Effect of Epinastine Hydrochloride, a Second-generation Histamine H1-receptor Antagonist, on Sensory Neurons in vitro

Abstract

Epinastine hydrochloride (epinastine) is a second-generation histamine Hi-receptor antagonist widely used as an anti-allergic and anti-pruritic. To explore possible new aspects of the anti-pruritic mechanism of epinastine, in particular any effects on the peripheral nervous system, we examined epinastine's effects on sensory neurons using cultured murine dorsal root ganglion (DRG). We performed a quantitative assessment of neurite growth and substance P (SP) release from isolated DRG in the presence versus the absence of epinastine. Mechanism(s) of epinastine’s effects on sensory neurons were detected by examining its neurotoxicity, inhibitory action on nerve growth factor (NGF), and modulatory function on NGFreceptors. The percentage of DRG with outgrowing neurites, total number of neurites, and average extension length of neurites were decreased by epinastine in a concentration-dependent manner. Epinastine did not exhibit any evidence of neurotoxicity on sensory neurons, degradation and inactivation ability on NGF, or effects on expression of NGF receptors. Also, no effects on neural progenitor cells of the central nervous system in culture were observed. Epinastine suppressed capsaicin-induced SP release from DRG neurons in a dosedependent fashion. The results demonstrate that epinastine has inhibitory effects on sensory neuronal growth, which may explain its clinical effects including potent anti-pruritic activity.