Research Article: Effect of dietary supplementation of potential probiotic Lacticaseibacillus casei on immune-related genes expression, intestinal microbiota and gut histology of zebrafish (Danio rerio) during Aeromonas hydrophila infection

The present research was conducted on ۶۰۰ zebrafish in four parallel groups, including two control and two experimental groups. The experimental groups (T۱, T۲) were fed commercial fish feed, along with probiotic Lacticaseibacillus casei, while the other two groups (T۳, C) only received commercial feed. At the end of four weeks of the feeding, Fish in the groups T۲ and T۳ were divided and exposed to Aeromonas hydrophila at two concentrations included ۱.۵×۱۰۸ (T۲ and T۳) and۱.۵×۱۰۴ (N۲ and N۳). In this study, the colonization of Lactobacillus in the gastrointestinal tract in the first and last days of the feeding, weight and length in days ۰, ۱۵ and ۳۰, and intestinal histology and expression of interleukin-۱β (IL-۱β) and tumor necrosis factor-α (TNF-α) genes using real-time PCR method on days ۰, ۱۵, ۳۰ and ۳۵ were done. Based on the results of the present study, feeding with L. casei led to the improved the expression of immune-related genes, enhancement epithelial integrity and goblet cells in the intestine, and weight and length of zebrafish (p<۰.۰۵). While it had no significant effect on the rate of colonization of Lactobacillus in the gastrointestinal tract (p>۰.۰۵). This results revealed that probiotic feeding led to the reduction of the mRNA levels of IL-۱β and TNF-α genes before exposure to the A. hydrophila (p<۰.۰۵). while, after exposure, there was a significant increase in the expression level of genes. This elevation was significantly higher in T۳ and N۳ than in T۲ and N۲ (p<۰.۰۵). As the results indicated, dietary supplementation of L. casei can be effective in enhancement of growth and protection of zebrafish against A. hydrophila by improving their mucosal immunity and modulating inflammatory responses. Since zebrafish is an animal model with genetic compatibility with humans and A. hydrophila pathogenicity in humans, the results obtained can be generalized to humans.

Keywords:

Lacticaseibacillus casei , IL-۱β , TNF-α , Aeromonas hydrophila , Zebrafish , Goblet cells