Gambogenic acid protects against high glucose-induced damage of renal tubular epithelial cells by inhibiting pyroptosis through regulating the AMPK–TXNIP pathway

Diabetic nephropathy, a chronic inflammatory disease, is characterized by hyperglycemia-stimulated pyroptosis of renal tubular epithelial cells. Gambogic acid, a primary component of gamboge resin, exerts detoxification, antioxidant, anticancer, anti-angiogenesis and anti-inflammatory capacities. However, the nephroprotective effect of gambogic acid on diabetic nephropathy remains unknown. Human kidney (renal) epithelial cell line HK-2 was treated with dextrorotatory-glucose (D-glucose) to establish an in vitro cell model of diabetic nephropathy, followed by incubation with gambogic acid. CCK-8 was designed to detect cell viability. Enzyme-linked-immunosorbent serologic assay (ELISA) was used to detect the levels of inflammation-related factors. Pyroptosis and underlying mechanism were investigated by Western blot assay. High glucose treatment decreased the viability of HK-2 cell line, while gambogic acid incubation restored the reduced cell viability. High glucose-induced increase in the levels of tumor necrosis factor-α (TNF-α), Interleukin (IL)-6, Monocyte chemoattractant protein-1 (MCP-1) and IL-1β were reduced by gambogic acid. The protein expressions of NLR family pyrin domain containing 3 (NLRP3), N-terminal domain of gasdermin D (GSDMD-N), caspase-1, IL-1β and IL-18 were up-regulated in HK-2 cells after high glucose condition, while down-regulated by incubation of gambogic acid. Gambogic acid attenuated high glucose-induced increase of thioredoxin-interacting protein (TXNIP) and phosphorylated 5' adenosine monophosphate-activated protein kinase (p-AMPK) in HK-2 cell line. Gambogenic acid protected renal tubular epithelial cells against high glucose-induced inflammation and pyroptosis through suppression of AMPK–TXNIP pathway, providing a potential strategy for the prevention of diabetic nephropathy.