Transient mechanical benefits of a deep inflation in the injured mouse lung.

The lasting effects of a recruitment maneuver (RM) in the injured lung are not well characterized. We speculated that the reduction in respiratory elastance (H) after a deep inflation (DI) is transient in nature and should be sustained longer at higher positive end-expiratory pressure (PEEP). Thirteen ventilated mice were given 2 DIs at various levels of PEEP before and after saline lavage. Forced oscillations were used to measure H periodically over 7 min after the DIs. Time constants (tau) were estimated for the post-DI recovery in H. Values for tau before lavage (80-115 s) were reduced after lavage (13-30 s) at all levels of PEEP (P = 0.0001). PEEP did not significantly influence tau before or after lavage. The plateau level and total recovery in H after a DI were significantly influenced by PEEP and lavage (P < 0.0001). Our results suggest that for a DI to be beneficial in the injured mouse lung, it may have to be applied several times a minute.     

Choosing the frequency of deep inflation in mice: balancing recruitment against ventilator-induced lung injury

Low tidal volume (Vt) ventilation is protective against ventilator-induced lung injury but can promote development of atelectasis. Periodic deep inflation (DI) can open the lung, but if delivered too frequently may cause damage via repeated overdistention. We therefore examined the effects of varying DI frequency on lung mechanics, gas exchange, and biomarkers of injury in mice. C57BL/6 males were mechanically ventilated with positive end-expiratory pressure (PEEP) of 2 cmH2O for 2 h. One high Vt group received a DI with each breath (HV). Low Vt groups received 2 DIs after each hour of ventilation (LV) or 2 DIs every minute (LVDI). Control groups included a nonventilated surgical sham and a group receiving high Vt with zero PEEP (HVZP). Respiratory impedance was measured every 4 min, from which tissue elastance (H) and damping (G) were derived. G and H rose progressively during LV and HVZP, but returned to baseline after hourly DI during LV. During LVDI and HV, G and H remained low and gas exchange was superior to that of LV. Bronchoalveolar lavage fluid protein was elevated in HV and HVZP but was not different between LV and LVDI. Lung tissue IL-6 and IL-1beta levels were elevated in HVZP and lower in LVDI compared with LV. We conclude that frequent DI can safely improve gas exchange and lung mechanics and may confer protection from biotrauma. Differences between LVDI and HV suggest that an optimal frequency range of DI exists, within which the benefits of maintaining an open lung outweigh injury incurred from overdistention.     

Expression of mutant human epidermal receptor 3 attenuates lung fibrosis and improves survival in mice.

Neuregulin-1 (NRG-1), binding to the human epidermal growth factor receptor HER2/HER3, plays a role in pulmonary epithelial cell proliferation and recovery from injury in vitro. We hypothesized that activation of HER2/HER3 by NRG-1 would also play a role in recovery from in vivo lung injury. We tested this hypothesis using bleomycin lung injury of transgenic mice incapable of signaling through HER2/HER3 due to lung-specific dominant-negative HER3 (DNHER3) expression. In animals expressing DNHER3, protein leak, cell infiltration, and NRG-1 levels in bronchoalveolar lavage fluid increased after injury, similar to that in nontransgenic littermate control animals. However, HER2/HER3 was not activated, and DNHER3 animals displayed fewer lung morphological changes at 10 and 21 days after injury (P = 0.01). In addition, they contained 51% less collagen in injured lungs (P = 0.04). Transforming growth factor-beta1 did not increase in bronchoalveolar lavage fluid from DNHER3 mice compared with nontransgenic littermate mice (P = 0.001), suggesting that a mechanism for the decreased fibrosis was lack of transforming growth factor-beta1 induction in DNHER3 mice. Severe lung injury (0.08 units bleomycin) resulted in 80% mortality of nontransgenic mice, but only 35% mortality of DNHER3 transgenic mice (P = 0.04). Thus inhibition of HER2/HER3 signaling protects against pulmonary fibrosis and improves survival.     

Body temperature control in sepsis-induced acute lung injury

Body temperature is precisely regulated to maintain homeostasis in homeothermic animals. Although it remains unproved whether change of body temperature constitutes a beneficial or a detrimental component of the septic response, temperature control should be an important entity in septic experiments. We investigated the effect of body temperature control on the lipopolysaccharide (LPS)-induced lung injury. Acute lung injury in rats was induced by intratracheal spray of LPS and body temperature was either clamped at 37 degrees C for 5 hours or not controlled. The severity of lung injury was evaluated at the end of the experiment. Intratracheal administration of aerosolized LPS caused a persistent decline in body temperature and a significant lung injury as indicated by an elevation of protein-concentration and LDH activity in the bronchoalveolar lavage (BAL) fluid and wet/dry weight (W/D) ratio of lungs. Administration of LPS also caused neutrophil sequestration and lipid peroxidation in the lung tissue as indicated by increase in myeloperoxidase (MPO) activity and malondialdehyde (MDA) production, respectively. Control of body temperature at 37 degrees C after LPS (LPS/BT37, n = 11) significantly reduced acute lung injury as evidenced by decreases in BAL fluid protein concentration (983 +/- 189 vs. 1403 +/- 155 mg/L) and LDH activity (56 +/- 10 vs. 123 +/- 17 deltamAbs/min) compared with the LPS group (n = 11). Although the W/D ratio of lung and MDA level were lower in the rats received temperature control compared with those received LPS only, the differences were not statistically significant. Our results demonstrated that intratracheal administration of aerosolized LPS induced a hypothermic response and acute lung injury in rats and controlling body temperature at a normal range may alleviate the LPS-induced lung injury.     

Role of complement in endotoxin/platelet-activating factor-induced lung injury.

C receptor-1 is a protein involved in the regulation of C3 and C5-convertases. Recombinant human soluble C receptor-1 has recently been produced and shown to reduce infarct size in a rat model of myocardial ischemia/reperfusion injury. The present study aimed to investigate whether recombinant human soluble C receptor-1 exerts any protective effect on pulmonary injury produced in a rodent model of adult respiratory distress syndrome. In this model, Escherichia coli endotoxin (LPS, 0.1 microgram/kg) combined with platelet-activating factor (1 pmol/kg/min over 60 min, n = 10) caused microvascular lung injury characterized by elevation of myeloperoxidase activity, deposition of C3 and C5b-9 on the endothelium of pulmonary vessels, and pulmonary edema. Furthermore, bronchoalveolar lavage revealed increased neutrophil count and elevated protein concentration. These pulmonary responses were associated with elevated serum TNF-alpha. Pretreatment (10 min, i.v.) with recombinant human soluble C receptor-1 at 10 mg/kg (n = 13), but not at 1 mg/kg, prevented the LPS/platelet-activating factor-induced pulmonary edema (p less than 0.01) and changes in the bronchoalveolar lavage fluid cell count (p less than 0.01) and protein concentration (p less than 0.05), and attenuated the deposition of C3 and C5b-9 to lung vessels. There was no effect on lung myeloperoxidase activity and serum TNF-alpha. Also, C depletion by cobra venom factor (500 U/kg, i.v.) eliminated the pulmonary edema and elevated leukocyte count in bronchoalveolar lavage fluid, but had no effect on lung myeloperoxidase activity and serum TNF-alpha. These data suggest that C factors may play an important role in the pathophysiology of adult respiratory distress syndrome.     

Lipopolysaccharide-Induced Lung Injury Is Independent of Serum Vitamin D Concentration

Vitamin D deficiency is increasing in incidence around the world. Vitamin D, a fat-soluble vitamin, has documented effects on the innate and adaptive immune system, including macrophage and T regulatory (Treg) cell function. Since Treg cells are important in acute lung injury resolution, we hypothesized that vitamin D deficiency increases the severity of injury and delays injury resolution in lipopolysaccharide (LPS) induced acute lung injury. Vitamin D deficient mice were generated, using C57BL/6 mice, through diet modification and limited exposure to ultraviolet light. At 8 weeks of age, vitamin D deficient and sufficient mice received 2.5 g/kg of LPS or saline intratracheal. At 1 day, 3 days and 10 days, mice were anesthetized and lung elastance measured. Mice were euthanized and bronchoalveolar lavage fluid, lungs and serum were collected. Ex vivo neutrophil chemotaxis was evaluated, using neutrophils from vitamin D sufficient and deficient mice exposed to the chemoattractants, KC/CXCL1 and C5a, and to bronchoalveolar lavage fluid from LPS-exposed mice. We found no difference in the degree of lung injury. Leukocytes were mildly decreased in the bronchoalveolar fluid of vitamin D deficient mice at 1 day. Ex-vivo, neutrophils from vitamin D deficient mice showed impaired chemotaxis to KC but not to C5a. Vitamin D deficiency modestly impairs neutrophil chemotaxis; however, it does not affect lung injury or its resolution in an LPS model of acute lung injury.     

L-Arg对LPS诱导的急性肺损伤大鼠肺表面活性物质和肺泡巨噬细胞功能的影响

目的:探讨L-精氨酸(L-Arg)对脂多糖(LPS)诱导的急性肺损伤大鼠肺表面活性物质和肺泡巨噬细胞功能的影响。方法:舌下静脉注射脂多糖(LPS)复制肺损伤模型。健康雄性SD大鼠48只,随机分为对照组、模型组(LPS组)和L-Arg治疗组(L-Arg组)(n=16)。分别于给予LPS 3 h或6 h后给予生理盐水(对照组及LPS组,ip)和L-Arg(500 mg/kg ip)(L-Arg治疗组),治疗3 h。原位杂交法(ISH)检测肺组织中肺表面活性蛋白A(SP-A)mRNA的表达;测定肺泡灌洗液(BALF)中的总蛋白(TP)。体外分离培养大鼠肺泡巨噬细胞,以LPS(终浓度10 mg/L)处理巨噬细胞,观察L-Arg对肺泡巨噬细胞的影响。结果:与对照组比较,大鼠肺损伤后SP-A mRNA表达减弱,BALF中TP增多(P<0.01)。肺损伤3 h用L-Arg治疗3 h后,SP-A mRNA阳性细胞表达明显增强,BALF中TP较LPS组相同时间点明显降低(P<0.05,P<0.01),肺损伤减轻。体外实验中,与正常对照组相比,LPS组细胞培养上清中乳酸脱氢酶(LDH)、一氧化氮(NO)、肿瘤坏死因子-α(TNFα-)和白细胞介素-6(IL-6)浓度明显增高(P<0.01);L-Arg明显减少LPS所致的LDH的释放,降低TNFα-和IL-6浓度。结论:L-Arg可减轻内毒素性肺损伤,此机制可能与增强SP-AmRNA表达有关;LPS可刺激巨噬细胞分泌促炎因子和NO,L-Arg可抑制LPS对巨噬细胞的作用。     

Sex Differences in Lung Gas Volumes After Lipopolysaccharide-Induced Chorioamnionitis in Fetal Sheep

BackgroundPreterm female infants have a survival advantage and enhanced lung development, which is an important determinant of preterm survival.ObjectiveGiven the modulation of lung development by fetal exposure to infection/inflammation, we hypothesized that female fetuses have enhanced lung maturational responses to chorioamnionitis compared with male fetuses.MethodsTime-pregnant ewes received intra-amniotic injections with saline (n = 60) or lipopolysaccharide (LPS) at 2 days (n = 30) or 7 days (n = 45) before surgical delivery at 123 to 125 days of gestation (term: ∼147 days). We assessed inflammatory responses in bronchoalveolar lavage fluid and cord blood, lung maturation with pressure-volume curves, and lung structure.ResultsLung gas volume showed differences between the sexes after 2 days LPS (male 4.6 [1.2] mL/kg, female 7.7 [4.4] mL/kg; P = 0.02) and 7 days LPS (male 20.5 [9.3] mL/kg, female 27.0 [7.0] mL/kg; P = 0.01). The control group was not different by sex (male 8.0 [3.6] mL/kg, female 8.9 [3.9] mL/kg; P > 0.05). No difference in lung structure and in pulmonary and systemic inflammatory response was evident by sex.ConclusionPreterm female sheep fetuses had increased lung gas volumes after exposure to LPS, without any detectable differences in fetal inflammatory responses.     

环孢菌素A对脂多糖诱导的小鼠急性肺损伤的保护作用

目的：探讨线粒体渗透性转换孔道抑制剂环孢菌素A（CsA）对脂多糖（LPS）诱导的小鼠急性肺损伤可能的保护作用。方法：LPS 4 mg/kg气管内滴入复制小鼠急性肺损伤模型,实验随机分为5组（n=24）：分别为正常对照组、LPS组、地塞米松组、CsA组和CsA＋苍术苷组。6 h后小鼠处死,测定各组支气管肺泡灌洗液乳酸脱氢酶（LDH）的含量,酶联免疫吸附法测定肺组织匀浆液TNF-α浓度,测定肺组织湿/干重比和肺毛细血管通透性指数。结果：气管内滴入LPS 6 h后,CsA组与LPS组相比,肺泡灌洗液中LDH活性降低,肺组织匀浆液TNF-α浓度下降,肺组织湿/干重比、肺毛细血管通透性指数均明显下降,但CsA＋Atr组与LPS组相比无明显区别。结论：环孢菌素A对脂多糖诱导的小鼠急性肺损伤有保护作用,其机制可能与其抑制线粒体渗透性转换孔道的开放有关。     

Immunopathology of a two-hit murine model of acid aspiration lung injury

In a two-hit model of acid aspiration lung injury, mice were subjected to nonlethal cecal ligation and puncture (CLP). After 48 h, intratracheal (IT) acid was administered, and mice were killed at several time points. Recruitment of neutrophils in response to acid was documented by myeloperoxidase assay and neutrophil counts in bronchoalveolar lavage (BAL) fluid and peaked at 8 h post-IT injection. Albumin in BAL fluid, an indicator of lung injury, also peaked at 8 h. When the contributions of the two hits were compared, neutrophil recruitment and lung injury occurred in response to acid but were not greatly influenced by addition of another hit. Neutrophil sequestration was preceded by elevations in KC and macrophage inflammatory protein-2alpha in plasma and BAL fluid. KC levels in BAL fluid were higher and peaked earlier than macrophage inflammatory protein-2alpha levels. When KC was blocked with specific antiserum, neutrophil recruitment was significantly reduced, whereas albumin in BAL fluid was not affected. In conclusion, murine KC mediated neutrophil recruitment but not lung injury in a two-hit model of aspiration lung injury.     

Role of lung injury in the pathogenesis of hyaline membrane disease in premature baboons

To test the hypothesis that hyaline membrane disease (HMD) has a multifactorial etiology in which barotrauma plays a major role, we compared the immediate institution of high-frequency oscillatory ventilation (HFOV; 15 Hz, n = 5) with positive-pressure ventilation with positive end-expiratory pressure (PPV; n = 7) in premature baboons (140-days gestation) with HMD. Measurements of ventilation settings and physiological parameters were obtained and arterial-to-alveolar O2 (PaO2-to-PAO2) ratio and oxygenation index [(PaO2/PAO2)-to-mean airway pressure ratio (IO2)] were calculated. At death (24 h), static pressure-volume (PV) curves were performed, and phospholipids (PL) and platelet-activating factor (PAF) were measured in lung lavage fluid. Morphological inflation patterns were analyzed using a panel of standards. By design, mean airway pressure was initially higher (19 vs. 13 cmH2O) in the HFOV animals. PaO2-to-PAO2 ratio and IO2 progressively deteriorated in the PPV animals and then stabilized at significantly lower levels than with HFOV. PV curves from HFOV animals had significant increases in lung volume at maximum distending pressure, deflation volume at 10 cmH2O, and hysteresis area compared with PPV, which showed no hysteresis. Seven of seven PPV and only one of five HFOV animals had morphological findings of HMD. PL amount and composition in both groups were consistent with immaturity, even though the quantity was significantly greater in the PPV group. PAF was present (greater than or equal to 0.10 pmol) in six of seven PPV and in the only HFOV animal with HMD. We conclude that HFOV protected PL-deficient premature baboons from changes in gas exchange, lung mechanics, and morphology typical of HMD in this model.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inhibition of Pyk2 blocks lung inflammation and injury in a mouse model of acute lung injury

Background

Proline-rich tyrosine kinase 2 (Pyk2) is essential in neutrophil degranulation and chemotaxis in vitro. However, its effect on the process of lung inflammation and edema formation during LPS induced acute lung injury (ALI) remains unknown. The goal of the present study was to determine the effect of inhibiting Pyk2 on LPS-induced acute lung inflammation and injury in vivo.

Methods

C57BL6 mice were given either 10 mg/kg LPS or saline intratracheally. Inhibition of Pyk2 was effected by intraperitoneal administration TAT-Pyk2-CT 1 h before challenge. Bronchoalveolar lavage analysis of cell counts, lung histology and protein concentration in BAL were analyzed at 18 h after LPS treatment. KC and MIP-2 concentrations in BAL were measured by a mouse cytokine multiplex kit. The static lung compliance was determined by pressure-volume curve using a computer-controlled small animal ventilator. The extravasated Evans blue concentration in lung homogenate was determined spectrophotometrically.

Results

Intratracheal instillation of LPS induced significant neutrophil infiltration into the lung interstitium and alveolar space, which was attenuated by pre-treatment with TAT-Pyk2-CT. TAT-Pyk2-CT pretreatment also attenuated 1) myeloperoxidase content in lung tissues, 2) vascular leakage as measured by Evans blue dye extravasation in the lungs and the increase in protein concentration in bronchoalveolar lavage, and 3) the decrease in lung compliance. In each paradigm, treatment with control protein TAT-GFP had no blocking effect. By contrast, production of neutrophil chemokines MIP-2 and keratinocyte-derived chemokine in the bronchoalveolar lavage was not reduced by TAT-Pyk2-CT. Western blot analysis confirmed that tyrosine phosphorylation of Pyk2 in LPS-challenged lungs was reduced to control levels by TAT-Pyk2-CT pretreatment.

Conclusions

These results suggest that Pyk2 plays an important role in the development of acute lung injury in mice and that pharmacological inhibition of Pyk2 might provide a potential therapeutic strategy in the pretreatment for patients at imminent risk of developing acute lung injury.     

Hyaluronan fragments contribute to the ozone-primed immune response to lipopolysaccharide

Hyaluronan is a high-molecular mass component of pulmonary extracelluar matrix, and lung injury can generate a low-molecular mass hyaluronan (HA) fragment that functions as endogenous ligand to cell surface receptors CD44 and TLR4. This leads to activation of intracellular NF-κB signaling and proinflammatory cytokine production. Based on previous information that ozone exposure causes increased HA in bronchial alveolar lavage fluid and ozone pre-exposure primes immune response to inhaled LPS, we hypothesized that HA production during ozone exposure augments the inflammatory response to LPS. We demonstrate that acute ozone exposure at 1 part per million for 3 h primes the immune response to low-dose aerosolized LPS in C57BL/6J mice, resulting in increased neutrophil recruitment into the airspaces, increased levels of protein and proinflammatory cytokines in the bronchoalveolar lavage fluid, and increased airway hyperresponsiveness. Intratracheal instillation of endotoxin-free HA (25 μg) enhances the biological response to inhaled LPS in a manner similar to ozone pre-exposure. In vitro studies using bone marrow-derived macrophages indicate that HA enhances LPS responses measured by TNF-α production, while immunofluorescence staining of murine alveolar macrophages demonstrates that HA induces TLR4 peripheralization and lipid raft colocalization. Collectively, our observations support that ozone primes macrophage responsiveness to low-dose LPS, in part, due to HA-induced TLR4 peripheralization in lung macrophages.     

Effects of mechanical ventilation at low lung volume on respiratory mechanics and nitric oxide exhalation in normal rabbits.

Lung mechanics, exhaled NO (NOe), and TNF-alpha in serum and bronchoalveolar lavage fluid were assessed in eight closed and eight open chest, normal anesthetized rabbits undergoing prolonged (3-4 h) mechanical ventilation (MV) at low volume with physiological tidal volumes (10 ml/kg). Relative to initial MV on positive end-expiratory pressure (PEEP), MV at low volume increased lung quasi-static elastance (+267 and +281%), airway (+471 and +382%) and viscolelastic resistance (+480 and +294%), and decreased NOe (-42 and -25%) in closed and open chest rabbits, respectively. After restoration of PEEP, viscoelastic resistance returned to control, whereas airway resistance remained elevated (+120 and +31%) and NOe low (-25 and -20%) in both groups of rabbits. Elastance remained elevated (+23%) only in closed-chest animals, being associated with interstitial pulmonary edema, as reflected by increased lung wet-to-dry weight ratio with normal albumin concentration in bronchoalveolar lavage fluid. In contrast, in 16 additional closed- and open-chest rabbits, there were no changes of lung mechanics or NOe after prolonged MV on PEEP only. At the end of prolonged MV, TNF-alpha was practically undetectable in serum, whereas its concentration in bronchoalveolar lavage fluid was low and similar in animals subjected or not subjected to ventilation at low volume (62 vs. 43 pg/ml). These results indicate that mechanical injury of peripheral airways due to their cyclic opening and closing during ventilation at low volume results in changes in lung mechanics and reduction in NOe and that these alterations are not mediated by a proinflammatory process, since this is expressed by TNF-alpha levels.     

Pentoxifylline reduces fibrin deposition and prolongs survival in neonatal hyperoxic lung injury.

Bronchopulmonary dysplasia is a leading cause of mortality and morbidity in preterm infants despite improved treatment modalities. Pentoxifylline, a phosphodiesterase inhibitor, inhibits multiple processes that lead to neonatal hyperoxic lung injury, including inflammation, coagulation, and edema. Using a preterm rat model, we investigated the effects of pentoxifylline on hyperoxia-induced lung injury and survival. Preterm rat pups were exposed to 100% oxygen and injected subcutaneously with 0.9% saline or 75 mg/kg pentoxifylline twice a day. On day 10, lung tissue was harvested for histology, fibrin deposition, and mRNA expression, and bronchoalveolar lavage fluid was collected for total protein concentration. Pentoxifylline treatment increased mean survival by 3 days (P = 0.0018) and reduced fibrin deposition by 66% (P < 0.001) in lung homogenates compared with untreated hyperoxia-exposed controls. Monocyte chemoattractant protein-1 expression in lung homogenates was decreased, but the expressions of TNF-alpha, IL-6, matrix metalloproteinase-12, tissue factor, and plasminogen activator inhibitor-1 were similar in both groups. Total protein concentration in bronchoalveolar lavage fluid was decreased by 33% (P = 0.029) in the pentoxifylline group. Pentoxifylline treatment attenuates alveolar fibrin deposition and prolongs survival in preterm rat pups with neonatal hyperoxic lung injury, probably by reducing capillary-alveolar protein leakage.     

Hyaluronate and type III procollagen peptide concentrations in bronchoalveolar lavage fluid as markers of disease activity in farmer's lung.

Ten patients were studied during an acute episode of farmer''s lung. Prominent findings were an impaired diffusion capacity (on average only 51% of predicted) and substantially increased amounts of hyaluronate and type III procollagen peptide recovered during bronchoalveolar lavage; mean concentrations of these constituents in lavage fluid were 547 (range 137-1125) and 9.7 (2.8-19.4) micrograms/l, respectively. In bronchoalveolar lavage fluid from healthy controls (n = 21) hyaluronate concentrations were less than 15 micrograms/l and procollagen peptide concentrations less than 0.2 micrograms/l. Lavage fluid concentrations of these potential markers of fibroblast activation declined during the recovery phase of farmer''s lung; four to 10 weeks after admission (n = 7) mean concentrations of hyaluronate and procollagen peptide were 154 (range 38-650) and 4.4 (0.6-15.8) micrograms/l, respectively. At clinical remission six to 14 months after admission concentrations of these markers had returned almost to normal, though slightly increased concentrations were still evident in about half the patients (n = 7). At that time lung volumes were normal but diffusion capacity remained slightly subnormal. It was concluded that in farmer''s lung release of hyaluronate and type III procollagen peptide reflects activity of the disease. Increased synthesis of these connective tissue components continuing in a patient avoiding mouldy plant material may signal an increased risk of developing fibrotic lung disease. The abnormal accumulation of hyaluronate in the smaller airways in acute farmer''s lung may be expected to immobilize water and thereby provide a possible mechanism of the interstitial inflammatory lung oedema with associated impaired gas diffusion. This hypothesis is supported by the relation found between hyaluronate in lavage fluid and reduced diffusion capacity.     

Altered function of pulmonary surfactant in fatty acid lung injury

To determine whether acute fatty acid lung injury impairs pulmonary surfactant function, we studied anesthetized ventilated rabbits given oleic acid (55 mg/kg iv, n = 11) or an equivalent volume of saline (n = 8). Measurements of pulmonary mechanics indicated a decrease in dynamic compliance within 5 min of injury and a decrease in lung volume that was disproportionately large at low pressures, consistent with diminished surfactant activity in vivo. Bronchoalveolar lavage fluid obtained 1 h after injury had significantly increased erythrocytes and total leukocytes, largely polymorphonuclear cells. The phospholipid content and composition of the cell-free fraction had only minor changes from those of controls, but the protein content was increased 35-fold. Measurements of lavage surface activity in vitro showed an increase in average minimum surface tension from 1.3 +/- 0.4 (SE) dyn/cm in controls to 20.2 +/- 3.9 dyn/cm in injured animals. The alterations in static pressure-volume curves and decrease in lavage surface activity suggest a severe alteration of surfactant function in this form of lung injury that occurs despite the presence of normal amounts of surfactant phospholipids.     

Role of CC chemokines (macrophage inflammatory protein-1 beta, monocyte chemoattractant protein-1, RANTES) in acute lung injury in rats

The role of the CC chemokines, macrophage inflammatory protein-1 beta (MIP-1 beta), monocyte chemotactic peptide-1 (MCP-1), and RANTES, in acute lung inflammatory injury induced by intrapulmonary deposition of IgG immune complexes injury in rats was determined. Rat MIP-1 beta, MCP-1, and RANTES were cloned, the proteins were expressed, and neutralizing Abs were developed. mRNA and protein expression for MIP-1 beta and MCP-1 were up-regulated during the inflammatory response, while mRNA and protein expression for RANTES were constitutive and unchanged during the inflammatory response. Treatment of rats with anti-MIP-1 beta Ab significantly decreased vascular permeability by 37% (p = 0.012), reduced neutrophil recruitment into lung by 65% (p = 0.047), and suppressed levels of TNF-alpha in bronchoalveolar lavage fluids by 61% (p = 0.008). Treatment of rats with anti-rat MCP-1 or anti-rat RANTES had no effect on the development of lung injury. In animals pretreated intratracheally with blocking Abs to MCP-1, RANTES, or MIP-1 beta, significant reductions in the bronchoalveolar lavage content of these chemokines occurred, suggesting that these Abs had reached their targets. Conversely, exogenously MIP-1 beta, but not RANTES or MCP-1, caused enhancement of the lung vascular leak. These data indicate that MIP-1 beta, but not MCP-1 or RANTES, plays an important role in intrapulmonary recruitment of neutrophils and development of lung injury in the model employed. The findings suggest that in chemokine-dependent inflammatory responses in lung CC chemokines do not necessarily demonstrate redundant function.     

Adrenomedullin ameliorates lipopolysaccharide-induced acute lung injury in rats

Adrenomedullin (AM), an endogenous peptide, has been shown to have a variety of protective effects on the cardiovascular system. However, the effect of AM on acute lung injury remains unknown. Accordingly, we investigated whether AM infusion ameliorates lipopolysaccharide (LPS)-induced acute lung injury in rats. Rats were randomized to receive continuous intravenous infusion of AM (0.1 microg x kg(-1) x min(-1)) or vehicle through a microosmotic pump. The animals were intratracheally injected with either LPS (1 mg/kg) or saline. At 6 and 18 h after intratracheal instillation, we performed histological examination and bronchoalveolar lavage and assessed the lung wet/dry weight ratio as an index of acute lung injury. Then we measured the numbers of total cells and neutrophils and the levels of tumor necrosis factor (TNF)-alpha and cytokine-induced neutrophil chemoattractant (CINC) in bronchoalveolar lavage fluid (BALF). In addition, we evaluated BALF total protein and albumin levels as indexes of lung permeability. LPS instillation caused severe acute lung injury, as indicated by the histological findings and the lung wet/dry weight ratio. However, AM infusion attenuated these LPS-induced abnormalities. AM decreased the numbers of total cells and neutrophils and the levels of TNF-alpha and CINC in BALF. AM also reduced BALF total protein and albumin levels. In addition, AM significantly suppressed apoptosis of alveolar wall cells as indicated by cleaved caspase-3 staining. In conclusion, continuous infusion of AM ameliorated LPS-induced acute lung injury in rats. This beneficial effect of AM on acute lung injury may be mediated by inhibition of inflammation, hyperpermeability, and alveolar wall cell apoptosis.