Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To elucidate the mechanism for the selective inhibition of prostaglandin E2 (PGE2) production in inflammatory tissue by T-614 (3-formylamino-7-methylsulfonylamino-6-phenoxy-4H-1-benzopyran-4-o ne), its effects on both the activity and the induction of cyclooxygenase (COX)-2 were investigated in vitro. T-614 inhibited the activity of purified COX-2 enzyme (IC50: 7.7 micrograms/ml), but was inactive against both COX-1 activities of microsomal and purified enzymes (IC50: > 300 micrograms/ml). On the other hand, when the inhibition of PGE2 production by T-614 was examined in the cultured fibroblasts stimulated with bradykinin, T-614 at 1 microgram/ml or less inhibited PGE2 release more effectively than that in the above cell-free system. Therefore, we examined which of the COX enzymes was expressed in bradykinin-stimulated fibroblasts by using both the reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot analyses. As a result, COX-1 mRNA was constitutively expressed in the cells, whereas COX-2 mRNA was not detected without stimulation with bradykinin, but was expressed within 30 min when stimulated. Furthermore, it was found that the addition of T-614 reduced the COX-2 mRNA levels in 30 min after stimulation. These studies suggest that at least some of inhibitory effects of T-614 on prostanoids production are mediated by the synergy of the inhibition of COX-2 activity and the inhibition of induction, and such an action of T-614 may explain the pharmacological properties of this drug.
 ...
PMID:T-614, a novel antirheumatic drug, inhibits both the activity and induction of cyclooxygenase-2 (COX-2) in cultured fibroblasts. 765 Aug 64

A second prostaglandin G/H synthase (PGHS-2), encoded by a gene separate from that for the original PGHS (PGHS-1), has recently been identified. We have shown that PGHS-2 is expressed in cultured mouse calvariae and have compared regulation of PGHS-2 and PGHS-1 messenger RNA (mRNA) levels. PGHS-2 mRNA was not detectable in freshly isolated bones, but was induced during culture and further stimulated by interleukin-1 (IL-1) and PTH. Both factors also increased PGHS-2 protein levels. Changes in medium prostaglandin E2 (PGE2) production correlated with increases in PGHS-2 mRNA levels. However, with IL-1, PGE2 production was increased more than PGHS-2 mRNA levels (treated/control ratio, 3.4 and 1.5, respectively), whereas with PTH there was a closer correspondence (2.0 and 2.1). Cortisol reduced PTH-stimulated PGE2 production (treated/control ratio decreased from 3.1 to 0.2) more than PGHS-2 mRNA levels (2.8 to 0.8). In the presence of exogenous arachidonic acid, changes in PGHS-2 mRNA levels with IL-1, PTH, and cortisol correlated closely with changes in PGE2 production. PGE2 itself increased PGHS-2 mRNA, and nonsteroidal antiinflammatory drugs decreased PGHS-2 mRNA levels by 80%. In contrast, PGHS-1 mRNA was expressed constitutively and was not affected by IL-1, PTH, or cortisol when measured by competitive reverse transcriptase-polymerase chain reaction. We conclude that regulation of PGE2 production is predominantly through PGHS-2, rather than PGHS-1; that IL-1 and cortisol may also regulate arachidonic acid release; and that PGE2 may amplify its own production through stimulation of PGHS-2.
 ...
PMID:Regulation of the two prostaglandin G/H synthases by parathyroid hormone, interleukin-1, cortisol, and prostaglandin E2 in cultured neonatal mouse calvariae. 807 Mar 58

The rate-limiting step in the formation of prostanoids is the conversion of arachidonic acid to prostaglandin H2 by cyclooxygenase, also known as prostaglandin G/H synthase/cyclooxygenase. Two forms of cyclooxygenase have been characterized: a ubiquitously expressed form (COX-1) and a recently described second form (COX-2) inducible by various factors including mitogens, hormones, serum and cytokines. Here we quantitate by the reverse transcriptase-polymerase chain reaction (RT-PCR) the expression of COX-1 and COX-2 mRNA in human tissues including lung, uterus, testis, brain, pancreas, kidney, liver, thymus, prostate, mammary gland, stomach and small intestine. All tissues examined contained both COX-1 and COX-2 mRNA and could be grouped according to the level of COX mRNA expression. The highest levels of COX mRNAs were detected in the prostate where approximately equal levels of COX-1 and COX-2 transcripts were present. In the lung high levels of COX-2 were observed whereas COX-1 mRNA levels were about 2-fold lower. An intermediate level of expression of both COX-1 and COX-2 mRNA was observed in the mammary gland, stomach, small intestine, and uterus. The lowest levels of COX-1 and COX-2 mRNA were observed in the testis, pancreas, kidney, liver, thymus, and brain.
 ...
PMID:Expression of mRNA for cyclooxygenase-1 and cyclooxygenase-2 in human tissues. 836 85

Using reverse transcriptase-polymerase chain reaction we have established that mRNAs for prostaglandin H synthases 1 and 2 (PGHS-1 and PGHS-2) are present in amnion, chorion and decidua from women both at term before and after the onset of labour and from women at 28-35 weeks of gestation before the onset of labour. By Western blot analyses we have demonstrated that epidermal growth factor, interleukin 1 beta and phorbol 12-myristate 13-acetate all increase PGHS-2 amounts in amnion cells. The degree of stimulation caused by these substances (218-311 per cent) is less than the increase in prostaglandin production usually generated (five- to 10-fold). Hence we believe that these substances may have multiple sites of action in the pathways of arachidonic acid metabolism.
 ...
PMID:Prostaglandin H synthase-2 in human gestational tissues: regulation in amnion. 876 68

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease that is characterized by selective destruction of insulin-secreting beta-cells. Cytokines have been implicated as effector molecules that participate in both islet inflammation and beta-cell destruction during the development of IDDM. In this study, the effects of cytokines on the expression of inducible nitric oxide synthase (iNOS) and inducible cyclooxygenase (COX-2) by human islets were examined. In combination, the cytokines, human recombinant interleukin-1 beta (IL-1 beta), human recombinant tumor necrosis factor-alpha (TNF-alpha), and human recombinant interferon-gamma (IFN-gamma), induce the time-dependent formation of nitrite and prostaglandin E2 (PGE2) by human islets. The nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) completely inhibits cytokine-induced nitrite formation and attenuates PGE2 production by human islets. L-NMMA does not inhibit cytokine-induced expression of COX-2 by human islets, suggesting that nitric oxide may directly activate cyclooxygenase, an effect that has been previously demonstrated for isolated rat islets. This combination of cytokines (IL-1 beta, TNF-alpha, and IFN-gamma) also induces the expression of iNOS mRNA by human islets as demonstrated by both reverse transcriptase-polymerase chain reaction and Northern blot analysis. We further show that the tyrosine kinase inhibitors genistein and herbimycin A prevent IL-1 beta plus IFN-gamma-induced expression of COX-2 and iNOS and the production of PGE2 and nitric oxide by human islets. These results demonstrate that cytokines induce the expression of iNOS and COX-2 by human islets and that cytokine-induced expression of both COX-2 and iNOS by human islets appears to require the activation of a tyrosine kinase(s).
 ...
PMID:Tyrosine kinase inhibitors prevent cytokine-induced expression of iNOS and COX-2 by human islets. 876 39

Prostaglandins are involved in mediating several important processes in mammalian reproduction, including the initiation of parturition. In the present study, we examined the expression in the rat uterus of two-rate limiting enzymes involved in prostaglandin production, cyclooxygenase (COX) 1 and 2. Expression of the COX-2 gene in the pregnant rat uterus gave rise to a single mRNA transcript of approximately 4.4 kb. COX-2 mRNA levels increased 3.5 fold between day 7 of pregnancy and the onset of parturition on day 22. In contrast, COX-1 mRNA levels remained constant during the same period. To investigate factors involved in mediating the regulation of COX-1 and COX-2 gene expression, rat endometrial stromal and epithelial cell lines, were used. In the stroma-derived cell line, CUS-V2, COX-2 gene expression was demonstrated by reverse transcriptase/polymerase chain reaction (RT-PCR) and by immunocytochemistry. In these cells, COX-2 gene expression was inducible by the cytokines interleukin-1 beta and tumor necrosis factor alpha, but not by interleukin-6. The two former cytokines also induced prostaglandin F2 alpha production. In contrast, COX-1 gene expression was constitutive in this cell line. In the endometrial epithelium-derived cell line, CUE-P both COX-1 and COX-2 genes were expressed in a constitutive fashion. In conclusion, the present in vivo and in vitro data indicate that decidual COX-2, but not COX-1, gene expression is regulated during pregnancy and implicate specific cytokines as possible inducers within the decidua.
 ...
PMID:Regulation of COX-2 gene expression in rat uterus in vivo and in vitro. 897 7

The inducible cyclooxygenase, COX-2, has been associated with vascular inflammation and cellular proliferation. We have discovered that hypoxia increases expression of the COX-2 gene in human vascular endothelial cells in culture independent of other stimuli. Western analysis of human umbilical vein endothelial cells (HUVEC) revealed a greater than 4-fold induction of protein by hypoxia (1% O2). The steady-state level of COX-2 mRNA was correspondingly elevated by both Northern blot and reverse transcriptase-polymerase chain reaction analysis. Using electrophoretic mobility shift assays with antibody supershifting, we also found that hypoxia causes increased binding of NF-kappaB p65 (Rel A) to the one out of the two NF-kappaB consensus elements in the COX-2 promoter which is closest to the transcription start site of the COX-2 gene. Transfection of an immortalized human microvascular endothelial cell line (HMEC-1) with mutation reporter gene constructs and HUVEC with both mutation and deletion reporter gene constructs suggested that transcription of the COX-2 gene was enhanced by hypoxia. In transcription factor decoy experiments, hypoxic HUVEC were exposed in culture to 20 microM of the same NF-kappaB element found to bind NF-kappaB protein. The wild type transcription factor decoy prevented hypoxic induction of COX-2, presumably by binding with cytoplasmic p65; however, mutated or scrambled oligonucleotides did not prevent the increase in COX-2 protein expression by hypoxia. Thus, the intracellular signaling mechanism that leads to induction of COX-2 by hypoxia includes binding of p65 to the relatively 3' NF-kappaB consensus element in the COX-2 upstream promoter region in human vascular endothelial cells.
 ...
PMID:Hypoxia induces cyclooxygenase-2 via the NF-kappaB p65 transcription factor in human vascular endothelial cells. 899 3

Expression of mRNAs encoding the two prostaglandin endoperoxide synthase (PGHS) isoenzymes (PGHS-1 and -2) was investigated in differentiating clonal Ob1771 mouse preadipocytes and in mouse adipose tissues. Northern analysis revealed that the expression level of PGHS-1 mRNA was reduced by 98+/-0.2% (P <0.01) during differentiation of Ob1771 cells, whereas PGHS-2 mRNA was not detected. By reverse transcriptase-polymerase chain reaction analysis, however, both PGHS-1 and -2 mRNA was detected in Ob1771 preadipose cells. In addition. mRNAs encoding both isoforms were markedly expressed in primary adipose precursor cells with considerably lower expression levels in mature adipocytes (56 75% reduction, P<0.01). Furthermore, exposure to dexamethasone (10 nM) for both 24 h (explants of adipose tissue) and 48 h (Ob1771 adipose cells) resulted in enhanced expression of PGHS-1 mRNA. whereas expression of PGHS-2 mRNA in explants of adipose tissue (24 h incubation) was reduced by 83 +/- 9% (P<0.05). In contrast, exposure to angiotensin II (100 nM) enhanced expression of PGHS-1 mRNA both in mature adipocytes (4 h incubation) and explants of adipose tissue (24 h incubation), and elevated PGHS-2 mRNA expression in mature adipocytes (4 h incubation). In conclusion, this report suggests a differential expression of PGHS mRNAs during adipose cell differentiation, and further suggests that the machinery for prostaglandin synthesis in mature adipocytes may be induced by various hormones.
 ...
PMID:Expression of the two isoforms of prostaglandin endoperoxide synthase (PGHS-1 and PGHS-2) during adipose cell differentiation. 925 65

In pre-eclampsia, the ratio of prostacyclin:thromboxane production rate is decreased favouring the vasoconstrictive thromboxane. One of the rate-limiting steps in prostaglandin synthesis is cyclooxygenase (COX) activity. Therefore, we investigated the expression of COX-1 and COX-2 in human placenta and placental bed. Tissue specimens from the 29th to 40th week of pregnancy were obtained from Caesarean sections after uncomplicated and pre-eclamptic pregnancies before the onset of labour. COX-1 and COX-2 were localized immunohistochemically with the identification of positive cells by double immunofluorescence staining. The protein and mRNA levels were analysed by immunoblotting and quantitative reverse transcriptase-polymerase chain reaction. Expression of both COX-1 and COX-2 could be observed in placenta and placental bed. COX-1-like immunoreactivity was observed in most cell types with strongest staining in macrophages. Only macrophages, endothelium, vascular leiomyocytes and fibroblasts stained positively for COX-2. In placenta, COX-1 and -2 expression was unchanged after pre-eclampsia. In placental bed, protein and mRNA levels of COX-1 were increased in the pre-eclamptic group (P < 0.05), whereas COX-2 expression did not differ significantly from normal pregnancies. An increased expression of COX-1 could be involved in the pathophysiology of pre-eclamptic changes within the placental bed. A therapy with drugs inhibiting COX-1 might be beneficial in this condition.
 ...
PMID:Cyclooxygenase-1 and -2 in human placenta and placental bed after normal and pre-eclamptic pregnancies. 940 2

Cyclooxygenase (COX) exists in 2 related but unique isoforms: one is constitutive (COX-1) and functions in normal cell physiology, and the other is inducible (COX-2) and is expressed in response to inflammatory stimuli. Nonsteroidal antiinflammatory drugs (NSAIDs) cause renal toxicity following inhibition of renal cyclooxygenases. Humans and animals exhibit differences in susceptibility to NSAID-related renal toxicity, which may be associated with differences in expression of 1 or both isoforms of COX in the kidney. In this study, we evaluated COX-1 and COX-2 expression in the kidneys of mixed-breed dogs, Sprague-Dawley rats, cynomolgus monkeys, and humans. In addition, the effect of volume depletion on renal COX expression was investigated in rats, dogs, and monkeys. COX expression was evaluated using 1 or more of the following procedures: reverse transcriptase polymerase chain reaction, in situ hybridization, and immunohistochemistry. We demonstrated that both COX isoforms are expressed in the kidneys of all species examined, with differences in the localization and level of basal expression. COX-1 is expressed at high levels in the collecting ducts and renal vasculature of all species and in a small number of papillary interstitial cells in rats, monkeys, and humans. Basal levels of COX-2 are present in the maculae densa, thick ascending limbs, and papillary interstitial cells in rats and dogs and in glomerular podocytes and small blood vessels in monkeys and humans. COX-2 expression is markedly increased in volume-depleted rats and dogs but not monkeys. These results indicate that significant interspecies differences exist in the presence and distribution of COX isoforms, which may help explain the difference in species susceptibility to NSAID-related renal toxicity.
 ...
PMID:Interspecies differences in renal localization of cyclooxygenase isoforms: implications in nonsteroidal antiinflammatory drug-related nephrotoxicity. 978 47


1 2 3 4 5 6 7 Next >>