Effect of silk fibroin microparticles on cellular immunity and liver of gilthead seabream (Sparus aurata L.) with and without experimental skin injuries

Abstract

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.