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)

The purpose of this investigation was to determine whether mouse lung fibroblast subsets have the ability to produce nitric oxide (NO), and if so, to characterize the induction and effects of its synthesis. Previously, we isolated Thy1+ and Thy1- subpopulations of mouse lung fibroblasts, which differ in terms of cytokine production, morphology, response to cytokines and radiation, and ability to present antigen to T lymphocytes. When treated with the proinflammatory cytokines IFN-gamma, TNF-alpha, and IL-1 alpha, these fibroblast lines produce micromolar quantities of NO2- and NO3-, two stable end products of the NO pathway. A combination of all three cytokines provided the greatest induction, and there was no measurable production of NO in unstimulated cells. Thy1+ fibroblasts have fewer requirements for induction of NO production than the Thy1- line, in that NO production could be induced by only two of the above cytokines, where the Thy1- fibroblasts required all three. Inducible NO synthase (iNOS) mRNA was shown to be present by the reverse transcriptase-polymerase chain reaction as early as 2 hr after cytokine treatment in both cell lines. Addition of the NO synthase inhibitors NG-monomethyl-L-arginine and aminoguanidine inhibited production of NO2- and NO3-, but not iNOS mRNA. This inhibition was partially reversed by the addition of an excess of L-arginine. Interestingly, inhibition of NO synthesis was shown to decrease IL-6 production by more than 50% in cytokine-treated Thy1+ fibroblasts. These results indicate for the first time that Thy1+ and Thy1- mouse lung fibroblast subsets have the capability to produce NO to differing extents in response to cytokines and may therefore play an important role in the inflammatory response in the lung as well as in the progression of lung disease.
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PMID:Induction of nitric oxide synthase in subsets of murine pulmonary fibroblasts: effect on fibroblast interleukin-6 production. 751 14

Alcohol abuse increases the incidence and severity of opportunistic lung infections and pneumonias. Inducible nitric oxide (NO) synthase (iNOS II) and NO may be a pivotal system in the intracellular bactericidal activity of macrophages. We tested the hypothesis that acute administration of ethanol (ETOH) suppressed Escherichia coli endotoxin lipopolysaccharide (LPS) mediated upregulation of the iNOS II system in the lung of the rat, in vivo. We also tested the effect of ETOH on alveolar macrophage (AM) production of free NO using microelectrodes. Male Sprague-Dawley rats were given ETOH (5.5 g/kg, IP) 30 min. before giving intratracheal sterile phosphate buffered saline solution (PBS, 0.5 ml) or LPS (1 mg/kg in a total volume of 0.5 ml PBS). The isolated lungs were subjected to bronchoalveolar lavage (BAL) 3.5 hr. later. Aliquots of the BAL fluid were assayed for tumor necrosis factor alpha TNF alpha and reactive nitrogen intermediates (nitrate and nitrite) (RNI) with chemiluminescence. Aliquots of AM were incubated 1 hr ex vivo for spontaneous production of RNI or frozen and assayed for iNOS II mRNA with competitor exchange reverse transcriptase polymerase chain reaction (cERT-PCR). The lung was homogenized and assayed for RNI. LPS increased BAL fluid TNF alpha and RNI, lung RNI, and the spontaneous production of RNI by AM, ex vivo. These effects were inhibited by in vivo administration of inhibitors of iNOS II. LPS increased iNOS mRNA in AM. This was unaffected by iNOS inhibitors. ETOH suppressed LPS-induced BAL fluid TNF, iNOS mRNA and RNI production by AM and the lung.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Ethanol suppresses LPS-induced mRNA for nitric oxide synthase II in alveolar macrophages in vivo and in vitro. 753 15

Nitric oxide (NO) is produced by numerous different cell types, and it is an important regulator and mediator of many processes including smooth muscle relaxation, neurotransmission, and murine macrophage-mediated cytotoxicity for microbes and tumor cells. Although murine macrophages produce NO readily after activation, human monocytes and tissue macrophages have been reported to produce only low levels of NO in vitro. The purpose of this study was to determine if stimulated human mononuclear phagocytes produce inducible nitric oxide synthase (iNOS) mRNA, protein, and enzymatic activity. By reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, we show that human monocytes can be induced to express iNOS mRNA after treatment with lipopolysaccharide (LPS) and/or interferon-gamma (IFN-gamma). By immunofluorescence and immunoblot analyses, we show monocytes and peritoneal macrophages contain detectable levels of iNOS antigen after stimulations with cytokines in vitro. Control monocytes or those cultured with LPS and/or various cytokines have low levels of NOS functional activity as measured by the ability of cell extracts to convert L-arginine to L-citrulline, and they produce low levels of the NO catabolites nitrite and nitrate. Peritoneal macrophages have significantly enhanced nitrite/nitrate production and NOS activity after treatment with LPS and/or IFN-gamma, whereas monocyte nitrite/nitrate production and NOS activity are not altered by the treatments. Monocytes cultured with various live or heat-killed bacteria, fungi, or human immunodeficiency virus (HIV)-1 do not produce high levels of nitrite/nitrate. Antibodies against transforming growth factor-beta (TGF-beta), a factor known to inhibit iNOS expression and NO production in mouse macrophages, do not enhance NO production in human monocytes or macrophages. Biopterin, an obligate cofactor of iNOS enzymatic activity, is undetectable in freshly isolated or cultured human monocytes and peritoneal macrophages. However, replenishment of intracellular levels of tetrahydrobiopterin by culture with the cell-permeable, nontoxic precursor sepiapterin does not enhance the abilities of the human mononuclear phagocytes to produce NO in vitro. Mixing experiments show no evidence of a functional NOS inhibitor in human mononuclear phagocytes. Thus, we demonstrate that human mononuclear phagocytes can produce iNOS mRNA and protein, and (despite this) their abilities to generate NO are very low.
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PMID:Human mononuclear phagocyte inducible nitric oxide synthase (iNOS): analysis of iNOS mRNA, iNOS protein, biopterin, and nitric oxide production by blood monocytes and peritoneal macrophages. 754 98

Nitric oxide synthesis requires the cofactor tetrahydrobiopterin. We have examined the effect on nitric oxide synthesis in experimental endotoxic shock of 2,4- diamino-6-hydroxypyrimidine (DAHP), an inhibitor of GTP cyclohydrolase I, the first and rate limiting enzyme for tetrahydrobiopterin synthesis. Rats given lipopolysaccharide (LPS, 10 mg/kg) showed a large rise in plasma nitrate at 4 and 8 hours which was significantly reduced by DAHP (1 g/kg) given at the same time as LPS. There was a 40-50% reduction in the haem-NO signal detected in kidney by electron paramagnetic resonance spectroscopy. LPS produced hypotension at 3 hours and 6 hours and this was ameliorated at 6 hours in rats given DAHP. DAHP abolished the rise in kidney tetrahydrobiopterin levels seen 4 hours after LPS but no effect was seen on induction of inducible nitric oxide synthase (iNOS) as assessed by immunohistochemistry and reverse transcriptase PCR, consistent with the effect of DAPH being by reduction of tetrahydrobiopterin levels. The results show that inhibition of tetrahydrobiopterin synthesis is an effective strategy to reduce nitric oxide synthesis by iNOS in vivo.
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PMID:Inhibition of tetrahydrobiopterin synthesis reduces in vivo nitric oxide production in experimental endotoxic shock. 860 31

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

Human hepatoma cells (HepG2) were exposed to several heavy metal salts and the induction of heat shock protein 70 (hsp70) mRNA was analysed by the reverse transcriptase-polymerase chain reaction (RT-PCR). Metals were added to the cell medium at concentrations ranging from 0.1 to 100 microM and incubation was continued for 4 h. In addition we analysed the time dependence of hsp70 induction by adding each metal at a certain concentration followed by an incubation for 0.5 to 24 h. CdCl2, NaAsO2, AgNO3 could be classified as very strong inducers (20-, 13- and 10-fold above control level) and they reached their maximum level of induction at 1-10 microM after 2 h. CuCl2, MnCl2, Pb(NO3)2, TlNO3, CoCl2 and NiCl2 were also strong inducing agents, giving a 4-6 fold induction at 10-100 microM after 4-8 h. ZnSO4, Hg(NO3)2 and AlCl3 were only weak inducers (1.5-2 fold at 50-100 microM after 4-8 h) of hsp70 mRNA. Cytotoxic effects (measured by release of lactate dehydrogenase) could only be detected for 100 microM Hg2+ after 4 h and when the cells were incubated with 5 microM Cd2+ for more than 8 h. We also tested a few combinations of these heavy metal salts for their hsp70-inducing ability. Zn2+ and Mn2+ were able to diminish Cd2+ induced hsp70 mRNA levels by 65%. Ag+ mediated induction was reduced by 40% when combined with Cu2+, whereas Hg2+ increased induction by Ag+ about 3-fold and led to a dramatic decrease in cell viability. In our study we were able to demonstrate that the analysis of hsp70 mRNA levels in chemically stressed HepG2 cells by RT-PCR can be a valuable tool for studying mechanisms of toxicity associated with elevated expression of hsp70.
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PMID:Analysis of hsp70 mRNA levels in HepG2 cells exposed to various metals differing in toxicity. 982 Jun 63

The effect of 44 different metal ions (Ag+, Al3+, As(O-)2, Au3+, Ba2+, Be2+, Bi3+, Cd2+, Ce3+, CO2+, Cr(O2-)4, Cr3+, Cs+, Cu2+, Fe3+, Fe2+, Ga3+, Ge4+, Hg2+, Ir4+, La3+, Li+, Mn2+, MO6+, Ni2+, OS4+, Pb2+, Pt4+, Rb+, Rh3+, Sb5+, Se(O2-)4, Se(O2-)3, Sn2+, Sr2+, Th4+, T1+, U(O2+)2, V(O-)3, VO2+, W(O2-)4, Y3+, Zn2+, and Zr4+) on the activity of the reverse transcriptase (RT) of the human immunodeficiency virus (HIV-1) was investigated in vitro. For this study, the RT activity assay was carried out by means of an enzyme-linked immunosorbent assay (ELISA) kit, using the template/primer hybrid poly(A) oligo(dT)15, which required some modifications: (1) possible interfering metal chelators (such as EDTA) in the original lysis buffer were avoided, and a new buffer (50 mM Tris-NO3, pH 7.8) was used throughout; (2) an amount of 2 ng of RT per well was considered to be optimal after checking the linearity of the reaction with increasing amounts of enzyme; (3) an incubation temperature of 37 degrees C and an incubation time of 1 h were chosen after preliminary studies in a wide range of temperature and time. At an incubation temperature > or = 40 degrees C, there was a dramatic loss of enzymatic activity. In addition, when RT alone was preincubated for 1 h at 5 degrees C, 25 degrees C, and 37 degrees C, there was a large (83%) loss of activity at 37 C as compared to that at 5 degrees C. These results are indicative of enzyme thermolability, which is higher in the absence of substrates. The effect of metal ions on RT activity was tested using two different metal salt concentrations (10(-4) M and 10(-5) M). Under such experimental conditions, the presence of five metal ions (Pt4+, Ag+, Rh3+, Zn2+, and Hg2+) decreased the RT activity in a dose-response fashion. The observed order of effectiveness with respect to inhibition was Pt4+ > Ag+ > Rh3+ > Zn2+ = Hg2+. Estimated mean inhibitory concentrations (IC50) were 7.8 microM for (NH4)2PtCl6, 14.1 microM for AgNO3, 46.8 microM for RhCl3, 53.7 microM for Zn(SO)4, and 56.2 microM for Hg(NO3)2. Because these data are of the same order of magnitude as the corresponding values related to other RT inhibitors used in anti-AIDS therapy, metal compounds or their derivatives could give an interesting contribution in the development of new RT inhibitors for clinical use.
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PMID:Effects of trace metal compounds on HIV-1 reverse transcriptase: an in vitro study. 1032 22

Expression of the inducible isoform of nitric oxide synthase (iNOS) is stimulated by cytokines in human epithelial cells. This work indicates that incubation of human umbilical cord endothelial cells with combinations of interleukin-1beta, tumor necrosis factor alpha, and interferon-gamma stimulated the synthesis of iNOS mRNA, as detected by reverse transcriptase-polymerase chain reaction. It is important to note that 50, 100, and 200 microM hydrogen peroxide was able to stimulate iNOS directly. Furthermore, 100 microM H2O2 enhanced synthesis of the oxidation products, nitrite (NO2-) and nitrate (NO3-) at 12 and 36 h. iNOS protein, detected by Western blot analysis, as well as L-citrulline levels, were also increased. When endothelial cell monolayers were incubated for 1 h with 100 microM H2O2 and subsequently with cytokines, iNOS mRNA was further augmented. Under the same conditions, we regularly observed an inhibition (25%) of intercellular adhesion molecule-1 (ICAM-1/CD54) expression. The latter was reversed when the NOS inhibitor N(G)-monomethyl-L-arginine was added, as shown by flow cytometry. These data suggest a specific effect of endogenous hydroperoxides on the biosynthesis and processing of the human endothelial iNOS isoform. We propose that H2O2 induces a temporary NO-dependent modulation of adhesion molecule expression to limit the tissue destruction that accompanies the vascular recruitment of leukocytes.
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PMID:Regulation of ICAM-1/CD54 expression on human endothelial cells by hydrogen peroxide involves inducible NO synthase. 1073 92

Nuclear and cytoplasmic proteins of human female breast cancer were analysed by one-dimensional sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Oestrogen receptor and progesterone receptor expression was determined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. The electropherograms were developed by silver nitrate staining and quantitative analysis was carried out by video densitometer using the software Gel-Pro Analyzer. Nuclear and cytoplasmic proteins of breast carcinomas and normal tissue differed both qualitatively and quantitatively. Nuclear polypeptides of 108, 53 and 48 kD as well as the 36 kD cytoplasmic polypeptide were specific for tumour samples, while the 51 kD nuclear polypeptide was detected only in normal tissue. Quantitative differences in band density were noted in the 32 kD nuclear polypeptide. This polypeptide was expressed in greatest concentration in infiltrating ductal carcinomas which also indicated the greatest oestrogen receptor gene expression. This relationship appeared to be statistically significant (p < 0.005). No correlations were evident between the 32 kD protein expression and the progesterone receptor gene expression in any of the tissue types examined, nor between the 32 kD protein and the patient's age or tumour grade.
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PMID:Female breast carcinomas: nuclear and cytoplasmic proteins versus steroid receptors. 1075 81

The mechanisms underlying the development of hypertension in obesity are not yet fully understood. We recently reported the development of hypertension in a rat model of diet-induced obesity. When Sprague-Dawley rats (n=60) are fed a moderately high fat diet (32 kcal% fat) for 10 to 16 weeks, approximately half of them develop obesity (obesity-prone [OP] group) and mild hypertension (158+/-3.4 mm Hg systolic pressure), whereas the other half (obesity-resistant [OR] group) maintains a body weight equivalent to that of a low fat control group and is normotensive (135.8+/-3.8 mm Hg). We examined the potential role of oxidative stress in the development of hypertension in this model. Lipid peroxides measured as thiobarbituric acid-reactive substances showed a significant increase in the LDL fraction of OP rats (2.8+/-0.32 nmol malondialdehyde/mg protein) compared with OR and control rats (0.9+/-0.3 nmol malondialdehyde/mg protein). Also, aortic and kidney thiobarbituric acid-reactive substances showed a significant (3- and 5- fold) increase in OP rats after 16 weeks of diet. In addition, superoxide generation by aortic rings, measured by lucigenin luminescence, showed a 2-fold increase in the OP group compared with both the OR and control groups. In addition, free isoprostane excretion and nitrotyrosine in the kidney showed an increase in OP rats only. The urine and plasma nitrate/nitrite measured by the LDH method showed a 1.8-fold decrease in OP rats compared with OR rats. However, endothelial NO synthase expression in the kidney cortex and medulla assessed by reverse transcriptase-polymerase chain reaction showed a strong increase in the OP rats versus OR and control rats (endothelial NO synthase/beta-actin ratio 1.3+/-0.04 in OP rats versus 0.44+/-0.02 in OR rats), suggesting a possible shift toward superoxide production by the enzyme. Collectively, the data show a decreased NO bioavailability in OP animals that is due in part to the increased oxidative stress.
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PMID:Oxidative stress in a rat model of obesity-induced hypertension. 1123 Mar 34


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