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

Correlation between Metal Ions and Cytokines in the Saliva of Patients with Oral Lichenoid Lesions

PURPOSE

We aimed to investigate the effect of metal ions from oral prostheses (OPs) released into the saliva of patients with oral lichenoid lesions (OLLs).

MATERIALS AND METHODS

Subjects (n=183) were divided into four groups according to the presence or absence of OLL and OP. Concentrations of the metal ions titanium, chromium (Cr), cobalt (Co), nickel (Ni), palladium (Pd), silver (Ag), platinum (Pt), gold (Au), and zirconium (Zr) were measured using a laser-ablation microprobe inductively coupled to a plasma mass spectrometer. Saliva levels of interleukin (IL)-6, IL-1β, IL-8, and tumor necrosis factor-α were detected using an enzyme-linked immunosorbent assay. The reticulation/keratosis, erythema, and ulceration (REU) scoring system was used to assess the severity of OLL.

RESULTS

Mean concentrations of IL-6 and IL-8 were statistically higher in OLL patients with OPs. The concentration of Ni was high in OLL groups. The concentrations of Cr, Ni, and Au ions in the saliva were positively correlated with IL-8. REU scores were positively correlated with salivary concentrations of IL-6 and IL-8, as well as with concentrations of Cr, Ni, and Au.

CONCLUSION

Increased concentrations of metal ions, especially Ni, in saliva were positively correlated with IL-8 and showed positive correlations with the severity of OLL.

Heavy metals contaminating the environment of a progressive supranuclear palsy cluster induce tau accumulation and cell death in cultured neurons

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder characterized by the presence of intracellular aggregates of tau protein and neuronal loss leading to cognitive and motor impairment. Occurrence is mostly sporadic, but rare family clusters have been described. Although the etiopathology of PSP is unknown, mutations in the MAPT/tau gene and exposure to environmental toxins can increase the risk of PSP. Here, we used cell models to investigate the potential neurotoxic effects of heavy metals enriched in a highly industrialized region in France with a cluster of sporadic PSP cases. We found that iPSC-derived iNeurons from a MAPT mutation carrier tend to be more sensitive to cell death induced by chromium (Cr) and nickel (Ni) exposure than an isogenic control line. We hypothesize that genetic variations may predispose to neurodegeneration induced by those heavy metals. Furthermore, using an SH-SY5Y neuroblastoma cell line, we showed that both heavy metals induce cell death by an apoptotic mechanism. Interestingly, Cr and Ni treatments increased total and phosphorylated tau levels in both cell types, implicating Cr and Ni exposure in tau pathology. Overall, this study suggests that chromium and nickel could contribute to the pathophysiology of tauopathies such as PSP by promoting tau accumulation and neuronal cell death.

Microstructure, Wettability, Corrosion Resistance and Antibacterial Property of Cu-MTa2O5 Multilayer Composite Coatings with Different Cu Incorporation Contents

Bacterial infection and toxic metal ions releasing are the challenges in the clinical application of Ti6Al4V alloy implant materials. Copper is a kind of long-acting, broad-spectrum and safe antibacterial element, and Ta2O5 has good corrosion resistance, wear-resistance and biocompatibility, they are considered and chosen as a potential coating candidate for implant surface modification. In this paper, magnetron sputtering technology was used to prepare copper doped Ta2O5 multilayer composite coating Cu-Ta2O5/Ta2O5/Ta2O5-TiO2/TiO2/Ti (Cu-MTa2O5 for short) on Ti6Al4V alloy surface, for studying the effect of copper incorporation on the microstructure, wettability, anticorrosion and antibacterial activities of the composite coating. The results showed that Cu-MTa2O5 coating obviously improves the hydrophobicity, corrosion resistance and antibacterial property of Ti6Al4V alloy. In the coating, both copper and Ta2O5 exhibit an amorphous structure and copper mainly presents as an oxidation state (Cu2O and CuO). With the increase of the doping amount of copper, the grain size, roughness, and hydrophobicity of the modified surface of Ti6Al4V alloy are increased. Electrochemical experiment results demonstrated that the corrosion resistance of Cu-MTa2O5 coated Ti6Al4V alloy slightly decreased with the increase of copper concentration, but this coating still acts strong anticorrosion protection for Ti6Al4V alloy. Moreover, the Cu-MTa2O5 coating can kill more than 97% of Staphylococcus aureus in 24 h, and the antibacterial rate increases with the increase of copper content. Therefore, Cu-MTa2O5 composite coating is a good candidate for improving anticorrosion and antibacterial properties of Ti6Al4V alloy implant medical devices.

The Preparation and Properties of Multilayer Cu-MTa2O5 Composite Coatings on Ti6Al4V for Biomedical Applications

For the enhancement of the anticorrosion and antibacterial performance of the biomedical alloy Ti6Al4V, a novel Cu incorporated multilayer Ta2O5ceramic composite coating Cu-Ta2O5/Ta2O5/Ta2O5-TiO2/TiO2/Ti (coating codeCu-MTa2O5) was developed by radio frequency (RF) and direct current (DC) reactive magnetron sputtering. Meanwhile, to better display the multilayer Ta2O5 coating mentioned above, a monolayer Ta2O5 ceramic coating was deposited onto the surface of Ti6Al4V alloy as a reference. The surface morphology, microstructure, phase constituents, and elemental states of the coating were evaluated by atomic force microscopy, scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy, respectively. The adhesion strength, wettability, anticorrosion and antibacterial properties of the coating were examined by a scratch tester, contact angle measurement, electrochemical workstations, and plate counting method, respectively. The results showed that the deposited coatings were amorphous and hydrophobic. Cu doped into the Ta2O5 coating existed as CuO and Cu2O. A Ta2O5-TiO2/TiO2/Ti multi-interlayer massively enhanced the adhesion strength of the coating, which was 2.9 times stronger than that of the monolayer Ta2O5coating. The multilayer Cu-MTa2O5 coating revealed a higher corrosion potential and smaller corrosion current density as compared to the uncoated Ti6Al4V, indicating the better anticorrosion performance of Ti6Al4V. Moreover, a 99.8% antibacterial effect of Cu-MTa2O5 coated against Staphylococcus aureuswas obtained.

Mito-targeted "turn-on" fluorescent probe for nickel (II) detection

In this paper, we unveil a new highly selective and sensitive mito-tracker (NiP) for Ni²⁺ detection. NiP itself held very weak fluorescence and exhibited a high selectivity (≥160-fold) toward Ni²⁺ over other metal ions, with a limit of detection of 21.6 nmol. We demonstrate the practicality of NiP for the rapid determination of Ni²⁺ levels in mitochondria of living cells. This approach offers advantages by being fast, simple and low cost.

Nickel-induced neurodegeneration in the hippocampus, striatum and cortex; an ultrastructural insight, and the role of caspase-3 and α-synuclein

Human overexposure to nickel (Ni) emanating from the increasing application of Ni compounds in modern technology is a major public health concern. Nickel has been shown to be teratogenic, immunotoxic, genotoxic and carcinogenic. The current knowledge on Ni neurotoxicity is still relatively limited. We have previously demonstrated that Ni treatment alters cognitive and locomotor behaviors, induces oxidative stress and neurodegeneration in brains of rats. In this study, we examine the ultrastructural changes to neurons in the hippocampus, striatum and cortex of the brain following Ni treatment, as well as attempt to delineate the roles for caspase-3 and α-synuclein in Ni-induced neurodegeneration. Rats were treated with either saline, 10 or 20 mg/kg of nickel chloride for 4 weeks via oral gavage. Electron microscopy analysis revealed ultrastructural alterations in neurons of the hippocampus, striatum and cortex following Ni treatment. Mitochondria structural integrity within neurons were markedly compromised. We also detected elevated caspase-3 activity in hippocampus and striatum, as well as overexpression of α-synuclein in the cortex following Ni treatment. Our study demonstrates that mitochondria are a key target in Ni-induced neurodegeneration. Additionally, we implicate apoptotic pathway via caspase-3 action as the executioner and perturbation of α-synuclein expression in Ni-induced neurodegeneration.

Particulate and ion forms of cobalt-chromium challenged preosteoblasts promote osteoclastogenesis and osteolysis in a murine model of prosthesis failure

This study investigated the interactive behavior of the particulate and ion forms of cobalt-chromium (Co-Cr) alloy challenged preosteoblasts during the process of prosthetic implant loosening. Preosteoblasts were challenged with Co-Cr particles or Co(II) ions for 72 h, followed by the proliferation and PCR assays. For in vivo test, a titanium pin was implanted into proximal tibia of SCID mice to mimic knee replacement. Co-Cr particles or Co(II) ion challenged preosteoblasts (5 × 10⁵ ) were intra-articularly injected into the implanted knee. The animals were sacrificed 5 weeks post-op, and the prosthetic knees were harvested for biomechanical pin-pullout testing, histological evaluations, and microCT assessment. In vitro study suggested that Co-Cr particles and Co(II) ions significantly suppressed the proliferation of preosteoblasts in a dose-dependent manner. RT-PCR data on the challenged cells indicated overexpression of receptor activator of nuclear factor kappa-B ligand (RANKL) and inhibited osteoprotegerin (OPG) gene expression. Introduction of the differently challenged preosteoblasts to the pin-implant mouse model resulted in reduced implant interfacial shear strength, thicker peri-implant soft-tissue formation, more TRAP+ cells, lower bone mineral density, and bone volume fraction. In conclusion, both Co-Cr particles and Co(II) ions interfered with the growth, maturation, and functions of preosteoblasts, and provides evidence that the metal ions as well play an important role in effecting preosteoblasts in the pathogenesis of aseptic loosening. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 187-194, 2019.

Nickel (II) nitrate hexahydrate triggered canine neutrophil extracellular traps release in vitro

Nickel (II) nitrate hexahydrate (Ni) is a common heavy metal material in battery manufacturing, electroplating alloy parts and ceramic staining, therefore we frequently contact with Ni-related products in daily life. In this study, we aimed to investigate the effects of Ni on neutrophils extracellular traps (NETs) release by canine polymorphonuclear neutrophils (PMNs). The structure of Ni-induced NETs was observed by fluorescence confocal microscopy. Ni-triggered NETs release was quantified by Pico Green^® and fluorescence microplate reader. In addition, the inhibitors of NADPH oxidase, ERK1/2-, p38 - signaling pathways were used for preliminary inquiry into the potential mechanism of this process. The results showed that Ni markedly triggered the formation of NETs-like structures, and these structures were mainly consisted of DNA decorated with NE and MPO. Furthermore, quantification experiments showed that Ni significantly increased NETs formation compared to control groups. These results forcefully confirmed that nickel nitrate possesses the ability to induce NETs formation. However, inhibiting the NADPH oxidase, ERK1/2- and p38 MAPK-signaling pathways did not significantly change the quantitation of Ni-induced NETs release. To our knowledge, this study is the first report of Ni-triggered NETs release in vitro, which might provide an entirely new mechanism of several diseases and health issues induced by nickel overexposure.

Rough Titanium Oxide Coating Prepared by Micro-Arc Oxidation Causes Down-Regulation of hTERT Expression, Molecular Presentation, and Cytokine Secretion in Tumor Jurkat T Cells

The response of the human Jurkat T cell leukemia-derived cell line (Jurkat T cells) after 24 h of in vitro exposure to a titanium substrate (12 × 12 × 1 mm³) with a bilateral rough (R_a = 2.2–3.7 μm) titanium oxide coating (rTOC) applied using the micro-arc method in a 20% orthophosphoric acid solution was studied. A 1.5-fold down-regulation of hTERT mRNA expression and decreases in CD3, CD4, CD8, and CD95 presentation and IL-4 and TNFα secretion were observed. Jurkat T cell inactivation was not correlated with the generation of intracellular reactive oxygen species (ROS) and was not mediated by TiO₂ nanoparticles with a diameter of 14 ± 8 nm at doses of 1 mg/L or 10 mg/L. The inhibitory effect of the rTOC (R_a = 2.2–3.7 μm) on the survival of Jurkat T cells (Spearman’s coefficient r_s = −0.95; n = 9; p < 0.0001) was demonstrated by an increase in the necrotic cell count among the cell population. In turn, an elevation of the Ra index of the rTOC was accompanied by a linear increase (r = 0.6; p < 0.000001, n = 60) in the magnitude of the negative electrostatic potential of the titanium oxide surface. Thus, the roughness of the rTOC induces an electrostatic potential and decreases the viability of the immortalized Jurkat T cells through mechanisms unrelated to ROS generation. This may be useful for replacement surgery applications of rough TiO₂ implants in cancer patients.

Interaction of primary human trabecular meshwork cells with metal alloy candidates for microinvasive glaucoma surgery

BACKGROUND

Microinvasive glaucoma surgery (MIGS) is a relatively new addition to the glaucoma treatment paradigm. Small metallic stents are inserted into the trabecular meshwork in order to increase aqueous humour drainage. MIGS procedures are rapidly being adopted owing to a more favourable side effect profile when compared with traditional surgery. Remarkably, this rapid rate of utilization has occurred without any published studies on the effect of metal alloys used in these stents on human trabecular meshwork cells (HTMCs). Therefore, this study aimed to determine the effect of candidate metal alloys for MIGS on HTMC morphology, viability and function.

METHODS

Human trabecular meshwork cells were cultured on the surfaces of titanium (polished and sandblasted), a titanium-nickel (nitinol) alloy and glass (as control substratum). Fluorescence imaging was used to assess cell morphology and spreading. A lactate dehydrogenase cytotoxicity assay, cell death detection ELISA, MTT cell viability assay, BrdU cell proliferation assay and fibronectin ELISA were also conducted.

RESULTS

Cells cultured on sandblasted titanium exhibited significantly greater spreading than cells cultured on other substrata. In comparison, HTMCs cultured on nitinol displayed poor spreading. Significantly more cell death, by both necrosis and apoptosis, occurred on nitinol than on titanium and glass. Also, cell viability and proliferation were suppressed on nitinol compared with titanium or glass. Finally, HTMCs on both titanium and nitinol produced greater amounts of fibronectin than cells grown on glass.

CONCLUSIONS

Substratum topography and metal alloy composition were found to impact morphology, viability and function of primary HTMC cultures.

Cell death affected by dental alloys: Modes and mechanisms

Previous reports have demonstrated that ions released from dental alloys might cause cytotoxicity. However, how dental alloys influence the organism has not been extensively studied. In order to make it clear, the cytotoxic effect of four dental alloys on L929 cells was evaluated by flow cytometry (FCM) and Real-time quantitative PCR assay (Real-time qPCR) to identify the cell death mode and its biological mechanism. The cells were treated with the leach liquors of cobalt-chromium (Co-Cr), commercially pure titanium (CP-Ti), palladium-based (Pd-based) and gold-platinum (Au-Pt) alloys for 48 and 72 h. FCM results indicated, apart from Au-Pt alloy, the major cell death of dental alloys was time-dependent early apoptosis rather than necrosis/late apoptosis. Caspase 3 and Caspase 9 mRNA expression were determined by Real-time qPCR, and shared the same trend in each group over time. Hence, except for Au-Pt alloy, dental alloys might cause time-dependent early apoptosis via the intrinsic pathway.

Toxic effect of NiCl2 on development of the bursa of Fabricius in broiler chickens

This study was conducted with objective of evaluating the toxic effects of nickel chloride (NiCl₂) on development of bursa of Fabricius in broilers fed on diets supplemented with 0, 300, 600 and 900 mg/kg of NiCl₂ for 42 days by using the methods of experimental pathology, flow cytometry (FCM), and quantitative real-time polymerase chain reaction (qRT-PCR). The results showed that dietary NiCl₂ in 300 mg/kg and over induced toxic suppression in the bursal development, which was characterized by decreasing lymphocytes histopathologically and relative weight, increasing G₀/G₁ phase (a prolonged nondividing state), reducing S phase (DNA replication) and proliferating index, and increasing percentages of apoptotic cells. Concurrently, the mRNA expression levels of bax, cytochrome c (cyt c), apoptotic peptidase activating factor 1 (Apaf-1), caspase-3, caspase-6, caspase-7 and caspase-9 were increased and the bcl-2 mRNA expression levels were decreased. The toxic suppression of bursal development finally impaired humoral immunity duo to the reduction of B lymphocyte population and B lymphocyte activity in the broiler chicken. This study provides new evidences for further studying the effect mechanism of Ni and Ni compoundson B-cell or bursa of Fabricius.

Cellular responses of osteoblast-like cells to 17 elemental metals

Elemental metals have been widely used to alloy metallic orthopedic implants. However, there is still insufficient research data elucidating the cell responses of osteoblastic cells to alloying elemental metals, which impedes the development of new metallic implant materials. In this study, the cellular responses of osteoblast-like cells (SaOS2) to 17 pure alloying elemental metals, that is, titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), silicon (Si), and tin (Sn) were comparatively investigated in vitro. Cellular responses including intracellular total protein synthesis and collagen content, cell adhesion, cell proliferation, and alkaline phosphatase (ALP) activity on these elemental metals were systematically assessed and compared. It was found that these elemental metals could be categorized into three groups based on the cellular functions on them. Group 1, including Ti, Zr, Hf, Nb, Ta, Cr, Ru, and Si, showed excellent cell proliferation and varied ALP activity for SaOS2 cells. Cells exposed to Group 2, including Mo and Sn, although initially attached and grew, did not proliferate over time. In contrast, Group 3, including V, Mn, Fe, Co, Ni, Cu, and Zn, showed severe cytotoxicity toward SaOS2 cells. It is vital to consider the cell responses to the elemental metals when designing a new metallic implant material and the findings of this study provide insights into the biological performance of the elemental metals. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 148-158, 2017.

Pathway underlying small intestine apoptosis by dietary nickel chloride in broiler chickens

The aims of this study were to investigate the pathways which dietary nickel chloride (NiCl2) affects small intestine apoptosis in broiler chickens by observing the ultrastructure, and bcl-2, bax, and caspase-3 protein expression and mRNA expression, and cytochrome C, bak and caspase-9 mRNA expression of the small intestine. A total of 240 one-day-old avian broilers were divided into four groups and fed a corn-soybean basal diet as the control diet or three experimental diets supplemented with 300, 600, and 900 mg/kg of NiCl2 for 42 days. Ultrastructurally, the microvilli were apparently exfoliated, and the mitochondria were swollen and the number of lysosomes increased in the intestinal cells of three experimental groups. As measured by TUNEL and flow cytometry (FCM), the percentage of apoptotic cells in the small intestine and the lymphocytes in the ileum were significantly increased in three experimental groups when compared with those of the control group. Meanwhile, immunohistochemistry, quantitative real-time polymerase chain reaction (qRT-PCR) and enzyme-linked immuno-sorbent assay (ELISA) tests showed that the protein expression, mRNA expression levels were decreased in the bcl-2, whereas those of bax and caspase-3, and the cytochrome C, bak and caspase-9 mRNA expression levels were increased in three experimental groups. The abovementioned results show that pathway of dietary NiCl2-induced small intestine apoptosis is related to the mitochondrial damage and promotion of the cytochrome C release from mitochondria, which activates the mitochondrion-mediated apoptosis pathway.

Municipal landfill leachate-induced testicular oxidative damage is associated with biometal accumulation and endocrine disruption in rats

Improper management of hazardous wastes adversely impacts the environment and the public health. The present study was aimed at investigating the influence of Olushosun municipal landfill leachate (OMLL) from Ojota in the Lagos State of Nigeria on testicular function by assessing the plasma concentrations of reproductive hormones, testicular biometal levels, and antioxidant levels as well as observing the histological alterations in testes and epididymides of rats after exposure to 0, 12.5, and 25% OMLL in drinking water for 7 days. Exposure to OMLL significantly decreased the daily fluid intake, but it resulted in testicular biometal accumulation as follows: lead > cadmium > nickel > iron > copper. Acute exposure to OMLL induced oxidative stress and increased the activities of marker enzymes of testicular function but markedly decreased the circulatory concentrations of luteinizing hormone, follicle-stimulating hormone, prolactin, testosterone, thyroid-stimulating hormone, triiodothyronine, and thyroxine. Testicular and epididymal degeneration with significant decrease in sperm quality and quantity were observed in OMLL-exposed rats. Collectively, the data presented herein indicate that exposure to OMLL-induced testicular dysfunction associated with biometal accumulation and endocrine disruption in rats. If the effects can be extrapolated to humans, OMLL may present significant health implications for individuals exposed to OMLL-contaminated substances.

Downregulation of TLR4 and 7 mRNA expression levels in broiler's spleen caused by diets supplemented with nickel chloride

Toll-like receptors (TLRs) are important immune receptors in discriminating self from nonself and in initiating the innate and adaptive immune response. TLR4 and TLR7 have been proven to be highly expressed in chicken's spleen. Thus, this study was to evaluate the TLR4 and TLR7 messenger RNA (mRNA) expression levels in the spleen of broilers fed diets supplemented with nickel chloride (NiCl2) using the methods of quantitative real-time PCR (qRT-PCR). Two hundred forty-one-day-old avian broilers were equally divided into 4 groups and fed on a corn-soybean basal diet as control diet or the same basal diet supplemented with 300, 600, and 900 mg/kg of NiCl2 for 42 days. Results showed that TLR4 and TLR7 mRNA expression levels in the spleen were lower (P < 0.05 or P < 0.01) in the 300, 600, and 900 mg/kg groups than those in the control group. It was concluded that dietary NiCl2 in excess of 300 mg/kg could lower TLR4 and TLR7 mRNA expression levels in the spleen of broilers, implying that NiCl2 could impair the innate and adaptive immunity in spleen by injuring immunocytes and/or decreasing the content of cytokines through TLRs.

Nickel nanowires induce cell cycle arrest and apoptosis by generation of reactive oxygen species in HeLa cells

Nickel nanowires (Ni NWs) have great potential to be used as a living cell manipulation tool and developed into an anticancer agent. However, their candidacy as biomedical appliances need detailed human cell studies, such as study of the interaction between Ni NWs and tumor cells. The present study investigated the cytotoxicity of Ni NWs in HeLa cells. A dose-dependent inhibition of cell growth was observed by using the MTT assay. We demonstrated that Ni NWs induced oxidative stress by generation of reactive oxygen species (ROS). Apoptosis induction was evidenced by flow cytometry, annexin V binding assay and DAPI staining. DNA flow cytometric analysis indicated that Ni NWs significantly increased the percentages of cells in S phase compared with control cells. This process was accompanied by the loss of mitochondrial membrane potential. These results revealed that Ni NWs induced apoptosis in HeLa cells via ROS generation and cell cycle arrest.

The association between splenocyte apoptosis and alterations of Bax, Bcl-2 and caspase-3 mRNA expression, and oxidative stress induced by dietary nickel chloride in broilers

Two hundred and forty avian broilers were equally divided into four groups, and raised with a corn-soybean basal diet or the same diet supplemented with 300, 600, 900 mg/kg NiCl₂ for 42 days. Numbers or percentages of apoptotic splenocytes by flow cytometry (FCM) and TUNEL were higher (p < 0.05 or p < 0.01) in the 300, 600 and 900 mg/kg groups than those in the control group. Results measured by qRT-PCR and ELISA showed that mRNA expression and contents were significantly higher (p < 0.05 or p < 0.01) in Bax and Caspase-3, and were significantly lower (p < 0.05 or p < 0.01) in Bcl-2 of the 300, 600 and 900 mg/kg groups. Also, the SOD, CAT and GSH-Px activities, and the ability to inhibit hydroxyl radical, and GSH contents were significantly decreased (p < 0.05 or p < 0.01), and MDA contents were increased (p < 0.05 or p < 0.01) in all groups. In conclusion, dietary NiCl₂ in excess of 300 mg/kg caused apoptosis, altered Bax, Bcl-2 and Caspase-3 mRNA expression levels and contents, and induced oxidative stress in the spleen. Also, splenocyte apoptosis was closely related to the alternations of Bax, Bcl-2 and Caspase-3 mRNA expression, and oxidative damage. The splenic immunity and blood filtration functions were impaired in broilers.

Electrochemical dissolution of nickel-titanium endodontic files induces periodontal ligament cell death

INTRODUCTION

Fractured endodontic files present a major problem. A novel method has been proposed to retrieve fractured nickel-titanium (NiTi) endodontic files by using electrochemical dissolution. However, the effect of file dissolution on adjacent soft tissues such as the periodontal ligament (PDL) has not been investigated. The aim of this study was to determine the effects of the dissolution products on PDL fibroblasts.

METHODS

Endodontic files were dissolved in sodium fluoride (NaF) by passing a 50-mA current through the NiTi files while immersed in the NaF solution. NaF/NiTi solutions were diluted with minimal essential medium-α media containing 10% serum. PDL cells were treated for up to 24 hours, and cell viability was quantified by using calcein AM to label live cells and ethidium homodimer to label dead cells. This was repeated by using artificial saliva (AS) as an alternative to NaF.

RESULTS

NaF solution reduced PDL cell survival, and the NaF/NiTi solution further reduced PDL cell survival. AS alone did not reduce cell survival, whereas AS/NiTi solution reduced PDL cell survival. Particles that resulted from the electrochemical dissolution of NiTi files were highly cytotoxic.

CONCLUSIONS

Electrochemically dissolving NiTi files in NaF results in solutions that are cytotoxic to PDL fibroblasts. AS may be a less toxic alternative for dissolving NiTi files.

Nickel and human health

This review focuses on the impact of nickel on human health. In particular, the dual nature of nickel as an essential as well as toxic element in nature is described, and the main forms of nickel that can come in contact with living systems from natural sources and anthropogenic activities are discussed. Concomitantly, the main routes of nickel uptake and transport in humans are covered, and the potential dangers that nickel exposure can represent for health are described. In particular, the insurgence of nickel-derived allergies, nickel-induced carcinogenesis as well as infectious diseases caused by human pathogens that rely on nickel-based enzymes to colonize the host are reviewed at different levels, from their macroscopic aspects on human health to the molecular mechanisms underlying these points. Finally, the importance of nickel as a beneficial element for human health, especially being essential for microorganisms that colonize the human guts, is examined.

Common pitfalls in nanotechnology: lessons learned from NCI's Nanotechnology Characterization Laboratory

The Nanotechnology Characterization Laboratory's (NCL) unique set-up has allowed our lab to handle and test a variety of nanoparticle platforms intended for the delivery of cancer therapeutics and/or imaging contrast agents. Over the last six years, the NCL has characterized more than 250 different nanomaterials from more than 75 different investigators. These submitted nanomaterials stem from a range of backgrounds and experiences, including government, academia and industry. This has given the NCL a unique and valuable opportunity to observe trends in nanoparticle safety and biocompatibility, as well as note some of the common mistakes and oversights of nanoformulation. While not exhaustive, this article aims to share some of the most common pitfalls observed by the NCL as they relate to nanoparticle synthesis, purification, characterization and analysis.

Nickel induces apoptosis in human neutrophils

Nickel is an ubiquitous transition metal that is industrially applied in many forms, which inevitably leads to a high degree of occupational and environmental exposure. Over-exposure to nickel can produce a variety of adverse effects on human health, including allergy and lung and nasal cancers. In the present study, it is demonstrated, for the first time, that nickel [(Ni(II)] (as a nickel nitrate salt) at concentrations that may be attained in vivo, induces neutrophils' apoptosis by the intrinsic pathway. The use of diphenyleneiodonium, a NADPH oxidase inhibitor, delayed Ni(II)-induced apoptosis, suggesting that NADPH oxidase-derived reactive oxygen species and subsequent signaling could contribute to this event. This is an important finding since increased apoptosis mediated by nickel may disrupt the physiological activities of neutrophils, with potential impact in its immunological and antimicrobial role.

Neurotoxicity of Nigerian bonny light crude oil in rats

Biometal accumulation may contribute to organ toxicity in individuals using the Nigerian bonny light crude oil (BLCO) for ailment management. We assessed the levels of biometals, antioxidant status, along with histomorphometric analysis to investigate the effect of BLCO, commonly use in folklore medicine, on the brain. Adult male Wistar rats were dosed by gavage with BLCO at 0, 200, and 800 mg/kg(-1) of BLCO for 7 days. Results showed the accumulation of iron, zinc, nickel and lead, in contrast to copper, in BLCO-treated rats. Administration of BLCO disrupted the brain's antioxidant system and significantly increased levels of hydrogen peroxide and lipid peroxidation. Although the Purkinje layer and maximum width of Purkinje cells were not affected, BLCO treatment significantly decreased molecular layer, granular layer, and density of Purkinje cells of the cerebellum. The neurotoxicity of BLCO may be the result of oxidative stress resulting from loss of biometal homeostasis as well as toxicant injury from other constituents of BLCO.

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.

Tissues distribution of heavy metals and erythrocytes antioxidant status in rats exposed to Nigerian bonny light crude oil

The harmful effects of folkloric uses of Nigerian bonny light crude oil (BLCO) in ailments management may outweigh the expected beneficial effects. We investigated the levels of heavy metal concentrations in the tissues as well as the effect of BLCO on the antioxidant status of erythrocytes of rats after oral exposure to 0, 200 and 800 mg/kg BLCO for 7 days. Analysis of heavy metal concentrations in BLCO showed that Zn > Fe > Pb > Cu > Ni. The trend of accumulation of the metals in the tissues is blood—Fe > Pb >Zn whereas Cu and Ni levels were not affected; Liver—Ni > Zn > Fe > Cu > Pb and Testes—Ni > Cu > Pb > Zn > Fe. The order of concentration of the metals in the tissues is as follows: iron—blood > liver > testes; zinc—liver > blood > testes; lead—blood > liver > testes; copper—testes > liver > blood; nickel—liver > testes > blood. Activities of the antioxidant enzymes of erythrocytes such as superoxide dismutase, catalase, glutathione S-transferase and glutathione peroxidase increased significantly in a dose-dependent manner with significant elevation in hydrogen peroxide and malondialdehyde levels, whereas glutathione level was not significantly decreased in BLCO-treated animals. Collectively, the results showed that BLCO induces oxidative damage to erythrocytes of rats.

Protective effects of grape seed procyanidin extract against nickel sulfate-induced apoptosis and oxidative stress in rat testes

This study determined whether nickel sulfate (Ni)-induced reproductive damage occurs via apoptosis and oxidative stress and to examine the expression of Bax and c-kit and their effects on Ni exposure. The study also explored the protective effects of grape seed proanthocyanidin extract (GSPE) against Ni toxicity in the testes. Wistar rats were treated with normal saline, Ni alone (1.25, 2.5, and 5 mg/kg/day), and Ni (2.5 mg/kg/day) plus GSPE (50 and 100 mg/kg/day). After 30 days, Ni significantly decreased sperm motility and the percentage of S-phase cells and enhanced testicular apoptosis in the 2.5 and 5 mg groups. The levels of malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and nitric oxide (NO) significantly increased. The decreased activity of glutathione peroxidase and catalase in the Ni groups showed that Ni could increase oxidative stress, especially at 2.5 and 5 mg. Western blot analysis showed that the expression of Bax protein and c-kit increased in 2.5 and 5 mg Ni groups compared with controls. Conversely, these changes were partially attenuated in rats simultaneously administered GSPE, especially in the 100 mg group. These results demonstrate the following: (1) Ni exhibits reproductive toxicity in rats by decreasing sperm at concentrations of 2.5 and 5 mg; (2) intratesticular apoptosis, oxidative stress, and c-kit overexpression play pivotal roles in reproductive damage induced by Ni; and (3) GSPE enhances sperm motility by down-regulating c-kit expression and offsetting the apoptosis and oxidative stress induced by Ni by directly decreasing MDA and NO, scavenging H₂O₂, and down-regulating Bax expression.

Titanium uptake, induction of RANK-L expression, and enhanced proliferation of human T-lymphocytes

There is increasing evidence that titanium ions are released from orthopedic implants by biocorrosion. The aim of this study was to investigate titanium uptake by human T-lymphocytes and its effects on phenotype and proliferation. Freshly isolated human nonadherent peripheral blood mononuclear cells (NA-PBMC), were exposed to TiCl4 [Ti(IV)]. Bioavailability and distribution of Ti(IV) in T-lymphocytes was determined by energy-filtered electron microscopy (EFTEM). The effects of Ti(IV) challenge on nonactivated and PHA-activated cells were assessed by flow cytometric analysis of surface markers, RANK-L production, and proliferation assays. EFTEM colocalized Ti(IV) with phosphorus in the nucleus, ribosomes, cytoplasmic membranes, and the surface membrane of T-lymphocytes. Ti(IV) increased significantly the expression of CD69, CCR4, and RANK-L in a concentration-dependent manner. Titanium enters T-lymphocytes through a currently unknown mechanism and binds to phosphorus-rich cell structures. Titanium influences phenotype and function of T-lymphocytes, resulting in activation of a CD69+ and CCR4+ T-lymphocyte population and secretion of RANK-L. These results strongly suggest the involvement of titanium ions challenged T-lymphocytes in the complex pathophysiological mechanisms of aseptic loosening of orthopedic implants.

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.

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.

Inhalative exposure to vanadium pentoxide causes DNA damage in workers: results of a multiple end point study

BACKGROUND

Inhalative exposure to vanadium pentoxide (V(2)O(5)) causes lung cancer in rodents.

OBJECTIVE

The aim of the study was to investigate the impact of V(2)O(5) on DNA stability in workers from a V(2)O(5) factory.

METHODS

We determined DNA strand breaks in leukocytes of 52 workers and controls using the alkaline comet assay. We also investigated different parameters of chromosomal instability in lymphocytes of 23 workers and 24 controls using the cytokinesis-block micronucleus (MN) cytome method.

RESULTS

Seven of eight biomarkers were increased in blood cells of the workers, and vanadium plasma concentrations in plasma were 7-fold higher than in the controls (0.31 microg/L). We observed no difference in DNA migration under standard conditions, but we found increased tail lengths due to formation of oxidized purines (7%) and pyrimidines (30%) with lesion-specific enzymes (formamidopyrimidine glycosylase and endonuclease III) in the workers. Bleomycin-induced DNA migration was higher in the exposed group (25%), whereas the repair of bleomycin-induced lesions was reduced. Workers had a 2.5-fold higher MN frequency, and nucleoplasmic bridges (NPBs) and nuclear buds (Nbuds) were increased 7-fold and 3-fold, respectively. Also, apoptosis and necrosis rates were higher, but only the latter parameter reached statistical significance.

CONCLUSIONS

V(2)O(5) causes oxidation of DNA bases, affects DNA repair, and induces formation of MNs, NPBs, and Nbuds in blood cells, suggesting that the workers are at increased risk for cancer and other diseases that are related to DNA instability.

Metals and apoptosis: recent developments

Apoptosis, also known as programmed cell death is a highly regulated and crucial process found in all multicellular organisms. It is not only implicated in regulatory mechanisms of cells, but has been attributed to a number of diseases, i.e. inflammation, malignancy, autoimmunity and neurodegeneration. A variety of toxins can induce apoptosis. Carcinogenic transition metals, viz. cadmium, chromium and nickel promote apoptosis along with DNA base modifications, strand breaks and rearrangements. Generation of reactive oxygen species, accumulation of Ca(2+), upregulation of caspase-3, down regulation of bcl-2, and deficiency of p-53 lead to arsenic-induced apoptosis. In the case of cadmium, metallothionein expression determines the choice between apoptosis and necrosis. Reactive oxygen species (ROS) and p53 contribute in apoptosis caused by chromium. Immuno suppressive mechanisms contribute in lead-induced apoptosis whereas in the case of mercury, p38 mediated caspase activation regulate apoptosis. Nickel kills the cells by apoptotic pathways. Copper induces apoptosis by p53 dependent and independent pathways. Beryllium stimulates the formation of ROS that play a role in Be-induced macrophage apoptosis. Selenium induces apoptosis by producing superoxide that activates p53. Thus, disorders of apoptosis may play a critical role in some of the most debilitating metal-induced afflictions including hepatotoxicity, renal toxicity, neurotoxicity, autoimmunity and carcinogenesis. An understanding of metal-induced apoptosis will be helpful in the development of preventive molecular strategies.

Wear particles, periprosthetic osteolysis and the immune system

The immune system modulates many key biological processes in humans. However, the exact role of the immune system in particle-associated periprosthetic osteolysis is controversial. Human tissue retrieval studies, in vivo and in vitro experiments suggest that the immune response to polymer particles is non-specific and macrophage-mediated. Lymphocytes may modulate this response. However direct lymphocyte activation by polymer particle-protein complexes seems unlikely. However, metallic byproducts may complex with serum proteins and lead to a Type IV, lymphocyte-mediated immune reaction. In predisposed individuals, this reaction may rarely lead to persistent painful joint effusions, necessitating debridement and excision of the bearing surfaces of the prosthesis. In these patients, retrieved periprosthetic tissues exhibit histological evidence of perivascular lymphocytic cuffing. These findings are worrisome, given the fact that increasing numbers of metal-on-metal joint implants are being implanted in younger more active individuals worldwide.