Effects of neuropeptide Y on the immune-protection and intestinal tract of juvenile Micropterus salmoides.

Neuropeptide Y is known to be directly or indirectly involved in immune regulation. The immune effects of NPY include immune cell transport, helper T cell differentiation, cytokine secretion, staining and killer cell activity, phagocytosis and production of reactive oxygen species. In this study, we investigated the immunoprotective effect of synthetic NPY on largemouth bass larvae. For the first time, the dose and time effects of NPY injection on largemouth bass was explored, and then Poly I:C and LPS infection was carried out in juvenile largemouth bass, respectively, after the injection of NPY. The results showed that NPY could reduce the inflammatory response by inhibiting the expression of il-1ß, tgf-ß, ifn-γ and other immune factors in head kidney, spleen and brain, and alleviate the immune stress caused by strong inflammatory response in the early stage of infection. Meanwhile, NPY injection ameliorated the intestinal tissue damage caused by infection. This study provides a new way to protect juvenile fish and improve its innate immunity.

Immuno-protective effect of neuropeptide Y immersion on the juvenile tilapia infected by Streptococcus agalactiae.

Neuropeptide Y (NPY), an important neurotransmitter, is widely distributed in the nervous systems of vertebrates. Multiple functions of NPY in mammals include the regulation of brain activity, emotion, stress response, feeding, digestion, metabolism and immune function. In the present study, we used synthetic NPY to immerse juvenile tilapia, thus firstly exploring the dose and time effect of this immersion. The results showed that the expression level of y8b and serum glucose increased after NPY immersion. When juvenile tilapia was challenged with Streptococcus agalactiae (S. agalactiae), no matter before or after the administration of NPY-immersion, it was found that NPY immersion could inhibit the expression of il-1ß induced by S. agalactiae in telencephalon, hypothalamus, spleen and head kidney, and then promote the expression of il-10. In addition, NPY-immersion could reduce the activity of serum SOD but increase that of lysozyme, and ameliorate tissue damage in the head kidney and spleen of juvenile tilapia caused by S. agalactiae infection. This study firstly proposes the potential of NPY to be an immune protect factor in juvenile fish, and the results can provide a reference for the application of immersion administration in the immune protection of juvenile fish.

Microarray and metabolome analysis of hepatic response to fasting and subsequent refeeding in zebrafish (Danio rerio).

BACKGROUND: Compensatory growth refers to the phenomenon in which organisms grow faster after the improvement of an adverse environment and is thought to be an adaptive evolution to cope with the alleviation of the hostile environment. Many fish have the capacity for compensatory growth, but the underlying cellular mechanisms remain unclear. In the present study, microarray and nontargeted metabolomics were performed to characterize the transcriptome and metabolome of zebrafish liver during compensatory growth. RESULTS: Zebrafish could regain the weight they lost during 3 weeks of fasting and reach a final weight similar to that of fish fed ad libitum when refed for 15 days. When refeeding for 3 days, the liver displayed hyperplasia accompanied with decreased triglyceride contents and increased glycogen contents. The microarray results showed that when food was resupplied for 3 days, the liver TCA cycle (Tricarboxylic acid cycle) and oxidative phosphorylation processes were upregulated, while DNA replication and repair, as well as proteasome assembly were also activated. Integration of transcriptome and metabolome data highlighted transcriptionally driven alterations in metabolism during compensatory growth, such as altered glycolysis and lipid metabolism activities. The metabolome data also implied the participation of amino acid metabolism during compensatory growth in zebrafish liver. CONCLUSION: Our study provides a global resource for metabolic adaptations and their transcriptional regulation during refeeding in zebrafish liver. This study represents a first step towards understanding of the impact of metabolism on compensatory growth and will potentially aid in understanding the molecular mechanism associated with compensatory growth.

Innate Immune Response to Fasting and Refeeding in the Zebrafish Kidney.

Animals acquire nutrients and energy through feeding to achieve a balance between growth and organismal health. When there is a change in nutrient acquisition, the state of growth changes and may also cause changes in the intrinsic immune system. Compensatory growth (CG), a specific growth phenomenon, involves the question of whether changes in growth can be accompanied by changes in innate immunity. The zebrafish (Danio rerio), a well-known fish model organism, can serve as a suitable model. In this study, the zebrafish underwent 3 weeks of fasting and refeeding for 3 to 7 day periods. It was found that CG could be achieved in zebrafish. Zebrafish susceptibility to Streptococcus agalactiae increased after starvation. In addition, the amount of melano-macrophage centers increased after fasting and the proportion of injured tubules increased after refeeding for 3 and 5 days, respectively. Furthermore, the kidneys of zebrafish suffering from starvation were under oxidative stress, and the activity of several antioxidant enzymes increased after starvation, including catalase, glutathione peroxidases and superoxide dismutase. Innate immune parameters were influenced by starvation. Additionally, the activity of alkaline phosphatase and lysozyme increased after starvation. The mRNA expression of immune-related genes like il-1ß was elevated to a different extent after fasting with or without lipopolysaccharides (LPS) challenge. This study showed that the function of the innate immune system in zebrafish could be influenced by nutrition status.

Molecular identification, tissue distribution and in vitro functional analysis of growth hormone and its receptors in red-spotted grouper (Epinephelus akaara).

Red-spotted grouper (Epinephelus akaara) is one of the high economic value grouper species, however, the knowledge regarding its growth is limited. In this study, full-length cDNAs of growth hormone (gh) and its receptors (ghr1 and ghr2) were cloned from the pituitary and liver of red-spotted grouper, respectively. Tissue distribution analysis showed that gh mRNA was predominantly expressed in the pituitary. ghr1 mRNA was highly expressed in the liver, muscle, fat and gonad, while ghr2 mRNA expression was ubiquitously high in the peripheral tissues. However, the mRNA expression of both ghr isoforms was relatively low in the central nervous system. Secretory recombinant grouper GH (rgGH) was expressed in yeast Pichia pastoris and verified. HEK293T cells transiently transfected with the GHR isoforms were used to elucidate the receptor-mediated signaling pathways related to growth regulation. rgGH activated rapid phosphorylation of Janus kinase 2, signal transducer and activator of transcription 5 (STAT5) and extracellular signal-regulated protein kinase 1/2 through GHR1, but only STAT5 was phosphorylated via GHR2. rgGH strongly activated STAT5 phosphorylation and significantly stimulated ghr1, ghr2 and insulin-like growth factor (igf1, igf2) mRNA expression in primary cultured hepatocytes. Data showed that the recombinant protein rgGH played effects on igf1/2 mRNA expression via GHR-mediated signaling pathways. Our findings provide essential information about GH and GHRs characteristics in red-spotted grouper.