Stage-dependent vulnerability of fetal mesencephalic neuroprogenitors towards dopaminergic neurotoxins

Although extensive knowledge exists on selective vulnerability of dopaminergic neurons against parkinsonism-inducing neurotoxins, there is a complete lack of such data on immature neuroprogenitors. Here we investigated the toxicity of 1-methyl-4-phenylpyridinium (MPP+), 6-hydroxydopamine (6-OHDA) and the free radical generator H2O2 on various developmental stages of predopaminergic mesencephalic neuroprogenitors (mNPCs) to evaluate stage-dependency of selective dopaminergic neurotoxicity. Striatal NPCs (sNPCs) without dopaminergic differentiation potential served as controls. Exposure of both undifferentiated NPCs to MPP+ resulted in concentration-dependent cell death at concentrations of >10 μM after 72 h without differences between both cell types, while 6-OHDA led to relevant cell death at 1000 μM after 24 h with significant higher sensitivity of mNPCs compared to sNPCs. H2O2 did not induce relevant cell death in all cell types. In NPC cultures differentiated for 14 days, MPP+ showed enhanced toxicity compared to the undifferentiated counterparts, but no significant differences between both NPC type and differentiation conditions. 6-OHDA showed similar toxicity pattern in differentiated compared to undifferentiated NPCs. By evaluating the toxicity of MPP+ on MAP2ab+ neurons derived from both mNPCs and sNPCs as well as tyrosine hydroxylase (TH)+ dopaminergic cells from mNPCs, we found concentration-dependent cell death of all cell types with no increased vulnerability of TH+ cells. Primary TH+ neurons showed significantly higher vulnerability to MPP+. Together, we demonstrated stage-dependent vulnerability of NPCs towards dopaminergic neurotoxins, but no selective vulnerability of NPC-derived TH+ dopaminergic cells towards MPP+. This cell system seems not suitable as a screening tool for selective dopaminergic toxicity.