Angiotensin II (Ang II) plays an essential role in maintaining body sodium and fluid balance and normal blood pressure by regulating proximal tubular sodium reabsorption. Ang II exerts powerful effects on sodium transport and cell growth by activating cell surface receptors on brush borders and basolateral membranes of proximal tubule cells. However, we have new evidence that a) extracellular Ang II is taken up by proximal tubule cells in vivo and in vitro; b) microinjection of Ang II directly into the cells increases intracellular calcium; and c) Ang II induces RNA transcription and expression in isolated nuclei. Our results suggest that internalized Ang II may act as an intracellular hormone to play important physiological and pathological roles in these cells. In this project, we propose to test the general hypothesis that extracellular Ang II is taken up by proximal tubule cells through AT1A receptor-mediated internalization, and that internalized Ang II binds to cytoplasmic and nuclear receptors to induce intracellular responses. To test this hypothesis, we will conduct both in vitro and in vivo studies, using complementary biochemical, morphological, cellular and molecular biology approaches.
In Aim I, we will study whether proximal tubular cells take up extracellular Ang II in vitro and in vivo and elucidate the mechanisms by which Ang II receptors and the endocytotic machinery regulate Ang II trafficking.
In Aim II, we will use confocal microscopy, state-of-the-art EM autoradiography and immunohistochemistry to trace intracellular trafficking pathways of internalized Ang II to the endosomal compartments and its translocaUon to the nucleus in vitro and in vivo.
In Aim III we will study whether microinjection of Ang II increases intracellular calcium through activation of cytoplasmic AT1 receptors and the cellular mechanisms involved. Finally, in Aim IV we will investigate whether internalized Ang II binds to intracellular Ang II receptors to activate transcription factor NFkappaB and its translocation to the nucleus, and whether internalized Ang II stimulates nuclear receptors to increase transcription and expression of the Na+/H+ exchanger NHE3 and pro-inflammatory cytokines. These studies will provide new insights into the important role of internalized Ang II in renal physiology and Ang II-induced hypertensive renal injury.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK067299-02
Application #
6860073
Study Section
Cardiovascular and Renal Study Section (CVB)
Program Officer
Ketchum, Christian J
Project Start
2004-03-01
Project End
2009-02-28
Budget Start
2005-03-01
Budget End
2006-02-28
Support Year
2
Fiscal Year
2005
Total Cost
$247,632
Indirect Cost
Name
Henry Ford Health System
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
073134603
City
Detroit
State
MI
Country
United States
Zip Code
48202
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 51 publications