Liguori Giovanna, Tafuri Simona, Miyoshi Chika, Yanagisawa Masashi, Squillacioti Caterina, De Pasquale Valeria, Mirabella Nicola, Vittoria Alfredo, Costagliola Anna
Department of Veterinary Medicine and Animal Productions, University of Naples Federico II, Via Delpino 1, 80137, Naples, Italy.
International Institute for Integrative Sleep Medicine (WPI-IIIS), University of Tsukuba, Ibaraki, 305-8575, Japan.
Acta Histochem. 2018 Apr;120(3):292-297. doi: 10.1016/j.acthis.2018.02.011. Epub 2018 Feb 26.
The peptides orexin A (OXA) and orexin B (OXB) derived from the proteolytic cleavage of a common precursor molecule, prepro-orexin, were originally described in the rat hypothalamus. Successively, they have been found in many other brain regions as well as in peripheral organs of mammals and other less evolved animals. The widespread localization of orexins accounts for the multiple activities that they exert in the body, including the regulation of energy homeostasis, feeding, metabolism, sleep and arousal, stress, addiction, and cardiovascular and endocrine functions. Both OXA and OXB peptides bind to two G-coupled receptors, orexin-1 (OX1R) and orexin-2 (OX2R) receptor, though with different binding affinity. Altered expression/activity of orexins and their receptors has been associated with a large number of human diseases. Though at present evidence highlighted a role for orexins and cognate receptors in mammalian reproduction, their central and/or local effects on gonadal functions remain poorly known. Here, we investigated the localization of OXB and OX2R in the rat epididymis. Immunohistochemical staining of sections from caput, corpus and cauda segments of the organ showed intense signals for both OXB and OX2R in the principal cells of the lining epithelium, while no staining was detected in the other cell types. Negative results were obtained from immunohistochemical analysis of hypothalamic and testicular tissues from OX2R knock-out mice (OX2R) and OX1R/OX2R double knock-out (OX1R; OX2R) mice, thus demonstrating the specificity of the rabbit polyclonal anti-OX2R antibody used in our study. On contrary, the same antibody clearly showed the presence of OX2R in sections from hypothalamus and testis of normal mice and rats which are well known to express the receptor. Thus, our results provide the first definite evidence for the immunohistochemical localization of OXB and OX2R in the principal cells of rat epididymis.
源自共同前体分子前食欲素原蛋白水解切割产生的肽类食欲素A（OXA）和食欲素B（OXB）最初是在大鼠下丘脑被发现的。随后，它们在许多其他脑区以及哺乳动物和其他进化程度较低动物的外周器官中也被发现。食欲素的广泛定位解释了它们在体内发挥的多种作用，包括能量稳态调节、进食、新陈代谢、睡眠与觉醒、应激、成瘾以及心血管和内分泌功能。OXA和OXB肽均与两种G蛋白偶联受体——食欲素-1（OX1R）和食欲素-2（OX2R）受体结合，不过结合亲和力不同。食欲素及其受体表达/活性的改变与大量人类疾病有关。尽管目前有证据表明食欲素及其同源受体在哺乳动物生殖中发挥作用，但其对性腺功能的中枢和/或局部影响仍知之甚少。在此，我们研究了OXB和OX2R在大鼠附睾中的定位。对该器官头段、体段和尾段切片进行免疫组织化学染色显示，衬里上皮的主细胞中OXB和OX2R均有强烈信号，而在其他细胞类型中未检测到染色。对OX2R基因敲除小鼠（OX2R）和OX1R/OX2R双基因敲除（OX1R；OX2R）小鼠的下丘脑和睾丸组织进行免疫组织化学分析得到阴性结果，从而证明了我们研究中使用的兔多克隆抗OX2R抗体的特异性。相反，同一抗体在正常小鼠和大鼠的下丘脑和睾丸切片中清楚地显示出OX2R的存在，众所周知这些组织表达该受体。因此，我们的结果为OXB和OX2R在大鼠附睾主细胞中的免疫组织化学定位提供了首个确切证据。
