The Protective Effect Of K-ATP Channel Blocker Glybenclamide Against Fe2+-induced Cell Toxicity In Dopaminergic SK-N-SH Cell

Parkinson’s disease (PD) is the secondly most prevalent neurodegenerative disease just after Alzheimer’s disease. Neuropathological hallmarks of the disease include the degeneration and loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) and the subsequent dopamine (DA) depletion in the striatum. ATP-sensitive potassium (K-ATP) channels have been implicated to the selective DA neurons damage in substantia nigra (SN) but not in the neighboring ventral tegmental area (VTA). The activation of K-ATP channels may result in hyperpolarization of cell membrane potential and mitochondrial function damage. Also it was reported that there was an accumulation of iron in the SN of PD patients. The iron plays a key role in oxidative stress, and the accumulation of iron may induce the increase of reactive oxygen species (ROS) and the decrease of adenosine triphosphate (ATP) which could subsequently activate K-ATP channels. Studies showed that divalent metal transport1(DMT1) is related to the accumulation of iron in SN area of PD patients and cell membrane hyperpolarization may enhance its iron-transporting function. In our study, laser confocal scanning microscopy, flow cytometry, western blots and other methods are used to observe the protective effect of K-ATP channel blocker glybenclamide against the SK-N-SH cell damages induced by ferrous iron (Fe2+), as well as the underlying mechanisms in SK-N-SH cell. The results were as follows:1. compared to the control group, Fe2+-treated cells released more lactate dehydrogenase(LDH)(P0.01), and the glybenclamide pretreated cells (5p,mol/L and10μmol/L) released less LDH compared to Fe2+-treated group (P＜0.01).2. there was a significant decrease in the fluorescence intensity in Fe2+-treated group compared to the glybenclamide pretreated group ((5μmol/L and10μmol/L)((Two-way ANOVA, F=24.885, P＜0.01, Fe2+vs. Control; P<0.01, glybenclamide vs. Fe2+).3. there was an apparent decrease of⊿Ψm in Fe2+-treated cells compared to the control (P<0.01) and this effects could be inhibited by pretreatment of glybenclamide (P<0.01).4. since SOD is a highly potent protective agent against cell injury during oxidative stress, we examined SOD expression in the SK-N-SH cells.5μmol/L and10μmol/L glybenclamide pretreated cells expressed more Cu/Zn-SOD compared to Fe2+-treated cells (P<0.01).The result above suggests that K-ATP channels blocker glybenclamide showed a protective effect against Fe2+-induced damages in SK-N-SH cells. The possible underlying mechanism may be that glybenclamide inhibits the activation of K-ATP channels which could alleviate the hyperpolarization of cell membrane, and the later may reduce the accumulation of iron by attenuating the function of DMT1.