Resiniferatoxin-induced loss of plasma membrane in vanilloid receptor expressing cells.
Resiniferatoxin (RTX), a potent analog of capsaicin, was evaluated electrophysiologically in dorsal root ganglion (DRG) cells and cell lines ectopically expressing the vanilloid receptor type 1 (VR1) to determine if cell phenotype influenced RTXs neurotoxic properties. Furthermore, capsaicin and heat activation of VR1 were evaluated in these cells to determine if cellular damage was unique to RTX activation of the receptors. RTX application to DRG cells identified as type 1, 2 or 5, cell types known to express VR1, induced large inward currents. RTX did not induce currents in DRG cells that do not express the receptor (type 4 cells). In cell lines ectopically expressing VR1, RTX-induced similar currents. RTX produced no effect in non-transfected cells. After exposure to RTX both DRG cells and transfected cells failed to respond to subsequent applications of the agonist. In addition, whole cell capacitance was reduced up to 70%. The decrease in capacitance was associated with the loss of plasma membrane, as determined by confocal microscopy. Cell phenotype, other than VR1 expression, did not influence the response to RTX. Interestingly, capsaicin and heat activation of vanilloid receptors also decreased cell capacitance, but the loss of membrane was not as great as with RTX and responses to these stimuli were not lost after the initial exposure. The loss of cell membrane required elevated intracellular levels of Ca2+. From these data it was concluded that the loss of cell membrane was dependent on the presence of both VR1 and intracellular Ca2+ accumulation, but not on cell phenotype.
Caudle
Robert M
RM
Department of Oral and Maxillofacial Surgery, University of Florida College of Dentistry and the University of Florida McKnight Brain Institute, 1600 Archer Road, P.O. Box 100416, Gainesville, FL 32610, USA. rcaudle@dental.ufl.edu
Karai
Laszlo
L
Mena
Narasaiah
N
Cooper
Brian Y
BY
Mannes
Andrew J
AJ
Perez
Federico M
FM
Iadarola
Michael J
MJ
Olah
Zoltan
Z
D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002522:Chlorocebus aethiops; D004224:Diterpenes / Q000633:toxicity*; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D051379:Mice; D041681:NIH 3T3 Cells; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011955:Receptors, Drug / Q000096:biosynthesis*
D004224:Diterpenes; D011955:Receptors, Drug; C024353:resiniferatoxin