Future of toxicology--iron chelators and differing modes of action and toxicity: the changing face of iron chelation therapy

Isosteric Replacement of Sulfur to Selenium in a Thiosemicarbazone: Promotion of Zn(II) Complex Dissociation and Transmetalation to Augment Anticancer Efficacy

We implemented isosteric replacement of sulfur to selenium in a novel thiosemicarbazone (PPTP4c4mT) to create a selenosemicarbazone (PPTP4c4mSe) that demonstrates potentiated anticancer efficacy and selectivity. Their design specifically incorporated cyclohexyl and styryl moieties to sterically inhibit the approach of their Fe(III) complexes to the oxy-myoglobin heme plane. Importantly, in contrast to the Fe(III) complexes of the clinically trialed thiosemicarbazones Triapine, COTI-2, and DpC, the Fe(III) complexes of PPTP4c4mT and PPTP4c4mSe did not induce detrimental oxy-myoglobin oxidation. Furthermore, PPTP4c4mSe demonstrated more potent antiproliferative activity than the homologous thiosemicarbazone, PPTP4c4mT, with their selectivity being superior or similar, respectively, to the clinically trialed thiosemicarbazone, COTI-2. An advantageous property of the selenosemicarbazone Zn(II) complexes relative to their thiosemicarbazone analogues was their greater transmetalation to Cu(II) complexes in lysosomes. This latter effect probably promoted their antiproliferative activity. Both ligands down-regulated multiple key receptors that display inter-receptor cooperation that leads to aggressive and resistant breast cancer.

Dye-sensitized lanthanide-doped upconversion nanoprobe for enhanced sensitive detection of Fe3+ in human serum and tap water

Iron ion (Fe3+) detection is crucial for human health since it plays a crucial role in many physiological activities. In this work, a novel Schiff-base functionalized cyanine derivative (CyPy) was synthesized, which was successfully assembled on the surface of upconversion nanoparticles (UCNPs) through an amphiphilic polymer encapsulation method. In the as-designed nanoprobe, CyPy, a recognizer of Fe3+, is served as energy donor and β-NaYF4:Yb,Er upconversion nanoparticles are adopted as energy acceptor. As a result, a 93-fold enhancement of upconversion luminescence is achieved. The efficient energy transfer from CyPy to β-NaYF4:Yb,Er endows the nanoprobe a high sensitivity for Fe3+ in water with a low detection limit of 0.21 μM. Moreover, the nanoprobe has been successfully applied for Fe3+ determination in human serum and tap water samples with recovery ranges of 95 %-105 % and 97 %-106 %, respectively. Moreover, their relative standard deviations are all below 3.72 %. This work provides a sensitive and efficient methodology for Fe3+ detection in clinical and environmental testing.

The role of cyclin-dependent kinase inhibitor 3 in the proliferation and migration of renal cell carcinoma

The cyclin-dependent kinase inhibitor 3 (CDKN3) gene, is over expressed in renal cell carcinoma (RCC). However, the cell biology functions of RCC are not well understood. The present study aimed to verify the ability of CDKN3 to promote the proliferation and migration of RCC through in vitro experiments. Subsequently, the clinical prognostic effects were analyzed using The Cancer Genome Atlas (TCGA; https://www.cancer.gov/) and Gene Expression Omnibus (GEO; https://www.ncbi.nlm.nih.gov/geo/). The chelators, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), an analogue of the anti-tumor agent, were screened through bioinformatics analysis. The expression of CDKN3 is positively correlated with the IC50 of Dp44mT. In two RCC cell lines, 786-0 and Caki-1, we conducted small interfering RNA (siRNA) knockdown of CDKN3 and overexpression of CDKN3 by transfection plasmid. Subsequently, we administered Dp44mT to examine the resulting alterations in cell proliferation, migration, and apoptosis, thereby elucidating the role of CDKN3 and Dp44mT in these processes. The results of the experiment revealed a positive association between CDKN3 expression and the proliferation of RCC cell lines. Down-regulating CDKN3 significantly increased the apoptosis rate and inhibited cell migration in 786-0 and Caki-1 cells. Furthermore, bioinformatics analysis revealed a high expression of CDKN3 in RCC and a negative association between CDKN3 expression and survival. Gene set enrichment analysis (GSEA) revealed a significant association between high CDKN3 expression and the cell cycle pathway. Furthermore, we identified Dp44mT as a drug highly correlated with CDKN3 through the database. Subsequent addition of Dp44mT resulted in similar findings to those observed upon CDKN3 knockdown. Our findings have important implications for the diagnosis and treatment of CDKN3 in RCC. Additionally, Dp44mT is likely to be a promising candidate for future clinical applications.

Coumarin derivative-functionalized nanoporous silica as an on-off fluorescent sensor for detecting Fe3+ and Hg2+ ions: a circuit logic gate

A highly efficient fluorescent sensor (S-DAC) was easily created by functionalizing the SBA-15 surface with N-(2-Aminoethyl)-3-Aminopropyltrimethoxysilane followed by the covalent attachment of 7-diethylamino 3-acetyl coumarin (DAC). This chemosensor (S-DAC) demonstrates selective and sensitive recognition of Fe3+ and Hg2+ in water-based solutions, with detection limits of 0.28 × 10-9 M and 0.2 × 10-9 M for Hg2+ and Fe3+, respectively. The sensor's fluorescence characteristics were examined in the presence of various metal ions, revealing a decrease in fluorescence intensity upon adding Fe3+ or Hg2+ ions at an emission wavelength of 400 nm. This sensor was also able to detect ferric and mercury ions in spinach and tuna fish. The quenching mechanism of S-DAC was investigated using UV-vis spectroscopy, which confirmed a static-type mechanism for fluorescence quenching. Moreovre, the decrease in fluorescence intensity caused by mercury and ferric ions can be reversed using trisodium citrate dihydrate and EDTA as masking agents, respectively. As a result, a circuit logic gate was designed using Hg2+, Fe3+, trisodium citrate dihydrate, and EDTA as inputs and the quenched fluorescence emission as the output.

Differential transmetallation of complexes of the anti-cancer thiosemicarbazone, Dp4e4mT: effects on anti-proliferative efficacy, redox activity, oxy-myoglobin and oxy-hemoglobin oxidation

The di-2-pyridylthiosemicarbazone (DpT) analogs demonstrate potent and selective anti-proliferative activity against human tumors. The current investigation reports the synthesis and chemical and biological characterization of the Fe(iii), Co(iii), Ni(ii), Cu(ii), Zn(ii), Ga(iii), and Pd(ii) complexes of the promising second generation DpT analog, di-2-pyridylketone-4-ethyl-4-methyl-3-thiosemicarbazone (Dp4e4mT). These studies demonstrate that the Dp4e4mT Co(iii), Ni(ii), and Pd(ii) complexes display distinct biological activity versus those with Cu(ii), Zn(ii), and Ga(iii) regarding anti-proliferative efficacy against cancer cells and a detrimental off-target effect involving oxidation of oxy-myoglobin (oxy-Mb) and oxy-hemoglobin (oxy-Hb). With regards to anti-proliferative activity, the Zn(ii) and Ga(iii) Dp4e4mT complexes demonstrate facile transmetallation with Cu(ii), resulting in efficacy against tumor cells that is strikingly similar to the Dp4e4mT Cu(ii) complex (IC50: 0.003-0.006 μM and 72 h). Relative to the Zn(ii) and Ga(iii) Dp4e4mT complexes, the Dp4e4mT Ni(ii) complex demonstrates kinetically slow transmetallation with Cu(ii) and intermediate anti-proliferative effects (IC50: 0.018-0.076 μM after 72 h). In contrast, the Co(iii) and Pd(ii) complexes demonstrate poor anti-proliferative activity (IC50: 0.262-1.570 μM after 72 h), probably due to a lack of transmetallation with Cu(ii). The poor efficacy of the Dp4e4mT Co(iii), Ni(ii), and Pd(ii) complexes to transmetallate with Fe(iii) markedly suppresses the oxidation of oxy-Mb and oxy-Hb. In contrast, the 2 : 1 Dp4e4mT: Cu(ii), Zn(ii), and Ga(iii) complexes demonstrate facile reactions with Fe(iii), leading to the redox active Dp4e4mT Fe(iii) complex and oxy-Mb and oxy-Hb oxidation. This study demonstrates the key role of differential transmetallation of Dp4e4mT complexes that has therapeutic ramifications for their use as anti-cancer agents.

Steric Blockade of Oxy-Myoglobin Oxidation by Thiosemicarbazones: Structure-Activity Relationships of the Novel PPP4pT Series

The di-2-pyridylketone thiosemicarbazones demonstrated marked anticancer efficacy, prompting progression of DpC to clinical trials. However, DpC induced deleterious oxy-myoglobin oxidation, stifling development. To address this, novel substituted phenyl thiosemicarbazone (PPP4pT) analogues and their Fe(III), Cu(II), and Zn(II) complexes were prepared. The PPP4pT analogues demonstrated potent antiproliferative activity (IC50: 0.009-0.066 μM), with the 1:1 Cu:L complexes showing the greatest efficacy. Substitutions leading to decreased redox potential of the PPP4pT:Cu(II) complexes were associated with higher antiproliferative activity, while increasing potential correlated with increased redox activity. Surprisingly, there was no correlation between redox activity and antiproliferative efficacy. The PPP4pT:Fe(III) complexes attenuated oxy-myoglobin oxidation significantly more than the clinically trialed thiosemicarbazones, Triapine, COTI-2, and DpC, or earlier thiosemicarbazone series. Incorporation of phenyl- and styryl-substituents led to steric blockade, preventing approach of the PPP4pT:Fe(III) complexes to the heme plane and its oxidation. The 1:1 Cu(II):PPP4pT complexes were inert to transmetalation and did not induce oxy-myoglobin oxidation.

Metal-Based Anticancer Complexes and p53: How Much Do We Know?

P53 plays a key role in protecting the human genome from DNA-related mutations; however, it is one of the most frequently mutated genes in cancer. The P53 family members p63 and p73 were also shown to play important roles in cancer development and progression. Currently, there are various organic molecules from different structural classes of compounds that could reactivate the function of wild-type p53, degrade or inhibit mutant p53, etc. It was shown that: (1) the function of the wild-type p53 protein was dependent on the presence of Zn atoms, and (2) Zn supplementation restored the altered conformation of the mutant p53 protein. This prompted us to question whether the dependence of p53 on Zn and other metals might be used as a cancer vulnerability. This review article focuses on the role of different metals in the structure and function of p53, as well as discusses the effects of metal complexes based on Zn, Cu, Fe, Ru, Au, Ag, Pd, Pt, Ir, V, Mo, Bi and Sn on the p53 protein and p53-associated signaling.

The role of the NDRG1 in the pathogenesis and treatment of breast cancer

Breast cancer (BC) is the leading cause of cancer death in women. This disease is heterogeneous, with clinical subtypes being estrogen receptor-α (ER-α) positive, having human epidermal growth factor receptor 2 (HER2) overexpression, or being triple-negative for ER-α, progesterone receptor, and HER2 (TNBC). The ER-α positive and HER2 overexpressing tumors can be treated with agents targeting these proteins, including tamoxifen and pertuzumab, respectively. Despite these treatments, resistance and metastasis are problematic, while TNBC is challenging to treat due to the lack of suitable targets. Many studies examining BC and other tumors indicate a role for N-myc downstream-regulated gene-1 (NDRG1) as a metastasis suppressor. The ability of NDRG1 to inhibit metastasis is due, in part, to the inhibition of the initial step in metastasis, namely the epithelial-to-mesenchymal transition. Paradoxically, there are also reports of NDRG1 playing a pro-oncogenic role in BC pathogenesis. The oncogenic effects of NDRG1 in BC have been reported to relate to lipid metabolism or the mTOR signaling pathway. The molecular mechanism(s) of how NDRG1 regulates the activity of multiple signaling pathways remains unclear. Therapeutic strategies that up-regulate NDRG1 have been developed and include agents of the di-2-pyridylketone thiosemicarbazone class. These compounds target oncogenic drivers in BC cells, suppressing the expression of multiple key hormone receptors including ER-α, progesterone receptor, androgen receptor, and prolactin receptor, and can also overcome tamoxifen resistance. Considering the varying role of NDRG1 in BC pathogenesis, further studies are required to examine what subset of BC patients would benefit from pharmacopeia that up-regulate NDRG1.

Designing Tailored Thiosemicarbazones with Bespoke Properties: The Styrene Moiety Imparts Potent Activity, Inhibits Heme Center Oxidation, and Results in a Novel "Stealth Zinc(II) Complex"

A novel, potent, and selective antitumor agent, namely (E)-3-phenyl-1-(2-pyridinyl)-2-propen-1-one 4,4-dimethyl-3-thiosemicarbazone (PPP44mT), and its analogues were synthesized and characterized and displayed strikingly distinctive properties. This activity was mediated by the inclusion of a styrene moiety, which through steric and electrochemical mechanisms prevented deleterious oxy-myoglobin or oxy-hemoglobin oxidation relative to other potent thiosemicarbazones, i.e., di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) or di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT). Structure-activity relationship analysis demonstrated specific tuning of PPP44mT electrochemistry further inhibited oxy-myoglobin or oxy-hemoglobin oxidation. Both PPP44mT and its Cu(II) complexes showed conspicuous almost immediate cytotoxicity against SK-N-MC tumor cells (within 3 h). In contrast, [Zn(PPP44mT)₂] demonstrated a pronounced delay in activity, taking 48 h before marked antiproliferative efficacy was apparent. As such, [Zn(PPP44mT)₂] was designated as a "stealth Zn(II) complex" that overcomes the near immediate cytotoxicity of PPP44mT or its copper complexes. Upon examination of the suppression of oncogenic signaling, [Zn(PPP44mT)₂] was superior at inhibiting cyclin D1 expression compared to DpC or Dp44mT.

Essential metals in health and disease

In total, twenty elements appear to be essential for the correct functioning of the human body, half of which are metals and half are non-metals. Among those metals that are currently considered to be essential for normal biological functioning are four main group elements, sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca), and six d-block transition metal elements, manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), zinc (Zn) and molybdenum (Mo). Cells have developed various metallo-regulatory mechanisms for maintaining a necessary homeostasis of metal-ions for diverse cellular processes, most importantly in the central nervous system. Since redox active transition metals (for example Fe and Cu) may participate in electron transfer reactions, their homeostasis must be carefully controlled. The catalytic behaviour of redox metals which have escaped control, e.g. via the Fenton reaction, results in the formation of reactive hydroxyl radicals, which may cause damage to DNA, proteins and membranes. Transition metals are integral parts of the active centers of numerous enzymes (e.g. Cu,Zn-SOD, Mn-SOD, Catalase) which catalyze chemical reactions at physiologically compatible rates. Either a deficiency, or an excess of essential metals may result in various disease states arising in an organism. Some typical ailments that are characterized by a disturbed homeostasis of redox active metals include neurological disorders (Alzheimer's, Parkinson's and Huntington's disorders), mental health problems, cardiovascular diseases, cancer, and diabetes. To comprehend more deeply the mechanisms by which essential metals, acting either alone or in combination, and/or through their interaction with non-essential metals (e.g. chromium) function in biological systems will require the application of a broader, more interdisciplinary approach than has mainly been used so far. It is clear that a stronger cooperation between bioinorganic chemists and biophysicists - who have already achieved great success in understanding the structure and role of metalloenzymes in living systems - with biologists, will access new avenues of research in the systems biology of metal ions. With this in mind, the present paper reviews selected chemical and biological aspects of metal ions and their possible interactions in living systems under normal and pathological conditions.

p53 and Zinc: A Malleable Relationship

A large percentage of transcription factors require zinc to bind DNA. In this review, we discuss what makes p53 unique among zinc-dependent transcription factors. The conformation of p53 is unusually malleable: p53 binds zinc extremely tightly when folded, but is intrinsically unstable in the absence of zinc at 37°C. Whether the wild-type protein folds in the cell is largely determined by the concentration of available zinc. Consequently, zinc dysregulation in the cell as well as a large percentage of tumorigenic p53 mutations can cause p53 to lose zinc, misfold, and forfeit its tumor suppressing activity. We highlight p53’s noteworthy biophysical properties that give rise to its malleability and how proper zinc binding can be restored by synthetic metallochaperones to reactivate mutant p53. The activity and mechanism of metallochaperones are compared to those of other mutant p53-targeted drugs with an emphasis on those that have reached the clinical trial stage.

Ascorbate-and iron-driven redox activity of Dp44mT and emodin facilitates peroxidation of micelles and bicelles

BACKGROUND

Iron (Fe)-induced oxidative stress leads to reactive oxygen species that damage biomembranes, with this mechanism being involved in the activity of some anti-cancer chemotherapeutics.

METHODS

Herein, we compared the effect of Fe complexes of the ligand, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), or the potential ligand, Emodin, on lipid peroxidation in cell membrane models (micelles and bicelles). These studies were performed in the presence of hydrogen peroxide (H₂O₂) and the absence or presence of ascorbate.

RESULTS

In the absence of ascorbate, Fe(II)/Emodin mixtures incubated with H₂O₂ demonstrated slight pro-oxidant properties on micelles versus Fe(II) alone, while the Fe(III)-Dp44mT complex exhibited marked antioxidant properties. Examining more physiologically relevant phospholipid-containing bicelles, the Fe(II)- and Fe(III)-Dp44mT complexes demonstrated antioxidant activity without ascorbate. Upon adding ascorbate, there was a significant increase in the peroxidation of micelles and bicelles in the presence of unchelated Fe(II) and H₂O₂. The addition of ascorbate to Fe(III)-Dp44mT substantially increased the peroxidation of micelles and bicelles, with the Fe(III)-Dp44mT complex being reduced by ascorbate to the Fe(II) state, explaining the increased reactivity. Electron paramagnetic resonance spectroscopy demonstrated ascorbyl radical anion generation after mixing ascorbate and Emodin, with signal intensity being enhanced by H₂O₂. This finding suggested Emodin semiquinone radical formation that could play a role in its reactivity via ascorbate-driven redox cycling. Examining cultured melanoma cells in vitro, ascorbate at pharmacological levels enhanced the anti-proliferative activity of Dp44mT and Emodin.

CONCLUSIONS AND GENERAL SIGNIFICANCE

Ascorbate-driven redox cycling of Dp44mT and Emodin promotes their anti-proliferative activity.

Iodide-enhanced Cu-MOF nanomaterials for the amplified colorimetric detection of Fe3

In this paper, a novel colorimetric strategy based on iodide ion (I^-) and Cu-MOF catalysis was developed for simple, low-cost, and naked-eye detection of Fe³⁺. Both I^- and MOFs display catalytic activity toward peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB). Adsorption and embedding of I^- in Cu-MOF generates Cu-MOF/I with a three-dimensional porous structure that exhibits higher specific surface area, providing more active sites to facilitate interaction with TMB, resulting in enhanced catalytic efficiency. Reports have shown that Fe³⁺ can oxidize TMB in the absence of H₂O₂. We found that as Fe³⁺ concentration increases, the color of the system gradually deepens and the UV absorption peak gradually increases, thus providing a colorimetric sensor for quantitative Fe³⁺ detection. The detection limit (LOD) obtained in the presence of I^- is 200 nM; however, in the absence of I^-, the LOD is approx. 10 μM. Thus, the sensing system is ideal for signal amplified analysis of Fe³⁺. In the presence of various interfering metal ions, the developed sensing system displays excellent selectivity. Additionally, the practical application to Fe³⁺ detection in real samples is explored.

Innovative therapies for neuroblastoma: The surprisingly potent role of iron chelation in up-regulating metastasis and tumor suppressors and down-regulating the key oncogene, N-myc

Iron is an indispensable requirement for essential biological processes in cancer cells. Due to the greater proliferation of neoplastic cells, their demand for iron is considerably higher relative to normal cells, making them highly susceptible to iron depletion. Understanding this sensitive relationship led to research exploring the effect of iron chelation therapy for cancer treatment. The classical iron-binding ligand, desferrioxamine (DFO), has demonstrated effective anti-proliferative activity against many cancer-types, particularly neuroblastoma tumors, and has the surprising activity of down-regulating the potent oncogene, N-myc, which is a major oncogenic driver in neuroblastoma. Even more significant is the ability of DFO to simultaneously up-regulate the potent metastasis suppressor, N-myc downstream-regulated gene-1 (NDRG1), which plays a plethora of roles in suppressing a variety of oncogenic signaling pathways. However, DFO suffers the disadvantage of demonstrating poor membrane permeability and short plasma half-life, requiring administration by prolonged subcutaneous or intravenous infusions. Considering this, the specifically designed di-2-pyridylketone thiosemicarbazone (DpT) series of metal-binding ligands was developed in our laboratory. The lead agent from the first generation DpT series, di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT), showed exceptional anti-cancer properties compared to DFO. However, it exhibited cardiotoxicity in mouse models at higher dosages. Therefore, a second generation of agents was developed with the lead compound being di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) that progressed to Phase I clinical trials. Importantly, DpC showed better anti-proliferative activity than Dp44mT and no cardiotoxicity, demonstrating effective anti-cancer activity against neuroblastoma tumors in vivo.

Design, synthesis and biological evaluation of novel thiosemicarbazone-indole derivatives targeting prostate cancer cells

To discover novel anticancer agents with potent and low toxicity, we designed and synthesized a range of new thiosemicarbazone-indole analogues based on lead compound 4 we reported previously. Most compounds displayed moderate to high anticancer activities against five tested tumor cells (PC3, EC109, DU-145, MGC803, MCF-7). Specifically, the represented compound 16f possessed strong antiproliferative potency and high selectivity toward PC3 cells with the IC₅₀ value of 0.054 μM, compared with normal WPMY-1 cells with the IC₅₀ value of 19.470 μM. Preliminary mechanism research indicated that compound 16f could significantly suppress prostate cancer cells (PC3, DU-145) growth and colony formation in a dose-dependent manner. Besides, derivative 16f induced G1/S cycle arrest and apoptosis, which may be related to ROS accumulation due to the activation of MAPK signaling pathway. Furthermore, molecule 16f could effectively inhibit tumor growth through a xenograft model bearing PC3 cells and had no evident toxicity in vivo. Overall, based on the biological activity evaluation, analogue 16f can be viewed as a potential lead compound for further development of novel anti-prostate cancer drug.

Gene therapies for transfusion dependent β-thalassemia: Current status and critical criteria for success

Thalassemia is one of the most prevalent monogenic diseases usually caused by quantitative defects in the production of β-globin leading to severe anemia. Technological advances in genome sequencing, stem cell selection, viral vector development, transduction and gene editing strategies now allow for efficient exvivo genetic manipulation of human stem cells that can lead to production of hemoglobin, leading to a meaningful clinical benefit in thalassemia patients. In this review, the status of the gene-therapy approaches available for transfusion dependent thalassemia are discussed, along with the critical criteria that affect efficacy and lessons that have been learned from the early phase clinical trials. Salient steps necessary for the clinical development, manufacturing, and regulatory approvals of gene therapies for thalassemia are also highlighted, so that the potential of these therapies can be realized. It is highly anticipated that gene therapies will soon become a treatment option for patients lacking compatible donors for hematopoietic stem cell transplant and will offer an alternative for definitive treatment of β-thalassemia.

Trying to Solve the Puzzle of the Interaction of Ascorbic Acid and Iron: Redox, Chelation and Therapeutic Implications

Iron and ascorbic acid (vitamin C) are essential nutrients for the normal growth and development of humans, and their deficiency can result in serious diseases. Their interaction is of nutritional, physiological, pharmacological and toxicological interest, with major implications in health and disease. Millions of people are using pharmaceutical and nutraceutical preparations of these two nutrients, including ferrous ascorbate for the treatment of iron deficiency anaemia and ascorbate combination with deferoxamine for increasing iron excretion in iron overload. The main function and use of vitamin C is its antioxidant activity against reactive oxygen species, which are implicated in many diseases of free radical pathology, including biomolecular-, cellular- and tissue damage-related diseases, as well as cancer and ageing. Ascorbic acid and its metabolites, including the ascorbate anion and oxalate, have metal binding capacity and bind iron, copper and other metals. The biological roles of ascorbate as a vitamin are affected by metal complexation, in particular following binding with iron and copper. Ascorbate forms a complex with Fe³⁺ followed by reduction to Fe²⁺, which may potentiate free radical production. The biological and clinical activities of iron, ascorbate and the ascorbate–iron complex can also be affected by many nutrients and pharmaceutical preparations. Optimal therapeutic strategies of improved efficacy and lower toxicity could be designed for the use of ascorbate, iron and the iron–ascorbate complex in different clinical conditions based on their absorption, distribution, metabolism, excretion, toxicity (ADMET), pharmacokinetic, redox and other properties. Similar strategies could also be designed in relation to their interactions with food components and pharmaceuticals, as well as in relation to other aspects concerning personalized medicine.

Redox Interactions of Vitamin C and Iron: Inhibition of the Pro-Oxidant Activity by Deferiprone

Ascorbic acid (AscH₂) is one of the most important vitamins found in the human diet, with many biological functions including antioxidant, chelating, and coenzyme activities. Ascorbic acid is also widely used in medical practice especially for increasing iron absorption and as an adjuvant therapeutic in iron chelation therapy, but its mode of action and implications in iron metabolism and toxicity are not yet clear. In this study, we used UV–Vis spectrophotometry, NMR spectroscopy, and EPR spin trapping spectroscopy to investigate the antioxidant/pro-oxidant effects of ascorbic acid in reactions involving iron and the iron chelator deferiprone (L1). The experiments were carried out in a weak acidic (pH from 3 to 5) and neutral (pH 7.4) medium. Ascorbic acid exhibits predominantly pro-oxidant activity by reducing Fe³⁺ to Fe²⁺, followed by the formation of dehydroascorbic acid. As a result, ascorbic acid accelerates the redox cycle Fe³⁺ ↔ Fe²⁺ in the Fenton reaction, which leads to a significant increase in the yield of toxic hydroxyl radicals. The analysis of the experimental data suggests that despite a much lower stability constant of the iron–ascorbate complex compared to the FeL1₃ complex, ascorbic acid at high concentrations is able to substitute L1 in the FeL1₃ chelate complex resulting in the formation of mixed L1₂AscFe complex. This mixed chelate complex is redox stable at neutral pH = 7.4, but decomposes at pH = 4–5 during several minutes at sub-millimolar concentrations of ascorbic acid. The proposed mechanisms play a significant role in understanding the mechanism of action, pharmacological, therapeutic, and toxic effects of the interaction of ascorbic acid, iron, and L1.

Recent progress in chemosensors based on pyrazole derivatives

Colorimetric and fluorescent probes based on small organic molecules have become important tools in modern biology because they provide dynamic information concerning the localization and quantity of the molecules and ions of interest without the need for genetic engineering of the sample. In the past five years, these probes for ions and molecules have attracted great attention because of their biological, environmental and industrial significance combined with the simplicity and high sensitivity of absorption and fluorescence techniques. Moreover, pyrazole derivatives display a number of remarkable photophysical properties and wide synthetic versatility superior to those of other broadly used scaffolds. This review provides an overview of the recent (2016-2020) findings on chemosensors containing pyrazole derivatives (pyrazoles, pyrazolines and fused pyrazoles). The discussion focuses on the design and physicochemical properties of chemosensors in order to realize their full potential for practical applications in environmental and biological monitoring (sensing of metal ions, anions, explosives, and biomolecules). We also present our conclusions and outlook for the future.

Thiosemicarbazones as Potent Anticancer Agents and their Modes of Action

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Thiosemicarbazones (TSCs) are a class of Schiff bases usually obtained by the condensation of thiosemicarbazide with a suitable aldehyde or ketone. TSCs have been the focus of chemists and biologists due to their wide range of pharmacological effects. One of the promising areas in which these excellent metal chelators are being developed is their use against cancer. TSCs have a wide clinical antitumor spectrum with efficacy in various tumor types such as leukemia, pancreatic cancer, breast cancer, non-small cell lung cancer, cervical cancer, prostate cancer and bladder cancer. To obtain better activity, different series of TSCs have been developed by modifying the heteroaromatic system in their molecules. These compounds possessed significant antineoplastic activity when the carbonyl attachment of the side chain was located at a position α to the ring nitrogen atom, whereas attachment of the side chain β or γ to the heterocyclic N atom resulted in inactive antitumor agents. In addition, replacement of the heterocyclic ring N with C also resulted in a biologically inactive compound suggesting that a conjugated N,N,S-tridentate donor set is essential for the biological activities of thiosemicarbazones. Several possible mechanisms have been implemented for the anticancer activity of thiosemicarbazones.

NDRG1 suppresses basal and hypoxia-induced autophagy at both the initiation and degradation stages and sensitizes pancreatic cancer cells to lysosomal membrane permeabilization

BACKGROUND

N-myc downstream regulated gene 1 (NDRG1) is an established stress-response protein. This study investigated the effects of NDRG1 on autophagic degradation and how this can be therapeutically exploited.

METHODS

Cell culture, western analysis, confocal microscopy, acridine orange staining, cholesterol determination, cellular proliferation assessment and combination index (CI) estimation.

RESULTS

NDRG1 expression suppressed autophagic degradation and autolysosome formation, measured by increased p62 expression and reduced co-localization between the well-characterized, autophagosomal and lysosomal markers, LC3 and LAMP2, respectively. NDRG1 elicited autophagic suppression at the initiation stage of autophagy. The NDRG1-inducer and anti-cancer agent, di-2-pyridylketone 4,4,-dimethyl-3-thiosemicarbazone (Dp44mT), was able to induce lysosomal membrane permeabilization (LMP). Over-expression of NDRG1 further sensitized cells to LMP mediated by both Dp44mT, or the redox active Dp44mT‑copper complex. This sensitization may be mediated via a decrease in cholesterol levels upon NDRG1 expression, as cholesterol stabilizes lysosomal membranes. However, the effect of NDRG1 on cholesterol appeared independent of the key energy homeostasis sensor, 5' AMP-activated protein kinase (AMPK), whose activation was significantly (p < 0.001) reduced by NDRG1. Finally, Dp44mT synergistically potentiated the anti-proliferative activity of Gemcitabine that activates autophagy. In fact, Dp44mT and Gemcitabine (Combination Index (CI): 0.38 ± 0.07) demonstrated higher synergism versus the autophagy inhibitor, Bafilomycin A1 and Gemcitabine (CI: 0.64 ± 0.19).

CONCLUSIONS AND GENERAL SIGNIFICANCE

Collectively, this study demonstrated a dual-inhibitory mechanism of NDRG1 on autophagic activity, and that NDRG1 expression sensitized cells to Dp44mT-induced LMP. Considering the ability of Dp44mT to inhibit autophagy, studies demonstrated the potential of combination therapy for cancer treatment of Dp44mT with Gemcitabine.

A naphthylamide based fluorescent probe for detection of Al3+, Fe3+, and CN- with high sensitivity and selectivity

A naphthylamide based fluorescent chemosensor, N,N'-(1,2-phenylene)bis(1-hydroxy-2-naphthamide) (H₄L), for detection of Fe³⁺ and Al³⁺ cations as well as CN^- anion is reported. This compound has been synthesized by a novel and facile synthetic method with high yield and characterized by FT-IR, ¹H NMR, elemental analysis, and UV-Vis spectroscopy. It could detect Fe³⁺ and Al³⁺ ions in different media with different excitation and emission wavelengths. In DMSO solution, H₄L showed selective ON-OFF quenching of its 451 nm emission in the presence of Fe³⁺. On the other hand, in DMF solution, H₄L exhibited selective OFF-ON fluorescence upon the addition of Al³⁺, the intensity at 429 nm increases drastically by 24-fold. Also, among the anions, the probe can selectively distinguish CN^- by deprotonation of OH and NH groups, as proved by ¹H NMR titration. TD-DFT calculation supports the UV-Vis and fluorescence measurements of the chemosensor.

Experimental and Theoretical Studies on a Simple S-S-Bridged Dimeric Schiff Base: Selective Chromo-Fluorogenic Chemosensor for Nanomolar Detection of Fe2+ & Al3+ Ions and Its Varied Applications

A simple S-S (disulfide)-bridged dimeric Schiff base probe, L, has been designed, synthesized, and successfully characterized for the specific recognition of Al3+ and Fe2+ ions as fluorometric and colorimetric "turn-on" responses in a dimethylformamide (DMF)-H2O solvent mixture, respectively. The probe L and each metal ion bind through a 1:1 complex stoichiometry, and the plausible sensing mechanism is proposed based on the inhibition of the photoinduced electron transfer process (PET). The reversible chemosensor L showed high sensitivity toward Al3+ and Fe2+ ions, which was analyzed by fluorescence and UV-vis spectroscopy techniques up to nanomolar detection limits, 38.26 × 10-9 and 17.54 × 10-9 M, respectively. These experimental details were advocated by density functional theory (DFT) calculations. The practical utility of the chemosensor L was further demonstrated in electrochemical sensing, in vitro antimicrobial activity, molecular logic gate function, and quantification of the trace amount of Al3+ and Fe2+ ions in real water samples.

Pesticide-derived bright chlorine-doped carbon dots for selective determination and intracellular imaging of Fe(III)

Inspired by the conversion from organics or biomass to fluorescent carbon dots (C-dots), the use of pesticide 4-chlorophenol (4-CP) as a precursor to prepare C-dots has been reported. The as-prepared chlorine-doped C-dots display a brightly blue emission at ∼445 nm with ∼22.8% quantum yield. Also, the surface of C-dots enriches functional groups, such as phenolic hydroxyl and carboxylic acid, etc., which can capture ferric ion (Fe(III)), resulting in the quenching of blue fluorescence of C-dots through an inner filter effect. The quantitative assay for Fe(III) was therefore realized by this probe with a 0.36 μM detection limit in the 0.6-25 μM concentration range. Most significantly, the cytotoxicity on Hela cells indicates the 4-CP-derived C-dots have a negligible cytotoxicity. The C-dots were applied in detection in environmental samples and imaging in Hela cells of Fe(III), demonstrating their good applicability, low toxicity and good biocompatibility, and providing an alterative approach to totally eliminate the harm of chlorophenols (CPs).

Iron chelation by curcumin suppresses both curcumin-induced autophagy and cell death together with iron overload neoplastic transformation

Iron overload, notably caused by hereditary hemochromatosis, is an excess storage of iron in various organs that causes tissue damage and may promote tumorigenesis. To manage that disorder, free iron depletion can be induced by iron chelators like deferoxamine that are of increasing interest also in the cancer field since iron stock could be a potent target for managing tumorigenesis. Curcumin, a well-known active substance extracted from the turmeric rhizome, destabilizes endoplasmic reticulum, and secondarily lysosomes, thereby increasing mitophagy/autophagy and subsequent apoptosis. Recent findings show that cells treated with curcumin also exhibit a decrease in ferritin, which is consistent with its chemical structure and iron chelating activity. Here we investigated how curcumin influences the intracellular effects of iron overload via Fe-nitriloacetic acid or ferric ammonium citrate loading in Huh-7 cells and explored the consequences in terms of antioxidant activity, autophagy, and apoptotic signal transduction. In experiments with T51B and RL-34 epithelial cells, we have found evidence that curcumin-iron complexation abolishes both curcumin-induced autophagy and apoptosis, together with the tumorigenic action of iron overload.

Anticancer Thiosemicarbazones: Chemical Properties, Interaction with Iron Metabolism, and Resistance Development

SIGNIFICANCE

During the past decades, thiosemicarbazones were clinically developed for a variety of diseases, including tuberculosis, viral infections, malaria, and cancer. With regard to malignant diseases, the class of α-N-heterocyclic thiosemicarbazones, and here especially 3-aminopyridine-2-carboxaldehyde thiosemicarbazone (Triapine), was intensively developed in multiple clinical phase I/II trials. Recent Advances: Very recently, two new derivatives, namely COTI-2 and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) have entered phase I evaluation. Based on the strong metal-chelating/metal-interacting properties of thiosemicarbazones, interference with the cellular iron (and copper) homeostasis is assumed to play an important role in their biological activity.

CRITICAL ISSUES

In this review, we summarize and analyze the data on the interaction of (α-N-heterocyclic) thiosemicarbazones with iron, with the special aim of bridging the current knowledge on their mode of action from chemistry to (cell) biology. In addition, we highlight the difference to classical iron(III) chelators such as desferrioxamine (DFO), which are used for the treatment of iron overload.

FUTURE DIRECTIONS

We want to emphasize that thiosemicarbazones are not solely removing iron from the cells/organism. In contrast, they should be considered as iron-interacting drugs influencing diverse biological pathways in a complex and multi-faceted mode of action. Consequently, in addition to the discussion of physicochemical properties (e.g., complex stability, redox activity), this review contains an overview on the diversity of cellular thiosemicarbazone targets and drug resistance mechanisms.

An iron(iii) complex selectively mediated cancer cell death: crystal structure, DNA targeting and in vitro antitumor activities

Three new iron(iii) complexes were prepared, and complex 3 exhibited a 14-fold higher selectivity index for HeLa vs. LO2 normal cells than cisplatin.

The role of iron metabolism in cancer therapy focusing on tumor-associated macrophages

Iron is an essential micronutrient in mammalian cells for basic processes such as DNA synthesis, cell cycle progression, and mitochondrial activity. Macrophages play a vital role in iron metabolism, which is tightly linked to their phagocytosis of senescent and death erythrocytes. It is now recognized that the polarization process of macrophages determines the expression profile of genes associated with iron metabolism. Although iron metabolism is strictly controlled by physiology, cancer has recently been connected with disordered iron metabolism. Moreover, in the environment of cancer, tumor-associated macrophages (TAMs) exhibit an iron release phenotype, which stimulates tumor cell survival and growth. Usually, the abundance of TAMs in the tumor is implicated in poor disease prognosis. Therefore, important attention has been drawn toward the development of tumor immunotherapies targeting these TAMs focussing on iron metabolism and reprogramming polarized phenotypes. Although further systematic research is still required, these efforts are almost certainly valuable in the search for new and effective cancer treatments.

Dual Sensing Performance of 1,2-Squaraine for the Colorimetric Detection of Fe3+ and Hg2+ Ions

A simple 1,2-squaraine based chemosensor material (SQ) has been reported to show dual sensing performance for colorimetric detection of Fe³⁺ and Hg²⁺ ions. Compared to common instrumental analysis, this method could provide fast and direct detection though colorimetric changes by the naked eye. The sensor has shown excellent selectivity over the other metal ions by tuning different solvent environments. The detection limit for Fe³⁺ could reach to 0.538 μM, which was lower than that in the environmental agency guideline (U.S. Environmental Protection Agency, U.S. EPA) in drinking water. And for Hg²⁺ detection, the limit was calculated as 1.689 μM in our case. A 1:1 binding mode between SQ⁻Fe³⁺ and SQ⁻Hg²⁺ ion were evidenced by Job's plot measurement and IR analysis. The proposed different binding mechanisms were also supported by Density Function Theory (DFT) calculation. All these findings provide a unique material and a simple, facile, and low cost colorimetric method for dual metal ions analysis and have shown preliminary analytical applications in industrial water sample analysis.

Growth Inhibition of a Novel Iron Chelator, DpdtC, against Hepatoma Carcinoma Cell Lines Partly Attributed to Ferritinophagy-Mediated Lysosomal ROS Generation

Some iron chelators display significant anticancer activity that may involve ferritin degradation either in proteasomes or in lysosomes, and the latter might involve ferritinophagy with a period. However, the correlation of ferritinophagy with anticancer activity of iron chelator was not fully determined. Revealing the underlying link therefore is required. Di-2-pyridylketone dithiocarbamate (DpdtC), a novel iron chelator, could mobilize iron from ferritin and displayed excellent antitumor against hepatoma carcinoma cell lines (IC_50s = 0.4 ± 0.2 for HepG2 and 3.5 ± 0.3 μM for Bel-7402, resp.); we speculated that the antiproliferative action of DpdtC might involve ferritinophagy. To this end, the alterations of ferritin, microtubule-associated protein light chain 3 (LC3-II), and nuclear receptor coactivator 4 (NCOA4) were investigated after exposure of DpdtC to the cells. The results revealed that DpdtC could cause increases of autophagic vacuoles and LC3-II. The data from cellular immunofluorescence and Western blotting showed a reciprocal relation between abundances of ferritin and LC3-II, but the trends of NCOA4 and LC3-II in abundance were in a similar manner, indicating that a ferritinophagy occurred. Further studies revealed that the ferritinophagy evoked an iron-driven intralysosomal oxidative reaction, resulting in LMP change and lipid peroxidation. Thus, a ferritinophagy-mediated lysosomal ROS generation playing a role in the antiproliferative action of DpdtC could be proposed, which will enrich our knowledge of iron chelator in cancer therapy.

Zinc Metallochaperones as Mutant p53 Reactivators: A New Paradigm in Cancer Therapeutics

Restoration of wild-type structure and function to mutant p53 with a small molecule (hereafter referred to as "reactivating" mutant p53) is one of the holy grails in cancer therapeutics. The majority of TP53 mutations are missense which generate a defective protein that is targetable. We are currently developing a new class of mutant p53 reactivators called zinc metallochaperones (ZMCs) and, here, we review our current understanding of them. The p53 protein requires the binding of a single zinc ion, coordinated by four amino acids in the DNA binding domain, for proper structure and function. Loss of the wild-type structure by impairing zinc binding is a common mechanism of inactivating p53. ZMCs reactivate mutant p53 using a novel two-part mechanism that involves restoring the wild-type structure by reestablishing zinc binding and activating p53 through post-translational modifications induced by cellular reactive oxygen species (ROS). The former causes a wild-type conformation change, the later induces a p53-mediated apoptotic program to kill the cancer cell. ZMCs are small molecule metal ion chelators that bind zinc and other divalent metal ions strong enough to remove zinc from serum albumin, but weak enough to donate it to mutant p53. Recently we have extended our understanding of the mechanism of ZMCs to the role of cells' response to this zinc surge. We found that cellular zinc homeostatic mechanisms, which normally function to maintain free intracellular zinc levels in the picomolar range, are induced by ZMCs. By normalizing zinc levels, they function as an OFF switch to ZMCs because zinc levels are no longer sufficiently high to maintain a wild-type structure. This on/off switch leads to a transient nature to the mechanism of ZMCs in which mutant p53 activity comes on in a few hours and then is turned off. This finding has important implications for the translation of ZMCs to the clinic because it indicates that ZMC concentrations need not be maintained at high levels for their activity. Indeed, we found that short exposures (as little as 15 min) were adequate to observe the mutant p53 reactivating activity. This switch mechanism imparts an advantage over other targeted therapeutics in that efficacy can be accomplished with minimal exposure which minimizes toxicity and maximizes the therapeutic window. This on/off switch mechanism is unique in targeted cancer therapeutics and will impact the design of human clinical trials.

Four Cu(ii) complexes based on antitumor chelators: synthesis, structure, DNA binding/damage, HSA interaction and enhanced cytotoxicity

Four novel copper(ii) complexes [Cu(II)(Bp4mT)(μ-Cl)]2 (), [Cu(II)(μ-Bp4mT)Br]2 (), [Cu(II)(HBpT)Cl] (), and [Cu(II)(HBpT)Br] () (Bp4mT = 2-benzoylpyridine-4-methylthiosemicarbazone, HBpT = 2-benzoylpyridine thiosemicarbazone), were synthesized and characterized using single-crystal X-ray diffraction, elemental analysis, infrared, and ultraviolet-visible spectroscopy. X-ray analysis revealed that complexes and based on the Bp4mT ligand presented dimeric structures in which the Cu(ii) ions were located in a five-coordinated distorted square-pyramidal geometry, whereas both and complexes were mononuclear with the Cu(ii) ions exhibiting a tetracoordinated square planar configuration. Their interactions with calf thymus DNA (CT-DNA) were investigated using viscosity measurements and fluorescence spectroscopy. Multispectroscopic evidence has shown interactions between these complexes and human serum albumin (HSA). All these complexes have exhibited efficient oxidative cleavage of supercoiled DNA in the presence of hydrogen peroxide, presumably via an oxidative mechanism. Furthermore, in vitro cytotoxicity studies of against human liver hepatocellular carcinoma cells (HepG-2), human large cell lung carcinoma cells (NCI-H460), and human cervical carcinoma cells (HeLa) indicated their promising antitumor activity with quite low IC50 values in the range of 0.08-1.98 μM, which are 83 times lower than those of cisplatin. The mechanistic studies revealed that four complexes, which induced early apoptosis, were involved in reactive oxygen species generation and DNA cleavage for their antitumor activities.

The role of nutrition in influencing mechanisms involved in environmentally mediated diseases

Human exposure to environmental contaminants such as persistent chlorinated organics, heavy metals, pesticides, phthalates, flame retardants, electronic waste and airborne pollutants around the world, and especially in Southeast Asian regions, are significant and require urgent attention. Given this widespread contamination and abundance of such toxins as persistent organic pollutants (POPs) in the ecosystem, it is unlikely that remediation alone will be sufficient to address the health impacts associated with this exposure. Furthermore, we must assume that the impact on health of some of these contaminants results in populations with extraordinary vulnerabilities to disease risks. Further exacerbating risk; infectious diseases, poverty and malnutrition are common in the Southeast Asian regions of the world. Thus, exploring preventive measures of environmental exposure and disease risk through new paradigms of environmental toxicology, optimal and/or healthful nutrition and health is essential. For example, folic acid supplementation can lower blood arsenic levels, and plant-derived bioactive nutrients can lower cardiovascular and cancer risks linked to pollutant exposure. Data also indicate that diets enriched with bioactive food components such as polyphenols and omega-3 polyunsaturated fatty acids can prevent or decrease toxicant-induced inflammation. Thus, consuming healthy diets that exhibit high levels of antioxidant and anti-inflammatory properties, is a meaningful way to reduce the vulnerability to non-communicable diseases linked to environmental toxic insults. This nutritional paradigm in environmental toxicology requires further study in order to improve our understanding of the relationship between nutrition or other lifestyle modifications and toxicant-induced diseases. Understanding mechanistic relationships between nutritional modulation of environmental toxicants and susceptibility to disease development are important for both cumulative risk assessment and the design and implementation of future public health programs and behavioral interventions.

Metallomics for Alzheimer's disease treatment: Use of new generation of chelators combining metal-cation binding and transport properties

Alzheimer's disease (AD) is a progressive neurodegenerative disorder affecting tens of million people. Currently marketed drugs have limited therapeutic efficacy and only slowing down the neurodegenerative process. Interestingly, it has been suggested that biometal cations in the amyloid beta (Aβ) aggregate deposits contribute to neurotoxicity and degenerative changes in AD. Thus, chelation therapy could represent novel mode of therapeutic intervention. Here we describe the features of chelators with therapeutically relevant mechanism of action. We have found that the tested compounds effectively reduce the toxicity of exogenous Aβ and suppress its endogenous production as well as decrease oxidative stress. Cholyl hydrazones were found to be the most active compounds. In summary, our data show that cation complexation, together with improving transport efficacy may represent basis for eventual treatment strategy in AD.

Novel chelators based on adamantane-derived semicarbazones and hydrazones that target multiple hallmarks of Alzheimer's disease

Novel adamantane-derived semicarbazones and hydrazones show multi-functional activity as potential therapeutics for Alzheimer's disease.

Repurposing an inhibitor of ribosomal biogenesis with broad anti-fungal activity

The lack of new antifungal compounds with unique mechanisms of action is a concern for therapeutic management of patients. To identify inhibitors against human pathogenic fungi, we screened ~3000 compounds provided by the Developmental Therapeutics Program of NIH/NCI against a panel of pathogenic fungi including Candida species, Aspergillus fumigatus, and Cryptococcus neoformans. NSC319726 (a thiosemicarbazone) had broad antifungal activity in the range of 0.1–2.0 µg/ml and was also inhibitory to fluconazole-resistant isolates of Candida species. Synergy was demonstrated with NSC319726 and azoles, as well as caspofungin. The inhibitory concentration 50% (IC₅₀) of NSC319726 was 35–800-fold higher than the Minimum Inhibitory Concentration 50% (MIC₅₀ values), which indicates low compound toxicity to human cells in vitro. Transcriptome analysis of treated and untreated C. albicans using Gene Ontology (GO) revealed a large cluster of down regulated genes that encode translational proteins, especially those with ribosome biogenesis functions. As NSC319726 was first shown to have anti-cancer activity, its affects against human pathogenic fungi establish NSC319726 as a repurposed, off-patent compound that has potential antifungal activity. The minimal in vitro toxicity of lead optimized NSC319726 and its reasonable inhibitory activity against pathogens suggest advancing this compound to in vivo toxicity testing and protection studies against candidiasis.

Photometric flow analysis system for biomedical investigations of iron/transferrin speciation in human serum

The Multicommutated Flow Analysis (MCFA) system for the estimation of clinical iron parameters: Serum Iron (SI), Unsaturated Iron Binding Capacity (UIBC) and Total Iron Binding Capacity (TIBC) has been proposed. The developed MCFA system based on simple photometric detection of iron with chromogenic agent (ferrozine) enables a speciation of transferrin (determination of free and Fe-bound protein) in human serum. The construction of manifold was adapted to the requirements of measurements under changing conditions. In the course of studies, a different effect of proteins on SI and UIBC determination has been proven. That was in turn the reason to perform two kinds of calibration methods. For measurements in acidic medium for SI/holotransferrin determination, the calibration curve method was applied, characterized by limit of determination and limit of quantitation on the level of 3.4 μmol L^-1 and 9.1 μmol L^-1, respectively. The determination method for UIBC parameter (related to apotransferrin level) in physiological medium of pH 7.4 forced the use of standard addition method due to the strong influence of proteins on obtaining analytical signals. These two different methodologies, performed in the presented system, enabled the estimation of all three clinical iron/transferrin parameters in human serum samples. TIBC corresponding to total transferrin level was calculated as a sum of SI and UIBC.

Interplay of the iron-regulated metastasis suppressor NDRG1 with epidermal growth factor receptor (EGFR) and oncogenic signaling

The iron-regulated metastasis suppressor N-myc downstream-regulated gene 1 (NDRG1) has been shown to inhibit numerous oncogenic signaling pathways in cancer cells. Recent findings have demonstrated that NDRG1 inhibits the ErbB family of receptors, which function as key inducers of carcinogenesis. NDRG1 attenuates ErbB signaling by inhibiting formation of epidermal growth factor receptor (EGFR)/human epidermal growth factor receptor 2 (HER2) and HER2/HER3 heterodimers and by down-regulating EGFR via a mechanism involving its degradation. Understanding the complex interplay between NDRG1, iron, and ErbB signaling is vital for identifying novel, more effective targets for cancer therapy.

A novel colorimetric and turn-on fluorescent chemosensor for iron(III) ion detection and its application to cellular imaging

A novel rhodamine-based dual probe Rh-2 for trivalent ferric ions (Fe(3+)) was successfully designed and synthesized, which exhibited a highly sensitive and selective recognition towards Fe(3+) with an enhanced fluorescence emission in methanol-water media (v/v=7/3, pH=7.2). The probe Rh-2 could be applied to the determination of Fe(3+) with a linear range covering from 3.0×10(-7) to 1.4×10(-5)M and a detection limit of 1.24×10(-8)M. Meanwhile, the binding ratio of Rh-2 and Fe(3+) was found to be 1:1. Most importantly, the fluorescence and color signal changes of the Rh-2 solution were specific to Fe(3+) over other commonly coexistent metal ions. Moreover, the probe Rh-2 has been used to image Fe(3+) in living cells with satisfying results.