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Sensitivity of the 2‐oxoglutarate carrier to alcohol intake contributes to mitochondrial glutathione depletion
Author(s) -
Coll Olga,
Colell Anna,
GarcíaRuiz Carmen,
Kaplowitz Neil,
FernándezCheca J. C.
Publication year - 2003
Publication title -
hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.488
H-Index - 361
eISSN - 1527-3350
pISSN - 0270-9139
DOI - 10.1053/jhep.2003.50351
Subject(s) - glutathione , sensitivity (control systems) , alcohol , chemistry , mitochondrion , medicine , biochemistry , enzyme , electronic engineering , engineering
The mitochondrial pool of reduced glutathione (mGSH) is known to play a protective role against liver injury and cytokine‐mediated cell death. However, the identification of the mitochondrial carriers involved in its transport in hepatocellular mitochondria remains unestablished. In this study, we show that the functional expression of the 2‐oxoglutarate carrier from HepG2 cells in mitochondria from Xenopus laevis oocytes conferred a reduced glutathione (GSH) transport activity that was inhibited by phenylsuccinate, a specific inhibitor of the carrier. In addition, the mitochondrial transport of GSH and 2‐oxoglutarate in isolated mitochondria from rat liver exhibited mutual competition and sensitivity to glutamate and phenylsuccinate. Interestingly, the kinetics of 2‐oxoglutarate transport in rat liver mitochondria displayed a single Michaelis‐Menten component with a Michaelis constant of 3.1 ± 0.3 mmol/L and maximum velocity of 1.9 ± 0.1 nmol/mg protein/25 seconds. Furthermore, the initial rate of 2‐oxoglutarate was reduced in mitochondria from alcohol‐fed rat livers, an effect that was not accompanied by an alcohol‐induced decrease in the 2‐oxoglutarate messenger RNA levels but rather by changes in mitochondrial membrane dynamics induced by alcohol. The fluidization of mitochondria by the fluidizing agent 2‐(2‐methoxyethoxy)ethyl 8‐(cis‐2‐n‐octylcyclopropyl) (A 2 C) restored the initial transport rate of both GSH and 2‐oxoglutarate. Finally, these changes were reproduced in normal liver mitochondria enriched in cholesterol where the fluidization of cholesterol‐enriched mitochondria with A 2 C restored the order membrane parameter and the mitochondrial 2‐oxoglutarate uptake. In conclusion, these findings provide unequivocal evidence for 2‐oxoglutarate as a GSH carrier and its sensitivity to membrane dynamics perturbation contributes in part to the alcohol‐induced mGSH depletion.