Inhibition of angiogenesis by nonsteroidal anti-inflammatory drugs: insight into mechanisms and implications for cancer growth and ulcer healing

Prostaglandins, but not tumor-derived IL-10, shut down concomitant tumor-specific CTL responses during murine plasmacytoma progression

IL-10 is assumed to be a major immunosuppressive factor produced by most B-cell tumors. The immunosuppressive role of tumor-derived IL-10 was analyzed using the MHC class II-negative BALB/c plasmacytoma ADJ-PC-5 as a model tumor. Immune monitoring of tumor-bearing mice was based on the measurement of tumor burden, tumor-specific CTL cytotoxicity and intracellular cytokine staining using FACS. ADJ-PC-5 tumor progression in syngeneic recipients is associated with strong, concomitant, tumor-specific CTL responses during early stages of tumor progression which are sufficient to cause rejection of small s.c. autologous test tumors. These initial CTL responses gradually decline during later tumor stages. Blocking of IL-10 in vivo did not abolish CTL suppression or retard tumor growth. More strikingly, application of anti-IL-10 antibodies during early tumor stages abrogated CTL induction and markedly accelerated tumor growth. In contrast to anti-IL-10 treatment, application of cyclo-oxygenase inhibitors to ADJ-PC-5 tumor-bearing mice led to enhanced tumor-specific CTL responses throughout all stages of tumor progression, paralleled by retarded tumor growth and a significantly delayed onset of suppression. Both findings contradict a dominant immunosuppressive role of IL-10 during B-cell tumor progression. Tumor-derived IL-10 must therefore be considered an immunostimulating factor, which accounts for the high immunogenicity of B-cell tumors, whereas prostaglandins, which are not produced by the tumor cells themselves, are the dominant immunosuppressors in this system.

Comparative effects of indomethacin on cell proliferation and cell cycle progression in tumor cells grown in vitro and in vivo

Considerable research effort is currently being directed towards understanding the mechanisms mediating the antiproliferative effects of non-steroidal anti-inflammatory drugs (NSAIDs) and, more recently, of cyclooxygenase (COX)-2 inhibitors as well. A key question is whether NSAIDs (excluding sulindac) exert their anticarcinogenic effects in vivo by a mechanism that is dependent on their capacity to inhibit COX activity. Some studies with cultured tumor cells in vitro have argued against such a linkage, showing that NSAIDs inhibit cell replication and/or augment apoptosis only at concentrations that exceed those required to inhibit COX activities 10- to 100-fold. The significance of these results for the observed anticarcinogenic effects of NSAIDs in vivo has not yet been evaluated. We addressed this question by comparing, for the same tumor cells, the effects of the NSAID indomethacin on cell growth parameters when the cells were grown in culture to the effects seen in the in vivo growing tumor in the mouse. Indomethacin added to cultured Lewis lung carcinoma cells exerted a potent antiproliferative effect ((3)H thymidine assay) and reduced cell viability (MTT[3-(4,5-dimethyl(thiazol-2-yl)-2,5 diphenyl tetrazolium bromide] assay) at low doses (10-20 microM) in parallel with its inhibitory effect on cellular cyclooxygenase. These effects of indomethacin appeared to arise from a clear antiproliferative shift in the profile of the cell cycle parameters towards a reduced percentage of cells at the S and G(2)/M phases, together with an increased percentage of cells at the G(1) phase. Significantly, similar results were seen when indomethacin was given in vivo at the low dose of 2 mg per kg/day, which blocked blood platelet COX activity and at the same time produced a delay in tumor growth initiation and attenuation of apparent primary tumor growth as well as growth of lung metastases. These results thus provide strong support for the notion that COX inhibition is a major determinant in the antitumorigenic effect of indomethacin in vivo.

Anti-lymphoma effect of naproxen and indomethacin in a patient with relapsed diffuse large B-cell lymphoma

A 77-year-old man with relapsed non-Hodgkin's lymphoma, diffuse large B-cell type, was treated with naproxen, a nonsteroidal anti-inflammatory drug (NSAID), for paraneoplastic fever. A dramatic disappearance of not only the fever but also generalized lymphadenopathy was observed. Naproxen was continued, and he maintained remission for 10 months. When relapse of lymphoma occurred in spite of continuous naproxen administration, indomethacin, another type of NSAID, was tried. Surprisingly, rapid regression of lymphoma occurred again and was maintained for almost 1 year. These results indicate that NSAIDs are effective in some patients with non-Hodgkin's lymphoma.

Role of leptin in ulcer healing

Leptin was shown to exhibit similar to cholecystokinin (CCK) cytoprotective activity against acute gastric lesions, but its role in ulcer healing has not been examined. The aims of this study were: (1) to compare the effects of exogenous leptin to those of CCK on the course of healing of chronic gastric ulcers; (2) to study the gene and protein expression of leptin at the ulcer margin during ulcer healing; and (3) to assess the effects of leptin administration on the mucosal gene expression of main growth factor such as transforming growth factor alpha (TGFalpha). Gastric ulcers were produced in rats by the acetic acid method. Rats with ulcers were divided in following treatment groups: (1) vehicle; (2) leptin (10 microg/kg i.p.); (3) CCK (10 microg/kg s.c.); and (4) leptin or CCK with or without tyrphostin A46 (200 microg/kg i.p.), an inhibitor of epidermal growth factor (EGF)-receptor tyrosine kinase or NG-nitro-L-arginine (20 mg/kg i.g.), a blocker of nitric oxide synthase. Animals were euthanized 9 days after ulcer induction. The area of gastric ulcers and the gastric blood flow at the ulcer area were determined. In addition, mucosal biopsy samples were taken from the ulcer area for histological evaluation as well as for the determination of mRNA and protein expression for leptin and constitutive nitric oxide synthase (cNOS) and inducibile nitric oxide synthase (iNOS) by reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blot, respectively. In addition, the gene expression for TGFalpha was analyzed by RT-PCR. Both leptin and CCK reduced significantly the ulcer area as compared to vehicle-treated group by approximately 50%. The treatment with tyrphostin or N(G)-nitro-L-arginine reversed in part the acceleration of ulcer healing by leptin and CCK. The expression of leptin mRNA and protein was significantly increased at the ulcer edge. The leptin-induced acceleration of ulcer healing was associated with increased expression of transcripts for TGFalpha as well as increased mRNA and protein expression for cNOS and iNOS at the ulcer margin. We conclude that leptin accelerates ulcer healing by mechanisms involving the up-regulation of TGFalpha and increased production of nitric oxide due to up-regulation of cNOS and iNOS in the ulcer area.

Angiogenesis: regulators and clinical applications

Angiogenesis is a fundamental process in reproduction and wound healing. Under these conditions, neovascularization is tightly regulated. Unregulated angiogenesis may lead to several angiogenic diseases and is thought to be indispensable for solid tumor growth and metastasis. The construction of a vascular network requires different sequential steps including the release of proteases from "activated" endothelial cells with subsequent degradation of the basement membrane surrounding the existing vessel, migration of endothelial cells into the interstitial space, endothelial cell proliferation, and differentiation into mature blood vessels. These processes are mediated by a wide range of angiogenic inducers, including growth factors, chemokines, angiogenic enzymes, endothelial specific receptors, and adhesion molecules. Finally, when sufficient neovascularization has occurred, angiogenic factors are down-regulated or the local concentration of inhibitors increases. As a result, the endothelial cells become quiescent, and the vessels remain or regress if no longer needed. Thus, angiogenesis requires many interactions that must be tightly regulated in a spatial and temporal manner. Each of these processes presents possible targets for therapeutic intervention. Synthetic inhibitors of cell invasion (marimastat, Neovastat, AG-3340), adhesion (Vitaxin), or proliferation (TNP-470, thalidomide, Combretastatin A-4), or compounds that interfere with angiogenic growth factors (interferon-alpha, suramin, and analogues) or their receptors (SU6668, SU5416), as well as endogenous inhibitors of angiogenesis (endostatin, interleukin-12) are being evaluated in clinical trials against a variety of solid tumors. As basic knowledge about the control of angiogenesis and its role in tumor growth and metastasis increases, it may be possible in the future to develop specific anti-angiogenic agents that offer a potential therapy for cancer and angiogenic diseases.

Cyclooxygenase inhibitors--current status and future prospects

Prostaglandins are formed from arachidonic acid by the action of cyclooxygenase and subsequent downstream synthetases. Two closely related forms of the cyclooxygenase have been identified which are now known as COX-1 and COX-2. Both isoenzymes transform arachidonic acid to prostaglandins, but differ in their distribution and their physiological roles. Meanwhile, the responsible genes and their regulation have been clarified. COX-1, the pre-dominantly constitutive form of the enzyme, is expressed throughout the body and performs a number of homeostatic functions such as maintaining normal gastric mucosa and influencing renal blood flow and platelet aggregation. In contrast, the inducible form is expressed in response to inflammatory and other physiological stimuli and growth factors, and is involved in the production of the prostaglandins that mediate pain and support the inflammatory process. All the classic NSAIDs inhibit both COX-1 and COX-2 at standard anti-inflammatory doses. The beneficial anti-inflammatory and analgesic effects are based on the inhibition of COX-2, but the gastrointestinal toxicity and the mild bleeding diathesis are a result of the concurrent inhibition of COX-1. Agents that inhibit COX-2 while sparing COX-1 represent a new attractive therapeutic development and could represent a major advance in the treatment of rheumatoid arthritis and osteoarthritis. Apart from its involvement in inflammatory processes, COX-2 seems to play a role in angiogenesis, colon cancer and Alzheimer's disease, based on the fact that it is expressed during these diseases. The benefits of specific and selective COX-2 inhibitors are currently under discussion and offer a new perspective for a further use of COX-2 inhibitors.

Cyclooxygenase 2 and the kidney

Cyclooxygenase metabolizes arachidonic acid to a family of bioactive fatty acids designated prostaglandins. Two isoforms of cyclooxygenase exist, designated COX1 and COX2. These isoforms are expressed in distinct but important areas of the kidney. COX1 predominates in vascular smooth muscle and collecting ducts, whereas COX2 predominates in the macula densa and nearby cells in the cortical thick ascending limb. COX2 is also highly expressed in medullary interstitial cells. Whereas COX1 expression does not exhibit dynamic regulation, COX2 expression is subject to regulation by several environmental conditions, including salt intake, water intake, medullary tonicity, growth factors, cytokines, and adrenal steroids. Recently, COX2-selective non-steroidal anti-inflammatory drugs have become widely available. Many of the renal effects of non-selective non-steroidal anti-inflammatory drugs (including sodium retention, decreased glomerular filtration rate, and effects on renin-angiotensin levels) appear to be mediated by the inhibition of COX2 rather than COX1. Therefore, in contrast to the gastrointestinal-sparing effects of COX2-selective non-steroidal anti-inflammatory drugs, when considering the kidney, the same caution must be applied when using COX2-selective inhibitors as has been used with traditional non-selective non-steroidal anti-inflammatory drugs.

NSAIDs inhibit the activation of egr-1 gene in microvascular endothelial cells. A key to inhibition of angiogenesis?

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin (IND), ibuprofen and newer cyclooxygenase-2 selective NSAIDs (e.g. celecoxib) delay gastric ulcer healing partly through the inhibition of angiogenesis, but the molecular mechanisms involved are not fully elucidated. Effective angiogenesis is required for ulcer healing to supply oxygen and nutrients to the healing site. The early growth response factor (Egr-1) is a transcription factor, which is rapidly activated by a variety of extracellular signals or tissue injury and is important for angiogenesis to occur. This study aimed to determine whether indomethacin (IND) and/or the selective COX-2 inhibitor, NS-398, interfere with egr-1 gene expression in human microvascular endothelial cells (HMVEC) in response to vascular endothelial growth factor (VEGF) stimulation. HMVEC were treated with 0.5 mM IND or 100 microM NS-398 for 16 h, and then VEGF (10 ng/ml) or vehicle was added. Egr-1 mRNA and protein expression levels were determined by RT-PCR and Western-blotting, respectively. VEGF treatment caused a significant elevation of Egr-1 mRNA (261+/-21%, P<0.001) and protein expression (174+/-15%, P<0.01) vs. vehicle. IND pre-treatment significantly inhibited VEGF-induced Egr-1 mRNA expression by 29+/-4% (P<0.01) and protein expression by 41+/-8% (P<0.05). NS-398 inhibited VEGF-induced Egr-1 mRNA and protein expression by 23+/-3% and 35+/-4%, respectively (both P<0.01). Since transcriptional activation of egr-1 is responsible for expression of proteins involved in proliferation of endothelial cells essential for angiogenesis, these results provide a new mechanism for NSAIDs' interference with angiogenesis.

Regeneration of gastric mucosa during ulcer healing is triggered by growth factors and signal transduction pathways

An ulcer is a deep necrotic lesion penetrating through the entire thickness of the gastrointestinal mucosa and muscularis mucosae. Ulcer healing is a complex and tightly regulated process of filling the mucosal defect with proliferating and migrating epithelial and connective tissue cells. This process includes the re-establishment of the continuous surface epithelial layer, glandular epithelial structures, microvessels and connective tissue within the scar. Epithelial cells in the mucosa of the ulcer margin proliferate and migrate onto the granulation tissue to re-epithelialize the ulcer. Growth factors, such as epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), trefoil peptides (TP), platelet derived growth factor (PDGF) and other cytokines produced locally by regenerating cells, control re-epithelialization and the reconstruction of glandular structures. These growth factors, most notably EGF, trigger epithelial cell proliferation via signal transduction pathways involving EGF-R- MAP (Erk1/Erk2) kinases. Granulation tissue, which develops at the ulcer base, consists of fibroblasts, macrophages and proliferating endothelial cells, which form microvessels under the control of angiogenic growth factors. These growth factors [bFGF, vascular endothelial growth factor (VEGF) and angiopoietins] promote angiogenesis--capillary vessel formation--thereby allowing for the reconstruction of microvasculature in the mucosal scar, which is essential for delivery of oxygen and nutrients to the healing site. The primary trigger to activate expression of angiogenic growth factors and their receptors appears to be hypoxia. During ulcer healing expression of growth factor genes is tightly regulated in a temporally and spatially ordered manner.

Up-regulation of cyclooxygenase-1 and -2 in human gastric ulcer

BACKGROUND

The expression of cyclooxygenase (COX) in human gastric ulcers is unknown.

AIM

To study the expression and cellular localization of cyclooxygenase in human gastric ulcers.

METHODS

A total of 38 surgical gastric ulcer specimens were studied; 20 were Helicobacter pylori-positive and 18 were associated with NSAID use. Twenty non-ulcerated, histologically normal gastric specimens were used as controls. The cellular localization of COX-1 and COX-2 were determined by immunohistochemistry and double immunofluorescence. Cyclooxygenase messenger RNA (mRNA) was measured by reverse transcription-polymerase chain reaction and localized by in situ hybridization.

RESULTS

In control specimens, COX-1 was detected in stromal cells in the lamina propria. There was focal and weak immunostaining for COX-2 in the foveolar epithelium. At the ulcer edge, COX-1 was significantly increased in lamina propria cells whereas COX-2 was strongly expressed in the hyperplastic foveolar epithelium in H. pylori- and non-steroidal anti-inflammatory drugs (NSAID)-associated ulcers. At the ulcer base, there was strong expression of COX-1 and COX-2 in myofibroblasts, macrophages and endothelial cells in the granulation tissue, irrespective of H. pylori status or NSAID use. Messenger RNA of COX-1 and COX-2 were demonstrated by reverse transcription-polymerase chain reaction. Double immunofluorescence and in situ hybridization confirmed the cellular localization of cyclooxygenase at protein and mRNA levels, respectively.

CONCLUSION

Both COX-1 and COX-2 are up-regulated in human gastric ulcers.

Cyclooxygenase-2 pathway correlates with VEGF expression in head and neck cancer. Implications for tumor angiogenesis and metastasis

We evaluated the role of COX-2 pathway in 35 head and neck cancers (HNCs) by analyzing COX-2 expression and prostaglandin E2 (PGE2) production in relation to tumor angiogenesis and lymph node metastasis. COX-2 activity was also correlated to vascular endothelial growth factor (VEGF) mRNA and protein expression. COX-2 mRNA and protein expression was higher in tumor samples than in normal mucosa. PGE2 levels were higher in the tumor front zone in comparison with tumor core and normal mucosa (P<.0001). Specimens from patients with lymph node metastasis exhibited higher COX-2 protein expression (P=.0074), PGE2 levels (P=.0011) and microvessel density (P<.0001) than specimens from patients without metastasis. A significant correlation between COX-2 and tumor vascularization (r(s)=0.450, P=.007) as well as between COX-2 and microvessel density with VEGF expression in tumor tissues was found (r(s)=0.450, P=.007; r(s)=0.620, P=.0001, respectively). The induction of COX-2 mRNA and PGE2 synthesis by EGF and Escherichia coli lipopolysaccharide (LPS) in A-431 and SCC-9 cell lines, resulted in an increase in VEGF mRNA and protein production. Indomethacin and celecoxib reversed the EGF- and LPS-dependent COX-2, VEGF, and PGE2 increases. This study suggests a central role of COX-2 pathway in HNC angiogenesis by modulating VEGF production and indicates that COX-2 inhibitors may be useful in HNC treatment.

Nonsteroidal anti-inflammatory drug gastropathy at the new millennium: mechanisms and prevention

OBJECTIVES

Nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal (GI) toxicity remains the most frequent adverse drug event in the United States. The objective of this review is to update clinicians in recent advances in basic and clinical investigation regarding the pathogenesis and management of NSAID gastropathy.

METHODS

Based upon an extensive review of the published literature and abstracts of key work within the past decade, the framework for new approaches to the prevention and treatment of NSAID-associated ulceration is summarized.

RESULTS

The pathophysiology of NSAID-induced injury to the GI tract is multifaceted and includes both prostaglandin-dependent and independent components. The pharmaceutical industry has capitalized on the identification of two different isoforms of cyclooxygenase, enabling the development of specific inhibitors of one isoform that minimizes prostaglandin-dependent mechanisms that contribute to NSAID-induced injury. Clinical trials support the efficacy and reduced toxicity of these agents. Because acid exacerbates the injury initiated by NSAIDs, potent acid suppressive therapy, typically with proton pump inhibitors, is another common approach to the treatment of NSAID-related dyspepsia as well as NSAID-induced ulcer disease.

CONCLUSIONS

Recent improvements in the understanding of NSAID-induced damage and new drug development have provided the opportunity for effective anti-inflammatory therapy with reduced GI toxicity. This illustrates the importance of identifying patients at risk for potential complications and the appropriate use of strategies to prevent and treat NSAID-induced complications.

Sulindac inhibits neointimal formation after arterial injury in wild-type and apolipoprotein E-deficient mice

Neointimal hyperplasia is a critical component of restenosis, a major complication of angioplasty and related therapeutic procedures. We studied the effects of hyperlipidemia and the nonsteroidal anti-inflammatory drugs, aspirin (acetyl-salicylic acid; ASA), and sulindac, on neointimal formation in a mouse femoral arterial injury model. At 2 months of age, normolipidemic, wild-type (WT), and hyperlipidemic, apolipoprotein E-deficient (apoE-/-) mice were divided into three treatment groups: Western-type diet (WD), WD + ASA (200 mg/kg food), and WD + sulindac (300 mg/kg food). After 1 week, mice underwent arterial injury and treatments were maintained for 4 weeks. Histomorphometry of the injured arteries showed striking effects of plasma cholesterol levels and drug treatment on neointimal hyperplasia. In the WD or WD + ASA groups, apoE-/- mice had twice the neointimal area than WT mice ( approximately 30,000 vs. 13,000 microm(2) per section; P < 0.0001). Compared with ASA or WD alone, sulindac treatment resulted in approximately 70% (P = 0.0001) and 50% (P = 0.01) reductions in the neointimal area in apoE-/- and WT mice, respectively. ASA, at a dose sufficient to inhibit platelet aggregation, did not affect neointimal formation in mice of either genotype. Evidence of macrophages was noted in the lesions of apoE-/- mice in the WD and WD + ASA groups, but remarkably, none was detectable with sulindac treatment, despite hyperlipidemia, suggesting early steps in the response to injury were abrogated. These results demonstrate sulindac reduces neointimal formation in both normolipidemic and hyperlipidemic settings and raise the possibility that similar benefits may be obtained in patients undergoing angioplasty and related procedures.

New insights into physiological and pathophysiological functions of cyclo-oxygenase-2

During the past few years specific inhibitors of the cyclo-oxygenase-2 enzyme have emerged as important pharmacological tools for treatment of patients with rheumatoid arthritis or osteoarthritis. In comparison to traditional nonsteroidal anti-inflammatory drugs, specific cyclo-oxygenase-2 inhibitors may provide equal efficacy in terms of antiinflammatory and analgesic action, with significantly fewer gastrointestinal side effects. Although cyclo-oxygenase-2 was once regarded as a source of pathological prostanoids, recent studies have indicated that this isoenzyme also fulfills a variety of physiological functions within the organism. The present review assesses recent advances in cyclo-oxygenase-2 research, with particular emphasis on new insights into the biology of this isoenzyme.

Clinical trials in coronary angiogenesis: issues, problems, consensus: An expert panel summary

The rapid development of angiogenic growth factor therapy for patients with advanced ischemic heart disease over the last 5 years offers hope of a new treatment strategy based on generation of new blood supply in the diseased heart. However, as the field of therapeutic coronary angiogenesis is maturing from basic and preclinical investigations to clinical trials, many new and presently unresolved issues are coming into focus. These include in-depth understanding of the biology of angiogenesis, selection of appropriate patient populations for clinical trials, choice of therapeutic end points and means of their assessment, choice of therapeutic strategy (gene versus protein delivery), route of administration, and the side effect profile. The present article presents a summary statement of a panel of experts actively working in the field, convened by the Angiogenesis Foundation and the Angiogenesis Research Center during the 72nd meeting of the American Heart Association to define and achieve a consensus on the challenges facing development of therapeutic angiogenesis for coronary disease.

Angiogenesis in inflammatory joint disease: a target for therapeutic intervention

The evidence reviewed here clearly supports the concept that pathological angiogenesis is an important component in inflammatory joint erosion. Of the primary angiogenic factors, VEGF-A is clearly a key participant in this mechanism and a range of anti-VEGF strategies is being developed to neutralize its biological function [54,55]. Currently available drugs are also being screened for VEGF antagonistic effects. In a study of the effects of existing disease-modifying anti-rheumatic drugs on cultured synovial cells, bucillamine and dexamethasone showed significant inhibition of VEGF production [56]. In addition, COX-1 and COX-2 non-steroidal anti-inflammatory drugs have been shown to inhibit angiogenesis by blocking VEGF-induced signal transduction [57]. Modulation of the immune network in RA using TNF-α antagonists is producing promising results, but as outlined in this review, this treatment on its own is unlikely to control joint angiogenesis. It is possible that combination therapy, e.g. TNF-α antagonist and a VEGF signal transduction inhibitor, will be more effective by using antagonists that block different but key control points in the disease pathology.

Cyclooxygenase-2 expression in Helicobacter pylori-associated premalignant and malignant gastric lesions

Expression of cyclooxygenase-2 (COX-2) in various stages of the Helicobacter pylori-associated gastric carcinogenesis pathway has not been elucidated. We investigated the distribution and intensity of COX-2 expression in premalignant and malignant gastric lesions, and monitored the changes after H. pylori eradication. Gastric biopsies from H. pylori-infected patients with chronic active gastritis, gastric atrophy, intestinal metaplasia (IM), gastric adenocarcinoma, and noninfected controls were studied. Expression of COX-2 was evaluated by immunohistochemistry and in situ hybridization. Endoscopic biopsies were repeated 1 year after successful eradication of H. pylori in a group of IM patients for comparing COX-2 expression and progression of IM. In all H. pylori-infected patients, COX-2 expression was predominantly found in the foveolar and glandular epithelium and, to a lesser extent, in the lamina propria. In the noninfected group, only 35% of cases demonstrated weak COX-2 expression. Intensity of COX-2 was not significantly different between the chronic active gastritis, gastric atrophy, IM, and gastric adenocarcinoma groups. In 17 patients with IM, COX-2 expressions in the epithelial cells and stromal cells were reduced 1 year after H. pylori eradication. However, the changes in COX-2 expression did not correlate with progression/regression of IM. Both premalignant and malignant gastric lesions demonstrate strong COX-2 expression. Successful eradication of H. pylori leads to down-regulation of COX-2 expression but failed to reverse IM at 1 year.

Radiation induces upregulation of cyclooxygenase-2 (COX-2) protein in PC-3 cells

PURPOSE

To investigate the impact of gamma-irradiation on cyclooxygenase-2 (COX-2) expression and its enzymatic activity in PC-3 cells. Cell cycle redistribution, viability, and apoptosis were quantitated in control and irradiated cells with or without the COX-2 inhibitor NS-398.

METHODS AND MATERIALS

Western blot analysis was used to assess COX-2 protein expression. Prostaglandin (PGE(2)) was measured after addition of arachidonic acid (AA) using a Monoclonal Immunoassay Kit. Cell cycle and apoptosis were assessed using flow cytometry.

RESULTS

We observed a dose-dependent increase in COX-2 of 37.0%, 79.7%, and 97.5% following irradiation with 5, 10, and 15 Gy, respectively. The PGE(2) level of irradiated cells was higher than in controls (1512 +/- 157.5 vs. 973.7 +/- 54.2 rhog PGE(2)/mL; p < 0.005, n = 4) while cells irradiated in the presence of NS-398 had reduced PGE(2) levels (218.8 +/- 80.1 rhog PGE(2)/mL; p < 0.005; n = 4). We found no differences in cell cycle distribution or apoptosis between cells irradiated in the presence or absence of NS-398.

CONCLUSIONS

COX-2 protein is upregulated and enzymatically active after irradiation, resulting in elevated levels of PGE(2). This effect can be suppressed by NS-398, which has clinical implications for therapies combining COX-2 inhibitors with radiation therapy.

Barrett's mucosa: remodelling by the microenvironment

Barrett's metaplasia and the associated adenocarcinoma are composed not only of epithelial cells, but also of inflammatory cells and endothelial cells in the lamina propria and around the tumour, respectively. The early incidence of vascular invasion and metastasis is a feature of Barrett's adenocarcinomas. A paper in this issue of The Journal of Pathology shows that vascular endothelial growth factor (VEGF) is expressed in both metaplastic cells and endothelial cells of pre-neoplastic Barrett's epithelium early in the development of neoplasia. It is becoming clearer that the harmful insults of acid and bile reflux alter not only the epithelium, but also the lamina propria. Cytokines such as tumour necrosis factor alpha (TNFalpha) or transforming growth factor (TGFalpha) are implicated in the formation of early Barrett's adenocarcinomas. From current knowledge it is possible to hypothesize that metaplastic cells, perhaps as a consequence of either TNFalpha or TGFalpha stimulation, secrete VEGF. VEGF can promote adjacent endothelial cell growth through phosphorylation of beta-catenin and vascular endothelial cadherin (VE-cadherin) in endothelial cells. In this de novo microenvironment, angiogenesis is therefore accelerated, enhancing the chance of microvascular invasion.

NSAID-induced gastric damage in rats: requirement for inhibition of both cyclooxygenase 1 and 2

BACKGROUND & AIMS

Selective cyclooxygenase (COX)-2 inhibitors produce less gastric damage than conventional nonsteroidal anti-inflammatory drugs (NSAIDs), suggesting that NSAIDs cause damage by inhibiting COX-1. We tested this hypothesis in rats by using a selective COX-1 inhibitor (SC-560).

METHODS

The effects of SC-560, celecoxib (selective COX-2 inhibitor), or a combination of both inhibitors on gastric damage and prostaglandin synthesis were determined. Selectivity of the drugs for COX-1 vs. COX-2 was assessed in the carrageenan-airpouch model. A COX-1-preferential inhibitor, ketorolac, was also evaluated. The effects of these inhibitors on leukocyte adherence to vascular endothelium and on gastric blood flow were assessed.

RESULTS

SC-560 markedly reduced gastric prostaglandin synthesis and platelet COX-1 activity, but spared COX-2 and did not cause gastric damage. Celecoxib did not affect gastric prostaglandin E(2) synthesis and did not cause gastric damage. However, the combination of SC-560 and celecoxib invariably caused hemorrhagic erosion formation, comparable to that seen with indomethacin. Ketorolac caused damage only at doses that inhibited both COX isoforms, or when given with a COX-2 inhibitor. Celecoxib, but not SC-560, significantly increased leukocyte adherence, whereas SC-560, but not celecoxib, reduced gastric blood flow.

CONCLUSIONS

Inhibition of both COX-1 and COX-2 is required for NSAID-induced gastric injury in the rat.

Palliative care in inflammatory bowel disease: an evidence-based approach

The management of the patient with inflammatory bowel disease (IBD) is challenging for both the physician and the patient. IBD imposes both a physical and emotional burden on patients' lives. Palliative care is important for IBD patients because it focuses on improving quality of life. While palliative care does not change the natural history of the disease, it provides relief from pain and other distressing symptoms. This article focuses on various aspects of care for IBD patients including pain control, management of oral and skin ulcerations, stomal problems in IBD patients, control of nausea and vomiting, management of chronic diarrhea and pruritus ani, evaluation of anemia, treatment of steroid-related bone disease, and treatment of psychological problems associated with IBD. Each of these areas is reviewed using an evidence-based approach. Evidence in category A refers to evidence from clinical trials that are randomized and well controlled. Category B Evidence refers to evidence from cohort or case-controlled studies. Category C is evidence from case reports or flawed clinical trials. Evidence from category D is limited to the clinical experience of the authors. Evidence labelled as category E refers to situations where there is insufficient evidence available to form an opinion. Algorithms for management of pain and nausea in IBD patients are presented.

Indomethacin inhibits endothelial cell proliferation by suppressing cell cycle proteins and PRB phosphorylation: a key to its antiangiogenic action?

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit angiogenesis in vivo and in vitro, but the mechanism of this action is unclear. Angiogenesis-formation of new capillary vessels-requires endothelial proliferation, migration, and tube formation. It is stimulated by basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). The cell cycle is regulated positively by cyclins and negatively by cyclin-dependent kinase inhibitors (CKI) and the retinoblastoma protein (pRb). Since the effects of NSAIDs on cell cycle-regulatory proteins in endothelial cells remain unknown, we examined the effect of indomethacin on bFGF-stimulated endothelial cell proliferation and on cell cycle regulatory proteins in rat primary aortic endothelial cells (RAEC). Indomethacin significantly inhibited basal and bFGF-stimulated endothelial cell proliferation. This inhibition correlated significantly with reduced cyclin D1 and increased p21 protein expression. Furthermore, indomethacin reduced pRb phosphorylation. These findings suggest that indomethacin arrests endothelial cell proliferation essential for angiogenesis by modulating cell cycle protein levels.

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.

Perioperative pain management

The management of perioperative pain starts with the use of approaches to minimize anxiety and distress before the procedure. The administration of analgesics or local anesthetics before the start of surgery reduces the nociceptive input occurring during the procedure and reduces the need for postoperative analgesics. As the animal recovers from anesthesia, it is important to administer analgesics to minimize the patient's experience of pain and to continue this therapy through at least the first 12 to 24 hours. Techniques that provide a continuous level of analgesia are more effective than those that allow the pain to return.

Host cyclooxygenase-2 modulates carcinoma growth

Cyclooxygenase-2 (COX-2; Ptgs2) acts as a tumor promoter in rodent models for colorectal cancer, but its precise role in carcinogenesis remains unclear. We evaluated the contribution of host-derived COX-1 and COX-2 in tumor growth using both genetic and pharmacological approaches. Lewis lung carcinoma (LLC) cells grow rapidly as solid tumors when implanted in C57BL/6 mice. We found that tumor growth was markedly attenuated in COX-2(-/-), but not COX-1(-/-) or wild-type mice. Treatment of wild-type C57BL/6 mice bearing LLC tumors with a selective COX-2 inhibitor also reduced tumor growth. A decrease in vascular density was observed in tumors grown in COX-2(-/-) mice when compared with those in wild-type mice. Because COX-2 is expressed in stromal fibroblasts of human and rodent colorectal carcinomas, we evaluated COX-2(-/-) mouse fibroblasts and found a 94% reduction in their ability to produce the proangiogenic factor, VEGF. Additionally, treatment of wild-type mouse fibroblasts with a selective COX-2 inhibitor reduced VEGF production by 92%.