Synthesis, Anti-Fibrotic Activity, and Density Functional Theory Calculations of Novel Carboxylic Acid Analogs Containing Pyrrole and Imidazole Rings

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease with limited treatment options and poor prognosis. Current therapies, Pirfenidone and Nintedanib, slow disease progression but cannot reverse established fibrosis, underscoring the urgent need for innovative strategies. Oxidative stress and hypoxia-inducible factor-1α (HIF-1α) signaling are central to IPF pathogenesis, where the interplay between reactive oxygen species (ROS), TGF-β1, and stabilized HIF-1α forms a self-perpetuating loop that promotes fibroblast activation and extracellular matrix (ECM) deposition. To interrupt this pathological cycle, we rationally designed and synthesized four small molecules, two imidazole- and two pyrrole-based derivatives, with dual antioxidants and HIF-1α inhibitory potential. Their antioxidant potential was assessed using DPPH and DCFDA assays, while density functional theory (DFT) calculations and ADME profiling confirmed their chemical stability and drug-likeness. In vitro screening identified compound 2a as the lead candidate based on its superior ability to inhibit HIF-1α and suppress fibrotic markers, including collagen III, fibronectin, and vimentin, in TGF-β1-stimulated A549 and MRC-5 cells. In vivo, 2a significantly attenuated collagen and fibronectin accumulation in a bleomycin-induced pulmonary fibrosis model. Mechanistically, 2a inhibited phosphorylation of Smad3 and ERK, implicating modulation of both Smad and non-Smad pathways in its anti-fibrotic effects. These findings position compound 2a as a promising dual-targeted therapeutic candidate for IPF, capable of disrupting the ROS–TGF-β1–HIF-1α axis and addressing key unmet clinical needs.