Protection against thermal stress: the role of Tex-OE® in inducing HSP70 and boosting defense mechanisms in Acipenser stellatus fry

Changes in temperature cause various bodily reactions in fish, such as activating their stress response and producing heat shock proteins (HSPs). These HSPs are important for counteracting stress by supporting antioxidant systems and immune responses. In the present study, our aim was to investigate the efficiency of Tex-OE®, a compound derived from prickly pear fruit (Opuntia ficus-indica), in inducing HSP70 production for the purpose of protecting stellate sturgeon fry from thermal stress. The fry was exposed to Tex-OE® as an HSP inducer (HSPi) at a concentration of 100 mg L−1 for a duration of 4 h. Subsequently, they were subjected to two thermal stresses (22 °C and 26 °C) to assess the potential of Tex-OE®. The expression of HSP70 gene; the immune parameters (lysozyme, IgM, and C3); antioxidant enzymes (including SOD, CAT, and T-AOC); and cortisol levels were measured. The findings revealed that applying HSPi before subjecting fish fry to thermal stress increased HSP70 gene expression. In addition, fish that were pre-treated with Tex-OE® and subsequently exposed to temperature stress exhibited higher levels of antioxidant enzymes and immune parameters as well as a decrease in cortisol compared to fish that were only exposed to temperature stress. In conclusion, our findings highlight the efficacy of Tex-OE® as an HSP inducer capable of promoting HSP70 production in stellate sturgeon fry. The induction of HSP70 by Tex-OE® demonstrated promising stress protection against thermal stress by modulating the expression of HSP70, immune system parameters, antioxidant enzymes, and cortisol levels.