Effects of acetylsalicylic acid (ASA) (aspirin) on the pathogenesis of fatty liver, cirrhosis and hepatocarcinogenesis caused by a choline-deficient L-amino acid-defined (CDAA) diet were examined in male Fischer 344 rats fed a CDAA diet supplemented with 0, 0.1, 0.2, 0.4 or 0.8% ASA for 30 weeks. ASA at concentrations of > 0.2% prevented the development of both cirrhosis and preneoplastic and neoplastic nodules, but without any directly associated prevention of fatty changes. ASA also prevented hepatocyte proliferation and the generation of thiobarbituric acid-reactive substances and 8-hydroxydeoxyguanosine caused by feeding the CDAA diet, analyzed, respectively, after 1, 12 and 12 weeks. The results clearly indicate that the anti-inflammatory drug ASA, which is not a lipotropic factor, can prevent the pathogenesis of cirrhosis and hepatocarcinogenesis caused by a CDAA diet, which is possibly partly associated with the prevention of reactive oxygen species production.

Effects of inhibitors of arachidonic acid (AA) metabolism on the development of fatty liver, cirrhosis, glutathione-S-transferase placental form (GST-P)-positive nodules and the generation of 8-hydroxydeoxyguanosine (8-OHdG) and thiobarbituric acid-reactive substances (TBARS), caused by a choline-deficient, L-amino acid-defined (CDAA) diet, were examined in male Fischer 344 rats by feeding CDAA diets supplemented with the inhibitors for 12 and 30 weeks. Acetylsalicylic acid (ASA) (at doses of 0.1 and 0.2%) and p-bromophenacylbromide (BPB) (0.1 and 0.2%) were used as inhibitors of, respectively, cyclo-oxygenase and phospholipase A2, and quercetin (QU) (0.75 and 1.5%) and nordihydroguaiaretic acid (NDGA) (0.1 and 0.2%) as inhibitors of lipoxygenase. None of the inhibitors affected the development of fatty liver caused by the CDAA diet. ASA at a doe of 0.2% almost completely prevented the appearance of cirrhosis, GST-P-positive nodules, 8-OHdG and TBARS in seven out of 11 (63.7%) rats. BPB at a dose of 0.2% also exerted inhibitory effects on all of these lesions but to a lesser extent than ASA. QU and NDGA exerted inhibitory effects limited to the GST-P-positive nodule case. The results indicate that a perturbed AA metabolism, particularly of the cyclo-oxygenase pathway, derived secondarily from depletion of labile methyl groups or phosphatidylcholine, might play key roles in the cirrhosis, hepatocarcinogenesis and oxidative stress caused by a CDAA diet. The results also indicated a possible involvement of the lipoxygenase pathway in hepatocarcinogenic processes.

The present study was performed to assess the roles of hepatocellular oxidative damage to DNA and constituents other than DNA in rat liver carcinogenesis caused by a choline‐deficient, l‐amino acid‐defined (CDAA) diet by examining the effects of the antioxidant N, N′‐diphenyl‐p‐phenylenediamine (DPPD). The parameters used for cellular oxidative damage were the level of 8‐hydroxyguanine (8‐OHGua) for DNA and that of 2‐thiobarbituric acid‐reacting substance (TBARS) for constituents other than DNA. A total of 40 male Fischer 344 rats, 6 weeks old, were fed the CDAA diet for 12 weeks with or without DPPD (0.05, 0.10 or 0.20%) or butylated hydroxytoluene (BHT, 0.25%). In the livers of the rats, the numbers and sizes of glutathione S‐transferasc (EC 2.5.1.18) placental form (GSTP)‐ and/or γ‐glutamyltransferase (GGT, EC 2.3.2.2)‐positive lesions and levels of 8‐OHGua and TBARS were determined. The GSTP‐positive lesions of 0.08 mm2 or larger were all stained positively for GGT as well in cross‐sectional area, whereas the smaller lesions were generally negative for GGT. DPPD and BHT reduced the size of the GSTP‐positive lesions without affecting their total numbers. At the same time, they reduced TBARS generation without affecting 8‐OHGua formation in DNA. The present results indicate that oxidative DNA damage (represented by 8‐OHGua formation) and damage to constituents other than DNA (represented by TBARS generation) may play different roles in rat liver carcinogenesis caused by the CDAA diet; the former appears to be involved in the induction of phenotypically altered hepatocyte populations while the latter may be related to the growth of such populations.

Groups of female Fischer-344 rats were fed a semipurified choline-deficient (CD) diet, or a semisynthetic L-amino acid-defined choline-deficient (CDAA) diet, for up to 12 wk and effects of the 2 diets on the liver were compared. Steatosis was diffuse and more severe throughout in rats fed the CDAA diet than in rats fed the CD diet. Greater elevations in serum aspartate and alanine aminotransferase activities were also present in the former rats, along with higher 2-bromodeoxyuridine labeling indices in the liver. Discrete amounts of 8-hydroxyguanine were detected in liver DNA, but were not significantly different in rats fed the 2 diets, or from those present in a group of control rats killed at 0 time. Glutathione S-transferase placental formpositive focal lesions were not observed in any of the rats. The results show that the CDAA diet causes more severe degrees of steatosis and liver cell death and proliferation than the CD diet, raising the possibility that it may, in contrast to the CD diet, result in the eventual induction of hepatocellular carcinomas in female Fischer-344 rats.

Previously, we have reported that aspirin, a cyclooxygenase (COX) inhibitor, can prevent the fibrosis, cirrhosis and generation of oxidative DNA damage, and the associated development of glutathione-S-transferase placental form (GST-P)-positive preneoplastic liver nodules, caused by a choline-deficient, L-amino acid-defined (CDAA) diet in rats. In the present study, in order to elucidate the role of COX pathway in liver lesion-induction by a CDAA diet, the modulatory effects of other distinct chemical classes of COX inhibitors were examined. A long-acting example, piroxicam (PIRO) (at doses of 0.01, 0.02, 0.04 and 0.06%) and the short-acting ibuprofen (IBU) (at doses of 0.02, 0.04 and 0.06%) and indomethacin (IND) (at doses of 0.005 and 0.008%) were administered in the CDAA diet to male F344 rats, and animals were killed after 12 and 30 weeks. In another experiment, IND was given in drinking water at doses of 0.001, 0.002 and 0.004%. None of the inhibitors affected the development of fatty liver caused by a CDAA diet, but PIRO at doses higher than 0.04%, strongly inhibited the development of GST-P-positive and neoplastic nodules as well as fibrosis, cirrhosis and formation of 8-hydroxydeoxyguanosine (8-OHdG) adducts. IBU at the highest dose also exhibited similar but much less pronounced inhibitory effects. With IND, there was only a tendency for inhibition with no clear dose-dependence. The results together with our previous findings, indicate that relatively strong COX inhibitors, acting irreversibly like aspirin or for extended periods like PIRO, can prevent the endogenous hepatocarcinogenesis associated with a CDAA diet, although not the development of a fatty liver, suggesting that an augmented COX pathway might play key roles in the causation of liver lesions in this model.