Effects of subcutaneous injection of λ/κ-carrageenin on the immune and liver antioxidant status of gilthead seabream (Sparus aurata).

Abstract

This study investigated the acute inflammatory response induced by subcutaneous injection of carrageenin (1%) or phosphate-buffered saline (control) in gilthead seabream (Sparusaurata). Skin mucus, serum, head kidney (HK) and liver were sampled at 1.5, 3 and 6hr post-injection (p.i.) to determine the immune and antioxidant status of this fish species. The skin mucus of the carrageenin group showed increased superoxide dismutase and peroxidase activities, lysozyme abundance, bactericidal activity against Vibrioanguillarum and Photobacteriumdamselae, and total immunoglobulins compared with those of the control group. However, the carrageenin-injected fish sampled at 6hr p.i. showed decreased protease activity in the skin mucus and peroxidase activity in the HK leucocytes compared with the control. Moreover, the carrageenin injection had no effects on the systemic immune system, but it reduced the liver catalase activities at both 3 and 6hr in the carrageenin group relative to those in the control group. The expression levels of several proinflammatory and cell marker genes in the HK and liver were also determined. In the HK, the expression levels of interleukin-1β and prostaglandin D synthase 1 were upregulated at 1.5 and 3hr, respectively, in the carrageenin group compared with those in the control group. Contrarily, the expression of the NADPH oxidase subunit phox40 (an acidophilic granulocyte marker) in the carrageenin group at 6hr was downregulated compared with that in the control group. These results suggested that subcutaneous injection of κ/λ-carrageenin in gilthead seabream triggered an acute skin inflammation characterized by the rapid recruitment of acidophilic granulocytes and the release of humoral mediators into the skin mucus.