Cytokine-induced nitric oxide formation in normal but not in neoplastic murine lung epithelial cell lines

Cytomix, a mixture of interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta, induces nitric oxide (NO) production in lung epithelial cell lines. It is not known whether neoplastic transformation alters a cell's ability to form NO in response to cytokines. The present study investigated NO formation in two murine lines of immortalized "normal" (nontumorigenic) lung epithelial cells of alveolar type II origin, E10 and C10, and their sibling spontaneous transformants, E9 and A5. Nontumorigenic cells elaborated much more NO after cytomix exposure than did their tumorigenic counterparts. NO production was prevented by inhibiting protein synthesis and NO synthase and attenuated by dexamethasone. Northern and Western blot analyses of inducible NO synthase (iNOS) demonstrated cytomix-induced induction of iNOS only in nontumorigenic cells. The deficiency in NO production in tumorigenic cells was not associated with reduced iNOS mRNA stability or with differences in cytomix-induced nuclear factor-kappaB activation. Although cytomix caused a greater production of NO in E10 cells than in E9 cells, the same treatment induced equivalent proliferation in both cell lines. These results indicate a specific deficiency in cytokine-induced NO synthesis in transformed murine lung epithelial cells relative to their normal progenitor cells and provide a model for investigating iNOS regulation.

Changes in pulmonary expression of hexokinase and glucose transporter mRNAs in rats adapted to hyperoxia

Impairment of lung aconitase activity, citric acid cycle, and mitochondrial respiration by hyperoxia necessitates the elevation of glycolysis for energy production and of pentose shunt activity for reducing equivalents. The molecular mechanisms that allow increased glucose utilization are unknown. Adult male and female rats were adapted to sublethal hyperoxia, equivalent to 83% oxygen at sea level, or air for 7 days. Lung RNA and protein increased in hyperoxia (197 and 57%, respectively), whereas total DNA was unchanged. In hyperoxia, lung total hexokinase (HK) activity increased threefold, and mRNAs for HK-II and -III were specifically upregulated. HK-I mRNA was unchanged. mRNAs for HK-II and -III gradually increased during the first 72 h in hyperoxia. HK-II mRNA was significantly elevated at 72 h, preceding changes in lung cell populations. Although virtually absent in air, HK-II activity was highly expressed in hyperoxia. Among lung glucose transporters, specific expression of mRNAs for GLUT-4 (insulin dependent) and sodium-glucose cotransporter-1 was decreased, whereas that for GLUT-1 was minimally changed. Adaptation to hyperoxia involves coordinated changes in gene expression for the proteins regulating pulmonary glucose transport.

Detection of thioredoxin in human serum and biological samples using a sensitive sandwich ELISA with digoxigenin-labeled antibody

Thioredoxin is a low molecular weight, redox active protein important in cellular proliferation, signal transduction and antioxidant function. Thioredoxin is secreted by normal as well as neoplastic cells and is potentially involved in paracrine cell communication as suggested by its co-cytokine activity. Thus, the thioredoxin level in biological fluids, cells and tissue homogenates could be an important indicator of physiological or pathophysiological conditions. Hence, an accurate and sensitive measurement is of paramount importance in studies involving thioredoxin. We present here an ultrasensitive enzyme linked immuno-absorbent assay (ELISA) for human thioredoxin using digoxigenin-labelled goat polyclonal anti-human thioredoxin. The assay could detect a minimum level of 15 pg/ml thioredoxin in human serum, cell culture media, and in cell and tissue samples. The assay was optimized for concentration of both antibodies, blocking agent, plates, incubation time and reaction volumes. Excellent linearity and reproducibility were obtained. The assay was applied to different baboon tissues and human serum samples. The intrassay coefficient of variation (CV) was between 6.0 to 14 and the interassay CV was from 1.6 to 11.1. Excellent parallelism of standards with serum samples, tissue homogenates or cell lysates was obtained. More than 90% recovery of human thioredoxin was observed in 10% human serum. The assay is easy to use, rapid, reproducible, but above all it is a quantitative, specific and sensitive way to measure thioredoxin in a variety of biological specimens.

Loss of lung mitochondrial aconitase activity due to hyperoxia in bronchopulmonary dysplasia in primates

The premature primate exposed to hyperoxia provides a useful model of bronchopulmonary dysplasia. A critical target in hyperoxic injury is the mitochondrial matrix enzyme aconitase. We hypothesized that this enzyme's activity would decline in the premature baboon lung during exposure to hyperoxia. Total aconitase activity was significantly decreased in the lungs of premature baboons of 140 days gestation with exposure to 100% oxygen for 6-10 days compared with as needed [pro re nada (PRN)] oxygen exposure and fetal controls (P = 0.0001). In activity gels, lungs from 100% oxygen-exposed animals (6-10 days) showed a nearly complete loss of mitochondrial aconitase activity relative to lungs from animals exposed only to PRN oxygen. Decreased lung aconitase activity was not a nonspecific effect of hyperoxia, causing mitochondrial damage or loss, because the activity of the mitochondrial respiratory enzyme cytochrome oxidase was not different in lungs of 100% oxygen-exposed relative to PRN oxygen-exposed newborns. In 125-day-gestation premature primates (age 6-10 days), lung total aconitase activity was correlated with inspired oxygen tension (r = 0.73 for fraction of inspired oxygen > 0.35), whereas, for animals of 140 days gestation, no such correlation was found. Thus the more premature animal's lung was more susceptible to loss of aconitase.

Glucose modulates cell death due to normobaric hyperoxia by maintaining cellular ATP

To determine whether glucose depletion is a principal determinant of hyperoxic cell death in vitro, human lung epithelial-like cells (A549) were exposed to hyperoxia (95% O2) in either 10, 30, or 50 ml of medium (Ham's F-12K). Glucose was depleted in the medium after 36, 60, or 96 h, respectively. Medium lactate dehydrogenase (LDH) activity increased only after glucose was depleted. To confirm that glucose depletion was critical to cell death, cells exposed to 95% O2 were supplemented with glucose at regular intervals to reestablish initial medium glucose concentrations. Other cells received no supplements. Without supplementation, glucose was depleted within 48 h, followed within 12 h by an almost complete loss of cell ATP and elevated medium LDH activity. Glucose-supplemented cells appeared normal microscopically and did not release LDH activity despite an extracellular pH of 6.5 due to fermentation. Additional experiments at sea-level pressure confirmed that glucose supplementation prevents extensive cell death in hyperoxia in cultured A549 cells.

Elevation of manganese superoxide dismutase gene expression by thioredoxin

Manganese superoxide dismutase (MnSOD) is a mitochondrial enzyme that dismutates potentially toxic superoxide radical into hydrogen peroxide and dioxygen. This enzyme is critical for protection against cellular injury due to elevated partial pressures of oxygen. Thioredoxin (TRX) is a potent protein disulfide reductase found in most organisms that participates in many thiol-dependent cellular reductive processes and plays an important role in antioxidant defense, signal transduction, and regulation of cell growth and proliferation. Here we describe induction of manganese superoxide dismutase by thioredoxin. MnSOD mRNA and activity were increased dramatically by low concentrations of TRX (28 microM). Elevation of MnSOD mRNA by TRX was inhibited by actinomycin D, but not cycloheximide, occurring both in cell lines and primary human lung microvascular endothelial cells. mRNAs for other antioxidant enzymes including copper-zinc superoxide dismutase and catalase were not elevated, demonstrating specificity of induction of MnSOD by TRX. Thiol oxidation by diamide or alkylation by chlorodinitrobenzene inhibited MnSOD induction, further indicating a requirement for reduced TRX. Because both oxidized and reduced thioredoxin (28 microM) induced MnSOD mRNA, the intracellular redox status of externally added Escherichia coli oxidized TRX was determined. About 45% of internalized E. coli TRX was reduced, with 8% in fully reduced form and about 37% in partially reduced form. However, when TRX reductase and nicotinamide adenine dinucleotide (NADPH) were added to the extracellular medium with TRX, more than 80% of E. coli TRX was found to be in a fully reduced state in human adenocarcinoma (A549) cells. Although lower concentrations of oxidized TRX (7 microM) did not induce MnSOD mRNA, this concentration of TRX, when reduced by NADPH and TRX reductase, increased MnSOD mRNA six-fold. In additional studies, MCF-7 cells stably transfected with the human TRX gene had elevated expression of MnSOD mRNA relative to vector-transfected controls. Thus, both endogenously produced and exogenously added TRX elevate MnSOD gene expression. These findings suggest a novel mechanism involving reduced TRX in regulation of MnSOD.

Comparison of exhaled nitric oxide, serum eosinophilic cationic protein, and soluble interleukin-2 receptor in exacerbations of pediatric asthma

The hypotheses tested in this study were that during acute asthma exacerbations (1) exhaled nitric oxide concentrations [eNO] are a more sensitive, noninvasive indicator of asthma disease activity than serum markers of inflammation such as eosinophil cationic protein (ECP) or soluble interleukin 2 receptor (sIL2R), and (2) elevated [eNO] are reduced after treatment with glucocorticoids (GC). Peak eNO levels were measured by chemiluminescence during slow expiration. Seven asthmatic subjects (mean age 11 yrs; mean morning FEV1 65% predicted) receiving inhaled GC, and with no radiographic evidence of acute sinusitis, were studied before and after a course of oral GC. Measurements of [eNO], ECP and sIL2R levels, and FEV1% were obtained before and after a course of GC. Six atopic nonasthmatic subjects (mean age 12 years; mean FEV1 94% predicted) and seven normal subjects (mean age 13 years; mean FEV1 100% predicted) were studied. The mean peak [eNO] level (parts per billion: ppb) for the asthma subjects before treatment (52 +/- 5 ppb SEM) was greater than the value for both nonasthmatic atopic and normal subjects (16 +/- 2 ppb and 14 +/- 2 ppb SEM, respectively; P < 0.0001). There was no significant difference in ECP or sIL2R values between asthmatic subjects and either atopic or normal subjects (P > 0.05). Baseline pre-GC treatment ECP levels in the asthmatic subjects were significantly higher (P < 0.002) than post-GC treatment values. The mean peak [eNO] level in the asthmatic subjects declined after oral GC treatment to 14 +/- 1 ppb (P < 0.0002) and was less than 2 ppb different from either control group (P > 0.75). We conclude that [eNO] is a more sensitive marker of asthma disease activity than ECP and sIL2R levels. In addition, [eNO] appears to be a more useful indicator of the beneficial response to GC therapy than these other measurements in pediatric asthma.

Activation of NF-kappaB by antineoplastic agents. Role of protein kinase C

Paclitaxel can induce tumor necrosis factor (TNF) and interleukin-1 gene expression, similar to lipopolysaccharides. Since lipopolysaccharide-induced expression of TNF is related to activation of NF-kappaB, we determined whether NF-kappaB could be activated by paclitaxel. In the human lung adenocarcinoma cell line A549, paclitaxel activated NF-kappaB in a dose-dependent manner with maximal activation after 2-4 h. Since paclitaxel could up-regulate TNF and interleukin-1 secretion and subsequent NF-kappaB activation could be caused by these cytokines, the effect of two other groups of anticancer drugs including vinca alkaloids (vinblastine and vincristine) and anthracyclines (daunomycin and doxorubicin), neither of which induce TNF or interleukin-1 gene expression, were examined. Like paclitaxel, vinblastine, vincristine, daunomycin, and doxorubicin each caused activation of NF-kappaB. Therefore, it is unlikely that activation of NF-kappaB caused by these agents or by paclitaxel is mediated via cytokine up-regulation. Furthermore, actinomycin D and cycloheximide, inhibitors of transcription and translation, respectively, did not inhibit paclitaxel-induced NF-kappaB activation. Several other transcription factors such as AP-1, AP-2, CREB, SP-1, or TFIID were not activated by antineoplastic agents demonstrating specificity of NF-kappaB activation. The involvement of both subunits in the NF-kappaB DNA binding complex was demonstrated by its abrogation by anti-p65 and by supershift by anti-p50 antibodies. Since protein phosphorylation is implicated in the activation of NF-kappaB, the effect of anticancer drugs on protein kinase C activity was measured. Vincristine, daunomycin, and paclitaxel significantly increased protein kinase C activity, and vinblastine and doxorubicin caused similar trends. Following treatment with antineoplastics (1-4 h), cytoplasmic IkappaBalpha degradation occurred concomitantly with translocation of p65 to the nucleus. Specific protein kinase C inhibitors (bisindolylmaleimide (GF109203X) and calphostin C) blocked the activation of NF-kappaB by each compound. Hence, protein kinase C activation may contribute to NF-kappaB activation by antineoplastic agents.

Failure of tumor necrosis factor and interleukin-1 to elicit superoxide production in the mitochondrial matrices of mammalian cells

Subversion of mitochondrial electron transport to the production of O2.- has been proposed as a mechanism of tumor necrosis factor (TNF)-mediated cell killing and to a lesser extent interleukin-1 (IL-1) and lipopolysaccharide (LPS) cytotoxicity. We utilized the O2.- -sensitive aconitases to measure changes in steady-state 02.- levels in the mitochondrial matrix and cytoplasm of cultured mammalian cells in response to these inflammatory mediators. TNF alpha did not measurably affect aconitase activity, and thus mitochondrial 02.- production, in either cultured human A549 cells or murine L929 cells while TNF alpha clearly caused cytotoxicity as revealed by impaired mitochondrial respiration. IL-1 alpha and Escherichia coli LPS also failed to affect the aconitase activity in A549 cells. Neither the O2.- scavenger Mn(III) TMPyP nor the H2O2 scavenger catalase protected L929 cells against the cytotoxicity of TNF alpha. In conclusion, TNF, IL-1, and LPS do not appear to exert cytotoxicity, or MnSOD gene induction effects, by eliciting mitochondrial O2.- production.

Superoxide scavenging by Mn(II/III) tetrakis (1-methyl-4-pyridyl) porphyrin in mammalian cells

The superoxide dismutase mimic Mn(II/III) tetrakis (1-methyl-4-pyridyl) porphyrin (Mn(II/III)TMPyP) was examined for its superoxide radical (O2.-)-scavenging ability in cultured mammalian cells. Mn(III)TMPyP (< 5 microM) added to culture media relieved growth inhibition and decreased the inactivation of the O2(.-)-sensitive enzyme aconitase in cells exposed to the O2(.-)-generating phenazine pyocyanine. Treatment of cells with Mn(III)TMPyP did not measurably affect cellular O2.- production as revealed by rates of cyanide-resistant respiration with or without added pyocyanine. In contrast, Mn(II/III)TMPyP enhanced O2.- production in cells when the redox-active naphthoquinone menadione was present as measured by both increased cyanide-resistant respiration rates and aconitase inactivation. In vitro, Mn(II/III)TMPyP catalyzed the oxidation of ascorbate, and menadione enhanced this effect. Mn(III)TMPyP did not protect aconitase when O2.- production was elicited in mitochondria by antimycin A and the uncoupler carbonyl cyanide p-trifluoromethoxyphenylhydrazone. The results support a reductant-O2.-:oxidoreductase mechanism for O2.- scavenging by Mn(II/III)TMPyP in the mammalian cytosol as proposed for its action in Escherichia coli, but also indicate that Mn(II/III)TMPyP can either scavenge or produce O2.- in cells depending upon the prevailing pathways of Mn(II/III)TMPyP oxidation-reduction.

Activation of NF-kappa B and elevation of MnSOD gene expression by thiol reducing agents in lung adenocarcinoma (A549) cells

The effect of reducing agents, including N-acetylcysteine (NAC), dithiothreitol (DTT), and 2-mercaptoethanol (2-ME) on nuclear transcription factor-kappa B (NF-kappa B) activation and manganese superoxide dismutase (MnSOD) expression was investigated in a pulmonary adenocarcinoma (A549) cell line. NAC, DTT, and 2-ME each activated the transcription factor NF-kappa B and increased steady-state levels of MnSOD mRNA and enzyme activity in these cells. In addition, NAC, DTT, and 2-ME increased chloramphenicol acetyltransferase (CAT) activity in cells transfected with a construct containing the CAT gene under the control of the rat MnSOD promoter. SOD and catalase (500 U/ml) plus ethanol (1 mM) did not inhibit activation of NF-kappa B or elevation of steady-state MnSOD mRNA levels by NAC, DTT, or 2-ME. Controls in which comparable amounts of O2-. to those produced by thiols were generated by hypoxanthine and xanthine oxidase, or in which H2O2 was added directly, had neither activated NF-kappa B nor elevated MnSOD mRNA. This shows that reactive oxygen intermediates, which may be formed during autooxidation, may not contribute to activation of NF-kappa B. Because the MnSOD promoter also contains potential binding sites for other transcription factors, such as promoter-selective transcription factor-1 (SP-1), activator protein-1 (AP-1), AP-2, adenosine 3',5'-cyclic monophosphate-regulator element binding factor (CREB), and transcription factor IID complex (TFIID), the effect of thiols on their activation also were evaluated. In contrast to findings with NF-kappa B, there was only minor activation of AP-1 by thiols, and none of the other transcription factors were activated by thiols. AP-1 activation was inhibited by catalase (500 U/ml) plus SOD plus ethanol (1 mM). Addition of 700 microM H2O2 also activated AP-1, and catalase at 500 U/ml prevented this activation. This indicates that H2O2 produced as a result of autooxidation of thiols can activate AP-1 but not NF-kappa B. Thus a close association between exposure to reducing agents, activation of NF-kappa B, and elevation of MnSOD gene expression is demonstrated.

Pulmonary vascular disorders masquerading as interstitial lung disease

During the acquisition of a series of 92 children with interstitial lung disease (ILD) over a 14 year period, a significant minority (8/92 or 9%) were initially diagnosed as having ILD, but were subsequently found to have a variety of arterial, venous, and/or capillary disorders that explained their initial pulmonary findings. This subgroup of patients has had a very high morbidity and mortality, with only three of eight patients currently surviving. The presentation, evaluation, and natural history of these eight children were reviewed. We developed a strategy of cardiac and pulmonary evaluation for children presenting with clinical and radiographic features of ILD that helped us to identify rapidly those with pulmonary vascular disorders.

Thiol modulation of TNF alpha and IL-1 induced MnSOD gene expression and activation of NF-kappa B

TNF alpha and IL-1 each can activate NF-kappa B and induce gene expression of manganese superoxide dismutase (MnSOD), a mitochondrial matrix enzyme which can provide critical protection against hyperoxic lung injury. The regulation of MnSOD gene expression is not well understood. Since redox status can modulate NF-kappa B and potential kappa B site(s) exist in the MnSOD promoter, the effect of thiols (including NAC, DTT and 2-ME) on TNF alpha and IL-1 induced activation of NF-kappa B and MnSOD gene expression was investigated. Activation of NF-kB and increased MnSOD expression were potentiated by thiol reducing agents. In contrast, thiol oxidizing or alkylating agents inhibited both NF-kappa B activation and elevated MnSOD expression in response to TNF alpha or IL-1. Since protease inhibitors TPCK and TLCK can inhibit NF-kappa activation, we also investigated the effect of these compounds on MnSOD expression and NF-kappa B activation. TPCK and TLCK each inhibited MnSOD gene expression and NF-kappa B activation. Since the MnSOD promoter also contains an AP-1 binding site, the effect of thiols and thiol modifying agents on AP-1 activation was investigated. Thiols had no consistent effect on AP-1 activation. Likewise, some of the thiol modifying compounds inhibited AP-1 activation by TNF alpha or IL-1, whereas others did not. Since diverse agents had similar effects on activation of NF-kappa B and MnSOD gene expression, we have demonstrated that activation of NF-kappa B and MnSOD gene expression are closely associated and that reduced sulfhydryl groups are required for cytokine mediation of both processes.

Superoxide radical and iron modulate aconitase activity in mammalian cells

Aconitase is a member of a family of iron-sulfur-containing (de)hydratases whose activities are modulated in bacteria by superoxide radical (O2-.)-mediated inactivation and iron-dependent reactivation. The inactivation-reactivation of aconitase(s) in cultured mammalian cells was explored since these reactions may impact important and diverse aconitase functions in the cytoplasm and mitochondria. Conditions which increase O2-. production including exposure to the redox-cycling agent phenazine methosulfate (PMS), inhibitors of mitochondrial ubiquinol-cytochrome c oxidoreductase, or hyperoxia inactivated aconitase in mammalian cells. Overproduction of mitochondrial Mn-superoxide dismutase protected aconitase from inactivation by PMS or inhibitors of ubiquinol-cytochrome c oxidoreductase, but not from normobaric hyperoxia. Aconitase activity was reactivated (t1/2 of 12 +/- 3 min) upon removal of PMS. The iron chelator deferoxamine impaired reactivation and increased net inactivation of aconitase by O2-.. The ability of ubiquinol-cytochrome c oxidoreductase-generated O2-. to inactivate aconitase in several cell types correlated with the fraction of the aconitase activity localized in mitochondria. Extracellular O2-. generated with xanthine oxidase did not affect aconitase activity nor did exogenous superoxide dismutase decrease aconitase inactivation by PMS. The results demonstrate a dynamic and cyclical O2-.-mediated inactivation and iron-dependent reactivation of the mammalian [4Fe-4S] aconitases under normal and stress conditions and provide further evidence for the membrane compartmentalization of O2-..

Aconitase is a sensitive and critical target of oxygen poisoning in cultured mammalian cells and in rat lungs

The effect of hyperoxia on activity of the superoxide-sensitive citric acid cycle enzyme aconitase was measured in cultured human epithelial-like A549 cells and in rat lungs. Rapid and progressive loss of > 80% of the aconitase activity in A549 cells was seen during a 24-hr exposure to a PO2 of 600 mmHg (1 mmHg = 133 Pa). Inhibition of mitochondrial respiratory capacity correlated with loss of aconitase activity in A549 cells exposed to hyperoxia, and this effect could be mimicked by fluoroacetate (or fluorocitrate), a metabolic poison of aconitase. Exposure of rats to an atmospheric PO2 of 760 mmHg or 635 mmHg for 24 hr caused respective 73% and 61% decreases in total lung aconitase activity. We propose that early inactivation of aconitase and inhibition of the energy-producing and biosynthetic reactions of the citric acid cycle contribute to the sequelae of lung damage and edema seen during exposure to hyperoxia.

Plasma cysteine concentrations in infants with respiratory distress

Because factors that predispose infants to persistent pulmonary hypertension of the newborn (PPHN) may cause oxidant stress, which in turn may increase demands for cysteine and glutathione, we investigated the availability of cysteine and its precursors in PPHN and related disorders. Plasma concentrations of four sulfur-containing and two non-sulfur-containing amino acids were measured by gas chromatography-mass spectrometry in blood from infants with PPHN, both those managed conventionally (PPHN group) and those treated with extracorporeal membrane oxygenation, as well as from infants with hyaline membrane disease. Concentrations also were measured in umbilical venous cord blood samples from a healthy control population, in venous plasma from infants receiving only intravenously administered glucose-containing solutions because they had noncardiopulmonary illnesses ("fasted" group), and from otherwise healthy, orally fed infants ("fed" group). The plasma total cyst(e)ine concentration was markedly lower in the three groups (PPHN, PPHN and extracorpeal membrane oxygenation, and hyaline membrane disease) receiving an elevated inspired oxygen concentration (0.6 to 1.0) than in fasted or fed control infants. In contrast, levels of plasma methionine, the other major sulfur amino acid, were low in the three groups receiving an elevated inspired oxygen concentration, as well as in fasted infants. Glycine and serine, two non-sulfur-containing amino acids, had a pattern similar to that of plasma methionine. Thus infants with PPHN and hyaline membrane disease have low plasma total cyst(e)ine levels, an effect that does not appear to result primarily from nutritional deprivation. We speculate that the role of cysteine in bioactivation of nitric oxide and as a precursor of glutathione may be relevant to the pathogenesis and evolution of PPHN and respiratory distress syndrome. Further studies are needed to determine whether increased demands for cysteine exist in these disorders.

Active compression-decompression CPR improves vital organ perfusion in a dog model of ventricular fibrillation

OBJECTIVES

This study was designed to assess whether a new method of cardiopulmonary resuscitation (CPR), termed active compression-decompression CPR, or ACD-CPR, improves organ perfusion when compared with standard (S) CPR in a dog model of ventricular fibrillation.

BACKGROUND

ACD-CPR has recently been shown to improve hemodynamic and respiratory parameters during cardiac arrest when compared with standard CPR. However, to our knowledge, the effects of ACD-CPR on tissue perfusion have not been investigated.

METHODS

Ventricular fibrillation was induced in eight anesthetized, intubated animals. ACD-CPR and standard CPR were each performed twice in alternating order. All interventions were preceded by 1 min of ventricular fibrillation, in which no CPR was performed, and consisted of 6 min of CPR with either technique during which tissue perfusion was measured. Compressions were performed at 80/min with a 50 percent duty cycle and 175 to 200 N downward force applied to the chest wall for both techniques. Epinephrine was administered at the beginning of each 6-min CPR interval. Hemodynamic monitoring of aortic and right atrial pressure was performed continuously and myocardial, cerebral, and renal blood flows were measured using the radiolabeled microsphere technique at baseline and during all interventions.

RESULTS

Baseline organ perfusion and hemodynamics were similar for all dogs. Baseline left ventricular, brain, and renal blood flows were 62.0 +/- 5.5, 14.1 +/- 2.1, and 476.3 +/- 55.5 ml/min/100 g, respectively (mean +/- SEM). Compared with standard CPR, ACD-CPR resulted in higher global left ventricular (22.5 +/- 6.2 vs 14.1 +/- 4.0 ml/min/100 g, p < 0.01), cerebral (12.0 +/- 2.4 vs 8.5 +/- 2.3 ml/min/100 g, p < 0.01), and renal cortical (27.8 +/- 5.0 vs 17.5 +/- 5.0 ml/min/100 g, p < 0.05) blood flows. Regional flows to the epicardium, endocardium, and midmyocardium as well as to the frontal, parietal, and occipital lobes of the brain were all significantly improved by ACD-CPR. Aortic systolic (61.7 +/- 4.1 vs 49.5 +/- 3.1 mm Hg, p < 0.01), aortic mean (31.6 +/- 2.8 vs 27.2 +/- 2.2 mm Hg, p = 0.001), and myocardial perfusion pressure (12.9 +/- 3.4 vs 10.4 +/- 3.4 mm Hg, ACD-CPR vs standard CPR, p < 0.01) were all higher during ACD-CPR than during standard CPR.

CONCLUSIONS

We conclude that ACD-CPR improves tissue perfusion and systemic hemodynamics compared with standard CPR.

Lung manganese superoxide dismutase increases during cytokine-mediated protection against pulmonary oxygen toxicity in rats

Parenteral injection of the cytokines interleukin-1 and tumor necrosis factor, or of endotoxin (lipopolysaccharide), protects rats against lethal pulmonary oxygen toxicity. To determine the potential importance of manganese superoxide dismutase (MnSOD) in this model, we measured MnSOD mRNA and activity in lung. In addition, we confirmed that increases in activities were related to changes in MnSOD protein, which was measured using an enzyme-linked immunosorbentassay (ELISA) technique. After cytokine or endotoxin administration, increases in lung MnSOD mRNA occurred promptly (4 h), with or without hyperoxic exposure. In parallel, lung MnSOD protein and activity were increased after 24 h, and protein levels remained elevated after 52 h. MnSOD activity and protein levels were closely correlated. Neither lung copper-zinc superoxide dismutase (CuZnSOD) mRNA nor activity increased following administration of cytokines. Small increases in CuZnSOD mRNA, which did not exceed those in beta-actin mRNA, occurred early (4 h) after endotoxin, but CuZnSOD activity was unchanged. Immunohistochemistry was used to demonstrate in which cell types the increase in MnSOD protein occurred after cytokine or endotoxin administration. In agreement with ELISA findings, immunoreactive MnSOD appeared to be increased in lung parenchyma, but not in lung neutrophils, 24 h after cytokine or endotoxin treatment. MnSOD was heavily concentrated in alveolar type II cells. However, the numbers of surfactant protein D-positive (type II) cells in lung sections did not appear to be increased after treatment with cytokines or endotoxin. We conclude that early and sustained increases in endogenous MnSOD, but not CuZnSOD or other antioxidant enzymes, are associated with protection of rat lungs against hyperoxic damage by cytokines or endotoxin.