Neuraminidase1 Activity Contributes to Vasopressin Receptor-mediated Augmentation of Water and Electrolyte Retention by the Kidney in Eln Haploinsufficient Mice

Elastin haploinsufficiency is a primary determinant of arteriopathy and hypertension that hallmark Williams syndrome (WS), a rare genetic disorder resulting from microdeletion of genes on human chromosome 7, including the elastin gene (ELN). Accumulating evidence suggests renal dysfunction, including enhanced sodium and water retention as an underlying cause of blood pressure elevation resulting from heterozygous deletion of Eln (Eln+/-) in mice that recapitulates the cardiovascular phenotype of WS. However, the underlying pathophysiological mechanisms are poorly understood. Here, we determined whether the activity of neuraminidase-1 (NEU1) of the elastin receptor complex (ERC) contributes to abnormal handling of water and electrolytes by the kidney in Eln haploinsufficiency. Adult male and female Eln+/+ and Eln+/- mice were subjected to acute extracellular fluid volume expansion with normal saline, combined with pharmacological intervention targeting vasopressin V2 receptor (V2R), NEU1, ENaC, and NKCC2. In male Eln+/+ mice, V2R blockade induced a dose-dependent increase in urine flow rate without affecting sodium excretion. Conversely, V2R stimulation with desmopressin markedly increased urinary sodium excretion in male Eln+/+ but not Eln+/- mice, while both sexes of Eln+/- mice exhibited marked suppression of urine flow rate. Abrogation of ERC signaling through NEU1 inhibition produced a modest increase in urinary sodium excretion in male mice of both genotypes but augmented urine flow rate only in male Eln+/+mice. NEU1 blockade strikingly enhanced the natriuretic effect of furosemide and amiloride in male Eln+/+ and modestly in Eln+/-mice. Taken together, we conclude that Eln haploinsufficiency disrupts vasopressin-dependent modulation of sodium and water reabsorption by sex-dependently altering ERC-mediated modulation of NKCC2 and ENaC. These findings reveal a novel mechanism by which abnormal ERC activity due to Eln haploinsufficiency potentially contributes to renal dysfunction and hypertension. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/731713v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@1870e8org.highwire.dtl.DTLVardef@9cbd8dorg.highwire.dtl.DTLVardef@60b2deorg.highwire.dtl.DTLVardef@7f31f1_HPS_FORMAT_FIGEXP M_FIG C_FIG AC, adenylyl cyclase; AQP2, aquaporin 2; CD, collecting duct; CNT, connecting tubule; DCT, distal convoluted tubule; EBP, elastin binding protein; Eln, elastin allele; ENaC, epithelial sodium channel; ERC, elastin receptor complex; Gs, stimulatory G subunit; NEU1, neuroaminidase1; NKCC2, sodium-potassium-chloride cotransporter; PPCA, protective protein/ cathepsin A; TAL, loop of Henle thick ascending limb; V2R, vasopressin receptor type 2