Hexavalent chromium induces oxidative stress and mitochondria-mediated apoptosis in isolated skin fibroblasts of Indo-Pacific humpback dolphin

Geographic and tissue-specific variations of the trace elements and trophic niches of three offshore cetaceans in Chinese waters

Systematical investigation on trace elements' (TEs) distribution and trophic niches of cetaceans are essential to understand marine mammal ecology and environmental toxicology. Here, the concentrations of 10 TEs and isotopic values in six tissues of stranded Stenella attenuata (SA) and Kogia breviceps (KB) from the northern South China Sea (SCS) and Peponocephala electra (PE) from the East China Sea (ECS) were investigated. The TEs levels of the studied cetaceans were characterized by geo- and tissue-specific distributions. For SA and KB, most TEs levels were in the normal ranges, with low toxicological risk. For PE, several toxic TEs accumulated above the thresholds up to 892.80 μg/g of Hg and 335.24 μg/g of Cd, indicating that land-based anthropogenic pollution may be an ongoing threat to top predators in the ECS. The liver, spleen, and kidney are the main organs that accumulate toxic TEs, and there are strong positive, such as Se-Hg, correlations in several tissues. In particular, for PE with severe Hg and Cd exposure, tissue-specific distribution and correlations were more obvious. The results of stable carbon and nitrogen isotopes showed partly overlapped trophic niches of the three cetaceans, with similar calculated trophic levels in a narrow range of 4.29-4.43.

Effects of hexavalent chromium on mitochondria and their implications in carcinogenesis

Hexavalent chromium (Cr(VI)) is a well-known occupational and environmental human carcinogen. The cellular effect of Cr(VI) is complex and often nonspecific due to its ability to modulate multiple cellular targets. The toxicity of Cr(VI) is strongly linked to the generation of reactive oxygen species (ROS) during its reduction process. ROS can cause oxidation of cellular macromolecules, such as proteins, lipids, and DNA, thereby altering their functions. A major genotoxic effect of Cr(VI) that contributes to carcinogenesis is the formation of DNA adducts, which can lead to DNA damage. Modulations of cellular signaling pathways and epigenetics may also contribute to the carcinogenic effects of Cr(VI). Cr(VI) has a major impact on many aspects of mitochondrial biology, including oxidative phosphorylation, mitophagy, and mitochondrial biogenesis. These effects have the potential to alter the trajectory of Cr(VI)-induced carcinogenic process. This perspective article summarizes current understandings of the effect of Cr(VI) on mitochondria and discusses the future directions of research in this area, particularly with regard to carcinogenesis.

Alternatives Exert Higher Health Risks than Bisphenol A on Indo-Pacific Humpback Dolphins

The detrimental effects of bisphenol (BP) exposure are a concern for vulnerable species, Indo-Pacific humpback dolphins (Sousa chinensis). To investigate the characteristics of BP profiles and their adverse impact on humpback dolphins, we assessed the concentrations of six BPs, including bisphenol A (BPA), bisphenol S (BPS), bisphenol F (BPF), bisphenol AF (BPAF), bisphenol B (BPB), and bisphenol P (BPP) in blubber (n = 26) and kidney (n = 12) of humpback dolphins stranded in the Pearl River Estuary, China. BPS accounted for the largest proportion of the total bisphenols (∑BPs) in blubber (55%) and kidney (69%). The concentration of ∑BP in blubber was significantly higher than that in the kidney and liver. The EC50 values of five BPA alternatives were lower than those of BPA in humpback dolphin skin fibroblasts (ScSF) and human skin fibroblasts (HSF). ScSF was more sensitive to BPS, BPAF, BPB, and BPP than HSF. The enrichment pathway of BPA was found to be associated with inflammation and immune dysregulation, while BPP and BPS demonstrated a preference for genotoxicity. BPA, BPP, and BPS, which had risk quotients (RQs) > 1, were found to contribute to subhealth and chronic disease in humpback dolphins. According to the EC50-based risk assessment, BPS poses a higher health risk than BPA for humpback dolphins. This study successfully evaluated the risks of bisphenols in rare and endangered cetacean cell lines using a noninvasive method. More in vivo and in field observations are necessary to know whether the BPA alternatives are likely to be regrettable substitutions.

Hexavalent-Chromium-Induced Disruption of Mitochondrial Dynamics and Apoptosis in the Liver via the AMPK-PGC-1α Pathway in Ducks

Hexavalent chromium (Cr(VI)) is a hazardous substance that poses significant risks to environmental ecosystems and animal organisms. However, the specific consequences of Cr(VI) exposure in terms of liver damage remain incompletely understood. This study aims to elucidate the mechanism by which Cr(VI) disrupts mitochondrial dynamics, leading to hepatic injury in ducks. Forty-eight healthy 8-day-old ducks were divided into four groups and subjected to diets containing varying doses of Cr(VI) (0, 9.28, 46.4, and 232 mg/kg) for 49 days. Our results demonstrated that Cr(VI) exposure resulted in disarranged liver lobular vacuolation, along with increasing the serum levels of ALT, AST, and AKP in a dose-dependent manner, which indicated liver damage. Furthermore, Cr(VI) exposure induced oxidative stress by reducing the activities of T-SOD, SOD, GSH-Px, GSH, and CAT, while increasing the contents of MDA and H2O2. Moreover, Cr(VI) exposure downregulated the activities of CS and MDH, resulting in energy disturbance, as evidenced by the reduced AMPK/p-AMPK ratio and PGC-1α protein expression. Additionally, Cr(VI) exposure disrupted mitochondrial dynamics through decreased expression of OPA1, Mfn1, and Mfn2 and increased expression of Drp-1, Fis1, and MFF proteins. This disruption ultimately triggered mitochondria-mediated apoptosis, as evidenced by elevated levels of caspase-3, Cyt C, and Bax, along with decreased expression of Bcl-2 and the Bcl-2/Bax ratio, at both the protein and mRNA levels. In summary, this study highlights that Cr(VI) exposure induces oxidative stress, inhibits the AMPK-PGC-1α pathway, disrupts mitochondrial dynamics, and triggers liver cell apoptosis in ducks.

Effects of Aronia melanocarpa and Hypericum perforatum aqueous extracts on hexavalent chromium induced toxicity in rat's thyrocytes

BACKGROUND

Hexavalent chromium known as oxidizing agent is able to form reactive oxygen species. Aronia melanocarpa and Hypericum perforatum are two plants known for their antioxidant effects. Our study aimed to establish if CrVI induces apoptosis and structural changes in thyrocytes and if its effect can be counteracted by the administration of both extracts.

MATERIALS AND METHODS

Wistar rats divided in five groups: C - distilled water (DW), Cr - 75 mg/L CrVI in DW for 3 months, Cr 2 - 75 mg/L CrVI in DW for 3 months followed by 1 month DW, CrA - 3 months 75 mg/L CrVI in DW and 1 month Aronia 2.5% extract, CrH - 3 months 75 mg/L CrVI in DW and 1 month Hypericum 2.5% extract. Histological assessment and qRT-PCR for evaluation of BAX and Bcl2 protein levels performed on thyroid samples.

RESULTS

The Cr and Cr2 groups were those with altered cytoarchitecture: increase in the diameter of many thyroid follicles, a decrease in their number, a decrease in the height of the follicular cells. The histological examination of the CrH group revealed almost recovery of structural architecture. The BAX gene levels were higher in the Cr and Cr2 groups indicating the apoptotic activity of chromium. In extract receiving groups the BAX gene expressions were significantly lower, but the lowest level presented the CrH group. Bcl2 gene expression levels indicate antiapoptotic activity being elevated in the Cr group, followed by CrA, Cr2, and CrH groups. The BAX/Bcl2 ratio which significantly increased in the case of the Cr and Cr2 group compared to the groups that were administered the two plant extracts.

CONCLUSION

The results obtained in this study confirm that CrVI has toxic effects on thyroid endocrine cells and H. perforatum has stronger antioxidant properties against the action of hexavalent chromium in thyrocytes than A. melanocarpa.

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.

Visible-light-driven CQDs/TiO2 photocatalytic simultaneous removal of Cr(VI) and organics: Cooperative reaction, kinetics and mechanism

CQDs/TiO₂ was synthesized with a coprecipitation method and characterized by XRD, SEM, TEM/HRTEM, BET, XPS, UV-Vis DRS and I-t curve technologies. UV-Vis DRS displayed that absorption spectrum of CQDs/TiO₂ enlarged to visible light zone, suggesting that CQDs/TiO₂ can be irradiated by visible light. I-t curve showed that photocurrent of CQDs/TiO₂ was higher than that of bare TiO₂, revealing that the doping of CQDs accelerated the transfer of photoelectrons and restrained the recombination of photoinduced carriers. Simultaneous removal of Cr(VI) and organics with CQDs/TiO₂ photocatalytic reaction was investigated and factors were optimized, and almost all Cr(VI) and organics were removed under the optimum conditions. Experimental results displayed that there was a distinct cooperation removal effect between Cr(VI) and organics in CQDs/TiO₂ photocatalytic reaction. XPS analysis proved that Cr(VI) was reduced to Cr(III) in situ on CQDs/TiO₂ surface. There were e^-, h⁺,·OH and ·O₂^- active species which were detected with DMPO in ESR test during CQDs/TiO₂ photocatalytic reaction, and scavenger experiment proved that e^- and h⁺ were the substantial reactants for Cr(VI) and organics, respectively. The pathway of photocatalytic simultaneous removal of Cr(VI) and organics underwent four steps: adsorption of Cr(VI) and organics on CQDs/TiO₂ surface; production of photo electrons and holes in visible light; reduction of Cr(VI) and oxidation of organics; desorption of Cr(III) and intermediates. Photocatalytic reaction kinetics of Cr(VI) and organics were both confirmed to pseudo first-order reaction. Life span and small scale real application tests both demonstrated that CQDs/TiO₂ had a potential application to wastewater containing Cr(VI) and organics.

Study on the mechanism of cadmium chloride pollution accelerating skin tissue metabolism disorder, aging and inhibiting hair regeneration

Drinking water contaminated by Cd2⁺ is one of the main pathways for Cd to enter the body. The skin barrier is destroyed when the skin is contaminated by environmental Cd2⁺, however, the detailed mechanism by which Cd2⁺ induces skin metabolic disorder, and senescence and affects hair regeneration is not completely understood. In this study, 18 C57BL/6 mice were randomly divided into a Control group, a Low-dose group, and a High-dose group with 6 mice in each group, and intragastrically administered with different concentrations of cadmium chloride once a day, respectively. After 1 month of intervention, the skin tissues on the back of mice were collected for non-targeted metabolomics analysis, and the related proteins were detected by immunofluorescence assay. Non-targeted metabolomics analysis result showed that compared with the Control group, there were 29 different metabolites, mainly including lysophospholipids, fatty acids, and bile acids, in the Low-dose group, and 39 differential metabolites in the High-dose group, in addition to the above compounds, there were more amino acid compounds, and most of the metabolites had a reduced response after administration. Immunofluorescence assay result showed that the higher the concentration of cadmium chloride led to the more obvious the proliferation inhibition and apoptosis promotion effects of skin cells, and the more significant damage to hair follicle stem cells. Thus, our findings demonstrate that cadmium chloride pollution can accelerate skin metabolism disorder, and aging and impair hair regeneration.

Long-term increase in mortality of Indo-Pacific humpback dolphins (Sousa chinensis) in the Pearl River Estuary following anthropic activities: Evidence from the stranded dolphin mortality analysis from 2003 to 2017

With the dramatic increase in anthropogenic threats to the Pearl River Estuary (PRE), the population size of the Indo-Pacific humpback dolphins (Sousa chinensis) has significantly decreased over the past decade. To understand the impact and potential risks of intense human activities on these dolphins, factors related to the mortality of humpback dolphins in the PRE were investigated by a detailed examination of 343 dolphin specimens stranded during 2003-2017. There was a significant (p < 0.01) increasing trend for humpback dolphin stranding, reflecting the accelerating rate of the population decline. A large proportion of strandings (35.88%) were neonates. A low recruitment rate implies slow population growth, and hence, limited capacity to resist anthropogenic stress. The most commonly diagnosed causes of death were vessel collision and net entanglement. The concentrations of trace metals, polychlorinated biphenyl (PCB) congeners, dichlorodiphenyltrichloroethane, polycyclic aromatic hydrocarbons, and most of per- and polyfluoroalkyl substances (PFASs) in the dolphin samples were greater than those previously reported in cetaceans globally. Furthermore, Cu, PCB77, PCB169, PCB81, PCB37, and PFASs (excluding PFBA, PFPeA, PFHxA, PFHxDA, and PFODA) were the major pollutants accumulated in neonates. 67% of PCB, 78% of Cu, and 100% of perfluorooctane sulfonate concentrations in the neonates exceeded the threshold for toxicological effects in marine mammals, suggesting that these compounds could be important factors contributing to the low survival rate of calves in this area. This study revealed that vessel transportation, fishing activities, and pollutant bioaccumulation are the three major causes of humpback dolphin mortality in the PRE. These results highlight the need for more efforts to restrict anthropogenic activities, especially vessel traffic, the catching of these marine animals and fishing, and pollutant discharge, in order to prevent vulnerable species from continuous population decline and further extinction.

Harzianopyridone Supplementation Reduced Chromium Uptake and Enhanced Activity of Antioxidant Enzymes in Vigna radiata Seedlings Exposed to Chromium Toxicity

This study explains the scarce information on the role of harzianopyridone (HZRP) in the alleviation of chromium (Cr) stress alleviation in Vigna radiata (L.). To this end, V. radiata seedlings primed with HZRP at 1 and 2 ppm were exposed to 50 mg kg^-1 Cr for 30 days. Cr stress reduced growth, chlorophyll (Chl) content, net photosynthetic rate, gas-exchange attributes along with enhanced oxidative damages, i.e., electrolyte leakage (EL), hydrogen peroxide (H₂O₂), and malondialdehyde (MDA). Application of HZRP enhanced intercellular carbon dioxide (CO₂) concentration, stomatal conductance, and net photosynthetic rate with decreased activity of the chlorophyllase (Chlase) enzyme in V. radiata seedlings exposed to Cr stressed conditions. To maintain Cr-induced oxidative damages, HZRP treatment increased the levels of antioxidant metabolites (phenolic and flavonoids) and the activity of antioxidative enzymes [superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD)] in V. radiata seedlings grown in normal and Cr-polluted potted soil. In addition to this, glycine betaine content was also increased in plants grown in Cr-contaminated soil. It is proposed the potential role of supplementation of HZRP in mitigating Cr stress. Further research should be conducted to evaluate the potential of HZRP in the mitigation of abiotic stresses in plants.

Comparative assessment of chromate bioremediation potential of Pantoea conspicua and Aspergillus niger

The recent work aims at the use of Pantoea conspicua (MT5) and Aspergillus niger (CRS3) to assess their bioremediation potential and growth restoration of Helianthus annuus L. under chromate (Cr⁺⁶) stress. The growth of the P. conspicua and A. niger was tested in Cr⁺⁶ supplemented media. The strains can withstand up to 1200 and 900 ppm respectively in the media and effectively bio-transform it to nontoxic form. Supplemented metal's levels significantly decreased the growth attribute of H. annuus (p< 0.05). On the other hand, P. conspicua and A. niger rescued the host plant by establishing higher colonization frequency with the host roots. Moreover, MT5 bio-transformed the toxic Cr⁺⁶ to non-toxic Cr⁺³ form in the rhizosphere. It also enhanced the host plant growth by producing phytohormones and ceasing Cr uptake and accumulation. Contrarily, CRS3 tends to accumulate and bio-transform metal in their hyphae. Nonetheless, both of the microbes tend to modulate phytohormones production and strengthening antioxidant system of the host. Improvement in the antioxidant system enabled the host plant to produce higher phenolics and flavonoids, and lower peroxidase. The associated plant species also exhibited higher ROS scavenging and lower ROS accumulation. Besides, the strains were able to produce higher amounts of phytohormones, including IAA, GA, and SA. Such activities rendered them as excellent phytostimulants, that can be used as biofertilizers in chromium polluted soils.

An oxo(corrolato)chromium(V) complex selectively kills cancer cells by inducing DNA damage

An oxo(corrolato)chromium(v) complex selectively kills leukemia cells. However, this complex did not induce cell death in primary non-cancer cells. It has been observed that oxo(corrolato)chromium(v) complex induced cell death is associated with DNA damage. Interestingly, the DNA in primary cells largely remained unaffected. DNA isolated from normal and cancerous cell lines also follows similar trends. A chemical reductant, DTT, was used to probe the mechanism of DNA damage. However, it does not show any additive effect on DNA damage.

Aronia melanocarpa Ameliorates Adrenal Cytoarchitecture Against the Hexavalent Chromium-Induced Injury

Hexavalent chromium is a toxin that penetrates the cell, triggering reactive oxygen species (ROS) production. Aronia melanocarpa, due to its proanthocyanidins, anthocyanins, and phenolic acid contents, is a valuable antioxidant. The aim was to observe the influence of hexavalent chromium Cr(VI) on the adrenal gland, and if this impact can be recovered by the administration of A. melanocarpa. Accordingly, 36 rats were divided into six groups: control; Aronia; Cr receiving Cr(VI) in distilled water for 3 months; CrA receiving a mix of Cr(VI) and A. melanocarpa at 2.5% aqueous extract for 3 months; Cr2 receiving, for 3 months, Cr(VI) in distilled water, and next, for 1 month, only distilled water; and respectively, CrA2 receiving, for 3 months, Cr(VI) in distilled water, followed by 1 month of Aronia at 2.5% extract administration. The adrenal gland samples were examined toward histological and molecular assessment, and results were statistically analyzed (ANOVA). Hexavalent chromium induced changes in the adrenal cortex expressed by focal or diffuse hypertrophies, cytoplasmic vacuolization (due to lipidic accumulation), and cells' shape and size alteration, including necrosis. These structural alterations were carried by Bax and Bcl2 gene expression: the Bax gene expression levels, increased significantly (p < 0.001) in all experimental groups, except the Aronia group, compared with control. In the Cr2, CrA, and CrA2 groups, notable reduction of Bax gene expression (p < 0.001) was reported compared with the Cr group. Regarding the Bcl2 gene expression (p < 0.001), a significant increase was observed in the experimental groups, compared with the control. The Bcl2 expression level had a similar pattern to Bax gene, consequently trying to compensate its overexpression. Aronia administered concomitantly, or after Cr(VI), diminished structural changes and expression of the studied genes, thus reducing the Bax/Bcl2 ratio and suggesting that the active ingredients from Aronia are capable of blocking apoptotic cascade induced by the pathway of Bax and Bcl2 proteins.

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.

A novel visible light-driven TiO2 photocatalytic reduction for hexavalent chromium wastewater and mechanism

Titanium dioxide (TiO₂) photocatalyst was prepared with a sol-gel method and its characterizations were analyzed TiO₂ photocatalytic reduction of Cr⁶⁺ was investigated in visible light irradiation and reduction mechanisms were calculated. Prepared TiO₂ is anatase with a bandgap of about 2.95 eV. Experimental results display that almost 100% of Cr⁶⁺ is removed by visible light-driven TiO₂ photocatalytic reduction after 120 min when Cr₂O₇^2- initial concentration is 1.0 mg·L^-1, TiO₂ dosage is 1.0 g·L^-1, and pH value is 3. In acidic aqueous solution, HCrO₄^- is the dominant existing form of Cr⁶⁺ and is adsorbed by TiO₂, forming a complex catalyst HCrO₄^-/TiO₂ with an increase in wavelength to the visible light zone, demonstrated by UV-Vis diffuse reflection spectroscopy. Based on X-ray photoelectron spectroscopy data, it can be deduced that Cr⁶⁺ is adsorbed on the surface of TiO₂ and then reduced to Cr³⁺ in situ by photoelectrons. Self-assembly of HCrO₄^-/TiO₂ complex catalyst and self-reduction of Cr⁶⁺ in situ are the key steps to start the visible light-driven TiO₂ photocatalytic reduction. Furthermore, TiO₂ photocatalytic reduction of Cr⁶⁺ fits well with pseudo-first-order kinetics and has the potential application to treat chemical industrial wastewater.

Improvement in the growth status and carbohydrate utilization of Labeo rohita (Hamilton, 1822) fingerlings with dietary supplementation of chromium picolinate

A 60-day feeding experiment was conducted to evaluate the effects of dietary chromium (Cr) on carbohydrate utilization and growth performance of Labeo rohita fingerlings. Fishes were fed with four high carbohydrate (53%), isonitrogenous (crude protein 35%), and isocaloric (415 Kcal, 100 gm^-1) experimental diets containing different levels of dietary chromium picolinate (Cr-Pic) viz.0, 400, 800, and 1200 μg kg^-1 diet. Weight gain (WG%), specific growth rate (SGR), feed efficiency ratio (FER), and protein efficiency ratio (PER) were significantly increased at 800 μg kg^-1 diet chromium supplementation (P < 0.05). Cr-Pic supplementation (800 μg kg^-1) also significantly (P < 0.05) enhanced the protein: DNA ratio in muscle, while DNA: RNA and DNA: tissue ratios were significantly (P < 0.05) decreased indicating higher growth. Significantly higher amylase, protease, and lipase activities were recorded in 800 μg Cr-Pic kg^-1 diet fed fishes (P < 0.05), while any of the experimental groups showing no significant (P > 0.05) change in hexokinase activity, indicating normal glycolysis in all. Furthermore, significant (P < 0.05) decrease of glucose-6-phospatase activity in 800 μg Cr-Pic kg^-1 diet fed group, showcasing an evidence for protein-sparing action with Cr-Pic supplementation. Significantly (P < 0.05) higher serum insulin and liver glycogen in 800 μg Cr-Pic kg^-1 diet fed fishes denote an improvement in carbohydrate metabolism. However, significantly (P < 0.05) higher ATPase and SOD activities were also observed when chromium supplementation was more than 800 μg kg^-1 diet, indicating stress at higher level. The present study indicates that growth and carbohydrate utilization can significantly (P < 0.05) be improved by feeding the L. rohita fingerlings with Cr-Pic (800 μg kg^-1 diet) supplemented diet in laboratory condition.

Role of inhibiting Chk1-p53 pathway in hepatotoxicity caused by chronic arsenic exposure from coal-burning

Arsenic is a naturally occurring environmental toxicant, chronic exposure to arsenic can cause multiorgan damage, except for typical skin lesions, liver damage is the main problem for health concern in population with arsenic poisoning. Abnormal apoptosis is closely related to liver-related diseases, and p53 is one of the important hallmark proteins in apoptosis progression. This study was to investigate whether arsenic poisoning-induced hepatocyte apoptosis and the underlying role of p53 signaling pathway. A rat model of arsenic poisoning was established by feeding corn powder for 90 days, which was baked with high arsenic coal, then were treated with Ginkgo biloba extract (GBE) for 45 days by gavage. The results showed that arsenic induced liver damage, increased hepatocyte apoptosis and elevated the expression level of Chk1 and the ratios of p-p53/p53 and Bax/Bcl-2 in liver tissues, which were significantly attenuated by GBE. Additionally, to further demonstrate the potential apoptosis-associated mechanism, L-02 cells were pre-incubated with p53 inhibitor pifithrin-α (PFTα), ataxia telangiectasia-mutated (ATM)/ataxia telangiectasia-mutated and Rad3-related (ATR) inhibitor (CGK733) or GBE, then treated with sodium arsenite (NaAsO₂) for 24 h. The results showed that GBE, PFTα or CGK733 significantly reduced arsenic-induced Chk1 expression and the ratios of p-p53/p53 and Bax/Bcl-2. In conclusion, Chk1-p53 pathway was involved in arsenic poisoning-induced hepatotoxicity, and inhibiting of Chk1-p53 pathway ameliorated hepatocyte apoptosis caused by coal-burning arsenic poisoning. The study provides a pivotal clue for understanding of the mechanism of arsenic poisoning-induced liver damage, and possible intervention strategies.

Hexavalent chromium induces mitochondrial dynamics disorder in rat liver by inhibiting AMPK/PGC-1α signaling pathway

Occupational exposure to hexavalent chromium (Cr(VI)) can cause cytotoxicity and carcinogenicity. In this study, we established a liver injury model in rats via intraperitoneal injection of potassium dichromate (0, 2, 4, and 6 mg/kg body weight) for 35 d to investigate the mechanism of Cr(VI)-induced liver injury. We found that Cr(VI) induced hepatic histopathological lesions, oxidative stress, and apoptosis and reduced the expression of mitochondrial-related regulatory factors such as adenosine 5'-monophosphate-activated protein kinase (AMPK) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) in a dose-dependent manner. Furthermore, Cr(VI) promoted mitochondrial division and inhibited fusion, leading to increased expression of caspase-3 and production of mitochondrial reactive oxygen species. Our study demonstrates that long-term exposure to Cr(VI) induces mitochondrial dynamics disorder by inhibiting AMPK/PGC-1α signaling pathway in rat liver.

Arsenic and chromium levels in hair correlate with actinic keratosis/non-melanoma skin cancer: results of an observational controlled study

BACKGROUND

The role of heavy metals in carcinogenetic process has been widely established; however, information on the most common environmental metals that serve as major risk factors for actinic keratosis (AK)/non-melanoma skin cancer (NMSC) are still lacking. The aim of this study was to evaluate levels of the most common environmental heavy metals in hair of patients with AK/NMSC as compared to healthy controls.

METHODS

Thirty-one patients diagnosed with AK/NMSC and 34 healthy controls were enrolled. Patients were interviewed for heavy metals exposure and underwent hair analysis for detection of arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni) and lead (Pb). Continuous variables were analyzed using Wilcoxon Non-Parametric Rank Test and proportions were compared by Fisher's Exact Test. Statistical significance was determined by P<0.05.

RESULTS

In our cohort we observed 48.4% patients had AKs, 16.1% basal cell carcinoma (BCC), 9.7% squamous cell carcinoma (SCC) and 25.9% of patients presented with a combination of these lesions. There were significantly elevated levels of As and Cr in AK-NMSC group as compared to controls.

CONCLUSIONS

We identified a strong positive correlation between As and Cr concentration and AK/NMSC adding new clues to the scenery of NMSC risk factors that should be taken under consideration in exposed populations.

Hexavalent chromium-induced autophagic death of WRL-68 cells is mitigated by aqueous extract of Cuminum cyminum L. seeds

In this study, we assessed the potential of aqueous extract (CSE_aq) of Cuminum cyminum L. (cumin) seeds in protecting WRL-68 cells from hexavalent chromium [Cr(VI)]-induced oxidative injury. Cells exposed to Cr(VI) (10 μM CrO₃) for 24 h demonstrated a twofold increase in ROS, which, in turn, led to extensive oxidative stress, consequently causing colossal decline in cell viability (by 58.82 ± 9.79%) and proliferation (as was evident from a reduced expression of Ki-67, a proliferation marker). Immunofluorescence studies showed that Cr(VI) diminished the expressions of mTOR and survivin in WRL-68 cells. It also led to a substantial elevation of BECN1 expression, which suggested autophagy. Overall, our results indicated that 24 h exposure of WRL-68 cells to Cr(VI) caused oxidative stress-induced autophagic cell death. CSE_aq was found to protect WRL-68 cells from the same fate by refurbishing their viability and proliferation in a dose-dependent manner. The extract reduced ROS in these cells, which consequently decreased the degree of autophagic cell death by restoring expressions of mTOR, survivin and BECN1 to their respective normal levels. Biochemical assays revealed that CSE_aq is rich in phenolic constituents. Total phenolic content of CSE_aq demonstrated positive correlations with (i) its antioxidant potential, (ii) its alleviation of cellular oxidative stress and (iii) its cytoprotective efficacy in Cr(VI)-treated WRL-68 cells. We also identified the major phenolic constituents of CSE_aq. Our study suggested that polyphenols in CSE_aq might be responsible for protecting WRL-68 cells from Cr(VI)-governed oxidative assault that would have otherwise led to survivin/mTOR-mediated autophagic death.

DDT exposure induces cell cycle arrest and apoptosis of skin fibroblasts from Indo-Pacific humpback dolphin via mitochondria dysfunction

Although the global use of the 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (p,p'-DDT) has been prohibited, its persistence in the environment has caused long-lasting exposure on marine mammals. Our previous studies revealed exceedingly high residue levels of DDTs in Indo-Pacific humpback dolphins (Sousa chinensis) from the Pearl River Estuary region, China. However, the molecular mechanisms of p,p'-DDT toxicity on the dolphin are largely unknown. This study conducted the first cytotoxicity effect exploration of p,p'-DDT on the dolphin skin fibroblasts (ScSFs) to enhance the understanding of the cellular and molecular regulation impacts. ScSF cells were exposed to p,p'-DDT (28∼168 μM) for 24, 48 and 72 h. The exposure remarkably decreased viability of ScSF cells, possibly due to the synergetic effects of cell cycle arrest and apoptosis via DNA damage and mitochondria dysfunction. The DNA damage and mitochondria dysfunction were likely triggered by an increase of cellular reactive oxygen species (ROS), alteration in mitochondrial membrane potential, reduction in the cellular ATP levels, decreased expression of the genes CDK1, CDK4, cyclin B1, cyclin D1 and apoptosis regulator Bcl-2, release of cytochrome c, and activation of caspase-3, caspase-8 and caspase-9. Moreover, caspase inhibitor displayed protective activity against p,p'-DDT-induced apoptosis, indicating that caspases played a central role in p,p'-DDT-triggered apoptosis in the ScSF cells. We hypothesize apoptosis likely plays a minor role in cytocidal effects induced by p,p'-DDT exposure, but the mechanisms remain unclear. Overall, this research provides new evidence of the cytotoxic mechanisms underlying p,p'-DDT exposure on humpback dolphin skin cells, and suggests that p,p'-DDT contamination is one of key health concern issues for the protection of this marine mammal.

As, Cr, Hg, Pb, and Cd Concentrations and Bioaccumulation in the Dugong Dugong dugon and Manatee Trichechus manatus: A Review of Body Burdens and Distribution

The death of dozens of manatees Trichechus manatus recently in Tabasco, Mexico, has captured international attention. Speculation about possible causes include water and food contamination by metals. Although federal authorities have ruled out water chemical pollution, the cause of these deaths is still awaiting conclusive laboratory results. Present work seeks to summarize information currently available on non-essential metals and those of great toxicological relevance in Sirenia (dugongs and manatees), highlighting its body distribution, presence in blood, and its relationship with their geographical distribution, gender and age, whenever possible. This paper focuses on the five elements: As, Cr, Hg, Pb and Cd, which are commonly considered as threats for marine mammals and reported in Sirenia. Some of these metals (Cr and Cd) were thought to be related to the recent deaths in Tabasco. All five elements are accumulated by Sirenia at different levels. Metal presence is associated to their diet but does not necessarily imply adverse effects for dugongs and manatees. Toxicological aspects and the human consumption risk in case of any illegal or traditional consumption in some cultures are discussed. Important toxicological research areas that need to be addressed are highlighted.