Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.5.1.19 (NOS)
 7,285 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Lipopolysaccharide (LPS) co-induces nitric oxide synthase (iNOS) and cyclo-oxygenase (COX-2) in J774.2 macrophages. Here we have used LPS-activated J774.2 macrophages to investigate the effects of exogenous or endogenous nitric oxide (NO) on COX-2 in both intact and broken cell preparations. NOS activity was assessed by measuring the accumulation of nitrite using the Griess reaction. COX-2 activity was assessed by measuring the formation of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) by radioimmunoassay. Western blot analysis was used to determine the expression of COX-2 protein. We have also investigated whether endogenous NO regulates the activity and/or expression of COX in vivo by measuring NOS and COX activity in the lung and kidney, as well as release of prostanoids from the perfused lung of normal and LPS-treated rats. 2. Incubation of cultured murine macrophages (J774.2 cells) with LPS (1 microgram ml-1) for 24 h caused a time-dependent accumulation of nitrite and 6-keto-PGF1 alpha in the cell culture medium which was first significant after 6 h. The formation of both 6-keto-PGF1 alpha and nitrite elicited by LPS was inhibited by cycloheximide (1 microM) or dexamethasone (1 microM). Western blot analysis showed that J774.2 macrophages contained COX-2 protein after LPS administration, whereas untreated cells contained no COX-2. 3. The accumulation of 6-keto-PGF1 alpha in the medium of LPS-activated J774.2 macrophages was concentration-dependently inhibited by chronic (24 h) exposure to sodium nitroprusside (SNP; 1-1000 microM). Sodium nitroprusside (1-1000 microM) also acutely (30 min) inhibited COX-2 activity in broken cell preparations of LPS-activated (12 h) J774.2 macrophages, in a similar concentration dependent manner. Addition of adrenaline (5 mM) and glutathione (0.1 mM) increased the activity of COX-2 in broken cell preparations. In the presence of these co-factors, SNP inhibited prostanoid production only at the highest concentration used (1 mM). When J774.2 cells were incubated in the presence of LPS (1 microg ml-1) and NG-monomethyl-L-arginine (L-NMMA: 1 mM) for 12 h, SNP at the highest concentration used (1 mM) acutely (30 min) inhibited the activity of COX-2 in cell homogenates with co-factors. However, when J774.2 macrophages were incubated for 24 or 12 h with LPS (1 microg ml-1)and L-NMMA (1 mM), the addition of SNP (0.001-1I000 microM) increased in a concentration-dependent manner the accumulation of 6-keto-PGF1a in intact cells (measured at 24 h) and COX-2 activity in cell homogenates in the presence of co-factors (determined at 12 h). SNP (1 mM; together with LPS for 12 h)decreased the amount of COX-2 protein induced by LPS in J774.2 macrophages.4. Indomethacin (30 1AM) abolished the formation of 6-keto-PGFa by LPS-activated macrophages, but had no effect on the release of nitrite. Conversely, L-NMMA, at the highest concentrations used (1 and 10 mM), increased the release of 6-keto-PGFIa an effect which was reversed by excess L-arginine (3 mM)but not by D-arginine. Similarly, the decrease in nitrite formation caused by L-NMMA was partially reversed by L-arginine (3 mM), but not by D-arginine. L-NMMA (10 mM; together with LPS for 12 h)increased the amount of COX-2 protein induced by LPS in J774.2 macrophages.5. In separate experiments, J774.2 macrophages were activated with LPS (1 microg ml-1), and L-NMMA(10 mM) was added for various times (0.5-24 h) before the collection of mediun at 24 h. L-NMMAenhanced the release of 6-keto-PGFI,, in a time-dependent manner, with the maximal enhancement seen when the NOS inhibitor was incubated with the cells for 24 h. 6. In experiments on male Wistar rats, we investigated the effect of L-NMMA on the release of prostanoids (6-keto-PGF1a prostaglandin E2, thromboxane B2) elicited by arachidonic acid (AA,30nmol) from ex vivo perfused kidneys and lungs. The release from the organs from normal and LPS-treated rats was unaffected by L-NMMA intraperitoneally (30 mg kg-1) for 6 h together with LPS(5 mg kg-1) or LPS vehicle. Similarly, acute (5 min) in vitro exposure to L-NMMA (1 mM) of the perfused organs from control and LPS-treated animals did not change the release of prostanoids elicited by AA (30 nmol).7. These results show that LPS causes the induction of iNOS and COX-2 in J774.2 macrophages. The co-release of NO and PGI2 induced by LPS is dependent on protein synthesis and occurs after a lag-time of 6-12 h. The formation of COX metabolites has no effect on NOS activity whereas NO inhibits both COX-2 activity and induction. These results demonstrate that NOS and COX can be co-induced in vitro and that under these conditions large amounts of NO inhibit the degree of COX expression and activity.In the absence of endogenous NO, lesser amounts of exogenous NO increase the activity of COX-2. In those situations in vivo when the level of NO induction is relatively low, NO does not regulate the increased activity of COX.
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PMID:Co-induction of nitric oxide synthase and cyclo-oxygenase: interactions between nitric oxide and prostanoids. 754 88

Although endogenous nitric oxide (NO) modulates basal tone in the fetal pulmonary and systemic circulations, little is known about its role in regulating ductus arteriosus (DA) tone. Immunostaining of DA tissue from late-gestation fetal lambs demonstrated strong staining for endothelial NO synthase (eNOS) in DA endothelium. To study the physiological role of the NO and guanosine 3',5'-cyclic monophosphate (cGMP) system in the DA in vivo, we measured the hemodynamic effects of NG-nitro-L-arginine (L-NNA; 30 mg), a NOS inhibitor, methylene blue (40 mg), a guanylate cyclase inhibitor, and indomethacin (0.8 mg), a cyclooxygenase inhibitor, in 10 chronically prepared late-gestation fetal lambs. L-NNA increased main pulmonary artery (MPA) and aortic pressures (P < 0.05 vs. baseline) but did not change the pressure gradient between the MPA and the aorta. L-NNA caused a small decrease in DA flow and a slight rise in resistance across the DA. Methylene blue increased both MPA pressure and the pressure gradient between the MPA and the aorta from 0.3 +/- 0.2 (baseline) to 7.0 +/- 2.7 mmHg (P < 0.05). Indomethacin increased both MPA pressure and the pressure gradient between the MPA and the aorta from 1.1 +/- 0.4 (baseline) to 6.3 +/- 1.5 mmHg (P < 0.05) after 40 min. Indomethacin decreased DA flow and increased DA resistance. We conclude that eNOS is in fetal DA endothelial cells and that NOS inhibition causes constriction of the DA in vivo. DA constriction after NOS inhibition is minimal, especially in comparison with cyclooxygenase inhibition. Methylene blue also constricts the DA, suggesting that guanylate cyclase activity contributes to DA relaxation. We speculate that, although the NO and cGMP system modulates DA tone, prostaglandins may play a greater role.
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PMID:Role of nitric oxide and cGMP system in regulation of ductus arteriosus tone in ovine fetus. 899 26

1. It has been proposed that in inflammatory conditions, in which both the inducible isoforms of nitric oxide synthase (iNOS) and cyclo-oxygenase (COX-2) are induced, inhibition of NOS also results in inhibition of arachidonic acid metabolism. In the present study we have investigated whether mercaptoalkylguanidines, a novel class of selective iNOS inhibitors, may also influence the activity of cyclo-oxygenase (COX). Therefore, the effect of mercaptoethylguanidine (MEG) and related compounds on the activity of the constitutive (COX-1) and the inducible COX (COX-2) was investigated in cells and in purified enzymes. Aminoguanidine, NG-methyl-L-arginine (L-NMA) and NG-nitro-L-arginine methyl ester (L-NAME) were also studied for comparative purposes. 2. Western blot analysis demonstrated a significant COX-1 activity in unstimulated J774 macrophages and in unstimulated human umbilical vein endothelial cells (HUVEC). Immunostimulation of the J774 macrophages by endotoxin (lipopolysaccharide of E. coli, LPS 10 micrograms ml-1) and interferon gamma (IFN gamma, 100 u ml-1) for 6 h resulted in a significant induction of COX-2, and a down-regulation of COX-1. No COX-2 immunoreactivity was detected in unstimulated HUVEC or unstimulated J774 cells. Therefore, in subsequent studies, the effect of mercaptoalkylguanidines on COX-1 activity was studied in HUVEC stimulated with arachidonic acid for 6 h, and in J774 cells stimulated with arachidonic acid for 30 min. The effect of mercaptoalkylguanidines on COX-2 activity was studied in immunostimulated J774 macrophages, both on prostaglandin production by endogenous sources, and on prostaglandin production in response to exogenous arachidonic acid stimulation. In addition, the effect of mercaptoalkylguanidines on purified COX-1 and COX-2 activities was also studied. 3. In experiments designed to measure COX-1 activity in HUVEC, the cells were stimulated by arachidonic acid (15 microM) for 6 h. This treatment induced a significant production of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha, the stable metabolite of prostacyclin), while nitrite production was undetectable by the Griess reaction. MEG (1 microM to 3 mM) caused a dose-dependent inhibition of the accumulation of 6-keto-PGF1 alpha, with an IC50 of 20 microM. However, aminoguanidine, L-NAME or L-NMA (up to 3 mM) did not affect the production of 6-keto-PGF1 alpha in this experimental system. In experiments designed to measure COX-1 activity in J774.2 macrophages, the cells were stimulated by arachidonic acid (15 microM) for 30 min; this also induced a significant production of 6-keto-PGF1 alpha and MEG (1 microM to 3 mM), aminoguanidine (at 1 and 3 mM), but neither L-NAME nor L-NMA inhibited the production of prostaglandins. 4. In experiments designed to measure prostaglandin production by COX-2 with endogenous arachidonic acid, J774.2 cells were immunostimulated for 6 h in the absence or presence of various inhibitors. In experiments designed to measure prostaglandin production by COX-2 with exogenous arachidonic acid, J774.2 cells were immunostimulated for 6 h, followed by a replacement of the culture medium with fresh medium containing arachidonic acid and various inhibitors. Both of these treatments induced a significant production of 6-keto-PGF1 alpha. Nitrite production, an indicator of NOS activity, was moderately increased after immunostimulation. MEG (1 microM to 3 mM) caused a dose-dependent inhibition of the accumulation of COX metabolites. Similar inhibition of LPS-stimulated 6-keto PGF1 alpha production was shown by other mercaptoalkylguanidines (such as N-methyl-mercaptoethylguanidine, N,N'-dimethyl-mercaptoethylguanidine, S-methyl-mercaptoethylguanidine and guanidino-ethyldisulphide), with IC50 values ranging between 34-55 microM. However, aminoguanidine, L-NAME and L-NMA (up to 3 mM) did not affect the production of prostaglandins.5. In comparative experiments indomethacin, a non selective COX inhibitor, and NS-398, a selective COX-2 inhibitor, reduced (LPS) stimulated 6-keto-PGF1alpha production in J774 macrophages in a dose-dependent manner without affecting nitrite release. Indomethacin, but not NS-398, inhibited 6-keto-PGF1alpha production in the HUVECs. 6.The inhibitory effect of MEG was due to direct inhibition of the catalytic activity of COX as indicated in experiments with purified COX-1 and COX-2. MEG dose-dependently inhibited the purified COX-1 and COX-2 activity with IC50 values of 33microM and 36microM, respectively. Aminoguanidine (at the highest concentrations) inhibited the formation of COX-1 metabolites, without affecting COX-2 activity. High doses of L-NAME (3mM) decreased COX-1 activity only, while L-NMA (up to 3mM) had no effect on the activity of either enzyme. 7.These results suggest that MEG and related compounds are direct inhibitors of the constitutive and the inducible cyclo-oxygenases, in addition to their effects on the inducible NOS. The additional effect of mercaptoalkylguanidines on COX activity may contribute to the beneficial effects of these agents in inflammatory conditions where both iNOS and COX-2 are expressed.
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PMID:The inhibitory effects of mercaptoalkylguanidines on cyclo-oxygenase activity. 903 36

Administration of tacrine (5 mg/kg i.p.), an anticholinesterase agent, in rats pretreated (24 h beforehand) with lithium chloride (LiCl; 12 mEq/kg i.p.) enhances the expression of neuronal nitric oxide (NO) synthase (NOS), increases NO, and causes seizures and hippocampal damage. Here we report immunohistochemistry evidence showing that in rat LiCl and tacrine enhance the expression of cyclooxygenase type 2 (COX-2) enzyme protein in the dorsal hippocampus and elevate brain PGE2 content during the preconvulsive period. The latter effect, but not enhanced COX-2 expression, is inhibited by previous (30 min before tacrine) administration of N omega-nitro-L-arginine-methyl ester (L-NAME; 10 mg/kg i.p.), an inhibitor of NO synthesis, thus implicating NO in the mechanism of stimulation of COX activity leading to elevation of brain PGE2 content. Indomethacin (10 mg/kg given i.p. 30 min before tacrine), an inhibitor of COX activity, prevented brain PGE2 elevation and abolished the expression of seizures and hippocampal damage thus supporting a role for this metabolite of the arachidonic acid cascade in the mechanisms of LiCl and tacrine-evoked neurotoxicity in rat.
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PMID:Systemic administration of N omega-nitro-L-arginine methyl ester and indomethacin reduces the elevation of brain PGE2 content and prevents seizures and hippocampal damage evoked by LiCl and tacrine in rat. 950 Sep 67

Transgenic sickle mice expressing human beta(S)- and beta(S-Antilles)-globins show intravascular sickling, red blood cell adhesion, and attenuated arteriolar constriction in response to oxygen. We hypothesize that these abnormalities and the likely endothelial damage, also reported in sickle cell anemia, alter nitric oxide (NO)-mediated microvascular responses and hemodynamics in this mouse model. Transgenic mice showed a lower mean arterial pressure (MAP) compared with control groups (90 +/- 7 vs. 113 +/- 8 mmHg, P < 0.00001), accompanied by increased endothelial nitric oxide synthase (eNOS) expression. N(G)-nitro-L-arginine methyl ester (L-NAME), a nonselective inhibitor of NOS, caused an approximately 30% increase in MAP and approximately 40% decrease in the diameters of cremaster muscle arterioles (branching orders: A2 and A3) in both control and transgenic mice, confirming NOS activity; these changes were reversible after L-arginine administration. Aminoguanidine, an inhibitor of inducible NOS, had no effect. Transgenic mice showed a decreased (P < 0.02-0.01) arteriolar dilation in response to NO-mediated vasodilators, i.e., ACh and sodium nitroprusside (SNP). Indomethacin did not alter the responses to ACh and SNP. Forskolin, a cAMP-activating agent, caused a comparable dilation of A2 and A3 vessels ( approximately 44 and 70%) in both groups of mice. Thus in transgenic mice, an increased eNOS/NO activity results in lower blood pressure and diminished arteriolar responses to NO-mediated vasodilators. Although the increased NOS/NO activity may compensate for flow abnormalities, it may also cause pathophysiological alterations in vascular tone.
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PMID:Impaired nitric oxide-mediated vasodilation in transgenic sickle mouse. 1084 75

Previous studies have demonstrated that responses to endothelium-dependent vasodilators are absent in the aortas from mice deficient in expression of endothelial nitric oxide synthase (eNOS -/- mice), whereas responses in the cerebral microcirculation are preserved. We tested the hypothesis that in the absence of eNOS, other vasodilator pathways compensate to preserve endothelium-dependent relaxation in the coronary circulation. Diameters of isolated, pressurized coronary arteries from eNOS -/-, eNOS heterozygous (+/-), and wild-type mice (eNOS +/+ and C57BL/6J) were measured by video microscopy. ACh (an endothelium-dependent agonist) produced vasodilation in wild-type mice. This response was normal in eNOS +/- mice and was largely preserved in eNOS -/- mice. Responses to nitroprusside were also similar in arteries from eNOS +/+, eNOS +/-, and eNOS -/- mice. Dilation to ACh was inhibited by N(G)-nitro-L-arginine, an inhibitor of NOS in control and eNOS -/- mice. In contrast, trifluoromethylphenylimidazole, an inhibitor of neuronal NOS (nNOS), decreased ACh-induced dilation in arteries from eNOS-deficient mice but had no effect on responses in wild-type mice. Indomethacin, an inhibitor of cyclooxygenase, decreased vasodilation to ACh in eNOS-deficient, but not wild-type, mice. Thus, in the absence of eNOS, dilation of coronary arteries to ACh is preserved by other vasodilator mechanisms.
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PMID:Vasodilator mechanisms in the coronary circulation of endothelial nitric oxide synthase-deficient mice. 1100 79

Cross-talk between inducible nitric oxide synthase (NOS II) and cyclooxygenase-2 (COX-2) was investigated in rat chondrocytes. In monolayers, interleukin-1beta (IL-1beta) induced COX-2 and NOS II expression in a dose- and time-dependent manner, to produce high prostaglandin E(2) (PGE(2)) and nitrite (NO(2)(-)) levels in an apparently coordinated fashion. COX-2 mRNA was induced earlier (30 min. versus 4 hr) and less markedly (4-fold versus 12-fold at 24 hr) than NOS II, and was poorly affected by the translational inhibitor cycloheximide (CHX). IL-1beta did not stabilize COX-2 mRNA in contrast to CHX. Indomethacin and NS-398 lacked any effect on NO(2)(-) levels whereas L-NMMA and SMT reduced PGE(2) levels at concentration inhibiting NO(2)(-) production from 50 to 90%, even when added at a time allowing a complete expression of both enzymes (8 hr). Basal COX activity was unaffected by NO donors. The SOD mimetic, CuDips inhibited COX-2 activity by more than 75% whereas catalase did not. Inhibition of COX-2 by CuDips was not sensitive to catalase, consistent with a superoxide-mediated effect. In tridimensional culture, IL-1beta inhibited radiolabelled sodium sulphate incorporation while stimulating COX-2 and NOS II activities. Cartilage injury was corrected by L-NMMA or CuDips but not by NSAIDs, consistent with a peroxynitrite-mediated effect. These results show that in chondrocytes: (i) COX2 and NOS II genes are induced sequentially and distinctly by IL-1beta; (ii) COX-1 and COX-2 activity are affected differently by NO-derived species; (iii) peroxynitrite accounts likely for stimulation of COX-2 activity and inhibition of proteoglycan synthesis induced by IL-1beta.
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PMID:Stimulation of cyclooxygenase-2-activity by nitric oxide-derived species in rat chondrocyte: lack of contribution to loss of cartilage anabolism. 1128 88

In the present study, we investigated a protective role of constitutively occurred nitric oxide (NO) against indomethacin-induced intestinal lesions in rats. Indomethacin (10 mg/kg) was given s.c. to animals without fasting, and the intestinal mucosa was examined for lesions 24 h later. The NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) was given s.c. 0.5 h before or 6 hr after indomethacin, while the NO donor (+/-)-(E)-ethyl-2-[(E)-hydroxyimino]-5-nitro-3-hexnamine (NOR-3) was given s.c. 0.5 h before indomethacin. Indomethacin caused hemorrhagic lesions in the small intestine, accompanied with an increase in intestinal motility and bacterial translocation. These lesions were markedly prevented or worsened, respectively, by later or prior administration of L-NAME (20 mg/kg), in a L-arginine-sensitive manner. The worsening effect of L-NAME (5-20 mg/kg) on these lesions was dose-dependently observed in association with further enhancement of the bacterial translocation and intestinal hypermotility following indomethacin. By contrast, prior administration of NOR-3 (1-6 mg/kg) dose-dependently prevented the development of intestinal lesions, together with suppression of the bacterial translocation and intestinal hypermotility in response to indomethacin. On the other hand, both indomethacin and L-NAME decreased intestinal mucus and fluid (water) secretion in the small intestine, while NOR-3 increased these secretions. These results suggest that (1) NO occurred constitutively exerts a protective action against indomethacin-induced intestinal ulceration, and (2) this effect is related with prevention of bacterial translocation, the process functionally associated with increase of mucus and fluid secretions as well as inhibition of intestinal hypermotility.
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PMID:Protection by constitutively formed nitric oxide of intestinal damage induced by indomethacin in rats. 1159 16

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

To study the impact of meconium aspiration on the biosynthesis of prostaglandins and nitric oxide, we investigated the effects of intratracheal meconium instillation on the expression of cyclooxygenase-1 (COX-1) and -2 (COX-2) and endothelial (NOS-3) and inducible (NOS-2) nitric oxide synthase in rat lungs. Anesthetized, tracheotomized, and ventilated rats received 3 mL/kg human meconium suspension intratracheally (n = 19), and 14 control rats received an equal volume of saline. Ten rats were pretreated with indomethacin, and 13 rats were pretreated with dexamethasone. The lungs were ventilated with 70% oxygen for 3 h after the insult, and the level of COX-1, COX-2, NOS-2, and NOS-3 mRNA in lung tissue was analyzed by Northern blot hybridization. Furthermore, the expression and localization of the enzyme proteins was analyzed by immunohistochemistry. COX-1 and NOS-3 were clearly expressed in the lungs of control rats, whereas the level of COX-2 and NOS-2 expression was minimal. Meconium administration did not affect the expression of COX-1, but COX-2 expression was up-regulated in the respiratory epithelium and alveolar macrophages. Meconium also induced up-regulation of NOS-2 in the pulmonary epithelium, vascular endothelium, and macrophages. Indomethacin pretreatment did not affect the enzyme expressions, whereas dexamethasone administration significantly inhibited the meconium-induced COX-2 and NOS-2 up-regulation. Our data thus indicate that intrapulmonary meconium up-regulates lung COX-2 and NOS-2 gene expression, suggesting an important role for prostaglandins and nitric oxide in the meconium aspiration-induced pulmonary inflammation and hemodynamic changes.
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PMID:Meconium aspiration stimulates cyclooxygenase-2 and nitric oxide synthase-2 expression in rat lungs. 1262 Nov 23


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