Original Article
AT1AA (Angiotensin II Type-1 Receptor Autoantibodies) Cause or Consequence of Human Primary Aldosteronism?
Maria Piazza,* Teresa Maria Seccia,* Brasilina Caroccia, Giacomo Rossitto, Riccardo Scarpa, Perla Persichitti, Daniela Basso, Gian Paolo Rossi
Abstract-AT1AA (Angiotensin II type-1 receptor autoantibodies) were first detected in patients with primary aldosteronism (PA) because of aldosterone-producing adenoma (APA) with an in-house developed assay, but it remained unclear if they can be ascertained also with commercially available assays and if they have a functional role. Aims of our study were to investigate if (1) commercially available kits allow detection of raised AT1AA titer in APA; (2) this titer is normalized by adrenalectomy; and (3) AT1AA display any biological roles in vitro. We measured with 2 ELISA kits the AT1AA titer in serum of APA patients and its changes after adrenalectomy. We also investigated AT1AA bioactivity by using AT1-R (angiotensin type-1 receptor)-transfected Chinese hamster ovary and human adrenocortical carcinoma cells, and by measuring aldosterone synthase (CYP11B2) expression in human adrenocortical carcinoma cells after incubation with IgG. Both kits allowed detection of higher AT1AA levels in APA patients than in healthy subjects; surgical cure of PA did not decrease this titer at 1-month follow-up. Human adrenocortical carcinoma cells stimulation with IgG purified from sera of APA patients increased both CYP11B2 expression and aldosterone release (+40% and +76%, respectively, versus healthy subjects). However, no detectable effect of IgG was seen in Chinese hamster ovary cells expressing AT1-R. These findings support the contentions that (1) the raised AT1AA titer does not seem to be a consequence of hyperaldosteronism as it did not normalize after its cure; (2) AT1AA act as weak stimulators of aldosterone biosynthesis, but this effect can be identified only by using a sensitive in vitro technique. (Hypertension. 2019;74:00-00. DOI: 10.1161/HYPERTENSIONAHA.119.13388.) · Online Data Supplement
American Heart Association.
Key Words: adenoma adrenalectomy aldosterone aldosteronism angiotensin antibodies
P rimary aldosteronism (PA) is the most common endocrine form of arterial hypertension. The distinction between its major subtypes, that is, unilateral aldosterone-producing ade- noma (APA) and bilateral adrenocortical hyperplasia, is key for optimal clinical management in as much as the former is best treated surgically, while the latter requires life-long med- ical treatment with MR (mineralocorticoid receptor) antago- nists, alone or combined with other agents.1,2
Immunohistochemical studies using monoclonal antibod- ies specific for human CYP11B2 (aldosterone synthase) de- veloped in Gomez-Sanchez laboratory highlighted that the pathology underlying PA is far more complex than simply bilateral adrenocortical hyperplasia and APA, as a single APA usually coexists with clusters of aldosterone-producing cells,3-5 which seem to accumulate with aging in humans,6 and might be an early stage of APA formation.7 Along with the concept of asymmetrical aldosterone excess in PA (Celso Gomez-Sanchez, personal communication), these findings suggested that a systemic stimulus can lead to clusters of
aldosterone-producing cells and eventually to APA formation, which could account for the existence of a continuum between APA and bilateral adrenocortical hyperplasia.
In 2013 using an in-house made ELISA kit, we described elevated titers of autoantibodies against AT1AA (angiotensin II type I receptor autoantibodies) in serum of patients with APA at levels comparable to those seen in women with pre- eclampsia, a prototype disease of raised AT1AA.8 This find- ing was thereafter confirmed by others,9,10 and particularly by Kem et al,9 who proposed that these AT1AA could have agonistic properties based on their finding of an AT1AA- activated ß-arrestin-dependent chemiluminescent signal in Chinese hamster ovary (CHO) cells engineered to express the AT1-R (angiotensin type-1 receptor) and enhanced aldoste- rone production in a human adrenocortical carcinoma cell-line (HAC15).
It remained, however, altogether unknown if this titer could be corrected by cure of PA by means of adrenalec- tomy and medical treatment targeting the MR, thus leaving
From the Department of Medicine-DIMED, University of Padua, Italy.
*These authors contributed equally to the work.
@ 2019 American Heart Association, Inc.
uncertain if the raised titer of AT1AA was a cause or a con- sequence of hyperaldosteronism. Hence, we set out this pro- spective study to answer the following questions: (1) does treatment with adrenalectomy normalize the titers of AT1AA? (2) can the reported agonist effect of AT1AA be confirmed in genetically engineered cells by using purified IgG from APA patients with high AT1AA titers?
Methods
The authors declare that all supporting data are available within the article and its in the online-only Data Supplement. Further data sup- porting the findings of this study are available from the authors on request.
Patients
We recruited for this study patients who had an APA confirmed by the 5 corners criteria2 (Table 1). At variance with recently proposed criteria,11 to assess clinical and biochemical success, recognizing the long-known fact that normalization of renin can lack even in patients who were unambiguously cured after surgery,12 we defined as bio- chemically cured the patients who showed normalized plasma aldos- terone concentration, serum K+, and 24-hour K+ excretion, besides a clearcut lowering of blood pressure, entailing cure, or improvement by the aforementioned criteria.11
Serum for measurement of AT1AA was obtained before and 1 month after adrenalectomy. Patients furnished written consent to the study, which was approved by the Institutional Review Board.
Enzyme-Linked Immunosorbent Assays
On the day of the assay, serum samples for AT1AA stored at -80℃ were thawed at room temperature. AT1AA was detected with 2 commercially available sandwich ELISA kits. The first exploits use of horseradish per- oxidase labeled-anti-human IgG and TMB substrate solution for AT1AA detection (CellTrend kit, Luckenwalde, Germany; see in the online- only Data Supplement). The second uses biotin-conjugate in addition to horseradish peroxidase labeled-anti-human IgG and TMB (Cusabio, Wuhan, China). Intra- and inter-assay coefficient of variation found in our laboratory were 5% and 6% for the first kit and 4% and 7% for the second. Both kits are currently used to measure AT1AA in kidney trans- plant recipients to identify those at high risk of allograft rejection.13-16
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In both assays, standard and diluted samples were added to the wells of a microtiter plate precoated with AT1-R and in- cubated for 2 hours. Optical density was read at 450 nm and then AT1AA concentration in the samples was obtained with a standard curve.
IgG Purification
IgG was purified from APA or control patients’ sera using the NAb Protein A/G spin kit following the manufacturer’s recommenda- tions (Pierce Biotechnology Rockford, IL) and quantified using the Nanodrop 2000c spectrophotometer.
Table 1. Five Corners Criteria for the Diagnosis of APA2
Biochemical evidence of PA (eg, an inappropriately high aldosterone/ renin ratio)
Lateralized aldosterone secretion by AVS
Detection of a nodule by imaging (CT or MRI) or an adenoma at pathology
Biochemical correction of PA after adrenalectomy
Detection of a CYP11B2-positive adenoma in the resected adrenal cortex at immunohistochemistry with a monoclonal antibody for human CYP11B2
APA indicates aldosterone-producing adenoma; AVS, adrenal vein sampling; CT, computed tomography; MRI, magnetic resonance imaging; and PA, primary aldosteronism.
CYP11B2 Gene Expression
The HAC15 human adrenocortical carcinoma cells (a gift of Dr W. E. Rainey, University of Michigan, Ann Arbor, MI) were cultured in DMEM-F12 supplemented with 10% Cosmic Calf serum at 37℃ under an atmosphere of 5% CO2 17 They were stimulated for 12 hours with angiotensin II (10-7 mol/L) or IgG (0.3 or 0.6 mg/mL). Irbesartan, or candesartan (both 10-5 mol/L), was used as AT1-R antagonists at concentrations chosen to be 100-fold higher than those of angiotensin II based on previous studies that showed abolishment of angiotensin II effects.18 After treatment, cells were lysed, and mRNA was isolated with high-pure RNA isolation kit (Roche Applied Science, Penzberg, Germany). CYP11B2 gene expression was quantified by real-time RT-polymerase chain reaction with universal probe library probes in the LightCycler 480 software (Roche Applied Science, Penzberg, Germany) using the comparative cycle threshold (2-44Ct) method: each sample was quantified against its PBGD (porphobilinogen de- aminase) transcript content and normalized to the control group.
Measurement of Aldosterone Production
Aldosterone levels were quantified by an aldosterone ELISA kit (Alpha Diagnostic International, San Antonio, TX). A total of 50 µL of cell medium was added to aldosterone-coated wells following the manufacturer’s instructions; the signal was detected in an ELISA reader (Berthold Technologies, Milan, Italy). Aldosterone levels were normalized to the amount of cell RNA content.19
B-Arrestin Recruitment Assay
The bioactivity of AT1AA was measured in AT1-R-transfected CHO cells engineered to express both the AT1-R and an intra- cellular ß-arrestin signaling pathway that, when activated by ag- onist binding AT1-R, develops a luminescent signal (DiscoveRx, Fremont, Canada). Briefly, CHO cells (n=104) were dispensed into each well of a 96-well culture plate and incubated for 48 hours. Ten microliter serum or purified IgG were then added and incubated for 90 minutes.
Each assay also comprised proper negative (buffer) and posi- tive (angiotensin II) controls following manufacturer’s recommen- dation. Detection reagents were then added, and chemiluminescent signal was read on a luminometer (LB960 Berthold, Bad Wildbad, Germany). A standard curve with angiotensin II was obtained (Figure S1 in the online-only Data Supplement), and ß-arrestin recruitment by sera or IgG was expressed as bioactivity of angiotensin II (pM/L).
Statistical Analysis
Direct renin concentration, plasma renin activity, plasma aldoste- rone concentration, and aldosterone to renin ratio values, which showed a skewed distribution, were analyzed after log transfor- mation. Distribution of categorical variables was investigated by x2 analysis. Bland-Altman plot was used to detect systematic and proportional errors and magnitude-dependent bias between AT1AA titers measured with the 2 assays.20 Deming regression was also used to look for systematic differences between methods. Paired t test was used to compare quantitative variables between baseline and follow-up and between buffer-stimulated and IgG-stimulated cells. The significance was set at P<0.05. Analyses were performed with Prism (vers. 8.1.2, GraphPad, San Diego, CA) and SPSS (vers. 25.0, IBM, Armonk, NY) for Mac.
Results
Clinical Features and AT1AA Levels of the APA Patients
We recruited for this study 27 APA patients (48% men, 52% women) aged 51±8 years, whose main clinical features at baseline and after adrenalectomy are shown in Table 2.
In 12 such patients, we measured AT1AA titer using both assays and found that they showed significantly higher
| Variable | Preadrenalectomy | Postadrenalectomy | P Value |
|---|---|---|---|
| Patients (n) | 27 | 27 | ... |
| SBP, mm Hg | 153±16 | 126±7 | 10-4 |
| DBP, mm Hg | 93±9 | 80±6 | 10-4 |
| K+, mmol/L | 3.2±0.4 | 4.2±0.4 | 3×10-3 |
| PAC, ng/dL | 20.9 (14.3-43.6) | 5.5 (4.4-8.7) | 10-4 |
| DRC, mIU/L | 2.0 (2.0-3.1) | 7.1 (2.5-16.9) | 10-4 |
| ARR, ng/mIU | 90.5 (57.0-214.2) | 7.3 (3.8-16.9) | 10-4 |
Data are presented as mean±SD or median (interquartile range). APA indicates aldosterone-producing adenoma; ARR, aldosterone to renin ratio; DBP, diastolic blood pressure; DRC, direct renin concentration; PAC, plasma aldosterone concentration; and SBP, systolic blood pressure.
titers of AT1AA than healthy volunteers (n=7; P<10-4 and P=3×10-3 for assays 1and 2, respectively; Figure 1A and 1B). A Bland-Altman plot of the results obtained with the 2 commercially available kits showed a good agreement, with no systematic or proportional errors, as all points fell within 2 SD; however, a funnel-like shape appearance suggested some magnitude-dependent bias (Figure 1C). Deming regression analysis confirmed that results obtained with the 2 assays did not differ by a constant amount or a
proportional difference, thus supporting their interchange- ability (Figure 1D). Hence, we used assay 1 in a larger co- hort of APA patients (n=27) to confirm that they had AT1AA titers higher than healthy donors, which was actually the case (P=3×10-2; Figure 2A).
Postadrenalectomy Results
Of the 27 patients with APA submitted to adrenalectomy, 26 showed full biochemical cure of PA after surgery, as evi- denced by normalization of plasma aldosterone concentration and serum potassium levels; one patient showed persistent hyperaldosteronism.
As regards blood pressure outcome, all patients were cured or markedly improved. Serum was available at follow-up in 14 patients, and therefore, assessment of biochemical cure was not feasible in all. In those who showed biochemical cure and cure or a marked improvement of blood, we could not observe any evident decrease of AT1AA levels at 1-month follow-up after removal of APA (Figure 2B).
Bioactivity of AT1AA
Two sets of experiments were undertaken to investigate if cir- culating AT1AA from APA patients could activate the AT1- R. In the first, CHO cells engineered to express the AT1-R were exposed to sera from APA patients using increasing
American Heart Association.
A
Assay 1
B
Assay 2 p=0.003
20-
p=0.0001
100
15-
AT1AA titer (U/mL)
AT1AA titer (ng/ml)
75
10-
50
5-
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APA
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Deming regression: Y = 0.99 x + 2.104e-006
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Z(AT1AA U/mL) - Z(AT1AA ng/ml)
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25
AT1AA titer (U/mL)
20
AT1AA titer (U/mL)
20
15.
15
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10
5
5
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Post
Adrenalectomy
concentrations of angiotensin II, ranging from 10-10 to 10-5 mol/L, as positive control. While angiotensin II elicited a clearcut concentration-dependent chemiluminescent re- sponse (Figure S1A), the serum did not induce any detect- able response as the readings were below the lowest detection threshold of the angiotensin II concentration-response curve (Figure S1B).
Several attempts to improve the sensitivity of this assay failed in that we could not detect a reproducible chemilumi- nescent signal. These results suggested that either the activity of AT1AA was below the detection threshold of this assay and that they were not biologically active.
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To further investigate these hypotheses, in a second set of experiments, HAC15 cells were exposed to IgG purified from serum of APA patients (n=10) with the highest AT1AA titer with both commercially available kits and CYP11B2 mRNA was measured as experimental end point (Figure 3). IgG induced a 40% increase in CYP11B2 gene expres- sion (Figure 3B), which, albeit statistically significant, was much lower than that induced by angiotensin II (Figure 3A). However, the purified IgG (n=8) enhanced the release of al- dosterone in the medium (Figure 4A and 4B). Pretreatment of HAC15 cells with irbesartan provided quite variable effects among patients; however, on average irbesartan blunted, albeit
A
p<0.0001
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60-
p<0.0001
2.0-
50-
CYP11B2 mRNA fold-change from vehicle (Ang II)
40
p=0.02
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Ang II Irbesartan
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p= 0.04
350
p= 0.04
300
NS
80-
Aldosterone (pg/ug RNA)
Aldosterone (%)
250
NS
60-
200
40-
150
100
20-
50
0
0
lgG (mg/mL)
0.3
0.3
lgG (mg/ml)
0.3
0.6
0.3
0.6
0.6
0.6
Ang II [10-7M]
HD
APA
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did not abolish, the increase in CYP11B2 mRNA induced by IgG from APA patients (Figure 3B).
Discussion
The discovery that APA patients, who usually show the most florid clinical PA phenotypes, have an increased titer in serum of autoantibodies against the AT1-R,8 followed by the report that these autoantibodies could have an agonistic effect on AT1-R, opened a new line of investigation as to why excess aldosterone production occurs in PA, in a fashion seemingly autonomous from angiotensin II.9
The present results provided novel pieces of information in this area by showing that the increased AT1AA titer could be detected not just with an in-house developed method using a peptide corresponding to the second extracellular loop of the human AT1-R, as originally reported,8 but also with 2 commercially available assays that uses microtiter plate pre- coated with recombinant AT1-R protein (Figure 1A and 1B). These findings indicate that the recombinant AT1-R protein used in the microplate retains a conformation similar to that of cell membrane AT1-R, which renders it accessible to the AT1AA. Accordingly, they testify the possibility of expand- ing research in this field by means of commercially available kits to groups of investigators that do not have in-house gen- erated assays.
The second important question to answer was if the el- evated AT1AA titer is a cause or a consequence of PA. We addressed this issue at 2 levels: first, we investigated the effect of surgical cure of PA by unilateral laparoscopic adrenalec- tomy on AT1AA titers and found no normalization of the raised autoantibodies titers, suggesting that PA by itself does not raise the titer of AT1AA. Accordingly, AT1AA might not simply represent a biomarker of the excess cardiovascular damage, which in PA has been well documented at the level of the heart, kidney, and vasculature.21 However, this conten- tion needs, in our view, to be tempered by considering the following. First, serum was available at follow-up in only
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14 patients, because some cured patients, who were from far away municipalities, after the initial follow-up visit 1 month after surgery could not to come back for further blood testing. Second, autoimmune diseases may need long time to resolve, which implies that the disappearance of circulating AT1AA levels could take a time longer than exploited in this study. Therefore, whether AT1AA production can be long-lasting and, moreover, if T-memory cells involved in AT1AA produc- tion are harbored in the APA, are important issues that deserve de Esta
As regards the biological role of ATTAA, when tested in vitro in AT1-R engineered CHO cells, under several exper- imental conditions and in a consistent manner, purified IgG from our APA patients with the highest antibodies titers did not elicit any detectable effect. These cells showed a clear- cut concentration-dependent response to angiotensin II even when tested in the presence patients’ serum, which ruled out a matrix effect. Hence, we could not confirm the elegant results reported by Kem et al9 using a similar cell system. The reasons for these discrepant results are currently unclear; however, we would like to suggest that engineered CHO cells might be not sensitive enough to allow detection of a weak biological ac- tivity of AT1AA, at least in our hands and at the titers found in our PA patients.
In line with this proposition, HAC15 cells exposed to purified IgG isolated from APA patients showed a 40% in- crease of CYP11B2 mRNA over IgG isolated from healthy subjects (Figure 3). This CYP11B2 mRNA increase was as- sociated with a 76% increase in aldosterone levels in the medium. Hence, AT1AA from APA patients exerted a weak effect, which was detectable only using highly sensitive in vitro assays, on aldosterone biosynthesis and secretion. Finally, it should also be considered that the the proportion of AT1AA in the IgG fraction is currently unknown; there- fore, differences between cohorts of APA patients could ex- plain the different findings obtained in different cohorts of patients.
An involvement of AT1-R activation in the stimulation of CYP11B2 gene expression induced by the IgG fraction of APA patients was suggested by our experiments with irbesartan, which exerted a blunting effect, albeit in a variable fashion. Further research is, however, necessary to dissect the reasons for these variable effects in different patients.
Conclusions
In summary, our results confirmed that elevated titers of AT1-R autoantibodies can be detected in serum of APA patients with 2 commercially available kits. These AT1AA might represent a biomarker of florid forms of PA but are unlikely to result from the excess cardiovascular damage documented in APA patients, as they remain elevated after biochemical cure of PA.22 Moreover, the AT1AA act as weak stimulators of aldosterone biosynthesis, albeit their effect could only be shown under well-defined conditions with a sensitive assay.
Perspectives
We found AT1AA not only in APA but also in some healthy donors, as similarly observed for other GPCR (G protein-cou- pled receptors) autoantibodies.23 Several relevant questions re- main, however, to be answered as, for example, which is the cutoff between normal subjects and APA patients, what pro- portion of purified IgG entails AT1AA, and even more impor- tantly, if healthy normotensive subjects represent a preclinical phase of PA as recently suggested.24
The persistence of an elevated AT1AA titer at times longer than 1 month after unilateral PA curative adrenalectomy, as well as investigation of an involvement of T-memory cells as possible determinants in an autoimmune process leading to the development of APA seem important lines of future inves- tigation at a stage when the mechanisms leading to clusters of aldosterone-producing cells and possible APA are being investigated with a great deal of success.2
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4. Gioco F, Seccia TM, Gomez-Sanchez EP, Rossi GP, Gomez-Sanchez CE. Adrenal histopathology in primary aldosteronism: is it time for a change? Hypertension. 2015;66:724-730. doi: 10.1161/HYPERTENSIONAHA. 115.05873
5. Omata K, Satoh F, Morimoto R, Ito S, Yamazaki Y, Nakamura Y, Anand SK, Guo Z, Stowasser M, Sasano H, Tomlins SA, Rainey WE. Cellular and ge- netic causes of idiopathic hyperaldosteronism. Hypertension. 2018;72:874- 880. doi: 10.1161/HYPERTENSIONAHA.118.11086
6. Omata K, Anand SK, Hovelson DH, Liu CJ, Yamazaki Y, Nakamura Y, Ito S, Satoh F, Sasano H, Rainey WE, Tomlins SA. Aldosterone-producing cell clusters frequently harbor somatic mutations and accumulate with age in normal adrenals. J Endocr Soc. 2017;1:787-799. doi: 10.1210/js. 2017-00134
7. Gomez-Sanchez CE, Williams TA. Visualizing adrenal steroids in pri- mary aldosteronism. Hypertension. 2018;72:1269-1271. doi: 10.1161/ HYPERTENSIONAHA.118.11369
8. Rossitto G, Regolisti G, Rossi E, Negro A, Nicoli D, Casali B, Toniato A, Caroccia B, Seccia TM, Walther T, Rossi GP. Elevation of angiotensin-II type-1-receptor autoantibodies titer in primary aldosteronism as a result of aldosterone-producing adenoma. Hypertension. 2013;61:526-533. doi: 10.1161/HYPERTENSIONAHA.112.202945
9. Kem DC, Li H, Velarde-Miranda C, Liles C, Vanderlinde-Wood M, Galloway A, Khan M, Zillner C, Benbrook A, Rao V, Gomez-Sanchez CE, Cunningham MW, Yu X. Autoimmune mechanisms activating the angio- tensin AT1 receptor in ‘primary’ aldosteronism. J Clin Endocrinol Metab. 2014;99:1790-1797. doi: 10.1210/jc.2013-3282
10. Sabbadin C, Ceccato F, Ragazzi E, Boscaro M, Betterle C, Armanini D. Evaluation of angiotensin II type-1 receptor antibodies in primary aldo- steronism and further considerations about their possible pathogenetic role. J Clin Hypertens (Greenwich). 2018;20:1313-1318. doi: 10.1111/ jch.13351
11. Williams TA, Lenders JWM, Mulatero P, et al. Outcomes after adrenal- ectomy for unilateral primary aldosteronism” an international consensus on outcome measures and analysis of remission rates in an international cohort. Lancet Diabetes Endocrinol. 2017;8587:1-11.
12. Rutherford JC, Taylor WL, Stowasser M, Gordon RD. Success of surgery for primary aldosteronism judged by residual autonomous aldosterone production. World J Surg. 1998;22:1243-1245.
13. Lefaucheur C, Viglietti D, Bouatou Y, Philippe A, Pievani D, Aubert O, Duong Van Huyen JP, Taupin JL, Glotz D, Legendre C, Loupy A, Halloran PF, Dragun D. Non-HLA agonistic anti-angiotensin II type 1 re- ceptor antibodies induce a distinctive phenotype of antibody-mediated re- jection in kidney transplant recipients. Kidney Int. 2019;96:189-201. doi: 10.1016/j.kint.2019.01.030
Acknowledgments
We are grateful to Mrs Chiara Berton for her precious help in collect- ing blood samples.
Sources of Funding
This work was supported by grants from the Italian Ministry of Health (RF2011-02352318) to T.M. Seccia and from the University of Padova (DOR1625891/16; DOR1670784/16; BIRD163255/16) to T.M. Seccia and G.P. Rossi.
Disclosures
None.
References
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2. Seccia TM, Caroccia B, Gomez-Sanchez EP, Gomez-Sanchez CE, Rossi GP. The biology of normal zona glomerulosa and aldosterone-pro- ducing adenoma: pathological implications. Endocr Rev. 2018;39:1029- 1056. doi: 10.1210/er.2018-00060
3. Omata K, Tomlins SA, Rainey WE. Aldosterone-producing cell clusters in normal and pathological states. Horm Metab Res. 2017;49:951-956. doi: 10.1055/s-0043-122394
14. Hesemann LE, Subramanian V, Mohanakumar T, Dharnidharka VR. De novo development of antibodies to kidney-associated self-antigens an- giotensin II receptor type I, collagen IV, and fibronectin occurs at early time points after kidney transplantation in children. Pediatr Transplant. 2015;19:499-503. doi: 10.1111/petr.12531
15. In JW, Park H, Rho EY, Shin S, Park KU, Park MH, Song EY. Anti- angiotensin type 1 receptor antibodies associated with antibody- mediated rejection in patients without preformed HLA-donor-specific antibody. Transplant Proc. 2014;46:3371-3374. doi: 10.1016/j.transproceed. 2014.09.096
16. Lee J, Huh KH, Park Y, et al; KNOW-KT Study Group. The clinico- pathological relevance of pretransplant anti-angiotensin II type 1 re- ceptor antibodies in renal transplantation. Nephrol Dial Transplant. 2017;32:1244-1250. doi: 10.1093/ndt/gfv375
17. Caroccia B, Seccia TM, Campos AG, Gioco F, Kuppusamy M, Ceolotto G, Guerzoni E, Simonato F, Mareso S, Lenzini L, Fassina A, Rossi GP. GPER-1 and estrogen receptor-ß ligands modulate aldoste- rone synthesis. Endocrinology. 2014;155:4296-4304. doi: 10.1210/en. 2014-1416
18. Vanderriele PE, Caroccia B, Seccia TM, Piazza M, Lenzini L, Torresan F, Iacobone M, Unger T, Rossi GP. The angiotensin type 2 re- ceptor in the human adrenocortical zona glomerulosa and in aldosterone- producing adenoma: low expression and no functional role. Clin Sci (Lond). 2018;132:627-640. doi: 10.1042/CS20171593
19. Caroccia B, Prisco S, Seccia TM, Piazza M, Maiolino G, Rossi GP. Macrolides blunt aldosterone biosynthesis: a proof-of-concept study in KCNJ5 mutated adenoma cells ex vivo. Hypertension. 2017;70:1238- 1242. doi: 10.1161/HYPERTENSIONAHA.117.10226
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Novelty and Significance
What Is New?
. The titer of AT1AA (angiotensin Il type-1 receptor autoantibodies) is in- creased in primary aldosteronism patients, and these autoantibodies are stimulators of aldosterone biosynthesis.
. This agonistic effect can be identified by using purified IgG and a sensi- tive in vitro technique.
. The raised AT1AA titer persisted 1 month after biochemical cure of pri- mary aldosteronism and, therefore, does not seem to be a consequence of hyperaldosteronism.
What Is Relevant?
. The AT1AA titer can be a biomarker of primary aldosteronism and can be measured with commercially available assays.
Summary
The raised AT1AA titer in aldosterone-producing aldosterone pa- tients, which persisted after cure of hyperaldosteronism suggests a pathogenetic role of AT1AA in raising aldosterone biosynthesis in primary aldosteronism.
American Heart Association.