The role of activation of neutrophils and microvascular pressure in acute pulmonary edema

Effects of vitamin E on pathological changes induced by diabetes in rat lungs

Twenty-fourmale rats were divided into three groups: Control (C), non-treated diabetic (NTD), and vitamin E-treated diabetic (VETD) groups. After 6 weeks, we evaluated the changes in the alveolar epithelium, alveolar septum thickness, Hcy, and cathepsin G levels in the lung tissue and plasma serine protease inhibitor levels.The results revealed a significant increase in alveolar septum thickness, a high number of type II pneumocytes, high number of glycogen granules, increased vascular elastic membrane thickness, and increased Hcy and cathepsin G levels in the diabetic rats. Plasma level of serine protease inhibitors showed a significant decrease in the NTD animals. The vitamin E-treated rats showed significant amelioration of lung tissue changes, as well as restoration of high cathepsin G, Hcy levels, and serine protease inhibitors when compared to the control rats. These results suggest that diabetes induces lung tissue changes that may be stimulated by Hcy and cathepsin G mediated oxidative stress by, and protective effect could be achieved by using vitamin E.

Gelam honey has a protective effect against lipopolysaccharide (LPS)-induced organ failure

Gelam honey exerts anti-inflammatory and antioxidant activities and is thought to have potent effects in reducing infections and healing wounds. The aim of this study was to investigate the effects of intravenously-injected Gelam honey in protecting organs from lethal doses of lipopolysaccharide (LPS). Six groups of rabbits (N = 6) were used in this study. Two groups acted as controls and received only saline and no LPS injections. For the test groups, 1 mL honey (500 mg/kg in saline) was intravenously injected into two groups (treated), while saline (1 mL) was injected into the other two groups (untreated); after 1 h, all four test groups were intravenously-injected with LPS (0.5 mg/kg). Eight hours after the LPS injection, blood and organs were collected from three groups (one from each treatment stream) and blood parameters were measured and biochemical tests, histopathology, and myeloperoxidase assessment were performed. For survival rate tests, rabbits from the remaining three groups were monitored over a 2-week period. Treatment with honey showed protective effects on organs through the improvement of organ blood parameters, reduced infiltration of neutrophils, and decreased myeloperoxidase activity. Honey-treated rabbits also showed reduced mortality after LPS injection compared with untreated rabbits. Honey may have a therapeutic effect in protecting organs during inflammatory diseases.

Chlorogenic acid protects mice against lipopolysaccharide-induced acute lung injury

Chlorogenic acid (CGA) is one of the most abundant polyphenol compounds in human diet. Our previous in vitro study demonstrates that CGA presents anti-inflammatory activities in RAW 264.7 cells. Here we show that CGA protects mice against lipopolysaccharide (LPS)-induced acute lung injury (ALI). We treated mice with CGA (5, 20 and 50 mg/kg body weight) 30 min or 3 h after intratracheal administration of LPS. The histological results showed that CGA, at dose of 50 mg/kg, protected mice from LPS-induced ALI which displayed by edema, haemorrhage, blood vessel and alveolar structural damage. CGA inhibited LPS-increased pulmonary MPO activity and migration of polymorphonuclear neutrophils (PMNs) into bronchoalveolar lavage fluid (BALF). Furthermore, CGA markedly decreased the activity of inducible nitric oxide synthase (iNOS) in lung tissues and thus prevented nitric oxide (NO) release in response to LPS challenge. In conclusion, these results indicated that CGA was greatly effective in inhibiting ALI and might act as a potential therapeutic reagent for treating ALI in the future.

Regulation of endothelial barrier function by reactive oxygen and nitrogen species

Excessive generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), by activated neutrophils and endothelial cells, has been implicated in the pathophysiology of endothelial barrier dysfunction. Disruption of the integrity of this barrier markedly increases permeability to fluids, solutes and inflammatory cells and is the hallmark of many disorders such as acute lung injury (ALI) and sepsis. There has been considerable progress in our understanding of the sequence of molecular and structural events that mediate the response of endothelial cells to oxidants and nitrosants. In addition, substantial experimental evidence demonstrates improvement of endothelial barrier dysfunction with antioxidant strategies. However, no significant benefits have been observed, so far, in clinical trials of antioxidants for the treatment of endothelial barrier dysfunction. This article will review the available evidence implicating ROS and RNS in endothelial barrier dysfunction, explore potential underlying mechanisms, and identify areas of further research.

Modeling error and stability of endothelial cytoskeletal membrane parameters based on modeling transendothelial impedance as resistor and capacitor in series

Transendothelial impedance across an endothelial monolayer grown on a microelectrode has previously been modeled as a repeating pattern of disks in which the electrical circuit consists of a resistor and capacitor in series. Although this numerical model breaks down barrier function into measurements of cell-cell adhesion, cell-matrix adhesion, and membrane capacitance, such solution parameters can be inaccurate without understanding model stability and error. In this study, we have evaluated modeling stability and error by using a χ2evaluation and Levenberg-Marquardt nonlinear least-squares (LM-NLS) method of the real and/or imaginary data in which the experimental measurement is compared with the calculated measurement derived by the model. Modeling stability and error were dependent on current frequency and the type of experimental data modeled. Solution parameters of cell-matrix adhesion were most susceptible to modeling instability. Furthermore, the LM-NLS method displayed frequency-dependent instability of the solution parameters, regardless of whether the real or imaginary data were analyzed. However, the LM-NLS method identified stable and reproducible solution parameters between all types of experimental data when a defined frequency spectrum of the entire data set was selected on the basis of a criterion of minimizing error. The frequency bandwidth that produced stable solution parameters varied greatly among different data types. Thus a numerical model based on characterizing transendothelial impedance as a resistor and capacitor in series and as a repeating pattern of disks is not sufficient to characterize the entire frequency spectrum of experimental transendothelial impedance.

Pulmonary neutrophil infiltration in murine sepsis: role of inducible nitric oxide synthase

Nitric oxide (NO) derived from inducible NO synthase (iNOS) contributes to the pathophysiology of acute lung injury (ALI). The effect of iNOS on pulmonary neutrophil infiltration in ALI is not known. Thus, we assessed pulmonary microvascular neutrophil sequestration through intravital videomicroscopy and pulmonary neutrophil infiltration, reflected by myeloperoxidase activity and lavage neutrophil counts, after induction of sepsis by cecal ligation/perforation in wild-type (iNOS+/+) versus iNOS-/- mice. Pulmonary microvascular neutrophil sequestration was attenuated in septic iNOS-/- versus iNOS+/+ mice (15 +/- 1 vs. 20 +/- 1 leukocytes per field, p < 0.05), but lavage neutrophil counts were greater in iNOS-/- mice (5.7 +/- 1.5% vs. 0.7 +/- 0.1%, p < 0.05) between 6 and 18 hours after cecal ligation and perforation. When iNOS+/+ bone marrow was transplanted into bone marrow-depleted iNOS-/- mice (+ to - chimeras; iNOS limited to marrow-derived inflammatory cells), septic pulmonary microvascular neutrophil sequestration and lavage neutrophil counts were restored to levels seen in septic iNOS+/+ mice. In contrast, in - to + chimeras, pulmonary neutrophil trafficking was similar to iNOS-/- mice. In vitro cytokine-stimulated neutrophil transendothelial migration was significantly greater for iNOS-/- versus iNOS+/+ neutrophils (7.9 +/- 0.7% vs. 3.8 +/- 0.6%, p < 0.05) but was independent of endothelial iNOS. Thus, neutrophil iNOS-derived NO is an important autocrine modulator of pulmonary neutrophil infiltration in murine sepsis.

The endothelium in sepsis: source of and a target for inflammation

OBJECTIVE

To discuss a possible role of the endothelium in sepsis.

DATA SOURCES

Studies published in biomedical journals and our own experimental results.

STUDY SELECTION

Studies on endothelial mechanisms in the context of sepsis.

DATA EXTRACTION AND SYNTHESIS

Changes in endothelial cells on activation by inflammatory stimuli are reviewed briefly; potential mechanisms that lead to endothelial damage during sepsis are discussed.

CONCLUSIONS

The endothelium is a key organ involved in the pathogenesis of sepsis. Dysfunction of or injury to the endothelium may be involved in the pathogenesis of multiple organ failure and should be discriminated from activation resulting from stimulation with inflammatory stimuli. Identification of the molecular mechanisms that contribute to endothelial dysfunction or damage is likely to provide novel targets for the treatment of sepsis.

The influence of polymorphonuclear leukocytes on altered pulmonary epithelial permeability during ozone exposure

Ozone (O3), a pulmonary irritant, and a major toxic component of photochemical smog, is capable of inducing pulmonary inflammation characterized by recruitment of polymorphonuclear leukocytes (PMNs) into the lung. The recruited PMNs, in turn, can release toxic mediators and produce lung injury. The mechanism of ozone-induced changes in lung permeability remains unknown. It is our hypothesis that PMNs migrating into the lung play a significant role in the pathophysiology following O3 exposure and that increasing the number of PMNs coming into the lung will exaggerate the changes in lung permeability. To test this hypothesis, we induced an influx of PMNs into the lungs of Sprague-Dawley rats by intratracheal instillation of 1% rabbit serum and then exposed the animals to either 0.8 ppm O3 or filtered air for 3 h. Control animals were intratracheally instilled with phosphate-buffered saline (PBS) and simultaneously exposed to O3 or filtered air in the same manner as the serum-treated animals. The animals were sacrificed and the lungs lavaged 10-12 h after exposure. The bronchoalveolar lavage fluid (BALF) was analyzed for albumin and protein, as indicators of permeability. In addition, BALF from the various groups was tested for its ability to alter epithelial resistance of pulmonary type II cells in culture. O3 exposure resulted in a significant increase in albumin and protein levels in the BALF as compared to air-exposed controls. The instillation of serum resulted in a significant increase in airway PMNs, but no significant elevations in albumin levels in both the O3 and air-exposed groups, as compared to PBS instillation. In vitro studies did not reveal a differential BALF effect on epithelial resistance. The data demonstrate that an excessive neutrophilia in the lung is not matched by a comparable amplification of epithelial injury. It is therefore suggested that a simple elevation in PMN number in the air spaces, as that induced by serum instillation, does not necessarily augment the lung pathophysiology, but that a more complex interaction with O3 may be required for cellular activation and release of toxic products.

Effects of a neutrophil elastase inhibitor (ONO-5046) on acute pulmonary injury induced by tumor necrosis factor alpha (TNFalpha) and activated neutrophils in isolated perfused rabbit lungs

The aim of this study was to examine the effect of ONO-5046, a neutrophil elastase (NE) inhibitor, on a model of acute lung injury induced by tumor necrosis factor alpha (TNFalpha) and phorbol myristate acetate (PMA)-activated neutrophils in isolated perfused rabbit lungs. 120 min after TNFalpha (4,000 JRU/ml) was injected into the pulmonary artery (PA), 5 x 10(7) PMA-stimulated neutrophils were infused into the PA together with 1251-rabbit serum albumin (RSA). In the ONO-5046-treated group (ONO), ONO-5046 (20 mg/kg/h) was continuously infused during the experimental period from 30 min prior to neutrophil administration. Saline, the ONO-5046 vehicle, was infused instead of ONO-5046 in the positive control group (ALD) and nonactivated neutrophils were infused without TNFalpha in the negative control group (Cont). PA pressure was monitored over a 240 min period, and bronchoalveolar lavage (BAL) was performed at the end of the experiment. Lung tissues were examined immunohistochemically for the expression of thrombomodulin (TM). The levels of TM in the perfusate were also measured by ELISA and the radioactivities in the BAL fluid, lung tissue and perfusate were determined to calculate the permeability index (PI) as an indicator of alveolar septal or vascular endothelial damage. The rabbit lungs infused with ONO-5046 showed slower and less increases in PA pressure compared with ALD group. The PI was significantly higher in ALD group (PI[BAL] = 0.028 +/- 0.014, PI[LUNG] = 0.04 +/- 0.003) than Cont (PI[BAL] = 0.002 +/- 0.001, PI[LUNG] = 0.015 +/- 0.003) and ONO group (PI[BAL] = 0.004 +/- 0.003, PI[LUNG] = 0.028 +/- 0.003 (p < 0.05). ALD group had higher TM levels in the perfusate and showed decreased expression of TM on the vascular endothelium compared to Cont and ONO group, suggesting that there was shedding of TM on endothelium and ONO-5046 attenuated a shedding of TM. In conclusion, ONO-5046 attenuated acute lung injury by inhibiting the alveolar epithelial and vascular endothelial injury triggered by activated neutrophils. NE appears to play an important role in the neutrophil-induced increase of pulmonary epithelial and microvascular permeability observed in acute lung injury.

Effects of ozone on the epithelial and inflammatory responses in the airways: role of tumor necrosis factor

We have investigated the possibility that tumor necrosis factor alpha (TNF) plays a role in the increased airway permeability and an inflammatory response following an acute ozone (O3) exposure. Male Sprague-Dawley rats were injected, intraperitoneally, with either rabbit anti-mouse antibody to TNF (anti-TNF) or preimmune rabbit serum, 2 h before a 3-h exposure to O3 or purified air. Permeability, as determined by [99mTc] diethylenetriamine pentaacetate (DTPA) transport, total protein and albumin concentrations in the bronchoalveolar lavage (BAL), and the inflammatory cell response in the BAL were assessed 10 h after the exposure was completed. The O3-exposed group that was injected with anti-TNF showed a significant decrease in permeability to DTPA in comparison to the O3- exposed group injected with preimmune rabbit serum. There was no difference between the anti-TNF group and the purified air group. In contrast, the total protein and albumin levels in the BAL were significantly greater in both of the O3-exposed groups than in the purified air group. The concentrations of protein and albumin in the anti-TNF group did, however, show an attenuating trend when compared to the preimmune O3-exposed group. The polymorphonuclear leukocytes (PMNs) in BAL of the anti-TNF group also showed an attenuating trend when compared to the preimmune O3-exposed group, but both of these O3-exposed groups were significantly greater than the purified air group. Lung sections stained with naphthol AS-D chloroacetate esterase showed an increase in the number of stained PMNs in the anti-TNF group in comparison to the preimmune O3- and air-exposed groups. These data suggest that TNF plays a role in the increase in tracheal permeability as determined by DTPA transport, while the contributing role that TNF plays in bronchoalveolar permeability and the inflammatory response seen following an acute exposure to 0.8 ppm O3 is less evident.

Biochemical and morphological alterations in xylazine-induced pulmonary edema

Sprague-Dawley rats were given 42 mg/kg xylazine intramuscularly, and lungs were lavaged with phosphate-buffered saline 3, 6, and 12 hr later. Total protein, lactate dehydrogenase (LDH), xanthine oxidase (XO), tumor necrosis factor (TNF), and interleukin 1 (IL-1) were measured in bronchoalveolar lavage fluid (BALF). Protein concentration, LDH, XO, and TNF levels were increased (p < 0.05) in the BALF from xylazine-treated rats as compared to controls. IL-1 level was unchanged at 3 and 6 hr and was reduced (p < 0.05) at 12 hr. Another group of rats was given 42 mg/kg xylazine intramuscularly, and lungs were fixed 0.5 and 12 hr later. Histologically, severe pulmonary edema (PE) involving the alveoli and perivascular stroma was observed. Fibrin, increased numbers of eosinophils, and macrophages with foamy cytoplasm were present in the alveoli of all treated animals. Ultrastructurally, endothelial damage, characterized by thinning, detachment from basement membranes, or bleb formation, was observed. The lesions were similar in both xylazine groups, differing mainly in severity with the 12-hr group having more severe lesions than the 0.5-hr group. To determine whether endothelial injury is caused by direct toxicity of xylazine, bovine pulmonary artery endothelial cells (BPAECs) were incubated with xylazine (0.3, 3, and 30 micrograms) for 0.5 or 3 hr. Xylazine did not have any effects on BPAECs, as indicated by phase-contrast microscopy and dye-exclusion viability assay. These results indicate that xylazine-induced PE is due to increased permeability resulting from endothelial injury, which is not caused by direct effect of xylazine on pulmonary endothelium. While oxygen radicals and TNF are possibly involved, IL-1 does not appear to play a role in xylazine-induced PE.

Neural regulation of neutrophil involvement in pulmonary inflammation

1. The high viscoelastic property of neutrophils is the major factor contributing to their extensive accumulation (more than 50% of circulating neutrophils) in the pulmonary microvasculature. 2. The cholinergic parasympathetic and adrenergic sympathetic nerves modulate the size of the pulmonary neutrophil pool by regulating arterial and venous pressures, increases in which promote or reduce neutrophil transit times, respectively. 3. Biochemical factors, such as the cytokines and complement, which act upon the neutrophils to increase their viscoelasticity and promote the interaction of neutrophil cell adhesion molecules with counter ligands on the endothelial cell, are the primary factors regulating the size of the pulmonary pool of vascular neutrophils. 4. The primary afferent nerves, through their release of substance P, are the most important neural elements regulating neutrophil accumulation and function. Substance P facilitates the actions of other inflammatory agents (e.g. LTB4, platelet activating factor) on neutrophil adhesion, migration and biochemical reactivity. 5. The sympathetic nervous system indirectly regulates neutrophil functions by regulating the release of an immunosuppressive factor from submandibular glands. 6. With continued, study of nervous system regulation of neutrophil function, the mechanisms by which psychological factors affect these cells will eventually be revealed.

Role of platelet-activating factor in pulmonary edema after coronary ligation in dogs

To evaluate whether PAF is related to the precipitation of pulmonary edema after myocardial ischemia, we studied the effect of a specific PAF antagonist, CV-6209, on the extravascular lung water level measured by the thermal-dye double indicator dilution method, ETV, after coronary ligation in dogs. Eight dogs served as sham control animals (group 1). The proximal left anterior descending coronary artery was ligated for 45 min in eight dogs (group 2), and the coronary artery was ligated after pretreatment with CV-6209 (1 mg/kg) in eight dogs (group 3). The ETV increased significantly after coronary ligation in groups 2 and 3. The amount of increase in ETV in group 2 was significantly larger than in group 3. Thus, CV-6209 can prevent the accumulation of extravascular lung water after coronary ligation without producing changes in pulmonary vascular dynamics, indicating that PAF may play an important role in pulmonary edema after myocardial ischemia.

Attenuation of ozone-induced airway permeability in rats by pretreatment with cyclophosphamide, FPL 55712, and indomethacin

Exposure of rats to ozone (O3) produces an increase in airway permeability and a concomitant influx of polymorphonuclear leukocytes in the lung. These observations raise the possibility that the inflammatory cells play a role in the cellular injury and increased airway permeability after O3 exposure. This study was therefore designed to determine if the inflammatory cells or their products are essential for the O3 effect. In a series of experiments, rats were rendered leukopenic with cyclophosphamide, treated with leukotriene B4 (LTB4), or with the inhibitors of lipoxygenase or cyclooxygenase products of arachidonic acid, followed by exposure to O3. A 2-h exposure to 0.8 ppm O3 caused a significant increase in the flux of proteins and albumin in bronchoalveolar lavage (BAL) and elevated the transport of 99mTc-diethylenetriaminepentaacetate (99mTc-DTPA) from trachea to blood. The treatment with cyclophosphamide caused a significant reduction in the circulating and pulmonary leukocytes and prevented an increase in tracheal mucosal permeability to 99mTc-DTPA and the protein and albumin flux in BAL. While the intratracheal instillation of LTB4 did not affect the permeability, tracheal permeability and albumin levels in BAL in rats treated with LTD4 antagonist FPL 55712 and exposed to O3 were lower than in the untreated O3-exposed rats. Pretreatment with indomethacin also prevented the O3 effects, as reflected by the decreased protein and albumin flux in BAL and 99mTc-DTPA transport from trachea to blood. These data show a reduction in the effect of O3 by agents that affect leukocytes or their products. The results support a mechanism of increased permeability that is dependent upon inflammatory cells and their products.

Interleukin-8 in sepsis: relation to shock and inflammatory mediators

Because of its neutrophil-activating properties, interleukin-8 (IL-8) may play an important role in the pathophysiology of sepsis. We measured circulating IL-8 levels in 47 patients with clinical sepsis. Levels on admission were elevated in 42 of the 47 patients (89%) and were comparable in patients with gram-positive or gram-negative infections. Patients with shock had significantly higher IL-8 levels than normotensive patients (P = 0.0014, Wilcoxon-Mann-Whitney test), whereas no differences in IL-8 levels were found between patients with or without adult respiratory distress syndrome. Patients who died had higher IL-8 levels on admission than the patients who survived. The largest differences in IL-8 levels between survivors and nonsurvivors was found when only patients with positive cultures were considered (P = 0.0342). IL-8 levels appeared to correlate significantly with lactate levels and inversely with leukocyte and platelet numbers and mean arterial pressure. In addition, the IL-8 level in the sepsis patients was found to correlate significantly with levels of IL-6, elastase-alpha 1-antitrypsin, and C3a. Serial observations revealed that in most patients IL-8 levels decreased, irrespective of the outcome. Thus, our results demonstrate that IL-8 levels are increased in most patients with sepsis and correlate with some important clinical, biochemical, and inflammatory parameters. These findings suggest a role for IL-8 in the pathophysiology of sepsis.

Activated neutrophils alter contractile properties of the pulmonary artery

Activated neutrophils produce a wide array of products (free radicals, arachidonate metabolites, degradative enzymes), cause hemodynamic effects and increased permeability in isolated blood-free perfused lungs, and evoke direct injury to cultured endothelial cells. The aims of this study were to investigate the response of isolated rat pulmonary arterial rings to activated neutrophils, the role of intact endothelium in these responses, and which neutrophil products were responsible for the observed effects. Neutrophils activated with phorbol myristate acetate caused an initial increase in tension and a subsequent decreased recovery contraction to KCl. Neutrophils activated with formylmethionylleucylphenylalanine also caused an increase in tension but did not result in decreased recovery, suggesting different mechanisms for these two effects. The contractile response was dependent on endothelium, whereas the decline in recovery still occurred in the absence of endothelium. Filtrate from activated neutrophils did not cause the contractile response, but recovery was decreased. Neither addition of catalase + superoxide dismutase nor decreased superoxide release due to prior activation of neutrophils altered the initial contraction or the decline in recovery contractile ability, suggesting that oxygen free radical products were not responsible for either effect. The cyclooxygenase inhibitors (ibuprofen and indomethacin), the thromboxane A2 synthetase inhibitor (OKY-046), and pretreatment of the neutrophils with aspirin inhibited the contractile response but did not prevent the decrease in recovery. A mixture of antiproteases did not protect the arterial muscle from the decline in recovery. Although cyclooxygenase products may be involved in initiating the contraction in response to activated neutrophils, the mechanism resulting in subsequent loss of force-developing ability is unclear.

Multiple Organ Failure Syndrome—Part I: Epidemiology, Prognosis, and Pathophysiology

The multiple organ failure syndrome (MOFS) is the leading cause of death in intensive care units. Although sepsis is an important cause of MOFS, it is clear that MOFS can occur in the absence of infection. The pathophysiology of MOFS is complex and multifactorial and includes derangements in oxygen delivery and consumption, the release of inflammatory and vasoactive mediators capable of inflicting tissue damage, and alterations in the barrier function of the intestinal mucosa. Although advances have been made in our understanding of MOFS, treatment remains nonspecific and largely supportive. Early and aggressive restoration of tissue perfusion, adequate treatment of infection, timely nutritional support, and support of individual failed organs remain the mainstay of therapy. Therapeutic agents directed against the various mediators associated with the pathophysiology of MOFS may prove useful in the future.

Ridogrel prevents the thromboxane-mediated pressor response and oedema induced by hydrogen peroxide in isolated rabbit lungs

Perfusion of isolated rabbit lungs with hydrogen peroxide (H2O2, 3 x 10(-5) M) raised the overflow of thromboxane B2 (TXB2) and the perfusion pressure. H2O2 induced oedema formation and endothelial distress, as evidenced by an increased production of 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha). Endothelial cell death did not occur since there was no release of lactate dehydrogenase. The thromboxane A2 (TXA2)-synthase inhibitor/receptor antagonist ridogrel (R68070) further enhanced 6-oxo-PGF1 alpha output, while inhibiting TXB2 release. Ridogrel prevented the rise in pulmonary artery pressure and oedema formation. These data indicate that TXA2 is probably involved in the acute pulmonary pressor response and concomitant oedema formation induced by H2O2. In order to assess the functional activity of the pulmonary endothelium, the uptake of 5-hydroxytryptamine (5-HT) was measured before and 15 min after exposure to H2O2. As the H2O2-induced effects were not associated with any change in the uptake of 5-hydroxytryptamine (5-HT), we conclude that the endothelial injury was reversible or that the 5-HT uptake was not sensitive enough to evaluate the integrity of the pulmonary endothelium during oxidant-induced injury.

Calcium ionophore-activated neutrophils prestimulated with endotoxin increase pulmonary arterial pressure and vascular leakage in isolated perfused rat lungs: role of platelet-activating factor

The influence of stimulated polymorphonuclear neutrophils on pulmonary arterial pressure and vascular leakage in isolated perfused rat lungs was investigated. We exposed isolated neutrophils to various stimuli in vitro, instilled the cells in the lung perfusate, and studied the effects on pulmonary arterial pressure and passage of fluorescently labeled dextran (4100 dalton) from the pulmonary circulation into the lung. We found that neutrophils stimulated with the calcium ionophore A23187 or with E. coli endotoxin had no significant influence on the pressure or the passage of dextran. On the other hand, neutrophils preincubated with endotoxin and then stimulated with A23187 caused significant increases, both in pulmonary arterial pressure and accumulation of dextran in the lung. Both these effects were attenuated by BN 52021, a specific platelet-activating factor antagonist, and by nordihydroguaiaretic acid, an agent that inhibited the generation of platelet-activating factor in A23187-stimulated neutrophils. These findings demonstrate that activated neutrophils can increase pulmonary arterial pressure and lung fluid accumulation and suggest that endotoxin-stimulated activated neutrophils exert at least some of their action via generation of platelet-activating factor.

Mechanisms of pulmonary edema induced by tumor necrosis factor-alpha

We tested the hypothesis that human recombinant tumor necrosis factor-alpha (TNF) promotes pulmonary edema by neutrophil-dependent effects on the pulmonary vasculature. The isolated guinea pig lung was perfused with phosphate-buffered Ringer's solution with or without human neutrophils. The infusion of neutrophils (9 x 10(6) total) into lungs isolated after the in vivo administration of TNF (3.2 x 10(5) units/kg) resulted in weight gain (+1.951 +/- 0.311 g versus -0.053 +/- 0.053 g in control) and an increase in the lung (wet-dry)-to-dry weight ratio (8.3 +/- 0.5 versus 6.0 +/- 0.2 in control), indicating the formation of pulmonary edema. The neutrophil-dependent pulmonary edema induced by TNF was associated with a combination of increased capillary permeability (capillary filtration coefficient [Kf,c], 0.170 +/- 0.048 g/min/cm H2O/g at 30 minutes versus 0.118 +/- 0.008 g/min/cm H2O/g at baseline) and increased pulmonary capillary pressure (Ppc, 12.8 +/- 0.8 cm H2O at 60 minutes versus 6.0 +/- 0.3 cm H2O at baseline). The Ppc increase was mediated by thromboxane A2 (TXA2) because the TXA2 synthetase inhibitor Dazoxiben (0.5 mM) prevented the effect (Ppc, 6.7 +/- 0.6 cm H2O at 60 minutes with Dazoxiben), and thromboxane B2 (TXB2) levels were increased in the pulmonary venous effluent (5,244 +/- 599 pg/ml at 60 minutes versus 60 +/- 13 pg/ml at baseline). Studies using WEB-2086 (37 microM), a platelet activating factor (PAF) receptor antagonist, indicated that PAF mediated the increased vascular permeability (Kf,c, 0.107 +/- 0.014 g/min/cm H2O/g at 30 minutes using WEB-2086) and, in part, the increased Ppc (Ppc, 8.4 +/- 0.7 cm H2O at 60 minutes using WEB-2086). In addition, alterations of endothelial peripheral actin bands were noted after TNF administration. The data indicate that TNF induces neutrophil-dependent pulmonary edema associated with increased Ppc (mediated by TXA2 and PAF), increased Kf,c (mediated by PAF), and changes in endothelial peripheral actin bands.