Antithrombin Attenuates Vascular Leakage via Inhibiting Neutrophil Activation in Acute Lung Injury

Abstract

Objective 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. Design Randomized controlled laboratory experiment. Setting University animal research facility. Subjects Eighteen chronically instrumented sheep. Interventions 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. Measurements and Main Results 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. Conclusions 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.

Nebulized anticoagulants in lung injury in critically ill patients—an updated systematic review of preclinical and clinical studies

“…Details regarding article selection are presented in Figure 1. Compared to our previous review published in 2012, the updated search found six additional articles reporting on preclinical studies (36,37,(42)(43)(44)(45), and eight new articles reporting on human trials of nebulized anticoagulants (50,51,(53)(54)(55)(56)60,61).…”

“…The reasons for not finding an inhibitory effect on inflammation in all studies remain unexplained. Interestingly, one animal study combining nebulized heparin with AT found antiinflammatory effects, while 'triple therapy' by adding TPA abolished the inhibitory effect on inflammation (42). Hence, anticoagulants may induce anti-inflammatory effects due to pathways crosslinking coagulation and inflammation in models of lung injury; however, combination of various anticoagulants and dosages are of importance in influencing these mechanisms.…”

“…An effect of nebulized heparin on systemic coagulation was reported in one study using a lung injury model (49), but not in studies using pulmonary infection models (36,49) or inhalation trauma models (38)(39)(40)(41)(42). None of these studies, however, showed systemic bleeding.…”

“…Nebulized heparin also affected various physiologic parameters and other outcomes, in particular during pulmonary infection (34,35), and inhalation trauma (38)(39)(40)(41)(42)). An effect of nebulized heparin on systemic coagulation was reported in one study using a lung injury model (49), but not in studies using pulmonary infection models (36,49) or inhalation trauma models (38)(39)(40)(41)(42).…”

“…Combining nebulized heparin with intravenously administered AT markedly decreased pulmonary inflammation and improved physiological parameters in a study of inhalation trauma (41), while combining nebulized heparin with intravenously administered lisofylline improved physiological parameters, but inflammation in a study using a similar model (39). Combining nebulized heparin with nebulized tissue plasminogen activator (TPA) and intravenously administered AT did not affect inflammation, but also significantly improved physiological parameters in a study of inhalation trauma (42). None of the studies of combined therapies showed more systemic bleeding or blood stream infections.…”