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.

Vanadate, an inhibitor of tyrosine phosphatases, induced premature anaphase in oocytes and aneuploidy and polyploidy in mouse bone marrow cells

Protein tyrosine phosphatases are needed for activating maturation promoting factor, meiotic spindle assembly and spindle checkpoint inactivation. The protein phosphatase inhibitor vanadate was used to upset the kinase-phosphatase equilibrium during oocyte maturation (OM) and the metaphase anaphase transition (MAT) prior to cytogenetic analyses of mouse oocytes and bone marrow cells. ICR females received pregnant mare serum gonadotrophin (PMSG) and 48h later received human chorionic gonadotrophin (hCG). Vanadate doses of 0, 5, 15, and 25mg/kg were administered intraperitoneally immediately after hCG and ovulated oocytes and bone marrow cells were processed for cytogenetic analyses 18h after hCG. Data were analyzed by Chi-square and Fisher's exact tests. Vanadate induced different cytogenetic abnormalities in oocytes and in bone marrow cells. The frequencies of oocytes exhibiting premature anaphase (spontaneous activation) in vanadate exposed mice were significantly (P<0.01) elevated over controls; whereas, in bone marrow cells, the levels of tetraploidy, hyperploidy and premature centromere separation were significantly (P<0.01) increased by vanadate treatment. These results suggest that alteration of the kinase-phosphatase equilibrium during OM and the MAT leads to cytogenetic abnormalities that differ between oocytes and bone marrow cells.

Vanadium-induced apoptosis and pulmonary inflammation in mice: Role of reactive oxygen species

Pulmonary exposure to metals and metal-containing compounds is associated with pulmonary inflammation, cell death, and tissue injury. The present study uses a mouse model to investigate vanadium-induced apoptosis and lung inflammation, and the role of reactive oxygen species (ROS) in this process. Aspiration of the pentavalent form of vanadium, V (V), caused a rapid influx of polymorphonuclear leukocytes into the pulmonary airspace with a peak inflammatory response at 6 h post-exposure and resolution by 72 h. During this period, the number of apoptotic lung cells which were predominantly neutrophils increased considerably with a peak response at 24 h accompanied by no or minimum necrosis. After 24 h when the V (V)-induced inflammation was in the resolution phase, an increased influx of macrophages and engulfment of apoptotic bodies by these phagocytes was observed, supporting the role of macrophages in apoptotic cell clearance and resolution of V (V)-induced lung inflammation. Electron spin resonance (ESR) studies using lavaged alveolar macrophages showed the formation of ROS, including O(2)(*-), H(2)O(2), and (*)OH radicals which were confirmed by inhibition with free radical scavengers. The mechanism of ROS generation induced by V (V) involved the activation of an NADPH oxidase complex and the mitochondrial electron transport chain. The ROS scavenger, catalase (H(2)O(2) scavenger), effectively inhibited both lung cell apoptosis and the inflammatory response, whereas superoxide dismutase (SOD) (O(2)(*-) scavenger) and the metal chelator, deferoxamine (inhibitor of (*)OH generation by Fenton-like reactions) had lesser effects. These results indicate that multiple oxidative species are involved in V (V)-induced lung inflammation and apoptosis, and that H(2)O(2) plays a major role in this process.

Cadmium and vanadate oligomers effects on methaemoglobin reductase activity from Lusitanian toadfish: in vivo and in vitro studies

Cadmium and two vanadate solutions as 'metavanadate' (containing ortho and metavanadate species) and 'decavanadate' (containing decameric species) (5 mM) were injected intraperitoneously in Halobatrachus didactylus (Lusitanian toadfish), in order to evaluate the effects of cadmium and oligomeric vanadate species on methaemoglobin reductase activity from fish red blood cells. Following short-term exposure (1 and 7 days), different changes were observed on enzyme activity. After 7 days of exposure, 'metavanadate' increased methaemoglobin reductase activity by 67% (P < 0.05), whereas, minor effects were observed on enzymatic activity upon cadmium and 'decavanadate' administration. However, in vitro studies indicate that decameric vanadate, in concentrations as low as 50 microM, besides strongly inhibiting methaemoglobin reductase activity, promotes haemoglobin oxidation to methaemoglobin. Although decameric vanadate species showed to be unstable in the different media used in this work, the rate of decameric vanadate deoligomerization is in general slow enough, making it possible to study its effects. It is concluded that the increase in H. didactylus methaemoglobin reductase activity is more pronounced upon exposition to 'metavanadate' than to cadmium and decameric species. Moreover, only decameric vanadate species promoted haemoglobin oxidation, suggesting that vanadate speciation is important to evaluate in vivo and in vitro effects on methaemoglobin reductase activity.

Activation of JNK by vanadate induces a Fas-associated death domain (FADD)-dependent death of cerebellar granule progenitors in vitro

Apoptosis is a highly regulated process that plays a critical role in neuronal development as well as the homeostasis of the adult nervous system. Vanadate, an environmental toxicant, causes developmental defects in the central nervous system. Here, we demonstrated that vanadate induced apoptosis in cultured cerebellar granule progenitors (CGPs). Treatment of cultured CGPs with vanadate activated ERKs and JNKs but not p38 MAPK and also induced c-Jun phosphorylation. In addition, vanadate induced FasL production, Fas (CD95) aggregation, and its association with the Fas-associated death domain (FADD), as well as the activation of caspase-8. Furthermore, vanadate generated reactive oxygen species (ROS) in CGPs; however, ROS was not involved in vanadate-mediated MAPK activation. Vanadate-induced FasL expression was ROS-dependent but JNK-independent. In contrast, vanadate-elicited Fas aggregation and Fas-FADD association, as well as caspase-8 activation, were dependent on JNK activation but were minimally regulated by ROS generation. The hydrogen peroxide scavenger, catalase, blocked vanadate-induced FasL expression and partially mitigated vanadate-induced cell death. On the other hand, dominant negative FADD and caspase-8 inhibitor completely eliminated vanadate-induced apoptosis. Thus, JNK signaling plays a major role in vanadate-mediated activation of the Fas-FADD-caspase-8 pathway that accounts for vanadate-induced apoptosis of CGPs.

Mechanisms of vanadate-induced cellular toxicity: role of cellular glutathione and NADPH

Besides its insulin-mimetic effects, vanadate is also known to have a variety of physiological and pharmacological properties, varying from induction of cell growth to cell death and is also a modulator of the multidrug resistance phenotype. However, the mechanisms underlying these effects are still not understood. The present report analyzes the mechanisms of vanadate toxicity in two cell lines previously found to have different susceptibilities to this compound. It was shown that catalase and GSH reversed the sensitivity of a vanadate-sensitive cell line and NADPH sensitized vanadate-resistant cells. NADPH also increased the residues of P-Tyr and the induction of Ras protein expression in vanadate-resistant cells, while GSH avoided these effects in vanadate-sensitive cells. Thus, it seems that the effects of vanadate in signal transduction are dependent on NADPH and are related to cell death. Based on the effects observed in the present study it was suggested that once inside the cell, vanadate is reduced to vanadyl in a process dependent on NADPH. Vanadyl then may react with H2O2 generating primarily peroxovanadium species (PV) rather than following the Fenton reaction. The PV compounds formed would be responsible for P-Tyr increase, Ras induction, and cell death. The results obtained also point to vanadate as a possible chemotherapic in the use of multidrug-resistant tumors.

Effect of pirfenidone against vanadate-induced kidney fibrosis in rats

Renal fibrosis is a complication of kidney injury and can contribute to organ failure. Currently, there are no drugs for the treatment of renal fibrosis. Pirfenidone (PD) has been proven to have antifibrotic effects in animal models of fibrosis. We tested the ability of PD against vanadate-induced kidney fibrosis in rats. The rats were injected subcutaneously with vehicle or vanadate solution (1mg vanadate/kg/day) for 12 or 16 days to produce varying degrees of kidney fibrosis. The vanadate- and vehicle-treated rats were fed a laboratory diet or the same diet mixed with 0.6% PD ad lib. One vanadate-injected group was initially fed the same diet without PD and later switched to the diet containing PD 2 days after the last injection. The rats were killed at 12 and 25 days following the last dose. The changes found in the kidney of vanadate-treated rats included increases in RNA and DNA content and increases in kidney weight. Treatment with PD diminished the vanadate-induced increases in kidney weight and RNA content. The hydroxyproline content of the kidney in vanadate-treated animals was increased significantly (P< or =0.05) from the control level of 1452 microg/kidney to 1765 microg/kidney. Treatment with PD for 37 days caused significant reductions in the vanadate-induced increases in the hydroxyproline level. Similarly, treatment for 41 days also caused significant reductions (1744 microg/kidney) in vanadate-induced increases in the hydroxyproline level (1996 microg/kidney). The histological evaluation revealed that the severity of the lesions in the vanadate-treated group was moderate to severe, and treatment with PD for 41 days decreased the severity to a mild level. In addition, the delayed treatment with PD also minimized the vanadate-induced increases in the collagen content of the kidney. Although it is speculative, PD may potentially be therapeutic in the management of renal fibrosis.

MAPKs mediate S phase arrest induced by vanadate through a p53-dependent pathway in mouse epidermal C141 cells

Mitogen-activated protein (MAP) kinases play an important role in mediation of the signal transduction pathway in cellular response to genotoxic stress. Cell growth arrest is considered as an early stage in response to the genotoxic stress. p53 is well-known as a tumor suppression gene involved in both cell growth arrest and apoptosis. The present study investigated the involvement of MAP kinases in vanadate-induced cell growth arrest and the relationship of p53. DNA content analysis showed that vanadate-induced S phase arrest is time- and dose-dependent in p53 wild-type C141 cells but not in p53-deficient C141 cells. Western blotting results indicated that vanadate caused an inactivation of p-cdk2 at Thr160, which is an important kinase for the progression of S phase, and an increase in expression of p21, which is a key for S phase arrest. In p53-deficient cells, vanadate did not induce any observable change in p21 or p-cdk2 level. In addition, vanadate up-regulated phospho-p38 and ERK, two members of MAP kinases. At the same time, vanadate increased the p53 activity as measured by luciferase assay. Addition of PD98059 and SB202190, inhibitors of ERK and p38, respectively, decreased vanadate-induced S phase arrest, reduced p21 levels, restored activation of p-cdk2, and decreased p53 activity. The study demonstrated that vanadate-induced S phase arrest is mediated by both ERK and p38 in a p53-dependent pathway.

Oxidative stress in toadfish (Halobactrachus didactylus) cardiac muscle. Acute exposure to vanadate oligomers

Vanadate solutions as "metavanadate" (containing ortho and metavanadate species) and "decavanadate" (containing mainly decameric species) (5 mM; 1 mg/kg) were injected intraperitoneously in Halobatrachus didactylus (toadfish), in order to evaluate the contribution of decameric vanadate species to vanadium (V) intoxication on the cardiac tissue. Following short-term exposure (1 and 7 days), different changes on antioxidant enzyme activities-superoxide dismutase (SOD), catalase (CAT), selenium-glutathione peroxidase (Se-GPx), total glutathione peroxidase (GPx), lipid peroxidation and subcellular vanadium distribution were observed in mitochondrial and cytosolic fractions of heart ventricle toadfish. After 1 day of vanadium intoxication, SOD, CAT and Se-GPx activities were decreased up to 25%, by both vanadate solutions, except mitochondrial CAT activity that increased (+23%) upon decavanadate administration. After 7 days of exposure, decavanadate versus metavanadate solutions promoted different effects mainly on cytosolic CAT activity (-56% versus -5%), mitochondrial CAT activity (-10% versus +10%) and total GPx activity (+1% versus -35%), whereas lipid peroxidation products were significantly increased (+82%) upon 500 microM decavanadate intoxication. Accumulation of vanadium in total (0.137+/-0.011 microg/g) and mitochondrial (0.022+/-0.001 microg/g) fractions was observed upon 7 days of metavanadate exposure, whereas for decavanadate, the concentration of vanadium increased in cytosolic (0.020+/-0.005 microg/g) and mitochondrial (0.021+/-0.009 microg/g) fractions. It is concluded that decameric vanadate species are responsible for a strong increase on lipid peroxidation and a decrease in cytosolic catalase activity thus contributing to oxidative stress responses upon vanadate intoxication, in the toadfish heart.

Effect of oxovanadium(IV) complexes on nondiabetic and streptozotocin-diabetic rats

The effects of vanadium complexes with organic ligands, [VO(phen)2]SO4.3H2O, [VO(bpy)2]SO4.2H2O, and [VOCl2(Hmcp)2H2O], on blood glucose and plasma lipid levels were studied in nondiabetic and streptozotocin-diabetic rats and compared to that of [VO(mal)2] (the reference compound). The present results provide evidence that the compounds examined possess lower toxicity than [VO(mal)2]. One of the compounds examined, viz. [VO(bpy)2]SO4.2H2O, decreases, statistically significantly, the glucose level and a second one, viz. [VOCl2(Hmcp)2H2O], decreases, also significantly, the total cholesterol level.

A short low-level exposure to metavanadate during a cell cycle-specific interval of time is sufficient to permanently derange the differentiative properties of Mel cells

Mouse erythroleukemia (Mel) cells have a cell cycle-dependent high sensitivity to chemical and physical mutagens. This report shows that a 5 h exposure to 0.1 or 0.01 microg/ml metavanadate during the initial period of erythroid differentiation induction was sufficient to permanently damage the ability of treated Mel cells and their progeny to undergo erythroid differentiation, without affecting cell viability and proliferation. Conversely, a 5 h pulse of metavanadate at 1 or 10 microg/ml inhibited both differentiation and cell proliferation. The cell cycle-dependent period of mutagenesis was essential for fixation of damage in the cell genome and the progeny of the cells treated with 0.1 or 0.01 microg/ml metavanadate stably inherited an impaired capacity to differentiate. The efficiency of the DNA repair synthesis machinery during the specific period of exposure of Mel cells seemed directly involved in damage fixation. In fact, the mutagenic effects of a 0.1 microg/ml metavanadate pulse was further increased in the presence of 1 mM hydroxyurea, an inhibitor of DNA repair synthesis. In contrast, 5 microg/ml vanillin, an antimutagenic agent that stimulates repair, completely restored the capacity of progeny of cells treated with 0.1 microg/ml metavanadate to complete differentiation. Determination of [(3)H]deoxythymidine in acid-insoluble DNA indicated that incorporation was stimulated by metavanadate alone and was further increased by metavanadate plus vanillin; conversely, incorporation of thymidine was reduced in the presence of hydroxyurea. The capacity of metavanadate to permanently damage Mel cell erythroid differentiation appeared to depend on the cell cycle-related efficiency of the DNA repair systems, activated to correct the induced alteration, rather than on a specific concentration.

Respective roles of protein tyrosine kinases and protein kinases C in the upregulation of beta-catenin distribution, and compaction in mouse preimplantation embryos: a pharmacological approach

The cellular distribution of beta-catenin was determined by western blotting and laser confocal scanning microscopy in both control and pharmacologically-manipulated mouse preimplantation embryos. Most of the stored maternal beta-catenin is Triton X-100-extractable and distributed throughout the cytoplasm. In 2-cell stage embryos, the remaining molecules are concentrated in regions of cell contact and, to a lesser extent, at non apposed surfaces. Association of beta-catenin with the cortex of non apposed membranes decreases as cleavage proceeds, and is lost at compaction. In contrast to the rapid cross-linking of cell surfaces induced by wheat germ agglutinin, the diacylglyceride-induced compaction-like adhesion of 2- and 4-cell embryos correlates with complete restriction of beta-catenin to the apposing membranes. On the contrary, tyrphostin B46, a specific protein tyrosine kinase inhibitor, fails to induce both premature beta-catenin relocalisation and compaction. In addition, we show that orthovanadate induces a dramatic increase in the level of phosphotyrosine labelling of cell-cell junctions in compacted 8-cell stage embryos without inducing their decompaction. However, most of these orthovanadate tyrosine-phosphorylated proteins are detergent-soluble, while beta-catenin restricted to the apposing membranes is not. In conclusion, our results confirm that diacylglycerol-dependent kinases upregulate both beta-catenin redistribution and compaction, and indicate that neither tyrosine kinases, nor tyrosine phosphatases are critical for the proper onset of compaction which seems, in addition, not causally linked to tyrosine dephosphorylation of beta-catenin.

Vanadate is toxic to adherent- growing multidrug-resistant cells

The development of multidrug resistance (MDR) is the primary cause of failure of cancer chemotherapy and circumventing this problem is a major challenge in oncology. Vanadate is known to inhibit the ATPase activity of the P-glycoprotein and multidrug-resistant associated protein. In the present study we show that adherent MDR cells are more sensitive to vanadate than adherent non-MDR ones, but the same is not true for suspension-growing cells. Vanadate induced stress fiber in the non-MDR adherent MDCK cell line, but destroyed the actin fibers of MDCK/60 and MA104 cells, two adherent MDR cell lines, suggesting that the sensitivity of these cells to vanadate is related to their actin cytoskeleton. The results suggest that vanadate may be used as an adjuvant in the chemotherapy of solid tumors, not only as an ATPase inhibitor but also because of its effect in the MDR cell cytoskeleton.

Vanadate-induced activation of activator protein-1: role of reactive oxygen species

The present study was undertaken to test the hypothesis that the toxicity and carcinogenicity of vanadium might arise from elevation of reactive oxygen species leading to activation of the transcription factor activator protein-1 (AP-1). The AP-1 transactivation response has been implicated as causal in transformation responses to phorbol esters and growth factors. To investigate the possible activity of vanadium in the activation of AP-1, we treated mouse epidermal JB6 P+ cells stably transfected with an AP-1 luciferase reporter plasmid with various concentrations of vanadate. This resulted in concentration-dependent transactivation of AP-1. Superoxide dismutase (SOD) and catalase inhibited AP-1 activation induced by vanadate, indicating the involvement of superoxide anion radical (O2-*), hydroxyl radical (*OH) and/or H2O2 in the mechanism of vanadate-induced AP-1 activation. However, sodium formate, a specific *OH scavenger, did not alter vanadate-induced AP-1 activation, suggesting a minimal role for the *OH radical. NADPH enhanced AP-1 activation by increasing vanadate-mediated generation of O2-*. N-acetylcysteine, a thiol-containing antioxidant, decreased activation, further showing that vanadate-induced AP-1 activation involved redox reactions. Calphostin C, a specific inhibitor of protein kinase C (PKC), inhibited activation of AP-1, demonstrating that PKC is involved in the cell signal cascades leading to vanadate-induced AP-1 activation. Electron spin resonance (ESR) measurements show that JB6 P+ cells are able to reduce vanadate to generate vanadium(IV) in the presence of NADPH. Molecular oxygen was consumed during the vanadate reduction process to generate O2-* as measured by ESR spin trapping using 5,5-dimethyl-L-pyrroline N-oxide as the spin trapping agent. SOD inhibited the ESR spin adduct signal, further demonstrating the generation of O2-* in the cellular reduction of vanadate. These results provide support for a model in which vanadium, like other classes of tumor promoters, transactivates AP-1-dependent gene expression. In the case of vanadium, AP-1 transactivation is dependent on the generation of O2-* and H2O2, but not *OH.

Reactive oxygen species signaling through regulation of protein tyrosine phosphorylation in endothelial cells

Tyrosine phosphorylation of proteins, controlled by tyrosine kinases and protein tyrosine phosphatases, plays a key role in cellular growth and differentiating. A wide variety of hormones, growth factors, and cytokines modulate cellular tyrosine phosphorylation to transmit signals across the plasma membrane to the nucleus. Recent studies suggest that reactive oxygen species (ROS) also induce cellular protein tyrosine phosphorylation through receptor or nonreceptor tyrosine kinases. To determine whether protein tyrosine phosphorylation by ROS regulates endothelial cell (EC) metabolism and function, we exposed vascular ECs to H2O2 or H2O2 plus vanadate. This resulted in a time- and dose-dependent increase in protein tyrosine phosphorylation of several proteins (M(r) 21-200 kDa), as determined by immunoprecipitation and Western blot analysis with antiphosphotyrosine antibody. Immunoprecipitation with specific antibodies identified increased tyrosine phosphorylation of mitogen-activated protein kinases (42-44 kDa), paxillin (68 kDa), and FAK (125 kDa) by ROS. An immediate signaling response to increased protein tyrosine phosphorylation by ROS was activation of phospholipases such as A2, C, and D. Suramin pretreatment inhibited ROS stimulation of phospholipase D (PLD), suggesting a role for growth factor receptors in this activation. Further, PLD activation by ROS was attenuated by N-acetylcysteine, indicating that intracellular thiol status is critical to ROS-mediated signal transduction. These results provide evidence that ROS modulate EC signal transduction via a protein tyrosine phosphorylation-dependent mechanism.

Vanadium as a factor that disturbs phosphorus metabolism in nervous tissue

Vanadium and its derivatives are the well-known environmental pollutants. We obtained that ammonium vanadate suppressed the alkaline (AlP) and acid (AcP) phosphatases activity in the variety of tissues. Vanadate inhibited the enzymes that take part in phosphoryl transfer reactions. Successive concentration-dependent decrease in AlP and AcP activities by vanadate (0.1 mM-1 mM) has been obtained in rat nervous tissue. Moreover, the observed reduction in the sensitivity of the enzymes to vanadate ions becomes more pronounced at the transition from higher and relatively young regions of nervous system to its more ancient parts. Phosphoprotein phosphatase (PP) activity has also been inhibited in various structures of brain tissue; in spinal cord, however, vanadate in comparatively low concentrations (10 microM) caused a steep rise in the enzyme activity. Only at high concentration (1 mM) vanadate exert the effect of moderate inhibition. The possibility of the existence of phylogenetically different molecular forms of nervous tissue PPs differed by their sensitivity to vanadate was supported in our comparative examination.

Influence of glycine on the damage induced in isolated perfused rat liver by five hepatotoxic agents

Livers of fasted rats were perfused over 120 min in a recirculating hemoglobin-free system. Hepatotoxic injury induced by the addition of 1-butanol (130.2 mmol/l), CdCl2 (0.1 mmol/l), CuCl2 (0.03 mmol/l), Na3VO4 (2 mmol/l) or t-butylhydroperoxide (t-BuOOH, 0.5 mmol/l) to the perfusate was shown by strong increases in lactate dehydrogenase (LDH) and glutamate-pyruvate transaminase (GPT) release, decreased oxygen consumption between 50 and 60%, and a nearly complete suppression of bile flow. Hepatic adenosine triphosphate (ATP) and reduced glutathione (GSH) concentrations were reduced by between 30 and 80%, and 20 and 80% respectively. Only Na3VO4 and t-BuOOH evoked increased releases of glutamate dehydrogenase (GLDH) in the perfusate. Malondialdehyde (MDA) concentrations were enhanced by all toxicants in the perfusate and by all except 1-butanol in the liver. The MDA increase, however, was much higher after Na3VO4 and t-BuOOH than after the other toxicants. When glycine (12 mmol/l) was added 30 min before the toxicants to the perfusate it prevented the enzyme releases induced by all hepatotoxic agents by about 80%. Furthermore, glycine prevented the Na3VO4 induced increase of MDA in liver and perfusate, the hepatic ATP and GSH level reductions induced by 1-butanol and attenuated the reduction of oxygen consumption induced by CuCl2 and t-BuOOH. Glycine, however, did not reverse the reductions of oxygen consumption induced by CdCl2 and Na3VO4, the suppressions of bile flow and, with the exception of 1-butanol, the decreases of hepatic ATP levels induced by all agents.

The mitogen-activated protein kinase pathway contributes to vanadate toxicity in vascular smooth muscle cells

Vanadate has been considered in the treatment of diabetes because of its insulin-like effects. However, it has severe toxic effects in both animal and man. In cultured cells, vanadate can either cause death or be growth stimulatory, depending on the cell type and growth conditions. Here, we report that in baboon aortic smooth muscle cells (SMCs), vanadate induced p42/p44 mitogen-activated protein kinase (MAPK) activity. This effect was abolished in the presence of the specific MAPK kinase (MAPKK) inhibitor PD098059. Although activation of p42/p44MAPK/MAPKK is generally thought to be necessary for proliferation, in SMCs, vanadate did not promote DNA synthesis and inhibited thymidine incorporation stimulated by platelet-derived growth factor (PDGF)-BB in a dose dependent fashion (IC50: 30 microM). Prolonged exposure to vanadate exerted cytotoxic effects. Cells retracted, rounded up and detached from the substratum. These vanadate-induced morphological changes were blocked in the presence of PD098059. The addition of PDGF-BB further activated p42/p44MAPK/MAPKK in the presence of vanadate and substantially increased vanadate toxicity. We conclude from these observations that activation of the p42/p44MAPK/MAPKK signalling module contributes to the cytotoxic effects induced by vanadate.

[Teratogenic effect of ammonium metavanadate in Swiss albino mice]

Far as it is known to us, there is only one report in the medical literature dealing with the teratogenous effect of vanadium on neural structures (1): while trying to experimentally induce anencephaly in the offsprings of swiss-albino mice through the administration of ammonium metavanadate via drinking water, during different stages of their lives; a neural tube defect consisting of arrhinencephaly was obtained; various degrees of hypoplasia or aplasia of both the olfactory bulbs and tracts were evidenced, as well as congenital lesions of variable intensity in other rhinencephalic structures. The probable mechanisms through which vanadium exercises its neural teratogenous effect are analyzed.

[Teratogenic effects of ammonium metavanadate on the CNS of the offspring of albino rats. A histological and histochemical study]

The vanadium is a metallic oligoelement present in the majority of tissues. Its abnormal biological disposal environment can be related with its possible teratogenicity and alteration in the contents of glycosaminoglycans acids (GAGs), which participate in the morphological processes and the maturation of Central Nervous System (CNS). The proposal of the project is to analyze the teratogenic effect of ammonium metavanadate (AMV) and its action on the GAGs in the CNS of the litter of albino rats. The ammonium metavanadate was diluted in distilled water in concentration of 100 and 200 ppm, drunk by the rats since their birth and/or weaning to adult age, except during the matching and gestation. The animals control drunk water without this metal. The litter were analyzed to detect possible congenital malformations, then CNS were removed of descendents and were processed by light microscope, cuts of 6 u were stained with H/E; Alcian Blue pH 3.5 and 5.6, this last one concentrations of C12Mg from 0.05 M to until 1.0 M. Previously parallels sections were treated with testicular hyaluronidase. The macroscopic analysis of the new born rats that came from rats that received AMV in concentrations 100 and 200 ppm, resulted in congenital anomalies like unilateral hypoplasia of olfactory bulbs and cerebral hemisphere. The microscopic analysis revealed changes in the layers patron of olfactory bulbs and an increased of alcianophilia in the pH 5.6 to 0.2 M MgC12, in the extracellular matrix of CNS of rats descendents treated with AMV to the dose 200 ppm, sensibles to the testicular hyaluronidase, corresponding to hyaluronic acid (HA) and chondroitin 4 and/or 6 sulphate (C4S or C6S) of low grade of sulphation. These results suggest that the AMV given to albino rats has a teratogenic result when it is used before the gestation and for long periods of animals life that alter the of GAGs of CNS contents during the development.

[Genotoxic effects of vanadium compounds]

Vanadium is a metal member of the periodic table VB group, with atomic weight 59.95 and atomic number 23 and it has some oxidizing states from -1 to +5. Vanadium has many industrial uses and its contribution with environmental contamination is growing every day. In the last 10 years research about the vanadium effects on living beings, has been increasing substantially, due to its presence in the environment from different sources. Interest for vanadium and their compounds is because its toxic effects and uses in some biomedical areas: such as antineoplastic, cholesterol and glucose level blood, diuretic, oxygen haemoglobin affinity. Vanadium toxic effects are so due to the fact of its property of inhibiting many enzymatic systems. Vanadate and vanadyl ions make chemical complexes exhibiting the property of inhibiting or increasing the activity of the enzymes participating in the DNA and RNA synthesis. They also induce mutagenic and genotoxic effects. Biochemical assays show cytotoxic effects, increase in the cellular differentiation, gene expression alterations and other biochemical and metabolic alterations. Research has been done with in vitro systems, but few with laboratory animals. It is necessary to carry out more work in the field of genetic toxicology with vanadium compounds. This type of compounds may be considered mutagenic and genotoxic, with cytotoxic and aneuploidogenous effects.

[Changes in female reproduction induced by ammonium metavanadate in Swiss albino mice]

Female reproduction alterations induced by vanadium salts, taken in periods no related with mating/gestation, correlated with histological alterations has not been reported. Vanadium is a metal from VB group of periodical table, and it has been detected in high concentrations in heavy petroleum produced in this region of our country, there have not had investigations about vanadium effect on species reproduction. In this work 100 and 200 ppm doses of ammonium vanadate (A.M.V.) prepared with demineralized water were administered orally to swiss albino mice in different periods. The administration of vanadium salt was suspended before mating. Pregnant mice were allowed to deliver and a statistical analysis were performed to pregnancy percent and pups means. Non pregnant mice were killed after 21 days of mating. Uterus and ovaries were weight, luteal bodies were counted and histological samples of ovaries were prepared. The results shown a non significative increase of pregnancy (p < 1) in mice exposed from weaning to adult, for animals exposed to maximum concentrations 200 ppm a significative reduction of pregnancy (p = 0.00001), to mean pups were detected (z = 0.68), and number of luteal bodies (s = 3.3 +/- 0.5). The microscopic observation shown polycystic ovary, atresic follicular increasing, follicle in mature stage and luteal bodies; hard decreasing; hard depletion was observed in thecoluteic cells of luteal bodies. A.M.V. modify reproduction even though if exposition have been made in period before mating and pregnancy. As doses and exposition periods increase detrimental effects induces alteration in the follicular phase and luteal of ovarian cycle. Epidemiological and genetic studies are recommended in regions where vanadium concentrations are high, and the drinking water and foods are contaminated with this metal, in order to know how it affect human reproduction.

[Toxic effects of ammonium metavanadate on the growth and number of the offspring of Swiss albino mice]

The present research show, an statistical study of the effects of ammonium metavanadate (AMV) on size, weight and number of offsprings of 56 albino swiss mice (male and female) was carried out. These mice ingested AMV in concentration of 100 and 200 ppm "ad libitum" since birth, continuing throughout breasting until mating. The control group received water free from the metal. The statistical results, obtained by the Duncan and Tukey method, were the following: a significant drop in body size in 200 ppm concentration of AMV, and in tail size in a concentrations of 100 and 200 ppm. A significant increase was observed in the number of the offsprings on the groups treated with AMV on a concentration of 200 ppm with respect to the control group.

Effects of vanadium upon polyl:C-induced responses in rat lung and alveolar macrophages

Hosts exposed to vanadium (V) display a subsequent decrease in their resistance to infectious microorganisms. Our earlier studies with rats inhaling occupationally relevant levels of V (as, ammonium metavanadate, NH4VO3) indicated that several nascent/inducible functions of pulmonary macrophages (PAM) were reduced. In the present study, V-exposed rats were examined to determine whether some of the same effects might also occur in situ. Rats were exposed nose-only to air or 2 mg V/m3 (as NH4VO3) for 8 h/d for 4 d, followed, 24 h later, by intratracheal (it) instillation of polyinosinic:polycytidilic acid (polyl:C) or saline. Analysis of lavaged lung cells/fluids after polyl:C instillation indicated that total lavageable cell/neutrophil numbers and protein levels, while significantly elevated in both exposure groups (as well as in saline-treated V-exposed rats), were always greater in V-exposed hosts. Exposure to V also affected the inducible production of interleukin 6 (IL-6) and interferon gamma (IFN gamma), but apparently not that of tumor necrosis factor-alpha (TNF alpha) or IL-1. Although polyl:C induced significant increases in lavage fluid IL-6 and IFN gamma levels in both exposure groups, levels were greater in V-exposed rats. If calculated with respect to total lavaged protein, however, V-exposed rats produced significantly less cytokine. Following polyl:C instillation, there were no marked exposure-related differences in basal or stimulated superoxide anion production by pooled lavaged cells or PAM specifically. With V-exposed rats, pooled cells recovered 24 h after saline instillation displayed reduced production (in both cases) compared to the air control cells; PAM-specific production was affected only after stimulation. In both exposure groups, polyl:C caused decreased superoxide production in recovered cells. Though less apparent with pooled cells, there was a time post polyl:C instillation-dependent decrease in stimulated PAM-specific superoxide production; this effect was greater in PAM from V-exposed rats than in PAM from air controls. Phagocytic activity of PAM from rats in both exposure groups was significantly increased by polyl:C instillation, although total activity in cells obtained from V-exposed rats was always significantly lower compared to air control cells. Our results indicate that short-term, repeated inhalation of occupationally relevant levels of V by rats modulates pulmonary immunocompetence. Modified cytokine production and PAM functionality in response to biological response modifiers (such as lipopolysaccharide, IFN gamma, or polyl:C) may be, at least in part, responsible for the increases in bronchopulmonary disease in humans occupationally exposed to V.