Osteogenic activity of vanadyl(IV)-ascorbate complex: evaluation of its mechanism of action

We have previously shown that different vanadium(IV) complexes regulate osteoblastic growth. Since vanadium compounds are accumulated in vivo in bone, they may affect bone turnover. The development of vanadium complexes with different ligands could be an alternative strategy of use in skeletal tissue engineering. In this study, we have investigated the osteogenic properties of a vanadyl(IV)-ascorbate (VOAsc) complex, as well as its possible mechanisms of action, on two osteoblastic cell lines in culture. VOAsc (2.5-25 microM) significantly stimulated osteoblastic proliferation (113-125% basal, p<0.01) in UMR106 cells, but not in the MC3T3E1 cell line. VOAsc (5-100 micrioM) dose-dependently stimulated type-I collagen production (107-156% basal) in osteoblasts. After 3 weeks of culture, 5-25 microM VOAsc increased the formation of nodules of mineralization in MC3T3E1 cells (7.7-20-fold control, p<0.001). VOAsc (50-100 microM) significantly stimulated apoptosis in both cell lines (170-230% basal, p<0.02-0.002), but did not affect reactive oxygen species production. The complex inhibited alkaline and neutral phosphatases from osteoblastic extracts with semi-maximal effect at 10 microM doses. VOAsc induced the activation and redistribution of P-ERK in a time- and dose-dependent manner. Inhibitors of the mitogen activated protein kinases (MAPK) pathway (PD98059 and UO126) partially blocked the VOAsc-enhanced osteoblastic proliferation and collagen production. In addition, wortmanin, a PI-3-K inhibitor and type-L channel blocker nifedipine also partially abrogated these effects of VOAsc on osteoblasts. Our in vitro results suggest that this vanadyl(IV)-ascorbate complex could be a useful pharmacological tool for bone tissue regeneration.     

Possible mode of action for insulinomimetic activity of vanadyl(IV) compounds in adipocytes

Vanadyl(IV) ions (+4 oxidation state of vanadium) and their complexes have been shown to have in vitro insulinomimetic activity and to be effective in treating animals with diabetes mellitus. Although, researchers have proposed many vanadyl compounds for the treatment of diabetes patients, the mode of action of vanadyl compounds remains controversial. In order to evaluate the mode of action of these compounds, we examined the insulinomimetic activity of VOSO4, bis(picolinato)oxovanadyl(IV), and bis(maltolato)oxovanadyl(IV) in the presence of several inhibitors relevant to the glucose metabolism. After confirming that these vanadyl compounds were incorporated in the adipocytes as estimated by ESR method, we evaluated the mode of action by examining free fatty acids (FFA) release in the adipocytes. Inhibition of FFA release by these vanadyl compounds was found to be reversed by the addition of inhibitors, typically by cytochalasin B (glucose transporter 4 (GLUT4) inhibitor), cilostamide (phosphodiesterase inhibitor), HNMPA-(AM)3 (tyrosine kinase inhibitor), and wortmannin (PI3-k inhibitor), indicating that these compounds affect primarily GLUT4 and phosphodiesterase, as named "ensemble mechanism". Based on these results, we suggest that vanadyl compounds act on at least four sites relevant to the glucose metabolism, and on GLUT4 and phosphodiesterase in particular in rat adipocytes, which in turn normalizes the blood glucose levels of diabetic animals. The obtained results provide evidence for the role of vanadyl ion and its complexes in stimulation of the uptake and degeneration of glucose.     

Synthesis of a new vanadyl(IV) complex with trehalose (TreVO): insulin-mimetic activities in osteoblast-like cells in culture

Vanadium compounds show interesting biological and pharmacological properties. Some of them display insulin-mimetic effects and others produce anti-tumor actions. The bioactivity of vanadium is present in inorganic species like the vanadyl(IV) cation or vanadate(V) anion. Nevertheless, the development of new vanadium derivatives with organic ligands which improve the beneficial actions and decrease the toxic effects is of great interest. On the other hand, the mechanisms involved in vanadium bioactivity are still poorly understood. A new vanadium complex of the vanadyl(IV) cation with the disaccharide trehalose (TreVO), Na(6)[VO(Tre)(2)].4H(2)O, here reported, shows interesting insulin-mimetic properties in two osteoblast cell lines, a normal one (MC3T3E1) and a tumoral one (UMR106). The complex affected the proliferation of both cell lines in a different manner. On tumoral cells, TreVO caused a weak stimulation of growth at 5 microM but it inhibited cell proliferation in a dose-response manner between 50 and 100 microM. TreVO significantly inhibited UMR106 differentiation (15-25% of basal) in the range 5-100 microM. On normal osteoblasts, TreVO behaved as a mitogen at 5-25 microM. Different inhibitors of the MAPK pathway blocked this effect. At higher concentrations (75-100 microM), the complex was a weak inhibitor of the MC3T3E1 proliferation. Besides, TreVO enhanced glucose consumption by a mechanism independent of the PI3-kinase activation. In both cell lines, TreVO stimulated the ERK phosphorylation in a dose- and time-dependent manner. Different inhibitors (PD98059, wortmannin, vitamins C and E) partially decreased this effect, which was totally inhibited by their combination. These results suggest that TreVO could be a potential candidate for therapeutic treatments.     

First evidences of the formation of a vanadyl(IV) complex of bleomycin

Results of visible/ultraviolet and infrared spectroscopic measurements, as well as chemical evidence are presented which support the formation of a 2:1 bleomycin-VO2+ complex. The information obtained also allows some considerations concerning the probable coordination sphere of the vanadyl ion.     

The mechanism of action of platinum(IV) complexes in ovarian cancer cell lines

The reduction potentials, lipophilicities, cellular uptake and cytotoxicity have been examined for two series of platinum(IV) complexes that yield common platinum(II) complexes on reduction: cis-[PtCl(4)(NH(3))(2)], cis,trans,cis-[PtCl(2)(OAc)(2)(NH(3))(2)], cis,trans,cis-[PtCl(2)(OH)(2)(NH(3))(2)], [PtCl(4)(en)], cis,trans-[PtCl(2)(OAc)(2)(en)] and cis,trans-[PtCl(2)(OH)(2)(en)] (en=ethane-1,2-diamine, OAc=acetate). As previously reported, the reduction occurs most readily when the axial ligand is chloride and least readily when it is hydroxide. The en series of complexes are marginally more lipophilic than their ammine analogues. The presence of axial chloride or acetate ligands results in a slighter higher lipophilicity compared with the platinum(II) analogue whereas hydroxide ligands lead to a substantially lower lipophilicity. The cellular uptake is similar for the platinum(II) species and their analogous tetrachloro complexes, but is substantially lower for the acetato and hydroxo complexes, resulting in a correlation with the reduction potential. The activities are also correlated with the reduction potentials with the tetrachloro complexes being the most active of the platinum(IV) series and the hydroxo being the least active. These results are interpreted in terms of reduction, followed by aquation reducing the amount of efflux from the cells resulting in an increase in net uptake.     

On the interaction of the vanadyl(IV) cation with lactose

A new vanadyl(IV) complex of the disaccharide lactose was obtained in aqueous solution at pH = 13. The sodium salt of the complex, of composition Na4[VO(lactose)2].3H2O, has been characterized by elemental analysis and by ultraviolet-visible, diffuse reflectance, and infrared spectroscopies. Its magnetic susceptibility and thermal behavior were also investigated. The inhibitory effect on alkaline phosphatase activity was tested for this compound as well as for the vanadyl(IV) complexes with maltose, sucrose, glucose, fructose, and galactose. For comparative purposes, the free ligands and the vanadyl(IV) cation were also studied. The free sugars and the sucrose/VO complex exhibited the lowest inhibitory effect. Lactose-VO, maltose-VO, and the free VO2+ cation showed an intermediate inhibition potential, whereas the monosaccharide/VO complexes appeared as the most potent inhibitory agents.     

The interaction of the vanadyl(IV) cation with phytic acid

The interactions of VO²⁺ with phytate to form both soluble and insoluble complexes, have been studied by electronic absorption spectroscopy. A soluble 1∶1 VO²⁺: phytate complex is formed at pH <1. At higher pH-values insoluble complexes are produced. Two different solid complexes, obtained respectively at pH=2 and 4, were isolated and characterized. The maximal bonding ratio of VO²⁺: phytate was found to be 4, on the basis of a pH binding profile.     

Evidence of oxidative stress following the viral infection of two lepidopteran insect cell lines.

The infection of Spodoptera frugiperda Sf-9 (Sf-9) and Trichoplusia ni BTI-Tn-5B1-4 (Tn-5B1-4) insect cell lines with Autographa californica multiple nucleopolyhedrovirus (AcMNPV) resulted in increased levels of lipid hydroperoxides and protein carbonyls. In addition, the viral infection resulted in a significant decrease in the reduced glutathione to oxidized glutathione (2GSH/GSSG) ratio. These results are all consistent with an increased level of oxidative stress as a result of the viral infection. It was also observed that the oxidative damage corresponded to reduced cell viability, i.e., the results are consistent with the premise that oxidative damage contributes to cell death. Finally, the measured intracellular activities of most of the antioxidant enzymes, specifically manganese superoxide dismutase (MnSOD), ascorbate peroxidase (APOX), and catalase (CAT, not present in Sf-9 cells), did not significantly decrease following viral infection. In contrast, the measured activity of copper-zinc superoxide dismutase (CuZnSOD) decreased in the Sf-9 and Tn-5B1-4 cells following AcMNPV infection.     

The interaction of the vanadyl (IV) cation with chondroitin sulfate A

The interaction of VO²⁺ with the muchopolysaccharide chondroitin sulfate A (CSA) has been investigated by electron absorption spectroscopy and infrared measurements in aqueous solutions at different pH-values and ligand to metal ratios up to 6:1. The generation of a VO(CSA)₂ species could be demonstrated. Coordination of the oxocation through the carboxylate group and the glycosidic oxygen of thed-glucuronate moieties is suggested. Infrared spectra of some poorly characterized solid VO/CSA complexes point to the same bonding characteristics. Preliminary results obtained at higher ligand to metal ratios suggest a different coordination behavior.     

The comparison of vanadyl(IV) and insulin-induced hyperpolarization of the mammalian muscle cell

Extracellularly applied vanadyl(IV) hyperpolarized the membrane potential of mouse diaphragm muscle from about −74.0 mV up to −81.7 mV. The hyperpolarizing effect of 10⁻⁴ mol·l⁻¹ vanadyl(IV) is comparable with hyperpolarization induced by 100 mU·ml⁻¹ insulin. Both compounds increased the intracellular K⁺ concentration, the hyperpolarizing effect of vanadyl(IV) and insulin is blocked by ouabain and is unaffected by removal of K⁺ from the external medium. Triggering of the release of intracellular K⁺ associated with cellular proteins is proposed as the mechanism of vanadyl(IV) and insulin-induced hyperpolarization.     

Interaction of the vanadyl (IV) cation with carnosine and related ligands

The interaction of the vanadyl (IV) (VO²⁺) cation with carnosine (the dipeptide β-alanyl-histidine) has been investigated by electron absorption spectroscopy at high ligand-to-metal ratios and at different pH values. The results show that in the range 6.0–8.5, the cation interacts with the imidazole group of four different carnosine molecules and points to the presence of an axially coordinated water molecule. These suppositions were confirmed by the behavior of the VO²⁺/imidazole system, which was investigated under similar experimental conditions, and supported by previous ENDOR (electron-nuclear double resonance) results. The study was complemented with additional measurements using the glycylglycine, glycylglycine/imidazole, and histidine systems as ligands.     

A benzimidazole-based ruthenium(IV) complex inhibits Pseudomonas aeruginosa biofilm formation by interacting with siderophores and the cell envelope,and inducing oxidative stress

Pseudomonas aeruginosa biofilm-associated infections are a serious medical problem, and new compounds and therapies acting through novel mechanisms are much needed. Herein, the authors report a ruthenium(IV) complex that reduces P. aeruginosa PAO1 biofilm formation by 84%, and alters biofilm morphology and the living-to-dead cell ratio at 1?mM concentration. Including the compound in the culture medium altered the pigments secreted by PAO1, and fluorescence spectra revealed a decrease in pyoverdine. Scanning electron microscopy showed that the ruthenium complex did not penetrate the bacterial cell wall, but accumulated on external cell structures. Fluorescence quenching experiments indicated strong binding of the ruthenium complex to both plasmid DNA and bovine serum albumin. Formamidopyrimidine DNA N-glycosylase (Fpg) protein digestion of plasmid DNA isolated after ruthenium(IV) complex treatment revealed the generation of oxidative stress, which was further proved by the observed upregulation of catalase and superoxide dismutase gene expression.     

Ameliorative effect of an oxovanadium (IV) complex against oxidative stress and nephrotoxicity induced by cisplatin

Objective: The present study was designed to investigate the chemoprotective efficacy of an L-cysteine-based oxovanadium (IV) complex, namely, oxovanadium (IV)-L-cysteine methyl ester complex (VC-IV) against cisplatin (CDDP)-induced renal injury in Swiss albino mice.

Methods: CDDP was administered intraperitoneally (5 mg/kg body weight) and VC-IV was administered orally (1 mg/kg body weight) in concomitant and 7 days pre-treatment schedule.

Results: CDDP-treated mice showed marked kidney damage and renal failure. Administration of VC-IV caused significant attenuation of renal oxidative stress and elevation of antioxidant status. VC-IV also significantly decreased serum levels of creatinine and blood urea nitrogen, and improved histopathological lesions. Western blot analysis of the kidneys showed that VC-IV treatment resulted in nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) through modulation of cytosolic Kelch-like ECH-associated protein 1. Thus, VC-IV stimulated Nrf2-mediated activation of antioxidant response element (ARE) pathway and promoted expression of ARE-driven cytoprotective proteins, heme oxygenase 1 and NAD(P)H:quinone oxidoreductase 1, and enhanced activity of antioxidant enzymes. Interestingly, VC-IV did not alter the bioavailability and renal accumulation of CDDP in mice.

Discussion: In this study, VC-IV exhibited strong nephroprotective efficacy by restoring antioxidant defense mechanisms and hence may serve as a promising chemoprotectant in cancer chemotherapy.     

A new halogenated antidiabetic vanadyl complex, bis(5-iodopicolinato)oxovanadium(IV): in vitro and in vivo insulinomimetic evaluations and metallokinetic analysis

A new vanadyl complex, bis(5-iodopicolinato)oxovanadium(IV), VO(IPA)2, with a VO(N2O2) coordination mode, was prepared by mixing 5-iodopicolinic acid and VOSO4 at pH 5, with the structure characterized by electronic absorption, IR, and EPR spectra. Introduction of the halogen atom on to the ligand enhanced the in vitro insulinomimetic activity (IC50 = 0.45 mM) compared with that of bis(picolinato)oxovanadium(IV) (IC50 = 0.59 mM). The hyperglycemia of streptozotocin-induced insulin-dependent diabetic rats was normalized when VO(IPA)2 was given by daily intraperitoneal injection. The normoglycemic effect continued for more than 14 days after the end of treatment. To understand the insulinomimetic action of VO(IPA)2, the organ distribution of vanadium and the blood disposition of vanadyl species were investigated. In diabetic rats treated with VO(IPA)2, vanadium was distributed in almost all tissues examined, especially in bone, indicating that the action of vanadium is not peripheral. Vanadyl concentrations in the blood of normal rats given VO(IPA)2 remain significantly higher and longer than those given other complexes because of its slower clearance rate. VO(IPA)2 binds with the membrane of erythrocytes, probably owing to its high hydrophobicity in addition to its binding with serum albumin. The longer residence of vanadyl species shows the higher normoglyceric effects of VO(IPA)2 among three complexes with the VO(N2O2) coordination mode. On the basis of these results, VO(IPA)2 is indicated to be a preferred agent to treat insulin-dependent diabetes mellitus in experimental animals.     

Role of oxidative stress in the pathogenesis of sickle cell disease

Sickle cell disease (SCD) is a class of hemoglobinopathy in humans, which causes a disruption of the normal activities in different systems. Although this disease begins with the polymerization of red blood cells during its deoxygenating phase, it can erupt into a cascade of debilitating conditions such as ischemia-reperfusion injury, inflammation, and painful vaso-occlusion crises. The purpose of this review is to discuss how these phenomena can result in the formation of oxidative stress as well as limit nitric oxide (NO) bioavailability and decrease antioxidant status. The cumulative effects of these traits cause an increase in other forms of reactive oxygen species (ROS), which in turn intensify the symptoms of SCD and generate a vicious circle. Finally, we will discuss antioxidant therapeutic strategies that limit ROS generation and subsequently increase NO bioavailability with respect to endothelial protection in SCD.     

Structure-activity relationship of new trans-platinum(II) and (IV) complexes with cyclohexylamine. Interference with cell cycle progression and induction of cell death

The new trans-Pt complexes, derived from trans-[PtCl2(amine)(dimethylamine)] and trans-[PtCl2(OH)2(amine)(dimethylamine)], were synthesized and characterized studying the structure-activity relationship and testing their antiproliferative activity. Their evaluation as cytotoxic agents towards different cancer and normal cell lines is presented. These compounds are active in a panel of tumor cell lines at low micromolar range. Compounds seems to be more active in tumoral than in normal primary human cell lines. Cytotoxic activity is closely related to the amine ligand. Cyclohexylamine ligand was the most active among the amine-ligands tested. Cytotoxic activity correlates with an increase in annexin V positive cells indicating an apoptotic effect of the compounds. Mechanistically, the antitumor activity correlates with a blockade of the cell cycle in S phase and a complete abolishment of G2/M checkpoint arrest suggesting physical interaction of compound with DNA inhibiting S phase transition.     

Synthesis and antitumor activity of a new mixed-ligand complex di-n-butyl-(4-chlorobenzohydroxamato)tin(IV) chloride

Reaction of di-n-butyltin(IV) dichloride with 4-chlorobenzohydroxamic acid at 1:1 ratio yielded a new mixed-ligand diorganotin(IV) complex, di-n-butyl-(4-chlorobenzohydroxamato)tin(IV) chloride(DBDCT). It was fully characterized by IR, ¹H, ¹³C, ¹¹⁹Sn NMR spectra and single crystal X-ray analysis. In DBDCT, the tin atom is five-coordinated in a trigonal bipyramidal geometry. DBDCT exhibited strong in vitro cytotoxic activity toward human immature granulocyte leukemia (HL-60), human salivary-gland carcinoma (SGC-7901), human henrietta carcinoma (Hela) and human urinary bladder (T24) cell lines which, in some cases, were equal to, or even higher than those of cis-dichlorodiammineplatinum(II) (cisplatin, DDP), the widely clinically used drug. The further in vivo antitumor tests of DBDCT towards the transplantation tumor models of sarcoma carcinoma (S₁₈₀), hepatocellular carcinoma (H₂₂) and Ehrlich’s ascites carcinoma (EAC) on mice were carried out via injection intraperitoneally with cisplatin as positive contrast drug. The results showed that DBDCT displayed in vivo antitumor activity against the hepatocellular carcinoma H₂₂ and sarcoma carcinoma S₁₈₀ which were close to those of cisplatin, meanwhile, the survival-extending rates at middle dose and high dose on mice Ehrlich’s ascites tumor EAC were higher than those of cisplatin, and there was a good dose-effect relationship.     

Cyto- and genotoxicity of a vanadyl(IV) complex with oxodiacetate in human colon adenocarcinoma (Caco-2) cells: potential use in cancer therapy

The complex of vanadyl(IV) cation with oxodiacetate, VO(oda) caused an inhibitory effect on the proliferation of the human colon adenocarcinoma cell line Caco-2 in the range of 25–100 μM (P < 0.001). This inhibition was partially reversed by scavengers of free radicals. The difference in cell proliferation in the presence and the absence of scavengers was statistically significant in the range of 50–100 μM (P < 0.05). VO(oda) altered lysosomal and mitochondria metabolisms (neutral red and MTT bioassays) in a dose–response manner from 10 μM (P < 0.001). Morphological studies showed important transformations that correlated with the disassembly of actin filaments and a decrease in the number of cells in a dose response manner. Moreover, VO(oda) caused statistically significant genotoxic effects on Caco-2 cells in the low range of concentration (5–25 μM) (Comet assay). Increment in the oxidative stress and a decrease in the GSH level are the main cytotoxic mechanisms of VO(oda). These effects were partially reversed by scavengers of free radicals in the range of 50–100 μM (P < 0.05). Besides, VO(oda) interacted with plasmidic DNA causing single and double strand cleavage, probably through the action of free radical species. Altogether, these results suggest that VO(oda) is a good candidate to be evaluated for alternative therapeutics in cancer treatment.