Plasma Myeloperoxidase Concentrations Research Articles

Changes in neutrophil surface receptor expression, degranulation, and respiratory burst activity after moderate- and high-intensity exercise.

Intense exercise stimulates the systemic release of a variety of factors that alter neutrophil surface receptor expression and functional activity. These alterations may influence resistance to infection after intense exercise. The aim of this study was to examine the influence of exercise intensity on neutrophil receptor expression, degranulation (measured by plasma and intracellular myeloperoxidase concentrations), and respiratory burst activity. Ten well-trained male runners ran on a treadmill for 60 min at 60% [moderate-intensity exercise (MI)] and 85% maximal oxygen consumption [high-intensity exercise (HI)]. Blood was drawn immediately before and after exercise and at 1 h postexercise. Immediately after HI, the expression of the neutrophil receptor CD16 was significantly below preexercise values (P < 0.01), whereas MI significantly reduced CD35 expression below preexercise values (P < 0.05). One hour after exercise at both intensities, there was a significant decline in CD11b expression (P < 0.05) and a further decrease in CD16 expression compared with preexercise values (P < 0.01). CD16 expression was lower 1 h after HI than 1 h after MI (P < 0.01). Immediately after HI, intracellular myeloperoxidase concentration was less than preexercise values (P < 0.01), whereas plasma myeloperoxidase concentration was greater (P < 0.01), indicating that HI stimulated neutrophil degranulation. Plasma myeloperoxidase concentration was higher immediately after HI than after MI (P < 0.01). Neutrophil respiratory burst activity increased after HI (P < 0.01). In summary, both MI and HI reduced neutrophil surface receptor expression. Although CD16 expression was reduced to a greater extent after HI, this reduction did not impair neutrophil degranulation and respiratory burst activity.

Prognostic Value of Myeloperoxidase in Patients With Chest Pain

Brennan, Marie-Luise; Penn, Marc S.; Van Lente, Frederick; Nambi, Vijay; Shishenbor, Mehdi H.; Aviles, Ronnier J.; Goormastic, Marlene; Pepoy, Michael L.; McErlean, Ellen S.; Topol, Eric J.; Nissen, Steven E.; Hazen, Stanley L.

Iron, nitric oxide, and myeloperoxidase in asthmatic patients.

Plasma nitric oxide (NO), myeloperoxidase (MPO), and iron (Fe) levels were determined in bronchial asthma. The relations among these parameters in different stages of asthma were interpreted. Their association with airway inflammation observed in patients with bronchial asthma as well as the roles and the contributions to the pathological processes were evaluated. A total of 62 individuals, 32 asthmatics and 30 controls, were included into the scope of this study. Plasma nitric oxide metabolites (NOx) and MPO and Fe levels were determined by the Griess reaction, ELISA, and the automated TPTZ (2,4,6-tri[2-pyridyl]-5-triazine) method, respectively. In the asthmatic individuals, plasma NOx, MPO, and Fe concentrations were 133 +/- 13 microM, 95 +/- 20 ng/ml, and 159 +/- 20 microg/dl, respectively; in the control group these values were 82 +/- 11 microM, 62 +/- 11 ng/ml, and 96 +/- 9 microg/dl. Increased values were detected for plasma MPO (p > 0.05), NOx (p < 0.01), and Fe (p < 0.01) concentrations in asthmatic individuals. Considering the facts that NO modulates the catalytic activity of MPO and induces the expression of heme oxygenase as important contributors to the mechanisms causing free Fe release, it is concluded that elevated NOx, MPO, and Fe levels observed in the asthmatic group act in a concerted manner and appear to be involved in the pathogenesis of asthma.

Polymorphonuclear leukocyte and monocyte activation induced by plasma from patients with heparin-induced thrombocytopenia in whole blood

Heparin-induced thrombocytopenia (HIT), a severe complication of heparin therapy, results from platelet activation by heparin-dependent antibodies. Previously, we have shown that plasma from patients with HIT (HIT plasma) induces leukocyteplatelet aggregation in blood. In this report, we examined leukocyte activation by HIT plasma and the contribution of heparin and platelets to this activation, in whole blood. Degranulation of leukocytes from HIT patients was evaluated as a leukocyte activation marker. We showed that polymorphonuclear leukocytes (PMN) and monocytes were the leukocyte subpopulations involved in platelet-leukocyte aggregation induced by HIT plasma in healthy donor blood. PMN and monocyte activation, reflected by increased surface expression of the CD11b adhesion molecule, was induced by HIT plasma in a heparin-dependent manner. The CD11b increase induced by HIT plasma was observed on PMN only when they were associated with platelets. Moreover, the increased CD11b expression on monocytes and PMN correlated strongly with the degree of platelet adhesion to these cells. Degranulation of leukocytes from HIT patients and control subjects (non-HIT heparin-treated patients and healthy subjects) was evaluated in vivo by measuring the plasma myeloperoxidase concentration. HIT plasma contained higher myeloperoxidase concentrations than control plasma, suggesting leukocyte degranulation during HIT. In conclusion, this study provides the first evidence that PMN activation is induced by HIT plasma. HIT plasma induced PMN and monocyte activation in a heparin-dependent manner. In whole blood, platelet association with monocytes and PMN, and the activation of these leukocytes by HIT plasma were interrelated. Finally, leukocyte degranulation could be involved in HIT physiopathology.

Impact of a competitive marathon race on systemic cytokine and neutrophil responses.

To investigate whether cytokines and neutrophils mediate exercise-related pathogenesis, we examined their responses and possible association after exhaustive exercise. Plasma and urine samples were obtained from 10 male runners before and after a 42.195-km marathon race. Major cytokines and neutrophil activation markers [myeloperoxidase (MPO) and lactoferrin (LTF)] were measured by enzyme-linked immunosorbent assays. Functional modulation of standard neutrophils and monocytes by plasma was determined on their luminol-dependent chemiluminescence responses. The race induced peripheral neutrophilia accompanied by an increase in band neutrophils and monocytosis. Plasma MPO and LTF concentrations increased significantly by 1.8 and 1.4 times after the race. There was a greater increase in urine concentrations of MPO and LTF, 12.3 and 3.5 times after exercise, respectively, suggesting that neutrophil activation occurred and that renal clearance exceeded the increase in plasma concentrations. Plasma interleukin (IL)-6, IL-8, IL-10, granulocyte colony-stimulating factor (G-CSF), macrophage CSF (M-CSF), and monocyte chemotactic protein 1 (MCP-1) increased significantly after the race, and urine IL-1beta, IL-6, G-CSF, M-CSF, and MCP-1 increased significantly. The plasma IL-6 responses correlated with the increases of band neutrophil count (r = 0.860, P < 0.01), suggesting IL-6-mediated bone marrow release of neutrophils. Furthermore, the increases in urine MPO concentration were correlated with increases in urine IL-6 (r = 0.868, P < 0.01) and G-CSF (r = 0.875, P < 0.01), suggesting that these cytokines promoted neutrophil activation. However, preincubation of neutrophils and monocytes with postexercise plasma could not cause priming responses, possibly because of the exercise-induced enhancement of plasma antioxidant activity. Although many cytokines recruiting and priming neutrophils and monocytes were secreted and functional after exhaustive exercise, overwhelming antioxidant and antiinflammatory defenses were induced, preventing exercise-induced oxidative stress.

Pathological Uterine Perfusion in the Second Trimester Is Not Associated with Neutrophil Activation

Objective: Preeclampsia and intrauterine growth retardation (IUGR) are associated with elevated concentrations of myeloperoxidase (MPO) and polymorphonuclear (PMN) elastase, which indicate maternal neutrophil activation. The aim of the study was to measure maternal MPO and PMN elastase plasma concentrations in second trimester pregnancies with pathological uterine perfusion that are a high risk group for preeclampsia and IUGR, and compare them to normal controls. Methods: The study includes 25 pregnancies with normal and 25 pregnancies with pathological uterine perfusion. In both groups, doppler‐sonographic measurement of uterine perfusion was performed in the twenty‐first week of gestation. Maternal plasma concentrations of MPO and PMN elastase were measured using a specific ELISA for both enzymes. Results: The plasma MPO concentration of pregnant women with normal perfusion did not differ significantly from that of the group with pathological perfusion (27.4 ± 3.3 vs. 23.7 ± 2.0 ng/mL). Likewise, the plasma PMN elastase‐concentration also did not show a significant difference between the groups (5.7 ± 0.5 ng/mL normal vs. 8.0 ± 1.0 ng/mL pathological). Patients with pathological perfusion that later developed preeclampsia or IUGR (9/25) showed unchanged MPO and PMN elastase values in the second trimenon compared to those with pathological perfusion and normal outcome. Conclusions: Pathological uterine perfusion in the second trimester was not associated with maternal neutrophil activation. The measurement of the MPO and PMN elastase concentration suggested that neutrophil activation in preeclampsia or IUGR is a secondary effect of the disease rather than a primary pathophysiological factor.

Plasma concentration of myeloperoxidase enzyme in pre- and post-climacterial people: related superoxide anion generation

Neutrophil granulocytes are involved in the pathogenesis of atherosclerosis also through their free radical generation. The aim of the study was to test how extracellular levels of myeloperoxidase (MPO; a granulocyte enzyme playing role in free radical production) change by age and what effect this change has on the production of the free radical superoxide anion by neutrophils. We also wanted to examine whether the antioxidant effect of different steroid hormones is realized through the MPO. Plasma myeloperoxidase concentrations of healthy blood donors were quantified by ELISA. Superoxide anion production was measured by photometry. Myeloperoxidase concentration was significantly lower in plasmas obtained from older women and men than in those from younger subjects. Adding the MPO inhibitors 4-aminobenzoic acid hydrazide (ABAH) and indomethacin to the granulocytes, the generation of superoxide anion increased and the decreasing effect of the steroids on superoxide production was inhibited. Incubating the neutrophils with the product of the reaction catalyzed by MPO itself (hypochlorite anion), we found significant decrease in superoxide generation. According to our results MPO seems to diminish the production of superoxide anion and so probably has an antioxidant ability. Therefore, its lower plasma levels may contribute to the increasing incidence of atherosclerosis and other free radical mediated disorders in old people. Thus, after further studies MPO might become one of the indicators of cardiovascular risk and the scavenger capacity in general.

Reduction of Neutrophil Activation by Vitamin E Modified Dialyzer Membranes

Background/Aim: Transient leukopenia during hemodialysis due to neutrophil activation is attributed to bioincompatibility of the dailysis membrane, but the mechanism remains unclear. We studied the mechanism of neutrophilic activation by comparing a vitamin E modified membrane (CLEE) and a regular cellulose membrane (CLSS). Methods: (1) CLSS and CLEE membranes were used in a crossover clinical study in 7 chronic hemodialysis patients. Neutropenia, CD11b expression, and plasma C3a and myeloperoxidase concentrations were compared between the two dialyzer membranes. (2) Normal blood was circulated through CLEE and CLSS minimodels, and the same parameters were compared. (3) Blood samples with modified complement activities (EDTA: both classical and alternative pathways inactivated; EGTA+Mg: classical pathway inactivated; heating: alternative pathway inactivated; control: no modification) were incubated in the CLSS minimodel, and the neutrophilic activation was compared. Results: In clinical hemodialysis, neutropenia, CD11b expression, and C3a and myeloperoxidase levels were significantly lower when CLEE membranes were used. The same tendency was observed in minimodels. However, the degrees of inhibition in clinical dialysis, especially at the venous line, were significantly higher than in minimodels. As compared with controls, CD11b expression and myeloperoxidase level were significantly lower when both classical and alternative pathways were inactivated or when the classical pathway alone was inactivated, but were not significantly different when the alternative pathway alone was inactivated. Conclusions: Vitamin E modification of the dialyzer reduces some reactions of neutrophilic activation, such as CD11b expression and myeloperoxidase release, more effectively in the clinical situation than in ex vivo models, suggesting a possible effect of vitamin E in inhibiting bioreactions due to pyrogen in the dialysate. The classical complement pathway is required in membrane-induced neutrophilic activation, at least during the initial stage.

Clinical Correlates in Acute Lung Injury: Response to Inhaled Nitric Oxide

The use of inhaled nitric oxide (NO) in the management of patients with ARDS has become widespread, although not all patients respond to this form of support. The aim of this study was to examine the relationship of responsiveness to inhaled NO and features of underlying disease. Prospective observational study. The ICU of a university-affiliated, tertiary referral hospital. Twenty-six adult patients with established ARDS. Conventional support for multiple organ failure, plus inhaled NO. Response to inhaled NO was assessed, and ARDS was characterized in terms of pulmonary morphology (scoring of high-resolution CT); inflammation (BAL neutrophil count and plasma myeloperoxidase concentration); and markers of lung injury severity (oxygenation deficit and pulmonary vascular resistance [PVR]). Fourteen patients responded to NO and 12 did not. There were no differences between the two groups in terms of CT score, inflammatory status, baseline oxygenation deficit, lung injury score, or PVR. Additionally, there was no difference in survival between responders and nonresponders. Patients who developed ARDS after thoracic surgery were significantly more likely to die than other patients (relative risk 4.1, p < 0.01). The oxygenation deficit and lung injury score correlated better with the extent of ground-glass opacification than with the volume of consolidated lung tissue. We were unable to identify features of disease likely to be associated with a clinically useful response to inhaled NO therapy using the parameters studied.

Effect of Prolonged Exercise on Neutrophil Myeloperoxidase Secretion

This study was designed to compare the effects of three prolonged exercises on plasma myeloperoxidase concentrations, used as marker of neutrophil degranulation. Seven healthy subjects underwent three effort trials (45% VO2max during 4 h, 60% VO2max during 3 h, 75% VO2max during 2 h) at one-month intervals. Blood samples were collected before, during and after exercise. Myeloperoxidase levels were measured by radioimmunoassay. We observed a significant increase in myeloperoxidase concentration (+85%) at the end of our three prolonged exercises (p < 0.05). This myeloperoxidase increase was not correlated with the modification of neutrophil count, suggesting that neutrophil degranulation is independent of their mobilisation.

Effects of methylprednisolone on exercise‐induced increases of plasma levels of polymorphonuclear elastase and myeloperoxidase in man. Preliminary results

The aim of the present study was to verify whether a single oral dose of methylprednisolone could modulate the exercise-induced release of polymorphonuclear neutrophil (PMN) elastase and myeloperoxidase. Four healthy, male subjects were submitted to a 20 min downhill run (−20%) at 60% VO2 max, 3 h after oral absorption of a placebo or a single dose of 32 mg methylprednisolone. A marked neutrophilia (+103% of basal PMN count; p < 0.02) was observed 3 h after methylprednisolone ingestion. During both exercise trials, placebo and methylprednisolone, PMN counts were increased by 46% and 19% (p < 0.05), respectively. The running test caused marked and significant (p < 0.05) increases in plasma myeloperoxidase concentration (MPO). The magnitude of MPO changes was the same in the two trials (+110%). Exercise also resulted in significant changes in plasma elastase concentration (EL) in both experimental conditions (placebo: +104%, p < 0.05; methylprednisolone: +338%, p < 0.005). Plasma elastase levels reached at the end of exercise on methylprednisolone were significantly higher than after placebo (p < 0.05). A significant relationship was found between EL and PMN in methylprednisolone trial only (r = 0.72; l0 < 0.005). These results showed that the transient exercise-induced release of elastase and myeloperoxidase were not decreased by methylprednisolone.

Exercise induces pentane production and neutrophil activation in humans. Effect of propranolol

The effect of beta-adrenergic receptor blockade on exercise-induced lipid peroxidation in man has been examined by measuring the production of pentane in expired air. For this purpose, five healthy male subjects were subjected to dynamic exercise of graded intensity on a cycle ergometer (10 min at 45%, 5 min at 60% and 75% maximal oxygen uptake 1 h after ingestion of either a placebo or 40-mg propranolol. At rest, mean pentane concentration [( pent]) with placebo was 4.13 pmol.l-1, SD 2.14. After exercise, this value significantly increased by 310% (17.1 pmol.l-1, SD 7.73, P less than 0.01). Oral administration of 40-mg propranolol significantly lowered the mean resting [pent] to 1.75 pmol.l-1, SD 0.77, P less than 0.05. After exercise, the increase of [pent] was much smaller (240%) and was less significant (P less than 0.2) than with the placebo. The mechanism of this inhibitory effect of propranolol remains to be elucidated. However, as indicated by the measurement of plasma myeloperoxidase concentration, it can be concluded that the antioxidant property of propranolol cannot be attributed to the inhibition of neutrophil activation, a possible source of free radicals during exercise.

Plasma Myeloperoxidase and Lactoferrin Measured by Radioimmunoassay: Relations to Neutrophil Kinetics

In 31 patients, covering a wide range of blood neutrophil counts and turnover rates, the plasma concentrations of myeloperoxidase and lactoferrin have been measured with radioimmunoassays and compared to neutrophil kinetic parameters, measured with DF32P-labeled neutrophils. It was found that the plasma concentrations of both proteins correlated significantly with the total number of neutrophils in the blood (TBGP=total blood granulocyte pool) as well as with the neutrophil turnover rate (GTR=granulocyte turnover rate), which is evidence that neutrophilic granulocytes are the main suppliers of myeloperoxidase and lactoferrin to the plasma. In contrast to the previously demonstrated better relationship between the GTR and plasma lysozyme, a protein also originating in neutrophil granules, both myeloperoxidase and lactoferrin correlated better with the TBGP. These differences may reflect differences in the mode of release of intragranular proteins from neutrophils to the plasma. The correlation of the plasma lactoferrin concentration with the TBGP was so good as to suggest its use in the clinical assessment of the TBGP.