Effect of N-chloroamino acids on the erythrocyte

Amino acids present in blood plasma may be targets for oxidation and chlorination by HOCl/OCl^?. N-Chloroamino acids have been reported to be less reactive, but more selective than HOCl/OCl^? in their reactions; therefore, they may act as secondary mediators of HOCl/OCl^?-induced injury. This study compared the effects of five N-chloroamino acids (AlaCl, LysCl, SerCl, AspCl and PheCl) on erythrocytes with the action of HOCl/OCl^?. The N-chloroamino acids differed in stability and reactivity. They had a weaker haemolytic action than HOCl/OCl^?; HOCl/OCl^?, AlaCl and PheCl increased osmotic fragility of erythrocytes at a concentration of 1 mm. Oxidation of glutathione, formation of protein-glutathione mixed disulphides and efflux of GSSG from erythrocytes were observed for erythrocytes treated with all the employed chloroderivatives, while increased oxidation of 2′,7′-dichlorofluorescin was detected only after treatment of the cells with 1 mm HOCl/OCl^?, AlaCl and PheCl. Generally, the reactivity of at least some N-chloroamino acids may be not much lower with respect to HOCl/OCl^?.     

Red wine activates plasma membrane redox system in human erythrocytes

In the present study, we report that polyphenols present in red wine obtained by a controlled microvinification process are able to protect human erythrocytes from oxidative stress and to activate Plasma Membrane Redox System (PMRS). Human plasma obtained from healthy subjects was incubated in the presence of whole red wine at a concentration corresponding to 9.13–73?μg/ml gallic acid equivalents to verify the capacity to protect against hypochlorous acid (HOCl)-induced plasma oxidation and to minimize chloramine formation. Red wine reduced hemolysis and chloramine formation induced by HOCl of 40 and 35%, respectively. PMRS present on human erythrocytes transfers electrons from intracellular molecules to extracellular electron acceptors. We demonstrated that whole red wine activated PMRS activity in human erythrocytes isolated from donors in a dose-dependent manner with a maximum at about 70–100?μg/ml gallic acid equivalents. We also showed that red wine increased glutathione (GSH) levels and erythrocytic antioxidant capacity, measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) quenching assay. Furthermore, we reported that GSH played a crucial role in regulating PMRS activity in erythrocytes. In fact, the effect of iodoacetamide, an alkylating agent that induces depletion of intracellular GSH, was completely counteracted by red wine. Bioactive compounds present in red wine, such as gallic acid, resveratrol, catechin, and quercetin were unable to activate PMRS when tested at the concentrations normally present in aged red wines. On the contrary, the increase of PMRS activity was associated with the anthocyanin fraction, suggesting the capacity of this class of compounds to positively modulate PMRS enzymatic activity.     

An Ecological Risk Assessment of Inorganic Chloramines in Surface Water

Inorganic chloramines are formed when chlorine and ammonia are combined in water. These substances are frequently used as a secondary disinfectant for drinking water and are by-products of processes involving the disinfection of wastewaters and the control of biological fouling in cooling water systems. For chloraminate drinking water, the total residual chlorine (TRC) concentration may be almost completely due to monochloramine. Based on 1995 and 1996 survey data, the most significant and prevalent TRC loading to the Canadian environment is from municipal wastewater releases. Drinking water releases are the next most important source of chloramine entry into the Canadian environment, while TRC releases from other sources, such as cooling water, zebra mussel control practices and industrial wastewater, are much less important. A probabilistic water quality model was used to model two wastewater discharges and a cooling water discharge to different freshwater systems. The resulting exposure distributions were then compared with three incipient lethality endpoints, i.e., 50% mortality to the invertebrate Ceriodaphnia dubia and 50% and 20% mortality to juvenile chinook salmon (Oncorhynchus tshawytscha). For each discharge scenario studied, there were moderate to high probabilities of significant adverse effects on aquatic life up to 1.9?km from the effluent sources.     

Chemiluminescence associated with amino acid oxidation mediated by hypochlorous acid

Although most amino acids readily react with hypochlorous acid (HOCl), only the reaction involving tryptophan (Trp) produces a measurable chemiluminescence (CL). Most of this luminescence takes place after total consumption of HOCl when the process is carried out in an excess of Trp. The quantum yield of the process is relatively low (2 × 10^?8 Einstein/mol HOCl reacted). The luminescence is attributed to free radical‐mediated secondary reactions of the initially produced chloramines. This is supported by experiments showing that the chloramines produced when HOCl reacts with alanine are able to induce Trp chemiluminescence, and that this luminescence is partially quenched by free radical scavengers. The spectral changes and the effect of pH upon the observed luminescence are compatible with light emission from products produced in the free radical oxidation of Trp. Copyright © 2002 John Wiley & Sons, Ltd.     

Mechanism of the action of biogenic chloramines and hypochlorite on the initial aggregation of platelets

The antiaggregant effect of two reactive oxidants—N,N-dichlorotaurine (a biogenic chloramine) and sodium hypochlorite—on the initial ADP-induced aggregation of rabbit blood platelets was studied. Platelet aggregation in reconstituted platelet-rich plasma was measured nephelometrically; an increase in the intensity of small-angle light scattering served as an index of aggregation. Addition of chloramine at relatively small concentrations (no greater than 1 mM available chlorine) directly to the reconstituted platelet-rich plasma suppressed the initial aggregation (formation of small aggregates) several times more strongly than preincubation of native plasma with chloramine. This suggests that N,N-dichlorotaurine realizes its antiaggregant effect on the platelet-rich plasma by directly interacting with cells. The effects of the inhibition of platelet aggregation in two variants of addition of high concentrations of N,N-dichlorotaurine did not differ significantly. In this case, a large amount of residual unreacted chloramine remained in the plasma, which caused the suppression of platelet aggregation during subsequent reconstitution of the platelet-rich plasma. Similar data were obtained in studying the antiaggregant effect of hypochlorite. N,N-Dichlorotaurine and hypochlorite at concentrations of 0.2–0.3 and 0.15 mM, respectively, strongly inhibited the initial aggregation of isolated platelets (approximately 2·10⁸ cells/ml) preliminarily activated for 1.5 min by addition of 0.1–0.5 μM ADP. However, the antiaggregants had a more profound suppressive effect on the aggregation of unstimulated platelets. The antiaggregant effects of N,N-dichlorotaurine and hypochlorite probably stem from the oxidative modification of the sulfur-containing groups in platelet plasma membrane.     

Luminol-enhanced chemiluminescence of rabbit polymorphonuclear leukocytes: The nature of oxidants that directly cause luminol oxidation

In this study, we investigated the pathways (including the formation of hydroxyl radicals and chloramines) leading to luminol chemiluminescence induced by hypochlorite generated in a suspension of stimulated rabbit polymorphonuclear leukocytes. Chemiluminescence of leukocytes stimulated by phorbol myristate acetate, which was enhanced by luminol (0.02 mM), did not change in the presence of dimethyl sulfoxide at moderate concentrations (0.02–2.6 mM), under which the latter should manifest the specific ability to scavenge hydroxyl radicals. This indicates that stimulation of polymorphonuclear leukocytes is not accompanied by the generation of hydroxyl radicals with the involvement of superoxide anion and hypochlorite synthesized by myeloperoxidase. At high concentrations of dimethyl sulfoxide (260 mM), chemiluminescence markedly declined because dimethyl sulfoxide directly reacts with hypochlorite. The luminol emission intensity considerably increased after its addition to a suspension of leukocytes that were preliminarily stimulated for 10 min. This effect was caused by the accumulation of hydrogen peroxide rather than chloramines. Exogenous amino acids and taurine at high concentrations (3–15 mM) quench chemiluminescence. All these data indicate that chemiluminescence in the system studied is largely determined by the direct initial reaction of hypochlorite with luminol, the emission intensity increasing as a result of oxidation of luminol transformation products by hydrogen peroxide.