Rizner Tea Lanisnik, Lin Hsueh K, Penning Trevor M
Department of Pharmacology, University of Pennsylvania, School of Medicine, 3620 Hamilton Walk, Philadelphia, PA 19104-6084, USA.
Chem Biol Interact. 2003 Feb 1;143-144:401-9. doi: 10.1016/s0009-2797(02)00179-5.
Four human aldo-keto reductases (AKRs) that belong to the AKR1C subfamily function in vitro as 3-keto-, 17-keto- and 20-ketosteroid reductases or as 3alpha-, 17beta- and 20alpha- hydroxysteroid oxidases to varying degrees. By acting as ketosteroid reductases or hydroxysteroid oxidases these AKRs can either convert potent sex hormones (androgens, estrogens and progestins) into their inactive metabolites or they can form potent hormones by catalyzing the reverse reaction. In this manner they may regulate occupancy and trans-activation of steroid hormone receptors. Tissue distribution studies previously indicated that AKR1C2 (type 3 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD)) and AKR1C3 (type 2 3alpha-HSD) are highly expressed in human prostate. An assessment of the directionality of these AKR1C isozymes in a cellular environment would help identify which isozymes are responsible for 5alpha-dihydrotestosterone (5alpha-DHT) formation or its elimination in the prostate. An imbalance in 5alpha-DHT levels has been implicated in development of prostate carcinoma and benign prostatic hyperplasia. We focused our attention on AKR1C2 since this is the isoform that will oxidize 3alpha-androstanediol (3alpha-diol) to 5alpha-DHT in vitro, suggesting it could elevate 5alpha-DHT levels. To determine whether AKR1C2 preferentially functions as a reductase or an oxidase in a cellular context, we transiently transfected AKR1C2 (pcDNA3-AKR1C2) into COS-1 cells and stably transfected pcDNA3-AKR1C2 and pLNCX-AKR1C2 constructs into PC-3 and LNCaP cells, respectively. COS-1 is a monkey kidney cell line, while PC-3 and LNCaP cells are androgen receptor (-) and (+) prostate adenocarcinoma cell lines, respectively. In transient COS-1-AKR1C2 and in stable PC3-AKR1C2 transfectants, AKR1C2 functioned as a 3-ketosteroid reductase inactivating 5alpha-DHT. In androgen dependent human prostate cancer cells LNCaP, it was not possible to ascertain the preferred direction of AKR1C2 by stable transfection due to the high rate of 5alpha-DHT and 3alpha-diol glucuronidation. Based on these findings AKR1C2 may diminish 5alpha-DHT and prevent this ligand from activating the androgen receptor in situ.
属于AKR1C亚家族的四种人类醛糖酮还原酶（AKRs）在体外不同程度地发挥3-酮、17-酮和20-酮类固醇还原酶的作用，或作为3α-、17β-和20α-羟基类固醇氧化酶发挥作用。通过作为酮类固醇还原酶或羟基类固醇氧化酶，这些AKRs可以将强效性激素（雄激素、雌激素和孕激素）转化为无活性的代谢产物，或者通过催化逆反应形成强效激素。通过这种方式，它们可能调节类固醇激素受体的占据和反式激活。先前的组织分布研究表明，AKR1C2（3型3α-羟基类固醇脱氢酶（3α-HSD））和AKR1C3（2型3α-HSD）在人前列腺中高度表达。评估这些AKR1C同工酶在细胞环境中的方向性将有助于确定哪些同工酶负责前列腺中5α-二氢睾酮（5α-DHT）的形成或消除。5α-DHT水平的失衡与前列腺癌和良性前列腺增生的发生有关。我们将注意力集中在AKR1C2上，因为这种同工型在体外会将3α-雄烷二醇（3α-二醇）氧化为5α-DHT，这表明它可能会提高5α-DHT水平。为了确定AKR1C2在细胞环境中是优先作为还原酶还是氧化酶发挥作用，我们将AKR1C2（pcDNA3-AKR1C2）瞬时转染到COS-1细胞中，并分别将pcDNA3-AKR1C2和pLNCX-AKR1C2构建体稳定转染到PC-3和LNCaP细胞中。COS-1是一种猴肾细胞系，而PC-3和LNCaP细胞分别是雄激素受体（-）和（+）的前列腺腺癌细胞系。在瞬时COS-1-AKR1C2和稳定的PC3-AKR1C2转染子中，AKR1C2作为3-酮类固醇还原酶使5α-DHT失活。在雄激素依赖性人前列腺癌细胞LNCaP中，由于5α-DHT和3α-二醇葡萄糖醛酸化的高发生率，通过稳定转染无法确定AKR1C2的优先作用方向。基于这些发现，AKR1C2可能会降低5α-DHT水平，并防止这种配体在原位激活雄激素受体。
