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COX-2 Activity (cox-2 + activity)
Selected AbstractsCOX-2 mRNA expression in esophageal squamous cell carcinoma (ESCC) and effect by NSAIDDISEASES OF THE ESOPHAGUS, Issue 1 2008X. Liu SUMMARY., To investigate cyclooxygenase-2 (COX-2) mRNA expression in human esophageal squamous cell carcinoma and the effect of a non-steroidal anti-inflammatory drug (NSAID) on it, in order to explore the mechanism of COX-2 in esophageal squamous cell carcinoma (ESCC) carcinogenesis and the ability of NSAID to prevent or treat ESCC. Frozen specimens of human ESCC and adjacent normal esophageal squamous epithelium pairs (n = 22) were examined for COX-2 mRNA expression by reverse-transcription polymerase chain reaction (RT-PCR). After incubation with aspirin (a non-selective COX inhibitor) or Nimesulide (a selective COX-2 inhibitor), the proliferation status of two human esophageal squamous cancer cell lines, EC-9706 and EC-109, was quantified by 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyltetrazolium bromide assay. The expression of COX-2 mRNA in these cells was detected by RT-PCR. COX-2 mRNA was expressed in 12 of 22 (54.5%) ESCC tissue samples, but it was undetectable in all the specimens of adjacent normal esophageal squamous epithelium COX-2 mRNA expression. Both aspirin (5,20 mmol/L) and Nimesulide (0.1,0.8 mmol/L) inhibited EC-9706 cell line proliferation and suppressed its COX-2 mRNA expression dose-dependently. However, only aspirin (5,20 mmol/L) could inhibit proliferation in the EC-109 cell line and suppress COX-2 mRNA expression. Nimesulide (0.1,0.8 mmol/L) could neither inhibit EC-109 cell growth nor suppress COX-2 mRNA expression. COX-2 mRNA expression is a frequent phenomenon in human ESCC tissue samples and plays an important role in the carcinogenesis of ESCC. NSAID may be useful in the chemoprevention and therapy of human ESCC and its effects are likely to be mediated by modulating COX-2 activity. [source] COX-2, but not COX-1, activity is necessary for the induction of perforant path long-term potentiation and spatial learning in vivoEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008T. R. Cowley Abstract The objectives of this research were to investigate the role played by the enzyme cyclooxygenase (COX) in learning and memory, synaptic plasticity and synaptic transmission in the rat brain in vivo. Male Wistar rats were treated with isoform-selective inhibitors for COX-1 and COX-2, either chronically and tested in the watermaze or acutely before electrophysiological recordings were made. We found a significant impairment in acquisition of the watermaze with inhibition of COX-2. Furthermore, we found COX-2 but not COX-1 inhibition significantly blocked long-term potentiation (LTP) induction but had no effect on already established LTP. Moreover, exogenous replacement of the main metabolite of COX-2 activity, PGE2, was sufficient to restore LTP induction and for normal downstream signalling to ensue, namely extracellular signalling-regulated kinase (ERK)-phosphorylation and c-FOS expression. We conclude that endogenous basal levels of PGE2 resulting from COX-2 but not COX-1 activity are necessary for synaptic plasticity and memory acquisition. [source] Cyclooxygenase-2 inhibitor celecoxib augments chemotherapeutic drug-induced apoptosis by enhancing activation of caspase-3 and -9 in prostate cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 3 2005Devendra S. Dandekar Abstract Many tumors constitutively express high levels of the inducible form of proinflammatory enzyme, cyclooxygenase-2 (COX-2). Increased COX-2 expression is associated with tumor cell resistance to many cytotoxic chemotherapy drugs. Furthermore, increased resistance to cytotoxic antitumor drugs is also known to be dependent on associated stromal cells in many tumors. We investigated whether prostate tumor-associated stromal cells, marrow-derived osteoblasts, affect cytotoxicity of 2 antitumor drugs, COL-3 and docetaxel (TXTR), and whether it is dependent on COX-2 activity. We further examined whether inhibiting the activity of COX-2 negate the stroma-induced decrease in drug sensitivity in tumor cells. COX-2-specific inhibitor celecoxib (CXB) was used to inhibit COX-2 activity and associated alteration in cell death signaling was investigated. Coculturing PC-3ML cells with osteoblasts decreased the cytotoxicity of the tested antitumor drugs and was associated with increased COX-2 activity in PC-3ML cells. A significant decrease in drug-induced PGE2 increase and an increase in cytotoxicity were observed when cells were treated with COL-3 or TXTR combined with CXB. Cytotoxicity of single or combination treatment increased apoptosis, which was associated with caspase-3 and -9 activation, PARP cleavage, increased BAD protein, but decreased protein levels of XIAP and BCL- xL. Oral administration of CXB (40 mg/kg) to mice with PC-3ML tumors for 42 days increased tumor latency, decreased tumor growth and enhanced tumor control with COL-3 or TXTR. Overall, a synergistic enhancement of antitumor activity in combination treatment was observed in vitro and an additive effect in vivo. These observations suggest a potential clinical use of combined dosing of COX-2 inhibitors and cytotoxic drugs at lower, nontoxic dose than currently used to treat advanced prostate cancer. © 2005 Wiley-Liss, Inc. [source] Cyclo-Oxygenase 2 Function Is Essential for Bone Fracture Healing,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 6 2002Ann Marie Simon Abstract Despite the molecular and histological similarities between fetal bone development and fracture healing, inflammation is an early phase of fracture healing that does not occur during development. Cyclo-oxygenase 2 (COX-2) is induced at inflammation sites and produces proinflammatory prostaglandins. To determine if COX-2 functions in fracture healing, rats were treated with COX-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) to stop COX-2-dependent prostaglandin production. Radiographic, histological, and mechanical testing determined that fracture healing failed in rats treated with COX-2-selective NSAIDs (celecoxib and rofecoxib). Normal fracture healing also failed in mice homozygous for a null mutation in the COX-2 gene. This shows that COX-2 activity is necessary for normal fracture healing and confirms that the effects of COX-2-selective NSAIDs on fracture healing is caused by inhibition of COX-2 activity and not from a drug side effect. Histological observations suggest that COX-2 is required for normal endochondral ossification during fracture healing. Because mice lacking Cox2 form normal skeletons, our observations indicate that fetal bone development and fracture healing are different and that COX-2 function is specifically essential for fracture healing. [source] Site-specific proteolysis of cyclooxygenase-2: A putative step in inflammatory prostaglandin E2 biosynthesisJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2007Arturo Mancini Abstract Cyclooxygenase-2 (COX-2) catalyzes the rate-limiting step in inflammatory prostanoid biosynthesis. Transcriptional, post-transcriptional, and post-translational covalent modifications have been defined as important levels of regulation for COX-2 gene expression. Here, we describe a novel regulatory mechanism in primary human cells involving regulated, sequence-specific proteolysis of COX-2 that correlates with its catalytic activity and ultimately, the biosynthesis of prostaglandin E2 (PGE2). Proinflammatory cytokines induced COX-2 expression and its proteolysis into stable immunoreactive fragments of 66, 42,44, 34,36, and 28 kDa. Increased COX-2 activity (PGE2 release) was observed coincident with the timing and degree of COX-2 proteolysis with correlation analysis confirming a linear relationship (R2,=,0.941). Inhibition of induced COX-2 activity with non-steroidal anti-inflammatory drugs (NSAIDs) and COX-2 selective inhibitors also abrogated cleavage. To determine if NSAID inhibition of proteolysis was related to drug-binding-induced conformational changes in COX-2, we assayed COX-inactive NSAID derivatives that fail to bind COX-2. Interestingly, these compounds suppressed COX-2 activity and cleavage in a correlated manner, thus suggesting that the observed NSAID-induced inhibition of COX-2 cleavage occurred through COX-independent mechanisms, presumably through the inhibition of proteases involved in COX-2 processing. Corroborating this observation, COX-2 cleavage and activity were mutually suppressed by calpain/cathepsin protease inhibitors. Our data suggest that the nascent intracellular form of COX-2 may undergo limited proteolysis to attain full catalytic capacity. J. Cell. Biochem. 101: 425,441, 2007. © 2006 Wiley-Liss, Inc. [source] ,2,1 integrin signalling enhances cyclooxygenase-2 expression in intestinal epithelial cellsJOURNAL OF CELLULAR PHYSIOLOGY, Issue 3 2006Oliver Jay Broom Inflammatory bowel diseases (IBD) are linked to an increased risk of developing colon cancer, by inflammatory mediators and alterations to the extracellular matrix (ECM). The events induced by inflammatory mediators lead to dysregulated activation and induction of inflammatory genes such as cyclooxygenase-2 (COX-2). COX-2 is involved in the conversion of arachidonic acid to biologically active prostanoids and is highly upregulated in colon cancer. Since inflammation-induced changes to the extracellular matrix could affect integrin activities, we here investigated the effect of integrin signalling on the level of COX-2 expression in the non-transformed intestinal epithelial cell lines, Int 407 and IEC-6. Adhesion of these cells to a collagen I- or IV-coated surface, increased surface expression of ,2,1 integrin. Activation of integrins with collagen caused an increased cox-2 promoter activity, with a subsequent increase in COX-2 expression. The signalling cascade leading to this increased expression and promoter activity of cox-2, involves PKC,, the small GTPase Ras and NF,B but not Erk1/2 or Src activity. The integrin-induced increase in cellular COX-2 activity is responsible for an elevated generation of reactive oxygen species (ROS) and increased cell migration. This signalling pathway suggests a mechanism whereby inflammation-induced modulations of the ECM, can promote cancer transformation in the intestinal epithelial cells. J. Cell. Physiol. 209: 950,958, 2006. © 2006 Wiley-Liss, Inc. [source] Postinjury estrogen treatment of chronic spinal cord injury improves locomotor function in ratsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2010Eric A. Sribnick Abstract Spinal cord injury (SCI) causes loss of neurological function and, depending on serverity, may cause paralysis. The only recommended pharmacotherapy for the treatment of SCI is high-dose methylprednisolone, and its use is controversial. We have previously shown that estrogen treatment attenuated cell death, axonal and myelin damage, calpain and caspase activities, and inflammation in acute SCI. The aim of this study was to examine whether posttreatment of SCI with estrogen would improve locomotor function by protecting cells and axons and reducing inflammation during the chronic phase following injury. Moderately severe injury (40 g · cm force) was induced in male Sprague-Dawley rats following laminectomy at T10. Three groups of animals were used: sham (laminectomy only), vehicle (dimethyl sulfoxide; DMSO)-treated injury group, and estrogen-treated injury group. Animals were treated with 4 mg/kg estrogen at 15 min and 24 hr postnjury, followed by 2 mg/kg estrogen daily for the next 5 days. After treatment, animals were sacrificed at the end of 6 weeks following injury, and 1-cm segments of spinal cord (lesion, rostral to lesion, and caudal to lesion) were removed for biochemical analyses. Estrogen treatment reduced COX-2 activity, blocked nuclear factor-,B translocation, prevented glial reactivity, attenuated neuron death, inhibited activation and activity of calpain and caspase-3, decreased axonal damage, reduced myelin loss in the lesion and penumbra, and improved locomotor function compared with vehicle-treated animals. These findings suggest that estrogen may be useful as a promising therapeutic agent for prevention of damage and improvement of locomotor function in chronic SCI. © 2010 Wiley-Liss, Inc. [source] PGE2 receptor EP1 renders dopaminergic neurons selectively vulnerable to low-level oxidative stress and direct PGE2 neurotoxicityJOURNAL OF NEUROSCIENCE RESEARCH, Issue 14 2007Emilce Carrasco Abstract Oxidative stress and increased cyclooxygenase-2 (COX-2) activity are both implicated in the loss of dopaminergic neurons from the substantia nigra (SN) in idiopathic Parkinson's disease (PD). Prostaglandin E2 (PGE2) is one of the key products of COX-2 activity and PGE2 production is increased in PD. However, little is known about its role in the selective death of dopaminergic neurons. Previously, we showed that oxidative stress evoked by low concentrations of 6-hydroxydopamine (6-OHDA) was selective for dopaminergic neurons in culture and fully dependent on COX-2 activity. We postulated that this loss was mediated by PGE2 acting through its receptors, EP1, EP2, EP3, and EP4. Using double-label immunohistochemistry for specific EP receptors and tyrosine hydroxylase (TH), we identified EP1 and EP2 receptors on dopaminergic neurons in rat SN. EP2 receptors were also found in non-dopaminergic neurons of this nucleus, as were EP3 receptors, whereas the EP4 receptor was absent. PGE2, 16-phenyl tetranor PGE2 (a stable synthetic analogue), and 17-phenyl trinor PGE2 (an EP1 receptor,selective agonist) were significantly toxic to dopaminergic cells at nanomolar concentrations; EP2- and EP3-selective agonists were not. We challenged dopaminergic neurons in embryonic rat mesencephalic primary neuronal cultures and tested whether these receptors mediate selective 6-OHDA toxicity. The nonselective EP1,3 receptor antagonist AH-6809 and two selective EP1 antagonists, SC-19220 and SC-51089, completely prevented the 40%,50% loss of dopaminergic neurons caused by exposure to 5 ,M 6-OHDA. Together, these results strongly implicate PGE2 activation of EP1 receptors as a mediator of selective toxicity in this model of dopaminergic cell loss. © 2007 Wiley-Liss, Inc. [source] In Vitro Cyclooxygenase-2 Protein Expression and Enzymatic Activity in Neoplastic CellsJOURNAL OF VETERINARY INTERNAL MEDICINE, Issue 5 2007David A. Heller Background: Cyclooxygenase-2 (COX-2) and its principle enzymatic metabolite, prostaglandin E2 (PGE2), are implicated in cancer progression. Based upon immunohistochemical (IHC) evidence that several tumor types in animals overexpress COX-2 protein, COX-2 inhibitors are used as anticancer agents in dogs and cats. Hypothesis: IHC is inaccurate for assessing tumor-associated COX-2 protein and enzymatic activity. Methods: Five mammalian cell lines were assessed for COX-2 protein expression by IHC and Western blot analysis (WB), and functional COX-2 activity was based upon PGE2 production. Results: Detection of COX-2 protein by IHC and WB were in agreement in 4 of 5 cell lines. In 1 cell line that lacked COX-2 gene transcription because of promoter hypermethylation (HCT-116), IHC produced false-positive staining for COX-2 protein expression. Functional COX-2 enzymatic activity was dissociated from relative IHC-based COX-2 protein expression in 2 cell lines (RPMI 2650 and SCCF1). The RPMI 2650 cell line demonstrated strong COX-2 protein expression but minimal PGE2 production. Conclusions and Clinical Importance: Western blot is more accurate than IHC for the detection of COX-2 protein in the cell lines studied. Furthermore, the semiquantitative identification of COX-2 protein by IHC or WB does not necessarily correlate with enzymatic activity. Based upon the potential inaccuracy of IHC and dissociation of COX-2 protein expression from enzymatic activity, the practice of instituting treatment of tumors with COX-2 inhibitors based solely on IHC results should be reconsidered. [source] Effects of tanshinone I isolated from Salvia miltiorrhiza Bunge on arachidonic acid metabolism and in vivo inflammatory responsesPHYTOTHERAPY RESEARCH, Issue 7 2002Sung Young Kim Abstract Arachidonic acid (AA) mainly released from the cell membrane by phospholipase A2 (PLA2) is converted to eicosanoids by the action of cyclooxygenase (COX) and lipoxygenase (LO). In order to find the specific inhibitors of AA metabolism especially PLA2 and COX-2, 300 plant extracts were evaluated for their inhibitory activity on PGD2 production from cytokine-induced mouse bone marrow-derived mast cells in vitro. From this screening procedure, the methanol extract of Salvia miltiorrhiza was found to inhibit PGD2 production and the ethyl,acetate subfraction gave the strongest inhibition of five subfractions tested. From this ethyl,acetate subfraction, an activity-guided isolation finally gave tanshinone I as an active principle. This investigation deals with the effects of tanshinone I on AA metabolism from lipopolysaccharide (LPS)-induced RAW 264.7 cells and in vivo antiinflammatory activity. Tanshinone I inhibited PGE2 formation from LPS-induced RAW macrophages (IC50,=,38,,M). However, this compound did not affect COX-2 activity or COX-2 expression. Tanshinone I was found to be an inhibitor of type IIA human recombinant sPLA2(IC50,=,11,,M) and rabbit recombinant cPLA2 (IC50,=,82,,M). In addition, tanshinone I showed in vivo antiinflammatory activity in rat carrageenan-induced paw oedema and adjuvant-induced arthritis. Copyright © 2002 John Wiley & Sons, Ltd. [source] PGE2 receptors rescue motor neurons in a model of amyotrophic lateral sclerosisANNALS OF NEUROLOGY, Issue 2 2004Masako Bilak PhD Recent studies suggest that the inducible isoform of cyclooxygenase, COX-2, promotes motor neuron loss in rodent models of ALS. We investigated the effects of PGE2, a principal downstream prostaglandin product of COX-2 activity, on motor neuron survival in an organotypic culture model of ALS. We find that PGE2 paradoxically protects motor neurons at physiological concentrations in this model. PGE2 exerts its downstream effects by signaling through a class of four distinct G-protein,coupled E-prostanoid receptors (EP1,EP4) that have divergent effects on cAMP. EP2 and EP3 are dominantly expressed in ventral spinal cord in neurons and astrocytes, and activation of these receptor subtypes individually or in combination also rescued motor neurons. The EP2 receptor is positively coupled to cAMP, and its neuroprotection was mimicked by application of forskolin and blocked by inhibition of PKA, suggesting that its protective effect is mediated by downstream effects of cAMP. Conversely, the EP3 receptor is negatively coupled to cAMP, and its neuroprotective effect was blocked by pertussis toxin, suggesting that its protective effect is dependent on Gi-coupled heterotrimeric signaling. Taken together, these data demonstrate an unexpected neuroprotective effect mediated by PGE2, in which activation of its EP2 and EP3 receptors protected motor neurons from chronic glutamate toxicity. Ann Neurol 2004;56:240,248 [source] More pronounced inhibition of cyclooxygenase 2, increase in blood pressure, and reduction of heart rate by treatment with diclofenac compared with celecoxib and rofecoxibARTHRITIS & RHEUMATISM, Issue 1 2006Burkhard Hinz Objective Recent findings suggest that permanent blockade of cyclooxygenase 2 (COX-2) is one factor contributing to the cardiovascular side effects of selective COX-2 inhibitors (coxibs) and nonsteroidal antiinflammatory drugs (NSAIDs). The present study compared the extent and time course of COX-2 inhibition and the effects on cardiovascular parameters (changes in blood pressure and heart rate) between various antirheumatic doses of diclofenac, celecoxib, and rofecoxib in healthy elderly volunteers. Methods A randomized, parallel-group study was conducted in volunteers receiving 75 mg diclofenac twice daily, 200 mg celecoxib twice daily, or 25 mg rofecoxib once daily for 8 days. Blood samples were obtained predose and at specified time points postdose, on days 1 and 8, for assay of drug plasma concentrations and COX-2 inhibition. Lipopolysaccharide-induced prostaglandin E2 synthesis was measured ex vivo as an index of COX-2 activity in human whole blood. Results COX-2 inhibition was significantly less pronounced after treatment with celecoxib and rofecoxib than with diclofenac. Maximal inhibitions after a single dose and at steady state, respectively, were as follows: 99% and 99% with diclofenac, 70% and 81% with celecoxib, and 56% and 72% with rofecoxib. At steady state, only diclofenac caused virtually complete COX-2 inhibition over the whole dose interval, and this corresponded to the highest increase in systolic blood pressure and greatest reduction in heart rate. Conclusion Diclofenac elicited the most pronounced COX-2 inhibition, blood pressure elevation, and suppression of heart rate. It is assumed that the extent and time course of intravascular COX-2 inhibition may determine the differential profile of cardiovascular side effects associated with NSAIDs and coxibs, but this has to be proven in future studies. [source] Pharmacokinetic,pharmacodynamic modelling of the analgesic effects of lumiracoxib, a selective inhibitor of cyclooxygenase-2, in ratsBRITISH JOURNAL OF PHARMACOLOGY, Issue 1 2010DA Vásquez-Bahena Background and purpose:, This study establishes a pharmacokinetic/pharmacodynamic (PK/PD) model to describe the time course and in vivo mechanisms of action of the antinociceptive effects of lumiracoxib, evaluated by the thermal hyperalgesia test in rats. Experimental approach:, Female Wistar fasted rats were injected s.c. with saline or carrageenan in the right hind paw, followed by either 0, 1, 3, 10 or 30 mg·kg,1 of oral lumiracoxib at the time of carrageenan injection (experiment I), or 0, 10 or 30 mg·kg,1 oral lumiracoxib at 4 h after carrageenan injection (experiment II). Antihyperalgesic responses were measured as latency time (LT) to a thermal stimulus. PK/PD modelling of the antinociceptive response was performed using the population approach with NONMEM VI. Results:, A two-compartment model described the plasma disposition. A first-order model, including lag time and decreased relative bioavailability as a function of the dose, described the absorption process. The response model was: LT=LT0/(1 +MED). LT0 is the baseline response, and MED represents the level of inflammatory mediators. The time course of MED was assumed to be equivalent to the predicted profile of COX-2 activity and was modelled according to an indirect response model with a time variant synthesis rate. Drug effects were described as a reversible inhibition of the COX-2 activity. The in vivo estimate of the dissociation equilibrium constant of the COX-2-lumiracoxib complex was 0.24 µg·mL,1. Conclusions:, The model developed appropriately described the time course of pharmacological responses to lumiracoxib, in terms of its mechanism of action and pharmacokinetics. [source] | |||||||||||||