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.     

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.     

Primed stimulation of isolated perfused rabbit lung by endotoxin and platelet activating factor induces enhanced production of thromboxane and lung injury.

Bacterial sepsis often precedes the development of the adult respiratory distress syndrome (ARDS) and bacterial endotoxin (LPS) produces a syndrome similar to ARDS when infused into experimental animals. We determined in isolated, buffer-perfused rabbit lungs, free of plasma and circulating blood cells that LPS synergized with platelet activating factor (PAF) to injure the lung. In lungs perfused for 2 h with LPS-free buffer (less than 100 pg/ml), stimulation with 1, 10, or 100 nM PAF produced transient pulmonary hypertension and minimal edema. Lungs perfused for 2 h with buffer containing 100 ng/ml of Escherichia coli 0111:B4 LPS had slight elevation of pulmonary artery pressure (PAP) and did not develop edema. In contrast, lungs exposed to 100 ng/ml of LPS for 2 h had marked increases in PAP and developed significant edema when stimulated with PAF. LPS treatment increased capillary filtration coefficient, suggesting that capillary leak contributed to pulmonary edema. LPS-primed, PAF-stimulated lungs had enhanced production of thromboxane B2 (TXB) and 6-keto-prostaglandin F1 alpha (6KPF). Indomethacin completely inhibited PAF-stimulated production of TXB and 6KPF in control and LPS-primed preparations, did not inhibit the rise in PAP produced by PAF in control lungs, but blocked the exaggerated rise in PAP and edema seen in LPS-primed, PAF-stimulated lungs. The thromboxane synthetase inhibitor dazoxiben, and the thromboxane receptor antagonist, SQ 29,548, similarly inhibited LPS-primed pulmonary hypertension and edema after PAF-stimulation. These studies indicate that LPS primes the lung for enhanced injury in response to the physiologic mediator PAF by amplifying the synthesis and release of thromboxane in lung tissue.     

Regional blood volume changes during acute pericardial tamponade

Using radionuclide blood pool imaging, we evaluated sequential changes in heart, lung, liver, and spleen intravascular volumes were evaluated before and during acute pericardial tamponade in 9 anesthetized dogs. Tamponade resulted in an abrupt (less than 1 min) decline in mean right heart (-30 +/- 5%, p less than 0.001 vs control) and left heart volumes (-27 +/- 4%, p less than 0.001 vs control), with a concomitant reduction in pulmonary volume (-17 +/- 3%, p less than 0.01 vs control). Within this short time frame, both hepatic (+19 +/- 3%) and splenic (+16 +/- 4%, both p less than 0.01 vs control) volumes rose. Five min after the production of tamponade, right and left heart volumes were still significantly reduced (-28 +/- 4, p less than 0.005 vs control and -23 +/- 2%, p less than 0.005 vs control), though pulmonary (+2 +/- 5%, p = NS vs control), hepatic (+7 +/- 3%, p less than 0.05 vs control) and splenic (+9 +/- 3%, p less than 0.05 vs control) volumes had returned toward baseline values. These volume changes were similar at 20 min after tamponade. Thus, tamponade resulted in a sudden shunting of blood from the central to the peripheral circulation, initially from both the lungs and heart. After 5 min pulmonary volumes returned to baseline values, while splenic and hepatic volumes remained slightly, though significantly elevated.     

Effects of antihistamines on the lung vascular response to histamine in unanesthetized sheep. Diphenhydramine prevention of pulmonary edema and increased permeability.

To see whether antihistamines could prevent and reverse histamine-induced pulmonary edema and increased lung vascular permeability, we compared the effects of a 4-h intravenous infusion of 4 mug/kg per min histamine phosphate on pulmonary hemodynamics, lung lymph flow, lymph and plasma protein content, arterial blood gases, hematocrit, and lung water with the effects of an identical histamine infusion given during an infusion of diphenhydramine or metiamide on the same variables in unanesthetized sheep. Histamine caused lymph flow to increase from 6.0+/-0.5 to 27.0+/-5.5 (SEM) ml/h (P less than 0.05), lymph; plasma globulin concentration ratio to increase from 0.62+/-0.01 to 0.67+/-0.02 (P less than 0.05), left atrial pressure to fall from 1+/-1 to -3+/-1 cm H2O (P less than 0.05), and lung lymph clearance of eight protein fractions ranging from 36 to 96 A molecular radius to increase significantly. Histamine also caused increases in lung water, pulmonary vascular resistance, arterial PCO2, pH, and hematocrit, and decreases in cardiac output and arterial PO2. Diphenhydramine (3 mg/kg before histamine followed by 1.5 mg/kg per h intravenous infusion) completely prevented the histamine effect on hematocrit, lung lymph flow, lymph protein clearance, and lung water content, and reduced histamine effects on arterial blood gases and pH. 6 mg/kg diphenhydramine given at the peak histamine response caused lymph flow and lymph: plasma protein concentration ratios to fall. Metiamide (10 mg/kg per h) did not affect the histamine lymph response. We conclude that diphenhydramine can prevent histamine-induced pulmonary edema and can prevent and reverse increased lung vascular permeability caused by histamine, and that histamine effects on lung vascular permeability are H1 actions.     

Recombinant tumor necrosis factor/cachectin and interleukin 1 pretreatment decreases lung oxidized glutathione accumulation, lung injury, and mortality in rats exposed to hyperoxia

Single, preexposure, parenteral injection with both recombinant tumor necrosis factor/cachectin (TNF/C) and interleukin-1 (IL-1) prolonged the survival of rats (144 +/- 9 h) in continuous hyperoxia (greater than 99% O2 at 1 atm) when compared with rats injected with boiled TNF/C and boiled IL-1 (61 +/- 2 h), TNF/C alone (61 +/- 2 h), IL-1 alone (62 +/- 2 h), or saline (64 +/- 3 h). After exposure to hyperoxia for 52 h, pleural effusion volume, pulmonary artery pressure, total pulmonary resistance, and lung morphologic damage were decreased in those rats given TNF/C and IL-1 as compared with saline-injected rats. In parallel, ratios of reduced (GSH) to oxidized (GSSG) glutathione were greater (P less than 0.05) in lungs of TNF/C + IL-1-injected rats (91 +/- 20) than of saline-injected rats (30 +/- 4) that had been exposed to hyperoxia for 52 h. No differences were found in superoxide dismutase, glutathione peroxidase, glutathione reductase, glucose-6-phosphate dehydrogenase, or catalase activities in lungs of TNF/C + IL-1- or saline-treated, hyperoxia-exposed rats. Our results indicate that pretreatment with TNF/C and IL-1 favorably altered lung glutathione redox status, decreased lung injury, and enhanced survival of rats exposed to hyperoxia.     

烟雾吸入致伤犬右侧肺引发左侧肺损伤的实验研究

目的：探讨烟雾致伤犬一侧肺对另侧肺的影响及其机制。方法：在Olympus(型号P10）纤维支气管镜引导下直视行双腔管气道插管,烟雾吸入致伤犬右侧肺,分别采用AVL990型自动血气分析仪、干湿重法、过氧化氢还原法、微量酸滴定法、TBA法、生物测定法检测犬动脉血气、肺含水量、髓过氧化物酶（MPO）活性、磷脂酶A2（PLA2）活性、脂质过氧化物丙二醛（MDA）及血小板活化因子（PAF）含量。结果：右侧肺烟雾吸入致伤后,犬呼吸频率明显增快,动脉血氧分压（PaO2)进行性下降,24小时达8．37kPa(1kPa=7.5mmHg)。但动脉血二氧化碳分压（PaCO2)仅24小时点与伤前比较显著升高。进一步研究发现,烟雾致伤后右侧肺后24小时,左侧肺含水量明显增加,粒细胞标志酶MPO活性、膜磷脂分解酶PLA2活性、炎性介质PAF及MDA含量与正常对照组比较均显著升高。病理检查见,致伤犬双肺弥漫性肺泡内水肿,间隔增厚,伴大量炎细胞浸润,惟左侧肺略轻。结论：烟雾吸入致伤犬一侧肺可引起另侧肺水肿,其机制与另侧肺组织继发性的白细胞浸润、PLA2活化、脂质过氧化损伤及炎性介质PAF增加有关。     

Oxidant-mediated epithelial cell injury in idiopathic pulmonary fibrosis.

Lung inflammatory cells of patients with idiopathic pulmonary fibrosis (IPF) were evaluated for their ability to injure 51Cr-labeled AKD alveolar epithelial cells in the presence and absence of IPF alveolar epithelial lining fluid (ELF). The IPF cells were spontaneously releasing exaggerated amounts of superoxide (O.2) and hydrogen peroxide (H2O2) compared with normal (P less than 0.02). Cytotoxicity of the AKD cells was markedly increased when the IPF inflammatory cells were incubated with autologous ELF (P less than 0.02). The majority of IPF patients had ELF myeloperoxidase levels above normal (P less than 0.002). Incubation of IPF ELF with AKD cells in the presence of H2O2 caused increased cellular injury (P less than 0.01 compared with control), which was suppressed by methionine, a myeloperoxidase system scavenger. IPF patients with high concentrations of ELF myeloperoxidase deteriorated more rapidly than those with low ELF myeloperoxidase (P less than 0.05). Thus, IPF is characterized by an increased spontaneous production of oxidants by lung inflammatory cells, the presence of high concentrations of myeloperoxidase in the ELF of the lower respiratory tract, and a synergistic cytotoxic effect of alveolar inflammatory cells and ELF on lung epithelial cells, suggesting oxidants may play a role in causing the epithelial cell injury of this disorder.     

Prevention of granulocyte-mediated oxidant lung injury in rats by a hydroxyl radical scavenger, dimethylthiourea

Toxic, partially reduced metabolites of oxygen (toxic oxygen radicals) are increasingly implicated in acute leukocyte-mediated tissue injury. To further probe the roles of oxygen radicals in acute lung edema, I studied the effects of a recently described and very potent oxygen radical scavenger, dimethylthiourea (DMTU) (Fox, R. B., R. N. Harada, R. M. Tate, and J. E. Repine, 1983, J. Appl. Physiol., 55:1456-1459) on polymorphonuclear leukocyte (PMN) oxidant function and on two types of lung injury mediated by oxygen radicals and PMN. DMTU (10 mM) blocked 79% of hydroxyl radical (OH) production by PMN in vitro without interfering with other PMN functions, such as O-2 production, myeloperoxidase activity, chemotaxis, degranulation, or aggregation. When isolated rat lung preparations were perfused with PMN activated to produce OH, lung weights were increased from 2.3 +/- 0.2 to 11.2 +/- 0.8 g. DMTU (10 mM) prevented 70% of these increases (lung weights, 5.0 +/- 1.1 g, P less than 0.005). Finally, when intact rats were exposed to 100% O2 for 66 h, lung weight:body weight ratios were increased from 5.78 +/- 0.33 to 8.87 +/- 0.16 g. DMTU (500 mg/kg) prevented 83% of this hyperoxia-induced lung edema in vivo (lung:body weight ratios, 6.05 +/- 0.21, P less than 0.001). Pharmacokinetic studies showed that DMTU diffused effectively into lung interstitial fluids and had a relatively long half-life (25-35 h) in the circulation. Because a variety of oxygen radicals, such as superoxide (O-2), hydrogen peroxide (H2O2), or OH are produced by PMN, there is usually some uncertainty about which one is responsible for injury. However, in these studies, DMTU did not scavenge O-2 and scavenged H2O2 only very slowly while scavenging OH very effectively. Therefore, DMTU may be useful in the investigation of the roles of oxygen radicals, especially OH, in acute granulocyte-mediated tissue injury.     

Infused salbutamol accentuates acid-induced lung injury in the rat

The effect in the rat of salbutamol infusion (1 microgram min-1 kg-1) on acid-induced lung injury has been determined. Severity of lung injury was assessed by two techniques: the pulmonary clearance of 99mTc-diethylenetriaminepenta-acetate (99mTc-DTPA) and the lung wet/dry weight ratio, giving indices of alveolar epithelial permeability and transendothelial water filtration respectively. Mean half-time of clearance of 99mTc-DTPA was increased significantly in rats who had intratracheal acid-induced injury and control (saline) intravenous infusion (19.4 +/- 2.6 min) compared with non-acid-treated rats (98.1 +/- 7.2) (P less than 0.0001). However, those animals who had intratracheal acid injury and subsequent salbutamol intravenous infusion had significantly faster clearance (11.5 +/- 1.9) than the acid and control infusion group (P less than 0.05). Gravimetric lung water in the acid-only rats (expressed as wet/dry weight ratio) was increased significantly (6.4 +/- 0.3) compared with the non-acid-treated controls (5.4 +/- 0.2) (P less than 0.01). Acid-treated rats who had salbutamol infused had dramatically increased lung water (10.0 +/- 0.6) (P less than 0.001 vs acid and control infusion). Intravenous salbutamol infusion itself produced no significant difference in the results for both techniques, compared with the non-acid-treated time-course controls. Infused salbutamol accentuates acid-induced lung injury in the rat. Possible factors responsible for these findings include beta 2-adrenergic agonist mediated inhibition of hypoxic pulmonary vasoconstriction (HPV) and a predominant beta 1-adrenergic agonist inotropic effect of salbutamol with resultant rise in pulmonary artery pressure.     

Spontaneous release of interleukin 2 by lung T lymphocytes in active pulmonary sarcoidosis is primarily from the Leu3+DR+ T cell subset.

The inflammation within the lower respiratory tract of individuals with pulmonary sarcoidosis is dominated by large numbers of helper T lymphocytes that proliferate and spontaneously release interleukin 2 (IL-2). To identify the lymphocyte subpopulation that releases IL-2 in this disorder, lung lymphocytes recovered by bronchoalveolar lavage were characterized using the monoclonal antibodies Leu4 (T lymphocyte), Leu3 (helper/inducer), Leu2 (suppressor/cytotoxic), and anti-HLA-DR, and separated by panning and flow cytometry. The majority of the IL-2 spontaneously released by T cells in the sarcoid lung was contributed by the Leu3+ cell population (Leu3+65 +/- 23 IL-2 units released/10(6) cells per 24 h; Leu2+ 9 +/- 8, P less than 0.04). Further characterization of the lung Leu3+ T cells in sarcoid demonstrated that 30 +/- 3% were expressing HLA-DR molecules on their surface compared with 6 +/- 1% in normals (P less than 0.01). Importantly, the subpopulation of Leu3+ lung T lymphocytes expressing a high intensity of HLA-DR molecules on their surface was responsible for the majority of the release of IL-2 in the sarcoid lung (Leu3+ high-intensity DR 42 +/- 17 U/10(6) cells per 24 h, Leu3+ low-intensity DR 8 +/- 1 U/10(6) cells per 24 h; P less than 0.01). Thus, the spontaneous release of IL-2 in the lung of sarcoid patients appears to be localized to a subset of Leu3+ high-intensity DR ("activated" lung helper/inducer) T lymphocytes. Because the sarcoid lung is characterized by markedly increased numbers of these cells, it is likely that this compartmentalized T cell population plays a major role in sustaining the exaggerated localized immune processes of this disorder.     

Thromboxane mediates the renal hemodynamic effects of platelet activating factor

The mechanism by which platelet-activating factor affects renal hemodynamics is controversial. In the present study we examined the hypothesis that thromboxane mediates the renal hemodynamic response to platelet activating factor (PAF) by determining the effects of pretreatment with a selective thromboxane receptor antagonist. Infusion of platelet-activating factor into the left renal artery of normal rats in a dose that failed to alter mean arterial pressure or blood hematocrit values reduced urinary flow rate from 25.9 +/- 6.3 to 12.6 +/- 1.5 microliters/min (P less than .01), reduced effective renal plasma flow rate from 14.01 +/- 2.09 to 5.42 +/- 2.38 ml/min/kg body weight (P less than .01), reduced glomerular filtration rate from 4.81 +/- 1.00 to 1.68 +/- 0.34 ml/min/kg (P less than .03), and increased the fractional excretion of protein from 0.021 +/- 0.008 to 0.094 +/- 0.005 percent (P less than .05). Pretreatment with the selective thromboxane receptor antagonist SKF 96148 (10 mg/kg) not only prevented PAF-induced reductions in effective renal plasma flow rate and glomerular filtration rate but increased these values (effective renal plasma flow rate: 14.09 +/- 2.76 vs. 16.84 +/- 2.08 ml/min/kg, P less than .05; glomerular filtration rate: 4.42 +/- 0.43 vs. 5.50 +/- 0.59 ml/min/kg, P less than .03) and aborted proteinuria. Pretreatment with indomethacin (2 mg/kg) ameliorated PAF-induced alterations in renal hemodynamics and glomerular permselectivity in the final collection period. Infusion of lyso-PAF, a biologically inactive precursor of PAF, or of indomethacin alone or SKF 96148 alone had no significant effect on measured parameters. These observations suggest that thromboxane mediates the renal hemodynamic and permselective effects of PAF.     

FLT3信号通路介导常规树突状细胞启动和调节急性肺损伤早期炎症反应的机制研究

目的 明确FLT3信号通路依赖的肺常规树突状细胞(cDCs)对急性肺损伤(ALI)早期炎症反应和肺损伤的影响及其调控机制.方法 SPF级C57BL/6小鼠30只按随机数字表法分为正常对照组、ALI组、FLT3L预处理组、来他替尼预处理组和DMSO对照组,分别给予FLT3L、来他替尼预处理5d后采用LPS气道内滴入复制ALI模型,6h及24h后处死小鼠留取肺组织,采用流式细胞术检测CD11c+ CD11b+双阳性细胞比例评价肺cDCs的数量,检测肺cDCs的MHCⅡ及CD80表达比例评价肺cDCs的成熟程度;ELISA检测IL-6、TNF-α评价肺部炎症反应的强度;计算肺湿质量/体质量比(LWW/BW)评价肺水肿程度;肺组织HE染色行组织病理学检查评价肺损伤程度;比色法检测肺MPO活性评价中性粒细胞的浸润;qRT-PCR检测转录因子T-bet及GATA-3mRNA的表达比例评价辅助性T细胞Th1/Th2亚群漂移;ELISA检测IFN-γ及IL-4表达评价Th1/Th2细胞因子的平衡.结果 肺cDCs聚集及成熟程度高峰出现于ALI成模后6h(P＜0.05).FLT3L预处理显著增加肺cDCs的聚集和成熟程度(P＜0.05),上调肺部炎症反应并加重肺损伤,同时肺MPO活性、T-bet/GATA-3的表达比例和肺IFN-γ水平均显著上升(P＜0.05).来他替尼预处理显著抑制肺cDCs的聚集和分化成熟(P＜0.05),下调肺部炎症反应并减轻肺损伤,同时肺MPO活性、T-bet/GATA-3的表达比例和肺IFN-γ水平均显著下降(P＜0.05).结论 肺cDCs可通过FLT3信号通路调节中性粒细胞的浸润和Th1/Th2免疫反应的平衡,进而启动和调节ALI早期炎症反应和肺损伤.     

Alveolar liquid pressure measured by micropuncture in isolated lungs of mature and immature fetal rabbits.

Increased alveolar surface tension due to surfactant deficiency is thought to result in a negative pressure surrounding pulmonary capillaries and to promote fluid filtration. To test this hypothesis, alveolar liquid pressure (Pliquid) was measured by micropuncture in isolated lungs of mature and immature fetal rabbits (with and without surfactant replacement) at different air inflation pressures (Pairway). Lung maturity was assessed by air pressure-volume (P-V) curves. Pliquid was correlated with surfactant content in the lungs and with alveolar size. Pliquid was lower in immature (2.3 +/- 0.7 cmH2O) than in mature (8.4 +/- 1.0 cmH2O) lungs at comparable Pairway (25 cmH2O) (P less than 0.01). The mean linear intercept, a measure of airspace dimensions was similar in all lungs (42.1 +/- 2.0 micron), but alveolar wash phospholipid/g wet lung was lower in immature than in mature lungs (0.05 +/- 0.01 vs. 0.49 +/- 0.30 mg) (P less than 0.01). Surfactant replacement in immature lungs resulted in P-V curves and Pliquid similar to those of mature lungs. If pericapillary interstitial liquid pressure approximates Pliquid, surfactant deficiency will predispose preterm infants to pulmonary edema.     

Ibuprofen prevents oxidant lung injury and in vitro lipid peroxidation by chelating iron.

Because ibuprofen protects from septic lung injury, we studied the effect of ibuprofen in oxidant lung injury from phosgene. Lungs from rabbits exposed to 2,000 ppm-min phosgene were perfused with Krebs-Henseleit buffer at 50 ml/min for 60 min. Phosgene caused no increase in lung generation of cyclooxygenase metabolites and no elevation in pulmonary arterial pressure, but markedly increased transvascular fluid flux (delta W = 31 +/- 5 phosgene vs. 8 +/- 1 g unexposed, P less than 0.001), permeability to albumin (125I-HSA) lung leak index 0.274 +/- 0.035 phosgene vs. 0.019 +/- 0.001 unexposed, P less than 0.01; 125I-HSA lavage leak index 0.352 +/- 0.073 phosgene vs. 0.008 +/- 0.001 unexposed, P less than 0.01), and lung malondialdehyde (50 +/- 7 phosgene vs. 24 +/- 0.7 mumol/g dry lung unexposed, P less than 0.01). Ibuprofen protected lungs from phosgene (delta W = 10 +/- 2 g; lung leak index 0.095 +/- 0.013; lavage leak index 0.052 +/- 0.013; and malondialdehyde 16 +/- 3 mumol/g dry lung, P less than 0.01). Because iron-treated ibuprofen failed to protect, we studied the effect of ibuprofen in several iron-mediated reactions in vitro. Ibuprofen attenuated generation of .OH by a Fenton reaction and peroxidation of arachidonic acid by FeCl3 and ascorbate. Ibuprofen also formed iron chelates that lack the free coordination site required for iron to be reactive. Thus, ibuprofen may prevent iron-mediated generation of oxidants or iron-mediated lipid peroxidation after phosgene exposure. This suggests a new mechanism for ibuprofen's action.     

Interleukin 1 suppresses inflammation in rabbit colitis. Mediation by endogenous prostaglandins.

Pretreatment with low-dose IL-1 has protective effects in animal models of inflammation or tissue injury, but the mechanisms of these protective effects are not established. To determine if prostaglandins are involved, we administered human recombinant IL-1 beta and measured rectal PGE2 production in rabbits with formalin-immune complex colitis. IL-1 beta (0.3 micrograms/kg) administered 24 h before induction of colitis increased PGE2 (231 +/- 36 to 1,299 +/- 572 pg/ml, P less than 0.01) and reduced subsequent inflammatory cell infiltration index (from 2.8 +/- 0.3 to 1.4 +/- 0.3, P less than 0.02) and edema (from 2.5 +/- 0.3 to 1.3 +/- 0.3, P less than 0.01) compared with vehicle-matched animals. Administration of ibuprofen (10 mg/kg i.v.) together with IL-1 beta prevented the stimulation of PGE2 and the reduction in inflammation. Colonic PGE2 production correlated inversely with subsequent severity of inflammation (P less than 0.02, r = -0.39) and edema (P less than 0.04, r = -0.35). IL-1-administration 30 min before induction of colitis did not affect the severity of inflammation. Similarly, pretreatment with a noninflammatory synthetic peptide (fragment 163-171) of human IL-1 beta, either 30 min or 24 h before colitis induction, did not reduce inflammation or increase prostaglandin synthesis. These data demonstrate that pretreatment with IL-1 beta 24 h before the induction of colitis reduces inflammation by a mechanism that requires prostaglandin synthesis.     

Platelet-activating factor causes ventilation-perfusion mismatch in humans.

We hypothesized that platelet-activating factor (PAF), a potent inflammatory mediator, could induce gas exchange abnormalities in normal humans. To this end, the effect of aerosolized PAF (2 mg/ml solution; 24 micrograms) on ventilation-perfusion (VA/Q) relationships, hemodynamics, and resistance of the respiratory system was studied in 14 healthy, nonatopic, and nonsmoking individuals (23 +/- 1 [SEM]yr) before and at 2, 4, 6, 8, 15, and 45 min after inhalation, and compared to that of inhaled lyso-PAF in 10 other healthy individuals (24 +/- 2 yr). PAF induced, compared to lyso-PAF, immediate leukopenia (P < 0.001) followed by a rebound leukocytosis (P < 0.002), increased minute ventilation (P < 0.05) and resistance of the respiratory system (P < 0.01), and decreased systemic arterial pressure (P < 0.05). Similarly, compared to lyso-PAF, PaO2 showed a trend to fall (by 12.2 +/- 4.3 mmHg, mean +/- SEM maximum change from baseline), and arterial-alveolar O2 gradient increased (by 16.7 +/- 4.3 mmHg) (P < 0.02) after PAF, because of VA/Q mismatch: the dispersion of pulmonary blood flow and that of ventilation increased by 0.45 +/- 0.1 (P < 0.01) and 0.29 +/- 0.1 (P < 0.04), respectively. We conclude that in normal subjects, inhaled PAF results in considerable immediate VA/Q inequality and gas exchange impairment. These results reinforce the notion that PAF may play a major role as a mediator of inflammation in the human lung.     

The complement regulators C1 inhibitor and soluble complement receptor 1 attenuate acute lung injury in rabbits

Because activation of the complement system plays a major role in the pathogenesis of acute lung injury, the availability of new specific complement inhibitors represents a promising therapeutic approach. In the present study we investigated pulmonary edema formation and pulmonary artery pressure (PAP) in acute complement-induced lung injury for possible therapeutic impact of the complement regulators C1 inhibitor and soluble complement receptor 1. Eighteen isolated and ventilated rabbit lungs were perfused with pooled normal human serum (NHS, final concentration 35%) in Krebs-Henseleit buffer in a recirculating system. Lung weight gain and PAP were continuously recorded. Complement activation was blocked by the addition of C1 inhibitor (1.0 U/mL, n = 6) or sCR 1 (2.0 microg/mL, n = 6). Lungs that received NHS without inhibitors served as controls (n = 6). This study was performed according to the Helsinki Declaration and approved by the local government. Application of NHS resulted in an increase of PAP within 20 min from 8+/-2 to 42+/-6 mmHg, which was significantly (P < 0.05) decreased by C1-Inh (25+/-5 mmHg) and sCRI (20 +/-3 mmHg). Moreover, pulmonary edema formation after NHS, as assessed by overall weight gain, was reduced by both C1-Inh and sCR1, compared with controls. These findings were paralleled with significantly decreased thromboxane release rates and reduced tissue deposition of C3c and C5b-9. C1 inhibitor and sCR1 attenuate the complement-induced pulmonary capillary leakage and PAP increase, indicating the protective effect of complement inhibition in isolated perfused rabbit lungs.     

Hypothermia induces interleukin-10 and attenuates injury in the lungs of endotoxemic rats

We recently reported that hypothermia protects against intrapulmonary nitric oxide overproduction and nitric oxide-mediated lung injury in endotoxemic rats. Few studies have been performed to investigate whether hypothermia reduces inflammation by affecting favorable changes in chemokine and pro- and anti-inflammatory cytokine profiles. In this study, we tested the hypothesis that hypothermia decreases concentrations of growth-related oncogene/cytokine-induced neutrophil chemoattractant-1 (GRO/CINC-1), interleukin (IL)-1beta, IL-6, and myeloperoxidase and increases concentration of IL-10 in the lungs endotoxemic rats. Twelve rats were anesthetized and randomized to treatment with either hypothermia (T = 18-24 degrees C; n = 6) or normothermia (T = 36-38 degrees C, n = 6). Endotoxin (15 mg/kg of Escherichia coli lipopolysaccharide) was administered intravascularly and lung tissue was harvested 150 min later. Three additional rats were sham instrumented and maintained as normothermic but not given endotoxin. Hematoxylin & eosin staining was performed for qualitative inspection of tissues. Quantitative analyses of lung homogenates were performed using enzyme-linked immunosorbent assays for IL-1beta, IL-6, IL-10, and GRO/CINC-1. Myeloperoxidase concentrations were determined using a colorimetric assay. Hypothermia attenuated the induction of intrapulmonary IL-1beta (P < 0.05), IL-6 (P < 0.05), GRO/CINC-1 (P < 0.05), and myeloperoxidase (P < 0.05) caused by endotoxin. Inspection of the lungs revealed that hypothermia similarly attenuated histological signs of injury, such as interstitial edema and neutrophil accumulation. Hypothermia increased the intrapulmonary concentration of IL-10 more than 3-fold over that measured in the normothermia (endotoxin-exposed) group (P < 0.05). Hypothermia inhibits neutrophil recruitment in the lungs of endotoxemic rats in part by decreasing proinflammatory cytokine expression. Additionally, hypothermia induces intrapulmonary IL-10 expression. Further studies are needed to investigate whether IL-10 mediates the anti-inflammatory effects of hypothermia.     

Use of low tidal volume in septic shock may decrease severity of subsequent acute lung injury

Recent studies have indicated that protective lung strategies may improve outcomes in acute lung injury. We hypothesized that the use of a lower tidal volume early during septic shock may protect against the subsequent development of acute lung injury. Fourteen fasted, anesthetized, invasively monitored, mechanically ventilated, female sheep (26.4 +/- 4.5 kg) underwent cecal ligation and perforation to induce sepsis. Sheep were then randomized to ventilation with low (6 mL/kg) or high (12 mL/kg) tidal volumes. A positive end-expiratory pressure of 10 cm H(2)O was applied in each case. Ringer's lactate was titrated to maintain pulmonary artery occlusion pressure at baseline levels. No vasoactive agents or antibiotics were used. Survival time was longer in the low- than in the high-tidal-volume group (21.8 +/- 2.4 vs. 17.6 +/- 4.1 h, respectively, P < 0.05). The times to develop hypotension and anuria were longer in the low-tidal-volume group (18.1 +/- 3.1 vs. 12.0 +/- 2.8 h, P < 0.05, and 17.6 +/- 1.6 vs. 14.1 +/- 3.8 h, P < 0.05). Although the Pao2/Fio2 tended to be lower in the low- than in the high-tidal-volume group (P = 0.06), postmortem examination showed a lower lung tissue wet/dry ratio in the low- than in the high-tidal-volume group (7.1 +/- 0.5 vs. 9.1 +/- 0.7, P < 0.05). A low-tidal-volume ventilation strategy applied early during septic shock may be beneficial in terms of reducing the amount of lung edema and prolonging survival time.