Protective effects of seaweed supplemented diet on antioxidant and immune responses in European seabass (Dicentrarchus labrax) subjected to bacterial infection

Abstract

European seabass (Dicentrarchus labrax) production is often hampered by bacterial infections such as photobacteriosis caused by Photobacterium damselae subsp. piscicida (Phdp). Since diet can impact fish immunity, this work investigated the effect of dietary supplementation of 5% Gracilaria sp. aqueous extract (GRA) on seabass antioxidant capacity and resistance against Phdp. After infection, mortality was delayed in fish fed GRA, which also revealed increased lysozyme activity levels, as well as decreased lipid peroxidation, suggesting higher antioxidant capacity than in fish fed a control diet. Dietary GRA induced a down-regulation of hepatic stress-responsive heat shock proteins (grp-78, grp-170, grp-94, grp-75), while bacterial infection caused a down-regulation in antioxidant genes (prdx4 and mn-sod). Diet and infection interaction down-regulated the transcription levels of genes associated with oxidative stress response (prdx5 and gpx4) in liver. In head-kidney, GRA led to an up-regulation of genes associated with inflammation (il34, ccr9, cd33) and a down-regulation of genes related to cytokine signalling (mif, il1b, defb, a2m, myd88). Additionally, bacterial infection up-regulated immunoglobulins production (IgMs) and down-regulated the transcription of the antimicrobial peptide leap2 in head kidney. Overall, we found that GRA supplementation modulated seabass resistance to Phdp infection.

Antioxidants in Fish Sperm and the Potential Role of Melatonin

“…Extracts from berries (rich in quercetin and catechins) like murtilla [ 141 ] and blueberries proved to inhibit sperm lipid peroxidation in Arctic char [ 6 ], while sesame seed powder diet, containing lignans like sesamin, was able to improve sperm motility duration, hatchability, and egg survival rate in African catfish [ 142 ]. Even algae extracts of Gracilaria sp., containing phenolic compounds, proved to have an antioxidant effect on European seabass challenged with a bacterial infection, decreasing lipid peroxidation and suggesting higher total antioxidant capacity in fish fed with experimental diet [ 143 ]. Other polyphenolic substances that have been widely used in many different types of antioxidant assays are honeybee products such as honey, propolis, and royal jelly.…”

Meta‐analysis of the use of seaweeds and their extracts as immunostimulants for fish: a systematic review

“…While there are some studies demonstrating antioxidant benefits of seaweed supplements in fish and aquaculture (e.g. reducing by half lipid peroxidation; Wan et al 2019; Peixoto et al 2019; Kamunde et al 2019), the potential for seaweeds to reduce oxidative stress in fish remains largely unknown (Peixoto et al 2016a).…”

“…While there are some studies demonstrating antioxidant benefits of seaweed supplements in fish and aquaculture (e.g. reducing by half lipid peroxidation; Wan et al 2019;Peixoto et al 2019;Kamunde et al 2019), the potential for seaweeds to reduce oxidative stress in fish remains largely unknown (Peixoto et al 2016a). These and other novel applications of seaweed in animal health include potential benefits for humans; for example, the antiviral activity of fucoidan from the brown seaweed Saccharina japonica against the SARS-CoV-2 virus was substantially higher than Remdesivir (GS-5734), which, at the time of writing was approved for emergency treatment of severe COVID-19 cases (Kwon et al 2020).…”

“…There is also much variation in the ways in which researchers deliver seaweeds to fish in experiments, with some using whole seaweeds (Satoh et al 1987) and others using various extracts (e.g. methanol; Peixoto et al 2019). Moreover, many different seaweed species have been trialled for various freshwater and marine fish species, using different methods and modes of delivery, different immune parameters have been measured and trials have been run under many different experimental conditions (Díaz‐Rosales et al 2005; de las Heras et al 2010; Cheng et al 2012; Kim et al 2014), making the merits of direct comparisons between individual studies questionable.…”

Molecular and histopathological characterization of Photobacterium damselae in naturally and experimentally infected Nile tilapia (Oreochromis niloticus)

“…However, P. damselae subsp. piscicida caused a down‐regulation in the hepatic antioxidant genes of European seabass ( Dicentrarchus labrax ), and there is no a significant difference between the control and infected group in serum samples (Peixoto et al., 2019).…”