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PubMed2005

Herb-drug interactions: interactions between kava and prescription medications.

Patients over age 50 typically present with one chronic disease per decade. Each chronic disease usually requires long-term drug therapy, meaning most older patients require several drugs to control their conditions and/or maintain their health. Simultaneously, the use of complementary and alternative medications (CAM) has increased in the United States over the last 20 years, reaching 36% in 2002; herbal medicine use accounts for approximately 22% of all CAM use. Older adults often add herbal medicines to medications prescribed by their physicians, yet do not always inform the physician. The drug metabolizing enzyme systems process all compounds foreign to the body including prescription drugs and herbal medications. Therefore use of both medicinals simultaneously has a potential for interactions of an adverse nature. This review, which will discuss kava, is one in a series covering the documented interactions between herbal medicines with proven efficacy and prescription drugs.

Aged↗

PubMed2005

Herb-drug interactions. Interactions between saw palmetto and prescription medications.

Patients over age 50 typically present with one chronic disease per decade. Each chronic disease typically requires long-term drug therapy, meaning most older patients require several drugs to maintain health. Simultaneously, use of complementary and alternative medicine (CAM) has increased in the United States in the last 20 years, reaching 36% in 2002; herbal medicine use accounts for approximately 22% of all CAM use. Older adults often add herbal medicines to prescription medications, yet do not always inform their physicians. The drug metabolizing enzyme systems process all compounds foreign to the body, including prescription and herbal medications. Therefore use of both medicinals simultaneously has a potential for adverse interactions. This review, which discusses saw palmetto, is the last in a series covering the documented interactions among the top 5 efficacious herbal medicines and prescription drugs.

Androgen Antagonists↗

PubMed1979

[Interactions between macromolecular adjuvants and drugs. Part 16: Effects of human serum albumin and Mg2+ on oxytetracycline-polyvinylpyrrolidone interactions (author's transl)].

Equilibrium dialyses and fluorescent spectroscopic measurements demonstrated that human serum albumin (HSA) affects the oxytetracycline (OTC)--polyvinyl-pyrrolidone K 90 (PVP) interactions. The preferential binding of OTC with HSA, as compared to PVP, was evidenced by means of a three-compartment model. The binding values increased with the increase of the portion of PVP in the PVP-HSA mixture. Superadditive OTC bindings occurred at a ratio of 1:1 (by weight). The addition of Mg2+ to PVP-containing solutions, at a molar ratio of 1:1, also produced an increase of the interactions of this antibiotic with PVP, whereby maximal OTC-PVP bindings of 50--60% were reached.

Dialysis↗

PubMed1996

Eosinophil-fibroblast interactions. Granule major basic protein interacts with IL-1 and transforming growth factor-beta in the stimulation of lung fibroblast IL-6-type cytokine production.

To test the hypothesis that eosinophil major basic protein (MBP) is an important regulator of fibroblast effector function, we characterized the effects of MBP on human lung fibroblast production of the IL-6-type cytokines, IL-6, IL-11, and leukemia inhibitory factor. Unstimulated fibroblasts did not produce substantial quantities of these cytokines, while IL-1 and TGF-beta(1) stimulated these cytokines in a potent fashion. MBP at doses < or = 44 micrograms/ml did not stimulate IL-6-type cytokine production. It did, however, interact in a synergistic, dose- and time-dependent fashion with rIL-1-alpha and TGF-beta(1) to further increase IL-6-type cytokine elaboration. These MBP-induced increases in cytokine production were associated with proportionate alterations in mRNA accumulation. In contrast, eosinophil-derived neurotoxin did not regulate fibroblast cytokine production, and MBP did not augment fibroblast granulocyte-macrophage-CSF, or type I collagen production, or fibroblast proliferation in this culture system. The effects of MBP could not be attributed to cell cytotoxicity or contaminants in the MBP preparations. They were, however, at least partially charge mediated, since heparin abolished the effects of MBP on IL-1-stimulated cells, and the surrogate cationic molecule poly-L-arginine mimicked the stimulatory effects of MBP on fibroblast IL-6-type cytokine elaboration. These studies demonstrate that MBP interacts in a synergistic fashion with rIL-1-alpha or TGF-beta(1) to further augment fibroblast IL-6-type cytokine production. They also demonstrate that this stimulation is pretranslationally mediated and due, in part, to the cationic nature of the MBP molecule. MBP regulation of fibroblast cytokine production may play an important role in the pathogenesis of eosinophilic disorders of the airway or other organs.

Blood Proteins↗

PubMedDate not supplied

Interaction of proton pump inhibitors with cytochromes P450: consequences for drug interactions.

Omeprazole, lansoprazole and pantoprazole are metabolized by several human cytochromes P450, most prominently by CYP2C19 and CYP3A4. Only pantoprazole is also metabolized by a sulfotransferase. Differences in the quantitative contribution of these enzymes and in the relative affinities of the substrates explain some of the observed interactions with carbamazepin, diazepam, phenytoin and theophylline and of the impact of the CYP2C19 (mephenytoin) genetic polymorphism. Of these drugs, pantoprazole has the lowest potential for interactions, both in vitro and in human volunteer studies.

Animals↗

PubMed1998

Stability and activity modulation of chymotrypsins in AOT reversed micelles by protein-interface interaction: interaction of alpha-chymotrypsin with a negative interface leads to a cooperative breakage of a salt bridge that keeps the catalytic active conformation (Ile16-Asp194).

The stability of alpha-chymotrypsin and delta-chymotrypsin was studied in reversed micelles of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) in isooctane. alpha-Chymotrypsin is inactivated at the interface and at the water pool, while delta-chymotrypsin is inactivated only at the water pool. The mechanism of inactivation at the interface is related to the interaction of N-terminal group alanine 149 (absent in delta-chymotrypsin) with the negative interface. The dependence of enzyme activity on water content of these two enzymes in reversed micelles of AOT is also related with the interface interaction, since delta-chymotrypsin does not have a bell-shaped curve as observed for alpha-chymotrypsin.

Animals↗

PubMed2006

Binding interactions and Raman spectral properties of pyridine interacting with bimetallic silver-gold clusters.

The binding interactions between pyridine and bimetallic silver-gold clusters are investigated using density functional theory (DFT). The binding energies of pyridine-bimetallic cluster complexes indicate that the bonding depends strongly on the binding site (Au or Ag atom) and bonding molecular orbitals in a given configuration. The donation of the lone-pair electrons of the nitrogen of pyridine to an appropriate unoccupied orbital of each metal cluster plays an important role. The low-lying excited states and charge-transfer states of four stable complexes of interest are calculated on the basis of a time-dependent DFT method. In nonresonance Raman scattering processes, the influence of binding interactions on the relative Raman intensity of totally symmetric pyridine vibrational modes is discussed. These calculated relative Raman intensities are compared with observed surface-enhanced Raman spectra of pyridine adsorbed on silver-gold alloy surfaces.

Journal Article↗

PubMedDate not supplied

Kinetic characterization of the interaction of biotinylated human interleukin 5 with an Fc chimera of its receptor alpha subunit and development of an ELISA screening assay using real-time interaction biosensor analysis.

The interaction of biotinylated human interleukin 5 ([BT]hIL5) with immobilized receptor was measured with a real-time biosensor, and these results were used as a basis for configuring an ELISA for screening antagonists of hIL5-receptor binding. The recombinant proteins used, hIL5 and shIL5R alpha-Fc (chimeric fusion receptor constructed by linking the soluble component of the hIL5 receptor alpha subunit to the constant domain (Fc) of immunoglobulin G), were produced by the expression of cloned vectors in Drosophila schneider (S2) cells. Initial attempts to develop a screening assay by direct immobilization of soluble IL5 receptor to microtiter plates proved unsatisfactory and led to use of the Fc chimera attached by oriented immobilization via protein A. Hence, shIL5R alpha-Fc was bound to protein A covalently immobilized on a carboxymethyl dextran (CM-5) biosensor chip. Specific binding was demonstrated of [BT]hIL5 to protein A/shIL5R alpha-Fc receptor complex. The binding was high affinity (Kdapp = 6 nM), reversible and saturable. The affinity of [BT]hIL5 was similar to that determined with the biosensor assay for unmodified hIL5. The observed kinetics of the interactions of Fc chimera with protein A (slow dissociation) and of [BT]hIL5 with immobilized Fc chimera (faster dissociation) were favorable for subsequently establishing a microtiter plate based ELISA assay. In the latter, Fc chimera was immobilized to the plate via protein A as in the biosensor experiment. Binding of [BT]hIL5 to immobilized Fc chimera in the ELISA was concentration dependent and was competed by both hIL5 and shIL5R alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1975

Drug-biomolecule interactions: mechanisms and kinetics of interactions of biomolecules at interfaces.

At the air-water interface, the area occupied by the molecules of each component of mixed monomolecular layers of cholesterol with hexadecyl alcohol, hexadecylic acid, or hexadecylamine was independent of the presence of the other component. The values of the free energy of mixing of these lipids were within the range of the entropic factor of the free energy even at high surface pressures. Mixed monolayers of cholesterol and bovine serum albumin showed a similar independence of the area per molecule and of the free energy of mixing values when the concentration of the protein was expressed in terms of amino acid residues per molecule of protein forming the mixed monolayer. Higher values of the free energy of mixing were obtained for mixed monolayers of cholesterol with dipalmitoyl lecithin and dipalmitoyl phosphatidylethanolamine than were expected from an entropic factor. The interaction between monomolecular layers of lipidic biomolecules with bulk subphase components, the energy of activation, interaction kinetics, and effects of added electrolytes were also studied. The implications of these data to a mechanism of action are discussed.

Cell Membrane↗

PubMed1980

Kinetics and mechanisms of monolayer interactions V: surface activities of alkylamides, alkylmonocarboxylic acids, and alkylketones and their interaction energies with phospholipid monolayers.

The adsorption free energies of the C1-C6 alkylamides, C3-C8 alkylketones, and C1-C10 alkylmonocarboxylic acids at the air-water interface, estimated from plots of the surface pressure (less than or equal to 5 dynes/cm) versus the bulk concentration, were linear functions of the total surface area per molecule (square angstroms per molecule), with a slope 46% higher for the alkylamides and 25% lower for the alkylketones than that for the monocarboxylic acids. The interaction energies of alkylamides with dipalmitoyl lecithin and dipalmitoyl phosphatidylethanolamine spread at the air-water interface, estimated from the surface pressure increase with increasing concentrations of the injected C1-C5 compounds, were linear functions of the total surface area per molecule. The diffusion free energies, delta Gdif, of the alkylamides within a phospholipid bilayer, predicted from the permeability equation and their interaction energies with dipalmitoyl lecithin monolayers by assuming the additivity of their free energies of adsorption and dehydration at the solution-bilayer interface, agreed with the literature data.

Adsorption↗

PubMed1985

Interactions in the solid state. I: Interactions of sodium bicarbonate and tartaric acid under compressed conditions.

The interaction of NaHCO3 and tartaric acid in powder mixtures and compressed tablets has been studied. It has been found that in an open system the reaction is simply a decarboxylation of NaHCO3 and that the effect of compression on the reaction rate can be attributed to the brittle fracture (and subsequent surface area increase) that occurs on compaction. In a closed system the decomposition of the mixture is an interaction between the acid and the base, and it is mediated by the amount of moisture in the system. This latter is a product of reaction, and a suitable kinetic scheme is described for this. It is shown that "curing" the sodium bicarbonate by heating it to, e.g., 90 degrees C stabilizes the system by virtue of the formation of surface Na2CO3, which acts as a moisture scavenger.

Bicarbonates↗

PubMed1993

Aldolase-tubulin interactions: removal of tubulin C-terminals impairs interactions.

Aldolase copelleted with taxol stabilized microtubules with a Bmax = 0.74 moles of aldolase per mole of tubulin dimer. Removal of the carboxy terminals from microtubules with limited subtilisin digestion, decreased binding to 0.16 moles of aldolase per mole of tubulin dimer. Aldolase inhibited subtilisin cleavage of the C-terminals while triose phosphate isomerase, an enzyme that does not interact with microtubules, did not affect subtilisin activity. These data indicate that the carboxy terminals are involved in tubulin-aldolase interactions.

Animals↗

PubMed1999

DP1 phosphorylation in multimeric complexes: weaker interaction with cyclin A through the E2F1 cyclin A binding domain leads to more efficient phosphorylation than stronger interaction through the p107 cyclin A binding domain.

Stable enzyme-substrate interaction has been recognized as a major mechanism underlying the substrate preferences of cyclin-dependent kinases (Cdks). To learn the relationship between stability of physical association and efficiency of phosphorylation, we studied DP1 phosphorylation by cyclin A-Cdk2 in multiprotein complexes. When DP1 was connected to cyclin A-Cdk2 through E2F4 and p107, its phosphorylation was very inefficient, although its association with cyclin A-Cdk2 was stable. In contrast, DP1 was efficiently phosphorylated when weakly connected to cyclin A-Cdk2 via E2F1 or E2F4 with a fused cyclin A binding domain of E2F1. The transactivation activity of E2F4-DP1 heterodimers was reduced when DP1 was phosphorylated, while a phosphorylation deficient mutant of DP1 resisted this down-regulation. Phosphorylation and functional regulation of DP1 were not due to nuclear localization. Thus, stronger physical association between the kinase and the substrate does not necessarily lead to more efficient phosphorylation than weaker interaction does.

Amino Acid Sequence↗

PubMed1998

Activator-sigma interaction: A hydrophobic segment mediates the interaction of a sigma family promoter recognition protein with a sliding clamp transcription activator.

Activation of transcription at bacteriophage T4 late promoters and coupling of late transcription to concurrent replication requires a peculiar transcriptional activator, the gp45 sliding clamp of the T4 DNA polymerase. In order to activate transcription, the topologically DNA-linked trimeric gp45 must interact with two T4-encoded RNA polymerase-binding proteins, the gp33 co-activator, and the gp55 late sigma factor. The carboxy termini of gp55 and gp33 share a similar sequence, which has been shown to be required for response of late transcription to activation by gp45. Alanine-scanning mutagenesis of the C terminus of gp55 shows that residues within the short hydrophobic sequence L(D/A)FLYE, are necessary for gp55 to bind to gp45, and to respond maximally to transcriptional activation by gp45. When fused to GST, the peptide SLDFLYE suffices for specific gp45 binding. Thus, it constitutes the main gp55 epitope for gp45 interaction.

Alanine↗

PubMedDate not supplied

Models for enzyme-copper-nucleic acid interaction. 1H NMR line broadening study of the interaction of some copper complexes with cytidine.

Sodium (salicylideneglycylglycinato) copper(II), bis(2,9-dimethyl-1, 10-phenanthroline)copper (II), and (1,5-bis (benzimidazol-2-yl)-3-thiapentane) copper(II) were interacted with cytidine in D2O. For all the complexes, the broadening of the 1H signals of cytidine is found to be in the order H(5) greater than H(6) greater than H(1'); this suggests the binding of N (3) and O2 sites of cytidine to copper. The possibility that the ribose moiety is also involved in coordination cannot be ruled out. The complete broadening of the H(5) signals for the last complex above is because of the coordinative unsaturation of the complex. It has been concluded that steric factors and coordinative unsaturation in the complexes affect the extent of interaction with cytidine.

Binding Sites↗

PubMed1997

Interaction of detergents with bovine lens alpha-crystallin: evidence for an oligomeric structure based on amphiphilic interactions.

We have studied the quaternary structure of alpha-crystallin in the presence of increasing concentrations of amphiphilic and neutral detergents using gel filtration, light-scattering, boundary and equilibrium sedimentation. We observed a continuous reduction of the molar mass of the polymeric alpha-crystallin on increasing the concentration of sodium dodecyl sulphate from 0.1 mM to 5 mM, ending up with the monomeric peptides. Dodecyltrimethylammonium bromide also disrupts the oligomeric structure of alpha-crystallin but the interaction appears to be cooperative: in the sharp transition region (for a 1 mg/ml protein solution) from 3 to 8 mM of the detergent, only the native protein and a mixture of monomeric and dimeric peptide-DTAB complexes can be observed. Concomitant studies of the circular dichroism in the far UV revealed a substantial decrease of the beta-sheet and increase of the alpha-helix secondary structure. The latter can be related to the presence of amphiphilic polypeptide sequences in the constituent alpha A and alpha B peptides. These studies reveal for the first time a direct relation between changes in the secondary structure of the alpha A and alpha B peptides and the formation of the oligomeric alpha-crystallin structure: the binding of the amphiphilic detergent reduces the beta-sheet content, induces the formation of alpha-helix secondary structure and reduces the tendency of the peptide to form large aggregates. The different mechanisms for reducing the oligomeric size by anionic and cationic detergents with identical apolar parts stresses the importance of charge interactions. Our findings support some aspects of the micelle model of alpha-crystallin and can be related to its chaperone activity.

Animals↗

PubMed2006

Receptor-receptor interactions as studied with microdialysis. Focus on NTR/D2 interactions in the basal ganglia.

Using mono and dualprobe(s) microdialysis in the basal ganglia of the freely moving rat evidence has been obtained that neurotensin (NT) in threshold concentrations can counteract the D(2) agonist (intrastriatally perfused) induced inhibition of striatal dopamine (DA) release and of pallidal GABA release from the striato-pallidal GABA pathway, effects that are blocked by a NTR(1) antagonist SR48692. These results indicate the existence of antagonistic intramembrane NTR/D(2) receptor interactions in the striatal DA terminals and in the somato-dendritic regions of the striato-pallidal GABA neurons. By the NT-induced reduction of the D(2) mediated signals at the striatal pre- and postjunctional level DA transmission is switched towards a D(1) mediated transmission leading to increased activity in the striatopallidal and striatonigral GABA pathways. The former action will contribute to the motor inhibition and catalepsy found with NT treatment and underlies the use of NT receptor antagonists as a treatment strategy for Parkinson's disease. Nigral NT by an antagonistic NTR/D(2) receptor interaction in the DA cell body and dendrites may also increase nigral DA release leading to a D(2) mediated inhibition of the nigrothalamic GABA pathway. Such an effect, will instead result in antiparkinsonian actions. Thus, increases in NT transmission will have different consequences for the motor system depending upon where in the basal ganglia the increase takes place.

Animals↗

PubMed2006

Receptor-receptor interactions in central cardiovascular regulation. Focus on neuropeptide/alpha(2)-adrenoreceptor interactions in the nucleus tractus solitarius.

The nucleus tractus solitarii (NTS) is a key nucleus in central cardiovascular control. In this mechanism it is well known the role of the alpha(2)-adrenoreceptors for the modulation of the autonomic pathways. Moreover a number of neuropeptides described in the NTS, including Neuropeptide Y (NPY), Galanin (GAL) and Angiotensin II (Ang II), have different roles in regulating the cardiovascular function within this nucleus. We show in this review several data which help to understand how these neuropeptides (NPY, GAL and Ang II) could modulate the cardiovascular responses mediated through alpha(2)-adrenoreceptors in the NTS. Also we show for the first time the interactions between neuropeptides in the brain, specifically the interactions between NPY, GAL, and Ang II, and its functional relevance for central cardiovascular regulation. These data strength the role of neuropeptides on central autonomic control and provide some evidences to understand the neurochemical mechanisms involved in the cardiovascular responses from the NTS.

Angiotensin II↗