title: Leptin activates cytosolic calcium responses through protein kinase-C dependent mechanism in immortalized RFamide-related peptide-3 neurons.
abstract: RFamide-related peptide-3 (RFRP-3), a mammalian ortholog of avian gonadotropin-inhibitory hormone (GnIH), seems to be an important regulator of the hypothalamus-pituitary-gonadal (HPG) reproductive axis. Leptin, a permissive hormonal regulator of fertility, provides energy signal to brain. According to current view, leptin does not act directly on gonadotrophin-releasing hormone (GnRH) neurons. RFRP-3 neurons have been shown to express leptin receptors. The goal of the present study was to examine whether leptin acts through RFRP-3 neurons to modulate activity of the GnRH neurons. For this aim, the effects of leptin on intracellular free Ca(2+) levels ([Ca(2+)]i) in RFRP-3 neurons were investigated by using in vitro calcium imaging system. In the present study, rHypoE-7 cell line was used as a model to explore the effects of leptin on RFRP-3 neurons. rHypoE-7 cells were placed on glass coverslip and loaded with 1 μM Fura-2 AM. [Ca(2+)]i responses were quantified by the changes in 340/380 ratio. Leptin (0.1-10 μM) caused increases in [Ca(2+)]i in a dose-dependent manner. The changes in [Ca(2+)]i were significantly attenuated by pre-treatment with protein kinase C inhibitor. These results demonstrate that leptin activates intracellular calcium signaling in RFRP-3 neurons through PKC-dependent pathway, and thus leptin may exert its effect on GnRH neurons by means of RFRP-3 cells.
authors.affiliation: Department of Biophysics, Faculty of Medicine, Firat University, Elazig TR23119, Turkey. Electronic address: meteozcan@hotmail.com.
authors.forename: Mete
authors.initials: M
authors.lastname: Ozcan
authors.affiliation: Department of Physiology Faculty of Medicine, Firat University, Elazig, Turkey.
authors.forename: Tugrul
authors.initials: T
authors.lastname: Saatci
authors.affiliation: Department of Physiology, Faculty of Medicine, Karadeniz Technical University, Trabzon, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Ayar
authors.affiliation: Department of Physiology Faculty of Medicine, Firat University, Elazig, Turkey.
authors.forename: Sinan
authors.initials: S
authors.lastname: Canpolat
authors.affiliation: Department of Physiology Faculty of Medicine, Firat University, Elazig, Turkey.
authors.forename: Haluk
authors.initials: H
authors.lastname: Kelestimur
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002460:Cell Line; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007028:Hypothalamic Hormones / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism* / Q000494:pharmacology; D009474:Neurons / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats
chemical_list: D007028:Hypothalamic Hormones; D020738:Leptin; C000588859:RFamide-related peptide-3, rat; D007987:Gonadotropin-Releasing Hormone; D011493:Protein Kinase C
keywords: Calcium signaling; Leptin; Protein kinase-C; RFamide-related peptide-3 neurons