Upregulation Of Transferrin Receptor Research Articles

Upregulation of Transferrin Receptor 1 (TfR1) but Not Glucose Transporter 1 (GLUT1) or CD98hc at the Blood-Brain Barrier in Response to Valproic Acid.

Transferrin receptor 1 (TfR1), glucose transporter 1 (GLUT1), and CD98hc are candidates for targeted therapy at the blood-brain barrier (BBB). Our objective was to challenge the expression of TfR1, GLUT1, and CD98hc in brain capillaries using the histone deacetylase inhibitor (HDACi) valproic acid (VPA). Primary mouse brain capillary endothelial cells (BCECs) and brain capillaries isolated from mice injected intraperitoneally with VPA were examined using RT-qPCR and ELISA. Targeting to the BBB was performed by injecting monoclonal anti-TfR1 (Ri7217)-conjugated gold nanoparticles measured using ICP-MS. In BCECs co-cultured with glial cells, Tfrc mRNA expression was significantly higher after 6 h VPA, returning to baseline after 24 h. In vivo Glut1 mRNA expression was significantly higher in males, but not females, receiving VPA, whereas Cd98hc mRNA expression was unaffected by VPA. TfR1 increased significantly in vivo after VPA, whereas GLUT1 and CD98hc were unchanged. The uptake of anti-TfR1-conjugated nanoparticles was unaltered by VPA despite upregulated TfR expression. VPA upregulates TfR1 in brain endothelium in vivo and in vitro. VPA does not increase GLUT1 and CD98hc proteins. The increase in TfR1 does not result in higher anti-TfR1 antibody targetability, suggesting targeting sufficiently occurs with available transferrin receptors without further contribution from accessory VPA-induced TfR1.

Defective ferritinophagy and imbalanced iron metabolism in PBDE-47-triggered neuronal ferroptosis and salvage by Canolol

The brominated flame retardant 2,2′,4,4′-tetrabromodiphenyl ether (PBDE-47) is a ubiquitous environmental pollutant that causes neurotoxicity. However, incomplete understanding of the underlying mechanisms has hampered the development of effective intervention strategies. Oxidative stress and related cell death are the modes of action for PBDE-47 neurotoxicity, which are also the characteristics of ferroptosis. Nonetheless, the role of ferroptosis in PBDE-47-induced neurotoxicity remains unclear. In the present study, we found that PBDE-47 triggered ferroptosis in neuron-like PC12 cells, as evidenced by intracellular iron overload, lipid peroxidation, and mitochondrial damage. This was confirmed by ferroptosis inhibitors including the lipid reactive oxygen species scavenger ferrostatin-1 and iron chelator deferoxamine mesylate. Mechanistically, PBDE-47 impaired ferritinophagy by disrupting nuclear receptor coactivator 4-mediated lysosomal degradation of the iron storage protein ferritin. Moreover, PBDE-47 disturbed iron metabolism by increasing cellular iron import via upregulation of transferrin receptor 1 and decreasing cellular iron export via downregulation of ferroportin 1 (FPN1). Intriguingly, rescuing lysosomal function by overexpressing cathepsin B (CatB) mitigated PBDE-47-induced ferroptosis by partially restoring dysfunctional ferritinophagy and enhancing iron excretion via the upregulation of FPN1. However, FPN1 knockdown reversed the beneficial effects of CatB overexpression on the PBDE-47-induced iron overload. Finally, network pharmacology integrated with experimental validation revealed that Canolol, the main phenolic compound in canola oil, protected against PBDE-47-evoked iron overload, resulting in ferroptosis by restoring defective ferritinophagy and improving abnormal iron metabolism via lowering iron uptake and facilitating iron excretion. Overall, these data suggest that ferroptosis is a novel mechanism of PBDE-47-induced neuronal death and that manipulation of ferritinophagy and iron metabolism via Canolol represents a promising therapeutic strategy.

Genetic Determined Iron Starvation Signature in Friedreich's Ataxia.

Early studies in cellular models suggested an iron accumulation in Friedreich's ataxia (FA), yet findings from patients are lacking. The objective is to characterize systemic iron metabolism, body iron storages, and intracellular iron regulation in FA patients. In FA patients and matched healthy controls, we assessed serum iron parameters, regulatory hormones as well as the expression of regulatory proteins and iron distribution in peripheral blood mononuclear cells (PBMCs). We applied magnetic resonance imaging with R2*-relaxometry to quantify iron storages in the liver, spleen, and pancreas. Across all evaluations, we assessed the influence of the genetic severity as expressed by the length of the shorter GAA-expansion (GAA1). We recruited 40 FA patients (19 women). Compared to controls, FA patients displayed lower serum iron and transferrin saturation. Serum ferritin, hepcidin, mean corpuscular hemoglobin and mean corpuscular volume in FA inversely correlated with the GAA1-repeat length, indicating iron deficiency and restricted availability for erythropoiesis with increasing genetic severity. R2*-relaxometry revealed a reduction of splenic and hepatic iron stores in FA. Liver and spleen R2* values inversely correlated with the GAA1-repeat length. FA PBMCs displayed downregulation of ferritin and upregulation of transferrin receptor and divalent metal transporter-1 mRNA, particularly in patients with >500 GAA1-repeats. In FA PBMCs, intracellular iron was not increased, but shifted toward mitochondria. We provide evidence for a previously unrecognized iron starvation signature at systemic and cellular levels in FA patients, which is related to the underlying genetic severity. These findings challenge the use of systemic iron lowering therapies in FA. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Correlation between ferroptosis and adriamycin resistance in breast cancer regulated by transferrin receptor and its molecular mechanism.

Breast cancer is the most prevalent malignant tumor in women. Adriamycin (ADR) is a primary chemotherapy drug, but resistance limits its effectiveness. Ferroptosis, a newly identified cell death mechanism, involves the transferrin receptor (TFRC), closely linked with tumor cells. This study aimed to explore TFRC and ferroptosis's role in breast cancer drug resistance. Bioinformatics analysis showed that TFRC was significantly downregulated in drug-resistant cell lines, and patients with low TFRC expression might demonstrate a poor chemotherapeutic response to standard treatment. High expression of TFRC was positively correlated with most of the ferroptosis-related driver genes. The research findings indicate that ferroptosis markers were higher in breast cancer tissues than in normal ones. In chemotherapy-sensitive cases, Ferrous ion (Fe2+ ) and malondialdehyde (MDA) levels were higher than in resistant cases (all p < .05). TFRC expression was higher in breast cancer than in normal tissue, especially in the sensitive group (all p < .05). Cytological experiments showed increased hydrogen peroxide (H2 O2 ) after ADR treatment in both sensitive and resistant cells, with varying MDA changes (all p < .05). Elevating TFRC increased Fe2+ and MDA in ADR-resistant cells, enhancing their sensitivity to ADR. However, TFRC upregulation combined with ADR increased proliferation and invasiveness in resistant cell lines (all p < .05). In conclusion, ADR resistance to breast cancer is related to the regulation of iron ion-mediated ferroptosis by TFRC. Upregulation of TFRC in ADR-resistant breast cancer cells activates ferroptosis and reverses ADR chemotherapy resistance of breast cancer.

Ferroptosis preceded the onset of oxidative stress under acute ammonia exposure and quercetin relieved ammonia-induced ferroptosis of yellow catfish (Pelteobagrus fulvidraco)

Ammonia is the most common pollutant and stressor in the aquaculture environment and can cause massive fish mortality. Its toxicity in fish is mainly related to the generation of oxidative stress, but the mechanisms are not well understood. Ferroptosis is a unique cell death pathway characterized by iron-dependent lipid peroxidation. However, little information is available regarding the association between oxidative stress and ferroptosis under ammonia stress and mitigation measures in fish. This study was divided into two parts. In the first part of the study, yellow catfish were exposed to three levels of ammonia (0 mg L−1, 5.7 mg L−1, 28.5 mg L−1) for 96 h. Results showed that ammonia poisoning could result in a decrease in survival rates, elevation of blood ammonia levels, ferroptosis activation (iron accumulation, reduced glutathione depletion, upregulation of transferrin receptor 1 and 15B-lipoxygenase, first increased then a decreased expression of glutamate/cystine antiporter system xc– and glutathione peroxidase 4) and oxidative stress (first increased and then decreased expression of superoxide dismutase and catalase). In the second part of the study, primary head-kidney macrophages were used for investigating the underlying mechanism of quercetin in protecting against ammonia-induced ferroptosis in vitro. Results showed that quercetin could decrease the production of reactive oxygen species, increase GSH contents, suppress the expression of TFR1 and LOX-15B, and upregulate the expression levels of FER, system xc– as well as GPX4. The results of this study suggested that oxidative stress induced by ferroptosis might be a prominent mechanism behind ammonia-induced cytotoxicity and quercetin exhibited good protective effects against macrophage ferroptosis under ammonia stress.

Nrf2 regulates iron-dependent hippocampal synapses and functional connectivity damage in depression

Neuronal iron overload contributes to synaptic damage and neuropsychiatric disorders. However, the molecular mechanisms underlying iron deposition in depression remain largely unexplored. Our study aims to investigate how nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2) ameliorates hippocampal synaptic dysfunction and reduces brain functional connectivity (FC) associated with excessive iron in depression. We treated mice with chronic unpredictable mild stress (CUMS) with the iron chelator deferoxamine mesylate (DFOM) and a high-iron diet (2.5% carbonyl iron) to examine the role of iron overload in synaptic plasticity. The involvement of Nrf2 in iron metabolism and brain function was assessed using molecular biological techniques and in vivo resting-state functional magnetic resonance imaging (rs-fMRI) through genetic deletion or pharmacologic activation of Nrf2. The results demonstrated a significant correlation between elevated serum iron levels and impaired hippocampal functional connectivity (FC), which contributed to the development of depression-induced CUMS. Iron overload plays a crucial role in CUMS-induced depression and synaptic dysfunction, as evidenced by the therapeutic effects of a high-iron diet and DFOM. The observed iron overload in this study was associated with decreased Nrf2 levels and increased expression of transferrin receptors (TfR). Notably, inhibition of iron accumulation effectively attenuated CUMS-induced synaptic damage mediated by downregulation of brain-derived neurotrophic factor (BDNF). Nrf2−/− mice exhibited compromised FC within the limbic system and the basal ganglia, particularly in the hippocampus, and inhibition of iron accumulation effectively attenuated CUMS-induced synaptic damage mediated by downregulation of brain-derived neurotrophic factor (BDNF). Activation of Nrf2 restored iron homeostasis and reversed vulnerability to depression. Mechanistically, we further identified that Nrf2 deletion promoted iron overload via upregulation of TfR and downregulation of ferritin light chain (FtL), leading to BDNF-mediated synapse damage in the hippocampus. Therefore, our findings unveil a novel role for Nrf2 in regulating iron homeostasis while providing mechanistic insights into poststress susceptibility to depression. Targeting Nrf2-mediated iron metabolism may offer promising strategies for developing more effective antidepressant therapies.

Transferrin-Targeted Liposomes in Glioblastoma Therapy: A Review.

Glioblastoma (GBM) is a highly aggressive brain tumor, and its treatment is further complicated by the high selectivity of the blood-brain barrier (BBB). The scientific community is urgently seeking innovative and effective therapeutic solutions. Liposomes are a promising new tool that has shown potential in addressing the limitations of chemotherapy, such as poor bioavailability and toxicity to healthy cells. However, passive targeting strategies based solely on the physicochemical properties of liposomes have proven ineffective due to a lack of tissue specificity. Accordingly, the upregulation of transferrin receptors (TfRs) in brain tissue has led to the development of TfR-targeted anticancer therapeutics. Currently, one of the most widely adopted methods for improving drug delivery in the treatment of GBM and other neurological disorders is the utilization of active targeting strategies that specifically target this receptor. In this review, we discuss the role of Tf-conjugated liposomes in GBM therapy and present some recent studies investigating the drug delivery efficiency of Tf-liposomes; in addition, we address some challenges currently facing this approach to treatment and present some potential improvement possibilities.

Dysregulation of iron homeostasis by TfR-1 renders EZH2 wild type diffuse large B-cell lymphoma resistance to EZH2 inhibition.

EZH2 has been regarded as an efficient target for diffuse large B-cell lymphoma (DLBCL), but the clinical benefits of EZH2 inhibitors (EZH2i) are limited. To date, only EPZ-6438 has been approved by FDA for the treatment of follicular lymphoma and epithelioid sarcoma. We have discovered a novel EZH1/2 inhibitor HH2853 with a better antitumor effect than EPZ-6438 in preclinical studies. In this study we explored the molecular mechanism underlying the primary resistance to EZH2 inhibitors and sought for combination therapy strategy to overcome it. By analyzing EPZ-6438 and HH2853 response profiling, we found that EZH2 inhibition increased intracellular iron through upregulation of transferrin receptor 1 (TfR-1), ultimately triggered resistance to EZH2i in DLBCL cells. We demonstrated that H3K27ac gain by EZH2i enhanced c-Myc transcription, which contributed to TfR-1 overexpression in insensitive U-2932 and WILL-2 cells. On the other hand, EZH2i impaired the occurrence of ferroptosis by upregulating the heat shock protein family A (Hsp70) member 5 (HSPA5) and stabilizing glutathione peroxidase 4 (GPX4), a ferroptosis suppressor; co-treatment with ferroptosis inducer erastin effectively overrode the resistance of DLBCL to EZH2i in vitro and in vivo. Altogether, this study reveals iron-dependent resistance evoked by EZH2i in DLBCL cells, and suggests that combination with ferroptosis inducer may be a promising therapeutic strategy.

Sinapine induced ferroptosis in non-small cell lung cancer cells by upregulating transferrin/transferrin receptor and downregulating SLC7A11.

Sinapine (SI) is a naturally occurring product with biological properties, but its activity against non-small cell lung cancer (NSCLC) remains unclear. This research examined the anti-tumour effects of SI in NSCLC cells and the underlying mechanisms of any effects. SI induced ferroptosis, a novel form of cell death, by increasing intracellular ferrous iron, lipid peroxidation, and reactive oxygen species (ROS) in NSCLC cells. SI treatment resulted in transferrin and transferrin receptor upregulation, and inhibition of transferrin or the transferrin receptor reduced the ferroptosis caused by SI. SI treatment also resulted in a p-53 dependent downregulation of SLC7A11. Finally, we evaluated the effects of SI in vivo and it was found that SI also successfully inhibited the growth of NSCLC in vivo. In summary, our data demonstrated that SI triggered ferroptosis in NSCLC cells and may be a promising therapeutic agent for this condition.

Fusaricide is a Novel Iron Chelator that Induces Apoptosis through Activating Caspase-3.

Nonsmall cell lung cancer (NSCLC) has been a fatal and refractory disease worldwide. Novel therapeutic developments based on fundamental investigations of anticancer mechanisms underlie substantial foundations to win the fight against cancer diseases. In this study, we isolated a natural product fusaricide (FCD) from an endophytic fungus of Lycium barbarum, identified as Epicoccum sp. For the first time, we discovered that FCD potently inhibited proliferation in a variety of human NSCLC cell lines, with relatively less toxicity to normal cells. Our study exhibited that FCD induced apoptosis, caused DNA damage and cell cycle arrest in G0/G1 phase, and activated caspase-3 as well as other apoptosis-related factors in human NSCLC NCI-H460 cells. FCD was proven to be an iron chelator that actively decreased levels of cellular labile iron pool in NCI-H460 cells in our study. FeCl3 supplement reversed FCD-induced apoptosis. The upregulation of transferrin receptor 1 (TfR1) and downregulation of ferritin heavy chain (FTH) expression were observed after FCD treatment. In summary, our study highlighted the potential anticancer effects of FCD against human NSCLCs and demonstrated that the FCD-mediated apoptosis depended on binding to intracellular iron.

ATF3 contributes to brucine-triggered glioma cell ferroptosis via promotion of hydrogen peroxide and iron

Ferroptotic cell death is characterized by iron-dependent lipid peroxidation that is initiated by ferrous iron and H2O2 via Fenton reaction, in which the role of activating transcription factor 3 (ATF3) remains elusive. Brucine is a weak alkaline indole alkaloid extracted from the seeds of Strychnos nux-vomica, which has shown potent antitumor activity against various tumors, including glioma. In this study, we showed that brucine inhibited glioma cell growth in vitro and in vivo, which was paralleled by nuclear translocation of ATF3, lipid peroxidation, and increases of iron and H2O2. Furthermore, brucine-induced lipid peroxidation was inhibited or exacerbated when intracellular iron was chelated by deferoxamine (500 μM) or improved by ferric ammonium citrate (500 μM). Suppression of lipid peroxidation with lipophilic antioxidants ferrostatin-1 (50 μM) or liproxstatin-1 (30 μM) rescued brucine-induced glioma cell death. Moreover, knockdown of ATF3 prevented brucine-induced accumulation of iron and H2O2 and glioma cell death. We revealed that brucine induced ATF3 upregulation and translocation into nuclei via activation of ER stress. ATF3 promoted brucine-induced H2O2 accumulation via upregulating NOX4 and SOD1 to generate H2O2 on one hand, and downregulating catalase and xCT to prevent H2O2 degradation on the other hand. H2O2 then contributed to brucine-triggered iron increase and transferrin receptor upregulation, as well as lipid peroxidation. This was further verified by treating glioma cells with exogenous H2O2 alone. Moreover, H2O2 reversely exacerbated brucine-induced ER stress. Taken together, ATF3 contributes to brucine-induced glioma cell ferroptosis via increasing H2O2 and iron.

Does iron overload in metabolic syndrome affect macrophage profile? A case control study

AimsDysmetabolic iron overload syndrome (DIOS) is common but the clinical relevance of iron overload is not understood. Macrophages are central cells in iron homeostasis and inflammation. We hypothesized that iron overload in DIOS could affect the phenotype of monocytes and impair macrophage gene expression. MethodsThis study compared 20 subjects with DIOS to 20 subjects with metabolic syndrome (MetS) without iron overload, and 20 healthy controls. Monocytes were phenotyped by Fluorescence-Activated Cell Sorting (FACS) and differentiated into anti-inflammatory M2 macrophages in the presence of IL-4. The expression of 38 genes related to inflammation, iron metabolism and M2 phenotype was assessed by real-time PCR. ResultsFACS showed no difference between monocytes across the three groups. The macrophagic response to IL-4-driven differentiation was altered in four of the five genes of M2 phenotype (MRC1, F13A1, ABCA1, TGM2 but not FABP4), in DIOS vs Mets and controls demonstrating an impaired M2 polarization. The expression profile of inflammatory genes was not different in DIOS vs MetS. Several genes of iron metabolism presented a higher expression in DIOS vs MetS: SCL11A2 (a free iron transporter, +76 %, p = 0.04), SOD1 (an antioxidant enzyme, +27 %, p = 0.02), and TFRC (the receptor 1 of transferrin, +59 %, p = 0.003). ConclusionsIn DIOS, macrophage polarization toward the M2 alternative phenotype is impaired but not associated with a pro-inflammatory profile. The up regulation of transferrin receptor 1 (TFRC) in DIOS macrophages suggests an adaptive role that may limit iron toxicity in DIOS.

Dual-Effect of Magnetic Resonance Imaging Reporter Gene in Diagnosis and Treatment of Hepatocellular Carcinoma.

ProposeThe early diagnosis of hepatocellular carcinoma (HCC) with ferritin heavy chain (Fth) modified by alpha-fetoprotein (AFP) promoter has been studied. However, no study has focused on the considerable upregulation and specific targeting effects of transferrin receptors (TfR) caused by the transfection of plasmids encoded with the AFP promoter. Thus, the objective of our study was to investigate whether the transfection of Fth gene modified with AFP promoter (AFP@Fth) could be used for early diagnosis and enhanced treatment of HCC.MethodsThe AFP@Fth plasmid was transfected into AFP positive cells. The expression of intracellular Ferritin was verified by Western blot, and the upregulation of TfR was confirmed by immunofluorescence and flow cytometry analysis. Cellular iron accumulation resulting in decreased imaging signals was examined by magnetic resonance imagining. Doxorubicin liposome modified with transferrin (Tf-LPD) was prepared to investigate the efficiency of the subsequent treatment after transfection. The enhanced drug distribution and effects were investigated both in vitro and in vivo.ResultsBoth Ferritin and TfR were overexpressed after transfection. The transfected cells showed higher intracellular iron accumulation and resulted in a lower MR T2-weighted imaging (T2WI) intensity, suggesting that the transfection of AFP@Fth could be a potential strategy for early diagnosis of liver cancer. The following treatment efficacy was revealed by Tf-LPD. As compared with un-transfected cells, transfected cells exhibited higher uptake of transferrin-modified liposomes (Tf-LP), which was due to the specific interaction between Tf and TfR overexpressed on the transfected cells. This is also the reason why Tf-LPD showed better in vitro and in vivo anticancer ability than doxorubicin loaded liposome (LPD). These results suggested that transfection of AFP@Fth could result in enhanced therapy of liver cancer.ConclusionTransfection of AFP@Fth could be used for early diagnosis and for enhanced treatment of live cancers.

Attenuation of White Matter Damage Following Deferoxamine Treatment in Rats After Spinal Cord Injury

With little information available on axonal and myelin damage surrounding the contusion, the study of spinal cord injury (SCI) so far has focused on neuronal death. In this study, we investigated the role of iron overload in long-term oligodendroglia death and progressive white matter damage to rats after SCI using the iron chelator, deferoxamine (DFX). Female Sprague-Dawley rats received either a contusion at T10 or sham-surgery. The rats were treated with DFX or vehicle. All rats were evaluated in behavioral assessments and then euthanized at different time points. Spinal cords were analyzed by diaminobenzidine-enhanced Perls' staining, non-heme iron measurements, Western blotting, immunohistochemistry, and transmission electron microscopy. Iron accumulation after SCI resulted in the upregulation of transferrin receptor and divalent metal transporter 1, which exacerbated the intracellular iron overload. DFX treatment reduced iron overload-induced delayed oligodendrocyte death (e.g., 21 days: 47.12 ± 10.5 vs. 20.02 ± 9.4 x 103/mm2 in the vehicle-treated group, n= 4, P < 0.05). After SCI, the markers of axonal damage and demyelination were increased in white matter in the vehicle-treated group compared with the DFX-treated group (P < 0.05). Iron overload plays an important role in progressive white matter damage after SCI. DFX may be an effective treatment for white matter damage after SCI.

1780-P: In High-Fat Diet-Induced Mice Skeletal Muscles, Iron Overload Plays a Critical Role in Leading Insulin Resistance

Aim/Hypotheses: Iron plays an important role in many physiological processes, including redox balance, inflammation, and mitochondrial respiratory metabolism. Abnormalities in iron metabolism lead to insulin resistance as well as diabetes. However, the abnormal mechanism of iron metabolism in the muscles of insulin resistance animal models is not precisely well known. Therefore, we investigated the molecular mechanism underlying iron dysregulation in high fat diet-induced C57BL/6J mice skeletal muscles. Methods: We measured intracellular iron content in skeletal muscle tissues and iron metabolism related protein levels, such as transferrin receptor1, heavy chain ferritin, light chain ferritin, DMT1, and ferroportin. To investigate the association between iron content and insulin resistance, we treated iron donor or chelator in an animal model and performed insulin tolerance tests and measurement of insulin signaling. Results: Interestingly, intracellular iron levels were increased in high fat diet-induced mice skeletal muscles. We also observed up-regulation of transferrin receptor 1 (TfR1), ferritin, but did not observe a change of DMT1 and ferroportin. Treatment with iron dextran, an iron donor, in C57BL/6J normal mice induced insulin resistance. However, treatment of desferrioxamine, an iron chelator, in high fat diet-induced insulin resistance mice recovered insulin resistance. Iron overload with iron dextran impaired insulin signaling in skeletal muscles, while iron chelation with desferrioxamine recovered high fat-induced dysregulated insulin signaling. Conclusions/interpretation: Therefore, we consider fine-tuning of skeletal muscle iron levels and highly suggest the use for preventing and/or treating insulin resistance and diabetes. Disclosure S. Choi: None. N. Lee: None. H. Moon: None. H. Kim: None. J. Jeon: None. Y. Kang: None. T. Kim: None. K. Lee: None.

Pseudolaric acid B triggers ferroptosis in glioma cells via activation of Nox4 and inhibition of xCT

Ferroptosis is a form of programmed cell death decided by iron-dependent lipid peroxidation, but its role in glioma cell death remains unclear. In this study, we found Pseudolaric acid B (PAB) inhibited the viabilities of glioma cells in vitro and in vivo, which was accompanied by abnormal increases of intracellular ferrous iron, H2O2 and lipid peroxidation, as well as depletion of GSH and cysteine. In vitro studies revealed that the lipid peroxidation and the cell death caused by PAB were both inhibited by iron chelator deferoxamine, but exacerbated by supplement of ferric ammonium citrate. Inhibition of lipid peroxidation with ferrostatin-1 or GSH rescued PAB-induced cell death. Morphologically, the cells treated with PAB presented intact membrane, shrunken mitochondria with increased membrane density, and normal-sized nucleus without chromatin condensation. Mechanistically, PAB improved intracellular iron by upregulation of transferrin receptor. The increased iron activated Nox4, which resulted in overproduction of H2O2 and lipid peroxides. Moreover, PAB depleted intracellular GSH via p53-mediated xCT pathway, which further exacerbated accumulation of H2O2 and lipid peroxides. Thus, PAB triggers ferroptosis in glioma cells and is a potential medicine for glioma treatment.

Cysteine Prevents the Reduction in Keratin Synthesis Induced by Iron Deficiency in Human Keratinocytes.

L-cysteine is currently recognized as a conditionally essential sulphur amino acid. Besides contributing to many biological pathways, cysteine is a key component of the keratin protein by its ability to form disulfide bridges that confer strength and rigidity to the protein. In addition to cysteine, iron represents another critical factor in regulating keratins expression in epidermal tissues, as well as in hair follicle growth and maturation. By focusing on human keratinocytes, the aim of this study was to evaluate the effect of cysteine supplementation as nutraceutical on keratin biosynthesis, as well as to get an insight on the interplay of cysteine availability and cellular iron status in regulating keratins expression in vitro. Herein we demonstrate that cysteine promotes a significant up-regulation of keratins expression as a result of de novo protein synthesis, while the lack of iron impairs keratin expression. Interestingly, cysteine supplementation counteracts the adverse effect of iron deficiency on cellular keratin expression. This effect was likely mediated by the up-regulation of transferrin receptor and ferritin, the main cellular proteins involved in iron homeostasis, at last affecting the labile iron pool. In this manner, cysteine may also enhance the metabolic iron availability for DNA synthesis without creating a detrimental condition of iron overload. To the best of our knowledge, this is one of the first study in an in vitro keratinocyte model providing evidence that cysteine and iron cooperate for keratins expression, indicative of their central role in maintaining healthy epithelia.

Repurposing the anti-malarial drug artesunate as a novel therapeutic agent for metastatic renal cell carcinoma due to its attenuation of tumor growth, metastasis, and angiogenesis.

Despite advances in the development of molecularly targeted therapies, metastatic renal cell carcinoma (RCC) is still incurable. Artesunate (ART), a well-known anti-malarial drug with low toxicity, exhibits highly selective anti-tumor actions against various tumors through generation of cytotoxic carbon-centered free radical in the presence of free iron. However, the therapeutic efficacy of ART against metastatic RCC has not yet been fully elucidated. In the analysis on a dataset from The Cancer Genome Atlas (TCGA) (n = 469) and a tissue microarray set from Samsung Medical Center (n = 119) from a cohort of patients with clear cell RCC (ccRCC), up-regulation of transferrin receptor 1 (TfR1), which is a well-known predictive marker for ART, was correlated with the presence of distant metastasis and an unfavorable prognosis. Moreover, ART exerted potent selective cytotoxicity against human RCC cell lines (Caki-1, 786-O, and SN12C-GFP-SRLu2) and sensitized these cells to sorafenib in vitro, and the extent of ART cytotoxicity correlated with TfR1 expression. ART-mediated growth inhibition of human RCC cell lines was shown to result from the induction of cell cycle arrest at the G2/M phase and oncosis-like cell death. Furthermore, ART inhibited cell clonogenicity and invasion of human RCC cells and anti-angiogenic effects in vitro in a dose-dependent manner. Consistent with these in vitro data, anti-tumor, anti-metastatic and anti-angiogenic effects of ART were also validated in human 786-O xenografts. Taken together, ART is a promising novel candidate for treating human RCC, either alone or in combination with other therapies.

Abstract 920: Mechanism of the transferrin receptor 1 dysregulation in hepatocarcinogenesis

Abstract Hepatocellular carcinoma (HCC) is one of the most prevalent life-threatening human cancers, with a rapidly increasing incidence worldwide. The pathogenesis of HCC is complex and consists of multiple interconnected molecular alterations. Current evidence indicates that altered iron metabolism plays an important role in the development and progression of HCC; however, there is a lack of conclusive information regarding the mechanisms of this dysregulation. In previous studies using different models of rodent carcinogenesis, we demonstrated prominent alterations of intracellular iron metabolism in preneoplastic livers, including changes in gene expression and the level of related proteins involved in the regulation of intracellular hepatic iron metabolism, primarily up-regulation of transferrin receptor 1 (TFRC). In the present study, we investigated the role and underlying mechanisms of the aberrant expression of TFRC, the main receptor controlling cellular iron uptake, in liver carcinogenesis. In both preneoplastic liver tissue from a relevant rat model of human HCC and in human HCC cells, there was a significant increase in the levels of TFRC mRNA and protein. This resulted in a substantial increase in TFRC/ferroportin (FPN) ratio, favoring an accumulation of iron in the HCC cells. The increase in levels of TFRC was attributed to a post-transcriptional microRNA-mediated mechanism. This was demonstrated by a computational analysis and confirmed experimentally by in vitro transfection experiments showing that transfection of human HCC cell lines with has-miR-152 effectively suppressed the expression of TFRC. Additionally, there was a strong inverse correlation between the level of TRFC and the expression of miR-152 in human HCC cells (r = -0.99, p = 4.7×10-9). Finally, the expression of TFRC and miR-152 in human HCC tissues was evaluated using the TCGA database. We observed an over-expression of TFRC in human HCC tissue samples and a markedly decreased level of miR-152 when compared to non-tumor liver tissue. These results demonstrate that dysregulation of cellular iron metabolism in liver carcinogenesis is driven by an up-regulation of TFRC, and indicate that miR-152-specific targeting of TFRC to decrease its levels may provide a selective anticancer therapeutic approach for the treatment of HCC. Citation Format: Iryna Kindrat, Volodymyr Tryndyak, Aline de Conti, Svitlana Shpyleva, Anna Erstenyuk, Frederick A. Beland, Igor Pogribny. Mechanism of the transferrin receptor 1 dysregulation in hepatocarcinogenesis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 920. doi:10.1158/1538-7445.AM2015-920

2,3,7,8-Tetrachlorodibenzo-p-Dioxin Promotes BHV-1 Infection in Mammalian Cells by Interfering with Iron Homeostasis Regulation

Mammalian cells require iron to satisfy metabolic needs or to accomplish specialized functions, and DNA viruses, like bovine herpesvirus 1 (BHV-1), require an iron-replete host to efficiently replicate, so that iron bioavailability is an important component of viral virulence. Cellular iron metabolism is coordinately controlled by the Iron Regulatory Proteins (IRP1 and IRP2), whose activity is affected by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a current and persistent environmental contaminant. Considering that TCDD enhances BHV-1 replication, herein we analyzed the effects of TCDD on iron metabolism during BHV-1 infection in MDBK cells, and presented evidences of a divergent modulation of IRP1 and IRP2 RNA-binding capacity. Moreover, an up-regulation of transferrin receptor 1 (TfR1) and a concomitant down-regulation of ferritin were observed. This scenario led to an expansion of the labile iron pool (LIP) and induces a significant enhance of viral titer, as confirmed by increased levels of BHV-1 infected cell protein 0 (bICP0), the major transcriptional regulatory protein of BHV-1. Taken together, our data suggest that TCDD increases the free intracellular iron availability thereby promoting the onset of BHV-1 infection and rendering bovine cells more vulnerable to the virus.