Oxford Centre for Diabetes, Endocrinology and Metabolism, NIHR Oxford Biomedical Research Centre, University of Oxford, Churchill Hospital, Oxford, OX3 7LE, UK.
Oxford Centre for Diabetes, Endocrinology and Metabolism, NIHR Oxford Biomedical Research Centre, University of Oxford, Churchill Hospital, Oxford, OX3 7LE, UK; Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, OX3 0BP, UK.
J Steroid Biochem Mol Biol. 2019 May;189:218-227. doi: 10.1016/j.jsbmb.2019.02.002. Epub 2019 Feb 12.
Steroid hormones, including glucocorticoids and androgens, have potent actions to regulate many cellular processes within the liver. The steroid A-ring reductase, 5β-reductase (AKR1D1), is predominantly expressed in the liver, where it inactivates steroid hormones and, in addition, plays a crucial role in bile acid synthesis. However, the precise functional role of AKR1D1 to regulate steroid hormone action in vitro has not been demonstrated. We have therefore hypothesised that genetic manipulation of AKR1D1 has the potential to regulate glucocorticoid availability and action in human hepatocytes. In both liver (HepG2) and non-liver cell (HEK293) lines, AKR1D1 over-expression increased glucocorticoid clearance with a concomitant decrease in the activation of the glucocorticoid receptor and the down-stream expression of glucocorticoid target genes. Conversely, knockdown of AKR1D1 using siRNA decreased glucocorticoid clearance and reduced the generation of 5β-reduced metabolites. In addition, the two 5α-reductase inhibitors finasteride and dutasteride failed to effectively inhibit AKR1D1 activity in either cell-free or hepatocellular systems. Through manipulation of AKR1D1 expression and activity, we have demonstrated its potent ability to regulate glucocorticoid availability and receptor activation within human hepatoma cells. These data suggest that AKR1D1 may have an important role in regulating endogenous (and potentially exogenous) glucocorticoid action that may be of particular relevance to physiological and pathophysiological processes affecting the liver.
甾体激素，包括糖皮质激素和雄激素，具有强大的作用，可以调节肝脏内的许多细胞过程。甾体 A 环还原酶，5β-还原酶（AKR1D1），主要在肝脏中表达，在肝脏中它使甾体激素失活，此外，它在胆汁酸合成中起着至关重要的作用。然而，AKR1D1 调节体外甾体激素作用的确切功能作用尚未得到证实。因此，我们假设 AKR1D1 的基因操作有可能调节人肝细胞中糖皮质激素的可用性和作用。在肝（HepG2）和非肝细胞（HEK293）系中，AKR1D1 的过表达增加了糖皮质激素的清除率，同时降低了糖皮质激素受体的激活和糖皮质激素靶基因的下游表达。相反，使用 siRNA 敲低 AKR1D1 降低了糖皮质激素的清除率，并减少了 5β-还原代谢物的生成。此外，两种 5α-还原酶抑制剂非那雄胺和度他雄胺在无细胞或肝细胞系统中均不能有效抑制 AKR1D1 的活性。通过操纵 AKR1D1 的表达和活性，我们证明了它在人肝癌细胞中调节糖皮质激素可用性和受体激活的强大能力。这些数据表明，AKR1D1 可能在调节内源性（和潜在外源性）糖皮质激素作用中发挥重要作用，这可能与影响肝脏的生理和病理生理过程特别相关。
