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4‐Hydroxynonenal Detoxification by Mitochondrial Glutathione S‐Transferase Is Compromised by Short‐Term Ethanol Consumption in Rats
Author(s) -
Chen Juanjuan,
Schenker Steven,
Henderson George I.
Publication year - 2002
Publication title -
alcoholism: clinical and experimental research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.267
H-Index - 153
eISSN - 1530-0277
pISSN - 0145-6008
DOI - 10.1111/j.1530-0277.2002.tb02664.x
Subject(s) - glutathione , chemistry , ethanol , lipid peroxidation , mitochondrion , biochemistry , 4 hydroxynonenal , glutathione s transferase , blot , inner mitochondrial membrane , submitochondrial particle , antioxidant , enzyme , gene
Background 4‐Hydroxynonenal (HNE), a toxic lipid peroxidation product, has been implicated in mitochondrial damage in rat liver by ethanol consumption. The present study assessed the effects of short‐term in vivo ethanol exposure on HNE detoxification by mitochondrial glutathione S‐transferase (GST). Methods Male Sprague Dawley® rats were administered 5 doses of ethanol (4 g/kg) at 12 hr intervals by gavage. Pair‐fed rats that received isocaloric dextrose instead of ethanol served as controls. Mitochondrial and submitochondrial fractions were prepared from the livers. Mitochondrial contents of HNE and HNE‐glutathione conjugate were measured by high‐performance liquid chromatography. GST isoforms were identified by Western blots in submitochondrial fractions. Results Whereas there was an 80% increase in mitochondrial HNE content after ethanol consumption, there was a 42% decrease in the content of HNE‐glutathione conjugate, compared with controls ( p < 0.05). After ethanol exposure, the GST activities toward HNE in intact mitochondria and in the membranous fraction were decreased by 37% and 45% ( p < 0.05), respectively, whereas that in the aqueous fraction was unchanged. Kinetic analysis of HNE conjugation by the membrane‐associated GST showed that ethanol decreased the V max nearly by half ( p < 0.05), whereas it did not affect the K m . HNE conjugation by the aqueous GST demonstrated a higher K m than that of the membrane‐associated GST, although its kinetics were not significantly altered by ethanol. Immunochemical analysis with Western blots demonstrated that both the membranous and the aqueous fractions of mitochondria contain GST‐α and GST‐μ isoforms, whereas GST‐π was absent. Conclusions HNE detoxification by mitochondrial GST is compromised by short‐term ethanol consumption, which may contribute to elevated mitochondrial HNE content and hence its toxicity in the ethanol‐exposed liver.