RF33 | PSAT79 Chronic Activation of Gq-Signaling in the Mouse Adrenal Cortex Disrupts Zonation and Causes Aldosterone Production in the Zona Fasciculata
Authors: Rooyen Desmaré Van , Ullenbruch Matthew , Taylor Matthew J , Rainey William E 
Published: November 2022

Abstract

Background
The mammalian adrenal cortex is composed of the zona glomerulosa (ZG), zona fasciculata (ZF), and in some species the zona reticularis (ZR). Each layer is characterized by a specific steroidogenic enzyme expression pattern that leads to selective production of mineralocorticoids, glucocorticoids or adrenal androgens. ZG-specific expression of cytochrome P450 aldosterone synthase (Cyp11b2) and aldosterone biosynthesis are renin-angiotensin-dependent processes in which the Gq-signaling pathway is activated by angiotensin II (AngII). Gq-signaling can be exogenously activated using Gq-coupled designer receptors exclusively activated by designer drug (GqDREADD) technology. Using transgenic mice with targeted expression of GqDREADD to the adrenal cortex, we previously demonstrated that short-term receptor activation increased adrenal Cyp11b2 and aldosterone production. Herein, we hypothesized that prolonged activation of mouse adrenal cortex Gq-signaling would exacerbate the aldosterone levels and promote the transdifferentiation of ZF cells to ZG cells.

Methods
Transgenic AS+/Cre hM3Dq (GqDREADD) female mice were engineered through crossing GqDREADD mice with Cyp11b2-regulated Cre recombinase mice. Mice were placed on a high sodium diet (to suppress physiologic renin) and orally provided the GqDREADD ligand, clozapine N-oxide (CNO; n=10) or control (n=8) for 6 weeks followed by collection of blood and adrenals. Mineralocorticoid levels were quantified using LC-MS/MS. Adrenal RNA was isolated and assessed by RNAseq for transcriptomic changes, and RT-qPCR analysis for ZG- and ZF-specific transcript markers, Cyp11b2 and Cyp11b1 (marker of ZF), respectively. Transcripts for β-catenin (Ctnnb1) and axin-2 (Axin2) (markers of the WNT signaling pathway) were also analyzed. Immunofluorescence (IF) studies examined adrenal expression of Cyp11b1 and Cyp11b2 in mice treated for 1 month.

Results
CNO treatment caused plasma aldosterone to increase 613-fold from 7.9 ±2.5 pg/mL to 4810.7 ±1110.7 pg/mL (p&lt;0.01). Levels of 18-hydroxycorticosterone increased 70-fold from 144.9 ±22.0 to 10143.2 ±1479.6 pg/mL (p&lt;0.0001). Corticosterone levels were unaffected. RT-qPCR analysis showed adrenal Cyp11b2 transcripts to be 224-fold higher (p&lt;0.0001) in the CNO-treated group while a 30% decrease in Cyp11b1 levels was observed (p&lt;0.01) compared to the controls. IF demonstrated hybrid ZF cells aberrantly expressing both Cyp11b2 and Cyp11b1. Within the normal mouse adrenal, the outer ZG exhibits high WNT/β-catenin (Ctnnb1) activation. To determine if chronic CNO treatment impacted overall adrenal WNT signaling, Ctnnb1 and Axin2 (a downstream β-catenin gene target) were examined. Analysis revealed no statistical difference in Ctnnb1 and Axin2 transcript levels in treated mice. RNAseq revealed that 242 transcripts were increased in adrenals from treated mice, while 109 decreased (&gt;3-fold change; p&lt;0.01). Induced transcripts include Cyp11b2 and its transcriptional regulators, Nr4a1 and Nr4a2.

Conclusion
Overall, these findings demonstrate that chronic Gq-signaling is sufficient to cause ZF cells to produce aldosterone and express Cyp11b2. The findings also suggest that the adrenocortical WNT signaling pathway is not increased by the activation of Gq-signaling.
Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 12:36 p.m. - 12:41 p.m.