Determination of critical cellular neurotoxic concentrations in human neuroblastoma (SH-SY5Y) cell cultures

By Forsby, A. - Pilli, F. - Bianchi, V. - Walum, E.

The effects of the neurotoxic compounds acrylamide. triethyltin chloride (TET), methyl mercury (II) chloride (MeHg) and lindane on selected neurospecific and general cell functions in differentiated human neuroblastoma SH-SY5Y cells were investigated in an attempt to determine critical cellular neurotoxic concentrations. The cultures were exposed to the neurotoxicants for three days, and then the effects on cell growth, neuronal signal transaction and the induction of axonopathy were measured. For comparison, general cytotoxicity was also determined in human epithelial (HeLa) cells. The cytotoxic activities (IC20 values) in the SHSY5Y cells were 0.18 +/- 0.03 micromolar for TET, 0.20 +/- 0.03 micromolar for MeHg, 32 +/- 10 micromolar for lindane and 810 +/- 170 micromolar for acrylamide. Inhibition of cell growth was similar in HeLa cells. Significantly lower concentrations of MeHg, acrylamide and TET than the IC20 values were sufficient to induce axonopathy. In addition, MeHg and acrylamide increased the basal intracellular free calcium concentration, [Ca2+]i, as well as the carbachol-induced Ca2+ fluxes and the depolarisation-stimulated increase of [Ca2+]i compared to control cells. The elevated [Ca2+]i may be a primary cause of the acrylamide-induced and MeHg-induced neuropathy. Treatment with lindane (1 micromolar) slightly decreased the depolarisation-evoked Ca2+ influx in the neuroblastoma cells. A parallel to the documented neurotoxic mechanism of lindane (i.e. inhibition of the gamma-aminobutyric acid-activated Cl- channels) is possible.