Abstract 217: Angiotensin II Stimulates Renin Synthesis and Secretion in Mouse Collecting Duct M-1 Cells via a PKCα-mediated cAMP Stimulation Mechanism
Angiotensin (Ang) II stimulates renin synthesis and secretion in collecting duct (CD) cells; via the Ang II type 1 receptor (AT1R), an effect that is in contrast to the well-known inhibition that it exerts on juxtaglomerular apparatus (JGA) renin. However, the intracellular signaling mechanisms involved in the Ang II-mediated stimulation of renin synthesis and secretion by the principal cells of the CD have not been elucidated. We recently demonstrated that Ang II increases renin synthesis via protein kinase C (PKC) in primary cultured rat IMCD cells. Additionally, we found that Ang II increases intracellular cAMP levels in IMCD cells, suggesting that in CD cells, PKA/CREB might be the downstream target of cAMP. In the present study, we used a mouse cortical CD cell line (M-1) to determine the role of the cAMP/PKA/CREB pathway in the stimulation of the Ang II-mediated renin synthesis and secretion by the principal cells, and to examine the role of PKC in the stimulation of cAMP levels in this mechanism. In M-1 cells, Ang II (10-7 M) treatment increased renin mRNA and protein levels. Renin content measured in the cell culture media was augmented in Ang II-treated cells by 6 hrs (Ang II: 31±4 vs. 19±4 ng Ang I/hr/ml; p<0.05). Ang II increased cAMP levels by 1 min (148±32 pmol/mg protein) and reached a peak at 30 min (290±27 vs. 44±0 pmol/mg protein; p<0.05). The adenlyate cyclase activator, forskolin (10-10M) and the analogue of cAMP, dibutyryl-cAMP (100 uM) both significantly increased renin transcript. Augmentation of renin mRNA by Ang II was prevented by PKA inhibition with H89 or PKI, and it was followed by increased pCREB levels. Importantly, PKC inhibition either with calphostin C (10-7M) or a PKCα dominant negative prevented the augmentation of intracellular levels of cAMP, pCREB and renin mRNA in M-1 cells treated with Ang II. We show here for the first time that in mouse collecting duct cells, Ang II stimulates renin synthesis and secretion via a PKCα-mediated cAMP stimulation mechanism. The sum of these findings suggests that in collecting duct cells, Ang II stimulates rather than inhibits renin, observations that contrast with the effect of PKC activity on JGA renin.
- © 2012 by American Heart Association, Inc.