Inhibitory effect of NH4Cl treatment on renal Tgfß1 signaling following unilateral ureteral obstruction.

BACKGROUND/AIMS Consequences of obstructive nephropathy include tissue fibrosis, a major pathophysiological mechanism contributing to development of end-stage renal disease. Transforming growth factor β 1 (Tgfβ1) is involved in the progression of renal fibrosis. According to recent observations, ammonium chloride (NH4Cl) prevented phosphate-induced vascular remodeling, effects involving decrease of Tgfβ1 expression and inhibition of Tgfβ1-dependent signaling. The present study, thus, explored whether NH4Cl influences renal Tgfβ1-induced pro-fibrotic signaling in obstructive nephropathy induced by unilateral ureteral obstruction (UUO). METHODS UUO was induced for seven days in C57Bl6 mice with or without additional treatment with NH4Cl (0.28 M in drinking water). Transcript levels were determined by RT-PCR as well as protein abundance by Western blotting, blood pH was determined utilizing a blood gas and chemistry analyser. RESULTS UUO increased renal mRNA expression of Tgfb1, Tgfβ-activated kinase 1 (Tak1) protein abundance and Smad2 phosphorylation in the nuclear fraction of the obstructed kidney tissues, effects blunted in NH4Cl treated mice as compared to control treated mice. The mRNA levels of the transcription factors nuclear factor of activated T cells 5 (Nfat5) and SRY (sex determining region Y)-box 9 (Sox9) as well as of tumor necrosis factor α (Tnfα), interleukin 6 (Il6), plasminogen activator inhibitor 1 (Pai1) and Snai1 were up-regulated in the obstructed kidney tissues following UUO, effects again significantly ameliorated following NH4Cl treatment. Furthermore, the increased protein and mRNA expression of α-smooth muscle actin (α-Sma), fibronectin and collagen type I in the obstructed kidney tissues following UUO were significantly attenuated following NH4Cl treatment. CONCLUSION NH4Cl treatment ameliorates Tgfβ1-dependent pro-fibrotic signaling and renal tissue fibrosis markers following obstructive nephropathy.