title: Effect of cholesterol depletion on the pore dilation of TRPV1.
abstract: The TRPV1 ion channel is expressed in nociceptors, where pharmacological modulation of its function may offer a means of alleviating pain and neurogenic inflammation processes in the human body. The aim of this study was to investigate the effects of cholesterol depletion of the cell on ion-permeability of the TRPV1 ion channel. The ion-permeability properties of TRPV1 were assessed using whole-cell patch-clamp and YO-PRO uptake rate studies on a Chinese hamster ovary (CHO) cell line expressing this ion channel. Prolonged capsaicin-induced activation of TRPV1 with N-methyl-D-glucamine (NMDG) as the sole extracellular cation, generated a biphasic current which included an initial outward current followed by an inward current. Similarly, prolonged proton-activation (pH 5.5) of TRPV1 under hypocalcemic conditions also generated a biphasic current including a fast initial current peak followed by a larger second one. Patch-clamp recordings of reversal potentials of TRPV1 revealed an increase of the ion-permeability for NMDG during prolonged activation of this ion channel under hypocalcemic conditions. Our findings show that cholesterol depletion inhibited both the second current, and the increase in ion-permeability of the TRPV1 channel, resulting from sustained agonist-activation with capsaicin and protons (pH 5.5). These results were confirmed with YO-PRO uptake rate studies using laser scanning confocal microscopy, where cholesterol depletion was found to decrease TRPV1 mediated uptake rates of YO-PRO. Hence, these results propose a novel mechanism by which cellular cholesterol depletion modulates the function of TRPV1, which may constitute a novel approach for treatment of neurogenic pain.
authors.affiliation: Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
authors.forename: Erik T
authors.initials: ET
authors.lastname: Jansson
authors.forename: Carolina L
authors.initials: CL
authors.lastname: Trkulja
authors.forename: Aikeremu
authors.initials: A
authors.lastname: Ahemaiti
authors.forename: Maria
authors.initials: M
authors.lastname: Millingen
authors.forename: Gavin Dm
authors.initials: GD
authors.lastname: Jeffries
authors.forename: Kent
authors.initials: K
authors.lastname: Jardemark
authors.forename: Owe
authors.initials: O
authors.lastname: Orwar
mesh_terms: D000818:Animals; D016466:CHO Cells; D002211:Capsaicin / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects; D002784:Cholesterol / Q000172:deficiency* / Q000494:pharmacology; D006224:Cricetinae; D003412:Cricetulus; D006358:Hot Temperature; D006801:Humans; D015640:Ion Channel Gating / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D016062:Porosity; D011522:Protons; D050916:TRPV Cation Channels / Q000378:metabolism*; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D011522:Protons; D050916:TRPV Cation Channels; C494482:TRPV1 protein, human; D047392:beta-Cyclodextrins; D002784:Cholesterol; C031215:betadex; D002211:Capsaicin