Vanadium compounds biological actions and potential as pharmacological agents

A Copper Paradodecatungstate-B Compound Decorated by Glycine Ligand: Synthesis, Structure, and Anticancer Activities

In this study, a polyoxometalate-based inorganic-organic hybrid material, Na4[Cu4(Gly)2(HGly)2(H4W12O42)]Cl2·20H2O (1) (Gly = glycine), was synthesized via a self-assembly approach by incorporating copper ions and glycine into the paradodecatungstate anion [H4W12O42]8-. The structure and properties of compound 1 were systematically characterized using single crystal X-ray diffraction, elemental analysis, powder X-ray diffraction, FTIR, Raman spectroscopy, cyclic voltammetry (CV), and UV-vis spectroscopy. Additionally, its anticancer activity was evaluated in vitro against human liver cancer cells (HepG2) and human renal epithelial cells (HEK293T) using the MTT assay, yielding an IC50 value of 36.232 ± 0.41 μM. The findings demonstrate that compound 1 effectively inhibits the proliferation of liver cancer cells, highlighting its potential as a candidate for polyoxotungstate (POT)-based anticancer drug development.

Encapsulated Oxovanadium(IV) and Dioxovanadium(V) Complexes into Solid Lipid Nanoparticles Increase Cytotoxicity Against MDA-MB-231 Cell Line

Introduction

Solid lipid nanoparticles (SLN) have been considered lately as promising drug delivery system in treatment of many human diseases including cancers. We previously studied potential drug compounds that were effective inhibitors of PTP1B phosphatase - possible target for breast cancer treatment. Based on our studies, two complexes were selected for encapsulation into the SLNs, the compound 1 ([VO(dipic)(dmbipy)] · 2 H₂O) and compound 2 ([VOO(dipic)](2-phepyH) · H₂O). Here, we investigate the effect of encapsulation of those compounds on cell cytotoxicity against MDA-MB-231 breast cancer cell line. The study also included the stability evaluation of the obtained nanocarriers with incorporated active substances and characterization of their lipid matrix. Moreover, the cell cytotoxicity studies against the MDA-MB-231 breast cancer cell line in comparison and in combination with vincristine have been performed. Wound healing assay was carried out to observe cell migration rate.

Methods

The properties of the SLNs such as particle size, zeta potential (ZP), and polydispersity index (PDI) were investigated. The morphology of SLNs was observed by scanning electron microscopy (SEM), while the crystallinity of the lipid particles was analyzed by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The cell cytotoxicity of complexes and their encapsulated forms was carried out against MDA-MB-231 breast cancer cell line using standard MTT protocols. The wound healing assay was performed using live imaging microscopy.

Results

SLNs with a mean size of 160 ± 25 nm, a ZP of -34.00 ± 0.5, and a polydispersity index of 30 ± 5% were obtained. Encapsulated forms of compounds showed significantly higher cytotoxicity also in co-incubation with vincristine. Moreover, our research shows that the best compound was complex 2 encapsulated into lipid nanoparticles.

Conclusion

We observed that encapsulation of studied complexes into SLNs increases their cell cytotoxicity against MDA-MB-231 cell line and enhanced the effect of vincristine.

A Novel and Cost-Effective CsVO3 Quantum Dots for Optoelectronic and Display Applications

Quantum dots (QDs) have an unparalleled ability to mimic true colors due to their size-tunable optical and electronic properties, which make them the most promising nanoparticles in various fields. Currently, the majority of QDs available in the market are cadmium, indium, and lead-based materials but the toxicity and unstable nature of these QDs restricts their industrial and practical applications. To avoid using heavy metal ions, especially cadmium, the current research is focused on the fabrication of perovskite and vanadate QDs. Herein, we report the facile synthesis of a novel and cost-effective CsVO₃ QDs for the first time. The sizes of the CsVO₃ QDs produced were tuned from 2 to 10 nm by varying the reaction temperature from 140 to 190 °C. On increasing QD size, a continuous red shift was observed in absorption and emission spectra, signifying the presence of quantum confinement. In addition, along with CsVO₃ QDs, the CsVO₃ nanosheets self-assembled microflower-like particles were found as residue after the centrifugation; the X-ray diffraction indicated an orthorhombic structure. Under 365 nm excitation, these CsVO₃ microflower-like particles exhibited broad emission with CIE coordinates in the white emission region. The acquired results suggest that CsVO₃ QDs may represent a new class of cadmium-free materials for optoelectronic and biomedical applications.

Reproductive Hormones Imbalance, Germ Cell Apoptosis, Abnormal Sperm Morphophenotypes and Ultrastructural Changes in Testis of African Giant Rats (Cricetomys gambianus) Exposed to Sodium Metavanadate Intoxication

Environmental exposure to vanadium has been on the increase in recent time. This metal is a known toxicant. The current study was conducted to investigate the reproductive toxicity of sodium metavanadate (SMV) in male African giant rats. Administration of SMV was done intraperitoneally daily for 14 consecutive days at a dosage of 3 mg/kg body weight. Sterile water was administered to the control group. Serum reproductive hormones, sperm reserve and quality as well as testicular ultrastructural changes following SMV treatment were analysed. Results showed SMV-exposed AGR group had statistically decreased concentrations of testosterone (4.7 ng/ml), FSH (3.4 IU/L) and LH (3.8 IU/L). Also, SMV-treated group had statistically decreased sperm motility and mass activity with increased percentage of abnormal morphophenotypes of spermatozoa and upregulation of P53 immunopositive cells. Ultrastructural study revealed vacuolation of germ and Sertoli cells cytoplasm and nucleus, and mitochondrial swelling and vacuolations were also observed. There was severe disintegration of the seminiferous tubules, atrophy and degeneration of myeloid cells and apoptosis of the Leydig, Sertoli and germ cells. In conclusion, intraperitoneal SMV exposure exerts severe adverse effects on some serum reproductive hormones, reduction in the sperm reserve and quality, apoptosis and degenerative changes of the Leydig, Sertoli and germ cells which can lead to infertility.

Vanadium(IV)-diamine complex with hypoglycemic activity and a reduction in testicular atrophy

The insulin enhancing activity, histological analysis and, testicular degeneration by a V^IVO-complex containing the 2,2'-(ethane-1,2-diylbis(azanediyl))diethanolate ligand, VO^IV(C₆H₁₄N₂O₂-κ²N,κ²O), abbreviated V^IVO(BHED), were investigated in diabetic male Wistar rats. The complex was administered by oral gavage of freshly prepared solutions of vanadium complex. Biological studies demonstrated that the vanadium complex normalized the elevated glucose levels in male Wistar rats with streptozotocin-induced diabetes and these compounds also avoided common responses in diabetic animals such as weight loss and reduction in the size of the epididymis, prostate, testis and seminal gland. The ⁵¹V NMR and EPR studies showed the formation of V^IVO(BHED) and the oxidation product [V^VO₂BHED]^- with two possible decomposition pathways. In summary, these studies demonstrate that the V^IVO(BHED) complex or its decomposition products show similar effects as insulin in decreasing elevated blood glucose levels.

Serum trace metal association with response to erythropoiesis stimulating agents in incident and prevalent hemodialysis patients

Alterations in hemodialysis patients' serum trace metals have been documented. Early studies addressing associations levels of serum trace metals with erythropoietic responses and/or hematocrit generated mixed results. These studies were conducted prior to current approaches for erythropoiesis stimulating agent (ESA) drug dosing guidelines or without consideration of inflammation markers (e.g. hepcidin) important for regulation of iron availability. This study sought to determine if the serum trace metal concentrations of incident or chronic hemodialysis patients associated with the observed ESA response variability and with consideration to ESA dose response, hepcidin, and high sensitivity C-reactive protein levels. Inductively-coupled plasma-mass spectrometry was used to measure 14 serum trace metals in 29 incident and 79 prevalent dialysis patients recruited prospectively. We compared these data to three measures of ESA dose response, sex, and dialysis incidence versus dialysis prevalence. Hemoglobin was negatively associated with ESA dose and cadmium while positively associated with antimony, arsenic and lead. ESA dose was negatively associated with achieved hemoglobin and vanadium while positively associated with arsenic. ESA response was positively associated with arsenic. Vanadium, nickel, cadmium, and tin were increased in prevalent patients. Manganese was increased in incident patients. Vanadium, nickel, and arsenic increased with time on dialysis while manganese decreased. Changes in vanadium and manganese were largest and appeared to have some effect on anemia. Incident and prevalent patients' chromium and antimony levels exceeded established accepted upper limits of normal.

Synthesis, structure and characterization of new dithiocarbazate-based mixed ligand oxidovanadium(iv) complexes: DNA/HSA interaction, cytotoxic activity and DFT studies

The synthesis, structure and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVOL^1–2(L^N–N)] (1–3) are reported. With a view to evaluating their biological activity, their DNA/HSA interaction and cytotoxicity activity have been explored.

The effect of vanadium(IV) complexes on development of Arabidopsis thaliana subjected to H2O2-induced stress

The impact of oxydiacetate oxidovanadium(IV) complexes on plants is currently unknown. This report demonstrates the influence of these complexes on Arabidopsis thaliana (L.) Heynh. In the presence of 10-6M vanadium(IV) complexes, plants proceeded through their entire life cycle, with the occurrence of proper morphological and cytological organisation of leaf and root tissues. The addition of 10-1M H2O2 caused root damage, leaf necrosis, and plant death at around the seventh day, due to the destruction of the root system. Pretreatment of the plants with 10-6M of vanadium(IV) compounds: VOSO4 and VO(oda), alleviated the effects of H2O2 to some extent. Plants pretreated with 10-6M vanadium(IV) complexes survived longer despite the presence of H2O2. Considering the higher rate of plant survival in the presence of VOSO4, and the relatively high photosynthetic parameters and anthocyanin contents in the cells, we conclude that this vanadium(IV) compound can have positive effects on plants that are grown under stress conditions.

Vanadium compounds and cellular death mechanisms in the A549 cell line: The relevance of the compound valence

Non-small lung cell carcinoma has a high morbidity and mortality rates. The elective treatment for stage III and IV is cisplatinum that conveys serious toxic side effects. Vanadium compounds are metal molecules with proven antitumor activity that depends on its valence. Therefore, a better understanding of the mechanism of action of vanadium compounds is required. The aim of our study was to investigate the mechanisms of cell death induced by sodium metavanadate (NaVO₃ [V(+5)]) and vanadyl sulfate (VOSO₄ [(+4)]), both of which have reported apoptotic-inducing activity. We exposed the A549 cell line to various concentrations (0-100 μM) and to different exposure times to each compound and determined the cell viability and expression of caspases, reactive oxygen species (ROS) production, Bcl2, Bax, FasL and NO. Our results showed that neither compounds modified the basal expression of caspases or pro- and anti-apoptotic proteins. The only change observed was the 12- and 14-fold significant increase in ROS production induced by NaVO₃ and VOSO₄ , respectively, at 100 μm concentrations after 48 hours. Our results suggest that classical apoptotic mechanisms are not related to the cell death induced by the vanadium compounds evaluated here, and showed that the higher ROS production was induced by the [(+4)] valence compound. It is possible that the difference will be secondary to its higher oxidative status and thus higher ROS production, which leads to higher cell damage. In conclusion, our results suggest that the efficacy of the cell death mechanisms induced by vanadium compounds differ depending on the valence of the compound.

Effects of sodium tungstate and vanadyl sulphate on the liberation of prostanoids of the mesenteric vascular bed in diabetic rats

The loss of the modulator role of the endothelium could be involved in the pathogenesis of diabetic vascular complications. Transition metal compounds, such as tungsten and vanadium, have been proposed as possible agents in the treatment of diabetes by simulating the effects of insulin. The mesenteric vascular bed intervenes in vascular resistance and is a source of vasoactive compounds, such as prostanoids. The aim of this work was to study the effects of sodium tungstate and vanadyl sulphate treatments on the metabolic parameters and the release of prostanoids of the mesenteric vascular bed in an experimental model of Streptozotocin-induced diabetes. In diabetic rats, a significant increase was observed in plasma levels of glucose, triglycerides and total cholesterol. On the other hand, there was a significant reduction in the release of vasodilator prostanoids, such as prostacyclin and prostaglandin E2 and vasoconstrictor thromboxane A2 through the mesenteric vascular bed. Both sodium tungstate and vanadyl sulphate normalised glycaemia, triglyceridaemia and cholesterolaemia in rats diabetics. On the other hand, only treatment with sodium tungstate reversed the reduction in the release of vasodilator prostanoids, improving in diabetic animals the prostacyclin/thromboxane ratio, an indicator of vascular dysfunction. In conclusion, unlike vanadyl sulphate, sodium tungstate is shown to be more effective in controlling metabolic changes and the production of vasodilator prostanoids observed in experimental diabetes induced by streptozotocin.

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.

The interactions of vanadate monomer with the mycelium of fungus Phycomyces blakesleeanus: reduction or uptake?

The possibility of reduction of vanadate monomer in the mycelium of fungus Phycomyces blakesleeanus was investigated in this study by means of polarography. Control experiments were performed with vanadyl [V(IV)] and vanadate [V(V)] in 10 mM Hepes, pH 7.2. Addition of P. blakesleeanus mycelium resulted in disappearance of all V(IV) polarographic waves recorded in the control. This points to the uptake of all available V(IV) by the mycelium, up to 185 µmol/g_FW, and suggests P. blakesleeanus as a potential agent in V(IV) bioremediation. Polarographic measurements of mycelium with low concentrations (0.1-1 mM) of V(V), that only allows the presence of monomer, showed that fungal mycelia removes around 27% of V(V) from the extracellular solution. Uptake was saturated at 104 ± 2 µmol/g_FW which indicates excellent bioaccumulation capability of P. blakesleeanus. EPR, ⁵¹V NMR and polarographic experiments showed no indications of any measurable extracellular complexation of V(V) monomer with fungal exudates, reduction by the mycelium or adsorption to the cell wall. Therefore, in contrast to vanadium oligomers, vanadate monomer interactions with the mycelium are restricted to its transport into the fungal cell, probably by a phosphate transporter.

Vanadium compounds for the treatment of human diabetes mellitus: A scientific curiosity? A review of thirty years of research

In the second part of the 1980s, and in the 1990s, a number of investigators demonstrated -mainly in streptozotocin-induced (STZ) diabetic rats-that the vanadate and vanadyl forms of vanadium possessed a number of insulin-like effects in various cells. It was hypothesized that oral vanadium could be an alternative treatment to parenteral insulin in the therapy of diabetes mellitus. However, the long-term and/or chronic administration of vanadium compounds should also mean tissue vanadium accumulation and risks of toxicity. The purpose of this review was to revise the current-state-of-the-art on the use of vanadium in the treatment of human diabetes. It has been conducted more than three decades after the first report on the beneficial insulin-mimetic effects of oral vanadium administration in STZ-diabetic rats. Although the antidiabetic effects of vanadium in STZ-diabetic rodents are well supported, in the few studies on human patients with positive results, that are available in the literature, vanadium compounds were administered during very short periods. We conclude that vanadium administration for the treatment of human diabetes is misplaced.

Why Antidiabetic Vanadium Complexes are Not in the Pipeline of "Big Pharma" Drug Research? A Critical Review

Public academic research sites, private institutions as well as small companies have made substantial contributions to the ongoing development of antidiabetic vanadium compounds. But why is this endeavor not echoed by the globally operating pharmaceutical companies, also known as "Big Pharma"? Intriguingly, today's clinical practice is in great need to improve or replace insulin treatment against Diabetes Mellitus (DM). Insulin is the mainstay therapeutically and economically. So, why do those companies develop potential antidiabetic drug candidates without vanadium (vanadium- free)? We gathered information about physicochemical and pharmacological properties of known vanadium-containing antidiabetic compounds from the specialized literature, and converted the data into explanations (arguments, the "pros and cons") about the underpinnings of antidiabetic vanadium. Some discoveries were embedded in chronological order while seminal reviews of the last decade about the Medicinal chemistry of vanadium and its history were also listed for further understanding. In particular, the concepts of so-called "noncomplexed or free" vanadium species (i.e. inorganic oxido-coordinated species) and "biogenic speciation" of antidiabetic vanadium complexes were found critical and subsequently documented in more details to answer the question.

Conservative tryptophan mutants of the protein tyrosine phosphatase YopH exhibit impaired WPD-loop function and crystallize with divanadate esters in their active sites

Catalysis in protein tyrosine phosphatases (PTPs) involves movement of a protein loop called the WPD loop that brings a conserved aspartic acid into the active site to function as a general acid. Mutation of the tryptophan in the WPD loop of the PTP YopH to any other residue with a planar, aromatic side chain (phenylalanine, tyrosine, or histidine) disables general acid catalysis. Crystal structures reveal these conservative mutations leave this critical loop in a catalytically unproductive, quasi-open position. Although the loop positions in crystal structures are similar for all three conservative mutants, the reasons inhibiting normal loop closure differ for each mutant. In the W354F and W354Y mutants, steric clashes result from six-membered rings occupying the position of the five-membered ring of the native indole side chain. The histidine mutant dysfunction results from new hydrogen bonds stabilizing the unproductive position. The results demonstrate how even modest modifications can disrupt catalytically important protein dynamics. Crystallization of all the catalytically compromised mutants in the presence of vanadate gave rise to vanadate dimers at the active site. In W354Y and W354H, a divanadate ester with glycerol is observed. Such species have precedence in solution and are known from the small molecule crystal database. Such species have not been observed in the active site of a phosphatase, as a functional phosphatase would rapidly catalyze their decomposition. The compromised functionality of the mutants allows the trapping of species that undoubtedly form in solution and are capable of binding at the active sites of PTPs, and, presumably, other phosphatases. In addition to monomeric vanadate, such higher-order vanadium-based molecules are likely involved in the interaction of vanadate with PTPs in solution.

Synthesis, Characterization, Antioxidant Status, and Toxicity Study of Vanadium-Rutin Complex in Balb/c Mice

A new trend was developed for the formation of a complex between vanadium and flavonoid derivatives in order to increase the intestinal absorption and to reduce the toxicity of vanadium compounds. The vanadium-rutin complex was characterized by several spectroscopic techniques like ultraviolet (UV)-visible, Fourier transform infrared (FTIR), NMR, mass spectrometry, and microscopic evaluation by scanning electron microscopy. The mononuclear complex was formed by the interaction between vanadium and rutin with 1:2 metal to ligand stoichiometry. Antioxidant activity of the complex was evaluated by 1,1-diphenyl-2 picrylhydrazyl, ferric-reducing power, and 2,2'-azin-obis 3-ethylbenzothiazoline-6-sulphonic acid methods. It was shown that radical scavenging activity and ferric-reducing potential of free rutin was lower as compared with vanadium-rutin complex. The study was also investigated for oral acute toxicity and 28 days repeated oral subacute toxicity study of vanadium-rutin complex in balb/c mice. The vanadium-rutin complex showed mortality at a dose of 120 mg/kg in the balb/c mice. In 28 days repeated oral toxicity study, vanadium-rutin complex was administered to both sex of balb/c mice at dose levels of 90, 45, and 20 ppm, respectively. In addition, subacute toxicity study of vanadium-rutin complex (at 90 ppm dose level) showed increase levels of white blood cell (WBC), total bilirubin, alanine aminotransferase (ALT), alkaline phosphatase (ALP), aspartate aminotransferase (AST), creatinine, and blood urea nitrogen and decrease level of total protein (TP) as compared with control group. Histopathological study of vanadium-rutin showed structural alteration in the liver, kidney, and stomach at 90 ppm dose level. No observed toxic level of vanadium-rutin complex at 20 ppm dose level could be good for further study.

Synthesis, characterisation and antioxidant activity of luteolin-vanadium(II) complex

The complex formation between luteolin (L) and vanadium(IV) oxide sulphate monohydrate (VOSO4·H2O) was examined under UV-visible, infra-red spectroscopy, mass spectroscopy and NMR techniques. The spectroscopic data indicated that luteolin reacts with vanadium oxide cation (VO(+2)) through 4-carbonyl-5-hydroxy chelation site in the two luteolin molecule. The free radical antioxidant activity of the complex with respect to the parent molecule was evaluated using 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and 2,2'-azinobis 3-ethylbenzothiazoline-6-sulphonic acid diammonium salt (ABTS) methods. It was observed that the free radical scavenging activity and ferric ion reducing potential of luteolin was increased after the formation of complex with vanadium oxide (VO(+2)) cation.

Inverse association of plasma vanadium levels with newly diagnosed type 2 diabetes in a Chinese population

Vanadium compounds have been proposed to have beneficial effects on the pathogenesis and complications of type 2 diabetes. Our objective was to evaluate the association between plasma vanadium levels and type 2 diabetes. We performed a case-control study involving 1,598 Chinese subjects with or without newly diagnosed type 2 diabetes (December 2004-December 2007). Cases and controls were frequency-matched by age and sex. Plasma vanadium concentrations were measured and compared between groups. Analyses showed that plasma vanadium concentrations were significantly lower in cases with newly diagnosed type 2 diabetes than in controls (P = 0.001). Mean plasma vanadium levels in participants with and without diabetes were 1.0 μg/L and 1.2 μg/L, respectively. Participants in the highest quartile of plasma vanadium concentration had a notably lower risk of newly diagnosed type 2 diabetes (odds ratio = 0.26, 95% confidence interval: 0.19, 0.35; P < 0.001), compared with persons in the lowest quartile. The trend remained significant after adjustment for known risk factors and in further stratification analyses. Our results suggested that plasma vanadium concentrations were inversely associated with newly diagnosed type 2 diabetes in this Chinese population.

Vanadate influence on metabolism of sugar phosphates in fungus Phycomyces blakesleeanus

The biological and chemical basis of vanadium action in fungi is relatively poorly understood. In the present study, we investigate the influence of vanadate (V5+) on phosphate metabolism of Phycomyces blakesleeanus. Addition of V5+ caused increase of sugar phosphates signal intensities in 31P NMR spectra in vivo. HPLC analysis of mycelial phosphate extracts demonstrated increased concentrations of glucose 6 phosphate, fructose 6 phosphate, fructose 1, 6 phosphate and glucose 1 phosphate after V5+ treatment. Influence of V5+ on the levels of fructose 2, 6 phosphate, glucosamine 6 phosphate and glucose 1, 6 phosphate (HPLC), and polyphosphates, UDPG and ATP (31P NMR) was also established. Increase of sugar phosphates content was not observed after addition of vanadyl (V4+), indicating that only vanadate influences its metabolism. Obtained results from in vivo experiments indicate catalytic/inhibitory vanadate action on enzymes involved in reactions of glycolysis and glycogenesis i.e., phosphoglucomutase, phosphofructokinase and glycogen phosphorylase in filamentous fungi.

Vanadyl sulfate treatment stimulates proliferation and regeneration of beta cells in pancreatic islets

We examined the effects of vanadium sulfate (VOSO4) treatment at 5 and 10 mg/kg for 30 days on endocrine pancreas activity and histology in nondiabetic and STZ-induced diabetic rats. In diabetic group, blood glucose levels significantly increased while insulinemia level markedly decreased. At the end of treatment, VOSO4 at a dose of 10 mg/Kg normalized blood glucose level in diabetic group, restored insulinemia, and significantly improved insulin sensitivity. VOSO4 also increased in a dose-dependent manner the number of insulin immunopositive beta cells in pancreatic islets of nondiabetic rats. Furthermore, in the STZ-diabetic group, the decrease in the number of insulin immunopositive beta cells was corrected to reach the control level mainly with the higher dose of vanadium. Therefore, VOSO4 treatment normalized plasma glucose and insulin levels and improved insulin sensitivity in STZ-experimental diabetes and induced beta cells proliferation and/or regeneration in normal or diabetic rats.

Role of vanadium (V) in the differentiation of C3H10t1/2 cells towards osteoblast lineage: a comparative analysis with other trace elements

In recent time, vanadium compounds are being used as antidiabetic drug and in orthopedic implants. However, the exact role of this incorporated vanadium in improving the quality of bone structure and morphology is not known. The impact of vanadium ion was studied and compared to other trace metal ions with respect to the proliferation and osteoblast differentiation of C3H10t1/2 cells. Toxicity profile of these trace metal ions revealed a descending toxicity trend of Fe(2+) > Zn(2+) > Cu(2+) > Co(2+) > Mn(2+) > V(5+) > Cr(2+). The effect of vanadium and other trace metal ions on osteoblast differentiation was evaluated by culturing the cells for 10 days in osteoblastic medium supplemented with different trace ions at concentrations lower than their cytotoxic doses. The results indicated that vanadium has maximum impact on the induction of osteoblast differentiation by upregulating alkaline phosphatase activity and mineralization by up to 145 and 150 %, respectively (p < 0.05), over control. Cu(2+) and Zn(2+) had a mild inhibitory effect, while Mn(2+), Fe(2+), and Co(2+) demonstrated a clear decrease in osteoblast differentiation when compared to the control. The data as presented here demonstrate that orthopedic implants, if supplemented with trace metals like vanadium, may provide a source of better model for bone formation and its turnover.

Novel ternary vanadium-betaine-peroxido species suppresses H-ras and matrix metalloproteinase-2 expression by increasing reactive oxygen species-mediated apoptosis in cancer cells

Vanadium is known for its antitumorigenicity. Poised to investigate the impact of well-defined forms of vanadium on processes and specific biomolecules (oncogenes-proteins) involved in cancer cell physiology, a novel ternary V(V)-peroxido-betaine compound was employed in experiments targeting cell viability, apoptosis, reactive oxygen species (ROS) production, H-ras signaling, and matrix metalloproteinase-2 (MMP-2) expression in human breast cancer epithelial and lung adenocarcinoma cells. The results reveal that vanadium imparts a significant decrease in cancer cell viability, reducing H-ras and MMP-2 expression by increasing ROS-mediated apoptosis, distinctly emphasizing the nature, structure and properties of ternary ligands on vanadium anti-tumor activity and its future potential as a metallodrug.

Spontaneous and pronase-induced HER2 truncation increases the trastuzumab binding capacity of breast cancer tissues and cell lines

A subgroup of HER2-overexpressing breast tumours co-expresses p95(HER2), a truncated HER2 receptor that retains a functional HER2 kinase domain but lacks the extracellular domain, thus impairing trastuzumab binding. We evaluated p95(HER2) expression in 99 frozen breast carcinoma samples by western blot analysis. The HER2-positive cell line BT474 treated with pervanadate or pronase was used as a positive control for p95(HER2) expression. Immunohistochemistry was performed on parallel formalin-fixed, paraffin-embedded sections of the same case series using antibodies directed against either the intra- or extra-cellular binding domain of HER2. In particular, biotinylated trastuzumab (BiotHER) was used to evaluate the binding capacity of the humanized antibody. To avoid a subjective evaluation of the score values and the percentage of immunostained cells, the slides were scanned and automatically analysed. The number of cases with HER2 overexpression (score 3+) and HER2 gene amplification was higher in the p185(HER2)-positive/p95(HER2)-positive samples than in the p185(HER2)-positive/p95(HER2)-negative group. Automated analysis confirmed a significantly higher percentage of 3+ scored cells in p95(HER2)-positive cases. Conversely, the percentage of 2+ scored cells was higher inp95(HER2)-negative cases. The status of the HER2 extracellular domain was then studied using flow cytometry on BT474 cells after pronase enzymatic digestion using trastuzumab and pertuzumab, while the presence of HER2-HER3 dimers was studied using a proximity-ligation assay. In vitro experiments showed that short-term pronase digestion of BT474 cells produced two HER2 fragments (of 95 and 150 kDa, detectable in tissue specimens as well), increased the binding affinity of trastuzumab, reduced the rate of HER2-HER3 dimers, and did not interfere with pertuzumab-binding capacity. In conclusion, the presence of p95(HER2 as detected by western blot analysis does not compromise the immunohistochemical detection of HER2. Our data suggest that a reduction of the receptor steric hindrance as induced by enzymatic shedding may facilitate the binding capacity of trastuzumab.

The interactions of vanadium with Phycomyces blakesleeanus mycelium: enzymatic reduction, transport and metabolic effects

The biological and chemical basis of vanadium action and transport in fungi is relatively poorly understood. In this study we investigated the interactions of vanadium in physiologically-relevant redox states: vanadate (+5) and vanadyl (+4), with mycelium of fungus Phycomyces blakesleeanus using EPR and (31)P NMR spectroscopy and biochemical assays. We determined that P. blakesleeanus reduces V(5+) to V(4+) in the extracellular compartment by the means of cell surface enzyme with ferricyanide reductase activity, which contains molybdenum-molybdopterin as a cofactor. Both, V(5+) and V(4+) bind to cell wall. They enter the cytoplasm via phosphate transporter and cation channels, respectively, and exhibit different metabolic effects. Vanadate provokes increased biomass production, the effects being inverted to toxic at higher V(5+) concentrations. In addition, V(5+) activates the synthesis of sugar phosphates and oligophosphates. On the other hand, V(4+) exhibits toxic effects even at low concentrations. The V(4+) detoxification route involves binding to vacuolar polyphosphates. Altogether our results imply that the mechanism of interaction of vanadium with P. blakesleeanus involves three major steps: extracellular enzymatic V(5+)/V(4+) reduction, V(4+) influx, and vacuolar storage, with an additional step - V(5+) import occurring at higher vanadate concentrations.

Template synthesis, spectroscopic characterization and preliminary insulin-mimetic activity of oxovanadium(IV) complexes with N₂O₂ diazadioxa macrocycles

A new series of diazadioxa oxovanadium(IV) macrocyclic complexes of type [VO(mac)]SO(4) have been synthesized via the condensation reaction of a 3-(phenyl/substituted phenyl)-4-amino-5-hydrazino-1,2,4-triazole (H(2)L) with salicylaldehyde/2-hydroxyacetophenone and 1,4-dibromobutane in the presence of oxovanadium(IV) sulfate in ethanol. All the newly synthesized compounds were characterized on the basis of elemental analyses, conductance measurements, magnetic properties, spectral (UV-Vis, IR, EPR) and XRD studies. The particle size of the complexes has been calculated from XRD spectra using Debye-Scherrer formula and these are found to be in 31-32 nm range. The efficacy of two macrocyclic complexes was also studied in streptozotocin-induced diabetic rats over a period of 30 days. The administration of these complexes in diabetic rats reversed the diabetic effect due to their insulin-mimetic effects.

Metavanadate at the active site of the phosphatase VHZ

Vanadate is a potent modulator of a number of biological processes and has been shown by crystal structures and NMR spectroscopy to interact with numerous enzymes. Although these effects often occur under conditions where oligomeric forms dominate, the crystal structures and NMR data suggest that the inhibitory form is usually monomeric orthovanadate, a particularly good inhibitor of phosphatases because of its ability to form stable trigonal-bipyramidal complexes. We performed a computational analysis of a 1.14 Å structure of the phosphatase VHZ in complex with an unusual metavanadate species and compared it with two classical trigonal-bipyramidal vanadate-phosphatase complexes. The results support extensive delocalized bonding to the apical ligands in the classical structures. In contrast, in the VHZ metavanadate complex, the central, planar VO(3)(-) moiety has only one apical ligand, the nucleophilic Cys95, and a gap in electron density between V and S. A computational analysis showed that the V-S interaction is primarily ionic. A mechanism is proposed to explain the formation of metavanadate in the active site from a dimeric vanadate species that previous crystallographic evidence has shown to be able to bind to the active sites of phosphatases related to VHZ. Together, the results show that the interaction of vanadate with biological systems is not solely reliant upon the prior formation of a particular inhibitory form in solution. The catalytic properties of an enzyme may act upon the oligomeric forms primarily present in solution to generate species such as the metavanadate ion observed in the VHZ structure.

The effects of vanadium (V) absorbed by Coprinus comatus on bone in streptozotocin-induced diabetic rats

The purpose of this study was to evaluate the effects of vanadium absorbed by Coprinus comatus (VACC) treatment on bone in streptozotocin (STZ)-induced diabetic rats. Forty-five Wistar female rats used were divided into three groups: (1) normal rats (control), (2) diabetic rats, and (3) diabetic rats treated with VACC. Normal and diabetic rats were given physiological saline, and VACC-treated rats were administered VACC intragastrically at doses of 0.18 mg vanadium/kg body weight once daily. Treatments were performed over a 12-week period. At sacrifice, one tibia and one femur were removed, subjected to micro computed tomography (micro-CT) for determination of trabecular bone structure, and then processed for histomorphometry to assess bone turnover. Another femoral was used for mechanical testing. In addition, bone samples were collected to evaluate the content of mineral substances in bones. Treatment with VACC increased trabecular bone volume fraction in diabetic rats. Vanadium-treated animals had significant increases in ultimate load, trabecular thickness, and osteoblast surface. However, vanadium treatment did not seem to affect bone stiffness, bone energy absorption, trabecular separation, and osteoclast number. P levels in the femurs of diabetic rats treated with VACC were significantly higher than those of diabetic animals. Ca levels in diabetic and diabetic rats treated with vanadium showed no obvious changes. In conclusion, our results provide an important proof of concept that VACC may represent a powerful approach to treating or reversing diabetic osteopathy in humans.

Use of antimony in the treatment of leishmaniasis: current status and future directions

In the recent past the standard treatment of kala-azar involved the use of pentavalent antimonials Sb(V). Because of progressive rise in treatment failure to Sb(V) was limited its use in the treatment program in the Indian subcontinent. Until now the mechanism of action of Sb(V) is not very clear. Recent studies indicated that both parasite and hosts contribute to the antimony efflux mechanism. Interestingly, antimonials show strong immunostimulatory abilities as evident from the upregulation of transplantation antigens and enhanced T cell stimulating ability of normal antigen presenting cells when treated with Sb(V) in vitro. Recently, it has been shown that some of the peroxovanadium compounds have Sb(V)-resistance modifying ability in experimental infection with Sb(V) resistant Leishmania donovani isolates in murine model. Thus, vanadium compounds may be used in combination with Sb(V) in the treatment of Sb(V) resistance cases of kala-azar.

Influence of vanadium supplementation on oxidative stress factors in the muscle of STZ-diabetic rats

In recent years, the role of free radical damage consequent to oxidative stress is widely discussed in diabetic complications. In this aspect, the protection of cell integrity by trace elements is a topic to be investigated. Vanadium is a trace element believed to be important for normal cell function and development. The aim of the present study was to investigate the effect of vanadyl sulfate supplementation on the antioxidant system in the muscle tissue of diabetic rats. Diabetes was induced by intraperitoneal injection of streptozotocin (STZ, 65 mg/kg body weight) to male Swiss albino rats. The rats were randomly divided into 4 groups: Group I, control; Group II, vanadyl sulfate control; Group III, STZ-diabetic untreated; Group IV, STZ-diabetic treated with vanadyl sulfate. Vanadyl sulfate (100 mg/kg) was given daily by gavage for 60 days. At the last day of the experiment, rats were killed, muscle tissues were taken, homogenized in cold saline to make a 10% (w/v) homogenate. Body weights and blood glucose levels were estimated at 0, 30 and 60th days. Antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), glutathione-S-transferase (GST), as well as carbonic anhydrase (CA), myeloperoxidase (MPO) activities and protein carbonyl content (PCC) were determined in muscle tissue. Vanadyl sulfate administration improved the loss in body weight due to STZ-induced diabetes and decreased the rise in blood glucose levels. It was shown that vanadium supplementation to diabetic rats significantly decrease serum antioxidant enzyme levels, which were significantly raised by diabetes in muscle tissue showing that this trace element could be used as preventive for diabetic complications.

Chemosensitization of human leukemia K562 cells to taxol by a Vanadium-salen complex

Vanadium complexes are a heterogeneous class of compounds exhibiting interesting biological properties. Herein, we report the effect of a vanadium-salen complex (VO-salen) on proliferative behavior of K562 cell line. The results revealed that VO-salen at 6-32 μM inhibited K562 proliferation with no distinct alteration in cell morphology, extent of apoptosis and/or differentiation. Our results indicated that VO-salen complex has just a cytostatic effect and capable of arresting the affected cells in G2/M phase of cell cycle. In addition, we evaluated the combined effects of VO-salen complex and taxol. The cell cycle analyses showed that VO-salen complex enhanced taxol-induced G2/M arrest and also increased taxol-induced apoptosis through a decrease in the ratio of Bcl-2/Bax which might account for the decrease in the apoptosis threshold among the affected cells. These findings support that combination of VO-salen, as a chemosensitizer, and taxol might constitute an affective new strategy for leukemia therapy.

Identification of a new anti-diabetic agent by combining VOSO4 and vitamin E in a single molecule: studies on its spectral, thermal and pharmacological properties

Vanadium(IV) complex of vitamin E (Vit E) ligand was reported. In this complex, binuclear ligand acts as a monodentate via oxygen of phenolic group. The vanadyl(II) ion is surrounded by two molecules of Vit E and two water molecules. The [VO(Vit E)(2)(H(2)O)(2)]2H(2)O complex was isolated by the reaction between VOSO(4) and vitamin E in ethanol/water solvent (50/50 w/w) at pH=8. The solid vanadyl(II) complex has been characterized by elemental analyses (CHN), photometric titrations, infrared spectra, molar conductivity, electronic spectra, TGA/DSC, SEM and XRD studies. Electronic and magnetic measurements are confirmed that the speculated geometry of vanadyl(II) complex is square pyramidal geometry. The microbial test was performed for the vanadyl complex against some kinds of bacteria and fungi. The [VO(Vit E)(2)(H(2)O)(2)]2H(2)O complex was proved effective in addressing diabetic of type I in case of experimental animal than other compounds were prepared in the literature.

Vanadium in the detection, prevention and treatment of cancer: the in vivo evidence

Vanadium, a dietary micronutrient, is yet to be established as an essential part of the human diet. Over the past century, several biological effects of vanadium, such as insulin-mimetic action as well as amelioration of hyperlipidemia and hypertension, have been discovered. This transition element is known to influence a battery of enzymatic systems, namely phosphatases, ATPases, peroxidases, ribonucleases, protein kinases and oxidoreductases. Multiple biochemical and molecular actions of vanadium have been implicated in its inhibitory effects on various tumor cells of human origin. Successful in vitro studies over the past few decades have advanced the anticancer research on vanadium into the preclinical stage. Vanadium in several animal cancer models provides protection against all stages of carcinogenesis--initiation, promotion, and progression. This review focuses on the current advances in cancer prevention and treatment as well as early detection by vanadium compounds in preclinical animal models while pointing to possible mechanisms of such diverse beneficial effects. Clinical pharmacokinetic and potential toxicity studies on vanadium are also highlighted in this review. Supporting and challenging evidence as well as future directions of vanadium research exploring the possibility of using this dietary agent for detection, prevention and treatment of human cancers are critically discussed.

The anti-diabetic effects and pharmacokinetic profiles of bis(maltolato)oxovanadium in non-diabetic and diabetic rats

The purpose of this study was to evaluate the anti-diabetic effects and pharmacokinetics of bis(maltolato)oxovanadium (BMOV) in rats. The anti-diabetic study was carried out in non-diabetic and diabetic rats by single-dose subcutaneous and intragastric administration. Pharmacokinetic investigation was performed using non-diabetic rats. Results showed that BMOV significantly decreased plasma glucose levels in diabetic rats at all given doses, and restored hyperglycaemic values to normal values after subcutaneous injections at doses of 4 and 8 mg vanadium (V)/kg or after intragastric administration at doses of 14 and 28 mgV/kg, respectively, but did not affect the plasma glucose level in non-diabetic rats. BMOV could be rapidly absorbed, slowly eliminated from plasma, widely distributed in various tissues and accumulated to a greater extent in the femur tissue. The average absolute bioavailability for intragastric administration at a single dose of 3, 6 and 12 mgV/kg was 28.1%, 33.7% and 21.4%, respectively. The presence of the peak vanadium level in the plasma was not coincident with that of the maximum effect of lowering plasma glucose levels. In conclusion, at the present dosing levels and administration routes, BMOV was effective in lowering plasma glucose levels in diabetic rats. BMOV has a promising outlook as an oral glucose-lowering drug.

Effects of dietary vanadium on growth and lipid storage in a larval anuran: results from studies employing ad libitum and rationed feeding

Vanadium (V) exerts a variety of effects related to metabolic function in vertebrates, including modifying glycolytic pathways and lipid metabolism. However, little is known about toxicity of V to wildlife in natural systems. We conducted parallel, independent studies to evaluate the effect of dietary exposure to vanadium on survival, metabolism, growth, and lipid storage of larval leopard frogs (Rana sphenocephala). In one study ("Ad lib") larvae were fed unlimited food and in the other ("Ration") larvae were fed a restricted diet. Experimental diets contained 10 ppm dw V(total) (Control, "C"), 109 ppm (Low, "L"), and 363 ppm (High, "H"). In neither study did V affect metabolic rate or survival to forelimb emergence. However, in the Ration study, 31% of individuals in H that had initiated metamorphosis died prior to completion of metamorphosis, compared with 22% in M and 9% in C, however the difference was not significant at alpha=0.05. Mortality during metamorphosis in the Ad lib study was more variable, yet followed a similar trend (26, 14, and 12% mortality in H, L, and C). In both studies, individuals that died during the metamorphic period were smaller at the time of forelimb emergence than those that survived. In the Ration study, individuals in H also had significantly lower growth rates, delayed metamorphosis, and reduced lipid content at metamorphosis compared to C and L. Growth was not affected by V in the Ad lib study. Our results suggest that habitat contamination by V may present risks to amphibians during the metamorphic period attributable to energetic responses influencing size at the initiation of metamorphosis and body lipid stores. Furthermore, while we cannot make formal comparisons between the studies, our results imply that protocols that employ ad libitum feeding regimes could fail to capture the effects of contaminants as they may be expressed in natural situations in which resources are typically more limited.

Synthesis, characterization and antidiabetic properties of N(1)-2,4-dihydroxybenzylidene-N(4)-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato-oxovanadium(IV)

A new oxovanadium(IV) chelate [VOL] (L: N(1)-2,4-dihydroxybenzylidene-N(4)-2-hydroxybenzylidene-S-methyl-thiosemicarbazidato) was synthesized and characterized by elemental analysis, conductivity and magnetic measurements, UV-vis, IR, EPR spectroscopy and mass spectrometry. The biochemical and immunohistochemical effects of the administration of the vanadium complex (VOL) into the pancreas of normal and streptozotocin-induced diabetic rats were profoundly investigated. The animals were randomly divided into four groups. Group I: control (intact) animals. Group II: control animals administered with VOL. Group III: STZ-induced diabetic animals. Group IV: STZ-induced diabetic animals administered with VOL. VOL was given to some of the experimental animals by gavage at a dose of 0.2mM/kg every day for 12 days. Blood samples were collected from animals, on 0 and 1, 6 and 12 days after STZ injection. On day 12, the pancreatic tissues were taken from the animals. The tissue sections were labelled with streptavidin biotin peroxidase technique for insulin. In the diabetic group, the blood glucose levels, aspartate and alanine transaminases, alkaline phosphatase activities were increased. But, in the diabetic+VOL groups, the blood glucose levels, aspartate and alanine transaminases, alkaline phosphatase activities were reduced. In the diabetic group, a decrease in the pancreatic glutathione levels, glutathione peroxidase and superoxide dismutase activities and an increase in the pancreatic lipid peroxidation level and catalase activities were observed. The administration of VOL to the diabetic rats reversed this diabetic effect due to its insulinomimetic effects. According to the immunohistochemical and biochemical results obtained, it was concluded that VOL can regenerate B cells of the pancreas in experimental diabetes and has an antidiabetic and protective effects on the pancreas.