RECENT FINDINGS: KCNJ5, ATP1A1, ATP2B3, CACNA1D, CTNNB1, and CACNA1H mutations are causal of primary aldosteronism. ARMC5 may cause bilateral lesions resulting in primary aldosteronism.LGR5, DACH1, and neuron-specific proteins are highly expressed in the zona glomerulosa and regulate aldosterone production.
SUMMARY: Most mutations causing primary aldosteronism are in genes encoding cation channels or pumps, leading to increased calcium influx. Genotype-phenotype analyses identified two broad subtypes of aldosterone-producing adenomas (APAs), zona fasciculata-like and zona glomerulosa-like, and the likelihood of under-diagnosed zona glomerulosa-like APAs because of small size. Zona fasciculata-like APAs are only associated with KCNJ5 mutations, whereas zona glomerulosa-like APAs are associated with mutations in ATPase pumps, CACNA1D, and CTNNB1. The frequency of APAs, and the multiplicity of causal mutations, suggests a pre-existing drive for these mutations. We speculate that these mutations are selected for protecting against tonic inhibition of aldosterone in human zona glomerulosa, which express genes inhibiting aldosterone production.
OBJECTIVE: We hypothesized that Cav1.3 blockade by cinnarizine may achieve similar, or greater, reduction in aldosterone secretion than nonselective Cav1.2/1.3 blockade by nifedipine.
METHODS: Separate wells of angiotensin II-stimulated HAC15 cells were treated with either cinnarizine (1-30 μM) or nifedipine (1-100 μM). Aldosterone concentrations were measured in culture medium; RNA extraction and quantitative polymerase chain reaction were performed to evaluate CYP11B2 expression. A prospective, open-label, crossover study was conducted of 15 adults with PA, treated with 2 weeks of cinnarizine 30 mg 3 times a day or nifedipine extended release 60 mg daily, separated by a 2-week washout. The hierarchical primary outcome was change in aldosterone-to-renin ratio (ARR), urinary tetrahydroaldosterone (THA), and plasma aldosterone concentration (PAC). Blood pressure change was a secondary outcome. Parametric analysis was undertaken on log-transformed data. (ClinicalTrials.gov: NCT05686993).
RESULTS: Both drugs reduced aldosterone concentrations and CYP11B2 expression in vitro. Mean changes ± SEM in fold change of aldosterone concentrations and CYP11B2 were -0.47 ± 0.05 and -0.56 ± 0.07, respectively, with cinnarizine 30 μM and -0.59 ± 0.05 and -0.78 ± 0.07 with nifedipine 100 μM. In the clinical crossover trial, ARR was reduced by nifedipine but not cinnarizine (F = 3.25; P = .047); PAC rose with both drugs (F = 4.77; P = .013), but urinary THA was unchanged.
CONCLUSION: A Cav1.3 ligand, cinnarizine, reduced aldosterone secretion from adrenocortical cells, but at maximum-soluble concentrations was less effective than the nonselective calcium blocker, nifedipine. At clinical doses, cinnarizine did not reduce plasma ARR in patients with PA, and, as in vitro, was inferior to nifedipine. The limited efficacy of high-dose nifedipine may be due to incomplete Cav1.3 blockade, or to a role for non-L-type calcium channels in aldosterone secretion.
OBJECTIVE: The objective of the study was to delineate a process in human ZG, which may regulate both aldosterone production and cell turnover.
DESIGN: This study included a comparison of 20 pairs of ZG and zona fasciculata transcriptomes from adrenals adjacent to an APA (n = 13) or a pheochromocytoma (n = 7).
INTERVENTIONS: Interventions included an overexpression of the top ZG gene (LGR5) or stimulation by its ligand (R-spondin-3).
MAIN OUTCOME MEASURES: A transcriptome profile of ZG and zona fasciculata and aldosterone production, cell kinetic measurements, and Wnt signaling activity of LGR5 transfected or R-spondin-3-stimulated cells were measured.
RESULTS: LGR5 was the top gene up-regulated in ZG (25-fold). The gene for its cognate ligand R-spondin-3, RSPO3, was 5-fold up-regulated. In total, 18 genes associated with the Wnt pathway were greater than 2-fold up-regulated. ZG selectivity of LGR5, and its absence in most APAs, were confirmed by quantitative PCR and immunohistochemistry. Both R-spondin-3 stimulation and LGR5 transfection of human adrenal cells suppressed aldosterone production. There was reduced proliferation and increased apoptosis of transfected cells, and the noncanonical activator protein-1/Jun pathway was stimulated more than the canonical Wnt pathway (3-fold vs 1.3-fold). ZG of adrenal sections stained positive for apoptosis markers.
CONCLUSION: LGR5 is the most selectively expressed gene in human ZG and reduces aldosterone production and cell number. Such conditions may favor cells whose somatic mutation reverses aldosterone inhibition and cell loss.