Astragaloside IV protects against podocyte apoptosis by inhibiting oxidative stress via activating PPARγ-Klotho-FoxO1 axis in diabetic nephropathy

Aims: Podocyte Apoptosis plays an important role in the pathogenesis of diabetic nephropathy (DN). Astragaloside IV (AS-IV) has been shown to protect against podocyte Apoptosis. Here we aim to investigate the mechanism responsible for the protective effects of AS-IV.

Main methods: Diabetic db/db mice and high glucose (HG)-cultured podocytes were treated with AS-IV. Renal function and histopathological changes were measured to evaluate the therapeutic effects of AS-IV against DN. Adenovirus-mediated Klotho overexpression, Klotho siRNA, and PPARγ Inhibitor were applied in vitro to investigate the potential mechanism. The expression levels of mRNA and proteins were analyzed by qRT-PCR, western blot or immunofluorescence. Intracellular ROS and mitochondrial superoxide were detected by DHE and MitoSOx Red, respectively. Cell Apoptosis was evaluated by TUNEL staining and flow cytometry.

Key findings: AS-IV improved renal function and ameliorated podocyte injury in db/db mice accompanied with enhanced Klotho expression in glomerular podocytes. In vitro, AS-IV inhibited HG-induced podocyte Apoptosis and restored HG-inhibited Klotho expression, whereas Klotho knockdown abrogated the anti-apoptosis action of AS-IV. Further study showed that adenovirus-mediated Klotho overexpression enhanced Forkhead transcription factor O1 (FoxO1)-dependent antioxidant activity and attenuated HG-evoked oxidative stress and Apoptosis. AS-IV prevented HG-induced FoxO1 inhibition and oxidative stress, whereas Klotho knockdown reversed these effects. Cotreatment with PPARγ Inhibitor T0070907 abolished AS-IV-induced Klotho expression and anti-apoptosis action.

Significance: These data suggested that AS-IV attenuated podocyte Apoptosis presumably by inhibiting oxidative stress via activating PPARγ-Klotho-FoxO1 signaling pathway, thereby ameliorating DN. This study provided new insights into the molecular mechanisms of AS-IV against DN.