Abstract 121: Hyperglycemia-induced Prorenin Receptor Abundance on Plasma Membrane of Kidney Collecting Duct Cells: is a Novel Mechanism to Explain Diabetic Nephropathy?

Activation of the renin-angiotensin system (RAS) leads to nephropathy during Diabetes Mellitus (DM). Prorenin levels are increased in the circulation of DM patients and predict microvascular damage. In streptozotocin (STZ)-induced type 1 DM rats, the collecting duct is the major source of prorenin in the kidney. The prorenin receptor (PRR), a new RAS component, elicits intracellular signals linked to fibrosis upon binding of prorenin at the cell plasma membrane (PM). We propose that PRR may contribute to the development of tubulointerstitial fibrosis by being locally activated by prorenin. To support this concept, we tested the hypothesis that hyperglycemia increases membrane bound PRR to collecting duct cells. To address this hypothesis, we used T1DM rats (N=10) induced with a single STZ injection (ip; 200ng/kg x 7 d) as well as mouse collecting duct M-1 cells, treated at different time intervals 0, 5 min, 1, 12, and 24 h with normal glucose (NG; 5mM glucose+20mM mannitol) and high glucose (HG; 25mM) to assess PRR trafficking alterations induced by glucose. After 7-days induction, STZ-rats showed plasma glucose as 428±13 vs.138±9 gr/dl and plasma insulin as 0.07±0.02 vs 2.42 ng/ml; compared to controls. By immunofluorescence (IF) in rat kidney sections, PRR was mainly localized on the apical aspect of collecting duct cells in STZ-rats, while in controls most of PRR signal was observed intracellularly. Although PRR mRNA levels did not differ in the collecting ducts between groups; its protein levels were augmented in STZ-rats. Importantly, compared with NG-treated cells, PRR protein levels (membrane bound) were significantly higher in PM extracts from M-1 cells treated with HG, and a maximum peak was observed at 1 h. Interestingly, in de-convoluted IF images of M-1 cells, PRR was localized mainly in the perinuclear areas during NG conditions; however, in HG-treated cells, PRR was found toward the cell surface. These data suggest that hyperglycemia induces PRR trafficking alterations of PRR. The present results suggest that hyperglycemia-induced PRR abundance on the PM in the collecting duct might be a novel mechanism underlying the development of diabetic nephropathy, particularly tissue fibrosis in DM. Grant support by the NIH-NIDDK (DK104375-01)