Involvement of cytosolic and mitochondrial iron in iron overload cardiomyopathy: an update

Decoding ferroptosis: Revealing the hidden assassin behind cardiovascular diseases

The discovery of regulatory cell death processes has driven innovation in cardiovascular disease (CVD) therapeutic strategies. Over the past decade, ferroptosis, an iron-dependent form of regulated cell death driven by excessive lipid peroxidation, has been shown to drive the development of multiple CVDs. This review provides insights into the evolution of the concept of ferroptosis, the similarities and differences with traditional modes of programmed cell death (e.g., apoptosis, autophagy, and necrosis), as well as the core regulatory mechanisms of ferroptosis (including cystine/glutamate transporter blockade, imbalance of iron metabolism, and lipid peroxidation). In addition, it provides not only a detailed review of the role of ferroptosis and its therapeutic potential in widely studied CVDs such as coronary atherosclerotic heart disease, myocardial infarction, myocardial ischemia/reperfusion injury, heart failure, cardiomyopathy, and aortic aneurysm but also an overview of the phenomenon and therapeutic perspectives of ferroptosis in lesser-addressed CVDs such as cardiac valvulopathy, pulmonary hypertension, and sickle cell disease. This article aims to integrate this knowledge to provide a comprehensive view of ferroptosis in a wide range of CVDs and to drive innovation and progress in therapeutic strategies in this field.

Compliance and clinical benefit of deferasirox granule and dispersible tablet formulation in pediatric patients with transfusional iron overload: in a randomized, open-label, multicenter, phase II study

CALYPSO (clinicaltrials gov. Identifier: NCT02435212), a randomized, open-label, multicenter, phase II study evaluated the compliance, clinical benefits, and safety of deferasirox granules and dispersible tablets (DT) in pediatric patients with iron overload. Iron chelation therapy-naive and iron chelation therapy-pretreated patients aged 2 to <18 years with transfusion- dependent anemias were enrolled. Patients were randomized 1:1 to deferasirox granules or DT for 48 weeks, stratified by age group and prior iron chelation therapy. In this study, the co-primary objectives are to evaluate compliance and change from baseline in serum ferritin after 24 weeks for both formulations in iron chelation therapy-naive patients. In total, 224 patients, mostly with β-thalassemia major (63.4%), were randomized to granules (N=112) or DT (N=112). Primary analysis was conducted when 96 iron chelation therapy-naive patients had completed 24 weeks of treatment/discontinued early; least squares mean (LSM) compliance in the deferasirox granules and DT groups, was 86.8% and 84.3% (difference 2.6%; P=0.360) respectively, while least squares mean change from baseline in serum ferritin was +4.8 and -171.5 ng/mL (difference: 176.4 ng/mL; P=0.255). Slight differences were observed in the observer/patient-reported outcome scores between the granule and dispersible-tablet groups and the overall scores indicate good adherence, satisfaction/preference, fewer concerns and good palatability with both deferasirox formulations. Safety analyses (N=221) found that the most frequently observed adverse events (granules and DT) were increased urine protein/creatinine ratio (>0.5 mg/mg; 24.5% and 34.2%), upper respiratory tract infection (28.2% and 29.7%), and pyrexia (26.4% and 23.4%). In iron chelation therapy-naive patients, mean compliance and change from baseline in serum ferritin with both deferasirox formulations were not significantly different. The safety profile was comparable between granule and DT formulations, and was consistent with the general safety profile of deferasirox.

Ferroptosis contributing to cardiomyocyte injury induced by silica nanoparticles via miR-125b-2-3p/HO-1 signaling

BACKGROUND

Amorphous silica nanoparticles (SiNPs) have been gradually proven to threaten cardiac health, but pathogenesis has not been fully elucidated. Ferroptosis is a newly defined form of programmed cell death that is implicated in myocardial diseases. Nevertheless, its role in the adverse cardiac effects of SiNPs has not been described.

RESULTS

We first reported the induction of cardiomyocyte ferroptosis by SiNPs in both in vivo and in vitro. The sub-chronic exposure to SiNPs through intratracheal instillation aroused myocardial injury, characterized by significant inflammatory infiltration and collagen hyperplasia, accompanied by elevated CK-MB and cTnT activities in serum. Meanwhile, the activation of myocardial ferroptosis by SiNPs was certified by the extensive iron overload, declined FTH1 and FTL, and lipid peroxidation. The correlation analysis among detected indexes hinted ferroptosis was responsible for the SiNPs-aroused myocardial injury. Further, in vitro tests, SiNPs triggered iron overload and lipid peroxidation in cardiomyocytes. Concomitantly, altered expressions of TfR, DMT1, FTH1, and FTL indicated dysregulated iron metabolism of cardiomyocytes upon SiNP stimuli. Also, shrinking mitochondria with ridge fracture and ruptured outer membrane were noticed. To note, the ferroptosis inhibitor Ferrostatin-1 could effectively alleviate SiNPs-induced iron overload, lipid peroxidation, and myocardial cytotoxicity. More importantly, the mechanistic investigations revealed miR-125b-2-3p-targeted HO-1 as a key player in the induction of ferroptosis by SiNPs, probably through regulating the intracellular iron metabolism to mediate iron overload and ensuing lipid peroxidation.

CONCLUSIONS

Our findings firstly underscored the fact that ferroptosis mediated by miR-125b-2-3p/HO-1 signaling was a contributor to SiNPs-induced myocardial injury, which could be of importance to elucidate the toxicity and provide new insights into the future safety applications of SiNPs-related nano products.

Copper homeostasis in chronic kidney disease and its crosstalk with ferroptosis

Chronic kidney disease (CKD) has become a global public health problem with high morbidity and mortality. Renal fibrosis can lead to end-stage renal disease (ESRD). However, there is still no effective treatment to prevent or delay the progression of CKD into ESRD. Therefore, exploring the pathogenesis of CKD is essential for preventing and treating CKD. There are a variety of trace elements in the human body that interact with each other within a complex regulatory network. Iron and copper are both vital trace elements in the body. They are critical for maintaining bodily functions, and the dysregulation of their metabolism can cause many diseases, including kidney disease. Ferroptosis is a new form of cell death characterized by iron accumulation and lipid peroxidation. Studies have shown that ferroptosis is closely related to kidney disease. However, the role of abnormal copper metabolism in kidney disease and its relationship with ferroptosis remains unclear. Here, our current knowledge regarding copper metabolism, its regulatory mechanism, and the role of abnormal copper metabolism in kidney diseases is summarized. In addition, we discuss the relationship between abnormal copper metabolism and ferroptosis to explore the possible pathogenesis and provide a potential therapeutic target for CKD.

The interplay of miRNAs and ferroptosis in diseases related to iron overload

Ferroptosis has been conceptualized as a novel cell death modality distinct from apoptosis, necroptosis, pyroptosis and autophagic cell death. The sensitivity of cellular ferroptosis is regulated at multiple layers, including polyunsaturated fatty acid metabolism, glutathione-GPX4 axis, iron homeostasis, mitochondria and other parallel pathways. In addition, microRNAs (miRNAs) have been implicated in modulating ferroptosis susceptibility through targeting different players involved in the execution or avoidance of ferroptosis. A growing body of evidence pinpoints the deregulation of miRNA-regulated ferroptosis as a critical factor in the development and progression of various pathophysiological conditions related to iron overload. The revelation of mechanisms of miRNA-dependent ferroptosis provides novel insights into the etiology of diseases and offers opportunities for therapeutic intervention. In this review, we discuss the interplay of emerging miRNA regulators and ferroptosis players under different pathological conditions, such as cancers, ischemia/reperfusion, neurodegenerative diseases, acute kidney injury and cardiomyopathy. We emphasize on the relevance of miRNA-regulated ferroptosis to disease progression and the targetability for therapeutic interventions.

Consumption of foods contaminated with heavy metals and their association with cardiovascular disease (CVD) using GAM software (cohort study)

Introduction

Heavy metals can enter the environment and food through industrial activities, acid rain, chemical fertilizers, pesticides, and sewage. A large amount of these metals is dangerous because they tend to bio accumulate. A concern with these metals is the long-term, low-dose exposure seen in the general population. HMs can cause disorders in the cardiovascular system through various mechanisms such as the production of free radicals, DNA damage, lipid peroxidation, and oxidative stress.

Material and method

Food items measured in the present study included rice, bread, and vegetables. 210 participants (105 controls and 105 patients) were randomly selected for this study. The demographic information of the subjects was obtained from the Hoveyzeh Cohort Center. The relationship between heavy metals in food and cardiovascular diseases is investigated by The Generalized Additive Model (GAM).

Result

The results of the present study showed that when urine Cd was smoothed based on rice Cd, there was a significant correlation between urine Cd and Cd consumed in vegetables and rice. The GAM coefficient for urinary Cd excreted in case-control groups and Cd consumed in vegetables were 479.79(SE: 6.49-73.87) and 818.56(SE: 11.96-68.43), respectively, and for rice consumed, it was 0.03(SE: 0.015-2.103) and 0.04(SE: 0.017-2.338), respectively. The GAM coefficient for As consumption in vegetables and As in urine of case and control groups was 1.61 (SE: 9.48-0.16) and 22.36 (SE: 13.60-1.64), respectively. The same coefficient for rice consumption in case and control groups was 4.5 (SE: 0.62-7.22) and 10.48 (SE: 1.46-7.16), respectively. There was a very strong and significant correlation between the Sr in the urine of both groups and the Sr in the food consumed, so that the urinary Sr in the control group is excreted more than in the cardiovascular group.

Conclusion

GAM analysis indicates that As in vegetable and rice is more than the standard limitation value. Also, Sr and Cd in vegetables, rice, and bread were more than the standard limitation value. According to the GAM model As had a significant value in rice and vegetables indicating that As is more than the standard limitation value, therefore, it is associated with CVD.

Ferroptosis in cardiovascular disease

In the 21st century, cardiovascular disease (CVD) has become one of the leading causes of death worldwide. The prevention and treatment of CVD remain pressing scientific issues. Several recent studies have suggested that ferroptosis may play a key role in CVD. Most studies conducted thus far on ferroptosis and CVD have supported the link. Ferroptosis mediated by different signaling and metabolic pathways can lead to ischemic heart disease, myocarditis, heart failure, ischemia-reperfusion injury, and cardiomyopathy. Still, the specific mechanism of ferroptosis in CVD, the particular organ areas affected, and the stage of disease involved need to be further studied. Therefore, understanding the mechanisms regulating ferroptosis in CVD may improve disease management. Throughout this review, we summarized the mechanism of ferroptosis and its effect on the pathogenesis of CVD. We also predicted and discussed future research directions, aiming to provide new ideas and strategies for preventing and treating CVD.

Evaluation of cardiac fibrosis and subclinical cardiac changes in children with sickle cell disease using magnetic resonance imaging, echocardiography, and serum galectin-3

BACKGROUND

Myocardial fibrosis has recently been proposed as one of the contributing factors to the diverse pathogenicity of cardiomyopathy in sickle cell disease.

OBJECTIVE

In this study, cardiac fibrosis and subclinical cardiac changes in children with sickle cell disease were evaluated using cardiac magnetic resonance imaging (MRI), tissue Doppler echocardiography and serum galectin-3.

MATERIALS AND METHODS

The study included 34 children with sickle cell disease who were compared with a similar number of healthy controls. Cardiac MRI was used to evaluate late gadolinium enhancement, native T1 mapping, extracellular volume, and T2* for estimation of iron load. Cardiac function and myocardial performance index (MPI, evaluated by tissue Doppler echocardiography) and serum galectin-3 were compared to controls.

RESULTS

The mean age of the included patients was 13.3 ± 3.2 years. Myocardial iron load by T2* was normal. The mean level of extracellular volume (35.41 ± 5.02%) was significantly associated with the frequency of vaso-occlusive crises (P = 0.017) and negatively correlated with hemoglobin levels (P = 0.005). Galectin-3 levels were significantly higher among cases than controls (P = 0.00), at a cutoff value on the receiver operating characteristic curve of 6.5 ng/ml, sensitivity of 82.5% and specificity of 72.8%. The extracellular volume was significantly higher in cases, with a MPI > 0.4.

CONCLUSION

Diffuse interstitial myocardial fibrosis can be detected early in children with sickle cell disease using T1 mapping and is associated with a high frequency of vaso-occlusive crisis. MPI of the left ventricle and serum galectin-3 are recommended screening tools for subclinical cardiac abnormalities.

The Role of Cellular Defense Systems of Ferroptosis in Parkinson's Disease and Alzheimer's Disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common rapidly developing neurodegenerative diseases that lead to serious health and socio-economic consequences. Ferroptosis is a non-apoptotic form of cell death; there is growing evidence to support the notion that ferroptosis is involved in a variety of pathophysiological contexts, and there is increasing interest in the role of ferroptosis in PD and AD. Simultaneously, cells may have evolved four defense systems to counteract the toxic effects of ferroptosis occasioned by lipid peroxidation. This review, which focuses on the analysis of ferroptosis in the PD and AD context, outlines four cellular defense systems against ferroptosis and how each of them is involved in PD and AD.

Mechanisms of ferroptosis regulating oxidative stress and energy metabolism in myocardial ischemia-reperfusion injury and a novel perspective of natural plant active ingredients for its treatment

Acute myocardial infarction remains the leading cause of death in humans. Timely restoration of blood perfusion to ischemic myocardium remains the most effective strategy in the treatment of acute myocardial infarction, which can significantly reduce morbidity and mortality. However, after restoration of blood flow and reperfusion, myocardial injury will aggravate and induce apoptosis of cardiomyocytes, a process called myocardial ischemia-reperfusion injury. Studies have shown that the loss and death of cardiomyocytes caused by oxidative stress, iron load, increased lipid peroxidation, inflammation and mitochondrial dysfunction, etc., are involved in myocardial ischemia-reperfusion injury. In recent years, with the in-depth research on the pathology of myocardial ischemia-reperfusion injury, people have gradually realized that there is a new form of cell death in the pathological process of myocardial ischemia-reperfusion injury, namely ferroptosis. A number of studies have found that in the myocardial tissue of patients with acute myocardial infarction, there are pathological changes closely related to ferroptosis, such as iron metabolism disorder, lipid peroxidation, and increased reactive oxygen species free radicals. Natural plant products such as resveratrol, baicalin, cyanidin-3-O-glucoside, naringenin, and astragaloside IV can also exert therapeutic effects by correcting the imbalance of these ferroptosis-related factors and expression levels. Combining with our previous studies, this review summarizes the regulatory mechanism of natural plant products intervening ferroptosis in myocardial ischemia-reperfusion injury in recent years, in order to provide reference information for the development of targeted ferroptosis inhibitor drugs for the treatment of cardiovascular diseases.

Effects of Inflammatory Cell Death Caused by Catheter Ablation on Atrial Fibrillation

Atrial fibrillation (AF) poses a serious healthcare burden on society due to its high morbidity and the resulting serious complications such as thrombosis and heart failure. The principle of catheter ablation is to achieve electrical isolation by linear destruction of cardiac tissue, which makes AF a curable disease. Currently, catheter ablation does not have a high long-term success rate. The current academic consensus is that inflammation and fibrosis are central mechanisms in the progression of AF. However, artificially caused inflammatory cell death by catheter ablation may have a significant impact on structural and electrical remodeling, which may affect the long-term prognosis. This review first focused on the inflammatory response induced by apoptosis, necrosis, necroptosis, pyroptosis, ferroptosis and their interaction with arrhythmia. Then, we compared the differences in cell death induced by radiofrequency ablation, cryoballoon ablation and pulsed-field ablation. Finally, we discussed the structural and electrical remodeling caused by inflammation and the association between inflammation and the recurrence of AF after catheter ablation. Collectively, pulsed-field ablation will be a revolutionary innovation with faster, safer, better tissue selectivity and less inflammatory response induced by apoptosis-dominated cell death.

OPG/RANK/RANKL axis relation to cardiac iron-overload in children with transfusion-dependent thalassemia

OPG/RANK/RANKL axis was reportedly involved in initiating various diseases, especially bone and cardiovascular diseases. This study aimed to assess the relationship between some OPG, RANK, and RANKL polymorphisms and alleles and iron-overload-induced cardiomyopathy in children with transfusion-dependent thalassemia (TDT). This study included 80 TDT children and 80 age and sex-matched controls. Real-time PCR was done for rs207318 polymorphism for the OPG gene and rs1805034, rs1245811, and rs75404003 polymorphisms for the RANK gene, and rs9594782 and rs2277438 polymorphisms for the RANKL gene. Cardiac T2* MRI and ejection fraction (EF) were done to assess the myocardial iron status and cardiac function. In this study, there were no significant differences in frequencies of the studied polymorphisms between cases and controls (p > 0.05 in all). In TDT children, OPG rs2073618 (G > C) had a significant relation to myocardial iron overload (p = 0.02). Its C allele had significantly more frequent normal EF than its G allele (p = 0.04). RANK rs75404403 (C > DEL) had a significant relation to cardiac dysfunction (p = 0.02). Moreover, the C allele of that gene had significantly more frequent affected EF than its DEL allele (p = 0.02). The A allele of RANKL rs2277438 (G > A) had significantly less frequent severe cardiac iron overload than the G allele (p = 0.04). In conclusion, the OPG/ RANK/RANKL genes may act as genetic markers for iron-induced cardiomyopathy in TDT children. Some of the studied genes' polymorphisms and alleles were significantly related to myocardial iron overload and cardiac dysfunction in TDT children.

Iron Status and Short-Term Recovery after Non-Severe Acute Myocarditis: A Prospective Observational Study

Pathomechanisms responsible for recovery from acute myocarditis (MCD) or progression to non-ischemic cardiomyopathy have not been comprehensively investigated. Iron, positioned at the crossroads of inflammation and the energy metabolism of cardiomyocytes, may contribute to the pathophysiology of inflammatory myocardial disease. The aim of this study was to evaluate whether systemic iron parameters are related to myocardial dysfunction in MCD patients. We prospectively enrolled 42 consecutive patients hospitalized for MCD. Their iron status and their clinical, laboratory, and echocardiographic indices were assessed during hospitalization and during ambulatory visits six weeks after discharge. A control group comprising healthy volunteers was recruited. The MCD patients had higher serum ferritin and hepcidin and lower serum iron concentration and transferrin saturation (TSAT) than the healthy controls (all p < 0.01). Six weeks after discharge, the iron status of the MCD patients was already comparable to that of the control group. During hospitalization, lower serum iron and TSAT correlated with higher NT-proBNP (both p < 0.05). In-hospital lower serum iron and TSAT correlated with both a lower left ventricular ejection fraction (LVEF) and worse left ventricular global longitudinal strain at follow-up visits (all p < 0.05). In conclusion, in patients with acute MCD, iron status is altered and normalizes within six weeks. Low serum iron and TSAT are related to greater in-hospital neurohormonal activation and subtle persistent left ventricular dysfunction.

Iron accumulation and lipid peroxidation: implication of ferroptosis in diabetic cardiomyopathy

Diabetic cardiomyopathy (DC) is a serious heart disease caused by diabetes. It is unrelated to hypertension and coronary artery disease and can lead to heart insufficiency, heart failure and even death. Currently, the pathogenesis of DC is unclear, and clinical intervention is mainly symptomatic therapy and lacks effective intervention objectives. Iron overdose mediated cell death, also known as ferroptosis, is widely present in the physiological and pathological processes of diabetes and DC. Iron is a key trace element in the human body, regulating the metabolism of glucose and lipids, oxidative stress and inflammation, and other biological processes. Excessive iron accumulation can lead to the imbalance of the antioxidant system in DC and activate and aggravate pathological processes such as excessive autophagy and mitochondrial dysfunction, resulting in a chain reaction and accelerating myocardial and microvascular damage. In-depth understanding of the regulating mechanisms of iron metabolism and ferroptosis in cardiovascular vessels can help improve DC management. Therefore, in this review, we summarize the relationship between ferroptosis and the pathogenesis of DC, as well as potential intervention targets, and discuss and analyze the limitations and future development prospects of these targets.

Ebselen: A promising therapy protecting cardiomyocytes from excess iron in iron-overloaded thalassemia patients

Iron-overload-associated cardiomyopathy has been one of the primary causes of mortality in thalassemia patients with iron burden. There is growing evidence citing the beneficial effects of ebselen as an antioxidant selectively blocking the divalent metal transporter 1 (DMT-1) to deter iron ingress into cardiomyocytes, raising internets in viewing this component in this population in order to treat and even prevent cardiomyopathy occurring from iron surplus. In this article, we reviewed the potential advantageous effects of ebselen in thalassemia patients who suffer from iron excess, susceptible to cardiomyopathy induced by iron overload. A systematic search in several databases, including PubMed, Scopus, and Web of Science, was conducted to explore the role of ebselen in controlling iron-overload-related cardiomyopathy in thalassemia patients by the keywords of Ebselen AND iron. The inclusion criteria were English-written preclinical and clinical studies investigating the efficacy and side effects of ebselen in an iron-overload context. After searching the databases, 44 articles were found. Next, of 19 published articles, 3 were included in this article. After reviewing the references of the included studies, no articles were added. In conclusion ebselen can be a promising adjuvant therapy in patients with thalassemia alongside the standard treatment with iron chelators, particularly in severe cases with cardiomyopathy, due to falling iron inflow by inhibiting DMT-1 and increasing ferroportin-1 expression and antioxidant properties. However, clinical studies need to be carried out to reach a definite conclusion.

Deficiency of mitochondrial calcium uniporter abrogates iron overload-induced cardiac dysfunction by reducing ferroptosis

Iron overload associated cardiac dysfunction remains a significant clinical challenge whose underlying mechanism(s) have yet to be defined. We aim to evaluate the involvement of the mitochondrial Ca2+ uniporter (MCU) in cardiac dysfunction and determine its role in the occurrence of ferroptosis. Iron overload was established in control (MCUfl/fl) and conditional MCU knockout (MCUfl/fl-MCM) mice. LV function was reduced by chronic iron loading in MCUfl/fl mice, but not in MCUfl/fl-MCM mice. The level of mitochondrial iron and reactive oxygen species were increased and mitochondrial membrane potential and spare respiratory capacity (SRC) were reduced in MCUfl/fl cardiomyocytes, but not in MCUfl/fl-MCM cardiomyocytes. After iron loading, lipid oxidation levels were increased in MCUfl/fl, but not in MCUfl/fl-MCM hearts. Ferrostatin-1, a selective ferroptosis inhibitor, reduced lipid peroxidation and maintained LV function in vivo after chronic iron treatment in MCUfl/fl hearts. Isolated cardiomyocytes from MCUfl/fl mice demonstrated ferroptosis after acute iron treatment. Moreover, Ca2+ transient amplitude and cell contractility were both significantly reduced in isolated cardiomyocytes from chronically Fe treated MCUfl/fl hearts. However, ferroptosis was not induced in cardiomyocytes from MCUfl/fl-MCM hearts nor was there a reduction in Ca2+ transient amplitude or cardiomyocyte contractility. We conclude that mitochondrial iron uptake is dependent on MCU, which plays an essential role in causing mitochondrial dysfunction and ferroptosis under iron overload conditions in the heart. Cardiac-specific deficiency of MCU prevents the development of ferroptosis and iron overload-induced cardiac dysfunction.

Heme: The Lord of the Iron Ring

Heme is an iron-protoporphyrin complex with an essential physiologic function for all cells, especially for those in which heme is a key prosthetic group of proteins such as hemoglobin, myoglobin, and cytochromes of the mitochondria. However, it is also known that heme can participate in pro-oxidant and pro-inflammatory responses, leading to cytotoxicity in various tissues and organs such as the kidney, brain, heart, liver, and in immune cells. Indeed, heme, released as a result of tissue damage, can stimulate local and remote inflammatory reactions. These can initiate innate immune responses that, if left uncontrolled, can compound primary injuries and promote organ failure. In contrast, a cadre of heme receptors are arrayed on the plasma membrane that is designed either for heme import into the cell, or for the purpose of activating specific signaling pathways. Thus, free heme can serve either as a deleterious molecule, or one that can traffic and initiate highly specific cellular responses that are teleologically important for survival. Herein, we review heme metabolism and signaling pathways, including heme synthesis, degradation, and scavenging. We will focus on trauma and inflammatory diseases, including traumatic brain injury, trauma-related sepsis, cancer, and cardiovascular diseases where current work suggests that heme may be most important.

New Insights into the Role of Ferroptosis in Cardiovascular Diseases

Cardiovascular diseases (CVDs) are the principal cause of disease burden and death worldwide. Ferroptosis is a new form of regulated cell death mainly characterized by altered iron metabolism, increased polyunsaturated fatty acid peroxidation by reactive oxygen species, depletion of glutathione and inactivation of glutathione peroxidase 4. Recently, a series of studies have indicated that ferroptosis is involved in the death of cardiac and vascular cells and has a key impact on the mechanisms leading to CVDs such as ischemic heart disease, ischemia/reperfusion injury, cardiomyopathies, and heart failure. In this article, we reviewed the molecular mechanism of ferroptosis and the current understanding of the pathophysiological role of ferroptosis in ischemic heart disease and in some cardiomyopathies. Moreover, the comprehension of the machinery governing ferroptosis in vascular cells and cardiomyocytes may provide new insights into preventive and therapeutic strategies in CVDs.

Iron Metabolism in Cardiovascular Disease: Physiology, Mechanisms, and Therapeutic Targets

The cardiovascular system requires iron to maintain its high energy demands and metabolic activity. Iron plays a critical role in oxygen transport and storage, mitochondrial function, and enzyme activity. However, excess iron is also cardiotoxic due to its ability to catalyze the formation of reactive oxygen species and promote oxidative damage. While mammalian cells have several redundant iron import mechanisms, they are equipped with a single iron-exporting protein, which makes the cardiovascular system particularly sensitive to iron overload. As a result, iron levels are tightly regulated at many levels to maintain homeostasis. Iron dysregulation ranges from iron deficiency to iron overload and is seen in many types of cardiovascular disease, including heart failure, myocardial infarction, anthracycline-induced cardiotoxicity, and Friedreich's ataxia. Recently, the use of intravenous iron therapy has been advocated in patients with heart failure and certain criteria for iron deficiency. Here, we provide an overview of systemic and cellular iron homeostasis in the context of cardiovascular physiology, iron deficiency, and iron overload in cardiovascular disease, current therapeutic strategies, and future perspectives.

Early adaptive responses in the skeletal muscle of young mice with hereditary hemochromatosis

BACKGROUND

Hereditary hemochromatosis (HH) is characterized by iron overload that can cause multiple organ dysfunction primarily due to uncontrolled iron-mediated oxidative stress. Although HH leads to muscular weakness, disorder, and fatigue, the mechanism by which HH affects skeletal muscle physiology is largely unknown.

METHODS

Using Hfe knockout mice (6-7 months old), a well-defined mouse model of HH, we examined iron status in the skeletal muscle, as well as other organs. As mitochondria are key organelle for muscular function, this study also explored how molecular markers for mitochondrial function and related systems are regulated in the HH skeletal muscle using western blots.

RESULTS

Although iron overload was evident at the systemic level, only mild iron overload was observed in the skeletal muscle of HH. Of note, mitochondrial electron transport chain complex I was upregulated in the HH skeletal muscle, which was accompanied by enhanced autophagy. However, these molecular changes were not associated with oxidative stress, suggesting altered mitochondrial metabolism in the muscle in response to iron overload.

CONCLUSIONS

These early adaptive responses may be important for supporting mitochondrial health before fully developing skeletal muscle dysfunction in HH. More studies are needed to determine the role of autophagy in the HH-related muscle mitochondrial dysfunction.

Iron stores in steady-state sickle cell disease children accessing care at a sickle cell disease clinic in Kumasi, Ghana: A cross-sectional study

Background and Aims

Children with sickle cell disease (SCD) have an increased risk of multiple hemotransfusions and this can predispose them to elevated iron stores. The objectives of the study were to determine the extent of elevated iron stores and the associated risk factors in a population of steady-state SCD children in Ghana.

Methods

This cross-sectional study was conducted at the pediatric sickle cell clinic at the Komfo Anokye Teaching Hospital. Complete blood count and serum ferritin assay were performed for (n = 178) steady-state SCD children. Descriptive and multivariate logistic regression analysis were performed. Elevated iron stores were defined as serum ferritin levels >300 ng/ml. Statistical significance was considered at p < 0.05.

Results

The mean (standard deviation) age of the participants was 9.61 (±4.34) years, and 51% of them were males. About 17% of SCD children had elevated iron stores and receiving at least three hemotransfusions during the last 12 months was strongly associated with elevated iron stores (p < 0.001). History of chronic hemotransfusion increased the odds of having elevated iron store (adjusted odds ratio [aOR] = 11.41; 95% confidence interval [CI] = 3.11-30.85; p < 0.001) but SCD patients on hydroxyurea treatment had reduced-odds of having elevated iron stores (aOR = 0.18; 95% CI = 0.06-0.602; p = 0.006). Moreover, red blood cell (Coef. = -0.84; 95% CI = -0.37, -1.32; p = 0.001), hemoglobin (Coef. = -0.83; 95% CI = -0.05, -1.61; p = 0.04), hematocrit (Coef. = -0.85; 95% CI = -0.08, -1.63; p = 0.03), mean cell volume (Coef. = 0.02; 95% CI = 0.01, 0.03; p = 0.001) and mean cell hemoglobin (Coef. = 0.04; 95% CI = 0.01, 0.07; p = 0.002) could significantly predict serum ferritin levels.

Conclusion

The magnitude of elevated iron stores was high among children with SCD in steady-state. Red cell indices could provide invaluable information regarding the risk of elevated iron stores. SCD children who have a history of chronic hemotransfusion or had received at least three hemotransfusions in a year should be monitored for elevated iron stores.

Molecular Mechanisms of Ferroptosis and Relevance to Cardiovascular Disease

Ferroptosis has recently been demonstrated to be a novel regulated non-apoptotic cell death characterized by iron-dependence and the accumulation of lipid peroxidation that results in membrane damage. Excessive iron induces ferroptosis by promoting the generation of both soluble and lipid ROS via an iron-dependent Fenton reaction and lipoxygenase (LOX) enzyme activity. Cytosolic glutathione peroxidase 4 (cGPX4) pairing with ferroptosis suppressor protein 1 (FSP1) and mitochondrial glutathione peroxidase 4 (mGPX4) pairing with dihydroorotate dehydrogenase (DHODH) serve as two separate defense systems to detoxify lipid peroxidation in the cytoplasmic as well as the mitochondrial membrane, thereby defending against ferroptosis in cells under normal conditions. However, disruption of these defense systems may cause ferroptosis. Emerging evidence has revealed that ferroptosis plays an essential role in the development of diverse cardiovascular diseases (CVDs), such as hemochromatosis-associated cardiomyopathy, doxorubicin-induced cardiotoxicity, ischemia/reperfusion (I/R) injury, heart failure (HF), atherosclerosis, and COVID-19–related arrhythmias. Iron chelators, antioxidants, ferroptosis inhibitors, and genetic manipulations may alleviate the aforementioned CVDs by blocking ferroptosis pathways. In conclusion, ferroptosis plays a critical role in the pathogenesis of various CVDs and suppression of cardiac ferroptosis is expected to become a potential therapeutic option. Here, we provide a comprehensive review on the molecular mechanisms involved in ferroptosis and its implications in cardiovascular disease.

Iron overload, oxidative stress and vascular dysfunction: Evidences from clinical studies and animal models

Although iron is a metal involved in many in vital processes due to its redox capacity, body iron overloads lead to tissue damage, including the cardiovascular system. While cardiomyopathy was the focus since the 1960s, the impact on the vasculature was comparatively neglected for about 40 years, when clinical studies correlating iron overload, oxidative stress, endothelial dysfunction, arterial stiffness and atherosclerosis reinforced an "iron hypothesis". Due to controversial results from some epidemiological studies investigating atherosclerotic events and iron levels, well-controlled trials and animal studies provided essential data about the influence of iron, per se, on the vasculature. As a result, the pathophysiology of vascular dysfunction in iron overload have been revisited. This review summarizes the knowledge obtained from epidemiological studies, animal models and "in vitro" cellular systems in recent decades, highlighting a more harmful than innocent role of iron excess for the vascular homeostasis, which supports our proposal to hereafter denominate "iron overload vasculopathy". Additionally, evidence-based therapeutic targets are pointed out to be tested in pre-clinical research that may be useful in cardiovascular protection for patients with iron overload syndromes.

Mild-intensity physical activity prevents cardiac and osseous iron deposition without affecting bone mechanical property or porosity in thalassemic mice

Thalassemia causes anemia, ineffective erythropoiesis, bone loss and iron accumulation in several tissues, e.g., liver, bone and heart, the last of which leads to lethal cardiomyopathy and arrhythmia. Although exercise reportedly improves bone density in thalassemic mice, exercise performance is compromised and might pose risk of cardiovascular accident in thalassemic patients. Therefore, we sought to explore whether mild-intensity physical activity (MPA) with 30–50% of maximal oxygen consumption was sufficient to benefit the heart and bone. Herein, male hemizygous β-globin knockout (BKO) mice and wild-type littermates were subjected to voluntary wheel running 1 h/day, 5 days/week for 3 months (MPA group) or kept sedentary (SDN; control). As determined by atomic absorption spectroscopy, BKO-MPA mice had less iron accumulation in heart and bone tissues compared with BKO-SDN mice. Meanwhile, the circulating level of fibroblast growth factor-23—a factor known to reduce serum iron and intestinal calcium absorption—was increased early in young BKO-MPA mice. Nevertheless, MPA did not affect duodenal calcium transport or body calcium retention. Although MPA restored the aberrant bone calcium-phosphorus ratio to normal range, it did not change vertebral calcium content or femoral mechanical properties. Microstructural porosity in tibia of BKO-MPA mice remained unaltered as determined by synchrotron radiation X-ray tomographic microscopy. In conclusion, MPA prevents cardiac and bone iron accumulation, which is beneficial to thalassemic patients with limited physical fitness or deteriorated cardiac performance. However, in contrast to moderate-intensity exercise, MPA does not improve bone mechanical properties or reduce bone porosity.

Nitrogen-doped graphene quantum dots induce ferroptosis through disrupting calcium homeostasis in microglia

Background

Along with the wild applications of nitrogen-doped graphene quantum dots (N-GQDs) in the fields of biomedicine and neuroscience, their increasing exposure to the public and potential biosafety problem has gained more and more attention. Unfortunately, the understanding of adverse effects of N-GQDs in the central nervous system (CNS), considered as an important target of nanomaterials, is still limited.

Results

After we found that N-GQDs caused cell death, neuroinflammation and microglial activation in the hippocampus of mice through the ferroptosis pathway, microglia was used to assess the molecular mechanisms of N-GQDs inducing ferroptosis because it could be the primary target damaged by N-GQDs in the CNS. The microarray data suggested the participation of calcium signaling pathway in the ferroptosis induced by N-GQDs. In microglial BV2 cells, when the calcium content above the homeostatic level caused by N-GQDs was reversed, the number of cell death, ferroptosis alternations and excessive inflammatory cytokines release were all alleviated. Two calcium channels of L-type voltage-gated calcium channels (L-VGCCs) in plasma membrane and ryanodine receptor (RyR) in endoplasmic reticulum (ER) took part in N-GQDs inducing cytosolic calcium overload. L-VGCCs and RyR calcium channels were also involved in promoting the excess iron influx and triggering ER stress response, respectively, which both exert excessive ROS generation and result in the ferroptosis and inflammation in BV2 cells.

Conclusion

N-GQDs exposure caused ferroptosis and inflammatory responses in hippocampus of mice and cultured microglia through activating two calcium channels to disrupt intracellular calcium homeostasis. The findings not only posted an alert for biomedical applications of N-GQDs, but also highlighted an insight into mechanism researches of GQDs inducing multiple types of cell death in brain tumor therapy in the future.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-022-00464-z.

Potential Role of APEX1 During Ferroptosis

Ferroptosis is a recently discovered category of programmed cell death. It is much different from other types of cell death such as apoptosis, necrosis and autophagy. The main pathological feature of ferroptosis is the accumulation of iron-dependent lipid peroxidation. The typical changes in the morphological features of ferroptosis include cell volume shrinkage and increased mitochondrial membrane area. The mechanisms of ferroptosis may be mainly related to lipid peroxidation accumulation, imbalance in amino acid antioxidant system, and disturbance of iron metabolism. Besides, hypoxia-inducible factor (HIF), nuclear factor-E2-related factor 2 (Nrf2), and p53 pathway have been demonstrated to be involved in ferroptosis. At present, the molecular mechanisms of ferroptosis pathway are still unmapped. In this review, an outlook has been put forward about the crucial role of apurinic/apyrimidinic endodeoxyribonuclease 1 (APEX1) in the regulation of ferroptosis. APEX1 plays an important role in the regulation of intracellular redox balance and can be used as a potential inhibitor of ferroptotic cell death. Bioinformatics analysis indicated that the mRNA level of APEX1 is decreased in cases of ferroptosis triggered by erastin. Besides, it was found that there was a significant correlation between APEX1 and genes in the ferroptosis pathway. We have discussed the possibility to employ APEX1 inducers or inhibitors in the regulation of ferroptosis as a new strategy for the treatment of various human diseases.

Mitochondrial-Targeted Therapy for Doxorubicin-Induced Cardiotoxicity

Anthracyclines, such as doxorubicin, are effective chemotherapeutic agents for the treatment of cancer, but their clinical use is associated with severe and potentially life-threatening cardiotoxicity. Despite decades of research, treatment options remain limited. The mitochondria is commonly considered to be the main target of doxorubicin and mitochondrial dysfunction is the hallmark of doxorubicin-induced cardiotoxicity. Here, we review the pathogenic mechanisms of doxorubicin-induced cardiotoxicity and present an update on cardioprotective strategies for this disorder. Specifically, we focus on strategies that can protect the mitochondria and cover different therapeutic modalities encompassing small molecules, post-transcriptional regulators, and mitochondrial transfer. We also discuss the shortcomings of existing models of doxorubicin-induced cardiotoxicity and explore advances in the use of human pluripotent stem cell derived cardiomyocytes as a platform to facilitate the identification of novel treatments against this disorder.

Signaling Integration of Hydrogen Sulfide and Iron on Cellular Functions

Significance: Hydrogen sulfide (H₂S) is an endogenous signaling molecule, regulating numerous physiological functions from vasorelaxation to neuromodulation. Iron is a well-known bioactive metal ion, being the central component of hemoglobin for oxygen transportation and participating in biomolecule degradation, redox balance, and enzymatic actions. The interplay between H₂S and iron metabolisms and functions impacts significantly on the fate and wellness of different types of cells. Recent Advances: Iron level in vivo affects the production of H₂S via nonenzymatic reactions. On the contrary, H₂S quenches excessive iron inside the cells and regulates the redox status of iron. Critical Issues: Abnormal metabolisms of both iron and H₂S are associated with various conditions and diseases such as iron overload, anemia, oxidative stress, and cardiovascular and neurodegenerative diseases. The molecular mechanisms for the interactions between H₂S and iron are unsettled yet. Here we review signaling links of the production, metabolism, and their respective and integrative functions of H₂S and iron in normalcy and diseases. Future Directions: Physiological and pathophysiological importance of H₂S and iron as well as their therapeutic applications should be evaluated jointly, not separately. Future investigation should expand from iron-rich cells and tissues to the others, in which H₂S and iron interaction has not received due attention. Antioxid. Redox Signal. 36, 275-293.

Heme in Cardiovascular Diseases: A Ubiquitous Dangerous Molecule Worthy of Vigilance

Heme, the protoporphyrin IX iron complex is widely present in the human body and it is involved in oxygen storage, electron transfer, and enzymatic reactions. However, free heme can be toxic as it catalyzes the production of reactive oxygen species, oxidizes lipids and proteins, and causes DNA damage, thereby inducing a pro-inflammatory environment. The generation, metabolism, and degradation of heme in the human body are regulated by precise mechanisms to ensure that heme remains non-toxic. However, in several types of cardiovascular diseases, impaired metabolism and exposure to heme may occur in pathological processes, including neovascularization, internal hemorrhage, ischemia, and reperfusion. Based on years of research, in this review, we aimed to summarize the underlying mechanisms by which heme contributes to the development of cardiovascular diseases through oxidative stress, relative pathway gene expression regulation and phenotypic changes in cells. Excess heme plays a detrimental role in atherosclerosis, heart failure, myocardial ischemia-reperfusion injury, degenerative aortic valve stenosis, cardiac iron overload. Recent researches revealed that in some cases heme involved in cardiac damage though ferroptosis. Thus, heme concentrations beyond normal levels are dangerous. Further research on the role of heme in cardiovascular diseases is needed.

Triad role of hepcidin, ferroportin, and Nrf2 in cardiac iron metabolism: From health to disease

Iron is an essential trace element required for several vital physiological and developmental processes, including erythropoiesis, bone, and neuronal development. Iron metabolism and oxygen homeostasis are interlinked to perform a vital role in the functionality of the heart. The metabolic machinery of the heart utilizes almost 90 % of oxygen through the electron transport chain. To handle this tremendous level of oxygen, the iron metabolism in the heart is utmost crucial. Iron availability to the heart is therefore tightly regulated by (i) the hepcidin/ferroportin axis, which controls dietary iron absorption, storage, and recycling, and (ii) iron regulatory proteins 1 and 2 (IRP1/2) via hypoxia inducible factor 1 (HIF1) pathway. Despite iron being vital to the heart, recent investigations have demonstrated that iron imbalance is a common manifestation in conditions of heart failure (HF), since free iron readily transforms between Fe²⁺ and Fe³⁺via the Fenton reaction, leading to reactive oxygen species (ROS) production and oxidative damage. Therefore, to combat iron-mediated oxidative stress, targeting Nrf2/ARE antioxidant signaling is rational. The involvement of Nrf2 in regulating several genes engaged in heme synthesis, iron storage, and iron export is beginning to be uncovered. Consequently, it is possible that Nrf2/hepcidin/ferroportin might act as an epicenter connecting iron metabolism to redox alterations. However, the mechanism bridging the two remains obscure. In this review, we tried to summarize the contemporary insight of how cardiomyocytes regulate intracellular iron levels and discussed the mechanisms linking cardiac dysfunction with iron imbalance. Further, we emphasized the impact of Nrf2 on the interplay between systemic/cardiac iron control in the context of heart disease, particularly in myocardial ischemia and HF.

A Novel Insight Into the Fate of Cardiomyocytes in Ischemia-Reperfusion Injury: From Iron Metabolism to Ferroptosis

Ischemia-reperfusion injury (IRI), critically involved in the pathology of reperfusion therapy for myocardial infarction, is closely related to oxidative stress the inflammatory response, and disturbances in energy metabolism. Emerging evidence shows that metabolic imbalances of iron participate in the pathophysiological process of cardiomyocyte IRI [also termed as myocardial ischemia-reperfusion injury (MIRI)]. Iron is an essential mineral required for vital physiological functions, including cellular respiration, lipid and oxygen metabolism, and protein synthesis. Nevertheless, cardiomyocyte homeostasis and viability are inclined to be jeopardized by iron-induced toxicity under pathological conditions, which is defined as ferroptosis. Upon the occurrence of IRI, excessive iron is transported into cells that drive cardiomyocytes more vulnerable to ferroptosis by the accumulation of reactive oxygen species (ROS) through Fenton reaction and Haber–Weiss reaction. The increased ROS production in ferroptosis correspondingly leads cardiomyocytes to become more sensitive to oxidative stress under the exposure of excess iron. Therefore, ferroptosis might play an important role in the pathogenic progression of MIRI, and precisely targeting ferroptosis mechanisms may be a promising therapeutic option to revert myocardial remodeling. Notably, targeting inhibitors are expected to prevent MIRI deterioration by suppressing cardiomyocyte ferroptosis. Here, we review the pathophysiological alterations from iron homeostasis to ferroptosis together with potential pathways regarding ferroptosis secondary to cardiovascular IRI. We also provide a comprehensive analysis of ferroptosis inhibitors and initiators, as well as regulatory genes involved in the setting of MIRI.

A systematic review on nephron protective AYUSH drugs as constituents of NEERI-KFT (A traditional Indian polyherbal formulation) for the management of chronic kidney disease

Chronic Kidney Disease (CKD) is a major health problem characterized by kidney dysfunction with progressive segmental glomerulosclerosis to end-stage renal disease (ESRD). Due to lack of scientific data and comprehensive reports, the current systematic review provides an inclusive understanding and prospective associated with phytopharmacology of NEERI-KFT in CKD. The data was collected from more than five databases such as Science Direct, Google Scholar, Elsevier, PubMed, Springer, ACS publication etc using keywords like CKD/Kidney disease, epidemiology/prevalence, modern therapies for CKD management, NEERI-KFT and its role in kidney disease. The study was performed based on scientific reports screened by experts according to inclusion and exclusion criteria. The pre-clinical and clinical findings suggested that NEERI-KFT has promising effects as nephroprotective and considered safe and well effective in primary care of kidney against disease. Phytopharmacological evaluation of NEERI-KFT suggest that it exhibit substantial potential against oxidative and inflammatory stress induced apoptosis by exerting antioxidants, nephroprotective and immunomodulatory effects. Hence, it can be enlighten that NEERI-KFT have potential herbs which exerts significant antioxidants, nephroprotective and immunomodulatory effects in the patients associated with renal dysfunction or CKD thus improving altered renal architecture and renal physiology. Clinically, it is concluded that NEERI-KFT works kidney malfunction and cease ESRD progression or even reduce the number of dialysis.

Role of endolysosome function in iron metabolism and brain carcinogenesis

Iron, the most abundant metal in human brain, is an essential microelement that regulates numerous cellular mechanisms. Some key physiological roles of iron include oxidative phosphorylation and ATP production, embryonic neuronal development, formation of iron-sulfur clusters, and the regulation of enzymes involved in DNA synthesis and repair. Because of its physiological and pathological importance, iron homeostasis must be tightly regulated by balancing its uptake, transport, and storage. Endosomes and lysosomes (endolysosomes) are acidic organelles known to contain readily releasable stores of various cations including iron and other metals. Increased levels of ferrous (Fe2+) iron can generate reactive oxygen species (ROS) via Fenton chemistry reactions and these increases can damage mitochondria and genomic DNA as well as promote carcinogenesis. Accumulation of iron in the brain has been linked with aging, diet, disease, and cerebral hemorrhage. Further, deregulation of brain iron metabolism has been implicated in carcinogenesis and may be a contributing factor to the increased incidence of brain tumors around the world. Here, we provide insight into mechanisms by which iron accumulation in endolysosomes is altered by pH and lysosome membrane permeabilization. Such events generate excess ROS resulting in mitochondrial DNA damage, fission, and dysfunction, as well as DNA oxidative damage in the nucleus; all of which promote carcinogenesis. A better understanding of the roles that endolysosome iron plays in carcinogenesis may help better inform the development of strategic therapeutic options for cancer treatment and prevention.

Iron Overload Induces Apoptosis and Cytoprotective Autophagy Regulated by ROS Generation in Mc3t3-E1 Cells

Iron overload has been found very common in diseases such as hereditary hemochromatosis, thalassemia, and sickle cell disease and in healthy postmenopausal women. Recent studies have shown that iron overload is considered an independent risk factor for osteoporosis. Studies have demonstrated that iron overload could induce apoptosis and inhibit viability in osteoblasts. However, the underlying mechanism still remains poorly understood. The purpose of the present study is to investigate possible mechanism of iron overload-induced apoptosis, and the roles autophagy and reactive oxygen species (ROS) played under iron overload conditions. Ferric ammonium citrate (FAC) (100-1600 μM) was utilized as iron donor to induce iron overload conditions. Intracellular iron concentration was measured using Iron Assay Kit. The viability was assessed by CCK-8 assay. Cell apoptosis was examined using Annexin V-FITC/PI staining with a flow cytometry, and levels of Bax, Bcl-2, cleaved caspase-3, and cleaved PARP were evaluated with Western blot. Cell autophagy was detected by evaluating LC3 with immunofluorescence and Western blot. The expressions of Beclin-1 and P62 were also assessed with Western blot. The intracellular ROS level was evaluated using a DCFH-DA probe with a flow cytometry, and NADPH oxidase 4 (Nox4) expressions were assessed with Western blot. Our results showed that FAC increased intracellular iron concentration and significantly inhibited cell viability. Furthermore, iron overload induced apoptosis and autophagy in osteoblast cells. What's more, pretreatment with autophagy inhibitor chloroquine (CQ) enhanced iron overload-induced osteoblast apoptosis via the activation of caspases. Moreover, iron overload increased ROS production and Nox4 expression. Inhibition of autophagy increased ROS production, and scavenging of ROS by antioxidant N-Acetyl-L-cysteine (NAC) inhibited caspases activity and rescued iron overload-induced apoptosis. These results suggested that autophagy exerted cytoprotective effect, and scavenging excessive intracellular ROS could be a novel approach for the treatment of iron overload-induced osteoporosis.

Fibroblast growth factor 21 attenuates iron overload-induced liver injury and fibrosis by inhibiting ferroptosis

Ferroptosis plays a role in several diseases such as iron overload-induced liver diseases. Manipulation of ferroptosis has been explored as a potential therapeutic strategy to treat related diseases. Numerous antioxidants have been identified to control ferroptosis but the cell-autonomous mechanisms responsible for regulating ferroptosis remain elusive. In the present study, we found that iron overload promoted ferroptosis in hepatocytes by excessively inducing HO-1 expression, which contributed to the progression of liver injury and fibrosis, accompanied by the upregulation of the FGF21 protein level in vitro and in vivo. Interestingly, both recombinant FGF21 and Fgf21 overexpression significantly protected against iron overload-induced hepatocytes mitochondria damage, liver injury and fibrosis by inhibiting ferroptosis. In contrast, the loss of FGF21 aggravated iron overload-induced ferroptosis. Notably, FGF21-induced HO-1 inhibition (via the promotion of HO-1 ubiquitination and degradation) and NRF2 activation provide a mechanistic explanation for this phenomenon. Taken together, we identified FGF21 as a novel ferroptosis suppressor. Thus, FGF21 activation may provide an effective strategy for the potential treatment of iron overload-induced ferroptosis-related diseases, such as hereditary haemochromatosis (HH).

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Iron overload robustly induces hepatic FGF21 expression both in vitro and in vivo.

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FGF21 suppresses iron overload-induced hepatocytes ferroptosis.

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Constitutive HO-1 activation contributes to iron overload-induced ferroptosis in hepatocytes.

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FGF21 protects hepatocytes from iron overload-induced ferroptosis by stimulating HO-1 ubiquitination and degradation.

Pathogenesis, Diagnosis, and Clinical Implications of Hereditary Hemochromatosis-The Cardiological Point of View

Hereditary hemochromatosis (HH) is a genetic disease leading to excessive iron absorption, its accumulation, and oxidative stress induction causing different organ damage, including the heart. The process of cardiac involvement is slow and lasts for years. Cardiac pathology manifests as an impaired diastolic function and cardiac hypertrophy at first and as dilatative cardiomyopathy and heart failure with time. From the moment of heart failure appearance, the prognosis is poor. Therefore, it is crucial to prevent those lesions by upfront therapy at the preclinical phase of the disease. The most useful diagnostic tool for detecting cardiac involvement is echocardiography. However, during an early phase of the disease, when patients do not present severe abnormalities in serum iron parameters and severe symptoms of other organ involvement, heart damage may be overlooked due to the lack of evident signs of cardiac dysfunction. Considerable advancement in echocardiography, with particular attention to speckle tracking echocardiography, allows detecting discrete myocardial abnormalities and planning strategy for further clinical management before the occurrence of substantial heart damage. The review aims to present the current state of knowledge concerning cardiac involvement in HH. In addition, it could help cardiologists and other physicians in their everyday practice with HH patients.

Ferritinophagy and ferroptosis in cardiovascular disease: Mechanisms and potential applications

Ferroptosis is a type of regulated cell death driven by iron dependent accumulation of cellular reactive oxygen species (ROS) when glutathione (GSH)-dependent lipid peroxidation repair systems are compromised. Nuclear receptor co-activator 4 (NCOA4)-mediated selective autophagy of ferritin, termed ferritinophagy, involves the regulation of ferroptosis. Emerging evidence has revealed that ferritinophagy and ferroptosis exert a significant role in the occurrence and development of cardiovascular disease. In the present review, we aimed to present a brief overview of ferritinophagy and ferroptosis focusing on the underlying mechanism and regulations involved. We summarize and discuss relevant research progress on the role of ferritinophagy and ferroptosis in cardiovascular diseases accompanied with potential applications of ferritinophagy and ferroptosis modulators in the treatment of ferroptosis-associated cardiovascular diseases.

Ferroptosis in Different Pathological Contexts Seen through the Eyes of Mitochondria

Ferroptosis is a recently described form of regulated cell death characterized by intracellular iron accumulation and severe lipid peroxidation due to an impaired cysteine-glutathione-glutathione peroxidase 4 antioxidant defence axis. One of the hallmarks of ferroptosis is a specific morphological phenotype characterized by extensive ultrastructural changes of mitochondria. Increasing evidence suggests that mitochondria play a significant role in the induction and execution of ferroptosis. The present review summarizes existing knowledge about the mitochondrial impact on ferroptosis in different pathological states, primarily cancer, cardiovascular diseases, and neurodegenerative diseases. Additionally, we highlight pathologies in which the ferroptosis/mitochondria relation remains to be investigated, where the process of ferroptosis has been confirmed (such as liver- and kidney-related pathologies) and those in which ferroptosis has not been studied yet, such as diabetes. We will bring attention to avenues that could be followed in future research, based on the use of mitochondria-targeted approaches as anti- and proferroptotic strategies and directed to the improvement of existing and the development of novel therapeutic strategies.

Modeling Secondary Iron Overload Cardiomyopathy with Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Excessive iron accumulation in the heart causes iron overload cardiomyopathy (IOC), which initially presents as diastolic dysfunction and arrhythmia but progresses to systolic dysfunction and end-stage heart failure when left untreated. However, the mechanisms of iron-related cardiac injury and how iron accumulates in human cardiomyocytes are not well understood. Herein, using human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), we model IOC and screen for drugs to rescue the iron overload phenotypes. Human iPSC-CMs under excess iron exposure recapitulate early-stage IOC, including oxidative stress, arrhythmia, and contractile dysfunction. We find that iron-induced changes in calcium kinetics play a critical role in dysregulation of CM functions. We identify that ebselen, a selective divalent metal transporter 1 (DMT1) inhibitor and antioxidant, could prevent the observed iron overload phenotypes, supporting the role of DMT1 in iron uptake into the human myocardium. These results suggest that ebselen may be a potential preventive and therapeutic agent for treating patients with secondary iron overload.

Targeting Ferroptosis against Ischemia/Reperfusion Cardiac Injury

Ischemic heart disease is a leading cause of death worldwide. Primarily, ischemia causes decreased oxygen supply, resulting in damage of the cardiac tissue. Naturally, reoxygenation has been recognized as the treatment of choice to recover blood flow through primary percutaneous coronary intervention. This treatment is the gold standard therapy to restore blood flow, but paradoxically it can also induce tissue injury. A number of different studies in animal models of acute myocardial infarction (AMI) suggest that ischemia-reperfusion injury (IRI) accounts for up to 50% of the final myocardial infarct size. Oxidative stress plays a critical role in the pathological process. Iron is an essential mineral required for a variety of vital biological functions but also has potentially toxic effects. A detrimental process induced by free iron is ferroptosis, a non-apoptotic type of programmed cell death. Accordingly, efforts to prevent ferroptosis in pathological settings have focused on the use of radical trapping antioxidants (RTAs), such as liproxstatin-1 (Lip-1). Hence, it is necessary to develop novel strategies to prevent cardiac IRI, thus improving the clinical outcome in patients with ischemic heart disease. The present review analyses the role of ferroptosis inhibition to prevent heart IRI, with special reference to Lip-1 as a promising drug in this clinicopathological context.

Primary Human Cardiomyocytes and Cardiofibroblasts Treated with Sera from Myocarditis Patients Exhibit an Increased Iron Demand and Complex Changes in the Gene Expression

Cardiac fibroblasts and cardiomyocytes are the main cells involved in the pathophysiology of myocarditis (MCD). These cells are especially sensitive to changes in iron homeostasis, which is extremely important for the optimal maintenance of crucial cellular processes. However, the exact role of iron status in the pathophysiology of MCD remains unknown. We cultured primary human cardiomyocytes (hCM) and cardiofibroblasts (hCF) with sera from acute MCD patients and healthy controls to mimic the effects of systemic inflammation on these cells. Next, we performed an initial small-scale (n = 3 per group) RNA sequencing experiment to investigate the global cellular response to the exposure on sera. In both cell lines, transcriptomic data analysis revealed many alterations in gene expression, which are related to disturbed canonical pathways and the progression of cardiac diseases. Moreover, hCM exhibited changes in the iron homeostasis pathway. To further investigate these alterations in sera-treated cells, we performed a larger-scale (n = 10 for controls, n = 18 for MCD) follow-up study and evaluated the expression of genes involved in iron metabolism. In both cell lines, we demonstrated an increased expression of transferrin receptor 1 (TFR1) and ferritin in MCD serum-treated cells as compared to controls, suggesting increased iron demand. Furthermore, we related TFR1 expression with the clinical profile of patients and showed that greater iron demand in sera-treated cells was associated with higher inflammation score (interleukin 6 (IL-6), C-reactive protein (CRP)) and advanced neurohormonal activation (NT-proBNP) in patients. Collectively, our data suggest that the malfunctioning of cardiomyocytes and cardiofibroblasts in the course of MCD might be related to alterations in the iron homeostasis.

Activation of TRPC (Transient Receptor Potential Canonical) Channel Currents in Iron Overloaded Cardiac Myocytes

BACKGROUND

Arrhythmias and heart failure are common cardiac complications leading to substantial morbidity and mortality in patients with hemochromatosis, yet mechanistic insights remain incomplete. We investigated the effects of iron (Fe) on electrophysiological properties and intracellular Ca²⁺ (Ca²⁺_i) handling in mouse left ventricular cardiomyocytes.

METHODS

Cardiomyocytes were isolated from the left ventricle of mouse hearts and were superfused with Fe³⁺/8-hydroxyquinoline complex (5-100 μM). Membrane potential and ionic currents including TRPC (transient receptor potential canonical) were recorded using the patch-clamp technique. Ca²⁺_i was evaluated by using Fluo-4. Cell contraction was measured with a video-based edge detection system. The role of TRPCs in the genesis of arrhythmias was also investigated by using a mathematical model of a mouse ventricular myocyte with the incorporation of the TRPC component.

RESULTS

We observed prolongation of the action potential duration and induction of early and delayed afterdepolarizations in myocytes superfused with 15 µmol/L Fe³⁺/8-hydroxyquinoline complex. Iron treatment decreased the peak amplitude of the L-type Ca²⁺ current and total K⁺ current, altered Ca²⁺_i dynamics, and decreased cell contractility. During the final phase of Fe treatment, sustained Ca²⁺_i waves and repolarization failure occurred and ventricular cells became unexcitable. Gadolinium abolished Ca²⁺_i waves and restored the resting membrane potential to the normal range. The involvement of TRPC activation was confirmed by TRPC channel current recordings in the absence or presence of functional TRPC channel antibodies. Computer modeling captured the same action potential and Ca²⁺_i dynamics and provided additional mechanistic insights.

CONCLUSIONS

We conclude that iron overload induces cardiac dysfunction that is associated with TRPC channel activation and alterations in membrane potential and Ca²⁺_i dynamics.

Mitophagy, Ferritinophagy and Ferroptosis in Retinal Pigment Epithelial Cells Under High Glucose Conditions: Implications for Diabetic Retinopathy and Age-Related Retinal Diseases

Diabetic retinopathy (DR) is a devastating disease leading to blindness among majority of working adults around the globe. Nonetheless, an effective treatment or cure for the disease is still to be achieved. This is because the cellular and molecular mechanisms of DR are complex and not fully understood yet. In this article, we describe how high glucose induced TXNIP upregulation and associated redox stress may cause mitochondrial dysfunction, mitophagy, ferritinophagy (iron release by autophagy) and lysosome destabilization. Labile irons react with hydrogen peroxide (H2O2) to generate hydroxyl radicals (.OH) by the Fenton reaction and cause membrane phospholipid peroxidation due to reduction in glutathione (GSH) level and glutathione peroxidase 4 (GPX4) activity, which cause ferroptosis, a recently identified non-apoptotic cell death mechanism. We used in this study a retinal pigment epithelial cell line, ARPE- 19 and exposed it to high glucose in in vitro cultures to highlight some of the intricacies of these cellular processes, which may be relevant to the pathogenesis of DR and age-related retinal neurodegenerative diseases, such as age-related macular degeneration, AMD.

Use of 2-dimensional cell monolayers and 3-dimensional microvascular networks on microfluidic devices shows that iron increases transendothelial adiponectin flux via inducing ROS production

BACKGROUND

Iron excess is a risk factor for cardiovascular diseases and it is important to understand the effect of iron on vascular permeability, particularly for the transport of large metabolic hormones such as adiponectin.

METHODS

We used 2-dimensional monolayers of cultured human dermal microvascular endothelial cells (HDMEC) and human umbilical vein endothelial cells (HUVEC) as well as 3-dimensional microvascular networks to measure transendothelial flux.

RESULTS

Iron supplementation reduced transendothelial electric resistance (TEER). Flux analysis indicated that under control conditions permeability of 70 kDa dextran and oligomeric forms of adiponectin were restricted in comparison with a 3 kDa dextran, however upon iron treatment permeability of the larger molecules was increased. The increased permeability and size-dependent trans-endothelial movement in response to iron was also observed in 3-dimensional microvascular networks. Mechanistically, the alteration in barrier functionality was associated with increased oxidative stress in response to iron since alterations in TEER and permeability were rescued when reactive oxygen species production was attenuated by pre-treatment with the antioxidant N-acetyl cysteine.].

CONCLUSIONS

Iron supplementation induced ROS production resulting in increased transendothelial permeability.

GENERAL SIGNIFICANCE

Altogether, this suggests that the oxidative stress associated with iron excess could play an important role in the regulation of endothelial functionality, controlling hormone action in peripheral tissues by regulating the first rate-limiting step controlling hormone access to target tissues.

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.

The Molecular Mechanisms of Iron Metabolism and Its Role in Cardiac Dysfunction and Cardioprotection

Iron is an essential mineral participating in different functions of the organism under physiological conditions. Numerous biological processes, such as oxygen and lipid metabolism, protein production, cellular respiration, and DNA synthesis, require the presence of iron, and mitochondria play an important role in the processes of iron metabolism. In addition to its physiological role, iron may be also involved in the adaptive processes of myocardial "conditioning". On the other hand, disorders of iron metabolism are involved in the pathological mechanisms of the most common human diseases and include a wide range of them, such as type 2 diabetes, obesity, and non-alcoholic fatty liver disease, and accelerate the development of atherosclerosis. Furthermore, iron also exerts potentially deleterious effects that may be manifested under conditions of ischemia/reperfusion (I/R) injury, myocardial infarction, heart failure, coronary artery angioplasty, or heart transplantation, due to its involvement in reactive oxygen species (ROS) production. Moreover, iron has been recently described to participate in the mechanisms of iron-dependent cell death defined as "ferroptosis". Ferroptosis is a form of regulated cell death that is distinct from apoptosis, necroptosis, and other types of cell death. Ferroptosis has been shown to be associated with I/R injury and several other cardiac diseases as a significant form of cell death in cardiomyocytes. In this review, we will discuss the role of iron in cardiovascular diseases, especially in myocardial I/R injury, and protective mechanisms stimulated by different forms of "conditioning" with a special emphasis on the novel targets for cardioprotection.

Iron Overload, Oxidative Stress and Calcium Mishandling in Cardiomyocytes: Role of the Mitochondrial Permeability Transition Pore

Iron (Fe) plays an essential role in many physiological processes. Hereditary hemochromatosis or frequent blood transfusions often cause iron overload (IO), which can lead to cardiomyopathy and arrhythmias; however, the underlying mechanism is not well defined. In the present study, we assess the hypothesis that IO promotes arrhythmias via reactive oxygen species (ROS) production, mitochondrial membrane potential (∆Ψm) depolarization, and disruption of cytosolic Ca dynamics. In ventricular myocytes isolated from wild type (WT) mice, both cytosolic and mitochondrial Fe levels were elevated following perfusion with the Fe3+/8-hydroxyquinoline (8-HQ) complex. IO promoted mitochondrial superoxide generation (measured using MitoSOX Red) and induced the depolarization of the ΔΨm (measured using tetramethylrhodamine methyl ester, TMRM) in a dose-dependent manner. IO significantly increased the rate of Ca wave (CaW) formation measured in isolated ventricular myocytes using Fluo-4. Furthermore, in ex-vivo Langendorff-perfused hearts, IO increased arrhythmia scores as evaluated by ECG recordings under programmed S1-S2 stimulation protocols. We also carried out similar experiments in cyclophilin D knockout (CypD KO) mice in which the mitochondrial permeability transition pore (mPTP) opening is impaired. While comparable cytosolic and mitochondrial Fe load, mitochondrial ROS production, and depolarization of the ∆Ψm were observed in ventricular myocytes isolated from both WT and CypD KO mice, the rate of CaW formation in isolated cells and the arrhythmia scores in ex-vivo hearts were significantly lower in CypD KO mice compared to those observed in WT mice under conditions of IO. The mPTP inhibitor cyclosporine A (CsA, 1 µM) also exhibited a protective effect. In conclusion, our results suggest that IO induces mitochondrial ROS generation and ∆Ψm depolarization, thus opening the mPTP, thereby promoting CaWs and cardiac arrhythmias. Conversely, the inhibition of mPTP ameliorates the proarrhythmic effects of IO.

Cardiomyopathy in Sickle Cell Disease

Sickle cell disease (SCD) is an inherited disorder that occurs due to point mutation in the beta-globin chain resulting in the production of hemoglobin S that tends to become rigid and sickle-shaped under low oxygen concentration. These sickle-shaped red blood cells (RBCs) obstruct the blood vessels leading to reduced blood flow to the organs, causing ischemia and tissue fibrosis. These sickle RBCs being abnormal in shape are frequently sequestered by the spleen, creating a state of chronic anemia in the body. This chronic anemia leads to a high cardiac output state causing cardiac remodeling. To tackle chronic anemia, patients are frequently treated with blood transfusions that makes them more prone to the risk of iron overload (from newly transfused RBCs and iron release from the RBCs that just got sequestered as well as from volume overload) and volume overload causing left ventricular (LV) dilation. The above-mentioned mechanism of cardiac hypertrophy, along with LV dilation together, makes SCD-related cardiomyopathy unique cardiomyopathy with features of restrictive cardiomyopathy with LV dilation. It is interesting to note here that even though there is a presence of LV dilatation, Systolic dysfunction is very uncommon in SCD-related cardiomyopathy.

UVA irradiation increases ferrous iron release from human skin fibroblast and endothelial cell ferritin: Consequences for cell senescence and aging

UVA irradiation of human dermal fibroblasts and endothelial cells induces an immediate transient increase in cytosolic Fe(II), as monitored by the fluorescence Fe(II) reporters, FeRhonox1 in cytosol and MitoFerroGreen in mitochondria. Both superoxide dismutase (SOD) inhibition by tetrathiomolybdate (ATM) and catalase inhibition by 3-amino-1, 2, 4-triazole (ATZ) increase and prolong the cytosolic Fe(II) signal after UVA irradiation. SOD inhibition with ATM also increases mitochondrial Fe(II). Thus, mitochondria do not source the UV-dependent increase in cytosolic Fe(II), but instead reflect and amplify raised cytosolic labile Fe(II) concentration. Hence control of cytosolic ferritin iron release is key to preventing UVA-induced inflammation. UVA irradiation also increases dermal endothelial cell H₂O₂, as monitored by the adenovirus vector Hyper-DAAO-NES(HyPer). These UVA-dependent changes in intracellular Fe(II) and H₂O₂ are mirrored by increases in cell superoxide, monitored with the luminescence probe L-012. UV-dependent increases in cytosolic Fe(II), H₂O₂ and L-012 chemiluminescence are prevented by ZnCl₂ (10 μM), an effective inhibitor of Fe(II) transport via ferritin's 3-fold channels. Quercetin (10 μM), a potent membrane permeable Fe(II) chelator, abolishes the cytosolic UVA-dependent FeRhonox1, Fe(II) and HyPer, H₂O₂ and increase in MitoFerroGreen Fe(II) signals. The time course of the quercetin-dependent decrease in endothelial H₂O₂ correlates with the decrease in FeRhox1 signal and both signals are fully suppressed by preloading cells with ZnCl₂. These results confirm that antioxidant enzyme activity is the key factor in controlling intracellular iron levels, and hence maintenance of cell antioxidant capacity is vitally important in prevention of skin aging and inflammation initiated by labile iron and UVA.