Inhibitive effects of nickel chloride (NiCl₂) on thymocytes

Mechanism of effects of nickel or nickel compounds on intestinal mucosal barrier

As an important metal in industry, national defense, and production, nickel widely exists in nature and is also a necessary trace element for human beings and animals. Nickel deficiency will affect the growth and development of animals, the contents of related active substances, enzymes and other essential elements in vivo. However, excessive nickel or longer nickel exposure can induce excessive free radicals (reactive oxygen species and reactive nitrogen) in the body, which can lead to a variety of cell damage, apoptosis and canceration, and ultimately pose negative effects on the health of the body. Among them, the intestinal tract, as the largest interface between the body and the external environment, greatly increases the contact probability between nickel or nickel compounds and the intestinal mucosal barrier, thus, the intestinal structure and function are also more vulnerable to nickel damage, leading to a series of related diseases such as enteritis. Therefore, this paper briefly analyzed the damage mechanism of nickel or its compounds to the intestinal tract from the perspective of four intestinal mucosal barriers: mechanical barrier, immune barrier, microbial barrier and chemical barrier, we hope to make a certain theoretical contribution to the further research and the prevention and treatment of nickel related diseases.

Nickel carcinogenesis mechanism: cell cycle dysregulation

Nickel (Ni) is a widely distributed metal in the environment and an important pollutant due to its widespread industrial applications. Ni has various toxicity in humans and experimental animals, including carcinogenicity. However, the carcinogenic effects of Ni remain troublesome. Cell cycle dysregulation may be an important carcinogenic mechanism and is also a potential molecular mechanism for Ni complexes anti-cancerous effects. Therefore, we conducted a literature review to summarize the effects of Ni on cell cycle. Up to now, there were three different reports on Ni-induced cell cycle arrest: (i) Ni can induce cell cycle arrest in G0/G1 phase, phosphorylation and degradation of IkappaB kinase-alpha (IKKα)-dependent cyclin D1 and phosphoinositide-3-kinase (PI3K)/serine-threonine kinase (Akt) pathway-mediated down-regulation of expressions of cyclin-dependent kinases 4 (CDK4) play important role in it; (ii) Ni can induce cell cycle arrest in S phase, but the molecular mechanism is not known; (iii) G2/M phase is the target of Ni toxicity, and Ni compounds cause G2/M cell cycle phase arrest by reducing cyclinB1/Cdc2 interaction through the activation of the ataxia telangiectasia mutated (ATM)-p53-p21 and ATM-checkpoint kinase inhibitor 1 (Chk1)/Chk2-cell division cycle 25 (Cdc25) pathways. Revealing the mechanisms of cell cycle dysregulation associated with Ni exposure may help in the prevention and treatment of Ni-related carcinogenicity and toxicology.

Update of the risk assessment of nickel in food and drinking water

The European Commission asked EFSA to update its previous Opinion on nickel in food and drinking water, taking into account new occurrence data, the updated benchmark dose (BMD) Guidance and newly available scientific information. More than 47,000 analytical results on the occurrence of nickel were used for calculating chronic and acute dietary exposure. An increased incidence of post-implantation loss in rats was identified as the critical effect for the risk characterisation of chronic oral exposure and a BMDL 10 of 1.3 mg Ni/kg body weight (bw) per day was selected as the reference point for the establishment of a tolerable daily intake (TDI) of 13 μg/kg bw. Eczematous flare-up reactions in the skin elicited in nickel-sensitised humans, a condition known as systemic contact dermatitis, was identified as the critical effect for the risk characterisation of acute oral exposure. A BMDL could not be derived, and therefore, the lowest-observed-adverse-effect-level of 4.3 μg Ni/kg bw was selected as the reference point. The margin of exposure (MOE) approach was applied and an MOE of 30 or higher was considered as being indicative of a low health concern. The mean lower bound (LB)/upper bound (UB) chronic dietary exposure was below or at the level of the TDI. The 95th percentile LB/UB chronic dietary exposure was below the TDI in adolescents and in all adult age groups, but generally exceeded the TDI in toddlers and in other children, as well as in infants in some surveys. This may raise a health concern in these young age groups. The MOE values for the mean UB acute dietary exposure and for the 95th percentile UB raises a health concern for nickel-sensitised individuals. The MOE values for an acute scenario regarding consumption of a glass of water on an empty stomach do not raise a health concern.

Effect of dietary NiCl2 on the cell cycle of cecal tonsil in the chicken broiler

Although the effects of nickel chloride (NiCl2) on the immune system have long been recognized, little is known about the effects of nickel (II) on the cell cycle and related signaling events in immune organs, such as cecal tonsil, a key immune organ of chicken. In the present study, we investigated the effect of NiCl2 on the cell cycle of cecal tonsil. The cell cycle was detected by the methods of flow cytometry (FCM), quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC). The results showed that dietary NiCl2 in excess of 300 mg/kg caused the G2/M cell cycle arrest and the reduction of cell proportion at S phase of the cecal tonsil. The G2/M cell cycle arrest was accompanied by the up-regulation of p53, p21 protein expression and mRNA expression, and down-regulation of cyclinB and proliferating cell nuclear antigen (PCNA) protein expression and mRNA expression. The data suggested that the cells' (mainly the T lymphocytes) proliferation in the cecal tonsil was inhibited by the high dietary NiCl2.

Immunotoxicity of nickel: Pathological and toxicological effects

Nickel (Ni) is a widely distributed metal in the environment and an important pollutant because of its many industrial applications. With increasing incidences of Ni contamination, Ni toxicity has become a global public health concern and recent evidence suggests that Ni adversely affects the immune system. Hence, this paper reviews the literature on immune-related effects of Ni exposure, the immunotoxicological effects of Ni, and the underlying mechanism of Ni immunotoxicity. The main focus was on the effect of Ni on the development of organs of immune system, lymphocyte subpopulations, cytokines, immunoglobulins, natural killer (NK) cells, and macrophages. Moreover, Ni toxicity also induces inflammation and several studies demonstrated that Ni could induce immunotoxicity. Excessive Ni exposure can inhibit the development of immune organs by excessively inducing apoptosis and inhibiting proliferation. Furthermore, Ni can decrease T and B lymphocytes, the specific mechanism of which requires further research. The effects of Ni on immunoglobulin A (IgA), IgG, and IgM remain unknown and while Ni inhibited IgA, IgG, and IgM levels in an animal experiment, the opposite result was found in research on humans. Ni inhibits the production of cytokines in non-inflammatory responses. Cytokine levels increased in Ni-induced inflammation responses, and Ni activates inflammation through toll like (TL)4-mediated nuclear factor-κB (NF-κB) and signal transduction cascades mitogen-activated protein kinase (MAPK) pathways. Ni has been indicated to inactivate NK cells and macrophages both in vitro and in vivo. Identifying the mechanisms underlying the Ni-induced immunotoxicity may help to explain the growing risk of infections and cancers in human populations that have been exposed to Ni for a long time. Such knowledge may also help to prevent and treat Ni-related carcinogenicity and toxicology.

Pathogenic Mechanisms and Therapeutic Implication in Nickel-Induced Cell Damage

Background:

Nickel (Ni) is mostly applied in a number of industrial areas such as printing inks, welding, alloys, electronics and electrical professions. Occupational or environmental exposure to nickel may lead to cancer, allergy reaction, nephrotoxicity, hepatotoxicity, neurotoxicity, as well as cell damage, apoptosis and oxidative stress.

Methods:

In here, we focused on published studies about cell death, carcinogenicity, allergy reactions and neurotoxicity, and promising agents for the prevention and treatment of the toxicity by Ni.

Results:

Our review showed that in the last few years, more researches have focused on reactive oxygen species formation, oxidative stress, DNA damages, apoptosis, interaction with involving receptors in allergy and mitochondrial damages in neuron induced by Ni.

Conclusion:

The collected data in this paper provide useful information about the main toxicities induced by Ni, also, their fundamental mechanisms, and how to discover new ameliorative agents for prevention and treatment by reviewing agents with protective and therapeutic consequences on Ni induced toxicity.

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.

Subchronic arsenism-induced oxidative stress and inflammation contribute to apoptosis through mitochondrial and death receptor dependent pathways in chicken immune organs

In many organ dysfunctions, arsenic and its compounds are well known to induce apoptosis by the mitochondria and death receptor apoptotic pathways in liver and airway. However, it is less reported that which signaling pathways contribute to excessive apoptosis of chicken immune organs, a major target of toxic metals biotransformation, which suffer from subchronic arsenism. In this study, we investigated whether the mitochondria or death receptor apoptotic pathways activated in the immune organs (spleen, thymus and bursa of Fabricius) of one-day-old male Hy-line chickens exposed to arsenic trioxide (As₂O₃), which were fed on diets supplemented with 0, 0.625, 1.25 and 2.5 mg/kg BW of As₂O₃ for 30, 60 and 90 days. We found that (1) Oxidative damage and inflammatory response were confirmed in the immune organs of chickens fed on As₂O₃ diet. (2) Subchronic arsenism induced typical apoptotic changes in ultrastructure. (3) TdT-mediated dUTP Nick-End Labeling (TUNEL) showed that the number of apoptotic cells significantly increased under subchronic arsenism. (4) As₂O₃-induced apoptosis of immune organs involved in mitochondrial pathway (decrease of B-cell lymphoma-2 (Bcl-2) and increase of protein 53 (p53), Bcl-2 Associated X Protein (Bax), caspase-9, caspase-3) and death receptor pathway (increase of factor associated suicide (Fas) and caspase-8). In conclusion, this work is the first to demonstrate that the activation of mitochondria and death receptor apoptosis pathways can lead to excessive apoptosis in immune organs of chickens, which suffer from subchronic arsenism, meanwhile, oxidative stress as well as subsequent inflammatory is a crucial driver of apoptosis.

Nickel chloride-induced apoptosis via mitochondria- and Fas-mediated caspase-dependent pathways in broiler chickens

Ni, a metal with industrial and commercial uses, poses a serious hazard to human and animal health. In the present study, we used flow cytometry, immunohistochemistry and qRT-PCR to investigate the mechanisms of NiCl₂-induced apoptosis in kidney cells. After treating 280 broiler chickens with 0, 300, 600 or 900 mg/kg NiCl₂ for 42 days, we found that two caspase-dependent pathways were involved in the induced renal tubular cell apoptosis. In the mitochondria-mediated caspase-dependent apoptotic pathway, cyt-c, HtrA2/Omi, Smac/Diablo, apaf-1, PARP, and caspase-9, 3, 6 and 7 were all increased, while. XIAP transcription was decreased. Concurrently, in the Fas-mediated caspase-dependent apoptotic pathway, Fas, FasL, caspase-8, caspase-10 and Bid levels were all increased. These results indicate that dietary NiCl₂ at 300+ mg/kg induces renal tubular cell apoptosis in broiler chickens, involving both mitochondrial and Fas-mediated caspase-dependent apoptotic pathways. Our results provide novel insight into Ni and Ni-compound toxicology evaluated in vitro and in vivo.

Nickel chloride (NiCl2) in hepatic toxicity: apoptosis, G2/M cell cycle arrest and inflammatory response

Up to now, the precise mechanism of Ni toxicology is still indistinct. Our aim was to test the apoptosis, cell cycle arrest and inflammatory response mechanism induced by NiCl₂ in the liver of broiler chickens. NiCl₂ significantly increased hepatic apoptosis. NiCl₂ activated mitochondria-mediated apoptotic pathway by decreasing Bcl-2, Bcl-xL, Mcl-1, and increasing Bax, Bak, caspase-3, caspase-9 and PARP mRNA expression. In the Fas-mediated apoptotic pathway, mRNA expression levels of Fas, FasL, caspase-8 were increased. Also, NiCl₂ induced ER stress apoptotic pathway by increasing GRP78 and GRP94 mRNA expressions. The ER stress was activated through PERK, IRE1 and ATF6 pathways, which were characterized by increasing eIF2α, ATF4, IRE1, XBP1 and ATF6 mRNA expressions. And, NiCl₂ arrested G₂/M phase cell cycle by increasing p53, p21 and decreasing cdc2, cyclin B mRNA expressions. Simultaneously, NiCl₂ increased TNF-α, IL-1β, IL-6, IL-8 mRNA expressions through NF-κB activation. In conclusion, NiCl₂ induces apoptosis through mitochondria, Fas and ER stress-mediated apoptotic pathways and causes cell cycle G₂/M phase arrest via p53-dependent pathway and generates inflammatory response by activating NF-κB pathway.

Nickel chloride (NiCl2) induces endoplasmic reticulum (ER) stress by activating UPR pathways in the kidney of broiler chickens

It has been known that overexposure to Ni can induce nephrotoxicity. However, the mechanisms of underlying Ni nephrotoxicity are still elusive, and also Ni- and Ni compound-induced ER stress has been not reported in vivo at present. Our aim was to use broiler chickens as animal model to test whether the ER stress was induced and UPR was activated by NiCl2 in the kidney using histopathology, immunohistochemistry and qRT-PCR. Two hundred and eighty one-day-old broiler chickens were divided into 4 groups and fed on a control diet and the same basal diet supplemented with 300 mg/kg, 600mg/kg and 900mg/kg of NiCl2 for 42 days. We found that dietary NiCl2 in excess of 300 mg/kg induced ER stress, which was characterized by increasing protein and mRNA expression of ER stress markers, e.g., GRP78 and GRP94. Concurrently, all the three UPR pathways were activated by dietary NiCl2. Firstly, the PERK pathway was activated by increasing eIF2a and ATF4 mRNA expression. Secondly, the IRE1 pathway was activated duo to increase in IRE1 and XBP1 mRNA expression. And thirdly, the increase of ATF6 mRNA expression suggested that ATF6 pathway was activated. The findings clearly demonstrate that NiCl2 induces the ER stress through activating PERK, IRE1 and ATF6 UPR pathways, which is proved to be a kind of molecular mechanism of Ni- or/and Ni compound-induced nephrotoxicity.

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.

Nickel chloride (NiCl2)-caused inflammatory responses via activation of NF-κB pathway and reduction of anti-inflammatory mediator expression in the kidney

Nickel (Ni) or Ni compounds target a number of organs and produce multiple toxic effects. Kidney is the major organ for Ni accumulation and excretion. There are no investigations on the Ni- or Ni compounds-induced renal inflammatory responses in human beings and animals at present. Therefore, we determined NiCl₂-caused alteration of inflammatory mediators, and functional damage in the broiler's kidney by the methods of biochemistry, immunohistochemistry and quantitative real-time polymerase chain reaction (qRT-PCR). Dietary NiCl₂ in excess of 300 mg/kg caused the renal inflammatory responses that characterized by increasing mRNA expression levels of the pro-inflammatory mediators including tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8) and interleukin-18 (IL-18) via the activation of nucleic factor κB (NF-κB), and decreasing mRNA expression levels of the anti-inflammatory mediators including interleukin-2 (IL-2), interleukin-4 (IL-4) and interleukin-13 (IL-13). Concurrently, NiCl₂ caused degeneration, necrosis and apoptosis of the tubular cells, which was consistent with the alteration of renal function parameters including elevated alkaline phosphatase (AKP) activity, and reduced activities of sodium-potassium adenosine triphosphatase (Na⁺/K⁺-ATPase), calcium adenosine triphosphatase (Ca²⁺-ATPase), lactic dehydrogenase (LDH), succinate dehydrogenase (SDH) and acid phosphatase (ACP) in the kidney. The above-mentioned results present that the activation of NF-κB pathway and reduction of anti-inflammatory mediator expression are main mechanisms of NiCl2-caused renal inflammatory responses and that the renal function is decreased or impaired after NiCl2-treated.

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.

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.

Dietary NiCl₂ causes G₂/M cell cycle arrest in the broiler's kidney

Here we showed that dietary NiCl2 in excess of 300 mg/kg caused the G2/M cell cycle arrest and the reduction of cell proportion at S phase. The G2/M cell cycle arrest was accompanied by up-regulation of phosphorylated ataxia telangiectasia mutated (p-ATM), p53, p-Chk1, p-Chk2, p21 protein expression and ATM, p53, p21, Chk1, Chk2 mRNA expression, and down-regulation of p-cdc25C, cdc2, cyclinB and proliferating cell nuclear antigen (PCNA) protein expression and the cdc25, cdc2, cyclinB, PCNA mRNA expression.

Modulation of the PI3K/Akt Pathway and Bcl-2 Family Proteins Involved in Chicken's Tubular Apoptosis Induced by Nickel Chloride (NiCl₂)

Exposure of people and animals to environments highly polluted with nickel (Ni) can cause pathologic effects. Ni compounds can induce apoptosis, but the mechanism and the pathway of Ni compounds-induced apoptosis are unclear. We evaluated the alterations of apoptosis, mitochondrial membrane potential (MMP), phosphoinositide-3-kinase (PI3K)/serine-threonine kinase (Akt) pathway, and Bcl-2 family proteins induced by nickel chloride (NiCl₂) in the kidneys of broiler chickens, using flow cytometry, terminal deoxynucleotidyl transferase 2ʹ-deoxyuridine 5ʹ-triphosphate dUTP nick end-labeling (TUNEL), immunohistochemstry and quantitative real-time polymerase chain reaction (qRT-PCR). We found that dietary NiCl₂ in excess of 300 mg/kg resulted in a significant increase in apoptosis, which was associated with decrease in MMP, and increase in apoptosis inducing factor (AIF) and endonuclease G (EndoG) protein and mRNA expression. Concurrently, NiCl₂ inhibited the PI3K/Akt pathway, which was characterized by decreasing PI3K, Akt1 and Akt2 mRNA expression levels. NiCl₂ also reduced the protein and mRNA expression of anti-apoptotic Bcl-2 and Bcl-xL and increased the protein and mRNA expression of pro-apoptotic Bax and Bak. These results show that NiCl₂ causes mitochondrial-mediated apoptosis by disruption of MMP and increased expression of AIF and EndoG mRNA and protein, and that the underlying mechanism of MMP loss involves the Bcl-2 family proteins modulation and PI3K/Akt pathway inhibition.