Acute and chronic stress-induced oxidative gastrointestinal mucosal injury in rats and protection by bismuth subsalicylate.

Reactive oxygen species (ROS) are implicated in the pathogenesis of stress-induced gastrointestinal mucosal injury. In the present study, we have investigated the effects of acute and chronic stress on the enhanced production of ROS including superoxide anion [SA; as determined by cytochrome c reduction (CCR)] and hydroxyl radicals (OH), and correlated the enhanced production of these free radicals with increased lipid peroxidation, membrane microviscosity and DNA fragmentation, indices of oxidative tissue damage, in the gastric and intestinal mucosa of female Sprague-Dawley rats. Furthermore, the protective ability of bismuth subsalicylate (BSS) against the gastrointestinal mucosal injury induced by acute and chronic stress was determined. Acute stress was induced for a period of 90 min, while chronic stress was induced for 15 min/day for 15 consecutive days. Half of the animals exposed to acute stress were pretreated orally with 15 mg BSS/kg 30 min prior to the exposure to acute stress. Similarly, half of the animals exposed to water-immersion restraint chronic stress were pretreated orally with 7.5 mg BSS/kg/day for 15 consecutive days 30 min prior to the exposure to chronic stress. Acute stress produced greater injury to both gastric and intestinal mucosa as compared to chronic stress. Acute stress increased CCR and OH production by 10.0- and 14.3-fold, respectively, in the gastric mucosa, and 10.4- and 17.0-fold, respectively, in the intestinal mucosa. Pretreatment with BSS prevented the acute stress-induced increase in CCR and OH production. Acute stress increased lipid peroxidation, DNA fragmentation and membrane microviscosity by 3.6-, 4.0- and 11.6-fold, respectively, in gastric mucosa, and 4.1-, 5.0- and 16.2-fold, respectively, in intestinal mucosa. BSS decreased acute stress-induced lipid peroxidation, DNA fragmentation and membrane microviscosity by approximately 26, 35 and 30%, respectively, in gastric mucosa, and by 20, 36 and 30%, respectively, in the intestinal mucosa. Chronic stress increased CCR and OH production by 4.8- and 6.3-fold, respectively, in gastric mucosa, and 4.6- and 6.9-fold, respectively, in intestinal mucosa. Chronic stress increased lipid peroxidation and DNA fragmentation by 2.9- and 3.3-fold, respectively, in gastric mucosa, and 3.3- and 4.2-fold, respectively, in intestinal mucosa. BSS decreased chronic stress-induced lipid peroxidation, DNA fragmentation and membrane microviscosity by approximately 41, 44 and 45%, respectively, in gastric mucosa, and by 39, 52 and 51%, respectively, in the intestinal mucosa. Daily administration of BSS provided greater protection against chronic stress-induced oxidative gastrointestinal injury as compared to the acute stress. These results demonstrate that both acute and chronic stress can induce gastrointestinal mucosal injury through enhanced production of ROS, and that BSS can significantly protect against gastrointestinal mucosal injury.

Stress, diet and alcohol-induced oxidative gastrointestinal mucosal injury in rats and protection by bismuth subsalicylate.

Oxygen free radicals are implicated in the pathogenesis of stress and food/alcohol-induced gastrointestinal injury. We have investigated the effects of restraint stress, spicy food diet, high-fat diet and 40% ethanol on the enhanced production of reactive oxygen species, including superoxide anion and hydroxyl radicals, and on DNA fragmentation, lipid peroxidation and membrane microviscosity (indices of oxidative tissue damage) in gastric and intestinal mucosa of Sprague-Dawley rats. Furthermore, the protective ability of bismuth subsalicylate (BSS; 15 mg kg(-1) was determined against the gastrointestinal mucosal injury induced by these stressors. Animals on the high-fat diet consumed 31% more food as compared to other animals. Animals on the spicy food diet consumed ca. 23% more water as compared to control animals, and the high-fat diet animals consumed 17% less water. Restraint stress provided greater injury to both gastric and intestinal mucosa as compared to other stressors. Restraint stress, spicy food diet, high-fat diet and ethanol increased superoxide anion production by 10.0-, 4.3-, 5.7- and 4.8-fold, respectively, in the gastric mucosa, and by 10.4-, 5.3-, 7.0- and 5.5-fold in the intestinal mucosa. Exposure to restraint stress, spicy food diet, high-fat diet and 40% ethanol also increased hydroxyl radical production by ca. 14.3-, 4.5-, 3.5- and 4.8-fold, respectively, in the gastric mucosa, and by 17.0-, 4.8-, 3.5- and 4.7-fold in the intestinal mucosa. Bismuth subsalicylate administration to the animals provided significant protection against superoxide anion and hydroxyl radical production. Restraint stress, spicy food diet, high-fat diet and ethanol increased lipid peroxidation by 3.6-, 2.4-, 2.6- and 2.0-fold, respectively, in the gastric mucosa, and by 4.1-, 3.5-, 3.6- and 2.7-fold in intestinal mucosa. Administration of BSS decreased restraint stress, spicy food diet, high-fat diet and ethanol-induced gastric mucosal lipid peroxidation by ca. 26%, 36%, 45% and 18%, and intestinal mucosa lipid peroxidation by 20%, 21%, 46% and 42%, respectively. Approximately 4.0-, 2.0-, 2.4- and 2.0-fold increases in DNA fragmentation were observed in the gastric mucosa of rats exposed to restraint stress, spicy food diet, high-fat diet and 40% ethanol, respectively, and similar increases in the intestinal mucosa. These same four stressors increased membrane microviscosity by 11.6-, 6.1-, 7.3- and 5.4-fold, respectively, in the gastric mucosa, and by 16.2-, 7.9-, 9.5- and 7.8-fold in the intestinal mucosa. Bismuth subsalicylate exerted significant protection against DNA damage and changes in membrane microviscosity induced by the four stressors. Excellent correlations existed between the production of reactive oxygen species and the tissue damaging effects in both gastric and intestinal mucosa. In summary, the results demonstrate that physical and chemical stressors can induce gastrointestinal oxidative stress and mucosal injury through enhanced production of reactive oxygen species, and that BSS can significantly attenuate gastrointestinal injury by scavenging these reactive oxygen species.

Protective effects of zinc salts on TPA-induced hepatic and brain lipid peroxidation, glutathione depletion, DNA damage and peritoneal macrophage activation in mice.

1. The comparative protective abilities of zinc L-methionine, zinc DL-methionine, zinc sulfate, zinc gluconate, L-methionine, DL-methionine, and vitamin E succinate (VES) on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced lipid peroxidation, DNA fragmentation, and glutathione depletion in the hepatic and brain tissues, and production of reactive oxygen species by peritoneal macrophages were assessed. In addition, mice were fed a zinc-deficient diet for 5 weeks, and treated with TPA and/or zinc L-methionine or zinc DL-methionine, and similar studies were conducted. 2. The zinc-deficient diet induced oxidative stress in the hepatic and brain tissues as well as in the peritoneal macrophages as evidenced by significantly enhanced lipid peroxidation. DNA fragmentation, glutathione depletion, and production of reactive oxygen species. 3. Treatment of mice with zinc L-methionine, zinc DL-methionine, and VES decreased TPA-induced reactive oxygen species production as evidenced by significant decreases in chemiluminescence in peritoneal macrophages by approximately 45%, 31%, and 47%, respectively, and cytochrome c reduction by approximately 54%, 35%, and 41%, respectively, as compared with control values. Similar results were observed with liver and brain lipid peroxidation, DNA fragmentation, and glutathione depletion. 4. Zinc salts and antioxidants provided significant protection against TPA-induced oxidative damage. Zinc L-methionine provided the best protection.

Protection against chemically-induced oxidative gastrointestinal tissue injury in rats by bismuth salts.

Oxygen free radicals (OFR) are implicated in the pathogenesis of stress, chemically induced gastric lesions, and gastrointestinal injury. The concentration-dependent scavenging abilities of bismuth subsalicylate (SBS), colloidal bismuth subcitrate (CBS), and selected OFR scavengers, including superoxide dismutase (SOD), catalase, mannitol, and allopurinol were examined against biochemically or chemically generated superoxide anion, hydroxyl radical, and hypochlorite radical plus hypochlorous acid based on a chemiluminescence assay. Furthermore, both gastric (GM) and intestinal mucosa (IM) were individually exposed in vitro to these free radical generating systems, and the concentration-dependent protective abilities of SBS and CBS against lipid peroxidation (LP) were compared with selected OFR scavengers. In addition, 24-hr fasted rats were orally treated with the necrotizing agents 0.6 M HCl, 0.2 M NaOH, 80% ethanol, and aspirin (200 mg/kg). The extent of tissue injury in the GM and IM was determined by assessing LP, DNA fragmentation, and membrane microviscosity. Dose- and time-dependent in vivo protective abilities of CBS (100 mg/kg) and SBS (15 mg/kg) were also assessed. Following incubations with superoxide anion and hydroxyl radical generating systems in the presence of 125 mg SBS/liter, approximately 47% and 61% inhibitions were observed in the chemiluminescence response, respectively, while 48% and 46% inhibitions were observed with 125 mg CBS/liter. SBS and CBS exerted similar abilities towards hypochlorite radical plus hypochlorous acid. Approx. 3.1- and 3.7-fold increases in LP were observed in the GM and IM of rats following oral administration of 0.6 M HCl. Pretreatment of the rats with SBS and CBS decreased 0.6 M HCl-induced LP in the GM by approx. 39% and 27%, respectively, with similar decreases in LP in the IM. SBS exhibited better protective abilities towards 0.6 M HCl and 0.2 m NaOH-induced GM and IM injury as compared to CBS. SBS and CBS provided similar protection towards 80% ethanol-induced gastric injury, while CBS exerted a superior protective ability towards aspirin-induced gastric injury. The results demonstrate that both SBS and CBS can scavenge reactive oxygen species and prevent tissue damage produced by OFR.

Oxygen free radical scavenging abilities of vitamins C and E, and a grape seed proanthocyanidin extract in vitro.

Proanthocyanidins, a group of polyphenolic bioflavonoids, have been reported to exhibit a wide range of biological, pharmacological and chemoprotective properties against oxygen free radicals. We have assessed the concentration-dependent oxygen free radical scavenging abilities of a grape seed proanthocyanidin extract (GSPE), vitamin C and vitamin E succinate (VES) as well as superoxide dismutase, catalase and mannitol against biochemically generated superoxide anion and hydroxyl radical using a chemiluminescence assay and cytochrome c reduction. A concentration-dependent inhibition was demonstrated by GSPE. At a 100 mg/l concentration, GSPE exhibited 78-81% inhibition of superoxide anion and hydroxyl radical. Under similar conditions, vitamin C inhibited these two oxygen free radicals by approximately 12-19%, while VES inhibited the two radicals by 36-44%. The combination of superoxide dismutase and catalase inhibited superoxide anion by approximately 83%, while mannitol resulted in an 87% inhibition of hydroxyl radical. The results demonstrate that GSPE is a more potent scavenger of oxygen free radicals as compared to vitamin C and VES.

Induction of oxidative stress by chronic administration of sodium dichromate [chromium VI] and cadmium chloride [cadmium II] to rats.

Recent studies have demonstrated that both chromium (VI) and cadmium (II) induce an oxidative stress, as determined by increased hepatic lipid peroxidation, hepatic glutathione depletion, hepatic nuclear DNA damage, and excretion of urinary lipid metabolites. However, whether chronic exposure to low levels of Cr(VI) and Cd(II) will produce an oxidative stress is not shown. The effects of oral, low (0.05 LD50) doses of sodium dichromate [Cr(VI); 2.5 mg/kg/d] and cadmium chloride [Cd(II); 4.4 mg/kg/d] in water on hepatic and brain mitochondrial and microsomal lipid peroxidation, excretion of urinary lipid metabolites including malondialdehyde, formaldehyde, acetaldehyde and acetone, and hepatic nuclear DNA-single strand breaks (SSB) were examined in female Sprague-Dawley rats over a period of 120 d. The animals were treated daily using an intragastric feeding needle. Maximum increases in hepatic and brain lipid peroxidation were observed between 60 and 75 d of treatment with both cations. Following Cr(VI) administration for 75 d, maximum increases in the urinary excretion of malondialdehyde, formaldehyde, acetaldehyde, and acetone were 2.1-, 1.8-, 2.1-, and 2.1-fold, respectively, while under the same conditions involving Cd(II) administration approximately 1.8-, 1.5-, 1.9-, and 1.5-fold increases were observed, respectively, as compared to control values. Following administration of Cr(VI) and Cd(II) for 75 d, approximately 2.4- and 3.8-fold increases in hepatic nuclear DNA-SSB were observed, respectively, while approximately 1.3- and 2.0-fold increases in brain nuclear DNA-SSB were observed, respectively. The results clearly indicate that low dose chronic administration of sodium dichromate and cadmium chloride induces an oxidative stress resulting in tissue damaging effects that may contribute to the toxicity and carcinogenicity of these two cations.