Therapeutic Potential of Peptides with Neutralizing Ability Towards the Venom and Toxin (CaTx-I) of Crotalus adamanteus

Ramar      Perumal Samy; Maung      Maung Thwin; Bradley      G. Stiles; Ho      Bow; Vincent      T.K. Chow; Ponnampalam      Gopalakrishnakone

Abstract

The CaTx-I (PLA2) toxin of Crotalus adamanteus venom is responsible for most of the symptoms observed during envenomation. Synthetic peptides were designed and screened for venom (0.8 μg/ml) and CaTx-I (0.1 μM) inhibition at varying doses of the peptide (10000- 0.0001 μM) using a Cayman chemical human secretory phospholipase A2 (sPLA2, Type II) assay kit. Further, in vitro neutralization studies were evaluated by a fixed dose of peptide (1 μM) against venom (0.8 μg/ml) and toxin (0.1 μM). Among the linear peptides (PIP-18, cyclic C and PIP59-67) that showed potent neutralizing effects against the venom/toxin of C. adamanteus. PIP-18 [IC50, 1.23 μM] and cyclic C [IC50, 1.27 μM] peptides possessed the strongest inhibitory effect against CaTx-I. A fixed dose of CaTx-I (75 μg/kg) was administered intraperitoneally (i.p.) into mice followed by an i.p. injection of peptides PIP-18 and cyclic C at (6 μg/mouse), venom (150 μg/kg) and toxin CaTx-I alone served as references. Mice treated with PIP-18 and cyclic C showed a very strong neutralizing effect and markedly reduced mortality compared to the control after 24 h. The CA venom and CaTx-I injected mice showed severe toxicity after 24 h. Peptides PIP-18 and cyclic C were non-hemolytic at 100 μM. They produced a significant decrease in lipid peroxidase (LPx) and enhancement of superoxide dismutase (SOD), catalase (CAT) and Glutathione-s-transferase (GST) levels indicating their antioxidant property against venom-induced changes in mice. This study confirmed the potent snake venom neutralizing properties of peptides.

Keywords: Crotalus adamanteus, phospholipase A2, phospholipase inhibitor, peptides, snakebite, neutralization, CaTx-I (PLA2), venom, mortality, enhancement of superoxide dismutase