02500nas a2200373   4500000000100000008004100001260001300042653001200055653001400067653001700081653003200098653001400130653001700144653003100161653003600192653001100228653003000239653005000269653001400319653002800333653002400361653002600385653001500411653001600426653001700442100001500459700001800474700001400492245009100506300001200597490000700609520149600616022001402112       2007                            d  c2007 May10aAnimals10aApoptosis10aBeta Catenin10aBone Morphogenetic Proteins10aCell Line10aChick Embryo10aGlycogen Synthase Kinase 310aGlycogen Synthase Kinase 3 beta10aHumans10aIn Situ Nick-End Labeling10aIntercellular Signaling Peptides and Proteins10aLimb Buds10aReactive Oxygen Species10aSignal Transduction10aSubcellular Fractions10aTeratogens10aThalidomide10aWnt Proteins1 aKnobloch J1 aShaughnessy J1 aRüther U00aThalidomide induces limb deformities by perturbing the Bmp/Dkk1/Wnt signaling pathway.  a1410-210 v213 a<p>Thalidomide, a sedative originally used to treat morning sickness and now used to treat leprosy and multiple myeloma, is also a teratogen that induces birth defects in humans such as limb truncations and microphthalmia. However, the teratogenic mechanism of action of this drug remains obscure. Thalidomide induces limb and eye defects in the chicken embryo at an EC50 of 50 microg/kg egg wt and apoptosis in primary human embryonic fibroblasts (HEFs) at an EC50 of 8.9 microM. Using these model systems, we demonstrate by semiquantitative reverse transcriptase-polymerase chain reaction and whole-mount in situ hybridization that thalidomide-induced oxidative stress enhances signaling through bone morphogenetic proteins (Bmps). This leads to up-regulation of the Bmp target gene and Wnt antagonist Dickkopf1 (Dkk1) with subsequent inhibition of canonical Wnt/beta-catenin signaling and increased cell death as shown by trypan blue and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. Thalidomide-induced cell death was dramatically reduced in HEFs and in embryonic limb buds by the use of inhibitors against Bmps, Dkk1, and Gsk3beta, a beta-catenin antagonist acting downstream of Dkk1 in the Wnt pathway. Most interestingly, blocking of Dkk1 or Gsk3beta dramatically counteracts thalidomide-induced limb truncations and microphthalmia. From this, we conclude that perturbing of Bmp/Dkk1/Wnt signaling is central to the teratogenic effects of thalidomide.</p>  a1530-6860