Specific expression of cytochrome P4501A1 gene in gill, intestine and liver of tilapia exposed to coastal sediments

Biomarker selection depends on gene function and organ: the case of the cytochrome P450 family genes in freshwater fish exposed to chronic pollution

Pollution and its effects have been of major concern in recent decades. Many strategies and markers have been developed to assess their effects on biota. Cytochrome P450 (CYP) genes have received significant attention in this context because of their relationship with detoxification and activation of exogenous compounds. While their expression has been identified as a pollution exposure biomarker, in most cases, it has been tested only after acute exposures and for CYP genes associated with exogenous compounds. To elucidate CYP gene expression patterns under chronic pollution exposure, we have used the silverside Basilichthys microlepidotus as a model, which inhabits the Maipo River Basin, a freshwater system with different pollution levels. We performed next-generation RNA sequencing of liver and gill tissues from polluted and non-polluted populations. We found most CYP genes were not dysregulated by pollution, and the seven genes that were present and differentially expressed in liver and gill were mainly downregulated. Three CYP genes associated with exogenous compounds showed differential expression in the gill, while four CYP genes associated with endogenous compounds showed differential expression in the liver. The findings presented here highlight the importance of CYP genes, his family, tissues and his interaction in the context of pollution biomarkers use.

Lingering Effects of Legacy Industrial Pollution on Yellow Perch of the Detroit River

We used yellow perch (Perca flavescens) captured at four sites differing in legacy industrial pollution in the Lake St. Clair-Detroit River system to evaluate the lingering sublethal effects of industrial pollution. We emphasized bioindicators of direct (toxicity) and indirect (chronic stress, impoverished food web) effects on somatic and organ-specific growth (brain, gut, liver, heart ventricle, gonad). Our results show that higher sediment levels of industrial contaminants at the most downstream Detroit River site (Trenton Channel) are associated with increased perch liver detoxification activity and liver size, reduced brain size, and reduced scale cortisol content. Trenton Channel also displayed food web disruption, where adult perch occupied lower trophic positions than forage fish. Somatic growth and relative gut size were lower in perch sampled at the reference site in Lake St. Clair (Mitchell's Bay), possibly because of increased competition for resources. Models used to determine the factors contributing to site differences in organ growth suggest that the lingering effects of industrial pollution are best explained by trophic disruption. Thus, bioindicators of fish trophic ecology may prove advantageous to assess the health of aquatic ecosystems. Environ Toxicol Chem 2023;42:2158-2170. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

DNA Damage and Repair in different Tissues of Fresh Water Fish, <i>Channa punctata</i> after Acute and Subchronic Exposure to bisphenol A

The present study was conducted to investigate the genotoxic effect of Bis-Phenol A (BPA) after acute and subchronic exposure in different tissues of Channa punctata. The recovery in DNA damage was also ascertained after 30 days of cessation of exposure. Fish were exposed to different sublethal concentrations of BPA along with two controls i.e., with positive (acetone) and negative (water) controls for 96h (acute exposure) and 60 days (subchronic exposure) and after that fish were allowed to recover for 30 days in freshwater. The blood, liver, and gill tissue samples were collected at 24, 48, 72 and 96h for acute exposure and after 20, 40, and 60 days post-exposure for subchronic exposure. Exposed groups showed significantly higher DNA damage in both acute and subchronic exposure as compared to control groups. In the case of acute exposure, the highest damage was observed at 24 h of exposure followed by a decline in the value of all the parameters, while in the later hours of exposure these values further increased. On the other hand, in the case of sub-chronic exposure, the highest damage was observed after 60 days of exposure. Recovery experiment showed a decrease in the values of all the parameters studied. The result of the study clearly showed that BPA caused DNA damage in Channa punctata after acute as well as subchronic exposure.

Malathion-Induced Hematoxicity and Its Recovery Pattern in Barbonymus gonionotus

An experiment was conducted to assess malathion-induced hematological responses of Barbonymus gonionotus (silver barb) and its recovery patterns in malathion-free water. Fish (45 days old) were exposed to two sublethal concentrations, namely, 25% and 50% (i.e., 3.78 and 7.56 ppm) of LC₅₀ (15.13 ppm) of malathion for 28 days, followed by a postexposure recovery period for the same time. The hematological parameters were examined after 1, 7, 14, 21, and 28 days of exposure as well as after the postexposure recovery time. Except in the case of the control group (0% of malathion), the obtained results revealed that malathion exposure resulted in significantly (p < 0.05) higher prevalence and severity of micronucleus and lower values of Hb, PCV, and RBC and significantly higher values of WBC in a concentration- and time-dependent manner. The values of blood glucose, MCV, MCH, and MCHC showed mixed trends during the experiment. During the recovery period, all blood parameters (micronucleus, glucose, Hb, PCV, RBC, WBC, MCV, MCH, and MCHC) partially recovered, which means that the recovery period was not long enough for the organisms to recover from the previous exposure. The study thus confirms that hematology is a sensitive indicator for fish to detect toxicity caused by different chemicals. Changes in these parameters can provide useful information about environmental conditions and risk assessment of aquatic organisms.

Bisphenol A induced toxicity in blood cells of freshwater fish Channa punctatus after acute exposure

The widespread use of bisphenol A (BPA) has led to its ubiquity in the natural environment. It is extensively incorporated into different industrial products and is associated with deleterious health effects on both public and wildlife. The current trial was conducted to determine the toxic potential of bisphenol A using various parameters viz haematological, biochemical, and cytological in freshwater fish Channa punctatus. For this purpose, fish were exposed to 1.81 mg/l (1/4 of LC₅₀) and 3.81 mg/l (1/2 of LC₅₀) of BPA along with positive (acetone) and negative controls (water) for 96 h. The blood samples were collected at 24, 48, 72, and 96 h post-exposure. Compared to the control group, fish after acute exposure to BPA showed a significant decrease in HB content, number of red blood cells, PCV values whereas a significant increase in WBCs count was recorded with an increase in the exposure period. Besides, oxidative stress (determined as malondialdehyde content) increased as BPA concentration increased. Further, the activity of different antioxidant enzymes like catalase, and superoxide dismutase decreased significantly after treatment. Results also showed significantly increased frequency of morphological alterations, nuclear changes, and increased DNA damage potential of BPA in red blood cells. Further structural analysis of erythrocytes in maximally damaged group using Scanning Electron Microscopy was performed. The study concludes that BPA exhibits genotoxic activity and oxidative stress could be one of the mechanisms leading to genetic toxicity.

Distortion of micronuclei and other peripheral erythrocytes caused by fenitrothion and their recovery assemblage in zebrafish

The experiment was explicated to investigate the fenitrothion persuaded genotoxicity in the peripheral erythrocytes of zebrafish (Danio rerio) through in vivo exposures (10 %, 20 % and 40 % of LC50 of fenitrothion, i.e., 0.8, 1.6, and 3.2 mg/L, respectively) for variable periods (1, 3, and 7 days) and its subsequent post-exposure recuperation array in pesticide-free water for similar intervals was also evaluated. With the exception of the control group (0% of fenitrothion), the obtained results pointed out that with the promotion of time and concentrations, fenitrothion induced significantly (p < 0.05) higher prevalence and severity of erythrocytic nuclear abnormalities (ENA) such as- notched, micronucleus, nuclear bridges, blebbed, binucleated, nuclear bud and also erythrocytic cellular abnormalities (ECA) such as - echinocytic, elongated, tear-drop, crescentic, twin, fusion, and spindle-shaped cells. Recuperation data stated that zebrafish cured spontaneously and aberrated erythrocytic anomalies in all treatments were renormalized according to the concentration and duration dependence. Hence, we concluded that fenitrothion has a dangerous effect on the zebrafish, and this technology can be used to anticipate the sensitivity of aquatic animals to environmental pollution.

Naphthalene-2-sulfonate induced toxicity in blood cells of freshwater fish Channa punctatus using comet assay, micronucleus assay and ATIR-FTIR approach

Present inquisition was undertaken to evaluate the genotoxicity of naphthalene-2-sulfonate (2NS), a sulfonated aromatic compound and a momentous intermediate involved in the synthesis of dyes and surfactants, in fresh water fish, Channa punctatus. After LC₅₀ determination, two sublethal concentrations i.e. 2.38 g/15 g b.w. (1/4 of LC₅₀) and 4.77 g/15 g b.w. (1/2 of LC₅₀) were selected for studying acute exposure. For evaluating sub chronic exposure 1/10th (0.238 g/L) and 1/20th (0.119 g/L) of safe application rate (SAR) were reckoned. Blood samples were collected after 24, 48, 72, and 96 h exposure period to study acute effect, and after 30 and 60 days exposure period for sub-chronic effect. Symbolic elevation in time and dose dependent DNA damage was observed by comet assay as well as micronucleus test revealing maximum damage after 60 days of exposure. After cessation of exposure to 2NS, evident recovery was observed after 30 days. Along with comet assay and micronucleus test, spectroscopic evaluation of DNA damage was also noted using Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR). The biomolecular range (800 cm^-1 - 1800cm-¹) in lyophilized red blood cell's extracted from 60 days exposed as well as control group exhibit significant alterations in their nucleic acid indicated through multivariate analysis i.e. Principal Component Analysis (PCA). Further structural analysis of erythrocytes in maximally damaged group using Scanning Electron Microscopy was performed. Thus the study proposed the genotoxic impact of 2NS which is further supported by other toxicity markers like ATR-FTIR and Scanning Electron Microscopy.

Toxic effect of some heavy metals on hematology and histopathology of major carp (Catla catla)

The current study was conducted to assess the hematological and histopathological changes in major carp (Catla catla) exposed to different concentrations of copper (Cu) and cadmium (Cd). For this purpose, Catla catla fish, weighing approximately 230-235 g, were randomly divided into four groups and then exposed to acute doses of Cu (1.25 ppm), Cd (4.5 ppm), and their mixture (2.25 ppm) for 96 h and then 20, 30, and 40% respectively for a period of 30 days. Results showed that red blood cells (RBCs), hemoglobin (Hb), hematocrit (Hct), lymphocyte, and monocyte decreased significantly, while the total white blood cell count and neutrophil population significantly increased in experimental groups as compared with the control one. Histopathological examination of liver tissues showed karyorrhexis, hepatic cells degeneration, congestion, and hemorrhages. Microscopic analysis of gills' sections revealed lamellar atrophy, telangiectasia, and necrosis of lamellar epithelial cells. In the kidneys, different histopathological ailments like atrophy of glomeruli, necrosis of renal tubular cells, increased urinary spaces, degeneration of renal tubules, and melanomacrophage aggregates were observed, while in the intestine, atrophy of villi, sloughing of epithelial villi, and congestion were seen after 30 days of exposure. In conclusion, the study indicates that exposure to Cu and Cd for longer period of time causes adverse hematological and histopathological changes in Catla catla fish.

Cloning and characterization of estrogen hydroxylase (cyp1a1 and cyp1b1) genes in the stinging catfish Heteropneustes fossilis and induction of mRNA expression during final oocyte maturation

Estrogen hydroxylases (EHs) are cytochrome P450 Family 1 (Cyp1, Clan 2) proteins involved in estrogen hydroxylations at 2-, 4- or 16- carbon positions to form catecholestrogens. EHs are encoded by CYP1A1, CYP1A2 and CYP1B1 in mammals. In the catfish Heteropneustes fossilis, cyp1a1 and cyp1b1 cDNAs were cloned and characterized from liver and ovary. The cyp1a1 cDNA is 2071 bp long and codes for a 518 amino acids (aa) long protein. The cloned cyp1b1 cDNA is 1927 bp long and codes for a 509 residue protein. The deduced proteins clustered distinctly into teleost Cyp1a1 and Cyp1b1 clades, distinct from the tetrapod clusters and featured common function domains and homology with other teleost proteins. In the qPCR assay, the transcripts were the most abundant in the liver, followed by brain and ovary, and moderate in gill, kidney and muscle. Evidence was presented to show the involvement of the genes in reproduction. Expression of brain and ovarian transcripts showed significant seasonal variations with the highest abundance in the spawning phase. In situ hybridization showed the transcripts in the follicular layer (theca and granulosa) of the ovarian follicles. Periovulatory changes in the expression cyp1a1 and cyp1b1 were obtained during final oocyte maturation (FOM) and ovulation induced by human chorionic gonadotropin (hCG), both in vivo and in vitro, and by 2-hydroxyestradiol-17β (catecholestrogen) in vitro. In the brain, the transcript levels increased with time but in the ovary, the increase was maximal at 16 h and decreased at 24 h. The periovulatory activation of the cyp1 genes was reported in this study and discussed on the basis of complex regulation of FOM and ovulation.

Oxidative stress and genotoxicity of co-exposure to chlorpyrifos and aflatoxin B1 in HepG2 cells

Chlorpyrifos (CPF) and aflatoxin B₁ (AFB₁) are each known to adversely affect hepatic tissue individually, but their combined hepatic effects have never been previously investigated. HepG2 cell viability, oxidative status, and genetic impairment were examined after exposing HepG2 cells to: (1) CPF alone, (2) AFB₁ alone, and (3) CPF and AFB₁ combined (20:1). CPF exposure decreased cell viability, reduced glutathione (GSH) content, and superoxide dismutase (SOD) activity but increased both glutathione peroxidase (GPx) and paraoxonase 1 activity. AFB₁ exposure decreased cell viability and GSH content but increased reactive oxygen species (ROS) production. CPF and AFB₁ combined exposure decreased GSH content (p < 0.05) further over individual CPF and AFB₁ exposures. Induction of micronucleus formation was detected in AFB₁-treated cells but undetected in both CPF and combination-treated cells. In conclusion, cytotoxic effects caused by combined exposure were antagonistic, as shown by a combination index value of 1.67. Although no change in ROS production was observed in CPF groups, the overall results confirmed the occurrence of oxidative stress through the alterations of GSH content, GPx, and SOD activity. Only intracellular GSH was evidently changed upon exposure to CPF and AFB₁ combined. Thus, this study suggested cellular GSH as a potential indicator for detecting the combined effects of CPF and AFB₁ in HepG2 cells, the detection of which could be adapted to estimate the potential toxicity of additional multiple toxicant exposures.

Bioaccumulation and toxicity of 2-naphthalene sulfonate: an intermediate compound used in textile industry

The aromatic compounds substituted with sulfonate groups, being xenobiotic, resist biodegradation in the environment and tend to accumulate up to toxic levels. The hydrophilic sulfonated group makes these compounds highly water soluble and they tend to pass through water-treatment plants. The release of untreated effluents from these industries results in pollution of water bodies affecting aquatic fauna. Thus, the toxicity regarding these compounds is of major concern. The 2-naphthalene sulfonate is a sulfonated aromatic compound being widely used in textile industries. Being non-biodegradable concern regarding its toxicity has risen. Thus in the light of above facts, the present study was undertaken to determine the toxicity of 2-naphthalene sulfonate in blood cells of Channa punctatus. For this, LD₅₀ was determined and after selection of sublethal doses oxidative stress, genotoxicity and bioaccumulation were studied. For oxidative stress determination, biochemical markers such as malondialdehyde content and activities of superoxide dismutase, catalase, and glutathione-S-transferase were studied. Genotoxicity was studied using comet and micronucleus assay. Significant increase in oxidative stress and DNA damage in the exposed groups as compared to control group (P ≤ 0.05) was observed till 96 h. However, decreased values of all the studied parameters at 720 h (30 days) indicate repair capacity of fish. Further, the bio accumulative potential of 2-naphthalene sulfonate was assessed in blood plasma using high-performance liquid chromatography. The study revealed the toxic potential of 2-naphthalene sulfonate to aquatic organisms thus stressed on the need for the implementation of stringent policies regarding the management of such toxic compounds.

Significance of the goby Zosterisessor ophiocephalus as a sentinel species for Venice Lagoon contamination: Combining biomarker responses and bioaccumulation

The Venice Lagoon is an interesting example of an ecosystem suffering for a considerable anthropogenic impact, resulting in high concentrations of persistent organic pollutants (POPs) in lagoon sediments and seafood. In this context, biomonitoring is a crucially important task. The present study aimed at evaluating the validity of a multiple biomarker approach in a benthic fish species. A total of 567 Zosterisessor ophiocephalus (Gobiidae) fish were collected in spring and autumn from three areas of Venice Lagoon (Porto Marghera, Val di Brenta, and Cà Roman) showing high, intermediate and low amounts of POPs, respectively. Aryl hydrocarbon receptor (AHR) and cytochrome P450 1A (CYP1A) mRNA levels, CYP1A protein amount and ethoxyresorufin O-deethylase activity (EROD) were measured in pooled liver and gills (mRNA levels only). Such biological data were then compared with polychlorinated biphenyls (PCBs) residues, measured in grass goby muscle by gas chromatography. Aryl hydrocarbon receptor and CYP1A mRNAs, protein and EROD were upregulated in accordance with PCB amounts measured in Z. ophiocephalus muscles. In fact, the highest AHR and CYP1A induction was observed in fish sampled in close proximity of the industrial area of Porto Marghera. Overall, the present study confirm the grass goby as a reliable sentinel species for Venice Lagoon, and AHR/CYP1A/EROD as a sensitive set of biomarkers of exposure for AHR ligands.

A Novel Discovery: Holistic Efficacy at the Special Organ Level of Pungent Flavored Compounds from Pungent Traditional Chinese Medicine

Pungent traditional Chinese medicines (TCMs) play a vital role in the clinical treatment of hepatobiliary disease, gastrointestinal diseases, cardiovascular diseases, diabetes, skin diseases and so on. Pungent TCMs have a vastness of pungent flavored (with pungent taste or smell) compounds. To elucidate the molecular mechanism of pungent flavored compounds in treating cardiovascular diseases (CVDs) and liver diseases, five pungent TCMs with the action of blood-activating and stasis-resolving (BASR) were selected. Here, an integrated systems pharmacology approach is presented for illustrating the molecular correlations between pungent flavored compounds and their holistic efficacy at the special organ level. First, we identified target proteins that are associated with pungent flavored compounds and found that these targets were functionally related to CVDs and liver diseases. Then, based on the phenotype that directly links human genes to the body parts they affect, we clustered target modules associated with pungent flavored compounds into liver and heart organs. We applied systems-based analysis to introduce a pungent flavored compound-target-pathway-organ network that clarifies mechanisms of pungent substances treating cardiovascular diseases and liver diseases by acting on the heart/liver organ. The systems pharmacology also suggests a novel systematic strategy for rational drug development from pungent TCMs in treating cardiovascular disease and associated liver diseases.

Genotoxicity of spent pot liner as determined with the zebrafish (Danio rerio) experimental model

Spent pot liner (SPL) is a solid waste generated during the primary smelting of aluminum, and its toxicity is attributed to the presence of fluoride, cyanide, and aluminum salts, which can be leached into aquatic ecosystems. Since the effects of this waste on aquatic life forms have not yet been investigated, the objective of our study was to evaluate the toxicity of simulated leachates of SPL on zebrafish (Danio rerio). Animals were exposed to 0 (control), 0.32, 0.64, or 0.95 g L^-1 of SPL for 24, 72, and 96 h, and genotoxicity was accessed through micronucleus and comet assays. All of the tested treatments induced DNA fragmentation, and the observed frequency of micronuclei and damaged nucleoids generally increased with increasing SPL concentration. The highest frequency of micronuclei (3.3 per 3000 erythrocytes) was detected after 96 h of exposure with 0.95 g L^-1 SPL. In the comet assay, nucleoids classified with highest level of damage in relation to the control were observed principally after 24 and 96 h of exposure. The data obtained in this study confirm the genotoxicaction and mutagenic potential of SPL and indicate that open-air deposits of the waste material could represent a health risk to humans and ecosystems alike.

Widely used non-ionic surfactant 4-nonylphenol: showing genotoxic effects in various tissues of Channa punctatus

The present study investigated the intertissue differences in genotoxicity induction in the fish, Channa punctatus, in response to 4-nonylphenol. The lethal concentration of 50 (LC₅₀) was estimated using a semi-static system. Fish were subjected to three sublethal concentrations of 4-nonylphenol (NP) for 24, 48, 72, and 96 h. Liver, gill, and kidney tissues were analyzed, and the genotoxicity was estimated using the micronucleus test and the comet assay. The frequency of micronucleated cells (MNCs), binucleated cells (BNCs), aberrant cells, and tail moment (TM) increased significantly. The time for maximum induction of genotoxicity for all the parameters considered in the micronucleus assay was 72 h of exposure, whereas the TM was highest at 24 h of exposure followed by a decline. The gill and liver showed higher genotoxicity than kidney tissue demonstrating organ-specific susceptibilities to NP in fish C. punctatus.

Effect of water accommodated fraction of 0# diesel oil and crude oil on EROD activity of liver of Sparus macrocephlus and its mRNA expression

We studied the effect of water accommodated fractions (WAF) of 0# diesel and crude oil on ethoxy resorufin o-deethylase (EROD) activity and CYP1A1 mRNA expression quantity in the liver of Sparus macrocephlus. We found that there were some differences in the EROD activity and CYP1A1 mRNA induction between these two petroleum hydrocarbons. Both the EROD activity and CYP1A1 mRNA expression of fish exposed to 0# diesel WAF were higher than those of crude oil WAF fish. The EROD activities and CYP1A1 mRNA expressions in the livers 0# diesel WAF exposed group declined faster than those of crude oil WAF and the recovery of EROD activity and CYP1A1 mRNA expression in the crude oil group was higher than that of 0# diesel group.

Effects of salinity on metal uptake and metallothionein mRNA levels in the organs of tilapia exposed to cadmium, copper, and zinc ions

This study aimed to determine the effects of salinity on metal uptake and metallothionein (MT) mRNA levels in tilapia exposed to three metal ions. Male Oreochromis niloticus × O. aureus juveniles (hereafter, "tilapia") were exposed to various concentrations (100, 500, and 1 ppm) of metal ions (Cd(2+), Cu(2+) and Zn(2+)) in freshwater and water with two levels of salinity (10 and 20 ppt) for 7 days. Tests were then performed to investigate the effects of salinity on metal concentrations and MT mRNA induction in the test subjects' organs. Saline decreased cadmium (Cd) uptake and MT mRNA fold induction in various internal organs, but it did not enhance MT mRNA induction in the gills. Exposure to Cu(2+) caused greater copper (Cu) levels in the brains, intestines and livers, but Cu uptake in the intestines and kidneys occurred only at 10 ppm. MT mRNA induction caused by Cu(2+) was observed in various internal organs, but it occurred in the gills only at greater levels of salinity. Exposure at greater salinities also decreased zinc (Zn) uptake and MT mRNA induction in all organs except the gills. Although greater salinity decreased Cd and Zn uptake, the metal content in the water correlated with the MT mRNA levels in most of the organs, except for the intestines. In conclusion, metal accumulations in the livers and kidneys of tilapia correlated with MT mRNA levels. The levels of MT mRNA in the livers and kidneys of tilapia might therefore be used as biomarkers of exposure to Cd(2+), Cu(2+) and Zn(2+) in water of various salinities.

Cytogenotoxicity assessment of monocrotophos and butachlor at single and combined chronic exposures in the fish Catla catla (Hamilton)

Cytogenotoxic effects in the form of micronuclei and deformed nucleus, nuclear buds, binucleated cells, vacuolated nucleus, vacuolated cytoplasm, echinocytes, and enucleus induced by two compounds belonging to two different chemical classes of agrochemicals (monocrotophos and butachlor) at sublethal concentrations (0.625, 1.3, and 2.3 ppm and 0.016, 0.032, and 0.064 ppm) in single and combined chronic exposures were studied under laboratory conditions for a period of 35 days in the economically important Indian fish Catla catla. Statistically significant duration-dependent increases in the frequencies of micronucleus (MN) and other cytological anomalies were observed. Compared to single exposures, a twofold increase in micronuclei frequency was noted at combined exposures indicating the synergistic phenomenon. Binucleated and enucleated cells appeared only in fishes exposed to sublethal concentrations of butachlor. The present study is the first of its kind in exploring a significant positive correlation between micronuclei and other nuclear anomalies suggesting them as new possible biomarkers of genotoxicity after agrochemical exposures. The study highlights the sensitivity of the assay in exploring various predictive biomarkers of genotoxic and cytotoxic events and also elicits the synergistic effects of agrochemicals in apparently healthy fishes. C. catla can be considered as a suitable aquatic biomonitoring sentinel species of contaminated water bodies.

Evaluation of γ-radiation-induced DNA damage in two species of bivalves and their relative sensitivity using comet assay

Ionizing radiation is known to induce genetic damage in diverse groups of organisms. Under accidental situations, large quantities of radioactive elements get released into the environment and radiation emitted from these radionuclides may adversely affect both the man and the non-human biota. The present study is aimed (a) to know the genotoxic effect of gamma radiation on aquatic fauna employing two species of selected bivalves, (b) to evaluate the possible use of 'Comet assay' for detecting genetic damage in haemocytes of bivalves as a biomarker for environmental biomonitoring and also (c) to compare the relative sensitivity of two species of bivalves viz. Paphia malabarica and Meretrix casta to gamma radiation. The comet assays was optimized and validated using different concentrations (18, 32 and 56 mg/L) of ethyl methanesulfonate (EMS), a direct-acting reference genotoxic agent, to which the bivalves were exposed for various times (24, 48 and 72 h). Bivalves were irradiated (single acute exposure) with 5 different doses (viz. 2, 4, 6, 8 and 10 Gy) of gamma radiation and their genotoxic effects on the haemocytes were studied using the comet assay. Haemolymph was collected from the adductor muscle at 24, 48 and 72 h of both EMS-exposed and irradiated bivalves and comet assay was carried out using standard protocol. A significant increase in DNA damage was observed as indicated by an increase in % tail DNA damage at different concentrations of EMS and all the doses of gamma radiation as compared to controls in both bivalve species. This showed a dose-dependent increase of genetic damage induced in bivalves by EMS as well as gamma radiation. Further, the highest DNA damage was observed at 24h. The damage gradually decreased with time, i.e. was smaller at 48 and 72 h than at 24h post irradiation in both species of bivalves. This may indicate repair of the damaged DNA and/or loss of heavily damaged cells as the post irradiation time advanced. The present study reveals that gamma radiation induces single strand breaks in DNA as measured by alkaline comet assay in bivalves and comet assay serves as a sensitive and rapid method to detect genotoxicity of gamma radiation. This study further indicates that both M. casta and P. malabarica exhibit almost identical sensitivity to gamma radiation as measured by DNA damage.

Optimization of recovery patterns in common carp exposed to roundup using response surface methodology: evaluation of neurotoxicity and genotoxicity effects and biochemical parameters

The present study is the first report on optimization of recovery conditions of fishes exposed to pesticides using response surface methodology-central composite rotatable design (RSM-CCRD). The sub-lethal toxicity bioassay of Roundup® (2 ppm ~10 percent LC₅₀, 96 h) in common carp (1, 4, 9, 16, 25, 35 and 40 day) was investigated. After exposure for 16 days to Roundup®, some the fishes were introduced to herbicide-free water. The effects of four recovery parameters including time (5-25 d), temperature (18-26 °C), water exchange rate (WER, 10-30), and salinity (0-8 ppt) on the levels of biomarkers of genotoxicity (DNA damage), neurotoxicity (acetylcholinesterase activity (AChE)), and the serum alanine (ALT) and aspartate (AST) aminotransferase in plasma were studied. The polynomial equations were significantly fitted for all response variables with high R² values (>0.95), which revealed no indication of lack of fit. The optimum conditions for the maximum AChE activity (37.14 nmol/min/mg protein) and the minimum levels of DNA damage (8.00 percent tail DNA), ALT (27.0 IU/L) and AST (91.0 IU/L) were time of 20 d, temperature of 20 °C, WER of 25 and water salinity of 6 ppt. Thus, a promising improvement for the recovery trend of fishes exposed to Roundup® stress was obtained under the optimized conditions using RSM-CCRD.

Chromium (VI) induced acute toxicity and genotoxicity in freshwater stinging catfish, Heteropneustes fossilis

Acute toxicity and genotoxicity of Chromium(VI) as K2Cr2O7 were evaluated in freshwater stinging catfish, Heteropneustes fossilis. Fish showed behavioral alterations after K2Cr2O7 exposure and 96h-LC50 was 35.724mg/L in semi-static bioassay. Fish were exposed to three sub-lethal concentrations (concentration I=1/4th of 96h-LC50, concentration II=1/10th of 96h-LC50 and concentration III=environmental concentration of Cr reported in the river Buriganga). Blood, liver and gill samples were collected after 48h, 96h and 192h. Micronucleus (MN) assay was conducted in blood erythrocytes and DNA damage was evaluated by comet assay in whole blood, gill and liver tissues. Cr(VI) significantly (p<0.05) induced MN frequency and tail DNA (percent) which increased in a concentration depended manner in all types of tissues. Frequency of MN and tail DNA (percent) increased after 48 and 96h of exposure which decreased after 192h of exposure. The liver was the most sensitive to chromium (VI) exposure among the tissues with highest tail DNA (33.70±0.68 percent) at 9.0mg/L after 96h. This study found MN and comet assays in combination as an adequate approach for ecotoxicological monitoring and Cr(VI) as potential genotoxic agent.

Bile benzo[a]pyrene concentration and hepatic CYP1A induction in hypoxic adult tilapia (Oreochromis niloticus)

Aquatic hypoxia is a seasonal condition in some coastal and continental wetlands where co-exposure with polycyclic aromatic hydrocarbons (PAHs) pollution may be detrimental to the biota. In the present study, adult tilapia, an euryoxic fish of high economic importance, were intraperitoneally injected with benzo[a]pyrene (BaP) (20 mg kg(-1)) and then exposed to graded hypoxia to assess combined effects on some detoxification and fitness parameters. Seventy-two hours after a stepped decrease in dissolved oxygen (<2 mg L(-1)), BaP treatment resulted in a significant diminution on the biliary BaP concentration (70% of normoxic group) and an increase in blood glucose levels (2.17-fold compared with normoxic group). These effects returned to control values in the following 48 h of hypoxia exposure. BaP-induced CYP1A mRNA levels were unaffected by hypoxia, suggesting that reduced bile BaP concentration may be related with effects on protein amount or enzyme activities. LDH mRNA levels, blood lactate and hematocrit remained without change, suggesting no extreme detrimental effects for tilapia in the short-term of the BaP-hypoxia challenge. Our results indicate that BaP treatment and hypoxia targeted glucose metabolism and biliary BaP elimination, probably by favoring the storage of BaP in tilapia tissues.

Assessing the genotoxic potentials of arsenic in tilapia (Oreochromis mossambicus) using alkaline comet assay and micronucleus test

This experiment was conducted to study the genotoxic potentials of sodium arsenite (NaAsO(2)) in freshwater fish Oreochromis mossambicus by using alkaline comet assay and micronucleus (MN) test. Fish were exposed to three different concentrations (3 ppm, 28 ppm and 56 ppm) of arsenic and gill, liver and blood tissue samples were collected after 48 h, 96 h and 192 h of exposure. Arsenic exposure induced DNA damage in all tissues examined in a concentration dependent manner. A significant (p<0.05) increase in the comet tail DNA (%) of the exposed fish liver, gill, and blood was observed after 48 h and 96 h of exposure, but a decline in DNA damage was recorded in all the tissues at all the three concentrations studied after 192 h of exposure. Liver tissue exhibited significantly (p<0.05) higher DNA damage at all the concentrations examined, followed by gill and blood. Higher liver tail DNA (51.38 ± 0.21%) refers that it is more prone to injury to arsenic toxicity than the gill and blood. In blood samples arsenic induced micronucleus formation in a concentration dependent manner and highest (5.8 ± 0.46%) value was recorded in 56 ppm after 96 h of exposure, whereas, it was decreased after 192 h of exposure at all the three concentrations of NaAsO(2) examined which refers to the DNA repairing ability of fish to arsenic toxicity. The results of this study depict the genotoxic potentials of arsenic to fish which in turns provide insight on advanced study in aquatic toxicology.

Investigation of the genotoxicity of malathion to freshwater teleost fish Channa punctatus (Bloch) using the micronucleus test and comet assay

Malathion [S-(1,2-dicarboethoxyethyl) O, O-dimethyl phosphorodithioate] is a widely used organophosphorus insecticide throughout the world. However, limited efforts have made to study its genotoxic effect in different fish tissues. The present investigation was aimed to assess the genotoxic potential of the pesticide to the freshwater teleost fish Channa punctatus at sublethal concentrations using the micronucleus test and comet assay. Initially, the 96-h LC50 value of commercial-grade malathion (50% EC) was determined as 5.93 ppm in a semistatic system. Based on LC50, three test concentrations (viz. sublethal I, sublethal II, and sublethal III) were determined to be 1.48, 0.74, and 0.59 ppm, respectively, and the fish specimens were exposed to these concentrations. Tissue samplings were done on days 0, 1, 3, 7, 15, 22 and 29 of malathion exposure for assessment of the induction of micronuclei (MN) frequency and DNA damage. The MN formation in the peripheral blood cells was found to be significantly higher (p < 0.05) in the treated specimens at all sampling intervals compared to the control. The MN frequency reached maximum on days 3 and 7 at sublethal I and II concentrations, respectively, followed by a nonlinear decline with the progression of the experiment. Similarly, significant effects (p < 0.05) of both concentration and time of exposure were observed on DNA damage in the gill, kidney, and lymphocytes. All of the tissues exhibited a concentration-dependent increase in DNA damage up to day 3, followed by a nonlinear decrease with the duration of exposure. A comparison of the extent of DNA damage among the tissues showed the sensitivity of gill tissue to malathion.

Molecular cloning of CYP1A gene and its expression by benzo(a)pyrene from goldfish (Carassius auratus)

We cloned and sequenced the cytochrome P450 1A (CYP1A) gene from goldfish (Carassius auratus). It has a 1581 bp open reading frame that encodes a 526 amino acid protein with a theoretical molecular weight of 59.02 kDa. The CYP1A amino acid sequence clusters in a monophyletic group with other fish CYP1As, and more closely related to zebrafish CYP1A (91% identity) than to other fish CYP1As. Exposure to benzo(a)pyrene (BaP) by intraperitoneal injection increased biliary BaP metabolites and liver CYP1A gene expression. BaP exposure also increased CYP1A gene expression in extrahepatic organs, including intestine, and gill, which are sensitive to aqueous and dietary exposure to Arylhydrocarbon receptor (AhR) agonists. Therefore, goldfish CYP1A identified in this study offers basic information for further research related to biomarker use of CYP1A of goldfish.

Effects of contaminated sediment from Cork Harbour, Ireland on the cytochrome P450 system of turbot

Hatchery-reared juvenile turbot (Scophthalmus maximus L.) were exposed for 3 weeks, under laboratory conditions, to inter-tidal sediments collected from polluted sites in Cork Harbour (Whitegate and Agahda) and a reference site at Ballymacoda Co., Cork, Ireland. The potential of the sediment exposure to induce cytochrome P450 activities and CYP1A1 in the fish was assessed. Chemical analysis revealed that the sediments originating from the reference and harbour sites were contaminated principally with PAHs-the harbour sites having double the levels of those at the reference site. Following 3 weeks exposure to the sediments western blotting demonstrated a strong immunogenic response for CYP1A1 in the liver, but not for gill or intestine. P450 activities were generally significantly higher than those exposed to reference site sediment. Liver was the most responsive tissue with significantly greater P450 activities compared with gill and intestinal tissues.

Long-term genotoxic effect of monocrotophos in different tissues of freshwater fish Channa punctatus (Bloch) using alkaline single cell gel electrophoresis

Monocrotophos, commonly known as azodrin, is one of the organophosphate pesticides extensively used in agricultural practices throughout the world. However, little information is available on its long-term genotoxic effects in different tissues of fish using genotoxicity biomarkers. The objective of the present study was to detect DNA damage, induced by monocrotophos in freshwater teleost fish Channa punctatus using the comet assay. The LC(50)-96 h value of technical-grade monocrotophos was estimated for the fish species in a semi-static system. On the basis of the LC(50) value, the sublethal and nonlethal concentrations were determined. The DNA damage was measured in the gill, kidney and lymphocytes as the percentage of DNA in comet tails of fish exposed to different sublethal and nonlethal concentrations of monocrotophos. In general, significant effects (P<0.01) from both concentration and time of exposure were observed in exposed fish. It was found that the tissues at all concentrations exhibited the highest DNA damage on day 4, after which there was a decline in percentage tail DNA. The comparison of DNA damage among tissues at different concentrations indicated that the gill cells were more sensitive to the pesticide than the kidney cells and lymphocytes. This study also explored the utility of the comet assay for in vivo laboratory studies using fish for screening the genotoxic potential of various agents.

Development of a marine fish model for studying in vivo molecular responses in ecotoxicology

A protocol for fixation and processing of whole adult marine medaka (Oryzias melastigma) was developed in parallel with in situ hybridization (ISH) and immunohistochemistry (IHC) for molecular analysis of in vivo gene and protein responses in fish. Over 200 serial sagittal sections (5microm) can be produced from a single adult medaka to facilitate simultaneous localization and quantification of gene-specific mRNAs and proteins in different tissues and subcellular compartments of a single fish. Stereological analysis (as measured by volume density, V(v)) was used to quantify ISH and IHC signals on tissue sections. Using the telomerase reverse transcriptase (omTERT) gene, omTERT and proliferating cell nuclear antigen (PCNA) proteins as examples, we demonstrated that it is possible to localize, quantify and correlate their tissue expression profiles in a whole fish system. Using chronic hypoxia (1.8+/-0.2 mgO(2)L(-1) for 3 months) as an environmental stressor, we were able to identify significant alterations in levels of omTERT mRNA, omTERT protein, PCNA (cell proliferation marker) and TUNEL (apoptosis) in livers of hypoxic O. melastigma (p<0.05). Overall, the results suggest that O. melastigma can serve as a model marine fish for assessing multiple in vivo molecular responses to stresses in the marine environment.

Studies on the genotoxicity of endosulfan in different tissues of fresh water fish Mystus vittatus using the comet assay

Endosulfan, a widely used organochlorine pesticide, is readily bio-accumulative in fishes and can be indirectly harmful to human populations. Limited efforts have been made to study long-term genotoxic effects of endosulfan in different tissues of fish using gentoxicity biomarkers. Therefore, the current investigation was undertaken to detect single-cell DNA strand breaks induced by endosulfan in the fresh water teleost fish Mystus vittatus using the comet assay. The LC(50) value of technical grade endosulfan was first determined for the fish species in a semistatic system, and on the basis of the LC(50) value, the sublethal and nonlethal concentrations were determined. The DNA damage was measured in gill, kidney, and erythrocytes as the percentage of DNA in comet tails of fish specimens exposed to the sublethal and nonlethal concentrations of endosulfan. In general, significant effects (p < 0.01) from both concentration and time of exposure were observed in exposed fishes. It was found that all the tissues at all concentrations exhibited the highest DNA damage on day 1, after which there was a nonlinear decline in the percentage of tail DNA. The comparison of DNA damage among the tissues at different concentrations could not show the sensitivity of particular tissue to endosulfan. The current study explored the utility of the comet assay for in vivo laboratory studies using fish species to screen the genotoxic potential of chemical agents.

Acute toxicity, behavioral changes, and histopathological effects of deltamethrin on tissues (gills, liver, brain, spleen, kidney, muscle, skin) of Nile tilapia (Oreochromis niloticus L.) fingerlings

Deltamethrin, a synthetic pyrethroid contaminating aquatic ecosystems as a potential toxic pollutant, was investigated in the present study for acute toxicity. The purpose of this study was to evaluate LC(50) values of deltamethrin on Nile tilapia (Oreochromis niloticus L.) fingerlings and investigate histopathological responses of fish exposed to deltamethrin. The 48 h LC(50) value for Nile tilapia fingerlings was estimated as 4.85 microg/L using static test system. In addition, behavioral changes at each deltamethrin concentration were observed closely. All fish, exposed to 5 microg/L deltamethrin revealed severe morphological alterations in the gills and liver. In the gills hyperemia, fusion of secondary lamellae and telangiectasis were observed; whereas hydropic degenerations in liver were observed in all examined fish. The results are significant for reporting acute deltamethrin toxicity in terms of behavioral and histopathological changes: Deltamethrin is highly toxic to fingerlings.

Induction of CYP1A mRNA in Carp (Cyprinus carpio) from the Kalamazoo River polychlorinated biphenyl-contaminated superfund site and in a laboratory study

The Kalamazoo River Superfund site in Michigan is contaminated with polychlorinated biphenyls (PCBs), which were heavily discharged into the river from several paper companies as part of the deinking process in the 1950s through 1970s. We characterized biomarkers of chronic PCB exposure in a resident fish population using real-time reverse transcriptase-polymerase chain reaction to examine mRNA expression levels of multiple genes in carp (Cyprinus carpio) liver from PCB contaminated and reference sites in the Kalamazoo River. We also measured these same genes in juvenile carp exposed to dietary PCBs for 4 months. Kalamazoo River carp had significantly increased levels of cytochrome P450 1A (CYP1A) mRNA as did carp fed PCBs in the laboratory. No significant mRNA upregulation occurred in the specific oxidative stress genes (gamma-glutamylcysteine synthetase and magnesium superoxide dismutase) and metabolic genes (phosphoenolpyruvate carboxykinase and nucleolin) examined. These data are consistent with the idea that carp from the Kalamazoo River Superfund Site are responding to PCB exposure via upregulation of CYP1A independent of activation of the oxidative stress response genes normally thought to be co-regulated with CYP1A.

Dioxin-like components in human breast milk collected from Hong Kong and Guangzhou

The H4IIE rat hepatoma cell line was employed as a cell model to screen 7-ethoxyresorufin O-deethylase (EROD)-TCDD equivalents (EROD-TEQ) of human breast milk samples collected from Hong Kong and Guangzhou, China. The screening methods employed a 96-well plate spectrofluorometer-EROD assay. For cell-line validation, our results demonstrated a dose-dependent increase in the Ah receptor-mediated response (i.e., CYP1A1 mRNA and EROD) of the cells upon exposure to a number of known Ah receptor agonists, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrachlorodibenzothiophene, benzo[a]pyrene, and beta-naphthaflavone. TCDD induced CYP1A1 mRNA and EROD was in a close positive correlation (r=0.98). For the screening of dioxin-like compounds, breast milk samples collected during lactation weeks 3-5 were used. One hundred (from Hong Kong) and 48 (from Guangzhou) breast milk samples were assayed, of which 65% and 68% of the samples, respectively, showed detectable dioxin-like activities using the H4IIE cell EROD screening method. For sixty-five samples from Hong Kong the mean EROD-TEQ values ranged from 58.1 to 96.5 pg/g of milk fat for those aged 21-36 years while 32 samples from Guangzhou had mean values of 98.8-202.1 pg/g of milk fat. In comparisons of the EROD-TEQ values for different age groups from both cities, there were no significant differences (P<0.05). However, the mean and median EROD-TEQ values of the Guangzhou population were in general higher than those of the Hong Kong population. The results of the present study indicate that it is feasible to use the H4IIE cell-line as a model for screening dioxin-like compounds in human breast milk. In addition, the method is rapid and cost-effective, particularly for a routine and high-throughput sample screening analysis, compared to the costly and time-intensive chemical analytical techniques.

Differential expression of CYP1A1 mRNA in gill, intestine and liver of tilapia fed with PCB Aroclor-1254 and Aroclor-1260 spiked food

The differential expression of cytochrome P4501A1 gene expression (CYP1A1) in liver, intestine and gill of juvenile tilapia following oral exposure to polychlorinated biphenyl (PCB) Aroclor-1254 or Aroclor-1260 spiked food were investigated. The fish was fed with 0.1 g/g of body weight each day of the spiked food with a concentration of approximately 8 ppm. Fish fed with betaNF- or acetone-spiked food were used as positive and negative controls, respectively. On day 1, 3 and 7 of post-treatment, the fish were sampled and analyzed for the total accumulated levels of PCBs, as well as the induced levels of CYP1A1 mRNA. Our results indicated that the fish fed with PCBs-spiked food showed a time-dependent bioaccumulation of PCBs. The time course studies also revealed that in the first 3 days of feeding, significant increases in CYP1A1 were found in intestine (betaNF: 320% and Aroclor-1260: 290%), followed by liver (betaNF: 144%, Aroclor-1260: 123% and Aroclor-1254: 110%). The transcript levels, then declined slowly. There was no induction of gill CYP1A1 mRNA expression in all treatment groups. Among all the tested tissues, the highest intestinal CYP1A1 transcripts induction has highlighted its prompt response to dietary PCBs exposure. Our study supported the important role of intestine in response to dietary PCBs exposure. In addition, in the present study the relative potency of Aroclor-1260 over Aroclor-1254 in stimulating CYP1A1 expression was discussed, indicating that the highly chlorinated PCBs had a higher potency of bioaccumulation and CYP1A1 mRNA induction.