title: Ghrelin and des-acyl ghrelin inhibit aromatase expression and activity in human adipose stromal cells: suppression of cAMP as a possible mechanism.
abstract: Aromatase converts androgens into estrogens and its expression within adipose stromal cells (ASCs) is believed to be the major driver of estrogen-dependent cancers in older women. Ghrelin is a gut-hormone that is involved in the regulation of appetite and known to bind to and activate the cognate ghrelin receptor, GHSR1a. The unacylated form of ghrelin, des-acyl ghrelin, binds weakly to GHSR1a but has been shown to play an important role in regulating a number of physiological processes. The aim of this study was to determine the effect of ghrelin and des-acyl ghrelin on aromatase in primary human ASCs. Primary human ASCs were isolated from adipose tissue of women undergoing cosmetic surgery. Real-time PCR and tritiated water-release assays were performed to examine the effect of treatment on aromatase transcript expression and aromatase activity, respectively. Treatments included ghrelin, des-acyl ghrelin, obestatin, and capromorelin (GHSR1a agonist). GHSR1a protein expression was assessed by Western blot and effects of treatment on Ca(2+) and cAMP second messenger systems were examined using the Flexstation assay and the Lance Ultra cAMP kit, respectively. Results demonstrate that pM concentrations of ghrelin and des-acyl ghrelin inhibit aromatase transcript expression and activity in ASCs under basal conditions and in PGE2-stimulated cells. Moreover, the effects of ghrelin and des-acyl ghrelin are mediated via effects on aromatase promoter PII-specific transcripts. Neither the GHSR1a-specific agonist capromorelin nor obestatin had any effect on aromatase transcript expression or activity. Moreover, GHSR1a protein was undetectable by Western blot and neither ghrelin nor capromorelin elicited a calcium response in ASCs. Finally, ghrelin caused a significant decrease in basal and forskolin-stimulated cAMP in ASC. These findings suggest that ghrelin acts at alternate receptors in ASCs by decreasing intracellular cAMP levels. Ghrelin mimetics may be useful in the treatment of estrogen-dependent breast cancer.
authors: Metabolism & Cancer Laboratory, MIMR-PHI Institute of Medical Research, Clayton, VIC, 3168, Australia.
authors: Maria M
authors: MM
authors: Docanto
authors: Fangyuan
authors: F
authors: Yang
authors: Brid
authors: B
authors: Callaghan
authors: CheukMan C
authors: CC
authors: Au
authors: Rahini
authors: R
authors: Ragavan
authors: Xuyi
authors: X
authors: Wang
authors: John B
authors: JB
authors: Furness
authors: Zane B
authors: ZB
authors: Andrews
authors: Kristy A
authors: KA
authors: Brown
mesh_terms: D000273:Adipose Tissue / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D001141:Aromatase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D001940:Breast / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D005260:Female; D054439:Ghrelin / Q000494:pharmacology*; D006801:Humans; D010880:Piperidines / Q000494:pharmacology; D011720:Pyrazoles / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D054440:Receptors, Ghrelin / Q000819:agonists; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017154:Stromal Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*
chemical_list: C433143:CP 424391; D054439:Ghrelin; D010880:Piperidines; D011720:Pyrazoles; D012333:RNA, Messenger; D054440:Receptors, Ghrelin; C422650:ghrelin, des-n-octanoyl; D000242:Cyclic AMP; D001141:Aromatase; D002118:Calcium