Discovery of non-electrophilic TRPA1 channel agonists with anti-nociceptive effects via rapid current desensitization

Desensitizing transient receptor potential ankyrin 1 (TRPA1) cation channel through agonists emerges as an effective strategy for developing analgesics. Many TRPA1 agonists are electrophilic irritants, including BITC and iodoacetamide (IA), which covalently bind to cysteine residues in the cytoplasmic region of the channel. The electrophile JT010 is also recognized as a potent TRPA1 agonist via covalent modification of Cys621, whose irritant effects have been confirmed in humans, highlighting a commonly undesirable property of these electrophilic agonists. Cryo-electron microscopy (cryo-EM) structures have shown that these electrophiles induce a strong driving force for conformational change through electrophilic modification of TRPA1. However, the stable activated conformation induced by electrophiles might delay subsequent desensitization, leading to prolonged TRPA1-mediated nociception responses in vivo. Therefore, developing non-electrophilic TRPA1 agonists may mitigate the irritation associated with electrophilic agonists by accelerating the desensitizing process. To test this hypothesis, we designed and synthesized a series of novel TRPA1 agonists by removing the electrophilic functional group of JT010. Among these synthetic compounds, whole-cell patch clamp recording assays identified compound 21 as a selective TRPA1 agonist with an EC₅₀ of 25.47 ± 1.56 μM for hTRPA1, exhibiting faster desensitization (τ = 20.02 ± 1.66 s) of mTRPA1 compared to electrophiles JT010 (41.71 ± 4.10 s) and BITC (68.05 ± 5.57 s). Importantly, compound 21 demonstrated effective analgesic properties without irritation in mice. Our findings support the hypothesis that facilitating rapid desensitization of TRPA1 by non-electrophilic channel agonists enhances anti-nociceptive effects. Compound 21 may serve as a promising lead for further optimization.

Anti-nociceptive effect; Desensitization; Irritation; Non-electrophilic agonists; Transient receptor potential ankyrin 1 cation channel.