Integrated compensatory network is activated in the absence of NCC phosphorylation
P. Richard Grimm, … , James B. Wade, Paul A. Welling
P. Richard Grimm, … , James B. Wade, Paul A. Welling
Published May 1, 2015; First published April 20, 2015
Citation Information: J Clin Invest. 2015;125(5):2136-2150. https://doi.org/10.1172/JCI78558.
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Research Article Nephrology

Integrated compensatory network is activated in the absence of NCC phosphorylation

Abstract

Thiazide diuretics are used to treat hypertension; however, compensatory processes in the kidney can limit antihypertensive responses to this class of drugs. Here, we evaluated compensatory pathways in SPAK kinase–deficient mice, which are unable to activate the thiazide-sensitive sodium chloride cotransporter NCC (encoded by Slc12a3). Global transcriptional profiling, combined with biochemical, cell biological, and physiological phenotyping, identified the gene expression signature of the response and revealed how it establishes an adaptive physiology. Salt reabsorption pathways were created by the coordinate induction of a multigene transport system, involving solute carriers (encoded by Slc26a4, Slc4a8, and Slc4a9), carbonic anhydrase isoforms, and V-type H+-ATPase subunits in pendrin-positive intercalated cells (PP-ICs) and ENaC subunits in principal cells (PCs). A distal nephron remodeling process and induction of jagged 1/NOTCH signaling, which expands the cortical connecting tubule with PCs and replaces acid-secreting α-ICs with PP-ICs, were partly responsible for the compensation. Salt reabsorption was also activated by induction of an α-ketoglutarate (α-KG) paracrine signaling system. Coordinate regulation of a multigene α-KG synthesis and transport pathway resulted in α-KG secretion into pro-urine, as the α-KG–activated GPCR (Oxgr1) increased on the PP-IC apical surface, allowing paracrine delivery of α-KG to stimulate salt transport. Identification of the integrated compensatory NaCl reabsorption mechanisms provides insight into thiazide diuretic efficacy.

Authors

P. Richard Grimm, Yoskaly Lazo-Fernandez, Eric Delpire, Susan M. Wall, Susan G. Dorsey, Edward J. Weinman, Richard Coleman, James B. Wade, Paul A. Welling

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Figure 5

Cellular remodeling process replaces α-ICs with PP-ICs and expands CNT with PCs in SPAK KO mice.

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Cellular remodeling process replaces α-ICs with PP-ICs and expands CNT w...
(A) Immunolocalization of PP-ICs (pendrin, red) in the kidney cortex of WT and SPAK KO mice. Scale bars: 100 μm. (B) Relative number of IC subtypes (β- and non-α/non-β ICs [PP-ICs] and α-ICs [AE1+]) in the late DCT (DCT2), CNT, and CCD. For these studies, calbindin and AQP2 were used to identify nephron segments (calbindin alone = DCT2; calbindin plus AQP2 = CNT; AQP2 alone = CCD). Data represent the mean ± SEM. n = 4 animals per group. *P < 0.05 by 2-tailed t test for WT versus KO. (C) Quantitative summary of CNT cell subtype counts (numbers of PCs, α-ICs, and PP-ICs per unit area are plotted in the stacked diagram). (D) Morphometric length measurements of DCT1, DCT2, CNT, and CCD in WT and SPAK KO mice. Data represent the mean ± SEM. n = 5 animals per genotype. *P < 0.05 by 2-tailed t test for WT versus KO. (DCT, identified by the presence of parvalbumin and NCC; DCT2, identified as calbindin- and NCC-positive tubules; CNT, identified as calbindin- and AQP2-positive tubules; and CCD, identified as calbindin-negative, AQP2-positive tubules).