Phenylbutyrate Derived Nitric Oxide Donor attenuates by renal fibrosis through extracellular matrix degradation pathway

Chronic kidney disease (CKD) is a major global health burden for which no curative therapy has been established. Decreased bioavailability of nitric oxide (NO) has been implicated in the pathogenesis and progression of CKD. In this study, we investigated the therapeutic potential of NPB, a novel NO donor independently synthesized by our group, in experimental CKD. In an adenine-induced CKD mouse model, NPB administration suppressed serum creatinine and blood urea nitrogen (BUN) to control levels, and Masson's trichrome staining revealed marked attenuation of renal fibrosis. In cultured renal fibroblasts, NPB significantly inhibited transforming growth factor-β1 (TGF-β1)-induced expression of fibronectin and α-smooth muscle actin (α-SMA). Importantly, OH-PB, a non-NO-donating derivative of NPB, showed no beneficial effects in either the in vivo or in vitro . Notably, NPB significantly reduced fibronectin expression even after fibrosis had been induced by TGF-β1 stimulation, an effect not reproduced by TGF-β receptor antagonists. Mechanistically, NPB had little effect on Smad2/3 phosphorylation, the central signaling cascade downstream of TGF-β. Instead, the anti-fibrotic effect of NPB on established fibronectin expression was partially attenuated by the matrix metalloproteinase (MMP) inhibitor doxycycline. Therefore, NPB is a promising therapeutic candidate for CKD that may act by promoting clearance of accumulated extracellular matrix.