Effects of hexavalent chromium on mouse splenic T lymphocytes

Exploration of Whole Blood Chromium as Biomarker of Hexavalent Chromium Exposure: Based on Literature Review and Monte Carlo Simulation

Hexavalent chromium (Cr(VI)) is a sort of common industrial poison and environmental pollutant posing great health threat to the population. Appropriate biomarkers are indispensable indicative tools in the biological monitoring and health risk assessment of Cr(VI). In this study, we explored the rationality and feasibility of whole blood Cr serving as the biomarker of internal exposure with corroboration drawn from literature review and Monte Carlo simulation. It was indicated that the whole blood Cr had practical operability in the large-scale population researches and robust biological significance with broad association with various Cr(VI)-related effect indices. The simulated distribution of whole blood Cr concentration in exposed populations was about three times higher than that of the control (13.52 ± 24.99 vs. 4.25 ± 11.37 μg/L, P < 0.05; 6.73 ± 10.92 μg/L vs. 1.96 ± 2.05 μg/L in China, P < 0.05), which suggested a great discriminatory ability that might be supported as evidence for its reasonable application.

Selenium-Enriched Yeast Relieves Hexavalent Chromium Toxicity by Inhibiting NF-κB Signaling Pathway in Broiler Spleens

Simple Summary

Hexavalent chromium is a common environmental pollution. It has been reported that hexavalent chromium threatens the health of humans and animals, so it is necessary to develop new, effective mitigation methods. Selenium is an indispensable micronutrient recently shown to be able to resist the toxicity of heavy metals. Selenium-enriched yeast has a high content of total selenium, which has the advantages of a high absorption rate and safety. Potassium dichromate and selenium-enriched yeast were used to construct single hexavalent chromium and combined selenium/hexavalent-chromium-exposed broiler models. Additionally, the ability to relieve the hexavalent chromium toxicity of selenium along with the molecular mechanisms focusing on inflammation induced by the NF-κB signaling pathway was investigated in this study. Histopathological assessment, serum biochemical tests, oxidative stress kits, enzyme-linked immunosorbent assay, quantitative real-time PCR, and Western blotting were used to detect indicators. We found that the oxidative stress induced by hexavalent chromium triggers NF-κB pathway-driven inflammatory responses in the broiler spleen and further reduces the immune function of broilers. Selenium-enriched yeast protects the spleen from the toxicity of hexavalent chromium exposure through inhibiting the NF-κB signaling pathway.

Abstract

This study was conducted to investigate the molecular mechanisms of selenium (Se) antagonism of hexavalent chromium (Cr⁶⁺)-induced toxicity. Potassium dichromate (K₂Cr₂O₇) and selenium-enriched yeast (SeY) were used to construct the single Cr⁶⁺ and combined Se/Cr⁶⁺ exposure broiler models, and then the broilers were randomly divided into four groups (C group, Se group, Se/Cr⁶⁺ group, and Cr⁶⁺ group). After a 42-day experiment, the spleen tissues of broilers were excised and weighted. The antagonistic mechanisms of Se and Cr⁶⁺ were evaluated using histopathological assessment, serum biochemical tests, oxidative stress kits, ELISA, qPCR, and Western blotting. On the whole, there were no significant changes between the C and Se groups. The spleen organ index in the Cr⁶⁺ group was significantly decreased, but SeY increased spleen organ index to a certain extent. The levels of SOD and GSH were reduced, and the MDA content was elevated by Cr⁶⁺; however, these changes were mitigated by Se/Cr⁶⁺ exposure. Importantly, Cr⁶⁺ exposure induced a series of histopathological injuries in broiler spleen tissues, while these symptoms were significantly relieved in the Se/Cr⁶⁺group. Furthermore, Cr⁶⁺ significantly decreased the levels of T-globulin, IgA, IgM, and IgG in serum. Contrarily, dramatically more T-globulin IgA, IgM, and IgG were found in the Se/Cr⁶⁺group than in the Cr⁶⁺ group. Revealed by the results of qPCR and WB, the expressions of NF-κB, IκBα, and p-IκBα were upregulated in Cr⁶⁺ groups, while they were downregulated in Se/Cr⁶⁺ group compared to that in Cr⁶⁺ group. Besides IFN-γ and IL-2, the expressions of pro-inflammatory cytokines were significantly increased by Cr⁶⁺ exposure, but the SeY supplement relived the expression levels mediated by Cr⁶⁺ exposure. In conclusion, our findings suggest SeY has biological activity that can protect broiler spleens from immunosuppression and inflammation induced by Cr⁶⁺, and we speculate that the NF-κB signaling pathway is one of its mechanisms.

Hexavalent chromium inhibits the formation of neutrophil extracellular traps and promotes the apoptosis of neutrophils via AMPK signaling pathway

As the most common heavy metal pollutant, hexavalent chromium [Cr(VI)] has caused serious environmental pollution and health damage. Although the toxic effect of Cr(VI) has been widely studied, and oxidative stress has been confirmed to be the main mechanism of its cytotoxicity, the toxicity of Cr(VI) to human immune system remains to be elucidated. Neutrophil extracellular traps (NETs) participate in the innate immune response, and the release of NETs is considered to be the most important part of the extracellular killing mechanism. We demonstrated in this study that Cr(VI) inhibited the formation of NETs in rat peripheral blood and induced neutrophils apoptosis by inhibiting the AMP-activated protein kinase (AMPK) signaling pathway. Cr(VI)-induced inhibition of NETs was accompanied by down-regulated myeloperoxidase (MPO)/Histones-3 (H3) protein expressions and decreased NETs-associated intracellular and extracellular DNA levels in the neutrophils. Metformin (Met), as an AMPK activator, triggered autophagy and thus alleviated the inhibitory effect of Cr(VI) on NETs. At the same time, Met can reduce the intracellular reactive oxygen species (ROS) level by activating the AMPK/nuclear factor erythroid-2 related factor 2 (Nrf2) signaling pathway, thus alleviating Cr(VI)-induced neutrophils apoptosis. In conclusion, this study elucidated the mechanism of Cr(VI)-induced neutrophils toxicity and the role of AMPK as a key regulatory signal, which could provide valuable experimental basis for the prevention and treatment of related diseases in Cr(VI)-exposed populations.

Shinorine ameliorates chromium induced toxicity in zebrafish hepatocytes through the facultative activation of Nrf2-Keap1-ARE pathway

Hexavalent chromium, a heavy metal toxicant, abundantly found in the environment showed hepatotoxic potential in zebrafish liver and instigated the Nrf2-Keap1-ARE pathway as a cellular stress response as reported in our previous studies. In the present study we have evaluated the ameliorating effect of shinorine, a mycosporine like amino acid (MAAs) and a mammalian Keap1 antagonist against chromium induced stress in zebrafish hepatocytes. Shinorine was found to be effective in increasing the cell viability of chromium treated hepatocytes through curtailing the cellular ROS content. Trigonelline, an Nrf2 inhibitor was found to reduce the viability of hepatocyte cultures co-exposed to shinorine and chromium. In other words, trigonelline being an Nrf2 blocker neutralised the alleviating effect of shinorine. This indicated that shinorine mediated cyto-protection in Cr [VI]-intoxicated cells is Nrf2 dependent. Further, qRT-PCR analysis revealed comparatively higher expression of nfe2l2 and nqo1 in shinorine + chromium treated hepatocytes than cells exposed to chromium alone indicating a better functioning of Nrf2-Keap1-Nqo1 axis. To further confirm if shinorine can lead to disruption of Nrf2-Keap1 interaction in zebrafish hepatocytes and render cytoprotection to chromium exposure, our in silico analysis through molecular docking revealed that shinorine could bind to the active amino acid residues of the DGR domain, responsible for Nrf2-Keap1 interaction of all the three Keap1s evaluated. This is the first report about shinorine that ameliorates chromium induced toxicity through acting as an Nrf2-Keap1 interaction disruptor. We additionally carried out in-silico pharmacokinetic and ADMET studies to evaluate druglikeness of shinorine whose promising results indicated its potential to be developed as an ideal therapeutic candidate against toxicant induced pathological conditions.

Disparities in Trace Metal Levels in Hodgkin/Non-Hodgkin Lymphoma Patients in Comparison with Controls

Lymphoma arises from cells of the immune system and trace metals augment the immune system and their imbalance may promote immunological disorders including tumorigenesis. The primary aim of the present investigation was to evaluate the levels of essential/toxic trace metals in the nails of non-Hodgkin and Hodgkin lymphomas patients in comparison with controls. The samples collected from patients and controls were digested in the mixture of HNO₃-HClO₄ and selected trace metals were analysed using flame atomic absorption spectrometry. The results showed that mean concentrations of some elements (Pb, Ni, Cd, Cu and Cr) in nails of non-Hodgkin lymphoma patients were significantly elevated (p < 0.05) than that of the controls whereas mean contents of Pb, Cu, Cd and Cr were observed to be significantly higher in the nails of Hodgkin lymphoma patients compared with healthy donors. Additionally, correlation study pointed out significantly diverse mutual associations of the trace metals among the patients and controls. The present results revealed noticeable disparities in the metal concentrations based on gender, food habits, tobacco use and types/stages of the donor's groups. Overall, the pathogenesis of disease significantly affected the trace metal balance in both patients' groups.

A study on the protective effects of taxifolin on human umbilical vein endothelial cells and THP-1 cells damaged by hexavalent chromium: a probable mechanism for preventing cardiovascular disease induced by heavy metals

Taxifolin suppressed the toxicity and THP-1 cell adhesion to HUVECs induced by Cr(vi) via regulating the p38 MAPK and JNK pathways.

Long-term effects of chromium on morphological and immunological parameters of Wistar rats

Hexavalent chromium raises high concern because of its wide industrial applications and reported toxicity. Long-term (135 days) oral exposure of Wistar rats to chromium in the form of K₂Cr₂O₇ (exposed group~20 mg/kg/day) led to a decrease in thymus mass and thymocytes' number and caused structural and functional changes in the lymph nodes and spleen, namely lymphoreticular hyperplasia and plasmocytic macrophage transformation. Programmed cell death was increased in both thymocytes and splenocytes and decreased in lymphocytes in the T-zones of spleen and lymph nodes. Moreover, Cr (VI) administration decreased myeloid cells' and neutrophils' number, while it increased lymphoid and erythroid cells' number in bone marrow. Cr (VI) immune system effects seem to be related to oxidative stress induction, as depicted by the increased levels of diene conjugates and malondialdehyde in the spleen and liver and by the decreased activity of catalase and superoxide dismutase in rats' erythrocytes. In addition, exposure to Cr (VI) decreased copper, nickel and iron concentrations in blood and liver, while Cr levels in blood, spleen and liver were increased, as expected. The observed changes in the series of immunological parameters studied contribute to the development of new approaches for the prevention of low level Cr exposure toxicity.