Surveillance imaging in mantle cell lymphoma in first remission lacks clinical utility

Mantle cell lymphoma (MCL) is a heterogeneous disease with high relapse rates. Limited data guide the use of surveillance imaging following treatment. We constructed a retrospective cohort from two academic institutions of patients with MCL who completed first-line therapy and underwent follow-up for relapse, analyzing the effect of surveillance imaging on survival. Of 217 patients, 102 had documented relapse, with 38 (37%) diagnosed by surveillance imaging and 64 (63%) by other methods. Relapse diagnosis by surveillance imaging had no significant advantage in overall survival from diagnosis date (hazard ratio [HR] = 0.80, p = .39) or relapse date (HR = 0.72, p = .22). Of 801 surveillance images, PET/CT had a positive predictive value (PPV) of 24% and number needed-to-scan/treat (NNT) of 51 to detect one relapse, and CT had a PPV of 49% and NNT of 24. For MCL after first-line therapy, relapse detection by surveillance imaging was not associated with improved survival and lacks clinical benefit.

Chronic alcohol ingestion exacerbates skeletal muscle myopathy in HIV-1 transgenic rats

Background

Separately, chronic alcohol ingestion and HIV-1 infection are associated with severe skeletal muscle derangements, including atrophy and wasting, weakness, and fatigue. One prospective cohort study reported that 41% of HIV-infected patients met the criteria for alcoholism, however; few reports exist on the co-morbid effects of these two disease processes on skeletal muscle homeostasis. Thus, we analyzed the atrophic effects of chronic alcohol ingestion in HIV-1 transgenic rats and identified alterations to several catabolic and anabolic factors.

Findings

Relative plantaris mass, total protein content, and fiber cross-sectional area were reduced in each experimental group compared to healthy, control-fed rats. Alcohol abuse further reduced plantaris fiber area in HIV-1 transgenic rats. Consistent with previous reports, gene levels of myostatin and its receptor activin IIB were not increased in HIV-1 transgenic rat muscle. However, myostatin and activin IIB were induced in healthy and HIV-1 transgenic rats fed alcohol for 12 weeks. Catabolic signaling factors such as TGFβ₁, TNFα, and phospho-p38/total-p38 were increased in all groups compared to controls. There was no effect on IL-6, leukemia inhibitory factor (LIF), cardiotrophin-1 (CT-1), or ciliary neurotrophic factor (CNTF) in control-fed, transgenic rats. However, the co-morbidity of chronic alcohol abuse and HIV-1-related protein expression decreased expression of the two anabolic factors, CT-1 and CNTF.

Conclusions

Consistent with previous reports, alcohol abuse accentuated skeletal muscle atrophy in an animal model of HIV/AIDS. While some catabolic pathways known to drive alcoholic or HIV-1-associated myopathies were also elevated in this co-morbid model (e.g., TGFβ₁), consistent expression patterns were not apparent. Thus, specific alterations to signaling mechanisms such as the induction of the myostatin/activin IIB system or reductions in growth factor signaling via CT-1- and CNTF-dependent mechanisms may play larger roles in the regulation of muscle mass in alcoholic, HIV-1 models.

Chronic ethanol ingestion potentiates TNF-alpha-mediated oxidative stress and apoptosis in rat type II cells

In septic patients, chronic alcohol abuse increases the incidence of the acute respiratory distress syndrome (ARDS). Because alveolar type II cell viability is critical for epithelial repair, our objective was to determine if chronic ethanol ingestion increased the sensitivity of type II cells to the inflammatory mediators upregulated during sepsis. In rats chronically fed ethanol, type II cell mitochondrial GSH was depleted, and tumor necrosis factor-alpha (TNF-alpha)-induced generation of mitochondrial reactive oxygen species (ROS) and apoptosis were potentiated. When added to the ethanol diet, the GSH precursor (-)-2-oxo-4-thiazolidinecarboxylic acid (Procysteine; Pro) but not N-acetylcysteine (NAC) normalized type II cell mitochondrial GSH. Likewise, Pro but not NAC normalized TNF-alpha-induced mitochondrial ROS and apoptosis. This suggested that chronic ethanol ingestion potentiated TNF-alpha-induced apoptosis in type II cells via mitochondrial GSH depletion. This may be particularly relevant in ARDS when type II cell viability is critical to repair of the damaged alveolar epithelium and may have important ramifications for the treatment of ARDS patients with a history of alcohol abuse.

Effect of chronic ethanol ingestion on alveolar type II cell: glutathione and inflammatory mediator-induced apoptosis

BACKGROUND

In septic patients, chronic alcohol abuse increases the incidence of the acute respiratory distress syndrome, a syndrome that requires alveolar type II cell proliferation and differentiation for repair of the damaged alveolar epithelium. We previously showed in a rat model that chronic ethanol ingestion decreased the antioxidant glutathione (GSH) in type II cells and exacerbated endotoxin-mediated acute lung injury. We hypothesized that this GSH depletion by ethanol, particularly mitochondrial GSH, predisposed type II cells to inflammatory mediator-induced apoptosis.

METHODS

Adult male rats were fed the Lieber-DeCarli diet for 2, 6, or 16 weeks. Alveolar type II cells were then isolated and treated with hydrogen peroxide or TNF-alpha. The effect on glutathione (cytosolic and mitochondrial), apoptotic events, and necrosis were determined. In other studies, rats were fed ethanol for 6 weeks and were treated with endotoxin and apoptosis of type II cells determined by the TUNEL method.

RESULTS

Chronic ethanol ingestion alone resulted in a progressive decrease in mitochondrial GSH and a progressive increase in the basal apoptosis and necrosis rate (p < or = 0.05). Furthermore, there was a progressive increase in the sensitivity of the cells to H2O2 or TNF-alpha induced cytochrome c release, caspase 3 activation, apoptosis, and necrosis (p < or = 0.05). Finally, there was a 2-fold increase in apoptotic type II cells in vivo when chronic ethanol ingestion was superimposed on endotoxemia.

CONCLUSIONS

These results suggested that chronic ethanol ingestion resulted in a progressive depletion of mitochondrial GSH and sensitization of type II cells to inflammatory mediator-induced apoptosis and necrosis. These effects may be particularly relevant during acute stress when proliferation and differentiation of these cells are critical to repair of the damaged alveolar epithelium and may have important ramifications for the treatment of acute respiratory distress syndrome in patients with a history of alcohol abuse.

Ethanol ingestion via glutathione depletion impairs alveolar epithelial barrier function in rats

We determined that rats fed a liquid diet containing ethanol (36% of calories) for 6 wk had decreased (P < 0.05) net vectorial fluid transport and increased (P < 0.05) bidirectional protein permeability across the alveolar epithelium in vivo compared with rats fed a control diet. However, both groups increased (P < 0.05) fluid transport in response to epinephrine (10(-5) M) stimulation, indicating that transcellular sodium transport was intact. In parallel, type II cells isolated from ethanol-fed rats and cultured for 8 days formed a more permeable monolayer as reflected by increased (P < 0.05) leak of [(14)C]inulin. However, type II cells from ethanol-fed rats had more sodium-permeant channels in their apical membranes than type II cells isolated from control-fed rats, consistent with the preserved response to epinephrine in vivo. Finally, the alveolar epithelium of ethanol-fed rats supplemented with L-2-oxothiaxolidine-4-carboxylate (Procysteine), a glutathione precursor, had the same (P < 0.05) net vectorial fluid transport and bidirectional protein permeability in vivo and permeability to [(14)C]inulin in vitro as control-fed rats. We conclude that chronic ethanol ingestion via glutathione deficiency increases alveolar epithelial intercellular permeability and, despite preserved or even enhanced transcellular sodium transport, renders the alveolar epithelium susceptible to acute edematous injury.

Mitochondrial glutathione replacement restores surfactant synthesis and secretion in alveolar epithelial cells of ethanol-fed rats

BACKGROUND

Chronic alcohol abuse increases the incidence and severity of acute lung injury in critically ill patients. Previously we determined that ethanol ingestion in rats dramatically decreased alveolar epithelial cellular levels of glutathione and surfactant synthesis and secretion in vitro. Previous studies in alcoholic liver disease suggest that mitochondrial glutathione levels, and not cellular levels per se, are involved in the pathogenesis of ethanol-mediated hepatotoxicity. Therefore, we hypothesized that alveolar epithelial mitochondrial glutathione depletion mediates the observed defects in surfactant synthesis and secretion in ethanol-fed rats.

METHODS

Male Sprague-Dawley rats were fed the Lieber-DeCarli liquid diet with or without ethanol (36% of total calories) for 6 weeks. In some experiments, ethanol-fed rats were then switched to the control diet for 1 week, with or without glutathione supplementation with either N-acetylcysteine (NAC) or procysteine (PRO). Alveolar epithelial type II cells were then isolated and glutathione levels (cytosolic and mitochondrial) and surfactant production (synthesis and secretion) were determined.

RESULTS

Ethanol ingestion decreased (p < 0.05) mitochondrial and cytosolic levels of glutathione, and surfactant synthesis and secretion in isolated type II cells when compared to cells from control-fed rats. NAC treatment restored (p < 0.05) cytosolic but not mitochondrial glutathione levels (p > 0.05), and had no effect (p > 0.05) on surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats. In contrast, PRO treatment restored (p < 0.05) cytosolic and mitochondrial glutathione levels, and normalized (p < 0.05) surfactant synthesis and secretion in type II cells isolated from ethanol-fed rats.

CONCLUSIONS

These results suggest that mitochondrial, and not simply cytosolic, replacement of glutathione is necessary to improve surfactant function in critically ill patients with a history of alcohol abuse.

Diabetic patients have a decreased incidence of acute respiratory distress syndrome

OBJECTIVE

Our ability to predict which critically ill patients will develop acute respiratory distress syndrome (ARDS) is imprecise. Based on the effects of diabetes mellitus on the inflammatory cascade, we hypothesized that a history of diabetes might alter the incidence of ARDS.

DESIGN

A prospective multicenter study.

SETTING

Intensive care units at four university medical centers.

PATIENTS

One hundred thirteen consecutive patients with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients were prospectively followed during their intensive care course for the development of ARDS. A history of diabetes was identified in 28% (32/113) of the patients. In this study, nondiabetics were more likely to develop septic shock from a pulmonary source (48%, 39/81) compared with diabetics (25%, 8/32) (p = .02). Forty-one percent (46/113) of the patients with septic shock developed ARDS. Forty-seven percent of the nondiabetic patients developed ARDS compared with only 25% of those with diabetes (p = .03, relative risk = 0.53, 95% confidence interval = 0.28-0.98). In a multivariate logistic regression analysis, when we adjusted for several variables including source of infection, the effect of diabetes on the incidence of ARDS remained significant (p = .03, odds ratio = 0.33, 95% confidence interval = 0.12-0.90).

CONCLUSIONS

In patients with septic shock, a history of diabetes is associated with a lower risk of developing ARDS compared with nondiabetics.

The effects of chronic alcohol abuse on pulmonary glutathione homeostasis

The incidence and severity of the acute respiratory distress syndrome (ARDS) is increased in critically ill patients with a prior history of chronic alcohol abuse; however, the specific mechanisms responsible for this association are unknown. Recently, we determined that chronic ethanol ingestion in rats decreased the alveolar epithelial lining fluid (ELF) concentration of the antioxidant glutathione (GSH), which is a characteristic finding in patients with ARDS. However, the effects of chronic alcohol abuse on the human alveolar epithelium are essentially unknown. Therefore, as a first step we asked if chronic alcohol abuse, independent of other comorbid conditions, decreases the concentration of GSH in the human lung. We determined that otherwise healthy chronic alcoholics had significantly decreased ELF concentrations of GSH compared with nonalcoholic control subjects (79 micromol [48 to 118 micromol] versus 576 micromol [493 to 728 mmol], p < 0.001). Furthermore, the percentage of GSH in the oxidized form was higher in the chronic alcoholics (9.8% [2.2 to 14.8%] versus 2.8% [0.4 to 4.0%] p = 0.05), indicative of increased utilization of GSH. This is the first report that chronic alcohol abuse alters GSH homeostasis in the human lung, and suggests a potential mechanism by which chronic alcohol abuse predisposes susceptible patients to develop ARDS.

Mitochondrial antioxidant function is a potential mechanism for organ differences in interleukin-1-mediated tolerance to oxidative injury

BACKGROUND

Pretreatment with interleukin-1 (IL-1) induces resistance to lung injury from hyperoxia exposure and to cardiac dysfunction after ischemia-reperfusion in animal models. In contrast, IL-1 pretreatment did not produce tolerance to ischemia-reperfusion injury and did not seem to alter antioxidant enzyme activities in the kidney. Recently, we determined that mitochondria scavenge superoxide anion via a nonenzymatic mechanism and that this newly identified intracellular antioxidant function was inducible in the lung. Based on these observations, we hypothesized that organ differences after IL-1 pretreatment between the lung and the heart, which become tolerant, and the kidney, which does not become tolerant, were a consequence of differential responses in mitochondrial superoxide scavenging.

METHODS

Rats were given IL-1alpha (50 ng intratracheally, 36 hrs before assay) and lung and kidney mitochondria were isolated. Mitochondrial scavenging of superoxide anion was then determined by using an assay that we developed and published previously. We then tested the effects of IL-1 pretreatment on lung mitochondrial scavenging of superoxide after hyperoxia exposure.

RESULTS

We found that intratracheal administration of IL-1 did not affect lung mitochondrial superoxide scavenging but decreased kidney mitochondrial superoxide scavenging by 75%. In addition, IL-1 pretreatment preserved lung mitochondrial superoxide scavenging in rats exposed to hyperoxia (95% O2 for 24 hours) compared with untreated rats exposed to hyperoxia in which lung mitochondrial superoxide scavenging was decreased by more than 50%.

CONCLUSIONS

We conclude that IL-1 pretreatment has divergent effects on mitochondrial antioxidant function in the lung and the kidney and speculate that this may reflect previously unidentified tissue-specific differences in mitochondrial function during systemic inflammation. This study offers new insights into why the lung, but not the kidney, acquires tolerance to subsequent oxidative injury after IL-1 pretreatment.

Ethanol ingestion increases activation of matrix metalloproteinases in rat lungs during acute endotoxemia

Previously we reported that alcohol abuse increases the incidence of the acute respiratory distress syndrome (ARDS) in septic patients, and that chronic ethanol ingestion in rats depletes alveolar epithelial glutathione and increases endotoxin-mediated lung edema. In this study we examined a potential mechanism by which ethanol-induced glutathione depletion could predispose to acute lung injury. We hypothesized that glutathione depletion activates matrix metalloproteinases (MMPs), thereby increasing degradation of the alveolar extracellular matrix (ECM) during sepsis. Ethanol-fed rats (20% vol/vol in water for 6 wk) were given endotoxin (2 mg/kg, intraperitoneally) followed 2 h later by lung isolation and ex vivo perfusion with n-formyl-methionyl-leucyl-phenylalanine (fMLP) (10(-)(7) M). Ethanol ingestion increased (p < 0.05) MMP-9 and MMP-2 activity, as determined by zymography, in the lung tissue and lavage fluid compared with control-fed rats, and increased (p < 0.05) levels of the 7S fragment of type IV collagen in the lung lavage fluid. Ethanol ingestion increased activation, but not production, of the MMP-9 and MMP-2 zymogens. Finally, although concomitant ingestion of N-acetylcysteine had no effect (p > 0.05) on MMP production, it increased (p > 0.05) lung glutathione levels, blocked (p < 0.05) MMP-9 and MMP-2 activation, and decreased (p < 0.05) levels of the 7S fragment of type IV collagen. We conclude that chronic ethanol ingestion, via glutathione depletion, activates MMPs during sepsis, thereby increasing degradation of the alveolar epithelial ECM. Lois M, Brown LAS, Moss IM, Roman J, Guidot DM. Ethanol ingestion increases activation of matrix metalloproteinases in rat lungs during acute endotoxemia.

Endotoxin pretreatment in vivo increases the mitochondrial respiratory capacity in rat hepatocytes

Administration of sublethal doses of endotoxin produces tolerance to subsequent oxidative stress in diverse animal models. Although endotoxin induces antioxidant enzymes, particularly manganous superoxide dismutase (Mn-SOD), the phenomenon of tolerance remains incompletely understood. Previously I determined that endotoxin treatment in rats increased lung mitochondrial respiration-dependent (i.e., independent of Mn-SOD) scavenging of superoxide anion. Because nonenzymatic scavenging of superoxide anion correlates with the mitochondrial membrane energy gradient, I hypothesized that endotoxin increases the mitochondrial transmembrane potential. Endotoxin treatment (500 micrograms/kg intraperitoneally 48 h earlier) increased the hepatocyte mitochondrial transmembrane potential as determined by two separate methods: the intramitochondrial sequestration of triphenylmethylphosphonium (electrical potential or delta psi) and the fluorescence intensity of the hepatocyte mitochondria when stained with rhodamine-123 and examined by confocal microscopy. These findings suggest that endotoxin treatment increased the total mitochondrial membrane potential per hepatocyte. In parallel, endotoxin treatment increased the fluorescence intensity of hepatocyte mitochondria after staining with 10-N-nonyl-acridine orange, a dye that binds to the mitochondrial inner membrane independently of the transmembrane potential. This suggests that an increase in mitochondrial inner membrane mass is responsible for the net increase in inner membrane potential per cell following endotoxin pretreatment. These findings complement previous studies in which endotoxin treatment increased the mitochondrial-specific antioxidant Mn-SOD and support the more recent finding that endotoxin treatment also increased nonenzymatic scavenging of superoxide by lung mitochondria. Taken, together, these observations suggest that mitochondrial biogenesis, and the subsequent increase in both enzymatic and nonenzymatic scavenging of superoxide anion, is a central feature of endotoxin-mediated tolerance to oxidative stress.

Chronic ethanol ingestion impairs alveolar type II cell glutathione homeostasis and function and predisposes to endotoxin-mediated acute edematous lung injury in rats

Chronic alcohol abuse increases the incidence and mortality of the acute respiratory distress syndrome (ARDS) in septic patients. To examine a potential mechanism, we hypothesized that ethanol ingestion predisposes to sepsis-mediated acute lung injury by decreasing alveolar type II cell glutathione homeostasis and function. Lungs isolated from rats fed ethanol (20% in water for >/= 3 wk), compared with lungs from control-fed rats, had greater (P < 0. 05) edematous injury (reflected by nonhydrostatic weight gain) after endotoxin (2 mg/kg intraperitoneally) and subsequent perfusion ex vivo with n-formylmethionylleucylphenylalanine (fMLP, 10(-7) M). Ethanol ingestion decreased (P < 0.05) glutathione levels in the plasma, lung tissue, and lung lavage fluid, and increased (P < 0.05) oxidized glutathione levels in the lung lavage fluid. Furthermore, ethanol ingestion decreased type II cell glutathione content by 95% (P < 0.05), decreased (P < 0.05) type II cell surfactant synthesis and secretion, and decreased (P < 0.05) type II cell viability, in vitro. Finally, treatment with the glutathione precursors S-adenosyl-L-methionine and N-acetylcysteine in the final week of ethanol ingestion significantly reduced lung edema during perfusion ex vivo. We conclude that ethanol ingestion in rats alters alveolar type II cell glutathione levels and function, thereby predisposing the lung to acute edematous injury after endotoxemia. We speculate that chronic alcohol abuse in humans predisposes to ARDS through similar mechanisms.

Modulating phosphatidic acid metabolism decreases oxidative injury in rat lungs

We determined that lisofylline, a potent inhibitor of oleate- and linoleate-containing phosphatidic acid formation (half-maximal inhibitory concentration = 40 nM), prevented oxidant-mediated capillary leak in isolated rat lungs given interleukin-8 (IL-8) intratracheally and perfused with human neutrophils. Lung leak was prevented by lung, but not neutrophil, lisofylline pretreatment. Furthermore, although lisofylline inhibited IL-8-stimulated neutrophil production of phosphatidic acid in vitro, it did not prevent IL-8-stimulated neutrophil adherence, chemotaxis, or intracellular calcium mobilization or N-formyl-Met-Leu-Phe (fMLP)-stimulated oxidant production in vitro. Lisofylline also prevented acute capillary leak in isolated rat lungs perfused only with the oxidant generator purine-xanthine oxidase but did not scavenge O2-(+) or H2O2 in vitro. Finally, lisofylline-mediated protection against lung leak in both models was associated with alterations in lung membrane free fatty acid acyl composition (as reflected by the decreased ratio [linoleate + oleate]/[palmitate]). We conclude that lisofylline prevented both neutrophil-dependent and neutrophil-independent oxidant-induced capillary leak in isolated rat lungs and that protection appears to be mediated by blocking intrinsic lung linoleoyl phosphatidic acid metabolism. We speculate that lisofylline, in addition to our previously reported effects on cytokine signaling by intrapulmonary mononuclear cells, alters intrinsic pulmonary capillary membrane composition and renders this barrier less vulnerable to oxidative damage.

Inhaled NO prevents IL-1-induced neutrophil accumulation and associated acute edema in isolated rat lungs

We determined previously that inhaled nitric oxide (NO) prevented oxidant-dependent capillary leak in isolated rat lungs perfused with human neutrophils and fMLP via a mechanism that was independent of vasodilatation. In the present investigation we determined that inhaled NO (50 ppm) prevented oxidant-dependent acute capillary leak (as reflected by weight gain and Ficoll retention) in isolated rat lungs given human recombinant interleukin-1 alpha (IL-1, 50 ng) intratracheally and perfused with human neutrophils. Inhaled NO also reduced neutrophil migration from the vascular to the airway compartment (as reflected by lung lavage fluid neutrophil numbers and levels of myeloperoxidase), in rats given IL-1 intratracheally and perfused with neutrophils. However, NO did not prevent IL-1-mediated increases in lung lavage levels of cytokine-induced neutrophil chemoattractant (CINC), a potent chemokine produced by alveolar macrophages and other resident cells that mediates IL-1-induced neutrophil infiltration in vivo. We conclude that inhaled NO prevented neutrophil migration and leak caused by intratracheal administration of IL-1 and neutrophil perfusion in isolated rat lungs. We speculate that NO directly inhibits neutrophil responsivity during lung inflammation, a premise that is consistent with the known effects of NO on neutrophil function in vitro. This study provides further evidence that inhaled NO may have important anti-inflammatory as well as vasodilator effects in acute lung injury.

Endotoxin treatment increases lung mitochondrial scavenging of extramitochondrial superoxide in hyperoxia-exposed rats

Mitochondria scavenge extramitochondrial superoxide anion via a respiration-dependent (i.e., non-enzymatic) mechanism. This study reports that hyperoxia exposure ( > 95 % O2 for 48h) reduced (P < 0.05) lung mitochondrial respiration-dependent superoxide scavenging by 56% compared to lung mitochondria from untreated control rats. In comparison, endotoxin treatment (5 micrograms insufflated intratracheally 24 h earlier) increased (P < 0.05) lung mitochondrial respiration-dependent superoxide scavenging by 57% compared to mitochondria from untreated control rats. Further, lung mitochondria from rats given endotoxin 24 h prior to hyperoxia exposure had more than twice the respiration-dependent superoxide scavenging capacity as compared to mitochondria from untreated rats exposed to hyperoxia (P < 0.05). In contrast, endotoxin treatment did not increase (P < 0.05) lung mitochondrial enzymatic (i.e., superoxide dismutase) scavenging activity when corrected for mitochondrial protein content in either hyperoxia-exposed or air-exposed rats. Therefore, hyperoxia exposure decreased, whereas endotoxin treatment increased, respiration-dependent lung mitochondrial scavenging of extramitochondrial superoxide. This recently identified cellular antioxidant defense appears to be an early target in hyperoxia but its induction provides an important component of endotoxin-induced tolerance to hyperoxic lung damage.

In vitro selection of RNA-based irreversible inhibitors of human neutrophil elastase

INTRODUCTION

We describe a new approach to drug discovery which joins the technologies of medicinal and combinatorial chemistry, allowing selection of the most active variant of a lead compound from a large (> 10(12)) pool. A small-molecule covalent inhibitor of elastase was coupled to a randomized pool of RNA, and this assembly was iteratively selected for oligonucleotide sequences that promote the covalent reaction of the inhibitor with the human neutrophil elastase (hNE) active site.

RESULTS

Incorporation of the covalent inhibitor into the randomized pool increases the second-order rate of inactivation of hNE by approximately 15-fold; sequences selected from this pool show an additional approximately 20-fold increase in activity. The relative rate of cross-reaction with another serine protease, cathepsin G, was reduced > 100-fold. Low doses of the inhibitor were found to prevent lung damage inflicted by human neutrophils in an isolated rat lung model of acute respiratory distress syndrome (ARDS).

CONCLUSIONS

This result supports the hypothesis that neutrophil elastase is a significant effector of inflammatory disease. More generally, our findings demonstrate that blending small molecules into combinatorial libraries is a feasible method of drug discovery.

Mitochondrial respiration scavenges extramitochondrial superoxide anion via a nonenzymatic mechanism

We determined that mitochondrial respiration reduced cytosolic oxidant stress in vivo and scavenged extramitochondrial superoxide anion (O2-.) in vitro. First, Saccharomyces cerevisiae deficient in both the cytosolic antioxidant cupro-zinc superoxide dismutase (Cu,Zn-SOD) and electron transport (Rho0 state) grew poorly (P < 0.05) in 21% O2 compared with parent yeast and yeast deficient only in electron transport or Cu,Zn-SOD, whereas anaerobic growth was the same (P > 0.05) in all yeast. Second, isolated yeast and mammalian mitochondria scavenged extramitochondrial O2-. generated by xanthine/xanthine oxidase. Yeast mitochondria scavenged 42% more (P < 0.05) extramitochondrial O2-. during pyruvate/malate-induced respiration than in the resting state. Addition of either antimycin (respiratory chain inhibitor) or FCCP (respiratory chain uncoupler) prevented increased O2-. scavenging. Mitochondria isolated from yeast deficient in the mitochondrial manganous superoxide dismutase (Mn-SOD) increased (P < 0.05) O2-. scavenging 56% during respiration. This apparent SOD activity, expressed in units of SOD activity per milligram of mitochondrial protein, was the same (9 +/- 0.6 vs. 10 +/- 1.0; P = 0.43) as the O2-. scavenging of mitochondria with Mn-SOD, suggesting that respiration-dependent mitochondrial O2-. scavenging was nonenzymatic. Finally, isolated rat liver and lung mitochondria also increased (P < 0.05) O2-. scavenging during respiration. We speculate that respiring mitochondria, via the protonmotive pump, present a polarized, proton-rich surface that enhances nonenzymatic dismutation of extramitochondrial O2-. and that this is a previously unrecognized function of mitochondrial respiration with potential physiological ramifications.

Inhaled nitric oxide prevents neutrophil-mediated, oxygen radical-dependent leak in isolated rat lungs

We found that ventilation with nitric oxide (NO, 50 ppm) significantly (P < 0.05) reduced capillary leak (as reflected by weight gain and Ficoll retention) in isolated rat lungs perfused for 60 min with N-formyl-methionyl-leucyl-phenylalanine (fMLP; 10(-7) M) and human neutrophils (1,300/microliters). Perfusion with previously heated neutrophils (48 degrees C for 10 min, which inactivates NADPH oxidase) did not cause weight gain or Ficoll retention, indicating that neutrophil-derived oxidants mediated lung leak. Although perfusion with fMLP and neutrophils increased mean pulmonary artery pressures (PAP) from 7 to 11.7 +/- 0.5 mmHg at 10 min, lungs perfused with fMLP and neutrophils in which PAP was maintained at 7 mmHg by reducing perfusion flow rates also developed significant (P < 0.05) weight gain and Ficoll retention. Furthermore, inhaled NO did not reduce (P > 0.05) PAP at 10 min and only modestly reduced PAP at 30 and 60 min of perfusion. Our results suggest that oxidative endothelial damage, and not increased hydrostatic pressure, was the primary cause of the capillary leak, and that the protection provided by inhaled NO was not solely a consequence of vasodilation. We conclude that inhaled NO prevents neutrophil-mediated, oxygen radical-dependent leak in isolated rat lungs, and speculate that inhaled NO has anti-inflammatory properties in addition to its ability to cause pulmonary vasodilation.

Phosphatidic acid signaling mediates lung cytokine expression and lung inflammatory injury after hemorrhage in mice

Because phosphatidic acid (PA) pathway signaling may mediate many basic reactions involving cytokine-dependent responses, we investigated the effects of CT1501R, a functional inhibitor of the enzyme lysophosphatidic acid acyltransferase (LPAAT) which converts lysophosphatidic acid (Lyso-PA) to PA. We found that CT1501R treatment not only prevented hypoxia-induced PA increases and lyso-PA consumption in human neutrophils, but also prevented neutrophil chemotaxis and adherence in vitro, and lung injury and lung neutrophil accumulation in mice subjected to hemorrhage and resuscitation. In addition, CT1501R treatment prevented increases in mRNA levels and protein production of a variety of proinflammatory cytokines in multiple lung cell populations after blood loss and resuscitation. Our results indicate the fundamental role of PA metabolism in the development of acute inflammatory lung injury after blood loss.

Interleukin-1 treatment increases neutrophils but not antioxidant enzyme activity or resistance to ischemia-reperfusion injury in rat kidneys

Hearts from rats treated with interleukin-1 (IL-1) intraperitoneally developed a rapid (6 h after IL-1), transient increase in neutrophils, tissue hydrogen peroxide (H2O2), and oxidized glutathione (GSSG) levels, and a subsequent (36 h after IL-1) increase in myocardial glucose-6-phosphate dehydrogenase (G6PD) activity and tolerance to ischemia-reperfusion. In the present investigation, we found that rats treated similarly with IL-1 had increased numbers of neutrophils in their kidneys, which were comparable to myocardial neutrophil increases, but did not develop increased renal tissue H2O2 or GSSG levels acutely (6 h after IL-1) or increased G6PD activity or resistance to ischemia-reperfusion injury later (36 h after IL-1). Our findings indicate that IL-1 treatment increased neutrophil accumulation in rat kidneys but did not increase oxidative stress, antioxidant enzyme activity, or resistance to ischemia-reperfusion injury. We conclude that organ-to-organ differences exist with respect to IL-1-induced tolerance.

Intrinsic 5-lipoxygenase activity is required for neutrophil responsivity

We found that intrinsic neutrophil 5-lipoxygenase activity was necessary for human neutrophil adherence and chemotaxis in vitro and human neutrophil-mediated acute edematous injury in isolated perfused rat lungs given interleukin 8 intratracheally. Treatment with either Zileuton (a specific reversible competitive inhibitor of 5-lipoxygenase) or MK886 (a specific irreversible inhibitor of the 5-lipoxygenase activator protein) prevented stimulated neutrophil adherence and chemotaxis (but not superoxide anion production) in vitro. Zileuton- or MK886-inhibited neutrophil chemotaxis was not restored by adding leukotriene B4 in vitro. Perfusion with neutrophils and either Zileuton or MK886, or with MK886-pretreated neutrophils (without adding MK886 to the perfusate), also prevented lung injury (reflected by lung weight gain and lung Ficoll retention) and perfusate leukotriene B4 increases in isolated rat lungs given interleukin 8 intratracheally. Again, adding leukotriene B4 to the perfusate did not damage interleukin 8-treated isolated lungs perfused with Zileuton-inhibited neutrophils. We conclude that intrinsic 5-lipoxygenase activity is required for neutrophil adherence and chemotaxis and neutrophil-mediated lung injury.

Intratracheal but not intravascular interleukin-1 causes acute edematous injury in isolated neutrophil-perfused rat lungs through an oxygen radical-mediated mechanism

Our goal was to determine whether administration of interleukin-1 (IL-1) intratracheally causes acute edematous injury in isolated rat lungs perfused only with neutrophils and physiologic buffer. We found that administration of native (50 ng) but not heated IL-1 intratracheally rapidly (60 minutes) increased (p < 0.05) lung weights and lung lavage Ficoll concentrations in isolated rat lungs perfused only with purified human neutrophils as compared with lungs given IL-1 intratracheally alone, lungs perfused with neutrophils alone, or untreated control lungs. In contrast, lung weights or lavage Ficoll concentrations did not increase (p > 0.05) when as much as 1 microgram of IL-1 was administered intravascularly with neutrophils. The mechanism of injury appeared to involve neutrophil-derived oxygen radicals, because acute edematous injury did not occur in isolated lungs given IL-1 intratracheally and then perfused with neutrophils previously heated at 48 degrees C for 10 minutes. The latter procedure decreased superoxide anion (O2-.) production but did not alter the adhesion or chemotactic properties of neutrophils in vitro. In parallel, incubation with IL-1 and human neutrophils did not lyse (as measured by chromium 51 release) cultured purified bovine pulmonary artery endothelial cells in vitro. Our results indicate that increased alveolar but not intravascular concentrations of IL-1 initiate a neutrophil-dependent, oxidant-mediated acute edematous lung injury.

Absence of electron transport (Rho 0 state) restores growth of a manganese-superoxide dismutase-deficient Saccharomyces cerevisiae in hyperoxia. Evidence for electron transport as a major source of superoxide generation in vivo

To address the possibility that electron transport is a biologically significant source of superoxide anion (O2-.) during exposure to hyperoxia in vivo, we constructed Saccharomyces cerevisiae strains with selective disruptions in the gene encoding the mitochondrial manganese-containing superoxide dismutase (Mn-SOD) and/or genes encoding proteins critical for complexes in electron transport. We hypothesized that complete absence of electron transport would restore growth in hyperoxia to a Mn-SOD-deficient yeast. We found that yeast deficient in Mn-SOD activity failed to grow normally in hyperoxia (95% O2, 5% CO2). In contrast, Mn-SOD-deficient yeast with complete absence of electron transport (the Rho 0 state) grew normally in hyperoxia. By comparison, Mn-SOD-deficient yeast which were deficient only in cytochrome-c-oxidase, the terminal step in electron transport, had only partially restored growth in hyperoxia. Our results indicate that electron transport is a major source of O2-. in vivo, and that the principal site of this O2-. production is proximal to the cytochrome-c-oxidase complex.

Hypoxia injures endothelial cells by increasing endogenous xanthine oxidase activity

Exposure to decreasing oxygen tensions progressively increased xanthine dehydrogenase (XD) and xanthine oxidase (XO) activities over 48 hr in cultured pulmonary artery endothelial cells (EC) without altering XD/XO ratios. Increases in XD and XO activity in EC induced by hypoxia were associated upon reoxygenation with increased (P less than 0.05) extracellular superoxide anion (O2-.) levels that were inhibited by treatment with XO inhibitors (tungsten, allopurinol) or an anion-channel blocker (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid). EC monolayers subjected to hypoxia/reoxygenation also leaked more preloaded 51Cr, were more adherent to neutrophils, and permitted greater albumin transit than control monolayers. Treatment with tungsten, allopurinol, and/or superoxide dismutase decreased (P less than 0.05) 51Cr release, neutrophil adherence, and albumin transit in EC monolayers exposed to hypoxia/reoxygenation. We conclude that prolonged hypoxia increases both XO and XD activity in EC and may predispose the endothelium to oxidative and inflammatory damage.

Tungsten treatment prevents tumor necrosis factor-induced injury of brain endothelial cells

Exposure to recombinant human tumor necrosis factor-alpha (TNF-alpha) or calcium ionophore (A23187) for 4 h increased (P less than 0.05) lactate dehydrogenase (LDH) release from cultured bovine brain endothelial cells (EC). In contrast, treatment with endotoxin or interleukin-1 did not increase (P greater than 0.05). LDH release from brain EC. Pretreatment with tungsten decreased (P less than 0.05) xanthine oxidase activity in brain EC and decreased (P less than 0.05) LDH release from brain EC following exposure to TNF. Our results suggest that TNF-alpha injures brain microvascular EC and that this effect may be mediated by xanthine oxidase.

Inactivation of xanthine oxidase by hydrogen peroxide involves site-directed hydroxyl radical formation

The mechanism of xanthine oxidase (XO) inactivation by hydrogen peroxide (H2O2) and its biologic significance are unclear. We found that addition of increasing concentrations of H2O2 progressively decreased xanthine oxidase activity in the presence but not the absence of xanthine in vitro. Inactivation of XO by H2O2 was also enhanced by anaerobic reduction of XO by xanthine. Inactivation of XO by H2O2 was accompanied by production of hydroxyl radical (.OH), measured as formation of formaldehyde from dimethylsulfoxide (DMSO). In contrast, addition of H2O2 to deflavo XO did not produce .OH. Inactivation of XO by H2O2 was decreased by simultaneous addition of the .OH scavenger, DMSO. However, inactivation of XO by H2O2 and formation of .OH were not decreased following addition of the metal chelator. DETAPAC, and/or the O2 scavenger, superoxide dismutase. The results suggest that inactivation of XO by H2O2 occurs by production of .OH following direct reduction of H2O2 by XO at the flavin site.