Mitochondrial glutathione replacement restores surfactant synthesis and secretion in alveolar epithelial cells of ethanol-fed rats.
BACKGROUND
Chronic alcohol abuse increases the incidence and severity of acute lung injury in critically ill patients. Previously we determined that ethanol ingestion in rats dramatically decreased alveolar epithelial cellular levels of glutathione and surfactant synthesis and secretion in vitro. Previous studies in alcoholic liver disease suggest that mitochondrial glutathione levels, and not cellular levels per se, are involved in the pathogenesis of ethanol-mediated hepatotoxicity. Therefore, we hypothesized that alveolar epithelial mitochondrial glutathione depletion mediates the observed defects in surfactant synthesis and secretion in ethanol-fed rats.


METHODS
Male Sprague-Dawley rats were fed the Lieber-DeCarli liquid diet with or without ethanol (36% of total calories) for 6 weeks. In some experiments, ethanol-fed rats were then switched to the control diet for 1 week, with or without glutathione supplementation with either N-acetylcysteine (NAC) or procysteine (PRO). Alveolar epithelial type II cells were then isolated and glutathione levels (cytosolic and mitochondrial) and surfactant production (synthesis and secretion) were determined.


RESULTS
Ethanol ingestion decreased (p < 0.05) mitochondrial and cytosolic levels of glutathione, and surfactant synthesis and secretion in isolated type II cells when compared to cells from control-fed rats. NAC treatment restored (p < 0.05) cytosolic but not mitochondrial glutathione levels (p > 0.05), and had no effect (p > 0.05) on surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats. In contrast, PRO treatment restored (p < 0.05) cytosolic and mitochondrial glutathione levels, and normalized (p < 0.05) surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats.


CONCLUSIONS
These results suggest that mitochondrial, and not simply cytosolic, replacement of glutathione is necessary to improve surfactant function in critically ill patients with a history of alcohol abuse.
Guidot
D M
DM
Atlanta Veterans Affairs Medical Center and Division of Pulmonary and Critical Care Medicine, Emory University School of Medicine, Atlanta, Georgia, USA. dguidot@emory.edu
Brown
L A
LA
D000818:Animals; D002478:Cells, Cultured; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism; D000431:Ethanol / Q000494:pharmacology*; D005978:Glutathione / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism; D011663:Pulmonary Surfactants / Q000096:biosynthesis / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D002492:Central Nervous System Depressants; D011663:Pulmonary Surfactants; D000431:Ethanol; D005978:Glutathione