mRNA expression is a relevant tool to identify developmental neurotoxicants using an in vitro approach

So far, only a few industrial chemicals have been identified as developmental neurotoxicants. Because the current developmental neurotoxicity (DNT) guideline (Organisation for Economic Co-operation and Development TG 426) is based entirely on in vivo studies that are both time consuming and costly, there is a need to develop alternative in vitro methods for initial screening to prioritize chemicals for further DNT testing. In this study, gene expression at the mRNA level was evaluated to determine whether this could be a suitable endpoint to detect potential developmental neurotoxicants. Primary cultures of rat cerebellar granule cells (CGCs) were exposed to well known (developmental) neurotoxicants (methyl mercury chloride, lead chloride, valproic acid, and tri-methyl tin chloride) for different time periods. A significant downregulation of the mRNA level for the neuronal markers (NF-68, NF-200, N-methyl D-aspartate glutamate receptor, and gamma-amino butyric acid receptor) was observed after exposure to methyl mercury chloride, valproic acid, and tri-methyl tin chloride. Moreover, a significant increase of the neural precursor marker nestin mRNA was also observed. The mRNA expression of the astrocytic markers (glial fibrillary acidic protein [GFAP] and S100beta) was unchanged. In contrast, exposure to lead chloride significantly decreased the mRNA level of the astrocytic marker GFAP, whereas the neuronal markers were less affected. These results suggest that gene expression could be used as a sensitive tool for the initial identification of DNT effects induced by different mechanisms of toxicity in both cell types (neuronal and glial) and at various stages of cell development and maturation.