Guaiacol counters renal fibrosis via BMP/ERK/Smad1/5/9 signaling in UUO-induced chronic kidney disease.

Chronic kidney disease (CKD) is characterized by progressive fibrosis and inflammation, with limited therapeutic options. Natural compounds have been studied for their potential to offer kidney-protective benefits, especially in CKD. Guaiacol, a lignin-based polyphenol and one of the key constituents of Angelica sinensis (Oliv.) Diels has been shown to have anti-oxidative and anti-inflammatory properties. Hence, we aimed to inspect and analyze the potential of guaiacol in the unexplored realm of renal fibrosis, integrating computational pharmacology and validating the outcomes in an experimental in-vitro recombinant human-transforming growth factor-beta 1 (rh-TGF-β1)-induced rat renal epithelial cells and in-vivo model of unilateral ureteral obstruction (UUO) in Wistar rats. Targets for CKD, as well as guaiacol, were first recognized using target databases, and the common targets were subsequently evaluated to elucidate their interactions through a protein-protein interaction network. Furthermore, network analyses using software such as Cytoscape and STRING led to the identification of critical hub proteins, which were subsequently subjected to gene ontology and pathway enrichment analyses. The core targets, as well as anti-fibrotic proteins, exhibited strong binding affinity with guaiacol, as evidenced by molecular docking studies. In-vitro studies revealed guaiacol's anti-inflammatory potential by downregulation of ACE and p-NF-κB levels, reinforcing computational predictions. Furthermore, animal experimentation revealed that guaiacol administration, over 21 days, significantly mitigated renal structural and functional parameters, as demonstrated by both biochemical and histopathological findings. Furthermore, immunohistochemical analyses revealed that guaiacol inhibited the expression of key fibrotic proteins, including collagen, fibronectin, and α-smooth muscle actin, which were significantly elevated in the unilateral ureteral obstruction group. Additionally, guaiacol notably reduced the phosphorylation of ERK and Smad1/5/9 proteins, along with Smad4, highlighting its therapeutic potential in renal fibrosis via modulation of the RAAS, NF-κB-mediated inflammation, and BMP/Smad1/5/9 anti-fibrotic signaling axis.