LAUSR

Podocytes are essential for the glomerular filtration barrier in the kidney. Podocyte injury can lead to chronic kidney disease (CKD). One of the leading causes of CKD is diabetes mellitus. Plasma urotensin II (UII) levels and renal tissue expression of UII and its receptor UT are increased in diabetic kidney disease. However, the role of the UII system in podocyte derangement is unexplored. In this study, we report for the first time that UT is expressed in mouse podocytes in culture and glomerular explants. UII increased intracellular Ca2+ levels ([Ca2+]i) in cultured podocytes bathed in zero Ca2+ solution, an effect abolished by ER Ca2+ ATPase inhibitor thapsigargin. Subsequent restoration of extracellular Ca2+ increased [Ca2+]i despite the blockade of voltage-gated Ca2+ channels, suggesting a store-operated Ca2+ entry (SOCE) mechanism activated by UII. UII precipitated ER injury in cultured podocytes, as indicated by an increase in ER stress marker GRP78. GSK1562590, a UT antagonist, reversed this effect. Next, we tested two putative SOCE pathways previously reported in podocytes, i.e., TRPC5 and TRPC6 ion channels. Activation of UT by UII significantly increased TRPC6 but not TRPC5 mRNA in cultured podocytes. Whole-cell patch-clamp recordings of cultured podocytes showed that UII stimulates cation currents, which SAR 7443, a selective TRPC6 blocker, attenuated. By contrast, UII-induced cation currents were not sensitive to AC 1903, a selective TRPC5 blocker. In line with patch-clamp experiments, Ca2+ imaging studies showed that TRPC6 blockade with SAR 7443 mitigated UII-induced increase in [Ca2+]i. Super-resolution microscopy of cultured podocytes revealed that activation of UT caused a significant increase in the fragmentation of actin filaments, as indicated by a decrease in the percentage of long filaments and an increase in short filaments. Together these findings suggest that: (1) UT is expressed in native and cultured podocytes. (2) UT activation in podocytes triggers ER Ca2+ release, activates SOCE pathways and leads to the development of ER stress. (3) TRPC6 is a probable SOCE pathway stimulated by UII in podocytes. (4) UII might cause podocyte injury by disrupting the actin cytoskeleton. Dr. Adebiyi: NIH R01 HL151735 and R01 DK127625; APS 2020 John F. Perkins, Jr. Research Career Enhancement Award. Dr. Kanthakumar: American Heart Association Postdoctoral Fellowship (830462). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.