Manuel Meneses

Resolution of lung injury after a single event of aspiration: a model of bilateral instillation of whole gastric fluid.

Gastric aspiration is a high-risk condition for lung injury. Consequences range from subclinical pneumonitis to respiratory failure, with fibrosis development in some patients. Little is known about how the lung repairs aspiration-induced injury. By using a rat model of single orotracheal instillation of whole gastric contents, we studied the time course of morphological and biochemical changes during injury and resolution, and evaluated whether repair involved long-term fibrosis. Anesthetized rats received one gastric fluid instillation. At 4, 12, and 24 hours and 4 and 7 days, we performed lung histological studies and biochemical measurements in bronchoalveolar lavage fluid and lung tissue. Physiological measurements were performed at 12 to 24 hours. Long-term outcome was studied histologically at day 60. During the first 24 hours, severe peribronchiolar injury involving edema, intra-alveolar proteinaceous debris, hemorrhage, increased neutrophils and cytokines, and physiological dysfunction were observed. At days 4 and 7, an organizing pneumonia (OP) pattern developed, with foreign-body giant cells and granulomas. Lung matrix metalloproteinase 9 and 2 activities increased, with metalloproteinase-9 linked to early inflammation and metalloproteinase-2 to OP. At day 60, lung architecture was normal. In conclusion, a continuum of alterations starting with severe injury, evolving toward OP and later resolving, characterizes the rat single aspiration event. In addition to identifying markers of staging and severity, this modelxa0reveals that OP participates in the repair of aspiration-induced injury.

Acute lung injury induced by whole gastric fluid: hepatic acute phase response contributes to increase lung antiprotease protection

BackgroundGastric contents aspiration in humans is a risk factor for severe respiratory failure with elevated mortality. Although aspiration-induced local lung inflammation has been studied in animal models, little is known about extrapulmonary effects of aspiration. We investigated whether a single orotracheal instillation of whole gastric fluid elicits a liver acute phase response and if this response contributes to enrich the alveolar spaces with proteins having antiprotease activity.MethodsIn anesthetized Sprague-Dawley rats receiving whole gastric fluid, we studied at different times after instillation (4xa0h −7xa0days): changes in blood cytokines and acute phase proteins (fibrinogen and the antiproteases alpha1-antitrypsin and alpha2-macroglobulin) as well as liver mRNA expression of the two antiproteases. The impact of the systemic changes on lung antiprotease defense was evaluated by measuring levels and bioactivity of antiproteases in broncho-alveolar lavage fluid (BALF). Markers of alveolar-capillary barrier derangement were also studied. Non-parametric ANOVA (Kruskall-Wallis) and linear regression analysis were used.ResultsSevere peribronchiolar injury involving edema, intra-alveolar proteinaceous debris, hemorrhage and PMNn cell infiltration was seen in the first 24xa0h and later resolved. Despite a large increase in several lung cytokines, only IL-6 was found elevated in blood, preceding increased liver expression and blood concentration of both antiproteases. These changes, with an acute phase response profile, were significantly larger for alpha2-macroglobulin (40-fold increment in expression with 12-fold elevation in blood protein concentration) than for alpha1-antitrypsin (2–3 fold increment in expression with 0.5-fold elevation in blood protein concentration). Both the increment in capillary-alveolar antiprotease concentration gradient due to increased antiprotease liver synthesis and a timely-associated derangement of the alveolar-capillary barrier induced by aspiration, contributed a 58-fold and a 190-fold increase in BALF alpha1-antitrypsin and alpha2-macroglobulin levels respectively (pu2009<u20090.001).ConclusionsGastric contents-induced acute lung injury elicits a liver acute phase response characterized by increased mRNA expression of antiproteases and elevation of blood antiprotease concentrations. Hepatic changes act in concert with derangement of the alveolar capillary barrier to enrich alveolar spaces with antiproteases. These findings may have significant implications decreasing protease burden, limiting injury in this and other models of acute lung injury and likely, in recurrent aspiration.

Elastin degradation products in acute lung injury induced by gastric contents aspiration

BackgroundGastric contents aspiration is a high-risk condition for acute lung injury (ALI). Consequences range from subclinical pneumonitis to respiratory failure, depending on the volume of aspirate. A large increment in inflammatory cells, an important source of elastase, potentially capable of damaging lung tissue, has been described in experimental models of aspiration. We hypothesized that in early stages of aspiration-induced ALI, there is proteolytic degradation of elastin, preceding collagen deposition. Our aim was to evaluate whether after a single orotracheal instillation of gastric fluid, there is evidence of elastin degradation.MethodsAnesthesized Sprague-Dawley rats received a single orotracheal instillation of gastric fluid and were euthanized 4, 12 and 24xa0h and at day 4 after instillation (nu2009=u20096/group). We used immunodetection of soluble elastin in lung tissue and BALF and correlated BALF levels of elastin degradation products with markers of ALI. We investigated possible factors involved in elastin degradation and evaluated whether a similar pattern of elastin degradation can be found in BALF samples of patients with interstitial lung diseases known to have aspirated. Non-parametric ANOVA (Kruskall-Wallis) and linear regression analysis were used.ResultsWe found evidence of early proteolytic degradation of lung elastin. Elastin degradation products are detected both in lung tissue and BALF in the first 24xa0h and are significantly reduced at day 4. They correlate significantly with ALI markers, particularly PMN cell count, are independent of acidity and have a similar molecular weight as those obtained using pancreatic elastase. Evaluation of BALF from patients revealed the presence of elastin degradation products not present in controls that are similar to those found in BALF of rats treated with gastric fluid.ConclusionsA single instillation of gastric fluid into the lungs induces early proteolytic degradation of elastin, in relation to the magnitude of alveolar-capillary barrier derangement. PMN-derived proteases released during ALI are mostly responsible for this damage. BALF from patients showed elastin degradation products similar to those found in rats treated with gastric fluid. Long-lasting effects on lung elastic properties could be expected under conditions of repeated instillations of gastric fluid in experimental animals or repeated aspiration events in humans.

Acute lung injury by gastric fluid instillation: activation of myofibroblast apoptosis during injury resolution

BackgroundGastric contents aspiration in humans has variable consequences depending on the volume of aspirate, ranging from subclinical pneumonitis to respiratory failure with up to 70% mortality. Several experimental approaches have been used to study this condition. In a model of single orotracheal instillation of gastric fluid we have shown that severe acute lung injury evolves from a pattern of diffuse alveolar damage to one of organizing pneumonia (OP), that later resolves leaving normal lung architecture. Little is known about mechanisms of injury resolution after a single aspiration that could be dysregulated with repetitive aspirations. We hypothesized that, in a similar way to cutaneous wound healing, apoptosis may participate in lung injury resolution by reducing the number of myofibroblasts and by affecting the balance between proteases and antiproteases. Our aim was to study activation of apoptosis as well as MMP-2/TIMP-2 balance in the sub-acute phase (4–14xa0days) of gastric fluid-induced lung injury.MethodsAnesthesized Sprague-Dawley rats received a single orotracheal instillation of gastric fluid and were euthanized 4, 7 and 14xa0days later (nu2009=u20096/group). In lung tissue we studied caspase-3 activation and its location by double immunofluorescence for cleaved caspase-3 or TUNEL and alpha-SMA. MMP-2/TIMP-2 balance was studied by zymography and Western blot. BALF levels of TGF-β1 were measured by ELISA.ResultsAn OP pattern with Masson bodies and granulomas was seen at days 4 and 7 that was no longer present at day 14. Cleaved caspase-3 increased at day 7 and was detected by immunofluorescence in Masson body-alpha-SMA-positive and –negative cells. TUNEL-positive cells at days 4 and 7 were located mainly in Masson bodies. Distribution of cleaved caspase-3 and TUNEL-positive cells at day 14 was similar to that in controls. At the peak of apoptosis (day 7), an imbalance between MMP-2 activity and TIMP-2 expression was produced by reduction in TIMP-2 expression.ConclusionsApoptosis is activated in Masson body-alpha-SMA–positive and –negative cells during the sub-acute phase of gastric fluid-induced lung injury. This mechanism likely contributes to OP resolution, by reducing myofibroblast number and new collagen production. In addition, pre-formed collagen degradation is favored by an associated MMP-2/TIMP-2 imbalance.

Changes in the pattern of fibrosis in the rat lung with repetitive orotracheal instillations of gastric contents: evidence of persistent collagen accumulation

Recurrent aspiration of gastric contents has been associated with several interstitial lung diseases. Despite this association, the pathogenic role of aspiration in these diseases has been poorly studied and little is known about extracellular matrix (ECM) changes in animal models of repetitive events of aspiration. Our aim was to study the repair phase of lung injury induced by each of several instillations of gastric fluid in Sprague-Dawley rats to evaluate changes in ECM and their reversibility. Anesthetized animals received weekly orotracheal instillations of gastric fluid for 1, 2, 3, and 4 wk and were euthanized at day 7 after last instillation. For reversibility studies, another group received 7 weekly instillations and was euthanized at day 7 or 60 after last instillation. Biochemical and histological measurements were used to evaluate ECM changes. Lung hydroxyproline content increased progressively and hematoxylin and eosin, Massons trichrome, and alpha-SMA stains showed that after a single instillation, intra-alveolar fibrosis predominated, whereas with repetitive instillations this fibrosis pattern became less prominent and interstitial fibrosis progressively became evident. Both type I and III collagen increased in intra-alveolar and interstitial fibrosis. Imbalance between matrix metalloproteinase-2 (MMP-2) activity and tissue inhibitor of metalloproteinase-2 (TIMP-2) expression was observed, favoring either collagen degradation or accumulation depending on the number of instillations. Caspase-3 activation was also dose dependent. ECM changes were partially reversible at long-term evaluation, since Masson bodies, granulomas, and foreign body giant cells disappeared, whereas interstitial collagen accumulated. In conclusion, repetitive lung instillations of gastric fluid induce progressive fibrotic changes in rat lung ECM that persist at long-term evaluation.

Electrocauterio y broncoscopía flexible como primera medida en la obstrucción central de la vía aérea y hemoptisis asociada

Background: Central airway obstruction caused by malignant or benign lesions, associated in some cases with hemoptysis, is a condition with high morbidity and mortality. The use of electrocautery by flexible bronchoscopy is an initial treatment option with immediate improvement of obstruction symptoms. It is as effective as Nd:YAG laser. Aim: To describe the usefulness of electrocautery in the management of central obstruction of the airway and hemoptysis. Material and Methods: A retrospective, descriptive study of patients referred for management of central airway obstruction or associated hemoptysis .Diagnoses, symptoms (dyspnea, cough, and hemoptysis) and radiology before and after the procedures were analyzed. Results: Eighteen patients aged 59 ± 12 years (66% males) were evaluated, registering 25 endoscopic procedures. Three conditions were found: partial or complete airway obstruction, hemoptysis and post lung transplant bronchial stenosis. Seventy two percent presented with dyspnea, 61% with cough and 33% with hemoptysis. Sixty six percent of patients had airway obstruction caused by malignant metastatic lesions. After electrocautery, 17 patients (94.4%) improved their symptoms and achieved complete airway clearing. Three patients had significant bronchial stenosis after lung transplant achieving subsequent clearing after electrocautery. Conclusions: Electrocautery during flexible bronchoscopy is an effective and safe procedure for the management of central airway obstruction and associated hemoptysis.BACKGROUNDnCentral airway obstruction caused by malignant or benign lesions, associated in some cases with hemoptysis, is a condition with high morbidity and mortality. The use of electrocautery by flexible bronchoscopy is an initial treatment option with immediate improvement of obstruction symptoms. It is as effective as Nd: YAG laser.nnnAIMnTo describe the usefulness of electrocautery in the management of central obstruction of the airway and hemoptysis.nnnMATERIAL AND METHODSnA retrospective, descriptive study of patients referred for management of central airway obstruction or associated hemoptysis. Diagnoses, symptoms (dyspnea, cough, and hemoptysis) and radiology before and after the procedures were analyzed.nnnRESULTSnEighteen patients aged 59 ± 12 years (66% males) were evaluated, registering 25 endoscopic procedures. Three conditions were found: partial or complete airway obstruction, hemoptysis and post lung transplant bronchial stenosis. Seventy two percent presented with dyspnea, 61% with cough and 33% with hemoptysis. Sixty six percent of patients had airway obstruction caused by malignant metastatic lesions. After electrocautery, 17 patients (94.4%) improved their symptoms and achieved complete airway clearing. Three patients had significant bronchial stenosis after lung transplant achieving subsequent clearing after electrocautery.nnnCONCLUSIONSnElectrocautery during flexible bronchoscopy is an effective and safe procedure for the management of central airway obstruction and associated hemoptysis.

Supervivencia de pacientes con fibrosis pulmonar idiopática diagnosticados por biopsia quirúrgica de pulmón: experiencia del Instituto Nacional del Tórax

BACKGROUNDnIdiopathic Pulmonary Fibrosis (IPF) is the most prevalent of all interstitial lung diseases. The usual underlying pathological picture is an interstitial pneumonia (UIP).nnnAIMnTo describe the evolution of a Chilean cohort of patients with IPF.nnnMATERIAL AND METHODSnPatients with the disease were identified at the pathology registry of National Institute of Thoracic Diseases, Santiago, Chile. Patients were included if they had surgical biopsy of UIP and compatible clinical and radiological characteristics. The medical records of included patients were reviewed, recording clinical information and lung function test results. Survival was analyzed obtaining death records from the Chilean National Identification Service.nnnRESULTSnData from 142 patients with a mean age of 58 years (42% men), were analyzed. Mean initial lung function showed a forced vital capacity (FVC) of 73%, carbon monoxide diffusing capacity (DLCO) of 57% and a distance covered in 6-minute walk (6MWT) of 95% of expected normal values. The median survival was 80 months. Predictors of survival were a DLCO of less than 40% and an oxygen saturation at the end of the 6MWT of less than 89%.nnnCONCLUSIONSnSurvival in this group of patients was higher than the figures reported elsewhere. DLCO and the fall of oxygen saturation after walking were predictors of mortality, as previously described in other populations.Background: Idiopathic Pulmonary Fibrosis (IPF) is the most prevalent of all interstitial lung diseases. The usual underlying pathological picture is an interstitial pneumonia (UIP). Aim: To describe the evolution of a Chilean cohort of patients with IPF. Material and methods: Patients with the disease were identified at the pathology registry of National Institute of Thoracic Diseases, Santiago, Chile. Patients were included if they had surgical biopsy of UIP and compatible clinical and radiological characteristics. The medical records of included patients were reviewed, recording clinical information and lung function test results. Survival was analyzed obtaining death records from the Chilean National Identification Service. Results: Data from 142 patients with a mean age of 58 years (42% men), were analyzed. Mean initial lung function showed a forced vital capacity (FVC) of 73%, carbon monoxide diffusing capacity (DLCO) of 57% and a distance covered in 6-minute walk (6MWT) of 95% of expected normal values. The median survival was 80 months. Predictors of survival were a DLCO of less than 40% and an oxygen saturation at the end of the 6MWT of less than 89%. Conclusions: Survival in this group of patients was higher than the figures reported elsewhere. DLCO and the fall of oxygen saturation after walking were predictors of mortality, as previously described in other populations.