Kidney Week

Abstract: PO1512

Ca²⁺-Permeable TRPV4 Channel Modulates Cystogenesis in ARPKD PCK453 Rats

Session Information

• Cystic Kidney Diseases: Mechanisms, Genetics, and Treatment
  October 22, 2020 | Location: On-Demand
  Abstract Time: 10:00 AM - 12:00 PM

Category: Genetic Diseases of the Kidneys

• 1001 Genetic Diseases of the Kidneys: Cystic

Authors

• Tomilin, Victor N., University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Victor N. Tomilin,

• Hassanzadeh Khayyat, Naghmeh, University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Naghmeh Hassanzadeh Khayyat,

• Zaika, Oleg L., University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Oleg L. Zaika,

• Pochynyuk, Oleh, University of Texas John P and Katherine G McGovern Medical School, Houston, Texas, United States

Oleh Pochynyuk,

Background

PKD is a cohort of monogenic disorders that result in the development of renal cysts filled with fluid. Deficient flow-mediated [Ca²⁺]_i responses have been linked to the development of PKD. We showed that mechanosensitive TRPV4 channel is preferentially expressed in the distal nephron where its activity is imperative for flow-dependent [Ca²⁺]_i elevations. We also found that TRPV4 activity was dramatically decreased in primary cells cultured from ADPKD patients thus contributing to their impaired [Ca²⁺]_i dynamics.

Methods

We tested how manipulation of TRPV4 activity with pharmacological or dietary means affects cystogenesis in PCK453 rats, a model of ARPKD using a combination of metabolic studies, biochemistry, and [Ca²⁺]_i imaging in freshly isolated cyst monolayers.

Results

Treatment with TRPV4 activator, GSK1016790A for 1 and 2 months attenuated ARPKD progression manifested as a significant decrease in kidney to total body weight ratio, reduced cyst numbers and area when compared to the control. TRPV4 blocker, GSK2193874 exacerbated ARPKD progression leading to a larger kidney volume and more pronounced cystogenesis. We showed that high K⁺ intake increased renal TRPV4 expression and activity. Consistently, high K⁺ diet (10% KCl) had similar to GSK1016790A beneficial actions on ARPKD progression. GSK2193874 reversed these effects suggesting their TRPV4-dependent nature. Unexpectedly, high K⁺ high alkali diet (10% K Bicarbonate/Citrate) dramatically accelerated cystogenesis despite augmented renal TRPV4 expression. TRPV4 activity (estimated as a GSK1016790A-dependent rise in [Ca²⁺]_i in freshly isolated cyst monolayers from PCK453 rat kidneys) was approximately 2 fold larger in cyst cells from high K⁺ diet treated compared to control. Basal [Ca²⁺]_i and flow-induced [Ca²⁺]_i levels were also larger on this condition. In contrast, TRPV4 activity was more than 2 fold lower in rats on high K⁺ high alkali diet.

Conclusion

We show a positive correlation between TRPV4 functional status and the time course of ARPKD progression in PCK 453 rats. Chronic alkali load renders TRPV4 to an inactive state, which contributes to exacerbated cystogenesis in PCK453 rats. We also posit that stimulation of TRPV4 with GSK1016790A or high K⁺ but not high K⁺ high alkali diet will be instrumental to attenuate the rate of PKD progression in clinic.

Funding

• Other NIH Support