Mechanisms for hypercalciuria in pseudohypoaldosteronism type II-causing WNK4 knock-in mice.
The mechanisms underlying hypercalciuria in pseudohypoaldosteronism type II (PHAII) caused by WNK4 mutations remain unclear. In this study, we used Wnk4(D561A/+) knock-in mice as a model of human PHAII for investigating the pathogenesis of hypercalciuria in PHAII. Serum and urine biochemistries were obtained from Wnk4(+/+) and Wnk4(D561A/+) littermates. Expression of the epithelial Ca(2+) channels [transient receptor potential channel vanilloid subtype 5 (TRPV5) and TRPV6] and calbindin-D28k (CBP-D28k) in the distal nephron and two upstream Na(+) transporters, Na(+)/H(+) exchanger 3 and Na(+)-K(+)-2Cl(-) cotransporter 2 involved in paracellular Ca(2+) reabsorption, were examined by real-time PCR, immunofluorescent staining, and immunoblotting. Compared with Wnk4(+/+) littermate controls, Wnk4(D561A/+) mice manifested hypercalciuria despite no significant differences in serum creatinine, ionized Ca(2+), PTH, and 1,25 hydroxylvitamin D(3) levels. There was no significant difference in TRPV5 expression, but a significant increase in TRPV6 and CBP-D28k was observed in Wnk4(D561A/+) mice. Despite no significant change in Na(+)/H(+) exchanger 3 expression, Na(+)-K(+)-2Cl(-) cotransporter 2 expression was significantly attenuated and urine Ca(2+) excretion rate in response to furosemide was blunted in Wnk4(D561A/+) mice. Decreased Ca(2+) reabsorption in the upstream nephron, especially in the thick ascending loops of Henle, with a secondary adaptive increase in TRPV6 and CBP-D28k expression in the distal tubules might be involved in the hypercalciuria of PHAII.
Yang
Sung-Sen
SS
Division of Nephrology, Department of Medicine, Tri-Service General Hospital, and School of Medicine, National Defense Medical Center, Neihu 114, Taipei, Taiwan.
Hsu
Yu-Juei
YJ
Chiga
Motoko
M
Rai
Tatemitsu
T
Sasaki
Sei
S
Uchida
Shinichi
S
Lin
Shih-Hua
SH
D000818:Animals; D015153:Blotting, Western; D064092:Calbindin 1; D064026:Calbindins; D002112:Calcifediol / Q000097:blood; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism; D003404:Creatinine / Q000097:blood; D005455:Fluorescent Antibody Technique; D053565:Hypercalciuria / Q000209:etiology* / Q000235:genetics / Q000378:metabolism; D017136:Ion Transport / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D009399:Nephrons / Q000378:metabolism*; D010281:Parathyroid Hormone / Q000097:blood; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011546:Pseudohypoaldosteronism / Q000150:complications* / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064030:S100 Calcium Binding Protein G / Q000235:genetics / Q000378:metabolism; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism; D064466:Solute Carrier Family 12, Member 1; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism
C576498:CALB1 protein, human; C576499:Calb1 protein, mouse; D064092:Calbindin 1; D064026:Calbindins; D015220:Calcium Channels; D010281:Parathyroid Hormone; D064030:S100 Calcium Binding Protein G; C578714:SLC12A1 protein, human; C578715:Slc12a1 protein, mouse; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D050916:TRPV Cation Channels; C492240:Trpv5 protein, mouse; C446923:Trpv6 protein, mouse; D003404:Creatinine; C499024:Prkwnk4 protein, mouse; D017346:Protein Serine-Threonine Kinases; D002112:Calcifediol