Mucosal Apoptosis Research Articles

Chronic exposure to subtoxic levels of peroxidized lipids suppresses mucosal cell turnover in rat small intestine and reversal by glutathione.

Oxidative challenge can compromise intestinal growth and death responses. This studyexamines the effect of chronic consumption of subtoxic levels of peroxidized lipids on intestinal redox balance and turnover and the effect of glutathione (GSH) supplementation. Male Sprague-Dawley rats were fed standard rat chow or 4% peroxidized menhaden oil chow (2-8 weeks). Intestinal GSH and glutathione disulfide (GSSG), GSH synthetic and redox enzymes as well as proliferative (ornithine decarboxylase, ODC) and apoptotic activities were evaluated. Chronic peroxide intake did not affect overall animal growth, but decreased intestinal GSH/GSSG ratio that directly correlated with decreased GSH and increased GSSG, and suppressed peak circadian ODC activities and post-prandial mucosal apoptosis. Supplementation with GSH restored the mucosal GSH/GSSG ratio and abrogated the peroxide-induced suppression of intestinal cell turnover. Collectively, the results show that chronic lipid peroxide consumption induces intestinal GSH redox imbalance that interferes with regulation of enterocyte death and proliferation in vivo. These disruptive effects of lipid peroxides were reversed by GSH supplementation in accordance with the normalization of tissue GSH/GSSG redox balance.

Nonsteroidal anti-inflammatory drugs, apoptosis, and colorectal adenomas

Background & Aims: Observational studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colorectal neoplasia. The mechanism of this effect could be via modification of apoptotic activity in colonic mucosa. We examined grossly normal rectal mucosa in patients with adenomas and adenoma-free controls to assess the associations between NSAID use, adenomatous polyps, and apoptosis. Methods: Study participants were drawn from consecutive patients who underwent colonoscopy between August, 1998, and February, 2000. Biopsy specimens were taken from normal-appearing rectal mucosa 10 cm from the anal verge. Apoptosis was scored from coded, H&E-stained sections using morphologic methods. Proliferation was scored using whole crypt mitotic counts. Univariate and multivariate regression analyses were conducted to estimate crude and adjusted odds ratios (ORs). Results: There were 226 patients with adenomas and 493 adenoma-free controls. After adjusting for sex, age, race, and body mass index (BMI), individuals in the highest tertile of regular NSAID use were substantially less likely to have adenomas (OR 0.4; 95% CI: 0.2–0.7) compared with occasional or nonusers. Similarly, compared with the lowest tertile, persons in the highest tertile of rectal mucosal apoptotic activity were much less likely to have adenomas (OR 0.12; 95% CI: 0.07–0.20). NSAID use and apoptotic activity were not correlated (r = 0.10). Mucosal proliferation was not related to adenomas or NSAID use. Conclusions: Our observations suggest that NSAID use and higher levels of mucosal apoptosis are independently associated with a lower prevalence of adenomas. The study shows a strong field effect for apoptosis.GASTROENTEROLOGY 2002;123:1770-1777

INOS enhances rat intestinal apoptosis after ischemia-reperfusion

The aim of this study was to demonstrate (i) the role of iNOS (inducible nitric oxide synthase) on apoptosis in the rat intestinal mucosa after ischemia-reperfusion, and (ii) the effect of iNOS on the release of cytochrome c from mitochondria. The superior mesenteric artery was occluded for 60 min and was followed by a 60 min reperfusion. Rats were pretreated with an intraperitoneal injection of the following iNOS inhibitors: N-nitro- l-arginine methyl ester, aminoguanidine, and (1S,5S,6R,7R)-7- chloro-3-imino-5-methyl-2-azabicyclo [4. 1. 0] heptane hydrochloride (ONO-1714). Apoptosis was evaluated and NO X in the portal vein was assayed. The amount of iNOS, caspase-3, and cytochrome c were determined by a Western blot analysis. Intestinal mucosal epithelial mitochondrial dehydrogenase activity was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoilium bromide. Ischemia-reperfusion increased intestinal mucosal apoptosis, NO X production in the portal vein, the amount of iNOS protein, and the release of cytochrome c, but not caspase-3. Inhibitors of iNOS significantly attenuated the induction of apoptosis, increased NO X production, and release of cytochrome c. Mitochondrial dysfunction was induced by ischemia-reperfusion, which was ameliorated by iNOS inhibitors. Our results indicate that iNOS is related to increased mucosal apoptosis in the rat small intestine after ischemia-reperfusion, which is partly explained by the release of cytochrome c from mitochondria to cytosols following mitochondrial dysfunction.

Protective effects of ex vivo graft radiation and tacrolimus on syngeneic transplanted rat small bowel motility

Background. Intestinal transplantation is unduly complicated by the nontolerogenic properties of the gut-associated lymphoid tissue. Because simultaneous graft irradiation and bone marrow infusion significantly prolong the survival of the small bowel transplanted animal, our objective was to determine the functional motility effects of the immune modulating, graft irradiation procedure in the presence and absence of tacrolimus immunosuppression. Methods. Four groups of syngeneic orthotopic small bowel transplanted animals were studied 48 hours after operations (untreated, tacrolimus, ex vivo graft irradiation, and tacrolimus + irradiation) and compared with controls. Histologic analysis was performed for mucosal apoptosis and neutrophilic infiltration into the muscularis externa. Gastrointestinal in vivo transit and in vitro circular muscle strip contractions were quantified in response to bethanechol (0.3-300 μmol/L). Results. Graft irradiation ex vivo alone or in the presence of tacrolimus significantly increases (> 10-fold) the number of apoptotic mucosal cells after transplantation. Functional measurements showed that transplantation resulted in a significant delay in gastrointestinal transit and a decrease in muscle strip contractility. Tacrolimus and graft irradiation significantly ameliorated the transplant-induced dysfunction. Conclusions. Given the endowed propensity of mucosal regeneration, the immunologic and functional benefits of ex vivo graft irradiation appear to outweigh the detrimental effects to the mucosa. (Surgery 2002;131:413-23.)

Ischemic preconditioning reduces intestinal apoptosis in rodents

Recent experimental studies have described the protective effect of ischemic preconditioning (IPC) on ischemia-reperfusion (I/R) injury of the intestine [1,2]. In order to reach a new point of view in the effect of IPC on the intestinal barrier function, the relationship between I/R-induced mucosal injury and apoptosis must be clarified. The present study was undertaken to investigate the relation between IPC and Bcl-2 expression immunohistochemically and apoptosis (by using conventional light microscopy, immunohistochemical staining for cytokeratin 18 [M30 cytodeath Ab], DNA agarose gel electrophoresis) in the intestine. Furthermore, we also investigated the effect of intestinal IPC on serum nitrite/nitrate levels. With approval of the Ethical Committee, 33 male Wistar rats weighing 250-300 g were randomized into three groups. A control group of rats (n = 11) was subjected laparotomy. In an ischemic group (n = 11), laparotomy was performed and the superior mesenteric artery (SMA) was occluded by an atraumatic clamp for 30 min. In the preconditioned group (n = 11), before the ischemia-reperfusion period, rats were subjected to initial 10 min of intestinal ischemia and 10 min of reperfusion. Twenty-four hours later, ileum and blood samples were collected. Nitrite/nitrate levels were measured in the blood samples. Serum nitrate level was found to be increased in the I/R group (16.2 ± 0.9 vs 34.3 ± 4.1) but not in the IPC group (11.3 ± 5.9) (P < 0.05). The numbers of apoptotic cells at 24 hours after I/R were significantly lower in IPC-treated rats. Diminished Bcl-2 expression observed on the ileal specimens of the I/R group was found to be prevented by IPC. Our results indicate that IPC provides a significant protective effect on ileum against I/R injury and that its effect is evidenced by a significant increase in the expression of Bcl-2 following the insult. This study shows that intestinal IPC may block the cascade of events that cause apoptosis that can lead to multiorgan failure. In the future, the use of agents causing Bcl-2 upregulation against the spontaneous I/R attacks as a preservative measure in criticial patients could be seriously considered.

Helicobacter pylori infection and molecular changes in gastric carcinogenesis.

In recent years there has been much progress in understanding the pathogenesis of gastric cancer. The role of individual factors in gastric carcinogenesis continues to be debated and is also subject to further analysis. In addition to the activation of oncogenes and the inactivation of tumor suppressor genes, alteration of adhesion molecules seems to be critical for the development of gastric cancer. Helicobacter pylori has been linked to an increased risk of developing gastric cancer, and the molecular changes induced by H. pylori are currently being investigated. Recent studies indicate that H. pylori induces cell proliferation and apoptosis during the early phase of chronic inflammation of the gastric mucosa, whereas in the malignant transformation of the gastric mucosa apoptosis is inhibited and adhesion of gastric epithelial cells is impaired. This review focuses on the role of H. pylori in the development of molecular changes in gastric cancer and its preneoplastic lesions.

The role of caspases in methotrexate-induced gastrointestinal toxicity

Background. Enterocolitis is the major toxicity of methotrexate-based cancer chemotherapy, which limits its clinical applications. Methotrexate induces gut mucosal apoptosis in vivo; however, little is known about the molecular mechanism involved. The effectors of apoptosis include the caspase family of proteases, which are selectively activated in a stimulus-specific and tissue-specific fashion. The aims of this study were (1) to establish an in vitro model of methotrexate-induced gut apoptosis and (2) to determine the role of caspases in methotrexate-induced apoptosis in intestinal epithelial cells. Methods. Rat intestinal epithelial cells (RIE-1) were treated with methotrexate in the absence or presence of ZVAD-fluoromethyl ketone, a general caspase inhibitor. Apoptosis was quantified by means of deoxyribonucleic acid (DNA) fragmentation assays and Hoechst nuclear staining. Caspase activation was measured with the use of fluorogenic substrates. Results. Methotrexate induced apoptosis and decreased cell number in RIE-1 cells. DNA fragmentation was preceded by the sequential activation of caspases 9, 2, and 3, whereas caspases 1 and 8 remained inactive. ZVAD-fluoromethyl ketone inhibited methotrexate-induced caspase activation, DNA fragmentation, and nuclear condensation. Conclusions. These results indicate that methotrexate activates specific caspases and induces apoptosis in RIE-1 cells. Furthermore, caspases may play an important role in methotrexate-induced apoptosis in RIE-1 cells and may be potential therapeutic targets to attenuate methotrexate-induced enterocolitis. (Surgery 2001;859-65.)

Induced gastric mucosal apoptosis in Helicobacter pylori positive patients taking low dose aspirin: A 6-month case-control study

Induced gastric mucosal apoptosis in Helicobacter pylori positive patients taking low dose aspirin: A 6-month case-control study

Induced gastric mucosal apoptosis in Helicobacter pylori positive patients taking low dose aspirin: A 6-month case-control study

Induced gastric mucosal apoptosis in Helicobacter pylori positive patients taking low dose aspirin: A 6-month case-control study

Effect of the Central Nervous System on Mucosal Growth and Apoptosis in the Small Intestine

Recently our studies have demonstrated that the central nervous system regulates in part mucosal cell growth and apoptosis in the rat small intestine. Ornithine decarboxylase (ODC) activity is a key enzyme for polyamine synthesis which plays an important role for the intestinal mucosal growth. We have demonstrated that the increase of ODC activity in the duodenum just before the dark period is abolished by truncal vagotomy and that the infusion of 2-deoxy-D-glucose into the third cerebroventricle activates ODC activity in the small intestine. Epithelial homeostasis is balanced by regulation of cell proliferation and cell death. Our preliminary data showed that intestinal mucosal apoptosis decreased in the ventromedial-hypothalamus-lesioned rat. These results indicate that the central nervous system, in addition to local factors, is related to regulation of mucosal homeostasis in the intestinal mucosa.

The COX-2 inhibitor nimesulide suppresses superoxide and 8-hydroxy-deoxyguanosine formation, and stimulates apoptosis in mucosa during early colonic inflammation in rats.

As we have shown previously [Tardieu,D., Jaeg,J.P., Cadet,J., Embvani,E., Corpet,D.E. and Petit,C. (1998) Cancer Lett, 134, 1-5], a 48-h treatment of 6% dextran sodium sulphate (DSS) in drinking water led to a reproducible 2-fold increase of the mutagenic oxidative lesion 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) in colonic mucosa DNA of rats in vivo. The aim of this study was to test the effect of nimesulide, a preferential COX-2 inhibitor, on the DSS-induced 8-oxodGuo increase. We show that nimesulide when administered orally, simultaneously with DSS at 5 mg/kg/day, not only totally prevents 8-oxodGuo formation but also suppresses the 5-fold increase of superoxide induced by DSS in the colonic mucosa. This was measured by in vivo formazan blue precipitation (P < 0.01 in the Wilcoxon test). Moreover, nimesulide enhances apoptosis by approximately 30% as compared with the already high level induced by DSS treatment (P < 0.01). It is suggested that the significant increase in mutagenic oxidative DNA damage, produced by mild acute colonic inflammation, could be important in the initiation of colon cancer in both animals and man. These effects may explain at least partly the well-documented protective action towards colon cancer by preferential COX-2 inhibitors, either xenobiotics such as nimesulide or natural nutrients.

Mucosal integrity and apoptosis: Efficient and rapid execution of programmed cell death in primary human intestinal epithelial cells which die of apoptosis as they reach the intestinal lumen

Mucosal integrity and apoptosis: Efficient and rapid execution of programmed cell death in primary human intestinal epithelial cells which die of apoptosis as they reach the intestinal lumen

Mucosal apoptosis induced by ischemia-reperfusion and fasting in the stomach compared to the small intestine in rats

We previously reported that apoptosis was induced in rats intestinal mucosa following long term fasting and ischemia-reperfusion. It is well known that a role of apoptosis in gastric mucosa is important in pathophysiological conditions such as Helicobacter pylori infection. The aim of the present experiment was to examine an effect of ischemia-reperfusion and fasting on apoptosis of gastric mucosa comparing to small intestinal mucosa. Method: Male SD rats(280 330g) were used in the experiments. Under halothane anesthesia, the celiac artery was occluded to induce ischemia in the stomach and the superior mesentric artery was occluded to induce intestinal ischemia. Sixty minutes reperfusion was followed after 60min ischemia. After ischemia-reperfusion, rats were sacrificed and ratios of fragmented DNA to total DNA, agarose gel electrophoresis, and immunohistochemical staining were examined. Additional rats were fasted for 48h before sacrificed to evaluate mucosal apoptosis. Results: The percentage of fragmented DNA after ischemia-reperfusion was significantly increase in the intestinal mucosa(20.7~2.1%) compared to the value in sham treated controls(5.7~1.0%). THe increase in intestinal apoptosis was observed in 48h fasted rats(29.8~4.4%). Agarose gel electrophoresis showed that DNA ladders in both conditions in the intestinal mucosa, indicating that a part of the intestinal mucosal cells were dead by apoptosis. Apoptotic cells in the intestinal mucosa were observed in the immunohistochemical staining. In contrast to the small intestine, the percentage of fragmented DNA after ischemia-reperfusion did not increased in the gastric mucosa after ischcrnia-rcperfusiontz.B'r U.S'a». Induction of apoptosis in the gastric mucosa was not observed following 48h fasting(1.4~0.2%). Neither significant increase in apoptotic cells in the immunohistochemical staining nor DNA ladders in agarose gel electrophoresis was observed in the gastric mucosa in either condition. Conclusion: The results of the present study indicated that induction of apoptosis in the rat gastric mucosa by ischemiareperfusion and fasting was less sensitive compared to the rat intestinal mucosa. The significance of the difference in the sensitivity for apoptosis is not clear, but this discrepancy might explain the difference an incidence of malignant disease and a turn-over ratio in these two organs.

Mice deficient in membrane bound fas ag fail to increase gastric mucosal cell apoptosis or proliferation in response to helicobacter infection

Mice deficient in membrane bound fas ag fail to increase gastric mucosal cell apoptosis or proliferation in response to helicobacter infection

Peroxynitrite induced mucosal cell apoptosis in hapten-induced colitis in the rat

Peroxynitrite induced mucosal cell apoptosis in hapten-induced colitis in the rat

The mechanism of gastric mucosal apoptosis induced by ammonia

The mechanism of gastric mucosal apoptosis induced by ammonia

Mucosal oxidant formaion with caspase-3 activation contributes to an enhancement of gastric mucosal apoptosis in streptozotocin-induced diabetic rats

Mucosal oxidant formaion with caspase-3 activation contributes to an enhancement of gastric mucosal apoptosis in streptozotocin-induced diabetic rats

Tumor necrosis factor alpha and interleukin 1beta up-regulate gastric mucosal Fas antigen expression in Helicobacter pylori infection.

Fas-mediated gastric mucosal apoptosis is gaining attention as a cause of tissue damage due to Helicobacter pylori infection. We explored the effects of H. pylori directly, and the effects of the inflammatory environment established subsequent to H. pylori infection, on Fas-mediated apoptosis in a nontransformed gastric mucosal cell line (RGM-1). Exposure to H. pylori-activated peripheral blood mononuclear cells (PBMCs), but not H. pylori itself, induced Fas antigen (Fas Ag) expression, indicating a Fas-regulatory role for inflammatory cytokines in this system. Of various inflammatory cytokines tested, only interleukin 1beta and tumor necrosis factor alpha induced Fas Ag expression, and removal of either of these from the conditioned medium abrogated the response. When exposed to Fas ligand, RGM-1 cells treated with PBMC-conditioned medium underwent massive and rapid cell death, interestingly, with a minimal effect on total cell numbers early on. Cell cycle analysis revealed a substantial increase in S phase cells among cells exposed to Fas ligand, suggesting an increase in their proliferative response. Taken together, these data indicate that the immune environment secondary to H. pylori infection plays a critical role in priming gastric mucosal cells to undergo apoptosis or to proliferate based upon their Fas Ag status.

Histaminergic effect on apoptosis of rat small intestinal mucosa after ischemia-reperfusion.

This study aimed to examine the relationship between a harmful effect of histamine and apoptosis following ischemia-reperfusion in the rat intestine. The superior mesenteric artery was occluded for 60 min followed by reperfusion for 60 min. Rats were infused with H1-receptor antagonist (chlorpheniramine maleate) or H2-receptor antagonist (cimetidine). Additional rats were pretreated with aminoguanidine (100 mg/kg). Percent apoptosis in the intestinal mucosa increased after reperfusion, but neither H1 nor H2 antagonists had any effect on apoptosis. Aminoguanidine pretreatment inhibited activity of diamine oxidase and increased the plasma histamine concentration. Aminoguanidine attenuated the increase in mucosal apoptosis following reperfusion. Apoptosis induced by an ischemic insult to the intestinal mucosa was not related to an undesirable effect of histamine. Attenuation of increased intestinal apoptosis might be due to increased plasma histamine level and/or other pharmacological action of aminoguanidine, including inhibition of inducible nitric oxide synthase.

Cigarette Smoke Increases Apoptosis in the Gastric Mucosa: Role of Epidermal Growth Factor

Background/Aims: Apoptosis is a common mechanism for the regulation of cell loss. It is associated with both tissue atrophy and metaplasia. Cigarette smoking has tremendous adverse effects on the stomach and also increases the risk of gastric cancer. This action may be through the change in apoptosis in the stomach. The aim of this study was to examine the effect of cigarette smoking on apoptosis in the gastric mucosa and the possible role of epidermal growth factor (EGF) in this action. Methods: Gastric blood flow was assessed by the laser Doppler technique. Serum and gastric mucosal EGF levels were measured by RIA. Gastric mucosal apoptosis was determined using TdT-mediated dUTP-biotin nick end labeling (TUNEL). Results: Cigarette smoke exposure decreased serum EGF which was accompanied by a reduction in gastric blood flow. Meanwhile, gastric mucosal cell apoptosis was increased. Administration of EGF (20 μg/kg i.v.) before each cigarette smoke exposure reversed these actions. Removal of salivary glands induced similar effects on the gastric blood flow, apoptosis, and serum EGF level as with cigarette smoke exposure. Conclusion: A reduction in serum EGF was involved in the decrease in gastric blood flow and increase in gastric mucosal apoptosis caused by cigarette smoking.