Hazard identification and dose response of inhaled nickel-soluble salts

Insights into the effects of chronic combined chromium-nickel exposure on colon damage in mice through transcriptomic analysis and in vitro gastrointestinal digestion assay

Heavy metals interact with each other in a coexisting manner to produce complex combined toxicity to organisms. At present, the toxic effects of chronic co-exposure to heavy metals hexavalent chromium [Cr(VI)] and divalent nickel [Ni(II)] on organisms are seldom studied and the related mechanisms are poorly understood. In this study, we explored the mechanism of the colon injury in mice caused by chronic exposure to Cr or/and Ni. The results showed that, compared with the control group, Cr or/and Ni chronic exposure affected the body weight of mice, and led to infiltration of inflammatory cells in the colon, decreased the number of goblet cells, fusion of intracellular mucus particles and damaged cell structure of intestinal epithelial. In the Cr or/and Ni exposure group, the activity of nitric oxide synthase (iNOS) increased, the expression levels of MUC2 were significantly down-regulated, and those of ZO-1 and Occludin were significantly up-regulated. Interestingly, factorial analysis revealed an interaction between Cr and Ni, which was manifested as antagonistic effects on iNOS activity, ZO-1 and MUC2 mRNA expression levels. Transcriptome sequencing further revealed that the expression of genes-related to inflammation, intestinal mucus and tight junctions changed obviously. Moreover, the relative contents of Cr(VI) and Ni(II) in the Cr, Ni and Cr+Ni groups all changed with in-vitro gastrointestinal （IVG）digestion, especially in the Cr+Ni group. Our results indicated that the chronic exposure to Cr or/and Ni can lead to damage to the mice colon, and the relative content changes of Cr(VI) and Ni(II) might be the main reason for the antagonistic effect of Cr+Ni exposure on the colon damage.

Microbial colony sequencing combined with metabolomics revealed the effects of chronic hexavalent chromium and nickel combined exposure on intestinal inflammation in mice

The pollution and toxic effects of hexavalent chromium [Cr(VI)] and divalent nickel [Ni(II)] have become worldwide public health issues. However, the potential detailed effects of chronic combined Cr(VI) and Ni exposure on colonic inflammation in mice have not been reported. In this study, 16S rDNA sequencing, metabolomics data analysis, qPCR and other related experimental techniques were used to comprehensively explore the mechanism of toxic damage and the inflammatory response of the colon in mice under the co-toxicity of chronic hexavalent chromium and nickel. The results showed that long-term exposure to Cr(VI) and/or Ni resulted in an imbalance of trace elements in the colon of mice with significant inflammatory infiltration of tissues. Moreover, Cr(VI) and/or Ni poisoning upregulated the expression levels of IL-6, IL-18, IL-1β, TNF-α, IFN-γ, JAK2 and STAT3 mRNA, and downregulated IL-10 mRNA, which was highly consistent with the trend in protein expression. Combined with multiomics analysis, Cr(VI) and/or Ni could change the α diversity and β diversity of the gut microbiota and induce significant differential changes in metabolites such as Pyroglu-Glu-Lys, Val-Asp-Arg, stearidonic acid, and 20-hydroxyarachidonic acid. They are also associated with disorders of important metabolic pathways such as lipid metabolism and amino acid metabolism. Correlation analysis revealed that there was a significant correlation between gut microbes and metabolites (P < 0.05). In summary, based on the advantages of comprehensive analysis of high-throughput sequencing sets, these results suggest that chronic exposure to Cr(VI) and Ni in combination can cause microbial flora imbalances, induce metabolic disorders, and subsequently cause colonic damage in mice. These data provide new insights into the toxicology and molecular mechanisms of Cr(VI) and Ni.

Characterization of nickel levels considering seasonal and intra-individual variation using three biological matrices

Nickel compounds are classified as group 1 carcinogens by the International Agency for Research on Cancer. However, only a few exposure assessment studies have been conducted on such compounds to date. In this study, we investigated the distribution of nickel in three biological types of samples (blood, serum, and urine) and its temporal variability through repeated measurements. From 2020 to 2021, blood and urine samples were collected for four times from 50 healthy participants. Nickel concentrations were determined using inductively coupled plasma mass spectrometry, and inter-individual correlation was calculated from linear mixed model. The overall geometric mean of nickel was 1.028 μg/L in blood, 0.687 μg/L in serum, and 1.464 μg/L in urine. Blood nickel was the highest in November (blood: 1.197 μg/L), and the geometric mean of nickel concentrations in the serum and urine were the highest in March (serum: 1.146 μg/L; urine: 1.893 μg/L). This matched seasonal trends for fine particulate matter concentrations from 2020 to 2021. Thus, seasonal effects significantly affect nickel levels in blood, serum, and urine. The inter-individual correlations were low as 0.081 for blood and 0.064 for urine. In addition, the correlation of nickel levels between each biological sample was low. It was also found that age, gender, commuting time, and different matrices affect concentrations. Blood and serum nickel levels were high in this study compared to other nationwide data, with urinary nickel ranking the second highest among the six countries examined. Therefore, biomonitoring study in the general population should be conducted, and finding a suitable matrix that can reflect nickel exposure to set exposure guideline levels is imperative.

Trace Elements and Consequent Ecological Risks in Mining-Influenced Streams of Appalachia

Appalachian (eastern USA) coal surface mines fracture geologic materials, causing release of both major ions and trace elements to water via accelerated weathering. When elevated above natural background, trace elements in streams may produce adverse effects on biota via direct exposure from water and sediment and via dietary exposure in food sources. Other studies have found elevated water concentrations of multiple trace elements in Appalachia's mining-influenced streams. Except for Se, trace-element concentrations in abiotic and biotic media of Appalachian mining-influenced streams are less well known. We analyzed environmental media of headwater streams receiving alkaline waters from Appalachian coal mines for eight trace elements (Al, As, Cd, Cu, Ni, Sr, V, and Zn) and assessed the potential consequent ecological risks. Streamwater, particulate media (sediment, biofilm, leaf detritus), and benthic macroinvertebrates (primary consumers, secondary consumers, crayfish) were sampled from six mining-influenced and three reference streams during low-flow conditions in two seasons. Dissolved Cu, Ni, and Sr were higher in mining-influenced streams than in reference streams; Ni, Sr, and Zn in fine sediments and Ni in macroinvertebrates were also elevated relative to reference-stream levels in samples from mining-influenced streams. Seasonal ratios of mining-influenced stream concentrations to maximum concentrations in reference streams also demonstrated mining-influenced increases for several elements in multiple media. In most media, concentrations of several elements including Ni were correlated positively. All water-column dissolved concentrations were below protective levels, but fine-sediment concentrations of Ni approached or exceeded threshold-effect concentrations in several streams. Further study is warranted for several elements (Cd, Ni, and Zn in biofilms, and V in macroinvertebrates) that approached or exceeded previously established dietary-risk levels. Environ Toxicol Chem 2023;42:2651-2665. © 2023 SETAC.

Nickel induces blood-testis barrier damage through ROS-mediated p38 MAPK pathways in mice

Nickel (Ni) is an essential common environmental contaminant, it is hazardous to male reproduction, but the precise mechanisms are still unknown. Blood-testis barrier (BTB), an important testicular structure consisting of connections between sertoli cells, is the target of reproductive toxicity caused by many environmental toxins. In this study, ultrastructure observation and BTB integrity assay results indicated that NiCl2 induced BTB damage. Meanwhile, BTB-related proteins including the tight junction (TJ), adhesion junction (AJ) and the gap junction (GJ) protein expression in mouse testes as well as in sertoli cells (TM4) were significantly decreased after NiCl2 treatment. Next, the antioxidant N-acetylcysteine (NAC) was co-treated with NiCl2 to study the function of oxidative stress in NiCl2-mediated BTB deterioration. The results showed that NAC attenuated testicular histopathological damage, and the expression of BTB-related proteins were markedly reversed by NAC co-treatment in vitro and vivo. Otherwise, NiCl2 activated the p38 MAPK signaling pathway. And, NAC co-treatment could significantly inhibit p38 activation induced by NiCl2 in TM4 cells. Furthermore, in order to confirm the role of the p38 MAPK signaling pathway in NiCl2-induced BTB impairment, a p38 inhibitor (SB203580) was co-treated with NiCl2 in TM4 cells, and p38 MAPK signaling inhibition significantly restored BTB damage induced by NiCl2 in TM4 cells. These results suggest that NiCl2 treatment destroys the BTB, in which the oxidative stress-mediated p38 MAPK signaling pathway plays a vital role.

Associations of nickel exposure with diabetes: evidence from observational studies

The results of environmental epidemiological studies regarding the relationship between human exposure to nickel and the risk of diabetes remain controversial. Therefore, we performed a meta-analysis to investigate the relationship between nickel exposure and diabetes. PubMed, Web of Science, and Embase electronic databases were thoroughly searched from their inception to May 2023 to obtain relevant studies. The random-effects model was employed to determine pooled odds ratios (ORs) and 95% confidence intervals (CIs). Stratified and sensitivity analyses were also performed. Cochran Q test and I2 statistic were employed to assess heterogeneity between studies. Begg's and Egger's tests were employed to evaluate publication bias. The indicated studies were evaluated using the ROBINS-E risk of bias tool. The dose-response relationship between nickel in urine and diabetes risk was estimated by restricted cubic spline. A total of 12 studies with 30,018 participants were included in this study. In this meta-analysis, comparing the highest vs. lowest levels of nickel exposure, the pooled ORs for diabetes were 1.42 (95% confidence interval 1.14-1.78) for urine and 1.03 (0.57-1.86) for blood, respectively. A linear relationship between urinary nickel and diabetes risk was discovered in the dose-response analysis (P nonlinearity = 0.6198). Each 1 µg/L increase of urinary nickel, the risk of diabetes increased by 7% (OR = 1.07, 95% CI 1.04-1.10). The risk of diabetes was positively correlated with urine nickel exposure, whereas the risk was not significantly correlated with blood nickel. In the future, more high-quality prospective studies are needed to validate this conclusion.

Comparison between pollutants found in breast milk and infant formula in the last decade: A review

Since ancient times, breastfeeding has been the fundamental way of nurturing the newborn. The benefits of breast milk are widely known, as it is a source of essential nutrients and provides immunological protection, as well as developmental benefits, among others. However, when breastfeeding is not possible, infant formula is the most appropriate alternative. Its composition meets the nutritional requirements of the infant, and its quality is subject to strict control by the authorities. Nonetheless, the presence of different pollutants has been detected in both matrices. Thus, the aim of the present review is to make a comparison between the findings in both breast milk and infant formula in terms of contaminants in the last decade, in order to choose the most convenient option depending on the environmental conditions. For that, the emerging pollutants including metals, chemical compounds derived from heat treatment, pharmaceutical drugs, mycotoxins, pesticides, packaging materials, and other contaminants were described. While in breast milk the most concerning contaminants found were metals and pesticides, in infant formula pollutants such as metals, mycotoxins, and packaging materials were the most outstanding. In conclusion, the convenience of using a feeding diet based on breast milk or either infant formula depends on the maternal environmental circumstances. However, it is important to take into account the immunological benefits of the breast milk compared to the infant formula, and the possibility of using breast milk in combination with infant formula when the nutritional requirements are not fulfilled only with the intake of breast milk. Therefore, more attention should be paid in terms of analyzing these conditions in each case to be able to make a proper decision, as it will vary depending on the maternal and newborn environment.

Nickel nanoparticles exert cytotoxic effects on trophoblast HTR-8/SVneo cells possibly via Nrf2/MAPK/caspase 3 pathway

Nickel nanoparticles are widely used in the industry and may affect the reproductive system. The potential molecular mechanism of exposing the first-trimester trophoblast cell line (HTR-8/SVneo) to nickel nanoparticles remains unclear. Hence, the aim of this study was to investigate the in vitro cytotoxicity of Ni NPs on HTR-8/SVneo cells. HTR-8/SVneo cells were subjected to various concentrations (0, 2.5, 5, 7.5, 10, and 12.5 μg/cm²) of Ni NPs. The toxicity of the Ni NPs was evaluated in HTR-8/SVneo cells by measuring cell viability. The underlying mechanism of nickel nanoparticles toxicity to HTR-8/SVneo cells was determined by measuring the content of intracellular reactive oxygen species, mitochondrial membrane potential, and the rate of cell apoptosis and cell cycle, by measuring adenosine triphosphate levels, intracellular lipid peroxidation malondialdehyde, total superoxide dismutase, and CuZn/Mn-SOD activities, and by determining proteins related to Nrf2, MAPK, and Cytochrome c. Our results showed that the nickel nanoparticles treatment reduced the viability of HTR-8/SVneo cells, while it increased their oxidative stress and lowered their mitochondrial respiratory capacity. Additionally, the nickel nanoparticles treatment induced cell S-phase arrest and apoptosis. These molecular events may be linked to the oxidative stress-Nrf2 pathway/MAPK/Caspase 3 cascade. Thus, nickel nanoparticles exert cytotoxic effects on HTR-8/SVneo cells, which could affect the function of the placenta in human.

Kinetic mechanisms by which nickel alters the calcium (Ca2+) transport in intact rat liver

In the present work, the multiple-indicator dilution (MID) technique was used to investigate the kinetic mechanisms by which nickel (Ni²⁺) affects the calcium (Ca²⁺) transport in intact rat liver. ⁴⁵Ca²⁺ and extra- and intracellular space indicators were injected in livers perfused with 1 mM Ni²⁺, and the outflow profiles were analyzed by a mathematical model. For comparative purposes, the effects of norepinephrine were measured. The influence of Ni²⁺ on the cytosolic Ca²⁺ concentration ([Ca²⁺]_c) in human hepatoma Huh7 cells and on liver glycogen catabolism, a biological response sensitive to cellular Ca²⁺, was also evaluated. The estimated transfer coefficients of ⁴⁵Ca²⁺ transport indicated two mechanisms by which Ni²⁺ increases the [Ca²⁺]_c in liver under steady-state conditions: (1) an increase in the net efflux of Ca²⁺ from intracellular Ca²⁺ stores due to a stimulus of Ca²⁺ efflux to the cytosolic space along with a diminution of Ca²⁺ re-entry into the cellular Ca²⁺ stores; (2) a decrease in Ca²⁺ efflux from the cytosolic space to vascular space, minimizing Ca²⁺ loss. Glycogen catabolism activated by Ni²⁺ was transient contrasting with the sustained activation induced by norepinephrine. Ni²⁺ caused a partial reduction in the norepinephrine-induced stimulation in the [Ca²⁺]_c in Huh7 cells. Our data revealed that the kinetic parameters of Ca²⁺ transport modified by Ni²⁺ in intact liver are similar to those modified by norepinephrine in its first minutes of action, but the membrane receptors or Ca²⁺ transporters affected by Ni²⁺ seem to be distinct from those known to be modulated by norepinephrine.

Biochemical profile and gene expression of Clarias gariepinus as a signature of heavy metal stress

Heavy metals have been found in increasing concentrations in the aquatic environment. Fishes exposed to such metals have altered gene expression, serum profiles, tissue histology and bioindices that serve as overall health biomarkers. The heavy metals (Ni, Cd, and Cr) accumulated in water and fish tissues, were beyond the permissible limits defined by the Central Pollution Control Board/World Health Organization. Metallothionein (MT) and glutathione peroxidase (GPX) genes expression patterns highlighted the metal-specific exposure of fish. An increased fold change of genes against beta-actin serves as a potential feature for toxicity. Metal toxicity is also reflected by an increased level of digestive enzymes (amylase and lipase) in the serum and alterations in values of reproductive hormones (11-Ketotestosterone and progesterone). Total serum bilirubin attribute to the liver and biliary tract disease in fishes. Histopathological studies show cellular degeneration, breakage, vacuolization signifying the chronic stress.

Biochemical, Toxicological, and Histopathological outcome in rat brain following treatment with NiO and NiO nanoparticles

Nickel oxide nanoparticle (NiO NPs) has been widely used in various fields such as catalysts, radiotherapy, and nanomedicine. The aim of this study was to compare the effects of nickel oxide (NiO) and NiO NPs on oxidative stress biomarkers and histopathological changes in brain tissue of rats. In this study, 49 male rats were randomly divided into one control group and 6 experimental groups (n = 7). The control group received normal saline and the treatment groups received NiO and NiO NPs at doses of 10, 25, and 50 mg/kg intraperitoneally for 8 days. After 8 days, animal was sacrificed, brain excised, homogenized, centrifuged, and then supernatant was collected for antioxidant assays. The results showed that activity of GST in NiO NPs groups with doses of 10, 25, and 50 mg/kg (79.42 ± 4.24, p = 0.035; 78.77 ± 8.49, p = 0.041; 81.38 ± 12.39, p = 0.042 to 47.26 ± 7.17) and catalase in NiO NPs groups with concentrations of 25 and 50 mg/kg (69.95 ± 8.65 to 39.75 ± 5.11, p = 0.02) and (68.80 ± 4.18 to 39.75 ± 5.11 p = 0.027) were significantly increased compared with the control, respectively. Total antioxidant capacity in NiONPs group with doses of 50 mg/kg was significantly decreased (345.00 ± 23.62, p = 0.015 to 496.66 ± 25.77) compared with control. The GSH level in all doses NiO and NiONPs was significantly decreased compared with the control (p = 0.002). MDA level in NiONPs and NiO groups with doses of 50 mg/kg was significantly increased (13.03 ± 1.29, p = < 0.01; 15.61 ± 1.08, p = < 0.001 to 7.32 ± 0.51) compared with the control, respectively. Our results revealed a range of histopathological changes, including necrosis, hyperemia, gliosis, and spongy changes in brain tissue. Thus, increasing level of MDA, GST, and CAT enzymes and decreasing GSH and TAC and also histopathological changes confirmed NiONPs and NiO toxicity.

The Association Between Thyroid Injury and Apoptosis, and Alterations of Bax, Bcl-2, and Caspase-3 mRNA/Protein Expression Induced by Nickel Sulfate in Wistar Rats

To study the toxicity induced by Nickel sulfate (NiSO₄) on thyroid tissue, and investigate the role of apoptosis as the possible mechanism, thirty-two male Wistar rats were randomly divided into control group (normal saline, ip), low dose group (2.5 mg/kg day NiSO₄, ip), middle dose group (5 mg/kg day NiSO₄, ip), high dose group (10 mg/kg day NiSO₄, ip). After 40 consecutive days of treatment, there were obvious pathological changes in the thyroids of high dose group. Free T₄ (FT₄) and thyroid-stimulating hormone (TSH) were significantly lower in the NiSO₄-treated groups than those in the control group (F = 4.992, p = 0.016; F = 4.524, p = 0.012). The mRNA expression of Caspase-3 was significantly higher (F = 10.259, p = 0.014) in all NiSO₄-treated groups, and the mRNA expression of Bcl-2 was significantly lower (F = 9.225, p = 0.018) only in the high dose group. Both control group and the NiSO₄-treated groups showed no changes in the mRNA expression of Bax gene. The ratio of Bcl-2/Bax decreased with the increase in exposure dose of NiSO₄ (F = 13.382, p = 0.015). The mRNA expression of Fas went up in high dose group (F = 66.632, p < 0.001). The Caspase-3, Fas, and the Bax protein expressions measured by immunohistochemistry were consistent with the mRNA expression. The expression of Bcl-2 protein was significantly lower in the test groups than in the control group (F = 3.873, p = 0.025). NiSO₄ as an Endocrine Disrupting Chemical may induce the thyroid injury through apoptosis and lead to hypothyroidism. Also, apoptosis in thyroid tissues was closely related to the alternations of Caspase-3, Bcl-2, and Fas mRNA and protein expression.

Insights into the heavy metal-induced immunotoxic and genotoxic alterations as health indicators of Clarias gariepinus inhabiting a rivulet

There is a dire need to assess the quality of fishes transported for human consumption as lately, their health is challenged because of anthropogenic activities. Heavy metals with a long environmental persistence are toxic to fishes and the humans. The study was conducted to evaluate the impact of heavy metals on Clarias gariepinus inhabiting popular Ganges rivulet at Narora (28.18° E, 78.39° N). The limnological values deviated from the international Standards (USEPA, WHO). Higher total dissolved solids (859 mg/L), total suspended solids (406 mg/L), low dissolved oxygen (5.60 mg/L), and pH (5.21) indicated the presence of contaminants. Heavy metals estimated followed the order Cd > Ni > Cu > Cr. Serum enzymes (hepatic and renal markers) viz., aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) were higher than the normal, whereas, creatine kinase (CK) was considerably low in both male and female fish. Stress induced was marked by elevation in cortisol and glucose. This had its impact on hematological parameters as well, as a decline in Total leucocyte count (TLC) & mean corpuscular volume (MCV) and increase in Mean cell hemoglobin (MCH) was observed. Erythrocytes also showed altered morphology. Marked histopathological alterations were observed in all immune organs (head-kidney, liver, spleen, thymus). Oxidative stress induced by heavy metals leads to the production of metal scavenging protein metallothionein (MT) and glutathione peroxidase (GPX). Maximum fold change in metallothionein (MT) gene expression was observed in the liver, followed by spleen, thymus, blood, and head-kidney. Glutathione peroxidase (GPX) gene expression was highest in the liver, followed by thymus, spleen, blood, and head-kidney. The gene expression studies further validated the increased level of heavy metals as potent contaminants of water and the non-condusive abiotic factors.

Role of calcium channels and endothelial factors in nickel induced aortic hypercontraction in Wistar rats

Aim: To investigate the mechanism of nickel augmented phenylephrine (PE)-induced contraction in isolated segments of Wistar rat aorta. Materials and Methods: Effect of varying concentrations of nickel on PE-induced contraction were investigated in isolated segments of Wistar rat aorta using an organ bath system. Aortic rings were pre-incubated with verapamil (1 µM and 20 µM), gadolinium, apocynin, indomethacin or N-G-nitro-L-arginine methyl ester (L-NAME) separately before incubation with nickel. Results: Endothelium intact aortic rings incubated with 100 nM, 1 µM or 100 µM of nickel exhibited 80%, 43% and 28% increase in PE-induced contraction, respectively, while no such enhancing responses were observed in endothelium denuded aorta. Incubation of aortic rings with 1 µM and 20 µM verapamil suggested an involvement of influx of calcium through T-type calcium channels in smooth muscle cells, while aortic rings pre-incubated with gadolinium showed no role of store operated calcium channels in the nickel effect on PE-induced contractions. The enhancing effect of nickel on PE-induced contractions was inhibited by apocynin, indomethacin or L-NAME. Conclusion: Nickel has caused augmentation of PE-induced contractions as a result of the endothelial generation of reactive oxygen species (ROS) and cyclooxygenase 2 (COX2) dependent endothelium contracting factors (EDCFs), which increases the influx of extracellular calcium through T-type Ca²⁺ channels in smooth muscle cells.

Nickel Carcinogenesis Mechanism: DNA Damage

Nickel (Ni) is known to be a major carcinogenic heavy metal. Occupational and environmental exposure to Ni has been implicated in human lung and nasal cancers. Currently, the molecular mechanisms of Ni carcinogenicity remain unclear, but studies have shown that Ni-caused DNA damage is an important carcinogenic mechanism. Therefore, we conducted a literature search of DNA damage associated with Ni exposure and summarized known Ni-caused DNA damage effects. In vitro and vivo studies demonstrated that Ni can induce DNA damage through direct DNA binding and reactive oxygen species (ROS) stimulation. Ni can also repress the DNA damage repair systems, including direct reversal, nucleotide repair (NER), base excision repair (BER), mismatch repair (MMR), homologous-recombination repair (HR), and nonhomologous end-joining (NHEJ) repair pathways. The repression of DNA repair is through direct enzyme inhibition and the downregulation of DNA repair molecule expression. Up to now, the exact mechanisms of DNA damage caused by Ni and Ni compounds remain unclear. Revealing the mechanisms of DNA damage from Ni exposure may contribute to the development of preventive strategies in Ni carcinogenicity.

Development of a New Sequential Extraction Procedure of Nickel Species on Workplace Airborne Particulate Matter: Assessing the Occupational Exposure to Carcinogenic Metal Species

Nickel (Ni) compounds and metallic Ni have many industrial and commercial applications, including their use in the manufacturing of stainless steel. Due to the specific toxicological properties of the different Ni species, there is a growing interest about the availability of analytical methods that allow specific risk assessment, particularly related to exposure to the Ni species classified as carcinogenic. In this paper, we described a speciation method of inorganic Ni compounds in airborne particulate matter, based on selective sequential extractions. The analytical method described in this paper allows the determination of soluble, sulfidic, metallic, and oxide Ni by a simple sequential extraction procedure and determination by Atomic Absorption Spectroscopy using small volumes of solutions and without long evaporation phases. The method has been initially set up on standard laboratory mixtures of known concentrations of different Ni salts. Then it has then been tested on airborne particulate matter (powder and filters) collected in different workstations of a large stainless steel production facility. The method has occurred effectively in the comparison of the obtained results with occupational exposure limit values set by the main international scientific and regulatory agencies for occupational safety and health, in order to prevent both toxic and carcinogenic effects in humans.

Dissolved trace elements in Hooghly (Ganges) River Estuary, India: Risk assessment and implications for management

The study presents a spatio-seasonal distribution of 13 trace elements in the surface water (0-5 cm) along the north-south gradient of Hooghly River Estuary, India, and subsequently evaluates the human health risk by adopting USEPA standards. An overall homogeneous spatial distribution of elements was pronounced, whereas an irregular and inconsistent seasonal pattern were recorded for the majority of the elements. The concentration range (μg/l) of the elements and their relative variability were obtained as follows in the decreasing order: Al (55,458-104,955) > Fe (35,676-78,427) > Mn (651.76-975.78) > V (85.15-147.70) > Si (16.0-153.88) > Zn (26.94-105.32) > Cr (21.61-106.02) > Ni (19.64-66.72) > Cu (34.70-65.80) > Pb (26.40-37.48) > Co (11.16-23.01) > As (0.10-8.20) > Cd (1.19-5.53). Although Pb, Ni, Cr, Al, Fe, and Mn exceeded the WHO prescribed threshold limit for drinking water, Metal Pollution Index values (8.02-11.86) superseded the upper threshold limit endorsing adverse impact on biota. The studied elements were justified to have a non-carcinogenic risk as derived from hazard quotient and hazard index values. However, the trace elements As, Cd, Pb, and Cr exceeded the upper limit of cancer risk (10^-4), thereby leading to carcinogenic risk concern for both children and adult population groups, where children are more susceptible than the adults. Hence, evaluation of bioavailable fractions of the elements is required for proper management of this stressed fluvial system.

Deposition, acute toxicity, and bioaccumulation of nickel in some freshwater organisms with best-fit functions modeling

Although nickel (Ni) frequently enters into water, documents on speciation of the metal and its toxicity to freshwater organisms are scanty. Laboratory experiments, made in this study, with 1.0-5.0 mg/L of Ni revealed that Ni was not quickly removed from water. Application of cubic regression followed by classical optimization technique showed that maximum reduction time (T) of Ni in water ranged between 60 to 65 h. Ninety-six hours of LC₅₀ value of Ni to crustacean Diaptomus forbesi, fish Cyprinus carpio, and worm Branchiura sowerbyi was respectively 5.43, 14.70, and 19.73 mg/L. Normalizing the lethal values and plotting them against time, it was observed that C. carpio was more sensitive than D. forbesi, which was not reflected in the 96-h LC₅₀ values. However, sensitivity of these organisms to Ni was better explained by power regression equation (M = aNi^b), which exhibited that mortality (M) of D. forbesi and B. sowerbyi increased slowly between 24 to 72 h, increasing sharply at 96 h, while mortality of C. carpio increased steadily every 24 till 96 h. Experiment with 1.0 mg/L of Ni in outdoor vats showed that crustacean zooplankton and worms accumulated high concentration of Ni, while only gut and liver tissues of fish C. carpio accumulated trace and moderately high concentration of Ni, respectively. It is assumed that toxicity of Ni to fish is mediated primarily through gill.

Prevalence of exposure of heavy metals and their impact on health consequences

Even in the current era of growing technology, the concentration of heavy metals present in drinking water is still not within the recommended limits as set by the regulatory authorities in different countries of the world. Drinking water contaminated with heavy metals namely; arsenic, cadmium, nickel, mercury, chromium, zinc, and lead is becoming a major health concern for public and health care professionals. Occupational exposure to heavy metals is known to occur by the utilization of these metals in various industrial processes and/or contents including color pigments and alloys. However, the predominant source resulting in measurable human exposure to heavy metals is the consumption of contaminated drinking water and the resulting health issues may include cardiovascular disorders, neuronal damage, renal injuries, and risk of cancer and diabetes. The general mechanism involved in heavy metal-induced toxicity is recognized to be the production of reactive oxygen species resulting oxidative damage and health related adverse effects. Thus utilization of heavy metal-contaminated water is resulting in high morbidity and mortality rates all over the world. Thereby, feeling the need to raise the concerns about contribution of different heavy metals in various health related issues, this article has discussed the global contamination of drinking water with heavy metals to assess the health hazards associated with consumption of heavy metal-contaminated water. A relationship between exposure limits and ultimate responses produced as well as the major organs affected have been reviewed. Acute and chronic poisoning symptoms and mechanisms responsible for such toxicities have also been discussed.

Relationship between increasing concentrations of two carcinogens and statistical image descriptors of foci morphology in the cell transformation assay

Cell Transformation Assays (CTAs) have long been proposed for the identification of chemical carcinogenicity potential. The endpoint of these in vitro assays is represented by the phenotypic alterations in cultured cells, which are characterized by the change from the non-transformed to the transformed phenotype. Despite the wide fields of application and the numerous advantages of CTAs, their use in regulatory toxicology has been limited in part due to concerns about the subjective nature of visual scoring, i.e. the step in which transformed colonies or foci are evaluated through morphological features. An objective evaluation of morphological features has been previously obtained through automated digital processing of foci images to extract the value of three statistical image descriptors. In this study a further potential of the CTA using BALB/c 3T3 cells is addressed by analysing the effect of increasing concentrations of two known carcinogens, benzo[a]pyrene and NiCl₂ , with different modes of action on foci morphology. The main result of our quantitative evaluation shows that the concentration of the considered carcinogens has an effect on foci morphology that is statistically significant for the mean of two among the three selected descriptors. Statistical significance also corresponds to visual relevance. The statistical analysis of variations in foci morphology due to concentration allowed to quantify morphological changes that can be visually appreciated but not precisely determined. Therefore, it has the potential of providing new quantitative parameters in CTAs, and of exploiting all the information encoded in foci. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Oxidative stress and inflammatory responses involved in dietary nickel chloride (NiCl2)-induced pulmonary toxicity in broiler chickens

The respiratory system is the primary target of nickel or nickel compound toxicity after inhalation exposure. There are no reports on the effects of nickel or nickel compounds on the lung via dietary administration at present. This study aimed to investigate pulmonary toxicity induced by dietary NiCl₂ in broiler chickens by using histopathology, qRT-PCR, and ELISA. In comparison with the control group, NiCl₂ intake induced oxidative damage to DNA (upregulation of 8-OHdG) and lipid peroxidation (upregulation of MDA), which was associated with the upregulation of NO and the downregulation of the expression levels and activities of pulmonary CuZn-SOD, Mn-SOD, CAT, GSH-Px, GR and GST mRNA. Also, the T-AOC activity, GSH content, ability to inhibit the generation of hydroxyl radicals, and ratio of GSH/GSSG were decreased in the groups treated with NiCl₂. Concurrently, the mRNA expression levels of iNOS, TNF-α, COX-2, IL-1β, IL-6, IL-8, IL-18 and IFN-γ were increased via the activation of NF-κB, and the mRNA expression levels of anti-inflammatory mediators including IL-2, IL-4 and IL-13 were decreased in the groups treated with NiCl₂. The above-mentioned results were the first to demonstrate that NiCl₂ intake induced pulmonary oxidative stress and inflammatory responses via the dietary pathway, which subsequently contributed to histopathological lesions and dysfunction.

Nickel Chloride (NiCl2) Induces Histopathological Lesions via Oxidative Damage in the Broiler's Bursa of Fabricius

The purpose of this study was to investigate the histopathological lesions, oxidative damage, changes of immunoglobulin G (IgG), immunoglobulin M (IgM), and immunoglobulin A (IgA) contents in the bursa of Fabricius and serum immunoglobulins (IgG, IgM, IgA) induced by dietary nickel chloride (NiCl2). Two hundred and eighty-one-day-old broilers were randomly divided into four groups and fed on a control diet and three experimental diets supplemented with 300, 600, and 900 mg/kg of NiCl2 for 42 days. Lesions were observed in the NiCl2-treated groups. Histopathologically, lymphocytes were decreased in lymphoid follicles with thinner cortices and wider medullae. Concurrently, the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and the ability to inhibit hydroxyl radical and glutathione (GSH) contents were significantly (p < 0.05 or p < 0.01) decreased, while malondialdehyde (MDA) contents were increased in the NiCl2-treated groups. The serum IgG, IgM, and bursa IgG and IgM contents were significantly (p < 0.05 or p < 0.01) lower in the NiCl2-treated groups than those in the control group. The above-mentioned results show that dietary NiCl2 in excess of 300 mg/kg can cause histopathological lesions via oxidative damage, which finally impairs the function of the bursa of Fabricius and reduces IgG and IgM contents of the serum and the bursa of Fabricius. The study is aimed to provide helpful materials for studies on Ni- or Ni compounds-induced B cell toxicity in both human and other animals in the future.

Toxicity of nickel in the marine calanoid copepod Acartia tonsa: Nickel chloride versus nanoparticles

Nickel compounds are widely used in industries and have been massively introduced in the environment in different chemical forms. Here we report the effect of two different chemical forms of nickel, NiCl2 and nickel nanoparticles (NiNPs), on the reproduction of the marine calanoid copepod Acartia tonsa. The behavior of nickel nanoparticles was analyzed with different techniques and with two protocols. In the "sonicated experiment" (SON) NiNP solution was sonicated while in the "non-sonicated experiment" (NON-SON) the solution was vigorously shaken by hand. Final nominal concentrations of 5, 10 and 50mgL(-1) and 1, 5 and 10mgL(-1) NiNPs were used for the acute and semichronic tests, respectively. Nanoparticle size did not change over time except for the highest concentration of 50mgL(-1) NiNPs, in which the diameter increased up to 843nm after 48h. The concentration of Ni dissolved in the water increased with NP concentration and was similar for SON and NON-SON solutions. Our results indicate that sonication does not modify toxicity for the copepod A. tonsa. Mean EC50 values were similar for NON-SON (20.2mgL(-1)) and SON experiments (22.14mgL(-1)) in the acute test. Similarly, no differences occurred between the two different protocols in the semichronic test, with an EC50 of 7.45mgL(-1) and 6.97mgL(-1) for NON-SON and SON experiments, respectively. Acute and semichronic tests, conducted exposing A. tonsa embryos to NiCl2 concentrations from 0.025 to 0.63mgL(-1), showed EC50 of 0.164 and 0.039mgL(-1), respectively. Overall, A. tonsa is more sensitive to NiCl2 than NiNPs with EC50 being one order of magnitude higher for NiNPs. Finally, we exposed adult copepods for 4 days to NiCl2 and NiNPs (chronic exposure) to study the effect on fecundity in terms of daily egg production and naupliar viability. Egg production is not affected by either form of nickel, whereas egg viability is significantly reduced by 0.025mgL(-1) NiCl2 and by 8.5mgL(-1) NiNPs. At NiNP concentration below the acute EC50 (17mgL(-1)) only 9% of embryos hatched after 4 days. Interestingly, the percentage of naupliar mortality (>82%) observed in the semichronic test at the nominal concentration of 10mgL(-1) NiNPs corresponding to almost 0.10mgL(-1) of dissolved Ni, was similar to that recorded at the same Ni salt concentration. Electron microscopical analyses revealed that A. tonsa adults ingest NiNPs and excrete them through fecal pellets. To the best of our knowledge, this is the first study investigating the toxicity of two different forms of Ni on the reproductive physiology of the copepod A. tonsa and showing the ability of the calanoid copepod to ingest nanoparticles from seawater.

Research Advances on Pathways of Nickel-Induced Apoptosis

High concentrations of nickel (Ni) are harmful to humans and animals. Ni targets a number of organs and produces multiple toxic effects. Apoptosis is important in Ni-induced toxicity of the kidneys, liver, nerves, and immune system. Apoptotic pathways mediated by reactive oxygen species (ROS), mitochondria, endoplasmic reticulum (ER), Fas, and c-Myc participate in Ni-induced cell apoptosis. However, the exact mechanism of apoptosis caused by Ni is still unclear. Understanding the mechanism of Ni-induced apoptosis may help in designing measures to prevent Ni toxicity.

Nickel exposure is associated with the prevalence of type 2 diabetes in Chinese adults

BACKGROUND

Nickel exposure can induce hyperglycaemia in rodents, but little is known about its association with abnormal glucose metabolism in humans. We aimed to investigate the association of nickel exposure with the prevalence of type 2 diabetes in Chinese adults.

METHODS

A total of 2115 non-institutionalized men and women aged 55 to 76 years from Beijing and Shanghai were included, and urinary nickel concentration was assessed by inductively coupled plasma mass spectroscopy. The prevalence of type 2 diabetes was compared across urinary nickel quartiles. Fasting plasma glucose, insulin, lipids, C-reactive protein and glycated haemoglobin A1c, as well as urinary albumin and creatinine were measured.

RESULTS

The median concentration of urinary nickel was 3.63 mg/l (interquartile range: 2.29–5.89 mg/l), and the prevalence of diabetes was 35.3% (747 cases/2115 persons). Elevated levels of urinary nickel were associated with higher fasting glucose, glycated haemoglobin A1c, insulin and homeostatic model assessment of insulin resistance (all P<0.01). The odds ratios (95% confidence interval) for diabetes across the increasing urinary nickel quartiles were 1.27 (0.97–1.67), 1.78 (1.36–2.32) and 1.68 (1.29–2.20), respectively (referencing to 1.00), after multivariate adjustment including lifestyle factors, body mass index and family history of diabetes (P for trend <0.001). The association remained unchanged after further controlling for urinary creatinine and C-reactive protein (P for trend <0.001).

CONCLUSIONS

Increased urinary nickel concentration is associated with elevated prevalence of type 2 diabetes in humans.

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.

Toxicological effects of nickel chloride on the cytokine mRNA expression and protein levels in intestinal mucosal immunity of broilers

The purpose of this study was to examine the toxicological effects of nickel chloride (NiCl2 ; 300, 600, and 900 mg kg(-1) diet) on the cytokine mRNA expression and protein levels in the intestinal mucosa and cecal tonsil, and on the ileac and cecal tonsil T cells in broilers by the methods of qRT-PCR, flow cytometry and ELISA for 42 days. Results showed that the IL-2, IL-6, IL-10, IL-17, IFN-γ, and TNF-α (LITAF) cytokine mRNA expression and protein levels were lower (P < 0.05 or P < 0.01) and the percentages of T-cell subsets were also lower in the 300, 600, and 900 mg kg(-1) groups than in the control group. It was concluded that dietary NiCl2 in excess of 300 mg kg(-1) could reduce cytokine mRNA expression and protein levels in the intestinal mucosa and cecal tonsil, and the percentages of ileac and cecal tonsil T-cell subsets. Decreasing in cytokine mRNA expression and protein levels of intestinal mucosa and cecal tonsil induced by NiCl2 was closely related to the reduction of T-cell population. Thus, the abnormal expression of these cytokines impacts the intestinal mucosal immune function by the pathways of reducing of lymphocyte population and activation. Also, this study first proved that NiCl2 at higher levels has the toxicological effects on intestinal mucosal immunity.

Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead

Low-dose exposures to common environmental chemicals that are deemed safe individually may be combining to instigate carcinogenesis, thereby contributing to the incidence of cancer. This risk may be overlooked by current regulatory practices and needs to be vigorously investigated.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.

Association of Serum Heavy Metals and Trace Element Concentrations with Reproductive Hormone Levels and Polycystic Ovary Syndrome in a Chinese Population

To investigate the serum concentrations of 11 heavy metals and trace elements in patients with polycystic ovary syndrome (PCOS). A total of 369 women (including 96 patients with PCOS) were studied. No differences with statistical significance in the median barium, cadmium, lead, arsenic, chromium, gallium, strontium, and vanadium concentrations were observed between the patients with PCOS and the control group. Serum nickel (Ni) (P = 0.000) and copper (Cu) (P = 0.000) levels were significantly higher, but zinc (Zn) levels (P = 0.009) were significantly lower in patients with PCOS compared with the control group. The results of the association between metal levels and hormone levels indicated that Ni, Cu, and Zn may play a role in the pathogenesis of PCOS related with reproductive hormone levels. The findings in the present study should be investigated with further trials in order to obtain new insights into PCOS.

Inhibitive effects of nickel chloride (NiCl₂) on thymocytes

The purpose of this study was to define the inhibitive effects of dietary nickel chloride (NiCl2) on thymocytes in broilers fed on diets supplemented with 0, 300, 600, and 900 mg/kg of NiCl2 for 42 days. We examined the changes of cell cycle phase, percentages of apoptotic cells, T cell subsets, cytokines, and mRNA expression of apoptotic proteins (bcl-2, bax, and caspase-3) in thymocytes by flow cytometry and quantitative real-time polymerase chain reaction (qRT-PCR). In the NiCl2-treated broilers, the percentages of thymocytes in G0/G1 phase were increased, whereas thymocytes in the S phase and the proliferation index were decreased. The percentages of apoptotic thymocytes were increased. Also, the mRNA expression levels of bax and caspase-3 were increased, and mRNA expression levels of bcl-2 were decreased. The percentages of CD3(+), CD3(+)CD4(+), and CD3(+)CD8(+) T lymphocytes in the thymus and peripheral blood were diminished. Concurrently, thymic cytokine (interleukin-1 beta (IL-1β), interleukin-2 (IL-2), interleukin-10 (IL-10), interleukin-12 p35 subunit (IL-12p35), interleukin-12 p40 subunit (IL-12p40), interleukin-21 (IL-21), interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), thymosin β4, thymosin β10, and thymosin β15) mRNA expression levels were decreased. The abovementioned results showed that dietary NiCl2 in excess of 300 mg/kg inhibited thymocyte growth by arresting cell cycle, increasing apoptosis percentage, altering apoptotic protein mRNA expression levels, and downregulating cytokine expression levels.

Derivation of PM10 size-selected human equivalent concentrations of inhaled nickel based on cancer and non-cancer effects on the respiratory tract

Abstract Nickel (Ni) in ambient air is predominantly present in the form of oxides and sulfates, with the distribution of Ni mass between the fine (particle aerodynamic diameter < 2.5 µm; PM2.5) and coarser (2.5-10 µm) size-selected aerosol fractions of PM10 dependent on the aerosol's origin. When deriving a long-term health protective reference concentration for Ni in ambient air, the respiratory toxicity and carcinogenicity effects of the predominant Ni compounds in ambient air must be considered. Dosimetric adjustments to account for differences in aerosol particle size and respiratory tract deposition and/or clearance among rats, workers, and the general public were applied to experimentally- and epidemiologically-determined points of departure (PODs) such as no(low)-effect concentrations, for both cancer and non-cancer respiratory effects. This approach resulted in the derivation of threshold-based PM10 size-selected equivalent concentrations (modified PODs) of 0.5 µg Ni/m(3) based on workers' cancer effects and 9-11 µg Ni/m(3) based on rodent respiratory toxicity effects. Sources of uncertainty in exposure extrapolations are described. These are not reference concentrations; rather the derived PM10 size-selected modified PODs can be used as the starting point for the calculation of ambient air reference concentrations for Ni. The described approach is equally applicable to other particulates.

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.

Dietary nickel chloride restrains the development of small intestine in broilers

The aim of this study was to determine the effects of dietary NiCl2 on the development of the small intestine in broilers by the methods of light microscopy, histochemistry and enzyme-linked immunosorbent assay. A total of 240 one-day-old avian broilers were divided into four groups and fed on a corn-soybean basal diet or the same basal diet supplemented with 300, 600 and 900 mg/kg of nickel chloride (NiCl2) for 42 days. Results showed that the small intestinal villus height, crypt depth and villus/crypt ratio were significantly decreased, and also the small intestinal goblet cells numbers and insulin-like growth factor-1 (IGF-1) and epidermal growth factor (EGF) contents were significantly decreased in the 300-, 600- and 900-mg/kg groups when compared with those of the control group. In conclusion, dietary NiCl2 in excess of 300 mg/kg reduced the villus height, crypt depth, the goblet cells population and the IGF-1 and EGF contents in the small intestine, indicating that the normal development and function of the small intestine were finally impaired in broilers. This study firstly provided the new experimental information for future studies on the effects of NiCl2 on the intestinal function in humans and other animals.

Dietary nickel chloride induces oxidative stress, apoptosis and alters Bax/Bcl-2 and caspase-3 mRNA expression in the cecal tonsil of broilers

The purpose of this study was to investigate the effects of dietary NiCl2 on antioxidant function, apoptosis, and the protein expression, mRNA expression and contents of the bcl-2, bax and caspase-3 in the cecal tonsil of broilers. 280 one-day-old avian broilers were divided into four 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. The activities of SOD, CAT and GSH-Px, and the ability to inhibit hydroxy radical, and GSH content were significantly decreased in all experimental groups. MDA content was significantly increased. The protein expression, mRNA expression and contents of bcl-2 were decreased, and bax and caspase-3 were increased in all experimental groups. The percentages of apoptotic lymphocytes were significantly increased. In conclusion, dietary NiCl2 in excess of 300 mg/kg caused oxidative stress, and then induced decreased the protein expression, mRNA expression and the contents of bcl-2, and increased protein expression, mRNA expression and the contents of bax and caspase-3 proteins in the cecal tonsil. The local intestinal mucosal immunity could finally be impaired due to the oxidative stress and apoptosis in the cecal tonsil caused by NiCl2.

Embryotoxic and teratogenic effects of nickel in Swiss albino mice during organogenetic period

The present study evaluates potential hazardous of nickel (Ni(+2) as NiCl2 ·6H2O) to Swiss albino mice fetus. Ni was administered orally on body weight base from days 6 to 13 of gestation period. Based on LD50, Ni doses (46.125, 92.25, and 184.5) mg Ni/kg b.wt. were used. On day 18 of gestation, uteri of the sacrificed dams were examined. A dose-dependent decrease (P < 0.01) in the body weight of the pregnant females and fetuses during the gestation period was observed. Number of implant sites and placental weight at all the three dose levels was lower compared with their respective control groups. Average number of live fetuses/dams reduced significantly (P < 0.01) at 184.5 mg Ni/kg b.wt. with concomitant increase in the percentage of postimplantation death and percentage of resorbed, macerated, and dead fetuses, respectively. Exposure increased the fetal malformations, namely, hydrocephaly, open eyelids, microphthalmia, exophthalmia, club foot, umbilical hernia, and skeletal anomalies. Reduced ossification of nasal, frontal, parietal, intraparietal, and supraoccipital bones, absence/gap between the ribs, reduced/fused sternebrae, vertebral centra, and caudal vertebrae, reduced pelvic elements, absence of carpals, metacarpals, tarsals, metatarsals, and phalanges were distinct. This indicates vulnerability of the mice fetus to nickel during prenatal exposure.

Oxidative damage effects in the copepod Tigriopus japonicus Mori experimentally exposed to nickel

Tigriopus japonicus Mori has been recognized as a good model for toxicological testing of marine pollutants. Recently, a large number of genes have been identified from this copepod, and their mRNA expression has been studied independently against exposure to marine pollutants; however, biochemical-response information is relatively scarce. The response of T. japonicus to nickel (Ni) additions was examined under laboratory-controlled conditions in 12 days exposure. Superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione-S-transferase (GST), acetylcholinesterase (AchE), reduced glutathione (GSH), the ratio of reduced to oxidized glutathione (GSH/GSSG) and metallothionein (MT) were analyzed for Ni treatments (0, 0.125, 0.25, 0.75 and 3.0 mg/L) after 1, 4, 7 and 12 days. The thiobarbituric reactive species assay was used to evaluate lipid peroxidation (LPO) level in copepods after exposure. The results showed that Ni remarkably affected the biochemical parameters (SOD, GPx, GST, GSH, and GSH/GSSG) after certain exposure durations. However, the copepod's LPO level was significantly decreased under metal treatments after exposure, hinting that the factors involved in LPO might not significantly depend on the operations and functions in the antioxidant system. Ni exhibited the neurotoxicity to copepods, because its use obviously elevated AchE activity. During exposure, Ni initially displayed an inhibition effect but induced MT synthesis in T. japonicus by day 12, probably being responsible for metal detoxification. Thus, Ni had intervened in the detoxification process and antioxidant system of this copepod, and it could be used as a suitable bioindicator of Ni exposure via measuring SOD, GPx, GST, and MT as biomarkers.

Nickel induces intracellular calcium mobilization and pathophysiological responses in human cultured airway epithelial cells

Environmental exposure to nickel is associated to respiratory disorders and potential toxicity in the lung but molecular mechanisms remain incompletely explored. The extracellular Ca(2+)-sensing receptor (CaSR) is widely distributed and may be activated by divalent cations. In this study, we investigated the presence of CaSR in human cultured airway epithelial cells and its activation by nickel. Nickel transiently increased intracellular calcium (-logEC(50)=4.67+/-0.06) in A549 and human bronchial epithelial cells as measured by epifluorescence microscopy. Nickel (20muM)-induced calcium responses were reduced after thapsigargin or ryanodine exposure but not by Ca(2+)-free medium. Inhibition of phospholipase-C or inositol trisphosphate release reduced intracellular calcium responses to nickel indicating activation of G(q)-signaling. CaSR mRNA and protein expression in epithelial cells was demonstrated by RT-PCR, western blot and immunofluorescence. Transfection of specific siRNA inhibited CaSR expression and suppressed nickel-induced intracellular calcium responses in A549 cells thus confirming nickel-CaSR activation. NPS2390, a CaSR antagonist, abolished the calcium response to nickel. Nickel-induced contraction, proliferation, alpha(1)(I)collagen production and inflammatory cytokines mRNA expression by epithelial cells as measured by traction microscopy, BrdU assay and RT-PCR, respectively. These responses were blocked by NPS2390. In conclusion, micromolar nickel concentrations, relevant to nickel found in the lung tissue of humans exposed to high environmental nickel, trigger intracellular Ca(2+) mobilization in human airway epithelial cells through the activation of CaSR which translates into pathophysiological outputs potentially related to pulmonary disease.

Carcinogenicity assessment of water-soluble nickel compounds

IARC is reassessing the human carcinogenicity of nickel compounds in 2009. To address the inconsistencies among results from studies of water-soluble nickel compounds, we conducted a weight-of-evidence analysis of the relevant epidemiological, toxicological, and carcinogenic mode-of-action data. We found the epidemiological evidence to be limited, in that some, but not all, data suggest that exposure to soluble nickel compounds leads to increased cancer risk in the presence of certain forms of insoluble nickel. Although there is no evidence that soluble nickel acts as a complete carcinogen in animals, there is limited evidence that suggests it may act as a tumor promoter. The mode-of-action data suggest that soluble nickel compounds will not be able to cause genotoxic effects in vivo because they cannot deliver sufficient nickel ions to nuclear sites of target cells. Although the mode-of-action data suggest several possible non-genotoxic effects of the nickel ion, it is unclear whether soluble nickel compounds can elicit these effects in vivo or whether these effects, if elicited, would result in tumor promotion. The mode-of-action data equally support soluble nickel as a promoter or as not being a causal factor in carcinogenesis at all. The weight of evidence does not indicate that soluble nickel compounds are complete carcinogens, and there is only limited evidence that they could act as tumor promoters.

Soluble and insoluble nickel compounds exert a differential inhibitory effect on cell growth through IKKalpha-dependent cyclin D1 down-regulation

It is well-known that insoluble nickel compounds possess much more potent carcinogenic activities as compared with soluble nickel compounds. Although it is assumed that the different entry and clearance rate are responsible for the difference, the mechanisms underlying the different carcinogenic activities are still not well understood yet. In the present study, we found that exposure to soluble, but not insoluble nickel compounds, caused a significant inhibition of cell growth and G1/G0 cell cycle arrest, which was concomitant with a marked down-regulation of cylin D1, an essential nuclear protein for controlling G1/S transition, while both soluble and insoluble nickel compounds showed similar effects on NFkappaB activation, HIF-1alpha protein accumulation and TNF-alpha transcription and CAP43 protein expression at same doses range. The down-regulation of cyclin D1 is due to protein degradation rather than inhibition of transcription, because the nickel compounds treatment did not change cyclin D1 mRNA level, while MG132, the proteasome inhibitor, can rescue the degradation of cyclin D1 caused by soluble nickel compound. Moreover, the soluble nickel-induced cyclin D1 degradation is dependent on its Thr286 residue and requires IKKalpha, but not HIF-1alpha, which are both reported to be involved in cyclin D1 down-regulation. Taken together, we demonstrate that soluble, but not insoluble nickel compound, is able to cause cyclin D1 degradation and a cell growth arrest in an IKKalpha-dependent manner. Given the role of cyclin D1 and cell proliferation in carcinogenesis, we anticipate that the different effects of soluble and insoluble nickel compounds on cyclin D1 degradation and cell growth arrest may at least partially account for their different carcinogenic activities.

Protective effect of cactus (Opuntia ficus indica) cladode extract upon nickel-induced toxicity in rats

The purpose of this study carried out on male Wistar rats, was to evaluate the protective effects of regular ingestion of juice from the prickly pear cactus (Opuntia ficus indica) cladodes against nickel chloride toxicity. Rats were given either normal tap water or water containing 25% of cactus juice for one month. Then, rats of each group were injected daily, for 10 days, with either NiCl(2) solution (4mg (30micromol)/kg body weight) or with the same volume of saline solution (300mM NaCl). Significant increases of lactate dehydrogenase, aspartate aminotransferase, alanine aminotransferase activities and of cholesterol, triglycerides and glucose levels were observed in blood of nickel-treated rats. In the liver, nickel chloride was found to induce an oxidative stress evidenced by an increase in lipid peroxidation and changes in antioxidant enzymes activities. Superoxide-dismutase (SOD) activity was found to be increased whereas glutathione peroxidase and catalase activities were decreased. These changes did not occur in animals previously given cactus juice, demonstrating a protective effect of this vegetal extract.