Leukotrienes constitute a class of potent biological mediators of inflammation and anaphylaxis (for reviews see refs 1 and 2). Their biosynthesis derives from 5-lipoxygenase-catalysed oxygenation of arachidonic acid in granulocytes, macrophages and mast cells. To examine the physiological importance of leukotrienes, we have disrupted the 5-lipoxygenase gene by homologous recombination in embryonic stem cells. 5-Lipoxygenase-deficient (5LX-/-) mice develop normally and are healthy. They show a selective opposition to certain inflammatory insults. Although there is no difference in their reaction to endotoxin shock, the 5LX-/- animals resist the lethal effects of shock induced by platelet-activating factor. Reaction to ear inflammation induced by phorbol ester is normal, whereas inflammation induced by arachidonic acid is markedly reduced. Contrasts were also found in two models of leukocyte chemotaxis in vivo. The phenotype of 5LX-/- mice under injurious insult identifies the role for leukotrienes in the pathophysiology of select inflammatory states.

Background In this descriptive case series, 80 soldiers from Fort Campbell, Kentucky, with inhalational exposures during service in Iraq and Afghanistan were evaluated for dyspnea on exertion that prevented them from meeting the U.S. Army's standards for physical fitness. Methods The soldiers underwent extensive evaluation of their medical and exposure history, physical examination, pulmonary-function testing, and high-resolution computed tomography (CT). A total of 49 soldiers underwent thoracoscopic lung biopsy after noninvasive evaluation did not provide an explanation for their symptoms. Data on cardiopulmonary-exercise and pulmonary-function testing were compared with data obtained from historical military control subjects. Results Among the soldiers who were referred for evaluation, a history of inhalational exposure to a 2003 sulfur-mine fire in Iraq was common but not universal. Of the 49 soldiers who underwent lung biopsy, all biopsy samples were abnormal, with 38 soldiers having changes that were diagnostic of constrictive bronchiolitis. In the remaining 11 soldiers, diagnoses other than constrictive bronchiolitis that could explain the presenting dyspnea were established. All soldiers with constrictive bronchiolitis had normal results on chest radiography, but about one quarter were found to have mosaic air trapping or centrilobular nodules on chest CT. The results of pulmonary-function and cardiopulmonary-exercise testing were generally within normal population limits but were inferior to those of the military control subjects. Conclusions In 49 previously healthy soldiers with unexplained exertional dyspnea and diminished exercise tolerance after deployment, an analysis of biopsy samples showed diffuse constrictive bronchiolitis, which was possibly associated with inhalational exposure, in 38 soldiers.

Free radicals have been implicated in the pathogenesis of an increasing number of diseases. Lipids, which undergo peroxidation, are major targets of free radical attack. We report the discovery of a pathway of lipid peroxidation that forms a series of isomers in vivo that are characterized by a substituted tetrahydrofuran ring structure, termed isofurans (IsoFs). We have proposed two distinct pathways by which IsoFs can be formed based on 18 O2 and H2 18 O labeling studies. Measurement of F2-isoprostanes (IsoPs), prostaglandin F2-like compounds formed nonenzymatically as products of lipid peroxidation, is considered one of the most reliable approaches for assessing oxidative stress status in vivo. However, one limitation with this approach is that the formation of IsoPs becomes limited at high oxygen tension. In contrast, the formation of IsoFs becomes increasingly favored as oxygen tension increases. IsoFs are present at readily detectable levels in normal fluids and tissues, and levels increase dramatically in CCl 4-treated rats, an animal model of oxidant injury. The ratio of IsoFs to IsoPs in major organs varies according to normal steady-state tissue oxygenation. In addition, IsoFs show a marked increase early in the course of hyperoxia-induced lung injury, whereas IsoPs do not significantly increase. We propose that combined measurement of IsoFs and IsoPs should provide a more reliable index of oxidant stress severity than quantification of either alone because of the opposing modulation of the two pathways by oxygen tension, which can vary widely in different organs and disease states.

Although airway epithelial cells provide important barrier and host defense functions, a crucial role for these cells in development of acute lung inflammation and injury has not been elucidated. We investigated whether NF-κB pathway signaling in airway epithelium could decisively impact inflammatory phenotypes in the lungs by using a tetracycline-inducible system to achieve selective NF-κB activation or inhibition in vivo. In transgenic mice that express a constitutively active form of IκB kinase 2 under control of the epithelial-specific CC10 promoter, treatment with doxycycline induced NF-κB activation with consequent production of a variety of proinflammatory cytokines, high-protein pulmonary edema, and neutrophilic lung inflammation. Continued treatment with doxycycline caused progressive lung injury and hypoxemia with a high mortality rate. In contrast, inducible expression of a dominant inhibitor of NF-κB in airway epithelium prevented lung inflammation and injury resulting from expression of constitutively active form of IκB kinase 2 or Escherichia coli LPS delivered directly to the airways or systemically via an osmotic pump implanted in the peritoneal cavity. Our findings indicate that the NF-κB pathway in airway epithelial cells is critical for generation of lung inflammation and injury in response to local and systemic stimuli; therefore, targeting inflammatory pathways in airway epithelium could prove to be an effective therapeutic strategy for inflammatory lung diseases.

The mechanism of steroid action in asthma is unknown. Because steroids have effects in vitro on eicosanoid synthesis, we determined the effect of oral prednisone for 6 to 9 days on eicosanoid levels in bronchoalveolar lavage (BAL) fluid of 14 atopic asthmatic volunteers at baseline and after allergen instillation. We also determined the effect of prednisone on the ex vivo release of eicosanoids from macrophage-rich BAL-fluid cells. Prednisone reduced symptoms and inhaler use but had no significant effect on BAL-fluid eicosanoid levels. At baseline, prostaglandin D2 (PGD2) levels were 101 +/- 37 pg/ml in BAL fluid (mean +/- SEM), versus 66 +/- 18 pg/ml after prednisone; likewise, 5-hydroxy eicosatetraenoic acid (5-HETE) levels were 59 +/- 15 versus 78 +/- 21; leukotriene E4 (LTE4) levels were 35 +/- 13 versus 51 +/- 21, and 15-hydroxy eicosatetraenoic acid (15-HETE) levels were 29 +/- 8 versus 19 +/- 7. Allergen-stimulated levels of PGD2 were 1274 +/- 565 versus 1468 +/- 679 after prednisone; likewise, allergen-stimulated 5-HETE levels were 95 +/- 21 versus 82 +/- 21; those of LTE4 were 54 +/- 20 versus 91 +/- 51; and those of 15-HETE were 63 +/- 19 versus 60 +/- 25. Prednisone reduced the synthesis of eicosanoids in macrophage-rich BAL-fluid cells in vitro. LTB4 levels fell significantly from 35 +/- 6.4 ng/10(6) BAL-fluid cells to 17 +/- 5.4 after prednisone; likewise, levels of thromboxane B2 (TXB2) fell from 35.7 +/- 7.5 to 20.7 +/- 6.6. Part of the action of steroids may involve alteration in macrophage eicosanoid synthesis.

Background Current asthma guidelines recommend assessing the level of a patient’s asthma control. Consequently, there is increasing use of asthma control as an outcome measure in clinical research studies. Several composite assessment instruments have been developed to measure asthma control. Objective National Institutes of Health (NIH) institutes and federal agencies convened an expert group to propose the most appropriate standardized composite score of asthma control instruments to be used in future asthma studies. Methods We conducted a comprehensive search of PubMed, using both the National Library of Medicine’s Medical Subject Headings (MeSH) and key terms to identify studies that attempted to develop and/or test composite score instruments for asthma control. We classified instruments as core (required in future studies), supplemental (used according to study aims and standardized), or emerging (requiring validation and standardization). This work was discussed at an NIH-organized workshop convened in March 2010 and finalized in September 2011. Results We identified 17 composite score instruments with published validation information; all had comparable content. Eight instruments demonstrated responsiveness over time; 3 demonstrated responsiveness to treatment. A minimal clinically important difference has been established for 3 instruments. The instruments have demographic limitations; some are proprietary, and their use could be limited by cost. Conclusion Two asthma composite score instruments are sufficiently validated for use in adult populations, but additional research is necessary to validate their use in nonwhite populations. Gaps also exist in validating instruments for pediatric populations.

F 2 -isoprostanes are produced in vivo by nonenzymatic peroxidation of arachidonic acid esterified in phospholipids. Increased urinary and plasma F 2 -isoprostane levels are associated with a number of human diseases. These metabolites are regarded as excellent markers of oxidant stress in vivo. Isoprostanes are initially generated in situ, i.e. when the arachidonate precursor is esterified in phospholipids, and they are subsequently released in free form. Although the mechanism(s) responsible for the release of free isoprostanes after in situ generation in membrane phospholipids is, for the most part, unknown, this process is likely mediated by phospholipase A 2 activity(ies). Here we reported that human plasma contains an enzymatic activity that catalyzes this reaction. The activity associates with high density and low density lipoprotein and comigrates with platelet-activating factor (PAF) acetylhydrolase on KBr density gradients. Plasma samples from subjects deficient in PAF acetylhydrolase do not release F 2 -isoprostanes from esterified precursors. The intracellular PAF acetylhydrolase II, which shares homology to the plasma enzyme, also catalyzes this reaction. We found that both the intracellular and plasma PAF acetylhydrolases have high affinity for esterified F 2 -isoprostanes. However, the rate of esterified F 2 -isoprostane hydrolysis is much slower compared with the rate of hydrolysis of other substrates utilized by these enzymes. Studies using PAF acetylhydrolase transgenic mice indicated that these animals have a higher capacity to release F 2 -isoprostanes compared with nontransgenic littermates. Our results suggested that PAF acetylhydrolases play key roles in the hydrolysis of F 2 -isoprostanes esterified on phospholipids in vivo.2 are a family of prostaglandin (PG)-like compounds produced in vivo primarily by a nonenzymatic, free radicalinduced oxidation of arachidonic acid (1). These compounds are generated in situ esterified to phospholipids through the formation of PGH 2 -like bicyclic endoperoxide intermediates. These intermediates can either undergo rearrangement to E 2 /D 2 -IPs, isothromboxanes, and highly reactive isoketals or become reduced to F 2 -IPs that have been characterized in detail. Following in situ oxidation, IPs are released in free form by the action of phospholipase(s) activity.The measurement of F 2 -IPs in biological fluids has become one of the most accepted quantitative assessments of lipid peroxidation and oxidant stress reactions that occur in vivo (2). This approach provides the advantage of being noninvasive, as F 2 -IPs circulate freely in plasma and are excreted in urine. Increased IP production has been observed in a number of human diseases associated with oxidant stress, including atherosclerosis, pulmonary and liver diseases, habitual smoking, neurological disorders, and diabetes (3-5). In addition, exposure of experimental animals to increased oxidant stress also results in remarkable increases in the levels of free IPs in the urine and in plasma (2, 6). P...

Protease-resistant prion protein, total prion protein, and glial fibrillary acidic protein were measured in various brain regions from 9 subjects with fatal familial insomnia. Six were homozygotes methionine/methionine at codon 129 (mean duration, 10.7 +/- 4 months) and 3 were heterozygotes methionine/valine (mean duration, 23 +/- 11 months). In all subjects, protease-resistant prion protein was detected in gray matter but not in white matter and peripheral organs. Its distribution was more widespread than that of the histopathological lesions, which were observed only in the presence of a critical amount of the abnormal protein. In the mediodorsal thalamic nucleus, however, a severe neuronal loss and astrogliosis were associated with relatively moderate amounts of protease-resistant prion protein, suggesting a higher vulnerability. There was no overall correlation between amount of protease-resistant prion protein and either glial fibrillary acidic protein or total prion protein. While protease-resistant prion protein was virtually limited to subcortical areas and showed a selective pattern of distribution in the subjects with disease of the shortest duration, it was more widespread in the subjects with a longer clinical course, indicating that with time the disease process spreads within the brain. The kinetics of the accumulation of protease-resistant prion protein varied among different brain regions: While in the neocortex and to a lesser extent in the limbic lobe and in the caudate nucleus, the amount increased with disease duration, in the mediodorsal thalamic nucleus and in the brainstem it was present in comparable amounts in all subjects regardless of the disease duration.(ABSTRACT TRUNCATED AT 250 WORDS)