K(ATP) channel block prevents proteasome inhibitor-induced apoptosis in differentiated PC12 cells

Abstract

Dysfunction of the proteasome system has been suggested to be implicated in neuronal degeneration. Modulation of KATP channels appears to affect the viability of neuronal cells exposed to toxic insults. However, the effect of KATP channel blockers on the neuronal cell death mediated by proteasome inhibition has not been studied. The present study investigated the effect of KATP channel blockers on proteasome inhibitor-induced apoptosis in differentiated PC12 cells and SH-SY5Y cells. 5-Hydroxydecanoate (a selective KATP channel blocker) and glibenclamide (a cell surface and mitochondrial KATP channel inhibitor) reduced the proteasome inhibitor-induced apoptosis. Addition of the KATP channel blockers attenuated the proteasome inhibitor-induced changes in the levels of apoptosis-related proteins, the loss of the mitochondrial transmembrane potential, the increase in the formation of reactive oxygen species and the depletion of glutathione in both cell lines. The results show that KATP channel blockers may attenuate proteasome inhibitor-induced apoptosis in PC12 cells by suppressing activation of the mitochondrial pathway and of the caspase-8- and Bid-dependent pathways. The preventive effect appears to be associated with the inhibition of the formation of reactive oxygen species and the depletion of glutathione. KATP channel blockade appears to prevent proteasome inhibition-induced neuronal cell death.

Keywords: 2′,7′-Dichlorofluorescin diacetate (Sigma-Aldrich Inc. PubChem CID 77718); 3,3′-Dihexyloxacarbocyanine iodide (Sigma-Aldrich Inc. PubChem CID 103765); 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (Sigma-Aldrich Inc. PubChem CID 64965); 5-Hydroxydecanoate (Sigma-Aldrich Inc. PubChem CID 1825); Apoptosis-related proteins; Glibenclamide (Sigma-Aldrich Inc. PubChem CID 3488); K(ATP) channel blockers; MG115 (EMD-Calbiochem PubChem CID 9868928); MG132 (EMD-Calbiochem PubChem CID 462382); PC12 cells; Proteasome inhibitors; Protection; z-Asp–(OMe)–Gln–Met–Asp(OMe) fluoromethyl ketone (EMD-Calbiochem PubChem CID 644197); z-Ile–Glu–(O-Me)–Thr–Asp(O-Me) fluoromethyl ketone (EMD-Calbiochem PubChem CID 9852164); z-Leu–Glu–(O-Me)–His–Asp(O-Me) fluoromethyl ketone (Sigma-Aldrich Inc. PubChem CID 10032582).