Increased renal oxidative stress in salt-sensitive human GRK4γ486V transgenic mice

Abstract

We tested the hypothesis that salt-sensitive hypertension is caused by renal oxidative stress by measuring the blood pressure and reactive oxygen species-related proteins in the kidneys of human G protein-coupled receptor kinase 4γ (hGRK4γ) 486V transgenic mice and non-transgenic (Non-T) littermates on normal and high salt diets. High salt diet increased the blood pressure, associated with impaired sodium excretion, in hGRK4γ486V mice. Renal expressions of NOX isoforms were similar in both strains on normal salt diet but NOX2 was decreased by high salt diet to a greater extent in Non-T than hGRK4γ486V mice. Renal HO-2, but not HO-1, protein was greater in hGRK4γ486V than Non-T mice on normal salt diet and normalized by high salt diet. On normal salt diet, renal CuZnSOD and ECSOD proteins were similar but renal MnSOD was lower in hGRK4γ486V than Non-T mice and remained low on high salt diet. High salt diet decreased renal CuZnSOD in hGRK4γ486V but not Non-T mice and decreased renal ECSOD to a greater extent in hGRK4γ486V than Non-T mice. Renal SOD activity, superoxide production, and NOS3 protein were similar in two strains on normal salt diet. However, high salt diet decreased SOD activity and NOS3 protein and increased superoxide production in hGRK4γ486V mice but not in Non-T mice. High salt diet also increased urinary 8-isoprostane and 8-hydroxydeoxyguanosine to a greater extent in hGRK4γ486V than Non-T mice. hGRK4γwild-type mice were normotensive and hGRK4γ142V mice were hypertensive but both were salt-resistant and in normal redox balance. Chronic tempol treatment partially prevented the salt-sensitivity of hGRK4γ486V mice. Thus, hGRK4γ486V causes salt-sensitive hypertension due, in part, to defective renal antioxidant mechanisms.

Sorting nexin 1 loss results in increased oxidative stress and hypertension

“…The primary antibodies were purchased from GeneTex (D 5 R), Origene (D 1 R), Abcam (3‐nitrotyrosine), Santa Cruz Biotechnology (AT 1 R, D 2 R, SNX2, SNX6, clathrin, HO‐1, NOX1, NOX2, p67 phox ), ProteinTech (SNX1, SNX5), Abbiotec (β‐arrestin), BD Biosciences (IR‐β), Chemicon (LEPR), Millipore (NKA, p47 phox , GAPDH), Bioworld (p22 phox , α 1A ‐AR), and Stressgen Biotechnologies (HO‐2, SOD1, SOD2, SOD3). Some antibodies used are proprietary and previously characterized (D 1 R, D 3 R, D 4 R, ETBR, NOX4) 18‐21 . The antibodies against NHE3, thiazide‐sensitive NaCl cotransporter (NCC), and NKCC2 were gifts from Dr Mark A. Knepper (Laboratory of Kidney and Electrolyte Metabolism, National Heart, Lung, and Blood Institute, National Institutes of Health).…”

Gastrorenal Axis

“…By contrast, overexpression of human GRK4 γ 142V in mice causes salt-resistant hypertension (85, 86) while overexpression of GRK4 γ 486V in mice causes salt-sensitive hypertension (88, 90). Increased expression of AT 1 R in GRK4 γ 142V (86) and GRK4 γ 486V (90) and production of reactive oxygen species in GRK4 γ 486V (90) but not in GRK4 γ 142V (89) contribute to the different blood pressure phenotype. GRK4 γ 142V also interacts with AT 1 R to increase vascular reactivity (87).…”

“…Only a few gene variants thought to be causal of hypertension in humans have been shown to produce hypertension in mice, e.g., AGT that encodes angiotensinogen (81), AGTR1 that encodes the AT 1 R (82), CYP11B2 that encodes aldosterone synthase (83), UMOD (84) that encodes uromodulin, and GRK4 (85-90). These genes fulfill the criteria for ascribing a gene as causal of a complex disorder, such as hypertension (91, 92).…”

“…The overexpression of human GRK4γ gene variants (A>65L, A>142V, and A>486V) in mice causes hypertension, although salt sensitivity depends on which is GRK4γ variant is present (85-90). Overexpression of human GRK4 γ wild-type in mice results in normal blood pressure and salt resistance (88).…”

Primary Pediatric Hypertension: Current Understanding and Emerging Concepts

“…Only the variants of genes of AGT that encodes angiotensinogen [118], AGTR1 that encodes the angiotensin II (Ang II) type 1 receptor (AT 1 R) [119], CYP11B2 that encodes aldosterone synthase [120], and GRK4 have been shown to cause hypertension in transgenic mice [121, 122]. Variants of ATP2B1, STK39 [123], GRK4, and SLC4A5 [124, 125] have been associated with salt sensitivity; GRK4γ486V causes salt-sensitive hypertension in transgenic mice [126]. …”