Nickel Exposure Research Articles

Synergistic genotoxic effect between gene and environmental pollutant: Oxidative DNA damage induced by thioredoxin reductase 1 silencing under nickel treatment

Nickel has been known to represent a lethal toxicity to human under environmental exposure. Particulary, nickel accumulation is able to cause oxidative DNA damage and tumor development. Redox imbalance by oxidative stress is rescued via modulation by redox factors which can scavenge excessively produced reactive oxygen species (ROS). Thioredoxin reductase 1 (Trr 1) is one of major redox factors having a potential role in cellular defense system against oxidative stress. In this study, we investigated whether Trr 1 has protective roles against nickel-induced oxidative stress and genotoxicity using ROS measurement, comet and micronucleus (MN) assay. We found significant increase of intracellular ROS generation in nickel-treated Trr 1 defective cells compared with Trr 1 proficient cells. In addition, under nickel treatment, Trr1 knockdown cells showed higher amount of DNA strand breaks as oxidative DNA damage rather than in Trr 1 wild type cells. Moreover, MN as a crucial biomarker for carcinogenicity was remarkably induced in the nickel-exposed Trr 1 silencing cells. Therefore, these results might provide novel insight on the role of Trr 1 in cellular protection from environmental nickelinduced genotoxicity. In conclusion, we emphasized the synergistic toxicity of Trr 1 knockdown and environmental nickel exposure in relevance to gene-environment interactions.

Nickel exposure induces oxidative damage to mitochondrial DNA in Neuro2a cells: the neuroprotective roles of melatonin

Recent studies suggest that oxidative stress and mitochondrial dysfunction play important roles in the neurotoxicity of nickel. Because mitochondrial DNA (mtDNA) is highly vulnerable to oxidative stress and melatonin can efficiently protect mtDNA against oxidative damage in various pathological conditions, the aims of this study were to determine whether mtDNA oxidative damage was involved in the neurotoxicity of nickel and to assay the neuroprotective effects of melatonin in mtDNA. In this study, we exposed mouse neuroblastoma cell lines (Neuro2a) to different concentrations of nickel chloride (NiCl(2), 0.125, 0.25, and 0.5 mm) for 24 hr. We found that nickel significantly increased reactive oxygen species (ROS) production and mitochondrial superoxide levels. In addition, nickel exposure increased mitochondrial 8-hydroxyguanine (8-OHdG) content and reduced mtDNA content and mtDNA transcript levels. Consistent with this finding, nickel was found to destroy mtDNA nucleoid structure and decrease protein levels of Tfam, a key protein component for nucleoid organization. However, all the oxidative damage to mtDNA induced by nickel was efficiently attenuated by melatonin pretreatment. Our results suggest that oxidative damage to mtDNA may account for the neurotoxicity of nickel. Melatonin has great pharmacological potential in protecting mtDNA against the adverse effects of nickel in the nervous system.

Nickel and cobalt allergy before and after nickel regulation – evaluation of a public health intervention

Over the 20th century, the frequent use of nickel in consumer products resulted in an increasing prevalence of nickel allergy. Risk items included suspenders in the 1950s-1960s; buttons, zippers and rivets in the 1970s; and ear-piercing jewellery in the 1980s. When subjects allergic to nickel were exposed to nickel in high concentrations, it often resulted in allergic nickel contact dermatitis and hand eczema. In 1990, the Danish government began to regulate consumer nickel exposure as a response to the increasing nickel allergy problem. In 1994, the EU Nickel Directive was passed, a regulation that was based on the Danish and Swedish nickel regulations. These major public health interventions were expected to change the epidemiology of nickel allergy and dermatitis in Europe. Furthermore, it was debated whether nickel would be replaced by cobalt in inexpensive jewellery and result in higher prevalence of cobalt allergy. An evaluation of the possible effects of the European nickel regulations is of importance to ensure protection of consumers and dermatitis patients. This doctoral thesis aimed to evaluate the effects of regulatory interventions on nickel exposure by investigating the development of nickel allergy and dermatitis before and after nickel regulation. Furthermore, a change in the association between nickel allergy and hand eczema was evaluated. The nickel spot test was validated to determine its value when used for screening purposes. Possible explanations for the persistence of nickel allergy were explored including genetic predisposition and consumer nickel exposure from jewellery and accessories. A cobalt spot test was developed and validated. Finally, it was evaluated whether a cobalt allergy epidemic had replaced the nickel allergy epidemic after nickel regulation in terms of increasing cobalt sensitization and cobalt exposure. The thesis showed that the prevalence of nickel allergy decreased significantly after nickel regulation in young Danish women from the general population (18-35 years) and in young Danish female dermatitis patients from a university patch test clinic (0-30 years). Stratification by ear-piercing status revealed that women ear pierced before 1990 had a significantly higher prevalence of nickel allergy and dermatitis than women ear pierced after 1990. Furthermore, the association between hand eczema and nickel allergy decreased in young women aged 18-35 years when a comparison was made between women who were patch tested and questioned in, respectively, 1990 and 2006. Despite the decreasing prevalence of nickel allergy, this condition remains prevalent in young Danish women, as about 10% are nickel allergic. Genetic predisposition to nickel allergy was evaluated by investigating the possible association between filaggrin null mutation status and nickel allergy. A positive association was found but it was also concluded that environmental nickel exposure is of much greater importance. Thus, of 354 consumer items purchased from 36 different stores in Copenhagen, 22% released nickel in concentrations that may result in nickel dermatitis in sensitized subjects. Therefore excessive consumer nickel exposure remains common in Denmark and may be an important explanation for the persistence of nickel allergy. Excessive nickel release was also frequent when samples of earrings purchased in Warsaw and London were examined with the nickel spot test, in particular earrings purchased from street markets and shops with independent ownership. Only very weak indications of an emerging cobalt allergy epidemic were found, as the prevalence of cobalt allergy has not yet increased in young people and only four of 354 consumer items purchased in Copenhagen released cobalt in concentrations that may result in cobalt dermatitis in sensitized individuals. The specificity of the nickel spot test was 98% and the sensitivity 59%. Also, a cobalt spot test was developed and validated and seemed to be a useful diagnostic tool. In conclusion, the Danish nickel regulation and the EU Nickel Directive have changed the epidemiology of nickel allergy in Denmark. However, the Nickel Directive and its reference methods need to be revised to better protect consumers and dermatitis patients.

Determination of nickel in cigarettes smoke by molecular fluorescence

Smoking represents the main avoidable cause of disease and death in the world. Cigarette smoke contains over 4700 chemical compounds including 60 known carcinogens. The inhalation of tobacco smoke is one of the most significant sources of nickel exposure for occupationally unexposed population. The aim of this work was to evaluate nickel contents present in cigarette smoke by using an automatic sample preparation step and solid surface fluorescence. A total of 250 cigarettes (brands available in Argentine) were smoked in a smoking device applying vacuum and forcing the mainstream smoke to pass through a filter holder containing a Nylon membrane treated with eosin dye (eo). Nickel present in smoke cigarette was selectively retained by eo as an association compound. Chemically enriched nickel on nylon membranes was subsequent quantified by spectrofluorimetry (λem=545nm, λexc=515nm), reaching quantitative recovery with a detection limit of 1.56ngL−1 and quantification limit of 5.52ngL−1. The calibration sensitivity using zeroth order calibration was 1 1012ngL−1 (r2=0.9992) for the methodology with a linear range of 5.52 to 5.17 104ngL−1 Ni(II). Standard addition method was satisfactorily applied to nickel determination in mainstream smoke cigarettes of twenty brands. Results can be good correlated with urinary nickel contents coming from fifty subjects with different levels of addiction.

Efficacy of oral hyposensitization in allergic contact dermatitis caused by nickel

Nickel contact allergy remains common in Western countries, and the dermatitis may require prolonged treatment. The development of new strategies aimed at improving the quality of life of affected individuals is needed. To investigate the efficacy of oral hyposensitization in nickel-allergic individuals and how this affects in vitro T cell responsiveness to the metal. Twenty-eight nickel-allergic patients received a daily dose of 50 µg of elemental nickel (given as NiSO(4) ·6H(2) O) in cellulose capsules for 3 months. Severity of clinical manifestations, in vivo nickel responsiveness and in vitro T cell responses to the metal were assessed after 1 and 3 months. Twenty-six patients finished the study. In these patients, oral hyposensitization ameliorated clinical manifestations despite continued nickel exposures, and increased the threshold of skin responsiveness to nickel. The 12 enrolled patients in the immunological study showed decreased in vitro T lymphocyte responsiveness to the metal, in terms of both cell proliferation and cytokine release. In the 1-year follow-up, 50% of the patients experienced relapses of the clinical manifestations at sites of topical exposure to nickel. Our study suggested therapeutic efficacy of oral hyposensitization in allergic individuals. Placebo-controlled studies are required to confirm the results and determine the optimal therapeutic regimen for prolonged beneficial effects.

Nickel response in function of temperature differences: Effects at different levels of biological organization in Daphnia magna

In this study, gene transcription profiling in combination with the assessment of systemic parameters at individual and population levels were applied to study the (toxic) effects induced through temperature stress in the presence or the absence of an additional chemical stressor (nickel) in Daphnia magna. It was illustrated that lower temperatures were mainly characterized by a reduction of growth and lipid content, while higher temperatures caused an increase of both endpoints. Many of the differentially regulated transcripts could be correlated with processes affected at higher hierarchical levels of biological organization. Gene clusters with probable roles in producing offspring (peak expression at 22 °C), enhancing the metabolic rate (temperature related expression) and translational processes (increased expression at 14 °C) were identified. However, it was not possible to pinpoint a specific subset of genes, exclusively responding to temperature or nickel and allowing a retrospective identification of the particular stressor. Overall, extreme temperatures caused a higher level of stress in the organisms in comparison to nickel exposure. Moreover, organisms subjected to the natural stressor appeared to be less capable of dealing with the additional chemical stressor and as a result activate or repress more gene pathways.

Effect of nickel and chromium exposure on buccal cells of electroplaters

The electroplating industry commonly involves the use of nickel and chromium. An assessment of the genotoxic effects of these metals can be carried out by micronucleus (MN) test in buccal cells. Other nuclear anomalies (NA) observed in buccal cells viz., karyorrhexis, pyknosis and karyolysis are also the indicators of genotoxicity. The current study aims at determining the extent of genotoxic damage in relation to the duration of exposure to nickel and hexavalent chromium via micronuclei induction and other nuclear anomalies. The present investigation included 150 subjects of which 50 individuals with no history of nickel/chromium exposure (Group I) were taken as control, 50 electroplaters exposed to nickel and hexavalent chromium for duration of less than 10 years (Group II) and 50 electroplaters exposed for ≥10 years (Group III) were included. Slides of buccal cells were prepared and the frequency of MN (‰) and NA (‰) were calculated. ANOVA was applied to test significance. Results were considered significant at p < 0.05 and p < 0.001. Group III showed the highest MN frequency (1.08 ± 0.54‰, p < 0.05), karyorrhexis (20.75 ± 6.29, p < 0.05), karyolysis (3.50 ± 1.91, p < 0.001), binucleate (4.75 ± 2.75, p < 0.05) and enucleated cells (5.75 ± 1.70, p < 0.05). Significant increase in frequencies between Group II and III was found as duration of exposure increased. Plasma nickel and chromium levels were also determined which showed a positive correlation with frequency MN and other nuclear abnormalities (p < 0.01).

A Cross-Talk Between NFAT and NF-&amp;#954;B Pathways is Crucial for Nickel- Induced COX-2 Expression in Beas-2B Cells

Cyclooxygenase-2 (COX-2) is a critical enzyme implicated in chronic inflammation-associated cancer development. Our studies have shown that the exposure of Beas-2B cells, a human bronchial epithelial cell line, to lung carcinogenic nickel compounds results in increased COX-2 expression. However, the signaling pathways leading to nickel-induced COX-2 expression are not well understood. In the current study, we found that the exposure of Beas-2B cells to nickel compounds resulted in the activation of both nuclear factor of activated T cell (NFAT) and nuclear factor-κB (NF-κB). The expression of COX-2 induced upon nickel exposure was inhibited by either a NFAT pharmacological inhibitor or the knockdown of NFAT3 by specific siRNA. We further found that the activation of NFAT and NF-κB was dependent on each other. Since our previous studies have shown that NF-κB activation is critical for nickel-induced COX-2 expression in Beas-2B cells exposed to nickel compounds under same experimental condition, we anticipate that there might be a cross-talk between the activation of NFAT and NF-κB for the COX-2 induction due to nickel exposure in Beas-2B cells. Furthermore, we showed that the scavenging of reactive oxygen species (ROS) by introduction of mitochondrial catalase inhibited the activation of both NFAT and NF-κB, and the induction of COX-2 due to nickel exposure. Taken together, our results defining the evidence showing a key role of the cross-talk between NFAT and NF-κB pathways in regulating nickel-induced COX-2 expression, further provide insight into the understanding of the molecular mechanisms linking nickel exposure to its lung carcinogenic effects.

Impaired Wound-Healing, Local Eczema, and Chronic Inflammation Following Titanium Osteosynthesis in a Nickel and Cobalt-Allergic Patient

Thomas, Peter MD1; Thomas, Manfred MD2; Summer, Burkhard PhD1; Dietrich, Karin MD1; Zauzig, Melanie3; Steinhauser, Erwin PhD3; Krenn, Veit MD4; Arnholdt, Hans MD5; Flaig, Michael J. MD1 Author Information

Methylation of RAR-β2, RASSF1A, and CDKN2A Genes Induced by Nickel Subsulfide and Nickel-carcinogenesis in Rats

Objective To investigate the expression variation of RAR-β2, RASSF1A, and CDKN2A gene in the process of nickel-induced carcinogenesis. Methods Nickel subsulfide (Ni 3S 2) at dose of 10 mg was given to Wistar rats by intramuscular injection. The mRNA expression of the three genes in induced tumors and their lung metastasis were examined by Real-time PCR. The methylation status of the 5' region of these genes were detected by Quantitative Real-time methylation specific PCR. Results The mRNA expressions of the three genes both in muscle and lung tumor were decreased distinctly in comparison with normal tissue. But hypermethylation was found only in muscle tumor. Conclusion These findings suggest that loss of function or decrease of RAR-β2, RASSF1A, and CDKN2A, as well as the hypermethylation of 5' region of these genes, are related with nickel exposure.

Nickel promotes the invasive potential of human lung cancer cells via TLR4/MyD88 signaling

Epidemiological studies have demonstrated a close correlation between nickel exposure and the incidence of lung cancer. Several studies have suggested that nickel contributes to tumor progression of human lung cancer. In this in vitro study, we found that nickel, as nickel chloride, could significantly enhance the invasive potential of human lung cancer cells, accompanied by elevated expression of IL-8, TGF-β, MMP2 and MMP9 in human lung cancer cells. Importantly, we demonstrated that nickel could activate TLR4 signaling in human lung cancer cells. Further studies showed that the TLR4/MyD88 signaling conferred the enhanced invasive potential of human lung cancer cells induced by nickel. Finally, we revealed that the p38MAPK pathway and NF-kB pathway were necessary for the enhanced invasive potential of human lung cancer cells induced by nickel. Our data provide a mechanistic explanation for nickel induced invasion of human lung cancer, and they suggest new strategies for nickel-related lung cancer clinical biotherapies.

Effects of Nickel Treatment on H3K4 Trimethylation and Gene Expression

Occupational exposure to nickel compounds has been associated with lung and nasal cancers. We have previously shown that exposure of the human lung adenocarcinoma A549 cells to NiCl2 for 24 hr significantly increased global levels of trimethylated H3K4 (H3K4me3), a transcriptional activating mark that maps to the promoters of transcribed genes. To further understand the potential epigenetic mechanism(s) underlying nickel carcinogenesis, we performed genome-wide mapping of H3K4me3 by chromatin immunoprecipitation and direct genome sequencing (ChIP-seq) and correlated with transcriptome genome-wide mapping of RNA transcripts by massive parallel sequencing of cDNA (RNA-seq). The effect of NiCl2 treatment on H3K4me3 peaks within 5,000 bp of transcription start sites (TSSs) on a set of genes highly induced by nickel in both A549 cells and human peripheral blood mononuclear cells were analyzed. Nickel exposure increased the level of H3K4 trimethylation in both the promoters and coding regions of several genes including CA9 and NDRG1 that were increased in expression in A549 cells. We have also compared the extent of the H3K4 trimethylation in the absence and presence of formaldehyde crosslinking and observed that crosslinking of chromatin was required to observe H3K4 trimethylation in the coding regions immediately downstream of TSSs of some nickel-induced genes including ADM and IGFBP3. This is the first genome-wide mapping of trimethylated H3K4 in the promoter and coding regions of genes induced after exposure to NiCl2. This study may provide insights into the epigenetic mechanism(s) underlying the carcinogenicity of nickel compounds.

L-carnitine protects against nickel-induced neurotoxicity by maintaining mitochondrial function in Neuro-2a cells

Mitochondrial dysfunction is thought to be a part of the mechanism underlying nickel-induced neurotoxicity. L-carnitine (LC), a quaternary ammonium compound biosynthesized from the amino acids lysine and methionine in all mammalian species, manifests its neuroprotective effects by improving mitochondrial energetics and function. The purpose of this study was to investigate whether LC could efficiently protect against nickel-induced neurotoxicity. Here, we exposed a mouse neuroblastoma cell line (Neuro-2a) to different concentrations of nickel chloride (NiCl 2) (0.25, 0.5, 1, and 2 mM) for 24 h, or to 0.5 mM and 1 mM NiCl 2 for various periods (0, 3, 6, 12, or 24 h). We found that nickel significantly increased the cell viability loss and lactate dehydrogenase (LDH) release in Neuro-2a cells. In addition, nickel exposure significantly elevated reactive oxygen species (ROS) and malondialdehyde (MDA) levels, disrupted the mitochondrial membrane potential (ΔΨ m), reduced adenosine-5′-triphosphate (ATP) concentrations and decreased mitochondrial DNA (mtDNA) copy numbers and mtRNA transcript levels. However, all of the cytotoxicities and mitochondrial dysfunctions that were triggered by nickel were efficiently attenuated by pretreatment with LC. These protective effects of LC may be attributable to its role in maintaining mitochondrial function in nickel-treated cells. Our results suggest that LC may have great pharmacological potential in protecting against the adverse effects of nickel in the nervous system.

Infant Clothing Snaps as a Potential Source of Nickel Exposure

Children's clothes with metal snaps are a potential source of nickel exposure to consider in infants and very young children. Further more avoidance of this exposure may help prevent nickel sensitization.

Systemic Contact Dermatitis to Nickel Present in Cocoa in 14‐Year‐Old Boy

Systemic contact dermatitis can be elicited in nickel sensitive individuals by oral nickel exposure from food with high content of this metal, such as cocoa. We present a case report of a nonatopic teenager who developed allergic contact dermatitis due to nickel, cobalt, copper, and palladium, but exacerbations of skin lesions were mainly related to cocoa consumption.

Binding of nickel to testicular glutamate-ammonia ligase inhibits its enzymatic activity

Exposure to nickel has been shown to cause damage to the testis in several animal models. It is not known if the testis expresses protein(s) that can bind nickel. To test this, we used a nickel-binding assay to isolate testicular nickel-binding proteins. We identified glutamate-ammonia ligase (GLUL) as a prominent nickel-binding protein by mass spectrometry. Protein analysis and reverse transcriptase polymerase chain reaction showed that GLUL is expressed in the testis, predominantly in interstitial cells. We determined that GLUL has a higher affinity for nickel than for its regular co-factor manganese. We produced an enzymatically active, recombinant GLUL protein. Upon binding, nickel interferes with the manganese-catalyzed enzymatic activity of recombinant GLUL protein. We also determined that GLUL activity in testes of animals exposed to nickel sulfate is reduced. Our results identify testicular GLUL as the first testicular protein shown to be affected by nickel exposure.

The EU Nickel Directive revisited-future steps towards better protection against nickel allergy

In July 2001, the EU Nickel Directive came into full force to protect European citizens against nickel allergy and dermatitis. Prior to this intervention, Northern European governments had already begun to regulate consumer nickel exposure. According to part 2 of the EU Nickel Directive and the Danish nickel regulation, consumer items intended to be in direct and prolonged contact with the skin were not allowed to release more than 0.5 µg nickel/cm2/week. It was considered unlikely that nickel allergy would disappear altogether as a proportion of individuals reacted below the level defined by the EU Nickel Directive. Despite this, the EU Nickel Directive part 2 was expected to work as an operational limit that would sufficiently protect European consumers against nickel allergy and dermatitis. This review presents the accumulation of epidemiological studies that evaluated the possible effect of this major public health intervention. Also, it evaluates recent exposure assessment studies that have been performed using the dimethyl glyoxime test. It is concluded that the EU Nickel Directive has started to change the epidemiology of nickel allergy in Europe but it should be revisited to better protect consumers and workers since nickel allergy and dermatitis remain very frequent.

Nickel sensitization in orthodontically treated and non-treated female adolescents

The importance of the nickel exposure from fixed orthodontic appliances is under continuous discussion. Our aim was to investigate nickel allergy and the risk of nickel sensitization among female adolescents during orthodontic treatment with fixed appliances as compared with non-treated female adolescents. Female patients starting or with ongoing orthodontic treatment (n = 30) and young females without a history of orthodontic treatment (n = 140) were studied. Patch testing with 5% nickel sulfate was carried out twice on each participant with an approximately 1-year interval. The subjects completed a questionnaire before the first testing. None of the 7 orthodontic patients with a positive patch test reaction to nickel had any clinically visible intraoral allergic symptoms during their treatment. No significant difference was seen in the occurrence of positive nickel reactions in regard to orthodontic treatment, or between the first and second tests. In the treatment group, 2 patients changed from nickel-positive to nickel-negative during the observation period, and one patient showed an opposite change. The quantity and course of changes in the repeated nickel patch test reactions did not differ significantly between the subjects with and without orthodontic treatment experience. Nickel sensitization from orthodontic appliances is improbable, but nickel sensitization may develop also during orthodontic treatment.

The characteristics of placental transfer and tissue concentrations of nickel in late gestational rats and fetuses

The dynamics of nickel (Ni) uptake, transfer, retention and clearance in fetuses and late gestational rats were investigated by assessing its distributions in placenta, maternal and fetal organs and tissues during the 24 h period after a single dose of 63Ni intraperitoneal injection on gestational day 20. Peak 63Ni radioactivity was detected at 0.5 h in maternal blood, at 3 h in placenta, fetal membranes, fetal blood, fetal heart, maternal kidney, lung, stomach, liver and brain, at 9 h in fetal kidney, stomach, liver and brain, and lastly at 24 h in fetal lung and amniotic fluid. The maximal 63Ni radioactivity among all samples was detected consistently in the fetal membranes and placenta. The 63Ni radioactivity in fetal blood was higher than that in maternal blood from 3 to 24 h. The fetal liver, heart, stomach and brain exhibited higher 63Ni radioactivity than the corresponding maternal organs from 6 to 24 h. However, maternal kidney consistently exhibited significantly higher 63Ni radioactivity than the fetal kidney. The 63Ni in fetal lung and amniotic fluid increased throughout the period of experimental observation. These observations corroborated previous finding that nickel is actively transferred across the blood-placenta-barrier into fetus, but hardly from fetus to mother. Moreover, these results suggest that the placenta has a high affinity for nickel and its barrier does not protect the fetus from nickel exposure. The fact that nickel concentrations are higher in most fetal organs and tissues than in corresponding maternal organs and tissues in late gestation indicates that, unlike the dam, fetuses lack effective means for getting rid of excessive nickel due to its confined environment and relatively weak kidney functions. The situation is exacerbated by mother-to-fetus unidirectional transfer. Consequently, the fetuses are particularly vulnerable to the damaging effects of nickel.

In-air microparticle induced X-ray emission analysis of particles in interstitial pneumonia lung tissue obtained by transbronchial biopsy

Interstitial pneumonia develops in association with inhaled particles. In-air microparticle induced X-ray emission (in-air micro) analysis was previously employed to assess the spatial distribution and content of particles in surgical lung biopsy specimens. The aim of this study was to assess the efficacy of in-air micro-analysis for transbronchial lung biopsy specimens in patients with or without occupational exposure. The elements composing lung particles and their locations could be identified by in-air micro-analysis. Silicon was the major component of particles. Quantitative analysis revealed that the elements composing lung particles varied between patients. In a patient with suspected nickel exposure, aluminium, vanadium, and calcium were detected, but was not detected. In a patient without a work history (housewife), various elements were detected. In-air micro-analysis was useful for assessing the spatial distribution and content of particles in specimens from patients. Occupational exposure was not necessarily associated with deposition of particles in the lungs. Therefore, in the diagnosis of, elemental analysis of specimens by in-air micro-analysis could be useful for assessing exposure to particles objectively.