Surfactant dysfunction in lung contusion with and without superimposed gastric aspiration in a rat model

Hypoxia‐inducible factor (HIF)‐1α‐induced regulation of lung injury in pulmonary aspiration is mediated through NF‐kB

Aspiration‐induced lung injury is a common grievance encountered in the intensive care unit (ICU). It is a significant risk factor for improving ventilator‐associated pneumonia (VAP) and acute respiratory distress syndrome (ARDS). Hypoxia‐inducible factor (HIF)‐1α is one of the primary transcription factors responsible for regulating the cellular response to changes in oxygen tension. Here, we sought to determine the role of HIF‐1α and specifically the role of type 2 alveolar epithelial cells in generating the acute inflammatory response following acid and particles (CASP) aspiration. Previous studies show HIF‐1 α is involved in regulating the hypoxia‐stimulated expression of MCP‐1 in mice and humans. The CASP was induced in C57BL/6, ODD‐Luc, HIF‐1α (+/+) control, and HIF‐1α conditional knockout (HIF‐1α (−/−) mice). Following an injury in ODD mice, explanted organs were subjected to IVIS imaging to measure the degree of hypoxia. HIF‐1α expression, BAL albumin, cytokines, and histology were measured following CASP. In C57BL/6 mice, the level of HIF‐1α was increased at 1 h after CASP. There were significantly increased levels of albumin and cytokines in C57BL/6 and ODD‐Luc mice lungs following CASP. HIF‐1α (+/+) mice given CASP demonstrated a synergistic increase in albumin leakage, increased pro‐inflammatory cytokines, and worse injury. MCP‐1 antibody neutralized HIF‐1α (+/+) mice showed reduced granuloma formation. The NF‐κB expression was increased substantially in the HIF‐1α (+/+) mice following CASP compared to HIF‐1α (−/−) mice. Our data collectively identify that HIF‐1α upregulation of the acute inflammatory response depends on NF‐κB following CASP.

Lungs from polytrauma donors with significant chest trauma can be safely used for transplantation

BACKGROUND

The use of organs from polytrauma donors for lung transplantation is controversial in the literature. For many centers, the radiologic manifestation of lung contusions is a clear reason to reject an organ offer. This results in the loss of potentially viable organs for the donor pool.

METHODS

We analyzed 1152 donor lungs procured by our transplant center between January 2010 and June 2018. These included 118 lungs with a history of polytrauma involving the chest. Sixteen polytrauma donor lungs were rejected after procurement. A total of 102 lungs were transplanted, divided into 2 groups: the polytrauma contusion group (n = 44), comprising polytrauma donors with radiologic signs of lung contusion at the time of offer, and the polytrauma clear group (n = 58), comprising polytrauma donors without lung contusion. Nontrauma donor lungs transplanted during the study period were assigned to a polytrauma control group (n = 650). Short- and long-term outcomes of the 3 groups were compared.

RESULTS

Basic demographic data and preoperative factors were similar in the 3 groups. Rates of primary graft dysfunction grade 3 at 72 hours did not differ among the 3 groups (0.0% vs 3.4% vs 3.9%; P = .409). The duration of ventilation was similar the 3 groups: 45 hours (interquartile range [IQR], 28-94 hours), 37 hours (IQR, 22-71 hours), and 42 hours (IQR, 22-96 hours), respectively (P = .674). Long-term graft survival was not impaired in the trauma groups compared with controls. One-year survival rates were 84.1% for the polytrauma contusion group, 93.1% for the polytrauma clear group, and 83.1% for the no polytrauma group. Five-year graft survival in the 3 groups was 74.7%, 87.2%, and 70.0%, respectively.

CONCLUSIONS

Lung transplantation using organs from polytrauma donors is associated with similar short- and long-term results as transplantation from nontrauma donors. The presence or absence of radiologic signs of lung contusion at the time of offer has no impact on primary graft function and long-term survival.

Investigation of histopathological and radiological effects of surfactant treatment in an experimental female rat model of lung contusion

Objective(s):

Pulmonary contusion (PC) is a clinical entity that often accompanies blunt traumas. We aimed to investigate the radiological and histopathological effects of surfactant treatment in an experimental rat model in which lung contusion was formed by blunt thoracic trauma.

Materials and Methods:

50 female Sprague-Dawley rats were used. Five groups were formed randomly. In groups 2, 4, and 5 lung contusion was made by the drop-weight method after anesthesia. Intratracheal surfactant was administered in the 4th hr in groups 3 and 4 and in the 24th hr in groups 4 and 5. All rats were sacrificed and their lungs removed at 48 hr after contusion. Alveolar edema, congestion, hemorrhage, destruction, leukocyte infiltration, immune staining were examined histopathologically.

Results:

When the first thoracic CT scans were evaluated, we observed two rats with rib fractures and four rats with pneumothorax. 4 and 48 hr thoracic CT evaluation contusion and atelectasis showed no statistically significant decrease (P>0.05). After sacrifice of group 2, in macroscopic evaluation, there was a heterogeneous contusion and hemorrhagic appearance in the lungs of rats and less hemorrhagic appearance was observed in Groups 4 and 5 than in Group 2. In comparison of Immunohistopathological findings, surfactant treatment showed a statistically significant decrease in leukocyte infiltration scores (P=0.046). Immunohistopathologically, surfactant group had more staining but only statistically significant when compared to groups 4 and sham. (P=0.036).

Conclusion:

Surfactant treatment may be of significant benefit in lung contusion secondary to blunt chest trauma, and further prospective evidence of its efficacy in such disorders is needed.

Hypoxia-Inducible Factor (HIF)-1α Promotes Inflammation and Injury Following Aspiration-Induced Lung Injury in Mice

Acid aspiration-induced lung injury is a common disease in the intensive care unit (ICU) and acute respiratory distress syndrome (ARDS). Hypoxia-inducible factor (HIF)-1α is a major transcription factor responsible for regulating the cellular response to changes in oxygen tension. A clear understanding of the function of HIF-1α in lung inflammatory response is currently lacking. Here, we sought to determine the role of HIF-1α in type 2 alveolar epithelial cells (AEC) in the generation of the acute inflammatory response following gastric aspiration (GA). GA led to profound hypoxia at very early time points following GA. This correlated to a robust increase in HIF-1α, tissue albumin and pro-inflammatory mediators following GA in AECs. The extent of lung injury and the release of pro/anti-inflammatory cytokines were significantly reduced in HIF-1α (-/-) mice. Finally, we report that HIF-1α upregulation of the acute inflammatory response is dependent on NF-κB following GA.

Effect of oleanolic acid for prevention of acute lung injury and apoptosis

Background

This study aims to evaluate the efficiency of oleanolic acid on acute lung injury and acute respiratory distress syndrome.

Methods

The study included 70 female Wistar albino rats (weighing 180 to 200 g). We created seven groups, each consisting of 10 rats. Then, we generated acute lung injuries by intra-tracheal peroxynitrite injection in every group except for the control group. We investigated the effect of oleanolic acid. For this purpose, we measured the levels of malondialdehyde, interleukin 1 beta, interleukin 4, interleukin 10 and tumor necrosis factor alpha in the collected blood samples from the rats. In addition, we examined the lung tissue samples histopathologically and assessed the rate of apoptosis.

Results

Peroxynitrite injected groups at 24 and 48 h showed a statistically significant increase in interleukin 1 beta, tumor necrosis factor alpha, interleukin 4, interleukin 10 and malondialdehyde levels, which are accepted as mediators of the inflammatory process, compared to the control group. When peroxynitrite injected groups at 24 and 48 h were compared to the treatment groups of the same hour, a statistically significant decrease was detected. According to histopathological examination, peroxynitrite injected groups at 24 and 48 h showed a significant increase of tissue injury scores compared to the control group. However, the groups that were treated with oleanolic acid showed a significant decrease compared to the peroxynitrite groups (p<0.001 for tumor necrosis factor alpha and apoptosis results at 48 h).

Conclusion

In this study, we confirmed that oleanolic acid can be an effective agent for the prevention of acute lung injury generated via peroxynitrite.

The possible protective role of pumpkin seed oil in an animal model of acid aspiration pneumonia: Light and electron microscopic study

Aspiration pneumonitis is a common problem occurring in many clinical disorders. Pumpkin seed oil (PO) is a rich source of antioxidants. This work aimed to assess the effect of PO on the lung histopathological changes induced by acid aspiration. Forty male albino rats assigned to four groups were used. Rats of control group were instilled intratracheally with normal saline 2mL/kg. HCL group instilled with 2mL/kg of HCL 0.1N, pH 1.25. PO group received pumpkin seed oil (PO) orally (∼1375mg/kgbw/day) for 7days. HCL+PO group instilled with 2mL/kg of HCL 0.1N, pH 1.25 and received PO at the same dose of PO group. Lung tissue samples were processed for light, electron microscopic and immunohistochemical study using anti inducible NO synthase (iNOS). The lung of HCL group demonstrated thickened interalveolar septa, inflammatory cell infiltration and significant increase in the area percent of collagenous fibers and immune expression of iNOS. Ultra structurally, disrupted alveolocapillay membrane, degenerated type II pneumocytes and plentiful alveolar macrophages were evident. PO administration partially attenuated these histological and ultra structural alterations and reduced iNOS immune-expression in lung tissue. In conclusion, PO has a protective effect against HCL aspiration lung injury most probably through its antioxidant activity.

Altered Lipid Composition of Surfactant and Lung Tissue in Murine Experimental Malaria-Associated Acute Respiratory Distress Syndrome

Malaria-associated acute lung injury (MA-ALI) and its more severe form malaria-associated acute respiratory distress syndrome (MA-ARDS) are common, often fatal complications of severe malaria infections. However, little is known about their pathogenesis. In this study, biochemical alterations of the lipid composition of the lungs were investigated as possible contributing factors to the severity of murine MA-ALI/ARDS. C57BL/6J mice were infected with Plasmodium berghei NK65 to induce lethal MA-ARDS, or with Plasmodium chabaudi AS, a parasite strain that does not induce lung pathology. The lipid profile of the lung tissue from mice infected with Plasmodium berghei NK65 developing MA-ALI/ARDS, but not that from mice without lung pathology or controls, was characterized by high levels of phospholipids -mainly phosphatidylcholine- and esterified cholesterol. The high levels of polyunsaturated fatty acids and the linoleic/oleic fatty acid ratio of the latter reflect the fatty acid composition of plasma cholesterol esters. In spite of the increased total polyunsaturated fatty acid pool, which augments the relative oxidability of the lung membranes, and the presence of hemozoin, a known pro-oxidant, no excess oxidative stress was detected in the lungs of Plasmodium berghei NK65 infected mice. The bronchoalveolar lavage (BAL) fluid of Plasmodium berghei NK65 infected mice was characterized by high levels of plasma proteins. The phospholipid profile of BAL large and small aggregate fractions was also different from uninfected controls, with a significant increase in the amounts of sphingomyelin and lysophosphatidylcholine and the decrease in phosphatidylglycerol. Both the increase of proteins and lysophosphatidylcholine are known to decrease the intrinsic surface activity of surfactant. Together, these data indicate that an altered lipid composition of lung tissue and BAL fluid, partially ascribed to oedema and lipoprotein infiltration, is a characteristic feature of murine MA-ALI/ARDS and possibly contribute to lung dysfunction.

Surfactant

Exogenous pulmonary surfactant, widely used in neonatal care, is one of the best-studied treatments in neonatology, and its introduction in the 1990s led to a significant improvement in neonatal outcomes in preterm infants, including a decrease in mortality. This chapter provides an overview of surfactant composition and function in health and disease and summarizes the evidence for its clinical use.

Activation of hypoxia-inducible factor-1α in type 2 alveolar epithelial cell is a major driver of acute inflammation following lung contusion

OBJECTIVE

Lung contusion is a major risk factor for the development of acute respiratory distress syndrome. Hypoxia-inducible factor-1α is the primary transcription factor that is responsible for regulating the cellular response to changes in oxygen tension. We set to determine if hypoxia-inducible factor-1α plays a role in the pathogenesis of acute inflammatory response and injury in lung contusion.

DESIGN

Nonlethal closed-chest unilateral lung contusion was induced in a hypoxia reporter mouse model and type 2 cell-specific hypoxia-inducible factor-1α conditional knockout mice. The mice were killed at 5-, 24-, 48-, and 72-hour time points, and the extent of systemic and tissue hypoxia was assessed. In addition, injury and inflammation were assessed by measuring bronchoalveolar lavage cells (flow cytometry and cytospin), albumin (permeability injury), and cytokines (inflammation). Isolated type 2 cells from the hypoxia-inducible factor-1α conditional knockout mice were isolated and evaluated for proinflammatory cytokines following lung contusion. Finally, the role of nuclear factor-κB and interleukin-1β as intermediates in this interaction was studied.

RESULTS

Lung contusion induced profound global hypoxia rapidly. Increased expression of hypoxia-inducible factor-1α from lung samples was observed as early as 60 minutes, following the insult. The extent of lung injury following lung contusion was significantly reduced in conditional knockout mice at all the time points, when compared with the wild-type littermate mice. Release of proinflammatory cytokines, such as interleukin-1β, interleukin-6, macrophage inflammatory protein-2, and keratinocyte chemoattractant, was significantly lower in conditional knockout mice. These actions are in part mediated through nuclear factor-κB. Hypoxia-inducible factor-1α in lung epithelial cells was shown to regulate interleukin-1β promoter activity.

CONCLUSION

Activation of hypoxia-inducible factor-1α in type 2 cell is a major driver of acute inflammation following lung contusion.

Alveolar macrophage depletion increases the severity of acute inflammation following nonlethal unilateral lung contusion in mice

BACKGROUND

Lung contusion (LC) is a common injury resulting from blunt thoracic trauma. LC is an important risk factor for the development acute lung injury, adult respiratory distress syndrome, and ventilator-associated pneumonia, all of which increase mortality from trauma. LC produces a nonspecific immune cellular response. Neutrophil recruitment is known to increase the severity of inflammation during LC. However, the exact role of macrophages in modulating the response to LC has not been well described.

METHODS

We used a cortical contusion impactor to induce unilateral LC in mice. Thoracic micro computed tomographic scans of these animals were obtained to document radiologic changes over time following LC. To understand the role of macrophages during LC, liposomal clodronate was used to deplete macrophage levels before traumatic insult. Acute inflammatory attributes after LC were assessed, by measuring pressure-volume mechanics; quantifying bronchial alveolar lavage levels of leukocytes, albumin, and cytokines; and finally examining lung specimen histopathology at 5, 24, 48, and 72 hours after injury.

RESULTS

After LC, alveolar macrophage numbers were significantly reduced and exhibited slowed recovery. Simultaneously, there was a significant increase in bronchial alveolar lavage neutrophil counts. The loss of macrophages could be attributed to both cellular apoptosis and necrosis. Pretreatment with clodronate increased the severity of lung inflammation as measured by worsened pulmonary compliance, increased lung permeability, amplification of neutrophil recruitment, and increases in early proinflammatory cytokine levels.

CONCLUSION

The presence of regulatory alveolar macrophages plays an important role in the pathogenesis of acute inflammation following LC.

Characterization of ultrasound-induced pulmonary capillary hemorrhage in rats

Routine pulmonary ultrasound for diagnosis of disease or injury relies on interpretation of image features, such as comet-tail artifacts, which can also be indicative of the poorly understood phenomenon of ultrasound-induced pulmonary capillary hemorrhage (PCH). Evans blue extraction and bronchoalveolar lavage (BAL) were evaluated for assessment of PCH induced by ultrasound scanning. Rats anesthetized with ketamine with or without xylazine received sham or scanning for 5 min with a 7.6 MHz linear array. Evans blue extraction and BAL albumin measurements failed to demonstrate significant increases for scanning, even though the induction of comet-tail artifacts was significant. BAL cell counts had an insignificant increase relative to shams at a near-threshold mechanical index (MI) of 0.52 (P=0.07), but a highly significant increase at MI=0.9 (P=0.001). The possibility of xylazine-induced elevated albumin was tested, but no significant decrease was found for sham or scanned rats with ketamine-only anesthesia. Interestingly, without xylazine, the widths of comet-tail artifacts in the ultrasound images were significantly smaller (P=0.001) and cell counts in BAL fluid also were reduced (P=0.014). The BAL cell-count method provides a valuable additional means of PCH quantification.

N-Acetylcysteine counteracts oxidative stress and protects alveolar epithelial cells from lung contusion-induced apoptosis in rats with blunt chest trauma

The aim of this study was to investigate the protective effects of N-acetylcysteine (NAC) on peroxidative and apoptotic changes in the contused lungs of rats following blunt chest trauma. The rats were randomly divided into three groups: control, contusion, and contusion + NAC. All the rats, apart from those in the control group, performed moderate lung contusion. A daily intramuscular NAC injection (150 mg/kg) was given immediately following the blunt chest trauma and was continued for two additional days following cessation of the trauma. Samples of lung tissue were taken in order to evaluate the tissue malondialdehyde (MDA) level, histopathology, and epithelial cell apoptosis using terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and active caspase-3 immunostaining. In addition, we immunohistochemically evaluated the expression of surfactant protein D (SP-D) in the lung tissue. The blunt chest trauma-induced lung contusion resulted in severe histopathological injury, as well as an increase in the MDA level and in the number of cells identified on TUNEL assay together with active caspase-3 positive epithelial cells, but a decrease in the number of SP-D positive alveolar type 2 (AT-2) cells. NAC treatment effectively attenuated histopathologic, peroxidative, and apoptotic changes, as well as reducing alterations in SP-D expression in the lung tissue. These findings indicate that the beneficial effects of NAC administrated following blunt chest trauma is related to the regulation of oxidative stress and apoptosis.

Effect of high advanced glycation end-product diet on pulmonary inflammatory response and pulmonary function following gastric aspiration

It is not clear why some patients with aspiration advance to acute lung injury or acute respiratory distress syndrome, whereas others do not. The Western diet is high in advanced glycation end-products (AGEs), which have been found to be proinflammatory. We hypothesize that dietary AGEs exaggerate the pulmonary inflammatory response following gastric aspiration. CD-1 mice were randomized to receive either a low-AGE (LAGE) or a high-AGE (HAGE) diet for 4 weeks. Five hours after intratracheal instillation of acidified small gastric particles, pulmonary function was determined. Polymorphonuclear neutrophil counts, albumin, cytokine/chemokine, and tumor necrosis factor soluble receptor II concentrations in the bronchoalveolar lavage and lung myeloperoxidase activity were measured. Compared with LAGE-fed animals, those fed a HAGE diet had increased lung tissue resistance (P = 0.017), bronchoalveolar lavage albumin concentration (P < 0.05), pulmonary polymorphonuclear neutrophil counts (P = 0.0045), and lung myeloperoxidase activity (P = 0.002) following aspiration. In addition, the plasma levels of tumor necrosis factor soluble receptor II were significantly elevated (P < 0.05), whereas paradoxically levels of keratinocyte chemoattractant and monocyte chemoattractant protein 1 were decreased in mice with HAGE diet. In conclusion, a diet high in AGEs exacerbates acute lung injury following gastric aspiration as evidenced by increases in neutrophil infiltration, airway albumin leakage, and decreased pulmonary compliance. This is the first evidence implicating exacerbation of acute inflammatory lung injury by dietary AGEs. Targeting AGEs in the circulatory system may offer a therapeutic strategy for limiting lung injury following gastric aspiration.

Lung Contusion: A Clinico-Pathological Entity with Unpredictable Clinical Course

Lung contusion is an entity involving injury to the alveolar capillaries, without any tear or cut in the lung tissue. This results in accumulation of blood and other fluids within the lung tissue. The excess fluid interferes with gas exchange leading to hypoxia. The pathophysiology of lung contusion includes ventilation/perfusion mismatching, increased intrapulmonary shunting, increased lung water, segmental lung damage, and a loss of compliance. Clinically, patient's presents with hypoxiemia, hypercarbia and increase in laboured breathing. Patients are treated with supplemental oxygen and mechanical ventilation whenever indicated. Treatment is primarily supportive. Computed tomography (CT) is very sensitive for diagnosing pulmonary contusion. Pulmonary contusion occurs in 25-35% of all blunt chest traumas.

Increased phospholipase A2 and lyso-phosphatidylcholine levels are associated with surfactant dysfunction in lung contusion injury in mice

OBJECTIVE

Surfactant dysfunction is an important pathologic disturbance in various forms of acute inflammatory lung injury. Previously we reported the presence of marked alterations in the composition and activity of pulmonary surfactant in bilateral lung contusions (LC) injury induced by blunt trauma in rats. This is extended here to a mouse model of unilateral LC with a focus on compositional and functional changes in surfactant associated with permeability injury and increases in activity of secretory phospholipase A2.

RESULTS

Surfactant-associated gene expression was not altered in mice with unilateral LC injury on the basis of Affymetrix analysis. LC mice had significant permeability injury with increased albumin and total protein in bronchoalveolar lavage at 5, 24, 48, and 72 hours after insult compared with uninjured controls. The percent content of large surfactant aggregates was depleted at all postinjury times, and pulmonary pressure-volume (P-V) mechanics and compliance were abnormal during this period. Surfactant dysfunction was evaluated in 24 hours, when permeability injury and P-V changes were most prominent. At this time, activity levels of secretory phospholipase A2 were increased in bronchoalveolar lavage, and chromatographic analysis showed that large surfactant aggregates had decreased levels of phosphatidylcholine and increased levels of lyso-phosphatidylcholine. These changes were accompanied by severe detriments in large aggregate surface activity by pulsating bubble surfactometry. Large aggregates from LC mice at 24 hours had minimum surface tensions of only 12.6 ± 1.1 mN/m after prolonged bubble pulsation (20 min) compared with 0.7 ± 0.03 mN/m for uninjured controls.

CONCLUSION

These results document important detriments in the composition and activity of pulmonary surfactant in LC injury in mice and suggest that active synthetic phospholipase-resistant exogenous surfactants may have utility in treating surfactant dysfunction in this clinically important condition.

Electroporation-mediated in vivo gene delivery of the Na+/K+-ATPase pump reduced lung injury in a mouse model of lung contusion

BACKGROUND

Lung contusion (LC) is an independent risk factor for acute respiratory distress syndrome. The final common pathway in ARDS involves accumulation of fluid in the alveoli. In this study, we demonstrate the application of a potential gene therapy approach by delivering the Na+/K+-ATPase pump subunits in a murine model of LC. We hypothesized that restoring the activity of the pump will result in removal of excess alveolar fluid and additionally reduce inflammation.

METHODS

Under anesthesia, C57/BL6 mice were struck along the right posterior axillary line 1 cm above the costal margin with a cortical contusion impactor. Immediately afterward, 100 μg of plasmid DNA coding for the α,β of the Na+/K+-ATPase pump were instilled into the lungs (LC-electroporation-pump group). Contusion only (LC-only) and a sham saline instillation group after contusion were used as controls (LC-electroporation-sham). By using a BTX 830 electroporator, eight electrical pulses of 200 V/cm field strength were applied transthoracically. Mice were killed at 24 hours, 48 hours, and 72 hours after delivery. Bronchial alveolar lavage was recollected to measure albumin and cytokines by enzyme-linked immunosorbent assay. Pulmonary compliance was measured, and lungs were subject to histopathologic analysis.

RESULTS

After the electroporation and delivery of genes coding for the α,β subunits of the Na+/K+-ATPase pump, there was a significant mitigation of acute lung injury as evidenced by reduction in bronchial alveolar lavage levels of albumin, improved pressure volume curves, and reduced inflammation seen on histology.

CONCLUSION

Electroporation-mediated gene transfer of the subunits of the Na+/K+-ATPase pump enhanced recovery from acute inflammatory lung injury after LC.

Role of macrophage chemoattractant protein-1 in acute inflammation after lung contusion

Lung contusion (LC), commonly observed in patients with thoracic trauma is a leading risk factor for development of acute lung injury/acute respiratory distress syndrome. Previously, we have shown that CC chemokine ligand (CCL)-2, a monotactic chemokine abundant in the lungs, is significantly elevated in LC. This study investigated the nature of protection afforded by CCL-2 in acute lung injury/acute respiratory distress syndrome during LC, using rats and CC chemokine receptor (CCR) 2 knockout (CCR2(-/-)) mice. Rats injected with a polyclonal antibody to CCL-2 showed higher levels of albumin and IL-6 in the bronchoalveolar lavage and myeloperoxidase in the lung tissue after LC. Closed-chest bilateral LC demonstrated CCL-2 localization in alveolar macrophages (AMs) and epithelial cells. Subsequent experiments performed using a murine model of LC showed that the extent of injury, assessed by pulmonary compliance and albumin levels in the bronchoalveolar lavage, was higher in the CCR2(-/-) mice when compared with the wild-type (WT) mice. We also found increased release of IL-1β, IL-6, macrophage inflammatory protein-1, and keratinocyte chemoattractant, lower recruitment of AMs, and higher neutrophil infiltration and phagocytic activity in CCR2(-/-) mice at 24 hours. However, impaired phagocytic activity was observed at 48 hours compared with the WT. Production of CCL-2 and macrophage chemoattractant protein-5 was increased in the absence of CCR2, thus suggesting a negative feedback mechanism of regulation. Isolated AMs in the CCR2(-/-) mice showed a predominant M1 phenotype compared with the predominant M2 phenotype in WT mice. Taken together, the above results show that CCL-2 is functionally important in the down-modulation of injury and inflammation in LC.

Surfactant therapy for acute lung injury and acute respiratory distress syndrome

This article examines exogenous lung surfactant replacement therapy and its usefulness in mitigating clinical acute lung injury (ALI) and the acute respiratory distress syndrome (ARDS). Surfactant therapy is beneficial in term infants with pneumonia and meconium aspiration lung injury, and in children up to age 21 years with direct pulmonary forms of ALI/ARDS. However, extension of exogenous surfactant therapy to adults with respiratory failure and clinical ALI/ARDS remains a challenge. This article reviews clinical studies of surfactant therapy in pediatric and adult patients with ALI/ARDS, focusing on its potential advantages in patients with direct pulmonary forms of these syndromes.

Management of the crushed chest

Thoracic injuries are very common among trauma victims. This article reviews the current literature on the management of multiple aspects of the care of the patient with severe chest injury. The mechanics of chest injury are complex and varied. Chest wall injuries are the most common and noticeable manifestation of thoracic trauma. Overall morbidity and mortality are primarily determined by associated injuries. New ventilatory strategies permit oxygenation of the severely hypoxic patient. Acute pain management modalities offer the potential of decreasing associated pulmonary complications. Surgical chest wall fixation is clearly indicated in extreme cases of pulmonary herniation and chest wall disruption. There are potential benefits of surgical fixation in other settings, although further trials are needed.

Predictive modeling and inflammatory biomarkers in rats with lung contusion and gastric aspiration

BACKGROUND

This study uses statistical predictive modeling and hierarchical cluster analyses to examine inflammatory mediators and cells in bronchoalveolar lavage (BAL) as putative biomarkers in rats with blunt trauma lung contusion (LC), gastric aspiration (combined acid and small gastric food particles, CASP), or a combination of the two.

METHODS

Specific parameters assessed in the innate pulmonary inflammatory response were leukocytes, macrophages, and polymorphonuclear neutrophils (PMNs) in BAL; whole lung myeloperoxidase activity; and a series of cytokines or chemokines present in BAL at 5 or 24 hours after injury: tumor necrosis factor-alpha, interleukin (IL)-1beta, IL-6, interferon-gamma, IL-10, macrophage inflammatory protein-2, cytokine-induced neutrophil chemoattractant-1, and monocyte chemoattractant protein-1.

RESULTS

Rats with LC, CASP, LC + CASP all had severe lung injury compared with uninjured controls based on decreased arterial oxygenation or increased BAL albumin at 5 or 24 hours postinsult. However, the injury groups had distinct overall patterns of inflammation that allowed them to be discriminated accurately by hierarchical cluster analysis (29 of 30 and 35 of 37 rats were correctly classified in hierarchical clusters at 5 and 24 hours, respectively). Moreover, predictive analyses based on an extension of standard receiver-operator characteristic methodology discriminated individual animals and groups with similar high accuracy based on a maximum of two inflammatory parameters per group (29 of 30 and 36 of 37 rats were correctly classified at 5 hours and 24 hours, respectively).

CONCLUSIONS

These results support the possibility that inflammatory biomarker profiles could be developed in the future to improve the diagnosis and management of trauma patients with unwitnessed (occult) gastric aspiration who have an increased risk of clinical acute lung injury or the acute respiratory distress syndrome.

Selective medicated (saline + natural surfactant) bronchoalveolar lavage in unilateral lung contusion. A clinical randomized controlled trial

OBJECTIVE

Open lung and low tidal volume ventilation appear to be a promising ventilation for chest trauma as it can reduce ARDS and improve outcome. Local therapy (e.g. BAL) can be synergic to remove from the lung the debris, mitigate inflammatory cascade and avoid damage spreading to not compromised lung areas.

MATERIALS AND METHODS

44 pulmonary contused patients were randomized to receive broncho-suction and volume controlled low tidal volume ventilation-VCLTVV (Control Group) or the same ventilation plus medicated (saline + surfactant) BAL (Treatment Group). Tidal volume <10 ml/kg, PEEP of 10-12 cm H(2)O and PaO(2) 60-100 mm Hg and PaCO(2) 35-45 mm Hg were used in both groups. BAL was performed using a fiberscope. 4 boluses of 25 ml saline with 2.4 mg/ml of surfactant were introduced into each contused lobe in which, subsequently, 240 mg of surfactant was instilled.

RESULTS

All patients survived. In the Control Group 18 patients developed pneumonia, 5 ARDS and days of intubation were 11.50 (3.83) compared to 5.05 (1.21) of Treatment Group in which OI and PaO(2)/FiO(2) significantly improved from 36 h.

CONCLUSIONS

VCLTVV alone was not able to prevent ARDS and infection in the Control Group as the reduction of intubation. In the Treatment Group, VCLTVV and medicated BAL facilitated the removal of degradated lung material and recruited the contused lung regions, enabling the healing of the lung pathology.

Exogenous surfactant instillation attenuates inflammatory response to acid-induced lung injury in rat

The present study was performed to investigate the role of exogenous surfactant on hydrochloric acid (HCL) - induced lung injury in rats. Six-week-old male Sprague-Dawley rats were anesthetized by intraperitoneal injection of pentobarbital sodium (40mg/kg) and HCL (0.1N, 2mL/kg) or normal saline (NS, 2mL/kg) was instilled into the trachea. Thirty minutes after HCL instillation, surfactant at a dose of 60mg (=2mL)/body or NS (2mL) was instilled into the rat lungs. Animals in another experimental group were also treated with the same dose of surfactant supplement 2hours after the first administration. Bronchoalveolar lavage fluid (BALF) was obtained 5hours after HCL instillation. In BALF, increases in total nuclear cell counts, neutrophil counts, optical density at 412nm as an indicator of pulmonary hemorrhage, neutrophil elastase activity, concentrations of albumin and cytokine-induced neutrophil chemoattractant (CINC) induced by HCL instillation were significantly attenuated by surfactant treatment. The wet-to-dry weight (W/D) ratio in the lung and partial oxygen tension (P(O2)) were also estimated; surfactant treatment significantly attenuated the W/D ratio and improved deteriorated P(O2) induced by HCL. Additional surfactant supplementation did not show further beneficial effects on HCL-induced lung injury compared with a single treatment. These results suggest that surfactant shows an anti-inflammatory effect on acid lung injury in rats but the beneficial effects may be dose limited.

Lung contusion: inflammatory mechanisms and interaction with other injuries

This article reviews current animal models and laboratory studies investigating the pathophysiology of lung contusion (LC), a common and severe condition in patients with blunt thoracic trauma. Emphasis is on studies elucidating cells, mediators, receptors, and processes important in the innate pulmonary inflammatory response that contribute to LC injury. Surfactant dysfunction in the pathogenesis of LC is also discussed, as is the potential role of epithelial cell or neutrophil apoptosis. Studies examining combination injuries where LC is exacerbated by secondary insults such as gastric aspiration in trauma patients are also noted. The need for continuing mechanism-based research to further clarify the pathophysiology of LC injury, and to define and test potential therapeutic interventions targeting specific aspects of inflammation or surfactant dysfunction to improve clinical outcomes in patients with LC, is also emphasized.

Neonatal oxygen adversely affects lung function in adult mice without altering surfactant composition or activity

Despite its potentially adverse effects on lung development and function, supplemental oxygen is often used to treat premature infants in respiratory distress. To understand how neonatal hyperoxia can permanently disrupt lung development, we previously reported increased lung compliance, greater alveolar simplification, and disrupted epithelial development in adult mice exposed to 100% inspired oxygen fraction between postnatal days 1 and 4. Here, we investigate whether oxygen-induced changes in lung function are attributable to defects in surfactant composition and activity, structural changes in alveolar development, or both. Newborn mice were exposed to room air or 40%, 60%, 80%, or 100% oxygen between postnatal days 1 and 4 and allowed to recover in room air until 8 wk of age. Lung compliance and alveolar size increased, and airway resistance, airway elastance, tissue elastance, and tissue damping decreased, in mice exposed to 60-80% oxygen; changes were even greater in mice exposed to 100% oxygen. These alterations in lung function were not associated with changes in total protein content or surfactant phospholipid composition in bronchoalveolar lavage. Moreover, surface activity and total and hydrophobic protein content were unchanged in large surfactant aggregates centrifuged from bronchoalveolar lavage compared with control. Instead, the number of type II cells progressively declined in 60-100% oxygen, whereas levels of T1alpha, a protein expressed by type I cells, were comparably increased in mice exposed to 40-100% oxygen. Thickened bundles of elastin fibers were also detected in alveolar walls of mice exposed to > or = 60% oxygen. These findings support the hypothesis that changes in lung development, rather than surfactant activity, are the primary causes of oxygen-altered lung function in children who were exposed to oxygen as neonates. Furthermore, the disruptive effects of oxygen on epithelial development and lung mechanics are not equivalently dose dependent.

Superimposed gastric aspiration increases the severity of inflammation and permeability injury in a rat model of lung contusion

INTRODUCTION

Lung contusion (LC) from blunt thoracic trauma is a clinically-prevalent condition that can progress to acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Patients with LC are at risk for gastric aspiration at the time of trauma, but the combined insults have not been well-studied in animal models. This study tests the hypothesis that concurrent gastric aspiration (combined acid and small gastric particles, CASP) at the time of trauma significantly increases permeability injury and inflammation compared with LC alone, and also modifies the inflammatory response to include distinct features compared with the aspiration component of injury.

MATERIALS AND METHODS

Four groups of adult male Long-Evans rats were studied (LC, CASP, LC+CASP, uninjured controls). LC was induced in anesthetized rats at a fixed impact energy of 2.0 J, and CASP (1.2 mL/kg body weight, 40 mg particles/mL, pH=1.25) was instilled through an endotracheal tube. Lung injury and inflammation were assessed by arterial blood gases and levels of albumin, cells, and cytokines/chemokines in bronchoalveolar lavage (BAL) at 5 and 24 h.

RESULTS

Rats with LC+CASP had lower mean PaO(2)/FiO(2) ratios compared with LC alone at 24 h, and higher BAL albumin concentrations compared with either LC or CASP alone. Rats with LC+CASP versus LC had more severe inflammation based on higher levels of PMN in BAL at 5 h, increased whole lung myeloperoxidase (MPO) activity at 5 and 24 h, and increased levels of inflammatory mediators in BAL (TNFalpha, IL-1beta, and MCP-1 at 5 and 24 h; IL-10, MIP-2, and CINC-1 at 5 h). Rats with LC+CASP also had distinct aspects of inflammation compared with CASP alone, i.e., significantly higher levels of IL-10 (5 and 24 h), IL-1beta (24 h), CINC-1 (24 h), and MCP-1 (24 h), and significantly lower levels of MPO (5 h), MIP-2 (5 h), and CINC-1 (5 h).

CONCLUSIONS

Concurrent gastric aspiration can exacerbate permeability lung injury and inflammation associated with LC, and also generates a modified inflammatory response compared with aspiration alone. Unwitnessed gastric aspiration has the potential to contribute to more severe forms of LC injury associated with progression to ALI/ARDS and pneumonia in patients with thoracic trauma.