Albuminuria enhances NHE3 and NCC via stimulation of mitochondrial oxidative stress/angiotensin II axis
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Zhanjun Jia1,2,*, Yibo Zhuang1,2,*, Caiyu Hu1,2, Xintong Zhang3, Guixia Ding1,2, Yue Zhang1,2, Rajeev Rohatgi4, Hu Hua1,2, Songming Huang1,2, John Ci-jiang He5, Aihua Zhang1,2
1Department of Nephrology, Nanjing Children’s Hospital, Affiliated with Nanjing Medical University, Nanjing, China
2Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China
3The First Clinical Medical College of Nanjing Medical University, Nanjing, China
4Department of Medicine, Mount Sinai School of Medicine, New York, New York, USA
5Division of Nephrology, Department of Medicine, Mount Sinai School of Medicine, New York, New York, USA
*These authors contributed equally to this work
Aihua Zhang, email: [email protected]
John Ci-jiang He, email: [email protected]
Keywords: albuminuria, NHE3, NCC, mitochondrial oxidative stress, angiotensin II
Received: October 30, 2015 Accepted: May 20, 2016 Published: June 13, 2016
Imbalance of salt and water is a frequent and challenging complication of kidney disease, whose pathogenic mechanisms remain elusive. Employing an albumin overload mouse model, we discovered that albuminuria enhanced the expression of NHE3 and NCC but not other transporters in murine kidney in line with the stimulation of angiotensinogen (AGT)/angiotensin converting enzyme (ACE)/angiotensin (Ang) II cascade. In primary cultures of renal tubular cells, albumin directly stimulated AGT/ACE/Ang II and upregulated NHE3 and NCC expression. Blocking Ang II production with an ACE inhibitor normalized the upregulation of NHE3 and NCC in cells. Interestingly, albumin overload significantly reduced mitochondrial superoxide dismutase (SOD2), and administration of a SOD2 mimic (MnTBAP) normalized the expression of NHE3, NCC, and the components of AGT/ACE pathway affected by albuminuria, indicating a key role of mitochondria-derived oxidative stress in modulating renin-angiotensin system (RAS) and renal sodium transporters. In addition, the functional data showing the reduced urinary excretion of Na and Cl and enhanced response to specific NCC inhibitor further supported the regulatory results of sodium transporters following albumin overload. More importantly, the upregulation of NHE3 and NCC and activation of ACE/Ang II signaling pathway were also observed in albuminuric patient kidneys, suggesting that our animal model accurately replicates the human condition. Taken together, these novel findings demonstrated that albuminuria is of importance in resetting renal salt handling via mitochondrial oxidative stress-initiated stimulation of ACE/Ang II cascade. This may also offer novel, effective therapeutic targets for dealing with salt and water imbalance in proteinuric renal diseases.
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