Hedgehog antagonist cyclopamine isomerizes to less potent forms when acidified.
The effect of acid treatment of cyclopamine, a natural antagonist of the hedgehog (Hh) signaling pathway and a potential anti-cancer drug, has been studied. Previous reports have shown that under acidic conditions, as in the stomach, cyclopamine is less effective. Also, it has been stated that cyclopamine converts to veratramine, which has side effects such as hemolysis. In this study, we examined in detail the influence of acidification on structure and activity of cyclopamine. We found that of acidified cyclopamine converts to two previously unreported isomers, which we have called cyclopamine (S) and cyclopamine (X). These have likely gone undetected because cyclopamine is often analyzed with fast and hence lower resolving chromatographic methods. Compared to natural cyclopamine, these cyclopamine isomers have a significantly reduced effect on the ciliary transport of the Hh receptor smoothened, and reduced inhibition on the Hedgehog signaling pathway. The side effects of these isomers are unknown. Our findings can partly explain a reduced efficiency of cyclopamine in a gastric environment, and may help with the rational design of more pH independent cyclopamine analogues.
Wilson
Steven Ray
SR
Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, NO-0315, Oslo, Norway. stevenw@kjemi.uio.no
Strand
Martin Frank
MF
Krapp
Andreas
A
Rise
Frode
F
Petersen
Dirk
D
Krauss
Stefan
S
D000818:Animals; D002853:Chromatography, Liquid; D005455:Fluorescent Antibody Technique; D053823:Hedgehog Proteins / Q000037:antagonists & inhibitors*; D007536:Isomerism; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D011789:Quantum Theory; D021241:Spectrometry, Mass, Electrospray Ionization; D014704:Veratrum Alkaloids / Q000737:chemistry* / Q000494:pharmacology
D053823:Hedgehog Proteins; D014704:Veratrum Alkaloids; C000541:cyclopamine