Novel apocynin regulates TRPV1 activity in the trigeminal system and controls pain in a temporomandibular joint neurogenic model

Abstract

Objective: Herein, we investigate the potential analgesic effect of a newly synthesized chalcone-derived apocynin in a neurogenic pain model.

Methods: Molecular docking was used to foretell the apocynin binding features and dynamics with the TRPV1 channel, and the activity was tested in vitro, using transfected HEK 293T cells with the rat TRPV1 receptor. The analgesic effect of apocynin was investigated using a capsaicin-induced pain model. The expression of TRPV1, TRPA1, TRPM8, and MAPKs was assessed by electrophoresis, and immunosorbent assays were performed to quantify the neurotransmitters Substance P, Glutamate, and CGRP. A survival assay using Galleria mellonella was carried out to determine the toxicity.

Results: We observed that apocynin exhibits greater thermodynamic stability. Upon apocynin ligand binding, it changes the electrostatic potential for a predominantly electronegative state in the interior and neutral in its external vanilloid pocket. Treatment of apocynin induces antinociceptive effects against the noxious challenge of capsaicin. Histologically, apocynin decreased the number of TRPV1⁺ immunopositive cells. Electrophoresis showed reduced phosphorylation of p44/42 (ERK1/2) and decreased protein levels of substance P, and CGRP. In the survival assay, apocynin showed low toxicity.

Conclusions: In conclusion, we provide proof-of-principles that the newly synthesized apocynin compound effectively prevented nociception in a neurogenic model of orofacial pain.

Keywords: Apocynin; Chalcone; Galleria mellonella; Orofacial pain; TRPV1; Trigeminal ganglion.