Agonist-specific patterns of beta 2-adrenoceptor responses in human airway cells during prolonged exposure.

BACKGROUND AND PURPOSE: Beta(2)-adrenoceptor agonists (beta(2)-agonists) are important bronchodilators used in the treatment of asthma and chronic obstructive pulmonary disease. At the molecular level, beta(2)-adrenergic agonist stimulation induces desensitization of the beta(2)-adrenoceptor. In this study, we have examined the relationships between initial effect and subsequent reduction of responsiveness to restimulation for a panel of beta(2)-agonists in cellular and in vitro tissue models. EXPERIMENTAL APPROACH: Beta(2)-adrenoceptor-induced responses and subsequent loss of receptor responsiveness were studied in primary human airway smooth muscle cells and bronchial epithelial cells by measuring cAMP production. Receptor responsiveness was compared at equi-effective concentrations, either after continuous incubation for 24 h or after a 1 h pulse exposure followed by a 23 h washout. Key findings were confirmed in guinea pig tracheal preparations in vitro. KEY RESULTS: There were differences in the reduction of receptor responsiveness in human airway cells and in vitro guinea pig trachea by a panel of beta(2)-agonists. When restimulation occurred immediately after continuous incubation, loss of responsiveness correlated with initial effect for all agonists. After the 1 h pulse exposure, differences between agonists emerged, for example isoprenaline and formoterol induced the least reduction of responsiveness. High lipophilicity was, to some extent, predictive of loss of responsiveness, but other factors appeared to be involved in determining the relationships between effect and subsequent loss of responsiveness for individual agonists. CONCLUSIONS AND IMPLICATIONS: There were clear differences in the ability of different beta(2) agonists to induce loss of receptor responsiveness at equi-effective concentrations.

Budesonide/formoterol effects on metalloproteolytic balance in TGFbeta-activated human lung fibroblasts.

In the airways of asthmatic patients, activated fibroblasts account for an excessive matrix production including proteoglycans (PGs). Transforming growth factor-beta (TGFbeta), metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play key roles in matrix turnover. It is unclear whether asthma therapy with combination of inhaled glucocorticoids and long-acting beta(2)-agonists affects metalloproteolytic equilibrium and by that counteracts airway fibrosis. The effects of the glucocorticoid, budesonide, and the long-acting beta(2)-agonist, formoterol, on the PG production and the activity of PGs' main regulators: MMP-3, MMP-9, MMP-2 and TIMP-1 were investigated in human lung fibroblasts (HFL-1) treated for 24h with TGFbeta1 (10 ng/ml) without/with budesonide (10(-9) to 10(-6)M) and/or formoterol (10(-11) to 10(-6)M). TGFbeta1 significantly increased production of PGs and TIMP-1, and the activity of MMP-3, MMP-9 and MMP-2. Concurrent budesonide/formoterol combination counteracted the enhanced: PG and TIMP-1 production, MMP-9 activity and MMP-9/TIMP-1 ratio, whereas MMP-2 and MMP-3 were not affected and so their ratios to TIMP-1 were significantly increased. Budesonide or formoterol alone achieved equal effects as budesonide/formoterol on MMP-9 and MMP-9/TIMP-1 ratio but had no effects on TIMP-1, MMP-2 or MMP-3. In the formoterol absence, higher budesonide concentrations were required to reduce the PG production, whereas formoterol alone had no effects. These results suggest that the budesonide/formoterol combination enhanced metalloproteolytic activity of human lung fibroblasts via a synergistic decrease of TIMP-1, and that this mechanism may be involved in the synergistic inhibition of the TGFbeta1-induced PG production. This implies that budesonide/formoterol combination therapy can counteract excessive matrix production and thus pathological airway fibrotic remodeling in asthma.

Specific haptoglobin expression in bronchoalveolar lavage during differentiation of circulating fibroblast progenitor cells in mild asthma.

Haptoglobin is an acute-phase glycoprotein considered to be involved in tissue repair and is produced by fibroblasts and inflammatory cells. By using a gel-based proteomic approach, we show for the first time a possible role for haptoglobin in the differentiation of fibroblast progenitor cells, termed fibrocytes, in patients with mild asthma. Bronchoalveolar lavage fluid (BALF) was performed to sample circulating fibrocytes from patients with mild asthma and nonasthmatic control subjects. Fibrocytes from the airway lumen were characterized by triple staining of the markers CD34/CD45R0/alpha-smooth muscle actin, and subjected to confocal microscopy. The protein expression pattern was analyzed using two-dimensional electrophoresis (2-DE) and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF). Elevated levels of haptoglobin expression in BALF was reported in a sub-group of patients with mild asthma (p < 0.05) when compared to the other subjects. In addition, this increase in haptoglobin was accompanied by differentiation of fibrocytes into fibroblast-like cells. When further analyzing the expression pattern of haptoglobin isoforms, a heterozygous expression was detected in the patients where fibrocyte differentiation could be observed. These data raise the possibility that an acute and specific inflammatory state facilitates the differentiation of fibroblast progenitor cells into activated fibroblasts. Furthermore, this study proposes a novel role for haptoglobin in airway remodeling in patients with asthma.

Lung fibroblast proteoglycan production induced by serum is inhibited by budesonide and formoterol.

Proteoglycans contribute to extracellular matrix remodeling in asthmatic airways. We investigated the effects of budesonide, a glucocorticoid, and formoterol, a long-acting beta2-adrenergic agonist, on serum-induced proteoglycan production by human lung fibroblasts. In 10% serum, total proteoglycan production was increased 1.5-fold (P < 0.01) compared with basal production in 0.4% serum. Budesonide (10(-8) M) reduced this increase by 44% (P < 0.01) and, whereas formoterol (10(-10)-10(-8) M) had no inhibitory effects, the drug combination abolished the increase (P < 0.01) without affecting fibroblast proliferation. This synergistic effect required functional glucocorticoid and beta-adrenergic receptors. The production of the proteoglycans decorin, biglycan, perlecan, and versican was increased 2.5- to 5-fold (P < 0.01) in 10% serum. Combination treatment with budesonide (10(-8) M) and formoterol (10(-10) M) abolished this increase to a significantly greater extent than either drug alone. In 10% serum, only versican mRNA was increased 1.4-fold (P < 0.05), whereas decorin mRNA was reduced to 39% (P < 0.01) of basal expression. These serum effects were counteracted by the drug combination, but there were no significant differences between the combination and either drug alone. Thus, the budesonide and formoterol combination seems to synergistically control serum-induced proteoglycan production, primarily at the post-transcriptional level. In conclusion, the proteoglycan upregulation characteristic of asthmatic airways may be limited by combination therapy with budesonide and formoterol.