Inhalation of β2 agonists impairs the clearance of nontypable Haemophilus influenzae from the murine respiratory tract
© Maris et al. 2006
Received: 29 January 2006
Accepted: 04 April 2006
Published: 04 April 2006
Nontypable Haemophilus influenzae (NTHi) is a common bacterial pathogen causing human respiratory tract infections under permissive conditions such as chronic obstructive pulmonary disease. Inhalation of β2-receptor agonists is a widely used treatment in patients with chronic obstructive pulmonary disease. The aim of this study was to determine the effect of inhalation of β2 agonists on the host immune response to respiratory tract infection with NTHi.
Mouse alveolar macrophages were stimulated in vitro with NTHi in the presence or absence of the β2 receptor agonists salmeterol or salbutamol. In addition, mice received salmeterol or salbutamol by inhalation and were intranasally infected with NTHi. End points were pulmonary inflammation and bacterial loads.
Both salmeterol and salbutamol inhibited NTHi induced tumor necrosis factor-α (TNFα) release by mouse alveolar macrophages in vitro by a β receptor dependent mechanism. In line, inhalation of either salmeterol or salbutamol was associated with a reduced early TNFα production in lungs of mice infected intranasally with NTHi, an effect that was reversed by concurrent treatment with the β blocker propranolol. The clearance of NTHi from the lungs was impaired in mice treated with salmeterol or salbutamol, an adverse effect that was prevented by propranolol and independent of the reduction in TNFα.
These data suggest that inhalation of salmeterol or salbutamol may negatively influence an effective clearance of NTHi from the airways.
Chronic obstructive pulmonary disease (COPD) is frequently associated with exacerbations marked by increased dyspnea, wheezing, cough and increased sputum volume and purulence. Although the causes of such exacerbations are not always clear, bacterial infections of the lower airways may contribute substantially to morbidity, primarily as an evoking event or secondarily as a complication [1, 2]. The bacteria most commonly isolated from patients are non typable Haemophilus influenzae (NTHi), Streptococcus pneumoniae and Moraxella catarrhalis, which account for 70 % of all exacerbations of COPD [1, 3].
β2-receptor agonists are frequently used in the treatment of COPD. These agents induce bronchodilation via activation of β2-adrenoceptors on smooth muscle cells . Apart from their presence on smooth muscle cells, β2-receptors are also found on cells involved in the regulation of inflammation like neutrophils, lymphocytes, monocytes and macrophages [5, 6]. Stimulation of β2-receptors results in a number of anti-inflammatory effects, including inhibition of neutrophil activation and oxygen release, reduction of neutrophil-endothelial cell adhesion and a reduced capacity to release proinflammatory cytokines such as tumor necrosis factor (TNF)α and interleukin (IL)-1β by macrophages [5, 6]. In line with these findings, we recently demonstrated that salmeterol, a long-acting β2-agonist, exerted anti-inflammatory effects in models of lipopolysaccharide (LPS)-induced lung inflammation in mice and humans, as reflected by a reduction in lung TNFα levels and an inhibition of neutrophil recruitment to the pulmonary compartment [7, 8].
We hypothesized that β2 adrenergic agonists such as salmeterol or salbutamol would influence the clearance of NTHi from the respiratory tract. This hypothesis was based on two lines of evidence. First, the prompt influx of neutrophils into the lungs is important for the clearance of NTHi from the airways . Thus, inhibition of neutrophil recruitment by salmeterol, such as observed during LPS-induced lung inflammation [7, 8], may impair normal host defense. Second, indirect evidence indicates that TNFα plays a role in the protective immune response to NTHi, i.e. immunization with formalin killed NTHi resulted in more pronounced TNFα production which correlated with enhanced bacterial clearance . Arguing that endogenous TNFα is of paramount importance for host defense against other bacterial respiratory pathogens. [11–14], we considered it conceivable that salmeterol-induced inhibition of TNFα production, such as found after pulmonary LPS challenge negatively impacts on the clearance of NTHi. Therefore, the present study was performed to determine the effects of salmeterol and salbutamol on the immune response to NTHi pneumonia.
Salmeterol and salbutamol were kind gifts from GlaxoSmithKline (Hertfordshire, United Kingdom). Propranolol (1 mg/ml) was obtained from Astra Zeneca (Zoetermeer, The Netherlands).
H. influenzae strain 12 (kindly donated by S.J. Barenkamp, St. Louis, MO) is a nontypable clinical isolate that has been used by our and other laboratories in investigations on murine pneumonia [15–18]. Classification, storage and inoculum preparation was performed as described before [17, 18]. The inoculum contained 2 × 108 colony forming units (CFU) per ml. For each experiment, the number of CFU was determined by plating serial 10-fold dilutions on chocolate agar plates.
Cell culture and stimulation
The murine alveolar macrophage cell line MH-S was obtained from American Type Culture Collection (ATCC CRL-2019; Rockville, MD). MH-S cells were cultured at 37°C in 5% CO2 in RPMI 1640 medium with 2 mM L-glutamine adjusted to contain 1.5 g/L sodium bicarbonate, 4.5 g/l glucose, 10 mM Hepes and 1.0 mM sodium pyruvate and supplemented with 10% FBS, 100 IU/ml penicillin, 100 μg/ml streptomycin and 0.05 mM 2-mercaptoethanol. For each experiment cells were seeded in 96-well plates (Greiner, Alphen a/d Rijn, The Netherlands) at a density of 0.5 × 105 per well and grown overnight. The next day cells were washed in medium and preincubated (5 minutes) with different concentrations of salmeterol or salbutamol (10-5 – 10-10 M) with or without propranolol (10-5 M). Salmeterol and salbutamol were each dissolved to stock concentrations in PBS to which 2 droplets of glacial acetic acid were added. Dilutions of stock concentrations were made in MH-S medium. Control solutions were prepared similarly without the addition of salmeterol or salbutamol. Cells were stimulated with 5 × 105 heat killed (HK) NTHi (70°C for 30 minutes) and supernatants were collected after 3, 6, 12 and 24 h and stored at -20°C until measurement of TNFα.
Female C57BL/6 mice were purchased from Harlan Sprague Dawley (Horst, The Netherlands). At the start of the experiments mice were 8 weeks old. All experiments were approved by the Animal Care and Use Committee of the Academic Medical Center (Amsterdam, the Netherlands). Pneumonia was induced by intranasal inoculation of 50 μl (107 CFU) bacterial suspension as described before [17, 18]; control mice received 50 μl sterile PBS. Mice were pretreated (at -30 minutes) with either control solution, salmeterol or salbutamol which were nebulized and inhaled. Salmeterol and salbutamol were each dissolved to stock concentrations in PBS to which 2 droplets of glacial acetic acid were added and dilutions were made in sterile 0.9% saline. Control solutions were prepared similarly without the addition of salmeterol or salbutamol. Inhalation of 1 ml control solution, salmeterol (2.4 mM) or salbutamol (2.4 mM) was achieved by attaching a plastic chamber (5 L) containing 8 conscious mice to an Aeroneb pro nebulizer (Medicare BV, Uitgeest, the Netherlands) as described . Salmeterol and salbutamol treatments were repeated 6 or 12 hourly respectively until mice were sacrificed, while mice inhaled control solution in other groups or at time points they did not not receive β2-agonists. Propranolol (10 mg/kg) was injected i.p. 30 minutes before salmeterol treatment and repeated every 2 hours to block β-adrenoceptors. In a separate experiment mice were pretreated i.p. with 250 μg of a neutralizing anti-mouse TNFα monoclonal antibody (TN3) or mouse IgG1 (Chemicon, Temecula, CA) 3 hours before inoculation with NTHi; these mice inhaled salmeterol or control solution 30 minutes before NTHi infection as described above. TN3 is a well-characterized neutralizing anti-mouse TNFα monoclonal antibody that effectively neutralized endogenous TNFα in a variety of mouse models [19–22] including pneumonia [12, 14].
Determination of bacterial outgrowth
Bronchoalveolar lavage and flow cytometry
Bronchoalveolar lavage (BAL), total and differential cell count was performed as described . The pellet was resuspended in FACS buffer (PBS supplemented with 0.5 % BSA, 0.01 % NaN3, and 0.35 mM EDTA) and expression of CD11b on neutrophils was determined by flow cytometric analysis as described previously, using rat anti-mouse CD11b PE and Gr-1 FITC (Ly-6G) antibodies (Pharmingen, San Diego, CA) .
In separate mice (n = 4 per treatment group at each time point) whole lungs were harvested for histologic examination 6 and 48 h after inoculation, fixed in 10 % formalin and embedded in paraffin. Sections of 4 μm were stained with hematoxylin and eosin, and analyzed by a pathologist who was blinded for the groups. Lung inflammation score was determined as described before [17, 18].
TNFα measurement and myeloperoxidase (MPO) assay
For TNFα measurement, lung homogenates were diluted 1:1 in lysis buffer (150 mM NaCl, 15 mM Tris, 1 mM MgCl.H2O, 1 mM CaCl2, 1 mM Triton X-100, 100 μg/ml Pepstatin A, Leupeptin and Aprotinin, pH 7.4) and incubated at 4°C for 30 minutes. Homogenates were centrifuged at 1500 × g for 20 minutes after which the supernatants were stored at -20°C until TNFα determination. TNFα was measured using a specific ELISA according to the manufacturers instructions (R&D Systems, Minneapolis, MN). The coefficient of variation was <10%. MPO activity in lung homogenates was measured as described previously .
Values are expressed as mean ± SEM unless indicated otherwise. Differences between groups were analyzed with the nonparametric Kruskal-Wallis test followed by Mann Whitney U as posttest. P < 0.05 (two-sided) was considered statistically significant.
Salmeterol and salbutamol inhibit TNFα production by mouse alveolar macrophages stimulated with heat killed NTHi
Salmeterol and salbutamol inhalation inhibit TNFα production in mouse lungs infected with NTHi
Salmeterol does not influence neutrophil influx or CD11b expression
Salmeterol treated mice display unaltered pulmonary inflammation after NTHi challenge
Salmeterol and salbutamol impair the clearance of NTHi from lungs
TNFα is not essential for the clearance of NTHi from mouse lungs
H. influenzae is a Gram-negative pathogen that frequently colonizes human respiratory mucosa. Nontypable strains are responsible for the majority of clinical disease caused by H. influenzae in the airways, and in particular patients with COPD, bronchiectasis and cystic fibrosis are susceptible to infection with NTHi . We here tested the hypothesis that inhalation of β2 agonists, a treatment often given to patients with COPD and other chronic pulmonary disorders that predispose subjects to NTHi infection, would negatively influence host defense against this bacterium. Our results provide evidence that inhalation of either salmeterol or salbutamol indeed impairs the clearance of NTHi from the mouse respiratory tract in vivo.
Our hypothesis was, in part, based on our recent studies that investigated the effect of salmeterol on LPS-induced lung inflammation [7, 8]. In these studies it was established that inhalation of salmeterol attenuated neutrophil influx into lungs after intrapulmonary delivery of LPS, concurrently reducing pulmonary TNFα concentrations. Here, we demonstrated that both salmeterol and salbutamol dose-dependently inhibit TNFα release by mouse alveolar macrophages stimulated with NTHi in vitro and that inhalation of either β2 agonist was associated with lower TNFα concentrations in lung tissue and BALF during NTHi pneumonia in vivo. The β2 agonist induced inhibition of TNFα release could be reversed by propranolol, indicating that the effect of these agents is mediated by β adrenergic receptors. Earlier studies reported on the systemic effects of β adrenergic agonists on TNFα release into the circulation after systemic (intravenous or intraperitoneal) administration of LPS [25–27].
We considered it conceivable that the reduced TNFα levels in β2 agonist treated mice was at least in part responsible for the impaired clearance of NTHi from the lungs. This assumption was based on various earlier findings. First, inhibition of TNFα in murine models of pneumonia caused by several respiratory pathogens, including Klebsiella pneumoniae and Streptococcus pneumoniae, resulted in a strongly enhanced bacterial outgrowth. [11–14]. Second, immunization with formalin killed NTHi accelerated bacterial clearance which was accompanied by increased TNFα production . However, the present data clearly establish that TNFα does not contribute to an effective clearance of NTHi from the airways. The same anti-TNFα antibody that strongly impaired host defense during pneumonia caused by S. pneumoniae  or K. pneumoniae  did not influence the bacterial load during NTHi pneumonia. Moreover, anti-TNFα treatment did also not alter the effect of inhaled salmeterol on NTHi clearance. Interestingly, it was previously reported that mice deficient for the type I TNFα receptor displayed a modestly enhanced early clearance of Pseudomonas aeruginosa from the lungs during acute pneumonia . Altogether these investigations suggest that early TNFα production in the lung is important for limiting the outgrowth of respiratory pathogens in the pulmonary compartment (i.e. S. pneumoniae and K. pneumoniae multiply in the mouse lung), whereas locally induced TNFα is of little importance for the immune response against bacteria that are cleared from the lungs (i.e. P. aeruginosa and NTHi) ( and the present study). A similar paradoxical role in murine pneumonia has been found for another prototypic proinflammatory cytokine IL-1, which facilitates host defense against S. pneumoniae [13, 29], while having a modest negative impact on the clearance of P. aeruginosa . It should be noted that in the current study we did not directly determine the capacity of anti-TNFα to neutralize TNFα activity in the lungs of mice infected with NTHi. Therefore, definitive proof that TNFα does not play a role in host defense against NTHi in this model is not provided. To obtain more insight into the role of TNF in host defense against NTHi pneumonia studies using TNFα or TNF receptor deficient mice are warranted. In addition, the potential protective effect of exogenous TNFα in mice treated with salmeterol could be evaluated using adenoviral TNFα gene transfer.
Neutrophils play an important role in the clearance of NTHi from the respiratory tract . Neither salmeterol nor salbutamol influenced the recruitment of neutrophils to the lungs after infection with NTHi, as reflected by an unaltered number of neutrophils in BALF and in lung tissue slides, as well as by a similar rise in lung MPO concentrations in mice treated with salmeterol. This finding contrasts with the strong effect of salmeterol on influx of neutrophils into the pulmonary compartment after local delivery of LPS [7, 8]. Notably, neutrophil emigration from the pulmonary circulation during inflammation caused by Gram-negative stimuli relies largely on expression of the β2 integrin CD11b/CD18 at the surface of neutrophils . We recently demonstrated that salmeterol reduces CD11b expression on neutrophils recruited to the lung after intranasal administration of LPS and that blocking CD11b on neutrophils reproduces the inhibition of neutrophil influx by salmeterol treatment . This led us to conclude that the effect of salmeterol on neutrophil influx during LPS-induced lung inflammation was at least in part due to a salmeterol-induced reduction in neutrophil CD11b expression . In the present study, salmeterol did not influence neutrophil CD11b expression during NTHi infection, whereas salbutamol only had a modest effect. We do not have a firm explanation for these apparently different effects of salmeterol and salbutamol on neutrophil CD11b, although clearly the effect of salbutamol is weak and of doubtful biological relevance. Conceivably, this lack of a strong effect on neutrophil CD11b at least in part explains the present finding that inhalation of β2 agonists did not affect neutrophil trafficking to the lung. Further studies are warranted to assess whether the impact of β2 agonists on neutrophil functions only applies to sterile stimuli eliciting a brisk but transient inflammatory response in the lung (e.g. such as induced by LPS).
Salmeterol achieves instantaneous topical concentrations at least as high as 1 μM in human lung . In vitro, salmeterol and salbutamol inhibited TNFα production by alveolar macrophages at concentrations as low as 0.1–10 nM (figure 1B), a concentration range that appears to be clinically relevant. In guinea pigs, inhaled salmeterol (0.12–12 mM) and salbutamol (0.2 and 2 mM) strongly inhibited histamine-induced bronchoconstriction which was argued to be of predictive value in terms of relative potencies and durations of action of inhaled β2 agonists in man . In the present study the doses of salbutamol and salmeterol (both 2.4 mM) were well within the effective range as tested in guinea pigs, and proved to be effective and propranolol sensitive (β receptor dependent) with respect to inhibition of both TNFα production and bacterial clearance after NTHi challenge. Together, these data suggest that salmeterol and salbutamol as nebulized in our model is present in lungs in sufficiently high topical and probably clinically relevant concentrations to cause β-adrenoceptor dependent inhibition of TNFα production and bacterial clearance in NTHi infected lungs.
It should be noted that our studies with salbutamol were focused on the most relevant time point of the time course studies using salmeterol. In addition, we did not determine the effect of propranolol in salbutamol treated mice. The salbutamol studies were done to exclude a salmeterol specific effect and to show that the effects observed were specific for the class of β2 agonists. Considering that both salmeterol and salbutamol inhibited the clearance of NTHi, our investigation provides proof for an effect that indeed is mediated by stimulation of β2 receptors.
Salmeterol and salbutamol consistently delayed the clearance of NTHi from the lungs, a finding that was reproduced in several experiments (figure 5A, 5B and 6). Considering that the β2 agonist induced inhibition of early TNFα release can not explain the adverse effect of salmeterol and salbutamol on the bacterial clearance, and considering that these agents did not influence neutrophil recruitment, other mechanisms must be involved. In this respect it should be noted that β2 agonists can inhibit several inflammatory cell functions considered important for defense against bacteria. For instance neutrophil respiratory burst activity  and exocytosis  were shown to be attenuated by β2 agonist treatment. Additionally, bacterial killing and superoxide anion release by alveolar macrophages was strongly suppressed by both salbutamol and formoterol . In contrast, no effect of β2 agonists on phagocytosis by neutrophils and alveolar macrophages was observed [37, 38]. Other studies have documented possible protective effects of β2 agonists on respiratory epithelium. In particular, preincubation of human nasal turbinates with salmeterol attenuated H. influenzae reduced epithelial damage without influencing the total number of bacteria adhering to the organ culture . Similar observations have been made in nasal turbinate cultures infected with P. aeruginosa .
Our study suggests that, at least in mice, inhalation of β2 agonists impairs the clearance of NTHi from the airways. Obviously, these data do not imply that the use of β2 agonists should be discouraged in patients with obstructive pulmonary diseases; rather they exemplify the complex anti-inflammatory actions of β2 agonists in the pulmonary compartment and that a potential role in the suppression of pulmonary antibacterial defenses must not be overlooked.
This work was supported by a grant from the Dutch Asthma Foundation (project 329909) to N.A. Maris.
- Jansen HM, Sachs AP, van Alphen L: Predisposing conditions to bacterial infections in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1995, 151:2073–2080.View ArticlePubMedGoogle Scholar
- Simpson SQ, Jones PW, Davies PD, Cushing A: Social impact of respiratory infections. Chest 1995, 108:63S-69S.View ArticlePubMedGoogle Scholar
- van Alphen L, Jansen HM, Dankert J: Virulence factors in the colonization and persistence of bacteria in the airways. Am J Respir Crit Care Med 1995, 151:2094–9; discussion 2099–100.View ArticlePubMedGoogle Scholar
- Busse WW: Long-and short-acting beta 2-adrenergic agonists. Effects on airway function in patients with asthma. Arch Intern Med 1996, 156:1514–1520.View ArticlePubMedGoogle Scholar
- Barnes PJ: Effect of beta-agonists on inflammatory cells. J Allergy Clin Immunol 1999, 104:S10–7.View ArticlePubMedGoogle Scholar
- Johnson M, Rennard S: Alternative mechanisms for long-acting beta(2)-adrenergic agonists in COPD. Chest 2001, 120:258–270.View ArticlePubMedGoogle Scholar
- Maris NA, van der Sluijs KF, Florquin S, de Vos AF, Pater JM, Jansen HM, van der Poll T: Salmeterol, a beta2-receptor agonist, attenuates lipopolysaccharide-induced lung inflammation in mice. Am J Physiol Lung Cell Mol Physiol 2004, 286:L1122–8.View ArticlePubMedGoogle Scholar
- Maris NA, de Vos AF, Dessing MC, Spek CA, Lutter R, Jansen HM, van der Zee JS, Bresser P, van der Poll T: Antiinflammatory effects of salmeterol after inhalation of lipopolysaccharide by healthy volunteers. Am J Respir Crit Care Med 2005, 172:878–884.View ArticlePubMedGoogle Scholar
- Toews GB, Vial WC, Hansen EJ: Role of C5 and recruited neutrophils in early clearance of nontypable Haemophilus influenzae from murine lungs. Infect Immun 1985, 50:207–212.PubMedPubMed CentralGoogle Scholar
- Foxwell AR, Kyd JM, Cripps AW: Kinetics of inflammatory cytokines in the clearance of non-typeable Haemophilus influenzae from the lung. Immunol Cell Biol 1998, 76:556–559.View ArticlePubMedGoogle Scholar
- Laichalk LL, Kunkel SL, Strieter RM, Danforth JM, Bailie MB, Standiford TJ: Tumor necrosis factor mediates lung antibacterial host defense in murine Klebsiella pneumonia. Infect Immun 1996, 64:5211–5218.PubMedPubMed CentralGoogle Scholar
- van der Poll T, Keogh CV, Buurman WA, Lowry SF: Passive immunization against tumor necrosis factor-alpha impairs host defense during pneumococcal pneumonia in mice. Am J Respir Crit Care Med 1997, 155:603–608.View ArticlePubMedGoogle Scholar
- Rijneveld AW, Florquin S, Branger J, Speelman P, Van Deventer SJ, van der Poll T: TNF-alpha compensates for the impaired host defense of IL-1 type I receptor-deficient mice during pneumococcal pneumonia. J Immunol 2001, 167:5240–5246.View ArticlePubMedGoogle Scholar
- van Westerloo DJ, Knapp S, van't Veer C, Buurman WA, de Vos AF, Florquin S, van der Poll T: Aspiration pneumonitis primes the host for an exaggerated inflammatory response during pneumonia. Crit Care Med 2005, 33:1770–1778.View ArticlePubMedGoogle Scholar
- Frick AG, Joseph TD, Pang L, Rabe AM, St Geme JW, Look DC: Haemophilus influenzae stimulates ICAM-1 expression on respiratory epithelial cells. J Immunol 2000, 164:4185–4196.View ArticlePubMedGoogle Scholar
- Humlicek AL, Pang L, Look DC: Modulation of airway inflammation and bacterial clearance by epithelial cell ICAM-1. Am J Physiol Lung Cell Mol Physiol 2004, 287:L598–607.View ArticlePubMedGoogle Scholar
- Branger J, Wieland CW, Florquin S, Maris NA, Pater JM, Speelman P, Shimizu T, Ishii S, van der Poll T: Platelet-activating factor receptor-deficient mice show an unaltered clearance of nontypeable Haemophilus influenzae from their respiratory tract. Shock 2004, 22:543–547.View ArticlePubMedGoogle Scholar
- Wieland CW, Florquin S, Maris NA, Hoebe K, Beutler B, Takeda K, Akira S, van der Poll T: The MyD88-dependent, but not the MyD88-independent, pathway of TLR4 signaling is important in clearing nontypeable haemophilus influenzae from the mouse lung. J Immunol 2005, 175:6042–6049.View ArticlePubMedGoogle Scholar
- Sheehan KC, Ruddle NH, Schreiber RD: Generation and characterization of hamster monoclonal antibodies that neutralize murine tumor necrosis factors. J Immunol 1989, 142:3884–3893.PubMedGoogle Scholar
- Williams RO, Feldmann M, Maini RN: Anti-tumor necrosis factor ameliorates joint disease in murine collagen-induced arthritis. Proc Natl Acad Sci U S A 1992, 89:9784–9788.View ArticlePubMedPubMed CentralGoogle Scholar
- Bemelmans MH, Gouma DJ, Greve JW, Buurman WA: Effect of antitumour necrosis factor treatment on circulating tumour necrosis factor levels and mortality after surgery in jaundiced mice. Br J Surg 1993, 80:1055–1058.View ArticlePubMedGoogle Scholar
- Suitters AJ, Foulkes R, Opal SM, Palardy JE, Emtage JS, Rolfe M, Stephens S, Morgan A, Holt AR, Chaplin LC, et al.: Differential effect of isotype on efficacy of anti-tumor necrosis factor alpha chimeric antibodies in experimental septic shock. J Exp Med 1994, 179:849–856.View ArticlePubMedGoogle Scholar
- Knapp S, Leemans JC, Florquin S, Branger J, Maris NA, Pater J, van Rooijen N, van der Poll T: Alveolar macrophages have a protective antiinflammatory role during murine pneumococcal pneumonia. Am J Respir Crit Care Med 2003, 167:171–179.View ArticlePubMedGoogle Scholar
- Rao VK, Krasan GP, Hendrixson DR, Dawid S, St Geme JW: Molecular determinants of the pathogenesis of disease due to non-typable Haemophilus influenzae. FEMS Microbiol Rev 1999, 23:99–129.View ArticlePubMedGoogle Scholar
- Sekut L, Champion BR, Page K, Menius JAJ, Connolly KM: Anti-inflammatory activity of salmeterol: down-regulation of cytokine production. Clin Exp Immunol 1995, 99:461–466.View ArticlePubMedPubMed CentralGoogle Scholar
- van der Poll T, Coyle SM, Barbosa K, Braxton CC, Lowry SF: Epinephrine inhibits tumor necrosis factor-alpha and potentiates interleukin 10 production during human endotoxemia. J Clin Invest 1996, 97:713–719.View ArticlePubMedPubMed CentralGoogle Scholar
- Wu CC, Liao MH, Chen SJ, Chou TC, Chen A, Yen MH: Terbutaline prevents circulatory failure and mitigates mortality in rodents with endotoxemia. Shock 2000, 14:60–67.View ArticlePubMedGoogle Scholar
- Skerrett SJ, Martin TR, Chi EY, Peschon JJ, Mohler KM, Wilson CB: Role of the type 1 TNF receptor in lung inflammation after inhalation of endotoxin or Pseudomonas aeruginosa. Am J Physiol 1999, 276:L715–27.PubMedGoogle Scholar
- Rijneveld AW, Florquin S, Speelman P, Edwards CK, Dinarello CA, van der Poll T: Interleukin-1 receptor antagonist transiently impairs antibacterial defense but not survival in murine pneumococcal pneumonia. Eur Cytokine Netw 2003, 14:242–245.PubMedGoogle Scholar
- Schultz MJ, Rijneveld AW, Florquin S, Edwards CK, Dinarello CA, van der Poll T: Role of interleukin-1 in the pulmonary immune response during Pseudomonas aeruginosa pneumonia. Am J Physiol Lung Cell Mol Physiol 2002, 282:L285–90.View ArticlePubMedGoogle Scholar
- Doerschuk CM, Tasaka S, Wang Q: CD11/CD18-dependent and -independent neutrophil emigration in the lungs: how do neutrophils know which route to take? Am J Respir Cell Mol Biol 2000, 23:133–136.View ArticlePubMedGoogle Scholar
- Anderson GP, Linden A, Rabe KF: Why are long-acting beta-adrenoceptor agonists long-acting? Eur Respir J 1994, 7:569–578.View ArticlePubMedGoogle Scholar
- Ball DI, Brittain RT, Coleman RA, Denyer LH, Jack D, Johnson M, Lunts LH, Nials AT, Sheldrick KE, Skidmore IF: Salmeterol, a novel, long-acting beta 2-adrenoceptor agonist: characterization of pharmacological activity in vitro and in vivo. Br J Pharmacol 1991, 104:665–671.View ArticlePubMedPubMed CentralGoogle Scholar
- Ottonello L, Morone P, Dapino P, Dallegri F: Inhibitory effect of salmeterol on the respiratory burst of adherent human neutrophils. Clin Exp Immunol 1996, 106:97–102.View ArticlePubMedPubMed CentralGoogle Scholar
- Van der Poll T: Effects of catecholamines on the inflammatory response. Sepsis 2001, 4:159–167.View ArticleGoogle Scholar
- Capelli A, Lusuardi M, Carli S, Zaccaria S, Trombetta N, Donner CF: In vitro effect of beta 2-agonists on bacterial killing and superoxide anion (O2-) release from alveolar macrophages of patients with chronic bronchitis. Chest 1993, 104:481–486.View ArticlePubMedGoogle Scholar
- Zetterlund A, Larsson PH, Muller-Suur C, Palmberg L, Larsson K: Budesonide but not terbutaline decreases phagocytosis in alveolar macrophages. Respir Med 1998, 92:162–166.View ArticlePubMedGoogle Scholar
- Silvestri M, Oddera S, Lantero S, Rossi GA: beta 2-agonist-induced inhibition of neutrophil chemotaxis is not associated with modification of LFA-1 and Mac-1 expression or with impairment of polymorphonuclear leukocyte antibacterial activity. Respir Med 1999, 93:416–423.View ArticlePubMedGoogle Scholar
- Dowling RB, Johnson M, Cole PJ, Wilson R: Effect of salmeterol on Haemophilus influenzae infection of respiratory mucosa in vitro. Eur Respir J 1998, 11:86–90.View ArticlePubMedGoogle Scholar
- Dowling RB, Rayner CF, Rutman A, Jackson AD, Kanthakumar K, Dewar A, Taylor GW, Cole PJ, Johnson M, Wilson R: Effect of salmeterol on Pseudomonas aeruginosa infection of respiratory mucosa. Am J Respir Crit Care Med 1997, 155:327–336.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.