Effects of troxerutin on mRNA expression of the genes encoding lysozyme and tumor necrosis factor-α and histology in goldfish (Carassius auratus) skin

Troxerutin, a derivative of the natural bioflavonoid rutin, has important biological effects, including immunostimulatory activity. This study aimed to evaluate the effects of dietary troxerutin supplement on histology and mRNA expression of the genes encoding lysozyme and tumor necrosis factor-α in goldfish, Carassius auratus skin. Fish fingerlings with mean initial weights of 2.74 ± 0.08 g were fed diets supplemented with 0.1, 0.3, 0.5 g troxerutin per kg feed for 80 days. For histological studies, skin from right side and near dorsal fin (0.5cm) was dissected and stored in 10% formalin buffer. For molecular assay on skin tissue, RNA extraction, cDNA synthesis, and real time PCR were performed. Histology results showed a significant increase in alarm cell density in the treatment groups compared to the control group (P<0.05). Alarm cell volumetric ratio to epidermis was significantly higher in the treatment groups, with highest level in fish administrated with medium and high dose of troxerutin, in comparison with the control group (P<0.05). Epidermis thickness did not show significant changes in comparison with the control group (P>0.05). Molecular assay results showed more increase in mRNA expression of the genes encoding lysozyme and tumor necrosis factor-α in the treatment groups, with the highest level in the high dose group, in comparison with the control group (P<0.05). The results indicate that feeding troxerutin at 0.5 g per kg feed has a potential to enhance histology indices and mRNA expression of the genes encoding lysozyme and tumor necrosis factor- α in goldfish (Carassius auratus) skin.