Nanoparticle Vaccines Based on the Receptor Binding Domain (RBD) and Heptad Repeat (HR) of SARS-CoV-2 Elicit Robust Protective Immune Responses.

Various vaccine strategies have been proposed in response to the global COVID-19 pandemic, each with unique strategies for eliciting immune responses. Here, we developed nanoparticle vaccines by covalently conjugating the self-assembled 24-mer ferritin to the receptor binding domain (RBD) and/or heptad repeat (HR) subunits of the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) spike (S) protein. Compared to monomer vaccines, nanoparticle vaccines elicited more robust neutralizing antibodies and cellular immune responses. RBD and RBD-HR nanoparticle vaccinated hACE2 transgenic mice vaccinated with RBD and/or RBD-HR nanoparticles exhibited reduced viral load in the lungs after SARS-CoV-2 challenge. RBD-HR nanoparticle vaccines also promoted neutralizing antibodies and cellular immune responses against other coronaviruses. The nanoparticle vaccination of rhesus macaques induced neutralizing antibodies, and T and B cell responses prior to boost immunization; these responses persisted for more than three months. RBD- and HR-based nanoparticles thus present a promising vaccination approach against SARS-CoV-2 and other coronaviruses.

A tandem activity-based sensing and labeling strategy reveals antioxidant response element regulation of labile iron pools.

Iron is an essential element for life owing to its ability to participate in a diverse array of oxidation-reduction reactions. However, misregulation of iron-dependent redox cycling can also produce oxidative stress, contributing to cell growth, proliferation, and death pathways underlying aging, cancer, neurodegeneration, and metabolic diseases. Fluorescent probes that selectively monitor loosely bound Fe(II) ions, termed the labile iron pool, are potentially powerful tools for studies of this metal nutrient; however, the dynamic spatiotemporal nature and potent fluorescence quenching capacity of these bioavailable metal stores pose challenges for their detection. Here, we report a tandem activity-based sensing and labeling strategy that enables imaging of labile iron pools in live cells through enhancement in cellular retention. Iron green-1 fluoromethyl (IG1-FM) reacts selectively with Fe(II) using an endoperoxide trigger to release a quinone methide dye for subsequent attachment to proximal biological nucleophiles, providing a permanent fluorescent stain at sites of elevated labile iron. IG1-FM imaging reveals that degradation of the major iron storage protein ferritin through ferritinophagy expands the labile iron pool, while activation of nuclear factor-erythroid 2-related factor 2 (NRF2) antioxidant response elements (AREs) depletes it. We further show that lung cancer cells with heightened NRF2 activation, and thus lower basal labile iron, have reduced viability when treated with an iron chelator. By connecting labile iron pools and NRF2-ARE activity to a druggable metal-dependent vulnerability in cancer, this work provides a starting point for broader investigations into the roles of transition metal and antioxidant signaling pathways in health and disease.

A form of inherited hyperferritinemia associated with bi-allelic pathogenic variants of STAB1.

Hyperferritinemia is a frequent finding in several conditions, both genetic and acquired. We previously studied eleven healthy subjects from eight different families presenting with unexplained hyperferritinemia. Their findings suggested the existence of an autosomal-recessive disorder. We carried out whole-exome sequencing to detect the genetic cause of hyperferritinemia. Immunohistochemistry and flow cytometry assays were performed on liver biopsies and monocyte-macrophages to confirm the pathogenic role of the identified candidate variants. Through a combined approach of whole-exome sequencing and homozygosity mapping, we found bi-allelic STAB1 variants in ten subjects from seven families. STAB1 encodes the multifunctional scavenger receptor stabilin-1. Immunohistochemistry and flow cytometry analyses showed absent or markedly reduced stabilin-1 in liver samples, monocytes, and monocyte-derived macrophages. Our findings show a strong association between otherwise unexplained hyperferritinemia and bi-allelic STAB1 mutations suggesting the existence of another genetic cause of hyperferritinemia without iron overload and an unexpected function of stabilin-1 in ferritin metabolism.

Iron, hemochromatosis genotypes, and risk of infections: a cohort study of 142 188 general population individuals.

ABSTRACT: It is unclear whether risk of infection is increased in individuals with hereditary hemochromatosis and in individuals with low or high plasma iron, transferrin saturation, or ferritin. Therefore, we tested whether high and low iron, transferrin saturation, and ferritin are associated with risk of infections observationally and genetically through HFE genotypes. We studied 142 188 Danish general population individuals. Iron, transferrin saturation, and ferritin were measured in 136 656, 136 599, and 38 020 individuals, respectively. HFE was genotyped for C282Y and H63D in 132 542 individuals. Median follow-up after study enrollment was 8 years (range, 0-38) for hospital and emergency room admissions with infections (n = 20 394) using the National Patient Register, covering all Danish hospitals. Hazard ratios for any infection were 1.20 (95% confidence interval [CI], 1.12-1.28) and 1.14 (95% CI, 1.07-1.22) in individuals with plasma iron ≤5th or ≥95th percentile compared with individuals with iron from 26th to 74th percentiles. Findings for transferrin saturation were similar, whereas infection risk was not increased in individuals with ferritin ≤5th or ≥95th percentile. Hazard ratios in C282Y homozygotes vs noncarriers were 1.40 (95% CI, 1.16-1.68) for any infection, 1.69 (95% CI, 1.05-2.73) for sepsis, and 2.34 (95% CI, 1.41-3.90) for death from infectious disease. Risk of infection was increased in C282Y homozygotes with normal plasma iron, transferrin saturation, or ferritin, and in C282Y homozygotes without liver disease, diabetes, and/or heart failure. In summary, low and high plasma iron and transferrin saturation were independently associated with increased infection risk. C282Y homozygotes had increased risk of any infection, sepsis, and death from infections. Even C282Y homozygotes with normal iron, transferrin saturation, or ferritin, not currently recommended for genotyping, had increased infection risk.

A mechanism of ferritin crystallization revealed by cryo-STEM tomography.

Protein crystallization is important in structural biology, disease research and pharmaceuticals. It has recently been recognized that nonclassical crystallization-involving initial formation of an amorphous precursor phase-occurs often in protein, organic and inorganic crystallization processes1-5. A two-step nucleation theory has thus been proposed, in which initial low-density, solvated amorphous aggregates subsequently densify, leading to nucleation4,6,7. This view differs from classical nucleation theory, which implies that crystalline nuclei forming in solution have the same density and structure as does the final crystalline state1. A protein crystallization mechanism involving this classical pathway has recently been observed directly8. However, a molecular mechanism of nonclassical protein crystallization9-15 has not been established9,11,14. To determine the nature of the amorphous precursors and whether crystallization takes place within them (and if so, how order develops at the molecular level), three-dimensional (3D) molecular-level imaging of a crystallization process is required. Here we report cryogenic scanning transmission microscopy tomography of ferritin aggregates at various stages of crystallization, followed by 3D reconstruction using simultaneous iterative reconstruction techniques to provide a 3D picture of crystallization with molecular resolution. As crystalline order gradually increased in the studied aggregates, they exhibited an increase in both order and density from their surface towards their interior. We observed no highly ordered small structures typical of a classical nucleation process, and occasionally we observed several ordered domains emerging within one amorphous aggregate, a phenomenon not predicted by either classical or two-step nucleation theories. Our molecular-level analysis hints at desolvation as the driver of the continuous order-evolution mechanism, a view that goes beyond current nucleation models, yet is consistent with a broad spectrum of protein crystallization mechanisms.

Electrophysiological Mechanisms and Validation of Ferritin-Based Magnetogenetics for Remote Control of Neurons.

Magnetogenetics was developed to remotely control genetically targeted neurons. A variant of magnetogenetics uses magnetic fields to activate transient receptor potential vanilloid (TRPV) channels when coupled with ferritin. Stimulation with static or RF magnetic fields of neurons expressing these channels induces Ca2+ transients and modulates behavior. However, the validity of ferritin-based magnetogenetics has been questioned due to controversies surrounding the underlying mechanisms and deficits in reproducibility. Here, we validated the magnetogenetic approach Ferritin-iron Redistribution to Ion Channels (FeRIC) using electrophysiological (Ephys) and imaging techniques. Previously, interference from RF stimulation rendered patch-clamp recordings inaccessible for magnetogenetics. We solved this limitation for FeRIC, and we studied the bioelectrical properties of neurons expressing TRPV4 (nonselective cation channel) and transmembrane member 16A (TMEM16A; chloride-permeable channel) coupled to ferritin (FeRIC channels) under RF stimulation. We used cultured neurons obtained from the rat hippocampus of either sex. We show that RF decreases the membrane resistance (Rm) and depolarizes the membrane potential in neurons expressing TRPV4FeRIC RF does not directly trigger action potential firing but increases the neuronal basal spiking frequency. In neurons expressing TMEM16AFeRIC, RF decreases the Rm, hyperpolarizes the membrane potential, and decreases the spiking frequency. Additionally, we corroborated the previously described biochemical mechanism responsible for RF-induced activation of ferritin-coupled ion channels. We solved an enduring problem for ferritin-based magnetogenetics, obtaining direct Ephys evidence of RF-induced activation of ferritin-coupled ion channels. We found that RF does not yield instantaneous changes in neuronal membrane potentials. Instead, RF produces responses that are long-lasting and moderate, but effective in controlling the bioelectrical properties of neurons.

NCOA4 requires a [3Fe-4S] to sense and maintain the iron homeostasis.

NCOA4 is a selective cargo receptor for ferritinophagy, the autophagic turnover of ferritin (FTH), a process critical for regulating intracellular iron bioavailability. However, how ferritinophagy flux is controlled through NCOA4 in iron-dependent processes needs to be better understood. Here, we show that the C-terminal FTH-binding domain of NCOA4 harbors a [3Fe-4S]-binding site with a stoichiometry of approximately one labile [3Fe-4S] cluster per NCOA4 monomer. By analyzing the interaction between NCOA4 and HERC2 ubiquitin ligase or NCOA4 and FTH, we demonstrate that NCOA4 regulates ferritinophagy by sensing the intracellular iron-sulfur cluster levels. Under iron-repletion conditions, HERC2 recognizes and recruits holo-NCOA4 as a substrate for polyubiquitination and degradation, favoring ferritin iron storage. Under iron-depletion conditions, NCOA4 exists in the form of apo-protein and binds ferritin to promote the occurrence of ferritinophagy and release iron. Thus, we identify an iron-sulfur cluster [3Fe-4S] as a critical cofactor in determining the fate of NCOA4 in favoring iron storage in ferritin or iron release via ferritinophagy and provide a dual mechanism for selective interaction between HERC2 and [3Fe-4S]-NCOA4 for proteasomal degradation or between ferritin and apo-NCOA4 for ferritinophagy in the control of iron homeostasis.

Redefining Iron Deficiency in Patients With Chronic Heart Failure.

A serum ferritin level <15 to 20 µg/L historically identified patients who had absent bone marrow iron stores, but serum ferritin levels are distorted by the systemic inflammatory states seen in patients with chronic kidney disease or heart failure. As a result, nearly 25 years ago, the diagnostic ferritin threshold was increased 5- to 20-fold in patients with chronic kidney disease (ie, iron deficiency was identified if the serum ferritin level was <100 µg/L, regardless of transferrin saturation [TSAT], or 100 to 299 µg/L if TSAT was <20%). This guidance was motivated not by the findings of studies of total body or tissue iron depletion, but by a desire to encourage the use of iron supplements to potentiate the response to erythropoiesis-stimulating agents in patients with renal anemia. However, in patients with heart failure, this definition does not reliably identify patients with an absolute or functional iron-deficiency state, and it includes individuals with TSATs (≥20%) and serum ferritin levels in the normal range (20-100 mg/L) who are not iron deficient, have an excellent prognosis, and do not respond favorably to iron therapy. Furthermore, serum ferritin levels may be distorted by the use of both neprilysin and sodium-glucose cotransporter 2 inhibitors, both of which may act to mobilize endogenous iron stores. The most evidence-based and trial-tested definition of iron deficiency is the presence of hypoferremia, as reflected by as a TSAT <20%. These hypoferremic patients are generally iron deficient on bone marrow examination, and after intravenous iron therapy, they exhibit an improvement in exercise tolerance and functional capacity (when meaningfully impaired) and show the most marked reduction (ie, 20%-30%) in the risk of cardiovascular death or total heart failure hospitalizations. Therefore, we propose that the current ferritin-driven definition of iron deficiency in heart failure should be abandoned and that a definition based on hypoferremia (TSAT <20%) should be adopted.

Effectiveness of ferritin-guided donation intervals in whole-blood donors in the Netherlands (FIND'EM): a stepped-wedge cluster-randomised trial.

BACKGROUND: Whole-blood donors are at increased risk for iron deficiency and anaemia. The current standard of haemoglobin monitoring is insufficient to ensure the maintenance of proper iron reserves and donor health. We aimed to determine the effects of ferritin-guided donation intervals for blood donor health and blood supply in the Netherlands. METHODS: In this stepped-wedge cluster-randomised trial (FIND'EM), the 138 fixed and mobile donation centres in the Netherlands are organised into 29 geographical clusters and the clusters were randomly assigned to four treatment groups, with two groups being further split into two per a protocol amendment. Eligible donors were whole-blood donors who consented for use of their leftover material in the study. Each group was sequentially crossed over from the existing policy (haemoglobin-based screening; control) to a ferritin-guided donation interval policy over a 3-year period. In the intervention groups, in addition to the existing haemoglobin screening, ferritin was measured in all new donors and at every fifth donation in repeat donors. Subsequent donation intervals were extended to 6 months if ferritin concentrations were 15-30 ng/mL and to 12 months if they were less than 15 ng/mL. Outcomes were measured cross-sectionally across all donation centres at four timepoints. Primary outcomes were ferritin and haemoglobin concentrations, iron deficiency, and haemoglobin-based deferrals. We assessed all outcomes by sex and menopausal status and significance for primary outcomes was indicated by a p value of less than 0·0125. This trial is registered in the Dutch trial registry, NTR6738, and is complete. FINDINGS: Between Sept 11, 2017, and Nov 27, 2020, 412 888 whole-blood donors visited a donation centre, and we did measurements on samples from 37 621 donations from 36 099 donors. Over 38 months, ferritin-guided donation intervals increased mean ferritin concentrations (by 0·18 log10 ng/mL [95% CI 0·15-0·22; p<0·0001] in male donors, 0·10 log10 ng/mL [0·06-0·15; p<0·0001] in premenopausal female donors, and 0·17 log10 ng/mL [0·12-0·21; p<0·0001] in postmenopausal female donors) and mean haemoglobin concentrations (by 0·30 g/dL [95% CI 0·22-0·38; p<0·0001] in male donors, 0·12 g/dL [0·03-0·20; p<0·0074] in premenopausal female donors, and 0·16 g/dL [0·05-0·27; p<0·0044] in postmenopausal female donors). Iron deficiency decreased by 36-38 months (odds ratio [OR] 0·24 [95% CI 0·18-0·31; p<0·0001] for male donors, 0·49 [0·37-0·64; p<0·0001] for premenopausal female donors, and 0·24 [0·15-0·37; p<0·0001] for postmenopausal female donors). At 36-38 months, haemoglobin-based deferral decreased significantly in male donors (OR at 36-38 months 0·21 [95% CI 0·10-0·40, p<0·0001]) but not significantly in premenopausal or postmenopausal female donors (0·81 [0·54-1·20; p=0·29] and 0·50 [95% CI 0·25-0·98; p=0·051], respectively). INTERPRETATION: Ferritin-guided donation intervals significantly improved haemoglobin and ferritin concentrations and significantly decreased iron deficiency over the study period. Haemoglobin-based deferrals decreased significantly for male donors, but not female donors. Although this intervention is overall beneficial for maintenance of iron and haemoglobin concentrations in donors, increased efforts are needed to recruit and retain donors. FUNDING: The Sanquin Research Programming Committee.

Brain Iron Dysregulation in Iron Deficiency Anemia-Related Restless Leg Syndrome Revealed by Neuron-Derived Extracellular Vesicles: A Case-Control Study.

Brain iron deficiency (ID) and, to a degree, systemic ID have been implicated in restless leg syndrome (RLS) pathogenesis. Previously, we found increased ferritin in neuron-derived extracellular vesicles (NDEVs) in RLS, suggesting a mechanism for depleting intracellular iron by secreting ferritin-loaded NDEVs. In this study, we hypothesized that increased NDEV ferritin occurs even in RLS accompanied by systemic ID and that neuronal intracellular iron depletion in RLS also manifests as NDEV abnormalities in other iron regulatory proteins, specifically, decreased transferrin receptor (TfR) and increased ferroportin. To address these hypotheses, we studied 71 women with ID anemia, 36 with RLS, and 35 without RLS. Subjects with RLS again showed higher NDEV ferritin and also decreased TfR, suggesting diminished neuronal capacity for iron uptake. Findings inform a more complete understanding of the pathogenic role of neuronal iron homeostasis and dissociate it from peripheral ID. ANN NEUROL 2024;96:560-564.

Serum Interleukin-6 and Serum Ferritin Levels Are the Independent Risk Factors for Pneumonia in Elderly Patients.

Pneumonia is a common infection in elderly patients. We explored the correlations of serum interleukin-6 (IL-6) and serum ferritin (SF) levels with immune function/disease severity in elderly pneumonia patients. Subjects were allocated into the mild pneumonia (MP), severe pneumonia (SP), and normal groups, with their age/sex/body mass index/ disease course and severity/blood pressure/comorbidities/medications/prealbumin (PA)/albumin (ALB)/C-reactive protein (CRP)/procalcitonin (PCT)/smoking status documented. The disease severity was evaluated by pneumonia severity index (PSI). T helper 17 (Th17)/regulatory T (Treg) cell ratios and IL-6/SF/immunoglobulin G (IgG)/Th17 cytokine (IL-21)/Treg cytokine (IL-10)/PA/ALB levels were assessed. The correlations between these indexes/independent risk factors in elderly patients with severe pneumonia were evaluated. There were differences in smoking and CRP/PCT/ALB/PA levels among the three groups, but only CRP/ALB were different between the MP/SP groups. Pneumonia patients exhibited up-regulated Th17 cell ratio and serum IL-6/SF/IL-21/IL-10/IgG levels, down-regulated Treg cell ratio, and greater differences were noted in severe cases. Serum IL-6/SF levels were positively correlated with disease severity, immune function, and IL-21/IL-10/IgG levels. Collectively, serum IL-6 and SF levels in elderly pneumonia patients were conspicuously positively correlated with disease severity and IL-21/IL-10/IgG levels. CRP, ALB, IL-6 and SF levels were independent risk factors for severe pneumonia in elderly patients.

Ferritin: Significance in viral infections.

As an indispensable trace element, iron is essential for many biological processes. Increasing evidence has shown that virus infection can perturb iron metabolism and play a role in the occurrence and development of viral infection-related diseases. Ferritin plays a crucial role in maintaining the body's iron homoeostasis. It is an important protein to stabilise the iron balance in cells. Ferritin is a 24-mer hollow iron storage protein composed of two subunits: ferritin heavy chain and ferritin light chain. It was reported that ferritin is not only an intra-cellular iron storage protein, but also a pathogenic mediator that enhances the inflammatory process and stimulates the further inflammatory pathway, which is a key member of the vicious pathogenic cycle to perpetuate. Ferritin exerts immuno-suppressive and pro-inflammatory functions during viral infection. In this review, we describe in detail the basic information of ferritin in the first section, including its structural features, the regulation of ferritin. In the second part, we focus on the role of ferritin in viral infection-related diseases and the molecular mechanisms by which viral infection regulates ferritin. The last section briefly outlines the potential of ferritin in antiviral therapy. Given the importance of iron and viral infection, understanding the role of ferritin during viral infection helps us understand the relationship between iron metabolic dysfunction and viral infection, which provides a new direction for the development of antiviral therapeutic drugs.

A small molecule redistributes iron in ferroportin-deficient mice and patient-derived primary macrophages.

Deficiencies of the transmembrane iron-transporting protein ferroportin (FPN1) cause the iron misdistribution that underlies ferroportin disease, anemia of inflammation, and several other human diseases and conditions. A small molecule natural product, hinokitiol, was recently shown to serve as a surrogate transmembrane iron transporter that can restore hemoglobinization in zebrafish deficient in other iron transporting proteins and can increase gut iron absorption in FPN1-deficient flatiron mice. However, whether hinokitiol can restore normal iron physiology in FPN1-deficient animals or primary cells from patients and the mechanisms underlying such targeted activities remain unknown. Here, we show that hinokitiol redistributes iron from the liver to red blood cells in flatiron mice, thereby increasing hemoglobin and hematocrit. Mechanistic studies confirm that hinokitiol functions as a surrogate transmembrane iron transporter to release iron trapped within liver macrophages, that hinokitiol-Fe complexes transfer iron to transferrin, and that the resulting transferrin-Fe complexes drive red blood cell maturation in a transferrin-receptor-dependent manner. We also show in FPN1-deficient primary macrophages derived from patients with ferroportin disease that hinokitiol moves labile iron from inside to outside cells and decreases intracellular ferritin levels. The mobilization of nonlabile iron is accompanied by reductions in intracellular ferritin, consistent with the activation of regulated ferritin proteolysis. These findings collectively provide foundational support for the translation of small molecule iron transporters into therapies for human diseases caused by iron misdistribution.

Intravenous iron for heart failure, iron deficiency definitions, and clinical response: the IRONMAN trial.

BACKGROUND AND AIMS: What is the relationship between blood tests for iron deficiency, including anaemia, and the response to intravenous iron in patients with heart failure? METHODS: In the IRONMAN trial, 1137 patients with heart failure, ejection fraction ≤ 45%, and either serum ferritin < 100 µg/L or transferrin saturation (TSAT) < 20% were randomized to intravenous ferric derisomaltose (FDI) or usual care. Relationships were investigated between baseline anaemia severity, ferritin and TSAT, to changes in haemoglobin from baseline to 4 months, Minnesota Living with Heart Failure (MLwHF) score and 6-minute walk distance achieved at 4 months, and clinical events, including heart failure hospitalization (recurrent) or cardiovascular death. RESULTS: The rise in haemoglobin after administering FDI, adjusted for usual care, was greater for lower baseline TSAT (Pinteraction < .0001) and ferritin (Pinteraction = .028) and more severe anaemia (Pinteraction = .014). MLwHF scores at 4 months were somewhat lower (better) with FDI for more anaemic patients (overall Pinteraction = .14; physical Pinteraction = .085; emotional Pinteraction = .043) but were not related to baseline TSAT or ferritin. Blood tests did not predict difference in achieved walking distance for those randomized to FDI compared to control. The absence of anaemia or a TSAT ≥ 20% was associated with lower event rates and little evidence of benefit from FDI. More severe anaemia or TSAT < 20%, especially when ferritin was ≥100 µg/L, was associated with higher event rates and greater absolute reductions in events with FDI, albeit not statistically significant. CONCLUSIONS: This hypothesis-generating analysis suggests that anaemia or TSAT < 20% with ferritin > 100 µg/L might identify patients with heart failure who obtain greater benefit from intravenous iron. This interpretation requires confirmation.

Frequency of HLA-DR+CD38hi T cells identifies and quantifies T-cell activation in hemophagocytic lymphohistiocytosis, hyperinflammation, and immune regulatory disorders.

BACKGROUND: Quantifying T-cell activation is essential for the diagnosis and evaluation of treatment response in various hyperinflammatory and immune regulatory disorders, including hemophagocytic lymphohistiocytosis. Plasma soluble IL-2 receptor (sIL-2R) is a well-established biomarker for evaluating systemic T-cell activation. However, the limited availability of sIL-2R testing could result in delayed diagnosis. Furthermore, high sIL-2R levels may not always reflect T-cell activation. OBJECTIVES: To address these limitations, this study investigated whether cell surface markers of T-cell activation, HLA-DR, and CD38, as assessed by flow cytometry, could be used to quantify systemic T-cell activation in a variety of inflammatory disease states and examine its correlation with sIL-2R levels. METHODS: Results for sIL-2R, CXCL9, and ferritin assays were obtained from patient's medical records. Frequency of HLA-DR+CD38high(hi) T-cells was assessed in different T-cell subsets using flow cytometry. RESULTS: In this study's cohort, activation in total CD8+ T (r = 0.65; P < .0001) and CD4+ (r = 0.42; P < .0001) T-cell subsets significantly correlated with plasma sIL-2R levels. At the disease onset, the frequency of HLA-DR+CD38hi T cells in CD8+ T (r = 0.65, P < .0001) and CD4+ T (r = 0.77; P < .0001) effector memory (TEM) compartments correlated strongly with sIL-2R levels. Evaluation of T-cell activation markers in follow-up samples also revealed a positive correlation for both CD4+ TEM and CD8+ TEM activation with sIL-2R levels; thus, attesting its utility in initial diagnosis and in evaluating treatment response. The frequency of HLA-DR+CD38hi T-cells in the CD8+ TEM compartment also correlated with plasma CXCL9 (r = 0.42; P = .0120) and ferritin levels (r = 0.32; P = .0037). CONCLUSIONS: This study demonstrates that flow cytometry-based direct T-cell activation assessed by HLA-DR+CD38hi T cells accurately quantifies T-cell activation and strongly correlates with sIL-2R levels across a spectrum of hyperinflammatory and immune dysregulation disorders.

Serum ferritin levels can predict long-term outcomes in patients with metabolic dysfunction-associated steatotic liver disease.

OBJECTIVE: Hyperferritinaemia is associated with liver fibrosis severity in patients with metabolic dysfunction-associated steatotic liver disease (MASLD), but the longitudinal implications have not been thoroughly investigated. We assessed the role of serum ferritin in predicting long-term outcomes or death. DESIGN: We evaluated the relationship between baseline serum ferritin and longitudinal events in a multicentre cohort of 1342 patients. Four survival models considering ferritin with confounders or non-invasive scoring systems were applied with repeated five-fold cross-validation schema. Prediction performance was evaluated in terms of Harrell's C-index and its improvement by including ferritin as a covariate. RESULTS: Median follow-up time was 96 months. Liver-related events occurred in 7.7%, hepatocellular carcinoma in 1.9%, cardiovascular events in 10.9%, extrahepatic cancers in 8.3% and all-cause mortality in 5.8%. Hyperferritinaemia was associated with a 50% increased risk of liver-related events and 27% of all-cause mortality. A stepwise increase in baseline ferritin thresholds was associated with a statistical increase in C-index, ranging between 0.02 (lasso-penalised Cox regression) and 0.03 (ridge-penalised Cox regression); the risk of developing liver-related events mainly increased from threshold 215.5 µg/L (median HR=1.71 and C-index=0.71) and the risk of overall mortality from threshold 272 µg/L (median HR=1.49 and C-index=0.70). The inclusion of serum ferritin thresholds (215.5 µg/L and 272 µg/L) in predictive models increased the performance of Fibrosis-4 and Non-Alcoholic Fatty Liver Disease Fibrosis Score in the longitudinal risk assessment of liver-related events (C-indices>0.71) and overall mortality (C-indices>0.65). CONCLUSIONS: This study supports the potential use of serum ferritin values for predicting the long-term prognosis of patients with MASLD.

Transferrin Receptor Is Necessary for Proper Oligodendrocyte Iron Homeostasis and Development.

To test the hypothesis that the transferrin (Tf) cycle has unique importance for oligodendrocyte development and function, we disrupted the expression of the Tf receptor (Tfr) gene in oligodendrocyte progenitor cells (OPCs) on mice of either sex using the Cre/lox system. This ablation results in the elimination of iron incorporation via the Tf cycle but leaves other Tf functions intact. Mice lacking Tfr, specifically in NG2 or Sox10-positive OPCs, developed a hypomyelination phenotype. Both OPC differentiation and myelination were affected, and Tfr deletion resulted in impaired OPC iron absorption. Specifically, the brains of Tfr cKO animals presented a reduction in the quantity of myelinated axons, as well as fewer mature oligodendrocytes. In contrast, the ablation of Tfr in adult mice affected neither mature oligodendrocytes nor myelin synthesis. RNA-seq analysis performed in Tfr cKO OPCs revealed misregulated genes involved in OPC maturation, myelination, and mitochondrial activity. Tfr deletion in cortical OPCs also disrupted the activity of the mTORC1 signaling pathway, epigenetic mechanisms critical for gene transcription and the expression of structural mitochondrial genes. RNA-seq studies were additionally conducted in OPCs in which iron storage was disrupted by deleting the ferritin heavy chain. These OPCs display abnormal regulation of genes associated with iron transport, antioxidant activity, and mitochondrial activity. Thus, our results indicate that the Tf cycle is central for iron homeostasis in OPCs during postnatal development and suggest that both iron uptake via Tfr and iron storage in ferritin are critical for energy production, mitochondrial activity, and maturation of postnatal OPCs.SIGNIFICANCE STATEMENT By knocking-out transferrin receptor (Tfr) specifically in oligodendrocyte progenitor cells (OPCs), we have established that iron incorporation via the Tf cycle is key for OPC iron homeostasis and for the normal function of these cells during the postnatal development of the CNS. Moreover, RNA-seq analysis indicated that both Tfr iron uptake and ferritin iron storage are critical for proper OPC mitochondrial activity, energy production, and maturation.

Antimalarial Delivery with a Ferritin-Based Protein Cage: A Step toward Developing Smart Therapeutics against Malaria.

Over the past two decades, the utilization of protein cages has witnessed exponential growth driven by their extensive applications in biotechnology and therapeutics. In the context of the recent Covid-19 pandemic, protein-cage-based scaffolds played a pivotal role in vaccine development. Beyond vaccines, these protein cages have proven valuable in diverse drug delivery applications thanks to their distinctive architecture and structural stability. Among the various types of protein cages, ferritin-based cages have taken the lead in drug delivery applications. This is primarily attributed to their ease of production, exceptional thermal stability, and nontoxic nature. While ferritin-based cages are commonly employed in anticancer drug delivery and contrast agent delivery, their efficacy in malarial drug delivery had not been explored until this study. In this investigation, several antimalarial drugs were encapsulated within horse spleen ferritin, and the binding and loading processes were validated through both experimental and computational techniques. The data unequivocally demonstrate the facile incorporation of antimalarial drugs into ferritin without disrupting its three-dimensional structure. Computational docking and molecular dynamics simulations were employed to pinpoint the precise location of the drug binding site within ferritin. Subsequent efficacy testing on Plasmodium revealed that the developed nanoconjugate, comprising the drug-ferritin conjugate, exhibited significant effectiveness in eradicating the parasite. In conclusion, the findings strongly indicate that ferritin-based carrier systems hold tremendous promise for the future of antimalarial drug delivery, offering high selectivity and limited side effects.

Oxygen modulates iron homeostasis by switching iron sensing of NCOA4.

To ensure proper utilization of iron and avoid its toxicity, cells are equipped with iron-sensing proteins to maintain cellular iron homeostasis. We showed previously that nuclear receptor coactivator 4 (NCOA4), a ferritin-specific autophagy adapter, intricately regulates the fate of ferritin; upon binding to Fe3+, NCOA4 forms insoluble condensates and regulates ferritin autophagy in iron-replete conditions. Here, we demonstrate an additional iron-sensing mechanism of NCOA4. Our results indicate that the insertion of an iron-sulfur (Fe-S) cluster enables preferential recognition of NCOA4 by the HERC2 (HECT and RLD domain containing E3 ubiquitin protein ligase 2) ubiquitin ligase in iron-replete conditions, resulting in degradation by the proteasome and subsequent inhibition of ferritinophagy. We also found that both condensation and ubiquitin-mediated degradation of NCOA4 can occur in the same cell, and the cellular oxygen tension determines the selection of these pathways. Fe-S cluster-mediated degradation of NCOA4 is enhanced under hypoxia, whereas NCOA4 forms condensates and degrades ferritin at higher oxygen levels. Considering the involvement of iron in oxygen handling, our findings demonstrate that the NCOA4-ferritin axis is another layer of cellular iron regulation in response to oxygen levels.

PTEN-induced kinase PINK1 supports colorectal cancer growth by regulating the labile iron pool.

Mitophagy is a cargo-specific autophagic process that recycles damaged mitochondria to promote mitochondrial turnover. PTEN-induced putative kinase 1 (PINK1) mediates the canonical mitophagic pathway. However, the role of PINK1 in diseases where mitophagy has been purported to play a role, such as colorectal cancer, is unclear. Our results here demonstrate that higher PINK1 expression is positively correlated with decreased colon cancer survival, and mitophagy is required for colon cancer growth. We show that doxycycline-inducible knockdown (KD) of PINK1 in a panel of colon cancer cell lines inhibited proliferation, whereas disruption of other mitophagy receptors did not impact cell growth. We observed that PINK KD led to a decrease in mitochondrial respiration, membrane hyperpolarization, accumulation of mitochondrial DNA, and depletion of antioxidant glutathione. In addition, mitochondria are important hubs for the utilization of iron and synthesizing iron-dependent cofactors such as heme and iron sulfur clusters. We observed an increase in the iron storage protein ferritin and a decreased labile iron pool in the PINK1 KD cells, but total cellular iron or markers of iron starvation/overload were not affected. Finally, cellular iron storage and the labile iron pool are maintained via autophagic degradation of ferritin (ferritinophagy). We found overexpressing nuclear receptor coactivator 4, a key adaptor for ferritinophagy, rescued cell growth and the labile iron pool in PINK1 KD cells. These results indicate that PINK1 integrates mitophagy and ferritinophagy to regulate intracellular iron availability and is essential for maintaining intracellular iron homeostasis to support survival and growth in colorectal cancer cells.