Involvement of VAMP-2 in exocytosis of IL-1β in turbot (Scophthalmus maximus) leukocytes after Vibrio anguillarum infection

Proteomics of the haemolymph of the terrestrial crustacean Porcellio scaber reveals components of its innate immunity under baseline conditions

The terrestrial crustacean Porcellio scaber is an established test organism in environmental research. We analysed the haemolymph proteome of P. scaber using a classical proteomic approach based on one-dimensional gel electrophoresis and tandem mass spectrometry. Using a publicly available protein database and our P. scaber transcriptome data, we have identified 76 proteins involved in cytoskeleton formation, protein degradation, vesicular transport, genetic information processing, detoxification, carbohydrate and lipid metabolism reflecting haemocyte metabolic activity, active intracellular transport, and intercellular communication. Compared with the data reported for other crustaceans, 28 of these P. scaber proteins have been linked to its immunity, among them hemocyanin, α-2-macroglobulin, phenoloxidase 3, superoxide dismutase, glutathione S-transferase, haemolymph clottable protein, and histones H4 and H2B. Our results thus provide a firm base for studying the innate immune response of P. scaber at the level of the haemolymph proteome. This knowledge is of particular importance in ecotoxicity studies with various environmental stressors where understanding physiological changes is important to reveal possible modes of action.

A Bioactive Extract Rich in Triterpenic Acid and Polyphenols from Olea europaea Promotes Systemic Immunity and Protects Atlantic Salmon Smolts Against Furunculosis

In the present study, the modulation of the transcriptional immune response (microarray analysis) in the head kidney (HK) of the anadromous fish Atlantic salmon (Salmo salar) fed a diet supplemented with an olive fruit extract (AQUOLIVE^®) was evaluated. At the end of the trial (133 days), in order to investigate the immunomodulatory properties of the phytogenic tested against a bacterial infection, an in vivo challenge with Aeromonas salmonicida was performed. A total number of 1,027 differentially expressed genes (DEGs) (805 up- and 222 downregulated) were found when comparing the transcriptomic profiling of the HK from fish fed the control and AQUOLIVE^® diets. The HK transcripteractome revealed an expression profile that mainly favored biological processes related to immunity. Particularly, the signaling of i-kappa B kinase/NF-kappa and the activation of leukocytes, such as granulocytes and neutrophils degranulation, were suggested to be the primary actors of the innate immune response promoted by the tested functional feed additive in the HK. Moreover, the bacterial challenge with A. salmonicida that lasted 12 days showed that the cumulative survival was higher in fish fed the AQUOLIVE^® diet (96.9 ± 6.4%) than the control group (60.7 ± 13.5%). These results indicate that the dietary supplementation of AQUOLIVE^® at the level of 0.15% enhanced the systemic immune response and reduced the A. salmonicida cumulative mortality in Atlantic salmon smolts.

Hepcidin Gene Cloning and Expression Pattern in Turbot (Scophthalmus maximus) after Vibrio. anguillarum Infection

BACKGROUND

Antimicrobial peptides play crucial roles in organisms as the first line of defense against invading pathogens.

OBJECTIVE

To isolate the hepcidin (hepc1) gene from the liver of turbot (Scophthalmus maximus) challenged with Vibrio anguillarum (GenBank accession number: AM113708), characterize it, and assess its expression level in various tissues.

MATERIALS AND METHODS

The DNA sequence of hepcidin from S. maximus was determined from the total RNA extracted and reverse transcribed from this fish. The expression levels of tissue-specific hepcidin transcripts were determined using reverse-transcriptase polymerase chain reactions.

RESULTS

Hepcidin levels increased in the livers, head kidneys and spleens of the fish. The transcriptional increase was especially noticeable in the liver after bacterial infection commencement. The presence of hepcidin and interleukin-beta (IL-1β) in blood leukocytes was compared at the transcription level and hepcidin transcripts were detected earlier than IL-1β transcripts after infection, indicating that hepcidin might serve as the first line of defense to kill bacteria and may also play a more direct and effective role than that of IL-1β during the initial stage of the innate immune response when turbot are exposed to bacteria invasion.

CONCLUSIONS

Hepcidin might serve as the first line of defense to kill bacteria and may also play a more direct and effective role than that of IL-1β during the initial stage of the innate immune response when turbot are exposed to bacteria invasion.

Scophthalmus maximus interleukin-1β limits Edwardsiella piscicida colonization in vivo

Interleukine-1β (IL-1β) is the first identified pro-inflammatory cytokine, which is cleaved by caspase-1 following the inflammasomes activation, playing critical roles in innate immunity. However, few studies have been performed to characterize the IL-1β in lower vertebrates. Herein, we distinguished the Scophthalmus maximus IL-1β (SmIL-1β) from three IL-1β like sequences and found that SmIL-1β was cleaved by S. maximus caspase at a non-conserved Asp⁸⁶, then targeted to the plasma membrane. Moreover, during the immersion infection of Edwardsiella piscicida, we found that E. piscicida were mainly colonized in gills at early time points and invaded to systemic sites after 5 days post infection, which was consistent with the dynamic up-regulated transcription of SmIL-1β. Furthermore, knockdown of SmIL-1β promotes the bacterial colonization in gills at early time points and result into systemic colonization, while overexpression of SmIL-1β hampers the bacterial colonization in both spleen and kidney. Taken together, these data provide new insights into the molecular mechanisms of SmIL-1β and reveal its role in limiting bacterial infection in vivo, which will support the idea for better understanding the evolutionary of IL-1β functions in teleost.

Lysosome fusion to the cell membrane is mediated by the dysferlin C2A domain in coronary arterial endothelial cells

Dysferlin has recently been reported to participate in cell membrane repair in muscle and other cells through lysosome fusion. Given that lysosome fusion is a crucial mechanism that leads to membrane raft clustering, the present study attempted to determine whether dysferlin is involved in this process and its related signalling, and explores the mechanism underlying dysferlin-mediated lysosome fusion in bovine coronary arterial endothelial cells (CAECs). We found that dysferlin is clustered in membrane raft macrodomains after Fas Ligand (FasL) stimulation as detected by confocal microscopy and membrane fraction flotation. Small-interfering RNA targeted to dysferlin prevented membrane raft clustering. Furthermore, the translocation of acid sphingomyelinase (ASMase) to membrane raft clusters, whereby local ASMase activation and ceramide production--an important step that mediates membrane raft clustering--was attenuated. Functionally, silencing of the dysferlin gene reversed FasL-induced impairment of endothelium-dependent vasodilation in isolated small coronary arteries. By monitoring fluorescence quenching or dequenching, silencing of the dysferlin gene was found to almost completely block lysosome fusion to plasma membrane upon FasL stimulation. Further studies to block C2A binding and silencing of AHNAK (a dysferlin C2A domain binding partner), showed that the dysferlin C2A domain is required for FasL-induced lysosome fusion to the cell membrane, ASMase translocation and membrane raft clustering. We conclude that dysferlin determines lysosome fusion to the plasma membrane through its C2A domain and it is therefore implicated in membrane-raft-mediated signaling and regulation of endothelial function in coronary circulation.

SNARE-mediated rapid lysosome fusion in membrane raft clustering and dysfunction of bovine coronary arterial endothelium

The present study attempted to evaluate whether soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) mediate lysosome fusion in response to death receptor activation and contribute to membrane raft (MR) clustering and consequent endothelial dysfunction in coronary arterial endothelial cells. By immunohistochemical analysis, vesicle-associated membrane proteins 2 (VAMP-2, vesicle-SNAREs) were found to be abundantly expressed in the endothelium of bovine coronary arteries. Direct lysosome fusion monitoring by N-(3-triethylammoniumpropyl)-4-[4-(dibutylamino)styryl]pyridinium dibromide (FM1-43) quenching demonstrated that the inhibition of VAMP-2 with tetanus toxin or specific small interfering ribonucleic acid (siRNA) almost completely blocked lysosome fusion to plasma membrane induced by Fas ligand (FasL), a well-known MR clustering stimulator. The involvement of SNAREs was further confirmed by an increased interaction of VAMP-2 with a target-SNARE protein syntaxin-4 after FasL stimulation in coimmunoprecipitation analysis. Also, the inhibition of VAMP-2 with tetanus toxin or VAMP-2 siRNA abolished FasL-induced MR clustering, its colocalization with a NADPH oxidase unit gp91(phox), and increased superoxide production. Finally, FasL-induced impairment of endothelium-dependent vasodilation was reversed by the treatment of bovine coronary arteries with tetanus toxin or VAMP-2 siRNA. VAMP-2 is critical to lysosome fusion in MR clustering, and this VAMP-2-mediated lysosome-MR signalosomes contribute to redox regulation of coronary endothelial function.

Innate immune gene expression in individual zebrafish after Listonella anguillarum inoculation

Zebrafish were intraperitoneally injected with 10(6)CFU (LD50) Listonella anguillarum. Three inoculated and control fish were collected at 1, 2, 4, 6 and 22h post infection (hpi) and the expression of genes related to the immune response (il1b, cebpb, tfa, mpx, tnfa, nitr9, tlr22, hsc70, cp, mrlp1, c3b and lyz) in each fish was monitored by means of real-time RT-PCR. A similar experiment was performed considering an intermediate time point at 15 hpi. Different relative levels of expression were found among genes. Also, wide interindividual variation in gene expression for most genes was detected among fish, inoculated or not. A steady increase of expression starting from the initial stages of the interaction was found for interleukin-1beta. An initial increase in levels of gene expression was found for the genes coding for the CCAAT/Enhancer Binding Protein subunit beta and the Novel Immune-Type Receptor 9, although their levels decreased later on and were indistinguishable from the controls at 22 hpi. Finally, some genes (Transferrin, Myeloid-specific Peroxidase and Tumour Necrosis Factor alpha) were upregulated at 22 hpi. Taken together, our results show an induction in gene expression of genes involved in the inflammatory and immune response upon L. anguillarum infection but also reveal the existence of a wide variation in the levels of expression of the studied genes in the zebrafish population.

Structural analysis of SNARE motifs from sea perch, Lateolabrax japonicus by computerized approaches

Three cDNA sequences encoding four SNARE (N-ethylmaleimide-sensitive fusion protein attachment protein receptors) motifs were cloned from sea perch, and the deduced peptide sequences were analyzed for structural prediction by using 14 different web servers and softwares. The "ionic layer" structure, the three dimensional extension and conformational characters of the SNARE 7S core complex by using bioinformatics approaches were compared respectively with those from mammalian X-ray crystallographic investigations. The result suggested that the formation and stabilization of fish SNARE core complex might be driven by hydrophobic association, hydrogen bond among R group of core amino acids and electrostatic attraction at molecular level. This revealed that the SNARE proteins interaction of the fish may share the same molecular mechanism with that of mammal, indicating the universality and solidity of SNARE core complex theory. This work is also an attempt to get the protein 3D structural information which appears to be similar to that obtained through X-ray crystallography, only by using computerized approaches.