Tectorigenin protects against unilateral ureteral obstruction by inhibiting Smad3‐mediated ferroptosis and fibrosis

Abstract

Renal tubular epithelial cell (TEC) injury and fibrosis are the key factors of the pathogenesis of chronic kidney disease. Here, we reported that tectorigenin is effectively protected against obstructive nephropathy established by unilateral ureteral obstruction (UUO). In vivo, tectorigenin administration significantly alleviated the deteriorations of renal functions including blood urea nitrogen and creatinine. Meanwhile, results from the histology suggested that renal injury characterized by tubular cell damage and fibrosis lesions of kidneys in UUO group were markedly attenuated following tectorigenin treatment. Mechanistically, we found that tectorigenin treatment greatly inhibited Smad3 phosphorylation, and the transcription and protein level of Nox4, a newly identified direct downstream molecule of Smad3 and a modulator of ferroptosis, while it indirectly restored the expression of glutathione peroxidase 4, a negative regulator of ferroptosis. Consistent with in vivo studies, treatment with tectorigenin also suppressed the ferroptosis induced by erastin/RSL3 and fibrosis stimulated by transforming growth factor β1 (TGF‐β1) in primary renal TECs. What is more, treatment with ferroptosis inhibitor, ferrostatin‐1, also impeded TGF‐β1 stimulated the profibrotic effects in TECs, indicating that tectorigenin may relieve fibrosis by inhibiting ferroptosis in TECs. In addition, tectorigenin treatment exhibited a similar tendency, which inhibited Smad3 activation, and the docking analysis revealed that tectorigenin docked well into the Smad3 binding cavity with strong binding affinity (−7.9 kcal/mol). Thus, this study deciphers the protective effect of tectorigenin against obstructive nephropathy through inhibiting Smad3‐mediated ferroptosis and fibrosis.

Therapeutic Implications of Ferroptosis in Renal Fibrosis

“…Recent studies have demonstrated that liproxstatin-1 attenuates renal fibrosis induced by UUO through inhibiting ferroptosis in renal tubular epithelial cells ( Zhang et al, 2021 ). Ferrostatin-1 is a widely used ferroptosis blocker, which exhibits renoprotective effects in obesity-induced renal fibrosis, inflammatory cell infiltration by inhibiting ferroptosis in high-fat diet mice ( Li et al, 2022 ). It might reverse pathological parameters and improve renal function of folic acid-induced AKI mice, which is a model for studying nephrotoxic tubule damage and gradual progression of renal fibrosis ( Li X. et al, 2020 ).…”

Mechanisms of ferroptosis in chronic kidney disease

“…In Pdk1 mutant mice, Fer-1 could inhibit ferroptotic cell death, Akt-mediated proliferation, S6, Stat3, and Rb signaling, delaying cyst growth in ADPKD mouse models ( Zhang et al, 2021 ). Treatment of STZ-induced DN animal models with rosiglitazone (an ACSL4 inhibitor), led to a reduction in lipid peroxidation and iron content in the kidneys, improving kidney function ( Bao et al, 2007 ; Wang et al, 2020 ; Li et al, 2022 ). In more recent studies, tectorigenin showed protective effects against kidney injury and fibrosis, two key factors during CKD pathogenesis ( Bebber et al, 2020 ).…”

Role of Ferroptosis in Fibrotic Diseases

“…Tectorigenin, a small molecule derived from the medicinal herbal Belamcanda chinensis, has proved to possess protective activities against ferroptosis and fibrosis both in vivo and in vitro, which is mediated by Smad3-induced expression of NADPH oxidase 4 (NOX4). 84 Nobiletin, a flavonoid in the peel of citrus fruits, ameliorates ferroptosis-associated injury and renal fibrosis in the kidney of UUO mice, suggesting that Nob treatment has anti-ferroptosis and antifibrotic effects. 85 Pretreatment of FG-4592, an inhibitor of prolyl hydroxylase of HIF, plays a protective role in the early stage of folic acid-induced kidney injury and retards the progression of renal fibrosis, mainly by alleviating ferroptosis via stabilizing HIF-1α and Akt/GSK-3βmediated Nrf2 activation.…”