Illicit Upregulation of Serotonin Signaling Pathway in Adrenals of Patients With High Plasma or Intra-Adrenal ACTH Levels

Julie Le Mestre, Céline Duparc, Yves Reznik, Fidéline Bonnet-Serrano, Philippe Touraine, Olivier Chabre, Jacques Young, Mari Suzuki, Mathilde Sibony, Françoise Gobet, Constantine A Stratakis, Gérald Raverot, Jérôme Bertherat, Hervé Lefebvre, Estelle Louiset
The Journal of Clinical Endocrinology & Metabolism, Volume 104, Issue 11, November 2019, Pages 4967–4980
https://doi.org/10.1210/jc.2019-00425

Abstract

Context

In the human adrenal, serotonin (5-HT), released by mast cells stimulates corticosteroid secretion through activation of type 4 serotonin receptors (5-HT₄R). In primary pigmented nodular adrenocortical disease cells, activation of the cAMP/protein kinase A (PKA) pathway by PRKAR1A mutations triggers upregulation of the 5-HT synthesizing enzyme tryptophan hydroxylase (TPH) and the 5-HT₄, 5-HT₆, and 5-HT₇ receptors. Because ACTH stimulates cortisol secretion through activation of PKA, adrenocortical tissues exposed to sustained stimulation by ACTH may harbor increased expression of TPH and 5-HT_4/6/7 receptors.

Objective

To investigate the effects of long-term ACTH stimulation on the serotonergic pathway in adrenals of patients with high plasma or intra-adrenal ACTH levels.

Methods

Adrenal tissues were obtained from patients with Cushing disease, ectopic secretion of ACTH [paraneoplastic Cushing syndrome; (paraCS)], 21-hydroxylase deficiency (21-OHD), primary bilateral macronodular adrenal hyperplasia with intra-adrenal ACTH presence, or cortisol-producing adenomas. TPH and 5-HT_4/6/7 receptor expression was investigated using RT-PCR and immunochemistry in comparison with normal adrenals. Primary cultured adrenocortical cells originating from a patient with paraCS were incubated with 5-HT and 5-HTR agonists/antagonists.

Results

TPH and/or 5-HT_4/6/7 receptors were overexpressed in the different types of tissues. In paraCS cultured cells, the cortisol response to 5-HT was exaggerated compared with normal adrenal cells and the stimulatory action of 5-HT was reduced by 5-HT₄R antagonist.

Conclusion

Our results indicate that prolonged activation of the cAMP/PKA pathway by ACTH induces an aberrant serotonergic stimulatory loop in the adrenal cortex that likely participates in the pathogenesis of corticosteroid hypersecretion.

You may also like...