Acute effects of angiotensin II on TRPC6 channels in the podocytes of the freshly isolated glomeruli

Abstract

There has been proposed a key role of the podocytes in the pathogenesis of nephrotic diseases since the injury of these cells leads to heavy proteinuria. It was also shown that angiotensin II (Ang II) caused release of intracellular Ca2+ in podocytes; members of the TRPC‐family channels emerged as prime candidates for this effect. Mutations in the gene encoding the TRPC6 channel result in development of focal segmental glomerulosclerosis. Here, we examined the effects of Ang II (0.1 to 10 μM) on Ca2+ levels in intact podocytes of freshly isolated Sprague Dawley rat glomeruli. Changes in intracellular Ca2+ stimulated by Ang II in the presence or absence of thapsigargin or TRPC inhibitor 2‐APB were measured in podocytes of the glomeruli loaded with Fura‐2AM. Depletion of internal Ca2+ stores did not affect the calcium flux activated by Ang II, whereas 2‐APB completely blocked it. Patch‐clamp analysis demonstrated that 100 nM Ang II acutely activates native TRPC‐like channels in the podocytes of freshly isolated glomeruli as well as TRPC6 channels transiently overexpressed in CHO cells, and this effect is mediated by changes in the channel open probability. Thus, we provide direct evidence of Ang II‐dependent activation of TRPC6 channels in podocytes, which might play a significant role in the development of kidney diseases. This research was supported by the NIH (HL108880) and Zeiss‐OPTEC LLC grant’2012.