Early and late asthmatic reaction after allergen challenge

Respiratory

Medicine

( 1994) 88, 103-l 14

Early and late asthmatic reaction after allergen challenge E. J. M. WEERSINK*,

D. S. POSTMA*,

R. AALBERS~

J. G. R.

AND

DE

MONCHY~5

*Department of Pulmonology, University Hospital, Groningen, The Netherlands; TDepartment of Allergology. University Hospital, Groningen, The Netherlands, and $Asthma Centre of The Netherlands, Davos CH, Switzerland

Introduction 1950s Herxheimer (1) clearly showed that two distinct components in the obstructive response to inhaled allergens could be discerned, which he named the immediate and late reaction. But it was not until the late 1960s before Pepys (2) and de Vries and coworkers (3) started to investigate the mechanisms of the immediate and late response to inhaled allergen by drug protection studies. Based on different effects of several drugs on the immediate and late reaction they concluded that different mechanisms must underlie these response patterns. It was suggested that the immediate reaction was due to constriction of the smooth airway muscles and the late reaction the result of inflammation. Gijkemeijer (4) showed that allergen challenge also leads to an increase in airway reactivity (AR). However, he found no relationship between the increase in AR and the immediate or late response. Then, Cockcroft et al. (5) demonstrated an increase in AR in association with the late allergic response (LAR). Later studies showed that subjects with an isolated EAR also develop an increase in AR, but to a much lesser extent than patients with a LAR (6). It has now generally been accepted that the increase in AR is usually associated with increased mucosal inflammation of the airways (7). Therefore, it is intriguing that AR is already increased 3 h after allergen challenge, when the FEV, has returned to prechallenge values, thus even preceding the LAR. With the introduction of fibreoptic bonchoscopy, in recent years, broncho-alveolar lavage (BAL) and biopsies have become new research tools to study the cellular events in asthmatic airways after allergen challenge which can be investigated directly by microscopic studies including sophisticated immunohistochemistry. In

the

early

§To whom correspondence should be addressed at: University Hospital, Oostersingel 59, 9713 EZ Groningen, The Netherlands. 0954-6111/94/020103+12

$08.0010

The present review includes a summary of recent developments in knowledge on the pathogenesis of the EAR and LAR. The focus is on the pathophysiological mechanisms of the EAR, LAR and associated AR. We will also discuss the different drugs that modulate the early and late reaction and the associated AR. Allergen

inhalation

Bronchial allergen challenge in sensitized atopic asthmatics results in bronchoconstriction that develops within 10 min, reaches a maximum between 15 and 30 min, and generally resolves within l-3 h. This period of bronchoconstriction is referred to as the early allergic response, which is defined as a fall in FEV, of 1S-20% or more, or a fall of 40% or more in SGAW (8). Three to four or more hours after the onset of the EAR, a second period of bronchoconstriction may occur constituting the late allergic response (8). The duration of the LAR as measured with spirometry may be 12 h or even longer. Although the LAR need not be preceded by a clinically evident early response, isolated late reactions are rare in adults. This is in contrast with children where isolated late reactions are a frequent occurrence. Diurnal variation in airway tone and the effect of medication withdrawal may interfere with the detection of the LAR, so this can be missed or not so pronounced (8). Hence, a control day, with saline challenge must be performed in that corrections for these confounders can be made [Fig. l(a) and (b)]. Pathophysiology of the asthmatic airways after allergen challenge INFLAMMATORY

PROCESSES DURING

THE

EAR

The exact mechanisms leading to immediate airway narrowing after allergen challenge are still 0

1994 W. B. Saunders

Company

Ltd.

104

Topical Review

a -3o-

Time (min)

Time (h)

Time (min)

Time (h)

Fig. I The effects after saline challenge on lung function (FEV,) on the control day (0) after allergen challenge on the provocation day (W) and on the provocation day corrected for control day (*).

unclear. Traditionally, the EAR has been associated with the activation of pulmonary mast cells with subsequent release of preformed histamine, tryptase and de nova synthesis of spasmogenic products of the cycloxygenase pathway of arachidonic acid metaboof the lism (PGD,, TxA,, along with products S-lipoxygenase pathway (leukotrienes) (9). Mast cells may be activated to secrete their mediators by a wide variety of mechanisms, the most familiar being the

IgE-dependent process [high-affinity IgE (Fc,RI) receptor] (10). Alveolar macrophages generally have a suppressive effect, but this may be impaired in asthma after allergen exposure (11,12). The alveolar macrophage has even been incriminated in the EAR, being activated by allergens via an IgE-dependent process [low-affinity IgE (Fc,RII) receptor] and releasing both acute phase and chemotactic mediators. These

Topical Review Table I

10.5

Effect of released inflammatory mediators after allergen inhalation

Mediator

Bronchoconstriction

Histamine PGD, PGF,,

+ +

PGE, TxA, LTB, L-E,, D,, E,

+ +

PAF

+

Kinins

+

Mucus secretion

Microvascular leakage

PROCESS

BETWEEN

Source Mast cell, Basophil Mast cell, Eosinophil Epithelial cell Epithelial cell Mast cell, Alv. macro. Alv. macro. Mast cell, Epithelial cell Eosinophil Alv. macro, Eosinophil Epithelial cell Mast cell

acute phase products include the spasmogenic TxA,, TxB, LTB4 and PAF, as well as reactive oxygen species and lysosomal enzymes, which may lead to local tissue damage (13,14). In addition to alveolar macrophages, dendritic cells are also very effective antigen-presenting cells and may therefore play a very important role in the initiation of an allergeninduced response (11). Additionally, airway epithelium may also play a role in this process. After antigenic stimulation, epithelial cells are able to release LTC,, 12-HETE, PGE,, and PGF,, and chemotactic mediators such as LTB,, 15HETE and possibly PAF (15). The above mentioned inflammatory mediators have important bronchospasmogenic effects, next to their stimulatory role in mucus secretion, vasodilation, microvascular leakage and chemotaxis (Table 1). These mediators may be at least responsible for the immediate clinical reaction after allergen challenge. Moreover, release of chemotactic mediators by mast cells, alveolar macrophages, dendritic cells and epithelial cells may also be involved in the development of the LAR. More disputable is the role of T cells during the EAR. But after local allergen challenge a direct increase in CD4+ -cells was shown in BAL fluid. This provides evidence to support the role of T cells in this early state of the asthmatic response (16).

INFLAMMATORY

Chemotaxis

THE

EAR AND

LAR

The role of mast-cell-dependent products in the development of the late-phase inflammatory events after allergen challenge in atopic asthmatics is still controversial. Some studies have reported that release of mast-cell-associated high-molecular-weight neutrophil chemotactic factor (NCF) as well as

eosinophil chemotactic factor (ECF) occurs during the EAR with a close relationship of NCF to the development of the ensuing LAR (17,18). The close relationship of NCF or ECF to the LAR may be relevant to the control of the mechanisms that govern the accumulation of eosinophils in the lung (19). More recently, it has become apparent that mast cells release, in an IgE-dependent fashion, an array of cytokines such as IL-3. IL-4, IL-5, GM-CSF. These cytokines have also been implicated in the pathogenesis of late-phase inflammatory events, especially in relation to eosinophils (2(X22). Although it has been suggested that one or more of the cytokines released by mast cells are in fact NCF or ECF, it should be pointed out that cytokine release does not start until 2 h after allergen challenge while NCF or ECF release occurs much earlier (17). Additionally, it should be recognized that most of the available data are derived from in vitro studies of murine mast cell lines. These results, therefore, can not be automatically applied to the human lung mast cell, but generally indicate that release of cytokines (IL-3, IL-4, IL-5 GM-CSF) or NCF and ECF by mast cells is relevant for the development of the LAR. It is known that IL-3, IL-5 and GM-CSF are involved in the control of eosinophil degranulation, activation of mature eosinophils in terms of increased cytotoxicity and oxidative metabolism and in prolonging eosinophi1 survival in vitro (23). In bronchial lavage fluid and biopsies of the submucosa of asthmatics an increase of activated eosinophils is seen 34 h after allergen challenge, well before the late phase reaction (24,25). However, no release of cytotoxic eosinophilmediator ECP is detected in BAL fluid at this point in time. Mast cells also release IL-4 which is involved in the survival and proliferation of T-helper cells, especially the T,2 phenotype (26).

106

Topical Review

Not only mast cells, but also alveolar macrophages release a diversity of cytokines. Human alveolar macrophages produce predominantly IL-1B. IL-l expression reaches its maximum 2-3 h after in vitro stimulation. Alveolar macrophages therefore, have the capacity to initiate an inflammatory response via the release of IL-l, which may activate T cells and dendritic cells are able to release IL-I as well (11). Human tracheal and bronchial epithelial cells are capable of synthesizing IL-l and TNF after allergen stimulation. IL-l and TNF may in turn induce the production of GM-CSF, IL-6 and IL-8 from epithelial cells (27). In addition to these cytokines, chemotactic factors (LTB,, 15-HETE, PAF) are liberated from mast cells, alveolar macrophages and epithelial cells. It is known that all of the above mentioned cytokines and chemotactic mediators can recruit, prime, and activate alveolar macrophages, T cells, neutrophils, eosinophils and basophils, and can also increase immunoglobulin secretion (IgE of B cells) and regulate the proliferation of mast cells (Table 2). However, the exact mechanisms responsible for selective recruitment of inflammatory cells into the airway (sub)mucosa in allergic inflammation are not fully known. Cytokines are thought to play a role in this recruitment by upregulation of adhesion molecules for cells involved in the LAR (28,29). Three types of adhesion molecules have been observed on endothelial cells: ELAM-1 (endothelial leucocyte adhesion moleculel), ICAM(intracellular adhesion molecule-l) and VCAM- 1 (vascular cell adhesion molecule- 1). ELAM-1 is expressed on endothelial cells after stimulation with IL-l, TNF, and INF, and may be expressed at sites of allergic inflammation (30). ICAM- 1 is constitutionally expressed on endothelial cells and is markedly up-regulated in allergically inflamed tissue and after IL-l/?, TNF, and IFN, incubation (31). Endothelial expression of VCAM-I may be upregulated by IL-4 (32). It is intriguing that these cytokines, TNFa, IL-l and IL-4, which stimulate the expression of the appropriate adhesion molecules, are released by allergen triggered mast cells and other cells. This provides an important link between mast cell activation, upregulation of adhesion molecules, and subsequent T cell and eosinophil recruitment. After appropriate stimulation, ELAM-1 is maximally expressed after 46 h, returning to baseline at 24 h (30). ICAMand VCAM-1 are expressed later, reaching a maximum at 24-48 h (31,32). It could be hypothesized that ELAM-1, which is maximally upregulated at the time of the LAR, is involved in the development of the LAR, whereas ICAM-I and VCAM-1 are not, but rather support the allergen-

induced inflammatory process for a longer period of time. Furthermore, it is known that VCAM-1 binds preferentially to specific adhesion molecules of eosinophils, whereas ELAM-1 and ICAMbind to specific adhesion molecules of both eosinophils and neutrophils (25). Adhesion molecules are also expressed on leucocytes where they may act as specific ligands for the molecules described above. Three heterodimers have been described, consisting of a common P-chain (CDIS) and different a-chains LFA-1 (CD1 la), MAC-l (CDllb), and P150,95 (CDllc). CDlla,b,c, and CD18 act as specific ligands for ICAMon endothelial cells. LFA-1 has been involved in T cell adhesion. All three heterodimers are involved to varying degrees in neutrophil, eosinophil, and mononuclear cell adhesion. More recently, it has been shown in vitro that recombinant IL-3 and recombinant GM-CSF selectively enhance basophil adhesiveness to endothelial cells and expression of CD 11 b on this cell (33,34). Very late antigens (VLA) l-6 are yet another type of adhesion molecule on leucocytes. VLA-1 is expressed on activated T cells while VLA-4 has only been detected on eosinophils adherent to VCAM-I on endothelium (32). Expression of these VLA adhesion molecules on leucocytes is observed 6 h after allergen challenge. Although many of these findings were mainly obtained in in vitro studies, Wegner et al. (31) have shown that in Ascaris sensitized monkeys repeated allergen challenge caused an increase in ICAMexpression on both airway epithelium and submucosal endothelium, accompanied by eosinophilic infiltration of the mucosa and increased AR to methacholine. The latter two events were attenuated by intravenous infusion or inhalation of a blocking anti-ICAMmonoclonal antibody. These observations support the view that ICAMplays an important role in the specific eosinophilic inflammatory response after allergeninhalation. Although the kinetics of its upregulation in tissue suggest that this may be especially the case in chronic allergic inflammation. In addition to chemotactic signals released from allergically inflamed tissue, these adhesion mechanisms may be important in the generation of selective recruitment of circulating leucocytes into the airways (Fig. 2). INFLAMMATORY

PROCESS

DURING

THE LAR

The role of the T cell in the regulation and expression of airway inflammation in atopic asthma has been given considerable attention (35). IL-l, released by alveolar macrophages, dendritic and epithelial cells, regulates maturation and activation of T cells (CD3+). Such cells can be divided into two

T-cell

Alv. macro. T,2 cell Eosinophil

T-cell

Neutrophil Eosinophil

Alv. macro. Eosinophil Neutrophil Epithelial cell

T-cell Alv. macro.

IL4

IL6

IL8

GM-CSF

INF,

TNFa

IL5

Eosinophil Mast cell Alv. macro. Mast cell Eosinophil

cell

Epithelial T,l-cell Eosinophil

Cell proliferation

ILl/3 IL2 IL3

Cell activation

of cytokines

T-cell

Effects

IL1

Cytokines

Table 2

Granulocyt

Eosinophil

Cell survival

Eosinophil Basophil

Neutrophil T-cell Basophil

Eosinophil Basophil

Basophil

Cell recruitment

+ +

+

+

+

Expression of adhesion molecules

Mast

+

+ +

cell cell, T cell

cell, T,

T, B cell, Mast cell Epithelial cell Endothelial cell Alv. macro. Alv. macro. T cell, Fibroblast Epithelial cell Endothelial cell Alv. macro., T cell Endothelial cell Epithelial cell Alv. macro., Mast cell Epithelial cell Mast cell, T cell Mast cell, T cell

Mast

+

Source Mast cell, Alv. macro. Epithelial cell Alv. macro. T, cell Mast cell. T cell

+-t

Effect on IgE production

108

Topical Review

Cell

Released

cytokines

Known

effects of cytokines

Id3 IL5 GM-CSF

1

between

EAR and LAR

I IL-3 IL4 II-5 GM-CSF LCF, ECF)

Mast cell P

Alveolar

Fig. 2

macrophage

Dendritic

cell v

Epithelial

cell-IL-I

Effects

of antigen

II-1 IL-4

1

11-1

IL-1 TNF

1

TNF

IL-4

-IGl

stimulation

on inflammatory

cells during

major immunocytochemical and functional subgroups, i.e. CD4 and CD8 cells. A decrease of CD4+ T cells and an increase in CD8 + T cells was shown in BAL fluid 6 h after allergen challenge of early responders. This is in contrast with dual responders, who showed an increase of CD4+ T cells and a much less pronounced increased in CD8+ T cells in BAL fluid (36). Recently, another study has reported that submucosal CDS+ T cells increased at 3 h and 24 h after allergen challenge by dual responders, and that appearance of these cells in biopsies correlated inversely with the severity of the LAR (37). The results of both studies provide evidence to support the hypothesis that CDS+ T cells may play a role in suppressing the LAR. CD4+ T cells (TH cells) are now recognized as important in allergic inflammatory responses. Antigen-activated T, cells can be divided into two functionally distinct subsets referred to as T,l and T,2, based on the pattern of cytokines secretion. T,l cells secrete only IL-2, INF,, TNF-P. T,2 cells secrete only IL-4, IL-5 and IL-6, which are thought to be involved in the cellular response during the LAR. In several studies (3840), a selective increase in T, cells in BAL fluid was observed 24 and 48 h after allergen challenge in those subjects who had previously been shown to develop a late-phase reaction. As these CD4+ T cells express positive hybridization signals specifically for IL-4, IL-5, and G M-CSF, but not for IL-2, IL-3 and INF, after 24 h, this indicates a cytokine secretion profile of the T,2 cell subtype upon allergen exposition (40,41). The same profile has been found in airway wall biopsies, showing an increase in mRNA expression for IL-5 and GM-CSF (42). T,2-cell-derived IL-4 is inti-

> Eosinophil survival and activation

z Th2xell

-r the EAR,

important

activation

ELAM-1 ICAM-

expression expression

>VCAM-1

expression

for the development

of the LAR.

mately involved in the regulation of IgE production, as it stimulates and switches the immunoglobulin production of B cells to IgE in response to airborne allergens. Also, the survival and proliferation of T,2 cells is dependent on IL-4. Other cytokines derived from T,2 such as IL-3, IL-5, GM-CSF, play a pivotal role in the activation, maturation and survival of eosinophils. It is well known that eosinophils in BAL fluid-increase during the LAR in asthmatic patients (43). Subsequently, biopsies of the inflamed submucosa of the airway 24 h after allergen challenge has demonstrated an association between activated (EG2+) eosinophils and the number of IL-5 mRNA positive cells (42) and this coincides with an increase in ECP (24). It is known that preformed eosinophils products, such as ECP, MBP, EDN, and EPO are cytotoxic and neurotoxic and induce degranulation of mast cells and basophils (39,43,44). MBP and ECP are cytotoxic to epithelial cells of the airway in vitro and give rise to desquamation of the epithelial layer (45). As a consequence detachment of ciliated cells and destruction of individual cells may occur, leaving behind only basal cells at the epithelium lining (46). By others, it has been shown that this destruction leads to an increased incidence of tight junction openings of bronchial epithelium or widening in the intercellular space epithelium. This again was associated with eosinophil infiltration (47). In addition to the release of basic proteins by activated eosinophils, other spasmogenic mediators such as LTC, PAF, PGE,,,, 15-HETE, TxB, and toxic oxygen-derived radicals are also released, which may induce an involvement in the allergic inflammatory process during the LAR (44). All these data support the role of the eosinophil as an important effector cell in this

Topical Review process while T,2-cells are possibly important for the regulation of the allergic inflammation in the airways during the LAR. In addition to eosinophils, neutrophils have also been implicated in the LAR (43,44). The neutrophil may be recruited earlier to sites of inflammation in the lung, but this trasient, soon giving way to an eosinophilic infiltration. . Basophils may be also important during the late phase reaction, since tissue basophilia is found 6 h after allergen challenge (45). IL-3 and GM-CSF activate basophils leading to release of histamine. In conclusion, T cells become activated during, and perhaps even before, the late phase reaction possibly as a consequence of IL-l and IL-4 release by mast cells and other cells. Activated T cells also release cytokines (IL-3, IL-5, GM-CSF) which are involved in the activation and survival of eosinophils, possibly also activating basophils and mast cells. The (pro)inflammatory mediators liberated by these activated inflammatory cells have numerous activities, including induction of smooth muscle contraction, increased mucus secretion, vasodilation and increased vascular leakage resulting in tissue edema, all of which are histological features during the LAR. Allergen-induced

dysfunction

of the neural pathways

Allergen-induced biphasic response may lead to impaired /I-adrenoreceptor function (48). Twentyfour hours after allergen challenge in asthmatics, /I-adrenoreceptor numbers were reduced by 20% while their function (as measured by c-AMP production) was diminished by 40%. These changes, measured in lymphocyte membranes, are the result of uncoupling and downregulation of the /I-adrenoreceptor. An in vitro study showed that preincubation of peripheral blood lymphocytes with IL-l, IL-2, IFN, and GM-CSF for 20 h diminished c-AMP production (49). These findings suggest that a defect in /I-adrenoreceptor function and a decrease in numbers of peripheral blood lymphocytes may be the consequence of allergen challenge, possibly caused by cytokine release, from allergen-triggered cells in the airways. There are indications that parasympathetic inhibitory muscarinic,-receptors dysfunction may occur in asthmatics, resulting in exaggerated cholinergic reflex response. This has been observed after allergen challenge and may contribute to the severity of the airway obstruction and increase in AR after the LAR, by increased release of acetylcholine (50,51). In addition to these neural systems human airways are also innervated by a noncholinergic

109

nonadrenergic-system (NANC) of which the inhibitory-NANC system releases neuropeptides such as vasoactive intestinal peptide (VIP) and nitrousoxide (NO) which are bronchodilatory. I-NANC activities can be impaired in animals after allergen challenge and this dysfunction may be due to associated protease release by mast cells (52). Overall these data suggest that allergen challenge results in a dysfunction of several neural regulating systems of the airways which contributes to bronchoconstriction and increased AR. Their exact role in humans is as yet however not fully clear. Allergen-induced

airway reactivity

Allergen-induced increase in non-specific AR has recently been shown to be present even before the LAR and is sustained for many days (5,44,53). Histamine and methacholine are normally used to measure allergen-induced AR and are more or less direct stimuli for smooth muscle contraction. This increase of non-specific AR, as measured by direct stimuli, is possibly the result of allergen induced decrease in the geometric diameter of the airways which could be caused by the airway wall oedema, vasodilation resulting in thickening of the wall and smooth muscle contraction. Indirect stimuli are also used to measure increases in AR, such as S-adenosine-monophosphate (AMP) and bradykinin (BK). One study compared methacholine with AMP and showed only an increase in AR to AMP 3 h after the allergen provocation, but not after 24 h, in contrast with AR to methacholine which is increased at both time-points (6). This finding with AMP may be due to either mast cell depletion after allergen challenge or descensitization of prejunctional AZ-receptors on cholinergic nerve endings during the LAR (5456). Airway reactivity to BK was higher than for methacholine at 8 h and 3 weeks after allergen provocation (57). This increase at 8 h after the provocation is thought to be due to allergeninduced irritability of sensory nerves endings, whereas the sustained increase in AR to BK could be a consequence of slow epithelial repair. The mechanisms underlying allergen-induced increase in non-specific AR are not fully known, but it is likely that activated eosinophils, mast cells and their mediators may play an important role. Allergen-triggered mast cells give a release of leukotrienes and PGD,. Inhalation of LTC,, LTD,, and LTE, has been shown to enhance histamine reactivity of human asthmatic airways 4 h after leukotriene inhalation (58). This is also the case for PGD,, which gives an increase in AR to inhaled

II0

Topical Review

histamine and methacholine in asthmatic subjects (59). It is known that activated eosinophils are increased 3 and 24 h after allergen challenge in BAL fluid and biopsies (25,424l). These allergeninduced changes in eosinophil numbers correlate with the increase in AR. Activated eosinophils release leukotrienes (LTC,, LTD,, LTEJ and PAF. The latter can induce acute (within 15 min) and persistent (as long as 7 days) increases in nonspecific AR as measured with methacholine (60). Thus, leukotrienes and PGD,, released directly in human airways after allergen challenge, have the potential to increase AR to other constrictor mediators. Thus these mediators could be important for the increase in AR already at 3 h. Additionally, PAF is a chemotactic factor for eosinophils and activates these cells resulting in release of basic proteins, which are cytotoxic to the airway epithelium. A recent study demonstrated that damage to the bronchial epithelium is correlated with more severe AR, and the authors hypothesized that this could be the result of exposing sensory nerves in the airway and depriving the airway of epithelium derived relaxing factors (47). Stimulation of these sensory nerves by inflammatory mediators such as histamine, prostaglandins, PAF, leukotrienes and bradykinin, known to be liberated during the EAR and LAR, can result in the release of many neuropeptides via a neural reflex. These neuropeptides of excitatory or E-NANC system may produce many of the pathophysiologic features of asthma. For instance, neurokinine A (NRA) is a very potent constrictor of human airways and enhances cholinergic neurotransmission. Substance P (SP) is a vasodilator, causes microvascular leakage and stimulates mucus secretion from submucosal glands and goblet cells. Calcitonin-gene related peptide (CGRP) is a potent and long-lasting vasodilator (61). These peptides may act on mast cells and other migratory cells. These neuropeptides are catabolized by neuroendopeptidase (derived from airway epithelial cells) and this counter-regulation is therefore decreased after shedding of the epithelium. I-NANC system neuropeptides such as VIP and NO are catabolized by tryptase released from mast cells in allergically inflamed tissue (62). It can thus by hypothesized that release of neuropeptides and increase in irritability of sensory nerves after shedding of airway epithelium is the underlying pathophysiology mechanism to increase AR when it is sustained for days. In considering parameters of airway reactivity, it is important to distinguish between the position of the dose-response curve to a non-specific stimulus and the presence of a plateau in the curve, both which

may be multicausally determined. It has been shown that allergen challenge, causing a dual response but not a single response, not only shifts the methacholine dose-response curve to the left but also increases the maximal airway narrowing or even causes a loss of the plateau of the curve 24 h after the exposure (63). This suggests that airway inflammation also is important for increase in maximal airway narrowing. It can be concluded that the release of inflammatory mediators gives submucosal oedema, increases in mucus secretion and shedding of the epithelium, which may directly influence neural reflex-pathways, resulting in an increase in more AR as well as enhance of maximal airway narrowing. Loss of the plateau in the dose-response curve for methacholine or histamine is associated with excessive airway narrowing, which is a characteristic feature in asthma (64).

Effect of drugs on the EAR and LAR In order to better understand the mechanisms underlying the EAR and LAR, several studies with drugs modulating inflammatory mediators or neural pathways have been performed. As histamine is thought to be a prime candidate bronchoconstrictor during the EAR, antihistamines have been investigated. In fact only terfenadine partially protected the EAR whereas azelastine and cetirizine had no effect (6566). This does, however, not exclude a role for histamine in the EAR, as it might well be that these oral drugs do not give adequate tissue levels in the airways. This notion is supported by the discrepancy between inhaled /I-adrenoceptor drugs that provide protection against histamine provocation and oral /3-adrenoceptor drugs that do not. As the cyclooxygenase inhibitor flurbiprofen is capable of reducing the LAR, but not the EAR, prostaglandins may have a prominent role during the LAR (65). A role for leukotrienes during the EAR is supported by a protective study with leukotriene-antagonists and a leukotriene synthethase inhibitor (67,68). Moreover, the reduction of urinary LTE, production was associated with a decrease of the EAR. An animal study showed that microvascular leakage was even more reduced than smooth muscle contraction by a leukotriene-antagonist (69). Effects of PAFanatagonists have been studied as well. While in animal studies, an inhaled PAF-antagonist reduced the LAR and the associated AR, no effect of an oral antagonist has been shown in humans (70,71). These results suggest a role for PAF during the LAR and in the induction of AR, nevertheless no effect was found

Topical Review by an oral antagonist, so a role in humans is till open for question. In addition to drugs which target one mediator, there are drugs with a more general mechanism, such as glucocorticosteroids, sodium cromoglycate, nedocromil sodium, and xanthine derivatives. A single dose of oral or inhaled corticosteroids before allergen challenge inhibits the LAR and the induced AR, but has no effect on the EAR. However, after a continuous treatment for several weeks, a reduction of the EAR, LAR and associated AR was observed (3,72,73). Protection studies with single dose sodium cromoglycate and nedocromil sodium show a significant reduction of the allergen-induced early-, and late reaction and increase in AR (3,74). There are indications of inhibitory effects of theophylline, especially the slow-release form, on the EAR, LAR and induced AR suggesting some anti-inflammatory properties in addition to their bronchodilating effects (7576). Conventional doses of bronchodilators such as terbutaline and salbutamol totally protect the EAR but not the LAR. However, a single high dose of salbutamol(2.5 mg) inhibits the EAR and LAR up to 7 h after the allergen challenge as well as the allergeninduced AR (77). More recently, it has been shown that a single dose of the new long-acting &agonist, salmeterol, ablates the EAR and LAR and inhibits the associated AR for 34 h (78). The authors suggested that salmeterol has pharmacological effects on allergen-induced inflammatory responses in addition to its bronchodilator action. These data are in contrast with a protection study with salmeterol we recently performed (79). After corrections for the bronchodilator action of salmeterol, incomplete inhibition was found for both the EAR and LAR. While no protection from allergen-induced increase of AR after 24 h was observed. It might be argued that these effects can be explained by a sustained bronchodilator action and functional antagonism of &agonist rather than inhibiting of the allergeninduced late phase reaction. Formoterol also has an inhibitory effect on the EAR, LAR and induced AR for at least 12-24 h (80). However, only a reduction of the LAR and induced AR occurred and not a total ablation. A methodologically correct analysis of lung function following bronchodilation is necessary in order to separate the bronchodilatory and anti-inflammatory effect of these drugs.

Conclusion Bronchial allergen tool for unravelling

challenge of the

is a useful research pathophysiology of

Ill

bronchial asthma. The dynamics and mechanisms of the allergen-induced airway response can be studied by measuring physiologic parameters, variations in serum constituents and by the effect of pretreatment with various drugs. Since the introduction of the fibreoptic bronchoscope direct information on the local allergic inflammatory response can be obtained using broncho-alveolar lavage and (sub)mucosal biopsies. Airway resident and infiltrating cells involved in the EAR and LAR can be studied as well as their activation state and released mediators. Available data suggest that the fall in FEV, during the EAR is not only a consequence of bronchospasm, but also results from increased vascular permeability and oedema. In addition, the release of cytokines and chemo-attractive mediators from mast cells, alveolar macrophages, dendritic cells and epithelial cells may be important for the recruitment (via expression of adhesion molecules on endothelial cells and on circulating leucocytes) and activation of eosinophils and T-cells into the lung. The release of these cytokines may be essential for the development of the LAR, especially release of IL-l which activates TH cells. Additionally, evidence is accumulating that activation of the eosinophil is also very important for the development of the LAR and the associated AR. This increased eosinophil activation may be initiated by the release of IL-3, IL-5 and GM-CSF by mast cells and T, cells, likely the T,2-subtypes. The release of many (pro)-inflammatory mediators by activated inflammatory cells and their effects on the neural system in the airways may account for the allergen-induced increase in AR. The well-known anti-inflammatory drugs, sodium cromoglycate, nedocromil sodium and glucocorticosteroids, reduce or prevent both EAR and LAR and the allergen-induced AR. Conventional doses of short-acting &agonists protect the EAR, whereas high doses affect both EAR and LAR. However, long-acting &agonists inhibit both the EAR and LAR. It is not yet clear whether this is due to the sustained bronchodilating effect and functional antagonism or to a ‘real’ anti-inflammatory effect. Since specific antagonists and specific synthesis inhibitors of inflammatory mediators, have shown only partial inhibition of the EAR and/or LAR it is likely that no single mediator can account for the early and/or late phase reaction. The allergic asthmatic reaction and allergen-induced increase in AR, is orchestrated by many (pro-) inflammatory mediators released by allergen-triggered resident cells, airway epithelium and circulating cells selectively infiltrating the airways. Therefore, it may be more realistic to consider the EAR, LAR and

112

Topical

Review

increase in AR as clinically measurable aspects of one and the same ongoing inflammatory process. 17.

Acknowledgement The authors thank E. Dubois reading and helpful corrections

Ph.D.,

for

critically

of this manuscript.

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References 1. Herxheimer H. The late bronchial reaction in induced asthma. Ifit Arch A%?Y APP~ Immunol 1952; 3: 3233 328. 2. Pepys J. Immunopathology of allergic lung disease. Clin Allergy 1973; 3: l-22. H, Orie NGM, de Vries K. Immediate and 3. Booij-Noord late bronchial obstructive reaction to inhalation of house dust and protective effects if disodium cromoglycast and prednisolone. J AIlergy Clin Immunol19?1; 48: 344354. 4. Gokemeijer JDM. Hyperreactiviteit van de luchtwegen. Thesis GcSkemeger 1976; 101-125, Groningen: The Netherlands. 5. Cockcroft DW, Murdock KY. Changes in bronchial responsiveness to histamine at intervals after allergen challenge. Thorax 1987; 42: 302-308. 6. Aalberi R, Kauffman HF, Koeter GH, Postma DS, de Vries K, de Monchy JGR. Dissimilarity in methacholine and AMP responsiveness 3 and 24 hours after allergen challenge. Am Rev Respir Dis 1991; 144: 3522357. 7. Djukanovic R, Roche WR, Wilson JW et al. Mucosal inflammation in asthma. Am Rev Respir Dis 1990; 142: 434457. 8. Melillo G, Aas K, Cartier A et al. Guidelines for the standardization of bronchial provocation tests with allergens. Allergy 1991; 46: 321-329. 9. Wenzel SE, Larsen GL, Johnston K, Voelkel NF, Westcott JY. Elevated levels of leukotriene C4 in bronchoalveolar lavage fluid from atopic asthmatics after endobronchial allergen challenge. Am Rev Respir Dis 1990; 142: 112-119. 10. Holgate ST. The mast cell and its function in allergic disease. Clin Exo Allerav 1991: 21 (suaol. 3): 1 l-16. gf antigen-presenting cell func11. Holt PG. Regulation tion(s) in lung and airway tissues. Eur Respir J 1993; 6: 120-129. 12. Aubus P, Cosso B, Godard P, Miche FB, Clot J. Decreased suppressor cell activity of alveolar macrophages in bronchial asthma. Am Rev Respir Dis 1991; 143: A801. 12 Fuller RW. Pharmacological regulation of airway macrophage function. Clin Exp Allergy 1991; 21: 65 l-654. 14. Fuller RW, Morris PK, Richmond R et al. Immunoglobulin E-dependent stimulation of human alveolar macrophages: significance in type 1 hypersensitivity. Clin Exp Immunol 1986; 65: 416426. 15. Churchill L, Chilton FH, Resau JH, Bascom R, Hubbard WC, Proud D. Cyclooxygenase metabolism of endogenous arachidonicacid by cultered human tracheal enithelial cells. Am Rev Resnir Dis 1989; 140: 449459. 16. Gratziou C, Carroll M, Walls A, Howarth PH, Holgate ST. Early changes in T lymphocytes recovered by

19.

20.

21.

22.

23.

24.

25.

26.

27.

28.

12.

29.

30.

31.

bronchoalveolar lavage after local allergen challenge of asthmatic airways. Am Rev Respir Dis 1992; 145: 1259-1264. Hakansson L, Rak S, Dahl R, Venge P. The formation of eosinophil and neutrophil chemotactic activity during a pollen season and after allergen challenge. J Allergy Clin Immunol 1989; 83: 933-939. Venae P, Dahl R. Hakansson L. Heat-labile neutronhil chemotactic activity in subjects with asthma after ailergen inhalation: Relation to the late asthmatic reaction and effects of asthma medication. J Allergy Clin Immunol 1987; 80: 679-688. Durham SR, Carrol M, Walsh GM, Kay AB. Leukocvte activation in allergen-induced late-phase asthmatic reactions. N Engl J Mid 1984; 311: 1398-1402. Wodnar-Filipowicz A, Heusser CH, Morani C. Production of the haemnoietic growth factor GM-CSF and interleukine-3 by mast cells in response to IgE-receptormediated activation. Nature 1989; 339: 15cl.52. Plaut M, Pierce JH, Watson CJ, Hanley-Hyde J, Nordan RP, Paul WE. Mast cells lines produce lymphokines in response to cross-linkage of FceRI or to calcium ionophores. Nature 1989; 339: 6467. Burd PR, Rogers HW, Gordon JR. Interleukine 3-dependent and independent mast cells stimulated with IgE and antigen express multiple cytokines. J Exp Med 1989; 170: 2455257. Lopez AF, Sanderson CJ, Gamble JR, Campbell HD, Young IG, Vadas MA. Recombinant human interleukine-5 is a selective activator of human eosinophi1 function. J Exp Med 1988; 167: 219-224. Rossi GA, Crimi E, Lantero S et al. Late-phase asthmatic reaction to inhaled allergen is associated with early recruitment of eosinophils in the airways. Am Rev Respir Dis 1991; 144: 379-383. Aalbers R, de Monchy JGR, Kauffman HF et al. Dynamics of eosinophil infiltration in the bronchial mucosa before and after the late asthmatic reaction. Eur Respir J 1994; 6: in press. Maggi E, Parronchi P, Manetti R et al. Reciprocal regulators role of INFa and IL-4 on the in vitro development of human Tnl Tn2 clones. J Zmmunol 1992; 148: 214222147. Cromwell 0, Hamid Q, Corrigan CJ et al. Expression and generation of interleukine-8 and granulocytemacrophage colony-stimulating factor by bronchial epithehal cells and enhancement by IL-lb and tumour necrosis factor-a. Immunologv 1992; 77: 330-337. Osborn L, Hession C, Tizard R et al. Direct expression cloning of vascular cell adhesion molecule 1, a cytokineinduced endothelial protein that binds to lymphocytes. Cell 1989; 59: 120331211. Kyan-Aung U, Hakard DO, Poston RN, Tornhill MH, Lee TH. ELAM-I and ICAM-I mediate the adhesion of eosinophils to endothelial cells in vitro and are expressed by endothelium in allergic cutaneous inflammation in vivo. J Zmmunol 1991; 146: 521-528. Leung DYM, Pober JS, Cotran RS. Expression of endothelial-leukocyte adhesion molecule-l in elicited late phase allergic reaction. J Clin Invest 1991; 87: 180551809. Wegner CD, Gundel RH, Reilly P, Haynes N, Gordon Letts L, Rothlein R. Intercellular adhesion molecule-l (ICAM-I) in the pathogenesis of asthma. Science 1990; 247: 456459.

Topical

TT, Walker C. The migration of eosino32. Hansel phils into the sputum of asthmatics: the role of adhesion molecules. Clin Exp Allergy 1992; 22: 345356. M, Hirai K, Shoji T et al. Haemopoietic 33. Yamaguchi growth factors induce human basophil migration in vitro. Clin Exp Allergy 1992; 22: 379-384. 34. Bochner BS, McKelvey AA, Sterbinsky SA et al. IL-3 augements adhesiveness for endothelium and CD1 lb expression in human basophils but not neutrophils. J. Zmmunol 1990; 145: 1832-1837. (CD4+) T cells and eosinophils in 35. Kay AB. ‘Helper’ allergy and asthma. Am Rev Respir Dis 1992; 145: S222S26. Gonzalez C, Diaz P, Galleguillos FR, Antic P, Cromwell 0, Kay AB. Allergen-induced recruitment of bronchoalveolar helper [OKT4] and suppressor [OKT8] T-cells in asthma. Am Rev Respir Dis 1987; 136: 600604. Aalbers R, Smith M, de Monchy JGR, Koeter GH, Kauffman HF, Timens W. Interaction of eosinophil and lymphocyte infiltration in the bronchial submucosa of atopic asthmatics following allergen challenge. Thesis R. Aalbers 1993 chapter 11; 177-198, Groningen, The Netherland. Gerblich AA, Salik H, Schuyler MR. Dynamic T cell changes in peripheral blood and bronchoalveolar lavage after antigen bronchoprovocation in asthmatics. Am Rev Respir Dis 1991; 143: 5333537. 39. Metzger WJ, Zavala D, Richerson HB et al. Local allergen challenge and bronchoalveolar lavage of allergic asthmatic lungs. Am Rev Respir Dis 1987; 135: 43340. 40. Robinson DS, Hamid Q, Bentley AM, Ying S, Kay AB, Durham SR. Activation of CD4+ T cells and increased IL-4, IL-5 and GM-CSF mRNA positive cells in bronchoalveolar lavage fluid (BAL) 24 hours after allergen inhalation challenge of stopic asthmatic patients. Thorax 1992; 47: 852. (Abstract). 41. Robinson DS, Hamid Q, Ying S et al. PredominantnT,,-like bronchoalveolar T-lymophocyte population in atopic asthma. N Engl J Med 1992; 326: 298-304. 42 Bentley AM, Meng Q, Robinson DS, Hamid Q, Kay AB, Durham SR. Increases in activated T lymphocytes, eosinophils, and cytokine mRNA expression for IL-5 and GM-CSF in bronchial biopsy specimens after allergen inhalation challenge in atopic asthmatic patients. Am J Respir Cell Mol Biol 1993; 8: 35-42. JGR, Kauffman HF, Venge P et al. Bron43 de Monchy choalveolar eosinophilia during allergen-induced late asthmatic reactions. Am Rev Respir Dis 1985; 131: 373-376. 44 Diaz P, Gonzalez C, Galleguillos FR ef al. Leukocytes and mediators in bronchoalveolar lavage during allergen-induced late-phase asthmatic reactions. Am Rev Respir Dis 1989; 139: 138331389. 45. Gleich GJ, Frigas E, Loegering DA, Wassom DL, Steinmuller D. Cytotoxic properties of the eosinophi1 major basic protein. J Immunol 1979; 123: 29255 2927. 46. Frigas E, Gleich GJ. The eosinophil and the pathophysiology of asthma. J Allergy C&r Immunol 1986; 77: 527-537.

Review

113

47. Ohashi Y, Motojima S, Fukuda T, Makino S. Airway hyperresponsiveness, increased spaces of bronchial epithelium, and increased infiltration of eosinophils and lymphocytes in bronchial mucosa in asthma. Am Rev Respir Dis 1992; 145: 1469-1476. 48. Meurs H, Koeter GH, de Vries K, Kauffman HF. The beta-adrenergic system and allergic bronchial asthma: changes in lymphocyte beta-adrenergic receptor number and adenylate cyclase activity after an allergeninduced asthmatic attack. J Allergy Clin Zmmunol 1982; 70: 272-280. 49. Van Oosterhout AJM, Stam WB, Vanderschueren RGJRA, Nijkamp FP. Effects of cytokines on B-adrenoceptor function of human peripheral blood mononuclear cells and guinea pig trachea. J Allergy Qin Zmmunol 1992; 90: 340-348. 50. Fryer AD, Wills-Karp M. Dysfunction of M,muscarine receptors in pulmonary parasympathetic nerves after antigen challenge. J Appl Physiol 1991; 71: 2255-2261. 51. ten Berge REJ, Roffel AF, van der Zande J, Santing RE, Zaagsma J. Dysfunction of prejunctional M,muscarinic receptors in tracheal preparations of IgEsensitized guinea pigs after the early allergic reaction. Am Rev Respir Dis 1992; 145: A437 (Abstract). M, Kimura K et al. Dysfunction of 52. Miura M, Ichinose nonadrenergic noncholinergic inhibitory system after antigen inhalation in actively sensitized cat airways. Am Rev Respir Dis 1992; 145: 70-74. 53. Cartier A, Thomson NC, Frith PA, Roberts R, Tech M, Hargreave FE. Allergen-induced increase in bronchial responsiveness to histamine: relationship to the late asthmatic response and change in airway caliber. J Allergy Clin Zmmunol 1982; 70: 170-177. AG, Kukoly CA, Metzger WJ, Mustafa SJ. 54. Driver Bronchial challenge with adenosine causes the release of serum neutrophil chemotactic factor in asthma. Am Rev Respir Dis 1991; 143: 100221007. P, Beasley R, Southgate P, Holgate S. The role 55. Rafferty of histamine in allergen and adenosine-induced bronchoconstriction. Znt Arch Allergy Appl Zmmun 1987; 82: 2922294. 56. Polosa R, Rajakulasingam K, Church MR, Holgate ST. Repeated inhalation of bradykinin attenuates adenosine 5’-monophosphate (AMP) induced bronchoconstriction in asthmatic airways. Em Respir J 1992; 5: 700-706. 57. Djukanovic R, Polosa R, Holgate ST. The effect of bronchial allergen challenge on methacholine [mch] and bradykinin [BK] airway responsiveness. Eur Respir J 1991; 4 (suppl. 14): 584. (Abstract). 58. O’Hickey SP, Hawksworth RJ, Fong CY, Arm JP, Spur BW, Lee TH. Leukotrienes C4, D4, E4 enhances histamine responsiveness in asthmatic airways. Am Rev Respir Dis 1991; 144: 1053-1057. 59. Fuller RW, Dixons CMS, Dollery CT, Barns PJ. Prostaglandin D, potentiates airway responsiveness to histamine and methacholine. Am Rev Respir Dis 1986; 133: 252-254. 60. Page CP. Mechanisms of hyperresponsiveness: Plateletactivating factor. Am Rev Respir Dis 1992; 145: S31s33. 61. Barnes PJ, Baraniuk JN, Belvisi MG. Neuropeptides in the respiratory tract. Part II. Am Rev Respir Dis 1991; 144: 1391-1399.

114

Topical

Review

62. Barnes PJ, Baraniuk JN, Belvisi MG. Neuropeptides in the respiratory tract. Am Rev Respir Dis 1991; 144: 1187-l 198. 63. Boonsawat W, Salome CM, Woolcock AJ. Effect of allergen inhalation on the maximal response plateau of the dose-response curve to methacholine. Am Rev Respir Dis 1992; 146: 5655569. 64. Sterk PJ, Be1 EH. Bronchial hyperresponsiveness: the need for a distinction between hypersensitivity and excessive airway narrowing. Eur Respir J 1989; 2: 261-214. 65. Hamid M, Rafferty P, Holgate ST. The inhibitory effect of terfenadine and fluriprofen on early and late phase bronchoconstriction following allergen challenge in atopic asthma. C/in Exp Allergy 1990; 20: 261-267. 66. Rafferty P, Phillips G, Clough J, Church MK, Aurich R, Ollier S. The inhibitory actions of azelastine hydrochloride on the early and late bronchoconstriction responses to inhaled allergen in atopic asthma. J AIIergy Clin Immunol 1989; 84: 6499657. 61. Rasmussen JB, Eriksson L-O, Margolskee DJ, Tagari P, Williams VC, Andersson K-E. Leukotriene D, receptor blockade inhibits the immediate and late bronchoconstrictor responses to inhaled antigen in patients with asthma. J Allergy Clin Immunol 1992; 90: 193-201. 68. Hui KP, Taylor- IK, Taylor GW, Kesterson J, Barnes NC. Barnes PJ. Effect of a S-linoxvgenase inhibitor on leukotriene generation and airway r&ponses after allergen challenge in asthmatic patients. Thorax 1991; 46: 184-189. 69. Hui KP, Lotall JO, Chung KF, Barnes PJ. Attenuation of inhaled allergen-induced airway microvascular leakage and airflow obstruction in guinea pigs by a 5-lipoxygenase inhibitor (A-63162). Am Rev Respir Dis 1991; 143: 1015-1019. 70. Tomioka K, Garride R, Ahmed R, Stevenson JS, Abraham WR. YM461, a PAF-antagonist, blocks antigen-induced late airways responses and airway hyperresponsiveness in allergic sheep. Eur J Pharmacol 1989; 170: 2099215. 71. Kuitert RM, Hui KP, Uthayarkumar S et al. Effect of the platelet-activating factor antagonist UK-74,505 on

72.

73.

74.

15.

76.

77.

78.

19.

80.

the early and late response to allergen, AM Rev Respir Dis 1993; 147: 82-86. Cockcroft DW, Murdock KY. Comparative effects of inhaled salbutamol, sodium cromoglycaat, and beclomethason dipropionate on allergen-induced early asthmatic responses, late asthmatic responses, and increased bronchial responsiveness to histamine. J Allergy Clin Immunol 1987; 79: 734740. Dahl R, Johansson S-A. Importance of duration of treatment with inhaled budesonide on the immediate and late bronchial reaction. Eur Respir J 1982; 63 (suppl. 122): 1677175. Aalbers R, Kauffman HF, Groen H, Koeter GH, de Monchy JGR. The effect of nedocromil sodium on the early and late reaction and allergen-induced bronchial hyperresponsiveness. J Allergy Clin Immunol 1991: 87: 993-1001. Crescioli S, Spinazzi A, Plebani M et al. Theophylline inhibits early and late asthmatic reactions induced by allergens in asthmatic subjects. Ann Allergy 1991; 66: 245-25 1. Pauwels R, Van Renterghem D, Van Der Straeten M, Johannesson N, Persson CGA. The effect of theophylline and enprofylline on allergen-induced bronchoconstriction. J Allergy Clin Immunol 1985; 76: 583-590. Twentyman OP, Finnerty JP, Holgate ST. The inhibitory effect of nebulized albuterol on the early and late asthmatic reactions and increase in airway responsiveness provoked by inhaled allergen in asthma. Am Rev Respir Dis 1991; 144: 7822787. Twentyman OP, Finnerty JP, Harris A, Palmer J, Holgate ST. Protection against allergen-induced asthma by salmeterol. Luncet 1900; 336: 1338-1342. Weersink EJM, Aalbers R, Koeter GH, Kauffman HF, de Monchy JGR, Postma DS. Partial inhibition of the early and late asthmatic reaction by a single dose of salmeterol. (submitted). Wong BJ, Dolovich J, Ramsdale EH et al. Formoterol compared with beclomethasone and placebo on allergeninduced asthmatic responses. Am Rev Respir Dis 1992; 146: 11561160.