Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0004135 (ATM)
 13,001 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent evidence suggests that oxidative mechanisms may be involved in vascular smooth muscle cell (VSMC) hypertrophy. We previously showed that angiotensin II (Ang II) increases superoxide production by activating an NADH/NADPH oxidase, which contributes to hypertrophy. In this study, we determined whether Ang II stimulation of this oxidase results in H2O2 production by studying the effects of Ang II on intracellular H2O2 generation, intracellular superoxide dismutase and catalase activity, and hypertrophy. Ang II (100 nmol/L) significantly increased intracellular H2O2 levels at 4 hours. Neither superoxide dismutase activity nor catalase activity was affected by Ang II; the SOD present in VSMCs is sufficient to metabolize Ang II-stimulated superoxide to H2O2, which accumulates more rapidly than it is degraded by catalase. This increase in H2O2 was inhibited by extracellular catalase, diphenylene iodonium, an inhibitor of the NADH/NADPH oxidase, and the AT1 receptor blocker losartan. In VSMCs stably transfected with antisense p22phox, a critical component of the NADH/NADPH oxidase in which oxidase activity was markedly reduced, Ang II-induced production of H2O2 was almost completely inhibited, confirming that the source of Ang II-induced H2O2 was the NADH/NADPH oxidase. Using a novel cell line that stably overexpresses catalase, we showed that this increased H2O2 is a critical step in VSMC hypertrophy, a hallmark of many vascular diseases. Inhibition of intracellular superoxide dismutase by diethylthiocarbamate (1 mmol/L) also resulted in attenuation of Ang II-induced hypertrophy (62+/-2% inhibition). These data indicate that AT1 receptor-mediated production of superoxide generated by the NADH/NADPH oxidase is followed by an increase in intracellular H2O2, suggesting a specific role for these oxygen species and scavenging systems in modifying the intracellular redox state in vascular growth.
 ...
PMID:Role of NADH/NADPH oxidase-derived H2O2 in angiotensin II-induced vascular hypertrophy. 974 Jun 15

In spite of very distinct genotypic assets, a number of congenital conditions include oxidative stress as a phenotypic hallmark. These disorders include Fanconi's anaemia, ataxia telangiectasia, xeroderma pigmentosum and Bloom's syndrome, as well as two frequent congenital conditions: Down's syndrome and cystic fibrosis. Cancer proneness is a clinical feature shared by these disorders, while other manifestations include early ageing, neurological symptoms or congenital malformations. The onset of oxidative stress has been related to excess formation, or defective detoxification, of reactive oxygen species (ROS). This can arise from either the abnormal expression or inducibility of ROS-detoxifying enzymes, or by defective absorption of nutrient antioxidants. Resulting oxidative injury has been characterized through: (i) DNA, protein or lipid oxidative damage; (ii) excess ROS formation (in vitro and ex vivo); (iii) sensitivity to oxygen-related toxicity; (iv) improvement of cellular defects by either hypoxia or antioxidants; and (v) circumstantial evidence for in vivo oxidative stress (as e.g. clastogenic factors). Investigations conducted so far have been confined to individual disorders. Comparative studies of selected indicators for oxidative stress could provide further insights into the pathogenesis of each individual condition. Such a unified approach may have wide-ranging consequences for studies of ageing and cancer.
 ...
PMID:Congenital disorders sharing oxidative stress and cancer proneness as phenotypic hallmarks: prospects for joint research in pharmacology. 979 4

Classically the AT1 receptors to angiotensin II are considered to be present on the smooth muscle cell membrane in the arterial wall, in which they diffusely regulate peripheral resistances. They are also present on numerous other cell types, including fibroblasts and myofibroblasts, monocytes and macrophages, endothelial cells, where they participate to the phenotypic modulation of the cell, involved in their activation leading to tissular remodeling. The intra-cellular pathway involving the phospholipase C activation and the mobilization of intra-cellular calcium is predominantly involved in the functional vasomotor response to angiotensin II. In contrast the intra-cellular signaling pathway leading to production of oxygen free radicals and activation of the NF-kappa-B system is probably mainly involved in the phenotypic modulation of target cells and their consequences on the vascular tissue remodeling.
 ...
PMID:[Effects of angiotensin ii on vascular remodeling]. 985 82

Angiotensin II (Ang II) and basic fibroblast growth factor (bFGF) are important modulators of cell growth under physiological and pathophysiological conditions. We and others have previously shown that these growth factors increase insulin-like growth factor-1 receptor (IGF-1R) number and mRNA in vascular smooth muscle cells and that this effect is transcriptionally regulated. To study the mechanisms and the signaling pathways involved, IGF-1R promoter reporter constructs were transiently transfected in CHO-AT1 cells that overexpress angiotensin AT1 receptors. Our findings indicate that Ang II and bFGF significantly increased IGF-1R promoter activity up to 7- and 3-fold, respectively. The effect induced by Ang II was mediated via a tyrosine kinase-dependent mechanism, since tyrphostin A25 largely inhibited the Ang II-induced increase in promoter activity. In addition, co-transfection of dominant negative Ras, Raf, and MEK1 or pretreatment with the MEK inhibitor PD 98059 dose-dependently decreased both the Ang II- and bFGF-induced increase in IGF-1R transcription and protein expression, suggesting that the Ras-Raf-mitogen-activated protein kinase kinase pathway is required for both growth factors. Reactive oxygen species have been shown to act as second messengers in Ang II-induced signaling, and activation of the transcription factor NF-kappaB is redox-sensitive. While co-transfection of dominant negative IkappaBalpha mutant completely inhibited the Ang II-induced increase in transcription, it had no effect on the bFGF signaling. In contrast, co-transfection studies indicated that the transcription factors STAT1, STAT3, and c-Jun and the Janus kinase 2 kinase are required in the signaling pathway of bFGF, whereas only dominant c-Jun inhibited the Ang II-induced effect. In summary, these data demonstrate that Ang II and bFGF increase IGF-1R gene transcription via distinct as well as shared pathways and have important implications for understanding growth-stimulatory effects of these growth factors on vascular cells.
 ...
PMID:Distinct and common pathways in the regulation of insulin-like growth factor-1 receptor gene expression by angiotensin II and basic fibroblast growth factor. 992 Aug 98

Acute hypoxic pulmonary vasoconstriction (HPV) may be mediated by vasoactive peptides. We studied eight conscious, chronically tracheostomized dogs kept on a standardized dietary sodium intake. Normoxia (40 min) was followed by hypoxia (40 min, breathing 10% oxygen, arterial oxygen pressures 36 +/- 1 Torr) during both control (Con) and losartan experiments (Los; iv infusion of 100 microg. min-1. kg-1 losartan). During hypoxia, minute ventilation (by 0.9 l/min in Con, by 1.3 l/min in Los), cardiac output (by 0.36 l/min in Con, by 0.30 l/min in Los), heart rate (by 11 beats/min in Con, by 30 beats/min in Los), pulmonary artery pressure (by 9 mmHg in both protocols), and pulmonary vascular resistance (by 280 and 254 dyn. s. cm-5 in Con and Los, respectively) increased. Mean arterial pressure and systemic vascular resistance did not change. In Con, PRA decreased from 4.2 +/- 0.7 to 2.5 +/- 0.5 ng ANG I. ml-1. h-1, and plasma ANG II decreased from 11.9 +/- 3.0 to 8.2 +/- 2.1 pg/ml. The renin-angiotensin system is inhibited during acute hypoxia despite sympathetic activation. Under these conditions, ANG II AT1-receptor antagonism does not attenuate HPV.
 ...
PMID:Acute hypoxic pulmonary vasoconstriction in conscious dogs decreases renin and is unaffected by losartan. 1036 56

Ataxia-telangiectasia (A-T) is characterized by a markedly increased sensitivity to ionizing radiation, increased incidence of cancer, and neurodegeneration, especially of the cerebellar Purkinje cells. Ionizing radiation oxidizes macromolecules and causes tissue damage through the generation of reactive oxygen species (ROS). We therefore hypothesized that A-T is due to oxidative damage resulting from loss of function of the A-T gene product. To assess this hypothesis, we employed an animal model of A-T, the mouse with a disrupted Atm gene. We show that organs which develop pathologic changes in the Atm-deficient mice are targets of oxidative damage, and that cerebellar Purkinje cells are particularly affected. These observations provide a mechanistic basis for the A-T phenotype and lay a rational foundation for therapeutic intervention.
 ...
PMID:Loss of the ataxia-telangiectasia gene product causes oxidative damage in target organs. 1044 94

We recently described a novel approach to measuring regional tumor oxygen tension using (19)F pulse burst saturation recovery (PBSR) nuclear magnetic resonance (NMR) echo planar imaging (EPI) relaxometry of hexafluorobenzene. We now compare oxygen tension measurements in a group of size-matched R3327-AT1 Dunning prostate rat tumors made using this new method with those using a traditional polarographic method: the Eppendorf histograph. Similar oxygen tension distributions were found using the two methods, and both techniques showed that tumors with volume greater than 3.5 cm(3) were significantly (P < 0.0001) less well oxygenated than smaller tumors (volume less than 2 cm(3)). Using the (19)F EPI approach, we also examined the response to respiratory challenge. Increasing the concentration of inspired oxygen from 33% to 100% O(2) produced a significant increase (P < 0.0001) in tumor oxygenation for a group of small tumors. In contrast, no change was observed in the mean pO(2) for a group of large tumors. Consideration of individual tumor regions irrespective of tumor size showed a strong correlation between the maximum pO(2) observed when breathing 100% O(2) compared with mean baseline pO(2). These results further demonstrate the usefulness of (19)F EPI to assess changes in regional tumor oxygenation.
 ...
PMID:Regional tumor oxygenation and measurement of dynamic changes. 1045 84

Highly reactive oxygen species (ROS) are involved in T-cell activation and in the defense against environmental pathogens. An imbalance of ROS generation and detoxifying scavenger enzymes could contribute to the increased susceptibility to cancer and infections in ataxia telangiectasia. We studied oxidative status, i.e. plasma total antioxidant capacity (TEAC), retinol, alpha-tocopherol, ubiquinol, and the number of activated T cells in 10 patients with ataxia telangiectasia (AT) compared to age-matched healthy controls. As expected, patients showed significantly increased levels of activated human leukocyte antigen-DR and CD45RO expressing T cells. TEAC levels as well as the exogenous antioxidants retinol and alpha-tocopherol were significantly reduced in patients. In addition, patients showed slightly reduced plasma levels of the endogenous ROS scavenger enzyme ubiquinol (Q10). Although no correlation between number of activated T-cells and antioxidant capacity could be demonstrated, an increase in ROS and a diminished reactive oxygen scavenger capacity may be involved in the disease process of patients with AT.
 ...
PMID:Anti-oxidative capacity in patients with ataxia telangiectasia. 1046 59

Oxygen consumption at peak exercise (peak VO2) is a strong independent predictor of the outcome in congestive heart failure (CHF). Renin-angiotensin system inhibition with either ACE or AT1 receptor blockers is effective on peak VO2. We evaluated whether mechanisms are similar for the 2 categories of drugs and whether their combination is able to produce a synergistic effect. Twenty CHF patients were randomized to receive, in a double-blind fashion, placebo + placebo (P+P), enalapril (20 mg/day) + placebo (E+P), losartan (50 mg/day) + placebo (L+P), and enalapril + losartan (E+L) or the same preparations in a reverse order, each for 8 weeks. Two patients did not complete the trial. Pulmonary function, cardiopulmonary exercise test, plasma neurohormones, and quality of life were assessed at the end of each treatment. Compared with P+P, E+P, and L+P similarly (16% and 15%, respectively) and significantly (p <0.01) augmented peak VO2. Enalapril improved lung function (reduced slope of ventilation vs carbon dioxide production and dead space to tidal volume ratio, and increased alveolar membrane conductance and tidal volume). Losartan likely activated the exercising muscle perfusion (raised delta VO2/delta work rate, which is a measure of aerobic work efficiency). In combination, they further increased peak VO2, 10% from E+P (p <0.05) and 11% from L+P (p <0.05). Compared with run-in, E+P and L+P significantly reduced plasma norepinephrine by 70 +/- 14 pg/ml and 100 +/- 16 pg/ml and aldosterone by 1.6 +/- 0.7 ng/dl and 1.6 +/- 0.8 ng/dl. These changes were significantly greater when the drugs were combined (140 +/- 20 pg/ml for norepinephrine, and 5.6 +/- 0.9 ng/dl for aldosterone). Quality-of-life score did not improve significantly at each treatment step. Thus, lorsartan and enalapril similarly increased peak VO2 in CHF patients, but mediators of this effect were, at least in part, different therapeutic targets that may be synergistic when the 2 drugs are combined.
 ...
PMID:Synergistic efficacy of enalapril and losartan on exercise performance and oxygen consumption at peak exercise in congestive heart failure. 1056 60

ATM (ataxia telangiectasia mutated), the gene mutated in ataxia telangiectasia, is related to a family of large phosphatidylinositol 3-kinase domain-containing proteins involved in cell cycle control and DNA repair. We found that ATM(-/-) DT40 cells were more susceptible than wild-type cells to apoptosis induced not only by ionizing radiation and bleomycin but also by non-DNA-damaging apoptotic stimuli such as C(2)-ceramide. Furthermore, the apoptosis induced by C(2)-ceramide and H(2)O(2) was blocked by anti-oxidants, indicating that the ATM(-/-) DT40 cells had a heightened susceptibility to apoptosis induced by reactive oxygen intermediates (ROI), presumably due to defective ROI-detoxification activities. In support of this hypothesis, we found that more ROI were generated in ATM(-/-) DT40 cells than in wild-type cells, following treatment with the above apoptotic stimuli. These results indicate that ATM plays important roles in the maintenance of the cell homeostasis in response to oxidative damage.
 ...
PMID:Protective roles for ATM in cellular response to oxidative stress. 1078 20


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>