Inhibition of hypochlorous acid-induced oxidative reactions by nitrite: is nitrite an antioxidant?

Hypochlorous acid water prevents postoperative intrauterine infection after microwave endometrial ablation

AIM

We investigated the effects of uterine cavity lavage using hypochlorous acid water (HClO) on preventing postoperative intrauterine infection after microwave endometrial ablation (MEA).

METHODS

Four hundred and eleven consecutive patients were enrolled in this study. The patients were divided into two groups: 214 cases in 2014-2016 with disinfection using povidone-iodine antiseptic solution alone (group A) and 197 cases in 2017-2019 with additional intrauterine douche using HClO (group B). HClO was used at a concentration of 200 ppm of residual chlorine. One gram of Ceftriaxone Sodium Hydrate was administered by drip infusion during MEA in both groups. Oral antibiotics were administered after MEA only in group A but not in group B.

RESULTS

Mean patient age (mean ± SD; years old) was 44.5 ± 4.6 in group A and 44.8 ± 5.4 in group B, and mean operation time (min) was 30.4 ± 19.1 in group A and 34.4 ± 22.6 in group B, respectively. Neither were significantly different between groups. The combined ablation techniques i.e. transcervical microwave myolysis and transcervical microwave adenomyolysis did not increase frequency of infection. Postoperative intrauterine infection cases in group B (8 cases) were significantly lower than those in group A (28 cases) (Chi-square test, P = 0.001). Hysterectomy was performed in three severe intrauterine infection cases in group A, but no cases of severe intrauterine infection was found in group B. No adverse effect of HClO was seen.

CONCLUSION

Intrauterine douche using HClO decreases postoperative intrauterine infection after MEA.

Inhibition of myeloperoxidase-mediated oxidative damage by nitrite in SH-SY5Y cells: Relevance to neuroprotection in neurodegenerative diseases

Myeloperoxidase (MPO) and MPO-catalyzed hypochlorous acid (HOCl) is elevated in many neurodegenerative diseases, and lead to severe tissue injuries. Nitrite (NO2(-)) is a widespread inorganic molecule that has recently been proposed as a direct NO donor to exert antioxidant properties in vivo and vitro. Since NO2(-) and MPO (and/or HOCl) were important mediators in brain function and disease, we investigated the effects of NO2(-) on MPO-mediated damage to human neuroblastoma SH-SY5Y cells. Here, we showed that exposure of SH-SY5Y cells to MPO (or HOCl) resulted in a significant loss in viability, ATP and glutathione levels, and treatment of neuronal cells with NO2(-) substantially attenuated MPO (or HOCl)-dependent cellular toxicity. The protective effects of NO2(-) on MPO (or HOCl)-induced cytotoxicity were because that (1) NO2(-) at high concentrations competed effectively with Cl(-) for MPO, thus limiting OCl(-) production by the enzyme; (2) HOCl was removed by reacting with NO2(-), forming less damaging compound; (3) NO2(-) significantly inhibited MPO-mediated inactivation of brain protein (enolase) and protein oxidation. Therefore, NO2(-) could show novel protective effects in some neurodegenerative diseases by preventing MPO-mediated oxidative damage.

Scavenging properties of neutrophil 4-hydroxyphenylpyruvate dioxygenase are based on a hypothesis that does not stand up to scrutiny

It was previously reported by D'Eufemia et al. [9] that neutrophil preparations from a patient with tyrosinemia type III, i.e. with inherited deficiency of 4-hydroxyphenylpyruvate dioxygenase (HPPD), exhibited a far higher NO release than controls, when NO was estimated in terms of nitrite content in the suspending media. It was hypothesized that HPPD might participate to NO sequestration in neutrophils and that excessive NO release might reflect the lack of the scavenging action in defective cells. In recent control experiments, we found that HPPD activity in neutrophils preparations from healthy subjects is below the detection limit of the enzymatic assay (less than 3nmol product/h per mg protein). This indicates that HPPD concentration in neutrophils is very low, if any, confirming what was already suggested in literature, and rules out the possibility of a prominent role of HPPD as NO scavenger in these cells. Moreover, we found that 500μM l-tyrosine increases nitrite release and accumulation in suspending media of U-937 cells, a human monoblast-like lymphoma cell line which displays many characteristics of macrophages, including the expression of inducible and endothelial nitric oxide synthases. We hypothesize that the increase of nitrite release by patient's neutrophils might be related to the presence of high l-tyrosine concentrations in the blood samples (426μmol/L instead of 52.1±10.9μmol/L as healthy subjects), rather than to HPPD deficiency of in these cells.

Selenium and psoriasis

Psoriasis is a chronic, immune-mediated skin disease characterized by production of reactive oxygen species due to the activation of tumor necrosis factor alpha (TNF-α), which is thought to be an important factor in inducing and maintaining psoriatic lesions. As an external factor, ultraviolet B (UVB) radiation stimulates TNF-α production and secretion by human keratinocytes in vitro and can also reach the upper dermis and suppress endothelial cells in vitro. The selenium level in psoriatic patients has been found to be lower than expected, but studies on its role in the pathogenesis of the disease are scarce. Selenium can influence immune response by changing the expression of cytokines and their receptors or by making immune cells more resistant to oxidative stress. It was reported that selenium supplementation had inhibitory effects on TNF-α levels in patients with psoriasis, but the details are not completely elucidated. Selenium compounds are also known to prevent the in vitro release of UVB-induced proinflammatory cytokines by inhibition of mRNA in human keratinocytes. In the present review, the protective role of selenium in oxidative stress, lesions, and immune system regulation in patients with psoriasis is summarized.

Myeloperoxidase-derived oxidation: mechanisms of biological damage and its prevention

There is considerable interest in the role that mammalian heme peroxidase enzymes, primarily myeloperoxidase, eosinophil peroxidase and lactoperoxidase, may play in a wide range of human pathologies. This has been sparked by rapid developments in our understanding of the basic biochemistry of these enzymes, a greater understanding of the basic chemistry and biochemistry of the oxidants formed by these species, the development of biomarkers that can be used damage induced by these oxidants in vivo, and the recent identification of a number of compounds that show promise as inhibitors of these enzymes. Such compounds offer the possibility of modulating damage in a number of human pathologies. This reviews recent developments in our understanding of the biochemistry of myeloperoxidase, the oxidants that this enzyme generates, and the use of inhibitors to inhibit such damage.

Evaluation of Vashe Wound Therapy in the clinical management of patients with chronic wounds

OBJECTIVE

To analyze if Vashe Wound Therapy (PuriCore, Malvern, Pennsylvania) is a valuable contribution to standard protocols of wound care.

DESIGN

Open, noncomparative study.

SETTING

Outpatient clinic.

PATIENTS

Thirty-one patients, primarily with venous or mixed venous/arterial leg ulcers.

INTERVENTIONS

Vashe Wound Therapy (hypochlorous acid, produced on site and on demand) was used as an adjunct to a standard wound care protocol.

MAIN OUTCOME MEASURES

Wound healing, reduction of pain, and odor.

MAIN RESULTS

At the end of the study, 86% of all lesions healed, and the average size of reduction in nonhealed wounds was 47%. Odor was present at the beginning of enrollment in 21 patients and was rated 4.58 on the visual analog scale. In all patients, the odor score at end of treatment was zero. Seventy-seven percent of all patients reported a positive pain score at the beginning of participation in the evaluation (average pain score, 4.7). At the end of the study, no patient experienced pain.

CONCLUSION

Vashe Wound Therapy is a valuable contribution to standard protocols of wound care.

Poly(ADP-Ribose) polymerase inhibition improves endothelial dysfunction induced by hypochlorite

Reactive oxygen species, such as myeloperoxidase-derived hypochlorite, induce oxidative stress and DNA injury. The subsequent activation of the DNA-damage-poly(ADP-ribose) polymerase (PARP) pathway has been implicated in the pathogenesis of various diseases, including ischemia-reperfusion injury, circulatory shock, diabetic complications, and atherosclerosis. We investigated the effect of PARP inhibition on the impaired endothelium-dependent vasorelaxation induced by hypochlorite. In organ bath experiments for isometric tension, we investigated the endothelium-dependent and endothelium-independent vasorelaxation of isolated rat aortic rings using cumulative concentrations of acetylcholine and sodium nitro-prusside. Endothelial dysfunction was induced by exposing rings to hypochlorite (100-400 microM). In the treatment group, rings were preincubated with the PARP inhibitor INO-1001. DNA strand breaks were assessed by the TUNEL method. Immunohistochemistry was performed for 4-hydroxynonenal (a marker of lipid peroxidation), nitrotyrosine (a marker of nitrosative stress), and poly(ADP-ribose) (an enzymatic product of PARP). Exposure to hypochlorite resulted in a dose-dependent impairment of endothelium-dependent vasorelaxation of aortic rings, which was significantly improved by PARP inhibition, whereas the endothelium-independent vasorelaxation remained unaffected. In the hypochlorite groups we found increased DNA breakage, lipidperoxidation, and enhanced nitrotyrosine formation. The hypochloride-induced activation of PARP was prevented by INO-1001. Our results demonstrate that PARP activation contributes to the pathogenesis of hypochlorite-induced endothelial dysfunction, which can be prevented by PARP inhibitors.

Urate oxidation during percutaneous transluminal coronary angioplasty and thrombolysis in patients with coronary artery disease

Thrombolysis and percutaneous transluminal coronary angioplasty (PTCA) are kinds of procedures that can be used to restore the blood flow of previously ischemic myocardium that can be the result of excessive production of reactive oxygen and nitrogen species, such as superoxide and hydroxyl radical, hypochlorous acid and peroxynitrite. Reaction of urate with some of these potent oxidants results in allantoin production. In this study, we measured the serum allantoin levels, an oxidation product of urate, and "in vivo" marker of free radical generation in reperfusion of ischemic myocardium. After an overnight fasting state, blood samples were collected from 35 patients with coronary occlusive diseases (7 women and 28 men) and 31 healthy subjects (8 women and 23 men). Serum allantoin and urate levels were measured by a GC-MS method. Serum allantoin levels of patients on PTCA therapy (mean+/-SD, 27.4 +/- 15.2 micromol/l) and thrombolytic therapy (24.6 +/- 8.6 micromol/l) were significantly higher than those of the patients without therapy (15.8 +/- 6.2 micromol/l, p < 0.05 with PTCA and p < 0.006 with thrombolysis) and healthy controls (12.6 +/- 6.3 micromol/l, p < 0.002 with PTCA and p < 0.0001 with thrombolysis). Although serum urate levels in PTCA (380.1 +/- 72.6 micromol/l) and thrombolysis (359.5 +/- 60.0 micromol/l) were higher than those in the non-therapy patients (336.6 +/- 53.8 micromol/l) and controls (318.3 +/- 81.0 micromol/l), there were no significant differences among groups (p > 0.05). The results of the study are consistent with others which have demonstrated, higher urate levels are associated with coronary occlusive diseases. Our data support the hypothesis that generation of ROS occurs during myocardial reperfusion. Increased allantoin levels may be used as an index of increased oxidative stress during reperfusion.

Myeloperoxidase: friend and foe

Neutrophilic polymorphonuclear leukocytes (neutrophils) are highly specialized for their primary function, the phagocytosis and destruction of microorganisms. When coated with opsonins (generally complement and/or antibody), microorganisms bind to specific receptors on the surface of the phagocyte and invagination of the cell membrane occurs with the incorporation of the microorganism into an intracellular phagosome. There follows a burst of oxygen consumption, and much, if not all, of the extra oxygen consumed is converted to highly reactive oxygen species. In addition, the cytoplasmic granules discharge their contents into the phagosome, and death of the ingested microorganism soon follows. Among the antimicrobial systems formed in the phagosome is one consisting of myeloperoxidase (MPO), released into the phagosome during the degranulation process, hydrogen peroxide (H2O2), formed by the respiratory burst and a halide, particularly chloride. The initial product of the MPO-H2O2-chloride system is hypochlorous acid, and subsequent formation of chlorine, chloramines, hydroxyl radicals, singlet oxygen, and ozone has been proposed. These same toxic agents can be released to the outside of the cell, where they may attack normal tissue and thus contribute to the pathogenesis of disease. This review will consider the potential sources of H2O2 for the MPO-H2O2-halide system; the toxic products of the MPO system; the evidence for MPO involvement in the microbicidal activity of neutrophils; the involvement of MPO-independent antimicrobial systems; and the role of the MPO system in tissue injury. It is concluded that the MPO system plays an important role in the microbicidal activity of phagocytes.

Interference of the polyphenol epicatechin with the biological chemistry of nitric oxide- and peroxynitrite-mediated reactions

The formation of reactive nitrogen species in mammalians has both beneficial and undesirable effects. Nitric oxide (NO) production in endothelial cells leads to vascular smooth muscle relaxation, but if reactive nitrogen species are generated in high amounts by cells under inflammatory conditions they are toxic. Flavonoids like (-)-epicatechin show an inverse association of their intake with diseases thought to be associated with overproduction of reactive nitrogen species. We found that the formation of cyclic GMP in cultured porcine aortic endothelial cells was not affected by up to 1 mM (-)-epicatechin. Half maximal inhibition of interferon-gamma/lipopolysaccharide induced nitrite accumulation in murine macrophages required about 0.5 mM of the flavonoid. In contrast, nitration of free tyrosine triggered by 0.1 and 1 mM authentic peroxynitrite was inhibited by (-)-epicatechin with IC(50) values of 6.6 and 28.0 microM, respectively. The presence of 15 mM sodium bicarbonate had no significant effect. Nitration of protein-bound tyrosine in phorbol 12-myristate 13-acetate treated HL-60 cells in the presence of nitrite was inhibited by (-)-epicatechin at a similar concentration range (IC(50)=10-100 microM). Myeloperoxidase activity of phorbol 12-myristate 13-acetate stimulated HL-60 cells was inhibited by (-)-epicatechin with an IC(50) value of 77.4 microM. Epicatechin inhibited dihydrorhodamine oxidation by 50 microM authentic peroxynitrite and 1 mM 3-morpholino-sydnonimine with IC(50) values of 11.8 and 0.63 microM, respectively. Our data suggest that at up to 0.1 mM (-)-epicatechin preferentially inhibits NO-related nitration and oxidation reactions without affecting NO synthesis and cyclic GMP signaling.

Nitrite-mediated protection against hypochlorous acid-induced chondrocyte toxicity: a novel cytoprotective role of nitric oxide in the inflamed joint?

OBJECTIVE

To examine the potential consequences of overproduction of nitric oxide (NO) and nitrite (NO(2) (-)) in the inflamed rheumatoid joint.

METHODS

Human articular chondrocytes in culture were exposed to HOCl (hypochlorous acid, a physiologic oxidant formed in increased amounts at sites of chronic inflammation), and assays of cell viability, intracellular ATP and glutathione (GSH), and lactate dehydrogenase (LDH) were performed. HOCl-induced lipid peroxidation and activation of the MAP kinases ERK-1/2, JNK-1/2, and p38 were also measured. The modulatory effects of NO-derived nitrite (NO(2) (-)) and nitrate (NO(3) (-)) on HOCl-mediated chondrocyte toxicity were investigated.

RESULTS

Exposure of human articular chondrocytes to HOCl resulted in a concentration- and time-dependent loss of viability, decrease in ATP and GSH levels, LDH leakage, and cell death. HOCl induced significant lipid peroxidation as well as activation of the MAP kinases ERK-1/2 and p38 but not JNK-1/2. However, the presence of NO(2) (-) but not NO(3) (-) substantially decreased HOCl-dependent cellular toxicity even when NO(2) (-) was added at low (microM) concentrations. In sharp contrast, NO(2) (-) (1 mM) did not inhibit superoxide-, hydroxyl radical-, H(2)O(2)-, or peroxynitrite-mediated cytotoxicity. Furthermore, culture media from cells treated with interleukin-1beta (to generate NO and NO(2) (-)) offered significantly more protection against HOCl-mediated cytotoxicity than culture media from untreated cells.

CONCLUSION

These data suggest that NO(2) (-) accumulation at chronically inflamed sites where both HOCl and NO are overproduced may be cytoprotective against damage induced by HOCl. Accumulation of NO(2) (-) could represent a novel cytoprotective role of NO in inflamed joints. A mechanism for this is suggested.