Expression of apolipoprotein A-I and A-II in rainbow trout reproductive tract and their possible role in antibacterial defence

Where do obesity and male infertility collide?

The parallel rise in obesity and male infertility in modern societies necessitates the identification of susceptibility genes underlying these interconnected health issues. In our study, we conducted a comprehensive search in the OMIM database to identify genes commonly associated with male infertility and obesity. Subsequently, we performed an insilico analysis using the REVEL algorithm to detect pathogenic single nucleotide polymorphisms (SNPs) in the coding region of these candidate genes. To validate our findings in vivo, we conducted a comprehensive analysis of SNPs and gene expression of candidate genes in 200 obese infertile subjects and 240 obese fertile individuals using ARMS-PCR. Additionally, we analyzed 20 fertile and 22 infertile obese individuals using Realtime-qPCR. By removing duplicated queries, we obtained 197 obesity-related genes and 102 male infertility-related genes from the OMIM database. Interestingly, the APOB gene was found in common between the two datasets. REVEL identified the rs13306194 variant as potentially pathogenic with a calculated score of 0.524. The study identified a significant association between the AA (P value = 0.001) genotype and A allele (P value = 0.003) of the APOB rs13306194 variant and infertility in obese men. APOB expression levels were significantly lower in obese infertile men compared to obese fertile controls (p < 0.01). Moreover, the AA genotype of rs13306194 APOB was associated with a significant decrease in APOB gene expression in obese infertile men (p = 0.05). There is a significant association between the Waist-to-Hip Ratio (WHR) and LH with infertility in the obese infertile group. These results are likely to contribute to a better understanding of the causes of male infertility and its association with obesity.

In vitro modelling of the influence of alternative feeds (Hermetia illucens, Arthrospira platensis) on the resistance of different rainbow trout populations (Oncorhynchus mykiss) against the viral haemorrhagic septicaemia virus and Yersinia ruckeri

Replacing fishmeal, a finite resource with high market demand, in the diet of carnivorous rainbow trout with proteins from alternative sources may be a challenge for these fish. Therefore, this study investigated whether replacing fishmeal with protein derived from Hermetia illucens or Arthrospira platensis could promote disease susceptibility in local trout populations with different growth performance. This was assessed in vitro by measuring susceptibility to infection with the viral haemorrhagic septicaemia virus (VHSV) or the bacterium Yersinia ruckeri. Analysis of fin tissue explants and primary cell cultures from scales from the three trout populations infected in vitro with VHSV and gill explants infected with Y. ruckeri showed no significant differences in virus replication or bacterial counts. Evaluation of the virucidal or bactericidal effect of skin mucus showed a significant reduction in viral load and bacterial count for all samples with mucus addition, but no significant difference was observed between the experimental groups. This study documents no apparent impairment of innate immune mechanisms in the skin and gills of trout after feeding a diet replacing fishmeal with Arthrospira or Hermetia proteins. This underlines the potential of these alternative protein sources for the further development of sustainable trout aquaculture.

High-Density Lipoproteins: A Role in Inflammation in COPD

Chronic obstructive pulmonary disease (COPD) is a widespread disease associated with high rates of disability and mortality. COPD is characterized by chronic inflammation in the bronchi as well as systemic inflammation, which contributes significantly to the clinically heterogeneous course of the disease. Lipid metabolism disorders are common in COPD, being a part of its pathogenesis. High-density lipoproteins (HDLs) are not only involved in lipid metabolism, but are also part of the organism's immune and antioxidant defense. In addition, HDL is a versatile transport system for endogenous regulatory agents and is also involved in the removal of exogenous substances such as lipopolysaccharide. These functions, as well as information about lipoprotein metabolism disorders in COPD, allow a broader assessment of their role in the pathogenesis of heterogeneous and comorbid course of the disease.

Circadian regulation of apolipoprotein gene expression affects testosterone production in mouse testis

The circadian clock system plays an important role in regulating testosterone synthesis in mammals. Male Bmal1^-/- mice are infertile with low serum testosterone levels and decreased expression of testicular steroidogenic genes, suggesting that circadian clock genes regulate testosterone biosynthesis by activating steroidogenic gene transcription. However, whether the circadian clock regulates testosterone production via other genes remains unknown. Using Bmal1^-/- mice and their wild-type (WT) siblings, we aimed to identify additional genes by which the circadian clock regulates testosterone synthesis. WT and Bmal1^-/- mouse testes sections had similar normal morphologies, although there was a decrease in testicular spermatozoa in the Bmal1^-/- mice. Low serum testosterone levels were detected in the Bmal1^-/- mice. RNA sequencing identified 37 and 48 genes that were differentially expressed between WT and Bmal1^-/- mouse testes at circadian time (CT2 and CT14), respectively. The cholesterol metabolism pathway was significantly enriched in the KEGG pathway analysis, and there was lower expression of three apolipoprotein genes (Apoa1, Apoa2, and Apoc3) at CT2 in the testes of Bmal1^-/- mice than in those of WT mice. These decreases in Apoa1, Apoa2, and Apoc3 expression were verified by quantitative polymerase chain reaction analysis, which also revealed downregulation of the expression of the circadian clock (Per2, Dbp, and Nr1d1) and steroidogenic (StAR, Cyp11a1, and Hsd17b3) genes. The expression of circadian clock genes was relatively stable in WT mice over a 20-h period, whereas there was clear circadian rhythmic expression of Apoa1, Apoa2, Apoc3, StAR, Cyp11a1, Hsd3b2, and Hsd17b3. Bmal1^-/- mice showed severely reduced expression of testicular circadian clock genes at three time points (CT4, CT12, and CT20), and a reduction in mRNA expression levels of Apo (Apoa1, Apoa2, and Apoc3) and steroidogenic (StAR, Cyp11a1, Hsd3b2, and Hsd17b3) genes. Oil Red O staining showed decreased lipid aggregation in the Leydig cells of Bmal1^-/- mouse testes. Considering the vital role of Apo genes in high-density lipoprotein formation and cholesterol transport, the present data suggest that the circadian clock system regulates testosterone production by orchestrating the rhythmic expression of Apo genes. These data extend our understanding of the role of the circadian clock in regulating testosterone production in mammals.

Deciphering influences of testosterone and dihydrotestosterone on lipid metabolism genes using brown trout primary hepatocytes

Despite of physiological and toxicological relevance, the potential of androgens to influence fish lipid metabolism remains poorly explored. Here, brown trout primary hepatocytes were exposed to six concentrations (1 nM to 100 μM) of dihydrotestosterone (DHT) and testosterone (T), to assess changes in the mRNA levels of genes covering diverse lipid metabolic pathways. Acsl1, essential for fatty acid activation, was up-regulated by T and DHT, whereas the lipogenic enzymes FAS and ACC were up-regulated by the highest (100 μM) concentration of T and DHT, respectively. ApoA1, the major component of high-density lipoprotein (HDL), was down-regulated by both androgens. PPARγ, linked to adipogenesis and peroxisomal β-oxidation, was down-regulated by T and DHT, while Acox1-3I, rate-limiting in peroxisomal β-oxidation, was down-regulated by T. Fabp1, StAR and LPL were not altered. Our findings suggest that androgens may impact on lipid transport, adipogenesis and fatty acid β-oxidation and promote lipogenesis in fish liver.

Antiviral Actions of 25-Hydroxycholesterol in Fish Vary With the Virus-Host Combination

Cholesterol is essential for building and maintaining cell membranes and is critical for several steps in the replication cycle of viruses, especially for enveloped viruses. In mammalian cells virus infections lead to the accumulation of the oxysterol 25-hydroxycholesterol (25HC), an antiviral factor, which is produced from cholesterol by the cholesterol 25 hydroxylase (CH25H). Antiviral responses based on CH25H are not well studied in fish. Therefore, in the present study putative genes encoding for CH25H were identified and amplified in common carp and rainbow trout cells and an HPLC-MS method was applied for determination of oxysterol concentrations in these cells under virus infection. Our results give some evidence that the activation of CH25H could be a part of the antiviral response against a broad spectrum of viruses infecting fish, in both common carp and rainbow trout cells in vitro. Quantification of oxysterols showed that fibroblastic cells are capable of producing 25HC and its metabolite 7α,25diHC. The oxysterol 25HC showed an antiviral activity by blocking the entry of cyprinid herpesvirus 3 (CyHV-3) into KFC cells, but not spring viremia of carp virus (SVCV) or common carp paramyxovirus (Para) in the same cells, or viral haemorrhagic septicaemia virus (VHSV) and infectious pancreatic necrosis virus (IPNV) into RTG-2 cells. Despite the fact that the CH25H based antiviral response coincides with type I IFN responses, the stimulation of salmonid cells with recombinant type I IFN proteins from rainbow trout could not induce ch25h_b gene expression. This provided further evidence, that the CH25H-response is not type I IFN dependent. Interestingly, the susceptibility of CyHV-3 to 25HC is counteracted by a downregulation of the expression of the ch25h_b gene in carp fibroblasts during CyHV-3 infection. This shows a unique interplay between oxysterol based immune responses and immunomodulatory abilities of certain viruses.

Health Surveillance of Wild Brown Trout (Salmo trutta fario) in the Czech Republic Revealed a Coexistence of Proliferative Kidney Disease and Piscine Orthoreovirus-3 Infection

The population of brown trout (Salmo trutta fario) in continental Europe is on the decline, with infectious diseases confirmed as one of the causative factors. However, no data on the epizootiological situation of wild fish in the Czech Republic are currently available. In this study, brown trout (n = 260) from eight rivers were examined for the presence of viral and parasitical pathogens. Salmonid alphavirus-2, infectious pancreatic necrosis virus, piscine novirhabdovirus (VHSV) and salmonid novirhabdovirus (IHNV) were not detected using PCR. Cell culturing showed no viruses as well, and serological analysis of 110 sera did not detect any specific antibodies against VHSV or IHNV. Fish from two rivers were positive for the presence of piscine orthoreovirus-3 (PRV-3), subtype PRV-3b. However, none of the PRV-3-positive fish showed gross pathologies typically associated with PRV infections. By far the most widespread pathogen was Tetracapsuloides bryosalmonae which was confirmed in each of the examined locations, with a prevalence of up to 65% and 100%, as established by immunohistochemistry and PCR, respectively. Furthermore, up to 43.8% of fish showed signs of proliferative kidney disease caused by T. bryosalmonae, suggesting that this parasite is a main health challenge for brown trout in the Czech Republic.

Gain and loss events in the evolution of the apolipoprotein family in vertebrata

Background

Various apolipoproteins widely distributed among vertebrata play key roles in lipid metabolism and have a direct correlation with human diseases as diagnostic markers. However, the evolutionary progress of apolipoproteins in species remains unclear. Nine human apolipoproteins and well-annotated genome data of 30 species were used to identify 210 apolipoprotein family members distributed among species from fish to humans. Our study focused on the evolution of nine exchangeable apolipoproteins (ApoA-I/II/IV/V, ApoC-I~IV and ApoE) from Chondrichthyes, Holostei, Teleostei, Amphibia, Sauria (including Aves), Prototheria, Marsupialia and Eutheria.

Results

In this study, we reported the overall distribution and the frequent gain and loss evolutionary events of apolipoprotein family members in vertebrata. Phylogenetic trees of orthologous apolipoproteins indicated evident divergence between species evolution and apolipoprotein phylogeny. Successive gain and loss events were found by evaluating the presence and absence of apolipoproteins in the context of species evolution. For example, only ApoA-I and ApoA-IV occurred in cartilaginous fish as ancient apolipoproteins. ApoA-II, ApoE, and ApoC-I/ApoC-II were found in Holostei, Coelacanthiformes, and Teleostei, respectively, but the latter three apolipoproteins were absent from Aves. ApoC-I was also absent from Cetartiodactyla. The apolipoprotein ApoC-III emerged in terrestrial animals, and ApoC-IV first arose in Eutheria. The results indicate that the order of the emergence of apolipoproteins is most likely ApoA-I/ApoA-IV, ApoE, ApoA-II, ApoC-I/ApoC-II, ApoA-V, ApoC-III, and ApoC-IV.

Conclusions

This study reveals not only the phylogeny of apolipoprotein family members in species from Chondrichthyes to Eutheria but also the occurrence and origin of new apolipoproteins. The broad perspective of gain and loss events and the evolutionary scenario of apolipoproteins across vertebrata provide a significant reference for the research of apolipoprotein function and related diseases.

Involvement of apolipoprotein A in maintaining tissue fluid balance in goldfish Carassius auratus

Mammalian plasma proteins play a key role in maintaining tissue fluid balance because they are retained within capillaries and thus create colloid osmotic pressure. Likewise, fish plasma contain a considerable concentration oligomeric proteins which likely serve a similar role. To elucidate the functions of these oligomeric proteins, we analyzed blood serum (BS) and interstitial fluid (IF) complexes in goldfish from the wild and under experimental conditions using 2D electrophoresis and matrix-assisted laser desorption/ionization (MALDI). We detected protein compounds with MWs ranging from 50 to 155 kDa, organized as oligomeric complexes. The protein compounds consisted of apolipoproteins АроА-I and Аро-14 which are homological to mammalian АроА-I and АроА-II, respectively. The 155-kDa and 50-125-kDa oligomer complexes were located very low-density lipoproteins (LDL) and high-density lipoproteins (HDL) areas on the BS/IF proteomic maps, respectively. The latter resembled mammalian HDL plasma particles by size and contained lipids, so we considered them as HDL particle populations. Investigation of the uniform dissociation/association mechanism for HDL and LDL oligomers in goldfish, from the wild and under critical salinity conditions, showed the "125/110 → 85/60 kDa" reorganization. This was associated with overcoming physiological stress during spawning and under critical salinity conditions. Opposite reorganization "85/60 → 125/110 kDa" was associated with restoration of metabolic processes after stress. The association/dissociation reorganizations promoted equilibration of BS and IF osmolarities in all fish groups. We discuss the connection of these reorganizations with total protein distribution across the capillary wall and salinity, as well as the role of oligomeric apolipoproteins as universal metabolic regulators.

Study of the plasma proteome of Atlantic cod (Gadus morhua): Changes due to crude oil exposure

Oil contamination is an environmental issue of great concern and the necessity for background studies and monitoring programs to continuously evaluate the levels of oil pollution is required. In this study, Atlantic cod (Gadus morhua) were exposed to dispersed crude oil for 1 and 4 weeks to simulate environmental contamination. Fractionated plasma samples were then analysed by tandem mass spectrometry. In total, 717 proteins were identified and 10 new protein biomarker candidates were found. The significant proteome changes were related to the immune response by alterations in the levels of specific immunoglobulins, alpha-2-macroglobulin and galectin-3-binding proteins. After 4 weeks of oil exposure, a lowered level of a NLRC3-like protein was also observed. The results from this study provide insight into the Atlantic cod plasma proteome and into the toxicological effects and potential response mechanisms of short and long-term exposure to crude oil.

Identification of differentially expressed proteins in testicular semen of sex-reversed female (XX) and normal male (XY) rainbow trout

Masculinized females, named sex-reversed females (SRF), have a male phenotype but retain the female genotype (XX) and all spermatozoa produced in their testes carry the X chromosome. Masculinization of females leads to incomplete testicular development and the production of lower-quality semen. The mechanism of masculinization is unknown at present. Therefore, the aim of our study was to identify differentially abundant proteins in testicular semen of normal males and SRF using a difference in-gel electrophoresis approach. Masculinization seemed to not lead to significant changes in the testicular seminal plasma proteome, but did have an impact on the proteome of SRF and normal male sperm. We identified 26 proteins enriched ( < 0.05) in testicular male spermatozoa compared to SRF. A total of 28 proteins were also found to be differentially expressed ( < 0.05) in testicular SRF sperm in comparison to normal males. Bioinformatic analysis highlighted pathways associated with energy production for normal male spermatozoa and pathways related to protein remodeling for SRF sperm. Normal male spermatozoa seemed to be equipped with proteins participating in diverse metabolic pathways, focusing on producing the energy required for sperm movement. On the other hand, SRF spermatozoa were characterized by the enhanced expression of proteins associated with cytoskeletal structures and those related to remodeling, which could indicate that spermatogenesis and spermiogenesis are not fully accomplished. These results can be the basis for further research on the molecular mechanisms of masculinization and toward the development of a method for separating X and Y fish sperm.

Study of the plasma proteome of Atlantic cod (Gadus morhua): Effect of exposure to two PAHs and their corresponding diols

Occurrence of polycyclic aromatic hydrocarbon (PAH) contamination in the marine environment represents a risk to marine life and humans. In this study, plasma samples from Atlantic cod (Gadus morhua) were analysed by shotgun mass spectrometry to investigate the plasma proteome in response to exposure to single PAHs (naphthalene or chrysene) and their corresponding metabolites (dihydrodiols). In total, 369 proteins were identified and ranked according to their relative abundance. The levels of 12 proteins were found significantly altered in PAH exposed fish and are proposed as new biomarker candidates. Eleven proteins were upregulated, primarily immunoglobulin components, and one protein was downregulated (antifreeze protein type IV.) The uniformity of the upregulated proteins suggests a triggered immune response in the exposed fish. Overall, the results provide valuable knowledge for future studies of the Atlantic cod plasma proteome and generate grounds for establishing new plasma protein biomarkers for environmental monitoring of PAH related exposure.

Aeromonas salmonicida type III secretion system-effectors-mediated immune suppression in rainbow trout (Oncorhynchus mykiss)

Aeromonas salmonicida subsp. salmonicida, the etiologic agent of furunculosis, is a major pathogen in aquaculture. Together with other pathogens, it is characterized by the presence of a type 3 secretion system (T3SS). The T3SS is the main virulence mechanism of A. salmonicida. It is used by the bacterium to secrete and translocate several toxins and effector proteins into the host cell. Some of these factors have a detrimental impact on the integrity of the cell cytoskeleton, likely contributing to impair phagocytosis. Furthermore, it has been suggested that effectors of the T3SS are able to modulate the host's immune response. Here we present the first partial characterization of the immune response in rainbow trout (Oncorhynchus mykiss) infected with distinct strains of A. salmonicida either carrying (i) a fully functional T3SS or (ii) a functionally impaired T3SS or (iii) devoid of T3SS ("cured" strain). Infection with an A. salmonicida strain either carrying a fully functional or a secretion-impaired T3SS was associated with a strong and persistent immune suppression. However, the infection appeared to be fatal only in the presence of a fully functional T3SS. In contrast, the absence of T3SS was neither associated with immune suppression nor fish death. These findings suggest that the T3SS and T3SS-delivered effector molecules and toxins of A. salmonicida do not only impair the host cells' cytoskeleton thus damaging cell physiology and phagocytosis, but also heavily affect the transcription of critical immune mediators including the shut-down of important warning signals to recognize infection and induce immune defense.

Identification of differentially expressed genes in the spleens of polyriboinosinic polyribocytidylic acid (poly I:C)-stimulated yellow catfish Pelteobagrus fulvidraco

The yellow catfish, Pelteobagrus fulvidraco (Siluriformes: Bagridae) is an economically important fish in China. However, genomic research and resources on this species are largely unavailable and still in infancy. In the present study, we constructed a cDNA library following poly I:C injection to screen for immune response genes in the spleens of P. fulvidraco using suppression subtractive hybridization (SSH). A total of 420 putative expressed sequence tag (EST) clones were identified at 24 h post-injection, which contain 103 genes consisting of 25 immune response genes, 12 cytoskeleton genes, 7 cell cycle and apoptosis genes, 7 respiration and energy metabolism genes, 7 transport genes, 26 metabolism genes, 10 stress response genes, 9 translational regulation genes, and 71 unknown genes. Real-time quantitative reverse transcription-PCR (qRT-PCR) results revealed that a set of randomly selected immune response genes were identified to be up-regulated after 24 h of poly I:C stimulation compared to controls. Our study provides an annotation of immune genes in detail and insight into fish immunity.

Apolipoprotein A-I in Labeo rohita: Cloning and functional characterisation reveal its broad spectrum antimicrobial property, and indicate significant role during ectoparasitic infection

Apolipoprotein A-I (ApoA-I) is the most abundant and multifunctional high-density lipoprotein (HDL) having a major role in lipid transport and potent antimicrobial activity against a wide range of microbes. In this study, a complete CDS of 771 bp of Labeo rohita (rohu) ApoA-I (LrApoA-I) encoding a protein of 256 amino acids was amplified, cloned and sequenced. Tissue specific transcription analysis of LrApoA-I revealed its expression in a wide range of tissues, with a very high level of expression in liver and spleen. Ontogenic study of LrApoA-I expression showed presence of transcripts in milt and 3 h post-fertilization onwards in the larvae. The expression kinetics of LrApoA-I was studied upon infection with three different types of pathogens to elucidate its functional significance. Its expression was found to be up-regulated in the anterior kidney of L. rohita post-infection with Aeromonas hydrophila. Similarly following poly I:C (poly inosinic:cytidylic) stimulation, the transcript levels increased in both the anterior kidney and liver tissues. Significant up-regulation of LrApoA-I expression was observed in skin, mucous, liver and anterior kidney of the fish challenged with the ectoparasite Argulus siamensis. Immunomodulatory effect of recombinant LrApoA-I (rApoA-I) produced in Escherichia coli was demonstrated against A. hydrophila challenge in vivo. L. rohita administered with rApoA-I at a dose of 100 μg exhibited significantly higher protection (∼55%) upon challenge with A. hydrophila 12 h post-administration of the protein, in comparison to that observed in control group, along with higher level of expression of immune-related genes. The heightened expression of ApoA-I observed post-infection reflected its involvement in immune responses against a wide range of infections including bacterial, viral as well as parasitic pathogens. Our results also suggest the possibility of using rApoA-I as an immunostimulant, particularly rendering protection against A. hydrophila.