Endocrine and metabolic changes in Anguilla anguilla L. following exposure to beta-naphthoflavone--a microsomal enzyme inducer

Association of exposure to polycyclic aromatic hydrocarbons with thyroid hormones in adolescents and adults, and the influence of the iodine status

Some studies of endocrine-disrupting polycyclic aromatic hydrocarbon (PAH) exposure and thyroid hormones (THs) are inconclusive. To assess the associations between PAHs and THs, and the influence of the iodine status on PAHs-THs, we employed 648 adolescents (12-19 years old) and 2691 adults from the National Health and Nutrition Examination Survey 2007-2008 and 2011-2012. PAH metabolites [1-hydroxynaphthalene (1-NAP), 2-NAP, 1-hydroxyphenanthrene (1-PHE), 2-PHE, 3-PHE, 2-hydroxyfluorene (2-FLU), 3-FLU, 9-FLU, and 1-hydroxypyrene (1-PYR)], THs [total and free thyroxine (TT4 and FT4), total and free triiodothyronine (TT3 and FT3), thyroid stimulating hormone (TSH), and thyroglobulin (Tg)], peripheral deiodinase activity (GD) and thyroid's secretory capacity (GT) were involved. Multiple linear regression and weighted quantile sum (WQS) regression models were used to assess PAH-TH associations and the interaction between PAHs and the iodine status. Stratification analyses were conducted based on sex, smoking and iodine status. For adolescents, in a multivariable-adjusted regression model (β; 95% CI), 1-PHE (4.08%; 1.01%, and 7.25%), 2-PHE (3.98%; 0.70%, and 7.25%) and 9-FLU (3.77%; 1.10%, 7.47%) were positively correlated with TT3; 3-PHE and 1-PYR interacted with the iodine status (P-int < 0.05); 9-FLU was positively correlated with GD in both sexes. Combined exposure to PAHs was positively associated with Tg (0.137; 0.030, and 0.243), and negatively correlated with TSH (-0.087; -0.166, and -0.008). For adults, 2-NAP was positively correlated with FT3 (0.90%; 0.20%, and 1.61%), FT4 (1.82%; 0.70%, and 2.94%), TT3 (1.31%; 0.10%, and 2.63%), TT4 (2.12%; 0.90%, and 3.36%) and GT (2.22%; 1.01%, and 3.46%), but negatively correlated with TSH (-4.97%; -8.33%, and -1.49%); 1-NAP interacted with the iodine status (P-int < 0.05); 1-PHE was inversely correlated with TT3 in males; 2-PHE was positively correlated with TT3 in females. Combined exposure to PAHs was positively associated with FT3 (0.008; 0.001, and 0.014). Combined exposure to PAHs was positively associated with FT3, TT3 and GD, and negatively correlated with FT4, TT4 and GT in non-smoking adults; but positively associated with Tg (β = 0.140; 95% CI: 0.042, 0.237) in smoking adults. Our results indicated that combined and individual PAH exposure might be related to THs, and the iodine status had an influence on PAH-TH associations. These associations were not identical between adolescents and adults, and there were sex and smoking status differences.

Associations between prenatal exposure to polycyclic aromatic hydrocarbons and thyroid hormones in umbilical cord blood

We explored the association between maternal urinary polycyclic aromatic hydrocarbon (PAH) metabolites and thyroid hormones in umbilical cord blood in 120 pairs of pregnant women and newborns. Maternal urinary PAH metabolites were measured using high-performance liquid chromatography with tandem mass spectrometry. Thyroid hormones were measured using a flow fluorescence assay. The dose-response relationship between PAH metabolites and thyroid hormones was analyzed using the generalized linear model and restricted cubic spline model. Results showed that ƩOH PAHs in maternal urine had a negative effect on triiodothyronine (T3). Associations between maternal urinary PAH metabolites and thyroid hormones in umbilical cord blood plasma were observed. Prenatal exposure to PAHs could affect neonatal thyroid hormones, thereby disrupting neonatal thyroid function.

Associations between repeated measurements of urinary polycyclic aromatic hydrocarbon metabolites and thyroid hormones among reproductive-aged men

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) have been shown to disrupt thyroid function in toxicological studies, but epidemiological evidence is inconsistent. Furthermore, little is known on potential effects of mixtures of PAHs.

OBJECTIVE

This study aimed to examine the associations of exposure to PAHs as individual chemicals and mixtures with thyroid hormones.

METHODS

We included 378 men from a Reproductive Medicine Center in Wuhan, China. Ten monohydroxylated PAH (OH-PAH) metabolites in repeated urine specimens collected at two-time points and three thyroid hormones [thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3)] in one serum sample were measured. Multivariable linear regression models were applied to assess the associations between individual OH-PAH metabolites and thyroid hormones, and the associations with mixtures of OH-PAH metabolites were assessed by Bayesian kernel machine regression (BKMR) models.

RESULTS

Multivariable linear regression models showed inverse associations between urinary 1-OHNa and TSH, between urinary 1-OHPh and 9-OHPh and FT3, as well as between urinary 2-OHPh, 3-OHPh, 9-OHPh and ∑OHPh and FT4, regardless of these individual OH-PAH metabolites modeled as continuous or tertile variables (e.g., -21.57 % in TSH; 95 % CI: -35.33 %, -4.88 % for the third vs first tertiles of 1-OHNa; p for trend = 0.014). BKMR models showed negative overall effects of all urinary OH-PAH metabolite mixtures on TSH, FT3, and FT4, and 1-OHNa, 9-OHPh, and 2-OHPh as the most important contributors, respectively, with linear inverse exposure-response associations when holding other OH-PAH metabolites at their median concentrations.

CONCLUSION

Urinary OH-PAH metabolites as individual chemicals and mixtures were adversely associated with thyroid hormones among reproductive-aged men.

The antibacterials ciprofloxacin, trimethoprim and sulfadiazine modulate gene expression, biomarkers and metabolites associated with stress and growth in gilthead sea bream (Sparus aurata)

The high consumption and subsequent input of antibacterial compounds in marine ecosystems has become a worldwide problem. Their continuous presence in these ecosystems allows a direct interaction with aquatic organisms and can cause negative effects over time. The objective of the present study was to evaluate the effects of exposure to three antibacterial compounds of high consumption and presence in marine ecosystems (Ciprofloxacin CIP, Sulfadiazine SULF and Trimethoprim TRIM) on the physiology of the gilthead sea bream, Sparus aurata. Plasma parameters, enzymatic biomarkers of oxidative stress and damage and expression of genes related to stress and growth were assessed in exposed S. aurata specimens. For this purpose, sea bream specimens were exposed to individual compounds at concentrations of 5.2 ± 2.1 μg L^-1 for CIP, 3.8 ± 2.7 μg L^-1 for SULF and 25.7 ± 10.8 μg L^-1 for TRIM during 21 days. Exposure to CIP up-regulated transcription of genes associated with the hypothalamic-pituitary-thyroid (HPT) (thyrotropin-releasing hormone, trh) and hypothalamic-pituitary-interrenal (HPI) axes (corticotropin-releasing hormone-binding protein, crhbp) in the brain, as well as altering several hepatic stress biomarkers (catalase, CAT; glutathione reductase, GR; and lipid peroxidation, LPO). Similar alterations at the hepatic level were observed after exposure to TRIM. Overall, our study indicates that S. aurata is vulnerable to environmentally relevant concentrations of CIP and TRIM and that their exposure could lead to a stress situation, altering the activity of antioxidant defense mechanisms as well as the activity of HPT and HPI axes.

Phenanthrene disrupting effects on the thyroid system of Arabian seabream, Acanthopagrus arabicus: In situ and in vivo study

Phenanthrene, a polycyclic aromatic hydrocarbon (PAH), is one of the endocrine disrupting chemicals (EDCs). The present study aimed to evaluate the effects of phenanthrene on histophysiology of thyroid in Arabian seabream (Acanthopagrus arabicus). In this regards, different concentrations of phenanthrene (2, 20 and 40 pg/gbw) were injected to Acanthopagrus arabicus and changes in thyroid tissue structure and the serum levels of triiodothyronine (T3) and Thyroxine (T4) were assessed. The experiment lasted 21 days. Alterations in thyroid tissue structure and T3 and T4 serum levels also were assessed in Acanthopagrus arabicus caught from different stations of the Persian Gulf (Jafari, Samail, Arvand, Zangi, Bahrakan). In addition, the concentration of phenanthrene was measured in the fish muscle and sediment samples from the stations. Phenanthrene concentration reached the maximum level in the muscle of all injected fish after 4 days and then decreased by the end of the experiment. The highest and lowest concentrations of phenanthrene were recorded in the fish muscle and sediment samples collected from Jafari and Bahrakan, respectively. The levels of T3 and T4 decreased dose dependently in phenanthrene-injected fish up to day 7 and then increased by the end of the experiment. The serum level of T3 and T4 in fish collected from different stations was as follows: Jafari<Samail<Arvand<Zangi≤Bahrakan. Some tissue changes observed in fish included decrease in the thickness of thyroid follicle epithelium and increase in follicle diameter. In conclusion, according to the results, phenanthrene significantly affected thyroid function in fish.

Association of exposure to polycyclic aromatic hydrocarbons and heavy metals with thyroid hormones in general adult population and potential mechanisms

Air pollution and fuel emissions are the common sources of human exposure to polycyclic aromatic hydrocarbons (PAHs) and heavy metals. Several studies have suggested potential associations between PAHs/heavy metals and thyroid hormones, however, reports have been inconsistent. In this study, we employed a subpopulation of the adults (n = 1254) who participated in the Korean National Environmental Health Survey 2015-2017, and investigated the association of PAHs and major heavy metals with thyroid hormones, and explored the underlying mechanisms of thyroid disruption. Four PAH metabolites and three heavy metals of lead (Pb), mercury (Hg), and cadmium (Cd) were measured either in urine or in total blood. In addition, thyroid hormones (T3 and T4), TSH, thyroxine-binding globulin (TBG), and thyroid autoantibodies were measured, and peripheral deiodinase activity (G_D) and thyroid's secretory capacity (G_T) were calculated. Urinary Hg was negatively associated with total T3 in both males and females, while it was positively associated with total T4 among females only. Urinary Hg was related to decreased G_D and increased G_T in both sexes. In contrast, urinary Cd was positively associated with total T3 and G_D in both male and female populations. Urinary Cd also showed a positive association with thyroid autoantibodies, but only in males. A multi-factor model considering co-exposure to multiple chemicals also resulted in similar associations. Among the measured PAH metabolites, only urinary 1-hydroxypyrene showed a negative association with total T3 in males. However, this association was marginal, and disappeared in a multi-chemical model. The present observations are suggestive that exposures to Hg and Cd might disrupt thyroid hormones, possibly through an alteration of deiodinase activity. Association of PAH exposure with thyroid hormone appears to be insignificant.

Trans-cinnamic acid application for rainbow trout (Oncorhynchus mykiss): I. Effects on haematological, serum biochemical, non-specific immune and head kidney gene expression responses

The present study investigated the effects of dietary trans-cinnamic acid (CA) on pre- and post-challenge haematological, serum biochemical, non-specific immune and head kidney gene expression responses of rainbow trout, Oncorhynchus mykiss juveniles. In this regard, fish with an average weight of 17.01 ± 0.05 g were divided into five groups, and fed daily with an additive free basal diet (control); 250, 500, 750 or 1500 mg kg^-1 CA for a 60-day period. Fish were sampled every 20 days during the experiment. On days 20, 40 and 60 (the pre-challenge period), the dietary CA especially at 250 and/or 500 mg kg^-1 significantly increased blood granulocyte percentage, and serum total protein, globulin, lysozyme and total immunoglobulin values. Furthermore, dietary CA increased activities of phagocytic activity, respiratory burst and potential killing, and increased the expression levels of immune related genes [serum amyloid A (SAA), interleukin 8 (IL-8), interleukin 1, beta (IL-1β), transforming growth factor beta (TGF-β), tumor necrosis factor (TNF-α), and immunoglobulin T (IgT)] in the head kidney of fish fed with 250 and/or 500 mg kg^-1 CA. Following 60 days of feeding, fish were challenged with Yersinia ruckeri and mortality was recorded for 20 days. Highest percentage survival (%) rate was found in the 250 and/or 500 mg kg^-1 CA-supplemented feeding groups. During the post-challenge period, red blood cell (RBC) count, hematocrit (%), respiratory burst activity, and total antiprotease activity increased in fish fed with feed containing 500 mg kg^-1 content. Moreover, markedly up-regulated the expression of related genes (SAA, IL-8, IL-1β, TGF-β, TNF-α, IFN-γ and IgM) in fish fed 250, 500 and/or 750 mg kg^-1 CA. Therefore, feeding O. mykiss for 60 days with dietary CA at 250-500 mg kg^-1 CA incorporation levels can be suggested as optimal to enhance the immunity and disease resistance against Y. ruckeri.

Effects of the environmental endocrine disrupting compound benzo[a]pyrene on thyroidal status of abu mullet (Liza abu) during short-term exposure

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The half-life of BaP is 3–4 days and then it metabolized in the liver.

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BaP concentration in the muscle of treated fish reached a maximum level after 4 days.

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Exposure of fish to BaP resulted in a decrease in T3 and T4 plasma levels up to day 4.

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Exposure of fish to BaP resulted in an increase in TSH plasma level up to day 4.

Benzo[a]Pyrene (BaP) is a ubiquitous polycyclic aromatic hydrocarbon (PAH) that has been shown to disrupt the metabolism of thyroid hormone. Then, the present investigation aimed to study the effects of BaP on thyroid function in Liza abu. Fish were injected with 2, 10 and 25 mg/kg-bw of BaP. Samples were taken from blood, thyroid and muscle tissues at days 1, 2, 4, 7, and 14. Blood was evaluated for changes in the plasma levels of TSH, T3 and T4. Also, BaP bioaccumulation in the fish muscle was measured. Thyroid tissues were processed for routine histology. BaP concentration in the muscle of treated fish reached a maximum level after 4 days. Exposure of fish to BaP resulted in a significant decrease in T3 and T4 plasma level and increase in TSH concentration up to day 4. Also some pathological alterations were observed in BaP-exposed fish such as hemorrhage and increased number of large follicles with squamous epithelium. In conclusion, according to the results of the present investigation, short term exposure to sublethal concentrations of BaP significantly affected thyroid function in fish. The results revealed BaP ability to alter thyroid function.

The response of thyroid hormones, biochemical and enzymological biomarkers to pyrene exposure in common carp (Cyprinus carpio)

Polycyclic Aromatic Hydrocarbons (PAHs) are discharged into aquatic environments through anthropogenic activities mainly industrial and municipal effluents. There is little information on the adverse effects of pyrene, a member of the PAH family which is classified as a priority pollutant by the USEPA, on fish biochemical and physiological endpoints, particularly thyroid hormones. The present study investigated the effects of subacute semi-static pyrene exposure on biochemical, enzymological and ionoregulatory responses as well as thyroid hormones in common carp (Cyprinus carpio). The fish (140±10g, 1(+) year) were exposed to 10, 50 and 100µg/l nominal concentrations of pyrene for 35 days. The results revealed that pyrene at these concentrations significantly altered plasma levels of glucose, cholesterol, triglyceride, total protein, albumin, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP). Moreover, plasma thyroid hormones (T3 and T4) were significantly decreased in fish exposed to pyrene. In contrast, plasma electrolytes (sodium, potassium and calcium) levels remained statistically unchanged after exposure to the various pyrene concentrations. In conclusion, the studied biomarkers may be used as monitoring tools to evaluate pyrene toxicity. Pyrene induced diverse effects on the physiological endpoints of common carp, thus this chemical should be considered in toxicity studies concerning PAHs. Furthermore, this study confirmed that there was an interaction between pyrene and the thyroid system in fish. Therefore, the thyroid system may be used to assess the impact of pyrene on fish.

Thyroid endocrine status of wild European eels (Anguilla anguilla) in the Loire (France). Relationships with organic contaminant body burdens

In teleost fish, thyroid function is involved in various critical physiological processes. Given the complexity of the hypothalamo-pituitary-thyroid (HPT) axis, a large number of genes and proteins can be the potential target of endocrine-disrupting compounds (EDCs). The aim of this study was to evaluate, in yellow and silver European eels (Anguilla anguilla), potential effects of EDCs on thyroid status by analyzing the associations between EDC body burdens and thyroid hormones (THs). In yellow individuals, greater free T3/T4 ratios (FT3/FT4) and lower plasma FT4 levels were associated with greater concentrations of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), as highlighted by significant correlations with many congeners. Few positive relationships with alkylphenols were noticed. In contrast, silver eels usually exhibited less significant correlations between THs and contaminant loads. Expression of a series of genes involved in the HPT axis was also investigated in the silver individuals. Concerning mRNA expression in silver females, some main correlations were noticed: thyroid-stimulating hormone (TSHβ) gene expression was significantly correlated to numerous PCBs, and hepatic mRNA levels of deiodinase 2 (Deio 2) were negatively correlated to 2-hydroxyfluorene (2-OHF) and 2-naphtol (2-OHNa). Thyroid receptor (TRα and TRβ) mRNA levels exhibited weak negative correlations with some PBDEs in silver females and males. Hepatic vitellogenin (Vtg) mRNA levels were detected in all silver males but at lower levels than in silver females. In males, Vtg mRNA levels were positively associated to FT4/TT4. In silver females, strong positive correlations were found between congeners of PCBs, PBDEs and PFAS suggesting potential estrogenic effects. Overall, the observed results indicate that several organic contaminants, mainly dl-, ndl-PCBs and PBDEs, could be associated with changes in thyroid homeostasis in these fish, via direct or indirect interactions with peripheral deiodination, metabolism of T4 and mechanisms involved in TSHβ, Deio 2 and Vtg gene transcription.

Toxicological effects of clofibric acid and diclofenac on plasma thyroid hormones of an Indian major carp, Cirrhinus mrigala during short and long-term exposures

In the present investigation, the toxicity of most commonly detected pharmaceuticals in the aquatic environment namely clofibric acid (CA) and diclofenac (DCF) was investigated in an Indian major carp Cirrhinus mrigala. Fingerlings of C. mrigala were exposed to different concentrations (1, 10 and 100μgL(-1)) of CA and DCF for a period of 96h (short term) and 35 days (long term). The toxic effects of CA and DCF on thyroid hormones (THs) such as thyroid stimulating hormone (TSH), thyroxine (T4) and triiodothyronine (T3) levels were evaluated. During the short and long-term exposure period TSH level was found to be decreased at all concentrations of CA (except at the end of 14(th) day in 1 and 10μgL(-l) and 21(st) day in 1μgL(-l)) whereas in DCF exposed fish TSH level was found to be increased when compared to control groups. T4 level was found to be decreased at 1 and 100μgL(-l) of CA exposure at the end of 96h. However, T4 level was decreased at all concentrations of CA and DCF during long-term (35 days) exposure period. Fish exposed to all concentrations of CA and DCF had lower level of T3 in both the treatments. These results suggest that both CA and DCF drugs induced significant changes (P<0.01 and P<0.05) on thyroid hormonal levels of C. mrigala. The alterations of these hormonal levels can be used as potential biomarkers in monitoring of pharmaceutical drugs in aquatic organisms.

Pyrene exposure influences the thyroid development of Sebastiscus marmoratus embryos

Thyroid hormones play crucial roles in regulating development, morphogenesis, growth, and behavior in fishes. Some environmental pollutants have adverse effects on either development or function of the thyroid gland in fish. However, there are few reports on the effects of polycyclic aromatic hydrocarbons (PAHs) on fish thyroid. In the present study, rockfish (Sebastiscus marmoratus) embryos were exposed to pyrene (Py) for 5 days at the concentrations of 0.5, 5, and 50 nmol/L. The results showed that Py exposure decreased the expression of thyroid primordium markers, Pax2.1 and Nk2.1a as detected by quantitative PCR and in situ hybridization, and reduced the concentration of T(3), but not T(4). Thyroid receptor genes (TRα and TRβ) expression was down-regulated by Py. At the same time, Py exposure impaired the expression of thyroid development related genes, Fgfr2 and Hoxa3a expression, and altered the mRNA levels of thyroid function related genes, Deio1, Ttr, and Tg. In conclusion, the results demonstrated Py exposure inhibited thyroid development and influenced the function of thyroid system in rockfish embryos.

Copper and the herbicide atrazine impair the stress response of the freshwater fish Prochilodus lineatus

In order to evaluate the effects of copper and atrazine on the stress response of the freshwater fish Prochilodus lineatus, juvenile fish were pre-exposed to copper (20 μg L(-1)) or atrazine (10 μg L(-1)) for 24 h and then submitted to air exposure for 3 min. Simultaneously fish kept in dechlorinated water for 24 h were subjected to air exposure and a non-stress group was not subjected to air stress or any contaminants. Animals were sampled immediately (t0) and after 1, 3 and 6 h of air exposure (t1, t3 and t6 respectively) for the analysis of plasma cortisol, glucose and Na(+), hepatic glycogen, branchial Na(+)/K(+)-ATPase (NKA), number of red blood cells per cubic millimeter of blood (RBC), hematocrit (Hct) and hemoglobin content (Hb). In fish pre-exposed to copper the stress response was inhibited, and at t1 and t3 both cortisol and glucose remained significantly lower compared to fish subjected to air stress only. In fish pre-exposed to atrazine there was no rise in cortisol, but there was an increase in plasma glucose, RBC, Hct and Hb at t0 and a return of these parameters to basal levels at t1, as they did not differ significantly in relation to non-stressed fish. Animals pre-exposed to either Cu or atrazine showed a significant reduction in NKA activity at t1 and t3, in relation to air stressed fish. These results clearly indicate that copper and atrazine impair cortisol stress response of P. lineatus and that fish subjected to a contaminant-induced stress, either by copper or atrazine, may not be able to respond to any additional stressors.

The hypothalamus-pituitary-thyroid axis in teleosts and amphibians: endocrine disruption and its consequences to natural populations

Teleosts and pond-breeding amphibians may be exposed to a wide variety of anthropogenic, waterborne contaminants that affect the hypothalamus-pituitary-thyroid (HPT) axis. Because thyroid hormone is required for their normal development and reproduction, the potential impact of HPT-disrupting contaminants on natural teleost and amphibian populations raises special concern. There is laboratory evidence indicating that persistent organic pollutants, heavy metals, pharmaceutical and personal care products, agricultural chemicals, and aerospace products may alter HPT activity, development, and reproduction in teleosts and amphibians. However, at present there is no evidence to clearly link contaminant-induced HPT alterations to impairments in teleost or amphibian population health in the field. Also, with the exception of perchlorate for which laboratory studies have shown a direct link between HPT disruption and adverse impacts on development and reproductive physiology, little is known about if or how other HPT-disrupting contaminants affect organismal performance. Future field studies should focus on establishing temporal associations between the presence of HPT-disrupting chemicals, the occurrence of HPT alterations, and adverse effects on development and reproduction in natural populations; as well as determining how complex mixtures of HPT contaminants affect organismal and population health.

Physiological responses to starvation in the European eel (Anguilla anguilla): effects on haematological, biochemical, non-specific immune parameters and skin structures

The physiological effects of short-term starvation on some haematological, biochemical and non-specific immune response parameters together with the histological structure of the skin, were investigated in the European eel, Anguilla anguilla. Blood haemoglobin and haematocrit, serum glucose and cortisol, hemolysins, haemagglutinins, and lysozyme in the plasma, kidney and epidermal extract, were measured in fish after 31, 42 and 58 days of starvation, and compared to those of fed fish. Starvation did not affect haemoglobin and haematocrit values, while an increase in glucose and cortisol levels was found in starved eels by day 42. Haemolytic and haemagglutinating activities decreased in starved eels. On the other hand, starvation caused an increase in the lysozyme content in the epidermal extracts, while no significant variations were observed in kidney and plasma. On the whole, no major changes in metabolic, haematological and non-specific immune parameters were observed when short-term (less than 2 months) starvation was applied to the European eel, suggesting an adaptive response to starvation, rather than a typical alarm-stress response, allowing this species to withstand food deprivation.

Evidence for thyroid endocrine disruption in wild fish in San Francisco Bay, California, USA. Relationships to contaminant exposures

It is well documented that many coastal and estuarine environments adjacent to developed and industrialized urban centers, such as the San Francisco Bay Area, are significantly contaminated by anthropogenic chemicals. However, it is not well understood to what extent existing contaminants, many with continuing inflows into the environment, may impact exposed wildlife. This study provided an initial characterization of thyroid endocrine-related effects and their relationship to accumulated contaminants in two indigenous fish species sampled from different San Franicsco Bay Area study sites. Plasma concentrations of thyroxine (T4) were significantly reduced in fish sampled from highly impacted locations such as Oakland Inner Harbor and San Leandro Bay as compared with fish from other locations representing relatively lower human impact, including Bodega Bay, Redwood City and a remote site on Santa Catalina Island. Triiodothyronine (T3) levels also varied significantly by location, with differing T3/T4 ratios in fish from some locations suggestive of altered peripheral deiodinase activity. The changes in thyroid endocrine parameters were significantly correlated with hepatic concentrations of certain environmental contaminants. A large number of polychlorinated biphenyl (PCB) congeners, both co-planar (dioxin-like) and non-co-planar, exhibited significant inverse correlations with T4 levels in the fish, while in contrast, T3 and T3/T4 ratio were positively correlated with PCB exposures. The positive correlation between T3/T4 ratio and PCBs supports the hypothesis that environmental PCBs may alter T4 deiodination or turnover, actions of PCBs reported in laboratory experiments. Some relationships between chlorinated pesticides including DDT and chlordanes, but fewer relationships with PAHs, were also observed. Together, these findings indicate that the thyroid endocrine system is exhibiting alterations associated with different aquatic environments in the San Francisco Bay Area, which are significantly related to current-day exposures of the fish to contaminant chemicals such as PCBs.

Effects of naphthalene, beta-naphthoflavone and benzo(a)pyrene on the diurnal and nocturnal indoleamine metabolism and melatonin content in the pineal organ of rainbow trout, Oncorhynchus mykiss

Polycyclic aromatic hydrocarbons (PAHs) have deleterious effects on neuroendocrine systems in teleost fish affecting, among other processes, reproductive function or stress responses. The hormone melatonin, mainly produced in the pineal organ of vertebrates, is involved in the regulation of biological rhythms as well as other important functions, and may also act as an antioxidant molecule. The effects of environmental pollutants on the endocrine and metabolic activity of the pineal organ have been studied only in mammals. We here evaluate the effects of the PAHs naphthalene (NAP) and benzo(a)pyrene (BaP) and the flavonoid beta-naphthoflavone (BNF) on the pineal organ of rainbow trout by quantifying the diurnal and nocturnal pineal content of some indoles and methoxyindoles, including melatonin. NAP mainly induced diurnal increases in the pineal content of melatonin and other methoxyindoles like 5-methoxytryptamine (5-MT), 5-methoxyindole-3-acetic acid (5-MIAA) or 5-methoxytryptophol (5-MTOL). Those increases did not occur at night, when even occasional decreases were observed compared with controls. NAP also induced some diurnal and nocturnal decreases in the levels of indolic compounds like serotonin (5-HT) and 5-hydroxyindole-3-acetic acid (5-HIAA), while pineal content of 5-hydroxytryptophan (5-HTP) was first decreased (few hours after injection) and then increased (few days after injection) during the day. BaP and BNF induced strong increases in diurnal levels of melatonin, whereas other pineal compounds were unaffected. It seems that an increase of the methylation capacity of the pineal organ takes place during the day, and a decrease occurs at night. Those effects could be mediated by changes in the activity of key enzymes involved in pineal melatonin biosynthesis, maybe as a result of the alteration of the cellular phototransduction mechanisms involved in the light-induced inhibition of melatonin synthesis in the pineal photoreceptor cells. These results demonstrate for the first time that environmental pollutants can disrupt the activity of the pineal organ of teleost fish. This disruption could be a threat for the survival of the animals in their natural environment, although the increases observed in melatonin levels could play a relevant role as a toxicity-protection factor.

beta-Naphthoflavone and benzo(a)pyrene alter dopaminergic, noradrenergic, and serotonergic systems in brain and pituitary of rainbow trout (Oncorhynchus mykiss)

In the present study we evaluate for the first time the potential of the flavonoid compound beta-naphthoflavone (BNF) and the high molecular weight- Polycyclic aromatic hydrocarbon (PAH) benzo(a)pyrene (BaP) to alter brain neurotransmitter metabolism in fish. Fish of three different groups were intraperitoneally (i.p.) injected (2 microl g(-1)) with vegetable oil alone (control) or containing BNF or BaP (10 mg kg(-1)) and sacrificed 3, 24, and 72 h after treatment. Contents of dopamine (DA), noradrenaline (NA) and serotonin (5HT), as well as the amine oxidative metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole-3-acetic acid (5HIAA) were assayed in telencephalon, hypothalamus, preoptic region, optic tectum, and brain stem, as well as the pituitary. Fish treated with PAHs showed after 3h decreases in 5HT content in telencephalon, hypothalamus, preoptic region (with both BNF and BaP), and pituitary (with BaP), resulting in increased 5HIAA/5HT ratio. An increased ratio was also observed in hypothalamus 24h after BaP, and in preoptic region 72 h after BNF, in both cases due to an increased 5HIAA content. In other brain regions PAHs effects on 5-HT metabolism were less consistent. With respect to the dopaminergic system, changes induced by PAHs mainly occurred after 24 and 72 h of treatment, with increased DOPAC/DA ratio in preoptic region and brain stem. In hypothalamus, tectum, and pituitary, changes in DA metabolism showed strong variability. Finally, a decreased content of NA was evident in preoptic region (3h) and in telencephalon (24h) after both BNF and BaP treatments. Therefore, both BNF and BaP seem to act in rainbow trout brain by impairing 5HT availability at short term (3h) and increasing neuronal metabolic utilization of both 5HT and DA after 24 and 72 h. Data collected in the present study suggest that brain monoamine neurotransmitters are potential targets of BNF and BaP, and their alteration could have a role in known effects of PAHs on several neuroendocrine processes that are centrally regulated or modulated by brain monoamines.

beta-Naphthoflavone and benzo(a)pyrene treatment affect liver intermediary metabolism and plasma cortisol levels in rainbow trout Oncorhynchus mykiss

To assess the effects of the polycyclic aromatic hydrocarbons (PAHs) beta-naphthoflavone (beta-NF) and benzo(a)pyrene (BaP) on liver intermediary metabolism and plasma steroid hormones, immature female rainbow trout (Oncorhynchus mykiss) were intraperitoneally injected (2 microl g(-1)) with vegetable oil alone (control) or containing beta-NF or BaP (10 mg kg(-1)) and returned to their tanks; 3, 24, and 72 h after injection, 11 fish were sampled from each group. On each sampling time, plasma hormone levels (cortisol and 17beta-estradiol) and metabolic parameters in plasma (glucose, lactate, and alpha-amino acid levels) and liver (glycogen, glucose, lactate, and alpha-amino acid levels, and HK, GK, PK, LDH, G6Pase, G6PDH, FBPase, GDH, Asp-AT, and HOAD activities) were assessed. Changes described for hormonal systems resulted in an increase in plasma levels of cortisol after 24 and 72 h of treatment with both PAHs whereas no changes were noticed for 17beta-estradiol levels. Changes in intermediary metabolism described effects in several pathways due to treatment with both PAHs. These changes can be summarized as increased glucose and lactate levels in plasma, and increased glycogenolysis and gluconeogenesis in liver after 24 and 72 h of treatment with both PAHs. Furthermore, beta-NF treatment stimulated amino acid catabolism in liver. These metabolic changes can be associated with increased levels of plasma cortisol, and suggest a different metabolic behavior depending on PAHs.

Spatial transcription of CYP1A in fish liver

BACKGROUND

The aim of this work was to study how evenly detoxifying genes are transcribed spatially in liver tissue of fish. Ten Atlantic salmon Salmo salar were intraperitoneally injected with 50 mg/kg of the strong CYP1A inducer beta-naphthoflavone and liver tissue harvested seven days later. The liver from 10 control and 10 exposed fish were split into eight sections, RNA extracted and three reference (beta-actin, elongation factor 1AB (EF1AB)) and two detoxifying genes (CYP1A and GST) quantified with real-time RT-PCR. The cellular localization of the EF1AB and CYP1A mRNA in the liver of control and beta-naphthoflavone treated fish was then determined by in situ hybridization (ISH) using EF1AB and CYP1A biotinylated oligonucleotide probes.

RESULTS

The study shows that genes encoding phase I and phase II conjugating enzymes are unevenly transcribed in different parts of the liver of Atlantic salmon seven days after a single-dose of beta-naphthoflavone exposure. Transcription of CYP1A and GST was higher in the middle section of the liver compared to the distal and proximal parts of the organ. The ISH data suggest that CYP1A transcription happens mainly in hepatocyte cells in the liver, and that hepatocytes in the vicinity of blood vessels respond stronger to beta-naphthoflavone than cells further away from the blood supply.

CONCLUSION

Overall, the qRT-PCR and ISH results reported here suggest that gene expression analysis should be performed on as pure cell populations as possible. If bulk tissue samples are to be used, one should always check how evenly the target genes are expressed in tissue sections and organs in every study.

Metabolic and thyroidal response in air-breathing perch (Anabas testudineus) to water-borne kerosene

To address the physiological compensatory adaptations in air-breathing fish to a toxicant, we studied the metabolite pattern, serum and liver enzymes and thyroidal response in a tropical air-breathing perch, Anabas testudineus (kept at 30 degrees C in a 12-h L:D cycle) after exposing the fish for 48h to the water-soluble fraction of kerosene. The concentrations of serum glucose (P <0.05), triglycerides (P <0.01) and liver total protein (P <0.05) were significantly increased in kerosene-exposed fish. The serum urea level, however, remained unaffected. A significant (P <0.05) increase in liver RNA occurred without changing the liver DNA concentration. Kerosene exposure decreased the level of aspartate aminotransferase activities in serum (P <0.001) and liver (P <0.05) but it increased (P <0.05) the liver alanine aminotransferase activity without changing its activity in serum. The levels of serum (P <0.01) and liver (P <0.001) lactate dehydrogenase activity were declined and the serum (P <0.05) and liver (P <0.05) alkaline phosphatase activity levels were elevated in kerosene-treated fish. The nominated levels (3.33-6.66ml/L) of kerosene significantly (P <0.01) elevated the thyroxine (T(4)) titre, and reduced (P <0.05) the triiodothyronine (T(3)) titre. The fish pretreated with either T(3) or T(4) and exposed to kerosene had a metabolic and thyroidal response that differed from that in control fish treated with kerosene: no rise in serum glucose was observed, nor in triglycerides, total protein and RNA in the liver, whereas declined levels of T(4) and T(3) were observed. The upregulation of the thyroid along with the marked metabolite changes point to a positive involvement of thyroid in energy metabolism during kerosene exposure. This is consistent with the hypothesis that the fish thyroid responds to the action of petroleum products and influences the metabolic homeostasis of this air-breathing fish.

Naphthalene treatment alters liver intermediary metabolism and levels of steroid hormones in plasma of rainbow trout (Oncorhynchus mykiss)

To assess the effects of naphthalene on liver intermediary metabolism and plasma steroid hormones, immature female rainbow trout (Oncorhynchus mykiss), in a first experiment, were intraperitoneally injected (2 microLg(-1)) with vegetable oil alone (control) or containing naphthalene (10 and 50 mgkg(-1)) and returned to their tanks. At 1, 3, and 6h after injection, eight fish were sampled from each group. A second experiment was similarly designed but used fish intraperitoneally implanted (10 microLg(-1)) with slow-release coconut oil implants alone (control) or containing naphthalene at doses of 10 and 50 mgkg(-1) body weight that were sampled 1, 3, and 5 days after injection. At each sampling time, plasma hormone levels (cortisol and 17beta-estradiol) and metabolic parameters in plasma (glucose and lactate) and liver (glucose, lactate, and glycogen levels and HK, GK, GPase, GDH, FBPase, and PK activities) were assessed. Changes described for both hormonal systems resulted in a decrease in plasma levels of cortisol and 17beta-estradiol. Changes observed in intermediary metabolism described effects in several pathways of liver energy metabolism due to naphthalene. These changes can be summarized as increased glycogenolysis, use of exogenous glucose, and glycolysis and decreased gluconeogenesis. The increased energy production in liver suggested by these changes can be related to the increased detoxification activity known to occur in liver after PAH exposure, and can be also related directly or indirectly to the changes observed in the levels of plasma steroids.

Effects of acute and prolonged naphthalene exposure on brain monoaminergic neurotransmitters in rainbow trout (Oncorhynchus mykiss)

We have shown previously that acute (1 to 6 h) and prolonged (1 to 5 days) exposure of rainbow trout to naphthalene resulted in decreased plasmatic cortisol and 17-beta-estradiol levels. In order to elucidate the mechanisms through which naphthalene might disrupt endocrine regulation, the present study investigated whether brain monoaminergic neurotransmitters are altered by the action of this polycyclic aromatic hydrocarbon. In a first experiment, immature rainbow trout were injected with vegetable oil alone or containing naphthalene (10 and 50 mg/kg, i.p.), and sacrificed 1, 3 and 6 h after treatment. In a second experiment, slow-coconut oil implants alone or containing naphthalene (doses of 10 and 50 mg/kg) were i.p. located and fish sacrificed 1, 3 and 5 days after treatment. Levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA) and noradrenaline (NA) were measured in several brain regions by HPLC. The results show that short-term naphthalene increases DA and 5-HT contents in hypothalamus and telencephalon, but differentially alter contents of the acid metabolites. Implants with naphthalene reduced DA content in hypothalamus and preoptic region but increased in telencephalon. 5-HT metabolism was decreased in hypothalamus, preoptic region, pituitary and brain stem after 3 to 6 days of treatment. In addition, the levels of NA were increased in hypothalamus and telencephalon after acute treatment and in hypothalamus and preoptic area after several days of exposure to naphthalene. These data suggest that brain neurotransmitter systems are sensitive to polycyclic aromatic hydrocarbons and could represent a target of the naphthalene-induced neuroendocrine disruption.

Joint action of polycyclic aromatic hydrocarbons: predictive modeling of sublethal toxicity

Polycyclic aromatic hydrocarbons (PAHs) typically contaminate the environment as complex assemblages of different chemical compounds. Modeling approaches provide a means of estimating the toxicity of these PAH mixtures. In the present study, we tested the hypothesis that the joint effects of four PAHs: pyrene, phenanthrene, fluoranthene and naphthalene, on the growth rate of the crustacean Daphnia magna during sub-chronic exposure could be accurately predicted using a mathematical algorithm for concentration addition based upon the assumption that these PAHs impact growth by a common mode of action. Assessment of the individual toxicity of the four PAHs confirmed that these compounds elicited the common effect of retarding growth of daphnids at concentrations below those that were lethal to the organisms. Using the experimentally derived toxicity parameters for the individual chemicals, the toxicity of multiple mixtures of these four PAHs was modeled. These mixtures were based on concentrations reported in the environment and on equi-toxic concentrations. The effects of over 140 combinations of four mixture formulations on the growth rate of daphnids were experimentally determined and compared to model predictions. The concentration addition models tended to over predict the joint toxicity of these PAH mixtures and experimental data was better represented by an alternative model based upon the concept of independent joint action. Mixtures at environmentally relevant concentrations were predicted and experimentally demonstrated to have no effect on daphnid growth rates. Results indicate that PAHs elicit toxicity to daphnids by multiple mechanisms and demonstrate an appropriate modeling approach to assess the toxicity of these mixtures.