A Buthus martensii Karsch scorpion sting targets Nav1.7 in mice and mimics a phenotype of human chronic pain

LmNaTx15, a novel scorpion toxin, enhances the activity of Nav channels and induces pain in mice

Polypeptide toxins are major bioactive components found in venomous animals. Many polypeptide toxins can specifically act on targets, such as ion channels and voltage-gated sodium (Nav) channels, in the nervous, muscle, and cardiovascular systems of the recipient to increase defense and predation efficiency. In this study, a novel polypeptide toxin, LmNaTx15, was isolated from the venom of the scorpion Lychas mucronatus, and its activity was analyzed. LmNaTx15 slowed the fast inactivation of Nav1.2, Nav1.3, Nav1.4, Nav1.5, and Nav1.7 and inhibited the peak current of Nav1.5, but it did not affect Nav1.8. In addition, LmNaTx15 altered the voltage-dependent activation and inactivation of these Nav channel subtypes. Furthermore, like site 3 neurotoxins, LmNaTx15 induced pain in mice. These results show a novel scorpion toxin with a modulatory effect on specific Nav channel subtypes and pain induction in mice. Therefore, LmNaTx15 may be a key bioactive component for scorpion defense and predation. Besides, this study provides a basis for analyzing structure-function relationships of the scorpion toxins affecting Nav channel activity.

An Overview of the Mechanisms Involved in Neuralgia

Neuralgia is a frequently occurring condition that causes chronic pain and burdens both patients and their families. Earlier research indicated that anti-inflammatory treatment, which was primarily utilized to address conditions like neuralgia, resulted in positive outcomes. However, recent years have witnessed the emergence of various novel mechanisms associated with pain-related disorders. This review provides a concise overview of the inflammatory mechanisms involved in neuralgia. It also examines recent advancements in research, exploring the influence of ion channels and synaptic proteins on neuralgia and its complications. Additionally, the interactions between these mechanisms are discussed with the aim of suggesting innovative therapeutic approaches and research directions for the management of neuralgia.

Functional Characterization of a New Degradation Peptide BmTX4-P1 from Traditional Chinese Scorpion Medicinal Material

Thermally processed Buthus martensii Karsch scorpion is an important traditional Chinese medical material that has been widely used to treat various diseases in China for over one thousand years. Our recent work showed that thermally processed Buthus martensii Karsch scorpions contain many degraded peptides; however, the pharmacological activities of these peptides remain to be studied. Here, a new degraded peptide, BmTX4-P1, was identified from processed Buthus martensii Karsch scorpions. Compared with the venom-derived wild-type toxin peptide BmTX4, BmTX4-P1 missed some amino acids at the N-terminal and C-terminal regions, while containing six conserved cysteine residues, which could be used to form disulfide bond-stabilized α-helical and β-sheet motifs. Two methods (chemical synthesis and recombinant expression) were used to obtain the BmTX4-P1 peptide, named sBmTX4-P1 and rBmTX4-P1. Electrophysiological experimental results showed that sBmTX4-P1 and rBmTX4-P1 exhibited similar activities to inhibit the currents of hKv1.2 and hKv1.3 channels. In addition, the experimental electrophysiological results of recombinant mutant peptides of BmTX4-P1 indicated that the two residues of BmTX4-P1 (Lys²² and Tyr³¹) were the key residues for its potassium channel inhibitory activity. In addition to identifying a new degraded peptide, BmTX4-P1, from traditional Chinese scorpion medicinal material with high inhibitory activities against the hKv1.2 and hKv1.3 channels, this study also provided a useful method to obtain the detailed degraded peptides from processed Buthus martensii Karsch scorpions. Thus, the study laid a solid foundation for further research on the medicinal function of these degraded peptides.

Makatoxin-3, a thermostable Nav1.7 agonist from Buthus martensii Karsch (BmK) scorpion elicits non-narcotic analgesia in inflammatory pain models

ETHNOPHARMACOLOGICAL RELEVANCE

Chronic pain management represents a serious healthcare problem worldwide. The use of opioid analgesics for pain has always been hampered by their side effects; in particular, the addictive liability associated with chronic use. Finding a morphine replacement has been a long-standing goal in the field of analgesia. In traditional Chinese medicine, processed Buthus martensii Karsch (BmK) scorpion has been used as a painkiller to treat chronic inflammatory arthritis and spondylitis, so called "Scorpio-analgesia". However, the molecular basis and the underline mechanism for the Scorpio-analgesia are still unclear.

AIM OF THE STUDY

The study aims to investigate the molecular basis of "Scorpio analgesia" and identify novel analgesics from BmK scorpion.

MATERIALS AND METHODS

In this study, the analgesic abilities were determined using formalin-, acetic acid- and complete Freund's adjuvant-induced pain models. The effect of BmK venom and processed BmK venom on Nav1.7 were detected by whole-cell voltage-clamp recordings on HEK293-hNav1.7 stable cell line. Action potentials in Dorsal root ganglion (DRG) neurons induced by Makatoxin-3-R58A were recorded in current-clamp mode. The content of Makatoxin-3 was detected using competitive enzyme-linked immunosorbent assay based on the Makatoxin-3 antibody. High performance liquid chromatography, western blot and circular dichroism spectroscopy were used to analysis the stability of Makatoxin-3.

RESULTS

Here we demonstrate that Makatoxin-3, an α-like toxin in BmK scorpion venom targeting Nav1.7 is the critical component in Scorpio-analgesia. The analgesic effect of Makatoxin-3 could not be reversed by naloxone and is more potent than Nav1.7-selective inhibitors and non-steroidal anti-inflammatory drugs in inflammatory models. Moreover, a R58A mutant of Makatoxin-3 is capable of eliciting analgesia effect without inducing pain response.

CONCLUSIONS

This study advances ion channel biology and proposes Nav1.7 agonists, rather than the presumed Nav1.7-only blockers, for non-narcotic relief of chronic pain.