Genotoxicity and antioxidant enzyme activity induced by hexavalent chromium inCyprinus carpioafterin vivoexposure

Arsenic and Chromium Induced Toxicity on Zebrafish Kidney: Mixture Effects on Oxidative Stress and Involvement of Nrf2-Keap1-ARE, DNA Repair, and Intrinsic Apoptotic Pathways

In polluted water, cooccurrences of two carcinogens, arsenic (As) and chromium (Cr), are extensively reported. Individual effects of these heavy metals have been reported in kidney of fishes, but underlying molecular mechanisms are not well established. There is no report on combined exposure of As and Cr in kidney. Thus, the present study investigated and compared individual and combined effects of As and Cr on zebrafish (Danio rerio) kidney treating at their environmentally relevant concentrations for 15, 30, and 60 days. Increased ROS levels, lipid peroxidation, GSH level, and decreased catalase activity implied oxidative stress in treated zebrafish kidney. Damage in histoarchitecture in treated groups was also noticed. The current study involved gene expression study of Nrf2, an important transcription factor of cellular stress responses along with its negative regulator Keap1 and downstream antioxidant genes nqo1 and ho1. Results indicated activation of Nrf2-Keap1 pathway after combined exposure. Expression pattern of ogg1, apex1, polb, and creb1 revealed the inhibition of base excision repair pathway in treatments. mRNA expression of tumor suppressor genes p53 and brca2 was also altered. Expressional alteration in bax, bcl2, caspase9, and caspase 3 indicated apoptosis (intrinsic pathway) induction, which was maximum in combined group. Inhibition of DNA repair and induction of apoptosis indicated that the activated antioxidant system was not enough to overcome the damage caused by As and Cr. Overall, this study revealed additive effects of As and Cr in zebrafish kidney after chronic exposure focusing cellular antioxidant and DNA damage responses.

Hexavalent chromium (Cr6+) induces oxidative stress, inflammatory response, apoptosis, and DNA damage in the liver of largemouth bass by inhibiting the Nrf2-Keap1 signal pathway

Heavy metal pollution poses a significant threat to the growth and health of fish, causing substantial economic losses in aquaculture. This study investigates the toxic effects of Cr6+ on the liver of Largemouth bass (Micropterus salmoides). Juvenile Largemouth bass were randomly divided into a control group (CON) and a chromium stress group (Cr6+), and subjected to a 96-h exposure test with Cr6+ at 96-h LC50 concentration. The results showed that in the Cr6+ group, liver cell nuclei were condensed, cells exhibited vacuolation, liver sinusoidal spaces were enlarged, and cell contours were unclear. Compared to the CON group, the Cr6+ group had significantly reduced activities of liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), with a significant decrease in T-AOC levels and a significant increase in MDA content (p < 0.05). Additionally, the relative mRNA expression levels of CAT, SOD, and GSH-Px were significantly decreased in the Cr6+ group (p < 0.05). The Nrf2-Keap1 Signal Pathway showed a significant increase in the relative mRNA expression of Nrf2 and a significant decrease in the relative mRNA expression of Keap1 in the Cr6+ group (p < 0.05). Furthermore, inflammatory response, apoptosis, and DNA damage were observed in the liver of Largemouth bass: the relative mRNA expression levels of interleukin-1β (IL-1β), interleukin-8 (IL-8), interleukin-15 (IL-15), and tumor necrosis factor-α (TNF-α) were significantly increased in the Cr6 + group (p < 0.05); the relative mRNA expression levels of Caspase-3, Caspase-8, Caspase-9, and Bax were significantly increased, while the Bcl-2 was significantly decreased; Tail length, Tail DNA (%), and Olive tail moment of liver cells were significantly increased (p < 0.05). In summary, Cr6+ induces oxidative stress, inflammatory response, apoptosis, and DNA damage in the liver of Largemouth bass by inhibiting the Nrf2-Keap1 signal pathway, thus affecting the health of the fish.

Effects of haloperidol on peripheral erythrocytes and brain neurotransmitter levels of juvenile African Sharptooth Catfish Clarias gariepinus

OBJECTIVE

The study investigated the effects of haloperidol on peripheral erythrocytes and brain neurotransmitter levels of juvenile African Sharptooth Catfish Clarias gariepinus.

METHODS

Juveniles were exposed to different concentrations of haloperidol (0.12, 0.24, and 0.48 mg/L) for 15 days and subsequently withdrawn from the drug for 5 days. Blood samples from the fish on days 1, 5, 10, and 15 and after the 5-day withdrawal period were analyzed for mutagenic changes, after which the fish were sacrificed. The brain was sampled for serotonergic and dopaminergic analyses.

RESULT

There was formation of micronuclei in the peripheral fish blood, which increased as the duration and concentrations of the drug increased. The drug significantly reduced the serotonin activity but increased dopamine activity. Some of the studied parameters, however, recovered from the effects of the drug after the 5-day withdrawal period.

CONCLUSION

Haloperidol is toxic to fish, and its use in the environment should be guarded to avoid adverse impacts on nontarget species like fish.

Chromium (IV) transfer to Amusium pleuronectes by LDPE microplastics: An experimental study

An experiment was carried out to investigate the potential of virgin LDPE microplastics to transfer heavy metals. Desired shapes (fibres, fragments, and films) and sizes (< 5 mm) of virgin LDPE microplastics were immersed in a known concentration (30 µg/l) of chromium (IV). These Cr-coated microplastics were introduced into a culture tank containing edible scallops (Amusium pleuronectes). After the completion of the experiment (5 days), the sediments in the culture tank and edible tissues of A. pleuronectes were tested for the presence of Cr. In the sediments, a maximum concentration of 1.934 µg/g of Cr was accumulated at a rate of R2 = 0.979, while in the tissues, the maximum accumulation concentration was 0.733 µg/g of Cr at a rate of R2 = 0.807. Energy Dispersive X-ray Spectroscopy analysis also confirmed the presence of Cr (2.61 ± 0.44 mass % and 1.80 ± 0.30 atom%) in the tissues of A. pleuronectes, which was absent in the control tissues. The study showed that when exposed to contaminants such as heavy metals, LDPE microplastics can adhere and transfer them to biotic tissues. LDPE showed the potential to transfer adhered contaminants; however, the effects caused by these transferred contaminants on biota must be studied further. Risk assessment study showed that potential ecological risk of Cr is < 40 indicating low risk however, the combined effect of Cr and LDPE can compound its toxicity which needs to be studied further.

Ecotoxicology of hexavalent chromium in fish: An updated review

Chromium (Cr) is prevalently found in trivalent and hexavalent forms. Though the former is toxicologically benign due to its poor cellular permeability, hexavalent chromium i.e. Cr [VI] crosses the biological membrane and induces toxic effects in organisms. While Cr [VI] toxicity in humans is a subject of occupational exposure at industries involved in ferrochrome production, leather tanning, textile dyeing etc., aquatic abundance of Cr [VI] due to discharge of Cr-laden effluents by these industries lead to extensive toxicity in piscine species. The present review aims to discuss the mode of Cr [VI] entry in fish and the several inimical effects that it imparts on fish health. Such effects have been reported in various studies through behavioral, hormonal and hematological alterations. Bio-accumulation of Cr [VI] in vital organs and subsequent perturbation of the oxidative homeostasis leads to organotoxic effects like changes in organo-somatic indices and histo-architecture. At cellular level, Cr [VI] induced genotoxicity is often found to trigger cellular demise including apoptosis. This review also highlights the stress response in fish against Cr [VI] induced toxicity that is mediated through the expressional alteration of a myriad of anti-oxidant and xenobiotic-metabolizing proteins which is, in turn, a function of activated transcription programs including the Nrf2-ARE pathway.

Effects of chromium (VI) on the toxicity of benzo[z]pyrene in 16HBE cells

Contamination of human habitats with complex mixtures of heavy metals and polycyclic aromatic hydrocarbons (PAHs) is an important environmental and industrial health problem. Hexavalent chromium (Cr(VI)) and benzo(a)pyrene (B[a] P) are typical of the two, respectively. In recent decades, a great deal of research has focused on their carcinogenicity and mechanisms of action. However, few studies have been conducted to evaluate their combined effects on humans and cells, which has important implications for overall understanding of their toxicity and interaction. In the current study, the combined toxic effects of B[a] P and Cr(VI) were studied in human bronchial epithelial cells (16 HBE). We measured the genotoxic activity and epigenetic changes of these two toxicants alone and in combination on these cells and analyzed the difference between their single and combined toxicity. The results showed that B[a]P caused DNA damage in 16HBE cells in a concentration-dependent manner, while the presence of Cr(VI) showed a sharp decrease in DNA damage, and it inhibited the expression of genes related to base excision repair induced by B[a]P. In addition, Cr(VI) also reduced B[a]P-triggered epigenetic changes in 16HBE cells. In conclusion, the combined effect of B[a]P and Cr(VI) on 16HBE cells was less toxic than single B[a]P exposure, indicating that the combined toxicity of the two toxicants is partially antagonistic. Further research is required to explore the mechanism of this antagonism.

Mechanism of chromium-induced toxicity in lungs, liver, and kidney and their ameliorative agents

Heavy metal Chromium (Cr), can adversely affect humans and their health if accumulated in organs of the body, such as the lungs, liver, and kidneys. Cr (VI) is highly toxic and has a higher solubility in water than Cr (III). One of the most common routes for Cr exposure is through inhalation and is associated with liver, lung, kidney damage, widespread dermatitis, GI tract damage, human lung cancer, cardiomyopathies, and cardiovascular disease. The increase in ROS production has been attributed to most of the damage caused by Cr toxicity. Cr-induced ROS-mediated oxidative stress has been seen to cause a redox imbalance affecting the antioxidant system balance in the body. The Nrf2 pathway dysregulation has been implicated in the same. Deregulation of histone acetylation and methylation has been observed, together with gene methylation in genes such as p16, MGMT, APC, hMLH1, and also miR-143 repression. Several ultra-structural changes have been observed following Cr (VI)-toxicity, including rough ER dilation, alteration in the mitochondrial membrane and nuclear membrane, pycnotic nuclei formation, and cytoplasm vacuolization. A significant change was observed in the metabolism of lipid, glucose, and the metabolism of protein after exposure to Cr. Cr-toxicity also leads to immune system dysregulations with changes seen in the expression of IL-8, IL-4, IgM, lymphocytes, and leukocytes among others. P53, as well as pro-and anti-apoptotic proteins, are involved in apoptosis. These Cr-induced damages can be alleviated via agents that restore antioxidant balance, regulate Nrf-2 levels, or increase anti-apoptotic proteins while decreasing pro-apoptotic proteins.

Effects of chronic dietary hexavalent chromium on bioaccumulation and immune responses in the sea cucumber Apostichopus japonicus

Sea cucumbers Apostichopus japonicus (3.54 ± 0.01 g of wet weight) were exposed to five concentrations of dietary hexavalent chromium (Cr⁶⁺) [0 (control), 100, 200, 400, and 800 mg Cr⁶⁺/kg dry weight] amended with K₂Cr₂O₇ for 30 days. The bioaccumulation and immune responses [antioxidant enzymes: superoxide dismutase (SOD) and catalase (CAT); hydrolytic enzymes: acid phosphatase (ACP) and alkaline phosphatase (AKP)] of sea cucumbers were subsequently evaluated. This study found that the order of Cr accumulation in the experimental tissues was respiratory tree > intestine > body wall. Significantly lower SOD activities occurred in the 400 mg/kg group compared to that in the control group. Higher dietary Cr⁶⁺ exposure (400 and 800 mg Cr⁶⁺/kg dry weight) did not negatively alter the CAT activities, but significantly inhibited CAT activities in 100 mg/kg group, compared to control group. ACP activities in groups 200, 400 and 800 mg/kg were significantly lower than those in control group, while no significant differences occurred in AKP activities among groups. The present study provides important information into the bioaccumulation and immune responses of the sea cucumber A. japonicus in response to chronic dietary Cr⁶⁺ exposure.

Heavy Metals and Probabilistic Risk Assessment via Pheretima (a Traditional Chinese Medicine) Consumption in China

Earthworms are known to accumulate inorganic contaminants from the soil; they are also used as a traditional Chinese medicine (TCM) called Pheretima, which might cause safety problems with long-term exposure. Here, this study was conducted to determine and analyze the level of heavy metal contamination such as arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), manganese (Mn), nickel (Ni), and lead (Pb) in Pheretima and then explore the probabilistic health risks caused by 8 heavy metals in 98 batches of Pheretima using Monte Carlo simulation. A risk assessment strategy was conducted to assess heavy metal-associated health risk of Pheretima based on consumption data. For random consumption sampling, the results found that the non-carcinogenic risk of As is higher than the acceptable level, and the carcinogenic risk levels of As and Cr exceeded the acceptable risk recommended by the USEPA. Cr and As were regarded as the priority metals for risk control in the present study. Finally, it was recommended that the dosing frequency should be less than 24 d/y. In general, this study conducted a probabilistic risk assessment of heavy metals in Pheretima, which would be of significance for policy makers to take effective strategies to improve the quality and safety of Pheretima.

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.

Toxicity and genotoxic evaluations in African catfish Clarias gariepinus (Burchell 1822) exposed to Act Force Gold®, Butaforce®, and Atraforce®

Act Force Gold^®, Butaforce^®, and Atraforce^® are among the most commonly used pesticides in Nigeria. The lethal concentrations and the respective toxic units for the three pesticides were determined. The genotoxic effects of the three pesticides were investigated in the red blood cells of Clarias gariepinus using micronucleus (MN) assay. The 96 h LC₅₀ was 4.75, 4.84, and 54.74 mg L^-1 for Act Force Gold^®, Butaforce^®, and Atraforce^®, respectively. The toxic units in ascending order of toxicity were 1.83, 20.66, and 21.05 for Act Force Gold^®, Butaforce^®, and Atraforce^® respectively. The estimated safe levels based on NAS/NAE varied from 4.75 × 10^-1-4.75 × 10^-5 in Act Force Gold^® through 4.64 × 10^-1-4.85 × 10^-5 in Butaforce^® to 5.74-5.74 × 10^-5 in Atraforce^®. Fish specimens were exposed to the pesticides and sampling was done at regular intervals at days 1, 7, 14, and 21 and after another 7-day recovery period. The results obtained indicated concentration- and duration-dependent increase in % MN formation with maximum values of 3.40 ± 0.25 for Act Force Gold^® on day 14 and 3.05 ± 0.36 and 2.35 ± 0.14 for Butaforce^® and Atraforce^® respectively on day 7 of exposure. The 7-day recovery period could not reverse the trend as the % MN values obtained were significantly different from the control. The results further support the use of MN assay in assessing the toxicity of aquatic pollutants and can be used in the monitoring of aquatic ecosystems.

Genotoxicity and Oxidative Stress Evaluations in Juvenile African Catfish Clarias gariepinus Exposed to NPK Fertilizer

Juvenile African Catfish (also known as Sharptooth Catfish) Clarias gariepinus were exposed to 2.26, 4.52, and 11.30 mg/L NPK (15-15-15) fertilizer for 21 d followed by 7 d of recovery to assess the genotoxic effects of the fertilizer in erythrocytes. Biomarkers of oxidative stress were evaluated in the liver and gill tissues. The fertilizer induced micronuclei formation with maximum effects on day 7 in erythrocytes of individuals that were exposed to 4.52 and 11.30 mg/L NPK, and on day 14 in individuals exposed to 2.26 mg/L of the same fertilizer. The lipid peroxidation, glutathione reductase, and reduced glutathione values in the exposed fish increased, while the values of catalase, superoxide dismutase, and glutathione peroxidase decreased. There were mixed trends in the recovery patterns after the 7-d withdrawal from the fertilizer. Careful use of the fertilizer in the field is recommended to avoid toxicological effects on nontarget organisms.

Hematological and immunological responses in the African catfish Clarias gairepinus exposed to sublethal concentrations of herbicide Ronstar®

The aim of the study was to investigate the effects of sublethal concentrations (0.3, 0.6 and 1.2 mg L^-1) of the herbicide Ronstar on the hematology and some immune parameters in Clarias gariepinus juvenile (mean weight and length 58.72 ± 2.46 g and 27.60 ± 1.62 cm, respectively). The hematological and some immune parameters were studied for 21 days in a static renewal bioassay system in which the water and the herbicide were changed daily. The erythrocyte count, hemoglobin concentration (Hb), and packed cell volume (PCV) were significantly (p < 0.05) reduced in the treatment groups. When compared with the control, there were significant (p < 0.05) leucocytosis, lymphocytosis, neutropenia and monocytopenia in the treatment groups. Both the mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV) were reduced ((p < 0.05) in the Ronstar-exposed fish. The result showed that the treated fish suffered hypochromic microcytic anemia. The total immunoglobulin and phagocytic indices (phagocytic capacity and phagocytic index) were significantly (p < 0.05) reduced in the treatment groups. while the respiratory burst was significantly (p < 0.05) increased in the treatment groups. The result showed that exposure to Ronstar had adverse effects on the hematology and immunocompetency of the fish.

Genotoxicity assessment of pesticide profenofos in freshwater fish Channa punctatus (Bloch) using comet assay and random amplified polymorphic DNA (RAPD)

The present study explored the induced genotoxicity (DNA damage) due to organophosphate pesticide profenofos (PFF) after in vivo exposure in freshwater fish Channa punctatus by the use of Comet assay and Random amplified polymorphic DNA (RAPD). The fish specimens were exposed to sub-lethal concentration of 1.16 ppb (50% of LC₅₀) in a semi-static system and the DNA damage was assessed in exposed and control fish. The DNA damage was measured in erythrocytes as the percentage of DNA damage in Comet tails and RAPD technique using oligonucleotide primers of fish specimens exposed to the sublethal concentrations of PFF. The most informative primers in terms of variation in RAPD profile were found to be OPA-01, OPA-03, OPB-02, OPB-01 and OPA-13. Appearance/disappearance of bands and increase/decrease in the band intensity were evident in the RAPD profile of fish specimens exposed to PFF as compared to the control. Findings from the present study suggest that the potential impacts of assessment of the genotoxic impact of pesticide on fish.

Diffuse sources of contamination in freshwater fish: Detecting effects through active biomonitoring and multi-biomarker approaches

Aquatic organisms are usually exposed to a mixture of xenobiotics that may exert a large effect even in low concentrations, and when information is obtained exclusively from chemical analyses the prediction of the deleterious effects is potentially hindered. Therefore, the application of complementary monitoring methods is a priority. Here, in addition to chemical analyses, an active biomonitoring study using multiple biomarker responses in Nile tilapia Oreochromis niloticus was conducted to assess the effects of a contamination gradient along four reservoirs in Iguaçu River. Chemical analysis in the muscle showed high levels of metals in fish from the reservoir closest to an industrialized and environmentally degraded area, however fish exposed to all studied reservoirs showed hepatic alterations (necrosis and inflammatory processes). Also, significant variations of biochemical biomarkers were observed with no clear indication of contamination gradient, since an indicative of higher impact was found in an intermediary reservoir, including high concentrations of biliary polycyclic aromatic hydrocarbons (PAHs). However, nuclear morphological alterations (NMA) were less frequent at the same reservoir. Thus, the multi-biomarker approach allied to active biomonitoring is a practical and important tool to assess deleterious effects of contamination in freshwater, providing data for monitoring and conservation protocols.

The impact of multiple stressors on the biomarkers response in gills and liver of freshwater breams during different seasons

Biomarkers attract increasing attention in environmental studies, as a tool for detection of exposure and effects of pollution, from both natural and anthropogenic sources. This study aims to assess the impact of multiple stressors during distinctive seasons, covering also extreme hydrological events (extensive flooding in the mid May 2014), on different levels of biological organization in the liver and gills of three closely related freshwater breams. Our previous study on DNA damage in blood cells of these specimens showed increased DNA damage in June 2014, one month after the flooding event. As a continuation of that research, the present study was conducted. As a biomarker of exposure DNA damage was measured by applying the alkaline comet assay, while histopathological alterations were monitored as a biomarker of effect. Additionally, concentrations of metals and metalloids in gills, liver and muscle were assessed. Sampling of fish tissues was performed in 2014, during winter (January and February), spring (March and early June) and summer (late June, July and August). Significant seasonal difference in DNA damage was observed for both tissues. During spring and summer the level of DNA damage in gills was significantly higher when compared to the liver. Histopathological analyses showed higher frequency of alterations in gills during spring, and in liver during summer, but without a significant seasonal difference. Gills had the highest concentration of metals and metalloids during the spring and summer, and liver during winter. Muscle was the least affected tissue during all three seasons. This study highlighted the importance of the multiple biomarker approach and the use of different fish tissues in assessment of surface water pollution.

Accumulation and detoxification dynamics of Chromium and antioxidant responses in juvenile rare minnow, Gobiocypris rarus

Hexavalent chromium (Cr⁶⁺) compounds are hazardous via all exposure routes. To explore the dynamics of Cr accumulation and elimination and to reveal the mechanisms underlying detoxification and antioxidation in juvenile Gobiocypris rarus, one-month old G. rarus larvae were exposed to 0.1mgL^-1 Cr⁶⁺ for four weeks for accumulation and subsequently placed to clean water for another week for depuration. The contents of Cr were measured weekly in the whole body of G. rarus juveniles. The activities of catalase (CAT), glutathione peroxidase (GPx), superoxide dismutase (SOD), glutathione S-transferase (GST) and glutathione reductase (GR), and contents of glutathione (GSH) and malonaldehyde (MDA), and transcripts of cat, Cu/Zn-sod, Mn-sod, gpx1, gstpi, gr, mt1, nrf2 and uba52 were determined. The results indicated that G. rarus juveniles had a strong ability to resist the Cr accumulation by Cr⁶⁺ exposure and to remove Cr from the body in clean water. In addition, GST and MT proteins may be involved in the detoxification of Cr⁶⁺. Moreover, Cr⁶⁺-induced GST detoxification in G. rarus juveniles might be accomplished through the Nrf2-mediated regulation of gene expressions. The antioxidant enzyme systems exhibited a response mechanism of the protective enzymes in organisms when they are subjected to external environmental stress. Two weeks of Cr⁶⁺ treatments could have led to the damage and consecutive degradation of antioxidant enzymes via ubiquitination, and MT proteins could be involved in protecting the activity of these enzymes. The capability of antioxidant enzyme systems to recover from the Cr⁶⁺-induced damage was strong in G. rarus juveniles after Cr⁶⁺ was removed from the water.

Evaluation of effects of melatonin and caffeic acid phenethyl ester on acute potassium dichromate toxicity and genotoxicity in rats

Objective:

The aim of this study is to investigate the possible protective effects of melatonin and caffeic acid phenethyl ester (CAPE) on potassium dichromate (K₂ Cr₂O₇)-induced nephrotoxicity and genotoxicity.

Methods:

A total of 40 Wistar albino rats were divided into five groups: control, K₂Cr₂O₇(K₂Cr₂O₇15 mg/kg, one dose, i.p.), K₂Cr₂O₇ + melatonin, K₂Cr₂O₇ + CAPE, and K₂Cr₂O₇ + melatonin + CAPE. Urine and blood samples were collected from rats before scarification. One kidney was collected for histopathological studies, and the other was stored at −80°C for further determination of catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), glutathione S-transferase (GST), and glutathione reductase (GR) levels with spectrophotometric method. Comet assay was used to evaluate the genotoxicity.

Results:

We observed a significant amelioration in genotoxicity by melatonin and simultaneous melatonin + CAPE treatment compared to K₂Cr₂O₇ group (p₁, p₂< 0.05). SOD, CAT, GSH, GST, and MDA levels did not change when compared with controls. When K₂Cr₂O₇ applied group was treated with melatonin and CAPE, neither melatonin nor CAPE made any changes in kidney GSH, GST, SOD, and MDA levels (P > 0.05). We noted that treatment with CAPE and melatonin + CAPE together caused a significant decrease in renal tissue damage, an upregulation in the kidney CAT levels (P < 0.05) and a slight healing at GR levels when compared with the K₂Cr₂O₇ group.

Conclusion:

Our results revealed, CAPE and melatonin may have protective effects on K₂Cr₂O₇ induced nephrotoxicity and cellular damage in rats.

Cytotoxic and genotoxic potential of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA complex in human hepatoma (HepG2) cells

Chromium (Cr) and ethylenediaminetetraacetate (EDTA) are common environmental pollutants and can be present in high concentrations in surface waters at the same time. Therefore, chelation of Cr with EDTA can occur and thereby stable Cr(III)-EDTA complex is formed. Since there are no literature data on Cr(III)-EDTA toxicity, the aim of our work was to evaluate and compare Cr(III)-EDTA cytotoxic and genotoxic activity with those of Cr(VI) and Cr(III)-nitrate in human hepatoma (HepG2) cell line. First the effect of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on cell viability was studied in the concentration range from 0.04 μg mL(-1) to 25 μg mL(-1) after 24 h exposure. Further the influence of non-cytotoxic concentrations of Cr(VI), Cr(III)-nitrate and Cr(III)-EDTA on DNA damage and genomic stability was determined with the comet assay and cytokinesis block micronucleus cytome assay, respectively. Cell viability was decreased only by Cr(VI) at concentrations above 1.0 μg mL(-1). Cr(VI) at ≥0.2 μg mL(-1) and Cr(III) at ≥1.0 μg mL(-1) induced DNA damage, while after Cr(III)-EDTA exposure no formation DNA strand breaks was determined. Statistically significant formation of micronuclei was induced only by Cr(VI) at ≥0.2 μg mL(-1), while no influence on the frequency of nuclear buds nor nucleoplasmic bridges was observed at any exposure. This study provides the first evidence that Cr(III)-EDTA did not induce DNA damage and had no influence on the genomic stability of HepG2 cells.

Contaminant-induced oxidative stress in fish: a mechanistic approach

The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described.

Acute and chronic effects of erythromycin exposure on oxidative stress and genotoxicity parameters of Oncorhynchus mykiss

Erythromycin (ERY) is a macrolide antibiotic used in human and veterinary medicine, and has been detected in various aquatic compartments. Recent studies have indicated that this compound can exert biological activity on non-target organisms environmentally exposed. The present study aimed to assess the toxic effects of ERY in Oncorhynchus mykiss after acute and chronic exposures. The here adopted strategy involved exposure to three levels of ERY, the first being similar to concentrations reported to occur in the wild, thus ecologically relevant. Catalase (CAT), total glutathione peroxidase (GPx), glutathione reductase (GRed) activities and lipid peroxidation (TBARS levels) were quantified as oxidative stress biomarkers in gills and liver. Genotoxic endpoints, reflecting different types of genetic damage in blood cells, were also determined, by performing analysis of genetic damage (determination of the genetic damage index, GDI, measured by comet assay) and of erythrocytic nuclear abnormalities (ENAs). The results suggest the occurrence of a mild, but significant, oxidative stress scenario in gills. For acutely exposed organisms, significant alterations were observed in CAT and GRed activities, and also in TBARS levels, which however are modifications with uncertain biological interpretation, despite indicating involvement of an oxidative effect and response. After chronic exposure, a significant decrease of CAT activity, increase of GPx activity and TBARS levels in gills was noticed. In liver, significant decrease in TBARS levels were observed in both exposures. Comet and ENAs assays indicated significant increases on genotoxic damage of O. mykiss, after erythromycin exposures. This set of data (acute and chronic) suggests that erythromycin has the potential to induce DNA strand breaks in blood cells, and demonstrate the induction of chromosome breakage and/or segregational abnormalities. Overall results indicate that both DNA damaging effects induced by erythromycin may be related to the oxidative damage observed, shown to occur at environmentally relevant concentrations of erythromycin.

Does the presence of microplastics influence the acute toxicity of chromium(VI) to early juveniles of the common goby (Pomatoschistus microps)? A study with juveniles from two wild estuarine populations

Toxicological interactions between microplastics (MP) and other environmental contaminants are of grave concern. Here, the potential influence of MP in the short-term toxicity of chromium to early juveniles of Pomatoschistus microps was investigated. Three null hypotheses were tested: (1) exposure to Cr(VI) concentrations in the low ppm range does not induce toxic effects on juveniles; (2) the presence of microplastics in the water does not influence the acute toxicity of Cr(VI) to juveniles; (3) the environmental conditions of the natural habitat where fish developed do not influence their sensitivity to Cr(VI)-induced acute stress. Fish were collected in the estuaries of Minho (M-est) and Lima (L-est) Rivers (NW Iberian Peninsula) that have several abiotic differences, including in the water and sediment concentrations of various environmental contaminants. After acclimatization to laboratory conditions, two 96h acute bioassays were carried out with juveniles from both estuaries to: (i) investigate the effects of Cr(VI) alone; (ii) investigate the effects of Cr(VI) in the presence of MP (polyethylene spheres 1-5μm ∅). Cr(VI) alone induced mortality (96h-LC50s: 14.4-30.5mg/l) and significantly decreased fish predatory performance (≤74%). Thus, in the range of concentrations tested (5.6-28.4mg/l) Cr(VI) was found to be toxic to P. microps early juveniles, therefore, we rejected hypothesis 1. Under simultaneous exposure to Cr(VI) and MP, a significant decrease of the predatory performance (≤67%) and a significant inhibition of AChE activity (≤31%) were found. AChE inhibition was not observed in the test with Cr(VI) alone and MP alone caused an AChE inhibition ≤21%. Mixture treatments containing Cr(VI) concentration ≥3.9mg/l significantly increased LPO levels in L-est fish, an effect that was not observed under Cr(VI) or MP single exposures. Thus, toxicological interactions between Cr(VI) and MP occurred, therefore, we rejected hypothesis 2. In the presence of MP, the negative effect caused by high concentrations of Cr(VI) on the predatory performance was significantly reduced in L-est fish but not in M-est fish, and Cr(VI) concentrations higher than 3.9mg/l caused oxidative damage in L-est fish but not in M-est fish. The acclimatization and test conditions were similar for fish from the two estuaries and these ecosystems have environmental differences. Thus, long-term exposure to distinct environmental conditions in the natural habitat during previous developmental phases influenced the sensitivity and responses of juveniles to Cr(VI), therefore, we rejected hypothesis 3. Overall, the results of this study indicate toxicological interactions between MP and Cr(VI) highlighting the importance of further investigating the combined effects of MP and other common contaminants.

The Comet Assay and its applications in the field of ecotoxicology: a mature tool that continues to expand its perspectives

Since Singh and colleagues, in 1988, launched to the scientific community the alkaline Single Cell Gel Electrophoresis (SCGE) protocol, or Comet Assay, its uses and applications has been increasing. The thematic areas of its current employment in the evaluation of genetic toxicity are vast, either in vitro or in vivo, both in the laboratory and in the environment, terrestrial or aquatic. It has been applied to a wide range of experimental models: bacteria, fungi, cells culture, arthropods, fishes, amphibians, reptiles, mammals, and humans. This document is intended to be a comprehensive review of what has been published to date on the field of ecotoxicology, aiming at the following main aspects: (i) to show the most relevant experimental models used as bioindicators both in the laboratory and in the field. Fishes are clearly the most adopted group, reflecting their popularity as bioindicator models, as well as a primary concern over the aquatic environment health. Amphibians are among the most sensitive organisms to environmental changes, mainly due to an early aquatic-dependent development stage and a highly permeable skin. Moreover, in the terrestrial approach, earthworms, plants or mammalians are excellent organisms to be used as experimental models for genotoxic evaluation of pollutants, complex mix of pollutants and chemicals, in both laboratory and natural environment. (ii) To review the development and modifications of the protocols used and the cell types (or tissues) used. The most recent developments concern the adoption of the enzyme linked assay (digestion with lesion-specific repair endonucleases) and prediction of the ability to repair of oxidative DNA damage, which is becoming a widespread approach, albeit challenging. For practical/technical reasons, blood is the most common choice but tissues/cells like gills, sperm cells, early larval stages, coelomocytes, liver or kidney have been also used. (iii) To highlight correlations with other biomarkers. (iv) To build a constructive criticism and summarize the needs for protocol improvements for future test applications within the field of ecotoxicology. The Comet Assay is still developing and its potential is yet underexploited in experimental models, mesocosmos or natural ecosystems.

Toxicological effects of carbosulfan in rats

Carbosulfan is often used in agriculture for pest control on crops and for treatment against pyrethroid-resistant mosquitoes. This study investigated the impact of carbosulfan on oxidative stress markers, antioxidant defense, hematological, biochemical, and enzymological parameters in Sprague Dawley rats. Rats were orally administered carbosulfan doses of 1.02 to 10.20 mg/kg body weight daily; after 96 h, blood samples were taken, and the liver, kidney, and brain were dissected out for study. Results indicate that carbosulfan significantly increased the levels of lipid peroxidation and suppressed the activity of reduced glutathione, glutathione reductase, catalase, glucose-6-phosphate dehydrogenase, and adenosine triphosphatase. A mixed trend was observed in the activity of superoxide dismutase, while an increase was observed in the levels of serum uric acid, urea, aspartate aminotransferase, and alanine aminotransferase. Hemoglobin and albumin levels decreased but no significant differences were observed in creatinine and bilirubin levels. Future studies should include a more detailed analysis of the effects of chronic carbosulfan exposure on these biomarkers to further assess the impact of the pesticide on mammalian models.

Oxidative stress and biochemical responses in the tissues of African catfish Clarias gariepinus juvenile following exposure to primextra herbicide

Primextra is a commercial herbicide formulation generally used in agriculture for weed control. The present study was designed to investigate the oxidative stress biomarkers and biochemical responses in the tissues of Clarias gariepinus juvenile exposed to primextra. Fish were exposed to 0.24 and 0.47 mgL(-1) corresponding to 1/20 and 1/10th of 96 h LC50 of the herbicide. The liver and muscle tissues were sampled on day 1, 5, 10 and 15 and results showed concentration and time dependent significant increase (p < 0.05) in the values of lipid peroxidation, glutathione peroxidase, catalase and alkaline phosphatase in both tissues. A marked significant increase (p < 0.05) was observed in the values of aspartate aminotransferase, alanine aminotransferase and glucose in the liver while a mixed trend in their values were observed in the muscle. The values of superoxide dismutase and protein in both tissues were comparable to the control except on day 15 in the liver where the values significantly declined. The condition factor was not directly affected but values of hepatosomatic index were significantly reduced. The present findings revealed that primextra induced toxic stress even at sublethal concentrations resulting in alterations of the studied parameters which were more evident in the fish liver than in the muscle tissue.