Rhinovirus-induced oxidative stress and interleukin-8 elaboration involves p47-phox but is independent of attachment to intercellular adhesion molecule-1 and viral replication.
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Virus-induced elaboration of proinflammatory cytokines is mediated by virus-induced oxidative stress. The purpose of these studies was to determine the source of the virus-induced oxidative stress. Inhibition of viral replication with antibody to intercellular adhesion molecule-1 had no effect on virus-induced oxidative stress or interleukin-8 (IL-8) response (597+/-88 vs. 668+/-78 pg/mL in control cells). Treatment of cells with diphenylene iodonium inhibited virus-induced oxidative stress and IL-8 elaboration, but allopurinol, ibuprofen, and rotenone had no effect. Studies in cell lines produced from a patient with gp91-phox deficiency revealed normal responses. In contrast, the oxidative response was decreased and the IL-8 concentration was 227+/-36 pg/mL in cells from a patient with p47-phox deficiency, compared with 664+/-48 pg/mL in control cells. These studies suggest that the stimulation of reactive oxygen species by viral challenge occurs at the cell surface even in the absence of viral replication and involves a flavoprotein that may act in concert with p47-phox. (+info)
The binding of oxidized low density lipoprotein (ox-LDL) to ox-LDL receptor-1 reduces the intracellular concentration of nitric oxide in endothelial cells through an increased production of superoxide.
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Oxidized low density lipoprotein (ox-LDL) has been suggested to affect endothelium-dependent vascular tone through a decreased biological activity of endothelium-derived nitric oxide (NO). Oxidative inactivation of NO is regarded as an important cause of its decreased biological activity, and in this context superoxide (O(2)) is known to inactivate NO in a chemical reaction during which peroxynitrite is formed. In this study we examined the effect of ox-LDL on the intracellular NO concentration in bovine aortic endothelial cells and whether this effect is influenced by ox-LDL binding to the endothelial receptor lectin-like ox-LDL receptor-1 (LOX-1) through the formation of reactive oxygen species and in particular of O(2). ox-LDL induced a significant dose-dependent decrease in intracellular NO concentration both in basal and stimulated conditions after less than 1 min of incubation with bovine aortic endothelial cells (p < 0.01). In the same experimental conditions ox-LDL also induced O(2) generation (p < 0.001). In the presence of radical scavengers and anti-LOX-1 monoclonal antibody, O(2) formation induced by ox-LDL was reduced (p < 0.001) with a contemporary rise in intracellular NO concentration (p < 0.001). ox-LDL did not significantly modify the ability of endothelial nitric oxide synthase to metabolize l-arginine to l-citrulline. The results of this study show that one of the pathophysiological consequences of ox-LDL binding to LOX-1 may be the inactivation of NO through an increased cellular production of O(2). (+info)
Reactive oxygen species production in association with suberization: evidence for an NADPH-dependent oxidase.
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In response to wounding, potato tubers generate reactive oxygen species (ROS) in association with suberization. Immediately following wounding, an initial burst of ROS occurs, reaching a maximum within 30 to 60 min. In addition to this initial oxidative burst, at least three other massive bursts occur at 42, 63 and 100 h post-wounding. These latter bursts are associated with wound healing and are probably involved in the oxidative cross-linking of suberin poly(phenolics). The source of ROS is likely to be a plasma membrane NADPH-dependent oxidase immunorelated to the human phagocyte plasma membrane oxidase. The initial oxidative burst does not appear to be dependent on new protein synthesis, but the subsequent bursts are associated with an increase in oxidase protein components. Oxidase activity is enhanced in vitro by hydroxycinnamic acids and conjugates associated with the wound healing response in potato. (+info)
A new vasoconstrictor, a preliminary report.
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Otrivin,(R) a compound of the hydrochloride salt of phenyl-aminomethylimidazoline, was administered to 74 patients for varying periods as a nasal vasoconstrictor. Seventy-three had relief of nasal congestion for from five to six hours-longer periods than had been obtained with other vasoconstrictors they had used. No pressor effect was noted. (+info)
Induction of defence gene expression by oligogalacturonic acid requires increases in both cytosolic calcium and hydrogen peroxide in Arabidopsis thaliana.
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Responses to oligogalacturonic acid (OGA) were determined in transgenic Arabidopsis thaliana seedlings expressing the calcium reporter protein aequorin. OGA stimulated a rapid, substantial and transient increase in the concentration of cytosolic calcium ([Ca2+]cyt) that peaked after ca. 15 s. This increase was dose-dependent, saturating at ca. 50 ug Gal equiv/ml of OGA. OGA also stimulated a rapid generation of H2O2. A small, rapid increase in H2O2 content was followed by a much larger oxidative burst, with H2O2 content peaking after ca. 60 min and declining thereafter. Induction of the oxidative burst by OGA was also dose-dependent, with a maximum response again being achieved at ca. 50 ug Gal equiv/mL. Inhibitors of calcium fluxes inhibited both increases in [Ca2+]cyt and [H2O2], whereas inhibitors of NADPH oxidase blocked only the oxidative burst. OGA increased strongly the expression of the defence-related genes CHS, GST, PAL and PR-1. This induction was suppressed by inhibitors of calcium flux or NADPH oxidase, indicating that increases in both cytosolic calcium and H2O2 are required for OGA-induced gene expression. (+info)
Sensitization of tumor cells toward chemotherapy: enhancing the efficacy of camptothecin with imidazolines.
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Activation of nuclear transcription factor kappaB (NF-kappaB) by chemotherapeutic agents was found to protect cells from apoptosis. In light of its central role in regulating the cellular resistance to apoptotic agents, inhibition of NF-kappaB-mediated gene transcription may sensitize tumor cells to chemotherapeutic agents and enhance their efficacy. We describe herein a noncytotoxic imidazoline scaffold that sensitizes leukemia T cells to the chemotherapeutic agent camptothecin. No significant induction of apoptosis was found when cells were treated with the imidazoline; however, pretreatment of cells with this agent resulted in a drastic enhancement in efficacy of camptothecin (approximately 75-fold). Elucidation of the potential cellular mechanism revealed that the imidazoline prevents nuclear translocation of NF-kappaB. These findings indicate that inhibition of NF-kappaB by this imidazoline may present improved strategies in the chemotherapeutic treatment of cancer. (+info)
Voltage- and NADPH-dependence of electron currents generated by the phagocytic NADPH oxidase.
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The phagocytic NADPH oxidase generates superoxide by transferring electrons from cytosolic NADPH to extracellular O2. The activity of the oxidase at the plasma membrane can be measured as electron current (I(e)), and the voltage dependence of I(e) was recently reported to exhibit a strong rectification in human eosinophils, with the currents being nearly voltage independent at negative potentials. To investigate the underlying mechanism, we performed voltage-clamp experiments on inside-out patches from human eosinophils activated with PMA. Electron current was evoked by bath application of different concentrations of NADPH, whereas slow voltage ramps (0.8 mV/ms), ranging from -120 to 200 mV, were applied to obtain 'steady-state' current-voltage relationships (I-V). The amplitude of I(e) recorded at -40 mV was minimal at 8 microM NADPH and saturated above 1 mM, with half-maximal activity (K(m)) observed at approx. 110 microM NADPH. Comparison of I-V values obtained at different NADPH concentrations revealed that the voltage-dependence of I(e) is strongly influenced by the substrate concentration. Above 0.1 mM NADPH, I(e) was markedly voltage-dependent and steeply decreased with depolarization within the physiological membrane potential range (-60 to 60 mV), the I-V curve strongly rectifying only below -100 mV. At lower NADPH concentrations the I-V curve was progressively shifted to more positive potentials and I(e) became voltage-independent also within the physiological range. Consequently, the K(m) of the oxidase decreased by approx. 40% (from 100 to 60 microM) when the membrane potential increased from -60 to 60 mV. We concluded that the oxidase activity depends on both membrane potential and [NADPH], and that the shape of the I(e)-V curve is influenced by the concentration of NADPH in the submillimolar range. The surprising voltage-independence of I(e) reported in whole-cell perforated patch recordings was most likely due to substrate limitation and is not an intrinsic property of the oxidase. (+info)
Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle.
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In vascular smooth muscle (VSM) of Squalus acanthias, endothelin-1 (ET-1) signals via the ET(B) receptor. In both shark and mammalian VSM, ET-1 induces a rise in cytosolic Ca(2+) concentration ([Ca(2+)](i)) via activation of the inositol trisphosphate (IP(3)) receptor (IP(3)R) and subsequent release of Ca(2+) from the sarcoplasmic reticulum (SR). IP(3)R-mediated release of SR Ca(2+) causes calcium-induced calcium release (CICR) via the ryanodine receptor (RyR), which can be sensitized by cyclic adeninediphosphate ribose (cADPR). cADPR is synthesized from NAD(+) by a membrane-bound bifunctional enzyme, ADPR cyclase. We have previously shown that the antagonists of the RyR, Ruthenium Red, high concentrations of ryanodine and 8-Br cADPR, diminish the [Ca(2+)](i) response to ET-1 in shark VSM. To investigate how ET-1 might influence the activity of the ADPR cyclase, we employed inhibitors of the cyclase. To explore the possibility that ET-1-induced production of superoxide (O(2)*-) might activate the cyclase, we used an inhibitor of NAD(P)H oxidase (NOX), DPI and a scavenger of O(2)*-, TEMPOL. Anterior mesenteric artery VSM was loaded with fura-2AM to measure [Ca(2+)](i). In Ca(2+)-free shark Ringers, ET-1 increased [Ca(2+)](i) by 104+/-8 nmol l(-1). The VSM ADPR cyclase inhibitors, nicotinamide and Zn(2+), diminished the response by 62% and 72%, respectively. Both DPI and TEMPOL reduced the response by 63%. The combination of the IP(3)R antagonists, 2-APB or TMB-8, with DPI or TEMPOL further reduced the response by 83%. We show for the first time that in shark VSM, inhibition of the ADPR cyclase reduces the [Ca(2+)](i) response to ET-1 and that superoxide may be involved in the activation of the cyclase. (+info)