The toxicity of chlorpyrifos towards differentiating mouse N2a neuroblastoma cells

The aim of this work was to study the effects of chlorpyrifos (CPF) on the outgrowth of axons by differentiating mouse N2a neuroblastoma cells. This w as achieved by morphological, Western blotting and enzymatic analyses of ce lls induced to differentiate in the presence and absence of CPF added eithe r at the same time (co-differentiation) or 16 h after (post-differentiation ) the induction of cell differentiation. The outgrowth of axon-like process es was impaired following 4 or 8 h exposure to CPF in both co- and post-dif ferentiation experiments. Western blotting analysis revealed reduced levels of neurofilament heavy chain (NF-H) following 8 h of exposure but no signi ficant effect at 4 h under both co- and post-differentiation conditions. By contrast, levels of the heat shock protein HSP-70 were raised at both time points, but only in co-differentiation experiments. Neuropathy target este rase (NTE) activity was lower than controls following 4 or 8 h of exposure under co-differentiation conditions, but not under any post-differentiation conditions. The results suggest that the inhibition of axon production and maintenance by CPF in differentiating N2a cells may involve multiple targe ts, which are different under co- and post-differentiation conditions. (C) 2001 Elsevier Science Ltd. All rights reserved.