Abstract 130: Down Regulation of Gamma-Adducin Diminishes Glomerular Function and Promotes Hypertension Related Chronic Kidney Disease

Abstract

Fawn Hooded Hypertensive (FHH) rats are a genetic model of hypertension-induced chronic kidney disease (CKD) in association with podocyte dysfunction. We previously identified an inactivating mutation of γ-Adducin (ADD3) is associated with the development of proteinuria in FHH rats and that knockdown of ADD3 disrupts actin cytoskeleton structure in the vascular smooth muscle cells. However, whether loss of ADD3 function also alters podocyte function in FHH rats has not been studied. The present study examined whether loss of ADD3 function in FHH also alters the actin cytoskeleton and podocyte function and contribute to the development of CKD. Knockdown of Add3 in the conditionally immortalized mouse podocytes using Add3 DsiRNA disrupted the actin cytoskeleton and increased F/G actin ratio using immunostaining and Western blots. Mean arterial pressure was similar, but proteinuria increased to a lesser extent in the DOCA/salt hypertensive FHH.Add3 transgenic (259 ± 5 mg/day, n=12) than FHH (484 ± 78 mg/day, n=21) rats. The convective permeability of isolated glomeruli to albumin (Palb) was lower in FHH.Add3 (0.13 ± 0.01, n=6, 157) than FHH (0.24 ± 0.02, n=4, 173) rats as assessed by a fluorescence dilution technique. Moreover, Palb increased to greater extent in FHH (0.36 ± 0.03, n=5, 140) than in FHH.Add3 (0.21 ± 0.03, n=3, 75) rats after DOCA/salt hypertension. Hypertensive FHH.Add3 rats exhibited less podocyte foot process effacement than FHH rats. The glomerular injury score averaged 2.50 ± 0.03 (n=9, 270) in DOCA/salt hypertensive FHH.Add3 versus 3.31 ± 0.01 (n=9, 270) in FHH rats. The percentage of fibrosis in the renal cortex was significantly lower in hypertensive FHH.Add3 than age-matched FHH rats. These results indicate that loss of ADD3 function contributes to the development of proteinuria and CKD in FHH rats by altering the actin cytoskeleton in podocytes, leading to podocyte effacement and glomerular barrier dysfunction.