Cyclooxygenase (COX) 1 and 2 in normal, inflamed, and ulcerated human gastric mucosa

BACKGROUND AND AIMS: Constitutive cyclooxygenase (COX) 1 is believed to mediate prostaglandin dependent gastric protection. However, gastric mucosa contains cells capable of expressing inducible COX-2. We therefore investigated COX-1 and COX-2 expression, localisation, and activity in normal and abnormal human gastric mucosa. METHODS: COX-1 and COX-2 distribution was investigated by light and electron microscopic immunohistochemistry and by western blot analysis, and their contribution to prostaglandin (PG)E(2) synthesis using selective enzyme inhibitors. RESULTS: There was strong parietal cell COX-1 and COX-2 immunoreactivity in all sections and isolated cells, with macrophage and myofibroblast reactivity in some sections. Immunostaining was specifically abolished by antigen absorption. Western blot analysis confirmed COX-1 and 2 expression. COX-1 and COX-2 immunostaining was increased in Helicobacter pylori gastritis, particularly the mid glandular zone and lamina propria inflammatory cells. This was associated with increased ex vivo PGE(2) synthesis (62.4 (13.5) pg/mg v 36.3 (15.5) pg/mg in uninflamed mucosa; p=0. 017) which was significantly inhibited by COX-1 but not COX-2 inhibition. Increased COX-2 immunostaining in macrophages, endothelial cells, and myofibroblasts (with reduced epithelial expression) was seen at the rim of ulcers. CONCLUSION: COX-2, as well as COX-1, is expressed by normal human gastric mucosa and is increased at the rim of ulcers. Although both are increased with H pylori, COX-1 contributes more than COX-2 to gastric PGE(2) production.     

Effects of cyclooxygenase-2 inhibitor on gastric acid secretion in Helicobacter pylori-infected C57BL/6 mice.

BACKGROUND: Helicobacter pylori-associated body gastritis inhibits gastric acid secretion. The aim of this study was to determine the effects of H. pylori infection on gastric acid secretion and further determine whether cyclooxygenase-2 was involved. METHODS: C57BL/6 mice (n = 40) were inoculated with the Sydney strain of H. pylori. Control mice (n = 40) were treated with vehicle only. Half of the infected and control mice were fed an experimental diet containing etodolac (10 mg/kg/day) from 1 week after inoculation until the end of the experiment. Before, 12 and 24 weeks after inoculation, the gastric acid secretion, prostaglandin E2 (PGE2) levels in the gastric mucosa, and gastritis scores according to the updated Sydney system were determined. Immunohistochemical staining of COX-2 protein was also performed. RESULTS: No significant changes in gastric acid secretion, gastritis scores or PGE2 levels in the gastric mucosa were observed in uninfected groups with or without etodolac treatment during the study period. In the H. pylori-infected group without etodolac treatment, gastric acid secretion was significantly decreased with increases in PGE2 levels in the gastric mucosa 24 weeks after inoculation compared with the controls. Gastritis score for activity was significantly higher, and strong staining for COX-2 protein was observed in the H. pylori-infected group. In the H. pylori-infected group with etodolac treatment, PGE2 in the gastric mucosa was decreased and acid secretion was restored to the same level as in the control group. CONCLUSION: One of the mechanisms by which H. pylori infection inhibits gastric acid secretion is increased release of PGE2 produced by COX-2, which is induced by H. pylori infection.     

COX-2 Is Essential for EGF Induction of Cell Proliferation in Gastric RGM1 Cells

Growth factors upregulate cyclooxygenase-2 (COX-2) expression and extracellular signal-regulated kinase (ERK) activity, yet little is known regarding the interaction between COX-2 and ERK in terms of mitogenic signal transduction pathways in gastric epithelial cells. Therefore, we examined the role of COX-2 in EGF-induced proliferation of gastric epithelial RGM1 cells. EGF treatment significantly induced ERK activity (peaked at 30 min) and significantly increased COX-2 protein (peaked at 6 hr), production of prostaglandin E2 (PGE2), and cell proliferation. MEK inhibitor (PD98059) decreased ERK activity and cell proliferation induced by EGF. The selective COX-2 inhibitor (NS-398) significantly reduced EGF-induced cell proliferation. Exogenous PGE2 partly reversed the NS-398-induced inhibitory action on cell proliferation, clearly indicating the importance of PGE2 in mitogenic pathway. The induction of COX-2 protein by EGF was completely blocked by preincubation with MEK inhibitor. These results suggest that the ERK-COX-2 pathway is critical for EGF-induced proliferation of gastric epithelial cells.     

环氧合酶-2表达与幽门螺杆菌相关性胃十二指肠疾病的研究

目的　探讨环氧合酶 2表达与幽门螺杆菌Helicobacterpylori ,H .pylori相关性胃十二指肠疾病的关系 ,并通过抗菌治疗评价根除H pylori感染对胃窦黏膜中COX 2表达的影响。方法　用免疫组化方法半定量检测 2 64例经胃镜和组织病理学检查患有十二指肠球部溃疡、胃溃疡、复合性溃疡、胃癌、单纯性慢性胃炎及胃黏膜正常者的胃窦黏膜COX 2蛋白的表达 ,比较H pylori感染与非感染者之间的差异。对检出的 3 5例H pylori的单纯慢性胃炎进行H pylori抗菌根除治疗 ,比较根除前后胃窦黏膜COX 2蛋白的表达变化。根据 2 0 0 0年 5月全国慢性胃炎研讨会共识意见 (江西 井冈山 )对胃黏膜炎症、活动性、异型增生、肠化生和H pylori密 ,度进行半定量测定。结果　胃黏膜表面上皮、腺上皮细胞和固有层间质细胞的浆中可见COX 2蛋白表达 ,但阳性染色细胞多集中在表层上皮。 2 53例中 ,14 3例H pylori者 (56 52 % )COX 2平均阳性细胞率显著高于 110例H pylori者 (43 48% ) ,(P =0 ) ,各疾病组H pylori患者的COX 2平均阳性细胞率均显著高于H pylori者 (P =0 ) ,各疾病组H pylori患者COX 2平均阳性细胞率也均显著高于正常对照组 (P <0 0 5)。 2 7例H pylori根除后的胃黏膜COX 2平均阳性细胞率明显下降 (P =0 ) ,但仍明显高于正     

Roles of Helicobacter pylori infection and cyclooxygenase-2 expression in gastric carcinogenesis

AIM: Cyclooxygenase (COX)-2 is over expressed in gastrointestinal neoplasm. Helicobacter pylori (H pylori) infection is causally linked to gastric cancer. However, the expression of COX-2 in various stages of H pylori-associated gastric carcinogenesis pathway has not been elucidated. Therefore, the aim of this study was to clarify the role of H pylori induced COX-2 expression during carcinogenesis in the stomach. METHODS: Gastric biopsies from 138 subjects (30 cases of chronic superficial gastritis (CSG), 28 cases of gastric glandular atrophy (GA), 45 cases of gastric mucosal intestinal metaplasia (IM), 12 cases of moderate gastric epithelial dysplasia and 23 cases of gastric cancer) were enrolled. H pylori infection was assessed by a rapid urease test and histological examination (modified Giemsa staining). The expression of COX-1 and COX-2 in human gastric mucosa was detected by immunohistochemical staining. RESULTS: H pylori infection rate was 64.3% in GA and 69.5% in gastric cancer, which was significantly higher than that (36.7%) in CSG (P<0.05). The positive expression rates of COX-2 were 10.0%, 35.7%, 37.8%, 41.7% and 69.5% in CSG, GA, IM, dysplasia and gastric cancer, respectively. From CSG to GA, IM, dysplasia and finally to gastric cancer, expression of COX-2 showed an ascending tendency, whereas COX-1 expression did not change significantly in the gastric mucosa. The level of COX-2 expression in IM and dysplasia was significantly higher in H pylori-positive than in H pylori-negative subjects (P<0.01). CONCLUSION: COX-2 expression induced by H pylori infection is a relatively early event during carcinogenesis in the stomach.     

幽门螺杆菌感染诱导胃粘膜环氧化酶-2表达

目的 探讨幽门螺杆菌（Hp)感染对胃粘膜环氧化酶－2（COX－2）表达的影响。方法 27例无任何症状健康检查者，经胃镜采取胃窦部粘膜组织，用于Hp检测、病理组织学检查及免疫组织化学检查COX－2的表达。结果 18例Hp感染者胃粘膜上皮细胞和炎症细胞表达COX－2，而9例Hp阴性者胃粘膜均不表达COX－2。结论 Hp感染诱导胃粘膜COX－2表达。     

Interaction between cyclooxygenase-2,Snail,and E-cadherin in gastric cancer cells

AIM:To investigate the mechanisms of how cyclooxygenase-2(COX-2)regulates E-cadherin in gastric cancer cells.METHODS:COX-2 expression in human gastric cancer cell lines SGC-7901,BGC-823,MGC-803 and AGS were measured at the mRNA and protein level.COX-2 rich cell line SGC-7901 was chosen for subsequent experiments.siRNA mediated gene knockdown was used to investigate the impact of COX-2 on nuclear factor-κB (NF-κB),Snail,and E-cadherin in gastric cancer cells.Gene expression was determined by Western blot and real-time polymerase chain reaction.To analyze whether NF-κB inhibition could interrupt the modulatory effect of COX-2 or prostaglandin E2(PGE2)on E-cadherin,gastric cancer cells were treated with celecoxib or PGE2,in the presence of NF-κB specific siRNA.RESULTS:Highest expression level of COX-2 was found in SGC-7901 cells,both at mRNA and protein levels.siRNA mediated down-regulation of COX-2 led to a reduced expression of NF-κB and Snail,but an increased expression of E-cadherin in SGC-7901 cells.siRNA mediated down-regulation of NF-κB also led to a reduced expression of E-cadherin and Snail in SGC-7901 cells.However,COX-2 expression did not alter after cells were treated with NF-κB specific siRNA in SGC-7901 cells.Treatment of SGC-7901 cells with celecoxib led to a reduced expression of Snail but an increased expression of E-cadherin.In contrast,treatment of SGC-7901 cells with PGE2 led to an increased Snail and a decreased E-cadherin.However,siRNAmediated knockdown of NF-κB partially abolished the effect of celecoxib and PGE2 on the regulation of E-cadherin and Snail in SGC-7901 cells.CONCLUSION:COX-2 likely functions upstream of NF-κB and regulates the expression of E-cadherin via NF-κB/Snail signaling pathway in gastric cancer cells.     

Expression of COX-2 proteins in gastric mucosal lesions

AIM: To investigate the expression of COX-2 proteins in gastric mucosal lesions and to assess the relationship between COX-2 expression and type, pathologic stage, differentiation, or lymph node metastasis in gastric cancer and the relationship between COX-2 expression and H pylori infection in gastric mucosal lesions. METHODS: Thirty patients with gastric carcinoma underwent surgical resection. Samples were taken from tumor site and paracancerous tissues, and ABC immunohistochemical staining was used to detect the expression of COX-2 proteins. H pylori was determined by rapid urea test combined with pathological stating/14C urea breath test. RESULTS: The positive rate and staining intensity of mutant COX-2 gene expression in gastric cancer were significantly higher than those in paracancerous tissues (66.7% vs 26.7%) (P<0.01, P<0.001). There was a significant correlation between COX-2 and pathologic stage or lymph node metastasis type of gastric carcinoma (76.0% vs 20.0%, 79.2% vs 16.7%) (P<0.05). No correlation was found between COX-2 expression and type or grade of differentiation (P>0.05). COX-2 expression of intestinal metaplasia (IM) or dysplasia (DYS) with positive H pylori was significantly higher than that with negative H pylori (50.6% vs 18.1%, 60.0% vs 33.3%) (P<0.05). CONCLUSION: COX-2 overexpression was found in a large proportion of gastric cancer tissues compared with matched non-cancerous tissues and was significantly associated with advanced tumor stage and lymph node metastasis. Overexpression of COX-2 plays an important role in tumor progression of gastric cancer. COX-2 may also play a role in the early development/promotion of gastric carcinoma and is associated with H pylori infection.     

Effects of cyclooxygenase-1 and -2 gene disruption on Helicobacter pylori-induced gastric inflammation

BACKGROUND: Cyclooxygenases (COXs) play important roles in inflammation and carcinogenesis. The present study aimed to determine the effects of COX-1 and COX-2 gene disruption on Helicobacter pylori-induced gastric inflammation. METHODS: Wild-type (WT), COX-1 and COX-2 heterozygous (COX-1+/- and COX-2+/-), and homozygous COX-deficient (COX-1-/- and COX-2-/-) mice were inoculated with H. pylori strain TN2 and killed after 24 weeks of infection. Uninfected WT and COX-deficient mice were used as controls. Levels of gastric mucosal inflammation, epithelial cell proliferation and apoptosis, and cytokine expression were determined. RESULTS: COX deficiency facilitated H. pylori-induced gastritis. In the presence of H. pylori infection, apoptosis was increased in both WT and COX-deficient mice, whereas cell proliferation was increased in WT and COX-1-deficient, but not in COX-2-deficient, mice. Tumor necrosis factor (TNF)-alpha and interleukin-10 mRNA expression was elevated in H. pylori-infected mice, but only TNF-alpha mRNA expression was further increased by COX deficiency. Prostaglandin E2 levels were increased in infected WT and COX-2-deficient mice but were at very low levels in infected COX-1-deficient mice. Leukotriene (LT) B4 and LTC4 levels were increased to a similar extent in infected WT and COX-deficient mice. CONCLUSIONS: COX deficiency enhances H. pylori-induced gastritis, probably via TNF-alpha expression. COX-2, but not COX-1, deficiency suppresses H. pylori-induced cell proliferation.     

Anti-Helicobacterpylori therapy followed by celecoxib on progression of gastric precancerous lesions

AIM： To evaluate whether celecoxib, a selective cyclooxygenase 2 （COX-2） inhibitor, could reduce the severity of gastric precancerous lesions following Hel/cobacter pylori （H pylorl） eradication. METHODS： H pylori-eradicated patients with gastric precancerous lesions randomly received either celecoxib （n = 30） or placebo （n = 30） for up to 3 mo. COX-2 expression and activity was determined by immunostaining and prostaglandin E2 （PGE2） assay, cell proliferation by Ki-67 immunostaining, apoptosis by TUNEL staining and angiogenesis by microvascular density （MVD） assay using CD31 staining.RESULTS： COX-2 protein expression was significantly increased in gastric precancerous lesions （atrophy, intestinal metaplasia and dysplasia, respectively） compared with chronic gastritis, and was concomitant with an increase in cell proliferation and angiogenesis. A significant improvement in precancerous lesions was observed in patients who received celecoxib compared with those who received placebo （P 〈 0.001）. Of these three changes, 84.6% of sites with dysplasia regressed in patients treated with celecoxib （P = 0.002） compared with 60% in the placebo group, suggesting that celecoxib was effective on the regression of dysplasia. COX-2 protein expression （P 〈 0.001） and COX-2 activity （P 〈 0.001） in the gastric tissues were consistently lower in celecoxib-treated patients compared with the placebo-treated subjects. Moreover, it was also shown that celecoxib suppressed cell proliferation （P 〈 0.01）, induced cell apoptosis （P 〈 0.01） and inhibited angiogenesis with decreased MVD （P 〈 0.001）. However, all of these effects were not seen in placebo-treated subjects. Furthermore, COX-2 inhibition resulted in the up-regulation of PPARy expression, a protective molecule with anti-neoplastic effects. CONCLUSION： H pylori eradication therapy followed by celecoxib treatment improves gastric precancerous lesions by inhibiting COX-2 activity, inducing apoptosis, and suppressing cell proliferation and angiogenesis.