High Affinity Antagonists of the Vanilloid Receptor
- Yun Wang1,1,
- Tamas Szabo1,
- Jacqueline D. Welter1,
- Attila Toth1,
- Richard Tran1,
- Jiyoun Lee2,
- Sang Uk Kang2,
- Young-Ger Suh2,
- Peter M. Blumberg1 and
- Jeewoo Lee
- 1National Cancer Institute, Bethesda, Maryland (Y.W., T.S., J.D.W., A.T., R.T., P.M.B.); and 2College of Pharmacy, Seoul National University, Seoul, Korea (Ji.L., S.U.K., Y.-G.S., Je.L.)
- Peter M. Blumberg, Ph.D., National Cancer Institute, Building 37, Room 3A01, 37 Convent Drive MSC 4255, Bethesda, MD 20892-4255. E-mail: blumberp{at}dc37a.nci.nih.gov
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 [3H]resiniferatoxin binding to rVR1 with an affinity of 53.5 ± 6.5 nM and antagonized capsaicin-induced calcium uptake with an EC50 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.
Footnotes
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↵1 Present address: Neuroscience Research Institute, Peking University, 100083, Beijing, People's Republic of China.
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This research was partly supported by a Fund 2000 grant from the Korea Research Foundation.
- Abbreviations:
- RTX
- resiniferatoxin
- HEK
- human embryonic kidney
- CHO
- Chinese hamster ovary
- rVR1
- cloned rat vanilloid receptor subtype-1
- CHO/rVR1 cell
- Chinese Hamster Ovary cells transfected with cloned rat vanilloid receptor subtype-1
- DRG
- dorsal root ganglion
- DMEM
- Dulbecco's modified Eagle's medium
- FBS
- fetal bovine serum
- JYL1421
- N-(4-tert-butylbenzyl)-N′-[3-fluoro-4-(methylsulfonylamino)benzyl]thiourea
- KJM429
- N-(4-tert-butylbenzyl)-N′-[4-(methylsulfonylamino)benzyl]thiourea
- DPBS
- Dulbecco's phosphate-buffered saline
- PBS
- phosphate-buffered saline
- CPZ
- capsazepine
- MES
- 2-[N-Morpholino]ethanesulfonic acid
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- Received March 12, 2002.
- Accepted July 16, 2002.
- U.S. Government
