Piscidin 1 and 2 of gilthead seabream (Sparus aurata): new insights into their role as host defense peptides

Researchers have shown considerable interest in host defense peptides (HDPs) as potential antibiotic alternatives due to their antimicrobial and immunomodulatory characteristics. Piscidins (Pisc), a group of α-helical peptides found exclusively in teleost fish, demonstrate potential for enhancing the health and well-being of aquaculture species. This research examined two piscidins (Pisc1 and Pisc2), identified in the gilthead seabream (Sparus aurata) genome, which exhibit unique physicochemical and structural features. Pisc1 demonstrated strong antioxidant properties and its minimum inhibitory concentrations (MICs) were established against various bacterial species, including Streptococcus agalactiae, Vibrio harveyi, V. anguillarum, V. alginolyticus, Photobacterium damselae subsp. piscicida, Aeromonas salmonicida (2014), and Flavobacterium psychrophilum. Additionally, Pisc1 was found to disrupt both outer and inner membranes of V. harveyi and showed antiparasitic effects against Neoparamoeba perurans. While Pisc1 exhibited hemolytic and cytotoxic properties, it did not impact chemotaxis of SAF-1 cells in the in vitro scratch assay. However, Pisc1 triggered extracellular traps (ETs) of head kidney leucocytes, underscoring its dual role as an antimicrobial agent and immunomodulator. In contrast, Pisc2 showed lower antioxidant activity, and no MICs were identified for the tested bacterial species. Nevertheless, Pisc2 could disrupt the outer membrane of V. harveyi and also displayed antiparasitic activity. Unlike Pisc1, Pisc2 was neither hemolytic nor cytotoxic and did not induce ETs or affect in vitro wound healing assay results. These findings provide valuable insights for the development of novel therapies in aquaculture based on HDPs use.