The effect of tumor necrosis factor-alpha on microvascular permeability in an isolated,perfused lung

This study examines the hypotheses that TNF-alpha causes a dose-dependent increase in the microvascular permeability of ex vivo buffer perfused lungs that is quantitatively similar to that caused by lipopolysaccharide (LPS) or thromboxane A2 (TxA2). We also postulated that TNF-alpha potentiates the effect of interleukin-1beta (IL-1beta) or TxA2 receptor activation on pulmonary microvascular permeability. Lungs harvested from Wistar rats were perfused ex vivo with Krebs-Henseleit buffer containing 0, 10, 100, or 1000 ng/mL recombinant rat TNF-alpha. Twenty minutes later pulmonary microvascular permeability was determined by measuring the capillary filtration coefficient (Kf) using a gravimetric technique. The effect of TNF-alpha (100 ng/mL) on pulmonary Kf was compared with that of lungs exposed to LPS (400 microg/mL; E. coli 0111:B4) or a TxA2 receptor agonist (U-46619; 7 x 10(-8)). In other experiments, perfused lungs were exposed to TNF-alpha plus IL-1beta (1 ng/mL) or TNF-alpha plus U-46619 after which Kf was measured. Exposure of ex vivo buffer perfused lungs to 10-1000 ng/mL TNF-alpha had no effect on Kf whereas LPS and U-46619 was associated with a two- and six-fold increase in Kf, respectively (P < 0.05). The Kf of lungs exposed to TNF-alpha plus IL-1 was similar to that of lungs exposed to TNF-alpha alone. Lastly, the Kf of lungs exposed to TNF-alpha plus U-46619 was not different than that of lungs exposed to U-46619 alone. In conclusion, TNF-alpha at least when administered for a relatively brief period of time does not affect microvascular permeability in an isolated, buffer-perfused lung model.     

Disruption of the Ah receptor gene alters the susceptibility of mice to oxygen-mediated regulation of pulmonary and hepatic cytochromes P4501A expression and exacerbates hyperoxic lung injury

Administration of supplemental oxygen is frequently encountered in infants suffering from pulmonary insufficiency and in adults with acute respiratory distress syndrome. However, hyperoxia causes acute lung damage in experimental animals. In the present study, we investigated the roles of the Ah receptor (AHR) in the modulation of cytochrome P4501A (CYP1A) enzymes and in the development of lung injury by hyperoxia. Adult male wild-type [AHR (+/+)] mice and AHR-deficient animals [AHR (-/-)] were maintained in room air or exposed to hyperoxia (>95% oxygen) for 24 to 72 h, and pulmonary and hepatic expression of CYP1A and lung injury were studied. Hyperoxia caused significant increases in pulmonary and hepatic CYP1A1 activities (ethoxyresorufin O-deethylase) and mRNA levels in wild-type (C57BL/6J) AHR (+/+), but not AHR (-/-) mice, suggesting that AHR-dependent mechanisms contributed to CYP1A1 induction. On the other hand, hyperoxia augmented hepatic CYP1A2 expression in both wild-type and AHR (-/-) animals, suggesting that AHR-independent mechanisms contributed to the CYP1A2 regulation by hyperoxia. AHR (-/-) mice exposed to hyperoxia were more susceptible than wild-type mice to lung injury and inflammation, as indicated by significantly higher lung weight/body weight ratios, increased pulmonary edema, and enhanced neutrophil recruitment into the lungs. In conclusion, our results support the hypothesis that the hyperoxia induces CYP1A1, but not CYP1A2, expression in vivo by AHR-dependent mechanisms, a phenomenon that may mechanistically contribute to the beneficial effects of the AHR in hyperoxic lung injury.     

Potentiation of oxygen-induced lung injury in rats by the mechanism-based cytochrome P-450 inhibitor, 1-aminobenzotriazole

In this investigation, we tested the hypothesis that the cytochrome P-450 (CYP) inhibitor 1-aminobenzotriazole (ABT) alters the susceptibility of rats to hyperoxic lung injury. Male Sprague-Dawley rats were treated i.p. with ABT (66 mg/kg), i.v. with N-benzyl-1-aminobenzotriazole (1 micromol/kg), or the respective vehicles, followed by exposure to >95% oxygen for 24, 48, or 60 h. Pleural effusion volumes were measured as estimates of hyperoxic lung injury, and lung microsomal ethoxyresorufin O-deethylation (EROD) (CYP1A1) activities and CYP1A1 apoprotein levels were determined by Western blotting. ABT-pretreated animals exposed to hyperoxia died between 48 and 60 h, whereas no deaths were observed with up to 60 h of hyperoxia in vehicle-treated animals. In addition, three of four ABT-treated rats exposed to hyperoxia for 48 h showed marked pleural effusions. Exposure of vehicle-treated rats to hyperoxia led to 6.3-fold greater lung EROD activities and greater CYP1A1 apoprotein levels than in air-breathing controls after 48 h, but both declined to control levels by 60 h. Liver CYP1A1/1A2 enzymes displayed responses to hyperoxia and ABT similar to the effects on lung CYP1A1. N-Benzyl-1-aminobenzotriazole markedly inhibited lung microsomal pentoxyresorufin O-depentylation (principally CYP2B1) activities in air-breathing and hyperoxic animals but did not affect lung EROD or liver CYP activities. In conclusion, the results suggest that induction of CYP1A enzymes may serve as an adaptive response to hyperoxia, and that CYP2B1, the major pulmonary CYP isoform, does not contribute significantly to hyperoxic lung injury.     

Targeted lung expression of interleukin-11 enhances murine tolerance of 100% oxygen and diminishes hyperoxia-induced DNA fragmentation.

Acute lung injury is a frequent and treatment-limiting consequence of therapy with hyperoxic gas mixtures. To determine if IL-11 is protective in oxygen toxicity, we compared the effects of 100% O2 on transgenic mice that overexpress IL-11 in the lung and transgene (-) controls. IL-11 markedly enhanced survival in 100% O2 with 100% of transgene (-) animals dying within 72-96 h and > 90% of transgene (+) animals surviving for more than 10 d. This protection was associated with markedly diminished alveolar-capillary protein leak, endothelial and epithelial membrane injury, lipid peroxidation, and pulmonary neutrophil recruitment. Significant differences in copper zinc superoxide dismutase and catalase activities were not noted and the levels of total, reduced and oxidized glutathione were similar in transgene (+) and (-) animals. Glutathione reductase, glutathione peroxidase, and manganese superoxide dismutase activities were slightly higher in transgene (+) as versus (-) mice after 100% O2 exposure, and IL-11 diminished hyperoxia-induced expression of IL-1 and TNF. Hyperoxia also caused cell death with DNA fragmentation in the lungs of transgene (-) animals and IL-11 markedly diminished this cell death response. These studies demonstrate that IL-11 markedly diminishes hyperoxic lung injury. They also demonstrate this protection is associated with small changes in lung antioxidants, diminished hyperoxia-induced IL-1 and TNF production, and markedly suppressed hyperoxia-induced DNA fragmentation.     

Hyperoxia: Influence on Lung Mechanics and Protein Synthesis

We studied the time-course of the influence of in vivo hyperoxia on lung mechanics and on protein synthesis. After 24 h of exposure to greater than 98% O2 at 1 atm there were no alterations in descending pressure-volume curves (air or saline) of lungs excised from O2-exposed rats compared to control rats. After 48 h of hyperoxia there was a decrease in lung compliance.To study protein synthesis, as indicated by L-[U-(24)C] leucine incorporation into protein, lung slices were incubated with L-[U-(14)C]leucine and surface-active material then obtained by ultracentrifugation of lung homogenates. We measured radioactivity in total protein and in protein in the surface-active fraction. There were no alterations in incorporation after 12 h of hypertoxia. After 24 h of hyperoxia there were significant decreases (P<0.05) in L-[U-(14)C]leucine incorporation into total protein and into protein of the surface-active fraction. After 48 h of hyperoxia incorporation into protein of the surface-active fraction was decreased to a greater extent than incorporation into total protein, 63+/-4% and 75+/-5%, respectively, (P<0.025).These studies show that hyperoxia produces a major decrease in protein synthesis, including synthesis of protein in a surface-active fraction, before the onset of any detectable changes in the static compliance of excised lungs.     

Quantitation of nitrotyrosine levels in lung sections of patients and animals with acute lung injury.

Activated alveolar macrophages and epithelial type II cells release both nitric oxide and superoxide which react at near diffusion-limited rate (6.7 x 10(9) M-1s-1) to form peroxynitrite, a potent oxidant capable of damaging the alveolar epithelium and pulmonary surfactant. Peroxynitrite, but not nitric oxide or superoxide, readily nitrates phenolic rings including tyrosine. We quantified the presence of nitrotyrosine in the lungs of patients with the adult respiratory distress syndrome (ARDS) and in the lungs of rats exposed to hyperoxia (100% O2 for 60 h) using quantitative immunofluorescence. Fresh frozen or paraffin-embedded lung sections were incubated with a polyclonal antibody to nitrotyrosine, followed by goat anti-rabbit IgG coupled to rhodamine. Sections from patients with ARDS (n = 5), or from rats exposed to hyperoxia (n = 4), exhibited a twofold increase of specific binding over controls. This binding was blocked by the addition of an excess amount of nitrotyrosine and was absent when the nitrotyrosine antibody was replaced with nonimmune IgG. In additional experiments we demonstrated nitrotyrosine formation in rat lung sections incubated in vitro with peroxynitrite, but not nitric oxide or reactive oxygen species. These data suggest that toxic levels of peroxynitrite may be formed in the lungs of patients with acute lung injury.     

Relative roles of vascular and airspace pressures in ventilator-induced lung injury

OBJECTIVE: To determine whether elevations in pulmonary vascular pressure induced by mechanical ventilation are more injurious than elevations of pulmonary vascular pressure of similar magnitude occurring in the absence of mechanical ventilation. DESIGN: Prospective comparative laboratory investigation. SETTING: University research laboratory. SUBJECTS: Male New Zealand white rabbits. INTERVENTIONS: Three groups of isolated, perfused rabbit lungs were exposed to cyclic elevation of pulmonary artery pressures arising from either intermittent positive pressure mechanical ventilation or from pulsatile perfusion of lungs held motionless by continuous positive airway pressure. Peak, mean, and nadir pulmonary artery pressures and mean airway pressure were matched between groups (35, 27.4 +/- 0.74, and 20.8 +/- 1.5 mm Hg, and 17.7 +/- 0.22 cm H2O, respectively). MEASUREMENTS AND MAIN RESULTS: Lungs exposed to elevated pulmonary artery pressures attributable to intermittent positive pressure mechanical ventilation formed more edema (6.8 +/- 1.3 vs. 1.1 +/- 0.9 g/g of lung), displayed more perivascular (61 +/- 26 vs. 15 +/- 13 vessels) and alveolar hemorrhage (76 +/- 11% vs. 26 +/- 18% of alveoli), and underwent larger fractional declines in static compliance (88 +/- 4.4% vs. 48 +/- 25.1% decline) than lungs exposed to similar peak and mean pulmonary artery pressures in the absence of tidal positive pressure ventilation. CONCLUSIONS: Isolated phasic elevations of pulmonary artery pressure may cause less damage than those occurring during intermittent positive pressure mechanical ventilation, suggesting that cyclic changes in perivascular pressure surrounding extra-alveolar vessels may be important in the genesis of ventilator-induced lung injury.     

Hyperoxia: A Stereologic Ultrastructural Examination of Its Influence on Cytoplasmic Components of the Pulmonary Granular Pneumocyte

We used the technique of lineal analysis to study the influence of 48 h of hyperoxia on cytoplasmic organelles of pulmonary granular pneumocytes with particular reference to their lamellar bodies. We undertook this study because lamellar bodies are considered to be storage granules for pulmonary surfactant and because we had found that hyperoxia decreased [(14)C]leucine incorporation into protein of a surface-active lung fraction.We found that for lamellar bodies the percent cytoplasmic volume was 12.8+/-1.5 (mean+/-SEM) and 8.4+/-2.2, the organelle area (mum(2)) per organelle was 0.98+/-0.13 and 0.62+/-0.10 and the organelle volume (mum(2)) was 0.35+/-0.04 and 0.18+/-0.01, for air- and oxygen-exposed rats, respectively, (P=<0.05). The surface density of the lamellar body membrane was 7.05+/-0.47 and 9.36+/-0.96 (P=<0.05) for air- and oxygen-exposed rats. There were no differences in lamellar body number per cytoplasmic area or per pneumocyte between air- and oxygen-exposed rats. There were no statistical differences in these parameters between mitochondria of air- or oxygen-exposed rats. The surface density of the rough endoplasmic reticulum was the same in both groups.This study indicates that granular pneumocytes of rats exposed to hyperoxia have the same number of lamellar bodies as control rats but the lamellar bodies are smaller. This findings in consistent with the hypothesis that the hyperoxia-induced decrease in protein synthesis by lung represents at least in part a decreased synthesis of the secretory lipoprotein-pulmonary surfactant.     

Characterization of a murine model of endotoxin-induced acute lung injury

Endotoxin-induced microvascular lung injury in mice is a commonly used experimental model of the acute respiratory distress syndrome (ARDS). The present paper aimed to characterize this popular model in a comprehensive and systematic fashion. Male C57bl/6 mice (n = 5) were administered an LD55 dose of E. coli endotoxin (15 mg/kg, i.p.), and lungs were harvested at several time points and evaluated for injury as well as for expression of a variety of inflammatory mediators. Endotoxin induced many features characteristic of acute microvascular lung injury. These included early (1-2 h) expression of inflammatory mediators (IL-1alpha, IL-1beta, IL-4, IL-6, IL-10, TNF-alpha, interferon-alpha, interferon gamma, and MCP-1) and leukocyte accumulation in lung tissue (lung myeloperoxidase activity 18.5 +/- 7.8 U/g tissue, P < 0.05), followed by pulmonary edema (lung water content index 17.4% +/- 2.5%, P < 0.05) and mortality. Histopathological evaluation of lung tissue was compatible with these findings. The characterization of this murine model of endotoxin-induced microvascular injury will facilitate its utilization in ARDS research.     

Attenuation of oxygen-induced abnormal lung maturation in rats by retinoic acid: possible role of cytochrome P4501A enzymes

Supplemental oxygen is frequently used in the treatment of infants having pulmonary insufficiency, but prolonged hyperoxia may contribute to the development of bronchopulmonary dysplasia in these infants. Cytochrome P4501A enzymes have been implicated in hyperoxic lung injury. Retinoic acid (RA) plays a key role in lung development. Here, we tested the hypotheses that newborn rats exposed to a combination of RA and hyperoxia would be less susceptible to lung injury than those exposed to hyperoxia only and that modulation of CYP1A enzymes by RA contribute to the beneficial effects of RA against hyperoxic lung injury. Newborn rats exposed to hyperoxia for 7 days showed higher lung weight/body weight ratios compared with those exposed to RA + hyperoxia. Hyperoxia for 7 days also caused a significant increase in hepatic and pulmonary CYP1A1/1A2 expression compared with air-breathing controls. RA + hyperoxia treatment lowered the expression of these genes. Seven to 30 days after withdrawal of hyperoxia, the animals showed marked induction of hepatic and pulmonary CYP1A1/1A2 expression, but animals that had been given RA + hyperoxia displayed lower expression of these enzymes. On postnatal days 22 or 38, the hyperoxic animals displayed retarded lung alveolarization; however, the RA + hyperoxia-exposed animals showed improved alveolarization. The improved alveolarization in animals given RA + hyperoxia, in conjunction with the attenuation of CYP1A1 and 1A2 expression in these animals, suggests that this phenomenon may play a role in the beneficial effects of RA.     

Effect of endogenous nitric oxide on hyperoxia and tumor necrosis factor-alpha-induced leukosequestration and proinflammatory cytokine release in rat airways

OBJECTIVE: To investigate the effects of endogenous nitric oxide on hyperoxia and tumor necrosis factor-alpha-induced leukosequestration and proinflammatory cytokine release in rat airways. DESIGN: Prospective, randomized, controlled animal study. SETTING: Experimental laboratory. SUBJECTS: Male Sprague-Dawley rats weighing 350-500 g. INTERVENTIONS: The rats were pretreated with N(G)-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg) or saline intravenously 4-6 mins before intratracheal administration of tumor necrosis factor-alpha, 95% oxygen, or both, when the vasopressor effect of L-NAME had reached a plateau. MEASUREMENTS AND MAIN RESULTS: Bronchoalveolar lavage fluid was recovered from the airway of rats after exposure to 95% oxygen and tumor necrosis factor-alpha for 6 hrs under ventilator support. Neutrophils in lavage fluid were isolated and examined for the inducible nitric oxide synthase expression by flow-cytometric assay. Tumor necrosis factor-alpha and interleukin-1 beta in lavage fluid were measured by enzyme-linked immunosorbent assay. The percentage of neutrophils in bronchoalveolar fluid was significantly higher in rats exposed to hyperoxia + tumor necrosis factor-alpha (29.7 +/- 12.5%) compared with rats with hyperoxia (16.3 +/- 1.2%), tumor necrosis factor-alpha (4.2 +/- 1.1%), or room air (5.0 +/- 1.8%) alone (p <.05). Rats exposed to hyperoxia + tumor necrosis factor-alpha had significantly higher concentrations of inducible nitric oxide synthase of neutrophils (350.1 +/- 75.7 mean fluorescence intensity), compared with rats with hyperoxia (64.9 +/- 1.6 mean fluorescence intensity), tumor necrosis factor-alpha (102.6 +/- 15.3 mean fluorescence intensity), or room air (111.2 +/- 25.8 mean fluorescence intensity) alone (p <.05). Rats exposed to hyperoxia + tumor necrosis factor-alpha significantly produced higher concentrations of tumor necrosis factor-alpha and interleukin-1 beta, compared with rats with tumor necrosis factor-alpha, hyperoxia, or room air alone. Hyperoxia + tumor necrosis factor-alpha also significantly increased growth-related oncogene/cytokine-induced neutrophil chemoattractant (GRO/CINC)-1 in bronchoalveolar fluid, compared with those receiving tumor necrosis factor-alpha alone, hyperoxia alone, or room air alone. L-NAME significantly enhanced the percentage of neutrophil recovery and the production of tumor necrosis factor-alpha, interleukin-1 beta, and GRO/CINC-1 in airways compared with the corresponding hyperoxia + tumor necrosis factor-alpha treatment alone. CONCLUSIONS: Endogenous nitric oxide may be an important endogenous inhibitor of hyperoxia + tumor necrosis factor-alpha-induced leukocyte recruitment and subsequently tumor necrosis factor-alpha, interleukin-1 beta, and GRO/CINC-1 release.     

粒细胞-巨噬细胞集落刺激因子联合骨髓间充质干细胞对高氧暴露新生大鼠肺损伤的干预作用

目的 探讨重组鼠粒细胞-巨噬细胞集落刺激因子(granulocyte macrophage-colony stimulating factor,GM-CSF)联合大鼠骨髓来源的间充质干细胞(mesenchymal stem cells,MSCs)对高氧暴露新生大鼠肺损伤的影响.方法 采用贴壁选择法分离、培养、扩增人鼠骨髓来源MSCs,并以4',6二脒基-2-苯吲哚(4',6-diamidino-2.phenylindole,DAPI)进行标记,注射前以PBS按要求剂最予以稀释;3日龄清洁级SD新生大鼠32只,置于95%氧环境下7 d后,随机(随机数字法)分为4组,每组8只;高氧+GM-CSF组+MSCs组(A),高氧+GM-CSF组(B),高氧+MSCs组(C),高氧对照组(D);A,B组大鼠于模型结束后皮下注射GM-GSF 9μg/kg,A组同时还予腹腔注射5×10~4MSCs;C组予模型后腹腔注射5×10~4 MSCs,D组仅注射相同容积的PBS,于注射后72 h(13日龄)处死全部动物,肺组织病理学检测辐射状肺泡计数(radical alveolar counts,RAC);EIASA法检测肺组织匀浆TNF-α,IL-β含量;免疫组化检测肺组织端粒酶逆转录酶(telomerase reverse transcrip tase,TERT)积分;荧光显微镜观察DAPI阳性细胞分布情况.结果 (1)四组在RAC(P<0.01)、肺组织匀浆TNRα(P<0.01),IL-β(P<0.01)水平等方面差异均有统计学意义;与D组相比,A,B,c三组RAC值增加(P<0.05),TNF-α,IL-β水平下降(P<0.05);A组与B、A组与C组差异也均有统汁学意义(P<0.05).(2)四组在TERT积分差异也有统计学意义(P<0.01);A,B组明显增高(P<0.05);而C,D两组间差异均无统计学意义(P>0.05).(3)免疫荧光显微镜下A,C组可见DAPI阳性细胞,分别为(6.23±1.88),(5.10±0.91)(P<0.05).结论 GM-CSF、MSCs对高氧暴露可引致新生大鼠肺损伤均具有保护作用,涉及多种作用机制,联合治疗具有协同作用.     

Azithromycin protects against hyperoxic lung injury in neonatal rats.

Bronchopulmonary dysplasia (BPD) is a pulmonary disorder that causes significant morbidity and mortality in premature infants. BPD is pathologically characterized by inflammation, fibrosis, and mucosal necrosis, which leads to emphysematous coalescence of alveoli. We tested the hypothesis that azithromycin, a macrolide antibiotic, would decrease the severity of lung injury in an animal model of BPD. Sixty-three rat pups were randomly divided equally into control, hyperoxia, and hyperoxia plus azithromycin groups. The hyperoxia groups were exposed to > 95% oxygen from days of life 4 to 14. On day 14, the animals were processed for lung histology and tissue analysis. Lung morphology was assessed by mean linear intercept, a measure of alveolar size, with larger values corresponding to lungs that are more emphysematous. The degree of lung inflammation was assessed by quantifying interleukin-6 (IL-6) from lung homogenate. Fifty pups survived to day 14 (control = 21, hyperoxia = 11, hyperoxia + azithromycin = 18). Mortality was increased in the hyperoxia group versus the control group (p < .0001). Treatment with azithromycin improved survival in animals subjected to hyperoxia (p < .05). Azithromycin significantly decreased lung damage as determined by the mean linear intercept in the hyperoxia groups (p < .001). Finally, azithromycin-treated pups had lower levels of IL-6 in lung homogenate from the hyperoxia groups (p < .05). Azithromycin treatment resulted in improved survival, less emphysematous change, and decreased IL-6 levels in an animal model of BPD.     

The role of endotoxin in protection of adult rats from oxygen-induced lung toxicity.

Adult rats show evidence of severe lung damage after 72h of continuous exposure to hyperoxia (96-98% O2). Treatment of adult rats with a solution of Plasmanate, inadvertently contaminated with endotoxin-producing organisms, or with purified endotoxin itself markedly altered the lung toxicity associated with hyperoxic exposure (survival in treated animals = 110/113 [97%] versus survival in untreated animals = 56/172 [33%]). After 72h of hyperoxic exposure, the endotoxin-treated rats demonstrated significant increases in lung superoxide dismutase, catalase, and glutathione peroxidase activity, a protectant enzyme response not seen in untreated adult rats. The basis for endotoxin's protective effect from hyperoxic lung damage is believed to be related to the stimulated increase in activity of the pulmonary antioxidant enzyme defense system. Some previously known actions of endotoxin are speculated to also serve a protective function by opposing some of the usual detrimental effects of high concentrations of O2 on the lung.     

富氢生理盐水对新生SD大鼠高氧肺损伤白介素-8含量及病理的影响

目的观察富氢生理盐水对新生SD大鼠高氧肺损伤的预防作用。 方法将新生SD大鼠随机分为3组,空气对照组、高氧对照组、高氧＋氢水组。高氧对照组、高氧＋氢水组大鼠置于氧浓度为90%~95%的氧气箱中,高氧＋氢水组每日腹腔注射富氢生理盐水2次（10 ml/kg）,空气对照组、高氧对照组每日腹腔注射生理盐水2次（10 ml/kg）,高氧暴露后第1、3、7、10天分别测量各组白介素（IL）-8水平,并观察肺部病理切片。 结果与空气对照组对比,高氧对照组IL-8含量明显升高,且肺部病理切片出现肺出血、肺泡间隔变薄,并出现大量肺泡融合现象;与高氧对照组比较,高氧+氢水组IL-8含量明显降低,病理图示肺出血、肺泡融合明显减少。 结论富氢生理盐水可一定程度减轻高氧对新生SD大鼠的肺部炎症损伤。     

Protection against oxygen toxicity by intravenous injection of liposome-entrapped catalase and superoxide dismutase

Survival of rats exposed to 100% oxygen was increased from 69.5 +/- 1.5 to 118.1 +/- 9.9 h (mean +/- SEM, P less than 0.05) when liposomes containing catalase and superoxide dismutase were injected intravenously before and during exposure. The increased survival time in 100% oxygen was also associated with significantly less fluid in the pleural cavity. Rats injected with catalase- and superoxide dismutase-containing liposomes, which had increased survival in 100% oxygen, had increased lung wet weight upon autopsy compared with saline-injected controls (2.9 +/- 0.2 g/lung vs. 4.8 +/- 0.4 g/lung, mean +/- SE, P less than 0.05). Intravenous injection of control liposomes along with catalase and superoxide dismutase in the suspending buffer decreased the mean pleural effusion volume 89% and had no significant effect on survival time. Lung catalase and superoxide dismutase activities were increased 3.1- and 1.7-fold, respectively, 2 h after a single intravenous injection of liposomes containing catalase or superoxide dismutase. Superoxide dismutase activity was also significantly greater than controls in both air- and 100% oxygen-exposed rat lungs, when enzyme activity was assayed 24 h after cessation of injection of control and oxygen-exposed rats with enzyme-containing liposomes every 12 h for 36 h. Free superoxide dismutase and catalase injected intravenously in the absence of liposomes did not increase corresponding lung enzyme activities, affect pleural effusion volume, lung wet weight, or extend the mean survival time of rats exposed to 100% oxygen. The clearance of liposome-augmented 125I-labeled catalase from lung and plasma obeyed first order kinetics according to a one-compartment model. When clearance of liposome-augmented catalase activity or radioactivity were the parameters used for pharmacokinetic studies, the half-life of augmented lung catalase was 1.9 and 2.6 h, respectively. The half-life of liposome-entrapped catalase and superoxide dismutase activity in the circulation was 2.5 and 4 h, respectively, while intravenously injected catalase and superoxide dismutase had a circulation half-life of 23 and 6 min, respectively.     

Platelet-activating factor mediates hemodynamic changes and lung injury in endotoxin-treated rats.

Within 20 min after intraperitoneal injection of Salmonella enteritidis endotoxin in rats, blood platelet-activating factor (PAF) increased from 4.3 +/- 1.3 to 13.7 +/- 2.0 ng/ml (P less than 0.01) and lung PAF from 32.3 +/- 4.9 to 312.3 +/- 19.6 ng (P less than 0.01), but not lung lavage PAF. We tested the effect of PAF receptor antagonists, CV 3988 and SRI 63-441, on endotoxin-induced hemodynamic changes and lung vascular injury. Pretreatment with CV 3988 attenuated systemic hypotension, preserved hypoxic pulmonary vasoconstriction, and prolonged survival of awake catheter-implanted endotoxin-treated (20 mg/kg) rats. Pretreatment with SRI 63-441 prevented the depressed hypoxic pulmonary vasoconstriction after low dose (2 mg/kg) endotoxin. Both CV 3988 and SRI 63-441 blocked the increased extravascular accumulation of 125I-albumin and water in perfused lungs isolated from endotoxin-treated rats. We conclude that PAF is produced in the lung during endotoxemia and may be an important mediator of the systemic and pulmonary hemodynamic changes as well as the acute lung vascular injury after endotoxemia.     

高浓度氧对未成年大鼠肺部炎症反应的影响

目的 探讨高浓度氧对未成年大鼠肺部炎症反应的影响.方法 将40只出生21 d的SD大鼠按随机数字表法分为空气对照组及高氧暴露12、24、48、72 h组,每组8只,分别将大鼠置于空气和常压高氧箱(氧含量达92%～94%)中.于相应时间点采用放血法处死大鼠后取肺组织,并行支气管肺泡灌洗.采用硫代巴比妥酸法和比色法分别测定肺组织丙二醛(MDA)含量及髓过氧化物酶(MPO)活性;采用酶联免疫吸附法(ELISA)检测支气管肺泡灌洗液(BALF)中肿瘤坏死因子-α(TNF-α)、白细胞介素-6(IL-6)和IL-10含量;观察肺组织病理改变,并进行肺损伤评分.结果 与空气对照组比较,高氧暴露12 h肺组织MDA含量(mmol/g)即显著升高(2.24±0.43比1.57±0.31),MPO活性(U/g)于高氧暴露24 h显著升高(1.24±0.25比0.69±0.22),并均随高氧暴露时间延长逐渐增加(P<0.05或P<0.01).BALF中TNF-α、IL-6和IL-10含量于高氧暴露24 h时较空气对照组显著增加[TNF-α(ng/L):135.2±44.0比94.5±22.3,IL-6(ng/L):73.1±14.2比55.7±17.3,IL-10(ng/L):67.9±21.7比48.2±7.6,P<0.05或P<0.01];但高氧暴露48 h时较24 h时显著降低(48 h时BALF中TNF-α、IL-6、IL-10分别为105.4±17.0,54.3±17.4,50.9±6.9,均P<0.05).高氧暴露12 h时肺损伤评分(分)即较空气对照组显著升高(4.5±1.4比1.3±0.5),并随高氧暴露时间延长进一步升高(P<0.05或P<0.01).结论 高浓度氧可引起未成年大鼠肺部炎症损伤;炎症细胞因子的出现高峰均在高氧暴露24 h.     

Protection against lung damage in reduced-size liver transplantation

OBJECTIVE: This study examined the effect of ischemic preconditioning on pulmonary damage associated with reduced-size orthotopic liver transplantation (ROLT) and attempted to identify the underlying protective mechanisms. DESIGN: Randomized and controlled animals study. SETTING: Experimental laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Lung damage was evaluated in ROLT with or without preconditioning. Nitric oxide and interleukin (IL)-1 actions were altered pharmacologically. MEASUREMENTS AND MAIN RESULTS: IL-1, tumor necrosis factor (TNF)-alpha, soluble TNF receptors (sTNFR), and inflammatory response in lung were measured after ROLT. Our results indicate the involvement of IL-1 in the lung damage following ROLT. Ischemic preconditioning, mediated by nitric oxide, reduced IL-1 release and protected against lung damage. Nitric oxide synthesis inhibition in the preconditioned group led to increased IL-1 levels and increased lung damage following ROLT, whereas the addition of IL-1 receptor antagonist protected against the injurious effects of nitric oxide inhibition. In addition, nitric oxide pretreatment gave similar results in terms of IL-1alpha and lung protection to those found in preconditioning. The benefits to the lung attributable to IL-1 inhibition might be linked to the effect of this cytokine on sTNFR, an endogenous mechanism that modulates systemic TNF actions. In fact, strategies aimed at inhibiting IL-1 action, including IL-1 receptor antagonist, ischemic preconditioning, and nitric oxide donor, increased systemic sTNFR2 and decreased free TNF, following ROLT. Similarly, nitric oxide synthesis inhibition in the preconditioned group, which increased IL-1alpha and lung damage, reduced systemic sTNFR2 and increased free TNF levels. These injurious effects were avoided when IL-1 action was inhibited. CONCLUSIONS: Ischemic preconditioning and pharmacologic strategies that simulate its benefits protected against lung damage in an experimental model of ROLT. Our results also suggest a potential relationship between nitric oxide, IL-1, and TNF/sTNF in the benefits of preconditioning on the lung damage associated with ROLT.