Nickel(II) induced JNK activation-regulated mitochondria-dependent apoptotic pathway leading to cultured rat pancreatic β-cell death

Metals link to diabetes: Insights from a national cross-sectional investigation

Diabetes and impaired fasting glucose (IFG) are significant global health concerns. However, the potential effects of mixed heavy metal exposure on these conditions remain underexplored. This study aims to investigate the combined effects of multiple metals on diabetes risk and explore the mediating role of Body Mass Index (BMI) in rural China. A cross-sectional analysis involved 2313 adults from 12 provinces in rural China. Urinary levels of zinc (Zn), chromium (Cr), nickel (Ni), cadmium (Cd), and lead (Pb) were quantified using inductively coupled plasma mass spectrometry. Fasting blood glucose (FBG) levels were measured with an automatic biochemical analyzer. Logistic regression models and the Bayesian Kernel Machine Regression (BKMR) model were used to examine associations and interactions. Mediation analysis was performed to assess the role of BMI. The results of our study indicate that there is a significant association between urinary Zn (OR = 2.38, 95 % CI: 1.57, 3.60), Cr (OR = 1.24, 95 % CI: 1.31, 1.61), and Ni (OR = 1.51, 95 % CI: 1.05, 2.18) and the diabetes risk. The study revealed that exposure to Ni amplified the associations between Zn, Cr and diabetes/IFG risk. Additionally, BMI was identified as a significant mediator in the relationship between metal exposure, particularly Cr/Cd, and diabetes risk. These findings reveal a complex link between multiple metals, such as Zn, Cr, and Ni, and diabetes risk, and emphasize the potential opposite mediating effects of BMI in different metal-induced diabetes mechanisms. Further investigation of these mechanisms is warranted.

Effects of Nickel Bioaccumulation on Hematological, Biochemical, Immune Responses, Neuroinflammatory, Oxidative Stress Parameters, and Neurotoxicity in Rats

Nickel (Ni) exposure is linked to numerous health issues, including dermatitis, immunotoxicity, and cancer. Emerging evidence suggests Ni may cross the blood-brain barrier, accumulating in the brain and causing neuroinflammation, oxidative stress, and neuronal apoptosis. Herein, we investigated the effect of Ni exposure through the intraperitoneal route, studying the Ni effect in subacute and chronic toxicity, on various health parameters in Wistar rats. Rats were randomly divided into four groups (n = 10 per group): two groups received a daily intraperitoneal injection of NiCl₂ at a dose of 0.25 mg/kg for subacute (21 days) or chronic (60 days) exposure periods, while the other two groups were treated with NaCl solution (0.9%) as a control for equivalent durations. The study assessed behavioral, biochemical, hematological, immunological, neurobiochemical, and histopathological effects over 21 and 60 days. Neurobehavioral tests, blood and tissue analyses, and organ examinations were conducted. This study demonstrates that Ni bioaccumulation in subacute and chronic exposure has significant health impacts in Wistar rats, including hematological, immunological, biochemical, AchE activity, neuroinflammatory, oxidative stress, and neurobehavioral changes. Chronic exposure results in higher Ni accumulation, particularly in the brain, causing neurotoxicity, inflammation, and behavioral disorders such as anxiety, depression, and memory impairment. The findings highlight the importance of limiting Ni exposure to prevent adverse health effects.

The relationship between plasma nickel concentrations and type 2 diabetes mellitus risk: A protective effect within a specific range

BACKGROUND

Nickel is considered an essential nutrient for certain microbial, plant, and animal species, but its role in human health remains controversial. Some studies have reported the relationship between nickel and type 2 diabetes mellitus (T2DM), but the results are not consistent and the mechanism is not clear, which needs further exploration.

AIM

To investigate the possible correlation between nickel and T2DM.

METHODS

We conducted a case-control study of 192 patients with T2DM and 189 healthy controls at a hospital in central China. Plasma concentrations of nickel and six other trace elements were measured with inductively coupled plasma mass spectrometry. Logistic regression models, restricted cubic spline models (RCS), and Bayesian kernel machine regression (BKMR) were used to evaluate the relationship between plasma nickel and T2DM and its metabolic risk factors, as well as the presence or absence of interactions between nickel and other elements.

RESULTS

The T2DM group exhibited considerably lower plasma nickel levels than the control group (P < 0.001). Whether using a crude or adjusted model, logistic regression analysis finds a negative correlation between nickel levels and the risk of T2DM (P trend < 0.001). According to the RCS, the risk of T2DM reduces with rising nickel levels when the value is below 6.1 μg/L; nickel has a negative linear correlation with fasting plasma glucose (FPG), an inverse U-shaped connection with superoxide dismutase (SOD), and a positive linear correlation with malondialdehyde (MDA) (all P overall < 0.05). The plasma nickel concentration was positively correlated with zinc, vanadium, and chromium (r = 0.23, 0.11, and 0.19, respectively; all P < 0.05) and negatively correlated with copper (r = - 0.11, P < 0.05). In the BKMR model, interactions of nickel with zinc on T2DM and SOD, nickel with chromium on T2DM and homeostasis model assessment of β cell (HOMA-β), and nickel with copper on FPG, homeostasis model assessment of insulin (HOMA-IR), and MDA were observed.

CONCLUSION

Nickel may have a dual effect on the risk of T2DM, with a protective range of less than 6.1 μg/L. Potential interactions between nickel, copper, zinc, and chromium existed in their associations with T2DM and its metabolic risk factors.

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.

Association of urinary nickel levels with diabetes and fasting blood glucose levels: A nationwide Chinese population-based study

Some epidemiological studies support a relationship between nickel exposure and diabetes in the general population. To address this, we tested the association of nickel exposure with diabetes in 10,890 adults aged ≥ 18 years old from the China National Human Biomonitoring study conducted in 2017-2018. Urinary nickel concentrations and fasting blood glucose (FBG) were measured, and lifestyle and demographic data were collected. Weighted logistic and linear regressions were used to estimate the associations of urinary nickel levels with diabetes prevalence and FBG. Restricted cubic splines (RCS) were used to test for the dose-response relationship. The odd ratio (95% confidence interval [CI]) of diabetes for the highest versus lowest quartiles of urinary nickel concentrations was 1.74 (1.28, 2.36) in the multivariate model (p _trend =0.001). Each one-unit increase in log-transformed urinary nickel concentrations was associated with a 0.36 (0.17, 0.55) mmol/L elevation in FBG. The RCS curves showed a monotonically increasing dose-response relationship of urinary nickel with diabetes as well as FBG levels, and then tended to flatten after about 4.75 μg/L of nickel exposure. The nickel-diabetes association was stronger in individuals with lower than those with higher rice consumption (OR: 2.39 vs. 1.72). Our study supports a positive association between nickel exposure and diabetes prevalence in Chinese adults, especially in individuals with lower rice consumption. Further large-scale prospective studies are needed to validate our findings.

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's Role in Pancreatic Ductal Adenocarcinoma: Potential Involvement of microRNAs

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancer types with a limited overall survival rate due to the asymptomatic progression of symptoms in metastatic stages of the malignancy and the lack of an early reliable diagnostic biomarker. MicroRNAs (miRs/miRNAs) are small (~18–24 nucleotides), endogenous, non-coding RNAs, which are closely linked to the development of numerous malignancies comprising PDAC. Recent studies have described the role of environmental pollutants such as nickel (Ni) in PDAC, but the mechanisms of Ni-mediated toxicity in cancer are still not completely understood. Specifically, Ni has been found to alter the expression and function of miRs in several malignancies, leading to changes in target gene expression. In this study, we found that levels of Ni were significantly higher in cancerous tissue, thus implicating Ni in pancreatic carcinogenesis. Hence, in vitro studies followed by using both normal and pancreatic tumor cell lines and increasing Ni concentration increased lethality. Comparing LC50 values, Ni-acetate groups demonstrated lower values needed than in NiCl₂ groups, suggesting greater Ni-acetate. Panc-10.05 cell line appeared the most sensitive to Ni compounds. Exposure to Ni-acetate resulted in an increased phospho-AKT, and decreased FOXO1 expression in Panc-10.05 cells, while NiCl₂ also increased PTEN expression in Panc-10.05 cells. Specifically, following NiCl₂ exposure to PDAC cells, the expression levels of miR-221 and miR-155 were significantly upregulated, while the expression levels of miR-126 were significantly decreased. Hence, our study has suggested pilot insights to indicate that the environmental pollutant Ni plays an important role in the progression of PDAC by promoting an association between miRs and Ni exposure during PDAC pathogenesis.

TMT-based quantitative proteomics analysis reveals the effect of bovine derived MFG-E8 against oxidative stress on rat L6 cells

Sarcopenia is an aging-associated oxidative stress-induced mitochondrial dysfunction characterized by a decline in skeletal muscle mass, strength and function. Milk fat globule-EGF factor 8 (MFG-E8) is a secreted matrix glycoprotein that plays a crucial role in regulating tissue homeostasis and protecting against skeletal muscle injury. To explore the molecular mechanism of MFG-E8 in ameliorating the rotenone (Rot)-induced L6 skeletal muscle cell oxidative stress injury, differential proteomics of inner L6 cells was conducted. Tandem mass tag (TMT) labeling combined with mass spectrometry (MS) was performed to find associations among control, Rot and Rot + MFG-E8 groups. Over 3248 proteins were identified in the L6 cells. A total of 639 significantly differential proteins were identified, including 294 up-regulated proteins (>1.2 fold) and 345 down-regulated proteins (<0.83 fold) after the exogenous intervention of MFG-E8. Based on the analysis of Gene Ontology (GO), STRING and KEGG databases, MFG-E8 relieves oxidative stress induced-L6 cell damage by regulating the expression of these differential proteins mainly via carbon metabolism, glutathione metabolism and mitochondria-mediated metabolic pathways, e.g. carbohydrate, lipid and amino acid metabolism. Furthermore, to verify the protective effect of MFG-E8 on oxidative stress injured L6 cells, the levels of intracellular reactive oxygen species (ROS), nicotinamide adenine dinucleotide/reduced nicotinamide adenine dinucleotide (NAD⁺/NADH) contents and the protein expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) were detected.

Research progress on the effects of nickel on hormone secretion in the endocrine axis and on target organs

BACKGROUND

Nickel, as one of the most abundant elements in the earth's crust, plays many roles in human reproduction and life. It is an essential trace element for the human body, but can be harmful in excess amounts. Nickel has a significant impact on endocrine hormones in humans and animals, potentially causing abnormal secretions and changing the structure and function of endocrine organs. This article systematically reviews the effects of nickel on hormone secretion and target organs in the endocrine system and identifies areas of insufficient research.

METHODS

All data in this article were extracted from peer-reviewed articles. The PubMed, SciFinder, Google Scholar, Web of Science, and China National Knowledge Infrastructure databases were searched for relevant articles. Data on nickel's effect on endocrine system hormones and target organs were retrieved, and manually sorted prior to inclusion in this review.

RESULTS

Nickel acts on the endocrine system and affects the release and regulation of endocrine hormones. Disorders of endocrine hormones may lead to retardation of human growth and mental development, disturbance of water and salt regulation, and even a decline in reproductive ability. Nickel affects the hypothalamus and pituitary gland by regulating organs upstream of the endocrine axis; it can cause abnormal secretion of pituitary hormones, which affects target organs of the endocrine axis, resulting in dysfunction therein and abnormal secretion of related hormones. Nickel also damages target organs, mainly by inducing apoptosis, which triggers oxidative stress, cell autophagy, free radical release, and DNA damage. However, there are few studies on the endocrine axis, and some of the data are contradictory. Nevertheless, it is clear that nickel affects the endocrine system.

CONCLUSIONS

Nickel can damage organs in the endocrine system, such as the hypothalamus and pituitary. It also affects the secretion of hormones and damages the target organs of these hormones; this can result in endocrine system dysfunction. However, the results have been equivocal and further research is needed.

Lactate released from human fibroblasts enhances Ni elution from Ni plate

Elution of Ni ions from medical devices induces inflammation and toxicity. We previously reported that elution of Ni ions from Ni wires induced COX-2 expression and increased lactate production, but whether lactate is involved in the further elution of Ni ions remains unclear. In this study, using KMST-6, a human fibroblast cell line, we examined the molecular mechanisms by which Ni ions increase lactate release and the role of lactate in enhancing the elution of Ni ions. When KMST-6 cells were incubated on a Ni plate or stimulated with NiCl₂ (1 mM), the expression of glucose transporter 1 (GLUT1), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), and the release of lactate were enhanced. The NiCl₂ (1 mM)-induced expression of these genes was inhibited by a hypoxia-inducible factor-1α (HIF-1α) inhibitor, PX-478 (10-25 μM). Stimulation of cells with a prolyl hydroxylase domain (PHD) inhibitor, roxadustat, increased the expression of these genes, lactate release, and elution of Ni ions at 10 μM. A monocarboxylate transporter-4 (MCT4) inhibitor, syrosingopine, inhibited lactate release from roxadustat-treated cells and reduced the elution of Ni ions by the cells at 10 μM. Finally, syrosingopine (10 μM) reduced the elution of Ni ions by the cells from the Ni plate. These results suggest that elution of Ni ions from metals promotes the production of lactate via HIF-1α-mediated gene expression and causes further Ni elution. Thus, Ni ions show a positive feedback mechanism of Ni elution, and this step may be potentially targeted to protect against metal elution from metal devices.

Toxicity of organic and inorganic nickel in pancreatic cell cultures: Comparison to cadmium

Nickel compounds are Group 1 carcinogens and possibly cancer-causing in the pancreas. We examined the toxicity of nickel in both 2-D and 3-D pancreatic cell cultures, to determine the LD50 for organic and inorganic nickel in normal and cancerous cells. Assays with cadmium chloride were performed to be a comparison to potential nickel-induced toxicity. Cells were exposed to twelve concentrations of NiCl2 or Ni-(Ac)2 for 48h (2-D), or six concentrations for 48 hours (3-D). There was a significant (P=0.0016) difference between HPNE and AsPC-1 LD50 values after cadmium exposure, at 69.9 µM and 29.2 µM, respectively. Neither form of nickel exhibited toxicity in 2-D or 3-D cultures, but after 48h, changes in spheroid morphology were observed. The inability of Ni to reduce viable cell numbers suggests a toxic mechanism that differs from cadmium, also a Group 1 carcinogen. The cell microenvironment was not a factor in nickel toxicity with no changes in viable cells in either 2-D or 3-D cultures. These studies only examined cytotoxicity, and not genotoxicity, a potential mechanism of nickel carcinogenicity. Alterations in DNA function or the expression of apoptotic proteins/processes would take longer to manifest. Current work focuses on cellular changes following extended nickel exposure.

The roles of calcium-sensing receptor (CaSR) in heavy metals-induced nephrotoxicity

The kidney is a vital organ responsible for regulating water, electrolyte and acid-base balance as well as eliminating toxic substances from the blood in the body. Exposure of humans to heavy metals in their natural and occupational environments, foods, water, and drugs has serious implications on the kidney's health. The accumulation of heavy metals in the kidney has been linked to acute or chronic renal injury, kidney stones or even renal cancer, at the expense of expensive treatment options. Therefore, unearthing novel biomarkers and potential therapeutic agents or targets against kidney injury for efficient treatment are imperative. The calcium-sensing receptor (CaSR), a G-protein-coupled receptor (GPCR) is typically expressed in the parathyroid glands and renal tubules. It modulates parathyroid hormone secretion according to the serum calcium (Ca²⁺) concentration. In the kidney, it modulates electrolyte and water excretion by regulating the function of diverse tubular segments. Notably, CaSR lowers passive and active Ca²⁺ reabsorption in distal tubules, which facilitates phosphate reabsorption in proximal tubules and stimulates proton and water excretion in collecting ducts. Moreover, at the cellular level, modulation of the CaSR regulates cytosolic Ca²⁺ levels, reactive oxygen species (ROS) generation and the mitogen-activated protein kinase (MAPK) signaling cascades as well as autophagy and the suppression of apoptosis, an effect predominantly triggered by heavy metals. In this regard, we present a review on the CaSR at the cellular level and its potential as a therapeutic target for the development of new and efficient drugs against heavy metals-induced nephrotoxicity.

Ameliorative effects of nano-selenium against NiSO4-induced apoptosis in rat testes

Nickel (Ni) is a common environmental pollutant, which has toxic effects on reproductive system. Nowadays, nano-selenium (Nano-Se) has aroused great attention due to its unique antioxidant effect, excellent biological activities and low toxicity. The aim of this study was to explore the protective effects of Nano-Se on NiSO₄-induced testicular injury and apoptosis in rat testes. Nickel sulfate (NiSO₄) (5 mg/kg b.w.) was administered intraperitoneally and Nano-Se (0.5, 1, and 2 mg Se/kg b.w., respectively) was given by oral gavage in male Sprague-Dawley rats. Histological changes in the testes were determined by H&E staining. The terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay and immunohistochemistry were performed to evaluate the apoptosis in testes. Expression levels of mitochondrial apoptosis-related genes and proteins were analyzed by RT-qPCR and Western blot. The results showed that Nano-Se improved lesions of testicular tissue induced by NiSO₄. Nano-Se significantly alleviated NiSO₄-induced apoptosis in rat testes, as well as significantly downregulated the Bak, cytochrome c, caspase-9 and caspase-3 and upregulated Bcl-2 expression levels, all of which were involved in mitochondria-mediated apoptosis. Altogether, we concluded that Nano-Se may potentially exert protective effects on NiSO₄-induced testicular injury and attenuate apoptosis, at least partly, via regulating mitochondrial apoptosis pathways in rat testes.

Effects of 17β-estradiol and tamoxifen on gastric cancer cell proliferation and apoptosis and ER-α36 expression

The present study aimed to investigate the effects of 17β-estradiol and tamoxifen, an agonist and inhibitor of the estrogen receptor (ER), respectively, on the proliferation and apoptosis of gastric cancer cells, as well as the messenger (m)RNA expression levels of ER-α36. Nested reverse transcription-polymerase chain reaction (RT-PCR) confirmed that ER-α36 was expressed in the BGC823, MKN45 and SGC7901 human gastric cancer cell lines. Subsequently, the BGC823 cell line was stimulated with various concentrations of 17β-estradiol or tamoxifen for 24 or 48 h, and the proliferation, apoptosis and mRNA expression levels of ER-α36 were determined by water-soluble tetrazolium (WST)-1 assay, flow cytometry and RT-quantitative PCR, respectively. The activity of BGC823 cells was significantly increased following treatment with 10⁻¹² mol/l 17β-estradiol for 24 h (P=0.013), as compared with the control, and reached a peak at 48 h (P=0.002). Notably, the activity of BGC823 cells was decreased with increasing concentrations of 17β-estradiol, although it remained higher compared with that of the control. In the tamoxifen-treated groups, the cell activity decreased as the drug concentration increased. The apoptosis rate was markedly reduced in the 17β-estradiol group after 24 h (10⁻¹² mol/l, P=0.013; 10⁻¹¹ mol/l, P=0.023; and 10⁻¹⁰ mol/l, P=0.017) and after 48 h (10⁻¹² mol/l, P=0.002; 10⁻¹¹ mol/l, P=0.011; and 10⁻¹⁰ mol/l, P=0.033), whereas the rate of apoptosis increased as the tamoxifen concentration increased (24 h: 5×10⁻⁶ mol/l, P=0.002; and 10⁻⁵ mol/l, P=0.001; and 48 h: 5×10⁻⁶ mol/l, P=0.014 and 10⁻⁵ mol/l, P=0.0021), as compared with the control group. The mRNA expression levels of ER-α36 were significantly increased after 24 h of treatment with 10⁻¹² mol/l (P=0.024), 10⁻¹¹ mol/l (P=0.0113) and 10⁻¹⁰ mol/l (P=0.0037) 17β-estradiol compared with the control group when the concentration of 17β-estradiol was low, and the same was observed after 48 h of treatment 10⁻¹² mol/l (P=0.0164), 10⁻¹¹ mol/l (P=0.0342) and 10⁻¹⁰ mol/l (P=0.0198) 17β-estradiol. The mRNA expression levels of ER-α36 were significantly decreased with increasing concentrations of tamoxifen after 24 h (5×10⁻⁶ mol/l, P=0.0233; and 10⁻⁵ mol/l, P=0.007) and after 48 h (5×10⁻⁶ mol/l, P=0.001; and 10⁻⁵ mol/l, P=0.0153). In addition, the ability of tamoxifen to inhibit the growth of gastric cancer cells was concentration-dependent. The results of the present study suggested that gastric cancer cells were sensitive to the effects of 17β-estradiol and tamoxifen, and that tamoxifen is able to induce gastric cancer cell apoptosis. The expression levels of ER-α36 were upregulated, and the growth of gastric cancer cells was increased, following treatment with 17β-estradiol, thus suggesting that gastric cancer tumors are stimulated by estrogen.

Nickel-Refining Fumes Induced DNA Damage and Apoptosis of NIH/3T3 Cells via Oxidative Stress

Although there have been numerous studies examining the toxicity and carcinogenicity of nickel compounds in humans and animals, its molecular mechanisms of action are not fully elucidated. In our research, NIH/3T3 cells were exposed to nickel-refining fumes at the concentrations of 0, 6.25, 12.50, 25, 50 and 100 μg/mL for 24 h. Cell viability, cell apoptosis, reactive oxygen species (ROS) level, lactate dehydrogenase (LDH) assay, the level of glutathione (GSH), activities of superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) level were detected. The exposure of NIH/3T3 cells to nickel-refining fumes significantly reduced cell viability and induced cell apoptotic death in a dose-dependent manner. Nickel-refining fumes significantly increased ROS levels and induced DNA damage. Nickel-refining fumes may induce the changes in the state of ROS, which may eventually initiate oxidative stress, DNA damage and apoptosis of NIH/3T3 cells.

Molybdenum induces pancreatic β-cell dysfunction and apoptosis via interdependent of JNK and AMPK activation-regulated mitochondria-dependent and ER stress-triggered pathways

Molybdenum (Mo), a well-known toxic environmental and industrial pollutant, causes adverse health effects and diseases in humans and has received attention as a potential risk factor for DM. However, the roles of Mo in the mechanisms of the toxicological effects in pancreatic β-cells are mostly unclear. In this study, the results revealed dysfunction of insulin secretion and apoptosis in the pancreatic β-cell-derived RIN-m5F cells and the isolated mouse islets in response to Mo. These effects were accompanied by a mitochondria-dependent apoptotic signals including a decreased in the MMP, an increase in cytochrome c release, and the activation of caspase cascades and PARP. In addition, ER stress was triggered as indicated by several key molecules of the UPR. Furthermore, exposure to Mo induced the activation of ERK1/2, JNK, AMPKα, and GSK3-α/β. Pretreatment with specific pharmacological inhibitors (in RIN-m5F cells and isolated mouse islets) of JNK (SP600125) and AMPK (Compound C) or transfection with si-RNAs (in RIN-m5F cells) specific to JNK and AMPKα effectively prevented the Mo-induced apoptosis and related signals, but inhibitors of ERK1/2 and GSK3-α/β (PD98059 and LiCl, respectively) did not reverse the Mo-induced effects. Additionally, both the inhibitors and specific si-RNAs could suppress the Mo-induced phosphorylation of JNK and AMPKα each other. Taken together, these results suggest that Mo exerts its cytotoxicity on pancreatic β-cells by inducing dysfunction and apoptosis via interdependent JNK and AMPK activation downstream-regulated mitochondrial-dependent and ER stress-triggered apoptosis pathways.

Nickel inhibits mitochondrial fatty acid oxidation

Nickel exposure is associated with changes in cellular energy metabolism which may contribute to its carcinogenic properties. Here, we demonstrate that nickel strongly represses mitochondrial fatty acid oxidation-the pathway by which fatty acids are catabolized for energy-in both primary human lung fibroblasts and mouse embryonic fibroblasts. At the concentrations used, nickel suppresses fatty acid oxidation without globally suppressing mitochondrial function as evidenced by increased glucose oxidation to CO2. Pre-treatment with l-carnitine, previously shown to prevent nickel-induced mitochondrial dysfunction in neuroblastoma cells, did not prevent the inhibition of fatty acid oxidation. The effect of nickel on fatty acid oxidation occurred only with prolonged exposure (>5 h), suggesting that direct inhibition of the active sites of metabolic enzymes is not the mechanism of action. Nickel is a known hypoxia-mimetic that activates hypoxia inducible factor-1α (HIF1α). Nickel-induced inhibition of fatty acid oxidation was blunted in HIF1α knockout fibroblasts, implicating HIF1α as one contributor to the mechanism. Additionally, nickel down-regulated the protein levels of the key fatty acid oxidation enzyme very long-chain acyl-CoA dehydrogenase (VLCAD) in a dose-dependent fashion. In conclusion, inhibition of fatty acid oxidation by nickel, concurrent with increased glucose metabolism, represents a form of metabolic reprogramming that may contribute to nickel-induced carcinogenesis.

Pre-exposure of Mycobacterium tuberculosis-infected macrophages to crystalline silica impairs control of bacterial growth by deregulating the balance between apoptosis and necrosis

Inhalation of crystalline silica (CS) particles increases the risk of pulmonary tuberculosis; however, the precise mechanism through which CS exposure facilitates Mycobacterium tuberculosis (Mtb) infection is unclear. We speculate that macrophage exposure to CS deregulates the cell death pathways that could explain, at least in part, the association observed between exposure to CS and pulmonary tuberculosis. We therefore established an in vitro model in which macrophages were exposed to CS and then infected with Mtb. Expression of surface markers was analyzed by flow cytometry, JNK1/2, ASK1, caspase 9, P-p38, Bcl-2 and Mcl-1 were analyzed by Western blot, and cytokines by ELISA. Our results show that exposure to CS limits macrophage ability to control Mtb growth. Moreover, this exposure reduced the expression of TLR2, Bcl-2 and Mcl-1, but increased that of JNK1 and ASK1 molecules in the macrophages. Finally, when the pre-exposed macrophages were infected with Mtb, the concentrations of TNFα, IL-1β and caspase-9 expression increased. This pro-inflammatory profile of the macrophage unbalanced the apoptosis/necrosis pathway. Taken together, these data suggest that macrophages exposed to CS are sensitized to cell death by MAPK kinase-dependent signaling pathway. Secretion of TNF-α and IL-1β by Mtb-infected macrophages promotes necrosis, and this deregulation of cell death pathways may favor the release of viable bacilli, thus leading to the progression of tuberculosis.

Nickel-induced structural and functional alterations in porcine granulosa cells in vitro

The present study was aimed at investigating the effect of nickel chloride (NiCl2) on secretion of progesterone (P), ultrastructure and apoptosis in porcine granulosa cells. NiCl2 was added to the cells to achieve a Ni(2+) concentration of 62.5, 125, 250, 500 and 1,000 μmol/L. A control group contained no NiCl2 addition. Quantification of P was performed directly from aliquots of the media from control and treated porcine granulosa cells after 48 h of culture using radioimmunoassay. Quantification of apoptotic cells was performed using terminal deoxynucleotidyl transferase dUTP nick end labelling assay, and ultrastructural changes were analyzed using transmission electron microscopy. A concentration-dependent depletion of P production was observed significantly for 1,000 μmol/L NiCl2. The percentage of apoptotic cells was increased in all experimental groups significantly only after addition of 1,000 μmol/L NiCl2. After addition of ≥250 μmol/L NiCl2, a higher incidence of euchromatin was observed. Also, lipid droplets and vacuoles in the cytoplasm increased after addition of ≥250 μmol/L NiCl2. NiCl2 induced the decrease in numbers of mitochondria and smooth endoplasmic reticulum after treatment with ≥500 μmol/L NiCl2. Our findings suggest a negative effect of NiCl2 on steroidogenesis and apoptosis as well as ultrastructure of porcine granulosa cells.

Identification of molecular candidates and interaction networks via integrative toxicogenomic analysis in a human cell line following low-dose exposure to the carcinogenic metals cadmium and nickel

Cadmium and nickel have been classified as carcinogenic to humans by the World Health Organization's International Agency for Research on Cancer. Given their prevalence in the environment, the fact that cadmium and nickel may cause diseases including cancer even at low doses is a cause for concern. However, the exact mechanisms underlying the toxicological effects induced by low-dose exposure to cadmium and nickel remain to be elucidated. Furthermore, it has recently been recognized that integrative analysis of DNA, mRNA and proteins is required to discover biomarkers and signaling networks relevant to human toxicant exposure. In the present study, we examined the deleterious effects of chronic low-dose exposure of either cadmium or nickel on global profiling of DNA copy number variation, mRNA and proteins. Array comparative genomic hybridization, gene expression microarray and functional proteomics were conducted, and a bioinformatics tool, which predicted signaling pathways, was applied to integrate data for each heavy metal separately and together. We found distinctive signaling networks associated with subchronic low-dose exposure to cadmium and nickel, and identified pathways common to both. ACTB, HSP90AA1, HSPA5 and HSPA8, which are key mediators of pathways related to apoptosis, proliferation and neoplastic processes, were key mediators of the same pathways in low-dose nickel and cadmium exposure in particular. CASP-associated signaling pathways involving CASP3, CASP7 and CASP9 were observed in cadmium-exposed cells. We found that HSP90AA1, one of the main modulators, interacted with HIF1A, AR and BCL2 in nickel-exposed cells. Interestingly, we found that HSP90AA1 was involved in the BCL2-associated apoptotic pathway in the nickel-only data, whereas this gene interacted with several genes functioning in CASP-associated apoptotic signaling in the cadmium-only data. Additionally, JUN and FASN were main modulators in nickel-responsive signaling pathways. Our results provide valuable biomarkers and distinctive signaling networks that responded to subchronic low-dose exposure to cadmium and nickel.

p53 activation by Ni(II) is a HIF-1α independent response causing caspases 9/3-mediated apoptosis in human lung cells

Hypoxia mimic nickel(II) is a human respiratory carcinogen with a suspected epigenetic mode of action. We examined whether Ni(II) elicits a toxicologically significant activation of the tumor suppressor p53, which is typically associated with genotoxic responses. We found that treatments of H460 human lung epithelial cells with NiCl2 caused activating phosphorylation at p53-Ser15, accumulation of p53 protein and depletion of its inhibitor MDM4 (HDMX). Confirming the activation of p53, its knockdown suppressed the ability of Ni(II) to upregulate MDM2 and p21 (CDKN1A). Unlike DNA damage, induction of GADD45A by Ni(II) was p53-independent. Ni(II) also increased p53-Ser15 phosphorylation and p21 expression in normal human lung fibroblasts. Although Ni(II)-induced stabilization of HIF-1α occurred earlier, it had no effect on p53 accumulation and Ser15 phosphorylation. Ni(II)-treated H460 cells showed no evidence of necrosis and their apoptosis and clonogenic death were suppressed by p53 knockdown. The apoptotic role of p53 involved a transcription-dependent program triggering the initiator caspase 9 and its downstream executioner caspase 3. Two most prominently upregulated proapoptotic genes by Ni(II) were PUMA and NOXA but only PUMA induction required p53. Knockdown of p53 also led to derepression of antiapoptotic MCL1 in Ni(II)-treated cells. Overall, our results indicate that p53 plays a major role in apoptotic death of human lung cells by Ni(II). Chronic exposure to Ni(II) may promote selection of resistant cells with inactivated p53, providing an explanation for the origin of p53 mutations by this epigenetic carcinogen.