CELL-PROLIFERATION, MIGRATION AND CAM-DEPENDENT NEURITE OUTGROWTH AS DEVELOPMENTAL IN-VITRO END-POINTS FOR SCREENING TERATOGENIC POTENTIAL - APPLICATION TO VALPROIC ACID AND RELATED ANALOGS OF VARYING POTENCY

The in vivo teratogenic potential of valproic acid (VPA) and related t eratogenic and non-teratogenic analogues has been correlated with thei r effects on specific in vitro endpoints of cell proliferation, migrat ion and CAM-dependent neurite outgrowth, as these events are common to crucial epochs of development. The (+/-)-2-n-propyl-4-pentynoic acid [(+/-)-4-yn-VPA] and S-2-n-propyl-4-pentynoic acid [S(-)-4-yn-VPA] ana logues increased the incidence of neural tube defects in mouse embryos exposed to a single dose, whereas the E-2-n-propyl-2-pentenoic acid ( E-2-en-VPA) analogue and R-2-n-propyl-4-pentynoic acid [R(+)-4-yn-VPA] enantiomer were without effect. VPA and related analogues tested exer ted comparable G1 phase antiproliferative effects in C6 glioma and lim b bud cells in a dose range of 0-3 mM; however, their relative potency did not correlate with in vivo teratogenicity. In contrast, VPA and a ll teratogenic analogues, at 3 mM, inhibited neuronal cell aggregation and limb bud chondrocyte differentiation in a manner that exhibited a reasonable correlation with their in vivo teratogenicity. The teratog enic S(-)-4-yn-VPA and non-teratogenic R(+)-4-yn-VPA enantiomers exhib ited a differential inhibition of primary neurone outgrowth of neurite s stimulated by cell adhesion molecules [L1 and N-cadherin (NCAD)]. Ha lf-maximal inhibition was observed at approximately 150 mu M for the t eratogenic S(-)-4-yn-VPA enantiomer, but not the non-teratogenic R(+)- 4-yn-VPA form. These results suggest that in vitro perturbations of di fferentiation are likely to provide the greatest discriminatory power for in vivo teratogenicity. (C) 1998 Elsevier Science Ltd. All rights reserved.