Studies of macrophage cellular response to the extracellular hydrogen peroxide by tilapia model

Dietary Agaricus blazei Spent Substrate Improves Disease Resistance of Nile Tilapia (Oreochromis niloticus) against Streptococcus agalactiae In Vivo

This study evaluated the effects of the feeding of spent mushroom substrate from Agaricus blazei on Nile tilapia (Oreochromis niloticus). The safety of 0–1000 μg/mL A. blazei spent substrate water extract (ABSSE) was demonstrated in the primary hepatic and splenic macrophages and the THK cell line (a cell line with characteristics of melanomacrophages) using a cytotoxicity assay. Here, 10 μg/mL of crude ABSSE promoted the phagocytic activity of macrophages and THK cells. Stimulating ABSSE-primed THK cells with lipopolysaccharides or peptidoglycan resulted in higher expression levels of four cytokine genes (e.g., interleukinz (IL)-1β, IL-12b, IL-8 and tumor necrosis factor α (TNFα)) and one cytokine gene (TNFα), respectively. An in vitro bacterial growth inhibition assay demonstrated that ABSSE could inhibit the growth of Streptococcus agalactiae. In the first feeding trial, Nile tilapia were fed with experimental feed containing 0, 1, or 5% of A. blazei spent substrate (ABSS) for seven and fourteen days followed by bacterial challenge assay. The best result was obtained when Nile tilapia were continuously fed for seven days on a diet containing 1% ABSS, with the survival rate being higher than in groups with 0% and 5% ABSS after challenge with S. agalactiae. In the second trial, fish were fed diets supplemented with 0% or 1% ABSS for seven days, and then all the groups were given the control feed for several days prior to bacterial challenge in order to investigate the duration of the protective effect provided by ABSS. The results showed that the protective effects were sustained at day 7 after the feed was switched. Overall, spent mushroom substrate from A. blazei is a cost-effective feed additive for Nile tilapia that protects fish from S. agalactiae infection.

Sarcodia suieae Acetyl-Xylogalactan Regulates Nile Tilapia (Oreochromis niloticus) Tissue Phagocytotic Activity and Serum Indices

Sarcodia suieae acetyl-xylogalactan was reported to induce macrophage polarisation, and could positively regulate macrophage activation. In this study, we evaluated the effect of Sarcodia suieae acetyl-xylogalactan on the Nile tilapia. First, we assessed the influence of acetyl-xylogalactan on the survival, glucose uptake, and phagocytic activity of tilapia head kidney (THK) melanomacrophage, and observed increased proliferation of these cells in the MTT assay after 12 and 24 h of treatment. Glucose uptake increased in THK melanomacrophage treated with 20 and 30 μg acetyl-xylogalactan for 24 h. Their phagocytic activity was positively enhanced following exposure to acetyl-xylogalactan. Nile tilapia were fed with acetyl-xylogalactan for 4 weeks. At the end of the experiment, Nile tilapia were sacrificed, and the lipopolysaccharide-induced liver and head-kidney apoptosis was examined under reducing conditions in comparison with controls. The phagocytic activities of liver and head-kidney cells were enhanced after 4 weeks of feeding. Blood biochemical analysis revealed a reduction in glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) levels after 4 weeks of feeding. Combined with in vitro and in vivo experiments results, the extracted S. suieae acetyl-xylogalactan could directly induce THK melanomacrophage proliferation, glucose uptake, and phagocytic activity. Acetyl-xylogalactan was able to induce Nile tilapia liver and head-kidney resident macrophage activity, and reduced LPS-induced liver and head-kidney cell apoptosis. S. suieae acetyl-xylogalactan may modulate Nile tilapia macrophage activation by polarising them into M1 macrophages to improve the Nile tilapia nonspecific immune response.

Immunostimulatory effects of Sarcodia suiae water extracts on Nile tilapia Oreochromis niloticus and its resistance against Streptococcus agalactiae

In this study, water extracts of the red seaweed Sarcodia suiae were obtained using solid-liquid extraction (SLE) or pressurized liquid extraction (PLE) methods. The extracts were used to investigate immunostimulatory activity by measuring the phagocytic activity of Nile tilapia (Oreochromis niloticus) hepatic and splenic macrophages and the tilapia head kidney (THK) cell line, and modulation of immune-related genes in primary head kidney (HK) cells and THK cells. At 10 μg/ml, both extracts promoted the proliferation of hepatic and splenic macrophages. Expression levels of proinflammatory cytokines (IL-1β and IL-8), antimicrobial peptides (TP2 and TP4), and pattern recognition receptors (TLR5) were elevated in SLE extracts-treated primary HK leukocytes. Similarly, IL-1β, IL-8, and TNFα expression was also induced by SLE extract in THK cells. Phagocytic activity in primary HK cells and THK cells was induced by SLE extract 12 h and 24 h post-stimulation, while PLE extract only induced phagocytic activity in THK cells at early time points. SLE extract (100 μg/g body weight) increased the expression of IL-1β, IL-8, TNFα, TP2, TP4, TLR2 and TLR5 in the spleen and immunoprotective efficiency against Streptococcus agalactiae infection. Taken together, these results show that S. suiae can differentially stimulate the immune response of tilapia in vitro and in vivo and could potentially be used as an immunomodulator in tilapia culture.

Molecular cloning, pathologically-correlated expression and functional characterization of the colonystimulating factor 1 receptor (CSF-1R) gene from a teleost, Plecoglossus altivelis

Colony-stimulating factor 1 receptor (CSF-1R) is an important regulator of monocytes/macrophages (MO/MΦ). Although several CSF-1R genes have been identified in teleosts, the precise role of CSF- 1R in ayu (Plecoglossus altivelis) remains unclear. In this study, we characterized the CSF-1R homologue from P. altivelis, and named it PaCSF-1R. Multiple sequence alignment and phylogenetic tree analysis showed that PaCSF-1R was most closely related to that of Japanese ricefish (Oryzias latipes). Tissue distribution and expression analysis showed that the PaCSF-1R transcript was mainly expressed in the head kidney-derived MO/MΦ, spleen, and head kidney, and its expression was significantly altered in various tissues upon Vibrio anguillarum infection. After PaCSF-1R neutralization for 48 h, the phagocytic activity of MO/MΦ was significantly decreased, suggesting that PaCSF-1R plays a role in regulating the phagocytic function of ayu MO/MΦ.

Identification and functional characterization of the CSF1R gene from grass carp Ctenopharyngodon idellus and its use as a marker of monocytes/macrophages

Colony-stimulating factor 1 receptor (CSF1R) is an important regulator of monocytes/macrophages (MO/MΦ). Although CSF1R gene has been identified and functionally studied in many fish, the precise role of CSF1R in grass carp (Ctenopharyngodon idellus) remains unclear. In this study, we determined the cDNA sequence of CSF1R (CiCSF1R) from a teleost fish, grass carp. Sequence comparison and phylogenetic tree analysis showed that CiCSF1R was most closely related to the CSF1R of zebrafish. The CiCSF1R transcript was mainly expressed in the spleen, head kidney, and head kidney-derived MO/MΦ, and its expression was altered in various tissues upon Aeromonas hydrophila infection. We prepared antibodies for neutralization of CiCSF1R on grass carp MO/MΦ. CiCSF1R neutralization or knockdown led to anti-inflammatory status in MO/MΦ upon A. hydrophila infection. CiCSF1R neutralization or knockdown also decreased the phagocytic activity of MO/MΦ. Flow cytometric analysis showed that more than 85% of grass carp MO/MΦ were CiCSF1R-positive cells. The percentage of CiCSF1R-positive cells in the head kidney of grass carp was above 10%, whereas it was only 5% and 4% in the spleen and liver, respectively. In conclusion, CSF1R is a specific surface marker of grass carp MO/MΦ, and it regulates the functions of MO/MΦ.