Iron and cardiovascular diseases

Research Progress on Histone Deacetylases Regulating Programmed Cell Death in Atherosclerosis

Histone deacetylases (HDACs) are epigenetic modifying enzyme that is closely related to chromatin structure and gene transcription, and numerous studies have found that HDACs play an important regulatory role in atherosclerosis disease. Apoptosis, autophagy and programmed necrosis as the three typical programmed cell death modalities that can lead to cell loss and are closely related to the developmental process of atherosclerosis. In recent years, accumulating evidence has shown that the programmed cell death mediated by HDACs is increasingly important in the pathophysiology of atherosclerosis. This paper first gives a brief overview of HDACs, the mechanism of programmed cell death, and their role in atherosclerosis, and then further elaborates on the role and mechanism of HDACs in regulating apoptosis, autophagy, and programmed necrosis in atherosclerosis, respectively, to provide new effective measures and theoretical basis for the prevention and treatment of atherosclerosis.

Hypoxia-inducible factor-prolyl hydroxylase inhibitor Roxadustat (FG-4592) reduces renal fibrosis in Dahl salt-sensitive rats

OBJECTIVE

Although hypoxia-inducible factor-prolyl hydroxylase (HIF-PH) inhibitors have been developed for the treatment of renal anemia, their effects on cardiac and renal dysfunction remain unknown. We previously reported on Dahl salt-sensitive rats, in a rat model of salt-sensitive hypertension, that exhibited anemia and impaired expression of duodenal iron transporters after the development of hypertensive cardiac and renal dysfunction. Therefore, we investigated the effects of Roxadustat (FG-4592), an HIF-PH inhibitor, on anemia, iron regulation, and cardiac and renal dysfunction in Dahl salt-sensitive rats.

METHODS

Six-week-old male Dahl salt-sensitive rats were fed a normal or high-salt diet for 8 weeks. A further subset of Dahl salt-sensitive rats, that were fed a high-salt diet, was administered Roxadustat for 8 weeks.

RESULTS

Dahl salt-sensitive rats fed a high-salt diet developed hypertension, cardiac and renal dysfunction, and anemia after 8 weeks of feeding. Roxadustat increased hemoglobin and serum erythropoietin levels in Dahl salt-sensitive rats fed a high-salt diet. With regard to the iron-regulating system, Roxadustat lowered hepatic hepcidin gene expression and increased the gene expression of duodenal iron transporters, such as cytochrome b and divalent metal transporter 1 , in Dahl salt-sensitive rats fed a high-salt diet. Roxadustat did not affect the development of hypertension and cardiac hypertrophy in Dahl salt-sensitive rats with a high-salt diet; however, Roxadustat treatment attenuated renal fibrosis in these rats.

CONCLUSIONS

Roxadustat ameliorated anemia with affecting the gene expression of the iron-regulating system, and did not affect cardiac hypertrophy but attenuated renal fibrosis in Dahl salt-sensitive rats fed a high-salt diet.

Spatial Metabolomics Identifies LPC(18:0) and LPA(18:1) in Advanced Atheroma With Translation to Plasma for Cardiovascular Risk Estimation

BACKGROUND

The metabolic alterations occurring within the arterial architecture during atherosclerosis development remain poorly understood, let alone those particular to each arterial tunica. We aimed first to identify, in a spatially resolved manner, the specific metabolic changes in plaque, media, adventitia, and cardiac tissue between control and atherosclerotic murine aortas. Second, we assessed their translatability to human tissue and plasma for cardiovascular risk estimation.

METHODS

In this observational study, mass spectrometry imaging (MSI) was applied to identify region-specific metabolic differences between atherosclerotic (n=11) and control (n=11) aortas from low-density lipoprotein receptor-deficient mice, via histology-guided virtual microdissection. Early and advanced plaques were compared within the same atherosclerotic animals. Progression metabolites were further analyzed by MSI in 9 human atherosclerotic carotids and by targeted mass spectrometry in human plasma from subjects with elective coronary artery bypass grafting (cardiovascular risk group, n=27) and a control group (n=27).

RESULTS

MSI identified 362 local metabolic alterations in atherosclerotic mice (log2 fold-change ≥1.5; P≤0.05). The lipid composition of cardiac tissue is altered during atherosclerosis development and presents a generalized accumulation of glycerophospholipids, except for lysolipids. Lysolipids (among other glycerophospholipids) were found at elevated levels in all 3 arterial layers of atherosclerotic aortas. LPC(18:0) (lysophosphatidylcholine; P=0.024) and LPA(18:1) (lysophosphatidic acid; P=0.025) were found to be significantly elevated in advanced plaques as compared with mouse-matched early plaques. Higher levels of both lipid species were also observed in fibrosis-rich areas of advanced- versus early-stage human samples. They were found to be significantly reduced in human plasma from subjects with elective coronary artery bypass grafting (P<0.001 and P=0.031, respectively), with LPC(18:0) showing significant association with cardiovascular risk (odds ratio, 0.479 [95% CI, 0.225-0.883]; P=0.032) and diagnostic potential (area under the curve, 0.778 [95% CI, 0.638-0.917]).

CONCLUSIONS

An altered phospholipid metabolism occurs in atherosclerosis, affecting both the aorta and the adjacent heart tissue. Plaque-progression lipids LPC(18:0) and LPA(18:1), as identified by MSI on tissue, reflect cardiovascular risk in human plasma.

Association between biomarkers of iron status and cardiometabolic risk in Spanish children aged 9-10 years. The ELOIN study

The relationship between iron metabolism and cardiometabolic risk factors has been scarcely studied in children, and the results are controversial. The objective of this study was to evaluate the association between iron parameters and lipid, glycemic and blood pressure alterations in the pediatric population. This was a cross-sectional study of 1954 children between 9 and 10 years of age in Madrid (Spain), participants in a longitudinal study of childhood obesity. Iron metabolism parameters, i.e., serum iron (Is), ferritin (Fs), transferrin (Tf) and transferrin saturation (STf) and lipid, glycemic and blood pressure profiles were evaluated. Odds ratios (ORs) were estimated using logistic regression models adjusted for sociodemographic characteristics, diet, physical activity, C-reactive protein and body mass index. Compared with the participants in the low Is and STf tertiles, those in the upper tertiles had a lower risk of low HDL-Chol (OR: 0.34; 95%CI: 0.17; 0.67) and OR: 0.44 (95%CI: 0.23; 0.84), respectively, and children in the upper Fs tertile had an OR of 2.07 (95%CI: 1.16; 3.68) for low HDL-Chol. Children in the highest Is and STf tertiles had a lower risk of prediabetes [OR: 0.63 (95%CI: 0.41; 0.97) and OR: 0.53 (95%CI: 0.34; 0.82)] and insulin resistance (IR) (OR: 0.37; 95%CI: 0.22; 0.64), and those in the upper Tf tertile had a higher risk of IR (OR: 1.90; 95%CI: 1.16; 3.12). An increased risk of hypertension was found only in children in the upper Fs tertile (OR: 1.46; 95%CI: 1.01; 2.13).

CONCLUSIONS

Biomarkers of iron metabolism are associated with cardiometabolic alterations in the pediatric population, with a variable direction and magnitude depending on the indicators used.

WHAT IS KNOWN

• Iron metabolism is related to important cardiometabolic alterations such as metabolic syndrome and its components. • Association between biomarkers of iron status and cardiometabolic risk have been less explored in children.

WHAT IS NEW

• Biomarkers of iron metabolism are associated with cardiometabolic alterations in the pediatric population. • Iron parameters in the pediatric population could be of great help to detect and prevent cardiometabolic abnormalities early.

Structures and coordination chemistry of transporters involved in manganese and iron homeostasis

A repertoire of transporters plays a crucial role in maintaining homeostasis of biologically essential transition metals, manganese, and iron, thus ensuring cell viability. Elucidating the structure and function of many of these transporters has provided substantial understanding into how these proteins help maintain the optimal cellular concentrations of these metals. In particular, recent high-resolution structures of several transporters bound to different metals enable an examination of how the coordination chemistry of metal ion-protein complexes can help us understand metal selectivity and specificity. In this review, we first provide a comprehensive list of both specific and broad-based transporters that contribute to cellular homeostasis of manganese (Mn2+) and iron (Fe2+ and Fe3+) in bacteria, plants, fungi, and animals. Furthermore, we explore the metal-binding sites of the available high-resolution metal-bound transporter structures (Nramps, ABC transporters, P-type ATPase) and provide a detailed analysis of their coordination spheres (ligands, bond lengths, bond angles, and overall geometry and coordination number). Combining this information with the measured binding affinity of the transporters towards different metals sheds light into the molecular basis of substrate selectivity and transport. Moreover, comparison of the transporters with some metal scavenging and storage proteins, which bind metal with high affinity, reveal how the coordination geometry and affinity trends reflect the biological role of individual proteins involved in the homeostasis of these essential transition metals.

Iron metabolism and atherosclerosis

Despite several decades of study, whether iron is involved in the development of atherosclerosis remains a controversial and unresolved issue. Here, we focus on the up-to-date advances in studies on role of iron in atherosclerosis and discuss possible reasons why patients with hereditary hemochromatosis (HH) do not show any increased incidence of atherosclerosis. In addition, we analyze conflicting results concerning the role of iron in atherogenesis from several epidemiological and animal studies. We argue that atherosclerosis is not observed in HH because iron homeostasis in the arterial wall, the actual location of atherosclerosis, is not significantly affected, and support a causal link between iron in the arterial wall and atherosclerosis.

The association between iron metabolism with the change of blood pressure and risk of hypertension: A large cross-sectional study

BACKGROUND

The relationship between iron metabolism and variations in blood pressure and hypertension risk is still not clear. This study aimed to determine whether iron metabolism is associated with changes in blood pressure and hypertension prevalence in the general United States population.

METHODS

The National Health and Nutrition Examination Survey (NAHNES) database contains data on 116876 Americans from 1999 to 2020 years. Data from the NHANES database were used to examine the relationships between iron metabolism (serum iron [SI], serum ferritin [SF], and soluble transferrin receptor [sTfR]) and changes in blood pressure and hypertension prevalence. Generalized linear models and restricted cubic spline (RCS) plot curves were used to estimate the relationship between iron metabolism and hypertension. Further, generalized additive models with smooth functions were used to identify the relationship between iron metabolism and blood pressure. Finally, a stratified subgroup analysis was performed.

RESULTS

A total of 6710 participants were included in our analysis. The RCS plot showed a linear relationship between SI, as well as sTfR, and hypertension prevalence. SF and hypertension prevalence were associated in a J-shape. In addition, the relationship between SI and systolic blood pressure (SBP) and diastolic blood pressure (DBP) decreased initially and then increased. A correlation between SF, SBP, and DBP first decreased, then increased, and finally decreased. A positive linear correlation existed between sTfR and SBP, but it increased and then decreased with DBP.

CONCLUSION

The correlation between SF and hypertension prevalence displayed a J-curve. In contrast, the correlation between SI, as well as sTfR, and hypertension risk was negative and positive, respectively.

Protective efficacy of Schizandrin B on ameliorating nephrolithiasis via regulating GSK3β/Nrf2 signaling-mediated ferroptosis in vivo and in vitro

Schizandrin B (SchB) protects against oxidative, inflammatory, and ferroptotic injury. Oxidative stress and inflammation are indispensably involved in nephrolithiasis and ferroptosis also plays an important role in stone formation. It is unclear whether SchB can ameliorate nephrolithiasis; its underlying mechanism is also unknown. First, we employed bioinformatics to investigate the mechanisms of nephrolithiasis. To evaluate the efficacy of SchB, HK-2 cell models of oxalate-induced damage, Erastin-induced ferroptosis, and the Sprague Dawley rat model of Ethylene Glycol-induced nephrolithiasis were established. Then, Nrf2 siRNA and GSK3β overexpression plasmids were transfected into HK-2 cells to elucidate the role of SchB in regulating oxidative stress-mediated ferroptosis. In our study, oxidative stress and inflammation were strongly associated with nephrolithiasis. Administration of SchB attenuated the cell viability, dysfunctional mitochondria, oxidative stress and inflammatory response in vitro and alleviated renal injury and crystal deposition in vivo. SchB treatment also reduced the levels of cellular Fe²⁺ accumulation, lipid peroxidation and MDA, and regulated ferroptosis-related proteins, including XCT, GPX4, FTH1 and CD71, in Erastin-induced or oxalate-induced HK-2 cells. Mechanistically, SchB facilitated Nrf2 nuclear translocation, and silencing Nrf2 or overexpressing GSK3β worsened oxalate-induced oxidative injury and abolished the beneficial effect of SchB against ferroptosis in vitro. To summarize, SchB could alleviate nephrolithiasis by positively regulating GSK3β/Nrf2 signaling-mediated ferroptosis.

Biomarkers of Micronutrients and Phytonutrients and Their Application in Epidemiological Studies

Nutritional biomarkers can be used as important indicators of nutritional status and play crucial roles in the prevention as well as prognosis optimization of various metabolism-related diseases. Measuring dietary with the deployment of biomarker assessments provides quantitative nutritional information that can better predict the health outcomes. With the increased availability of nutritional biomarkers and the development of assessment tools, the specificity and sensitivity of nutritional biomarkers have been greatly improved. This enables efficient disease surveillance in nutrition research. A wide range of biomarkers have been used in different types of studies, including clinical trials, observational studies, and qualitative studies, to reflect the relationship between diet and health. Through a comprehensive literature search, we reviewed the well-established nutritional biomarkers of vitamins, minerals, and phytonutrients, and their association with epidemiological studies, to better understand the role of nutrition in health and disease.

Naringenin protects against iron overload-induced osteoarthritis by suppressing oxidative stress

BACKGROUND

The traditional Chinese medicine Gusuibu, the rhizome of Rhizoma Drynariae, is used to treat rheumatism and fractures. Naringenin (NAR) is an active ingredient in Gusuibu and has significant anti-inflammatory and antioxidant effects. However, the role of naringenin in iron overload-induced osteoarthritis (IOOA) is unknown.

HYPOTHESIS

NAR reduces cartilage damage in IOOA.

METHODS

The effects of NAR on the viability of IOOA chondrocytes and the synthesis ability of type II collagen were evaluated using cell counting kit (CCK8) and toluidine blue assays. To determine the mechanism of action and characteristics of NAR, the intracellular iron ion content, apoptosis rate, and mitochondrial membrane potential (MMP) change, and malondialdehyde (MDA) levels, as well as the degree of reactive oxygen species (ROS) and lipid hydroperoxide (LPO) accumulation in the cells were detected in vitro and verified using western blotting and quantitative real-time PCR (qRT-PCR). To verify the role of NAR in vivo, IOOA mice were established using iron dextran and surgery-induced destabilised medial meniscus. Changes in the articular cartilage and subchondral bone were examined using Safranin O-fast Green staining (S-O), haematoxylin-eosin staining (H&E), and microcomputed tomography (μCT).

RESULTS

In vitro, NAR attenuated the impairment of cell viability, apoptosis, and MMP caused by ferric ammonium citrate and interleukin-1β co-culture, increased the levels of MDA, reduced the expression of matrix metallopeptidase (MMP)3, MMP13, and Bax, and restored the expression of type II collagen (Col II). NAR showed a slight iron accumulation-reducing effect. NAR alleviated the accumulation of ROS and LPO in IOOA chondrocytes and upregulated antioxidant genes nuclear factor E2-related factor 2 (NRF2) and haem oxygenase 1 (HO-1). When ML385, a specific NRF-2 inhibitor, was added, the protective effect of NAR was significantly inhibited. In vivo, NAR reduced synovitis and attenuated cartilage damage and subchondral bone proliferation in IOOA mice.

CONCLUSIONS

NAR can reduce oxidative stress through the NRF2-HO-1 pathway, alleviate cartilage damage under iron overload, and has the potential to treat IOOA.

The Role of Iron in Atherosclerosis in Apolipoprotein E Deficient Mice

The role of iron in atherosclerosis is still a controversial and unsolved issue. Here, we investigated serum iron, expression of iron regulatory, transport and storage proteins, pro-inflammatory chemokines and cytokines in ApoE–/– mice. We demonstrated that ApoE–/– induced atherosclerosis and an increase in iron contents, expression of transferrin receptor 1 (TfR1), iron regulatory proteins (IRPs), heme oxygenase 1 (HO1), cellular adhesion molecules and pro-inflammatory cytokines, production of reactive oxygen species (ROS), and a reduction in expression of superoxide dismutase and glutathione peroxidase enzyme in aortic tissues. All of these changes induced by ApoE deficiency could be significantly abolished by deferoxamine. The data showed that the increased iron in aortic tissues was mainly due to the increased iron uptake via IRP/TfR1 upregulation. These findings plus a brief analysis of the controversial results reported previously showed that ApoE deficiency-induced atherosclerosis is partly mediated by the increased iron in aortic tissues.

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.

Research Progress on Relationship Between Iron Overload and Lower Limb Arterial Disease in Type 2 Diabetes Mellitus

Iron is one of the most important trace elements in life activities. It participates in a variety of important physiological processes in the body through oxidation-reduction reaction. A large number of studies show that iron overload (IO) is closely related to the progression of diabetes and its various chronic complications. However, the mechanism of iron overload in the pathogenesis of diabetes and the mechanism of iron overload in atherosclerosis (AS) are still controversial, and the relationship between iron overload and diabetic lower extremity arterial disease (LEAD) remains still unclear. Some recent reviews and original research articles suggest further studies to explain the complex relationship between iron metabolism and atherosclerosis. This article reviews the relationship between iron overload and diabetes and its relationship with LEAD, and discusses its mechanisms from various aspects, such as lipid peroxidation induced by iron overload, so as to provide clinical diagnosis and treatment ideas for diabetic lower extremity arterial disease. It is hoped that early evaluation, diagnosis and treatment of LEAD will be inspired.

SIRT1-autophagy axis inhibits excess iron-induced ferroptosis of foam cells and subsequently increases IL-1Β and IL-18

OBJECTIVE

Ferroptosis is a new form of programmed cell death characterized by an iron-dependent increase in lipid ROS. It has recently been reported that elevated iron levels in macrophages in plaques are associated with atherosclerosis(AS). However, it is not clear whether iron induces ferroptosis and the mechanism of ferroptosis induced by iron in macrophages in plaque.

METHODS

THP-1 macrophages were treated with ox-LDL and ferric ammonium citrate(FAC). Activate SIRT1 using SRT1720. Use of RAPA and CQ to promote and suppress autophagy. The expression of SIRT1, GPX4 was detected by Western Blot, and the cell activity and lipid ROS level were also performed. IL-1β and IL-18 levels were measured using qRT-PCR and ELISA.

RESULTS

In this study, we determined that FAC can induce a decrease in foam cell activity rather than macrophage activity, increase lipid ROS levels, decrease GPX4 expression and inhibit SIRT1 expression, and increase IL-1β and IL-18 levels. SRT1720 activated SIRT1 and reversed the above changes induced by FAC. CQ partially prevents the above changes caused by activating SIRT1.

CONCLUSION

Activation of SIRT1 can inhibit the ferroptosis and IL-1β and IL-18 levels of foam cells in excess iron by autophagy, providing a novel therapeutic target for AS.

Iron Metabolism and Ferroptosis in Epilepsy

Epilepsy is a disease characterized by recurrent, episodic, and transient central nervous system (CNS) dysfunction resulting from an excessive synchronous discharge of brain neurons. It is characterized by diverse etiology, complex pathogenesis, and difficult treatment. In addition, most epileptic patients exhibit social cognitive impairment and psychological impairment. Iron is an essential trace element for human growth and development and is also involved in a variety of redox reactions in organisms. However, abnormal iron metabolism is associated with several neurological disorders, including hemorrhagic post-stroke epilepsy and post-traumatic epilepsy (PTE). Moreover, ferroptosis is also considered a new form of regulation of cell death, which is attributed to severe lipid peroxidation caused by the production of reactive oxygen species (ROS) and iron overload found in various neurological diseases, including epilepsy. Therefore, this review summarizes the study on iron metabolism and ferroptosis in epilepsy, in order to elucidate the correlation between iron and epilepsy. It also provides a novel method for the treatment, prevention, and research of epilepsy, to control epileptic seizures and reduce nerve injury after the epileptic seizure.