To establish a rat model of renal fibrosis induced by unilateral ureteral obstruction (UUO), and investigate the mechanism of the Yishen Qufeng Formula (YQF) improves renal fibrosis through regulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) axis to mediate ferroptosis.

Eight-week-old SD rats were randomly divided into the sham-operation group, model group, positive control group (dapagliflozin at 20 mg·kg^-1·d^-1), and experimental -L,-M,-H groups (Yishen Qufeng Formula at 15.21, 22.82 and 30.42 g·kg^-1·d^-1). Except for the sham operation group, rats in the other groups were subjected to left ureteral ligation to establish a renal interstitial fibrosis (RIF) model. After successful modeling, the positive control group and the -L, -M, and -H dose experimental groups were given the corresponding drugs by gavage, while the sham operation group and model group were given an equal volume of 0.9% NaCl by gavage. All rats in the 6 groups were administered once a day for 14 consecutive days. Serum creatinine, urea nitrogen and urine protein levels were detected using a fully automatic integrated biochemical analyzer. The content of transforming growth factor-β1 (TGF-β1) was measured by enzyme-linked immunosorbent assay (ELISA). The changes in the relative expression levels of fibrosis-related, oxidative stress-related and ferroptosis-related proteins in renal tissues were determined by Western blotting.

The levels of serum creatinine in the experimental -M, -H groups, sham operation group, model group and positive control group were (50.24±7.81), (49.15±8.87), (41.96±5.25), (59.44±11.93) and (52.14±8.38)μmol·L^-1, respectively; the levels of urea nitrogen were (4.58±0.56), (4.45±0.55), (4.32±0.60), (6.00±1.03) and (6.55±1.02)mmol·L^-1, respectively; the levels of urine protein were (640.59±205.70), (538.74±237.98), (526.51±192.62), (982.91±349.13) and (964.26±456.84)mg·d^-1, respectively; the relative protein expression levels of glutathione peroxidase 4 (GPX4) were 1.62±0.15, 3.01±0.41, 2.25±0.27, 1.01±0.51 and 2.15±0.63, respectively; the relative protein expression levels of cystine/glutamate antiporter (xCT) were 0.62±0.10, 1.02±0.06, 1.65±0.13, 0.52±0.20 and 1.18±0.13, respectively; the relative protein expression levels of Nrf2 were 0.66±0.12, 1.04±0.16, 1.20±0.10, 0.54±0.03 and 1.19±0.14, respectively; the relative protein expression levels of HO-1 were 1.13±0.15, 1.21±0.18, 2.21±0.17, 0.64±0.44 and 1.57±0.26, respectively; the relative protein expression levels of α-smooth muscle actin (α-SMA) were 1.63±0.47, 1.13±0.57, 0.49±0.91, 2.88±0.97 and 1.05±0.60, respectively. There were statistically significant differences in the above indicators between the high-dose experimental group and the model group (all P<0.05).

Yishen Qufeng Formula may inhibit ferroptosis by activating the Nrf2/HO-1 signaling pathway, thereby effectively alleviating renal interstitial fibrosis in UUO rats. This provides important theoretical evidence for the mechanism by which the Yishen Qufeng Formula improves renal fibrosis through regulation of ferroptosis.