A Novel Hematopoietic Granulin Induces Proliferation of Goldfish (Carassius auratus L.) Macrophages

Evidence of binding between diethylstilbestrol (DES) and the goldfish (Carassius auratus) membrane progesterone receptor α

BACKGROUND

In a previous study, diethylstilbestrol (DES) was shown to induce oocyte maturation in fish. In the present study, the interaction of DES on goldfish membrane progesterone receptor α (GmPRα) was investigated using a competitive binding assay with radiolabeled steroids. The results indicate that DES exerts its effects on membrane progesterone receptor alpha (mPRα) and induces oocyte maturation through nongenomic steroid mechanisms. This study provides empirical data that demonstrate the binding between DES and GmPRα.

METHODS

Binding of DES to GmPRα was achieved by using radiolabeled DES and recombinant GmPRα expressed in culture cells or purified GmPRα proteins that coupled to graphene quantum dots (GQDs). Additionally, the competitive binding of fluorescently labeled progesterone to GmPRα-expressing cells was evaluated.

RESULTS

Although significant nonspecific binding of radiolabeled DES to the cell membrane that expresses GmPRα has been observed, specific binding of DES to GmPRα has been successfully identified in the presence of digitonin. Furthermore, the specific binding of DES to GmPRα was confirmed by a binding assay using GQD-GmPRα. The radiolabeled DES was shown to bind to GQD-GmPRα. Additionally, the competition for the binding of fluorescently labeled progesterone to GmPRα-expressing cells was achieved with the DES.

CONCLUSIONS

The results of the experiments revealed that DES binds to GmPRα. Thus, it can be concluded that DES induces goldfish oocyte maturation by binding to GmPRα.

Animal granulins: In the GRN scheme of things

Granulins are conserved in nearly all metazoans, with an intriguing loss in insects. These pleiotropic peptides are involved in numerous physiological and pathological processes yet have been overwhelmingly examined in mammalian systems. While work in other animal models has been informative, a richer understanding of the proteins should be obtained by integrating knowledge from all available contexts. The main bodies of work described here include 1) the structure-function relationships of progranulin and its cleavage products, 2) the role of expanded granulin gene families and different isoforms in fish immunology, 3) the release of granulin peptides to promote host angiogenesis by parasitic worms, 4) a diversity of molluscan uses for granulins, including immune activation in intermediate hosts to trematodes, 5) knowledge gained on lysosomal functions from C. elegans and the stress-related activities of granulins. We provide an overview of functional reports across the Metazoa to inform much-needed future research.

The goldfish primary kidney macrophage system

Miodrag (Mike) Belosevic and collaborators profoundly influenced the development of primary kidney macrophage culturing system (PKM) to study fish immunology in various aspects of comparative immunology. Their application of using PKM model, opened a new path for studying the development of macrophages, regulation of hematopoiesis, and cell specific response against various pathogens. By measuring histopathological and immunological outcomes, the biological implications of a variety of cytokines and signal transduction molecules could be elucidated with the established PKM system. A variety of growth factors mediating hematopoiesis and cytokines regulating the immune responses were functionally characterized, which served as a fundamental basis for making goldfish an excellent model to study fish immunology. Specifically, using in vivo and PKM based in vitro assays, the Belosevic lab advanced the goldfish-M. marinum model to study the anti-mycobacteria responses in teleosts, thus paving a way for the development of novel therapeutic approaches which could be applied in aquaculture settings or utilized as a model for human disease. In this review, we will look at the contribution of Dr. Mike Belosevic to teleost macrophage development, multiple cytokine functional characterization, and host-pathogen interactions.

Identification and functional characterization of Interleukin-11 in goldfish (Carassius auratus L.)

Interleukin-11 (IL-11) is a versatile cytokine that modulates cellular differentiation and proliferation in various cell types and tissues. In this study, IL-11 gene from goldfish (Carassius auratus L.) has been identified and characterized. Goldfish IL-11 (gfIL-11) has an open reading frame (ORF) that spans 591 base pairs (bp). The ORF encodes a precursor protein consisting of 196 amino acids (aa), which includes a 26 aa signal peptide and a conserved domain belonging to the IL-11 superfamily. Based on phylogenetic analysis, gfIL-11 was found to be closely related to other IL-11 homologues identified in various fish species. The gfIL-11 transcript exhibited varied expression levels across all the analyzed tissues, with the highest expression observed in the gill and spleen. Treatment of goldfish head kidney leukocytes (HKLs) with LPS and live Aeromonas hydrophila, increased gfIL-11 mRNA expression level. Recombinant gfIL-11 protein (rgIL-11) induced a dose-dependent production of TNF-α and IFNγ from goldfish HKLs. Furthermore, the administration of rgIL-11 to goldfish HKLs triggered an increase in the expression of various transcription factors such as MafB, cJun, GATA2, and Egr1, which play a vital role in the differentiation of myeloid precursors into macrophages and monocytes. Our findings provide evidence that IL-11 is a crucial cytokine that promotes cell proliferation, immune response, and differentiation across various hematopoietic lineages and stages of goldfish.

Expression analysis of Carassius auratus-leukocyte-immune-type receptors (CaLITRs) during goldfish kidney macrophage development and in activated kidney leukocyte cultures

Carassius auratus leukocyte immune-type receptors (CaLITRs) were recently discovered immunoregulatory receptors in goldfish that have diverse immunoglobulin-like (Ig-like) ectodomains and intracellular signaling motifs. Genomic analysis shows that CaLITR-types are also located as distinct gene clusters across multiple goldfish chromosomes. For example, CaLITR1 (unplaced) is a functionally ambiguous receptor having two Ig-like domains, a transmembrane domain (TM), and a short cytoplasmic tail (CYT) devoid of any recognizable signaling motifs. CaLITR2 (Chr47) is a putative inhibitory receptor containing four Ig-like domains, a TM, and a long CYT with an immunoreceptor tyrosine-based inhibition motif (ITIM) and immunoreceptor tyrosine-based switch motif (ITSM). A putative activating receptor-type, CaLITR3 (Chr3), has four Ig-like domains, a TM, and a short CYT containing a positively charged histidine residue and CaLITR4 (ChrLG28B) is a receptor with putative multifunctional signaling potential as well as five Ig-like domains, a TM, and a long tyrosine-motif containing CYT region. The variable genomic locations of the CaLITRs suggest that they are likely under the influence of different cis- and/or trans-regulatory elements. To better understand the transcriptional activities of select CaLITRs from variable genomic regions, we used an RT-qPCR-based approach to examine the expression of CaLITR1, CaLITR2, CaLITR3, and CaLITR4 during goldfish primary kidney macrophage (PKM) development and in mixed leukocyte reaction cultures (MLRs) of the goldfish. Our results showed that the select CaLITRs are differentially expressed during PKM development and in goldfish MLRs exposed to T-cell mitogens/immunosuppressive drugs, supporting that the transcription of these CaLITRs is likely regulated by distinct cis- and/or trans-regulatory elements.

Granulin as an important immune molecule involved in lamprey tissue repair and regeneration by promoting cell proliferation and migration

Progranulin (PGRN) is an autocrine growth factor that regulates cell proliferation, migration, wound healing, and tissue repair in mammals. Lamprey is the most primitive of the extant vertebrates and is regarded as the survivor of a once flourishing group of paleozoic vertebrates, with a history of more than 500 million years. To date, the evolutionary dynamics and the underlying function of the PGRNs remain largely unclear in lamprey. Here, we screened four genes encoding PGRNs from the genomes of Lethenteron reissneri and Petromyzon marinus, including one long form (named Lr-PGRN-L) and three short forms (named Lr-PGRN-S1, Lr-PGRN-S2, and Lr-PGRN-S3), and performed phylogenetic tree, functional domain, and synteny analyses to identify the evolutionary history of the four Lr-PGRNs. In addition, the expressions of the four Lr-pgrn family genes and the immune response against various pathogenic challenges were also investigated. We found that these genes were widely distributed in various tissues of lamprey and performed a variety of functions. Moreover, our results suggest that Lr-PGRN-S1 induces cell migration and proliferation, and is involved in repair after skin and spinal cord injury under appropriate conditions. Our findings are valuable because they improve the understanding of the evolutionary relationship of vertebrate pgrn genes, as well as providing new insights into the diverse and important roles of Lr-PGRNs.

The goldfish Carassius auratus: an emerging animal model for comparative cardiac research

The use of unconventional model organisms is significantly increasing in different fields of research, widely contributing to advance life sciences understanding. Among fishes, the cyprinid Carassius auratus (goldfish) is largely used for studies on comparative and evolutionary endocrinology, neurobiology, adaptive and conservation physiology, as well as for translational research aimed to explore mechanisms that may be useful in an applicative biomedical context. More recently, the research possibilities offered by the goldfish are further expanded to cardiac studies. A growing literature is available to illustrate the complex networks involved in the modulation of the goldfish cardiac performance, also in relation to the influence of environmental signals. However, an overview on the existing current knowledge is not yet available. By discussing the mechanisms that in C. auratus finely regulate the cardiac function under basal conditions and under environmental challenges, this review highlights the remarkable flexibility of the goldfish heart in relation not only to the basic morpho-functional design and complex neuro-humoral traits, but also to its extraordinary biochemical-metabolic plasticity and its adaptive potential. The purpose of this review is also to emphasize the power of the heart of C. auratus as an experimental tool useful to investigate mechanisms that could be difficult to explore using more conventional animal models and complex cardiac designs.

Progranulin/GP88, A Complex and Multifaceted Player of Tumor Growth by Direct Action and via the Tumor Microenvironment

Investigation of the role of progranulin/GP88 on the proliferation and survival of a wide variety of cells has been steadily increasing. Several human diseases stem from progranulin dysregulation either through its overexpression in cancer or its absence as in the case of null mutations in some form of frontotemporal dementia. The present review focuses on the role of progranulin/GP88 in cancer development, progression, and drug resistance. Various aspects of progranulin identification, biology, and signaling pathways will be described. Information will be provided about its direct role as an autocrine growth and survival factor and its paracrine effect as a systemic factor as well as via interaction with extracellular matrix proteins and with components of the tumor microenvironment to influence drug resistance, migration, angiogenesis, inflammation, and immune modulation. This chapter will also describe studies examining progranulin/GP88 tumor tissue expression as well as circulating level as a prognostic factor for several cancers. Due to the wealth of publications in progranulin, this review does not attempt to be exhaustive but rather provide a thread to lead the readers toward more in-depth exploration of this fascinating and unique protein.

A novel way to synthesize pantothenate in bacteria involves β-alanine synthase present in uracil degradation pathway

Pantothenate is an indispensable vitamin precursor of the synthesis of coenzyme A (CoA), a key metabolite required in over 100 metabolic reactions. β-Alanine (β-ala) is an indispensable component of pantothenate. Due to the metabolic relevance of this pathway, we assumed that orthologous genes for ß-alanine synthesis would be present in the genomes of bacteria, archaea, and eukaryotes. However, comparative genomic studies revealed that orthologous gene replacement and loss of synteny occur at high frequency in panD genes. We have previously reported the atypical plasmid-encoded location of the pantothenate pathway genes panC and panB (two copies) in R. etli CFN42. This study also revealed the unexpected absence of a panD gene encoding the aspartate decarboxylase enzyme (ADC), required for the synthesis of β-ala. The aim of this study was to identify the source of β-alanine in Rhizobium etli CFN42. In this study, we present a bioinformatic analysis and an experimental validation demonstrating that the source of β-ala in this R. etli comes from β-alanine synthase, the last enzyme of the uracil degradation pathway.

A potent tilapia secreted granulin peptide enhances the survival of transgenic zebrafish infected by Vibrio vulnificus via modulation of innate immunity

Progranulin (PGRN) is a multi-functional growth factor that mediates cell proliferation, survival, migration, tumorigenesis, wound healing, development, and anti-inflammation activity. A novel alternatively spliced transcript from the short-form PGRN1 gene encoding a novel, secreted GRN peptide composed of 20-a.a. signal peptide and 41-a.a. GRN named GRN-41 was identified to be abundantly expressed in immune-related organs including spleen, head kidney, and intestine of Mozambique tilapia. The expression of GRN-41 and PGRN1 were further induced in the spleen of tilapia challenged with Vibrio vulnificus at 3 h post infection (hpi) and 6 hpi, respectively. In this study, we established three transgenic zebrafish lines expressing the secreted GRN-41, GRN-A and PGRN1 of Mozambique tilapia specifically in muscle. The relative percent of survival (RPS) was enhanced in adult transgenic zebrafish expressing tilapia GRN-41 (68%), GRN-A (32%) and PGRN1 (36%) compared with control transgenic zebrafish expressing AcGFP after challenge with V. vulnificus. It indicates tilapia GRN-41 is a potent peptide against V. vulnificus infection. The secreted tilapia GRN-41 can induce the expression of innate immune response-related genes, such as TNFa, TNFb, IL-8, IL-1β, IL-6, IL-26, IL-21, IL-10, complement C3, lysozyme (Lyz) and the hepatic antimicrobial peptide hepcidin (HAMP), in adult transgenic zebrafish without V. vulnificus infection. The tilapia GRN-41 peptide can enhance the innate immune response by further elevating TNFb, IL-1β, IL-8, IL-6, and HAMP expression in early responsive time to the V. vulnificus challenge in transgenic zebrafish. Our results suggest that the novel GRN-41 peptide generated from alternative splicing of the tilapia PGRN1 gene is a potent peptide that defends against V. vulnificus in the transgenic zebrafish model by modulation of innate immunity.

Isolation and Characterization of Serum Extracellular Vesicles (EVs) from Atlantic Salmon Infected with Piscirickettsia Salmonis

Secretion of extracellular vesicles (EVs) is a common feature of both eukaryotic and prokaryotic cells. Isolated EVs have been shown to contain different types of molecules, including proteins and nucleic acids, and are reported to be key players in intercellular communication. Little is known, however, of EV secretion in fish, or the effect of infection on EV release and content. In the present study, EVs were isolated from the serum of healthy and Piscirickettsia salmonis infected Atlantic salmon in order to evaluate the effect of infection on EV secretion. P. salmonis is facultative intracellular bacterium that causes a systemic infection disease in farmed salmonids. EVs isolated from both infected and non-infected fish had an average diameter of 230–300 nm, as confirmed by transmission electron microscopy, nanoparticle tracking, and flow cytometry. Mass spectrometry identified 180 proteins in serum EVs from both groups of fish. Interestingly, 35 unique proteins were identified in serum EVs isolated from the fish infected with P. salmonis. These unique proteins included proteasomes subunits, granulins, and major histocompatibility class I and II. Our results suggest that EV release could be part of a mechanism in which host stimulatory molecules are released from infected cells to promote an immune response.

Endogenous growth factor stimulation of hemocyte proliferation induces resistance to Schistosoma mansoni challenge in the snail host

Digenean trematodes are a large, complex group of parasitic flatworms that infect an incredible diversity of organisms, including humans. Larval development of most digeneans takes place within a snail (Gastropoda). Compatibility between snails and digeneans is often very specific, such that suitable snail hosts define the geographical ranges of diseases caused by these worms. The immune cells (hemocytes) of a snail are sentinels that act as a crucial barrier to infection by larval digeneans. Hemocytes coordinate a robust and specific immunological response, participating directly in parasite killing by encapsulating and clearing the infection. Hemocyte proliferation and differentiation are influenced by unknown digenean-specific exogenous factors. However, we know nothing about the endogenous control of hemocyte development in any gastropod model. Here, we identify and functionally characterize a progranulin [Biomphalaria glabrata granulin (BgGRN)] from the snail B. glabrata, a natural host for the human blood fluke Schistosoma mansoni Granulins are growth factors that drive proliferation of immune cells in organisms, spanning the animal kingdom. We demonstrate that BgGRN induces proliferation of B. glabrata hemocytes, and specifically drives the production of an adherent hemocyte subset that participates centrally in the anti-digenean defense response. Additionally, we demonstrate that susceptible B. glabrata snails can be made resistant to infection with S. mansoni by first inducing hemocyte proliferation with BgGRN. This marks the functional characterization of an endogenous growth factor of a gastropod mollusc, and provides direct evidence of gain of resistance in a snail-digenean infection model using a defined factor to induce snail resistance to infection.

Goldfish (Carassius auratus L.) as a model system to study the growth factors, receptors and transcription factors that govern myelopoiesis in fish

The process of myeloid cell development (myelopoiesis) in fish has mainly been studied in three cyprinid species: zebrafish (Danio rerio), ginbuna carp (Carassius auratus langsdorfii) and goldfish (C. auratus, L.). Our studies on goldfish myelopoiesis have utilized in vitro generated primary kidney macrophage (PKM) cultures and isolated primary kidney neutrophils (PKNs) cultured overnight to study the process of macrophage (monopoiesis) and neutrophil (granulopoiesis) development and the key growth factors, receptors, and transcription factors that govern this process in vitro. The PKM culture system is unique in that all three subpopulations of macrophage development, namely progenitor cells, monocytes, and mature macrophages, are simultaneously present in culture unlike mammalian systems, allowing for the elucidation of the complex mixture of cytokines that regulate progressive and selective macrophage development from progenitor cells to fully functional mature macrophages in vitro. Furthermore, we have been able to extend our investigations to include the development of erythrocytes (erythropoiesis) and thrombocytes (thrombopoiesis) through studies focusing on the progenitor cell population isolated from the goldfish kidney. Herein, we review the in vitro goldfish model systems focusing on the characteristics of cell sub-populations, growth factors and their receptors, and transcription factors that regulate goldfish myelopoiesis.

Bovine lactoferrin regulates cell survival, apoptosis and inflammation in intestinal epithelial cells and preterm pig intestine

Bovine lactoferrin (bLF) may modulate neonatal intestinal inflammation. Previous studies in intestinal epithelial cells (IECs) indicated that moderate bLF doses enhance proliferation whereas high doses trigger inflammation. To further elucidate cellular mechanisms, we profiled the porcine IEC proteome after stimulation with bLF at 0, 0.1, 1 and 10g/L by LC-MS-based proteomics. Key pathways were analyzed in the intestine of formula-fed preterm pigs with and without supplementation of 10g/L bLF. Levels of 123 IEC proteins were altered by bLF. Low bLF doses (0.1-1g/L) up-regulated 11 proteins associated with glycolysis, energy metabolism and protein synthesis, indicating support of cell survival. In contrast, a high bLF dose (10g/L) up-regulated three apoptosis-inducing proteins, down-regulated five anti-apoptotic and proliferation-inducing proteins and 15 proteins related to energy and amino acid metabolism, and altered three proteins enhancing the hypoxia inducible factor-1 (HIF-1) pathway. In the preterm pig intestine, bLF at 10g/L decreased villus height/crypt depth ratio and up-regulated the Bax/Bcl-2 ratio and HIF-1α, indicating elevated intestinal apoptosis and inflammation. In conclusion, bLF dose-dependently affects IECs via metabolic, apoptotic and inflammatory pathways. It is important to select an appropriate dose when feeding neonates with bLF to avoid detrimental effects exerted by excessive doses.

BIOLOGICAL SIGNIFICANCE

The present work elucidates dose-dependent effects of bLF on the proteomic changes of IECs in vitro supplemented with data from a preterm pig study confirming detrimental effects of enteral feeding with the highest dose of bLF (10g/L). The study contributes to further understanding on mechanisms that bLF, as an important milk protein, can regulate the homeostasis of the immature intestine. Results from this study urge neonatologists to carefully consider the dose of bLF to supplement into infant formula used for preterm neonates.

Nesfatin-1 as a new positive inotrope in the goldfish (Carassius auratus) heart

The hypothalamic neuropeptide Nesfatin-1 is present in both mammals and teleosts in which it elicits anorexigenic effects. In mammals, Nesfatin-1 acts on the heart by inducing negative inotropism and lusitropism, and cardioprotection against ischemic damages. We evaluated whether in teleosts, Nesfatin-1 also influences cardiac performance. In the goldfish (Carassius auratus), mature, fully processed Nesfatin-1 was detected in brain, gills, intestine and skeletal muscle, but not in the cardiac ventricle. However, on the isolated and perfused working goldfish heart, exogenous Nesfatin-1 induced a positive inotropic effect, revealed by a dose-dependent increase of stroke volume (SV) and stroke work (SW). Positive inotropism was abolished by inhibition of adenylate cyclase (AC; MDL123330A) and cAMP-dependent kinase (PKA; KT5720), suggesting a cAMP/PKA-mediated pathway. This was confirmed by the increased cAMP concentrations revealed by ELISA on Nesfatin-1-treated hearts. Perfusion with Diltiazem, Thapsigargin and PD98059 showed the involvement of L-type calcium channels, SERCA2a pumps and ERK1/2, respectively. The role of ERK1/2 and phospholamban in Nesfatin-1-induced cardiostimulation was supported by Western blotting analysis. In conclusion, this is the first report showing that in teleosts, Nesfatin-1 potentiates mechanical cardiac performance, strongly supporting the evolutionary importance of the peptide in the control of the cardiac function of vertebrates.

Functional characterization and molecular mechanism exploration of three granulin epithelin precursor splice variants in biomineralization of the pearl oyster Pinctada fucata

The granulin/epithelin precursor (GEP) encodes a glycoprotein precursor which exhibits pleiotropic tissue growth factor activity with multiple functions. Here, GEP was isolated and its role in the shell biomineralization process of the pearl oyster Pinctada fucata was investigated. Three forms of GEP mRNA were isolated from the pearl oyster (designated PfGEP-1, PfGEP-2 and PfGEP-3). Genomic DNA flanking the splicing region of the PfGEP variants was sequenced and it was found that PfGEP-2 splices out Exon 4, whereas PfGEP-3 splices out Exon 3 compared to PfGEP-1. PfGEP-1 (1505 amino acids) consists of 18 granulin domains, whereas PfGEP-2 (1459 amino acids) and PfGEP-3 (1471 amino acids) consist of 17.5 granulin domains, respectively. Analyses of PfGEP-1 and PfGEP-3 mRNA showed differential patterns in the tissues and developmental stages. Western blotting results showed that the three splice variants can translate to proteins in HEK293T cells. A knockdown experiment using PfGEP dsRNA showed decreased PfGEP-1/PfGEP-3 and PfMSX mRNA, and irregular crystallization of the nacreous layer using scanning electron microscopy. In luciferase assays, co-transfection of PfGEP-1 could activate as well as repress luciferase expression of the reporter plasmid driven by the PfMSX promoter, whereas PfGEP-3 stimulated the expression, elucidating the molecular mechanisms involved in the correlation between PfGEP and PfMSX. These results suggested that GEP variants might function differently during the biomineralization process, which provides new knowledge on the mechanism regulating nacre formation.

Recombinant goldfish thrombopoietin up-regulates expression of genes involved in thrombocyte development and synergizes with kit ligand A to promote progenitor cell proliferation and colony formation

Thrombopoietin (TPO) is the principal regulator of thrombopoiesis and promotes the proliferation, differentiation and maturation of megakaryocytic progenitor cells in mammals. In this study we report on the molecular and functional characterization of goldfish TPO. Quantitative expression analysis of goldfish tpo revealed the highest mRNA levels in heart, followed by spleen, liver, brain, intestine and kidney tissues. Significant decrease of tpo and c-mpl expressions in goldfish primary kidney macrophage (PKM) cultures, as progenitor to macrophage development progressed, indicates that TPO is not involved in monopoiesis. Recombinant goldfish TPO (rgTPO) alone did not induce significant proliferation of progenitor cells, but TPO in cooperation with recombinant goldfish kit ligand A (rgKITLA) supported proliferation of progenitor cells in a dose-dependent manner. In response to rgTPO or a combination of rgTPO and rgKITLA, the mRNA levels of thrombopoietic markers cd41 and c-mpl as well as thrombo/erythropoietic transcription factors gata1 and lmo2 in sorted progenitor cells were up-regulated, while the mRNA levels of granulopoietic markers (cebpα and gcsfr) and the lymphoid transcription factor gata3 were down-regulated. Furthermore, rgTPO and rgKITLA synergistically stimulated thrombocytic colony-formation. Our results demonstrate that goldfish TPO has similar functions to mammalian TPO as a regulator of thrombopoiesis, and suggests a highly conserved molecular mechanism of thrombocyte development throughout evolution of vertebrates.

Identification of interferon-γ-inducible-lysosomal thiol reductase (GILT) gene in goldfish (Carassius auratus) and its immune response to LPS challenge

The interferon-γ-inducible lysosomal thiol reductase (GILT) has been demonstrated to play an important role in the processing and presentation of MHC class II restricted antigen (Ag) by catalyzing disulfide bond reduction. In this study, we cloned a GILT gene homolog from goldfish (designated gGILT), a kind of precious freshwater fish with high market value. The open reading frame of gGILT consists of 756 bases encoding a protein of 251 amino acids with an estimated molecular mass of 27.8 kDa and a theoretical isoelectric point of 5.24. The deduced protein possesses the typical structural features of known GILT proteins, including an active-site motif, a GILT signature sequence, and 10 conserved cysteines. RT-PCR results showed that gGILT and gIFN-γ (goldfish IFN-γ) mRNA were expressed in a tissue-specific manner and obviously up-regulated in splenocytes and the cells from head kidney after induction with LPS. Recombinant gGILT fused with His6 tag was efficiently expressed in Escherichia coli BL21 (DE3) and purified by Ni-NTA affinity chromatography. Further study revealed that gGILT was capable of catalyzing the reduction of the interchain disulfide bonds from intact IgG. This study shows that gGILT may be involved in the immune response to bacteria challenge and maintain first line of innate immune defense at basal level in goldfish. It also provides the basis for investigating on the role of GILT using goldfish as an animal model.

Morpho-functional characterization of the goldfish (Carassius auratus L.) heart

Using morphological and physiological approaches we provided, for the first time, a structural and functional characterization of Carassius auratus L. heart. Besides to the classical four chambers, i.e. sinus venosus, atrium, ventricle, bulbus, we described two distinct structures corresponding to the atrio-ventricular (AV) region and the conus arteriosus. The atrium is very large and highly trabeculated; the ventricle shows an outer compacta, vascularized by coronary vessels, and an inner spongiosa; the bulbus wall is characterized by a high elastin/collagen ratio, which makes it extremely compliant. Immunolocalization revealed a strong expression of activated "eNOS-like" isoforms both at coronary endothelium and, to a lesser extent, in the myocardiocytes and the endocardial endothelium (EE). The structural design of the heart appears to comply with its mechanical function. Using an in vitro working heart preparation, cardiac performance was evaluated at different filling and afterload pressures. The hearts were very sensitive to filling pressure increases. Maximum Stroke volume (SV=1.08 ± 0.09 mL/kg body mass) was obtained with an input pressure of 0.4 kPa. The heart was not able to sustain afterload increases, values higher than 1.5 kPa impairing its performance. These morpho-functional features are consistent with a volume pump mechanical performance.

Meta-type analysis of dopaminergic effects on gene expression in the neuroendocrine brain of female goldfish

Dopamine (DA) is a major neurotransmitter important for neuroendocrine control and recent studies have described genomic signaling pathways activated and inhibited by DA agonists and antagonists in the goldfish brain. Here we perform a meta-type analysis using microarray datasets from experiments conducted with female goldfish to characterize the gene expression responses that underlie dopaminergic signaling. Sexually mature, pre-spawning [gonadosomatic index (GSI) = 4.5 ± 1.3%] or sexually regressing (GSI = 3 ± 0.4%) female goldfish (15-40 g) injected intraperitoneally with either SKF 38393, LY 171555, SCH 23390, sulpiride, or a combination of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and α-methyl-p-tyrosine. Microarray meta-type analysis identified 268 genes in the telencephalon and hypothalamus as having reciprocal (i.e., opposite between agonism and antagonism/depletion) fold change responses, suggesting that these transcripts are likely targets for DA-mediated regulation. Noteworthy genes included ependymin, vimentin, and aromatase, genes that support the significance of DA in neuronal plasticity and tissue remodeling. Sub-network enrichment analysis (SNEA) was used to identify common gene regulators and binding proteins associated with the differentially expressed genes mediated by DA. SNEA analysis identified gene expression targets that were related to three major categories that included cell signaling (STAT3, SP1, SMAD, Jun/Fos), immune response (IL-6, IL-1β, TNFs, cytokine, NF-κB), and cell proliferation and growth (IGF1, TGFβ1). These gene networks are also known to be associated with neurodegenerative disorders such as Parkinsons' disease, well-known to be associated with loss of dopaminergic neurons. This study identifies genes and networks that underlie DA signaling in the vertebrate CNS and provides targets that may be key neuroendocrine regulators. The results provide a foundation for future work on dopaminergic regulation of gene expression in fish model systems.

The effects of ghrelin on energy balance and psychomotor activity in a goldfish model: an overview

The goldfish (Carassius auratus) has a number of merits as a laboratory animal, and we have extensively identified the mechanisms by which ghrelin regulates food intake in this species. For the first time, we have purified and characterized 11 molecular variants of ghrelin that are present in goldfish intestine and shown that 17-residue ghrelin, the predominant form with n-octanoyl modification, is biologically active and implicated in the regulation of food intake as an endogenous orexigenic factor. Ghrelin and its receptor system are present not only in peripheral tissues such as stomach and intestine, but also in the central nervous system. Recent studies have also revealed that a number of neuropeptides are widely distributed in the brain in key areas of emotional regulation, and their role as modulators of behavioral states is being increasingly recognized. Interestingly, administration of ghrelin induces an orexigenic effect and also modifies locomotor activity, suggesting the involvement of ghrelin in feeding control and regulation of energy balance. Information derived from studies of ghrelin has been increasing, and important results have been obtained from both fish and mammals. Here, we present an overview of the effects of ghrelin on energy balance and psychomotor activity in the goldfish as an animal model. The available data provide an insight into evolutionary background of ghrelin's multiple actions on energy homeostasis in vertebrates.

Progranulin expression is upregulated after spinal contusion in mice

Progranulin (proepithelin) is a pleiotropic growth-factor associated with inflammation and wound repair in peripheral tissues. It also has been implicated in the response to acute traumatic brain injury as well as to chronic neurodegenerative diseases. To determine whether changes in progranulin expression also accompany acute spinal cord injury, C57BL/6 mice were subjected to mid-thoracic (T9 level) contusion spinal cord injury and analyzed by immunohistochemical and biochemical methods. Whereas spinal cord sections prepared from non-injured laminectomy control animals contained low basal levels of progranulin immunoreactivity in gray matter, sections from injured animals contained intense immunoreactivity throughout the injury epicenter that peaked 7-14 days post injury. Progranulin immunoreactivity colocalized with myeloid cell markers CD11b and CD68, indicating that expression increased primarily in activated microglia and macrophages. Immunoblot analysis confirmed that progranulin protein levels rose after injury. On the basis of quantitative polymerase chain reaction analysis, increased protein levels resulted from a tenfold rise in progranulin transcripts. These data demonstrate that progranulin is dramatically induced in myeloid cells after experimental spinal cord injury and is positioned appropriately both spatially and temporally to influence recovery after injury.

Molecular and functional characterization of kita and kitla of the goldfish (Carassius auratus L.)

Kit ligand and its type III tyrosine kinase receptor Kit promotes the survival, proliferation and differentiation of progenitor cells involved in mammalian myelopoiesis. In this study we report on the molecular and functional characterization of kit receptor A (kita) and kit ligand A (kitla) from the goldfish. Both kita and kitla were ubiquitously expressed in goldfish tissues, with higher mRNA levels observed in the kidney and spleen, the major hematopoietic organs of fish. Furthermore, both kita and kitla expressions decreased in a time-dependent manner in goldfish primary kidney macrophage (PKM) cultures, as progenitor to macrophage development progressed, and the highest expressions of both the receptor and ligand were observed in sorted progenitor cell populations. Activation of mature macrophage cultures increased both kita and kitla expressions. Kit ligand A induced chemotactic response, proliferation and survival of PKM cells in a dose-dependent manner, but did not induce differentiation of early PKM cells. These results are consistent with the role of kita and kitla during myelopoiesis of higher vertebrates and suggest a conserved mechanism of macrophage development throughout vertebrates.

Development of macrophages of cyprinid fish

The innate immune responses of early vertebrates, such as bony fishes, play a central role in host defence against infectious diseases and one of the most important effector cells of innate immunity are macrophages. In order for macrophages to be effective in host defence they must be present at all times in the tissues of their host and importantly, the host must be capable of rapidly increasing macrophage numbers during times of need. Hematopoiesis is a process of formation and development of mature blood cells, including macrophages. Hematopoiesis is controlled by soluble factors known as cytokines, that influence changes in transcription factors within the target cells, resulting in cell fate changes and the final development of specific effector cells. The processes involved in macrophage development have been largely derived from mammalian model organisms. However, recent advancements have been made in the understanding of macrophage development in bony fish, a group of organisms that rely heavily on their innate immune defences. Our understanding of the growth factors involved in teleost macrophage development, as well as the receptors and regulatory mechanisms in place to control them has increased substantially. Furthermore, model organisms such as the zebrafish have emerged as important instruments in furthering our understanding of the transcriptional control of cell development in fish as well as in mammals. This review highlights the recent advancements in our understanding of teleost macrophage development. We focused on the growth factors identified to be important in the regulation of macrophage development from a progenitor cell into a functional macrophage and discuss the important transcription factors that have been identified to function in teleost hematopoiesis. We also describe the findings of in vivo studies that have reinforced observations made in vitro and have greatly improved the relevance and importance of using teleost fish as model organisms for studying developmental processes.

The goldfish (Carassius auratus) as a model for neuroendocrine signaling

Goldfish (Carassius auratus) are excellent model organisms for the neuroendocrine signaling and the regulation of reproduction in vertebrates. Goldfish also serve as useful model organisms in numerous other fields. In contrast to mammals, teleost fish do not have a median eminence; the anterior pituitary is innervated by numerous neuronal cell types and thus, pituitary hormone release is directly regulated. Here we briefly describe the neuroendocrine control of luteinizing hormone. Stimulation by gonadotropin-releasing hormone and a multitude of classical neurotransmitters and neuropeptides is opposed by the potent inhibitory actions of dopamine. The stimulatory actions of gamma-aminobutyric acid and serotonin are also discussed. We will focus on the development of a cDNA microarray composed of carp and goldfish sequences which has allowed us to examine neurotransmitter-regulated gene expression in the neuroendocrine brain and to investigate potential genomic interactions between these key neurotransmitter systems. We observed that isotocin (fish homologue of oxytocin) and activins are regulated by multiple neurotransmitters, which is discussed in light of their roles in reproduction in other species. We have also found that many novel and uncharacterized goldfish expressed sequence tags in the brain are also regulated by neurotransmitters. Their sites of production and whether they play a role in neuroendocrine signaling and control of reproduction remain to be determined. The transcriptomic tools developed to study reproduction could also be used to advance our understanding of neuroendocrine-immune interactions and the relationship between growth and food intake in fish.

Molecular and functional characterization of granulin-like molecules of insects

Granulins are a group of highly conserved growth factors that have been described from a variety of organisms spanning the metazoa. Here, we report on the identification of two partial transcripts encoding granulin-like molecules from Aa23 embryonic cells of Aedes albopictus and primary haemocytes from Manduca sexta. Both these partial transcripts had the characteristic 12-cysteine motif that is a hallmark of the granulin family and they represent the first granulin mRNA transcripts identified from insects. Moreover, we demonstrate that the recombinant granulin molecule that we originally cloned in the goldfish, induced proliferation of both Aa23 embryonic cells and primary haemocytes. Interestingly, this proliferative effect was upregulated in the presence of the intracellular symbiotic bacterium Wolbachia pipientis. Thus, granulin appears to be a highly conserved growth factor not only in lower vertebrates but also invertebrates.

Toxicogenomic analysis of immune system-related genes in Japanese flounder (Paralichthys olivaceus) exposed to heavy oil

Heavy oil contamination is one of the most important environmental issues. Toxicities of polycyclic aromatic hydrocarbons (PAHs), including immune toxicities, are well characterized, however, the immune toxic effects of heavy oil, as a complex mixture of PAHs, have not been investigated. In the present study, we selected Japanese flounder (Paralichthys olivaceus) as a model organism, and observed alteration of immune function by the exposure to heavy oil. To analyze the expression profiles of immune system-related genes, we selected 309 cDNAs from our flounder EST library, and spotted them on a glass slide. Using this cDNA array, alteration of gene expression profiles was analyzed in the kidneys of flounders exposed to heavy oil. Six Japanese flounders (mean body weight: 197 g) were acclimated to laboratory conditions at 19-20 degrees C. Three fish were exposed to heavy oil C (bunker C) at a concentration of 3.8 g/L for 3 days, and the others were kept in seawater without heavy oil and used as the control. After the exposure period, the fish were transferred into control seawater and maintained for 4 days, and then they were dissected and their kidneys were removed. Total RNA was extracted from the kidney samples to use in gene expression analyses. The microarray detected alteration of immune system-related genes in the kidneys of heavy oil-exposed flounders, including down-regulation of immunoglobulin light chain, CD45, major histocompatibility complex class II antigens and macrophage colony-stimulating factor precursor, and up-regulation of interleukin-8 and lysozyme. These results suggest that pathogen resistance may be weakened in heavy oil-exposed fish, causing a subsequent bacterial infection, and then proinflammatory genes may be induced as a defensive response against the infection. Additionally, we found candidate genes for use as biomarkers of heavy oil exposure, such as N-myc downstream regulated gene 1 and heat shock cognate 71 kDa proteins.

Growth Factors of Lower Vertebrates

Colony-stimulating factor-1 (CSF-1) regulates mononuclear cell proliferation, differentiation, and survival. The functions of CSF-1 are well documented in mammals; however, little is known about CSF-1 biology in lower vertebrates. This is the first report on the identification and functional characterization of a fish CSF-1 molecule expressed highly in the spleen and in phorbol 12-myristate 13-acetate-stimulated monocytes. Goldfish CSF-1 is a 199-amino acid protein that possesses the required cysteine residues to form important intra-chain and inter-chain disulfide bonds that allow CSF-1 to form a functional homodimer and to interact with its high affinity receptor, CSF-1R. Recombinant goldfish CSF-1 formed a homodimer and bound to the soluble goldfish CSF-1R. The addition of the recombinant CSF-1 to sorted goldfish progenitor cells, monocytes, and macrophages induced the differentiation of monocytes into macrophages and the proliferation of monocyte-like cells. The proliferation of these cells was abrogated by addition of an anti-CSF-1R antibody as well as the soluble CSF-1R. The ability of the soluble CSF-1R to inhibit CSF-1-induced proliferation represents a novel mechanism for the regulation of CSF-1 function.

Interleukin-6 family cytokine M17 induces differentiation and nitric oxide response of goldfish (Carassius auratus L.) macrophages

Cytokines belonging to the interleukin-6 (IL-6) family function in many biological processes and display a high degree of redundancy within the family. Although a number of mRNA transcripts from teleost fish that resemble IL-6 family cytokines have been identified none have been functionally characterized to confirm their identity. We report on the identification and functional characterization of goldfish M17, a molecule possessing sequence and mRNA expression patterns similar to the mammalian and avian ciliary neurotrophic factor and mammalian leukemia inhibitory factor. Goldfish M17 was found to induce the production of nitric oxide in goldfish macrophages and stimulate the proliferation of macrophage progenitor cells when added in combination with cell-conditioned medium. Moreover, goldfish M17 was found to facilitate the differentiation of sorted monocytes into macrophages at biologically relevant concentrations.