title: Chemerin inhibits IGF-1-induced progesterone and estradiol secretion in human granulosa cells.
abstract: BACKGROUND
  Chemerin is a novel adipokine involved in the regulation of adipocyte development, inflammation and metabolic functions. To date, no role of this adipokine in reproductive functions has been described. In the present study, we identified chemerin and its receptor, CMKLR1 (chemokine-like receptor 1), in primary human granulosa cells (hGCs) and in a human ovarian granulosa-like tumour cell line (KGN). We also investigated the effects of recombinant human chemerin (rhChem) on steroid production and on various signalling pathways.
  
  
  RESULTS
  By RT-PCR immunoblotting and immunohistochemistry, we showed that chemerin and CMKLR1 are expressed in hGCs and KGN cells. By ELISA, we also found chemerin in human follicular fluid and we observed that in 8 of 10 women the chemerin level was at least 2-fold higher in follicular fluid than in plasma. rhChem (10 or 100 ng/ml) significantly decreased insulin-like growth factor-1 (IGF-1) (10(-8) M)-induced secretion of progesterone and estradiol (as determined by radioimmunoassay) but did not affect basal-or FSH (10(-8) M)-induced steroid secretion in hGCs and KGN cells. In parallel, it also decreased IGF-1-induced p450 aromatase protein levels without affecting the protein levels of other factors involved in steroidogenesis (steroidogenic acute regulatory protein, 3-beta-hydroxysteroid dehydrogenase and p450 side-chain cleavage enzyme) in hGCs cells. All these changes were associated with a decrease in the IGF-1-induced tyrosine phosphorylation of IGF-1 receptor beta subunit and phosphorylation of mitogen-activated protein kinase extracellular signal-regulated kinases 1/2 (MAPK ERK1/2) and Akt. In hGCs and KGN cells, rhChem also decreased IGF-1-induced thymidine incorporation. Finally, we showed that rhChem rapidly activates MAPK ERK1/2, MAPK P38 and Akt phosphorylation and more slowly AMP-activated protein kinase phosphorylation under basal conditions (no IGF-1 or FSH) in primary hGC cells.
  
  
  CONCLUSIONS
  Taken together, chemerin and its receptor (CMKLR1) are present and active in hGCs. Chemerin reduces IGF-1-induced steroidogenesis and cell proliferation through a decrease in the activation of IGF-1R signalling pathways in primary hGCs.
authors.affiliation: Unité de Physiologie de la Reproduction et des Comportements, Institut National de la Recherche Agronomique, Nouzilly, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Reverchon
authors.forename: Marion
authors.initials: M
authors.lastname: Cornuau
authors.forename: Christelle
authors.initials: C
authors.lastname: Ramé
authors.forename: Fabrice
authors.initials: F
authors.lastname: Guerif
authors.forename: Dominique
authors.initials: D
authors.lastname: Royère
authors.forename: Joëlle
authors.initials: J
authors.lastname: Dupont
mesh_terms: D045744:Cell Line, Tumor; D018925:Chemokines / Q000032:analysis / Q000097:blood / Q000494:pharmacology*; D004958:Estradiol / Q000096:biosynthesis / Q000378:metabolism*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000494:pharmacology; D015571:Follicular Fluid / Q000737:chemistry; D006106:Granulosa Cell Tumor / Q000737:chemistry; D006107:Granulosa Cells / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D036341:Intercellular Signaling Peptides and Proteins; D011374:Progesterone / Q000096:biosynthesis / Q000378:metabolism*; D017526:Receptor, IGF Type 1 / Q000187:drug effects / Q000502:physiology; D019707:Receptors, Chemokine / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects
chemical_list: C102741:CMKLR1 protein, human; D018925:Chemokines; D036341:Intercellular Signaling Peptides and Proteins; C478630:RARRES2 protein, human; D019707:Receptors, Chemokine; D011994:Recombinant Proteins; D011374:Progesterone; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D005640:Follicle Stimulating Hormone; D017526:Receptor, IGF Type 1