A Novel Hypothesis for Thalidomide-Induced Limb Teratogenesis: Redox Misregulation of the NF-κB Pathway

Abstract

Several hypotheses have been proposed to explain the mechanisms of thalidomide teratogenesis, although none adequately accounts for the observed malformations and explains the basis for species specificity. Recent observations that thalidomide increases the production of free radicals and elicits oxidative stress, coupled with new insights into the redox regulation of nuclear transcription factors, lead to the suggestion that thalidomide may act through redox misregulation of the limb outgrowth pathways. Oxidative stress, as marked by glutathione depletion/oxidation and a shift in intracellular redox potential toward the positive, occurs preferentially in limbs of thalidomide-sensitive rabbits, but not in resistant rats. DNA binding of nuclear factor kappa-B (NF-kappaB), a redox-sensitive transcription factor and key regulator of limb outgrowth, was shown to be significantly attenuated in rabbit limb cells and could be restored following the addition of a free radical spin-trapping agent, phenyl N-tert-butyl nitrone. The inability of NF-kappaB to bind to its DNA promoter results in the failure of limb cells to express fibroblast growth factor (FGF)-10 and twist in the limb progress zone (PZ) mesenchyme, which in turn attenuates expression of FGF-8 in the apical ectodermal ridge (AER). Failure to establish an FGF-10/FGF-8 feedback loop between the PZ and AER results in the truncation of limb outgrowth. We hypothesize that species-selective alterations in redox microenvironment caused by free radical production from thalidomide results in attenuation of the NF-kappaB-mediated gene expression that is responsible for limb outgrowth.

Thalidomide Resistance Is Based on the Capacity of the Glutathione-Dependent Antioxidant Defense

“…The overall embryonic redox potential and in particular that of limb buds is much more oxidative in sensitive rabbits than in rats, and rat limb buds possess higher GSH stores than rabbit limb buds. 15 We show here that thalidomide induces apoptosis in sensitized MEFs via the same key molecules (Bmps, Dkk1, PTEN, Gsk3 ) that mediate the effects of thalidomide in CEFs, HEFs, isolated chicken limb bud cells and in vivo in chicken limb buds. Accordingly, thalidomide-free supernatants of thalidomide-treated CEFs drive MEFs into apoptosis, and this effect is impaired by blocking the activity of Bmps, Dkk1, PTEN or Gsk3 .…”

“…15 Interestingly, NF-κB is a negative regulator of Bmp signaling, 17 and treatment of mice with a superoxide scavenger results in decreased Bmp4 expression. 18 Thus, superoxide generated by thalidomide might impair the repressor activity of NF-κB on Bmp expression in embryonic cells.…”

Thalidomide induces limb defects by preventing angiogenic outgrowth during early limb formation

“…A large number of models and hypotheses have been previously published that try to explain the basis of thalidomide-induced limb defects (8,(12)(13)(14)(15). Such models include changes in gene expression (8,(12)(13)(14)(15), induction of oxidative stress (8,14,15), effects on chrondrogenesis (8), mutation of DNA (8), limb bud distalization (13), and induction of cell death (8,12).…”

“…However, whether the antiangiogenic effect does cause limb defects has neither been confirmed in vivo nor is it known why the limb vasculature would be targeted specifically. Others have proposed that thalidomide affects limb development by inducing changes in gene expression (8,(12)(13)(14)(15). Again, neither the mechanism by which thalidomide targets limb gene expression preferentially nor whether such changes are the primary cause of the limb defects has been established.…”

Pharmacological safety during pregnancy: the principles of teratogenesis and teratogenicity of drugs

“…Предполагается участие окислительного стресса в патогенезе некоторых врож-денных аномалий, включающих пороки развития и дефор-мации костно-мышечной системы, дефекты развития нервной трубки, орофациальные расщелины и сердечно-сосудистые дефекты [42,43]. Некоторые лекарственные средства известны в качестве агентов окислительно-вос-становительного цикла и подвержены одноэлектронным восстановительным реакциям с образованием АФК, что, как считается, может служить основой их тератогенного эффекта [43][44][45]. Примером таких препаратов являются талидомид, фенитоин, вальпроевая кислота, антиаритми-ческие средства III класса, препараты железа и различные химиотерапевтические средства [43,46,47].…”