Imaging mass spectrometry reveals co-accumulation of aldosterone and 18-oxocortisol with CYP11B2 in pre-adenomatous states of primary aldosteronism
Primary aldosteronism (PA) is a secondary hypertensive disease caused by autonomous aldosterone production that mainly results from adenoma (APA) or idiopathic hyperaldosteronism. Immunohistochemistry of aldosterone synthase (CYP11B2) has shown the presence of aldosterone-producing cell clusters (APCCs) even in non-PA adult adrenal cortex and APCC-to-APA transitional regions (pAATLs) in PA adrenals, leading us to hypothesize that these pre-adenomatous legions account for transitional states towards APA (JCEM 2010;95:2296-305; JCEM 2016;101:6-9; PNAS 2015;112:E4591-9). However, whether APCCs actually produce aldosterone or 18-oxocortisol (18-oxoF), a clinical PA marker, remains unknown.
In adrenals from 8 PA patients diagnosed pathologically as APCC (Cases #1-4), pAATL (#5) or APA (#6-8), MALDI-imaging methods with high-sensitive Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) enabled visualization of various adrenal steroids, and further analyses by imaging MS3 (tandem MS) allowed us to differentially visualize aldosterone from cortisone, which share identical m/z with single MS.
We visualized the accumulation of aldosterone and 18-oxoF not only in APAs, but also in APCCs. In adrenals with multiple APCCs, aldosterone and 18-oxoF were detected only in APCCs; therefore, APCCs may be aldosterone-producing lesions responsible for hyperaldosteronism. Moreover, the results support our hypothesis that APCC is the origin of APA, because (i) APCC-like portion of a pAATL had potent aldosterone-producing cells (~100%) as in APCCs, (ii) a subcapsular area of a small APA included potent aldosterone-producing cells similar to the ones in APCC-like portion of pAATL, and (iii) aldosterone producing cells were detected only in an edge of a large APA, which might be grown from an APCC.
We visualized the accumulation of aldosterone and 18-oxoF not only in APAs, but also in APCCs. 18-oxoF is autonomously generated through CYP11B2-expressing cells under early pre-adenomatous states such as APCC and pAATL, and serves as a reliable metabolic marker of pathological aldosterone production, shedding light on the relationship between adrenal cell lineages and their hormone-producing function.
Funding: This study was supported by funding from the KAKENHI grant (to KN, #15K10650), Hidaka Research Project grant (to KN, #28-D-13), Yamaguchi Endocrine Research Foundation research grant (to KN), a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (to YS, #26111006), and a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (to YS, 16H06145).