The involvement of Eag1 potassium channels and miR-34a in rotenone-induced death of dopaminergic SH-SY5Y cells

The loss of dopaminergic neurons and the resultant motor impairment are hallmarks of Parkinson's disease. The SH-SY5Y cell line is a model of dopaminergic neurons, and allows for the study of dopaminergic neuronal injury. Previous studies have revealed changes in Ether à go-go 1 (Eag1) potassium channel expression during p53-induced SH-SY5Y apoptosis, and the regulatory involvement of microRNA-34a (miR-34a) was demonstrated. In the present study, the involvement of Eag1 and miR-34a in rotenone-induced SH-SY5Y cell injury was investigated. Rotenone is a neurotoxin, which is often used to generate models of Parkinson's disease, since it causes the death of nigrostriatal neurons by inducing intracellular aggregation of alpha synuclein and ubiquitin. In the present study, rotenone resulted in a dose-dependent decrease in cell viability, as revealed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and trypan blue cell counting assays. In addition, Eag1 was demonstrated to be constitutively expressed by SH-SY5Y cells, and involved in cell viability. Suppression of Eag1 with astemizole resulted in a dose-dependent decrease in cell viability, as revealed by MTT assay. Astemizole also enhanced the severity of rotenone-induced injury in SH-SY5Y cells. RNA interference against Eag1, using synthetic small interfering RNAs (siRNAs), corroborated this finding, as siRNAs potentiated rotenone-induced injury. Eag1-targeted siRNAs (kv10.1-3 or EAG1hum_287) resulted in a statistically significant 16.4–23.5% increase in vulnerability to rotenone. An increased number of apoptotic nuclei were observed in cells transfected with EAG1hum_287. Notably, this siRNA intensified rotenone-induced apoptosis, as revealed by an increase in caspase 3/7 activity. Conversely, a miR-34a inhibitor was demonstrated to exert neuroprotective effects. The viability of cells exposed to rotenone for 24 or 48 h and treated with miR-34a inhibitor was restored by 8.4–8.8%. In conclusion, Eag1 potassium channels and miR-34a are involved in the response to rotenone-induced injury in SH-SY5Y cells. The neuroprotective effect of mir-34a inhibitors merits further investigations in animal models of Parkinson's disease.