Carbon tetrachloride-induced free radical mediated protein oxidation in vitro and in vivo

Early nifurtimox-induced biochemical and ultrastructural alterations in rat heart

Nifurtimox (Nfx) and Benznidazole (Bz) are being used for the treatment of the acute phase of Chagas' disease. Recently, they were also considered for use in the indeterminate phase. Both the nitroheterocyclic drugs have serious toxic side effects. The mechanism of Nfx toxicity is associated with the formation of reactive oxygen species (ROS) generated during nitroreduction. Potential effects on cardiac function have not been established yet, despite the well-known cardiopathy often produced by the disease itself. We describe experiments testing some acute effects of Nfx on the male Sprague Dawley rat heart. Nifurtimox was present in the heart at 1, 3 and 6 h after intragastric (i.g) treatment. In vitro studies on Nfx microsomal and cytosolic nitroreductase activities showed that only the microsomal fraction had the ability to nitroreduce it. Cytochrome P450 and cytochrome P450 reductase would be involved in the process as suggested by their response to specific inhibitors. Nifurtimox increased the cardiac protein carbonyl content at 1 and 3 h and decreased the protein sulfhydryl content at 3 h. In addition, 24 h after treatment ultrastructural alterations such as marked cytoplasmic vacuolization, separation and loss of myofibrils and mitochondrial swelling were observed. Results suggest that Nfx administration might aggravate pre-existing adverse cardiac conditions. Human & Experimental Toxicology (2007) 26, 781 — 788

Acetaldehyde content and oxidative stress in the deleterious effects of alcohol drinking on rat uterine horn

After alcohol exposure through a standard Lieber and De Carli diet for 28 days, a severe atrophy in the rat uteirne horn was observed, accompanied by significant alterations in its epithelial cells. Microsomal pathway of acetaldehyde production was slightly increased. Hydroxyl radicals were detected in the cytosolic fraction, and this was attributed to participation of xanthine oxidoreductase. They were also observed in the microsomal fraction in the presence of NADPH generating system. No generation of 1-hydroxyethyl was evidenced. The t-butylhydroperoxide-induced chemiluminescence analysis of uterine horn homogenates revealed a significant increase in the chemiluminiscence emission due to ethanol exposure. In the animals repeatedly exposed to alcohol, sulfhydryl content from uterine horn proteins was decreased, but no significant changes were observed in the protein carbonyl content from the same samples. Minor but significant decreasing changes were observed in the GSH content accompanied by a tendency to decrease in the GSH/GSSG ratio. A highly significant finding was the diminished activity content of glutathione peroxidase. Results suggest that acetaldehyde accumulation plus the oxidative stress may play an additional effect to the alcohol-promoted hormonal changes in the uterus reported by others after chronic exposure to alcohol.

Metabolization of nifurtimox and benznidazole in cellular fractions of rat mammary tissue

Two nitroheterocyclic drugs, nifurtimox (NFX) and benznidazole (BZ), used in the treatment of Chagas' disease have serious side effects attributed to their nitroreduction to reactive metabolites. Here, we report that these drugs reach the mammary tissue and there they could undergo in situ bioactivation. Both were detected in mammary tissue from female Sprague-Dawley rats after their intragastric administration. Only NFX was biotransformed by pure xanthine-oxidoreductase and from tissue cytosol. These activities were purine dependent and were inhibited by allopurinol. Also, only NFX was biotransformed by microsomes in the presence of β-nicotinamide adenine dinucleotide phosphate, reduced form (NADPH), and was inhibited by carbon monoxide and partially by diphenyleneiodonium. NFX treatment produced significant decrease in protein sulfhydryl content after 1, 3 and 6 hours; no increases in protein carbonyl content at any time tested and significantly higher levels of lipid hydroperoxides at 3 and 6 hours; besides, ultrastructural observations after 24 hours showed significant differences in epithelial cells compared to control. These findings indicate that NFX might be more deleterious to mammary tissue than BZ and could correlate with early reports on its ability to promote rat mammary tissue toxicity.

Deleterious effects induced by oxidative stress in liver nuclei from rats receiving an alcohol-containing liquid diet

Highly purified rat-liver nuclei were previously shown to have nuclear ethanol (EtOH) metabolizing system able to bioactivate alcohol to acetaldehyde and 1-hydroxyethyl radicals. These reactive metabolites were able to covalently bind to nuclear proteins and lipids potentially being able to provoke oxidative stress of nuclear components. In this study, the above-mentioned possibility was explored. Sprague Dawley male rats (125-150 g) were fed a standard Lieber and De Carli liquid diet for 28 days. Controls were pair-fed with a diet, in which EtOH was isocalorically replaced with carbohydrate. The presence of a chlorzoxazone hydroxylase activity inducible by the repetitive EtOH drinking further suggested the presence of CYP2E1 in the highly purified nuclei. Nuclei from EtOH-drinking rats evidenced significantly increased susceptibility to a t-butyl hydroperoxide challenge as detected by chemiluminescence emission, increased formation of protein carbonyls, and decreased content of protein sulfhydryls. In contrast, no significant changes in the nuclear lipid hydroperoxides formation or even decreases in the 8-oxo-7,8-dihydro-2-deoxyguanosine were observed. No significant differences were observed in different parameters of the alkaline Comet assay. In immunohistochemical studies performed, no expression of p53 was observed in the livers of the animals under the experimental conditions tested. Since nuclear proteins and lipids are known to play a role in cell growth, differentiation, repair and signaling, their alterations by either oxidative stress, or by covalent binding might be of relevance to liver tumor promotion.

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.