The role of phospholipase A2 (PLA2) in acute lung leak induced by intestinal ischemia was investigated in association with neutrophilic respiratory burst. To induce lung leak, we generated intestinal ischemia for 60 min prior to the 120 min reperfusion by clamping superior mesenteric artery in Sprague-Dawley rats. Acute lung leak was confirmed by the increased lung leak index and protein content in bronchoalveolar fluid. These changes were inhibited by mepacrine, the non-specific PLA2 inhibitor. The lung myeloperoxidase (MPO) activity denoting the pulmonary recruitment of neutrophils was increased by intestinal I/R, but decreased by mepacrine. Simultaneously, the number of leukocytes in bronchoalveolar fluid was increased by intestinal ischemia/reperfusion (I/R) and decreased by mepacrine. Gamma glutamyl transferase activity, an index of oxidative stress in the lung, was increased after intestinal I/R but decreased by mepacrine, which implicates that PLA2 increases oxidative stresscaused by intestinal I/R. The PLA2 activity was increased after intestinal I/R not only in the intestine but also in the lung. These changes were diminished by mepacrine. In the cytochemical electron microscopy to detect hydrogen peroxide, intestinal I/R increased the generation of the hydrogen peroxide in the lung as well as in the intestine. Expression of interleukin-1 (IL-1) in the lung was investigated through RT-PCR. The expression of IL-1 after intestinal I/R was enhanced, and again, the inhibition of PLA2 suppressed the expression of IL-1 in the lung. Taken together, intestinal I/R seems to induce acute lung leak through the activation of PLA2, the increase of IL-1 expression associated with increased oxidative stress by neutrophilic respiratory burst.
Acute Lung Injury* ; Constriction ; Free Radicals* ; Hydrogen Peroxide ; Interleukin-1 ; Intestines ; Ischemia ; Leukocytes ; Lung ; Mesenteric Artery, Superior ; Microscopy, Electron ; Neutrophils ; Oxidative Stress ; Peroxidase ; Phospholipases A2* ; Phospholipases* ; Quinacrine ; Rats, Sprague-Dawley ; Reperfusion ; Respiratory Burst ; Respiratory Distress Syndrome, Adult ; Transferases

BACKGROUND: Neutrophils are considered to play critical roles in the development of acute respiratory distress syndrome. Histamine, which is distributed abundantly in lung tissue, increases the rolling of neutrophills via increase of P-selectin expression on the surface of endothelial cells and is known to have some interrelationships with IL-1, IL-8 and TNF-alpha. We studied to investigate the effect of the histamine on the acute lung injury of the rats induced by intratracheal insufflation of TNF-alpha which has less potency to cause lung injury compared to IL-1 in rats. METHODS: We intratracheally instilled saline or TNF(R&D, 500ng), IL-1(R&D, 50ng)or histamine of varius dose(1.1, 11 and 55 microg/kg) with and without TNF separately in Sprague-Dawley rats weighing 270-370 grams. We also intratracheally treated IL-l(50ng) along with histamine(55 microg/kg). In cases, there were synergistic effects induced by histamine on the parameters of TNF-induced acute lung injury, antihistainmes(Sigma, mepyramine as a H1 receptor blockade and ranitidine as a H2 receptor blockade, 10 mg/kg in each)were co-administered intravenously to the rats treated TNF along with histamine(1.1 microg/kg) intratracheally. Then after 5 h we measured lung lavage neutrophil numbers, lavage cytokine-induced neutrophil chemoatt- ractants(CINC), lung myeloperoxidase activity(MPO) and lung leak. We also intratracheally insufflated TNF with/without histamine(11 microg/kg), then after 24 h measured lung leak in rats. Statistical analyses were done by Kruskal-Wallis nonparametric ANOVA test with Dunn's multiple comparison test or by Mann-Whitney U test. RESULTS: We found that rats given TNF, histamine alone(11 and 55 microg/kg), and TNF with histamine(1.1, 11, and 55 microg/kg) intratracheally had increased (P<0.05) lung MPO activity compared with saline-treated control rats. TNF with histamine 11 microg/kg had increased MPO activity (P=0.0251) compared with TNF-treated rats. TNF and TNF with histamine(l.l, 11,, and 55 microg/kg) intratracheally had all increased (P<0.05) lung leak, lavage neutophil numbers and lavage CINC activities compared with saline. TNF with histamine 1.1 microg/kg had increased (P=0.0367) lavage neutrophil numbers compared with TNF treated rats. But there were no additive effect of histamine with TNF compared with TNF alone in acute lung leak on 5 h and 24 h in rats. Treatment of rats with the H1 and H2 antagonists resulted in inhibitions of lavage neutrophil accumulations and lavage CINC activity elevations elicited by co-treated histamine in TNF-induced acute lung injury intratracheally in rats. We also found that rats given IL-1 along with histamine intratracheally did not have increase in lung leak compared with IL-1 treated rats. CONCLUSION: Histamine administered intratracheally did not have synergistic effects on TNF-induced acute lung leak inspite of additive effects on increase in MPO activity and lavage neutrophil numbers in rats. These observations suggest that instilling histamine intratracheally would not play synergistic roles in neutrophil-mediated acute lung injury in rats.
Acute Lung Injury* ; Animals ; Bronchoalveolar Lavage ; Endothelial Cells ; Histamine* ; Insufflation ; Interleukin-1 ; Interleukin-8 ; Lung ; Lung Injury ; Neutrophils ; P-Selectin ; Peroxidase ; Pyrilamine ; Ranitidine ; Rats* ; Rats, Sprague-Dawley ; Respiratory Distress Syndrome, Adult ; Therapeutic Irrigation ; Tumor Necrosis Factor-alpha