New perspectives on the molecular basis of the interaction between oxygen homeostasis and iron metabolism

Ironing out macrophages in atherosclerosis

<p indent="0mm">The most common cause of death worldwide is atherosclerosis and related cardiovascular disorders. Macrophages are important players in the pathogenesis of atherosclerosis and perform critical functions in iron homeostasis due to recycling iron by phagocytosis of senescent red blood cells and regulating iron availability in the tissue microenvironment. With the growth of research on the "iron hypothesis" of atherosclerosis, macrophage iron has gradually become a hotspot in the refined iron hypothesis. Macrophages with the M1, M2, M(Hb), Mox, and other phenotypes have been defined with different iron-handling capabilities related to the immune function and immunometabolism of macrophages, which influence the progression of atherosclerosis. In this review, we focus on macrophage iron and its effects on the development of atherosclerosis. We also cover the contradictory discoveries and propose a possible explanation. Finally, pharmaceutical modulation of macrophage iron is discussed as a promising target for atherosclerosis therapy.</p>.

Iron metabolism and iron deficiency anemia in women

Iron deficiency (ID) and iron deficiency anemia (IDA) are highly prevalent among women across their reproductive age. An iron-deficient state has been associated with and causes a number of adverse health consequences, affecting all aspects of the physical and emotional well-being of women. Heavy menstrual bleeding, pregnancy, and the postpartum period are the major causes of ID and IDA. However, despite the high prevalence and the impact on quality of life, ID and IDA among women in their reproductive age is still underdiagnosed and undertreated. In this chapter we summarized the iron metabolism and the diagnosis and treatment of ID and IDA in women.

Iron Mining for Erythropoiesis

Iron is necessary for essential processes in every cell of the body, but the erythropoietic compartment is a privileged iron consumer. In fact, as a necessary component of hemoglobin and myoglobin, iron assures oxygen distribution; therefore, a considerable amount of iron is required daily for hemoglobin synthesis and erythroid cell proliferation. Therefore, a tight link exists between iron metabolism and erythropoiesis. The liver-derived hormone hepcidin, which controls iron homeostasis via its interaction with the iron exporter ferroportin, coordinates erythropoietic activity and iron homeostasis. When erythropoiesis is enhanced, iron availability to the erythron is mainly ensured by inhibiting hepcidin expression, thereby increasing ferroportin-mediated iron export from both duodenal absorptive cells and reticuloendothelial cells that process old and/or damaged red blood cells. Erythroferrone, a factor produced and secreted by erythroid precursors in response to erythropoietin, has been identified and characterized as a suppressor of hepcidin synthesis to allow iron mobilization and facilitate erythropoiesis.

Hypoxia represses early responses of prostate and renal cancer cells to YM155 independent of HIF-1α and HIF-2α

The imidazolium compound Sepantronium Bromide (YM155) successfully promotes tumor regression in various pre-clinical models but has shown modest responses in human clinical trials. We provide evidence to support that the hypoxic milieu of tumors may limit the clinical usefulness of YM155. Hypoxia (1% O2) strongly (>16-fold) represses the cytotoxic activity of YM155 on prostate and renal cancer cells in vitro. Hypoxia also represses all early signaling responses associated with YM155, including activation of AMPK and retinoblastoma protein (Rb), inactivation of the mechanistic target of rapamycin complex 1 (mTORC1), inhibition of phospho-ribosomal protein S6 (rS6), and suppression of the expression of Cyclin Ds, Mcl-1 and Survivin. Cells pre-incubated with hypoxia for 24 ​h are desensitized to YM155 even when they are treated with YM155 under atmospheric oxygen conditions, supporting that cells at least temporarily retain hypoxia-induced resistance to YM155. We tested the role of hypoxia-inducible factor (HIF)-1α and HIF-2α in the hypoxia-induced resistance to YM155 by comparing responses of YM155 in VHL-proficient versus VHL-deficient RCC4 and 786-O renal cancer cells and silencing HIF expression in PC-3 prostate cancer cells. Those studies suggested that hypoxia-induced resistance to YM155 occurs independent of HIF-1α and HIF-2α. Moreover, the hypoxia mimetics deferoxamine and dimethyloxalylglycine, which robustly induce HIF-1α levels in PC-3 ​cells under atmospheric oxygen, did not diminish their early cellular responses to YM155. Collectively, our data support that hypoxia induces resistance of cells to YM155 through a HIF-1α and HIF-2α-independent mechanism. We hypothesize that a hypothetical hypoxia-inducer factor (HIF-X) represses early signaling responses to YM155.

Ironing out Macrophage Immunometabolism

Over the last decade, increasing evidence has reinforced the key role of metabolic reprogramming in macrophage activation. In addition to supporting the specific immune response of different subsets of macrophages, intracellular metabolic pathways also directly control the specialized effector functions of immune cells. In this context, iron metabolism has been recognized as an important component of macrophage plasticity. Since macrophages control the availability of this essential metal, changes in the expression of genes coding for the major proteins of iron metabolism may result in different iron availability for the macrophage itself and for other cells in the microenvironment. In this review, we discuss how macrophage iron can also play a role in immunometabolism.

Iron Metabolism in Liver Cancer Stem Cells

Cancer stem cells (CSC) which have been identified in several tumors, including liver cancer, represent a particular subpopulation of tumor cells characterized by properties similar to those of adult stem cells. Importantly, CSC are resistant to standard therapies, thereby leading to metastatic dissemination and tumor relapse. Given the increasing evidence that iron homeostasis is deregulated in cancer, here we describe the iron homeostasis alterations in cancer cells, particularly in liver CSC. We also discuss two paradoxically opposite iron manipulation-strategies for tumor therapy based either on iron chelation or iron overload-mediated oxidant production leading to ferroptosis. A better understanding of iron metabolism modifications occurring in hepatic tumors and particularly in liver CSC cells may offer new therapeutic options for this cancer, which is characterized by increasing incidence and unfavorable prognosis.

The Impact of Trace Minerals on Bone Metabolism

Bone is a metabolically active tissue that responds to alterations in dietary intake and nutritional status. It is ~ 35% protein, mostly collagen which provides an organic scaffolding for bone mineral. The mineral is the remaining ~ 65% of bone tissue and composed mostly of calcium and phosphate in a form that is structurally similar to mineral within the apatite group. The skeletal tissue is constantly undergoing turnover through resorption by osteoclasts coupled with formation by osteoblasts. In this regard, the overall bone balance is determined by the relative contribution of each of these processes. In addition to macro minerals such as calcium, phosphorus, and magnesium which have well-known roles in bone health, trace elements such as boron, iron, zinc, copper, and selenium also impact bone metabolism. Effects of trace elements on skeletal metabolism and tissue properties may be indirect through regulation of macro mineral metabolism, or direct by affecting osteoblast or osteoclast proliferation or activity, or finally through incorporation into the bone mineral matrix. This review focuses on the skeletal impact of the following trace elements: boron, iron, zinc, copper, and selenium, and overviews the state of the evidence for each of these minerals.

[Hfeprotein impact on iron metabolism]

Hereditary hemochromatosis type 1 is an autosomal recessive disorder caused by HFE gene mutations, which is an iron homeostasis metabolism controlling co-factor. Adults with male predomination present with clinical symptoms derived by iron overload in organs. The phenotype expression is individual with an influence of individual and environmental factors. Despite the fact that HFE variants are widespread, its impact still remains unknown. The article reviews the literature considering the role of HFE gene mutations regarding its impact in children.

Dual Role of ROS as Signal and Stress Agents: Iron Tips the Balance in favor of Toxic Effects

Iron is essential for life, while also being potentially harmful. Therefore, its level is strictly monitored and complex pathways have evolved to keep iron safely bound to transport or storage proteins, thereby maintaining homeostasis at the cellular and systemic levels. These sequestration mechanisms ensure that mildly reactive oxygen species like anion superoxide and hydrogen peroxide, which are continuously generated in cells living under aerobic conditions, keep their physiologic role in cell signaling while escaping iron-catalyzed transformation in the highly toxic hydroxyl radical. In this review, we describe the multifaceted systems regulating cellular and body iron homeostasis and discuss how altered iron balance may lead to oxidative damage in some pathophysiological settings.