nitrophenols and Hypoxia

Oligonucleotides containing 4-O-(4-NO2-benzyl)thymine residues were synthesized to assess potential prodrug-type action against hypoxic cells. These modified oligonucleotides were incapable of stable duplex formation under non-hypoxic conditions. However, following deprotection of the thymine residues under bioreductive conditions, the deprotected oligonucleotides were able to form stable duplexes with target oligonucleotides.

Topics: Chromatography, High Pressure Liquid; Hypoxia; Molecular Structure; Nitrophenols; Oligonucleotides; Oxidation-Reduction; Thymine

Both phosphatidylinositide 3-kinase (PI3K)/Akt/mammalian target of rapamycin signaling and antiapoptotic Bcl-2 family members are critical for survival of acute myeloid leukemia (AML) cells. Here, we demonstrate the antileukemic effects of simultaneous inhibition of PI3K by the selective class I PI3K inhibitor GDC-0941 and of Bcl-2 family members by the BH3 mimetic ABT-737 in the context of the bone marrow microenvironment, where hypoxia and interactions with bone marrow stromal cells promote AML cell survival and chemoresistance. The combination of GDC-0941 and ABT-737 profoundly downregulated antiapoptotic Mcl-1 expression levels, activated BAX, and induced mitochondrial apoptosis in AML cells co-cultured with bone marrow stromal cells under hypoxic conditions. Hypoxia caused degradation of Mcl-1 and rendered Mcl-1-overexpressing OCI-AML3 cells sensitive to ABT-737. Our findings suggest that pharmacologic PI3K inhibition by GDC-0941 enhances ABT-737-induced leukemia cell death even under the protective conditions afforded by the bone marrow microenvironment.. Combined blockade of PI3K and Bcl-2 pathways down-regulates anti-apoptotic Mcl-1 expression PI3K and Bcl-2 induced Mcl-1 down-regulation activates BAX PI3K and Bcl-2 blockage induces apoptosis in AML under hypoxic BM microenvironment.

Topics: Apoptosis; Biphenyl Compounds; Bone Marrow; Cell Line, Tumor; Cell Proliferation; Coculture Techniques; Drug Synergism; Gene Expression Regulation, Leukemic; Humans; Hypoxia; Indazoles; Leukemia, Myeloid, Acute; Mesenchymal Stem Cells; Myeloid Cell Leukemia Sequence 1 Protein; Nitrophenols; Phosphoinositide-3 Kinase Inhibitors; Piperazines; RNA Interference; Sulfonamides; Tumor Microenvironment

Regions of low oxygen concentration (hypoxia) occur in both normal human physiology and under pathophysiological conditions. Fluorescent probes for the direct imaging of cellular hypoxia could be useful tools that complement radiochemical imaging and immunohistochemical staining methods. In this work, we set out to characterize the hypoxia-selective enzymatic metabolism of a simple nitroaryl probe, 6-nitroquinoline (1). We envisioned that this compound might undergo hypoxia-selective, bioreductive conversion to the fluorescent product, 6-aminoquinoline (2). The probe 1 was, indeed, converted to a fluorescent product selectively under hypoxic conditions by the one-electron reducing enzyme NADPH:cytochrome P450 reductase. However, inspection of the fluorescence spectrum and LC-MS analysis of the reaction mixture revealed that the expected product 2 was not formed. Rather, the 63-fold increase in fluorescence emission at 445 nm resulting from the hypoxic metabolism of 1 was due to formation of the azoxy-helicene product, pyrido[3,2-f]quinolino[6,5-c]cinnoline 3-oxide (4). The generation of 4 involves an unusual biaryl bond formation under reductive conditions. The mechanism of this process remains uncertain but could proceed via combination of a nitroaryl radical anion with a neutral nitrosoaryl radical, followed by tautomerization and intramolecular condensation between the resulting hydroxylamine and nitroso functional groups. Bioreductive metabolism of nitroaryl compounds represents a promising strategy for the selective delivery of cytotoxic agents and fluorescent markers to hypoxic tissue, but the results described here provide an important glimpse of the chemical complexity that can be associated with the enzymatic one-electron reduction of nitroaryl compounds.

Topics: Aminoquinolines; Cell Hypoxia; Electrons; Fluorescent Dyes; Humans; Hypoxia; Molecular Structure; NADPH-Ferrihemoprotein Reductase; Nitrophenols; Oxidation-Reduction; Polycyclic Compounds; Pyridines; Quinolines

Solid tumors contain hypoxic regions in which cancer cells are often resistant to chemotherapy-induced apoptotic cell death. Therapeutic strategies that specifically target hypoxic cells and promote apoptosis are particularly appealing, as few normal tissues experience hypoxia. We have found that the compound ABT-737, a Bcl-2 homology domain 3 (BH-3) mimetic, promotes apoptotic cell death in human colorectal carcinoma and small cell lung cancer cell lines exposed to hypoxia. This hypoxic induction of apoptosis was mediated through downregulation of myeloid cell leukemia sequence 1 (Mcl-1), a Bcl-2 family protein that serves as a biomarker for ABT-737 resistance. Downregulation of Mcl-1 in hypoxia was independent of hypoxia-inducible factor 1 (HIF-1) activity and was consistent with decreased global protein translation. In addition, ABT-737 induced apoptosis deep within tumor spheroids, consistent with an optimal hypoxic oxygen tension being necessary to promote ABT-737–induced cell death. Tumor xenografts in ABT-737–treated mice also displayed significantly more apoptotic cells within hypoxic regions relative to normoxic regions. Synergies between ABT-737 and other cytotoxic drugs were maintained in hypoxia, suggesting that this drug may be useful in combination with chemotherapeutic agents. Taken together, these findings suggest that Mcl-1–sparing BH-3 mimetics may induce apoptosis in hypoxic tumor cells that are resistant to other chemotherapeutic agents and may have a role in combinatorial chemotherapeutic regimens for treatment of solid tumors.

Topics: Animals; Apoptosis; Biphenyl Compounds; Cell Line, Tumor; Down-Regulation; Drug Resistance, Neoplasm; Drug Screening Assays, Antitumor; Humans; Hypoxia; Inhibitory Concentration 50; Male; Mice; Myeloid Cell Leukemia Sequence 1 Protein; Neoplasm Transplantation; Neoplasms; Nitrophenols; Peptide Fragments; Piperazines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Sulfonamides

A role for BCL-xL in regulating neuronal activity is suggested by its dramatic effects on synaptic function and mitochondrial channel activity. When recombinant BCL-xL is injected into the giant presynaptic terminal of squid stellate ganglion or applied directly to mitochondrial outer membranes within the living terminal, it potentiates synaptic transmission acutely, and it produces mitochondrial channel activity. The squid, however, is a genetically intractable model, making it difficult to apply genetic tools in squid to explore the role of endogenous BCL-xL in synaptic function. Therefore the small molecule inhibitor ABT-737, a mimetic of the BH3-only protein BAD, binding to the BH3-binding domain pocket, was tested in squid, revealing a dual role for BCL-xL. ABT-737 slowed recovery of synaptic responses after repetitive synaptic activity, indicating that endogenous BCL-xL is necessary for timely recovery of rapidly firing synapses. Unexpectedly, however, ABT-737 also protected neurons from hypoxia-induced synaptic rundown and from increased permeability of the mitochondrial outer membrane during hypoxia. This implies that endogenous BCL-xL or a modified form of BCL-xL, such as the N-truncated, proteolytic, pro-apoptotic cleavage product, DeltaN BCL-xL, contributes to injurious responses of the hypoxic synapse. To determine if ABT-737 is also an inhibitor of DeltaN BCL-xL, recombinant DeltaN BCL-xL protein was injected into the synapse. ABT-737 potently inhibited synaptic rundown induced by recombinant DeltaN BCL-xL. These observations support the possibility that endogenous proteolysis or a functionally equivalent modification of BCL-xL is responsible for the deleterious effects of hypoxia on synaptic activity.

Topics: Animals; bcl-X Protein; Biphenyl Compounds; Dose-Response Relationship, Radiation; Electric Stimulation; Ganglia, Invertebrate; Hypoxia; Loligo; Membrane Potentials; Mitochondrial Membranes; Mutation; Neurons; Nitrophenols; Piperazines; Presynaptic Terminals; Sulfonamides; Synaptic Transmission

The anti-ischemic and anti-anoxic effects of efonidipine, a dihydropyridine calcium antagonist, were studied in several models for cerebral ischemia and anoxia in mice and rats, and the effects were compared with those of nicardipine and flunarizine. Both efonidipine and flunarizine showed protective effects in the models of KCN-induced anoxia and complete ischemia induced by decapitation in mice 6 hr after the treatment, while nicardipine did not show such a long-lasting effect. Efonidipine (1 mg/kg, i.p.), but not nicardipine and flunarizine, prolonged the tolerance times in the asphyxic anoxia model. In mice, efonidipine (4 mg/kg, i.p.) significantly reduced the cumulative mortality rate after bilateral carotid artery ligation. The survival rates at 20 hr after bilateral carotid artery ligation were 33% in the group treated with efonidipine, significantly higher than that in the control group, 0%. On the other hand, the treatment with nicardipine or flunarizine did not increase the rates at 20 hr after the ligation. Moreover, efonidipine attenuated the disturbance of cerebral energy metabolism induced by decapitation in rats. These effects of efonidipine observed in this study were on the whole superior to those of the reference drugs, strongly suggesting the improving effect of efonidipine on cerebral ischemia and anoxia.

Topics: Animals; Brain Ischemia; Calcium Channel Blockers; Dihydropyridines; Flunarizine; Hypoxia; Male; Mice; Mice, Inbred ICR; Nicardipine; Nitrophenols; Organophosphorus Compounds; Rats; Rats, Wistar

Evidence indicates that the diffusion of O2 and CO in tissue may be facilitated by a carrier molecule having a P50 that approximates tissue O2 partial pressure (PO2; 1-15 Torr) and a much higher affinity for CO than for O2. To determine whether cytochrome P-450 in lung satisfies these criteria, we measured the effect of hypoxia and of CO on the rate of metabolism of the cytochrome P-450 mediated O-demethylation of p-nitroanisole in isolated perfused rabbit lungs. Metabolism was inhibited by 50% of a control at an estimated tissue PO2 fo 4 Torr (5.5 microM). When inspired CO2 was kept at 200 Torr and inspired CO partial pressure (PCO) varied an estimated tissue PCO/PO2 ratio of 0.025 reduced the reaction rate by 50% of control, but some metabolism persisted at PCO/PO2 ratios larger than one. The relationship between reaction rate and PCO/PO2 ratio could not be fit by a single value for Haldane constant for M (CO affinity/O2 affinity) but could be described with a two-component model in which metabolism was equally divided between a high-affinity cytochrome (M = 200) and a low-affinity cytochrome (M = 2). These findings suggest that cytochrome P-450 could act as a carrier for O2 and CO in tissue with low PO2's.

Topics: Animals; Carbon Monoxide; Cytochrome P-450 Enzyme System; Dealkylation; Hypoxia; In Vitro Techniques; Kinetics; Lung; Male; Nitroanisole O-Demethylase; Nitrophenols; Oxygen Consumption; Rabbits; Time Factors

Topics: Animals; Binding Sites; Diphosphates; Enzyme Activation; Hypoxia; Liver; Male; Malonates; Mitochondria, Liver; Nitrophenols; Oxaloacetates; Pressure; Protein Binding; Protein Denaturation; Quinones; Rats; Spectrophotometry; Succinate Dehydrogenase; Succinates; Time Factors; Ubiquinone

Topics: Adenine Nucleotides; Animals; Anura; Cell Membrane; Fluorides; Gastric Mucosa; Histamine; Hydrogen-Ion Concentration; Hypoxia; In Vitro Techniques; Kinetics; Nitrophenols; Organophosphorus Compounds; Ouabain; Phosphoric Monoester Hydrolases; Potassium; Rana catesbeiana; Thiocyanates; Time Factors

Topics: Animals; Electrophysiology; Hypoxia; In Vitro Techniques; Insecta; Intestine, Large; Nitrophenols; Ouabain; Temperature

Topics: Aminoisobutyric Acids; Animals; Biological Transport, Active; Carbon Isotopes; Cell Membrane Permeability; Depression, Chemical; Hypoxia; Manometry; Muscle Denervation; Muscles; Muscular Diseases; Nitrophenols; Ouabain; Oxygen Consumption; Rats; Tendons

Topics: Fluoroacetates; Hypoxia; Iodoacetates; Muscle Contraction; Myocardium; Nitrophenols

Topics: 2,4-Dinitrophenol; Animals; Dinitrophenols; Hypoxia; Nitrogen; Nitrophenols; Oxygen Consumption; Rats

Topics: Amino Acids; Dipeptidases; Glycine; Hypoxia; Intestine, Small; Intestines; Methionine; Nitrophenols; Peptide Hydrolases

Topics: Age Factors; Animals; Anura; Depression; Depressive Disorder; Humans; Hypoxia; Nitrophenols; Phosphorylation

Topics: Animals; Biological Transport; Dinitrophenols; Glucose; Hypoxia; Insulin; Muscles; Myocardium; Nitrophenols; Phosphorylation; Rats; Salicylates

Topics: Body Temperature; Dinitrophenols; Hypoxia; Nitrophenols; Thermogenesis

Topics: Biochemical Phenomena; Hypoxia; Nitrophenols; Oxygen; Phosphorylation; Starvation

The results reported in this paper indicate that dinitrophenol acts directly on the isolated heart, increasing its metabolic rate. It also produces heart failure associated with a low phosphocreatine content of the muscle but with no change in adenosine triphosphate, which may or may not be due to a relative hypoxia of the cardiac tissue. Experimental arterial hypoxaemia, if severe, produces a similar picture of heart failure with a decrease in phosphocreatine and no change in adenosine triphosphate. Ligation of the coronary arteries results in disappearance of the major part of the phosphocreatine within a few minutes regardless of whether or not ventricular fibrillation ensues; the adenosine triphosphate remains unchanged.

Topics: Adenosine Triphosphate; Animals; Blood Circulation; Coronary Vessels; Dinitrophenols; Dogs; Heart; Heart Failure; Humans; Hypoxia; Ischemia; Myocardium; Nitrophenols; Phosphocreatine; Phosphorus; Phosphorus Compounds

Topics: 2,4-Dinitrophenol; Acetates; Heart; Hypoxia; Nitrophenols

Topics: Body Fluids; Hepatocytes; Hypoxia; In Vitro Techniques; Liver; Nitrophenols; Osmotic Pressure; Oxidative Phosphorylation; Oxygen; Phosphorylation; Water