cDNA cloning and expression of a xenobiotic metabolizing cytochrome P4501A (CYP1A) from the yellow catfish, Pelteobagrus fulvidraco (Siluriformes)

Microplastics aggravate the bioaccumulation of three veterinary antibiotics in the thick shell mussel Mytilus coruscus and induce synergistic immunotoxic effects

Marine bivalves living in pollution-prone coastal areas may be simultaneously coexposed to veterinary antibiotic residuals and microplastics (MPs). However, the synergistic effects of these two types of emergent pollutants have not been fully elucidated in mussel species. Therefore, the immunotoxic effects of the three representative antibiotics, oxytetracycline (OTC, 270 ng/L), florfenicol (FLO, 42 ng/L), and sulfamethoxazole (SMX, 140 ng/L), with and without the copresence of polystyrene MPs (0.26 mg/L, dimeter: 500 nm), were investigated in the thick shell mussel. Our data showed that the immunity was significantly hampered by exposure to the pollutants and MP-antibiotic coexposure induced synergistic immunotoxicity. For instance, compared to those treated with antibiotics (OTC, FLO, and SMX) alone, mussels coexposed to antibiotic and MPs had significantly lower phagocytic rate (further decline by approximately 28.80%, 34.21%, and 11.22%, respectively) and total hemocyte count (further reduced by approximately 37.45%, 61.67%, and 46.32%, respectively). Exposure to the pollutants tested also led to inductions in intracellular reactive oxygen species (ROS), decreases in the F-actin cytoskeleton, declines in the cell viability of hemocytes, and downregulation of cytoskeleton- and immune-related genes. In addition, mussels coexposed to antibiotic-MP accumulated significantly greater amounts of antibiotics, which may partially explain the synergic immunotoxic effect detected. Exposure to pollutants tested also led to suppression in the activity of glutathione-S-transferase (GST) and downregulation of detoxification-related genes whereas induction in the level of lipid peroxidation (indicated by MDA content) in gills, which may facilitate the entry whereas constrain the exclusion of antibiotics and therefore result in an elevation in accumulation of antibiotics.

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.

Biotransformation in the fish Prochilodus lineatus: An organ-specific approach to cyp1a gene expression and biochemical activity

The biotransformation ability of the organism is the result of organ-specific responses. This paper presents a molecular and biochemical approach to elucidate the biotransformation mechanisms in different organs of Prochilodus lineatus induced at 6, 24, and 96 h after a benzo[a]pyrene (B[a]P) injection. The induction in cyp1a transcription showed an organ-specific intensity at every tested time time. The EROD (ethoxyresorufin-O-deethylase) activity increased rapidly (6 h) in the liver and the kidney; the gills and the brain showed an increase at 24 h; and the gills demonstrated the highest activity among all the organs tested. There was no increase in glutathione S-transferase (GST) activity or lipoperoxidation. The decreased hepatic glutathione content (GSH) may be due to its role as an antioxidant. B[a]P was detected in the bile, confirming the xenobiotic efflux from the metabolizing organs. The gills, liver, brain, and kidney of P. lineatus presented an integrated mechanism to deal with the xenobiotic biotransformation.

Gene structure and comparative and phylogenetic analyses of Catla catla CYP1A full-length cDNA and its responsiveness to benzo(a)pyrene and copper sulphate at early developmental stages

In the present study, full-length CYP1A cDNA from Catla catla (Catla) has been identified, and its real-time quantitative reverse transcription PCR (qRT-PCR) expression has been evaluated in different tissues, developmental stages (0, 3, 6, 12 and 24 h and 5, 7 and 9 days post-fertilization) and copper sulphate and benzo(a)pyrene (BaP)-treated 5-day post-fertilization (dpf) larvae (6 to 6.5 mm). Various structural, comparative and phylogenetic analyses of the deduced amino acid sequence revealed that the identified gene of Catla belongs to the CYP1A1 subfamily. Among different tissues of Catla, the highest CYP1A expression was observed in the kidney followed by the liver, muscle, gill, intestine and brain. CYP1A mRNA expression was detected during all the larval developmental stages, including the unfertilized egg with the highest expression on 9 dpf. BaP (3.5 ppb) and copper sulphate (sublethal dose 0.516 ppm) challenge test for 96 h to Catla larvae revealed the highest CYP1A1 expression at 48 h post-challenge. CYP1A1 transcript also showed a concentration-dependent increase in expression following exposure at 1.75 and 3.5 ppb of BaP for 48 h. Its expression profiling indicates that it is functional at early developmental stages. It can also be used to develop a specific biomarker tool for monitoring environmental pollution.

Effects of norfloxacin on hepatic genes expression of P450 isoforms (CYP1A and CYP3A), GST and P-glycoprotein (P-gp) in Swordtail fish (Xiphophorus Helleri)

The presence of antibiotics including norfloxacin in the aquatic environment may cause adverse effects in non-target organisms. But the toxic mechanisms of fluoroquinolone to fish species are still not completely elucidated. Thus, it is essential to investigate the response of fish to the exposure of fluoroquinolone at molecular or cellular level for better and earlier prediction of these environmental pollutants toxicity. The sub-chronic toxic effects of norfloxacin (NOR) on swordtail fish (Xiphophoru s helleri) were investigated by measuring mRNA expression of cytochrome P450 1A (CYP1A), cytochrome P450 3A (CYP3A), glutathione S-transferase (GST) and P-glycoprotein (P-gp) and their corresponding enzyme activities (including ethoxyresorufin O-deethylase, erythromycin N-demethylase and GST. Results showed that NOR significantly affected the expression of CYP1A, CYP3A, GST and P-gp genes in swordtails. The gene expressions were more responsive to NOR exposure than their corresponding enzyme activities. Moreover, sexual differences were found in gene expression and enzyme activities of swordtails exposed to NOR. Females displayed more dramatic changes than males. The study further demonstrated that the combined biochemical and molecular parameters were considered as useful biomarkers to improve our understanding of potential ecotoxicological risks of NOR exposure to aquatic organisms.

Characterization and sexual dimorphic expression of Cytochrome P450 genes in the hypothalamic-pituitary-gonad axis of yellow catfish

Yellow catfish (Pelteobagrus fulvidraco) is an important freshwater fish species in China. In particular, an all-male population has been commercially produced for the males grow faster than females. However, the molecular mechanisms underlying sexual dimorphism of body size and sex differentiation are still unclear in yellow catfish. This study attempts to characterize and analyze the expression of Cytochrome P450 (CYP) family members that have been shown to play an important role in sex differentiation and metabolism in teleosts. A total of 25 CYP genes were identified from our transcriptomes by 454 pyrosequencing and Solexa sequencing, including 17 genes with complete open reading frame (ORF). Phylogenetic analyses were conducted to compare these genes with their counterparts from other teleosts. In the tissues of hypothalamic-pituitary-gonad (HPG) axis, most of the genes were expressed at uniform level in both sexes. However, multiple CYP genes displayed sexual dimorphic expression, such as cyp2AD, cyp4b, cyp8a, cyp11b2, cyp17a and cyp27a expressed at higher level in testis than in ovary, whereas cyp2g, cyp7a, cyp8b, cyp19a1a and cyp26a expressed at higher level in ovary than in testis. The expression response of six CYP genes in ovary was also assessed after 17α-methyltestosterone (MT) treatment. Testis-biased expressed cyp11b2 and cyp17a were significantly up-regulated, while cyp11a and cyp19a1a were reduced in ovary after MT treatment. Our work is helpful for understanding molecular evolution of CYP genes in vertebrates and the mechanism of sexual dimorphism in teleosts.

Effects of triclosan on the detoxification system in the yellow catfish (Pelteobagrus fulvidraco): expressions of CYP and GST genes and corresponding enzyme activity in phase I, II and antioxidant system

Triclosan (TCS), a broad-spectrum antibacterial agent widely used in pharmaceuticals and personal case products (PPCPs), has been universally detected in aquatic ecosystem in recent years. Unfortunately, there is limited information about its potential impacts on responses of genes and enzymes related to fish detoxification. In the present work, we cloned CYP3A and alpha-GST of yellow catfish (Pelteobagrus fulvidraco) and tested the transcriptional expression of CYP1A, CYP3A and GST as well as the alterations of their corresponding enzymes, including ethoxyresorufin-O-deethylase (EROD), aminopyrine N-demethylase (APND), erythromycin N-demethylase (ERND), glutathione S-transferase (GST) and catalase (CAT), and also the oxidative product malondialdehyde (MDA) content in the liver of P. fulvidraco exposed to TCS. Amino acids of CYP3A and GST were deduced and phylogenetic tree was constructed respectively. High identity percent was exhibited between P. fulvidraco and other species, such as other fish, birds and mammals. Results indicated that TCS significantly elevated CYP1A and GST but decreased CYP3A expression, EROD activity and MDA content at lower concentrations of TCS at 24h. Moreover, CYP3A and GST were significantly inhibited at 72 h but induced at 168 h at lower concentrations. However, CYP3A was always induced at the highest concentration during the exposure period. Furthermore, CYP3A, GST, GST enzyme and MDA content exhibited a dose-effect relationship to some extent, but no significant responses were observed in ERND, APND and CAT except for individual treatments. Taken together, EROD was the most sensitive to TCS exposure as compared to other enzymes. Meanwhile, mRNA responses were more sensitive in yellow catfish.

The yellow catfish, Pelteobagrus fulvidraco (Siluriformes) metallothionein cDNA: molecular cloning and transcript expression level in response to exposure to the heavy metals Cd, Cu, and Zn

Metallothionein (MT) has been used extensively as a potential molecular biomarker to detect heavy metal pollution in aquatic organisms. In order to investigate the modulation effect of heavy metals and to establish suitable biomarkers for the monitoring of heavy metal pollution, Pelteobagrus fulvidraco metallothionein gene was characterized as the first report in the family Bagridae. Pf-MT transcript was detected at high levels in liver, gonad, kidney, and brain compared to other tissues. A time-course study in response to waterborne Cd (5 ppm) revealed that a significant increase in the Pf-MT transcript abundance was observed at 6 h in gill, kidney, and liver. These elevated levels were kept for 96 h, implying that Cd distributed fast into different organs and was involved in the tissue-specific induction pattern. We observed a significant Pf-MT transcript increase in liver tissues at 48 h, followed by gill at 12 h and intestine at 48 h after Cd exposure. This indicates hepatic MT expression as a potential biomarker of acute Cd exposure in this species. Cd-binding ability of recombinant Pf-MT protein provided evidence for sensitivity to Cd and other heavy metal exposure. In the case of Zn exposure (1 ppm), a significant increase in Pf-MT transcript abundance was observed at 12 h, and a peak induction level reaching sixfold at 24 h was kept until 48 h, showing similar transcript induction patterns with Cd. A high level of Pf-MT mRNA after exposure to Cu (1 ppm) was observed at 12 h that gradually increased until 96 h with a 12-fold induction, revealing a long-lasting induction and somewhat dissimilar pattern compared to other metals in liver. Our results demonstrate that Pf-MT can be induced by heavy metals in a tissue-specific and metal-specific manner and plays probably a conserved role in metal detoxification. This study provides new information on P. fulvidraco metallothionein gene for the use of biomarkers indicating metal pollution in fish.

Cytochrome P450 (CYP) in fish

Cytochrome P450 (CYP) enzymes are members of the hemoprotein superfamily, and are involved in the mono-oxygenation reactions of a wide range of endogenous and exogenous compounds in mammals and plants. Characterization of CYP genes in fish has been carried out intensively over the last 20 years. In Japanese pufferfish (Takifugu rubripes), 54 genes encoding P450s have been identified. Across all species of fish, 137 genes encoding P450s have been identified. These genes are classified into 18 CYP families: namely, CYP1, CYP2, CYP3, CYP4, CYP5, CYP7, CYP8, CYP11, CYP17, CYP19, CYP20, CYP21, CYP24, CYP26, CYP27, CYP39, CYP46 and CYP51.We pinpointed eight CYP families: namely, CYP1, CYP2, CYP3, CYP4, CYP11, CYP17, CYP19 and CYP26 in this review because these CYP families are studied in detail. Studies of fish P450s have provided insights into the regulation of P450 genes by environmental stresses including water pollution. In this review, we present an overview of the CYP families in fish.

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.

Molecular cloning and beta-naphthoflavone-induced expression of a cytochrome P450 1A (CYP1A) gene from an anadromous river pufferfish, Takifugu obscurus

In recent years, there has been a decline in the wild populations of river pufferfish, Takifugu obscurus. Besides overexploitation for commercial purposes, environmental pollution is believed to have contributed to its decline. However, almost no information exists about genes involved in metabolism of xenobiotics by this species. Nevertheless, there is interest in fugu fishes, since they possess the smallest genome among vertebrates. We cloned and characterized the full-length cDNA sequence of a cytochrome P450 1A (CYP1A) gene from T. obscurus. Phylogenic relationship of T. obscurus CYP1A was also compared to other fish species. The tissue distribution and time-dependant induction of CYP1A mRNA were studied by real-time PCR in T. obscurus exposed to an aryl hydrocarbon receptor (Ahr) agonist, beta-naphthoflavone (BNF). The greatest basal expression in livers of control as well as BNF-treated individuals. However, brain, gill, gonad, intestine, and kidney also expressed CYP1A. Muscles expressed the least CYP1A. The results of the time-course study revealed induction in brain and gills after 6h and at 12h in most tissues. Except for gills, all other organs retained induced expression of CYP1A mRNA up to 96h.