Aliskiren reduces the release of soluble (pro)renin receptor from human umbilical vein endothelial cells

Abstract

(Pro)renin receptor [(P)RR] has been implicated in diverse biological processes through binding to its ligands, which include renin, prorenin, Wnt signaling molecules and subunits of vascular H⁺-ATPase. Recent studies have reported that (P)RR is implicated in pathophysiological conditions including retinopathy and pancreatic ductal adenocarcinoma, and the soluble form of this receptor [s(P)RR] is considered as a useful biomarker for diseases. The present study examined the effect of aliskiren, the first orally active direct renin inhibitor, on the protein levels of (P)RR using cultured human umbilical vein endothelial cells (HUVECs). The cells were treated with or without aliskiren (10 nM) at 37°C for different durations (0, 8, 16 and 24 h). Aliskiren-treated HUVECs exhibited reduced proliferation compared with those treated without the drug. Furthermore, aliskiren treatment decreased not only the level of exogenous prorenin that bound to the membranes of HUVECs, but also the renin activity derived from this binding activity. These results indicate that the quantity of full-length (P)RR was reduced by aliskiren treatment, and furthermore, that the level of s(P)RR released from HUVECs was decreased with the treatment. Recent study has reported that s(P)RR exerted antidiuretic function. The current study suggests that the levels of s(P)RR, as a potential antidiuretic molecule and prospective disease biomarker, may be decreased during anti-hypertensive treatments with aliskiren.

Keywords: aliskiren; human umbilical vein endothelial cells; prorenin; soluble (pro)renin receptor.

Figure 1.

Treatment protocol of human umbilical vein endothelial cells. Medium-1-3 were collected and used for determining the concentrations of soluble (pro)renin receptor, unbound prorenin and angiotensin I, respectively.

Figure 2.

Effect of aliskiren on the growth of HUVECs. HUVECs were cultured for different durations in the presence (filled squares) or absence (open circles) of aliskiren. Following each incubation time, the total number of cells per well was counted using a hemocytometer. Statistical differences were identified between aliskiren-treated cells and controls by a two-tailed unpaired Student's t-test with P<0.05 as the limit of significance. HUVEC, human umbilical vein endothelial cell.

Figure 3.

Effect of aliskiren on the cell-surface expression of full-length (P)RR. (A) Percentage of prorenin bound to the HUVEC membrane. The concentration of unbound prorenin in Medium-2 was determined by ELISA, and the bound prorenin was determined as described in the Materials and methods section. (B) Percentage of bound prorenin per HUVEC. The percentage of bound prorenin was divided by the cell number. (C) Renin activity per cell for aliskiren-treated cells and controls. The concentration of AngI in Medium-3 was determined by ELISA to calculate renin activity. Renin activity was divided by the cell number. Filled squares represent aliskiren-treated cells and open circles represent controls. Statistical differences were identified between aliskiren-treated cells and controls by a two-tailed unpaired Student's t-test with P<0.05 as the limit of significance. HUVEC, human umbilical vein endothelial cell; AngI, angiotensin I; (P)RR, (pro)renin receptor.

Figure 4.

Effect of aliskiren on the level of s(P)RR released from HUVECs. (A) Concentration of released s(P)RR. The concentration of s(P)RR in Medium-1 was determined by sandwich ELISA. (B) s(P)RR concentration per HUVEC cell. s(P)RR concentration was divided by the cell number. Filled squares represent aliskiren-treated cells and open circles represent controls. Statistical differences were identified between aliskiren-treated cells and controls by a two-tailed unpaired Student's t-test with P<0.05 as the limit of significance. s(P)RR, soluble (pro)renin receptor; HUVEC, human umbilical vein endothelial cell.