Long term control of blood pressure involves Na+ homeostasis through the precise regulation of the Epithelial Na+ Channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN). ENaC dysfunction is causative for disturbances in total body Na+ levels associated with abnormal regulation of blood volume, blood pressure, and lung fluid balance. We provide preliminary evidence that epidermal growth factor (EGF) can serve as an ENaC ligand and hypothesize that members of the EGF-family and Rac1 modulate ENaC-mediated Na+ transport in the ASDN and participate in the development of salt-sensitive hypertension. EGF and its related EGF-family members bind to ErbB receptors and act as signaling factors responsible for renal development, physiology and pathophysiology. Under physiological conditions, ErbB receptors play an important role in the regulation of renal hemodynamics and electrolyte handling by the kidney, while in different pathophysiological states ErbB activation may mediate either beneficial or detrimental effects on the kidney. Stimulation of ErbB receptors activates an intracellular cascade involving small GTPases, particularly Rac1. Small G proteins and their regulatory proteins contribute to the pathology of renal and cardiovascular diseases. Our preliminary results, including electrophysiological experiments using isolated, split open ASDN, demonstrate that ENaC is regulated by EGF and Rac1, possibly through a convergent mechanism. Dahl salt-sensitive (SS) rats used in these studies develop severe hypertension on high-salt diet. We provide preliminary data indicating that ENaC contributes to the development of hypertension in the SS rat strain. Furthermore, our preliminary data reveal that EGF concentration is reduced in the SS rats, which we propose would enhance ENaC activity, sodium retention and hypertension. Building upon this preliminary data and our previously published findings, the specific objective of this proposal is to determine whether EGF acting through Rac1 is important for physiologic control of renal sodium handling through regulation of ENaC and define the precise mechanisms of EGF- and Rac1-mediated changes in ENaC activity. A combination of electrophysiological, immunohistochemical, biochemical, microscopy and chronic studies in vivo and in vitro will be used in this proposal to provide mechanistic insights on how ENaC is regulated by member of the EGF-family and Rac1 and how changes in this pathway contributes to salt induced hypertension in SS rats. These studies will address three Specific Aims: 1) To identify and quantify the role of EGF and related growth factors in the physiological regulation of ENaC activity in the ASDN and establish the role of this pathway in the development of salt-sensitive hypertension;2) To establish the physiological role of RhoGDI and Rac1 in regulation of ENaC and determine the role of Rac1 in mediating EGF effects on ENaC;and 3) To define the cellular and molecular mechanism by which Rac1 modulates ENaC activity: do WAVEs convey Rac1 regulation to ENaC?

Public Health Relevance

The control of blood pressure occurs via Na+ homeostasis in the kidney and involves the precise regulation of the Epithelial Na+ Channel (ENaC) in the aldosterone-sensitive distal nephron (ASDN). The current proposal will study how members of the epidermal growth factors family and small GTPase Rac1 modulate ENaC- mediated Na+ transport in the ASDN and participate in the development of salt-sensitive hypertension. This work has the potential to provide new insights into the control and function of this important ion channel and uncover mechanisms involved in diseases associated with fluid imbalance and hypertension.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
1R01HL108880-01A1
Application #
8245462
Study Section
Special Emphasis Panel (ZRG1-DKUS-A (04))
Program Officer
Maric-Bilkan, Christine
Project Start
2011-12-01
Project End
2016-11-30
Budget Start
2011-12-01
Budget End
2012-11-30
Support Year
1
Fiscal Year
2012
Total Cost
$382,500
Indirect Cost
$132,500
Name
Medical College of Wisconsin
Department
Physiology
Type
Schools of Medicine
DUNS #
937639060
City
Milwaukee
State
WI
Country
United States
Zip Code
53226
Hye Khan, Md Abdul; Pavlov, Tengis S; Christain, Sarah V et al. (2014) Epoxyeicosatrienoic acid analogue lowers blood pressure through vasodilation and sodium channel inhibition. Clin Sci (Lond) 127:463-74
Pavlov, Tengis S; Levchenko, Vladislav; Staruschenko, Alexander (2014) Role of Rho GDP dissociation inhibitor ? in control of epithelial sodium channel (ENaC)-mediated sodium reabsorption. J Biol Chem 289:28651-9
Endres, Bradley T; Priestley, Jessica R C; Palygin, Oleg et al. (2014) Mutation of Plekha7 attenuates salt-sensitive hypertension in the rat. Proc Natl Acad Sci U S A 111:12817-22
Ilatovskaya, Daria V; Palygin, Oleg; Chubinskiy-Nadezhdin, Vladislav et al. (2014) Angiotensin II has acute effects on TRPC6 channels in podocytes of freshly isolated glomeruli. Kidney Int 86:506-14
Staruschenko, Alexander (2014) To cleave or not to cleave: role of ADAM17 in cell proliferation in PKD. Am J Physiol Renal Physiol 307:F658-9
Staruschenko, Alexander; Safonova, Tatiana A (2014) PC and PKC: in vivo vs. in vitro. Am J Physiol Renal Physiol 306:F507-8
Mironova, Elena; Bugay, Vladislav; Pochynyuk, Oleh et al. (2013) Recording ion channels in isolated, split-opened tubules. Methods Mol Biol 998:341-53
Ilatovskaya, Daria V; Pavlov, Tengis S; Levchenko, Vladislav et al. (2013) ROS production as a common mechanism of ENaC regulation by EGF, insulin, and IGF-1. Am J Physiol Cell Physiol 304:C102-11
Hye Khan, Md Abdul; Neckar, Jan; Manthati, Vijay et al. (2013) Orally active epoxyeicosatrienoic acid analog attenuates kidney injury in hypertensive Dahl salt-sensitive rat. Hypertension 62:905-13
Ilatovskaya, Daria V; Palygin, Oleg; Levchenko, Vladislav et al. (2013) Pharmacological characterization of the P2 receptors profile in the podocytes of the freshly isolated rat glomeruli. Am J Physiol Cell Physiol 305:C1050-9

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