Vanadium in cancer treatment

Origin and Fate of Vanadium in the Hazeltine Creek Catchment following the 2014 Mount Polley Mine Tailings Spill in British Columbia, Canada

Results from the analysis of aqueous and solid-phase V speciation within samples collected from the Hazeltine Creek catchment affected by the August 2014 Mount Polley mine tailings dam failure in British Columbia, Canada, are presented. Electron microprobe and X-ray absorption near-edge structure (XANES) analysis found that V is present as V³⁺ substituted into magnetite and V³⁺ and V⁴⁺ substituted into titanite, both of which occur in the spilled Mount Polley tailings. Secondary Fe oxyhydroxides forming in inflow waters and on creek beds have V K-edge XANES spectra exhibiting E1/2 positions and pre-edge features consistent with the presence of V⁵⁺ species, suggesting sorption of this species on these secondary phases. PHREEQC modeling suggests that the stream waters mostly contain V⁵⁺ and the inflow and pore waters contain a mixture of V³⁺ and V⁵⁺. These data, and stream, inflow, and pore water chemical data, suggest that dissolution of V(III)-bearing magnetite, V(III)- and V(IV)-bearing titanite, V(V)-bearing Fe(-Al-Si-Mn) oxhydroxides, and V-bearing Al(OH)₃ and/or clay minerals may have occurred. In the circumneutral pH environment of Hazeltine Creek, elevated V concentrations are likely naturally attenuated by formation of V(V)-bearing secondary Fe oxyhydroxide, Al(OH)₃, or clay mineral colloids, suggesting that the V is not bioavailable. A conceptual model describing the origin and fate of V in Hazeltine Creek that is applicable to other river systems is presented.

Vanadocene complexes bearing N,N'-chelating ligands: Synthesis, structures and in vitro cytotoxic studies on the A549 lung adenocarcinoma cell line

Ten new vanadocene complexes bearing N,N'-chelating ligands were prepared, characterized, and their cytotoxicity toward a panel of cancer cells was measured. Structures of four vanadocene compounds were determined by single crystal X-ray diffraction analysis. Complexes containing 1,2-bis(phenylimino)acenaphthene (bian) and 1,2-bis(4-methoxyphenylimino)acenaphthene (4-MeO-bian) exhibit higher cytotoxicity than those with dipyrido[3,2-a:2',3'-c]phenazine (dppz) and (E)-N-((pyridin-2-yl)methylene)benzenamine (pyma). In light of the finding, cytotoxic mechanisms of two highly effective complexes [(η⁵-C₅H₄Me)₂V(bian)][OTf]₂ (3b) and [(η⁵-C₅H₄Me)₂V(4-MeO-bian)][OTf]₂ (4b) against human A549 lung adenocarcinoma cells were investigated by following membrane leakage of intracellular lactate dehydrogenase, Trypan Blue staining and activation of tumor protein p53 (p53). Evaluated complexes have a potent dose-dependent antiproliferative activity, causing cell cycle redistribution by the increased accumulation of cells in the G2 and S phase. In accord with the observed cell cycle deceleration, cyclin-dependent kinase inhibitor-interacting protein 1 (p21^WAF1/Cip1), extracellular signal-regulated kinases 1 and 2 (ERK1/2), Checkpoint kinase 1 (Chk1), Checkpoint kinase 2 (Chk2) and their phosphorylated forms Chk1 at serine 345 and Chk2 at threonine 68 increased. In the cells exposed to complexes, dose- and time-dependent apoptotic process is initiated by the activation of the initiator caspase 8, followed by activation of effector caspase 3/7 and phosphatidylserine externalization. Moreover, because of treatment, A549 cells activate prosurvival mitogen-activated protein kinases (MAPK) signaling and up-regulate antiapoptotic protein B-cell lymphoma (Bcl-2), thereby promoting evasion of cell death. Both complexes exhibited considerably higher cytotoxic effect than the reference anticancer drug cis-platin and the cytotoxicity was more pronounced at higher treatment time.

Hypoxia protects against the cell death triggered by oxovanadium-galactomannan complexes in HepG2 cells

BACKGROUND

Polysaccharides from various sources have been used in traditional medicine for centuries. The beneficial pharmacological effects of plant-derived polysaccharides include anti-tumor activity.

METHODS

Here, we evaluated the anti-cancer effect of the MSAGM:VO complex under hypoxic conditions (1% oxygen). MSAGM:VO is a complex of the hydrolysate of galactomannan (MSAGM) from Schizolobium amazonicum with oxovanadium (IV/V). The hepatocellular carcinoma (HCC) cell line HepG2 was selected as HCC are one of the most hypoxic solid tumors.

RESULTS

Our results showed that the strong apoptotic activity of MSAGM:VO observed in HepG2 cells under normoxic conditions was completely lost under hypoxic conditions. We found a dynamic balance between the pro- and anti-apoptotic members of the Bcl-2 protein family. The expressions of anti-apoptotic Mcl-1 and Bcl-XL increased in hypoxia, whereas the expression of pro-apoptotic Bax decreased. MSAGM:VO strongly induced autophagy, which was previously characterized as a pro-survival mechanism in hypoxia. These results demonstrate total elimination of the anti-cancer activity of MSAGM:VO with activation of autophagy under conditions of hypoxia.

CONCLUSION

Although this study is a proof-of-concept of the impact of hypoxia on the potential of polysaccharides, further study is encouraged. The anti-tumor activity of polysaccharides could be achieved in normoxia or through raising the activity of the immune system. In addition, combination strategies for therapy with anti-autophagic drugs could be proposed.

Experimental and theoretical investigations of novel oxidovanadium(IV) juglone complex: DNA/HSA interaction and cytotoxic activity

A new oxidovanadium(IV) complex VO(L)(Jug) (HL = 5-methoxy-1,3-bis (1-methyl-1H-benzo[d]imidazol-2-yl)benzene, Jug = juglone) was synthesized and characterized. Interactions of the V(IV) complex with calf thymus DNA (CT DNA) and human serum albumin were studied using different techniques such as UV-vis and fluorescence emission spectroscopy. The experimental results were confirmed by the molecular docking study. The oxidovanadium(IV) complex can efficiently cleave pUC19 DNA in the presence of Hydrogen peroxide. Also, the in vitro cytotoxicity properties of the oxidovanadium(IV) complex was evaluated against MCF-7, HPG-2 and HT-29 cancer cell lines and HEK293 non-malignant fibroblasts were evaluated and compared with free ligands, VOSO₄ and cisplatin as reference drugs.Communicated by Ramaswamy H. Sarma.

Vanadium in Biological Action: Chemical, Pharmacological Aspects, and Metabolic Implications in Diabetes Mellitus

Vanadium compounds have been primarily investigated as potential therapeutic agents for the treatment of various major health issues, including cancer, atherosclerosis, and diabetes. The translation of vanadium-based compounds into clinical trials and ultimately into disease treatments remains hampered by the absence of a basic pharmacological and metabolic comprehension of such compounds. In this review, we examine the development of vanadium-containing compounds in biological systems regarding the role of the physiological environment, dosage, intracellular interactions, metabolic transformations, modulation of signaling pathways, toxicology, and transport and tissue distribution as well as therapeutic implications. From our point of view, the toxicological and pharmacological aspects in animal models and humans are not understood completely, and thus, we introduced them in a physiological environment and dosage context. Different transport proteins in blood plasma and mechanistic transport determinants are discussed. Furthermore, an overview of different vanadium species and the role of physiological factors (i.e., pH, redox conditions, concentration, and so on) are considered. Mechanistic specifications about different signaling pathways are discussed, particularly the phosphatases and kinases that are modulated dynamically by vanadium compounds because until now, the focus only has been on protein tyrosine phosphatase 1B as a vanadium target. Particular emphasis is laid on the therapeutic ability of vanadium-based compounds and their role for the treatment of diabetes mellitus, specifically on that of vanadate- and polioxovanadate-containing compounds. We aim at shedding light on the prevailing gaps between primary scientific data and information from animal models and human studies.

Redox chemistry of vanadium in soils and sediments: Interactions with colloidal materials, mobilization, speciation, and relevant environmental implications- A review

Vanadium (V), although serving as an important component of industrial activities, has bioinorganic implications to pose highly toxic hazards to humans and animals. Soils and sediments throughout the world exhibit wide ranges of vanadium concentrations. Although vanadium toxicity varies between different species, it is mainly controlled by soil redox potential (E_H). Nonetheless, knowledge of the redox geochemistry of vanadium lags in comparison to what is known about other potentially toxic elements (PTEs). In particular, the redox-induced speciation and mobilization of vanadium in soils and sediments and the associated risks to the environment have not been reviewed to date. Therefore, this review aims to address 1) the content and geochemical fate of vanadium in soils and sediments, 2) its redox-induced release dynamics, 3) redox-mediated chemical reactions between vanadium and soil organic and inorganic colloidal materials in soil solution, 4) its speciation in soil solution and soil-sediments, and 5) the use of advanced geochemical and spectroscopic techniques to investigate these complex systems. Vanadium (+5) is the most mobile and toxic form of its species while being the thermodynamically stable valence state in oxic environments, while vanadium (+3) might be expected to be predominant under euxinic (anoxic and sulfidic) conditions. Vanadium can react variably in response to changing soil E_H: under anoxic conditions, the mobilization of vanadium can decrease because vanadium (+5) can be reduced to relatively less soluble vanadium (+4) via inorganic reactions such as with H₂S and organic matter and by metal-reducing microorganisms. On the other hand, dissolved concentrations of vanadium can increase at low E_H in many soils to reveal a similar pattern to that of Fe, which may be due to the reductive dissolution of Fe(hydr)oxides and the release of the associated vanadium. Those differences in vanadium release dynamics might occur as a result of the direct impact of E_H on vanadium speciation in soil solution and soil sediments, and/or because of the E_H-dependent changes in soil pH, chemistry of (Fe)(hydr)oxides, and complexation with soil organic carbon. Release dynamics of vanadium in soils may also be affected positively by soil pH and the release of aromatic organic compounds. X-ray absorption spectroscopy (XAS) is a powerful tool to investigate the speciation of vanadium present in soil. X-ray absorption near edge structure (XANES) is often used to constrain the average valence state of vanadium in soils and sediments, and in limited cases extended X-ray absorption fine structure (EXAFS) analysis has been used to determine the average molecular coordination environment of vanadium in soil components. In conclusion, this review presents the state of the art about the redox geochemistry of vanadium and thus contributes to a better understanding of the speciation, potential mobilization, and environmental hazards of vanadium in the near-surface environment of uplands, wetlands, and agricultural ecosystems as affected by various colloidal particles. Further research is needed to elucidate the geochemistry and speciation of vanadium in the dissolved, colloidal, and soil sediments phases, including the determination of factors that control the redox geochemistry of vanadium.

A Study on the Electronic Effect of para-substituents in the Aryloxy Ring of the Hydrazone Ligands on the Vanadium Centre in the mixed-ligand [VIVO(ONO)(NN)] families

The hyperfine coupling constant (Aıı) and the redox potential (E½) values of vanadium(IV) in its mixed-ligand hydrazone complexes [VIVO(L)(bipy)], 1–4 and [VIVO(L)(phen)], 5–8, [which have been synthesised from the reaction of VIVO(acac)2 with the hydrazone ligand H2L in the presence of equimolar amount of 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen) in methanol], exhibit a linear relationship with the Hammett constant (σ) of the para-substituents in the aryloxy ring of the hydrazone ligands.

Anticancer properties of a new non-oxido vanadium(IV) complex with a catechol-modified 3,3'-diindolylmethane ligand

In order to identify new active drug candidates against cancer diseases we investigated the tumor cell growth inhibition, formation of reactive oxygen species, mitochondrial membrane damage, cell cycle arrest and DNA binding activity of a new bis(triethylammonium) tris[1,1-bis(indol-3-yl)-1-(3,4-catecholate)methane]vanadate(IV) complex. It exhibited significant antiproliferative activity against various cancer cell lines, showed a stronger DNA binding than cisplatin and led to mitochondrial damage, a formation of reactive oxygen species, and a cell cycle arrest in the G2/M phase of cancer cells.

New Oxidovanadium(IV) Coordination Complex Containing 2-Methylnitrilotriacetate Ligands Induces Cell Cycle Arrest and Autophagy in Human Pancreatic Ductal Adenocarcinoma Cell Lines

Pancreatic cancer is characterized by one of the lowest five-year survival rates. In search for new treatments, some studies explored several metal complexes as potential anticancer drugs. Therefore, we investigated three newly synthesized oxidovanadium(IV) complexes with 2-methylnitrilotriacetate (bcma3-), N-(2-carbamoylethyl)iminodiacetate (ceida3-) and N-(phosphonomethyl)-iminodiacetate (pmida4-) ligands as potential anticancer compounds using pancreatic cancer cell lines. We measured: Cytotoxicity using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), neutral red (NR) and lactate dehydrogenase (LDH) assay; antiproliferative activity by bromodeoxyuridine BrdU assay; reactive oxygen species (ROS) generation and cell cycle analysis by flow cytometry; protein level by Western blot and cellular morphology by confocal laser scanning microscopy. The results showed that these oxidovanadium(IV) complexes were cytotoxic on pancreatic cancer cells (PANC-1 and MIA PaCa2), but not on non-tumor human immortalized pancreas duct epithelial cells (hTERT-HPNE) over the concentration range of 10⁻25 μM, following 48 h incubation. Furthermore, molecular mechanisms of cytotoxicity of [4-NH₂-2-Me(Q)H][VO(bcma)(H₂O)]2H₂O (T1) were dependent on antiproliterative activity, increased ROS generation, cell cycle arrest in G2/M phase with simultaneous triggering of the p53/p21 pathway, binucleation, and induction of autophagy. Our study indicates that oxidovanadium(IV) coordination complexes containing 2-methylnitrilotriacetate ligand are good candidates for preclinical development of novel anticancer drugs targeting pancreatic cancer.

Three peroxidovanadium(v) compounds mediated by transition metal cations for enhanced anticancer activity

The mediation of transition metal cations leads to superior antiproliferative activity and cell-type selectivity of peroxidovanadium(v) compounds.

Synthesis, crystal structure, DFT calculations, protein interaction, anticancer potential and bromoperoxidase mimicking activity of oxidoalkoxidovanadium(v) complexes

Intriguing structure–activity relationships (SARs) indicating an apparent dependence of anticancer and haloperoxidase activities on the carbon chain length of the alkoxo group.

Hydrophobicity may enhance membrane affinity and anti-cancer effects of Schiff base vanadium(v) catecholate complexes

Anti-cancer activities of vanadium compounds have generated recent interest because of a combination of desirable properties for chemotherapy, i.e., strong cytotoxicities, anti-metastatic activities and relatively low systemic toxicities. Certain hydrophobic vanadium(v) Schiff base/catecholate compounds, which as shown herein, have increased stability in aqueous media and affinity for membrane interfaces. Depending on their hydrophobicity, they may be able to enter cells intact. In this manuscript, two hydrophobic V(v) catecholate substituted analogues, [VO(Hshed)(cat)] and [VO(Hshed)(dtb)], (Hshed = N-(salicylideneaminato)-N'-(2-hydroxyethyl)-1,2-ethanediamine, cat = pyrocatechol, and dtb = 3,5-di(tert-butyl)catechol and the vanadium(v) precursor [V(O)2(Hshed)]) were synthesized for their ability to interact with membranes and their anti-cancer effects. Using 51V and 1H NMR spectroscopy, the presence and location of the free ligand, H2shed, and the three V(v) complexes were examined in a model membrane microemulsion system. The stability of the three complexes was measured in aqueous solution, cell media and an inhomogeneous microemulsion system. Our results demonstrated that free ligand H2shed and the intact V(v) complexes associated with the interface but that the V-complexes hydrolyzed to some extent because oxovanadates were observed by 51V NMR spectroscopy and decreasing complex by absorption spectroscopy in cell media. When determining the effects of V(v) catecholate complexes on bone cancer cells, the strongest effects were observed with the more stable hydrophobic complex [VO(Hshed)(dtb)] that was able to best associate and penetrate the model membrane system intact. These studies are consistent with the membrane permeability studies being a good predictor for in vitro cytotoxicity assays because [VO(Hshed)(dtb)] can pass through the cellular membrane intact, which may enhance its anti-cancer activities.

In vitrocytotoxicity and catalytic evaluation of dioxidovanadium(v) complexes in an azohydrazone ligand environment

Synthesis, characterization,in vitrocytotoxicity and catalytic potential of the dioxidovanadium(v) complexes of azohydrazones.

Vanadium in Biosphere and Its Role in Biological Processes

Ultra-trace elements or occasionally beneficial elements (OBE) are the new categories of minerals including vanadium (V). The importance of V is attributed due to its multifaceted biological roles, i.e., glucose and lipid metabolism as an insulin-mimetic, antilipemic and a potent stress alleviating agent in diabetes when vanadium is administered at lower doses. It competes with iron for transferrin (binding site for transportation) and with lactoferrin as it is secreted in milk also. The intracellular enzyme protein tyrosine phosphatase, causing the dephosphorylation at beta subunit of the insulin receptor, is inhibited by vanadium, thus facilitating the uptake of glucose inside the cell but only in the presence of insulin. Vanadium could be useful as a potential immune-stimulating agent and also as an antiinflammatory therapeutic metallodrug targeting various diseases. Physiological state and dose of vanadium compounds hold importance in causing toxicity also. Research has been carried out mostly on laboratory animals but evidence for vanadium importance as a therapeutic agent are available in humans and large animals also. This review examines the potential biochemical and molecular role, possible kinetics and distribution, essentiality, immunity, and toxicity-related study of vanadium in a biological system.

Synthesis, in vitro cytotoxicity, and structure-activity relationships (SAR) of multidentate oxidovanadium(iv) complexes as anticancer agents

Multidentate oxidovanadium(iv) complexes with different geometric configurations [VO(ox)(bpy)(H2O)] 1, [VO(ox)(phen)(H2O)] 2, [VO(ida)(bpy)]·2H2O 3, (phen)[VO(ida)(phen)]·4H2O 4, and (Hphen)[VO(H2O)(nta)]·2H2O 5 [ox = oxalic acid, bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, ida = iminodiacetic acid, nta = nitrilotriacetic acid] have been obtained from the reactions of oxidovanadium sulfate or vanadium pentoxide with oxalates, amino-polycarboxylates and N-heterocyclic ligands in neutral solution by the hydrothermal method, and have been fully characterized by elemental, thermogravimetric analyses and single crystal X-ray diffraction, as well as a wide range of spectroscopic techniques such as FT-IR, UV/Vis, NMR, ESI-MS. The anti-tumor properties of oxidovanadium compounds 1-5 were further evaluated in human HepG2 and SMMC-7721 hepatocellular carcinoma cell lines in vitro. The profiles of cytotoxicity, cell cycle distribution, as well as cell apoptosis upon test compound exposure, were determined by MTT and flow cytometry assays. Compound 2 exhibited a much higher anti-tumor activity than others. The IC50 values of 2 were 5.34 ± 0.034 μM and 29.07 ± 0.017 μM in SMMC-7721 and HepG2 cells after 48 h treatment, respectively. Furthermore, compound 2 could significantly arrest the cell cycle in the S and G2/M phases and further induce cell apoptosis in a dose-dependent manner. The structure-activity relationship (SAR) studies revealed that structural elements, for example, metal components, variations of coordination mode, labile water molecules, chelated ligands etc., probably exert an essential cooperative effect on the antitumor activity. In short, these findings not only provide an accessible model system to exploit V-based complexes as potential simple, safe and effective multifunctional antitumor agents, but also open up a rational approach to shed new light on the selection and optimization of ideal drug candidates.

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications

In the last 30 years, since the discovery that vanadium is a cofactor found in certain enzymes of tunicates and possibly in mammals, different vanadium-based drugs have been developed targeting to treat different pathologies. So far, the in vitro studies of the insulin mimetic, antitumor and antiparasitic activity of certain compounds of vanadium have resulted in a great boom of its inorganic and bioinorganic chemistry. Chemical speciation studies of vanadium with amino acids under controlled conditions or, even in blood plasma, are essential for the understanding of the biotransformation of e.g. vanadium antidiabetic complexes at the physiological level, providing clues of their mechanism of action. The present article carries out a bibliographical research emphaticizing the chemical speciation of the vanadium with different amino acids and reviewing also some other important aspects such as its chemistry and therapeutical applications of several vanadium complexes.

Speciation in human blood of Metvan, a vanadium based potential anti-tumor drug

The first report on the anti-cancer activity of the compound Metvan, [V^IVO(Me₂phen)₂(SO₄)], where Me₂phen is 4,7-dimethyl-1,10-phenanthroline, dates back to 2001. Although it was immediately identified as one of the most promising multitargeted anti-cancer V compounds, no development on the medical experimentation was carried out. One of the possible reasons is the lack of information on its speciation in aqueous solution and its thermodynamic stability, factors which influence the transport in the blood and the final form which reaches the target organs. To fill this gap, in this work the speciation of Metvan in aqueous solution and human blood was studied by instrumental (EPR, electronic absorption spectroscopy, ESI-MS and ESI-MS/MS), analytical (pH-potentiometry) and computational (DFT) methods. The results suggested that Metvan transforms at physiological pH into the hydrolytic species cis-[VO(Me₂phen)₂(OH)]⁺ and that both citrate and proteins (transferrin and albumin in the blood serum, and hemoglobin in the erythrocytes) form mixed complexes, denoted [VO(Me₂phen)(citrH_-1)]^2- and VO-Me₂phen-Protein with the probable binding of His-N donors. The measurements with erythrocytes suggest that Metvan is able to cross their membrane forming mixed species VO-Me₂phen-Hb. The redox stability in cell culture medium was also examined, showing that ca. 60% is oxidized to V^V after 5 h. Overall, the speciation of Metvan in the blood mainly depends on the V concentration: when it is larger than 50 μM, [VO(Me₂phen)(citrH_-1)]^2- and VO-Me₂phen-Protein are the major species, while for concentrations lower than 10 μM, (VO)(hTf) is formed and Me₂phen is lost. Therefore, it is plausible that the pharmacological activity of Metvan could be due to the synergic action of free Me₂phen, and V^IVO and V^VO/V^VO₂ species.

Vanadyl complexes discriminate between neuroblastoma cells and primary neurons by inducing cell-specific apoptotic pathways

Vanadium compounds have arisen as potential therapeutic agent for the treatment of cancers over the past decades. A few studies suggested that vanadyl complexes may discriminate between the cancerous and the normal cells. Here, we reported the investigation on the pro-apoptotic effect and the underlying mechanism of bis(acetylacetonato) oxovanadium(IV) ([VO(acac)₂]) on SH-SY5Y neuroblastoma cells in comparison with that of mouse primary cortex neurons. The experimental results revealed that [VO(acac)₂] showed about 10-fold higher cytotoxicity (IC50 ~16 μM) on the neuroblastoma cells than on normal neurons (IC50 ~250 μM). Further analysis indicated that the vanadyl complex suppressed the growth of neuroblastoma cells via different pathways depending on its concentration. It induced a special cyclin D-mediated and p53-independent cell apoptosis at <50 μM but cell cycle arrests at >50 μM. In contrast, [VO(acac)₂] promoted cell viability of primary neurons in the concentration range of 0-150 μM; while [VO(acac)₂] at hundreds of μM would cause neuronal death possibly via the reactive oxygen species (ROS)-mediated signal pathways. The extraordinary discrimination between neuroblastoma cells and primary neurons suggests potential application of vanadyl complexes for therapeutic treatment of neuroblastoma. In addition, the p53-independent apoptotic pathways induced by vanadyl complexes may provide new insights for future discovery of new anticancer drugs overcoming the chemo-resistance due to p53 mutation.

Real-time Analysis of Impedance Alterations by the Effects of Vanadium Pentoxide on Several Carcinoma Cell Lines

Objectives

Vanadium compounds have various pharmacologic effects and all available evidence reveals that the effects of vanadium compounds depend on many factors, mainly on the type of cells and dose. The proapoptotic or antiapoptotic effect of vanadium compounds depends strongly on the cell type.

Materials and Methods

In this study, the effects of vanadium pentoxide (V₂O₅) were investigated using several tumor cell lines: a colorectal cancer cell line (Colo-205), a human breast adenocarcinoma cell line (MCF-7), and a normal human fibroblast cell line. Five different concentrations of V₂O₅ between 25-200 µM were applied on the cells and xCELLigence real-time cell analysis was conducted to evaluate the impedance alterations. This study is the first to show V₂O₅'s effects on Colo-205 and MCF-7 and human fibroblast cell lines in a real-time manner.

Results

In the Colo-205 cell line, cell index (CI) alterations decreased slightly at 25 µM and 50 µM, and increased at 100 µM, 150 µM and 200 µM concentrations. In the MCF-7 cell line, CI alterations increased at all concentrations compared with the untreated control. However, in the healthy fibroblast cell line, the CI alterations decreased at all concentrations compared with the untreated control, which limits the use of V₂O₅ for its cytotoxic effect in vivo.

Conclusion

The combination of conventional anticancer drugs can be used to increase the effectiveness and reduce the adverse effects of these drugs considering stages of cancer and cancer type. Our results suggest that V₂O₅ has disparate effects on several cancer cells at different concentrations.

Trends in vanadium neurotoxicity

Vanadium, atomic number 23, is a transition metal widely distributed in nature. It is a major contaminant of fossil fuels and is widely used in industry as catalysts, in welding, and making steel alloys. Over the years, vanadium compounds have been generating interests due to their use as therapeutic agents in the control of diabetes, tuberculosis, and some neoplasms. However, the toxicity of vanadium compounds is well documented in literature with occupational exposure of workers in vanadium allied industries, environmental pollution from combustion of fossil fuels and industrial exhausts receiving concerns as major sources of toxicity and a likely predisposing factor in the aetiopathogenesis of neurodegenerative diseases. A lot has been done to understand the neurotoxic effects of vanadium, its mechanisms of action and possible antidotes. Sequel to our review of the subject in 2011, this present review is to detail the recent insights gained in vanadium neurotoxicity.

Vanadium Compounds as PTP Inhibitors

Phosphotyrosine signaling is regulated by the opposing actions of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Here we discuss the potential of vanadium derivatives as PTP enzyme inhibitors and metallotherapeutics. We describe how vanadate in the V oxidized state is thought to inhibit PTPs, thus acting as a pan-inhibitor of this enzyme superfamily. We discuss recent developments in the biological and biochemical actions of more complex vanadium derivatives, including decavanadate and in particular the growing number of oxidovanadium compounds with organic ligands. Pre-clinical studies involving these compounds are discussed in the anti-diabetic and anti-cancer contexts. Although in many cases PTP inhibition has been implicated, it is also clear that many such compounds have further biochemical effects in cells. There also remain concerns surrounding off-target toxicities and long-term use of vanadium compounds in vivo in humans, hindering their progress through clinical trials. Despite these current misgivings, interest in these chemicals continues and many believe they could still have therapeutic potential. If so, we argue that this field would benefit from greater focus on improving the delivery and tissue targeting of vanadium compounds in order to minimize off-target toxicities. This may then harness their full therapeutic potential.

Syntheses, crystal structures, DFT calculations, protein interaction and anticancer activities of water soluble dipicolinic acid-imidazole based oxidovanadium(iv) complexes

Three novel water soluble neutral mononuclear oxidovanadium(iv) complexes 1-3, [VOLB₂] (where H₂L = dipicolinic acid (DPA) and B = imidazole (1)/1-methylimidazole (2)/1-allylimidazole (3)), were synthesized by the reaction of [VOL(H₂O)₂] with imidazole/1-methylimidazole/1-allylimidazole in ethanol. The complexes were thoroughly characterized by elemental analysis, IR, UV-Vis and EPR spectroscopy, magnetic susceptibility, cyclic voltammetry and single crystal X-ray diffraction techniques. In all the complexes the vanadium(iv) centre assumes a distorted octahedral environment. All the three complexes have similar structures and contain a range of intramolecular interactions such as hydrogen bonding, C-Hπ, and ππ stacking dominating their supramolecular architectures. A thermal study of the complexes was carried out to analyze their stability. The energy of non-covalent interactions and frontier orbitals for the complexes were also calculated by DFT. In order to investigate the binding interactions and conformational changes of the secondary structure of bovine serum albumin (BSA) with the complexes, absorption, fluorimetric titration and circular dichroism measurements in aqueous medium were carried out. Molecular docking studies have also been carried out to understand the binding modes and interaction patterns of the oxidovanadium(iv) complexes with BSA. The anticancer activities of the ligand and complexes 1-3 were tested against the human hepatic carcinoma cell line Hep3B. The complexes showed prominent cytotoxicity towards cancer cells.

Deciphering the effect of an oxovanadium(iv) complex with the flavonoid chrysin (VOChrys) on intracellular cell signalling pathways in an osteosarcoma cell line

Vanadium complexes were studied during recent years and considered as a representative of a new class of non-platinum metal antitumor agents in combination with their low toxicity. However, a few challenges still remain in the discovery of new molecular targets for these novel metal-based drugs. The study of cell signaling pathways related to vanadium drugs, which is highly critical for identifying specific targets that play an important role in the antitumor activity of vanadium compounds, is scarce. This research deals with the alterations in intracellular signaling pathways promoted by an oxovanadium(iv) complex with the flavonoid chrysin [VO(chrysin)2EtOH]2 (VOChrys) in a human osteosarcoma cell line (MG-63). Herein we report for the first time the effect of [VO(chrysin)2EtOH]2 on the relative abundance of 224 proteins, which are involved in the most common intracellular pathways. Besides, full-length human recombinant (FAK and AKT1) kinases are produced using an in situ IVTT system and then we have evaluated the variation of relative tyrosine-phosphorylation levels caused by the [VO(chrysin)2EtOH]2 compound. The results of the differential protein expression levels reveal that several proteins such as PKB/AKT, PAK, DAPK, Cdk 4, 6 and 7, FADD, AP2, NAK, and JNK, among others, were altered. Moreover, cell signaling pathways related to the PTK2B, FAK, PKC families suggests an important role associated with the antitumor activity of [VO(chrysin)2EtOH]2 was demonstrated. Finally, the effect of this compound on in situ expressed FAK and AKT1 is validated by determining the phosphorylation level, which decreased in the former and increased in the latter.

Multi-modal Potentiation of Oncolytic Virotherapy by Vanadium Compounds

Oncolytic viruses (OV) are an emerging class of anticancer bio-therapeutics that induce antitumor immunity through selective replication in tumor cells. However, the efficacy of OVs as single agents remains limited. We introduce a strategy that boosts the therapeutic efficacy of OVs by combining their activity with immuno-modulating, small molecule protein tyrosine phosphatase inhibitors. We report that vanadium-based phosphatase inhibitors enhance OV infection in vitro and ex vivo, in resistant tumor cell lines. Furthermore, vanadium compounds increase antitumor efficacy in combination with OV in several syngeneic tumor models, leading to systemic and durable responses, even in models otherwise refractory to OV and drug alone. Mechanistically, this involves subverting the antiviral type I IFN response toward a death-inducing and pro-inflammatory type II IFN response, leading to improved OV spread, increased bystander killing of cancer cells, and enhanced antitumor immune stimulation. Overall, we showcase a new ability of vanadium compounds to simultaneously maximize viral oncolysis and systemic anticancer immunity, offering new avenues for the development of improved immunotherapy strategies.

Vanadium(V) complexes with hydrazides and their spectroscopic and biological properties

The present study explores the synthesis and inhibitory potential of vanadium(V) complexes of hydrazides (1c-12c) against oxidative enzymes including xanthine oxidase and lipoxygenase (LOX). In addition, non-enzymatic radical scavenging activities of these complexes were also determined. On the basis of spectral, elemental and physical data, synthesized vanadium(V) complexes are tentatively assigned to have an octahedral geometry with two hydrazide ligands and two oxo groups forming a negatively charged sphere complex with ammonium as counter ion. This is further verified by the conductivity studies of the complexes. Results show that hydrazide ligands (1-12) and their respective vanadium(V) complexes (1c-12c) posses scavenging and inhibition potential against DPPH and LOX, respectively. However, contrary to that uncoordinated ligands showed no activity against nitric oxide, superoxide and xanthine oxidase whereas their complexes showed varying degree of activity. These studies indicate that geometry of complex, nature and position of substituent groups play a vital role in scavenging and inhibition potential of these compounds.

Geochemistry of vanadium (V) in Chinese coals

Vanadium in coals may have potential environmental and economic impacts. However, comprehensive knowledge of the geochemistry of V in coals is lacking. In this study, abundances, distribution and modes of occurrence of V are reviewed by compiling >2900 reported Chinese coal samples. With coal reserves in individual provinces as the weighting factors, V in Chinese coals is estimated to have an average abundance of 35.81 μg/g. Large variation of V concentration is observed in Chinese coals of different regions, coal-forming periods, and maturation ranks. According to the concentration coefficient of V in coals from individual provinces, three regions are divided across Chinese coal deposits. Vanadium in Chinese coals is probably influenced by sediment source and sedimentary environment, supplemented by late-stage hydrothermal fluids. Specifically, hydrothermal fluids have relatively more significant effect on the enrichment of V in local coal seams. Vanadium in coals is commonly associated with aluminosilicate minerals and organic matter, and the modes of V occurrence in coal depend on coal-forming environment and coal rank. The Chinese V emission inventory during coal combustion is estimated to be 4906 mt in 2014, accounting for 50.55 % of global emission. Vanadium emissions by electric power plants are the largest contributor.

Analysis of oxovanadium(IV) complexes using electrospray mass spectrometry: Molecular ion formed by loss of an electron, and its product ions trapping oxygen

RATIONALE

In addition to their biological properties, oxovanadium complexes have been widely applied as catalysts because of their excellent catalytic-oxidation capability. Recently, monometallic oxovanadium(IV) complexes have been used as catalysts in the electrophilic trifluoromethylation of silyl ketene imines. The study of catalysts can contribute to an understanding of the reaction mechanism.

METHODS

Six monometallic oxovanadium(IV) complexes were analyzed by electrospray ionization time-of flight mass spectrometry (ESI-TOFMS), and collision-induced dissociation mass spectrometry (CID-MS) experiments were conducted for selected cations [M]⁺ of oxovanadium(IV) complexes as well as a deuterium-labeled complex. Different collision gases were used to understand the source of the O₂ and H₂ O engaged in the gas-phase ion-molecule reaction.

RESULTS

The oxovanadium(IV) complexes formed [M]⁺ ions by loss of an electron, with [M + 14]⁺ ions being formed from [M]⁺ by loss of H₂ O and addition of O₂ . The fragmentation pathways of the [M]⁺ cations were further studied by ESI-MS/MS, and several ions produced by gas-phase ion-molecule reactions were detected and characterized, including vanadium-oxo, -peroxo and derivatives.

CONCLUSIONS

Several unexpected ions were detected, including [M]⁺ , [M + 14]⁺ and ions produced from gas-phase ion-molecule reactions. The study has contributed to the understanding of the structure and character of oxovanadium(IV) complexes, and it could facilitate the design of new oxovanadium catalysts and an understanding of their reaction mechanism.

Selective cytotoxicity of vanadium complexes on human pancreatic ductal adenocarcinoma cell line by inducing necroptosis, apoptosis and mitotic catastrophe process

The pancreatic cancer is the fourth leading cause of cancer-related death and characterized by one of the lowest five-year survival rate. The current therapeutic options are demonstrating minimal effectiveness, therefore studies on new potential anticancer compounds, with non-significant side effects are highly desirable. Recently, it was demonstrated that vanadium compounds, in particular organic derivatives, exhibit anticancer properties against different type of tumor as well as favorable biodistribution from a pancreatic cancer treatment perspective. In this research, we showed selective cytotoxic effect of vanadium complexes, containing phenanthroline and quinoline as an organic ligands, against human pancreatic ductal adenocarcinoma cell line (PANC-1), compared to non-tumor human immortalized pancreas duct epithelial cells (hTERT-HPNE). Results exhibited that vanadium complexes inhibited autophagy process in selective cytotoxic concentration as well as caused the cell cycle arrest in G2/M phase associated with mitotic catastrophe and increased level of reactive oxygen species (ROS). Moreover, in higher concentration, vanadium derivatives induced a mix type of cell death in PANC-1 cells, including apoptotic and necroptotic process. Our investigation emphasizes the anticancer potential of vanadium complexes by indicating their selective cytotoxic activity, through different process posed by alternative type of cell deaths to apoptosis-resistant cancer cells. Further studies supporting the therapeutic potential of vanadium in pancreatic cancer treatment is highly recommended.

Solid Phase Speciation and Solubility of Vanadium in Highly Weathered Soils

Vanadium (V) is increasingly recognized both as a medical trace element with essential biological functions and as a potentially toxic environmental pollutant, yet the current knowledge on V speciation in soils is limited. Here, we investigated the chemical speciation and extractability of V in highly weathered tropical soils, which are often rich in V compared to soils of temperate climatic regions. Vanadium K-edge X-ray absorption near edge structure (XANES) spectra of soil samples, along with a range of reference compounds differing in V-oxidation state and coordination chemistry, revealed the predominance of V^4+/5+ in a primarily octahedral or tetrahedral coordination. The soil spectra were best fitted with linear combinations of reference spectra of V⁴⁺ in the structure of kaolinite, V⁵⁺ adsorbed to kaolinite, and other V⁵⁺-sorbed solids. Vanadate adsorbed to goethite, ferrihydrite, gibbsite, and/or Fe(III)-natural organic matter complexes and V⁴⁺ in the structure of goethite may be present, but cannot unequivocally be distinguished from each other by XANES spectroscopy. Sequential and single chemical extractions provided complementary information on the solubility of V under various conditions. The most labile V fractions, interpreted as weakly and strongly adsorbed V⁵⁺, are the most relevant to V mobility and bioavailability in the environment, and accounted for only ∼2% of total soil V. Our results demonstrate that kaolinite and Fe oxides can effectively sequester V in highly weathered soils by mechanisms of adsorption and structural incorporation and are relevant to other Fe-oxide-rich environments under acidic and oxic conditions.

Brain Metal Distribution and Neuro-Inflammatory Profiles after Chronic Vanadium Administration and Withdrawal in Mice

Vanadium is a potentially toxic environmental pollutant and induces oxidative damage in biological systems including the central nervous system (CNS). Its deposition in brain tissue may be involved in the pathogenesis of certain neurological disorders which after prolonged exposure can culminate into more severe pathology. Most studies on vanadium neurotoxicity have been done after acute exposure but in reality some populations are exposed for a lifetime. This work was designed to ascertain neurodegenerative consequences of chronic vanadium administration and to investigate the progressive changes in the brain after withdrawal from vanadium treatment. A total of 85 male BALB/c mice were used for the experiment and divided into three major groups of vanadium treated (intraperitoneally (i.p.) injected with 3 mg/kg body weight of sodium metavanadate and sacrificed every 3 months till 18 months); matched controls; and animals that were exposed to vanadium for 3 months and thereafter the metal was withdrawn. Brain tissues were obtained after animal sacrifice. Sagittal cut sections of paraffin embedded tissue (5 μm) were analyzed by the Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to show the absorption and distribution of vanadium metal. Also, Haematoxylin and Eosin (H&E) staining of brain sections, and immunohistochemistry for Microglia (Iba-1), Astrocytes (GFAP), Neurons (Neu-N) and Neu-N + 4',6-diamidine-2'-pheynylindole dihydrochloride (Dapi) Immunofluorescent labeling were observed for morphological and morphometric parameters. The LA-ICP-MS results showed progressive increase in vanadium uptake with time in different brain regions with prediction for regions like the olfactory bulb, brain stem and cerebellum. The withdrawal brains still show presence of vanadium metal in the brain slightly more than the controls. There were morphological alterations (of the layering profile, nuclear shrinkage) in the prefrontal cortex, cellular degeneration (loss of dendritic arborization) and cell death in the Hippocampal CA1 pyramidal cells and Purkinje cells of the cerebellum, including astrocytic and microglial activation in vanadium exposed brains which were all attenuated in the withdrawal group. With exposure into old age, the evident neuropathology was microgliosis, while progressive astrogliosis became more attenuated. We have shown that chronic administration of vanadium over a lifetime in mice resulted in metal accumulation which showed regional variabilities with time. The metal profile and pathological effects were not completely eliminated from the brain even after a long time withdrawal from vanadium metal.

Investigation of Phenols Activity in Early Stage Oxidation of Edible Oils by Electron Paramagnetic Resonance and 19F NMR Spectroscopies Using Novel Lipid Vanadium Complexes As Radical Initiators

A novel dynamic method for the investigation of the phenols activity in early stage oxidation of edible oils based on the formation of α-tocopheryl radicals initiated by oil-soluble vanadium complexes is developed. Two new vanadium complexes in oxidation states V and IV were synthesized by reacting 2,2'-((2-hydroxyoctadecyl)azanediyl)bis(ethan-1-ol) (C18DEA) with [VO(acac)₂] and 1-(bis(pyridin-2-ylmethyl)amino)octadecan-2-ol (C18DPA) with VOCl₂. Addition of a solution of either complex in edible oils resulted in the formation of α-tocopheryl radical, which was monitored by electron paramagnetic resonance (EPR) spectroscopy. The intensity of the α-tocopheryl signal in the EPR spectra was measured versus time. It was found that the profile of the intensity of the α-tocopheryl signal versus time depends on the type of oil, the phenolic content, and the storage time of the oil. The time interval until the occurrence of maximum peak intensity be reached (t_m), the height of the maximum intensity, and the rate of the quenching of the α-tocopheryl radical were used for the investigation of the mechanism of the edible oils oxidation. ¹⁹F NMR of the ¹⁹F labeled phenolic compounds (through trifluoroacetate esters) and radical trap experiments showed that the vanadium complexes in edible oil activate the one electron reduction of dioxygen to superperoxide radical. Superperoxide reacts with the lipids to form alkoperoxyl and alkoxyl lipid radicals, and all these radicals react with the phenols contained in oils.