Aims

In the present study, NAN-190 [1-(2-methoxyphenyl)-4-[4-(2-phthalimido) butyl] piperazine] was identified as a Nav1.7 blocker. In the meantime, the compound could alleviate the Complete Freund's Adjuvant (CFA)-induced inflammatory pain. To understand the molecular mechanisms of NAN-190 on pain, the effect of NAN-190 on Nav1.7 sodium channels was studied.

Main methods

Inflammatory pain was induced by injection of CFA solution into the plantar side of the left hindpaw. Thermal hyperalgesia and mechanical allodynia were measured. Whole-cell patch clamp methods were used to record sodium channels and other pain-related targets in the cultured recombinant cells and dorsal root ganglion neurons.

Key findings

Nan-190 was identified as an inhibitor of Nav1.7 sodium channels and animal experiments showed that NAN-190 significantly alleviated CFA-induced inflammatory pain. Mechanism studies demonstrated that NAN-190 was a state-dependent Nav1.7 blocker with IC₅₀ value on the inactivated state ten-fold more potent than that on the rest state. NAN-190 leftward-shifted the fast and slow inactivation curves about 9.07 mV and 38.56 mV, respectively, but had no effects on channel activation. The compound also slowed the recovery from fast and slow inactivation and showed use-dependent properties. Further, the site-directed mutagenesis experiments demonstrated that NAN-190 mainly worked on the open state of Nav1.7 channels by interacting with sites similar as local anesthetics. In DRG neurons, NAN-190 mainly blocks TTX-sensitive currents but is less sensitive to TTX-R sodium currents.

Significance

Taken together, our results indicated that NAN-190 alleviated pain behaviors by blocking sodium channels by interacting with the open state.