Ethanol Withdrawal Provokes Opening of the Mitochondrial Membrane Permeability Transition Pore in an Estrogen-Preventable Manner

Abstract

We have reported that the major endogenous estrogen, 17␤-estradiol (E2), protects against oxidative injury during ethanol withdrawal (EW) in a cultured hippocampal cell line (HT22). Here, we investigated whether the pro-oxidant nature of EW mediates opening of the mitochondrial membrane permeability transition pore (PTP) in a manner protected by E2. Excess PTP opening provokes mitochondrial membrane swelling (MMS) and the collapse of membrane potential (⌬⌿m). HT22 cells were collected at the end of ethanol exposure (100 mM) for 24 h or at 4 h of EW to assess MMS by monitoring absorbance decline at 540 nm and to assess ⌬⌿m using flow cytometry. Protective effects of E2 on PTP were compared with an antioxidant butylated hydroxytoluene (BHT) and an E2 analog, ZYC26 [(3-hydroxy-2-adamantyl(1)-4-methyl-estra-1,3,5(10)-17-one], with higher antioxidant potency than E2. To assess cellular consequences of PTP opening, effects of a PTP inhibitor (cyclosporin A) on EW-induced cell death were assessed using the calcein assay. Major findings were that: 1) EW resulted in rapid MMS and ⌬⌿m collapse; 2) cyclosporin A attenuated EW-induced cell death; and 3) E2 treatment restricted to the EW phase protected against the PTP opening more prominently than BHT and to a similar degree to ZYC26. These findings suggest that EW provokes PTP opening partly but not entirely through the pro-oxidant nature and that E2 counteracts EW-associated factors to protect against the PTP opening.

Aberrant Histone Acetylation Promotes Mitochondrial Respiratory Suppression in the Brain of Alcoholic Rats

“…Suberic bishydroxamate induces the entry of apoptotic Bax to mitochondria (Zhang et al, 2004), triggering mitochondrial damage. We have demonstrated that repeated EW provokes the leakage of mitochondrial cytochrome c in male rats and the collapse of mitochondrial membrane potential in HT22 cells (Jung et al, 2009). These studies suggest that aberrant histone acetylation has a potential to impede mitochondrial integrity (Bernhard et al, 1999;Burgess et al, 2001) through factors involving mitochondrial apoptosis.…”

Alcohol and thiamine deficiency trigger differential mitochondrial transition pore opening mediating cellular death

“…In addition, 17β-estradiol protects more efficiently against the ethanol-dependent oxidative stress-induced MPT pore opening than PYC an efficient antioxidant [66]. These findings suggest that ethanol-related oxidative stress provokes partial opening of MPT pore [66]. Following these observations, ethanol-induced death of neonatal granule cells would be partially shared between proapoptotic Bax and ethanolincreased ROS production [70].…”

“…However, Kane et al [69] reported that in cerebellar granule cells, isolated from 4-day-old rats exposed to ethanol in vivo, neither ROS production nor neuron death are showed. In addition, 17β-estradiol protects more efficiently against the ethanol-dependent oxidative stress-induced MPT pore opening than PYC an efficient antioxidant [66]. These findings suggest that ethanol-related oxidative stress provokes partial opening of MPT pore [66].…”

“…When isolated from ethanol-treated 7-day-old mouse pups, brain mitochondria did not display any more change in MPT pore regulation [52]. Conversely, in vitro studies using either primary cultures of cerebellar granule cells [64,65] or cultured hippocampal cells line, Jung et al [66] show that ethanol exposure at physiologically relevant concentrations causes neuron death, supporting the notion that ethanol can kill neuron directly resulting in rapid mitochondrial membrane swelling and the collapse of membrane potential [66]. These observations indicate that ethanol-induced MPT pore opening is mediated by cytosolic factors.…”

Estrogen and Brain Protection

“…In addition to this well known glutamate neurotransmission, ethanol withdrawal perturbs the homeostasis of redox balance and signaling mechanisms. For instance, ethanol withdrawal provokes the intense generation of reactive oxygen species and activates stress-responding protein kinases (Jung et al, 2009). In addition, ethanol withdrawal inflicts mitochondrial membranes/membrane potential and suppresses mitochondrial enzymes such as cytochrome c oxidase, all of which impair fundamental functions of mitochondria (Jung et al, 2007(Jung et al, , 2009).…”