Folic Acid Suppression of Nicotine-induced Teratogenesis in Zebrafish Embryos

Children of smoking mothers have an increased risk for developmental abnormalities such as low birth weight as well as specific craniofacial anomalies including cleft lip and palate (Romotti et al 1998). Previous reports describe the teratogenic potential of nicotine in developing mouse embryos. We have extended this observation to zebrafish embryos. Independent animal studies and human epidemiologic intervention trials have demonstrated the capacity of folic acid to decrease the incidence of neural tube defects and orofacial clefts. Objective: The objective of this work was to identify the minimal concentration of nicotine necessary to alter the morphology of developing zebrafish embryos and to characterize the phenotypes observed. Subsequent studies examined the hypothesis that folic acid can suppress the teratogenic effects of nicotine. Methods: Within 1.5 hours post-fertilization, zebrafish embryos were bathed in 1.25 mM or 1.5 mM L-nicotine in the absence or presence of folic acid (concentrations between 0.05 mM and 1.0 mM) for 24 hours. Control (untreated) embryos were bathed in egg water. After 24 hours of treatment, embryos were transferred to new dishes and bathed in egg water. Embryo morphology was assessed at 48 hours and 5 days. Results: Embryos exposed to 1.25 mM and 1.5 mM nicotine displayed a spectrum of developmental malformations in more than half of the 48 hour and 5 day old fish. Treatment of folic acid with nicotine displayed a dose dependent suppression of the teratogenic effects of nicotine, however, only 1.0 mM folic acid was effective at suppressing the effects of both 1.25 and 1.5 mM nicotine. Conclusion: Our preliminary data supports the view that nicotine is a potent teratogen, particularly affecting early vertebrate embryogenesis. Furthermore, it suggests that folic acid may be an effective agent to counteract the negative effects of nicotine during vertebrate development.