Effect of IL-1 beta on responses of cultured human airway smooth muscle cells to bronchodilator agonists.

Abstract

Decreased beta-adrenergic responsiveness is a characteristic feature of asthma. In order to determine whether cytokines released in the asthmatic airway contribute to this phenomenon, we measured changes in stiffness of cultured human airway smooth muscle (HASM) cells induced by isoproterenol (ISO) in control HASM cells and HASM cells pretreated with IL-1 beta (20 ng/ml for approximately 42 h). Stiffness was measured by magnetic twisting cytometry. HASM cells were obtained from normal tracheal tissue obtained at lung transplant, and studied in passages 4-7. In control cells, ISO caused a dose-related decrease in cell stiffness. IL-1 beta had no effect on baseline cell stiffness. However, IL-1 beta caused a rightward shift in the concentration-response curve to ISO and decreased the maximal effectiveness of this agonist. Decreased responses to ISO were also obtained with 2 ng/ml IL-1 beta, or when cells were pretreated with IL-1 beta (20 ng/ml) for 22 h. This effect of IL-1 beta was not altered by pretreatment of the cells with pertussis toxin (100 ng/ml throughout the IL-1 beta exposure period). IL-1 beta also significantly attenuated the ability of prostaglandin E2 (PGE2) to decrease cell stiffness. In contrast, IL-1 beta had no effect on cell stiffness responses to dibutryl cAMP, a cell permeant analog of cAMP suggesting that the cytokine does not influence either the ability of cAMP to activate kinases, or the targets of these kinases which ultimately mediate cell relaxation. IL-1 beta (20 ng/ml for 40 h) caused a small (30%) but significant (P < 0.02) increase in basal cAMP, but also resulted in a 2-3-fold decrease in the changes in cAMP formation induced by either ISO or PGE2. In contrast, IL-1 beta had no effect on cAMP formation in response to forskolin, suggesting that IL-1 beta does not mediate its effects via changes in the expression or activity of adenylyl cyclase. Pretreatment with IL-1 beta had no significant effect on beta 2 adrenoceptor number assessed by [125I]-CYP binding in these cells, nor was there any significant effect of IL-1 beta on Gsa expression assessed by Western blot. In summary, our results indicate that IL-1 beta causes a concentration- and time-dependent decrease in responses of HASM cells to ISO and are consistent with the hypothesis that the effects of IL-1 beta are mediated by uncoupling of beta-receptors from Gs-induced activation of adenylyl cyclase.

Airway smooth muscle cells: contributing to and regulating airway mucosal inflammation?

“…Intratracheal administration of IL-1b to rats induced an attenuation of b-adrenergic receptorinduced airway relaxation through mechanisms involving a reduction in b-adrenoceptors and an increase in the inhibitory G protein, G i a subunit, coupled to a reduction in adenylyl cyclase activity [67]. Similar observations were made with in vitro human airway smooth muscle cells incubated with IL-1b with a decreased response in muscle stiffness to isoprenaline mediated by uncoupling of breceptors from stimulatory G s -induced activation of adenylyl cyclase, perhaps through the release of PGE 2 [68,69]. TNF-a can also induce a reduction in isoprenalinestimulated adenylyl cyclase activity [70], together with increased expression of Ga 1±2 and G q a but not of G s a proteins [71].…”

The Role of Airway Smooth Muscle in the Pathogenesis of Airway Wall Remodeling in Chronic Obstructive Pulmonary Disease

“…The activity of ␤-receptors may be decreased together with uncoupling of ␤ 2 -receptor adenylate cyclase; activity of the phosphodiesterase enzymes that degrade cyclic adenosine monophosphate may be enhanced. IL-1␤, which is present in COPD airways, can induce an attenuation of ␤-receptorϪ induced airway relaxation (86,87) through mechanisms involving a reduction in ␤-receptors, an increase in the G i␣ subunit, and a defect in adenylyl cyclase activity (87). This effect of IL-1␤ in impairing ␤-receptor-mediated relaxation may be reversed partially by corticosteroids through an up-regulation of G-protein-coupled receptor kinases (88), which could underlie the beneficial effect of the combination of corticosteroids and longacting ␤-agonists.…”

Cyclooxygenase-2 and MicroRNA-155 Expression Are Elevated in Asthmatic Airway Smooth Muscle Cells

“…Hyporesponsiveness to b 2 -adrenoceptor agonists due to heterologous desensitization is an important limitation to the successful control of asthma symptoms (1)(2)(3)(4)(5). Several of the cytokines that are elevated in the bronchoalveolar lavage fluid of patients with asthma (including IL-1b and TNF-a) promote b 2 -adrenoceptor hyporesponsiveness (1,(3)(4)(5)(6)(7).…”

“…Several of the cytokines that are elevated in the bronchoalveolar lavage fluid of patients with asthma (including IL-1b and TNF-a) promote b 2 -adrenoceptor hyporesponsiveness (1,(3)(4)(5)(6)(7). In vitro studies of airway smooth muscle suggest that cytokine-mediated up-regulation of cyclooxygenase-2 (COX-2) leads to enhanced secretion of PGE 2 , activation of the cAMP/PKA pathway, and disruption of coupling of b 2 -adrenoceptors with Gas (2,4,5).…”