Abstract: Objective   To investigate the mechanism by which astragaloside IV alleviates renal fibrosis in unilateral ureteral obstruction (UUO) rats by inhibiting ferroptosis through modulation of the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling pathway.  Methods   Specific pathogen-free (SPF) male Sprague-Dawley (SD) rats were used to establish UUO models and randomly divided into four groups (n=6 per group): sham operation group, model group, AS-IV group [40 mg/(kg·d)], and losartan group [10.3 mg/(kg·d)]. Intragastric administration began one day post-surgery and continued for 14 days. Serum creatinine (Scr), blood urea nitrogen (BUN), and cAMP levels were measured. Renal histopathology was assessed via hematoxylin-eosin (HE) and Masson staining. Immunohistochemistry evaluated fibrosis markers [α-smooth muscle actin (α-SMA), fibronectin (FN), collagen type I (COL-I)], while Western blotting analyzed PKA and ferroptosis-related markers [glutathione peroxidase 4 (GPX4), heme oxygenase-1 (HO-1), solute carrier family 7 member 11 (xCT)].  Results  No significant differences in Scr were observed among groups (F=2.815, P=0.065). Compared to the sham group, the model group exhibited elevated BUN (t=26.306, P＜0.001), which was reduced in the astragaloside IV and losartan potassium groups (t=−5.241, −3.469; P＜0.001, P=0.002, respectively). HE and Masson staining revealed severe renal fibrosis in the obstructed kidneys of rats in the model group, while fibrosis was attenuated in the astragaloside IV and losartan potassium groups. Compared with the sham operation group, the model group exhibited increased expression of α-SMA, FN, COL-I (t =17.728, 9.202, 13.710, all  P＜0.001), cAMP levels (t =9.601, P＜0.001), and PKA (t =32.321, P＜0.001). In the astragaloside IV and losartan potassium groups, the expression of α-SMA (t =-11.457, -5.519, P＜0.001, P =0.001), FN (t =-6.301, -4.725, P＜0.001, P =0.001), COL-I (t =-6.087, -3.243, P＜0.001, P=0.012), cAMP levels (t =-6.629,-5.809, both P＜0.001), and PKA (t =-22.754, -23.294, both  P＜0.001) was decreased compared with the model group. Compared with the sham operation group, the model group showed decreased expression of GPX4, HO-1, and xCT (t =-38.397, -41.713, -56.779, all  P＜0.001). In the astragaloside IV and losartan potassium groups, the expression of GPX4 (t =25.504, 16.786, both P＜0.001), HO-1 (t=10.611, 42.007, both P＜0.001), and xCT (t=7.192, 3.181, P＜0.001, P =0.013) was increased compared with the model group.   Conclusions  Astragaloside IV improves renal function and mitigates fibrosis in UUO rats, potentially by suppressing ferroptosis through regulation of the cAMP/PKA signaling pathway.

Key words: Astragaloside IV, cAMP/PKA signaling pathway, Ferroptosis, Renal fibrosis