C-type lectin 17A and macrophage-expressed receptor genes are magnified by fungal ß-glucan after Vibrio parahaemolyticus infection in Totoaba macdonaldi cells.

C-type lectins are a principal carbohydrate recognition mechanism as glucans on cell surfaces. This study identified and investigated molecular characterization and immune roles of a novel c-type lectin 17A from Totoaba macdonaldi (TmCLEC17A), which were described in head-kidney leukocytes after immunostimulation with fungal ß-glucan 197A and Vibrio parahaemolyticus infection. This nucleotide sequence from totoaba was acquired using NGS and bioinformatics tools. Its full-length cDNA sequence consisted of 1128 bp (including the stop codon) and an open reading frame (ORF) of 771 bp encoding a 256 amino acid protein, 5´-UTR of 48 bp and 3´-UTR of 309 bp. The TmCLEC17A protein revealed a C-terminal-C-type lectin (CTL, also named carbohydrate-recognition domain, CRD), a N-terminal trans-membrane domain and a coiled coil motif, showing the highest similarity (80%) and identity (96%) with Larimichthys crocea. Fungal ß-glucan 197A plus V. parahaemolyticus enhanced transcriptions of CLEC17A and TLR2 significantly besides the macrophage receptors, such as macrophage mannose receptor 1 and macrophage colony-stimulating factor 1 receptor 2. In addition, natural resistance-associated macrophage protein 2 was significantly up-regulated in leukocytes challenged with live V. parahaemolyticus. Overall, these results indicated that CLEC17A might be implicated in T. macdonaldi innate immunity as a pattern recognition receptor; fungal ß-glucan 197A could stimulate cellular immune mechanisms in head-kidney leukocytes; and it could be used as potential immunostimulant in fish aquaculture.

Characterization of nuclear factor of activated T-cells-c3 (NFATc3) and gene expression of upstream-downstream signaling molecules in response to immunostimulants in Pacific red snapper cells.

The nuclear factor of activated T cells (NFAT) proteins have crucial roles in the development and function of the immune system since they not only regulate activation of T cells but are also involved in the control of thymocyte development and T-cell differentiation. In this study, NFATc3 was characterized from the Pacific red snapper, Lutjanus peru. LpNFAtc3, which contains an open reading of 3300 bp frame coding for a protein of 1100 aa with a predicted molecular weight of 118.52 kDa. The predicted protein showed a conserved NFAT family structure with signature motifs and domains, sharing high identity (up to 76%) compared to other fish sequences. NFATc3 gene expression was analyzed by real time-PCR in head-kidney cells (leukocytes and lymphocytes) following yeast, zymosan and Vibrio parahaemolyticus stimulation along with the expression of upstream (ILF2, ILF3 and CaN) and downstream (CD3, TCRß, IL-6 and IL-12) molecules. This study revealed a broad expression of NFATc3 with a relative strong expression in intestine and lymphocytes. The expression of NFATc3 was differentially up-regulated after stimulation with yeast in head-kidney leukocytes and after bacterial infection in lymphocytes at 24 h. Interestingly, the yeast and zymosan were able to activate ILF2, ILF3 and CaN mRNA gene expression in both kinds of cells. On the other hand, NFAT downstream genes such as CD3, TCRß, IL-6 and IL-12 were significantly up-regulated in leukocytes stimulated with yeast or zymosan at 12 h; however in lymphocytes, this up-regulation was detected when cells reacted to V. parahaemolyticus stimuli at 24 h. Stimulating Pacific red snapper leukocytes with immunostimulants as yeast significantly up-regulated the expression of NFATc3, and up- and down-stream molecular genes and NFATc3 lymphocytes expression were potentially involved in responses to invasion of bacterial pathogens in an early immune response.

Prolactin-induced activation of phagocyte NADPH oxidase in the teleost fish gilthead seabream involves the phosphorylation of p47phox by protein kinase C.

The pituitary hormone prolactin (PRL) is a multifunctional polypeptide which act as a key component of the neuroendocrine-immune loop and as a local regulator of the macrophage response. The involvement of PRL in regulating monocyte/macrophage functions is suggested by the presence of PRL receptors in these cells. Recently, we reported that physiological concentrations of native PRL were able to induce the expression of the pro-inflammatory cytokines IL-1ß and TNFα, and the production of reactive oxygen species (ROS) in head kidney leukocytes and macrophages from the teleost fish gilthead seabream (Sparus aurata L.). In this study, we show that the NADPH oxidase subunit p47phox becomes phosphorylated in leukocytes stimulated with PRL, an effect that is blocked when neutralizing polyclonal antibodies to PRL are added. Additionally, the pharmacological inhibition of either protein kinase C (PKC) with calphostin C or the Jak/Stat signaling pathway with AG490 impaired PKC activation, p47phox phosphorylation and ROS production in seabream leukocytes activated with PRL. Taken together, our results demonstrate for the first time the need for PKC in regulating the PRL-mediated phosphorylation of p47phox, the activation of NADPH oxidase and the production of ROS by macrophages in vertebrates.