Plasminogen activator and thromboplastin activity from sheep alveolar macrophages

Spontaneous and lipopolysaccharide-induced expression of procoagulant activity by equine lung macrophages in comparison with blood monocytes and blood neutrophils

The procoagulant activity (PCA) associated with equine bronchoalveolar lavage cells was determined and compared with that expressed by peripheral blood mononuclear cells and neutrophils. Lung cell preparations from horses affected with chronic pulmonary disease were included in all experiments and there was no difference in the qualitative type of response compared with lung cells which were obtained from healthy horses. Significant amounts of PCA were expressed by cells freshly procured from bronchoalveolar lavages of healthy and diseased horses. When adherent lung cells were kept in culture for some time, cell-associated PCA slightly decreased within 4 h, reached its lowest point after approximately 24 h and rose again during the second week of culture. In contrast, freshly isolated blood mononuclear cells or neutrophils expressed little PCA. Following culture for 24 h, mononuclear cells began to express increased PCA levels. Both cultivated lung cells (comprised mainly on alveolar macrophages) and blood mononuclear cells responded to LPS by dramatically increased PCA expression, whereas neutrophils showed a small augmentation of PCA on LPS stimulation. Fresh mononuclear cells and cultivated lung cells differed in their PCA response to LPS in several respects. Blood mononuclear cells were more sensitive to LPS than lung macrophages and responded to a 100-fold lower LPS concentration than the latter. Mononuclear cell-associated PCA peaked 4 h after stimulation whereas that of cultured macrophages continued to increase up to 24 h after stimulation. Lung macrophages cultured in adherence responded to LPS stimulation with a much higher PCA increase than macrophages cultured in suspension, in teflon containers. However, the culture vessel did not influence the PCA expressed by unstimulated cells. PCA expression depended to a large extent on transcription and translation, as evidenced by a 60-85% reduction of PCA in cycloheximide- or actinomycin D-treated, LPS-stimulated lung macrophages. PCA was largely cell-associated; only a small proportion of cell-associated PCA was shed into the medium. The PCA associated with mononuclear cells and with lung macrophages was tissue factor because of its dependence on clotting factor VII and its independence from clotting factor VIII. The expression of PCA by freshly isolated cells, the lower sensitivity to LPS, and the loss of PCA in the first 24 h of cultivation are indicative of in vivo activation of lung macrophages.

Procoagulant activity in bronchoalveolar lavage of severely traumatized patients--relation to the development of acute respiratory distress

In a prospective study in severely traumatized patients, procoagulant activity (PCA) was determined in bronchoalveolar lavage fluids (BAL). Bronchoscopy with lavage was serially performed during the first 15 days after injury (in total 148 samples of 25 patients). PCA was measured as recalcification times in the absence or presence of excess phosphatidylethanolamine and translated into procoagulant unit equivalents using standard thromboplastin. The data were correlated to the extent of respiratory failure in the injured patients and were compared to PCA in 29 lavage samples obtained from 10 healthy control subjects. A several-fold increase in BAL PCA was noted in all trauma victims, evident already within the first 24 h after injury. A progressive rise in PCA occurred from the 4th posttraumatic day and was highly significantly more pronounced in patients developing serious respiratory failure than in those with only mild pulmonary dysfunction. Significant correlations were noted between PCA increase and alveolar protein-leakage, granulocyte-influx and surfactant alterations, however with correlation coefficients not surpassing 0.55. We conclude that a marked increase in procoagulant activity occurs in severely injured patients, which may favour alveolar fibrin deposition and is related to the development of acute respiratory failure.

Evidence that exposure to fibrinogen or to antibodies directed against Mac-1 (CD11b/CD18; CR3) modulates human monocyte effector functions

We have recently shown that the treatment of fibrinogen-coated monocytes (MO) with anti-fibrinogen as well as the exposure of MO to surface-bound fibrinogen (Fg) or to albumin haptenized with the Fg C-gamma-terminal pentadecapeptide, induces on oxidative burst. Using chemiluminescence (CL) for indicating an oxidative burst, and the ingestion of IgG-coated erythrocytes as a test of phagocytosis, we have now studied the impact of Fg on MO effector functions. MO that had been either pretreated with Fg and washed, or that were exposed to surface-adsorbed Fg, exhibited impaired Fc receptor-mediated phagocytosis. A similar impairment was observed when MO were pretreated with activating agents such as phorbol myristate acetate, n-formyl-methionyl-leucyl-phenylalanine (fMLP) or the calcium ionophore A23187. Moreover, following exposure to Fg or IgG, MO exhibited a reduced oxidative burst upon stimulation with a variety of agents. Similarly, MO pretreated or coincubated with anti-Mac-1 exhibited a reduced oxidative burst upon stimulation. Our results raise the possibility that inflammatory mononuclear phagocytes experience a functional modulation upon encountering fibrin by interacting with specific receptors for fibrin(ogen). This type of modulation is analogous to effects induced by the triggering of Fc gamma receptors. MO showed a decreased oxidative burst when either pretreated or coincubated with anti-Mac-1 antibodies, whereas antibodies directed against other MO surface constituents had no, or a weak effect only. This is compatible with the suggestion that Mac-1 acts as a fibrin (ogen) receptor.

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.

In vitro fibrinolytic activity and viability of rat alveolar macrophages treated with inflammation generating mineral dusts

Rat alvolar macrophages demonstrated plasminogen dependent fibrinolysis in vitro which was inhibited to varying degrees by the addition of zymosan, the non-toxic particulate titanium dioxide, and the toxic dusts quartz and chrysotile asbestos. Assessment of viability suggested that the inhibition produced by zymosan and titanium dioxide could be accounted for by cytotoxic effects but in the case of quartz and chrysotile asbestos there was evidence that stimulation of fibrinolysis preceded cell death. Zymosan, which caused no observeable enhancement of alveolar macrophage fibrinolysis was found to markedly stimulate peritoneal macrophage fibrinolysis. The choice of assays of cell function to assess the action of toxic dusts are discussed.