The synthetic peptide, PnPP-15, derived from the PnTx2-6 toxin of the spider Phoneutria nigriventer, induces peripheral antinociception involving neprilysin, opioid, and cannabinoid systems

Background

The PnTx2–6 toxin is isolated from the Phoneutria nigriventer spider venom. The synthetic peptide PnPP-19 is derived from this toxin and induces antinociception. When topically applied, it is cleaved by proteases generating a 15 amino acid residues peptide, PnPP-15. PnPP-15 showed an antinociceptive effect in neuropathic pain developed by streptozotocin-induced diabetic mice. The present work aimed to investigate if PnPP-15 is also effective against the inflammatory pain induced by PGE₂. We also evaluated its cytotoxicity in vitro and studied its possible action mechanism in the pain pathway.

Methods

The nociceptive threshold was assessed using the mechanical paw pressure test. Paw tissue was collected for protein extraction and western blot analyses. The FRET enzymatic assay measured neprilysin activity. The two-electrode voltage clamp technique measured evoked electrical currents in Xenopus laevis oocytes. Cytotoxicity was measured using multiple cell lines.

Results

PnPP-15 has peripheral antinociceptive activity via µ-opioid and CB₁ cannabinoid receptors and inhibits neprilysin. In addition, it induced direct activation of mu-opioid receptors expressed in Xenopus laevis oocytes. PnPP-15 was not cytotoxic against mammalian kidney, liver, heart, nerve, or lung cells.

Conclusion

This work demonstrated the antinociceptive effect of PnPP-15 in an inflammatory pain model, suggesting its use as a possible tool for developing new analgesic drugs.