Stress-Immune-Growth Interactions: Cortisol Modulates Suppressors of Cytokine Signaling and JAK/STAT Pathway in Rainbow Trout Liver

Synergistic toxic effects and mechanistic insights of beta-cypermethrin and pyraclostrobin exposure on hook snout carp (Opsariichthys bidens): A biochemical, transcriptional, and molecular approach

The extensive utilization of pesticides results in their frequent detection in aquatic environments, often as complex mixtures, posing risks to aquatic organisms. The hook snout carp (Opsariichthys bidens) serves as a valuable bioindicator for evaluating the impacts of environmental pollutants in aquatic ecosystems. However, few studies examined the toxic effects of pesticides on O.bidens, let alone the characterization of the combined effects resulting from their mixtures. This study aims to elucidate the toxic effects of beta-cypermethrin and pyraclostrobin on O.bidens, individually and in combination, focusing on biochemical, transcriptional, and molecular responses. By organizing and analyzing the toxicogenomic databases, both pesticides were identified as a contributor to processes such as apoptosis, oxidative stress, and inflammatory responses. The acute toxicity test revealed comparable acute toxicity of beta-cypermethrin and pyraclostrobin on O.bidens, with LC50 being 0.019 and 0.027 mg/L, respectively, whereas the LC50 decreased to 0.0057 and 0.0079 mg/L under the combined exposure, indicating potential synergistic effects. The activities of enzymes involved in oxidative stress and detoxification were significantly altered after exposure, with superoxide dismutase (SOD) and catalase (CAT) increasing, while malondialdehyde (MDA) levels decreased. The activity of CYP450s was significantly changed. Likewise, the expression levels of genes (mn-sod, p53, esr, il-8) associated with oxidative stress, apoptosis, endocrine and immune systems were significantly increased. Combined exposure to the pesticides significantly exacerbated the aforementioned biological processes in O.bidens. Furthermore, both pesticides can modify protein activity by binding to the surface of SOD molecules and altering protein conformation, contributing to the elevated enzyme activity. Through the investigation of the synergistic toxic effects of pesticides and molecular mechanisms in O.bidens, our findings highlight the importance of assessing the combined effects of pesticide mixtures in aquatic environments.

JAK-STAT signaling in inflammation and stress-related diseases: implications for therapeutic interventions

The Janus kinase-signal transducer and transcription activator pathway (JAK-STAT) serves as a cornerstone in cellular signaling, regulating physiological and pathological processes such as inflammation and stress. Dysregulation in this pathway can lead to severe immunodeficiencies and malignancies, and its role extends to neurotransduction and pro-inflammatory signaling mechanisms. Although JAK inhibitors (Jakinibs) have successfully treated immunological and inflammatory disorders, their application has generally been limited to diseases with similar pathogenic features. Despite the modest expression of JAK-STAT in the CNS, it is crucial for functions in the cortex, hippocampus, and cerebellum, making it relevant in conditions like Parkinson's disease and other neuroinflammatory disorders. Furthermore, the influence of the pathway on serotonin receptors and phospholipase C has implications for stress and mood disorders. This review expands the understanding of JAK-STAT, moving beyond traditional immunological contexts to explore its role in stress-related disorders and CNS function. Recent findings, such as the effectiveness of Jakinibs in chronic conditions such as rheumatoid arthritis, expand their therapeutic applicability. Advances in isoform-specific inhibitors, including filgotinib and upadacitinib, promise greater specificity with fewer off-target effects. Combination therapies, involving Jakinibs and monoclonal antibodies, aiming to enhance therapeutic specificity and efficacy also give great hope. Overall, this review bridges the gap between basic science and clinical application, elucidating the complex influence of the JAK-STAT pathway on human health and guiding future interventions.

Whole-Genome Methylation Sequencing of Large Yellow Croaker (Larimichthys crocea) Liver Under Hypoxia and Acidification Stress

Large yellow croaker (Larimichthys crocea) is an important aquaculture species in China. This study analysed whole-genome methylation differences in liver tissues of young fish under different hypoxic and acidification conditions. Differentially methylated regions (DMRs) and differentially methylated genes (DMGs) were identified. Gene ontology (GO) and Kyoto encyclopaedia of genes and genomes (KEGG) enrichment analyses of DMGs were conducted to explore the mechanism of coping with hypoxic acidification. The main methylation type was CG, accounting for > 70% of total methylation, significantly higher than CHG and CHH methylation types. GO enrichment analysis of DMGs revealed strong enrichment of nervous system development, cell periphery, plasma membrane, cell junction organisation, cell junction, signalling receptor activity, molecular sensor activity, cell-linked tissue junction organisation, cell-cell adhesion and nervous system development. KEGG enrichment analysis of DMR-related genes identified cell adhesion molecules, cortisol synthesis and secretion and aldosterone synthesis and secretion as the three key pathways regulating the physiological responses to hypoxia and acidification. Long-term hypoxic and acidification stress affected the immune system, nervous system and stress responses of large yellow croaker. Whole-genome sequencing analysis of exposed tissues was used to investigate changes that occur in L. crocea in response to hypoxic and acidic conditions at the DNA methylation level. The findings contribute to our comprehensive understanding of functional methylation in large yellow croaker and will support future research on the response mechanisms of this species under different environmental pressures.

Liver fibrosis in fish research: From an immunological perspective

Liver fibrosis is a pathological process whereby the liver is subjected to various acute and chronic injuries, resulting in the activation of hepatic stellate cells (HSCs), an imbalance of extracellular matrix generation and degradation, and deposition in the liver. This review article summarizes the current understanding of liver fibrosis in fish research. Liver fibrosis is a common pathological condition that occurs in fish raised in aquaculture. It is often associated with poor water quality, stressful conditions, and the presence of pathogens. The review describes the pathophysiology of liver fibrosis in fish, including the roles of various cells and molecules involved in the development and progression of the disease. The review also covers the various methods used to diagnose and assess the severity of liver fibrosis in fish, including histological analysis, biochemical markers, and imaging techniques. In addition, the article discusses the current treatment options for liver fibrosis in fish, including dietary interventions, pharmaceuticals, and probiotics. This review highlights the need for more in-depth research in this area to better understand the mechanisms by which liver fibrosis in fish occurs and to develop effective prevention and treatment strategies. Finally, improved management practices and the development of new treatments will be critical to the sustainability of aquaculture and the health of farmed fish.

Genome-wide evolutionary signatures of climate adaptation in spotted sea bass inhabiting different latitudinal regions

Consideration of the thermal adaptation of species is essential in both evolutionary biology and climate-change biology because it frequently leads to latitudinal gradients of various phenotypes among populations. The spotted sea bass (Lateolabrax maculatus) has a broad latitudinal distribution range along the marginal seas of the Northwest Pacific and thus provides an excellent teleost model for population genetic and climate adaptation studies. We generated over 8.57 million SNP loci using whole-genome resequencing from 100 samples collected at 14 geographic sites (five or ten samples per site). We estimated the genetic structure of the sampled fish and clustered them into three highly differentiated populations. The genetic differentiation pattern estimated by multivariable models combining geographic distance and sea surface temperature differences suggests that isolation by distance and isolation by environment both have significant effects on this species. Further investigation of genome-wide evolutionary signatures of climate adaptation identified many genes related to growth, muscle contraction, and vision that are under positive natural selection. Moreover, the contrasting patterns of natural selection in high-latitude and low-latitude populations prompted different strategies of trade-offs between growth rate and other traits that may play an essential role in adaptation to different local climates. Our results offer an opportunity to better understand the genetic basis of the phenotypic variation in eurythermal fishes inhabiting different climatic regions.

Chronic stress negatively impacts wound healing, welfare, and stress regulation in internally tagged Atlantic salmon (Salmo salar)

The desire to understand fish welfare better has led to the development of live monitoring sensor tags embedded within individuals for long periods. Improving and understanding welfare must not come at the cost of impaired welfare due to a tag’s presence and implantation process. When welfare is compromised, the individual will experience negative emotions such as fear, pain, and distress, impacting the stress response. In this study, Atlantic salmon (Salmo salar) underwent surgical implantation of a dummy tag. Additionally, half of this group was introduced to daily crowding stress. Both groups and an untagged group were followed for 8 weeks using triplicate tanks per group. Sampling took place once a week, and where stress was given, it was conducted 24 h before sampling. Stress-related measurements were taken to understand if tagging caused chronic stress and explore the chronic stress response and its impact on wound healing. Primary stress response hormones measured included CRH, dopamine, adrenocorticotropic hormone, and cortisol. Secondary stress response parameters measured included glucose, lactate, magnesium, calcium, chloride, and osmolality. Tertiary stress response parameters measured included weight, length, and five fins for fin erosion. Wound healing was calculated by taking the incision length and width, the inflammation length and width, and the inside wound length and width. The wound healing process showed that stressed fish have a larger and longer-lasting inflammation period and a slower wound healing process, as seen from the inside wound. The tagging of Atlantic salmon did not cause chronic stress. In contrast, daily stress led to an allostatic overload type two response. ACTH was elevated in the plasma after 4 weeks, and cortisol followed elevation after 6 weeks, highlighting a breakdown of the stress regulation. Fin erosion was elevated alongside cortisol increase in the stressed group. This data suggests that tagging previously unstressed fish in a controlled environment does not negatively affect welfare regarding stress responses. It also indicates that stress delays wound healing and increases the inflammatory response, highlighting how continued stress causes a breakdown in some stress responses. Ultimately, the tagging of Atlantic salmon can be successful under certain conditions where proper healing is observed, tag retention is high, and chronic stress is not present, which could allow for the possible measurement of welfare indicators via smart-tags.

Long-term feeding of Atlantic salmon with varying levels of dietary EPA + DHA alters the mineral status but does not affect the stress responses after mechanical delousing stress

Atlantic salmon were fed diets containing graded levels of EPA + DHA (1·0, 1·3, 1·6 and 3·5 % in the diet) and one diet with 1·3 % of EPA + DHA with reduced total fat content. Fish were reared in sea cages from about 275 g until harvest size (about 5 kg) and were subjected to delousing procedure (about 2·5 kg), with sampling pre-, 1 h and 24 h post-stress. Delousing stress affected plasma cortisol and hepatic mRNA expression of genes involved in oxidative stress and immune response, but with no dietary effects. Increasing EPA + DHA levels in the diet increased the trace mineral levels in plasma and liver during mechanical delousing stress period and whole body at harvest size. The liver Se, Zn, Fe, Cu, and Mn and plasma Se levels were increased in fish fed a diet high in EPA + DHA (3·5 %) upon delousing stress. Furthermore, increased dietary EPA + DHA caused a significant increase in mRNA expression of hepcidin antimicrobial peptide (HAMP), which is concurrent with downregulated transferrin receptor (TFR) expression levels. High dietary EPA + DHA also significantly increased the whole-body Zn, Se, and Mn levels at harvest size fish. Additionally, the plasma and whole-body Zn status increased, respectively, during stress and at harvest size in fish fed reduced-fat diet with less EPA + DHA. As the dietary upper limits of Zn and Se are legally added to the feeds and play important roles in maintaining fish health, knowledge on how the dietary fatty acid composition and lipid level affect body stores of these minerals is crucial for the aquaculture industry.

The early function of cortisol in liver during Aeromonas hydrophila infection: Dynamics of the transcriptome and accessible chromatin landscapes

In China, channel catfish (Ictalurus punctatus) is an important aquaculture species; however, haemorrhagic disease (Aeromonas hydrophila induced disease) in these fish has caused tremendous economic loss due to high morbidity and mass mortality in the breeding industry. The role of cortisol in bacterial diseases, particularly in the acute phase, remains unclear. In this study, liver transcriptome (RNA-seq) and chromatin accessibility (ATAC-seq) analyses were employed to investigate the early functional role of cortisol in Aeromonas hydrophila-stimulated responses. Our experiments confirmed that A. hydrophila infection can initially significantly increase serum cortisol levels at 1 h after infection. At this time point, the increased serum cortisol levels can significantly regulate A. hydrophila-regulated genes by affecting both transcriptome and chromatin accessibility. Cross-analysis of RNA-seq and ATAC-seq revealed that a certain gene group (92 target_DEGs) was regulated at an early time point by cortisol. KEGG enrichment analysis revealed that the top three pathways according to target_DEGs were cancer, glutathione metabolism, and the Notch signalling pathway. The protein-protein interaction analysis of target_DEGs revealed that they may be primarily involved in cell proliferation, CD8⁺ T cell function, glutathione synthesis, and activation of the NF-κB signalling pathway. This suggests that after the emergence of immune stress, the early regulation of cortisol is positive against the immune response. It is possible that in this situation, the animal is attempting to avoid dangerous situations and risks and then cope with the imbalance produced by the stressor to ultimately restore homeostasis. Our results will contribute to future research on fish and provide valuable insight regarding the mechanism of immune regulation by cortisol and the study of bacterial haemorrhagic disease in channel catfish.

Social status-dependent regulation and function of the somatotropic axis in juvenile rainbow trout

Juvenile rainbow trout (Oncorhynchus mykiss) develop social hierarchies when competing for resources in a constrained environment. Among the physiological consequences of social status are changes in organismal energy metabolism, which generally favour anabolic pathways in dominant fish and catabolic pathways in subordinate fish. The somatotropic axis is an important regulator of metabolism and growth that could be involved in mediating metabolic changes in response to social status in juvenile rainbow trout. Here we used juvenile trout housed either in dyads or individually (sham controls) to determine whether social status changes indices of somatotropic axis function. Although pituitary growth hormone expression (gh1 and gh2) did not differ among groups, circulating growth hormone (GH) increased ∼12-fold in subordinate fish compared to sham and dominant fish. Social status caused consistent differential expression of GH receptor paralogues in liver and muscle, two principal target tissues of GH. Compared to dominant and/or sham fish, ghra paralogue expression (ghra1 and ghra2) was lower, while ghrb1 expression was higher in subordinate fish. Across tissues, ghra paralogue expression was generally positively correlated with expression of insulin growth factors (igf1, igf2), while ghrb1 expression was positively correlated with transcript abundance of hormone sensitive lipase (hsl1). Because igf and hsl expression are subject to context-dependent GH control in rainbow trout, these results suggest that increased circulating GH in conjunction with differential expression of ghr paralogues may translate into prioritization of downstream catabolic lipolytic pathways in subordinate rainbow trout. These findings support a social context-dependent role for GH signalling in mediating metabolic changes in juvenile rainbow trout.

Glucocorticoid Treatment Strategies in Liver Failure

Liver failure is characterized by serious liver decompensation and high mortality. The activation of systemic immune responses and systemic inflammation are widely accepted as the core pathogenesis of liver failure. Glucocorticoids (GCs) are most regularly utilized to suppress excessive inflammatory reactions and immunological responses. GCs have been used in the clinical treatment of liver failure for nearly 60 years. While there has been no unanimity on the feasibility and application of GC treatment in liver failure until recently. The most recent trials have produced conflicting results when it comes to the dose and time for GC therapy of different etiology of liver failure. Our review outlines the issues and options in managing GC treatment in liver failure based on an investigation of the molecular mechanism that GC may give in the treatment.

Interleukin-6 mediates lipopolysaccharide-inhibited irisin secretion in Nile tilapia (Oreochromis niloticus)

Irisin is a novel immunomodulatory adipomyokine released upon cleavage of the fibronectin type III domain-containing protein 5 (FNDC5). We aimed to examine interleukin-6 (IL-6) role in mediating irisin secretion in immunologically challenged animal and primary head kidney leukocytes cultured from tilapia. Intraperitoneal injection of lipopolysaccharide (LPS) increased plasma IL-6 levels and decreased irisin secretion, suggesting a causal relationship between the induction of IL-6 and irisin. To address this relationship, we further produced recombinant tilapia IL-6 and the anti-tilapia IL-6 polyclonal antiserum. Intraperitoneal injection of recombinant tilapia IL-6 inhibited plasma irisin levels. Consistent with this observation, LPS-induced inhibition of plasma irisin was significantly attenuated by neutralizing circulating IL-6 using an IL-6 antiserum. Besides, IL-6 treatment could inhibit irisin secretion and FNDC5 gene expression in primary cultures of tilapia head kidney leukocytes. In parallel experiments, both LPS and IL-6 blockade of irisin secretion could be reverted by IL-6 receptor antagonism. At the level of the leukocyte, IL-6 treatment also triggered rapid phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), whereas IL-6-reduced irisin secretion could be negated by inhibiting the JAK2 and STAT3 signaling pathways. These results, as a whole, provide the first evidence that IL-6 is the mediator of LPS-inhibited irisin secretion via activation of the JAK2/STAT3 signaling pathway.

Prolonged cortisol elevation alters whole body and tissue metabolism in rainbow trout (Oncorhynchus mykiss)

Chronic elevation of circulating cortisol is known to have deleterious effects on fish, but information about the consequences of prolonged cortisol elevation on the metabolism of fish is scarce. To test the effects of chronic cortisol elevation on the aerobic performance of rainbow trout, we examined how two severities of chronically elevated plasma cortisol levels affected the oxygen uptake during rest and after exhaustive exercise using a high (HC) and a medium cortisol (MC) treatment. High cortisol doses significantly affected standard (SMR) and maximum metabolic rates (MMR) compared to control fish. In comparison, the medium cortisol treatment elevated maximum metabolic rates (MMR) but did not significantly influence SMR compared to a sham group (S) and control group (C). The medium cortisol treatment resulted in a significantly increased metabolic scope due to an elevation of MMR, an effect that was abolished in the HC group due to co-occuring elevations in SMR. The elevated SMR of the HC-treated fish could be explained by increased in vitro oxygen uptake rates (MO₂) of specific tissues, indicating that the raised basal metabolism was caused, in part, by an increase in oxygen demand of specific tissues. Haematological results indicated an increased reliance on anaerobic metabolic pathways in cortisol-treated fish under resting conditions.

Revelation of candidate genes and molecular mechanism of reproductive seasonality in female rohu (Labeo rohita Ham.) by RNA sequencing

BACKGROUND

Carp fish, rohu (Labeo rohita Ham.) is important freshwater aquaculture species of South-East Asia having seasonal reproductive rhythm. There is no holistic study at transcriptome level revealing key candidate genes involved in such circannual rhythm regulated by biological clock genes (BCGs). Seasonality manifestation has two contrasting phases of reproduction, i.e., post-spawning resting and initiation of gonadal activity appropriate for revealing the associated candidate genes. It can be deciphered by RNA sequencing of tissues involved in BPGL (Brain-Pituitary-Gonad-Liver) axis controlling seasonality. How far such BCGs of this fish are evolutionarily conserved across different phyla is unknown. Such study can be of further use to enhance fish productivity as seasonality restricts seed production beyond monsoon season.

RESULT

A total of ~ 150 Gb of transcriptomic data of four tissues viz., BPGL were generated using Illumina TruSeq. De-novo assembled BPGL tissues revealed 75,554 differentially expressed transcripts, 115,534 SSRs, 65,584 SNPs, 514 pathways, 5379 transcription factors, 187 mature miRNA which regulates candidate genes represented by 1576 differentially expressed transcripts are available in the form of web-genomic resources. Findings were validated by qPCR. This is the first report in carp fish having 32 BCGs, found widely conserved in fish, amphibian, reptile, birds, prototheria, marsupials and placental mammals. This is due to universal mechanism of rhythmicity in response to environment and earth rotation having adaptive and reproductive significance.

CONCLUSION

This study elucidates evolutionary conserved mechanism of photo-periodism sensing, neuroendocrine secretion, metabolism and yolk synthesis in liver, gonadal maturation, muscular growth with sensory and auditory perception in this fish. Study reveals fish as a good model for research on biological clock besides its relevance in reproductive efficiency enhancement.

Effects of long-term cortisol treatment on growth and osmoregulation of Atlantic salmon and brook trout

Cortisol is the final product of the hypothalamic-pituitary-interrenal (HPI) axis and acts as a gluco- and mineralo-corticoid in fish. Long-term elevations of cortisol have been linked to reduced growth in fishes, but the mechanism(s) and relative sensitivities of species are still unclear. We carried out experiments to examine the relative effects of cortisol on growth and gill NKA activity in two salmonids: Atlantic salmon (Salmo salar) and brook trout (Salvelinus fontinalis). Treatment with intraperitoneal cortisol implants for 30 days resulted in reduced growth in both species, but with greater sensitivity to cortisol in brook trout. Gill NKA activity was strongly upregulated by cortisol in Atlantic salmon, and weakly upregulated in brook trout but with no statistically significant effect. Cortisol treatment resulted in reduced plasma levels of insulin-like growth factor I and increased plasma growth hormone levels in Atlantic salmon. Our results demonstrate that there are species differences in the sensitivity of growth and osmoregulation to cortisol, even among species in the same family (Salmonidae).

Poly (I:C)-Potentiated Vaccination Enhances T Cell Response in Olive Flounder (Paralichthys olivaceus) Providing Protection against Viral Hemorrhagic Septicemia Virus (VHSV)

Viral hemorrhagic septicemia (VHS), caused by viral hemorrhagic septicemia virus (VHSV), is a viral disease affecting teleosts, and is the major cause of virus-related deaths in olive flounder (Paralichthys olivaceus). Research has focused on ways to control VHS, and recently, the use of polyinosinic-polycytidylic acid poly (I:C)-potentiated vaccination has been investigated, whereby fish are injected with poly (I:C) and then with live pathogenic virus, resulting in a significant decrease in VHSV-related mortality. T cell responses were investigated in the present study after vaccinating olive flounder with poly (I:C)-potentiated vaccination to understand the ability of poly (I:C) to induce T cell immunity. Stimulation of T cell responses with the poly (I:C)-potentiated vaccination was confirmed by examining levels of CD3+ T cells, CD4-1+ T cells and CD4-2+ T cells. Higher levels of CD4-2+ T cells were found in vaccinated fish than CD4-1+ T cells, believed to result from a synergistic effect between poly (I:C) administration and pathogenic VHSV immunization. More importantly, the role of CD4-2+ T cells in the antiviral response was clearly evident. The results of this study suggest that the outstanding protection obtained with the poly (I:C)-potentiated vaccination is due to the robust immune response initiated by the CD4-2+ T cells.

Controlled experiments to explore the use of a multi-tissue approach to characterizing stress in wild-caught Pacific halibut (Hippoglossus stenolepis)

The integration of multiple tissues in physiological and ecological analyses can enhance methodological approaches, increase applications for data and extend interpretation of results. Previous investigations of the stress response in fish have focused primarily on cortisol levels in a single matrix-blood plasma-which confines interpretations of cortisol levels to a short temporal frame. Epidermal mucus has been proposed as an alternative or complement to plasma that may provide a view to cortisol levels over a different temporal window allowing comparative assessment. Here, we explore the potential for multi-tissue cortisol analysis using both plasma and epidermal mucus in Pacific halibut (Hippoglossus stenolepis). The relative timing at which cortisol increased and decreased in the two matrices as well as cortisol concentrations at estimated peak levels were compared in two trials after (i) inducing cortisol synthesis by adrenocorticotropic hormone (ACTH_1-24) administration and (ii) inducing cortisol elimination using cortisol (hydrocortisone, 98%) injection. The ACTH treatment elicited a peak plasma cortisol response approximately 12 hours post-injection, while mucus cortisol concentrations peaked later at approximately 62 hours post-injection. Exogenous cortisol treatments suggested relatively little transfer of cortisol from plasma to mucus, potentially reflecting differential effects of endogenous and exogenous cortisol. Our results suggest the potential utility of mucus as a sampling matrix that provides an extended window for detection of the stress response as compared to plasma. Results also suggest the utility of a multi-tissue approach to cortisol analysis with potential applications to applied fisheries research. Increased understanding of the relative scale of the cortisol response to stress (e.g. capture) will allow researchers and managers to better interpret the physiological condition and survival outcome of fish subjected to regulatory discard.

Cortisol regulates insulin-like growth-factor binding protein (igfbp) gene expression in Atlantic salmon parr

The growth hormone (Gh)/insulin-like growth-factor (Igf)/Igf binding protein (Igfbp) system regulates growth and osmoregulation in salmonid fishes, but how this system interacts with other endocrine systems is largely unknown. Given the well-documented consequences of mounting a glucocorticoid stress response on growth, we hypothesized that cortisol inhibits anabolic processes by modulating the expression of hepatic igfbp mRNAs. Atlantic salmon (Salmo salar) parr were implanted intraperitoneally with cortisol implants (0, 10, and 40 μg g^-1 body weight) and sampled after 3 or 14 days. Cortisol elicited a dose-dependent reduction in specific growth rate (SGR) after 14 days. While plasma Gh and Igf1 levels were unchanged, hepatic igf1 mRNA was diminished and hepatic igfbp1b1 and -1b2 were stimulated by the high cortisol dose. Plasma Igf1 was positively correlated with SGR at 14 days. Hepatic gh receptor (ghr), igfbp1a, -2a, -2b1, and -2b2 levels were not impacted by cortisol. Muscle igf2, but not igf1 or ghr, levels were stimulated at 3 days by the high cortisol dose. As both cortisol and the Gh/Igf axis promote seawater (SW) tolerance, and particular igfbps respond to SW exposure, we also assessed whether cortisol coordinates the expression of branchial igfbps and genes associated with ion transport. Cortisol stimulated branchial igfbp5b2 levels in parallel with Na⁺/K⁺-ATPase (NKA) activity and nka-α1b, Na⁺/K⁺/2Cl^--cotransporter 1 (nkcc1), and cystic fibrosis transmembrane regulator 1 (cftr1) mRNA levels. The collective results indicate that cortisol modulates the growth of juvenile salmon via the regulation of hepatic igfbp1s whereas no clear links between cortisol and branchial igfbps previously shown to be salinity-responsive could be established.

Downregulation of SOCS gene expression can inhibit the formation of acute and persistent BDV infections

High expression of suppressors of cytokine signalling (SOCS) has been detected during various viral infections. As a negative feedback regulator, SOCS participates in the regulation of multiple signalling pathways. In this study, to study the related mechanism between SOCS and BDV and to explore the effect of SOCS on IFN pathways in nerve cells, downregulated of SOCS1/3 in oligodendroglial (OL) cells and OL cells persistently infected with BDV (OL/BDV) were constructed with RNA interference technology. An interferon inducer (poly I:C, PIC) and an IFN-α/β R1 antibody were used as stimulation in the SOCS1/3 low-expression cell models, qRT-PCR was used to detect type I IFN and BDV nucleic acid expression, Western blot was used to detect the expression of BDV P40 protein. After BDV acute infection with OL cells which with downregulated SOCS expression, the virus accounting was not detected, and the viral protein expression was lower than that of OL/BDV cells; the OL/BDV cells with downregulated SOCS expression had lower virus nucleic acid and protein expression than OL/BDV cells. Stimulated by IFN-α/β R1 antibody, the expression of type I interferon in OL/BDV cells decreased, and the content of BDV nucleic acid and protein increased, which was higher than that of OL/BDV cells. From the results, it was concluded that downregulating SOCS1/3 can inhibit the formation of acute BDV infection and virus replication in persistent BDV infection by promoting the expression of IFN-α/β and that SOCS can be used as a new target for antiviral therapy.

Prolactin peptide (pPRL) induces anti-prolactin antibodies, ROS and cortisol but suppresses specific immune responses in rainbow trout

Prolactin has several immune functions in fish however, the effects on innate and specific components of rainbow trout immunity are currently unknown. Therefore in this study, prolactin peptide (pPRL) injection in rainbow trout generated anti-PRL antibodies that were confirmed through Western blot assays of fish brain tissue extract. At the same time, this group of fish was immunized with a viral antigen (VP2) and the specific antibody titer generated by the rainbow trout was subsequently determined, as well as the sero-neutralizing capacity of the antibodies. Interestingly, this group of fish (pPRL-VP2) generated approximately 150% less antibodies compared with fish immunized only with the viral antigen (VP2), and pPRL-VP2 fish increased their cortisol level by 4 times compared to the control. Additionally, through qPCR assay, we determined that the pPRL-VP2 fish group decreased pro-inflammatory transcript expression, and the serum of these (pPRL-VP2) fish stimulated ROS production in untreated fish leukocytes, a phenomenon that was blocked by the pharmacological cortisol receptor inhibitor (RU486). Collectively, this is the first report that indicates that pPRL could modulate both components of immunity in rainbow trout.

Modulation of inflammatory response by cortisol in the kidney of spotted scat (Scatophagus argus) in vitro under different osmotic stresses

Salinity changes on renal osmoregulation have often been investigated while the immune response of the kidney under osmotic stress is poorly understood in teleosts. Acute stress is generally associated with enhancement of circulating cortisol. The effects of osmotic stress on renal immune response and its regulation by cortisol deserve more attention. In the present study, the effects of exogenous cortisol treatment on the lipopolysaccharide (LPS)-induced immune response were analyzed in renal masses of Scatophagus argus under different osmotic stresses in vitro. mRNA expression of pro-inflammatory cytokines (TNF-α, IL1-β and IL-6) and immune-regulatory related genes (GR and SOCS1) was measured over a short course (15 h). Comprehensive analysis reveals that transcript abundances of pro-inflammatory cytokine genes such as TNF-α, IL-1β, and IL-6 induced by LPS, alone or in the combination of cortisol, are tightly associated with osmoregulation under acute osmotic stress. Our results showed that osmotic challenge could significantly enhance mRNA expression levels of pro-inflammatory cytokines in renal masses in vitro. Based on our analysis, it can be inferred that cortisol suppresses the magnitude of renal inflammatory response and attenuates LPS-induced immune response through GR signaling in the face of challenging environmental conditions.

[High expression of STAT2 in ovarian cancer and its effect on metastasis of ovarian cancer cells]

OBJECTIVE

To investigate the expression of signal transduction and activator of transcription 2 (STAT2) in ovarian cancer and its correlation with the prognosis of ovarian cancer patients and explore the role of STAT2 inregulating metastasis of ovarian cancer cells.

METHODS

RT-qPCR was performed to detect the expression of STAT2 mRNA in 62 fresh frozen ovarian cancer tissues and 62 normal ovarian tissues; immunohistochemistry was used to detect STAT2 protein expressions in 95 paraffin-embedded ovarian cancer samples and 33 normal ovarian tissues. Kaplan-Meier method was used to analyze the correlation between the expression of STAT2 and the prognosis of the patients. We also examined the relationship between STAT2 and the patients' prognosis by analyzing the data in Kaplan-Meier Plotter database. Western blotting was performed to detect the expression of STAT2 in different ovarian cancer cell lines. In A2780 cells with the highest STAT2 expression, we examined the effects of STAT2 interference on cell migration and invasiveness using Transwell migration assay and on the expressions of the downstream molecule epidermal growth factor receptor (EGFR).

RESULTS

Ovarian cancer tissues expressed significantly higher levels of STAT2 mRNA than normal ovarian tissue. A high STAT2 mRNA expression was correlated with an advanced FIGO stage. Immunohistochemistry showed that 67.4% of the ovarian cancer samples, as compared with 28.3% of normal ovarian tissues, showed high STAT2 expressions. In ovarian cancer patients, a high expression of STAT2 protein was associated with ascites volume, distant metastasis and FIGO stage (P < 0.05). Survival analysis showed that ovarian cancer patients with a high expression of STAT2 protein had poor overall survival (P=0.021) and progression-free survival (P=0.018). STAT2 was overexpressed in all the ovarian cancer cell lines tested, and A2780 cell lines showed the highest expression. Interference of STAT2 significantly suppressed the migration and invasiveness (P < 0.01) and lowered the expression level of EGFR in A2780 cells.

CONCLUSIONS

STAT2 is overexpressed in ovarian cancer. A high expression of STAT2 is associated with a poor prognosis of ovarian cancer patients. STAT2 may promote the metastasis of ovarian cancer by enhancing the expression of EGFR.

Liver transcriptome analysis and cortisol immune-response modulation in lipopolysaccharide-stimulated in channel catfish (Ictalurus punctatus)

Channel catfish (Ictalurus punctatus) is an important aquaculture species in China. In channel catfish, diseases such as haemorrhagic, sepsis and tail-rot disease are all caused by bacteria as general in China. Most of the pathogenic bacteria are Gram-negative bacteria. Liver transcriptome analysis of the co-injection of cortisol and lipopolysaccharide (LPS) was performed in this study. Preliminary evidence from the results suggest that after the emergence of immune stress, cortisol will up-regulate the complement cascade pathway, down-regulate the coagulation cascade pathway, down-regulate the platelet activation pathway, down-regulate antigen presentation pathway, and show complex regulation relationship to inflammatory factors. At 12 h, the number of differential genes regulated by cortisol was about half less than the number of differential genes regulated by LPS. At 24 h, there was no significant difference between the number of differential genes regulated by cortisol and LPS, but the types of differential genes vary widely. KEGG enrichment analysis found that cortisol regulated LPS-stimulated immune responses mainly focus on cytokines, complement and coagulation cascades pathways, antigen presentation pathways, haematopoiesis, and inflammation. It is suggested that there may be some strategic choice in the regulation of immune response by cortisol. These results will help understand the pathogenesis and host defence system in bacterial disease caused by Gram-negative bacteria.

How different rearing temperatures affect growth and stress status of Siberian sturgeon Acipenser baerii larvae

Environmental temperature is one of the critical factors affecting fish development. The aim of this study was to examine the impact of three different rearing temperatures (16, 19 and 22°C) throughout the endogenous feeding phase of the Siberian sturgeon Acipenser baerii. This was performed by assessing (a) larval survival and growth; (b) immunofluorescence localization and expression of genes involved in muscle development and growth - myog and Igf1; and (c) stress status through the expression of thermal stress genes - Hsp70, Hsp90α and Hsp90β - and whole body cortisol. Overall survival rate and larval weight did not differ significantly across temperatures. Larvae subjected to 22°C showed faster absorption of the yolk-sac than larvae subjected to 19 or 16°C. Both at schooling and at the end of the trial, larvae reared at 16°C showed significantly lower levels of cortisol than those reared at 19 or 22°C. IGF-1 immunopositivity was particularly evident in red muscle at schooling stage in all temperatures. The expression of all Hsps as well as the myog and Igf1 genes was statistically higher in larvae reared at 16°C but limited to the schooling stage. Cortisol levels were higher in larvae at 22°C, probably because of the higher metabolism demand rather than a stress response. The observed apparent incongruity between Hsps gene expression and cortisol levels could be due to the lack of a mature system. Further studies are necessary, especially regarding the exogenous feeding phase, in order to better understand if this species is actually sensitive to thermal stress.

Effects of temperature on the transcriptomes of pituitary and liver in Golden Pompano Trachinotus blochii

Fish growth can be modulated dynamically through the brain-pituitary-liver regulation axis. In the present study, whole transcriptomes of the pituitary and liver from Golden Pompano Trachinotus blochii were sequenced in seawater at 20 °C (T_low) and 25 °C (T_high). A total of 187,277,583 paired-end reads were assembled to obtain 100,495 transcripts, corresponding to 83,974 genes. These reads were mapped to T. blochii transcripts, and the mapping accuracy ranged from 80.4 to 94.9%. Two lists of differentially expressed genes were obtained by comparisons of pituitary and liver T_low versus T_high groups, comprising 458 and 205 genes, respectively. Of these, 33 differentially expressed genes were common between the two lists. Twelve GO terms were overrepresented for the 458 differentially expressed genes in the pituitary, and it is noteworthy that the GO term galanin receptor activity (GO: 0004966) related to the modulation of appetite and metabolism, whose genes made up half of all assembled genes in the term. For the 205 differentially expressed genes in the liver, 19 overrepresented GO terms were mainly related to immune regulation, digestion, and protein metabolism. Among the common differentially expressed genes, there were 32 genes that had identical changing trends in both pituitary and liver comparisons. Furthermore, two GO terms inorganic diphosphatase activity and MHC protein complex were overrepresented. These results indicate that the brain could regulate pituitary function through galanin signal mechanism and that the metabolism of liver was further optimized to modulate immunity and growth under different temperatures.

Differential immune gene response in gills, skin, and spleen of rainbow trout Oncorhynchus mykiss infected by Ichthyophthirius multifiliis

Infection of rainbow trout with the parasitic ciliate Ichthyopthirius multifiliis induces differential responses in gills, skin and spleen. A controlled experimental infection was performed and expression of immune-relevant genes in skin, gills, and spleen were recorded by qPCR at day 1 and 8 after parasite exposure. Infection induced a marked reaction involving regulation of innate and adaptive immune genes in rainbow trout at day 8 post-infection. The expression level of a total of 22 out of 24 investigated genes was significantly higher in gills compared to skin reflecting the more sensitive and delicate structure of gills. Especially pro-inflammatory cytokines IL-6, IL-17 C1, regulatory cytokines IL-4/13A, IL-10, TGFβ, complement factor C5, chemokines CK10, CK12, acute phase proteins (precerebellin, hepcidin) and immunoglobulins (IgM, IgT) displayed differential expression levels. The spleen, a central immune organ with no trace of the parasite, showed elevated expression of IgM, IgT, complement factor C5 and chemokine CK10 (compared to skin and gills directly exposed to the parasite), indicating an interaction between the infected surface sites and central immune organs. This communication could be mediated by chemokines CK10 and CK12 and cytokine IL-4/13A and may at least partly explain the establishment of a systemic response in rainbow trout against the parasite.

Stocking density induces differential expression of immune-related genes in skeletal muscle and head kidney of fine flounder (Paralichthys adspersus)

Immunity can be modulated by different internal and external factors, being stress one of the most important. However, the stress effects on the immunocompetence of the skeletal muscle has not been studied in detail in earlier vertebrates. Here, we examine the effect of chronic (4 and 7 weeks) crowding stress on the immunocompetence of skeletal muscle and head kidney in the fine flounder (Paralichthys adspersus). Corticosteroid receptor transcript levels and their target genes; pro-inflammatory cytokines, and Toll-, NOD-, and RIG-like receptors were quantified by qPCR. The results indicate that chronic stress down-regulates the expression of these genes in muscle, compromising skeletal muscle immunocompetence, while the expression of these genes is upregulated in head kidney after seven weeks of crowding stress. The data suggests that chronic stress modulates the expression of these immune-related genes in a tissue-specific manner.

Vaccine-induced antibody level as the parameter of the influence of environmental salinity on vaccine efficacy in Nile tilapia

To effectively increase production and improve economic returns, the co-culture of Nile tilapia (Oreochromis niloticus) and marine shrimp has been adopted in many countries, including China. Although O. niloticus is an euryhaline fish that can tolerate elevated salinities and even full-strength seawater, fluctuations in salinity levels can undoubtedly induce stress and affect the immune response of this fish. Therefore, this study assessed the impact of salinity on vaccine efficacy in Nile tilapia, which used serum antibody level as a surrogate marker to detect vaccine efficacy. Nile tilapia were acclimatized to 0, 10, 20, or 30 ppt salinity, and then immunized with a formalin-inactivated Streptococcus agalactiae vaccine. Significantly lower levels of antibody in vaccinated fish were found at 20 and 30 ppt salinity compared to 0 and 10 ppt salinity. White blood cell counts, absolute blood lymphocyte counts, and serum bactericidal activity levels were all significantly lower in vaccinated fish at 20 and 30 ppt salinity. Elevated cortisol levels were detected in all of the fish exposure to salinity. Concentrations of serum electrolytes (Na⁺ and Cl^-) were significantly higher in fish at 30 ppt salinity, as compared to fish at lower salinities. Furthermore, the mRNA transcription levels of three of the immune-related genes analyzed (IgM, IL-1β, and IFN-γ, but not Hsp70) were significantly inhibited in the vaccinated fish at 20 and 30 ppt salinity. A suppressed immune response and decreased vaccine efficacy were also indicated by the lower survival rate of vaccinated fish at 20 ppt salinity when challenged with S. agalactiae. Therefore, salinities ≥20 ppt negatively affected antibody production in Nile tilapia, ultimately affecting vaccine efficacy.

Maturation-associated changes in the non-specific immune response against Flavobacterium psychrophilum in Ayu Plecoglossus altivelis

In this study, we investigated maturation-associated changes in non-specific immune responses of ayu against Flavobacterium psychrophilum. The gonadosomatic index was minimum on 16 June, began to increase on 17 July, and reached the maximum value during August. The highest phagocytic rate (16.3%) was observed on 16 June, which decreased significantly to 5.6% on 26 August. The number of viable bacteria after the serum treatment was highest during August, suggesting that bactericidal activity of the serum decreased along with the sexual maturation. Gene expression levels of interleukin-8, and tumor necrosis factor-α in the spleen did not change significantly during this period, whereas the level of suppressor of cytokine signaling (SOCS)3 was significantly higher on 26 August than that on 16 July (p < 0.05). These results suggest that phagocytic activity of trunk kidney leukocytes and serum bactericidal activity against F. psychrophilum decreased with sexual maturation, and that SOCS3 may be related to the decrease in non-specific immune activity in ayu.

Effects of cortisol and lipopolysaccharide on expression of select growth-, stress- and immune-related genes in rainbow trout liver

Many studies have shown that stress-induced cortisol levels negatively influence growth and immunity in finfish. Despite this knowledge, few studies have assessed the direct effects of cortisol on liver immune function. Using real-time PCR, the expression of three cortisol-responsive genes (GR: glucocorticoid receptor, IGF-1: insulin-like growth factor-I and SOCS-1: suppressor of cytokine signaling-I), genes involved with innate and adaptive immunity (IL-1β: interleukin-1 beta, IgM: immunoglobin-M and Lyz: lysozyme), and liver-specific antimicrobial peptides (hepcidin and LEAP-2A: liver-expressed antimicrobial peptide-2A) was studied in vitro using rainbow trout liver slices. The abundances of GR, SOCS-1 and IGF-1 mRNAs were suppressed by cortisol treatment. Abundance of IL-1β mRNA was upregulated by LPS and suppressed by cortisol treatment in a time-dependent manner. While abundance of IgM mRNA was suppressed by cortisol treatment and stimulated by LPS, there were no effects of cortisol or LPS on abundance of Lyz mRNA. Abundance of hepcidin and LEAP-2A mRNA levels were suppressed by cortisol treatment and stimulated by LPS. These results demonstrate that cortisol directly suppresses abundance of GR, IGF-1, IL-1β, IgM, hepcidin, LEAP-2A and SOCS-1 mRNA transcripts in the rainbow trout liver. We report for the first time, a suppressive effect of cortisol (within 8 h of treatment) on hepcidin and LEAP-2A mRNAs in rainbow trout liver, which suggests that acute stress may negatively affect liver immune function in rainbow trout.

Extended fasting does not affect the liver innate immune response in rainbow trout

Activation of immune response pathway is energy demanding. We tested the hypothesis that negative energy balance will curtail the liver's capacity to evoke an immune response in rainbow trout (Oncorhynchus mykiss). Fish were either fed or fasted for 118 d and challenged with lipopolysaccharide (LPS) to determine the liver capacity to elicit an immune response. Fasting led to negative specific growth rate, reduced tissue metabolite levels, and higher transcript abundance of SOCS-2. LPS treatment increased the liver transcript abundances of IL-1β and IL-8 and serum amyloid protein A, while SOCS-2 was reduced. LPS lowered plasma cortisol level only in the fasted fish, but did not affect liver glucocorticoid or mineralocorticoid receptor protein expressions. Extended fasting did not suppress the liver capacity to evoke an immune response. Upregulation of liver SOCS-2 may be playing a key role in the energy repartitioning, thereby facilitating immune response activation despite extended fasting in trout.

Novel IFNγ homologue identified in Nile tilapia (Oreochromis niloticus) links with immune response in gills under different stimuli

Interferon gamma (IFN-γ) has important roles in both innate and adaptive immune responses. This cytokine plays a very important role in defining Th1 immune response in all vertebrates. In the present study, we identified and isolated for the first time the gene coding for Nile tilapia (Oreochromis niloticus) IFNγ from spleen lymphocytes. The isolated tilapia IFNγ has between 24 and 62% of amino acid identity as compared to reported sequences for other teleost fishes. It has close phylogenetic relationships with IFNγ molecules belonging to the group of Perciforms and presents the typical structural characteristics of gamma interferon molecules. The tissue expression analysis showed that IFNγ is expressed constitutively in head kidney, skin, intestine, muscle and brain. Its expression was not detected in gills by conventional RT-PCR. However, under conditions of stimulation with Poly I:C and LPS, IFNγ expression was up-regulated in gills after 24 h post-stimulation. IFNγ expression was also induced in gills 24 h after Edwardsiella tarda infection suggesting its important role in immunity against intracellular bacteria. The recombinant protein produced in Escherichia coli induced Mx gene transcription in head kidney primary culture cells. These results are the first steps to characterize the role of tilapia IFNγ in the defense against pathogens in tilapia. Furthermore, the isolation of this molecule provides a new tool to characterize the cellular immune response to various stimuli in this organism.

MicroRNA-based transcriptomic responses of Atlantic salmon during infection by the intracellular bacterium Piscirickettsia salmonis

MicroRNAs (miRNAs) are small non-coding RNAs that have emerged as key regulators in diverse biological processes across taxa. However, despite the importance of these transcripts, little is known about their role during the immune response in salmonids. Because of this, we use deep sequencing technologies to explore the microRNA-based transcriptomic response of the Atlantic salmon (Salmo salar) to the intracellular bacteria Piscirickettsia salmonis, one of the main threats to salmon aquaculture in Chile. Hence, 594 different miRNAs were identified from head kidney and spleen transcriptomic data. Among them, miRNA families mir-181, mir-143 and mir-21 were the most abundant in control groups, while after infection with P. salmonis, mir-21, mir-181 and mir-30 were the most predominant families. Furthermore, transcriptional analysis revealed 84 and 25 differentially expressed miRNAs in head kidney and spleen respectively, with an overlapping response of 10 miRNAs between the analyzed tissues. Target prediction, coupled with GO enrichment analysis, revealed that the possible targets of the most regulated miRNAs were genes involved in the immune response, such as cortisol metabolism, chemokine-mediated signaling pathway and neutrophil chemotaxis genes. Among these, predicted putative target genes such as C-C motif chemokine 19-like, stromal cell-derived factor 1-like, myxovirus resistance protein 2 and hepcidin-1 were identified. Overall, our results suggest that miRNA expression in co-modulation with transcription activity of target genes is related to putative roles of non-coding RNAs in the immune response of Atlantic salmon against intracellular bacterial pathogens.

Chronic stress inhibits growth and induces proteolytic mechanisms through two different nonoverlapping pathways in the skeletal muscle of a teleost fish

Chronic stress detrimentally affects animal health and homeostasis, with somatic growth, and thus skeletal muscle, being particularly affected. A detailed understanding of the underlying endocrine and molecular mechanisms of how chronic stress affects skeletal muscle growth remains lacking. To address this issue, the present study assessed primary (plasma cortisol), secondary (key components of the GH/IGF system, muscular proteolytic pathways, and apoptosis), and tertiary (growth performance) stress responses in fine flounder ( Paralichthys adspersus) exposed to crowding chronic stress. Levels of plasma cortisol, glucocorticoid receptor 2 ( gr2), and its target genes ( klf15 and redd1) mRNA increased significantly only at 4 wk of crowding ( P < 0.05). The components of the GH/IGF system, including ligands, receptors, and their signaling pathways, were significantly downregulated at 7 wk of crowding ( P < 0.05). Interestingly, chronic stress upregulated the ubiquitin-proteasome pathway and the intrinsic apoptosis pathways at 4wk ( P < 0.01), whereas autophagy was only significantly activated at 7 wk ( P < 0.05), and meanwhile the ubiquitin-proteasome and the apoptosis pathways returned to control levels. Overall growth was inhibited in fish in the 7-wk chronic stress trial ( P < 0.05). In conclusion, chronic stress directly affects muscle growth and downregulates the GH/IGF system, an action through which muscular catabolic mechanisms are promoted by two different and nonoverlapping proteolytic pathways. These findings provide new information on molecular mechanisms involved in the negative effects that chronic stress has on muscle anabolic/catabolic signaling balance.

Cortisol plays a role in the high environmental ammonia associated suppression of the immune response in zebrafish

Exposure to high environmental ammonia (HEA) levels increases the vulnerability of fishes to parasitic, viral and bacterial diseases. We tested the hypothesis that elevated plasma cortisol levels play a role in the HEA-mediated immunosuppression in fishes. To this end, we tested the effect of exogenous cortisol treatment on the lipopolysaccharide (LPS)-induced immune response in zebrafish (Danio rerio). Also, to test whether glucocorticoid receptor (GR) signaling is involved in HEA-mediated immunosuppression, zebrafish were treated with mifepristone, a GR antagonist, and the LPS-induced immune response assessed after HEA exposure. We evaluated a panel of important immunity-related genes including interleukin 1β (il1b) and suppressor of cytokine signaling (socs-1a, 2, 3) and acute phase response genes [serum amyloid A (saa), transferrin (tfa), leukocyte cell-derived chemotaxin 2-like (lect2l), haptoglobin (hp), hepcidin (=hepatic anti-microbial peptide hamp), and complement component 3b (c3b)] by real-time quantitative PCR. Our results demonstrate that exogenous cortisol administration as well as elevated cortisol levels in response to HEA exposure modulate mRNA transcript levels of key mediators of the innate immune response in zebrafish. Mifepristone treatment reduced whole body cortisol levels and eliminated the HEA-mediated changes in transcript abundance of socs1a, il1b, as well as APR genes. Together, these results suggest that the HEA effect on the innate immune response is in part mediated by cortisol signaling, while the mode of action, including the receptors involved remains to be elucidated.

Effects of Cellular 11β-hydroxysteroid Dehydrogenase 1 on LPS-induced Inflammatory Responses in Synovial Cell Line, SW982

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) catalyzes the conversion of inactive cortisone into active cortisol, which has pleiotropic roles in various biological conditions, such as immunological and metabolic homeostasis. Cortisol is mainly produced in the adrenal gland, but can be locally regenerated in the liver, fat, and muscle. Its diverse actions are primarily mediated by binding to the glucocorticoid receptor. SW982, a human synovial cell line, expresses 11β-HSD type 1, but not type 2, that catalyzes the conversion of cortisone to cortisol. In this study, therefore, we investigated the control of lipopolysaccharide (LPS)-induced inflammatory responses by prereceptor regulation-mediated maintenance of cortisol levels. Preliminarily, cell seeding density and incubation period were optimized for analyzing the catalytic activity of SW982. Additionally, cellular 11β-HSD1 still remained active irrespective of monolayer or spheroid culture conditions. Inflammatory stimulants, such as interleukin (IL)-1β, tumor necrosis factor (TNF)α, and LPS, did not affect the catalytic activity of 11β-HSD1, although a high dose of LPS significantly decreased its activity. Additionally, autocrine effects of cortisol on inflammatory responses were investigated in LPS-stimulated SW982 cells. LPS upregulated pro-inflammatory cytokines, including IL-6 and IL-1β, in SW982 cells, while cortisol production, catalyzed by cellular 11β-HSD1, downregulated LPS-stimulated cytokines. Furthermore, suppression of NFκB activation-mediated pro-inflammatory responses by cortisol was revealed. In conclusion, the activity of cellular 11β-HSD1 was closely correlated with suppression of LPS-induced inflammation. Therefore, these results partly support the notion that prereceptor regulation of locally regenerated cortisol could be taken into consideration for treatment of inflammation-associated diseases, including arthritis.

Development of a zebrafish sepsis model for high-throughput drug discovery

Sepsis is a leading cause of death worldwide. Current treatment modalities remain largely supportive. Intervention strategies focused on inhibiting specific mediators of the inflammatory host response have been largely unsuccessful, a consequence of an inadequate understanding of the complexity and heterogeneity of the innate immune response. Moreover, the conventional drug development pipeline is time consuming and expensive and the low success rates associated with cell-based screens underline the need for whole organism screening strategies, especially for complex pathological processes. Here, we established an LPS-induced zebrafish endotoxemia model, which exhibits the major hallmarks of human sepsis including, edema and tissue/organ damage, increased vascular permeability and vascular leakage accompanied by an altered expression of cellular junction proteins, increased cytokine expression, immune cell activation and ROS production, reduced circulation and increased platelet aggregation. We tested the suitability of the model for phenotype-based drug screening using three primary readouts: mortality, vascular leakage, and ROS production. Preliminary screening identified fasudil, a drug known to protect against vascular leakage in murine models, as a lead hit thereby validating the utility of our model for sepsis drug screens. This zebrafish sepsis model has the potential to rapidly analyze sepsis associated pathologies and cellular processes in the whole organism, as well as to screen and validate large numbers of compounds that can modify sepsis pathology in vivo.

Transcriptomic analysis of the hepatic response to stress in the red cusk-eel (Genypterus chilensis): Insights into lipid metabolism, oxidative stress and liver steatosis

Teleosts exhibit a broad divergence in their adaptive response to stress, depending on the magnitude, duration, and frequency of stressors and the species receiving the stimulus. We have previously reported that the red cusk-eel (Genypterus chilensis), an important marine farmed fish, shows a physiological response to stress that results in increased skeletal muscle atrophy mediated by over-expression of components of the ubiquitin proteasome and autophagy-lysosomal systems. To better understand the systemic effects of stress on the red cusk-eel metabolism, the present study assessed the transcriptomic hepatic response to repetitive handling-stress. Using high-throughput RNA-seq, 259 up-regulated transcripts were found, mostly associated with angiogenesis, gluconeogenesis, and triacylglyceride catabolism. Conversely, 293 transcripts were down-regulated, associated to cholesterol biosynthesis, PPARα signaling, fatty acid biosynthesis, and glycolysis. This gene signature was concordant with hepatic metabolite levels and hepatic oxidative damage. Moreover, the increased plasmatic levels of AST (aspartate aminotransferase), ALT (alanine aminotransferase) and AP (alkaline phosphatase), as well as liver histology suggest stress-induced liver steatosis. This study offers an integrative molecular and biochemical analysis of the hepatic response to handling-stress, and reveals unknown aspects of lipid metabolism in a non-model teleost.

Clobetasol propionate causes immunosuppression in zebrafish (Danio rerio) at environmentally relevant concentrations

Synthetic glucocorticoids (GCs) are potential endocrine disrupting compounds that have been detected in the aquatic environment around the world in the low ng/L (nanomolar) range. GCs are used as immunosuppressants in medicine. It is of high interest whether clobetasol propionate (CP), a highly potent GC, suppresses the inflammatory response in fish after exposure to environmentally relevant concentrations. Bacterial lipopolysaccharide (LPS) challenge was used to induce inflammation and thus mimic pathogen infection. Zebrafish embryos were exposed to ≤1000nM CP from ~1h post fertilization (hpf) to 96 hpf, and CP uptake, survival after LPS challenge, and expression of inflammation-related genes were examined. Our initial experiments were carried out using 0.001% DMSO as a solvent vehicle, but we observed that DMSO interfered with the LPS challenge assay, and thus masked the effects of CP. Therefore, DMSO was not used in the subsequent experiments. The internal CP concentration was quantifiable after exposure to ≥10nM CP for 96h. The bioconcentration factor (BCF) of CP was determined to be between 16 and 33 in zebrafish embryos. CP-exposed embryos showed a significantly higher survival rate in the LPS challenge assay after exposure to ≥0.1nM in a dose dependent manner. This effect is an indication of immunosuppression. Furthermore, the regulation pattern of several genes related to LPS challenge in mammals supported our results, providing evidence that LPS-mediated inflammatory pathways are conserved from mammals to teleost fish. Anxa1b, a GC-action related anti-inflammatory gene, was significantly down-regulated after exposure to ≥0.05nM CP. Our results show for the first time that synthetic GCs can suppress the innate immune system of fish at environmentally relevant concentrations. This may reduce the chances of fish to survive in the environment, as their defense against pathogens is weakened.

A comparative examination of cortisol effects on muscle myostatin and HSP90 gene expression in salmonids

Cortisol, the primary corticosteroid in teleost fishes, is released in response to stressors to elicit local functions, however little is understood regarding muscle-specific responses to cortisol in these fishes. In mammals, glucocorticoids strongly regulate the muscle growth inhibitor, myostatin, via glucocorticoid response elements (GREs) leading to muscle atrophy. Bioinformatics methods suggest that this regulatory mechanism is conserved among vertebrates, however recent evidence suggests some fishes exhibit divergent regulation. Therefore, the aim of this study was to evaluate the conserved actions of cortisol on myostatin and hsp90 expression to determine if variations in cortisol interactions have emerged in salmonid species. Representative salmonids; Chinook salmon (Oncorhynchus tshawytscha), cutthroat trout (Oncorhynchus clarki), brook trout (Salvelinus fontinalis), and Atlantic salmon (Salmo salar); were injected intraperitoneally with a cortisol implant (50μg/g body weight) and muscle gene expression was quantified after 48h. Plasma glucose and cortisol levels were significantly elevated by cortisol in all species, demonstrating physiological effectiveness of the treatment. HSP90 mRNA levels were elevated by cortisol in brook trout, Chinook salmon, and Atlantic salmon, but were decreased in cutthroat trout. Myostatin mRNA levels were affected in a species, tissue (muscle type), and paralog specific manner. Cortisol treatment increased myostatin expression in brook trout (Salvelinus) and Atlantic salmon (Salmo), but not in Chinook salmon (Oncorhynchus) or cutthroat trout (Oncorhynchus). Interestingly, the VC alone increased myostatin mRNA expression in Chinook and Atlantic salmon, while the addition of cortisol blocked the response. Taken together, these results suggest that cortisol affects muscle-specific gene expression in species-specific manners, with unique Oncorhynchus-specific divergence observed, that are not predictive solely based upon mammalian stress responses.

First Proliferative Kidney Disease outbreak in Austria, linking to the aetiology of Black Trout Syndrome threatening autochthonous trout populations

Proliferative Kidney Disease (PKD) was diagnosed in juvenile autochthonous brown trout Salmo trutta for the first time in Austria during summer 2014. Cytology showed Tetracapsuloides bryosalmonae sporoblasts, and histology revealed sporogonic (coelozoic) and extrasporogonic (histozoic) stages. Analysis of malacosporean ribosomal small subunit revealed that this strain is closely related to European isolates, although its source is unknown. Infection and high pathogenicity were reproduced upon a pre-restocking test with specific pathogen free (SPF) juvenile trout, resulting in 100% mortality between 28 and 46 d post exposure (dpe), with high ectoparasitosis. Fish showed grade 2 of the Kidney Swelling Index and grade 3 of the PKD histological assessment. T. bryosalmonae enzootic waters were demonstrated in further locations along the River Kamp, with infected bryozoans retrieved up to 6 km upstream of the farm with the PKD outbreak. Fredericella sultana colonies collected from these locations were cultivated in laboratory conditions. Released malacospores successfully induced PKD, and contextually Black Trout Syndrome (BTS), in SPF brown trout. In the absence of co-infections mortality occurred between 59 and 98 dpe, with kidneys enlarged up to 6.74% of total body weight (normal 1.23%). This study confirms the first isolation of a pathogenic myxozoan from an Austrian river tributary of the Danube, where its 2-host life cycle is fully occurring. Its immunosuppressant action could link PKD as a key factor in the multifactorial aetiology of BTS. This T. bryosalmonae isolation provides an impetus to undertake further multi-disciplinary research, aiming to assess the impact of PKD and BTS spreading to central European regions.

Type II SOCS as a feedback repressor for GH-induced Igf1 expression in carp hepatocytes

Type II suppressor of cytokine signaling (SOCS) serve as feedback repressors for cytokines and are known to inhibit growth hormone (GH) actions. However, direct evidence for SOCS modulation of GH-induced insulin-like growth factor 1 (Igf1) expression is lacking, and the post-receptor signaling for SOCS expression at the hepatic level is still unclear. To shed light on the comparative aspects of SOCS in GH functions, grass carp was used as a model to study the role of type II SOCS in GH-induced Igf1 expression. Structural identity of type II SOCS, Socs1-3 and cytokine-inducible SH2-containing protein (Cish), was established in grass carp by 5'/3'-RACE, and their expression at both transcript and protein levels were confirmed in the liver by RT-PCR and LC/MS/MS respectively. In carp hepatocytes, GH treatment induced rapid phosphorylation of JAK2, STATs, MAPK, PI3K, and protein kinase B (Akt) with parallel rises in socs1-3 and cish mRNA levels, and these stimulatory effects on type II SOCS were shown to occur before the gradual loss of igf1 gene expression caused by prolonged exposure of GH. Furthermore, GH-induced type II SOCS gene expression could be negated by inhibiting JAK2, STATs, MEK1/2, P38 (MAPK), PI3K, and/or Akt respectively. In CHO cells transfected with carp GH receptor, over-expression of these newly cloned type II SOCS not only suppressed JAK2/STAT5 signaling with GH treatment but also inhibited GH-induced grass carp Igf1 promoter activity. These results, taken together, suggest that type II SOCS could be induced by GH in the carp liver via JAK2/STATs, MAPK, and PI3K/Akt cascades and serve as feedback repressors for GH signaling and induction of igf1 gene expression.

Detection and Validation of QTL Affecting Bacterial Cold Water Disease Resistance in Rainbow Trout Using Restriction-Site Associated DNA Sequencing

Bacterial cold water disease (BCWD) causes significant economic loss in salmonid aquaculture. Using microsatellite markers in a genome scan, we previously detected significant and suggestive QTL affecting phenotypic variation in survival following challenge with Flavobacterium psychrophilum, the causative agent of BCWD in rainbow trout. In this study, we performed selective genotyping of SNPs from restriction-site associated DNA (RAD) sequence data from two pedigreed families (2009070 and 2009196) to validate the major QTL from the previous work and to detect new QTL. The use of RAD SNPs in the genome scans increased the number of mapped markers from ~300 to ~5,000 per family. The significant QTL detected in the microsatellites scan on chromosome Omy8 in family 2009070 was validated explaining up to 58% of the phenotypic variance in that family, and in addition, a second QTL was also detected on Omy8. Two novel QTL on Omy11 and 14 were also detected, and the previously suggestive QTL on Omy1, 7 and 25 were also validated in family 2009070. In family 2009196, the microsatellite significant QTL on Omy6 and 12 were validated and a new QTL on Omy8 was detected, but none of the previously detected suggestive QTL were validated. The two Omy8 QTL from family 2009070 and the Omy12 QTL from family 2009196 were found to be co-localized with handling and confinement stress response QTL that our group has previously identified in a separate pedigreed family. With the currently available data we cannot determine if the co-localized QTL are the result of genes with pleiotropic effects or a mere physical proximity on the same chromosome segment. The genetic markers linked to BCWD resistance QTL were used to query the scaffolds of the rainbow trout reference genome assembly and the QTL-positive scaffold sequences were found to include 100 positional candidate genes. Several of the candidate genes located on or near the two Omy8 QTL detected in family 2009070 suggest potential linkages between stress response and the regulation of immune response in rainbow trout.