Evaluation of immunotoxicity of sodium metavanadate following drinking water exposure in female B6C3F1/N mice in a 28-day study

Sodium metavanadate (NaVO3 ) is a pentavalent vanadium compound used in the metal industry and dietary supplements; human exposure occurs through inhalation of fumes and dust and ingestion of NaVO3 -containing products. The objective of this study was to assess the potential immunotoxicity of NaVO3 . Female B6C3F1/N mice were exposed to 0-500 ppm NaVO3 in drinking water for 28 days and evaluated for effects on immune cell populations and innate, cellular-mediated, and humoral-mediated immunity. There was a decreasing trend in body weight (BW) and BW gain in NaVO3 exposed mice, with a decrease (p ≤ 0.05) in BW gain at ≥250 ppm, relative to control. Conversely, increasing trends in spleen weights and an increase (p ≤ 0.05) in the spleen:BW ratio at ≥250 ppm NaVO3 were observed. NaVO3 exposure altered antibody production against sheep red blood cells (SRBC). Antibody forming cells (AFC)/106 spleen cells exhibited a decreasing trend, with a decrease (p ≤ 0.05) at 500 ppm NaVO3 , concurrent with an increase in percent B cells. NaVO3 had no effect on the serum anti-SRBC IgM antibody titers or anti-keyhole limpet hemocyanin antibody production. Exposure to NaVO3 decreased the percentage of natural killer cells at all dose levels (p ≤ 0.05), with no effect on the lytic activity. NaVO3 altered T-cell populations at 500 ppm but had no effect on T-cell proliferative responses or the lytic activity of cytotoxic T cells. Collectively, these data indicate that NaVO3 exposure can adversely affect the immune system by inducing alterations in humoral-mediated immunity, specifically the AFC response, with no effect on cell-mediated or innate immunity.

Effective photodegradation of antibiotics by guest-host synergy between photosensitizer and bismuth vanadate: Underlying mechanism and toxicity assessment

The removal of antibiotics in wastewater has attracted increasing attention. Herein, a superior photosensitized photocatalytic system was developed with acetophenone (ACP) as the guest photosensitizer, bismuth vanadate (BiVO₄) as the host catalyst and poly dimethyl diallyl ammonium chloride (PDDA) as the bridging complex, and used for the removal of sulfamerazine (SMR), sulfadiazine (SDZ) and sulfamethazine (SMZ) in water under simulated visible light (λ > 420 nm). The obtained ACP-PDDA-BiVO₄ nanoplates attained a removal efficiency of 88.9%-98.2% for SMR, SDZ and SMZ after 60 min reaction and achieved kinetic rate constant approximately 10, 4.7 and 13 times of BiVO₄, PDDA-BiVO₄ and ACP-BiVO₄, respectively, for SMZ degradation. In the guest-host photocatalytic system, ACP photosensitizer was found to have a great superiority in enhancing the light absorption, promoting the surface charge separation-transfer and efficient generation of holes (h⁺) and superoxide radical (·O₂^-), greatly contributing to the photoactivity. The SMZ degradation pathways were proposed based on the identified degradation intermediates, involving three main pathways of rearrangement, desulfonation and oxidation. The toxicity of intermediates was evaluated and the results demonstrated that the overall toxicity was reduced compared with parent SMZ. This catalyst maintained 92% photocatalytic oxidation performance after five cyclic experiments and displayed a co-photodegradation ability to others antibiotics (e.g., roxithromycin, ciprofloxacin et al.) in effluent water. Therefore, this work provides a facile photosensitized strategy for developing guest-host photocatalysts, which enabling the simultaneous antibiotics removal and effectively reduce the ecological risks in wastewater.

Toxicity of Nanocomplexes Containing Gadolinium Orthovanadate Nanoparticles and Cholesterol

Previous studies have shown the ability of nanocomplexes (NCs), which consist of nanoparticles (NPs) of orthovanadates of rare earth metals (GdYVO₄:Eu³⁺) and cholesterol, to inhibit the growth of Ehrlich's ascites carcinoma (EAC). However, the biosafety of these NCs remains unclear. Our objective was to investigate the acute and subchronic toxicity of NCs. NCs were administered to BALB/c mice in NPs concentration of 5.9; 29.5; 59.1; and 118.2 mg/kg. Acute toxicity was induced by a single administration of NCs, subchronic-by repeated daily administration of NCs for 14 days. On day 15 and on day 31 for acute and subchronic toxicity, respectively, the percentage of animal survival, body weight, condition of visceral organs, and activities of γ-glutamyl transferase (GGT) and glucose-6-phosphate dehydrogenase (G-6-PDH) were determined. It was found that administration of NCs in the concentration of 5.9 mg/kg and 29.5 mg/kg of NPs did not influence on survival of animals or have a negative impact on their performance status, morphological and quantitative characteristics of visceral organs, and activities of the GGT and G-6-PDH in the liver. For acute toxicity, the semi-lethal dose (LD₅₀) of nanocomplexes was determined (118.2 mg/kg of NPs). As to subchronic toxicity, it was found that repeated (for 14 days) administration of NCs containing 59.1 mg/kg of NPs decrease survival of animals to 50%. The coefficient of accumulation (C_acum = 7) indicates the low accumulative ability of NCs upon long-term use. Thus, from the LD₅₀ and accumulation coefficient, NCs can be referred to as low-toxic substances and used in conditionally therapeutic doses in oncological practice to develop nanostructured formulations of drugs.

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.

Systemic exposure and urinary excretion of vanadium following perinatal subchronic exposure to vanadyl sulfate and sodium metavanadate via drinking water

Vanadium is a ubiquitous environmental contaminant although there are limited data to assess potential adverse human health impact following oral exposure. In support of studies investigating the subchronic toxicity of vanadyl sulfate (V4+) and sodium metavanadate (V5+) following perinatal exposure via drinking water in male and female rats, we have determined the internal exposure and urinary excretion of total vanadium at the end of study. Water consumption decreased with increasing exposure concentration following exposure to both compounds. Plasma and urine vanadium concentration normalized to total vanadium consumed per day increased with the exposure concentration of vanadyl sulfate and sodium metavanadate suggesting absorption increased as the exposure concentration increased. Additionally, females had higher concentrations than males (in plasma only for vanadyl sulfate exposure). Animals exposed to sodium metavanadate had up to 3-fold higher vanadium concentration in plasma and urine compared to vanadyl sulfate exposed animals, when normalized to total vanadium consumed per day, demonstrating differential absorption, distribution, metabolism, and excretion properties between V5+ and V4+ compounds. These data will aid in the interpretation of animal toxicity data of V4+ and V5+ compounds and determine the relevance of animal toxicity findings to human exposures.

Jointed Synchronous Photocatalytic Oxidation and Chromate Reduction Enabled by the Defect Distribution upon BiVO4: Mechanism Insight and Toxicity Assessment

Exploring active and ecological materials for the restoration of complex pollution system is highly desired. This study presents a facile defect-tailoring strategy for combined pollutants purification with BiVO₄ photocatalysis in which the jointed synchronous reaction of oxidation and reduction is integrated instead of the sequential reaction in two individual systems. XPS and EPR reveal that BiVO₄ with a suitable oxygen vacancies (OVs) concentration and distribution exhibits superior photocatalytic activity under the coexistence of TC-HCl and Cr(VI) with Cr(VI) reduction efficiency increased by 71 times compared with the individual Cr(VI) system along with TC-HCl removal efficiency comparable to a single TC-HCl system. The mechanism of synchronous redox reactions mediated by surface OVs is revealed by comprehensive characterization together with reaction kinetic analysis, and the electronic band structure adjustment induced by the OVs variation is confirmed. Active species identification tests and intermediate product analysis confirm that singlet oxygen (¹O₂) accounts for the selective oxidation of TC-HCl, while electrons dominate the reduction of Cr(VI), under a coexistent environment. The influence of water quality parameters (e.g., pH, cations, anions, and organic substances) on the photocatalytic activity is investigated considering the complexity of the real aquatic environment. Importantly, toxicity assessment with Gram-negative strain E. coli as a model bacterium validates that the toxicity of the intermediates can be reduced to low or even ultralow levels. This work is dedicated to the mechanistic study of defect photocatalysis over BiVO₄ and provides a jointed synchronous reaction system for combined pollutant purification.

Internal dose of vanadium in rats following repeated exposure to vanadyl sulfate and sodium orthovanadate via drinking water

Vanadium is a ubiquitous environmental contaminant that exists in multiple oxidation states. Humans are exposed to vanadyl (V4+) and vanadate (V5+) from dietary supplements, food, and drinking water and hence there is a concern for adverse human health. The current investigation is aimed at identifying vanadium oxidation states in vitro and in vivo and internal concentrations following exposure of rats to vanadyl sulfate (V4+) or sodium metavanadate (V5+) via drinking water for 14 d. Investigations in simulated gastric and intestinal fluids showed that V4+ was stable in gastric fluid while V5+ was stable in intestinal fluid. Analysis of rodent plasma showed that the only vanadium present was V4+, regardless of the exposed compound suggesting conversion of V5+ to V4+ in vivo and/or instability of V5+ species in biological matrices. Plasma, blood, and liver concentrations of total vanadium, after normalizing for vanadium dose consumed, were higher in male and female rats following exposure to V5+ than to V4+. Following exposure to either V4+ or V5+, the total vanadium concentration in plasma was 2- to 3-fold higher than in blood suggesting plasma as a better matrix than blood for measuring vanadium in future work. Liver to blood ratios were 4-7 demonstrating significant tissue retention following exposure to both compounds. In conclusion, these data point to potential differences in absorption and disposition properties of V4+ and V5+ salts and may explain the higher sensitivity in rats following drinking water exposure to V5+ than V4+ and highlights the importance of internal dose determination in toxicology studies.

Biochemical and ultrastructural changes in kidney and liver of African Giant Rats (Cricetomysgambianus, Waterhouse, 1840) exposed to intraperitoneal sodium metavanadate (vanadium) intoxication

We studied the hepatic and renal impact of sodium metavanadate (SMV) exposure in African giant rats (AGR). Twelve male AGR were used and divided into two groups. The control group received sterile water while the SMV-exposed group received 3 mg/kg SMV intraperitoneally for 14 days. SMV exposed AGR groups showed significantly decreased activities of serum AST, ALT, ALP and creatinine concentration but increased blood urea nitrogen (BUN), albumin and globulin concentrations. Kidney ultrastructure examination revealed atrophy of the glomerular tuft, loss of podocytes, distortions of the endothelium and glomerular basement membrane. The liver sinusoids fenestration phenotypes were abnormal. Hepatocytes exhibited hypertrophy with uneven, crenated and dentate nuclei. SMV exposure induced activation of monocytes, as well as Kupffer and fibrous cells. Alterations in glomerular podocytes and cell-cell and cell matrix contact and inflammatory liver fibrosis are key events in progressive glomerular failure and hepatic damage due to SMV intoxication.

Intraperitoneal sodium metavanadate exposure induced severe clinicopathological alterations, hepato-renal toxicity and cytogenotoxicity in African giant rats (Cricetomys gambianus, Waterhouse, 1840)

Pollution of environment due to increased exploitation of minerals has been on the rise, and vanadium, a metal in the first transition series essential for mammalian existence, is a major component of air pollution. This study investigated the clinico-pathological, hepato-renal toxicity, and cytogenotoxicity of intraperitoneal exposure of African giant rats (AGRs), a proposed model for ecotoxicological research to sodium metavanadate. A total of 27 adult male African giant rats weighing 975 ± 54.10 g were distributed into two major groups: sodium metavanadate (SMV) treated and control. They were observed daily for clinical signs of toxicity. Four rats from each group were randomly collected and sacrificed after 3, 7, and 14 days of SMV treatment. Liver, kidney, and bone marrow were analyzed for histopathology and micronucleated normochromated and polychromated erythrocytes (MNNCE and MNPCE), respectively. Clinical signs in treated AGR include sluggish and weak movements, un-groomed fur, and labored breathing. Histology of the kidney revealed severe glomerular atrophy, tubular ectasia, and vacuolar degeneration of tubular epithelium, while liver histology showed sinusoidal congestion and severe hepatocellular necrosis after 14 days SMV exposure. Also, MNNCE and MNPCE significantly increased with a decrease in PCE/NCE ratio in SMV-treated AGR, suggestive of alternations in bone marrow cell proliferation. Hence, SMV treatment to AGR resulted to severe clinicopathologic alterations, kidney, and liver dysfunction and cytogenotoxicity evident by somatic mutation induction which could be severe with prolonged exposure. This suggests African giant rat as an ecotoxicological model to measure major health risks to animals and human populations in highly polluted environment.

Resveratrol Ameliorates Tau Hyperphosphorylation at Ser396 Site and Oxidative Damage in Rat Hippocampal Slices Exposed to Vanadate: Implication of ERK1/2 and GSK-3β Signaling Cascades

The objective of this study was to investigate the effect of resveratrol (a natural polyphenolic phytostilbene) on tau hyperphosphorylation and oxidative damage induced by sodium orthovanadate (Na₃VO₄), the prevalent species of vanadium (vanadate), in rat hippocampal slices. Our results showed that resveratrol significantly inhibited Na₃VO₄-induced hyperphosphorylation of tau at the Ser396 (p-S396-tau) site, which is upregulated in the hippocampus of Alzheimer's disease (AD) brains and principally linked to AD-associated cognitive dysfunction. Subsequent mechanistic studies revealed that reduction of ERK1/2 activation was involved in the inhibitory effect of resveratrol by inhibiting the ERK1/2 pathway with SL327 mimicking the aforementioned effect of resveratrol. Moreover, resveratrol potently induced GSK-3β Ser9 phosphorylation and reduced Na₃VO₄-induced p-S396-tau levels, which were markedly replicated by pharmacologic inhibition of GSK-3β with LiCl. These results indicate that resveratrol could suppress Na₃VO₄-induced p-S396-tau levels via downregulating ERK1/2 and GSK-3β signaling cascades in rat hippocampal slices. In addition, resveratrol diminished the increased extracellular reactive oxygen species generation and hippocampal toxicity upon long-term exposure to Na₃VO₄ or FeCl₂. Our findings strongly support the notion that resveratrol may serve as a potential nutraceutical agent for AD.

Decavanadate Toxicology and Pharmacological Activities: V10 or V1, Both or None?

This review covers recent advances in the understanding of decavanadate toxicology and pharmacological applications. Toxicological in vivo studies point out that V10 induces several changes in several oxidative stress parameters, different from the ones observed for vanadate (V1). In in vitro studies with mitochondria, a particularly potent V10 effect, in comparison with V1, was observed in the mitochondrial depolarization (IC50 = 40 nM) and oxygen consumption (99 nM). It is suggested that mitochondrial membrane depolarization is a key event in decavanadate induction of necrotic cardiomyocytes death. Furthermore, only decavanadate species and not V1 potently inhibited myosin ATPase activity stimulated by actin (IC50 = 0.75 μM) whereas exhibiting lower inhibition activities for Ca(2+)-ATPase activity (15 μM) and actin polymerization (17 μM). Because both calcium pump and actin decavanadate interactions lead to its stabilization, it is likely that V10 interacts at specific locations with these proteins that protect against hydrolysis but, on the other hand, it may induce V10 reduction to oxidovanadium(IV). Putting it all together, it is suggested that the pharmacological applications of V10 species and compounds whose mechanism of action is still to be clarified might involve besides V10 and V1 also vanadium(IV) species.

Detoxification Processes from Vanadate at the Root Apoplasm Activated by Caffeic and Polygalacturonic Acids

In the root apoplasm, V(V) and V(IV) toxicity can be alleviated through redox and complexation reactions involving phenolic substances and the polyuronic components. In such context we report the role of polygalacturonic acid (PGA) on the reducing activity of caffeic acid (CAF) towards V(V). The redox reaction was particularly effective at pH 2.8 leading to the formation of oxidation products with redox activity towards V(V). An o-quinone was identified as the first product of the reaction which is further involved in the formation of CAF dimers. At pH ≥ 3.6 the redox activity decreased and a yield in V(IV) equal to 38, 31, 21 and 14% was found at pH 3.6, 4.0. 5.0 and 6.0 respectively compared with that obtained at pH 2.8. The redox reaction was faster in the presence of PGA and a higher yield of V(IV) was found in the 4.0-6.0 pH range with respect to the CAF-V(V) binary system. The higher efficiency of the redox reaction in the presence of PGA was related with the ability of PGA to bind V(IV). The biological significance of the redox reaction between CAF and V(V), as well as the role of PGA in such reaction, was established "in vivo" using triticale plants. Results showed that PGA reduced significantly the phytotoxic effects of the V(V)-CAF system.

Vanadium bioavailability in soils amended with blast furnace slag

Blast furnace (BF) slags are commonly applied as soil amendments and in road fill material. In Sweden they are also naturally high in vanadium. The aim of this study was to assess the vanadium bioavailability in BF slags when applied to soil. Two soils were amended with up to 29% BF slag (containing 800 mg V kg(-1)) and equilibrated outdoors for 10 months before conducting a barley shoot growth assay. Additional soil samples were spiked with dissolved vanadate(V) for which assays were conducted two weeks (freshly spiked) and 10 months (aged) after spiking. The BF slag vanadium was dominated by vanadium(III) as shown by V K-edge XANES spectroscopy. In contrast, results obtained by HPLC-ICP-MS showed that vanadium(V), the most toxic vanadium species, was predominant in the soil solution. Barley shoot growth was not affected by the BF slag additions. This was likely due to limited dissolution of vanadium from the BF slag, preventing an increase of dissolved vanadium above toxic thresholds. The difference in vanadium bioavailability among treatments was explained by the vanadium concentration in the soil solution. It was concluded that the vanadium in BF slag is sparingly available. These findings should be of importance in environmental risk assessment.

Vanadium toxicity in the thymic development

The purpose of this study was to define the toxic effects of vanadium on thymic development in broilers fed on diets supplemented with 0, 5, 15, 30, 45 and 60 mg/kg of vanadium for 42 days. We examined the changes of relative weigh, cell cycle phase, apoptotic cells, and protein expression of Bcl-2, Bax, and caspase-3 in the thymus by the methods of flow cytometry, TUNEL (terminal-deoxynucleotidyl transferase mediated nick end labeling) and immunohistochemistry. The results showed that dietary high vanadium (30 mg/kg, 45 mg/kg and 60 mg/kg) caused the toxic effects on thymic development, which was characterized by decreasing relative weigh, increasing G0/G1 phase (a prolonged nondividing state), reducing S phase (DNA replication) and proliferating index (PI), and increasing percentages of apoptotic thymocytes. Concurrently, the protein expression levels of Bax and caspase-3 were increased, and protein expression levels of Bcl-2 were decreased. The thymic development suppression caused by dietary high vanadium further leads to inhibitive effects on T lymphocyte maturity and activity, and cellular immune function. The above-mentioned results provide new evidences for further understanding the vanadium immunotoxicity. In contrast, dietary 5 mg/kg vanadium promoted the thymic development by increasing relative weigh, decreasing G0/G1 phase, increasing S phase and PI, and reducing percentages of apoptotic thymocytes when compared to the control group and high vanadium groups.

Cyclooxygenase-1 as the main source of proinflammatory factors after sodium orthovanadate treatment

Vanadium is a metal present in air pollution. Its compounds may have both anticancer and carcinogenic properties. Vanadium compounds are tested in treatment of diabetes and cancer. An important research direction aimed at better understanding of the mechanisms of action of the vanadium compounds is a more detailed insight into their impact on inflammatory reactions. The aim of this study was to examine the effect of micromolar concentrations of sodium orthovanadate, Na3VO4, on the activity and expression of cyclooxygenases: COX-1 and COX-2. PMA-activated THP-1 macrophages were incubated in vitro for 48 h with micromolar concentrations of sodium orthovanadate. As shown by an ELISA assay, sodium orthovanadate increases the quantity of prostaglandin E2 being released into the medium in a dose-dependent manner as well as impacts the quantity of the stable metabolite of thromboxane A2: thromboxane B2. The use of a COX-2 inhibitor, NS-398, revealed that this effect was independent of changes in the activity of COX-2. Western blotting analysis showed that sodium orthovanadate increased the expression of COX-2 when used with NS-398. Quantitative real-time PCR measurements of mRNA levels of genes PTGS1 and PTGS2 revealed no effect of the tested vanadium compound on the levels of analyzed transcripts.

Sodium metavanadate exhibits carcinogenic tendencies in vitro in immortalized human bronchial epithelial cells

Pentavalent vanadium compounds induce intracellular changes in vitro that are consistent with those of other carcinogenic substances. While there is no clear evidence that vanadium compounds cause cancer in humans, vanadium pentoxide causes lung cancer in rodents after long-term inhalation exposures and in turn IARC has categorized it as a group 2B possible human carcinogen. The goal of this study was to investigate the carcinogenicity of NaVO3 in the human immortalized bronchial epithelial cell line, Beas-2B. Cells were treated with 10 μM NaVO3 for 5 weeks, with or without recovery time, followed by gene expression microarray analysis. In a separate experiment, cells were exposed to 1-10 μM NaVO3 for 4 weeks and then grown in soft agar to test for anchorage-independent growth. A dose-dependent increase in the number of colonies was observed. In scratch tests, NaVO3-transformed clones could repair a wound faster than controls. In a gene expression microarray analysis of soft agar clones there were 2010 differentially expressed genes (DEG) (adjusted p-value ≤ 0.05) in NaVO3-transformed clones relative to control clones. DEG from this experiment were compared with the DEG of 5 week NaVO3 exposure with or without recovery, all with adjusted p-values < 0.05, and 469 genes were altered in the same direction for transformed clones, 5 week NaVO3-treated cells, and the recovered cells. The data from this study imply that chronic exposure to NaVO3 causes changes that are consistent with cellular transformation including anchorage-independent growth, enhanced migration ability, and gene expression changes that were likely epigenetically inherited.

Astrogliosis and HSP 70 activation in neonate rats' brain exposed to sodium metavanadate through lactation

The effect of sodium metavanadate (NaVO3) exposure on lipid oxidative damage in the CNS of suckling rats was studied. Using histological markers of cellular injury, we also studied the morphological alterations of neurons and astroglial cells in different regions of neonate rats CNS after NaVO3 exposure. Dams of treated litters were intraperitoneally injected with 3mgNaVO3/kgbody weight/day during 12days starting on post-natal day (PND) 10. On the 21st PND, four pups of each litter were sacrificed by decapitation and six brain areas were removed for lipid peroxidation assay by the thiobarbituric acid (TBA) reaction, the other four were transcardially perfused-fixed and their brains were removed and cut with a cryostat. Brain sections were processed for: NADPHd histochemistry and anti-HSP70, anti-GFAP and anti-S100 immunohistochemistry. The relative optical density of the NADPHd stained layers and of S100 (+) astrocytes and the GFAP (+) astrocyte surface area in Cer and Hc were measured. Although MDA levels, S100 immunostaining and NADPHd activity didn't show differences between experimental and control groups, both astrogliosis and HSP70 activation were detected in Cer, while only the former was detected in Hc of V-exposed pups.

The role of silver and vanadium release in the toxicity of silver vanadate nanowires toward Daphnia similis

Nanomaterials are used in a wide spectrum of applications, including nanowires that are objects with at least one of its dimensions in the range of 1 to 100 nm. Recently, a new type of silver vanadate nanowire decorated with silver nanoparticles (SVSN-LQES1) with promising antimicrobial activity against different pathogenic bacteria was described. The objective of the present study was to evaluate the role of silver and vanadium release in the acute toxicity of this material using Daphnia similis. To verify the effect of the presence of the nanowires in the test solution, tests were performed before and after filtration. Total silver release to the testing media was determined using the method of inductively coupled plasma atomic emission spectroscopy (ICP-AES). Silver vanadate nanowires decorated with silver nanoparticles (SVSN-LQES1) are acutely toxic to D. similis. The release of silver from the nanomaterial trapped in the gut along with the silver released to the test media seems to be responsible for the observed toxicity. Although toxic to Daphnia, vanadium does not contribute to the toxicity of SVSN-LQES1. The observed increase in lipid droplets appears to be related to the exposure of the organisms to the nanomaterials, but the significance of this response needs further investigation.

A multifunctional biphasic suspension of mesoporous silica encapsulated with YVO4:Eu3+ and Fe3O4 nanoparticles: synergistic effect towards cancer therapy and imaging

Polyol mediated synthesized luminescent YVO(4):Eu(3+) nanoparticles (NPs) have been encapsulated in mesoporous silica nanoparticles (MSNs) using the sol-gel process. X-ray diffraction and Fourier transform infrared spectroscopy along with transmission electron microscopy confirm the encapsulation of the YVO(4):Eu(3+) NPs in the SiO(2) matrix. N(2) adsorption/desorption analysis confirms the mesoporous nature of the MSNs and YVO(4):Eu(3+)-MSNs. No significant quenching of the YVO(4):Eu(3+) luminescence is observed for YVO(4):Eu(3+)-MSNs. This nanocomposite has been tested as a potential drug carrier. Efficient loading of doxorubicin hydrochloride (DOX), a typical anticancer drug, is observed which reaches up to 93% in 8 mg ml(-1) of YVO(4):Eu(3+)-MSNs. pH sensitive release of DOX is observed, with 54% release for pH 4.3 and 31% in a physiological environment (pH 7.4). Both MSNs and YVO(4):Eu(3+)-MSNs nanocomposites do not show accountable toxicity to two cell lines, i.e. HeLa and MCF-7. However, as desired, toxicity is observed when cells are incubated with DOX loaded YVO(4):Eu(3+)-MSNs. Laser scanning confocal microscopy images confirm the uptake of the nanocomposite in both cell lines. The morphology of the cells (MCF-7) changes after incubation with DOX loaded YVO(4):Eu(3+)-MSNs, indicating an interaction of DOX with the cells. More cytotoxicity to both cell lines with ∼90% killing is observed due to the synergistic effect of magnetic fluid hyperthermia and chemotherapy using a biphasic suspension of superparamagnetic iron oxide magnetic nanoparticles and DOX loaded YVO(4):Eu(3+)-MSNs. In addition, an AC magnetic field triggers an enhanced drug release.

Metal based new triazoles: their synthesis, characterization and antibacterial/antifungal activities

A series of new triazoles and their oxovanadium(IV) complexes have been synthesized, characterized and evaluated for antibacterial/antifungal properties. The new Schiff bases ligands (L(1))-(L(5)) were prepared by the condensation reaction of 3,5-diamino-1,2,4-triazole with 2-hydroxy-1-naphthaldehyde, pyrrole-2-carboxaldehyde, pyridine-2-carboxaldehyde, 2-acetyl pyridine and 2-methoxy benzaldehyde. The structures of the ligands have been established on the basis of their physical, spectral (IR, (1)H and (13)C NMR and mass spectrometry) and elemental analytical data. The prepared ligands were used to synthesize their oxovanadium(IV) complexes (1)-(5) which were also characterized by their physical, spectral and analytical data and proposed to have a square pyramidal geometry. The ligands and their complexes were screened for in vitro antibacterial activity against six bacterial species such as, Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, and Bacillus subtilis and for in vitro antifungal activity against six fungal strains, Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, and Candida glabrata. Cytotoxic nature of the compounds was also reported using brine shrimp bioassay method against Artemia salina.

Effect of 12-week vanadate and magnesium co-administration on chosen haematological parameters as well as on some indices of iron and copper metabolism and biomarkers of oxidative stress in rats

Changes in some blood parameters after 12-week administration of sodium metavanadate (SMV; 0.125mgV/ml) or/and magnesium sulphate (MS; 0.06mgMg/ml) in drinking water were studied in outbred male Wistar rats (16 rats/each group) to explore the probable mechanism(s) underlying SMV toxicity and check whether Mg at the level selected during SMV co-administration can protect, at least in part, from a possible deleterious action of SMV. Exposure to SMV alone and in combination with MS (a) led to a decrease in fluid and food intake and body weight gain; (b) predisposed the animals to the development of microcytic-hypochromic anaemia (with excessive liver and spleen Fe deposition, unaltered plasma Fe level and enhanced Zn concentration in the erythrocytes (RBCs) characterized by a reduced haematocrit (Ht) index and haemoglobin (Hb) level, unchanged erythrocyte and reticulocyte count, anisocytosis, lowered total iron binding capacity (TIBC) and elevated transferrin saturation (TS); (c) disturbed Cu homeostasis, but (d) did not influence the leukocyte count and the plasma total antioxidant status (TAS). We suggest that abnormal metabolism and accumulation of Fe as well as an altered Cu status and the RBC Zn level might lead to defective Fe utilization and be a factor promoting the development of Fe-utilization anaemia. The disturbances in the antioxidative capacity reported previously in rats' RBCs after SMV intoxication (Ścibior, Zaporowska, Environ. Toxicol. Pharmacol. 30 (2010) 153-161) may suggest that oxidative stress (OS) could also be, in part, involved in the mechanism responsible for the development of anaemia. The Mg dose ingested in combination with V under SMV-MS co-administration (a) was able to decrease, to some extent, the V concentration in the blood, (b) normalized the RBC Mg and Fe levels and (c) restored the values of some parameters of the Fe status near the control values. These results allow a supposition that a higher Mg dose consumed during SMV exposure could have better protective potential and be more effective in limiting the SMV toxicity observed.

Evaluation of the interaction of vanadium with glutathione in human blood components

Metallo-elements including Vanadium (V) have strong affinity for sulfhydryl (-SH) groups in biological molecules including Glutathione (GSH) in tissues. Because of this fact it was of interest to further investigate the interaction of Ammonium Vanadate [NH(4)VO(3)] with Glutathione as a biomarker of toxicity and the role of Glutathione in the detoxification and conjugation pr(o)Cesses in whole blood components including plasma and cytosolic fraction. Effects of different concentrations of Ammonium Vanadate [NH(4)VO(3)] on the level of reduced Glutathione in whole blood components (Plasma and Cytosolic fraction) were examined. GSH depletion in plasma and cytosolic fraction was Ammonium Vanadate's concentration-dependent. Depleted GSH level was more pronounced with more incubation time period. These findings show that changes in the GSH status produced by Ammonium Vanadate could be due to either by adduct formation of Vanadium and glutathione i.e. (V-SG) or by increased production of oxidized Glutathione (2GSH +V(+5) → GSSG). This change in GSH metabolic status provides some information regarding the mechanism of toxicity by Ammonium Vanadate and the protective role of glutathione.

A tea/vanadate decoction delivered orally over 14 months to diabetic rats induces long-term glycemic stability without organ toxicity

Vanadium can induce potent hypoglycemic effects in type 1 and type 2 diabetes mellitus animals, but toxic adverse effects have inhibited the translation of these findings. Administration of vanadate in a black tea decoction has shown impressive hypoglycemic effects without evidence of toxicity in short-term studies. The purpose of this study was to investigate the hypoglycemic action and the toxic adverse effects of a tea/vanadate (T/V) decoction in diabetic rats over a 14-month treatment period. Streptozotocin-induced type 1 diabetes mellitus rats were orally gavaged with 40 mg sodium vanadate in a black tea decoction only when blood glucose levels were greater than 10 mmol/L. Glycemic status and liver and kidney function were monitored over 14 months. All of the diabetic rats in this treatment group (n = 25) required treatment with the T/V decoction at the start of the study to reduce blood glucose levels to less than 10 mmol/L. Diarrhea was uncommon among the T/V-treated animals during the first week of T/V treatment and was absent thereafter. There was no evidence of liver or kidney dysfunction or injury. From 2 to 6 months, fewer animals required the T/V treatment to maintain their blood glucose levels. After 9 months of treatment, none of the diabetic animals required any T/V to maintain their blood glucose levels at less than 10 mmol/L. Oral administration of a T/V decoction provides safe, long-acting hypoglycemic effects in type 1 diabetes mellitus rats. The typical glycemic signs of diabetes were absent for the last 5 months of the study.

Dietary vanadium induces oxidative stress in the intestine of broilers

The purpose of this study was to examine oxidative stress induced by dietary vanadium in the mucosa of different parts of intestine including duodenum, jejunum, ileum, and cecal tonsil. A total of 420 1-day-old avian broilers were divided into six groups and fed on a corn-soybean basal diet as control diet or the same basal diet supplemented with 5, 15, 30, 45, and 60 mg/kg vanadium as ammonium metavanadate. During the experimental period of 42 days, oxidative stress parameters were determined for both control and experimental groups. The results showed that malondialdehyde content was significantly higher (p < 0.05 or p < 0.01) in 30, 45, and 60 mg/kg groups than in control group. In contrast, the activities of superoxide dismutase, catalase, and glutathione peroxidase, and ability to inhibit hydroxyl radical, and glutathione hormone content were significantly decreased (p < 0.05 or p < 0.01) mainly in 45 and 60 mg/kg groups in comparison with those of control group. However, the abovementioned oxidative stress parameters were not significantly changed (p > 0.05) in 5 and 15 mg/kg groups. It was concluded that dietary vanadium in excess of 30 mg/kg could cause obvious oxidative stress in the intestinal mucosa, which could impact the antioxidant function of intestinal tract in broilers.

Vertical administration of vanadium through lactation induces behavioural and neuromorphological changes: protective role of vitamin E

The work investigated the protective role of vitamin E on vanadium induced neurotoxicity. Three adult female rats were divided into three groups, A-C with each dam and her pups forming a group. Group A served as control. The dam in Group B was given 3mg/kg b.w./day of vanadium from PND 1 while the Group C dam were given 3mg/kg b.w./day of vanadium, for 14 days and 500mg/kg b.w. of vitamin E 72 hourly in the same time frame. The results showed that pups from Group B, exhibited behavioural deficits in most tests, a significant reduction in body weight gain and absolute brain weight; in addition immunohistochemistry showed reactive astrogliosis induced by vanadium exposure. All these findings were however attenuated in pups whose dam was exposed to vanadium and vitamin E depicting the significant protective effects of this antioxidant against vanadium. This study is novel in that both vanadium and vitamin E were introduced through the lactation route. We conclude that though caution remains essential in the posology of vitamin E, the management of lactating mothers who have been exposed to vanadium occupationally, environmentally or therapeutically with supplementation of this antioxidant may be beneficial at least in the short term to both mother and offspring.

Differential patterns of accumulation and depuration of dietary selenium and vanadium during metamorphosis in the Gray Treefrog (Hyla versicolor)

Selenium (Se) and vanadium (V) are contaminants commonly found in aquatic systems affected by wastes derived from fossil fuels. To examine their effects on a widely distributed species of amphibian, we exposed gray tree frogs (Hyla versicolor) to Se (as SeO₂) or V (as NaVO₃) in their diet from the early larval period to metamorphosis. Concentrations of Se in Se-enriched food were 1.0 (Se control), 7.5 (Se low), and 32.7 (Se high) μg/g dw. Concentrations of V in V-enriched food were 3.0 (V control), 132.1 (V low), and 485.7 (V high) μg/g dw. Although we observed bioaccumulation of both metals throughout the larval period, no effects on growth, survival, metabolic rate, or lipid content were observed. Se concentrations in tissues did not vary among life stages, neither in Se low nor Se high treatments, such that maximum accumulation had occurred by the mid-larval period. In addition, there was no evidence of depuration of Se in either the Se low or the Se high treatments during metamorphosis. A strikingly different pattern of accumulation and depuration occurred in V-exposed individuals. In treatments V low and V high, maximum body burdens occurred in "premetamorphs" (i.e., animals with developed forelimbs but in which tail resorption had not begun), whereas body burdens in animals having completed metamorphosis were much lower and similar to those in larvae. These results suggest that compared with Se-exposed animals, V-exposed animals were able to depurate a substantial amount of accumulated V during the metamorphic period. In an ecologic context, it appears that amphibians exposed to Se during the larval period may serve as a vector of the metal to terrestrial predators, yet potential transfer of accumulated V to predators would largely be restricted to the aquatic habitat.

A Rhodobacter capsulatus member of a universal permease family imports molybdate and other oxyanions

Molybdenum (Mo) is an important trace element that is toxic at high concentrations. To resolve the mechanisms underlying Mo toxicity, Rhodobacter capsulatus mutants tolerant to high Mo concentrations were isolated by random transposon Tn5 mutagenesis. The insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. During growth under Mo-replete conditions, the wild-type strain accumulated considerably more Mo than the permease mutant. For mutants defective for the permease, the high-affinity molybdate importer ModABC, or both transporters, in vivo Mo-dependent nitrogenase (Mo-nitrogenase) activities at different Mo concentrations suggested that ModABC and the permease import molybdate in nanomolar and micromolar ranges, respectively. Like the permease mutants, a mutant defective for ATP sulfurylase tolerated high Mo concentrations, suggesting that ATP sulfurylase is the main target of Mo inhibition in R. capsulatus. Sulfate-dependent growth of a double mutant defective for the permease and the high-affinity sulfate importer CysTWA was reduced compared to those of the single mutants, implying that the permease plays an important role in sulfate uptake. In addition, permease mutants tolerated higher tungstate and vanadate concentrations than the wild type, suggesting that the permease acts as a general oxyanion importer. We propose to call this permease PerO (for oxyanion permease). It is the first reported bacterial molybdate transporter outside the ABC transporter family.

Modulation of NAD(P)H:quinone oxidoreductase by vanadium in human hepatoma HepG2 cells

Recent studies demonstrated the carcinogenicity and the mutagenicity of vanadium compounds. In addition, vanadium (V(5+)) was found to enhance the effects of other genotoxic agents. However, the mechanism by which V(5+) induce toxicity remain unknown. In the current study we examined the effect of V(5+) (as ammonium metavanadate, NH(4)VO(3)) on the expression of NAD(P)H: quinone oxidoreductase 1 (NQO1) in human hepatoma HepG2 cells. Therefore, HepG2 cells were treated with increasing concentrations of V(5+) in the presence of two NQO1 inducers, the 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and isothiocyanate sulforaphane (SUL). Our results showed that V(5+) inhibited the TCDD- and SUL-mediated induction of NQO1 at mRNA, protein and activity levels. Investigating the effect of V(5+) at transcriptional levels revealed that V(5+) significantly inhibited the TCDD- and SUL-mediated induction of antioxidant responsive element (ARE)-dependent luciferase reporter gene expression. In addition, V(5+) was able to decrease the TCDD- and SUL-induced nuclear accumulation of nuclear factor erythroid 2-related factor-2 (Nrf2) without affecting Nrf2 mRNA or protein levels. Looking at the post-transcriptional level, V(5+) did not affect NQO1 mRNA stability, thus eliminating the possible role of V(5+) in decreasing NQO1 mRNA levels through this mechanism. In contrast, at post-translational level, V(5+) was able to significantly decrease NQO1 protein half-life. The present study demonstrates for the first time that V(5+) down-regulates NQO1 at the transcriptional and post-translational levels in the human hepatoma HepG2 cells via AhR- and Nrf2-dependent mechanisms.

Proteomics of proteins associated with astaxanthin accumulation in the green algae Haematococcus lacustris under the influence of sodium orthovanadate

An extensive proteomics analysis has identified proteins associated with astaxanthin accumulation in the green algae Haematococcus lacustris under oxidative stress induced by sodium orthovanadate (SOV). Measurement of total carotenoid accumulation per cell biomass showed an increase from 81 to 136 pg/cell after being exposed to 2.5 mM SOV, when compared to the control cells at day 3 of cultivation. A total of 83 proteins were differentially expressed in SOV-treated H. lacustris in comparison with control cells. They consisted of 34 down-regulated and 49 up-regulated proteins. Of these, 17 highly-expressed proteins were analyzed by MALDI-TOF-MS to identify the function of the differentially expressed proteins in response to oxidative stress in H. lacustris.

[RAPD-analysis of soybean cell line with cross-resistance to tungsten and vanadium oxyanions]

The effect of vanadium oxyanions on genome of soybean (Glycine max L., Merr.) in tungsten-resistant cell line was studied. The line is resistant to V(5+)-oxyanions. RAPD-amplicons with identical length are differentially synthesized from DNAs of tungsten-resistant cell line as well as of the initial culture was shown by using the lethal dose of oxyanions W6+ and then V5+. The presence of instable loci in soybean genome under different stressors is discussed.

Preliminary studies on the effect of zinc and selenium on vanadium-induced cytotoxicity in vitro

In the present work, we investigated the cytotoxicity of vanadium and the influence of zinc and selenium on vanadium-dependent cell damage in the BALB/c 3T3 cell culture. Treatment of cells for 24 hours with medium containing 50, 100 and 200 microM NaVO3 caused a significant decrease in the cell viability as measured by MTT test. Furthermore, the assays for reactive oxygen species (NBT reduction and phenol red oxidation) demonstrated the increase in superoxide and hydrogen peroxide production. In the cotreatment studies, the cells were exposed to NaVO3 (50, 100 and 200 microM) in the presence of nontoxic concentrations of ZnCl2 (5 microM) or Na2SeO3 (0.5 microM). Following 24 h incubation, the cell viability (assessed in MTT assay) and reactive oxygen species generation were evaluated. Our data suggest that zinc and selenium, in the concentrations mentioned above, provide no protection against adverse actions induced by sodium metavanadate at concentration levels of 50, 100 and 200 microM. To our knowledge, this is the first report from in vitro studies on interaction between pentavalent vanadium and trace elements that function as antioxidants: zinc and selenium.

Vanadium (V)-Induced Neurotoxicity in the Rat Central Nervous System: A Histo-Immunohistochemical Study

As vanadium was found to induce oxidative stress in the central nervous system, the morphological alterations of neurons and astroglial cells in adult rat central nervous system after vanadium exposure was studied, using histological markers of cellular injury. Animals were intraperitoneally injected with 3 mg/kg body weight of sodium metavanadate for 5 consecutive days. NADPH diaphorase histochemistry and heat shock protein (hsp) 70, glial fibrillary acidic protein (GFAP), and S-100 immunohistochemistry were performed in floating sections of several brain areas. NADPHd staining was higher in the molecular and granular layers of the cerebellar cortex, and small NADPHd-stained interneurons were observed in hippocampal sections in V(+5)-exposed animals. hsp 70 immunostaining showed the presence of reactive neurons in cerebellum of treated animals. GFAP and S-100 immunohistochemistry showed enlarged astrocytes in cerebellum and hippocampus in the V(+5)-exposed animals. The histological markers used showed that the main areas affected by vanadium-mediated free-radical generation were the hippocampus and the cerebellum.

Relationship Between Phosphatase Activity and Cytotoxic Effect of Two Protein Phosphatase Inhibitors, Okadaic Acid and Pervanadate, on Human Myeloid Leukemia Cell Line

Protein phosphatases are signalling molecules that regulate a variety of fundamental cellular processes including cell growth, metabolism and apoptosis. The aim of this work was to correlate the cytotoxicity of pervanadate and okadaic acid on HL60 cells and their effect on the phosphatase obtained from these cells. The cytotoxicity of these protein phosphatase inhibitors was evaluated on HL60 cells using phosphatase activity, protein quantification and MTT reduction as indices. The major phosphatase presents in the cellular extract showed high activity (80%) and affinity (Km = 0.08 mM) to tyrosine phosphate in relation to p-nitrophenyl phosphate (pNPP)-(Km = 0.51 mM). Total phosphatase (pNPP) was inhibited in the presence of 10 mM vanadate (98%), 200 microM pervanadate (95%) and 100 microM p-chloromercuribenzoate (80%) but okadaic acid caused a slight increase in enzyme activity (25%). When the HL60 cells were treated with the phosphatase inhibitors (pervanadate and okadaic acid) for 24hours, only 20% residual activity was observed in presence of 200 microM pervanadate, whereas in the presence of okadaic acid this inhibitory effect was not observed. However, in respect to mitochondrial function, cell viability decreased about 80% in the presence of 100 nM okadaic acid. The total protein content was decreased 25% when the cells were treated with 100 nM okadaic acid in combination with 200 microM pervanadate. Our results suggest that both phosphatase inhibitors presented different mechanisms of action on HL60 cells. However, their effect on the cell redox status have to be considered.

Vanadate induces necrotic death in neonatal rat cardiomyocytes through mitochondrial membrane depolarization

Besides the well-known inotropic effects of vanadium in cardiac muscle, previous studies have shown that vanadate can stimulate cell growth or induce cell death. In this work, we studied the toxicity to neonatal rat ventricular myocytes (cardiomyocytes) of two vanadate solutions containing different oligovanadates distribution, decavanadate (containing decameric vanadate, V 10) and metavanadate (containing monomeric vanadate and also di-, tetra-, and pentavanadate). Incubation for 24 h with decavanadate or metavanadate induced necrotic cell death of cardiomyocytes, without significant caspase-3 activation. Only 10 microM total vanadium of either decavanadate (1 microM V 10) or metavanadate (10 microM total vanadium) was needed to produce 50% loss of cell viability after 24 h (assessed with MTT and propidium iodide assays). Atomic absorption spectroscopy showed that vanadium accumulation in cardiomyocytes after 24 h was the same when incubation was done with decavanadate or metavanadate. A decrease of 75% of the rate of mitochondrial superoxide anion generation, monitored with dihydroethidium, and a sustained rise of cytosolic calcium (monitored with Fura-2-loaded cardiomyocytes) was observed after 24 h of incubation of cardiomyocytes with decavanadate or metavanadate concentrations close to those inducing 50% loss of cell viability produced. In addition, mitochondrial membrane depolarization within cardiomyocytes, monitored with tetramethylrhodamine ethyl esther or with 3,3',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide, were observed after only 6 h of incubation with decavanadate or metavanadate. The concentration needed for 50% mitochondrial depolarization was 6.5 +/- 1 microM total vanadium for both decavanadate (0.65 microM V 10) and metavanadate. In conclusion, mitochondrial membrane depolarization was an early event in decavanadate- and monovanadate-induced necrotic cell death of cardiomyocytes.

Mitochondria as a target for decavanadate toxicity in Sparus aurata heart

In a previous in vivo study we have reported that vanadium distribution, antioxidant enzymes activity and lipid peroxidation in Sparus aurata heart are strongly dependent on the oligomeric vanadate species being administered. Moreover, it was suggested that vanadium is accumulated in mitochondria, in particular when V10 was intravenously injected. In this work we have done a comparative study of the effects of V10 and monomeric vanadate (V1) on cardiac mitochondria from S. aurata. V10 inhibits mitochondrial oxygen consumption with an IC(50) of 400 nM, while the IC(50) for V1 is 23 microM. V10 also induced mitochondrial depolarization at very low concentrations, with an IC(50) of 196 nM, and 55 microM of V1 was required to induce the same effect. Additionally, up to 5 microM V10 did inhibit neither F(0)F(1)-ATPase activity nor NADH levels and it did not affect respiratory complexes I and II, but it induced changes in the redox steady-state of complex III. It is concluded that V10 inhibits mitochondrial oxygen consumption and induces membrane depolarization more strongly than V1, pointing out that mitochondria is a toxicological target for V10 and the importance to take into account the contribution of V10 to the vanadate toxic effects.

Vanadate-induced cell death is dissociated from H2O2 generation

Vanadium is an environmentally toxic metal with peculiar and sometimes contradictory cellular effects. It is insulin-mimetic, it can either stimulate cell growth or induce cell death, and it has both mutagenic and antineoplastic properties. However, the mechanisms involved in those effects are poorly understood. Several studies suggest that H(2)O(2) is involved in vanadate-induced cell death, but it is not known whether cellular sensitivity to vanadate is indeed related to H(2)O(2) generation. In the present study, the sensitivity of four cell lines from different origins (K562, K562-Lucena 1, MDCK, and Ma104) to vanadate and H(2)O(2) was evaluated and the production of H(2)O(2) by vanadate was analyzed by flow cytometry. We show that cell lines very resistant to H(2)O(2) (K562, K562-Lucena 1, and Ma104 cells) are much more sensitive to vanadate than MDCK, a cell line relatively susceptible to H(2)O(2), suggesting that vanadate-induced cytotoxicity is not directly related to H(2)O(2) responsiveness. In accordance, vanadate concentrations that reduced cellular viability to approximately 60-70% of the control (10 mumol/L) did not induce H(2)O(2) formation. A second hypothesis, that peroxovanadium (PV) compounds, produced once vanadate enters into the cells, are responsible for the cytotoxicity, was only partially confirmed because MDCK cells were resistant to both vanadate and PV compounds (10 micromol/L each). Therefore, our results suggest that vanadate toxicity occurs by two distinct pathways, one dependent on and one independent of H(2)O(2) production.

Comparison of the effect of VOSO4, Na3VO4 and NaVO3 on proliferation, viability and morphology of H35-19 rat hepatoma cell line

This study presents the investigation and comparison the influence of VOSO4 [V(IV)I, Na3VO4 and NaVO3 [V(V)] in the range of 0.5-20.0 microM on the rat hepatoma cell line H35-19. The cells were tested with crystal violet (N-hexamethylpararosaniline), and counted in a Bürker chamber to determine their rate of proliferation, while the survival level was established with neutral red and MTT [bromide 3-(4,5-dimetyltioazo-2)-2,5-diphenyl-tetrazole]. Parallel independent pathomorphological studies with electron microscopic examinations were done. We found progressive growth inhibition of rat hepatoma H35-19 cells within the range 0.5-20.0 concentrations of three vanadium salts. The most effective (and/or toxic) was NaVO3, whereas VOSO4 showed a relatively mild action. As compared with metavanadate or vanadyl sulphate and especially organic vanadium derivatives, previously studied by the same authors under similar experimental conditions, sodium orthovanadate showed an intermediate effect. Electron microscopic examinations confirmed these results. Vanadium salts in low concentration in medium (0.5 microM) were observed to normalize cell morphology. Higher doses of vanadium salts (greater than 2.5 or 5.0 microM) resulted in damaging cell organelles and the more cytotoxic the compounds seemed to be.

Stress proteins (Hsp72/73, Grp94) expression pattern in rat organs following metavanadate administration. Effect of green tea drinking

Expression pattern of heat shock proteins (Hsp) 72/73 and glucose regulated protein (Grp) 94 was studied in liver, kidney and testis of rats injected with sublethal doses of ammonium metavanadate (5 mg/kg/day). In addition, some batches of animals were given green tea decoction, known to be rich in anti-oxidative compounds, as sole beverage in order to evaluate its protective properties. In control animals, the stress proteins expression was found to be organ-dependent: anti-Grp94 antibody revealed two bands at 96 and 98 kDa in kidney and liver whereas the 98 kDa band only was found in testis; anti-Hsp72/73 antibody revealed that the constitutive Hsp73 was present in all organs whereas the inducible Hsp72 was only present in kidney and testis. In kidney of vanadium-treated rats, Hsp73 was over-expressed by about 50% whereas Hsp72 was down-regulated by 50-80%. No such effects were observed in liver and testis. In liver and kidney of vanadium-treated rats, Grp94 was over-expressed by 50% and 150% respectively whereas no change was found in testis. In rats given green tea as sole beverage, the 96 kDa protein expression level in liver was reduced both in controls and in vanadium-treated animals. However, green tea drinking failed to prevent the vanadium-induced Hsp72 under-expression in kidney of vanadium-treated rats.

Critical roles of AMP-activated protein kinase in the carcinogenic metal-induced expression of VEGF and HIF-1 proteins in DU145 prostate carcinoma

Epidemiological and experimental animal data indicate that exposure to both metals and metalloid species exacerbates the risk of human diseases, particularly cancers. Vascular endothelial growth factor (VEGF), which performs a primary function in both tumor progression and angiogenesis, is up-regulated due to exposure to an array of carcinogenic metals, but the mechanisms responsible for the metal activation remain somewhat poorly understood. Recently, we demonstrated that AMP-activated protein kinase (AMPK), which acts as an energy sensor, providing metabolic adaptation effects under ATP-deprived conditions, is critical for the expression of VEGF under oxygen- and glucose-deprived conditions. As carcinogenic metals are potent VEGF expression inducers, we hypothesized that AMPK would also play a crucial role in metal-induced VEGF expression. Here, we present evidence that carcinogenic metals such as arsenite, vanadate, and cobalt, induce AMPK activation and VEGF expression via several different mechanisms, and that AMPK is able to regulate the expression of VEGF mRNA in a hypoxia-inducible factor-1-dependent or -independent manner, depending on the metal applied. We also attempted to characterize the relevant signal transduction pathways in metal-induced VEGF expression and AMPK activation, as well as the role of reactive oxygen species within this context. Overall, our data suggest that AMPK is a critical regulatory component in metal-induced VEGF expression, which further implies its intrinsic involvement in metal-induced carcinogenesis.

Characteristics of in vivo murine erythropoietic response to sodium orthovanadate

Current knowledge about the effects of vanadium compounds on erythropoiesis is still reduced and even contradictory. The aim of this work was to evaluate the in vivo effects of a single dose of sodium orthovanadate (OV, 33 mg/kg i.p.) on CF-1 mice in a time course study (0-8 days). Murine erythropoiesis was assessed through a combinatory of experimental approaches. Classical peripheral and bone marrow (BM) hematological parameters were determined. Erythroid maturation in blood stream and hemopoietic tissues (59Fe uptake assays), BM erythroid progenitor frequency (clonogenic assays) and erythroid crucial protein expressions for commitment and survival: GATA-1, erythropoietin receptor (Epo-R) and Bcl-xL (immunoblottings) were evaluated. Neither BM cellularities nor BM viabilities changed noticeably during the study. Peripheral reticulocytes showed a biphasic increment on days 2 and 8 post-OV. hematocrits enhanced transiently between days 2 and 4. 59Fe uptake percentages enhanced in peripheral blood nearly two-fold over control values between 4 and 8 days (p<0.01) without changes in BM and spleen. Additionally, mature erythroid BM compartments: polychromatophilic erythroblasts and orthochromatic normoblasts increased by the eighth day. BFU-E colonies remained near basal values during the whole experience, whilst CFU-E colonies raised 60% over control at 8 days post-OV (p<0.05). GATA-1 and Epo-R were significantly over-expressed from the third until the end of the experimental protocol (p<0.01). Surprisingly, Bcl-xL showed a constitutive expression pattern without changes during the experience. Experimental data let us suggest that OV does not to cause bone marrow cytotoxicity and that it accelerates maturation of BM committed erythroid precursors. Moreover, there are significant correlations among erythroid-related protein expressions: GATA-1 and Epo-R and the frequency of CFU-E. In addition, Bcl-xL expression invariance during the time course study would indicate that the stimulatory effect of OV treatment on erythropoiesis was mainly exerted on the maturation of red cell precursors rather than on the antiapoptosis of erythroid terminal progenitors.

Assessment of the in vivo genotoxicity of vanadate: Analysis of micronuclei and DNA damage induced in mice by oral exposure

Vanadium compounds are able to interact with living cells exerting a variety of biological effects. The pentavalent form is the most stable and toxic form of the element. In systems in vitro pentavalent vanadium is an effective genotoxic agent, inducing DNA damage and chromosome malsegregation at low doses. On the other hand, no adequate in vivo data are available for the characterization of the genotoxic hazard following oral intake, the most relevant route of human exposure. In this study, the genotoxic effects produced by the oral intake of sodium ortho-vanadate (Na(3)VO(4)) were investigated. Male CD-1 mice were treated for 5 weeks with a range of concentrations of Na(3)VO(4) in drinking water (0.75-1500 mg/l). Both micronuclei and primary DNA lesions as detected by comet assay were assessed in several tissues. Statistically significant increases of micronuclei in bone marrow were observed in mice receiving the two highest concentrations of Na(3)VO(4) (750 and 1500 mg/l). A significant increase of comet tail length was observed in splenocytes of mice receiving Na(3)VO(4) at 1500 mg/l, whereas no effect was observed in bone marrow and testis cells. No treatment-related effect on sperm chromatin structure or on testis cell population was observed. The determination of vanadium content in mouse tissues at the end of treatment highlighted a very low internal exposure, especially in soft tissues. Overall, the results obtained indicate that the genotoxic activity of pentavalent vanadium is expressed in vivo only following high dose exposure, possibly as a consequence of the poor bioavailability of the element.

Orthovanadate increased the frequency of aneuploid mouse sperm without micronucleus induction in mouse bone marrow erythrocytes at the same dose level

The objective of the current study was to investigate the ability of orthovanadate to induce aneuploidy in mouse sperm and micronuclei in mouse bone marrow cells at the same dose levels. The BrdU-incorporation assay was performed to test if the chemical treatment altered the duration of the meiotic divisions. It was found that orthovanadate (25mg/kg bw) treatment did not cause meiotic delay. To determine the frequencies of hyperhaploid and diploid sperm, male mice were treated by intraperitoneal (i.p.) injection with 5, 15 or 25mg/kg bw orthovanadate and sperm were sampled from the Caudae epididymes 22 days later. Fluorescence in situ hybridization (FISH) was performed with DNA-probes for chromosomes 8, X or Y. Significant increases in the frequencies of total hyperhaploid sperm (p<0.01) were found with 15 and 25mg/kg bw orthovanadate, indicating induced non-disjunction during male meiosis. The dose-response was described best by a linear equation. Orthovanadate did not significantly increase the frequencies of diploid sperm at any of the three doses tested, indicating that no complete meiotic arrest occurred. Orthovanadate was investigated also by the micronucleus test at i.p. doses of 1, 5, 15 or 25mg/kg bw, followed by bone marrow sampling 24h after treatment. None of the orthovanadate doses caused a significant increase in the rates of micronuclei (MN). Since the results show that orthovanadate induced non-disjunction during male meiosis without an accompanying induction of MN in bone marrow erythrocytes under the present experimental conditions and doses, it is concluded that male germ cells (meiosis) are more sensitive to the aneugenic effects of orthovanadate than somatic cells (mitosis). However, induction of micronuclei was reported in the literature with orthovanadate, vanadylsulfate and ammonium metavanadate, which contradicts the notion that vanadium compounds might be unique germ cell aneugens.

Vanadate oligomers: in vivo effects in hepatic vanadium accumulation and stress markers

The formation of vanadate oligomeric species is often disregarded in studies on vanadate effects in biological systems, particularly in vivo, even though they may interact with high affinity with many proteins. We report the effects in fish hepatic tissue of an acute intravenous exposure (12, 24 h and 7 days) to two vanadium(V) solutions, metavanadate and decavanadate, containing different vanadate oligomers administered at sub-lethal concentration (5 mM; 1 mg/kg). Decavanadate solution promotes a 5-fold increase (0.135 +/- 0.053 microg V(-1) dry tissues) in the vanadium content of the mitochondrial fraction 7 days after exposition, whereas no effects were observed after metavanadate solution administration. Reduced glutathione (GSH) levels did not change and the overall reactive oxygen species (ROS) production was decreased by 30% 24 h after decavanadate administration, while for metavanadate, GSH levels increased 35%, the overall ROS production was depressed by 40% and mitochondrial superoxide anion production decreased 45%. Decavanadate intoxication did not induce changes in the rate of lipid peroxidation till 12 h, but later increased 80%, which is similar to the increase observed for metavanadate after 24 h. Decameric vanadate administration clearly induces different effects than the other vanadate oligomeric species, pointing out the importance of taking into account the different vanadate oligomers in the evaluation of vanadium(V) effects in biological systems.

Decavanadate effects in biological systems

Vanadium biological studies often disregarded the formation of decameric vanadate species known to interact, in vitro, with high-affinity with many proteins such as myosin and sarcoplasmic reticulum calcium pump and also to inhibit these biochemical systems involved in energy transduction. Moreover, very few in vivo animal studies involving vanadium consider the contribution of decavanadate to vanadium biological effects. Recently, it has been shown that an acute exposure to decavanadate but not to other vanadate oligomers induced oxidative stress and a different fate in vanadium intracellular accumulation. Several markers of oxidative stress analyzed on hepatic and cardiac tissue were monitored after in vivo effect of an acute exposure (12, 24 h and 7 days), to a sub-lethal concentration (5 mM; 1 mg/kg) of two vanadium solutions ("metavanadate" and "decavanadate"). It was observed that "decavanadate" promote different effects than other vanadate oligomers in catalase activity, glutathione content, lipid peroxidation, mitochondrial superoxide anion production and vanadium accumulation, whereas both solutions seem to equally depress reactive oxygen species (ROS) production as well as total intracellular reducing power. Vanadium is accumulated in mitochondria in particular when "decavanadate" is administered. These recent findings, that are now summarized, point out the decameric vanadate species contributions to in vivo and in vitro effects induced by vanadium in biological systems.

Modulation of Protein Tyrosine Phosphatase Activity Alters the Subunit Assembly in Native N-Methyl-d-aspartate Receptor Complex

The N-methyl-D-aspartate (NMDA) receptor is crucial for development and neuroplasticity as well as excitotoxicity. The biochemical basis of the disassembly and reassembly of NMDA receptor has never been reported. Using coimmunoprecipitation, Western blotting, and mass spectrometry, we show that inhibition of tyrosine phosphatases triggers disassembly of NR1, NR2A, and NR2B in cortical NMDA receptor complexes. Furthermore, the disassembly of the NMDA receptor subunits is immediate, dose-dependent, and reversible and seems to occur through mechanisms linked to Src kinases. Together, these results define a novel role for tyrosine phosphatases in the complex mechanism of NMDA receptor regulation.

pdf1, a palmitoyl protein thioesterase 1 Ortholog in Schizosaccharomyces pombe: a yeast model of infantile Batten disease

Infantile Batten disease is a severe neurodegenerative storage disorder caused by mutations in the human PPT1 (palmitoyl protein thioesterase 1) gene, which encodes a lysosomal hydrolase that removes fatty acids from lipid-modified proteins. PPT1 has orthologs in many species, including lower organisms and plants, but not in Saccharomyces cerevisiae. The fission yeast Schizosaccharomyces pombe contains a previously uncharacterized open reading frame (SPBC530.12c) that encodes the S. pombe Ppt1p ortholog fused in frame to a second enzyme that is highly similar to a previously cloned mouse dolichol pyrophosphatase (Dolpp1p). In the present study, we characterized this interesting gene (designated here as pdf1, for palmitoyl protein thioesterase-dolichol pyrophosphate phosphatase fusion 1) through deletion of the open reading frame and complementation by plasmids bearing mutations in various regions of the pdf1 sequence. Strains bearing a deletion of the entire pdf1 open reading frame are nonviable and are rescued by a pdf1 expression plasmid. Inactivating mutations in the Dolpp1p domain do not rescue the lethality, whereas mutations in the Ppt1p domain result in cells that are viable but abnormally sensitive to sodium orthovanadate and elevated extracellular pH. The latter phenotypes have been previously associated with class C and class D vacuolar protein sorting (vps) mutants and vacuolar membrane H(+)-ATPase (vma) mutants in S. cerevisiae. Importantly, the Ppt1p-deficient phenotype is complemented by the human PPT1 gene. These results indicate that the function of PPT1 has been widely conserved throughout evolution and that S. pombe may serve as a genetically tractable model for the study of human infantile Batten disease.

Codelivery of a tea extract prevents morbidity and mortality associated with oral vanadate therapy in streptozotocin-induced diabetic rats

Oral administration of vanadate has a strong hypoglycemic effect but results in toxic side effects like life-threatening diarrhea. Tea is known to have potent antidiarrhea effects. We investigated the potential of suspending the vanadate in a tea decoction to reduce the diarrheatic action of vanadate. A concentrated extract of Lichee black tea was, therefore, added to sodium orthovanadate. Streptozotocin (STZ)-induced diabetic rats were orally gavaged with vanadate suspended in water or in the tea decoction, or with the tea extract alone. Blood glucose levels were assessed daily over 11 weeks with levels greater than 10 mmol/L warranting therapeutic intervention. Both the vanadate/water and vanadate/tea solutions acutely reduced blood glucose. The tea extract alone had no effect. The majority of vanadate/water-treated rats developed diarrhea and mortality rates approached 40%. Vanadate/tea-treated diabetic rats experienced no diarrhea or mortality and liver and kidney analyses (plasma ALT and creatinine, blood urea nitrogen [BUN], and urine-specific gravity) were normal. Animals treated with vanadate/tea retained blood glucose levels less than 10 mmol/L for an average of 24 consecutive days without subsequent treatments. Cataract formation was completely prevented. The mechanism of action of vanadate may have involved beta-cell stimulation because vanadate/tea-treated diabetic rats exhibited normal plasma insulin levels. In summary, because of its long-lasting effects, oral administration, and lack of side effects, vanadate/tea represents a potentially important alternative therapy for an insulin-deficient diabetic state.

Metavanadate causes cellular accumulation of copper and decreased lysyl oxidase activity

Selected indices of copper metabolism in weanling rats and fibroblast cultures were progressively altered in response to increased levels of sodium metavanadate. In diets, vanadium was added in amounts ranging from 0 to 80 microg V/g of diet, that is, 0-1.6 micromol V/g of diet. In fibroblast cultures, vanadium ranged from 0 to 400 nmol V/ml. The inhibition of P-ATPase-7A activity by metavanadate, important to copper egress from cells, was a primary focus. In skin, and tendon, the copper concentration was increased in response to increased dietary levels of metavanadate, whereas lysyl oxidase activity, a secreted cuproprotein, was reduced. The reduction in lysyl oxidase activity was also accompanied by reduced redox cycling potential of isolated fractions of lysyl oxidase, presumably due to reduced lysyltyrosyl quinone (LTQ) formation at the active site of lysyl oxidase. In contrast, liver copper concentrations and plasma ceruloplasmin activity were not affected by metavanadate exposure. However, semicarbazide-sensitive benzylamine oxidase (SCBO) activity, which was taken as an indirect measure of vascular adhesive protein-1 (VAP-1), was increased. In cultured fibroblasts, cellular copper was also increased and lysyl oxidase decreased in response to metavanadate. Moreover, the steady-state levels of atp7a and lysyl oxidase mRNAs were not affected by addition of metavanadate to culture medium up to 200 nmol/ml. Taken together, these data suggest that pathways involving copper egress and lysyl oxidase activation are particularly sensitive to metavanadate exposure through processes that are predominately posttranslational.

Vanadium--an element of atypical biological significance

The biological image of the transition element vanadium ferments a great deal of contradiction-from toxicity to essentiality. Importance of this element as micro-nutrient is yet to be unequivocally accepted by biologists and biomedical scientists. In spite of toxicity, it seems interesting to analyze the different biological roles of the element. Vanadium compounds have been proven to be associated with various implications in the pathogenesis of some human diseases and also in maintaining normal body functions. Salts of vanadium interfere with an essential array of enzymatic systems such as different ATPases, protein kinases, ribonucleases and phosphatases. While vanadium deficiency accounts for several physiological malfunctionings including thyroid, glucose and lipid metabolism, etc., several genes are regulated by this element or by its compounds, which include genes for tumor necrosis factor-alpha (TNF-alpha), Interleukin-8 (IL-8), activator protein-1 (AP-1), ras, c-raf-1, mitogen activated protein kinase (MAPK), p53, nuclear factors-kappaB, etc. All these seem to be not far from its recognition as an element of pharmacological and nutritional significance, which is revealed through its increasing therapeutic uses in diabetes. Vanadium is also emerging as a potent anti-carcinogenic agent. This review summarizes the developments related to vanadium biology as a whole by analyzing the general biochemical functions of vanadium.

Acute effects of vanadate oligomers on heart, kidney, and liver histology in the Lusitanian toadfish (Halobatrachus didactylus)

The contribution of vanadate oligomers to the acute histological effects of vanadium was analyzed in the heart, kidney, and liver of Halobatrachus didactylus (Schneider, 1801). A sublethal vanadium dose (5 mM, 1 mL/kg) in the form of metavanadate (containing ortho and metameric species) or in the form of decavanadate (containing only decameric species) was intraperitoneally administered by injection, and specimens of H. didactylus were sacrificed at one and seven days postinjection. Sections of heart ventricle and renal and hepatic tissue were stained with hematoxylin-eosin and examined by light microscopy to identify vanadium-induced tissue injury. In addition, PicroSirius-stained ventricular sections were analyzed by bipolarized light microscopy to determine the fraction of myocardium occupied by the ventricular wall structural elements (collagen I, collagen III, and cardiac muscle). Both vanadate solutions produced similar effects in the renal tissue. Morphological alterations included damaged renal tubules showing disorganized epithelial cells in different states of necrosis. Reabsorbed renal tubules and hyperchromatic interstitial tissue were also observed. The hepatic tissue presented hyperchromatic and hypertrophied nuclei, along with necrotic and hypertrophied hepatocytes, and more severe changes were observed in the liver with exposure to decavanadate. Vanadate oligomers promoted evident tissue lesions in the kidney and liver, but not in the cardiac tissue. However, cardiac tissue structural changes were produced. For example, decavanadate induced a hypertrophy of the ventricle due to a decrease in the percentage of myocardium occupied by collagen fibers. In general, decavanadate was shown to be more toxic than metavanadate.