Biological activity in vitro and in vivo of an in silico designed secretagogue peptide to be used in fish
Abstract
In teleost fish, secretion of the growth hormone (GH) is regulated by several hypothalamic factors that are influenced by the physiological state of the animal. GH in fish is involved in many physiological processes that are not overtly growth-related such as: saltwater osmoregulation, antifreeze protein synthesis, and the regulation of sexual maturation and immune functions. This study was conducted to characterize a decapeptide A233 (GKFDLSPEHQ) designed by molecular modeling to evaluate its function as a GH secretagogue (GHS). In pituitary cell culture, the peptide A233 induces GH secretion and it is also able to increase superoxide production in tilapia head-kidney leukocyte cultures. This effect is blocked by preincubation with the GHS receptor antagonist [D-Lys3]-GHRP6. Immunoneutralization of GH by addition of anti-tilapia GH monoclonal antibody blocked the stimulatory effect of A233 on superoxide production. These experiments suggest a GH-mediated mechanism for the action of A233. The in vivo biological action of the decapeptide was also demonstrated for growth stimulation in goldfish and tilapia larvae (p < 0.001). Superoxide dismutase levels, antiprotease activity, and lectin titer were enhanced in tilapia larvae treated with this novel molecule. The decapeptide A233 is able to function as GHS in teleosts and enhance parameters of the innate immune system in the fish larvae. This study won the Annual Award of the Academy of Sciences of Cuba in 2012.
