Endothelin-1 Enhances Acid-sensitive Ion Channel Currents In Rat Primary Sensory Neurons

Objective:Endothelin-1(ET-1),an endogenous vasoactive peptide,has been found to play an important role in peripheral pain signaling.Acid-sensing ion channels(ASICs)are key sensors for extracellular protons and contribute to pain caused by tissue acidosis.It remains unclear whether an interaction exists between ET-1 and ASICs in primary sensory neurons.In this study,we reported that ET-1enhanced the activity of ASICs in rat dorsal root ganglia(DRG)neurons.Methods:In whole-cell voltage-clamp recording,Electrophysiological experimentswere performed on both rat DRG neurons and Chinese hamster ovary(CHO)cells expressing ASICs and ET_A,ET_B receptors,while animal behavior to detect amiloride or APETx2 of ASICs reacts to mechanical hyperalgesia induced by ET-1Results:ASIC currents were evoked by brief local application of pH 6.0external solution in the presence of TRPV1 channel blocker AMG9810.Pre-application with ET-1(1-100?nM)dose-dependently increased the proton-evoked ASIC currents with an EC50 value of 7.42±0.21?nM.Pre-application with ET-1(30?nM)shifted the concentration-response curve of proton upwards with a maximal current response increase of 61.11%?±?4.33%.We showed that ET-1 enhanced ASIC currents through endothelin-A receptor(ETAR),but not endothelin-B receptor(ETBR)in both DRG neurons and CHO cells co-expressing ASIC3 and ET_AR.ET-1enhancement was inhibited by blockade of G-protein or protein Kinase C signaling.In current-clamp recording,pre-application with ET-1(30?nM)significantly increased acid-evoked firing in rat DRG neurons.Finally,we showed that pharmacological blockade of ASICs by amiloride or APETx2 significantly alleviated ET-1-induced flinching and mechanical hyperalgesia in rats.Conclusions:These results suggest that ET-1 sensitizes ASICs in primary sensory neurons via ET_AR and PKC signaling pathway,which may contribute to peripheral ET-1-induced nociceptive behavior in rats.