NARI-29: A Novel Epalrestat Derivative Attenuates Pulmonary Fibrosis by Modulating the TGF-β/Smad Signaling

Pulmonary fibrosis is a chronic and debilitating lung disease marked by excessive collagen and extracellular matrix accumulation, leading to lung scarring and impaired lung function. Though pirfenidone and nintedanib are approved drugs, their efficacy is suboptimal. The current study aims to examine the antifibrotic activity of a novel epalrestat (aldose reductase) analog (NARI-29) using <i>in vitro</i> and <i>in vivo</i> rat models. The TGF-β-induced differentiation model utilized LL29/DHLF cells, while the bleomycin (BLCN)-induced pulmonary fibrosis (intratracheal route) model in rats was employed to evaluate the antifibrotic effects of NARI-29 using various molecular biology, histopathology, and lung function techniques. In the <i>in vitro</i> model, results from RT-qPCR and immunocytochemistry analysis demonstrated that NARI-29 treatment (2.5, 5, and 10 μM) significantly attenuated the expression of fibrotic markers induced by TGF-β. In the <i>in vivo</i> model, NARI-29 treatment (3.75, 7.5, and 15 mg/kg) significantly improved body weight and survival rates compared to the BLCN induction group. Gene and protein analysis showed elevated fibrotic markers expression (α-SMA, collagen1α1, fibronectin and other fibrotic markers) in the BLCN induction group, whereas NARI-29 or PFD treatment significantly reduced the same. Histology revealed that NARI-29 mitigated BLCN-induced fibrotic tissue formation, alveolar wall thickening, and lung distortion in a dose-dependent manner. Furthermore, pulmonary functional analysis revealed that NARI-29 treatment significantly attenuated BLCN-induced increases in Newtonian resistance and elastance, while enhancing inspiratory capacity and quasi-static compliance in a dose-dependent manner. The mechanistic evaluation revealed that NARI-29 alleviated fibrosis by modulating TGF-β/Smad signaling in lung tissues, as corroborated by molecular docking studies. Overall, the results of the current study demonstrated that treatment with NARI-29 significantly improved pulmonary fibrosis and lung function, highlighting its potential as a therapeutic candidate for IPF.