β-catenin activation and illicit receptor expression in adrenocortical cells

Adrenal cortisol-producing tumors can express illicit membrane receptors such as luteinizing hormone (LH), glucose-dependent insulinotropic peptide (GIP) or type 4 and 7 serotonin (5-HT4/7) receptors. Abnormal expression of the LH receptor (LH-R) has been ascribed to activation of the Wnt/β-catenin signaling pathway in adrenocortical cells. In the present study, we have investigated whether β-catenin activation may also trigger illegitimate expression of GIP and 5-HT receptors. Three models of β-catenin activation in adrenocortical cells were used: an APC-mutated adrenocortical tumor, human transfected adrenocortical cells and genetically modified mouse adrenal glands. The methods employed included RT-qPCR, immunohistochemistry, and measurement of cortisol secretion by cultured tumor cells. Abnormal expression of the GIP, 5-HT7 and LH receptors was observed in the APC-mutated adrenocortical tumor tissue. In addition, GIP, 5-HT and hCG stimulated cortisol production from tumor cells in primary culture. Conversely, only the LHCGR was upregulated in human and mouse adrenocortical cells harboring activation of β-catenin. Moreover, LH-R immunoreactivity was detected in clusters of zona fasciculata cells in the β-catenin-activated mouse model. Our data indicate that activation of the β-catenin signaling pathway can promote illicit expression of functional LH receptors in adrenal zona fasciculata cells but does not favor abnormal expression of GIP and 5-HT receptors.

Transcriptomic Response Dynamics of Human Primary and Immortalized Adrenocortical Cells to Steroidogenic Stimuli

Adrenal steroid hormone production is a dynamic process stimulated by adrenocorticotropic hormone (ACTH) and angiotensin II (AngII). These ligands initialize a rapid and robust gene expression response required for steroidogenesis. Here, we compare the predominant human immortalized cell line model, H295R cell, with primary cultures of adult adrenocortical cells derived from human kidney donors. We performed temporally resolved RNA-seq on primary cells stimulated with either ACTH or AngII at multiple time points. The magnitude of the expression dynamics elicited by ACTH was greater than AngII in primary cells. This is likely due to the larger population of adrenocortical cells that are responsive to ACTH. The dynamics of stimulus-induced expression in H295R cells are mostly recapitulated in primary cells. However, there are some expression responses in primary cells absent in H295R cells. These data are a resource for the endocrine community and will help researchers determine whether H295R is an appropriate model for the specific aspect of steroidogenesis that they are studying.

BEX1 Is Differentially Expressed in Aldosterone-Producing Adenomas and Protects Human Adrenocortical Cells From Ferroptosis

Aldosterone-producing adenomas (APAs) are a major cause of primary aldosteronism. Somatic mutations in ion channels and transporters drive the aldosterone overproduction in the majority of APAs with mutations in the KCNJ5 G protein-coupled potassium channel predominating in most reported populations. Our objective was to gain insight into biological mechanisms of APA tumorigenesis by comparing transcriptomes of APAs of distinct sizes by mRNA sequencing analysis (9 APAs with adenoma diameter ≥30 mm versus 12 APAs ≤10 mm). Genes with significantly altered expression levels between these 2 groups were identified in APAs with no mutation detected (348 genes) and with a KCNJ5 mutation (155 genes). We validated the differential expression of 10 genes with a known function related to cell death and proliferation in an expanded sample set of 71 APAs by real-time quantitative polymerase chain reaction (58 macro-APAs, diameter ≥10 mm; 13 micro-APAs, diameter <10 mm). We focused on BEX1 that was upregulated in micro-APAs relative to macro-APAs (2.76-fold, P <0.001) and compared with paired adrenal cortex (3.85-fold, P <0.05), and showed a linear negative correlation with APA diameter in the no mutation detected group (r=−0.501, P =0.007). Compared with control cells, stable expression of BEX1 in human adrenocortical cells did not alter cell cycle progression or sensitivity to apoptosis but conferred protection from ferroptosis ( P <0.01), a form of regulated cell death, measured by flow cytometry. Taken together, these findings demonstrate that BEX1 promotes cell survival in adrenal cells by mediating the inhibition of ferroptosis and suggest a function for BEX1 in the pathogenesis of APAs.

PKA Cα subunit mutation triggers caspase-dependent RIIβ subunit degradation via Ser114 phosphorylation

Mutations in the PRKACA gene are the most frequent cause of cortisol-producing adrenocortical adenomas leading to Cushing’s syndrome. PRKACA encodes for the catalytic subunit α of protein kinase A (PKA). We already showed that PRKACA mutations lead to impairment of regulatory (R) subunit binding. Furthermore, PRKACA mutations are associated with reduced RIIβ protein levels; however, the mechanisms leading to reduced RIIβ levels are presently unknown. Here, we investigate the effects of the most frequent PRKACA mutation, L206R, on regulatory subunit stability. We find that Ser114 phosphorylation of RIIβ is required for its degradation, mediated by caspase 16. Last, we show that the resulting reduction in RIIβ protein levels leads to increased cortisol secretion in adrenocortical cells. These findings reveal the molecular mechanisms and pathophysiological relevance of the R subunit degradation caused by PRKACA mutations, adding another dimension to the deregulation of PKA signaling caused by PRKACA mutations in adrenal Cushing’s syndrome.

HIF1α is a direct regulator of steroidogenesis in the adrenal gland

Endogenous steroid hormones, especially glucocorticoids and mineralocorticoids, derive from the adrenal cortex, and drastic or sustained changes in their circulatory levels affect multiple organ systems. Although hypoxia signaling in steroidogenesis has been suggested, knowledge on the true impact of the HIFs (Hypoxia-Inducible Factors) in the adrenocortical cells of vertebrates is scant. By creating a unique set of transgenic mouse lines, we reveal a prominent role for HIF1α in the synthesis of virtually all steroids in vivo. Specifically, mice deficient in HIF1α in adrenocortical cells displayed enhanced levels of enzymes responsible for steroidogenesis and a cognate increase in circulatory steroid levels. These changes resulted in cytokine alterations and changes in the profile of circulatory mature hematopoietic cells. Conversely, HIF1α overexpression resulted in the opposite phenotype of insufficient steroid production due to impaired transcription of necessary enzymes. Based on these results, we propose HIF1α to be a vital regulator of steroidogenesis as its modulation in adrenocortical cells dramatically impacts hormone synthesis with systemic consequences. In addition, these mice can have potential clinical significances as they may serve as essential tools to understand the pathophysiology of hormone modulations in a number of diseases associated with metabolic syndrome, auto-immunity or even cancer.

The Adrenal Cortex, an Underestimated Site of SARS-CoV-2 Infection

BackgroundThe majority of the critically ill patients may have critical illness-related corticosteroid insufficiency (CIRCI). The therapeutic effect of dexamethasone may be related to its ability to improve cortical function. Recent study showed that dexamethasone can reduce COVID-19 deaths by up to one third in critically ill patients. The aim of this article is to investigate whether SARS-CoV-2 can attack the adrenal cortex to aggravate the relative adrenal insufficiency.MethodsWe summarized the clinical features of COVID-19 reported in currently available observational studies. ACE2 and TMPRSS2 expression was examined in human adrenal glands by immunohistochemical staining. We retrospectively analyzed serum cortisol levels in critically ill patients with or without COVID-19.ResultsHigh percentage of critically ill patients with SARS-COV-2 infection in the study were treated with vasopressors. ACE2 receptor and TMPRSS2 serine protease were colocalized in adrenocortical cells in zona fasciculata and zona reticularis. We collected plasma cortisol concentrations in nine critically ill patients with COVID-19. The cortisol levels of critically ill patients with COVID-19 were lower than those in non-COVID-19 critically ill group. Six of the nine COVID-19 critically ill patients had random plasma cortisol concentrations below 10 µg/dl, which met the criteria for the diagnosis of CIRCI.ConclusionWe demonstrate that ACE2 and TMPRSS2 are colocalized in adrenocortical cells, and that the cortisol levels are lower in critically ill patients with COVID-19 as compared to those of non-COVID-19 critically ill patients. Based on our findings, we recommend measuring plasma cortisol level to guide hormonal therapy.