Tadahito Shimada

Characteristics of the peroxisome proliferator activated receptor γ (PPARγ) ligand induced apoptosis in colon cancer cells

Background: Involvement of peroxisome proliferator activated receptor γ (PPARγ) in the growth response of colon cancer cells has been suggested. Aims: To investigate the characteristics of PPARγ induced apoptosis in colon cancer cells. Methods: The effects of ligands for each of the PPAR subtypes (α, δ, and γ) on DNA synthesis and cell viability were examined in HT-29 colon cancer cells. Modulation of apoptosis related gene expression by PPARγ ligands was screened with cDNA arrays, and the results were confirmed by quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Results: PPARα, PPARδ, and PPARγ were all expressed in HT-29 cells. PPARγ ligands, 15-deoxy-δ12,14-prostaglandin J2 (15d-PGJ2) and troglitazone (TGZ), suppressed DNA synthesis of HT-29 cells whereas ligands for PPARα and PPARδ had no significant effects. Both 15d-PGJ2 and TGZ induced HT-29 cell death in a dose dependent manner which was associated with an increase in fragmented DNA and was sensitive to a caspase inhibitor. Among several genes selected by cDNA array screening, quantitative RT-PCR analysis confirmed downregulation of c-myc expression and upregulation of c-jun and gadd153 expression by 15d-PGJ2 and TGZ. PPARγ induced apoptosis was antagonised by the presence of serum in the culture medium, and interaction between PPARγ signalling and cell survival signalling through the phosphatidylinositol 3-kinase pathway was suggested. Conclusions: As c-myc is an important target gene of the adenomatous polyposis coli (APC)/β-catenin and/or APC/γ-catenin pathway, activation of PPARγ signalling appears to compensate for deregulated c-myc expression caused by mutated APC. The present results suggest the potential usefulness of PPARγ ligands for chemoprevention and treatment of colon cancers.

Chemokine expression in Helicobacter pylori-infected gastric mucosa.

Abstract: Inflammatory response to Helicobacter pylori is characterized by infiltration of neutrophils, monocytes, and lymphocytes into the gastric mucosa. Interleukin-8 (IL-8), a prototype of the CXC-chemokine subfamily, may be a key modulator in inducing neutrophil migration and activation in H. pylori-infected gastric mucosa. IL-8 is produced by gastric epithelial cells in response to H. pylori infection, and IL-8 expression is induced by local production of proinflammatory cytokines and attachment of H. pylori organisms to the gastric epithelial cell surface. Multiple genes in the H. pylori cag pathogenicity island seem to be involved in inducing the epithelial IL-8 response to H. pylori attachment. Activation of the transcription factor, nuclear factor κB (NF-κB), is associated with this IL-8 response. Reactive oxygen intermediates whose production is increased in H. pylori-infected gastric mucosa may also modulate IL-8 expression in the gastric mucosa. Recent reports also suggest that the local production of CC-chemokines, another chemokine subfamily, is important in H. pylori-associated gastritis.

Proton-coupled transport of glycylglycine in rabbit renal brush-border membrane vesicles

Transport of glycylglycine into rabbit renal brush-border membrane vesicles was found to be Na+-independent, H+ gradient-dependent and electrogenic. Marked overshoot uptake of the dipeptide was observed when an inward-directed proton gradient and inside-negative potential difference were imposed simultaneously across the vesicular membranes. Saturable depolarization of vesicular membranes could be demonstrated with glycylglycine by use of a fluorescent cyanine dye, di-S-C3(5). The results indicate that glycylglycine is contransported with H+ across the membranes.

Redox Regulation of Interleukin-8 Expression in MKN28 Cells

Recent evidence suggests a role of reactiveoxygen intermediates (ROI) in intracellular signalingand regulation of gene expression. We examined whetherexpression of interleukin-8 (IL-8), a key cytokine in the inflammatory responses of gastricepithelial cells, is sensitive to antioxidants andoxidative stress. IL-8 secretion was quantified by IL-8enzymelinked immunosorbent assay, and IL-8 mRNAexpression was determined by northern blot analysis.Electrophoretic mobility shift assay was performed todetect the transcription factor, nuclear factor κB(NF-κB). N-Acetylcysteine (NAC) ordimethylsulfoxide inhibited IL-8 expression induced by tumornecrosis factor-α (TNF-α) orinterleukin-1β (IL-1β). Externally appliedH2O2 significantly up-regulatedIL-8 expression. TNF-α-induced activation of NF-κB activity was suppressed by NAC,and H2O2 caused significantactivation of NF-κB. Since ROI production isincreased in the inflamed gastric mucosa, for example,in H. pylori-associated gastritis, the present results suggest that ROImay be an important modulator of IL-8 expression ingastric mucosal cells.

Na+-dependent elevation of the acidic cell surface pH (microclimate pH) of rat jejunal villus cells induced by cyclic nucleotides and phorbol ester: possible mediators of the regulation of the Na+/H+ antiporter

The effects of cyclic nucleotides and phorbol ester on the acidic cell surface pH of rat jejunal villi were studied by using single-barrelled pH-sensitive microelectrodes. Addition of dibutyryl cAMP (1 mM) to the mucosal bathing solution caused an elevation of the cell surface pH from 6.19 +/- 0.04 (n = 12 measurements from three animals) to 6.53 +/- 0.03 (12) in the presence of Na+ in the medium. However, dibutyryl cAMP had no significant effect in the absence of Na+ and presence of 1 mM amiloride. Dibutyryl cGMP (1 mM) also had an Na+-dependent inhibitory effect on the cell surface pH. A phorbol ester, phorbol 12-myristate 13-acetate, caused an elevation of the cell surface pH only in the presence of Na+ from 6.14 +/- 0.07 (12) to 6.46 +/- 0.08 (12). Phorbol and phorbol 13-acetate, which do not stimulate protein kinase C, were without significant effects. These results suggest that increased levels of the intracellular cyclic nucleotides and activation of protein kinase C raise the acidic cell surface pH by inhibiting the activity of the brush-border Na+/H+ antiporter in the rat jejunal villus cells.

Comparison between endoscopic papillary balloon dilatation and endoscopic sphincterotomy for the treatment of common bile duct stones

BackgroundThis study was designed to evaluate the therapeutic outcome and early postoperative complications, especially pancreatitis, of endoscopic papillary balloon dilation (EPBD) and endoscopic sphincterotomy (EST) in patients with common bile duct stones in our department.MethodsOne hundred eighty patients with common bile duct stones were randomized to undergo EPBD or EST. An 8-mm dilatation balloon was used for EPBD. Modified Cotton’s criteria, in which relatively mild pancreatitis is also included as a complication, were used to determine the incidence of postoperative complications.ResultsThe rate of complete removal of stones was significantly higher in the EST group (95.6%) than in the EPBD group (86.6%); for stones less than 10 mm in diameter, however, the rate with EPBD (93.8%) was almost equivalent to that with EST (98.1%). According to modified Cotton’s criteria, the incidence of postoperative pancreatitis was significantly higher in the EPBD group (16.7%) than in the EST group (6.7%). Bleeding was encountered in one patient (1.1%) in the EST group, but in none in the EPBD group. No fatal complication occurred in either the EPBD or the EST group.ConclusionsAlthough EPBD appears to be comparable to EST for removal of small common bile duct stones, mild postoperative pancreatitis is more likely to occur with EPBD than with EST.

Massive gastrointestinal hemorrhage in systemic lupus erythematosus: successful treatment with corticosteroid pulse therapy

Although mesenteric vasculitis due to systemic lupus erythematosus (SLE) is relatively uncommon, it is the most dangerous manifestation associated with high mortality. We describe the case of a SLE patient with life-threatening gastrointestinal hemorrhage due to mesenteric vasculitis in whom methylprednisolone pulse therapy was quite effective in controlling the hemorrhage and resulted in a satisfactory long term outcome. A 47-yr-old woman presenting with high fever, rash, and melena was diagnosed with SLE from positive antinuclear antibodies, anti-dsDNA, and low complement titers. Although fever and rash subsided with administration of prednisolone, massive hematemesis appeared with melena. Endoscopy demonstrated bleeding ulceration of the antrum, which was intractable despite intensive antiulcer therapy and transfusion. Surgical exploration revealed ileal penetration, and multiple bleeding ulcerations were observed over the resected ileum as well as the antral ulceration. However, bleeding persisted after surgery and surgical findings prompted us to select methylprednisolone pulse. Hemorrhage responded promptly to the therapy, and the patient has remained well since then for >10 yr. Our report indicates that corticosteroid pulse may serve as one of the therapeutic options for SLE with massive hemorrhage due to widespread mesenteric vasculitis.

A case of primary gastric choriocarcinoma and a review of the Japanese literature

A 63-year old woman who had experienced melena for 2 weeks was admitted to Tokyo University Hospital. Gastric adenocarcinoma was diagnosed endoscopically and histologically, and a total gastrectomy was performed soon thereafter. Pathological examination of the resected stomach revealed choriocarcinoma of the stomach. Although chemotherapy was administered after surgery, she died 3 months after admission. Autopsy confirmed the diagnosis of primary gastric choriocarcinoma, a rare, but highly malignant tumor. It is characteristic; macroscopically it forms a necrotic mass with bleeding, and microscopically it often consists of adenocarcinoma and choriocarcinoma. Since its prognosis is extremely poor, we must take into account the possibility of primary gastric choriocarcinoma when a hemorrhagic gastric tumor with necrosis is found.

Role of Na+/H+ antiport in intracellular pH regulation by rabbit enterocytes

The steady-state intracellular pH (pHi) of isolated rabbit enterocytes was determined using 9-aminoacridine, a fluorescent weak base, and the null-point method with digitonin. When cells are incubated in a Na+-containing solution, the estimated value of pHi was in the range of 7.10-7.20, whereas it was 6.60-6.70 when cells were incubated in a Na+-free solution, indicating an important role of external Na+ in maintaining pHi at a slightly alkaline level. Pulse injection of Na+ into a Na+-free cell suspension induced a slowly developing alkalinization of pHi. The time course of the alkalinization was found to be dependent on the Na+ concentration. Li+ had the same effect as Na+, while K+ had a slight effect. Amiloride inhibited the effects of Na+ dose-dependently. These results indicate that the Na+/H+ antiport plays an important role in maintaining the pHi at a neutral or slightly alkaline level in the intact enterocytes.

Effect of PPARgamma ligands on the viability of gastric epithelial cells.

Peroxisome proliferator‐activated receptors (PPAR) are a family of three nuclear receptors (PPARα, PPARδ, and PPARγ). Although recent evidence suggests a role for PPARγ in the regulation of colonic epithelial cell growth, the role for PPARγ in the stomach has not been established.