Thyroid-stimulating hormone stimulates interleukin-6 release from 3T3-L1 adipocytes through a cAMP-protein kinase A pathway.
OBJECTIVE
Thyroid-stimulating hormone (TSH) is a novel modulator of adipokine release from human and mouse adipocytes. The aim of our study was to identify the signal transduction pathways activated by TSH that stimulate interleukin (IL)-6 production.


METHODS
Mouse 3T3-L1 preadipocyte and differentiated adipocyte cell cultures were studied. The effect of 0 to 1 microM TSH on IL-6 protein release into the medium over 0 to 24 hours was assessed. TSH signaling pathways responsible for regulating IL-6 were studied through the use of 1 muM forskolin, 100 microM 8-pCPT-2'-O-Me-cAMP, 10 microM H89, 50 microM PD98059, and 2 mug/mL actinomycin D.


RESULTS
TSH stimulated IL-6 release by 2.6-fold from 3T3-L1 adipocytes at concentrations as low as 0.01 microM but did not alter IL-6 production of corresponding preadipocytes. Forskolin (elevates intracellular cAMP) stimulated IL-6 release from 3T3-L1 adipocytes (n = 3, p < 0.005), and H89, an inhibitor of cAMP-dependent protein kinase A (PKA), reduced TSH-stimulated IL-6 release by 66% (n = 3, p < 0.01), indicating a requirement for cAMP-dependent PKA. Inhibition of the mitogen-activated protein kinase pathway with PD98059 did not affect TSH-stimulated IL-6 release. Activation of an alternate cAMP target, the exchange protein of cAMP, with 8-pCPT-2'-O-Me-cAMP, had no effect on IL-6 release. TSH raised the level of IL-6 mRNA, and blockade of transcription with actinomycin D abrogated IL-6 protein release by TSH (n = 3, p < 0.05).


CONCLUSIONS
TSH stimulates IL-6 release from differentiated 3T3-L1 adipocytes, but not preadipocytes, by signaling through cAMP-PKA to activate IL-6 gene transcription.
Antunes
Tayze T
TT
Department of Medicine, University of Ottawa, Ottawa Health Research Institute, Ontario, Canada.
Gagnon
Annemarie
A
Bell
Andrea
A
Sorisky
Alexander
A
D016475:3T3 Cells; D017667:Adipocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D051379:Mice; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D013961:Thyroid Gland / Q000378:metabolism; D013972:Thyrotropin / Q000494:pharmacology*
C473217:8-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate; D005419:Flavonoids; D015850:Interleukin-6; D007546:Isoquinolines; D011500:Protein Synthesis Inhibitors; D013449:Sulfonamides; D003609:Dactinomycin; D005576:Colforsin; D013972:Thyrotropin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one