Polycystic kidney diseases (PKD) are a group of inherited nephropathies characterized by the formation of fluid-filled cysts along the nephron. Autosomal Recessive form of PKD (ARPKD) has an incidence of 1 in 20,000 live births; infants with this disease that survive beyond the perinatal period develop chronic renal failure by adolescence and eventually require kidney transplantation. This proposal focuses on the sodium transport regulation in the renal collecting ducts in ARPKD and potential means of pharmacological intervention with the cysts' progression. Specifically, we have determined that Epithelial Sodium Channels (ENaCs), which are expressed in the collecting ducts and represent the rate-limiting step of sodium reabsorption in this nephron segment, are involved into the process of cystogenesis in the ARPKD setting. Our preliminary data indicate that ENaC expression and activity are significantly lower in the cystic epithelial cells of a rat model of ARPKD, as assessed with immunohistochemistry and single channel analysis in isolated cysts; furthermore, chronic administration of the ENaC-specific inhibitor, benzamil, aggravated cyst formation. Thus, we propose that ENaC inhibition exacerbates PKD progression. Using a novel enzymatic microbiosensors approach we established that concentration of adenosine triphosphate (ATP) was significantly higher in PCK rat cortical cysts compared to control rats. ATP was shown to inhibit ENaC via signaling cascades initiated by binding to its receptors. Therefore, we hypothesize here that accumulation of excessive levels of ATP in the lumen of the dilated collecting ducts affects specific purinergic receptors in the cystic cells (primary candidates being P2Y2 or P2X7) and results in ENaC inhibition; this suppresses normal sodium reabsorption in these collecting ducts, and thus promotes fluid accumulation and cysts' expansion. The integrative experimental approach used in this study will include single nephron electrophysiology, in vivo animal studies, genetics, biochemistry, biosensors amperometry and confocal microscopy and will address the clinically relevant problem of cyst expansion in ARPKD. Specifically, this proposal will identify the involvement of the ATP- triggered signaling into regulation of sodium reabsorption in this setting. This proposal will address the following specific aims: 1. Determine the relationship between ENaC activity and cystogenesis in ARPKD; 2. Elucidate the cellular and molecular mechanism by which excessive levels of ATP modulate sodium transport, promoting cyst growth; and 3. Explore if P2 receptor agonists/antagonists and suppression of the ATP levels can affect cystogenesis.

Public Health Relevance

Autosomal recessive form of the polycystic kidney disease (ARPKD) is a genetic disorder that has an incidence of 1 in 20,000 live births; infants affected with this disorder, if survive beyond the perinatal period, develop chronic renal failure by adolescence and eventually require kidney transplantation. The project is focused on the role of renal sodium reabsorption in the mechanism of this disease development. Anticipated results will provide novel therapeutic targets potentially useful for the treatment of the disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Transition Award (R00)
Project #
4R00DK105160-03
Application #
9606769
Study Section
Special Emphasis Panel (NSS)
Program Officer
Maric-Bilkan, Christine
Project Start
2018-02-15
Project End
2021-01-31
Budget Start
2018-02-15
Budget End
2019-01-31
Support Year
3
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Medical University of South Carolina
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
183710748
City
Charleston
State
SC
Country
United States
Zip Code
29403
Shuyskiy, L S; Levchenko, V V; Negulyaev, Y A et al. (2018) Role of the Scaffold Protein MIM in the Actin-Dependent Regulation of Epithelial Sodium Channels (ENaC). Acta Naturae 10:97-103
Palygin, Oleg; Ilatovskaya, Daria V; Levchenko, Vladislav et al. (2018) Characterization of purinergic receptor expression in ARPKD cystic epithelia. Purinergic Signal 14:485-497
Ilatovskaya, Daria V; Blass, Gregory; Palygin, Oleg et al. (2018) A NOX4/TRPC6 Pathway in Podocyte Calcium Regulation and Renal Damage in Diabetic Kidney Disease. J Am Soc Nephrol 29:1917-1927
Pavlov, Tengis S; Levchenko, Vladislav; Ilatovskaya, Daria V et al. (2016) Renal sodium transport in renin-deficient Dahl salt-sensitive rats. J Renin Angiotensin Aldosterone Syst 17: