Serotonin as a physiological substrate for myeloperoxidase and its superoxide-dependent oxidation to cytotoxic tryptamine-4,5-dione

2009 ◽  
Vol 425 (1) ◽  
pp. 285-293 ◽  
Author(s):  
Valdecir F. Ximenes ◽  
Ghassan J. Maghzal ◽  
Rufus Turner ◽  
Yoji Kato ◽  
Christine C. Winterbourn ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Nadph Oxidase ◽  
Tissue Damage ◽  
Acid Production ◽  
Hypochlorous Acid ◽  
Human Neutrophils ◽  
Toxic Metabolite ◽  
Inflammatory Processes ◽  
Physiological Substrates ◽  
Inflammatory Tissue

During inflammatory events, neutrophils and platelets interact to release a variety of mediators. Neutrophils generate superoxide and hydrogen peroxide, and also discharge the haem enzyme myeloperoxidase. Among numerous other mediators, platelets liberate serotonin (5-hydroxytryptamine), which is a classical neurotransmitter and vasoactive amine that has significant effects on inflammation and immunity. In the present study, we show that serotonin is a favoured substrate for myeloperoxidase because other physiological substrates for this enzyme, including chloride, did not affect its rate of oxidation. At low micromolar concentrations, serotonin enhanced hypochlorous acid production by both purified myeloperoxidase and neutrophils. At higher concentrations, it almost completely blocked the formation of hypochlorous acid. Serotonin was oxidized to a dimer by myeloperoxidase and hydrogen peroxide. It was also converted into tryptamine-4,5-dione, especially in the presence of superoxide. This toxic quinone was produced by stimulated neutrophils in a reaction that required myeloperoxidase. In plasma, stimulated human neutrophils oxidized serotonin to its dimer using the NADPH oxidase and myeloperoxidase. We propose that myeloperoxidase will oxidize serotonin at sites of inflammation. In doing so, it will impair its physiological functions and generate a toxic metabolite that will exacerbate inflammatory tissue damage. Consequently, oxidation of serotonin by myeloperoxidase may profoundly influence inflammatory processes.

scholarly journals Intracellular pH regulation during spreading of human neutrophils.

1996 ◽  
Vol 133 (6) ◽  
pp. 1391-1402 ◽  
Author(s):  
N Demaurex ◽  
G P Downey ◽  
T K Waddell ◽  
S Grinstein
Keyword(s):  
Nadph Oxidase ◽  
Acid Production ◽  
Ph Regulation ◽  
Superoxide Production ◽  
Human Neutrophils ◽  
Acid Generation ◽  
Diphenylene Iodonium ◽  
Physiological Values ◽  
Cytosolic Acidification ◽  
Intracellular Acid

The regulation of the intracelluar pH (pHi) during spreading of human neutrophils was studied by a combination of fluorescence imaging and video microscopy. Spreading on adhesive substrates caused a rapid and sustained cytosolic alkalinization. This pHi increase was prevented by the omission of external Na+, suggesting that it results from the activation of Na+/H+ exchange. Spreading-induced alkalinization was also precluded by the compound HOE 694 at concentrations that selectively block the NHE-1 isoform of the Na+H+ antiporter. Inhibition of Na+/H+ exchange by either procedure unmasked a sizable cytosolic acidification upon spreading, indicative of intracellular acid production. The excess acid generation was caused, at least in part, by the activation of the respiratory burst, since the acidification closely correlated with superoxide production, measured in single spreading neutrophils with dihydrorhodamine-123, and little acid production was observed in the presence of diphenylene iodonium, a blocker of the NADPH oxidase. Moreover, neutrophils from chronic granulomatous disease patients, which do not produce superoxide, failed to acidify. Comparable pHi changes were observed when beta 2 integrins were selectively activated during spreading on surfaces coated with anti-CD18 antibodies. When integrin engagement was precluded by pretreatment with soluble anti-CD18 antibody, the pHi changes associated with spreading on fibrinogen were markedly reduced. Inhibition of microfilament assembly with cytochalasin D precluded spreading and concomitantly abolished superoxide production and the associated pHi changes, indicating that cytoskeletal reorganization and/or an increase in the number of adherence receptors engaged are required for the responses. Neutrophils spread normally when the oxidase was blocked or when pHi was clamped near physiological values with nigericin. Spreading, however, was strongly inhibited when pHi was clamped at acidic values. Our results indicate that neutrophils release superoxide upon spreading, generating a burst of intracellular acid production. The concomitant activation of the Na+/H+ antiport not only prevents the deleterious effects of the acid released by the NADPH oxidase, but induces a net cytosolic alkalinization. Since several functions of neutrophils are inhibited at an acidic pHi, the coordinated activation of pHi regulatory mechanisms along with the oxidase is essential for sustained microbicidal activity.

scholarly journals Inhibition of the lymphocyte metabolic switch by the oxidative burst of human neutrophils

2015 ◽  
Vol 129 (6) ◽  
pp. 489-504 ◽  
Author(s):  
Philip A. Kramer ◽  
Lynn Prichard ◽  
Balu Chacko ◽  
Saranya Ravi ◽  
E. Turner Overton ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Nadph Oxidase ◽  
Oxidative Burst ◽  
Effector Function ◽  
Human Neutrophils ◽  
Glycolytic Metabolism ◽  
Metabolic Switch ◽  
Nadph Oxidase 2

The lymphocyte metabolic switch, a transition from a mitochondrial to a more glycolytic metabolism, is prevented by neutrophil-derived hydrogen peroxide (H2O2). We propose that NADPH oxidase-2 (NOX-2) mediates the neutrophil-dependent suppression of lymphocyte effector function.

Visualizing hypochlorous acid production by human neutrophils with fluorescent graphene quantum dots

2021 ◽  
Author(s):  
Lena Golubewa ◽  
Tatsiana Kulahava ◽  
Aliona Klimovich ◽  
Danielis Rutkauskas ◽  
Ieva Matulaitiene ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Quantum Dots ◽  
Biomedical Applications ◽  
Fluorescence Spectra ◽  
Hypochlorous Acid ◽  
Graphene Quantum Dots ◽  
Cellular Systems ◽  
Human Neutrophils ◽  
High Concentrations ◽  
Living Organisms

Abstract In living organisms, redox reactions play a crucial role in the progression of disorders accompanied by the overproduction of reactive oxygen and reactive chlorine species, such as hydrogen peroxide and hypochlorous acid, respectively. We demonstrate that green fluorescence graphene quantum dots (GQDs) can be employed for revealing the presence of the hypochlorous acid in aqueous solutions and cellular systems. Hypochlorous acid modifies the oxygen-containing groups of the GQD, predominantly opens epoxide rind C–O–C, forms excessive C=O bonds and damages the carbonic core of GQDs. These changes, which depend on the concentration of the hypochlorous acid and exposure time, manifest themselves in the absorbance and fluorescence spectra of the GQD, and in the fluorescence lifetime. We also show that the GQD fluorescence is not affected by hydrogen peroxide. This finding makes GQDs a promising sensing agent for selective detecting reactive chlorine species produced by neutrophils. Neutrophils actively accumulate GQDs allowing to visualize cells and to examine the redox processes via GQDs fluorescence. At high concentrations GQDs induce neutrophil activation and myeloperoxidase release, leading to the disruption of GQD structure by the produced hypochlorous acid. This makes the GQDs a biodegradable material suitable for various biomedical applications.

scholarly journals Mechanism of inactivation of myeloperoxidase by 4-aminobenzoic acid hydrazide

1997 ◽  
Vol 321 (2) ◽  
pp. 503-508 ◽  
Author(s):  
Anthony J. KETTLE ◽  
Craig A. GEDYE ◽  
Christine C. WINTERBOURN
Keyword(s):  
Hydrogen Peroxide ◽  
Acid Production ◽  
Hypochlorous Acid ◽  
Potent Inhibitor ◽  
Reduced Glutathione ◽  
Acid Hydrazide ◽  
Inflammatory Cells ◽  
Aminobenzoic Acid ◽  
Irreversible Inhibition ◽  
Enzyme Turnover

Hypochlorous acid is the most powerful oxidant generated by neutrophils and is likely to contribute to the damage mediated by these inflammatory cells. The haem enzyme myeloperoxidase catalyses its production from hydrogen peroxide and chloride. 4-Aminobenzoic acid hydrazide (ABAH) is a potent inhibitor of hypochlorous acid production. In this investigation we show that, in the presence of hydrogen peroxide, ABAH irreversibly inactivates myeloperoxidase. ABAH was oxidized by myeloperoxidase, and kinetic analysis of the inactivation conformed to that for a mechanism-based inhibitor. Inactivation was exacerbated by concentrations of hydrogen peroxide greater than 50 ƁM and by the absence of oxygen. Hydrogen peroxide alone caused minimal inactivation. Reduced glutathione inhibited the oxidation of ABAH as well as the irreversible inhibition of myeloperoxidase. In the presence of oxygen, ABAH and hydrogen peroxide initially converted myeloperoxidase into compound III, which susequently lost haem absorbance. In the absence of oxygen, the enzyme was converted into ferrous myeloperoxidase and its haem groups were rapidly destroyed. We propose that myeloperoxidase oxidizes ABAH to a radical that reduces the enzyme to its ferrous intermediate. Ferrous myeloperoxidase reacts either with oxygen to allow enzyme turnover, or with hydrogen peroxide to give irreversible inactivation.

scholarly journals Sex-dependent dysregulation of human neutrophil responses by bisphenol A

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Wioletta Ratajczak-Wrona ◽  
Marzena Garley ◽  
Malgorzata Rusak ◽  
Karolina Nowak ◽  
Jan Czerniecki ◽  
...  
Keyword(s):  
Nadph Oxidase ◽  
Bisphenol A ◽  
Total Concentration ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Human Neutrophils ◽  
Boyden Chamber ◽  
No Production ◽  
Pathogen Elimination ◽  
Latex Beads

Abstract Background In the present study, we aimed to investigate selected functions of human neutrophils exposed to bisphenol A (BPA) under in vitro conditions. As BPA is classified among xenoestrogens, we compared its action and effects with those of 17β-estradiol (E2). Methods Chemotaxis of neutrophils was examined using the Boyden chamber. Their phagocytosis and nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) oxidase activity were assessed via Park’s method with latex beads and Park’s test with nitroblue tetrazolium. To assess the total concentration of nitric oxide (NO), the Griess reaction was utilized. Flow cytometry was used to assess the expression of cluster of differentiation (CD) antigens. The formation of neutrophil extracellular traps (NETs) was analyzed using a microscope (IN Cell Analyzer 2200 system). Expression of the investigated proteins was determined using Western blot. Results The analysis of results obtained for both sexes demonstrated that after exposure to BPA, the chemotactic capacity of neutrophils was reduced. In the presence of BPA, the phagocytic activity was found to be elevated in the cells obtained from women and reduced in the cells from men. Following exposure to BPA, the percentage of neutrophils with CD14 and CD284 (TLR4) expression, as well as the percentage of cells forming NETs, was increased in the cells from both sexes. The stimulatory role of BPA and E2 in the activation of NADPH oxidase was observed only in female cells. On the other hand, no influence of E2 on the expression of CD14 and CD284, chemotaxis, phagocytosis, and the amount of NET-positive neutrophils was found for both sexes. The study further showed that BPA intensified NO production and iNOS expression in the cells of both sexes. In addition, intensified expression of all tested PI3K-Akt pathway proteins was observed in male neutrophils. Conclusions The study demonstrated the influence of BPA on neutrophil functions associated with locomotion and pathogen elimination, which in turn may disturb the immune response of these cells in both women and men. Analysis of the obtained data showed that the effect of this xenoestrogen on the human neutrophils was more pronounced than E2.

Sign in / Sign up

Export Citation Format

Share Document