Regulator Of Iron Homeostasis Research Articles

Encapsulated Ferritin-like Proteins: A Structural Perspective.

Encapsulins are self-assembling nano-compartments that naturally occur in bacteria and archaea. These nano-compartments encapsulate cargo proteins that bind to the shell's interior through specific recognition sequences and perform various metabolic processes. Encapsulation enables organisms to perform chemical reactions without exposing the rest of the cell to potentially harmful substances while shielding cargo molecules from degradation and other adverse effects of the surrounding environment. One particular type of cargo protein, the ferritin-like protein (FLP), is the focus of this review. Encapsulated FLPs are members of the ferritin-like protein superfamily, and they play a crucial role in converting ferrous iron (Fe+2) to ferric iron (Fe+3), which is then stored inside the encapsulin in mineralized form. As such, FLPs regulate iron homeostasis and protect organisms against oxidative stress. Recent studies have demonstrated that FLPs have tremendous potential as biosensors and bioreactors because of their ability to catalyze the oxidation of ferrous iron with high specificity and efficiency. Moreover, they have been investigated as potential targets for therapeutic intervention in cancer drug development and bacterial pathogenesis. Further research will likely lead to new insights and applications for these remarkable proteins in biomedicine and biotechnology.

#2898 Exposure response model describing hematologic changes with chronic treatment of CKD anemia with vadadustat

Abstract Background and Aims Vadadustat (VADA) is an oral hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor, a class of drugs that stabilize HIF and stimulate endogenous erythropoietin production, increasing iron mobilization and red blood cell production. VADA is approved in 36 countries globally and is indicated in the European Union for the treatment of symptomatic anaemia associated with chronic kidney disease (CKD) in adults on chronic maintenance dialysis and is an alternative to treatment with erythropoiesis-stimulating agents (ESAs). The aim of this work was to develop a predictive, semi-mechanistic model to understand the effects of VADA and erythropoiesis-stimulating agents (ESAs) on hemoglobin response and to evaluate the impact of intrinsic and extrinsic patient characteristics on that response for non-dialysis dependent (NDD) and dialysis-dependent (DD) patient populations. Method A predictive semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model for VADA and ESA treatment was developed using nonlinear mixed effects methods. The model describes changes in reticulocyte count (RETICs), mature erythrocytes (RBCs) and hemoglobin (Hb) as a function of drug exposure and subject-specific characteristics. The dataset was based on data from 7 Phase 1 to Phase 3 studies (Table 1; N = 894 for VADA; N = 560 for ESA modeling) in healthy volunteers and subjects with NDD- or DD-CKD who were either ESA-naïve or ESA experienced but not receiving treatment at screening. Prior population PK modeling of VADA provided estimated drug exposures for VADA-treated subjects, while dose normalized to standard units (IU/kg/wk) was used as the exposure metric for subjects on ESA. Each of these exposure metrics could vary with time, as the dose was adjusted according to observed Hb response. This work evaluated alternative model structures, as well as covariate effects affecting Hb individual response. Results A predictive semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model for VADA and ESA treatment was developed using nonlinear mixed effects methods. The model describes changes in reticulocyte count (RETICs), mature erythrocytes (RBCs) and hemoglobin (Hb) as a function of drug exposure and subject-specific characteristics. The dataset was based on data from 7 Phase 1 to Phase 3 studies (Table 1; N = 894 for VADA; N = 560 for ESA modeling) in healthy volunteers and subjects with NDD- or DD-CKD who were either ESA-naïve or ESA experienced but not receiving treatment at screening. Prior population PK modeling of VADA provided estimated drug exposures for VADA-treated subjects, while dose normalized to standard units (IU/kg/wk) was used as the exposure metric for subjects on ESA. Each of these exposure metrics could vary with time, as the dose was adjusted according to observed Hb response. This work evaluated alternative model structures, as well as covariate effects affecting Hb individual response. A similar model structure was found to describe early changes in RETICs and longer-term changes in Hb for both VADA and ESAs. In each case, the magnitude of response increases with increased drug exposure up to a maximum value (Emax), and the Emax values were similar between VADA and ESAs. Subject intrinsic predictors of response included eGFR, subject age, BMI, and serum albumin, while extrinsic factors affecting response included geographic region, limits on acceptable Hb values (which also differ by geographic region) and the presence of previous ESA treatment. Interestingly, Hb responses were also correlated with changes in serum hepcidin, a key regulator of iron homeostasis, following both VADA and ESA treatment. Differences between the response to VADA and ESA were also described, including differences in temporal changes in RETICs and Hb. Conclusion This model showed an exposure-response relationship between VADA or ESA treatment and changes in RETICs and Hb for ESA naïve or ESA-experienced CKD subjects. The model will be used to inform dosage recommendations for VADA based on patient characteristics.

Understanding iron homeostasis in MDS: the role of erythroferrone.

Myelodysplastic neoplasms (MDS) are a heterogenous group of clonal stem cell disorders characterized by dysplasia and cytopenia in one or more cell lineages. Anemia is a very common symptom that is often treated with blood transfusions and/or erythropoiesis stimulating factors. Iron overload results from a combination of these factors together with the disease-associated ineffective erythropoiesis, that is seen especially in MDS cases with SF3B1 mutations. A growing body of research has shown that erythroferrone is an important regulator of hepcidin, the master regulator of systemic iron homeostasis. Consequently, it is of interest to understand how this molecule contributes to regulating the iron balance in MDS patients. This short review evaluates our current understanding of erythroferrone in general, but more specifically in MDS and seeks to place in context how the current knowledge could be utilized for prognostication and therapy.

A Hemoglobin Bionics-Based System for Combating Antibiotic Resistance in Chronic Diabetic Wounds via Iron Homeostasis Regulation.

Owing to the increased tissue iron accumulation in patients with diabetes, microorganisms may activate high expression of iron-involved metabolic pathways, leading to the exacerbation of bacterial infections and disruption of systemic glucose metabolism. Therefore, an on-demand transdermal dosing approach that utilizes iron homeostasis regulation to combat antimicrobial resistance is a promising strategy to address the challenges associated with low administration bioavailability and high antibiotic resistance in treating infected diabetic wounds. Here, it is aimed to propose an effective therapy based on hemoglobin bionics to induce disturbances in bacterial iron homeostasis. The preferred "iron cargo" is synthesized by protoporphyrin IX chelated with dopamine and gallium (PDGa), and is delivered via a glucose/pH-responsive microneedle bandage (PDGa@GMB). The PDGa@GMB downregulates the expression levels of the iron uptake regulator (Fur) and the peroxide response regulator (perR) in Staphylococcus aureus, leading to iron nutrient starvation and oxidative stress, ultimately suppressing iron-dependent bacterial activities. Consequently, PDGa@GMB demonstrates insusceptibility to genetic resistance while maintaining sustainable antimicrobial effects (>90%) against resistant strains of both S. aureus and E. coli, and accelerates tissue recovery (<20 d). Overall, PDGa@GMB not only counteracts antibiotic resistance but also holds tremendous potential in mediating microbial-host crosstalk, synergistically attenuating pathogen virulence and pathogenicity.

CRISPR/Cas9 edited StbHLH47 lines exhibit altered expression profiling of iron regulating genes and increased iron content in Solanum tuberosum

Iron is an essential plant nutrient, and a continuous supply of it is required as it is a key factor in various metabolic processes, including photosynthesis, chlorophyll synthesis, and respiration. Various transcription factors are known to regulate iron homeostasis in plants, and the bHLH transcription factor family is one of them. The StbHLH47 is a homologue of the Arabidopsis POPEYE (PYE), which is known to repress iron homeostasis-related genes in Arabidopsis. Potato is the most consumed vegetable in the world and is low in iron content. We have generated CRISPR/Cas9-edited StbHLH47 lines and performed a detailed analysis of these lines. The analysis revealed that the roots of StbHLH47 edited lines have decreased ferric chelate reductase (FCR) activity compared to the roots of the wild-type (WT) plant. We also observed that CRISPR/Cas9 edited lines have fewer trichomes when compared to the WT plant. The expression of genes associated with iron homeostasis was also measured. Compared to the control, the expression of StbHLH47 was downregulated in the edited lines, while the expression of StNAS4, StOPT3, and StFRO3 was upregulated. This suggests the negative regulation of StbHLH47 in modulating iron. The iron content was also quantified using inductively coupled plasma mass spectrometry (ICP-MS) and found to be increased in the generated transgenic lines when compared to WT plants. Overall, this study reveals that StbHLH47 negatively regulates the expression of iron homeostasis-related genes. StbHLH47 edited lines exhibited decreased FCR activity, changes in phenotype, and increased iron content in the potato plants. Key messageThis study provides novel insight into the role of StbHLH47 in modulating iron content in Solanum tuberosum and controlling the expression of various iron homeostasis-related genes.

Study of the Relationship Between Insulin Resistance, Iron Status Markers, and Body Weight in a Sample of Egyptian Population.

Iron plays a key role in the regulation of body iron homeostasis and is used as a clinical marker for iron deficiency (ID) and hemochromatosis. The idea that iron dysregulation may contribute to various metabolic diseases, such as obesity, insulin resistance, MetS, and T2DM, is a hot topic of discussion. The aim of this study is to investigate the relationship insulin resistance, iron status markers, and body weight in a sample of Egyptian population. A case control study was conducted on 90 subjects with age ranging from 18 to 70 years old from a diabetes outpatient clinic, and they were divided to three groups: Group I, non-obese- non-diabetic as the control group; Group II, obese-non-diabetic; and Group III, obese-diabetic. In our study, there was no statistically significant difference between the three studied groups regarding the different iron parameters. Similarly, we found that neither HOMA-IR nor body weight had a significant correlation with iron status markers. On the contrary, we detected significant positive correlations between the TIBC and the fasting blood glucose, between the serum iron and the LDL, between the TSAT and the systolic blood pressure, and between the HOMA-IR and hematocrit. Our study demonstrated no direct statistical significant relationship between the different iron parameters, obesity, and insulin resistance, either in the diabetic or non-diabetic subjects. This may be due to the complex metabolic dysregulation and the small number of the sample for future investigations.

The interplay between electron transport chain function and iron regulatory factors influences melanin formation in Cryptococcus neoformans.

Mitochondrial functions are critical for the ability of the fungal pathogen Cryptococcus neoformans to cause disease. However, mechanistic connections between key functions such as the mitochondrial electron transport chain (ETC) and virulence factor elaboration have yet to be thoroughly characterized. Here, we observed that inhibition of ETC complex III suppressed melanin formation, a major virulence factor. This inhibition was partially overcome by defects in Cir1 or HapX, two transcription factors that regulate iron acquisition and use. In this regard, loss of Cir1 derepresses the expression of laccase genes as a potential mechanism to restore melanin, while HapX may condition melanin formation by controlling oxidative stress. We hypothesize that ETC dysfunction alters redox homeostasis to influence melanin formation. Consistent with this idea, inhibition of growth by hydrogen peroxide was exacerbated in the presence of the melanin substrate L-DOPA. In addition, loss of the mitochondrial chaperone Mrj1, which influences the activity of ETC complex III and reduces ROS accumulation, also partially overcame antimycin A inhibition of melanin. The phenotypic impact of mitochondrial dysfunction was consistent with RNA-Seq analyses of WT cells treated with antimycin A or L-DOPA, or cells lacking Cir1 that revealed influences on transcripts encoding mitochondrial functions (e.g., ETC components and proteins for Fe-S cluster assembly). Overall, these findings reveal mitochondria-nuclear communication via ROS and iron regulators to control virulence factor production in C. neoformans.IMPORTANCEThere is a growing appreciation of the importance of mitochondrial functions and iron homeostasis in the ability of fungal pathogens to sense the vertebrate host environment and cause disease. Many mitochondrial functions such as heme and iron-sulfur cluster biosynthesis, and the electron transport chain (ETC), are dependent on iron. Connections between factors that regulate iron homeostasis and mitochondrial activities are known in model yeasts and are emerging for fungal pathogens. In this study, we identified connections between iron regulatory transcription factors (e.g., Cir1 and HapX) and the activity of complex III of the ETC that influence the formation of melanin, a key virulence factor in the pathogenic fungus Cryptococcus neoformans. This fungus causes meningoencephalitis in immunocompromised people and is a major threat to the HIV/AIDS population. Thus, understanding how mitochondrial functions influence virulence may support new therapeutic approaches to combat diseases caused by C. neoformans and other fungi.

The Transcription Factors AcuK and AcuM Influence Siderophore Biosynthesis of Aspergillus fumigatus.

The mold Aspergillus fumigatus employs two high-affinity uptake systems, reductive iron assimilation (RIA) and siderophore-mediated iron acquisition (SIA), for the acquisition of the essential trace element iron. SIA has previously been shown to be crucial for virulence in mammalian hosts. Here, we show that a lack of AcuK or AcuM, transcription factors required for the activation of gluconeogenesis, decreases the production of both extra- and intracellular siderophores in A. fumigatus. The lack of AcuM or AcuK did not affect the expression of genes involved in RIA and SIA, suggesting that these regulators do not directly regulate iron homeostasis genes, but indirectly affect siderophore production through their influence on metabolism. Consistent with this, acetate supplementation reversed the intracellular siderophore production defect of ΔacuM and ΔacuK. Moreover, ΔacuM and ΔacuK displayed a similar growth defect under iron limitation and iron sufficiency, which suggests they have a general role in carbon metabolism apart from gluconeogenesis. In agreement with a potential role of the glyoxylate cycle in adaptation to iron starvation, transcript levels of the malate synthase-encoding acuE were found to be upregulated by iron limitation that is partially dependent on AcuK and AcuM. Together, these data demonstrate the influence of iron availability on carbon metabolism.

Using Biotinylated Iron-Responsive Element to Analyze the Activity of Iron Regulatory Proteins.

Iron regulatory proteins (IRP1 and IRP2) are the master regulators of mammalian iron homeostasis. They bind to the iron-responsive elements (IREs) of the transcripts of iron-related genes to regulate their expression, thereby maintaining cellular iron availability. The primary method to measure the IRE-binding activity of IRPs is the electrophoresis mobility shift assay (EMSA). This method is particularly useful for evaluating IRP1 activity, since IRP1 is a bifunctional enzyme and its protein levels remain similar during conversion between the IRE-binding protein and cytosolic aconitase forms. Here, we exploited a method of using a biotinylated-IRE probe to separate IRE-binding IRPs followed by immunoblotting to analyze the IRE-binding activity. This method allows for the successful measurement of IRP activity in cultured cells and mouse tissues under various iron conditions. By separating IRE-binding IRPs from the rest of the lysates, this method increases the specificity of IRP antibodies and verifies whether a band represents an IRP, thereby revealing some previously unrecognized information about IRPs. With this method, we showed that the S711-phosphorylated IRP1 was found only in the IRE-binding form in PMA-treated Hep3B cells. Second, we found a truncated IRE-binding IRP2 isoform that is generated by proteolytic cleavage on sites in the 73aa insert region of the IRP2 protein. Third, we found that higher levels of SDS, compared to 1-2% SDS in regular loading buffer, could dramatically increase the band intensity of IRPs in immunoblots, especially in HL-60 cells. Fourth, we found that the addition of SDS or LDS to cell lysates activated protein degradation at 37 °C or room temperature, especially in HL-60 cell lysates. As this method is more practical, sensitive, and cost-effective, we believe that its application will enhance future research on iron regulation and metabolism.

Fibroblast growth factor 23 is pumping iron: C-terminal-fibroblast growth factor 23 cleaved peptide and its function in iron metabolism.

Iron deficiency regulates the production of the bone-derived phosphaturic hormone fibroblast growth factor 23 (FGF23) but also its cleavage, to generate both intact (iFGF23) and C-terminal (Cter)-FGF23 peptides. Novel studies demonstrate that independently of the phosphaturic effects of iFGF23, Cter-FGF23 peptides play an important role in the regulation of systemic iron homeostasis. This review describes the complex interplay between iron metabolism and FGF23 biology. C-terminal (Cter) FGF23 peptides antagonize inflammation-induced hypoferremia to maintain a pool of bioavailable iron in the circulation. A key mechanism proposed is the down-regulation of the iron-regulating hormone hepcidin by Cter-FGF23. In this manuscript, we discuss how FGF23 is produced and cleaved in response to iron deficiency, and the principal functions of cleaved C-terminal FGF23 peptides. We also review possible implications anemia of chronic kidney disease (CKD).

Rocaglamide regulates iron homeostasis by suppressing hepcidin expression

The anemia of inflammation (AI) is characterized by the presence of inflammation and abnormal elevation of hepcidin. Accumulating evidence has proved that Rocaglamide (RocA) was involved in inflammation regulation. Nevertheless, the role of RocA in AI, especially in iron metabolism, has not been investigated, and its underlying mechanism remains elusive. Here, we demonstrated that RocA dramatically suppressed the elevation of hepcidin and ferritin in LPS-treated mice cell line RAW264.7 and peritoneal macrophages. In vivo study showed that RocA can restrain the depletion of serum iron (SI) and transferrin (Tf) saturation caused by LPS. Further investigation showed that RocA suppressed the upregulation of hepcidin mRNA and downregulation of Fpn1 protein expression in the spleen and liver of LPS-treated mice. Mechanistically, this effect was attributed to RocA's ability to inhibit the IL-6/STAT3 pathway, resulting in the suppression of hepcidin mRNA and subsequent increase in Fpn1 and TfR1 expression in LPS-treated macrophages. Moreover, RocA inhibited the elevation of the cellular labile iron pool (LIP) and reactive oxygen species (ROS) induced by LPS in RAW264.7 cells. These findings reveal a pivotal mechanism underlying the roles of RocA in modulating iron homeostasis and also provide a candidate natural product on alleviating AI.

Effects of cholecalciferol and omega-3 fatty acids on hepcidin levels in 5/6 nephrectomy rats

Background: Anemia is a common complication of chronic kidney disease (CKD). In patients with CKD-related anemia, an inverse relationship between vitamin D and hepcidin levels has been observed. Hepcidin is a key regulator of iron homeostasis, mediated via binding to ferroportin. The aim of this study was to investigate the effects of cholecalciferol and omega-3 fatty acids (FA) on hepcidin levels using 5/6 nephrectomized (Nx) rats.Methods: Male Sprague-Dawley rats were divided into five groups: sham control, 5/6 Nx, 5/6 Nx treated with cholecalciferol, 5/6 Nx treated with omega-3 FA, and 5/6 Nx treated with both cholecalciferol and omega-3 FA. We measured the hepcidin and ferroportin levels in the kidney and liver by enzyme-linked immunosorbent assays and Western blots. We evaluated hepcidin expression in the kidney by immunohistochemical staining.Results: Among the five groups, 5/6 Nx rats exhibited the worst kidney function. Compared with the sham controls, 5/6 Nx rats showed significantly increased serum hepcidin levels and decreased vitamin D levels. Supplementation with either omega-3 FA or cholecalciferol decreased hepcidin and increased vitamin D levels, with a concurrent improvement of anemia. Furthermore, 5/6 Nx rats treated with omega-3 FA/cholecalciferol showed decreased ferroportin and ferritin levels, while iron and total iron-binding capacity levels increased.Conclusions: Treatment with a combination of cholecalciferol and omega-3 FA may improve anemia in a CKD rat model by decreasing hepcidin levels.

Endothelial ZIP8 plays a minor role in BMP6 regulation by iron in mice

AbstractIron-mediated induction of bone morphogenetic protein (BMP)6 expression by liver endothelial cells is essential for iron homeostasis regulation. We used multiple dietary and genetic mouse cohorts to demonstrate a minor functional role for the metal-ion transporter ZIP8 in regulating BMP6 expression under high-iron conditions.

Plasticity changes in iron homeostasis in hibernating Daurian ground squirrels (Spermophilus dauricus) may counteract chronically inactive skeletal muscle atrophy.

Disuse-induced muscular atrophy is frequently accompanied by iron overload. Hibernating animals are a natural animal model for resistance to disuse muscle atrophy. In this paper, we explored changes in skeletal muscle iron content of Daurian ground squirrels (Spermophilus dauricus) during different periods of hibernation as well as the regulatory mechanisms involved. The results revealed that compared with the summer active group (SA), iron content in the soleus muscle (SOL) decreased (- 65%) in the torpor group (TOR), but returned to normal levels in the inter-bout arousal (IBA); splenic iron content increased in the TOR group (vs. SA, + 67%), decreased in the IBA group (vs. TOR, - 37%). Expression of serum hepcidin decreased in the TOR group (vs. SA, - 22%) and returned to normal levels in the IBA groups; serum ferritin increased in the TOR group (vs. SA, + 31%), then recovered in the IBA groups. Soleus muscle transferrin receptor 1 (TfR1) expression increased in the TOR group (vs. SA, + 83%), decreased in the IBA group (vs. TOR, - 30%); ferroportin 1 increased in the IBA group (vs. SA, + 55%); ferritin increased in the IBA group (vs. SA, + 42%). No significant differences in extensor digitorum longus in iron content or iron metabolism-related protein expression were observed among the groups. Significantly, all increased or decreased indicators in this study returned to normal levels after the post-hibernation group, showing remarkable plasticity. In summary, avoiding iron overload may be a potential mechanism for hibernating Daurian ground squirrels to avoid disuse induced muscular atrophy. In addition, the different skeletal muscle types exhibited unique strategies for regulating iron homeostasis.

First-in-Human Phase 1 Study Evaluating the Safety, Pharmacokinetics, and Pharmacodynamics of DISC-0974, an Anti-Hemojuvelin Antibody, in Healthy Participants.

Pathologic elevations in hepcidin, a key regulator of iron homeostasis, contribute to anemia of inflammation in chronic disease. DISC-0974 is a monoclonal antibody that binds to hemojuvelin and blocks bone morphogenetic protein signaling, thereby suppressing hepcidin production. Reduction of systemic hepcidin levels is predicted to increase iron absorption and mobilize stored iron into circulation, where it may be utilized by red blood cell (RBC) precursors in the bone marrow to improve hemoglobin levels and to potentially alleviate anemia of inflammation. We conducted a first-in-human, double-blind, placebo-controlled, single-ascending dose study to evaluate safety, pharmacokinetics, and pharmacodynamics of DISC-0974 in healthy participants. Overall, 42 participants were enrolled and received a single dose of placebo or DISC-0974 at escalating dose levels (7-56mg), administered intravenously (IV) or subcutaneously (SC). DISC-0974 was well tolerated, with a safety profile comparable to that of placebo. Pharmacokinetic data was dose and route related, with a terminal half-life of approximately 7 days. The bioavailability of SC dosing was ∼50%. Pharmacodynamic data showed dose-dependent decreases in serum hepcidin, with reductions of nearly 75% relative to baseline at the highest dose level tested, and corresponding increases in serum iron in response to DISC-0974 administration. Dose-dependent changes in serum ferritin and hematology parameters were also observed, indicating mobilization of iron stores and downstream effects of enhanced hemoglobinization and production of RBCs. Altogether, these data are consistent with the mechanism of action of DISC-0974 and support the selection of a biologically active dose range for evaluation in clinical trials for individuals with anemia of inflammation.

Dietary Iron Overload Triggers Hepatic Metabolic Disorders and Inflammation in Laying Hen.

Iron, an essential trace element, is involved in various physiological processes; however, consumption of excessive iron possesses detrimental effects. In practical feed production, the iron content added to feeds often far exceeds the actual demand, resulting in an excess of iron in the body. The liver as a central regulator of iron homeostasis is susceptible to damage caused by disorders in iron metabolism. A model of hepatic iron overload in laying hens was developed in this study by incorporating iron into their diet, and the specific mechanisms underlying iron overload-induced hepatic injury were investigated. Firstly, this study revealed that a high-iron diet resulted in hepatic iron overload, accompanied by impaired liver function. Next, assessment of oxidative stress markers indicated a decrease in activities of T-SOD and CAT, coupled with an increase in MDA content, pointing to the iron-overloaded liver oxidative stress. Thirdly, the impact of iron overload on hepatic glycolipid and bile acid metabolism-related gene expressions were explored, including PPAR-α, GLUT2, and CYP7A1, highlighting disruptions in hepatic metabolism. Subsequently, analyses of inflammation-related genes such as iNOS and IL-1β at both protein and mRNA levels demonstrated the presence of inflammation in the liver under conditions of dietary iron overload. Overall, this study provided comprehensive evidence that dietary iron overload contributed to disorders in glycolipid and bile acid metabolism, accompanied by inflammatory responses in laying hens. Further detailing the specific pathways involved and the implications of these findings could offer valuable insights for future research and practical applications in poultry nutrition.

The deletion of ppr2 interferes iron sensing and leads to oxidative stress response in Schizosaccharomyces pombe

Pentatricopeptide repeat proteins are involved in mitochondrial both transcriptional and posttranscriptional regulation. Schizosaccharomyces pombe Ppr2 is a general mitochondrial translation factor that plays a critical role in the synthesis of all mitochondrial DNA-encoded oxidative phosphorylation subunits, which are essential for mitochondrial respiration. Our previous analysis showed that ppr2 deletion resulted in increased expression of iron uptake genes and caused ferroptosis-like cell death in S. pombe. In the present work, we showed that deletion of ppr2 reduced viability on glycerol- and galactose-containing media.Php4 is a transcription repressor that regulates iron homeostasis in fission yeast. We found that in the ppr2 deletion strain, Php4 was constitutively active and accumulated in the nucleus in the stationary phase. We also found that deletion of ppr2 decreased the ferroptosis-related protein Gpx1 in the mitochondria. Overexpression of Gpx1 improves the viability of Δppr2 cells. We showed that the deletion of ppr2 increased the production of ROS, downregulated heme synthesis and iron-sulfur cluster proteins, and induced stress proteins. Finally, we observed the nuclear accumulation of Pap1-GFP and Sty1-GFP, suggesting that Sty1 and Pap1 in response to cellular stress in the ppr2 deletion strain. These results suggest thatppr2 deletion may cause mitochondrial dysfunction, which is likely to lead to iron-sensing defect and iron starvation response, resulting in perturbation of iron homeostasis and increased hydroxyl radical production. The increased hydroxyl radical production triggers cellular responses in theppr2 deletion strain.

Echinatin mitigates sevoflurane-induced neurotoxicity through regulation of ferroptosis and iron homeostasis.

Surgery and anesthesia are vital medical interventions, but concerns over their potential cognitive side effects, particularly with the use of inhalational anesthetics like sevoflurane, have surfaced. This study delves into the neuroprotective potential of Echinatin against sevoflurane-induced neurotoxicity and the underlying mechanisms. Echinatin, a natural compound, has exhibited anti-inflammatory, antioxidant, and anticancer properties. Sevoflurane, while a popular anesthetic, is associated with perioperative neurocognitive disorders (PND) and neurotoxicity. Our investigation began with cellular models, where Echinatin demonstrated a significant reduction in sevoflurane-induced apoptosis. Mechanistically, we identified ferroptosis, a novel form of programmed cell death characterized by iron accumulation and lipid peroxidation, as a key player in sevoflurane-induced neuronal injury. Echinatin notably suppressed ferroptosis in sevoflurane-exposed cells, suggesting a pivotal role in neuroprotection. Expanding our research to a murine model, we observed perturbations in iron homeostasis, inflammatory cytokines, and antioxidants due to sevoflurane exposure. Echinatin treatment effectively restored iron balance, mitigated inflammation, and preserved antioxidant levels in vivo. Behavioral assessments using the Morris water maze further confirmed Echinatin's neuroprotective potential, as it ameliorated sevoflurane-induced spatial learning and memory impairments. In conclusion, our study unveils Echinatin as a promising candidate for mitigating sevoflurane-induced neurotoxicity. Through the regulation of ferroptosis, iron homeostasis, and inflammation, Echinatin demonstrates significant neuroprotection both in vitro and in vivo. These findings illuminate the potential for Echinatin to enhance the safety of surgical procedures involving sevoflurane anesthesia, minimizing the risk of cognitive deficits and neurotoxicity.

Iron–sulfur cluster assembly scaffold protein IscU is required for activation of ferric uptake regulator (Fur) in Escherichiacoli

It was previously postulated that when intracellular free iron content is elevated in bacteria, the Ferric uptake regulator (Fur) binds its co-repressor a mononuclear ferrous iron to regulate intracellular iron homeostasis. However, the proposed iron-bound Fur had not been identified in any bacteria. In previous studies, we have demonstrated that Escherichia coli Fur binds a [2Fe-2S] cluster in response to elevation of intracellular free iron content, and that binding of the [2Fe-2S] cluster turns on Fur as an active repressor to bind a specific DNA sequence known as the Fur-box. Here we find that the iron-sulfur cluster assembly scaffold protein IscU is required for the [2Fe-2S] cluster assembly in Fur, as deletion of IscU inhibits the [2Fe-2S] cluster assembly in Fur and prevents activation of Fur as a repressor in E. coli cells in response to elevation of intracellular free iron content. Additional studies reveal that IscU promotes the [2Fe-2S] cluster assembly in apo-form Fur and restores its Fur-box binding activity in vitro. While IscU is also required for the [2Fe-2S] cluster assembly in the Haemophilus influenzae Fur in E. coli cells, deletion of IscU does not significantly affect the [2Fe-2S] cluster assembly in the E. coli ferredoxin and siderophore-reductase FhuF. Our results suggest that IscU may have a unique role for the [2Fe-2S] cluster assembly in Fur, and that regulation of intracellular iron homeostasis is closely coupled with iron-sulfur cluster biogenesis in E. coli.

BHLH121 and clade IVc bHLH transcription factors synergistically function to regulate iron homeostasis in Arabidopsis thaliana.

Iron is an essential micronutrient for plant growth and development. In Arabidopsis thaliana, an intricate regulatory network involving several basic helix-loop-helix (bHLH) transcription factors controls the homeostasis of iron. Among these transcription factors, bHLH121 plays a crucial role. bHLH121 interacts in vivo with clade IVc bHLH transcription factors and activates the expression of FIT and clade Ib bHLH transcription factors to stimulate the uptake of iron. How bHLH121 and clade IVc bHLH transcription factors function collectively and efficiently to maintain iron homeostasis is still unclear. Herein, we found that double loss-of-function mutants involving bhlh121 and one of the clade IVc bHLH transcription factors displayed more severe iron deficiency-associated growth defects than each of the single mutants. We also found that among the four clade IVc bHLH transcription factors, only bHLH34 and bHLH105 could partially complement the iron-associated growth defects of bhlh121 when overexpressed. These data, together with protein localization analysis, support that bHLH121 and clade IVc bHLH transcription factors act synergistically to regulate iron homeostasis and that different bHLH121/clade IVc and clade IVc/clade IVc protein complexes are involved in this process.