Involvement of cyclooxygenase-2--prostaglandin E2 pathway in interleukin-8 production in gastric cancer cells.

Prostaglandin E(2) (PGE(2)) is thought to play an important role in both inflammatory and anti-inflammatory effects. The effect of PGE(2) on the proinflammatory chemokine interleukin-8 (IL-8) in the gastric epithelial cells has not been defined yet. A gastric cancer cell line (MKN45) and primary gastric fibroblasts were cocultured with Helicobacter pylori standard strain (NCTC11637). The expressions of IL-8 and cyclooxygenase 2 (COX-2) mRNA were examined by reverse transcription polymerase chain reaction (RT-PCR) amplification. The amount of IL-8 antigen secreted by the MKN45 cells and gastric fibroblasts was measured by enzyme-linked immunosorbent assay (ELISA). We examined the effects of H pylori stimulation on IL-8 and COX-2 expression levels and the effects of COX-2 inhibitor on H pylori-induced IL-8 production in the MKN45 cells and gastric fibroblasts. Furthermore, we examined the expressions of subtypes of PGE(2) receptors, the effects of arachidonic acid and PGE(2) on IL-8 production, and the effects of PGE(2) on the total cellular cyclic adenosine monophosphate (cAMP) in MKN45 cells. MKN45 cells and gastric fibroblasts expressed IL-8 and COX-2 mRNA under stimulation with H pylori. The MKN45 cells produced IL-8 and PGE(2) antigen into the culture medium with H pylori stimulation, and the production level of IL-8 and PGE(2) antigen decreased significantly with COX-2 inhibitor pretreatment (concentration: 50 muM). On the other hand, the gastric fibroblasts strongly produced IL-8 antigen even in the unstimulated condition, and the amount of IL-8 antigen was not affected by H pylori stimulation and/or COX-2 inhibitor pretreatment. The MKN45 cells expressed IL-8 mRNA and released IL-8 antigen slightly, and the expression level of IL-8 mRNA and the amount of IL-8 antigen increased significantly with PGE(2) treatment in a dose-dependent manner. PGE(2)-induced IL-8 production was inhibited by pretreatment with EP2 and EP4 antagonists. The MKN45 cells expressed EP2 and EP4 subtypes of PGE(2) receptors, and these expression levels were not affected by H pylori stimulation or PGE(2) treatment. The amount of IL-8 antigen increased slightly, but not significantly, with arachidonic acid treatment. PGE(2) treatment for 15 minutes increased the total cellular cAMP in the MKN45 cells. These results suggest that the COX-2-PGE(2) pathway may be involved in IL-8 production in gastric epithelial cells.

Expressions of urokinase-type plasminogen activator, its receptor and plasminogen activator inhibitor-1 in gastric cancer cells and effects of Helicobacter pylori.

OBJECTIVE: Destruction of the extracellular matrix is essential for tumor invasion and metastasis. The relationship between Helicobacter pylori (H. pylori) infection and destruction of the extracellular matrix is not yet clear. Urokinase-type plasminogen activator (uPA) plays an important role in the destruction of the extracellular matrix and basement membrane. Urokinase-type plasminogen activator receptor (uPAR) and plasminogen activator inhibitor-1(PAI-1) appear to be associated with these processes. To clarify the role of H. pylori infection in the processes of destruction of the extracellular matrix and basement membrane in cancerous tissue, the effect of H. pylori on the expressions of uPA, uPAR and PAI-1 in cancer cells was investigated. MATERIALS AND METHODS: Gastric cancer cell lines (MKN45, KATO-III) were co-cultured with H. pylori standard strain (NCTC11637), cagA-negative strain and clinical isolated strain. The specific inductions of uPA, uPAR and PAI-1 mRNA were examined by reverse transcription-polymerase chain reaction (RT-PCR) amplification. The secreted uPA antigen was measured by enzyme-linked immunosorbent assay (ELISA). To evaluate the role of transcription factor NF-kappaB in uPA and uPAR gene transcription with H. pylori stimulation, the effect of NF-kappaB inhibitor MG132 on H. pylori-induced uPA and uPAR mRNA expression was examined. RESULTS: The expressions of both uPA and uPAR mRNAs in the gastric cancer cell lines (MKN45 and KATO- III) were increased markedly (uPA mRNA; MKN45: 12-fold, KATO-III: 5-fold) (uPAR mRNA; MKN45: 3-fold, KATO-III: 3-fold) with H. pylori NCTC11637 strain stimulation, whereas the expression levels of uPA and uPAR mRNA did not increase with cagA-negative strain stimulation. These cancer cell lines slightly secreted uPA antigen into the culture medium, and the amount of uPA antigen increased dramatically by stimulation with H. pylori NCTC11637 and cagA-positive clinical isolated strains. These gastric cancer cell lines also slightly secreted PAI-1 antigen into the culture medium, and the amount of PAI-1 antigen was not affected by H. pylori NCTC11637 stimulation. H. pylori-induced uPA and uPAR mRNA expressions were strongly down-regulated by pretreatment with MG132 in both cell lines. CONCLUSIONS: The results of this study indicated the possibility that cagA-positive H. pylori may play an important role not only in tissue remodeling, angiogenesis and wound healing but also in the process of degradation of the extracellular matrix breakdown, tumor invasion and metastasis by inducing uPA and uPAR complex in the gastric cancer cells.

Expression of urokinase-type plasminogen activator and its receptor in gastric fibroblasts and effects of nonsteroidal antiinflammatory drugs and prostaglandin.

In acute inflammatory condition, little is known about the expression of the urokinase-type plasminogen activator (uPA) and its receptor (uPAR) in the gastric fibroblasts. To clarify the role of human gastric fibroblasts in acute inflammatory conditions such as gastric ulcer, the effects of interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha on the expression of uPA and uPAR, which were suggested to be associated with tissue remodeling, in gastric fibroblasts were investigated. The expression level of uPA mRNA and the amount of uPA antigen increased significantly on treatment with each concentration of IL-1beta (1 and 10 ng/ml) and 10 ng/ml TNF-alpha. On the other hand, the amounts of uPA antigen on cell surfaces were not affected significantly by IL-1beta and TNF-alpha stimulation. The expression level of uPAR mRNA increased in a dose-dependent manner on IL-1beta stimulation. The effect of indomethacin on uPA and uPAR expression in these cells was also examined. When gastric fibroblasts were treated with 50 microM indomethacin, the expression level of uPA mRNA decreased significantly, and the amount of uPA antigen in the culture medium and on cell surfaces decreased significantly with indomethacin in a dose-dependent manner. The increased uPAR mRNA expression caused by IL-1beta was reduced to the basal level by treatment with 50 microM indomethacin. Furthermore, we investigated the role of prostaglandin E2 (PGE2), which is suggested to play major roles in acute inflammation of the stomatch, on uPA and uPAR expression in gastric fibroblasts. The expression level of uPAR mRNA and the amount of uPA antigen on cell surfaces increased in a dose-dependent manner on treatment with PGE2 (10 and 50 ng/ml). These results suggest that uPA and uPAR expression in gastric fibroblasts is involved in the regulating system of PGE2 and that NSAIDs may delay healing of gastric mucosal injury in part through suppressing uPA production via inhibition of endogenous PG production.

Dynamic MR cholangiography after fatty meal loading: cystic contractility and dynamic evaluation of biliary stasis.

PURPOSE: Dynamic MR cholangiography was conducted on patients with cholelithiasis or choledocholithiasis who had consumed a fatty test meal (Molyork) and the cystic contractility and dynamics of biliary stasis was evaluated. SUBJECTS AND METHOD: The subjects were 25 with intracystic cholelithiasis, 10 with choledocholithiasis and 10 normal controls. For an imaging sequence, the rapid acquisition with relaxation enhancement (RARE) method was employed and imaging was conducted for 40 min (every 30 s following Molyork administration) without breath-holding. The gallbladder contraction ratio was computed and the contractile ratio for the common bile duct was calculated. To determine the bile flow to the duodenum, the high-intensity signal, indicating the flow from the lower common bile duct, and perfusion of the duodenum were observed in dynamic mode on the monitor with the naked eye and interpreted as positive bile flow. The frequency of this flow was visually monitored. RESULTS: The gallbladder contractile ratio was significantly reduced in patients with cholelithiasis or choledocholithiasis compared with the controls. In a comparison with the normal controls, no sequential changes were noted in the mean contractile ratio of the common bile duct of the patients with cholelithiasis or choledocholithiasis. The mean frequency of bile flow observed for each 40 min period was 13+/-2.4, 6+/-2.2, and 4+/-1.3 times for the controls, those with intracystic cholelithiasis, and those with choledocholithiasis, respectively. Compared with the controls, the latter two patient groups showed evident reductions in the frequency of bile flow to the duodenum (p<0.001). CONCLUSION: Dynamic MRC combined with Molyork loading makes it possible to compute cystic contractile ratios and perform a dynamic examination of bile flow under non-invasive, near-physiological conditions.