Cr (VI) induces abnormalities in glucose and lipid metabolism through ROS/Nrf2 signaling

Nrf2/cyclooxygenase 2 signaling in Cr(VI)-induced carcinogenesis

Long-term exposure to hexavalent chromium [Cr(VI)] has been linked to lung cancer, and cyclooxygenase-2 (COX-2) is a well-known inflammatory factor. However, the role and mechanism of COX-2 in Cr(VI)-induced carcinogenesis are not clear yet. To address this question, we employed a mouse model exposed to Cr(VI) through intranasal instillation of particulate zinc chromate (ZnCrO4) for 12 weeks. Metabolomics and RNA-seq assays revealed enhanced activity of the arachidonic acid (AA)/eicosanoid metabolism pathway in lung tissues from mice exposed to Cr(VI). COX-2, the key enzyme of the AA/eicosanoid pathway, was significantly upregulated in Cr(VI)-exposed lung tissues, as well as in the Cr(VI)-induced transformed (Cr-T) cells compared to parental BEAS-2B (B2B) cells. We then employed multidisciplinary in vitro and in vivo functional assays to characterize the role of COX-2 in Cr(VI)-induced lung cancer. The results indicated that COX-2 functioned as an oncogene to promote the malignant transformation of B2B cells and enhance the proliferation, migration, tumor growth, and angiogenesis of Cr-T cells. Nuclear factor E2-related factor-2 (Nrf2) was identified as a transcription factor for COX-2. Nrf2 was upregulated in response to Cr(VI) exposure and contributed to Cr(VI)-induced lung cancers, in part by upregulating COX-2 expression. Moreover, microRNA-379 (miR-379) was found to target COX-2 to inhibit its expression posttranscriptionally. MiR-379 was downregulated in Cr(VI)-exposed lung tissues and Cr-T cells, and ectopic miR-379 expression reduced Cr-T cell viability and migration, with partial reversal upon COX-2 restoration. In summary, our study revealed the oncogenic role of COX-2 and identified two novel regulatory mechanisms for COX-2 overexpression in Cr(VI)-induced carcinogenesis.

Resveratrol attenuates Cr(VI)-induced disorders of glycolipid metabolism by regulating HNF1b/GPX1 in mice

Epidemiological studies have indicated that exposure to hexavalent chromium (Cr(VI)) is associated with increased morbidity in the population. Resveratrol (Res) is a polyphenolic compound known for its role in mitigating oxidative stress and inflammation. In this study, we investigated the effects of resveratrol on Cr(VI)-induced disorders of glycolipid metabolism and elucidated its mechanisms. Male C57BL/6 mice were exposed to resveratrol and Cr(VI) for 45 days. Cr(VI) exposure led to elevated blood glucose levels, impaired glucose tolerance and insulin resistance, oxidative and inflammatory responses, and alterations in glycolipid metabolism molecules such as PCK1 and SREBP1, along with inhibition of HNF1b and GPX1. Resveratrol pretreatment increased the expression of HNF1b and GPX1, reduced oxidative and inflammatory responses, and ultimately ameliorated Cr(VI)-induced glycolipid metabolism disorders. These findings suggest potential new targets for the prevention and treatment of dysglycolipidosis.

Dietary Iron Overload Triggers Hepatic Metabolic Disorders and Inflammation in Laying Hen

Iron, an essential trace element, is involved in various physiological processes; however, consumption of excessive iron possesses detrimental effects. In practical feed production, the iron content added to feeds often far exceeds the actual demand, resulting in an excess of iron in the body. The liver as a central regulator of iron homeostasis is susceptible to damage caused by disorders in iron metabolism. A model of hepatic iron overload in laying hens was developed in this study by incorporating iron into their diet, and the specific mechanisms underlying iron overload-induced hepatic injury were investigated. Firstly, this study revealed that a high-iron diet resulted in hepatic iron overload, accompanied by impaired liver function. Next, assessment of oxidative stress markers indicated a decrease in activities of T-SOD and CAT, coupled with an increase in MDA content, pointing to the iron-overloaded liver oxidative stress. Thirdly, the impact of iron overload on hepatic glycolipid and bile acid metabolism-related gene expressions were explored, including PPAR-α, GLUT2, and CYP7A1, highlighting disruptions in hepatic metabolism. Subsequently, analyses of inflammation-related genes such as iNOS and IL-1β at both protein and mRNA levels demonstrated the presence of inflammation in the liver under conditions of dietary iron overload. Overall, this study provided comprehensive evidence that dietary iron overload contributed to disorders in glycolipid and bile acid metabolism, accompanied by inflammatory responses in laying hens. Further detailing the specific pathways involved and the implications of these findings could offer valuable insights for future research and practical applications in poultry nutrition.

Deciphering the impact of heavy metal mixed exposure on lipid metabolism using three statistical models

Lipid metabolism disorders pose a significant threat to human health. However, the relationship between heavy metal mixed exposure and lipid metabolism remains poorly understood. This study recruited 1717 residents living near a chromium factory in northeast China. The concentrations of blood Cr, Mn, Cd, Pb, V, and serum CHOL, TG, LDL and HDL levels were measured. Generalized linear model (GLM), quantile g-computation (Qg-comp), and Bayesian kernel machine regression (BKMR) were simultaneously employed to investigate the associations between heavy metal mixed exposure and lipid markers levels. GLM analysis revealed significant associations between blood Cr concentration and HDL (β =  -0.07; 95%CI:  -0.09,  -0.05), LDL (β =  -0.06; 95%CI:  -0.11,  -0.02), and CHOL (β = 0.07; 95%CI: 0.01, 0.12) levels. V concentration was positively associated with HDL (β = 0.12; 95%CI: 0.06, 0.18) and LDL (β = 0.17; 95%CI: 0.04, 0.30) levels. Qg-comp analysis indicated a negative association between heavy metal mixed exposure and HDL (β =  -0.040; 95%CI:  -0.073,  -0.006) level. BKMR model further confirmed the negative relationship between heavy metal mixed exposure and HDL, with the interaction between blood Cr (> 1.05 μg/L) and blood V (> 5.16 μg/L) contributing to decreased HDL levels. Our findings suggested that heavy metal mixed exposure had impacts on HDL and CHOL levels, and the Cr and V may mutually play a predominant role in the observed abnormal HDL levels.

Impact of anthropogenic activities and the associated heavy metal pollution in Sundarbans waterways: threats to commercial fish and human health

The exposure of fish to heavy metals is a significant concern for human health and natural ecosystems. Despite being a critical issue, the extent of contamination in tropical fish from developing countries like Bangladesh remains somewhat unexplored. In this study, ten economically vital fish species (Osteogeneiosus militaris, Arius gagora, Harpadon nehereus, Mugil ephalus, Pseudapocryptes elongates, Apocryptes bato, Labeo bata, Tenualosa toil, Notopterus notopterus, and Pampus chinensis) from the Pasur River, Bangladesh, were analyzed by atomic absorption spectrometer for the concentrations of four concerned heavy metals, viz., As, Cr, Cd, and Pb, and the associated human health risks. The mean concentrations (mg/kg) followed the order of As (3.30 ± 1.43) > Pb (2.32 ± 0.73) > Cr (0.63 ± 0.29) > Cd (0.37 ± 0.24). Additionally, the bioaccumulation factor of the metals in the investigated fish species followed a decreasing trend of As (824.75) > Cr (781.25) > Cd (744) > Pb (385.83). While most species fell below the minimum bioaccumulation line, a few exceptions were noted for some species specific to metals. Health risk assessments indicated no significant carcinogenic and non-carcinogenic risks for both children and adults, although children exhibited greater vulnerability to both types of health effects. Multivariate analysis and local perceptions supported the conclusion that heavy metals primarily originated from anthropogenic sources related to development activities adjacent to the riverine areas.

Hexavalent chromium reduces testosterone levels by impairing lipophagy and disrupting lipid metabolism homeostasis: Based on a metabolomic analysis

Hexavalent chromium (Cr(VI)) causes testicular damage and reduces testosterone secretion. Testosterone synthesis relies on cholesterol as a raw material, and its availability can be affected by lipophagy. However, the role of lipophagy in Cr(VI)-induced testicular damage and reduced testosterone secretion remains unclear. In this study, we investigated the effect of Cr(VI) on lipid metabolism and lipophagy in the testes of ICR mice. Forty mice were randomly divided into four groups and exposed to different doses of Cr(VI) (0, 75, 100, 125 mg/kg) for thirty days. Cr(VI) increased the rate of sperm abnormalities, decreased testosterone level, and decreased the levels of testosterone synthesis-related proteins, namely steroidogenic acute regulatory (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD) proteins. Through metabolomic analysis, Oil Red O staining, and biochemical indicator (triglyceride and total cholesterol) analysis, Cr(VI) was found to disrupt testicular lipid metabolism. Further investigation revealed that Cr(VI) inhibited the AMP-activated protein kinase (AMPK)/sterol regulatory element-binding protein 1 (SREBP1) pathway, elevated levels of the autophagy-related proteins microtubule-associated protein 1 light chain 3B (LC3B) and sequestosome 1 (SQSTM1)/P62 and lipophagy-related proteins Rab7 and Rab10, while increasing colocalization of LC3B and Perilipin2. These findings suggest that Cr(VI) exposure leads to abnormal lipid metabolism in the testes by suppressing the AMPK/SREBP1 pathway and disrupting lipophagy, ultimately reducing testosterone level and inducing testicular damage.

Attenuation of chromium (VI) and arsenic (III)-induced oxidative stress and hepatic apoptosis by phloretin, biochanin-A, and coenzyme Q10 via activation of SIRT1/Nrf2/HO-1/NQO1 signaling

Heavy metal contamination is an alarming concern on a global scale, as drinking tainted water significantly increases human susceptibility to heavy metals. In a realistic scenario, humans are often exposed to a combination of harmful chemicals rather than a single toxicant. Phloretin (PHL), biochanin-A (BCA), and coenzyme Q10 (CoQ10) are bioactive compounds owning plentiful pharmacological properties. Henceforth, the current research explored the putative energizing effects of selected nutraceuticals in combined chromium (Cr) and arsenic (As) intoxicated Swiss albino mice. Potassium dichromate (75 ppm) and sodium meta-arsenite (100 ppm) were given in the drinking water to induce hepatotoxicity, conjugated with PHL and BCA (50 mg/kg each), and CoQ10 (10 mg/kg) intraperitoneally for 2 weeks. After the statistical evaluation, it was observed that the hepato-somatic index, metal load, and antioxidant activity (lipid peroxidation and protein carbonyl content) increased along with the concomitant decrease in the antioxidants (catalase, glutathione-S-transferase, superoxide dismutase, reduced glutathione, and total thiol) in the Cr and As intoxicated mice. Additionally, light microscopy observations, DNA breakages, decreased silent information regulator 1 (SIRT1), nuclear factor (erythroid-derived 2)-like 2 (Nrf2), heme oxygenase (HO-1), and NAD(P)H quinone dehydrogenase 1 (NQO1) gene expressions, together with stimulated apoptotic cell death manifested by the increased expressions of caspase 8 and caspase 3, thus, proved consistency with the aforementioned outcomes. Importantly, the treatment with nutraceuticals not only restored the antioxidant activity but also favorably altered the expressions of SIRT1, Nrf2, HO-1, and NQO1 signaling and apoptosis markers. These findings highlight the crucial role of the PHL, BCA, and CoQ10 combination in reducing Cr and As-induced hepatotoxicity in mice. By averting the triggered apoptosis in conjunction with oxidative stress, this combination increases the SIRT1, Nrf2, HO-1, and NQO1 signaling, thereby reassuringly maintaining the cellular equilibrium.

Exposome-Wide Ranking to Uncover Environmental Chemicals Associated with Dyslipidemia: A Panel Study in Healthy Older Chinese Adults from the BAPE Study

BACKGROUND

Environmental contaminants (ECs) are increasingly recognized as crucial drivers of dyslipidemia and cardiovascular disease (CVD), but the comprehensive impact spectrum and interlinking mechanisms remain uncertain.

OBJECTIVES

We aimed to systematically evaluate the association between exposure to 80 ECs across seven divergent categories and markers of dyslipidemia and investigate their underpinning biomolecular mechanisms via an unbiased integrative approach of internal chemical exposome and multi-omics.

METHODS

A longitudinal study involving 76 healthy older adults was conducted in Jinan, China, and participants were followed five times from 10 September 2018 to 19 January 2019 in 1-month intervals. A broad spectrum of seven chemical categories covering the prototypes and metabolites of 102 ECs in serum or urine as well as six serum dyslipidemia markers [total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein (Apo)A1, ApoB, and ApoE4] were measured. Multi-omics, including the blood transcriptome, serum/urine metabolome, and serum lipidome, were profiled concurrently. Exposome-wide association study and the deletion/substitution/addition algorithms were applied to explore the associations between 80 EC exposures detection frequency > 50 % and dyslipidemia markers. Weighted quantile sum regression was used to assess the mixture effects and relative contributions. Multi-omics profiling, causal inference model, and pathway analysis were conducted to interpret the mediating biomolecules and underlying mechanisms. Examination of cytokines and electrocardiograms was further conducted to validate the observed associations and biomolecular pathways.

RESULTS

Eight main ECs [1-naphthalene, 1-pyrene, 2-fluorene, dibutyl phosphate, tri-phenyl phosphate, mono-(2-ethyl-5-hydroxyhexyl) phthalate, chromium, and vanadium] were significantly associated with most dyslipidemia markers. Multi-omics indicated that the associations were mediated by endogenous biomolecules and pathways, primarily pertinent to CVD, inflammation, and metabolism. Clinical measures of cytokines and electrocardiograms further cross-validated the association of these exogenous ECs with systemic inflammation and cardiac function, demonstrating their potential mechanisms in driving dyslipidemia pathogenesis.

DISCUSSION

It is imperative to prioritize mitigating exposure to these ECs in the primary prevention and control of the dyslipidemia epidemic. https://doi.org/10.1289/EHP13864.

Chronic low-dose chromium VI exposure induces oxidative stress and apoptosis with altered expressions of DNA repair genes and promoter hypermethylation in the liver of Swiss albino mice

The present investigation dealt with harmful effects of hexavalent chromium (Cr [VI]) on liver of Swiss albino mice. This variant exhibited cytotoxicity, mutagenicity, and carcinogenicity. Our study focused on elucidating the hepatotoxic effects of chronic low-dose exposure to Cr (VI) (2, 5, and 10 ppm) administered via drinking water for 4 and 8 months. The observed elevation in SGPT, ALP, and SGOT and increased oxidative stress markers unequivocally confirmed the severe disruption of liver homeostasis at these low treatment doses. Noteworthy alterations in histoarchitecture, body weight, and water intake provided further evidences of the harmful effects of Cr (VI). Production of reactive oxygen species (ROS) during metabolism led to DNA damages. Immunohistochemistry and qRT-PCR analyses revealed that chronic low-dose exposure of Cr (VI) induced apoptosis in liver tissue. Our study exhibited alterations in the expression pattern of DNA repair genes (Rad51, Mutyh, Mlh1, and Ogg1), coupled with promoter hypermethylation of Mutyh and Rad51, leading to transcriptional inhibition. Our findings underscored the potential of low-dose Cr (VI) exposure on hepatotoxicity by the intricate interplay between apoptosis induction and epigenetic alterations of DNA repair genes.

Heavy Metal Exposure and Cardiovascular Disease

Heavy metals are harmful environmental pollutants that have attracted widespread attention due to their health hazards to human cardiovascular disease. Heavy metals, including lead, cadmium, mercury, arsenic, and chromium, are found in various sources such as air, water, soil, food, and industrial products. Recent research strongly suggests a connection between cardiovascular disease and exposure to toxic heavy metals. Epidemiological, basic, and clinical studies have revealed that heavy metals can promote the production of reactive oxygen species, which can then exacerbate reactive oxygen species generation and induce inflammation, resulting in endothelial dysfunction, lipid metabolism distribution, disruption of ion homeostasis, and epigenetic changes. Over time, heavy metal exposure eventually results in an increased risk of hypertension, arrhythmia, and atherosclerosis. Strengthening public health prevention and the application of chelation or antioxidants, such as vitamins and beta-carotene, along with minerals, such as selenium and zinc, can diminish the burden of cardiovascular disease attributable to metal exposure.

Sourdough bread as nutritional intervention tool for improvement of cognitive dysfunction in diabetic rats

BACKGROUND

The current research targeted to study the impact of nutritional intervention by two sourdough breads in improvement of cognitive dysfunction in diabetic rats.

METHODS

Type-2 diabetes was induced in rats by Streptozotocin-Nicotinamide (STZ-NC). Diabetic rats were fed on balanced diet or balanced diet containing 20% of sourdough bread I or II for a month. Lipid profile, oxidative stress, inflammatory markers and cognitive functions were assessed in all rats. Gene expression of brain-derived neurotrophic factor (BDNF) and nuclear respiratory factor 2 (NRF-2) were assessed in hippocampal tissue, while expression of phosphoenol pyruvate carboxy kinase (PEPCK), and glucose transporter 2 (GLUT2) genes were evaluated in hepatic tissue. Chemical composition and fatty acids profile were evaluated in the prepared sourdough bread.

RESULTS

Sourdough bread II showed higher content of phenolic compounds, fat, fiber and carbohydrates. Fatty acids profile revealed that sourdough bread I was higher in saturated fatty acids (16.08%), while sourdough bread sample II was higher in unsaturated fatty acids (79.33%). Sourdough bread I or II feeding rats' showed significant improvement in hyperglycemia, oxidative stress markers, inflammatory markers, lipid profile, liver and kidney functions in association with improvement in cognitive function. Gene expression of BDNF and NRF2 in hippocampal tissue were increased significantly, while hepatic GLUT2 and PEPCK gene expression were down-regulated in diabetic given sourdough bread I or II.

CONCLUSION

Sourdough bread II was superior in all the studied parameters. The anti-diabetic effect and protection from cognitive dysfunction of sourdough bread samples may be ascribed to the occurrence of dietary fibers, phenolic compounds, and polyunsaturated fatty acids.

Hepato-renal toxicity of low dose metal(oid)s mixture in real-life risk simulation in rats: Effects on Nrf2/HO-1 signalling and redox status

The understanding that humans are exposed to a low level of toxic metals and metalloids in their lifetime has resulted in a shift in scientific and regulatory perspectives from the traditional evaluation of single metal toxicity to complex mixtures, relevant to real-life exposure. Therefore, the aim of this study was to examine the impact of real-life, 90-days exposure to mixture of toxic metal(oid)s, Cd, Pb, Ni, Cr, As and Hg, on the nuclear factor erythroid 2-related factor 2 and hemoxygenase-1 (Nrf2/HO-1) signalling and redox status by assessing total sulfhydryl groups (SH), glutathione (GSH), superoxide dismutase activity (SOD), malondialdehyde (MDA), and ischemia modified albumin (IMA) in the liver and kidney of Wistar rats. Animals (20 males and 20 females) were randomized in 2 control and 6 treated groups that received by oral gavage mixture of metal(oid)s solutions in doses that reflect blood metal(oid) levels determined in previous human biomonitoring study as benchmark dose (F/M _BMD), median (F/M _MED), and 95th percentile (F/M _95). Our results have shown that metal(oid)s mixture impaired the activation of the Nrf2/HO-1 pathway in the kidney and liver of male rats and kidney of female rats, followed by depletion of GSH levels in males. Additionally, in males elevated levels of IMA in the liver were observed, while in both genders increased MDA levels were observed in the kidney. Interestingly, the effects were more pronounced in male than in female rats. This study is among the first that examined hepato-renal toxic mechanisms of real-life metal mixture exposure, while our results might be of immense importance for assessing the risk of exposure to mixtures of toxic substances.

Role of NF-κB signaling pathway in hexavalent chromium-induced hepatotoxicity

Hexavalent chromium Cr (VI) is a primary human carcinogen with damaging toxic effects on multiple organs. Cr (VI) exposure can induce hepatotoxicity through oxidative stress, but its exact mechanism of action was still unclear. In our study, a model of acute Cr (VI) induced liver injury was established by exposing mice to different concentrations (0, 40, 80, and 160 mg/kg) of Cr (VI); RNA-seq was used to characterize changes in liver tissue transcriptome of C57BL/6 mice after exposing to 160 mg/kg Bw of Cr (VI). Changes in liver tissue structures, proteins, and genes were observed by hematoxylin and eosin (H&E), western blot, immunohistochemistry and RT-PCR. After Cr (VI) exposure, abnormal liver tissue structure, hepatocyte injury, and hepatic inflammatory response were observed in mice in a dose-dependent manner. RNA-seq transcriptome results indicated that oxidative stress, apoptosis, and inflammatory response pathways were increased after Cr (VI) exposure; KEGG pathway analysis found that activation of NF-κB signaling pathway was significantly upregulated. Consistent with the RNA-seq results, immunohistochemistry showed that Cr (VI) exposure resulted in infiltrating of Kupffer cells and neutrophils, increasing expression of inflammatory factors (TNF-α, IL-6, IL-1β), and activating of NF-κB signaling pathways (p-IKKα/β and p-p65). However, ROS inhibitor, N-acetyl-L-cysteine (NAC), could reduce infiltration of Kupffer cells and neutrophils and expression of inflammatory factors. Besides, NAC could inhibit NF-κB signaling pathway activation, and alleviate Cr (VI)-induced liver tissue damage. Our findings strongly suggested that inhibition of ROS by NAC might help in the development of new strategies for Cr (VI)-associated liver fibrosis. Our findings revealed for the first time that Cr (VI) induced liver tissue damage through the inflammatory response mediated by the NF-κB signaling pathway, and inhibition of ROS by NAC might help in the development of new strategies for Cr (VI)-associated hepatotoxicity.

Coenzyme Q10, Biochanin A and Phloretin Attenuate Cr(VI)-Induced Oxidative Stress and DNA Damage by Stimulating Nrf2/HO-1 Pathway in the Experimental Model

Hexavalent chromium [Cr(VI)] has emerged as a prevailing environmental and occupational contaminant over the past few decades. However, the knowledge is sparse regarding Cr(VI)-induced neurological aberrations, and its remediation through natural bioactive compounds has not been fully explored. This study intended to probe the possible invigorative effects of nutraceuticals such as coenzyme Q10 (CoQ10), biochanin A (BCA), and phloretin (PHL) on Cr(VI) intoxicated Swiss albino mice with special emphasis on Nrf2/HO-1/NQO1 gene expressions. Mice received potassium dichromate (75 ppm) through drinking water and were simultaneously co-treated intraperitoneally with CoQ10 (10 mg/kg), BCA, and PHL (50 mg/kg) each for 30-day treatment period. The statistics highlight the elevated levels of lipid peroxidation (LPO) and protein carbonyl content (PCC) with a concomitant reduction in the superoxide dismutase (SOD), glutathione-S-transferase (GST), reduced glutathione (GSH), total thiols (TT), catalase (CAT), and cholinesterase activities in the Cr(VI)-exposed mice. The collateral assessment of DNA fragmentation, DNA breakages, and induced histological alterations was in conformity with the above findings in conjugation with the dysregulation in the Nrf2 and associated downstream HO-1 and NQO1 gene expressions. Co-treatment with the selected natural compounds reversed the above-altered parameters significantly, thereby bringing cellular homeostasis in alleviating the Cr(VI)-induced conciliated impairments. Our study demonstrated that the combination of different bioactive compounds shields the brain better against Cr(VI)-induced neurotoxicity by revoking the oxidative stress-associated manifestations. These compounds may represent a new potential combination therapy due to their ability to modulate the cellular antioxidant responses by upregulating the Nrf2/HO-1/NQO1 signaling pathway against Cr(VI)-exposed population. HIGHLIGHTS: Cr(VI)-associated heavy metal exposure poses a significant threat to the environment, especially to living organisms. Cr(VI) exposure for 30 days resulted in the free radical's generation that caused neurotoxicity in the Swiss albino mice. Natural compounds such as coenzyme Q10, biochanin A, and phloretin counteracted the neurotoxic effect due to Cr(VI) exposure in scavenging of free radicals by enhancing Nrf2/HO-1/NQO1 gene expressions in maintaining the cellular homeostasis.

Attenuating effects of selenium and zinc against hexavalent chromium-induced oxidative stress, hormonal instability, and placenta damage in preimplanted rats

As a toxic metal, hexavalent chromium (CrVI) has effects on both the reproductive and endocrine systems. This study aimed to evaluate the protective effects of selenium (Se) and zinc (Zn) against the toxicity of chromium on the placenta in pregnant Wistar albino rats. Thirty pregnant Wistar rats were divided into control and four treated groups, receiving subcutaneously (s.c) on the 3rd day of pregnancy, K₂Cr₂O₇ (10 mg/kg body weight (bw)) alone, or in association with Se (0.3 mg/kg bw), ZnCl₂ (20 mg/kg bw), or both of them simultaneously. Plasma steroid hormones, placenta histoarchitecture, oxidative stress profile, and developmental parameters were investigated. These results showed that K₂Cr₂O₇ exposure induced a significant increase in the levels of both plasma estradiol (E₂) and placenta malondialdehyde (MDA), the number of fetal resorptions, and percent of post-implantation loss. On the other hand, K₂Cr₂O₇ significantly reduced developmental parameters, maternal body and placenta weight, and plasma progesterone (P) and chorionic gonadotropin hormone (β HCG) levels. However, K₂Cr₂O₇ significantly decreased the placenta activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), reduced glutathione (GSH), and nonprotein sulfhydryl (NPSH). These changes have been reinforced by histopathological evaluation of the placenta. Se and/or ZnCl₂ supplementation provoked a significant improvement in most indices. These results suggest that the co-treatment with Se or ZnCl₂ strongly opposes the placenta cytotoxicity induced by K₂Cr₂O₇ through its antioxidant action.

Toxic and carcinogenic effects of hexavalent chromium in mammalian cells in vivo and in vitro: a recent update

Chromium VI (Cr (VI)) can cross cell membranes readily and causes the formation of Cr-DNA adducts, genomic damages, elevation of reactive oxygen species (ROS) and alteration of survival signaling pathways, as evidenced by the modulation in p53 signaling pathway. Mammals, including humans are exposed to Cr, including Cr (VI), frequently through inhalation, drinking water, and food. Several studies demonstrated that Cr (VI) induces cellular death through apoptosis and autophagy, genotoxicity, functional alteration of mitochondria, endocrine and reproductive impairments. In the present review, studies on deleterious effects of Cr (VI) exposure to mammalian cells (in vivo and in vitro) have been documented. Special attention is paid to the underlying molecular mechanism of Cr (VI) toxicity.

Independent, combine and interactive effects of heavy metal exposure on dyslipidemia biomarkers: A cross-sectional study in northeastern China

Dyslipidemia is a common disease in the older population and represents a considerable disease burden worldwide. Epidemiological and experimental studies have indicated associations between heavy metal exposure and dyslipidemia; few studies have investigated the effects of heavy metal mixture and interactions between metals on dyslipidemia. We recruited 1121 participants living in heavy metal-contaminated and control areas in northeast China from a cross-sectional survey (2017-2019). Urinary metals including chromium (Cr), cadmium (Cd), lead (Pb), and manganese (Mn) and dyslipidemia biomarkers, namely triglycerides (TG), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels, were measured. The generalized linear model (GLM) was used to explore the association of a single metal with dyslipidemia biomarkers. Bayesian kernel machine regression (BKMR) and multivariable linear regression were performed to explore the overall effect of metal mixture and the interaction between metals on dyslipidemia. Heavy metal mixture was positively associated with LDL-C, TC, and TG and negatively with HDL-C. In multivariable linear regression, Pb and Cd exhibited a synergistic association with LDL-C in the participants without hyperlipemia. Mn-Cd and Pb-Cr also showed a synergistic association with increasing the level of LDL-C in subjects without hyperlipemia. Cd-Cr showed an antagonistic association with HDL-C, respectively. Cr-Mn exhibited an antagonistic association with decreased HDL-C and TG levels. No significant interaction was noted among the three metals. Our study indicated that exposure to heavy metals is associated with dyslipidemia biomarkers and the presence of potential synergistic or antagonistic interactions between the heavy metals.

Selenium regulates Nrf2 signaling to prevent hepatotoxicity induced by hexavalent chromium in broilers

Hexavalent chromium (Cr(Ⅵ)) is considered to be a common environmental pollutant, which widely exists in industrial effluents and wastes and then potentially noxious effects to the health of the poultry. Studies have reported that selenium (Se), which is one of the essential trace elements of the poultry and participates in the oxidative metabolism, can alleviate Cr(Ⅵ)-induced organ damage by inhibiting oxidative stress, but its specific molecular mechanism remains unclear. Herein, animal models of Cr(Ⅵ)- and Se-exposure were constructed using broilers to investigate the antagonistic mechanism of Se to Cr(Ⅵ)-induced hepatotoxicity. In this experiment, the four groups of broiler models were used as the research objects: control, Se, Se plus Cr, and Cr groups. Histopathology and ultrastructure liver changes were observed. Liver-somatic index, serum biochemistry, oxidative stress, Nrf2 pathway related factors, and autophagy-related genes were also determined. Overall, Se was found to ameliorate the disorganized structure, hepatic insufficiency, and oxidative damage caused by Cr(Ⅵ) exposure. Electron microscopy analysis further showed that the number of autophagosomes was obviously decreased after Se treatment compared to Cr group. Furthermore, gene and protein expression analyses illustrated that the levels of Nrf2, glutathione peroxidase 1 (GPx-1), NAD(P)H: quinone oxidoreductase 1 (NQO1), and mechanistic target of rapamycin (mTOR) in the Se&Cr group was upregulated, along with decreased expression of Beclin 1, ATG5 and LC3 compared to the Cr group. These suggest that Se can repair the oxidative lesion and autophagy induced by Cr(Ⅵ) exposure in broiler livers by upregulating the Nrf2 signaling pathway.

Hexavalent Chromium Causes Apoptosis and Autophagy by Inducing Mitochondrial Dysfunction and Oxidative Stress in Broiler Cardiomyocytes

Hexavalent chromium (Cr(VI)) is a common environmental pollutant, which has a strong toxic effect on humans and animals. However, the cardiac toxicity of Cr(VI) in broilers remains to be explored. The development of heart disease is often linked to mitochondrial dysfunction especially exposure to toxic substances. In order to investigate the role of mitochondrial dysfunction in apoptosis and autophagy of broiler cardiomyocytes induced by hexavalent chromium, broiler cardiomyocytes were cultured in potassium dichromate of 0 mM, 16 mM, and 32 mM medium for 24 h. The results showed that, compared with the control group, reactive oxygen species (ROS) and apoptosis rate in the Cr(VI) treatment group increased in a dose-dependent manner, the mRNA levels of apoptosis-related genes Bax and p53 were significantly increased, and the mRNA level of Bcl-2 was significantly decreased. Compared with the control group, the mRNA level of autophagy-related genes (LC3-I, LC3-II, and Beclin1) in the Cr(VI) treatment group was significantly increased, the mRNA level of mTOR was significantly decreased, and the protein level of p62/SQSTM1 was significantly decreased. The protein level of Beclin1 and the ratio of LC3-II/LC3-I significantly increased. In addition, compared with the control group, mitochondrial membrane potential decreased in a dose-dependent manner, and mitochondrial dynamics-related genes SIRT1, SIRT3, and Mfn2 mRNA decreased significantly in the Cr(VI) treatment group. In this study, we concluded that Cr(VI) could cause broiler myocardial apoptosis and autophagy by inducing mitochondrial dysfunction and oxidative stress.

Protective Effect of Isoorientin on Oleic Acid-Induced Oxidative Damage and Steatosis in Rat Liver Cells

The harm of nonalcoholic fatty liver disease to human health is increasing, which calls for urgent prevention and treatment of the disease. Isoorientin is an effective ingredient of Chinese herbal medicine with anti-inflammatory and antioxidant effects. However, the effect of isoorientin in nonalcoholic fatty liver disease is still unclear. In this study, combined in vivo and in vitro experiments, through pathological observation, flow cytometry, immunofluorescence and western blot analysis to explore the role of isoorientin in steatosis and reveal its molecular mechanism. The results demonstrated that oleic acid treatment significantly increased the content of ROS and lipid droplets in rat hepatocytes, and promoted the expression of γH2AX, HO-1, PPARγ, SREBP-1c, FAS. The ROS content in the cells of co-treated with isoorientin and oleic acid was significantly reduced compared to the oleic acid group, and the expression of γH2AX, HO-1, PPARγ, SREBP-1c, FAS, and the nuclear translocation of NF-κB p65 were also significantly inhibited. Our data showed that oleic acid induce oxidative damage and steatosis in hepatocytes both in vitro and in vivo, and activate the PPARγ/NF-κB p65 signal pathway. Moreover, isoorientin can significantly reduce oleic acid -induced oxidative damage and steatosis by regulating the PPARγ/NF-kB p65 signal pathway.

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.

Comparative Evaluation of Forsythiae Fructus From Different Harvest Seasons and Regions by HPLC/NIR Analysis and Anti-inflammatory and Antioxidant Assays

Forsythiae Fructus (FF), the dry fruit of Forsythia suspensa (Thunb.) Vahl, has a long history of use in traditional Chinese Medicine for its heat-clearing and detoxifying properties. It possesses clinical therapeutic effects and biological functions showing efficacy in handling different diseases. To investigate the FF differences in Henan, Shanxi, and Shaanxi in August and October, the surface morphology, mid-infrared and near-infrared spectrums, and HPLC were analyzed. Concurrently, the anti-inflammatory and antioxidant effects on LPS-induced J774A.1 cells were evaluated by western blot and RT-qPCR. The results showed that FF from different Harvest Seasons and Regions are provided with different microstructures and mid-infrared and near-infrared spectrums, and the levels of forsythiaside A and phillyrin of FF from Shanxi in August and phillygenin of FF from Shaanxi in August were the highest. Meanwhile, FF from Shanxi and Shaanxi in August markedly reduced the levels of inflammatory cytokines and mediators (TNF-α, IL-1β, NF-κB, and iNOS) and the protein expression levels of phosphorylated total IKKα/β and nuclear NF-κB. In August, SXFF and SAXFF also promoted the mRNA expression levels of HO-1 and NQO1 and the protein expression levels of HO-1 and nuclear Nrf2 and suppressed the protein expression levels of KEAP1. Spearman correlation analysis showed that phillygenin had a strong correlation with the protein expression on LPS-induced J774A.1 cells. In summary, our results showed that FF from harvest seasons and regions contributed to the distinct differences in microstructure, the mid-infrared and near-infrared spectrums, and compound content. More importantly, FF from Shanxi and Shaanxi in August showed marked anti-inflammatory and antioxidant activities, but with some differences, which may be because of different contents of phillygenin and phillyrin of lignans in FF.

Effects of nanometer alumina and humic acid on the retention and transport of hexavalent chromium in porous media

Column experiments were conducted to investigate the effects of ion type, ion strength, humic acid (HA), and nanometer alumina (NA) particles on the transport of hexavalent chromium (HC) in saturated porous media. A one-dimensional model is developed to simulate the migration of HC affected by NA particles. The results show that nano-alumina particles would enhance the mobility of HC in saturated porous media. However, the influence of NA on the migration of HC in porous media is complex. When the concentration of NA reaches 30 mg/L, HC has minimum retention parameter and best mobility. The transport of HC also is affected by ion strength and ion type. Higher ionic strength would decrease the retention of HC and enhance its mobility. Compared with sodium ion, calcium ion has larger effects on the transport of HC. Moreover, HA can improve the mobility of HC in saturated porous media, but the corresponding promoting effect decreases with the increase of HA concentration. As nanometer contaminants and HC come into the subsurface environment, findings from this study elucidate the key factors and processes controlling the transport of HC in porous media, which can promote the prediction and assessment of HC in the groundwater system.