title: Skeletal muscle: a dual system to measure glucocorticoid-dependent transactivation and transrepression of gene regulation.
abstract: The use of chronic glucocorticoid (GC) therapy for the treatment of inflammatory diseases is limited by associated metabolic side effects, including muscle atrophy. Therefore, selective glucocorticoid receptor-(GR)-binding ligands that maintain anti-inflammatory activity and demonstrate diminished side-effect profiles would have great therapeutic utility. In this work, we use Taqman PCR and ELISA methods to show that GCs can inhibit basal, and lipopolysaccharide (LPS)-stimulated levels of cytokines IL-6 and TNFalpha, and also the chemokine MCP-1 in a non-inflammatory system such as primary human skeletal muscle cells. In the murine C2C12 skeletal muscle cell line we observe a similar effect of GCs on IL-6 and MCP-1; however, in contrast to previous reports, we observe a time-dependent repression of TNFalpha. Furthermore, in skeletal muscle cells, concomitant with cytokine repression, GCs transcriptionally induce glutamine synthetase (GS), a marker for muscle wasting, in an LPS independent manner. Similarly, administration of dexamethasone to mice, previously administered LPS, results in an increase in GS and an inhibition of TNFalpha and MCP-1 in skeletal muscle tissue. Thus, skeletal muscle cells and tissues present a novel system for the identification of selective GR-binding ligands, which simultaneously inhibit cytokine expression in the absence of GS induction.
authors.affiliation: Merck Research Laboratories, Department of Pharmacology, P.O. Box 2000, Rahway, NJ 07065, USA.
authors.forename: Ester
authors.initials: E
authors.lastname: Carballo-Jane
authors.forename: Shilpa
authors.initials: S
authors.lastname: Pandit
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Santoro
authors.forename: Concetta
authors.initials: C
authors.lastname: Freund
authors.forename: Silvi
authors.initials: S
authors.lastname: Luell
authors.forename: Georgianna
authors.initials: G
authors.lastname: Harris
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Forrest
authors.forename: Ayesha
authors.initials: A
authors.lastname: Sitlani
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects*; D015850:Interleukin-6 / Q000378:metabolism; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D015533:Transcriptional Activation / Q000187:drug effects*
chemical_list: D017931:DNA Primers; D015850:Interleukin-6; D003907:Dexamethasone