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At least 19 recordsLinked to original sources
PubMed2006

IkappaB is a sensitive target for oxidation by cell-permeable chloramines: inhibition of NF-kappaB activity by glycine chloramine through methionine oxidation.

Hypochlorous acid (HOCl) is produced by the neutrophil enzyme, myeloperoxidase, and reacts with amines to generate chloramines. These oxidants react readily with thiols and methionine and can affect cell-regulatory pathways. In the present study, we have investigated the ability of HOCl, glycine chloramine (Gly-Cl) and taurine chloramine (Tau-Cl) to oxidize IkappaBalpha, the inhibitor of NF-kappaB (nuclear factor kappaB), and to prevent activation of the NF-kappaB pathway in Jurkat cells. Glycine chloramine (Gly-Cl) and HOCl were permeable to the cells as determined by oxidation of intracellular GSH and inactivation of glyceraldehyde-3-phosphate dehydrogenase, whereas Tau-Cl showed no detectable cell permeability. Both Gly-Cl (20-200 muM) and HOCl (50 microM) caused oxidation of IkappaBalpha methionine, measured by a shift in electrophoretic mobility, when added to the cells in Hanks buffer. In contrast, a high concentration of Tau-Cl (1 mM) in Hanks buffer had no effect. However, Tau-Cl in full medium did modify IkappaBalpha. This we attribute to chlorine exchange with other amines in the medium to form more permeable chloramines. Oxidation by Gly-Cl prevented IkappaBalpha degradation in cells treated with TNFalpha (tumour necrosis factor alpha) and inhibited nuclear translocation of NF-kappaB. IkappaBalpha modification was reversed by methionine sulphoxide reductase, with both A and B forms required for complete reduction. Oxidized IkappaBalpha persisted intracellularly for up to 6 h. Reversion occurred in the presence of cycloheximide, but was prevented if thioredoxin reductase was inhibited, suggesting that it was due to endogenous methionine sulphoxide reductase activity. These results show that cell-permeable chloramines, either directly or when formed in medium, could regulate NF-kappaB activation via reversible IkappaBalpha oxidation.

Active Transport, Cell Nucleus↗
PubMed1989

Formation of chloramine derivatives of histamine: role of histamine chloramines in bronchoconstriction.

Hypochlorous acid generated by myeloperoxidase reacts with histamine to produce chloramines. At pH 7, one mole of histamine monochloramine (HisCl) was generated per mole of H2O2 provided as substrate for myeloperoxidase. At pH 5, one mole of histamine dichloramine (HisCl2) was generated per two moles of H2O2. HisCl and HisCl2 had two and four oxidizing equivalents per molecule, respectively. In vitro, 30 microM HisCl and HisCl2 induced mepyramine-sensitive guinea pig lung parenchyma contraction with 89 and 56 percent of the response of an equivalent concentration of histamine. Pretreatment of lung strips with chloramines reduced the subsequent contractile response of the tissues to methacholine. These results suggest that H-1 histamine receptors provide for targeting of histamine chloramines to pulmonary tissue which may facilitate modification of tissue responses.

Animals↗
PubMed1993

Chloramine-T in radiolabeling techniques. I. Kinetics and mechanism of the reaction between chloramine-T and amino acids.

The determination of the rate and pH dependency of chlorination of amino acids by chloramine-T (CAT) using the model compounds beta-alanine, L-alanine, and L-alanine ethyl ester was investigated. The reactions were studied under pseudo-first-order conditions where the amino acid concentration was in large excess over CAT. The rates of the reactions were determined spectrophotometrically by following the disappearance of CAT. The overall reaction was found to obey second-order kinetics. The effect of pH was studied over the range 6.1 to 12.0. The reaction rate was found to be independent of pH in the range 6.1 to 8.5, and to decrease with increasing pH above 8.5. The pH dependency was rationalized by assuming that un-ionized CAT reacts with the un-ionized amino group of the amino acid. The value of the resulting second-order rate constant (1.9 x 10(7) M-1 min-1) was of the same order of magnitude as rate constants reported for similar N-chlorination reactions. A cyclic transition state involving a water molecule is proposed.

Amino Acids↗
PubMed1992

NTP Toxicology and Carcinogenesis Studies of Chlorinated Water (CAS Nos. 7782-50-5 and 7681-52-9) and Chloraminated Water (CAS No. 10599-90-3) (Deionized and Charcoal-Filtered) in F344/N Rats and B6C3F1 Mice (Drinking Water Studies).

Chlorine and chloramine are used as disinfectants in water supplies to prevent the spread of waterborne diseases. The U.S. Environmental Protection Agency and the U.S. Congress, through the Safe Drinking Water Acts and Amendments, initiated studies to determine the most effective way to disinfect water supplies and, at the same time, minimize any potential long-term health effects associated with direct chemical exposure or indirect chemical exposure through the formation of byproducts. As part of this evaluation, 2-year studies of chlorinated or chloraminated deionized charcoal-filtered drinking water were conducted in F344/N rats and B6C3F1 mice to determine the potential toxicity and carcinogenicity associated with prolonged exposure and eliminate possible confounding effects of byproducts of chlorination. Chlorinated Water Studies: Water containing 0, 70, 140, or 275 ppm chlorine (based on available atomic chlorine) was provided to groups of 70 F344/N rats or B6C3F1 mice of each sex for up to 2 years. Groups of 10 rats or mice of each sex were predesignated for evaluation at 14 or 15 weeks and 66 weeks. Survival at 2 years of rats and mice receiving chlorinated water was similar to that of the controls. Mean body weights of dosed male rats, high-dose female rats, and dosed mice were slightly lower than those of their respective control groups. There was a dose-related decrease in water consumption by rats and mice. Water consumption by high-dose rats during the second year of the studies was 21% lower than controls for males and 23% lower than controls for females; water consumption by high-dose mice was 31% lower than controls for males and 26% lower than controls for females. The incidence of mononuclear cell leukemia in mid-dose, but not high-dose, female rats was significantly higher than that in controls (control, 8/50; low-dose, 7/50; mid-dose, 19/51; high-dose, 16/50). The proportion of female rats that died of leukemia before the end of the study and the mean time for observation of animals dying with leukemia were similar among all dose groups and controls. Although the marginal increase in leukemia incidence in the mid- and high-dose female rats suggested a possible association with the administration of chlorinated water, the incidence of leukemia was not clearly dose related. There was no indication of reduced latency of leukemia, and the incidence of leukemia in concurrent controls was less than the mean for historical controls; furthermore, there was no supporting evidence of an effect in male rats. Thus, the marginal increase in leukemia incidence in female rats was considered equivocal evidence of carcinogenic activity. There were no neoplasms or nonneoplastic lesions in male rats or in male or female mice that were clearly associated with the consumption of chlorinated water. Chloraminated Water Studies: Water containing 50, 100, or 200 ppm chloramine was provided to groups of 70 F344/N rats or B6C3F1 mice of each sex for up to 2 years. The same control groups were used for the chlorinated water and chloraminated water studies. Groups of 9 or 10 rats or mice of each sex were evaluated at 14 or 15 weeks and 66 weeks. Survival at 2 years of rats and mice receiving chloraminated water was similar to that of the controls. Mean body weights of high-dose rats and dosed mice were lower than those of their respective control groups. There was a dose-related decrease in water consumption by rats and mice. Water consumption during the second year of the studies by high-dose rats was 34% lower than controls for males and 31% lower than controls for females; water consumption by high-dose mice was 42% lower than controls for males and 40% lower than controls for females. Mononuclear cell leukemia occurred with a marginally increased incidence in the mid- and high-dose female rats receiving chloraminated water (control, 8/50; low dose, 11/50; mid dose, 15/50; and high dose, 16/50). As in female rats receiving chlorinated water, the proportion of female rats that died of leukemia before the end of the study and t that died of leukemia before the end of the study and the mean time for observation of animals dying with leukemia were similar among all dose groups and controls. The marginal increase in leukemia incidence in females receiving chloraminated water was considered equivocal evidence of carcinogenic activity for the same reasons given for female rats receiving chlorinated water. There were no neoplasms or nonneoplastic lesions in male rats or in male or female mice that were clearly associated with the consumption of chloraminated water. Conclusions: Under the conditions of these 2-year drinking water studies, there was no evidence of carcinogenic activity of chlorinated water in male F344/N rats receiving 70, 140, or 275 ppm. There was equivocal evidence of carcinogenic activity of chlorinated water in female F344/N rats based on an increase in the incidence of mononuclear cell leukemia. There was no evidence of carcinogenic activity of chlorinated water in male or female B6C3F1 mice receiving 70, 140, or 275 ppm. Under the conditions of these 2-year drinking water studies, there was no evidence of carcinogenic activity of chloraminated water in male F344/N rats receiving 50, 100, or 200 ppm. There was equivocal evidence of carcinogenic activity of chloraminated water in female F344/N rats based on an increase in the incidence of mononuclear cell leukemia. There was no evidence of carcinogenic activity of chloraminated water in male or female B6C3F1 mice receiving 50, 100, or 200 ppm.

Journal Article↗
PubMed1987

Removal of sodium inactivation and block of sodium channels by chloramine-T in crayfish and squid giant axons.

Modification of sodium channels by chloramine-T was examined in voltage clamped internally perfused crayfish and squid giant axons using the double sucrose gap and axial wire technique, respectively. Freshly prepared chloramine-T solution exerted two major actions on sodium channels: (a) an irreversible removal of the fast Na inactivation, and (b) a reversible block of the Na current. Both effects were observed when chloramine-T was applied internally or externally (5-10 mM) to axons. The first effect was studied in crayfish axons. We found that the removal of the fast Na inactivation did not depend on the states of the channel since the channel could be modified by chloramine-T at holding potential (from -80 to -100 mV) or at depolarized potential of -30 mV. After removal of fast Na inactivation, the slow inactivation mechanism was still present, and more channels could undergo slow inactivation. This result indicates that in crayfish axons the transition through the fast inactivated state is not a prerequisite for the slow inactivation to occur. During chloramine-T treatment, a distinct blocking phase occurred, which recovered upon washing out the drug. This second effect of chloramine-T was studied in detail in squid axons. After 24 h, chloramine-T solution lost its ability to remove fast inactivation but retained its blocking action. After removal of the fast Na inactivation, both fresh and aged chloramine-T solutions blocked the Na currents with a similar potency and in a voltage-dependent manner, being more pronounced at lower depolarizing potentials. A similar voltage-dependent block was observed with aged chloramine-T solution in an axon with intact inactivation. In contrast to the action of the fresh solution, the aged chloramine-T solution was found to accelerate the decay of Na currents.These results suggest that chloramine-T solution contains at least two active molecular forms that act at different sites in the Na channel.

Animals↗
PubMed2001

Relative reactivities of N-chloramines and hypochlorous acid with human plasma constituents.

Hypochlorous acid (HOCl), the major strong oxidant produced by the phagocyte enzyme myeloperoxidase, reacts readily with free amino groups to form N-chloramines. Since different N-chloramines have different stabilities and reactivities depending on their structures, we investigated the relative reactivities of three model N-chloramines and HOCl with human plasma constituents. TheN-chloramines studied were N(alpha)-acetyl-lysine chloramine (LysCA, a model of protein-associated N-chloramines), taurine chloramine (TaurCA, the primary N-chloramine produced by activated neutrophils), and monochloramine (MonoCA, a lipophilic N-chloramine). Addition of these chlorine species (100--1000 microM each) to plasma resulted in rapid loss of thiols, with the extent of thiol oxidation decreasing in the order TaurCA = LysCA > MonoCA = HOCl. The single reduced thiol of albumin was the major target. Loss of plasma ascorbate also occurred, with the extent decreasing in the order HOCl > LysCA > TaurCA > MonoCA. Experiments comparing equimolar albumin thiols and ascorbate showed that while HOCl caused equivalent loss of thiols and ascorbate, theN-chloramines reacted preferentially with thiols. The chlorine species also inactivated alpha(1)-antiproteinase, implicating oxidation of methionine residues, and ascorbate provided variable protection depending on the chlorine species involved. Together, our data indicate that in biological fluids N-chloramines react more readily with protein thiols than with methionine residues or ascorbate, and thus may cause biologically relevant, selective loss of thiol groups.

Ascorbic Acid↗
PubMed1993

Inhibitory action of chloramine on formate-metabolizing system. Studies suggested by an unusual case record.

We previously reported on a patient exposed simultaneously to methyl chloride and chloramine gas who developed metabolic acidosis and permanent blindness [M. Minami et al., Hum Exp Toxicol 11: 27-34, 1992]. The case report suggested the possibility of potentiation of methyl chloride toxicity by chloramine. The potentiating mechanism was investigated by exposing mice to methyl chloride followed by ammonia chloramine, and then the level of formate in urine samples was measured with an enzyme coupling method to detect disturbance of formate metabolism. Mice dosed with 0.05 mL 1.0 mM chloramine after methyl chloride exposure excreted a significantly larger amount of urinary formate than mice treated with only methyl chloride. There was no difference in urinary formate levels between mice treated with only 0.05 mL 1.0 mM chloramine and those given only the vehicle (0.1 M phosphate buffer pH 6.0) for chloramine. The underlying biochemical mechanism of deterioration of formate metabolism was found to be the inhibition of the enzyme, N10-formyl tetrahydrofolate (N10-f-THF) dehydrogenase by 0.56-3.35 microM chloramine in the in vitro experiment using the purified enzyme. Positive control mice, given orally 0.1 mL 10% methanol in 0.1 M phosphate buffer (pH 6.0) excreted the same amount of urinary formate as those receiving 0.05 mL 1.0 mM chloramine after methanol administration. This was ascribed to the inhibitory effect of chloramine on formaldehyde dehydrogenase and depletion of substrate for further metabolism. The inhibition of the enzyme by chloramine (2.7-100.8 microM) was confirmed by in vitro experiments, using the purified enzyme, formaldehyde dehydrogenase.

Aldehyde Oxidoreductases↗
PubMed1987

Mutagenic activity of chloramines.

Mutagenesis by chloramines and hypochlorous acid (HOCl) was studied to determine whether these agents could contribute to the mutagenic and potentially carcinogenic activity of stimulated leukocytes and whether environmental exposure to these agents is a cause for concern. Mutagenic activity was measured using the S. typhimurium TA97a, TA100 and TA102 tester strains. Because chloramines and HOCl are bactericidal, react rapidly with cell components, and can destroy the histidine and biotin required for the mutagenesis assay, activity can't be compared directly with that of less toxic or reactive agents. Nevertheless, chloramines were mutagenic when tested under appropriate conditions. TA100 was the most sensitive strain, and the most active mutagens were lipophilic dichloramines (RNCl2) including derivatives of histamine, ethanolamine and putrescine. Lipophilic monochloramines (RNHCl) such as histamine-monochloramine and NH2Cl were less active. Hydrophilic chloramines such as taurine-chloramines had low activity, and HOCl was inactive. The metabolic state of the bacteria was critical. Chloramines were mutagenic when added to bacteria with glucose at 37 degrees C, but killing predominated when chloramines were added at 4 degrees C or 25 degrees C, or at 37 degrees C without glucose. Production of chloramines and HOCl by leukocytes in vivo could contribute to the association of chronic inflammation and cancer as a result of: (1) the entry of membrane-permeable chloramines into normal cells followed by attack on intracellular components including DNA, and (2) the production of secondary mutagens such as compounds with carbonyl groups or carbon-chlorine bonds. On the other hand, chlorination of water supplies is perhaps more likely to destroy than create mutagens, and chloramines from the environment are unlikely to penetrate the skin and mucous membranes.

Chloramines↗
PubMed2003

Histamine chloramine reactivity with thiol compounds, ascorbate, and methionine and with intracellular glutathione.

Histamine is stored in granules of mast cells and basophils and released by inflammatory mediators. It has the potential to intercept some of the HOCl generated by the neutrophil enzyme, myeloperoxidase, to produce histamine chloramine. We have measured rate constants for reactions of histamine chloramine with methionine, ascorbate, and GSH at pH 7.4, of 91 M(-1)s(-1), 195 M(-1)s(-1), and 721 M(-1)s(-1), respectively. With low molecular weight thiols, the reaction was with the thiolate and rates increased exponentially with decreasing thiol group pK(a). Comparing rate constants for different chloramines reacting with ascorbate or a particular thiol anion, these were higher when there was less negative charge in the vicinity of the chloramine group. Histamine chloramine was the most reactive among biologically relevant chloramines. Consumption of histamine chloramine and oxidation of intracellular GSH were examined for human fibroblasts. At nontoxic doses, GSH loss over 10 min was slightly greater than that with HOCl, but the cellular uptake of histamine chloramine was 5-10-fold less. With histamine chloramine, GSSG was a minor product and most of the GSH was converted to mixed disulfides with proteins. HOCl gave a different profile of GSH oxidation products, with significantly less GSSG and mixed disulfide formation. There was irreversible oxidation and losses to the medium, as observed with HOCl and other cell types. Thus, histamine chloramine shows high preference for thiols both in isolation and in cells, and in this respect is more selective than HOCl.

Ascorbic Acid↗
PubMed1992

Microtiter plate assay for phagocyte-derived taurine-chloramines.

Despite their potential importance, the role of phagocyte-derived chloramines ("long-lived oxidants") has not yet been investigated in inflammatory or infectious diseases. We have developed a sensitive spectrophotometric microtiter plate assay for chloramines based on their capacity to oxidize potassium iodide (KI). Consistent levels of endogenous chloramines were detected in normal human polymorphonuclear neutrophil (PMN) supernatants after stimulation by phorbol myristate acetate (PMA) or opsonized zymosan. Exogenous taurine strongly enhanced chloramine secretion and was used to quantify the chlorinating potential of PMN. Taurine-chloramines were also detectable in monocyte supernatants, although in smaller amounts. The specificity of the KI assay was assessed both in terms of effect of compounds inhibiting (KBr) or interacting with (sodium azide and catalase) chloramine formation and by showing that PMN from patients with chronic granulomatous disease, due to a hereditary lack of oxidative response capacity, were unable to produce chloramines. Taurine-chloramine levels secreted by PMA (but not zymosan)-stimulated PMN were closely related to the cellular luminol-amplified chemiluminescence (CL) responses although the CL assay failed to detect chloramines in PMN supernatants. We consider that this KI assay should be of use in studying the role of long-lived phagocyte-derived oxidants in clinical medicine.

Chloramines↗
PubMed1989

[Phagocytosis of chloramine B sensitive and resistant staphylococci isolated from healthy persons and patients].

Phagocytic reaction with respect to antibiotic and chloramine B sensitive and resistant staphylococci isolated from healthy persons and patients, air and stock of medical institutions was studied on albino mice. It was shown that the staphylococcal isolates included strains simultaneously sensitive to antibiotics and chloramine, sensitive to antibiotics and resistant to chloramine, resistant to antibiotics and sensitive to chloramine and simultaneously resistant to antibiotics and chloramine. Activity, intensity and completeness of phagocytosis by leucocytes from mouse abdominal cavity exudates with respect to the staphylococcal strains sensitive to antibiotics and resistant to chloramine, resistant to antibiotics and sensitive to chloramine and simultaneously resistant to antibiotics and chloramine were lower than the values of the phagocytic reaction with respect to the isolates simultaneously sensitive to antibiotics and chloramine. This suggested that not only antibiotic resistance of microbes but also their resistance to disinfectants could be referred to complicating factors of hospital infections.

Animals↗
PubMed2005

Taurine chloramine is more selective than hypochlorous acid at targeting critical cysteines and inactivating creatine kinase and glyceraldehyde-3-phosphate dehydrogenase.

Hypochlorous acid (HOCl) and chloramines are produced by the neutrophil enzyme, myeloperoxidase. Both react readily with thiols, although chloramines differ from HOCl in discriminating between low molecular weight thiols on the basis of their pKa. Here, we have compared the reactivity of HOCl and taurine chloramine with thiol proteins by examining inactivation of creatine kinase (CK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). With both enzymes, loss of activity paralleled thiol loss. For CK both were complete at a 1:1 taurine chloramine:thiol mole ratio. For GAPDH each chloramine oxidized two thiols. Three times more HOCl than taurine chloramine was required for inactivation, indicating that HOCl is less thiol specific. Competition studies showed that thiols of CK were 4 times more reactive with taurine chloramine than thiols of GAPDH (rate constants of 1200 and 300 M-1s-1 respectively). These compare with 205 M-1s-1 for cysteine and are consistent with their lower pKa's. Both enzymes were equally susceptible to HOCl. GSH competed directly with the enzyme thiols for taurine chloramine and protected against oxidative inactivation. At lower GSH concentrations, mixed disulfides were formed. We propose that chloramines should preferentially attack proteins with low pKa thiols and this could be important in regulatory processes.

Animals↗
PubMed1992

Abolition with chloramine-T of inactivation in barnacle muscle fibers results in stimulation of the ouabain-insensitive sodium efflux.

The hypothesis that chloramine-T stimulates the basal Na+ efflux in barnacle fibers as the result of the entry of trigger Ca2+ into the myoplasm from the bathing medium was examined in this study. Two reasons for doing so can be given. One is that the oxidant is known to abolish inactivation in sodium and potassium channels. The other is that L-type Ca2+ channels are present in barnacle fibers, and an increase in internal free Ca2+ in these fibers is known to stimulate the Na+ efflux, particularly in ouabain-poisoned fibers. The results of the experiments are as follows: (i) Chloramine-T exerts a biphasic effect on the Na+ efflux: inhibition is followed by stimulation, the threshold concentration being 10(-5) M. This is also found to be the threshold concentration for shortening of these fibers. (ii) The kinetics of the inhibitory effect resemble those of ouabain. (iii) Ouabain is without effect on the stimulatory phase caused by chloramine-T. (iv) Application of chloramine-T after the full effect of 10(-4) M-ouabain is reached elicits solely a stimulatory response. (v) The dose-response curves for the stimulatory action of chloramine-T in unpoisoned and ouabain-poisoned fibers are alike except that the threshold concentration is less than 10(-5) M in poisoned fibers. (vi) Basal light emission from unpoisoned and ouabain-poisoned fibers loaded with the photoprotein, aequorin, some 60 min beforehand increases as soon as they are exposed to 10(-4) M chloramine-T. The response recorded in unpoisoned fibers is monophasic and usually transitory, whereas it is multiphasic and usually sustained in ouabain-poisoned fibers. (vii) The dose-response curve for chloramine-T shows a shift to the left in poisoned fibers. (viii) The magnitude of the rise in light emission depends on the external Ca2+ concentration. A rise fails to take place in the nominal absence of external Ca2+. Taken together, these results support the above hypothesis that chloramine-T causes the entry of trigger Ca2+ into the myoplasm from the outside and provide evidence that stimulation of the Na+ efflux is associated not only with this event but also with a reduced Na+ gradient resulting from inhibition of the membrane Na+/K(+)-ATPase system by the oxidant. Thus, the suggestion put forward is that this oxidant promotes reverse Na+/Ca2+ exchange and is able to exert multiple effects on membrane transport.

Animals↗
PubMed1992

Pholasin: a new chemiluminescent probe for the detection of chloramines derived from human phagocytes.

We have previously reported that normal human polymorphonuclear neutrophils (PMN) release taurine-chloramine, a long-lived oxidant, in response to stimulation by phorbol myristate acetate (PMA) or opsonized zymosan in the presence of exogenous taurine. We now describe a new, simple, and highly sensitive method for the detection of chloramines, including taurine-chloramine, using the chemiluminescent probe Pholasin, the luciferin of the mollusc Pholas dactylus. Taurine-chloramine (N-chlorotaurine) detection was assessed with both a colorimetric method (based on the oxidation of potassium iodide) and with the Pholasin-dependent chemiluminescence (CL) method. The taurine-chloramine concentration in PMN supernatants determined using the potassium iodide (KI) method correlated closely with Pholasin-dependent CL. This CL was also assessed in nonoxidative conditions. No taurine-chloramine was detected in supernatants of lymphocytes and PMN from patients with an oxidative burst defect (chronic granulomatous disease, CGD) with the KI method, but Pholasin-dependent CL was consistently observed. The use of methionine, a specific chloramine scavenger in our incubation conditions, allowed us to define a methionine-inhibitable fraction of Pholasin-dependent CL (i.e., chloramine-induced CL).

Child↗
PubMed2002

Hypochlorite-induced damage to DNA, RNA, and polynucleotides: formation of chloramines and nitrogen-centered radicals.

Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl is a key bactericidal agent, but can also damage host tissue. As there is a strong link between chronic inflammation and some cancers, we have investigated HOCl damage to DNA, RNA, and polynucleotides. Reaction of HOCl with these materials is shown to yield multiple semistable chloramines (RNHCl/RR'NCl), which are the major initial products, and account for 50-95% of the added HOCl. These chloramines decay by thermal and metal-ion catalyzed processes, to give nucleoside-derived, nitrogen-centered, radicals. The latter have been characterized by EPR spin trapping. The propensity for radical formation with polynucleotides is cytidine > adenosine = guanosine > uridine = thymidine. The rates of decay, and yield of radicals formed, are dependent on the nature of the nucleobase on which they are formed, with chloramines formed from ring heterocyclic amine groups being less stable than those formed on exocyclic amines (RNH2 groups). Evidence is presented for chlorine transfer from the former, kinetically favored, sites to the more thermodynamically favored exocyclic amines. EPR experiments have also provided evidence for the rapid addition of pyrimidine-derived nitrogen-centered radicals to other nucleobases to give dimers and the oxidation of DNA by radicals derived from preformed nucleoside chloramines. Direct reaction of HOCl with plasmid DNA gives rise to single- and double-strand breaks via chloramine-mediated reactions. Preformed nucleoside chloramines also induce plasmid cleavage, though this only occurs to a significant extent with unstable thymidine- and uridine-derived chloramines, where radical formation is rapid. Overall the data rationalize the preferential formation of chlorinated 2'-deoxycytidine and 2'-deoxyadenosine in DNA and suggest that DNA damage induced by HOCl, and preformed chloramines, occurs at sequence-specific sites.

Chloramines↗
PubMed1986

The alteration of hamster serum elastase inhibitory capacities by chloramine T, in vitro and in vivo.

The major elastase inhibitor of human serum, alpha-1 proteinase inhibitor (A1PI), is susceptible to oxidative inactivation by a variety of agents, including chloramine T. We have examined the effects of chloramine T on the catalytic activity of porcine pancreatic (PPE) and human leukocyte elastase (HLE) and on the elastase inhibitory capacity of hamster, rat, and human serum as well as pure human A1PI. Both PPE and HLE, but not trypsin, were inhibited in a concentration-dependent manner by concentrations of chloramine T greater than 0.1 mM. The abilities of rat and human serum and pure human A1PI to inhibit both PPE and HLE were inhibited in a concentration-dependent manner by chloramine T. In contrast only the ability of hamster serum to inhibit HLE was altered by exposure to chloramine T: inhibition of PPE was not effected. Gel exclusion chromatography disclosed the existence of two major peaks of elastase inhibitory activity in hamster plasma: one, with an approximate molecular weight of 55 K, eluting in the region of A1PI that was sensitive to chloramine T inactivation and one with a molecular weight of approximately 180 K which was chloramine T insensitive. The parenteral administration of chloramine T to hamsters resulted in a modest and transient diminution of the serum HLE inhibitory activity and an equally modest and transient elevation of PPE inhibitory activity.

Animals↗