Impairment in Coupled Beta-Adrenergic Receptor and Adenylate Cyclase System during Bleomycin-Induced Lung Fibrosis in Hamsters

Abstract

The purpose of this study was to evaluate the coupled beta-adrenergic receptor (BAR) and adenylate cyclase (AC) system of the lung during the course of the bleomycin-(Bleo) induced pulmonary fibrosis in hamsters. The BAR population, dissociation constants (Kd), AC activity, and its sensitivity to various stimulators were studied at 2, 4, 7, 14, and 21 days after intratracheal administration of either 1 unit of Bleo or an equivalent volume of saline. The BAR population in the lungs of Bleo-treated animals did not differ from control at the early times, but it was significantly reduced to 5.9 X 10(3) fmol and 3.6 X 10(3) fmol from the control values of 1.1 X 10(4) fmol and 1.5 X 10(4) fmol per lung at 14 and 21 days after treatment, respectively. The Kd values for control hamster lung ranged from 2.5 X 10(-11) M to 3.7 X 10(-11) M, and for Bleo-treated hamster lung, from 2.7 X 10(-11) M to 4.8 X 10(-11) M. The Kd at the earliest time, 2 days after treatment, did not differ significantly from the Kd values at the subsequent times in control, while for Bleo-treated hamster lung, the Kd values at 7, 14, and 21 days were significantly higher than the Kd at 2 days after treatment. The Kd values for Bleo-treated hamster lung were also significantly higher than control at 14 and 21 days. The AC activity of the lung in Bleo-treated hamster was significantly reduced to 67%, 40%, 38%, and 50% of their respective controls in response to H2O (basal), GTP (10(-4) M), GTP + isoproterenol (10(-4) M each), and NaF (10 mM) at 21 days after treatment. The extent of AC stimulation in Bleo-treated hamster lung in response to various stimulators was generally less than that of saline control. Reductions in the BAR population and increased Kd values in Bleo-treated hamster lung were attributed to its fibrogenic ability and not to nutritional deficiency, which may partly be accountable for decreased AC activity of the lung in these animals. However, there were qualitative differences in the lung AC activity between Bleo-treated and nutritionally deprived hamsters, since the enzyme from the latter group was generally more responsive to stimulators than the enzyme from the former group. It was concluded from the findings of this study that an impairment in the coupled BAR and AC system of the lung may be partly responsible for the fibrogenic ability of bleomycin.

Fibrotic Lung Fibroblasts Show Blunted Inhibition by cAMP Due to Deficient cAMP Response Element-Binding Protein Phosphorylation

“…Although these observations differ from our current results (in that we do not observe differences in cAMP generation (Fig. 3), Giri et al (1987) reached a similar conclusion regarding impairment in the cAMP pathway as partly responsible for the fibrogenic response. Therefore, fibrogenesis in human lung may share some commonality with experimentally induced pulmonary fibrosis in rodents.…”

“…Other, nontraditional signaling pathways activated by EP receptors perhaps contribute to the disparate response to PGE 2 compared with other agents that we tested. Giri et al (1987) described that signaling via the ␤-adrenergic receptor/adenylyl cyclase system is defective in a rat model of bleomycin-induced pulmonary fibrosis (Giri et al, 1987). Although these observations differ from our current results (in that we do not observe differences in cAMP generation (Fig.…”

“…Some evidence suggests the importance of the G s -AC-cAMP pathway in IPF. This includes results showing compromise of this pathway after experimental pulmonary fibrosis induced by the cancer chemotherapeutic drug bleomycin (Giri et al, 1987) and the diminished capacity to generate PGE 2 of fibroblasts from IPF patients due to insufficient induction of cyclooxygenase expression (Wilborn et al, 1995;Keerthisingam et al, 2001). Moreover, elevation of cAMP production inhibits cell proliferation, collagen synthesis, and the differentiation of pulmonary fibroblasts into profibrogenic myofibroblasts (Kolodsick et al, 2003;Liu et al, 2004).…”

Olodaterol shows anti‐fibrotic efficacy in in vitro and in vivo models of pulmonary fibrosis

“…With this observation in mind, we checked the expression of β 2 -adrenoceptors in other data sets. Our in-house next-generation sequencing (NGS) data of murine bleomycin models, the mouse AAV6.2m-TGF-β1 overexpression model and TGF-β-treated primary HLF and the analysis of external NGS studies (GSE1066; Konishi et al, 2009;GSE52463;Nance et al, 2014) together with current and earlier literature (Giri et al, 1987;Bauer et al, 2015) revealed a general down-regulation of β 2 -adrenoceptors in IPF lung samples and IPF-related in vitro and in vivo models. This is in contrast to our observation that, in vitro, cultures of IPF-LF and HLF showed no significant differences in expression of β 2 -adrenoceptors.…”

Modulation Of Stem And Progenitor Cells, And Bleomycin-induced Pulmonary Fibrosis By Spiperone In Mice

“…In our opinion, anti-fibrotic effect of the drug in bleomycininduced fibrosis can be partially is connected with disturbance of serotonin mechanism fibroblast proliferation and collagen synthesis by fibroblasts both and levels of TGF-β 1 , connective tissue growth factor and plasminogen activator inhibitor-1 is decreased in the lung [44]. Some authors attribute the synthesis of collagen fibers in the lung to adrenergic receptors activity [45,46]. Due to the fact that spiperone is α1B-adrenoceptor antagonist, we do not exclude the realization of adrenergic mechanism.…”