Further studies on the potential contribution of acetaldehyde accumulation and oxidative stress in rat mammary tissue in the alcohol drinking promotion of breast cancer.

There is available evidence supporting a positive association between alcohol intake and risk of breast cancer. However, there is limited information regarding possible mechanisms for this effect. Past studies from our laboratory suggest that acetaldehyde accumulation in mammary tissue after alcohol intake may be of particular relevance and that cytosolic and microsomal in situ bioactivation of ethanol to acetaldehyde and free radicals and the resulting stimulation of oxidative stress could be a significant early event related to tumor promotion. In the present studies repetitive alcohol drinking for 28 days was found to produce significant decreases in the mammary tissue content of GSH and alpha tocopherol and in glutathione S-transferase or glutathione reductase activities. In contrast, glutathione peroxidase activity was slightly increased. Malondialdehyde determinations did not show the occurrence of lipid peroxidation while the xylenol orange procedure gave positive results. The mammary microsomal metabolism of ethanol to acetaldehyde was not induced after an acute dose of ethanol or acetone able to induce the activity of its liver counterpart. The cytosolic pathway of alcohol metabolism instead was significantly enhanced by these two treatments. No increased generation of comet images was found either in mammary tissue or in liver under the experimental conditions tested. Results suggest that, while acetaldehyde accumulation in mammary tissue could be a critical event resulting from increasing production of acetaldehyde in situ plus an additional amount of it arriving via blood, other factors such as poor handling of the accumulated acetaldehyde could be also relevant.

Diallyl disulfide prevention of cis-Diamminedichloroplatinum-induced nephrotoxicity and leukopenia in rats: potential adjuvant effects.

Cisplatin (CisPt) is an effective chemotherapeutic agent against several human cancers, but it produces important nephrotoxicity, leukopenia, and mortality. In this work, we report initial results on the potential ability of diallyl disulfide (DADS) to block these toxicities without compromising chemotherapy. Male Sprague Dawley rats were used (control, DADS, CisPt, and CisPt/DADS). CisPt was administered sc as a single dose (10.5 mg/kg) in saline. DADS was given daily intragastrically in olive oil (292.5 mg/kg) 1 h before CisPt administration the first day and 146.25 mg/kg during the next 3 days. The animals were sacrificed at the fifth day after CisPt administration. DADS significantly decreased CisPt-induced nephrotoxicity as evaluated by histology and by seric urea (CisPt: 11.05 +/- 3.59; CisPt/DADS: 6.53 +/- 1.74) and creatinine (CisPt: 24.74 +/- 3.03; CisPt/DADS: 14.83 +/- 2.07). DADS also decreased leukopenia (CisPt: 13.5% and CisPt/DADS: 43.4% respect the control), and mortality (CisPt: 50%; CisPt/DADS: 29%). DADS showed ability to interact with reactive oxygen species (H(2)O(2), hydroperoxides, OH*) and with iron. DADS treatment does not change Platinum levels in kidney (CisPt: 15.2 +/- 5.1; CisPt/DADS: 13.9 +/- 4.5). Because DADS is known to inhibit cellular replication and to promote apoptosis of tumor cells, results suggest that DADS merit to be tested as a potential coadjuvant of CisPt chemotherapy in tumor-bearing animals.

Nifurtimox nitroreductase activity in different cellular fractions from male rat pancreas. Biochemical and ultrastructural alterations.

Nifurtimox (Nfx) is a nitroheterocyclic drug used in the treatment of Chagas' disease. It has serious side effects which frequently force to interrupt the treatment. Nfx toxicity has been linked to its nitroreduction to a nitroanion radical with a subsequent redox cycling which generate reactive oxygen species. We analyzed the ability of Sprague Dawley male rat pancreas to nitroreduce Nfx and whether this drug may cause deleterious effects in this organ. The microsomal fraction exhibited Nfx nitroreductase activity in the presence of NADPH under anaerobic atmosphere, which was fully inhibited under air but not altered when N2 was replaced by pure CO. The cytosol nitroreduced Nfx in the presence of hypoxanthine under N2; it was inhibited by allopurinol and negligible in aerobiosis. Nfx reached pancreatic tissue at 1, 3 or 6 h after intragastric administration (100 mg/kg). Six hours after drug administration, a significant increase in t-buthylhydroperoxide promoted chemiluminiscence was detected. Pancreatic protein sulfhydryl content significantly decreased at either 1, 3 or 6 h after Nfx administration. No changes in either protein carbonyl or in lipid hydroperoxides were observable. Ultrastructural alterations were observed in the endoplasmic reticulum and nuclei from acinar cells and in the insulin-containing granules from the pancreas. However, the seric amylase levels were not changed, but the blood glucose levels were slightly but significantly increased 24 h after Nfx administration. These studies might suggest that Nfx treatment could impose an increased risk to patients exposed to other insults provoking oxidative stress or having preexisting pathologies in the pancreas.

Ethanol-induced oxidative stress and acetaldehyde formation in rat mammary tissue: potential factors involved in alcohol drinking promotion of breast cancer.

Recent studies from our laboratory provided evidence that part of the carcinogenic effects of ethanol consumption might be related to its in situ metabolism at cytosolic and microsomal levels, to the mutagen acetaldehyde and to hydroxyl and 1-hydroxyethyl radicals. In this work, we report on our experiments where Sprague-Dawley female rats were exposed to the standard Lieber & De Carli diet for 28 days. We observed: the induction of the (xanthineoxidoreductase mediated) cytosolic and microsomal (lipoxygenase mediated) pathways of ethanol metabolism; promotion of oxidative stress as shown by increased formation of lipid hydroperoxides; delay in the t-butylhydroperoxide induced chemiluminiscence, and a significant decrease in protein sulfhydryls. In addition, the epithelial cells showed ultrastructural alterations consisting of markedly irregular nuclei, with frequent invaginations at the level of the nuclear envelope, condensation of chromatin around the inner nuclear membrane, and marked dilatation of the nuclear pores showing filamentous material exiting to the cytoplasm. In conclusion, the presence in mammary epithelial cells of cytosolic and microsomal pathways of ethanol bioactivation to carcinogenic and to tumorigenic metabolites might play a role in alcohol promotion of breast cancer.

Benznidazole-induced ultrastructural and biochemical alterations in rat esophagus.

Benznidazole (Bz) is a drug used in the chemotherapy of the acute and intermediate phases of Chagas' disease (American Trypanosomiasis), an endemic parasitic disease afflicting more than 16 million people in Latin America. Serious toxic side effects of Bz have been reported in treated human beings and in experimental animals. Bz toxicity would be linked to its nitroreductive bioactivation to reactive intermediates and to the corresponding amine known to occur in vivo and mediated by different enzymatic systems. In the present study the presence of Bz nitroreductases in rat esophagus and the occurrence of Bz induced esophageal cell injury are described. Already 1 and 3 h after an intragastric Bz administration to Sprague-Dawley male rats (240-260 g body weight) at a dose of 100 mg/kg esophageal levels of the drug were 66.4+/-4.0 and 149.2+/-14.3 nmol per g tissue, respectively. The esophageal mucosa homogenates exhibited Bz nitroreductase activity attributable to the participation of cytochrome P450 reductase and xanthine oxidoreductase (XOR). The ultrastructural observation of esophageal tissue from Bz treated animals 24 h after its administration evidenced: detachment and conglomeration of polyribosomes, reduction in the presence of desmosomes and of the amount of bacteria on its surface. The potential significance of these alterations is not fully clear at present. However, these deleterious effects might be additive or synergistic with those induced by the evolution of the disease.

Liver nuclear and microsomal CYP2E1-mediated metabolism of xenobiotics in rats chronically drinking an alcohol-containing liquid diet.

In previous studies from our laboratory, the presence in highly purified liver nuclei of metabolic pathways for processing ethanol (EtOH), N-nitrosodimethylamine (NDMA), carbon tetrachloride and chloroform was reported. All these chemicals are known to be metabolized in liver microsomes, via cytochrome P450 2E1 (CYP2E)-mediated processes. In the present work we checked whether rat liver nuclei from rats chronically drinking an alcohol-containing liquid diet exhibited an enhanced ability to metabolize chemicals known to require CYP2E1 participation for given metabolic transformations. The nicotinamide adenosine dinucleotide phosphate (NADPH)-requiring metabolism of p-nitrophenol to p-nitrocathecol; the activation of carbon tetrachloride to trichloromethyl radicals, covalently binding to proteins; and the ring hydroxylation of aniline and o-toluidine were studied. Comparison of the obtained nuclear activities against the one present in the microsomal counterpart, and their respective response to the EtOH inductive effect after repetitive exposure to it, was studied. The obtained results showed that rat liver nuclei exhibited less p-nitrophenol hydroxylase activity than microsomes, but it was inducible by repetitive alcohol drinking to equivalent levels of those of microsomes from control animals. Nuclei exhibited the ability to activate CCl4, which was significantly enhanced by alcohol drinking. Aniline was ring hydroxylated in liver microsomes but not in nuclei from either control or EtOH-treated animals. In contrast, nuclei and microsomes metabolized o-toluidine to ring hydroxylated products. They are considered less toxic in nature but other authors reported a genotoxic effect for one of them. The production of the ring hydroxylated metabolites was enhanced by repetitive EtOH drinking. Results suggest that nuclear metabolism of xenobiotics might be relevant for either activations or detoxications mediated by CYP2E1 and that repetitive exposure to EtOH might significantly modulate those processes.