Inhibitor Nimesulide Research Articles

COX‐2 inhibitors suppress integrin α5 expression in human lung carcinoma cells through activation of Erk: Involvement of Sp1 and AP‐1 sites

Tumor cell expression of COX-2 has been implicated in the progression of murine and human lung cancer. Inhibition of COX-2 by nonsteroidal antiinflammatory drugs reduces the risk of cancer development in humans and suppresses tumor growth in animal models. However, the underlying mechanisms for this beneficial effect are not fully understood. Here we explore the potential link between the anticancer effects of COX-2 inhibitors and the expression of the integrin alpha5beta1. Expression of this integrin in carcinoma cells is associated with invasiveness and malignant progression. This, together with our studies showing that fibronectin, the ligand of alpha5beta1, stimulates the growth of human lung carcinoma cells, and that this effect is mediated through alpha5beta1-dependent signals, has prompted us to examine the effects of COX-2 inhibitors on alpha5beta1 expression in human non small cell lung carcinoma (NSCLC) cells. We found that the selective COX-2 inhibitors NS398 and Nimesulide decreased mRNA expression and protein production of the integrin alpha5 subunit. This effect was associated with inhibition of NSCLC cell adhesion to fibronectin. The COX-2 inhibitors triggered the phosphorylation of extracellular signal-regulated kinase (Erk) in a time-dependent manner, and the inhibitor of Mek-1/Erk PD98095 prevented their inhibitory effects on integrin alpha5 expression. Transient transfection assays showed that the COX-2 inhibitors affected integrin alpha5 gene transcription by acting between -92 to -41 bp of the human integrin alpha5 gene promoter. Gel mobility shift assays showed that the COX-2 inhibitors increased Sp1 DNA binding, but decreased that of AP-1. These effects were accompanied by an increase in Sp1 protein and a decrease in c-Jun protein expression, as well as inhibition of SAPK/JNK phosphorylation. The Sp1 inhibitor, Mithramycin A, also blocked the inhibitory effect of the COX-2 inhibitors on alpha5 expression and promoter activity. Overall, these findings suggest that COX-2 inhibitors suppress alpha5beta1 integrin expression in NSCLC through effects on integrin alpha5 gene transcription mediated by Erk activation, increased Sp1, decreased AP-1 DNA binding and inactivation of SAPK/JNK signals. Our observations unveil a new mechanism of action against NSCLC for COX-2 inhibitors that relates to regulation of integrin alpha5 gene expression and, consequently, recognition of extracellular matrices (i.e., fibronectin) by tumor cells. (c) 2005 Wiley-Liss, Inc.

Effects of the cyclooxygenase-2 inhibitor nimesulide on cerebral infarction and neurological deficits induced by permanent middle cerebral artery occlusion in the rat

BackgroundPrevious studies suggest that the cyclooxygenase-2 (COX-2) inhibitor nimesulide has a remarkable protective effect against different types of brain injury including ischemia. Since there are no reports on the effects of nimesulide on permanent ischemic stroke and because most cases of human stroke are caused by permanent occlusion of cerebral arteries, the present study was conducted to assess the neuroprotective efficacy of nimesulide on the cerebral infarction and neurological deficits induced by permanent middle cerebral artery occlusion (pMCAO) in the rat.MethodsIschemia was induced by permanent occlusion of the middle cerebral artery in rats, via surgical insertion of a nylon filament into the internal carotid artery. Infarct volumes (cortical, subcortical and total) and functional recovery, assessed by neurological score evaluation and rotarod performance test, were performed 24 h after pMCAO. In initial experiments, different doses of nimesulide (3, 6 and 12 mg/kg; i.p) or vehicle were administered 30 min before pMCAO and again at 6, 12 and 18 h after stroke. In later experiments we investigated the therapeutic time window of protection of nimesulide by delaying its first administration 0.5–4 h after the ischemic insult.ResultsRepeated treatments with nimesulide dose-dependently reduced cortical, subcortical and total infarct volumes as well as the neurological deficits and motor impairment resulting from permanent ischemic stroke, but only the administration of the highest dose (12 mg/kg) was able to significantly (P < 0.01) diminish infarct volume. The lower doses failed to significantly reduce infarction but showed a beneficial effect on neurological function. Nimesulide (12 mg/kg) not only reduced infarct volume but also enhanced functional recovery when the first treatment was given up to 2 h after stroke.ConclusionsThese data show that nimesulide protects against permanent focal cerebral ischemia, even with a 2 h post-treatment delay. These findings have important implications for the therapeutic potential of using COX-2 inhibitors in the treatment of stroke.

The Selective Cyclooxygenase-2 Inhibitor Nimesulide Prevents Helicobacter pylori -Associated Gastric Cancer Development in a Mouse Model

Helicobacter pylori infection can lead to gastric cancer, and cyclooxygenase-2 (COX-2) is overexpressed in the stomach during H. pylori infection. Therefore, we investigated whether nonsteroidal anti-inflammatory drugs might protect against this form of cancer. Specifically, we examined the chemopreventive effect of the COX-2 inhibitor nimesulide on H. pylori-associated gastric carcinogenesis in mice. C57BL/6 mice were treated with the carcinogen N-methyl-N-nitrosourea (MNU) and/or H. pylori. To determine the effect of COX-2 inhibition, nimesulide was mixed with feed pellets and administered for the duration of the experiment. All of the mice were sacrificed 50 weeks after the start of the experiment. Histopathology, immunohistochemistry, and Western blotting for COX-2, Bax and Bcl-2 were performed in stomach tissues. In vitro experiments with the human gastric cancer cell line AGS were also performed to identify mechanisms underlying cancer chemoprevention by nimesulide. Gastric tumors developed in 68.8% of mice that were given both MNU and H. pylori, whereas less than 10% developed gastric tumors when given either MNU or H. pylori alone. These findings indicate that H. pylori promotes carcinogen-induced gastric tumorigenesis. In mice treated with both MNU and H. pylori, nimesulide administration substantially reduced H. pylori-associated gastric tumorigenesis, whereas substantial inductions of apoptosis were observed. In vitro studies demonstrated that nimesulide and H. pylori when combined acted synergistically to induce more apoptosis than either alone. Our data show that nimesulide prevents H. pylori-associated gastric carcinogenesis, and suggest that COX-2 may be a target for chemoprevention of gastric cancer.

Docking studies on NSAID/COX-2 isozyme complexes using Contact Statistics analysis

The selective inhibition of COX-2 isozymes should lead to a new generation of NSAIDs with significantly reduced side effects; e.g. celecoxib (Celebrex) and rofecoxib (Vioxx). To obtain inhibitors with higher selectivity it has become essential to gain additional insight into the details of the interactions between COX isozymes-and NSAIDs. Although X-ray structures of COX-2 complexed with a small number of ligands are available, experimental data are missing for two well-known selective COX-2 inhibitors (rofecoxib and nimesulide) and docking results reported are controversial. We use a combination of a traditional docking procedure with a new computational tool (Contact Statistics analysis) that identifies the best orientation among a number of solutions to shed some light on this topic.

Cyclooxygenase-2 is a possible target of treatment approach in conjunction with photodynamic therapy for various disorders in skin and oral cavity.

Anti-cancer effects of cyclooxygenase (COX)-2 inhibitors have been reported, but not fully investigated in skin and oral diseases. 5-aminolaevulinic acid (ALA)-based photodynamic therapy (PDT) for treating those patients with skin and oral lesions is a highly sophisticated procedure, but the incidence of disease recurrence after treatment is rather significant. To confirm that COX-2 could be a molecular target in adjunctive therapy to ALA-based PDT, we investigated (i) COX-2 expression in various skin and oral diseases, and (ii) the inhibitory effects on cellular growth of COX-2 selective inhibitor (nimesulide), ALA-based PDT and their combination on human oral squamous cell carcinoma (SCC) cell lines. A total of 129 biopsy samples from the skin and oral mucosal lesions were tested immunohistochemically for COX-2 expression. Then the in vitro effects of nimesulide, ALA-based PDT, and their combination were determined on two SCC cell lines, HSC-2 and HSC-4. Three different methods (MTT assay, double-staining for annexin V and propidium iodide, caspase-3/CPP32 fluorometric protease assay) were applied for evaluation of their inhibitory effects on these two cell lines. Among the skin diseases, a considerable number of COX-2 high expressers were found in actinic keratosis (15 of 25, 60%), Bowen's disease (13 of 17, 76%) and extramammary Paget's disease (15 of 15, 100%). In contrast, only one of 33 (3%) basal cell carcinoma tumours was a COX-2 high expresser. Among the oral mucosal biopsies, the proportion of COX-2 high expressers increased gradually from hyperplasia (one of six, 17%) through mild dysplasia (five of eight, 63%) and moderate dysplasia (20 of 23, 87%) to severe dysplasia (two of two, 100%). Nimesulide had an inhibitory effect in vitro on HSC-2 (proven to be a COX-2 high expresser), but not on HSC-4 (a COX-2 non-expresser). While ALA-based PDT showed an inhibitory effect on both HSC-2 and HSC-4, most importantly the combination of nimesulide and ALA-based PDT demonstrated a significant synergistic effect on the cellular growth inhibition of only HSC-2, but not of HSC-4. Our study strongly suggests that COX-2 can be one of the molecular targets in treating various skin and oral diseases. The results from our in vitro experiments also prompt us to develop a new protocol with a combination of COX-2 selective inhibitor and ALA-based PDT for more effective treatment of those diseases.

P01.32: Haemodynamically significant ductal constriction in the 3rd trimester fetus following maternal self‐medication with the COX‐2 selective inhibitor nimesulide

Results: DC was detected in 19 cases (0.3%) and premature closure of FO in 2 (0.03%). Two fetuses with DC presented with ascites and polyhydramnion. In two cases DC coexisted with CALM. Once there was DC of one of the twins. DC was present at mean 33 wks of gestation. In 12 cases there was maternal pharmacotherapy. Abnormal DC was present at the mean on 3rd day of pharmacotherapy. In addition to DC there were also other abnormalities: myocardial hypertrophy, tricuspid valve regurgitation, pulmonary regurgitation, pericardial effusion, or disproportion. Two fetuses presented arrhythmias. Mean 25 days after DC there was or vaginal delivery (10×) or CS (9×). Mean birth weight was 3074, mediana of Apgar score-9. There was 17 survivors. In neonatal echo in all cases still right ventricular hypertrophy was present with no clinical adverse outcome. During the same period 2 cases of premature closure of FO were observed. The first one presented with ascites at 28 wks of gestation and died in utero. The second one presented with acute cardiomegaly, disproportion, right ventricular wall hypokinesis and tricuspid valve regurgitation, had emergency CS at 35 wks of gestation. This baby was discharged home at 15th day of life with no clinical symptoms. Conclusions: 1. Premature DC usually caused by maternal pharmacotherapy with transient myocardial hypertrophy, TR, disproportion, but without cardiomegaly and this anomaly was reversible during fetal life. 2. Premature closure of foramen ovale was very rare phenomenon presented with acute cardiomegaly, right ventricle dyskinesis, TR and should prompt to emergency CS.

Cyclooxygenase-2 inhibitor nimesulide suppresses telomerase activity by blocking Akt/PKB activation in gastric cancer cell line.

Nonsteroidal antiinflammatory drugs (NSAIDs) have been reported to have antiproliferative effects in neoplastic cells of different origin during the past few decades. We aimed to study the effects of the selective COX-2 inhibitor, nimesulide, on cell viability and telomerase and Akt/PKB activity in the human gastric cancer cell line MKN-45 and to explore the molecular mechanism for the antitumor activity of the selective COX-2 inhibitor. We tested the influence of nimesulide on the gastric cancer cell line MKN-45 in vitro. Trypan blue exclusion was used to determine the cell viability after incubation for 0, 12, 24, and 48 hr in different concentrations of nimesulide 0, 25, 50, 100, 200 microM). After treatment or no treatment with 100 microM nimesulide for 0, 12, 24, or 48 hr in the presence or absence of 300 nM okadaic acid for 2 hr, telomerase and Akt/PKB activity was measured using TRAP PCR-ELISA and nonradioactive IP kinase assays, respectively. In the gastric cancer cell line MKN-45 nimesulide caused a time- and dose-dependent reduction in cell numbers and significantly inhibited telomerase and Akt/PKB activity; the inhibition of telomerase activity was partly associated with the attenuation of Akt/PKB activity. These results demonstrate that the selective COX-2 inhibitor suppresses the telomerase activity of gastric cancer cells, in part by blocking the activation of protein kinase B, which provides a new signaling mechanism responsible for the anticancer effects of the selective COX-2 inhibitor.

The role of cyclooxygenase inhibition in the effect of α-melanocyte-stimulating hormone on reactive oxygen species production by rat peritoneal neutrophils

The effect of α-MSH on reactive oxygen species (ROS) production by rat peritoneal neutrophils and the effect of cyclooxygenase (COX) inhibition were investigated using the chemiluminescence (CL) technique. Cells were obtained by peritoneal lavage 4 h after administration of oyster glycogen to rats and were stimulated with lipopolysaccharide (LPS) from Salmonella enderitidis and phorbol 12-myristate 13-acetate (PMA). The increasing concentrations of α-MSH (10 –12–10 –6 M) were added to stimulated cells alone or along with the COX inhibitors indomethacin, ketorolac or nimesulide (10 −8–10 −5 M). Luminol and lucigenin CL levels were significantly increased in cells stimulated with LPS and PMA compared to unstimulated ones. α-MSH significantly reduced lucigenin CL values and this effect was completely reversed in the presence of indomethacin (10 −8 and 10 −7 M). In conclusion, α-MSH inhibits the production of superoxide radicals by activated rat peritoneal neutrophils and COX contributes to this effect.

Spinal Prostaglandin Formation and Pain Perception Following Thoracotomy: A Role for Cyclooxygenase-2

Prostaglandins (PGs) generated in the spinal cord may play a major role in pain perception. Consequently, the suppression of spinal cyclooxygenase (COX) and PG formation may contribute to the analgesic effect of nonsteroidal anti-inflammatory drugs (NSAIDs) in pain following surgery. Which isoform of COX is responsible for postsurgical pain and, consequently, should be targeted, is unclear. Prospective randomized blinded study. University teaching hospital. Thirty patients undergoing thoracotomy for lobectomy were recruited. Patients were randomized to receive the COX-2 selective inhibitor nimesulide, 100 mg orally twice daily, or ibuprofen (nonselective), 400 mg orally three times daily, in an open-label study. In addition, there was a randomized control group that received no NSAIDs. Cerebrospinal fluid (CSF) was analyzed for 6-keto-PGF(1)alpha, the principle metabolite of prostacyclin. COX-1 and COX-2 activity was determined by measuring serum thromboxane (TX) B(2) and endotoxin-induced PGE(2) generation in whole blood. Pain perception was measured by visual analog scores, and blinded assessment of opioid analgesic requirements and expiratory peak flow measurements were performed. At the doses used, nimesulide was selective for COX-2, while ibuprofen was nonselective based on serum TXB(2) levels. The mean (+/- SEM) levels of 6-keto-PGF(1)alpha in CSF increased following surgery from 32 +/- 4.9 to 127 +/- 29 pg/mL (p < 0.001), and this was suppressed by nimesulide (49 +/- 9.3 pg/mL; p = 0.0025) but not by ibuprofen (122 +/- 35 pg/mL). Pain scores (p < 0.001), morphine requirement (p = 0.0175), and the fall in peak expiratory flow rate (p < 0.001) were significantly lower in the nimesulide group. Increases in spinal PG synthesis after thoracotomy are repressed by a selective COX-2 inhibitor. This suggests that the inducible COX-2 mediates central PG synthesis, which may be important in the generation of pain, as the use of nimesulide also resulted in significant decreases in postoperative pain perception.

Regulatory role of vHL/HIF-1α in hypoxia-induced VEGF production in hepatic stellate cells

Activated hepatic stellate cells (HSCs) produce cyclooxygenase-2 (COX-2) protein to induce vascular endothelial growth factor (VEGF) production that participates in angiogenesis in injured liver. To reveal the unknown regulatory mechanism, we used hypoxic atmosphere mimicking injured-tissue microenvironment to induce VEGF expression in a rat hepatic stellate cell line (T6-HSCs). The present study showed that hypoxia up-regulated the protein levels of COX-2 and hypoxia-inducible factor-1-α (HIF-1α), but rapidly effected degradation of von Hippel–Lindau (vHL) protein. As a result, expression of VEGF in HSCs was markedly elevated; and pretreatment with COX-2 inhibitors (nimesulide or indomethacin) could significantly ameliorate the angiogenic event. Collectively, hypoxic HSCs increased accumulation of HIF-1α protein and induced VEGF expression in a time-dependent manner. Inhibition of COX-2 activities would prevent vHL protein from degradation and suppress HIF-1α up-regulation. Thus, vHL/HIF-1α has a regulatory role in COX-2-mediated VEGF production in hypoxic stellate cells in injured liver.

Wide therapeutic time window for nimesulide neuroprotection in a model of transient focal cerebral ischemia in the rat

Results from several studies indicate that cyclooxygenase-2 (COX-2) is involved in ischemic brain injury. The purpose of this study was to evaluate the neuroprotective effects of the selective COX-2 inhibitor nimesulide on cerebral infarction and neurological deficits in a standardized model of transient focal cerebral ischemia in rats. Three doses of nimesulide (3, 6 and 12 mg/kg; i.p.) or vehicle were administered immediately after stroke and additional doses were given at 6, 12, 24, 36 and 48 h after ischemia. In other set of experiments, the effect of nimesulide was studied in a situation in which its first administration was delayed for 3–24 h after ischemia. Total, cortical and subcortical infarct volumes and functional outcome (assessed by neurological deficit score and rotarod performance) were determined 3 days after ischemia. The effect of nimesulide on prostaglandin E 2 (PGE 2) levels in the injured brain was also investigated. Nimesulide dose-dependently reduced infarct volume and improved functional recovery when compared to vehicle. Of interest is the finding that neuroprotection conferred by nimesulide (reduction of infarct size and neurological deficits and improvement of rotarod performance) was also observed when treatment was delayed until 24 h after ischemia. Further, administration of nimesulide in a delayed treatment paradigm completely abolished PGE 2 accumulation in the postischemic brain, suggesting that COX-2 inhibition is a promising therapeutic strategy for cerebral ischemia to target the late-occurring inflammatory events which amplify initial damage.

The effects of nimesulide combined with cisplatin on lung cancer.

To study the effects of cyclooxygenase 2 selective inhibitor Nimesulide (NIM) combined with Cisplatin (DDP) on human lung cancer and the possible mechanisms, the proliferation and apoptosis of human lung cancer cell line A549 were evaluated by MTT reduction assay and flow cytometry respectively. The inhibitory effect on neoplasia in vivo was tested on nude mice subcutaneously implanted tumor. Our results showed that NIM and DDP could inhibit A549 cell proliferation in a concentration-dependent pattern; this action was enhanced when NIM (25 micromol/L) was given in combination with DDP and they worked in a synergistic or additive pattern as DDP concentration > or = 1 microg/ml. NIM and DDP could induce A549 cells apoptosis and the action was augmented when used in combination (P<0.01). NIM and DDP could inhibit the growth of subcutaneously implanted tumors on nude mice (P<0.05, P<0.01) and the inhibitory rate of NIM combined with DDP was significantly higher than that of NIM or DDP group (P<0.01, P<0.01). It is concluded that combined use of NIM and DDP has significant synergistic antitumor effects on lung cancer cell line A549 and in animals in vivo. The synergy may be achieved by growth inhibition and apoptosis induction.

Optimal suppression of thromboxane a2formation by aspirin during percutaneous transluminal coronary angioplasty: no additional effect of a selective cyclooxygenase-2 inhibitor

ObjectivesWe examined the contribution of cyclooxygenase (COX)-1 and -2 to the generation of prostacyclin, thromboxane (Tx) A2, and 8-epi prostaglandin (PG) F2αduring percutaneous transluminal coronary angioplasty (PTCA). BackgroundBoth TxA2and 8-epi PGF2αactivate platelets and are mitogenic, whereas prostacyclin is a platelet inhibitor, and therefore may influence the outcome of PTCA. MethodsTwenty-one patients undergoing PTCA while receiving aspirin 300 mg daily or aspirin plus the selective COX-2 inhibitor nimesulide were compared with 13 patients treated only with fradafiban, a glycoprotein IIb/IIIa antagonist. Urine was analyzed for the metabolites of TxA2(Tx-M) and prostacyclin (PGI-M) and for the isoprostane, 8-epi PGF2α. ResultsIn the fradafiban group, there was a marked increase in Tx-M during PTCA (mean, 1,973; 95% confidence interval [CI] 112 to 3,834 rising to mean 7,645; 95% CI 2,009 to 13,281 pg/mg creatinine, p = 0.018). The Tx-M excretion was similarly reduced by aspirin and the combination of aspirin and nimesulide. In contrast, the combination of nimesulide and aspirin inhibited PGI-M excretion to a greater extent than aspirin (p = 0.001). Urinary 8-epi PGF2αexcretion was elevated following PTCA compared with normal subjects (p = 0.002) and appeared to be unaffected by any of the treatments. ConclusionsThe increase in TxA2during PTCA is primarily COX-1 dependent, and aspirin alone is effective in suppressing its formation. In contrast, prostacyclin generation is both COX-1 and COX-2 dependent. The inhibition of COX-1 and COX-2 did not prevent the production of 8-epi PGF2α, suggesting that this is not enzymatically derived. The persistent generation of 8-epi PGF2αmay contribute to the thrombosis and restenosis that complicate PTCA.

Modulatory Effect of Cyclooxygenase Inhibitors on Sildenafil-Induced Antinociception

Peripheral activation of the NO-cGMP pathway has been implicated in various nociceptive conditions. The antinociceptive effect of the PDE-5 inhibitor, sildenafil, alone or in combination with cyclooxygenase inhibitor diclofenac and nimesulide, was assessed in the different animal models of peripheral nociception. In the present study we investigated the possible interaction between cyclooxygenase and NO-cGMP pathway in writhing assay and carrageenan-induced hyperalgesia in mice and rats, respectively. Sildenafil [1–2 mg/kg, i.p. or 50–100 µg/paw, intraplantar (i.pl.)], nimesulide (1–2 mg/kg, i.p. or 25–50 µg/paw, i.pl.) and diclofenac (1–2 mg/kg, i.p. or 25–50 µg/paw, i.pl.) exhibited an antinociceptive effect in both the models. When ineffective doses of sildenafil (0.5 mg/kg, i.p and 25 µg/paw, i.pl.) were co-administered with ineffective doses of nimesulide (0.5 mg/kg, i.p. and 10 µg/paw, i.pl.) and diclofenac (0.5 mg/kg, i.p. and 10 µg/paw, i.pl.), there was a significant increase in the antinociceptive effect in both the models of peripheral nociception. Further, the potentiation of the effect was blocked by L-NAME (20 mg/kg, i.p., 100 µg/paw, i.pl.), a non-selective NOS inhibitor and methylene blue (1 mg/kg, i.p.), a guanylate cyclase inhibitor. L-NAME or methylene blue itself had little or no effect on both the models of hyperalgesia. These results suggest that cyclooxygenase, NO and cGMP are relevant in the combination-induced antinociception. In conclusion, sildenafil induced antinociception, and its potentiation of the effect of the cyclooxygenase inhibitors nimesulide and diclofenac was probably mediated through the activation of the NO-cGMP pathway and inhibition of cyclic GMP degradation.

Arachidonic acid cascade inhibitors modulate phorbol ester-induced oxidative stress in female ICR mouse skin: differential roles of 5-lipoxygenase and cyclooxygenase-2 in leukocyte infiltration and activation.

We recently developed a short-term assay for skin H2O2 generation induced by double 12-O-tetradecanoylphorbol-13-acetate (TPA) applications for mechanistic study on skin epidermal carcinogenesis. In the present study, we investigated the individual roles of arachidonic acid metabolism in H2O2 generation in mouse skin inflammation. The experiments using inhibitors of arachidonic acid (AA) metabolism showed that corticosteroid and a lipoxygenase (LO) inhibitor expectedly suppressed double TPA application-induced H2O2 generation through the interference of chemotactic action but not by direct decomposition or scavenging. We also demonstrated that the treatment of AA (1 mumol) and 5-LO metabolites including leukotriene B4 (LTB4) partly mimicked, though soybean LO-derived lipid hydroperoxide and prostaglandins did not, the priming effect evaluated by edema formation and leukocyte infiltration. We also confirmed that inflammatory leukocytes accumulated by LTB4 generated a significant amount of H2O2 by TPA stimulation. These results suggested that 5-LO metabolites of AA are the potential key molecules in the TPA-induced priming event. Interestingly, the cyclooxygenase (COX-) 2-selective inhibitor nimesulide (NS) and celecoxib (CXB) showed different responses than those of other inhibitors. These agents showed no specific potential to inhibit the priming event but significantly suppressed H2O2 generation, lipid peroxidation, and hyperplasia in mouse skin. From the results based on an in vitro leukocyte differentiation model, we speculated that the antioxidant effect of the COX-2 inhibitors might be partly associated with both counteraction of proinflammatory cytokine-enhanced ROS generation and inhibition of CD11b, an important molecule for cell adhesion, expression. Indeed, the topical application of NS attenuated the number of infiltrated leukocytes induced by TPA in mouse skin. Thus, these gathered data indicated the differential roles of 5-LO and COX-2 in leukocyte adhesion, infiltration, and H2O2 generation.

Cyclooxygenase-2 (COX-2) inhibitors sensitize tumor cells specifically to death receptor-induced apoptosis independently of COX-2 inhibition.

Cyclooxygenase-2 (COX-2) is involved in diverse processes such as inflammation, carcinogenesis and apoptosis. As COX-2 inhibitors interfere with these processes, inhibition of COX-2 has been suggested as a promising anticancer treatment. However, the role of COX-2 in modulation of apoptosis as well as the death pathways affected by COX-2 inhibitors are poorly characterized. Here we demonstrate that the selective COX-2 inhibitors NS-398 and nimesulide increased TNF sensitivity of TNF-resistant HeLa H21 and TNF-sensitive HeLa D98 cells, although this cytokine induced significant COX-2 activity, as judged by prostaglandin E(2) (PGE(2)) production, only in H21 cells. TNF did also not induce PGE(2) production in MCF-7/casp-3 cells stably expressing COX-2; however, nimesulide strongly enhanced TNF-induced apoptosis in these cells. Furthermore, COX-2 activity in HeLa H21 cells could be inhibited by NS-398 concentrations that were 10 000-fold lower compared to those required for the induction of cell death. Most intriguingly, sensibilization to apoptosis was specifically observed in response to activation of death receptors. Not only TNF-induced cell death but also apoptosis triggered by the CD95 and TRAIL receptors was enhanced by nimesulide. In contrast, apoptosis induced by the anticancer drugs doxorubicine and etoposide that target the mitochondrial death pathway remained unaffected. Together, our data suggest that COX-2 inhibitors overcome apoptosis resistance and selectively sensitize tumor cells to the extrinsic death receptor-induced apoptotic pathway independently of COX-2.

Delayed treatment with nimesulide reduces measures of oxidative stress following global ischemic brain injury in gerbils

Metabolism of arachidonic acid by cyclooxygenase is one of the primary sources of reactive oxygen species in the ischemic brain. Neuronal overexpression of cyclooxygenase-2 has recently been shown to contribute to neurodegeneration following ischemic injury. In the present study, we examined the possibility that the neuroprotective effects of the cyclooxygenase-2 inhibitor nimesulide would depend upon reduction of oxidative stress following cerebral ischemia. Gerbils were subjected to 5 min of transient global cerebral ischemia followed by 48 h of reperfusion and markers of oxidative stress were measured in hippocampus of gerbils receiving vehicle or nimesulide treatment at three different clinically relevant doses (3, 6 or 12 mg/kg). Compared with vehicle, nimesulide significantly ( P<0.05) reduced hippocampal glutathione depletion and lipid peroxidation, as assessed by the levels of malondialdehyde (MDA), 4-hydroxy-alkenals (4-HDA) and lipid hydroperoxides levels, even when the treatment was delayed until 6 h after ischemia. Biochemical evidences of nimesulide neuroprotection were supported by histofluorescence findings using the novel marker of neuronal degeneration Fluoro-Jade B. Few Fluoro-Jade B positive cells were seen in CA1 region of hippocampus in ischemic animals treated with nimesulide compared with vehicle. These results suggest that nimesulide may protect neurons by attenuating oxidative stress and reperfusion injury following the ischemic insult with a wide therapeutic window of protection.

PGE 2 is generated by specific COX-2 activity and increases VEGF production in COX-2-expressing human pancreatic cancer cells

In some cancers cyclooxygenase (COX) inhibition appears to be anti-mitogenic and anti-angiogenic, but the actions of COX-derived prostaglandins in pancreatic cancer (PaCa) are unknown. In this study COX-2 was detected in three of six PaCa cell lines while COX-1 was identified in all cell lines. COX-2 expression correlated with basal and arachidonic acid (AA) stimulated PGE 2 production. PGE 2 production was inhibited by the COX-2 inhibitor nimesulide. In COX-2 expressing cells, exogenous AA and PGE 2 increased VEGF synthesis via the EP 2 receptor. Whereas PGE 2 stimulated intracellular cAMP formation in COX-2 positive and negative cells, 8-bromo cAMP stimulated VEGF production only in COX-2 expressing cells. Stimulating COX-2 expressing PaCa cell lines with AA enhanced migration of endothelial cells, an effect which was inhibited by a COX-2 inhibitor and EP 2 receptor antagonist. These data identify a subset of human PaCa cell lines that express functional COX-2 enzyme. PGE 2 generated by specific COX-2 activity increases VEGF secretion in human PaCa cells through an autocrine mechanism.

Mechanisms of angiotensin-converting enzyme inhibitor induced thrombolysis in Wistar rats

Our in vivo assay for thrombolysis consisted of recording the weight of platelet-rich thrombi adhering to a collagen strip that was superfused with arterial blood in extracorporal circulation of anaesthetised Wistar rats. Immediate thrombolysis occurred in response to intravenously administrated angiotensin-converting enzyme inhibitor (ACE-I) at non-hypotensive doses of 3–30 μg kg−1 (captopril<perindopril<quinapril). The thrombolytic response lasted up to 3 h with maximum reduction of the weight of thrombus by 75%. Pretreatment with COX-1 and COX-3 inhibitors (aspirin at a low dose of 1 mg kg−1, SC 560 and acetaminophen, 0.3–3 mg kg−1) slightly augmented thrombolysis by ACE-I, while COX-2 inhibitors (nimesulide and coxibs at doses <1 mg kg−1 and aspirin at a high dose of 50 mg kg−1) or a kinin B2 receptor antagonist (icatibant) abolished it. NOS inhibition by l-NAME blunted and delayed thrombolysis by ACE-I. In parallel to maximum thrombolysis by quinapril (30 μg kg−1), plasma levels of 6-keto-PGF1α rose significantly from 40±7 to 554±91 pg ml−1 (n=5, mean±S.D.), while basal levels of PGE2 (12±3 pg ml−1) and TXB2 (47±11 pg ml−1) remained essentially unchanged. Pretreatment with celecoxib (0.1–1.0 mg kg−1) abolished not only thrombolysis by quinapril but also the quinapril-induced rise in plasma 6-keto-PGF1α. In cultured bovine aortic endothelial cells, perindoprilate (30 μM) increased cytosolic free calcium [Ca2+]i, but this effect was by three to four orders of magnitude weaker than that of bradykinin (Bk). In aortas of Wistar rats, the transcripts of COX-2 and PGI-S were overexpressed as compared to COX-1. Thus, in blood vessels of Wistar rats, the preferable route of the PGI2 generation might lead through the COX-2 pathway.We conclude that in Wistar rats, ACE-I induces thrombolysis via accumulation of endogenous kinins over the endothelium and a subsequent activation of B2 receptors followed by the release of prostacyclin and nitric oxide. Thrombolysis by ACE-I seems to be mediated mainly through prostacyclin that is made by COX-2. It may well be that an increase in endothelial [Ca2+]i by ACE-I activates phospholipase A2, which supplies COX-2 with the substrate for making thrombolytic prostacyclin.

Hippocampal kindling epileptogenesis upregulates neuronal cyclooxygenase-2 expression in neocortex

Recurrent and spontaneous seizures in epilepsy result from poorly defined cell signaling aberrations thought to include synaptic and extracellular matrix remodeling. Here we have used a rat hippocampal kindling model to study cyclooxygenase-2 (COX-2) gene expression in epileptogenesis. COX-2, encoded in an early-response gene, increases in a synaptic activity-dependent fashion and also during kainic acid-induced hippocampal damage. We found that during kindling, COX-2 induction occurred initially only in hippocampal neurons, and then spread to neocortical neurons. When rats were rekindled 34 days later, this spreading of COX-2 expression persisted. Induction of hippocampal and neocortical cytosolic phospholipase A 2 (cPLA 2), an enzyme that catalyzes the synthesis of COX-2 substrate arachidonic acid (AA), occurred after 4 days of stimulation during kindling and rekindling. Moreover the COX-2 selective inhibitor nimesulide attenuated kindling development. We conclude that neuronal COX-2 gene induction and cPLA 2 activation are key signaling events in epileptogenesis.