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Biomedical subjects

Jack R Lancaster

Publications and source records attributed to Jack R Lancaster.

At least 19 recordsLinked to original sources
PubMed2006

Tumors face NO problems?

The effect of nitric oxide (NO) synthase (NOS) II expression on cancer biology is unclear and difficult to define, with multiple reports of pro- and anti-cancer actions. Here we address the major factors that seem likely to account for these paradoxical behaviors, which include variability in NO production, heterogeneity in NO chemistry (and thus its cellular actions), and differential cellular responses. In addition, we suggest that a major determinant of the outcome of NO actions in the tumor environment is cellular adaptation/selection to the cytotoxic actions of NO.

Animals↗
PubMed2006

Xanthine oxidase-dependent regulation of hypoxia-inducible factor in cancer cells.

During chemical hypoxia induced by cobalt chloride (CoCl2), hypoxia-inducible factor 1alpha (HIF1-alpha) mediates the induction of a variety of genes including erythropoietin and vascular endothelial growth factor. We used glioma cells with oxidative phosphorylation-dependent (D54-MG) and glycolytic-dependent (U251-MG) phenotypes to monitor HIF1-alpha regulation in association with redox responsiveness to CoCl2 treatment. We showed that CoCl2 increased xanthine oxidase (XO)-derived reactive oxygen species (ROS), which causes accumulation of HIF1-alpha protein in U251-MG cells. Under these conditions, blockade of XO activity by pharmacologic (N-acetyl-L-cysteine or allopurinol) or molecular (by small interfering RNA) approaches significantly attenuated HIF1-alpha expression. Exogenous H2O2 stabilizes HIF1-alpha protein. XO was present in these cells and was the primary source of free radicals. We also showed higher XO activity in cells exposed to CoCl2 compared with cells grown in normoxia. From the experiments shown here, we concluded that ROS were indeed generated in D54-MG cells exposed to CoCl2 but it was unlikely that ROS participated in the hypoxic signal transduction pathways in this cell type. Possibly, cell type-dependent and stimulus-dependent factors may control ROS dependency or redox sensitivity of HIF1-alpha and thus HIF1-alpha activation either directly or by induction of specific signaling cascades. Our findings reveal that XO-derived ROS is a novel and critical component of HIF1-alpha regulation in U251-MG cells, pointing toward a more general role of this transcription factor in tumor progression.

Acetylcysteine↗
PubMed2006

Mechanisms of cystic fibrosis transmembrane conductance regulator activation by S-nitrosoglutathione.

We investigated the mechanisms by which S-nitrosoglutathione (GSNO) alters cystic fibrosis transmembrane conductance regulator (CFTR) mediated chloride (Cl(-)) secretion across Calu-3 cells, an extensively used model of human airway gland serous cells. Confluent monolayers of Calu-3 cells, grown under an air-liquid interface, were mounted in Ussing chambers for the measurements of chloride short circuit current (I(sc)) and trans-epithelial resistance (R(t)). Addition of GSNO into the apical compartment of these chambers resulted in significant and sustained increase of I(sc) with an IC(50) of 3.2 +/- 1 mum (mean +/- 1 S.E.; n = 6). Addition of either glibenclamide or pre-treatment of Calu-3 cells with the soluble guanylate cyclase inhibitor 1H-(1,2,4)-oxadiazolo[4,3-a]quinoxalin-1-one totally prevented the GSNO-induced increase of I(sc). Conversely, BAY 41-2272, a sGC stimulator, increased I(sc) in a dose-response fashion. The GSNO increase of I(sc) was reversed by addition of two phosphatases (PP2A1, PP2A2) into the apical compartment of Ussing chambers containing Calu-3 monolayers. Oxy-myoglobin (oxy-Mb, 300 mum) added into the apical compartment of Ussing chambers either prior or after GSNO either completely prevented or immediately reversed the increase of I(sc). However, smaller concentrations of oxy-Mb (1-10 mum), sufficient to scavenge NO in the medium (as assessed by direct measurement of NO in the Ussing chamber using an ISO-NO meter) decreased I(sc) partially. Oxy-Mb did not reverse the increase of I(sc) following addition of GSNO and cysteine (50 mum). These findings indicate that GSNO stimulates Cl secretion via both cGMP-dependent and cGMP-independent mechanisms.

Bronchodilator Agents↗
PubMed2006

Nitroxidative, nitrosative, and nitrative stress: kinetic predictions of reactive nitrogen species chemistry under biological conditions.

A freely available Windows-based program, RNSim1A, is utilized to predict metal-independent reactive nitrogen species (RNS) chemistry (oxidation, nitrosation, and nitration) under simulated biological conditions and make the following specific predictions. (1) The peak in oxidative reactions that occurs in vitro with 1:1 fluxes of (*)NO and O(2)(*)(-) does not occur under biological conditions. (2) By far, the quantitatively dominant (92-99.6%) process in vivo is oxidation, compared to nitrosation and nitration. (3) Only five of the many possible RNS reactions involving thiol (glutathione, GSH) and tyrosine are quantitatively important biologically. (4) Under inflammatory conditions, approximately 1% of O(2)(*)(-) reacts with (*)NO to produce ONOO(-), with the remainder reacting with SOD. (5) The dominant reaction of tyrosyl radical is a radical swap with GSH, producing the glutathiyl radical and regenerating tyrosine. (6) Nitrosothiol is formed virtually exclusively via radical recombination (RS(*) + (*)NO) as opposed to reaction with nitrous anhydride (N(2)O(3)). (7) Nitrosothiol is an intermediate, not an endproduct, and responds dynamically to changes in the immediate chemical environment. (8) The formation of a nitroso group on a particular thiol can be considered a marker of increased reactivity of that thiol, and it is likely that other modifications of that thiol (oxidation, glutathiolation) are more abundant than nitrosation and may be the functionally significant modification. (9) Specific chemical mechanisms are proposed for posttranslational protein modification via nitrosation, nitration, glutathiolation, and also dithiol/disulfide exchange, with important roles for the thiolate anion and O(2) (suggesting possible mechanisms for O(2) sensing) and variable degrees of exposure of cysteine thiol and tyrosine phenolate. (10) Patterns of reactivity are similar for low (20 nM) and high (500 nM) steady-state levels of NO. (11) The dominant reactions are those involving reactants at the highest concentrations (CO(2), thiol, O(2)). Because of the dominance of oxidative processes caused by RNS, the term nitroxidative stress is proposed, emphasizing the oxidative (as opposed to nitrosative or nitrative) stress that dominates RNS actions under biological conditions.

Kinetics↗
PubMed2005

Moderate hypoxia induces xanthine oxidoreductase activity in arterial endothelial cells.

Xanthine oxidoreductase (XOR) activity has been previously noted to be responsive to changes in O2 tension. While prior studies have focused on the extremes (0-3% and 95-100%) of O2 tensions, we report the influence of 10% O2 on endothelial cell XOR, a concentration resembling modest arterial hypoxia commonly found in patients with chronic cardiopulmonary diseases. Exposure of bovine aortic endothelial cells to 10% O2 increased XOR mRNA and protein abundance by 50%. Concomitantly, there was a 3-fold increase in XOR activity, XOR-dependent reactive oxygen species production, and cellular export of active enzyme. Although increases in mRNA and immunoreactive protein levels were observed, inhibition of transcription, translation, or protein degradation did not significantly alter cellular XOR specific activity, suggesting only modest contributions to 10% O2-induced effects. Exposure to 10% O2 did not increase cellular HIF-1alpha protein levels and hypoxia mimics did not alter XOR activity. Treatment of control cells with adenosine resulted in increased XOR activity similar to hypoxia. Exposure to the adenosine receptor agonist NECA increased enzymatic activity 4-fold while 8SPT, an adenosine receptor antagonist, reduced hypoxic induction of XOR activity approximately 50%. Combined, these data reveal that moderate hypoxia significantly enhances endothelial XOR specific activity, release, and XOR-derived reactive oxygen species generation. These effects appear to be mediated in part via adenosine-dependent processes.

Adenine↗
PubMed2005

Nitric oxide synthase II suppresses the growth and metastasis of human cancer regardless of its up-regulation of protumor factors.

Inducible nitric oxide (NO) synthase (NOS) II has been implicated in macrophage-mediated antitumor activity. However, use of the NOS II gene in cancer therapy is problematic because of the double-edged nature of NO action. Herein we show that adenoviral vectors mediated effective NOS II gene transfer into various human tumors. Production of NO significantly up-regulated multiple angiogenic molecules. However, the NO-producing tumor cells did not form tumors or metastases in ectopic or orthotopic xenograft nude mouse models. The dramatic loss of malignancy was due to NO-mediated apoptosis. We also generated a series of adenoviral vectors harboring mutant NOS II genes that expressed mutant NOS II proteins with defined levels of enzymatic activity. Tumor cells transduced with these NOS II genes produced NO at different levels, which directly correlated with the antitumor activity in vitro and in vivo. This demonstration using a relevant biological system shows that NO produces dose-dependent antitumor activity in vitro and in vivo, regardless of its up-regulation of protumor factors.

Adenoviridae↗
PubMed2005

Polarographic measurement of hydrogen sulfide production and consumption by mammalian tissues.

The role of nitric oxide (NO) in redox cell signaling is widely accepted. However, the biological role of another candidate small inorganic signaling molecule and the subject of this study, hydrogen sulfide (H2S), is much less known. H2S as a reductant and nucleophile has numerous potential cellular targets; however, its rapid biological oxidation suggests a fleeting cellular existence. The challenge of accurate real-time measurement of H2S at low micromolar or nanomolar concentrations in biological preparations represents a major impediment to H2S investigations. We here demonstrate the use of a novel polarographic H2S sensor (PHSS) to follow rapid changes in H2S concentration in common buffered biological solutions with a detection limit near 10 nM. The PHSS, used in combination with O2 and NO sensors in multisensor respirometry, shows stability, a high signal-to-noise ratio, and signal specificity for H2S. Preparations of rat vascular tissue exhibit H2S production on the addition of sulfhydryl-bearing amino acid substrates and H2S consumption when supplied with exogenous H2S. Taken together, these findings suggest the existence of dynamic steady-state cellular H2S levels. The PHSS should facilitate the investigation of H2S biology by providing a previously unattainable continuous record of H2S under biologically relevant conditions.

Animals↗
PubMed2005

Fatty acid transduction of nitric oxide signaling. Nitrolinoleic acid is a hydrophobically stabilized nitric oxide donor.

The aqueous decay and concomitant release of nitric oxide (*NO) by nitrolinoleic acid (10-nitro-9,12-octadecadienoic acid and 12-nitro-9,12-octadecadienoic acid; LNO2) are reported. Mass spectrometric analysis of reaction products supports a modified Nef reaction as the mechanism accounting for the generation of *NO by the aqueous reactions of fatty acid nitroalkene derivatives. Nitrolinoleic acid is stabilized by an aprotic milieu, with LNO2 decay and *NO release strongly inhibited by phosphatidylcholine/cholesterol liposome membranes and detergents when present at levels above their critical micellar concentrations. The release of *NO from LNO2 was induced by UV photolysis and triiodide-based ozone chemiluminescence reactions currently used to quantify putative protein nitrosothiol and N-nitrosamine derivatives. This reactivity of LNO2 complicates the qualitative and quantitative analysis of biological oxides of nitrogen when applying UV photolysis and triiodide-based analytical systems to biological preparations typically abundant in nitrated fatty acids. The results reveal that nitroalkene derivatives of linoleic acid are pluripotent signaling mediators that act not only via receptor-dependent mechanisms, but also by transducing the signaling actions of *NO via pathways subject to regulation by the relative distribution of LNO2 to hydrophobic versus aqueous microenvironments.

Animals↗
PubMed2005

The emerging biology of the nitrite anion.

Nitrite has now been proposed to play an important physiological role in signaling, blood flow regulation and hypoxic nitric oxide homeostasis. A recent two-day symposium at the US National Institutes of Health highlighted recent advances in the understanding of nitrite biochemistry, physiology and therapeutics.

Animals↗
PubMed2003

Control of mitochondrial respiration by NO*, effects of low oxygen and respiratory state.

Nitric oxide (NO.) inhibits mitochondrial respiration by binding to the binuclear heme a3/CuB center in cytochrome c oxidase. However, the significance of this reaction at physiological O2 levels (5-10 microM) and the effects of respiratory state are unknown. In this study mitochondrial respiration, absorption spectra, [O2], and [NO.] were measured simultaneously at physiological O2 levels with constant O2 delivery, to model in vivo respiratory dynamics. Under these conditions NO. inhibited mitochondrial respiration with an IC50 of 0.14 +/- 0.01 microm in state 3 versus 0.31 +/- 0.04 microM in state 4. Spectral data indicate that the higher sensitivity of state 3 respiration to NO. is due to greater control over respiration by an NO.-dependent spectral species in the respiratory chain in this state. These results are discussed in the context of regulation of respiration by NO. in vivo and its implications for the control of vessel-parenchymal O2 gradients.

Electron Transport↗
PubMed2003

Sickle cell disease: loss of the blood's WD40?

Sickle cell disease (SCD) is characterized by malformed erythrocytes and results in many vascular complications, including the lysis of a minor proportion of these cells, liberating free hemoglobin, which is a potent scavenger of nitric oxide (NO). SCD involves inflammatory activation, including the upregulation of vascular coagulation. Because NO possesses important anti-coagulant and anti-adhesion properties, the increased scavenging of NO in SCD undoubtedly is a major contributor to the pathology of this disease.

Anemia, Sickle Cell↗
PubMed2002

Nitric oxide is consumed, rather than conserved, by reaction with oxyhemoglobin under physiological conditions.

Although irreversible reaction of NO with the oxyheme of hemoglobin (producing nitrate and methemoglobin) is extremely rapid, it has been proposed that, under normoxic conditions, NO binds preferentially to the minority deoxyheme to subsequently form S-nitrosohemoglobin (SNOHb). Thus, the primary reaction would be conservation, rather than consumption, of nitrogen oxide. Data supporting this conclusion were generated by using addition of a small volume of a concentrated aqueous solution of NO to a normoxic hemoglobin solution. Under these conditions, however, extremely rapid reactions can occur before mixing. We have thus compared bolus NO addition to NO generated homogeneously throughout solution by using NO donors, a more physiologically relevant condition. With bolus addition, multiple hemoglobin species are formed (as judged by visible spectroscopy) as well as both nitrite and nitrate. With donor, only nitrate and methemoglobin are formed, stoichiometric with the amount of NO liberated from the donor. Studies with increasing hemoglobin concentrations reveal that the nitrite-forming reaction (which may be NO autoxidation under these conditions) competes with reaction with hemoglobin. SNOHb formation is detectable with either bolus or donor; however, the amounts formed are much smaller than the amount of NO added (less than 1%). We conclude that the reaction of NO with hemoglobin under normoxic conditions results in consumption, rather than conservation, of NO.

Hemoglobins↗
PubMed2002

Nitric oxide uptake by erythrocytes is primarily limited by extracellular diffusion not membrane resistance.

The process of NO transfer into erythrocytes (RBCs) is of critical biological importance because it regulates the bioavailability and diffusional distance of endothelial-derived NO. It has been reported that the rate of NO reaction with oxyhemoglobin (Hb) within RBCs is nearly three orders of magnitude slower than that by equal amounts of free oxyhemoglobin. Consistent with early studies on oxygen uptake by RBCs, the process of extracellular diffusion was reported to explain this much lower NO uptake by RBC encapsulated Hb (Liu, X., Miller, M. J., Joshi, M. S., Sadowska-Krowicka, H., Clark, D. A., and Lancaster, J. R., Jr. (1998) J. Biol. Chem. 273, 18709-18713). However, it was subsequently proposed that the RBC membrane provides the main resistance to NO uptake rather than the process of extracellular diffusion (Vaughn, M. W., Huang, K. T., Kuo, L., and Liao, J. C. (2000) J. Biol. Chem. 275, 2342-2348). This conclusion was based on competition experiments that were assumed to be able to determine the rate constant of NO uptake by RBCs without extracellular diffusion limitation. To test the validity of this hypothesis, we theoretically analyzed competition experiments. Here, we show that competition experiments do not eliminate the extracellular diffusion limitation. Simulation of the competition data indicates that the main resistance to NO uptake by RBCs is caused by extracellular diffusion in the unstirred layer surrounding each RBC but not by the RBC membrane. This extracellular diffusion resistance is responsible for preventing interference of NO signaling in the endothelium without the need for special NO uptake by intracellular hemoglobin or a unique membrane resistance mechanism.

Binding, Competitive↗