Phenytoin inhibits expression of microtubule-associated protein 2 and influences cell-viability and neurite growth of cultured cerebellar granule cells

Prenatal effects of antiepileptic drugs

Antiepileptic drugs (AEDs) target ion channels and neurotransmitter systems in the brain; these same targets are responsible for regulation of processes essential for brain development. In this review, experimental findings on adverse effects of AEDs in the developing mammalian brain will be presented, including interference with physiological apoptotic cell death, cell proliferation and migration, neurogenesis, axonal arborization, synaptogenesis, and synaptic plasticity.

Diphenylhydantoin plays a role in gene expression related to cytoskeleton and protein adhesion in human normal palate fibroblasts

AIMS

Morphogenetic processes during palate development are related to extracellular matrix composition. The cell-extracellular matrix relation plays a role in cell activity and in gene expression. We studied the effect of diphenylhydantoin, a teratogen known to induce cleft palate in human newborns, on extracellular matrix production. We investigated whether diphenylhydantoin treatment caused any differences in glycosaminoglycans, collagen synthesis and gene expression in human normal palate fibroblasts.

METHODS

Human palate fibroblasts were maintained for 24 hours in serum-free 199 medium containing 5 microg/mL (3)H-glucosamine or (3)H proline hydrochloride. Collagen and glycosaminoglycan classes were then measured using biochemical methods, gene expression with microarray analysis and cytoskeleton components with immunofluorescent antibodies and computer analysis.

RESULTS

In normal fibroblasts diphenylhydantoin reduced collagen and glycosaminoglycan synthesis with a marked effect on sulphated glycosaminoglycans. There were also substantial decreases in tubulin, vimentin and alpha-actin staining and an increase of vinculin compared to controls. Diphenylhydantoin acted on several genes related to the synthesis of cytoskeleton and adhesion membrane proteins. It inhibited caderin, caveolin, RTK and alpha-actin, and increased nectin, cytoplasmatic FRG vinculin, ITGA, ITGB extracellular matrix ligand and EDG2 gene expression. DNA binding gene expression, which plays a role in cell growth and senescence, was activated.

CONCLUSIONS

Since cell activity is dependent on the cell morphology and extracellular matrix composition, these findings indicate that in human normal palate fibroblasts diphenylhydantoin can modify cytoskeletal components and extracellular matrix-cell adhesion, with consequent effects on gene expression. These changes might be related to anomalous palate development.

Possible function of astrocyte cytochrome P450 in control of xenobiotic phenytoin in the brain: in vitro studies on murine astrocyte primary cultures

[4-(14)C]Phenytoin underwent a rapid cellular uptake by diffusion within 5 min when applied in a concentration of 10 microM to mouse brain astrocyte cultures. Subsequently, a slow linear increase of intracellular radioactivity indicated metabolic trapping of the drug, with final concentrations reaching 144 pmol phenytoin/mg protein in the astrocytes. Phenytoin levels from 1 to 10 microM decreased cell viability by 15%. The action of cytochrome P450 present in astrocytes in concentrations of 16-17 pmol P450/mg protein could explain these slight cytotoxic effects by generating intermediate metabolites of phenytoin. In contrast, concentrations of 50 microM strongly inhibited cell proliferation. A Cyp2c29 immunorelated P450 isoform was expressed in nearly all astrocytes in culture. Intracellular [4-(14)C]phenytoin was degraded to its major metabolites dihydrodiol, p-HPPH, and m-HPPH through a P450-dependent reaction with a specific activity of 0.66 pmol/min x mg protein, or 0.12 pmol/min x mg protein as measured in cell homogenates. These data underscore the importance of astrocytes as brain cells active in the detoxification of foreign substrates, but also in their toxification due to reactive metabolites generated during these metabolic processes. After diffusionary influx of drugs and other xenobiotics, the astrocyte P450 monooxygenases perform an essential role in the mediation of toxicity most frequently encountered in highly vulnerable neurons.