Oral administration of Cr(VI) induced oxidative stress, DNA damage and apoptotic cell death in mice

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.

Characterization of airborne endotoxin in personal exposure to fine particulate matter (PM2.5) and bioreactivity for elderly residents in Hong Kong

The heavy metals and bioreactivity properties of endotoxin in personal exposure to fine particulate matter (PM2.5) were characterized in the analysis. The average personal exposure concentrations to PM2.5 were ranged from 6.8 to 96.6 μg/m3. The mean personal PM2.5 concentrations in spring, summer, autumn, and winter were 32.1±15.8, 22.4±11.8, 35.3±11.9, and 50.2±19.9 μg/m3, respectively. There were 85 % of study targets exceeded the World Health Organization (WHO) PM2.5 threshold (24 hours). The mean endotoxin concentrations ranged from 1.086 ± 0.384-1.912 ± 0.419 EU/m3, with a geometric mean (GM) varied from 1.034 to 1.869. The concentration of iron (Fe) (0.008-1.16 μg/m3) was one of the most abundant transition metals in the samples that could affect endotoxin toxicity under Toll-Like Receptor 4 (TLR4) stimulation. In summer, the interleukin 6 (IL-6) levels showed statistically significant differences compared to other seasons. Spearman correlation analysis showed endotoxin concentrations were positively correlated with chromium (Cr) and nickel (Ni), implying possible roles as nutrients and further transport via adhering to the surface of fine inorganic particles. Mixed-effects model analysis demonstrated that Tumor necrosis factor-α (TNF-α) production was positively associated with endotoxin concentration and Cr as a combined exposure factor. The Cr contained the highest combined effect (0.205-0.262), suggesting that Cr can potentially exacerbate the effect of endotoxin on inflammation and oxidative stress. The findings will be useful for practical policies for mitigating air pollution to protect the public health of the citizens.

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.

A comparative study on chromium-induced micronuclei assessment in the peripheral blood of Hsd:ICR mice

This study investigated the genotoxic effects of chromium (Cr) in Hsd:ICR mice, considering factors such as oxidative state, apoptosis, exposure pathway, duration, pregnancy, and transplacental exposure. Genotoxicity was assessed using the erythrocytes' micronucleus (MN) assay, while apoptosis was evaluated in nucleated blood cells. The results showed that Cr(III) (CrK(SO4 )2 and CrCl3 ) did not induce any marked genotoxic damage. However, Cr(VI) (CrO3 , K2 Cr2 O7 , Na2 Cr2 O7 , and K2 CrO4 ) produced varying degrees of genotoxicity, with CrO3 being the most potent. MN frequencies increased following 24-h exposure, with a greater effect in male mice. Administering 20 mg/kg of CrO3 via gavage did not lead to significant effects compared to intraperitoneal administration. Short-term oral treatment with a daily dose of 8.5 mg/kg for 49 days elevated MN levels only on day 14 after treatment. Pregnant female mice exposed to CrO3 on day 15 of pregnancy exhibited reduced genotoxic effects compared to nonpregnant animals. However, significant increases in MN levels were found in their fetuses starting 48 h after exposure. In summary, data indicate the potential genotoxic effects of Cr, with Cr(VI) forms inducing higher genotoxicity than Cr(III). These findings indicate that gender, exposure route, and pregnancy status might influence genotoxic responses to Cr.

ATP-induced cell death: a novel hypothesis for osteoporosis

ATP-induced cell death has emerged as a captivating realm of inquiry with profound ramifications in the context of osteoporosis. This study unveils a paradigm-shifting hypothesis that illuminates the prospective involvement of ATP-induced cellular demise in the etiology of osteoporosis. Initially, we explicate the morphological attributes of ATP-induced cell death and delve into the intricacies of the molecular machinery and regulatory networks governing ATP homeostasis and ATP-induced cell death. Subsequently, our focus pivots towards the multifaceted interplay between ATP-induced cellular demise and pivotal cellular protagonists, such as bone marrow-derived mesenchymal stem cells, osteoblasts, and osteoclasts, accentuating their potential contributions to secondary osteoporosis phenotypes, encompassing diabetic osteoporosis, glucocorticoid-induced osteoporosis, and postmenopausal osteoporosis. Furthermore, we probe the captivating interplay between ATP-induced cellular demise and alternative modalities of cellular demise, encompassing apoptosis, autophagy, and necroptosis. Through an all-encompassing inquiry into the intricate nexus connecting ATP-induced cellular demise and osteoporosis, our primary goal is to deepen our comprehension of the underlying mechanisms propelling this malady and establish a theoretical bedrock to underpin the development of pioneering therapeutic strategies.

Heavy metals concentration in zooplankton (copepods) in the western Bay of Bengal

Along the coastline, urbanisation and industrialization pose significant challenges to marine habitats and biodiversity. Most wastewater that reaches the marine environment contains toxic metals, which, as they are non-biodegradable, accumulate in the biota and enter the marine food chain. This study presents the concentration of nine heavy metals (Fe, Zn, Cu, Co, Cr, Mn, Ni, Pb, and Cd) in zooplankton (copepods) during the Spring Intermonsoon/Pre-Monsoon (April 2019) in the western Bay of Bengal (BoB). Higher Fe concentrations were found in copepods both nearshore (42,352 µg/g) and offshore (9835 µg/g). However, the relative amounts of heavy metals in copepods from 16 locations (eight nearshore and eight offshore) varied in the order of Fe > Zn > Cu > Co > Cr > Mn > Ni > Pb > Cd. The copepods in the nearshore locations had higher concentrations of heavy metals than those offshore. Compared to earlier data on heavy metals, particularly those that are physiologically non-essential and toxic, the current study demonstrates higher amounts of these metals in copepods in the inshore BoB [Ni (avg. 58.7 ± 5.5 µg/g), Pb (avg. 25.6 ± 4.7 µg/g), and Cd (avg. 16.4 ± 0.9 µg/g)]. Considering the strong East India Coastal Currents in the western BoB, trace metal-concentrated copepods could be transported too far along the Indian coastline from the current study area.

A review of chromium (Cr) epigenetic toxicity and health hazards

Carcinogenic metals affect a variety of cellular processes, causing oxidative stress and cancer. The widespread distribution of these metals caused by industrial, residential, agricultural, medical, and technical activities raises concern for adverse environmental and human health effects. Of these metals, chromium (Cr) and its derivatives, including Cr(VI)-induced, are of a public health concern as they cause DNA epigenetic alterations resulting in heritable changes in gene expression. Here, we review and discuss the role of Cr(VI) in epigenetic changes, including DNA methylation, histone modifications, micro-RNA changes, biomarkers of exposure and toxicity, and highlight prevention and intervention strategies to protect susceptible populations from exposure and adverse occupational health effects. Cr(VI) is a ubiquitous toxin linked to cardiovascular, developmental, neurological, and endocrine diseases as well as immunologic disorders and a high number of cancer types in humans following inhalation and skin contact. Cr alters DNA methylation levels as well as global and gene-specific histone posttranslational modifications, emphasizing the importance of considering epigenetics as a possible mechanism underlying Cr(VI) toxicity and cell-transforming ability. Our review shows that determining the levels of Cr(VI) in occupational workers is a crucial first step in shielding health problems, including cancer and other disorders. More clinical and preventative measures are therefore needed to better understand the toxicity and safeguard employees against cancer.

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.

Neuroprotective effect of tangeretin against chromium-induced acute brain injury in rats: targeting Nrf2 signaling pathway, inflammatory mediators, and apoptosis

Potassium dichromate (PD) is an environmental xenobiotic commonly recognized as teratogenic, carcinogenic, and mutagenic in animals and humans. The present study was conducted to investigate the role of tangeretin (TNG) as a neuro-protective drug against PD-induced brain injury in rats. Thirty-two male adult Wistar rats were blindly divided into four groups (8 rats/group). The first group received saline intranasally (i.n.). The second group received a single dose of PD (2 mg/kg, i.n.). The third group received TNG (50 mg/kg; orally), for 14 days followed by i.n. of PD on the last day of the experiment. The fourth group received TNG (100 mg/kg; orally) for 14 days followed by i.n. of PD on the last day of the experiment. Behavioral indices were evaluated 18 h after PD administration. Neuro-biochemical indices and histopathological studies were evaluated 24 h after PD administration. Results of the present study revealed that rats intoxicated with PD induced- oxidative stress and inflammation via an increase in malondialdehyde (MDA) and a decrease in nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway and glutathione(GSH) levels with an increase in brain contents of tumor necrosis factor-alpha (TNF-α) and interleukin (IL-6). Pre-treatment with TNG (100 mg/kg; orally) ameliorated behavior, cholinergic activities, and oxidative stress and decreased the elevated levels of pro-inflammatory mediators; TNF-α and IL-6 with a decrease in brain content of chromium residues detected by Plasma-Optical Emission Spectrometer. Also, the histopathological picture of the brain was improved significantly in rats that received TNG (100 mg/kg). Additionally, TNG decreased caspase-3 expression in the brain of PD rats. In conclusion, TNG possesses a significant neuroprotective role against PD-induced acute brain injury via modulating the Nrf2 signaling pathway and quenching the release of inflammatory mediators and apoptosis in rats.

Insights into the antioxidative mechanisms of melatonin in ameliorating chromium-induced oxidative stress-mediated hepatic and renal tissue injuries in male Wistar rats

Chromium (Cr), a hazardous heavy metal, is toxic to human health and the environment. Severe detrimental effects of Cr on different physiological systems involve oxidative stress. In the current study, sodium dichromate di-hydrate was subcutaneously injected to male Wistar rats at a dose of 5 mg/kg b.w. and experimented up to 14 days to induce alterations in hepatic and renal tissues. Another group of rats was pre-treated with melatonin at three different doses (5, 10, and 20 mg/kg b.w.; orally) and 20 mg/kg b.w. dose was evidenced to provide maximal protection against Cr-induced alterations. The study demonstrated that melatonin efficiently preserved body weight, organ weight, intracellular antioxidant enzymes, and tissue morphology. Furthermore, melatonin was also found to protect organ damage markers, oxidative stress-biomarkers, activities of pro-oxidant enzymes, levels of reactive oxygen species (ROS), nitric oxide (NO), and collagen content through its antioxidative mechanisms. Moreover, melatonin effectively decreased tissue Cr content through its metal-chelating activity. Hence, the present study has established melatonin as a promising antioxidant for conserving the liver and kidney tissues from Cr-induced oxidative damage thereby strengthening the notion that this small indoleamine can act as a future therapeutic against Cr-induced oxidative stress-mediated tissue damage.

Selenium Alleviates Chromium(VI)-Induced Ileum Damage and Cecal Microbial Disturbances in Mice

Hexavalent chromium [Cr(VI)] is one of the most common environmental contaminants caused by its broad industrial applications. Importantly, exposure to Cr(VI) induces oxidative damage and apoptosis in animal cells. Studies have shown that selenium (Se) can alleviate the toxic effects of Cr(VI) by functioning as an antioxidant and/or by chelating Cr(VI) into biologically inert complexes, but the underlying mechanism remains unknown. Here, we evaluated whether Se can ameliorate ileum damage and cecal microbial disturbances induced by Cr(VI) in vivo. Mice administered Cr(VI) for 30 days presented histopathological damage, reduced responses to oxidative stress, and increased expression of apoptosis-related genes in the ileum compared with those in the control (non-exposed) group. Se alleviated the histopathological damage and decreased the oxidative stress and apoptosis induced by Cr(VI) in the ileum. In addition, Cr(VI) disturbed cecal microflora, and it was partially reversed by Se treatment. These findings demonstrate that the damaging and potentially pathological effects of Cr(VI) on the ileum and cecal microflora can be effectively alleviated with Se treatment.

Influence of heavy metals in Parkinson's disease: an overview

Parkinson's disease (PD) is an ageing disorder with deterioration of dopamine neurons which leads to motor complications like tremor, stiffness, slow movement and postural disturbances. In PD, both genetics as well as environmental factors both play a major role in causing the pathogenesis. Though there are surfeit of risk factors involved in PD occurrence, till now there is lack of an exact causative agent as a risk for PD with confirmative findings. The role of heavy metals reported to be a significant factor in PD pathogenesis. Heavy metal functions in cell maintenance but growing pieces of evidences reported to cause dyshomeostasis with increased PD rate. Metals disturb the molecular processes and results in oxidative stress, DNA damage, mitochondrial dysfunction, and apoptosis. The present review elucidates the role of cobalt, nickel, mercury, chromium, thallium metals in α-synuclein aggregation and its involvement in blood brain barrier flux. Also, the review explains the plausible role of aforementioned metals with a mechanistic approach and therapeutic recommendations in PD.

Metallic nanoparticles for catalytic reduction of toxic hexavalent chromium from aqueous medium: A state-of-the-art review

The ever increasing concentration of toxic and carcinogenic hexavalent chromium (Cr (VI)) in various environmental mediums including water-bodies due to anthropogenic activities with rapid civilization and industrialization have become the major issue throughout the globe during last few decades. Therefore, developing new strategies for the treatment of Cr(VI) contaminated wastewaters are in great demand and have become a topical issue in academia and industry. To date, various techniques have been used for the remediation of Cr(VI) contaminated wastewaters including solvent extraction, adsorption, catalytic reduction, membrane filtration, biological treatment, coagulation, ion exchange and photo-catalytic reduction. Among these methods, the transformation of highly toxic Cr(VI) to benign Cr(III) catalyzed by metallic nanoparticles (M-NPs) with reductant has gained increasing attention in the past few years, and is considered to be an effective approach due to the superior catalytic performance of M-NPs. Thus, it is a timely topic to review this emerging technique for Cr(VI) reduction. Herein, recent development in synthesis of M-NPs based non-supported, supported, mono-, bi- and ternary M-NPs catalysts, their characterization and performance for the reduction of Cr(VI) to Cr(III) are reviewed. The role of supporting host to stabilize the M-NPs and leading to enhance the reduction of Cr(VI) are discussed. The Cr(VI) reduction mechanism, kinetics, and factors affecting the kinetics are overviewed to collect the wealthy kinetics data. Finally, the challenges and perspective in Cr(VI) reduction catalyzed by M-NPs are proposed. We believe that this review will assist the researchers who are working to develop novel M-NPs catalysts for the reduction of Cr(VI).

Protective Effect of Resveratrol against Hexavalent Chromium-Induced Genotoxic Damage in Hsd:ICR Male Mice

The aim of this study is to examine the ability of resveratrol to counteract hexavalent chromium [Cr(VI)]-induced genetic damage, as well as the possible pathways associated with this protection. Hsd:ICR male mice are divided into groups of the following five individuals each: (a) control 1, distilled water; (b) control 2, ethanol 30%; (c) resveratrol, 50 mg/kg by gavage; (d) CrO₃, 20 mg/kg intraperitoneally; (e) resveratrol + CrO₃, resveratrol administered 4 h prior to CrO₃. The assessment is performed on peripheral blood. Micronuclei (MN) kinetics are measured from 0 to 72 h, while 8-hydroxydeoxyguanosine (8-OHdG) adduct repair levels, endogenous antioxidant system biomarkers, and apoptosis frequency were quantified after 48 h. Resveratrol reduces the frequency of Cr(VI)-induced MN and shows significant effects on the 8-OHdG adduct levels, suggesting that cell repair could be enhanced by this polyphenol. Concomitant administration of resveratrol and Cr(VI) results in a return of the activities of glutathione peroxidase and catalase to control levels, accompanied by modifications of superoxide dismutase activity and glutathione levels. Thus, antioxidant properties might play an important role in resveratrol-mediated inhibition of Cr(VI)-induced oxidant genotoxicity. The increase in apoptotic cells and the decrease in necrosis further confirmed that resveratrol effectively blocks the actions of Cr(VI).

Hair, serum and urine chromium levels in children with cognitive defects: A systematic review and meta-analysis of case control studies

Environmental chromium exposure may cause impaired development of children. We conducted a systematic review and meta-analysis. Electronic databases including PubMed, Embase, Web of Science and CINAHL were searched to identify case-control studies that reported childhood Cr exposure and cognitive development. The Newcastle-Ottawa Scale (NOS) was used to ensure the quality of the included studies. Cr levels were compared in cases and controls, and a random effect meta-analysis was performed using Stata version 16. Twelve of 61 studies identified in the literature search were eligible for this analysis. Hair, serum and urine Cr measurements were reported by seven, two and one studies, respectively. In addition, one study reported both serum and hair Cr exposure and another reported urine and hair Cr exposure. The pooled standard mean differences (SMD) showed that hair Cr levels were non-significantly lower among children with cognitive defects (-0.01 μg/g, 95% CI: -0.04, 00, p = 0.27). In serum and urine, the pooled SMD was higher in children with cognitive deficits compared with healthy control children (0.32 μg/g, 95% CI: -0.78, 1.42, p = 0.56 and 0.64 μg/g, CI: -0.07,1.36, p = 0.08; respectively). In summary, this systematic review found no significant differences in hair, serum and urine Cr levels between children with cognitive deficits and healthy control children when all study data were pooled in the meta-analysis. Larger studies using standardized criteria and longitudinal assessment of cognitive development are needed to determine whether there is a dose response effect of childhood Cr exposure on cognitive development of children.

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

The hexavalent form of chromium, Cr (VI), has been associated with various diseases in humans. In this study, we examined the mechanisms underlying the effect of Cr (VI) on glucose and lipid metabolism in vivo and in vitro. We found that Cr (VI) induced abnormal liver function, increased fasting blood glucose (FBG), as well as glucose and insulin intolerance in mice. Furthermore, Cr (VI) decreased glucose-6-phosphate (G6P) level and glucose transporter-2 (GLUT2) expression, increased the levels of triglyceride (TG), low-density lipoprotein-cholesterol (LDL-C), reduced high-density lipoprotein-cholesterol (HDL-C), and increased sterol regulatory element-binding proteins 1 (SREBP1) and fat synthase (FAS) in vitro and in vivo. Moreover, Cr (VI) promoted intracellular ROS production in vitro, and induced reduction of antioxidant enzyme level and Nrf2/HO-1 expression in vitro and in vivo. Also, N-acetyl cysteine (NAC, effective antioxidant and free radical scavenger) pretreatment inhibited the production of intracellular ROS, significantly suppressed Cr (VI)-induced oxidative stress, lipid accumulation, decreased G6P and GLUT2, and improved impaired glucose tolerance and glucose and insulin intolerance caused by Cr (VI) in mice. Dh404 activated expression of Nrf2 decreased ROS level, increased HO-1 expression, ameliorated activity of the antioxidant enzyme, inhibited Cr (VI) increase of SREBP1, FAS level, and reduction of G6P and GLUT2. To sum up, these data suggest that dysregulation of ROS/Nrf2/HO-1 has an important role in Cr (VI)-induced glucose/lipid metabolic disorder.

The Effect of Global DNA Methylation on PDCD5 Expression in the PBMC of Occupational Chromate Exposed Workers

OBJECTIVES

To evaluate the alteration of protein of programmed cell death 5 (PDCD5) in peripheral blood mononuclear cells (PBMC) and DNA methylation caused by hexavalent chromium exposure.

METHODS

There were 112 workers and 56 controls in this study. The chromium in RBC and urine, PBMC with PDCD5+, DNA methylation, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and score of DNA damage were measured.

RESULTS

In chromate exposed workers, the percent of PBMC with PDCD5+, urine 8-OHdG, and score of DNA damage were significantly higher, whereas global DNA methylation was significantly lower. The binary logistic regression and generalized linear mixed model analysis showed that the percent of PBMC with PDCD5+ was significantly associated with global DNA hypomethylation.

CONCLUSIONS

The aberrant DNA hypomethylation plays an important role in PBMC apoptosis of occupational hexavalent chromium exposure.

Evaluation of nutritional composition of Citrullus lanatus Linn. (watermelon) seed and biochemical assessment of the seed oil in rats

The present study investigated the nutritional composition of watermelon seeds and the effect of extracted oil on the biochemical parameters in rats after 28 days of oral administration. The watermelon seeds showed considerable proximate values but with less moisture, crude fiber, ash, and phytochemical components. The maximal dose of 50 ml/kg of watermelon seed oil (WMSO) showed no sign of toxicity in rats. WMSO significantly decreased serum cholesterol, triglyceride, LDL, ALT, and MDA but enhanced the level of HDL, VLDL, SOD, and CAT without compromising the liver integrity. For glucose tolerance, a positive oral glucose-lowering was observed. The fatty acid analysis showed the presence of three major fatty acids; 9,12-octadecadienoic acid (52.32%), n-hexadecenoic acid (21.23%), and oleic acid (10.11%) with good oxidative stability and fatty acid ratio. The outcome of this study suggests that the seeds and oil from watermelon could have a beneficial effect on man. PRACTICAL APPLICATIONS: Plant-based oils have gained significant interest globally as a source of food, cosmetics, and compounds with therapeutic potential against certain human diseases. The watermelon seed oil is a rich source of oleic acid, linoleic, and palmitic acid. These prominent biologically active fatty acid components have contributed to the robust biochemical effects observed in this study. Based on the data obtained in this work on the nutritional analysis of the watermelon seed and potent antioxidative capacity, improved liver biomarkers, good oxidative stability, and the fatty acid ratio of WMSO, we proposed that consumption of the seed and its oil could offer a cheap and affordable nutraceutical for human benefits. However, we recommend further studies on the biological activity and safety aspect of watermelon seed oil for its long-term usage.

Antigenotoxic effects of (-)-epigallocatechin-3-gallate (EGCG) and its relationship with the endogenous antioxidant system, 8-hydroxydeoxyguanosine adduct repair (8-OHdG), and apoptosis in mice exposed to chromium(VI)

This study aimed to investigate the relationship between endogenous antioxidant system, 8-hydroxydeoxyguanosine adduct (8-OHdG) repair, and apoptosis in mice treated with chromium(VI) alone and in the presence of the antigenotoxic compound (-)-epigallocatechin-3-gallate (EGCG). Groups of 5 Hsd:ICR male mice were divided and treated as follows: (1) control, vehicle only; (2) EGCG, 8.5 mg/kg by gavage alone; (3) CrO₃, 20 mg/kg intraperitoneally alone; and (4) EGCG combined with CrO₃, EGCG was administered 4 hr prior to CrO₃. Peripheral blood parameters were analyzed before treatment administration (time 0), and 48 hr after exposure. The administration of EGCG increased 8-OHdG levels and superoxide dismutase (SOD) activity. Treatment with CrO₃ increased number of micronucleus (MN) presence, elevated apoptotic/necrotic cells frequencies, decreased 8-OHdG levels, diminished total antioxidant capacity (TAC), increased glutathione (GSH) total levels, and lowered SOD activity. Administration of EGCG prior to treatment with CrO₃ resulted in lower concentrations of MN, reduced apoptotic and necrotic cell number, and restored TAC and SOD activity to control levels. It is conceivable that the dose of EGCG plays an important role in the genotoxic damage protection pathways. Thus, this study confirms the action of EGCG as an antigenotoxic agent against chromium(VI)-induced oxidative insults and demonstrates potential protective pathways for EGCG actions to counteract genotoxic damage induced by this metal.

Perspectives of Genetic Damage and Epigenetic Alterations by Hexavalent Chromium: Time Evolution Based on a Bibliometric Analysis

Compounds containing hexavalent chromium [Cr(VI)] have been classified as Group I human carcinogens in 1990 by the International Agency for Research on Cancer, known to induce human lung cancers. To determine the nature of Cr(VI) carcinogenesis, much has been learned about genetic damage and epigenetic alterations. On the basis of bibliometric analysis of the available literature found between 1966 and 2020, the present study investigated the evolution of author keywords; provided a summary of relevant studies focused on populations, animals/plants, or cells; and depicted the co-operation among countries or institutions and research group development. Additionally, multiomics technology and bioinformatics analysis can be a valuable tool for figuring out new biomarkers from different molecular levels like gene, RNA, protein, and metabolite and ascertaining the mechanism pathways of Cr(VI) genotoxicity and carcinogenesis.

Polyethylene glycol-stabilized bimetallic nickel–zero valent iron nanoparticles for efficient removal of Cr(vi)

In order to solve the agglomeration of nanoscale zero-valent iron (nZVI) and improve its performance in pollutant treatment, polyethylene glycol-stabilized nickel modified nZVI (Ni/Fe–PEG) was synthesized by a liquid-phase reduction method and used to treat Cr(vi) solution for the first time.

Emerging contaminant 1,3,6,8-tetrabromocarbazole induces oxidative damage and apoptosis during the embryonic development of zebrafish (Danio rerio)

Since polyhalogenated carbazoles (PHCs) have been widely detected at high concentrations in multiple environmental media in recent years, the health risk of exposure to these compounds has drawn increasing attention. Most studies have mainly focused on their dioxin-like toxicity, which is induced through the AhR pathway, because PHCs have structures similar to those of polychlorinated dibenzofurans (PCDFs). In addition, most xenobiotic compounds induce oxidative stress in organisms, which is a more common mechanism of toxicity induction. However, there is limited information regarding the oxidative stress and damage induced by PHCs in vivo. The PHC 1,3,6,8-tetrabromocarbazole (1368-TBCZ) is detected at high concentration and frequency. In the present study, the toxic effects (acute toxicity, developmental toxicity, oxidative stress, and apoptosis) induced by 1368-TBCZ at three different concentrations were investigated using zebrafish embryos. It was concluded that the 96 h median lethal concentration (LC₅₀) of 1368-TBCZ for zebrafish embryos was greater than 2.0 mg L^-1. The results showed that 1368-TBCZ had little effect on the hatching rate of zebrafish embryos. However, 1368-TBCZ at 0.5 and 2.0 mg L^-1 inhibited skeletal and cardiac development. It promoted ROS production, CAT enzyme activity, lipid peroxidation, DNA damage, and apoptosis, even at the lowest dose (0.1 mg L^-1). In addition, 1368-TBCZ influenced oxidative stress-related gene expression, upregulating the expression of caspase 3 and p53 at 2.0 mg L^-1 and inhibiting the expression of caspase 9, FoxO3b, and Bcl-2/Bax. The present study comprehensively evaluated 1368-TBCZ-induced toxicity in zebrafish, providing valuable data for better evaluation of the potential risks posed by this PHC.

Biotransformation and oxidative stress responses in relation to tissue contaminant burden in Clarias gariepinus exposed to simulated leachate from a solid waste dumpsite in Calabar, Nigeria

In this study, we have investigated biotransformation and oxidative stress responses in relation to tissue contaminant burden in the African sharptooth catfish (Clarias gariepinus) exposed to simulated leachate from a solid waste dumpsite in Calabar, Nigeria. Fish were exposed to simulated leachate, diluted to 0:0 (negative control), 1:10, 1:50, 1:100 and phenanthrene (a PAH: 50 μg/L used as a positive control) for 3, 7 and 14 days. Hepatic transcripts for cat, sod1, gpx1, gr, gst, cyp1a, cyp2d3, and cyp27 were analyzed by real-time PCR, while enzymatic assays for ethoxyresorufin O-deethylase (EROD), buthoxyresorufin O-deethylase (BROD), methoxyresorufin O-deethylase (MROD), pentoxyresorufin O-deethylase (PROD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), uridine diphospho-glucuronosyltransferase (UDPGT) and lipid peroxidase (LPO) were measured using standard methods. In addition, protein expression for CYP1A, CYP3A and metallotheionin (MT) were measured by immunoblotting. Fish muscle samples were analyzed for selected group of contaminants after 14 days exposure showing significantly high uptake of heavy metals (Cd, Hg and Pb), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), chlorophenols, organochlorine (OC) and organophosphate pesticides in exposed fish. We observed significant concentration- and time-specific increases in biotransformation and oxidative stress responses at transcript and functional (enzyme and protein) levels, that paralleled tissue contaminants bioaccumulation patterns, after exposure to the simulated leachates. Our results highlighted the potential environmental, wildlife and public health consequences from improper solid waste disposal. In addition, it also provides a scientific basis for local sensitization and inform legislative decisions and policy formulation towards sustainable environmental management of solid wastes in Nigeria and other developing countries.

Evaluation of some heavy metals and physicochemical properties of public refuse dumpsites in Nsukka metropolis, Nigeria

This study assessed some physicochemical properties and heavy metal contamination of four major dumpsites in Nsukka metropolis. Soil samples were collected randomly at depth of 15 cm. Physicochemical properties were determined. Levels of lead, chromium, iron, manganese, zinc, cadmium, and copper were analyzed using atomic absorption spectrophometer (AAS). Soil pH ranged 5.68-6.82, temperature 25.30^-29.67 ° C, and moisture 2.23-7.66%. Soil particle size distribution had higher percentages of sand 40-55% followed by silt 15-35% and clay 10-30%. Average levels of Pb, Cr, Fe, Mn, Zn, Cd, and Cu from the dumpsites ranged from 0.08 ± 0.04 mg/kg to 1.40 ± 0.15 mg/kg, 0.17 ± 0.09 mg/kg to 1.66 ± 0.87 mg/kg, 14.05 ± 5.13 mg/kg to 21.08 ± 0.01 mg/kg, 4.47 ± 0.54 mg/kg to 16.83 ± 0.80 mg/kg, 9.10 ± 3.05 mg/kg to19.33 ± 0.12 mg/kg, 0.02 ± 0.01 mg/kg to 1.15 ± 0.30 mg/kg, and 0.77 ± 0.26 mg/kg to 7.29 ± 2.65 mg/kg, respectively. Heavy metal profile in the dumpsite soils was Fe > Zn > Mn > Cu > Cr > Pb > Cd. Heavy metal load by dumpsites was Obimo > Ikenga Hotel > UNN > Obukpa. All the heavy metals evaluated except Fe increased as pH, temperature, and sand contents of dumpsite soil increased. Retention of Fe by soil was positively related to its clay contents. The values of heavy metals in soils from the dumpsites were far below the permissible limits set by European Regulatory Standard (EURS STD), US Environmental Protection Agency (USEPA), and Federal Environmental Protection Agency (FEPA) for standard soil. The dumpsites require no remediation as at the time of this study.

Removal of dental alloys and titanium attenuates trace metals and biological effects on liver and kidney

To determine whether the potential effects on liver and kidney caused by dental alloys could be reduced or terminated by the removal of nickel-chromium (Ni-Cr) alloy, cobalt-chromium (Co-Cr) alloy, and commercially pure titanium (CP-Ti), they were placed in the cheek pouches of Syrian hamsters according to ISO 10993-10. Then, the peak/plateau and end times of trace metals in the blood were determined with or without the removal of the dental alloys. Based on these time points, the trace metals and their effects on liver and kidney were examined. We found that trace metals released from these dental alloys and titanium were accumulated transiently in the blood, liver, and kidney but had no effect on the histopathology of the liver or kidney. Although the functions of the liver and kidney were compromised, the function of these tissues seemed to be clinically acceptable compared to those in control Syrian hamsters. In addition, the apoptotic effect on renal cells was terminated by removing the Ni-Cr and Co-Cr alloys, and that on hepatocytes was also eliminated by removing the Ni-Cr alloy. In contrast, the effect of the Co-Cr alloy on hepatocytes was temporary and recovered by itself. Taken together, Ni- and Co-based dental alloys and titanium have no effect on the histopathology or function of liver and kidney. Moreover, Ni-Cr and Co-Cr alloys induce transient trace metal accumulation and apoptotic effects in liver and kidney, which can be reduced or terminated by the removal of the alloys, while CP-Ti shows favorable biocompatibility.

Cr(VI) induces ROS-mediated mitochondrial-dependent apoptosis in neuronal cells via the activation of Akt/ERK/AMPK signaling pathway

Hexavalent chromium (Cr(VI)), a well-known toxic industrial and environmental pollutant, has been shown to cause serious toxic and health effects. However, limited information is available on Cr(VI)-induced neurotoxic potential, with the underlying toxicological mechanisms remain mostly unclear. The present study demonstrated that the mitochondria-dependent apoptosis pathway was involved in Cr(VI)-induced SH-SY5Y cell (the human neuroblastoma cell line) death, which was accompanied by the appearance of cell shrinkage, increased mitochondrial membrane potential (MMP) depolarization and cytochrome c release, and the activation of caspase cascades and poly (ADP-ribose) polymerase (PARP). Cr(VI) treatment also increased the generation of intracellular reactive oxygen species (ROS). Pretreatment of SH-SY5Y cells with antioxidant N-acetylcysteine (NAC) effectively attenuated ROS production and reversed these Cr(VI)-induced cytotoxicity and apoptotic responses. Furthermore, exposure to Cr(VI) significantly increased the phosphorylation levels of Akt, extracellular regulated kinase (ERK)1/2, and AMP-activated protein kinase (AMPK)α. NAC and the pharmacological inhibitor of Akt (LY294002), ERK1/2 (PD980590), and AMPKα (Compound C) markedly abrogated the Cr(VI)-induced activation of Akt, ERK1/2, and AMPKα signal, respectively, with the concomitant inhibition of mitochondrial dysfunction and caspase activation. Additionally, all these inhibitors suppressed Cr(VI)-induced phosphorylation of Akt, ERK1/2, and AMPKα and of each other. Collectively, these results suggest that Cr(VI) exerts its cytotoxicity on neuronal cells by inducing mitochondria-dependent apoptosis through the interdependent activation of Akt, ERK1/2, and AMPKα, which are mainly mediated by ROS generation.

Hexavalent chromium intoxication induces intrinsic and extrinsic apoptosis in human renal cells

Hexavalent chromium [Cr(VI)], is a well-known toxic form of the heavy metal chromium in the natural environment. Clinical evidence has indicated that exposure to Cr(VI) can cause severe renal damage. The production of reactive oxygen species (ROS) due to intracellular reduction of Cr(VI) is the main mechanism underlying the induction of cellular dysfunction and apoptosis. The present study aimed to investigate in detail the apoptotic pathways induced by Cr(VI)-exposure in a human immortalized proximal tubular epithelial cell line HK-2, in order to understand the mechanism involved therein. Exposure to 10 µM potassium dichromate (K₂Cr₂O₇), a toxic compound of Cr(VI), significantly decreased cell viability after 24 and 48 h of incubation and induced intracellular ROS generation. The expression levels of markers that activate the apoptotic pathway including cleaved caspase-3 and poly (ADP-ribose) polymerase were significantly upregulated in K₂Cr₂O₇-exposed HK-2 cells. In addition, the induction of intrinsic and extrinsic apoptotic markers was detected in K₂Cr₂O₇-exposed HK-2 cells. In summary, the present study described for the first time the novel apoptotic mechanism of Cr(VI)-toxicity in human renal cells which may be beneficial in designing optimal clinical treatment for renal damage caused by acute Cr(VI) toxicity.

Cellular pathologies and genotoxic effects arising secondary to heavy metal exposure: A review

Environmental pollution is significant and oftentimes hazardous in the areas, where mining, foundries and smelters and other metallurgical operations are located. Systematic research on the chronic effects of metals started during the past century; nevertheless, it is evident that even today, there are large gaps in knowledge regarding the assessment of the health effects caused by environmental and occupational exposures to these metals. Heavy metals induce the production of reactive oxygen species (ROS) causing oxidative stress, make several repair-inhibiting cellular changes and alter the DNA repair processes. They favour the ‘false’ repairing of double-strand breaks (DSBs), propagate DNA mutations and induce carcinogenesis. A detailed literature search was performed using the MedLine/PubMed database. Depending on the mechanism of action, arsenicals can act as genotoxins, non-genotoxic agents and carcinogens. Cadmium can bind to proteins, reduce DNA repair, activate protein degradation, up-regulate cytokines and proto-oncogenes (c-fos, c-jun and c-myc), induce the expression of metallothionein, haeme-oxygenases, glutathione transferases, heat-shock proteins, acute-phase reactants and DNA polymerase β at lower concentrations. Inorganic mercury damages oxidative phosphorylation and electron transport pathways at the ubiquinone–cytochrome b5 locus and thus induces ROS production. Abandoned mining areas generate environmentally persistent waste. These specific sites urgently require maximally efficient and cheap remediation. This bears the need for methodologies employing green and sustainable remediation. Phytoremediation is important in that it is a prevalent in situ remediation technique. Its advantages include the use of solar energy, cost-effectiveness, easy operation, reduction in secondary contaminants, the use of biomass for biofuel production and low-cost adsorbents.

Hexavalent chromium-induced toxic effects on the antioxidant levels, histopathological alterations and expression of Nrf2 and MT2 genes in the branchial tissue of Ctenopharyngodon idellus

Ability of hexavalent chromium to accumulate and induce oxidative stress has been studied in the gills of Ctenopharyngodon idellus, with the resulting damage in the form of altered endogenous antioxidant enzyme activity and, histopathology in the tissue. The fish were exposed to 5.3 (C1) and 10.63 mg/L (C2) of hexavalent chromium and were scrutinised on 15th, 30^th and 45th day of toxicant exposure. Oxidative stress studied in terms of lipid peroxidation and glutathione levels and the antioxidant enzymes activity also exhibited alterations. The histopathological modifications in gills announced lesions in the form of hyperplasia, aneurysm, lamellar fusion, focal proliferation, epithelial degeneration and necrosis with loss of lamellae, bringing irreversible damage on 45th day with mean degree of tissue change value of 100.35 ± 10.69. Bioaccumulation of chromium, and increased anomalies in branchial tissue exhibited damage in concentration and time-dependent manner. The ultrastructural anomalies in the cellular morphology in the epithelial cells of filaments and lamellae, exhibited pleomorphic nuclei, swollen mitochondria, extensive vacuolation and loss of microridges in pavement cells. The tissue also displayed altered regulation of Nrf2 and Mt2 following Cr(VI) exposure with maximum downregulation on 45th day by 61 and 53%, respectively. PCA generated two principal components, PC1 (GSH, GST, CAT and SOD) and PC2 (DTC, MDA and Cr(VI) concentration). Thus, it can be concluded that accumulation of Cr(VI) induces alteration in the gene expression of Nrf2 and Mt2 leading to the development of oxidative stress, ensuing various pathological changes creating hindrance in fish survival.

Optimal Regimen of N-Acetylcysteine on Chromium-Induced Renal Cell Damage

Chromium (Cr) is a well-known heavy metal that can cause renal damage. The production of reactive oxygen species (ROS) due to chromium-induced toxicity induces cell dysfunction, apoptosis, and death. N-acetylcysteine (NAC) is an antioxidant used as an antidote for chromium-induced toxicity. However, the optimal regimen and protective mechanisms of NAC are not fully understood in human renal cells. Our results showed that exposure to 10 μM K₂Cr₂O₇, a toxic Cr(VI) compound, induced apoptosis and production of intracellular ROS in the human proximal tubular epithelial cell line HK-2. Supplements of 600 or 1000 µg/mL NAC inhibited intracellular ROS in HK-2 cells exposed to Cr(VI) and significantly increased cell viability within 2 h of Cr(VI)-induced cytotoxicity. Moreover, Cr(VI) induced the expression of apoptosis markers, including cleaved-caspase-3, cleaved-poly (ADP-ribose) polymerase, cleaved-caspase 8, and cleaved-caspase 9, and altered the expression ratio of Bax/Bcl-xL. Expression of apoptosis markers within 2 h of Cr(VI)-induced cytotoxicity in cells treated with 600 µg/mL NAC was significantly suppressed. However, delayed treatment with NAC at 4 h and 8 h after exposure to Cr did not suppress the activation of apoptotic pathways. In summary, our study reports the optimum timing and dose of NAC for the protection of human renal proximal tubular cells from Cr(VI)-induced cell death. The NAC treatment strategy described could be applied in clinical practice to suppress renal cell apoptosis, which in turn could rescue renal function.

Oxidative stress and genotoxic effects in earthworms induced by five imidazolium bromide ionic liquids with different alkyl chains

In this study, the acute and subchronic toxicity of 1-alkyl-3-methyl imidazole bromide ionic liquids (ILs) [C_nmim]Br (n = 2, 4, 6, 10, 12) was evaluated utilizing earthworms (Eisenia fetida) as a basis for their impact on terrestrial ecosystems. The filter paper tests and artificial soil tests were conducted as acute toxicity tests to investigate the LC₅₀ of ILs, while in subchronic toxicity tests, earthworms were exposed to ILs in artificial soil (5, 10, 20 and 40 mg kg^-1) for 28 d. Reactive oxygen species (ROS), antioxidant enzymes, detoxifying enzymes and oxidative damage were measured to determine subchronic effects of ILs on E. fetida. The results showed that when the earthworms were exposed to these five ILs in acute toxicity experiments, [C₂mim]Br had the lowest toxicity, as the alkyl length increased, the toxicity increased up to [C₁₀mim]Br: a "cut-off effect" (decreased toxicity) was observed at [C₁₂mim]Br. The results highlight the varying toxicity of ILs with different alkyl chains to E. fetida and provide valuable data for detailing the impact of ILs on ecological receptors.

Bioaccumulation and toxicity of pentachloronitrobenzene to earthworm (Eisenia fetida)

Pentachloronitrobenzene (PCNB) has been widely utilized as a fungicide to control diseases. However, toxic effect data of PCNB on terrestrial invertebrate are not available till now. Herein, the earthworms (Eisenia fetida) were exposed to soil containing different levels of PCNB. Mortality, weight, accumulation, and physiological indexes of earthworms were determined on certain days. PCNB inhibited the growth of earthworms and induced a significant increase in the activity of antioxidative enzymes. ROS, SOD, and MDA of earthworms in the highest treatment group were 6.8, 4.4, and 3.8 times higher than those in the control group, respectively. In addition, earthworm coelomocytes were successfully extracted, cultured, and innovatively employed in in-vitro toxicity test to evaluate the toxic effect of PCNB. The biomarkers utilized in in-vitro toxicity test, including cell viability, intracellular ROS and extracellular LDH showed significant correlations with the PCNB in the culture media, indicating that the in-vitro toxicity test may serve as a useful tool for toxic assessment of pollutants to earthworms and other organisms.

Correlating Live Cell Viability with Membrane Permeability Disruption Induced by Trivalent Chromium

Cr(III) is often regarded as a trace essential micronutrient that can be found in many dietary supplements due to its participation in blood glucose regulation. However, increased levels of exposure have been linked to adverse health effects in living organisms. Herein, scanning electrochemical microscopy (SECM) was used to detect variation in membrane permeability of single cells (T24) resulting from exposure to a trivalent Cr-salt, CrCl₃. By employing electrochemical mediators, ferrocenemethanol (FcMeOH) and ferrocenecarboxylic acid (FcCOO^-), initially semipermeable and impermeable, respectively, complementary information was obtained. Three-dimensional COMSOL finite element analysis simulations were successfully used to quantify the permeability coefficients of each mediator by matching experimental and simulated results. Depending on the concentration of Cr(III) administered, three regions of membrane response were detected. Following exposure to low concentrations (up to 500 μM Cr(III)), their permeability coefficients were comparable to that of control cells, 80 μm/s for FcMeOH and 0 μm/s for FcCOO^-. This was confirmed for both mediators. As the incubation concentrations were increased, the ability of FcMeOH to permeate the membrane decreased to a minimum of 17 μm/s at 7500 μM Cr(III), while FcCOO^- remained impermeable. At the highest examined concentrations, both mediators were found to demonstrate increased membrane permeability. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell viability studies were also conducted on Cr(III)-treated T24 cells to correlate the SECM findings with the toxicity effects of the metal. The viability experiments revealed a similar concentration-dependent trend to the SECM cell membrane permeability study.

Toxicity of 1-alkyl-3-methyl imidazolium nitrate ionic liquids to earthworms: The effects of carbon chains of different lengths

Ionic liquids (ILs), which are alternatives to traditional organic solvents, have the potential to enter soil and cause negative effects on the soil micro-environment, especially soil organisms. The objective of this study was to determine the "alkyl chain effect" and "cut-off effect" mechanisms underlying the toxicity of ILs. The assessment for subchronic toxicity toward earthworms (Eisenia fetida) by five common imidazole nitrate ILs ([C_nmim]NO₃ (n = 4, 6, 8, 10, and 12)) was conducted on day 28 after exposure to five concentrations (0, 5, 10, 20, and 40 mg kg^-1) of ILs. Earthworms showed oxidative stress and oxidative damage, and both "alkyl chain effect" and "cut-off effect" (occurred in C₁₀) were observed. In addition, the toxicity of ILs increased with the increase in concentration. Analysis of imidazolium ILs in artificial soil at the end of the experiment indicated that these selected ILs remained relatively stable, with a rate of change of less than 7.39%. The present study provides theoretical support for decisions regarding IL use and helps to establish a friendly IL structure database.

Toxic effect of [Omim]BF4 and [Omim]Br on antioxidant stress and oxidative damage in earthworms (Eisenia fetida)

In this paper, model soil organism, earthworms (Eisenia fetida), were selected to examine the chronic toxic effect of two different ionic liquids (ILs) [Omim]BF₄ and [Omim]Br. Earthworms were put into different ILs concentrations (0, 5, 10, 20, 40 mg/kg) in artificial soil and random selected on days 7, 14, 21 and 28. Reactive oxygen species (ROS), antioxidant enzymes and detoxifying enzyme glutathione-S-transferase (GST) were researched for determination of antioxidant stress. Malondialdehyde (MDA) and olive tail moment (OTM) were researched to determine the oxidative damage. Both the pollutants had the same effect on earthworms: ILs led to accumulation of ROS, and then antioxidant enzymes and detoxification enzyme all changed to eliminate the effects of ROS, and the above process led to lipid peroxidation and DNA damage in earthworms. This paper shows that [Omim]BF₄ and [Omim]Br both caused toxicity to earthworms and had the similar toxicity levels.

Ameliorative effects of nano-elemental selenium against hexavalent chromium-induced apoptosis in broiler liver

The current study examined the ameliorative effects of nano-elemental selenium (Nano-Se) against chromium-VI (K₂Cr₂O₇)-induced apoptosis in chickens. The expression of apoptosis-related genes was evaluated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot. A total of 60, one-day-old broiler chickens allotted to six equal groups, i.e., control group (standard diet), Cr(VI)-exposed group (K₂Cr₂O₇ via drinking water), Nano-Se group (Nano-Se at 0.5 mg/kg via diet), protection group (K₂Cr₂O₇ + Nano-Se), cure group (K₂Cr₂O₇ for initial 2 weeks and then Nano-Se), and prevention group (opposite to the cure group) and were detected by the activities of pro-apoptosis (Bax, Caspase-3) and anti-apoptosis (Bcl-2) genes expression at day 35 of the experiment. Intense apoptosis was observed in liver tissues of chickens exposed to K₂Cr₂O₇. The Nano-Se supplementation caused a significant decrease (P < 0.01) in the mRNA expression levels of Bax and Caspase-3 genes, while significantly elevated (P < 0.05) mRNA expression level of Bcl-2 gene was observed in Nano-Se experimental groups as compare to control and Cr(VI)-exposed group. The results quantified by the RT-qPCR were further confirmed by the western blot analysis. Altogether, these results suggest anti-apoptotic effects of Nano-Se in the chicken liver, which is interesting for further study. The present findings suggested that Nano-Se has protective effects against K₂Cr₂O₇-induced apoptosis in broilers liver and can serve a key role as a protective agent against apoptosis.

Ascorbic acid protects male rat brain from oral potassium dichromate-induced oxdative DNA damage and apoptotic changes: the expression patterns of caspase-3, P 53, Bax, and Bcl-2 genes

Our study designed to study the potential of potassium dichromate (K₂Cr₂O₇) oral exposure to induce damage in male rat brain and to compare the possible protective role of vitamin C (VC) either pre and/or concurrent supply against (K₂Cr₂O₇) induced changes. Thirty male rats were divided into five groups. First control group received distilled water (C), second received 120 mg/kg b.wt (VC), third received 25 mg/kg b.wt K₂Cr₂O₇ (Cr), fourth group received VC together with K₂Cr₂O₇ by the same former doses (VC + Cr), and the fifth group received the same oral doses of VC 2 weeks prior to and along with K₂Cr₂O₇ for 6 weeks (VC + Cr pro/co treated). The obtained results revealed that K₂Cr₂O₇ induced a significant decrease in cholinergic activity, glutathione reductase GR activity, reduced glutathione content GSH and ATP levels. Furthermore, K₂Cr₂O₇ induced a significant increase in oxidative DNA damage indicated by 8-hydroxy 2'-deoxyguanosine (8OH2'dG) and formation of apoptotic DNA ladders, significant increase in malondialdehyde (MDA), protein carbonyl, and lactate dehydrogenase enzyme. Increased mRNA expression of pro-apoptotic genes, including caspase-3, p53, and Bax, unlike Bcl-2 expression, was decreased. K₂Cr₂O₇ increased caspase-3 and decreased Bcl-2 immuno-labeling. VC supply noticeably ameliorates K₂Cr₂O₇-induced changes which were more significantly in VC pro and concurrent supplement rather than VC concurrent supply only. Finally, it is concluded that K₂Cr₂O₇ oral administration induced oxidative apoptotic changes in rat brain and confirms the usefulness of VC pre and concurrent supply for the amelioration of K₂Cr₂O₇-induced events more significantly than VC concurrent supply only.

Oxidative Damage and Genetic Toxicity Induced by DBP in Earthworms (Eisenia fetida)

Di-n-butyl phthalate (DBP) is one of the most ubiquitous plasticizers used worldwide. However, it has negatives effects on the soil, water, atmosphere, and other environmental media and can cause serious pollution. According to the artificial soil test and previous studies, this study was conducted to evaluate the toxicity of earthworms induced by DBP at different concentrations (0, 0.1, 1.0, 10, and 50 mg kg^-1) on the 7th, 14th, 21st, and 28th days of exposure. The variations in the antioxidant activities of enzymes, such as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and glutathione-S-transferase (GST), in the amounts of malondialdehyde (MDA) and reactive oxygen species (ROS) and in the amount of DNA damage were measured to evaluate the toxic impact of DBP in earthworms. Upon exposure to DBP, the SOD, CAT, POD, and GST activities were significantly increased, with the exception of the 0.1 mg kg^-1 treatment dose. High concentrations of DBP (10 and 50 mg kg^-1) induced superfluous ROS to be produced and caused the MDA content to increase significantly. Therefore, we proposed that DBP led to DNA damage in earthworm coelomocytes in a dose-dependent manner, which means that DBP is a source of oxidative damage and genetic toxicity in earthworms.

Pathological and Clinical Pathological Changes Induced by Four-week, Repeated-dose, Oral Administration of the Wood Preservative Chromated Copper Arsenate in Wistar Rats

Chromated copper arsenate (CCA) is used as a wood preservative worldwide. Exposure to it may adversely affect human health. Some events have increased human exposure to CCA, including the Great East Japan Earthquake, which generated a large amount of lumber debris from CCA-treated woods. We elucidated the toxicity due to daily exposure to CCA over a 4-week period at doses of 0, 8, 40, and 80 mg/kg/day in Wistar Hannover rats. Chromium (Cr) and arsenic (As), but not copper, were detected in the plasma samples of rats treated with various doses of CCA. Males and females showed sedation, and males had poor body weight gain. The clinical pathologies observed in both sexes included hypochromic and microcytic anemia, hepatic and renal dysfunction, and changes in lipid and glucose levels. Histopathologically, males and females showed forestomach hyperkeratosis, mucosal epithelial hyperplasia in the small intestine, rectal goblet cell hypertrophy, and lipofuscin deposition in the proximal renal tubule. Females showed diffuse hepatocellular hypertrophy with increased 8-hydroxydeoxyguanosine levels. These results indicated that oral administration of CCA mainly affected hematopoietic, gastrointestinal, hepatic, and renal systems owing to the toxic effects of As and/or Cr. Major toxic effects were observed in both sexes receiving 40 and 80 mg/kg/day.

Alteration in DNA structure, molecular responses and Na+ -K+ -ATPase activities in the gill of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) in response to sub-lethal verapamil

The ecotoxicological consequences of residues from pharmaceutical drugs on aquatic biota have necessitated the development of sensitive and reliable techniques to assess the impact of these xenobiotics on aquatic organisms. This study investigated the alteration in DNA structure, molecular responses and the activities of Na⁺ -K⁺ -ATPase and antioxidant enzymes in the gill of Nile tilapia, Oreochromis niloticus, exposed to long-term effects at the concentrations (0.14, 0.28 and 0.57mgL^-1) of verapamil in static renewal system for 15, 30, 45 and 60 days. Evaluation of DNA structure, using single cell gel electrophoresis, revealed certain degree of DNA damages in the gill in a time and concentration-dependent relationship. Transcription of mRNA of superoxide dismutase (sod), catalase (cat) and heat shock protein (hsp70) genes in the gill of the fish showed the genes were up-regulated. Na⁺-K⁺-ATPase activity was inhibited in a concentration and time dependent manner. The indices of oxidative stress biomarkers (lipid peroxidation and carbonyl protein) as well as superoxide dismutase, glutathione peroxidase, glutathione-S-transferase were elevated in the treated fish in comparison to the control. Further, the level of reduced glutathione and catalase activity were inhibited at 0.28mgL^-1 after day 30. Long-term exposure to sub-lethal concentration of verapamil can cause DNA damages, molecular effects and oxidative stress in O. niloticus. The biomarkers analysed can be used as early warning signals in environmental biomonitoring and assessment of drug contamination in aquatic ecosystem.

Melatonin protects against chromium (VI) induced hepatic oxidative stress and toxicity: Duration dependent study with realistic dosage

The present study was undertaken to assess the degree of oxidative stress and toxic effects induced by chromium on hepatic tissue in male Wistar rats exposed to a realistic dosage of Cr(VI) (20 mg/kg/b.w./day) through drinking water, based on the levels of these metals found in the environment, for a duration of 15, 30 and 60 days. The protective effect of melatonin (10 mg/kg) was also studied by simultaneous administration with the metal. Levels of enzymatic and non-enzymatic antioxidants as well as lipid peroxidation were assessed. There was a significant decrease in enzymatic as well as non-enzymatic antioxidants and an increase in the lipid peroxidation level, which were prevented and maintained at near-normal levels by the administration of melatonin in all treatment periods. Metal accumulation was maximal at 15 days, with gradual decreases till 60 days. Histopathological observations also demonstrated the fact that Cr (VI) exposure leads to cytological lesions in the hepatic tissue promoting cellular necrotic/apoptotic changes, while melatonin was able to counteract insults induced by Cr (VI) at all treatment periods. It also prevented alterations in insulin and glucose levels. Overall, the present study suggests a duration-dependent effect of Cr on hepatic oxidative stress and cytotoxicity and shows the potent activity of melatonin in preventing the negative effects of Cr (VI).