title: High affinity antagonists of the vanilloid receptor.
abstract: The vanilloid receptor VR1 has attracted great interest as a sensory transducer for capsaicin, protons, and heat, and as a therapeutic target. Here we characterize two novel VR1 antagonists, KJM429 [N-(4-tert-butylbenzyl)-N'-[4-(methylsulfonylamino)benzyl]thiourea] and JYL1421 [N-(4-tert-butylbenzyl)-N'-[3-fluoro-4-(methylsulfonylamino)benzyl]thiourea], with enhanced activity compared with capsazepine on rat VR1 expressed in Chinese hamster ovary (CHO) cells. JYL1421, the more potent of the two novel antagonists, inhibited [(3)H]resiniferatoxin binding to rVR1 with an affinity of 53.5 +/- 6.5 nM and antagonized capsaicin-induced calcium uptake with an EC(50) of 9.2 +/- 1.6 nM, reflecting 25- and 60-fold greater potencies than capsazepine. Both JYL1421 and KJM429 antagonized RTX as well as capsaicin and their mechanism was competitive. The responses to JYL1421 and KJM429 differed for calcium uptake by rVR1 induced by heat or pH. JYL1421 antagonized the response to both pH 6.0 and 5.5, whereas KJM429 antagonized at pH 6.0 but was an agonist at lower pH (<5.5). For heat, JYL1421 fully antagonized and KJM429 partially antagonized. Capsazepine showed only weak antagonism for both pH and heat. Responses of rVR1 to different activators could thus be differentially affected by different ligands. In cultured dorsal root ganglion neurons, JYL1421 and KJM429 likewise behaved as antagonists for capsaicin, confirming that the antagonism is not limited to heterologous expression systems. Finally, JYL1421 and KJM429 had little or no effect on ATP-induced calcium uptake in CHO cells lacking rVR1, unlike capsazepine. We conclude that JYL1421 is a competitive antagonist of rVR1, blocking response to all three of the agonists (capsaicin, heat, and protons) with enhanced potency relative to capsazepine.
authors.affiliation: National Cancer Institute, Bethesda, Maryland 20892, USA.
authors.forename: Yun
authors.initials: Y
authors.lastname: Wang
authors.forename: Tamas
authors.initials: T
authors.lastname: Szabo
authors.forename: Jacqueline D
authors.initials: JD
authors.lastname: Welter
authors.forename: Attila
authors.initials: A
authors.lastname: Toth
authors.forename: Richard
authors.initials: R
authors.lastname: Tran
authors.forename: Jiyoun
authors.initials: J
authors.lastname: Lee
authors.forename: Sang Uk
authors.initials: SU
authors.lastname: Kang
authors.forename: Young-Ger
authors.initials: YG
authors.lastname: Suh
authors.forename: Peter M
authors.initials: PM
authors.lastname: Blumberg
authors.forename: Jeewoo
authors.initials: J
authors.lastname: Lee
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001692:Biological Transport; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology; D002478:Cells, Cultured; D006224:Cricetinae; D004224:Diterpenes / Q000494:pharmacology; D006358:Hot Temperature; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D011522:Protons; D051381:Rats; D011955:Receptors, Drug / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013449:Sulfonamides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D013890:Thiourea / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D004224:Diterpenes; C466314:JYL 1421; C466315:KJM 429; D011522:Protons; D011955:Receptors, Drug; D013449:Sulfonamides; C024353:resiniferatoxin; D013890:Thiourea; D002211:Capsaicin; D002118:Calcium