Lipopolysaccharide-induced pulmonary vascular sequestration of polymorphonuclear leukocytes is complement independent

Lipopolysaccharide (LPS) injected intravenously produces leukopenia and sequestration of polymorphonuclear leukocytes (PMN) in the pulmonary vascular bed. To evaluate the role of complement in this process, we used C5-sufficient (B10.D2/nSn) and C5-deficient (B10.D2/oSn) mice and Sprague-Dawley rats depleted of complement with Naja naja cobra venom factor (CVF). We found a comparable increase in the number of PMN in lung tissue of C5-sufficient and C5-deficient mice given Escherichia coli LPS (0127:B8, 3 mg/kg), revealing that LPS acts independently of C5 and its biologically active fragments. Intravenous injection of LPS (3 mg/kg) into rats caused significant intravascular complement activation as assessed by serum CH50 and resulted in an almost 10-fold increase in numbers of PMN in lung tissue. Pretreatment of rats with CVF (50 U) did not reduce LPS-induced PMN sequestration, suggesting that the process is independent of C3. As reported previously, we found large numbers of PMN in bronchoalveolar lavage samples of 24 h after injection of LPS (3 mg/kg). Complement depletion did not prevent LPS-induced migration of PMN. No PMN migration occurred 2, 6, 12, 24, or 48 h after injection of CVF alone, indicating that complement activation is not sufficient to cause PMN migration. In contrast to our findings in rats, no PMN migrated into airspaces of C5-sufficient and C5-deficient mice 24 or 48 h after injection of LPS (3 to 20 mg/kg).     

Polymorphonuclear leukocyte participation in acute oleic-acid-induced lung injury

The purpose of this study was twofold: (1) to analyze the cellular components of bronchoalveolar lavage fluid throughout the development of oleic-acid-induced lung injury in the rat and (2) to investigate the role of polymorphonuclear leukocytes (PMN) in the pathogenesis of this disease. Animals were killed and lavaged at various times after a single intravenously administered injection of oleic acid. The results demonstrate that a significant influx of inflammatory cells appear in the lavage fluid as early as 4 h after the administration of oleic acid. The PMN are the first cells to appear, and significant levels persist through Day 5 after injection. There is a transient yet significant influx of lymphocytes between 3 and 7 days after treatment. Rats treated with oleic acid displayed significant increases in lung vascular permeability over control animals at 1 and 4 h after injection. Depletion of PMN by anti-PMN serum significantly decreased the permeability changes induced by oleic acid. Treatment of oleic-acid-injected animals with catalase, superoxide dismutase, or dimethyl sulfoxide failed to inhibit lung permeability changes induced in this model.     

Comparative study of peritoneal macrophage functions in mice receiving lethal and non-lethal doses of LPS

In previous studies, we have observed changes in several functions of peritoneal macrophages from female BALB/c mice with lethal endotoxic shock caused by intraperitoneal injection of Escherichia coli O55:B5 lipopolysaccharide (LPS; 100 mg/kg), which were associated with a high production of superoxide anion and tumor necrosis factor alpha (TNF-alpha). In the present work, both a lethal dose (250 mg/kg) and a non-lethal dose (100 mg/kg) of LPS were used in female Swiss mice. In peritoneal macrophages, the following functions were studied at 2, 4, 12 and 24 h after LPS injection: adherence to substrate, chemotaxis, ingestion of particles, and superoxide anion and TNF-alpha production. In both groups, the results showed a stimulation of adherence, ingestion and superoxide production as well as a decrease of chemotaxis, whereas TNF-alpha could not be detected in either of the two groups. These effects were more evident with the 250 mg/kg dose, especially as regards superoxide anion production, which was higher in the animals treated with a lethal dose of LPS.     

Lipopolysaccharide-induced lung injury in mice. I. Concomitant evaluation of inflammatory cells and haemorrhagic lung damage

Intratracheal instillation of lipopolysaccharide (LPS) induces an inflammatory response characterized by infiltration of polymorphonuclear neutrophils (PMNs) into the extracellular matrix and by the release of mediators that play a fundamental role in lung damage. In the present study, we developed a mouse model which allows correlation of the inflammatory response and haemorrhagic tissue injury in the same animal. In particular, the different steps of the inflammatory response and tissue damage were evaluated by the analysis of three parameters: myeloperoxidase (MPO) activity in the parenchyma, reflecting PMNs accumulation into the lung, inflammatory cells count in the bronchoalveolar lavage fluid (BALF), reflecting their extravasation, and total haemoglobin estimation in BALF, a marker of haemorrhagic tissue damage consequent to PMNs degranulation. In our experimental conditions, intra-tracheal administration of 10 microg/mouse of LPS evoked an increase of MPO activity in the lung at 4 h (131%) and 6 h (147%) from endotoxin challenge. A significant increase of PMNs in the BALF was noticed at these times with a plateau between the 12nd and 24th h. PMN accumulation produced a time-dependent haemorrhagic lung damage until 24 h after LPS injection (4 h: +38%; 6 h: +23%; 12 h: +44%; 24 h: +129% increase of haemoglobin concentration in the BALF vs. control). Lung injury was also assessed histopathologically. Twenty-four hours after the challenge, diffuse alveolar haemorrhage, as well as PMN recruitment in the interstitium and alveolus were observed in the LPS group. This model was pharmacologically characterized by pretreatment of LPS-treated mice with antiinflammatory drugs acting on different steps of the . We demonstrated that: a) betamethasone (1, 3, 10, 30 mg/kg p.o.) reduced in a dose-dependent manner the MPO activity, the number of inflammatory cells and, at the same time, lung injury; b) pentoxifylline, a TNFalpha production inhibitor (200 mg/kg i.p.), inhibited PMN extravasation and lung haemorrhage but it was not able to reduce MPO activity in the lung; c) L-680,833, an anti-elastase compound (30 mg/kg po), decreased significantly only the haemorrhagic lung damage; d) indomethacin, a non steroidal antiinflammatory drug (5 mg/kg p.o.), did not show any effect on any of the parameters considered. In conclusion, our in vivo mouse model is a practical alternative to animal models of ARDS (Adult Respiratory Distress Syndrome) recently described and it permits to dissect and to characterize the different steps of PMNs infiltration and, at the same time, the damage caused by their activation.     

急性肺损伤大鼠多形核白细胞L选择素变化及其在肺内扣押中的作用

目的 探讨急性肺损伤(ALI)大鼠循环血多形核白细胞(PMN)L选择素表达的变化及其于肺内扣押中的作用.方法 通过静脉注射内毒素(5 mg/kg)复制大鼠ALI模型,56只大鼠随机分为7组,每组8只.分别为(1)内毒素5 min组;(2)内毒素15 min组;(3)内毒素30 min组;(4)内毒素60 min组;(5)fucodin干预5 min组;(6)Fucodin干预15 min组静脉注射fucodin 5 mg/kg后,立即静脉注射内毒素5 mg/kg;(7)正常对照组静脉注射等量生理盐水替代内毒素.用免疫荧光间接法和流式细胞仪检测大鼠ALI过程中PMN L选择素蛋白表达的变化;用髓过氧化酶(MPO)分析法及组织学检查定量ALI过程中PMN于肺内的扣押量.结果 (1)PMN L 选择素的表达于静脉注射内毒素后5 min为7.8±1.6,与对照组(10.5±2.1)比较差异有显著性(P<0.05),静脉注射内毒素后15 min(2.9±0.5)、30 min(3.5±0.7)和60 min(4.9±0.7)与对照组比较差异更具显著性(P<0.01).(2)大鼠肺组织MPO活力于静脉注射内毒素后5 min [(0.359±0.074) U/mg肺组织]、15 min [(0.490±0.069) U/mg肺组织]、30 min [(0.565±0.111 ) U/mg肺组织]、60 min [(0.710±0.112) U/mg肺组织]与对照组[(0.069±0.011) U/mg肺组织]比较差异有显著性(P<0.01);fucodin干预5 min组[(0.391±0.071)U/mg肺组织]和对应时相点的内毒素组[(0.359±0.074) U/mg肺组织]比较差异无显著性,fucodin干预15 min组[(0.396±0.061) U/mg肺组织]和对应时相点的内毒素组[(0.490±0.069) U/mg肺组织]比较差异有显著性(P<0.05).结论 (1)正常状态下L选择素在PMN表面呈结构性表达,内毒素致伤后PMN L选择素表达迅速减少,伤后15 min时最低,其后呈回升趋势.(2)内毒素性ALI大鼠PMN肺内的早期扣押可能是L选择素非依赖性的,但L选择素对维持肺PMN的持续扣押仍然是重要的.     

粒细胞集落刺激因子在急性肺损伤发病机制中作用的初步 …

目的：探讨粒细胞集落刺激因子（Ｇ－ＣＳＦ）在急性肺损伤（ＡＬＩ）发病过程中的作用。方法通过大鼠腹腔内注射内毒素建立ＡＬＩ模型。建立３０只大鼠分为５组：正常对照组及内毒素注射后２ｈ、４ｈ、６ｈ、８ｈ４个时相组,采用逆转录多聚酶链反应（ＲＴ－ＰＣＲ）的方法检测肺组织内Ｇ－ＣＳＦ ｍＲＮＡ表达水平及相关指标。结果内毒素腹腔注射２ｈ组肺内Ｇ－ＣＳＦ ｍＲＮＡ表达明显高于正常对照组,４ｈ组达到最高值,２ｈ组     

Lipopolysaccharide Tolerance in Relation to Intrabronchial Influx of Neutrophils in the Rat

Lipopolysaccharide (LPS) is a potent chemotactic component for polymorphonuclear leukocytes (PMN, neutrophils). Since LPS tolerance was first described, many studies have been reported about the hyporesponsiveness in vitro corresponding to attenuating production of proinflammatory cytokines. We hypothesized that in vivo daily exposure to LPS stimuli impairs neutrophil accumulation in the rat airway. Interleukin 8 (IL-8) and/or CXC-chemokine, a neutrophil chemoattractant and activating cytokine, have been implicated as proinflammatory mediators in gram-negative respiratory tract infections. It is possible that the tolerance to LPS has occurred in relation to this chemoattractant cytokine production. To settle this issue, we examined whether the neutrophil count in bronchoalveolar lavage fluid (BALF) decreases after daily inhalation of Pseudomonas aeruginosa LPS into the rat airway. Repeated inhalation of LPS into the airway resulted in reduction in neutrophil recruitment. We measured rat CXC-chemokine (rat GRO/CINC1) levels in recovered BALF. There were noted reductions of rat GRO corresponding to the diminished neutrophil trafficking. We also confirmed that the HLA-DR positive lymphocyte number in BALF gradually increased after daily inhalation of LPS. These results suggest that continuous stimuli of LPS mitigate the accumulation of inflammatory cells in the airway by reducing chemokine production with a consequent change in the appearance of local inflammation to a chronic state. Accepted for publication 25 May 2000     

Effects of Ventilation on Hyaluronan and Protein Concentration in Pleural Liquid of Anesthetized and Conscious Rabbits

The hypothesis of this study is that pleural lubrication is enhanced by hyaluronan acting as a boundary lubricant in pleural liquid and by pleural filtration as reflected in changes in protein concentration with ventilation. Anesthetized rabbits were injected intravenously with Evans blue dye and ventilated with 100% O₂ at either of two levels of ventilation for 6 h. Postmortem values of hyaluronan, total protein, and Evans blue-dyed albumin (EBA) concentrations in pleural liquid were greater at the higher ventilation, consistent with increases in boundary lubrication, pleural membrane permeability, and pleural filtration. To determine whether these effects were caused by hyperoxia or anesthesia, conscious rabbits were ventilated with either 3% CO₂ or room air in a box for 6, 12, or 24 h. Similar to the anesthetized rabbits, pleural liquid hyaluronan concentration after 24 h was higher in the conscious rabbits with the hypercapnic-induced greater ventilation. By contrast, the time course of total protein and EBA in pleural liquid was similar in both groups of conscious rabbits, indicating no effect of ventilation on pleural permeability. The increase in pleural liquid hyaluronan concentration might be the result of mesothelial cell stimulation by a ventilation-induced increase in pleural liquid shear stress. Accepted for publication: 30 January 1998     

内毒素致大鼠急性肺损伤模型的建立

目的建立经尾静脉注射脂多糖致大鼠急性肺损伤动物模型。方法大鼠尾静脉注射5 mg/kg脂多糖,造成急性肺损伤,于注射脂多糖2 h后,分别测定动脉血气分析、血清蛋白含量、肺泡灌洗液中蛋白、细胞间粘附分子-1的含量、肿瘤坏死因子-α、白介素-8,计算肺湿/干重比、肺通透指数,观察肺组织病理学改变。实验设置生理盐水对照组。结果肺组织病理切片提示脂多糖组肺间质大量炎性细胞浸润,出血、水肿,而生理盐水组肺组织损伤轻微。对照组肺湿/干重比、肺泡通透指数、肺泡灌洗液中中性粒细胞比均显著低于脂多糖组(P<0.05),而动脉血氧分压则高于脂多糖组(P<0.05)。脂多糖组肺泡灌洗液中肿瘤坏死因子-α、细胞间粘附分子-1、白介素-8浓度高于对照组(P<0.05)。结论此模型基本符合急性肺损伤诊断标准及动物模型的考察指标符合临床,说明本模型是成功可靠的。     

Apparent effect of catalase on airway edema in guinea pigs. Role of endotoxin contamination

The airway edema that develops in guinea pigs after exposure to toluene diisocyanate (TDI) requires the presence of polymorphonuclear leukocytes (PMN). To determine whether this airway edema is mediated by the release of hydrogen peroxide from PMN, we treated animals intravenously with catalase bound to polyethylene glycol and examined the extravasation of Evans blue dye into the tracheal wall after exposure to air or 3 ppm TDI for 1 h. Catalase (25,000, 100,000, and 300,000 IU/kg) caused a dose-dependent inhibition of the TDI-induced increase in dye extravasation. However, treatment with catalase, inactivated at the peroxide binding site with 3-aminotriazole, inhibited dye extravasation after exposure to TDI as effectively as the equimolar 100,000 IU/kg dose of active catalase. Injection of polyethylene glycol alone was without effect. Dose-dependent decreases in extravascular migration of PMN and in circulating PMN also were noted after catalase treatment. These results suggest that the catalase preparations used in these studies inhibited the PMN-dependent airway edema by an effect other than hydrogen peroxide scavenging. Examination of this and other commercially available catalase preparations revealed trace concentrations of endotoxin at levels that could be responsible for the observed effects on PMN function. Treatment of animals with doses of Escherichia coli endotoxin similar to those inadvertantly administered to the catalase-treated groups (0.1 ng/kg to 100 ng/kg, intravenously) inhibited TDI-induced extravasation of Evans blue dye in a dose-dependent manner. These results suggest that contaminating endotoxin may contribute to some of the protective effects of preparations of catalase observed in previous studies of vascular permeability.     

气体信号分子硫化氢对大鼠急性肺损伤的保护作用

目的 观察急性肺损伤(acute lung injury,ALI)时,内源性硫化氢(hydrogen sulfide,H2S)生成的变化以及应用外源性H2S后对ALI的影响.方法 Sprague-Dawley大鼠随机分为对照组、脂多糖(lipopolysaccharide,LPS)组、硫氢化钠(sodium hydrosulfide,NaHS)+LPS组以及NaHS+生理盐水(normal saline,NS)组(n均=12).LPS组大鼠每只气管内滴注LPS(100 μg/200 μl),对照组滴注等量NS.NaHS+LPS组大鼠滴注LPS前10 min腹腔注射NaHS(28 μmol/kg).各组均于滴注后4 h和8 h测定大鼠肺系数变化,光镜下观察肺组织形态学改变,检测肺组织中氧化性损伤产物丙二醛(malondialdehyde,MDA)含量以及支气管肺泡灌洗液(bronchoalveolar lavage fluid,BALF)中蛋白含量及中性粒细胞(polymorphonuclear neutrophil,PMN)计数的改变,并测定血浆中的H2S含量.结果 与对照组相比,LPS滴注4 h和8 h后,大鼠肺系数、肺组织中MDA含量、BALF中PMN数目及蛋白含量均明显升高(P值均＜0.01);而血浆中H2S含量则明显降低(P值均＜0.01);光镜下见肺泡萎陷、甚至结构消失,肺泡腔及间质弥漫性炎细胞浸润,部分肺泡代偿性气肿,且其病理改变随LPS滴注时间的延长而逐渐加重.与相应时间点的LPS组比较.NaHS+LPS组大鼠肺系数、肺组织中MDA含量、BALF中PMN数目及蛋白含量明显降低,血浆中H2S含量则明显升高(P值均＜0.01);光镜下肺间质和肺泡中炎细胞浸润程度明显减轻.结论 内源性H2S生成不足参与了ALI的形成过程,外源性H2S可以部分拮抗ALI,对肺组织起到细胞保护作用.     

Reactive oxygen species and acute modulation of albumin microvascular leakage in the microcirculation of diabetic rats in vivo

Endothelial cells have been reported to generate reactive oxygen species such as the superoxide anion, hydrogen peroxide, and the hydroxyl radical. The aim of this work was to evaluate the role of reactive oxygen species in diabetes-induced changes in vascular permeability. Intravital videomicroscopy was used to study albumin microvascular leakage in the cremaster muscle. The extravasation of a fluorescent macromolecular tracer (FITC-albumin) was measured for 1 h and, after computer-aided image analysis, was expressed as variations of normalized gray levels (arbitrary units). The extravasation of the macromolecular tracer was greater in diabetic rats (5.28 +/- 1.29 vs. 1.96 +/- 0.41 AU at 1 h in diabetic and control rats, respectively). Administration of superoxide dismutase (SOD), which dismutates.O(-)(2) to H(2)O(2), and of catalase which reacts with H(2)O(2) to form H(2)O and molecular oxygen failed to inhibit the increased extravasation of the macromolecular tracer when administered separately. However, a significant inhibition of diabetic increase in albumin extravasation was found when these 2 drugs were administered simultaneously, and in this case, the extravasation of the macromolecular tracer at 1 h was similar in diabetic rats (2.11 +/- 0.61 AU) and normoglycemic rats (1.43 +/- 0. 48 AU). No difference was found in adherent leukocytes or in the leukocyte rolling flux between diabetic and normoglycemic rats. We conclude that reactive oxygen species are responsible for an increase in microvascular permeability likely via leukocyte-independent mechanisms.     

Effect of Silica Inhalation on the Pulmonary Clearance of a Bacterial Pathogen in Fischer 344 Rats

Silica inhalation predisposes workers to bacterial infection and impairments in pulmonary defense function. In this study, we evaluated the effect of pre-exposure to silica on lung defense mechanisms by use of a rat pulmonary Listeria monocytogenes infection model. Male Fischer 344 rats were exposed by inhalation to filtered air or silica (15 mg/m³× 6 h/day × 5 days/wk). After 21 or 59 days of silica exposure, the rats were inoculated intratracheally with 5 × 10³ L. monocytogenes. At 0 (noninfected controls), 3, and 7 days after infection, the left lungs were removed, homogenized, and the number of viable L. monocytogenes was counted after an overnight culture at 37° C. Bronchoalveolar lavage (BAL) was performed on the right lungs. Alveolar macrophages (AM) were collected, and the AM production of chemiluminescence (CL), an index of reactive oxygen species generation, was measured. The number of lavagable neutrophils (PMNs) and acellular BAL lactate dehydrogenase (LDH) activity were determined as indices of inflammation and injury, respectively. Pre-exposure to silica for 59 days caused substantial increases in PMN number and LDH activity compared with the air controls, whereas silica inhalation for both 21 and 59 days significantly enhanced the pulmonary clearance of L. monocytogenes compared with air controls. Dramatic elevations were also observed in zymosan- and phorbol myristate acetate (PMA)–stimulated CL production by lung phagocytes recovered from rats pre-exposed to silica for 59 days. These results demonstrate that short-term exposure to inhaled silica particles activates lung phagocytes, as evidenced by increases in reactive oxygen species. This up-regulation in the production of antimicrobial oxidants is likely responsible for the enhancement in pulmonary clearance of L. monocytogenes observed with short-term silica inhalation. Accepted for publication: 2 October 2000     

Ebselen Decreases Ozone-Induced Pulmonary Inflammation in Rats

We studied the effects of ebselen on rat lung inflammatory responses against ozone exposure. Rats were treated with ebselen every 12 h from 1 h before a single 4-h exposure to 2 ppm ozone. Treatment with ebselen (10 mg/kg) significantly decreased pulmonary inflammation as indicated by the albumin concentration and the number of neutrophils in the bronchoalveolar lavage fluid 18 h after the ozone exposure. Although treatment with ebselen did not alter the macrophage expression of inducible nitric oxide synthase after the ozone exposure, it did markedly inhibit the nitration reaction of tyrosine residues, suggesting that ebselen scavenges peroxynitrite during ozone-induced pulmonary inflammation. Treatment with ebselen also enhanced the pulmonary expression of both copper, zinc, and manganous superoxide dismutases at the same time point. These enzymes may also contribute to a decrease in the formation of peroxynitrite by lowering the concentration of superoxide. Thus, ebselen represents a useful compound for protecting against certain acute lung injuries by modulating the oxidant-related inflammatory process. Accepted for publication: 8 May 2000     

Nitric oxide modulates pancreatic edema formation in rat caerulein-induced pancreatitis

This study was designed to investigate the role of nitric oxide (NO) in the formation of pancreatic edema in caerulein-induced pancreatitis in rats. Pancreatitis was produced by two intraperitoneal injections of caerulein, and plasma amylase concentration, pancreatic edema index (pancreatic wet weight/body weight), and Evans blue extravasation (as a measure of vascular permeability) were evaluated 5h after the first injection. Four doses (1, 2.5, 5, and 10 mg/kg) of N^G-nitro-L-arginine (l-NNA), an NO synthase inhibitor, were subcutaneously administered at −0.5, 0.5, 1.5, 2.5, and 3.5h after the first injection of caerulein.l-NNA significantly lowered the edema index, the wet/dry weight ratio of the pancreas, and Evans blue extravasation in the rats with pancreatitis. The maximal effect was obtained byl-NNA at a dose of 2.5 mg/kg; this inhibited the increase in pancreatic edema formation from the control value by 60%–70%. Intraperitoneal injections (20 mg/kg, five times) ofl-arginine, a substrate for NO production, partly reversed thel-NNA-induced inhibition of pancreatic edema formation, butd-arginine, an enantiomer ofl-arginine, did not show any effect. Plasma amylase concentrations were not significantly affected by any dose of L-NNA, nor were they affected byl- ord-arginine. These findings strongly suggest that endogenous NO plays an important role in the formation of pancreatic edema in caerulein-induced pancreatitis in rats, probably by increasing vascular permeability and protein extravasation.     

Increased adrenomedullin expression in lungs in endotoxaemia

Adrenomedullin (AM) is a peptide involved in cardiovascular homeostasis and in inflammation. We examined its expression in a rat model of endotoxaemia. Male Sprague-Dawley rats received intraperitoneal injection of 5 or 10 mg/kg lipopolysaccharide (LPS), or saline as control. Rats were killed at 1, 3, 6, 12 and 24 h after injection. LPS at 5 mg/kg, but not saline, increased plasma AM significantly at 3 h. At 10 mg/kg, plasma AM was raised at 3, 6 and 12 h. Immunoreactive AM concentration in lung increased after 5 or 10 mg/kg LPS, but not saline. PreproAM mRNA level in lung was significantly increased at 3 and 6 h. In conclusion, endotoxin stimulates the expression of AM in the lungs and increases its circulatory concentration. AM may be involved in the systemic response to sepsis.     

Protective effects of sphingosine 1-phosphate in murine endotoxin-induced inflammatory lung injury

Our prior in vitro studies indicate that sphingosine 1-phosphate (S1P), a phospholipid angiogenic factor, produces endothelial cell barrier enhancement through ligation of endothelial differentiation gene family receptors. We hypothesized that S1P may reduce the vascular leak associated with acute lung injury and found that S1P infusion produced a rapid and significant reduction in lung weight gain (more than 50%) in the isolated perfused murine lung. The effect of S1P was next assessed in a murine model of LPS-mediated microvascular permeability and inflammation with marked increases in parameters of lung injury at both 6 and 24 hours after intratracheal LPS. Each parameter assessed was significantly reduced by intravenous S1P (1 microM final) and in selected experiments by the S1P analogue FTY720 (0.1 mg/kg, intraperitoneally) delivered 1 hour after LPS. S1P produced an approximately 40-50% reduction in LPS-mediated extravasation of Evans blue dye albumin, bronchoalveolar lavage protein content, and lung tissue myeloperoxidase activity (reflecting phagocyte infiltration). Consistent with systemic barrier enhancement, S1P significantly decreased Evans blue dye albumin extravasation and myeloperoxidase content in renal tissues of LPS-treated mice. These studies indicate that S1P significantly decreases pulmonary/renal vascular leakage and inflammation in a murine model of LPS-mediated acute lung injury and may represent a novel therapeutic strategy for vascular barrier dysfunction.     

Modulation by pentobarbital of neutrophil responses to inhaled E. coli endotoxin in sheep: role of lung epithelium.

Neutrophils (PMNs) are implicated in the pathogenesis of acute respiratory distress syndrome (ARDS). The role of the epithelium in the modulation of PMN migration within the lungs was examined. Epithelial integrity and PMN concentrations in the lung air spaces and lymph were measured in sheep anaesthetized with either halothane (1-2.5%) or intravenous pentobarbital (12+/-4 mg x kg(-1) x h(-1)). Ventilation with an aerosol containing 25 mg Escherichia Coli endotoxin (lipopolysaccharide; LPS) effected neutrophil recruitment to the air spaces. Lymphatic clearance of aerosolized 99mTc-DTPA provided an index of epithelial integrity. Three hours after the deposition of LPS, the lung lining fluid of sheep anaesthetized with halothane (n=7) had 4.9+/-3.2x10(6) PMN.mL(-1), but the lung lymph had almost no PMNs (3+/-8%). Sheep anaesthetized with pentobarbital (n=6) had fewer PMNs in the air spaces (2.4+/-1.2X10(6) mL(-1)) and more PMNs in the lung lymph (30+/-20%). Control sheep (n=5) that received no LPS had almost no PMNs in the airspaces or lung lymph, regardless of the anaesthesia. Three additional sheep that remained awake after receiving LPS also had no PMNs in the lung lymph. The PMN fraction in the lung lymph correlated well with the extra-alveolar epithelial permeability measured by lymphatic clearance of aerosolized diethylenetriamine penta-acetic acid (r=0.81, p<0.001). Aerosolized lipopolysaccharide recruits neutrophils into the lungs of sheep, but they appear to remain in the airspaces unless extra-alveolar permeability is increased by agents such as pentobarbital.     

Aerosolized lipopolysaccharide increases pulmonary clearance of 99mTc-DTPA in rabbits.

Bacterial endotoxins alter the permeability of endothelium, but little is known of their effect on epithelium. We exposed specific pathogen-free rabbits to aerosolized Pseudomonas aeruginosa LPS or saline and performed serial measurements of RL, Cdyn, BP, WBC count and differential, and platelet counts. Pulmonary 99mTc-DTPA half-life was measured 4, 6, or 8 h after exposure. The animals were sacrificed and BAL performed. Background and PMA-stimulated superoxide production was measured from individual AM using electrooptical determination of reduction of NBT. Lung tissue was processed for light microscopy and ratio of wet to dry weight. 99mTc-DTPA half-life was significantly shorter in LPS-exposed animals at 6 h (p < 0.05) and 8 h (p < 0.001). There were no differences in Cdyn, RL, BP, WBC, differential, platelet, or BAL cell count at any time between groups. No histologic changes or differences in lung wet to dry weight ratios were found. PMA-stimulated AM superoxide production was significantly increased (p < 0.01) in LPS-exposed animals. This effect was time dependent and could be duplicated in AM from control animals following a 4-h incubation with LPS, lavage fluid from LPS-exposed animals, or recombinant murine TNF. These results demonstrate that aerosolized Pseudomonas LPS increases pulmonary epithelial permeability and primes AM superoxide production.     

Role of Active Oxygen Species and Lipid Peroxidation in Mepirizole-Induced Duodenal Ulcers in Rats

The role of active oxygen species and lipidperoxidation in the pathogenesis of duodenal ulcersinduced by mepirizole was investigated in rats. Oraladministration of mepirizole (200 mg/kg) resulted in ulcer lesions in the proximal duodenum.Thiobarbituric acid-reactive substances (TBA-reactivesubstances), an indicator of lipid peroxidation, alsosignificantly increased in the duodenal mucosa.Myeloperoxidase (MPO) activity in the duodenal mucosa, a signof polymorphonuclear leukocyte (PMN) accumulation,significantly increased. Combination treatment withpolyethylene glycol-modified Serratia Mn-SOD andcatalase significantly decreased the size of the ulcersand TBA-reactive substances in the duodenal mucosa.Allopurinol, a xanthine oxidase inhibitor, also reducedthe size of duodenal ulcers. Both the size of the ulcers and the increase in TBA-reactivesubstances in the duodenal mucosa were significantlylower in PMN-depleted rats. Mepirizole increased thesurface expression of adhesion molecule CD18 on PMNs in vitro. These results suggest that lipidperoxidation, mediated by active oxygen speciesgenerated from xanthine oxidase and PMNs, plays animportant role in the pathogenesis of duodenal ulcersinduced by mepirizole.