can potentially cause cellular damage and death, as wel as numerous diseases through the aberrant production of highly reactive oxidative species (hROS). Protein-free or weakly-protein-bound Fe ions play a pivotal role as catalytic reactants of the Fenton reaction. In this reaction, hROS, such as hydroxyl radicals and high valent-iron-oxo species, are generated by a reaction between hydrogen peroxide and Fe(II), which is re-generated through reduction using abundant intracellular reductants, such as glutathione. This results in the catalytic evolution of hROS. Thus, selective detection of the catalytic Fe(II) in the living systems can explain both of the pathological and physiological functions of Fe(II). Written from the perspective of their modes of actions, this paper presents recent advances in the development of fluorescent and bioluminescent probes that can selectively detect catalytic Fe(II) together with their biological applications.

Development of Chemical Tools for Imaging of Fe(II) Ions in Living Cells: A Review

Intracellular labile iron is an iron species which is not or weakly bound to proteins and depicts an important effect on homeostatic regulation in cells. An excess or deficiency of iron can cause oxidative damage to key cellular biomolecules. The behavior and concentrations of labile iron are difficult to monitor, but the specific redox state of the Fe ions is relevant to the physiological and pathological properties that we would like to study. We have developed a series of turn-on type fluorescent probes that are highly selective to the labile Fe(II) ions, and we have tested their applications to cellular level imaging. These probes are based on N-oxide chemistry with a range of fluorophores that depict optimal performance for specific applications. Herein, I review the recent progress of our research and discuss prospects for future work to understand the relation between intracellular ion and oxidative stress.

Fe(II) Ion Release during Endocytotic Uptake of Iron Visualized by a Membrane-Anchoring Fe(II) Fluorescent Probe

Iron is an essential transition metal species for all living organisms and plays various physiologically important roles on the basis of its redox activity; accordingly, the disruption of iron homeostasis triggers oxidative stress and cellular damage. Therefore, cells have developed sophisticated iron-uptake machinery to acquire iron while protecting cells from uncontrolled oxidative damage during the uptake process. To examine the detailed mechanism of iron uptake while controlling the redox status, it is necessary to develop useful methods with redox state selectivity, sensitivity, and organelle specificity to monitor labile iron, which is weakly bound to subcellular ligands. Here, we report the development of Mem-RhoNox to monitor local Fe(II) at the surface of the plasma membrane of living cells. The redox state-selective fluorescence response of the probe relies on our recently developed N-oxide strategy, which is applicable to fluorophores with dialkylarylamine in their π-conjugation systems. Mem-RhoNox consists of the N-oxygenated rhodamine scaffold, which has two arms, both of which are tethered with palmitoyl groups as membrane-anchoring domains. In an aqueous buffer, Ac-RhoNox, a model compound of Mem-RhoNox, shows a fluorescence turn-on response to the Fe(II) redox state-selectively. An imaging study with Mem-RhoNox and its derivatives reveals that labile Fe(II) is transiently generated during the major iron-uptake pathways: endocytotic uptake and direct transport. Furthermore, Mem-RhoNox is capable of monitoring endosomal Fe(II) in primary cultured neurons during endocytotic uptake. This report is the first example that identifies the generation of Fe(II) over the course of cellular iron-uptake processes.

Activity-based sensing fluorescent probes for iron in biological systems

Iron is an essential nutrient for life, and its capacity to cycle between different oxidation states is required for processes spanning oxygen transport and respiration to nucleotide synthesis and epigenetic regulation. However, this same redox ability also makes iron, if not regulated properly, a potentially dangerous toxin that can trigger oxidative stress and damage. New methods that enable monitoring of iron in living biological systems, particularly in labile Fe²⁺ forms, can help identify its contributions to physiology, aging, and disease. In this review, we summarize recent developments in activity-based sensing (ABS) probes for fluorescence Fe²⁺ detection.