Potential physiological effects of pharmaceutical compounds in Atlantic salmon (Salmo salar) implied by transcriptomic analysis

A synthesis on the sub-lethal toxicity of atenolol, a beta-blocker, in teleost fish

Blood pressure medications like atenolol are detected in aquatic ecosystems. The objectives here were to (1) map the global presence of atenolol in surface water and sewage; (2) present current knowledge regarding removal efficiency and degradation of atenolol; (3) identify biological endpoints sensitive to exposure; (4) reveal molecular biomarkers that may be useful for exposure studies in fish; (5) determine whether toxicology studies are within environmental relevance. In fish, atenolol exposure affects endocrine and immune systems, metabolism, and epigenetics. Fewer than half of all studies measuring biological responses use environmentally-relevant concentrations. Heart rate appeared most sensitive to atenolol exposure relative to other endpoints. Data are lacking for behavioral responses to atenolol. Molecular biomarkers for atenolol may include those associated with acute kidney injury, cholestasis, and hypertriglyceridemia. Head kidney and liver may therefore be useful for detecting atenolol-induced effects. This review synthesizes knowledge regarding atenolol-induced toxicity in fish.

Adsorptive and photocatalytic degradation potential of porous polymeric materials for removal of pesticides, pharmaceuticals, and dyes-based emerging contaminants from water

Life on earth is dependent on clean water, which is crucial for survival. Water supplies are getting contaminated due to the growing human population and its associated industrialization, urbanization, and chemically improved agriculture. Currently, a large number of people struggle to find clean drinking water, a problem that is particularly serious in developing countries. To meet the enormous demand of clean water around the world, there is an urgent need of advanced technologies and materials that are affordable, easy to use, thermally efficient, portable, environmentally benign, and chemically durable. The physical, chemical and biological methods are used to eliminate insoluble materials and soluble pollutants from wastewater. In addition to cost, each treatment carries its limitations in terms of effectiveness, productivity, environmental effect, sludge generation, pre-treatment demands, operating difficulties, and the creation of potentially hazardous byproducts. To overcome the problems of traditional methods, porous polymers have distinguished themselves as practical and efficient materials for the treatment of wastewater because of their distinctive characteristics such as large surface area, chemical versatility, biodegradability, and biocompatibility. This study overviews improvement in manufacturing methods and the sustainable usage of porous polymers for wastewater treatment and explicitly discusses the efficiency of advanced porous polymeric materials for the removal of emerging pollutants viz. pesticides, dyes, and pharmaceuticals whereby adsorption and photocatalytic degradation are considered to be among the most promising methods for their effective removal. Porous polymers are considered excellent adsorbents for the mitigation of these pollutants as they are cost-effective and have greater porosities to facilitate penetration and adhesion of pollutants, thus enhance their adsorption functionality. Appropriately functionalized porous polymers can offer the potential to eliminate hazardous chemicals and making water useful for a variety of purposes thus, numerous types of porous polymers have been selected, discussed and compared especially in terms of their efficiencies against specific pollutants. The study also sheds light on numerous challenges faced by porous polymers in the removal of contaminants, their solutions and some associated toxicity issues.

Investigation of potential behavioral and physiological effects of caffeine on D. magna

With the ever-increasing consumption of pharmaceutical compounds, their presence in the environment is now an undisputable reality. The majority of these compounds are released into the wild after their therapeutic use, as biotransformation products or in their original form. The presence of this class of compounds in the environment, due to their biological properties, can exert effects on non-target organisms, with adverse consequences. In addition, some bioactive substances, such as stimulants of the central nervous system, are also used by humans as part of their diet. The adverse consequences posed by such chemicals may be permanent or transient, if the exposure to xenobiotics is halted; it is thus of the paramount importance to study effects that result from long-term exposure to toxicants, but also the recovery of organisms previously exposed to such substances, especially if such chemicals may cause some type of addiction. Caffeine (1,3,7-trimethylxanthine) is a naturally occurring alkaloid found in many plants, being one of the most common stimulant/pharmaceutical compounds found in the environment. In addition, it is addictive, and strongly consumed by humans, a factor that contributes also for its continuous presence in the aquatic environment. The aim of this study was to evaluate the effects of environmentally relevant concentrations (0.08; 0.4; 2; 10; and 50 μg/L) of caffeine on behavior and physiological parameters (that are proxies of metabolic traits, such as oxygen uptake and glycogen content), in individuals of the freshwater crustacean species Daphnia magna, of distinct ages, and with or without a recovery period in the absence of caffeine. Regarding behavior, the results indicated that caffeine exposure altered the moved distance of the test organisms, but not according to a coherent pattern; low concentrations of caffeine reduced the movement of exposed daphnids, while higher levels did not have any measurable effect on this parameter. In addition, it was possible to identify subtle withdrawal effects (animals exposed to caffeine during 21 days and kept in uncontaminated media for 2 days). Regarding the other two studied parameters, caffeine exposure did not result in any significant modification in oxygen uptake and glycogen stores/reserves of the test organisms, in animals continuously exposed, or in those subjected to a recovery period, suggesting that despite a behavioral stimulatory effect, this was not followed by any metabolic change, and no addictive effect was possible to infer. The results showed that the presence of caffeine in environmental concentrations can induce mild behavioral effects at low, albeit realistic levels, but not capable of establishing clear biochemical changes.

Microbe mediated remediation of dyes, explosive waste and polyaromatic hydrocarbons, pesticides and pharmaceuticals

•

Environmental pollutants dyes, pesticides, pharmaceuticals, explosive waste and polyaromatic hydrocarbons.

•

Environmental pollutants toxicity.

•

Possible microbial biodegradation pathways of environmental pollutants.

Industrialization and human activities have led to serious effects on environment. With the progress taking place in the biodegradation field, it is important to summarize the latest advancement. In this review, we intend to provide insights on the recent progress on the biodegradation of environmental contaminants such as dyes, pesticides, pharmaceuticals, explosive waste and polyaromatic hydrocarbons by microorganisms. Along with the biodegradation of environmental contaminants, toxicity effects have also been discussed.

Multi-omic approach to evaluate the response of gilt-head sea bream (Sparus aurata) exposed to the UV filter sulisobenzone

Sulisobenzone (BP-4) is one of the benzophenone type UV filters most frequently detected in aquatic ecosystems. As a suspected endocrine disrupting compound, scarce information is available yet about other molecular effects and its mechanism of action. Here, we used an integrated transcriptomic and metabolomic approach to improve the current understanding on the toxicity of BP-4 towards aquatic species. Gilt-head sea bream individuals were exposed at environmentally relevant concentrations (10 μg L^-1) for 22 days. Transcriptomic analysis revealed 371 differentially expressed genes in liver while metabolomic analysis identified 123 differentially modulated features in plasma and 118 in liver. Integration of transcriptomic and metabolomic data showed disruption of the energy metabolism (>10 pathways related to the metabolism of amino acids and carbohydrates were impacted) and lipid metabolism (5 glycerophospholipids and the expression of 3 enzymes were affected), suggesting oxidative stress. We also observed, for the first time in vivo and at environmental relevant concentrations, the disruption of several enzymes involved in the steroid and thyroid hormones biosynthesis. DNA and RNA synthesis was also impacted by changes in the purine and pyrimidine metabolisms. Overall, the multiomic workflow presented here increases the evidence on suspected effects of BP-4 exposure and identifies additional modes of action of the compounds that could have been overlooked by using single omic approaches.

Removal of pharmaceutical compounds commonly-found in wastewater through a hybrid biological and adsorption process

Nowadays, alternative options to conventional wastewater treatment should be studied due to rising concerns emerged by the presence of pharmaceuticals compounds (PhCs) in the aquatic environment. In this work, a combined system including biological treatment by activated sludge plus adsorption with activated carbon is proposed to remove three selected drugs (acetaminophen (ACT), caffeine (CAF) and ibuprofen (IBU)) in a concentration of 2 mg L^-1 of each one. For it three sequencing batch reactors (SBR) were operated. SBR-B treated a synthetic wastewater (SWW) without target drugs and SBR-PhC and SBR-PhC + AC operated with SWW doped with the three drugs, adding into SBR-PhC + AC 1.5 g L^-1 of a mesoporous granular activated carbon. Results showed that the hybrid system SBR-activated carbon produced an effluent free of PhCs, which in addition had higher quality than that achieved in a conventional activated sludge treatment in terms of lower COD, turbidity and SMP concentrations. On the other hand, five possible routes of removal for target drugs during the biological treatment were studied. Hydrolysis, oxidation and volatilization pathways were negligible after 6 h of reaction time. Adsorption route only was significant for ACT, which was adsorbed completely after 5 h of reaction, while only 1.9% of CAF and 5.6% of IBU were adsorbed. IBU was the least biodegradable compound.

Using a high-throughput zebrafish embryo screening approach to support environmental hazard ranking for cardiovascular agents

Cardiovascular agents are among the most frequently prescribed pharmaceuticals worldwide. They are widely detected in aquatic ecosystems, while their ecotoxicological implications are rarely explored. Here, by the use of a new developed high-throughput zebrafish embryo screening approach, we systematically assessed the cardiovascular disruptive effects of 32 commonly used cardiovascular agents at environmental relevant concentrations and above (0.04, 0.2 and 1 µM). Multiple endpoints, including cardiac output, heart rate and blood flow, were quantified via customized video analysis approaches. Among the 32 agents, simvastatin and lovastatin exhibited the strongest toxicities to fish embryos, and the lethal doses were observed at 0.2 µM and 1 µM. Beta-blockers such as atenolol and metoprolol significantly decreased heart rates by up to 15% and 12% and increased blood flows by up to 14% and 14%, respectively, at concentrations as low as 0.04 µM. Several hypertension/hyperlipidemia medications such as pravastatin and enalapril led to significant inhibition of heart rates (up to 14% and 16% decreases, respectively) as well as slightly decreases of the cardiac outputs and blood flows. In addition, a tentative risk assessment clearly demonstrated that some compounds such as atenolol, metoprolol and bezafibrate pose considerable risks to aquatic organisms at environmental or slightly higher than surface water concentrations. Our results provided novel insights into understanding of the potential risks of cardiovascular agents and contributed to their environmental hazard ranking.

Oxidative degradation of atenolol by heat-activated persulfate: Kinetics, degradation pathways and distribution of transformation intermediates

Atenolol (ATL) has been widely detected in wastewater and aquatic environment. Although satisfactory removal of ATL from wastewater could be achieved, the mineralization ratio is usually low, which may result in the accumulation of its transformation products in the effluent and cause additional ecological risk to the environment. The aim of this study is to explore the effectiveness of heat activated persulfate (PS) in the removal of ATL from wastewater. Influencing factors including temperature, PS dosage, solution pH, existence of NO₃^-, Cl^-, HCO₃^- and Suwannee river fulvic acid (SRFA) were examined. Complete removal of ATL was achieved within 40 min at pH 7.0 and 70 °C by using 0.5 mM PS. Inhibitive effects of HCO₃^- and FA had been observed on ATL oxidation, which was increased with the increase of their concentration. Sulfate radical (SO₄^-) was determined as the main reactive species by quenching experiment. Eight intermediates produced in ATL degradation were identified, and four degradation pathways were proposed based on the analysis of mass spectrum and frontier electron densities. The distribution of major intermediates was influenced by reaction temperature. Hydroxylation intermediates and deamidation intermediate were the most prominent at 50 °C and 60 °C, respectively. All intermediates were completely degraded in 40 min except P134 at 70 °C. Effective removal of TOC (74.12%) was achieved with 0.5 mM PS, pH 7.0 and 70 °C after 240 min. The results proved that heat activation of PS is a promising method to remove organic pollutants in wastewater.

Transcriptome analysis of the brain of the sea bream (Sparus aurata) after exposure to human pharmaceuticals at realistic environmental concentrations

Human pharmaceuticals such as Acetaminophen, Atenolol and Carbamazepine are pseudo persistent aquatic pollutants with yet unknown sub-lethal effects at environmentally relevant concentrations. Gilthead seabream (Sparus aurata) were exposed to Acetaminophen: 31.90 ± 11.07 μg L^-1; Atenolol: 0.95 ± 0.38 μg L^-1 and Carbamazepine: 6.95 ± 0.13 μg L^-1 in a 28 day flow through experiment to (1) determine whether exposure to low concentrations in the μg·L^-1 range of the pharmaceuticals alters the brain transcriptome and, (2) identify different expression profiles and treatment specific modes of action and pathways. Despite low exposure concentrations, 411, 7 and 612 differently expressed transcripts were identified in the individual treatments with Acetaminophen, Atenolol and Carbamazepine, respectively. Functional analyses of differentially expressed genes revealed a significant over representation of several biological processes, cellular compartment features and molecular functions for both Acetaminophen and Carbamazepine treatments. Overall, the results obtained in seabream brain suggest similar physiological responses to those observed in humans also at environmental concentrations, as well as the existence of treatment specific processes that may be useful for the development of biomarkers of contamination.

The sub-lethal effects and tissue concentration of the human pharmaceutical atenolol in rainbow trout (Oncorhynchus mykiss)

Atenolol is a highly prescribed anti-hypertensive pharmaceutical and a member of the group of β-blockers. It has been detected at concentrations ranging from ng L(-1) to low μg L(-1) in waste and surface waters. The present study aimed to assess the sub-lethal effects of atenolol on rainbow trout (Oncorhynchus mykiss) and to determine its tissue-specific bioconcentration. Juvenile rainbow trout were exposed for 21 and 42 days to three concentration levels of atenolol (1 μg L(-1) - environmentally relevant concentration, 10 μg L(-1), and 1000 μg L(-1)). The fish exposed to 1 μg L(-1) atenolol exhibited a higher lactate content in the blood plasma and a reduced haemoglobin content compared with the control. The results show that exposure to atenolol at concentrations greater than or equal to 10 μg L(-1) significantly reduces both the haematocrit value and the glucose concentration in the blood plasma. The activities of the studied antioxidant enzymes (catalase and superoxide dismutase) were not significantly affected by atenolol exposure, and only the highest tested concentration of atenolol significantly reduced the activity of glutathione reductase. The activities of selected CYP450 enzymes were not affected by atenolol exposure. The histological changes indicate that atenolol has an effect on the vascular system, as evidenced by the observed liver congestion and changes in the pericardium and myocardium. Atenolol was found to have a very low bioconcentration factor (the highest value found was 0.27). The bioconcentration levels followed the order liver>kidney>muscle. The concentration of atenolol in the blood plasma was below the limit of quantification (2.0 ng g(-1)). The bioconcentration factors and the activities of selected CYP450 enzymes suggest that atenolol is not metabolised in the liver and may be excreted unchanged.

The antidepressant drug carbamazepine induces differential transcriptome expression in the brain of Atlantic salmon, Salmo salar

Concerns are being expressed recently over possible environmental effects of human pharmaceuticals. Although the likelihood of acute toxicity is low, the continuous discharge of pharmaceuticals into the aquatic environment means that sublethal effects on non-target organisms need to be seriously considered. One-year-old Atlantic salmon parr were exposed to 7.85±0.13μgL(-1) of the antidepressant drug Carbamazepine (CBZ) for five days to investigate changes of mRNA expression in the brain by means of a custom 17k Atlantic salmon cDNA microarray. The selected concentration is similar to upper levels that can be found in hospital and sewage treatment plant effluents. After treatment, 373 features were differently expressed with 26 showing up- or down-regulation of ≥2-fold (p≤0.05). Among the mRNAs showing the highest change were the pituitary hormones encoding features somatolactin, prolactin and somatotropin, or growth hormone. Functional enrichment and network analyses of up- and down-regulated genes showed that CBZ induced a highly different gene expression profile in comparison to untreated organisms. CBZ induced expression of essential genes of the focal adhesion and extracellular matrix - receptor interaction pathways most likely through integrin alpha-6 (itga6) activation. Negative regulation of apoptotic process, extracellular matrix organization and heme biosynthesis were the most enriched biological process related GO-terms, with the simultaneous enrichment of collagen and extracellular region related cellular component GO-terms, and extracellular matrix structural constituent, hormone activity and chromatin binding molecular function related GO-terms. These results show that relatively low doses of CBZ may affect brain physiology in exposed salmon parr, targeting similar processes as in human, indicating a high degree of conservation of targets of CBZ action. However, and since the mRNAs showing most changes in expression are critical for adaptation to different stressors and life history transitions in Atlantic salmon, more research should be undertaken to assess CBZ effects to avoid impairment of normal development and maintenance of natural populations.

Effects of triclocarban, N,N-diethyl-meta-toluamide, and a mixture of pharmaceuticals and personal care products on fathead minnows (Pimephales promelas)

Pharmaceuticals and personal care products (PPCPs) have been detected widely in aquatic ecosystems, but little is known about their mechanisms of toxicity. We exposed adult fathead minnows (Pimephales promelas) for 48 h to triclocarban (1.4 µg/L), N,N-diethyl-meta-toluamide (DEET; 0.6 µg/L), or a mixture of PPCPs consisting of atenolol (1.5 µg/L), caffeine (0.25 µg/L), diphenhydramine (0.1 µg/L), gemfibrozil (1.5 µg/L), ibuprofen (0.4 µg/L), naproxen (1.6 µg/L), triclosan (2.3 µg/L), progesterone (0.2 µg/L), triclocarban (1.4 µg/L), and DEET (0.6 µg/L). Quantitative real-time polymerase chain reaction revealed an upregulation in vitellogenin (vtg) in livers of females and males exposed to triclocarban. Also, an upregulation of hepatic lipoprotein lipase (lpl) and a downregulation of androgen receptor (ar) and steroidogenic acute regulatory protein (star) were observed in testes. The group treated with DEET only showed a significant decrease in ar in females. In contrast, the PPCP mixture downregulated vtg in females and males and expression of estrogen receptor alpha (erα), star, and thyroid hormone receptor alpha 1 (thra1) in testes. The authors' results show that the molecular estrogenic effects of triclocarban are eliminated (males) or reversed (females) when dosed in conjunction with several other PPCP, once again demonstrating that results from single exposures could be vastly different from those observed with mixtures. Environ Toxicol Chem 2014;33:910-919. © 2013 SETAC.

Family-specific differences in growth rate and hepatic gene expression in juvenile triploid growth hormone (GH) transgenic Atlantic salmon (Salmo salar)

Growth hormone transgenic (GHTg) Atlantic salmon (Salmo salar) have enhanced growth when compared to their non-transgenic counterparts, and this trait can be beneficial for aquaculture production. Biological confinement of GHTg Atlantic salmon may be achieved through the induction of triploidy (3N). The growth rates of triploid GH transgenic (3NGHTg) Atlantic salmon juveniles were found to significantly vary between families in the AquaBounty breeding program. In order to characterize gene expression associated with enhanced growth in juvenile 3NGHTg Atlantic salmon, a functional genomics approach (32K cDNA microarray hybridizations followed by QPCR) was used to identify and validate liver transcripts that were differentially expressed between two fast-growing 3NGHTg Atlantic salmon families (AS11, AS26) and a slow-growing 3NGHTg Atlantic salmon family (AS25); juvenile growth rate was evaluated over a 45-day period. Of 687 microarray-identified differentially expressed features, 143 (116 more highly expressed in fast-growing and 27 more highly expressed in slow-growing juveniles) were identified in the AS11 vs. AS25 microarray study, while 544 (442 more highly expressed in fast-growing and 102 more highly expressed in slow-growing juveniles) were identified in the AS26 vs. AS25 microarray study. Forty microarray features (39 putatively associated with fast growth and 1 putatively associated with slow growth) were present in both microarray experiment gene lists. The expression levels of 15 microarray-identified transcripts were studied using QPCR with individual RNA samples to validate microarray results and to study biological variability of transcript expression. The QPCR results agreed with the microarray results for 12 of 13 putative fast-growth associated transcripts, but QPCR did not validate the microarray results for 2 putative slow-growth associated transcripts. Many of the 39 microarray-identified genes putatively associated at the transcript expression level with fast-growing 3NGHTg salmon juveniles (including APOA1, APOA4, B2M, FADSD6, FTM, and GAPDH) are involved in metabolism, iron homeostasis and oxygen transport, and immune- or stress-related responses. The results of this study increase our knowledge of family-specific impacts on growth rate and hepatic gene expression in juvenile 3NGHTg Atlantic salmon. In addition, this study provides a suite of putative rapid growth rate-associated transcripts that may contribute to the development of molecular markers [e.g. intronic, exonic or regulatory region single nucleotide polymorphisms (SNPs)] for the selection of GHTg Atlantic salmon broodstock that can be utilized to produce sterile triploids of desired growth performance for future commercial applications.

Transcriptomic analysis of the host response to early stage salmonid alphavirus (SAV-1) infection in Atlantic salmon Salmo salar L

Salmon pancreas disease, caused by salmonid alphavirus (SAV) of the family Togaviridae, is an economically important disease affecting farmed Atlantic salmon (Salmo salar L.) in Scotland, Norway, and Ireland. The virus causes characteristic lesions in the pancreas, heart, kidney and skeletal muscle of infected fish. The mechanisms responsible for the pathology and the immune responses elicited in infected Atlantic salmon are not fully understood. A microarray-based study was therefore performed to evaluate the host transcriptomic response during the early stages of an experimentally-induced SAV-1 infection. Atlantic salmon parr were injected intra-peritoneally with viral cell culture supernatant or cell culture supernatant without virus. RNA, extracted from head kidney sampled from infected and control fish at 1, 3 and 5 days post-injection (d.p.i.), was interrogated with the 17 k TRAITS/SGP cDNA microarray. The greatest number of significantly differentially expressed genes was recorded at 3 d.p.i., mainly associated with immune and defence mechanisms, including genes involved in interferon I pathways and Major Histocompatibility Complex Class I and II responses. Genes associated with apoptosis and cellular stress were also found to be differentially expressed between infected and uninfected individuals, as were genes involved in inhibiting viral attachment and replication. The microarray results were validated by follow-on analysis of eight genes by real-time PCR. The findings of the study reflect mechanisms used by the host to protect itself during the early stages of SAV-1 infection. In particular, there was evidence of rapid induction of interferon-mediated responses similar to those seen during mammalian alphavirus infections, and also early involvement of an adaptive immune response. This study provides essential knowledge to assist in the development of effective control and management strategies for SAV-1 infection.

Venlafaxine and atenolol disrupt epinephrine-stimulated glucose production in rainbow trout hepatocytes

The beta-blocker atenolol (ATEN), and the selective serotonin and norepinephrine reuptake inhibitor, venlafaxine (VEN) are found in municipal wastewater effluents, but little is known about the effect of these pharmaceuticals on aquatic animals. We tested the hypothesis that VEN and ATEN disrupt acute stress mediated glucose production in fish liver. To this end, rainbow trout (Oncorhynchus mykiss) hepatocytes were exposed in vitro to different concentrations (0, 0.1, 10, 1000 nM) of VEN or ATEN and glucose production in response to either cortisol or epinephrine (two key stress hormones) was ascertained. Both VEN and ATEN did not affect either the unstimulated or cortisol (100 ng/mL)-stimulated glucose release over a 24 h period. The acute (3 h) unstimulated glucose production by isolated hepatocytes in suspension was also not modified by ATEN, while VEN (100 and 1000 nM) reduced basal glucose release. However, ATEN, even at concentration as low as 0.01 nM completely abolished epinephrine (1 μM)-induced glucose production in trout hepatocytes. Interestingly, VEN also suppressed epinephrine-induced glucose production but only at higher concentrations (100 and 1000 nM). Neither VEN nor ATEN significantly impacted the glucose production in response to either 8-bromo-cAMP (cAMP analogue) or glucagon (a metabolic hormone that increases glucose production) stimulation. ATEN but not VEN attenuated the epinephrine-induced increase in glucose transporter 2 (GLUT2) mRNA abundance in trout hepatocytes. Taken together, our results suggest that the impact of ATEN and VEN on glucose production involves inhibition of β-adrenoceptor signaling in trout hepatocytes. Overall, VEN and ATEN are beta-blockers and may disrupt the adaptive acute glucose response to a secondary stressor in rainbow trout.

Multiple tissue transcriptomic responses toPiscirickettsia salmonisin Atlantic salmon (Salmo salar)

The bacterium Piscirickettsia salmonis is the etiological agent of salmonid rickettsial septicemia (SRS), a severe disease that causes major economic losses to the Atlantic salmon aquaculture industry every year. Little is known about the infective strategy of P. salmonis, which is able to infect, survive within, and replicate inside salmonid macrophages as an intracellular parasite. Similarly there is little knowledge concerning the fish host's response to invasion by this pathogen. We have examined the transcriptional response of postsmolt Atlantic salmon ( Salmo salar) to P. salmonis at 48 h following infection in three tissues, liver, head kidney, and muscle, using an Atlantic salmon oligonucleotide microarray (Salar_2, Agilent 4x44K). The infection led to a large alteration of transcriptional activity in all the tissues studied. In infected salmon 886, 207, and 153 transcripts were differentially expressed in liver, head kidney, and muscle, respectively. Assessment of enrichment for particular biological pathways by gene ontology analysis showed an upregulation of genes involved in oxidative and inflammatory responses in infected fish, indicative of the activation of the innate immune response. The downregulation of genes involved in the adaptive immune response, G protein signaling pathway, and apoptotic process in infected fish may be reflective of mechanisms used by P. salmonis to survive, replicate, and escape host defenses. There was also evidence of differential responses between studied tissues, with protein metabolism being decreased in muscle of infected fish and with a concomitant increase being shown in liver.

Hepatic transcriptomics and protein expression in rainbow trout exposed to municipal wastewater effluent

Municipal wastewater effluents (MWWEs) represent one of the largest point sources of contamination, but few studies have addressed the impact on fish populations. We tested the hypothesis that MWWEs disrupt multiple stress-related pathways by examining expression of genes and proteins in rainbow trout (Oncorhynchus mykiss). A caging study was undertaken by placing juvenile trout for 14 d either at an upstream control or 100%, 50%, and 10% MWWE sites. A custom-made low-density rainbow trout cDNA microarray was utilized for transcriptomics, and select gene expression was confirmed with quantitative real-time PCR. MWWE exposure significantly elevated plasma cortisol, glucose, and vitellogenin levels, and altered the expression of a number of hepatic genes. Notably, expression of stress-related genes, hormone receptors, glucose transporter 2, and genes related to immune function were altered. The gene and protein expression of glucocorticoid receptor, heat shock proteins 70 and 90, and cytochrome P4501A1 were also impacted by MWWE exposure. Our results demonstrate that tertiary-treated MWWEs elicit an organismal and cellular stress response in trout and may lead to an enhanced energy demand in the exposed fish. The disruption in multiple stress-related pathways suggests that tertiary-treated MWWEs exposure may reduce fish performance to subsequent stressors.