Triolein increases microvascular permeability in isolated perfused rabbit lungs: role of neutrophils

Saturated Fatty Acid Emulsions Open the Blood-Brain Barrier and Promote Drug Delivery in Rat Brains

We performed this study to evaluate whether saturated fatty acid (SFA) emulsions affect the BBB and determine the duration of BBB opening, thereby promoting drug delivery to the brain. Butyric, valeric, caproic, enanthic, and caprylic acid emulsions were infused into the carotid artery of the rat model. We evaluated the BBB opening and drug delivery over time. The trypan blue and doxorubicin delivery studies were repeated from 30 min to 6 h. In the 1 h rats in each group, transmission electron microscopy (TEM) was performed to morphologically evaluate tight junctions, and the delivery of temozolomide was assessed by desorption electrospray ionization mass spectrometry. The ipsilateral hemisphere was positive for trypan blue staining in all the five SFA emulsion groups. In the valeric, enanthic, and caprylic acid emulsion groups, RGB ratios were significantly higher at 30 min and decreased thereafter. Doxorubicin delivery increased in all emulsion groups at all time points. Tight junctions were observed to be open in all groups. TMZ delivery was significantly higher in the ipsilateral hemisphere. In conclusion, intra-arterially infused SFA emulsions opened the BBB and promoted drug delivery within 30 min, which decreased thereafter. Therefore, SFA emulsions may aid BBB research and promote drug delivery to the brain.

Human airway construct model is suitable for studying transcriptome changes associated with indoor air particulate matter toxicity

In vitro models mimicking the human respiratory system are essential when investigating the toxicological effects of inhaled indoor air particulate matter (PM). We present a pulmonary cell culture model for studying indoor air PM toxicity. We exposed normal human bronchial epithelial cells, grown on semi-permeable cell culture membranes, to four doses of indoor air PM in the air-liquid interface. We analyzed the chemokine interleukin-8 concentration from the cell culture medium, protein concentration from the apical wash, measured tissue electrical resistance, and imaged airway constructs using light and transmission electron microscopy. We sequenced RNA using a targeted RNA toxicology panel for 386 genes associated with toxicological responses. PM was collected from a non-complaint residential environment over 1 week. Sample collection was concomitant with monitoring size-segregated PM counts and determination of microbial levels and diversity. PM exposure was not acutely toxic for the cells, and we observed up-regulation of 34 genes and down-regulation of 17 genes when compared to blank sampler control exposure. The five most up-regulated genes were related to immunotoxicity. Despite indications of incomplete cell differentiation, this model enabled the comparison of a toxicological transcriptome associated with indoor air PM exposure.

Pathophysiology of fat embolism: a rabbit model

OBJECTIVES

The objective of this study was to assess the effects of fat embolism on rabbit physiology.

METHODS

After anesthetic administration, both femoral condyles of the right knee only of 23 New Zealand white rabbits were exposed through a medial parapatellar approach to the knee. In the pulmonary fat embolism group (n = 15), the femoral canal was drilled in a retrograde fashion and then reamed and pressurized with a 1- to 1.5-mL cement injection. In the no-pressurization group (n = 4), after reaming, no cement was injected. In the control group (n = 4), the knee incision was immediately closed. Animals were then observed for 5 hours. Hemodynamics and blood gases were recorded at standard intervals. Postmortem, the lungs were removed en bloc and fixed for histologic assessment and quantitative histomorphometry.

RESULTS

Four intraoperative deaths occurred in the pulmonary fat embolism group immediately after pressurization and may have been associated with hypotension and cardiac arrest. In the pulmonary fat embolism group, pulmonary artery pressure increased, and both mean arterial pressure and PaO2 decreased after pressurization. Approximately 2% of lung volume was occupied by intravascular fat and there were no signs of perivascular inflammation. Control and no-pressurization animals remained stable throughout the experiment.

CONCLUSIONS

This model simulates pulmonary fat embolism after long-bone fractures. Despite cardiorespiratory dysfunction, there was no evidence of fat initiating pulmonary inflammation based on histologic data within the timeframe of the investigation.

Cardiorespiratory effects of venous lipid micro embolization in an experimental model of mediastinal shed blood reinfusion

BACKGROUND

Retransfusion of the patient's own blood during surgery is used to reduce the need for allogenic blood transfusion. It has however been found that this blood contains lipid particles, which form emboli in different organs if the blood is retransfused on the arterial side. In this study, we tested whether retransfusion of blood containing lipid micro-particles on the venous side in a porcine model will give hemodynamic effects.

METHODS

Seven adult pigs were used. A shed blood surrogate containing 400 ml diluted blood and 5 ml radioactive triolein was produced to generate a lipid embolic load. The shed blood surrogate was rapidly (<2 minutes) retransfused from a transfusion bag to the right atrium under general anesthesia. The animals' arterial, pulmonary, right and left atrial pressure were monitored, together with cardiac output and deadspace. At the end of the experiment, an increase in cardiac output and pulmonary pressure was pharmacologically induced to try to flush out lipid particles from the lungs.

RESULTS

A more than 30-fold increase in pulmonary vascular resistance was observed, with subsequent increase in pulmonary artery pressure, and decrease in cardiac output and arterial pressure. This response was transient, but was followed by a smaller, persistent increase in pulmonary vascular resistance. Only a small portion of the infused triolein passed the lungs, and only a small fraction could be recirculated by increasing cardiac output and pulmonary pressure.

CONCLUSION

Infusion of blood containing lipid micro-emboli on the venous side leads to acute, severe hemodynamic responses that can be life threatening. Lipid particles will be trapped in the lungs, leading to persistent effects on the pulmonary vascular resistance.

Experimental pulmonary fat embolism: computed tomography and pathologic findings of the sequential changes

This study was done to demonstrate the computed tomography (CT) and pathologic findings of the sequential changes for experimental pulmonary fat embolism (PFE), and to correlate the CT and pathologic findings of rabbit lung. PFE was induced by an intravenous injection of 0.2 mL linoleic acid in 24 rabbits. The rabbits were divided into 4 groups of 6 rabbits each. CT scans were obtained sequentially at 2 hr (n= 24), day 1 (n=18), day 3 (n=12) and day 7 (n=6) after fat embolization. The pathologic findings were analyzed and CT-pathologic correlation was done. CT scans showed bilateral ground-glass opacity (GGO), consolidation and nodule in all cases. The findings of PFE at 2 hr after fat embolization were areas of decreased attenuation, GGO, consolidation and nodule. These findings were aggravated on the follow- up CT after 1 day and 3 days. The follow-up CT revealed linear density in the subpleural lungs after 7 days. On CT-pathology correlation, wedge-shaped ischemic necrosis in the subpleural lungs correlated with nodule at 2 hr. GGO and consolidation at day 1 on CT correlated with congestion and edema, and these findings at day 3 were correlated with inflammation and hemorrhagic edema. The linear density in the subpleural lungs correlated with interstitial fibrosis and pleural contraction at day 7. In conclusion, PFE was caused by using linoleic acid which is kind of free fatty acid and this study served as one model of the occurrence of nontraumatic PFE. CT accurately depicted the natural evolution of PFE in the serial followup, and this correlated well with the pathologic findings.

Nitric oxide mediates acute lung injury caused by fat embolism in isolated rat's lungs

BACKGROUND

The involvement of nitric oxide (NO) in acute lung injury (ALI) induced by fat embolism (FE) has not been investigated. The present study elucidated the role of NO in ALI because of FE.

METHODS

FE was produced by introduction of fatty acid (corn oil micelles) into the isolated rat's lungs. Nonselective NO synthase (NOS) and selective inducible NOS (iNOS) inhibitors, N-nitro-l-arginine methyl ester (l-NAME) and l-N(1-iminoethyl)-lysine (l-Nil) as well as NO donors, sodium nitroprusside (SNP), and S-nitroso-N-acetylpenicillamine (SNAP) at a dose of 10 mol/L were given 60 minutes before FE. There were six groups of isolated lungs randomly assigned to receive vehicle (physiologic saline solution), FE, FE with pretreatment of l-NAME, l-Nil, SNP, or SNAP. Each group was observed for 4 hours.

RESULTS

FE significantly increased the lung weight changes, pulmonary arterial pressure, and microvascular permeability. The concentration of nitrate or nitrite, methyl guanidine, tumor necrosis factor-alpha, and interleukin-1beta was significantly elevated after FE. Hisotopathologic examination revealed lung edema with multiple fatty droplets in lung tissue. Pretreatment with l-NAME or l-Nil attenuated, whereas SNP or SNAP exacerbated most of the FE-induced changes. Addition of NO donors (SNP or SNAP) into the isolated lungs did not produce significant changes in the lungs, suggesting that NO donation alone without FE does not exerts harmful effect.

CONCLUSIONS

Our results suggest that NO production through the iNOS isoform plays a detrimental role in the FE-induced ALI. Free radical and proinflammatory cytokines may also be involved in the pathogenesis of ALI because of FE.

N-acetylcysteine attenuates acute lung injury induced by fat embolism

OBJECTIVES

Fat embolism syndrome is a clinical issue in subjects with long-bone fracture. It may lead to acute lung injury. The mechanisms and therapeutic regimen remain unclear. The present study was designed to investigate the pathologic and biochemical changes after fat embolization in isolated rat lungs, and to test the effects of posttreatment with N-acetylcysteine (NAC).

DESIGN

Prospective, randomized, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

A total of 36 perfused lungs isolated from Sprague-Dawley rats.

INTERVENTIONS

The isolated lungs were randomly assigned to receive physiologic saline solution (vehicle group), fat embolism (FE group), or FE with NAC posttreatment (FE + NAC group). There were 12 isolated lungs in each group. FE was produced by introduction of corn oil micelles. NAC at a dose 150 mg/kg was given 10 mins after FE.

MEASUREMENTS AND MAIN RESULTS

The extent of acute lung injury was evaluated by lung weight change, protein concentration in bronchoalveolar lavage, and exhaled nitric oxide. We also measured the pulmonary arterial pressure and capillary filtration coefficient and determined the nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate. Histopathologic changes of the lung were examined and quantified. The levels of neutrophil elastase and myeloperoxidase were determined. The expression of inducible nitric oxide synthase was detected. FE caused acute lung injury as evidenced by the lung weight changes, increases in exhaled nitric oxide and protein concentration in bronchoalveolar lavage, pulmonary hypertension, increased capillary filtration coefficient, and lung pathology. The insult also increased nitrate/nitrite, methylguanidine, tumor necrosis factor-alpha, and interleukin-1beta in lung perfusate, increased neutrophil elastase and myeloperoxidase levels, and upregulated inducible nitric oxide synthase expression. Posttreatment with NAC abrogated these changes induced by FE.

CONCLUSION

FE caused acute lung injury and associated biochemical changes. Posttreatment with NAC was effective to alleviate the pathologic and biochemical changes caused by FE.

A neutrophil elastase inhibitor, sivelestat, improves leukocyte deformability in patients with acute lung injury

BACKGROUND

The objective of this study was to evaluate whether the neutrophil elastase (NE) inhibitor, sivelestat, improves leukocyte deformability and pulmonary function in patients with acute lung injury (ALI).

PATIENTS AND METHODS

Twenty-four patients with systemic inflammatory response syndrome (SIRS) were divided into two groups: those with ALI (ALI group, n = 14), and those without ALI (non-ALI group, n = 10). Within 72 hours after the diagnosis, we measured the total leukocyte count (TLC), C-reactive protein (CRP) level, NE concentration, APACHE II score, Goris multiple organ failure (MOF) index, respiratory index (RI), lung injury score (LIS), and oxygenation index (P/F ratio). Leukocyte deformability was examined with a microchannel array etched on a single-crystal silicon tip that simulates the microvasculature. The number of obstructed microchannels (NOM) because of stiffened neutrophils and transit time (TT), defined as the time needed for 100 microL of whole blood to pass through the microchannels, were determined. We then administered sivelestat (4.8 mg/kg/d) to nine ALI patients (sivelestat group) for 5 days and compared with seven ALI patients treated previously without sivelestat (conventional group). The factors described above were measured before and 5 days after treatment.

RESULTS

There were no significant differences in age, TLC, CRP, APACHE II score, and MOF index between ALI and non-ALI group. RI and LIS were higher and the P/F ratio was significantly lower in the ALI group than in the non-ALI group. NE concentration, NOM, and TT were significantly higher in the ALI group than in the non-ALI group (p < 0.05). After 5 days of treatment with sivelestat, the APACHE II score, MOF index, RI, LIS, NE concentration, TT, and NOM were lower and the P/F ratio was significantly higher than baseline values and those in the conventional group (p < 0.05).

CONCLUSION

NE concentration and neutrophil rigidity are significantly increased in SIRS patients with ALI. Sivelestat appears to reduce NE concentration and neutrophil stiffness and improve pulmonary oxygenation in patients with ALI.

Protective effects of a selective neutrophil elastase inhibitor (sivelestat) on lipopolysaccharide-induced acute dysfunction of the pulmonary microcirculation

OBJECTIVE

The purpose of this study was to evaluate the effect of a neutrophil elastase inhibitor, sivelestat, on lipopolysaccharide-induced acute lung injury through analysis of hemodynamic changes in the pulmonary microcirculation.

DESIGN

Randomized animal study.

SETTING

Medical school laboratory.

SUBJECTS

Twenty-seven Wistar rats (15 rats for microspectroscopic observations, 12 rats for measurements of neutrophil elastase activity and wet-to-dry ratio).

INTERVENTIONS

Thoracosternotomy was performed on male Wistar rats under continuous anesthesia and mechanical ventilation. Rats were divided into three groups (n = 5 each groups) on the basis of the reagent used: lipopolysaccharide group (100 microg/kg lipopolysaccharide intravenously), sivelestat group (10 mg/kg sivelestat; 100 microg/kg lipopolysaccharide intravenously), and control group (saline only, intravenously).

MEASUREMENTS AND MAIN RESULTS

We measured morphologic changes and hemodynamic variables, including tissue blood flow, erythrocyte velocity, erythrocyte count, thickness of interalveolar septa, and leukocyte adhesion in the pulmonary microcirculation, with a video-rate (33 msec/frame) dual-spot microspectroscopy system (DSMSS) and a laser-Doppler flowmeter. Blood-free wet-to-dry ratio and neutrophil elastase activity in bronchoalveolar lavage fluid, serum, and supernatant of lung homogenate were measured in another set of experiments (n = 4 for each group). Sixty minutes after lipopolysaccharide administration, severe thickening of the interalveolar septa was observed in the lipopolysaccharide but not the sivelestat group. In the lipopolysaccharide group, DSMSS measurements of erythrocyte velocity and hemoglobin oxygenation in single capillaries were decreased significantly (vs. control p < .05, vs. sivelestat p < .01), whereas tissue blood flow and erythrocyte velocity measurements from laser-Doppler flowmeter were increased significantly (vs. control p < .05, vs. sivelestat p < .01). The number of adherent leukocytes was increased significantly in the lipopolysaccharide group at 30, 45, and 60 mins after lipopolysaccharide administration (vs. control p < .01, vs. sivelestat p < .05). The number of adherent leukocytes did not increase in the sivelestat group. The wet-to-dry ratio was significantly higher in the lipopolysaccharide group than in control (p < .05) and sivelestat (p < .05) groups. Neutrophil elastase activities in the bronchoalveolar lavage fluid, serum, and lung tissue were all significantly lower in the sivelestat group than in the lipopolysaccharide group (p < .05).

CONCLUSIONS

Lipopolysaccharide induces leukocyte adhesion in the pulmonary microcirculation, resulting in decreased tissue hemoglobin oxygen and alveolar and interstitial edema. The selective neutrophil elastase inhibitor sivelestat reduces neutrophil elastase activity and attenuates acute changes in the pulmonary microcirculation.

Embolia gordurosa: uma revisão para a prática ortopédica atual

A embolia gordurosa (EG) é a oclusão de pequenos vasos por gotículas de gordura, geralmente originadas nas fraturas do fêmur, tíbia e bacia, e nas artroplastias do joelho e quadril. Normalmente não causa danos aos órgãos atingidos, a menos que seja maciça. Em poucos casos a EG evolui para a "síndrome da embolia gordurosa" (SEG) a qual afeta principalmente os pulmões e o cérebro, embora qualquer órgão ou estrutura do organismo possa ser afetada. A gordura embolizada é hidrolizada pela lipase, originando os ácidos graxos livres (AGL) que agem toxicamente sobre o endotélio capilar e que intensificam a ação das integrinas as quais acentuam a adesividade dos neutrófilos às células endoteliais, facilitando a ação das enzimas proteolíticas dos lisossomas desses neutrófilos sobre o endótelio. O resultado dessas reações é a ruptura da rede capilar seguida de hemorragia e edema nos órgãos afetados. A SEG apresenta desde insuficiência respiratória e alterações neurológicas variadas até convulsões e coma profundo. O diagnóstico da SEG é puramente clínico, não existindo nenhum exame laboratorial que o confirme. Dentre os exames de imagens, apenas a ressonância magnética cerebral demonstra claramente as áreas do edema perivascular e dos infartos. O tratamento da EG com inúmeras drogas não apresentou resultados positivos; no entanto, a medida mais requisitada para a SEG é a assistência ventilatória. A mortalidade é quase de 100% nas formas fulminantes; aproximadamente de 20% nas formas sub-agudas e não há mortalidade na forma sub-clínica. Para prevenir a SEG é fundamental evitar o choque e a hipóxia desde a cena do acidente, e proceder à fixação precoce das fraturas, o que diminui a incidência de SARA e a mortalidade pós-trauma.

The Impact of Intravenous Fat Emulsion Administration in Acute Lung Injury

The aim of this study was to evaluate the effect of parenteral nutrition containing medium- and long-chain triglycerides on the function of the respiratory system and to investigate mechanisms involved in this process. We studied 13 patients with acute respiratory distress syndrome (ARDS), 8 receiving lipid and 5 placebo, and 6 without ARDS, receiving lipid. Bronchoalveolar lavage (BAL) was performed before and 1 hour after administration of lipid or placebo. In patients with ARDS, lipid administration resulted in deterioration of oxygenation (Pa(O(2))/FI(O(2)): from 129 +/- 37 to 95 +/- 42), compliance of respiratory system (from 39.2 +/- 12 to 33.1 +/- 9.2 ml/cm H(2)O), and pulmonary vascular resistance (from 258 +/- 47 to 321 +/- 58 dyne x s x cm(-5)). In the BAL fluid of the same group, an increase in total protein and phospholipid concentrations, phospholipase activities, platelet-activating factor and neutrophils, as well as alterations in BAL lipid profile were observed. No significant changes were observed in the control or in the ARDS-Placebo groups. In conclusion, this study indicates that administration of medium- and long-chain triglycerides in patients with ARDS causes alterations in lung function and hemodynamics. Inflammatory cells, possibly activated by lipids, release phospholipase A(2) and platelet-activating factor, enhancing edema formation, inflammation, and surfactant alterations.

Proteases and lung injury

OBJECTIVE

Acute respiratory distress syndrome (ARDS) represents an inflammatory process that is initiated by diverse systemic and/or pulmonary insults, resulting in a clinical syndrome of severe respiratory distress and refractory hypoxemia. Neutrophils and their cytotoxic products, including oxidants and proteases, such as elastase, have been implicated as playing a key role in the pathophysiology of ARDS. This article reviews some of the physiologic actions of proteases, specifically elastase, the evidence for neutrophil elastase involvement in ARDS, and the potential therapeutic use of neutrophil elastase inhibitors in lung injury.

DATA SOURCE

A review of published literature (original articles and reviews) in English from 1965 to 2002.

CONCLUSION

Although the data support a key role for neutrophil elastase in the pathogenesis of ARDS, further study is needed to fully define the actions of neutrophil elastase, and how these actions affect host functions, before we can exploit this knowledge for therapeutic benefit.

The role of neutrophil elastase in acute lung injury

Beside its physiological function as a powerful host defense, neutrophil elastase is also known as one of the most destructive enzymes in the body. Current notion holds that neutrophil elastase is able to escape from regulation by multiple protease inhibitors at inflammatory sites. Once unregulated, this enzyme disturbs the function of the lung permeability barrier and induces the release of pro-inflammatory cytokines. These actions then cause symptoms that are typical in the pathophysiology of acute lung injury. In this article, we review recent progress in the understanding of the physiological activity of neutrophil elastase and its role in acute lung injury. Evidence in this review that supports the involvement of neutrophil elastase in the pathophysiology of acute lung injury includes: (1) neutrophil elastase levels are increased in both clinical and animal models of acute lung injury; (2) topical or systemic administration of neutrophil elastase produces typical symptoms of acute lung injury both in vitro and in vivo; and (3) inhibition of increased neutrophil elastase activity reduces symptoms of acute lung injury in animal models. A greater understanding of the role of this enzyme in the pathophysiology of acute lung injury will lead to better treatments for this complicated disease.