BUSCADOR RECOLECTA

The role of hepcidins, antimicrobial peptides involved in iron metabolism, immunity, and inflammation is studied. First, gilthead seabream (Sparus aurata L.) head-kidney leucocytes (HKLs) were incubated with λ-carrageenin to study the expression of hepcidin and iron metabolism-related genes. The expression of most of the genes studied was up-regulated, whereas the ferroportin gene (slc40a) was down-regulated in HKLs incubated with λ-carrageenin. In the second part of the study, seabream specimens were injected with λ-carrageenin or buffer (control). The expression of the same genes was evaluated in the head kidney, liver, and skin at different time points after injection. The expression of Hamp1m, ferritin b and ferroportin genes (hamp1, fthb, and slc40a) was up-regulated in the head kidney of fish from the λ-carrageenin group, while the expression of Hamp2C and Hamp2E genes (hamp2.3 and hamp2.7) was down-regulated. In the liver, the expression of hamp1, ferritin a (ftha), slc40a, Hamp2J and Hamp2D (hamp2.5/6) genes was down-regulated in the λ-carrageenin group. In the skin, the expression of hamp1 and (Hamp2A Hamp2C) hamp2.1/3/4 genes was up-regulated in the λ-carrageenin group. A bioinformatic analysis was performed to predict the presence of transcription factor binding sites in the promoter region of hepcidins. Structural and physicochemical variations were found in the different mature hepcidin peptides. This study sheds light on the poorly understood roles of hepcidins in fish. The results provide insight into the regulatory mechanisms of inflammation in fish and could contribute to the development of new strategies for treat inflammation in farm animals.

Silk fibroin microparticles (SF) were administered in the diet of gilthead seabream with or without experimental skin wounds to study the effects on cellular immunity and liver. A commercial diet was enriched with different SF contents: 0, 50 and 100 mg kg-1 (control, SF50 and SF100 diet, respectively). The animals were fed for 30 days and half of them were sampled. Similar experimental wounds were then performed to the rest of fish and they continued to be fed the same diet. At 7 days post-wounding, samples were taken from the wounded fish. Cellular immunity was studied on head kidney leucocytes (phagocytosis, respiratory and peroxidase content) and liver status (histological study and gene expression) were studied. Our results showed that experimental wounds affect both cellular immunity (by decreasing leucocyte respiratory burst and peroxidase activity) and altered liver histology (by inducing vascularization and congestion of blood vessels). In addition, it affects the expression of genes indicative of oxidative stress, endoplasmic reticulum stress and apoptosis. More specifically, it was the highest dose of silk fibroin (SF100) that significantly increased the phagocytic capacity of leucocytes as well as vascularization in the liver. In addition, increased expression of antioxidant genes (cat and gsr) and decreased expression of genes related to reticulum endoplasmic stress (grp94 and grp170) and apoptosis (nos and jnk) were detected in these fish fed with SF100 and wounded. In conclusion, fed fish with SF100 had many beneficial effects as cellular immunostimulant and hepatoprotection in wounded fish. Its use could be of great interest for stress management in farmed fish conditions.

Carrageenan, a high molecular weight sulphated polysaccharide, has been used in the screening of anti-inflammatory molecules in mammals. In this sense, Chiliadenus glutinosus (L.) Fourr., an endemic species of plant has been reported in the Spanish popular medicine due to their anti-inflammatory properties in humans. However, their properties have poorly been studied in fish. In this assay, different concentrations (0, 0.001, 0.01, 0.125, 0.25, 0.5 and 1 mg mL-1) of aqueous, ethanolic and methanolic extracts of this plant were elaborated, and the antioxidant, bactericidal (against four marine fish pathogen) and cytotoxic activity, as well as several immunological parameters in head-kidney leucocytes (HKLs) of gilthead seabream (Sparus aurata) were evaluated in a first experiment to determinate the extract with the best properties. Our results showed a dose-dependent antioxidant activity of each plant extract increasing with the concentration, a species- and extract-specific bactericidal activity, as well as a cytotoxic activity against the PLHC1 tumour cell line by the ethanolic and methanolic extracts. However, taking into account the cytotoxic effects of these two extracts on HKLs and the strong immunosuppressive effects on the immunological parameters assayed (peroxidase, respiratory burst activity and phagocytic capacity), a second experiment was developed by using only adjusted doses of the aqueous extract (0, 0.25 and 0.5 mg mL-1), in which immune parameters, cell morphology and inflammatory-related genes were studied in HKLs stimulated with λ-carrageenan. The present results offer a detailed view of the biological effects of C. glutinosus extracts, which could be interesting to the aquaculture sector due to their possible anti-inflammatory effects.