Albuminuria confers renal resistance to loop diuretics via the stimulation of NLRP3 inflammasome/prostaglandin signaling in thick ascending limb

// Yibo Zhuang 1, 2, * , Zhanjun Jia 1, 2, * , Caiyu Hu 1, 2 , Guixia Ding 1, 2 , Xintong Zhang 3 , Yue Zhang 1, 2 , Guangrui Yang 1, 2 , Rajeev Rohatgi 4 , Songming Huang 1, 2 , John Ci-Jiang He 5 and Aihua Zhang 1, 2 1 Department of Nephrology, Nanjing Children’s Hospital, Affiliated to Nanjing Medical University, Nanjing, China 2 Jiangsu Key Laboratory of Pediatrics, Nanjing Medical University, Nanjing, China 3 The First Clinical Medical College of Nanjing Medical University, Nanjing, China 4 Department of Medicine, Mount Sinai School of Medicine, New York, NY, USA 5 Division of Nephrology, Department of Medicine, Mount Sinai School of Medicine, New York, NY, USA * These authors have contributed equally to this work Correspondence to: Aihua Zhang, email: zhaihua@njmu.edu.cn John Ci-Jiang He, email: cijiang.he@mssm.edu Keywords: albuminuria, NLRP3 inflammasome, COX-2, mPGES-1, NKCC2 Received: January 06, 2016     Accepted: May 05, 2016     Published: June 23, 2016 ABSTRACT Renal resistance to loop diuretics is a frequent complication in a number of kidney disease patients with elusive mechanism. Employing human renal biopsy specimens, albumin overload mouse model, and primary cultures of mouse renal tubular cells, albuminuria effect on NKCC2 expression and function and the underlying mechanisms were investigated. In the renal biopsy specimens of albuminuric patients, we found that NKCC2 was significantly downregulated with a negative correlation with albuminuria severity as examined by immunohistochemistry. Meanwhile, NLRP3 and mPGES-1 were stimulated in NKCC2 positive tubules (thick ascending limb, TAL) paralleled with increased urinary PGE2 excretion. To examine the role of albuminuria in the downregulation of NKCC2 and the potential role of NLRP3/prostaglandin signaling in NKCC2 downregulation, an albumin overload mouse model was employed. Interestingly, we discovered that albuminuria downregulated NKCC2 protein expression in murine kidney and impaired the renal response to loop diuretic furosemide. Specifically, albuminuria suppressed NKCC2 expression and function through NLRP3/prostaglandin dependent signaling in TAL. In primary cultures of renal tubular cells, albumin directly reduced NKCC2 but enhanced NLRP3, COX-2, and mPGES-1 expression. These novel findings demonstrated that albuminuria is of importance in mediating the renal resistance to loop diuretics via NLRP3/prostaglandin signaling-dependent NKCC2 downregulation in TAL. This may also offer novel, effective targets for dealing with the resistance of loop diuretics in proteinuric renal diseases.