Involvement of Na+-Ca2+ exchanger in intracellular Ca2+ increase and neuronal injury induced by polychlorinated biphenyls in human neuroblastoma SH-SY5Y cells

In SH-SY5Y, a human neuroblastoma cell line, Aroclor 1254 (A1254), induced a dose-dependent (10-50 microg/ml) intracellular calcium concentration (Ca2+]i) increase. Two rather specific sodium-calcium (Na+-Ca2+) exchanger (NCX) inhibitors, bepridil (10 microM) and KB-R7943 2-2-4-(4-nitrobenzyloxy) phenyl]ethyl]isothiourea methanesulfonate] (10 microM), reduced A1254-induced Ca2+]i increase. A 24-h exposure to 30 microg/ml A1254 caused remarkable SH-SY5Y neuroblastoma cell damage. It is noteworthy that both bepridil and KB-R7943 counteracted A1254-induced neuronal injury. These results indicate that NCX contributes to Ca2+]i increase and neuronal injury induced by A1254. RT-PCR experiments revealed in SH-SY5Y neuroblastoma cells the expression of NCX1 and NCX3 isoforms. To investigate which isoform was involved in Ca2+]i increase and neuronal damage induced by A1254, we used specific antisense oligodeoxynucleotides (ODNs) to reduce NCX1 or NCX3 protein expression. The results showed that only NCX1 ODN reduced Ca2+]i increase and neuronal injury induced by A1254. In conclusion, these results indicate that NCX1 may participate to Ca2+]i increase and neurotoxicity evoked by A1254 in SH-SY5Y neuroblastoma cells.