ToxSci Advance Access originally published online on April 14, 2008
Toxicological Sciences 2008 104(1):189-197; doi:10.1093/toxsci/kfn076
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Dose- and Route-Dependent Teratogenicity, Toxicity, and Pharmacokinetic Profiles of the Hedgehog Signaling Antagonist Cyclopamine in the Mouse
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* Molecular and Environmental Toxicology Center, School of Medicine and Public Health, University of Wisconsin-Madison WI 53703
Department of Surgery, School of Medicine and Public Health, University of Wisconsin-Madison WI 53703
School of Pharmacy, University of Wisconsin-Madison WI 53703
Department of Comparative Medicine, University of Washington, Seattle WA 98195
1 To whom correspondence should be addressed at Department of Surgery, University of Wisconsin School of Medicine and Public Health, K6/562 Clinical Science Center, 600 Highland Avenue, Madison, WI 53792. Fax: (608) 265-8133. E-mail: bushman{at}surgery.wisc.edu.
Received January 29, 2008; accepted April 4, 2008
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Abstract |
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The Hedgehog (Hh) signaling pathway is an essential regulator of embryonic development and appears to play important roles in postnatal repair and cancer progression and metastasis. The teratogenic Veratrum alkaloid cyclopamine is a potent Hh antagonist and is used experimentally both in vitro and in vivo to investigate the role of Hh signaling in diverse biological processes. Here, we set out to establish an administration regimen for cyclopamine-induced teratogenicity in the mouse. The dysmorphogenic concentration of cyclopamine was determined in vitro via mouse whole-embryo culture assays to be 2.0µM. We administered cyclopamine to female C57BL/6J mice at varied doses by oral gavage, ip injection, or osmotic pump infusion and assessed toxicity and pharmacokinetic (PK) models. Bolus administration was limited by toxicity and rapid clearance. In vivo cyclopamine infusion at 160 mg/kg/day yielded a dam serum steady-state concentration of 
2µM with a corresponding amniotic fluid concentration of approximately 1.5µM. Gross facial defects were induced in 30% of cyclopamine-exposed litters, with affected embryos exhibiting cleft lip and palate. This is the first report describing the PKs and teratogenic potential of cyclopamine in the mouse and demonstrates that transient Hh signaling inhibition induces facial clefting anomalies in the mouse that mimic common human birth defects.
Key Words: cyclopamine; Hedgehog signaling; pharmacokinetics; cleft lip/palate.