Differences In Lung Injury Research Articles

Lung-Protective Ventilation Attenuates Mechanical Injury While Hypercapnia Attenuates Biological Injury in a Rat Model of Ventilator-Associated Lung Injury.

Background and Objective: Lung-protective mechanical ventilation is known to attenuate ventilator-associated lung injury (VALI), but often at the expense of hypoventilation and hypercapnia. It remains unclear whether the main mechanism by which VALI is attenuated is a product of limiting mechanical forces to the lung during ventilation, or a direct biological effect of hypercapnia. Methods: Acute lung injury (ALI) was induced in 60 anesthetized rats by the instillation of 1.25 M HCl into the lungs via tracheostomy. Ten rats each were randomly assigned to one of six experimental groups and ventilated for 4 h with: 1) Conventional HighV E Normocapnia (high VT, high minute ventilation, normocapnia), 2) Conventional Normocapnia (high VT, normocapnia), 3) Protective Normocapnia (VT 8 ml/kg, high RR), 4) Conventional iCO 2 Hypercapnia (high VT, low RR, inhaled CO2), 5) Protective iCO 2 Hypercapnia (VT 8 ml/kg, high RR, added CO2), 6) Protective endogenous Hypercapnia (VT 8 ml/kg, low RR). Blood gasses, broncho-alveolar lavage fluid (BALF), and tissue specimens were collected and analyzed for histologic and biologic lung injury assessment. Results: Mild ALI was achieved in all groups characterized by a decreased mean PaO2/FiO2 ratio from 428 to 242 mmHg (p < 0.05), and an increased mean elastance from 2.46 to 4.32 cmH2O/L (p < 0.0001). There were no differences in gas exchange among groups. Wet-to-dry ratios and formation of hyaline membranes were significantly lower in low VT groups compared to conventional tidal volumes. Hypercapnia reduced diffuse alveolar damage and IL-6 levels in the BALF, which was also true when CO2 was added to conventional VT. In low VT groups, hypercapnia did not induce any further protective effect except increasing pulmonary IL-10 in the BALF. No differences in lung injury were observed when hypercapnia was induced by adding CO2 or decreasing minute ventilation, although permissive hypercapnia decreased the pH significantly and decreased liver histologic injury. Conclusion: Our findings suggest that low tidal volume ventilation likely attenuates VALI by limiting mechanical damage to the lung, while hypercapnia attenuates VALI by limiting pro-inflammatory and biochemical mechanisms of injury. When combined, both lung-protective ventilation and hypercapnia have the potential to exert an synergistic effect for the prevention of VALI.

A comparison of four different models of acute respiratory distress syndrome in sheep

BackgroundAcute respiratory distress syndrome (ARDS) can have various causes. The study objective was to investigate whether different pathophysiologic models of ARDS would show different respiratory, cardiovascular and inflammatory outcomes.MethodsWe performed a prospective, randomized study in 27 ventilated ewes inducing ARDS using three different techniques to mimic the pulmonary causes of ARDS (ARDSp): warm saline lavage (n = 6), intratracheal hydrochloric acid (HCl; n = 6), intratracheal albumin (n = 10), and one technique to mimic an extrapulmonary cause of ARDS (ARDSexp): intravenous lipopolysaccharide (LPS iv; n = 5). ARDS was defined when PaO2 was < 15 kPa (112 mmHg) when ventilated with PEEP 10 cm H2O and FiO2 = 1.0. The effects on gas exchange were investigated by calculating the oxygenation index (OI) and the ventilation efficacy index (VEI) every 30 min for a period of 4 h. Post mortem lung lavage was performed to obtain broncho-alveolar lavage fluid (BALF) to assess lung injury and inflammation. Lung injury and inflammation were assessed by measuring the total number and differentiation of leukocytes, the concentration of protein and disaturated phospholipids, and interleukine-6 and -8 in the BALF. Histology of the lung was evaluated by measuring the mean alveolar size, alveolar wall thickness and the lung injury score system by Matute-Bello et al., as markers of lung injury. The concentration of interleukin-6 was determined in plasma, as a marker of systematic inflammation.ResultsThe OI and VEI were most affected in the LPS iv group and thereafter the HCl group, after meeting the ARDS criteria. Diastolic blood pressure was lowest in the LPS iv group. There were no significant differences found in the total number and differentiation of leukocytes, the concentration of protein and disaturated phospholipids, or interleukin-8 in the BALF, histology of the lung and the lung injury score. IL-6 in BALF and plasma was highest in the LPS iv group, but no significant differences were found between the other groups. It took a significantly longer period of time to meet the ARDS criteria in the LPS iv group.ConclusionsThe LPS model caused the most severe pulmonary and cardiovascular insufficiency. Surprisingly, there were limited significant differences in lung injury and inflammatory markers, despite the different pathophysiological models, when the clinical definition of ARDS was applied.

Combinations of Epidemiological and Experimental Studies in Air Pollution Research: A Narrative Review.

Scientific literature is evolving to include more systematic reviews that encompass epidemiological and experimental papers so that the whole picture can be examined. The aim of this narrative review is to bridge that gap by combining epidemiological and experimental studies based on the same setting: Examples of Bitterfeld, Utah Valley, Beijing Olympic Games, and Viadana. This review looks at four examples that incorporate multiple epidemiological and experimental papers about air pollution exposure and health effects. The Bitterfeld (spatial) and Utah Valley (temporal) examples showed that particle composition causes the biggest difference in lung injury. In Beijing, a temporal difference of before/after and during the Olympics showed that traffic and industry air pollution-related health effects like lung cancer and cardiovascular disease could be reduced by improvement of air quality. The Viadana example showed a spatial difference in respiratory injury caused by particle composition and interactions with genotoxicity. Combining experimental and epidemiological methods gives a more in-depth look into the whole picture of exposure and health effects. Our review exemplifies the strength of this strategy and encourages further use of it.

An experiment on the pathogenesis of early biotrauma in ventilator-induced lung injury

To investigate the pathogenesis of early biotrauma in ventilator-induced lung injury (VILI). Twenty-four 8-week-old male specific-pathogen-free Sprague-Dawley (SD) rats weighing 250-300 g were randomly divided into sham group (S group), conventional mechanical ventilation group (L group) and high tidal volume (VT) mechanical ventilation group (H group) with 8 rats in each group. All rats received tracheostomy after anesthesia. Rats in S group received no mechanical ventilation but breathe room air spontaneously. All other parameters of the ventilator were the same in both mechanical ventilation groups, and the fraction of oxygen was set to 0.21, the rats in L group received 7 mL/kg VT, and those in H group received 28 mL/kg VT. Four hours after ventilation all rats were sacrificed and the lung tissues were harvested for wet/dry (W/D) ratio. Pathological injury score was evaluated by hematoxylin and eosin (HE) staining. Transferase-mediated deoxyuridine triphosphate-biotin nick end labeling stain (TUNEL) was performed to count the apoptosis cell in lung epithelial. Western Blot was performed to evaluate hemi-channel protein Pannexin-1 expression in lung homogenate. Bronchoalveolar lavage fluid (BALF) was collected, and the concentration of lactate dehydrogenase (LDH), isoprostane, adenosine triphosphate (ATP) and white cell count in BALF were measured. Yo-pro-1/propidium iodide (PI) double stain was performed to evaluate early apoptosis cell in BALF. There was no significant difference in lung injury between S group and L group. Compared with S group and L group, rats in H group showed significant lung injury, represented as alveolar rupture, inflammatory cell infiltration, interstitial edema and airway epithelial exfoliation, and the lung W/D ratio was increased significantly (5.1±0.2 vs. 4.4±0.2, 4.3±0.4, both P < 0.01), pathological score was significantly increased [4.00 (4.00, 8.00) vs. 1.00 (0, 4.00), 2.00 (0, 4.75), both P < 0.01], the white cell in BALF was significantly increased (×106/L: 2.97±0.46 vs. 1.03±0.26, 0.79±0.19, both P < 0.01), the level of LDH was significantly increased (U/L: 148.6±38.2 vs. 34.4±13.5, 78.6±13.9, both P < 0.01), and the expression of Pannexin-1 in lung homogenate was significantly increased (Pannexin-1/GAPDH: 0.89±0.21 vs. 0.48±0.25, 0.61±0.17, both P < 0.01), the ATP concentration in BALF was also significantly increased (nmol/L: 456.84±148.72 vs. 19.23±13.34, 113.26±57.90, both P < 0.01). There was no significant difference in the apoptosis cell in lung tissue or the apoptosis cell rate, isoprostane level in BALF among the three groups [apoptosis cell in lung (cells/HP): 4.00 (3.00, 5.00) vs. 5.00 (4.00, 6.00), 4.00 (3.25, 6.00); apoptosis cell rate in BALF: (0.57±0.20)% vs. (0.42±0.16)%, (0.58±0.19)%; isoprostane in BALF (μg/L): 3.85±0.46 vs. 3.83±0.60, 3.59±0.69, all P > 0.05]. The early pathogenesis of biotrauma in VILI is related to the release of inflammation mediator via membrane channel after activating by pressure stress, but not apoptosis and lipid peroxidation.

Differences in lung injury after IMRT or proton therapy assessed by 18FDG PET imaging

Background and purposeTo compare lung injury among non-small cell lung cancer (NSCLC) patients treated with IMRT or proton therapy as revealed by 18F-FDG post-treatment uptake and to determine factors predictive for clinically symptomatic radiation pneumonitis. Material and methodsFor 83 patients treated with IMRT or proton therapy, planning CT and follow up 18F-FDG PET-CT were analyzed. Post-treatment PET-CT was aligned with planning CT to establish a voxel-to-voxel correspondence between PET and planning dose images. 18F-FDG uptake as a function of radiation dose to normal lung was obtained for each patient. PET image-derived parameters as well as demographic, clinical, treatment and dosimetric patient characteristics were correlated with clinical symptoms of pneumonitis. ResultsThe dose distributions for the two modalities were significantly different; V5 was higher for IMRT, whereas V60 was higher for protons. The mean lung dose (MLD) was similar for the two modalities. The slope of linear 18F-FDG-uptake – dose response did not differ significantly between the two modalities. The MLD, slope, and 95th percentile of SUV were identified as three major factors associated with radiation pneumonitis. ConclusionsDespite significantly different dose distributions for IMRT and for protons, the slope of the SUV–dose linear regression line previously shown to be associated with RP did not differ between IMRT and protons. Patients who developed radiation pneumonitis had statistically significantly higher MLD and higher slope regardless of treatment modality.

Effectiveness of individualized lung recruitment strategies at birth: an experimental study in preterm lambs.

Respiratory transition at birth involves rapidly clearing fetal lung liquid and preventing efflux back into the lung while aeration is established. We have developed a sustained inflation (SIOPT) individualized to volume response and a dynamic tidal positive end-expiratory pressure (PEEP) (open lung volume, OLV) strategy that both enhance this process. We aimed to compare the effect of each with a group managed with PEEP of 8 cmH2O and no recruitment maneuver (No-RM), on gas exchange, lung mechanics, spatiotemporal aeration, and lung injury in 127 ± 1 day preterm lambs. Forty-eight fetal-instrumented lambs exposed to antenatal steroids were ventilated for 60 min after application of the allocated strategy. Spatiotemporal aeration and lung mechanics were measured with electrical impedance tomography and forced-oscillation, respectively. At study completion, molecular and histological markers of lung injury were analyzed. Mean (SD) aeration at the end of the SIOPT and OLV groups was 32 (22) and 38 (15) ml/kg, compared with 17 (10) ml/kg (180 s) in the No-RM (P = 0.024, 1-way ANOVA). This translated into better oxygenation at 60 min (P = 0.047; 2-way ANOVA) resulting from better distal lung tissue aeration in SIOPT and OLV. There was no difference in lung injury. Neither SIOPT nor OLV achieved homogeneous aeration. Histological injury and mRNA biomarker upregulation were more likely in the regions with better initial aeration, suggesting volutrauma. Tidal ventilation or an SI achieves similar aeration if optimized, suggesting that preventing fluid efflux after lung liquid clearance is at least as important as fluid clearance during the initial inflation at birth.

An observational study of Donor Ex Vivo Lung Perfusion in UK lung transplantation: DEVELOP-UK.

Many patients awaiting lung transplantation die before a donor organ becomes available. Ex vivo lung perfusion (EVLP) allows initially unusable donor lungs to be assessed and reconditioned for clinical use. The objective of the Donor Ex Vivo Lung Perfusion in UK lung transplantation study was to evaluate the clinical effectiveness and cost-effectiveness of EVLP in increasing UK lung transplant activity. A multicentre, unblinded, non-randomised, non-inferiority observational study to compare transplant outcomes between EVLP-assessed and standard donor lungs. Multicentre study involving all five UK officially designated NHS adult lung transplant centres. Patients aged ≥ 18 years with advanced lung disease accepted onto the lung transplant waiting list. The study intervention was EVLP assessment of donor lungs before determining suitability for transplantation. The primary outcome measure was survival during the first 12 months following lung transplantation. Secondary outcome measures were patient-centred outcomes that are influenced by the effectiveness of lung transplantation and that contribute to the health-care costs. Lungs from 53 donors unsuitable for standard transplant were assessed with EVLP, of which 18 (34%) were subsequently transplanted. A total of 184 participants received standard donor lungs. Owing to the early closure of the study, a non-inferiority analysis was not conducted. The Kaplan-Meier estimate of survival at 12 months was 0.67 [95% confidence interval (CI) 0.40 to 0.83] for the EVLP arm and 0.80 (95% CI 0.74 to 0.85) for the standard arm. The hazard ratio for overall 12-month survival in the EVLP arm relative to the standard arm was 1.96 (95% CI 0.83 to 4.67). Patients in the EVLP arm required ventilation for a longer period and stayed longer in an intensive therapy unit (ITU) than patients in the standard arm, but duration of overall hospital stay was similar in both groups. There was a higher rate of very early grade 3 primary graft dysfunction (PGD) in the EVLP arm, but rates of PGD did not differ between groups after 72 hours. The requirement for extracorporeal membrane oxygenation (ECMO) support was higher in the EVLP arm (7/18, 38.8%) than in the standard arm (6/184, 3.2%). There were no major differences in rates of chest radiograph abnormalities, infection, lung function or rejection by 12 months. The cost of EVLP transplants is approximately £35,000 higher than the cost of standard transplants, as a result of the cost of the EVLP procedure, and the increased ECMO use and ITU stay. Predictors of cost were quality of life on joining the waiting list, type of transplant and number of lungs transplanted. An exploratory model comparing a NHS lung transplant service that includes EVLP and standard lung transplants with one including only standard lung transplants resulted in an incremental cost-effectiveness ratio of £73,000. Interviews showed that patients had a good understanding of the need for, and the processes of, EVLP. If EVLP can increase the number of usable donor lungs and reduce waiting, it is likely to be acceptable to those waiting for lung transplantation. Study limitations include small numbers in the EVLP arm, limiting analysis to descriptive statistics and the EVLP protocol change during the study. Overall, one-third of donor lungs subjected to EVLP were deemed suitable for transplant. Estimated survival over 12 months was lower than in the standard group, but the data were also consistent with no difference in survival between groups. Patients receiving these additional transplants experience a higher rate of early graft injury and need for unplanned ECMO support, at increased cost. The small number of participants in the EVLP arm because of early study termination limits the robustness of these conclusions. The reason for the increased PGD rates, high ECMO requirement and possible differences in lung injury between EVLP protocols needs evaluation. Current Controlled Trials ISRCTN44922411. This project was funded by the NIHR Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 20, No. 85. See the NIHR Journals Library website for further project information.

Human mesenchymal stem cells attenuate early damage in a ventilated pig model of acute lung injury

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) is a major cause of global morbidity and mortality. Mesenchymal stem cells (MSC) have shown promise in treating inflammatory lung conditions. We hypothesised that human MSC (hMSC) can improve ALI/ARDS through their anti-inflammatory actions. We subjected pigs (n=6) to intravenous oleic acid (OA) injury, ventilation and hMSC infusion, while the controls (n=5) had intravenous OA, ventilation and an infusion vehicle control. hMSC were infused 1h after the administration of OA. The animals were monitored for additional 4h. Nuclear translocation of nuclear factor-light chain enhancer of activated B cells (NF-κB), a transcription factor that mediates several inflammatory pathways was reduced in hMSC treated pigs compared to controls (p=0.04). There was no significant difference in lung injury, assessed by histological scoring in hMSC treated pigs versus controls (p=0.063). There was no difference in neutrophil counts between hMSC-treated pigs and controls. Within 4h, there was no difference in the levels of IL-10 and IL-8 pre- and post-treatment with hMSC. In addition, there was no difference in hemodynamics, lung mechanics or arterial blood gases between hMSC treated animals and controls. Subsequent studies are required to determine if the observed decrease in inflammatory transcription factors will translate into improvement in inflammation and in physiological parameters over the long term.

Is Time the Missing Component in Protective Ventilation Strategies?*

Is Time the Missing Component in Protective Ventilation Strategies?*

Magnesium Sulfate Mitigates Acute Lung Injury in Endotoxemia Rats

Magnesium sulfate (MgSO4) possesses potent anti-inflammation capacity. We sought to elucidate the effects of MgSO4 on mitigating acute lung injury induced by endotoxemia. MgSO4 is an antagonist of the L-type calcium channels and the N-methyl-D-aspartate (NMDA) receptor. The roles of the L-type calcium channels and NMDA receptor in this regard were also elucidated. Ninety-six adult male rats were randomized to receive normal saline, MgSO4 (100 mg/kg), lipopolysaccharide (LPS), LPS plus MgSO4 (10, 50, or 100 mg/kg), LPS plus MgSO4 (100 mg/kg) plus the L-type calcium channel activator BAY-K8644, or LPS plus MgSO4 (100 mg/kg) plus exogenous NMDA (n=12 in each group). Between-group differences in lung injury were evaluated. Histologic findings, in concert with assays of leukocyte infiltration (polymorphonuclear leukocytes/alveoli ratio and myeloperoxidase activity) and lung water content (wet/dry weight ratio), confirmed that LPS induced acute lung injury. LPS also caused significant inflammatory response (increases in chemokine, cytokine, and prostaglandin E2 concentrations) and imposed significant oxidative stress (increases in nitric oxide and malondialdehyde concentrations) in rat lungs. MgSO4 at the dosages of 50 mg/kg and 100 mg/kg, but not at 10 mg/kg, significantly mitigated the acute lung injury, lung inflammatory response, and oxidative stress caused by endotoxemia. Moreover, the protective effects of MgSO4 were counteracted by BAY-K8644 and exogenous NMDA. MgSO4 mitigates lung inflammatory response, oxidative stress, and acute lung injury in endotoxemia rats in a dose-dependent manner. The mechanisms may involve antagonizing the L-type calcium channels and the NMDA receptor.

Hormonal Influences on Airway Biology and Naphthalene‐ Mediated Clara Cell Injury

Women have a greater chance of developing adult onset asthma, COPD, and some forms of lung cancer than men. Naphthalene (NA), a bioactivated cytotoxicant, is used to model distal Clara cell airway injury and repair. Our laboratory has shown that female mice are more sensitive than male mice to NA toxicity. The objective of the current study was to evaluate the role of hormones in normal airway biology and in NA mediated injury. This was achieved by 1) measuring estrogen receptors (ESR) gene expression by RT PCR in airways by estrus cycle stage, 2) measuring glutathione levels in airways by cycle stage, and 3) comparing airway damage in response to NA in intact vs. gonadectomized animals. Airway level specific responses were defined in microdissected airways. In comparison to non‐cycling mice, ESR expression was decreased in both diestrus and proestrus and increased in the estrus phase of the cycle. Glutathione levels were decreased in the airways of mice during diestrus and metestrus compared to male mice. Depletion of glutathione within the Clara cell plays a major role in NA cytotoxity. Confocal microscopy of microdissected airways as well as high resolution resin sections showed less extensive injury in ovariectomized mice compared to intact female mice. These findings support the hypothesis that sex differences in lung injury are influenced by hormones. Funded by NIH grants ES012720, HL007013‐29, and TRDRP 14RT‐0191.

γδ T Cells Regulate the Early Inflammatory Response toBordetella pertussisInfection in the Murine Respiratory Tract

The role of gammadelta T cells in the regulation of pulmonary inflammation following Bordetella pertussis infection was investigated. Using a well-characterized murine aerosol challenge model, inflammatory events in mice with targeted disruption of the T-cell receptor delta-chain gene (gammadelta TCR-/- mice) were compared with those in wild-type animals. Early following challenge with B. pertussis, gammadelta TCR-/- mice exhibited greater pulmonary inflammation, as measured by intra-alveolar albumin leakage and lesion histomorphometry, yet had lower contemporaneous bacterial lung loads. The larger numbers of neutrophils and macrophages and the greater concentration of the neutrophil marker myeloperoxidase in bronchoalveolar lavage fluid from gammadelta TCR-/- mice at this time suggested that differences in lung injury were mediated through increased leukocyte trafficking into infected alveoli. Furthermore, flow cytometric analysis found the pattern of recruitment of natural killer (NK) and NK receptor+ T cells into airspaces differed between the two mouse types over the same time period. Taken together, these findings suggest a regulatory influence for gammadelta T cells over the early pulmonary inflammatory response to bacterial infection. The absence of gammadelta T cells also influenced the subsequent adaptive immune response to specific bacterial components, as evidenced by a shift from a Th1 to a Th2 type response against the B. pertussis virulence factor filamentous hemagglutinin in gammadelta TCR-/- mice. The findings are relevant to the study of conditions such as neonatal B. pertussis infection and acute respiratory distress syndrome where gammadelta T cell dysfunction has been implicated in the inflammatory process.

Lung albumin accumulation is spatially heterogeneous but not correlated with regional pulmonary perfusion.

The contribution of pulmonary perfusion heterogeneity to the development of regional differences in lung injury and edema is unknown. To test whether regional differences in pulmonary perfusion are associated with regional differences in microvascular function during lung injury, pigs were mechanically ventilated in the prone position and infused with endotoxin (Escherichia coli 055:B5, 0.15 microg. kg(-1). h(-1); n = 8) or saline (n = 4) for 4 h. Extravascular albumin accumulation and perfusion were measured in multiple approximately 0.7-ml lung regions by injecting pigs with radiolabeled albumin and radioactive microspheres, respectively. Extravascular albumin accumulation was spatially heterogeneous but not correlated with regional perfusion. Extravascular albumin accumulation was greater in dorsal than ventral regions, and regions with similar albumin accumulation were spatially clustered. This spatial organization was less evident in endotoxemic than control pigs. We conclude that there are regional differences in lung albumin accumulation that are spatially organized but not mediated by regional differences in pulmonary perfusion. We speculate that regional differences in microvascular pressure or endothelial function may account for the observed distribution of extravascular albumin accumulation.

Liquid lung ventilation reduces neutrophil sequestration in a neonatal swine model of cardiopulmonary bypass.

Liquid lung ventilation has been demonstrated to improve cardiorespiratory function after cardiopulmonary bypass. We hypothesized that liquid lung ventilation (LLV) would decrease the pulmonary inflammatory response after cardiopulmonary bypass (CPB). Prospective, randomized, experimental, controlled, nonblinded study. Animal research laboratory at a university setting. A total of 24 neonatal piglets. After intubation with a cuffed endotracheal tube, swine were conventionally ventilated. After surgical cannulation, each piglet was placed on conventional nonpulsatile CPB and cooled to 18 degrees C (64.4 degrees F). Subsequently, the animals were exposed to 90 mins of low-flow CPB (35 mL/kg/min). Animals were rewarmed to 37 degrees C (98.6 degrees F), removed from CPB, and ventilated for 90 min. Ten animals received conventional gas ventilation only (control), seven received initiation of LLV before CPB (prevention), and seven received initiation of LLV during the rewarming phase of CPB (treatment). After the animals were killed, the lungs were removed en bloc. The left lobe was dissected and formalin-fixed at 20 cm H2O overnight, followed by paraffin embedding. Sections were taken from the paraffin-embedded lungs. Neutrophil accumulation and lung injury were assessed by histochemical staining with leukocyte esterase and morphometrics, respectively. One hundred microscopic images were digitized from each tissue sample for lung morphometrics, and neutrophil counts were obtained from every fifth image. Lung tissue sections showed a significantly lower number of neutrophils per alveolar area in the prevention and treatment groups than in the control group (control 681 +/- 65, prevention 380 +/- 49, treatment 412 +/- 101 neutrophils per alveolar area [cells/mm2]; p <.05 for both prevention and treatment compared with control). There were no differences in lung injury as assessed with morphometrics or hemodynamic measurements between any of the three groups. The data suggest that LLV reduces the CPB-induced neutrophil sequestration in the pulmonary parenchyma independent of its effects on the circulatory physiology or evidence of early lung injury.

INDUCTION OF ADAPTATION TO INHALED LIPOPOLYSACCHARIDE E IN YOUNG AND OLD RATS AND MIC

Lipopolysaccharide (LPS) is a component of the gram-negative bacterial cell wall that is known to activate inflammatory cells and enhance the production of inflammatory mediators in the lung. As it is a ubiquitous compound, inhalation exposure is highly likely in the human environment. Adaptation is a phenomenon by which a previous exposure results in improved survival or reduced injury as compared to a single exposure alone. We hypothesized that the basic proinflammatory effects of LPS in the lung could result in the development of adaptation in animals. Based on evidence of age- and species-related differences in lung injury, we used an acute lung injury model with inhaled LPS to compare the development of adaptation in young and old Fisher 344 rats and C57Bl/6J mice. Animals were exposed to low-dose (predicted lung deposition 20 ng in rats and 5 ng in mice) LPS aerosols for 10 min on 3 consecutive days; on day 4, a high dose (rats 200 ng; mice 25 ng) was delivered. Another group of animals received only the high LPS dose on day 4, whereas controls were unexposed. Twenty-four hours after the last exposure, cellular and inflammatory parameters in bronchoalveolar lavage (BAL) were determined. An adaptive response was found in both rats and mice. Adapted animals showed significantly fewer BAL neutrophils compared to nonadapted ones; there was also a significantly lower release of oxidants from phorbol methyl ester-stimulated BAL cells from adapted compared to nonadapted animals, which, in turn, showed a greater response than controls. Furthermore, studies in old animals (21 mo of age) showed that adaptation also occurs in this age group. The adaptive response is clear in old mice; in rats, there is greater variability in the response, but an adaptive trend is apparent. Therefore, we have demonstrated that inhaled low-dose LPS can induce adaptation to subsequent higher doses, much as has been shown for other toxicants that induce oxidative lung injury.

CHRONIC INFLAMMATION AND TUMOR FORMATION IN RATS AFTER INTRATRACHEAL INSTILLATION OF HIGH DOSES OF COAL DUSTS, TITANIUM DIOXIDES, AND QUARTZ

Lipopolysaccharide (LPS) is a component of the gram-negative bacterial cell wall that is known to activate inflammatory cells and enhance the production of inflammatory mediators in the lung. As it is a ubiquitous compound, inhalation exposure is highly likely in the human environment. Adaptation is a phenomenon by which a previous exposure results in improved survival or reduced injury as compared to a single exposure alone. We hypothesized that the basic proinflammatory effects of LPS in the lung could result in the development of adaptation in animals. Based on evidence of age- and species-related differences in lung injury, we used an acute lung injury model with inhaled LPS to compare the development of adaptation in young and old Fisher 344 rats and C57Bl/6J mice. Animals were exposed to low-dose (predicted lung deposition approximately 20 ng in rats and approximately 5 ng in mice) LPS aerosols for 10 min on 3 consecutive days; on day 4, a high dose (rats approximately 200 ng; mice approximately 25 ng) was delivered. Another group of animals received only the high LPS dose on day 4, whereas controls were unexposed. Twenty-four hours after the last exposure, cellular and inflammatory parameters in bronchoalveolar lavage (BAL) were determined. An adaptive response was found in both rats and mice. Adapted animals showed significantly fewer BAL neutrophils compared to nonadapted ones; there was also a significantly lower release of oxidants from phorbol methyl ester-stimulated BAL cells from adapted compared to nonadapted animals, which, in turn, showed a greater response than controls. Furthermore, studies in old animals (21 mo of age) showed that adaptation also occurs in this age group. The adaptive response is clear in old mice; in rats, there is greater variability in the response, but an adaptive trend is apparent. Therefore, we have demonstrated that inhaled low-dose LPS can induce adaptation to subsequent higher doses, much as has been shown for other toxicants that induce oxidative lung injury.

Effects of antibiotic therapy on Pseudomonas aeruginosa-induced lung injury in a rat model.

The effect of antibiotics on the acute lung injury induced by virulent Pseudomonas aeruginosa PA103 was quantitatively analyzed in a rat model. Lung injury was induced by the instillation of PA103 directly into the right lower lobes of the lungs of anesthetized rats. The alveolar epithelial injury, extravascular lung water, and total plasma equivalents were measured as separate, independent parameters of acute lung injury. Four hours after the instillation of PA103, all the parameters were increased linearly depending on the dose of P. aeruginosa. Next, we examined the effects of intravenously administered antibiotics on the parameters of acute lung injury in D-galactosamine-sensitized rats. One hour after the rats received 10(7) CFU of PA103, an intravenous bolus injection of aztreonam (60 mg/kg) or imipenem-cilastatin (30 mg/kg) was administered. Despite an MIC indicating resistance, imipenem-cilastatin improved all the measurements of lung injury; in contrast, aztreonam, which had an MIC indicating sensitivity, did not improve any of the lung injury parameters. The antibiotics did not generate different quantities of plasma endotoxin; therefore, endotoxin did not appear to explain the differences in lung injury. This in vivo model is useful to quantitatively compare the efficacies of parenteral antibiotic administration on Pseudomonas airspace infections.

Urine Hydrogen Peroxide During Adult Respiratory Distress Syndrome in Patients With and Without Sepsis

The lung injury in adult respiratory distress syndrome (ARDS) has been associated with increased expiratory hydrogen peroxide (H2O2) concentrations. Furthermore, patients with sepsis and ARDS are reported to have greater serum scavenging of H2O2 than patients with ARDS only. We hypothesized that the systemic presence of H2O2 would be detectable in the urine of these two groups of patients and that, in the case of ARDS sepsis, the relative contribution of each disease to the production this analyte would be discernible. Accordingly, we used an in vitro radioisotope assay to follow the weekly course of urine H2O2 levels in ARDS patients with and without sepsis, and in samples from control non-ARDS patients with sepsis with indwelling urinary catheters and in samples provided by healthy volunteers. Thirty patients with ARDS were included in the study: 23 had sepsis and 7 were sepsis free. An indwelling catheter was used to collect urine from each patient over a 24-h period, first within 48 h of ICU admission and then every seventh day over the course of their illness. Urine H2O2 was measured by competitive decarboxylation of 1-14C-alpha-ketoglutaric acid by H2O2. Urine samples were provided by 20 healthy volunteers while, in 10 non-ARDS patients with sepsis, urine was collected over one 24-h period following a 5-day minimum with an indwelling urinary catheter. Urine H2O2 concentration in healthy control subjects (88 +/- 4 mumol/L) and non-ARDS patients with urinary catheters (96 +/- 5 mumol/L) was not significantly different. During the first 48 h in the ICU, urine H2O2 in patients with ARDS only (295 +/- 29 mumol/L) was significantly lower (p < 0.05) than patients with ARDS and sepsis (380 +/- 13 mumol/L); however, the lung injury scores of these two groups did not differ. Furthermore, within the first 48 h, the urine H2O2 of the patients with ARDS and sepsis who did not survive (427 +/- 19 mumol/L; n = 7) was significantly higher than that in patients who survived sepsis (352 +/- 14 mumol/L; n = 15). Thereafter, the lung injury scores and urine H2O2 levels of the nonsurvivor ARDS-sepsis group remained significantly higher compared with the other two groups. At lung injury scores of 3 and 2, regardless of days in ICU, the patients with ARDS only had significantly lower urine H2O2 (266 +/- 30 mumol/L and 167 +/- 24 mumol/L, respectively) compared with the survivor ARDS-sepsis group (376 +/- 19 mumol/L and 250 +/- mumol/L). When the patients with ARDS (both ARDS only and with sepsis) recovered, their urine H2O2 concentration did not differ from the control groups (healthy donors and patients without ARDS). Lung injury scores did not differentiate patients with ARDS and sepsis from patients with ARDS only during the first 10 days in the ICU; however, urine H2O2 levels were significantly greater in the patients with ARDS and sepsis. Moreover, despite no initial difference in lung injury, patients who did not survive ARDS and sepsis had consistently greater urine H2O2 concentration than patients who survived sepsis. The urine H2O2 level in the ARDS-only group was about 70 percent of the level in the survivor ARDS and sepsis group, suggesting that ARDS alone is the major contributor to the H2O2 oxidant processes during combined ARDS and sepsis. Furthermore, these studies demonstrate that urine H2O2 may be a useful analyte to differentiate the severity of oxidant processes in patients with ARDS and sepsis albeit the prognosis appears to be survival or nonsurvival.

The effect of dopamine on pulmonary hemodynamics and tissue damage after inhalation injury in an ovine model.

Hypoxic pulmonary vasoconstriction and reduced blood flow occur as a result of smoke inhalation. The aim of this study was to investigate how the amelioration of blood flow reduction by the vasodilator dopamine affects histopathologic outcome. We exposed the left lungs of chronically instrumented sheep (n = 12) to smoke, awakened them, and studied them for 24 hours. Six hours after inhalation injury, the sheep received randomized infusions of dopamine (9 micrograms/kg/min) or equal volumes of 0.9% saline solution. Pulmonary resistance in the left lungs of animals in the group that received saline solution rose continuously throughout the study period (624 +/- 48 dyne.sec.cm-5/m2 to 1747 +/- 140 dyne.sec.cm-5/m2, baseline to 24 hours after injury). Dopamine treatment caused a significantly lower vascular resistance in the injured lung than did saline solution between 8 and 24 hours after injury. The histologic evaluation of the injured lungs showed epithelial necrosis and cast formation in both groups in addition to an increased wet/dry ratio. No difference in lung injury between the groups could be distinguished. We conclude that the amelioration of blood flow reduction by treatment with dopamine in the lungs that were exposed to smoke did not affect pulmonary damage after inhalation injury.