The role of vanadium in biology

Simultaneous formation of non-oxidovanadium(iv) and oxidovanadium(v) complexes incorporating phenol-based hydrazone ligands in aerobic conditions

A family of non-oxidovanadium(iv) complexes incorporating multidentate hydrazone ligands were synthesized through a thermodynamically unfavourable process along with oxidovanadium(v) species.

Vanadium and Oxidative Stress Markers - In Vivo Model: A Review

This review article is an attempt to summarize the current state of knowledge of the impact of Vanadium (V) on Oxidative Stress (OS) markers in vivo. It shows the results of our studies and studies conducted by other researchers on the influence of different V compounds on the level of selected Reactive Oxygen Species (ROS)/Free Radicals (FRs), markers of Lipid peroxidation (LPO), as well as enzymatic and non-enzymatic antioxidants. It also presents the impact of ROS/peroxides on the activity of antioxidant enzymes modulated by V and illustrates the mechanisms of the inactivation thereof caused by this metal and reactive oxygen metabolites. It also focuses on the mechanisms of interaction of V with some nonenzymatic compounds of the antioxidative system. Furthermore, we review the routes of generation of oxygen-derived FRs and non-radical oxygen derivatives (in which V is involved) as well as the consequences of FR-mediated LPO (induced by this metal) together with the negative/ positive effects of LPO products. A brief description of the localization and function of some antioxidant enzymes and low-molecular-weight antioxidants, which are able to form complexes with V and play a crucial role in the metabolism of this element, is presented as well. The report also shows the OS historical background and OS markers (determined in animals under V treatment) on a timeline, collects data on interactions of V with one of the elements with antioxidant potential, and highlights the necessity and desirability of conducting studies of mutual interactions between V and antioxidant elements.

Models for the acute and chronic aqueous toxicity of vanadium to Daphnia pulex under a range of surface water chemistry conditions

Alberta's oil sands petroleum coke (PC) generation has in recent years surpassed 10 million tonnes. Petroleum coke has been proposed as an industrial-scale sorbent to reduce concentrations of organic chemicals in oil sands process-affected water (OSPW). However, PC contains up to 1000 mg of vanadium (V) per kg of PC, and during the treatment it leaches from coke reaching levels of up to 7 mg/L in "treated" OSPW. Little information is available on how common water quality variables affect the toxicity of V to aquatic organisms. Here descriptive relationships are presented to describe how site-specific surface water characteristics representative of the Alberta oil sands region influence the toxicity of V to Daphnia pulex. Results revealed that when D. pulex was exposed to an increase in pH, a threshold relationship was found where acute V toxicity increased from a lethal median concentration (LC₅₀) of 1.7 to 1.2 mg V/L between pH 6 and 7 and then levelled off at around 1 mg V/L. When alkalinity (from 75 to 541 mg/L as CaCO₃) and sulphate (from 54 to 394 mg/L) increased, the acute toxicity of V decreased slightly with LC₅₀s changing from 0.6 to 1.6, and from 0.9 to 1.4, respectively. When the length of V exposure was extended (from 2 to 21 d), only an increase of sulphate from 135 to 480 mg/L caused a slight increase in V toxicity from a LC₅₀ of 0.6 to 0.4 mg V/L, the opposite trend seen in the acute exposures. In addition, the influence of two OSPW representative mixtures of increasing sodium and sulphate, and increasing alkalinity and sulphate on V acute toxicity to D. pulex were evaluated; only the mixture of increasing sodium (from 18 to 536 mg/L) and sulphate (from 55 to 242 mg/L) caused a slight decrease in V acute toxicity (LC₅₀ 1.0-2.1 mg V/L). Evidence is presented that variations in surface water chemistry can affect V toxicity to daphnids, although only to a small degree (i.e. within a maximum factor of 2 in all cases evaluated here). These relationships should be considered when creating new water quality guidelines or local benchmarks for V.

Vanadium-basidiomycete fungi interaction and its impact on vanadium biogeochemistry

Fungi are well known to strongly interact with metals, thereby influencing metal biogeochemistry in the terrestrial environment. To assess and quantify potential fungi-vanadium (V) interactions, Amanita muscaria, Armillaria cepistipes, Xerocomus badius and Bjerkandera adusta were cultured in media containing soluble V (VOSO₄ or NaVO₃) or solid-phase V of different chemical forms and oxidation state (V₂O₃, VO₂, V₂O₅, or V-Ti magnetite slag). All fungi underwent physiological and structural changes, as revealed by alterations in FT-IR peak positions and intensities relative to the control, and morphological changes of mycelia, as observed by scanning electron microscopy. The diametric growth size generally decreased with decreasing oxidation state of V and with increasing concentrations of VOSO₄ and NaVO₃, implying that V toxicity is dependent on V speciation. The tolerance index, the ratio of treated and control mycelium (dry weight), shows different tendencies, suggesting additional factors influencing fungi weight, such as the formation of extrahyphal crystals. Vanadium accumulation from VOSO₄ and NaVO₃ medium in all fungi (up to 51.3 mg g^-1) shows the potential of fungi to immobilise soluble V, thereby reducing its impacts on environmental and human health. Uptake and accumulation of V in slag was insignificant, reflecting the association of slag V with insoluble crystalline materials. The fungal accumulation of V in medium amended with V-oxides demonstrates the ability of fungi to solubilise solid-phase V compounds, thereby introducing previously immobile V into the V biogeochemical cycle and into the food chain where it may impact ecological and human health. A.muscaria lowered the pH of the medium substantially during cultivation, indicating acidolysis and complexolysis via excretion of organic acids (e.g. oxalic acid). Oxidation of VOSO₄ was observed by a colour change of the medium to yellow during B. adusta cultivation, revealing the role of fungally-mediated redox transformation in V (im)mobilisation. The calculated removal efficiencies of soluble V were 40-90% for A. cepistipes and X. badius, but a much lower recovery (0-20%) was observed from V oxides and slag (0-20%) by all fungi. This suggests the probable application of fungi for bio-remediation of mobile/soluble V in contaminated soils but not of V incorporated in the lattice of soil minerals.

Nanoscale Tungsten-Microbial Interface of the Metal Immobilizing Thermoacidophilic Archaeon Metallosphaera sedula Cultivated With Tungsten Polyoxometalate

Inorganic systems based upon polyoxometalate (POM) clusters provide an experimental approach to develop artificial life. These artificial symmetric anionic macromolecules with oxidometalate polyhedra as building blocks were shown to be well suited as inorganic frameworks for complex self-assembling and organizing systems with emergent properties. Analogously to mineral cells based on iron sulfides, POMs are considered as inorganic cells in facilitating prelife chemical processes and displaying "life-like" characteristics. However, the relevance of POMs to life-sustaining processes (e.g., microbial respiration) has not yet been addressed, while iron sulfides are very well known as ubiquitous mineral precursors and energy sources for chemolithotrophic metabolism. Metallosphaera sedula is an extreme metallophilic and thermoacidophilic archaeon, which flourishes in hot acid and respires by metal oxidation. In the present study we provide our observations on M. sedula cultivated on tungsten polyoxometalate (W-POM). The decomposition of W-POM macromolecular clusters and the appearance of low molecular weight W species (e.g., WO) in the presence of M. sedula have been detected by electrospray ionization mass spectrometry (ESI-MS) analysis. Here, we document the presence of metalloorganic assemblages at the interface between M. sedula and W-POM resolved down to the nanometer scale using scanning and transmission electron microscopy (SEM and TEM) coupled to electron energy loss spectroscopy (EELS). High-resolution TEM (HR-TEM) and selected-area electron diffraction (SAED) patterns indicated the deposition of redox heterogeneous tungsten species on the S-layer of M. sedula along with the accumulation of intracellular tungsten-bearing nanoparticles, i.e., clusters of tungsten atoms. These results reveal the effectiveness of the analytical spectroscopy coupled to the wet chemistry approach as a tool in the analysis of metal-microbial interactions and microbial cultivation on supramolecular self-assemblages based on inorganic metal clusters. We discuss the possible mechanism of W-POM decomposition by M. sedula in light of unique electrochemical properties of POMs. The findings presented herein highlight unique metallophilicity in hostile environments, extending our knowledge of the relevance of POMs to life-sustaining processes, understanding of the transition of POMs as inorganic prebiotic model to life-sustainable material precursors and revealing biogenic signatures obtained after the decomposition of an artificial inorganic compound, which previously was not associated with any living matter.

The bio-relevant metals of the periodic table of the elements

The bio-relevant metals (and derived compounds) of the Periodic Table of the Elements (PTE) are in the focus. The bulk elements sodium (Na), potassium (K), magnesium (Mg), and calcium (Ca) from the s-block, which are essential for all kingdoms of life, and some of their bio-activities are discussed. The trace elements of the d-block of the PTE as far as they are essential for humans (Mn, Fe, Co, Cu, Zn, Mo) are emphasized, but V, Ni, Cd, and W, which are essential only for some forms of life, are also considered. Chromium is no longer classified as being essential. From the p-block metals only the metalloid (half-metal) selenium (Se) is essential for all forms of life. Two other metalloids, silicon and arsenic, are briefly mentioned, but they have not been proven as being essential for humans. All metals of the PTE and a plethora of their compounds are used in industry and many of them are highly toxic, like lead (Pb), which is discussed as a prime example. Several metals of the PTE, that is, their ions and complexes, are employed in medicine and we discuss the role of lithium, gallium, strontium, technetium, silver, gadolinium (the only f-block element), platinum, and gold.

Vanadium Compounds as Enzyme Inhibitors with a Focus on Anticancer Effects

Vanadium salts and coordination compounds have desirable cellular anticancer effects, and although they have been investigated in detail as a potential treatment for diabetes, less attention has been given to the anticancer effects. The inhibition of some signal transduction enzymes is known, and studies of the metabolism and activation pathways both in vitro and in vivo are important for future investigations and development of vanadium's role as a new potential drug. In addition, a new approach has demonstrated that the enhancement of oncolytic viruses using vanadium salts and coordination complexes for immunotherapy is very promising. Some differences exist between this approach and current antidiabetic and anticancer studies because vanadium(iv) complexes have been found to be most potent in the latter approach, but the few compounds investigated with oncolytic viruses show that vanadium(v) systems are more effective. We conclude that recent studies demonstrate effects on signal transduction enzymes and anticancer pathways, thus suggesting potential applications of vanadium as anticancer agents in the future both as standalone treatments as well as combination therapies.

Metalloproteins in the Biology of Heterocysts

Cyanobacteria are photoautotrophic microorganisms present in almost all ecologically niches on Earth. They exist as single-cell or filamentous forms and the latter often contain specialized cells for N₂ fixation known as heterocysts. Heterocysts arise from photosynthetic active vegetative cells by multiple morphological and physiological rearrangements including the absence of O₂ evolution and CO₂ fixation. The key function of this cell type is carried out by the metalloprotein complex known as nitrogenase. Additionally, many other important processes in heterocysts also depend on metalloproteins. This leads to a high metal demand exceeding the one of other bacteria in content and concentration during heterocyst development and in mature heterocysts. This review provides an overview on the current knowledge of the transition metals and metalloproteins required by heterocysts in heterocyst-forming cyanobacteria. It discusses the molecular, physiological, and physicochemical properties of metalloproteins involved in N₂ fixation, H₂ metabolism, electron transport chains, oxidative stress management, storage, energy metabolism, and metabolic networks in the diazotrophic filament. This provides a detailed and comprehensive picture on the heterocyst demands for Fe, Cu, Mo, Ni, Mn, V, and Zn as cofactors for metalloproteins and highlights the importance of such metalloproteins for the biology of cyanobacterial heterocysts.

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.

Synthesis, characterization, DFT calculations and anticancer activity of a new oxidovanadium(iv) complex with a ligand derived from o-vanillin and thiophene

New vanadium complex was synthesized and fully characterized showing promising anticancer activity on triple negative breast cancer cells.

Metformin-decavanadate treatment ameliorates hyperglycemia and redox balance of the liver and muscle in a rat model of alloxan-induced diabetes

MetfDeca treatment ameliorate glucose and insulin levels, and reduce the levels of oxidized glutathione, reactive oxygen species, malondialdehyde, and 4-hydroxyalkenal; the superoxide and catalase activities, and glutathione levels were regulated.

Tuning the interactions of decavanadate with thaumatin, lysozyme, proteinase K and human serum proteins by its coordination to a pentaaquacobalt(ii) complex cation

Inorganic functionalization of the decavanadate anion promotes a different type of interaction with model proteins thaumatin, lysozyme, proteinase K, human serum albumin and transferrin.

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.

Controlled one pot synthesis of polyoxofluorovanadate molecular hybrids exhibiting peroxidase like activity

V^V/IV mixed-valence polyoxofluorovanadate clusters have been synthesized through one pot preparation process. The trigonal bipyramidal coordinated vanadium atoms mimic the structure of the active site and activity of the vanadium peroxidases.

Effects of green tea polyphenols on trace metals level of rats on food restriction and high-fat diet

Little evidence showed the interplay between tea and diet in the regulation of trace metal. Here, we examined the effects of green tea polyphenols (GTPs) on the level of trace elements (TEs) in rats on food restriction or high-fat diet. Thirty-six rats (Wistar, male) were randomly divided into 6 groups and fed on standard diet, food restriction and high-fat diet with or without GTPs (200 mg/kg bw/day) supplementation, respectively. Levels of vanadium (V), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), selenium (Se), molybdenum (Mo) and cobalt (Co) in feed, whole blood, femur and urine were measured by inductively coupled plasma mass spectrometry (ICP-MS). Blood glucose, total cholesterol (TC), triglycerides (TG), high and low density lipoprotein-cholesterol (LDL-C, HDL-C) in serum were determined. Decreased daily intakes of TEs were observed in rats on food restriction and high-fat diet. Decreased whole blood level of Zn, femur level of Co and increase urinary excretion of Se were observed in rats fed on high-fat diet. GTPs altered the whole blood level of several TEs in rats on food restriction (V, Zn, Co) or high-fat diet (V, Se), respectively, but not in rats fed on standard diet. The level of several TEs in femur and the daily urinary excretion of V and Mo were altered by GTPs in rats on all of the three diets. In addition, rats fed on high-fat diet developed dyslipidemia, which was ameliorated by GTPs. The data indicated that diet status played a role in the effects of GTPs on TEs and lipid metabolism, and trace elements may play a role in the modulation of lipid metabolic disturbances by high-fat diet and GTPs.

Effects of vanadate on the mycelium of edible fungus Coprinus comatus

Vanadate is proposed to play a pivotal role in application of edible fungus Coprinus comatus for medical purposes. In this study the concentration of extracellular vanadate acceptable for the submerged cultivation of C. comatus mycelium was established. The mycelium could grow, and overcome vanadate toxic effects, up to the concentration of 3.3 mM. Moreover, in this condition, at the end of the exponential phase of growth, biomass yield was almost identical to that in the control. ³¹P NMR spectroscopy showed that addition of 10 mM vanadate to the mycelium in the exponential phase of growth provoked instantaneous increase of a sugar phosphates level which could be related to changes in activities of glycolytic enzymes. Exposure to higher vanadate concentration was toxic for the cell. ⁵¹V NMR measurements revealed that monomer of vanadate is present in the cytoplasm causing the metabolic changes. C. comatus has also capacity for vanadate reduction, as shown by EPR measurements, but vanadyl uptake is significantly less comparing to vanadate.

Vanadate inhibits transcription of the rat insulin receptor gene via a proximal sequence of the 5'flanking region

Vanadate, a protein tyrosine phosphatase inhibitor which elicits insulin-like effects, has previously been shown to inhibit expression of the insulin receptor gene at the transcriptional level in rat hepatoma cells. In an attempt to identify the DNA sequence and transcription factors potentially involved in this effect, a fragment of the proximal 5'flanking region of the IR gene (-1143/-252 upstream the ATG codon) has been cloned and functionally characterized. RNase protection allowed the identification of several transcription start sites in the conserved region of the gene, among which two major sites at -455 and -396. Upon fusion to the luciferase gene and transient transfection into hepatoma cells, the -1143/-252 fragment showed promoter activity. This was unaffected by deletion of the -1143/-761 sequence, but markedly decreased (90%) by additional deletion of the -760/-465 sequence. Treatment of hepatoma cells with vanadate led to a dose-dependent decrease in promoter activity of the 1143/-252, -760/-252 and -464/-252 constructs (change relative to untreated cells, 40, 55 and 23% at 125 μM, and 70, 85 and 62% at 250 μM, respectively). These data suggest that although the entire DNA sequence upstream the transcription start sites is probably involved in vanadate-induced inhibition, the short sequence downstream of position -464 and is sufficient for inhibition. Potential targets of vanadate are the transcription factors FoxO1 and HMGA1, two downstream targets of the insulin signaling pathway which have been shown to mediate the inhibitory effect of insulin on IR gene expression.

Decavanadate Salts of Cytosine and Metformin: A Combined Experimental-Theoretical Study of Potential Metallodrugs Against Diabetes and Cancer

Cytosine, a DNA and RNA building-block, and Metformin, the most widely prescribed drug for the treatment of Type 2 Diabetes mellitus were made to react separately with ammonium or sodium metavanadates in acidic aqueous solutions to obtain two polyoxovanadate salts with a 6:1 ratio of cation-anion. Thus, compounds [HCyt]6[V10O28]·4H2O, 1 and [HMetf]6[V10O28]·6H2O, 2 (where HCyt = Cytosinium cation, [C4H6N3O]+ and HMetf = Metforminium cation, [C4H12N5]+) were obtained and characterized by elemental analysis, single crystal X-ray diffraction, vibrational spectroscopy (IR and Raman), solution 51V-NMR, thermogravimetric analysis (TGA-DTGA), as well as, theoretical methods. Both compounds crystallized in P1 ¯   space group with Z' = 1/2, where the anionic charge of the centrosymmetric ion [V10O28]6- is balanced by six Cytosinium and six Metforminium counterions, respectively. Compound 1 is stabilized by π-π stacking interactions coming from the aromatic rings of HCyt cations, as denoted by close contacts of 3.63 Å. On the other hand, guanidinium moieties from the non-planar HMetf in Compound 2 interact with decavanadate μ2-O atoms via N-H···O hydrogen bonds. The vibrational spectroscopic data of both IR and Raman spectra show that the dominant bands in the 1000-450 cm-1 range are due to the symmetric and asymmetric ν(V-O) vibrational modes. In solution, 51V-NMR experiments of both compounds show that polyoxovanadate species are progressively transformed into the monomeric, dimeric and tetrameric oxovanadates. The thermal stability behavior suggests a similar molecular mechanism regarding the loss of water molecules and the decomposition of the organic counterions. Yet, no changes were observed in the TGA range of 540-580°C due to the stability of the [V10O28]6- fragment. Dispersion-corrected density functional theory (DFT-D) calculations were carried out to model the compounds in aqueous phase using a polarized continuum model calculation. Optimized structures were obtained and the main non-covalent interactions were characterized. Biological activities of these compounds are also under investigation. The combination of two therapeutic agents opens up a window toward the generation of potential metalopharmaceuticals with new and exciting pharmacological properties.

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.

Vanadium stimulates pepper plant growth and flowering, increases concentrations of amino acids, sugars and chlorophylls, and modifies nutrient concentrations

Vanadium (V) can be absorbed by plants and regulate their growth and development, although contrasting effects have been reported among species and handling conditions. The objective of this work was to evaluate the beneficial effect of V on pepper plants (Capsicum annuum L.). The plants were grown in a hydroponic system with the application of four V concentrations (0, 5, 10, and 15 μM NH₄VO₃). Four weeks after the beginning of the treatments, growth, flowering, biomass, chlorophyll concentration, total amino acids, total soluble sugars, and nutrients were determined in leaves, stems, and roots. The application of 5 μM V increased plant growth, induced floral bud development, and accelerated flowering. The chlorophyll concentration varied according to the type of plant part analyzed. The concentrations of amino acids and sugars in leaves and roots were higher with 5 μM. With 10 and 15 μM V, the plants were smaller and showed toxicity symptoms. The K concentration in leaves decreased as the V dose increased (0 to 15 μM). However, 5 μM V increased the concentrations of N, P, K, Ca, Mg, Cu, Mn, and B, exclusively in stems. The application of 15 μM V decreased the concentrations of Mg and Mn in leaves, but increased those of P, Ca, Mg, Cu, and B in roots. We conclude that V has positive effects on pepper growth and development, as well as on the concentrations of amino acids and total sugars. V was antagonistic with K, Mg, and Mn in leaves, while in stems and roots, there was synergism with macro and micronutrients. Vanadium is a beneficial element with the potential to be used in biostimulation approaches of crops like pepper.

Hepatotoxicity of vanadyl sulfate in nondiabetic and streptozotocin-induced diabetic rats

This study examined the effects of vanadyl sulfate (VOSO₄) on the livers of nondiabetic and streptozotocin-induced diabetic rats. Rats were divided into 6 groups. Groups 1, 2, and 3 consisted of nondiabetic rats that were, respectively, control animals or those receiving an intraperitoneal (i.p.) injection of either 5 or 10 mg·kg^-1 (i.p.) VOSO₄ for 30 days. Groups 4, 5, and 6 consisted of diabetic animals that were, respectively, control animals or those treated with 5 or 10 mg·kg^-1 (i.p.) VOSO₄ for 30 days. Results showed that VOSO₄ reduced body mass in nondiabetic rats, whereas it increased body mass in diabetic groups. Plasma transaminases (aspartate aminotransferase, alanine aminotransferase), lactate dehydrogenase, and alkaline phosphatase activities and malondialdehyde levels were increased, while liver catalase and superoxide dismutase activities were profoundly decreased in diabetic animals in comparison with enzyme activities in the nondiabetic group. Rats in the diabetic group also showed notable oxidative damage to the liver. Treatment of diabetic rats with VOSO₄ decreased the hepatotoxic markers, significantly restored the activities of antioxidant enzymes, and attenuated histopathological changes in liver tissue. In nondiabetic rats, VOSO₄ treatment increased most of the hepatotoxic markers, reduced antioxidant enzyme activities, and induced pronounced oxidative damage in liver tissue. These data suggest that treatment with VOSO₄ exerts toxic effects in healthy animals and significantly prevents liver oxidative damage in streptozotocin-induced diabetic rats, but without total safety. Further studies are needed to clarify its mechanism of action.

From sea squirts to squirrelfish: facultative trace element hyperaccumulation in animals

The hyperaccumulation of trace elements is a widely characterized phenomenon in plants, bacteria, and fungi, but has received little attention in animals. However, there are numerous examples of animals that specifically and facultatively accumulate trace elements in the absence of elevated environmental concentrations. Metal hyperaccumulating animals are usually marine invertebrates, likely owing to environmental (e.g. constant exposure via the water) and physiological (e.g. osmoconforming and reduced integument permeability) factors. However, there are examples of terrestrial animals (insect larvae) and marine vertebrates (e.g. squirrelfish) that accumulate high body and/or tissue metal burdens. This review examines examples of animal hyperaccumulation of the elements arsenic, copper, iron, titanium, vanadium and zinc, describing mechanisms by which accumulation occurs and, where possible, hypothesizing functional roles. Groups such as the ascidians (sea squirts), molluscs (gastropods, bivalves and cephalopods) and polychaete annelids feature prominently as animals with hyperaccumulating capacity. Many of these species are potential model organisms offering insight into fundamental processes underlying metal handling, with relevance to human disease and aquatic metal toxicity, and some offer promise in applied fields such as bioremediation.

Altered homeostasis of trace elements in the blood of SCA2 patients

Spinocerebellar ataxia type 2 (SCA2) is a neurological disorder characterized by cerebellar dysfunction. The possible association between metals and neurodegenerative diseases is under constant investigation, with particular focus on their involvement in oxidative stress and their potential role as biomarkers of these pathologies. Whole blood samples of SCA2 patients and of healthy individuals were subjected to multi-elemental analysis by inductively coupled plasma-mass spectrometry (ICP-MS). Reduced levels of manganese and copper were found in SCA2 patients, while zinc and vanadium concentrations were significantly higher in patients compared to controls. Copper, manganese and zinc are cofactors of many enzymes (such as superoxide dismutase, SOD) involved in the cellular antioxidant response, whereas vanadium is a transition metal able to produce reactive radicals. A marked decrease of the antioxidant response has been previously reported in SCA2 patients. We suggest that an unbalance of transitional elements in the blood may reflect altered antioxidant homeostasis in SCA2 patients and could constitute a future peripheral biomarker for this disease. In addition, we suggest a possible role of vanadium in the altered lipid metabolism of SCA2 patients.

Comparative assessment of metal-specific adipogenic activity in zinc and vanadium-citrates through associated gene expression

Diabetes mellitus comprises a group of metabolic abnormalities due to insulin deficiency and/or resistance. Obesity contributes to diabetes, with a strong causal relationship existing between diabetes and insulin resistance, especially in patients with Diabetes mellitus II. Adipocytes emerge as key constituents of adipose tissue physiology. In their pre-mature form to mature state transformation, adipocytes fully exemplify one of the key adipogenic actions of insulin. Poised to a) gain insight into adipogenesis leading to antidiabetic factors, and b) investigate adipogenesis through careful examination of insulin contributions to interwoven mechanistic pathways, a systematic comparative study was launched involving well-defined metal-citrates (zinc and vanadium), the chemical reactivity of which was in line with their chemistry under physiological conditions. Selection of the specific compounds was based on their common aqueous coordination chemistry involving the physiological chelator citric acid. Cellular maturation of pre-adipocytes to their mature form was pursued in the presence-absence of insulin and employment of closely linked genetic targets, key to adipocyte maturation (Peroxisome proliferator-activated receptor gamma (PPAR-γ), Glucose transporter 1,3,4 (GLUT 1,3,4), Adiponectin (ADIPOQ), Glucokinase (GCK), and Insulin receptor (INS-R)). The results show a) distinct adipogenic biological profiles for the metalloforms involved in a dose-, time- and nature-dependent manner, and b) metal ion-specific adipogenic response-signals at the same or higher level than insulin toward all selected targets. Collectively, the foundations have been established for future exploitation of the distinct metal-specific adipogenic factors contributing to the functional maturation of adipose tissue and their use toward hyperglycemic control in Diabetes mellitus.

Vanadate-Induced Renal cAMP and Malondialdehyde Accumulation Suppresses Alpha 1 Sodium Potassium Adenosine Triphosphatase Protein Levels

It has been demonstrated that vanadate causes nephrotoxicity. Vanadate inhibits renal sodium potassium adenosine triphosphatase (Na, K-ATPase) activity and this is more pronounced in injured renal tissues. Cardiac cyclic adenosine monophosphate (cAMP) is enhanced by vanadate, while increased cAMP suppresses Na, K-ATPase action in renal tubular cells. There are no in vivo data collectively demonstrating the effect of vanadate on renal cAMP levels; on the abundance of the alpha 1 isoform (α₁) of the Na, K-ATPase protein or its cellular localization; or on renal tissue injury. In this study, rats received a normal saline solution or vanadate (5 mg/kg BW) by intraperitoneal injection for 10 days. Levels of vanadium, cAMP, and malondialdehyde (MDA), a marker of lipid peroxidation were measured in renal tissues. Protein abundance and the localization of renal α₁-Na, K-ATPase was determined by Western blot and immunohistochemistry, respectively. Renal tissue injury was examined by histological evaluation and renal function was assessed by blood biochemical parameters. Rats treated with vanadate had markedly increased vanadium levels in their plasma, urine, and renal tissues. Vanadate significantly induced renal cAMP and MDA accumulation, whereas the protein level of α₁-Na, K-ATPase was suppressed. Vanadate caused renal damage, azotemia, hypokalemia, and hypophosphatemia. Fractional excretions of all studied electrolytes were increased with vanadate administration. These in vivo findings demonstrate that vanadate might suppress renal α₁-Na, K-ATPase protein functionally by enhancing cAMP and structurally by augmenting lipid peroxidation.

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.

Colorimetric detection of hydrogen peroxide by dioxido-vanadium(V) complex containing hydrazone ligand: synthesis and crystal structure

Dioxido-vanadium(V) complex has been synthesized in good yield, the complex was characterized by IR, UV-visible and ¹H NMR spectroscopy. Single crystal X-ray crystallography techniques were used to assign the structure of the complex. Complex crystallized with monoclinic P2₁/c space group with cell parameters a (Å) = 39.516(5), b (Å) = 6.2571(11), c (Å) = 17.424(2), α (°) = 90, β (°) = 102.668(12) and γ (°) = 90. The hydrazone ligand is coordinate to metal ion in tridentate fashion through -ONO- donor atoms forming a distorted square pyramidal geometry around the metal ion.

Primary study on the toxic mechanism of vanadyl trehalose in Kunming mice

It has been shown that vanadyl trehalose could lower blood glucose but show mild toxicity to the stomach and intestine in diabetic Kunming mice. We analysed antioxidant levels, pro-inflammatory cytokine expression, apoptosis factors and intestinal microflora alteration to explore the mechanism of vanadyl trehalose toxicity in Kunming mice. The results revealed that oral administration of vanadyl trehalose at tested dose caused significant changes in oxidative stress factor (MDA levels elevated but SOD and T-AOC decreased), expression of inflammatory factor (IL-1β, COX-2, TNF-α and iNOS increased), and apoptosis factor (Bcl-2/Bax decreased and caspase-3 increased), and intestinal microflora dysbiosis (the number of Enterobacteriaceae and Enterococcus increased and Lactobacillus and Bifidobacterium decreased) relative to the control of Kunming mice. These results suggest that the toxic mechanisms of vanadyl trehalose on the stomach and intestine likely involve activation of the oxidative stress system, increased inflammatory response, promotion of apoptosis and the disruption of the normal intestinal microflora.

A new redox-based and stepwise synthetic strategy lead to an unprecedented mixed-valence Keggin-type tungstovanadophosphate (WVI/VIV) bi-capped by vanadium(VIII)-complexes

A new POM-based V^III-organic coordination compound has been prepared using a redox-based and stepwise synthetic strategy.