title: Autocrine down-regulation of glucocorticoid receptors by interleukin-11 in human osteoblast-like cell lines.
abstract: It has recently been suggested that interleukin (IL)-11 plays a role in the pathogenesis of glucocorticoid (GC)-induced osteoporosis. IL-11 belongs to the gp130 cytokine family, which includes also IL-6. We have previously investigated GC-IL-6 interplay, showing that GC inhibits IL-6 release and IL-6 up-regulates GC receptor (GR) numbers in the human osteoblast-like cell lines Saos-2 and MG-63, which constitutively have an opposite pattern of expression for GR, IL-11, IL-6, alkaline phosphatase and osteoprotegerin (OPG). The aim of this study was to investigate GC-IL-11 interplay in the same two cell lines. First, cells were incubated with cortisol (0.01-1 microM) for 20 h in the presence and in the absence of a known IL-11 secretagogue (IL-1beta); cell media were assayed for IL-11 by ELISA. Secondly, cells were incubated with IL-11 (0.1-100 ng/ml) or specific anti-IL-11 monoclonal antibody for 20 h, and then assayed for GR by a radioligand binding assay. Similar to IL-6, both constitutive and IL-1beta-inducible IL-11 release were dose-dependently inhibited by cortisol (P<0.01); at variance with IL-6, exogenous IL-11 dose-dependently decreased GR numbers in MG-63 cells (P<0.05), while anti-IL-11 antibody significantly increased GR numbers in both cell lines (P<0.05). IL-11-induced reduction of GR in MG-63 cells was confirmed by Western blot analysis. While exerting opposite effects on GR numbers, neither IL-6 nor IL-11 significantly modified GC-dependent inhibition of OPG release. Our data indicate that even physiological concentrations of cortisol negatively modulate IL-11 secretion and demonstrate, for the first time, an inhibitory effect of the cytokine on GR. Thus, the concept of autocrine-paracrine loops that modulate GC action and involve gp130 cytokines is corroborated. These loops could have clinical relevance for the dynamics of bone loss in patients given GC and having high concentrations of these cytokines in the bone microenvironment.
authors.affiliation: Clinica Medica Generale, Dipartimento di Scienze Cliniche e Biologiche, University of Turin, Regione Gonzole 10, 10043 Orbassano (TO), Italy.
authors.forename: A
authors.initials: A
authors.lastname: Dovio
authors.forename: M L
authors.initials: ML
authors.lastname: Sartori
authors.forename: R G
authors.initials: RG
authors.lastname: Masera
authors.forename: B
authors.initials: B
authors.lastname: Ceoloni
authors.forename: G
authors.initials: G
authors.lastname: Reimondo
authors.forename: P
authors.initials: P
authors.lastname: Prolo
authors.forename: S
authors.initials: S
authors.lastname: Racca
authors.forename: A
authors.initials: A
authors.lastname: Angeli
mesh_terms: D000911:Antibodies, Monoclonal / Q000494:pharmacology; D019898:Autocrine Communication; D002352:Carrier Proteins / Q000032:analysis; D002460:Cell Line; D015536:Down-Regulation; D006023:Glycoproteins / Q000032:analysis; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D017370:Interleukin-11 / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D015850:Interleukin-6 / Q000032:analysis; D008562:Membrane Glycoproteins / Q000032:analysis; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear / Q000032:analysis; D011965:Receptors, Glucocorticoid / Q000187:drug effects*; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D000911:Antibodies, Monoclonal; D002352:Carrier Proteins; D006023:Glycoproteins; D007375:Interleukin-1; D017370:Interleukin-11; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D053244:Osteoprotegerin; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018160:Receptors, Cytoplasmic and Nuclear; D011965:Receptors, Glucocorticoid; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; C505686:TNFRSF11A protein, human; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human; D006854:Hydrocortisone