Reduced oxidative activity of circulating neutrophils in patients after myocardial infarction

Antioxidant effect of the active metabolites of tibolone

Certain steroidal compounds have an antioxidant effect in humans. Our aim was to test whether the synthetic steroid tibolone and its metabolites are also able to display such a property. For this, granulocytes from healthy men and women were incubated for two hours with different concentrations (10(-7), 10(-8), 10(-9 )M) of either estradiol, tibolone, 3α-hydroxytibolone, 3β-hydroxytibolone, Δ(4)-tibolone, 3α-sulfated-tibolone, 3α-17β-disulfated-tibolone, 3β-sulfated-tibolone or 3β-17β-disulfated-tibolone. Superoxide anion generation of neutrophils was measured by photometry. Results of different steroids were given as percentages of their controls. A more simple superoxide generating system, the xanthine-xanthine oxidase reaction was also tested. We found that granulocyte superoxide production did not differ from the control using 10(-9 )M of steroids. Using 10(-8 )M concentration: estradiol (80.9 ± 2.5%); 3β-sulfated-tibolone (83.3 ± 4.7%); 3β-17β-disulfated-tibolone (81.0 ± 4.2%) caused a significant decrease in superoxide production, compared to the control. In addition at 10(-7 )M, 3β-hydroxytibolone and 3α-sulfated-tibolone also showed antioxidant effects. In the xanthine-xanthine oxidase system estradiol (67.4 ± 1.0%), 3α-sulfated-tibolone (85.8 ± 5.3%), 3α-17β-disulfated-tibolone (71.9 ± 2.5%), 3β-sulfated-tibolone (73.9 ± 5.0%), and 3β-17β-disulfated-tibolone (65.8 ± 3.4%) caused a significant decrease in superoxide production. Conclusively, although tibolone itself did not show significant antioxidant capacity, most of its active metabolites have antioxidant effects.

The effect of estrogens on superoxide anion generation by human neutrophil granulocytes: possible consequences of the antioxidant defense

The present study aimed to test whether, beyond the known antioxidant effect of estradiol, such a property is also possessed by estrone and estriol. For this purpose, an in vitro investigation of the effect of estrone and estriol on superoxide anion production by human neutrophil granulocytes was carried out. Blood samples were obtained from healthy volunteers and neutrophil granulocytes were separated for measurement of superoxide anion generation after incubation with estrone, estriol (10(-7), 10(-6) and 10(-5) M) and 17beta-estradiol (10(-7) M). Superoxide anion production of isolated neutrophil granulocytes was quantified by photometry and using the reduction of ferricytochrome-C. When adding estrone and estriol to neutrophil granulocyte suspensions, the production of superoxide anion fell (10(-5) M: 84.17 +/- 3.14% and 88.77 +/- 1.98% of control production, p < 0.01 and p < 0.05, respectively). Estradiol produced an antioxidant effect at lower concentration (10(-7) M: 72.91 +/- 7.94% of control production, p < 0.001). The weak estrogens estrone and estriol, similarly to estradiol, are also able to reduce the superoxide anion release in our experimental model. This may have importance in the antioxidant defense of biological systems.

Activated PMNs lead to oxidative stress on chondrocytes: a study of swine knees

Using an in vitro model, based on primary cultured chondrocytes, we examined possible oxidative injury caused by activated polymorphonuclear neutrophil granulocytes (PMNs), which are thought to be part of the pathomechanism of hemarthrosis. Chondrocytes were isolated from swine knee joints and divided into three groups. Pure chondrocytes acted as the control population (group I). PMNs from the systemic circulation, and hydrogen peroxide (as an artificial source of reactive oxygen species (ROS)) were added to groups II and III, respectively. All cultures were incubated for 6 hours. After the experiment, lipid membrane degradation by ROS was assessed by monitoring changes in the levels of malondialdehyde (MDA) and 4-hydroxyalkenal contents of the chondrocyte specimens. Changes in the endogenous scavenger status of the chondrocytes were characterized by measuring of reductions in glutathione (GSH) concentration and superoxide dismutase (SOD) activity. Significant increases in MDA/4-hydroxyalkenal levels and SOD activity as well as an expressive reduction in intracellular GSH content were highlighted by comparing the control to the PMN- or H2O2-treated cell populations. These findings confirm previous suggestions that PMN-derived ROS contribute to degradation of cartilage in hemarthrosis.

Induced myeloperoxidase activity and related superoxide inhibition during hormone replacement therapy

OBJECTIVE

To test whether the menopause entails any changes in the myeloperoxidase activity of neutrophil granulocytes. The effects of hormone replacement therapy on myeloperoxidase activity and related changes in free radical production were also investigated.

DESIGN

Laboratory investigation of the effect of oestrogen on intracellular myeloperoxidase activity and release from human neutrophil granulocytes. Analysis of related changes in superoxide anion generation.

SETTING

2nd Department of Medicine and 1st Department of Obstetrics and Gynaecology, Semmelweis University, Budapest.

SAMPLES

Intracellular myeloperoxidase activity (mean peroxidase index) was measured automatically in blood samples obtained for general laboratory work-up from 135 randomly selected patients in our department. Blood samples from 11 postmenopausal women were analysed before and during hormone replacement therapy. Blood samples from 20 healthy volunteers were obtained and neutrophil granulocytes separated for in vitro measurement of superoxide anion production after adding myeloperoxidase to the incubation media.

METHODS

The mean peroxidase index was measured using a Technicon H-3 instrument. myeloperoxidase release from neutrophils was quantified by ELISA technique. Superoxide production of isolated neutrophil granulocytes was measured by photometry.

MAIN OUTCOME MEASURES

Intracellular activity of myeloperoxidase, concentration of myeloperoxidase-protein in supernatant of neutrophils, release of superoxide anion from neutrophil granulocytes.

RESULTS

1. Intracellular myeloperoxidase activity in neutrophils was lower in postmenopausal women, than in females with regular cycles (-1.84 +/- 3.06 versus 1.59 +/- 3.55, P < 0,001). 2. In postmenopausal women intracellular myeloperoxidase activity and myeloperoxidase release increased during hormone replacement therapy (-5.54 +/- 6.63 versus -0.2 +/- 6.05; P < 0.001 and 52.74 mU/ml +/- 25.73 versus 251.4 +/-234.1 mU/ml; P < 0.05). 3. Adding myeloperoxidase to neutrophil granulocyte suspensions, the production of superoxide anion fell (e.g. adding 280 ng/ml myeloperoxidase: 77.9 +/- 14.04 % of control production, P < 0.001).

CONCLUSION

Hormone replacement restores the reduced myeloperoxidase activity in menopausal women. Adding myeloperoxidase to neutrophil granulocytes, the production of free radicals decreases.

In vitro effects of different steroid hormones on superoxide anion production of human neutrophil granulocytes

Neutrophil granulocytes play an important role in atherogenesis also through their free radical generation. According to recent studies, a point of action by which estrogens can provide protection against atherosclerosis is their inhibiting effect on superoxide anion production. The aim of our study was to test whether this means a common effect of steroids on superoxide production, or whether various steroid hormones have different action on superoxide generation of human granulocytes. Neutrophils were separated from the blood samples of twelve healthy volunteers. Isolated cells were incubated with different concentrations (10(-9), 10(-8), 10(-7) M) of hydrocortisone, aldosterone, cortexolone, 17-beta-estradiol, progesterone, and testosterone. Superoxide anion production was determined by photometry using the reduction of ferricytochrome-C. Compared to that of control cells neutrophils incubated with 17-beta-estradiol, progesterone, testosterone and hydrocortisone showed significantly reduced superoxide production. No significant alteration of superoxide anion production was found after the incubation of cells with aldosterone and cortexolone. It is concluded that similarly to estradiol other sex steroids and cortisol can inhibit the free radical production of human granulocytes, but mineralocorticoid aldosterone and Reichstein's substance S do not show such activity. Our results provide new evidence supporting the theory that certain types of steroid hormones have antioxidant capacity. This may give further reasons for investigating the molecular background of the existence or absence of this property and thus might lead to the development of new free radical scavengers.

Endothelin-A receptor antagonism improves small bowel graft perfusion and structure after ischemia and reperfusion

BACKGROUND

We hypothesized that endothelin-A (ET-A) receptor activation plays a central role in intestinal ischemia-reperfusion-induced hemodynamic changes and may trigger the process of mucosal barrier destruction. Our aims were to investigate and compare the effects of systemic and intragraft ET-A receptor antagonist therapy during the early revascularization phase of small bowel transplants.

METHODS

In Groups 1, 2, and 3 orthotopic small bowel autotransplants were performed in anesthetized dogs. Group 4 served as sham-operated control. Group 2 was treated i.v. with the ET-A receptor antagonist ETR-p1/fl peptide at the onset of reperfusion. In Group 3, intragraft infusion of the ETR-p1/fl peptide was applied during cold ischemia. The mucosal myeloperoxidase activity and the free radical-producing capacity of the granulocytes passing the intestinal graft were determined, and the systemic hemodynamic features were recorded. The extent of the mucosal injury was determined from tissue biopsies taken after 4 hr of reperfusion.

RESULTS

Reperfusion progressively decreased the mesenteric blood flow, increased the mesenteric vascular resistance, and enhanced the accumulation and free radical production capacity of the leukocytes. These changes were significantly inhibited in Group 2 with systemic (i.v.) administration of the ET-A receptor antagonist. The local, intragraft treatment improved the mesenteric hemodynamic changes and decreased the accumulation but not the activation of the circulating leukocytes. The structural injury of the graft was prevented in both treated groups.

CONCLUSIONS

Endothelins are involved in the hemodynamic events leading to structural injury of the intestinal graft after ischemia-reperfusion. The antagonism of intestinal ET-A receptors by a combination of local and systemic drug delivery offers a rational treatment modality in these conditions.

Bisaramil and antiarrhythmics as inhibitors of free radical generation

The aim of this study was to investigate the effect of bisaramil--an antiarrhythmic drug under clinical trials-on free radical generation of isolated polymorph neutrophil granulocytes (PMN) and furthermore to compare its activity to that of well-known antiarrhythmics which have different modes of action. PMNs were isolated from healthy beagle dogs, and superoxide radical generation was induced by phorbol-myristate-acetate. Stimulated free radical generation capacity of PMNs and the time lag necessary for the initiation of free radical production were measured. All compounds were used at the concentrations of 10, 25, 50, 75, 100 micrograms ml-1. None of the antiarrhythmics stimulated by itself the free radical generation. Bisaramil exerted concentration dependent inhibitory effect on PMA-stimulated free radical generation and prolonged the time lag concentration dependently. At the investigated concentration range of antiarrhythmics only propafenon, mexiletine and diltiazem showed similar activity to bisaramil, but clear concentration dependency could not be seen in any of the cases. According to the results of this study inhibition of the stimulated free radical production of isolated PMNs cannot be closely connected merely to either membrane stabilizing or Ca-antagonistic activity of drugs. In vitro and earlier measured in vivo inhibitory action of bisaramil on free radical generation indicate a possible cardioprotective effect existing independently from its antiarrhythmic one. This observation may be important in outlining of the clinical indication field of bisaramil, and may be useful in the treatment of reperfusional damage.

Flow resistance of individual neutrophils in coronary artery disease: decreased pore transit times in acute myocardial infarction

OBJECTIVE

To investigate single neutrophil flow resistance in coronary artery disease, including myocardial infarction before initiation of reperfusion therapy.

DESIGN

Neutrophil flow resistance was measured in 93 subjects in five groups: (group 1) 28 patients within 12 hours after the onset of myocardial infarction, before reperfusion therapy; (group 2) 18 with unstable angina; (group 3) 13 with stable angina; (group 4) 13 age matched patients without coronary disease, and (group 5) 21 healthy volunteers. MAIN PARAMETERS: Single neutrophil transit times through 8 microns oligopore filters determined with a modified cell transit analyser.

RESULTS

Leucocyte count (10(9)/l) was increased in coronary disease, especially in myocardial infarction and unstable angina (mean and 95% confidence intervals for groups 1 to 5: 12.6 (11.0 to 14.2), 11.3 (8.5 to 14.1), 8.5 (7.4 to 9.6), 8.0 (6.0 to 10.0), 7.0 (6.1 to 7.9)). Polymorphonuclear granulocyte (PMN) flow resistance correlated negatively with white blood cell (WBC) count and was significantly decreased in coronary artery disease (CAD), especially in myocardial infarction; mean transit times (ms) for groups 1 to 5 were: 13.6 (11.8 to 15.4), 16.9 (13.9 to 19.0), 16.9 (12.8 to 21.0), 22.0 (19.6 to 24.4), and 18.6 (15.7 to 21.5).

CONCLUSION

Neutrophil flow resistance was decreased in CAD, especially in myocardial infarction before reperfusion therapy. In contrast to previous findings in reperfused myocardial infarction, the present study showed that stiffened PMNs were not yet present in the circulating blood pool. Thus a pharmacological approach aimed at suppressing leucocyte activation before or during reperfusion therapy may be feasible.

Alpha-tocopherol pretreatment improves endothelium-dependent vasodilation in aortic strips of young and aging rats exposed to oxidative stress

Acetylcholine-induced, endothelium-dependent relaxation of norepinephrine-precontracted aortic strips, was severely impaired after exposure to a hypoxanthine/xanthine oxidase reaction generating oxygen radicals. This effect was more evident in aortic strips of aging rats (24 months old) in comparison to young rats (3 months old). The addition of authentic .NO (1 microM) completely relaxed aortic strips exposed to oxidative stress both in young and aging rats. In vitro EPR measurements showed that the .NO signal was reduced by enzymatic O2.- generating reaction. The activity of a partial purified preparation of constitutive NO synthase from rat cerebellum was significantly decreased after exposure to exogenous oxygen radicals. Pretreatment of aortic strips with 100 microM alpha-tocopherol-phosphate, produced a significant improvement of acetylcholine-dependent relaxation in the aortic strips exposed to oxidative stress, particularly in the aged vessel. The content of malondialdehyde in aortic tissue did not change after oxidative stress or alpha-tocopherol pretreatment. Alpha-tocopherol was unable to recover the NO synthase activity depressed in vitro by hypoxanthine/xanthine oxidase reaction. This study confirms that an oxidative stress impairs the endothelium-mediated vasodilation. Alpha-tocopherol pretreatment protects the vessel against this damage. The mechanism of action of alpha-tocopherol is unknown, but seems unrelated to an antioxidant activity.

Treatment of acute myocardial infarction with streptokinase does not appear to modulate circulating neutrophil function

The administration of thrombolytic therapy is the most common method of achieving patency of the occluded coronary artery in patients with acute myocardial infarction (AMI). However, thrombolytic agents and the byproducts of fibrinolysis have the potential to affect neutrophil activation and thus function, thereby augmenting myocardial damage further. This study assessed the effect of streptokinase administration on the function of circulating neutrophils in patients with AMI. For this neutrophil adherence to human umbilical vein endothelial cells, homotypic neutrophil aggregation, and CD11b and L-selectin expression on the neutrophil membrane prior to and 1 h and 6 h after thrombolytic therapy was monitored. The study population included patients with AMI who received aspirin and streptokinase, and healthy laboratory workers who received aspirin only; all subjects acted as their own controls. Circulating fibrin degradation products and white cells were markedly raised following administration of streptokinase. No significant differences in neutrophil adherence to endothelium, homotypic neutrophil interactions, and CD11b or L-selectin expression were demonstrated between neutrophils, either pre- or post-thrombolytic therapy in the infarct group, or between neutrophils from the infarct group and from the control group. It was concluded that streptokinase produces an abrupt neutrophil leukocytosis together with a marked increase in circulating levels of fibrin degradation products. The assay systems used were unable to show significant sequential changes in circulating neutrophil adhesion and L-selectin or CD11b expression in patients with AMI following thrombolytic therapy or when these patients were compared with controls.

Spontaneous superoxide generation by polymorphonuclear leukocytes isolated from patients with stable angina after physical exercise

The activation of circulating polymorphonuclear leukocytes was determined in terms of O2.- generation and elastase release in patients with stable angina (n = 12) and in control subjects (n = 8) after maximal physical exercise and after a 15-min recovery. There was no spontaneous O2.- formation under basal conditions in both groups of patients. On the contrary, there was significant formation of O2.- (p < 0.001) from patients with stable angina measured directly after exercise, along with a slight spontaneous O2.- formation in control subjects (p < 0.05). After recovery, the spontaneous polymorphonuclear leukocyte-O2.- formation decreased but was still present in the patients with stable angina, while in the healthy subjects these values returned to resting levels. The activation of polymorphonuclear leukocytes with phorbol 12-myristate 13-acetate enhanced O2.- formation both in healthy subjects and in patients with stable angina, with a lesser effect in the latter. Moreover, no differences were observed in polymorphonuclear leukocyte-stimulated O2.- formation during the protocol, both in the angina stable patients and healthy subjects. No changes were found in plasma elastase levels among stable angina patients nor in control subjects as a consequence of exercise or recovery. This study indicates there is an early activation of circulating polymorphonuclear leukocytes in terms of O2.- production in stable angina patients during maximal exercise, which is still present after a 15-min recovery. Such activation occurs without elastase release. However, in healthy subjects maximal exercise resulted in very little increase in neutrophil activation.