Unravelling drug-drug interactions in pigs: Induction of hepatic cytochrome P450 1A (CYP1A) metabolism after the in-feed medication with the anthelmintic fenbendazole

The anthelmintic fenbendazole (FBZ) undergoes hepatic S‑oxygenation by monooxygenases belonging to the cytochrome P450 (CYP) and flavin-monooxygenase (FMO) families. The in-feed medication with FBZ induced CYP1A-dependent metabolism in pig liver. This fact may alter the metabolism of the anthelmintic itself, and of CYP1A substrates like aflatoxin B1 (AFB1). This work evaluated the effect of the in-feed administration of FBZ on CYP1A-dependent metabolism, on its own pattern of hepatic S‑oxygenation, and on the metabolism of AFB1. Landrace piglets remained untreated (n = 5) or received a pre-mix of FBZ (n = 6) in feed for 9 days. Pigs were slaughtered for preparation of liver microsomes used for: CYP content determination; monitoring the CYP1A-dependent enzyme activities, 7-ethoxyresorufin O-deethylase (EROD) and 7-methoxyresorufin O-demethylase (MROD); measurement of FBZ (50 μM) S‑oxygenation, and AFB1 (16 nM) disappearance from the incubation medium. In microsomes of FBZ-treated animals, EROD and MROD increased 19-fold (p = 0.002) and 14-fold (p = 0.003), respectively. An enhanced (3-fold, p = 0.004) participation of the CYP pathway in FBZ S‑oxygenation was observed in the liver of piglets treated with the anthelmintic (210 ± 69 pmol/min.nmol CYP) compared to untreated animals (68 ± 34 pmol/min.nmol CYP). AFB1 metabolism was 93% higher (p = 0.009) in the liver of FBZ-treated compared to untreated pigs. Positive and significant (p < 0.05) correlations were observed between CYP1A-dependent enzyme activities and FBZ or AFB1 metabolism. The sustained administration of FBZ caused an auto-induction of the CYP1A-dependent S‑oxygenation of this anthelmintic. The CYP1A induction triggered by the anthelmintic could amplify the production of AFB1 metabolites in pig liver, including the hepatotoxic AFB1-derived epoxide.+.

A combination of three antioxidants decreases the impact of rural particulate pollution in Normal human keratinocytes

OBJECTIVE

It is well established that exposure of human skin to airborne pollution, particularly in the form of particulate matter sized 2.5 μm (PM2.5 ), is associated with oxidative stress, DNA damage and inflammation, leading to premature signs of skin aging. Because much of the damage results from oxidative stress, we examined the effects of a topical composition containing three antioxidants in an in vitro model system to assess the potential for amelioration of premature aging. The use of multiple antioxidants was of interest based on the typical composition of therapeutic skincare products. It is important to determine the efficacy of multiple antioxidants together and develop a short-term assay for larger scale efficacy testing.

METHODS

Normal human epidermal keratinocytes were exposed to a rural-derived source of PM2.5 in the presence and absence of an antioxidant mixture of resveratrol, niacinamide and GHK peptide. Endpoints related to inflammation, premature aging and carcinogenicity were monitored after 5 h of exposure and included IL-6, CXCL10, MMP-1 and NRF2. Differentially expressed genes were monitored by RNA-seq.

RESULTS

Pre-treatment of keratinocytes with the antioxidant preparation in the absence of PM2.5 reduced baseline levels of MMP-1, IL-6 and CYP1A1 and reduced PM2.5 -induced increases in all four endpoints, MMP-1, IL-6, CXCL10 and CYP1A1. Antioxidants significantly increased NRF2 protein in the presence of PM2.5 , indicating a protective response. RNA-seq interrogation of antioxidant-treated cells further showed increased expression of NRF2 inducible genes. The expression of CYP1A1 and genes related to aryl hydrocarbon activation were induced by PM2.5 and suppressed by antioxidants.

CONCLUSIONS

Specific signalling pathways known to be correlated with skin inflammation and aging were examined based on their suitability for use in efficacy testing for the prevention of skin damage due to ambient hydrocarbon pollution. Endpoints examined after only 5 h of exposure provide a useful method amenable to high through-put screening. The results obtained reinforce the concept that a multiple antioxidant preparation, topically applied, may reduce pro-inflammatory signalling and cellular damage and thereby reduce premature skin aging due to exposure to rural-derived airborne pollution.

PE (0:0/14:0), an endogenous metabolite of the gut microbiota, exerts protective effects against sepsis-induced intestinal injury by modulating the AHR/CYP1A1 pathway

Sepsis is known to cause damage to the intestinal mucosa, leading to bacterial translocation, and exacerbation of both local and remote organ impairments. In the present study, fecal samples were collected from both septic and healthy individuals. Analysis through 16s rRNA sequencing of the fecal microbiota revealed that sepsis disrupts the balance of the gut microbial community. Recent research has highlighted the association of lipid metabolism with disease. By analyzing the fecal metabolome, four lipid metabolites that showed significant differences between the two groups were identified: PE (O-16:0/0:0), PE (17:0/0:0), PE (0:0/14:0), and PE (12:0/20:5 (5Z, 8Z, 11Z, 14Z, 17Z)). Notably, the serum levels of PE (0:0/14:0) were higher in the healthy group. Subsequent in vitro and in vivo experiments demonstrated the protective effects of this compound against sepsis-induced intestinal barrier damage. Label-free proteomic analysis showed significant differences in the expression levels of the aryl hydrocarbon receptor (AHR), a protein implicated in sepsis pathogenesis, between the LPS-Caco-2 and LPS-Caco-2 + PE (0:0/14:0) groups. Further analysis, with the help of Discovery Studio 3.5 software and co-immunoprecipitation assays, confirmed the direct interaction between AHR and PE (0:0/14:0). In the cecal ligation and puncture (CLP) model, treatment with PE (0:0 /14:0) was found to up-regulate the expression of tight junction proteins through the AHR/Cytochrome P450, family 1, subfamily A, and polypeptide 1 (CYP1A1) pathway. This highlights the potential therapeutic use of PE (0:0/14:0) in addressing sepsis-induced intestinal barrier damage.

Early-life exposure to cigarette smoke primes lung function and DNA methylation changes at Cyp1a1 upon exposure later in life

Prenatal and early-life exposure to cigarette smoke (CS) has repeatedly been shown to induce stable, long-term changes in DNA methylation (DNAm) in offspring. It has been hypothesized that these changes might be functionally related to the known outcomes of prenatal and early-life CS exposure, which include impaired lung development, altered lung function, and increased risk of asthma and wheeze. However, to date, few studies have examined DNAm changes induced by prenatal CS in tissues of the lung, and even fewer have attempted to examine the specific influences of prenatal versus early postnatal exposures. Here, we have established a mouse model of CS exposure which isolates the effects of prenatal and early postnatal CS exposures in early life. We have used this model to measure the effects of prenatal and/or postnatal CS exposures on lung function and immune cell infiltration as well as DNAm and expression of Cyp1a1, a candidate gene previously observed to demonstrate DNAm differences on CS exposure in humans. Our study revealed that exposure to CS prenatally and in the early postnatal period causes long-lasting differences in offspring lung function, gene expression, and lung Cyp1a1 DNAm, which wane over time but are reestablished on reexposure to CS in adulthood. This study creates a testable mouse model that can be used to investigate the effects of prenatal and early postnatal CS exposures and will contribute to the design of intervention strategies to mediate these detrimental effects.NEW & NOTEWORTHY Here, we isolated effects of prenatal from early postnatal cigarette smoke and showed that exposure to cigarette smoke early in life causes changes in offspring DNA methylation at Cyp1a1 that last through early adulthood but not into late adulthood. We also showed that smoking in adulthood reestablished these DNA methylation patterns at Cyp1a1, suggesting that a mechanism other than DNA methylation results in long-term memory associated with early-life cigarette smoke exposures at this gene.

PM2.5 leads to adverse pregnancy outcomes by inducing trophoblast oxidative stress and mitochondrial apoptosis via KLF9/CYP1A1 transcriptional axis

Epidemiological studies have demonstrated that fine particulate matter (PM2.5) is associated with adverse obstetric and postnatal metabolic health outcomes, but the mechanism remains unclear. This study aimed to investigate the toxicological pathways by which PM2.5 damaged placental trophoblasts in vivo and in vitro. We confirmed that PM2.5 induced adverse gestational outcomes such as increased fetal mortality rates, decreased fetal numbers and weight, damaged placental structure, and increased apoptosis of trophoblasts. Additionally, PM2.5 induced dysfunction of the trophoblast cell line HTR8/SVneo, including in its proliferation, apoptosis, invasion, migration and angiogenesis. Moreover, we comprehensively analyzed the transcriptional landscape of HTR8/SVneo cells exposed to PM2.5 through RNA-Seq and observed that PM2.5 triggered overexpression of pathways involved in oxidative stress and mitochondrial apoptosis to damage HTR8/SVneo cell biological functions through CYP1A1. Mechanistically, PM2.5 stimulated KLF9, a transcription factor identified as binding to CYP1A1 promoter region, which further modulated the CYP1A1-driven downstream phenotypes. Together, this study demonstrated that the KLF9/CYP1A1 axis played a crucial role in the toxic progression of PM2.5 induced adverse pregnancy outcomes, suggesting adverse effects of environmental pollution on pregnant females and putative targeted therapeutic strategies.

In vitro differences in toddalolactone metabolism in various species and its effect on cytochrome P450 expression

CONTEXT

Toddalolactone, the main component of Toddalia asiatica (L.) Lam. (Rutaceae), has anticancer, antihypertension, anti-inflammatory, and antifungal activities.

OBJECTIVE

This study investigated the metabolic characteristics of toddalolactone.

MATERIALS AND METHODS

Toddalolactone metabolic stabilities were investigated by incubating toddalolactone (20 μM) with liver microsomes from humans, rabbits, mice, rats, dogs, minipigs, and monkeys for 0, 30, 60, and 90 min. The CYP isoforms involved in toddalolactone metabolism were characterized based on chemical inhibition studies and screening assays. The effects of toddalolactone (0, 10, and 50 µM) on CYP1A1 and CYP3A5 protein expression were investigated by immunoblotting. After injecting toddalolactone (10 mg/kg), in vivo pharmacokinetic profiles using six Sprague-Dawley rats were investigated by taking 9-time points, including 0, 0.25, 0.5, 0.75, 1, 2, 4, 6 and 8 h.

RESULTS

Monkeys showed the greatest metabolic capacity in CYP-mediated and UGT-mediated reaction systems with short half-lives (T_1/2) of 245 and 66 min, respectively, while T_1/2 of humans in two reaction systems were 673 and 83 min, respectively. CYP1A1 and CYP3A5 were the major CYP isoforms involved in toddalolactone biotransformation. Induction of CYP1A1 protein expression by 50 μM toddalolactone was approximately 50% greater than that of the control (0 μM). Peak plasma concentration (C_max) for toddalolactone was 0.42 μg/mL, and T_max occurred at 0.25 h post-dosing. The elimination t_1/2 was 1.05 h, and the AUC_0-t was 0.46 μg/mL/h.

CONCLUSIONS

These findings demonstrated the significant species differences of toddalolactone metabolic profiles, which will promote appropriate species selection in further toddalolactone studies.

Integrative assessment of biomarker responses in pale chub (Zacco platypus) exposed to copper and benzo[a]pyrene

Multi-level biomarker responses (molecular/biochemical and histological/physiological levels) were studied to assess the sublethal toxicities of copper (Cu: 1.25, 5, and 20μg/L) and benzo[a]pyrene (BaP: 0.5, 5, and 50μg/L) induced in the freshwater pale chub Zacco platypus. Except for the kidney tissues when exposed to 20μg Cu/L, no significant differences were observed at the histological or physiological levels among the treatment groups. However, various molecular and biochemical responses were observed in Z. platypus, and these responses primarily depended on exposure time. Upon Cu exposure, both DNA single-strand breaks (COMET) and metallothionein (MT) concentration significantly increased after 4 days, whereas there were no significant changes after 14 days of exposure. Both 4 and 14 days of BaP exposure induced significant increases in COMET and 7-ethoxyresorufin-O-deethylase (EROD) activity, but there was no significant difference between them. Additionally, both Cu and BaP induced acetylcholinesterase (AChE) activity only after 14 days of exposure. The current findings demonstrate that the differences in the responses of MT and EROD are associated with each chemical's particular mode of action. Biomarker responses at the molecular and biochemical levels were quantized in terms of the integrated biomarker response (IBR) index to compare the toxicities of Cu and BaP. The IBR values were well correlated with the concentrations of Cu and BaP, and the correlations were enhanced at 4 days of exposure (r(2)=0.849 and 0.945, respectively) compared with 14 days (r(2)=0. 412 and 0.634, respectively). These results suggest that the IBR index may be a useful tool for the integrative quantification of the molecular and biochemical biomarker responses in a short-term exposure to Cu and BaP.

Quantitative analysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin-induced proteome alterations in 5L rat hepatoma cells using isotope-coded protein labels

In an effort to contribute to a better understanding of the hepatic toxicity of the ubiquitous environmental pollutant and hepatocarcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a comprehensive quantitative proteome analysis was performed on 5L rat hepatoma cells exposed to 1 nM TCDD for 8 h. Changes in the abundances of individual protein species in TCDD-treated cells as compared to untreated cells were analysed using the nongel-based isotope-coded protein label (ICPL) method [Schmidt, A., Kellermann, J., Lottspeich, F., Proteomics 2005, 5, 4-15]. 89 proteins were identified as up- or down-regulated by TCDD. For the majority of the altered proteins, an impact of TCDD on their abundance had not been known before. Due to the physicochemical properties or the translational regulation of a large number of the affected proteins, their alteration would have escaped detection by gel-based methods for proteome analysis and by standard mRNA expression profiling, respectively. The identified proteins with TCDD-altered abundance include several proteins implicated in cell cycle regulation, growth factor signalling and the control of apoptosis. The results thus provide new starting-points for the investigation of specific aspects of the toxicity and carcinogenicity of dioxin in liver.

Tumor-selective drug activation: a GDEPT approach utilizing cytochrome P450 1A1 and AQ4N

Drug metabolizing transgene products, which activate bioreductive cytotoxins, can be used to target treatment-resistant hypoxic tumors. The prodrug AQ4N is bioreduced in hypoxic cells by cytochrome P450s (CYPs) to the cytotoxin AQ4. Previously we have shown that intra-tumoral injection of CYP3A4 and CYP2B6 transgenes with AQ4N and radiation inhibits tumor growth. Here we examine the ability of other CYPs, in particular CYP1A1, to metabolize AQ4N, and to enhance radiosensitization. Metabolism of AQ4N was assessed using microsomes prepared from baculovirus-infected cells transfected with various CYP isoforms. AQ4N metabolism was most efficient with CYP1A1 (66.7 nmol/min/pmol) and 2B6 (34.4 nmol/min/pmol). Transient transfection of human CYP1A1+/-CYP reductase (CYPRED) was investigated in hypoxic RIF-1 mouse cells in vitro using the alkaline comet assay. There was a significant increase in DNA damage following transient transfection of CYP1A1 compared to non-transfected cells; inclusion of CYPRED provided no additional effect. In vivo, a single intra-tumoral injection of a CYP1A1 construct in combination with AQ4N (100 mg/kg i.p.) and 20 Gy X-rays caused a 16-day delay in tumor regrowth compared to tumors receiving AQ4N plus radiation and empty vector (P=0.0344). The results show the efficacy of a CYP1A1-mediated GDEPT strategy for bioreduction of AQ4N.

Characterization of antimutagenic mechanism of 3-allyl-5-substituted 2-thiohydantoins against 2-amino-3-methylimidazo[4,5-f]quinoline

3-Allyl-5-substituted 2-thiohydantoins (ATH-amino acids) derived from allyl isothiocyanate and amino acids can inhibit the mutagenicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the Salmonella assay. In this report, we studied possible mechanisms for the inhibition using rat liver S9 in assays for ethoxyresorufin O-deethylase (EROD), a marker activity for cytochrome P450 1A (CYP1A), which activates heterocyclic amines, and the Salmonella assays with the direct-acting mutagen 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline (N-hydroxy-IQ). Quantitative analysis of ATH-amino acids and IQ during incubation with rat liver S9 fraction by HPLC showed that ATH-amino acids could act as S9-inhibitors, thereby inhibiting metabolic activation of IQ. Among the tested ATH-amino acids, ATH-Phe, ATH-Trp, ATH-Leu and ATH-Val showed a dose-dependent inhibition of EROD activity. ATH-Gly, ATH-Glu, and ATH-Asp behaved as blocking agents toward N-hydroxy-IQ, but exhibited no inhibition of EROD activity.

Expression of cytochrome P450 1A1 and its contribution to oxidation of a potential human carcinogen 1-phenylazo-2-naphthol (Sudan I) in human livers

Cytochrome P450 1A1 (CYP1A1) is one of the most important enzymes implicated in the metabolic activation of carcinogens. To date, there is still conflicting evidence for the expression of enzymatically functional CYP1A1 in human liver. In the present work, we clearly demonstrate that CYP1A1 capable of metabolizing a carcinogen 1-phenylazo-2-naphthol (Sudan I) is expressed in livers of eight American Caucasian donors. Using two independent methods (immunoblotting and N-terminal sequencing), CYP1A1 protein was detected and quantified in all human hepatic microsomes tested in the study. Its levels, ranging from 0.97 to 3.0 pmol/mg protein, correlated with activities catalyzed by this enzyme [7-ethoxyresorufin O-deethylation (EROD) and oxidation of Sudan I], indicating the presence of enzymatically active CYP1A1. Even though levels of CYP1A1 expression are low, <0.7% of total hepatic CYP, the CYP1A1 contribution to oxidation of carcinogenic Sudan I in the test set of human liver microsomes ranges from 12 to 30%.

Oxidative stress and sex steroid levels in fish following short-term exposure to pulp-mill effluents

This study investigates the relationship between oxidative stress and reproductive dysfunction in wild white sucker (Catostomus commersoni) with short-term exposures to pulp-mill effluent. Hepatic oxidative damage, as quantified using 2-thiobarbituric acid-reactive substances (TBARS), was often increased with effluent exposure within 4-8 d, but responses varied by species, sex, and effluent. Fatty acyl-coenzyme A (CoA) oxidase (FAO) and ethoxyresorufin O-deethylase (EROD) activities were also significantly induced between 4 and 8 d of exposure. There were marked species differences in oxidative stress, as TBARS, FAO, and EROD responses in white sucker differed dramatically from those of longnose sucker (Catostomus catostomus) exposed under identical conditions. Exposure for 8 d to pulp-mill effluent delayed ovulation in white sucker, and these delays were independent of changes in circulating testosterone and 17alpha,20beta-dihydroxy-4-pregnen-3-one titers. Evaluations of the effects of pulp mill effluent on in vivo plasma steroid levels and in vitro steroidogenic capacities were compromised due to caging stress. In vivo preexposure to pulp-mill effluent did not reduce in vitro ovarian follicle steroidogenic capacities when exposed to additional reactive oxygen species (ROS) generators. Endocrine and oxidative stress parameters may be interrelated, as the in vivo administration of ferric nitrilotriacetate (Fe(3+)NTA) significantly reduced circulating sex steroids. Administration of a superactive GnRH analog containing a dopamine inhibitor significantly increased TBARS within 24 h, indicating endocrine status is capable of modifying oxidative stress responses. This study provides new knowledge regarding the onset of oxidative stress and changes in reproductive endpoints in fish following pulp-mill effluent exposure.

Cultured gill epithelial cells from tilapia (Oreochromis niloticus): a new in vitro assay for toxicants

A culture gill epithelium from seawater-adapted tilapia (Oreochromis niloticus) was developed for testing PAHs and dioxin-like contaminants in seawater. The epithelia consists two to three layers of epithelial cells incorporating both pavement cells and mitochondria-rich cells (MRCs). Polarity and a stable transepithelial resistance (TER) were maintained, and closely resembled those in fish gills in vivo. The tightness (integrity) of the epithelia remained unchanged upon exposure to benzo[a]pyrene (B[a]P), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and 3,3',4,4',5-pentachlorobiphenyl (PCB#126), while a concentration-dependent response of EROD activity in the epithelia was induced within 18-24 h when the apical side was exposed to these toxicants. The 24 h EC50 of EROD activity was 2.77x10(-7) M for PCB#126, 1.85x10(-7) M for B[a]P and 7.38x10(-10) M for TCDD, showing that the preparation was not only sensitive to PAHs and dioxin-like compounds, but also able to produce inductive potency of AhR agonists that generally agreed with those derived from other established in vitro and in vivo systems. The results suggest that the cultured gill epithelia from seawater-adapted tilapia may serve as a simple, rapid and cost-effective tool for assessing exposure and potential effects of toxicants in marine waters.

Human hepatic and renal microsomes, cytochromes P450 1A1/2, NADPH:cytochrome P450 reductase and prostaglandin H synthase mediate the formation of aristolochic acid-DNA adducts found in patients with urothelial cancer

Aristolochic acid (AA), a naturally occurring nephrotoxin and carcinogen, has been associated with the development of urothelial cancer in humans. Understanding which human enzymes are involved in AA activation and/or detoxication is important in the assessment of an individual's susceptibility to this plant carcinogen. Using the (32)P postlabeling assay, we examined the ability of microsomal samples from 8 human livers and from 1 human kidney to activate AAI, the major component of the plant extract AA, to metabolites forming adducts in DNA. Microsomes of both organs generated DNA adduct patterns reproducing those found in renal tissues from humans exposed to AA. 7-(deoxyadenosin-N(6)-yl)aristolactam I, 7-(deoxyguanosin-N(2)-yl)aristolactam I and 7-(deoxyadenosin-N(6)-yl)aristolactam II were identified as AA-DNA adducts formed from AAI by all human hepatic and renal microsomes. To define the role of human microsomal enzymes in the activation of AAI, we investigated the modulation of AAI-DNA adduct formation by cofactors and selective inhibitors of microsomal reductases, cytochrome P450 (CYP) enzymes, NADPH:CYP reductase and NADH:cytochrome b(5) reductase. We also determined whether the activities of CYP and NADPH:CYP reductase in different human hepatic microsomal samples correlated with the levels of AAI-DNA adducts formed by the same microsomal samples. On the basis of these studies, we attribute most of the activation of AAI in human hepatic microsomes to CYP1A2. In contrast to human hepatic microsomes, in human renal microsomes NADPH:CYP reductase is more effective in AAI activation. In addition, prostaglandin H synthase is another enzyme activating AAI in renal microsomes. The results demonstrate for the first time the potential of microsomal enzymes in human liver and kidney to activate AAI by nitroreduction.

Sparus aurata L. liver EROD and GST activities, plasma cortisol, lactate, glucose and erythrocytic nuclear anomalies following short-term exposure either to 17beta-estradiol (E2) or E2 combined with 4-nonylphenol

Immature Sparus aurata L. (gilthead seabream) were exposed to 17beta-estradiol (E(2)) 4000 ng/l and to the same E(2) concentration mixed with 50,000 ng/l 4-nonylphenol (E(2) + NP) during 4, 8, 12 and 16 h. E(2) availability and E(2) plasma level variations were assessed. Liver biotransformation capacity was measured as ethoxyresorufin-O-deethylase (EROD) and glutathione-S-transferase (GST) activities. Plasma cortisol, lactate and glucose were also determined. Genotoxicity was assessed through erythrocytic nuclear anomalies (ENA) frequency. Liver EROD activity significantly decreased during the whole experiment for both treatments, with the exception of 16 h exposure to E(2). Liver GST activity was significantly increased after 8 and 12 h of exposure either to E(2) or E(2) + NP. An endocrine disruption expressed as plasma cortisol decrease was observed after 16 h exposure under both tested conditions, concomitantly with a plasma lactate increase. No genotoxic responses, measured as ENA frequency, were detected. Analyzing the E(2) water concentration in aquaria without fish it was demonstrated an intense and fast E(2) loss, considerably reducing its availability to fish. In the presence of fish, E(2) water levels were drastically reduced after 4 h exposure, being this reduction more pronounced in E(2) aquarium when compared to E(2) + NP aquarium. In addition, it was demonstrated a rapid E(2) uptake from the water since the highest E(2) plasma concentrations were observed after 4 h exposure, followed by a continuous decrease, which became more pronounced between 8 and 12 h of exposure. Furthermore, during the first 8 h exposure to E(2) and E(2) + NP, seabream plasma E(2) concentrations were higher than the initial water exposure concentration. Comparing the E(2) plasma levels in both seabream-exposed groups, it was clear that its concentration is always higher in E(2) + NP-treated fish. Despite the previous results, no significant differences were found in the measured responses between E(2) and E(2) + NP.

Interaction of non-ionic surfactants with hepatic CYP in Prochilodus scrofa

Cytochromes P450 (CYP) constitute a superfamily of hemeproteins that play a vital role in the metabolism of a wide variety of endogenous and xenobiotic compounds. Xenobiotic metabolism and the role of CYP are of particular interest in studies regarding the prevention of the damage caused by chemical pollutants. We investigated, in this study, the interaction of Triton X-100 and Tween 80 with CYP and antioxidant defenses in Curimbata, a Brazilian fish. Aiming to clarify the effects of non-ionic surfactants in the monooxigenase system of fish through in vitro study, the effects of Triton X-100 and Tween 80 were analyzed using monooxygenases and antioxidant system as experimental model. Total CYP and EROD were strongly inhibited by Triton X-100 and Tween 80 in a concentration-dependent way; the content of CYP was reduced until zero while EROD activity was completely inhibited in the presence of Triton X-100 and more than 40% inhibited in the presence of Tween 80. Each surfactant causes a different effect on each antioxidant enzyme. No effect was detected in SOD activity in the presence of even Triton X-100 or Tween 80. Triton X-100 increase catalase activity, while Tween 80 decreases this enzyme activity. The molecular structure of the surfactants causes the alteration of this system, since they are able to interact with the microsomal protein, especially with monooxigenase's components, altering their conformation and, consequently destroying their function. Our results suggest that surfactants can interact with components of the microsomal system leading to inhibition of CYP. Therefore, CYP activity, which has been used as a biomarker of xenobiotic exposure, should be used as a marker in association with other enzymes.

Potent inhibition of recombinant human cytochrome p-450 1A1 by pentamethoxystilbene

Previously it was reported that various hydroxystilbene compounds strongly inhibit human cytochrome P-450 1 enzymes and were postulated as candidate chemopreventive agents. In this study, the inhibitory potential of P-450 1 enzyme activities by 3,5,3,4,5-pentamethoxystilbene (PMS), a synthetic stilbene compound, was evaluated with the Escherichia coli (E. coil) membranes of recombinant human cytochrome P-450 1A1, 1A2, or 1B1 coexpressed with human NADPH-P-450 reductase. PMS produced a significant inhibition of ethoxyresorufin O-deethylation (EROD) activities with IC50 values of 0.14, 934, and 3.2 M for 1A1, 1A2, and 1B1, respectively. PMS did not significantly inhibit EROD activities in human liver microsomes. To elucidate the mechanism of inhibition by PMS, kinetic studies were performed. Analysis of the mode of inhibition indicated a mixed-type inhibition of P-450 1A1. The inhibition of P-450 1A1-mediated EROD activity by PMS was not irreversible-mechanism based. The loss of EROD activity of P-450 1A1 with PMS was blocked by trapping agents such as glutathione, N-acetylcysteine, or dithiothreitol. Moreover, PMS significantly suppressed P-450 1A1-mediated EROD activity and P-450 1A1 gene expression in HepG2 cells induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Taken together, the results suggested that PMS is a potent and selective inhibitor of human P-450 1A1 and may be considered for use as a cancer chemopreventive agent in humans.

Skf 525-A induces cocaine N-demethylase, ethoxyresorufin O-deethylase, and pentoxyresorufin O-dealkylase activities by induction of cytochrome p-450 2B in female B6C3F1 mice

Studies demonstrated that cocaine-induced immunosuppression is mediated by metabolites of cocaine. Although SKF 525-A inhibited cocaine N-demethylation in liver S9 fractions isolated from female B6C3F1 mice, our study showed that pretreatment of mice with SKF 525-A potentiated cocaine-induced suppression of the antibody response to sheep red blood cells. An increase in formaldehyde generation was subsequently shown following incubation of cocaine with the S9 fractions prepared from SKF 525-A-treated mice, indicating the possibility of cytochrome P-450 (CYP) induction. Therefore, the inductive effects of SKF 525-A on CYP enzyme activities and proteins were investigated in female B6C3F1 mice to elucidate the potentiation of cocaine-induced immunosuppression by SKF 525-A. When SKF 525-A was administered at 10, 20, or 40 mg/kg/d intraperitoneally for 7 consecutive days, both ethoxyresorufin O-deethylase and pentoxyresorufin O-dealkylase activities were induced dose-dependently. Furthermore, the induction of enzymatic activity was time dependent. Meanwhile, when the type of isozyme induced by SKF 525-A was analyzed by Western immunoblotting with monospecific anti-CYP 1A and anti-CYP 2B antibodies, only the CYP 2B appeared to be induced. From in vitro inhibition studies with monoclonal antibodies, it was confirmed that the induced activity of ethoxyresorufin O-deethylase by SKF 525-A was due to increased levels of CYP 2B proteins. Our present results provide an explanation for the potentiation of cocaine-induced immunosuppression by repeated exposure to SKF 525-A. Our results also indicate that ethoxyresorufin O-deethylase, a selective substrate for CYP 1A, may also be catalyzed by CYP 2B.

Synergistic embryotoxicity of polycyclic aromatic hydrocarbon aryl hydrocarbon receptor agonists with cytochrome P4501A inhibitors in Fundulus heteroclitus

Widespread contamination of aquatic systems with polycyclic aromatic hydrocarbons (PAHs) has led to concern about effects of PAHs on aquatic life. Some PAHs have been shown to cause deformities in early life stages of fish that resemble those elicited by planar halogenated aromatic hydrocarbons (pHAHs) that are agonists for the aryl hydrocarbon receptor (AHR). Previous studies have suggested that activity of cytochrome P4501A, a member of the AHR gene battery, is important to the toxicity of pHAHs, and inhibition of CYP1A can reduce the early-life-stage toxicity of pHAHs. In light of the effects of CYP1A inhibition on pHAH-derived toxicity, we explored the impact of both model and environmentally relevant CYP1A inhibitors on PAH-derived embryotoxicity. We exposed Fundulus heteroclitus embryos to two PAH-type AHR agonists, ss-naphthoflavone and benzo(a)pyrene, and one pHAH-type AHR agonist, 3,3 ,4,4 ,5-pentachlorobiphenyl (PCB-126), alone and in combination with several CYP1A inhibitors. In agreement with previous studies, coexposure of embryos to PCB-126 with the AHR antagonist and CYP1A inhibitor alpha-naphthoflavone decreased frequency and severity of deformities compared with embryos exposed to PCB-126 alone. In contrast, embryos coexposed to the PAHs with each of the CYP1A inhibitors tested were deformed with increased severity and frequency compared with embryos dosed with PAH alone. The mechanism by which inhibition of CYP1A increased embryotoxicity of the PAHs tested is not understood, but these results may be helpful in elucidating mechanisms by which PAHs are embryotoxic. Additionally, these results call into question additive models of PAH embryotoxicity for environmental PAH mixtures that contain both AHR agonists and CYP1A inhibitors.

Expression and activities of several drug-metabolizing enzymes in LLC-PK1 cells

LLC-PK1 cells are frequently used in toxicology research, but little information is available concerning the capacity of these cells to metabolize xenobiotics. We examined the expression and activities of cytochromes P450 (P450) 1A1/1A2 (CYP 1A1/1A2), 2E1 (CYP 2E1), flavin monooxygenase (FMO), 5-lipoxygenase (5-LO) and prostaglandin H synthase (PHS)-associated cyclooxygenase-1 (COX-1). We prepared S9 fractions from LLC-PK1 cells, rat liver, and rat kidney, and measured enzyme activities using ethoxyresorufin O-deethylation (EROD) for CYP 1A1/1A2 and ethoxycoumarin O-deethylation (ECOD) for CYP 2E1, benzydamine N-oxidation (BNO) for FMO, leukotriene B(4) (LTB(4)) formation for 5-LO, and thromboxane B(2) (TXB(2)) formation for COX-1 activities. To assure that product formation was due to enzymatic activity, we used the following inhibitors: 1-aminobenzotriazole (ABT) for P450, methimazole for FMO, caffeic acid for 5-LO and acetylsalicylic acid (ASA) for COX-1. We also performed Western blot analysis to confirm our observations. All five enzyme activities were demonstrable in rat liver at much greater levels than in rat kidney S9 fractions. Activities in LLC-PK1 cells were significantly lower than activities in rat liver S9 fraction and generally less than activities in rat kidney S9 fraction. Enzyme inhibitors decreased product formation in all three tissues and Western blot analysis supported our observations of low enzyme activity in LLC-PK1 cells. These results indicate that LLC-PK1 cells have very low content of relevant drug-metabolizing enzyme activities.

Polycyclic aromatic hydrocarbon sources related to biomarker levels in fish from Prince William Sound and the Gulf of Alaska

Seafloor sediments in Prince William Sound (PWS) and the eastern Gulf of Alaska (GOA) have a substantial regional hydrocarbon background from natural sources including oil seeps and eroding sedimentary rocks along the eastern GOA coast. Polycyclic aromatic hydrocarbons (PAH) from that background appear to be bioavailable to fish. Fish collected from PWS and the GOA in a 1999--2000 biomarker study (bile fluorescent aromatic contaminants and liver ethoxyresorufin O-deethylase) show evidence of exposure to low levels of PAH at all categories of sites sampled. Seafloor sediments at fish sampling sites in the GOA east of PWS and at three PWS site categories (nonspill path, spill path oiled, and spill path not oiled) contain hydrocarbons from four principal sources: regional background, combustion products, residues from the 1989 Exxon Valdez oil spill (EVOS), and Monterey (CA) petroleum residues. GOA sediments between PWS and Yakutat Bay, approximately 350 km to the east, are dominated by regional petrogenic background hydrocarbons (total PAH (TPAH) range approximately 60-3400 ng/g) that are the probable cause of low biomarker levels measured in halibut from this area. PWS sediments contain varying proportions of regional background, combustion products, Monterey residues, and EVOS residues at some spill path sites. Rockfish caught in PWS embayments in 1999 have liver EROD activities that correlate positively with the pyrogenic PAH indicator ratio (FI+Py)/C24Ph. Although traces (<5-100 ng/g TPAH) of EVOS residues were detected in seafloor sediments at some nearshore spill path sites, biomarker levels in fish from those sites are not elevated relative to other sites in PWS.

Role of estrogen receptor in regulation of polycyclic aromatic hydrocarbon metabolic activation in lung

Epidemiological and biochemical studies have indicated that females may be at greater risk of smoking associated lung cancer compared with males. Among lung cancer patients, female smokers have been found to have higher levels of PAH-related DNA adducts and CYP1A1 gene expression in their normal lung tissue compared to male smokers. A possible role of steroid hormones in these sex differences via interactions between aryl hydrocarbon receptor and estrogen receptor mediated cellular effects has been suggested. In the present study the impact of the estrogen receptor (ERalpha) on CYP1A1 and CYP1B1 gene expression was studied in vitro in human bronchial epithelial cells. Transient transfection of the BEP2D cell line with ERalpha influenced neither constitutive expression of CYP1A1 or CYP1B1 nor induction of these genes by TCDD as measured by real-time RT-PCR. ERalpha had no effect on the constitutive or TCDD-induced enzymatic activity of CYP1A1 (EROD). We also studied the effect of steroid hormones on lung PAH metabolic activation in A/J mice. Intact and ovariectomized female mice were orally exposed to a single dose of benzo[a]pyrene. Ovariectomy did not influence the levels of either benzo[a]pyrene-derived protein or DNA adducts in the lung tissue measured by HPLC and 32P-postlabeling, respectively. In conclusion, the present data do not support the hypothesis of a role of estrogen or the ERalpha in regulating the metabolic activation of polycyclic aromatic hydrocarbons in lung.

The Experimental Antitumor Agents Phortress and Doxorubicin are Equiactive Against Human-Derived Breast Carcinoma Xenograft Models

Phortress (the dihydrochloride salt of the lysylamide prodrug of 2-(4-amino-3-methylphenyl)-5-fluoro-benzothiazole (5F 203)) is an experimental antitumor agent with potent and selective activity against human-derived carcinomas of breast, ovarian and renal origin. UK clinical trials of Phortress are scheduled to begin in 2004. The mechanism of action of Phortress is distinct from all classes of chemotherapeutic agents currently in the clinic, and involves metabolic activation by cytochrome P450 (CYP) 1A1 to electrophilic species, which generate DNA adducts in sensitive tumors only. In the present study, the antitumor efficacy of Phortress has been compared with that of doxorubicin (Dox) in nine human-derived mammary carcinoma xenograft models, cultivated subcutaneously in the flanks of nude mice. In addition, cyp1a1 mRNA expression was measured in tumors of control and treated animals. Phortress compared favorably with Dox: significant activity, independent of estrogen receptor (ER) status, was established in 7/9 xenografts; in one xenograft model, Phortress elicited superior antitumor activity; no model demonstrated complete resistance to Phortress. In accordance with this observation, all xenografts available for examination (8) displayed clear induction of cyp1a1 expression upon treatment of mice with Phortress whereas Dox failed to induce cyp1a1 expression in all models. Prolonged viability of tumor fragments, recovered for treatment ex vivo could not be sustained; thus correlations between tumor cells' response to Phortress and cyp1a1 or cyp1b1 inducibility following 5F 203 treatment could not be determined with confidence.

Hepatic ethoxyresorufin O-deethylase (EROD) activity in flounder (Platichthys flesus) from contaminant impacted estuaries of the United Kingdom: continued monitoring 1999-2001

The determination of hepatic ethoxyresorufin O-deethylase (EROD) has been used to assess the induction of the mixed function oxygenase system (MFO) of flounder (Platichthys flesus) in UK estuaries. Induction of the MFO system denotes possible exposure to certain organic contaminants (e.g. polycyclic aromatic hydrocarbons, polychlorinated biphenyls) and its measure has been incorporated in national monitoring programmes. This study presents EROD monitoring data from 5 UK estuaries taken between 1999 and 2001 and builds on data from previous years. The results reveal that for all sampled estuaries EROD values have been significantly (p < 0.05) elevated on the majority of occasions in comparison with the reference estuary, the Alde in Suffolk, UK. However, the limited temporal scale of the reported monitoring does not allow any conclusions to be drawn with respect to trends in the data. Possible factors influencing the data (size, gender, seasonality, reproductive status, etc.) are discussed and recommendations for continued monitoring are made.

EROD activities in a primary cell culture of grass carp (Ctenopharyngodon idellus) hepatocytes exposed to polychlorinated aromatic hydrocarbonas

Aryl hydrocarbon (Ah) receptor (Ah-agonist) effects of environmental samples containing polychlorinated aromatic hydrocarbons were evaluated using a 7-ethoxyresorufin-O-deethylase (EROD) assay of a primary hepatocyte culture from grass carp (Ctenopharyngodon idellus). The results were compared with those obtained from the assay using the rat hepatoma cell line H4IIE and chemical analysis using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). A dose-response relationship was observed between the EROD activities, either from primary hepatocyte culture assay or from H4IIE assay, and concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The results showed that the assay based on the H4IIE cell line (EC50=0.83 pg/mL) is more sensitive to TCDD than the assay based on primary hepatocyte culture (EC50=9.7 pg/mL). In tests of environmental samples, the results from the assay using primary hepatocyte culture were comparable to those from the assay using the H4IIE cell line and chemical analysis of concentrations of mixtures of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/PCDF). The lack of a change in the activities of glutathione-S-transferase (GST) and lactate dehydrogenase (LDH) in cell culture upon exposure to TCDD indirectly indicates that the compound is persistent to biodegradation in the cell culture system.

Enzymatic and estrogenic responses in fish exposed to organic pollutants in the New York-New Jersey (USA) Harbor Complex

This study examines biochemical and hormonal responses in resident and migratory fish from the New York-New Jersey (USA) Harbor Complex (NY-NJHC) and those treated with sediment-associated organic contaminants. Following laboratory exposures to organic extracts of NY-NJHC sediments (injection), livers from adult male mummichogs, Fundulus heteroclitus, were analyzed for vitellogenin (VTG), cytochrome P4501A (CYPIA), CYP3A, and estradiol 2-hydroxylase (E2OHase) and ethoxyresorufin-O-deethylase (EROD) activities. Levels of CYP1A (311-391% of control) and EROD (267-361% of control) were elevated in mummichogs exposed to high doses of sediment extracts, while VTG, CYP3A, and E2OHase were unaffected. In field studies, reproductively mature male mummichogs collected from a highly contaminated area, Newark Bay (NJ, USA), did not have detectable levels of VTG but did exhibit elevated levels of CYP1A and EROD. Vitellogenin was also not detected in juvenile striped bass (Morone saxatilis) collected from the main stem of the lower Hudson River (NY, USA). Similar to results in the sediment extract-treated fish. CYP3A and E2OHase were unaltered in Newark Bay F. heteroclitus. The lack of response of CYP3A and E2OHase activities to contaminant mixtures, either environment or sediment derived, suggests that compounds in these mixtures either do not alter these enzymes, produce antagonistic effects in mixtures, are present at ineffective concentrations, or are regulated in a species-specific manner.

Trace metal concentrations and susceptibility to oxidative stress in the polychaete Sabella spallanzanii (Gmelin) (Sabellidae): potential role of antioxidants in revealing stressful environmental conditions in the Mediterranean

The polychaete Sabella spallanzanii (Gmelin) (Sabellidae) is a widely distributed species throughout the Mediterranean where it is commonly found in sheltered shallow areas and up to 30 m depth in more exposed waters. The sedentary habit, the filter-feeding behavior and its capability to colonize disturbed environments such as harbors, suggest the potential utility of this organism as a bioindicator in environmental monitoring programs. The aim of this work was a preliminary characterization of S. spallanzanii, integrating chemical data on trace metal concentrations with the biochemical analysis of antioxidant defenses which play an important role in mediating responses and adaptation to stressful environmental conditions. Organisms were collected in four locations of the Adriatic and Tyrrhenian Sea, characterized by a moderate impact or influenced by organic enrichment or sulphuric emissions. Trace metal concentrations (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) were comparable to those of other invertebrate species and quite typical for unpolluted environments. Analyses of individual antioxidants (superoxide dismutase, catalase, glutathione peroxidases, glutathione S-transferases, glutathione reductase) were integrated with measurement of the total oxyradical scavenging capacity toward specific forms of ROS; the TOSC assay, quantifying the overall capability of a tissue to neutralize specific reactive oxygen species provide a more integrated picture of the balance between prooxidant factors and antioxidant defenses, with important indications about the role of different ROS in appearance of oxidative disease. The antioxidant profile was influenced by the different physiological functions of the analyzed tissues, namely the branchial crown, involved in filtration of large volumes of seawater, and the thorax where digestive processes occur. The analysis of antioxidant defenses revealed significant variations in polychaetes from various sampling sites suggesting the influence of specific environmental conditions like those limiting oxygen availability. Our results confirm the role of antioxidants in adaptation to stressful environmental conditions and their importance in ecotoxicological studies for the sensitivity in revealing the occurrence of biological disturbance.

Cytological changes in association with ethoxyresorufin o-deethylase induction in fish upon dietary exposure to benzo[a]pyrene

Juvenile areolated grouper (Epinephelus areolatus) were exposed to two levels of dietary benzo[a]pyrene (BaP; 0.25-12.5 microg/g body wt/d) for four weeks, followed by four weeks of depuration. Significant increase in hepatic ethoxyresorufin O-deethylase (EROD) activities was found after one week, preceding an increase in lipopigments (as measured by quantitative transmission electron microscopy) in week 2 of exposure. The EROD activities in the BaP-treated fish subsided at week 4 of exposure and throughout the depuration period. Lipopigments in the high-dose group appeared to be more persistent than that of the EROD activity during the exposure period and remained significantly higher than that of the controls at week 4. Levels of lipopigments, however, rapidly subsided on withdrawal of BaP exposure. These results appear to suggest that changes in EROD activities would precede cytological changes and that both the observed cytological and biochemical changes are reversible. Results of the present study also lend further support to our earlier findings on Solea ovata, that a significant relationship exists between EROD activity and lipopigment accumulation (as measured by volume density, absolute volume, numerical density, and absolute density; r = 0.483-0.358, p < 0.05), regardless of fish species (S. ovata and aerolated grouper) as well as the routes of exposure to BaP (intraperitoneal injection or dietary exposure). This provides strong supporting evidence that elevated EROD activities in fish liver do not merely indicate exposure to polyaromatic hydrocarbons (PAHs) but are also associated with significant biological effects. Our results showed that hepatic EROD activity and lipopigments could be used to indicate recent exposure of the fish to BaP/PAHs.

Cell-specific CYP1A expression and benzo[a]pyrene adduct formation in gills of rainbow trout (Oncorhynchus mykiss) following CYP1A induction in the laboratory and in the field

The effect of cytochrome P4501A (CYP1A) induction on cell-specific benzo[a]pyrene (BaP) adduct formation was studied in rainbow trout (Oncorhynchus mykiss) gills. Fish preexposed to beta-naphthoflavone (betaNF) or caged in a polluted river were exposed to waterborne 3H-benzo[a]pyrene (3H-BaP). The 3H-benzo[a]pyrene adducts in the gill filaments were localized by autoradiography and CYP1A protein by immunohistochemistry. Ethoxyresorufin O-deethylase (EROD) activity was measured using a gill filament-based ex vivo assay. Branchial 3H-BaP binding and EROD activity were enhanced by exposure to betaNF or to the river water, and completely blocked by the CYP1A inhibitor ellipticine. The predominant sites of adduct formation were in epithelium of the secondary lamellae and in epithelium of the efferent edge of the gill filament. In betaNF-exposed fish, the strongest CYP1A immunoreactivity was observed in differentiating cells and in pillar cells. In fish caged in the polluted river, strong CYP1A immunoreactivity was found in most cells in the secondary lamellae, whereas the primary lamellae were almost devoid of immunoreactivity. Our results reveal a discrepancy between the localization of CYP1A protein and BaP adducts in the gill. Consequently, other factors, such as bioavailability of waterborne polycyclic aromatic hydrocarbons (PAHs) to the target cells, are important for the localization of PAH adducts in the gill.

Interaction of tributyltin with hepatic cytochrome P450 and uridine diphosphate-glucuronosyl transferase systems of fish: in vitro studies

Hepatic microsomes of red mullet (Mullus barbatus) and flounder (Platichthys flesus) were preincubated in the presence of a concentration range of the antifouling agent tributyltin (TBT) chloride, and the interactions of TBT with cytochrome P450 and uridine diphosphate-glucuronyl transferase systems were investigated. The enzyme systems were examined in terms of cytochrome P4501A (CYP1A)-catalyzed 7-ethoxyresorufin O-deethylase (EROD) activity and benzo[a]pyrene (BaP) metabolism and in terms of glucuronidation of testosterone and 17beta-estradiol, respectively. Ethoxyresorufin O-deethylase and BaP hydroxylase (BPH) activities of both fish species were progressively inhibited by increasing concentrations of TBT, and the effects were more pronounced for EROD than for BPH (maximal inhibition at 100 microM TBT for EROD and 250-500 microM TBT for BPH). Hydroxylated metabolites of BaP (3-hydroxy-, 7,8-dihydrodiol, and 9,10-dihydrodiol), representing 95% of the total metabolites formed, were reduced up to 75% in the presence of 100 to 500 microM TBT, whereas the formation of other metabolites was less affected. This may alter BaP toxicity and carcinogenicity. Overall, the results were consistent with a specific inhibitory effect of TBT on CYP1A in the two fish species. Additionally, the conjugation of testosterone was significantly inhibited (20%) at low TBT doses (5 microM), with no effect on the glucuronidation of estradiol.

Reproductive and biochemical biomarkers in largemouth bass sampled downstream of a pulp and paper mill in Florida

The objective of this study was to evaluate the effects of bleached/unbleached kraft mill effluents (B/UKME) on the reproductive parameters of free-ranging Florida largemouth bass (Micropterus salmoides floridanus). The reproductive parameters measured included gonadosomatic index (GSI), histological evaluation of gonads, and plasma concentrations of vitellogenin (VTG), 17beta-estradiol, and 11-ketotestosterone (11-KT). Hepatic ethoxyresorufin-O-deethylase (EROD) activity was measured as a marker of exposure to cytochrome P450-inducing agents in these effluents. Endpoints were compared among adult bass sampled from tributary and mainstream effluent-contaminated and reference sites. Females sampled from the site closest to the mill outfall had a significant five-fold increase in EROD activity compared to bass sampled from reference streams. Although sex hormones were significantly reduced in bass from exposed sites, there were no differences in VTG and GSI across sites. The absence of organism-level responses was probably not related to a lack of sensitivity, as previous studies in our laboratory have shown that bass exposed to these effluents exhibit changes in GSI and in other measures associated with reproductive success. In females, inverse relationships were observed between VTG and GSI and EROD activity. These relationship, however, were not consistent within all of the sites studied. Collectively, our findings indicate that hepatic EROD induction is an effective marker of B/UKME exposure in largemouth bass and that it might be associated with antiestrogenic effects in this species.

Enzymatic and nonenzymatic antioxidants as an adaptation to phagocyte-induced damage in Anguilla anguilla L. following in situ harbor water exposure

Anguilla anguilla L. were caged for 8 and 48 h in harbor water of Aveiro Lagoon, Portugal. Respiratory burst activity (RBA) of peritoneal, head kidney, and gill phagocytes was measured. Lipid peroxidation (LPO) was estimated in gill, kidney, and liver. Liver ethoxyresorufin-O-deethylase (EROD) activity, cytochrome P450 (Cyt P450) content, and bile metabolites were assayed. Various antioxidant enzymes, viz., glutathione peroxidase, catalase, and glutathione S-transferase and nonenzymatic antioxidant, viz., total reduced glutathione were also studied. Harbor water xenobiotics induced a significant RBA increase in gill after 8 h; whereas in peritoneum and head kidney it increased after 48 h exposure. These responses were adversely associated with tissue-specific peroxidative damage since significant LPO increase was observed in gill (8 and 48 h), kidney (48 h), and liver (48 h). The tissue most affected was gill. Moreover, liver EROD activity, Cyt P450 content and bile metabolites remain unaltered after 8 h; in contrast, 48 h exposure showed significant EROD activity decrease and pyrene-type bile metabolites increase. Decreased EROD activity may be associated with concomitant liver damage, as increased LPO was observed after 48 h. Furthermore, the tissue-specific damage corresponded to the differences in the antioxidant potentials of the tissues, since the initial exposure period caused a significant increase in liver antioxidant activities, whereas gill and kidney showed a significant decrease, demonstrating that liver is highly adaptive to oxidative damage. However, at 48 h exposure gill, kidney, and liver showed a suppressive antioxidant effect, probably due to PAHs, since a significant induction at PAH-type bile metabolites has been seen. Our results demonstrate that phagocyte activation and associated peroxidative damage are concomitantly corroborated with enzymatic and nonenzymatic antioxidant activity differences. In addition, hepatic antioxidant induction after short-term exposure may serve as a potent biomarker for water pollutants in fish.

Effects of green tea on carcinogen-induced hepatic CYP1As in C57BL/6 mice

Green tea (GT) drinking showed chemopreventive effects on various cancers. In addition, inhibition of CYP1A activity by green tea components--polyphenols--has been suggested as a chemoprevention against carcinogens that were bioactivated by CYP1As. Therefore, any changes in hepatic CYP1As may be considered as a biomarker for GT chemoprevention and clarify whether whole GT is chemopreventive for the population who are exposed to CYP1A specifically-bioactivated carcinogens. In this study, we investigated the changes in CYP1A levels by pre- and concurrent GT drinking against a CYP1A-inducing carcinogen, 3-methylcholanthrene (MC), in aryl hydrocarbon receptor responsive C57 BL/6 mice. We found that GT drinking itself induced hepatic CYP1As and enhanced MC-induced ethoxyresorufin-O-demethylase (EROD) activity (P<0.05). However, our studies of CYP1A monoclonal antibody and western blots revealed that the enhanced hepatic EROD activity by GT did not come from CYP1As. Therefore, our results suggest that GT may work to biotransform CYP1A inducing carcinogens into non-carcinogenic metabolites by modulation of other microsomal enzymes rather than CYP1As. In addition, the mechanism of GT chemoprevention may be different from that of GT components, such as polyphenols that reduce CYP1As activity.

Hepatic CYP1A levels and EROD activity in English sole: biomonitoring of marine contaminants in Vancouver Harbour

To assess chemical contaminant stress in the marine environment, ethoxyresorufin-O-deethylase (EROD) activity and cytochrome P450 1A (CYP1A) expression were measured in 88 English Sole (Pleuronectes vetulus) collected during May and June 1999 from four sites in Vancouver Harbour and at an expected reference site outside the harbour. Hepatic microsomes were prepared from the fish and analyzed for total CYP content, EROD activity, and CYP1A protein levels. Hepatic EROD activity and CYP1A protein levels were elevated in fish from two sites in the inner harbour. A comparison with sediment chemistry data showed that fish with increased EROD activity and CYP1A levels came from sites containing relatively high levels of polycyclic aromatic hydrocarbons and polychlorinated biphenyls. Unexpectedly high levels of EROD activity and CYP1A protein were also found in fish from a reference site near Gibsons, in Howe Sound. The elevated EROD activity and CYP1A expression in fish from this site cannot be explained by the chemical analysis data collected.

Computational prediction of 7-ethoxyresorufin-O-diethylase (EROD) and luciferase (luc) inducing potency for 75 congeners of chloronaphthalene

Based on available toxicological data and matrix of structural descriptors 7-ethoxyresorufin-O-diethylase (EROD) and luciferase (luc) inducing potency for 75 congeners of chloronaphthalene was predicted using quantitative structure-activity relationships (QSAR) strategy. The most active congeners in EROD and luciferase bioassays were CN congeners nos. 75 and 67. Some empirical rules describing toxic PCNs were formulated.

The identification of readily bioavailable pollutants in Lake Shkodra/Skadar using semipermeable membrane devices (SPMDs), bioassays and chemical analysis

GOAL, SCOPE AND BACKGROUND

Lake Shkodra/Skadar is the largest lake in the Balkans region and located on the border between Albania to the south and Montenegro to the north. Because of the wide range of endemic, rare or endangered plant and animal species it supports, Lake Shkodra/Skadar and its extensive associated wetlands are internationally recognised as a site of significance and importance (Ramsar site). In recent years, social and economic changes in both Albania and Montenegro have lead to unprecedented levels of urban and industrial effluent entering the lake. Of particular concern is the increasing input of toxic hydrophobic organic pollutants (HOPs) into the lake and the degree to which these compounds are available for uptake by aquatic biota. Semipermeable membrane devices (SPMDs) have been shown to sample the readily bioavailable fraction (dissolved phase) of waterborne HOPs and in doing so provide relevant data for exposure assessment. The aim of the current study was to use SPMD-based sampling in conjunction with appropriate bioassays and chemical analysis to identify readily bioavailable HOPs in the lake.

METHODS

SPMDs were constructed and deployed at three sites in the Albanian sector and three sites in the Montenegrin sector of Lake Skadar/Shkodra for 21 days. Following the dialytic recovery of target analytes and size exclusion chromatographic clean-up, aliquots of SPMD samples were subjected to GC-MS scan analysis for major components, GC-MS SIM analysis for 16 priority pollutant polycyclic aromatic hydrocarbons (PP-PAHs) and assayed for EROD-inducing, estrogenic and mutagenic potential using rainbow trout liver cells (RTL-W1), the yeast estrogen screen (YES) and the Ames Test, respectively.

RESULTS AND DISCUSSION

A total of 39 compounds were tentatively identified in SPMD samples from the six sampling sites. Alkylated PAHs were the most abundant and ubiquitous compounds present along with various sterols and sterol derivatives. Numerous other compounds remain unidentified. 15 of the 16 targeted PP-PAHs were present in samples from one or more of the sampling sites indicating these compounds are both readily bioavailable and widely distributed in Lake Shkodra/Skadar. Total PP-PAH concentrations ranged between 3991 ng/SPMD and 10695 ng/SPMD. Bioassays carried out on SPMD samples revealed significant EROD-inducing and estrogenic potential at five of the six sampling sites indicating toxicologically relevant compounds are readily available for uptake by resident aquatic biota. EROD-inducing potential was positively correlated with targeted PP-PAH concentration (r2 = 0.74). However, comparison of bioassay- and analytically-derived toxicity equivalents revealed targeted PP-PAHs were responsible for less than 0.06% of the total EROD-inducing potential.

CONCLUSIONS AND OUTLOOK

The combination of SPMD-based sampling with appropriate bioassays and chemical analysis provided an effective tool for the identification of environmentally relevant waterborne pollutants in Lake Shkodra/Skadar. Our results show that toxicologically relevant HOPs including EROD-inducing and potentially estrogenic compounds are widely distributed in the lake and readily available for uptake by aquatic biota. Our results also suggest that alkylated PAHs rather than parent compounds may be of greater toxicological relevance in the lake. As anthropogenic influences continue to increase, SPMD-based sampling is expected to play a central role in future research concerned with the identification, monitoring and assessment of the risk posed by HOPs to Lake Shkodra/Skadar's aquatic biota.

European starling (Sturnus vulgaris): avian model and monitor of polychlorinated biphenyl contamination at a Superfund site in southern Illinois, USA

Accumulation and effects of polychlorinated biphenyls (PCBs) in avian species were evaluated at a Superfund site located at Crab Orchard National Wildlife Refuge (IL, USA). European starlings (Sturnus vulgaris) were monitored at nest boxes constructed at each of two study and two reference sites. During the breeding season, starling productivity and adult provisioning behavior were monitored. At 15 d after hatch, chicks and adults were collected for contaminant and biomarker analyses. Chicks and adults were necropsied. ethoxyresorufin-O-deethylase (EROD) activity was measured in liver tissue, and polychlorinatedbiphenyl (PCB; Aroclor 1254) and 34 chlorinated biphenyl (CB) congener concentrations were measured in carcasses. Polychlorinated biphenyl and CB concentrations also were measured in eggs that failed to hatch. Mean Aroclor 1254 and quantified CB concentrations were greater (p < 0.001) in eggs that failed to hatch, 15-d-old chicks, and adults collected from PCB-contaminated sites (hereafter PCB sites) compared to those collected from reference sites. The EROD activity was greater (p = 0.005) in 15-d-old chicks, but not adults (p = 0.972), collected from PCB sites compared to those collected from reference sites. No differences were found among study and reference sites in number of eggs laid or percent of eggs hatched; however, reduced nest provisioning behavior and decreased chick survival were observed at PCB sites. Polychlorinated biphenyl concentrations measured in samples collected from the PCB sites are similar to concentrations previously associated with adverse effects in avian species. Other avian species utilizing these sites also may be exposed to PCBs with associated adverse effects. This study demonstrates that starling nestlings are good biological monitors of local contamination and continued monitoring may provide useful data for evaluating the effectiveness of proposed remediation.

Genotoxic and biochemical responses in caged eel (Anguilla anguilla L.) after short-term exposure to harbour waters

European eel (Anguilla anguilla L.) were caged and exposed in situ for 8 and 48 h to the Aveiro offward fishing harbour water (HW) and to clean seawater under laboratory conditions (Control). Eel liver biotransformation (Phase I) was measured as ethoxyresorufin-O-deethylase (EROD) activity, cytochrome P450 (P450) and glutathione S-transferase (GST) activity (Phase II). Genotoxic responses were determined as blood, liver and kidney DNA strand breaks as well as erythrocytic nuclear abnormalities (ENAs). HW failed to significant increase liver EROD, GST activities and ENA frequency. Nevertheless, P450 content was significantly increased after 8 and 48 h exposure. Genotoxicity measured as DNA integrity decrease was found in blood after 8 and 48 h exposure to HW, whereas in liver and kidney, it was observed after 48 h exposure to HW. Blood, kidney and liver genotoxicity may be due to the presence of polycyclic aromatic hydrocarbons (PAHs) which are genotoxic compounds and the main HW organic contaminants.

CYP1A1 and XRCC1 gene polymorphisms in SCC of the larynx

The present study was undertaken to examine CYP1A1 and XRCC1 polymorphisms as potential genetic susceptibility markers for laryngeal squamous cell carcinoma (SCC). Eighty-eight patients with laryngeal SCC and 178 randomly selected healthy blood donors from the same Caucasian population (Porto, Northern Portugal) were analysed for CYP1A1 (MspI and NcoI) and XRCC1 (Arg194Trp and Arg399Gln) polymorphisms, using PCR-RFLP techniques. CYP1A1 MspI MH (mutant homozygous) and CYP1A1 NcoI HT (heterozygous) genotypes were more frequent in patients than in controls, with those carrying a CYP1A1 NcoI HT genotype having a 2.3-fold higher risk for tumour development. On the other hand, polymorphisms in XRCC1 codon 399 and codon 194 do not seem to play a role in the aetiology of smoking-related laryngeal SCC, once its distribution was similar in both analysed groups. All the significant associations observed were exclusively due to differences between controls and larynx glottic cancer patient subgroup. Furthermore, lower lifetime tobacco consumption was observed in laryngeal SCC patients carrying the MspI and NcoI polymorphisms, than in those who did not show the polymorphic variants. This investigation seems to support the importance of CYP1A1 gene polymorphism as a potential genetic marker of laryngeal cancer development, specially concerning smokers who have inherited the at-risk genotypes CYP1A1 MspI MH or CYP1A1 NcoI HT, who do appear to be more susceptible to the development of SCC of the glottic larynx.

Long-term exposure effects in vitellogenin, sex hormones, and biotransformation enzymes in female carp in relation to a sewage treatment works

In the present study, the estrogenic response in the reproductive cycle of female carp, Cyprinus carpio, in relation to a sewage treatment works (STWs) was measured as: alterations in plasmatic and hepatic vitellogenin (VTG) content, plasma levels of testosterone (T) and estradiol (E2), and effects on key enzymes of phases I and II biotransformation, ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST). Low plasma VTG content in females collected 4 km downstream of an effluent discharge suggested possible estrogenic disturbances; however, hepatic VTG content and sex hormone levels did not mirror this. In fact, E2 and T largely fluctuated among fish, with individual variations even greater than among sampling stations or periods. This suggests that at moderately polluted sites, biological variations of female carp and genetic particularities are prevalent. Hepatic biotransformation enzymes, such as EROD, increased with increasing water temperature while, in contrast, GST was maximal at the lowest water temperature.

Using reproductive endpoints in small forage fish species to evaluate the effects of Athabasca Oil Sands activities

The main objective of this study was to evaluate the influence of naturally occurring oil sands-related compounds (OSRC) on reproductive function in fish in order to assess the impacts of anthropogenic point-source inputs. The health of slimy sculpin (Cottus cognatus) and pearl dace (Semotilus margarita) collected from the Alberta Athabasca Oil Sands (Canada) watershed were examined. Two rivers were selected for study: the Steepbank and the Ells. These rivers originate outside the oil sands formation, where fish are unexposed (Ref), exposed to naturally occurring oil sands-related compounds (Nat), or exposed to naturally occurring compounds as well as adjacent to surface mining activity (Dev). Assessment endpoints included gonadosomatic indices (GSI), fecundity, and in vitro gonadal steroid production. In vitro gonadal incubations demonstrated lower levels of steroid production at sites along the Steepbank River within the oil sands deposit. Hepatic 7-ethoxyresorufin-O-deethylase (EROD) activity, an indicator of exposure to OSRC, was elevated twofold at the site with natural compounds and up to 10-fold at the site adjacent to development compared to EROD activity in fish from the reference site. Fish collected in the Ells River had a threefold induction in EROD activity but no significant reduction in steroid production when compared to reference fish. No consistent alterations in gonadal development were seen in fish collected from sites within the oil sands deposit. This research in the Athabasca River basin provides baseline information of the health of fish populations within the oil sands deposit prior to further development in the area.

Impacts from PCB accumulation on amphibians inhabiting streams flowing from the Paducah Gaseous Diffusion Plant

Contamination at the Paducah Gaseous Diffusion Plant (PGDP), Paducah, Kentucky, has been under evaluation for many years. We studied amphibians in selected outfalls (drainage ditches) flowing from the PGDP to determine if PCBs were accumulating in their tissues and how this might affect local populations. We determined relative amphibian species richness and abundance among seven outfalls and three reference streams by listening to their calls during audio surveys. We also captured amphibians from each study site during the summers of 2000 and 2001 and analyzed their carcasses for PCBs (Aroclor 1260 and 34 congeners) and livers for ethoxyresorufin O-deethylase (EROD) activity, a biomarker of PCBs and other organic contamination. Ten species were heard across study sites, and abundance and richness at outfalls were similar to those observed at reference sites. However, there were significant differences in abundance (p = 0.001) and richness (p = 0.048) of amphibians between continuously flowing and intermittent outfalls. There were no significant differences in PCB concentrations (p = 0.113) in amphibians captured from study sites, although Aroclor 1260 concentrations tended to be higher in amphibians collected from one outfall (outfall 12) on the east side of the plant (x = 1260 microg/kg) compared with all other study sites (x = 489 microg/kg). EROD activity measured in the liver was not indicative of Aroclor 1260 concentrations in amphibians at the PGDP, and EROD did not differ by study site, species, age class, or gender. PCB concentrations measured in amphibians at the PGDP were similar to concentrations measured at reference sites and did not appear to negatively affect individual amphibians or abundance and richness.

Biomarkers in fish from Prince William Sound and the Gulf of Alaska: 1999-2000

To test the hypothesis that biomarker levels in fish collected at Prince William Sound (PWS) sites impacted by the 1989 Exxon Valdez oil spill were higher than those collected at unimpacted sites, a 1999-2000 study collected five fish species and associated benthic sediments from 21 sites in PWS and the eastern Gulf of Alaska (GOA). PWS sites were divided in three oiling categories based upon 1989 shoreline assessments: nonspill path (NSP), spill path oiled (SPO), and spill path not oiled (SPNO). Rockfish (N = 177), rock sole (N = 30), and kelp greenling (N = 49) were collected at near-shore locations (approximately 50-500 m from shore); Pacific halibut (N = 131) and Pacific cod (N = 81) were collected further offshore (approximately 500-7000 m). Fish were assayed for bile fluorescent aromatic contaminants (FAC) and cytochrome P4501A (CYP1A) levels measured as liver ethoxyresorufin O-deethylase (EROD) activity and by immunohistochemistry (IHC) of various tissues. For all species studied at all sites, bile FAC concentrations and CYP1A levels were low and in the same range for fish collected at PWS SPO and SPNO sites relative to NSP sites in PWS and the GOA. Consequently, the hypothesis is rejected for the species studied. The bile FAC results further indicate a pervasive exposure of fish at all sites, including those in the GOA far removed from the effects of the spill, to low levels of polycyclic aromatic hydrocarbons. Analysis of the benthic sediments indicates that the probable sources of this exposure are petrogenic hydrocarbons derived from natural oil seeps and eroding sedimentary rocks in the eastern GOA.

Stress status of gudgeon (Gobio gobio) from rivers in Switzerland with and without input of sewage treatment plant effluent

To assess the importance of sewage treatment plant effluents on fish health, we studied gudgeon in two rivers in the Swiss midlands (Canton Lucerne). Both rivers receive pollution from diffuse sources, while one also receives the effluent of a sewage treatment plant. Male and female gudgeon during and outside of the spawning season were compared with respect to reproductive parameters and health status across both rivers as well as upstream and downstream of the STP. Several biomarkers were studied, including cytochrome P4501A, 7-ethoxyresorufin-O-deethylase, plasma vitellogenin, ovotestis, lipid, liver histology, condition factor, gonadosomatic index, splenosomatic index, parasites of spleen and liver, population structure, and species diversity. Gudgeons of both rivers exhibited signs of a moderately impaired health status. By a stepwise backward analysis, the cytochrome P4501A content, the splenosomatic index, and the incidence of parasites in the liver were found to provide the best discrimination of the three sampling sites. Evidence of a significant elevation in response to the sewage treatment plant effluent was found neither in vitellogenin concentration nor in the ovotestis rate. While population structure was analyzed upstream and downstream of the sewage treatment plant, only gudgeons of the latter site revealed a disturbed population structure, most probably caused by a former nitrite discharge.

Quantitative evaluation of hepatic cytochrome P4501A transcript, protein, and catalytic activity in the striped sea bream (Lithognathus mormyrus)

Hepatic cytochrome P4501A (CYP1A) expression was partially characterized in the striped sea bream (Lithognathus mormyrus) from the Mediterranean coast of Israel as part of the process of establishing the CYP1A gene as an environmental biomarker. Reverse transcription-competitive polymerase chain reaction, competitive enzyme-linked immunosorbent assay, and ethoxyresorufin O-deethylase (EROD) assay were used for evaluating transcript, protein, and catalytic activity levels, respectively, in absolute units. Highest elucidated transcript, protein, and catalytic activity levels were 0.264 +/- SD 0.084 fmol/microg total RNA, 0.88 +/- 0.52 pmol/microg total protein, and 1.11 +/- 0.52 pmol resorufin/min/microg total protein, respectively, and the lower levels were 0.009 +/- 0.007 fmol/microg total RNA, 0.17 +/- 0.08 pmol/microg total protein, and 0.11 +/- 0.06 pmol resorufin/min/microg total protein, respectively, demonstrating substantial induction potential. All alternate pairs of seven examined field samples, revealing a transcript-level ratio higher than 1.7, also demonstrated a significant difference between their transcript levels, indicating a potential to detect relatively small biomarker changes (1.7-fold) caused by environmental effects. Simultaneous triple measurements of transcript, protein, and catalytic activity were carried out in individuals from two field samples and during a 318-d decay experiment. Fish from the field samples revealed significant alternate bivariate correlation between transcript, protein, and enzymatic activity. Conflicting results were found when analyzing the decay experiment, in which both protein and catalytic activity levels decreased significantly to basal levels, in contrast to no significant change in transcript levels throughout the experiment. No significant difference was observed between males and females regarding the levels of CYP1A transcript, protein, and EROD.

Integrating enzymatic responses to organic chemical exposure with total oxyradical absorbing capacity and DNA damage in the European eel Anguilla anguilla

In this work, susceptibility to oxidative stress was analyzed under laboratory conditions in the European eel Anguilla anguilla. Eels were treated with increasing concentrations of benchmark environmental pollutants, namely, benzo[a]pyrene ([BaP], at 0, 0.1, 1, 10, and 50 mg/kg), beta-naphthoflavone ([BNF], at 0, 0.1, 1, 10, and 50 mg/kg), Arochlor 1254 (at 0, 0.1, 1, 10, and 50 mg/kg), and 2,3,7,8-tetrachlorodibenzo p-dioxin ([TCDD], at 0, 0.01, 0.1, 1, and 2 microg/kg). The integral relationships were analyzed between induction of ethoxyresorufin O-deethylase (EROD) activity, its involvement in perturbing oxyradical metabolism, and the role of cytochrome P450 and/or oxidative stress in mediating genotoxic effects. To reveal whether the oxidative status in exposed organisms was altered as a result of chemical exposure, measurements of the main endogenous antioxidant defenses were integrated with the measurement of total oxyradical scavenging capacity (TOSC) toward peroxyl radicals and hydroxyl radicals (*OH). This approach permits discriminating the resistance of a tissue toward different forms of oxyradicals, thereby indicating a differential role for specific reactive oxygen species (ROS) in perturbing the balance between prooxidant and antioxidant mechanisms. All the analyzed chemicals promoted EROD induction (reflective of CYP1A) and altered either the levels or the activities of the antioxidants studied, which might be anticipated to exert alterations in oxyradical metabolism. Analysis of TOSC suggested the prevalence of metabolic oxidative pathways leading to the more reactive *OH on exposure to the chemicals studied. Of these chemicals, enhanced EROD activity correlated with genotoxic damage only in the cases of the nonhalogenated hydrocarbons BaP and BNF. The highest degree of genotoxic damage was consistently observed in organisms in which the capacity to absorb or scavenge OH was lowest. These data suggest a general relationship between oxidative stress and loss of DNA integrity in juvenile eels exposed to the chemicals studied herein.

Effect-directed identification of oxygen and sulfur heterocycles as major polycyclic aromatic cytochrome P4501A-inducers in a contaminated sediment

Heterocyclic polyaromatic compounds, including dinaphthofurans, 2-(2-naphthalenyl)benzothiophene, methylated chrysene, and benz[a]anthracene, were identified and confirmed as major cytochrome P4501A (CYP1A)-inducing compounds in a contaminated sediment close to the industrial site of Bitterfeld (Germany). Identification was achieved by the application of an effect-directed fractionation and analysis approach. This approach comprised the combination of a rainbow trout liver cell line (RTL-W1) bioassay to select for CYP1A-inducing effects by measuring 7-ethoxyresorufin-O-deethylase activity, a multistep fractionation procedure, and various methods of chemical characterization. The identified nonpriority pollutants were found to be significantly more potent than the reference compound, benzo[a]pyrene, and among the most potent polycyclic inducers known. On the basis of the history of industrial activity at the contaminated site, the heterocyclic compounds identified in this study are thought to stem from 2-naphthol production. 2-Naphthol is one of the most high-tonnage products of the aniline dye industry in general, thereby indicating the potential environmental relevance of the identified heterocyclic aromatic compounds. To date, however, no or very little knowledge exists about their occurrence, fate, and biological effects.

Inhalation exposure of rats to asphalt fumes generated at paving temperatures alters pulmonary xenobiotic metabolism pathways without lung injury

Asphalt fumes are complex mixtures of various organic compounds, including polycyclic aromatic hydrocarbons (PAHs). PAHs require bioactivation by the cytochrome P-450 monooxygenase system to exert toxic/carcinogenic effects. The present study was carried out to characterize the acute pulmonary inflammatory responses and the alterations of pulmonary xenobiotic pathways in rats exposed to asphalt fumes by inhalation. Rats were exposed at various doses and time periods to air or to asphalt fumes generated at paving temperatures. To assess the acute damage and inflammatory responses, differential cell counts, acellular lactate dehydrogenase (LDH) activity, and protein content of bronchoalveolar lavage fluid were determined. Alveolar macrophage (AM) function was assessed by monitoring generation of chemiluminescence and production of tumor necrosis factor-alpha and interleukin-1. Alteration of pulmonary xenobiotic pathways was determined by monitoring the protein levels and activities of P-450 isozymes (CYP1A1 and CYP2B1), glutathioneS-transferase (GST), and NADPH:quinone oxidoreductase (QR). The results show that acute asphalt fume exposure did not cause neutrophil infiltration, alter LDH activity or protein content, or affect AM function, suggesting that short-term asphalt fume exposure did not induce acute lung damage or inflammation. However, acute asphalt fume exposure significantly increased the activity and protein level of CYP1A1 whereas it markedly reduced the activity and protein level of CYP2B1 in the lung. The induction of CYP1A1 was localized in nonciliated bronchiolar epithelial (Clara) cells, alveolar septa, and endothelial cells by immunofluorescence microscopy. Cytosolic QR activity was significantly elevated after asphalt fume exposure, whereas GST activity was not affected by the exposure. This induction of CYP1A1 and QR with the concomitant down-regulation of CYP2B1 after asphalt fume exposure could alter PAH metabolism and may lead to potential toxic effects in the lung.