Cadmium-induced injury and the ameliorative effects of selenium on chicken splenic lymphocytes: mechanisms of oxidative stress and apoptosis

Cadmium induces oxidative stress and apoptosis in lung epithelial cells

Cadmium (Cd) is one of the well-known highly toxic environmental and industrial pollutants. Cd first accumulates in the nucleus and later interacts with zinc finger proteins of antiapoptotic genes and inhibit the binding of transcriptional factors and transcription. However, the role of Cd in oxidative stress and apoptosis is less understood. Hence, the present study was undertaken to unveil the mechanism of action. A549 cells were treated with or without Cd and cell viability was measured by MTT assay. Treatment of cells with Cd shows reduced viability in a dose-dependent manner with IC₅₀ of 45 μM concentration. Cd significantly induces the reactive oxygen species (ROS), lipid peroxidation followed by membrane damage with the leakage of lactate dehydrogenase (LDH). Cells with continuous exposure of Cd deplete the antioxidant super oxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzymes. Further, analysis of the expression of genes involved in apoptosis show that both the extrinsic and intrinsic apoptotic pathways were involved. Death receptor marker tumor necrosis factor-α (TNF-α), executor caspase-8 and pro-apoptotic gene (Bax) were induced, while antiapoptotic gene (Bcl-2) was decreased in Cd-treated cells. Fluorescence-activated cell sorting (FACS) analysis further confirms the induction of apoptosis in Cd-treated A549 cells.

Oxidative Stress and Cell Apoptosis in Caprine Liver Induced by Molybdenum and Cadmium in Combination

To investigate the effects of co-exposure to molybdenum (Mo) and cadmium (Cd) on oxidative stress and cell apoptosis in caprine livers, 36 Boer goats were randomly divided into four groups with nine goats in each group. Three groups were randomly assigned with one of three oral treatments of CdCl2 (0.5 mg Cd kg(-1)·BW) and [(NH4)6Mo7O24·4H2O] (15 mg Mo kg(-1)·BW, 30 mg Mo kg(-1)·BW, 45 mg Mo kg(-1)·BW), while the control group received deionized water. Liver tissues on days 0, 25, and 50 were subjected to determine antioxidant activity indexes and the messenger RNA (mRNA) expression levels of ceruloplasmin (CP), cysteinyl aspartate-specific proteinase-3 (caspase-3), second mitochondria-derived activator of caspases (Smac), and cytochrome-C (Cyt-C) genes. The results showed that significant reductions were observed in total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD) activities (P < 0.05), while activities or contents of malondialdehyde (MDA), nitric oxide (NO), and nitric oxide synthase (NOS) were increased (P < 0.05). The mRNA expression levels of CP, caspase-3, Smac, and Cyt-C genes were upregulated (P < 0.05). In addition, histopathological lesions showed different degrees of vacuolar degeneration and edematous and mitochondrial swelling. The results suggest that co-exposure to Mo and Cd could induce oxidative stress and cell apoptosis possibly associated with mitochondrial intrinsic pathway in goat liver and show possible synergistic effects between the two elements.

Effect of Stress from Cadmium Combined with Different Levels of Molybdenum on Serum Free Radical and Expression of Related Apoptosis Genes in Goat Livers

Molybdenum (Mo) is an essential element for human beings and animals; however, high dietary intake of Mo can lead to adverse reactions. Cadmium (Cd) is one of the major transitional metals which have toxic effects in animals. The toxicity of simple Cd or Mo has been researched frequently. However, the toxicity of Mo combined with Cd was rarely studied. To investigate the toxicity of Mo combined with Cd in liver of goats, 36 Boer goats were randomly divided into four groups and assigned with one of the three oral treatments of CdCl2 (0.5 mg kg(-1) Cd) and [(NH4)6Mo7O24·4H2O] (15 mg kg(-1) Mo, group I; 30 mg kg(-1) Mo, group II; 45 mg kg(-1) Mo, group III), while the control group received deionized water. Blood samples were collected on days 0, 10, 20, 30, 40, and 50 to determine antioxidant indices in serum. In addition, liver tissues were collected on days 0, 25, and 50 for detecting the messenger RNA (mRNA) expression levels of Bcl-2 and Bax. Moreover, liver tissues at 50 days were subjected to histopathological analysis with the optical microscope. The results revealed a significant increase (P < 0.05 or P < 0.01) in the levels of nitric oxide (NO), malonaldehyde (MDA), and the activity of nitrix oxide synthase (NOS) and a significant decline (P < 0.05) in the activities of total superoxide dismutase (T-SOD) and total antioxidative capacity (T-AOC). The mRNA expression level of Bcl-2 was suppressed (P < 0.05), while the expression of Bax was increased (P < 0.05) in liver. The histopathological changes were observed in the liver of goats including a small amount of erythrocyte, the unclear structure of hepatic cord and hepatic sinusoid, granular degeneration, vacuolar degeneration, and steatosis. In conclusion, combined chronic toxicity of Cd with different levels of Mo might induce goat liver cell apoptosis and cause oxidative stress in serum, and it showed a possible synergistic relationship between the two elements.

Varying Dietary Levels of Molybdenum Inducing Cell Apoptosis of Spleen Under Cadmium Stress in Caprine

The present experiment aims at evaluating chronic toxic effects of the combination of cadmium (Cd) and molybdenum (Mo) according to residual element contents, apoptosis gene expression, and ultrastructure and histopathology changes of caprine spleen. In total, 36 Boer goats were randomly divided into four groups with the equal number in each group. The control group was orally administered with deionized water while the experimental groups I, II, and III were administered with the equal quantity of CdCl2 (1 mg kg(-1) BW) and (NH4)6·Mo7O24·4H2O including 15, 30, and 45 mg·Mo kg(-1) BW, respectively. Three individuals from each group were treated with euthanasia on days 0, 25, and 50. The data showed that the content of splenic residual Mo and Cd increased (P < 0.05) in the experimental groups on days 25 and 50, while no significant difference was observed in the content of Cu. The apoptosis-related gene expression levels including Bcl-2, Bax, Caspase-3, Smac, and ceruloplasmin (CP) were also determined. Results showed that significant reductions were observed in Bcl-2 and CP expressions (P < 0.01), while Caspase-3 gene was up-regulated (P < 0.05). However, no significant difference was observed in Smac and Bax expressions. Furthermore, on day 50, spleen tissues were presented to observe ultrastructural changes in lesions by means of transmission electron microscopy, with fragmentized nucleus, vesiculation of cytoplasm, mitochondria hyperplasia, and increasing lysosomes included. In addition, histopathology results corroborated the toxicity by showing cell hemorrhage, thickening central arteries, and enhanced capsule thickness. To sum up, our study revealed that the combination of Cd and Mo could induce remarkable damage to the spleen of goats by promoting cell apoptosis in the mitochondrial pathway and affecting the deposition of Mo and Cd.

Mitochondrial oxidative stress-induced hepatocyte apoptosis reflects increased molybdenum intake in caprine

Molybdenum (Mo) is an essential trace element for animals and humans. However, the high dietary intake of Mo leads to disease conditions in heavy metal pollution areas. To the best of our knowledge, the effect of high levels of Mo on the apoptosis of hepatocyte in goats has not been investigated. Therefore, the aim of the present in vivo study was to investigate the impact of Mo on mitochondrial oxidative stress and apoptosis genes in the liver using real-time quantitative polymerase chain reaction (RT-qPCR) and transmission electron microscopy, respectively. Thirty-six healthy goats were randomly divided into three groups: two groups treated with ammonium molybdate [(NH4)6·Mo7O24·H2O] at 15 and 45 mg Mo kg(-1) BW, respectively, and a control group without treatment. Liver samples were collected from individual goats at different time intervals. The levels of oxidative stress in the mitochondrial membrane and expression of liver-related apoptosis genes, including Bcl-2, Cyt c, caspase-3, and Smac, were examined. The results demonstrated that the levels of superoxide dismutase (SOD) and catalase (CAT) expression were significantly down-regulated in liver cells, whereas malondialdehyde (MDA), nitric oxide (NO), and total nitric oxide synthase (T-NOS) expression was up-regulated (P < 0.01). The expression of Smac, Cyt c, and caspase-3 was significantly up-regulated, whereas Bcl-2 expression was down-regulated in liver cells (P < 0.01). In addition, histopathological examination revealed varying degrees of vacuolization, irregularity, nuclear fission, and mitochondrial swelling and high-density electrons in the cytoplasm of hepatocytes in groups treated with 15 and 45 mg Mo kg(-1) BW. Thus, these results suggested that high molybdenum induced hepatocyte apoptosis and might involve a mitochondrial pathway.

Cadmium Protection Strategies--A Hidden Trade-Off?

Cadmium (Cd) is a non-essential transition metal which is introduced into the biosphere by various anthropogenic activities. Environmental pollution with Cd poses a major health risk and Cd toxicity has been extensively researched over the past decades. This review aims at changing the perspective by discussing protection mechanisms available to counteract a Cd insult. Antioxidants, induction of antioxidant enzymes, and complexation of Cd to glutathione (GSH) and metallothionein (MT) are the most potent protective measures to cope with Cd-induced oxidative stress. Furthermore, protection mechanisms include prevention of endoplasmic reticulum (ER) stress, mitophagy and metabolic stress, as well as expression of chaperones. Pre-exposure to Cd itself, or co-exposure to other metals or trace elements can improve viability under Cd exposure and cells have means to reduce Cd uptake and improve Cd removal. Finally, environmental factors have negative or positive effects on Cd toxicity. Most protection mechanisms aim at preventing cellular damage. However, this might not be possible without trade-offs like an increased risk of carcinogenesis.

Protective Roles of Selenium on Nitric Oxide and the Gene Expression of Inflammatory Cytokines Induced by Cadmium in Chicken Splenic Lymphocytes

Cadmium (Cd) is an environmental toxicant and an inflammation-related xenobiotic. Selenium (Se) is a well-known nutritional trace element and a potent chemopreventive agent. The present study aimed to investigate the effect of Se on the cytotoxicity of Cd in bird immunocytes in vitro. Chicken splenic lymphocytes exposed to CdCl2 (10(-6) mol/L), Na2SeO3 (10(-7) mol/L), or a mixture of the two (10(-7) mol/L Na2SeO3 and 10(-6) mol/L CdCI2) were incubated for 12, 24, 36, 48, or 60 h. Cd significantly increased (P < 0.05 or P < 0.01) the messenger RNA (mRNA) expression levels of nuclear factor kappaB (NF-κB), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor (TNF-α), and prostaglandin E2 (PGE2), and similar results were observed in the protein expression levels of NF-κB and COX-2. In addition, the nitric oxide (NO) content and the inducible iNOS activity were increased in the Cd-treated group compared to the control group. Furthermore, the protective effects of Se against Cd toxicity in chicken splenic lymphocytes were illustrated by the increase in select cytokines (NF-κB, iNOS, COX-2, TNF-α, and PGE2), NO content and iNOS activity. The biochemical parameters exhibited sensitivity to Se and Cd, suggesting that they may act as potential biomarkers for assessing the effects of Se and Cd risk on chicken splenic lymphocytes.

Ameliorative Effects of Selenium on Cadmium-Induced Oxidative Stress and Endoplasmic Reticulum Stress in the Chicken Kidney

The harmful influences of dietary cadmium (Cd) on the chicken kidney and the protective role of selenium (Se) against Cd-induced nephrotoxicity in the chicken are relatively unexplored subjects. The aim of this study was to investigate the ameliorative role of Se on the effects of Cd-induced oxidative stress, endoplasmic reticulum stress, and apoptosis in chicken kidneys. For this study, 100-day-old chickens received Se (as 10 mg Na2SeO3/kg dry weight of diet), Cd (as 150 mg CdCl2/kg dry weight of diet), or Cd + Se in their diets for 60 days. Then, the histopathological changes, Cd and Se contents, levels of oxidative stress, inducible nitric oxide synthase-nitric oxide (iNOS-NO) system activity, levels of endoplasmic reticulum (ER) stress, results of the terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay of apoptosis, and expression levels of Bcl-2 and caspase 3 in the kidney were examined. The results showed that Cd exposure caused histopathological and ultrastructural damage and apoptosis of the kidneys. Cd administration significantly increased the accumulation of Cd, the malondialdehyde (MDA) content, NO production, iNOS activity, iNOS expression levels, expression levels of ER stress-related genes (GRP78, GRP94, ATF4, ATF6, and IRE) and the pro-apoptosis gene caspase 3, and the rate of apoptosis. Cd administration markedly decreased the Se content, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, and anti-apoptosis gene Bcl-2 expression levels. Co-treatment with Se and Cd obviously reduced the accumulation of Cd, Cd-induced histopathological and ultrastructural changes, oxidative stress, iNOS-NO system activity, ER stress, caspase 3 expression levels, and the rate of apoptosis in the kidneys. These results suggested that Cd exposure caused renal injury and that Se ameliorated Cd-induced nephrotoxicity in chickens.

Cell apoptosis of caprine spleen induced by toxicity of cadmium with different levels of molybdenum

In order to clarify the effects of the combination of Mo and Cd on goat and relationship between the two elements, combined chronic toxicity of cadmium with different levels of molybdenum in vivo on apoptosis gene and ultrastructure of spleen was evaluated with the methods of RT-qPCR and transmission electron microscopy. A total of thirty-six goats were randomly distributed in equal number into four groups. These groups were randomly assigned with one of three oral treatments of CdCl2 (0.5 mgCd kg(-1)) and [(NH4)6Mo7O24·4H2O] (15 mg Mo kg(-1), group I; 30 mg Mo kg(-1), group II; 45 mg Mo kg(-1), group III), while the control group received deionized water. Spleen tissues were taken from individual goat at different time intervals to measure the levels of apoptosis genes including Bcl-2, Bax, Cyt c, Caspase-3, Smac and ceruloplasmin (Cp). The results revealed that a significant suppression in Bcl-2 expression and increase in Cyt c, Caspase-3 and Cp expression in splenic cells. The Bax expression in group I and II was up-regulated, however, it displayed reduction in group III, whereas no statistical significance was observed on Smac expression. In addition, histopathologic injury revealed remarkable morphplogical changes on the splenocytes in the means of apoptosis including fragmentized nucleus, apoptotic body and vesiculation of cytoplasma and mitochondria. Taken together, combined chronic toxicity of cadmium with different levels of molybdenum induce goat spleen cell apoptosis associated with mitochondrial intrinsic pathway, and the two elements showed possible antergic relationship.

Effects of selenium and cadmium on changes in the gene expression of immune cytokines in chicken splenic lymphocytes

Cadmium (Cd) is an environmental pollutant that is considered to be a potent toxin to organisms. Selenium (Se) has been known for its concomitant biological effects and characteristics with Cd. Due to the lack of the research regarding how the duality of Cd/Se affects immune cytokines in poultry, this paper aims to partly tackle this question. Chicken splenic lymphocytes with Cd (10(-6) mol/L CdCl2), Se (10(-7) mol/L Na2SeO3), Cd + Se (10(-7) mol/L Na2SeO3 and 10(-6) mol/L CdCl2), and a control group were incubated for 12, 24, 36, 48, and 60 h, respectively. At each time point, the cells were collected and the messenger RNA (mRNA) expression levels of interleukin (IL)-1β, IL-2, IL-4, IL-10, IL-17, and interferon-γ (IFN-γ) were also examined. Compared with the control group and the Se-alone-treated group, the mRNA expression levels of IL-2, IL-4, IL-10, IL-17, and IFN-γ decreased significantly in the Cd-alone-treated group. By contrast, the mRNA expression level of IL-1β markedly increased. Levels of IL-2, IL-4, IL-10, IL-17, and IFN-γ in Cd + Se-treated groups were significantly higher than those in Cd-alone-treated groups; however, the levels were not as high as the Se-alone-treated groups and the control group. The mRNA expression level of IL-1β in the Cd + Se-treated group was lower than in the Cd-alone-treated group. The relationships with IL-2, IL-4, and IL-10 were found to be closer in the PC 1 matrix and 3D plot of the principal component analysis (PCA) loadings. IL-17 and IFN-γ were closer in the matrix of PC 2. However, IL-1β gene expression appeared to be isolated in the matrix of PC 3. In addition, the results of cytokine cluster analysis showed that IL-2, IL-4, IL-10, IL-17, and IFN-γ were in the first group and that IL-1β was in the second group. Therefore, Se partly attenuate immune toxicity induced by Cd in chicken splenic lymphocytes.