title: Transforming growth factor-beta1 inhibits beta2-adrenoceptor gene transcription.
abstract: Transforming growth factor-beta1 (TGF-beta1) has been shown to modulate beta-adrenoceptor number and function in cultured human tracheal smooth muscle cells and cardiac fibroblasts, but the mechanism is unclear. In this study, we have characterized the beta2-adrenoceptor expression by radioligand binding assay, Northern blot analysis and measurement of intracellular cAMP accumulation in a human embryonic lung fibroblast cell line (HEL299 cells). Treatment with TGF-beta1 caused a time-dependent decrease in beta2-adrenoceptor mRNA, and in receptor number after 24 h. Furthermore, nuclear run-on assays showed a 35% reduction in the transcription rate of the beta2-adrenoceptor gene with no alteration in stability of the beta2-adrenoceptor mRNA. After TGF-beta1 treatment, the basal, procaterol- and forskolin-stimulated cAMP accumulations were also decreased. Cycloheximide inhibited TGF-beta1-mediated reduction of beta2-adrenoceptor mRNA and protein, whilst alone caused induction of beta2-adrenoceptor mRNA without any effect on receptor number. In summary, TGF-beta1 induces beta2-adrenoceptor desensitization through the alteration in adenylyl cyclase activity and down-regulation of beta2-adrenoceptor mRNA and protein through the reduction in the rate of beta2-adrenoceptor gene transcription.
authors.affiliation: Department of Thoracic Medicine, Imperial College School of Medicine at the National Heart and Lung Institute, London, UK. j.mak@ic.ac.uk
authors.forename: J C
authors.initials: JC
authors.lastname: Mak
authors.forename: J
authors.initials: J
authors.lastname: Rousell
authors.forename: E B
authors.initials: EB
authors.lastname: Haddad
authors.forename: P J
authors.initials: PJ
authors.lastname: Barnes
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D001667:Binding, Competitive; D015152:Blotting, Northern; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression; D006801:Humans; D007093:Imidazoles / Q000378:metabolism / Q000494:pharmacology; D007457:Iodine Radioisotopes; D007700:Kinetics; D008168:Lung / Q000187:drug effects / Q000378:metabolism; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D011412:Propanolamines / Q000378:metabolism / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011869:Radioligand Assay; D018343:Receptors, Adrenergic, beta-2 / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
chemical_list: D000319:Adrenergic beta-Antagonists; D007093:Imidazoles; D007457:Iodine Radioisotopes; D011412:Propanolamines; D012333:RNA, Messenger; D018343:Receptors, Adrenergic, beta-2; C508960:TGFB1 protein, human; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; C026777:ICI 118551; C029247:3-iodopindolol; D010869:Pindolol; C049763:CGP 20712A; D000242:Cyclic AMP