Propofol modulates agonist-induced transient receptor potential vanilloid subtype-1 receptor desensitization via a protein kinase Cε-dependent pathway in mouse dorsal root ganglion sensory neurons

Abstract

Background: The activity of transient receptor potential vanilloid subtype-1 (TRPV1) receptors, key nociceptive transducers in dorsal root ganglion sensory neurons, is enhanced by protein kinase C ε (PKCε) activation. The intravenous anesthetic propofol has been shown to activate PKCε. Our objectives were to examine whether propofol modulates TRPV1 function in dorsal root ganglion neurons via activation of PKCε. Methods: Lumbar dorsal root ganglion neurons from wildtype and PKCε-null mice were isolated and cultured for 24 h. Intracellular free Ca2+ concentration was measured in neurons by using fura-2 acetoxymethyl ester. The duration of pain-associated behaviors was also assessed. Phosphorylation of PKCε and TRPV1 and the cellular translocation of PKCε from cytosol to membrane compartments were assessed by immunoblot analysis. Results: In wild-type neurons, repeated stimulation with capsaicin (100 nM) progressively decreased the transient rise in intracellular free Ca2+ concentration. After desensitization, exposure to propofol rescued the Ca2+ response. The resensitizing effect of propofol was absent in neurons obtained from PKCε-null mice. Moreover, the capsaicin-induced desensitization of TRPV1 was markedly attenuated in the presence of propofol in neurons from wild-type mice but not in neurons from PKCε-null mice. Propofol also prolonged the duration of agonist-induced pain associated behaviors in wild-type mice. In addition, propofol increased phosphorylation of PKCε as well as TRPV1 and stimulated translocation of PKCε from cytosolic to membrane fraction. Discussion: Our results indicate that propofol modulates TRPV1 sensitivity to capsaicin and that this most likely occurs through a PKCε-mediated phosphorylation of TRPV1. Copyright © 2010.