μ-TRTX-Hhn1b (HNTX-IV) is a 35-amino acid peptide isolated from the venom of the spider, Ornithoctonus hainana. It inhibits voltage-gated sodium channel Nav1.7, which has been considered as a therapeutic target for pain. The goal of the present study is to elucidate the analgesic effects of synthetic μ-TRTX-Hhn1b on animal models of pain. The peptide was first synthesized and then successfully refolded/oxidized. The synthetic peptide had the same inhibitory effect on human Nav1.7 current transiently expressed in HEK 293 cells as the native toxin. Furthermore, the analgesic potentials of the synthetic peptide were examined on models of inflammatory pain and neuropathic pain. μ-TRTX-Hhn1b produced an efficient reversal of acute nociceptive pain in the abdominal constriction model, and significantly reduced the pain scores over the 40-min period in the formalin model. The efficiency of μ-TRTX-Hhn1b on both models was equivalent to that of morphine. In the spinal nerve model, the reversal effect of μ-TRTX-Hhn1b on allodynia was longer and higher than mexiletine. These results demonstrated that μ-TRTX-Hhn1b efficiently alleviated acute inflammatory pain and chronic neuropathic pain in animals and provided an attractive template for further clinical analgesic drug design.

Human voltage-gated sodium channel (VGSC) Nav1.7 (hNav1.7) is involved in the generation and conduction of neuropathic and nociceptive pain signals. Compelling genetic and preclinical studies have validated that hNav1.7 is a therapeutic target for the treatment of pain, however there is a dearth of currently available compounds capable of targeting hNav1.7 with high potency and specificity. Hainantoxin-III (HNTX-III) is a 33-residue polypeptide from the venom of the spider Ornithoctonus hainana. It is a selective antagonist of neuronal tetrodotoxin-sensitive voltage-gated sodium channels. Here, we report the engineering of improved potency and Nav selectivity of hNav1.7 inhibition peptides derived from the HNTX-III scaffold. Alanine scanning mutagenesis showed key residues for HNTX-III interacting with hNav1.7. Site-directed mutagenesis analysis indicated key residues on hNav1.7 interacting with HNTX-III. Molecular docking was conducted to clarify the binding interface between HNTX-III and Nav1.7 and guide the molecular engineering process. Ultimately, we obtained H4 [K0G1-P18K-A21L-V] based on molecular docking of HNTX-III and hNav1.7 with a 30-fold improved potency (IC50 0.007 ± 0.001 μM) and > 1000-fold selectivity against Nav1.4 and Nav1.5. H4 also showed robust analgesia in the acute and chronic inflammatory pain model and neuropathic pain model. Thus, our results provide further insight into peptide toxins that may prove useful in guiding the development of inhibitors with improved potency and selectivity for Nav subtypes with robust analgesia.

One-step pyrolysis of amino acid zinc chelates and levodopa polymers and ferrocene using a gas diffusion strategy endows Fe-NCNF-120 with a hierarchically porous morphology and dense and accessible Fe–N _x sites, thus significantly improving ORR performance.