[Effects of astragaloside IV on delaying kidney aging and its mechanisms]

To investigate the mechanisms of Astragaloside Ⅳ on inhibiting apoptosis and delaying kidney aging in rats by regulating SIRT1/p53 signaling pathway.

The aging model was established by subcutaneous injection of D-galactose 200 mg/(kg·d). SPF-grade healthy male SD rats were randomly divided into 4 groups: normal control group (intragastric infusion of 5 ml/(kg·d) normal saline), aging model group (intragastric infusion of 5 ml/(kg·d) normal saline), Astragaloside IV group (intragastric infusion of 40 mg/(kg·d) Astragaloside IV),and SRT1720 group( intragastric infusion of 20 mg/(kg·d) SRT1720), with 10 rats in each group. After 8 weeks, the serum samples of rats were collected to detect the levels of renal function (creatinine and urea nitrogen) and senescent associated secretory phenotype (TGF-β and IL-6) by ELISA. The renal tissues of rats were obtained for HE and Masson staining. The protein and mRNA expressions of SIRT1, p53, Bcl-2, Bax, p21 and pRb were detected by Western blot and RT-PCR.

Serum creatinine and urea nitrogen levels in the aging model group were higher than those in the normal group, but there was no significant difference in each group (P＞0.05). The serum levels of TGF-β and IL-6 in the aging model group were higher than those in the normal group (P＜0.05), and which in the Astragaloside IV group and SRT1720 group were lower than those in the model group (P＜0.05). There was no significant differences between Astragaloside IV group and SRT1720 group (P＞0.05). The results of pathological staining of renal tissues showed that, compared with the normal group, the renal tubules dilated, local atrophy, infiltration of inflammatory cells and proliferation of collagen fibers were observed in the aging model group. Compared with the aging model group, the pathological changes were alleviated in Astragaloside IV group and SRT1720 group. The results of Western blot and RT-PCR showed that, compared with the normal group, the protein and mRNA expressions of SIRT1 and pRb in the renal tissue of the aging group were decreased, the protein expression of Bcl-2 was decreased(P＜0.05), and the protein and mRNA expressions of p53 and p21 were increased, the protein expression of Bax was increased(P＜0.05). Compared with the aging group, Astragaloside IV and SRT1720 improved the above-mentioned indexes (P＜0.05).

Astragaloside IV can delay kidney aging by regulating the SIRT1/p53 signaling pathway.