Ozcan Mete, Saatci Tugrul, Ayar Ahmet, Canpolat Sinan, Kelestimur Haluk
Department of Biophysics, Faculty of Medicine, Firat University, Elazig TR23119, Turkey.
Department of Physiology Faculty of Medicine, Firat University, Elazig, Turkey.
Brain Res. 2015 Mar 19;1601:8-14. doi: 10.1016/j.brainres.2014.12.053. Epub 2015 Jan 6.
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.
RF酰胺相关肽-3（RFRP-3）是鸟类促性腺激素抑制激素（GnIH）的哺乳动物直系同源物，似乎是下丘脑-垂体-性腺（HPG）生殖轴的重要调节因子。瘦素是一种对生育有允许作用的激素调节因子，为大脑提供能量信号。根据目前的观点，瘦素并不直接作用于促性腺激素释放激素（GnRH）神经元。RFRP-3神经元已被证明表达瘦素受体。本研究的目的是检验瘦素是否通过RFRP-3神经元来调节GnRH神经元的活性。为了这个目的，利用体外钙成像系统研究了瘦素对RFRP-3神经元细胞内游离钙离子水平（[Ca²⁺]i）的影响。在本研究中，rHypoE-7细胞系被用作模型来探索瘦素对RFRP-3神经元的影响。将rHypoE-7细胞置于玻璃盖玻片上，并用1μM 荧光素-2 AM进行负载。[Ca²⁺]i反应通过340/380比值的变化进行定量。瘦素（0.1 - 10μM）以剂量依赖的方式引起[Ca²⁺]i升高。用蛋白激酶C抑制剂预处理后，[Ca²⁺]i的变化显著减弱。这些结果表明，瘦素通过蛋白激酶C依赖的途径激活RFRP-3神经元内的钙信号，因此瘦素可能通过RFRP-3细胞对GnRH神经元发挥作用。
