Analysis of apolipoprotein multigene family in spotted sea bass (Lateolabrax maculatus) and their expression profiles in response to Vibrio harveyi infection

Characterization of Myxovirus resistance (Mx) gene from Chinese seabass Lateolabrax maculatus: Insights into the evolution and function of Mx genes

Chinese seabass (Lateolabrax maculatus) stands out as one of the most sought-after and economically significant species in aquaculture within China. Diseases of L. maculatus occur frequently due to the degradation of the germplasm, the aggravation of environmental pollution of water, and the reproduction of pathogenic microorganisms, inflicting considerable economic losses on the Chinese seabass industry. The Myxovirus resistance (Mx) gene plays pivotal roles in the antiviral immune response ranging from mammals to fish. However, the function of the Mx gene in L. maculatus is still unknown. Firstly, the origin and evolutionary history of Mx proteins was elucidated in this study. Subsequently, an Mx gene from L. maculatus (designed as LmMxA gene) was identified, and its functions in combating antiviral and antibacterial threats were investigated. Remarkably, our findings suggested that while Mx group genes were present in chordates, DYN group genes were present in everything from single-celled animals to humans. Furthermore, our investigation revealed that the LmMxA mRNA level increased in the kidney, spleen and liver subsequent to Vibrio anguillarum and poly(I:C) challenged. Immunofluorescence analysis indicated that LmMxA is predominantly localization in the nucleus and the cytoplasm. Notably, the expression of MAVS, IFN1 and Mx1 increased when LmMxA was overexpression within the EPC cells. Moreover, through assessment via cytopathic effect (CPE), virus titer, and antibacterial activity, it becomes evident that LmMxA exerts a dual role in bolstering both antiviral and antibacterial immune responses. These compelling findings laid the foundation for further exploring the mechanism of LmMxA in response to innate immunity of L. maculatus.

Amino Acid-Induced Chemotaxis Plays a Key Role in the Adaptation of Vibrio harveyi from Seawater to the Muscle of the Host Fish

Vibrio harveyi is a normal flora in natural marine habitats and a significant opportunistic pathogen in marine animals. This bacterium can cause a series of lesions after infecting marine animals, in which muscle necrosis and ulcers are the most common symptoms. This study explored the adaptation mechanisms of V. harveyi from the seawater environment to host fish muscle environment. The comprehensive transcriptome analysis revealed dramatic changes in the transcriptome of V. harveyi during its adaptation to the host fish muscle environment. Based on Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, flagellar assembly, oxidative phosphorylation, bacterial chemotaxis, and two-component systems play crucial roles in V. harveyi's adaptation to host fish muscle. A comparison of biological phenotypes revealed that V. harveyi displayed a significant increase in flagellar length, swimming, twitching, chemotaxis, adhesion, and biofilm formation after induction by host fish muscle, and its dominant amino acids, especially bacterial chemotaxis induced by host muscle, Ala and Arg. It could be speculated that the enhancement of bacterial chemotaxis induced by amino acids plays a key role in the adaptation of V. harveyi from seawater to the muscle of the host fish.

Multi-Omics Approaches for Freshness Estimation and Detection of Illicit Conservation Treatments in Sea Bass (Dicentrarchus Labrax): Data Fusion Applications

Fish freshness consists of complex endogenous and exogenous processes; therefore, the use of a few parameters to unravel illicit practices could be insufficient. Moreover, the development of strategies for the identification of such practices based on additives known to prevent and/or delay fish spoilage is still limited. The paper deals with the identification of the effect played by a Cafodos solution on the conservation state of sea bass at both short-term (3 h) and long-term (24 h). Controls and treated samples were characterized by a multi-omic approach involving proteomics, lipidomics, metabolomics, and metagenomics. Different parts of the fish samples were studied (muscle, skin, eye, and gills) and sampled through a non-invasive procedure based on EVA strips functionalized by ionic exchange resins. Data fusion methods were then applied to build models able to discriminate between controls and treated samples and identify the possible markers of the applied treatment. The approach was effective in the identification of the effect played by Cafodos that proved to be different in the short- and long-term and complex, involving proteins, lipids, and small molecules to a different extent.

Identification of antimicrobial peptide genes from transcriptomes in Mandarin fish (Siniperca chuatsi) and their response to infection with Aeromonas hydrophila

Mandarin fish (Siniperca chuatsi) is a valuable freshwater fish species widely cultured in China. Its aquaculture production is challenged by bacterial septicaemia, which is one of the most common bacterial diseases. Antimicrobial peptides (AMPs) play a critical role in the innate immune system of fish, exhibiting defensive and inhibitory effects against a wide range of pathogens. This study aimed to identify the antimicrobial peptide genes in mandarin fish using transcriptomes data obtained from 17 tissue in our laboratory. Through nucleotide sequence alignment and protein structural domain analysis, 15 antimicrobial peptide genes (moronecidin, pleurocidin, lysozyme g, thymosin β12, hepcidin, leap 2, β-defensin, galectin 8, galectin 9, apoB, apoD, apoE, apoF, apoM, and nk-lysin) were identified, of which 9 antimicrobial peptide genes were identified for the first time. In addition, 15 AMPs were subjected to sequence characterization and protein structure analysis. After injection with Aeromonas hydrophila, the number of red blood cells, hemoglobin concentration, and platelet counts in mandarin fish showed a decreasing trend, indicating partial hemolysis. The expression change patterns of 15 AMP genes in the intestine after A. hydrophila infection were examined by using qRT-PCR. The results revealed, marked up-regulation (approximately 116.04) of the hepcidin gene, down-regulation of the piscidin family genes expression. Moreover, most AMP genes were responded in the early stages after A. hydrophila challenge. This study provides fundamental information for investigating the role of the different antimicrobial peptide genes in mandarin fish in defense against A. hydrophila infection.

Macrophage-specific deletion of MIC26 (APOO) mitigates advanced atherosclerosis by increasing efferocytosis

BACKGROUND AND AIMS

Recent studies have suggested that MIC26 (apolipoprotein O, APOO), a novel mitochondrial inner membrane protein, is involved in inflammation. Thus, the role of macrophage MIC26 in acute inflammation and chronic inflammatory disease atherosclerosis was investigated.

METHODS

Macrophage-specific MIC26 knockout mice (MIC26LysM) were generated by crossing Apooflox/flox and LysMcre+/- mice. An endotoxemia mouse model was generated to explore the effects of macrophage MIC26 deficiency on acute inflammation, while an atherosclerosis mouse model was constructed by crossing MIC26LysM mice with Apoe-/- mice and challenged with a Western diet. Atherosclerotic plaques, primary macrophage function, and mitochondrial structure and function were analyzed.

RESULTS

MIC26 knockout did not affect the median survival time and post-injection serum interleukin 1β concentrations in mice with endotoxemia. Mice with MIC26 deficiency in an Apoe-/- background had smaller atherosclerotic lesions and necrotic core than the control group. In vitro studies found that the loss of MIC26 did not affect macrophage polarization, apoptosis, or lipid handling capacity, but increased efferocytosis (the ability to clear apoptotic cells). An in situ efferocytosis assay of plaques also showed that the ratio of macrophage-associated apoptotic cells to free apoptotic cells was higher in the MIC26-deficient group than in the control group, indicating increased efferocytosis. In addition, an in vivo thymus efferocytosis assay indicated that MIC26 deletion promoted efferocytosis. Mechanistically, the loss of MIC26 resulted in an abnormal mitochondrial inner membrane structure, increased mitochondrial fission, and decreased mitochondrial membrane potential. Loss of MIC26 reduced mitochondria optic atrophy type 1 (OPA1) protein, and OPA1 silencing in macrophages promoted efferocytosis. Overexpression of OPA1 abolished the increase in efferocytosis produced by MIC26 deficiency.

CONCLUSIONS

Macrophage MIC26 deletion alleviated advanced atherosclerosis and necrotic core expansion by promoting efferocytosis. This mechanism may be related to the increased mitochondrial fission caused by reduced mitochondrial OPA1.

Acute septicemia and immune response of spotted sea bass (Lateolabrax maculatus) to Aeromonas veronii infection

A previous study confirmed that spotted sea bass (Lateolabrax maculatus), an economically important cultured species in East Asia, is a new host of Aeromonas veronii, which can cause acute death in these fish, but there is little in-depth understanding of this disease. In the present study, the virulence of 10 isolates of A. veronii derived from spotted sea bass was determined. It was found that the 18BJ181 isolate was a virulent strain and led to the fastest death of spotted sea bass. Death was determined to be within in 2-12 h, and resulted in abdominal effusion and varying degrees of hemorrhage in internal organs. Bacterial colonization analysis showed that the bacterial load in the spleen was highest, and was up to 3.1 × 10⁵ cfu g^-1. In addition, the bacteria proliferated massively in the blood and reached 2.4 × 10⁷ cfu mL^-1 at 12 h after 18BJ181 strain infection, which was also a typical feature of acute septicemia. Histopathology of the spleen revealed edema in interstitial tissue, degeneration, and necrosis in lymphoid tissue, and hemorrhage in the capillary network. Transcriptome analysis of the spleen showed that the expression level of HSP70, CCL19, and IL-1β was extremely significantly up-regulated at 8 h after infection (P < 0.01), and the expression of these genes was normal at 24 h. These results revealed that A. veronii infection could rapidly activate the chemokine signal pathway and stimulate the acute inflammatory response in the host. The bacterial colonization, pathological features, and gene expression patterns in immune pathways will help us to better understand acute septicemia in spotted sea bass caused by A. veronii.

Effect of temperature on the toxicokinetics and gene expression of the pacific cupped oyster Crassostrea gigas exposed to cadmium

In this study, we investigated the influence of temperature on the bioaccumulation and depuration of Crassostrea gigas exposed to Cd associated with its molecular responses. Oysters were acclimatized to different temperatures (10 °C, 15 °C, 20 °C, 25 °C, and 30 °C) for 14 d and then exposed to 10 μg/L Cd for 28 d, followed by a depuration period of 35 d. Oysters were sampled for chemical analysis by inductively coupled plasma mass spectrometry (ICP-MS) and for mRNA quantification by qPCR. In the digestive gland, gill, and mantle, the cadmium concentration at 10 °C was significantly lower than that at 25 °C and 30 °C in both the whole experiments. The use of a two-compartment model showed that the uptake rate k₁ in the above three tissues increased with increasing temperatures ranging from 15 to 25 °C. The fastest elimination rates and shortest half-lives were observed at 15-25 °C. The induction of metallothionein (MT) only occurred in the digestive gland at 15 °C and 20 °C at the end of the accumulation phase. In the mantle and gills, the expression of P-glycoprotein (P-gp) was significantly induced at the end of the accumulation phase and significantly inhibited at the end of the depuration phase. In the digestive gland, the expression of P-gp was induced at the end of both the accumulation and depuration phases. Heat shock protein (hsp70) expression exhibited an overall increasing trend throughout the experiment.

Heterogeneity effects of nanoplastics and lead on zebrafish intestinal cells identified by single-cell sequencing

Plastic particles in water environment can adsorb heavy metals, leading to combined toxicity on aquatic organisms. However, current conclusions are mostly obtained based on cell population-average responses. Heterogeneity effects among cell populations in aquatic organisms remain unclear. This study firstly analyzed the basic toxic effects of 20 μg L^-1, 200 μg L^-1 100 nm polystyrene nanoplastics (PS-NPs), 50 μg L^-1 lead (Pb), and their combined exposures on zebrafish intestine. Results found that combined exposure of 200 μg L^-1 PS-NPs and 50 μg L^-1 Pb induced highest MDA, 8-OHdG, and TNF-α levels. Thus 200 μg L^-1 PS-NPs, 50 μg L^-1 Pb and their combined exposures were chosen to analyze the heterogeneity effects on zebrafish intestine cells by single-cell RNA sequencing. A total of 38,640 zebrafish intestinal cells were obtained and identified as seven cell populations, including enterocytes, macrophages, neutrophils, B cells, T cells, enteroendocrine cells, and goblet cells. 200 μg L^-1 PS-NPs exposure had the greatest influence on macrophages, while Pb exposure mostly influenced enterocytes. Results of MDA, 8-OHdG, and TNF-α analyses indicated that 20 μg L^-1 and 200 μg L^-1 PS-NPs increased the Pb toxicity. However, the scRNA-seq showed that the synergistic effects did not exist in most cell populations, except for goblet cells. Co-exposure of 200 μg L^-1 PS-NPs and Pb caused similar transcriptome profiles with 200 μg L^-1 PS-NPs exposure in macrophages, which changed immunological recognition and apoptosis processes. The Pb exposure influenced the macrophages by direct cytotoxicity. However, the Pb alone and combined exposures induced similar toxicities in the enterocytes, including the generation of oxidative stress and abnormality of lipid metabolism. This study shows the scRNA-seq is a powerful method to identify the target cell populations and corresponding toxic effects during combined exposure of pollutants.

Differential Expression of the Apolipoprotein AI Gene in Spotnape Ponyfish (Nuchequula nuchalis) Inhabiting Different Salinity Ranges at the Top of the Estuary and in the Deep-Bay Area of Gwangyang Bay, South Korea

Spotnape ponyfish (Nuchequula nuchalis) is a dominant species that is broadly distributed from estuarine to deep-bay areas, reflecting a euryhaline habitat. Apolipoprotein AI (ApoAI) is a main component of plasma lipoproteins and has crucial roles in lipid metabolism and the defense immune system. In this study, we characterized the N. nuchalis ApoAI gene and analyzed the expression of the ApoAI transcript in N. nuchalis collected at various sites in the estuary and the deep-bay area which have different salinities. Owing to the fish’s mobility, we conducted stable isotope analyses to confirm the habitat characteristics of N. nuchalis. Carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) from N. nuchalis indicated different feeding sources and trophic levels in the estuarine and deep-bay habitats. The characterized N. nuchalis ApoAI displayed residual repeats that formed a pair of alpha helices, indicating that the protein belongs to the apolipoprotein family. In the phylogenetic analysis, there was no sister group of N. nuchalis ApoAI among the large clades of fish species. The transcriptional expression level of ApoAI was higher in N. nuchalis inhabiting the deep-bay area with a high salinity (over 31 psu) than in N. nuchalis inhabiting the top of the estuary with a low salinity (6~15 psu). In addition, the expression patterns of N. nuchalis ApoAI were positively correlated with environmental factors (transparency, pH, TC, and TIC) in the high salinity area. These results suggest that ApoAI gene expression can reflect habitat characteristics of N. nuchalis which traverse broad salinity ranges and is associated with functional roles of osmoregulation and lipid metabolism for fish growth and development.

Metabolism and antioxidation regulation of total flavanones from Sedum sarmentosum Bunge against high-fat diet-induced fatty liver disease in Nile tilapia (Oreochromis niloticus)

Diet-induced fatty liver is a considerable threaten to fish aquaculture due to the popularity of the high-fat diet (HFD) feeding. Our study aims to investigate the effects of flavanones from Sedum sarmentosum Bunge (FSSB) on the liver function to identify a potential treatment for HFD-induced fatty liver disease. Physiological and pathological indicators were tested in the liver of Nile tilapia (Oreochromis niloticus) and results showed parameters including lipid metabolites, redox parameters, and inflammatory factors could be adequately restored to normal level by addition of 150 mg/kg FSSB to HFD. Proteomics analysis was performed in liver tissues from tilapia with normal diet (ND), HFD, and HFD+FSSB. Totally, 51 upregulated proteins and 77 downregulated proteins were identified in HFD groups and 67 proteins of them were restored after treated with FSSB. Bioinformatics analysis showed that differentially expressed proteins (DEPs) in HFD+FSSB150 group compared with HFD group are mainly enriched in acety-CoA metabolic process, adenosine-triphosphate (ATP) biosynthetic process, lipid metabolic process, and phospholipid metabolic process. The dysregulated proteins were involved in peroxidosome proliferators-activated receptor (PPAR) signaling pathway, fat digestion and absorption, and immune system. The quantitative real-time PCR (qRT-PCR) assay further revealed that the expression of GST, PPARα, PPARγ, and multiple-inflammatory cytokines could be also reversed in HFD group under the treatment of 150 mg/kg FSSB. Our findings demonstrated FSSB is efficient for the treatment of fatty liver disease through regulation of lipid metabolism and antioxidation in Nile tilapia, providing a new treatment of non-alcoholic fatty liver disease (NAFLD) in fish aquaculture.

A First Report of Aeromonas veronii Infection of the Sea Bass, Lateolabrax maculatus in China

The sea bass, Lateolabrax maculatus is commercially farmed in Zhuhai, located in the Guangdong Province of China. L. maculatus in aquaculture have suffered acute death, characterized by ulcerations on the body surface, congestion, and hemorrhage in internal organs such as liver, kidney, and spleen. The dominant infecting strain of bacteria isolated from the kidneys of diseased fish was identified as Aeromonas veronii (strain 18BJ181). This identification was based on analysis of morphological, physiological, and biochemical features, as well as 16S rRNA and gyrB gene sequences. Drug sensitivity testing showed that the strain 18BJ181 isolate was resistant to four antibacterial drugs, including amoxicillin, madinomycin, penicillin and sulfamethoxazole, while moderately sensitive to erythromycin and rifampicin. The detection of growth characteristics showed that the strain 18BJ181 exhibited adaptability to the environment. In addition, some virulence genes, such as aer, act, gcaT, tapA and fla, were detected in the strain 18BJ181. The median lethal dosage of the strain 18BJ181 isolate in L. maculatus was 8.5 × 10⁵ and 4.2 × 10⁵ cfu/g under the conditions of intraperitoneal injection and intramuscular injection, respectively. The experimentally induced infection showed that the 18BJ181 isolate caused considerable histological lesions in L. maculatus, including tissue degeneration, necrosis, and different degrees of hemorrhage. These results provided evidence for a more comprehensive understanding of A. veronii strain 18BJ181 infection in L. maculatus.

Slc4 Gene Family in Spotted Sea Bass (Lateolabrax maculatus): Structure, Evolution, and Expression Profiling in Response to Alkalinity Stress and Salinity Changes

The solute carrier 4 (SLC4) family is a class of cell membranes transporters involved in base transport that plays crucial roles in diverse physiological processes. In our study, 15 slc4 genes were identified and annotated in spotted sea bass, including five members of Cl⁻/HCO₃⁻ exchangers, eight genes coding Na⁺-dependent HCO₃⁻ transporters, and two copies of Na⁺-coupled borate transporters. The gene sequence and structure, chromosomal and syntenic arrangement, phylogenetic and evolution profiles were analyzed. Results showed that the slc4 gene in teleosts obviously expanded compared with higher vertebrates, arising from teleost-specific whole genome duplication event. Most gene sites of slc4 in spotted sea bass were under strong purifying selection during evolution, while positive selection sites were only detected in slc4a1b, slc4a8, and slc4a10b. Additionally, qRT-PCR results showed that different slc4 genes exhibited distinct branchial expression patterns after alkalinity and salinity stresses, of which the strongly responsive members may play essential roles during these physiological processes. Our study provides the systemic overview of the slc4 gene family in spotted sea bass and enables a better understanding for the evolution of this family and further deciphering the biological roles in maintaining ion and acid–base homeostasis in teleosts.

Effects of Vibrio harveyi infection on serum biochemical parameters and expression profiles of interleukin-17 (IL-17) / interleukin-17 receptor (IL-17R) genes in spotted sea bass

Vibrio harveyi is regarded as serious pathogen for marine fishes. To evaluate the physiological responses of spotted sea bass (Lateolabrax maculatus) after V. harveyi infection, four biochemical biomarkers including alanine amino transferase (ALT), albumin (ALB), total protein (TP) and glucose (GLU) were measured in serum. Our results showed that V. harveyi infection significantly influenced the concentration of ALT, ALB and GLU. Additionally, five interleukin-17 (IL-17) and five IL-17 receptors (IL-17R) genes were identified in spotted sea bass and their gene structures were characterized. Furthermore, the expression patterns of IL-17 and IL-17R genes were determined by qPCR in liver, intestine, spleen and head kidney after V. harveyi infection. All IL-17 and IL-17R genes exhibited time- and tissue-dependent expressions. Several tested genes were dramatically induced by V. harveyi treatment, particularly IL-17A/F1 in liver and head kidney, IL-17A/F2 in head kidney, IL-17RC in spleen with more than 10-fold increases, which suggested their potential essential roles against bacterial infection.

Apolipoprotein F: a natural inhibitor of cholesteryl ester transfer protein and a key regulator of lipoprotein metabolism

PURPOSE OF REVIEW

The aim of this study is to highlight recent studies that have advanced our understanding of apolipoprotein F (ApoF) and its role in lipid metabolism.

RECENT FINDINGS

Previous studies showed that ApoF hepatic mRNA levels are suppressed by fat-enriched diets. Recent studies show this downregulation is mediated by agonist-induced binding of liver X receptor (LXR) and PPARalpha to a regulatory element in the ApoF promoter. First-of-kind in-vivo studies show ApoF lowers low-density lipoprotein levels and enhances reverse cholesterol transport in fat-fed hamsters.

SUMMARY

Diverse studies collectively provide compelling evidence that cholesteryl ester transfer protein (CETP) plays an important role in regulating lipid metabolism. Inhibiting CETP raises HDL cholesterol. However, considering the recent failures of pharmacological inhibitors of CETP in clinical trials, it does not seem likely that global inhibition of CETP will be beneficial. ApoF is a minor apolipoprotein that functions as a natural inhibitor of CETP. However, ApoF is not a general inhibitor of CETP, but rather it preferentially inhibits CETP activity with LDL. Therefore, ApoF tailors CETP activity so that less tissue-derived cholesterol traffics from HDL into the LDL compartment. Lower LDL cholesterol levels have recognized clinical benefit for reduced cardiovascular disease.

First High-Density Linkage Map and QTL Fine Mapping for Growth-Related Traits of Spotted Sea bass (Lateolabrax maculatus)

Possessing powerful adaptive capacity and a pleasant taste, spotted sea bass (Lateolabrax maculatus) has a broad natural distribution and is one of the most popular mariculture fish in China. However, the genetic improvement program for this fish is still in its infancy. Growth is the most economically important trait and is controlled by quantitative trait loci (QTL); thus, the identification of QTLs and genetic markers for growth-related traits is an essential step for the establishment of marker-assisted selection (MAS) breeding programs. In this study, we report the first high-density linkage map of spotted sea bass constructed by sequencing 333 F1 generation individuals in a full-sib family using 2b-RAD technology. A total of 6883 SNP markers were anchored onto 24 linkage groups, spanning 2189.96 cM with an average marker interval of 0.33 cM. Twenty-four growth-related QTLs, including 13 QTLs for body weight and 11 QTLs for body length, were successfully detected, with phenotypic variance explained (PVE) ranging from 5.1 to 8.6%. Thirty potential candidate growth-related genes surrounding the associated SNPs were involved in cell adhesion, cell proliferation, cytoskeleton reorganization, calcium channels, and neuromodulation. Notably, the fgfr4 gene was detected in the most significant QTL; this gene plays a pivotal role in myogenesis and bone growth. The results of this study may facilitate marker-assisted selection for breeding populations and establish the foundation for further genomic and genetic studies investigating spotted sea bass.