Damage to surfactant-specific protein in acute respiratory distress syndrome
CS Baker, TW Evans, BJ Randle, PL Haslam - The Lancet, 1999 - thelancet.com
CS Baker, TW Evans, BJ Randle, PL Haslam
The Lancet, 1999•thelancet.comBackground Acute respiratory distress syndrome (ARDS) develops in association with many
serious medical disorders. Mortality is at least 40%, and there is no specific therapy. A
massive influx of activated neutrophils, which damage pulmonary vascular endothelium and
alveolar epithelium, leads to alveolar oedema and pulmonary surfactant dysfunction. In-vitro
studies show that neutrophil elastase can cleave surfactant-specific proteins and impair
surfactant function. If this happens in vivo in ARDS, the response to surfactant therapy will be …
serious medical disorders. Mortality is at least 40%, and there is no specific therapy. A
massive influx of activated neutrophils, which damage pulmonary vascular endothelium and
alveolar epithelium, leads to alveolar oedema and pulmonary surfactant dysfunction. In-vitro
studies show that neutrophil elastase can cleave surfactant-specific proteins and impair
surfactant function. If this happens in vivo in ARDS, the response to surfactant therapy will be …
Background
Acute respiratory distress syndrome (ARDS) develops in association with many serious medical disorders. Mortality is at least 40%, and there is no specific therapy. A massive influx of activated neutrophils, which damage pulmonary vascular endothelium and alveolar epithelium, leads to alveolar oedema and pulmonary surfactant dysfunction. In-vitro studies show that neutrophil elastase can cleave surfactant-specific proteins and impair surfactant function. If this happens in vivo in ARDS, the response to surfactant therapy will be limited.
Methods
Samples of pulmonary surfactant were obtained from the lungs of 18 patients with ARDS and six healthy controls by bronchoalveolar lavage. We separated proteins in these samples according to molecular weight by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). We then used western blotting with monoclonal antibody E8 to detect the major surfactant-specific protein A (SP-A).
Findings
By contrast with controls, 14 of 18 patients had evidence of in-vivo damage to SP-A that resembled damage caused to SP-A when it is cleaved by neutrophil elastase. Controls showed a single band of normal dimers at 66 kDa, whereas 14 of 18 patients showed multiple bands at 66 kDa, 55 kDA, and 30–36 kDa, and six showed additional bands at 36–40 kDa.
Interpretation
Direct damage to surfactant-specific proteins occurs in lungs of patients with ARDS, probably by proteolysis. Trials of protein-containing therapeutic surfactant are in progress in ARDS, and our results indicate that the frequent failure to maintain response may result from continuing damage to surfactant by products of activated neutrophils. A combination of surfactant and antiprotease therapy may improve therapeutic prospects.
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