Rapid inhibition of leptin signaling by glucocorticoids in vitro and in vivo.
Elevated secretion of glucocorticoids (GCs) or hypersensitivity to GCs has a permissive effect on the development of obesity and leads to abnormalities of body fat distribution. Recent studies demonstrated GCs act as antagonists of leptin in rodents. However, little is known about the interaction between GCs and leptin signaling. In the present study, we investigated the effects of GCs on leptin action in vitro and in vivo. GCs rapidly inhibited the leptin-induced STAT3 phosphorylation in a dose- and time-dependent manner, as assayed by Western blotting using anti-phosphospecific-STAT3 in human hepatoma cell lines (Huh7) transiently expressing long form leptin receptor. GCs also inhibited the leptin-induced JAK2 tyrosine phosphorylation but unaltered the specific binding of (125)I-leptin to the cells. Parallel experiments, however, demonstrated that the inhibitory effects of GCs were not observed in either IL-6- or LIF-induced STAT3 phosphorylation. Furthermore, we examined the feeding behavior and hypothalamic leptin signaling following intracerebroventricular (icv) infusion of GCs prior to icv leptin infusion in Sprague-Dawley rats. The food intake after 24 h of icv leptin injection increased 3-fold in GCs-treated animals. In addition, central infusion of GCs resulted in a marked reduction of hypothalamic STAT3 phosphorylation in response to icv infusion of leptin. To clarify the molecular mechanism by which GCs rapidly reduce leptin-induced JAK/STAT signaling, we examined the intracellular signal transduction pathway potentially mediated by GCs. PD98059, a specific MEK inhibitor, blocked the inhibitory effects of GCs on leptin-induced JAK/STAT activation in Huh7 cells. These results suggest GCs antagonize leptin action by a rapid inhibition of the leptin-induced JAK/STAT pathway partly via MAPK cascade.
Ishida-Takahashi
Ryoko
R
Division of Immunology, Endocrinology, and Metabolism, Department of Medical and Dental Sciences, Graduate School of Biomedical Science, Nagasaki University, 1-7-1 Sakamoto, Nagasaki 852-8501, Japan.
Uotani
Shigeo
S
Abe
Takahiro
T
Degawa-Yamauchi
Mikako
M
Fukushima
Tetsuya
T
Fujita
Naruhiro
N
Sakamaki
Hiroyuki
H
Yamasaki
Hironori
H
Yamaguchi
Yoshihiko
Y
Eguchi
Katsumi
K
D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005938:Glucocorticoids / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D020738:Leptin / Q000737:chemistry / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism; D014162:Transfection; D014443:Tyrosine / Q000737:chemistry
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D005938:Glucocorticoids; D020738:Leptin; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; C494088:Stat3 protein, rat; D015534:Trans-Activators; D014443:Tyrosine; D003907:Dexamethasone; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one