Leukocytes, oxygen radicals, and myocardial injury due to ischemia and reperfusion

Flavonoids in myocardial ischemia-reperfusion injury: Therapeutic effects and mechanisms

Ischemic heart diseases are one of the major causes of death worldwide. Effective restoration of blood flow can significantly improve patients’ quality of life and reduce mortality. However, reperfusion injury cannot be ignored. Flavonoids possess well-established antioxidant properties; They also have other benefits that may be relevant for ameliorating myocardial ischemia-reperfusion injury (MIRI). In this review, we focus on flavonoids with cardiovascular-protection function and emphasize their pharmacological effects. The main mechanisms of flavonoid pharmacological activities against MIRI involve the following aspects: a) antioxidant, b) anti-inflammatory, c) anti-platelet aggregation, d) anti-apoptosis, and e) myocardial-function regulation activities. We also summarized the effectiveness of flavonoids for MIRI.

Clastogenic Factors as Potential Biomarkers of Increased Superoxide Production

The formation of clastogenic factors (CF) and their damaging effects are mediated by superoxide, since superoxide dismutase is regularly protective. CF are produced via superoxide and stimulate the production of superoxide by monocytes and neutrophils. This results in a selfsustaining and longlasting process of clastogenesis, which may exceed the DNA repair system and ultimately lead to cancer (Emerit, 1994). An increased cancer risk is indeed observed in conditions accompanied by CF formation. These include irradiated persons, patients with chronic inflammatory diseases, HIV-infected persons and the chromosomal breakage syndromes ataxia telangiectasia, Bloom's syndrome and Fanconi's anemia. Biochemical analysis has identified lipid peroxidation products, arachidonic acid metabolites, nucleotides of inosine and cytokines, in particular tumor necrosis factor alpha, as the clastogenic and also superoxide stimulating components of CF. Due to their chromosome damaging effects, these oxidants can be detected with classical cytogenetic techniques. Their synergistic action renders the CF-test particularly sensitive for the detection of a pro-oxidant state. Correlations were observed between CF and other biomarkers of oxidative stress such as decreases in total plasma thiols or increases in TBARS or chemiluminescence. Correlations between CF and disease activity, between CF and radiation exposure, suggest the study of CF for monitoring these conditions. CF may also be useful as biochemical markers and intermediate endpoints for the evaluation of promising antioxidant drugs.

CF formation represents a link between chronic inflammation and carcinogenesis. Prophylactic use of superoxide scavengers as anticarcinogens is therefore suggested.

Myocardial ischaemia-reperfusion injury in haematopoietic cell-restricted beta1 integrin knockout mice

Evidence indicates that the intercellular adhesion molecule-1 and its counter-receptor beta2 integrin are cardioprotective proteins during myocardial ischaemia-reperfusion, but no data are available concerning the role of blood cell beta1 integrins in this process. We studied the effects of temporary myocardial ischaemia and reperfusion in blood cell-restricted beta1 integrin knockout mice (beta1(-/-)). The left descending coronary artery in conditional beta1(-/-) integrin (beta1(-/-)), beta1 integrin +/+ (beta1(+/+)) and beta1 integrin -/- bone marrow chimeric (beta1(-/-) BM) mice was ligated for 30 min, followed by reperfusion of either 3 h or 3 weeks. Plasma levels of troponin T were evaluated as an index of cardiac cellular damage. The histological evaluation of tissue damage was performed with Haematoxylin and Eosin stained sections. Cell infiltrations in the ischaemic area were investigated by immunofluorescence studies. It was found that plasma troponin T was at a similar level in beta1(-/-), beta1(+/+) and beta1(-/-) BM mice treated with 30 min ischaemia and 3 h reperfusion. Histological analysis showed that ischaemia-reperfusion resulted in marked myocardial injury in all groups of animals, but the damage score of the hearts was not significantly different between beta1(-/-), beta1(+/+) and beta1(-/-) BM mice after 3 h of reperfusion following 30 min of ischaemia (2.8 +/- 0.5, 2.6 +/- 0.5 and 2.8 +/- 0.6, respectively, n.s.). Furthermore, no difference in scar sizes in ischaemia-injured hearts was found 3 weeks after ischaemia. Semi-quantification of cells demonstrated that, compared with beta1(+/+) mice, the number of infiltrating neutrophils was significantly reduced in beta1(-/-) and beta1(-/-) BM mice, whereas MAC-1(CD11b/CD18)-positive cells in the ischaemic regions were similar in myocardial tissues of all groups. We conclude that absence of beta1 integrin expression in haematopoietic cells results in reduced neutrophil infiltration in the ischaemic regions, but does not influence myocardial damage of ischaemic hearts.

Involvement of intracellular free Ca2+ in enhanced release of herpes simplex virus by hydrogen peroxide

Background

It was reported that elevation of the intracellular concentration of free Ca²⁺ ([Ca²⁺]i) by a calcium ionophore increased the release of herpes simplex virus type 1 (HSV-1). Freely diffusible hydrogen peroxide (H₂O₂) is implied to alter Ca²⁺ homeostasis, which further enhances abnormal cellular activity, causing changes in signal transduction, and cellular dysfunction. Whether H₂O₂ could affect [Ca²⁺]i in HSV-1-infected cells had not been investigated.

Results

H₂O₂ treatment increased the amount of cell-free virus and decreased the proportion of viable cells. After the treatment, an elevation in [Ca²⁺]i was observed and the increase in [Ca²⁺]i was suppressed when intracellular and cytosolic Ca²⁺ were buffered by Ca²⁺ chelators. In the presence of Ca²⁺ chelators, H₂O₂-mediated increases of cell-free virus and cell death were also diminished. Electron microscopic analysis revealed enlarged cell junctions and a focal disintegration of the plasma membrane in H₂O₂-treated cells.

Conclusion

These results indicate that H₂O₂ can elevate [Ca²⁺]i and induces non-apoptotic cell death with membrane lesions, which is responsible for the increased release of HSV-1 from epithelial cells.

MCI-186 (3-Methyl-1-phenyl-2-pyrazolin-5-one) Attenuated Simulated Ischemia/Reperfusion Injury in Cultured Rat Hippocampal Cells

The reactive oxygen species and Ca2+ overload play a critical role in ischemia/reperfusion (I/R) injury. MCI-186 has potent effects in the brain as a free radical scavenger in ischemia-reperfusion. Acute glucose-oxygen deprivation and subsequent reoxygenation were used to model ischemia/reperfusion injury in cultured hippocampal cells. MCI-186 reduced malondialdehyde level and raised the SOD activity when applied upon reoxygenation in a dose-dependent manner compared with the untreated group. The peak neuroprotective effects occurred at 100 and 300 microM. Intracellular free calcium concentration ([Ca2+]i) was significantly reduced in the 100 microM MCI-186-treated group compared to the untreated group (32.5+/-4.0 versus 50.2+/-3.6, p<0.01). Treatment with 100 microM MCI-186 significantly inhibited the decrease of mitochondria membrane potential after simulated ischemia/reperfusion (204+/-11.6% compared with the untreated group, p<0.01). Cell apoptotic rate was significantly decreased following MCI-186 treatment from 33.7+/-2.3% (untreated group) to 16.6+/-1.4% (100 microM MCI-186 treated group). There was no significantly protective difference between 100 and 300 microM MCI-186. MCI-186 effectively protects neuron injury after simulated ischemia/reperfusion by inhibiting lipid peroxidation, reducing Ca2+ overload, elevating mitochondria membrane potential, and decreasing apoptosis.

Edaravone Prevented Deteriorated Cardiac Function After Myocardial Ischemia-Reperfusion via Inhibiting Lipid Peroxidation in Rat

Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) has potent effects in the brain as a free radical scavenger in ischemia-reperfusion as well as in ischemic injuries. However, whether this free radical scavenger prevents deterioration of cardiac function and lethal ventricular arrhythmias after ischemia-reperfusion in rat heart is not clear. We aimed to assess whether free radical scavenging by edaravone maintains cardiac function and suppresses life-threatening ventricular tachyarrhythmia after myocardial ischemia-reperfusion. Twenty-nine 7-week-old male Sprague-Dawley rats had acute myocardial ischemia induced by ligation of the left coronary artery for 5 minutes followed by reperfusion. Eleven were treated by intravenous injection of edaravone at 3 mg/kg 2 minutes after coronary ligation, and 18 were left untreated. The index of systolic function (contractility; end-systolic elastance, Ees) and hemodynamics were measured by pressure-volume relationships every 5 minutes before ligation to 25 minutes after reperfusion. Blood levels of malondialdehyde (MDA) and the ischemic areas were also measured 25 minutes after reperfusion. There were no differences in the ischemic areas between the groups. Lethal reperfusion tachyarrhythmia was observed in 5 untreated rats but not in those having edaravone treatment. Ees was significantly greater in the edaravone-treated than in untreated rats from 5 to 25 minutes after reperfusion (1789 +/- 866 in untreated versus 2809 +/- 273 mm Hg/mL in edaravone-treated rats at 25 minutes, P < 0.001). MDA level was significantly lower in edaravone-treated than in untreated rats (1.44 +/- 0.29 nmol/L in edaravone-treated versus 1.90 +/- 0.28 nmol/L in untreated group, P < 0.05). The results suggest that edaravone treatment before reperfusion prevented lethal reperfusion ventricular tachyarrhythmias and deteriorated cardiac function with ischemia and ischemia-reperfusion injuries through inhibiting lipid peroxidation in terms of scavenging for free radicals.

Relation of nonperfused myocardial volume and surface area to left ventricular performance in coronary microembolization

BACKGROUND

After occlusion of an epicardial artery, left ventricular (LV) dysfunction is closely related to the volume of nonperfused myocardium (NPM). The impact of coronary microembolization (ME) on LV function, however, is larger relative to the total volume of NPM. We hypothesized that the total surface area (SA), rather than the total volume, of NPM is the major determinant of ME-induced LV dysfunction.

METHODS AND RESULTS

We injected microspheres of 10-, 30-, or 100-microm diameter at each of 3 doses selectively into the left anterior descending coronary artery of 48 anesthetized pigs. Electron beam computed tomography (CT) was used to measure regional myocardial perfusion and changes in LV wall thickening (DeltaWT) and stroke volume (DeltaSV) after ME. At postmortem, a transmural "biopsy" of 1 to 2 cm3 of embolized myocardium was imaged by micro-CT, resulting in 3D images that provided volumes and SAs of the individual nonperfused foci. Additionally, in 9 pigs, creatine phosphokinase (CK) activity in embolized myocardium was measured as an index of washout of substances from the NPM. After ME, DeltaWT, DeltaSV, and CK washout were correlated more closely with the total SA (r=0.95, P<0.001; r=0.68, P<0.01; and r=0.88, P=0.01, respectively) than with the total NPM volume (r=0.59, P>0.05; 0.46, P>0.05; and r=0.69, P=0.04, respectively).

CONCLUSIONS

After coronary ME, LV dysfunction is more closely related to the total SA than to the total volume of nonperfused microregions in the myocardium.

Nitric oxide-dependent generation of reactive species in sickle cell disease. Actin tyrosine induces defective cytoskeletal polymerization

The intermittent vascular occlusion occurring in sickle cell disease (SCD) leads to ischemia-reperfusion injury and activation of inflammatory processes including enhanced production of reactive oxygen species and increased expression of inducible nitric-oxide synthase (NOS2). Appreciating that impaired nitric oxide-dependent vascular function and the concomitant formation of oxidizing and nitrating species occur in concert with increased rates of tissue reactive oxygen species production, liver and kidney NOS2 expression, tissue 3-nitrotyrosine (NO(2)Tyr) formation and apoptosis were evaluated in human SCD tissues and a murine model of SCD. Liver and kidney NOS2 expression and NO(2)Tyr immunoreactivity were significantly increased in SCD mice and humans, but not in nondiseased tissues. TdT-mediated nick end-label (TUNEL) staining showed apoptotic cells in regions expressing elevated levels of NOS2 and NO(2)Tyr in all SCD tissues. Gas chromatography mass spectrometry analysis revealed increased plasma protein NO(2)Tyr content and increased levels of hepatic and renal protein NO(2)Tyr derivatives in SCD (21.4 +/- 2.6 and 37.5 +/- 7.8 ng/mg) versus wild type mice (8.2 +/- 2.2 and 10 +/- 1.2 ng/mg), respectively. Western blot analysis and immunoprecipitation of SCD mouse liver and kidney proteins revealed one principal NO(2)Tyr-containing protein of 42 kDa, compared with controls. Enzymatic in-gel digestion and MALDI-TOF mass spectrometry identified this nitrated protein as actin. Electrospray ionization and fragment analysis by tandem mass spectrometry revealed that 3 of 15 actin tyrosine residues are nitrated (Tyr(91), Tyr(198), and Tyr(240)) at positions that significantly modify actin assembly. Confocal microscopy of SCD human and mouse tissues revealed that nitration led to morphologically distinct disorganization of filamentous actin. In aggregate, we have observed that the hemoglobin point mutation of sickle cell disease that mediates hemoglobin polymerization defects is translated, via inflammatory oxidant reactions, into defective cytoskeletal polymerization.

Myocardial ischemia/reperfusion injury in NADPH oxidase-deficient mice

Previous studies have suggested that oxygen-derived free radicals are involved in the pathophysiology of myocardial ischemia/reperfusion (MI/R) injury. Specifically, neutrophils have been shown to mediate postischemic ventricular arrhythmias and myocardial necrosis. We hypothesized that MI/R injury would be reduced in the absence (-/-) of NADPH oxidase. Heterozygous control mice (n=23) and NADPH oxidase(-/-) mice (n=24) were subjected to 30 minutes of coronary artery occlusion and 24 hours of reperfusion. Myocardial area at risk per left ventricle was similar in heterozygous control hearts (55+/-3%) and NADPH oxidase(-/-) hearts (61+/-4%). Contrary to our hypothesis, the size of infarct area at risk was similar in the heterozygous control mice (42+/-4%) and NADPH oxidase(-/-) mice (34+/-5%) (P=not significant). In addition, echocardiographic examination of both groups revealed that left ventricle fractional shortening was similar in NADPH oxidase(-/-) mice (n=8; 27+/-2.5%) and heterozygous control mice (n=10; 23.3+/-3. 3%) after MI/R. Superoxide production, as detected by cytochrome c reduction, was significantly impaired (P<0.01) in NADPH oxidase(-/-) mice (n=6) compared with heterozygous mice (n=7) (0.04+/-0.03 versus 2.2+/-0.08 nmol O(2).min(-1).10(6) cells(-1)). Intravital microscopy of the inflamed mesenteric microcirculation demonstrated that leukocyte rolling and adhesion were unaffected by the absence of NADPH oxidase. Oyster glycogen-stimulated neutrophil transmigration into the peritoneum was also similar in both the heterozygous control mice and NADPH oxidase(-/-) mice (P:=not significant). These findings suggest that NADPH oxidase does not contribute to the development of myocardial injury and dysfunction after MI/R.

Protein carbonyl formation and tyrosine nitration as markers of oxidative damage during ischaemia-reperfusion injury to rat sciatic nerve

We have investigated the role of oxidative damage in peripheral nerve ischaemia-reperfusion injury using a rat sciatic nerve model. After 5 h ischaemia blood flow to the sciatic nerve was restarted and markers of oxidative damage measured after various times of reperfusion. As a marker of protein oxidative damage, protein carbonyl formation was measured using a sensitive enzyme-linked immunosorbent assay. Protein carbonyl content was unaffected by ischaemia alone, but increased by 55% after 12-18 h reperfusion, correlating with the onset of nerve pathology. Pretreatment with the xanthine oxidase inhibitor allopurinol prevented these abnormalities, suggesting that xanthine oxidase activity is proximal to oxidative damage during reperfusion injury. To determine whether formation of the potent oxidant peroxynitrite from nitric oxide and superoxide contributed to ischaemia-reperfusion injury, we measured the accumulation of 3-nitrotyrosine residues in proteins. Only one protein of 49,000 mol. wt contained significant amounts of 3-nitrotyrosine residues which was shown to be glial fibrillary acidic protein, an abundant cytoskeletal protein in Schwann cells. However glial fibrillary acidic protein contained 3-nitrotyrosine residues prior to ischaemia-reperfusion, and the amount of nitrated tyrosine residues in total glial fibrillary acidic protein did not increase significantly during reperfusion, therefore it was not possible to draw conclusions about the role of peroxynitrite in nerve reperfusion injury.

Reduction of myocardial infarct size with sCR1sLe(x), an alternatively glycosylated form of human soluble complement receptor type 1 (sCR1), possessing sialyl Lewis x

1 This study investigated the effects of soluble complement receptor type 1 (sCR1) or sCR1sLex, agents which function as a complement inhibitor or as a combined complement inhibitor and selectin adhesion molecule antagonist, respectively, on the infarct size and cardiac troponin T (cTnT) release caused by regional myocardial ischaemia and reperfusion in the rat. 2 Eighty-two, male Wistar rats were subjected to 30 min occlusion of the left anterior descending coronary artery (LAD) followed by 2 h of reperfusion. Haemodynamic parameters were continuously recorded and at the end of the experiments infarct size (with p-nitro-blue tetrazolium) and cTnT release were determined. 3 Infusion of sCR1 (1, 5 or 15 mg kg-1, each n=7) or sCR1sLe(x) (1, 5 or 15 mg kg-1, n=7, 13 or 13, respectively) 5 min prior to LAD-reperfusion caused a reduction in infarct size from 59+/-2% (PBS - control, n=12) to 46+/-6%, 25+/-9% and 37+/-6% or 42+/-6%, 35+/-6% and 35+/-4%, respectively. 4 Infusion of sCR1 (15 mg kg-1, n=5) or sCR1sLe(x) (15 mg kg-1, n=5) also reduces the myocardial TnT release from 80+/-20 ng ml-1 (control) to 13+/-7 or 4+/-1 ng ml-1, respectively. 5 Thus, sCR1 or sCRsLe(x) significantly reduce infarct size and cardiac TnT release caused by 30 min of regional myocardial ischaemia and 2 h of reperfusion in the rat. The mechanisms of the cardioprotective effects of sCR1 or sCR1sLe(x) are not entirely clear, but may be due complement inhibition and/or prevention of the adhesion and activation of neutrophils.

Loss of GSH and thiol enzymes in endothelial cells exposed to sublethal concentrations of hypochlorous acid

We investigated the effect of sublethal concentrations of hypochlorous acid (HOCl) on intracellular thiol groups. Exposure of human umbilical vein endothelial cells to HOCl caused a decrease in cell viability, with concentrations of </=25 microM HOCl being sublethal. At these concentrations, we saw a loss of glutathione and total protein thiol groups. Of the thiol enzymes we investigated, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was particularly susceptible to inactivation, creatine kinase was moderately susceptible, and lactate dehydrogenase was unaffected by HOCl at the concentrations used. Similar results were obtained with HOCl generated over 30 min by myeloperoxidase. GAPDH activity could be regenerated on reincubation of cells in Hanks' balanced salt solution or reduction with dithiothreitol. In contrast, glutathione loss was not reversible, and further decreased with time. Cellular ATP levels decreased with sublethal HOCl concentrations and this appeared to be unrelated to the inactivation of GAPDH. Our results demonstrate that intracellular thiol groups differ in their reactivity with HOCl and suggest that HOCl may be able to regulate specific cellular functions.

Poly(ADP-ribose) polymerase inhibition in oxidant-stressed endothelial cells prevents oncosis and permits caspase activation and apoptosis

Endothelial cells (EC) are subject to oxidative-induced cell death. Activation of poly(ADP-ribose) polymerase (PARP) occurs early in oxidant-induced EC injury and putatively mediates cell death by depleting its substrate, NAD(+). In this study, the role of PARP in H(2)O(2)-induced EC death was investigated. EC were exposed to oxidant stress and viability continuously monitored using fluorescent dye exclusion. Inhibition of PARP with 1, 5-dihydroxyisoquinoline (DIQ) delayed the time course of oxidant-induced EC death. Concurrent addition of the protein synthesis inhibitor, cycloheximide, or the endonuclease inhibitor, aurintricarboxylic acid, to PARP-inhibited cells further delayed the onset and attenuated the extent of H(2)O(2)-induced cell lysis, consistent with an active mode of cell death. Caspase-3-like activity, a hallmark of apoptosis, was negligible in oxidant-treated EC alone, however, inhibition of PARP by 3-aminobenzamide or DIQ dramatically increased caspase-3-like activity. Morphological assessment confirmed that the primary mode of death in oxidant-stressed EC was oncosis. However, following PARP inhibition, the cells switched to apoptosis. Since inflammation is associated with oncosis and not apoptosis, the results presented here could explain the beneficial effects seen with PARP inhibition in various in vivo models of oxidant injury and provide a mechanism to manipulate this injury into a state of cell death that could ultimately be controlled.

Potential roles of myoglobin autoxidation in myocardial ischemia-reperfusion injury

The source(s) of reactive partially reduced oxygen species associated with myocardial ischemia/reperfusion injury remain unclear and controversial. Myoglobin has not been viewed as a participant but is present in relatively high concentrations in heart muscle and, even under normal conditions, undergoes reactions that generate met (Fe3+) species and also superoxide, hydrogen peroxide, and other oxidants, albeit slowly. The degree to which the decrease in pH and the freeing of copper ions, as well as the variations in pO2 associated with ischemia and reperfusion increase the rates of such myoglobin reactions has been investigated. Solutions of extensively purified myoglobin from bovine heart in 50 mM sodium phosphate buffer were examined at 37 degrees C. Sufficiently marked rate increases were observed to indicate that reactions of myoglobin can indeed contribute substantially to the oxidant stress associated with ischemia/reperfusion injury in myocardial tissues. These findings provide additional targets for therapeutic interventions.

Diffusion, perfusion, and T2 magnetic resonance imaging of anti-intercellular adhesion molecule 1 antibody treatment of transient middle cerebral artery occlusion in rat

The effect of anti-intercellular adhesion molecule-1 (anti-ICAM-1) antibody treatment of transient (2 h) middle cerebral artery (MCA) occlusion in the rat was measured using diffusion (DWI)-, T2 (T2I)- and perfusion (PWI)-weighted magnetic resonance imaging. Rats were treated upon reperfusion with an anti-ICAM-1 monoclonal antibody (n=11) or a control antibody (n=7). DWI, T2I and PWI were performed before, during, and after induction of focal cerebral ischemia from 1 h to 7 days. In both groups, the apparent diffusion coefficient of water (ADCw) and cerebral blood flow (CBF) values in the ischemic region significantly declined from the preischemic ADCw values (p<0. 05). The post ischemic increase in T2 of the control group was significantly higher at 48 h than in the anti-ICAM-1 treated group (p<0.05). CBF was not significantly different between the two groups. The temporal profiles of MRI cluster analysis, which combines ADCw and T2 maps into a single image, was significantly different between groups. These data suggest that the neuroprotective effect of anti-ICAM-1 antibody treatment is reflected in reductions of T2 and lesion growth during reperfusion and may not be associated with increased cerebral perfusion.

Involvement of ecto-ATPase and extracellular ATP in polymorphonuclear granulocyte-endothelial interactions

The adhesion of human polymorphonuclear granulocytes (PMN) with confluent human endothelial cells (line EAhy926) and with solid substrate coated by collagen and fibronectin (Fn) was studied by phase contrast microscopy and by the measurement of myeloperoxidase activity. The ecto-ATPase inhibitors suramin and Reactive Blue 2 (RB2) more than doubled the adhesion of PMN to endothelial cells. The cells hydrolyzed added ATP and this reaction was inhibited by suramin and RB2. The degree of ATP hydrolysis during PMN adherence depended on solid substrata and decreased in the order: non-stimulated endothelial cells, TNF-stimulated endothelial cells, collagen-coated surface, Fn-coated surface. In the same order adherence increased. The endogenous level of extracellular ATP in the PMN-endothelial coculture was around 25 nM. We conclude that PMN-endothelial adhesion is counteracted by an ecto-ATPase or by ATP receptors with ATPase activity. Such interactions may play a role in PMN rolling and diapedesis as well as in the pathophysiology of PMN activation by an anergic endothelium.

Host tissue damage by phagocytes

Evidence continues to accumulate on the importance of neutrophils (PMNs) and phagocytes in the causation of tissue and endothelial injury that frequently accompanies the inflammatory response. Increased production of superoxide anions in combination with decreased endothelial antioxidant activity may contribute to the development of vascular disease including atherosclerosis, vasospasm, diabetic vascular complications, tissue damage in ischemia-reperfusion, and hypotension. Free radicals generated in the vascular wall may act directly on smooth muscle or interact with each other thus producing biologically active endogenous mediators. Derangement of macrophage function may occur in conditions characterized by protein malnutrition, thus leading to failure to develop a specific immunoresponse and to an increase in the production of oxygen intermediate radicals, which may cause tissue damage. A local inflammatory response followed by endothelial cell activation could also facilitate migration of immunocompetent cells into the parenchyma of grafted organs and stimulate dendritic cells in the graft. There is now convincing evidence that excessive and prolonged production of NO contributes to tissue damage in septicemia, ischemia/reperfusion injury, and other inflammatory conditions. There is also increasing evidence that the complement system plays an important role in tissue damage in association with phagocytes, e.g., in ischemia/reperfusion injury, carcinogenesis, and aging. It can therefore be surmised that phagocytic cells may act both as "friends" and as "foes" and that they are important mediators of tissue damage in a variety of conditions.

Cardioprotective effect of interleukin-10 in murine myocardial ischemia-reperfusion

We investigated the cardioprotective effects of rat interleukin-10 in a murine model of myocardial ischemia-reperfusion (20 min ischemia, 24 h reperfusion). Interleukin-10 (100 microg/rat) administered 15 min prior to reperfusion, significantly (P < 0.01) attenuated myocardial injury compared to rats receiving only 0.9% saline as a vehicle, as indicated by a reduced loss of myocardial creatine kinase from the ischemic-reperfused myocardium. Cardiac myeloperoxidase activity was also significantly (P < 0.01) attenuated by interleukin-10 within the ischemic-reperfused region compared to vehicle treated rats. To further investigate the mechanism of interleukin-10 we observed the in vitro adherence of neutrophil to rat vascular endothelium. Interleukin-10 treatment significantly (P < 0.05) attenuated neutrophil adherence to rat superior mesenteric artery endothelium stimulated with interleukin-1beta. Thus, interleukin-10 demonstrated significant cardioprotective effects as evidenced by a decrease in myocardial creatine kinase loss as well as an inhibition of neutrophil accumulation within the myocardium. It appears as though interleukin-10 mediates its effects, at least in part, by inhibiting leukocyte-endothelial interactions.

Beditine, a new benzodioxane derivative, as a suppressor of human polymorphonuclear leukocyte and platelet activation

Beditine, 2-(2-amino-4-thiazolyl)-1,4-benzodioxane hydrochloride is a new substance which reduced platelet activation and degranulation, prevented aggregation and superoxide generation by activated human polymorphonuclear leukocytes (PMNL) and inhibited the activation of arachidonate 5-lipoxygenase. Beditine may, therefore, be a useful agent in the treatment of cardiovascular disease.

Ischemic reperfusion causes lipid peroxidation and fiber degeneration

Although the neuropathology of ischemic fiber degeneration (IFD) is relatively well known, its pathogenesis is poorly understood. One putative mechanism of IFD is oxidative stress, causing a breakdown of the blood-nerve barrier (BNB) and lipid peroxidation. We evaluated the effect of ischemic reperfusion of rat sciatic-tibial nerve seeking biochemical and pathologic evidence of BNB disruption and lipid peroxidation. Ischemia, caused by the ligation of the supplying arteries to sciatic-tibial nerve, was maintained for 3 h, followed by reperfusion. Reperfusion resulted in an increase in nerve lipid hydroperoxides, greatest at 3 h, followed by a gradual decline over the next month. Nerve edema and IFD consistently became more severe with reperfusion, indicating that oxidative stress impairs the BNB (edema) and causes IFD. Reduced reperfusion was greatest over distal sciatic nerve and midtibial nerve at day 7. The most ischemic segment (midtibial), of nonreperfused ischemic nerves (duration 3 h), underwent both edema and IFD that was as pronounced as those of other segments after reperfusion, and underwent a smaller increase with reperfusion, suggesting that ischemia alone can also cause IFD and edema. The type of fiber degeneration was that of axonal degeneration.

Postischemic treatment (2-4 h) with anti-CD11b and anti-CD18 monoclonal antibodies are neuroprotective after transient (2 h) focal cerebral ischemia in the rat

We investigated the effects of F(ab')2 fragments of anti-CD11b and anti-CD18 monoclonal antibodies on ischemic cell damage in the rat when administered upon reperfusion and at 2 h of reperfusion after transient (2 h) middle cerebral artery (MCA) occlusion. 2 h of MCA occlusion was induced by intraluminal insertion of a monofilament. The following groups of animals were investigated. Anti-CD11b groups (n = 15): an intact anti-CD11b antibody (1B6c) and an anti-CD11b F(ab')2 fragment of 1B6c were infused upon reperfusion (4 mg/kg i.v.). Anti-CD18 group (n = 8): an anti-CD18 F(ab')2 fragment of CL26 was infused upon reperfusion (2 mg/kg i.v.), and at 22 h of reperfusion (1 mg/kg i.v.). Anti-CD11b delayed group (n = 9): an anti-CD11b F(ab')2 fragment of 1B6c was infused at 2 h of reperfusion (4 mg/kg i.v.), and at 22 h after reperfusion (2 mg/kg i.v.). Control groups (n = 18): an isotype-matched control antibody (mouse IgG1) was administered: (a) upon reperfusion (n = 13), and (b) at 2 h and 22 h of reperfusion (n = 5). Rats were sacrificed at 7 days of reperfusion. In a separate population of rats subjected to 2 h of MCA occlusion (n = 9), brain myeloperoxidase (MPO) activity was measured at 46 h of reperfusion. The vehicle groups had infarct volumes of 35.21 +/- 2.82% to 41.39 +/- 2.73% of the contralateral hemisphere, respectively. Infarct volume was significantly reduced after treatment with: the intact anti-CD11b antibody upon reperfusion (19.0 +/- 6.6%) (P < 0.05), the fragments of mAbs of anti-CD11b administered upon reperfusion (19.7 +/- 2.7%) (P < 0.05), and at 2 h of reperfusion (22.2 +/- 4.8%) (P < 0.05), and anti-CD18 administered upon reperfusion (20.4 +/- 4.8%) (P < 0.05). Anti-CD11b treatment significantly (P < 0.05) inhibited the increase of MPO activity in the ischemic hemisphere. Our data demonstrate that anti-CD11b and anti-CD18 mAb fragments significantly reduce infarct volume and inhibit the increase of MPO activity in the ischemic lesion; administration of anti-CD11b mAb fragment even at 2 h of reperfusion significantly reduces infarct volume. These data support importance of the beta 2 integrin CD11b/CD18 in ischemia/reperfusion injury and indicate that the therapeutic window for intervention to reduce ischemic cell damage in this model is at least 4 h from the onset of MCA occlusion.

Plasma from patients exposed to ischemia reperfusion contains clastogenic factors and stimulates the chemiluminescence response of normal leukocytes

Clastogenic factors (CFs) are released by cells exposed to superoxide radicals and are found in various situations of oxidative stress. Certain of their components stimulate further superoxide production by competent cells, as shown with cytochrome c assay in previous work. In the present study, we report CF formation after ischemia reperfusion in patients undergoing coronary bypass surgery. Plasma ultrafiltrates, collected 20 min after reperfusion, had clastogenic properties in contrast to those collected before ischemia. We also show that the luminol-enhanced chemiluminescence response of neutrophils from healthy persons is increased when these cells are exposed to CF-containing postreperfusion samples from patients. Light emission was reduced to control values in the presence of superoxide dismutase. The burst of oxyradicals upon reperfusion is probably the initiating event of CF formation, which in turn leads to further oxyradical generation. This amplification process may explain why detectable levels of CF need a delay of at least 10 min. The activated state of neutrophils in ischemia reperfusion is at once a consequence and a source of CFs. Individual variation in the persistence of this clastogenic and leukocyte-activating material was observed. Therefore, antioxidants for prevention of ischemia reperfusion injury should be continued during the postoperative course.

Anti-intercellular adhesion molecule-1 antibody reduces ischemic cell damage after transient but not permanent middle cerebral artery occlusion in the Wistar rat

BACKGROUND AND PURPOSE

Postischemic cerebral inflammation may contribute to ischemic cell damage. Intercellular adhesion molecule-1 (ICAM-1) is a glycoprotein expressed on endothelial cells that facilitates leukocyte adhesion. We investigated the effect of administration of an anti-ICAM-1 antibody (1A29) on ischemic cell damage after transient (2-hour) or permanent middle cerebral artery (MCA) occlusion in the Wistar rat.

METHODS

Groups studied were as follows: (1) transient MCA occlusion: rats were subjected to 2 hours of MCA occlusion, and after 1 hour of reperfusion they were treated with 1A29 (n = 11) or an isotype control antibody (n = 9); and (2) permanent MCA occlusion: rats were treated with 1A29 (n = 9) or an isotype control antibody (n = 7) 2 hours after onset of MCA occlusion. All animals were killed 1 week after onset of ischemia. Brain sections were stained with hematoxylin and eosin for histological evaluation.

RESULTS

Significant reductions (P < .05) in both volume (44%) of the ischemic lesion and weight loss were found in animals subjected to transient MCA occlusion and treated with 1A29 compared with vehicle-treated animals. In contrast, in animals subjected to permanent MCA occlusion the lesion and the temporal profile of body weight were not altered by 1A29 administration.

CONCLUSIONS

Ischemic cell damage is promoted by postischemic inflammatory response after 2 hours of transient MCA occlusion, and ischemic cell damage is reduced by administration of an anti-ICAM-1 antibody during reperfusion.

Effects of the reactive oxygen species hypochlorous acid and hydrogen peroxide on force production and calcium sensitivity of rat cardiac myofilaments

Neutrophil activation occurs after myocardial infarction/ischaemia. They produce the reactive oxygen species (ROS) hypochlorous acid (HOCl) and hydrogen peroxide (H2O2) which could contribute to contractile dysfunction upon reperfusion. The myofilaments of 'skinned' rat cardiac muscle were exposed to ROS in various states of activation. Isometric force was measured at controlled degrees of activation. A single application of 10 microM HOCl for 1 min increased log [Ca2+] for half-maximal activation (log K1/2) from 5.23 to 5.32, initial maximum Ca-activated force (FCa, max) was reduced by 18.8 +/- 5.8% and resting tension increased to 15.4 +/- 8.0% of FCa, max. At 50 microM, a 1-min exposure to HOCl produced a greater increase in Ca-sensitivity (log K1/2 increased from 5.23 to 5.47), a greater reduction in FCa, max (falling by 42.3 +/- 23.2%) and a greater increase in resting tension (to 25 +/- 10.7% of FCa, max). The nature of the resting tension rise was examined by reducing pH before and during exposure to HOCl; the results are consistent with 'rigor-like' cross-bridges being involved. H2O2 was without effect on the myofilaments at physiologically relevant (< 10 microM) concentrations. These results suggest that ROS associated with inflammation could contribute to post-ischaemic myocardial dysfunction.

Inhibitory effect of allopurinol on adjuvant arthritis in rats

The effect of Allopurinol (ALLO), on adjuvant arthritis was studied in rats and compared with the effect of indomethacin (IND). Drugs were given by intraperitoneal injection for each day beginning from the day of adjuvant injection (day 0) and continued until the 16th day. Paw swelling was measured on days 4, 17 and 29, and secondary lesions were assessed on days 17 and 29. Polymorphonuclear leukocyte (PMNs) count was also evaluated on day 17. ALLO, at relatively high doses (25-50 mg/kg), reduced paw swelling of the adjuvant-injected extremity on day 4; lower doses (6.25-12.5 mg/kg), however, elicited the same inhibitory effect on day 17. IND (0.25 mg/kg) also prevented paw swelling on days 4 and 17. Both ALLO and IND reduced the secondary lesions on days 17 and 29 and prevented the increase in polymorphonuclear leukocytes during the development of adjuvant arthritis. Possible mechanisms of the antiinflammatory effect of ALLO in adjuvant arthritis are discussed.

Prevention of cardiac reperfusion injury following global ischemia by a monoclonal antibody, R2-1A6

The effect of R2-1A6 monoclonal antibody on the reperfusion injury of heterotopically transplanted rat cardiac tissues after global ischemia was studied. Histological, functional as well as myocardial energy status were evaluated in control and R2-1A6-treated rats. The strong binding of neutrophils to cardiac endothelial cell surface and strong tissue edema were present at 10 min after the initiation of reperfusion and subsequently interstitial hemorrhage and myocardial degeneration were present in the control group. The mean survival date of grafted hearts was about 7.7 days in the control group. In contrast, the significantly less severe binding of neutrophils to endothelial cells, tissue edema, interstitial hemorrhage, and myocardial degeneration were present in R2-1A6-treated rats. All grafted hearts survived up to 14 days in R2-1A6-treated group. Myocardial ATP content decreased from preischemic value of about 4 mumol/g to post-ischemic value of 0.57 mumol/g. After reperfusion of ischemic hearts, myocardial ATP values remained to be a range of 1.27-1.03 mumol/g in control group. However, myocardial ATP values recovered up to 2.28 mumol/g in R2-1A6-treated group. Thus, these experiments indicated that neutrophil adherence to endothelial cells is a critical early event in the process leading to post-ischemic reperfusion injury in global ischemia and the R2-1A6 treatment resulted in significant protection against cardiac reperfusion injury following global ischemia.

Anti-CD11b monoclonal antibody reduces ischemic cell damage after transient focal cerebral ischemia in rat

We investigated the effect of an anti-CD11b monoclonal antibody (1B6c) on ischemic cell damage after transient middle cerebral artery occlusion. We divided animals into three groups: MAb 1 group (n = 5)--rats were subjected to 2 hours of transient occlusion and 1B6c (1 mg/kg) was administered intravenously at 0 and 22 hours of reperfusion; MAb 2 group (n = 5)--same experimental protocol as MAb 1 group, except that the initial dose of 1B6c was increased to 2 mg/kg; and control group (n = 5)--same experimental protocol as MAb 2 group, except that an isotype-matched control antibody was administered. Animals were weighed and tested for neurological function before and after occlusion of the middle cerebral artery. Forty-six hours after reperfusion, brain sections were stained with hematoxylin and eosin for histology evaluation. We observed a significant reduction of weight loss and improvement in neurological function after ischemia in the MAb 2 animals compared to MAb 1 and vehicle-treated animals (p < 0.05). The lesion volume was significantly smaller in the MAb 2 group (19.5 +/- 1.9%) compared to MAb 1 (29.9 +/- 2.6%) and vehicle-treated (34.2 +/- 5.4%) groups (p < 0.01). Tissue polymorphonuclear cell numbers were reduced in both 1B6c-administered groups. Our data demonstrate that administration of anti-CD11b antibody results in a dose-dependent, significant functional improvement and reduction of ischemic cell damage after transient focal cerebral ischemia in the rat.

Postischemic administration of an anti-Mac-1 antibody reduces ischemic cell damage after transient middle cerebral artery occlusion in rats

BACKGROUND AND PURPOSE

Postischemic cerebral inflammation may contribute to ischemic cell damage. The CD11b/18 (Mac-1) integrin mediates stimulated neutrophil binding to endothelia. We therefore investigated the effect of administration of an anti-Mac-1 monoclonal antibody on cerebral ischemic cell damage in the rat.

METHODS

Rats (n = 10) were subjected to 2 hours of middle cerebral artery occlusion; the anti-Mac-1 antibody was administered at a dose of 2 mg/kg i.v. at 1 hour of reperfusion and 1 mg/kg i.v. at 22 hours of reperfusion or an isotype-matched control antibody (n = 10) was administered using the same experimental protocol. Rats were killed at 46 hours of reperfusion, and brain sections were stained with hematoxylin and eosin for histological evaluation. In a separate population of rats given either vehicle (n = 8) or anti-Mac-1 antibodies (n = 9), intraparenchymal neutrophils were measured by means of a myeloperoxidase assay.

RESULTS

The lesion volume was significantly smaller (28%) in the anti-Mac-1 antibody group compared with the vehicle control group (P < .01). Numbers of intraparenchymal polymorphonuclear cells were significantly reduced (P < .05) in the cortex of the anti-Mac-1 antibody group compared with the vehicle control group.

CONCLUSIONS

Our data demonstrate that administration of anti-Mac-1 antibody 1 hour after onset of reperfusion results in significant reductions of ischemic cell damage and intraparenchymal neutrophils after transient (2-hour) focal cerebral ischemia in the rat.

The addition of glutathione (YM737) to a crystalloid cardioplegic solution enhances myocardial protection

The effectiveness of a glutathione preparation, YM737, as a free radical scavenger when added to hypothermic (4 degrees C) crystalloid cardioplegic solution was evaluated in this study. Rabbit hearts were preserved for 3 h in cardioplegic arrest by infusing 20 ml crystalloid cardioplegic solution initially, with additional 10-ml boluses administered every 30 min, while maintaining a myocardial temperature of 10 degrees C. They were then reperfused with Krebs-Henseleit bicarbonate buffer at 37 degrees C in a perfusion circuit for 60 min. The hearts were divided into two groups of six: One in which crystalloid cardioplegic solution was perfused (group 1); and one in which crystalloid cardioplegic solution containing YM737 1 mg/ml was perfused (group 2). The postischemic developed pressure (mmHg) in group 2 was significantly greater than that in group 1 after 60 min of reperfusion, being 44.8 +/- 8.4 versus 87.8 +/- 5.2 in groups 1 and 2, respectively (P < 0.01). Moreover, group 2 exhibited significantly lower postischemic left ventricular compliance after 60 min than group 1 (P < 0.01) and a significantly higher postischemic peak LV dp/dt (mmHg/sec) after 60 min of reperfusion, being 925 +/- 213 versus 1,550 +/- 111 in groups 1 and 2, respectively (P < 0.05). Based on the comparisons of postischemic hemodynamics it was concluded that the addition of glutathione to crystalloid cardioplegic solution does in fact enhance myocardial protection.

Antioxidant effectiveness in ischemia-reperfusion tissue injury

In summary, much evidence supports the formation of toxic oxygen metabolites in ischemic reperfused tissue. Tissues are equipped with both an intracellular and extracellular antioxidant defense system. The defense system can also be divided into enzymatic and nonenzymatic defenses. Important components of a nonenzymatic antioxidant include alpha-tocopherol, ascorbic acid, and beta-carotene as well as other compounds that can react with radicals to form less reactive products such as sulfur-containing amino acids. Extracellular fluid comprises a second line of defense against oxidant injury. These extracellular antioxidants include ceruloplasmin, albumin, transferrin, haptoglobin, and uric acid. The oxidant injury can potentially occur during ischemia and reperfusion due to (1) an excess production of oxygen free radicals, (2) a decrease in antioxidant defenses, or (3) both. Because antioxidants function by removing the toxic oxygen metabolites, they are generally highly effective in reducing ischemia-reperfusion injury.

Role of catalase in myocardial protection against ischemia in heat shocked rats

It was recently reported that in rats exposure to heat shock leads to appearance of a myocardial heat shock protein (HSP 70) and to an increase in myocardial catalase activity. This correlated with an improvement in post-ischemic function either in Langendorff-perfused hearts after low-flow ischemia or in working hearts after short-term, no-flow ischemia. We investigated the effect of the same hyperthermic treatment on functional recovery from no-flow ischemia of various durations in isolated working rat hearts performing at high or low external workloads. Rats were heated to core temperature of 42 degrees C for 15 min. No significant protein oxidation (% oxidized methionine) was observed 2.5 hr after treatment. A protein with migration characteristics similar to HSP 70 was observed in hearts of heat shocked rats 24 hr after this treatment while their myocardial catalase activity was not increased. Hearts of similarly treated rats were excised 24 hr after hyperthermia and perfused in a working mode with Krebs-Henseleit buffer (1.25 mM Ca2+, 11 mM glucose). At 15 cm H2O preload and 100 cm H2O afterload after 30 min no-flow ischemia, control hearts recovered to 36.9%, 2%, 47.6%, and 21.5% of the preischemic values of heart rate-peak systolic pressure product (RPP), aortic output, coronary flow, and cardiac output, respectively. After only 25 min of ischemia the respective recovered values were 61.6%, 11.5%, 58.7%, and 33.5%. Throughout the recovery period these hemodynamic values were consistently higher in hearts of heat shocked animals than in those of control hearts but the differences were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of hypochlorous acid and hydrogen peroxide on coronary flow and arrhythmogenesis in myocardial ischemia and reperfusion

The purpose of this study was to investigate the effect of the oxidants hypochlorous acid (HOCl) and hydrogen peroxide (H2O2) on the vulnerability of the myocardium to reperfusion-induced arrhythmias following global ischemia. After a 15 min equilibration period with or without experimental intervention, isolated perfused rat hearts in the Langendorff mode were made globally ischemic for 5 min by cross-clamping the aortic line. No dysrhythmias were evoked upon reperfusion at the 5 min global ischemia time period. HOCl or H2O2 were added to the perfusate 5 min into the equilibration period with a total exposure of 10 min. Global ischemia was then induced for 5 min followed by 10 min of reperfusion. A dose-response curve for HOCl (50-200 microM) indicated the development of idioventricular rhythms, in a concentration-dependent way. Furthermore, coronary flow of the hearts exposed to 100 and 200 microM HOCl, at 5 min post-reperfusion, was decreased; methionine (10 microM to 1 mM), an accepted scavenger for HOCl, prevented the responses to 200 microM HOCl, in a concentration-dependent manner. All hearts exposed to 200 microM H2O2 developed ventricular dysrhythmias during the reperfusion period. Coronary flow increased after 5 min of exposure to 200 microM H2O2 and remained elevated during reperfusion. It is concluded that toxic oxygen derived products are capable of increasing the susceptibility of the myocardium to reperfusion induced arrhythmias, and that although the electrical responses to exposure to those two oxidants were similar, the effects on the vasculature were not the same.

Lidocaine and dextran sulfate inhibit leukocyte accumulation but not postischemic contractile dysfunction in a canine model

Leukocytes have been implicated as a possible factor in the pathogenesis of postischemic contractile dysfunction, probably through the release of oxygen free radicals. Lidocaine and dextran sulfate are known to inhibit leukocyte adherence to endothelial cells in vitro and in vivo. In an acute open-chest canine model both agents were found to inhibit the augmented accumulation of indium-111-labeled leukocytes in briefly ischemic and subsequently reperfused myocardium. Pharmacologic inhibition of leukocyte accumulation by lidocaine and dextran sulfate, however, was not associated with improvement in postischemic contractile dysfunction.

Lipid peroxidation in experimental spinal cord injury: time-level relationship

Damage which occurs following spinal traumas is often irreversible. During recent years free oxygen radicals formed due to the pathological changes following neural tissue ischemia have been identified as being responsible for the ethio-pathogenesis of such damage. In our experimental study, model lesions are formed in spinal cords of rats by standard trauma. Malondialdehyde (MDA), a lipid peroxidation product, was measured in the spinal tissues distal to the trauma in order to examine indirectly the time-quantity relationship of free oxygen radicals in the area. For this study 60 rats in six groups, including one control group, were used to determine the formation of MDA. Under a surgical microscope, the spines of all rats were exposed by C5-Th6 laminectomy, and pressure was applied to the spinal cords of animals, except the members of the control group, at the level of C7 by a Yaşargil aneurysm clip. MDA was measured in spinal cord tissues in order to determine free oxygen radicals at the first and fifteenth minutes and at the first, second, and fourth hours. The statistical evaluation of the findings revealed a significant increase in MDA, starting from the 15th minute after the compression, reaching a maximum at 1 hour, and then decreasing. This observation may provide an important guide for studies on prevention of neural destruction.

Superoxide dismutase and allopurinol prevent the pressor effects of angiotensin II and histamine in the guinea-pig isolated perfused lung exposed to hypoxia

1. In the guinea-pig isolated perfused lung exposed to hypoxia by infusing N2-gassed Krebs solution, angiotensin II and histamine produced a reduced vasoconstrictor response when compared with the responses obtained in nonhypoxic lung. 2. These reduced vasoconstrictor responses were prevented by prior addition of superoxide dismutase or allopurinol to the medium. 3. These results were taken as evidence for the initiation of the cascade free radical formation in the guinea-pig lung during hypoxia and the primary role of the released intracellular xanthine oxidase. 4. Possible mechanisms of the reduced responses to angiotensin II and histamine and tissue protective activities of allopurinol and superoxide dismutase are discussed.

Free radical formation during splanchnic artery occlusion shock

Free radical (FR) formation in the rat intestinal lumen was measured using the spin-trapping technique and electron paramagnetic resonance spectroscopy. Intestinal ischemia was produced by occluding the celiac and the superior mesenteric arteries for 30 min followed by reperfusion. The lumen was filled with a solution of PBN (N-tert-butyl-alpha-phenyl-nitrone) and the intestine was squeezed to enhance the interaction between the PBN solution and the intestinal mucosal cells. Free radicals were produced upon reperfusion, with peaks at 5 and 90 min. Post-ischemic treatment with superoxide dismutase (20 mg.kg(-1)) inhibited the increase of FR production during the second peak by 36%. In a single study in a group of leucocytopenic rats (WBC < 1500/mm(3)), the increase of FR production during the second peak was decreased by 80%. However, these treatments did not inhibit the FR production during the first peak in either group. In contrast, pretreatment with allopurinol (40 and 100 mg.kg(-1) injection at 24 and 3 hours before ischemia, respectively) inhibited the FR production during the first peak by 76%, but did not inhibit during the second peak. The changes in lipid peroxidation in the intestinal mucosa, specific gravity of the intestine and in the hematocrit were correlated to the FR production in the second peak. These results suggest that a major cause of tissue injury after reperfusion in the ischemic intestine may largely be produced by neutrophils.

Fibrin (ogen)-derived peptide B beta 30-43 is a sensitive marker of activated neutrophils during fibrinolytic-treated acute myocardial infarction in man

Neutrophils, elastase, the specifically elastase-derived fibrin split product, B beta 30-43, and C-reactive protein were determined in 30 consecutive patients with acute myocardial infarction. At admission to the coronary care unit 4.2 +/- 0.8 hours after the onset of symptoms, all elements were increased above the reference levels, while compared with convalescent levels, only neutrophils and B beta 30-43 were increased. After the streptokinase treatment, neutrophils, elastase, and B beta 30-43 increased abruptly and peaked (p less than 0.0001) within 1.5 hours. Plasma creatine kinase MB and C-reactive protein reached their peak levels after about 12 and 24 hours, respectively. Peak indices of neutrophils and creatine kinase correlated (r = 0.60, p less than 0.0006). Compared with the age-matched reference range, the convalescent level of B beta 30-43 was increased (p less than 0.0001). Of the tested elements suggestive of neutrophil activation, B beta 30-43 showed signs of being the most sensitive. In keeping with animal studies, neutrophils are activated early during the course of acute myocardial infarction and their activation seems to become accelerated by fibrinolytic treatment. Neutrophils may remain activated in the convalescent phase.

A comparative study on defense systems for lipid peroxidation by free radicals in spontaneously hypertensive and normotensive rat myocardium

1. Antiperoxidation ability and lipid peroxidation in myocardium were examined in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY) at 6 and 16 weeks of age. 2. Glutathione peroxidase activity was higher in SHR at 6 weeks of age, but lower at 16 weeks compared to that in WKY. alpha-Tocopherol content was lower in SHR at both 6 and 16 weeks of age than in WKY. 3. In vitro formation of free malondialdehyde was more pronounced in SHR myocardium than in WKY. 4. Coincidence of lower antiperoxidation ability and higher peroxidation of membrane phospholipid indicate myocardial cell vulnerability in SHR hypertrophied myocardium.

Ischemia and reperfusion injury in isolated rat heart: effect of reperfusion duration on xanthine oxidase, lipid peroxidation, and enzyme antioxidant systems in myocardium

The aim of this work was to assess the catalytic activity of xanthine oxidase, the level of lipid peroxides and enzymic antioxidant systems in isolated rat heart muscle subjected to a globally partial ischemia followed by varying durations of reperfusion. After 40 min of globally partial ischemia (residual perfusion flow rate: 0.1 ml/min), four different durations of reperfusion were investigated (0, 20, 40, and 60 min). After each experimental ischemia/reperfusion sequence, the heart was frozen in liquid nitrogen. Lipid peroxides were assayed in the cardiac homogenate and the catalytic activity of xanthine oxidase and enzymic antioxidant systems (glutathione peroxidase, superoxide dismutase and catalase) were determined in the centrifuged supernatant. In the different experimental protocols studied in this work, there was no significant increase in the activity of cardiac xanthine oxidase or in the level of lipid peroxides when compared to the non reperfused or to the continuously perfused hearts. Indeed, enzymic antioxidant systems were also not significantly modified in the different periods of reperfusion when compared to control hearts (continuously perfused hearts). These results suggest that xanthine oxidase is apparently not a major source of free radicals in the course of an ischemia-reperfusion sequence in heart muscle, in particular, if we consider the early phases of reperfusion. The process of lipid peroxidation, assessed by assaying thiobarbituric acid reactants, is not a predominant phenomenon of reperfusion-induced injury, at least in the experimental model used here. However, enzymic antioxidant systems investigated in this study do not seem modified. This could mean that the small quantity of oxygen free radicals produced does not overwhelm the enzymic antioxidant systems of myocardium which is in agreement with peroxidatized lipid results.

Correlation between CD11b/CD18 and increase of aggregability of granulocytes in coronary artery disease

Recent studies suggest that granulocytes (PMNs) play a role in the pathogenesis of acute and chronic myocardial ischemia and extension of myocardial injury. Rabbit-derived antiserum-dependent reduction of circulating PMNs in the dog or using monoclonal antibody anti-CD11b/CD18 of PMNs resulted in smaller myocardial infarcts. Experience in humans shows the modification of PMN function in angina and during myocardial ischemia. In our studies, patients affected by coronary artery disease presented an increase in granulocyte aggregability in coronary sinus and showed a related higher expression of CD11b/CD18 in coronary sinus with respect to aorta leukocytes. The potential role of this modification of PMNs was analyzed.

Clinical and experimental aspects of myocardial stunning

Although the mechanisms involved in stunning remain incompletely defined, it appears that intracellular calcium overload, sarcoplasmic reticulum dysfunction, and the generation of OFR are important components of post-ischemic myocyte dysfunction. It is likely that a variety of mechanisms, some possibly remaining to be elucidated, are operative in the pathogenesis of stunning, and that the contribution of a particular process may be influenced by the model and the method of inducing ischemia. Myocardial stunning has been shown to be prevalent in patients with diverse cardiac diseases. Small clinical trials have suggested that electrocardiography, echocardiography, and radionuclide imaging techniques may be useful in identifying patients with stunned myocardium. In patients with depressed cardiac performance due to stunning, therapy with inotropic agents may recruit the viable but injured myocardium to contract and improve cardiac output in the short term. An important issue that will be addressed over the next decade is whether aggressive therapy aimed at reducing myocardial stunning in stable patients should be attempted. Some authorities have suggested that stunning may represent an adaptive response to limit reperfusion injury, and that interfering with this response may not be beneficial in the long term. Further investigation into the cellular and molecular basis of ischemic injury should provide insight into these and other important aspects of myocardial stunning. Methods of attenuating postischemic ventricular dysfunction that appear convincing in the research laboratory may not translate to clinical benefit when applied to humans.

Leukocytic .O2- and cardiac dysfunctions in isolated perfused rat hearts

Superoxide radicals are supposed to contribute to myocardial reperfusion injury. Their origin, however, is still a matter of debate. Polymorphonuclear leukocytes (PMNL) have been discussed as a major postischaemic .O2- source [Lucchesi and Mullane (1986) Ann Rev Pharmacol Toxicol 26: 201-224]. We studied the role of .O2- derived from human polymorphonuclear leukocytes in reperfused and normoxic perfused isolated rat hearts. During reperfusion PMNL exerted deleterious effects on different parameters (e.g. contractility, coronary flow) of isolated rat hearts. Under normoxic perfusion conditions stimulation of PMNL with N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) caused bradycardia and a transient vasoconstriction. Superoxide dismutase (SOD) administration did not influence any of the PMNL effects mentioned, suggesting that leukocytic .O2- was not involved in PMNL-induced cardiac dysfunctions.

The evolution of oxidative stress indicators in the course of myocardial ischemia

Two studies were carried out in patients suffering from Unstable Angina (UA) and Myocardial Infarction (MI). The first study investigated the variations of the Malondialdehyde (MDA) rate at 1st, 5th, 12th day of treatment in 27 patients (15 UA and 12 MI), compared to 15 controls. This rate varied in a different way, with a first peak and a rapid decrease in UA, where it regularly decreases in MI. The second study focused on the variations of MDA, Superoxide Dismutase (SOD), Glutathion Peroxydase (GPX) rates at 2nd, 12th days in 53 patients (19 UA and 34 MI), compared to 35 controls. Here again, the rate of MDA was high on day 2 and decreased on day 12. The rate of GPX showed similar evolution while the SOD rate had an opposite evolution. These two studies confirm the evidence of oxidative stress in acute coronary deficiency.

Granulocyte activation after coronary angioplasty in humans

To determine whether percutaneous transluminal coronary angioplasty (PTCA) would lead to neutrophil activation with subsequent discharge of proteolytic enzymes, like elastase, and oxygen free radicals, like superoxide anion, blood samples were taken from the coronary sinus and aorta in 14 patients with stable angina and one-vessel disease who underwent PTCA. Neutrophils were separated by means of the Ficoll-Hypaque system and were stimulated to detect release of elastase and generation of superoxide anion. Plasma levels of elastase were also measured by an immunoenzymatic method. PTCA was successful in all patients. Plasma elastase levels increased significantly at the end of the procedure compared with pre-PTCA values both in the coronary sinus (from 129.2 +/- 16.6 to 286.6 +/- 39.7 micrograms/l, p less than 0.005) and in the aorta (from 117.4 +/- 13.6 to 258.1 +/- 41.3 micrograms/l, p less than 0.005). On the other hand, superoxide anion released in the supernatants after neutrophil stimulation by phorbol-myristate-acetate decreased after PTCA in the coronary sinus (before PTCA, 60.1 +/- 7.1; after PTCA, 40.7 +/- 6.8 nmol 1 x 10(7) granulocytes/ml/15 min, p less than 0.05), whereas a mild but not significant decrease was observed in the aorta (from 58.3 +/- 10.9 to 55.3 +/- 8.6 nmol 1 x 10(7) granulocytes/ml/15 min, p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of oxidants on Na,K,ATPase and its reversal

Ischemia-reperfusion heart cell injury may be mediated, at least in part, through the generation of oxy radicals. Therefore, mechanisms of action of two oxidants on a membrane model, partially purified Na,K,ATPase, were investigated. Effects of H2O2, an oxygen intermediate postulated to play a primary role in reperfusion injury, on the function of the enzyme were time-dependent and potentiated by Fe ions. The inhibition of enzyme activity was prevented by chelators, but not by hydroxyl radical scavengers. The results support the view that the possible mode of enzyme modification involves H2O2-derived, Fe ion-catalyzed, localized ("site-specific") hydroxyl radical formation. The action of hypochlorous acid (HOCl), a powerful oxidant postulated to be produced by activated neutrophils, was quantitatively similar to that of H2O2 plus Fe ions in causing enzyme dysfunction. This is partly because relatively large doses of oxidants were required, due to the presence of physiological anti-oxidant defense mechanisms in the membrane. Although a combination of deferoxamine (Fe ion chelator) and dithiothreitol (DTT) (sulfhydryl reducing agent) was most effective in preventing the enzyme modification, once enzyme inactivation by oxidants is in progress, deferoxamine plus DTT could only arrest further deterioration of the enzyme function. Therefore, the oxidant-induced change in membrane dysfunction advances with time; the advance can be stalled, but the enzyme activity cannot be restored to normal.