Redox signaling of NF-kappaB by membrane NAD(P)H oxidases in normal and malignant cells.

Evidence is rapidly accumulating that low-activity NAD(P)H oxidases homologous to that in phagocytic cells generate reactive oxygen species as signaling intermediates. In this review we discuss evidence that signaling NAD(P)H oxidases in part influence normal and malignant cell division by activating the redox-regulated transcription factor nuclear factor kappaB. The roles of growth-regulatory NAD(P)H oxidases in human airway smooth muscle and malignant melanoma are used as examples.

Reactive oxygen species from NAD(P)H:quinone oxidoreductase constitutively activate NF-kappaB in malignant melanoma cells.

The transcription factor nuclear factor-kappaB (NF-kappaB) is constitutively activated in malignancies from enhanced activity of inhibitor of NF-kappaB (IkappaB) kinase, with accelerated IkappaBalpha degradation. We studied whether redox signaling might stimulate these events. Cultured melanoma cells generated superoxide anions (O(2)(-)) without serum stimulation. O(2)(-) generation was reduced by the NAD(P)H:quinone oxidoreductase (NQO) inhibitor dicumarol and the quinone analog capsaicin, suggesting that electron transfer from NQO through a quinone-mediated pathway may be an important source of endogenous reactive oxygen species (ROS) in tumor cells. Treatment of malignant melanoma cells with the H(2)O(2) scavenger catalase, the sulfhydryl donor N-acetylcysteine, the glutathione peroxidase mimetic ebselen, or dicumarol decreased NF-kappaB activation. Catalase, N-acetylcysteine, ebselen, dicumarol, and capsaicin also inhibited growth of melanoma and other malignant cell lines. These results raise the possibility that ROS produced endogenously by mechanisms involving NQO can constitutively activate NF-kappaB in an autocrine fashion and suggest the potential for new antioxidant strategies for interruption of oxidant signaling of melanoma cell growth.

Calcium oxalate and iron accumulation in sarcoidosis.

BACKGROUND: In many patients with sarcoidosis, the granulomas contain inclusion bodies within giant cells. Many giant cells contain crystalline oxalate that chemically coordinates iron on the surface of the crystal. If this iron is incompletely coordinated and capable of redox cycling, then oxalate might contribute to granuloma formation in the lung. METHODS: Using human tissues, isolated alveolar macrophages and respiratory epithelial cells, we measured the ability of calcium oxalate to sequester iron, stimulate cytokine release and cause granuloma formation. We then studied the effects of in vivo oxalate instillation on pulmonary granuloma formation over 3 to 6 months in rats. RESULTS: Calcium oxalate present in human sarcoid granulomas sequesters significant amounts of iron and ferritin. In alveolar macrophage cultures, oxalate accumulates iron and stimulates ferritin production and giant cell formation. In cultured respiratory epithelial cells, calcium oxalate increases the release of two interleukins (IL), IL-8 and IL-6, involved in granuloma formation by 8 to 10 fold within 24 hours. Intratracheal instillation of calcium oxalate crystals into the lungs of rats is associated with pulmonary iron and ferritin accumulation and organic carbonyl formation consistent with sustained oxidative stress. These exposures were accompanied by influx of alveolar macrophages, giant cell formation, and a granulomatous response in the lung. CONCLUSIONS: These results support an association between calcium oxalate deposition in the lung, iron mediated oxidative stress and formation of some of the granulomas of sarcoidosis.

Nonanticoagulant heparin inhibits NF-kappaB activation and attenuates myocardial reperfusion injury.

Heparin reduces ischemia-reperfusion injury to myocardium. This effect has been attributed to complement inhibition, but heparin also has other activities that might diminish ischemia-reperfusion. To further probe these mechanisms, we compared heparin or an o-desulfated nonanticoagulant heparin with greatly reduced anticomplement activity. When given at the time of coronary artery reperfusion in a canine model of myocardial infarction, heparin or o-desulfated heparin equally reduced neutrophil adherence to ischemic-reperfused coronary artery endothelium, influx of neutrophils into ischemic-reperfused myocardium, myocardial necrosis, and release of creatine kinase into plasma. Heparin or o-desulfated heparin also prevented dysfunction of endothelial-dependent coronary relaxation following ischemic injury. In addition, heparin and o-desulfated heparin inhibited translocation of the transcription nuclear factor-kappaB (NF-kappaB) from the cytoplasm to the nucleus in human endothelial cells and decreased NF-kappaB DNA binding in human endothelium and ischemic-reperfused rat myocardium. Thus heparin and nonanticoagulant heparin decrease ischemia-reperfusion injury by disrupting multiple levels of the inflammatory cascade, including the novel observation that heparins inhibit activation of the proinflammatory transcription factor NF-kappaB.

Requirement for reactive oxygen species in serum-induced and platelet-derived growth factor-induced growth of airway smooth muscle.

Reactive oxygen species have been recently identified as important mediators of mitogenic signaling in a number of cell types. We therefore explored their role in mediating mitogenesis of airway smooth muscle. The antioxidants catalase, N-acetylcysteine, and probucol significantly reduced proliferation in primary cultures of rat tracheal smooth muscle stimulated with fetal bovine serum or platelet-derived growth factor, without affecting cell viability or inducing apoptosis. N-Acetylcysteine also significantly reduced serum-stimulated elevation of c-Fos but did not prevent the normal mitogen-induced increase in c-fos mRNA. Fractionation of ribosomes by sucrose density centrifugation and subsequent dot-blot Northern analysis revealed that antioxidants reduced incorporation of c-fos mRNA into the heaviest polyribosomes, suggesting redox regulation of c-fos mRNA translation. Serum treatment of monolayers produced a small but reproducibly significant rise in superoxide dismutase-inhibitable reduction of ferricytochrome c by myocyte monolayers. Serum-induced ferricytochrome c reduction, cellular proliferation, and c-Fos elevation were decreased by the flavoprotein-dependent enzyme inhibitor dipheyleneiodonium. Growth responses to fetal bovine serum and superoxide dismutase-inhibitable reduction of ferricytochrome c were not different between cultured tracheal myocytes from wild-type versus gp91 phagocyte oxidase null mice. These results suggest that mitogen stimulation of airway smooth muscle induces signal transduction of cell proliferation that is in part dependent on generation of partially reduced oxygen species, generated by an NADH or NADPH oxidoreductase that is different from the oxidase in phagocytic cells.

Dehydroepiandrosterone and analogs inhibit DNA binding of AP-1 and airway smooth muscle proliferation.

The adrenal steroid dehydroepiandrosterone (DHEA) and its analogs reduce growth of immortalized and malignant cell lines. We therefore explored their effects on the growth of airway smooth muscle, whose hyperplasia may lead to fixed airways obstruction and enhanced airways hyperresponsiveness in severe chronic asthma. DHEA and its potent analog 16 alpha-bromoepiandrosterone dramatically reduced proliferation in primary cultures of rat tracheal smooth muscle stimulated with fetal bovine serum or platelet-derived growth factor. Growth inhibition was dose-dependent and could not be attributed to interference with glucose-6-phosphate dehydrogenase activity or cholesterol metabolism, as reported for immortalized or malignant cell lines, respectively. Expression of the early response gene c-fos remained intact, but DHEA and 16 alpha-bromoepiandrosterone decreased DNA binding of the transcription factor activator protein-1, a later response important for expression of genes that mediate DNA synthesis and cell cycle progression. These results suggest that the nonglucocorticoid steroid DHEA and its analogs may impair activation of secondary growth response genes in a fashion analogous to that reported for glucocorticoids and that they may prove useful for treatment of asthmatic airway remodeling in the human.

Depletion of iron and ascorbate in rodents diminishes lung injury after silica.

Exposures of the lung to iron chelates can be associated with an injury. The catalysis of oxygen-based free radicals is postulated to participate in this injury. Such oxidant generation by mineral oxide particles can be dependent on availability of both iron and a reductant. We tested the study hypothesis that lung injury after silica is associated with the availability of both iron and ascorbate in the host by depleting this metal and reductant in the lungs of rats and guinea pigs, respectively. Rats were fed either a normal diet or a diet deficient of iron. After 30 days, animals were instilled with either saline or 1.0 mg Minusil-5 silica. Relative to saline, silica significantly increased neutrophils and lavage protein. Iron depletion significantly diminished both the cellular influx and injury but only at 1 week after silica exposure. Guinea pigs were provided either a normal diet supplemented with 1,000 ppm vitamin C or a diet deficient in ascorbate. After 14 days, the guinea pigs were instilled with either saline or 1.0 mg silica. Silica exposure significantly increased neutrophils and lavage protein. Ascorbate depletion significantly diminished the influx of inflammatory cells and injury at both 1 day and 1 week after silica exposure. We conclude that host concentrations of both iron and ascorbate can affect lung injury after silica exposure.

Alterations in the course of acid-induced lung injury in rats after general anesthesia: volatile anesthetics versus ketamine.

UNLABELLED: Pulmonary aspiration of gastric acid is a complication that occurs during anesthesia. The effects of the often used anesthetics on the inflammatory response after aspiration of acid are not known. We examined the effects of three different inhaled anesthetics--halothane, enflurane, and isoflurane--as well as parenteral ketamine, on the associated immediate mortality, alveolar protein leakage, and morphometric changes after intrapulmonary instillation of acidic solution in rats. Animals in deep state of anesthesia had a higher mortality after the instillation of acidic solutions than those in lighter stages (82.5% vs 31.6%). Protein leakage over 5 h was greater in the animals receiving volatile anesthetics (range 0.9-1.2) compared with those receiving ketamine (0.6 +/- 0.05). Desferoxamine did not decrease protein leakage in acid-injured animals (1.1 +/- 0.06 vs 1.02 +/- 0.08). Furthermore, volatile anesthetics resulted in an increase in the acute inflammatory response and leukocytic infiltration compared with ketamine in acid-injured lungs. We conclude that the administration of inhaled anesthetics was associated with exacerbation of an acute inflammatory response after aspiration of acidic solution. Lung injury was not increased with ketamine anesthesia. This difference was the result of the hypotensive effects of inhaled anesthetics. IMPLICATIONS: This study reveals that the use of inhaled anesthetics aggravates inflammation secondary to gastric aspiration and should be avoided on diagnosis of the situation.

Ferritin expression after in vitro exposures of human alveolar macrophages to silica is iron-dependent.

The increased availability of catalytically active iron after silica exposure can present an oxidative injury to a living system. Sequestration of reactive iron would, therefore, confer a protective effect. The intracellular storage of iron by ferritin within macrophages can limit the potential for radical generation and cellular injury resulting from exposure to a metal chelate. We tested the hypothesis that in vitro exposure of human alveolar macrophages to silica increases the expression of ferritin through a posttranscriptional mechanism. Exposure of 1.0 x 10(6) macrophages to 100 microg/ml silica for 4 h increased light-subunit (L)-ferritin protein concentrations in both cell supernatants and lysates. Inclusion of 1.0 mM deferoxamine in the reaction mixtures inhibited increases in ferritin after silica. To test for a posttranscriptional regulation of ferritin protein expression, cells were incubated with acid-washed particles, silica with complexed zinc cation, and silica with complexed iron cation. L-ferritin protein concentrations were increased in both cell supernatants and lysates after 4 h of exposure to silica with complexed iron cation. There were no increases in L-ferritin after incubations with acid-washed particles or silica with complexed zinc cation. There were no significant differences in levels of L-ferritin cDNA between any of the exposures, suggesting a posttranscriptional control of ferritin expression.

Postexposure treatment with aminophylline protects against phosgene-induced acute lung injury.

Pretreatment with aminophylline has been shown to protect against various types of acute lung injury. Mechanisms responsible for protection are multifactorial but are thought to involve upregulation of cAMP. While previous studies focused on pretreatment, the present investigation examined post-treatment in rabbits following exposure to a lethal dose of the oxidant gas phosgene. Rabbits, 2-3 kg, were exposed to a cumulative dose of phosgene to attain a c x t exposure effect of 1500 ppm.min. Lungs were isolated in situ and perfused for 90-100 min after exposure with Krebs-Henseleit buffer at 40 mL/min. Pulmonary artery pressure (Ppa), tracheal pressure (Pt), and lung weight gain (lwg) were measured continuously. Leukotrienes C4/D4/E4 were measured in the perfusate every 20 min during perfusion. At the immediate conclusion of the experiment, lung tissue was frozen in liquid N2 and analyzed for reduced GSH, GSSG, cAMP, and lipid peroxidation (TBARS). Post-treatment with aminophylline 80-90 min after exposure significantly lowered Ppa, Pt, and lwg. Aminophylline significantly reduced TBARS and perfusate LTC4/D4/E4, and prevented phosgene-induced decreases in lung tissue cAMP. These data suggest that protective mechanisms observed with aminophylline involve decreased LTC4/D4/E4-mediated pulmonary capillary permeability and attenuated lipid peroxidation. Direct antipermeability effects of cAMP on cellular contraction may also be important in protection against phosgene-induced lung injury.

Disruption of protein tyrosine phosphate homeostasis in bronchial epithelial cells exposed to oil fly ash.

Residual oil fly ash (ROFA) is a toxic air pollutant that we have previously shown induces inflammatory mediator expression in human bronchial epithelial cells. To identify intracellular signaling mechanisms activated by ROFA, we studied its effect on protein tyrosine phosphate metabolism in the human bronchial epithelial cell line BEAS. Noncytotoxic levels of ROFA induced significant dose- and time-dependent increases in protein tyrosine phosphate levels in BEAS cells. ROFA-induced increases in protein phosphotyrosines were associated with its soluble fraction and were mimicked by vanadyl [V(IV)]- and vanadate [V(V)]-containing solutions. Ferrous, ferric, and nickel (II) ion solutions failed to increase phosphotyrosine levels. Tyrosine phosphatase activity, which was known to be inhibited by vanadium ions, was markedly diminished after ROFA treatment. Tyrosine kinase activity was unaffected. We conclude that ROFA exposure induces vanadium ion-mediated inhibition of tyrosine phosphatase activity, leading to accumulation of protein phosphotyrosines in BEAS cells. These findings demonstrate that ROFA exposure disrupts protein tyrosine phosphate homeostasis in BEAS cells and suggest a possible mechanism that leads to increased synthesis of proinflammatory proteins in airway epithelial cells exposed to PM10.

Tyloxapol inhibits NF-kappa B and cytokine release, scavenges HOCI, and reduces viscosity of cystic fibrosis sputum.

Cystic fibrosis (CF) patients develop progressive cytokine-mediated inflammatory lung disease, with abundant production of thick, tenacious, protease- and oxidant-rich purulent airway secretions that are difficult to clear even with physiotherapy. In the search for a potential treatment, we have tested tyloxapol, an alkylaryl polyether alcohol polymer detergent previously used as a mucolytic agent in adult chronic bronchitis. Tyloxapol inhibits activation of the transcription factor nuclear factor-kappa B (NK-kappa B), reduces resting secretion of the cytokine interleukin-8 (IL-8) in cultured human monocytes, and inhibits lipopolysaccharide (LPS)-stimulated release of tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, IL-6, IL-8, granulocyte-macrophage colony-stimulating factor (GM-CSF), and the eiconsanoids thromboxane A2 and leukotriene B4 (LTB4). We have previously shown that tyloxapol is a potent antioxidant for hydroxyl radicals ( OH). Tyloxapol (0.05 to 0.1% wt/vol) effectively scavenges the oxidant hypochlorous acid (HOCl; 1 to 7.5 mM) in vitro, and protects from HOCl-mediated lung injury in rats. Tyloxapol also reduces the viscosity of CF sputum (from 463 +/- 133 to 128 +/- 52 centipoise). We conclude that tyloxapol is potentially useful as a new antiinflammatory therapy for CF lung disease, and could possibly promote clearance of secretions in the CF airway.

Intratracheal administration of DBcAMP attenuates edema formation in phosgene-induced acute lung injury.

Phosgene, a toxic gas widely used as an industrial chemical intermediate, is known to cause life-threatening latent noncardiogenic pulmonary edema. Mechanisms related to its toxicity appear to involve lipoxygenase mediators of arachidonic acid (AA) and can be inhibited by pretreatment with drugs that increase adenosine 3',5'-cyclic monophosphate (cAMP). In the present study, we used the isolated buffer-perfused rabbit lung model to investigate the mechanisms by which cAMP protects against phosgene-induced lung injury. Posttreatment with dibutyryl cAMP (DBcAMP) was given 60-85 min after exposure by an intravascular or intratracheal route. Lung weight gain (LWG) was measured continuously. AA metabolites leukotriene (LT) C4, LTD4, and LTE4 and 6-ketoprostaglandin F1 alpha were measured in the perfusate at 70, 90, 110, 130, and 150 min after exposure. Tissue malondialdehyde and reduced and oxidized glutathione were analyzed 150 min postexposure. Compared with measurements in the lungs of rabbits exposed to phosgene alone, posttreatment with DBcAMP significantly reduced LWG, pulmonary arterial pressure, and inhibited the release of LTC4, LTD4, and LTE4. Intratracheal administration of DBcAMP was more effective than intravascular administration in reducing LWG. Posttreatment also decreased MDA and protected against glutathione oxidation observed with phosgene exposure. We conclude that phosgene causes marked glutathione oxidation, lipid peroxidation, release of AA mediators, and increases LWG. Posttreatment with DBcAMP attenuates these effects, not only by previously described inhibition of pulmonary endothelial or epithelial cell contraction but also by inhibition of AA-mediator production and a novel antioxidant effect.

Protective effects of N-acetylcysteine treatment after phosgene exposure in rabbits.

We examined the effects of treatment with N-acetylcysteine (NAC) on pulmonary edema formation in isolated perfused rabbit lungs following in vivo phosgene exposure. This study focused on posttreatment intratracheal administration of NAC after exposure. Rabbits, 2 to 3 kg, were exposed to a cumulative dose of phosgene to attain a concentration x time exposure effect of 1,500 ppm/min. Lungs were perfused with Krebs-Henseleit buffer at 40 ml/min from 70 to 150 min after exposure. Pulmonary artery pressure (Ppa), tracheal pressure (Pt), and the rate of lung weight gain (LWG) were measured continuously. Perfusate concentration of peptide leukotrienes LTC4, D4, and E4 were measured every 20 min during perfusion. At the conclusion of the experiment, lung tissue was analyzed for reduced and oxidized glutathione (GSH and GSSG) and lipid peroxidation (thiobarbituric acid-reactive substances, TBARS). Exposure to phosgene significantly increased Pt, LWG, LTC4, D4, and E4, TBARS, and GSSG over time compared with controls. Compared with phosgene, intratracheal NAC lowered Ppa, LWG, LTC4, D4, and E4, TBARS, and GSSG. We conclude that NAC protected against phosgene-induced lung injury by acting as an antioxidant by maintaining protective levels of glutathione, reducing both lipid peroxidation and production of arachidonic acid metabolites.

Complexation of iron cation by sodium urate crystals and gouty inflammation.

Gouty inflammation can be suppressed by an iron chelator. We therefore hypothesized that arthritis associated with sodium urate crystal deposition could follow the incomplete complexation of iron cation with subsequent oxidant generation as the metal cycles through reduced and oxidized states. Urate crystals adsorbed Fe3+ in vitro and crystals collected from a human tophus had significant concentrations of ionizable iron. Urate crystals oxidized deoxyribose to a thiobarbituric acid (TBA)-reactive product, augmented luminol chemiluminescence by neutrophils, released leukotriene B4 from neutrophils, activated complement, and promoted neutrophil chemotaxis. All of these events increased with the concentration of complexed iron and were suppressed by the iron chelator deferoxamine or the .OH scavenger dimethylthiourea. These results suggest that some portion of gouty inflammation after urate crystal deposition could result from the incomplete complexation of iron with subsequent catalytic generation of reactive oxygen species.

Nontuberculous mycobacteria. An underappreciated cause of geriatric lung disease.

Nontuberculous mycobacteria (NTM) infection is a frequent opportunistic infection in patients infected with the human immunodeficiency virus. However, NTM infection may also occur in nonimmunocompromised hosts. In order to determine the spectrum of mycobacterial infection in the nonacademic setting, we analyzed the demographic and clinical characteristics of all patients presenting to a suburban multispecialty clinic during a 24-mo period. Twenty-one patients presented with active mycobacterial lung infections during the study period. Of these, only one had Mycobacterium tuberculosis. The remaining 20 had lung infections with NTM. One patient was infected with M. kansasii, three had M. abscessus, and 16 had M. avium complex. One patient with disseminated M. avium infection met the diagnostic criteria for the acquired immunodeficiency syndrome. The remaining 19 were largely normal at presentation and were predominantly elderly (mean age, 71 +/- 11 yr), female (79%), nonsmokers (89%) who presented with cough (94%) and localized radiographic infiltrates (84%), often in the right middle lobe and/or lingula (73%). The predominance of nontuberculous mycobacteria over M. tuberculosis in our practice was mirrored by results of an 11-yr review of experience from a nearby suburban hospital, where 65% of mycobacterial infections in the previous 5 yr were with NTM. We conclude that infection with NTM represents a previously underappreciated cause of chronic lung infection among elderly middle-class patients in the community setting.

DNA strand breaks following in vitro exposure to asbestos increase with surface-complexed [Fe3+].

Surface functional groups on silicate dusts complex iron cations which can cycle through reduction and oxidation states to generate free radicals. These oxidants have a capacity to produce DNA strand breaks and mutations which are primary events in cancer induction. A differential in the capacity of fibrous silicates to produce carcinoma is recognized with the amphiboles demonstrating a greater biologic effect than the serpentine fiber chrysotile. We tested the hypothesis that the differences in genotoxicity of these fibrous silicates correspond to varying concentrations of iron complexed to the surface. Relative to chrysotile, the amphibole fibers complexed greater amounts of iron cations from both inorganic and in vivo sources. Increased concentrations of surface-complexed iron were associated with greater oxidant generation, measured as thiobarbituric acid-reactive products of deoxyribose, and more covalently closed, circular DNA strand scission. These results indicate that genotoxic effects of these fibers may correspond to their capacity to complex iron at the surface.

PO2-dependent hydroxyl radical production during ischemia-reperfusion lung injury.

Pulmonary ischemia-reperfusion results in transient hypertension and edema formation. Implicated in this injury are partially reduced oxygen species including the highly reactive hydroxyl radical. We measured ischemia-reperfusion injury and hydroxyl radical production following 90 min of either air-ventilated, N2-ventilated, or nonventilated ischemia in an isolated rabbit lung preparation. We found that edema formation was independent of alveolar oxygen tension (PO2); all ischemic groups had similar edema formation, regardless of the type of ventilation. Weight gain was 37-50 g of fluid during 40 min of reperfusion. Production of hydroxyl radical, measured by nonenzymatic hydroxylation of salicylate, was influenced by PO2 with a significant increase after air-ventilated ischemia (P < 0.05) but not after N2-ventilated ischemia. Treatment with dimethylthiourea or superoxide dismutase reduced edema formation 60-80% after air (P < 0.05)- and N2 (P < 0.05)-ventilated ischemia, whereas treatment with catalase protected only N2-ventilated ischemia (P < 0.05). Our results implicate two distinct mechanisms by which partially reduced oxygen species may contribute to pulmonary ischemia-reperfusion injury. One is by a mechanism capable of generating hydroxyl radical at normal PO2; the second is from reactions active at low PO2, the products of which are metabolized readily by extracellular enzymatic scavengers. The precise mechanisms of oxidant generation are not clear, but the findings suggest that a complex oxidative injury occurs during ischemia-reperfusion.

Protection against platelet-activating factor-induced injury by interferon inducer in perfused rabbit lung.

Platelet-activating factor (PAF) and the interferons (IFN) are released during sepsis and the adult respiratory distress syndrome. The proinflammatory nature of PAF and anti-inflammatory property of IFN led us to investigate interactions between these two mediators in an isolated perfused lung (IPL) preparation. In the IPL, mean pulmonary arterial pressure (Ppa), lung weight gain, and peak airway pressure (Paw) were monitored continuously for 1 h in six groups of rabbits: 1) control, 2) the IFN-alpha/beta inducer polyinosinic:cytidylic acid (polyI:C) alone, 3) PAF alone, 4) polyI:C + PAF, 5) indomethacin + PAF, and 6) AA861 (a 5-lipoxygenase inhibitor) + PAF. At the end of 1 h, microvascular pressure was determined by double-occlusion technique and partition of total pulmonary vascular resistance (RT) was calculated. Serial eicosanoid concentrations in the perfusate also were measured. PAF increased Ppa, Paw, lung weight gain, and RT. These changes were associated with increased thromboxane B2 and decreased leukotriene production. PolyI:C, which induced high levels of serum IFN in rabbits, blocked the PAF-induced increase in Ppa, Paw, lung weight gain, and RT, similar to indomethacin and AA861. PolyI:C suppressed PAF-stimulated release of thromboxane B2 and increased leukotriene levels in the perfusate. The PAF-induced lung responses also were attenuated by pretreatment with human recombinant IFN. These data indicate that polyI:C protects against PAF-induced responses in the rabbit IPL, most likely via its induction of IFN. This effect is related in part to inhibition of thromboxane A2 production stimulated by PAF and leukotrienes.