cytochrome-c-t and 1-(4-methoxyphenyl)pyridinium

Inhibition of astrocytic apoptosis has been regarded as a novel prospective strategy for treating neurodegenerative disorders such as Parkinson's disease. In the present study, we demonstrated that iptakalim (IPT), an ATP-sensitive potassium channel (K(ATP) channel) opener, exerted protective effect on MPP(+)-induced astrocytic apoptosis, which was reversed by selective mitochondrial K(ATP) channel blocker 5-hydroxydecanoate. Further study revealed that IPT inhibited glutathione (GSH) depletion, mitochondrial membrane potential loss and subsequent release of pro-apoptotic factors (cytochrome c and apoptosis-inducing factor (AIF), and c-Jun NH(2)-terminal kinase/mitogen-activated protein kinases (MAPK) phosphorylation induced by MPP(+). Meanwhile, extracellular signal-regulated kinase (ERK) 1/2 inhibitor PD98059 inhibited the protective effect of IPT on MPP(+)-induced astrocytic apoptosis. Furthermore, IPT could also activate ERK/MAPK and maintain increased phospho-ERK1/2 level after MPP(+) exposure. Taken together, these findings reveal for the first time that IPT protects against MPP(+)-induced astrocytic apoptosis via inhibition of mitochondria apoptotic pathway and regulating the MAPK signal transduction pathways by opening mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels in astrocytes. And targeting K(ATP) channels expressed in astrocytes may provide a novel therapeutic strategy for neurodegenerative disorders.

Topics: Animals; Apoptosis; Astrocytes; Blotting, Western; Cells, Cultured; Cytochromes c; Flow Cytometry; Glutathione; JNK Mitogen-Activated Protein Kinases; Membrane Potentials; Mitochondria; Mitogen-Activated Protein Kinases; Nerve Tissue Proteins; Phosphorylation; Propylamines; Pyridinium Compounds; Rats; Rats, Sprague-Dawley; Signal Transduction

Opening of the mitochondrial permeability transition pore has been recognized to be involved in cell death. The present study investigated the effect of trifluoperazine and W-7 on the MPP+-induced mitochondrial damage and cell death in undifferentiated PC12 cells. Calmodulin antagonists (trifluoperazine, W-7 and calmidazolium) at 0.5-1 microM significantly reduced the loss of cell viability in PC12 cells treated with 500 microM MPP+. Trifluoperazine and W-7 (0.5-1 microM) inhibited the nuclear damage, the loss of the mitochondrial transmembrane potential followed by cytochrome c release, and the elevation of intracellular Ca2+ levels due to MPP+ in PC12 cells and attenuated the formation of reactive oxygen species and the depletion of GSH. Calmodulin antagonists at 5-10 microM exhibited a cytotoxic effect on PC12 cells, and compounds at 10 microM did not attenuate cytotoxicity of MPP+. Calmodulin antagonists (0.5-1 microM) significantly reduced rotenone-induced mitochondrial damage and cell death, whereas they did not attenuate cell death and elevation of intracellular Ca2+ levels due to H2O2 or ionomycin. The results show that trifluoperazine and W-7 exhibit a differential inhibitory effect against cytotoxicity of MPP+ depending on concentration. Both compounds at the concentrations less than 5 microM may attenuate the MPP+-induced viability loss in PC12 cells by suppressing change in the mitochondrial membrane permeability and by lowering the intracellular Ca2+ levels.

Topics: Animals; Antipsychotic Agents; Calcium; Calcium-Calmodulin-Dependent Protein Kinases; Calmodulin; Caspase 3; Caspases; Cell Death; Cytochromes c; DNA Fragmentation; Enzyme Inhibitors; Flow Cytometry; Glutathione; Indicators and Reagents; Mitochondria; PC12 Cells; Permeability; Pyridinium Compounds; Rats; Reactive Oxygen Species; Rotenone; Sulfonamides; Trifluoperazine