Isorhapontigenin ameliorates high glucose-induced podocyte and vascular endothelial cell injuries via mitigating oxidative stress and autophagy through the AMPK/Nrf2 pathway

Abstract

Background: Diabetic nephropathy (DN) is a severe microvascular complication of diabetes mellitus and a primary reason for end-stage renal disease (ESRD). Isorhapontigenin (ISO), a natural derivative of stilbene, has significant anti-inflammatory and antioxidant effects. Nevertheless, its impact on DN remains elusive.

Methods: Human vascular endothelial cells (HUVECs) and podocytes were damaged by high glucose (HG). Cell viability and apoptosis were testified by the cell counting kit-8 (CCK-8) assay and flow cytometry, respectively. The mRNA profiles of antioxidant factors HO-1, NQO1, and Prx1 were monitored by real-time quantitative polymerase chain reaction (RT-qPCR). Western blotting (WB) was implemented to verify the expression of apoptosis-related proteins (Bax, Bad, and Bcl-XL), antioxidant factors (HO-1, NQO1, and Prx1), autophagy-related proteins (Beclin-1, ATG5, p62), podocalyxin (podocin, nephrin, and synaptopodin) and the AMPK/Nrf2 pathway. The levels of oxidative stress-related markers MDA, SOD and CAT were assessed with the corresponding kits. Compound C (CC), an inhibitor of AMPK, was deployed to probe the effects of modulating the AMPK/Nrf2 pathway on ISO in oxidative stress and autophagy in HUVECs and podocytes. Streptozotocin (STZ) was injected intraperitoneally into mice to establish an animal model of diabetes mellitus and to clarify the impact of ISO on the renal parameters such as serum creatinine, urea nitrogen and urinary protein in diabetic mice.

Results: ISO notably facilitated cell proliferation, impeded apoptosis, elevated the expression of antioxidant-related factors, alleviated HG-induced oxidative stress and activated autophagy in HUVECs and podocytes. ISO activated the AMPK/Nrf2 pathway. Attenuating AMPK diminished the protective effect of ISO on HUVECs and podocytes, curbed cell proliferation, intensified apoptosis and oxidative stress, and dampened autophagy. In-vivo experiments also displayed that ISO reduced histopathological damage, lowered serum creatinine, urea nitrogen and urinary ACR levels, and eased kidney damage in DN mice.

Conclusion: ISO attenuates HG-induced oxidative stress and activates autophagy by motivating the AMPK/Nrf2 pathway, exerting a protective effect on HUVECs and podocytes and reducing renal injury in DN mice.

Keywords: Isorhapontigenin; Podocyte; The AMPK/Nrf2 pathway; Vascular endothelial cell.