Eaton Joy, Pradhan Devaleena S, Barske Julia, Fusani Leonida, Canoine Virginie, Schlinger Barney A
Department of Integrative Biology and Physiology, University of California, Los Angeles, United States.
Department of Integrative Biology and Physiology, University of California, Los Angeles, United States; Laboratory for Neuroendocrinology, University of California, Los Angeles, United States.
Gen Comp Endocrinol. 2018 Jan 15;256:43-49. doi: 10.1016/j.ygcen.2017.09.016. Epub 2017 Sep 18.
The prohormone, dehydroepiandrosterone (DHEA) circulates in vertebrate blood with the potential for actions on target tissues including the central nervous system (CNS). Many actions of DHEA require its conversion into more active products, some of which are catalyzed by the enzyme 3β-hydroxysteroid-dehydrogenase/isomerase (3β-HSD). Studies of birds show both expression and activity of 3β-HSD in brain and its importance in regulating social behavior. In oscine songbirds, 3β-HSD is expressed at reasonably high levels in brain, possibly linked to their complex neural circuitry controlling song. Studies also indicate that circulating DHEA may serve as the substrate for neural 3β-HSD to produce active steroids that activate behavior during non-breeding seasons. In the golden-collared manakin (Manacus vitellinus), a sub-oscine bird, low levels of courtship behavior are displayed by males when circulating testosterone levels are basal. Therefore, we asked whether DHEA circulates in blood of manakins and whether the brain expresses 3β-HSD mRNA. Given that the spinal cord is a target of androgens and likely important in regulating acrobatic movements, we also examined expression of this enzyme in the manakin spinal cord. For comparison, we examined expression levels with those of an oscine songbird, the zebra finch (Taeniopygia guttata), a species in which brain, but not spinal cord, 3β-HSD has been well studied. DHEA was detected in manakin blood at levels similar to that seen in other species. As described previously, 3β-HSD was expressed in all zebra finch brain regions examined. By contrast, expression of 3β-HSD was only detected in the manakin hypothalamus where levels were greater than zebra finches. In spinal cord, 3β-HSD was detected in some but not all regions in both species. These data point to species differences and indicate that manakins have the substrate and neural machinery to convert circulating DHEA into potentially active androgens and/or estrogens.
激素原脱氢表雄酮（DHEA）在脊椎动物血液中循环，有可能作用于包括中枢神经系统（CNS）在内的靶组织。DHEA的许多作用需要将其转化为更具活性的产物，其中一些是由3β-羟基类固醇脱氢酶/异构酶（3β-HSD）催化的。对鸟类的研究表明，3β-HSD在大脑中表达且具有活性，并且在调节社会行为方面具有重要作用。在鸣禽中，3β-HSD在大脑中以相当高的水平表达，这可能与它们控制鸣叫的复杂神经回路有关。研究还表明，循环中的DHEA可能作为神经3β-HSD的底物，产生在非繁殖季节激活行为的活性类固醇。在亚鸣禽金领侏儒鸟（Manacus vitellinus）中，当循环睾酮水平处于基础水平时，雄性表现出低水平的求偶行为。因此，我们询问DHEA是否在侏儒鸟的血液中循环，以及大脑是否表达3β-HSD mRNA。鉴于脊髓是雄激素的靶器官，并且在调节杂技动作方面可能很重要，我们还研究了这种酶在侏儒鸟脊髓中的表达。为了进行比较，我们将表达水平与鸣禽斑胸草雀（Taeniopygia guttata）进行了比较，斑胸草雀是一种大脑中3β-HSD已得到充分研究但脊髓中未研究的物种。在侏儒鸟血液中检测到的DHEA水平与其他物种相似。如先前所述，在所有检测的斑胸草雀脑区中均表达3β-HSD。相比之下，仅在侏儒鸟的下丘脑中检测到3β-HSD的表达，其水平高于斑胸草雀。在脊髓中，在两个物种的一些但不是所有区域都检测到了3β-HSD。这些数据表明了物种差异，并表明侏儒鸟具有将循环中的DHEA转化为潜在活性雄激素和/或雌激素的底物和神经机制。
