Lung Epithelial Permeability Research Articles

Biochemical detection of type I cell damage after nitrogen dioxide-induced lung injury in rats

We have previously shown that injury to lung epithelial type I cells can be detected biochemically by measuring the airway fluid content of a type I cell-specific protein, rTI40, in a model of severe acute lung injury [M. C. McElroy, J.-F. Pittet, S. Hashimoto, L. Allen, J. P. Wiener-Kronish, and L. G. Dobbs. Am. J. Physiol. 268 (Lung Cell. Mol. Physiol. 12): L181-L186, 1995]. The first objective of the present study was to evaluate the utility of rTI40 in the assessment of alveolar injury in a model of milder acute lung injury. Rats were exposed to 18 parts/ million NO2 for 12 h; control rats received filtered air for 12 h. In NO2-exposed rats, the total amount of rTI40 in bronchoalveolar fluid was elevated 2-fold compared with control values (P < 0.001); protein concentration was 8.5-fold of control values (P < 0.001). The increase in rTI40 was associated with morphological evidence of injury to type I cells limited to the proximal alveolar regions of the lung. The second objective was to correlate the severity of alveolar type I cell injury with functional measurements of lung epithelial barrier integrity. NO2 inhalation stimulated distal air space fluid clearance despite a significant increase in lung endothelial and epithelial permeability to protein. These data demonstrate that rTI40 is a useful biochemical marker for mild focal injury and that exposure to NO2 alters lung barrier function. Taken together with our earlier studies, these results suggest that the quantity of recoverable rTI40 can be used as an index of the severity of damage to the alveolar epithelium.

Lung Epithelial Permeability and Bronchial Responsiveness in Subjects With Stable Asthma

Lung epithelial permeability of asthmatic patients has been reported to be similar or lower than that of healthy subjects and to be correlated or not to bronchial hyperresponsiveness. To clarify these discrepancies, we evaluated 99mTc-DTPA pulmonary clearance in a group of carefully selected asthmatic patients with mild, stable asthma (n = 13; seven women; mean age +/- SD = 27.69 +/- 6.63 years), and compared them with a group of healthy, nonsmoking subjects (n = 8; six women; mean age +/- SD = 24.38 +/- 5.15 years). Selection criteria for asthmatics were as follows: baseline FEV1 > or = 80% of predicted values, no bronchial infections, and/or no asthma attacks during 4 weeks prior to study and peak expiratory flow rate variability lower than 20%, over a period of 3 weeks. Patients controlled symptoms with beta 2-adrenergic drugs only, regularly or on demand. Mean baseline FEV1 (+/-SD) as percent of predicted was 102.38 +/- 13.97 and 112.88 +/- 18.36, respectively (p < 0.05). In the asthmatic group, bronchial responsiveness to methacholine (PC20 M FEV1) ranged between 0.55 and 28.5 mg/mL. Mean value (+/-SD) of DTPA clearance from lungs to blood (evaluated on the first 10 min out of 30 min of the curves) in the asthmatic group was not different from that of control group (68.31 +/- 21.46 and 69.5 +/- 15.73). In the asthmatic patients, there was no correlation between PC20 M values and DTPA T1/2 min of the whole lung, nor between PC20 M and inner and outer lung clearance zones. Moreover, both in asthmatics and healthy subjects, DTPA clearance of outer (alveolar) zones was significantly faster than that of inner (bronchial) zones (57.69 +/- 19.94 vs 102.08 +/- 38.19, p < 0.001, and 59.75 +/- 12.49 vs 103.5 +/- 31.86, p < 0.003, respectively). Our data show that DTPA clearance in patients with stable asthma is similar to that found in healthy subjects; it is not correlated to degree of bronchial responsiveness and occurs more rapidly in the outer zones than in the inner zones, both in asthmatic patients and in healthy subjects. Thus, to date, DTPA clearance index is not a valid tool for identifying and/or monitoring asthmatic patients.

Lung injury related to consuming Sauropus androgynus vegetable.

Taking Sauropus androgynus, a Malaysian food, to reduce weight began as a fad in Taiwan in 1994. Some advocates of this fad developed pulmonary dysfunction. The aim of this study is to report the lung injury in patients taking Sauropus androgynus. From July 1995 to November 1995, we investigated 104 nonsmoking patients (one male and 103 females) with chest roentgenography, pulmonary function, test, and Technetium 99m-labeled diethylene triamine penta-acetate (Tc-99m DTPA) radioaerosol inhalation lung scintigraphy. Among the 90 patients receiving Tc-99m DTPA inhalation lung scan, 46 (51.1%) patients had increased clearance of Tc-99m DTPA from lung and 20 (22.2%) patients had inhomogeneous deposition of the submicronic radioaerosol. Eighteen (18/100) patients had obstructive ventilatory impairment in pulmonary function test. Analyzing the results, we found that the patients with respiratory symptoms (n = 42) took more vegetables (p = 0.016), had increased clearance of Tc-99m DTPA (p = 0.010) and had lower FEV1 (p = 0.001), FEV1/FVC (p < 0.001), FEF25-75 (p = 0.001), VC (p = 0.002) and DLCO (p = 0.009) than the patients without respiratory symptoms (n = 62). FEV1 and FEV1/FVC were significantly reduced in patients with severe impairment of alveolar permeability. The cumulative dosage and duration of exposure were significantly associated with the reduction of FEV1 and FEV1/FVC. The lung injury after taking Sauropus androgynus involves alveoli and/or small airways and is manifest as obstructive ventilatory impairment with inhomogeneous aerosol distribution and increased lung epithelial permeability.

Antibodies against CD14 protect primates from endotoxin-induced shock.

Lipopolysaccharide (LPS), residing in the outer membrane of all gram-negative bacteria, is considered a major initiating factor of the gram-negative septic shock syndrome in humans. LPS forms a complex with the LPS binding protein (LBP) in plasma, and LPS-LBP complexes engage a specific receptor, CD14, on the surface of myeloid cells, leading to the production of potent proinflammatory cytokines. The major goal of this study was to test the importance of the CD14 pathway in vivo in a primate model that is similar to human septic shock. Primates were pretreated with one of two different inhibitory anti-CD14 mAbs, then challenged with intravenous endotoxin (375 microg/kg/h) for 8 h. The anti-CD14 treatment regimens were successful in preventing profound hypotension, reducing plasma cytokine levels (TNF-alpha, IL-1beta, IL-6, and IL-8), and inhibiting the alteration in lung epithelial permeability that occurred in animals treated with LPS and an isotype-matched control antibody. These results demonstrate for the first time the importance of the CD14 pathway in a primate model that is similar to human septic shock. Inhibition of the CD14 pathway represents a novel therapeutic approach to treating this life-threatening condition.

Differential effects of salmeterol on lung endothelial and epithelial leakage in sheep.

Salmeterol has been shown to prevent the influx of proteins into the air spaces of lungs of guinea pigs given intravenous histamine. To determine whether the salmeterol acts to stabilize the epithelial or endothelial barrier, we ventilated anesthetized sheep with aerosolized salmeterol before infusing histamine intravenously at a rate of 4 micrograms.kg-1.min-1 for 3 h. Changes in endothelial permeability were assessed by measuring the flow of lymph and proteins from the lungs. The influx of proteins into the air spaces was detected by performing single-cycle lavages to measure the concentration of circulating 125I-albumin in the epithelial lining fluid. Intravenous histamine increased the lymph flow to 13.2 +/- 6.8 ml/h compared with the control value of 5.6 +/- 2.8 ml/h (P < 0.05). Histamine also increased the concentration of 125I-albumin in the epithelial lining fluid from 1.8 +/- 0.9 to 8.5 +/- 2.5% of the plasma concentration (P < 0.01) and the postmortem lung water volume from 3.5 +/- 0.5 to 5.0 +/- 0.8 mg/g dry lung wt (P < 0.05). Pretreatment with 2.5 mg of aerosolized salmeterol prevented the influx of proteins into the air spaces and the increase in the postmortem lung water volume but it also increased the lung lymph flow even further to 20.0 +/- 5.6 ml/h (P < 0.05), increased the lymph-to-plasma protein ratio from 0.77 to 0.91, and tripled the increase in alveolar-arterial oxygen gradient caused by histamine alone. Pretreatment with 2.5 mg of intravenous salmeterol had essentially the same effect as salmeterol administered by aerosol. We conclude that salmeterol decreases lung epithelial permeability but increases lung endothelial permeability due to intravenous histamine in sheep.

Alveolar endotoxin increases alveolar liquid clearance in rats.

Under some pathological conditions, ion transport across alveolar epithelial cells is downregulated, whereas under other pathological conditions, it may be upregulated. Because endotoxin is a biologically relevant pathological stimulus, we investigated the effect of endotoxin on alveolar epithelial liquid clearance in vivo. Escherichia coli endotoxin (220 micrograms/kg) was instilled into the lungs via the trachea of rats. Then, 24 or 40 h after endotoxin instillation, alveolar and lung liquid clearances were studied over 1 h by instillation of a 5% albumin solution with 1.5 microCi of 125I-labeled albumin (6 ml/kg into both lungs). Alveolar liquid clearance was significantly greater at 24 h (36 +/- 5%) and 40 h (38 +/- 7%) after endotoxin exposure than in saline-instilled controls (27 +/- 6%). Although there was an influx of neutrophils into the air space, there was no increase in lung epithelial permeability to protein at 24 or 40 h. Amiloride (2 x 10(-3) M), a sodium channel inhibitor, significantly reduced alveolar liquid clearance in the rats exposed to endotoxin. However, the increase in alveolar liquid clearance was not inhibited when propranolol (2 x 10(-5) M) was added to the 5% albumin solution. Thus exposure to alveolar endotoxin upregulates net alveolar fluid clearance in vivo for up to 40 h, a potentially important mechanism for accelerating alveolar fluid clearance under some pathological conditions. The increase in alveolar liquid clearance 24 and 40 h after instillation of endotoxin into the air spaces is mediated by an increased uptake of sodium through amiloride-sensitive sodium channels.

Tc-99m DTPA aerosol lung clearance test in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) can affect every organ. Involvement of the lung in systemic lupus erythematosus may be a significant cause of morbidity and mortality. To evaluate alveolar epithelial damage in SLE, we studied lung epithelial permeability by measuring the clearance of inhaled Tc-99m DTPA aerosol. Twenty-three SLE patients without clinical pulmonary manifestations were studied. Of the 23 patients, 16 had normal clearance rates of Tc-99m DTPA (T1/2 > 60mins) and normal chest X-ray findings. A mild increase in the clearance rate was found in 5 cases (T1/2 between 40-60 min) and a significant increase in clearance rate in the remaining 2 (T1/2 < 40mins). Totally, 30% (7/23) of SLE patients have abnormal lung permeability. Of the 7 patients with abnormal clearance of Tc-99m DTPA, 3 had abnormal findings in chest X-rays and four had normal chest X-rays. Our study suggests that the clearance of Tc-99m DTPA aerosol may be a useful complementary study to assess pulmonary involvement in SLE.

Changes in lung permeability correlate with lung histology in a chronic exposure model.

In a simulated military flight-line exposure protocol, the effects of JP-8 jet fuel exposure on lung epithelial permeability were evaluated in male Fischer 344 rats (F344). Exposures were nose-only and for one hour daily. Groups were exposed for 7, 28, and 56 days. A protocol for administering a low dose (500mg/m3/hr) and a high dose (813-1094mg/m3/hr) of JP-8 jet fuel was used. Longitudinal sham-exposure groups (no jet fuel) for 7, 28, and 56 days were included in the protocol. Lung epithelial permeability was measured by clearance of technetium-labeled diethylenetriamine pentaacetate (99mTcDTPA, molecular weight = 492 daltons, physical half-life = 6.02 hours). The percent clearance of 99mTcDTPA per minute was calculated. Alveolar epithelial clearance for JP-8-exposed rats was dependent on both exposure concentration and duration. It was noted that at low-dose exposure concentrations alveolar epithelial clearance of 99mTcDTPA returned to low levels (LD56 = 1.09% per min; LC56 = 0.98% per min), suggesting recovery as evidenced by microscopic exam. The corresponding 56-day high-dose group (n = 10) had a significantly higher (p < 0.05) value of 2.25% per minute. The 28-day low-dose (n = 15) and high-dose (n = 20) groups had clearance values that were significantly increased from their longitudinal control group (n = 17). The alveolar epithelial permeability values were 2.51, 1.95, and 1.20, respectively. The seven-day longitudinal control, low-dose, and high-dose groups had alveolar permeability values of 1.57, 2.16, and 2.07, respectively. The lung histology correlated with the clearance values. Electron micrographs showed that all groups had interstitial edema resulting from endothelial damage. There was apparent thickening of the alveolar septa, and alveolar macrophages were activated in all groups. Lung permeability data, as determined by 99mTcDTPA alveolar clearance, indicated that lung injuries peaked at 28 days of jet fuel exposure, and this finding corresponded with the histology data. There was a discrepancy in the seven-day group between the number of cells and the 99mTcDTPA clearance values. The HD7 group had a total cell count significantly higher than all other groups, but the 99mTcDTPA clearance values in that group were not significantly different from that of any other group.

Vitamin E does not prevent exercise-induced increase in pulmonary clearance

It has been observed that sustained exercise results in a prolonged increase in alveolar epithelial permeability, as assessed by the pulmonary clearance rate of aerosolized 99mTc-labeled diethylenetriaminepentaacetate (Lorino et al. J. Appl. Physiol. 67: 2055-2059, 1989). The involvement of lipid peroxidation in this increased permeability was tested in seven nonsmoking volunteers by comparing the exercise-induced increases in pulmonary 99mTc-diethylenetriaminepentaacetate clearance before and after a 3-wk supplementation with oral vitamin E (1,000 IU/day), according to a protocol designed as a single-blind crossover study. The 60-min exercise was performed on a treadmill at a constant load corresponding to 80% of maximal O2 uptake. Administration of vitamin E, a very important antioxidant, did not reduce the exercise-induced increase in lung clearance, suggesting that the exercise-induced increase in lung epithelial permeability does not primarily result from the occurrence of lipid peroxidation in the alveolar membrane. This result thus corroborates the hypothesis of an alteration of the intercellular tight junctions due to the mechanical effects of hyperventilation.

An investigation of the role of glutathione in increased epithelial permeability induced by cigarette smoke in vivo and in vitro.

Airspace epithelial permeability is known to increase in cigarette smokers. To study the role of the antioxidant reduced glutathione (GSH) in this phenomenon, we used an in vitro model of the epithelial permeability of a monolayer of human type II alveolar epithelial cells (A549 cell line). Both whole (WSC) and vapor (VSC) smoke condensates induced a recoverable, concentration-dependent increase in epithelial permeability to 125iodine-labeled bovine serum albumin (125IBSA), associated with a profound fall in intracellular GSH. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor, decreased GSH levels in A549 epithelial cells, significantly increased A549 epithelial cell permeability, and enhanced both WSC and VSC-induced A549 epithelial cell permeability. Co-culturing epithelial cells and GSH (500 microM) reduced WSC-induced, but not VSC-induced A549 epithelial cell permeability. Increasing intracellular GSH also ameliorated the smoke-induced increased epithelial permeability. Concentrations of cigarette smoke condensate of < 20% increased A549 epithelial cell permeability without associated cell detachment and lysis, which was also the case with BSO-induced increased epithelial permeability. WSC and VSC, instilled intratracheally, significantly increased rat lung epithelial permeability to 125IBSA, 6 h postinstillation, associated with a significant recruitment of neutrophils into the airspaces. This was associated with a small increase in GSH in the lung tissue of VSC-treated rats. However, both WSC and VSC markedly reduced GSH in bronchoalveolar lavage (BAL) fluid. Reduction in lung GSH to 95% but not to 68% of control values by BSO increased lung epithelial permeability in vivo. However, there was no additive effect on epithelial permeability of WSC and BSO.(ABSTRACT TRUNCATED AT 250 WORDS)

Endotoxin-stimulated alveolar macrophages impair lung epithelial Na+ transport by an L-Arg-dependent mechanism.

The Na+ transport function of alveolar epithelium represents an important mechanism for air space fluid clearance after acute lung injury. We studied the effect of endotoxin-stimulated rat alveolar macrophages on lung epithelial ion transport and permeability in vitro. Cultured rat distal lung (alveolar) epithelial monolayers incubated with both endotoxin and macrophages demonstrated a 75% decline in transepithelial resistance and a selective 60% reduction in amiloride-sensitive short-circuit current (Isc). Single-channel patch-clamp analysis demonstrated a 60% decrease in the density of 25-pS nonselective cation (NSC) channels on the apical membrane of epithelium exposed to both endotoxin and macrophages. A concurrent reduction in epithelial F-actin content suggested a role for actin depolymerization in mediating this effect. Incubation of cocultures with the methylated L-arginine (Arg) derivative NG-monomethyl-L-arginine prevented the reduction in epithelial Isc, as did substitution of L-Arg with D-Arg or incubation in L-Arg-free medium. Furthermore, the stable and products of Arg metabolism were found to have no effect on epithelial ion transport. These studies show that endotoxin-stimulated alveolar macrophages impair distal lung epithelial ion transport by an L-Arg-dependent mechanism by inactivating amiloride-sensitive 25-pS NSC channels. This may represent a novel mechanism whereby local inflammatory cells regulate lung epithelial ion transport. This could affect the ability of the lung to clear fluid from the air space.

ANF decreases active sodium transport and increases alveolar epithelial permeability in rats.

Previous studies reported that atrial natriuretic factor (ANF) decreased lung edema in guinea pigs. To determine whether ANF protects against lung edema by increasing active Na+ transport and lung edema clearance, ANF (10(-7) M) was instilled into the air spaces (n = 5) or perfused through the pulmonary circulation (n = 5) of isolated perfused liquid-filled rat lungs. These animals were compared with five control rats and four rats having amiloride (10(-5) M) instilled into the air space. Amiloride reduced lung edema clearance by 65%, perfused ANF reduced lung edema clearance by 32%, and instilled ANF did not change edema clearance compared with responses in control rats after 70 min of experimental protocol. Passive Na+ movement increased by 91% with perfused ANF and by 52% with instilled ANF compared with that in control rats. Albumin flux from the perfusate into the air space increased in ANF-perfused lungs compared with control lungs (P < 0.05) but not when ANF or amiloride was instilled into the air spaces. These results suggest that ANF instilled into rat air spaces or perfused through the pulmonary circulation increases lung epithelial permeability and that ANF perfused through the pulmonary circulation decreases lung edema clearance due to impaired active Na+ transport. Conceivably, the previously observed protective effect of ANF was due to reduced pressures across the pulmonary circulation, which resulted in less edema formation.

Asbestos directly increases lung epithelial permeability.

Asbestos causes the fibrotic lung disease asbestosis, but the biologic basis for this is unknown. Lung epithelial dysfunction including increased permeability is hypothesized to contribute to lung scarring in other forms of pulmonary fibrosis. Lung epithelial permeability is increased in both animals and humans exposed to asbestos. It is not known whether the increased epithelial permeability results from direct effects of asbestos or occurs as a result of the inflammatory reaction to asbestos fibers. To address this question we used a cultured human lung epithelial model, and we measured the direct effect of asbestos on lung epithelial barrier integrity as measured by mannitol permeability. We exposed the monolayer to chryogenically ground, respirable-sized chrysotile asbestos particles. This chrysotile asbestos caused a dose- and time-dependent increase in mannitol permeability across the epithelial monolayer. Increased mannitol permeability occurred both in the presence and in the absence of serum, was not due to cytotoxicity as measured by lactate dehydrogenase release, and was not associated with altered actin cytoskeleton at the light microscopic level. Permeability to 70 kDa neutral dextran also increased after asbestos exposure; however, the absolute permeability to dextran was less than mannitol permeability. Neither latex beads nor tantalum caused any change in permeability, suggesting that our findings are not explained by nonspecific effects of particles. Increased permeability did not reverse in the continued presence of asbestos and persisted even after removing the asbestos. Finally, surface-bound iron did not appear to be necessary for this effect because neither chelating iron with deferoxamine nor iron-loading the asbestos altered the effect on mannitol permeability. These results show that asbestos has direct effects on lung epithelial permeability. Together with the recent observation that asbestos directly increases epithelial fibrinolytic activity, our results suggest a novel mechanism for asbestos-induced lung injury.

Bronchoalveolar lavage and 99mTc-DTPA clearance as prognostic factors in asbestos workers with and without asbestosis

The aims of this study are to investigate the change-over time of lung function and chest radiographic findings in patients with asbestosis (AS) and asbestos workers without asbestosis (AW). Secondly, to correlate these changes with broncho-alveolar lavage (BAL) profiles and with lung epithelial permeability, as detected by half-time lung-to-blood ( t 1 2 LB) clearance of an inhaled aerosol of diethylene triamine pentacetate labelled with technetium 99 ( 99mTc-DTPA) obtained a mean period of 4·2 yr (range 2·3–5·8) previously. Thirty-three patients with asbestosis and 24 asbestos workers with substantial asbestos exposure were followed-up. Nineteen healthy smokers (HS) with no asbestos exposure who were followed up for a mean period of 3·9 yr were taken as a control group for spirometric changes. Compared with AW, FEV 1, FVC and T lCO were lower in AS ( P < 0·0001 in each case). Smoker AS and AW had lower numbers ( P < 0·03) and percentages ( P < 0·004) of BAL lymphocytes and higher numbers ( P < 0·04) and percentages ( P < 0·02) of BAL neutrophils plus eosinophils than ex- and non-smokers. Annual declines of FEV 1 (dFEV 1 yr −1) and FVC (dFVC yr −1) in AS and AW were significantly greater than in HS and predicted annual declines ( P < 0·002 in each case). Annual declines of T lCO (d T lCO yr −1) and KCO (d KCO yr −1) in AS and AW were significantly greater than predicted annual declines ( P < 0·002 in each case). No significant differences were noted between AS and AW in annual declines in any lung function measurement. d T lCO yr −1, d KCO yr −1 were significantly greater in smokers than in ex- and non-smokers, ( P < 0·05 and P < 0·04 respectively). Annual decline did not relate to base line values for any lung function measurement. Numbers and proportions of BAL lymphocyte were higher ( P < 0·008 and P < 0·02, respectively) and numbers and proportions of BAL neutrophils and eosinophils were lower ( P < 0·02 and P < 0·03, respectively) in patients in whom d T lCO yr −1 was less than 0·3 mmol min −1 kPa −1 than in patients in whom d T lCO yr −1 was more than 0·3 mmol min −1 kPa −1. d T lCO yr −1 inversely correlated with t 1 2 LB; r = 0·51; ( P < 0·008). Patients in whom the radiograph remained unchanged had higher numbers ( P < 0·002) and percentages ( P < 0·001) of BAL lymphocytes than patients in whom the radiograph deteriorated. It is concluded that decline in lung function is greater in AS and AW than in controls. Increased BAL neutrophils and faster DTPA clearance are associated with worse functional and radiological outcome than increased BAL lymphocytes and slower DTPA clearance.

Clearance of 99mTc-labeled albumin from lungs in anesthetized guinea pigs.

Gamma imaging was used to measure the rate of clearance of aerosolized 99mTc-human serum albumin (HSA) from the lungs of control guinea pigs and guinea pigs that received increased lung inflation or lung injury. Anesthetized guinea pigs were ventilated for 6 min with an aerosol of HSA and the radioactivity in the chest was monitored for 2 h with a gamma camera to determine whether the clearance rate would be a reliable assessment of lung epithelial permeability. Increased lung volumes were effected by application of 5 or 7 cm H2O positive end-expired pressure (5-PEEP and 7-PEEP, respectively). Lung injury was induced either by intravenous oleic acid (OA, 27-73 microliters/kg) or inhalation of nitrogen dioxide (NO2, 80-100 ppm) for 2 h. Postmortem extravascular lung water volume (EVLW) provided an assessment of the degree of lung injury. Tracer clearance rates in animals receiving 5 or 7 cm H2O PEEP were not significantly different from controls (K = 0.15 +/- 0.05 and 0.24 +/- 0.10 vs 0.12 +/- 0.03%/min, respectively, p > .05). Animals exposed to NO2 had faster tracer clearance rates (K = 0.33 +/- 0.21%/min, p < .05) and higher EVLW (5.8 +/- 3.0 vs 3.7 +/- 0.2 mL/g dry lung, p < .05) than controls. Clearance rates of HSA from the lungs of NO2-exposed guinea pigs correlated well with injury as assessed by EVLW (r = .93, p < .01). Clearance rates of HSA and EVLW in animals receiving oleic acid were significantly higher than controls and the group receiving 5 cm H2O PEEP (K = 0.58 +/- 0.41%/min, EVLW = 8.1 +/- 0.8 mL/g dry lung tissue, p < .05), but there was no correlation between these parameters in this injury model. It is concluded that imaging of the disappearance of radiolabeled HSA in the guinea pig can be a useful index of lung epithelial permeability, but this technique is limited to certain models of lung injury.

Aerosolized Pseudomonas elastase and lung fluid balance in anesthetized sheep.

The role of the lung epithelium in lung fluid balance was studied by ventilating anesthetized sheep with an aerosol of 20 mg of elastase from Pseudomonas aeruginosa (Ps. elastase) to increase lung epithelial permeability without affecting lung endothelial permeability or lung vascular pressures. Ps. elastase had no effect on the lung vascular pressures, the alveolar-arterial PO2 gradient (A-aPO2), the flow or protein concentration of the lung lymph, or the postmortem water volume of the lungs. The morphological alveolar flooding score in these sheep was 2.5 times the control level, but this was only marginally significant. Elevation of the left atrial pressure by 20 cmH2O alone increased the postmortem lung water volume but had no effect on A-aPO2, the alveolar flooding score, or the lung epithelial permeability assessed by the clearance of 99mTc-labeled human serum albumin. Addition of aerosolized Ps. elastase to these sheep had no effect on the total lung water volume, but it caused a redistribution of water into the air spaces, as evidenced by significant increases in the alveolar flooding score and A-aPO2 (P less than 0.01). Elevation of the left atrial pressure by 40 cmH2O without elastase caused the same response as elevation of the left atrial pressure by 20 cmH2O with elastase, except the higher pressure caused a greater increase in the total lung water volume. We conclude that alteration of the integrity of the lung epithelium with aerosolized Ps. elastase causes a redistribution of lung water into the alveoli without affecting the total lung water volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of Acute Exposure to O3On Rats: Sequence of Epithelial and Inflammatory Changes in the Distal Airways

AbstractThis study involves the analysis of the sequence of changes in lung epithelial permeability, free cells in the airways, prostaglandin E2 (PGE2) levels, polymorphonuclear leukocyte (PMN) flux, and alveolar lesions in rats exposed to 0.8 ppm ozone (O3) for 3 h and then studied at 4-h intervals up to 24 h postexposure. Protein content of the bronchoalveolar lavage (BAL) increased immediately after O3 exposure and returned to control levels by 16 h postexposure. Albumin concentration in the BAL also increased with time after O3 exposure, but the increase was more gradual than the protein increase. The lower albumin concentrations at 20 and 24 h postexposure were still higher than the control levels. While the total protein in the BAL could be attributed to tissue injury and increased transmucosal transport, the albumin primarily reflected elevated transport from the serum. Total cells in the BAL decreased immediately after the O3 exposure, but returned to near normal levels by 4 h. PGE, levels did not...

Increased Lung Permeability following Long-term Use of Free-base Cocaine (Crack)

The clearance of inhaled 99mTc DTPA aerosol from the lungs is used as an index of lung epithelial permeability. Using the radioaerosol method, we investigated the effects of long-term "crack" (free-base cocaine) inhalation on lung permeability in 23 subjects. Eighteen control subjects (12 nonsmokers and 6 cigarette smokers) with no history of drug use were also studied. Subjects inhaled approximately 150 muCi (approximately 5.6 MBq) of 99mTc DTPA aerosol and quantitative gamma camera images of the lungs were acquired at 1-min increments for 25 minutes. Regions of interest (ROIs) were selected to include the following: (1) both lungs; (2) each individual lung; and (3) the upper, middle, and lower thirds of each lung. 99mTc DTPA lung clearance was determined from the slopes of the respective time-activity plots for the different RIOs. Radioaerosol clearance half-times (T1/2) for the seven nonsmoking crack users (61.5 +/- 18.3 minutes) were longer than for the seven cigarette-smoking crack users (27.9 +/- 16.9 minutes) and nine cigarette-smoking crack plus marijuana users (33.5 +/- 21.6 minutes). T1/2 for the nonsmoking crack users was significantly shorter (p less than 0.001) than for the nonsmoking control group (123.8 +/- 28.7 minutes). T1/2 for the cigarette-smoking drug users was similar to that of the cigarette-smoking control group (33.1 +/- 17.8 minutes), suggesting a similar mechanism of damage from the smoke of crack and tobacco. From these groups, one nonsmoker and 11 cigarette smokers displayed biexponential 99mTc DTPA clearances, indicative of greater lung injury than found in the usual cases of monoexponential clearance. The upper lungs of all crack users groups cleared faster than the lower lungs. The faster and biexponential clearance properties of inhaled 99mTc DTPA aerosol were the principal functional abnormalities found in all the drug users. In contrast, 19 of 23 crack users had normal spirometry and gas exchange. These results indicate that 99mTc DTPA may provide a sensitive and useful assay to evaluate the physiologic effects of cocaine inhalation in the lung.

Differential responses of the endothelial and epithelial barriers of the lung in sheep to Escherichia coli endotoxin.

Although intravenous Escherichia coli endotoxin has been used extensively in experimental studies to increase lung endothelial permeability, the effect of E. coli endotoxin on lung epithelial permeability has not been well studied. To examine this issue in sheep, bidirectional movement of protein across the lung epithelial barrier was studied by labeling the vascular space with 131I-albumin and by instilling 3 ml/kg of an isosmolar protein solution with 125I-albumin into the alveoli. E. coli endotoxin was administered according to one of three protocols: intravenous alone (5-500 micrograms/kg), intravenous (5 micrograms/kg) plus low-dose alveolar endotoxin (10 micrograms/kg), and high-dose alveolar endotoxin alone (50-100 micrograms/kg). Alveolar liquid clearance was estimated based on the concentration of the instilled native protein. Sheep were studied for either 4 or 24 h. Although intravenous E. coli endotoxin produced a marked increase in transvascular protein flux and interstitial pulmonary edema, there was no effect on the clearance of either the vascular (131I-albumin) or the alveolar (125I-albumin) protein tracer across the epithelial barrier. High-dose alveolar E. coli endotoxin caused a 10-fold increase in the number of leukocytes, particularly neutrophils, that accumulated in the air spaces. In spite of the marked chemotactic effect of alveolar endotoxin, there was no change in the permeability of the epithelial barrier to the vascular or alveolar protein tracers. Also, alveolar epithelial liquid clearance was normal. Morphologic studies confirmed that the alveolar epithelial barrier was not injured by either intravenous or alveolar E. coli endotoxin. Thus, the alveolar epithelium in sheep is significantly more resistant than the lung endothelium to the injurious effects of E. coli endotoxin.

Effects of platelet-activating factor on lung epithelial permeability in the guinea-pig

We examined the effects of platelet-activating factor (PAF) on lung epithelial permeability by measuring the clearance of intratracheally administered 99m-technetium-labeled diethylene triamine penta-acetic acid ( 99mTc-DTPA) in guinea-pigs which were anaesthetised, paralysed and mechanically ventilated. The clearance of the radiolabeled tracer molecule 99mTc-DTPA from airways to the blood was expressed as changes in counts/min corrected for background. For each guinea-pig, 99mTc-DTPA clearance was assessed before and after i.v. PAF administration, when tracheal pressure had returned to near control values. Doses of 10, 50 and 100 ng/kg of PAF caused dose-dependent increases in 99mTc-DTPA clearance of 7 ± 3%, 38 ± 7% and 65 ± 11% respectively. The respective effects of 0.5 mg/kg of the beta 2-adrenergic agonist salbutamol and 0.3mg/kg of the alpha,-adrenergic agonist methoxamine on the increase in lung epithelial permeability induced by 50 ng/kg PAF were also studied. Salbutamol significantly reduced the acute bronchoconstrictor effects of PAF, but did not affect the increase in lung epithelial permeability, which was 58 ± 10%. Conversely, methoxamine significantly enhanced the broncho-constrictor effects of PAF but inhibited the lung epithelial permeability increase, which was only 10 ± 13%. In the absence of PAF, salbutamol significantly increased this permeability by 49 ± 11%, whereas methoxamine alone slightly reduced it, by −11 ± 4%. These results demonstrate that PAF increases lung epithelial permeability and suggest that vascular surface area recruitment may explain this increase.