Mitochondrial GSH determines the toxic or therapeutic potential of superoxide scavenging in steatohepatitis.
OBJECTIVE
Steatohepatitis (SH) is associated with mitochondrial dysfunction and excessive production of superoxide, which can then be converted into H(2)O(2) by SOD2. Since mitochondrial GSH (mGSH) plays a critical role in H(2)O(2) reduction, we explored the interplay between superoxide, H(2)O(2), and mGSH in nutritional and genetic models of SH, which exhibit mGSH depletion.


METHODS
We used isolated mitochondria and primary hepatocytes, as well as in vivo SH models showing mGSH depletion to test the consequences of superoxide scavenging.


RESULTS
In isolated mitochondria and primary hepatocytes, superoxide scavenging by SOD mimetics or purified SOD decreased superoxide and peroxynitrite generation but increased H(2)O(2) following mGSH depletion, despite mitochondrial peroxiredoxin/thioredoxin defense. Selective mGSH depletion sensitized hepatocytes to cell death induced by SOD mimetics, and this was prevented by RIP1 kinase inhibition with necrostatin-1 or GSH repletion with GSH ethyl ester (GSHee). Mice fed the methionine-choline deficient (MCD) diet or MAT1A(-/-) mice exhibited reduced SOD2 activity; in vivo treatment with SOD mimetics increased liver damage, inflammation, and fibrosis, despite a decreased superoxide and 3-nitrotyrosine immunoreactivity, effects that were ameliorated by mGSH replenishment with GSHee, but not NAC. As a proof-of-principle of the detrimental role of superoxide scavenging when mGSH was depleted transgenic mice overexpressing SOD2 exhibited enhanced susceptibility to MCD-mediated SH.


CONCLUSIONS
These findings underscore a critical role for mGSH in the therapeutic potential of superoxide scavenging in SH, and suggest that the combined approach of superoxide scavenging with mGSH replenishment may be important in SH.
IDIBAPS, Liver Unit-Hospital Clinic, and Department of Cell Death and Proliferation, IIBB-CSIC, 08036-Barcelona, Spain.
Claudia
C
von Montfort
Núria
N
Matias
Anna
A
Fernandez
Raquel
R
Fucho
Laura
L
Conde de la Rosa
Maria Luz
ML
Martinez-Chantar
José M
JM
Mato
Keigo
K
Machida
Hidekazu
H
Tsukamoto
Michael P
MP
Murphy
Abdellah
A
Mansouri
Neil
N
Kaplowitz
Carmen
C
Garcia-Ruiz
Jose C
JC
Fernandez-Checa
D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D017209:Apoptosis; D002796:Choline Deficiency / Q000150:complications; D004032:Diet; D004195:Disease Models, Animal; D005234:Fatty Liver / Q000097:blood / Q000201:enzymology / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000494:pharmacology; D005978:Glutathione / Q000378:metabolism*; D022781:Hepatocytes / Q000201:enzymology / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D008297:Male; D008665:Metalloporphyrins / Q000494:pharmacology; D008715:Methionine / Q000172:deficiency; D008716:Methionine Adenosyltransferase / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008930:Mitochondria, Liver / Q000201:enzymology / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects*; D010421:Pentanoic Acids / Q000494:pharmacology; D061105:Peroxiredoxin III / Q000378:metabolism; D061251:Primary Cell Culture; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism; D000099156:Superoxide Dismutase 2
D000410:Alanine Transaminase; D000968:Antimycin A; D016166:Free Radical Scavengers; D005978:Glutathione; D006861:Hydrogen Peroxide; D008665:Metalloporphyrins; D008715:Methionine; D008716:Methionine Adenosyltransferase; D010421:Pentanoic Acids; D061105:Peroxiredoxin III; D017382:Reactive Oxygen Species; D013482:Superoxide Dismutase; D013481:Superoxides; D013879:Thioredoxins; D000099156:Superoxide Dismutase 2; C516116:Prdx3 protein, mouse; C516112:Txn2 protein, mouse; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; C080194:3-hydroxy-4-pentenoic acid; C490703:Mat1a protein, mouse