Local abnormalities of coagulation and fibrinolysis and alveolar fibrin deposition in sheep with oleic acid-induced lung injury.

Extravascular, primarily intra-alveolar, fibrin deposition is a histologic hallmark of acute lung injury in humans and experimental animals, but the mechanisms leading to this finding are poorly understood. To determine whether local abnormalities in the fibrinolytic-procoagulant balance contribute to alveolar fibrin deposition in acute lung injury, we studied bronchoalveolar lavage (BAL) fluids of anesthetized sheep that received intravenous oleic acid. Prominent alveolar fibrin deposition was observed within 2 h after oleic acid-induced lung injury. Procoagulant and fibrinolytic activities were determined in BAL samples of anesthetized, mechanically ventilated sheep before and 2 h after intravenous oleic acid or saline. BAL procoagulant activity was found to be due mainly to tissue factor associated with Factor VII. In baseline BAL samples, we found relatively low levels of procoagulant activity and relatively high levels of fibrinolytic activity. After induction of oleic acid-induced lung injury, the procoagulant activity of BAL was markedly increased, whereas fibrinolytic activity was either depressed or undetectable. Antiplasmin activity was detectable in BAL of sheep after oleic acid-induced lung injury, which contributed at least in part to the depressed fibrinolytic activity observed. These perturbations occurred with the appearance of extensive alveolar fibrin deposition. In control sheep, BAL fibrinolytic activity was decreased, and antiplasmin activity increased modestly after 2 h of mechanical ventilation, but procoagulant activity was unchanged and alveolar fibrin was not observed. Procoagulant activity in lung lymph and plasma after lung injury did not differ from baseline values, and fibrinolytic activity was undetectable in lymph or plasma samples. These data indicate that increased procoagulant activity and concurrent disruption of the balance of coagulation and fibrinolysis establish local conditions that promote acute fibrin deposition in the alveoli of mechanically ventilated, oleic acid-injured sheep.

Bronchoalveolar lavage procoagulant activity in bleomycin-induced lung injury in marmosets. Characterization and relationship to fibrin deposition and fibrosis.

Although pulmonary fibrin deposition and coagulation abnormalities have been observed in acute lung injury in humans, their role in the pathogenesis of pulmonary disorders is unclear. In order to gain further insights into the role of the coagulation in lung injury, we examined the relationship between procoagulant activity in bronchoalveolar lavage (BAL) fluids and the evolution of bleomycin-induced lung injury in marmosets. The BAL procoagulant activity was increased at 1, 2, and 4 wk after bleomycin challenge compared with that in control subjects, and it was capable of shortening the recalcification times of plasmas deficient in factor VII and factor VIII but not in factor X. This profile suggested the presence in BAL of an activator of factor X. Activation of purified human factor X by BAL was demonstrated by measuring the amidolytic activity of the generated factor Xa on its N-benzoyl-L-isoleucyl L-glutamyl-glycyl-L-argenine-p-nitroanilide substrate. Factor X activating activity was increased in BAL at 2 wk after bleomycin challenge. Cleavage of 125I-labeled human factor X by BAL from bleomycin-challenged marmosets yielded a 55,500 Mr product that comigrated with factor Xa, the appearance of which correlated strongly with amidolytic evidence of factor Xa activity. Electron microscopy of the lungs of animals from all groups revealed pulmonary fibrin deposition at 2 wk after bleomycin challenge, at the time of increased BAL procoagulant and factor X activating activity. The BAL procoagulant activity was completely sedimentable by ultracentrifugation and was inhibited by concanavalin A and phospholipase C. Activation of purified factor X by BAL was inhibited by monospecific polyclonal goat and rabbit antibodies to human factor VII as well as antibody to bovine tissue factor, demonstrating that factor X activating activity in BAL was attributable to tissue factor associated with material similar to factors VII or VIIa. We conclude that procoagulant activity in BAL increases after bleomycin challenge in marmosets and is attributable to activation of factor X by tissue factor associated with factors VII or VIIa-like material. Increased BAL procoagulant activity is temporally associated with pulmonary fibrin deposition and pulmonary fibrosis during bleomycin-induced pulmonary injury in the marmoset.