Carvedilol binding to β₂-adrenergic receptors inhibits CFTR-dependent anion secretion in airway epithelial cells

Abstract

Carvedilol functions as a nonselective ␤-adrenergic receptor (AR)/␣1-AR antagonist that is used for treatment of hypertension and heart failure. Carvedilol has been shown to function as an inverse agonist, inhibiting G protein activation while stimulating ␤-arrestin-dependent signaling and inducing receptor desensitization. In the present study, short-circuit current (Isc) measurements using human airway epithelial cells revealed that, unlike ␤-AR agonists, which increase Isc, carvedilol decreases basal and 8-(4-chlorophenylthio)adenosine 3=,5=-cyclic monophosphatestimulated current. The decrease in Isc resulted from inhibition of the cystic fibrosis transmembrane conductance regulator (CFTR). The carvedilol effect was abolished by pretreatment with the ␤2-AR antagonist ICI-118551, but not the ␤1-AR antagonist atenolol or the ␣ 1-AR antagonist prazosin, indicating that its inhibitory effect on Isc was mediated through interactions with apical ␤2-ARs. However, the carvedilol effect was blocked by pretreatment with the microtubuledisrupting compound nocodazole. Furthermore, immunocytochemistry experiments and measurements of apical CFTR expression by Western blot analysis of biotinylated membranes revealed a decrease in the level of CFTR protein in monolayers treated with carvedilol but no significant change in monolayers treated with epinephrine. These results demonstrate that carvedilol binding to apical ␤ 2-ARs inhibited CFTR current and transepithelial anion secretion by a mechanism involving a decrease in channel expression in the apical membrane. inverse agonists; bias ligands; ␤-arrestin signaling; carvedilol

A Systematic Review of Inverse Agonism at Adrenoceptor Subtypes

“…In a follow-up study, they confirmed the original findings with fenoterol; timolol added after pre-treatment with fenoterol restored airway contraction, but it remains unclear whether IA was involved, as timolol had no effects on airway contraction in the absence of pre-treatment with fenoterol [ 125 ]. Other investigators found that salbutamol increased the short circuit (I sc ) current in Calu-3 human airway adenocarcinoma cells, whereas carvedilol decreased under basal conditions and after stimulation with a cAMP-mimetic [ 126 ]. The carvedilol effect was abolished after pretreatment with ICI-118551, which questions whether IA was involved in this observation.…”

Ion channels of the lung and their role in disease pathogenesis

“…Additionally, the question of whether ENaC regulates CFTR activity remains unclear (46). Furthermore, understanding the mechanism of the ENaC-CFTR cross talk in airway epithelia is complicated by the fact that CFTR activity and ENaC function are often affected by the same physiological [␤-agonists (7,179)] and environmental factors that include oxidative stress (19,20,175,203,218,248), hypoxia (36,244), inflammatory responses (28,30,169,202,241), and influenza infections (102,109,144,189,235).…”

CFTR Involvement in Cell Migration and Epithelial Restitution

“…This effect could be reproduced using carvedilol, a β 2 -AR agonist that functions as a bias ligand to activate cAMP-independent, β-arrestin-dependent signaling cascades [110]. The inhibitory effects of β 2 -AR agonists could be blocked if cells were pretreated with an inhibitor of PP2A phosphatase, indicating that PP2A activation was a critical step in regulating cell migration [111,112].…”