Study of the DNA binding mechanism and in vitro activity against cancer cells of iron(III) and aluminium(III) kojic acid derivative complexes.

Metal ions have unique electrochemical and spectroscopical properties that cannot be attained by purely organic compounds. Most of the metal ions are toxic to humans, but paradoxically, metallodrugs are used in medicine as therapeutics and theranostics. Metallodrugs are eliminated in urine and faeces, and therefore release toxic metals and ligands into aquatic ecosystems, thereby raising concerns regarding environmental risks. The use of metallodrugs based on essential metal ions (i.e., iron, copper and zinc), instead of toxic ions, is a new alternative with minor hazards. Kojic acid is an Asperigillus oryzae metabolite of low toxicity used in the food and cosmetics industries. Its derivatives form stable complexes with iron(III) ions, which bind effectively to DNA and inhibit DNA polymerization. The iron(III)/S2 ligand complexes reduce in vitro colon carcinoma (Caco2) cell viability and significantly decrease the cell number. The kojic acid derivative complexes with iron(III) presented here are an alternative to the currently used platinum complexes in cancer therapy.

Thymosin ß4 Is an Endogenous Iron Chelator and Molecular Switcher of Ferroptosis.

Thymosin ß4 (Tß4) was extracted forty years agofrom calf thymus. Since then, it has been identified as a G-actin binding protein involved in blood clotting, tissue regeneration, angiogenesis, and anti-inflammatory processes. Tß4 has also been implicated in tumor metastasis and neurodegeneration. However, the precise roles and mechanism(s) of action of Tß4 in these processes remain largely unknown, with the binding of the G-actin protein being insufficient to explain these multi-actions. Here we identify for the first time the important role of Tß4 mechanism in ferroptosis, an iron-dependent form of cell death, which leads to neurodegeneration and somehow protects cancer cells against cell death. Specifically, we demonstrate four iron2+ and iron3+ binding regions along the peptide and show that the presence of Tß4 in cell growing medium inhibits erastin and glutamate-induced ferroptosis in the macrophage cell line. Moreover, Tß4 increases the expression of oxidative stress-related genes, namely BAX, hem oxygenase-1, heat shock protein 70 and thioredoxin reductase 1, which are downregulated during ferroptosis. We state the hypothesis that Tß4 is an endogenous iron chelator and take part in iron homeostasis in the ferroptosis process. We discuss the literature data of parallel involvement of Tß4 and ferroptosis in different human pathologies, mainly cancer and neurodegeneration. Our findings confronted with literature data show that controlled Tß4 release could command on/off switching of ferroptosis and may provide novel therapeutic opportunities in cancer and tissue degeneration pathologies.

Undercover Toxic Ménage à Trois of Amylin, Copper (II) and Metformin in Human Embryonic Kidney Cells.

In recent decades, type 2 diabetes complications have been correlated with amylin aggregation, copper homeostasis and metformin side effects. However, each factor was analyzed separately, and only in some rare cases copper/amylin or copper/metformin complexes were considered. We demonstrate for the first time that binary metformin/amylin and tertiary copper (II)/amylin/metformin complexes of high cellular toxicity are formed and lead to the formation of aggregated multi-level lamellar structures on the cell membrane. Considering the increased concentration of amylin, copper (II) and metformin in kidneys of T2DM patients, our findings on the toxicity of amylin and its adducts may be correlated with diabetic nephropathy development.

Kojic acid derivatives as double face ligands for metal and phosphate ions.

A family of combined Kojic acid and polyamine derivatives has been synthesized as phosphate anion and metal ion ligands. The stoichiometry, stability and structure of the ion/ligand adducts were determined by 1H NMR spectroscopy, potentiometry, EXAFS and DFT calculations. The presented dual ligands bind effectively both phosphate anions and metal ions and could be used as effective ion receptors in challenging water conditions in the broad pH range. A careful analysis of the heatmaps of the stability constants allows to choose the most appropriate ligand for the ion for qualitative and/or quantitative analysis in water, without analyte pre-treatment. Extremely high-water solubility (>0.6 M) and ion(s)/ligand stability of the adducts in the pH 3-11 are the greatest advantages of the presented here molecules over other known ion sensors. The presented here molecules represent an innovative class of dual metal/anion ligands, with perspective of medical and environmental use.

Iron Chelation for Iron Overload in Thalassemia.

This chapter is devoted to the chelation treatment of transfusion-dependent thalassemia patients. After a brief overview on the pathophysiology of iron overload and on the methods to quantify it in different organs, the chelation therapy is discussed, giving particular attention to the chemical and biomedical requisites. The main tasks of an iron chelator should be the scavenging of excess iron, allowing an equilibrium between iron supplied by transfusions and that removed with chelation, and protection of the individual from the poisonous effects of circulating iron. The chelating agents in clinical use are presented, illustrating the main chemical and pharmacological features, together with a comparative cost analysis of their treatments. As a final section, an overview is provided on chelators undergoing clinical trials, and on research in progress.

A new tripodal kojic acid derivative for iron sequestration: Synthesis, protonation, complex formation studies with Fe3+, Al3+, Cu2+ and Zn2+, and in vivo bioassays.

This work presents the simple and low cost synthesis of a new tripodal ligand, in which three units of kojic acid are coupled to a tris(2-aminoethyl)amine (tren) backbone molecule. The protonation equilibria, together with the complex formation equilibria of this ligand with Fe3+, Al3+, Cu2+ and Zn2+ ions were studied. The complementary use of potentiometric, spectrophotometric and NMR techniques, and of Density Functional Theory (DFT) calculations, has allowed a thorough characterization of the different species involved in equilibrium. The stability of the formed complexes with Fe3+ and Al3+ are high enough to consider the new ligand for further studies for its clinical applications as a chelating agent. Biodistribution studies were carried out to assess the capacity the ligand for mobilization of gallium in 67Ga-citrate injected mice. These studies demonstrated that this ligand efficiently chelates the radiometal in our animal model, which suggests that it can be a promising candidate as sequestering agent of iron and other hard trivalent metal ions. Furthermore, the good zinc complexation capacity appears as a stimulating result taking into a potential use of this new ligand in analytical chemistry as well as in agricultural and environmental applications.

Equilibrium studies of new bis-hydroxypyrone derivatives with Fe3+, Al3+, Cu2+ and Zn2.

This paper presents an easy and low cost synthesis of chelating agents for potential medical and environmental applications, and the evaluation of the stability of their complexes with Fe3+, Al3+, Cu2+ and Zn2+. In the last years, we synthesized and characterized effective iron chelators based on two kojic acid units joined by different linkers in position 6. In this study, we preserved kojic acid (a cheap and non-toxic molecule) as the basic unit but joined the two kojic acid units through ethylene diamine, propylene diamine and butylene diamine by reacting them with the OH groups in position 2. The different anchoring position of the linker, as well as the linker length, can affect both protonation and complex formation equilibria. A thorough study of the protonation and complex formation equilibria of the three ligands toward the metal ions is presented based on combined potentiometric and spectroscopic studies, and 1H NMR. The obtained results allow remarking that the orientation of the oxygen atoms in the kojic acid units, related to the anchoring position of the linker, strongly affects the protonation constants, while the chelating ability is practically unaffected. The trivalent metal ions form stable complexes with a 2:3 metal to ligand stoichiometry through the oxygen donor atoms of the ligands, whereas divalent metal ions form binuclear complexes for which the nitrogen atoms from the linker might be involved in the coordination sphere. The stability of the complexes decreases with linker length, and the selectivity of the ligands toward metal ions grows in the order Zn2+ < Cu2+ < Al3+ < Fe3+.

Salicylamide derivatives for iron and aluminium sequestration. From synthesis to complexation studies.

This paper presents an easy, fast and economic synthesis of chelating agents for medical, environmental and analytical applications, and the evaluation of the stability of their complexes with Fe3+ and Al3+. Complex formation equilibria with Cu2+ and Zn2+ metal ions were also studied to evaluate if the chelating agents can perturb the homeostatic equilibria of these essential metal ions. Effective chelating agents for metal ions, in addition to their well-known medical uses, find an increasing number of applications in environmental remediation, agricultural applications (supplying essential elements in an easily available form), and in analytical chemistry as colorimetric reagents. Besides the stability of the complexes, the lack of toxicity and the low cost are the basic requisites of metal chelating agents. With these aims in mind, we utilized ethyl salicylate, a cheap molecule without toxic effects, and adopted a simple synthetic strategy to join two salicylate units through linear diamines of variable length. Actually, the mutual position of the metal binding oxygen groups, as well as the linker length, affected protonation and complex formation equilibria. A thorough study of the ligands is presented. In particular, the complex formation equilibria of the three ligands toward Fe3+, Al3+, Zn2+ and Cu2+ ions were investigated by combined potentiometric and spectrophotometric techniques. The results are encouraging: all the three ligands form stable complexes with all the investigated metal ions, involving the oxygen donor atoms from the 2-hydroxybenzamido unit, and nitrogen atoms in copper and zinc coordination.

Depleted Uranium and Human Health.

Depleted uranium (DU) is generally considered an emerging pollutant, first extensively introduced into environment in the early nineties in Iraq, during the military operation called "Desert Storm". DU has been hypothesized to represent a hazardous element both for soldiers exposed as well as for the inhabitants of the polluted areas in the war zones. In this review, the possible consequences on human health of DU released in the environment are critically analyzed. In the first part, the chemical properties of DU and the principal civil and military uses are summarized. A concise analysis of the mechanisms underlying absorption, blood transport, tissue distribution and excretion of DU in the human body is the subject of the second part of this article. The following sections deal with pathological condition putatively associated with overexposure to DU. Developmental and birth defects, the Persian Gulf syndrome, and kidney diseases that have been associated to DU are the arguments treated in the third section. Finally, data regarding DU exposure and cancer insurgence will be critically analyzed, including leukemia/lymphoma, lung cancer, uterine cervix cancer, breast cancer, bladder cancer and testicular cancer. The aim of the authors is to give a contribution to the debate on DU and its effects on human health and disease.

Tungsten or Wolfram: Friend or Foe?

Tungsten or wolfram was regarded for many years as an enemy within the tin smelting and mining industry, because it conferred impurity or dirtiness in tin mining. However, later it was considered an amazing metal for its strength and flexibility, together with its diamond like hardness and its melting point which is the highest of any metal. It was first believed to be relatively inert and an only slightly toxic metal. Since early 2000, the risk exerted by tungsten alloys, its dusts and particulates to induce cancer and several other adverse effects in animals as well as humans has been highlighted from in vitro and in vivo experiments. Thus, it becomes necessary to take a careful look at all the most recent data reported in the scientific literature, covering the years 2001-2016. In fact, the findings indicate that much more attention should be devoted to thoroughly investigate the toxic effects of tungsten and the involved mechanisms of tungsten metal or tungsten metal ions.

Gold - Old Drug with New Potentials.

BACKGROUND: Research into gold-based drugs for a range of human diseases has seen a revival in recent years. This article reviews the most important applications of gold products in different fields of human pathology. Au(I) and Au(III) compounds have been re-introduced in clinical practice for targeting the cellular components involved in the onset and progression of viral and parasitic diseases, rheumatoid arthritis and cancer. RESULTS: After some brief historical notes, this article takes into account the applications of gold compounds against Mycobacterium tuberculosis, and also in tuberculosis and in rheumatoid arthritis treatment. The use of gold containing drugs in the cure of cancer are then considered, with special emphasis to the use of nanoparticles and to the photo-thermal cancer therapy. The use of colloidal gold in diagnostics, introduced in the last decade is widely discussed. As a last point a survey on the adverse effects and on the toxicity of the various gold derivatives in use in medicine is presented. CONCLUSION: In this review, we described the surprisingly broad spectrum of possible uses of gold in diagnostics and in therapeutic approaches to multiple human diseases, ranging from degenerative to infectious diseases, and to cancer. In particular, gold nanoparticles appear as attractive elements in modern clinical medicine, combining high therapeutic properties, high selectivity in targeting cancer cells and low toxicity.

Interaction of a chelating agent, 5-hydroxy-2-(hydroxymethyl)pyridin-4(1H)-one, with Al(III), Cu(II) and Zn(II) ions.

5-Hydroxy-2-(hydroxymethyl)pyridin-4(1H)-one ligand, an iron chelator, was evaluated for its coordination ability toward Al(III), Cu(II) and Zn(II) ions by using potentiometric, NMR, EPR and UV-Vis techniques. The behavior of the ligand with the non-essential Al(III) ion has been examined, as well as its potential influence on the homeostatic equilibria of the essential Cu(II) and Zn(II) ions. Structural information on the complex formation equilibria have been obtained from 1D and 2D NMR study. The donor atoms involved in the coordination of Al(III), Cu(II) and Zn(II) ions are (O, O) the same as for Fe(III) at physiological pH value, even if from the complexation competition study the ligand appears to be more selective toward Fe(III) ions supporting that it can be used as an iron chelating agent. The involvement of N-donor atoms at high pH in Cu(II) coordination has been determined by using EPR and UV-Vis techniques.

Fluoroquinolones: A micro-species equilibrium in the protonation of amphoteric compounds.

The knowledge of the speciation of fluoroquinolones is of great actuality for the implications on the activity, bioavailability and pharmacokinetics. Literature reports a number of contrasting evaluations on the existence of tautomeric forms of mono-protonated species, described by a set of protonation micro-constants. Here the protonation sequence and the related protonation constants of four representative molecules are evaluated by a combined potentiometric-spectrophotometric method. The experimental observations necessary to differentiate between a protonation scheme represented by macro-constants alone, and the one that requires the introduction of a micro-protonation scheme, are clearly delineated based on a careful analysis of experimental data and of simulated models. The role of the medium was investigated and UV-vis spectra in water- methanol solution were analyzed. The existence of the zwitterionic species alone at physiological pH in water, and an increase of the relative amount of the neutral species with the lipophilicity of the medium were remarked. This surely affects the bioavailability of FQs, with the increase of the neutral species when the molecules approach the local lipophilic environment close to the cellular membranes. NMR studies allowed the attribution of the protonation sites of the different forms. Quantum chemical evaluation of all the possible existent forms with different protonation degrees and in different sites strongly substantiates the experimental results. The study of the relevant frontier molecular orbitals completed the detailed theoretical characterization of the species.

Chemical features of in use and in progress chelators for iron overload.

An excessive amount of iron may become extremely toxic both for its ability to generate reactive oxygen species, and for the lack of regulatory mechanisms for iron excretion in humans. Chelation therapy has been introduced in clinical practice in the 1970's to defend thalassemia patients from the effects of iron overload and it has dramatically changed both life expectancy and quality of life. The disadvantages of the drugs in clinical use make the research for new, more suitable iron chelating agents, urgent. This review defines the requirements of an iron chelator, then points out the principal chemical features of the iron chelators in use. Finally, a survey on the last ten years of the literature relative to iron chelators is done, and the most interesting ligands are presented, with particular emphasis to those that reached clinical trials.

Toxicity of nanoparticles.

Nowadays more than thousands of different nanoparticles are known, though no well-defined guidelines to evaluate their potential toxicity and to control their exposure are fully provided. The way of entry of nanoparticles together with their specificities such as chemistry, chemical composition, size, shape or morphology, surface charge and area can influence their biological activities and effects. A specific property may give rise to either a safe particle or to a dangerous one. The small size allows nanoparticles to enter the body by crossing several barriers, to pass into the blood stream and lymphatic system from where they can reach organs and tissues and strictly interact with biological structures, thus damaging their normal functions in different ways. This review provides a summary of what is known on the toxicology related to the specificity of nanoparticles, both as technological tools or ambient pollutants. The aim is to highlight their potential hazard and to provide a balanced update on all the important questions and directions that should be focused in the near future.

A new bis-3-hydroxy-4-pyrone as a potential therapeutic iron chelating agent. Effect of connecting and side chains on the complex structures and metal ion selectivity.

This work reports the synthesis, characterization and study of complex formation equilibria of the new ligand 6,6'-(2-(diethylamino)ethylazanediyl)bis(methylene)bis(5-hydroxy-2-hydroxymethyl-4H-pyran-4-one) with Fe(III), Al(III), Cu(II) and Zn(II). On the basis of previous encouraging results with tetradentate bis-kojic acid chelators, this ligand was designed to improve the pharmacokinetic properties: increase the solubility, neutral at physiological pH7.4, and enhancement of membrane crossing ability. Fe(III) and Al(III) complexation gave evidence of high metal-sequestering capacity of L9. Cellular assays showed that the ligand is capable of crossing cellular membranes and it does not present toxic effects. Complex formation equilibria with the essential metal ions Cu(II) and Zn(II) have been furthermore studied to evaluate disturbances of this chelator on the homeostatic equilibria of these essential metal ions. A variety of techniques (potentiometry, UV-visible spectrophotometry, 1D and 2D NMR spectroscopy, ESI-MS (electrospray ionization-mass spectrometry), quantum mechanical calculations and X-ray diffraction) have facilitated the characterization of the ligand, and the corresponding iron and zinc complexes, together with an exhaustive analysis of the protonation and complex equilibria.

Searching for new aluminium chelating agents: a family of hydroxypyrone ligands.

Attention is devoted to the role of chelating agents in the treatment of aluminium related diseases. In fact, in spite of the efforts that have drastically reduced the occurrence of aluminium dialysis diseases, they so far constitute a cause of great medical concern. The use of chelating agents for iron and aluminium in different clinical applications has found increasing attention in the last thirty years. With the aim of designing new chelators, we synthesized a series of kojic acid derivatives containing two kojic units joined by different linkers. A huge advantage of these molecules is that they are cheap and easy to produce. Previous works on complex formation equilibria of a first group of these ligands with iron and aluminium highlighted extremely good pMe values and gave evidence of the ability to scavenge iron from inside cells. On these bases a second set of bis-kojic ligands, whose linkers between the kojic chelating moieties are differentiated both in terms of type and size, has been designed, synthesized and characterized. The aluminium(III) complex formation equilibria studied by potentiometry, electrospray ionization mass spectroscopy (ESI-MS), quantum-mechanical calculations and (1)H NMR spectroscopy are here described and discussed, and the structural characterization of one of these new ligands is presented. The in vivo studies show that these new bis-kojic derivatives induce faster clearance from main organs as compared with the monomeric analog.

Iron(III) and aluminium(III) complexes with substituted salicyl-aldehydes and salicylic acids.

The chelating properties toward iron(III) and aluminium(III) of variously substituted salicyl-aldehydes and salicylic acids have been evaluated, together with the effect of methoxy and nitro substituents in ortho and para position with respect to the phenolic group. The protonation and iron and aluminium complex formation equilibria have been studied by potentiometry, UV-visible spectrophotometry and (1)H NMR spectroscopy. The overall results highlight that salicyl-aldehydes present good chelating properties toward iron(III), with pFe ranging from 14.2 with nitro to 15.7 with methoxy substituent, being ineffective toward aluminium; the pFe values for salicylic acids are generally lower than those for salicyl-aldehydes, and about 4 units higher than the corresponding pAl values. The effect of the two substituents on the chelating properties of the ligands can be rationalized in terms of the Swain-Lupton treatment which accounts for the field and resonance effects. The structural characterization of the 1:2 iron complex with p-nitro salicylic acid shows that iron(III) ion exhibits an octahedral surrounding where two salicylate chelating ligands supply two O-phenolate and two O-carboxylate donor atoms in a roughly equatorial plane. The trans-apical sites are occupied by two aqua ligands.

A family of hydroxypyrone ligands designed and synthesized as iron chelators.

The use of chelating agents for iron and aluminum in different clinical applications has found increasing attention in the last thirty years. Desferal, deferiprone and deferasirox, chelating agents nowadays in use, are based on hydroxamic groups, hydroxyl-substituted pyridinones or aromatic ring systems. With the aim of designing new chelators, we synthesized a series of kojic acid derivatives composed by two kojic units joined by linkers variously substituted. The huge advantages of these molecules are that they are easy and cheap to produce. Preliminary works on complex formation equilibria of the first group of ligands with iron and aluminium highlighted extremely good pMe values and gave evidence of the ability to scavenge iron from inside cells. On these bases a second set of bis-kojic ligands, whose linkers between the kojic chelating moieties are differentiated both in terms of type and size, has been designed, synthesized and characterized. The structural characterization of these new ligands is presented, and the protonation and iron(III) complex formation equilibria studied by potentiometry, UV-Visible spectrophotometry, electrospray ionization mass (ESI-MS) and (1)H NMR spectroscopy will be described and discussed.

Different approaches to the study of chelating agents for iron and aluminium overload pathologies.

Our objective is to illustrate the activity of the groups operating in Italy involved in identification and study of new chelating agents, mainly intended for treatment of human pathology correlated with metal overload. The objective of "chelation therapy" is removal of toxic metal ions from the human body or attenuation of their toxicity by transforming them into less toxic compounds or by dislocating them from the site at which they exert a toxic action. Because most of this research activity is related to chelating agents for iron and aluminium, diseases related to these two metal ions are briefly treated. Iron overload is the most common metal toxicity disease worldwide. The toxicity of aluminium in dialysis patients was a serious problem for haemodialysis units in the seventies and eighties of the last century. In particular, this review focuses on research performed by the group at Cagliari and Ferrara, and by that at Padova. The former is studying, above all, bisphosphonate and kojic acid derivatives, and the latter is investigating 3,4-hydroxypyridinecarboxylic acids with differently substituted pyridinic rings.