Anti-fibrotic effect of wogonin in renal tubular epithelial cells via Smad3-dependent mechanisms.

Renal fibrosis, a common feature and leading cause for End Stage Renal Disease, still lacks effective therapy. In the current study, we detected and compared the anti-fibrotic effects of wogonin and wogonoside, two major components of Scutellaria baicalensis Georgi, in TGF-β1-treated tubular epithelial cells of human and murine origins. Results consistently showed that compared with wogonoside, wogonin inhibits TGF-β1-induced upregulated mRNA and protein levels of collagen I and α-SMA with more efficiency, which was further confirmed by the immunofluorescence results that wogonin decreased the percentage of collagen I and α-SMA positive cells in TGF-β1-treated tubular epithelial cells. Mechanistically, wogonin mainly decreased Smad3 phosphorylation, but had marginal effect on non-canonical TGF-β signaling pathways, such as p38 and ERK MAP Kinase. Furthermore, in the cells deficient for TGF-β signaling or downstream Smad3, results demonstrated that even high concentration of wogonin failed to further decrease the level of collagen I and α-SMA, indicating the essential role of TGF-β/Smad3 signaling inhibition in the therapeutic action of wogonin in TGF-β1-stimulated tubular epithelial cells. Collectively, our results indicated that wogonin may be utilized as a potential anti-fibrotic Traditional Chinese Medicine monomer in the treatment of renal fibrosis.