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

Vanadium Pentoxide Exposure Causes Strain-Dependent Changes in Mitochondrial DNA Heteroplasmy, Copy Number, and Lesions, but Not Nuclear DNA Lesions

Interstitial lung diseases (ILDs) are lethal lung diseases characterized by pulmonary inflammation and progressive lung interstitial scarring. We previously developed a mouse model of ILD using vanadium pentoxide (V2O5) and identified several gene candidates on chromosome 4 associated with pulmonary fibrosis. While these data indicated a significant genetic contribution to ILD susceptibility, they did not include any potential associations and interactions with the mitochondrial genome that might influence disease risk. To conduct this pilot work, we selected the two divergent strains we previously categorized as V2O5-resistant C57BL6J (B6) and -responsive DBA/2J (D2) and compared their mitochondrial genome characteristics, including DNA variants, heteroplasmy, lesions, and copy numbers at 14- and 112-days post-exposure. While we did not find changes in the mitochondrial genome at 14 days post-exposure, at 112 days, we found that the responsive D2 strain exhibited significantly fewer mtDNA copies and more lesions than control animals. Alongside these findings, mtDNA heteroplasmy frequency decreased. These data suggest that mice previously shown to exhibit increased susceptibility to pulmonary fibrosis and inflammation sustain damage to the mitochondrial genome that is evident at 112 days post-V2O5 exposure.

Vanadium exposure exacerbates allergic airway inflammation and remodeling through triggering reactive oxidative stress

Background

Metal components of environmental PM2.5 are associated with the exacerbation of allergic diseases like asthma. In our recent hospital-based population study, exposure to vanadium is shown to pose a significant risk for current asthma, but the causal relationship and its underlying molecular mechanisms remain unclear.

Objective

We sought to determine whether vanadium co-exposure can aggravate house dust mite (HDM)-induced allergic airway inflammation and remodeling, as well as investigate its related mechanisms.

Methods

Asthma mouse model was generated by using either vanadium pentoxide (V₂O₅) or HDM alone or in combination, in which the airway inflammation and remodeling was investigated. The effect of V₂O₅ co-exposure on HDM-induced epithelial-derived cytokine release and oxidative stress (ROS) generation was also examined by in vitro analyses. The role of ROS in V₂O₅ co-exposure-induced cytokine release and airway inflammation and remodeling was examined by using inhibitors or antioxidant.

Results

Compared to HDM alone, V₂O₅ co-exposure exacerbated HDM-induced airway inflammation with increased infiltration of inflammatory cells and elevated levels of Th1/Th2/Th17 and epithelial-derived (IL-25, TSLP) cytokines in the bronchoalveolar lavage fluids (BALFs). Intriguingly, V₂O₅ co-exposure also potentiated HDM-induced airway remodeling. Increased cytokine release was further supported by in vitro analysis in human bronchial epithelial cells (HBECs). Mechanistically, ROS, particularly mitochondrial-derived ROS, was significantly enhanced in HBECs after V₂O₅ co-exposure as compared to HDM challenge alone. Inhibition of ROS with its inhibitor N-acetyl-L-cysteine (NAC) and mitochondrial-targeted antioxidant MitoTEMPO blocked the increased epithelial release caused by V₂O₅ co-exposure. Furthermore, vitamin D₃ as an antioxidant was found to inhibit V₂O₅ co-exposure-induced increased airway epithelial cytokine release and airway remodeling.

Conclusions

Our findings suggest that vanadium co-exposure exacerbates epithelial ROS generation that contribute to increased allergic airway inflammation and remodeling.

Vanadium exposure exacerbates allergic airway inflammation and remodeling through triggering reactive oxidative stress

Background

Metal components of environmental PM2.5 are associated with the exacerbation of allergic diseases like asthma. In our recent hospital-based population study, exposure to vanadium is shown to pose a significant risk for current asthma, but the causal relationship and its underlying molecular mechanisms remain unclear.

Objective

We sought to determine whether vanadium co-exposure can aggravate house dust mite (HDM)-induced allergic airway inflammation and remodeling, as well as investigate its related mechanisms.

Methods

Asthma mouse model was generated by using either vanadium pentoxide (V2O5) or HDM alone or in combination, in which the airway inflammation and remodeling was investigated. The effect of V2O5 co-exposure on HDM-induced epithelial-derived cytokine release and oxidative stress (ROS) generation was also examined by in vitro analyses. The role of ROS in V2O5 co-exposure-induced cytokine release and airway inflammation and remodeling was examined by using inhibitors or antioxidant.

Results

Compared to HDM alone, V2O5 co-exposure exacerbated HDM-induced airway inflammation with increased infiltration of inflammatory cells and elevated levels of Th1/Th2/Th17 and epithelial-derived (IL-25, TSLP) cytokines in the bronchoalveolar lavage fluids (BALFs). Intriguingly, V2O5 co-exposure also potentiated HDM-induced airway remodeling. Increased cytokine release was further supported by in vitro analysis in human bronchial epithelial cells (HBECs). Mechanistically, ROS, particularly mitochondrial-derived ROS, was significantly enhanced in HBECs after V2O5 co-exposure as compared to HDM challenge alone. Inhibition of ROS with its inhibitor N-acetyl-L-cysteine (NAC) and mitochondrial-targeted antioxidant MitoTEMPO blocked the increased epithelial release caused by V2O5 co-exposure. Furthermore, vitamin D3 as an antioxidant was found to inhibit V2O5 co-exposure-induced increased airway epithelial cytokine release and airway remodeling.

Conclusions

Our findings suggest that vanadium co-exposure exacerbates epithelial ROS generation that contribute to increased allergic airway inflammation and remodeling.

Identification of Potential Artefacts in In Vitro Measurement of Vanadium-Induced Reactive Oxygen Species (ROS) Production

We investigated vanadium, i.e., a redox-active heavy metal widely known for the generation of oxidative stress in cultured mammalian cells, to determine its ability to interfere with common oxidative stress-related bioassays in cell-free conditions. We first assessed the prooxidant abilities (H₂O₂ level, oxidation of DHR 123, and DCFH-DA dyes) and antioxidant capacity (ABTS, RP, OH, and DPPH methods) of popular mammalian cell culture media, i.e., Minimal Essential Medium (MEM), Dulbecco's Minimal Essential Medium (DMEM), Dulbecco's Minimal Essential Medium-F12 (DMEM/F12), and RPMI 1640. Out of the four media studied, DMEM has the highest prooxidant and antioxidant properties, which is associated with the highest concentration of prooxidant and antioxidant nutrients in its formulation. The studied vanadium compounds, vanadyl sulphate (VOSO₄), or sodium metavanadate (NaVO₃) (100, 500, and 1000 µM), either slightly increased or decreased the level of H₂O₂ in the studied culture media. However, these changes were in the range of a few micromoles, and they should rather not interfere with the cytotoxic effect of vanadium on cells. However, the tested vanadium compounds significantly stimulated the oxidation of DCFH-DA and DHR123 in a cell-independent manner. The type of the culture media and their pro-oxidant and antioxidant abilities did not affect the intensity of oxidation of these dyes by vanadium, whereas the vanadium compound type was important, as VOSO₄ stimulated DCFH-DA and DHR oxidation much more potently than NaVO₃. Such interactions of vanadium with these probes may artefactually contribute to the oxidation of these dyes by reactive oxygen species induced by vanadium in cells.

Vanadium pentoxide induced oxidative stress and cellular senescence in human lung fibroblasts

Both environmental exposure to vanadium pentoxide (V2O5, V+5 for its ionic counterparts) and fibroblast senescence are associated with pulmonary fibrosis, but whether V+5 causes fibroblast senescence remains unknown. We found in a dose-response study that 2-40 μM V+5 caused human lung fibroblasts (HLF) senescence with increased senescence-associated β-galactosidase activity and p16 expression, while cell death occurred at higher concentration (LC50, 82 μM V+5). Notably, measures of reactive oxygen species (ROS) production with fluorescence probes showed no association of ROS with V+5-dependent senescence. Preloading catalase (polyethylene-conjugated), a H2O2 scavenger, did not alleviate the cellular senescence induced by V+5. Analyses of the cellular glutathione (GSH) system showed that V+5 oxidized GSH, increased GSH biosynthesis, stimulated cellular GSH efflux and increased protein S-glutathionylation, and addition of N-acetyl cysteine inhibited V+5-elevated p16 expression, suggesting that thiol oxidation mediates V+5-caused senescence. Moreover, strong correlations between GSSG/GSH redox potential (Eh), protein S-glutathionylation, and cellular senescence (R2 > 0.99, p < 0.05) were present in V+5-treated cells. Studies with cell-free and enzyme-free solutions showed that V+5 directly oxidized GSH with formation of V+4 and GSSG in the absence of O2. Analyses of V+5 and V+4 in HLF and culture media showed that V+5 was reduced to V+4 in cells and that a stable V+4/V+5 ratio was rapidly achieved in extracellular media, indicating ongoing release of V+4 and reoxidation to V+5. Together, the results show that V+5-dependent fibroblast senescence is associated with a cellular/extracellular redox cycling mechanism involving the GSH system and occurring under conditions that do not cause cell death. These results establish a mechanism by which environmental vanadium from food, dietary supplements or drinking water, can cause or contribute to lung fibrosis in the absence of high-level occupational exposures and cytotoxic cell death.

Effects of Sodium Pyruvate on Vanadyl Sulphate-Induced Reactive Species Generation and Mitochondrial Destabilisation in CHO-K1 Cells

Vanadium is ranked as one of the world’s critical metals considered important for economic growth with wide use in the steel industry. However, its production, applications, and emissions related to the combustion of vanadium-containing fuels are known to cause harm to the environment and human health. Pyruvate, i.e., a glucose metabolite, has been postulated as a compound with multiple cytoprotective properties, including antioxidant and anti-inflammatory effects. The aim of the present study was to examine the antioxidant potential of sodium pyruvate (4.5 mM) in vanadyl sulphate (VOSO₄)-exposed CHO-K1 cells. Dichloro-dihydro-fluorescein diacetate and dihydrorhodamine 123 staining were performed to measure total and mitochondrial generation of reactive oxygen species (ROS), respectively. Furthermore, mitochondrial damage was investigated using MitoTell orange and JC-10 staining assays. We demonstrated that VOSO₄ alone induced a significant rise in ROS starting from 1 h to 3 h after the treatment. Additionally, after 24 and 48 h of exposure, VOSO₄ elicited both extensive hyperpolarisation and depolarisation of the mitochondrial membrane potential (MMP). The two-way ANOVA analysis of the results showed that, through antagonistic interaction, pyruvate prevented VOSO₄-induced total ROS generation, which could be observed at the 3 h time point. In addition, through the independent action and antagonistic interaction with VOSO₄, pyruvate provided a pronounced protective effect against VOSO₄-mediated mitochondrial toxicity at 24-h exposure, i.e., prevention of VOSO₄-induced hyperpolarisation and depolarisation of MMP. In conclusion, we found that pyruvate exerted cytoprotective effects against vanadium-induced toxicity at least in part by decreasing ROS generation and preserving mitochondrial functions

Potential mechanisms of some selected heavy metals in the induction of inflammation and autoimmunity

Inflammation is a physiological event that protects tissues from infection and injury. Chronic inflammation causes immune cell over activation and sustained release of inflammatory cytokines and chemokines cause pathologic conditions including autoimmune diseases. Heavy metals exposure affects innate and adaptive immune systems through triggering inflammatory responses. It seems that extended inflammatory responses could accelerate heavy metal-induced autoimmunity. In the present review we discuss the exposure route and toxicity of Cadmium (Cd), Lead (Pb), Mercury (Hg), Vanadium (V) and Platinum (Pt) and their effects on inflammatory responses by innate and adaptive immune system and autoimmunity.

Associations of prenatal exposure to vanadium with early-childhood growth: A prospective prenatal cohort study

Prenatal vanadium exposure is reported to be associated with restricted fetal growth and adverse birth outcomes. However, trimester-specific vanadium exposure in relation to early-childhood growth still remains unclear. A total of 1873 Chinese mother-infant pairs from whom a complete series of maternal urinary samples were collected over three stages of pregnancy were included from 2014 to 2016. The urinary concentrations of vanadium were analyzed. Children's anthropometric parameters were measured at birth, 6, 12 and 24 months. In boys, each doubling increase in vanadium concentrations at middle pregnancy was inversely associated with weight-for-length [- 9.07% (-17.21%, -0.93%)] and BMI z-score [- 9.66% (-18.05%, -1.28%)] at 24 months. Moreover, vanadium exposure at late pregnancy was negatively associated with weight [- 9.85% (-16.42%, -3.28%)], weight-for-length [- 11.00% (-18.40%, -3.60%)], and BMI z-scores [- 11.05% (-18.67%, -3.42%)] at 24 months in boys. However, the negative associations were not observed in girls, and we found evidence for sex difference (FDR p for interaction=0.01, 0.01 and 0.03 for weight, weight-for-length and BMI z-scores, respectively). Prenatal vanadium exposure may have an adverse effect on early-childhood growth, and the middle and late pregnancy could be windows of vulnerability for the adverse effects of vanadium exposure on growth development.

Histopathology of the fetal inflammatory response to intra-amniotic pathogens

Obstetric endorsement of the utility of placental histologic examination remains infrequent, especially from obstetricians who do not have a placental pathologist as part of their own local clinical care team. Placental pathologic examinations are viewed as useless if they do not provide answers to urgent clinical questions. Increasingly, however, it is appreciated that while placental analysis should be considered with regard to its longer term value; results can assess lifelong risks of a wide range of diseases that have been tied to prenatal exposures (e.g., [1]), including distinguishing sex-specific differences in those risks. (e.g., [2]) This review will focus solely on acute fetal (?) inflammation, more specifically, the fetal neutrophil responses in umbilical cord, chorionic plate vessels and to some degree, the fetal system as a whole. This histologic fetal inflammatory response is often the most readily accessible aspect of "FIR" piece of FIRS (the fetal inflammatory response syndrome). Some researchers have defined FIRS by a combination of both cytokine (especially IL-6) levels and the histopathologic FIR (Musilova et al., 2018) [3]. As we and others have noted, many histology based FIR cases, even those associated with neurodevelopmental outcomes such as cerebral palsy, are clinically silent.(e.g., [4]) Current clinical diagnostic criteria may have high specificity as they are very good at identifying non-FIR cases. However, that high specificity is coupled with very low specificity, identifying only 10% of FIR (Doty et al., 2018 Jul) [5]. Our aim is to provide a conceptual framework for the readers of the journal to better understand how to answer the following questions: What is a neutrophil and how is it important in FIR? What is the differential diagnosis for histologic FIR? How long has there been FIR? What secondary processes may have been recruited (and when) to contribute to the final pathology and pathophysiology of the given pregnancy?

The role of the non-ciliated bronchiolar cell in tolerance to inhaled vanadium of the bronchiolar epithelium

The Non-Ciliated Bronchiolar Cell (NCBC) is responsible for the defense and maintenance of the bronchiolar epithelium. Several cellular defense mechanisms have been associated with an increase in the secretion of CC16 and changes in the phenotype of the cell; these mechanisms could be linked to tolerance to the damage due to exposure to inhaled Particulate Matter (PM) of the epithelium. These defense mechanisms have not been sufficiently explored. In this article, we studied the response of the NCBC to inhaled vanadium, an element which adheres to PM. This response was measured by the changes in the phenotype of the NCBC and the secretion of CC16 in a mouse model. Mice were exposed in two phases to different vanadium concentrations; 1.27 mg/m³ in the first phase and 2.56 mg/m³ in the second phase. Mice were sacrificed on the 2nd, 4th, 5th, 6th and 8th weeks. In the second phase, we observed the following: sloughing of the NCBC, hyperplasia and small inflammatory foci remained without changes and that the expression of CC16 was higher in this phase than in phase I. We also observed a change in the phenotype with a slow decrease in both phases. The increase in the secretion of CC16 and the phenotype reversion could be due to the anti-inflammatory activity of CC16. The changes observed in the second phase could be attributed to the tolerance to inhaled vanadium.

In vitro effect of vanadyl sulfate on cultured primary astrocytes: cell viability and oxidative stress markers

Exposure to vanadium has been associated with deleterious effects on the central nervous system in animals and humans. Although vanadium-derived pro-oxidant species were reported to be involved in vanadium-mediated neurotoxicity, the ability of this metal to induce oxidative stress markers in glial cells remains to be elucidated. In this study, we investigated the cytotoxicity and the generation of reactive oxygen species (ROS) and nitric oxide (NO) by mouse primary astrocytes after treatment with vanadyl sulfate (VOSO₄ ) at concentrations of 20, 50, 100, 200, and 500 μM. The resazurin assay revealed that treatment with VOSO₄ for 24 and 48 h at concentrations of 50 and 100 μM, respectively, or higher substantially induced astrocytic cytotoxicity. Intracellular ROS increased after 6-h exposure to the lowest concentration tested (20 μM VOSO₄ ) and tended to intensify after 24- and 48-h treatments reaching significant values for 20 and 500 μM VOSO₄ . In turn, NO production in the examined cells was elevated after exposure to all concentrations at the 6-, 24-, and 48-h incubation periods. Our study demonstrated the ability of VOSO₄ to induce H₂ O₂ generation in cell-free DMEM/F12 medium. The H₂ O₂ levels were in the micromolar range (up to 5 μM) and were detected mostly during the first few minutes after VOSO₄ addition, suggesting that the generated H₂ O₂ could not induce toxic effects on the cells. Taken together, these results show VOSO₄ induced cytotoxicity in primary astrocyte cells, which may have resulted from vanadyl-stimulated intracellular ROS and NO generation in these cells.

Protective Effects of Dietary Antioxidants against Vanadium-Induced Toxicity: A Review

Vanadium (V) in its inorganic forms is a toxic metal and a potent environmental and occupational pollutant and has been reported to induce toxic effects in animals and people. In vivo and in vitro data show that high levels of reactive oxygen species are often implicated in vanadium deleterious effects. Since many dietary (exogenous) antioxidants are known to upregulate the intrinsic antioxidant system and ameliorate oxidative stress-related disorders, this review evaluates their effectiveness in the treatment of vanadium-induced toxicity. Collected data, mostly from animal studies, suggest that dietary antioxidants including ascorbic acid, vitamin E, polyphenols, phytosterols, and extracts from medicinal plants can bring a beneficial effect in vanadium toxicity. These findings show potential preventive effects of dietary antioxidants on vanadium-induced oxidative stress, DNA damage, neurotoxicity, testicular toxicity, and kidney damage. The relevant mechanistic insights of these events are discussed. In summary, the results of studies on the role of dietary antioxidants in vanadium toxicology appear encouraging enough to merit further investigations.

Vanadium in Biological Action: Chemical, Pharmacological Aspects, and Metabolic Implications in Diabetes Mellitus

Vanadium compounds have been primarily investigated as potential therapeutic agents for the treatment of various major health issues, including cancer, atherosclerosis, and diabetes. The translation of vanadium-based compounds into clinical trials and ultimately into disease treatments remains hampered by the absence of a basic pharmacological and metabolic comprehension of such compounds. In this review, we examine the development of vanadium-containing compounds in biological systems regarding the role of the physiological environment, dosage, intracellular interactions, metabolic transformations, modulation of signaling pathways, toxicology, and transport and tissue distribution as well as therapeutic implications. From our point of view, the toxicological and pharmacological aspects in animal models and humans are not understood completely, and thus, we introduced them in a physiological environment and dosage context. Different transport proteins in blood plasma and mechanistic transport determinants are discussed. Furthermore, an overview of different vanadium species and the role of physiological factors (i.e., pH, redox conditions, concentration, and so on) are considered. Mechanistic specifications about different signaling pathways are discussed, particularly the phosphatases and kinases that are modulated dynamically by vanadium compounds because until now, the focus only has been on protein tyrosine phosphatase 1B as a vanadium target. Particular emphasis is laid on the therapeutic ability of vanadium-based compounds and their role for the treatment of diabetes mellitus, specifically on that of vanadate- and polioxovanadate-containing compounds. We aim at shedding light on the prevailing gaps between primary scientific data and information from animal models and human studies.

The role of cellular reactive oxygen species in cancer chemotherapy

Most chemotherapeutics elevate intracellular levels of reactive oxygen species (ROS), and many can alter redox-homeostasis of cancer cells. It is widely accepted that the anticancer effect of these chemotherapeutics is due to the induction of oxidative stress and ROS-mediated cell injury in cancer. However, various new therapeutic approaches targeting intracellular ROS levels have yielded mixed results. Since it is impossible to quantitatively detect dynamic ROS levels in tumors during and after chemotherapy in clinical settings, it is of increasing interest to apply mathematical modeling techniques to predict ROS levels for understanding complex tumor biology during chemotherapy. This review outlines the current understanding of the role of ROS in cancer cells during carcinogenesis and during chemotherapy, provides a critical analysis of the methods used for quantitative ROS detection and discusses the application of mathematical modeling in predicting treatment responses. Finally, we provide insights on and perspectives for future development of effective therapeutic ROS-inducing anticancer agents or antioxidants for cancer treatment.

Protective activity of pyruvate against vanadium-dependent cytotoxicity in Chinese hamster ovary (CHO-K1) cells

With increasing human exposure to vanadium-containing compounds and growing concern over their impact on human health, identification of safe methods for efficient treatment of vanadium poisoning may be of value. In this study, using Chinese hamster ovary (CHO-K1) cells, we show that the toxicity of vanadyl sulphate (VOSO₄) is mitigated in the presence of sodium pyruvate. The exposure of CHO-K1 cells to 100 μM VOSO₄ for 48 h induced significant cytotoxicity (measured with a resazurin assay) and elevation of the contents of malondialdehyde (MDA), a lipid peroxidation product, in the examined cells. When added simultaneously with VOSO₄ to the culture medium, pyruvate (4.5 mM) reduced VOSO₄-mediated cytotoxicity by twofold and inhibited MDA formation. Phase-contrast microscopy confirmed that the general morphology of cell cultures treated with 100 μM VOSO₄ and 4.5 mM pyruvate was improved compared to VOSO₄-only treated cells. The two-way analysis of variance revealed that the reduction of the adverse effects of VOSO₄ in the presence of pyruvate was due to the independent action of pyruvate as well as antagonistic interaction between VOSO₄ and pyruvate. From these data, it can be concluded that the pyruvate treatment may play a beneficial role in reducing vanadium-triggered health hazards.

DUOX expression in human keratinocytes and bronchial epithelial cells: Influence of vanadate

Dual oxygenases (DUOX) 1 and 2, expressed in many animal tissues, participate in host defense at mucosal surfaces and may have important signaling roles through generation of reactive oxygen. Present work addresses their expression in cultured human epidermal keratinocytes and effects of cytokines and metal/metalloid compounds. Both DUOX1 and 2 were expressed at much higher levels after confluence than in the preconfluent state. Maximal DUOX1 mRNA levels were 50 fold those of DUOX2. DUOX1 and 2 were induced ≈3 fold by interleukin 4, but only DUOX1 was induced by interferon gamma (IFNγ). In human bronchial HBE1 cells, by contrast, interleukin 4 induced only DUOX 1, and IFNγ induced only DUOX2. A survey in the keratinocytes of metal/metalloid compounds showed that arsenite, antimonite, chromate, cadmium, copper, lead and vanadate suppressed DUOX1 levels but did not prevent interleukin 4 stimulation. Effects on DUOX2 were less dramatic, except that vanadate potentiated the stimulation by IFNγ up to 7 fold. The results indicate that epithelial cell types of different tissue origins can differ in their cytokine regulation and that epidermal cells can exhibit striking alterations in response due to certain metal/metalloid exposures.

Pituitary Adenylate Cyclase-Activating Polypeptide Reverses Ammonium Metavanadate-Induced Airway Hyperresponsiveness in Rats

The rate of atmospheric vanadium is constantly increasing due to fossil fuel combustion. This environmental pollution favours vanadium exposure in particular to its vanadate form, causing occupational bronchial asthma and bronchitis. Based on the well admitted bronchodilator properties of the pituitary adenylate cyclase-activating polypeptide (PACAP), we investigated the ability of this neuropeptide to reverse the vanadate-induced airway hyperresponsiveness in rats. Exposure to ammonium metavanadate aerosols (5 mg/m³/h) for 15 minutes induced 4 hours later an array of pathophysiological events, including increase of bronchial resistance and histological alterations, activation of proinflammatory alveolar macrophages, and increased oxidative stress status. Powerfully, PACAP inhalation (0.1 mM) for 10 minutes alleviated many of these deleterious effects as demonstrated by a decrease of bronchial resistance and histological restoration. PACAP reduced the level of expression of mRNA encoding inflammatory chemokines (MIP-1α, MIP-2, and KC) and cytokines (IL-1α and TNF-α) in alveolar macrophages and improved the antioxidant status. PACAP reverses the vanadate-induced airway hyperresponsiveness not only through its bronchodilator activity but also by counteracting the proinflammatory and prooxidative effects of the metal. Then, the development of stable analogs of PACAP could represent a promising therapeutic alternative for the treatment of inflammatory respiratory disorders.

Investigation into the role of Cu/Zn-SOD delivery system on its antioxidant and antiinflammatory activity in rat model of peritonitis

BACKGROUND

The current study evaluated the role of delivery system (solution, conventional liposomes and PEG-ylated liposomes) on superoxide dismutase (SOD) antioxidant and antiinflammatory properties in a rat model of lipopolysaccharide (LPS)-induced peritonitis.

METHODS

Fifty male albino rats (Wistar-Bratislava) were divided into five groups (n=10). Control group received saline and the other four groups received intraperitoneal injections of LPS (5mg/kg). Among the LPS-injected groups, one was LPS control group and the other three groups received the endotoxin injection 30min after receiving the same dose of SOD (500U/kg, ip) in different delivery systems: saline solution (SOD-S), conventional liposomes (SOD-L) or PEG-ylated liposomes (SOD-PL). The animals were euthanized 6h after LPS injection, blood samples were collected and acute phase response (total and differential leukocytes count; tumor necrosis factor α), antioxidants (total antioxidants; reduced glutathione), oxidative stress (total oxidants; lipid peroxidation) and nitrosative stress (nitric oxide metabolites; nitrotyrosine) were evaluated.

RESULTS

Intraperitoneal administration of LPS to rats induced a marked inflammatory and oxidative response in plasma. On the other hand, all SOD formulations had protective effect against endotoxin-induced inflammation and oxidative/nitrosative stress, but PEG-ylated liposomes had the most significant activity. Thus, SOD-PL administration significantly reduced the effects of LPS on bone marrow acute phase response, the oxidative status and production of nitric oxide metabolites, while increasing the markers of antioxidant response in a significant manner.

CONCLUSION

SOD supplementation interferes both with inflammatory and oxidative pathways involved in LPS-induced acute inflammation, PEG-ylated liposomal formulation being of choice among the tested delivery systems.

Role of ERK/NFκB in vanadium (IV) oxide mediated osteoblast differentiation in C3H10t1/2 cells

Vanadium (V) compounds are reported to have insulin mimicking action, which render them to show excellent osteogenic activity. In the current study we investigated the effect of various vanadium compounds on osteoblast differentiation of mouse mesenchymal stem cells, C3H10t1/2 cells, and analyzed the underlying mechanism of vanadium for this action. Our data showed that treatment of C3H10t1/2 cells with V (IV) oxide complex (at 7-25 μM concentrations) induced osteoblast differentiation maximally as compared to V2O5. On the other hand, ammonium vanadate was found to dampen the osteoblast differentiation process. Based on this data, V (IV) oxide was investigated further to analyze its probable mode of action as an osteoblastic agent. The key factors implicated in osteoblast differentiation i.e., NFκB, ERK ½, AP1 and CRE were examined in response to V (IV) oxide exposure. Exposure to V (IV) oxide caused 2- and 5-folds induction of luciferase activities in cells transfected with SRE-luc and NFκB-luc reporter vectors respectively (p < 0.05). Further, exposure to V (IV) oxide enhanced the phosphorylation of ERK ½, IκB and NFκBp65 proteins. In addition, RT-PCR analysis, alizarin red staining and immunoblot analysis showed that inhibition of osteoblast differentiation in presence of PD98059 and parthenolide (inhibitors of ERK and NFκB pathways respectively) was rescued in presence of V (IV) oxide. These results suggest that V (IV) oxide up regulates osteoblast differentiation through ERK and NFκB pathways and hence could be utilized as an agent for bone formation after further analysis and validation.

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

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

Oxidative stress and metal carcinogenesis

Occupational and environmental exposures to metals are closely associated with an increased risk of various cancers. Although carcinogenesis caused by metals has been intensively investigated, the exact mechanisms of action are still unclear. Accumulating evidence indicates that reactive oxygen species (ROS) generated by metals play important roles in the etiology of degenerative and chronic diseases. This review covers recent advances in (1) metal-induced generation of ROS and the related mechanisms; (2) the relationship between metal-mediated ROS generation and carcinogenesis; and (3) the signaling proteins involved in metal-induced carcinogenesis, especially intracellular reduction-oxidation-sensitive molecules.

Nickel (II)-induced cytotoxicity and apoptosis in human proximal tubule cells through a ROS- and mitochondria-mediated pathway

Nickel compounds are known to be toxic and carcinogenic in kidney and lung. In this present study, we investigated the roles of reactive oxygen species (ROS) and mitochondria in nickel (II) acetate-induced cytotoxicity and apoptosis in the HK-2 human renal cell line. The results showed that the cytotoxic effects of nickel (II) involved significant cell death and DNA damage. Nickel (II) increased the generation of ROS and induced a noticeable reduction of mitochondrial membrane potential (MMP). Analysis of the sub-G1 phase showed a significant increase in apoptosis in HK-2 cells after nickel (II) treatment. Pretreatment with N-acetylcysteine (NAC) not only inhibited nickel (II)-induced cell death and DNA damage, but also significantly prevented nickel (II)-induced loss of MMP and apoptosis. Cell apoptosis triggered by nickel (II) was characterized by the reduced protein expression of Bcl-2 and Bcl-xL and the induced the protein expression of Bad, Bcl-Xs, Bax, cytochrome c and caspases 9, 3 and 6. The regulation of the expression of Bcl-2-family proteins, the release of cytochrome c and the activation of caspases 9, 3 and 6 were inhibited in the presence of NAC. These results suggest that nickel (II) induces cytotoxicity and apoptosis in HK-2 cells via ROS generation and that the mitochondria-mediated apoptotic signaling pathway may be involved in the positive regulation of nickel (II)-induced renal cytotoxicity.

The effect of dietary vanadium on cell cycle and apoptosis of liver in broilers

The objective of this study was to clarify the effects of dietary vanadium on cell cycle and apoptosis of liver in broilers. Four hundred and twenty one-day-old avian broilers were divided into six groups and fed on a corn-soybean basal diet as control diet or the same diet amended to contain 5, 15, 30, 45, and 60 mg/kg vanadium supplied as ammonium metavanadate for 42 days. As tested by flow cytometry, hepatocytes in G (0)/G (1) phase were significantly increased in number in 45 and 60 mg/kg groups, and hepatocytes in S, G (2) + M phases in 45 and 60 mg/kg groups and the proliferation index of hepatocytes in 30, 45, and 60 mg/kg were markedly decreased when compared with those of control group. At the same time, the percentage of hepatocyte apoptosis was markedly increased in both 45 and 60 mg/kg groups. The results showed that dietary vanadium in the range of 45 ∼ 60 mg/kg caused cell cycle arrest and apoptosis of hepatocytes in broilers.

Vanadium pentoxide inhalation

Context:

This mini-review describes the toxic effects of vanadium pentoxide inhalation principally in the workplace and associated complications with breathing and respiration. Although there are some material safety data sheets available detailing the handling, hazards and toxicity of vanadium pentoxide, there are only two reviews listed in PubMed detailing its toxicity.

Aim:

To collate information on the consequences of occupational inhalation exposure of vanadium pentoxide on physiological function and wellbeing.

Materials and Methods:

The criteria used in the current mini-review for selecting articles were adopted from proposed criteria in The International Classification of Functioning, Disability and Health. Articles were classified from an acute and chronic exposure and toxicity thrust.

Results:

The lungs are the principal route through which vanadium pentoxide enters the body. It can injure the lungs and bronchial airways possibly involving acute chemical pneumonotis, pulmonary edema and/or acute tracheobronchitis. It may adversely influence cardiac autonomic function. It stimulates the secretion of cytokines and chemokines by hepatocytes and disrupts mitochondria function. It disrupts the permeability of the epithelium and promotes access of inflammatory mediators to the underlying neuronal tissue causing injury and neuronal death. When renal brush border membrane vesicles are exposed to vanadium pentoxide, there is a time-dependent inhibition of citrate uptake and Na⁺ K⁺ ATPase in the membrane possibly contributing to nephrotoxicity. Exposure results in necrosis of spermatogonium, spermatocytes and Sertoli cells contributing to male infertility.

Conclusion:

Vanadium pentoxide certainly has adverse effects on the health and the well-being and measures need to be taken to prevent hazardous exposure of the like.

Vanadium pentoxide (V(2)O(5)) induced mucin production by airway epithelium

Exposure to environmental pollutants has been linked to various airway diseases and disease exacerbations. Almost all chronic airway diseases such as chronic obstructive pulmonary disease and asthma are caused by complicated interactions between gene and environment. One of the major hallmarks of those diseases is airway mucus overproduction (MO). Excessive mucus causes airway obstruction and significantly increases morbidity and mortality. Metals are major components of environmental particulate matters (PM). Among them, vanadium has been suggested to play an important role in PM-induced mucin production. Vanadium pentoxide (V(2)O(5)) is the most common commercial source of vanadium, and it has been associated with occupational chronic bronchitis and asthma, both of which are MO diseases. However, the underlying mechanism is not entirely clear. In this study, we used both in vitro and in vivo models to demonstrate the robust inductions of mucin production by V(2)O(5). Furthermore, the follow-up mechanistic study revealed a novel v-raf-1 murine leukemia viral oncogene homolog 1-IKK-NF-κB pathway that mediated V(2)O(5)-induced mucin production. Most interestingly, the reactive oxygen species and the classical mucin-inducing epidermal growth factor receptor (EGFR)-MAPK pathway appeared not to be involved in this process. Thus the V(2)O(5)-induced mucin production may represent a novel EGFR-MAPK-independent and environmental toxicant-associated MO model. Complete elucidation of the signaling pathway in this model will not only facilitate the development of the treatment for V(2)O(5)-associated occupational diseases but also advance our understanding on the EGFR-independent mucin production in other chronic airway diseases.

Vanadium pentoxide induces pulmonary inflammation and tumor promotion in a strain-dependent manner

Background

Elevated levels of air pollution are associated with increased risk of lung cancer. Particulate matter (PM) contains transition metals that may potentiate neoplastic development through the induction of oxidative stress and inflammation, a lung cancer risk factor. Vanadium pentoxide (V₂O₅) is a component of PM derived from fuel combustion as well as a source of occupational exposure in humans. In the current investigation we examined the influence of genetic background on susceptibility to V₂O₅-induced inflammation and evaluated whether V₂O₅ functions as a tumor promoter using a 2-stage (initiation-promotion) model of pulmonary neoplasia in mice.

Results

A/J, BALB/cJ (BALB), and C57BL/6J (B6) mice were treated either with the initiator 3-methylcholanthrene (MCA; 10 μg/g; i.p.) or corn oil followed by 5 weekly aspirations of V₂O₅ or PBS and pulmonary tumors were enumerated 20 weeks following MCA treatment. Susceptibility to V₂O₅-induced pulmonary inflammation was assessed in bronchoalveolar lavage fluid (BALF), and chemokines, transcription factor activity, and MAPK signaling were quantified in lung homogenates. We found that treatment of animals with MCA followed by V₂O₅ promoted lung tumors in both A/J (10.3 ± 0.9 tumors/mouse) and BALB (2.2 ± 0.36) mice significantly above that observed with MCA/PBS or V₂O₅ alone (P < 0.05). No tumors were observed in the B6 mice in any of the experimental groups. Mice sensitive to tumor promotion by V₂O₅ were also found to be more susceptible to V₂O₅-induced pulmonary inflammation and hyperpermeability (A/J>BALB>B6). Differential strain responses in inflammation were positively associated with elevated levels of the chemokines KC and MCP-1, higher NFκB and c-Fos binding activity, as well as sustained ERK1/2 activation in lung tissue.

Conclusions

In this study we demonstrate that V₂O₅, an occupational and environmentally relevant metal oxide, functions as an in vivo lung tumor promoter among different inbred strains of mice. Further, we identified a positive relationship between tumor promotion and susceptibility to V₂O₅-induced pulmonary inflammation. These findings suggest that repeated exposures to V₂O₅ containing particles may augment lung carcinogenesis in susceptible individuals through oxidative stress mediated pathways.

Nickel(II)-induced oxidative stress, apoptosis, G2/M arrest, and genotoxicity in normal rat kidney cells

In order to elucidate the effects of nickel (Ni) on oxidative stress, apoptosis, and genotoxicity in renal cells, the levels of intracellular oxidants, lipid peroxidation, apoptotic proteins, and DNA damage were measured in normal rat kidney (NRK) cells after nickel chloride (NiCl(2)) treatment. NiCl(2) appeared to increase the formation of the fluorescent oxidized compound (dichlorofluorescein, DCF) and levels of thiobarbituric acid-reactive substances (TBARS). In flow cytometric analysis, a rise in cell proportion in sub-G1 phase occurred in a concentration-dependent manner. After Ni treatment, there was reduced expression of Bcl-2 and Bcl-xL proteins, while induced Bad and Bax proteins expression was higher. Single-strand DNA breakage induced by Ni in NRK cells was determined by comet assay. Significant increase DNA damage score (arbitrary units) was noted in a concentration-related manner after treatment with Ni. Induction of intracellular oxidants by Ni was accompanied by an increasing frequency of DNA strand breakage. Our data indicate that Ni-induced oxidative stress and genotoxicity in NRK cells may involve reactive oxygen intermediates, and that Bcl family-mediated signaling pathway may be involved in positive regulation of Ni-induced renal cytotoxicity.

Role of Foxa1 in regulation of bcl2 expression during oxidative-stress-induced apoptosis in A549 type II pneumocytes

Forkhead box protein A1 (Foxa1) is an evolutionarily conserved winged helix transcription factor that was traditionally considered to be involved in embryonic development and cell differentiation. However, little is known about the role of Foxa1 in oxidative-stress-induced apoptosis. In this study, hydrogen peroxide (H(2)O(2))-induced apoptosis, upregulation of Foxa1, and the role of Foxa1 in the regulation of bcl2 gene expression were studied in A549 type II pneumocytes. H(2)O(2) upregulated Foxa1 mRNA and protein in a time- and dose-dependent manner. Overexpression of Foxa1 promoted apoptosis, whereas Foxa1 deficiency, induced by antisense oligonucleotides, decreased A549 cell apoptosis induced by H(2)O(2), as shown by flow cytometry. Moreover, Foxa1 overexpression decreased the expression of bcl2, while Foxa1 depletion increased the expression of bcl2. Electrophoretic mobility shift assay and chromatin immunoprecipitation revealed that Foxa1 bound to bcl2 promoter, and H(2)O(2) promoted its DNA binding activity. Luciferase reporter showed that Foxa1 also decreased the transcription activity of bcl2 promoter under normal conditions and oxidative stress. These results indicate that Foxa1 plays a pro-apoptotic role by inhibiting the expression of anti-apoptotic gene bcl2.

Early signalling pathways in rice roots under vanadate stress

Vanadate is beneficial to plant growth at low concentration. However, plant exposure to high concentrations of vanadate has been shown to arrest cell growth and lead to cell death. We are interested in understanding the signalling pathways of rice roots in response to vanadate stress. In this study, we demonstrated that vanadate induced rice root cell death and suppressed root growth. In addition, we found that vanadate induced ROS accumulation, increased lipid peroxidation and elicited a remarkable increase of MAPKs and CDPKs activities in rice roots. In contrast, pre-treatment of rice roots with ROS scavenger (sodium benzoate), serine/threonine protein phosphatase inhibitor (endothall), and CDPK antagonist (W7), reduced the vanadate-induced MAPKs activation. Furthermore, the expression of a MAPK gene (OsMPK3) and four tyrosine phosphatase genes (OsDSP3, OsDSP5, OsDSP6, and OsDSP10) were regulated by vanadate in rice roots. Collectively, these results strongly suggest that ROS, protein phosphatase, and CDPK may function in the vanadate-triggered MAPK signalling pathway cause cell death and retarded growth in rice roots.

A review of current toxicological concerns on vanadium pentoxide and other vanadium compounds: gaps in knowledge and directions for future research

Vanadium pentoxide (V(2)O(5)) and other inorganic vanadium compounds have recently been evaluated by several occupational exposure limit (OEL) setting (occupational exposure limit, OEL) committees and expert groups in response to the publication of several new studies, including the U.S. National Toxicology Program (NTP, 2002) carcinogenicity study of inhaled V(2)O(5) in rats and mice, which concluded that clear evidence of lung tumors was seen in mice of both genders and that there was some evidence of carcinogenicity in male rats. This study reviews the expert evaluations of several OEL committees and expert groups and attempts to understand the strengths and weaknesses in their scientific arguments. This study also evaluates some key studies relating to potential genotoxicity, carcinogenicity, and respiratory effects of vanadium compounds and discusses how they might elucidate the mechanism(s) by which V(2)O(5) induces lung cancer in mice. All expert groups appear to agree that the lung tumors induced in mice in the NTP (2002) study are a site-specific response and, in general, verify that existing in vitro and in vivo studies suggest that tumors were induced by a secondary mechanism (presumably non-genotoxic), which is supported, though not conclusively, by a mechanistic data set. As some vanadium compounds produce a range of DNA and chromosome damage, there is no consensus on which of these changes is critical for the carcinogenic process for V(2)O(5) or whether the findings for the lung tumors seen in mice exposed to V(2)O(5) can be extrapolated to other inorganic vanadium compounds. As such, the various expert committees used the evidence differently, some to read across, i.e., to predict an endpoint for a substance based on the endpoint information of another with similar characteristics (e.g., physicochemical properties [solubility, bioaccessibility, bioavailability], structure, fate [toxicokinetics], and toxicology) for carcinogenicity from V(2)O(5) to other inorganic vanadium compounds. It is noteworthy that the toxicity of metals does not necessarily relate to carcinogenicity in a direct manner; thus, no assumptions should be made a priori when trying to extrapolate from V(2)O(5) to other inorganic vanadium compounds. Recent studies evaluated in this review provided some further insights into possible mechanisms but do not cover all relevant endpoints, address only a limited number of vanadium compounds, and have not established no-effect thresholds for carcinogenicity or respiratory tract irritation. Thresholds need to be established in order for arguments to be made for setting a health-based OEL for non-genotoxic or secondary genotoxic carcinogens. In conclusion, important knowledge gaps preclude confident classification and risk assessment for all vanadium compounds. Evidence suggests that further research that may address some of these critical gaps is needed.

Pulmonary toxicity and environmental contamination: radicals, electron transfer, and protection by antioxidants

The atmosphere is replete with a mixture of toxic substances, both natural and man-made. Inhalation of toxic substances produces a variety of insults to the pulmonary system. Lung poisons include industrial materials, particulates from mining and combustion, agricultural chemicals, cigarette smoke, ozone, and nitrogen oxides, among a large number of other chemicals and environmental contaminants. Many proposals have been advanced to explain the mode of action of pulmonary toxicants. In this review we focus on mechanisms of pulmonary toxicity that involve ET, ROS, and OS. The vast majority of toxicants or their metabolites possess chemical ET functionalities that can undergo redox cycling. Such recycling may generate ROS that can injure various cellular constituents in the lung and in other tissues. ET agents include quinones, metal complexes, aromatic nitro compounds, and conjugated iminium ions. Often, these agents are formed metabolically from parent toxicants. Such metabolic reactions are often catalytic and require only small amounts of the offending material. Oxidative attack is commonly associated with lipid peroxidation and oxidation of DNA, and it may result in strand cleavage and 8-OH-DG production. Toxicity is often accompanied by depletion of natural AOs, which further exacerbates the toxic effect. It is not surprising that the use of AOs, both natural in fruits and vegetables, as well as synthetic, may provide protection from the adverse effects of toxicant exposure. The mechanistic framework described earlier is also applicable to some of the more prominent pulmonary illnesses, such as asthma, COPD, and cancer.

Environmental toxicity, oxidative stress and apoptosis: ménage à trois

Apoptosis is an evolutionary conserved homeostatic process involved in distinct physiological processes including organ and tissue morphogenesis, development and senescence. Its deregulation is also known to participate in the etiology of several human diseases including cancer, neurodegenerative and autoimmune disorders. Environmental stressors (cytotoxic agents, pollutants or toxicants) are well known to induce apoptotic cell death and to contribute to a variety of pathological conditions. Oxidative stress seems to be the central element in the regulation of the apoptotic pathways triggered by environmental stressors. In this work, we review the established mechanisms by which oxidative stress and environmental stressors regulate the apoptotic machinery with the aim to underscore the relevance of apoptosis as a component in environmental toxicity and human disease progression.

Possible involvement of MAP kinase pathways in acquired metal-tolerance induced by heat in plants

Cross tolerance is a phenomenon that occurs when a plant, in resisting one form of stress, develops a tolerance to another form. Pretreatment with nonlethal heat shock has been known to protect cells from metal stress. In this study, we found that the treatment of rice roots with more than 25 muM of Cu(2+) caused cell death. However, heat shock pretreatment attenuated Cu(2+)-induced cell death. The mechanisms of the cross tolerance phenomenon between heat shock and Cu(2+) stress were investigated by pretreated rice roots with the protein synthesis inhibitor cycloheximide (CHX). CHX effectively block heat shock protection, suggesting that protection of Cu(2+)-induced cell death by heat shock was dependent on de novo protein synthesis. In addition, heat pretreatment downregulated ROS production and mitogen-activated protein kinase (MAPK) activities, both of which can be greatly elicited by Cu(2+) stress in rice roots. Moreover, the addition of purified recombinant GST-OsHSP70 fusion proteins inhibited Cu(2+)-enhanced MAPK activities in an in vitro kinase assay. Furthermore, loss of heat shock protection was observed in Arabidopsis mkk2 and mpk6 but not in mpk3 mutants under Cu(2+) stress. Taken together, these results suggest that the interaction of OsHSP70 with MAPKs may contribute to the cellular protection in rice roots from excessive Cu(2+) toxicity.

Impact du thé vert sur l'effet oxydatif du métavanadate d'ammonium chez le rat male pubère

Transitional metals, as vanadium, are known to exert noxious effects by generating oxidative stress. Addition of antioxidants in the diet could decrease the cytotoxic effect related to the oxidative stress. The present study, carried out in Wistar rats, is a contribution to the evaluation of protective effects of green tea Camellia sinensis, which is known to be rich in antioxidant compounds (polyphenols...). Rats were divided into four groups: (C) was control, (V) was given ammonium metavanadate (AMV), (TH) was given herbal tea as drink (66 g/l) and TH + V was given tea and metavanadate. Group (TH) was given herbal tea one month before vanadium treatment. Metavanadate was daily i.p. injected (5 mg NH4VO3/kg body weight) for 10 days. (C) and (TH) groups received i.p. injections of 0.9% NaCl during the same period. Changes in lipid peroxidation levels (TBARS) in kidney, liver and testes, serum concentrations of vitamins E and A and superoxidismutase (SOD) and catalase (CAT) activities in blood cells were determined. One month pre-treatment with green tea, followed by 10 days of treatment (TH) did not change TBARS in liver and testes as compared to controls, but induced a clear decrease of TBARS in kidneys. Intraperitoneal administration of AMV to rats (V) induced a time-dependant increase of TBARS in kidney, liver and testes that was lowered in rats (V + TH) drinking tea. Vitamin E concentrations were found to be drastically decreased from day 1 to 10 in rats (V). Vitamin A concentration was decreased at day 10 only. Drinking tea lowered AMV inhibitory effects in rats (V + TH), and conversely an increase of vitamins A and E concentrations were found at day 10. SOD and catalase activities were found increased in the blood cells from day 1 to day 5 and conversely decreased at day 10. In contrast, associated to green tea, AMV did not affect SOD and catalase activities compared to controls.

Biological activity of vanadium compounds

Vanadium compounds are characterised by a broad spectrum of action in vivo and in vitro. Their insulin-mimetic activity is manifested in their ability to normalize changes observed in both clinical and experimental diabetes (i.e. hyperglycaemia, hyperlipidaemia, lowered cell sensitivity to insulin) through the regulation of carbohydrate and lipid metabolism and the removal of secondary symptoms of this disease (as e.g. retinopathy, cardiomyopathy, nephropathy). Nevertheless, vanadium is considered to be a toxic element in both cationic and anionic form, although the latter type has more serious side effects. This is accounted for by the faster absorption of anionic forms, although the chemical structure, geometry, and the manner of synthesis of its derivatives also contributes to this elevated toxicity. Besides their antidiabetic properties, vanadium derivatives have also been observed to influence processes related to mitogenic cell responses (apoptosis, proliferation, neoplastic transformation). However, both anti-and pro-neoplastic properties of vanadium are reported.

Nickel and vanadium metal ions induce apoptosis of T-lymphocyte Jurkat cells

Metal alloys are used as prosthetic components in the orthopaedic and dental field. However, there is growing concern over the reported leaching of metal ions from implants. Ions released from metals have been thought to be associated with local immune dysfunction, inflammation, and tissue cell death. The objective of our study was to investigate whether nickel(II) and vanadium(V), present at a smaller percentage in most alloys, are cytotoxic to T-lymphocyte cell models. Jurkat T cells possess characteristics similar to human T-lymphocytes and proliferate at a faster rate. Jurkat T cells were incubated with control media alone or with concentrations of 1, 10, and 100 microg/mL of Ni(II) or V(V) for 24 h. Both types of metal ions reduced cell viability and proliferation in a dose-dependent manner. Ni(II) at 10 microg/mL and V(V) at 100 microg/mL activated Caspase-3 expression. Hoechst 33258 staining and transmission electron microscopy revealed chromatin condensation, as well as nuclear blebbing and fragmentation. Induction of DNA fragmentation by Ni(II) at 100 microg/mL was also indicated by agarose electrophoresis. Our observations indicate that Ni and V ions kill T cells via apoptotic and nonapoptotic pathways.

Vanadium promotes hydroxyl radical formation by activated human neutrophils

This study was undertaken to investigate the effects of vanadium in the +2, +3, +4, and +5 valence states on superoxide generation, myeloperoxidase (MPO) activity, and hydroxyl radical formation by activated human neutrophils in vitro, using lucigenin-enhanced chemiluminescence (LECL), autoiodination, and electron spin resonance with 5,5-dimethyl-l-pyrroline N-oxide as the spin trap, respectively. At concentrations of up to 25 microM, vanadium, in the four different valence states used, did not affect the LECL responses of neutrophils activated with either the chemoattractant, N-formyl-l-methionyl-l-leucyl-l-phenylalanine (1 microM), or the phorbol ester, phorbol 12-myristate 12-acetate (25 ng/ml). However, exposure to vanadium in the +2, +3, and +4, but not the +5, valence states was accompanied by significant augmentation of hydroxyl radical formation by activated neutrophils and attenuation of MPO-mediated iodination. With respect to hydroxyl radical formation, similar effects were observed using cell-free systems containing either hydrogen peroxide (100 microM) or xanthine/xanthine oxidase together with vanadium (+2, +3, +4), while the activity of purified MPO was inhibited by the metal in these valence states. These results demonstrate that vanadium in the +2, +3, and +4 valence states interacts prooxidatively with human neutrophils, competing effectively with MPO for hydrogen peroxide to promote formation of the highly toxic hydroxyl radical.

Induction of COX-2 protein expression by vanadate in A549 human lung carcinoma cell line through EGF receptor and p38 MAPK-mediated pathway

Vanadate is a transition metal widely distributed in the environment. It has been reported that vanadate associated with air pollution particles can modify DNA synthesis, causing cell growth arrest, and apoptosis. Moreover, vanadium exposure was also found to cause the synthesis of inflammatory cytokines, such as interleukin-1, tumor necrosis factor-alpha, and prostaglandin E(2). Here, we found that exposure of A549 human lung carcinoma cells to vanadate led to extracellular signal-regulated kinase, c-Jun NH(2)-terminal protein kinases (JNKs), p38 mitogen-activated protein kinase (p38) activation, and COX-2 protein expression in a dose-dependent manner. SB203580, a p38 MAPK inhibitor, but not PD098059 and SP600125, specific inhibitor of MKK1 and selective inhibitor of JNK, respectively, suppressed COX-2 expression. Furthermore, the epithelial growth factor (EGF) receptor specific inhibitor (PD153035) reduced vanadate-induced COX-2 expression. However, scavenging of vanadate-induced reactive oxygen species by catalase, a specific H(2)O(2) inhibitor, or DPI, an NADPH oxidase inhibitor, resulted in no inhibition on COX-2 expression. Together, we suggested that EGF receptor and p38 MAPK signaling pathway may be involved in vanadate-induced COX-2 protein expression in A549 human lung carcinoma cell line.

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.

Regulation of Fas (CD95)-induced apoptotic and necrotic cell death by reactive oxygen species in macrophages

Although reactive oxygen species (ROS) have long been suspected to play a key role in Fas (CD95)-induced cell death, the identity of specific ROS involved in this process and the relationship between apoptotic and necrotic cell death induced by Fas are largely unknown. Using electron spin resonance (ESR) spectroscopy, we showed that activation of Fas receptor by its ligand (FasL) in macrophages resulted in a rapid and transient production of hydrogen peroxide (H2O2) and hydroxyl radicals (*OH). The response was visible as early as 5 min and peaked at approximately 45 min post-treatment. Morphological analysis of total death response (apoptosis vs. necrosis) showed dose and time dependency with apoptosis significantly increased at 6 h after the treatment, while necrosis remained at a baseline level. Only at a 35-fold increase in apoptosis did necrosis become significant. Inhibition of apoptosis by a pan-caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-(OMe) fluoromethyl ketone (zVAD-fmk), significantly inhibited cell necrosis, indicating the linkage between the two events. Catalase (H2O2 scavenger) and deferoxamine (*OH scavenger) effectively inhibited the total death response as well as the ESR signals, while superoxide dismutase (SOD) (O2*- scavenger) had minimal effects. These results established the role for H2O2 and *OH as key participants in Fas-induced cell death and indicated apoptosis as a primary mode of cell death preceding necrosis. Because the Fas death pathway is implicated in various inflammatory and immunologic disorders, utilization of antioxidants and apoptosis inhibitors as potential therapeutic agents may be advantageous.

Metal-induced oxidative stress and signal transduction

Occupational and environmental exposures to metals are associated with the development of various cancers. Although carcinogenesis caused by metals has been intensively investigated, the mechanisms of action, especially at the molecular level, are still unclear. Accumulating evidence indicates that reactive oxygen species generated by metals may play an important role in the etiology of disease. This review covers recent advances in (1) metal-induced generation of reactive oxygen species; (2) the receptors, kinases, and nuclear transcription factors affected by metals and metal-induced oxidative stress, including growth factor receptors, src kinase, ras signaling, mitogen-activated protein kinases, the phosphoinositide 3-phosphate/Akt pathway, nuclear transcription factor kappaB, activator protein 1, p53, nuclear factor of activated T cells, and hypoxia-inducible factor 1; and (3) global cellular phenomena (signal transduction, cell cycle regulation, and apoptosis) associated with metal-induced ROS production and gene expression.

Extracellular superoxide dismutase attenuates lipopolysaccharide-induced neutrophilic inflammation

Extracellular superoxide dismutase (EC-SOD) is an abundant antioxidant in the lung and vascular walls. Previous studies have shown that EC-SOD attenuates lung injury in a diverse variety of lung injury models. In this study, we examined the role of EC-SOD in mediating lipopolysaccharide (LPS)-induced lung inflammation. We found that LPS-induced neutrophilic lung inflammation was exaggerated in EC-SOD-deficient mice and diminished in mice that overexpressed EC-SOD specifically in the lung. Similar patterns were seen for bronchoalveolar lavage cytokines, such as tumor necrosis factor-alpha, keratinocyte-derived chemokines, and macrophage inflammatory protein-2 as well as expression of lung intercellular adhesion molecule-1, vascular cell adhesion molecule-1, endothelial cell selectin, and platelet selectin. In a macrophage cell line, EC-SOD inhibited LPS-induced macrophage cytokine release, but did not alter expression of intercellular adhesion molecules in endothelial cells. These results suggest that EC-SOD plays an important role in attenuating the inflammatory response in the lung most likely by decreasing release of proinflammatory cytokines from phagocytes.

Mitochondrial transmembrane potential is diminished in phorbol myristate acetate-stimulated peritoneal resident macrophages isolated from wild-type mice, but not in those from gp91-phox-deficient mice

Macrophages produce superoxide (O2-) during phagocytosis or upon stimulation with a variety of agents including phorbol myristate acetate (PMA) through the activation of NADPH oxidase, and the formed O2- is converted to other reactive oxygen species (ROS) such as hydrogen peroxide (H2O2). The aim of the present study was to elucidate the effect of the intracellularly produced ROS on mitochondrial transmembrane potential (MTP) in mouse (C57BL/6) peritoneal resident macrophages stimulated with PMA. Using a fluorescent dye, succinimidyl ester of dichlorodihydrofluorescein (H2DCFDA), O2- was visualized in intracellular compartments in a certain subpopulation of macrophages isolated from wild-type mice. Cells deficient in gp91-phox, one of the membrane components of NADPH oxidase, were negative for the fluorescence. When cells were loaded with both H2DCFDA and MitoCapture, a fluorescent dye for mitochondria, mitochondrial fluorescence was diminished in O2- -producing cells, but not in O2- -deficient cells. Flow cytometry also revealed the decrease of mitochondrial fluorescence in wild-type cells, but not in gp91-phox-deficient cells. The loss of mitochondrial fluorescence was prevented by microinjection of catalase into cells. The present findings demonstrate that MTP is diminished by ROS, including the H2O2 dismutated from O2-, produced intracellularly by activation of the NADPH oxidase in mouse peritoneal resident macrophages stimulated with PMA.

Synchronized generation of reactive oxygen species with the cell cycle

A possible appearance of reactive oxygen species (ROS) with the normal cell cycle was studied to find how ROS are generated in cells in relation to the cell cycle. The production of ROS in relation to the cell cycle was examined by determining the changes in intracellular ROS concentrations at different phases of the cell cycle by culturing BALB 3T3 cells in the presence and absence of aphidicolin. The amounts of intracellular ROS and the cell population at specific phases (S and G2/M) were determined as the fluorescence of dichlorodihydrofluorescein and propidium iodide taken up simultaneously by the cells, respectively, by flow cytometry. Although intracellular ROS remained at the control levels when the cell growth was arrested with aphidicolin at the G1 phase, they increased when the arrest was released to result in the increase of the cell population at the S phase. Furthermore, ROS was shown to disturb/stop the cell cycle by means of the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. The cell cycle was regulated through oxidative stress by exposure to hydrogen peroxide and glutathione ethyl ester. The cell cycle was prevented more sensitively in metallothionein-null cells than in the wild type cells. Based on the present observations, we proposed for the first time that ROS are generated synchronously with the normal cell cycle, and that they have to be controlled at certain level for normal progress of the cell cycle.

Role of NADPH oxidase in arsenic-induced reactive oxygen species formation and cytotoxicity in myeloid leukemia cells

Arsenic has played a key medicinal role against a variety of ailments for several millennia, but during the past century its prominence has been displaced by modern therapeutics. Recently, attention has been drawn to arsenic by its dramatic clinical efficacy against acute promyelocytic leukemia. Although toxic reactive oxygen species (ROS) induced in cancer cells exposed to arsenic could mediate cancer cell death, how arsenic induces ROS remains undefined. Through the use of gene expression profiling, interference RNA, and genetically engineered cells, we report here that NADPH oxidase, an enzyme complex required for the normal antibacterial function of white blood cells, is the main target of arsenic-induced ROS production. Because NADPH oxidase enzyme activity can also be stimulated by phorbol myristate acetate, a synergism between arsenic and the clinically used phorbol myristate acetate analog, bryostatin 1, through enhanced ROS production can be expected. We show that this synergism exists, and that the use of very low doses of both arsenic and bryostatin 1 can effectively kill leukemic cells. Our findings pinpoint the arsenic target of ROS production and provide a conceptual basis for an anticancer regimen.