Lipopolysaccharide binding protein and CD14 interaction induces tumor necrosis factor-alpha generation and neutrophil sequestration in lungs after intratracheal endotoxin.

It has been proposed that lipopolysaccharide (LPS) bound to the 60-kD LPS binding protein (LBP) forms an LPS/LBP complex that, in turn, binds to the CD14 receptor on monocytes/macrophages and stimulates the release of cytokines. We examined the role of LBP and CD14 in tumor necrosis factor-alpha (TNF-alpha) production and neutrophil (polymorphonuclear leukocyte [PMN]) sequestration in lungs induced by intratracheal instillation of LPS using rabbit lungs perfused at constant flow with lactated Ringer-albumin solution. LPS alone (Salmonella minnesota, wild type; 20 ng) or in the presence of LBP (500 ng) was injected intratracheally. In some experiments, human PMNs (5 x 10(7)) were added to the perfusate after a 2-hour period of perfusion. Samples of lung perfusate were collected every 30 minutes for 180 minutes when bronchoalveolar lavage was also performed. TNF-alpha concentrations in the perfusate and bronchoalveolar lavage fluid were determined by use of a bioassay with L-929 fibroblasts, and PMN accumulation in lungs was determined by myeloperoxidase assay of lung homogenates. LPS alone did not significantly increase TNF-alpha production or lung PMN accumulation, whereas the LPS/LBP complex increased TNF-alpha concentration in perfusate twofold and PMN accumulation twofold compared with the effect of LPS alone. Intratracheal instillation of anti-CD14 monoclonal antibody MY4 (40 micrograms) with the LPS/LBP complex prevented TNF-alpha release and PMN sequestration, whereas an isotype-matched control monoclonal antibody was ineffective. Therefore, LBP in the airspace enhances the LPS effect on TNF-alpha production via a CD14-dependent pathway, and as a result, CD14 activation can contribute to lung PMN sequestration.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of antioxidant substances in bronchoalveolar lavage cells and fluid from humans, guinea pigs, and rats.

Antioxidants located in the lining layer of the respiratory tract may be important in determining sensitivity of lung tissues to inhaled pollutants. This study addressed species differences in the amounts of ascorbic acid (AH2), glutathione (GSH), uric acid (UA), and alpha-tocopherol (AT) in bronchoalveolar lavage (BAL) fluid and cells of humans, guinea pigs, and rats. Protein and lipid phosphorus (lipid P) were used as normalizing factors. More than 90% of the lavageable AH2, UA, GSH, protein, and lipid P was present in the extracellular fraction of BAL in rats and guinea pigs, while over 95% of the lavageable AT was located in the BAL cells. BAL fluid AH2/protein in rats was 7- to 9-fold higher than in humans and guinea pigs. However, human BAL fluid had 2- to 8-fold higher UA/protein, GSH/protein, and AT/protein ratios than rats and guinea pigs. In BAL cells, rats had higher AH2/protein and AT/protein ratios than guinea pigs and humans, and both rats and guinea pigs had higher GSH and AT/protein ratios than humans. Individual variability among humans in the BAL fluid and cellular antioxidants was generally greater than in the laboratory animals. These data demonstrate that some large species differences exist in BAL fluid and cellular antioxidants which could affect susceptibility to oxidant pollutants.

Effects of nordihydroguaiuretic acid on sulfidopeptide leukotriene activity and hypoxic pulmonary vasoconstriction in the isolated sheep lung.

Sulfidopeptide leukotrienes have been proposed as mediators of hypoxic pulmonary vasoconstriction. We studied the effects of nordihydroguaiuretic acid (NDGA), a lipoxygenase inhibitor, on hypoxic pulmonary vasoconstriction and on immunoreactive leukotriene C4 (i-LTC4) levels in lung lymph, perfusate and bronchoalveolar lavage (BAL) fluid in isolated, indomethacin treated, sheep lungs perfused with blood at a constant flow of 100 ml/kg/min. The protocol consisted of two randomized periods with inspired 02 concentration either 28.2 or 4.2%. Five groups of lungs were studied with calculated NDGA concentrations of 0 to 1300 microM. At the end of each period, i-LTC4 was measured in lung lymph, perfusate and BAL. NDGA levels were also measured. Consistent with our previous findings (10), hypoxia did not increase i-LTC4 levels in lymph, perfusate or BAL fluid. Although NDGA decreased i-LTC4 in perfusate in a dose-dependent manner, it did so at concentrations which were ten times lower than those causing inhibition of hypoxic vasoconstriction. These NDGA concentrations also inhibited vasomotor responses to KCl, serotonin and PGF2 alpha suggesting nonspecificity. These observations are not consistent with mediation of hypoxic vasoconstriction by i-LTC4.

Sympathectomy and beta-adrenergic blockade during lung maturation stimulated by TRH and cortisol in fetal sheep.

To test whether beta-adrenergic mechanisms and the sympathetic nervous system are involved in the synergistic action of thyrotropin-releasing hormone (TRH) and cortisol on lung maturation, fetal sheep (n = 32) were infused from 121 to 128 days of gestation with saline, TRH + cortisol, TRH + cortisol + beta-adrenergic blocker, or TRH + cortisol after chemical sympathectomy with 6-hydroxydopamine. TRH + cortisol increased lung distensibility and stability and alveolar concentrations of saturated phosphatidylcholine two- to threefold over control fetuses. beta-Adrenergic blockade prevented the increase in distensibility in response to TRH + cortisol. Sympathectomy did not impair the increase in distensibility and stability in response to TRH + cortisol but inhibited the increase in alveolar total phospholipids. Tissue concentrations of saturated phosphatidylcholine increased in TRH + cortisol-treated fetuses after either sympathectomy or beta-adrenergic blockade. We concluded that during lung maturation by TRH + cortisol 1) sympathetic mechanisms are requisite for surfactant release, 2) nonneurogenic beta-adrenergic mechanisms are requisite for the maturation of the mechanical properties of the lung and 3) stimulation of surfactant synthesis is independent of beta-adrenergic action and the sympathetic nervous system.

The effect of zardaverine, an inhibitor of phosphodiesterase isoenzymes III and IV, on endotoxin-induced airway changes in rats.

Zardaverine is a novel phosphodiesterase III/IV inhibitor, developed as a potential therapeutic agent for asthma. In this study we evaluated the effect of zardaverine in an in vivo animal model of airway inflammation and hyperresponsiveness. Endotoxin exposure in rats causes a transient increase in airway responsiveness and a neutrophilic inflammation of the bronchi, which are both at least partly mediated through the secondary release of tumour necrosis factor alpha (TNF alpha). Groups of 10 animals each were pretreated with placebo or zardaverine (1, 10, 30 mumol/kg) i.p., 30 min prior to exposure to aerosolized endotoxin (LPS) or saline. Ninety minutes later, airway responsiveness to 5-HT was assessed and bronchoalveolar lavage (BAL) performed. Zardaverine did not influence baseline lung resistance (RL), but inhibited dose dependently the 5-HT induced increase in RL in control animals. In placebo pretreated animals LPS exposure caused a significant decrease in PC50RL5-HT (provocative concentration of 5-HT causing a 50% increase in RL), compared to the saline exposed control group (1.1 +/- 0.1 vs 2.7 +/- 0.4 micrograms/kg) (P < 0.01). This decrease in PC50RL5-HT was significantly inhibited by zardaverine 30 mumol/kg (5.4 +/- 1.8 vs 1.1 +/- 0.1 micrograms/kg) (P < 0.05). Compared to placebo pre-treated, LPS exposed animals, zardaverine 30 mumol/kg also significantly inhibited to LPS induced neutrophil increase (193.0 +/- 50.0 vs 915.6 +/- 181.3 x 10(3)) (P < 0.01), increase in elastase activity (23 +/- 11 vs 54 +/- 9 nmol substrate/h/ml) (P < 0.05) and TNF alpha release in BAL fluid (93.1 +/- 19.5 vs 229.5 +/- 24.8 U/ml BAL fluid) (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Compartmentalization of the acute cytokine response in humans after intravenous endotoxin administration.

Lung cytokine production was examined after the intravenous administration of endotoxin to 23 normal human subjects. Bronchoalveolar lavage (BAL) was performed 7 days before and 1.5 or 5 h after endotoxin (4 ng/kg). Cytokine mRNA was evaluated in cell pellets (> 98% macrophages) by use of reverse transcription and the polymerase chain reaction. Immunoreactivity was measured by enzyme-linked immunosorbent assay of 20- to 40-fold concentrated BAL. Interleukin- (IL) 8 was detected in BAL (4-130 pg/ml) but not in the serum at baseline. Few neutrophils were found in BAL (< 1%) despite this IL-8 gradient. Peak serum IL-8 levels occurred 2 h after endotoxin (3,930 +/- 241 pg/ml), but BAL neutrophils and IL-8 did not increase. Peak serum tumor necrosis factor (TNF) levels occurred 1.5 h after endotoxin (1,844 +/- 210 pg/ml), but TNF was detected in only 1 of 20 BAL samples. TNF and IL-8 mRNA were detected by polymerase chain reaction in > 70% of the BAL samples before endotoxin, whereas IL-1 alpha, IL-1 beta, and IL-6 were detected in < 25% of the BAL samples. After endotoxin, no change was detected in cytokine mRNA expression. Actinomycin D treatment of the BAL did not alter the pattern of cytokine mRNA expression. These data suggest that mechanisms exist to insulate the alveolar space from the stimulatory effects of endotoxin and high circulating levels of cytokines. Additional factors appear to control the chemotactic effects of IL-8 on neutrophils in the air spaces during acute systemic inflammation.

Inter-strain variation in susceptibility to hyperoxic injury of murine airways.

The contribution of genetic background in susceptibility to hyperoxic lung injury is not clear. We utilized inbred mice to: 1) characterize inter-strain variation in hyperoxia-induced effects on lavageable indicators of airway epithelial injury; 2) test the hypothesis that hyperoxia-induced change in airway permeability is under Mendelian control. Male mice (5-7 wk, 20-25 g) from six inbred strains were exposed to 95-99% oxygen (O2) or room air for 0, 48, or 72 h. Hyperoxia-induced alteration in lung permeability was estimated by changes in lung wet weight:dry weight ratio and total bronchoalveolar lavage (BAL) protein concentration. The airway inflammatory response to O2 was assessed by changes in cellular profiles in BAL fluid. At least two distinct phenotypes were found among the strains exposed to O2 for 72 h. The susceptible phenotype (exemplified by C57BL/6J [B6] mice) was characterized by mean BAL protein concentration that was approximately 10 times greater than the resistant phenotype (e.g. C3H/HeJ [C3] mice). Hyperoxia caused LWW:LDW to double in susceptible B6 mice relative to controls, while no significant change was found in resistant C3 mice. Compared to air-exposed controls, hyperoxia also decreased the mean number of BAL alveolar macrophages and increased polymorphonuclear leukocytes in B6 mice, but the inflammatory cell profile of C3 mice was not affected after 72 h. The observed ratios of resistant to susceptible phenotypes of F1, F2, and back-cross progeny from B6 and C3 progenitors were not consistent with the hypothesis that susceptibility to hyperoxia is under Mendelian control.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological model for airway hypersensitivity produced by propranolol and reserpine in guinea pigs.

Combined treatment with propranolol and reserpine enhanced acetylcholine-induced dose-response curves for bronchoconstriction in guinea pigs in vivo. This airway hyperreactivity model was investigated pharmacologically. (1) Increased capillary permeability and increases in leukocytes in bronchoalveolar lavage fluid (BALF) were not observed after this combined treatment. (2) The increased airway sensitivity to acetylcholine produced by propranolol and reserpine was inhibited by ketotifen and theophylline, reported in clinical studies to inhibit airway hyperreactivity. (3) Two leukotriene (LT) receptor antagonists, MCI-826 and FPL-55712, clearly inhibited this increased airway reactivity. (4) A thromboxane A2 (TXA2) receptor antagonist, ONO-3708, and TXA2 synthetase inhibitor, OKY-046, also inhibited this increased airway reactivity. These results suggest that the airway hyperreactivity model produced by propranolol and reserpine in guinea pigs is a valuable pharmacological tool for investigating a remedy and LT and TXA2 may be involved in the onset of this airway hyperreactivity.

N-acetylcysteine delays the infiltration of inflammatory cells into the lungs of paraquat-intoxicated rats.

We investigated a possible role for N-acetylcysteine (NAC), a well-known antioxidant and free radical scavenger, against oxidative lung damage as observed in the in vivo model of paraquat-intoxicated rats. The administration of two ip doses of 50 mg/kg NAC to paraquat-intoxicated animals did not change the glutathione status of the lungs, as determined by the measurement of nonprotein sulfhydryl (NP-SH) groups. The administration of NAC did however suppress the paraquat-induced release of chemoattractants for neutrophils in the bronchoalveolar fluid when the lavage was carried out 12 hr after the administration of 30 mg/kg paraquat. Also, in the intoxicated NAC-treated animals, the infiltration of inflammatory cells was significantly reduced, as demonstrated by the examination of the cell composition of the bronchoalveolar lavage (BAL), 24 hr after paraquat. Phorbol myristate acetate-stimulated superoxide anion production from the AM isolated from the BAL of paraquat-intoxicated nontreated animals was lower than that of controls, whereas in the NAC-treated animals, it was close to that of the controls. The obtained results indicate that NAC has a protective effect against oxidative lung damage by delaying inflammation. It also prevents the paraquat-induced reduction of superoxide anion production by stimulated AM. In the present model, however, the NAC administration regimen did not affect the survival rate of paraquat-intoxicated rats.

Effect of formoterol on superoxide anion generation from bronchoalveolar lavage cells after antigen challenge in guinea pigs.

It is well known that antigen challenge of sensitized subjects can induce an immediate and late asthmatic response, airway eosinophilia, and hyperreactivity. Using our modified guinea pig asthma model, we investigated the superoxide anion generation from eosinophils and macrophages recovered from bronchoalveolar lavage (BAL) 24 h after antigen (ovalbumin) challenge. We also investigated the effect of formoterol, a new long-acting selective beta 2-agonist, on these functions. Antigen challenge increased the total cell counts and the ratio of eosinophils in BAL. Eosinophils and macrophages were collected using discontinuous density centrifugation. Antigen challenge enhanced superoxide anion generation from eosinophils, from 5.39 +/- 1.08 to 13.19 +/- 1.95 nmol 60 min after phorbol myristate acetate (PMA) (1 ng/ml) activation, and 0.22 +/- 0.49 to 3.34 +/- 1.67 nmol 40 min after platelet-activating factor (PAF) (10(-6) M) activation. Formoterol treatment before antigen challenge prevented these enhancements. Superoxide anion generation from macrophages was also enhanced by antigen challenge, from 6.57 +/- 0.76 to 10.66 +/- 0.88 nmol 60 min after PMA activation, and 4.20 +/- 1.17 to 6.63 +/- 0.64 nmol 60 min after PAF activation. Formoterol, however, failed to inhibit enhancement of superoxide anion generation from macrophages. These results show antigen challenge of sensitized guinea pigs induces an increase of eosinophils and macrophages in BAL and enhances the functional characteristics of both cells. Formoterol had inhibitory effects on the enhancement of superoxide anion generation from eosinophils but did not have this effect on macrophages.

Modulation of biochemical and cytological profile of bronchoalveolar lavage constituents in rats following split-dose multiple inhalation exposure to methyl isocyanate.

1. Studies were carried out to explore the acute pulmonary effects of equal, split-dose, multiple inhalation exposures of rats to methyl isocyanate (MIC), (0.32 mg l-1, 8 min x 10 exposures) as reflected by alterations in bronchoalveolar lavage fluid (BALF) constituents and to evaluate recovery, if any, following survival in a MIC-free environment, 10 d after the last MIC exposure. 2. In the BALF of MIC-exposed rats, there was an increase in the total number of cells and the number of cells showing enhanced dye uptake and reduction of nitroblue tetrazolium chloride. The cell-free BALF showed increases in total protein, sialic acids and lactic acid contents and lactate dehydrogenase activity. 3. In rats exposed to MIC and sacrificed 10 d after survival in a MIC-free environment, there was a reduction in the cellular and biochemical constituents of BALF. The phagocytic potential of macrophages was, however, also decreased under this regime.

Hyperoxic lung injury in Fischer-344 and Sprague-Dawley rats in vivo.

Supplemental oxygen remains an important therapy for pulmonary insufficiency, despite the potential adverse effects of hyperoxic exposures. Recently, He et al. reported that hyperoxic ventilation more readily damaged isolated perfused lungs from Fischer-344 rats than from Sprague-Dawley rats (Am. J. Physiol. 259:L451), which correlates with the previously reported strain differences in hepatic responses to diquat-induced oxidant stress in vivo (J. Pharmacol. Exp. Ther. 235:172). We therefore examined the differences in hyperoxic lung injury in Fischer-344 and Sprague-Dawley rats in vivo. Adult male rats were exposed to > 95% O2 and were sacrificed after 24, 48, or 60 h. Control animals were maintained in room air. Dramatically greater increases in pleural effusions and bronchoalveolar lavage protein concentrations in response to hyperoxia were observed in the Fischer-344 rats than in the Sprague-Dawley rats (p < .05 at both 48 and 60 h for both measurements). Additionally, the glutathione concentrations in alveolar lining fluid decreased from 800 microM to 115 microM in Fischer-344 rats after 60 h of > 95% O2, but did not change in Sprague-Dawley rats. We conclude that the greater susceptibility of Fischer-344 than of Sprague-Dawley rats to hyperoxic lung injury in vitro reported previously also is observed in vivo and that this strain difference offers unique opportunities to study mechanisms of hyperoxic lung injury.

Pulmonary toxicity of deferoxamine in iron-poisoned mice.

Previously we have shown that a group of patients treated for iron overdose with prolonged deferoxamine (DFO) infusion died of adult respiratory distress syndrome (ARDS). We now describe a model to investigate the mechanism of this pulmonary toxicity. Mice treated with 1 oral dose of iron (Fe) and then multiple injections of DFO, or with the chelated product ferrioxamine alone, did not develop lung lesions, even at doses which induced mortality. To potentiate any possible free radical reaction, other groups of mice were treated similarly while exposed to 75-80% O2 over a 4-day period. Ten of 12 mice receiving 0.75 mg Fe and then DFO (10 mg, 4 times/day for 4 days) with hyperoxia died suddenly. At autopsy the lungs were dark red and solid; sections showed hyaline membranes and alveolar exudates of edema, fibrin, and PMN. Electron microscopy showed massive destruction of the alveolar epithelium; using cerium chloride, a free radical reaction product was demonstrated at the alveolar surface. Lung lavage fluid contained 10-12 x normal levels of protein when the Fe-DFO-O2 group was compared to air or O2 controls. Mice receiving DFO or Fe, plus O2, showed only slight injury and a small increase in alveolar protein. The results indicate that Fe plus DFO generates free radicals in the lung, a reaction potentiated by hyperoxia to produce an ARDS-like picture. This suggests that the pulmonary toxicity of DFO in iron-poisoned patients is due to its prooxidant activity resulting in free radical destruction of the airblood barrier.

Acrolein increases airway sensitivity to substance P and decreases NEP activity in guinea pigs.

The effects of acrolein exposure on airway responses to intravenous substance P were determined in guinea pigs exposed to vehicle or 1.6 ppm acrolein for 7.5 h on 2 consecutive days and examined 1, 4, 8, 15, and 28 days after exposure by use of pulmonary mechanics and bronchoalveolar lavage (BAL). Lung, trachea, liver, and BAL fluid were also assayed for neutral endopeptidase (NEP) activity 1, 7, and 28 days after exposure. Pulmonary inflammation and epithelial damage were prominent 1 day after acrolein exposure. NEP activity was decreased in the lungs, trachea, and liver 1 and 7 days after acrolein. Twenty-eight days after exposure, NEP activity in the lungs and liver was not significantly different in vehicle- and acrolein-exposed guinea pigs but was still reduced in tracheal tissue. The BAL NEP activity in acrolein-exposed guinea pigs was approximately twice that of vehicle control guinea pigs at all three time points. Acrolein caused a prolonged increase in airway sensitivity to substance P. Experiments performed in the presence of thiorphan suggested that the acrolein-induced reduction in NEP may contribute to increased airway sensitivity to aerosolized substance P, but the increase in airway sensitivity to intravenous substance P may occur by additional mechanisms.

Endotoxin priming followed by high altitude causes pulmonary edema in rats.

Rapid ascent to high altitude may be associated with the development of high-altitude pulmonary edema (HAPE) in susceptible individuals. Because lung lavage fluid obtained from such patients can be rich in protein and neutrophils, we considered that an element of lung injury and inflammation contributed to the pathogenesis of some forms of HAPE. On the basis of such a likely contribution of inflammatory mechanisms, we induced pulmonary lung injury and inflammation by priming rats with Salmonella enteritidis endotoxin (ETX) (0.1 or 0.5 mg/kg body wt ip) and examined the influence of added exposure to simulated hypobaric hypoxia (24 h, 4,300 m). The animals that were primed with ETX and exposed to hypoxia, but not those that received either ETX or hypoxia alone, developed lung vascular damage. This vascular damage manifested itself histologically and by increases in the lung vascular permeability-surface area product and the lung bloodless wet weight-to-dry weight ratio. The bronchoalveolar lavage fluid of ETX-primed hypoxia-exposed rats contained a greater number of white blood cells and a higher concentration of protein compared with that of the ETX-primed rats. Hearts of ETX + hypoxia-treated rats showed an increased ratio of right ventricular weight divided by body weight (RV/BW). Neutropenia prevented the development of pulmonary edema and the increase in ETX + hypoxia rats with a Ca2+ entry blocker inhibited lung injury and RV hypertrophy, these results indicate that ETX priming causes pulmonary edema at high altitude and suggest a role for neutrophils and Ca2+ in this rat model of lung injury.

Low molecular weight PLA: a suitable polymer for pulmonary administered microparticles?

Beclomethasonedipropionate (BDP)-containing microparticles were prepared by the solvent evaporation/extraction method. Different preparation parameters were optimized before investigations. Polylactic acid (PLA) and polylactic/glycolic acid (PLGA) with molecular weights of 2000 and 15,000 were used as matrix polymers. In all experiments the mean diameter of the microparticles was 1-5 microns with a drug content > or = 23 per cent. Microparticles of PLA, MW 2000, showed a prolonged and complete release over 8 h, whereas those of PLGA liberated only 20 per cent of the encapsulated drug within 8 h. BDP was determined by a validated reversed-phase HPLC method with a detection limit of 20 ng/ml. The encapsulated steroid seemed to be dissolved within the polymer, as differential scanning calorimetry suggested. Considering mean particle size, drug load, release characteristics and the status of the drug inside the matrix, the dosage form showed very good characteristics for inhalatory application. Surface characteristics of the microparticles were visualized by scanning electron microscopy (SEM). Although in vitro studies with human bronchial fluid resulted in a strong deterioration of microparticles, main structures were still visible by SEM after an incubation of 36 h in diluted bronchial fluid ex vivo. Degradation in phosphate buffered saline, protein solution and even in port liver esterase suspension resulted in minor effects on the particle surface.

Pharmacokinetic measurement of drugs in lung epithelial lining fluid by microdialysis: aminoglycoside antibiotics in rat bronchi.

A novel technique for in vivo intrabronchial pharmacokinetic measurements using microdialysis is described. The technique was applied to the measurement of tobramycin and gentamicin in the anesthetized rat. The concentration versus time profiles of the drugs in the lung epithelial lining fluid (ELF) following intravenous bolus administration were determined. The mean penetration ratios into the ELF were determined and found to be 0.36 +/- 0.06 (mean +/- SEM, n = 5) for gentamicin and 0.56 +/- 0.09 (mean +/- SEM, n = 5) for tobramycin. The findings suggest that the technique can be used for intrabronchial pharmacokinetic measurement of drugs in the lung, either as an extension of the bronchoalveolar lavage technique or as a practical alternative to it.

Lavage phospholipid concentration after silica instillation in the rat is associated with complexed [Fe3+] on the dust surface.

The basis for surfactant accumulation after silica exposure is not known. As a result of an association between elevations in extracellular surfactant and oxidant exposures, we tested the hypothesis that (1) surfactant-enriched material can function as an in vitro target for oxidants catalyzed by Fe3+ complexed to the surface of silica, and (2) in vivo alveolar accumulation of surfactant after exposure of the lower respiratory tract to silica is associated with the concentration of Fe3+ complexed to the dust surface. Surfactant-enriched material was incubated in both chemical and cellular systems with either Gey's balanced salt solution, acid-washed silica, deferoxamine-treated silica, wetted silica, or iron-loaded silica. The absorbance of oxidized products was associated with concentrations of complexed iron on the surface of the silica dust. Rats (n = 10/group) were intratracheally instilled with either normal saline, 6.0 mg acid-washed silica, 6.0 mg deferoxamine-treated silica, 6.0 mg wetted silica, or 6.0 mg iron-loaded silica. Ninety-six hours after tracheal instillation, silica significantly increased extracellular surfactant as reflected by lipid phosphorous in the total lavage fluid. Lipid accumulation was associated with concentrations of surface complexed iron on the surface of the silica.

Lung retention of phosphatidylcholine and cholesterol from liposomes: effects of oxygen exposure and fasting.

Antioxidants such as glutathione may play a role in prevention and treatment of several lung diseases. Liposomes can be used to deliver antioxidants to the lung and increase their retention. In addition, liposomes alone may protect against oxidant-induced damage. In addition, liposomes alone may protect against oxidant-induced damage. This study was designed to characterize the retention and distribution of liposomes in the lung under normal circumstances and during either fasting, exposure to 100% oxygen, or a combination of the two. Positively charged liposomes, consisting of phosphatidylcholine (PC), cholesterol, and stearylamine plus either [14C]cholesterol or [3H]PC, were instilled intratracheally. Five minutes to 5 days later the lungs were removed and the radioactivity determined. Both [14C]cholesterol and [3H]PC labels had prolonged and equal retention in the lung, but their distribution within lung compartments differed. The cholesterol label increased in lung tissue over time, comprising 78% of the remaining label after 5 days, whereas the PC label persisted at high levels in lavage fluid and became equally distributed between lung tissue and bronchoalveolar lavage fluid. Fasting had little effect on the retention of the labels and no effect on their distribution within the lung. Exposure to 100% oxygen increased lung retention of both radiolabels and altered their distribution such that [14C]cholesterol label decreased and [3H]PC label increased in lung tissue. These results demonstrate the prolonged retention of intratracheally administered liposomes or their components in the lung and the effects of two clinically relevant conditions, fasting and hyperoxic exposure. Furthermore, they provide a basis for designing future studies using liposomes.

Cecal ligation and puncture is associated with pulmonary injury in the rat: role of cyclooxygenase pathway products.

The present studies evaluated the role cyclooxygenase products play in bacterial sepsis induced pulmonary injury in the rat. Lung injury was assessed by determining the pulmonary capillary filtration coefficient (Kf) and the lung lavage protein concentration four and 18 hours after cecal ligation and puncture. Four hours after cecal ligation, the Kf was unchanged from control, however, by 18 hours, the Kf was increased 171% (p < .05). Similarly, lung lavage protein levels were unchanged four hours after cecal ligation but were significantly (p < .05) elevated at 18 hours. On the other hand, pulmonary lavage immunoreactive thromboxane B2 (iTXB2) levels were increased both four and 18 hours after the initiation of sepsis. In order to determine if cyclooxygenase products played a role in the sepsis associated lung injury, ibuprofen was administered prior to cecal ligation. Ibuprofen pretreatment prevented the sepsis associated increase in both Kf and lung lavage protein concentration. These studies suggest that bacterial sepsis in the rat is associated with pulmonary injury and that early administration of ibuprofen ameliorates this damage.