Liguori Giovanna, Pelagalli Alessandra, Assisi Loredana, Squillacioti Caterina, Costagliola Anna, Mirabella Nicola
Department of Veterinary Medicine and Animal Productions, University of Naples "Federico II", Via Delpino 1, 80137, Naples, Italy.
Department of Advanced Biomedical Sciences, University of Naples "Federico II", Via Pansini 5, 80131 Naples, Italy; Institute of Biostructures and Bioimages, National Research Council, Via De Amicis 95, 80131 Naples, Italy.
Anim Reprod Sci. 2018 May;192:313-320. doi: 10.1016/j.anireprosci.2018.03.032. Epub 2018 Mar 31.
The steroidogenic enzyme P450 aromatase (ARO) has a key role in the conversion of testosterone (T) into estrogens (E), expressed as 17β-estradiol. The presence and localization of this key enzyme have not been described before in the South American camelid alpaca (Vicugna pacos). In our previous studies of the expression and biological effects of orexin A (OxA) and OxB on the alpaca testis demonstrated that OxA, via its specific receptor 1 (OX1R), stimulated T synthesis. In order to extend these findings, we presently explored the presence and localization of ARO in the alpaca male gonad, and the possible correlation between ARO and the orexinergic complex. Western blotting and immunohistochemistry demonstrated the presence of ARO in tissue homogenates and its localization in the tubular and interstitial compartments of the alpaca testis, respectively. The addition of OxA to fresh testicular slices decreased the 17β-estradiol E levels. This effect was annulled by the sequential addition of the selective OX1R antagonist, SB-408124. OxB incubation did not have any effect on the biosynthesis of E. Furthermore, the OxA-mediated down-regulation of E secretion could be ascribed to ARO inhibition by exogenous OxA, as indicated by measurement of ARO activity in tissue slices incubated with OxA. Overall, our findings suggest that locally secreted OxA interacting with OX1R could indirectly inhibit ARO activity, disabling the conversion of T to E, and consequently lowering E biosynthesis and increasing the production of T in mammalian testis.
类固醇生成酶细胞色素P450芳香化酶（ARO）在睾酮（T）转化为雌激素（E，即17β-雌二醇）的过程中起关键作用。此前，在南美骆驼科动物羊驼（小羊驼）中尚未描述过这种关键酶的存在和定位情况。在我们之前关于食欲素A（OxA）和食欲素B（OxB）对羊驼睾丸的表达及生物学效应的研究中，发现OxA通过其特异性受体1（OX1R）刺激T的合成。为了拓展这些发现，我们目前探究了ARO在羊驼雄性性腺中的存在和定位情况，以及ARO与食欲素能复合体之间可能存在的关联。蛋白质免疫印迹法和免疫组织化学分别证实了组织匀浆中存在ARO及其在羊驼睾丸的曲细精管和间质区室中的定位。向新鲜睾丸切片中添加OxA可降低17β-雌二醇E的水平。依次添加选择性OX1R拮抗剂SB-408124可消除这种效应。孵育OxB对E的生物合成没有任何影响。此外，如在与OxA一起孵育的组织切片中测量ARO活性所示，OxA介导的E分泌下调可能归因于外源性OxA对ARO的抑制作用。总体而言，我们的研究结果表明，局部分泌的OxA与OX1R相互作用可能间接抑制ARO活性，使T无法转化为E，从而降低E的生物合成并增加哺乳动物睾丸中T的产生。
