Research advances on molecular mechanism and natural product therapy of iron metabolism in heart failure

The progression of heart failure (HF) is complex and involves multiple regulatory pathways. Iron ions play a crucial supportive role as a cofactor for important proteins such as hemoglobin, myoglobin, oxidative respiratory chain, and DNA synthetase, in the myocardial energy metabolism process. In recent years, numerous studies have shown that HF is associated with iron dysmetabolism, and deficiencies in iron and overload of iron can both lead to the development of various myocarditis diseases, which ultimately progress to HF. Iron toxicity and iron metabolism may be key targets for the diagnosis, treatment, and prevention of HF. Some iron chelators (such as desferrioxamine), antioxidants (such as ascorbate), Fer-1, and molecules that regulate iron levels (such as lactoferrin) have been shown to be effective in treating HF and protecting the myocardium in multiple studies. Additionally, certain natural compounds can play a significant role by mediating the imbalance of iron-related signaling pathways and expression levels. Therefore, this review not only summarizes the basic processes of iron metabolism in the body and the mechanisms by which they play a role in HF, with the aim of providing new clues and considerations for the treatment of HF, but also summarizes recent studies on natural chemical components that involve ferroptosis and its role in HF pathology, as well as the mechanisms by which naturally occurring products regulate ferroptosis in HF, with the aim of providing reference information for the development of new ferroptosis inhibitors and lead compounds for the treatment of HF in the future.

Ferroptosis inhibitor improves cardiac function more effectively than inhibitors of apoptosis and necroptosis through cardiac mitochondrial protection in rats with iron-overloaded cardiomyopathy

Iron overload cardiomyopathy (IOC) is the leading cause of death in cases of iron overload in patients. Previous studies demonstrated that iron overload led to cardiomyocyte dysfunction and death through multiple pathways including apoptosis, necroptosis and ferroptosis. However, the dominant cell death pathway in the iron-overloaded heart needs clarification. We tested the hypothesis that ferroptosis, an iron-dependent cell death, plays a dominant role in IOC, and ferroptosis inhibitor exerts greater efficacy than inhibitors of apoptosis and necroptosis on improving cardiac function in iron-overloaded rats. Iron dextran was injected intraperitoneally into male Wistar rats for four weeks to induce iron overload. Then, the rats were divided into 5 groups: treated with vehicle, apoptosis inhibitor (z-VAD-FMK), necroptosis inhibitor (Necrostatin-1), ferroptosis inhibitor (Ferrostatin-1) or iron chelator (deferoxamine) for 2 weeks. Cardiac function, mitochondrial function, apoptosis, necroptosis and ferroptosis were determined. The increased expression of apoptosis-, necroptosis- and ferroptosis-related proteins, were associated with impaired cardiac and mitochondrial function in iron-overloaded rats. All cell death inhibitors attenuated cardiac apoptosis, necroptosis and ferroptosis in iron-overloaded rats. Ferrostatin-1 was more effective than the other drugs in diminishing mitochondrial dysfunction and Bax/Bcl-2 ratio. Moreover, both Ferrostatin-1 and deferoxamine reversed iron overload-induced cardiac dysfunction as indicated by restored left ventricular ejection fraction and E/A ratio, whereas z-VAD-FMK and Necrostatin-1 only partially improved this parameter. These results indicated that ferroptosis could be the predominant form of cardiomyocyte death in IOC, and that inhibiting ferroptosis might be a potential novel treatment for IOC.

Cardiac iron metabolism during aging - Role of inflammation and proteolysis

Iron is the most abundant trace element in the human body. Since iron can switch between its 2-valent and 3-valent form it is essential in various physiological processes such as energy production, proliferation or DNA synthesis. Especially high metabolic organs such as the heart rely on iron-associated iron-sulfur and heme proteins. However, due to switches in iron oxidation state, iron overload exhibits high toxicity through formation of reactive oxygen species, underlining the importance of balanced iron levels. Growing evidence demonstrates disturbance of this balance during aging. While age-associated cardiovascular diseases are often related to iron deficiency, in physiological aging cardiac iron accumulates. To understand these changes, we focused on inflammation and proteolysis, two hallmarks of aging, and their role in iron metabolism. Via the IL-6-hepcidin axis, inflammation and iron status are strongly connected often resulting in anemia accompanied by infiltration of macrophages. This tight connection between anemia and inflammation highlights the importance of the macrophage iron metabolism during inflammation. Age-related decrease in proteolytic activity additionally affects iron balance due to impaired degradation of iron metabolism proteins. Therefore, this review accentuates alterations in iron metabolism during aging with regards to inflammation and proteolysis to draw attention to their implications and associations.

Cyclovirobuxine D pretreatment ameliorates septic heart injury through mitigation of ferroptosis

Myocardial dysfunction is a frequent complication in patients with severe sepsis. However, effective drugs for the prevention of myocardial dysfunction and the molecular mechanisms of the disease remain elusive. The present study demonstrated that Cyclovirobuxine D (CVB-D) could improve cardiac dysfunction in a cecal ligation and puncture (CLP) model in rodents and in a lipopolysaccharide (LPS) model in vitro. Echocardiography and histopathological examination were used to detect changes in cardiac structure and function. Kits were used to detect indicators of cardiac injury, transmission electron microscopy to detect structural changes in mitochondria and reverse transcription-quantitative PCR to detect prostaglandin-endoperoxide synthase 2 and hamp expression levels. L-Glutathione and malondialdehyde levels and superoxide dismutase activity were measured using kits. Cell viability was measured with the Cell Counting Kit-8. Iron metabolism-related proteins, inflammatory factor levels and related pathway proteins were detected using western blot analysis. Changes in L-type calcium currents were detected by membrane clamp, and contractility of cardiomyocytes was measured by Ion Optix. CVB-D attenuated CLP-induced cardiac malfunction in septic rats, with changes observed in myocardial pathological structure, creatine kinase isoenzyme (CK-MB), lactate dehydrogenase (LDH) and cardiac troponin I (cTnI). CVB-D attenuated sepsis-induced lipid peroxidation and iron overload. In addition, CVB-D decreased the expression of CK-MB, LDH and cTnI, suppressed oxidative stress index levels and reduced the production of reactive oxygen species. CVB-D decreased LPS-induced cytoplasmic iron overload by increasing upregulation of iron uptake molecules. Conversely, CVB-D significantly increased the upregulation of ferroportin 1. CVB-D pretreatment significantly reduced the levels of hamp mRNA compared with the LPS-treated group. CVB-D pretreatment significantly reduced inflammatory factor levels and the ratio of phosphorylated vs. total signal transducer and activator of transcription 3. The expression of SLC7A11 and GPX4 was upregulated in septic cells pretreated with CVB-D, however treatment with ML385 largely decreased this upregulation. Of note, CVB-D inhibited the inward flow of calcium ions through the LTCC. In conclusion, these findings suggest that CVB-D alleviated sepsis-induced cardiac iron toxicity by alleviating iron metabolism.

Inflammation, dysregulated iron metabolism, and cardiovascular disease

Iron is an essential trace element associated with both pathologic deficiency and toxic overload. Thus, systemic and cell iron metabolism are highly controlled processes regulated by protein expression and localization, as well as turnover, through the action of cytokines and iron status. Iron metabolism in the heart is challenging because both iron overload and deficiency are associated with cardiac disease. Also associated with cardiovascular disease is inflammation, as many cardiac diseases are caused by or include an inflammatory component. In addition, iron metabolism and inflammation are closely linked. Hepcidin, the master regulator of systemic iron metabolism, is induced by the cytokine IL-6 and as such is among the acute phase proteins secreted by the liver as part of the inflammatory response. In an inflammatory state, systemic iron homeostasis is dysregulated, commonly resulting in hypoferremia, or low serum iron. Less well characterized is cardiac iron metabolism in general, and even less is known about how inflammation impacts heart iron handling. This review highlights what is known with respect to iron metabolism in the heart. Expression of iron metabolism-related proteins and processes of iron uptake and efflux in these cell types are outlined. Evidence for the strong co-morbid relationship between inflammation and cardiac disease is also reviewed. Known connections between inflammatory processes and iron metabolism in the heart are discussed with the goal of linking inflammation and iron metabolism in this tissue, a connection that has been relatively under-appreciated as a component of heart function in an inflammatory state. Therapeutic options connecting inflammation and iron balance are emphasized, with the main goal of this review being to bring attention to alterations in iron balance as a component of inflammatory diseases of the cardiovascular system.

Chrysin: A polyedric flavone as a tool to explore new phytotherapeutic applications and drug design

In the field of pharmaceutical research, a branch that has become more and more interesting is phytochemistry. Among phytochemicals, flavonoids have been studied a lot over the past 30 years. This review summarizes the chemical characteristics, metabolism, applications, and toxicity of a particular flavonoid, chrysin, recorded in the last 10 years and supported by solid biological assays. Furthermore, this review highlights some derivatives of chrysin investigated to obtain more bioavailable molecules that maintain or improve chrysin's bioactivities, enclosing a chrysin patent section, as well.

Amlodipine rescues advanced iron overload cardiomyopathy in hemojuvelin knockout murine model: Clinical implications

Background

Iron overload cardiomyopathy (IOC) is a major co-morbidity of genetic hemochromatosis and secondary iron overload with limited therapeutic options. We aim to investigate mechanisms of rescue action of amlodipine in the murine model of iron overload, characterize changes in human cardiac tissue due to IOC, and compare them to the changes in the animal model of IOC.

Methods and results

As an animal model, we used male hemojuvelin knockout (HJVKO) mice, which lacked hemojuvelin (a co-receptor protein for hepcidin expression). The mice were fed a high-iron diet from 4 weeks to 1 year of age. As a rescue, iron-fed mice received the Ca²⁺ channel blocker, amlodipine, from 9 to 12 months. Iron overload resulted in systolic and diastolic dysfunctions and changes in the cardiac tissue similar to the changes in the explanted human heart with IOC. An IOC patient (β-thalassemia) with left-ventricular ejection fraction (LVEF) 25% underwent heart transplantation. The murine model and the explanted heart showed intra-myocyte iron deposition, fibrosis, hypertrophy, oxidative stress, remodeling of Ca²⁺ cycling proteins, and metabolic kinases typical of heart failure. Single-myocyte contractility and Ca²⁺ release were diminished in the murine model. The amlodipine-treated group exhibited normalization of cellular function and reversed fibrosis, hypertrophy, oxidative stress, and metabolic remodeling. We also report a clinical case of primary hemochromatosis successfully treated with amlodipine.

Conclusions

The aged HJVKO murine model on the iron-rich diet reproduced many features of the human case of IOC. The use of amlodipine in the murine model and clinical case reversed IOC remodeling, demonstrating that amlodipine is effective adjuvant therapy for IOC.

Amlodipine: Can act as an antioxidant in patients with transfusion-dependent β-thalassemia? A double-blind, controlled, crossover trial

BACKGROUND AND AIM

This study aimed to assess the antioxidant effects of amlodipine in transfusion-dependent β-thalassemia (TDT) patients.

METHODS

This crossover trial consisted of two sequences (AP and PA). In the AP sequence, nine cases received amlodipine 5 mg daily (phase I) and then were switched to placebo (phase II). In PA sequence, 10 patients took the placebo (phase I) and were shifted to amlodipine (phase II). The washout period was 2 weeks. The length of each phase was 6 months. Serum malondialdehyde (MDA, μmol/L), carbonyl (protein CO, μM/L), glutathione (GSH, nM/L), and total antioxidant capacity (TAC, μmol FeSO4/L) were measured in the beginning and at the end of phases I and II. The clinical significance was viewed as a minimum change difference of 5% for each outcome between amlodipine and placebo.

RESULTS

Seventeen cases completed the study. According to the baseline MDA values, the adjusted Hedges's g for MDA was -0.59, 95% confidence interval [CI] -1.26 to 0.08. After controlling the baseline protein CO values, Hedges's g computed for protein CO was -0.11, 95% CI -0.76 to 0.55. The estimated values of the adjusted Hedges's g for GSH and TAC were also 0.26, 95% CI -0.40 to 0.91, and 0.42, 95% CI -0.24 to 1.09, respectively. The change difference for MDA was 8.3% (protein CO 2.2%, GSH 3.1%, and TAC 12.9%).

CONCLUSION

Clinically, amlodipine therapy is an efficacious adjuvant treatment with conventional iron chelators for improving the levels of MDA and TAC in patients with TDT.

From Iron Metabolism to Ferroptosis: Pathologic Changes in Coronary Heart Disease

Coronary heart disease (CHD) is closely related to oxidative stress and inflammatory response and is the most common cardiovascular disease (CVD). Iron is an essential mineral that participates in many physiological and biochemical reactions in the human body. Meanwhile, on the negative side, iron has an active redox capacity, which leads to the accumulation of reactive oxygen species (ROS) and lipid peroxidation. There is growing evidence that disordered iron metabolism is involved in CHD's pathological progression. And the result of disordered iron metabolism is associated with iron overload-induced programmed cell death, often called ferroptosis. That features iron-dependent lipid peroxidation. Ferroptosis may play a crucial role in the development of CHD, and targeting ferroptosis may be a promising option for treating CHD. Here, we review the mechanisms of iron metabolism in cardiomyocytes (CMs) and explain the correlation between iron metabolism and ferroptosis. Meanwhile, we highlight the specific roles of iron metabolism and ferroptosis in the main pathological progression of CHD.

Clinical and Molecular Aspects of Iron Metabolism in Failing Myocytes

Heart failure (HF) is a common disease that causes significant limitations on the organism's capacity and, in extreme cases, leads to death. Clinically, iron deficiency (ID) plays an essential role in heart failure by deteriorating the patient's condition and is a prognostic marker indicating poor clinical outcomes. Therefore, in HF patients, supplementation of iron is recommended. However, iron treatment may cause adverse effects by increasing iron-related apoptosis and the production of oxygen radicals, which may cause additional heart damage. Furthermore, many knowledge gaps exist regarding the complex interplay between iron deficiency and heart failure. Here, we describe the current, comprehensive knowledge about the role of the proteins involved in iron metabolism. We will focus on the molecular and clinical aspects of iron deficiency in HF. We believe that summarizing the new advances in the translational and clinical research regarding iron deficiency in heart failure should broaden clinicians' awareness of this comorbidity.

Comparison of the effects of calcium channel blockers plus iron chelation therapy versus chelation therapy only on iron overload in children and young adults with transfusion-dependent thalassemia: A randomized double-blind placebo-controlled trial

BACKGROUND

Myocardial iron deposition is a significant cause of morbidity and mortality in patients with transfusion-dependent thalassemia (TDT). Amlodipine, L-type calcium channel blocker with regular chelation therapy may reduce myocardial iron overload. Lack of randomized trials prompted this study to assess the effect of calcium channel blocker (amlodipine) in combination with iron chelation therapy on iron overload in patients with TDT.

METHODS

Sixty-four eligible patients were randomized to receive either amlodipine and chelation (group A) or chelation alone (group B) in double-blind placebo-controlled trial. Myocardial iron concentration (MIC) using T2* magnetic resonance imaging (MRI), liver iron concentration (LIC), left ventricular ejection fraction (LVEF), and serum ferritin were measured at baseline and 12 months.

RESULTS

In the amlodipine group, mean cardiac T2* value significantly increased from 18.11 ± 8.47 to 22.15 ± 7.61 (p = .002) at 12 months, whereas in control group, there was a nonsignificant increase (p = .62) in cardiac T2* value from 19.50 ± 8.84 to 20.03 ± 9.07. There was a significant decrease in MRI-derived MIC in the amlodipine group compared to control group (1.93 ± 1.61 to 1.29 ± 0.90, p = .01). Changes in the LVEF (p = .45), MRI-derived LIC (p = .09), and serum ferritin (p = .81) were not significant between the two groups.

CONCLUSION

Amlodipine is safe and when combined with chelation therapy appears to be more effective in reducing cardiac iron overload than chelation only in children and young adults with TDT.

Iron overload cardiomyopathy: Using the latest evidence to inform future applications

Iron overload can be the result of either dysregulated iron metabolism in the case of hereditary hemochromatosis or repeated blood transfusions in the case of secondary hemochromatosis (e.g. in β-thalassemia and sickle cell anemia patients). Under iron overload conditions, transferrin (Tf) saturation leads to an increase in non-Tf bound iron which can result in the generation of reactive oxygen species (ROS). These excess ROS can damage cellular components, resulting in the dysfunction of vital organs including iron overload cardiomyopathy (IOC). Multiple studies have demonstrated that L-type and T-type calcium channels are the main routes for iron uptake in the heart, and that calcium channel blockers, given either individually or in combination with standard iron chelators, confer cardioprotective effects under iron overload conditions. Treatment with antioxidants may also provide therapeutic benefits. Interestingly, recent studies have suggested that mitochondrial dynamics and regulated cell death (RCD) pathways are potential targets for pharmacological interventions against iron-induced cardiomyocyte injury. In this review, the potential therapeutic roles of iron chelators, antioxidants, iron uptake/metabolism modulators, mitochondrial dynamics modulators, and inhibitors of RCD pathways in IOC are summarized and discussed.

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.

Calcium chelator BAPTA‑AM protects against iron overload‑induced chondrocyte mitochondrial dysfunction and cartilage degeneration

Osteoarthritis (OA) is a common joint disease that is characterized by cartilage degradation. Iron deposition in the joints is common during the pathogenic progression of OA and recent studies have indicated that iron overload is an important contributor to OA progression. Calcium chelators have been reported to inhibit iron influx via modulating transferrin receptor protein 1 internalization, and they have been identified as a potential approach to the treatment of iron overload‑induced diseases. The aim of the present study was to investigate the effect of calcium chelators on the progression of iron overload‑induced OA. Primary chondrocytes were treated with various concentrations of ferric ammonium citrate (FAC) to mimic iron overload in vitro, followed by co‑treatment with the calcium chelator BAPTA acetoxymethyl ester (BAPTA‑AM). Subsequently, intracellular iron levels, cell viability, reactive oxygen species (ROS) levels, mitochondrial function and morphological changes, as well as MMP levels, were detected using commercial kits. It was demonstrated that FAC treatment significantly promoted chondrocyte apoptosis and the expression of MMPs, and these effects were reversed by co‑treatment with BAPTA‑AM. Moreover, BAPTA‑AM suppressed iron influx into chondrocytes and inhibited iron overload‑induced ROS production and mitochondrial dysfunction. These results indicated that calcium chelators may be of value in the treatment of iron metabolism‑related diseases and iron overload‑induced OA progression.

Aerobic exercise ameliorates cardiac hypertrophy by regulating mitochondrial quality control and endoplasmic reticulum stress through M2 AChR

Aerobic exercise increases M2 AChR, which thus improves cardiac function in cardiovascular disease (CVD) rats. This study aimed to determine whether aerobic exercise could ameliorate pressure overload-induced heart hypertrophy through M2 AChR, and to elucidate the underlying mechanisms of action. Mice were used to establish the myocardial hypertrophy model by transverse aortic constriction (TAC), and subjected to 2, 4, and 8 weeks of moderate-intensity aerobic exercise and choline intervention (14 mg/kg/day). Our results showed that 4 and 8 weeks of exercise and choline intervention reduced excessive mitochondrial fission and autophagy of myocardial mitochondria, thereby improving the ultrastructure and function of mitochondria after TAC. Moreover, 8-week exercise and choline intervention have enhanced parasympathetic function and promoted the expression of M2 AChR. In addition, 8-week exercise and choline intervention also inhibited the protein expression of myocardial MFN2, PERK/eIF2α/ATF4, and NLRP3/caspase-1/IL-1β signaling pathways, thereby effectively reducing mitochondrial fusion, endoplasmic reticulum stress, and inflammation. Taken together, these data suggest that pressure overload led to cardiac hypertrophy, cardiac dysfunction, and decreased parasympathetic function in cardiac tissues. Aerobic exercise attenuated cardiac dysfunction by modulating the expression of proteins involved in mitochondrial quality control, and induced endoplasmic reticulum stress and inflammation, thereby reducing cardiac hypertrophy and improving cardiac function in impaired heart tissues following TAC, which was likely mediated by M2 AChR activation.

Iron Overload-Induced Ferroptosis Impairs Porcine Oocyte Maturation and Subsequent Embryonic Developmental Competence in vitro

Accumulating evidence indicates that ferroptosis is an iron-dependent form of regulated cell death. This type of iron-dependent programmed cell death is different from traditional forms of regulated cell death, such as apoptosis and autophagy. However, the role of ferroptosis in porcine oocyte maturation and the associated mechanism remain unclear. In the present research, we investigated the effects of ferric ammonium citrate (FAC), a specific ferroptosis inducer, on porcine oocyte meiotic maturation and quality and subsequent embryonic developmental competence. FAC treatment caused obvious accumulation of intracellular ferrous ions in porcine oocytes. At the end of the in vitro maturation (IVM) period, there was a significant decrease in the polar body (PB) extrusion rate and an increase in the percentage of abnormal oocytes in the FAC treatment groups, indicating that iron overload-induced ferroptosis may suppress the meiotic process during porcine oocyte maturation. We also found that after FAC treatment, the subsequent two-cell rate, four-cell rate and blastocyst formation rate were significantly decreased in porcine parthenogenetic activation (PA) embryos, indicating that iron overload-induced ferroptosis decreased porcine oocyte quality. Further analysis revealed that FAC treatment not only enhanced intracellular reactive oxygen species (ROS) generation, decreased intracellular free thiol levels and induced mitochondrial dysfunction but also triggered autophagy in porcine oocytes. Taken together, these findings suggest that iron overload-induced ferroptosis impairs porcine oocyte meiosis and decreases porcine oocyte quality, possibly by increasing oxidative stress, inducing mitochondrial dysfunction and triggering autophagy.

Fetal Cardiac Cellular Damage Caused by Anemia in Utero in Hb Bart's Disease

BACKGROUND

Severe fetal anemias can cause high output cardiac failure. Mitochondria are key regulators of cardiac function. However, the effects of an early phase of fetal anemia on the fetal heart and cardiac mitochondrial function are not known.

OBJECTIVE

The aim of this study is to compare mitochondrial function and cardiac biochemical alterations in the fetal cardiac tissue between anemic and non-anemic fetuses.

MATERIALS AND METHODS

A cross-sectional study was conducted in Fetuses affected by Hb Bart's disease (n=18) and non-anemic fetuses (n=10) at 17-20 weeks. Echocardiograms had been carried out in all cases to assess prenatal cardiac function. Cardiac tissues were collected after pregnancy termination for the determination of cardiac iron accumulation, mitochondrial function, including mitochondrial ROS production, mitochondrial depolarization and mitochondrial swelling, mitochondrial dynamics, inflammation, and apoptosis.

RESULTS

Prenatal cardiac function evaluated by ultrasound was comparable between the Hb Bart's and non-anemic groups. In Bart's group, the levels of cardiac mitochondrial depolarization and swelling, and the TNF-α level were significantly higher, compared to the non-anemic group. On the contrary, anti-inflammatory (IL-10) levels were significantly lower in the Hb Bart's group. Additionally, active caspase-3 and Bcl-2 expression were also significantly higher (P= 0.001, P=0.035) in Bart's group. The mitochondrial fission protein expression, including p-DRP1/total DRP1, was significantly higher in Bart's group. However, there was no difference in cardiac iron accumulation levels between these two groups.

CONCLUSION

Despite equivalent prenatal cardiac function and comparable cardiac iron accumulation in the Bart's and non-anemic groups, fetal anemia is significantly associated with cardiac mitochondrial dysfunction, increased mitochondrial fission, and increased inflammation and apoptosis. These findings indicate that an early phase of fetal anemia without cardiac iron overload can lead to cardiac mitochondrial dysfunction in fetuses with Hb Bart's.

Silencing of lipocalin-2 improves cardiomyocyte viability under iron overload conditions via decreasing mitochondrial dysfunction and apoptosis

This study aimed to investigate the mechanistic roles of LCN-2 and LCN-2 receptors (LCN-2R) as iron transporters in cardiomyocytes under iron overload condition. H9c2 cardiomyocytes were treated with either LCN-2 small interfering RNA (siRNA) or LCN-2R siRNA or L-type or T-type calcium channel (LTCC or TTCC) blockers, or iron chelator deferiprone (DFP). After the treatments, the cells were exposed to Fe³⁺ or Fe²⁺ , after that biological parameters were determined. Silencing of lipocalin-2 or its receptor improved cardiomyocyte viability via decreasing iron uptake, mitochondrial fission, mitophagy and cleaved caspase-3 only in the Fe³⁺ overload condition. In contrast, treatments with LTCC blocker and TTCC blocker showed beneficial effects on those parameters only in conditions of Fe²⁺ overload. Treatment with DFP has been shown beneficial effects both in Fe²⁺ and Fe³⁺ overload condition. All of these findings suggested that LTCC and TTCC play crucial roles in the Fe²⁺ uptake, whereas LCN-2 and LCN-2R were essential for Fe³⁺ uptake into the cardiomyocytes under iron overload conditions.

Iron and Heart Failure: Diagnosis, Therapies, and Future Directions

To date, 3 clinical trials have shown symptomatic benefit from the use of intravenous (IV) iron in patients with heart failure (HF) with low serum iron. This has led to recommendations in support of the use of IV iron in this population. However, the systemic and cellular mechanisms of iron homeostasis in cardiomyocyte health and disease are distinct, complex, and poorly understood. Iron metabolism in HF appears dysregulated, but it is still unclear whether the changes are maladaptive and pathologic or compensatory and protective for the cardiomyocytes. The serum markers of iron deficiency in HF do not accurately reflect cellular and mitochondrial iron levels, and the current definition based on the ferritin and transferrin saturation values is broad and inclusive of patients who do not need IV iron. This is particularly relevant in view of the potential risks that are associated with the use of IV iron. Reliable markers of cellular iron status may differentiate subgroups of HF patients who would benefit from cellular and mitochondrial iron chelation rather than IV iron.

Keeping heart homeostasis in check through the balance of iron metabolism

Highly active cardiomyocytes need iron for their metabolic activity. In physiological conditions, iron turnover is a delicate process which is dependent on global iron supply and local autonomous regulatory mechanisms. Though less is known about the autonomous regulatory mechanisms, data suggest that these mechanisms can preserve cellular iron turnover even in the presence of systemic iron disturbance. Therefore, activity of local iron protein machinery and its relationship with global iron metabolism is important to understand cardiac iron metabolism in physiological conditions and in cardiac disease. Our knowledge in this respect has helped in designing therapeutic strategies for different cardiac diseases. This review is a synthesis of our current knowledge concerning the regulation of cardiac iron metabolism. In addition, different models of cardiac iron dysmetabolism will be discussed through the examples of heart failure (cardiomyocyte iron deficiency), myocardial infarction (acute changes in cardiac iron turnover), doxorubicin-induced cardiotoxicity (cardiomyocyte iron overload in mitochondria), thalassaemia (cardiomyocyte cytosolic and mitochondrial iron overload) and Friedreich ataxia (asymmetric cytosolic/mitochondrial cardiac iron dysmetabolism). Finally, future perspectives will be discussed in order to resolve actual gaps in knowledge, which should be helpful in finding new treatment possibilities in different cardiac diseases.

The effects of iron overload on mitochondrial function, mitochondrial dynamics, and ferroptosis in cardiomyocytes

Excessive iron accumulation in the heart can lead to iron overload cardiomyopathy (IOC), the leading cause of death in hemochromatosis patients. Current understanding regarding the mechanism by which iron overload causes a deterioration in cardiac performance, mitochondrial dysfunction, and impaired mitochondrial dynamics remains limited. Ferroptosis, a newly identified form of regulated cell death, has recently been revealed influencing the pathophysiological process of IOC. Nevertheless, the direct effect of cardiac iron overload on ferroptotic cell death is incompletely characterized. This review article comprehensively summarizes and discusses the effects of iron overload on cardiac mitochondrial function, cardiac mitochondrial dynamics, ferroptosis of cardiomyocytes, and left ventricular function in in vitro and in vivo reports. This review also provides relevant consistent and controversial information which can facilitate further mechanistic investigation into iron-induced cardiac dysfunction in the clinical setting in the near future.

Combined iron chelator with N-acetylcysteine exerts the greatest effect on improving cardiac calcium homeostasis in iron-overloaded thalassemic mice

The morbidity and mortality in thalassemia patients are predominantly caused by iron overload cardiomyopathy (IOC). Iron-induced cardiac intracellular Ca²⁺ ([Ca²⁺]_i) dysregulation is among the core pathophysiological processes in IOC-related heart failure. Although cardioprotective roles of deferiprone (DFP) and N-acetylcysteine (NAC) have been reported, their effect on cardiac [Ca²⁺]_i transients and Ca²⁺-regulatory protein expression in thalassemic mice is unknown. In the present study, iron overload condition was induced in wild-type (WT) and heterozygous β-thalassemic (HT) mice by a high-iron diet. The iron-overloaded mice subsequently received a vehicle, DFP, NAC, or DFP plus NAC co-therapy. In both WT and HT iron-overloaded mice, DFP and NAC had similar efficacy in decreasing plasma non-transferrin-bound iron, decreasing cardiac iron concentration (CIC) and relieving systolic dysfunction. DFP plus NAC co-therapy, however, was better than the monotherapy in reducing CIC and restoring cardiac [Ca²⁺]_i transient amplitude and rising rate. All regimens produced no change in cardiac Ca²⁺-regulatory protein expression. We provided the first evidence regarding the synergistic effect of combined iron chelator-antioxidant therapy on cardiac [Ca²⁺]_i homeostasis in iron-overloaded thalassemic mice, with consistent improvement of cardiac contractility.

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

Iron overload cardiomyopathy (IOC) is a major cause of death in patients with diseases associated with chronic anemia such as thalassemia or sickle cell disease after chronic blood transfusions. Associated with iron overload conditions, there is excess free iron that enters cardiomyocytes through both L- and T-type calcium channels thereby resulting in increased reactive oxygen species being generated via Haber-Weiss and Fenton reactions. It is thought that an increase in reactive oxygen species contributes to high morbidity and mortality rates. Recent studies have, however, suggested that it is iron overload in mitochondria that contributes to cellular oxidative stress, mitochondrial damage, cardiac arrhythmias, as well as the development of cardiomyopathy. Iron chelators, antioxidants, and/or calcium channel blockers have been demonstrated to prevent and ameliorate cardiac dysfunction in animal models as well as in patients suffering from cardiac iron overload. Hence, either a mono-therapy or combination therapies with any of the aforementioned agents may serve as a novel treatment in iron-overload patients in the near future. In the present article, we review the mechanisms of cytosolic and/or mitochondrial iron load in the heart which may contribute synergistically or independently to the development of iron-associated cardiomyopathy. We also review available as well as potential future novel treatments.

Non-transferrin-bound iron transporters

Most cells in the body acquire iron via receptor-mediated endocytosis of transferrin, the circulating iron transport protein. When cellular iron levels are sufficient, the uptake of transferrin decreases to limit further iron assimilation and prevent excessive iron accumulation. In iron overload conditions, such as hereditary hemochromatosis and thalassemia major, unregulated iron entry into the plasma overwhelms the carrying capacity of transferrin, resulting in non-transferrin-bound iron (NTBI), a redox-active, potentially toxic form of iron. Plasma NTBI is rapidly cleared from the circulation primarily by the liver and other organs (e.g., pancreas, heart, and pituitary) where it contributes significantly to tissue iron overload and related pathology. While NTBI is usually not detectable in the plasma of healthy individuals, it does appear to be a normal constituent of brain interstitial fluid and therefore likely serves as an important source of iron for most cell types in the CNS. A growing body of literature indicates that NTBI uptake is mediated by non-transferrin-bound iron transporters such as ZIP14, L-type and T-type calcium channels, DMT1, ZIP8, and TRPC6. This review provides an overview of NTBI uptake by various tissues and cells and summarizes the evidence for and against the roles of individual transporters in this process.

Role of iron metabolism in heart failure: From iron deficiency to iron overload

Iron metabolism is a balancing act, and biological systems have evolved exquisite regulatory mechanisms to maintain iron homeostasis. Iron metabolism disorders are widespread health problems on a global scale and range from iron deficiency to iron-overload. Both types of iron disorders are linked to heart failure. Iron play a fundamental role in mitochondrial function and various enzyme functions and iron deficiency has a particular negative impact on mitochondria function. Given the high-energy demand of the heart, iron deficiency has a particularly negative impact on heart function and exacerbates heart failure. Iron-overload can result from excessive gut absorption of iron or frequent use of blood transfusions and is typically seen in patients with congenital anemias, sickle cell anemia and beta-thalassemia major, or in patients with primary hemochromatosis. This review provides an overview of normal iron metabolism, mechanisms underlying development of iron disorders in relation to heart failure, including iron-overload cardiomyopathy, and clinical perspective on the treatment options for iron metabolism disorders.

The effect of different digoxin concentrations on heart tissue and antioxidant status in iron-overloaded rats

BACKGROUND

Thalassaemia is a hereditary disorder and has an economic burden on patients and the government. The most prevalent complication in these patients is iron overload which is followed by cardiomyopathy. Digoxin is considered as a treatment against heart failure in thalassaemia. The present study evaluated the effect of two digoxin concentrations on iron content and antioxidative defense in cardiac tissue of iron-overloaded rats.

METHODS

The study was conducted on 48 rats which were divided into 6 groups. Group 1 was the control group and did not receive any treatment and group 2 was the iron overload group. In addition groups 3 and 4 were the digoxin control groups which received 1 and 5 mg/kg/day of digoxin, respectively. Groups 5 and 6 received 1 and 5 mg/kg/day of digoxin plus iron-dextran, respectively. After 1 month, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX), and total antioxidant status (TAS) were assessed in cardiac tissues.

RESULTS

Co-administration of iron-dextran and digoxin (1 and 5 mg/kg/day) significantly increased SOD and TAS levels (P < 0.0010) and reduced MDA (P < 0.0010) in heart tissue compared to control and iron overload groups. GPX levels significantly reduced in groups 5 and 6 (iron + digoxin 1 (P < 0.0500) and iron + digoxin 5) (P < 0.0010) compared to the iron control group.

CONCLUSION

Digoxin remarkably facilitates iron uptake by cardiomyocytes by affecting other channels such as L-type and T-type Ca2+ channels (LTCC and TTCC). Digoxin administration in the iron-overloaded rat model deteriorated antioxidative parameters and increased iron entry into heart tissue at higher doses. Therefore, in patients with beta thalassaemia major, digoxin must be administered with great care and serum iron and ferritin must be regularly monitored.

Increased sympathovagal imbalance evaluated by heart rate variability is associated with decreased T2* MRI and left ventricular function in transfusion-dependent thalassemia patients

Early detection of iron overload cardiomyopathy is an important strategy for decreasing the mortality rate of patients with transfusion-dependent thalassemia (TDT). Although cardiac magnetic resonance (CMR) T2* is effective in detecting cardiac iron deposition, it is costly and not generally available. We investigated whether heart rate variability (HRV) can be used as a screening method of iron overload cardiomyopathy in TDT patients. HRV, evaluated by 24-h Holter monitoring, non-transferrin bound iron (NTBI), serum ferritin, left ventricular (LV) ejection fraction (LVEF), and CMR-T2* were determined. Patients with a cardiac iron overload condition had a significantly higher low frequency/high frequency (LF/HF) ratio than patients without a cardiac iron overload condition. Log-serum ferritin (r = -0.41, P=0.008), serum NTBI (r = -0.313, P=0.029), and LF/HF ratio (r = -0.286, P=0.043) showed a significant correlation with CMR-T2*, however only the LF/HF ratio was significantly correlated with LVEF (r = -0.264, P=0.043). These significant correlations between HRV and CMR-T2* and LVEF in TDT confirmed the beneficial role of HRV as a potential early screening tool of cardiac iron overload in thalassemia patients, especially in a medical center in which CMR T2* is not available. A larger number of TDT patients with cardiac iron overload are needed to confirm this finding.

Cardiac complications in beta-thalassemia: From mice to men

Beta-thalassemia is an inherited hemoglobin disorder caused by reduced or absent synthesis of the beta globin chains of hemoglobin. This results in variable outcomes ranging from clinically asymptomatic to severe anemia, which then typically requires regular blood transfusion. These regular blood transfusions can result in an iron overload condition. The iron overload condition can lead to iron accumulation in various organs, especially in the heart, leading to iron overload cardiomyopathy, which is the major cause of mortality in patients with thalassemia. In the past decades, there is no doubt that the use of β-thalassemic mice as a study model to investigate the pathophysiology of iron overload cardiomyopathy and the role of various pharmacological interventions, has shed some light in understanding this serious complication and in improving the associated cardiac dysfunction. In this review, the effects that iron overload has on the hearts of β-thalassemic mice under conditions of iron overload as well as the efficacy of pharmacological interventions to combat these adverse effects on the heart are reviewed and discussed. The in-depth understanding of biomolecular alterations in the heart of these iron overload thalassemic mice will help give guidance for more effective therapeutic approaches in the near future. Impact statement Iron overload cardiomyopathy is a major cause of morbidity and mortality in patients with thalassemia. Since investigation of iron overload cardiomyopathy in thalassemia patients has many limitations, a search for an animal model for this condition has been ongoing for decades. In the past decades, there is no doubt that the use of β-thalassemic mice as a study model to investigate the pathophysiology of iron overload cardiomyopathy and the role of various pharmacological interventions, has shed some light in understanding this serious complication and in improving the associated cardiac dysfunction. In this review, the effects of iron overload on the hearts of β-thalassemic mice under conditions of iron overload as well as the efficacy of pharmacological interventions to combat these adverse effects on the heart are reviewed and discussed.

Restoring the impaired cardiac calcium homeostasis and cardiac function in iron overload rats by the combined deferiprone and N-acetyl cysteine

Intracellular calcium [Ca²⁺]_i dysregulation plays an important role in the pathophysiology of iron overload cardiomyopathy. Although either iron chelators or antioxidants provide cardioprotection, a comparison of the efficacy of deferoxamine (DFO), deferiprone (DFP), deferasirox (DFX), N-acetyl cysteine (NAC) or a combination of DFP plus NAC on cardiac [Ca²⁺]_i homeostasis in chronic iron overload has never been investigated. Male Wistar rats were fed with either a normal diet or a high iron (HFe) diet for 4 months. At 2 months, HFe rats were divided into 6 groups and treated with either a vehicle, DFO (25 mg/kg/day), DFP (75 mg/kg/day), DFX (20 mg/kg/day), NAC (100 mg/kg/day), or combined DFP plus NAC. At 4 months, the number of cardiac T-type calcium channels was increased, whereas cardiac sarcoplasmic-endoplasmic reticulum Ca²⁺ ATPase (SERCA) was decreased, leading to cardiac iron overload and impaired cardiac [Ca²⁺]i homeostasis. All pharmacological interventions restored SERCA levels. Although DFO, DFP, DFX or NAC alone shared similar efficacy in improving cardiac [Ca²⁺]i homeostasis, only DFP + NAC restored cardiac [Ca²⁺]i homeostasis, leading to restoring left ventricular function in the HFe-fed rats. Thus, the combined DFP + NAC was more effective than any monotherapy in restoring cardiac [Ca²⁺]_i homeostasis, leading to restored myocardial contractility in iron-overloaded rats.

Effects of iron overload, an iron chelator and a T-Type calcium channel blocker on cardiac mitochondrial biogenesis and mitochondrial dynamics in thalassemic mice

Although cardiac mitochondrial dysfunction is involved in the pathophysiology of iron-overload cardiomyopathy, the precise mechanisms of iron-induced mitochondrial dysfunction, and the roles of the iron chelator deferiprone and the T-type calcium channel blocker efonidipine on cardiac mitochondrial biogenesis in thalassemic mice are still unknown. β-thalassemic (HT) mice were fed with a normal diet (ND) or a high iron-diet (FE) for 90 days. Then, the FE-fed mice were treated with deferiprone (75mg/kg/day) or efonidipine (4mg/kg/day) for 30 days. The hearts were used to determine cardiac mitochondrial function, biogenesis, mitochondrial dynamics and protein expressions for oxidative phosphorylation (OXPHOS) and apoptosis. ND-fed HT mice had impaired heart rate variability (HRV), increased mitochondrial dynamic proteins and caspase-3, compared with ND-fed wild-type mice. Iron overload led to increased plasma non-transferrin bound iron, oxidative stress, and the impairments of HRV and left ventricular function, cardiac mitochondrial function and mitochondrial dynamics, and decreased complex IV in thalassemic mice. Our results suggested that deferiprone and efonidipine treatment showed similar benefit in attenuating cardiac iron deposit and oxidative stress, and improved cardiac mitochondrial function, leading to improved left ventricular function, without altering the cardiac mitochondrial biogenesis, and apoptosis proteins in iron-overload thalassemic mice.

The surge of flavonoids as novel, fine regulators of cardiovascular Cav channels

Ion channels underlie a wide variety of physiological processes that involve rapid changes in cell dynamics, such as cardiac and vascular smooth muscle contraction. Overexpression or dysfunction of these membrane proteins are the basis of many cardiovascular diseases that represent the leading cause of morbidity and mortality for human beings. In the last few years, flavonoids, widely distributed in the plant kingdom, have attracted the interest of many laboratories as an emerging class of fine ion, in particular Ca_v, channels modulators. Pieces of in vitro evidence for direct as well as indirect effects exerted by various flavonoids on ion channel currents are now accumulating in the scientific literature. This activity may be responsible, at least in part, for the beneficial and protective effects of dietary flavonoids toward cardiovascular diseases highlighted in several epidemiological studies. Here we examine numerous studies aimed at analysing this feature of flavonoids, focusing on the mechanisms that promote their sometimes controversial activities at cardiovascular Ca_v channels. New methodological approaches, such as molecular modelling and docking to Ca_v1.2 channel α_1c subunit, used to elucidate flavonoids intrinsic mechanism of action, are introduced. Moreover, flavonoid-membrane interaction, bioavailability, and antioxidant activity are taken into account and discussed.