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I have spent my entire professional life at Harvard Medical School, beginning as a medical student. I have enjoyed each day of a diverse career in four medical subspecialties while following the same triad of preclinical areas of investigation-cysteinyl leukotrienes, mast cells, and complement-with occasional translational opportunities. I did not envision a career with a predominant preclinical component. Such a path simply evolved because I chose instinctively at multiple junctures to follow what proved to be propitious opportunities. My commentary notes some of the highlights for each area of interest and the mentors, collaborators, and trainees whose counsel has been immensely important at particular intervals or over an extended period.

Objective: To review the role of cysteinyl leukotrienes (cysLTs) in allergic rhinitis and the scientific rationale for therapy with leukotriene receptor antagonists (LTRAs)., Data Sources: Relevant basic science and clinical articles were identified by a search of the PubMed database for articles published from 1984 to 2004 using the following keywords: allergic rhinitis; nose; immune response; allergen challenge; leukotrienes C, D, and E; cysteinyl leukotriene; cysteinyl leukotriene receptor; cytokine; leukocyte; montelukast; zafirlukast; and pranlukast., Study Selection: The authors' expert opinion was used to select studies for inclusion in this review., Results: CysLTs are synthesized via 5-lipoxygenase metabolism of arachidonic acid by mast cells and basophils during the early-phase response to antigen and by eosinophils and macrophages during the late phase. The cysLT levels in nasal secretions are elevated after short-term allergen instillation and in allergy season in patients with allergic rhinitis. These lipid mediators act locally and systemically by interacting with receptors, particularly the cysLT1 receptor, on target cells. Evidence derived from topical application of cysLTs in the nose and from the effects of LTRAs indicates that cysLTs contribute to nasal mucous secretion, congestion, and inflammation. CysLTs promote allergic inflammation by enhancing immune responses and the production, adhesion, migration, and survival of inflammatory cells such as eosinophils. They also increase the generation of an array of other proinflammatory mediators, such as cytokines, which in turn increase the production of and receptors for cysLTs. Clinical trials have demonstrated that LTRAs have significant but modest efficacy as single agents but additive efficacy when used with other classes of agents., Conclusions: CysLTs fulfill the criteria for relevant mediators of allergic rhinitis via their diverse effects on immune, inflammatory, and local structural components of disease. By blocking the cysLT1 receptor responsible for most of these effects, LTRAs represent a useful approach to treatment of this important and prevalent disorder.

The cysteinyl leukotrienes (cys-LTs) are a family of potent bioactive lipids that act through two structurally divergent G protein-coupled receptors, termed the CysLT(1) and CysLT(2) receptors. The cloning and characterization of these two receptors has not only reconciled findings of previous pharmacologic profiling studies of contractile tissues, but also has uncovered their expression on a wide array of circulating and tissue-dwelling leukocytes. With the development of receptor-selective reagents, as well as mice lacking critical biosynthetic enzymes, transporter proteins, and the CysLT(1) receptor, diverse functions of cys-LTs and their receptors in immune and inflammatory responses have been identified. We review cys-LT biosynthesis; the molecular biology and distribution of the CysLT(1) and CysLT(2) receptors; the functions of cys-LTs and their receptors in the recruitment and activation of effector leukocytes and induction of adaptive immunity; and the development of fibrosis and airway remodeling in animal models of lung injury and allergic inflammation.

Unexpected aspects of the antiasthmatic efficacy of leukotriene modifiers and glucocorticosteroids have been observed. For both classes, the observed effects may be partially explainable on the basis of underrecognized interactions involving leukotrienes. This review examines the interactions between leukotrienes and other mediators of asthma. It details the effects of glucocorticosteroids on leukotriene synthesis and on leukocyte populations in asthmatic airways. Unexpected controller effects of the leukotriene modifiers may reflect the fact that leukotrienes and other mediators of asthma, such as T(H)2 cytokines, positively influence each other's generation. The ability of the leukotriene modifiers to disrupt such extensive interactions means that other relevant mediators are targeted indirectly by leukotriene blockade. Among asthma therapies, the glucocorticosteroids have numerous anti-inflammatory activities, but their effects may be unpredictable. Many processes involved in inflammation appear to escape modulation by glucocorticosteroids, including leukotriene synthesis, and leukotriene generation is among them. Understanding whether glucocorticosteroids reduce cysteinyl leukotriene levels in the airway is important in determining the clinical value of combining glucocorticosteroid therapy with leukotriene modifier therapy.

The understanding that asthma pathophysiology includes an inflammatory component has spurred the more aggressive use of anti-inflammatory therapies and created a need for effective tools to measure inflammation. Biomarkers of airway inflammation proposed are obtained by methods that are direct but highly invasive (bronchial biopsy, bronchoalveolar lavage), moderately direct, and less invasive (indirect sputum, exhaled air, breath condensate) or indirect and least invasive (blood, urine). Several studies described in this review have implicated the cysteinyl leukotrienes (CysLTs) as inflammatory mediators in a wide range of diseases, implying that their biological activities reach far beyond acute bronchoconstriction, the activity traditionally ascribed to them. The validity of examining sputum for "biomarkers" has improved the understanding of asthma pathophysiology, optimization of asthma treatment and management, and investigation of the relation between CysLTs and airway inflammation in asthma. Nitric oxide is also a surrogate marker of asthma and reflects airway inflammation. The anti-inflammatory effects of the leukotriene receptor antagonists and the markers of their activity continue to grow.

A new paradigm for asthma pathogenesis is presented in which exaggerated inflammation and remodeling in the airways are a consequence of abnormal injury and repair responses arising from a subject's susceptibility to components of the inhaled environment. An epithelial-mesenchymal trophic unit becomes activated to drive pathologic remodeling and smooth muscle proliferation through complex cytokine interactions. Histamine, prostanoids, and cysteinyl leukotrienes (CysLTs) are potent contractile agonists of airway smooth muscle (ASM). The CysLTs appear to play a central role in regulating human ASM motor tone and phenotypic alterations, manifested as hypertrophy and hyperplasia in chronic severe asthma. The CysLTs augment growth factor-induced ASM mitogenesis through activation of CysLT receptors. Although they mediate their contractile effects by increasing phosphoinositide turnover and inducing increased cytosolic calcium, new data suggest that part of the contractile effect may be independent of calcium mobilization. Prostaglandin E(2), the predominant eicosanoid product of the airway epithelium, is a potent inhibitor of mitogenesis, collagen synthesis, and mesenchymal cell chemotaxis and therefore can suppress inflammation and fibroblast activation. The capacity of the epithelium for CysLT synthesis is inversely related to its ability to make PGE(2). The ASM is capable of expressing both leukotriene-synthesizing enzymes and CysLT receptors, and cytokines upregulate the receptor expression. This may be an explanation for the CysLTs promoting airway hyperresponsiveness in asthma. The CysLTs play an important role in the airway remodeling seen in persistent asthma that includes increases of airway goblet cells, mucus, blood vessels, smooth muscle, myofibroblasts, and airway fibrosis. Evidence from a mouse model of asthma demonstrated that CysLT(1) receptor antagonists inhibit the airway remodeling processes, including eosinophil trafficking to the lungs, eosinophil degranulation, T(H)2 cytokine release, mucus gland hyperplasia, mucus hypersecretion, smooth muscle cell hyperplasia, collagen deposition, and lung fibrosis.

Angiotensin II (Ang II) is a vasopressor peptide involved in the pathogenesis of cardiovascular diseases associated with diabetes mellitus. We have previously reported that the 5-lipoxygenase-derived products, particularly the cysteinyl leukotrienes (CysLTs), are involved in Ang II-induced contraction. In this study, we demonstrated that CysLTs contribute to the contraction elicited by Ang II in isolated aortas from streptozotocin-induced diabetic (SS) rats but not from insulin-treated diabetic rats, fructose-fed rats, or control rats. In an organ bath, pretreatment with the 5-lipoxygenase inhibitor (AA861, 10 micromol/L) reduced by 37.6+/-8.2% and 30.1+/-10.9% the Ang II-induced contractions in intact and endothelium-denuded aortic rings, respectively, from SS rats. In contrast, the CysLT(1) receptor antagonist (MK571, 1 micromol/L) or the dual CysLT(1)/CysLT(2) receptor antagonist (BAY-u9773, 0.1 micromol/L) did not affect Ang II-induced contraction. In addition, Ang II induced a 6.2+/-1.5-fold increase in CysLT release through the stimulation of the Ang II type 1 receptor. Furthermore, the urinary excretion of leukotriene E(4) was increased in SS rats (leukotriene E(4), 13.7+/-2.9 ng/24 h [SS rats, n=10] versus 1.5+/-0.5 ng/24 h [control rats, n=6]; P<0.0004). These data suggest the activation of the 5-lipoxygenase pathway in SS rats and the involvement of 5-lipoxygenase-derived products, particularly the CysLTs, in Ang II-induced contraction in aortas from SS rats through stimulation of CysLT receptors different from the well-characterized CysLT(1) or CysLT(2) receptor.

Arachidonic acid metabolism via 5-lipoxygenase gives rise to a group of biologically active lipids known as leukotrienes: leukotriene B(4), which is a potent activator of leukocyte chemotaxis, and cysteinyl leukotrienes (leukotriene C(4), D(4)and E(4)) which account for the spasmogenic activity previously described as slow-reacting substance of anaphylaxis. The biological actions of leukotrienes and the observations that leukotrienes are synthesised in the lung following antigen provocation and are elevated in asthma, stimulated considerable activity in the pharmaceutical industry to find drugs that modulate the synthesis or actions of leukotrienes. Three cysteinyl leukotriene antagonists (zafirlukast [Accolate], montelukast [Singulair] and pranlukast) and one 5-lipoxygenase inhibitor (zileuton) have received regulatory approval for the treatment of asthma. The clinical data obtained from using these drugs are generally consistent and complimentary. As a class the leukotriene modulators produce a rapid improvement in lung function after the first oral dose. Lung function improvements are maintained on chronic administration and are associated with reductions in a variety of asthma symptom scores. All of the available data are consistent with the hypothesis that all the leukotriene modulators exert their clinical benefit primarily through interference with cysteinyl leukotrienes. There are no compelling clinical data for an additional contribution by leukotriene B(4)in human asthma. In other respiratory conditions such as COPD, which are characterised by pronounced neutrophil infiltration, it may be that the chemotactic properties of leukotriene B(4)are more important and therefore evaluation of 5-lipoxygenase inhibitors in this condition is warranted. The introduction of the leukotriene modulators into clinical practice is the culmination of over 60 years of research since the initial discovery of the slow-reacting substances. The leukotriene modulators, and in particular the cysteinyl leukotriene antagonists, provide respiratory physicians with an oral therapeutic option and have set an efficacy standard which new oral anti-inflammatory approaches will have to beat.

Objective: Non specific lipoxygenase inhibitors have been reported to reduce the in vitro constrictor response and the in vivo pressor effect of angiotensin II in rats. The aim of this study was to assess the role of cysteinyl leukotrienes, in the vascular response to angiotensin II in spontaneously hypertensive rats (SHR)., Methods: Rings of thoracic aorta from SHR and normotensive Wistar-Kyoto rats (WKY) were compared in terms of contractile responses and release of cysteinyl leukotrienes in response to angiotensin II., Results: Pretreatment with the specific 5-lipoxygenase inhibitor AA861 10 microM reduced the efficacy of angiotensin II in intact and endothelium-denuded aorta from SHR (% inhibition vs. control: 65+/-12.6% with endothelium (n=6), P<0.05; 43+/-7.2% without endothelium (n=6), P<0.05) but not in aorta from WKY. In addition, in aorta from SHR, the CysLT(1) receptor antagonist MK571 1 microM reduced by 55+/-6.1% (n=6, P<0.05) the contractile effects of angiotensin II in rings with endothelium but not in endothelium-denuded rings. Angiotensin II induced a 8.6+/-2.1-fold increase in cysteinyl leukotriene production in aorta rings from SHR with endothelium which was prevented by the AT(1) receptor antagonist losartan 1 microM but not by the AT(2) receptor antagonist PD123319 0.1 microM. In aorta rings from WKY, cysteinyl leukotriene production remained unchanged after exposition to angiotensin II. The cysteinyl leukotrienes (up to 0.1 microM) induced contractions in aorta rings from SHR but not from WKY., Conclusions: These data suggest that cysteinyl leukotrienes, acting at least in part on endothelial CysLT(1) receptors, are involved in the contractile response to angiotensin II in isolated aorta from SHR but not from WKY.

The aim of the study was to estimate an eventual contribution of leukotrienes in respiratory mechanic changes observed in guinea-pig during bronchial anaphylaxis. Twenty-eight guinea-pigs, actively sensitized to ovalbumin, were anesthetized and curarized before being challenged, during controlled ventilation, with antigen administered as an aerosol. Antigen challenge was performed before and after pretreatment with nebulized FPL55712 and BW755C, respectively used as an antagonist of leukotrienes and as a cyclo-oxygenase/lipoxygenase inhibitor. The experiments were carried out during continuous recording of tracheal pressure (Ptr), airflow (V) and tidal volume (VT) signals variations evidencing respiratory asynchronism (AS) and allowing measurements of the changes in airway resistance (AR) and dynamic compliance (Cdyn) during all the challenge. Administration of nebulized ovalbumin was stopped at the onset of AS appearance chosen as the threshold of the antigen-induced bronchoconstriction. The results showed that separate or combined pretreatment with FPL55712 and BW755C did not significantly modify the threshold of the ovalbumin-induced bronchoconstriction in guinea-pigs. Nevertheless pretreatment with nebulized FPL55712 reduced significantly the intensity and the duration of the response of these animals to inhaled leukotriene D4 (LTD4). Moreover the response of guinea-pigs to inhaled LTD4, characterized by a starting decrease in Cdyn, appeared quite different from the response to the antigen starting by an abrupt rise in RA induced by a sudden bronchoconstriction. From these results, we concluded that leukotrienes seem not to be the main mediator of the bronchial anaphylaxis in guinea-pigs.

Peptidoleukotrienes reproduce some of the functional and histological features of clinical asthma, such as potent bronchoconstriction, airway microvascular leakage, mucus hypersecretion, eosinophilic airway infiltration, in addition to inducing bronchial hypersensitivity. An important role for peptidoleukotrienes has been demonstrated in experimental challenge studies in asthmatic patients and in acute asthma attacks. Antagonists of peptidoleukotrienes can inhibit bronchoconstriction in response to inhaled allergen, exercise or inhaled cold air, and oral or inhaled aspirin. These compounds demonstrate beneficial effects in clinical studies with improvement in symptoms and lung function. Peptidoleukotriene antagonists may provide a new therapeutic approach for the treatment of asthma.

The hypothesis of 35 years ago that slowreacting substance of anaphylaxis would prove to be a pathobiologic mediator of reversible airway disease in the human has been validated. The multidisciplinary approach required to achieve this goal has been particularly prominent and consistent for the entire period in the program described in this presentation.

The purpose of the study was to investigate whether allergen-induced hyperresponsiveness to methacholine and an increase in airway smooth muscle (ASM) in Brown Norway (BN) rats could be mediated by LTD4, an important mediator of allergic airway responses. Male BN rats, 8 to 12 wk of age, were sensitized with ovalbumin (OA). Rats were exposed 2 wk later to aerosols of saline (n = 6), OA (n = 8), or OA after pretreatment with the LTD4 antagonist MK-571 (2 mg/kg intraperitoneally, n = 9), on six occasions at 5-day intervals. Airway responsiveness to methacholine (the concentration required to double pulmonary resistance, EC200 RL) was measured immediately before the first aerosol exposure and 2 days after the last exposure. ASM was quantitated by morphometry, and areas were standardized for size using the epithelial basement membrane length (BM). Following OA challenges EC200 RL decreased from 6.5 to 3.1 mg/ml (p < 0.05) but did not change significantly after saline or OA exposures in MK-571-pretreated animals. ASM/BM2 in the large airways was significantly greater, 3.41 +/- 0.19 x 10(-3), after OA compared with 2.35 +/- 0.22 x 10(-3) for saline exposures (p < 0.01). The ASM/BM2 after OA exposures but with MK-571 pretreatment (2.75 +/- 0.25 x 10(-3)) was intermediate in value. The results indicate that both the increase in airway responsiveness and the increase in ASM following repeated antigen exposures appear to be mediated predominantly by LTD4.

The kinase inhibitors H7 and staurosporin dose-dependently stimulate adhesion U-937 cells to plastic but fail to inhibit the CD11b/CD18-dependent adhesion of U-937 cells induced by phorbol ester. The protein kinase C activity of U-937 cells, measured as phorbol ester-stimulated phosphorylation of pep epsilon in streptolysin-O permeabilized cells, is strongly inhibited by the kinase inhibitors. H7 and staurosporin efficiently overcome the inhibitory effect of phorbol-12,13-dibutyrate (PDBu) on leukotriene D4-induced increase in intracellular Ca2+. The results suggest that U-937 cell adhesion may be controlled by a protein kinase C isoform not sensitive to the inhibitors. In addition, the data indicate that selective pharmacological interference with different protein kinase C-mediated processes is achievable.

To investigate the renal actions of leukotrienes (LT), we infused arachidonic acid into the renal artery of anesthetized dogs during systemic cyclooxygenase inhibition (with ibuprofen) alone or in combination with lipoxygenase inhibition or LTD4/LTE4 receptor antagonism. Renal arachidonic acid infusion following ibuprofen alone decreased urine osmolality (945 +/- 143 to 698 +/- 144 mosm/kg; p < 0.01) and increased urine flow rate (0.34 +/- 0.11 to 0.56 +/- 0.16; p < 0.05) without altering renal blood flow, glomerular filtration rate or sodium excretion. In separate groups, prior inhibition of lipoxygenase (propylgallate) or blockade of LTD4/LTE4 receptors (LY171883) prevented the changes in urine osmolality and urine flow rate. Intrarenal oleic acid infusion following ibuprofen had no effect on renal function. Analysis of the renal papillae at the end of the experiment indicated that interstitial osmolality and sodium, potassium and urea contents were the same in all groups, ruling out a decrease in papillary interstitial osmolality as the cause of the decrease in urine osmolality in the arachidonic acid-infused group. Our experiments suggest that renal LT can decrease urine osmolality and increase urine flow rate and may play a role in renal water excretion.

We assessed the role of leukotrienes (LTs) in Munich-Wistar rats with passive Heymann nephritis (PHN), an animal model of human membranous nephropathy. 10 d after injection of anti-Fx1A antibody, urinary protein excretion rate (Upr) in PHN was significantly higher than that of control. Micropuncture studies demonstrated reduced single nephron plasma flow and glomerular filtration rates, increased transcapillary hydraulic pressure difference, pre- and postglomerular resistances, and decreased ultrafiltration coefficient in PHN rats. Glomerular LTB4 generation from PHN rats was increased. Administration of the 5-LO activating protein inhibitor MK886 for 10 d markedly blunted proteinuria and normalized glomerular hemodynamic abnormalities in PHN rats. An LTD4 receptor antagonist SK&F 104353 led to an immediate reduction in Upr and to reversal of glomerular hemodynamic impairment. Ia(+) cells/glomerulus were increased in PHN rats. In x-irradiated PHN rats, which developed glomerular macrophage depletion, augmented glomerular LT synthesis was abolished. Thus, in the autologous phase of PHN, LTD4 mediates glomerular hemodynamic abnormalities and a hemodynamic component of the accompanying proteinuria. The synthesis of LTD4 likely occurs directly from macrophages or from macrophage-derived LTA4, through LTC4 synthase in glomerular cells.

Leukotrienes, lipid mediators derived from arachidonic acid by the 5-lipoxygenase pathway, have been implicated in a variety of myocardial ischemic events including myocardial infarction and coronary spasm. We have examined the comparative effects of leukotriene C4 in isolated human non-atherosclerotic and atherosclerotic coronary arteries to gain an insight into the role of leukotrienes in coronary heart disease. Human coronary arteries, obtained from recipient hearts at the time of cardiac transplantation, were cut into rings and examined in an isolated organ bath. In atherosclerotic arteries leukotriene C4 (1nM-100nM) produced a maximal contractile response of 54.9 +/- 7.98% KCI (n = 7) and the mean EC50 value was 11.1nM (95% confidence interval: 9.4-13.0). The leukotriene receptor antagonist ICI-198,615 (3 x 10(-8)M) produced an approximate 50-fold rightward shift of the leukotriene C4 dose-response curve (n = 5). In contrast, non-atherosclerotic arteries were either non-responsive (n = 5) or only weakly responsive (n = 2) to leukotriene C4 (1nM-100nM), producing an average maximum response of 3.65 +/- 3.05% KCI (n = 7; p < 0.01 atherosclerotic vs non-atherosclerotic). In the presence of indomethacin and in vessels denuded of endothelium, non-atherosclerotic arteries remained unresponsive to leukotriene C4 (n = 3). In addition, leukotriene C4 did not relax preconstricted vessels (n = 7). In vitro autoradiography showed specific [3H]-leukotriene C4 binding to smooth muscle in both non-atherosclerotic and atherosclerotic arteries, with no evidence of endothelium-dependent binding.(ABSTRACT TRUNCATED AT 250 WORDS)

The cysteinyl leukotrienes (LTC4/D4/E4) are putative mediators of asthma. In this study we used sheep allergic to Ascaris suum antigen to examine the effects of a novel orally active cysteinyl LT antagonist, ONO-1078, on antigen-induced early and late responses, airway inflammation, post challenge (24 h) airway hyperresponsiveness (AHR) and mucociliary clearance. Airway responses to antigen were determined by measuring specific lung resistance (SRL) before and for 8 h after challenge, bronchoalveolar lavage (BAL) was used to estimate airway inflammation, and airway responsiveness was measured by determining the carbachol dose that increased SRL by 400% (PC400). We also used a radiographic technique to measure the antigen-induced change in tracheal mucus velocity (TMV), a marker of mucociliary clearance. In two trials separated by at least 21 days, sheep were treated once with ONO-1078 (30 mg/kg, p.o.) and once with placebo (0.5% methylcellulose), 2 h before and 4 h after antigen challenge. Treatment with ONO-1078 (n = 7) provided 40% protection (p < 0.10) against the peak early increase in SRL, resulted in a more rapid reversal of the early response, and provided 96% protection against the peak late (6-8 h) increase in SRL. ONO-1078 also inhibited the AHR 24 h after challenge. In the drug trial, PC400 was unchanged as compared to pre-challenge, whereas in the placebo trial, PC400 was decreased 1.4-fold (p < 0.05). Treatment however, did not affect BAL cell numbers or differential.(ABSTRACT TRUNCATED AT 250 WORDS)

We studied the effects of two structurally unrelated sulfidopeptide leukotriene receptor antagonists on endotoxin-induced pulmonary dysfunction in chronically instrumented unanesthetized sheep. The agents employed were L-660,711 (MK-571) (Merck-Frosst, Canada) and SK&F 104,353 (Smith Kline and French, King of Prussia, PA). The efficacy and specificity of the agents were verified in sheep by administering boluses of exogenous leukotrienes (LTB4, LTC4, LTD4, and LTE4) in doses as great as 100 micrograms while monitoring lung mechanics and vascular pressures. The antagonists blocked the changes in lung mechanics and pulmonary hemodynamics induced by the sulfidopeptide leukotrienes (LTC4, LTD4, and LTE4) while having no effect on the animals' responses to LTB4. The endotoxin studies were performed by administering endotoxin alone (Escherichia coli endotoxin 0.75 microgram/kg) or endotoxin after pretreatment with one of the sulfidopeptide leukotriene receptor antagonists. In control studies, each animal received a continuous infusion of one of the receptor antagonists for a duration identical to that of the endotoxin studies. Neither L-660,711 nor SK&F 104,353 significantly altered the endotoxin-induced changes in pulmonary hemodynamics, lung mechanics, lung fluid and solute exchange, oxygenation, or leukopenia. Peak lung lymph thromboxane B2 levels were significantly lower in sheep pretreated with L-660,711. When the antagonists were given alone, no effects were seen. We conclude that (1) sulfidopeptide leukotrienes do not measurably contribute to endotoxin-induced pulmonary dysfunction in chronically instrumented sheep; (2) sulfidopeptide leukotrienes may contribute to thromboxane release after endotoxin.

Platelet-activating factor (PAF) and leukotrienes (LTs) are potent pulmonary hypertensive and inflammatory mediators produced by the lung. Previously we showed that a rapid injection of PAF into the pulmonary artery of an isolated rat lung produced an extended elevation in mean pulmonary arterial pressure (PAP). The objective of the present study was to determine whether the extended pressor response induced by PAF was caused by prolonged activation of the 5-lipoxygenase pathway or slow clearance of LTs from the lung parenchyma. Rat lungs were perfused with a nonrecirculating physiological salt solution that contained indomethacin and albumin. Five minutes after a rapid injection of PAF into the pulmonary artery catheter, the following elevations (mean % above baseline) were observed: PAP (83%), LTB4 (3,260%), LTC4 (1,490%), LTD4 (970%), and LTE4 (1,500%). At 20 min these levels declined but were still significantly elevated above baseline. The 5-lipoxygenase inhibitor diethylcarbamazine (DEC), administered before the PAF injection, inhibited the elevations of PAP and all LTs. DEC administration that began 5 min after PAF reduced PAP and only LTC4 levels at 20 min in comparison to lungs with no DEC. The 5-lipoxygenase-activating protein inhibitor MK886, administered orally 2-6 h before perfusion, also inhibited the pressor response to PAF as well as LT production, as did DEC. We conclude that 1) the extended pulmonary hypertension induced by PAF was caused mainly by prolonged activation of 5-lipoxygenase with LTC4 production, 2) the relative overall lung clearance of LTB4, LTD4, and LTE4 was slower than that of LTC4, and 3) LTB4, LTD4, and LTE4 had no appreciable pressor effect.

A major target organ in generalized candidiasis is the kidney. The purpose of this study was to investigate the role of eicosanoids in the kidney infected by proteinase-positive and proteinase-negative Candida albicans. Prostaglandin (PG) E2-like activity was found to be significantly decreased while leukotriene (LT) C4-like activity increased within 10 days in the kidneys of mice infected with C. albicans. These results indicate that arachidonic acid metabolism is shifted to the lipoxygenase pathway and lipid peroxides, produced via this enzyme system may play an important role in the kidney damage induced by C. albicans.

Leukotrienes C4 and D4 are potent vasoconstrictors and have been proposed as mediators of the severe gastric mucosal injury caused by a variety of necrotizing agents. The purpose of this study was to investigate the role of leukotrienes on the less severe gastric mucosal injury caused by low concentrations of bile acid. Prior to injury with 5 mM acidified taurocholate (pH 1.2), rat stomachs were pretreated with either normal saline, leukotrienes C4 or D4 (10(-6), 10(-8), and 10(-9) M), or SKF-104353 (a leukotriene D4 receptor antagonist 10(-7) M). Injury was assessed by measuring net transmucosal hydrogen ion flux, luminal appearance of DNA, and histologic injury. Topical pretreatment with LTC4 and LTD4 significantly increased bile acid-induced luminal hydrogen ion loss and DNA accumulation in a dose-dependent manner. Leukotriene receptor blockade with SKF-104353 significantly decreased these parameters. Thus, both LTC4 and LTD4 exacerbate the gastric mucosal injury caused by the application of low concentrations of bile acid while leukotriene receptor blockade reduces this injury (corroborated by histologic injury analysis). This study suggests that leukotrienes may be mediators of bile acid-induced gastric mucosal injury.

In order to clarify the role of leukotriene in the antigen-induced asthmatic response, we carried out mite-antigen, leukotriene D4 (LTD4) and histamine inhalation tests in 21 mite-sensitive atopic asthma patients, and investigated the relationship between the bronchial responsiveness to mite (PD20-Mite) and that to LTD4 and histamine (PD20-LTD4, PD20-Hist). We then compared PD20-LTD4 and PD20-Hist between the groups with and without late asthmatic response (LAR), and investigated the relationship between the peak percentage fall of FEV1.0 in LAR (magnitude of LAR) and PD20-LTD4 and PD20-Hist. There were significant correlations between PD20-LTD4 and PD20-Mite (r = 0.590, p < 0.01), and between PD20-Hist and PD20-Mite (r = 0.669, p < 0.001). The bronchial responsiveness to LTD4 and histamine was significantly higher in the group with LAR. In addition, PD20-LTD4 showed a significant negative correlation with the magnitude of LAR (r = 0.724, p < 0.001). Furthermore we analyzed the relationship between PD20-LTD and the ratio of the magnitude of LAR to that of IAR (immediate asthmatic response), because there was a significant correlation between the magnitude of IAR and that of LAR (r = 0.842, p < 0.001) in 16 asthmatic patients with dual asthmatic response, and found that the correlation coefficient was also very high (r = -0.836, p < 0.001). These results suggest an important role of leukotriene in the antigen-induced asthmatic response.

Eicosanoids, derivatives of arachidonic acid, play a role in several inflammatory diseases of the bowel. To determine whether prostaglandin E2 (PGE2), leukotriene B4 (LTB4), and leukotriene C4D4E4 (LTC4D4E4), have a role in hypoxic insult to the intestine, we examined the levels of these mediators in a hypoxic neonatal rabbit model. One group of animals underwent hypoxic insult postnatally, the second group did not undergo hypoxia and served as a control. The levels of PGE2, LTB4, and LTC4D4E4 were determined by radioimmunoassay. PGE2 in the hypoxic group was 1,779 +/- 142 pg/mg protein (mean +/- SD) as opposed to 2,380 +/- 197 pg/mg protein in the control group (p less than 0.02). LTB4 level was 5,446 +/- 3,492 pg/mg protein in the hypoxic rabbits and 3,362 +/- 2,570 pg/mg protein in the control group (p less than 0.03). There was no statistically significant difference in the level of LTC4D4E4 between the two groups. Our study shows that hypoxia shifts the arachidonic acid metabolism toward enhanced lipoxygenase activity with a resultant increase in LTB4 levels and a concomitant decrease in cyclooxygenase activity with reduced PGE2 levels in the bowel. The shift in the balance between these eicosanoids may play a role in the pathogenesis of ischemic-hypoxic bowel diseases by enhancing the inflammatory response in the intestine, and simultaneously, diminishing cytoprotection.

The leukotrienes and tumor necrosis factor (TNF) play an important role in the pathophysiology of septic shock, in which hypotension, leukopenia, thrombocytopenia, and hemoconcentration are observed. This study was performed to examine the effects of a 5-lipoxygenase inhibitor (AA-861), a selective leukotriene receptor antagonist (ONO-1078), and a cyclooxygenase inhibitor (indomethacin) on endotoxin-induced mortality and TNF production in mice. Mice were injected intraperitoneally with carrageenan (5 mg per mouse), which we previously reported as an effective priming agent for lipopolysaccharide (LPS)-induced TNF production and mortality (M. Ogata, S. Yoshida, M. Kamochi, A. Shigematsu, and Y. Mizuguchi, Infect. Immun. 59:679-683, 1991). The indicated doses of AA-861, ONO-1078, indomethacin, or controls were administrated subcutaneously 30 min before LPS (50 micrograms per mouse) provocation. The mortality of mice was significantly decreased by pretreatment with AA-861 (P less than 0.001) or ONO-1078 (P less than 0.01) but not by pretreatment with indomethacin. The 50% lethal dose of LPS in the mice treated with dimethyl sulfoxide or ethanol was 32 or 33 micrograms, respectively, and it increased to 83 micrograms with AA-861 or 59 micrograms with ONO-1078, respectively. Neither AA-861 nor ONO-1078 suppressed LPS-induced TNF production in sera. Treatment with AA-861 significantly decreased the leukopenia and thrombocytopenia, and ONO-1078 significantly decreased the hemoconcentration and thrombocytopenia. The role of endogenous TNF was also examined in the carrageenan-pretreated mice. Treatment with 2 x 10(5) U of rabbit anti TNF-alpha antibody intravenously 2 h before LPS challenge significantly suppressed the LPS-induced TNF activity and decreased the mortality. Therefore, both leukotrienes and TNF play important roles in endotoxin-induced shock and mortality.

Group B beta-hemolytic streptococcus (GBS) infection is an important cause of neonatal pneumonia and sepsis. GBS infection is frequently associated with persistent pulmonary hypertension of the newborn. To better understand the early pulmonary hypertension phase of GBS-induced acute lung injury in a conscious animal, we characterized the pulmonary and systemic hemodynamic response of spontaneously breathing, chronically instrumented newborn lambs to injections of heat-killed type Ib GBS, 0.1-9.0 x 10(9) colony forming units. Heat-killed GBS caused marked dose-dependent increases in mean pulmonary arterial pressure and calculated pulmonary vascular resistance, 190 and 370% at the maximum dose, respectively. Similarly, GBS caused dose-dependent increases in mean systemic arterial pressure and systemic vascular resistance (28.5 and 108% at the maximum dose, respectively) and a decrease in cardiac output (33.5%). Arterial oxygen tension worsened at the higher doses. GBS-induced pulmonary hypertension was decreased by two structurally unrelated, putative leukotriene D4 receptor antagonists. Pretreatment with LY171883 blocked GBS-induced pulmonary hypertension by 95%, and WY48,252 attenuated this effect by 27%. Both drugs completely blocked the hemodynamic effects of exogenous leukotriene D4. For comparison, several lambs received bolus injections of live GBS, either alone or after pretreatment with LY171883. The hemodynamic response to live GBS and attenuation of that response by LY171883 were similar to those caused by similar doses of heat-killed GBS. Thus, bolus injections of heat-killed GBS provide a reproducible model of pulmonary hypertension in conscious newborn lambs. In addition, the sulfidopeptide leukotrienes appear to be important mediators of GBS-induced pulmonary hypertension in newborn lambs.

Leukotriene (LT) has been suggested to play an important role in the pathogenesis of bronchial asthma. In the present study, the effects of intravenous administration of LTC4 and LTD4 on bronchial smooth muscle in guinea pigs were investigated by measurement of dynamic compliance and dynamic respiratory resistance using a formula that excludes the effect of differences in airway wall thickness. With this formula, the ratio of bronchial smooth muscle constriction by histamine can be estimated as an index of bronchial hyperresponsiveness. Administration of LTC4 and LTD4 induced airway wall edema. The ratio of bronchial smooth muscle constriction by histamine was significantly enhanced by the administration of LTC4 and LTD4. Moreover, the LT antagonist ONO-1078 inhibited the effect of LTC4 and LTD4 administration. These results suggest that LTC4 and LTD4 can be important mediators affecting bronchial hyperresponsiveness.

The effects of colonic inflammation induced by trinitrobenzene sulfonic acid and influence of previous treatment with specific antagonists of inflammatory mediators (platelet-activating factor, leukotrienes, prostaglandins, and thromboxanes) on colonic transit were examined in conscious rats which were permanently fitted with an intracolonic catheter inserted into the proximal colon. Colonic inflammation was induced by intracolonic administration of trinitrobenzene acid (80 mg/kg) in 50% ethanol. Colonic transit time was evaluated by intracolonic administration of a radiolabeled marker [( 51Cr]sodium chromate) and collection of the feces per hour on a conveyor belt. Excretion of the marker was then plotted vs. time, permitting calculations of the times elapsed to recover 25%, 50%, and 75% of the marker injected (T25, T50, and T75, respectively). In control (saline) animals, excretion of the marker described a regular sigmoid curve with 50% of the marker recovered at 6.92 +/- 0.40 hours after intracolonic administration (T25 = 6.4 +/- 0.43 hours; T75 = 7.49 +/- 0.39 hours). Ethanol (vehicle), 50%, did not modify the profile of marker recovery. On the contrary, single intracolonic administration of trinitrobenzene sulfonic acid/ethanol induced a biphasic response consisting of an early pool of radiolabeled feces (T25 = 4.03 +/- 0.55 hours) with a delayed total one (T50 = 11.74 +/- 0.83 hours; T75 = 13.70 +/- 0.49 hours). Antagonists of the leukotriene pathway, i.e., MK = 886, a lipoxygenase inhibitor, and SKF 104,353 and SR 2640, two different leukotriene D4 receptor antagonists, blocked the effects of trinitrobenzene sulfonic acid on colonic transit time and restored a control profile of radiolabeled marker excretion. In contrast, indomethacin, a cyclooxygenase inhibitor, and SC 19220, a specific prostaglandin E2 receptor antagonist, were inefficient in blocking the effects of trinitrobenzene sulfonic acid on colonic transit time. Specific thromboxane A2 receptor antagonists, KT1-32 and GR 32191B, did not show any improvement in colonic transit after trinitrobenzene sulfonic acid administration. Previous injection of the specific platelet-activating factor receptor antagonists, BN 52021 or BN 50730, was also unable to restore a normal marker excretion profile after administration of trinitrobenzene sulfonic acid. It is concluded that the alterations of colonic transit immediately observed after intracolonic trinitrobenzene sulfonic acid administration are mediated through the release of leukotriene D4. In contrast, platelet-activating factor, prostaglandins, and thromboxanes are not involved in the mediation of these transit disturbances.

The effects of several inflammatory mediators on the patency of the Eustachian tube were evaluated in 15 mongrel dogs. Histamine, leukotriene C4(LTC4) and D4(LTD4), and platelet activating factor (PAF) were perfused through the Eustachian tube of anesthetized dogs at concentrations detected in human middle ear effusion of patients with otitis media. The patency of the Eustachian tube was then evaluated by perfusion pressure and opening pressure. Histamine at concentrations of more than 10(-5) M caused increased tubal resistance and opening pressure rapidly. LTC4 and LTD4 caused a rapid increase of tubal resistance and opening pressure at far lower concentrations, i.e. 10(-12) M. Doses of PAF over 10(-9) M may cause an increase in the opening pressure. These results indicate that various inflammatory mediators are capable of affecting the Eustachian tube function.

Septic shock is a major complication during the treatment of intense care patients. A similar pathologic state can be experimentally induced in rodents by application of endotoxins. There is circumstantial as well as direct evidence for a participation of leukotriene D4 in this experimental multiorgan failure. Due to liver-specific sensitivation by galactosamine endotoxin-induced multiorgan failure can be experimentally transposed to a single organ, i.e. hepatic failure. Data presented here show a participation of the eicosanoid leukotriene D4 in either model of sepsis. We have recently described a cellular system modelling endotoxin-induced hepatic failure. In this system based on the coculture of hepatocytes and nonparenchymal liver cells leukotriene D4 is required for the development of cytotoxicity. It is concluded that the three models share pivotal mechanistic principles and might be used complementary to each other in order to study underlying molecular events.

The involvement of histamine, leukotriene D4 (LTD4) and platelet-activating factor (PAF) in cutaneous anaphylaxis was investigated in a guinea pig model. When given alone, the H1 receptor antagonist chlorpheniramine, the LTD4/E4 antagonist LY171883 and the PAF antagonist WEB2086 were unable to inhibit increased microvascular plasma protein leakage in passive cutaneous anaphylaxis (PCA) reactions, as monitored by the extravasation of intravenously injected 125I-albumin. Furthermore the H2 receptor antagonist cimetidine and the serotonin antagonist methysergide were unable to reduce PCA responses when given alone or in combination with chlorpheniramine. In marked contrast, combinations of antagonists were able to reduce plasma leakage significantly. A combination of chlorpheniramine, LY171883 and WEB2086 virtually abolished plasma leakage during the PCA response, but did not influence the plasma protein leakage induced by intradermal injection of bradykinin. These results demonstrate that these allergic reactions involve several mediators and that the inability of an individual mediator antagonist to reduce responses does not necessarily rule out a role for that mediator.

The relative role of thromboxane (TxA2) and sulfidopeptide leukotrienes C4 (LTC4) and D4 (LTD4) in the acute renal failure induced by cyclosporine was studied in the rats. Bolus i.v. administration of 20 mg/kg of CsA but not vehicle to adult male Sprague-Dawley rats resulted in a significant fall in glomerular filtration rate from 0.85 +/- 0.10 and renal plasma flow (RPF) 2.45 +/- 0.14 ml/min/100 g body wt to values at 20 min of 0.47 +/- 0.03 and 1.01 +/- 0.12 ml/min/100 g body wt (P less than 0.01), respectively, without a fall in mean arterial pressure. This hemodynamic effect was maintained for the following 40-min period. Pretreatment of rats with the TxA2 receptor antagonist GR32191 (3 mg/kg i.v.) allowed a partial but significant preservation of GFR (0.60 +/- 0.05 ml/min/100 g body wt) and RPF (1.55 +/- 0.12 ml/min/100 g body wt). In addition, the antagonism of endogenously produced LTC4 and LTD4 with the putative receptor antagonist L-649,923 (1 mg/kg i.v.) partially prevented the fall in GFR (0.65 +/- 0.07 ml/min/100 g body wt) and RPF (1.80 +/- 0.18 ml/min/100 g body wt) at 20 min after CsA injection. The combined administration of GR32191 and L-649,923 completely abolished the CsA-induced decline in GFR (0.80 +/- 0.09 ml/min/100 g body wt) and RPF (2.40 +/- 0.12 ml/min/100 g body wt). These findings suggest that TxA2 and LTC4/LTD4 participate in mediating renal function deterioration induced by acute CsA administration in the rat.

Recent studies suggest that granulocytes (PMNs) play a role in the pathogenesis of acute and chronic myocardial ischemia and extension of myocardial injury. A positive correlation was also found between leukocyte count and severity of coronary artery disease. Rabbit derived antiserum dependent-reduction of circulating PMNs in the dog or using monoclonal antibody anti-CD11b/CD18 of PMNs resulted in smaller myocardial infarcts. Granulocytes can release a variety of mediators tissue injury and synergize with these different mediators and other cells resulting in amplification of neutrophil stimulation and rising to additional products with enhanced endothelial injury. This paper reviews "in vivo" studies that have been instrumental in demonstrating this role of granulocytes as a mediator of myocardial ischemia. Experience in humans shows the modification of PMNs function in angina and during myocardial ischemia, and data from our group demonstrated that their aggregability is increased in the coronary sinus of patients with angiographically documented coronary disease. Upon re-perfusion PMNs accumulate and produce an inflammatory response resulting in endothelial injury. Free radicals formed during ischemia or re-perfusion produce deleterious effects on cell membranes, endothelial cell and myocardium. On the other hand the PMNs activation occurring during coronary angioplasty (PTCA) by the release of proteolytic enzymes and the generation of oxygen-free radicals, may aggravate the endothelial damage induced by PTCA and further stimulate platelets having potential implications in subsequent development of restenosis. An other aspect of PMNs function is related to leukotriene C4 release; the vasoconstrictor effect of this leukotriene on coronary arteries is synergistic with that induced by platelet-released thromboxane A2, as well as the decrease in coronary flow produced by the combination of both substances is greater than the sum of changes caused by the two eicosanoids separately administered. The potential role of leukocytes, oxygen radicals, leukotrienes and granulocyte enzymes in pathophysiology of myocardial injury due to a regional ischemia and reperfusion is an area of intense investigation. Experimental and clinical studies to elucidate these events should not only provide insights into acute and chronic pathologic tissue damage, but may also lead to the identification of important new targets of pharmacologic intervention.

Gonadotropin-releasing hormone (GnRH) stimulated the formation of two major metabolites of the 5-lipoxygenase pathway, leukotriene (LT) B4 and LTC4, as well as luteinizing hormone (LH) release in primary cultures of rat anterior pituitary cells. Several lines of evidence suggested the presence of a GnRH-dependent pituitary endocrine system in which LTs act as second messengers for LH release: (i) GnRH-dependent LT formation was observed within 1 min and immediately preceded GnRH-induced LH release, whereas exogenous LTs stimulated LH release at low concentrations; (ii) the dose responses of GnRH-induced LT production and LH release were similar and both effects required the presence of extracellular Ca2+ ions; (iii) GnRH-induced LH release was blocked by up to 45% following the administration of several LT receptor antagonists; (iv) LTE4 action on LH secretion was entirely abolished by LT receptor antagonists; and (v) an activator of protein kinase C acted synergistically with LTE4 to induce LH release. The major source of LT formation in the pituitary cell cultures appeared to be the gonadotrophs, as shown by GnRH receptor desensitization experiments. The results demonstrate the presence of a GnRH-activatable 5-lipoxygenase pathway in anterior pituitary cells and provide strong support for the hypothesis that LTs play a role in LH release in the GnRH signaling pathway.

The extent of ethanol-induced acute gastric lesions, gastric leukotriene C4 (LTC4) levels, and the number of gastric mucosal mast cells were examined in mast cell-deficient W/Wv mice, normal litter-mate +/+ mice, and bone marrow-reconstituted W/Wv mice. After administration of ethanol, +/+ mice developed gastric lesions and elevation of gastric LTC4 levels in a dose dependent manner. In mast cell-deficient W/Wv mice, the extent of gastric lesions was far less than that of +/+ mice and the level of gastric LTC4 was not significantly altered. This difference was not due to anemia because blood-transfused non-anemic W/Wv mice were still resistant to ethanol-induced gastric lesions. When W/Wv mice were reconstituted with +/+ bone marrow cells, their natural resistance against ethanol-induced gastric lesions was abrogated. The extent of gastric lesions of bone marrow-reconstituted W/Wv mice paralleled with the increase in number of gastric mucosal mast cells and also with the level of gastric LTC4. Furthermore, ethanol-induced gastric lesions in bone marrow-reconstituted W/Wv mice was inhibited by pretreatment with 5-lipoxygenase inhibitor, AA-861, in a dose dependent manner. These results suggest that LTC4 may, even if it is not a prerequisite factor for ethanol induced acute gastric lesions, act as the amplitier in the sequential events of the pathogenesis.

1. The right bronchus with the right vagus nerve remaining intact was isolated from the guinea-pig. Stimulating the end of the right vagus nerve distal to the bronchus resulted in a biphasic contractile response with a rapid first phase and a second phase which persisted after the cessation of stimulation. The first phase was selectively sensitive to atropine, while the second phase was non-cholinergic, but abolished by pre-treatment with the sensory C fibre toxin, capsaicin. This biphasic contraction was mimicked by electrical field stimulation of the bronchus and strips of the distal aspect of the trachea. 2. The capsaicin-sensitive second phase produced by either vagus nerve stimulation or electrical field stimulation, was inhibited by greater than 50% by the selective peptidoleukotriene receptor antagonist SKF 104353, whereas the inactive stereoisomer of SKF 104353, SKF 104373, was without effect. SKF 104353 did not inhibit the cholinergic first phase, nerve conduction along the vagus nerve, or contractions to exogenously added substance P and neurokinin A. 3. The inhibitory effect of SKF 104353 on second-phase contractions was mimicked by two structurally unrelated selective peptidoleukotriene receptor antagonists, WY 48252 and ICI 198615, and by the 5'-lipoxygenase inhibitor REV 5901. 4. Exogenously added leukotriene D4 (1 nM) potentiated the second-phase contractions in the trachea and this effect was reversed by 0.1 microM-SKF 104353. Leukotriene D4 did not affect responses to exogenously added substance P or neurokinin A. 5. Stimulation of the right vagus nerve produced plasma extravasation in the trachea and in the main bronchi of atropine- and propranolol-pre-treated guinea-pigs. This was inhibited by about 50% by SKF 104353 (10 mg/kg, I.V.), whereas SKF 104373 (10 mg/kg, I.V.) was without effect. 6. It is suggested that endogenous peptidoleukotrienes make a significant contribution to the airway smooth muscle and vascular effects of capsaicin-sensitive nerve stimulation in the guinea-pig.

In vitro studies have suggested that leukotrienes are involved in acute allergic bronchoconstriction, though this has not been definitively corroborated yet in in vivo studies. On the other hand, edema production during antigenic challenge could be an additional factor favouring such bronchoconstriction. In the present work we quantified immunoreactive leukotriene C4 (iLTC4) concentrations in bronchoalveolar lavages during allergic bronchoconstriction induced by 1 mg/kg i.v. ovalbumin (OA) in immunized guinea pigs, as well as water content in guinea pig lung fragments obtained before and during this bronchoconstriction. We found that basal concentrations of iLTC4 (median 1.06 ng/ml) were not significantly modified at 2, 5 and 10 min (median 1.10, 0.29 and 1.37 ng/ml, respectively) of the bronchoconstrictor response. Water content in lung fragments did not change among non-immunized guinea pigs, immunized ones and at 15 min of bronchoconstriction (mean +/- SEM 79.32% +/- 0.18, 79.10% +/- 0.31 and 79.13% +/- 0.40%, respectively). In addition, isoproterenol (20 micrograms/kg, i.v.) rapidly reverted about 70% of the bronchoconstriction induced by a higher antigenic dose (OA, 3.1 mg/kg i.v.); residual obstruction was not associated with increased water content in lung fragments (78.13% +/- 0.43). These results suggest that in this model, acute allergic bronchoconstriction is not due to an increased iLTC4 release or to edema production, and that airway smooth muscle contraction is the main component of this response.

The bioconversion of leukotriene (LT) C4 to LTD4 via gamma-glutamyl transpeptidase is clearly defined in guinea pig trachea. Acivicin, an inhibitor of gamma-glutamyl transpeptidase, was used to study the contractile responses elicited by either endogenously released or exogenously administered LTC4 and the antagonistic nature of LY 171883 and ICI 204,219, LTD4/LTE4 receptor antagonists, on guinea pig tracheal strips. Pretreating tracheal strips with acivicin resulted in a concentration-related, selective leftward shift in the LTC4 concentration-response curves. Potency of LTC4 was increased 3-fold. Likewise, antigen concentration response curves were potentiated in acivicin-pretreated tissues. Antagonism of LTC4 and antigen contractile responses by LY 171883 and ICI 204,219 were reduced or abolished by acivicin-pretreatment. In contrast, these receptor antagonists effectively blocked LTD4 responses in control and acivicin-pretreated tissues. The results demonstrated that inhibition of gamma-glutamyl transpeptidase by acivicin blocked the bioconversion of LTC4 to LTD4 regardless of the source of LTC4. Data indicated that endogenously formed LTC4 was able to activate the LTC4 receptor in guinea pig tracheal strips.

Intragastric ethanol stimulates mucosal formation of leukotriene C4 in the rat stomach. The present study demonstrates that the increase in leukotriene C4 formation begins within 30 seconds and is maximal within 5 minutes, closely paralleled by the appearance of hemorrhagic lesions. Leukotriene C4 formation returns to prechallenge levels within 3 hours, although erosions still persist. Intragastric 0.2N NaOH, acidified 100 mmol/L taurocholate, 25% NaCl, or 0.6N HCl did not consistently increase leukotriene C4 formation despite severe mucosal injury. A number of sulfhydryl-containing or sulfhydryl-blocking agents as well as metals protected against mucosal damage and simultaneously prevented the stimulation of leukotriene C4 formation induced by ethanol. None of the agents increased and some virtually abolished mucosal formation of prostaglandin E2, indicating that gastroprotection can occur completely independently of the endogenous prostaglandin system. The leukotriene biosynthesis inhibitor MK-886 markedly suppressed gastric leukotriene C4 formation but did not protect against damage caused by ethanol, NaOH, NaCl, or acidified taurocholate. Oral indomethacin reduced the ex vivo formation of both prostaglandin E2 and, to a lesser extent, leukotriene C4 in the gastric mucosa, inducing a shift in the balance from protective prostaglandins to proulcerogenic leukotriene C4. Pretreatment with MK-886, however, did not significantly diminish indomethacin-induced lesions. These data suggest that leukotriene C4 is not the exclusive mediator of gastric injury caused by necrotizing agents or indomethacin. On the other hand, certain protective compounds exhibit a striking parallelism between protection and inhibition of ethanol-induced leukotriene C4 formation, suggesting that they may affect a target crucial for both mucosal injury and stimulation of 5-lipoxygenase.

To elucidate a possible interaction between alveolar macrophages and airway epithelial cells in allergic conditions, we studied the effect of immunologically stimulated macrophages on ciliary beat frequency (CBF) of cultured canine tracheal epithelium by a photoelectric method. Administration of supernatants from macrophages incubated with anti-dinitrophenyl (DNP) IgE antibody and anti-dinitrophenyl-human serum albumin dose-dependently increased ciliary beat frequency, the maximal increase from the baseline being 30.4 +/- 5.0% (mean +/- SE, P less than 0.01), an effect that was accompanied by the release of leukotriene (LT) C4 and leukotriene D4. This ciliostimulation was not affected by pretreatment of macrophages with indomethacin but was inhibited by that with nordihydroguaiaretic acid. Addition of FPL 55712 abolished the response of ciliary beat frequency to the stimulated macrophages, and exogenously administered leukotriene C4 and leukotriene D4 dose-dependently increased ciliary beat frequency. These results suggest that macrophages increase respiratory ciliary motility through the IgE-mediated release of leukotrienes and may modulate mucociliary transport function in the airway.

The extent of acute gastric lesions produced by intragastric administration of ethanol in mice paralleled gastric leukotriene (LT) C4 levels. Furthermore, an inverse dose-response relationship was observed between the extent of gastric lesions and the number of mast cells in the gastric mucosa. When mice were pretreated with the 5-lipoxygenase inhibitor, AA-861, both the extent of ethanol-induced gastric lesions and the level of gastric LTC4 decreased dose-dependently. In contrast, when mice were pretreated with the LTC4 receptor antagonist, FPL-55712, the extent of ethanol-induced gastric lesions was depressed without significant reduction of gastric LTC4 level. These results indicate that both production of LTC4 and also subsequent binding of LTC4 to the receptors is important for the pathogenesis of gastric lesions and suggest that mast cell-derived LTC4 plays a major role in the development of ethanol-induced gastric lesions.

Arachidonic acid solution (2 to 15 mg/ml) was infused into the right forebrain white matter of anaesthetised cats over three hours to evaluate its contribution to the genesis and pathophysiology of vasogenic brain oedema. The 0.6 ml infusion increased local white matter water content by a mean of 11.3 ml/100 g tissue but did not increase cortical water content. Histological studies revealed local expansion and trabeculation of the white matter with aggregations of granulocytic neutrophils in the venules and perivenular brain. The adjacent cortical cytoarchitecture was normal. The white matter around the infusion site was stained lightly and over a variable area (15-20 mm2) by intravenously administered Evans Blue dye 2%. Regional cerebral blood flow (rCBF) adjacent to the frontal infusion did not change significantly during the period of infusion and remained similar to rCBF in the contralateral hemisphere. Following the arachidonic acid infusion regional CBF CO2 reactivity was normal and three was no asymmetry of either cortical somatosensory evoked potential (SEP) or motor evoked potential (MEP) waveforms. The increase in brain water content and changes in the ICP and ICP related biodynamics (pressure-volume index, lumped craniospinal compliance and CSF outflow resistance) were similar to those seen following infusion of 0.6 ml saline. These studies suggest that free intraparenchymal arachidonic acid, at concentrations exceeding those occurring in most neuropathological conditions, can increase the normal brain parenchymal capillary permeability but does not disrupt focal cerebrovascular and electrophysiological function. The clinical implications of these findings are discussed.