Potassium channels are involved in zinc‐induced apoptosis in MES23.5 cells

Abstract

There is evidence that zinc may be involved in the pathogenesis of Parkinson's disease by an apoptotic pathway. However, the mechanisms underlying zinc-induced apoptosis are unknown. Previous studies showed that 6-hydroxydopamine (6-OHDA)-enhanced potassium channels are involved in apoptosis of dopaminergic neurons. Our study was designed to test whether zinc-induced apoptosis was mediated by potassium channels. First we demonstrated cell apoptosis with zinc treatment by Hoechst staining assay. The results showed that 13.38% +/- 0.6% of MES23.5 cells were apoptotic after 24 hr of incubation with 60 microM zinc sulfate. Then we observed that the tyrosine hydroxylase (TH) protein expression and the dopamine content decreased, as detected by Western blots and high-performance liquid chromatography-electrochemical detection (HPLC-ECD). We further elucidated the mechanism of cell apoptosis by using whole-cell patch clamp recording. The data demonstrated that MES23.5 cells exhibited a tetraethylammonium (TEA)-sensitive outward K(+) current with delayed rectifier characteristics. Increases of K(+) current density were recorded following the treatment with 60 microM zinc for 4-8 hr. After incubation with 20 mM TEA, the zinc-induced enhancement of K(+) currents was fully blocked. Furthermore, incubation with TEA blocked zinc-mediated caspase-3 activation and cell apoptosis. These data suggest that zinc-induced apoptosis of MES23.5 dopaminergic cells may due to the enhancement of TEA-sensitive K(+) channel activity.

Rosmarinic Acid Antagonized 1-Methyl-4-Phenylpyridinium (MPP+)-Induced Neurotoxicity in MES23.5 Dopaminergic Cells

“…Cells were seeded in 25 cm 2 flask, pretreated with 10 −9 mol/L RA for 30 minutes, followed by 200 µmol/L MPP + treatment for 24 hours and then the samples were prepared as previously described, in our laboratory. 19 Separation was achieved on a PE C18 reversed-phase column. The mobile phase consisted of 20 mmol/L citromalic acid, 50 mmol/L sodium caproate, 0.134 mmol/L EDTA-2Na, 3.75 mmol/L sodium octane sulphonic acid, 1 mmol/L di-sec-butylamine, and contained 5% (v/v) methanol; the flow rate was 1 mL/min.…”

Pretreatment with potassium channel blockers of 4-aminopyridine and tetraethylammonium attenuates behavioural symptoms of Parkinsonism induced by intrastriatal injection of 6-hydroxydopamine; the role of lipid peroxidation

“…These data suggest that zinc-induced apoptosis of MES23.5 dopaminergic cells may due to the enhancement of TEA-sensitive K + channel activity. 32 6-OHDA induced the SN dopaminergic neurodegeneration through mitochondrial dysfunction and oxidative stress. It is noteworthy that the general term "oxidative stress" is commonly and intimately associated with nigral cell death in the PD literature.…”