Chronic ethanol consumption enhances sensitivity to Ca2+-mediated opening of the mitochondrial permeability transition pore and increases cyclophilin D in liver

Abstract

Chronic ethanol consumption increases mitochondrial oxidative stress and sensitivity to form the mitochondrial permeability transition pore (MPTP). The mechanism responsible for increased MPTP sensitivity in ethanol-exposed mitochondria and its relation to mitochondrial Ca(2+) handling is unknown. Herein, we investigated whether increased sensitivity to MPTP induction in liver mitochondria from ethanol-fed rats compared with controls is related to an ethanol-dependent change in mitochondrial Ca(2+) accumulation. Liver mitochondria were isolated from control and ethanol-fed rats, and Ca(2+)-mediated induction of the MPTP and mitochondrial Ca(2+) retention capacity were measured. Levels of proposed MPTP proteins as well as select pro- and antiapoptotic proteins were measured along with gene expression. We observed increased steatosis and TUNEL-stained nuclei in liver of ethanol-fed rats compared with controls. Liver mitochondria from ethanol-fed rats had increased levels of proapoptotic Bax protein and reduced Ca(2+) retention capacity compared with control mitochondria. We observed increased cyclophilin D (Cyp D) gene expression in liver and protein in mitochondria from ethanol-fed animals compared with controls, whereas there was no change in the adenine nucleotide translocase and voltage-dependent anion channel. Together, these results suggest that enhanced sensitivity to Ca(2+)-mediated MPTP induction may be due, in part, to higher Cyp D levels in liver mitochondria from ethanol-fed rats. Therefore, therapeutic strategies aimed at normalizing Cyp D levels may be beneficial in preventing ethanol-dependent mitochondrial dysfunction and liver injury.