Effects of subcutaneous injection of λ/κ‐carrageenin on the immune and liver antioxidant status of gilthead seabream (Sparusaurata)

Abstract

This study investigated the acute inflammatory response induced by subcutaneous injection of carrageenin (1%) or phosphate‐buffered saline (control) in gilthead seabream (Sparus aurata). Skin mucus, serum, head kidney (HK) and liver were sampled at 1.5, 3 and 6 hr 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 Vibrio anguillarum and Photobacterium damselae, and total immunoglobulins compared with those of the control group. However, the carrageenin‐injected fish sampled at 6 hr 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 6 hr 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 3 hr, 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 6 hr 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.

Implication of adipocytes from subcutaneous adipose tissue and fatty acids in skin inflammation caused by λ-carrageenin in gilthead seabream (Sparus aurata)

“…According to our histological study, an increase in adipocyte area in SAT was detected in fish injected with λ-carrageenin at 3 h p.i. These results could be the morphological evidence of the response of adipocytes to the proinflammatory mediators that are released, in the area of inflammation, by immune cells recruited at this time point (3 h) [36,38,40]. This morphological change could be necessary to induce the polarization of adipocytes in the inflamed zone towards a proinflammatory phenotype.…”

“…6 h p.i., compared to the control group. In addition, although carrageenin injection had no impact on systemic immunity of gilthead seabream, it led to an increase in the number of skin mucus-secreting cells and acidophilic granulocytes, as well as up-regulation of proinflammatory genes in the skin near the injection site [38,40]. These events were associated with increased skin thickness, edema, and emphysema in the underlying muscle, which were the symptoms observed in human necrotizing fasciitis [39].…”

“…In fish, carrageenin has been used to induce inflammation at different body sites in several fish species, such as plaice (Pleuronectes platessa) [29], carp (Cyprinus carpio) [23], Nile tilapia (Oreochromis niloticus) [30], pacu (Piaractus mesopotamicus) [31,32] and zebrafish (Danio rerio) [33][34][35]. More recently, the inflammatory response of gilthead seabream (Sparus aurata) has been studied by our team, providing diverse information on gene expression [36,37], humoral and cellular immune parameters [38] and the use of non-invasive techniques such as real-time ultrasound or micro-CT to study this complex process [39]. In addition, previous work has evidenced the local effect of mucus-secreting cells of the skin in the inflamed area at 3 h after carrageenin injection by immunohistochemical assay [40].…”

Participation of Hepcidins in the Inflammatory Response Triggered by λ-Carrageenin in Gilthead Seabream (Sparus aurata)

“…However, as homeostatic mechanism seemed to be initiated in in vivo assays at 12 and 24 h after carrageenin injection in seabream, we focused on earlier sampling times (1.5, 3, and 6 h p.i.) (Campos-Sánchez et al 2021a , b , c , d , 2022a , b ). Therefore, different and consistent expression patterns of hepcidins were found in HK (particularly in leucocytes), liver, and skin during the inflammatory response caused by intramuscular injection of λ-carrageenin.…”

“…Carrageenin also triggers inflammation in several fish species [carp ( Cyprinus carpio ) (Fujiki et al 1997 ), Nile tilapia ( Oreochromis niloticus ) (Matushima and Mariano 1996 ), zebrafish ( D. rerio ) (Huang et al 2014 ; Ribas et al 2016 ; Belo et al 2021 ), and gilthead seabream ( S. aurata )] (Campos-Sánchez et al 2021b , c , d ). Recently, we have optimized an in vivo carrageenin-induced acute inflammation model for gilthead seabream (Campos-Sánchez et al 2021a ; 2022a ). In addition, the use of non-invasive techniques such as real-time ultrasound or micro-CT has also provided high-quality images of this complex process (Campos-Sánchez et al 2022b ).…”