A multiscale functional approach to assess pharmacologocal interactions between huwentoxin-IV spider peptide and sodium channel subtypes

International audience

English. The huwentoxin-IV (HwTx-IV) from Chinese bird spider is described to be a highly potent blocker of NaV1.7 subtype of voltage-gated sodium (NaV) channels, a genetically validated analgesic target. Despite of being a promising potential lead molecule for the development of novel pain therapeutics, the characterization of interactions between HwTx-IV and NaV channel subtypes was not exhaustive.In the present study, using multiscale (from in vivo to cellular level) functional approaches, the effect of HwTx-IV was investigated on NaV channels, in particular on NaV1.7 and closely related NaV1.6 subtype mainly expressed in nerves innervating muscles. The potential analgesic effect of the peptide was confirmed since HwTx-IV was approximatively 850 times more efficient to inhibit tetrodotoxin (TTX)-sensitive than TTX-resistant sodium currents recorded from mouse dorsal root ganglia neurons. Moreover, HwTx-IV was approximatively 2 times more efficient than TTX to block the compound muscle action potential recorded from the mouse skeletal neuromuscular system in vivo, and approximatively 30 times more effective to inhibit nerve-evoked than directly-elicited muscle contractile force of isolated mouse hemidiaphragms. These later results strongly suggest that HwTx-IV preferentially blocked the NaV1.6, compared to NaV1.4, channel subtype. This was confirmed by whole-cell automated patch-clamp experiments performed on human embryonic kidney (HEK)-293 cells overexpressing hNaV1.1-1.8 channel subtypes. Finally, HwTx-IV induced in vivo toxicity, probably by blocking NaV1.6 channel subtype, although this toxicity was lower than that of TTX.In conclusion, our results highlight the effects of HwTx-IV on NaV1.6 channel subtype, at doses close to those described as therapeutic, and allow a better understanding of the in vivo side-effect mechanisms.