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In vitro screening for anticonvulsant-induced teratogenesis in neural primary cultures and cell lines
C M Regan1, A M Gorman, O M Larsson
1Department of Pharmacology, University College, Belfield, Dublin, Ireland.
Abstract:
To establish inherent potential for the induction of neural tube defects the ability of selected anticonvulsant agents to interfere with cell division has been established in vitro using an antiproliferative assay in clonal cell lines and a cytotoxicity assay using primary cultures of cerebral cortex neurons at different stages of development. In order to evaluate the relative toxicities of these agents their in vitro effects were determined at 2-3 times the plasma therapeutic level. By these procedures valproate and the benzodiazepines, diazepam and clonazepam, exerted a potent antiproliferative action which could not be attributed to increased cytotoxicity. In contrast phenytoin was markedly cytotoxic but was without an antiproliferative action. This cytotoxicity was most pronounced during the periods of extensive fibre outgrowth. When compared to epidemiological and animal study data, agents which inhibited cell proliferation within twice therapeutic concentration were consistently associated with major neural tube malformations. However phenytoin, found to be positive in the cell cytotoxicity assay, is not associated with neural tube malformations but rather is primarily associated with mental retardation. Thus assessment of antiproliferative activity of anticonvulsant drugs may be one criterion for identification of teratogenic potential during neurulation.
Insights
Anticonvulsant drugs like valproate and benzodiazepines can disrupt cell division, increasing neural tube defect risks. Phenytoin, however, is cytotoxic but doesn't affect cell proliferation, linking it to mental retardation instead.
Area of Science:
- Developmental neurobiology
- Pharmacology
- Teratology
Background:
- Neural tube defects (NTDs) are serious birth anomalies.
- Anticonvulsant drugs are frequently prescribed, necessitating safety evaluations.
Purpose of the Study:
- To investigate the in vitro antiproliferative and cytotoxic effects of anticonvulsant agents.
- To correlate these effects with the potential for inducing neural tube defects.
Main Methods:
- Utilized antiproliferative assays in clonal cell lines.
- Employed cytotoxicity assays on primary cerebral cortex neuron cultures.
- Evaluated drug effects at 2-3 times the plasma therapeutic level.
Main Results:
- Valproate and benzodiazepines (diazepam, clonazepam) showed potent antiproliferative action.
- Phenytoin exhibited marked cytotoxicity, particularly during neuronal fiber outgrowth.
- Antiproliferative agents correlated with NTDs; cytotoxic-only agents like phenytoin did not.
Conclusions:
- Antiproliferative activity of anticonvulsants is a potential indicator for neural tube defect teratogenicity.
- Cytotoxicity without antiproliferative effects may be linked to other developmental issues, such as mental retardation.
- In vitro assays can help predict the teratogenic potential of anticonvulsant drugs during neurulation.