The Effects of Treatment on Serum Hepcidin and Iron Homeostasis in HIV-1-Infected In-dividuals

Background: Hepcidin is the principal regulator of iron absorption and its tissue distribution. Its correlation with iron homeostasis in individuals infected with human immunodeficiency virus type-1 (HIV-1) treated with different regimens of highly active antiretroviral therapy (HAART) was investigated. Methods: Serum hepcidin levels were determined in 448 volunteers. Of these, 372 were HIV-1-infected individuals, and 93 did not receive HAART (ART-naïve) while 279 received HAART consisting of a non-nucleoside reverse transcriptase inhibitor (NNRTI-based) and protease inhibitors (PI-based);both were used in association with a nucleoside reverse transcriptase inhibitor (NRTI). Seventy-six additional HIV-1 seronegative individuals were enrolled in the study. The following parameters were quantified: hematological parameters, iron biomarkers and markers of infection (CD4+ and CD8+ T-cells), and HIV-1 RNA (viral load). Results: Serum hepcidin, iron and ferritin levels, as well as the marker of infection, CD4+ T-cells, were significantly lower in the ART-naïve group compared with other groups. Additionally, transferrin saturation, iron binding capacity, hemoglobin level and erythrocyte level were not significantly different, and anemia was not observed in the different groups. Conclusions: HIV-1 infection affected serum hepcidin, iron and ferritin levels in the ART-naïve group, and the different HAART regimens restored the levels of hepcidin and iron homeostasis in HIV-1-infected individuals who have undetectable HIV-1 RNA levels.

An Arabidopsis ABC Transporter Mediates Phosphate Deficiency-Induced Remodeling of Root Architecture by Modulating Iron Homeostasis in Roots

The remodeling of root architecture is a major developmental response of plants to phosphate （Pi） deficiency and is thought to enhance a plant＇s ability to forage for the available Pi in topsoil. The underlying mechanism controlling this response, however, is poorly understood. In this study, we identified an Arabidopsis mutant, hps 10 （hypersensitive to Pi starvation 10）, which is morphologically normal under Pi sufficient condition but shows increased inhibition of primary root growth and enhanced production of lateral roots under Pi defi- ciency, hpslO is a previously identified allele （als3-3） of the ALUMINUM SENSITIVE3 （ALS3） gene, which is involved in plant tolerance to aluminum toxicity. Our results show that ALS3 and its interacting protein AtSTAR1 form an ABC transporter complex in the tonoplast. This protein complex mediates a highly electro- genic transport in Xenopus oocytes. Under Pi deficiency, als3 accumulates higher levels of Fe3＋ in its roots than the wild type does. In Arabidopsis, LPR1 （LOW PHOSPHATE ROOT1） and LPR2 encode ferroxidases, which when mutated, reduce Fe3＋ accumulation in roots and cause root growth to be insensitive to Pi defi- ciency. Here, we provide compelling evidence showing that ALS3 cooperates with LPR1/2 to regulate Pi deficiency-induced remodeling of root architecture by modulating Fe homeostasis in roots.

Biochemistry of mammalian ferritins in the regulation of cellular iron homeostasis and oxidative responses

Ferritin,an iron-storage protein,regulates cellular iron metabolism and oxidative stress.The ferritin structure is characterized as a spherical cage,inside which large amounts of iron are deposited in a safe,compact and bioavailable form.All ferritins readily catalyze Fe(II)oxidation by peroxides at the ferroxidase center to prevent free Fe(II)from participating in oxygen free radical formation via Fenton chemistry.Thus,ferritin is generally recognized as a cytoprotective stratagem against intracellular oxidative damage.The expression of cytosolic ferritins is usually regulated by iron status and oxidative stress at both the transcriptional and post-transcriptional levels.The mechanism of ferritin-mediated iron recycling is far from clarified,though nuclear receptor co-activator 4(NCOA4)was recently identified as a cargo receptor for ferritin-based lysosomal degradation.Cytosolic ferritins are heteropolymers assembled by H-and L-chains in different proportions.The mitochondrial ferritins are homopolymers and distributed in restricted tissues.They play protective roles in mitochondria where heme-and Fe/S-enzymes are synthesized and high levels of ROS are produced.Genetic ferritin disorders are mainly related to the L-chain mutations,which generally cause severe movement diseases.This review is focused on the biochemistry and function of mammalian intracellular ferritin as the major iron-storage and anti-oxidation protein.

Disruption of iron homeostasis and resultant health effects upon exposure to various environmental pollutants:A critical review

Environmental pollution has become one of the greatest problems in the world, and the concerns about environmental pollutants released by human activities from agriculture and industrial production have been continuously increasing. Although intense efforts have been made to understand the health effects of environmental pollutants, most studies have only focused on direct toxic effects and failed to simultaneously evaluate the long-term adaptive, compensatory and secondary impacts on health. Burgeoning evidence suggests that environmental pollutants may directly or indirectly give rise to disordered element homeostasis, such as for iron. It is crucially important to maintain concerted cellular and systemic iron metabolism. Otherwise, disordered iron metabolism would lead to cytotoxicity and increased risk for various diseases, including cancers. Thus, study on the effects of environmental pollutants upon iron homeostasis is urgently needed. In this review, we recapitulate the available findings on the direct or indirect impacts of environmental pollutants, including persistent organic pollutants（POPs）, heavy metals and pesticides, on iron homeostasis and associated adverse health problems. In view of the unanswered questions, more efforts are warranted to investigate the disruptive effects of environmental pollutants on iron homeostasis and consequent toxicities.

New insights into disruption of iron homeostasis by environmental pollutants

Among the numerous health conditions environmental pollutants can cause, chronic exposure to pollutants including persistent organic pollutants（POPs） and heavy metals has been shown to disturb a specific biological homeostatic process, the iron metabolism in human body. Disorders of iron metabolism are among the common diseases of humans and encompass a broad spectrum of diseases with different clinical manifestations, ranging from anemia to iron overload, and possibly to neurodegenerative diseases and cancer.Hepcidin–ferroportin（FPN） signaling is one of the key mechanisms responsible for iron supply, utilization, recycling, and storage, and recent studies demonstrated that exposure to environmental pollutants including POPs and heavy metals could lead to disruption of the hepcidin–FPN axis along with disordered systemic iron homeostasis and diseases. This article introduces and highlights the accompanying review article by Drs. Xu and Liu in this journal, which elaborates in detail the adverse effects of environmental pollutants on iron metabolism, and the mechanisms responsible for these toxicological outcomes. It also points out the knowledge gaps still existing in this subject matter. Research that will fill these gaps will improve our understanding of the issue and provide useful information to prevent or treat diseases induced by environmental pollutants.

Phylogenetic and sequence analyses of insect transferrins suggest that only transferrin 1 has a role in iron homeostasis

Iron is essential to life,but surprisingly little is known about how iron is managed in nonvertebrate animals.In mammals,the well-characterized transferrins bind iron and are involved in iron transport or immunity,whereas other members of the transferrin family do not have a role in iron homeostasis.In insects,the functions of transferrins are still poorly understood.The goals of this project were to identify the transferrin genes in a diverse set of insect species,resolve the evolutionary relationships among these genes,and predict which of the transferrins are likely to have a role in iron homeostasis.Our phylogenetic analysis of transferrins from 16 orders of insects and two orders of noninsect hexapods demonstrated that there are four orthologous groups of insect transferrins.Our analysis suggests that transferrin 2 arose prior to the origin of insects,and transferrins/,i,and 4 arose early in insect evolution.Primary sequence analysis of each of the insect transferrins was used to predict signal peptides,carboxyl-terminal transmembrane regions,GPI-anchors,and iron binding.Based on this analysis,we suggest that transferrins 2,and 4 are unlikely to play a major role in iron homeostasis.In contrast,the transferrin 1 orthologs are predicted to be secreted,soluble,iron-binding proteins.We conclude that transferrin 1 orthologs are the most likely to play an important role in iron homeostasis.Interestingly,it appears that the louse,aphid,and thrips lineages have lost the transferrin 1 gene and,thus,have evolved to manage iron without transferrins.

The correlation between iron homeostasis and telomere maintenance

Eukaryotic organisms require iron to sustain genome stability, cell proliferation and development. Chromosomes contain telomeres to ensure complete replications and avoid fusions. Numerous evidences reveal that iron can act directly or indirectly on telomere maintenance. In human, disruption of systemic or cellular iron homeostasis is reportedly to cause serious health problems such as iron overload （hereditary hemochromatosis）, iron deficiency anemia, carcinogenesis and acceleration of aging process. These processes commonly associate with abnormal telomere length. Additionally, cells containing mutations in iron-containing proteins such as DNA polymerases （Pola, g, and ~）, regulator of telomere length 1 （RTEL1） and the small subunit of ribonucleotide reductases （RNRs） have abnormal telomere length. This review briefly summarizes current understandings on iron homeostasis and telomere maintenance in cancer and aging process, followed by discussing their direct and indirect correlation, and the possible regulatory mechanisms.

Ferroptosis mechanism and Alzheimer's disease

Regulated cell death is a genetically determined form of programmed cell death that commonly occurs during the development of living organisms.This process plays a crucial role in modulating homeostasis and is evolutionarily conserved across a diverse range of living organisms.Ferroptosis is a classic regulatory mode of cell death.Extensive studies of regulatory cell death in Alzheimer’s disease have yielded increasing evidence that fe rroptosis is closely related to the occurrence,development,and prognosis of Alzheimer’s disease.This review summarizes the molecular mechanisms of ferroptosis and recent research advances in the role of ferro ptosis in Alzheimer’s disease.Our findings are expected to serve as a theoretical and experimental foundation for clinical research and targeted therapy for Alzheimer’s disease.

Inhibition of Sirtuin 2 exerts neuroprotection in aging rats with increased neonatal iron intake

Impaired iron homeostasis may cause damage to dopaminergic neurons and is critically involved in the pathogenesis of Parkinson’s disease. At present, very little is understood about the effect of neonatal iron intake on behavior in aging animals. Therefore, we hypothesized that increased neonatal iron intake would result in signiifcant behavior abnormalities and striatal dopamine depletion during aging, and Sirtuin 2 contributes to the age-related neurotoxicity. In the present study, we observed that neonatal iron intake （120 μg/g per day） during postnatal days 10–17 resulted in significant behavior abnormalities and striatal dopamine depletion in aging rats. Furthermore, after AK-7 （a selective Sirtuin 2 inhibitor） was injected into the substantia nigra at postnatal 540 days and 570 days （5 μg/side per day）, striatal dopamine depletion was signiifcant-ly diminished and behavior abnormality was improved in aging rats with neonatal iron intake. Experimental ifndings suggest that increased neonatal iron intake may result in Parkinson’s dis-ease-like neurochemical and behavioral deifcits with aging, and inhibition of Sirtuin 2 expression may be a neuroprotective measure in Parkinson’s disease.

Ferroptosis:a critical player and potential therapeutic target in traumatic brain injury and spinal cord injury

Ferroptosis,a new non-necrotizing programmed cell death(PCD),is driven by iron-dependent phospholipid peroxidation.Ferroptosis plays a key role in secondary traumatic brain injury and secondary spinal cord injury and is closely related to inflammation,immunity,and chronic injuries.The inhibitors against ferroptosis effectively improve iron homeostasis,lipid metabolism,redox stabilization,neuronal remodeling,and functional recovery after trauma.In this review,we elaborate on the latest molecular mechanisms of ferroptosis,emphasize its role in secondary central nervous trauma,and update the medicines used to suppress ferroptosis following injuries.

Two NPF transporters mediate iron long-distance transport and homeostasis in Arabidopsis

Iron(Fe)transport and reallocation are essential to Fe homeostasis in plants,but it is unclear how Fe homeostasis is regulated,especially under stress.Here we report that NPF5.9 and its close homolog NPF5.8 redundantly regulate Fe transport and reallocation in Arabidopsis.NPF5.9 is highly upregulated in response to Fe deficiency.NPF5.9 expresses preferentially in vasculature tissues and localizes to the trans-Golgi network,and NPF5.8 showed a similar expression pattern.Long-distance Fe transport and allocation into aerial parts was significantly increased in NPF5.9-overexpressing lines.In the double mutant npf5.8 npf5.9,Fe loading in aerial parts and plant growth were decreased,which were partially rescued by Fe supplementation.Further analysis showed that expression of PYE,the negative regulator for Fe homeostasis,and its downstream target NAS4 were significantly altered in the double mutant.NPF5.9 and NPF5.8 were shown to also mediate nitrate uptake and transport,although nitrate and Fe application did not reciprocally affect each other.Our findings uncovered the novel function of NPF5.9 and NPF5.8 in long-distance Fe transport and homeostasis,and further indicated that they possibly mediate nitrate transport and Fe homeostasis independently in Arabidopsis.

Molecular processes in iron and zinc homeostasis and their modulation for biofortification in rice

More than a billion people suffer from iron or zinc deficiencies globally. Rice(Oryza sativa L.) iron and zinc biofortification; i.e., intrinsic iron and zinc enrichment of rice grains, is considered the most effective way to tackle these deficiencies. However, rice iron biofortification, by means of conventional breeding, proves difficult due to lack of sufficient genetic variation. Meanwhile,genetic engineering has led to a significant increase in the iron concentration along with zinc concentration in rice grains. The design of impactful genetic engineering biofortification strategies relies upon vast scientific knowledge of precise functions of different genes involved in iron and zinc uptake, translocation and storage. In this review, we present an overview of molecular processes controlling iron and zinc homeostasis in rice. Further,the genetic engineering approaches adopted so far to increase the iron and zinc concentrations in polished rice grains are discussed in detail, highlighting the limitations and/or success of individual strategies. Recent insight suggests that a few genetic engineering strategies are commonly utilized for elevating iron and zinc concentrations in different genetic backgrounds, and thus, it is of great importance to accumulate scientific evidence for diverse genetic engineering strategies to expand the pool of options for biofortifying farmer-preferred cultivars.

Requirement and Functional Redundancy of Ib Subgroup bHLH Proteins for Iron Deficiency Responses and Uptake in Arabidopsis thaliana

The Ib subgroup of the bHLH gene family in Arabidopsis contains four members （AtbHLH38, AtbHLH39, AtbHLHIO0, and AtbHLH101）. AtbHLH38 and AtbHLH39 were previously confirmed to interact with FER-like iron deft-ciency induced transcription factor （FIT）, directly functioning in activation of the expression of ferric-chelate reductase FRO2 and high-affinity ferrous iron transporter IRT1. In this work, we characterized the functions of AtbHLH100 and AtbHLH101 in the regulation of the iron-deficiency responses and uptake. Yeast two-hybrid analysis and bimolecular fluorescence complementation assay demonstrated that both AtbHLH100 and AtbHLH101 could interact with FIT. Dual expression of either AtbHLH100 or AtbHLH101 with FIT in yeast cells activated the GUS expression driven by promoters of FRO2 and IRT1. The plants overexpressing FIT together with AtbHLHI01 showed constitutive expression of FRO2 and IRT1 in roots, and accumulated more iron in shoots. Further, the single, double, and triple knockout mutants of AtbHLH38, AtbHLH39, AtbHLH100, and AtbHLH101 were generated and characterized. The FRO2 and IRT1 expression in roots and the iron content in shoots were more drastically decreased in the triple knockout mutant of AtbHLH39, AtbHLH100, and AtbHLH101 than that of the other available double and triple mutants of the four genes. Comparison of the physiological responses as well as the expression of FRO2 and IRT1 in the multiple knockout mutants under iron deficiency revealed that AtbHLH100, AtbHLH38, AtbHLH101, and AtbHLH39 played the gradually increased important role in the iron-deficiency responses and uptake. Taken all together, we conclude that the four Ib subgroup bHLH proteins are required and possess redundant functions with differential significance for activation of iron-deficiency responses and uptake in Arabidopsis.

Essential functions of iron-requiring proteins n DNA replication, repair and cell cycle contro

Eukaryotic cells contain numerous iron-requiring pro- teins such as iron-sulfur （Fe-S） cluster proteins, hemoproteins and ribonucleotide reductases （RNRs）. These proteins utilize iron as a cofactor and perform key roles in DNA replication, DNA repair, metabolic catalysis, iron regulation and cell cycle progression. Disruption of iron homeostasis always impairs the functions of these iron- requiring proteins and is genetically associated with diseases characterized by DNA repair defects in mam- mals. Organisms have evolved multi-layered mecha- nisms to regulate iron balance to ensure genome stability and cell development. This review briefly pro- vides current perspectives on iron homeostasis in yeast and mammals, and mainly summarizes the most recent understandings on iron-requiring protein functions involved in DNA stability maintenance and cell cycle control.

Neuroprotective effects of kukoamine A on 6-OHDA-induced Parkinson’s model through apoptosis and iron accumulation inhibition

Objective: Parkinson’s disease(PD) is characterized by the loss of dopaminergic neurons in substantia nigra(SN). Our previous study demonstrated kukoamine A(KuA) to exhibit strong neuroprotective effects through antioxidative stress, and autophagy in MPTP/MPP+-induced PD models in vivo and in vitro. It is necessary to evaluate the efficacy of the anti-PD effects under various models.Methods: In the present study, total chemical synthesis was used to obtain KuA, which performed low content in Lycii Cortex. Then, 6-OHDA-induced PD model of PC12 cells was used to investigate the effects of KuA on PD.Results: Our results demonstrated that KuA ameliorated cell loss and mitochondrial membrane potential(MMP) loss, and inhibited Bax/Bcl-2 ratio increase that were induced by 6-OHDA. Iron accumulation in SN is thought to participate in neuronal death in PD, which subsequently resulted in oxidative stress and overexpression of a-synuclein caused by iron metabolism protein disorder. In our study, KuA could chelate cellular iron content and decrease iron influx. Moreover, KuA could upregulate the expression of ferroportin1 and Hephaestin, downregulate the expression of DMT1, TfR, and Ferritin to maintain cellular iron homeostasis avoiding neuronal death from cellular iron deposition. Moreover, KuA could decrease the expression of a-synuclein in cells. All the results indicated that KuA protected against neurotoxininduced PD due to the apoptosis inhibition and iron homeostasis maintaining.Conclusion: KuA treatment might represent a neuroprotective treatment for PD.

Sorting nexin 3 exacerbates doxorubicin-induced cardiomyopathy via regulation of TFRC-dependent ferroptosis

The clinical utilization of doxorubicin(Dox)in various malignancies is restrained by its major adverse effect:irreversible cardiomyopathy.Extensive studies have been done to explore the prevention of Dox cardiomyopathy.Currently,ferroptosis has been shown to participate in the incidence and development of Dox cardiomyopathy.Sorting Nexin 3(SNX3),the retromer-associated cargo binding protein with important physiological functions,was identified as a potent therapeutic target for cardiac hypertrophy in our previous study.However,few study has shown whether SNX3 plays a critical role in Dox-induced cardiomyopathy.In this study,a decreased level of SNX3 in Dox-induced cardiomyopathy was observed.Cardiac-specific Snx3 knockout(Snx3-cKO)significantly alleviated cardiomyopathy by downregulating Dox-induced ferroptosis significantly.SNX3 was further demonstrated to exacerbate Dox-induced cardiomyopathy via induction of ferroptosis in vivo and in vitro,and cardiac-specific Snx3 transgenic(Snx3-cTg)mice were more susceptible to Dox-induced feroptosis and cardiomyopathy.Mechanistically,SNX3 facilitated the recycling of transferrin 1 receptor(TFRC)via direct interaction,disrupting iron homeostasis,increasing the accumulation of iron,triggering ferroptosis,and eventually exacerbating Dox-induced cardiomyopathy.Overall,these findings established a direct SNX3-TFRC-ferroptosis positive regulatory axis in Dox-induced cardiomyopathy and suggested that targeting SNX3 provided a new effective therapeutic strategy for Dox-induced cardiomyopathy through TFRCdependentferroptosis.

Primary Non-HFE Hemochromatosis:A Review

Iron homeostasis is a complex process in which iron uptake and use are tightly balanced.Primary Type 1 or HFE hemochromatosis results from homozygous mutations in the gene that encodes human homeostatic iron regulator(known as human factors engineering,HFE)protein,a regulator of hepcidin,and makes up approximately 90%of all hemochromatosis cases.However,four types of hemochromatosis do not involve the HFE gene.They are non-HFE hemochromatosis type 2A(HFE2,encoding HJV),type 2B(HAMP,encoding hepcidin),type 3(TFR2,encoding transferring receptor-2),and types 4A and B(SLC40A1,encoding ferroportin.NonHFE hemochromatosis is extremely rare.Pathogenic allele frequencies have been estimated to be 74/100,000 for type 2A,20/100,000 for type 2B,30/100,000 for type 3,and 90/100,000 for type 4 hemochromatosis.Current guidelines recommend that the diagnosis be made by ruling out HFE mutations,history,physical examination,laboratory values(ferritin and transferrin saturation),magnetic resonance or other imaging,and liver biopsy if needed.While less common,non-HFE hemochromatosis can cause iron overload as severe as the HFE type.In most cases,treatment involves phlebotomy and is successful if started before irreversible damage occurs.Early diagnosis and treatment are important because it prevents chronic liver disease.This review updates the mutations and their pathogenetic consequences,the clinical picture,diagnostic guidelines,and treatment of hemochromatosis.

Sequence Diversity and Enzyme Activity of Ferric-Chelate Reductase LeFRO1 in Tomato

Ferric-chelate reductase which functions in the reduction of ferric to ferrous iron on root surface is a critical protein for iron ho- meostasis in strategy I plants. LeFROI is a major ferric-chelate reductase involved in iron uptake in tomato. To identify the natural variations of LeFRO1 and to assess their effect on the ferric-chelate reductase activity, we cloned the coding sequences of LeFRO1 from 16 tomato varieties collected from different regions, and detected three types of LeFRO1 （LeFRO1MM, LeFRO1Ailsa and LeFRO1Monita） with five amino acid variations at the positions 21, 24, 112, 195 and 582. Enzyme activity assay revealed that the three types of LeFRO1 possessed different ferric-chelate reductase activity （LeFRO1AiISa 〉 LeFRO1MM 〉 LeFRO1M^nita）. The 112th amino acid residue Ala of LeFRO1 is critical for maintaining the high activity of ferric-chelate reductase, because modification of this amino acid resulted in a significant reduction of enzyme activity. Further, we showed that the combination of the amino acid residue lie at the site 24 with Lys at the site 582 played a positive role in the enzyme activity of LeFRO1. In conclusion, the findings are helpful to understand the natural adaptation mechanisms of plants to iron-limiting stress, and may provide new knowledge to select and manipulate LeFRO1 for improving the iron deficiency tolerance in tomato.