Amiloride off-target effect inhibits podocyte urokinase receptor expression and reduces proteinuria.
The urokinase receptor (uPAR) and its soluble form play a key role in the pathogenesis of focal segmental glomerulosclerosis (FSGS). The modification of uPAR pathological actions on podocytes will become an important task for the development of improved nephroprotective therapeutics. Here we show that podocyte uPAR expression can be reduced using amiloride. Amiloride has a significant role in the reduction of podocyte cell motility in vitro and proteinuria in mice. Amiloride inhibited the induction of uPAR protein and PLAUR messenger RNA (encoding uPAR) and with that it reduced uPAR-mediated β3 integrin activation in lipopolysaccharide (LPS)-treated podocytes. Transwell migration assay and wound healing assay showed that directed and random podocyte motility of LPS-treated podocytes were increased and substantially reduced by amiloride. The off-target effect of amiloride was independent of its function as epithelial sodium channel blocker and different from triamterene. Amiloride was also effective in the LPS mouse model of transient proteinuria (LPS mice) and in the 5/6 nephrectomy rat FSGS model (NTX) by significantly inhibiting podocyte uPAR induction, reducing proteinuria. In addition, amiloride attenuated glomerulosclerosis, as determined by glomerulosclerotic index. Thus, our observations show that amiloride inhibits podocyte uPAR induction and reduces proteinuria in NTX rats and LPS mice. Given the pathological relevance of the uPAR-β3 integrin signaling axis in FSGS, amiloride may be utilized in patients with FSGS.