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

Interleukin 1 (IL-1) induces prostanoid biosynthesis in endothelial cells by promoting cyclooxygenase expression, but little is known about its activity on the biosynthesis of hydroxyeicosatetraenoic acids (HETEs). We studied the effect of human recombinant IL-1 beta on the conversion of arachidonic acid (AA) to 15-HETE, a powerful inhibitor of the biosynthesis of proinflammatory eicosanoids. Cultured human umbilical vein endothelial cells were incubated with or without IL-1 beta prior to the addition of labeled AA. The eicosanoids produced were analyzed by RP-HPLC. Untreated cells produced little amounts of 15-HETE (6 +/- 3 pmol/10(6) cells), but IL-1 beta treated cells increased 15-HETE formation in a dose-dependent manner (4-5-fold at 10 U/ml IL-1). The production of HETEs by IL-1 beta was dependent on protein synthesis. Aspirin inhibited prostanoids, HHT and 11-HETE dose dependently, whereas it was unable to totally inhibit 15-HETE in IL-1 beta-treated cells (50-60%). Nordihydroguaiaretic acid, a general lipoxygenase inhibitor, preferably inhibited 15-HETE formation but also reduced the synthesis of the other eicosanoids in a dose-dependent manner. Indomethacin and ETYA completely suppressed prostanoids, 11-HETE and 15-HETE formation in resting and IL-1 beta-activated cells. Using specific 15-lipoxygenase oligonucleotides and the reverse transcriptase polymerase chain reaction technique, we were unable to evidence detectable 15-lipoxygenase mRNA both in resting and IL-1-activated endothelial cells. Overall, these results provide evidence that in human endothelial cells IL-1 beta increases 15-HETE production. Data strongly suggest that this effect is mediated by cyclooxygenase rather than 15-lipoxygenase activity or expression.
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PMID:Interleukin-1 increases 15-hydroxyeicosatetraenoic acid formation in cultured human endothelial cells. 769 Nov 82

Melatonin, a major hormone of pineal gland, was recently shown to attenuate acute gastric lesions induced by strong irritants because of the scavenging of free radicals but its role in ulcer healing has been little investigated. In this study we compared the effects of intragastric (i.g.) administration of melatonin and its precursor, L-tryptophan, with or without concurrent treatment with luzindole, a selective antagonist of melatonin MT2 receptors, on healing of chronic gastric ulcers induced by serosal application of acetic acid (ulcer area 28 mm2). The involvement of endogenous prostaglandins (PG), nitric oxide (NO) and sensory nerves in ulcer healing action of melatonin and L-tryptophan was studied in rats treated with indomethacin and NG-nitro-L-arginine (L-NNA) to suppress, respectively, cyclo-oxygenases (COX) and NO synthases or in those with functionally deactivated sensory nerves with capsaicin. The influence of melatonin on gastric secretion during ulcer healing was tested in separate group of rats with gastric ulcer equipped with gastric fistulas (GF). At day 8 and 15 upon the ulcer induction, the area of gastric ulcers was measured by planimetry, the mucosal blood flow (GBF) was determined by H2-gas clearance technique and gastric luminal NO2-/NO3- levels was assessed by Griess reaction. Plasma melatonin and gastrin levels were measured by specific radioimmunoassay (RIA). Biopsy mucosal samples were taken for expression of constitutive NO-synthase (cNOS) and inducible NOS (iNOS) by reverse transcriptase-polymerase chain reaction (RT-PCR). Melatonin (2.5-20 mg/kg-d i.g.) and L-tryptophan (25-100 mg/kg-d i.g.) dose-dependently accelerated ulcer healing, the dose inhibiting by 50% (ED50) of ulcer area being 10 and 115 mg/kg, respectively. This inhibitory effect of melatonin (10 mg/kg-d i.g.) and L-tryptophan (100 mg/kg-d i.g.) on ulcer healing was accompanied by a significant rise in the GBF at ulcer margin and an increase of plasma melatonin. luminal NO2-/NO3- and plasma gastrin levels. Gastric acid and pepsin outputs were significantly inhibited during the ulcer healing in melatonin-treated gastric mucosa as compared with those in vehicle-treated animals. Luzindole abolished completely the healing effects of melatonin and L-tryptophan and attenuated significantly the rise in plasma gastrin evoked by the hormone and its precursor. Indomethacin (5 mg/kg-d i.p). that blocked PG biosynthesis by 90% or L-NAME (20 mg/kg i.v), inhibitor of NOS. that suppressed luminal NO release, attenuated significantly melatonin and L-tryptophan-induced acceleration of ulcer healing and accompanying rise in GBF at ulcer margin and luminal NO release. The melatonin-induced acceleration of ulcer healing, hyperemia at ulcer margin and increase in the release of NO were enhanced when L-arginine but not D-arginine was added to L-NAME. The ulcer healing and the GBF effects of melatonin and L-tryptophan were significantly impaired in rats with capsaicin-induced denervation of sensory nerves and both, ulcer healing and the hyperemia at ulcer margin were restored in these rats by addition of exogenous CGRP to melatonin and L-tryptophan. Expression of cNOS mRNA was detected by RT-PCR in the intact gastric mucosa as well as at the edge of gastric ulcers treated with both, vehicle and melatonin, while iNOS mRNA that was undetectable in the intact gastric mucosa, appeared during ulcer healing and especially this was strongly up-regulated in the melatonin-treated gastric mucosa. We conclude that (1) exogenous melatonin and that derived from its precursor, L-tryptophan, accelerate ulcer healing probably via interaction with MT2 receptors; (2) this ulcer healing action is caused by an enhancement by melatonin of the microcirculation at the ulcer margin possibly mediated by COX-derived PG and NO because of overexpression of iNOS and (3) gastrin, which exhibits trophic activity in the gastric mucosa and calcitonin gene related peptide (CGRP), released from sensory nerves, may also contribute to the ulcer healing action of melatonin.
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PMID:Role of prostaglandins, nitric oxide, sensory nerves and gastrin in acceleration of ulcer healing by melatonin and its precursor, L-tryptophan. 1207 98

Melatonin attenuates acute gastric lesions induced by topical strong irritants because of scavenging of free radicals, but its role in the pathogenesis of stress-induced gastric lesions has been sparingly investigated. In this study we compared the effects of intragastric (i.g.) or intracerebroventricular (i.c.v.) administration of melatonin and its precursor, L-tryptophan, with or without concurrent treatment with luzindole, a selective antagonist of melatonin MT2 receptors, on gastric lesions induced by water immersion and restraint stress (WRS). The involvement of pineal gland, endogenous prostaglandins (PG) and sensory nerves in gastroprotective action of melatonin and L-tryptophan against WRS was studied in intact or pinealectomized rats or those treated with indomethacin or rofecoxib to suppress cyclooxygenase (COX)-1 and COX-2, respectively, and with capsaicin to induce functional ablation of the sensory nerves. In addition, the influence of i.c.v. and i.g. melatonin on gastric secretion was tested in a separate group of rats equipped with gastric fistulas. At 3.5 hr after the end of WRS, the number of gastric lesions was counted, the gastric blood flow (GBF) was determined by H2-gas clearance technique and plasma melatonin and gastrin levels were measured by specific radioimmunoassay (RIA). Biopsy mucosal samples were taken for determination of expression of mRNA for COX-1 and COX-2 by reverse transcriptase-polymerase chain reaction (RT-PCR) and of the mucosal generation of prostaglandin E2 (PGE2) by RIA. Melatonin applied i.g. (1.25-10 mg/kg) or i.c.v. (1.25-10 microg/kg) dose-dependently inhibited gastric acid secretion and significantly attenuated the WRS-induced gastric damage. This protective effect of melatonin was accompanied by a significant rise in the GBF and plasma melatonin and gastrin levels and in mucosal generation of PGE2. Pinealectomy, which suppressed plasma melatonin levels, aggravated the gastric lesions induced by WRS and these effects were counteracted by i.g. or i.c.v. application of melatonin. Luzindole abolished completely the gastroprotective effects of melatonin and L-tryptophan and attenuated significantly the rise in GBF evoked by the indoleamine and its precursor. Indomethacin and rofecoxib, which diminished PGE2 biosynthesis by c. 90 and 75% or capsaicin denervation, attenuated significantly melatonin- and L-tryptophan-induced protection and the rise in the GBF. Both the protection and the hyperemia were restored by addition of exogenous CGRP to capsaicin-denervated animals. COX-1 mRNA was detected by RT-PCR in the intact and melatonin-treated gastric mucosa, while COX-2 mRNA, which was undetectable in the intact gastric mucosa, appeared in WRS-exposed mucosa, especially in the melatonin-treated animals and this was accompanied by increased generation of PGE2 in gastric mucosa. Pinealectomy downregulated COX-2 mRNA and this effect was reversed by supplementation of pinealectomized animals with melatonin. We conclude that, (a) exogenous melatonin and its precursor, L-tryptophan, attenuates WRS-induced gastric lesions via interaction with MT2 receptors, (b) this protective action of melatonin is because of an enhancement of gastric microcirculation, probably mediated by PGE2 derived from COX-2 overexpression and activity, the activation of brain-gut axis involving CGRP released from sensory nerves, and the release of gastrin and (c) the pineal plays an important role in the limitation of WRS-induced gastric lesions via releasing melatonin, which exerts gastroprotective and hyperemic activities against stress ulcerogenesis.
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PMID:Importance of the pineal gland, endogenous prostaglandins and sensory nerves in the gastroprotective actions of central and peripheral melatonin against stress-induced damage. 1620 93

To assess effects of Celecoxib, selective cyclo-oxygenase (COX)-2 inhibitor, on matrix synthesis by chondrocytes under mechanical stress in vitro. Chondrocytes from 7-day-old rat articular cartilage were cultured. Cyclic mechanical stress (0.5 Hz, 7% elongation) was loaded using a Flexercell strain unit in the presence of Celecoxib, Indomethacin, and Ketoprofen. Concentrations of chondroitin sulfate (CS) in culture media were measured by high-performance liquid chromatography. Nitric oxide (NO) formation was detected by measuring NO2-accumulation in culture supernatants during the Griess reaction, using sodium nitrite as a standard. Levels of mRNA for aggrecan (AGC), type II collagen (CII), COX-2, and membrane-associated prostaglandin E synthase-1 (mPGES-1) were measured using real time reverse transcriptase-polymerase chain reaction. Under mechanical stress, levels of AGC and CII mRNA were decreased, while COX-2 mRNA levels were increased. Of the three drugs tested, only Celecoxib prevented the decrease of AGC mRNA and inhibited the release of CS. In addition, Celecoxib suppresses the level of mPGES-1 mRNA. These findings show that excessive mechanical stress decreases synthesis of matrix components in chondrocytes through a NO-regulated pathway, and suggest that Celecoxib has a protective effect on matrix metabolism.
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PMID:The influence of Celecoxib on matrix synthesis by chondrocytes under mechanical stress in vitro. 1627 90