Research

Recombinant human activated protein C attenuates endotoxin-induced lung injury in awake sheep

Kristine Waerhaug¹ , Vladimir N Kuklin¹ , Mikhail Y Kirov^1,2 , Mikhail A Sovershaev³ , Bodil Langbakk⁴ , Ole C Ingebretsen⁵ , Kirsti Ytrehus⁶ and Lars J Bjertnaes¹

¹Department of Anesthesiology, Institute of Clinical Medicine, Faculty of Medicine, University of Tromsø, Norway

²Department of Anesthesiology, Northern State Medical University, Arkhangelsk, Russian Federation

³Department of Biochemistry, Institute of Medical Biology, Faculty of Medicine, University of Tromsø, Norway

⁴Department of Medical Biochemistry, University Hospital of North Norway, Tromsø, Norway

⁵Department of Medical Biochemistry, Institute of Medical Biology, Faculty of Medicine, University of Tromsø, Norway

⁶Department of Medical Physiology, Institute of Medical Biology, Faculty of Medicine, University of Tromsø, Norway

author email corresponding author email

Critical Care 2008, 12:R104doi:10.1186/cc6985

Published:	15 August 2008

See related commentary by Rehberg et al., http://ccforum.com/content/12/5/179

Abstract

Introduction

Acute lung injury often complicates severe sepsis. In Gram-negative sepsis, bacterial endotoxin activates both coagulation and inflammation. Enhanced lung vascular pressures and permeability, increased extravascular lung water content and deteriorated gas exchange characterize ovine endotoxin-induced lung injury, a frequently used model of acute lung injury. Recombinant human activated protein C (rhAPC), with its anticoagulant, anti-inflammatory, fibrinolytic and antiapoptotic effects, reportedly reduces the respirator-dependent days and the mortality of patients with severe sepsis. We speculate whether rhAPC antagonizes endotoxin-induced lung injury in sheep.

Methods

Two groups of sheep were exposed to Escherichia coli endotoxin (lipopolysaccharide) 15 ng/kg/minute intravenously from 0 to 24 hours; one group received only lipopolysaccharide throughout (n = 8), and the other group received lipopolysaccharide in combination with rhAPC 24 μg/kg/hour from 4 to 24 hours (n = 9). In addition, one group received rhAPC as above as the only intervention (n = 4), and four sham-operated sheep were used for determination of the α and ε isoforms of protein kinase C in pulmonary tissue. Data were assessed by one-way analysis of variance for repeated measurements. Biochemical data were analyzed using Student's t test, or using the Mann–Whitney U test when appropriate.

Results

Infusion of endotoxin caused lung injury, manifested by increments in pulmonary artery pressure, in pulmonary micro-occlusion pressure, in pulmonary vascular downstream resistance, in pulmonary vascular permeability index, in extravascular lung water index and in deterioration of oxygenation that were all attenuated by infusion of rhAPC. Endotoxemia led to changes in inflammation and coagulation, including pulmonary neutrophil accumulation paralleled by increased TNFα and decreased protein C and fibrinogen in animal plasma, which all improved following infusion of rhAPC. Moreover, rhAPC prevented the translocation of protein kinase C α and ε isoforms from the cytosolic fraction of lung tissue extracts.

Conclusion

In awake sheep, rhAPC alleviates endotoxin-induced lung injury – as characterized by improvements of oxygenation, coagulation and inflammation, as well as by reversal of pulmonary hemodynamic and volumetric changes.