Primed neutrophils injure rat lung through a platelet-activating factor-dependent mechanism (original) (raw)
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Pulmonary Pharmacology & Therapeutics, 2000
Intratracheal instillation of lipopolysaccharide (LPS) induces an inflammatory response characterized by infiltration of polymorphonuclear neutrophils (PMNs) into the extracellular matrix and by the release of mediators that play a fundamental role in lung damage. In the present study, we developed a mouse model which allows correlation of the inflammatory response and haemorrhagic tissue injury in the same animal. In particular, the different steps of the inflammatory response and tissue damage were evaluated by the analysis of three parameters: myeloperoxidase (MPO) activity in the parenchyma, reflecting PMNs accumulation into the lung, inflammatory cells count in the bronchoalveolar lavage fluid (BALF), reflecting their extravasation, and total haemoglobin estimation in BALF, a marker of haemorrhagic tissue damage consequent to PMNs degranulation. In our experimental conditions, intra-tracheal administration of 10 g/mouse of LPS evoked an increase of MPO activity in the lung at 4 h (131%) and 6 h (147%) from endotoxin challenge. A significant increase of PMNs in the BALF was noticed at these times with a plateau between the 12nd and 24th h. PMN accumulation produced a time-dependent haemorrhagic lung damage until 24 h after LPS injection (4 h: +38%; 6 h: +23%; 12 h: +44%; 24 h: +129% increase of haemoglobin concentration in the BALF vs. control). Lung injury was also assessed histopathologically. Twenty-four hours after the challenge, diffuse alveolar haemorrhage, as well as PMN recruitment in the interstitium and alveolus were observed in the LPS group. This model was pharmacologically characterized by pretreatment of LPS-treated mice with antiinflammatory drugs acting on different steps of the 'inflammatory cascade'. We demonstrated that: a) betamethasone (1, 3, 10, 30 mg/kg po) reduced in a dose-dependent manner the MPO activity, the number of inflammatory cells and, at the same time, lung injury; b) pentoxifylline, a TNF production inhibitor (200 mg/kg ip), inhibited PMN extravasation and lung haemorrhage but it was not able to reduce MPO activity in the lung; c) L-680,833, an anti-elastase compound (30 mg/kg po), decreased significantly only the haemorrhagic lung damage; d) indomethacin, a non steroidal antiinflammatory drug (5 mg/kg po), did not show any effect on any of the parameters considered. In conclusion, our in vivo mouse model is a practical alternative to animal models of ARDS (Adult Respiratory Distress Syndrome) recently described and it permits to dissect and to characterize the different steps of PMNs infiltration and, at the same time, the damage caused by their activation.
The role of neutrophils in LPS-induced changes in pulmonary function in conscious rats
Pulmonary Pharmacology & Therapeutics, 2004
We have previously reported on a model of lipopolysaccharide (LPS)-induced pulmonary inflammation in rats, where LPS-challenged animals develop a significant pulmonary neutrophilia and mucus hypersecretion. In the current studies, we utilized whole body plethysmography and computer assisted data acquisition to examine changes in pulmonary parameters, e.g. frequency ðf Þ; tidal volume and Penh as a measure of bronchoconstriction, due to LPS-challenge in conscious rats. Compared to saline challenge, LPS-challenged rats displayed a significant increase in ðf Þ; which began within 30 min, peaked by 2 h and remained elevated up to 24 h. Mirroring this increase in ðf Þ was a decrease in the observed tidal volume of LPS-challenged rats. Additionally, compared to saline challenge, LPS-challenge provoked a significant and spontaneous bronchoconstriction, as measured by Penh, 2 h after challenge. In order to further understand these observed LPS-induced pulmonary changes, we utilized two classes of pulmonary obstructive disease standards, namely, bronchodilators and antiinflammatory agents, and examined their ability to affect the spontaneous bronchoconstriction and the increase in ðf Þ seen at two discrete time points, i.e. 2 and 24 h after LPS-challenge. While ineffective on either the 2 h increase in ðf Þ or the LPS-induced inflammation, animals pretreated with salbutamol (10 mg/kg, p.o.) were protected from the increase in ðf Þ seen at the 24 h time point after LPS-challenge. In contrast, when animals were pretreated with theophylline (10 mg/kg, p.o.) no effect on the LPS-induced pulmonary inflammation or increase in ðf Þ was noted. Meanwhile, in animals pretreated with either betamethasone (3 mg/kg, p.o.) or SB207499 (10 mg/kg, p.o.), a PDE4 inhibitor, doses previously shown to block the LPS-induced neutrophilic inflammation, the persistent increase in ðf Þ seen at 24 h was attenuated, but neither compound was able to attenuate either the increase in ðf Þ or the spontaneous bronchoconstriction seen at 2 h. In summary, the intra-tracheal LPS-challenge of rats results in pulmonary inflammation and dysfunction, which is similar to that seen in COPD patients. We conclude that the early increase in ðf Þ and bronchoconstriction are not dependent upon airway inflammation, but airway inflammation most likely contributes to the persistent increase in ðf Þ seen at 24 h.
American Journal of …, 2005
Infiltration of activated neutrophils (polymorphonuclear leukocytes; PMN) into the lung is an important component of the inflammatory response in acute lung injury. The signals required to direct PMN into the different compartments of the lung have not been fully elucidated. In a murine model of LPS-induced lung injury, we investigated the sequential recruitment of PMN into the pulmonary vasculature, lung interstitium, and alveolar space. Mice were exposed to aerosolized LPS and bronchoalveolar lavage fluid (BAL) and lungs were harvested at different time points. We developed a flow cytometry-based technique to assess in-vivo trafficking of PMN in the intravascular and extravascular lung compartments. Aerosolized LPS induced consistent PMN migration into all lung compartments. We found that sequestration in the pulmonary vasculature occurred within the first hour. Transendothelial migration into the interstitial space started one hour after LPS-exposure and increased continuously until a plateau was reached between twelve and 24 hours.
Journal of Surgical Research, 2001
-2) regulate tissue neutrophil polymorphonuclear neutrophil (PMN) accumulation in a multitude of inflammatory states. We hypothesized that TNFRI signaling dictates PMN accumulation in the lung via regulation of chemokine molecule production. Therefore, the purposes of this study were to (1) delineate LPS-induced lung TNF-␣ production and (2) characterize the contribution of both TNF receptors to lung chemokine production and neutrophil influx following systemic LPS.
Anesthesia & Analgesia, 2004
Small-dose endotoxin (Etx) prevents pulmonary perfusion redistribution away from edematous dorsal lung regions after oleic acid (OA)-induced injury in dogs, causing a significant deterioration in oxygenation. We hypothesized that small-dose Etx might mediate this effect via polymorphonuclear neutrophil (PMN) priming with release of inflammatory mediators such as platelet activating factor (PAF) or secretory phospholipase A 2 (sPLA 2 ). To test this hypothesis, we administered specific inhibitors directed against each mediator and used two strategies to generate neutropenia. PAF and sPLA 2 inhibitors were administered before OA injury, followed 2 h later by small-dose Etx (n ϭ 4 each
The Journal of Immunology, 2006
Increased nuclear accumulation of NF-B in LPS-stimulated peripheral blood neutrophils has been shown to be associated with more severe clinical course in patients with infection associated acute lung injury. Such observations suggest that differences in neutrophil response may contribute to the pulmonary inflammation induced by bacterial infection. To examine this question, we sequentially measured LPS-induced DNA binding of NF-B in neutrophils collected from healthy humans on at least three occasions, each separated by at least 2 wk, and then determined pulmonary inflammatory responses after instillation of LPS into the lungs. Consistent patterns of peripheral blood neutrophil responses, as determined by LPSinduced NF-B DNA binding, were present in volunteers, with a >80-fold difference between individuals in the mean area under the curve for NF-B activation. The number of neutrophils recovered from bronchoalveolar lavage after exposure to pulmonary LPS was significantly correlated with NF-B activation in peripheral blood neutrophils obtained over the pre-LPS exposure period (r ؍ 0.65, p ؍ 0.009). DNA binding of NF-B in pulmonary neutrophils also was associated with the mean NF-B area under the curve for LPS-stimulated peripheral blood neutrophils (r ؍ 0.63, p ؍ 0.01). Bronchoalveolar lavage levels of IL-6 and TNFRII were significantly correlated with peripheral blood neutrophil activation patterns (r ؍ 0.75, p ؍ 0.001 for IL-6; and r ؍ 0.48, p ؍ 0.049 for TNFRII. These results demonstrate that stable patterns in the response of peripheral blood neutrophils to LPS exist in the human population and correlate with inflammatory response following direct exposure to LPS in the lung.
Clinical and Experimental Immunology, 2008
The purpose of this study was to characterize the role of tumour necrosis factor (TNF) and neutrophils (PMN) in the pathogenesis of pulmonary oedema induced by endotoxin (lipopolysac-charide (LPS)). Intraperitoneal administration to BALB/c mice of 0–6–1 mg of LPS caused pulmonary oedema and lethality. This was associated with production of TNF in serum and bronchoalveolar lavage fluid and with accumulation of PMN in the lung. In this experimental model, we could block TNF production by different means: pretreatment 30 min before LPS with 4 mg/kg of i.p. chlorpromazine (CPZ), 3 mg/kg of i.p. dexamethasone (DEX), 1 g/kg p.o. of N-acctylcysteine (NAC, an antioxidant precursor of glutathione), or an anti-TNF MoAb. CPZ, DEX and anti-TNF completely prevented LPS lethality but not pulmonary oedema or pulmonary PMN infiltration, indicating that: (i) lung oedema is not the main cause of death after LPS; and (ii) lung oedema induced by LPS is not mediated by TNF. Pretreatment with NAC not only inhibited TNF production but also protected against LPS-induced pulmonary oedema, indicating that reactive oxygen intermediates are implicated. NAC also blocked TNF production in blood and in bronchoalveolar lavage. We also tested the effect of PMN depletion induced with cyclophosphamide (CP) or 5-fluorouracil (5-FU). While no pulmonary PMN infiltrate was observed in PMN-depleted mice, neutropenia did not prevent LPS lethality or oedema, indicating PMN do not play an important role in the toxic effects of LPS in this experimental model.