COL4A3 is degraded in allergic asthma and degradation predicts response to anti-IgE therapy.

BACKGROUND: Asthma is a heterogeneous syndrome substantiating the urgent requirement for endotype-specific biomarkers. Dysbalance of fibrosis and fibrolysis in asthmatic lung tissue leads to reduced levels of the inflammation-protective collagen 4 (COL4A3). OBJECTIVE: To delineate the degradation of COL4A3 in allergic airway inflammation and evaluate the resultant product as a biomarker for anti-IgE therapy response. METHODS: The serological COL4A3 degradation marker C4Ma3 (Nordic Bioscience, Denmark) and serum cytokines were measured in the ALLIANCE cohort (paediatric cases/controls: n=134/n=35; adult cases/controls: n=149/n=31). Exacerbation of allergic airway disease in mice was induced by sensitising to ovalbumin (OVA), challenge with OVA aerosol and instillation of poly(cytidylic-inosinic). Fulacimstat (chymase inhibitor; Bayer) was used to determine the role of mast cell chymase in COL4A3 degradation. Patients with cystic fibrosis (n=14) and cystic fibrosis with allergic bronchopulmonary aspergillosis (ABPA; n=9) as well as patients with severe allergic uncontrolled asthma (n=19) were tested for COL4A3 degradation. Omalizumab (anti-IgE) treatment was assessed using the Asthma Control Test. RESULTS: Serum levels of C4Ma3 were increased in asthma in adults and children alike and linked to a more severe, exacerbating allergic asthma phenotype. In an experimental asthma mouse model, C4Ma3 was dependent on mast cell chymase. Serum C4Ma3 was significantly elevated in cystic fibrosis plus ABPA and at baseline predicted the success of the anti-IgE therapy in allergic, uncontrolled asthmatics (diagnostic OR 31.5). CONCLUSION: C4Ma3 levels depend on lung mast cell chymase and are increased in a severe, exacerbating allergic asthma phenotype. C4Ma3 may serve as a novel biomarker to predict anti-IgE therapy response.

New Perspectives for Mucolytic, Anti-inflammatory and Adjunctive Therapy with 1,8-Cineole in COPD and Asthma: Review on the New Therapeutic Approach.

The mucolytic monoterpene 1,8-cineole (eucalyptol), the major constituent of eucalyptus species, is well known for its anti-inflammatory, antioxidant, bronchodilatory, antiviral and antimicrobial effects. The main protective antiviral, anti-inflammatory and mucolytic mechanisms of 1,8-cineole are the induction of interferon regulatory factor 3 (IRF3), the control of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) along with decreasing mucin genes (MUC2, MUC19). In normal human monocytes direct inhibition was shown of reactive oxygen species (ROS)-mediated mucus hypersecretion and of steroid resistence inducing superoxides (O2·-) and pro-inflammatory hydrogen peroxides (H2O2) with partial control of superoxide dismutase (SOD), which enzymatically metabolizes O2·- into H2O2. By inhibition of NF-κB, 1,8-cineole, at relevant plasma concentrations (1.5 µg/ml), strongly and significantly inhibited in normal human monocyte lipopolysaccharide (LPS)-stimulated cytokines relevant for exacerbation (tumour necrosis factor alpha (TNFα), interleukin (IL)-1ß and systemic inflammation (IL-6, IL-8). Infectious agents and environmental noxa have access via TNFα and IL-1ß to the immune system with induction of bronchitis complaints and exacerbations of chronic obstructive pulmonary disease (COPD), asthma and asthma-COPD overlap. In lymphocytes from healthy human donors 1,8-cineole inhibited TNFα, IL-1ß, IL-4 and IL-5 and demonstrated for the first time control of Th1/2-type inflammation. 1,8-Cineole at relevant plasma levels increased additively in vitro the efficacy of inhaled guideline medications of budesonide (BUD) and budesonide + formoterol ,and preliminary data also showed increased efficacy of long-acting muscarinic receptor antagonist (LAMA)-mediated cytokine inhibition in vitro. On the basis of the preclinical data, earlier randomised controlled studies with adjunctive therapy of 1,8-cineole (3 × 200 mg/day) for 6 months showed improvement of uncontrolled asthma by significant improvement of lung function, nocturnal asthma and quality of life scores and in COPD decrease of exacerbations (- 38.5%) (during wintertime). This review reports an update with reference to the literature of 1,8-cineole, also as adjunctive therapy, as a therapeutic agent for the protection and control of inflammatory airway diseases.

Pulmonary arterial hypertension in patients with sarcoidosis: the Pulsar single center experience.

Sarcoidosis is a systemic granulomatous disease with unknown etiology. Lungs and lymph nodes are commonly affected. Also, cases of pulmonary hypertension (PH) and pulmonary arterial hypertension (PAH) are described. However, the exact prevalence of PAH in patients with sarcoidosis is unclear. A 111 patients with proven sarcoidosis were recruited from January 2010 to October 2010. All patients were studied prospectively by transthoracic echocardiography (TTE) for the presence of PH. In assumed PH, a right heart catheterization (RHC) followed if there were no other reasons for PH. In 23 of the 111 patients (21%) PH was assumed in TTE. Three patients presented with severe mitral insufficiency III° and IV°, in eight patients PH was supposed to be caused by chronic heart failure or relevant diastolic dysfunction > II°, two patients declined undergoing RHC. Of the ten patients investigated with RHC, four showed a precapillary pulmonary arterial hypertension and in one patient a postcapillary hypertension was diagnosed. All four patients with precapillary PH had a radiologic stage III and IV. In three of the four patients a significantly reduced transfer factor for carbon monoxide (TLCO) <50% was found. All patients with precapillary PH had a chronic course of sarcoidosis lasting ≥13 years. This is the first study which prospectively investigated a large cohort of patients with sarcoidosis for the prevalence of PH and PAH. The prevalence of precapillary PH was found to be at least 3.6% (4/111) and therefore exceeds the prevalence of PAH in the normal population by far. A chronic and progressive lung involvement due to sarcoidosis seems to be the most evident risk factor for developing a sarcoidosis PH.

ß2-adrenoceptors and muscarinic receptors mediate opposing effects on endothelin-1 expression in human lung fibroblasts.

Human lung fibroblasts are a potential source of endothelin-1 (ET-1), a pro-fibrotic mediator. The present study explored possible muscarinic and ß-adrenergic modulations of ET-1 expression in human lung fibroblasts. MRC-5 human lung fibroblasts were cultured. Expression of prepro-endothelin-1 (ppET-1) mRNA was determined by quantitative real time PCR. [(3)H]-Proline incorporation was determined as measure of collagen synthesis. The muscarinic agonist oxotremorine induced, in a tiotropium-sensitive manner, a three-fold increase in ppET-1 mRNA. The ß(2)-adrenoceptor agonist olodaterol caused a reduction of ppET-1 mRNA by 45%. Olodaterol also opposed the stimulatory effect of oxotremorine. The effect of olodaterol was mimicked by the protein kinase A agonist 6-Bnz-cAMP, whereas the Epac (exchange protein activated by cAMP) agonist 8-CPT-2'-O-Me-cAMP was less effective. Transforming growth factor-ß(1) (TGF-ß, 0.3 and 1 ng/ml) induced a three- and eight-fold increase in pp-ET-1 mRNA, respectively. Olodaterol opposed the effect of 0.3, but not that of 1 ng/ml TGF-ß. Likewise, 6-Bnz-cAMP opposed the effect of 0.3, but not that of 1 ng/ml TGF-ß. TGF-ß inhibited ß(2)-adrenoceptor mRNA expression, maximally by 90%. Muscarinic agonist-induced stimulation of [(3)H]-proline incorporation was attenuated by the endothelin ET1 receptor antagonist bosentan. In conclusion, ET-1 expression in human lung fibroblasts is regulated by stimulatory muscarinic receptors and inhibitory ß(2)-adrenoceptors. Since muscarinic up-regulation of ET-1 contributes to pro-fibrotic effects of muscarinic stimuli, inhibition of ET-1 expression could contribute to long-term beneficial effects of long-acting ß(2)-adrenoceptor agonists and long-acting muscarinic antagonists. However, excessive exposure to TGF-ß results in loss of ß-adrenoceptor expression and function of its down-stream signaling.

Obstructive sleep apnoea as a risk factor for atherosclerosis - implication for preventive and personalised treatment.

Atherosclerosis with its manifestations and associated diseases is a main cause of morbidity and mortality in industrial countries. The pathomechanisms underlying atherosclerosis are complex and comprise exogenous factors as well as genetic predisposition. Beyond the well-defined risk factors for the development of atherosclerosis, obstructive sleep apnoea (OSA) merits more and more attention. A growing body of evidence has associated OSA with vascular pathologies. Although the exact mechanisms involved are not known, the occurrence of intermittent hypoxia typical for OSA may lead to oxidative stress, inflammation, metabolic and neural changes which in turn are responsible for vessel dysfunction underlying atherosclerosis. It has been demonstrated that therapy with continuous positive airway pressure (CPAP) plays a vasoprotective role. This review summarises data resulting from epidemiological and clinical studies with emphasis on the possible mechanisms linking OSA with atherosclerosis, predictive biomarkers helping identify OSA patients at high cardiovascular risk and personalised treatment approaches.

Inflammatory responses after endothelin B (ETB) receptor activation in human monocytes: new evidence for beneficial anti-inflammatory potency of ETB-receptor antagonism.

Endothelin (ET) stimulates potent ETA/ETB receptors important in the pathogenesis of pulmonary arterial hypertension (PAH) and fibrosis. Though therapy with ET-receptor antagonists is well established uncertainty exists whether selective ETA or dual ETA/ETB-receptor antagonism is superior in PAH. The objective of this study was to further elucidate the pro-inflammatory effects of ET-1 on ETB receptors in cultured human monocytes (10(5)/20 h) compared with non-specific stimulation with LPS in vitro and to define the antagonizing effects of bosentan, a dual ETA/ETB-receptor antagonist, on inflammatory mediator production. We further hypothesized that ETB-receptor antagonism reduces the requirement of PGE2 to control inflammatory mediator production. Activation of the monocyte ETB subtype by ET (1 ng/ml) concentration-dependently stimulated TNF-alpha (744%) >PGE2 (570%) > IL-1 beta (112%) and had no effect on 5-lipoxygenase metabolism. Compared with ET a different profile of IL-1 beta >TNF-alpha >PGE2 was induced by LPS. ETB-receptor antagonism attenuated ET- and LPS-responses in monocytes, in particular of TNF-alpha and PGE2 to a similar extend (40%) that were only demonstrable following LPS at therapeutic plasma concentrations of bosentan and had no effect on IL-1 beta. Inhibition of ETB receptors in LPS-stimulated monocytes by bosentan was responded with suppression of PGE2 and increased production of leukotrienes indicating strong effects in the cyclooxygenase pathway that is known to control cellular ET transcription. These data suggest an important signaling pathway between ET-induced cytokine production following ETB-receptor activation with no further control of ET transcription by PGE2 required following ETB receptor antagonism. Therefore, in states of inflammation increased ETB-receptor expression and activation mediated by elevated ET concentrations may be an underestimated mechanism, which warrants the application of combined ETA/ETB-receptor antagonists.

Inhibition of NADPH oxidase by apocynin inhibits lipopolysaccharide (LPS) induced up-regulation of arginase in rat alveolar macrophages.

Reactive oxygen species participate in the pathogenesis of inflammatory airway diseases, in which increased arginase may play a role by interfering with nitric oxide (NO) synthesis and providing substrate for collagen synthesis. Therefore a modulatory role of reactive oxygen species for arginase was explored in alveolar macrophages using the NADPH oxidase inhibitor apocynin. The effects of lipopolysacharides (LPS) and apocynin on nitrite accumulation, arginase activity and mRNA for inducible NO synthase (iNOS), arginase I and II were determined. Superoxide anion (O(2)(-)) release was analysed by the iodonitrotetrazolium (INT) formazan assay. LPS (1 microg/ml) caused a 55%, transient increase in INT formation, i.e. O(2)(-) release which was inhibited by apocynin (500 microM). LPS caused a 2 fold increase in arginase activity and a marked increase in mRNA encoding arginase I, the predominant isoenzyme. Both effects were largely attenuated by apocynin. Apocynin did not affect the stability of arginase I mRNA, but accelerated the decline of arginase activity when protein synthesis was inhibited by cycloheximide. Apocynin also reduced LPS-induced nitrite accumulation (by 30%) and iNOS mRNA expression, but the magnitude of these effects was smaller than that on arginase I. Arginase I mRNA was also increased following exposure to hydrogen peroxide (H(2)O(2), 200 muM). In conclusion, inhibition of NADPH oxidase in alveolar macrophages causes down-regulation of arginase, indicating that reactive oxygen species exert stimulatory effects on arginase. Enhanced transcription of arginase mRNA and prolongation of the life time of the active enzyme appear to contribute to the enhanced arginase activity.

[Diagnostics and therapy of idiopathic pulmonary hemosiderosis]. / Die idiopathische pulmonale Hämosiderose.

Idiopathic pulmonary hemosiderosis (IPH) is a rare clinical entity characterized by recurrent episodes of diffuse alveolar hemorrhage. The disease--also called Ceelen's syndrome--was subsequently defined as a clinical entity comprising the triade of hemoptysis, opacities in X-ray, and anemia, in which the etiology is still unknown. Intensive search for a specific etiology ends up negative, and there are no features, which are specifically pathognomonic for IPH. Therefore, the diagnosis relies solely on the exclusion of other disorders in which diffuse alveolar hemorrhage is a cardinal sign. Acute episodes may occur frequently, eventually leading to lung fibrosis in the chronic stage. Usually, the therapy consists of high doses of corticosteroids, which can be combined with immunosuppressive drugs. In addition to this review, a case having Ceelen's syndrome is presented. After a complicated clinical course, the patient could finally be stabilized with a combination therapy of prednisolone and azathioprine.

[End therapeutic nihilism towards COPD]. / Für eine frühe und stadiengerechte Behandlung der COPD. Neue Leitlinien gegen therapeutischen Nihilismus.

Prevention of COPD requires appropriate patient education, especially of adolescents, as well as the establishment of an effective national health policy. The new GOLD guidelines represent the current standard of knowledge on the management of chronic, progressive, obstructive pulmonary diseases. It points out that COPD is avoidable and treatable,and hence, there is no reason for therapeutic nihilism. Chronic bronchitis preceding a progressive respiratory obstruction cannot be improved with the presently available respiratory therapeutics. For this reason, therapeutic measures concentrate on the avoidance of exacerbations, which are primarily responsible for the severity of the course of COPD.

New evidence of H1-receptor independent COX-2 inhibition by fexofenadine HCl in vitro.

BACKGROUND/AIMS: Fexofenadine HCl (FEX) has previously been shown to have anti-inflammatory properties in relieving nasal congestion in allergic rhinitis. The objective of this study was to further elucidate the mechanism of action behind the anti-inflammatory properties of FEX in addition to its H(1)-receptor antagonism. METHODS: The effects of two antihistamines, FEX and loratadine (LOR), were investigated on cyclooxygenase (COX)-1 and -2 enzymes in vitro. FEX (10(-9)-10(-3) mol/l) and LOR (10(-9)-10(-4) mol/l) were incubated with arachidonic acid in a COX screening assay with either ovine COX-1 or COX-2 or human COX-2. COX-2 enzyme inhibitory activity for the antihistamines was compared with the known selective COX-2 inhibitor DuP-679. RESULTS: High concentrations of FEX (10(-3) mol/l) significantly inhibited arachidonic acid-mediated ovine COX-1 activity, but low concentrations had no effect. Low concentrations of FEX (10(-8) mol/l) inhibited ovine COX-2 activity, and this inhibition decreased with increasing concentrations. The inhibition of COX-2 activity by FEX was similar to that seen with the selective COX-2 inhibitor, DuP-679. Conversely, LOR inhibited COX-1 activity at low concentrations (10(-8) mol/l), but had little inhibitory effect on COX-1 at high concentrations. LOR (10(-5) mol/l) markedly stimulated COX-2 activity. CONCLUSION: FEX showed selective arachidonic acid-mediated COX-2 inhibitory enzyme activity, which differed markedly from the COX inhibitory enzyme activity of LOR. This selective COX-2 inhibitor activity by FEX may contribute to its anti-inflammatory properties in relieving nasal congestion in allergic rhinitis.

Muscarinic receptors mediate stimulation of human lung fibroblast proliferation.

Airway remodeling is a structural alteration associated with chronic inflammatory and obstructive airway diseases, wherein fibroblasts are crucially involved. The present study investigates whether lung fibroblast proliferation is influenced by muscarinic mechanisms. For this purpose, expression of muscarinic receptors in MRC-5 human lung fibroblasts was characterized by semiquantitative RT-PCR, and the effects of muscarinic agonists and antagonists on ((3)H)-thymidine incorporation as a measure of proliferative activity were studied under different culture conditions. MRC-5 fibroblasts express mRNA encoding different subtypes of muscarinic receptors (M(2) > M(3) > M(4), traces for M(5) and no M(1)). Expression of M(2) and M(3) receptors was confirmed at the protein level by immunoblot analysis. Under different culture conditions, carbachol (up to 10 microM) or oxotremorine (10 microM) stimulated ((3)H)-thymidine incorporation, with maximum increases between about 40 and 100%. The stimulatory effect of 10 microM carbachol was prevented by pretreatment with pertussis toxin and antagonized in a concentration-dependent manner by the muscarinic receptor antagonists tiotropium, AQ-RA 741, AF-DX 384, 4-diphenylacetoxy-N-methylpiperidine methoiodide, himbacine, p-fluorohexahydrosiladifenidol, and pirenzepine, with concentrations producing 50% inhibition of 14 pM, 24, 64, 127, 187, 452 nM, and 1.5 microM, respectively. Primary human lung fibroblasts were also found to express mRNA for muscarinic receptors (M(2) > M(1) > M(3), traces for M(4) and no M(5)), and showed a pertussis toxin-sensitive proliferative response to muscarinic receptor stimulation. In conclusion, proliferation of human lung fibroblasts can be stimulated by activation of muscarinic receptors with a pharmacologic profile correlating best to M(2) receptors.

Control by cholinergic mechanisms.

In the respiratory tract acetylcholine is neurotransmitter in ganglia and postganglionic parasympathetic nerves, but in addition is paracrine mediator released from various non-neuronal cells. Almost every cell type present in the respiratory tract expresses nicotinic and muscarinic receptors and therefore appears to be a target for acetylcholine. The present review describes the mechanisms of synthesis and release of acetylcholine from neuronal and non-neuronal cells and the differential control mechanisms. The different cholinoceptors, multiple nicotinic and muscarinic receptors and their signalling are outlined and their involvement in the modulation of the function of various target cells, smooth muscles, nerves, surface epithelial, secretory cells, fibroblasts and inflammatory cells is discussed in detail.

Differential effects of fexofenadine on arachidonic acid metabolism in cultured human monocytes.

The relief of nasal congestion with the antihistamine fexofenadine in seasonal allergic rhinitis is thought to be due to its additional anti-inflammatory properties. The objective of this study was to evaluate the in vitro effects of fexofenadine on stimulated arachidonic acid metabolism. Human monocytes, isolated from blood and donated by 5 healthy volunteers, were either incubated for 20 h with 10 microg/ml lipopolysaccharide, with and without fexofenadine (10(-8)-10(-3) mol/l, n = 8-19), or were incubated for 20 h, with and without fexofenadine, and then stimulated with 0.5 mg/ml zymosan for 2 h. Leukotriene B4 (LTB4), LTC4, LTD4 and LTE4, prostaglandin E2 (PGE2) and F2alpha (PGF2alpha) production was determined by enzyme immunoassay. Zymosan-stimulated production of LTC4, LTD4 and LTE4 was significantly inhibited by clinically relevant concentrations of fexofenadine HCl: 10(-7) mol/l (22% inhibition vs. control, p = 0.008) and 10(-6) mol/l (24% inhibition vs. control, p = 0.020). Higher concentrations of fexofenadine (10(-4) and 10(-3) mol/l) inhibited LTB(4) generation. Lipopolysaccharide-stimulated production of PGE2 was significantly inhibited by fexofenadine HCl 10(-6) mol/l (26% inhibition, p = 0.035) and 10(-5) mol/l (40% inhibition, p = 0.001). Higher concentrations of fexofenadine HCl (10(-4) and 10(-3) mol/l) significantly inhibited PGF2alpha production by 50% (p = 0.026) and 63% (p = 0.001), respectively. Fexofenadine, at both clinically relevant and higher concentrations, inhibits LTC4, LTD4, LTE4 and PGE2 in cultured human monocytes. These additional anti-inflammatory properties may underlie the relief of nasal congestion observed in clinical studies.

Inhibitory activity of 1,8-cineol (eucalyptol) on cytokine production in cultured human lymphocytes and monocytes.

BACKGROUND: The therapeutic value of secretolytic agents in COPD and asthma is still disputed. For this reason, in a preclinical study we aimed to test the potential anti-inflammatory efficacy of 1,8-cineol (eucalyptol) in inhibiting polyclonal stimulated cytokine production by human unselected lymphocytes and LPS-stimulated monocytes. METHODS: Cytokine production was determined following 20 h of incubation cells with 1,8-cineol simultaneously with the stimuli in culture supernatants by enzyme immunoassay. RESULTS: Therapeutic concentrations of 1,8-cineol (1.5 microg/ml=10(-5)M) inhibited significantly (n=13-19, p=0.0001) cytokine production in lymphocytes of TNF-alpha > IL-1beta> IL-4> IL-5 by 92, 84, 70, and 65%, respectively. Cytokine production in monocytes of TNF-alpha > IL-1beta> IL-6> IL-8 was also significantly (n=7-16, p<0.001) inhibited by 99, 84, 76, and 65%, respectively. In the presence of 1,8-cineol (0.15 microg/ml=10(-6)M) production of TNF-alpha>IL-1beta by monocytes and of IL-1beta> TNF-alpha by lymph-ocytes was significantly inhibited by 77, 61 and by 36, 16%, respectively. 1,8-cineol (10(-6)M) had a larger impact on TNF-alpha and IL-1beta-production in monocytes compared to lymphocytes (p<0.03) and similar effects (p>0.59) at therapeutically relevant concentrations of 1,8-Cineol (10(-5)M). CONCLUSION: These results characterize 1,8-cineol as strong inhibitor of TNF-alpha and IL-1beta and suggest smaller effects on chemotactic cytokines. This is increasing evidence for the role of 1,8-cineol to control airway mucus hypersecretion by cytokine inhibition, suggesting long-term treatment to reduce exacerbations in asthma, sinusitis and COPD.

Comparison of in vitro-activity of commonly used topical glucocorticoids on cytokine- and phospholipase inhibition.

BACKGROUND AND OBJECTIVES: Topical glucocorticoids (GCs) are potent inhibitors of cellular inflammatory mediator production. Differences in receptor binding activities are believed to correlate with inhibition of mediator release and anti-inflammatory efficacy in vivo. To further assess this hypothesis we compared in cultured human monocytes the inhibitory activity of classic synthetic GCs on leukotriene B4 (LTB4), prostaglandin E2 (PGE2), interleukin 1 beta (IL-1beta) and c-phospholipase A 2 activity (cPLA2). METHODS: Normal human monocytes (10(5) /ml) were tested for 20 hrs with increasing concentrations (range 10(-12) -10(-5) M) of triamcinolone acetonide (TAA) compared to beclomethasone dipropionate (BDP), budesonide (BUD), dexamethasone (DEX), or the ethanol diluent together with 10 microg/ml of lipopolysaccharide (LPS). Mediator production and spontaneous cPLA subset 2-activity was determined by direct enzyme immunoassay methods. RESULTS: TAA at therapeutically relevant concentration (10(-8) M) inhibited significantly (p<0.01, n = 9) mediator production of TNF-alpha > IL-1beta > TxB2 > LTB subset 4 in a dose dependent manner by 75%, 65%, 41%, and 33%. IL-1beta inhibition at 10(-8) M by TAA (65%)> BDP (52%)> BUD (47%) was not different (ANOVA, p>0.2). Also spontaneous cPLA2-activity at 10(-8) M was inhibited to a similar degree (ANOVA, p> 0.6) by BUD (17.3%) > TAA (11.4%) > BDP (8.6%). In the same culture conditions spontaneous PGE2-secretion was inhibited by BDP (28.8%) > BUD (24.2%) > TAA (11.4%) with no significant effect for TAA. CONCLUSION: Clinically well established GCs have a similar inhibitory capacity on monocyte cytokine production and surprisingly only weak effects on AA-metabolism. Small receptor binding activity may account for the lack of cytokine inhibition by subtherapeutic (<10(-8) M) airway concentrations of TAA and BDP. Partial mediator inhibition by GCs at therapeutically known airway concentrations may be relevant to control bursts of airway inflammation during acute exacerbation but unfavourable to effectively delay progression of chronic airway inflammation.

Different mechanisms of action of beta2-adrenergic receptor agonists: a comparison of reproterol, fenoterol and salbutamol on monocyte cyclic-AMP and leukotriene B4 production in vitro.

BACKGROUND: Beta2-adrenergic receptor agonists have several effects on airway function, most of which are mediated in a variety of cell types resulting in increased c-AMP-production and inhibition of inflammatory mediator production. However, their stimulating effects on cAMP-production became known to be inversed by increasing phosphodiesterase (PDE) activity and degradation of cAMP. Therefore, in this study we have evaluated the efficacy of reproterol, a dual acting beta2-adrenoceptor agonist and PDE-inhibitor, as compared to salbutamol and fenoterol with respect to production of cAMP and LTB4 in cultured monocytes. METHODS: Isolated human monocytes (10(5)/ml) were incubated (n = 9) in suspension with beta2-adrenoceptor agonists (10(-10) -10(-4) M) for 30 minutes with and without IBMX. Then, cAMP production was determined following treatment with Triton-X100. Production of LTB4 was measured following incubation of beta2-adrenoceptor agonists for 4 hrs in the presence of LPS (10 mg/ml). cAMP and LTB subset 4 were measured in culture supernatants by enzyme immunoassay. RESULTS: At 10(-5) M, production of cAMP was significantly stimulated by reproterol > fenoterol > salbutamol in a dose-dependent manner to an extent of *128%, *65%, 13% (*p<0.04) respectively. In contrast, LTB4-production was inhibited significantly to a similar degree by salbutamol and reproterol in a dose-dependent manner by 59% and 49% (10(-5) M, p<0.03), respectively, with decreasing inhibition (15%) after fenoterol. Following co-incubation with IBMX, cAMP production only increased significantly (p<0.002) after fenoterol (+110%) compared to salbutamol (+29%) and reproterol (+50%) (ANOVA, p<0.001). CONCLUSION: These data suggest effects of the theophylline constituent of reproterol to inhibit adenylyl cyclase induced phosphodiesterase activity. The advantageous synergistic effects of reproterol on cAMP-production need to be further explored in trials.