Inhibition of histone deacetylase activity on specific embryonic tissues as a new mechanism for teratogenicity.
BACKGROUND
the inhibition of histone deacetylase (HDAC) has been reported as an effective mechanism on therapy in neoplastic diseases. Among HDAC inhibitors, Trichostatin A (TSA) and Valproic Acid (VPA) prevent the tumorigenesis in rodent and human models. Malformations as neural tube and axial skeletal defects are well-known VPA side effects. Recent hypotheses suggest the HDAC inhibitor activity as the teratogenic mechanism of VPA. The teratogenic potency of TSA is, at the moment, unknown. The aim of the present work is to investigate the HDAC inhibition on embryos exposed in utero to TSA or VPA and to compare the teratogenic potential of these two molecules on the axial skeleton morphogenesis.


METHODS
Pregnant CD mice were i.p. treated on day 8 post coitum (9.00 a.m.) with 400 mg/kg VPA or with 0, 2, 4, 8, 16 mg/kg TSA. Embryos explanted 1 hr after the treatment from some females exposed to 400 mg/kg VPA or to 16 mg/kg TSA were processed for Western blotting and immunohistochemical analysis, in order to evaluate the histone hyperacetylation in the total embryo homogenates and to visualize the hyperacetylated tissues. Foetuses at term were processed for skeletal examination.


RESULTS
Both VPA and TSA were able to induce hyperacetylation on embryos, specifically at the level of the caudal neural tube and of somites. At term, TSA showed teratogenic effects at the axial skeleton, quite similar to those observed after VPA exposure.


CONCLUSIONS
In conclusion, both VPA and TSA are teratogenic in mice. A direct correlation between somite hyperacetylation and axial abnormalities could suggest the HDAC inhibition as the mechanism of the teratogenic effects.
Menegola
Elena
E
Department of Biology, University of Milan, Milan, Italy. elena.menegola@unimi.it
Di Renzo
Francesca
F
Broccia
Maria L
ML
Prudenziati
Michela
M
Minucci
Saverio
S
Massa
Valentina
V
Giavini
Erminio
E
D000014:Abnormalities, Drug-Induced / Q000209:etiology*; D000107:Acetylation; D000818:Animals; D001842:Bone and Bones / Q000187:drug effects / Q000196:embryology / Q000201:enzymology*; D002356:Cartilage / Q000187:drug effects / Q000196:embryology / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000633:toxicity; D005260:Female; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006877:Hydroxamic Acids / Q000633:toxicity; D051379:Mice; D011247:Pregnancy; D014635:Valproic Acid / Q000633:toxicity
D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; C012589:trichostatin A; D014635:Valproic Acid; D006655:Histone Deacetylases