Expression of cyclooxygenase 1 and 2 by human gastric endothelial cells

Dbl oncogene expression in MCF-10 A epithelial cells disrupts mammary acinar architecture, induces EMT and angiogenic factor secretion

The proteins of the Dbl family are guanine nucleotide exchange factors (GEFs) of Rho GTPases and are known to be involved in cell growth regulation. Alterations of the normal function of these proteins lead to pathological processes such as developmental disorders, neoplastic transformation, and tumor metastasis. We have previously demonstrated that expression of Dbl oncogene in lens epithelial cells modulates genes encoding proteins involved in epithelial-mesenchymal-transition (EMT) and induces angiogenesis in the lens. Our present study was undertaken to investigate the role of Dbl oncogene in epithelial cells transformation, providing new insights into carcinoma progression.To assess how Dbl oncogene can modulate EMT, cell migration, morphogenesis, and expression of pro-apoptotic and angiogenic factors we utilized bi- and 3-dimensional cultures of MCF-10 A cells. We show that upon Dbl expression MCF-10 A cells undergo EMT. In addition, we found that Dbl overexpression sustains Cdc42 and Rac activation inducing morphological alterations, characterized by the presence of lamellipodia and conferring a high migratory capacity to the cells. Moreover, Dbl expressing MCF-10 A cells form altered 3D structures and can induce angiogenesis by producing proangiogenic factors such as CCL2. These results support a role for Dbl oncogene in epithelial cell differentiation and transformation and suggest the relevance of GEF deregulation in tumor onset and progression.

Erythropoietin inhibits HIF-1α expression via upregulation of PHD-2 transcription and translation in an in vitro model of hypoxia-ischemia

Hypoxia inducible factor (HIF)-1α is the central transcriptional factor for the regulation of oxygen-associated genes in response to hypoxia. Erythropoietin (EPO), a hematopoietic growth factor, increases oxygen availability during hypoxia/ischemia and is associated with neuroprotection following hypoxia-ischemia in laboratory models of stroke. However, EPO has failed to translate in a clinical setting. Thus, it is critical to elucidate the key players in EPO-induced neuroprotection. Our preliminary studies have shown that EPO, as a downstream gene of HIF, inhibits HIF-1α in a dose-dependent manner in an in vitro model of hypoxia-ischemia. This study is designed to elucidate the primary mediator of EPO-induced HIF-1α inhibition and subsequent cell survival/neuroprotection. Oxygen and glucose deprivation (OGD) of nerve growth factor-differentiated rat pheochromocytoma (PC-12) cells were used to model hypoxia-ischemia in an in vitro environment. The profile of HIF-1α, HIF-2α and prolyl hydroxylase domain 2 (PHD-2) expression; HIF-1α and prolyl hydroxylase (PHD-2) mRNA levels; matrix metalloproteinase (MMP)-9; and cell death was evaluated in the presence and absence of either EPO or PHD-2 inhibitor during OGD. Our findings showed that EPO treatment resulted in an increase in PHD-2 transcription and translation, inhibition of HIF-1α expression, reactive oxygen species formation, and MMP-9 activity, resulting in increased cell survival after OGD. We also observed that EPO-induced cell survival/neuroprotection was reversed by siRNA silencing of PHD-2. This led to the conclusion that PHD-2 is a key mediator of EPO-induced HIF-1α inhibition and subsequent neuroprotection in an in vitro model of hypoxia-ischemia.

Involvement of COX-2/PGE2 signalling in hypoxia-induced angiogenic response in endothelial cells

To evaluate the impact of hypoxia on the angiogenic capability of endothelial cells (ECs), and further investigate whether the cyclooxygenase-2 (COX-2)/prostaglandin E(2) (PGE(2)) signalling is involved in the angiogenic response of ECs to hypoxia. We explored the impact of various periods (1, 3, 6, 12, 24 hrs) of hypoxia (2% O(2)) on human umbilical vein endothelial cells (HUVECs) in vitro. We observed cell viability, migration, tube formation, analysed COX-2, vascular endothelial growth factor (VEGF), AQP1 mRNA transcription, protein expression and measured PGE(2), VEGF protein concentration in cell supernatants. Then we treated HUVECs with COX-2 selective inhibitor NS398, EP1/2 combined antagonist AH6809 and exogenous PGE(2) to investigate the role of COX-2/PGE(2) signalling in the angiogenic response of ECs to hypoxia. The results demonstrated that short-term hypoxic treatment enhanced HUVECs proliferation, migration, tube formation, significantly up-regulated COX-2, VEGF, AQP1 mRNA level, protein expression and promoted PGE(2) , VEGF release. The pharmacological inhibition study revealed that exposure of HUVEC to NS398 and AH6809 under hypoxia impaired the biological responses of ECs to hypoxia. Exogenous PGE(2) augments the effects of hypoxia on HUVECs, and partially reversed the inhibitory effects of NS398 on HUVECs proliferation and angiogenic capability. Short-term hypoxic treatment enhanced angiogenic capability of ECs, and COX-2/PGE(2) signalling may play a critical role in the biological response of ECs to hypoxia.

Cyclooxygenase-2 supports tumor proliferation in vestibular schwannomas

BACKGROUND

Recent studies have shown that cyclooxygenase-2 (COX-2) plays an important role in tumor growth and neovascularization. However, COX-2 expression in vestibular schwannomas (VSs) has not been investigated.

OBJECTIVE

To analyze the pattern of COX-2 expression in sporadic and neurofibromatosis type 2 (NF2)-associated VSs and its relationship with tumor proliferation and microvessel density.

METHODS

Fifteen sporadic and 15 NF2-associated VSs were examined for COX-2 expression, microvessel density, and proliferation rate by immunohistochemical methods. Immunohistochemical scores were used to interpret the extent and intensity of COX-2 staining. Microvessel density (MVD) was determined using von Willebrand factor (vWf). Proliferation rate was quantified using Ki-67. The relationship among COX-2 expression, MVD, and proliferation rate was statistically analyzed.

RESULTS

COX-2 expression was detected in 29 (96.67%) of 30 VSs, with no significant difference between sporadic and NF2-associated VSs (P = .722). In 6 (20%) VSs, COX-2 expression was graded as strong, in 12 (40%) as moderate, and in 11 (36.7%) as weak. VSs with high proliferation showed significantly higher COX-2 expression (P = .015) than VSs with low proliferation. COX-2 expression and MVD did not show specific biological correlations (P = .035).

CONCLUSION

Our data demonstrate that COX-2 is expressed in VSs. High COX-2 expression in VSs with high proliferation rates suggests that the COX-2 pathway may be involved in the development and growth of VSs.

Expression of cyclooxygenase genes in the jejunum of horses during low-flow ischemia and reperfusion

OBJECTIVE

To determine expression of cyclooxygenase (COX) genes 1 and 2 (also called prostaglandin-endoperoxide synthases 1 and 2) and stability of housekeeping gene expression during low-flow ischemia and reperfusion in the jejunum of horses.

ANIMALS

5 healthy adult horses.

PROCEDURES

Horses were anesthetized, and two 30-cm segments of jejunum were surgically exteriorized. Blood flow was maintained at baseline (untreated) values in 1 (control) segment and was decreased to 20% of baseline (low-flow ischemia) for 75 minutes, followed by 75 minutes of reperfusion, in the other (experimental) segment. Biopsy samples were collected from experimental segments at baseline (T0), after 75 minutes of ischemia (T1), and after 75 minutes of reperfusion (T2); samples were collected from control segments at T0 and T2. Horses were euthanized 24 hours after induction of ischemia (T3), and additional samples were collected. Samples were evaluated histologically. Total RNA was extracted; expression of COX genes and stability of 8 housekeeping genes were determined via quantitative real-time PCR assays.

RESULTS

COX-1 and COX-2 genes were constitutively expressed in baseline samples. Low-flow ischemia resulted in significant upregulation of COX-2 gene expression at each subsequent time point, compared with baseline values. The most stably expressed reference genes were β-actin and hypoxanthine phosphoribosyltransferase, whereas glyceraldehyde 3-phosphate dehydrogenase and β-2 microglobulin were the least stably expressed.

CONCLUSIONS AND CLINICAL RELEVANCE

Low-flow ischemia resulted in upregulation of COX-2 gene expression in the jejunum of horses. Housekeeping genes traditionally used as internal standards may not be stable in this tissue during arterial low-flow ischemia and reperfusion.

Short-term therapy with celecoxib and lansoprazole modulates Th1/ Th2 immune response in human gastric mucosa

BACKGROUND

Selective cyclooxygenase-2 (COX-2) inhibitors and proton pump inhibitors may exert immune-mediated effects in human gastric mucosa. T-cell immune response plays a role in Helicobacter pylori-induced pathogenesis. This study evaluated effects of celecoxib and lansoprazole on T-helper (Th) 1 and Th2 immune response in human gastric mucosa.

METHODS

Dyspeptic patients with or without osteoarticular pain were given one of the following 4-week therapies: celecoxib 200 mg, celecoxib 200 mg plus lansoprazole 30 mg, and lansoprazole 30 mg daily. Expression of COX-2, T-bet, and pSTAT6 and production of prostaglandin E₂ (PGE₂), interferon (IFN)-γ, and interleukin (IL)-4 were determined in gastric biopsies before and after therapy. Histology was evaluated.

RESULTS

Cyclooxygenase-2 expression and PGE₂ production was higher, and Th1 signaling pathway was predominant in H. pylori-infected vs. uninfected patients. T-bet expression and IFN-γ production increased, while STAT6 activation and IL-4 production decreased following therapy with celecoxib and celecoxib plus lansoprazole, respectively. Th1 and Th2 signaling pathways down-regulated after therapy with lansoprazole, and this was associated with an improvement of gastritis. Effect of therapy was not affected by H. pylori status.

CONCLUSION

Celecoxib and lansoprazole modulate Th1/Th2 immune response in human gastric mucosa. The use of these drugs may interfere with long-term course of gastritis.

Antibacterial and ulcer healing effects of organoselenium compounds in naproxen induced and Helicobacter pylori infected Wistar rat model

Aim of the present study was to evaluate in vitro toxicity and in vivo antibacterial, anti-inflammatory, antiulcer, and antioxidant activities of two organoselenium compounds, selenocystine (SeCys) and ebselen (Ebs). The study was conducted in experimentally induced ulcers in rodent model infected with Helicobacter pylori (H. pylori). In vitro toxicological studies on normal splenic lymphocytes revealed that SeCys and Ebs were non-toxic to the cells even at 100 μM concentration. Antibacterial activity was observed at 500 μg/mL concentration of either of the compounds against H. pylori. In vivo studies after treatment with SeCys and Ebs (500 μg/kg/day) resulted in significant reduction in ROS production and inhibition of lipid peroxidation in gastric tissue. The antioxidant and anti-inflammatory activities of both the compounds were also confirmed by their ability to lower GSH reduction, to induce the expression of antioxidant genes such as GPx-4, and MnSOD and to suppress inflammatory genes namely COX-2, TNF-α and TGF-β. In addition, the immunomodulatory activity of both the compounds was evident by enhance of the CD4 levels and maintenance of the IgG, IL-6 and IL-10 levels. Persistent treatment (500 μg/kg, for 28 days) with both the compounds showed considerable (p<0.05) ulcer healing property supporting its role in gastro protection. In conclusion, the results of our study suggest that both SeCys and Ebs possess broad spectrum of activities without any potential toxicity.

A randomized, placebo-controlled study of the effects of naproxen, aspirin, celecoxib or clopidogrel on gastroduodenal mucosal healing

BACKGROUND

Many individuals with gastroduodenal ulcers require on-going, non-steroidal anti-inflammatory drug (NSAID) or anti-platelet therapy.

AIMS

To evaluate the effects of these agents on gastroduodenal mucosal healing.

METHODS

Helicobacter pylori-negative volunteers were randomized to receive naproxen, celecoxib, aspirin, clopidogrel or placebo. Antral and duodenal lesions were created endoscopically with a biopsy forceps. After 7 days of medication dosing, each lesion was scored [from 0 (low) to 8 (high)] using a validated methodology. The primary endpoint was the mean injury score. The secondary endpoint was the percentage of subjects with > or = 1 unhealed lesion.

RESULTS

In all, 108 subjects completed the study. Naproxen impaired antral lesion healing more than placebo, clopidogrel, aspirin or celecoxib (mean injury score of 4.3 vs. 3.0, 2.7, 3.2, and 3.2, respectively, P < 0.05). Naproxen impaired duodenal lesion healing more than placebo, clopidogrel or aspirin (mean injury score of 4.0 vs. 2.4, 2.6, and 2.2, respectively, P < 0.05). More subjects taking naproxen than placebo or clopidogrel had > or =1 unhealed antral lesions (72.2% vs. 36.0% and 32.0%, respectively, P < 0.05) and unhealed duodenal lesions (61.1% vs. 16.0% and 28.0%, respectively, P < 0.05).

CONCLUSIONS

Naproxen may impair gastroduodenal healing more than aspirin or celecoxib in H. pylori negative subjects. Clopidogrel did not impair mucosal healing.

Modulation of cyclooxygenase in endothelial cells by fibronectin: relevance to angiogenesis

Cyclooxygenases (COX), which catalyze the formation of prostaglandins (PGs), have been implicated in angiogenesis. Adhesion of endothelial cells (ECs) to extracellular matrix (ECM) induces the expression of COX-2 and PG production. The present study was carried out to analyze the influence of the adhesive ECM protein, fibronectin (FN), in modulating COX expression and its implications to angiogenesis using in vitro cultures of human umbilical vein ECs. RT-PCR analysis showed that the level of COX-2 mRNA was significantly high while that of COX-1 decreased in ECs maintained on FN. On treatment with p38 MAPK inhibitor and anti-alpha(5)beta(1) integrin antibody, FN dependent effect on COX expression was not observed. Analysis by ELISA and immunoblotting confirmed FN-dependent upregulation of COX-2 protein. The ratio of PG E(2):PG D(2) was significantly high in cells maintained on FN and on treatment with p38 MAPK inhibitor, the relative level of PG D(2) increased and that of PG E(2) decreased. Concomitant with the modulation of COX-2 and changes in PGs, ECs maintained on FN showed angiogenic response in an alpha(5)beta(1) integrin/p38 MAPK dependent manner as evidenced by the expression of angiogenic markers, CD 31 and E-selectin. These results suggest a FN-alpha(5)beta(1)/FAK/p38 MAPK dependent upregulation of COX-2 causing a shift in the relative levels of PGs in HUVECs which contributes to the angiogenic effect of FN.

Selective inhibition of cyclooxygenase-2 suppresses the growth of pancreatic cancer cells in vitro and in vivo

Cyclooxygenase-2 (COX-2), a prostaglandin synthetase, is involved in development of certain tumors. We therefore analyzed COX-2 expression in pancreatic cancer tissues (53 samples) and Panc-1 human pancreatic cancer cells by immunohistochemistry, RT-PCR and western-blotting analyses. Also, immunohistochemistry of proliferating cell nuclear antigen (PCNA) was performed. We found expression of COX-2 was dramatically upregulated in 36 of 53 cases (67.9%) and the expression of COX-2 was associated with the diameter (> 3 cm) of the tumors (p < 0.05), but not with the age, gender, tumor location, differentiation, lymph-node metastases and TNM stage. The positivity rate of PCNA expression in the pancreatic cancer cells of the COX-2 positive group (32.88 +/- 13.26%) was significantly higher than that in the COX-2 negative group (24.56 +/- 11.51%) (p < 0.05). Then we investigated the effect of selective inhibitors of COX-2 (NS398 and celecoxib) on proliferation of Panc-1 cells by 3-(4,5 dimethyl-2-thiazolyl)-2.5-diphenyl-2H-tetrazolium bromide (MTT) assay. Either NS398 or celecoxib suppressed proliferation of Panc-1 cells dose-dependently in vitro. Furthermore, Panc-1 cells were implanted into nude mice, and celecoxib was administrated orally with feed. The volume of the tumor xenografted into nude mice was decreased by 51.6% in the celecoxib group (p < 0.01). In conclusion, the increased expression of COX-2 may be responsible for rapid proliferation of pancreatic cancer, and specific inhibition of COX-2 suppresses proliferation of Panc-1 cells in vitro and in nude mice. The selective inhibitor of COX-2 may be an effectual agent for pancreatic cancer chemoprevention.

Mechanical loading and ?12prostaglandin J2induce bone morphogenetic protein-2, peroxisome proliferator-activated receptor ?-1, and bone nodule formation in an osteoblastic cell line

BACKGROUND AND OBJECTIVE

We have previously reported that mechanical strain applied at a 1% level to an osteoblastic cell line induces the transcription of prostaglandin D2 synthase and increases the levels of prostaglandin D2 and its Delta12prostaglandin J2 metabolite. Mechanical strain also induces the expression of peroxisome proliferator-activated receptor gamma-1 and bone nodule formation. We hypothesized that mechanical load induces bone formation via Delta12prostaglandin J2-dependent synthesis of bone morphogenetic proteins. Our goal was to investigate the molecular events involved in osteogenesis induced by mechanical loading and Delta12prostaglandin J2, namely the induction of bone morphogenetic proteins and peroxisome proliferator-activated receptor gamma-1, a nuclear receptor for Delta12prostaglandin J2.

MATERIAL AND METHODS

Osteoblast monolayers were stretched for 1 h with a 1-h resting period and stretched for another hour at 1 Hz with 1% elongation. Cells were collected 0, 1, 6 and 16 h after stretching. Cyclooxygenase inhibitors and Delta12prostaglandin J2 were added in some experiments. Relative quantitative reverse transcriptase-polymerase chain reaction was used to examine whether the mRNA of bone morphogenetic protein-2, -4, -6, -7 and peroxisome proliferator-activated receptor gamma-1 was induced. Immunohistochemistry was used to evaluate bone morphogenetic protein expression in cells.

RESULTS

Mechanical strain significantly increased the mRNA expression of bone morphogenetic protein-2, -6, -7 and of peroxisome proliferator-activated receptor gamma-1, but not of bone morphogenetic protein-4. In stretched cells, bone morphogenetic protein-2 and peroxisome proliferator-activated receptor gamma-1 expression was blocked by cyclooxygenase inhibitors, but restored by exogenous Delta12prostaglandin J2. Delta12Prostaglandin J2 significantly enhanced bone nodule formation and bone morphogenetic protein-2 expression when added alone to resting osteoblasts.

CONCLUSION

These results suggest that the osteoblastic biomechanical pathways that trigger bone formation involve cyclooxygenase and prostaglandin D2 synthase activation, induction of Delta12prostaglandin J2 and its nuclear receptor, peroxisome proliferator-activated receptor gamma-1, and increased expression of bone morphogenetic protein-2. These data suggest that the Delta12prostaglandin J2/peroxisome proliferator-activated receptor gamma-1/bone morphogenetic protein-2 pathway plays an important role in osteogenesis.

Enhanced activation of cyclooxygenase-2 downregulates Th1 signaling pathway in Helicobacter pylori-infected human gastric mucosa

BACKGROUND

Evidence suggests that an impaired T-cell response against Helicobacter pylori plays a role in the pathogenesis of H. pylori-related diseases. Cyclooxygenase (COX) 2 has been shown to inhibit the production of T-helper (Th) 1 cytokines. This study aimed to ascertain whether COX-2 downregulates Th1 signaling pathway in human gastric mucosa colonized by H. pylori.

METHODS

COX-2 expression and prostaglandin E(2) (PGE(2)) production were determined in total proteins extracted from freshly obtained gastric biopsies of H. pylori-infected and uninfected patients by Western blotting and enzyme-linked immunosorbent assay (ELISA). Phosphorylated (p)STAT4, pSTAT1, T-bet, and pSTAT6 expression and interleukin (IL)-12, interferon (IFN)-gamma, and IL-4 production were also determined by Western blotting and ELISA, respectively, in total protein extracts from gastric biopsy cultures of H. pylori-infected patients treated without and with COX-2 inhibitor NS-398.

RESULTS

Enhanced expression of COX-2 and production of PGE(2) was found in H. pylori-infected compared to uninfected patients. COX-2 inhibition significantly increased expression of Th1 transcription factors along with production of IL-12 and IFN-gamma. By contrast, no changes in the expression of STAT6 and production of IL-4 were found.

CONCLUSION

This study provides a mechanism by which H. pylori may actually interfere with normal T-cell activation in human gastric mucosa, possibly enhancing its pathogenicity. The use of COX-2 selective inhibitors as immunomodulators in the course of H. pylori infection deserves investigations.

Cyclooxygenase-2 expression and its association with increased angiogenesis in human abdominal aortic aneurysms

Although the mechanism whereby non-steroidal anti-inflammatory drugs may reduce abdominal aortic aneurysm (AAA) development is unknown, one potential route is via inhibition of the cyclooxygenase (COX) enzyme. Despite the fact that evidence from animal models suggests a role for the COX-2 isoform in promotion of AAA development, only very limited data exist on COX-2 expression in human AAAs. Semiquantitative immunohistochemistry for COX-2 was performed on a series of formalin-fixed, paraffin-embedded human AAAs (n = 49). Associated clinicopathological data, including the degree of inflammatory cell infiltration and neorevascularization, were obtained. COX-2 protein was detected in 46 of 49 (94%) human AAAs. Expression of COX-2 protein varied widely between AAAs. COX-2 protein localized to cells in the inflammatory infiltrate with a morphology characteristic of macrophages. COX-2 expression increased with the extent of inflammatory cell infiltration (P < 0.001) and with the degree of AAA neorevascularization (P < 0.001). Logistic regression analysis identified neorevascularization (P < 0.001) as the only significant independent predictor of COX-2 positivity in human AAAs. COX-2 protein is present at increased levels in the majority of human AAAs and is expressed by mononuclear cells in the inflammatory cell infiltrate. Promotion of angiogenesis by COX-2 may play a role in AAA development.

Capsaicin and gastric ulcers

In recent years, infection of the stomach with the organism Helicobacter Pylori has been found to be the main cause of gastric ulcers, one of the common ailments afflicting humans. Excessive acid secretion in the stomach, reduction in gastric mucosal blood flow, constant intake of non-steroid anti-inflammatory drugs (NSAIDS), ethanol, smoking, stress etc. are also considered responsible for ulcer formation. The prevalent notion among sections of population in this country and perhaps in others is that "red pepper" popularly known as "Chilli," a common spice consumed in excessive amounts leads to "gastric ulcers" in view of its irritant and likely acid secreting nature. Persons with ulcers are advised either to limit or avoid its use. However, investigations carried out in recent years have revealed that chilli or its active principle "capsaicin" is not the cause for ulcer formation but a "benefactor." Capsaicin does not stimulate but inhibits acid secretion, stimulates alkali, mucus secretions and particularly gastric mucosal blood flow which help in prevention and healing of ulcers. Capsaicin acts by stimulating afferent neurons in the stomach and signals for protection against injury causing agents. Epidemiologic surveys in Singapore have shown that gastric ulcers are three times more common in the "Chinese" than among Malaysians and Indians who are in the habit of consuming more chillis. Ulcers are common among people who are in the habit of taking NSAIDS and are infected with the organism "Helicobacter Pylori," responsible for excessive acid secretion and erosion of the mucosal layer. Eradication of the bacteria by antibiotic treatment and avoiding the NSAIDS eliminates ulcers and restores normal acid secretion.

A novel genetic model of selective COX-2 inhibition: comparison with COX-2 null mice

Prostaglandin H Synthase (PGHS) is a bi-functional enzyme with a cyclooxygenase (COX) activity and a functionally linked peroxidase (POX) activity that exists in two isoforms (COX-1, COX-2). Non-steroidal anti-inflammatory drugs (NSAIDs), including the selective COX-2 inhibitors, block COX activity while leaving POX activity unscathed. Recently, some selective COX-2 inhibitors were withdrawn from the market due to elevated cardiovascular risk in placebo-controlled trials. Mice deficient for PGHS2 were developed in 1995 and through numerous subsequent studies have revealed significant roles in renal development, ductus arteriosus patency/closure, skin carcinogenesis and cardiovascular function. In this short review, we compare a novel genetic COX-2 selective inhibition mouse model with the originally described COX-2 null mice in these different physiological functions.

Vitamin E prevents the neuronal cell death by repressing cyclooxygenase-2 activity

The accumulation of damage caused by oxidative stress exacerbates cell death in many neurodegenerative diseases. We evaluated the mechanism of neuronal cell death raised by glutamate-induced toxicity, using the immortalized mouse hippocampal cell line HT-22. Our results showed that vitamin E prevented glutamate-induced cell death, accompanied by the decline of cyclooxygenase-2 expression confirmed by reverse transcriptase polymerase chain reaction and immunocytochemistry. Moreover, the neuroprotection was still effective even when vitamin E was supplied after glutamate treatment. The decline of cyclooxygenase-2 activity was also highly correlated with the neural protective effect against glutamate-induced toxicity. These results represent new insights about the timing of vitamin E supplementation after toxic stimulation and one mechanism by which vitamin E could prevent neuronal cell death by controlling cyclooxygenase-2 activity.

Cyclooxygenase-2 expression associated with severity of PanIN lesions: a possible link between chronic pancreatitis and pancreatic cancer

BACKGROUND

Cyclooxygenase-2 (COX-2) is a key modulatory molecule in inflammation and neoplasia. Increasing evidence suggests a role for COX-2 in pancreatic cancer (PAC). However, expression of COX-2 in pancreatic intraepithelial neoplasia (PanIN), the precursor lesion of PAC which is often present in chronic pancreatitis (CP), has received little attention.

METHOD

COX-2 immunostaining was performed on sections of PAC (n = 26), CP (n = 34), PanIN (n = 68) and normal pancreas (n = 11). Sections were also stained for macrophages (CD68), activated pancreatic stellate cells (alphaSMA), and collagen (Sirius Red) as markers of fibrosis. Semiquantitative scoring was based on the extent and intensity of immunostaining.

RESULTS

COX-2 expression was increased in PAC compared to normal (p = 0.02) with 89% of cases exceeding COX-2 immunostaining in normal ducts. In PanIN lesions, COX-2 expression increased with escalating severity of the PanIN change (p < or = 0.01). COX-2 expression was increased in PanIN-2/3 compared to normal pancreas and CP (p < or = 0.001). In ducts of CP, COX-2 expression did not differ from that in normal tissue. There was no association between COX-2 expression and clinicopathological variables.

CONCLUSION

The high level of COX-2 expression in PanIN lesions suggests that this enzyme could be a therapeutic target at a non-invasive stage of pancreatic carcinogenesis and feasible for chemoprevention in CP.

The rationale for nonsteroidal anti-inflammatory drug therapy for inflammatory myofibroblastic tumors: a Children's Oncology Group study

BACKGROUND

Inflammatory myofibroblastic tumors (IMTs) are neoplasms that are highly vascularized, have an intermediate prognosis, and are associated with infiltration, obstruction, local recurrence, and rare metastasis. Resection of large IMTs can lead to substantial morbidity and even mortality. Anecdotal experience suggests that nonsteroidal anti-inflammatory drugs may eradicate large IMTs or shrink them to a more readily resectable size and configuration. To support the hypothesis that nonsteroidal anti-inflammatory drugs are antiangiogenic for IMTs by interfering with vascular endothelial growth factor (VEGF) signaling via cyclooxygenase 2 (COX-2) inhibition, IMT specimens were immunohistochemically examined for expression of COX-2 enzyme and VEGF.

METHODS

The diagnosis of IMT was confirmed in all 18 cases comprising the study. Intensity of COX-2 and VEGF staining was graded, and staining uniformity was examined. ALK-1 protein expression, found in up to two thirds of IMTs, was also determined.

RESULTS

COX-2 and VEGF expression were identified in all tissue examined, with staining intensity varying independently. ALK-1 protein expression was identified in 33% of specimens. Its presence was not related to the intensity of COX-2 or VEGF staining.

CONCLUSIONS

Our data suggest that the mediators of angiogenesis, VEGF and COX-2, are present and may play an important role in the growth of IMTs.

Penta- O -galloyl-beta- d -glucose suppresses tumor growth via inhibition of angiogenesis and stimulation of apoptosis: roles of cyclooxygenase-2 and mitogen-activated protein kinase pathways

Recent studies have revealed that 1,2,3,4,6-penta-O-galloyl-beta-d-glucose (PGG) has anti-tumorigenic activity in vitro. In the present work, we evaluated the in vitro and in vivo antiangiogenic and antitumor activities of PGG and examined its molecular mechanisms. PGG significantly inhibited the proliferation and tube formation in basic fibroblast growth factor (bFGF)-treated human umbilical vein endothelial cells (HUVECs) at non-cytotoxic concentrations. PGG effectively disrupted the bFGF-induced neo-vascularization in chick chorioallantoic membrane (CAM) and in Matrigel plugs in the mice. When mice were intraperitoneally injected, PGG also significantly inhibited tumor angiogenesis induced by Lewis lung carcinoma (LLC) and the growth of LLC by 57 and 91% of control tumor weight at 4 and 20 mg/kg, respectively. Immunohistochemical analysis revealed decreased microvessel density, decreased expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF), reduced tumor cell proliferation and increased tumor cell apoptosis. Similarly, PGG significantly attenuated the expression of COX-2 and VEGF and reduced the secretion of VEGF and prostaglandin E2 in bFGF-treated HUVECs. Furthermore, the COX-2 inhibitor NS398 significantly inhibited tube formation and neo-vascularization in CAM, supporting the role of COX-2 in PGG inhibition of angiogenesis. PGG diminished the phosphorylation of extracellular signal regulated kinase 1/2, Jun NH2-terminal kinase and activated phospho-p38 mitogen-activated protein kinase (MAPK) in a dose-dependent manner in bFGF-treated HUVECs. In addition, p38 inhibitor SB203580 abolished the downregulation of COX-2, VEGF and the antiproliferative activity by PGG. Taken together, our data demonstrate that PGG exerts antitumor activity primarily via inhibition of angiogenesis through COX-2 and MAPK- dependent pathways.

COX-1, COX-2 and the topical effect in NSAID-induced enteropathy

The side effects of NSAIDs are equally evident in the stomach and the small bowel. The latter is increasingly seen as being clinically significant, contributing substantially to the iron-deficiency anaemia that is so common in patients with rheumatoid arthritis. Furthermore, NSAID-enteropathy may be associated with life-threatening events. The pathogenesis of NSAID-enteropathy is uncertain but inhibition of COX-1 is believed to be of pivotal importance. However there is increasing evidence that COX-2 inhibition and the topical effect may have a synergistic detrimental action. We examined the role of COX-1, COX-2 and the so called topical effect of acidic NSAIDs. We found that COX-1 or COX-2 inhibition and the topical effect alone do not damage the GI tract. Dual inhibition of COX-1 and COX-2 results in intestinal inflammation similar to that caused by Indomethacin. The topical effect may act synergistically in this damage. The conventional view that the mechanism of gastrointestinal damage is principally caused by COX-1 inhibition needs to be revised in view of recent studies using selective inhibitors of the COX enzymes and COX knockout animals.

Estrogen up-regulates cyclooxygenase-2 via estrogen receptor in human uterine microvascular endothelial cells

OBJECTIVE

To investigate the effects of 17beta-estradiol (E(2)) on cyclooxygenase-2 (COX-2) expression and prostaglandin E(2) (PGE(2)) synthesis in primary human uterine microvascular endothelial cells (HUMEC).

DESIGN

Prospective study.

SETTING

Basic research laboratory at an academic medical center.

PATIENT(S)

Primary HUMEC of three women donors and primary human dermal microvascular endothelial cells of three women donors (as control), purchased from a third-party source.

INTERVENTION(S)

The HUMEC were cultured in specific media in a humidified atmosphere with 5% CO(2) at 37 degrees C.

MAIN OUTCOME MEASURE(S)

Measures of COX-2 mRNA and protein, PGE(2) production, and estrogen receptor alpha and beta mRNA and protein.

RESULT(S)

Treatment with E(2) (10(-10) to 10(-6) M) increased COX-2 mRNA levels by 2.3-fold to 2.4-fold in HUMEC. Treatment of HUMEC with E(2) (10(-8) M) resulted in a time-dependent increase of COX-2 mRNA levels. This was accompanied by a 2.8-fold increase in COX-2 protein level and a 1.5-fold increase in PGE(2) synthesis. Pretreatment of HUMEC with a selective COX-2 inhibitor, NS-398, abolished E(2)-induced PGE(2) synthesis, suggesting that E(2) specifically up-regulates COX-2 activity. The estrogen receptor antagonist ICI 182,780 fully reversed the stimulation of COX-2 mRNA and protein levels and PGE(2) synthesis by E(2). Interestingly, estrogen receptor beta mRNA and protein were abundant in HUMEC, whereas estrogen receptor alpha mRNA or protein was barely detectable.

CONCLUSION(S)

We conclude that various levels of E(2) can significantly increase COX-2 expression and PGE(2) synthesis in HUMEC via the estrogen receptor.

Effects of flunixin meglumine or etodolac treatment on mucosal recovery of equine jejunum after ischemia

OBJECTIVE

To examine the effects of flunixin meglumine and etodolac treatment on recovery of ischemic-injured equine jejunal mucosa after 18 hours of reperfusion.

ANIMALS

24 horses.

PROCEDURE

Jejunum was exposed to 2 hours of ischemia during anesthesia. Horses received saline (0.9% NaCl) solution (12 mL, i.v., q 12 h), flunixin meglumine (1.1 mg/kg, i.v., q 12 h), or etodolac (23 mg/kg, i.v., q 12 h). Tissue specimens were obtained from ischemic-injured and nonischemic jejunum immediately after ischemia and 18 hours after recovery from ischemia. Transepithelial electric resistance (TER) and transepithelial flux of tritium-labeled mannitol measured mucosal permeability. Denuded villous surface area and mean epithelial neutrophil count per mm2 were calculated. Western blot analysis for cyclooxygenase (COX)-1 and -2 was performed. Pharmacokinetics of flunixin and etodolac and eicosanoid concentrations were determined.

RESULTS

Ischemic-injured tissue from horses treated with flunixin and etodolac had significantly lower TER and increased permeability to mannitol, compared with that from horses treated with saline solution. Epithelial denudation after ischemia and 18 hours after recovery was not significantly different among treatments. Both COX-1 and -2 were expressed in ischemic-injured and nonischemic tissues. Ischemia caused significant upregulation of both COX isoforms. Eicosanoid concentrations were significantly lower in tissues from flunixin and etodolac-treated horses, compared with that from horses treated with saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Flunixin and etodolac treatment retarded recovery of intestinal barrier function in jejunal mucosa after 18 hours of reperfusion, whereas tissues from horses treated with saline solution recovered baseline values of TER and permeability to mannitol.

Cutting edge: cyclooxygenase-2 activation suppresses Th1 polarization in response to Helicobacter pylori

Helicobacter pylori infection causes a Th1-driven mucosal immune response. Cyclooxygenase (COX)-2 is up-regulated in lamina propria mononuclear cells in H. pylori gastritis. Because COX-2 can modulate Th1/Th2 balance, we determined whether H. pylori activates COX-2 in human PBMCs, and the effect on cytokine and proliferative responses. There was significant up-regulation of COX-2 mRNA and PGE(2) release in response to H. pylori preparations. Addition of COX-2 inhibitors or an anti-PGE(2) Ab resulted in a marked increase in H. pylori-stimulated IL-12 and IFN-gamma production, and a decrease in IL-10 levels. Addition of PGE(2) or cAMP, the second messenger activated by PGE(2), had the opposite effect. Similarly, stimulated cell proliferation was increased by COX-2 inhibitors or anti-PGE(2) Ab, and was decreased by PGE(2). Our findings indicate that COX-2 has an immunosuppressive role in H. pylori gastritis, which may protect the mucosa from severe injury, but may also contribute to the persistence of the infection.

Effects of aspirin and indomethacin on endothelial cell proliferation in vitro

BACKGROUND AND AIM

Non-steroidal anti-inflammatory drugs (NSAID) are associated with delayed peptic ulcer healing. Ulcer healing is dependent on angiogenesis, which requires endothelial cell (EC) proliferation. The present study aimed to determine whether NSAID and prostaglandin E2 (PGE2) inhibited EC proliferation in vitro.

METHODS

Effects of 50 micro L aspirin (10 micro M-1 mM), indomethacin (10 micro M-1 mM) and PGE2 (1 micro M-0.1 mM) on the proliferation, viability and cell cycle of human dermal microvascular (HuDMEC) and human umbilical vein (HUVEC) EC were assessed using dual staining cell viability, 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide and flow cytometry assays.

RESULTS

Proliferation of HuDMEC and HUVEC was significantly inhibited by 0.1 mM/1 mM indomethacin, 1 mM aspirin and 100 micro M PGE2, with a significant (P < 0.05) increase in EC necrosis with 1 mM indomethacin and 100 micro M PGE2. No effects on cell cycle were demonstrated.

CONCLUSIONS

High concentrations of NSAID inhibit both HuDMEC and HUVEC proliferation in vitro by cytotoxic (indomethacin) or cytostatic (aspirin and indomethacin) mechanisms. Interestingly, PGE2 was also antiproliferative. Inhibition of EC proliferation may prevent angiogenesis at the ulcer site, which may in part explain the delayed ulcer healing associated with NSAID.

The role of COX-2 in angiogenesis and rheumatoid arthritis

Recent evidence suggests that cyclooxygenase (COX)-2 is a mediator of angiogenesis, and COX-2 activity is known to be upregulated in the rheumatoid arthritis (RA) synovium. We examined whether mediation of angiogenesis by COX-2 was occuring in cells of the RA synovium and in microvascular endothelial cells (ECs) that are similar to those found in the RA synovium. We demonstrate that rofecoxib, a selective COX-2 inhibitor, acts directly on human dermal microvascular ECs (HMVECs) to inhibit their chemotactic and tube forming ability. Likewise, pretreatment of HMVECs with rofecoxib significantly inhibited their ability to form tubes induced by conditioned media (CM) of activated RA synovial fibroblasts. When RA synovial fibroblasts were pretreated with rofecoxib for 16 h and then stimulated with interleukin (IL)-1beta, their CM induced significantly less HMVEC tube formation when compared with CM from vehicle-treated RA synovial fibroblasts. ELISAs performed on activated RA fibroblast CM for known proangiogenic factors demonstrated a significant reduction in bFGF, in addition to the expected decrease in PGE(2). Our studies suggest that COX-2-induced angiogenic activity is an active mechanism within diseased synovium and may provide an additional rationale for the use of COX-2 inhibitors in RA.

Interstitial cell cyclooxygenase-2 expression is associated with increased angiogenesis in human sporadic colorectal adenomas

Cyclooxygenase (COX)-2 plays an important role in intestinal tumorigenesis and angiogenesis in animal models. In superficial areas of human sporadic colorectal adenomas, COX-2 is expressed predominantly by interstitial macrophages, in close proximity to microvessels. The aim of this study was to investigate the association between microvessel density (MVD) and COX-2 expression in human sporadic colorectal adenomas. Immunohistochemistry and immunofluorescence for CD31 and COX-2 were performed on a well-characterized series of human sporadic colorectal adenomas (n = 37). The mean MVD and COX-2 expression level (scored 0-3) in superficial and deep interstitial cells of adenomas were assessed by two independent observers. Superficial MVD was increased in COX-2-positive adenomas, compared with COX-2-negative adenomas (p = 0.037). There was a significant correlation between superficial MVD and increasing superficial interstitial cell COX-2 expression score (p = 0.048). COX-2-expressing interstitial cells aggregated in areas of high MVD. No relationship was evident between MVD and COX-2 expression in either deep interstitial cells or epithelial cells. Multivariate analysis demonstrated that only adenoma size (p = 0.005) was a significant independent predictor of MVD. COX-2 protein expression by superficial interstitial cells in human sporadic colorectal adenomas is associated with increased angiogenesis. Promotion of angiogenesis may play a role in the pro-tumourigenic activity of COX-2 during growth of human colorectal adenomas.

Analysis of cyclooxygenase expression in human colorectal adenomas

INTRODUCTION

Evidence from rodent intestinal tumorigenesis models suggests that both cyclooxygenase-1 and cyclooxygenase-2 may play important roles in the development and progression of human sporadic colorectal adenomas. However, previous studies of cyclooxygenase isoform expression in human colorectal adenomas have produced conflicting data. Cyclooxygenase-1 expression has been poorly studied, and cyclooxygenase-2 positivity of adenomas has been variable depending on the detection technique used. It also remains unclear whether villous adenomas express cyclooxygenase-2.

METHODS

Cyclooxygenase isoform expression in human sporadic colorectal adenomas was analyzed by reverse transcription-polymerase chain reaction, Western blot analysis, and immunohistochemistry.

RESULTS

Variable cyclooxygenase-1 expression was detected in all adenomas (n = 9) by both reverse transcription-polymerase chain reaction and Western blot analysis. Cyclooxygenase-2 expression was detected in eight (89 percent) of nine adenomas by reverse transcription-polymerase chain reaction and immunohistochemistry. Cyclooxygenase-2 protein was not detected by Western blot analysis in any adenoma. Cyclooxygenase-2 was expressed by all histopathologic types of adenoma and localized predominantly to superficial interstitial cells, in which it was associated with increased adenoma size.

CONCLUSION

Cyclooxygenase-1 is expressed at variable levels by all adenomas. Cyclooxygenase-2 is expressed by the majority of adenomas, including those of the villous type, at levels below the sensitivity of Western blot analysis.

Angiogenic markers, neovascularization and malignant deformation of Barrett's esophagus

The molecular events underlying progression of Barrett's esophagus to adenocarcinoma remain an area of active investigation. Neovascularization and angiogenesis have been studied in esophageal adenocarcinomas by counting of microvessels after staining with vascular markers, and by immunohistochemistry for vascular endothelial growth factor. Angiogenesis appears to be increased early in the neoplastic process, but has poor prognostic value. We have demonstrated that expression levels of two important genes that regulate cell growth, namely inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, are frequently upregulated in Barrett's esophagus and associated adenocarcinomas. COX-2 expression may be related to reflux of bile salts, which induce COX-2 expression in Barrett's tissues and esophageal adenocarcinoma cells in vitro. COX-2 inhibition induces apoptosis and blocks proliferation in COX-2-expressing esophageal adenocarcinoma cells in vitro, and blocks angiogenesis in both in vivo and in vitro models. Although controversial, recent evidence suggest that iNOS-derived NO can inhibit angiogenesis in some model systems. In conclusion, both iNOS and COX-2 appear to be involved in Barrett's-associated neoplastic progression, but COX-2 inhibition is more promising as a chemopreventive strategy. COX-2 inhibition may exert beneficial effects by decreasing angiogenesis and epithelial proliferation, and by facilitating apoptosis of epithelial cells that have undergone DNA damage.

Cyclooxygenase-2-dependent prostacyclin formation is regulated by low density lipoprotein cholesterol in vitro

Reduction of plasma low density lipoprotein (LDL) levels is associated with a reduced risk of myocardial infarction, stroke, and death. Some of this clinical benefit may be derived from an improvement in endothelium-dependent vasodilation. In the present study, we examined the effects of LDL reduction on cyclooxygenase (COX) activity and prostacyclin (PGI2) production. Human umbilical vein endothelial cells exposed to reduced concentrations of LDL demonstrated increased PGI2 production in a dose-dependent manner (from 0.75+/-0.2 to 2.6+/-0.2 ng/mL, P<0.0001). This alteration in PGI2 production did not result from LDL-induced changes in PGI2 synthase expression. However, selective inhibition of COX-2, but not COX-1, blocked PGI2 production under low cholesterol conditions. Addition of exogenous cholesterol induces dose-dependent reductions in endothelial COX-2 expression as measured by reverse transcription-polymerase chain reaction and by Western blotting. Pretreatment of cells with actinomycin D, a transcription inhibitor, reduced COX-2-derived PGI2 production by 45.9% (from 0.55+/-0.09 to 0.25+/-0.08 ng/mL). Taken together, these observations indicate that endothelial PGI2 production is regulated by cholesterol at the transcriptional level and that cholesterol-sensitive transcriptional pathways that regulate COX-2 expression are present in vascular tissue.

Cyclooxygenase-2: a therapeutic target

Cyclooxygenase (COX), also known as prostaglandin endoperoxide synthase, is the key enzyme required for the conversion of arachidonic acid to prostaglandins. Two COX isoforms have been identified, COX-1 and COX-2. In many situations, the COX-1 enzyme is produced constitutively (e.g., in gastric mucosa), whereas COX-2 is highly inducible (e.g., at sites of inflammation and cancer). Traditional nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both enzymes, and a new class of COX-2 selective inhibitors (COXIBs) preferentially inhibit the COX-2 enzyme. This review summarizes our current understanding of the role of COX-1 and COX-2 in normal physiology and disease.

PGE(2) receptors and synthesis in human gastric mucosa: perturbation in cancer

Recent evidence suggests that prostanoids are an important participant in the pathobiology of gastric adenocarcinoma, but the location and identity of cells in tumor-adjacent gastric mucosa able to synthesize and/or bind specific prostanoids is not clear. Using probes for cyclooxygenase 1 and 2 mRNA and protein as well as for the EP family of PGE(2) receptors, we sought to define the biology of prostanoids in adjacent human gastric mucosa at the site of tumor invasion. In mucosa adjacent to an invasive gastric adenocarcinoma, expression of cyclooxygenase was prominent, with COX 1 primarily in mucosal T lymphocytes surrounding nests of tumor cells. Densitometry showed these tumor-adjacent cells had substantial levels of COX 1 immunoreactive protein (relative intensity, 3.2). Cyclooxygenase 2 was newly expressed among these cells as well, but was limited in number (<25% of cyclooxygenase-positive T lymphocytes) in tumor-adjacent mucosa. Further, CD3(+) mononuclear cells, adjacent to tumor, strongly expressed prostanoid receptor EP(4) (relative intensity, 8.0), but cells with this receptor were not evident in the tumor itself. In contrast, normal gastric mucosa showed a consistent and structured expression of cyclooxygenase and PGE(2) receptor immunoreactive protein among mucosal cells. Cyclooxygenase 1 and PGE(2) receptor EP(4) were expressed on mucosal CD3(+) T lymphocytes in the lumenal (upper) third of gastric mucosa; and prostanoid receptors EP(2), EP(3) and EP(4), on gastric epithelia lining gastric pits. In situ hybridization with COX cDNAs confirmed these findings, and neither COX 2-specific mRNA nor protein was detected in normal gastric tissue. Our studies suggest that synthetic machinery and receptors for PGE(2), prominently expressed by T lymphocytes in gastric mucosa at the boundary of normal mucosa with tumor cells, may play a central role in prostanoid-driven tumorigenesis of this tissue.

Gastrointestinal safety of COX-2 specific inhibitors

Coxibs are a major advance in the therapy of patients with painful and inflammatory conditions. At present, the theoretical harm that derives from inhibiting vascular COX-2 has not emerged as a significant risk, although more research is needed. What has emerged is that some NSAIDs, particularly naproxen, may have an aspirin-like effect in reducing the risk of vascular disease, although more research is needed. Whether this finding is sufficient to recommend naproxen for the management of patients with arthritis who also require vascular protection is intriguing and worth further evaluation. It is widely believed and maintained that coxibs have the greatest potential value in patients with other risk factors for ulcer disease, and this seems likely to be the case for patients taking corticosteroids or anticoagulants and probably those who are elderly. Dosing should be [figure: see text] cautious in old patients, however, because of the ability of NSAIDs and coxibs to cause fluid retention, heart failure, and hypertension. It is less clear that coxibs reduce risk sufficiently in patients with previous ulceration (particularly recent) to make them a better strategy than acid co-therapy. This possibility requires further evaluation, as does the competing value of the 2 strategies for patients infected with H. pylori. If coxibs are used in patients with H. pylori-associated risks, there are grounds to recommend eradication. For patients taking aspirin or drugs [figure: see text] with an aspirin-like effect, the intrinsic risk of these drugs may mandate use of acid suppression and obviate the use of coxibs (Fig. 8). Available data suggest that the risk reduction in patients with no risk factors who use coxibs may be almost as great as in patients with risk factors, with the added advantage that patients may be taken to a state that is virtually free of any risk of ulcer complications that otherwise might require additional therapy. Contrary to current popular truisms, the greatest value of coxibs may be in patients without risk factors because it is in this unconfounded group that the ability of coxibs to free patients of ulcer risk appears to be delivered in full.

The retinoid fenretinide inhibits proliferation and downregulates cyclooxygenase-2 gene expression in human colon adenocarcinoma cell lines

Fenretinide [N-(4-Hydroxyphenyl)retinamide, 4-HPR] (10(-10)-10(-6) M) treatment of HT-29 human colon cancer cells for 24-72 h significantly inhibited their growth. Using HCT-15 cells, 4-HPR had limited inhibitory effects on cell proliferation over the same concentration range and time period. The inhibitory effects of 4-HPR on cell growth in HT-29 cells were markedly reduced in the presence of exogenously added prostaglandins (PGs), suggesting a possible role for inhibition of PG synthesis as a mechanism for 4-HPR's antiproliferative effects. Inhibition of PGE(2) production was caused by 4-HPR in a concentration-dependent manner and decreased COX-2 but not COX-1 mRNA levels; this is the first indication that 4-HPR selectively inhibits COX-2 gene expression. Our findings suggest a possible mechanism for the chemopreventive and anti-proliferative effects of 4-HPR.

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.

Gastroduodenal mucosal defense

The gastroduodenal mucosa is a model system of defense with several structural levels and biologic strategies that are closely interrelated with each other to cope with the harmful ingredients of ingested food and the potentially deleterious effects of gastric acid and pepsin. Experimental and clinical research carried out during the review period added to the understanding of each component of the multiple mechanisms of gastroduodenal mucosal protection. In the first place, mucosal integrity is defended by the mucus gel barrier, the epithelial cell barrier, and the immune barrier. The properties of these barriers are maintained by adequate regulation of mucus production, bicarbonate secretion, mucosal microcirculation, and motor activity. These regulatory systems are alarmed by nociceptive neurons and the mucosal immune system which includes chemokine-secreting epithelial cells. The ultimate defense system is rapid repair of the injured mucosa under the control of several growth factors. Progressing insight into the network of mucosal defense not only will improve existing therapies of inflammation and ulceration but also will provide new leads for the management of functional diseases in the gastroduodenal region.

Nonsteroidal anti-inflammatory drug gastropathy

By inhibiting prostaglandin synthesis, nonsteroidal anti-inflammatory drugs (NSAIDs) compromise gastroduodenal defense mechanism including blood flow and mucus/bicarbonate secretion. This has led to NSAIDs being the most widely reported drug cause of adverse events. While NSAIDs also cause dyspepsia, inhibition of prostaglandin synthesis may reduce this from even higher levels that would otherwise prevail and mask ulcer-related dyspepsia, making anticipatory management difficult. On average, the risk of ulcer complications increases 4-fold, resulting in 1.25 additional hospitalizations per 100 patient-years according to one estimate. Older patients, those with a past history, and those taking anticoagulants or corticosteroids are at higher risk. Risk is dose dependent and is lower with ibuprofen at low doses than with other NSAIDs. It is unlikely that Helicobacter pylori increases the risk, and under some circumstances it may be protective. Selective inhibitors of the inducible cyclooxygenase 2 spare gastric mucosal prostaglandin synthesis and do not damage the gastric mucosa. Their place in therapy, compared with use of misoprostol or proton pump inhibitors, is currently emerging. Future competitors may include nitric oxide-donating, zwitterionic, or R-enantiomer NSAIDs.

Eicosanoids and the stomach

Eicosanoids are arachidonic acid derivatives that include prostaglandins, thromboxanes, and leukotrienes. During the last three decades, it has become evident that these bioactive lipids play a pivotal role in gastric physiology. The goal of the present review is to describe their involvement in the normal regulation of gastric secretion and gastric motility, as well as in gastric mucosal defense. Their role in gastric mucosal mitogenesis, apoptosis, inflammation, and immune modulatory responses is also discussed.

The effect of non-steroidal anti-inflammatory drugs on human colorectal cancer cells: evidence of different mechanisms of action

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit proliferation and induce apoptosis in human colorectal cancer cells in vitro. It remains unclear whether individual NSAIDs act by cyclooxygenase-2 (COX-2) inhibition and how NSAIDs exert their anti-proliferative effects. We investigated the effects of NS-398 (a selective COX-2 inhibitor), indomethacin (a non-selective COX inhibitor) and aspirin on four human colorectal cancer cell lines (HT29.Fu, HCA-7, SW480 and HCT116). NS-398 completely inhibited proliferation, induced G1 arrest and promoted apoptosis in COX-2-expressing cells (HT29.Fu and HCA-7). However, indomethacin had similar effects on all cells, regardless of COX-2 expression. NS-398 also had anti-proliferative activity on COX-2-negative cell lines (SW480 and HCT116). Aspirin inhibited proliferation of all cell lines but did not induce apoptosis. Indomethacin decreased beta-catenin protein expression in all cells (unlike NS-398 or aspirin). NSAIDs act on human colorectal cancer cells via different mechanisms. Decreased beta-catenin protein expression may mediate the anti-proliferative effects of indomethacin.

Cancer chemoprevention through interruption of multistage carcinogenesis. The lessons learnt by comparing mouse skin carcinogenesis and human large bowel cancer

Whilst in the early stages, neoplastic development is predominantly triggered by environmental genotoxic and non-genotoxic carcinogens, tumour progression becomes more and more autonomous at later stages. In this context a dysregulation of arachidonic acid metabolism seems to play a disastrous role. Conversely, non-steroidal anti-inflammatory drugs (NSAIDs) rank among the most potent and most promising agents for cancer chemoprevention probably because of their ability to inhibit prostaglandin biosynthesis, in particular, at the level of the 'pro-inflammatory' enzyme cyclooxygenase-2 (COX-2). A pathological overexpression of COX-2 resulting in excessive prostaglandin production has been found already in early stages of carcinogenesis and seems to be a consistent feature of neoplastic development in a wide variety of tissues. COX-2 overexpression is thought to occur along signalling pathways of inflammation and tissue repair which become activated in the course of tumour promotion and, due to autocrine and auto-stimulatory mechanisms, finally lead to some autonomy of tumour development (self-promotion). Prostaglandins formed along a dysregulated COX pathway have been shown to mediate tumour promotion in animal experiments and may play a role, in addition, in other processes involved in tumour growth such as angiogenesis, metastasis and immunosuppression. Moreover, genotoxic byproducts such as organic free radicals, reactive oxygen species and malondialdehyde produced in the course of prostanoid biosynthesis may contribute to genetic instability (mutator phenotype) of neoplastic cells thereby promoting malignant progression. Such mixtures of physiologically highly active mediators and genotoxic byproducts are, in addition, formed along the various lipoxygenase-catalysed pathways of arachidonic acid metabolism some of which also become dysregulated during tumour development and, therefore, provide novel targets of future chemopreventive approaches.

Thromboxane A(2) regulation of endothelial cell migration, angiogenesis, and tumor metastasis

Prostaglandin endoperoxide H synthases and their arachidonate products have been implicated in modulating angiogenesis during tumor growth and chronic inflammation. Here we report the involvement of thromboxane A(2), a downstream metabolite of prostaglandin H synthase, in angiogenesis. A TXA(2) mimetic, U46619, stimulated endothelial cell migration. Angiogenic basic fibroblast growth factor (bFGF) or vascular endothelial growth factor (VEGF) increased TXA(2) synthesis in endothelial cells three- to fivefold. Inhibition of TXA(2) synthesis with furegrelate or CI reduced HUVEC migration stimulated by VEGF or bFGF. A TXA(2) receptor antagonist, SQ29,548, inhibited VEGF- or bFGF-stimulated endothelial cell migration. In vivo, CI inhibited bFGF-induced angiogenesis. Finally, development of lung metastasis in C57Bl/6J mice intravenously injected with Lewis lung carcinoma or B16a cells was significantly inhibited by thromboxane synthase inhibitors, CI or furegrelate sodium. Our data demonstrate the involvement of TXA(2) in angiogenesis and development of tumor metastasis.