In the United States, one in three adults will develop hypertension and require antihypertensive treatments in their lifetime. More importantly, only 50% of patients with hypertension have blood pressure controlled with current antihypertensive drugs. Poorly controlled hypertension is very prevalent in aging men and postmenopausal women with impaired pressure natriuresis response. The factors contributing to poorly controlled hypertension remain to be determined. It is clear, however, the development of all forms of hypertension will require continuously resetting of the pressure natriuresis response to higher pressures. Although previous studies have implicated the Na+/H+ exchanger 3 (NHE3) in the pressure natriuresis response and angiotensin II (ANG II)-dependent hypertension, whether NHE3 in the proximal tubules of the kidney is directly involved in the physiological pressure natriuresis response and its resetting in ANG II-induced hypertension has never been specifically investigated previously. We have strong preliminary evidence that conditional deletion of NHE3 selectively in the proximal tubules (PT-NHE3-KO), or pharmacological inhibition of NHE3 selectively in the kidney, primarily in the proximal tubules, with a novel orally absorbable NHE3 inhibitor significantly increases the pressure natriuresis response and attenuates ANG II- and salt-induced hypertension by restoring pressure natriuresis response in mice. In this revised proposal, we will test the hypotheses that NHE3 in the proximal tubules of the kidney is directly involved in the physiological pressure natriuresis response and its resetting in ANG II-induced hypertension, and that pharmacological inhibition of NHE3 selectively in the kidney, primarily in the proximal tubules, will attenuate hypertension in animal models of genetic-, ANG II-, aging-, and sex-associated hypertension by restoring pressure natriuresis responses.
In Specific Aim 1, we will test whether deletion of NHE3 selectively in the proximal tubules will increase pressure natriuresis response and lower blood pressure by inhibiting proximal tubule Na+ reabsorption, whereas upregulation, via overexpression, of NHE3 selectively in the proximal tubules will impair and reset pressure natriuresis response to higher pressures by stimulating proximal tubule Na+ reabsorption and promoting salt sensitivity of blood pressure. In a revised Specific Aim 2, we will test whether NHE3 in the proximal tubules is directly involved in the physiological pressure natriuresis responses to acute saline volume expansion, natriuretic peptides, or activation of AT2 receptor/NO/cGMP signaling, and in the resetting of pressure natriuresis responses in ANG II-, L-NAME-, aging- and sex-associated hypertension.
In Specific Aim 3, we will test whether inhibition of NHE3 selectively in the kidney, primarily in the proximal tubules, with an orally absorbable NHE3 inhibitor will attenuate genetic-, ANG II-, aging- and sex-associated hypertension by restoring pressure natriuresis responses. The successful outcomes of this proposal will help develop novel drugs to treat poorly controlled or resistant hypertension by selectively targeting NHE3 in the proximal tubules.

Public Health Relevance

Impaired pressure natriuresis response contributes to poorly controlled hypertension in aging men and postmenopausal women. This project will identify the Na+/H+ exchanger 3 (NHE3) in the proximal tubules of the kidney as a key factor for impaired pressure natriuresis response and therefore a therapeutic target in poorly controlled hypertension. OMB No. 0925-0001/0002 (Rev. 08/12 Approved Through 8/31/2015) Page Continuation Format Page

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK102429-05
Application #
9717253
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Ketchum, Christian J
Project Start
2017-08-17
Project End
2022-05-31
Budget Start
2019-06-01
Budget End
2020-05-31
Support Year
5
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of Mississippi Medical Center
Department
Pharmacology
Type
Schools of Medicine
DUNS #
928824473
City
Jackson
State
MS
Country
United States
Zip Code
39216
Zhuo, Jia L; Li, Xiao C (2018) De Novo DNA (de)Methylation in the Kidney. Hypertension 72:1084-1086
Li, Xiao C; Soleimani, Manoocher; Zhu, Dongmin et al. (2018) Proximal Tubule-Specific Deletion of the NHE3 (Na+/H+ Exchanger 3) Promotes the Pressure-Natriuresis Response and Lowers Blood Pressure in Mice. Hypertension 72:1328-1336
Li, Xiao C; Zhu, Dongmin; Zheng, Xiaowen et al. (2018) Intratubular and intracellular renin-angiotensin system in the kidney: a unifying perspective in blood pressure control. Clin Sci (Lond) 132:1383-1401
Li, Xiao C; Zhang, Jianfeng; Zhuo, Jia L (2017) The vasoprotective axes of the renin-angiotensin system: Physiological relevance and therapeutic implications in cardiovascular, hypertensive and kidney diseases. Pharmacol Res 125:21-38
Ferrão, Fernanda M; Cardoso, Luiza H D; Drummond, Heather A et al. (2017) Luminal ANG II is internalized as a complex with AT1R/AT2R heterodimers to target endoplasmic reticulum in LLC-PK1 cells. Am J Physiol Renal Physiol 313:F440-F449
Fan, Fan; Pabbidi, Mallikarjuna R; Ge, Ying et al. (2017) Knockdown of Add3 impairs the myogenic response of renal afferent arterioles and middle cerebral arteries. Am J Physiol Renal Physiol 312:F971-F981
Zhuo, Jia L; Kobori, H; Li, Xiao C et al. (2016) Augmentation of angiotensinogen expression in the proximal tubule by intracellular angiotensin II via AT1a/MAPK/NF-?B signaling pathways. Am J Physiol Renal Physiol 310:F1103-12
Li, Xiao C; Zhuo, Jia L (2016) Recent Updates on the Proximal Tubule Renin-Angiotensin System in Angiotensin II-Dependent Hypertension. Curr Hypertens Rep 18:63
Roman, Richard J; Fan, Fan; Zhuo, Jia L (2016) Intrarenal Renin-Angiotensin System: Locally Synthesized or Taken up Via Endocytosis? Hypertension 67:831-3
Li, Xiao C; Shull, Gary E; Miguel-Qin, Elisa et al. (2015) Role of the Na+/H+ exchanger 3 in angiotensin II-induced hypertension in NHE3-deficient mice with transgenic rescue of NHE3 in small intestines. Physiol Rep 3:

Showing the most recent 10 out of 15 publications