Objective  To investigate the effect of astragaloside Ⅳ (AS-Ⅳ) on renal ischemia-reperfusion injury (RIRI) and its specific mechanism.

Methods  Forty-eight rats were randomly divided into 6 groups, with 8 rats in each group: sham operation group (Sham group), RIRI group, RIRI + AS-Ⅳ (10 mg/kg) group, RIRI + AS-Ⅳ (20 mg/kg) group, RIRI + AS-Ⅳ (40 mg/kg) group and RIRI + AS-Ⅳ + Brusatol group Brusatol is a nuclear factor E2-related factor 2 (Nrf2) inhibitor. Serum creatinine (Scr) and blood urea nitrogen (BUN) levels of rats were detected using an automatic biochemical analyzer; the pathological damage degree of rats kidney tissue was evaluated by hematoxylin-eosin staining and scored; the levels of superoxide dismutase (SOD) and malondialdehyde (MDA) in rats serum, and interleukin (IL)-1β and IL-18 in rats kidney tissue were detected by enzyme-linked immunosorbent assay; the degree of cell apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling; real-time fluorescence quantitative polymerase chain reaction and Western blotting were used to determine the messenger RNA (mRNA) and protein levels of Nrf2/heme oxygenase-1 (HO-1) signaling pathway and cell pyroptosis regulatory factors in rats kidney tissue.

Results  Compared with the Sham group, the BUN and Scr levels in the RIRI group were increased, the renal function and tissue damage were more severe, the degree of cell apoptosis was aggravated, the MDA level was increased, and the SOD activity was decreased, the Nrf2 and HO-1 protein and mRNA levels were downregulated, the NOD-like receptor protein 3 (NLRP3), Cle-Caspase-1 (the activated form of Caspase-1) and gasdermin D (GSDMD)-N protein levels were upregulated, the NLRP3, Caspase-1 and GSDMD-N mRNA levels were increased, and the release of IL-1β and IL-18 was increased. Compared with the RIRI group, the BUN and Scr levels in rats after AS-Ⅳ treatment were decreased, the degree of renal function and tissue damage was reduced, the degree of cell apoptosis was decreased, the MDA level was decreased, and the SOD activity was increased, the Nrf2 and HO-1 protein and mRNA levels were increased, the NLRP3, Cle-Caspase-1 and GSDMD-N protein levels were decreased, the NLRP3, Caspase-1 and GSDMD-N mRNA levels were decreased, and the release of IL-1β and IL-18 was reduced. Compared with the RIRI + AS-Ⅳ (20 mg/kg) group, the MDA level and SOD activity in rats of the RIRI + AS-Ⅳ + Brusatol group were increased, the Nrf2 and HO-1 protein and mRNA levels were decreased, the NLRP3, Cle-Caspase-1 and GSDMD-N protein levels were upregulated, the NLRP3, Caspase-1 and GSDMD-N mRNA levels were increased, and the release of IL-1β and IL-18 was increased.

Conclusions  AS-Ⅳ may alleviate RIRI in rats by inhibiting oxidative stress response and pyroptosis, and this mechanism is related to the activation of Nrf2/HO-1 signaling pathway.