The Potential Roles of Leukotrienes in Bronchial Asttuna'" GIORGIO L. PIACENTINI and MICHAEL A. KALINER
Introduction The relevance of slow-reacting substance of anaphylaxis (SRS-A) in the pathogenesis of bronchial asthma was suggested almost 50 yr ago by Kellaway and Trethewie (1). Since that original report, many studies have investigated the actions of SRS-A in the asthmatic lung, showing its possible contribution to some of the features of asthma. SRS-A is now recognized to be made up of the leukotrienes (LTs) C 4 , D 4 , and E 4 , a series of closely related conjugated trienes derived from arachidonic acid. The purpose of this review is to briefly summarize the recent literature on leukotrienes and asthma from a pathogenetic viewpoint.
Structure and Synthesis LTsare derived from arachidonic acid (AA), a ubiquitous, polyunsatured, 20-carbon fatty acid (5,8,11,14 cis-eicosatetraenoic acid) generated through the 5-lipoxygenase pathway (2). The unstable 5 S-hydroperoxy-6,8-trans-11,14 cis-eicosatetraenoic acid (5-HPETE) is the first intermediate synthesized through the 5-lipoxygenase enzyme system starting from AA released from cell membranes by the action of the enzyme phospholipase A 2 (3). 5-HPETE can be converted either to 5-hydroxyeicosatetraenoic acid (5 HETE) or, by the further action of 5-lipoxygenase enzyme, to the unstable allylic epoxide intermediate LT~ (5,6-trans-oxido-7,9-trans-11,14-cis-eicosatetraenoic acids (3). LTA4 may be transformed either to several distinct 5,12-dihydroxyeicosatetraenoic acids (4); to a specific diHETE, LTB4 (5S-12R-dyhydroxy-16,14-ciseicosatetraenoic acid); or, alternatively, to LTC4 (5S-hydroxy-6R-glutathionyl-7,9-trans11,14-cis-eicosatetraenoic acid). LTC4 is synthesized from LTA4 by the addition of glutathione to the sixth position, through the action of the enzyme glutathione S-transferase (5). The removal of a glutamic acid residue from LTC4 (5S-hydroxy-6R-S-cysteinylglycyl7 ,9-trans-11 ,14-eicosatetraenoic acid) (6). LTD4 may be further converted through the loss of a glycinyl residue to its 6 cysteinyl analog LTE 4 (5S-hydroxy-6R-S-cysteinyl-7,9trans-11,14-cis-eicosatetraenoic acid) (7). LTC4 , LTD4 , and LTE4 are also termed "sulphidopeptide leukotrienes" or "cysteinyl leukotrienes" because each contains a thioetherlinked peptide. LTC4 has been shown to be synthesized by eosinophils (8, 9), mast cells (10), macrophages and monocytes (2), as well as basophils (11). The production of LTs in lung tissue after challenge in vitro (12) and their presence in bronchoalveolar lavage fluid from asthmatic patients (13) have also been shown, suggesting their participation in the events underlying asthma.
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SUMMARY Leukotrienes (LTs),in particular LTC4 , LTD4 , and LTE4 , have been shown to be capable of participating in the induction of three related processes observed during the immediate reaction in bronchial asthma: edema formation, mucus secretion, and muscle contraction. Despite impressive evidence potentially implicating the LTs, the role of LTs in asthma is still unproved, and a positive answer to their critical actions in causing airflow obstruction will require studies with specific antagonists. AM REV RESPIR DIS 1991; 143:S96-S99
Actions of SUlphidopeptide Leukotrienes in Asthma The putative roles of LTs as mediators of bronchial asthma have been demonstrated by studies showing the presence of sulphidopeptide LTsin the sputum (14), urine (15), bronchoalveolar lavage fluid (13),plasma (16),and nasal secretions (17) of asthmatic patients. Furthermore, fragments of lung (12)and peripheral blood leukocytes from allergic asthmatic patients (18) have been shown to be able to release LTsafter specific antigen challenge
in vitro. The airflow obstruction in bronchial asthma is attributable to four major components: swelling of the airway wall, increased luminal secretions, increased inflammatory cells in the airway walls, and muscle contraction (19). The immediate asthmatic response after allergen challenge is undeniably due to allergen-IgE-induced mast-cell degranulation. The airflow obstruction is evident within minutes and is due to swelling, vasodilation, muscle constriction, and increased mucus secretion. Mast cells release a number of chemical mediators during this phase of the allergic reaction (table 1). Although there is a great deal of redundancy and overlap in the responses elicited by these mediators (table 2), LTs are capable of participating in the elicitation.
Vascular Permeability Increased vascular permeability with exudation of plasma into the airway wall and lumen may play an important role in the pathogenesis of bronchial asthma (20). Vascular permeability occurs at the site of postcapillary venules and is due to the formation of endothelial gaps through which macromolecules extravasate, attract water, and cause edema formation (21). In the rat, passively sensitized airways in vivo rapidly undergo a process of increased vascular permeability after allergen challenge (22). The responsive blood vesselsare postcapillary venules located just beneath the epithelial basement membrane. The resultant edema fluid causes airway obstruction and leads to the rapid extravasation of plasma proteins into the airway lumin. Histamine, LTs,substance P, and selected other compounds are able to
stimulate the increased vascular permeability (table 2) (21).Studies in guinea pig (23-26), rat (27), or hamster cheek pouch (28) demonstrate the extravasation of markers such as Evans blue dye, 131 1_or 1251-labeled albumin, or fluorescein-conjugated macromolecules through the microvasculature after either intradermal injection or topical application of LTC4 , LTD4 , or LTE 4 • Most of these studies indicate a much higher potency for the sulphidopeptide LTs in inducing an increase in vascular permeability as compared with histamine. The local effects of LTC4 , LTD4 , and LTE 4 have been investigated in humans (29,30) and demonstrated that a wheal and flare reaction is caused by intradermal LTs. The administration of 1 umol/site ofLTC4 , LTD4 , or LTE4 was shown to be able to elicit erythema and whealing within 2 min, the former persisting for more than 2 h, the latter for 6 h (30). More recently, the effects of inflammatory mediators on airway microvascular permeability has also been evaluated in the guinea pig's nasal mucosa, larynx, trachea, main bronchi, and intrapulmonary airways by measuring the extravasation of intravenously administered Evans blue dye (31). LTD 4 , as well as PAF, were shown to cause increased microvascular leakage throughout the respiratory tract, unlike histamine, which failed to cause a significant increase in dye extravasation in the intrapulmonary airways. PAF was shown to exert the most potent activity, being approximately lO-fold more potent than LTD4 and 1,ODD-fold more potent than histamine in the trachea.
Mucus Secretion The excessive production of mucus is an important feature of bronchial asthma as well 1 From the Allergic Disease Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland. 2 Correspondence should be addressed to Michael A. Kaliner, M.D., National Institutes of Health, 9000 Rockville Pike, Bldg. 10, llC205, Bethesda, MD 20892. Requests for reprints should be addressed to Paul Rubin, M.D., Immunoscience Venture Head, Abbott Laboratories, One Abbott Park Road, Abbott Park, IL 60064-3500.
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TABLE 1 MAST CELL-DERIVED MEDIATORS Preformed rapidly released under physiologic conditions: Histamine Eosinophil chemotactic factors of anaphylaxis Neutrophil chemotactic factors Kininogenase Arylsulfatase A Secondary or newly generated mediators: Superoxide and other reactive oxygen species Leukotrienes C4 , D4 , E4 Prostaglandins Monohydroxyeicosatetraenoic acids Hydroperoxyeicosatetraenoic acids Hydroxyheptadecatetraenoic acid Thromboxanes Prostaglandin-generating factor of anaphylaxis Adenosine Bradykinin Platelet-activating factor Granule-associated mediators: Heparin or other proteoglycans Tryptase Chymotryptic proteinase Arylsulfatase B Inflammatory factors of anaphylaxis Peroxidase Superoxide dismutase
TABLE 2 PATHOLOGIC CHANGES IN ASTHMA AND THE MEDIATORS POSSIBLY RESPONSIBLE Pathologic Changes
Mast Cell Mediator Responsible
Bronchial smooth muscle contraction
Histamine (H 1 response) Leukotrienes C4 , D4 • E4 Prostaglandins and thromboxane A2 Bradykinin Platelet-activating factor Chymotryptic proteinase
Mucosal edema
Histamine (H1 response) Leukotrienes C4 , D4 • E4 Prostaglandin E2 Bradykinin Platelet-activating factor
Mucosal inflammation
Inflammatory factors or anaphylaxis Eosinophil chemotactic factors Neutrophil chemotactic factors Monohydroxyeicosatetraenoic acids Leukotrienes B4 Platelet-activati ng factor
Mucus secretion
Histamine (H2 response) Prostaglandins and thromboxane A2 Chymotryptic proteinase Monohydroxyeicosatetraenoic acids Leukotrienes C4 • D4 • E4 Platelet-activating factor
as of other pulmonary diseases. Mucus secretion is a major contributing factor in causing mortality in asthmatic patients (32, 33). The precise mechanisms responsible for increased mucus production have been investigated,and the association between allergic pulmonary reactions and mucorrhea suggests that immediate hypersensitivity reactions lead to the release or generation of potent secretagogues. Ll'Ca-mediated enhancement in mucus production from tracheal submucosal glands
has been demonstrated in a canine model in vivo (34), and a recent study indicates that intravenous administrations of 5-, 12-, and 15-HETE, LTD4 and LTE4 significantly increase tracheal mucous gel layer thickness in a dose-dependent manner in rats (35). In the early 1980s, a model was developed to identify factors capable of influencing mucus secretion employing human airways cultured in the presence of radiolabeled aminosugars, which become incorporated into mucous
glycoproteins (36). A study performed using this model showed that both LTC4 and LTD4 were able to produce dose-related increases in mucus production at a concentration of 1 to 1,000 picograms/ml, with a somewhat higher potency for LTD4 than for LTC4 • Both molecules were active in the quantities anticipated to be generated during allergic reactions (picogram-nanogram). LTD4 is the most potent stimulant of human airway mucus secretion that has been studied (36). More recently, the allergic mediator, platelet-activating factor (PAF), has been examined employingthe same method (37).PAF was capable of causing mucus secretion from cultured airways, but the effect was prevented when LT synthesis was prevented. Thus, it appeared that LTs not only are generated during allergicresponses, but they are also formed in response to PAF, and that increased mucus secretion would occur in both cases. Another study, evaluating the effects of LTC4 and LTD4 in stimulating secretion of glycoproteins from human bronchial mucosa in vitro, confirmed the high potency of LTs compared with that of methacholine, and furthermore demonstrated that, whereas methacholine caused the release of both glycoproteins and lysozyme, LTs induced a selectiveincrease in the release of glycoproteins but not lysozyme (38).
Muscle Contraction The role of sulphidopeptide leukotrienes in airway muscle contraction has been investigated in a wide number of studies, both in vitro and in vivo, and in animal and in human model systems. In vitro studies demonstrate the potent actions of LTs in airway constriction, particularly in human (39) and guinea-pig smooth muscle (40, 41), whereas somewhat less activity has been shown in monkey (42), rat, cat, and dog airways (43). In vitro studies on human airways from both nonasthmatic and asthmatic subjects have been performed (39, 44-49). Dalhen and coworkers (39) in 1980 compared the contractile action of LTC4 , LTD4 , and histamine in human bronchi in vitro showing that LTC4 is at least 1,000times more potent than histamine in causing muscle contraction and that LTD4 presents a potency very similar to LTC4 • Jones and colleagues (46) reported similar results in bronchial contraction for LTC4 and LTD4 , and they further extended their observations showing a marked contractile activity of LTs on human tracheal smooth muscle. LTC4 - and Lf'Da-mediated contractions of human bronchi with a lower contractile activity on human parenchymal tissue than that of histamine have been described by Hanna and coworkers (47). In contrast, Chagnon and coworkers (48) showed that LTA4 , LTC4 , and LTD4 are at least 200 times more potent than histamine in human lung parenchyma in vitro. A further study by Dahlen and coworkers (49) in 1983demonstrated in vitro the specific induction of LTC4 , LTD4 , and LTE4 in lung tissue from two asthmatic patients after anti-
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gen challenge. This study also showed that the release of these LTs was correlated with the contraction evoked by allergen in bronchi isolated from the same asthmatic subjects (49). In vivo studies in humans have been performed in both normal volunteers and asthmatic patients, confirming that LTsare a potent stimulation of airwaysmuscle, and showing that LTC4 and LTD4 are more potent bronchoconstrictors than is LTE4 , whereas LTE4 causes longer lasting contractions (50). The onset of bronchoconstrictive effects in humans are seen more rapidly for LTD4 and LTE4 (4 to 6 min) than for LTC4 (10to 20 min) (51),and, therefore, it has been suggested that LTC4 needs to be metabolized to LTD4 before it can produce its maximai effect (51). This suggestion is supported by the similar potencies of LTC4 and LTD4 (52). Although the in vivo studies in humans demonstrate that sulphidopeptide LTs elicit potent bronchoconstriction, comparison of responsiveness between asthmatic patients and healthy control subjects leads to some contradictory conclusions. In 1983, Griffin and coworkers (53) reported less bronchial hyperresponsiveness to inhaled LTD4 than to histamine (ratio, 3:100) in six subjects with bronchial asthma as compared with data previously shown in normal volunteers. In contrast, Bisgaard and colleagues (54) evaluated the reactivity to inhaled LTD4 in asthmatic patients and in a control group of healthy subjects and demonstrated that asthmatic patients are more reactive to LTD4 than are control subjects. These investigatorsobserved that the degree of reactivity was similar for LT and for histamine. Similar results also arise from a study by Smith and coworkers (55), demonstrating a 25 to 100 times higher sensitivity to inhaled LTD4 for asthmatic patients than for normal control subjects. In a subsequent study by Adelroth and colleagues (56), a linear correlation between the degree of airway responsivenessto methacholine and to inhaled LTC4 or LTD4 was observed. However, a lower relative potency of LTs in asthmatic patients was seen compared with that in normal control subjects. More recently,Davidson and coworkers (50)investigatedthe bronchoconstrictive effects of LTE4 in normal and in asthmatic subjects, finding significant differences between the two groups on the basis of FEV 1 but no significant difference when the flow rate measured at 300/0 of vital capacity from partial and maximal expiratory maneuvers (V 3 0 P and V3 0 M) was evaluated. Therefore, these investigators suggested that the degree of responsiveness to LTs may appear substantially different when different parameters are considered for the assessment of airway responsiveness. A further study by O'Hickey and colleagues (57) showed a correlation between the dose of LTE4 leading to a fall in specific airway conductance with both histamine and methacholine. Analysis of these studies suggest that there is less of a difference in airway reactivity in asthmatics than in nonasthmatic control subjects to LTs than to other agonists. It has been
suggested that this differential sensibility might be related to the underlying role of LT in actually causing airway reactivity. Conclusion
Allergic reactions lead to both immediate and late-phase allergic reactions. The airflow obstruction observed in the immediate reaction is due to three related processes: edema, mucus secretion, and muscle contraction. Sulphidopeptide-LTs are capable of participating in the induction of all three processes, and the potency of LTs is such that they may be of paramount importance. Whereas antihistamines have proved very useful in preventing the symptoms of allergic rhinitis, they have had less impact on asthma. One possibility is that the lung tissue is more responsive to the LTs relative to histamine or that relatively more LTs are released in the lung. Lung mast cells may generate more LTs than nasal mast cells, or the responding tissue may be more sensitive to LTs than in the nasal mucosa. Of the three contributing factors of airflow obstruction, LTs are certainly more active than histamine on a molar basis in causing mucus secretion and small airways muscle contraction. The answer to the critical role LTs play in causing airflow obstruction will require a potent and specific antagonist. Preliminary data with several LT antagonists suggest that they havesome potential for effectivetreatment of asthma, but this possibility remains to be proved. Until such time, the role of LTs in asthma remains provocative. References 1. Kellaway CH, Trethewie RE. The liberation of a slow reacting smooth muscle stimulating substance of anaphylaxis. Q 1 Exp Physiol 1940; 30:121-45. 2. Samuelsson B. Leukotrienes: mediators of immediate hypersensitivity reactions and inflammation. Science 1983; 220:568-75. 3. Radmark D, Malmsten C, Samuelsson B, Goto G, Marfat A, Corey Ef. Leukotriene A. Isolation from human polymorphonuclear leukocytes.1 Biol Chern 1980; 255:11828-31. 4. Radmark D, Malmesten C, Samuelsson B, et aJ. Leukotriene A: sterochemistry and conversion to leukotriene B. Biochem Biophys Res Commun 1980; 92:954-61. 5. Murphy RC, Hammarstrom S, Samuelsson B. Leukotriene C: a slow reacting substance from murine mastocytoma cells. Proc Nat! Acad Sci USA 1979; 76:4275-9. 6. Orning L, Hammarstrom S, Samuelsson B. Leukotriene D: a slow reacting substance from rat basophilic leukemia cells. Proc Natl Acad Sci USA 1980; 7:2014-7. 7. Parker CW, Koch D, Huber MM, Falkenhein SF. Formation of slow-reacting substance of anaphylaxis (leukotriene E) in human plasma. Biochern Biophys Res Commun 1980; 97:1038-46. 8. Weller PK, Lee CW, Foster DW, Corey El, Austen KF, LewisRA. Generation and metabolism of 5-lipoxygenase pathway leukotrienes by human eosinophils: predominant production of leukotriene C 4 • Proc Nat! Acad Sci USA 1983; 80:7626-30. 9. Jorg A, Henderson WR, Murphy RC, Klebanoff Sl. Leukotriene generation by eosinophils. 1 Exp Med 1982; 155:390-402. 10. Lewis RA, Soter NA, Diamond PT, Austen
KF, Oates lA, Roberts LJ II. Prostaglandin n, generation after activation of rat and human mast cells with anti-IgE. J Immunol1982; 129:1627-31. 11. MacGlashan DW Jr, Schleimer RP, Peters SP, et al. Comparative studies of human basophils and mast cells. Fed Proc 1983; 42:2504-9. 12. Dahlen SE, Hansson G, Hedqvist P, Bjork T, Granstrom E, Dahlen B.Allergen challenge of lung tissue from asthmatics elicits bronchial contraction that correlates with release of leukotrienes C4 , D4 , and E 4 • Proc Natl Acad Sci USA 1983;80:1712-6. 13. WardlawAl, Hay H, Cromwell0, Collins lW, KayAB. Leukotrienes, LTC and LTB4 in bronchoalveolar lavage in bronchial asthma and other respiratory diseases. 1 Allergy Clin Immunol 1989; 84:19-26. 14. Lam S, Chan H, LeRiche .IC, Chan-Yeung M, Salari H. Release of leukotrienes in patients with bronchial asthma. 1 Allergy Clin Immunol 1988; 81:1711-7. 15. Taylor GW, Taylor I, Black P, et al. Urinary leukotriene E 4 after antigen challenge in acute asthma and in allergicrhinitis. Lancet 1989; 1:584-8. 16. Okubo T, Takahashi H, Sumitano M, Shimdoh K, Suzuki S. Plasma levels of leukotrienes C4 and D4 during wheezing attack in asthmatic patients. Int Arch Allergy Appl Immunol 1987; 84:149-55. 17. Ferreri NR, Howland WC, Stevenson DD, Spiegelberg HL. Release of leukotrienes, prostaglandins, and histamine into nasal secretion of aspirin-sensitiveasthmatics during reaction to aspirin. Am Rev Respir Dis 1988; 137:847-54. 18. Mita H, Yiu Y, Yasueda H, Kajita T, Saito, Shida T. Allergen induced histamine released and immunoreactive-leukotriene C4 generation from leukocytes in mite sensitive asthmatic patients. Prostaglandins 1986; 31:869-86. 19. Kaliner M, Eggleston PA, Mathews KP. Rhinitis and asthma. lAMA 1987; 258:2851-71. 20. Hogg rc, Pare PD, Moreno R. The effect of submucosal edema on airway resistance. Am Rev Respir Dis 1987; 135(Suppl:54-6). 21. Kaliner MA, Basic mechanisms in asthma: An emergine - and personal- view. 1 Respir Dis 1987; 135(Suppl:6). 22. Didier A, Kowalski ML, lay 1, Kaliner MA. Neurogenic inflammation, vascular permeability and mast cells. Capsaicin desensitization fails to influence IgE-anti-DNP-induced vascular permeability in rat airways. Am Rev Respir Dis 1990; 141:398-406. 23. Lewis RA, Drazen 1M, Corey E, Austen KF. Structural and functional characteristics of the leukotriene components of slow reacting substance of anaphylaxis. In: Piper PJ, ed. SRS-A and leukotrienes. New York: John Wiley, 1981; 101-17. 24. Peck MJ, Piper Pl, Williams rr. The effects of leukotrienes C4 and D4 on the microvasculature of guinea pigs. Prostaglandins 1981; 21:315-21. 25. Williams TJ, Piper PJ. The actions of chemically pure SRS-A in the microcirculation in vivo. Prostaglandins 1980; 19:779-89. 26. Hua X-Y, Dahlen SE, Lundberg 1M, Hedqvist P. Leukotrienes C 4 , D4 , and E 4 cause widespread and extensive plasma extravasation in the guinea pig. Naunyn Schmiedebergs Arch Pharmacol1985; 330:136-41. 27. Ueno A, Tanaka K, Katori M, Arai Y.Species differences in increased vascular permeability by synthetic leukotrienes C 4 and D4 • Prostaglandins 1981; 21:637-48. 28. Dahlen SE, Bjork J, Hedqvist P, et al. Leukotrienes promote plasma leakage and leukocyte adhesion in postcapillary venules. In vivo effects with relevanceto the acute inflammatory response. Proc Natl Acad Sci USA 1981; 78:3887-91. 29. Camp RDR, Coutts AA, Greaves MW, Kay
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AB, Walfort MJ. Responses of human skin to intradermal injection of leukotrienes C 4 , D 4 , and B4 • Br J Pharmacol 1980; 80:497-502. 30. Soter NA, Lewis RA, Corey EJ, Austen KF. Local effects of synthetic leukotrienes (LTC4 , LTD4 , LTE4 , and LTB4 ) in human skin. J Invest Dermatol 1983; 80:115-9. 31. Evans TW, Rogers DF, Aursudkij B, Chung KF, Barnes PJ. Regional and time dependent effects of inflammatory mediators on airway microvascular permeability in the guinea pig. Clin Sci 1989; 76:479-85. 32. Kaliner MA, Blennerhasset J, Austen KF. Bronchial asthma. In: Meisher PA, MullerEberhard JJ, eds. Textbook of immunopathology. New York: Grune & Stratton, 1976; 387-401. 33. Messer JW, Peters GA, Bennet WA. Causes of death and pathologic findings in 304 cases of bronchial asthma. Dis Chest 1960; 38:616-24. 34. Johnson HG, Chinn RA, Chow AW, Bach MK, Nadel JA. Leukotriene-C, enhances mucus production from submucosal glands in canine trachea in vivo. Int J Immunopharmacol1983; 5:391-6. 35. Yanni JM, Foxwell MH, Whitman LL, Smith WL, Nolan JC. Effect of intravenously administered lipoxygenase metabolites on rat tracheal mucous gel layer thickness. Int Arch Allergy Appl Immunol 1989; 90:307-9. 36. Marom Z, Shelhamer JH, Bach MK, Morton DR, Kaliner MA. Slow reacting substances, leukotrienes C 4 and D 4 , increase the release of mucus from human airways in vitro. Am Rev Respir Dis 1982: 126:449-51. 37. Lundgren JD, Kaliner M, Logan C, Shelhamer JH. Platelet activating factor and tracheobronchial respiratory glycoconjugate release in feline and human explants: involvement of lipoxygenase pathway. Agent Actions 1990; 30:329-37. 38. Coles SJ, Neill KH, Reid LM, et at. Effects of leukotrienes C 4 and D4 on glycoprotein and lyso-
zyme secretion by human bronchial mucosa. Prostaglandins 1983; 25:155-70. 39. Dahlen SE, Hedqvist P, Hammarstrom S, Samuelsson B. Leukotrienes are potent constrictors of human bronchi. Nature 1980; 228:484-6. 40. LewisRA, Austen KF, Drazen JM, Clark DA, Marfat A, Corey EJ. Slow reacting substances of anaphylaxis: identification of leukotrienes C 1 and D from human and rat sources. Proc Natl Acad Sci USA 1980; 77:3710-4. 41. Piper PJ, Sanhoum MN, Tippins JR, Williams TJ, Palmer MA, Peck MJ. Pharmacological studies on pure SRS-A, and synthetic leukotrienes C and D 4 • In: Piper PJ, ed. SRS-A and leukotrienes. New York: John Wiley, 1981; 81-99. 42. Smedegard GP, Hedqvist GP, Dahlen SE, Hammarstrom S, Samuelsson B. Leukotriene C 4 affects pulmonary and cardiovascular dynamics in monkey. Nature 1982; 295:327-9. 43. Krell RD, Osborn R, Vickery L, et at. Contraction of isolated airways smooth muscle by synthetic leukotrienes C 4 and D4 • Prostaglandins 1981; 22:387-409. 44. Samhoun MN, Piper PJ. Comparative actions of leukotrienes in lung from various species. In: Piper PJ, ed. Leukotrienes and other lipoxygenase products. New York: John Wiley 1983; 161-77. 45. Barnes NC, Piper PJ, Costello JF. Comparative actions of inhaled leukotriene C, leukotriene D4 and histamine in normal subjects. Thorax 1984; 39:500-4. 46. Jones TR, Davis C, Daniel EE. Pharmacological study of the contractile activity of leukotriene C4 and D4 on isolated human airway smooth muscle. Can J Physiol Pharmacol 1982; 60:638-43. 47. Hanna CJ, Bach MK, Pare PD, Schellenberg RR. Slow-reactingsubstance (leukotrienes) contract human airway and pulmonary vascular smooth muscle in vitro. Nature 1981; 290:343-4.
599 48. Chagnon M, Gentile J, Gladu M, Sirois P. The mechanism of action of leukotrienes A 4 , C 4 , and D 4 on human lung parenchyma in vitro. Lung 1985; 163:55-62. 49. Dahlen SE, Hannson G, Hedqvist P, Bjorck T, Granstrom E, Dahlen B. Allergen challenge of lung tissue from asthmatics elicits bronchial constriction that correlates with the release of leukotrienes C 4 , D 4 , and D 4 • Proc Natl Acad Sci USA 1983; 80:1712-6. 50. Davidson AE, Lee TH, Scanlon PD, et at. Bronchoconstrictor effects of leukotriene E 4 in normal and asthmatic subjects. Am Rev Respir Dis 1987; 135:333-7. 51. Drazen JM. Comparative contractile responses to sulfidopeptide leukotrienes in normal and asthmatic human subjects. Ann NY Acad Sci 1988; 524:289-97. 52. Piper PJ. Leukotrienes and airways. Eur J Anaesthesiol 1989; 6:241-55. 53. Griffin M, Weiss JW, Leitch AG. Effects of leukotriene D on the airways in asthma. N Engl J Med 1983; 308:436-9. 54. Bisgaard H, Groth S, Masden F. Bronchial hyperreactivity to leukotriene D 4 in exogenous asthma. Br Med J 1985; 290:1468-71. 55. Smith LJ, Greenberger PA, Patterson R, Krell RD, Berstein PRoThe effect of inhaled leukotriene D4 in humans. Am Rev Respir Dis 1985;131:368-72. 56. Adelroth E, Morris MM, Hargreave FE, O'Byrne PM. Airways responsiveness to leukotrienes C 4 and D4 and to methacholine in patients with asthma and normal controls. N Engl J Med 1986; 315:480-4. 57. O'Hickey SP, Arm PJ, Rees PJ, Spur BW,Lee TH. The relative responsiveness to inhaled leukotriene E 4 , methacholine and histamine in normal and asthmatic subjects. Eur Respir J 1988; 1:913-7.
Introduction The relevance of slow-reacting substance of anaphylaxis (SRS-A) in the pathogenesis of bronchial asthma was suggested almost 50 yr ago by Kellaway and Trethewie (1). Since that original report, many studies have investigated the actions of SRS-A in the asthmatic lung, showing its possible contribution to some of the features of asthma. SRS-A is now recognized to be made up of the leukotrienes (LTs) C 4 , D 4 , and E 4 , a series of closely related conjugated trienes derived from arachidonic acid. The purpose of this review is to briefly summarize the recent literature on leukotrienes and asthma from a pathogenetic viewpoint.
Structure and Synthesis LTsare derived from arachidonic acid (AA), a ubiquitous, polyunsatured, 20-carbon fatty acid (5,8,11,14 cis-eicosatetraenoic acid) generated through the 5-lipoxygenase pathway (2). The unstable 5 S-hydroperoxy-6,8-trans-11,14 cis-eicosatetraenoic acid (5-HPETE) is the first intermediate synthesized through the 5-lipoxygenase enzyme system starting from AA released from cell membranes by the action of the enzyme phospholipase A 2 (3). 5-HPETE can be converted either to 5-hydroxyeicosatetraenoic acid (5 HETE) or, by the further action of 5-lipoxygenase enzyme, to the unstable allylic epoxide intermediate LT~ (5,6-trans-oxido-7,9-trans-11,14-cis-eicosatetraenoic acids (3). LTA4 may be transformed either to several distinct 5,12-dihydroxyeicosatetraenoic acids (4); to a specific diHETE, LTB4 (5S-12R-dyhydroxy-16,14-ciseicosatetraenoic acid); or, alternatively, to LTC4 (5S-hydroxy-6R-glutathionyl-7,9-trans11,14-cis-eicosatetraenoic acid). LTC4 is synthesized from LTA4 by the addition of glutathione to the sixth position, through the action of the enzyme glutathione S-transferase (5). The removal of a glutamic acid residue from LTC4 (5S-hydroxy-6R-S-cysteinylglycyl7 ,9-trans-11 ,14-eicosatetraenoic acid) (6). LTD4 may be further converted through the loss of a glycinyl residue to its 6 cysteinyl analog LTE 4 (5S-hydroxy-6R-S-cysteinyl-7,9trans-11,14-cis-eicosatetraenoic acid) (7). LTC4 , LTD4 , and LTE4 are also termed "sulphidopeptide leukotrienes" or "cysteinyl leukotrienes" because each contains a thioetherlinked peptide. LTC4 has been shown to be synthesized by eosinophils (8, 9), mast cells (10), macrophages and monocytes (2), as well as basophils (11). The production of LTs in lung tissue after challenge in vitro (12) and their presence in bronchoalveolar lavage fluid from asthmatic patients (13) have also been shown, suggesting their participation in the events underlying asthma.
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SUMMARY Leukotrienes (LTs),in particular LTC4 , LTD4 , and LTE4 , have been shown to be capable of participating in the induction of three related processes observed during the immediate reaction in bronchial asthma: edema formation, mucus secretion, and muscle contraction. Despite impressive evidence potentially implicating the LTs, the role of LTs in asthma is still unproved, and a positive answer to their critical actions in causing airflow obstruction will require studies with specific antagonists. AM REV RESPIR DIS 1991; 143:S96-S99
Actions of SUlphidopeptide Leukotrienes in Asthma The putative roles of LTs as mediators of bronchial asthma have been demonstrated by studies showing the presence of sulphidopeptide LTsin the sputum (14), urine (15), bronchoalveolar lavage fluid (13),plasma (16),and nasal secretions (17) of asthmatic patients. Furthermore, fragments of lung (12)and peripheral blood leukocytes from allergic asthmatic patients (18) have been shown to be able to release LTsafter specific antigen challenge
in vitro. The airflow obstruction in bronchial asthma is attributable to four major components: swelling of the airway wall, increased luminal secretions, increased inflammatory cells in the airway walls, and muscle contraction (19). The immediate asthmatic response after allergen challenge is undeniably due to allergen-IgE-induced mast-cell degranulation. The airflow obstruction is evident within minutes and is due to swelling, vasodilation, muscle constriction, and increased mucus secretion. Mast cells release a number of chemical mediators during this phase of the allergic reaction (table 1). Although there is a great deal of redundancy and overlap in the responses elicited by these mediators (table 2), LTs are capable of participating in the elicitation.
Vascular Permeability Increased vascular permeability with exudation of plasma into the airway wall and lumen may play an important role in the pathogenesis of bronchial asthma (20). Vascular permeability occurs at the site of postcapillary venules and is due to the formation of endothelial gaps through which macromolecules extravasate, attract water, and cause edema formation (21). In the rat, passively sensitized airways in vivo rapidly undergo a process of increased vascular permeability after allergen challenge (22). The responsive blood vesselsare postcapillary venules located just beneath the epithelial basement membrane. The resultant edema fluid causes airway obstruction and leads to the rapid extravasation of plasma proteins into the airway lumin. Histamine, LTs,substance P, and selected other compounds are able to
stimulate the increased vascular permeability (table 2) (21).Studies in guinea pig (23-26), rat (27), or hamster cheek pouch (28) demonstrate the extravasation of markers such as Evans blue dye, 131 1_or 1251-labeled albumin, or fluorescein-conjugated macromolecules through the microvasculature after either intradermal injection or topical application of LTC4 , LTD4 , or LTE 4 • Most of these studies indicate a much higher potency for the sulphidopeptide LTs in inducing an increase in vascular permeability as compared with histamine. The local effects of LTC4 , LTD4 , and LTE 4 have been investigated in humans (29,30) and demonstrated that a wheal and flare reaction is caused by intradermal LTs. The administration of 1 umol/site ofLTC4 , LTD4 , or LTE4 was shown to be able to elicit erythema and whealing within 2 min, the former persisting for more than 2 h, the latter for 6 h (30). More recently, the effects of inflammatory mediators on airway microvascular permeability has also been evaluated in the guinea pig's nasal mucosa, larynx, trachea, main bronchi, and intrapulmonary airways by measuring the extravasation of intravenously administered Evans blue dye (31). LTD 4 , as well as PAF, were shown to cause increased microvascular leakage throughout the respiratory tract, unlike histamine, which failed to cause a significant increase in dye extravasation in the intrapulmonary airways. PAF was shown to exert the most potent activity, being approximately lO-fold more potent than LTD4 and 1,ODD-fold more potent than histamine in the trachea.
Mucus Secretion The excessive production of mucus is an important feature of bronchial asthma as well 1 From the Allergic Disease Section, Laboratory of Clinical Investigation, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland. 2 Correspondence should be addressed to Michael A. Kaliner, M.D., National Institutes of Health, 9000 Rockville Pike, Bldg. 10, llC205, Bethesda, MD 20892. Requests for reprints should be addressed to Paul Rubin, M.D., Immunoscience Venture Head, Abbott Laboratories, One Abbott Park Road, Abbott Park, IL 60064-3500.
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TABLE 1 MAST CELL-DERIVED MEDIATORS Preformed rapidly released under physiologic conditions: Histamine Eosinophil chemotactic factors of anaphylaxis Neutrophil chemotactic factors Kininogenase Arylsulfatase A Secondary or newly generated mediators: Superoxide and other reactive oxygen species Leukotrienes C4 , D4 , E4 Prostaglandins Monohydroxyeicosatetraenoic acids Hydroperoxyeicosatetraenoic acids Hydroxyheptadecatetraenoic acid Thromboxanes Prostaglandin-generating factor of anaphylaxis Adenosine Bradykinin Platelet-activating factor Granule-associated mediators: Heparin or other proteoglycans Tryptase Chymotryptic proteinase Arylsulfatase B Inflammatory factors of anaphylaxis Peroxidase Superoxide dismutase
TABLE 2 PATHOLOGIC CHANGES IN ASTHMA AND THE MEDIATORS POSSIBLY RESPONSIBLE Pathologic Changes
Mast Cell Mediator Responsible
Bronchial smooth muscle contraction
Histamine (H 1 response) Leukotrienes C4 , D4 • E4 Prostaglandins and thromboxane A2 Bradykinin Platelet-activating factor Chymotryptic proteinase
Mucosal edema
Histamine (H1 response) Leukotrienes C4 , D4 • E4 Prostaglandin E2 Bradykinin Platelet-activating factor
Mucosal inflammation
Inflammatory factors or anaphylaxis Eosinophil chemotactic factors Neutrophil chemotactic factors Monohydroxyeicosatetraenoic acids Leukotrienes B4 Platelet-activati ng factor
Mucus secretion
Histamine (H2 response) Prostaglandins and thromboxane A2 Chymotryptic proteinase Monohydroxyeicosatetraenoic acids Leukotrienes C4 • D4 • E4 Platelet-activating factor
as of other pulmonary diseases. Mucus secretion is a major contributing factor in causing mortality in asthmatic patients (32, 33). The precise mechanisms responsible for increased mucus production have been investigated,and the association between allergic pulmonary reactions and mucorrhea suggests that immediate hypersensitivity reactions lead to the release or generation of potent secretagogues. Ll'Ca-mediated enhancement in mucus production from tracheal submucosal glands
has been demonstrated in a canine model in vivo (34), and a recent study indicates that intravenous administrations of 5-, 12-, and 15-HETE, LTD4 and LTE4 significantly increase tracheal mucous gel layer thickness in a dose-dependent manner in rats (35). In the early 1980s, a model was developed to identify factors capable of influencing mucus secretion employing human airways cultured in the presence of radiolabeled aminosugars, which become incorporated into mucous
glycoproteins (36). A study performed using this model showed that both LTC4 and LTD4 were able to produce dose-related increases in mucus production at a concentration of 1 to 1,000 picograms/ml, with a somewhat higher potency for LTD4 than for LTC4 • Both molecules were active in the quantities anticipated to be generated during allergic reactions (picogram-nanogram). LTD4 is the most potent stimulant of human airway mucus secretion that has been studied (36). More recently, the allergic mediator, platelet-activating factor (PAF), has been examined employingthe same method (37).PAF was capable of causing mucus secretion from cultured airways, but the effect was prevented when LT synthesis was prevented. Thus, it appeared that LTs not only are generated during allergicresponses, but they are also formed in response to PAF, and that increased mucus secretion would occur in both cases. Another study, evaluating the effects of LTC4 and LTD4 in stimulating secretion of glycoproteins from human bronchial mucosa in vitro, confirmed the high potency of LTs compared with that of methacholine, and furthermore demonstrated that, whereas methacholine caused the release of both glycoproteins and lysozyme, LTs induced a selectiveincrease in the release of glycoproteins but not lysozyme (38).
Muscle Contraction The role of sulphidopeptide leukotrienes in airway muscle contraction has been investigated in a wide number of studies, both in vitro and in vivo, and in animal and in human model systems. In vitro studies demonstrate the potent actions of LTs in airway constriction, particularly in human (39) and guinea-pig smooth muscle (40, 41), whereas somewhat less activity has been shown in monkey (42), rat, cat, and dog airways (43). In vitro studies on human airways from both nonasthmatic and asthmatic subjects have been performed (39, 44-49). Dalhen and coworkers (39) in 1980 compared the contractile action of LTC4 , LTD4 , and histamine in human bronchi in vitro showing that LTC4 is at least 1,000times more potent than histamine in causing muscle contraction and that LTD4 presents a potency very similar to LTC4 • Jones and colleagues (46) reported similar results in bronchial contraction for LTC4 and LTD4 , and they further extended their observations showing a marked contractile activity of LTs on human tracheal smooth muscle. LTC4 - and Lf'Da-mediated contractions of human bronchi with a lower contractile activity on human parenchymal tissue than that of histamine have been described by Hanna and coworkers (47). In contrast, Chagnon and coworkers (48) showed that LTA4 , LTC4 , and LTD4 are at least 200 times more potent than histamine in human lung parenchyma in vitro. A further study by Dahlen and coworkers (49) in 1983demonstrated in vitro the specific induction of LTC4 , LTD4 , and LTE4 in lung tissue from two asthmatic patients after anti-
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gen challenge. This study also showed that the release of these LTs was correlated with the contraction evoked by allergen in bronchi isolated from the same asthmatic subjects (49). In vivo studies in humans have been performed in both normal volunteers and asthmatic patients, confirming that LTsare a potent stimulation of airwaysmuscle, and showing that LTC4 and LTD4 are more potent bronchoconstrictors than is LTE4 , whereas LTE4 causes longer lasting contractions (50). The onset of bronchoconstrictive effects in humans are seen more rapidly for LTD4 and LTE4 (4 to 6 min) than for LTC4 (10to 20 min) (51),and, therefore, it has been suggested that LTC4 needs to be metabolized to LTD4 before it can produce its maximai effect (51). This suggestion is supported by the similar potencies of LTC4 and LTD4 (52). Although the in vivo studies in humans demonstrate that sulphidopeptide LTs elicit potent bronchoconstriction, comparison of responsiveness between asthmatic patients and healthy control subjects leads to some contradictory conclusions. In 1983, Griffin and coworkers (53) reported less bronchial hyperresponsiveness to inhaled LTD4 than to histamine (ratio, 3:100) in six subjects with bronchial asthma as compared with data previously shown in normal volunteers. In contrast, Bisgaard and colleagues (54) evaluated the reactivity to inhaled LTD4 in asthmatic patients and in a control group of healthy subjects and demonstrated that asthmatic patients are more reactive to LTD4 than are control subjects. These investigatorsobserved that the degree of reactivity was similar for LT and for histamine. Similar results also arise from a study by Smith and coworkers (55), demonstrating a 25 to 100 times higher sensitivity to inhaled LTD4 for asthmatic patients than for normal control subjects. In a subsequent study by Adelroth and colleagues (56), a linear correlation between the degree of airway responsivenessto methacholine and to inhaled LTC4 or LTD4 was observed. However, a lower relative potency of LTs in asthmatic patients was seen compared with that in normal control subjects. More recently,Davidson and coworkers (50)investigatedthe bronchoconstrictive effects of LTE4 in normal and in asthmatic subjects, finding significant differences between the two groups on the basis of FEV 1 but no significant difference when the flow rate measured at 300/0 of vital capacity from partial and maximal expiratory maneuvers (V 3 0 P and V3 0 M) was evaluated. Therefore, these investigators suggested that the degree of responsiveness to LTs may appear substantially different when different parameters are considered for the assessment of airway responsiveness. A further study by O'Hickey and colleagues (57) showed a correlation between the dose of LTE4 leading to a fall in specific airway conductance with both histamine and methacholine. Analysis of these studies suggest that there is less of a difference in airway reactivity in asthmatics than in nonasthmatic control subjects to LTs than to other agonists. It has been
suggested that this differential sensibility might be related to the underlying role of LT in actually causing airway reactivity. Conclusion
Allergic reactions lead to both immediate and late-phase allergic reactions. The airflow obstruction observed in the immediate reaction is due to three related processes: edema, mucus secretion, and muscle contraction. Sulphidopeptide-LTs are capable of participating in the induction of all three processes, and the potency of LTs is such that they may be of paramount importance. Whereas antihistamines have proved very useful in preventing the symptoms of allergic rhinitis, they have had less impact on asthma. One possibility is that the lung tissue is more responsive to the LTs relative to histamine or that relatively more LTs are released in the lung. Lung mast cells may generate more LTs than nasal mast cells, or the responding tissue may be more sensitive to LTs than in the nasal mucosa. Of the three contributing factors of airflow obstruction, LTs are certainly more active than histamine on a molar basis in causing mucus secretion and small airways muscle contraction. The answer to the critical role LTs play in causing airflow obstruction will require a potent and specific antagonist. Preliminary data with several LT antagonists suggest that they havesome potential for effectivetreatment of asthma, but this possibility remains to be proved. Until such time, the role of LTs in asthma remains provocative. References 1. Kellaway CH, Trethewie RE. The liberation of a slow reacting smooth muscle stimulating substance of anaphylaxis. Q 1 Exp Physiol 1940; 30:121-45. 2. Samuelsson B. Leukotrienes: mediators of immediate hypersensitivity reactions and inflammation. Science 1983; 220:568-75. 3. Radmark D, Malmsten C, Samuelsson B, Goto G, Marfat A, Corey Ef. Leukotriene A. Isolation from human polymorphonuclear leukocytes.1 Biol Chern 1980; 255:11828-31. 4. Radmark D, Malmesten C, Samuelsson B, et aJ. Leukotriene A: sterochemistry and conversion to leukotriene B. Biochem Biophys Res Commun 1980; 92:954-61. 5. Murphy RC, Hammarstrom S, Samuelsson B. Leukotriene C: a slow reacting substance from murine mastocytoma cells. Proc Nat! Acad Sci USA 1979; 76:4275-9. 6. Orning L, Hammarstrom S, Samuelsson B. Leukotriene D: a slow reacting substance from rat basophilic leukemia cells. Proc Natl Acad Sci USA 1980; 7:2014-7. 7. Parker CW, Koch D, Huber MM, Falkenhein SF. Formation of slow-reacting substance of anaphylaxis (leukotriene E) in human plasma. Biochern Biophys Res Commun 1980; 97:1038-46. 8. Weller PK, Lee CW, Foster DW, Corey El, Austen KF, LewisRA. Generation and metabolism of 5-lipoxygenase pathway leukotrienes by human eosinophils: predominant production of leukotriene C 4 • Proc Nat! Acad Sci USA 1983; 80:7626-30. 9. Jorg A, Henderson WR, Murphy RC, Klebanoff Sl. Leukotriene generation by eosinophils. 1 Exp Med 1982; 155:390-402. 10. Lewis RA, Soter NA, Diamond PT, Austen
KF, Oates lA, Roberts LJ II. Prostaglandin n, generation after activation of rat and human mast cells with anti-IgE. J Immunol1982; 129:1627-31. 11. MacGlashan DW Jr, Schleimer RP, Peters SP, et al. Comparative studies of human basophils and mast cells. Fed Proc 1983; 42:2504-9. 12. Dahlen SE, Hansson G, Hedqvist P, Bjork T, Granstrom E, Dahlen B.Allergen challenge of lung tissue from asthmatics elicits bronchial contraction that correlates with release of leukotrienes C4 , D4 , and E 4 • Proc Natl Acad Sci USA 1983;80:1712-6. 13. WardlawAl, Hay H, Cromwell0, Collins lW, KayAB. Leukotrienes, LTC and LTB4 in bronchoalveolar lavage in bronchial asthma and other respiratory diseases. 1 Allergy Clin Immunol 1989; 84:19-26. 14. Lam S, Chan H, LeRiche .IC, Chan-Yeung M, Salari H. Release of leukotrienes in patients with bronchial asthma. 1 Allergy Clin Immunol 1988; 81:1711-7. 15. Taylor GW, Taylor I, Black P, et al. Urinary leukotriene E 4 after antigen challenge in acute asthma and in allergicrhinitis. Lancet 1989; 1:584-8. 16. Okubo T, Takahashi H, Sumitano M, Shimdoh K, Suzuki S. Plasma levels of leukotrienes C4 and D4 during wheezing attack in asthmatic patients. Int Arch Allergy Appl Immunol 1987; 84:149-55. 17. Ferreri NR, Howland WC, Stevenson DD, Spiegelberg HL. Release of leukotrienes, prostaglandins, and histamine into nasal secretion of aspirin-sensitiveasthmatics during reaction to aspirin. Am Rev Respir Dis 1988; 137:847-54. 18. Mita H, Yiu Y, Yasueda H, Kajita T, Saito, Shida T. Allergen induced histamine released and immunoreactive-leukotriene C4 generation from leukocytes in mite sensitive asthmatic patients. Prostaglandins 1986; 31:869-86. 19. Kaliner M, Eggleston PA, Mathews KP. Rhinitis and asthma. lAMA 1987; 258:2851-71. 20. Hogg rc, Pare PD, Moreno R. The effect of submucosal edema on airway resistance. Am Rev Respir Dis 1987; 135(Suppl:54-6). 21. Kaliner MA, Basic mechanisms in asthma: An emergine - and personal- view. 1 Respir Dis 1987; 135(Suppl:6). 22. Didier A, Kowalski ML, lay 1, Kaliner MA. Neurogenic inflammation, vascular permeability and mast cells. Capsaicin desensitization fails to influence IgE-anti-DNP-induced vascular permeability in rat airways. Am Rev Respir Dis 1990; 141:398-406. 23. Lewis RA, Drazen 1M, Corey E, Austen KF. Structural and functional characteristics of the leukotriene components of slow reacting substance of anaphylaxis. In: Piper PJ, ed. SRS-A and leukotrienes. New York: John Wiley, 1981; 101-17. 24. Peck MJ, Piper Pl, Williams rr. The effects of leukotrienes C4 and D4 on the microvasculature of guinea pigs. Prostaglandins 1981; 21:315-21. 25. Williams TJ, Piper PJ. The actions of chemically pure SRS-A in the microcirculation in vivo. Prostaglandins 1980; 19:779-89. 26. Hua X-Y, Dahlen SE, Lundberg 1M, Hedqvist P. Leukotrienes C 4 , D4 , and E 4 cause widespread and extensive plasma extravasation in the guinea pig. Naunyn Schmiedebergs Arch Pharmacol1985; 330:136-41. 27. Ueno A, Tanaka K, Katori M, Arai Y.Species differences in increased vascular permeability by synthetic leukotrienes C 4 and D4 • Prostaglandins 1981; 21:637-48. 28. Dahlen SE, Bjork J, Hedqvist P, et al. Leukotrienes promote plasma leakage and leukocyte adhesion in postcapillary venules. In vivo effects with relevanceto the acute inflammatory response. Proc Natl Acad Sci USA 1981; 78:3887-91. 29. Camp RDR, Coutts AA, Greaves MW, Kay
POTENTIAL ROLES OF LEUKOTRIENES IN BRONCHIAL ASTHMA
AB, Walfort MJ. Responses of human skin to intradermal injection of leukotrienes C 4 , D 4 , and B4 • Br J Pharmacol 1980; 80:497-502. 30. Soter NA, Lewis RA, Corey EJ, Austen KF. Local effects of synthetic leukotrienes (LTC4 , LTD4 , LTE4 , and LTB4 ) in human skin. J Invest Dermatol 1983; 80:115-9. 31. Evans TW, Rogers DF, Aursudkij B, Chung KF, Barnes PJ. Regional and time dependent effects of inflammatory mediators on airway microvascular permeability in the guinea pig. Clin Sci 1989; 76:479-85. 32. Kaliner MA, Blennerhasset J, Austen KF. Bronchial asthma. In: Meisher PA, MullerEberhard JJ, eds. Textbook of immunopathology. New York: Grune & Stratton, 1976; 387-401. 33. Messer JW, Peters GA, Bennet WA. Causes of death and pathologic findings in 304 cases of bronchial asthma. Dis Chest 1960; 38:616-24. 34. Johnson HG, Chinn RA, Chow AW, Bach MK, Nadel JA. Leukotriene-C, enhances mucus production from submucosal glands in canine trachea in vivo. Int J Immunopharmacol1983; 5:391-6. 35. Yanni JM, Foxwell MH, Whitman LL, Smith WL, Nolan JC. Effect of intravenously administered lipoxygenase metabolites on rat tracheal mucous gel layer thickness. Int Arch Allergy Appl Immunol 1989; 90:307-9. 36. Marom Z, Shelhamer JH, Bach MK, Morton DR, Kaliner MA. Slow reacting substances, leukotrienes C 4 and D 4 , increase the release of mucus from human airways in vitro. Am Rev Respir Dis 1982: 126:449-51. 37. Lundgren JD, Kaliner M, Logan C, Shelhamer JH. Platelet activating factor and tracheobronchial respiratory glycoconjugate release in feline and human explants: involvement of lipoxygenase pathway. Agent Actions 1990; 30:329-37. 38. Coles SJ, Neill KH, Reid LM, et at. Effects of leukotrienes C 4 and D4 on glycoprotein and lyso-
zyme secretion by human bronchial mucosa. Prostaglandins 1983; 25:155-70. 39. Dahlen SE, Hedqvist P, Hammarstrom S, Samuelsson B. Leukotrienes are potent constrictors of human bronchi. Nature 1980; 228:484-6. 40. LewisRA, Austen KF, Drazen JM, Clark DA, Marfat A, Corey EJ. Slow reacting substances of anaphylaxis: identification of leukotrienes C 1 and D from human and rat sources. Proc Natl Acad Sci USA 1980; 77:3710-4. 41. Piper PJ, Sanhoum MN, Tippins JR, Williams TJ, Palmer MA, Peck MJ. Pharmacological studies on pure SRS-A, and synthetic leukotrienes C and D 4 • In: Piper PJ, ed. SRS-A and leukotrienes. New York: John Wiley, 1981; 81-99. 42. Smedegard GP, Hedqvist GP, Dahlen SE, Hammarstrom S, Samuelsson B. Leukotriene C 4 affects pulmonary and cardiovascular dynamics in monkey. Nature 1982; 295:327-9. 43. Krell RD, Osborn R, Vickery L, et at. Contraction of isolated airways smooth muscle by synthetic leukotrienes C 4 and D4 • Prostaglandins 1981; 22:387-409. 44. Samhoun MN, Piper PJ. Comparative actions of leukotrienes in lung from various species. In: Piper PJ, ed. Leukotrienes and other lipoxygenase products. New York: John Wiley 1983; 161-77. 45. Barnes NC, Piper PJ, Costello JF. Comparative actions of inhaled leukotriene C, leukotriene D4 and histamine in normal subjects. Thorax 1984; 39:500-4. 46. Jones TR, Davis C, Daniel EE. Pharmacological study of the contractile activity of leukotriene C4 and D4 on isolated human airway smooth muscle. Can J Physiol Pharmacol 1982; 60:638-43. 47. Hanna CJ, Bach MK, Pare PD, Schellenberg RR. Slow-reactingsubstance (leukotrienes) contract human airway and pulmonary vascular smooth muscle in vitro. Nature 1981; 290:343-4.
599 48. Chagnon M, Gentile J, Gladu M, Sirois P. The mechanism of action of leukotrienes A 4 , C 4 , and D 4 on human lung parenchyma in vitro. Lung 1985; 163:55-62. 49. Dahlen SE, Hannson G, Hedqvist P, Bjorck T, Granstrom E, Dahlen B. Allergen challenge of lung tissue from asthmatics elicits bronchial constriction that correlates with the release of leukotrienes C 4 , D 4 , and D 4 • Proc Natl Acad Sci USA 1983; 80:1712-6. 50. Davidson AE, Lee TH, Scanlon PD, et at. Bronchoconstrictor effects of leukotriene E 4 in normal and asthmatic subjects. Am Rev Respir Dis 1987; 135:333-7. 51. Drazen JM. Comparative contractile responses to sulfidopeptide leukotrienes in normal and asthmatic human subjects. Ann NY Acad Sci 1988; 524:289-97. 52. Piper PJ. Leukotrienes and airways. Eur J Anaesthesiol 1989; 6:241-55. 53. Griffin M, Weiss JW, Leitch AG. Effects of leukotriene D on the airways in asthma. N Engl J Med 1983; 308:436-9. 54. Bisgaard H, Groth S, Masden F. Bronchial hyperreactivity to leukotriene D 4 in exogenous asthma. Br Med J 1985; 290:1468-71. 55. Smith LJ, Greenberger PA, Patterson R, Krell RD, Berstein PRoThe effect of inhaled leukotriene D4 in humans. Am Rev Respir Dis 1985;131:368-72. 56. Adelroth E, Morris MM, Hargreave FE, O'Byrne PM. Airways responsiveness to leukotrienes C 4 and D4 and to methacholine in patients with asthma and normal controls. N Engl J Med 1986; 315:480-4. 57. O'Hickey SP, Arm PJ, Rees PJ, Spur BW,Lee TH. The relative responsiveness to inhaled leukotriene E 4 , methacholine and histamine in normal and asthmatic subjects. Eur Respir J 1988; 1:913-7.
