Influence of vitamin E on gastric mucosal injury induced by Helicobacter pylori infection

We investigated the effect of vitamin E on gastric mucosal injury induced by Helicobacter pylori (H. pylori) infection. Male Mongolian gerbils were divided into 4 groups (normal group without H. pylori infection, vitamin E-deficient, -sufficient and -supplemented groups with H. pylori infection). Following oral inoculation with H. pylori (ATCC43504 2 x 10(8) CFU), animals were fed diets alpha-tocopherol 2 mg/100 g diet in the normal and vitamin E-sufficient groups and alpha-tocopherol 0.1 mg/100 g and 50 mg/100 g in the vitamin E-deficient and -supplemented groups, respectively, for 24 weeks. Chronic gastritis was detected in all gerbils inoculated H. pylori. Gastric ulcer was detected in 2 of 7 gerbils only in the vitamin E-deficient group. In the vitamin E-deficient group, myeloperoxidase activity and mouse keratinocyte derived chemokine (KC) in gastric mucosa was significantly higher than in the vitamin E supplemented group. Subsequently, in an in vitro study expression of CD11b/CD18 on neutrophils was enhanced by H. pylori water extract. This effect was suppressed in a dose dependent manner by the addition of alpha-tocopherol. These results suggest that vitamin E has a protective effect on gastric mucosal injury induced by H. pylori infection in gerbils, through the inhibition of accumulation of activated neutrophils.     

慢性胃炎肠化生CD_(44)、CD_(44V6)及Cyclin D_1、Cyclin E的表达和意义

目的探讨慢性胃炎胃粘膜肠化生CD44、CD44V6及cyclin D1、Cyclin E表达的意义。方法利用免疫细胞化学技术对39例伴有肠化生的慢性胃炎和5例正常人胃窦粘膜的活检组织进行检查。结果正常人胃窦粘膜上皮,腺上皮对CD44、CD44V6、Cyclin D1和Cyclin E均为阴性,但在有神经内分泌样细胞的粘膜,CD44V6和cyclin D1为阳性。慢性胃炎肠化生区和不典型增生区除CD44为阴性外,CD44V6、cyclin D1和cyclin E均呈现不同的阳性反应,但未见有阳性的神经内分泌样细胞。间质细胞大都呈阳性反应。结论CD44V6、cyclin D1和cyclin E可能是胃癌前状态的早期事件,而CD44可能为胃癌晚期的标志物。     

Effect of antioxidant vitamins on radiation-induced apoptosis in cells of a human lymphoblastic cell line

Modulating the amount of radiation-induced apoptosis by administering antioxidant vitamins offers a possible way to influence radiation-induced side effects in normal tissues. Therefore, we investigated the effect of beta-carotene, vitamin C and alpha-tocopherol on radiation-induced apoptosis in cells in culture. Human T-lymphoblastic MOLT-3 cells were irradiated with a dose of 3 Gy 1 h after or immediately prior to the addition of vitamins in three concentrations (0.01 microM, 1 microM and 100 microM). Eight hours later, apoptosis was scored morphologically by staining the nuclear DNA with Hoechst 33342. When given prior to irradiation, beta-carotene and vitamin E reduced the amount of radiation-induced apoptosis significantly at concentrations of 0.01 microM and 1 microM. In contrast, vitamin C did not show any protective effect when given at these two concentrations and caused a slight but significant radiosensitization at 100 microM. At 0.01 microM, all combinations of two vitamins showed a protective effect. This was also observed for the combination of all three vitamins at concentrations of 0.01 and 1 microM. When given immediately after irradiation, each of the three vitamins showed a protective effect at 0.01 microM. In addition, the combination of alpha-tocopherol and vitamin C reduced radiation-induced apoptosis slightly when given at 1 microM. In all other cases, no statistically significant modulation of radiation-induced apoptosis was observed. In our experimental system, the protective effect of beta-carotene and vitamin E was dependent on concentration and occurred only in the micromolar and sub-micromolar concentration range, while vitamin C alone, but not in combinations, had a sensitizing effect, thus arguing for a careful consideration of vitamin concentrations in clinical settings.     

Protective effects of ascorbic acid, Dl-α-tocopherol acetate, and sodium selenate on ethanol-induced gastric mucosal injury of rats

In this study, the effect of ascorbic acid (vitamin C), Dl-α-tocopherol acetate (vitamin E), and sodium selenate (selenium) on ethanol-induced gastric mucosal injury in rats was investigated morphologically and biochemically. The gastric mucosal injury was produced by administration of 1 mL of absolute ethanol to each rat. Animals received vitamin C (250 mg/kg), vitamin E (250 mg/kg), and selenium (0.5 mg/kg) for 3 d 1 h prior to the administration of absolute ethanol. In gastric mucosa of rats given ethanol according to control groups, neuronal nitric oxide expression decreased. This immunoreactivity was much lower in the group given ethanol+vitamin C+vitamin E+selenium than the control group and the ethanol-induced group. Scanning electron microscopic evaluation of the ethanol-induced group, when compared to control groups, revealed degenerative changes in gastric mucosa, whereas a good arrangement in surface topography of gastric mucosa in the group given ethanol + vitamin C+vitamin E + selenium was observed. In the group administered ethanol, a reduction of the stomach glutathione (GSH) and serum total protein levels and increases in serum sialic acid, triglycerides, and stomach lipid peroxidation (LPO) levels were observed. Vitamin C+vitamin E+Se administration to alcohol-treated rats significantly increased the serum total protein, triglyceride levels, and stomach GSH levels and significantly lowered the levels of serum sialic acid and stomach LPO compared to untreated alcohol-supplemented rats. As a result of these findings, we can say that the combination of vitamin C, vitamin E, and selenium has a protective effect on ethanol-induced gastric mucosal injury of rats.     

Enhancement of gastric mucosal integrity by Lactobacillus rhamnosus GG

The gastric mucosa is frequently exposed to different exogenous and endogenous ulcerative agents. Alcoholism is one of the risk factors for the development of mucosal damage in the stomach. This study aimed to assess if a probiotic strain Lactobacillus rhamnosus GG (LGG) is capable of protecting the gastric mucosa from acute damage induced by intragastric administration of ethanol. Pre-treatment of rats with LGG at 10(9) cfu/ml twice daily for three consecutive days markedly reduced ethanol-induced mucosal lesion area by 45%. LGG pre-treatment also significantly increased the basal mucosal prostaglandin E(2) (PGE(2)) level. In addition, LGG attenuated the suppressive actions of ethanol on mucus-secreting layer and transmucosal resistance and reduced cellular apoptosis in the gastric mucosa. It is suggested that the protective action of LGG on ethanol-induced gastric mucosal lesions is likely attributed to the up-regulation of PGE(2), which could stimulate the mucus secretion and increase the transmucosal resistance in the gastric mucosa. All these would protect mucosal cells from apoptosis in the stomach.     

Effects of antioxidant vitamin supplements on Helicobacter pylori-induced gastritis in Mongolian gerbils

BACKGROUND: Epidemiological studies show that high intake of food-bound vitamin C and E reduces the risk of gastric cancer. Whether dietary supplementation with antioxidant micronutrients interferes with Helicobacter pylori infection and associated diseases is unclear. The aim of this study was to investigate if dietary vitamin C or E supplementation influences the progression of gastritis, gastric mucosal nitrosative and oxidative protein damage, gastric mucosal lipid peroxidation, or gastric mucosal oxidative DNA damage in H. pylori-infected Mongolian gerbils. MATERIALS AND METHODS: Gerbils were divided into four groups: H. pylori-infected animals fed with vitamin C- or vitamin E-supplemented food, and infected and uninfected animals given standard rodent food. Subgroups of animals were killed at different time-points until 52 weeks postinfection. Concentrations of 3-nitrotyrosine and thiobarbituric acid-reactive substances (TBARS) in the gastric mucosa were determined with an immunodot blot and a fluorometric method, respectively. Mucosal concentrations of carbonyl carbons on proteins and 8-hydroxydeoxyguanosine were determined by enzyme-linked immunosorbent assay. Gastritis was scored semiquantitatively. RESULTS: Vitamin supplements had no effect on the colonization with H. pylori. Vitamin C as well as vitamin E supplements reduced mucosal 3-nitrotyrosine concentrations to normal levels in infected animals. Vitamin E supplements decreased mucosal protein carbonyls and TBARS in short-term gastritis. In addition, vitamin C supplements caused attenuated mucosal oxidative DNA damage and milder mucosal inflammation in short-term gastritis. CONCLUSION: Vitamin C or vitamin E supplementation leads to some short-term protective effects on H. pylori-induced gastritis in Mongolian gerbils. These effects seem to subside over time when the infection persists.     

Celastrol inhibits tumor cell proliferation and promotes apoptosis through the activation of c-Jun N-terminal kinase and suppression of PI3 K/Akt signaling pathways

Celastrol, a plant triterpene has attracted great interest recently, especially for its potential anti-inflammatory and anti-cancer activities. In the present report, we investigated the effect of celastrol on proliferation of various cancer cell lines. The mechanism, by which this triterpene exerts its apoptotic effects, was also examined in detail. We found that celastrol inhibited the proliferation of wide variety of human tumor cell types including multiple myeloma, hepatocellular carcinoma, gastric cancer, prostate cancer, renal cell carcinoma, head and neck carcinoma, non-small cell lung carcinoma, melanoma, glioma, and breast cancer with concentrations as low as 1 μM. Growth inhibitory effects of celastrol correlated with a decrease in the levels of cyclin D1 and cyclin E, but concomitant increase in the levels of p21 and p27. The apoptosis induced by celastrol was indicated by the activation of caspase-8, bid cleavage, caspase-9 activation, caspase-3 activation, PARP cleavage and through the down regulation of anti-apoptototic proteins. The apoptotic effects of celastrol were preceded by activation of JNK and down-regulation of Akt activation. JNK was needed for celastrol-induced apoptosis, and inhibition of JNK by pharmacological inhibitor abolished the apoptotic effects. Overall, our results indicate that celastrol can inhibit cell proliferation and induce apoptosis through the activation of JNK, suppression of Akt, and down-regulation of anti-apoptotic protein expression.     

Enhanced intracellular calcium promotes metabolic and secretory disturbances in rat gastric mucosa during ethanol-induced gastritis

Changes in the Ca(2+) homeostasis have been implicated in cell injury and death. However, Ca(2+) participation in ethanol-induced chronic gastric mucosal injury has not been elucidated. We have developed a model of ethanol-induced chronic gastric injury in rats, characterized by marked alterations in plasma membranes from gastric mucosa and a compensatory cell proliferation, which follows ethanol withdrawal. Therefore, the present study explored the possible role of intracellular Ca(2+) in the oxidative metabolism and in acid secretion in this experimental model. Glucose oxidation was greatly enhanced in the injured mucosa, as evaluated by CO(2) production by isolated mucosal preparations incubated with (14)C-radiolabeled glucose in different carbons. Oxygen consumption and acid secretion (aminopyrine accumulation) were also stimulated. A predominating secretory status was morphologically identified by electron microscopy in oxyntic cells of gastric mucosa from ethanol-treated rats. A coupling between secretory and metabolic effects induced by ethanol (demonstrated by an inhibitory effect of omeprazole in both parameters) was found. These ethanol-induced effects were also inhibited by addition of Ca(2+) chelators to isolated gastric mucosa samples. Lanthanum, a Ca(2+) channel blocker, inhibited ethanol-promoted increase of oxidative metabolism. In addition, a stimulated Ca(2+) uptake by mucosal minces and increased in vivo Ca(2+) levels in cytosolic and mitochondrial fractions, were also noticed. Enhanced glucose and oxygen consumptions were associated with higher ATP and NADP+ availability, whereas cytosolic NAD/NADH ratio (assessed by mucosal levels of lactate and pyruvate) was not significantly modified by the chronic ethanol administration. In conclusion, changes in Ca(2+) homeostasis, probably mainly due to increased extracellular Ca(2+) uptake, could mediate secretory and metabolic alterations found in the gastric mucosa from rats chronically treated with ethanol.     

The vitamin E analog tocopherol succinate strongly inhibits gap junctional intercellular communication in rat liver epithelial cells (IAR203)

Vitamin E is a scavenger molecule trapping free radicals in biological membranes. However, it has also been shown to elicit the formation of reactive oxygen species and apoptosis in cancer cells. In this study, we tested the ability of alpha-tocopherol, tocopherol acetate, tocopherol phosphate and tocopherol succinate (TS) to modulate gap junctional intercellular communication in the rat liver epithelial cell line IAR203, as measured by the transfer of Lucifer yellow. While alpha-tocopherol, tocopherol acetate and tocopherol phosphate moderately reduced the dye transfer, TS at 10 and 25 microM strongly inhibited it, probably via the induction of the hypophosphorylation of connexin 43. Our results show that, besides their interesting antioxidant properties, vitamin E analogs, especially TS, can exert adverse effects on gap junctional intercellular communication, which could explain their controversial effects in carcinogenesis.     

Cyclin D1 is an essential mediator of apoptotic neuronal cell death.

Many neurons in the developing nervous system undergo programmed cell death, or apoptosis. However, the molecular mechanism underlying this phenomenon is largely unknown. In the present report, we present evidence that the cell cycle regulator cyclin D1 is involved in the regulation of neuronal cell death. During neuronal apoptosis, cyclin D1-dependent kinase activity is stimulated, due to an increase in cyclin D1 levels. Moreover, artificial elevation of cyclin D1 levels is sufficient to induce apoptosis, even in non-neural cell types. Cyclin D1-induced apoptosis, like neuronal apoptosis, can be inhibited by 21 kDa E1B, Bcl2 and pRb, but not by 55 kDa E1B. Most importantly, however, overexpression of the cyclin D-dependent kinase inhibitor p16INK4 protects neurons from apoptotic cell death, demonstrating that activation of endogenous cyclin D1-dependent kinases is essential during neuronal apoptosis. These data support a model in which neuronal apoptosis results from an aborted attempt to activate the cell cycle in terminally differentiated neurons.     

Adoptive transfer of splenocytes in SCID mice implicates CD4+ T cells in apoptosis and epithelial proliferation associated with Helicobacter pylori-induced gastritis

Helicobacter pylori causes severe, rapidly progressive gastritis in severe combined immunodeficient (SCID) mouse recipients of congenic splenocytes. The H. pylori-infected and uninfected C57BL/6J and recipient SCID mice were evaluated to detect CD4+ and CD8+ T cells, B cells, apoptotic epithelial cells, and epithelial cell proliferation at postinoculation weeks 5, 6, 8, and 12. Serum was evaluated for anti-H. pylori IgG and IgM. In all H. pylori-infected mice, gastric CD4+ cell scores were increased, compared with scores for uninfected controls. Recipient mice differed, however, according to the source of the transferred CD4+ cells. The CD4+ cell scores for recipients of splenocytes from H. pylori-infected (immune) donors were indistinguishable from those for wild-type donor mice at all time points. In contrast, gastric mucosal CD4+ cell scores did not become significantly high until two weeks after transfer (postinoculation week 6) in recipients of cells from uninfected (na?ve) donors. Gastric epithelial apoptosis and the gastric epithelial proliferation zone were significantly (P < 0.05) increased in infected recipient and donor, compared with non-recipient and uninfected mice at postinoculation week 12. Results indicated that CD4 cells are sensitized in vivo and migrate to the gastric mucosa where they induce gastritis in response to H. pylori antigens. Influx of CD4 cells and gastritis are correlated with epithelial proliferation and apoptosis, and suggest that CD4-dependent H. pylori gastritis leads to epithelial damage with attendant proliferative and metaplastic responses.     

Antiproliferative mechanism of a cannabinoid agonist by cell cycle arrest in human gastric cancer cells

For gastric cancers, the antineoplastic activity of cannabinoids has been investigated in only a few reports and knowledge regarding the mechanisms involved is limited. We have reported previously that treatment of gastric cancer cells with a cannabinoid agonist significantly decreased cell proliferation and induced apoptosis. Here, we evaluated the effects of cannabinoids on various cellular mediators involved in cell cycle arrest in gastric cancer cells. AGS and MKN-1 cell lines were used as human gastric cancer cells and WIN 55,212-2 as a cannabinoid agonist. Cell cycles were analyzed by flow cytometry and western blotting. Treatment with WIN 55,212-2 arrested the cell cycle in the G0/G1 phase. WIN 55,212-2 also upregulated phospho-ERK1/2, induced Kip1/p27 and Cip1/WAF1/p21 expression, decreased cyclin D1 and cyclin E expression, decreased Cdk 2, Cdk 4, and Cdk 6 expression levels, and decreased phospho-Rb and E2F-1 expression. ERK inhibitor decreased the proportion of G0/G1 phase which was induced by WIN 55,212-2. Inhibition of pAKT led to cell cycle arrest in gastric cancer cells. Cell cycle arrest preceded apoptotic response. Thus, this cannabinoid agonist can reduce gastric cancer cell proliferation via G1 phase cell cycle arrest, which is mediated via activation of the MAPK pathway and inhibition of pAKT.     

Ascorbic acid spares alpha-tocopherol and decreases lipid peroxidation in neuronal cells

Ascorbic acid is considered an antioxidant in the central nervous system, but direct evidence that ascorbate protects neuronal cells from oxidant stress is lacking. Differentiated SH-SY5Y cells in culture took up ascorbic acid on the sodium-dependent vitamin C transporter Type 2 and retained it much more effectively than dehydroascorbic acid. Intracellular ascorbate spared alpha-tocopherol, both in cells loaded with alpha-tocopherol in culture and in cells under oxidant stress due to extracellular ferricyanide. Sparing of alpha-tocopherol in response to ferricyanide was associated with protection against lipid peroxidation in cell membranes. These results show that neuronal cells concentrate ascorbate, and that intracellular ascorbate, either directly or through sparing of alpha-tocopherol, protects them against oxidant stress.     

Prostaglandin E2 protects gastric mucosal cells from apoptosis via EP2 and EP4 receptor activation

Prostaglandin E(2) (PGE(2)) has a strong protective effect on the gastric mucosa in vivo; however, the molecular mechanism of a direct cytoprotective effect of PGE(2) on gastric mucosal cells has yet to be elucidated. Although we reported previously that PGE(2) inhibited gastric irritant-induced apoptotic DNA fragmentation in primary cultures of guinea pig gastric mucosal cells, we show here that PGE(2) inhibits the ethanol-dependent release of cytochrome c from mitochondria. Of the four main subtypes of PGE(2) receptors, we also demonstrated, using subtype-specific agonists, that EP(2) and EP(4) receptors are involved in the PGE(2)-mediated protection of gastric mucosal cells from ethanol-induced apoptosis. Activation of EP(2) and EP(4) receptors is coupled with an increase in cAMP, for which a cAMP analogue was found here to inhibit the ethanol-induced apoptosis. The increase in cAMP is known to activate both protein kinase A (PKA) and phosphatidylinositol 3-kinase pathways. An inhibitor of PKA but not of phosphatidylinositol 3-kinase blocked the PGE(2)-mediated protection of cells from ethanol-induced apoptosis, suggesting that a PKA pathway is mainly responsible for the PGE(2)-mediated inhibition of apoptosis. Based on these results, we considered that PGE(2) inhibited gastric irritant-induced apoptosis in gastric mucosal cells via induction of an increase in cAMP and activation of PKA, and that this effect was involved in the PGE(2)-mediated protection of the gastric mucosa from gastric irritants in vivo.     

Effect of ninhydrin on the biochemical and histopathological changes induced by ethanol in gastric mucosa of rats

Studies on the effect of ninhydrin in the normal gastric mucosa and against the ethanol induced gastric injury were undertaken in rats in view of the presence of a carbonyl function as well as hydroxyl groups in its chemical structure. In spite of its potentials to generate hydroxyl radicals, it is deemed to possess antioxidant property by virtue of its electrophilic nature. Recent studies have shown gastro-protection to mediate through a reaction between the electrophilic compounds and sulfhydryl groups of the mucosa. Hence it was found worthwhile to evaluate the interaction between the oxidant and antioxidant functions in the structure of the same compound. The effects of ninhydrin pretreatment on gastric mucosal injuries caused by 80% ethanol, 25% NaCl and 0.2M NaOH were investigated in rats. The gastric tissue in ethanol-treated rats was analyzed for different histopathological lesions. In addition, the effects on ethanol-induced changes in the gastric levels of proteins, nucleic acids, non-protein sulfhydryl (NP-SH) and malondialdehyde (MDA) were also evaluated. Ninhydrin, as such, failed to induce any significant changes in normal gastric mucosa, while its pretreatment at oral doses of 5, 10 and 20 mg/kg was found to provide a dose-dependent protection against the ulcers induced by ethanol, NaOH and NaCl. The results of histopathological evaluation revealed a protective effect of ninhydrin on congestion, hemorrhage, edema, erosions and necrosis caused by ethanol. Furthermore, the pretreatment afforded a dose-dependent inhibition of the ethanol-induced depletion of proteins, nucleic acids, NP-SH and increase of MDA in the gastric tissue. The results obtained clearly demonstrate the anti-ulcerogenic activity of ninhydrin. The exact mechanism of action is not known. However, the carbonyl function in ninhydrin appears to achieve antioxidant balance and protect the gastric mucosa from the ethanol-induced gastric injury. Further studies are warranted to investigate the toxicity and detailed mechanism of action of this potent compound before any clinical trials, especially at the effective lower doses.