Postnatal Expression of Androgen Receptor (AR) and the Alternative “Backdoor” Pathway to Dihydrotestosterone (DHT) in Normal and 21-Hydroxylase Deficient Human Adrenal Cortex

Presentation Number: SAT-0753
Date of Presentation: June 21st, 2014

Maria Sonia Baquedano*1, Sabrina Madjinca1, Paula Aliberti1, Nora Isabel Saraco2, Diana M. Warman3, Marco A. Rivarola1 and Alicia Belgorosky1
1Garrahan Pediatric Hospital, Buenos Aires, Argentina, 2Hospital de Pediatria Garrhan, Buenos Aires, Argentina, 3Hospital de Pediatria Garrahan, Buenos Aires, Argentina

Abstract

17-Hydroxyprogesterone (17OHP) can be converted to DHT via the backdoor pathway without the intermediacy of testosterone. This is a major route to DHT in pathological states in which 17OHP accumulates, including 21-hydroxylase (21OH) and POR deficiencies. However, the relevance of the backdoor pathway to human adrenal physiology is unknown.

Adrenal tissue from a 7 year-old 21OH-deficient patient resistant to hydrocortisone replacement therapy (21OHD-Res), but responsive to high doses of dexamethasone, and normal human adrenal tissues (HAT) were collected from 3 postnatal age groups (Grs): Gr1: <3 months, n=9, fetal zone involution; Gr2: 3 months to 6yr, n=9, pre-adrenarche; and Gr3: >6 to 20yr, n=8, post-adrenarche period.

By quantitative real-time RT-PCR, Gr3 mRNA levels (mean±SD, arbitrary units) of AKR1C1 (1.86±0.64) and AKR1C2 (1.89±0.50) were similar to GR2 but higher (p<0.05) than in GR1 (1.14±0.39 and 1.13±0.32, respectively). AKR1C3 mRNA in Gr3 (3.06±0.78) was higher than in Gr1 (2.00±0.67) and Gr2 (1.24±0.54), p<0.05. SRDA1 and RoDH mRNAs were readily amplified from HAT without difference among age Grs. SRDA2 and AKR1C4 mRNA were undetectable in the three age Grs. In all cases, mRNA expression from 21OHD-Res (AKR1C1, 1.74±0.09; AKR1C2, 1.78±0.09; AKR1C3, 2.99±0.12; SRDA1, 2.47±0.16 and RoDH, 1.8±0.08) was within the ±2SD range of Gr3 HAT. Laser capture microdissection of zona reticularis (ZR) and zona fasciculata (ZF) from Gr3 HAT showed no differences in adrenal zone-specific backdoor enzyme expression, except for a higher ZR expression of AKR1C1 and AKR1C3.  

AR mRNA was expressed in micro-dissected ZR (1.22±0.11) and ZF (1.11±0.26) without differences among the 3 age Grs (Gr1, 1.70±0.32; Gr2, 2.12±0.22; Gr3, 2.02±0.21). AR protein expression was confirmed by immunofluorescence. Impaired 21OHD-Res AR mRNA expression (1.22±0.04), below -2SD of HAT Gr3 expression was observed.

These results indicate that postnatal HAT would express all enzymes needed to complete the steps in the backdoor pathway to DHT. The reported activation of the backdoor pathway in 21OHD seems not to be due to a transcriptional activation of the pathway enzymes, suggesting that it might only be related to an excess of the 17OHP substrate. These data support a physiological role of the backdoor pathway in the postnatal human adrenal cortex. Finally, our data might suggest that proper activation of AR signaling is required to control adrenal cortex sensitivity to ACTH in 21OHD. 

 

Nothing to Disclose: MSB, SM, PA, NIS, DMW, MAR, AB