β2-Adrenoceptor mRNA expression in human lung fibroblasts is highly up-regulated by endothelin-1 (ET-1) and β2-adrenoceptors

Lisa J Juergens, Mareille Warnken-Uhlich, Ina Schütz, Margarita Fuhrmann, Racké Racké. Univ. Bonn, Inst. Pharmacology, Germany.

Background: Recent observations indicate that the expression of β2-adrenoceptors in human lung fibroblasts is highly regulated via receptor mediated signals, among others it is markedly up-regulated via β2-adrenoceptors (e.g. Warnken-Uhlich et al. (2011) Naunyn-Schmiedeberg´s Arch Pharmacol 383 (Suppl. 1):46). Since human lung fibroblasts express a functional endothelinergic system (Ahmedat et al. (2010) Naunyn-Schmiedeberg´s Arch Pharmacol 381 (Suppl. 1):56; see also Ahmedat et al. this Meeting), the present study aimed to explore possible ET-1-mediated effects on β2-adrenoceptor expression in human lung fibroblasts.

Methods: MRC-5 human lung fibroblasts were first cultured for 24 h in presence of 10% FCS. After further 24 h in absence of FCS, cells were exposed to test drugs for 60 - 90 min, followed by β2-adrenoceptor mRNA determination by quantitative real time PCR.

Results: The long-acting β2-adrenoceptor agonist olodaterol, previously known as BI 1744 CL (1, 10 and 100 nM, 60 min), caused an increase in β2-adrenoceptor mRNA expression by 89±21%, 122±26% and 110±11% (means±s.e.mean), respectively. ET-1 (10 and 100 nM, 60 min) enhanced β2-adrenoceptor mRNA expression by 81±19% and 64±11%, respectively. Combined presence of olodaterol (100 nM) and ET-1 (10 or 100 nM) resulted in an increase in β2-adrenoceptor mRNA expression by 286±52% and 213±42%, respectively. The role of ET-A and/or ET-B receptors for the up-regulation of β2-adrenoceptor is currently under investigation by use of subtype selective antagonists BQ123 and BQ788. Forskolin (10 µM, 60 min) and the EP2-selective agonist butaprost (100 nM, 60 min) induced also an increase in β2-adrenoceptor mRNA expression by 90±13% and 95±15%, respectively. However, combined presence of olodaterol with either forskolin or butaprost did not result in any additive effects, in contrast to the additive interaction between olodaterol and ET-1.

Conclusions: ET-1 receptors and β2-adrenoceptors can mediate additive stimulatory effects on the expression of β2-adrenoceptors mRNA in human lung fibroblasts, indicating that Gs and Gq coupled receptors may synergistically contribute to the maintenance of β2-adrenoceptor expression in these cells.

Supported by Boehringer Ingelheim and Bonfor University of Bonn.