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2-Acetyl-1,3-cyclopentanedione-oxovanadium(IV) complexes. Acidity and implications for gastrointestinal absorption.

Since vanadyl sulphate has demonstrated insulin-like effects on glucose metabolism in animal and human trials, and organic vanadium complexes are better absorbed by the intestinal tract than vanadyl species, in this work the complexation of oxovanadium(IV) with 2-acetyl-1,3-cyclopentanedione is studied. Kinetic and equilibria in aqueous 1:1 chelation are investigated spectrophotometrically in aqueous solution at 25 degrees C. The mechanism proposed to account for the kinetic data involves a reversible pathway where VO(+2) reacts with the enolate ion of the ligand. From calculated kinetic and thermodynamic parameters, it can be expected that the rates between final and initial monocharged complex concentration could help a better control of the absorption through the lipophilic membranes in the intestinal tract.

Animals↗

A new orally active antidiabetic vanadyl complex--bis(alpha-furancarboxylato)oxovanadium(IV).

Bis(alpha-furancarboxylato)oxovanadium(IV)--a new orally active antidiabetic vanadyl complex has been synthesized, characterized, and tested for bioactivity as insulin-enhancing agents. The complex was administered intragastrically to both normal and STZ-diabetic rats for 4 weeks. The results show that the complex at a dose of 10.0 and 20.0 mg V kg(-1), could significantly lower the blood glucose level rats and ameliorated impaired glucose tolerance in STZ-diabetic, but not in normal rats. It was suggested that the complex exerted an antidiabetic effect in STZ-diabetic rats, which maybe was related to increasing the sensitivity to insulin.

Administration, Oral↗

Synthesis and characterization of mononuclear oxovanadium(IV) complexes and their enzyme inhibition studies with a carbohydrate metabolic enzyme phosphodiesterase I.

The increasing interest in vanadium coordination chemistry is based on its well-established chemical and biological functions. A beta-diketonato complex of oxovanadium(IV) is known to be having numerous catalytic applications and also exhibits promising insulin mimetic properties. In continuation of our structure activity relationship studies of metal complexes, we report herein the synthesis and characterization of the vanadium complexes of beta-diketonato ligand system with systematic variations of electronic and steric factors. Two complexes, VO(tmh)(2) (tmh = 2,2,6,6,-tetramethyl-3,5-heptanedione), and VO(hd)(2) (hd = 3,5-heptanedione) were synthesized and characterized by using different spectroscopic techniques. Elemental and mass spectral analysis supports the presence of two beta-diketonato ligands per VO(2+) unit. UV-Vis spectra in different solvents indicate coordination of coordinating solvent molecules at sixth position resulting in red shift of the band I transition. NMR and IR spectra reveal binding of coordinating solvent molecule at vacant sixth position trans to oxo group without releasing beta-diketonato ligands. Enzyme inhibition studies of these and other related oxovanadium(IV) complexes with beta-diketonato ligand system are conducted with snake venom phosphodiesterase I (SPVDE). All of these complexes showed significant inhibitory potential and were found to be non-competitive inhibitors against this enzyme.

Animals↗

Vanadium (V) peroxocomplexes: structure, chemistry and biological implications.

A short account on the identification in solution of diverse type of vanadium peroxocomplexes is offered. The methodology used is a combination of several techniques, i.e., multinuclear NMR spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and theoretical calculation. The analysis has been carried out in aqueous alcoholic solutions, and in some case also in the presence of appropriate ligands, in order to model some of the natural conditions where vanadium-dependent haloperoxidase enzymes (VHPO) work. With the results obtained, it has been possible to shed light on important aspects of the catalytic cycle of VHPO. Furthermore, a number of synthetic aspects of the reactivity of the various vanadium peroxocomplexes is reviewed.

Histidine↗

Synthesis, characterisation and insulin-mimetic activity of oxovanadium(IV) complexes with amidrazone derivatives.

The complexation of VO(2+) ion by ten acetamidrazone and 2-phenylacetamidrazone derivatives (L) was studied. Sixteen novel VO(2+) complexes were synthesised and characterised through the combined application of analytical and spectroscopic (EPR (electron paramagnetic resonance), FT-IR and diffuse reflectance electronic absorption) techniques. Eight are 1:2 species of composition [VOL(2)]SO(4) x xH(2)O and eight are 1:1 species with formula [VOL(SO(4))](n) x xH(2)O. The experimental data suggest a bidentate coordination mode for L with the donor set formed by the imine nitrogen and the carbonyl oxygen. EPR spectra indicate a square-pyramidal geometry for the 1:1 complexes and a penta-coordinated geometry intermediate between the square-pyramid and the trigonal-bipyramid for the 1:2 species. The hyperfine coupling constant along z axis, A(z), of the 1:2 complexes exhibits a marked reduction with respect to the predicted value (approximately 148x10(-4)cm(-1) vs. approximately 170x10(-4)cm(-1)). IR spectroscopic evidence supports the presence of sulphate as a counter-ion in the 1:2, and as a bridging bidentate ligand in the 1:1 complexes. Insulin-mimetic tests on modified fibroblasts, based on a modified MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide) assay, performed on three of the bis-chelated and eight of the mono-chelated derivatives, indicate that they are biologically active. The similar hydro/lipophilicity and the lack of ligand substituents recognizable by cell membrane receptors prevent substantial differentiation in the insulin-mimetic action.

Amides↗

Two new scorpionates vanadium haloperoxidases model complexes: synthesis and structure of VO(O2)(pzH)(HB(pz)3) and VO(O2)(pzH)(B(pz)4) (pzH = pyrazole(C3H4N2)).

Using vanadate, poly(1H-pyrazol-1-yl)borate and pyrazole as starting materials, two new neutral peroxovanadium(V) complexes with poly(1H-pyrazol-1-yl)borate, VO(O(2))(pzH)(HB(pz)(3))(1) and VO(O(2))(pzH)(B(pz)(4))(2), were synthesized successfully. Both complexes were characterized by elemental analysis, IR, UV-vis and NMR spectra. And the structure of complex 1 was determined by X-ray diffraction, which is somewhat relevant for haloperoxidase enzymes. Cytotoxic effects also are discussed on 3T3 cell proliferation. In the concentration range (0.1-100mumol), both complexes have an inhibiting cellular proliferation effect. When the cells cultivated with the complexes at high dose, the toxicity effect of both complexes is more and more predominant.

Magnetic Resonance Spectroscopy↗

Effects of luminal ATPase inhibitors on electrogenic ion transport in rat distal colon.

BACKGROUND: The involvement of transport proteins, other than chloride channels, expressed in the luminal membrane of epithelial cells in regulated chloride secretion in native colon remains poorly understood. There are at least two distinct ATPases expressed in the apical membrane of rat colonocytes. They can be distinguished by their different sensitivity to the vanadium-derived compound orthovanadate. The objective was to study the effects of luminal ATPase inhibitors on regulated chloride secretion using elecrophysiological and pharmacological approaches. MATERIALS AND METHODS: Unstripped rat distal colon segments were mounted in Ussing chambers. Potential difference, transepithelial resistance, and short-circuit current across unstripped colon segments were monitored with a dual voltage/current clamp. RESULTS: Luminal application of VO4(3-) did not alter baseline electrical values in rat distal colon but dose-dependently inhibited forskolin-stimulated Isc. Luminal ouabain (1 mm) did not blunt the response to the cAMP agonist. The inhibitory effect of luminal VO4(3-) occurred at a site distal to cAMP generation and was rather specific for the cyclic nucleotide-dependent signaling pathway, because the response to the Ca2+ agonist carbachol was largely preserved. CONCLUSION: VO4(3-) inhibits cAMP-stimulated Cl- secretion in rat distal colon at a site distal to cAMP generation without altering intestinal permeability. Ouabain-sensitive luminal K+-ATPases do not seem to contribute to forskolin-stimulated electrogenic ion transport. These findings may suggest new therapeutic targets for secretory diarrhea.

Adenosine Triphosphatases↗

Effect of insulin-mimetic vanadyl sulfate on cytochrome P450 2E1-dependent p-nitrophenol hydroxylation in the liver microsomes of streptozotocin-induced type 1 diabetic rats.

CYP2E1 is known to be induced in streptozotocin (STZ)-treated diabetic rats (STZ rats), and its induction is improved by insulin. We have examined the age-dependent changes of CYP2E1 in the liver microsomes of type 1 diabetic STZ rats, the effects of VOSO4 on the contents of total P450 and CYP2E1, and the activities of CYP2E1 in terms of p-nitrophenol hydroxylation. The contents of P450 and CYP2E1 and CYP2E1 activity were enhanced with the development of diabetes. When the hyperglycemia of STZ rats was improved by daily intraperitoneal injections of VOSO4 for 10 days at the doses of 7 mg/kg body weight for 5 days, 5 mg/kg for the following 3 days, and then 2.5 mg/kg for 2 days, the P450 and CYP2E1 levels and CYP2E1 activity were lowered than those in the untreated STZ rats. To understand the mechanism underlying CYP2E1-dependent hydroxylation activity, the production of reactive oxygen species was examined in the NADPH-liver microsomal systems by ESR spin-trapping. Singlet oxygen (1O2) was detected in all microsomal systems, while superoxide anion radical(*O2-) and hydroxyl radical (*OH) were not. On the basis of these results, we conclude that (1) CYP2E1 level and activity are enhanced in the diabetic state, however, they are improved by VOSO4 treatment, and (2) 1O2 is generated during CYP2E1-dependent substrate oxygenation.

Age Factors↗

Ependymal epithelium disruption after vanadium pentoxide inhalation. A mice experimental model.

The blood-brain barrier (BBB) protects the CNS against chemical insults. Regulation of blood-brain tissue exchange is accomplished by ependymal cells, which possess intercellular tight junctions. Loss of BBB function is an etiologic component of many neurological disorders. Vanadium (V) is a metalloid widely distributed in the environment and exerts potent toxic effects on a wide variety of biological systems. The current study examines the effects of Vanadium pentoxide (V2O5) inhalation in mice ependymal epithelium, through the analysis of the brain metal concentrations and the morphological modifications in the ependymal cells identified by scanning and transmission electron microscopy after 8 weeks of inhalation, in order to obtain a possible explanation about the mechanisms that V uses to enter and alter the CNS. Our results showed that V2O5 concentrations increase from the first week of study, stabilizing its values during the rest of the experiment. The morphological effects included cilia loss, cell sloughing and ependymal cell layer detachment. This damage can allow toxicants to modify the permeability of the epithelium and promote access of inflammatory mediators to the underlying neuronal tissue causing injury and neuronal death. Thus, understanding the mechanisms of BBB disruption would allow planning strategies to protect the brain from toxicants such as metals, which have increased in the atmosphere during the last decades and constitute an important health problem.

Administration, Inhalation↗

Hippocampal cell alterations induced by the inhalation of vanadium pentoxide (V(2)O(5)) promote memory deterioration.

Spatial memory may be severely impaired as a consequence of ageing and neurodegenerative diseases, conditions that include neuronal damage. Vanadium (V) is a metalloid widely distributed in the environment and exerts severe toxic effects on a wide variety of biological systems. Reports about V inhalation toxicity on the CNS are limited, thus the purpose of this study is to determine the effects of Vanadium pentoxide (V(2)O(5)) inhalation (0.02M) on the memory and its correlation with the cytology of the hippocampus CA1. Forty eight CD-1 male mice were trained in spatial memory tasks and inhaled 1h twice a week; after each inhalation animals were evaluated and sacrificed from 1 to 4 weeks, perfused and processed for Golgi method and for ultrastructure evaluation. The cytological analysis consisted in counting the number of dendritic spines of 20 pyramidal neurons of hippocampus CA1, as well as ultrastructural characteristics. Results show that V inhalation produces a time dependent loss of dendritic spines, necrotic-like cell death, and notorious alterations of the hippocampus CA1 neuropile, which correlate with spatial memory impairment. Our data suggest that V induces important cellular and functional alterations, fact that deserves special attention since the concentration's trend of this element in the atmosphere is increasing.

Administration, Inhalation↗

Effect of vanadyl sulfate on the status of lipid parameters and on stomach and spleen tissues of streptozotocin-induced diabetic rats.

Diabetes mellitus is a significant risk factor for cardiovascular complications. Experimental evidence suggests that oxidative stress plays a dominant role in the pathogenesis of diabetes mellitus. This study was undertaken to investigate the effect of vanadyl sulfate on blood glucose, serum and tissue lipid profiles and on stomach and spleen tissues in STZ-induced diabetic rats. In this study, male 6-6.5-month-old Swiss albino rats were used. Rats were randomly divided into four groups. Group I: control animals (normal, nondiabetic animals) (n = 13); Group II: vanadyl sulfate controls (n = 5); Group III: streptozotocin (STZ)-diabetic, untreated animals (n = 11); and Group IV: STZ diabetic animals given vanadyl sulfate (n = 11). Experimental diabetes was induced by intraperitoneal (i.p.) injection of STZ in a single dose of 65 mg kg(-1) body weight. Vanadyl sulfate was administered by gavage at a dose of 100 mg kg(-1). The levels of cholesterol, phospholipid, high density lipoprotein-cholesterol (HDL-), low density lipoprotein-cholesterol (LDL-), very low density lipoprotein-cholesterol (VLDL-), triglycerides and lipid peroxidation (LPO) in serum and cholesterol in liver were assayed according to standard procedures. The levels of lipid peroxidation, glutathione (GSH) and nonenzymatic glycosylation (NEG) in stomach and lipid peroxidation and glutathione (GSH) in spleen tissues were analyzed. After 60 days of treatment, serum cholesterol, LDL-cholesterol, triglyceride, phospholipid, VLDL-cholesterol, LPO, blood glucose levels, stomach LPO and NEG, spleen LPO significantly increased, but serum HDL-cholesterol, stomach GSH and spleen GSH levels significantly decreased in the diabetic group. On the other hand, treatment with vanadyl sulfate reversed these effects. These results reveal that diabetes mellitus increased oxidative damage in stomach and spleen tissues and vanadyl sulfate has an ameliorating effect on the oxidative stress via its antioxidant property. The administration of vanadyl sulfate may be able to reduce hyperglycemia and hyperlipidemia related to the risk of diabetes mellitus.

Administration, Oral↗

EPR parameters and local geometry for Cr3+ and V2+ ions in HfS2 crystals.

From the high-order perturbation formulas of EPR parameters (zero-field splitting D, g factors gparallel, gperpendicular and hyperfine structure constants Aparallel, Aperpendicular) based on the two spin-orbit coupling parameter model for 3d3 ions in trigonal symmetry, the EPR parameters of Cr3+ and V2+ ions in HfS2 crystals are calculated. From the calculations, it is found that the local trigonal distortion angle theta of impurity center in HfS2:Cr3+ is smaller than that in HfS2:V2+. The dominant cause of the small zero-field splitting |D| and g-anisotropy |Deltag|=|gparallel-gperpendicular| in HfS2:Cr3+ (compound to HfS2:V2+) is due to the small local trigonal distortion angle theta rather than to the small impurity-ligand distance R in HfS2:Cr3+.

Chromium↗

An EPR and optical absorption study of VO2+ ions in sodium hydrogen oxalate monohydrate (NaHC2O4.H2O) single crystals.

Electron paramagnetic resonance of VO(2+) doped sodium hydrogen oxalate monohydrate (NaHC(2)O(4).H(2)O) single crystals and powders are examined at room temperature. Single crystal rotations in each of the three mutually orthogonal crystalline planes namely ac*, b*c* and ab* indicate four different VO(2+) complexes with intensity ratios of 4:2:1:1. It is found from the EPR analysis that the Na(+) ions are replaced with the substitutional magnetically inequivalent VO(2+) ions. The powder spectrum also clearly indicates four different VO(2+) complexes, confirming the single crystal analysis. Crystalline field around the VO(2+) ion is nearly axial. The optical absorption spectrum show two bands centered at 15408 and 12453 cm(-1). Spin Hamiltonian parameters and molecular orbital coefficients are calculated from the EPR and optical data, and results are discussed.

Absorption↗

Cytotoxicity of nanosize V(2)O(5) particles to selected fibroblast and tumor cells.

Two kinds of nanosize V(2)O(5) particles were synthesized in our own laboratory and concomitantly applied to V79 and L929 fibroblasts and SCCVII, B16F10 and FsaR tumor cells. The morphologies of the cells were monitored using an inverted inverse microscope equipped with digital camera, while quantitative determination of the cytotoxicity of nanosize V(2)O(5) particles was measured using crystal violet bioassay. Twenty four hours after the addition of nanosize V(2)O(5) particles (20muM), noticeable changes in the morphology and density of fibroblast and cancer cells were observed. Reculturing in a freshly prepared medium for the next 24h showed a high recovery effect on V79, SCCVII and B16F10 cells, while FsaR and L929 cells were seriously damaged and unable to recover. At a higher concentration of nanosize V(2)O(5) particles (100muM), the cytotoxicity of V(2)O(5) prevailed against the recovery effect in all cell types. Quantitative measurements have shown that the resistance of investigated cell cultures to the cytotoxicity of nanosize V(2)O(5) particles decreases in the order V79>SCCVII>B16F10>FsaR>L929. The high cytotoxic effect found on FsaR cells suggests that nanosize V(2)O(5) particles could be regarded as poisoning material in the treatment of FsaR fibrosarcoma cells. Possible mechanisms involved in the cytotoxicity of nanosize V(2)O(5) particles were discussed.

Cell Line↗

Induction of apoptosis in vivo in the rabbit brain with focused ultrasound and Optison.

Histologic effects of focused ultrasound (FUS) exposures combined with an ultrasound contrast agent (Optison) were investigated to examine whether the lesions were dominated by apoptosis or necrosis. The rabbit brains (n = 17) were sonicated (1.5 MHz, peak rarefactional pressure amplitude: 1.4 to 8.8 MPa) after Optison was injected intravenously (IV). MRI and light microscopy were used to examine tissue effects. To detect apoptosis, TUNEL staining based on labeling of DNA strand breaks was used. The average number of apoptotic and necrotic cells in 300 x 220 microm microscopic fields were counted in 18 representative lesions. Lesions in the rabbit brains were created at lowered acoustic power levels when FUS was combined with Optison. In histology, the lesions exhibited red blood cell extravasations and destruction of blood vessels. At 4 h after sonication, the lesions lost many cells, and the remaining cells exhibited both necrotic and apoptotic features. Overall, apoptosis dominated; there were, on average, 32.3 +/- 13.2 apoptotic cells per microscopic field compared with only 5.1 +/- 3.4 necrotic cells per field. In conclusion, FUS combined with Optison could produce lesions that are dominated by apoptosis, presumably induced primarily via ischemia after cavitation-produced damage to the brain vasculature.

Albumins↗

An enzyme-linked immunosorbent assay (ELISA) for the determination of mucin levels in bronchoalveolar lavage fluid.

INTRODUCTION: A method to measure the mucin concentration in bronchoalveolar lavage (BAL) fluid was developed to aid efforts to identify pharmacologically the mechanisms that modulate pathophysiological mucin secretion. Mucins are the major macromolecular components of mucus. In the airways, mucus is the first line of defense against inhaled microorganisms (infection) and particulates (irritation). METHODS: An enzyme-linked immunosorbent assay (ELISA) was developed, comparing two monoclonal anti-mucin antibodies (A10G5 and 45M1) raised to human mucin, to quantify the mucin in BAL fluid from animal models of pulmonary inflammation. To validate the ELISA method, rats were exposed to ovalbumin (OVA, in sensitized rats), lipopolysaccharide (LPS), vanadium pentoxide (V(2)O(5)), or saline. One hundred microliters of BAL fluid was analyzed for mucin concentration. Pooled BAL fluid from untreated rats was used as an internal "plate standard", as a standard mucin that cross-reacts with A10G5 was unavailable. RESULTS: We found both antibodies reacted with rat, human, and guinea-pig mucin; where the 45M1 antibody also reacted with the mucin in porcine BAL, while A10G5 did not. We determined the mucin concentration in each BAL fluid sample relative to the standard, defined as a mucin concentration of 100 plate units. BAL fluid from LPS (218+/-25 plate units, n=5), OVA (386+/-31, n=3), V(2)O(5) (1208+/-450, n=6) challenged rats displayed significantly elevated mucin concentration over their saline controls (126+/-22, n=12). Subsequently, the 45M1 antibody displayed immunoreactivity with a commercially available crude preparation of porcine stomach mucin, allowing us to calculate the concentration of mucin directly compared to the known concentration of the porcine stomach mucin standard. Both the 45M1 and A10G5 based ELISA assays detected higher mucin content in the saline challenged rat than the saline challenged guinea pig BAL. DISCUSSION: The recent availability of the 45M1 antibody and the use of the crude purification of porcine stomach mucin as a reference standard should allow for direct comparison of mucin concentration in BAL (and other fluids).

Animals↗

Susceptibility of cyclooxygenase-2-deficient mice to pulmonary fibrogenesis.

The cyclooxygenase (COX)-2 enzyme has been implicated as an important mediator of pulmonary fibrosis. In this study, the lung fibrotic responses were investigated in COX-1 or COX-2-deficient (-/-) mice following vanadium pentoxide (V(2)O(5)) exposure. Lung histology was normal in saline-instilled wild-type and COX-deficient mice. COX-2(-/-), but not COX-1(-/-) or wild-type mice, exhibited severe inflammatory responses by 3 days following V(2)O(5) exposure and developed pulmonary fibrosis 2 weeks post-V(2)O(5) exposure. Western blot analysis and immunohistochemistry showed that COX-1 protein was present in type 2 epithelial cells, bronchial epithelial cells, and airway smooth muscle cells of saline or V(2)O(5)-exposed wild-type and COX-2(-/-) mice. COX-2 protein was present in Clara cells of wild-type and COX-1(-/-) terminal bronchioles and was strongly induced 24 hours after V(2)O(5) exposure. Prostaglandin (PG) E(2) levels in the bronchoalveolar lavage (BAL) fluid from wild-type and COX-1(-/-) mice were significantly up-regulated by V(2)O(5) exposure within 24 hours, whereas PGE(2) was not up-regulated in COX-2(-/-) BAL fluid. Tumor necrosis factor-alpha was elevated in the BAL fluid from all genotypes after V(2)O(5) exposure, but was significantly and chronically elevated in the BAL fluid from COX-2(-/-) mice above wild-type or COX-1(-/-) mice. These findings indicate that the COX-2 enzyme is protective against pulmonary fibrogenesis, and we suggest that COX-2 generation of PGE(2) is an important factor in resolving inflammation.

Animals↗

Pulmonary response and intrapulmonary lipids in rats exposed to bismuth orthovanadate dust by inhalation.

Rats were exposed to 0, 1.2, or 0.11 mg/liter of uncoated bismuth orthovanadate (BOV), 1.3 or 0.15 mg/liter of silica-coated BOV, or 1.9 mg/liter of silica-coated TiO2 for 2 weeks. Rats were killed 0, 1, 3, 6, and 12 months postexposure (PE). After the rats were exposed for 2 weeks their pulmonary response to silica-coated TiO2 was characterized by dust-laden macrophage (dust cell) response with hyperplasia of type II pneumocytes. The lung reaction to uncoated BOV or silica-coated BOV was both similar to that of silica-coated TiO2 and dose-related. After the rats were exposed for 3 months, foamy macrophage infiltration in silica-coated TiO2 was evident. Alveolar proteinosis, foamy macrophages with cholesterol clefts, and hyperplastic type II pneumocytes were observed in rats exposed to uncoated BOV or silica-coated BOV. By 6 months PE, the lung exposed to silica-coated TiO2 was restored to essentially normal architecture with removal of most dust cells. In the silica-coated BOV or uncoated BOV exposure groups, alveolar proteinosis and cholesterol granulomas became obvious with degenerative foamy macrophages. After 1 year PE, the lungs exposed to silica-coated TiO2 were almost normal with only a few dust cell aggregates remaining. The pulmonary lesions of silica-coated or uncoated BOV were reduced but alveolar proteinosis and cholesterol granulomas still persisted. Electron microscopy revealed massive accumulation of intraalveolar phospholipid material with hyperplastic type II pneumocytes showing overloaded myelin figures after 2 weeks exposure. The increase in phospholipid at 1 month PE and sterol content at 3 months PE in the lungs correlated with the accumulation of intraalveolar myelin figures and lamellar structure, foamy macrophage infiltration, and occurrence of cholesterol clefts.

Animals↗