Iron as a target of chemoprevention for longevity in humans

An "Iron-phagy" nanoparticle inducing irreversible mitochondrial damages for antitumor therapy

Cellular iron is inseparably related with the proper functionalities of mitochondria for its potential to readily donate and accept electrons. Though promising, the available endeavors of iron chelation antitumor therapies have tended to be adjuvant therapies. Herein, we conceptualized and fabricated an "iron-phagy" nanoparticle (Dp44mT@HTH) capable of inducing the absolute devastation of mitochondria via inhibiting the autophagy-removal of impaired ones for promoting cancer cell death. The Dp44mT@HTH with hyaluronic acid (HA) as hydrophilic shell can specifically target the highly expressed CD44 receptors on the surface of 4T1 tumor cells. After internalization and lysosomal escape, the nanoparticle disassembles in response to the reactive oxygen species (ROS), subsequently releasing the iron chelator Dp44mT and autophagy-inhibitory drug hydroxychloroquine (HCQ). Dp44mT can then seize cellular Fe2+ to trigger mitochondrial dysfunction via respiratory chain disturbance, while HCQ not only lessens Fe2+ intake, but also impedes fusions of autophagosomes and lysosomes. Consequentially, Dp44mT@HTH induces irreversible mitochondrial impairments, in this respect creating a substantial toxic stack state that induces apoptosis and cell death. Initiating from the perspective of endogenous substances, this strategy illuminates the promise of iron depletion therapy via irreversible mitochondrial damage induction for anticancer treatment.

Clinicopathological characteristics, molecular features and novel diagnostic strategies for the detection of malignant transformation of endometriosis (Review)

Endometriosis is a benign gynecological disease that affects women of reproductive age. Although malignant transformation of endometriosis is rare, physicians must be aware of this due to the high incidence of clear cell carcinoma of the ovary (CCC) in Japan. The most prevalent histological subtype of ovarian cancer is CCC (~70%) followed by endometrioid carcinoma (30%). The present review discusses the clinicopathological and molecular features of endometriosis-associated ovarian cancer (EAOC) as well as prospects for novel diagnostic strategies. Papers published between 2000 and 2022 in the PubMed and Google Scholar databases were included. Contents of the endometriotic cyst fluid may be involved in carcinogenesis, although the underlying mechanisms are largely unknown. Some studies have proposed a possible mechanism wherein excessive hemoglobin, heme and iron could cause an imbalance in intracellular redox homeostasis in endometriotic cells. Combined with DNA damage and mutations, the imbalances may induce the development of EAOC. Endometriotic cells evolve to adapt to the prolonged unfavorable oxidative microenvironmental stress. On the other hand, macrophages enhance the antioxidative defense mechanism and protect endometriotic cells against oxidative damage through intercellular crosstalk and signaling pathways. Therefore, changes in redox signaling, energy metabolism and the tumor immune microenvironment could be the key elements in the malignant transformation of certain endometriotic cell clones. Additionally, non-invasive bioimaging (i.e., magnetic resonance relaxometry) and biomarkers (i.e., tissue factor pathway inhibitor 2) may be promising tools for early-stage detection of the disease. In conclusion, the present review summarizes the latest advancements in research on the biological characteristics and early diagnosis of malignant transformation of endometriosis.

A Nano-QSTR model to predict nano-cytotoxicity: an approach using human lung cells data

BACKGROUND

The widespread use of new engineered nanomaterials (ENMs) in industries such as cosmetics, electronics, and diagnostic nanodevices, has been revolutionizing our society. However, emerging studies suggest that ENMs present potentially toxic effects on the human lung. In this regard, we developed a machine learning (ML) nano-quantitative-structure-toxicity relationship (QSTR) model to predict the potential human lung nano-cytotoxicity induced by exposure to ENMs based on metal oxide nanoparticles.

RESULTS

Tree-based learning algorithms (e.g., decision tree (DT), random forest (RF), and extra-trees (ET)) were able to predict ENMs' cytotoxic risk in an efficient, robust, and interpretable way. The best-ranked ET nano-QSTR model showed excellent statistical performance with R² and Q²-based metrics of 0.95, 0.80, and 0.79 for training, internal validation, and external validation subsets, respectively. Several nano-descriptors linked to the core-type and surface coating reactivity properties were identified as the most relevant characteristics to predict human lung nano-cytotoxicity.

CONCLUSIONS

The proposed model suggests that a decrease in the ENMs diameter could significantly increase their potential ability to access lung subcellular compartments (e.g., mitochondria and nuclei), promoting strong nano-cytotoxicity and epithelial barrier dysfunction. Additionally, the presence of polyethylene glycol (PEG) as a surface coating could prevent the potential release of cytotoxic metal ions, promoting lung cytoprotection. Overall, the current work could pave the way for efficient decision-making, prediction, and mitigation of the potential occupational and environmental ENMs risks.

Iron accumulation with age alters metabolic pattern and circadian clock gene expression through the reduction of AMP-modulated histone methylation

Iron accumulates with age in mammals, and its possible implications in altering metabolic responses are not fully understood. Here, we report that both high-iron diet and advanced age in mice consistently altered gene expression of many pathways, including those governing the oxidative stress response and the circadian clock. We used a metabolomic approach to reveal similarities between metabolic profiles and the daily oscillation of clock genes in old and iron-overloaded mouse livers. In addition, we show that phlebotomy decreased iron accumulation in old mice, partially restoring the metabolic patterns and amplitudes of the oscillatory expression of clock genes Per1 and Per2. We further identified that the transcriptional regulation of iron occurred through a reduction in AMP-modulated methylation of histone H3K9 in the Per1 and H3K4 in the Per2 promoters, respectively. Taken together, our results indicate that iron accumulation with age can affect metabolic patterns and the circadian clock.

Regulation of ferroptosis by bioactive phytochemicals: Implications for medical nutritional therapy

Ferroptosis is an iron- and lipotoxicity-dependent regulated cell death that has been implicated in various diseases, such as cancer, neurodegeneration and stroke. The biosynthesis of phospholipids, coenzyme Q₁₀, and glutathione, and the metabolism of iron, amino acids and polyunsaturated fatty acid, are tightly associated with cellular sensitivity to ferroptosis. Up to now, only limited drugs targeting ferroptosis have been documented and exploring novel effective ferroptosis-modulating compound is needed. Natural bioactive products are conventional resources for drug discovery, and some of them have been clinically used against cancers and neurodegenerative diseases as dietary supplements or pharmaceutic agents. Notably, increasing evidence demonstrates that natural compounds, such as saponins, flavonoids and isothiocyanates, can either induce or inhibit ferroptosis, further expanding their therapeutic potentials. In this review, we highlight current advances of the emerging molecular mechanisms and disease relevance of ferroptosis. We also systematically summarize the regulatory effects of natural phytochemicals on ferroptosis, and clearly indicate that saponins, terpenoids and alkaloids induce ROS- and ferritinophagy-dependent ferroptosis, whereas flavonoids and polyphenols modulate iron metabolism and nuclear factor erythroid 2-related factor 2 (NRF2) signaling to inhibit ferroptosis. Finally, we explore their clinical applications in ferroptosis-related diseases, which may facilitate the development of their dietary usages as nutraceuticals.

Soluble Fe release from iron-bearing clay mineral particles in acid environment and their oxidative potential

Soluble iron from atmospheric aerosol particles has toxicological effects on ambient environment due to their oxidative potential. However, the dissolution process and factors affecting this process are poorly understood. In this study, by solid phase characterization and aqueous dissolution experiments, we investigated the influence of acids, including HCl, H₂SO₄ and HNO₃, and H⁺ concentration on iron dissolution rate, solubility and speciation of iron in chlorite, illite, kaolinite and pyrite. The dissolution of iron-bearing clay minerals, i.e. chlorite, illite and kaolinite, was a multi-stage process with a rapid rate in the initial stage and then decreasing rate in the following stages. In contrast, the regularly crystallized pyrite proceeded with an extremely rapid dissolution rate at very beginning and then remained almost constant. In all acid solutions, the dissolution rate was in the order of pyrite > illite > chlorite > kaolinite. H₂SO₄ was stronger than HCl and HNO₃ in the destruction of mineral structures to release iron, while HNO₃ dissolved more iron in pyrite (FeS₂). High H⁺ concentration easily destroyed the mineral structures to release the structural or interlayer iron, whereas low H⁺ concentration increased the proportion of Fe (II) in clay minerals. Non-linear fitting of continuous dissolution models showed that the iron dissolution rates and iron redox speciation as functions of time were well predicted, with r² > 0.99 for chlorite and illite, and r² > 0.96 for kaolinite. Oxidative potential analysis proved that the dissolved iron possessed a considerable potential to generate reactive oxygen species.

Non-thermal plasma specifically kills oral squamous cell carcinoma cells in a catalytic Fe(II)-dependent manner

Oral cancer accounts for ~2% of all cancers worldwide, and therapeutic intervention is closely associated with quality of life. Here, we evaluated the effects of non-thermal plasma on oral squamous cell carcinoma cells with special reference to catalytic Fe(II). Non-thermal plasma exerted a specific killing effect on oral squamous cell carcinoma cells in comparison to fibroblasts. Furthermore, the effect was dependent on the amounts of catalytic Fe(II), present especially in lysosomes. After non-thermal plasma application, lipid peroxidation occurred and peroxides and mitochondrial superoxide were generated. Cancer cell death by non-thermal plasma was promoted dose-dependently by prior application of ferric ammonium citrate and prevented by desferrioxamine, suggesting the association of ferroptosis. Potential involvement of apoptosis was also observed with positive terminal deoxynucleaotidyl transferase-mediated dUTP nick end labeling and annexin V results. Non-thermal plasma exposure significantly suppressed the migratory, invasive and colony-forming abilities of squamous cell carcinoma cells. The oral cavity is easily observable; therefore, non-thermal plasma can be directly applied to the oral cavity to kill oral squamous cell carcinoma without damaging fibroblasts. In conclusion, non-thermal plasma treatment is a potential therapeutic option for oral cancer.

Urinary ionomic analysis reveals new relationship between minerals and longevity in a Han Chinese population

Human longevity involves genetic, nutritional, environmental and many other factors playing a key role in healthy aging. Previous studies have shown that mineral metabolism and homeostasis are associated with lifespan extension. However, the majority of them have focused on a limited number of elements and ignored the complex relationship between them. In this study, we carried out a network-based approach to investigate the urinary ionome of nonagenarians and centenarians (longevity group) when compared with their biologically unrelated and younger family members (control group) from a Han Chinese population. Several differentially changed elements were identified, almost all of which showed an elevated level in the longevity group. Correlation analysis of the ionome revealed significant element-element interactions in each group. We then divided each group into distinct subgroups according to age ranges, and built the elemental correlation network for each of them. Significant elemental correlations and correlation changes involving all examined elements were identified within or between different subgroups, implying a highly dynamic and complex crosstalk among the elements during human life. Finally, more similar elemental patterns were observed between extremely old and middle-aged people. Overall, our data reveal new relationship between urinary minerals and human longevity, which may extend our understanding of the mechanism of healthy aging.

Fluoride-induced iron overload contributes to hepatic oxidative damage in mouse and the protective role of Grape seed proanthocyanidin extract

Emerging evidence has demonstrated that iron overload plays an important role in oxidative stress in the liver. This study aimed to explore whether fluoride-induced hepatic oxidative stress is associated with iron overload and whether grape seed proanthocyanidin extract (GSPE) alleviates oxidative stress by reducing iron overload. Forty Kunming male mice were randomly divided into 4 groups and treated for 5 weeks with distilled water (control), sodium fluoride (NaF) (100 mg/L), GSPE (400 mg/kg bw), or NaF (100 mg/L) + GSPE (400 mg/kg bw). Mice exposed to NaF showed typical poisoning changes of morphology, increased aspartate aminotransferase and alanine aminotransferase activities in the liver. NaF treatment also increased MDA accumulation, decreased GSH-Px, SOD and T-AOC levels in liver, indicative of oxidative stress. Intriguingly, all these detrimental effects were alleviated by GSPE. Further study revealed that NaF induced disorders of iron metabolism, as manifested by elevated iron level with increased hepcidin but decreased ferroportin expression, which contributed to hepatic oxidative stress. Importantly, the iron dysregulation induced by NaF could be normalized by GSPE. Collectively, these data provide a novel insight into mechanisms underlying fluorosis and highlight the potential of GSPE as a naturally occurring prophylactic treatment for fluoride-induced hepatotoxicity associated with iron overload.

Consequences of Inadequate Intakes of Vitamin A, Vitamin B12, Vitamin D, Calcium, Iron, and Folate in Older Persons

Purpose of Review

This review broadly discusses the consequences of inadequate consumption, by deficit or excess, of selected micronutrients on the quality of life and morbidity during aging, specifically considering increases in life expectancy and the costs of care in the older persons.

Recent Findings

A literature review of the periods 2012 to 2018, focusing on vitamins A, B₁₂, and D, calcium, iron and folate, was completed as these micronutrients are found to significantly affect the aging process. Causation and application of these micronutrients to disorders related to aging are controversial and mixed. This review highlights research needs and controversial points on the role of these micronutrients.

Summary

Micronutrient deficiencies are a common and avoidable contributor to decreased quality of life and healthcare costs in the older persons. Further research is needed to determine adequate intakes and innovative uses, including appropriate thresholds for improved health outcomes for this population.

A Bacterial Component to Alzheimer's-Type Dementia Seen via a Systems Biology Approach that Links Iron Dysregulation and Inflammagen Shedding to Disease

The progression of Alzheimer's disease (AD) is accompanied by a great many observable changes, both molecular and physiological. These include oxidative stress, neuroinflammation, and (more proximal to cognitive decline) the death of neuronal and other cells. A systems biology approach seeks to organize these observed variables into pathways that discriminate those that are highly involved (i.e., causative) from those that are more usefully recognized as bystander effects. We review the evidence that iron dysregulation is one of the central causative pathway elements here, as this can cause each of the above effects. In addition, we review the evidence that dormant, non-growing bacteria are a crucial feature of AD, that their growth in vivo is normally limited by a lack of free iron, and that it is this iron dysregulation that is an important factor in their resuscitation. Indeed, bacterial cells can be observed by ultrastructural microscopy in the blood of AD patients. A consequence of this is that the growing cells can shed highly inflammatory components such as lipopolysaccharides (LPS). These too are known to be able to induce (apoptotic and pyroptotic) neuronal cell death. There is also evidence that these systems interact with elements of vitamin D metabolism. This integrative systems approach has strong predictive power, indicating (as has indeed been shown) that both natural and pharmaceutical iron chelators might have useful protective roles in arresting cognitive decline, and that a further assessment of the role of microbes in AD development is more than highly warranted.

Role of catalytic iron and oxidative stress in nitrofen-induced congenital diaphragmatic hernia and its amelioration by Saireito (TJ-114)

Congenital diaphragmatic hernia (CDH) is a life-threatening neonatal disease that leads to lung hypoplasia and pulmonary hypertension. We recently found that maternal prenatal administration of Saireito (TJ-114) ameliorates fetal CDH in a nitrofen-induced rat model. Here, we studied the role of iron and oxidative stress in neonates of this model and in lung fibroblasts IMR90-SV in association with nitrofen and Saireito. We observed increased immunostaining of 8-hydroxy-2'-deoxyguanosine in the lungs of neonates with CDH, which was ameliorated by maternal Saireito intake. Pulmonary transferrin receptor expression was significantly decreased in both CDH and CDH after Saireito in comparison to normal controls, indicating functional lung immaturity, whereas catalytic Fe(II) and pulmonary DMT1/ferroportin expression remained constant among the three groups. Saireito revealed a dose-dependent scavenging capacity with electron spin resonance spin trapping in vitro against hydroxyl radicals but not against superoxide. Finally, nitrofen revealed dose-dependent cytotoxicity to IMR90-SV cells, accompanied by an increase in oxidative stress, as seen by 5(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate and catalytic Fe(II). Saireito ameliorated all of these in IMR90-SV cells. In conclusion, catalytic Fe(II)-dependent oxidative stress by nitrofen may be the pathogenic cause of CDH, and the antioxidative activity of Saireito is at least partially responsible for improving nitrofen-induced CDH.

Iron and thiol redox signaling in cancer: An exquisite balance to escape ferroptosis

Epidemiological data indicate a constant worldwide increase in cancer mortality, although the age of onset is increasing. Recent accumulation of genomic data on human cancer via next-generation sequencing confirmed that cancer is a disease of genome alteration. In many cancers, the Nrf2 transcription system is activated via mutations either in Nrf2 or Keap1 ubiquitin ligase, leading to persistent activation of the genes with antioxidative functions. Furthermore, deep sequencing of passenger mutations is clarifying responsible cancer causative agent(s) in each case, including aging, APOBEC activation, smoking and UV. Therefore, it is most likely that oxidative stress is the principal initiating factor in carcinogenesis, with the involvement of two essential molecules for life, iron and oxygen. There is evidence based on epidemiological and animal studies that excess iron is a major risk for carcinogenesis, suggesting the importance of ferroptosis-resistance. Microscopic visualization of catalytic Fe(II) has recently become available. Although catalytic Fe(II) is largely present in lysosomes, proliferating cells harbor catalytic Fe(II) also in the cytosol and mitochondria. Oxidative stress catalyzed by Fe(II) is counteracted by thiol systems at different functional levels. Nitric oxide, carbon monoxide and hydrogen (per)sulfide modulate these reactions. Mitochondria generate not only energy but also heme/iron sulfur cluster cofactors and remain mostly dysfunctional in cancer cells, leading to Warburg effects. Cancer cells are under persistent oxidative stress with a delicate balance between catalytic iron and thiols, thereby escaping ferroptosis. Thus, high-dose L-ascorbate and non-thermal plasma as well as glucose/glutamine deprivation may provide additional benefits as cancer therapies over preexisting therapeutics.

Oxidative stress as an iceberg in carcinogenesis and cancer biology

After the conquest of numerous infectious diseases, the average life span for humans has been enormously prolonged, reaching more than 80 years in many developed countries. However, cancer is one of the top causes of death, and its incidence continues to increase in many countries, including Japan. I was deeply influenced during my career as a cancer researcher by the concept of oxidative stress, which was established by Helmut Sies in 1985. I have no doubt that oxidative stress is a major cause of carcinogenesis in humans but that other factors and chemicals modify it. Notably, established cancer cells are more oxidatively stressed than their non-tumorous counterparts are, and this stress may be associated with selection under oxidative stress and, thus, faster proliferation compared with non-tumorous cells. For cancer prevention, both avoidance of specific risks that are associated with genetic susceptibility and decreasing oxidative stress in general should delay carcinogenesis. For cancer therapy, individualization and precision medicine require further research in the future. In addition to the currently burgeoning array of humanized antibodies and protein kinase inhibitors, novel methods to increase oxidative stress only in cancer cells would be helpful.

Potential scenarios leading to ovarian cancer arising from endometriosis

OBJECTIVES

The aim of this review was to highlight recent advances in our understanding of the pathogenesis of malignant transformation of endometriosis.

METHODS

This study reviewed the English-language literature concerning basic science studies of the potential promotion of carcinogenesis.

RESULTS

Repeated episodes of hemorrhage occur in endometriosis at the onset of menstruation. Extracellular hemoglobin, heme, and iron derivatives in endometriosis cause DNA damage and mutations, which create increased cellular susceptibility to oxidant-mediated cell killing. Excess DNA damage and mutations are linked to cell death, but not carcinogenesis. In response to an oxidative and inflammatory microenvironment, endometriotic cells and macrophages secrete antioxidants that control excess oxidative stress in the surrounding environment. Exposure of endometriotic cells to a sublethal level of oxidative stress may lead to carcinogenesis. Macrophages also secrete immunosuppressive factors that lead to promotion of malignant transformation.

DISCUSSION

At least two potential scenarios could result in ovarian cancer arising from endometriosis. The first step: extracellular hemoglobin, heme, and iron cause cellular oxidative damage by promoting reactive oxygen species formation, which results in DNA damage and mutations (ovarian cancer initiation from endometriosis). The second step: cancer progression may be associated with persistent antioxidant production favoring a protumoral microenvironment.

Iron signature in asbestos-induced malignant pleural mesothelioma: A population-based autopsy study

Malignant pleural mesothelioma (MPM) is an aggressive cancer with poor prognosis. The development of MPM is frequently linked to inhalation of asbestos fibers. A genetic component of susceptibility to this disease is suggested by the observation that some individuals develop MPM following lower doses of asbestos exposure, whereas others exposed to higher quantities do not seem to be affected. This hypothesis is supported also by frequent reports of MPM familial clustering. Despite the widely recognized role of iron (Fe) in cellular asbestos-induced pulmonary toxicity, the role of the related gene polymorphisms in the etiology of MPM has apparently not been evaluated. Eighty-six single-nucleotide polymorphisms (SNPs) of 10 Fe-metabolism genes were examined by exploiting formalin-fixed paraffin-embedded postmortem samples from 77 patients who died due to MPM (designated AEM) and compared with 48 who were exposed to asbestos but from died in old age of cause other than asbestos (designated AENM). All subjects showed objective signs of asbestos exposure. Three SNPs, localized in the ferritin heavy polypeptide, transferrin, and hephaestin genes, whose frequencies were distributed differently in AEM and AENM populations, were identified. For ferritin and transferrin the C/C and the G/G genotypes, respectively, representing intronic polymorphisms, were significantly associated with protection against MPM and need to be considered as possible genetic markers of protection. Similarly, the C/C hephaestin SNP, a missense variation of this multicopper ferroxidase encoding gene, may be related, also functionally, with protection against MPM. In conclusion, it is proposed that three Fe metabolism-associated genes, significantly associated with protection against development of MPM, may serve as protective markers for this aggressive tumor.

Ovarian endometriosis-associated stromal cells reveal persistently high affinity for iron

Ovarian endometriosis is a recognized risk for infertility and epithelial ovarian cancer, presumably due to iron overload resulting from repeated hemorrhage. To find a clue for early detection and prevention of ovarian endometriosis-associated cancer, it is mandatory to evaluate catalytic (labile) ferrous iron (catalytic Fe(II)) and to study iron manipulation in ovarian endometriotic lesions. By the use of tissues from women of ovarian endometriosis as well as endometrial tissue from women with and without endometriosis, we for the first time performed histological analysis and cellular detection of catalytic Fe(II) with a specific fluorescent probe (HMRhoNox-M), and further evaluated iron transport proteins in the human specimens and in co-culture experiments using immortalized human eutopic/ectopic endometrial stromal cells (ESCs) in the presence or absence of epithelial cells (EpCs). The amounts of catalytic Fe(II) were higher in ectopic endometrial stromal cells (ecESCs) than in normal eutopic endometrial stromal cells (n-euESCs) both in the tissues and in the corresponding immortalized ESCs. ecESCs exhibited higher transferrin receptor 1 expression both in vivo and in vitro and lower ferroportin expression in vivo than n-euESCs, leading to sustained iron uptake. In co-culture experiments of ESCs with iron-loaded EpCs, ecESCs received catalytic ferrous iron from EpCs, but n-euESCs did not. These data suggest that ecESC play a protective role for cancer-target epithelial cells by collecting excess iron, and that these characteristics are retained in the immortalized ecESCs.

Malignant mesothelioma as an oxidative stress-induced cancer: An update

Malignant mesothelioma (MM) is a relatively rare cancer that occurs almost exclusively following respiratory exposure to asbestos in humans. Its pathogenesis is closely associated with iron overload and oxidative stress in mesothelial cells. On fiber exposure, mesothelial cells accumulate fibers simultaneously with iron, which either performs physical scissor function or catalyzes free radical generation, leading to oxidative DNA damage such as strand breaks and base modifications, followed by activation of intracellular signaling pathways. Chrysotile, per se without iron, causes massive hemolysis and further adsorbs hemoglobin. Exposure to indigestible foreign materials also induces chronic inflammation, involving consistent generation of free radicals and subsequent activation of NALP3 inflammasomes in macrophages. All of these contribute to mesothelial carcinogenesis. Genomic alterations most frequently involve homozygous deletion of INK4A/4B, and other pathways such as Hippo and TGF-β pathways are also affected in MM. Recently, analyses of familial MM sorted out BAP1 as a novel responsible tumor suppressor gene, whose function is not fully elucidated. Five-year survival of mesothelioma is still ~8%, and this cancer is increasing worldwide. Connective tissue growth factor, a secretory protein creating a vicious cycle mediated by β-catenin, has been recognized as a hopeful target for therapy, especially in sarcomatoid subtype. Recent research outcomes related to microRNAs and cancer stem cells also offer additional novel targets for the treatment of MM. Iron reduction as chemoprevention of mesothelioma is helpful at least in an animal preclinical study. Integrated approaches to fiber-induced oxidative stress would be necessary to overcome this currently fatal disease.

Iron-induced damage in cardiomyopathy: oxidative-dependent and independent mechanisms

The high incidence of cardiomyopathy in patients with hemosiderosis, particularly in transfusional iron overload, strongly indicates that iron accumulation in the heart plays a major role in the process leading to heart failure. In this context, iron-mediated generation of noxious reactive oxygen species is believed to be the most important pathogenetic mechanism determining cardiomyocyte damage, the initiating event of a pathologic progression involving apoptosis, fibrosis, and ultimately cardiac dysfunction. However, recent findings suggest that additional mechanisms involving subcellular organelles and inflammatory mediators are important factors in the development of this disease. Moreover, excess iron can amplify the cardiotoxic effect of other agents or events. Finally, subcellular misdistribution of iron within cardiomyocytes may represent an additional pathway leading to cardiac injury. Recent advances in imaging techniques and chelators development remarkably improved cardiac iron overload detection and treatment, respectively. However, increased understanding of the pathogenic mechanisms of iron overload cardiomyopathy is needed to pave the way for the development of improved therapeutic strategies.

Separation of hepatic iron and fat by dual-source dual-energy computed tomography based on material decomposition: an animal study

Objective

To explore the feasibility of dual-source dual-energy computed tomography (DSDECT) for hepatic iron and fat separation in vivo.

Materials and Methods

All of the procedures in this study were approved by the Research Animal Resource Center of Shanghai Ruijin Hospital. Sixty rats that underwent DECT scanning were divided into the normal group, fatty liver group, liver iron group, and coexisting liver iron and fat group, according to Prussian blue and HE staining. The data for each group were reconstructed and post-processed by an iron-specific, three-material decomposition algorithm. The iron enhancement value and the virtual non-iron contrast value, which indicated overloaded liver iron and residual liver tissue, respectively, were measured. Spearman's correlation and one-way analysis of variance (ANOVA) were performed, respectively, to analyze statistically the correlations with the histopathological results and differences among groups.

Results

The iron enhancement values were positively correlated with the iron pathology grading (r = 0.729, p<0.001). Virtual non-iron contrast (VNC) values were negatively correlated with the fat pathology grading (r = −0.642,p<0.0001). Different groups showed significantly different iron enhancement values and VNC values (F = 25.308,p<0.001; F = 10.911, p<0.001, respectively). Among the groups, significant differences in iron enhancement values were only observed between the iron-present and iron-absent groups, and differences in VNC values were only observed between the fat-present and fat-absent groups.

Conclusion

Separation of hepatic iron and fat by dual energy material decomposition in vivo was feasible, even when they coexisted.

Iron and thiols as two major players in carcinogenesis: friends or foes?

Iron is the most abundant metal in the human body and mainly works as a cofactor for proteins such as hemoglobin and various enzymes. No independent life forms on earth can survive without iron. However, excess iron is intimately associated with carcinogenesis by increasing oxidative stress via its catalytic activity to generate hydroxyl radicals. Biomolecules with redox-active sulfhydryl function(s) (thiol compounds) are necessary for the maintenance of mildly reductive cellular environments to counteract oxidative stress, and for the execution of redox reactions for metabolism and detoxification. Involvement of glutathione S-transferase and thioredoxin has long attracted the attention of cancer researchers. Here, I update recent findings on the involvement of iron and thiol compounds during carcinogenesis and in cancer cells. It is now recognized that the cystine/glutamate transporter (antiporter) is intimately associated with ferroptosis, an iron-dependent, non-apoptotic form of cell death, observed in cancer cells, and also with cancer stem cells; the former with transporter blockage but the latter with its stabilization. Excess iron in the presence of oxygen appears the most common known mutagen. Ironically, the persistent activation of antioxidant systems via genetic alterations in Nrf2 and Keap1 also contributes to carcinogenesis. Therefore, it is difficult to conclude the role of iron and thiol compounds as friends or foes, which depends on the quantity/distribution and induction/flexibility, respectively. Avoiding further mutation would be the most helpful strategy for cancer prevention, and myriad of efforts are being made to sort out the weaknesses of cancer cells.

Oxidative stress and labile plasmatic iron in anemic patients following blood therapy

AIM: To determine the plasmatic iron content and evaluate the oxidative stress (OS) markers in subjects receiving blood therapy.

METHODS: Thirty-nine individuals with unspecified anemia receiving blood transfusions and 15 healthy subjects were included in the study. Anemic subjects were divided into three subgrouP: (1) those that received up to five blood transfusions (n = 14); (2) those that received from five to ten transfusions (n = 11); and (3) those that received more than ten transfusions (n = 14). Blood samples were collected by venous arm puncture and stored in tubes containing heparin. The plasma and cells were separated by centrifugation and subsequently used for analyses. Statistical analyses were performed using Kruskal-Wallis analysis of variance followed by Dunn’s multiple comparison tests when appropriate.

RESULTS: The eletrophoretic hemoglobin profiles of the subjects included in this study indicated that no patients presented with hemoglobinopathy. Labile plasmatic iron, ferritin, protein carbonyl, thiobarbituric acid-reactive substances (TBARS) and dichlorofluorescein diacetate oxidation were significantly higher (P < 0.05), whereas total thiol levels were significantly lower (P < 0.05) in transfused subjects compared to controls. Additionally, the activity of catalase, superoxide dismutase and glutathione peroxidase were significantly lower in the transfused subjects (P < 0.05). Antioxidant enzyme activities and total thiol levels were positively correlated (P < 0.05), and negatively correlated with the levels of protein carbonyl and TBARS (P < 0.05). In contrast, protein carbonyl and TBARS were positively correlated (P < 0.05). Altogether, these data confirm the involvement of OS in patients following therapy with repeated blood transfusions.

CONCLUSION: Our data reveal that changes in OS markers are correlated with levels of labile plasmatic iron and ferritin and the number of transfusions.

Genotoxicity and carcinogenicity risk of carbon nanotubes

Novel materials are often commercialized without a complete assessment of the risks they pose to human health because such assessments are costly and time-consuming; additionally, sometimes the methodology needed for such an assessment does not exist. Carbon nanotubes have the potential for widespread application in engineering, materials science and medicine. However, due to the needle-like shape and high durability of multiwalled carbon nanotubes (MWCNTs), concerns have been raised that they may induce asbestos-like pathogenicity when inhaled. Indeed, experiments in rodents supported this hypothesis. Notably, the genetic alterations in MWCNT-induced rat malignant mesothelioma were similar to those induced by asbestos. Single-walled CNTs (SWCNTs) cause mitotic disturbances in cultured cells, but thus far, there has been no report that SWCNTs are carcinogenic. This review summarizes the recent noteworthy publications on the genotoxicity and carcinogenicity of CNTs and explains the possible molecular mechanisms responsible for this carcinogenicity. The nanoscale size and needle-like rigid structure of CNTs appear to be associated with their pathogenicity in mammalian cells, where carbon atoms are major components in the backbone of many biomolecules. Publishing adverse events associated with novel materials is critically important for alerting people exposed to such materials. CNTs still have a bright future with superb economic and medical merits. However, appropriate regulation of the production, distribution and secondary manufacturing processes is required, at least to protect the workers.

Novel chelators for cancer treatment: where are we now?

SIGNIFICANCE

Under normal circumstances, cellular iron levels are tightly regulated due to the potential toxic effects of this metal ion. There is evidence that tumors possess altered iron homeostasis, which is mediated by the perturbed expression of iron-related proteins, for example, transferrin receptor 1, ferritin and ferroportin 1. The de-regulation of iron homeostasis in cancer cells reveals a particular vulnerability to iron-depletion using iron chelators. In this review, we examine the absorption of iron from the gut; its transport, metabolism, and homeostasis in mammals; and the molecular pathways involved. Additionally, evidence for alterations in iron processing in cancer are described along with the perturbations in other biologically important transition metal ions, for example, copper(II) and zinc(II). These changes can be therapeutically manipulated by the use of novel chelators that have recently been shown to be highly effective in terms of inhibiting tumor growth.

RECENT ADVANCES

Such chelators include those of the thiosemicarbazone class that were originally thought to target only ribonucleotide reductase, but are now known to have multiple effects, including the generation of cytotoxic radicals.

CRITICAL ISSUES

Several chelators have shown marked anti-tumor activity in vivo against a variety of solid tumors. An important aspect is the toxicology and the efficacy of these agents in clinical trials.

FUTURE DIRECTIONS

As part of the process of the clinical assessment of the new chelators, an extensive toxicological assessment in multiple animal models is essential for designing appropriate dosing protocols in humans.

Dendritic cell-based immunotherapy in mesothelioma

Mesothelioma is a rare thoracic malignancy with a dismal prognosis. Current treatment options are scarce and clinical outcomes are rather disappointing. Due to the immunogenic nature of mesothelioma, several studies have investigated immunotherapeutic strategies to improve the prognosis of patients with mesothelioma. In the last decade, progress in knowledge of the modulation of the immune system to attack the tumor has been remarkable, but the optimal strategy for immunotherapy has yet to be unraveled. Because of their potent antigen-presenting capacity, dendritic cells are acknowledged as a promising agent in immunotherapeutic approaches in a number of malignancies. This review gives an update and provides a future perspective in which immunotherapy may improve the outcome of mesothelioma therapy.

Distinct affinity of nuclear proteins to the surface of chrysotile and crocidolite

The inhalation of asbestos is a risk factor for the development of malignant mesothelioma and lung cancer. Based on the broad surface area of asbestos fibers and their ability to enter the cytoplasm and nuclei of cells, it was hypothesized that proteins that adsorb onto the fiber surface play a role in the cytotoxicity and carcinogenesis of asbestos fibers. However, little is known about which proteins adsorb onto asbestos. Previously, we systematically identified asbestos-interacting proteins and classified them into eight sub-categories: chromatin/nucleotide/RNA-binding proteins, ribosomal proteins, cytoprotective proteins, cytoskeleton-associated proteins, histones and hemoglobin. Here, we report an adsorption profile of proteins for the three commercially used asbestos compounds: chrysotile, crocidolite and amosite. We quantified the amounts of adsorbed proteins by analyzing the silver-stained gels of sodium dodecyl sulfate-polyacrylamide gel electrophoresis with ImageJ software, using the bands for amosite as a standard. We found that histones were most adsorptive to crocidolite and that chromatin-binding proteins were most adsorptive to chrysotile. The results suggest that chrysotile and crocidolite directly interact with chromatin structure through different mechanisms. Furthermore, RNA-binding proteins preferably interacted with chrysotile, suggesting that chrysotile may interfere with transcription and translation. Our results provide novel evidence demonstrating that the specific molecular interactions leading to carcinogenesis are different between chrysotile and crocidolite.

Bovine lactoferrin ameliorates ferric nitrilotriacetate-induced renal oxidative damage in rats

Milk provides a well-balanced source of amino acids and other ingredients. One of the functional ingredients in milk is lactoferrin (LF). LF presents a wide variety of bioactivities and functions as a radical scavenger in models using iron-ascorbate complexes and asbestos. Human clinical trials of oral LF administration for the prevention of colon polyps have been successful and demonstrated that dietary compounds exhibit direct interactions. However, antioxidative properties of LF in distant organs require further investigation. To study the antioxidant property of LF, we employed bovine lactoferrin (bLF) using the rat model of ferric nitrilotriacetate (Fe-NTA)-induced renal tubular oxidative injury. We fed rats with bLF (0.05%, w/w) in basal chow for 4 weeks and sacrificed them after Fe-NTA treatment. After intraperitoneal administration of 9.0 mg iron/kg Fe-NTA for 4 and 24 h, bLF pretreatment suppressed elevation of serum creatinine and blood urea nitrogen levels. In addition, we observed protective effects against renal oxidative tubular damage and maintenance of antioxidant enzyme activities in the bLF-pretreated group. We thus demonstrated the antioxidative effect of bLF against Fe-NTA-induced renal oxidative injury. These results suggest that LF intake is useful for the prevention of renal tubular oxidative damage mediated by iron.

Iron overload signature in chrysotile-induced malignant mesothelioma

Exposure to asbestos is a risk for malignant mesothelioma (MM) in humans. Among the commercially used types of asbestos (chrysotile, crocidolite, and amosite), the carcinogenicity of chrysotile is not fully appreciated. Here, we show that all three asbestos types similarly induced MM in the rat peritoneal cavity and that chrysotile caused the earliest mesothelioma development with a high fraction of sarcomatoid histology. The pathogenesis of chrysotile-induced mesothelial carcinogenesis was closely associated with iron overload: repeated administration of an iron chelator, nitrilotriacetic acid, which promotes the Fenton reaction, significantly reduced the period required for carcinogenesis; massive iron deposition was found in the peritoneal organs with high serum ferritin; and homozygous deletion of the CDKN2A/2B/ARF tumour suppressor genes, the most frequent genomic alteration in human MM and in iron-induced rodent carcinogenesis, was observed in 92.6% of the cases studied with array-based comparative genomic hybridization. The induced rat MM cells revealed high expression of mesoderm-specific transcription factors, Dlx5 and Hand1, and showed an iron regulatory profile of active iron uptake and utilization. These data indicate that chrysotile is a strong carcinogen when exposed to mesothelia, acting through the induction of local iron overload. Therefore, an intervention to remove local excess iron might be a strategy to prevent MM after asbestos exposure.

Iron and genome stability: an update

Iron is an essential micronutrient which is required in a relatively narrow range for maintaining metabolic homeostasis and genome stability. Iron participates in oxygen transport and mitochondrial respiration as well as in antioxidant and nucleic acid metabolism. Iron deficiency impairs these biological pathways, leading to oxidative stress and possibly carcinogenesis. Iron overload has been linked to genome instability as well as to cancer risk increase, as seen in hereditary hemochromatosis. Iron is an extremely reactive transition metal that can interact with hydrogen peroxide to generate hydroxyl radicals that form the 8-hydroxy-guanine adduct, cause point mutations as well as DNA single and double strand breaks. Iron overload also induces DNA hypermethylation and can reduce telomere length. The current Recommended Dietary Allowances (RDA) for iron, according with Institute of Medicine Dietary Reference Intake (DRI), is based in the concept of preventing anemia, and ranges from 7mg/day to 18mg/day depending on life stage and gender. Pregnant women need 27mg/day. The maximum safety level for iron intake, the Upper Level (UL), is 40-45mg/day, based on the prevention of gastrointestinal distress associated to high iron intakes. Preliminary evidence indicates that 20mg/day iron, an intake slightly higher than the RDA, may reduce the risk of gastrointestinal cancer in the elderly as well as increasing genome stability in lymphocytes of children and adolescents. Current dietary recommendations do not consider the concept of genome stability which is of concern because damage to the genome has been linked to the origin and progression of many diseases and is the most fundamental pathology. Given the importance of iron for homeostasis and its potential influence over genome stability and cancer it is recommended to conduct further studies that conclusively define these relationships.

Impaired iron status in aging research

Aging is associated with disturbances in iron metabolism and storage. During the last decade, remarkable progress has been made toward understanding their cellular and molecular mechanisms in aging and age-associated diseases using both cultured cells and animal models. The field has moved beyond descriptive studies to potential intervention studies focusing on iron chelation and removal. However, some findings remain controversial and inconsistent. This review summarizes important features of iron dyshomeostasis in aging research with a particular emphasis on current knowledge of the mechanisms underlying age-associated disorders in rodent models.

Iron overload-induced rat liver injury: Involvement of protein tyrosine nitration and the effect of baicalin

Baicalin has been reported to protect against liver injury in iron-overload mice, however, the mechanisms underlying the hepatoprotective properties of baicalin are poorly understood. In this study, we systematically studied the protective effect of baicalin on iron overload induced liver injury, as well as the underlying mechanism based on nitrative stress in rat model. We found that when iron overload rats (500mgiron/kg) were fed baicalin-containing diet (0.3% and 1% w/w) for 45days, baicalin dose dependently protected against iron overload induced liver injury, including alleviation of hepatic pathological damage, decrease of SOD activity, iron content, carbonyl content, and the thiobarbituric acid-reactive substances level in hepatic tissues. It also increased serum iron content, SH content and GPx activity, decreased serum ALT and AST activities. Immunohistochemistry and immunoprecipitation analysis revealed that baicalin could also inhibit iron overload induced protein tyrosine nitration in liver. Moreover, in iron overload rat liver, we found that baicalin decreased the iron overload increased level of glutathione-S-transferases (GSTs) expression, oxidation and nitration. These results suggest that not only oxidative stress, but also nitrative stress, is involved in iron overload induced liver injury, and the underlying mechanism might partially relate to the involvement of GSTs expression and post-translational modification. Baicalin can effectively prevent iron overload caused abnormality and can be a candidate medicine for iron overload diseases.

Asbestos induces reduction of tumor immunity

Asbestos-related cancers such as malignant mesothelioma and lung cancer are an important issue in the world. There are many conflicts concerning economical considerations and medical evidence for these cancers and much confusion regarding details of the pathological mechanisms of asbestos-induced cancers. For example, there is uncertainty concerning the degree of danger of the iron-absent chrysotile compared with iron-containing crocidolite and amosite. However, regarding bad prognosis of mesothelioma, medical approaches to ensure the recognition of the biological effects of asbestos and the pathological mechanisms of asbestos-induced carcinogenesis, as well as clinical trials to detect the early stage of mesothelioma, should result in better preventions and the cure of these malignancies. We have been investigating the immunological effects of asbestos in relation to the reduction of tumor immunity. In this paper, cellular and molecular approaches to clarify the immunological effects of asbestos are described, and all the findings indicate that the reduction of tumor immunity is caused by asbestos exposure and involvement in asbestos-induced cancers. These investigations may not only allow the clear recognition of the biological effects of asbestos, but also present a novel procedure for early detection of previous asbestos exposure and the presence of mesothelioma as well as the chemoprevention of asbestos-related cancers.

[Mechanisms of asbestos-induced carcinogenesis]

Several types of fibrous stone called asbestos have been an unexpected cause of human cancer in the history. This form of mineral is considered precious in that they are heat-, friction-, and acid-resistant, are obtained easily from mines, and can be modified to any form with many industrial merits. However, it became evident that the inspiration of asbestos causes a rare cancer called malignant mesothelioma. Because of the long incubation period, the peak year for malignant mesothelioma is expected to be 2025 in Japan. Thus, it is necessary to elucidate the mechanisms of asbestos-induced mesothelial carcinogenesis. In this review, we summarize the cutting edge results of our 5-year project funded by a MEXT grant, in which local iron deposition and the characteristics of mesothelial cells are the key issues.