Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

T lymphocytes are exquisitely sensitive to the antiproliferative effects of nitric oxide. We examined the effects of oral administration of two nitric oxide synthase inhibitors, Nw-nitro-L-arginine methyl ester (L-NAME) and L-N6-(1-iminoethyl)lysine (L-NIL), on the course of T cell-dependent autoimmune interstitial nephritis in Brown Norway rats. Kidneys from rats immunized to produce interstitial nephritis display a net generation of nitric oxide end products. By immunohistochemical staining, the cytokine-inducible nitric oxide synthase (iNOS) is expressed in cortical tubular epithelial cells. Treatment with either inhibitor results in markedly more severe disease following immunization. Animals receiving L-NAME were hypertensive, while those treated with L-NIL, a highly selective inhibitor of iNOS, were not. Evaluation of the expression of IFN-gamma, IL-2, and IL-4 in diseased kidneys by quantitative reverse transcriptase-PCR demonstrated that L-NAME-treated animals displayed significantly augmented levels of IFN-gamma and IL-2 with preserved ratios of IFN-gamma/IL-4 and IL-2/IL-4, while L-NIL-treated animals had augmented levels of IL-2 and IFN-gamma with augmented IFN-gamma/IL-4 and IL-2/IL-4 ratios. Animals treated with L-NAME or L-NIL both had augmented Ag-specific IgG responses. The L-NAME group demonstrated increases in both the IgG2a and IgG1 subtypes, with a constant IgG2a/IgG1 ratio, while the L-NIL group demonstrated an increase in the ratio of the IgG2a/IgG1 response. These Ab and cytokine data suggest that the L-NIL-treated animals had a skewing of their immune response toward a Th1-like response. We conclude that in autoimmune interstitial nephritis, generation of nitric oxide through the iNOS pathway has host-protective effects, and suggest that this may be broadly applicable to T cell-mediated pathologies.
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PMID:Inhibition of inducible nitric oxide synthase intensifies injury and functional deterioration in autoimmune interstitial nephritis. 955 Apr 31

We hypothesized that nitric oxide (NO) production by the fetal ductus arteriosus is limited because of low fetal PO2, but that at neonatal PO2, NO might be an important regulator of ductus arteriosus tone. We exposed isolated rings of fetal lamb ductus arteriosus to elevated PO2. L-NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), and methylene blue and 6-anilino-5,8-quinolinedione (LY83583), inhibitors of guanylate cyclase, produced constriction of the ductus arteriosus. When ductus arteriosus rings were exposed to low PO2, L-NAME had no effect, and methylene blue and LY83583 had only a small effect on ductus arteriosus tone. Sodium nitroprusside and calcium ionophore A23187 relaxed ductus arteriosus rings more than aortic rings, and relaxed ductus arteriosus rings from immature fetuses more than those from late gestation fetuses. In contrast, ductus arteriosus rings from both early and late gestation were equally sensitive to 8-bromo-cGMP. By both reverse transcriptase-polymerase chain reaction and immunohistochemistry, endothelial cell NOS and inducible calcium-independent NOS, but not nerve cell NOS, were detected in the ductus arteriosus. Inducible NOS was expressed only by endothelial cells lining the ductus arteriosus lumen; in contrast, endothelial cell NOS was expressed by both luminal and vasa vasorum endothelial cells. The role of inducible NOS in the ductus arteriosus is uncertain because the potency of a specific inducible NOS inhibitor in constricting the ductus arteriosus was negligible compared with that of an endothelial cell NOS inhibitor. We speculate that NO may be an important regulator of ductus arteriosus tone at high but not low PO2. The endothelial cell NOS isoform found in vasa vasorum may be an important source of NO because removal of ductus arteriosus luminal endothelium only partially blocks the effects of L-NAME, methylene blue, and LY83583.
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PMID:Regulation of ductus arteriosus patency by nitric oxide in fetal lambs: the role of gestation, oxygen tension, and vasa vasorum. 958 10

1. We have previously shown that nitric oxide (NO) production is essential for cholinergic inhibition of the beta-adrenergic stimulated L-type calcium current (ICa-L) in rabbit pacemaker (sino-atrial node (SAN)) cells. The present experiments demonstrate the presence of constitutive nitric oxide synthase (cNOS) in SAN cells, and characterize the NO-mediated cholinergic response. 2. Immunohistochemical staining, using an antibody prepared against endothelial cNOS, demonstrated that this enzyme was present in single myocytes obtained from the SAN. 3. The activation of cNOS is known to be Ca2+ and calmodulin dependent. Strongly buffering intracellular Ca2+ with the membrane-permeable chelator BAPTA-AM (10 microM) significantly reduced (and in some cases abolished) the attenuation of ICa-L by the muscarinic agonist carbamylcholine (CCh). In contrast, the CCh-induced activation of an outward K+ current, IK,ACh, was unaffected by buffering of [Ca2+]i. The calmodulin inhibitor 48/80 (20 microM) also abolished the attenuation of ICa-L by CCh, with no change in the activation of IK,ACh. 4. Neither thapsigargin nor ryanodine (5-10 microM), agents which deplete intracellular Ca2+ stores, significantly changed the attenuation of ICa-L by CCh. 5. Pertussis toxin (PTX) completely abolished both the inhibitory action of CCh on ICa-L and the activation of IK,ACh. This establishes that a PTX-sensitive GTP-binding protein links the muscarinic receptor to NO synthase activation in SAN cells. 6. Our hypothesis is that NO leads to activation of a cyclic GMP (cGMP)-activated phosphodiesterase (PDE II) as a mechanism for enhanced cyclic AMP breakdown and ICa-L attenuation. This was supported by showing that a specific inhibitor of PDE II, erythro-9-(2-hydroxy-3-nonyl) adenine (EHNA), blocks the effect of CCh on ICa-L, but not on IK,ACh. Using reverse transcriptase-polymerase chain reaction techniques, we have established that PDE II is the dominant cyclic nucleotide phosphodiesterase isoform in SAN cells.
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PMID:Characteristics of nitric oxide-mediated cholinergic modulation of calcium current in rabbit sino-atrial node. 959 96

The retinoic acid (RA) and differentiation dependence of constitutive expression of the nitric oxide synthase (NOS) isoforms, iNOS, eNOS, and bNOS, was examined by reverse transcriptase polymerase chain recitation (RT-PCR) in cultured, normal, human, tracheobronchial epithelial (NHTBE) cells. In the presence of RA (RA+), early passage NHTBE cells grown in air-liquid interface (ALI) cultures undergo mucous differentiation; in the absence of RA (RA-), they undergo metaplastic squamous differentiation. Under both conditions the respective differentiated phenotype develops around day 10 of culture. We found that iNOS mRNA levels were much higher in RA+ cultures, expressing the mucous phenotype, than in RA- cultures, expressing the metaplastic squamous phenotype. In contrast, eNOS mRNA levels were much higher in RA- cultures than in RA+ cultures. Expression of bNOS was not significantly affected by the RA status. The pattern of expression of NOS isoforms was then studied during the course of development of the two cellular phenotypes. During the early stages of differentiation, expression of iNOS (RA+) and eNOS (RA-) was very low, indicating that the expression of these two isoforms was not only dependent on the presence or absence of RA, but also on the degree of differentiation. The differentiation dependence of bNOS mRNA was less obvious. Four days of RA treatment of RA- cultures, which reverses the squamous phenotype and restores mucous differentiation, induced iNOS expression in a concentration-dependent manner. eNOS expression was depressed by 10(-8) M RA, while bNOS mRNA levels were slightly reduced by 10(-6) M RA. No NOS proteins were detected in unstimulated RA+ and RA- cultures. iNOS protein was induced by cytokine treatment in RA+ cultures, in contrast to eNOS and bNOS protein levels, which were unaffected. Our studies show that constitutive expression of the NOS isoforms is differentially regulated and that iNOS and eNOS mRNA levels are dependent on the stage of mucous and squamous differentiation, respectively. bNOS expression was only marginally affected by the RA or differentiation status.
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PMID:Expression of nitric oxide synthase isoforms in normal human tracheobronchial epithelial cells in vitro: dependence on retinoic acid and the state of differentiation. 963 56

There is increasing evidence that nitric oxide (NO) is an important factor in the pathogenesis of septic shock. It is known that polymorphonuclear neutrophils (PMNs) are activated during sepsis or after surgical stress, and they then release various toxic mediators including free radicals. It has not been clear whether NO synthesis can be induced in circulating PMNs. Blood samples were obtained from 11 patients with sepsis, 23 patients with systemic inflammatory response syndrome (SIRS), and 16 patients without SIRS (nonSIRS) who underwent operation. We examined mRNA expression of inducible NO synthase (iNOS) in circulating PMNs from those patients pre- and postoperatively using the reverse transcriptase polymerase chain reaction (RT-PCR) method and measured their serum nitrate (NO2-) + nitrate (NO3-) concentration, peripheral blood white cell (WBC) count, and serum C-reactive protein (CRP) level. The frequency of iNOS expression in PMNs increased in sepsis (100%) and SIRS (70%) patients compared to that in nonSIRS patients (18%) (p < 0.001). The peripheral WBC count and CRP level were significantly higher in iNOS-positive patients than in iNOS-negative patients (p < 0.05 and p < 0.01, respectively). Postoperatively, the serum NO2- + NO3- concentration increased in 87% of septic patients and in 56% of patients with SIRS (p < 0.05 for both). Our study indicated that iNOS mRNA expression is induced in human circulating PMNs of patients with postoperative sepsis and SIRS and may be involved in the pathogenesis of the sepsis syndrome.
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PMID:Expression of inducible nitric oxide synthase in circulating neutrophils of the systemic inflammatory response syndrome and septic patients. 967 45

We have investigated the interleukin-12 (IL-12) and tumor necrosis factor-alpha (TNFalpha)-induced regulation of human natural killer (NK) cell function and their relationship with nitric oxide (NO) generation. We demonstrate that both cytokines were efficient to trigger the transcription of the inducible nitric oxide synthase (iNOS) mRNA, as detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis and intracytoplasmic fluorescence showed that iNOS protein was also induced by both cytokines. However, our data indicate that NO does not play a significant role in the effector phase of the cytotoxic activity mediated by NK-stimulated cells, inasmuch as the lytic activity was not affected in the presence of specific NO synthase inhibitors. When aminoguanidine (AMG), an inhibitor of iNOS, was added during the afferent phase of NK stimulation with IL-12 and TNFalpha, a subsequent increase in the lytic potential of the effector cells towards the NK-sensitive target cells (K562) and lymphokine-activated killer (LAK) target cells (Daudi) was observed. Conversely, the addition of chemical NO donors during the afferent step resulted in a dose-dependent inhibition of the NK and LAK cytotoxicity. Our data suggest that the enhancement of NK-cell cytotoxic activity resulting from iNOS inhibition may be correlated, at least in part, to an increase in interferon-gamma production and granzyme B expression.
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PMID:The induction of nitric oxide by interleukin-12 and tumor necrosis factor-alpha in human natural killer cells: relationship with the regulation of lytic activity. 973 Oct 67

> Objective: The purpose of this study was to determine the type of nitric oxide synthase isoform and to measure the quantities of nitric oxide synthase mRNA in the human placenta. Methods: The isoforms of nitric oxide synthase were determined in ten placentas of normal pregnant women using information regarding calcium dependence and inhibition by arginine analogs and findings from Western blot analyses and reverse transcriptase-polymerase chain reaction. Results: The activity of nitric oxide synthase was largely calcium dependent, although a small element of calcium-independent activity was observed. A stronger inhibition was shown with Nomega-nitro-l-arginine than with Nomega-monomethyl-l-arginine. On Western blots endothelial nitric oxide synthase was detected as a band of 140 kilodaltons, without evidence of inducible nitric oxide synthase. Messenger RNA of endothelial nitric oxide synthase was readily detected by reverse transcriptase-polymerase chain reaction, but that of inducible nitric oxide synthase was barely detected. The quantity of mRNA of inducible nitric oxide synthase was about 100-fold less than that of endothelial nitric oxide synthase. Conclusions: These results point to the constitutive endothelial type as the predominant isoform of nitric oxide synthase in human placenta from 37 to 41 weeks gestation, although protein and mRNA of inducible nitric oxide synthase may exist.
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PMID:Comparisons of Nitric Oxide Synthases in Normal Human Placenta from 37 to 41 Weeks Gestation: Qualitative and Quantitative Analyses. 974 1

Comparative study on effect of refined Xuefu capsule, Xuefu Zhuyu capsule and diltiazem on mRNA expression of nitric oxide synthase (NOS) and release of LDH-L, CK, GOT of hypoxic hypoglycemic cultured myocytes were studied by using the serum pharmacological method, reverse transcriptase-polymerase chain reaction (RT-PCR) and Northen blotting. It was shown that the three drugs can reduce release of LDH-L,CK,GOT of myocytes (P < 0.01), the effect of refined Xuefu capsule and diltiazem were obvious than that of Xuefu Zhuyu capsule in reducing LDH-L release and NOS mRNA expression (P < 0.01), and effect of refined Xuefu capsule was the strongest (P < 0.01). These findings indicated that all 3 drugs have significant effect in protecting myocytes which related to their effect on NO production of myocyte particularly the refined Xuefu capsule and diltiazem.
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PMID:[Effect of refined xuefu capsule on mRNA expression of nitric oxide synthase of hypoxic ischemic myocytes evaluated by northern blotting]. 977 18

In order to investigate quantitatively the differentiation and maturation process of granule cells in the postnatal development of rat cerebellum, nitric oxide synthase (NOS) activities were determined in the micro-dissected developing cerebellar layers, using our microassay method. NOS activities were increased in the molecular and internal granular layers (IGLs) during development and the activity was measurable in the neuroblastic external granular layers (EGLs). Newly devised micro-immunoblot analysis semi-quantitatively showed more amount of endothelial NOS (eNOS) and non-negligible amount of neuronal NOS (nNOS) in microsamples from EGL, compared with other developing and adult cerebellar layers. nNOS mRNA was also detected using RT-PCR (reverse transcriptase-polymerase chain reaction) in the microsamples from this germinal layer. Intraperitoneal administration of NG-nitro-l-arginine inhibited NOS activity in vivo and disturbed the layer formation in developing cerebellum.
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PMID:Quantitative analysis of nitric oxide synthase expressed in developing and differentiating rat cerebellum. 980 96

Although ethanol has long been recognized as an immunosuppressant, the effects of ethanol on immune functions in the central nervous system (CNS) have not been well characterized. Glial cells function as immune effector cells within the CNS. Nitric oxide (NO), generated by inducible NO synthase (iNOS) of activated glial cells, appears to participate in the immune defense and the pathogenesis of brain injury and several neurologic diseases. The goal of the present study was to examine the effects of ethanol on NO production and mRNA expression of iNOS following its induction by bacterial endotoxin lipopolysaccharide (LPS) in cultured glial cells. After incubation of mixed glia with LPS for 24 hr, the levels of nitrite in the culture medium were assayed by Griess reaction. We found that LPS (10-500 ng/ml) induced a concentration-dependent increase in the production of NO which was abolished by the selective iNOS inhibitor aminoguanidine. While ethanol treatment (25 to 400 mM, 24 hr exposure) had no direct effect on basal NO production, it significantly suppressed the LPS-induced increase of nitrite levels in a concentration-dependent manner. Using a semiquantitative reverse transcriptase polymerase chain reaction, we found that while ethanol by itself was unable to induce iNOS mRNA, it nevertheless suppressed LPS-induced iNOS mRNA expression. Our results that ethanol had no direct effect on NO production but inhibited LPS-induced NO, indicated an immunomodulatory role by ethanol. These findings suggest that ethanol may ameliorate the consequences of overwhelming NO generation through iNOS induction in glial cells following infection, inflammation or CNS injuries.
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PMID:Ethanol modulates induction of nitric oxide synthase in glial cells by endotoxin. 980 68


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