The High-Affinity cAMP-Specific Phosphodiesterase 8B Controls Steroidogenesis in the Mouse Adrenal Gland

Abstract

The functions of the phosphodiesterase 8B (PDE8) family of phosphodiesterases have been largely unexplored because of the unavailability of selective pharmacological inhibitors. Here, we report a novel function of PDE8B as a major regulator of adrenal steroidogenesis using a genetically ablated PDE8B mouse model as well as cell lines treated with either a new PDE8-selective inhibitor or a short hairpin RNA (shRNA) construct against PDE8B. We demonstrate that PDE8B is highly enriched in mouse adrenal fasciculata cells, and show that PDE8B knockout mice have elevated urinary corticosterone as a result of adrenal hypersensitivity toward adrenocorticotropin. Likewise, ablation of PDE8B mRNA transcripts by an shRNA construct potentiates steroidogenesis in the commonly used Y-1 adrenal cell line. We also observed that the PDE8-selective inhibitor (PF-04957325) potentiates adrenocorticotropin stimulation of steroidogenesis by increasing cAMP-dependent protein kinase activity in both primary isolated adrenocortical cells and Y-1 cells. It is noteworthy that PDE8s have their greatest control under low adrenocorticotropin-stimulated conditions, whereas other higher K m PDE(s) modulate steroidogenesis more effectively when cells are fully stimulated. Finally, both genetic ablation of PDE8B and long-term pharmacological inhibition of PDE8s cause increased expression of steroidogenic enzymes. We conclude that PDE8B is a major regulator of one or more pools of cAMP that promote steroidogenesis via both short-and long-term mechanisms. These findings further suggest PDE8B as a potential therapeutic target for the treatment of several different adrenal diseases.

Phosphodiesterases in the rat ovary: effect of cAMP in primordial follicles

“…Both PDE7 and PDE8 are most active at low cAMP concentrations (K m !100 nM) and PDE8 has been suggested to regulate the resting levels of cAMP (Bender & Beavo 2006, Tsai et al 2011, Shimizu-Albergine et al 2012 and it can speculated that PDE7 and PDE8 share the same function in the ovary. In contrast, PDE4 has a lower affinity for cAMP (K m Z1-10 mM) meaning that this enzyme is mainly active at higher cAMP concentrations observed during hormonal stimulation of cAMP production as seen for instance with hCG stimulation (Park et al 2003, Bender & Beavo 2006.…”

Genetics of tumors of the adrenal cortex

“…A single base substitution c.914A>C/p.His305Pro was identified in a young girl with PPNAD, who had presented Cushing's syndrome at the age of 2 years, decreased activity of the mutant PDE8B being confirmed in vitro in HEK293 cells . The functional role of PDE8B in the adrenal cortex was confirmed in mouse models, PDE8B-knockout mice exhibiting elevated urinary corticosterone as a result of adrenal hypersensitivity toward ACTH (Tsai et al 2011).…”

Phosphodiesterases in endocrine physiology and disease

“…PDE2A PDE2A is the predominant PDE in the adrenal cortex and may be implicated in adrenal physiology (25,27,28). To date, the regulation of intracellular cAMP accumulation after ACTH stimulation is not fully elucidated.…”

“…PDE8B Recently, it was demonstrated that PDE8B is a major regulator of adrenal steroidogenesis by both acute and chronic mechanisms (28). Indeed, PDE8B knockout mouse have elevated levels of corticosterone due to adrenal hypersensitivity to ACTH.…”