The occurrence of two types of hemopexin-like protein in medaka and differences in their affinity to heme

Identification and characterization of warm temperature acclimation proteins (Wap65s) in rainbow trout (Oncorhynchus mykiss)

Hemopexin is a vital glycoprotein for processing excessive iron in blood and functions as an iron scavenger in mammals. Teleosts however, unlike mammals, have two known hemopexin paralogs called warm temperature acclimation-related 65 kDa protein (Wap65-1 and Wap65-2, collectively termed Wap65s). Although Wap65s in rainbow trout have been considered notable biomarkers with significantly higher and/or lower expression under conditions of stress or disease, the individual roles, similarities and differences between the two paralogs are not well known. The aim of this study was to gain an understanding of the characteristics and functions of trout Wap65s from the perspective of iron-metabolism, physiological roles, and relevant immunological responses. The expression of Wap65-1 and -2 in this study was determined in the face of challenges by Aeromonas salmonicida, infectious hematopoietic necrosis virus (IHNV), and iron-dextran. Immuno-histochemistry (IHC) was employed to localize the major cell types for Wap65-2 expression, and trout leukocytes were isolated and incubated with LPS and OxLDL for comprehending the immunological characteristics of Wap65-2. We demonstrate that Wap65-1 is expressed only in the liver but Wap65-2 is systemically expressed in most organs and tissues. Interestingly, Wap65-1 expression was not significantly changed under A. salmonicida and iron-dextran administration, but was significantly decreased under IHNV. In contrast, Wap65-2 was up-regulated in all challenged groups, however with different expression patterns in the blood and liver. These results suggested that the two paralogs may participate in different biological roles. IHC showed that Wap65-2 antibody had high affinity for leukocyte-like cells, and macrophages but not lymphocytes significantly increased expression under LPS and OxLDL stimulation. These results support the conclusion that trout Wap65-2, not Wap65-1 may have conventional hemopexin functions such as reported in mammals including effects on iron metabolism, inflammation, and acute-phase protein.

Host–Pathogen Interactions of Marine Gram-Positive Bacteria

Simple Summary

Complex interactions between marine Gram-positive pathogens and fish hosts in the marine environment can result in diseases of economically important finfish, which cause economic losses in the aquaculture industry. Understanding how these pathogens interact with the fish host and generate disease will contribute to efficient prophylactic measures and treatments. To our knowledge, there are no systematic reviews on marine Gram-positive pathogens. Therefore, here we reviewed the host–pathogen interactions of marine Gram-positive pathogens from the pathogen-centric and host-centric points of view.

Abstract

Marine Gram-positive bacterial pathogens, including Renibacterium salmoninarum, Mycobacterium marinum, Nocardia seriolae, Lactococcus garvieae, and Streptococcus spp. cause economic losses in marine fish aquaculture worldwide. Comprehensive information on these pathogens and their dynamic interactions with their respective fish–host systems are critical to developing effective prophylactic measures and treatments. While much is known about bacterial virulence and fish immune response, it is necessary to synthesize the knowledge in terms of host–pathogen interactions as a centerpiece to establish a crucial connection between the intricate details of marine Gram-positive pathogens and their fish hosts. Therefore, this review provides a holistic view and discusses the different stages of the host–pathogen interactions of marine Gram-positive pathogens. Gram-positive pathogens can invade fish tissues, evade the fish defenses, proliferate in the host system, and modulate the fish immune response. Marine Gram-positive pathogens have a unique set of virulence factors that facilitate adhesion (e.g., adhesins, hemagglutination activity, sortase, and capsules), invasion (e.g., toxins, hemolysins/cytolysins, the type VII secretion system, and immune-suppressive proteins), evasion (e.g., free radical quenching, actin-based motility, and the inhibition of phagolysosomal fusion), and proliferation and survival (e.g., heme utilization and siderophore-mediated iron acquisition systems) in the fish host. After infection, the fish host initiates specific innate and adaptive immune responses according to the extracellular or intracellular mechanism of infection. Although efforts have continued to be made in understanding the complex interplay at the host–pathogen interface, integrated omics-based investigations targeting host–pathogen–marine environment interactions hold promise for future research.

Characterization of carp seminal plasma Wap65-2 and its participation in the testicular immune response and temperature acclimation

Two functionally distinct isoforms of warm-temperature acclimation related 65-kDa protein (Wap65-1 and Wap65-2) with a role in the immune response are present in fish. To our knowledge, contrary to Wap65-1, Wap65-2 has neither been isolated nor functionally characterized in carp especially in reproductive system. The aim of this study was to characterize Wap65-2 and ascertain its functions in immune response and temperature acclimation within reproductive system. Wap65-2 corresponded to one of the most abundant proteins in carp seminal plasma, with a high immunologic similarity to their counterparts in seminal plasma of other fish species and a wide tissue distribution, with predominant expression in the liver. The immunohistochemical localization of Wap65-2 to spermatogonia, Leydig cells, and the epithelium of blood vessels within the testis suggests its role in iron metabolism during spermatogenesis and maintenance of blood-testis barrier integrity. Wap65-2 secretion by the epithelial cells of the spermatic duct and its presence around spermatozoa suggests its involvement in the protection of spermatozoa against damage caused by heme released from erythrocytes following hemorrhage and inflammation. Our results revealed an isoform-specific response of Wap65 to temperature acclimation and Aeromonas salmonicida infection which alters blood-testis barrier integrity. Wap65-2 seems to be related to the immune response against bacteria, while Wap65-1 seems to be involved in temperature acclimation. This study expands the understanding of the mechanism of carp testicular immunity against bacterial challenge and temperature changes, in which Wap65-2 seems to be involved and highlights their potential usefulness as biomarkers of inflammation and temperature acclimation.

Identification of warm temperature acclimation-associated 65-kDa protein-2 in Kumgang fat minnow Rhynchocypris kumgangensis

Warm temperature acclimation-associated 65-kDa protein (Wap65) is known to respond to elevated water temperatures and the corresponding gene from several fish species has been cloned. Expression of Wap65 gene is induced by various physiological stresses, such as increase in water temperature, immune response and heavy metal exposure. Two isolated Wap65 genes, Wap65-1 and Wap65-2, display distinct tissue distribution and physiological functions despite high sequence homology. In a previous study, we identified the Wap65-1 gene (kmWap65-1) from Kumgang fat minnow, Rhynchocypris kumgangensis, a small freshwater fish endemic to Korea. The kmWap65-1 gene showed sequence homology with teleost Wap65-1 and mammalian hemopexin, and was highly expressed in response to increased water temperature and bacterial lipopolysaccharide (LPS) exposure. Here, we isolated kmWap65-2 from liver tissue of Kumgang fat minnow and compared the expression profiles of both kmWap65 genes following exposure to various physiological stresses, including thermal changes, bacterial challenge, and environmental toxins. Notably, while kmWap65-1 expression was significantly increased in response to high water temperature, LPS, cadmium, and iron, kmWap65-2 displayed no alterations in expression at high water temperature. However, kmWap65-2 expression was upregulated slightly in response to LPS and highly in presence of copper, bisphenol A, and estradiol. Based on the collective findings, we propose that kmWap65-1 and kmWap65-2 are multifunctional proteins with distinct functions that could serve as useful biomarkers for assessing physiological stress and associated responses in Kumgang fat minnow.

Physiological responses of reared sea bream (Sparus aurata Linnaeus, 1758) to an Amyloodinium ocellatum outbreak

Amyloodiniosis represents a major bottleneck for semi-intensive aquaculture production in Southern Europe, causing extremely high mortalities. Amyloodinium ocellatum is a parasitic dinoflagellate that can infest almost all fish, crustacean and bivalves that live within its ecological range. Fish mortalities are usually attributed to anoxia, associated with serious gill hyperplasia, inflammation, haemorrhage and necrosis in heavy infestations; or with osmoregulatory impairment and secondary microbial infections due to severe epithelial damage in mild infestation. However, physiological information about the host responses to A. ocellatum infestation is scarce. In this work, we analysed the proteome of gilthead sea bream (Sparus aurata) plasma and relate it with haematological and immunological indicators, in order to enlighten the different physiological responses when exposed to an A. ocellatum outbreak. Using 2D-DIGE, immunological and haematological analysis and in response to the A. ocellatum contamination we have identified several proteins associated with acute-phase response, inflammation, lipid transport, homoeostasis, and osmoregulation, wound healing, neoplasia and iron transport. Overall, this preliminary study revealed that amyloodiniosis affects some fish functional pathways as revealed by the changes in the plasma proteome of S. aurata, and that the innate immunological system is not activated in the presence of the parasite.

Nutritional Immunity Triggers the Modulation of Iron Metabolism Genes in the Sub-Antarctic Notothenioid Eleginops maclovinus in Response to Piscirickettsia salmonis

Iron deprivation is a nutritional immunity mechanism through which fish can limit the amount of iron available to invading bacteria. The aim of this study was to evaluate the modulation of iron metabolism genes in the liver and brain of sub-Antarctic notothenioid Eleginops maclovinus challenged with Piscirickettsia salmonis. The specimens were inoculated with two P. salmonis strains: LF-89 (ATCC^® VR-1361™) and Austral-005 (antibiotic resistant). Hepatic and brain samples were collected at intervals over a period of 35 days. Gene expression (by RT-qPCR) of proteins involved in iron storage, transport, and binding were statistically modulated in infected fish when compared with control counterparts. Specifically, the expression profiles of the transferrin and hemopexin genes in the liver, as well as the expression profiles of ferritin-M, ferritin-L, and transferrin in the brain, were similar for both experimental groups. Nevertheless, the remaining genes such as ferritin-H, ceruloplasmin, hepcidin, and haptoglobin presented tissue-specific expression profiles that varied in relation to the injected bacterial strain and sampling time-point. These results suggest that nutritional immunity could be an important immune defense mechanism for E. maclovinus against P. salmonis injection. This study provides relevant information for understanding iron metabolism of a sub-Antarctic notothenioid fish.

Immune relevant molecules identified in the skin mucus of fish using -omics technologies

This review will give an overview of immune relevant molecules in fish skin mucus. The skin of fish is continuously exposed to a water environment, and unlike that of terrestrial vertebrates, it is a mucosal surface with a thin epidermis of live cells covered by a mucus layer. The mucosa plays an important role in maintaining the homeostasis of the fish and preventing the entry of invading pathogens. This review provides an overview of proteins, RNA, DNA, lipids and carbohydrates found in the skin mucus of studied species. Proteins such as actin, histones, lectins, lysozyme, mucin, and transferrin have extracellular immune relevant functions. Complement complement molecules, heat shock molecules and superoxide dismutase present in mucus show differential expression during pathogen challenge in some species, but their functions in mucus, if any, need to be shown. RNA, DNA, lipids, carbohydrates and metabolites in mucus have been studied to a limited extent in fish, the current knowledge is summarized and knowledge gaps are pointed out.

Dietary Yeast Cell Wall Extract Alters the Proteome of the Skin Mucous Barrier in Atlantic Salmon (Salmo salar): Increased Abundance and Expression of a Calreticulin-Like Protein

In order to improve fish health and reduce use of chemotherapeutants in aquaculture production, the immunomodulatory effect of various nutritional ingredients has been explored. In salmon, there is evidence that functional feeds can reduce the abundance of sea lice. This study aimed to determine if there were consistent changes in the skin mucus proteome that could serve as a biomarker for dietary yeast cell wall extract. The effect of dietary yeast cell wall extract on the skin mucus proteome of Atlantic salmon was examined using two-dimensional gel electrophoresis. Forty-nine spots showed a statistically significant change in their normalised volumes between the control and yeast cell wall diets. Thirteen spots were successfully identified by peptide fragment fingerprinting and LC-MS/MS and these belonged to a variety of functions and pathways. To assess the validity of the results from the proteome approach, the gene expression of a selection of these proteins was studied in skin mRNA from two different independent feeding trials using yeast cell wall extracts. A calreticulin-like protein increased in abundance at both the protein and transcript level in response to dietary yeast cell wall extract. The calreticulin-like protein was identified as a possible biomarker for yeast-derived functional feeds since it showed the most consistent change in expression in both the mucus proteome and skin transcriptome. The discovery of such a biomarker is expected to quicken the pace of research in the application of yeast cell wall extracts.

The warm temperature acclimation protein (Wap65) has an important role in the inflammatory response of turbot (Scophthalmus maximus)

Wap65 is a molecule similar to the mammalian hemopexin that is a serum glycoprotein produced mainly by the liver with high affinity to heme. Its primary role is participating in iron metabolism scavenging heme that is released into the plasma and transporting it to the liver. It has been reported an important role of hemopexin in the inflammation as an acute-phase protein and its production is up-regulated by pro-inflammatory cytokines. There are also some evidences suggesting this immune-induction in fish Wap65 genes. Most teleost species presents two Wap65 genes but their physiological functions have not been completely elucidated; in fact, the transcriptional patterns of Wap65 genes to stimulatory treatments are variable and contradictory. In the present study two Wap65 genes, Wap65-1 and Wap65-2, have been characterized for the first time in turbot (Scophthalmus maximus). Their constitutive expression and differential modulation by thermal treatments, immune challenges (bacterial and viral), as well as iron supplementation, have been investigated. Both genes were mainly expressed in liver, but they were detected in all tested tissues. Whereas Wap65-1 and Wap65-2 were up-regulated by temperature rise and bacterial challenge, VHSV infection inhibited the expression of both genes. Moreover, iron-dextran administration induced only the overexpression of Wap65-1. Interestingly, these induction were observed in head kidney buy not in liver. The effect of Wap65 protein purified from turbot serum by hemin-agarose affinity chromatography was also studied to demonstrate a possible anti-inflammatory role, analyzing its inhibitory effect on leucocytes migration induced by zymosan injection to the peritoneal cavity.

Genomic organization and functional diversification of two warm-temperature-acclimation-associated 65-kDa protein genes in rockbream (Oplegnathus fasciatus; Perciformes)

Two paralogue genes of warm-temperature-acclimation-associated 65-kDa protein were characterized and their mRNA expression patterns during various experimental stimulations were examined in the rockbream (Oplegnathus fasciatus; Perciformes). Rockbream Wap65 isoforms (rbWap65-1 and rbWap65-2) share basically common structural features with other teleostean orthologues and human hemopexin (HPX) at both amino acid (conserved cysteine and histidine residues) and genomic levels (ten-exon structure), although the rbWap65-2 reveals more homologous characteristics to human HPX than does rbWap65-1 isoform. Southern blot analysis indicates that each rbWap65 isoform exists as a single copy gene in the rockbream genome. Both rbWap65 genes were predicted to possess various transcription factor (TF) binding motifs related with stress and innate immunity in their 5ʹ-upstream regions, in which inflammation-related motifs were more highlighted in the rbWap65-2 than in rbWap65-1. Based on the RT-PCR assay, the liver-predominant expression pattern was more apparent in rbWap65-1 than rbWap65-2 isoform. During thermal elevation, clear upregulation was found only for the rbWap65-1. In contrast, immune stimulations (bacterial challenges, viral infection and iron overload) activated more preferentially the rbWap65-2 isoform in overall, although the inducibility was affected by the kinds of stimulators and tissue types. Taken together, our data suggest that the two paralogue rbWap65 isoforms have experienced subfunctionalization and/or neofunctionalization during their evolutionary history, in which the rbWap65-2 has retained closer, functional orthology to the human HPX while the rbWap65-1 have been diversified to be more related with thermal acclimation physiology.

Adaptive functional divergence of the warm temperature acclimation-related protein (WAP65) in fishes and the ortholog hemopexin (HPX) in mammals

Gene duplication is an important mechanism that leads to genetic novelty. Different, nonexclusive processes are likely involved, and many adaptive and nonadaptive events may contribute to the maintenance of duplicated genes. In some teleosts, a duplicate copy of the mammalian ortholog Hemopexin (HPX) is present, known as the warm temperature acclimation-related protein (WAP65). Both WAP65 and HPX have been associated with iron homeostasis due to the affinity to bind the toxic-free heme circulating in the blood stream. We have assessed the evolutionary dynamics of WAP65 and HPX genes to understand the adaptive role of positive selection at both nucleotide and amino acid level. Our results showed an asymmetrical evolution between the paralogs WAP65-1 and WAP65-2 after duplication with a slight acceleration of the evolutionary rate in WAP65-1, but not in WAP65-2, and few sites contributing to the functional distinction between the paralogs, whereas the majority of the protein remained under negative selection or relaxed negative selection. WAP65-1 is functionally more distinct from the ancestral protein function than WAP65-2. HPX is phylogenetically closer to WAP65-2 but even so functional divergence was detected between both proteins. In addition, HPX showed a fast rate of evolution when compared with both WAP65-1 and WAP65-2 genes. The assessed 3-dimensional (3-D) structure of WAP65-1 and WAP65-2 suggests that the functional differences detected are not causing noticeable structural changes in these proteins. However, such subtle changes between WAP65 paralogs may be important to understand the differential gene retention of both copies in 20 out of 30 teleosts species studied.

The serum proteome of Atlantic salmon, Salmo salar, during pancreas disease (PD) following infection with salmonid alphavirus subtype 3 (SAV3)

Salmonid alphavirus is the aetological agent of pancreas disease (PD) in marine Atlantic salmon, Salmo salar, and rainbow trout, Oncorhynchus mykiss, with most outbreaks in Norway caused by SAV subtype 3 (SAV3). This atypical alphavirus is transmitted horizontally causing a significant economic impact on the aquaculture industry. This histopathological and proteomic study, using an established cohabitational experimental model, investigated the correlation between tissue damage during PD and a number of serum proteins associated with these pathologies in Atlantic salmon. The proteins were identified by two-dimensional electrophoresis, trypsin digest and peptide MS/MS fingerprinting. A number of humoral components of immunity which may act as biomarkers of the disease were also identified. For example, creatine kinase, enolase and malate dehydrogenase serum concentrations were shown to correlate with pathology during PD. In contrast, hemopexin, transferrin, and apolipoprotein, amongst others, altered during later stages of the disease and did not correlate with tissue pathologies. This approach has given new insight into not only PD but also fish disease as a whole, by characterisation of the protein response to infection, through pathological processes to tissue recovery.

BIOLOGICAL SIGNIFICANCE

Salmonid alphavirus causes pancreas disease (PD) in Atlantic salmon, Salmo salar, and has a major economic impact on the aquaculture industry. A proteomic investigation of the change to the serum proteome during PD has been made with an established experimental model of the disease. Serum proteins were identified by two-dimensional electrophoresis, trypsin digest and peptide MS/MS fingerprinting with 72 protein spots being shown to alter significantly over the 12week period of the infection. The concentrations of certain proteins in serum such as creatine kinase, enolase and malate dehydrogenase were shown to correlate with tissue pathology while other proteins such as hemopexin, transferrin, and apolipoprotein, altered in concentration during later stages of the disease and did not correlate with tissue pathologies. The protein response to infection may be used to monitor disease progression and enhance understanding of the pathology of PD.

Genetic organization of two types of flounder warm-temperature acclimation-associated 65-kDa protein and their gene expression profiles

We isolated and characterized two cDNA clone encoding warm-temperature acclimation-associated 65-kDa proteins (PoWap65-1 and PoWap65-2) from the olive flounder, Paralichthys olivaceus. The deduced amino acid sequences of PoWap65s showed overall identities of 33-73% with other fish Wap65 and mammalian hemopexin-like proteins. The 5'-flanking regions of both PoWap65-encoding genes contained various putative transcriptional elements. While PoWap65-1 and PoWap65-2 were structurally similar, they exhibited highly differential patterns of expression. PoWap65-1 was expressed only in the liver, whereas PoWap65-2 transcripts were detected in a wide range of tissues. The accumulation of PoWap65s mRNA was expressed differentially during development. Expression of them in warm temperatures also differed in flounder embryonic cells. PoWap65-1 was upregulated by temperature stimulation whereas PoWap65-2 was not detected. PoWap65s were highly regulated by Edwardsiella tarda infection and hypoxia. Pathogen challenge induced PoWap65-2 expression in the liver whereas PoWap65-1 was downregulated. Hypoxia induced the expression of both PoWap65s in the liver of juvenile fish.

Molecular cloning, characterization and expression analysis of a novel wap65-1 gene from Plecoglossus altivelis

Warm temperature acclimation associated 65-kDa protein 1 (WAP65-1) is a specific fish plasma glycoprotein that is possibly involved in various physiological or pathological processes. In this study, we obtained the cDNA and genomic DNA sequences of the Plecoglossus altivelis wap65-1 (Pawap65-1) gene. Multiple sequence alignment showed that Pawap65-1 is similar in structure to wap65-1 in fish. Phylogenetic analysis revealed that Pawap65-1 is most closely related to that of a rainbow trout. Pawap65-1 transcripts are present in various tissues and are most abundant in the liver. We expressed recombinant PaWAP65-1 in Escherichia coli and raised antiserum against it in mouse. Western blot analysis revealed that the higher molecular mass of PaWAP65-1 in blood plasma was caused by post-translational N-glycosylation. Quantitative real-time quantitative PCR (qPCR) and Western blot analysis data showed that the hepatic mRNA and blood plasma levels of PaWAP65-1 were both influenced by warm temperature acclimation and cadmium exposure, but not by Listonella anguillarum infection, hypo-osmotic, or cold temperature acclimation. In conclusion, our data reveals that PaWAP65-1 is a stress-related protein, and may play a role in fish acclimation to warm temperature and cadmium exposure.

[Cloning, physical and chemical property analysis of the Japanese sea bass Wap65-2 gene and its expression following Vibrio harveyi infection]

The warm temperature acclimation related 65 kDa protein-2 (Wap65-2), a teleost plasma glycoprotein, plays an important role in immune regulation against bacterial infection. Here, for the first time we determined the full length cDNA sequence of the Japanese sea bass Wap65-2 gene (1 601 bp in length excluding the 3'-polyA tail). The sequence contains an open reading frame that encodes a protein of 436 amino acids with a molecular weight of 4.87×10(4). The predicted protein had a signal peptide in the N-terminal domain containing 19 residues. Sequence comparison and phylogenetic tree analysis showed that the Japanese sea bass Wap65-2 has a relatively high similarity to the Dicentrarchus labrax Wap65-2. In the healthy Japanese sea bass, Wap65-2 mRNA was expressed mainly in the liver and weakly in the heart and muscle. qRT-PCR results revealed that liver Wap65-2 transcripts were significantly increased after a Vibrio harveyi infection, and peaked 24 hour post injection (6.89 fold increase). The Japanese sea bass Wap65-2 protein was expressed in Escherichia coli and subsequently used for antiserum preparation. Western blot analysis showed that Wap65-2 was significantly increased in V. harveyi infected Japanese sea bass and reached a maximum of 5.33-fold increase at 36 h. In conclusion, the alteration of Japanese sea bass Wap65-2 expression was tightly associated with the progression of the V. harveyi bacterial infection.

Modulation of warm-temperature-acclimation-associated 65-kDa protein genes (Wap65-1 and Wap65-2) in mud loach (Misgurnus mizolepis, Cypriniformes) liver in response to different stimulatory treatments

Two paralogous isoform cDNAs of warm-temperature-acclimation-associated 65-kDa protein (Wap65-1 and Wap65-2) were isolated from the cypriniform species, mud loach (Misgurnus mizolepis), and characterized. The deduced amino acid sequences of the two mud loach Wap65 isoforms (mlWap65-1 and mlWap65-2) share moderate levels of sequence homology with their corresponding orthologues from teleosts and with human hemopexin, a possible mammalian homologue. Both isoforms display conserved features, including essential motifs and/or residues that are important for the protein structure of hemopexin. In overall, mlWap65-2 is more homologous to human hemopexin than is mlWap65-1. Both mud loach Wap65 transcripts are predominantly expressed in liver, although the transcripts are ubiquitously detectable in most tissues with variable basal expression. Both mlWap65 isoforms are differentially regulated during embryonic development, and the changes in transcript levels during embryogenesis are greater for mlWap65-2 than for mlWap65-1. The transcription of the mlWap65 genes is differentially modulated by various stimuli, including thermal changes, immune challenge (lipopolysaccharide injection or bacterial infection), and heavy metal exposure (cadmium, copper, or nickel). The isoform mlWap65-1 is more responsive to warm temperature treatments than mlWap65-2, whereas mlWap65-2 is much more strongly stimulated by immune and heavy metal challenges than is mlWap65-1. Taken together, the results of this study suggest that mud loach Wap65 isoforms are potentially involved in multiple cellular pathways and that the two mud loach Wap65 isoforms undergo functional partitioning or subfunctionalization.

Specialization of the sting venom and skin mucus of Cathorops spixii reveals functional diversification of the toxins

Cathorops spixii is the most common venomous fish on the Brazilian coast. Apart from the involvement with defense against pathogens, the possible contribution of skin mucus components to the development of injuries caused by venomous fish species has not been investigated. Thus, the present study was conducted to gain a better understanding of the peptide and protein components of fish skin mucus and the sting venom from the catfish C. spixii. Our results show that sting venom and skin mucus have distinct constituents that distinguished them like structural proteins, chaperones, ion transport, carbohydrate metabolism, oxidoreductase, cell cycle and protein binding present in sting venom and like tropomyosin 3 isoform 2 and energy metabolim proteins in skin mucus. But in a group of common 13 proteins we identified and isolated a WAP65 protein. The peptide fractions caused more harmful effects, such as venular stasis, hemorrhage and changes in the arteriolar wall diameter, and the protein fractions produced a typical inflammatory process in post-capillary venules. And finally we showed for the first time the presence WAP65 in sting venom and skin mucus of C. spixii using LC/MS/MS and also we purified this protein in the sting venom. Wap65 shows inflammatory action, working at different doses inducing an increase in the number of leukocytes rolling and adhering to the endothelium.

Use of suppressive subtractive hybridization to identify differentially expressed genes in ayu (Plecoglossus altivelis) associated with Listonella anguillarum infection

Suppressive subtractive hybridization (SSH) was employed to identify differentially expressed genes in ayu (Plecoglossus altivelis) associated with Listonella anguillarum infection. 800 random clones were selected from forward and reverse subtractive libraries and 787 were successfully sequenced. After assembling, 105 contigs and 414 singletons were finally obtained, some of which were immune-related genes. A real-time quantitative PCR (RT-qPCR) analysis of the expression patterns of 28 transcripts showed that the false-positive rate was approximately 7.1%. Furthermore, Wap65-2 was overexpressed in Escherichia coli, purified and used for antiserum preparation. Western blot analysis revealed that serum Wap65-2 of ayu significantly increased after bacterial infection, suggesting that it was a positive acute-phase protein (APP).

Transcriptional responses in juvenile Atlantic cod (Gadus morhua) after exposure to mercury-contaminated sediments obtained near the wreck of the German WW2 submarine U-864, and from Bergen Harbor, Western Norway

The main aim of the present work was to investigate the effects of mercury (Hg)-enriched sediments on fish. Sediments near the sunken German WW2 submarine U-864, which according to historical documents included 67 tons of metallic Hg in its cargo, are enriched of Hg leaking from the wreckage. Juvenile Atlantic cod (Gadus morhua) were exposed to two field-collected polluted sediments (U-864: inorganic Hg and Bergen Harbor (Vågen): inorganic Hg, PCB and PAH) or two comparable reference sediments for 5 weeks in the laboratory, and transcriptional responses evaluated in gills and liver. Gills of fish exposed to the Hg-enriched sunken WW2 submarine U-864 sediment contained four fold higher Hg levels compared to the control fish. An increase in Hg content in liver in the U-864 fish was also observed. The transcriptional results showed that calreticulin, HSP70 and heme oxygenase mRNA were significantly up-regulated in gills in fish exposed to the Hg-enriched sediments, whereas calreticulin, heme oxygenase, transferrin and WAP65 were significantly up-regulated and glutathione peroxidase 4B and zona pellucida 3 were significantly down-regulated in liver tissue. In gills and liver of cod exposed to the mixed-contaminated Vågen sediment, CYP1A showed the highest induction. In conclusion, the experiment shows that sediment-bound Hg is available to the fish and affects the transcription of oxidative stress responsive enzymes, suggesting that the Hg-enriched sediments may negatively affect the local wildlife. Furthermore, the mixed contaminated sediments of Vågen affected similar responses in addition to Ah-receptor mediated responses reflecting exposure to PAHs and PCBs.

Emergence of the acute-phase protein hemopexin in jawed vertebrates

When released from damaged erythrocytes free heme not only provides a source of iron for invading bacteria but also highly toxic due to its ability to catalyze free radical formation. Hemopexin (Hx) binds free heme with very high-affinity and thus protects against heme toxicity, sequesters heme from pathogens, and helps conserve valuable iron. Hx is also an acute-phase serum protein (APP), whose expression is induced by inflammation. To date Hx has been identified as far back in phylogeny as bony fish where it is called warm-temperature acclimation-related 65 kDa protein (WAP65), as serum protein levels are increased at elevated environmental temperatures as well as by infection. During analysis of nurse shark (Ginglymostoma cirratum) plasma we isolated a Ni(2+)-binding serum glycoprotein and characterized it as the APP Hx. We subsequently cloned Hx from nurse shark and another cartilaginous fish species, the little skate Leucoraja erinacea. Functional analysis showed shark Hx, like that of mammals, binds heme but is found at unusually high levels in normal shark serum. As an Hx orthologue could not be found in the genomes of jawless vertebrates or lower deuterostomes it appears to have arisen just prior to the emergence of jawed vertebrates, coincident with the second round of genome-wide duplication and the appearance of tetrameric hemoglobin (Hb).

Evolutionary aspects of hemoglobin scavengers

With the evolution of fish, systems appeared for the disposal of the hemoglobin (Hb) that was inevitably released from erythrocytes. Thus, a plasma protein that bound free Hb with great affinity, haptoglobin (Hp), evolved from a protease of the innate immune system. In parallel, other proteins appeared (for example, hemopexin and alpha(1)-microglobulin), which bound and mediated the removal of free heme groups. Remarkably, Hp later disappeared in some vertebrate lineages, suggesting that it could also be disadvantageous. In the avian lineage, a soluble protein evolved, possibly from a scavenger receptor, which in some birds seems to have replaced Hp. Among mammals, multimeric forms of Hp appeared independently at two discrete times, suggesting that this form of the protein confers an advantage on the bearer, possibly by improving resistance to infection.

Changes in gene expression profile of medaka with acute toxicity of Arochlor 1260, a polychlorinated biphenyl mixture

Differential gene expression profiling was performed with a cDNA microarray in the liver tissue of the medaka fish, Oryzias latipes, after exposure to Arochlor 1260, a polychlorinated biphenyl (PCB) mixture, which is used as a coolant and insulating fluid for transformers and capacitors and is classified as a persistent organic pollutant. Twenty-six differentially expressed candidate genes were identified. The expression of 12 genes was up-regulated and that of 14 genes was down-regulated. These genes are associated with the cytoskeleton, development, endocrine/reproduction, immunity, metabolism, nucleic acid/protein binding, and signal transduction, or are uncategorized. The transcription of molecular biomarkers known to be involved in endocrine disruption (e.g., vitellogenins, choriogenins, and estrogen receptor alpha) was highly up-regulated. The same tendencies in gene expression changes were observed with real-time quantitative PCR (qRT-PCR) analysis, which was conducted to examine 12 selected candidate genes. These genes could be used as molecular biomarkers for biological responses to toxic chemicals, especially endocrine disrupting and carcinogenic chemical contamination in aquatic environments.

Evolution of a multifunctional gene: The warm temperature acclimation protein Wap65 in the European seabass Dicentrarchus labrax

The warm temperature acclimation protein Wap65 has been shown to be involved in temperature acclimation, in immune response as well as in development. In teleosts, two types of Wap65 proteins, Wap65-1 and Wap65-2 are found, both acting as a multifunctional agent in several biological processes. In the present study we identified both transcripts Wap65-1 and Wap65-2 for the European seabass (Dicentrarchus labrax), examined their evolutionary rate and performed selection tests. The two paralogues were shown to be under moderate positive selection indicating their evolutionary adaptation. This functional diversification was further explored through expression studies. Both transcripts were differentially expressed during development as well as in various tissues and pathogen challenges, showing that Wap65-1 and Wap65-2 have evolved diverse functions. These results direct to the hypothesis that Wap65 proteins may, similarly to heat-shock proteins, have a general role in cell physiology.

Characterisation of the warm acclimated protein gene (wap65) in the Antarctic plunderfish (Harpagifer antarcticus)

Physiological adaptation to increased environmental temperatures has been studied experimentally in a number of fish species, with the up-regulation of several genes identified as being associated with the process, such as the warm-acclimated protein (wap65). This article describes the cloning and characterisation of the wap65-2 gene from the Antarctic plunderfish (Harpagifer antarcticus). The transcriptional expression of this gene in response to elevated seawater temperatures over a time course series is presented. Initially there is strong down-regulation of this gene to a maximum of 40-fold within 4 h, followed by recovery to almost control levels within 48 h, indicating that this gene does not play a role in the potential temperature adaptation of H. antarcticus.

Molecular cloning of liver Wap65 cDNA in ayu (Plecoglossus altivelis) and mRNA expression changes following Listonella anguillarum infection

The teleost warm temperature acclimation related 65 kDa protein (Wap65) is a plasma glycoprotein with the potential roles in heat adaptation, heme recycling, immune response and copper metabolism. It is most homologous to the mammalian hemopexin, which is the plasma transporter of heme. A full-length cDNA clone of the Wap65 gene, 1,534 bp in size, was isolated from the fish ayu (Plecoglossus altivelis). Its deduced amino acid sequence of 439 residues had 60.4-65.4% and 38.3-47.3% identical to fish Wap65-2-type and Wap65-1-type sequences, respectively. In phylogenetic analysis, aWap65 grouped tightly with those fish Wap65-2-type sequences. In healthy control fish, the highest mRNA signal for aWap65 was from the liver, moderately high in brain and gill, and but weaker in spleen, kidney, muscle, heart and intestine. In Listonella anguillarum-infected fish, aWap65 transcripts were significantly increased in liver, while no obvious changes in other tissues at 12 hpi. However, aWap65 transcripts were significantly increased in various tissues at 24 hpi when hemolysis developing, suggesting that aWap65 might be involved in the immune response of ayu.

Expression of warm temperature acclimation-related protein 65-kDa (Wap65) mRNA, and physiological changes with increasing water temperature in black porgy, Acanthopagrus schlegeli

We isolated the warm temperature acclimation-related protein 65-kDa (Wap65) cDNA from the liver of black porgy and investigated the expression by increasing water temperature in black porgy, Acanthopagrus schlegeli. Black porgy Wap65 full-length cDNA consists of 1,338 nucleotides, including an open reading frame, predicted to encode a protein of 425 amino acids and showed high homology to pufferfish (79%), Medaka (73%), carp (70%), and goldfish (68%) Wap65. Increase in water temperature (20 degrees C --> 30 degrees C; 1 degrees C/day) induced the rise of Wap65 mRNA expression in liver of black porgy. Also, the levels of cortisol and glucose in plasma were significantly higher at 30 degrees C than at 20 degrees C. To determine the high water temperature stressor specificity of the induction of Wap65, black porgy were transferred from seawater (SW) to freshwater (FW) for 24 hr. Wap65 expression was not detected when the fish were transferred from SW to FW (in fish transferred from SW to FW), although the levels of cortisol and glucose in plasma were increased. These results suggest that increase in Wap65 gene is related to high water temperature stress and play important roles in high water temperature environment of black porgy.

Identification of Wap65, a human homologue of hemopexin as a copper-inducible gene in swordtail fish, Xiphophorus helleri

Copper is one of the major heavy metal pollutants found in the aquatic environment. Therefore, it is important for determining the genes that play a key role in copper metabolism in aquatic organisms. This study, thus, aimed to identify a new copper-inducible gene in swordtail fish, Xiphophorus helleri. Using ACP-based RT-PCR coupled with RLM-RACE, we cloned Wap65, a mammalian homologue of hemopexin gene. The gene exhibits high identity at amino acid levels with the Wap65 gene of other fish species (42-68%) and mammalian hemopexin gene (35-37%). In addition, ten cysteine and two histidine residues are conserved in the swordtail fish Wap65 gene. These cysteine residues are vital for structural integrity, and histidine residues provide high binding affinity towards heme. As revealed by RT-PCR, the gene was upregulated in swordtail fish that were exposed to copper in a dose- and time-dependent manner. Therefore, the identification of Wap65, a mammalian homologue of hemopexin, as a new copper-inducible gene will provide greater insight into the role of this gene in copper metabolism.

The warm temperature acclimation protein Wap65 as an immune response gene: its duplicates are differentially regulated by temperature and bacterial infections

The warm temperature acclimation related 65kDa protein (Wap65) in teleost fish shares high structural similarities with mammalian hemopexins. Recent studies using microarray analysis indicated that this temperature acclimation protein may also be involved in immune responses. To provide evidence of its potential involvement in immune responses after bacterial infections, we have identified and characterized two types of Wap65 genes in channel catfish, referred to as Wap65-1 and Wap65-2, respectively. While Wap65-1 and Wap65-2 are both structurally similar to the mammalian hemopexins, they exhibit highly differential patterns of spatial expression. Wap65-1 was expressed in a wide range of tissues, whereas Wap65-2 was only expressed in the liver. Their regulation with warm temperature and bacterial infections was also highly different: Wap65-1 was constitutively expressed, whereas Wap65-2 was highly regulated by both warm temperature and bacterial infections, and warm temperature and bacterial infections appeared to synergistically induce the expression of Wap65-2. The great contrast of expression patterns and regulation of the two catfish Wap65 genes suggested both neofunctionalization and partitioning of their functions. Phylogenetic analysis indicated that the duplicated catfish Wap65 genes were evolved not only from whole genome duplication, but also from tandem, intrachromosomal gene duplications. Taken together, the results of this study suggest that Wap65 genes are not only important for its classical role as a warm temperature acclimation protein, but more importantly, may also function as an immune response protein.

Identification of differentially expressed genes from contaminant and thermal exposed goldfish Carassius auratus in Gaobeidian Lake in Beijing, China

Gaobeidian Lake, located in Beijing, China, derives its water mainly from the effluent of the Gaobeidian Wastewater Treatment Plant, which is moderately polluted. Additionally, as this water is used as a coolant in the nearby thermal power plant, the water of this lake has an elevated temperature. To screen differential gene expression in Gaobeidian Lake, suppressive subtractive hybridization (SSH) methodology was performed on RNA in goldfish Carassius auratus hepatic tissues from the lake, using Huairou Reservoir as reference site. A total of 768 candidate clones were selected to perform differential screening. Of these, 264 clones were differentially expressed between the two sites, 124 of which were then subjected to DNA sequencing. Consequently, 36 different genes with known functions were obtained, and some of these differential genes were further confirmed by semiquantitative RT-PCR experiments. Many genes related to detoxification, stress and immune response, and metabolism, such as glutathione S-transferase (GST), cytochrome P450, family 2, subfamily b, polypeptide 10 (CYP2B10), CYP2X10, alpha-1-antitrypsin, and apolipoprotein A-I (Apo-AI), had higher expression levels in goldfish hepatic tissue from Gaobeidian Lake than those from the reference site. A set of nine genes with known functions were downregulated in Gaobeidian Lake compared to the reference site. The results provided evidence that organisms inhabiting Gaobeidian Lake were suffering a complex stress process and showing metabolism changes and disturbance of homeostasis.

Increased levels of mitochondrial gene transcripts in the thermally selected rainbow trout (Oncorhynchus mykiss) strain during embryonic development

To investigate molecular mechanisms involved in thermal resistance of rainbow trout, Oncorhynchus mykiss, embryos from thermally selected strain in various developmental stages were treated at 22 degrees C for 30 min and subsequently developed at 12 degrees C using the Donaldson strain as a reference. The embryos were evaluated for their hatching rate along with the ratio of embryos having an abnormal appearance and subjected to mRNA arbitrarily primed reverse transcription-polymerase chain reaction (RAP RT-PCR). One of the genes dominantly expressed in the thermally selected strain (COX II) coded for cytochrome c oxidase subunit II. Northern blot analysis revealed that the accumulated levels of COX II transcripts were more abundant in embryos and unfertilized eggs from the thermally selected strain than those from the Donaldson strain. Furthermore, the differential expression patterns of the ATPase 6-8 gene were similar to those of the COX II gene, whereas the ATP synthase beta-subunit gene showed no significant differences between the two strains.

Temperature-dependent growth rates and gene expression patterns of various medaka Oryzias latipes cell lines derived from different populations

Medaka Oryzias latipes has several geographically and genetically distinct populations. We examined temperature acclimation response in various medaka cell lines derived from different populations. Measurement of cell growth at various temperatures suggested that 15 degrees Celsius was the permissive growth temperature in all cell lines from the Northern Japanese and East Korean populations, but not in those from the Southern Japanese population and medaka-related species Oryzias celebensis, which inhabits a tropical zone. RT-PCR for 102 temperature-responsive genes, previously reported in other species, revealed that the accumulated mRNA level of a gene encoding HSP47 was lower at 25 degrees Celsius than at 33 degrees Celsius, and vice versa for 12 genes including IkappaBalpha and Rab-1c, in OLHNI-1 cell line from the Northern Japanese population. Further analysis by real-time PCR demonstrated that the accumulated mRNA levels of IkappaBalpha and Rab-1c in OLHNI-1 and OLSOK-e7 cell lines from the East Korean population were increased when the culture temperature was shifted from 33 to 15 degrees Celsius, but not in OLHdrR-e3 cell line from the Southern Japanese population. Since IkappaBalpha and Rab-1c are related to the NFkappaB cascade and endoplasmic reticulum-to-Golgi transport, respectively, it is inferred that immune responses and intracellular transport are possibly critical to temperature adaptation for medaka.

Genomic sequences encoding two types of medaka hemopexin-like protein Wap65, and their gene expression profiles in embryos

Medaka genomic BAC clones, which contained two types of medaka hemopexin-like protein gene (Wap65), mWap65-1 and mWap65-2, were screened and their genomic sequences were determined by the shotgun strategy. The exon-intron organizations were highly conserved between both mWap65s and human hemopexin genes. The 5'-flanking regions of mWap65-1 and mWap65-2 contained various putative transcription factor binding sites including elements for developmental regulation. The expression patterns of mWap65s during embryonic development were examined by quantitative real-time PCR, demonstrating that both mWap65 transcripts were observed in early embryonic stages, but their expression patterns were different. Interestingly, in situ hybridization revealed that mWap65-2 transcripts were restricted to liver, whereas mWap65-1 transcripts were detected along the edge of pectoral fin buds and the median fin fold of tail buds in embryos at stage 32. Furthermore, we generated transgenic medaka expressing GFP driven by mWap65-1 and mWap65-2 promoters and observed GFP expression patterns during ontogeny. Although localizations of GFP varied among individuals, embryos uniformly expressed GFP 1 day after injection of mWap65-1-hrGFP and mWap65-2-hrGFP constructs, suggesting that mWap65-1 and mWap65-2 promoters were activated in very early stages. The differences between mWap65-1 and mWap65-2 in their expression profiles indicate their distinct roles during ontogeny.