A venom fraction from the Philippine tarantula (Orphnaecus sp.) reveals low-molecular-weight compounds that potentiate drug-like neurobehavioral responses in Danio rerio.

Abstract

Background: Spider venoms are rich natural sources of bioactive chemicals ranging from low-molecular-mass compounds to larger molecules such as low molecular mass peptides, proteins, and enzymes. Some compounds have been reported to exhibit neuroactivity and show potential as therapeutic agents against neurological disorders. Thus, this study analyzed the neurobehavioral effects of selected venom fractions from Philippine tarantula species compared to FDA-approved drugs targeting neuroreceptors, ion channels, and enzymes.

Methods: The venom was collected from the tarantula by electrostimulation and fractionated by reverse-phase high-performance liquid chromatography (RP-HPLC). Nine of the eleven fractions were subjected to neurobehavioral analysis using zebrafish (Danio rerio) as the animal model. The fractions were administered intraperitoneally, and their neurobehavioral effects were examined using the novel tank test, fear response, social interaction, and mirror biting tests. Donepezil, lidocaine, and diazepam were used as positive controls, and normal saline solution (NSS) as the negative control of the study. The swimming patterns and trajectories of the zebrafish were monitored using idTracker and were graphed using GraphPad Prism v.9.0. Components of the most polar fraction were further analyzed by Ultra Performance Liquid Chromatography - Quadrupole Time of Flight Data Dependent Analysis to identify the components structurally.

Results: Preliminary screening of all the fractions revealed that Fraction 1 with 0.1 µg/µL exhibited donepezil-like behavior based on similar rapid-swimming movement from 0 to 31 time intervals, Fraction 4 with 0.1 µg/µL concentration exhibited diazepam-like behavior due to non-significant differences in its time spent on top of the tank ranging from20 to 40 minutes, and Fraction 8 with 0.1 µg/µL concentration exhibited lidocaine-like behavior based on both rapid swimming movement and time spent on top of the tank. Fractions 1, 4, and 8 were further evaluated by determining their dose-dependent response, which follows the effect of their corresponding positive control. Analysis of Fraction 1 resulted in the annotation of several non-peptidic components 4-OH-PhLac434 and its isomer using VenoMS and isopimaric acid, palmitamide, 9-octadecenamide, and 13-docosenamide as putative compounds present in this spider venom using GNPS.

Conclusion: Overall, the fractions of venom from the Orphnaecus tarantula species appear to induce distinct neurobehavioral effects, which may include hyperactivity, anxiolytic-like responses, and potential antinociceptive properties.