Puerarin restores the autophagic flux to alleviate cadmium-induced endoplasmic reticulum stress in NRK-52E cells

Cadmium (Cd) is a heavy metal that can accumulate and cause damage to a variety of tissues and organs. The kidney is the primary target organ for Cd accumulation and toxic damage. Autophagy, which is a critical intracellular process, serves an important role in maintaining the homeostasis of the intracellular environment. Endoplasmic reticulum stress (ERS) is another key process that functions to promote cell survival or results in cell injury and death. Both autophagy and ERS are associated with oxidative stress; however, the mechanism by which ERS is regulated by autophagy in Cd-induced nephrotoxicity remains unclear. The present study employed a rat NRK-52E cell model, where alterations in cell morphology, density and viability, the accumulation of reactive oxygen species, an increase in malondialdehyde generation and a decrease in antioxidant enzyme activity and apoptosis were induced by Cd treatment. Cd induced the activation of nuclear factor erythroid 2-related factor 2 (NRF2), an obstruction of autophagic flux and ERS, which were attenuated by puerarin administration. Furthermore, puerarin failed to alleviate ERS following knockdown of autophagy-related protein 7 in NRK-52E cells. Overexpression of Ras-related protein Rab-7, which promotes the fusion of autophagosomes and lysosomes, efficiently reduced ERS. Taken together, these results indicate that puerarin administration restored the autophagic flux to alleviate ERS, via blocking the activation of NRF2.