Response In Acute Lung Injury Research Articles

Nitric Oxide Causes Apoptosis in Pulmonary Vascular Smooth Muscle Cells

Nitric oxide (NO), a product of certain cytokine-activated cells, affects rates of apoptosis, a mechanism of programmed cell death. We asked whether NO affected rates of apoptosis in pulmonary vascular cells. Using rat pulmonary artery smooth muscle cells, we studied direct effects of the NO donorSG-nitroso-acetyl-d,l-penicillamine (SNAP) and the effects of NO endogenously synthesized in response to bacterial lipopolysaccharide (LPS) and inflammatory cytokines interleukin-1β, interferon-γ, and tumor necrosis factor-α (a combination called cytomix for convenience). We determined apoptosis on the basis of light microscopy and the bromodeoxyuridine terminal deoxynucleotidyl transferase reaction (BrdUTdT). Both SNAP- and cytomix-induced synthesis of NO resulted in histologic evidence of apoptosis based upon fluorescence microscopy using propidium iodide. SNAP (10−5M) increased BrdUTdT-positive cells from 17.5 to 78.4% compared with basal medium alone, with the maximal response occurring at 15 h or exposure. Exposing cells to LPS and cytokines induced NO production (from 0.1 ± 0.1 to 24.6 ± 0.5 μM,P< 0.05) caused cytological changes consistent with apoptosis and led to an increase of increased BrdUTdT-positive cells from 11 to 41% at 12 h compared with basal medium alone. The competitive NO synthase inhibitorNG-monomethyl-l-arginine inhibited both NO synthesis and NO apoptosis, returning the proportion of BrdUTdT-positive cells (6%) to levels below control.l-Arginine (0.5 mM) restored percentages to those increase in response to endogenously synthesized NO, and NO is a potential mechanism of acute lung injury in response to inflammatory cytokines.

Lung injury following exposure of rats to relatively high mass concentrations of nitrogen dioxide

Human inhalation exposures to relatively high mass concentrations of the oxidant gas nitrogen dioxide (NO 2) can result in a variety of pulmonary disorders, including life-threatening pulmonary edema, pneumonia, and bronchiolitis obliterans. Inasmuch as most experimental studies to date have examined NO 2-induced lung injury following exposures to near ambient or supra-ambient concentrations of NO 2, e.g., ≤ 50 ppm, little detailed information about the pulmonary injurious responses following the acute inhalation of higher NO 2 concentrations that are more commensurate with some actual human exposure conditions is currently available. Described in this report are the results from a series of investigations in which various aspects of the inhalation toxicity of high concentrations of NO 2 have been examined in laboratory rats. In the first component of our study, we characterized the kinetic course of development of lung injury following acute exposures to high concentrations of NO 2 delivered over varying durations, and we assessed the relative importance of NO 2 exposure concentration versus exposure time in producing lung injury. For a given exposure duration, the resulting severity of lung injury was found to generally scale proportionately with inhaled mass concentration, whereas for a given concentration of inhaled NO 2, the magnitude of resulting injury was not directly proportional to exposure duration. Moreover, evidence was obtained that indicated exposure concentration is more important than exposure time when high concentrations of NO 2 are inhaled. In a second component of our investigation, we assessed the pulmonary injurious response that occurs when NO 2 is inhaled during very brief, “high burst” exposures to very high concentrations of NO 2. Such exposures resulted in significant lung injury, with the magnitude of such injury being directly proportional to exposure concentration. Comparisons of results obtained from this and the first component studies additionally revealed that brief exposures to the very high concentrations of NO 2 are more hazardous than longer duration exposures to lower concentrations. In a third study series, we examined pre-exposure, exposure, and post-exposure modifiers of NO 2-induced lung injury, including dietary taurine, minute ventilation, and post-exposure exercise. Results from these studies indicated: (i) dietary taurine does not protect the rat lung against high concentration NO 2 exposure, (ii) the severity of acute lung injury in response to NO 2 inhalation is increased by an increase in minute ventilation during exposure, and (iii) the performance of exercise after NO 2 exposure can significantly enhance the injurious response to NO 2. In a final, more mechanistic study component in which we investigated the acute hyperpermeability response to high NO 2 and the recruitment of inflammatory cells into the alveoli, evidence was obtained to suggest that no important relationship exists between the hyperpermeability response to NO 2 and elevations of polymorphonuclear leukocytes and alveolar macrophages in the alveoli.

Changes of Pulmonary Glucocorticoid Receptor and Phospholipase A2in Sheep with Acute Lung Injury after High Dose Endotoxin Infusion

In a sheep model of acute lung injury induced by an Escherichia coli endotoxin (5 micrograms/kg) with chronic lung lymph fistula (n = 15), we measured the changes in glucocorticoid receptor (GCR) binding capacity in lung tissue by means of radioligand binding assay. The content of cortisol and the activity of phospholipase A2 (PLA2) were also measured. The results showed that the maximal binding capacity (Bmax) of GCR in lung cytoplasma decreased continuously 2 h (113 +/- 3 versus 66 +/- 2 fmol/mg protein, p < 0.01), 4 h (105 +/- 6 versus 52 +/- 3 fmol/mg protein, p < 0.01), and 6 h (105 +/- 5 versus 37 +/- 2 fmol/mg protein, p < 0.01) after endotoxin infusion. Its affinity decreased markedly (p < 0.05) at 6 h after the infusion. The contents of cortisol in plasma elevated at 0.5 h and remained at a high level until 4 h after the infusion. PLA2 activity rose from 97 +/- 25 to 188 +/- 12 U (p < 0.05), 99 +/- 13 to 285 +/- 25 U (p < 0.01), and 106 +/- 14 to 354 +/- 32 U (p < 0.01) at 2, 4, and 6 h after endotoxin infusion, respectively. There was a negative correlation between the Bmax of GCR and PLA2 activity (r = -0.87, p < 0.01). The findings indicate that there was a secondary GCR abnormality and a higher PLA2 activity during endotoxin-induced lung injury. The glucocorticoid hypofunction caused by reduced GCR binding capacity may accelerate the pathologic response of acute lung injury.(ABSTRACT TRUNCATED AT 250 WORDS)