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Scientific Reports Jan 2019We report herein on the design, synthesis and biological activity of Ru-based self-assembled supramolecular bowls as a potent anticancer therapeutic in human...
We report herein on the design, synthesis and biological activity of Ru-based self-assembled supramolecular bowls as a potent anticancer therapeutic in human hepatocellular cancer. The potent complex induces production of reactive oxygen species (ROS) by higher fatty acid β-oxidation and down-regulation of glucose transporter-mediated pyruvate dehydrogenase kinase 1 via reduced hypoxia-inducible factor 1α. Also, overexpressed acetyl-CoA activates the tricarboxylic acid cycle and the electron transport system and induces hypergeneration of ROS. Finally, ROS overexpressed through this pathway leads to apoptosis. Furthermore, we demonstrate that the naphthalene derived molecular bowl activates classical apoptosis via crosstalk between the extrinsic and intrinsic signal pathway. Our work into the mechanism of Ru-based self-assembled supramolecular bowls can provide valuable insight into the potential for use as a promising anticancer agent.
Topics: Antineoplastic Agents; Apoptosis; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Survival; Coordination Complexes; Humans; Liver Neoplasms; Models, Theoretical; Reactive Oxygen Species; Rubidium
PubMed: 30659228
DOI: 10.1038/s41598-018-36755-9 -
The Journal of Biological Chemistry Jan 2018Procedures to define kinetic mechanisms from catalytic activity measurements that obey the Michaelis-Menten equation are well established. In contrast, analytical tools...
Procedures to define kinetic mechanisms from catalytic activity measurements that obey the Michaelis-Menten equation are well established. In contrast, analytical tools for enzymes displaying non-Michaelis-Menten kinetics are underdeveloped, and transient-state measurements, when feasible, are therefore preferred in kinetic studies. Of note, transient-state determinations evaluate only partial reactions, and these might not participate in the reaction cycle. Here, we provide a general procedure to characterize kinetic mechanisms from steady-state determinations. We described non-Michaelis-Menten kinetics with equations containing parameters equivalent to and and modeled the underlying mechanism by an approach similar to that used under Michaelis-Menten kinetics. The procedure enabled us to evaluate whether Na/K-ATPase uses the same sites to alternatively transport Na and K This mechanism is supported by transient-state studies but contradicted to date by steady-state analyses claiming that the release of one cationic species as product requires the binding of the other ( mechanism). To derive robust conclusions about the Na/K-ATPase transport mechanism, we did not rely on ATPase activity measurements alone. During the catalytic cycle, the transported cations become transitorily occluded ( trapped within the enzyme). We employed radioactive isotopes to quantify occluded cations under steady-state conditions. We replaced K with Rb because K has a short half-life, and previous studies showed that K- and Rb-occluded reaction intermediates are similar. We derived conclusions regarding the rate of Rb deocclusion that were verified by direct measurements. Our results validated the ping-pong mechanism and proved that Rb deocclusion is accelerated when Na binds to an allosteric, nonspecific site, leading to a 2-fold increase in ATPase activity.
Topics: Humans; Ion Transport; Kinetics; Models, Chemical; Potassium; Rubidium; Sodium; Sodium-Potassium-Exchanging ATPase
PubMed: 29191836
DOI: 10.1074/jbc.M117.799536 -
British Journal of Anaesthesia Mar 1976The effects of acute and long-term lithium (LiCl) and rubidium chloride (RbCl) treatments on the sleeping time caused by intravenous thipentone, methohexitone, ketamine,... (Comparative Study)
Comparative Study
The effects of acute and long-term lithium (LiCl) and rubidium chloride (RbCl) treatments on the sleeping time caused by intravenous thipentone, methohexitone, ketamine, propanidid. Althesin and diazepam were studied in white mice. The doses of the anasthetic agents were selected from the dose-response experiments. When given acutely, LiCl 5 m-equiv/kg prolonged significantly the sleeping time caused by both of the barbiturates, whereas RbCl given for 21 days in tap water shortened the sleeping time induced by methohexitone and ketamine. Both LiCl and RbCl, given acutely, enhanced the sleeping time caused by diazepam. The rectal temperatures were lower in the LiCl-treated mice than in the control and RbCl-treated mice.
Topics: Alfaxalone Alfadolone Mixture; Anesthesia, Intravenous; Animals; Diazepam; Dose-Response Relationship, Drug; Drug Synergism; Ketamine; Lithium; Male; Methohexital; Mice; Propanidid; Rubidium; Sleep; Thiopental; Time Factors
PubMed: 1259882
DOI: 10.1093/bja/48.3.185 -
The Journal of Physiology Oct 2003KCNQ1 K+ channels in humans are important for repolarization of cardiac action potentials and for K+ secretion in the inner ear. The pore-forming channel subunits form...
KCNQ1 K+ channels in humans are important for repolarization of cardiac action potentials and for K+ secretion in the inner ear. The pore-forming channel subunits form heteromeric complexes with small regulatory subunits of the KCNE family, in particular with KCNE1 to form channels that conduct a slow delayed rectifier K+ current, IKs. This association leads to alteration of biophysical properties, including a slowing of activation, a suppression of inactivation and an increase of the apparent single-channel conductance. In addition, inward Rb+ currents conducted by homomeric KCNQ1 channels are about threefold larger than K+ currents, whereas heteromeric KCNQ1-KCNE1 channels have smaller inward Rb+ currents compared to K+ currents. We determined inactivation properties and compared K+ vs. Rb+ inward currents for channels formed by co-assembly of KCNQ1 with KCNE1, KCNE3 and KCNE5, and for homomeric KCNQ1 channels with point mutations in the pore helix S5 or S6 transmembrane domains. Several of the channels with point mutations eliminated the apparent inactivation of KCNQ1, as described previously (Seebohm et al. 2001). We found that the extent of inactivation and the ratio of Rb+/K+ currents were positively correlated. Since the effect of Rb+ on the current size has been shown previously to be related to a fast 'flickery' process, our results suggest that inactivation of KCNQ1 channels is related to a fast flicker of the open channel. A kinetic model incorporating two open states, no explicit inactivated state and a fast flicker that is different for the two open states is able to account for the apparent inactivation and the correlation of inactivation and large Rb+ currents. We conclude that an association between KCNQ1 and KCNE subunits or removal of inactivation by mutation of KCNQ1 stabilizes the open conformation of the pore principally by altering an interaction between the pore helix and the selectivity filter and with S5/S6 domains.
Topics: Action Potentials; Algorithms; Animals; Electrophysiology; Extracellular Space; Ion Channel Gating; KCNQ Potassium Channels; KCNQ1 Potassium Channel; Kinetics; Membrane Potentials; Models, Molecular; Oocytes; Patch-Clamp Techniques; Potassium; Potassium Channel Blockers; Potassium Channels; Potassium Channels, Voltage-Gated; Rubidium; Sodium; Xenopus laevis
PubMed: 14561821
DOI: 10.1113/jphysiol.2003.046490 -
The Journal of General Physiology May 1971IN THE DEVELOPMENT OF OUABAIN INHIBITION OF RUBIDIUM INFLUX IN HUMAN RED BLOOD CELLS A TIME LAG CAN BE DETECTED WHICH IS A FUNCTION OF AT LEAST THREE VARIABLES: the...
IN THE DEVELOPMENT OF OUABAIN INHIBITION OF RUBIDIUM INFLUX IN HUMAN RED BLOOD CELLS A TIME LAG CAN BE DETECTED WHICH IS A FUNCTION OF AT LEAST THREE VARIABLES: the concentrations of external sodium, rubidium, and ouabain. The inhibition is antagonized by rubidium and favored by sodium. Similar considerations could be applied to the binding of ouabain to membrane sites. The total influx of rubidium as a function of external rubidium concentration can be separated into two components: (a) a linear uptake not affected by external sodium or ouabain and not requiring an energy supply, and (b) a saturable component. The latter component, on the basis of the different effects of the aforementioned factors, can be divided into three fractions. The first is ouabain-sensitive, inhibited by external sodium at low rubidium, and requires an energy supply; this represents about 70-80% of the total uptake and is related to the active sodium extrusion mechanism. The second is ouabain-insensitive, activated by external sodium over the entire range of rubidium concentrations studied, and dependent on internal ATP; this represents about 15% of the total influx; it could be coupled to an active sodium extrusion or belong to a rubidium-potassium exchange. The third, which can be called residual influx, is ouabain-insensitive, unaffected by external sodium, and independent of internal ATP; this represents about 10-20% of the total influx.
Topics: Adenosine Triphosphate; Binding Sites; Biological Transport, Active; Erythrocytes; Humans; Kinetics; Ouabain; Radioisotopes; Rubidium; Sodium; Time Factors
PubMed: 5553102
DOI: 10.1085/jgp.57.5.576 -
Journal of Ocular Pharmacology and... Feb 2010The primary objective of this study was to examine the possibility of inhibiting oxidative damage to the lens in vitro by caffeine.
PURPOSE
The primary objective of this study was to examine the possibility of inhibiting oxidative damage to the lens in vitro by caffeine.
METHODS
Oxidative damage was inflicted by incubating mouse lenses in Tyrode medium containing 0.1 mM Fe(8)Br(8), an iron complex soluble in aqueous medium. Parallel incubations were conducted in the presence of caffeine (5 mM).
RESULTS
Lenses incubated in the medium containing Fe(8)Br(8) undergo oxidative stress, as evidenced by the inhibition of Na(+)-K(+) ATPase-driven rubidium transport and the loss of tissue glutathione and ATP. These effects were prevented in presence of caffeine. That the effects are due to the oxyradicals produced was ascertained further by parallel studies with Tempol (5 mM), a well-known scavenger of reactive oxygen species (ROS) with its activity being more pronounced with hydroxyl radicals as compared to other ROS.
CONCLUSIONS
Caffeine was found to be effective in preventing oxidative stress to the lens induced by iron under ambient conditions. The protective effect is attributable to its ability to scavenge ROS, particularly the hydroxyl radical.
Topics: Adenosine Triphosphate; Animals; Antioxidants; Biological Transport; Caffeine; Cyclic N-Oxides; Free Radical Scavengers; Glutathione; Hydroxyl Radical; In Vitro Techniques; Iron Compounds; Lens, Crystalline; Mice; Mice, Inbred Strains; Oxidative Stress; Reactive Oxygen Species; Rubidium; Sodium-Potassium-Exchanging ATPase; Spin Labels
PubMed: 20148663
DOI: 10.1089/jop.2009.0097 -
Biochimica Et Biophysica Acta May 2013A comprehensive study of the interaction between Na(+) and K(+) with the Na(+)/K(+)-ATPase requires dissecting the incidence of alternative cycling modes on activity...
A comprehensive study of the interaction between Na(+) and K(+) with the Na(+)/K(+)-ATPase requires dissecting the incidence of alternative cycling modes on activity measurements in which one or both of these cations are absent. With this aim, we used membrane fragments containing pig-kidney Na(+)/K(+)-ATPase to perform measurements, at 25°C and pH=7.4, of ATPase activity and steady-state levels of (i) intermediates containing occluded Rb(+) at different [Rb(+)] in media lacking Na(+), and (ii) phosphorylated intermediates at different [Na(+)] in media lacking Rb(+). Most relevant results are: (1) Rb(+) can be occluded through an ATPasic cycling mode that takes place in the absence of Na(+) ions, (2) the kinetic behavior of the phosphoenzyme formed by ATP in the absence of Na(+) is different from the one that is formed with Na(+), and (3) binding of Na(+) to transport sites during catalysis is not at random unless rapid equilibrium holds.
Topics: Adenosine Diphosphate; Adenosine Triphosphate; Animals; Biocatalysis; Dose-Response Relationship, Drug; Kidney Medulla; Kinetics; Models, Biological; Phosphorylation; Protein Binding; Rubidium; Sodium; Sodium-Potassium-Exchanging ATPase; Swine
PubMed: 23357355
DOI: 10.1016/j.bbamem.2013.01.010 -
Molecules (Basel, Switzerland) Sep 2018Ion association is an important process in aqueous dissolution, precipitation, and crystallization of ionic inorganic, organic, and biological materials....
Ion association is an important process in aqueous dissolution, precipitation, and crystallization of ionic inorganic, organic, and biological materials. Polyoxometalates (POMs) are good model compounds for understanding the complex relationships between lattice energy, ion-pairing in solution, and salt solubility. Here we perform calorimetric measurements to elucidate trends in cluster stability, lattice energy, and ion-pairing behavior studies of simple hexatantalate salts in neat water, parent hydroxide solutions, and molybdate melts, extending previous studies on the isostructural hexaniobates. High temperature calorimetry of alkali salts of hexatantalate reveals that the enthalpies of formation from oxides of the K, Rb, and Cs salts are more similar to each other than they are for their niobate analogues and that the tantalate cluster is energetically less stable than hexaniobate. Aqueous dissolution calorimetry reveals that the cesium salt of hexatantalate has a similar concentration dependence on its dissolution enthalpy to that of hexaniobate. However, unlike rubidium hexaniobate, rubidium hexatantalate also exhibits increased concentration dependence, indicating that hextantalate can undergo increased ion-pairing with alkali salts other than cesium, despite the dilute environments studied. Dissolution enthalpies of POM salts in the parent alkali hydroxides shows that protonation of clusters stabilizes lattices even more than the strongly associating heavy alkali cations do. Additionally, neither weak nor strong lattice ion associations necessarily correlates with respectively high or low aqueous solubility. These studies illuminate the importance of considering ion-pairing among the interrelated processes in the aqueous dissolution of ionic salts that can be extended to serving as a model of cation association to metal oxide surfaces.
Topics: Calorimetry; Cesium; Hot Temperature; Ions; Metals, Alkali; Rubidium; Salts; Thermodynamics; Tungsten Compounds; Water
PubMed: 30250000
DOI: 10.3390/molecules23102441 -
Journal of Nuclear Medicine : Official... Oct 1983In order to validate a new method for quantifying coronary blood flow, we injected intravenously a bolus of rubidium-82 (Rb-82) into 28 open-chested dogs under a wide...
In order to validate a new method for quantifying coronary blood flow, we injected intravenously a bolus of rubidium-82 (Rb-82) into 28 open-chested dogs under a wide range of flow and physiologic conditions, using beta probes to monitor myocardial radioactivity. Extraction fraction and perfusion were measured using a functional model that separates the data into the free and trapped myocardial rubidium. Extraction and uptake of rubidium were lower during acidosis than during alkalosis and were unchanged by glucose-insulin, digoxin, or propranolol. Myocardial flow, as indicated by rubidium, correlated linearly with simultaneous measurements of flow by microspheres in the same sample volume over a wide range of flow (r = 0.97, n = 106, range 0.02-7.76 ml/min/g). Regional myocardial blood flow can be accurately determined using generator-produced Rb-82. Studies using current state-of-the-art, fast positron-emission tomographic cameras are required to determine the utility of this approach in man.
Topics: Animals; Coronary Circulation; Digoxin; Dogs; Heart; Hydrogen-Ion Concentration; Hyperglycemia; Methods; Microspheres; Myocardium; Propranolol; Radioisotopes; Radionuclide Imaging; Rubidium
PubMed: 6619961
DOI: No ID Found -
The Journal of Physiology Aug 19821. The effects of low concentrations of Cs(+) (0.01-3mM) on the fully activated I-V relation ī(f)(E) for the pace-maker current in calf Purkinje fibres have been...
1. The effects of low concentrations of Cs(+) (0.01-3mM) on the fully activated I-V relation ī(f)(E) for the pace-maker current in calf Purkinje fibres have been investigated. The action of Cs(+) is two-fold: in the negative region of the I-V curve Cs(+) induces a channel blockade; on the other hand, at more positive potentials Cs(+) can produce the opposite effect, i.e. a current increase.2. Cs(+)-induced blockade is concentration- and voltage-dependent, as observed on other cation channels. Data in the far negative voltage range (about - 150 to - 50 mV) can be fitted by a simple block model (Woodhull, 1973), which gives a mean value of 0.71 for the fraction of membrane thickness (delta) crossed by Cs(+) ions before reaching the blocking site. The value of delta does not appear to be affected by either external Na or external K concentrations. Values for the dissociation constant of the blocking reaction at E = 0 mV (k(0)) are found in the range 0.5-3.7 mM. In the positive region of the ī(f)(E) relation the current depression caused by channel blockade vanishes. Unexpectedly, in this range the current can be observed to increase with Cs(+), and ī(f)(E) curves in different Cs(+) concentrations show cross-over.3. Changing external K(+) also produces similar cross-over phenomena. Investigation of this effect reveals that the increase in slope of the I-V curve on raising the external K(+) concentration follows Michaelis-Menten kinetics, and can be interpteted in terms of K(+)-induced channel activation. It is found that 44+/-6 mM-K(+) half-saturates the channel activating reaction.4. The Cs(+)-induced current increase is large in low-K(+) solutions and vanishes in high-K(+) solutions, suggesting a competition between Cs(+) and K(+) ions in their activating action. Increasing Na(+) also limits the Cs(+)-induced current increase.5. Rb(+) also blocks the i(f) channel, though less efficiently than Cs(+). The block caused by Rb(+) is, unlike that of Cs(+), nearly voltage-independent, and is explained by assuming that the blocking reaction occurs near the external mouth of the channel (mean value of delta is 0.05). The zero-voltage dissociation constant (k(0)) of the Rb(+)-blocking reaction ranges between 1.4 and 5.4 mM, and is lower in low-Na(+), high-K(+) solutions.6. A possible characterization of the i(f) channel which explains these results includes an inner ;blocking' site, to which external Cs(+) ions bind, blocking the channel, and a more external ;activatory' site, to which K(+), Cs(+), Rb(+) and possibly Na(+) ions bind. Binding of K(+) to this site induces a current increase either by modulating the channel, or actually by opening the channel itself. A similar mechanism can apply to Cs(+) and to Rb(+) binding.
Topics: Animals; Binding, Competitive; Cattle; Cesium; Dose-Response Relationship, Drug; Heart Conduction System; In Vitro Techniques; Ion Channels; Kinetics; Membrane Potentials; Potassium; Purkinje Fibers; Rubidium
PubMed: 6292407
DOI: 10.1113/jphysiol.1982.sp014315