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Torcetrapib induces aldosterone and cortisol production in an intracellular calcium-dependent mechanism

ABSTRACT: ILLUMINATE (Investigation of Lipid Level Management to Understand its Impact in Atherosclerotic Events), the phase 3 morbidity and mortality trial of torcetrapib, a cholesteryl ester transfer protein (CETP) inhibitor, identified previously undescribed changes in plasma levels of potassium, sodium, bicarbonate, and aldosterone. A key question after this trial is whether the failure of torcetrapib was a result of CETP inhibition or of some other pharmacology of the molecule. The direct effects of torcetrapib and related molecules on adrenal steroid production were assessed in cell culture using the H295R as well as the newly developed HAC15 human adrenal carcinoma cell lines. Torcetrapib induced the synthesis of both aldosterone and cortisol in these two in vitro cell systems. Analysis of steroidogenic gene expression indicated that torcetrapib significantly induced the expression of CYP11B2 and CYP11B1, two enzymes in the last step of aldosterone and cortisol biosynthesis pathway, respectively. Transcription profiling indicated that torcetrapib and angiotensin II share overlapping pathways in regulating adrenal steroid biosynthesis. Hormone-induced steroid production is mainly mediated by two messengers, calcium and cAMP. An increase of intracellular calcium was observed after torcetrapib treatment, whereas cAMP was unchanged. Consistent with intracellular calcium being the key mediator of torcetrapib’s effect in adrenal cells, calcium channel blockers completely blocked torcetrapib-induced corticoid release and calcium increase. A series of compounds structurally related to torcetrapib as well as structurally distinct compounds were profiled. The results indicate that the pressor and adrenal effects observed with torcetrapib and related molecules are independent of CETP inhibition.

ORGANISM(S): Homo sapiens

PROVIDER: GSE15918 | GEO | 2009/05/02

SECONDARY ACCESSION(S): PRJNA116921

REPOSITORIES: GEO

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Project description:Steroid hormones regulate essential physiological processes and inadequate levels are associated with various pathological conditions. In testosterone-producing Leydig cells, steroidogenesis is strongly stimulated by LH via its receptor leading to increased cAMP production and expression of the steroidogenic acute regulatory (STAR) protein, which is essential for the initiation of steroidogenesis. Leydig cell steroidogenesis then passively decreases following the rapid degradation of cAMP into AMP by phosphodiesterases. In this study, we show that AMP-activated protein kinase (AMPK) is activated following cAMP breakdown in MA-10 and MLTC-1 Leydig cells. Activated AMPK then actively inhibits cAMP-induced steroidogenesis by repressing the expression of key regulators of steroidogenesis including Star and Nr4a1. Similar results were obtained in Y-1 adrenal cells and in the constitutive steroidogenic cell line R2C. Our data identify AMPK as an active repressor of steroid hormone biosynthesis in steroidogenic cells that is essential to preserve cellular energy and prevent excess steroid production. Steroid hormones regulate essential physiological processes and inadequate levels are associated with various pathological conditions. In testosterone-producing Leydig cells, steroidogenesis is strongly stimulated by LH via its receptor leading to increased cAMP production and expression of the steroidogenic acute regulatory (STAR) protein, which is essential for the initiation of steroidogenesis. Leydig cell steroidogenesis then passively decreases following the rapid degradation of cAMP into AMP by phosphodiesterases. In this study, we show that AMP-activated protein kinase (AMPK) is activated following cAMP breakdown in MA-10 and MLTC-1 Leydig cells. Activated AMPK then actively inhibits cAMP-induced steroidogenesis by repressing the expression of key regulators of steroidogenesis including Star and Nr4a1. Similar results were obtained in Y-1 adrenal cells and in the constitutive steroidogenic cell line R2C. Our data identify AMPK as an active repressor of steroid hormone biosynthesis in steroidogenic cells that is essential to preserve cellular energy and prevent excess steroid production. MA-10 Leydig cells were treated with either DMSO (control), 10 uM forskolin or forskolin+Aicar (1 mM) for 1.5 h before total RNA extraction

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Torcetrapib induces aldosterone and cortisol production in an intracellular calcium-dependent mechanism

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