Apo- and holo-transferrin differentially interact with hephaestin and ferroportin in a novel mechanism of cellular iron release regulation

A multi-component paclitaxel -loaded β-elemene nanoemulsion by transferrin modification enhances anti-non-small-cell lung cancer treatment

A multi-component paclitaxel (PTX) -loaded β-elemene nanoemulsion by transferrin modification (Tf-PE-MEs) was developed to enhance non-small-cell lung cancer (NSCLC) treatment. After transferrin modification, the particle size of Tf-PE-MEs was (14.87 ± 1.84) nm, and the zeta potential was (-10.19 ± 0.870) mV, respectively. In vitro experiments showed that Tf-PE-MEs induced massive apoptosis in A549 cells, indicating that it had significant cytotoxicity to A549 cells. Through transferrin modification, Tf-PE-MEs accumulated at the tumor site efficiently with overexpressed transferrin receptor (TfR) on the surface of A549 cells. This will allow increasing PTX and β-elemene concentration in the target cells, enhancing the therapeutic effect. Compared to PTX alone, Tf-PE-MEs displayed good anti-tumor efficacy and diminished systemic toxicity in vivo studies. With favourable therapeutic potential, this study provides a new strategy for the combined anticancer treatment of non-small cell lung cancer.

Trace metals and astrocytes physiology and pathophysiology

Several trace metals, including iron, copper, manganese and zinc are essential for normal function of the nervous system. Both deficiency and excessive accumulation of these metals trigger neuropathological developments. The central nervous system (CNS) is in possession of dedicated homeostatic system that removes, accumulates, stores and releases these metals to fulfil nervous tissue demand. This system is mainly associated with astrocytes that act as dynamic reservoirs for trace metals, these being a part of a global system of CNS ionostasis. Here we overview physiological and pathophysiological aspects of astrocyte-cantered trace metals regulation.

Brain iron acquisition depends on age and sex in iron-deficient mice

Adequate and timely delivery of iron is essential for brain development. The uptake of transferrin-bound (Tf) iron into the brain peaks at the time of myelination, whereas the recently discovered H-ferritin (FTH1) transport of iron into the brain continues to increase beyond the peak in myelination. Here, we interrogate the impact of dietary iron deficiency (ID) on the uptake of FTH1- and Tf-bound iron. In the present study, we used C57BL/6J male and female mice at a developing (post-natal day (PND) 15) and adult age (PND 85). In developing mice, ID results in increased iron delivery from both FTH1 and Tf for both males and females. The amount of iron uptake from FTH1 was higher than the Tf and this difference between the iron delivery was much greater in females. In contrast, in the adult model, ID was associated with increased brain iron uptake by both FTH1 and Tf but only in the males. There was no increased uptake from either protein in the females. Moreover, transferrin receptor expression on the microvasculature as well as whole brain iron, and H and L ferritin levels revealed the male brains became iron deficient but not the female brains. Last, under normal dietary conditions, 55 Fe uptake was higher in the developing group from both delivery proteins than in the adult group. These results indicate that there are differences in iron acquisition between the developing and adult brain for FTH1 and Tf during nutritional ID and demonstrate a level of regulation of brain iron uptake that is age and sex-dependent.

Structural insights into ferroportin mediated iron transport

Iron is a vital trace element for almost all organisms, and maintaining iron homeostasis is critical for human health. In mammals, the only known gatekeeper between intestinally absorbed iron and circulatory blood plasma is the membrane transporter ferroportin (Fpn). As such, dysfunction of Fpn or its regulation is a key driver of iron-related pathophysiology. This review focuses on discussing recent insights from high-resolution structural studies of the Fpn protein family. While these studies have unveiled crucial details of Fpn regulation and structural architecture, the associated functional studies have also at times provided conflicting data provoking more questions than answers. Here, we summarize key findings and illuminate important remaining questions and contradictions.

Normal and dysregulated crosstalk between iron metabolism and erythropoiesis

Erythroblasts possess unique characteristics as they undergo differentiation from hematopoietic stem cells. During terminal erythropoiesis, these cells incorporate large amounts of iron in order to generate hemoglobin and ultimately undergo enucleation to become mature red blood cells, ultimately delivering oxygen in the circulation. Thus, erythropoiesis is a finely tuned, multifaceted process requiring numerous properly timed physiological events to maintain efficient production of 2 million red blood cells per second in steady state. Iron is required for normal functioning in all human cells, the erythropoietic compartment consuming the majority in light of the high iron requirements for hemoglobin synthesis. Recent evidence regarding the crosstalk between erythropoiesis and iron metabolism sheds light on the regulation of iron availability by erythroblasts and the consequences of insufficient as well as excess iron on erythroid lineage proliferation and differentiation. In addition, significant progress has been made in our understanding of dysregulated iron metabolism in various congenital and acquired malignant and non-malignant diseases. Finally, we report several actual as well as theoretical opportunities for translating the recently acquired robust mechanistic understanding of iron metabolism regulation to improve management of patients with disordered erythropoiesis, such as anemia of chronic inflammation, β-thalassemia, polycythemia vera, and myelodysplastic syndromes.

Membrane Transporters Involved in Iron Trafficking: Physiological and Pathological Aspects

Iron is an essential transition metal for its involvement in several crucial biological functions, the most notable being oxygen storage and transport. Due to its high reactivity and potential toxicity, intracellular and extracellular iron levels must be tightly regulated. This is achieved through transport systems that mediate cellular uptake and efflux both at the level of the plasma membrane and on the membranes of lysosomes, endosomes and mitochondria. Among these transport systems, the key players are ferroportin, the only known transporter mediating iron efflux from cells; DMT1, ZIP8 and ZIP14, which on the contrary, mediate iron influx into the cytoplasm, acting on the plasma membrane and on the membranes of lysosomes and endosomes; and mitoferrin, involved in iron transport into the mitochondria for heme synthesis and Fe-S cluster assembly. The focus of this review is to provide an updated view of the physiological role of these membrane proteins and of the pathologies that arise from defects of these transport systems.