Chronic ethanol consumption causes alterations in the structural integrity of mitochondrial DNA in aged rats

Abstract

Chronic ethanol consumption adversely affects the respiratory activity of rat liver mitochondria. It causes increased cellular production of oxygen radical species and selectively decreases mitochondrial glutathione (GSH) levels. Here we show, using Southern hybridization techniques on total rat genomic DNA, that long-term (11-13 months) ethanol feeding, using the Lieber-DeCarli diet, results in a 36% (P F .05; n ‫؍‬ 4) decrease in hepatic mitochondrial DNA (mtDNA) levels when compared with paired controls. UV quantitation of mtDNA isolated from hepatic mitochondria showed that chronic ethanol intake (11-13 months) causes a 44% (P F .01; n ‫؍‬ 6) decrease in the amount of mtDNA per milligram of mitochondrial protein. No significant decline in mtDNA levels was seen in ethanol-fed animals maintained on the diet for 1 to 5 months. Ethanol feeding caused a 42% (P F .01; n ‫؍‬ 4) and a 132% (P F .05; n ‫؍‬ 3) increase in 8-hydroxydeoxyguanosine (8-OHdG) formation in mtDNA in animals maintained on the diet for 3 to 6 months and 10 to 11 months, respectively. In addition, agarose gel electrophoresis revealed a 49% increase (P F .05; n ‫؍‬ 3) in mtDNA single-strand breaks (SSB) in animals fed ethanol for more than 1 year. These findings suggest that chronic ethanol consumption causes enhanced oxidative damage to mtDNA in older animals along with increased strand breakage, and that this results in its selective removal/ degradation by mtDNA repair enzymes. (HEPATOLOGY 1999; 30:881-888.)

Mitochondrial dysfunction and oxidative stress in the pathogenesis of alcohol- and obesity-induced fatty liver diseases

“…Moreover, this decrease in ADP-stimulated respiration is linked to decreased electron transport in all segments of the respiratory chain as chronic alcohol consumption decreases the activities of all the respiratory complexes, except complex II [41,42]. Several laboratories have presented strong evidence that inhibition of mitochondrial protein synthesis [43] linked to mtDNA damage [44][45][46] and ribosomal defects [47,48] contribute, in part, to decreased functioning of the oxidative phosphorylation system following chronic alcohol consumption. These alterations translate into profound modifications to the mitochondrial proteome that encompass not only losses in the 13 mitochondrial encoded polypeptides, but also decreases in numerous nuclear encoded proteins that make up the oxidative phosphorylation complexes [46].…”

Elevated PTEN Levels Account for the Increased Sensitivity of Ethanol-exposed Cells to Tumor Necrosis Factor-induced Cytotoxicity

“…Such studies point to a lowering of the threshold to induction of the MPT evoked by ethanol. This may be partly explained by the changes caused in the mitochondria by ethanol exposure, such as a decrease of mitochondrial glutathione or a lowering of mitochondrial ribosomal and DNA content (17)(18)(19). However, it is unclear how ethanol exposure modifies upstream signaling * This study was supported by National Institute on Alcohol Abuse and Alcoholism Grants K01-AA-00330-1 and 1-R01-12897-01A2.…”

Oxidative Mitochondrial DNA Damage and Deletion in Hepatocytes of Rejecting Liver Allografts in Rats: Role of TNF-α *

“…The oxidation of deoxyguanosine to 8-hydroxy-2Ј-deoxyguanosine (8-OHdG) and subsequent mutations of mtDNA are reported to be involved in the pathogenesis of many chronic conditions. [9][10][11][12][13][14] We hypothesized that severe oxidative mtDNA damage in hepatocytes occurs acutely by the release of inflammatory cytokines such as TNF-␣ during acute rejection, and that this damage is not repaired completely, leading to deletions that contribute to liver failure after transplantation. To test this hypothesis, we first measured the levels of 8-OHdG in mtDNA, the frequency of 4,834-bp deletions of mtDNA, and the levels of TNF-␣ in rats receiving syngeneic liver grafts, grafts destined to rejected, and grafts accepted despite a major histocompatibility barrier.…”