Granulocytes mediate acute edematous lung injury in rabbits and in isolated rabbit lungs perfused with phorbol myristate acetate: role of oxygen radicals

Abstract

Acute edematous lung injury is associated with a marked increase in the number of granulocytes in the alveoli and microvasculature of the lung. Phorbol myristate acetate (PMA) causes granulocytes to adhere, aggregate, and release oxygen radicals and granular enzymes. We found that intravenously injected PMA caused a protein-rich edema in lungs of control rabbits but not in granulocytopenic rabbits pretreated with nitrogen mustard. Specifically, control rabbits treated with PMA had higher lung weight to body weight ratios (6.4 +/- 1.0 X 10(-3)) and lung lavage albumin concentrations (190 +/- 44 mg/dl) than granulocytopenic rabbits pretreated with nitrogen mustard and then given PMA (4.74 +/- 0.23 X 10(-3) and 9.9 +/- 3.8 mg/dl, respectively). To further clarify the role of granulocytes in the production of edema, additional experiments were conducted in an isolated perfused rabbit lung. Addition of purified granulocytes and PMA to the balanced salt perfusate caused lung edema, whereas neither granulocytes nor PMA alone caused edema. Specifically, increases in lung weights (42 +/- 9.2 g) and albumin concentrations (1,182 +/- mg/dl) in lung lavages from isolated lungs exposed to granulocytes and PMA were greater than increases in lung weights or albumin concentrations in lung lavages from isolated lungs exposed to granulocytes alone (2.0 +/- 0.4 g and 15 +/- 0.6 mg/dl), or to PMA alone (6.0 +/- 0.6 g and 81 +/- 34 mg/dl). To determine the contribution of oxygen radicals to the pathogenesis of the edema, chronic granulomatous disease granulocytes, which are deficient in oxygen radical production, were added to the isolated lung perfusate. Chronic granulomatous disease granulocytes and PMA did not cause edema in isolated lungs (delta lung weight 1.0 +/- 0.2 g and lavage albumin 12 +/- 5.0 mg/dl) whereas granulocytes from normal human subjects and PMA did (delta lung weight 43 +/- 5.2 g and lavage albumin 1,120 +/- 54 mg/dl). These data suggest that oxygen radicals released from stimulated granulocytes contribute to the pathogenesis of acute edematous lung injury.