From traditional medicine to targeted therapy: Structure-activity relationship-guided optimization of scorpion toxin DKK2 for pain-associated sodium channel blockade.

ETHNOPHARMACOLOGICAL RELEVANCE: Scorpion toxins, as critical bioactive components in traditional Chinese medicine (TCM), show potential as non-addictive analgesics targeting the pain-associated sodium channels (NaV1.7, NaV1.8, and NaV1.9). However, their clinical application is limited by off-target effects on the subtypes distributed in cardiac (NaV1.5) and skeletal muscle (NaV1.4).

AIM OF THE STUDY: This study aims to enhance the analgesic activity and reduce the adverse effects of scorpion toxin DKK2 through modern pharmacological research methods, thereby improving its potential for clinical application.

METHODS

Structure-activity relationships (SAR) between DKK2 and different NaV subtypes were investigated through computer simulations. Saturation mutagenesis of critical residues on the toxin was used to produce high subtype selectivity mutants. Analgesic activity was evaluated in vivo using formalin-induced paw licking test, while adverse reactions were assessed by forced swimming test, blood assay, and cell viability assays. In addition, whole-cell patch-clamp was employed to clarify the inhibition of DKK2 and its mutants against NaV1.4, NaV1.5, and NaV1.7.

RESULTS

Residue 18 of DKK2 was identified as a key determinant of its NaV subtype selectivity. The N18W mutant demonstrated significantly enhanced analgesic effects with reduced adverse effects on the skeletal and cardiac muscle compared to the wild-type DKK2.

CONCLUSION

By integrating TCM-derived toxin insights with SAR-guided mutagenesis, we developed a scorpion toxin mutant (N18W) with optimized analgesic properties and minimized off-target effects. This study provides a translational framework for refining traditional medicine into targeted therapeutics.