Ubiquitin-proteasome inhibitor enhances tumour necrosis factor-alpha-induced apoptosis in rat gastric epithelial cells

PDZK1 induces resistance to apoptosis in esophageal adenocarcinoma cells

BACKGROUND

Esophageal cancer is a lethal malignancy with a poor prognosis. The incidence of esophageal adenocarcinoma, which develops from Barrett's esophagus (BE), has recently been increasing. In a previous study, we found that PDZK1 expression is higher in long segment BE compared to that in short-segment BE. However, the function of PDZK1 in the mucosa of BE is unclear.

AIMS

Clarify the role of PDZK1 in BE mucosa using PDZK1 overexpressed cells.

METHODS

Human adenocarcinoma-derived OE33 cells were used as a parental cell line and transfected to generate PDZK1 overexpressed OE33 cells (PC cells) or transfected with empty vector as control cells (NC cells). Cell growth of NC and PC cells in 10% fetal bovine serum was evaluated by cell counting. The effect of PDZK1 on proteasome inhibitor (PSI)-induced apoptosis was qualified by fluorescence microscopy and quantified by flow cytometry. Expression of apoptosis-related proteins was evaluated by western blotting.

RESULTS

There were no significant differences in cell growth between NC and PC cells. PSI significantly increased apoptosis in NC cells, but not in PC cells. In response to PSI, increased levels of cleaved-caspase3 and decreased pro-caspase3 levels were found in NC cells, but not in PC cells. In NC cells, PSI significantly decreased Bcl-2 expression without affecting Bax levels. In contrast, high expression of both Bcl-2 and Bax was observed in PC cells.

CONCLUSION

Overexpression of PDZK1 protein induces an apoptosis-resistant phenotype in BE cells, which may be a potential therapeutic target.

Dose-dependent inhibition of gastric injury by hydrogen in alkaline electrolyzed drinking water

Background

Hydrogen has been reported to relieve damage in many disease models, and is a potential additive in drinking water to provide protective effects for patients as several clinical studies revealed. However, the absence of a dose–response relationship in the application of hydrogen is puzzling. We attempted to identify the dose–response relationship of hydrogen in alkaline electrolyzed drinking water through the aspirin induced gastric injury model.

Methods

In this study, hydrogen-rich alkaline water was obtained by adding H₂ to electrolyzed water at one atmosphere pressure. After 2 weeks of drinking, we detected the gastric mucosal damage together with MPO, MDA and 8-OHdG in rat aspirin induced gastric injury model.

Results

Hydrogen-dose dependent inhibition was observed in stomach mucosal. Under pH 8.5, 0.07, 0.22 and 0.84 ppm hydrogen exhibited a high correlation with inhibitory effects showed by erosion area, MPO activity and MDA content in the stomach. Gastric histology also demonstrated the inhibition of damage by hydrogen-rich alkaline water. However, 8-OHdG level in serum did not have significant hydrogen-dose dependent effect. pH 9.5 showed higher but not significant inhibitory response compared with pH 8.5.

Conclusions

Hydrogen is effective in relieving the gastric injury induced by aspirin-HCl, and the inhibitory effect is dose-dependent. The reason behind this may be that hydrogen-rich water directly interacted with the target tissue, while the hydrogen concentration in blood was buffered by liver glycogen, evoking a suppressed dose–response effect. Drinking hydrogen-rich water may protect healthy individuals from gastric damage caused by oxidative stress.

Bortezomib attenuates acute graft-vs.-host disease through interfering with host immature dendritic cells

OBJECTIVE

To explore the conditions under which proteasome inhibitor bortezomib improves acute graft-vs.-host disease (aGVHD) and the mechanism underlying the differential effects of bortezomib on aGVHD.

MATERIALS AND METHODS

Murine aGVHD models (C57BL/6→BALB/c) of different severities were set up by infusing with decreasing doses of donor splenocytes (SC). Bortezomib were administered immediately or 6 days after bone marrow transplantation (BMT). Serum levels of tumor necrosis factor-α (TNF-α) and lipopolysaccharide along with the number of donor TNF-α(+) T cells in recipients before intervention were determined. Major histocompatibility complex II expression and interleukin-12 production were analyzed to evaluate the maturation state of host dendritic cells (DCs) before intervention. Phenotypic changes, apoptosis, allogeneic stimulation, and IκBα expression levels in bortezomib-treated mature DCs or immature DCs were analyzed in vitro.

RESULTS

Neither early bortezomib (day 0 BMT) administration in a modest (SC 1 × 10(7)) or severe (SC 2 × 10(7)) aGVHD model, nor delayed administration (day +6 BMT) could protect mice form aGVHD. Marked inhibition of aGVHD was observed in a mild aGVHD model (SC 5 × 10(6)) with early intervention. This inhibition correlated with a relatively immature state of host DCs before intervention. Additional in vitro studies showed that, in comparison to mature DCs, bortezomib inhibited phenotypic and functional maturation as well as induced more potent apoptosis in immature DCs through suppression of nuclear factor-κB activity.

CONCLUSIONS

Manipulating host immature DCs may represent a novel mechanism by which bortezomib improves aGVHD.

Reactive oxygen species-quenching and anti-apoptotic effect of polaprezinc on indomethacin-induced small intestinal epithelial cell injury

BACKGROUND

To protect the small intestine from mucosal injury induced by nonsteroidal anti-inflammatory drugs is one of the critical issues in the field of gastroenterology. Polaprezinc (PZ), a gastric muco-protecting agent, has been widely used for the treatment of gastric ulcer and gastritis for its unique effects, such as its strong reactive oxygen species (ROS)-quenching effect. The aim of this study was to clarify the mechanism by which indomethacin-induced small intestinal mucosal injury occurs, by using a rat intestinal epithelial cell line (RIE-1). In addition, the protective role of PZ and the possible mechanism of its effect on indomethacin-induced small intestinal injury were investigated.

METHODS

Cell death was evaluated by methyl thiazolyl tetrazolium (MTT) assay and a double-staining method with Hoechst33342 dye and propidium iodide. Indomethacin-induced ROS production was evaluated by detecting the oxidation of a redox-sensitive fluorogenic probe, RedoxSensor, and the oxidation of cysteine residues of proteins (protein S oxidation). The activation of cytochrome c, smac/DIABLO, and caspase-3 was assessed by western blotting. In some experiments, PZ or its components, L: -carnosine and zinc, were used.

RESULTS

We found that indomethacin caused apoptosis in RIE-1 cells in a dose- and time-dependent manner. Indomethacin also induced ROS production and an increase in the protein S oxidation of RIE-1. Pretreatment of RIE-1 with PZ or zinc sulfate, but not L: -carnosine, significantly reduced the indomethacin-induced apoptosis. PZ prevented ROS production and the increase in protein S-oxidation. PZ inhibited indomethacin-induced cytochrome c and smac/DIABLO release and subsequent caspase-3 activation.

CONCLUSIONS

The protective effect of PZ on indomethacin-induced small intestinal injury may be dependent on its ROS-quenching effect.

Involvement of reactive oxygen species in indomethacin-induced apoptosis of small intestinal epithelial cells

BACKGROUND

The precise pathogenic mechanism of nonsteroidal antiinflammatory drug-induced small intestinal injury is still unknown. In the present study, we investigated the mechanism by which indomethacin induced mucosal injury by using an in vitro model of small intestine.

METHODS

The colon cancer cell line Caco-2, exhibiting a small intestinal phenotype starting as a crypt cell and differentiating to a villous phenotype, and RIE, a rat intestinal epithelial cell line, were employed. Indomethacin was added to differentiated the Caco-2 and RIE monolayer, and cell death was quantified by MTT assay and LDH release in the cell culture supernatant. Indomethacin-induced cell death was also qualified by fluorescent probes under the fluorescent microscope. As a functional study, the permeability of the Caco-2 monolayer was assessed by measuring transepithelial electrical resistance (TEER) and the flux of FITC-conjugated dextran across the monolayer. Indomethacin-induced reactive oxygen species production in Caco-2 and RIE was evaluated by redoxsensitive fluorogenic probes using a fluorometer. In some experiments, antioxidants were used to clarify the role of reactive oxygen species on indomethacin-induced Caco-2 cell death.

RESULTS

Indomethacin caused cell death (mainly apoptosis) of Caco-2 and RIE in a dose-and time-dependent manner that was correlated with increased permeability of the Caco-2 monolayer. Exposure of Caco-2 and RIE with indomethacin also resulted in a significant reactive oxygen species production that was inhibited by the pretreatment of these cells with antioxidants.

CONCLUSIONS

Taken together, reactive oxygen species production is one of the mechanisms by which indomethacin induced small intestinal injury.

Methylparaben potentiates UV-induced damage of skin keratinocytes

For many years, methylparaben (MP) has been used as a preservative in cosmetics. In this study, we investigated the effects of ultraviolet-B (UVB) exposure on MP-treated human skin keratinocytes. HaCaT keratinocyte was cultured in MP-containing medium for 24h, exposed to UVB (15 or 30 mJ/cm(2)) and further cultured for another 24h. Subsequent cellular viability was quantified by MTT-based assay and cell death was qualified by fluorescent microscopy and flow cytometry. Oxidative stress, nitric oxide (NO) production and cellular lipid peroxidation were measured using fluorescent probes. In addition, activation of nuclear factor kappa B and activator protein-1 was assessed by electro-mobility gel-shift assay. Practical concentrations of MP (0.003%) had a little or no effect on cellular viability, oxidative stress, NO production, lipid peroxidation and activation of nuclear transcription factors in HaCaT keratinocytes. Low-dose UVB also had little or no effect on these parameters in HaCaT keratinocytes. However, UVB exposure significantly increased cell death, oxidative stress, NO production, lipid peroxidation and activation of transcription factors in MP-treated HaCaT keratinocytes. These results indicate that MP, which has been considered a safe preservative in cosmetics, may have harmful effects on human skin when exposed to sunlight.

Acute gastric changes after intracerebral hemorrhage in rats

Severe intracerebral hemorrhage (ICH) produces gastric pathology in about 30% of the patient population, even after the standard treatment of H2 receptor blockers or proton pump inhibitors. This study was undertaken to establish a rat model of ICH-induced gastric ulcer. Adult male Sprague-Dawley rats (300-350 g) were divided into two hemorrhage groups and a sham control group. ICH was produced either by injection of 100 microl of autologous arterial blood or by injection of 4 microl saline containing 0.6 unit of bacterial collagenase VII into the right basal ganglia. Rats were sacrificed at 24, 48, 72 h, and 7 days after ICH to harvest brains and stomachs. Greater degrees of hemorrhage and brain edema were observed in collagenase-induced ICH. Motor behavior decreased significantly after 24 h in both models. The incidence of acute ulceration with destruction of the forestomach epithelium was extremely low at 8.7% in the collagenase injection model and 4.8% in the blood injection rats. Small, pinpoint hemorrhages (petechiae) were noticed in 38% of rats after blood injection and 22% after collagenase injection, in the glandular portion of the gastric mucosa with penetration of red blood cells and inflammatory cells into the gastric mucosa. Enhanced tumor necrosis factor alpha (TNFalpha) and cyclooxygenase 2 (COX-2) expressions were observed in gastric tissues after ICH with more intense staining occurring at 24 and 48 h. Due to the low incidence of ulceration, ICH-induced gastric ulceration in rodents may not appropriate for evaluating the potential human risk of gastric ulceration after ICH.

Tumor necrosis factor-alpha stimulates gastric epithelial cell proliferation

TNF-alpha is a cytokine produced during gastric mucosal injury. We examined whether TNF-alpha could promote mucosal repair by stimulation of epithelial cell proliferation and explored further the underlying mechanisms in a rat gastric mucosal epithelial cell line (RGM-1). TNF-alpha treatment (1-10 ng/ml) for 12 or 24 h significantly increased cell proliferation but did not induce apoptosis in RGM-1 cells. TNF-alpha treatment significantly increased cytosolic phospholipase A(2) and cyclooxygenase-2 (COX-2) protein expression and PGE(2) level but did not affect the protein levels of EGF, basic fibroblast growth factor, and COX-1 in RGM-1 cells. The mRNA of TNF receptor (TNF-R) 2 but not of TNF-R1 was also increased. Dexamethasone dose dependently inhibited the stimulatory effect of TNF-alpha on cell proliferation, which was associated with a significant decrease in cellular COX-2 expression and PGE(2) level. A selective COX-2 inhibitor 3-(3-fluorophenyl)-4-[4-(methylsulfonyl)phenyl]-5,5-dimethyl-(5)H-furan-2-one (DFU) by itself had no effect on basal cell proliferation but significantly reduced the stimulatory effect of TNF-alpha on RMG-1 cells. Combination of dexamethasone and DFU did not produce an additive effect. PGE(2) significantly reversed the depressive action of dexamethasone on cell proliferation. These results suggest that TNF-alpha plays a regulatory role in epithelial cell repair in the gastric mucosa via the TNF-alpha receptor and activation of the arachidonic acid/PG pathway.

Blocking of NF-kappaB activation enhances the tumor necrosis factor alpha-induced apoptosis of a human gastric cancer cell line

The transcription factor NF-kappaB is constitutively activated in many human cancers and induces the expression of multiple genes, including those of anti-apoptotic proteins. This study investigated the mechanism by which human gastric cancer cells (MKN45) are resistant to apoptosis induced by tumor necrosis factor alpha (TNF-alpha). Confluent monolayers of MKN45 cells were either pretreated or not for 60 min with PSI, a peptide aldehyde known to specifically inhibit the chymotrypsin-like activity of 26S proteasome. Cells were subsequently stimulated with recombinant human TNF-alpha, and cell viabilities were determined by the WST-1 assay. Apoptosis was confirmed by fluorescence microscopy after staining with Hoechst 33342, and DNA fragmentation was determined by a DNA fragmentation detection kit. A 24-h incubation with either TNF-alpha or PSI alone did not affect cell viabilities; however, pretreatment with PSI significantly enhanced the level of apoptosis induced by TNF-alpha. Therefore, this study suggests the possibility that blocking of NF-kappaB activity renders gastric cancer cells susceptible to the apoptosis induced by TNF-alpha.