Comparative Neuroprotective Effects of Biopeptide Fractions from Two Viperidae Snakes, Bothrops jararaca and Daboia siamensis, in Zebrafish Exposed to Oxidative Stress

Snake venoms are rich sources of bioactive peptides with therapeutic potential, particularly against neurodegenerative diseases linked to oxidative stress. While the peptide fraction (< 10 kDa) from Bothrops jararaca venom has shown in vitro neuroprotection, analogous fractions from related species remain unexplored in vivo. This study comparatively evaluated the neuroprotective effects of two peptide fractions (pf) from Daboia siamensis (pf-Ds) and B. jararaca (pf-Bj) against H₂O₂-induced oxidative stress using in vitro (PC12 cells) and in vivo (zebrafish, Danio rerio) models. In vitro, pf-Ds (1 µg⋅mL⁻¹) did not protect PC12 cells against H₂O₂-induced cytotoxicity, unlike previously reported effects of pf-Bj. In vivo, neither pf-Ds nor pf-Bj (1-20 µg⋅mL⁻¹) induced significant developmental toxicity in zebrafish larvae up to 120 hours post-fertilization (hpf). The neuroprotective effects of both pf were evaluated using two experimental models: (I) Larvae at 96 hpf were exposed to either pf-Ds or pf-Bj (10 µg⋅mL⁻¹) for 4 hours, followed by co-exposure to H₂O₂ (0.2 mmol⋅L⁻¹) for an additional 10 hours to induce oxidative stress (4–20 hours model); (II) Embryos at 4 hpf were treated with pf-Ds or pf-Bj (10 µg⋅mL⁻¹) continuously until 96 hpf, after which they were exposed to H₂O₂ (0.2 mmol⋅L⁻¹) for another 24 hours (96–120 hours model). In a short-term treatment model, neither fraction reversed H₂O₂-induced deficits in metabolism or locomotor activity. However, in a prolonged treatment model, pf-Bj significantly reversed the H₂O₂-induced locomotor impairment, whereas pf-Ds did not confer protection. These findings demonstrate, for the first time, the in vivo neuroprotective potential of pf-Bj against oxidative stress-induced behavioral deficits in zebrafish, contingent on the treatment regimen. The differential effects between pf-Ds and pf-Bj highlight species-specific venom composition and underscore the value of zebrafish for evaluating venom-derived peptides.