9-10-epoxy-12-octadecenoate and Pulmonary-Edema

We examined the mechanism of leukotoxin, 9,10-epoxy-12-octadecenoate (Lx)-induced lung injury in blood-free, physiological salt solution-perfused rat lungs under constant flow conditions. Mean pulmonary arterial (Ppa) and pulmonary capillary pressure (Pcap, estimated by the double-occlusion method), wet lung weight (WLW), pulmonary capillary filtration coefficient (Kfc), lung perfusate lactate dehydrogenase (LDH) activity, and nitrite levels were assessed. Bolus injection of Lx (200 microM) caused insidious and significant lung weight gain, which was not associated with remarkable elevation of Ppa or Pcap but was associated with an increase of perfusate LDH activity and nitrite levels. Lx (20 microM) elevated Kfc, indicating that Lx had affected pulmonary vascular permeability. Because Lx causes endothelium dependent pulmonary vasodilation, we studied the effect of NG-monomethyl-L-arginine (L-NMMA), NG-monomethyl-D-arginine (D-NMMA), superoxide dismutase (SOD), human oxyhemoglobin (oxyHb), and methylene blue (MB) on Lx-induced lung injury. L-NMMA, SOD, and oxyHb, but not MB or D-NMMA, protected the lungs against Lx (200 microM)-induced injury. Lx increased pulmonary vascular permeability and caused lung injury. Because both nitric oxide synthase inhibitors and SOD inhibited the Lx-induced lung injury, it is possible that peroxynitrite is involved in the mechanism whereby Lx causes lung injury.

Topics: Amino Acid Oxidoreductases; Animals; Arginine; Blood Vessels; Enzyme Activation; Exotoxins; L-Lactate Dehydrogenase; Linoleic Acids; Lung; Male; Nitric Oxide Synthase; Nitrites; omega-N-Methylarginine; Oxyhemoglobins; Perfusion; Pulmonary Edema; Rats; Rats, Sprague-Dawley; Superoxide Dismutase

We have observed that neutrophils biosynthesize linoleate epoxide, 9,10-epoxy-12-octadecenoate, and have named it leukotoxin because of its cytotoxic effect. In this experiment, the effect of leukotoxin on the lung was investigated. Acute effect of leukotoxin: Using Wistar rats, leukotoxin (100 mumol/kg) was injected intravenously for the leukotoxin group, and linoleate (100 mumol/kg) for the linoleate group. Physiological saline was injected as the control. Ten min after injection, rats were divided into 3 groups: (1) lungs were isolated, and lung wet weight, and dry weight were measured; (2) lung lavages were performed, and albumin concentration and activity of angiotensin converting enzyme (ACE) were measured; (3) morphological changes were studied by light and electron microscope. After administration of leukotoxin, lung wet weight/body weight ratios and dry weight/wet weight ratios were increased. Albumin concentration and ACE activity in lung lavages were also increased. Pulmonary edema was also confirmed by light microscopic findings. Alveolar epithelial cell damage and endothelium damage were also observed. Linoleate had no significant effect on these biochemical parameters and morphological findings. Subacute effect of leukotoxin: Twelve hr after administration of leukotoxin (50 mumol/kg) or linoleate (50 mumol/kg), the same studies were performed as in the acute experiments. Immediately after administration of leukotoxin, no significant effect was observed. However, 12 hr later similar changes were observed as in the acute experiments. Linoleate did not show any significant effect 12 hr after injection. These results indicate that leukotoxin biosynthesized by neutrophils might be closely related to the genesis of inflammatory edema.

Topics: Animals; Linoleic Acids; Lung; Neutrophils; Pulmonary Edema; Rats; Rats, Inbred Strains; Toxins, Biological

Pulmonary influxed neutrophils have been suggested to be involved in the development of hyperoxia-induced lung injury. We recently revealed that a highly toxic substance, 9,10-epoxy-12-octadecenoate, is biosynthesized by human neutrophils, thus it was named leukotoxin. Because hyperoxia-induced lung injury is a model of adult respiratory distress syndrome (ARDS), this study was designed to investigate whether or not leukotoxin is involved in the genesis of pulmonary oxygen toxicity and ARDS. After exposure to hyperoxia for 60 h, rats showed acute pulmonary edema, which was evidenced by increased lung weight, albumin concentrations, and angiotensin-converting enzyme (ACE) activities in lung lavages. These changes were correlated with an increased number of neutrophils. We detected leukotoxin in lung lavages of rats after exposure to hyperoxia for 60 h by high performance liquid chromatography and gas-chromatography/mass spectrometry. After intravenous injection of leukotoxin (100 mumol/kg) to rats, acute edematous lung injury occurred showing increases in lung weight, lung lavage albumin concentrations, and lung lavage ACE activities. In the lung lavages obtained from 5 patients with ARDS, significant increases in albumin concentrations and ACE activities were observed compared with those from subjects without pulmonary disease. Moreover, considerable amounts of leukotoxin, 38.5 +/- 21.9 nmol/lung lavage, were observed in the lavages from patients with ARDS. These findings suggest that leukotoxin plays an important role in the genesis of acute edematous lung damage in pulmonary oxygen toxicity, and that leukotoxin also links with the development of lung injury observed in patients with ARDS.

Topics: Animals; Bronchoalveolar Lavage Fluid; Disease Models, Animal; Exotoxins; Female; Humans; Leukocyte Count; Linoleic Acids; Neutrophils; Oxygen; Pulmonary Edema; Rats; Rats, Inbred Strains; Respiratory Distress Syndrome