Abstract
Conditions of impaired adrenal function and tissue destruction, such as in Addison’s disease, and treatment resistance of adrenocortical carcinoma (ACC) necessitate improved understanding of the pathophysiology of adrenal cell death. Due to relevant oxidative processes in the adrenal cortex, our study investigated the role of ferroptosis, an iron-dependent cell death mechanism and found high adrenocortical expression of glutathione peroxidase 4 (GPX4) and long-chain-fatty-acid CoA ligase 4 (ACSL4) genes, key factors in the initiation of ferroptosis. By applying MALDI mass spectrometry imaging to normal and neoplastic adrenocortical tissue, we detected high abundance of arachidonic and adrenic acid, two long chain polyunsaturated fatty acids which undergo peroxidation during ferroptosis. In three available adrenal cortex cell models (H295R, CU-ACC1 and CU-ACC-2) a high susceptibility to GPX4 inhibition with RSL3 was documented with EC50 values of 5.7 × 10−8, 8.1 × 10−7 and 2.1 × 10−8 M, respectively, while all non-steroidogenic cells were significantly less sensitive. Complete block of GPX4 activity by RSL3 led to ferroptosis which was completely reversed in adrenal cortex cells by inhibition of steroidogenesis with ketoconazole but not by blocking the final step of cortisol synthesis with metyrapone. Mitotane, the only approved drug for ACC did not induce ferroptosis, despite strong induction of lipid peroxidation in ACC cells. Together, this report is the first to demonstrate extraordinary sensitivity of adrenal cortex cells to ferroptosis dependent on their active steroid synthetic pathways. Mitotane does not induce this form of cell death in ACC cells.
Highlights
Cell death in the adrenal cortex is poorly understood but of high clinical relevance
We initially investigated expression of genes involved in ferroptosis execution in adrenocortical cells, normal adrenal gland tissue and adrenocortical tumors
glutathione peroxidase 4 (GPX4) and lysophosphatidylcholine acyltransferase 3 (LPCAT3), an enzyme involved in incorporating polyunsaturated fatty acids (PUFAs) into membrane phopholipids, were clearly overexpressed in the adrenal cortex
Summary
Cell death in the adrenal cortex is poorly understood but of high clinical relevance. In Addison’s disease, destruction of adrenocortical cells leads to a lack of adrenal steroids which—if untreated—may be fatal[1]. While it has become clear that polymorphisms of genes involved in the control of autoimmunity[2,3] predispose to Addison’s disease, it is unclear how dying adrenocortical cells initiate antigen exposure that results in adrenal cortex destruction. Uncontrolled proliferation of adrenocortical cells can result in neoplasms like adrenocortical carcinoma (ACC), a very rare malignancy with an overall poor prognosis[4,5]. Treatment options for ACC are scarce with mitotane (o,p′-DDD) being the only approved drug and used both for adjuvant treatment and in metastatic disease[6,7]. Adverse effects are frequent and often dose-limiting[5]
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