(Pro)renin Receptor-Dependent Induction of Profibrotic Factors Is Mediated by COX-2/EP4/NOX-4/Smad Pathway in Collecting Duct Cells

Abstract

The binding of prorenin to the (pro)renin receptor (PRR) triggers the activation of MAPK/ERK1/2 pathway, induction of cyclooxygenase-2 (COX-2), NOX-4-dependent production of reactive oxygen species (ROS), and the induction of transforming growth factor β (TGF-β) and profibrotic factors connecting tissue growth factor (CTGF) and plasminogen activator inhibitor (PAI-I) in collecting duct (CD) cells. However, the role of COX-2 and the intracellular pathways involved are not clear. We hypothesized that the PRR activation increases profibrotic factors through COX-2-mediated PGE2 activation of E prostanoid receptor 4 (EP4), upregulation of NOX-4/ROS production, and activation of Smad pathway in mouse CD cells. Recombinant prorenin increased ROS production and protein levels of CTGF, PAI-I, and TGF-β in M-1 CD cell line. Inhibition of MAPK, NOX-4, and COX-2 prevented this effect. Inhibition of MEK, COX-2, and EP4 also prevented the upregulation of NOX-4. Because TGF-β activates Smad pathway, we evaluate the phosphorylation of Smad2 and 3. COX-2 inhibition or EP4 antagonism significantly prevented phosphorylation of Smad 2/3. Mice that were infused with recombinant prorenin showed an induction in the expression of CTGF, PAI-I, TGF-β, fibronectin, and collagen I in isolated collecting ducts as well as the expression of alpha smooth muscle actin (α-SMA) in renal tissues. COX-2 inhibition prevented this induction. These results indicate that the induction of TGF-β, CTGF, PAI-I, and ROS occurs through PRR-dependent activation of MAPK and NOX-4; however, this mechanism depends on COX-2-derived PGE2 production and the activation of EP4 and Smad pathway.

High glucose induces trafficking of prorenin receptor and stimulates profibrotic factors in the collecting duct

“…Increased PRR abundance in the CD might be twice harmful. On one side, it results in increases in renin activity and intratubular Ang II formation 9 , 28 , 29 , if renal AGT and ACE activity, are present. On the other side, it triggers intracellular signals that upregulate pro-fibrotic factors 12 , 48 , 52 .…”

“…The M-1 cell line derived from the CD of mice 28 , was purchased from American Type Culture Collection (ATCC, Manassas, VA). M-1 cells are composed by principal and intercalated cells, this cell model has been validated previously 29 – 31 . Prior to the experiments, M-1 cells were maintained in Dulbecco′s modified Eagle’s medium (DMEM)/F-12 medium (LIFE TECHNOLOGIES, Carlsbad, CA) containing 10% fetal bovine serum (FBS), growth factors (transferrin, insulin, and sodium selenite at physiological concentrations), 100 nmol/L dexamethasone and 5 mM glucose.…”

The interaction partners of (pro)renin receptor in the distal nephron

“…A similar effect was observed in the 2‐kidney, 1‐clip (2K1C) renal ischemia rats, where PRR shRNA treatment significantly attenuated the COX‐2 expression in kidney but the Ang II levels in the renal interstitial fluid were unaffected 38 . In addition, PGE 2 augments prorenin/renin protein expression in cultured M‐1 CD cells, subsequently activates PRR to stimulate the COX‐2 expression and further PGE 2 synthesis, 39 then increases the expression of plasminogen activator inhibitor (PAI‐1) and connecting tissue growth factor (CTGF) via EP 4 receptor and TGF‐β receptor‐dependent Smad pathway 16 …”

“…38 In addition, PGE 2 augments prorenin/renin protein expression in cultured M-1 CD cells, subsequently activates PRR to stimulate the COX-2 expression and further PGE 2 synthesis, 39 then increases the expression of plasminogen activator inhibitor (PAI-1) and connecting tissue growth factor (CTGF) via EP 4 receptor and TGF-β receptor-dependent Smad pathway. 16 The binding of prorenin to PRR not only induces the non-proteolytic activation of prorenin to increase its enzymatic activity, but also triggers the activation of ERK1/2 5 . As discussed above, enhanced ERK1/2 activity but not the increased enzymatic activity of prorenin/renin contributes to the upregulation of COX-2 expression in MD and/or renal medulla.…”

“…13,14 Strong evidence has demonstrated a crucial role of PRR-mediated intrarenal RAS in hypertension, cardiovascular disease, and kidney diseases. 5,6 PRR also serves a multitude of functions via multiple signal transduction pathways including Wnt/β-catenin signaling, 10,15 cyclooxygenase-2 (COX-2)/prostaglandin E 2 (PGE 2 )/prostaglandin E 2 type 4 (EP 4 ) receptor signaling, [16][17][18] and NADPH oxidase 4 (NOX4)/H 2 O 2 signaling, 19 as well as works as a component of the V-ATPase 13,20 independently of angiotensin II (Ang II). Interestingly, emerging evidence suggests that PRR and Wnt/βcatenin signaling, 10,15 or COX-2/PGE 2 signaling, 18,21,22 or apelinergic system, 23 regulate the expression/activity of each other in the renal medulla.…”