Coenzyme Q10 Prevents Apoptosis by Inhibiting Mitochondrial Depolarization Independently of Its Free Radical Scavenging Property

Laura Papucci,Nicola Schiavone,Ewa Witort,Martino Donnini,Andrea Lapucci,Alessio Tempestini,Lucia Formigli,Sandra Zecchi-Orlandini,Giovanni Orlandini,Giuseppe Carella,Rosario Brancato,Sergio Capaccioli

doi:10.1074/jbc.m302297200

Abstract

The permeability transition pore (PTP) is a mitochondrial channel whose opening causes the mitochondrial membrane potential (deltapsi) collapse that leads to apoptosis. Some ubiquinone analogues have been demonstrated previously to modulate the PTP open-closed transition in isolated mitochondria and thought to act through a common PTP-binding site rather than through oxidation-reduction reactions. We have demonstrated recently both in vitro and in vivo that the ubiquitous free radical scavenger and respiratory chain coenzyme Q10 (CoQ10) prevents keratocyte apoptosis induced by excimer laser irradiation more efficiently than other antioxidants. On this basis, we hypothesized that the antiapoptotic property of CoQ10 could be independent of its free radical scavenging ability and related to direct inhibition of PTP opening. In this study, we have verified this hypothesis by evaluating the antiapoptotic effects of CoQ10 in response to apoptotic stimuli, serum starvation, antimycin A, and ceramide, which do not generate free radicals, in comparison to control, free radical-generating UVC irradiation. As hypothesized, CoQ10 dramatically reduced apoptotic cell death, attenuated ATP decrease, and hindered DNA fragmentation elicited by all apoptotic stimuli. This was accompanied by inhibition of mitochondrial depolarization, cytochrome c release, and caspase 9 activation. Because these events are consequent to mitochondrial PTP opening, we suggest that the antiapoptotic activity of CoQ10 could be related to its ability to prevent this phenomenon.

Highlights

The permeability transition pore (PTP) is a mitochondrial channel whose opening causes the mitochondrial membrane potential (⌬␺) collapse that leads to apoptosis
UVC Irradiation, Antimycin A, C2-ceramide, and Serum Starvation Committed Cultured Keratocytes to Apoptosis—We have previously optimized by time-lapse videomicroscopy the doses of stimuli necessary to commit a substantial number of RCE keratocytes to apoptosis, but not to necrosis, within 24 h after treatments
Free Radical Generation Was Restricted to UVC-Irradiation—We have analyzed the effects of the apoptotic doses of UVC irradiation, antimycin A, C2-ceramide and serum starvation on free radical generation

Summary

Introduction

The permeability transition pore (PTP) is a mitochondrial channel whose opening causes the mitochondrial membrane potential (⌬␺) collapse that leads to apoptosis. CoQ10 but Not Vitamin E Increased Cell Survival in Response to Free Radical Independent Apoptotic Stimuli—Once ascertained that apoptosis by antimycin A, C2-ceramide and serum starvation was not consequent to free radical generation, the effects of a 2-h pretreatment with 10 ␮M CoQ10 or vitamin E on cell survival at the 24th h following application of apoptotic stimuli was evaluated by the MTT assay.

Results

Conclusion