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At least 937 records · Page 52Linked to original sources
PubMed1979

Myeloperoxidase, hydrogen peroxide, chloride antimicrobial system: nitrogen-chlorine derivatives of bacterial components in bactericidal action against Escherichia coli.

In the presence of Escherichia coli, myeloperoxidase-catalyzed oxidation of chloride ion resulted in formation of long-lived chloramine and/or chloramide derivatives of bacterial components. The same amount of these nitrogen-chlorine (N-Cl) derivatives was obtained with either hypochlorous acid (HOCl) or the myeloperoxidase system, indicating that myeloperoxidase catalyzed the oxidation of chloride to HOCl. Identical killing was obtained with HOCl or the myeloperoxidase system. About 30 to 50% of the oxidizing equivalents of HOCl were detected as N-Cl derivatives of peptides or peptide fragments that were released from the bacteria. The apparent molecular weight distribution of the peptides decreased with increasing amounts of HOCl, suggesting that peptides were fragmented by oxidative cleavage of chloramide derivatives of peptide bonds. The remaining 50 to 70% of the oxidizing equivalents of HOCl were rapidly consumed in peptide bond cleavage or the oxidation of other bacterial components. There was a close correspondence between the oxidation of bacterial sulfhydryls and bactericidal action. The N-Cl derivatives were lost and the oxidation of bacterial sulfhydryls increased over a period of several h at 37 degrees C. These changes were accompanied by increased killing. The increase in sulfhydryl oxidation and killing could be prevented by washing the bacteria to remove the N-Cl derivatives. Therefore, the N-Cl derivatives could oxidize bacterial components long after the myeloperoxidase-catalyzed oxidation of chloride was complete.

Chloramines↗
PubMed1987

Hypochlorous acid-promoted loss of metabolic energy in Escherichia coli.

Oxidation of Escherichia coli by hypochlorous acid (HOCl) or chloramine (NH2Cl) gives rise to massive hydrolysis of cytosolic nucleotide phosphoanhydride bonds, although no immediate change occurs in either the nucleotide pool size or the concentrations of extracellular end products of AMP catabolism. Titrimetric curves of the extent of hydrolysis coincide with curves for loss of cell viability, e.g., reduction in the adenylate energy charge from 0.8 to 0.1-0.2 accompanies loss of 99% of the bacterial CFU. The oxidative damage caused by HOCl is irreversible within 100 ms of exposure of the organism, although nucleotide phosphate bond hydrolysis requires several minutes to reach completion. Neither HOCl nor NH2Cl reacts directly with nucleotides to hydrolyze phosphoanhydride bonds. Loss of viability is also accompanied by inhibition of induction of beta-galactosidase. The proton motive force, determined from the distribution of 14C-radiolabeled lipophilic ions, declines with incremental addition of HOCl after loss of respiratory function; severalfold more oxidant is required for the dissipation of the proton motive force than for loss of viability. These observations establish a causal link between loss of metabolic energy and cellular death and indicate that the mechanisms of oxidant-induced nucleotide phosphate bond hydrolysis are indirect and that they probably involve damage to the energy-transducing and transport proteins located in the bacterial plasma membrane.

Adenosine Diphosphate↗
PubMed1996

Bacterial glutathione: a sacrificial defense against chlorine compounds.

Aerobic organisms possess a number of often overlapping and well-characterized defenses against common oxidants such as superoxide and hydrogen peroxide. However, much less is known of mechanisms of defense against halogens such as chlorine compounds. Although chlorine-based oxidants may oxidize a number of cellular components, sulfhydrl groups are particularly reactive. We have, therefore, assessed the importance of intracellular glutathione in protection of Escherichia coli cells against hydrogen peroxide, hypochlorous acid, and chloramines. Employing a glutathione-deficient E. coli strain (JTG10) and an otherwise isogenic glutathione-sufficient E. coli strain (AB1157), we find that glutathione-deficient organisms are approximately twice as sensitive to killing by both hydrogen peroxide and chlorine compounds. However, the mode of protection by glutathione in these two cases appears to differ: exogenous glutathione added to glutathione-deficient E. coli in amounts equal to those which would be present in a similar suspension of the wild-type bacteria fully restored resistance of glutathione-deficient bacteria to chlorine-based oxidants but did not change resistance to hydrogen peroxide. Furthermore, in protection against chlorine compounds, oxidized glutathione is almost as effective as reduced glutathione, implying that the tripeptide and/or oxidized thiol undergo further reactions with chlorine compounds. Indeed, in vitro, 1 mol of reduced glutathione will react with approximately 3.5 to 4.0 mol of hypochlorous acid. We conclude that glutathione defends E. coli cells against attack by chlorine compounds and hydrogen peroxide but, in the case of the halogen compounds, does so nonenzymatically and sacrificially.

Chloramines↗
PubMed1980

Oxidation of methionine residues in lutropin.

Bovine lutropin and its subunits were submitted to oxidation by sodium periodate or chloramine T. Methionine residues were easily oxidized but partial destruction of fucose was observed. After oxidation treatment most of the lutropin exhibits the same elution volume in gel filtration as the native hormone. Sucrose gradient sedimentation or gel filtration experiments show however that the oxidation of isolated subunits is accompanied by aggregation of conformational changes even in the case of porcine beta subunit which contains only one methionine residue, unit and intact alpha subunit exhibit very low residual activity.

Amino Acids↗
PubMed2003

Differential modulation of voltage-dependent K+ currents in colonic smooth muscle by oxidants.

The effect of oxidants on voltage-dependent K+ currents was examined in mouse colonic smooth muscle cells. Exposure to either chloramine-T (Ch-T), an agent known to oxidize both cysteine and methionine residues, or the colon-specific oxidant monochloramine (NH2Cl) completely suppressed the transient outward K+ current (Ito) while simultaneously enhancing the sustained delayed rectifier K+ current (Idr). In contrast, the cysteine-specific oxidants hydrogen peroxide (H2O2) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) exhibited partial and slow suppression of Ito by inducing a shift in channel availability of -18 mV without affecting Idr. After enhancement by NH2Cl or Ch-T, Idr was sensitive to 10 mM tetraethylammonium but not to other K+ channel blockers, suggesting that it represented activation of the resting Idr and not a separate K+ conductance. Extracellular dithiothreitol (DTT) partially reversed the effect of H2O2 and DTNB on Ito but not the actions of NH2Cl and Ch-T on either Idr or Ito. Dialysis of myocytes with GSH (5 mM) or DTT (5 mM) prevented suppression of Ito by H2O2 and DTNB but did not alter the effects of NH2Cl or Ch-T on either Idr or Ito. Ch-T and NH2Cl completely blocked Ito generated by murine K(v)4.1, 4.2, and 4.3 in Xenopus oocytes, an effect not reversible by intracellular DTT. In contrast, intracellular DTT reversed the effect of H2O2 and DTNB on the cloned channels. These results suggest that I(to) is suppressed via modification of both methionine and cysteine residues, whereas enhancement of Idr likely results from methionine oxidation alone.

Animals↗
PubMed2005

Intracellular Ca(2+) and Zn(2+) signals during monochloramine-induced oxidative stress in isolated rat colon crypts.

During acute exacerbations of inflammatory bowel diseases, oxidants are generated through the interactions of bacteria in the lumen, activated granulocytes, and cells of the colon mucosa. In this study we explored the ability of one such class of oxidants, represented by monochloramine (NH(2)Cl), to serve as agonists of Ca(2+) and Zn(2+) accumulation within the colonocyte. Individual colon crypts prepared from Sprague-Dawley rats were mounted in perfusion chambers after loading with fluorescent reporters fura 2-AM and fluozin 3-AM. These reporters were characterized, in situ, for responsiveness to Ca(2+) and Zn(2+) in the cytoplasm. Responses to different concentrations of NH(2)Cl (50, 100, and 200 microM) were monitored. Subsequent studies were designed to identify the sources and mechanisms of NH(2)Cl-induced increases in Ca(2+) and Zn(2+) in the cytoplasm. Exposure to NH(2)Cl led to dose-dependent increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) in the range of 200-400 nM above baseline levels. Further studies indicated that NH(2)Cl-induced accumulation of Ca(2+) in the cytoplasm is the result of release from intracellular stores and basolateral entry of extracellular Ca(2+) through store-operated channels. In addition, exposure to NH(2)Cl resulted in dose-dependent and sustained increases in intracellular Zn(2+) concentration ([Zn(2+)](i)) in the nanomolar range. These alterations were neutralized by dithiothreitol, which shields intracellular thiol groups from oxidation. We conclude that Ca(2+)- and Zn(2+)-handling proteins are susceptible to oxidation by chloramines, leading to sustained, but not necessarily toxic, increases in [Ca(2+)](i) and [Zn(2+)](i). Under certain conditions, NH(2)Cl may act not as a toxin but as an agent that activates intracellular signaling pathways.

Animals↗
PubMed1991

Intracellular measurements from a rapidly adapting sensory neuron.

1. The femoral tactile spine of the cockroach contains a single sensory neuron with its cell body in the lumen of the spine. Step movements of the spine produce rapidly adapting bursts of action potentials that decay to 0 in 1 s. Previous work has shown that a large part of this adaptation occurs during action potential encoding. 2. Intracellular recordings from the tactile spine neuron were obtained by lowering a microelectrode through the spine lumen and penetrating the cell body. Injection of Lucifer yellow followed by fluorescence microscopy confirmed the morphology of the soma, with a diameter of 30 microns, and showed an axon of 9 microns leaving the spine and proceeding proximally along the femur. 3. Membrane-potential records were digitized and examined at high resolution during bursts of action potentials produced by depolarizing current pulses. No significant changes in action potential shape were detected during adaptation. However, the rate of depolarization between action potentials slowed dramatically during the burst. This slowing could be reduced and the burst substantially prolonged by chloramine-T (CT), an agent that reduces sodium channel inactivation in several preparations. 4. A 100 Hz sinusoidal current was superimposed on depolarizing current pulses to test for changes in membrane conductance during a burst of action potentials. No such changes were detected, indicating that rapid adaptation is not due to changes in membrane permeability.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed2002

Advanced glycation end products and advanced oxidation protein products in hemodialyzed patients.

Chronic renal failure is associated with increased oxidative and carbonyl stresses that contribute to long-term uremic complications. In our study, we determined two markers of these stresses--AGEs (advanced glycation end products) and AOPP (advanced oxidation protein products)--in chronic hemodialysis patients in order to find out their relationship to the dialysis treatment. Plasmas of 20 hemodialyzed patients treated with modified cellulose membranes were examined at 0 and 15 min and at the end (i.e. after 4 h) of the dialysis session. AGEs were estimated using a spectrofluorometric method (excitation 350 nm, emission 440 nm) and are expressed in AU (arbitrary units)/g protein. AOPP were determined spectrophotometrically (absorbance at 340 nm) and are expressed in chloramine units per gram of protein (micromol/g). AOPP decrease slightly from 0 to 15 min of the dialysis procedure (4.0 +/- 1.5 vs. 3.0 +/- 0.9 micromol/g, p < 0.01). However, they are increased at the end of the session (5.0 +/- 2.1 micromol/l vs. 15 min, p < 0.01, not significant vs. beginning). On the other hand, AGEs decrease continuously from the beginning to the end of the session (mainly in the first minutes of the dialysis) (1.52 +/- 0.34 x 10(4) AU/g at 0 min, 1.39 +/- 0.33 x 10(4) AU/g at 15 min, p < 0.001 vs. beginning, 1.30 +/- 0.33 x 10(4) AU/g at the end, p < 0.001 vs. beginning, not significant vs. 15 min). Neither AGEs nor AOPP correlate with the age of hemodialyzed patients and with the number of years of the dialysis treatment. AOPP correlate with AGEs before the dialysis session (r = 0.62, p < 0.05) but not after the session (r = 0.29, not significant). According to our results, AGEs may serve more as a marker of chronic damage while AOPP may better describe acute oxidative stress during the dialysis treatment.

Aged↗
PubMed1984

Oxidation of plasma alpha 1-antitrypsin in smokers and nonsmokers and by an oxidizing agent.

The inhibitor activity of the protease inhibitor alpha 1-antitrypsin (alpha 1-protease inhibitor) is decreased by oxidizing agents such as those found in cigarette smoke. We have compared specific elastase and specific trypsin inhibitor activity, under defined conditions, in 26 smokers and 26 nonsmokers. Contrary to some previous reports, we have not found a difference between them. The oxidizing agent chloramine T was used to provide an additional oxidant stress for the comparison of plasma from nonsmokers and smokers. Although there was considerable variation between individual subjects in the extent of inactivation of inhibitor activity of alpha 1-antitrypsin, there was no significant difference between nonsmokers and smokers. Apparently there was sufficient antioxidant activity in the plasma of the smokers we tested to prevent the detection of oxidized inactivated alpha 1-antitrypsin.

Adult↗
PubMed1985

Generation of free radical intermediates from foreign compounds by neutrophil-derived oxidants.

A large number of foreign compounds, including many drugs, industrial pollutants, and environmental chemicals, can be oxidized under appropriate conditions to potentially toxic free radical intermediates. We evaluated the ability of the oxidants produced by the neutrophil myeloperoxidase system to generate free radical intermediates from several such compounds. Sodium hypochlorite or hypochlorous acid produced by human peripheral blood neutrophils and trapped in the form of taurine chloramine were both found to be capable of producing free radicals from chlorpromazine, aminopyrine, and phenylhydrazine. These radical intermediates were demonstrated by visible light spectroscopy and by direct electron spin resonance (for the chlorpromazine and aminopyrine radicals) or by spin-trapping (for the phenyl radical generated from phenylhydrazine). Stable oxidants produced by the neutrophils (i.e., those present in the supernatants of stimulated neutrophils in the absence of added taurine) also were found to be capable of generating free radical intermediates. The production of the oxidants and the ability of neutrophil supernatants to generate these radicals were almost completely eliminated by sodium azide, a myeloperoxidase inhibitor. We suggest that the oxidation by neutrophils of certain chemical compounds to potentially damaging electrophilic free radical forms may represent a new metabolic pathway for these substances and could be important in the processes of drug toxicity and chemical carcinogenesis.

Aminopyrine↗
PubMed1986

Effects of the putative neutrophil-generated toxin, hypochlorous acid, on membrane permeability and transport systems of Escherichia coli.

Titrimetric addition of hypochlorous acid (HOCl) or chloramine (NH2Cl) to suspensions of Escherichia coli decreases their ability to accumulate 14C-labeled glutamine, proline, thiomethylgalactoside, and leucine in a manner that approximately coincides with loss of cell viability; quantitative differences in cellular response are observed with the two oxidants. Inhibition of beta-galactosidase activity in E. coli ML-35, a strain lacking functional lactose permease, is complex and also depends upon the identity of the oxidant. Membrane proton conductivities and glycerol permeabilities are unchanged by addition of HOCl or NH2Cl in excess of that required for inactivation. The combined results are interpreted to indicate that the locus of HOCl attack is the cell envelope, that HOCl inactivation does not occur by loss of membrane structural integrity, that loss of transport function can be identified with either selective oxidative inhibition of the transport proteins or loss of cellular metabolic energy, and that different mechanisms of inactivation may exist for HOCl and NH2Cl.

Cell Membrane Permeability↗
PubMed1992

Oxidation of a specific methionine in thrombomodulin by activated neutrophil products blocks cofactor activity. A potential rapid mechanism for modulation of coagulation.

Endothelial thrombomodulin (TM) plays a critical role in hemostasis as a cofactor for thrombin-dependent formation of activated protein C, a potent anticoagulant. Chloramine T, H2O2, or hypochlorous acid generated from H2O2 by myeloperoxidase rapidly destroy 75-90% of TM cofactor activity. Activated PMN, the primary in vivo source of biological oxidants, also rapidly inactivate TM. Oxidation of TM by PMN is inhibited by diphenylene iodonium, an inhibitor of NADPH oxidase. Both Met291 and Met388 in the six epidermal growth factor-like repeat domain are oxidized; however, only substitutions of Met388 lead to TM analogues that resist oxidative inactivation. We suggest that in inflamed tissues activated PMN may inactivate TM and demonstrate further evidence of the interaction between the inflammatory process and induction of thrombotic potential.

Adult↗
PubMedDate not supplied

Non-dehalogenation mechanisms for excretion of radioiodine after administration of labeled antibodies.

In patients or mice with cancer the pharmacokinetic behavior of radioiodinated and radiometal chelated antibodies has been observed to be different. Rapid clearance from the tissues and excretion into the urine can occur after injection of radioiodinated antibodies. These observations have been interpreted to reflect in vivo dehalogenation of the antibody. This publication describes a variety of other mechanisms that can underlie these phenomena. These mechanisms include receptor uptake and catabolism of antibody and instability of the labeled antibody due to the labeling conditions. Specifically, the relative masses of chloramine-T and antibody in the iodination reaction mixture, the level of iodination of the antibody, and the amount of antibody administered to the recipient are all factors which can influence the clearance of radioiodinated antibody from the recipient. The final determinant for the different behavior of radioiodinated and In-111 metal chelated antibody relate to the different biologic pathways of indium when compared to iodine.

Animals↗
PubMed1978

The distribution of biologically active and inactive radioiodinated human calcitonin in the rat.

The anatomical distribution of a biologically active and biologically inactive preparation of radioiodinated human calcitonin (hCT) was studied in rats. The former was prepared by electrolysis and the latter by chloramine-T oxidation. When administered iv, the distribution of the two species of [125I]hCT was nearly identical. The kidney was the principle organ of distribution for the hormone while less was present in liver, intestine, or bone. In vitro, kidney homogenates rapidly degraded [125I]hCT. This degradation was partially blocked by trypsin inhibitor and fully blocked by ACTH at both 4 and 37 C. These studies demonstrate the importance of kidney in the metabolism of calcitonin and suggest that the in vivo distribution of biologically active and inert species of the hormone may be indistinguishable.

Animals↗
PubMed1982

Critical analysis of [131I]- and [125I]human thyroglobulin labels for radioimmunoassay use.

[125I]- and [131I]thyroglobulin (Tg) tracers obtained by two different oxidation methods, chloramine-T (Chl-T) and lactoperoxidase (LP-ase), were analyzed to assess their suitability in the development of a RIA. Pairs of tracers which were prepared on a single day using these methods with a single source of 131I and 125I were compared. The following conclusions were reached. 1) Both 131I and 125I isotopes, using CHl-T or LP-ase oxidants, produce suitable tracers. 2) [131I]Tg can be used repeatedly for 2 weeks without repurification. 3) [125I]Tg, in contrast, has to be rechromatographed weekly on Sephadex G-200 to maintain assay sensitivity and adequate maximal binding. 4) Under these conditions, 2- or 9-day tracers with either isotope using Chl-T or LP-ase give similar Tg determinations in the serum. 5) The LP-ase-chromatographed 125I tracer seems to lead to higher maximal binding in the assay than the Chl-T-repurified tracer.

Chloramines↗
PubMed2004

Hypochlorite scavenging activity of flavonoids.

Scavengers of hypochlorite, a highly reactive oxidant produced by activated phagocytes, could have potential therapeutic effects in diseases in which this oxidant plays a pathogenic role. Flavonoids are polyphenolic substances present in food plants and have been extensively studied for their antioxidant properties against various free radicals. Less is known about their reactivity with hypochlorite. In this study, the hypochlorite scavenging activity of flavonoids was investigated using a microplate assay recently developed in our laboratory. This method evaluates the ability of a substance to inhibit the formation of chloramines in human serum albumin upon oxidation by hypochlorite. Thirteen flavonoids were tested. Most of them inhibited human serum albumin oxidation at micro-molar concentrations and appeared more active than Trolox, a water-soluble equivalent of vitamin E. It was observed that the greater the number of hydroxyl substitutions, the greater the scavenging activity. The 3-hydroxy substitution seemed to be particularly important for scavenging activity, whereas the presence of a 2,3-double bond in the C ring did not. Flavonoids were found to be good hypochlorite scavengers in-vitro and further information is provided about the chemical aspects important for scavenging activity. Thus, flavonoids could have beneficial effects in diseases such as atherosclerosis in which hypochlorite plays a pathogenic role.

Antioxidants↗
PubMed1994

Development of glycoside-bound radiopharmaceuticals: novel radioiodination method for digoxin.

We combined 2-hydroxy-3-methylbenzoylhydrazide (HMBH) with glycosides as a novel method for the radioiodination of physiologically active glycosides. This method was tested using digoxin, which is one of the cardiac glycosides. A digoxin-HMBH conjugate was synthesized by periodate cleavage of the third sugar ring, and was readily radiolabeled with Na[125I] by the chloramine-T method. 125I labelled digoxin-HMBH conjugate retained Na+, K(+)-ATPase binding in vivo and in vitro, and also retained immunoreactivity to an anti-digoxin antibody. Thus, this 125I labelled digoxin-HMBH conjugate represents a potential radiopharmaceutical for Na+, K(+)-ATPase imaging, as well as for the radioimmunoassay of digoxin.

Animals↗