Physiologically aldosterone acts at the renal tubule to promote salt and water retention. Its production regulates vascular volume and hence blood pressure. Inappropriate secretion of aldosterone for the salt status of an individual is pathogenic, inducing structural and functional alterations in the heart, kidneys, and vasculature by advancing disease processes such as cardiac fibrosis, nephrosclerosis and arteriosclerosis. Although aldosterone induced cardiovascular and renal damage has been associated with the activation of the ligand-activated nuclear mineralocorticoid receptor (MR), pathogenic contributions of aldosterone that are independent of the MR, such as impairment in vascular reactivity, are now well-acknowledged . Therefore, there is a strong rationale for exploring therapies that are complementary to MR blockade that directly target the production of aldosterone. Aldosterone production from adrenal zona glomerulosa (ZG) cells is Ca-dependent and circulating Ang II is the predominant aldosterone secretagogue. Nevertheless, because the ZG layer of the adrenal gland is highly vascularized, every ZG cells is adjacent to an endothelial cell, and thus ZG cells are also targets for regulation by locally produced abluminally secreted endothelin (ET-1). In this proposal we test the novel hypothesis that aldosterone production is stimulated by systemic and paracrine hormones that convert the quiescent ZG cell into an electrically excitable one that serves to sensitize the production of aldosterone to low concentrations of physiological secretagogues. Using techniques of patch-clamp electrophysiology, molecular mutagenesis and radioimmunoassay we evaluate the following specific aims:
Aim 1 : Establish the ionic basis for ZG cell membrane excitability. Specifically we will: (1.1) Define the basic properties of regenerative Vm spiking in ZG cells;(1.2) Identify the role of Cav3.2 channels and IKCa in the initiation and/or propagation of pacemaking;(1.3) Characterize the control of regenerative Vm spiking elicited by Ang II and/or ET-1;(1.4) Quantify the impact of regenerative Vm spiking on net calcium entry.
Aim 2 : Determine the molecular basis for the regulation of Cav3.2 channels by PKC??PKD and its contribution to electrical excitability and the stimulation of aldosterone production elicited by Ang II and/or endothelin. Specifically we will: (1.1) Identify critical residues on the Cav3.2 channel protein that mediate stimulation of whole-cell and single channel activity by PKC??PKD;(1.2) Determine the contribution of PKC??PKD-mediated channel regulation to channel activation and electrical excitability elicited by Ang II and/orET-1;(1.3) Introduce PKC??PKD regulation resistant channels into adrenal zona glomerulosa cells to perturb Ang II and or ET-1 induced electrical excitability and evaluate the regulation of aldosterone production elicited by Ang II and/or ET-1. It is likely that the recognition of the electrical excitability of the ZG cell will revolutionize therapeutic strategies to efficiently inhibit the production of aldosterone.

Public Health Relevance

In appropriate production of aldosterone induces structural and functional alterations in the heart, kidneys and vasculature by advancing disease processes such as cardiac fibrosis, nephrosclerosis and arteriosclerosis. However, because not all cardiovascular and renal damage has been associated with the activation of the aldosterone nuclear receptor (MR) there is a strong rationale for exploring therapies that are complementary to MR blockade that target directly the regulation of aldosterone production. In this application we explore important mechanisms that regulate the production of aldosterone and provide data showing that the aldosterone producing cell of the adrenal gland is electrically excitable which revolutionizes the view of this endocrine cell and in itself changes the way in which aldosterone production could be targeted for inhibition by new drug therapies.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL036977-23
Application #
8207847
Study Section
Cellular and Molecular Biology of the Kidney Study Section (CMBK)
Program Officer
Lathrop, David A
Project Start
1987-07-01
Project End
2013-12-31
Budget Start
2012-01-01
Budget End
2012-12-31
Support Year
23
Fiscal Year
2012
Total Cost
$374,963
Indirect Cost
$127,463
Name
University of Virginia
Department
Pharmacology
Type
Schools of Medicine
DUNS #
065391526
City
Charlottesville
State
VA
Country
United States
Zip Code
22904
Freedman, Bethany D; Kempna, Petra Bukovac; Carlone, Diana L et al. (2013) Adrenocortical zonation results from lineage conversion of differentiated zona glomerulosa cells. Dev Cell 26:666-73
Orestes, Peihan; Osuru, Hari Prasad; McIntire, William E et al. (2013) Reversal of neuropathic pain in diabetes by targeting glycosylation of Ca(V)3.2 T-type calcium channels. Diabetes 62:3828-38
Hu, Changlong; Rusin, Craig G; Tan, Zhiyong et al. (2012) Zona glomerulosa cells of the mouse adrenal cortex are intrinsic electrical oscillators. J Clin Invest 122:2046-53
Guagliardo, Nick A; Yao, Junlan; Hu, Changlong et al. (2012) TASK-3 channel deletion in mice recapitulates low-renin essential hypertension. Hypertension 59:999-1005
Guagliardo, Nick A; Yao, Junlan; Bayliss, Douglas A et al. (2011) TASK channels are not required to mount an aldosterone secretory response to metabolic acidosis in mice. Mol Cell Endocrinol 336:47-52
Hu, Changlong; Depuy, Seth D; Yao, Junlan et al. (2009) Protein kinase A activity controls the regulation of T-type CaV3.2 channels by Gbetagamma dimers. J Biol Chem 284:7465-73
Davies, Lucinda A; Hu, Changlong; Guagliardo, Nick A et al. (2008) TASK channel deletion in mice causes primary hyperaldosteronism. Proc Natl Acad Sci U S A 105:2203-8
Nelson, Michael T; Joksovic, Pavle M; Su, Peihan et al. (2007) Molecular mechanisms of subtype-specific inhibition of neuronal T-type calcium channels by ascorbate. J Neurosci 27:12577-83
Xie, Xinmin; Van Deusen, Amy L; Vitko, Iuliia et al. (2007) Validation of high throughput screening assays against three subtypes of Ca(v)3 T-type channels using molecular and pharmacologic approaches. Assay Drug Dev Technol 5:191-203
Nelson, Michael T; Woo, Jiwan; Kang, Ho-Won et al. (2007) Reducing agents sensitize C-type nociceptors by relieving high-affinity zinc inhibition of T-type calcium channels. J Neurosci 27:8250-60

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