Newly Discovered Action of HpTx3 from Venom of Heteropoda venatoria on Nav1.7 and Its Pharmacological Implications in Analgesia

Abstract

It has been reported that Heteropodatoxin3 (HpTx3), a peptidic neurotoxin purified from the venom of the spider species Heteropoda venatoria, could inhibit Kv4.2 channels. Our present study newly found that HpTx3 also has potent and selective inhibitory action on Nav1.7, with an IC50 of 135.61 ± 12.98 nM. Without effect on the current–voltage (I-V) relationship of Nav1.7, HpTx3 made minor alternation in the voltage-dependence of activation and steady-state inactivation of Nav1.7 (4.15 mV and 7.29 mV, respectively) by interacting with the extracellular S3–S4 loop (S3b–S4 sequence) in domain II and the domain IV of the Nav channel subtype, showing the characteristics of both pore blocker and gate modifier toxin. During the interaction of HpTx3 with the S3b–S4 sequence of Nav1.7, the amino acid residue D in the sequence played a key role. When administered intraperitoneally or intramuscularly, HpTx3 displayed potent analgesic activity in a dose-dependent manner in different mouse pain models induced by formalin, acetic acid, complete Freund’s adjuvant, hot plate, or spared nerve injury, demonstrating that acute, inflammatory, and neuropathic pains were all effectively inhibited by the toxin. In most cases HpTx3 at doses of ≥ 1mg/kg could produce the analgesic effect comparable to that of 1 mg/kg morphine. These results suggest that HpTx3 not only can be used as a molecular probe to investigate ion channel function and pain mechanism, but also has potential in the development of the drugs that treat the Nav1.7 channel-related pain.

Overexpressed NaV1.7 Channels Confer Hyperexcitability to in vitro Trigeminal Sensory Neurons of CaV2.1 Mutant Hemiplegic Migraine Mice

“…While the low-threshold T-type Ca 2+ current has kinetics similar to Na V 1.7 current, this conductance is mostly inactivated at the resting membrane potential (−60 to −70 mV), and requires significant hyperpolarization to remove voltage-dependent channel inactivation (Lovinger and White, 1989;Yoshida and Oka, 1998;Seo et al, 2013) making it an unlikely contributor to firing modulation in our mouse model. Our results accord with previous studies (Shields et al, 2018;Wu et al, 2019;Neff et al, 2020;Siebenga et al, 2020) reporting pharmacological evidence that Na v 1.7 inhibition by its blockers may be involved in relieving pain.…”

Tetrodotoxin, a Potential Drug for Neuropathic and Cancer Pain Relief?

“…Thus, intrathecal administration of ProTx-II from the spider Thrixopelma pruriens , with a potent and exquisite selectivity for Na V 1.7, reduced pain behaviors associated to cancer chemotherapy [ 42 ] or diabetes [ 91 ]. Another spider toxin, named Heteropodatoxin3 (HpTx3), isolated from the venom of Heteropoda venatoria also has high potency and selectivity against Na V 1.7; the systemic administration of HpTx3 reduced mechanical allodynia in the SNI model in mice [ 92 ]. HnTX-IV and HwTx-IV isolated from the venom of the spiders Ornithoctonus hainana and Ornithoctonus huwena respectively, both have good selectivity for several TTX-sensitive VGSC, and they were able to attenuate mechanical allodynia in the SNI model after systemic administration [ 93 , 94 ].…”

Pain-related toxins in scorpion and spider venoms: a face to face with ion channels

“…In scorpion venoms, a few toxins with analgesic activity in mammals have been identified and their molecular target determined [ 32 - 34 ]. The situation is quite different for spider venoms, where in parallel with the discovery of excitatory toxins inhibiting potassium channels or activating sodium channels, a large number of peptides with analgesic properties have been isolated [ 35 - 37 ]. These analgesic toxins target ion channels involved in pain transmission pathways and are becoming essential tools for the study of pain mechanisms [ 38 , 39 ].…”

“…The venom from the large araneomorph Heteropoda venatoria contains the HpTx3 peptide, a Kv4.2 potassium channel inhibitor, which was recently found to be a potent and selective hNav1.7 blocker (IC 50 136 nM) [ 35 ]. Its interaction in S3-S4 loop in domains II and IV of Nav is representative of a mixt pore blocking and gating modifier effect.…”

“…Its interaction in S3-S4 loop in domains II and IV of Nav is representative of a mixt pore blocking and gating modifier effect. When HpTx3 (0.2-5 mg/kg) is peripherally injected in mice, analgesic effects are observed in acute (acetic acid, hot plate), inflammatory (formalin, CFA) and neuropathic (SNI) pain models [ 35 ].…”