Inhibition of neuronal nitric oxide synthase in ovine model of acute lung injury
ABSTRACT Acute respiratory distress syndrome/acute lung injury is a serious complication of burn patients with concomitant smoke inhalation injury. Nitric oxide has been shown to play a major role in pulmonary dysfunction from thermal damage. In this study, we have tested the hypothesis that inhibition of neuronal nitric oxide synthase could ameliorate the severity of acute lung injury using our well-established ovine model of cutaneous burn and smoke inhalation.
Prospective, randomized, controlled, experimental animals study.
Investigational intensive care unit at university hospital.
Adult female sheep.
Female sheep (n = 16) were surgically prepared for the study. Seven days after surgery, all sheep were randomly allocated into three study groups: sham (noninjured, nontreated, n = 6); control (injured, treated with saline, n = 6); and neuronal nitric oxide synthase (injured, treated with specific neuronal nitric oxide synthase inhibitor, ZK 234238 (n = 4). Control and neuronal nitric oxide synthase groups were given a cutaneous burn (40% of total body surface, third degree) and insufflated with cotton smoke (48 breaths, <40 degrees C) under halothane anesthesia. Animals in sham group received fake injury also under halothane anesthesia. After injury or fake injury procedure, all sheep were placed on ventilators and resuscitated with lactated Ringer's solution. Neuronal nitric oxide synthase group was administered with continuous infusion of ZK 234238 started 1 hr postinjury with a dose of 100 microg/kg/hr. Sham and control groups received same amount of saline.
Cardiopulmonary hemodynamics monitored during the 24-hr experimental time period was stable in the sham group. Control sheep developed multiple signs of acute lung injury. This pathophysiology included decreased pulmonary gas exchange and lung compliance, increased pulmonary edema, and inflammatory indices, such as interleukin-8. Treatment of injured sheep with neuronal nitric oxide synthase inhibitor attenuated all the observed pulmonary pathophysiology.
The results provide definitive evidence that inhibition of neuronal nitric oxide synthase-derived excessive nitric oxide may be a novel and beneficial treatment strategy for pulmonary pathology in burn victims with smoke inhalation injury.
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ABSTRACT: Pulmonary coagulopathy has become an important therapeutic target in adult respiratory distress syndrome (ARDS). We hypothesized that combining intravenous recombinant human antithrombin (rhAT), nebulized heparin, and nebulized tissue plasminogen activator (TPA) more effectively improves pulmonary gas exchange compared with a single rhAT infusion, while maintaining the anti-inflammatory properties of rhAT in ARDS. Therefore, the present prospective, randomized experiment was conducted using an established ovine model. Following burn and smoke inhalation injury (40% of total body surface area, third-degree flame burn, and 4 × 12 breaths of cold cotton smoke), 18 chronically instrumented sheep were randomly assigned to receive intravenous saline plus saline nebulization (control), intravenous rhAT (6 IU/kg/h) started 1 hour after injury plus saline nebulization (AT i.v.) or intravenous rhAT combined with nebulized heparin (10,000 IU every 4 hours, started 2 hours after injury), and nebulized TPA (2 mg every 4 hours, started 4 hours after injury) (triple therapy, n = 6 each). All animals were mechanically ventilated and fluid resuscitated according to standard protocols during the 48-hour study period. Both treatment approaches attenuated ARDS compared with control animals. Notably, triple therapy was associated with an improved PaO2/FiO2 ratio (p = 0.007), attenuated pulmonary obstruction (p = 0.02) and shunting (p = 0.025), as well as reduced ventilatory pressures (p < 0.05 each) versus AT i.v. at 48 hours. However, the anti-inflammatory effects of sole AT i.v., namely, the inhibition of neutrophil activation (neutrophil count in the lymph and pulmonary polymorphonuclear cells, p < 0.05 vs. control each), pulmonary transvascular fluid flux (lymph flow, p = 0.004 vs. control), and systemic vascular leakage (cumulative net fluid balance, p < 0.001 vs. control), were abolished in the triple therapy group. Combining intravenous rhAT with nebulized heparin and nebulized TPA more effectively restores pulmonary gas exchange, but the anti-inflammatory effects of sole rhAT are abolished with the triple therapy. Interferences between the different anticoagulants may represent a potential explanation for these findings.01/2014; 76(1):126-33. DOI:10.1097/TA.0b013e3182ab0785
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ABSTRACT: To test the hypothesis that restoration of antithrombin plasma concentrations attenuates vascular leakage by inhibiting neutrophil activation through syndecan-4 receptor inhibition in an established ovine model of acute lung injury. Randomized controlled laboratory experiment. University animal research facility. Eighteen chronically instrumented sheep. Following combined burn and smoke inhalation injury (40% of total body surface area, third-degree flame burn; 4 × 12 breaths of cold cotton smoke), chronically instrumented sheep were randomly assigned to receive an IV infusion of 6 IU/kg/hr recombinant human antithrombin III or normal saline (n = 6 each) during the 48-hour study period. In addition, six sham animals (not injured, continuous infusion of vehicle) were used to obtain reference values for histological and immunohistochemical analyses. Compared to control animals, recombinant human antithrombin III reduced the number of neutrophils per hour in the pulmonary lymph (p < 0.01 at 24 and 48 hr), alveolar neutrophil infiltration (p = 0.04), and pulmonary myeloperoxidase activity (p = 0.026). Flow cytometric analysis revealed a significant reduction of syndecan-4-positive neutrophils (p = 0.002 vs control at 24 hr). Treatment with recombinant human antithrombin III resulted in a reduction of pulmonary nitrosative stress (p = 0.002), airway obstruction (bronchi: p = 0.001, bronchioli: p = 0.013), parenchymal edema (p = 0.044), and lung bloodless wet-to-dry-weight ratio (p = 0.015). Clinically, recombinant human antithrombin III attenuated the increased pulmonary transvascular fluid flux (12-48 hr: p ≤ 0.001 vs control each) and the deteriorated pulmonary gas exchange (12-48 hr: p < 0.05 vs control each) without increasing the risk of bleeding. The present study provides evidence for the interaction between antithrombin and neutrophils in vivo, its pathophysiological role in vascular leakage, and the therapeutic potential of recombinant human antithrombin III in a large animal model of acute lung injury.Critical care medicine 10/2013; 41(12). DOI:10.1097/CCM.0b013e318298ad3a · 6.15 Impact Factor
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ABSTRACT: Biological soil crusts occur extensively in semi-arid regions. In the western part of Niger, they are associated with various types of physical soil crusts in fallows and in the “tiger bush ecosystem” (a landscape with a typical banded pattern consisting of densely vegetated bands of small trees and shrubs alternating with bare soil bands). Despite their widespread occurrence, not much research has been done regarding their role on runoff generation in the Sahelian environment. The present study aims at: (i) highlighting the relative contribution of biological soil crusts in infiltration and runoff on crusted soil in respect with other soil factors; (ii) assessing the impact of underlying physical crusts associated with a wide range of microbial cover; and (iii) gathering the data required for an evaluation of the potential of microbial cover in water redistribution in an arid environment and for modelling purposes. The study was based on runoff measurements performed in situ at the level of ten plots, 1m2 each, under two simulated rainfalls. Those experiments were coupled with the visual characterization and image analysis of soil surface conditions as well as micromorphological examinations, using a light microscope, both on the field and at the laboratory.Visual estimation of crust cover was found consistent with the estimation based on the image analysis. Biological soil crusts capped the summit of pre-existing physical soil crusts, i.e. structural crusts, formed in situ by the impact of water drop and erosion crusts, resulting from water or wind erosion of structural crusts. The percentage of microbial cover in the 1-m2 plots range from 39 to 80% (55% in average) on structural crusts compared to 4 to 29% (17% in average) on erosion crusts. Runoff coefficient varied with both the level of microbial cover and the type of physical soil crust. Higher runoff coefficients were found where biological soil crusts had developed on erosion crusts as compared to structural crusts. Runoff coefficients recorded from erosion crusts increased with the level of microbial cover while negative correlations were found on structural crusts. They show that the clogging effect of microbial cover for the plasmic layer of erosion crusts is higher than that of the sand layer of structural crusts. Separating biological soil crusts according to the types of the underlying physical crusts explain, therefore, the contradictory findings related to their role on infiltration and runoff generation. Those data will help to evaluate the potential role of biological soil crusts in the modelling of water redistribution in the arid environment of the western part of Niger.Geoderma 11/2011; 167:22-29. DOI:10.1016/j.geoderma.2011.09.013 · 2.51 Impact Factor