Hideaki Kazumori

Strategic compartmentalization of Toll-like receptor 4 in the mouse gut.

Pattern recognition receptors (PRRs), which include the Toll-like receptors (TLRs), are involved in the innate immune response to infection. TLR4 is a model for the TLR family and is the main LPS receptor. We wanted to determine the expression of TLR4 and compare it with that of TLR2 and CD14 along the gastrointestinal mucosa of normal and colitic BALB/c mice. Colitis was induced with 2.5% dextran sodium sulfate (DSS). Mucosa from seven segments of the digestive tract (stomach, small intestine in three parts, and colon in three parts) was isolated by two different methods. Mucosal TLR4, CD14, TLR2, MyD88, and IL-1β mRNA were semiquantified by Northern blotting. TLR4 protein was determined by Western blotting. TLR4/MD-2 complex and CD14 were evaluated by immunohistochemistry. PRR genes were constitutively expressed and were especially stronger in colon. TLR4 and CD14 mRNA were increased in the distal colon, but TLR2 mRNA was expressed more strongly in the proximal colon, and MyD88 had a uniform expression throughout the gut. Accordingly, TLR4 and CD14 protein levels were higher in the distal colon. TLR4/MD-2 and CD14 were localized at crypt bottom epithelial cells. TLR4/MD2, but not CD14, was found in mucosal mononuclear cells. Finally, DSS-induced inflammation was localized in the distal colon. All genes studied were up-regulated during DSS-induced inflammation, but the normal colon-stressed gut distribution was preserved. Our findings demonstrate that TLR4, CD14, and TLR2 are expressed in a compartmentalized manner in the mouse gut and provide novel information about the in vivo localization of PRRs.

Bile acids directly augment caudal related homeobox gene Cdx2 expression in oesophageal keratinocytes in Barrett’s epithelium

Background and aims: The mechanism of transformation to intestinal metaplasia in Barrett’s oesophagus has not been clarified. We investigated the effects of various bile acids on expression of the caudal related homeobox gene Cdx2 in cultured oesophageal squamous epithelial cells. In addition, morphological and histochemical changes in squamous cells to intestinal epithelial cells were studied in response to bile acid induced expression of Cdx2. Methods: A rat model of Barrett’s oesophagus was created by anastomosing the oesophagus and jejunum, and Cdx2 expression was investigated by immunohistochemistry. Also, the response of various bile acids on Cdx2 gene expression was studied in the human colon epithelial cell lines Caco-2 and HT-29, as well as in cultured rat oesophageal squamous epithelial cells using a Cdx2 promoter luciferase assay. In addition, primary cultured oesophageal squamous epithelial cells were transfected with Cdx2 expression vectors and their possible transformation to intestinal-type epithelial cells was investigated. Results: Oesophagojejunal anastomoses formed intestinal goblet cell metaplasia in rat oesophagus specimens and metaplastic epithelia strongly expressed Cdx2. When the effects of 11 types of bile acids on Cdx2 gene expression were examined, only cholic acid (CA) and dehydrocholic acid dose dependently increased Cdx2 promoter activity and Cdx2 protein production in Caco-2 and HT-29 cells, and cultured rat oesophageal keratinocytes. Results from mutation analysis of Cdx2 promoter suggested that two nuclear factor κB (NFκB) binding sites were responsible for the bile acid induced activation of the Cdx2 promoter. When bile acids were measured in oesophageal refluxate of rats with experimental Barrett’s oesophagus, the concentration of CA was found to be consistent with the experimental dose that augmented Cdx2 expression in vitro. Furthermore, transfection of the Cdx2 expression vector in cultured rat oesophageal keratinocytes induced production of intestinal-type mucin, MUC2, in cells that expressed Cdx2. Conclusions: We found that CA activates Cdx2 promoter via NFκB and stimulates production of Cdx2 protein in oesophageal keratinocytes with production of intestinal-type mucin. This may be one of the mechanisms of metaplasia in Barrett’s oesophagus.

Essential Role of MD-2 in TLR4-Dependent Signaling during Helicobacter pylori-Associated Gastritis

TLR4, a member of pattern recognition receptors, is the main receptor of LPS. MD-2 physically associates with TLR4 on the cell surface and confers LPS responsiveness. Helicobacter pylori LPS is one of the major virulence factors for induction of gastritis. We demonstrated in this study the role of MD-2 in TLR4-dependent signaling in H. pylori-associated gastritis. Gastric biopsy samples collected from patients with and without H. pylori infection and four gastric cancer cell lines were used for this study. TLR-4 and MD-2 expression in biopsy specimens and the cell lines was examined by using RT-PCR. Localization of TLR-4 in histological sections was evaluated by immunohistochemistry. For in vitro functional assays, we established stable transfectants of AGS cells expressing TLR4 and MD-2. Cellular distribution of TLR4 was examined by flow cytometry. NF-κB activation and activation of IL-8 and MD-2 promoters were assessed by reporter gene assay. H. pylori infection up-regulated the TLR4 and MD-2 expression in gastric mucosa. TLR4 staining was observed predominantly in epithelial cells, located in both the cytoplasm and at the apical surface. MD-2 transfection in AGS cells markedly increased cell surface expression of TLR4 and augmented the activation of NF-κB and IL-8 promoter upon stimulation with H. pylori LPS. Live H. pylori also stimulated transcriptional activation of MD-2. This study revealed that MD-2 expression is elevated in gastric epithelial cells during H. pylori infection, suggesting that the TLR4/MD-2 system is a potent receptor complex involved in the response to H. pylori LPS in the stomach.

Transgenic overexpression of Reg protein caused gastric cell proliferation and differentiation along parietal cell and chief cell lineages

Reg (regenerating gene product) was originally identified as a growth factor involved in pancreatic regeneration. During the healing course of gastric erosion, Reg expression is highly increased in the enterochromaffin-like (ECL) cells surrounding the ulcer crater, suggesting its role as a regulator of gastric mucosal regeneration. However, there has been no direct in vivo evidence of a growth-promoting role of Reg for the gastric mucosal cells. In the current study, Reg-transgenic mice were created and gastric mucosa were analysed for histological changes. Transgenic mice showed a marked increase in the thickness of the fundic mucosa. Anti-proliferating cell nuclear antigen (PCNA) staining of the fundic mucosa demonstrated the enlargement of the proliferating neck zone and the lower PCNA-negative zone. Histological analysis employing antibodies against cell-type markers revealed expansion of the chief cell and parietal cell populations and no change in the number of surface mucus-producing cells, ECL cells, or G cells. In conclusion, Reg has a growth-promoting effect on gastric progenitor cells and an activity to direct the differentiation of the cells into chief cell and parietal cell lineages. This was in contrast to other factors, all of which had been shown to drive differentiation towards mucus producing cells in vivo. In the injured gastric mucosa, Reg may play a unique and important part in the reconstruction of the properly organized mucosal architecture.

Can PPARγ Ligands Be Used in Cancer Therapy

The role of peroxisome-proliferator activated receptor (PPAR)gamma in tumor growth inhibition has been extensively studied during last seven years but still remains debated. Many in vitro and xenograft studies have demonstrated that PPARgamma ligands are anti-tumorigenic due to anti-proliferative, pro-differentiation and anti-angiogenic effects. In animal models, PPARgamma ligands have shown preventive effects against chemical carcinogenesis. On the other hand, evidences are accumulating against the possible use of this ligand activated nuclear receptor in molecular targeting for cancer therapy. The growth inhibitory effects of certain PPARgamma ligands have recently been shown to be independent of PPARgamma-activation. Studies have also come up with results indicating the growth promoting effects of PPARgamma-activation, particularly in certain animal models genetically predisposed to cancer development. Loss-of-function mutations of PPARgamma in tumors and increased susceptibility of PPARgamma heterozygote knockout mice to carcinogenesis suggested a tumor-suppressing role of PPARgamma. However, recent findings do not support PPARgamma as a tumor suppressor gene. Although initial clinical trials with PPARgamma ligand troglitazone reported promising results in liposarcoma and prostate cancers, recent studies failed to show the expected therapeutic values in advanced colorectal and breast cancers. In this review, we have addressed these controversies on potential use of PPARgamma ligands in cancer therapy.

A new water instillation method for colonoscopy without sedation as performed by endoscopists-in-training

BACKGROUND Colonoscopy may be associated with discomfort when performed without sedation. A study was conducted to determine whether instillation of water into the colon at the beginning of the procedure reduces intubation time as well as patient discomfort and pain. METHODS Colonoscopy was performed in 259 patients by 3 endoscopists-in-training with limited experience. Patients were randomly allocated to 2 groups. In one, a technique was used in which 500 to 1000 mL of water is instilled into the colon by enema at the beginning of the procedure (instillation group, n = 130). In the other, patients underwent a conventional colonoscopy (control group, n = 129). Intubation time was measured and compared between the groups, and subjective discomfort experienced by the patients was measured upon completion of the examination. RESULTS Success rates for insertion to the cecum were similar, (95.4%, instillation group; 96.1%, control group). Detection rates for any colorectal diseases were not different between the groups (30.0% vs. 32.6%). Mean time to cecal intubation was 10.5 minutes in the instillation group and 16.2 minutes in the control group (p < 0.0001). The proportion of patients who complained of abdominal pain during the procedure was 17.1% in the instillation group and 33.3% in the control group (p < 0.001). CONCLUSIONS When used by endoscopists-in-training, the water-instillation colonoscopy technique was associated with less discomfort and faster cecal intubation with no decrease in the rate of detection of colorectal diseases.

A Japanese case of eosinophilic esophagitis

Eosinophilic esophagitis (EE) is a rarely diagnosed condition involving eosinophilic infiltration of the esophageal mucosa. Here we present a case of EE in a 69-year-old Japanese man, who presented with abdominal pain, appetite loss, and a history of bronchial asthma. Laboratory findings included peripheral eosinophilia and an increased serum immunoglobulin E level. Computed tomography showed diffuse severe thickening of the esophageal wall, and a barium esophagogram revealed a small caliber of the middle and lower portion of the esophagus, without normal peristaltic contractions. Endoscopy of the esophagus showed a pale mucosa, with adherent whitish exudates resembling fungal infection, and prominent ring-like contractions. Histologic examination of a biopsy specimen revealed marked eosinophil infiltration into the esophageal mucosa. Endoscopic ultrasonography (EUS) demonstrated marked circumferential thickening of the esophageal submucosal layer, and an esophageal manometry study showed a high percentage of ineffective esophageal peristalsis and high-amplitude esophageal body contractions. EUS findings showed no change even after oral corticosteroid therapy, although the histological findings were improved. This is thought to be the first documented Japanese case of EE. EE should be considered in the differential diagnosis in cases of esophageal motility disturbance, even if the patients do not complain of dysphagia.

Roles of caudal-related homeobox gene Cdx1 in oesophageal epithelial cells in Barrett's epithelium development

Background and aims: The mechanism of transformation to intestinal metaplasia in Barrett’s oesophagus has not been clarified. We previously reported that bile acids activate the Cdx2 promoter via nuclear factor kappa B (NF-κB) and stimulate production of Cdx2 protein in oesophageal keratinocytes with a resulting production of intestinal type mucin. In addition to Cdx2, Cdx1 may play an important role in the development of Barrett’s oesophagus. Therefore, we studied the direct effects of bile acids on the expression of Cdx1 as well as the precise mechanisms of Cdx1 expression in cultured oesophageal squamous epithelial cells. Furthermore, we investigated the relationship between Cdx1 and Cdx2 expression in cultured oesophageal squamous epithelial cells. Methods: A rat model of Barrett’s oesophagus was produced by anastomosing the oesophagus and jejunum. The expression of Cdx1 was investigated by immunohistochemistry, while the response of that expression to bile acids was studied using a Cdx1 promoter luciferase assay. In addition, oesophageal squamous epithelial cells were transfected with a Cdx1 or Cdx2 expression vector, after which their possible transformation to intestinal-type epithelial cells was investigated. Results: In our Barrett’s rat model, the metaplastic epithelium and adjoining squamous epithelium strongly expressed Cdx1. Further, the bile acids mixture dose-dependently increased Cdx1 promoter activity and Cdx1 protein in oesophageal epithelial cells. Transfection of the Cdx1 expression vector in cultured oesophageal epithelial cells induced production of Cdx2 protein. Conclusion: Bile acid-induced sequential expression of Cdx1 followed by Cdx2 may have an important role in the development of Barrett’s epithelium.

Inflammatory bowel disease: review from the aspect of genetics

Regardless of how inflammatory bowel disease (IBD) is defined, the term “genetic susceptibility” is always included. Due to substantial progress in the characterization of susceptible genes that interact with environmental influences, a number of review articles offering the latest insights continue to be presented. To date, more than 30 novel IBD susceptible loci have been found, while several promising associations between IBD and gene variants have also been identified and replicated effectively. The present review highlights recent insights regarding linkage analysis and genome-wide association presented in studies of IBD susceptible genes, which provide additional evidence supporting their involvement in disease pathogenesis, based on linking to innate immune systems as a result of interactions with intestinal microbial flora. An improved understanding of IBD genetics will promote the identification of novel therapeutic agents, making it possible to identify environmental factors related to intestinal inflammation.

Reg protein is overexpressed in gastric cancer cells, where it activates a signal transduction pathway that converges on ERK1/2 to stimulate growth.

Reg is a growth factor with mitogenic effects on pancreatic β cells and gastric stem cells. To date, there has been no information available on Reg‐mediated intracellular signal transduction pathways. The role of Reg in the gastric carcinogenesis is also unknown. In the current study, the Reg signaling pathway in gastric cancer cell was examined. Reg treatment of MKN45 gastric cancer cells resulted in tyrosyl‐phoshorylation of several cellular proteins and subsequent activation of classical MAPK, ERK1/2. Reg also stimulated thymidine incorporation in MKN45 and AGS gastric cancer cells in a dose‐dependent manner. Finally, Reg was shown to be highly expressed in a large number of gastric cancers in vivo. Taken together, these data suggest that gastric cancer cells have gained the ability to overexpress Reg protein, which confer upon themselves added proliferative capacities, resulting in a considerable growth advantage.